Protein oxidation - Formation mechanisms, detection and relevance as biomarkers in human diseases

In the paper

“Sulfur-containing moieties such as the sulfhydryl group of cysteine and the thioether group of methionine are targeted by oxidative stress and a plethora of posttranslational protein modifications is formed (Fig. 1) [15].”

What the sources say

• Supported

  The “Reactive oxygen, nitrogen and chlorine species” section says that reactive species modify proteins and that cysteine’s free thiol group is readily oxidised to several products. It also describes methionine oxidation to sulfoxide and sulfone; Fig. 1 identifies both residues as sites of oxidative post-translational modification. (LLM, conf=0.94)

  cites [15] Ryan, 2014, Oxidative post-translational modifications and their involvement in the pathogenesis of autoimmune diseases, Redox Biol. source

In the paper

“Furthermore, a higher level of damage may arise from increased oxidant generation and/or a decrease or failure of defense systems under several conditions such as diseases and aging [3,4].”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Kregel, 2007, An integrated view of oxidative stress in aging: basic mechanisms, functional effects, and pathological considerations, Am. J. Physiol. Regul. Integr. Comp. Physiol. source
• Supported

  The Pathophysiology of oxidative stress section says oxidative stress can result from excess RONS production and/or an impaired ability to neutralize them or repair damage. The aging and age-related diseases sections connect oxidative damage with aging and diseases. No page numbers are provided in our copy. (LLM, conf=0.93)

  cites [4] Liguori, 2018, Oxidative stress, aging, and diseases, Clin. Interv. Aging source

In the paper

“After enolization, the main product of this reaction is the fluorescent protein crosslink ortho,ortho-dityrosine [23].”

What the sources say

• Partly supported

  The Introduction (page not provided) calls o,o′-dityrosine the major product of the tyrosyl-radical reaction, and the Methods describe protein-bound dityrosine measured by fluorescence. Our copy does not describe enolization as a step preceding its formation. (LLM, conf=0.88)

  cites [23] Heinecke, 1993, Tyrosyl radical generated by myeloperoxidase catalyzes the oxidative cross-linking of proteins, J. Clin. Invest. sourceExperimental — accuracy not yet measured

In the paper

“The irreversible modification 3-nitrotyrosine (3-NT) is formed by nitration of tyrosine via attack of the nitrogen dioxide radical at the ortho-position of the aromatic ring [74].”

What the sources say

• Partly supported

  The “Nitration as a free radical process” section (page unavailable) states that nitration places a nitro group at position 3 of tyrosine’s phenolic ring and that the tyrosine radical reacts with •NO2 to yield 3-nitrotyrosine. It does not establish that the resulting 3-nitrotyrosine modification is irreversible; its discussion of reversal concerns the tyrosine-radical intermediate, not the nitrated product. (LLM, conf=0.85)

  cites [74] Bartesaghi, 2018, Fundamentals on the biochemistry of peroxynitrite and protein tyrosine nitration, Redox Biol. sourceExperimental — accuracy not yet measured

In the paper

“Although the latter mechanism is non-oxidative, the reactive precursor glyoxal is mainly formed by oxidative degradation of carbohydrates, lipids, nucleotides, and serine [37].”

What the sources say

• Partly supported

  Table 1 (appearing in our copy under Closing remarks) lists lipid peroxidation, oxidative degradation of serine, monosaccharide degradation, and nucleotide degradation as sources of glyoxal. It does not say that all four pathways are oxidative or that they are collectively the main sources; it also lists degradation of glycated proteins and food and beverages. (LLM, conf=0.84)

  cites [37] Rabbani, 2015, Dicarbonyl stress in cell and tissue dysfunction contributing to ageing and disease, Biochem. Biophys. Res. Commun. sourceExperimental — accuracy not yet measured

In the paper

“Protein carbonyls, 3-NT and methionine sulfoxide are biomarkers of protein oxidation which are commonly analyzed via immunochemical methods [75,82,92].”

What the sources say

• Partly supported

  The indexed title identifies the paper as an analysis of protein carbonylation methods, and its keywords include “immunoaffinity.” The available passages do not say that immunochemical methods are commonly used for protein carbonyls, or address 3-nitrotyrosine or methionine sulfoxide; the broader claim is therefore not established by this copy. (LLM, conf=0.72)

  cites [75] Rogowska-Wrzesinska, 2014, Analysis of protein carbonylation--pitfalls and promise in commonly used methods, Free Radic. Res. sourceExperimental — accuracy not yet measured
• Partly supported

  The Introduction identifies protein carbonyls as a marker of protein oxidation and describes their detection by immunoblotting and ELISA; the Conclusion also discusses both methods. The paper mentions methionine sulfoxides as oxidation products but does not describe their immunochemical analysis, and the passages found do not address 3-nitrotyrosine. Thus it supports the sentence for protein carbonyls, not for all three biomarkers. (LLM, conf=0.88)

  cites [82] Weber, 2015, Determination of protein carbonyls in plasma, cell extracts, tissue homogenates, isolated proteins: focus on sample preparation and derivatization conditions, Redox Biol sourceExperimental — accuracy not yet measured
• Partly supported

  Section 5, “Quantification of 3-nitrotyrosine in biological samples” (page not provided), says that a large part of 3-NT research has used antibody-based methods. The paper supports that part of the sentence, but the cited passages do not establish that protein carbonyls or methionine sulfoxide are commonly analyzed by immunochemical methods. (LLM, conf=0.88)

  cites [92] Teixeira, 2016, 3-Nitrotyrosine quantification methods: current concepts and future challenges, Biochimie sourceExperimental — accuracy not yet measured

In the paper

“Sulfur-containing amino acids, such as cysteine and methionine are highly susceptible to diverse forms of oxidation processes [118,119].”

What the sources say

• Supported

  The Abstract says methionine and cysteine are extremely sensitive to almost all forms of reactive oxygen species. The Methionine and Cysteine sections also describe their residues as readily oxidized. This supports the cited paraphrase. (LLM, conf=0.94)

  cites [118] Bin, 2017, Oxidation resistance of the sulfur amino acids: methionine and cysteine, BioMed Res. Int. source
• Partly supported

  In “Methionine and cysteine in proteins” (p. 1636S), the paper says surface-exposed methionine residues are susceptible to oxidation; the 1636S discussion also describes cysteine forming disulfide bonds. It does not say that both amino acids are highly susceptible to diverse forms of oxidation, and it limits the methionine observation to exposed residues. (LLM, conf=0.84)

  cites [119] Brosnan, 2006, The sulfur-containing amino acids: an overview, J. Nutr. sourceExperimental — accuracy not yet measured

In the paper

“By using a LC-MS/MS approach, they found elevated cysteine sulfonic acid in human serum albumin of type 2 diabetes (T2D) patients compared to control subjects, indicating the potential of trioxidized peptides as prognostic biomarker of protein oxidation in human disease [125].”

What the sources say

• Partly supported

  The Introduction says site-specific trioxidized human serum albumin could be a biomarker of diabetes diagnosis and prognosis. The Conclusion limits the proposed prognostic use to diabetes and says its relationship to disease severity and outcomes still needs a larger longitudinal study. The claim extends that potential to human disease generally. (LLM, conf=0.86)

  cites [125] Paramasivan, 2020, Serum albumin cysteine trioxidation is a potential oxidative stress biomarker of type 2 diabetes mellitus, Sci. Rep. sourceExperimental — accuracy not yet measured

In the paper

“One major difficulty in detection of glycoxidation products for standardized clinical research is their structural complexity and heterogeneity, deriving from various formation mechanisms [154,155].”

What the sources say

• Supported

  Section 4, “Measurements of AGEs,” says that glycation’s complex nature and the wide range of chemical structures make AGE measurement difficult, and that no standardized method exists for comparing results across laboratories. Section 2, “AGE’s Biochemistry,” describes their heterogeneous structures and multiple formation mechanisms. The supplied passages do not give page numbers. (LLM, conf=0.91)

  cites [154] Perrone, 2020, Advanced glycation end products (AGEs): biochemistry, signaling, analytical methods, and epigenetic effects, Oxid Med Cell Longev source
• ?Not checked — no full text of the sourcecites [155] Nedic, 2013, Molecular effects of advanced glycation end products on cell signalling pathways, ageing and pathophysiology, Free Radic. Res. source

In the paper

“Although ELISAs are easy to perform and ensure high sample throughput, their specificity and reproducibility have been criticized, especially by the limited description of applied antibodies, associated with different outcomes [158].”

