Oxalic acid and diacylglycerol 36:3 are cross-species markers of sleep debt

Probably not a substantial claim: may not pass S3 (load-bearing).

Of the 38 rat features unique to acute sleep restriction, 28 were identified.

“Of the 38 that were unique to SR (Fig. 1C, Left), 28 were identified.”

May combine two claims.

After sleep restriction, phospholipids were elevated in both species, and metabolites linked to an oxidizing environment were also observed.

“Elevated phospholipids were also noted after sleep restriction in both species, as well as metabolites associated with an oxidizing environment.”

May combine two claims.

In sleep-restricted humans, tryptophan, phenylalanine, pipecolic acid, and 1-Methyl-4-pyridone-5-carboxamide were elevated, while oxalic acid was reduced.

“the amino acids tryptophan (Trp), phenylalanine (Phe), as well as pipecolic acid and 1-Methyl-4-pyridone-5-carboxamide (4-Pyr) were elevated, but oxalic acid was reduced.”

May combine two claims.

In humans, most altered metabolites recovered to pre-sleep-restriction levels, with 30 identified and 46 unknown recovered, while 7 identified and 11 unknown did not recover.

“the majority of metabolites (30 identified and 46 unknown) recovered to pre-SR levels, whereas 7 identified and 11 unknown did not recover over the period measured.”

May combine two claims.

In rats, three sphingomyelin species recovered and three choline plasmalogen species did not recover using P < 0.05 and FDR < 0.2 thresholds compared with baseline.

“Intriguingly, three SM species recovered, and three PlsCho species did not recover based on our statistical thresholds (P < 0.05, FDR < 0.2 compared with baseline).”

May combine two claims.

In both rats and humans, oxalic acid and diacylglycerol 36:3 were strongly and quantitatively decreased after sleep restriction and returned to near baseline after recovery sleep, with P < 0.05 and false-discovery rate < 0.2.

“two metabolites, oxalic acid and diacylglycerol 36:3, were robustly and quantitatively reduced in both species following sleep restriction, and recovered to near baseline levels after sleep restriction (P < 0.05, false-discovery rate < 0.2).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Across two independent rat serum studies, 3,380 unique metabolite species were detected.

“A total of 3,380 unique metabolite species were detected across the two independent studies of rat serum.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Of the 3,380 rat serum metabolite species, 407 were identified.

“Of these species, 407 were identified.”

May combine two claims.

After 5 days of chronic sleep restriction in rats, 44 features were significantly altered across studies A and B; 23 were unique to sleep restriction, 18 were named, and 15 of the named features were lipids.

“Following 5 d of chronic SR, 44 features were significantly altered across studies A and B: 23 were unique to the SR condition (Fig. 1C, Right), and 18 were named, of which 15 were lipids.”

May combine two claims.

In rats, polar metabolites were mainly altered after acute sleep restriction, and only glycine was specifically altered after chronic sleep restriction.

“In contrast, polar metabolites were primarily altered following acute SR, with only glycine specifically altered following chronic SR.”

May combine two claims.

In humans, comparison of baseline and 5-day sleep-restriction samples revealed 92 altered features, of which 37 were identified.

“Comparison of the human BL and SR samples revealed 92 features that were altered, of which 37 were identified (Fig. 3B; unidentified metabolites not shown for clarity).”

May combine two claims.

In chronically sleep-restricted rats, glycine was reduced, while malate and sucrose were elevated.

“Glycine was reduced and the Krebs cycle intermediate malate and sucrose were elevated.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Arachidonic acid was not significantly changed by the study's criteria.

“Our results further indicate a significant clustering relationship between oxalate and arachidonic acid (Fig. S4), which is the substrate for COX-2, although we note that arachidonic acid was not significantly changed by our criteria.”

May combine two claims.

In rats, 38 features changed across independent experiments, and most were classified as lipids, with 18 of 28 identified features being lipids.

“A total of 38 features were changed across independent experiments, with the majority classified as lipids (18 from 28 identified).”

May combine two claims.

In a parallel human study, 92 metabolites were identified as potentially significant, and most were classified as lipids, with 32 of 37 identified metabolites being lipids.

“In a parallel human study, 92 metabolites were identified as potentially significant, with the majority also classified as lipids (32 of 37 identified).”