What the sources say

• Supported

  The Bioanalytical Techniques section says ELISA assays have inadequate reproducibility because antibody specificity is often difficult to characterize. The ELISA section adds that antibody specificity is often incompletely characterized and documents discrepant results, supporting the paraphrase about differing outcomes. Page numbers were not supplied in our copy. (LLM, conf=0.90)

  cites [158] Ashraf, 2015, Recent advances in detection of AGEs: immunochemical, bioanalytical and biochemical approaches, IUBMB Life source

In the paper

“The measurement correlates well with the total amount of AGEs in skin biopsies”

What the sources say

• Partly supported

  The section on skin autofluorescence as a surrogate for AGE accumulation says SAF measurements were validated against biochemical analyses of skin biopsies. However, the Measurement of the Skin Autofluorescence section explains that some AGEs do not fluoresce and that other substances also contribute to autofluorescence. The paper supports SAF as a surrogate for skin AGE accumulation, but does not establish that it correlates well with the total amount of AGEs in biopsies. (LLM, conf=0.83)

  cites [161] Stirban, 2014, Skin autofluorescence - a non-invasive measurement for assessing cardiovascular risk and risk of diabetes, Eur. Endocrinol. sourceExperimental — accuracy not yet measured

In the paper

“Thus, cysteine and its oxidized forms, such as cystine and further cysteine disulfide species, are considered as potential biomarkers of protein oxidation in human disease [120,121].”

What the sources say

• Partly supported

  The 'Cysteine and redox homeostasis' section (page unavailable) says cysteine is readily oxidized to cystine and describes oxidation of cysteine residues. The paper does not identify cysteine, cystine, or other cysteine disulfides as potential biomarkers of protein oxidation in human disease. (LLM, conf=0.82)

  cites [120] Paul, 2018, Cysteine metabolism in neuronal redox homeostasis, Trends Pharmacol. Sci. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [121] Oliveira, 2018, Implications of plasma thiol redox in disease, Clin. Sci. (Lond.) source

In the paper

“This indicates their relevance in the progression of metabolic diseases, including neurodegenerative disease, chronic kidney disease (CDK), CVD, and cancer, but in particular, T2D and related complications as reviewed elsewhere [152].”

What the sources say

• Partly supported

  The Introduction and Section 5 link advanced glycation end products (AGEs) to T2D and diabetic complications, including nephropathy and cardiovascular disease (page numbers unavailable). The copy does not establish their relevance to neurodegenerative disease or cancer, and its kidney-disease discussion focuses on diabetic nephropathy rather than CKD generally. (LLM, conf=0.88)

  cites [152] Nowotny, 2015, Advanced glycation end products and oxidative stress in type 2 diabetes mellitus, Biomolecules sourceExperimental — accuracy not yet measured

In the paper

“By analyzing hydrolysates of native and modified protein samples, the amino acid composition can provide information about the loss of parent proteins, but also the formation of products [101].”

What the sources say

• ?Could not verify

  The Metabolomics Analysis section describes measuring amino acids in blood plasma, and Results §3.2 reports differences between SCA7 patients and controls. Neither addresses hydrolysates of native and modified proteins or whether amino acid composition reveals loss of parent proteins and formation of products. Searches for those terms and for protein hydrolysis found no supporting passage. (LLM, conf=0.76)

  cites [101] Nambo-Venegas, 2020, Altered plasma acylcarnitines and amino acids profile in Spinocerebellar ataxia type 7, Biomolecules sourceExperimental — accuracy not yet measured

In the paper

“They used a UPLC-MS/MS approach for simultaneous quantification of thiols as well as disulfides and found higher levels of cysteine disulfides in plasma of patients with sickle-cell disease and sepsis compared to healthy donors [124].”

What the sources say

• Supported

  The Figure 3 caption and accompanying text report significantly elevated plasma protein-bound cysteine, a cysteine disulfide, in patients with sickle-cell disease and sepsis compared with healthy donors. The Introduction also states that the authors used UPLC-MS/MS to quantify thiols and disulfides simultaneously. (LLM, conf=0.93)

  cites [124] Fu, 2019, Cysteine disulfides (Cys-ss-X) as sensitive plasma biomarkers of oxidative stress, Sci. Rep. source

In the paper

“all other recent studies revealed higher concentrations of protein carbonyls in adults and elderly compared to younger individuals (Table 4)”

What the sources say

• Partly supported

  Table 2 (listed under Conclusions; page unavailable) shows higher mean saliva and plasma protein carbonyl concentrations in middle-aged and elderly participants than in the young group. But this paper cannot establish that *all other recent studies* found the same pattern: its Discussion says prior findings were mixed and notes a study that found no relationship with age. (LLM, conf=0.86)

  cites [148] Wang, 2015, Age-related variations of protein carbonyls in human saliva and plasma: is saliva protein carbonyls an alternative biomarker of aging?, Age (Dordr) sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [233] Hatch, 2015, Cardiovascular and psychiatric characteristics associated with oxidative stress markers among adolescents with bipolar disorder, J. Psychosom. Res. source
• ?Not checked — no full text of the sourcecites [234] Abdul Sani, 2018, DNA damage and protein oxidation associated with ageing correlate with cognitive dysfunction in a Malaysian population, Free Radic. Res. source

In the paper

“They used a UPLC-MS/MS approach for simultaneous quantification of thiols as well as disulfides and found higher levels of cysteine disulfides in plasma of patients with sickle-cell disease and sepsis compared to healthy donors [124].”

What the sources say

• Supported

  The passage accompanying Figure 3 (Introduction) reports that patients with sepsis had significantly elevated plasma protein-bound cysteine compared with healthy donors. Protein-bound cysteine is a cysteine disulfide, supporting the attributed comparison. (LLM, conf=0.91)

  cites [124] Fu, 2019, Cysteine disulfides (Cys-ss-X) as sensitive plasma biomarkers of oxidative stress, Sci. Rep. source

In the paper

“The formation and accumulation of glycoxidation products occurs during normal, but especially under certain physiological conditions, such as hyperglycemia, hyperlipidemia, and oxidative stress.”

What the sources say

• Partly supported

  Section 2, “AGEs in Diabetes: An Overview” (page not specified), says AGE formation occurs as part of physiological metabolism, is accelerated in diabetes by elevated glucose and oxidative stress, and that oxidative stress triggers glycoxidation products. It identifies lipid peroxidation as a pathway to AGE formation, but does not establish that hyperlipidemia itself especially increases their formation or accumulation. (LLM, conf=0.85)

  cites [152] Nowotny, 2015, Advanced glycation end products and oxidative stress in type 2 diabetes mellitus, Biomolecules sourceExperimental — accuracy not yet measured

In the paper

“a growing body of evidence reveals that levels of glycoxidation products increase as a function of age in several tissues, dependent on the dietary intake and the presence of hyperglycemic conditions [152,153]”

What the sources say

• Partly supported

  Section 2 (page unavailable) reports increased AGE formation and tissue levels in diabetes, and says dietary AGE intake correlates with serum AGE levels. It does not report that glycoxidation products increase with age across several tissues; the age-related part of the claim is therefore unsupported by this paper's text. (LLM, conf=0.85)

  cites [152] Nowotny, 2015, Advanced glycation end products and oxidative stress in type 2 diabetes mellitus, Biomolecules sourceExperimental — accuracy not yet measured
• Supported

  The section on AGE buildup during aging reports accumulation in several tissues, including the eye lens with age and skin collagen in diabetic patients. The sections on dietary AGEs and AGE chemistry describe diet as an exogenous source and report elevated glycation products under hyperglycemic conditions. Together, these passages support the broad claim, though they do not quantify how much each factor changes tissue levels. (LLM, conf=0.85)

  cites [153] Chaudhuri, 2018, The role of advanced glycation end products in aging and metabolic diseases: bridging association and causality, Cell Metabol. source

In the paper

“elevated protein carbonyl levels have been found in neurodegenerative disease, such as AD”

What the sources say

• ?Not checked — no full text of the sourcecites [63] Dalle-Donne, 2003, Protein carbonylation in human diseases, Trends Mol. Med. source
• Supported

  The Introduction reports increased protein carbonyl levels in the hippocampus and neocortex in AD. The Results and discussion also report higher plasma protein carbonyl levels in AD males than in healthy male controls, while noting that the plasma finding differs by sex. (LLM, conf=0.93)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“However, a strong limitation for the analysis of cysteine species is their instability due to the dynamic nature, since oxidation products of protein cysteine residues can be easily reduced by other thiols [122,123].”