Classified as probably not a substantial claim. May combine two claims.

Some metabolites overlapped between sleep restriction and forced activity groups, but the analysis focused on those specific to sleep restriction.

“Although a number of metabolites were common to SR and FA groups, we focused on those specific to SR.”

May combine two claims.

In this study, sleep restriction increased all of these common metabolites except acylcarnitines C10:0 and C12:0, which were reduced.

“In our study, SR led to increases in all of these metabolites except acylcarnitines C10:0 and C12:0, which were reduced.”

May combine two claims.

The two TG species elevated in humans were relatively short, with at most 48 carbons and an average chain length of at most 16 carbons.

“Of note, the two TG species elevated in humans were relatively short (≤48 carbons, average chain length ≤16 carbons).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Acute total sleep deprivation in the laboratory increases stress hormones such as catecholamines and cortisol.

“In humans, acute total sleep deprivation in the laboratory increases levels of stress hormones, such as catecholamines and cortisol (e.g., refs.20 and 21).”

• cites [20] sourceNot checked yet

  Not checked in the free run.

• cites [21] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The difference between the rat studies may arise from variation in environmental and sampling procedures or in the analytical analysis.

“This difference may result from variation in the environmental and sampling procedures or in the analytical analysis.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Lipidomics analysis has identified a set of lipids that oscillate across biological subtypes defined by lipid composition.

“Lipidomics analysis has elucidated a set of lipids that oscillate across biological subtypes defined by stratification by lipid composition (11).”

• cites [11] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Many laboratory studies report that sleep restriction does not significantly affect cortisol levels.

“many laboratory studies have reported that SR, the type of sleep loss we used in our study, does not produce significant effects on cortisol levels (e.g., ref. 22).”

• cites [22] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Total sleep deprivation causes a measurable perturbation of the human blood metabolome.

“Recent work indicates that total sleep deprivation induces a measurable perturbation to the blood metabolome (19)”

• cites [19] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Gene-expression profiling has established a complex but defined interaction between the circadian system and sleep homeostasis in humans.

“Gene-expression profiling has established that there is a complex, but defined, interaction between the circadian system and sleep homeostasis (8) in humans.”

• cites [8] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

The findings suggest a possible connection between pathologies associated with reduced sleep duration and metabolic dysfunction, and they suggest possible biomarkers for sleep loss.

“The findings provide a potential link between known pathologies of reduced sleep duration and metabolic dysfunction, and potential biomarkers for sleep loss.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Gut metabolism likely contributes to the observed metabolic profile.

“Finally, gut metabolism also likely plays a role in the observed metabolic profile (23).”

• cites [23] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Tryptophan is a major precursor for serotonin and melatonin and is elevated under acute total sleep deprivation.

“Trp is a major precursor for serotonin and melatonin and is elevated under acute total sleep deprivation (19).”

• cites [19] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

DG 36:3 is regulated in a circadian fashion in humans and may indicate both circadian time and sleep debt.

“This metabolite is also regulated in a circadian fashion in humans (11), and as such may be an indicator of both circadian time and sleep debt.”

• cites [11] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Davies et al. identified metabolites that increased but found none that decreased under total sleep deprivation.

“The study of Davies et al. (19) identified metabolites that increased but found none that decreased under total sleep deprivation.”

• cites [19] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Sleep restores antioxidant balance in peripheral tissues.

“This finding is consistent with several studies suggesting that the function of sleep is restorative and involves metabolite clearance from the brain (9), and that sleep restores antioxidant balance in peripheral tissues (46).”

• cites [46] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

This idea is consistent with other evidence for oxidative stress and peroxisomal activation.

“This idea is consistent with the other evidence for oxidative stress and peroxisomal activation described below.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Dallman et al. found 33 of 40 lipid species regulated in a circadian manner, with carnitine C12:0 overlapping with this study.

“Dallman et al. (12) found that 33 of 40 lipid species were regulated in a circadian manner, of which carnitine C12:0 overlaps with our study.”

• cites [12] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Based on these data and controlled fasting and diet, the observed reduction in blood oxalate is due to either reduced synthesis or increased gut microbiota processing and is not of dietary origin.

“Based on these data, as well as the highly regulated nature of presample fasting and diet for our rat and human studies, we postulate that the observed reduction in blood oxalate is a result of either reduced synthesis or increased gut microbiota processing and is not of dietary origin.”

May combine two claims.

Although dietary oxalate with high bioavailability increases plasma and urine levels, excreted oxalate is minimally dependent on diet in an epidemiological cohort.

“Although dietary oxalate with high bioavailability increases plasma and urine levels (29), excreted oxalate is minimally dependent on diet in an epidemiological cohort (30).”

• cites [29] sourceNot checked yet

  Not checked in the free run.

• cites [30] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Recent evidence suggests that blood oxalate levels are influenced by gut microbiota, with over a dozen oxalate-degrading gut bacterial species identified.

“Recent evidence suggests that blood levels are also influenced by gut microbiota, with over a dozen oxalate-degrading gut bacterial species identified (28).”

• cites [28] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Sleep is restorative and involves clearance of metabolites from the brain.

“This finding is consistent with several studies suggesting that the function of sleep is restorative and involves metabolite clearance from the brain (9), and that sleep restores antioxidant balance in peripheral tissues (46).”

• cites [9] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Effects on peripheral clocks cannot be excluded, and some metabolic phenotypes could arise from loss of synchrony between central and peripheral clocks.

“We cannot exclude effects on peripheral clocks, and note that some of the metabolic phenotypes could arise from a loss of synchrony between central and peripheral clocks.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Investigation of the human plasma metabolome suggests that amino acid metabolism is particularly perturbed as a function of sleep restriction.

“Investigation of the human plasma metabolome suggests that amino acid metabolism is particularly perturbed as a function of SR (26).”

• cites [26] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

A 10- to 12-hour fast before metabolomic sampling was used to separate metabolic effects from sleep effects so that changes could be attributed to sleep restriction.

“Thus, we also attempted to separate the metabolic effects from the sleep effects by enforcing a 10-to 12-h fasting period before metabolomic sampling, such that observed changes could be attributed to sleep/sleep restriction effects.”

• AssumptionRests on an assumption: A 10- to 12-hour fast before sampling allows observed metabolic changes to be attributed to sleep or sleep restriction rather than other factors.

May combine two claims.

Oxalic acid and DG 36:3 come from highly disparate metabolic pathways yet behave in the same manner, and thus may provide a robust measure of sleep debt.

“These metabolites are from highly disparate metabolic pathways yet behave in the same manner, and thus may provide a robust measure of sleep debt (Fig. 4C and Fig. S3).”

Classified as probably not a substantial claim. May combine two claims.

The primary sources of blood oxalate are diet-derived plant sources, vitamin C degradation, and endogenous synthesis in erythrocytes and liver.

“The primary sources of blood oxalate are diet-derived plant sources, vitamin C (ascorbate) degradation, and endogenous synthesis pathways in erythrocytes and liver (27).”

• cites [27] sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Although these metabolites do not share obvious metabolic pathways, they may be linked by cellular function such as peroxisomal processing.

“Although these metabolites do not share obvious metabolic pathways, they may be linked by cellular function, such as peroxisomal processing, as described below.”

Probably not a substantial claim: may not pass S3 (load-bearing).

A reduction in total blood TGs in humans has been observed before with a similar protocol.

“Reduction in total blood TGs of humans has been observed previously using a similar protocol (47).”

• cites [47] sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim.

Physical activity was limited in the human subjects.

“For the human study, physical activity levels in our subjects were limited.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The acylcarnitine discrepancy may reflect the difference in protocol, 1 day versus 5 days and total sleep deprivation versus chronic sleep restriction, leading to different relative energy requirements.

“the discrepancy may be a function of the difference in protocol (1 d vs. 5 d and total sleep deprivation vs. chronic SR), leading to a difference in relative energy requirements.”

Classified as probably not a substantial claim.

Mass spectral features were considered significant if P < 0.1 and FDR < 0.2 in each study, so that the pooled result would yield P < 0.01.

“Mass spectral features were judged significant if P < 0.1 and FDR < 0.2 in each study, such that the pooled result would yield P < 0.01 (Table S2).”

Classified as probably not a substantial claim. May combine two claims.

Statistical comparisons used t tests with multiple test correction, with 1,000 permutations, unpaired for animal data and paired for human data.