What the sources say

• Supported

  In “Thiol-disulfide exchange” (page not provided), the paper says disulfide bonds in thiol-containing mixtures are not fixed: they can undergo exchange, including reductive recycling after attack by other free thiols. It identifies this reactivity as a challenge for analysis, requiring thiol blocking to preserve native disulfide patterns. (LLM, conf=0.88)

  cites [122] Poole, 2015, The basics of thiols and cysteines in redox biology and chemistry, Free Radic. Biol. Med. source
• ?Not checked — no full text of the sourcecites [123] Turell, 2020, Mechanisms and consequences of protein cysteine oxidation: the role of the initial short-lived intermediates, Essays Biochem. source

In the paper

“By using a LC-MS/MS approach, they found elevated cysteine sulfonic acid in human serum albumin of type 2 diabetes (T2D) patients compared to control subjects, indicating the potential of trioxidized peptides as prognostic biomarker of protein oxidation in human disease [125].”

What the sources say

• Supported

  The Results section, ‘Quantitative study of HSA Cys trioxidation in plasma samples using MRM’ (page not provided), reports significantly higher cysteine trioxidation in patients with diabetes than in healthy controls. It identifies the measured modifications as sulfonic acid (SO3H) on human serum albumin peptides. (LLM, conf=0.94)

  cites [125] Paramasivan, 2020, Serum albumin cysteine trioxidation is a potential oxidative stress biomarker of type 2 diabetes mellitus, Sci. Rep. source

In the paper

“Weber et al. found no correlation between protein carbonyls and aging in two of three cohorts from the European MARK-AGE study”

• Also stated in: § Carbonylation in human diseases and aging · plain

  “Positive correlation between protein carbonyl levels and age in RASIG groupNo correlation between protein carbonyl levels and age in GO and SGO groups”

What the sources say

• Supported

  The Results report that a weak, statistically significant correlation between protein carbonyls and age was observed only in the RASIG group. This supports the claim that the other two MARK-AGE study groups showed no significant correlation; it does not imply their correlation coefficients were exactly zero. (LLM, conf=0.90)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev source

In the paper

“together indicating the relevance of protein carbonyls in aging and age-related diseases”

What the sources say

• ?Not checked — no full text of the sourcecites [63] Dalle-Donne, 2003, Protein carbonylation in human diseases, Trends Mol. Med. source
• Partly supported

  The Introduction describes protein carbonyls as markers of pathological oxidative stress and reports elevated levels in Alzheimer’s and Parkinson’s disease, supporting their relevance to age-related diseases. It calls glycation—not protein carbonylation—age-dependent, and the cited passages do not establish a role for protein carbonyls in aging itself. Page numbers are unavailable in our copy. (LLM, conf=0.82)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol sourceExperimental — accuracy not yet measured

In the paper

“Recent clinical studies focused mainly on reactive intermediates 4-HNE and MDA, which are prominent precursors of ALE formation [174].”

What the sources say

• Supported

  The Introduction describes 4-HNE as a reactive lipid-peroxidation product that forms protein adducts, and MDA as one of the most abundant aldehydes that reacts with protein residues. It identifies these reactive aldehydes as precursors of advanced lipid peroxidation end products (ALEs). (LLM, conf=0.91)

  cites [174] Negre-Salvayre, 2008, Advanced lipid peroxidation end products in oxidative damage to proteins. Potential role in diseases and therapeutic prospects for the inhibitors, Br. J. Pharmacol. source

In the paper

“| Psoriasis | Skin, serum | Healthy individuals and psoriasis patients (n = 40 per group) | Skin AF,ELISA | Higher skin AF, total AGEs and pentosidine levels in patients with psoriasis | [239] |”

What the sources say

• Partly supported

  The Results report higher skin AGE fluorescence in 40 patients with severe psoriasis than in 40 healthy controls (2.87 versus 1.86; p = 0.01). The study also included 40 patients with mild psoriasis, but the cited comparison does not establish the same finding for psoriasis patients generally. (LLM, conf=0.88)

  cites [239] Papagrigoraki, 2017, Advanced glycation end products are increased in the skin and blood of patients with severe psoriasis, Acta Derm. Venereol. sourceExperimental — accuracy not yet measured

In the paper

“| Psoriasis | Skin, serum | Healthy individuals and psoriasis patients (n = 40 per group) | Skin AF,ELISA | Higher skin AF, total AGEs and pentosidine levels in patients with psoriasis | [239] |”

What the sources say

• Partly supported

  The Results report significantly higher serum pentosidine in patients with severe psoriasis than in healthy subjects (p < 0.0001). The study included 40 people in each of those groups (Results, Table I). The finding is specific to severe psoriasis; the claim's unqualified reference to psoriasis patients could also include the mild-psoriasis group, for which this comparison is not reported. (LLM, conf=0.86)

  cites [239] Papagrigoraki, 2017, Advanced glycation end products are increased in the skin and blood of patients with severe psoriasis, Acta Derm. Venereol. sourceExperimental — accuracy not yet measured

In the paper

“| RA | Serum | Control subjects (n = 30) vs. RA patients (n = 80) | ELISA | Higher CML and pentosidine levels in RA patients | [237,238] |”

What the sources say

• ?Not checked — no full text of the sourcecites [237] Knani, 2018, Increased serum concentrations of N(varepsilon)-carboxymethyllysine are related to the presence and the severity of rheumatoid arthritis, Ann. Clin. Biochem. source
• Partly supported

  The Discussion says that CML and pentosidine were increased in RA, citing the authors’ earlier work. This paper studied 80 RA patients and 30 controls, but its Methods specify ELISA measurements of MGO and sRAGE, not pentosidine. It therefore does not establish that pentosidine was measured by ELISA or was higher in this particular cohort. (LLM, conf=0.88)

  cites [238] Knani, 2018, Methylglyoxal: a relevant marker of disease activity in patients with rheumatoid arthritis, Dis. Markers sourceExperimental — accuracy not yet measured

In the paper

“| Multiple sclerosis | CSF, plasma, brain tissue | Non-demented control subjects (n = 10) vs. multiple sclerosis patients (n = 15) | UPLC-MS/MS,IHC | No difference in plasma free and protein-bound CML levels | [168] |”

What the sources say

• Partly supported

  The Results section ('MG-H1 Is Increased in the Lesion Area of MS Patients'; page unavailable) reports no difference in free or protein-bound CML between MS lesions and control brain tissue, using samples from 15 MS patients and 10 non-demented controls. The Methods ('α-Dicarbonyl and AGE Measurements'; page unavailable) confirm UPLC-MS/MS measurement, but the plasma samples came from 18 MS patients and were analyzed for plasma–CSF correlations, not compared with those controls. The claimed absence of a difference in plasma CML is therefore unsupported. (LLM, conf=0.89)

  cites [168] Wetzels, 2019, Methylglyoxal-derived advanced glycation endproducts accumulate in multiple sclerosis lesions, Front. Immunol. sourceExperimental — accuracy not yet measured

In the paper

“together indicating the relevance of AGEs as biomarkers of aging and age-related diseases”

What the sources say

• Supported

  The section on AGE buildup during aging says AGEs may be a biomarker of aging and reports an association between plasma CML and mortality in older adults. The neurodegeneration section also describes elevated AGE-albumin as a potential biomarker for neurodegenerative diseases. Together, these passages support the claimed relevance without asserting that AGEs are established clinical biomarkers. (LLM, conf=0.92)

  cites [153] Chaudhuri, 2018, The role of advanced glycation end products in aging and metabolic diseases: bridging association and causality, Cell Metabol. source

In the paper

“| Autism spectrum disorders | Plasma | Healthy children (n = 31) vs. children with autism spectrum disorders (n = 38) | LC-MS/MS | Increased plasma CML levels in children with autism spectrum disorders | [143] |”

What the sources say

• Partly supported

  The Results report increased CML in plasma protein from children with ASD, and the Methods say plasma-protein adducts were measured by LC-MS/MS. Although the Subject recruitment section lists 38 children with ASD and 31 typically developing children, Results Table 2 gives 27 and 21, respectively, for the plasma-protein measurements. The cited row therefore uses the recruitment totals rather than the numbers underlying the reported CML increase. (LLM, conf=0.90)

  cites [143] Anwar, 2018, Advanced glycation endproducts, dityrosine and arginine transporter dysfunction in autism - a source of biomarkers for clinical diagnosis, Mol. Autism. sourceExperimental — accuracy not yet measured

In the paper

“These methods represent the gold standard for the identification of glycoxidation structures and detection in free and protein-bound forms”

What the sources say

• Partly supported

  The Liquid Chromatography-Mass Spectroscopy section (page unavailable) calls LC-MS the most accurate technique for detecting AGEs and early glycation products, supporting the comparison with other methods. It also says identifying glycation modifications is often difficult. The paper calls HPLC a gold standard specifically for HbA1c determination, not for identifying glycoxidation structures or detecting them in both free and protein-bound forms. (LLM, conf=0.86)

  cites [158] Ashraf, 2015, Recent advances in detection of AGEs: immunochemical, bioanalytical and biochemical approaches, IUBMB Life sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [163] Thornalley, 2014, Detection of oxidized and glycated proteins in clinical samples using mass spectrometry--a user's perspective, Biochim. Biophys. Acta source
• Partly supported

  Section 3, “Measurement of AGEs,” calls high- and ultra-high-performance liquid chromatography, usually combined with mass spectrometry, the technique of choice for measuring both free and protein-bound AGEs. Table 1 also lists accurate measurement of specific AGEs as an advantage. The paper does not say these methods identify glycoxidation structures, so that part of the claim is not established. (LLM, conf=0.82)

  cites [164] de Vos, 2016, Advanced glycation end products: an emerging biomarker for adverse outcome in patients with peripheral artery disease, Atherosclerosis sourceExperimental — accuracy not yet measured

In the paper

“However, 4-HNE is activating or inhibiting certain age-related signaling pathways, including NF-ĸB, Nrf2 or mTOR pathways, and might be therefore contributing to the aging process [179,180].”

What the sources say

• Supported

  The Summary and future prospective section discusses HNE’s potential contribution to NF-κB, Nrf2, and mTOR signaling pathways implicated in aging. The paper leaves HNE’s causal role in aging uncertain, which is consistent with the claim’s ‘might’ qualifier. (LLM, conf=0.92)

  cites [179] Zhang, 2017, 4-hydroxynonenal-mediated signaling and aging, Free Radic. Biol. Med. source
• Supported

  The Abstract says HNE has been implicated in tissue damage and injury associated with aging, supporting the hedged claim that it might contribute to aging. The Biological Functions of HNE section also describes its effects on NF-κB and Nrf2 signaling. (LLM, conf=0.88)

  cites [180] Shoeb, 2014, 4-Hydroxynonenal in the pathogenesis and progression of human diseases, Curr. Med. Chem. source

In the paper

“| >Aging (and Diabetes) | Skin, urine, serum, bone | Patients with spine disease | Skin AF,ELISA,HPLC | Age-related increase in serum, urine, bone and skin pentosidine levels | [170] |”

What the sources say

• Supported

  The Discussion states that serum and urine pentosidine increase with advancing age, and reports age-related increases in bone and skin collagen pentosidine. The Abstract Results also report a significant age-related increase in tissue pentosidine. No page numbers are available in our copy. (LLM, conf=0.91)

  cites [170] Kida, 2019, Non-invasive skin autofluorescence, blood and urine assays of the advanced glycation end product (AGE) pentosidine as an indirect indicator of AGE content in human bone, BMC Muscoskel. Disord. source

In the paper

“Kida and colleagues performed their analysis in different specimens of spinal surgery patients and found strong correlations between serum, urine, bone, and skin pentosidine levels with age [170].”

What the sources say

• Partly supported

  The Methods describe 100 spinal surgery patients, and Table 2 in the Results reports significant positive correlations with age for serum, urine, bone, and skin pentosidine in the full cohort. However, the correlations range from r = 0.359 to 0.525, so describing all four as strong overstates the results; some age-group correlations were not significant. No page number is available in our copy. (LLM, conf=0.90)

  cites [170] Kida, 2019, Non-invasive skin autofluorescence, blood and urine assays of the advanced glycation end product (AGE) pentosidine as an indirect indicator of AGE content in human bone, BMC Muscoskel. Disord. sourceExperimental — accuracy not yet measured

In the paper

“| Prediabetes | Plasma | Women with normal fasting glucose vs. women with impaired fasting glucose (n = 30 per group) | LC-MS/MS | No difference between groups in free CML levels | [169] |”

What the sources say

• Partly supported

  The Results section (‘AGE levels in individuals with NFG and IFG’; page not provided) reports no significant difference in plasma CML between women with normal and impaired fasting glucose, with 30 women per group. However, the Methods (‘Measurement of AGEs’; page not provided) say CML was measured by LC-MS/MS after hydrolysis of plasma proteins; they do not identify it as free plasma CML. (LLM, conf=0.88)

  cites [169] Teichert, 2015, Association between advanced glycation end products and impaired fasting glucose: results from the SALIA study, PLoS One sourceExperimental — accuracy not yet measured

In the paper

“but their use in routine clinical studies is limited, in particular, due to high costs [158,163,164]”

What the sources say

• Partly supported

  The Liquid Chromatography-Mass Spectroscopy section says LC-MS is very expensive and therefore unsuitable for regular clinical use. But the High-Performance Liquid Chromatography section describes routine HbA1c analysis using HPLC, so the cost-based limitation does not apply to chromatography-based methods generally. (LLM, conf=0.86)

  cites [158] Ashraf, 2015, Recent advances in detection of AGEs: immunochemical, bioanalytical and biochemical approaches, IUBMB Life sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [163] Thornalley, 2014, Detection of oxidized and glycated proteins in clinical samples using mass spectrometry--a user's perspective, Biochim. Biophys. Acta source
• Supported

  Table 1 lists (ultra-)high-performance liquid chromatography as expensive because it requires specific equipment and dedicated personnel. The Conclusion says most studies used the AGE Reader instead. Together, these passages support the claim that cost limits routine use of chromatography-based AGE measurements. (LLM, conf=0.86)

  cites [164] de Vos, 2016, Advanced glycation end products: an emerging biomarker for adverse outcome in patients with peripheral artery disease, Atherosclerosis source

In the paper

“The most sensitive approaches for detection of glycoxidation products are methods based on chromatography, including HPLC und UPLC that are mainly combined with MS/MS.”

What the sources say

• Partly supported

  The Liquid Chromatography-Mass Spectroscopy section (page unavailable) calls LC-MS the most accurate technique for detecting AGEs and early glycation products and describes UPLC separation and LC-MS/MS measurement. The High-Performance Liquid Chromatography section (page unavailable) also describes HPLC detection. The paper does not establish that these are the most sensitive approaches, and it notes that MS can miss low-abundance glycation adducts. (LLM, conf=0.86)

  cites [158] Ashraf, 2015, Recent advances in detection of AGEs: immunochemical, bioanalytical and biochemical approaches, IUBMB Life sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [163] Thornalley, 2014, Detection of oxidized and glycated proteins in clinical samples using mass spectrometry--a user's perspective, Biochim. Biophys. Acta source
• Partly supported

  Section 3, “Measurement of AGEs” (page not specified), calls high- and ultra-high-performance liquid chromatography, most often combined with mass spectrometry, the techniques of choice for measuring AGEs. Table 1 describes chromatography as accurate and precise, but the copy does not establish that these are the most sensitive methods or specify tandem mass spectrometry (MS/MS). (LLM, conf=0.84)

  cites [164] de Vos, 2016, Advanced glycation end products: an emerging biomarker for adverse outcome in patients with peripheral artery disease, Atherosclerosis sourceExperimental — accuracy not yet measured

In the paper

“| Alcoholic liver disease (ALD) | Human hepatic tissue | Normal ALD (n = 8) vs. end stage ALD(n = 9) | IHC | Elevated 4-HNE in liver sample of ALD patients | [223] |”

What the sources say

• Supported

  The Results report significantly increased 4-HNE staining in hepatocytes from patients with ALD-dependent cirrhosis compared with normal hepatic tissue. Materials and Methods (Human Tissue; Histological Evaluation) give the group sizes as nine end-stage ALD patients and eight normal controls and specify immunohistochemical staining. The paper calls the comparison group normal controls, not patients with 'normal ALD.' (LLM, conf=0.92)

  cites [223] Shearn, 2015, Increased hepatocellular protein carbonylation in human end-stage alcoholic cirrhosis, Free Radic. Biol. Med. source

In the paper

“However, 4-HNE is activating or inhibiting certain age-related signaling pathways, including NF-ĸB, Nrf2 or mTOR pathways, and might be therefore contributing to the aging process [179,180].”