“In each case, comparisons were done by t test using multiple test correction (1,000 permutations, unpaired for animal and paired for human data).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The direct relationship between oxalate, hypoxanthine, and medium-chain acylcarnitines in cluster analysis may also be explained by peroxisomal processes.

“Finally, the direct relationship between oxalate, hypoxanthine, and medium-chain acylcarnitines (C6, C10, C12, C12:1) in cluster analysis (Fig. S4) may also be explained by peroxisomal processes.”

• AssumptionRests on an assumption: PPARs play a critical role in lipid and glucose metabolism.

May combine two claims.

In a mouse model, bezafibrate, a PPAR-α agonist, affects baseline sleep and recovery sleep after sleep restriction.

“Bezafibrate, an antihyperlipidemic PPAR-α agonist, has been shown in a mouse model to affect both BL sleep, with increased EEG δ-power, and recovery sleep following sleep restriction, with a reduced rebound in EEG δ-power (49).”

• cites [49] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Reduced oxalate in humans and rats and reduced glycine in rats at SR5 might be explained by depletion of glyoxylate, a common peroxisomal precursor of both substances.

“Reduction in both oxalate (humans and rats) and glycine (rats, SR5) might be explained by depletion of glyoxylate, which is a common precursor to both substances in peroxisomes.”

• AssumptionRests on an assumption: Glyoxylate is a common precursor to both oxalate and glycine in peroxisomes.

Classified as probably not a substantial claim.

The second rat study included a forced activity control group that walked the same distance as sleep-restricted animals in the dark phase but had enough time to sleep, in order to separate forced activity from sleep restriction.

“To differentiate the effects of FA from SR, the second study included a FA control group in which animals walked the same distance as SR animals in the dark phase, but had sufficient time to sleep.”

May combine two claims.

The comprehensive metabolite profiling results depict an oxidative environment affecting lipid metabolism and processing, with some differences between species.

“Our comprehensive metabolite profiling results present a picture of an oxidative environment impacting lipid metabolism and processing, albeit with some interspecies variations.”

Classified as probably not a substantial claim.

Mounting evidence indicates that sleep loss induces an oxidative metabolic state.

“Mounting evidence points to sleep loss inducing an oxidative metabolic state (8,48).”

• cites [8] sourceNot checked yet

  Not checked in the free run.

• cites [48] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

The combination of an oxidative environment, long-chain fatty acid β-oxidation implied by TAG shortening, and the acylcarnitine-oxalate association suggests a distinct role for peroxisomes, possibly through PPARs.

“The combination of an oxidative environment, β-oxidation of long-chain fatty acids as implied by TAG shortening, as well as the observed association of acylcarnitines with oxalate (Fig. S4), suggests a distinct role for peroxisomes, possibly via peroxisome proliferator-activated receptors (PPARs).”

• AssumptionRests on an assumption: PPARs play a critical role in lipid and glucose metabolism.

Classified as probably not a substantial claim. May combine two claims.

The peroxisome is the central site for processing fatty acid alcohols, producing diacylphospholipids or ether-linked phospholipids.

“The peroxisome is the central site of fatty acid alcohol processing (52), which generates either diacylphospholipids or ether-linked phospholipids.”

• cites [52] sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Induction of peroxisome biogenesis is consistent with decreased fatty alcohols in humans and increased phospholipid species in humans and rats, especially plasmalogens.

“Induction of peroxisome biogenesis is consistent with the observed decrease in both fatty alcohols (humans) and an increase in phospholipid species (humans and rats), particularly plasmalogens.”

• AssumptionRests on an assumption: PPARs play a critical role in lipid and glucose metabolism.

Classified as probably not a substantial claim.

Sampling occurred during the 2 hours after waketime to control for morning-evening effects.

“To control for morning-evening effects, sampling occurred during the 2 h following waketime (between 0800 hours and 1000 hours on BL1 and SR5 and between 1000 hours and 1200 hours on R1).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Direct conversion of oxalate to hypoxanthine has been observed in extreme oxidative environments.

“Direct conversion of oxalate to hypoxanthine has been observed in extreme oxidative environments (53), although it is not clear if this occurs in vivo.”

• cites [53]Not checked yet

  Not checked in the free run.