What the sources say

• Supported

  The Summary and future prospective identifies NF-κB, Nrf2, and mTOR as aging-related pathways to which HNE may contribute. The pathway sections report that HNE can activate or inhibit NF-κB, activate Nrf2, and modulate mTOR signaling. The paper frames its contribution to aging as potential, consistent with the citing sentence’s hedge. (LLM, conf=0.93)

  cites [179] Zhang, 2017, 4-hydroxynonenal-mediated signaling and aging, Free Radic. Biol. Med. source
• Partly supported

  Section 3, “Biological Functions of HNE,” says HNE can up-regulate NF-κB at micromolar concentrations, inhibit it at higher concentrations, and activate Nrf2 nuclear translocation at nontoxic levels. Our copy does not establish that HNE activates or inhibits mTOR; searches for “mTOR” and “rapamycin” found no relevant passage. The Abstract links HNE to injury associated with aging, but the specific mTOR pathway attribution is unsupported. (LLM, conf=0.88)

  cites [180] Shoeb, 2014, 4-Hydroxynonenal in the pathogenesis and progression of human diseases, Curr. Med. Chem. sourceExperimental — accuracy not yet measured

In the paper

“| PD and AD | Plasma | Control subjects (n = 34) vs. AD (n = 40) and PD patients (n = 70) | UPLC-MS/MS | Higher protein-bound CML levels in AD and PD patients compared to controls | [151] |”

What the sources say

• Supported

  The Materials and methods section reports 40 AD patients, 70 PD patients, and 34 healthy controls, and states that protein-bound CML in plasma was analyzed by UPLC-MS/MS. The Results and discussion section reports significantly higher plasma CML in both patient groups than in controls, for males and females alike. The supplied passages have section labels but no page numbers. (LLM, conf=0.94)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“studies from 2019 suggest an age-related increase in skin AF, pentosidine levels and total amount of AGEs [141,170,171]”

What the sources say

• Partly supported

  Results §3.3 reports higher AGE levels in saliva and plasma of older participants, supporting an age-related increase in the AGE measure studied. Methods §2.8 identifies that measure as AGE-specific fluorescence in samples; the paper does not report skin autofluorescence, pentosidine levels, or a measured total amount of AGEs. No page numbers are available in our copy. (LLM, conf=0.88)

  cites [141] Maciejczyk, 2019, Salivary antioxidant barrier, redox status, and oxidative damage to proteins and lipids in healthy children, adults, and the elderly, Oxid Med Cell Longev sourceExperimental — accuracy not yet measured
• Supported

  The Results (page unavailable) report significant positive correlations of age with pentosidine content and skin AGEs. The Methods (page unavailable) specify that skin AGE accumulation was assessed using skin autofluorescence (AF), supporting the claim’s reference to skin AF. The finding concerns skin AGEs, not a direct measurement of total AGEs throughout the body. (LLM, conf=0.88)

  cites [170] Kida, 2019, Non-invasive skin autofluorescence, blood and urine assays of the advanced glycation end product (AGE) pentosidine as an indirect indicator of AGE content in human bone, BMC Muscoskel. Disord. source
• ?Not checked — no full text of the sourcecites [171] Paolillo, 2019, Advanced glycation endproducts as biomarkers for risk of diabetes and cardiovascular diseases by skin autofluorescence: a noninvasive optical screening, Photobiomodul Photomed Laser Surg source

In the paper

“| RA | Serum | Control subjects (n = 30) vs. RA patients (n = 80) | ELISA | Higher CML and pentosidine levels in RA patients | [237,238] |”

What the sources say

• ?Not checked — no full text of the sourcecites [237] Knani, 2018, Increased serum concentrations of N(varepsilon)-carboxymethyllysine are related to the presence and the severity of rheumatoid arthritis, Ann. Clin. Biochem. source
• Partly supported

  The Discussion reports that CML levels were increased in RA, citing the authors’ earlier work. But this paper’s Methods and Results describe ELISA measurements of MGO and sRAGE—not CML—in its 80 RA patients and 30 controls. It therefore does not establish the claimed CML measurement for that cohort. (LLM, conf=0.88)

  cites [238] Knani, 2018, Methylglyoxal: a relevant marker of disease activity in patients with rheumatoid arthritis, Dis. Markers sourceExperimental — accuracy not yet measured

In the paper

“| T2D | Serum | Control subjects (n = 9) vs. T2D patients (n = 11) | ELISA | Higher levels of 4-HNE in patients with T2D | [240] |”

What the sources say

• Supported

  The Results section (“The elevation of serum 4-HNE level in diabetic patients”) reports significantly higher serum 4-HNE in 11 T2DM patients than in 9 controls. The Materials and methods section (“4-HNE determination in zebrafish larvae and patients”) specifies that patient sera were measured using a 4-Hydroxynonenal ELISA kit. (LLM, conf=0.95)

  cites [240] Lou, 2020, Elevated 4-hydroxynonenal induces hyperglycaemia via Aldh3a1 loss in zebrafish and associates with diabetes progression in humans, Redox Biol source

In the paper

“| >Aging (and Diabetes) | Saliva, plasma | Children (2–14 years), adults (25–45 years), elderly (65–85 years, n = 30 per group) | Spectrophotometry | Higher AGE levels in saliva and plasma of elderly people compared to children and adults | [141] |”

What the sources say

• Supported

  The Discussion (section 4) reports significantly higher AGE levels in the saliva and plasma of elderly participants than in middle-aged participants and children. The Abstract gives the matching age groups—65–85, 25–45, and 2–14 years—and states that the 90 participants were divided equally among them. (LLM, conf=0.94)

  cites [141] Maciejczyk, 2019, Salivary antioxidant barrier, redox status, and oxidative damage to proteins and lipids in healthy children, adults, and the elderly, Oxid Med Cell Longev source

In the paper

“| Psoriasis | Skin, serum | Healthy individuals and psoriasis patients (n = 40 per group) | Skin AF,ELISA | Higher skin AF, total AGEs and pentosidine levels in patients with psoriasis | [239] |”

What the sources say

• Partly supported

  Table II (Discussion) reports higher total serum AGEs in the 40 patients with severe psoriasis than in the 40 healthy individuals. The claim omits the severity qualifier: the paper also studied 40 patients with mild psoriasis, whose mean total AGE level was lower than that of healthy individuals. (LLM, conf=0.88)

  cites [239] Papagrigoraki, 2017, Advanced glycation end products are increased in the skin and blood of patients with severe psoriasis, Acta Derm. Venereol. sourceExperimental — accuracy not yet measured

In the paper

“For instance, while Ravassa et al. found higher 3-NT levels in T2D patients with additional cardiovascular events, no differences were observed by Segre and colleagues although baseline parameters of the study populations and the used methods were similar [189,190].”

What the sources say

• ?Not checked — no full text of the sourcecites [189] Ravassa, 2015, Association of low GLP-1 with oxidative stress is related to cardiac disease and outcome in patients with type 2 diabetes mellitus: a pilot study, Free Radic. Biol. Med. source
• Supported

  The citation to Segre and colleagues supports the sentence’s finding of no difference, not the finding attributed to Ravassa et al. In the Results (Table 2; page unavailable), nitrotyrosine levels did not differ significantly between diabetic patients with coronary artery disease and diabetic controls (p = 0.77). (LLM, conf=0.93)

  cites [190] Segre, 2015, Troponin in diabetic patients with and without chronic coronary artery disease, BMC Cardiovasc. Disord. source

In the paper

“Except of Zablocka-Slowinska and colleagues, showing no differences between healthy subjects and patients with lung cancer [183], all clinical investigations using the TBARS assay consistently found elevated MDA levels in diverse human metabolic disease, as shown in Table 6.”

What the sources say

• Supported

  The Methods describe measuring serum MDA by reaction with thiobarbituric acid, consistent with a TBARS assay. In the Results table, neither the women’s nor the men’s lung-cancer-versus-healthy-control MDA comparison is marked as significant. Citation [183] supports that exception; the claim about all other investigations is not attributed to this paper. (LLM, conf=0.90)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One source

In the paper

“| ALC | Serum | Healthy subjects (n = 130) vs. ALC patients (n = 57) | TBARS assay | Higher MDA levels in patients with ALC | [222] |”

What the sources say

• Supported

  The Results report 130 controls and 57 patients with alcoholic liver cirrhosis, with significantly higher MDA levels in the patient group. The Lipid Peroxidation Assessment methods describe measuring MDA in serum with a thiobarbituric acid assay. (LLM, conf=0.93)

  cites [222] Galicia-Moreno, 2016, Behavior of oxidative stress markers in alcoholic liver cirrhosis patients, Oxid Med Cell Longev source

In the paper

“In combination with lower MDA levels in elderly male and female AD and PD patients compared to healthy subjects as well as unchanged concentrations between lung cancer patients and control individuals at advanced age [151,183], this suggests that MDA is no suitable marker for human aging and age-related diseases.”

What the sources say

• Supported

  The Results and discussion section reports lower MDA in both male and female AD and PD patients than in healthy controls. Material and methods gives mean ages of 69 for PD patients, 73 for AD patients, and 68 for age-matched controls, supporting the description of an elderly cohort. (LLM, conf=0.94)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“For instance, while Ravassa et al. found higher 3-NT levels in T2D patients with additional cardiovascular events, no differences were observed by Segre and colleagues although baseline parameters of the study populations and the used methods were similar [189,190].”

What the sources say

• ?Not checked — no full text of the sourcecites [189] Ravassa, 2015, Association of low GLP-1 with oxidative stress is related to cardiac disease and outcome in patients with type 2 diabetes mellitus: a pilot study, Free Radic. Biol. Med. source
• Supported

  The Results report no significant difference in nitrotyrosine (3-NT) between diabetic patients with coronary artery disease and controls. Table 2 gives median levels of 27.9 versus 28.7 nm/mL (p = 0.77). (LLM, conf=0.94)

  cites [190] Segre, 2015, Troponin in diabetic patients with and without chronic coronary artery disease, BMC Cardiovasc. Disord. source

In the paper

“| Aging | Erythrocytes | Healthy subjects aged ≤65 years (n = 27) and ≥65 years (n = 30) | TBARS assay | No differences between the groups | [243] |”

What the sources say

• Partly supported

  The Results report similar erythrocyte TBARS concentrations in the two normotensive control groups (0.230 versus 0.238 μmol/gHb), and Laboratory methods describe a thiobarbituric-acid assay. The paper reports TBARS, not MDA specifically; it also defines the younger group as <65, rather than ≤65. No page numbers are available in our copy. (LLM, conf=0.84)

  cites [243] Pawluk, 2017, Biomarkers of antioxidant status and lipid peroxidation in elderly patients with hypertension, Redox Rep. sourceExperimental — accuracy not yet measured

In the paper

“In combination with lower MDA levels in elderly male and female AD and PD patients compared to healthy subjects as well as unchanged concentrations between lung cancer patients and control individuals at advanced age [151,183], this suggests that MDA is no suitable marker for human aging and age-related diseases.”

What the sources say

• Partly supported

  The Discussion reports no significant difference in serum MDA between lung cancer patients and controls. However, Table 1 (Materials and methods; page unavailable) shows that male controls had a median age of 49.5 years, versus 62 years for male patients, so the comparison was not entirely between people of advanced age. (LLM, conf=0.84)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One sourceExperimental — accuracy not yet measured

In the paper

“| Aging | Saliva, plasma | Children (2–14 years), adults (25–45 years), elderly (65–85 years, n = 30 per group) | TBARS assay | Higher MDA levels in saliva and plasma of elderly people compared to children and adults | [141] |”

What the sources say

• Supported

  The Abstract states that 90 participants were divided equally into groups aged 2–14, 25–45, and 65–85 (30 per group). Results §3.3 reports significantly higher MDA in both forms of saliva and in plasma of the elderly compared with the other groups; Methods §2.8 identifies TBARS as the MDA assay. Page numbers were not supplied in our copy. (LLM, conf=0.94)

  cites [141] Maciejczyk, 2019, Salivary antioxidant barrier, redox status, and oxidative damage to proteins and lipids in healthy children, adults, and the elderly, Oxid Med Cell Longev source

In the paper

“In combination with lower MDA levels in elderly male and female AD and PD patients compared to healthy subjects as well as unchanged concentrations between lung cancer patients and control individuals at advanced age [151,183], this suggests that MDA is no suitable marker for human aging and age-related diseases.”

What the sources say

• Supported

  The Results and discussion section reports lower MDA in both male and female AD and PD patients than in healthy controls, supporting the comparison for which this paper is cited. The broader statement that MDA is unsuitable for human aging and age-related diseases is the citing authors’ inference, not a conclusion attributed to this source by the citation placement. (LLM, conf=0.90)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source
• Supported

  The Discussion reports no significant difference in serum MDA between lung cancer patients and controls, which is the finding attributed to this source in the citing sentence. The broader conclusion that MDA is unsuitable as a marker of human aging and age-related diseases is the citing authors’ inference, not a finding attributed to this paper. (LLM, conf=0.90)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One source

In the paper

“| Lung cancer | Serum | Control subjects (n = 40) vs. lung cancer patients (n = 92) | ELISA | Higher levels of 4-HNE in male and female lung cancer patients | [183] |”

What the sources say

• Partly supported

  The Results report higher serum 4-HNE in lung cancer patients, and the Discussion says the increase occurred regardless of sex. The Methods specify an ELISA assay. The sample sizes are misstated: the study included 92 lung cancer patients and 82 controls; 40 was the number of male controls, not all controls (Methods and Results, Table 2; page numbers unavailable). (LLM, conf=0.91)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One sourceExperimental — accuracy not yet measured

In the paper

“| T2D with vascular complications | Plasma | Healthy individuals (n = 94) vs. T2D patients with vascular complications(n = 93) | TBARS assay | Higher levels of MDA in T2D patients with vascular complications | [149] |”

What the sources say

• Supported

  Section 2.2.4 says MDA-reactive products were measured in plasma using the thiobarbituric acid method. Table 1 identifies 93 patients with vascular complications and 94 healthy controls; the Results (section 3.2) report higher oxidative-marker levels in the diabetic group, including MDA. (LLM, conf=0.93)

  cites [149] Goycheva, 2019, Predictive value of some pro-oxidants in type 2 diabetes mellitus with vascular complications, Biosci Trends source

In the paper

“| Aging | Serum | Adults (Age 20–50 years) vs. elderly (Age ≤ 60 years, n = 30 per group) | TBARS assay | Higher MDA levels in elderly | [242] |”

What the sources say

• Partly supported

  The Discussion reports higher TBARS levels in elderly than young hypertensive groups, and the serum-TBARS methods section confirms the assay; Table 1 lists 30 people per subgroup and young participants aged 20–50. However, the paper reports TBARS rather than directly measured serum MDA, and Table 1 gives elderly mean ages of 69.5 and 72.1 years, inconsistent with the claim’s “age ≤60 years.” Page numbers are unavailable in our copy. (LLM, conf=0.88)

  cites [242] Yavuzer, 2016, Biomarkers of lipid peroxidation related to hypertension in aging, Hypertens. Res. sourceExperimental — accuracy not yet measured

In the paper

“Already in 2008, Pacher et al. published an outstanding and detailed review about the role of peroxynitrite and 3-NT formation in human health and disease, indicating their relevance as diagnostic biomarker for several pathologic conditions [188].”

What the sources say

• Partly supported

  In Biological Chemistry (page unavailable), the review calls nitrotyrosine an important biological marker and reports its detection in many disease-affected tissues. The neurodegenerative-disorders section (page unavailable) says elevated free nitrotyrosine in cerebrospinal fluid has been proposed as a marker of neurodegeneration. These passages support relevance as disease-associated markers, but do not establish peroxynitrite and 3-NT formation as diagnostic biomarkers for several specific conditions. (LLM, conf=0.82)

  cites [188] Pacher, 2007, Nitric oxide and peroxynitrite in health and disease, Physiol. Rev. sourceExperimental — accuracy not yet measured

In the paper

“| PD | Serum | Control subjects (n = 46) vs. PD patients (n = 40) | TBARS assay | Elevated MDA levels in PD patients | [185] |”

What the sources say

• Supported

  Results > Biomarkers (Table 3) reports TBARS in nmol MDA/mL serum for 40 PD patients and 46 controls. The PD median was higher than the control median (11.72 versus 8.89; P = 0.001), supporting the stated elevation measured by TBARS. (LLM, conf=0.95)

  cites [185] Medeiros, 2016, Iron and oxidative stress in Parkinson's disease: an observational study of injury biomarkers, PLoS One source

In the paper

“Reversed-phase HPLC coupled with fluorescence detection has been further used by Sharma and colleagues, revealing lower levels of MDA in AD and PD patients compared to controls [151].”

What the sources say

• Supported

  The Results and discussion section reports lower plasma MDA in both female and male AD and PD patients than in healthy controls. The Material and methods section states that plasma MDA was measured by reversed-phase HPLC coupled with fluorescence detection. (LLM, conf=0.94)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“3-NT, the stable endproduct of peroxynitrite-mediated oxidation formed via nitration of free or protein-bound tyrosine, has been primarily used for the determination of protein nitration and nitrosative stress in clinical settings [186,187].”

What the sources say

• Partly supported

  The section on in vivo detection reports using antibodies against 3-nitrotyrosine to detect protein nitration in plants. The Introduction also describes nitrotyrosine as a footprint of peroxynitrite. The paper does not establish that 3-NT has been used primarily in clinical settings; its examples concern plants. (LLM, conf=0.82)

  cites [186] Corpas, 2013, Protein tyrosine nitration in higher plants grown under natural and stress conditions, Front. Plant Sci. sourceExperimental — accuracy not yet measured
• Partly supported

  The Introduction (page unavailable) describes protein 3-nitrotyrosine as a well-established biomarker of nitroxidative stress and says antibodies against it have been useful for detecting nitrated proteins in a variety of disease conditions. It does not establish that this use is primarily in clinical settings, as opposed to research settings. (LLM, conf=0.85)

  cites [187] Radi, 2013, Protein tyrosine nitration: biochemical mechanisms and structural basis of functional effects, Acc. Chem. Res. sourceExperimental — accuracy not yet measured

In the paper

“| Aging | Plasma | 3 study groups from MARK-AGE project:RASIG (n = 794), GO (n = 493), SGO(n = 272)Participants divided in 4 groups:55-59, 60–64, 65–69 and 70–75 years | RP-HPLC | No correlation in all groups between MDA levels and age | [194] |”

What the sources say

• Supported

  The Discussion states that malondialdehyde was not associated with age in any of the three study groups. The Results give the cited group sizes, and Methods §2.4 specifies RP-HPLC measurement of plasma malondialdehyde; Methods §2.7 describes comparisons across five-year age groups. (LLM, conf=0.94)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev source

In the paper

“Except of Zablocka-Slowinska and colleagues, showing no differences between healthy subjects and patients with lung cancer [183], all clinical investigations using the TBARS assay consistently found elevated MDA levels in diverse human metabolic disease, as shown in Table 6.”

What the sources say

• Supported

  The Results state that serum MDA concentrations were comparable between lung cancer patients and control subjects. The Methods identify the controls as healthy people, so this supports the attributed finding of no difference between the groups. (LLM, conf=0.94)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One source

In the paper

“| PD and AD | Plasma | Control subjects (n = 34) vs. AD (n = 40) and PD patients (n = 70) | RP-HPLC | Lower MDA levels in AD and PD patients compared to control subjects | [151] |”

What the sources say

• Supported

  The Results and discussion section reports lower plasma MDA in both male and female AD and PD patients than in healthy controls. Material and methods gives the stated group sizes (34 controls, 40 AD, 70 PD) and says plasma MDA was measured by RP-HPLC with fluorescence detection. (LLM, conf=0.95)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“| Lung cancer | Serum | Control subjects (n = 40) vs. lung cancer patients (n = 92) | TBARS assay | No differences in MDA levels between the groups | [183] |”

What the sources say

• Partly supported

  The Results state that serum MDA concentrations were comparable between lung cancer patients and controls, and Methods describe a thiobarbituric-acid-based serum assay. But Methods report 92 patients and 82 controls enrolled, not 40 controls; the Results table lists 40 male controls, with MDA measurements available for 39 of them. Thus the cited group sizes do not describe the overall MDA comparison. (LLM, conf=0.90)

  cites [183] Zablocka-Slowinska, 2019, Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism, PLoS One sourceExperimental — accuracy not yet measured

In the paper

“Higher levels of protein-bound 3-NT in T2D patients”

What the sources say

• Supported

  The Subjects section specifies that serum protein-bound nitrotyrosine was quantified by ELISA. The Results section reports significantly higher serum nitrotyrosine levels in both T2DM subgroups than in nondiabetic controls. The study population had poorly controlled T2DM. (LLM, conf=0.94)

  cites [244] Stankova, 2019, Serum levels of carbamylated LDL, nitrotyrosine and soluble lectin-like oxidized low-density lipoprotein receptor-1 in poorly controlled type 2 diabetes mellitus, Folia Med. (Plovdiv) source

In the paper

“elevated 3-NT levels in age-related diseases, such as AD and PD, indicate the impact of 3-NT accumulation in human aging”

What the sources say

• Partly supported

  The Discussion (page unavailable) reports elevated 3-nitrotyrosine in AD lymphocytes and suggests that nitrosative stress might link ageing and AD. The paper does not establish elevated 3-NT in Parkinson’s disease or show that 3-NT accumulation affects human aging generally; its aging link is tentative. (LLM, conf=0.88)

  cites [191] Tramutola, 2018, Protein nitration profile of CD3(+) lymphocytes from Alzheimer disease patients: novel hints on immunosenescence and biomarker detection, Free Radic. Biol. Med. sourceExperimental — accuracy not yet measured
• Partly supported

  The Plasma 3-NT and ox-LDL level section and Table 3 report significantly higher plasma 3-NT in AD patients than in healthy controls. The paper does not report elevated 3-NT in PD or establish that 3-NT accumulation affects human aging; its findings concern AD and AD severity. (LLM, conf=0.88)

  cites [192] Zhao, 2014, Expression and significance of plasma 3-NT and ox-LDL in patients with Alzheimer's disease, Genet. Mol. Res. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [195] Yeo, 2015, Mass spectrometric analysis of protein tyrosine nitration in aging and neurodegenerative diseases, Mass Spectrom. Rev. source

In the paper

“No correlation in GO and SGO groups between 3-NT levels and age”

What the sources say

• ?Could not verify

  The Results report a significant positive correlation between 3-nitrotyrosine and age across participants, but do not give separate age correlations for GO and SGO. The Discussion’s statement that correlation was observed only in RASIG concerns protein carbonyls, not 3-nitrotyrosine. The subgroup-specific claim therefore cannot be verified from our copy. (LLM, conf=0.72)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev sourceExperimental — accuracy not yet measured

In the paper

“Higher 3-NT levels in male AD patients compared to PD patients and controls”

What the sources say

• Supported

  The Results and discussion section reports higher 3-nitrotyrosine (3-NT) values in male AD patients than in male controls and PD patients, with p = 0.0134 and p = 0.0256, respectively. Material and methods states that plasma 3-NT was measured by an in-house ELISA. (LLM, conf=0.94)

  cites [151] Sharma, 2020, Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease, Redox Biol source

In the paper

“Positive correlation between 3-NT levels and age in RASIG group”

What the sources say

• Partly supported

  The Results report a positive correlation between 3-nitrotyrosine and age, and Methods §2.5 identifies plasma ELISA as the measurement method. The Results do not specify that this age correlation was found within the RASIG group; the statement about similar RASIG correlations refers to correlations among biomarkers, not with age. Page numbers are unavailable in our copy. (LLM, conf=0.84)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev sourceExperimental — accuracy not yet measured

In the paper

“Higher plasma 3-NT concentrations in AD patients”

What the sources say

• Supported

  The 'Plasma 3-NT and ox-LDL level' results and Table 3 report higher 3-NT in AD patients than in healthy controls (119.46 ± 21.82 versus 55.09 ± 9.63 nM). The 'Measurement of plasma 3-NT and ox-LDL' section specifies that concentrations were measured by ELISA. Page numbers are not provided in the supplied copy. (LLM, conf=0.95)

  cites [192] Zhao, 2014, Expression and significance of plasma 3-NT and ox-LDL in patients with Alzheimer's disease, Genet. Mol. Res. source

In the paper

“Two of three cohorts showed no differences between the age groups”

What the sources say

• Supported

  The Results report that, of the three older MARK-AGE study groups, only GO had higher 3-nitrotyrosine than the middle-aged reference group. This supports no significant difference for RASIG and SGO in that comparison. The finding concerns comparisons with the middle-aged reference group, not every age interval within each cohort. (LLM, conf=0.88)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev source

In the paper

“Two of three cohorts showed no differences between the age groups,”

What the sources say

• Partly supported

  The Discussion (page unavailable) says there might have been no dramatic difference in 3-nitrotyrosine across age groups, and the Results (page unavailable) report that only GO had higher 3-nitrotyrosine than the middle-aged reference group. Neither passage establishes the claimed finding specifically for age-group comparisons within two of the three MARK-AGE cohorts. (LLM, conf=0.78)

  cites [194] Weber, 2017, Associations between specific redox biomarkers and age in a large European cohort: the MARK-AGE project, Oxid Med Cell Longev sourceExperimental — accuracy not yet measured

In the paper

“Higher protein-bound 3-NT levels in MetS subjects”

What the sources say

• Supported

  The Results section, “Phenotypic Differences between subjects with MetS and Healthy controls,” reports markedly higher baseline protein-bound 3-nitrotyrosine in subjects with MetS than in healthy controls. The Methods section, “Detailed phenotype characterization of subjects with MetS,” specifies that it was measured in plasma by LC-ESI-MS/MS. (LLM, conf=0.95)

  cites [247] Pennathur, 2017, Structured lifestyle intervention in patients with the metabolic syndrome mitigates oxidative stress but fails to improve measures of cardiovascular autonomic neuropathy, J. Diabet. Complicat. source

In the paper

“Increased total 3-NT levels in PBMC of AD patients”

What the sources say

• Partly supported

  The Redox proteomics data section reports about 25% higher total protein nitration in AD T-cells than in non-demented T-cells, and the Figure Legends identify slot blot as the method. The Subjects section says PBMCs were collected and then fractionated; the reported increase is for T-cells, not PBMCs as a whole. Page numbers are unavailable in our copy. (LLM, conf=0.90)

  cites [191] Tramutola, 2018, Protein nitration profile of CD3(+) lymphocytes from Alzheimer disease patients: novel hints on immunosenescence and biomarker detection, Free Radic. Biol. Med. sourceExperimental — accuracy not yet measured

In the paper

“No differences between the groups”

What the sources say

• Supported

  The Results (Table 2; page unavailable) report no significant difference in nitrotyrosine between the CAD and control groups (27.9 vs 28.7; p = 0.77). The Methods identify both groups as having type 2 diabetes, describe collection of plasma, and specify a solid-phase ELISA for nitrotyrosine. (LLM, conf=0.94)

  cites [190] Segre, 2015, Troponin in diabetic patients with and without chronic coronary artery disease, BMC Cardiovasc. Disord. source

In the paper

“The use of cysteine modifications as biomarkers of aging has not been investigated in recent years, but a review by Oliveira and Laurindo in 2018 highlights the association of changes in the thiolred/thiolox redox couple in aging and age-related disease, including cancer, CVD, and neurodegenerative disease [121].”

In the paper

“Elevated levels of 3-NT have been also found in a variety of human diseases in recent research, including T2D, cancer, and neurodegenerative diseases, but the available data are partially conflicting (Table 7).”

In the paper

“Elevated levels of 3-NT have been also found in a variety of human diseases in recent research, including T2D, cancer, and neurodegenerative diseases, but the available data are partially conflicting (Table 7).”

In the paper

“Independent of the applied method, three of five studies found no correlation between MDA and advanced age although they partially included large cohorts, e.g., from the European MARK-AGE study (Table 6).”

In the paper

“Consequently, a wide variety of distinct posttranslational protein modifications is formed by protein oxidation, glycoxidation, and lipoxidation.”

In the paper

“Certain protein oxidation products are chemically stable and formed in large quantity, which makes them promising candidates to become biomarkers of oxidative damage.”

In the paper

“Studies reveal an age-related increase in the level of oxidatively modified proteins [10,11]”

What the sources say

• ?Not checked — no full text of the sourcecites [10] Gil, 2006, Age-associated analysis of oxidative stress parameters in human plasma and erythrocytes, Free Radic. Res. source
• ?Not checked — no full text of the sourcecites [11] Mutlu-Turkoglu, 2003, Age-related increases in plasma malondialdehyde and protein carbonyl levels and lymphocyte DNA damage in elderly subjects, Clin. Biochem. source

In the paper

“and many diseases have an oxidative etiology [9,[12], [13], [14]].”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [9,[12], [13], [14]]

In the paper

“Cysteine residues can be protected against “overoxidation” by S-glutathionylation, which is the reversible addition of glutathione via disulfide linkage.”

What the sources say

• ?Not checked — no full text of the sourcecites [18] Curis, 2005, Almost all about citrulline in mammals, Amino Acids source

In the paper

“Proteins are major targets for oxidation reactions, because of their rapid reaction rates with oxidants and their high abundance in cells, extracellular tissues, and body fluids.”

In the paper

“However, even if these preventive and repair systems are interconnected and work efficiently, they cannot fully prevent oxidative damage to cellular components.”

In the paper

“The modification of a peptide may alter its ionization properties greatly, especially when ionizable groups are introduced or removed. This needs to be considered when comparing ion intensities between a certain peptide and its modified form.”

In the paper

“However, the comparison of different sample groups (such as healthy and diseased) can provide important information without examining the exact modification site.”

In the paper

“Tryptophan is oxidized by hydroxyl radicals to hydroxytryptophan, which is cleaved by oxygen to yield N-formyl kynurenine (Fig. 2C) [26].”

What the sources say

• ?Not checked — no full text of the sourcecites [26] Josimović, 1993, Radiation induced decomposition of tryptophan in the presence of oxygen, Radiat. Phys. Chem. source

In the paper

“For the detection of oxidative protein modifications, untargeted methods are only of limited help.”

In the paper

“One of the most abundant dialdehyde RCS resulting from lipid peroxidation is malondialdehyde (MDA).”

In the paper

“In general, untargeted approaches are mostly used to scan for certain proteins in biological samples and check for proteome changes in samples of healthy versus diseased individuals and not to analyze specific protein modifications.”

In the paper

“Since fluorescence is not limited to oxidation products, the method without prior chromatographic separation is only of minor importance for biomarker analysis of protein oxidation.”

In the paper

“Hence, CML is not only considered as an AGE, but also as an advanced lipoxidation endproduct (ALE) [48].”

What the sources say

• ?Not checked — no full text of the sourcecites [48] Fu, 1996, The advanced glycation end product, N-(carboxymethyl) lysine, is a product of both lipid peroxidation and glycoxidation reactions, J. Biol. Chem. source

In the paper

“Reaction of protein bound tyrosyl radicals with hydroxyl radicals leads to 3-hydroxytyrosine, which is an analogue of the neurotransmitter 3,4-dihydroxyphenylalanine (DOPA) [24].”

What the sources say

• ?Not checked — no full text of the sourcecites [24] Hensley, 1997, Quantitation of protein-bound 3-nitrotyrosine and 3, 4-dihydroxyphenylalanine by high-performance liquid chromatography with electrochemical array detection, Anal. Biochem. source

In the paper

“Oxidation of histidine by metal catalyzed reaction with hydroxyl radicals leads to 2-oxohistidine (Fig. 2D) [27,28].”

What the sources say

• ?Not checked — no full text of the sourcecites [27] Schöneich, 2000, Mechanisms of metal-catalyzed oxidation of histidine to 2-oxo-histidine in peptides and proteins, J. Pharmaceut. Biomed. Anal. source
• ?Not checked — no full text of the sourcecites [28] Uchida, 1993, 2‐Oxo‐histidine as a novel biological marker for oxidatively modified proteins, FEBS Lett. source

In the paper

“One plausible approach is the analysis of protein structure that can provide information concerning the degree of protein modification without analyzing specific oxidation products.”

In the paper

“The basic amino acids lysine and arginine are readily modified by glycation. The reaction results in the formation of intermediate Amadori products and subsequently advanced glycation endproducts (AGEs).”

In the paper

“Additionally, •NO or higher nitrogen oxides including dinitrogen trioxide (N2O3) can directly and reversibly modify cysteine residues by S-nitrosation [73].”

What the sources say

• ?Not checked — no full text of the sourcecites [73] Hogg, 2002, The biochemistry and physiology of S-nitrosothiols, Annu. Rev. Pharmacol. Toxicol. source