HIV-TAT dysregulates microglial lipid metabolism through SREBP2/miR-124 axis: Implication of lipid droplet accumulation microglia in NeuroHIV

May combine two claims.

HIV infection or HIV proteins dysregulate lipid and cholesterol metabolism in the central nervous system and promote the pathogenesis of HIV-associated neurological disorders (HAND)/NeuroHIV.

“Additionally, HIV infection or HIV proteins have been shown to dysregulate lipid and cholesterol metabolism in the central nervous system (CNS) and promote the pathogenesis of HIV-associated neurological disorders (HAND)/NeuroHIV [10, 11].”

• cites [10] Mohseni Ahooyi T,, Dysregulation of Neuronal Cholesterol Homeostasis upon Exposure to HIV-1 Tat and Cocaine Revealed by RNA-Sequencing. Sci Rep, 2018. 8(1): p. 16300. 30390000 PMC6215004 sourceSupported
• cites [11] Cotto B,, Cocaine and HIV-1 Tat disrupt cholesterol homeostasis in astrocytes: Implications for HIV-associated neurocognitive disorders in cocaine user patients. Glia, 2018. 66(4): p. 889– 902. 29330881 PMC5769965 sourcePartly supported

  The Results (page unavailable) show that HIV-1 Tat reduced cholesterol levels and cholesterol release in cultured astrocytes, supporting the metabolism finding for an HIV protein. But the Abstract and Introduction describe a possible contribution to HAND, not a demonstrated promotion of its pathogenesis; the findings also do not establish the claim for HIV infection generally. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

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

Metabolites such as lipid, free fatty acid, and glucose are capable of stimulating microglia and metabolic reprogramming has inherent linkage with microglial activation.

“Recently, acuumulating evidence show that metabolites such as lipid, free fatty acid, and glucose are capable of stimulating microglia and metabolic reprogramming has inherent linkage with microglial activation (immunobolism) [17–20].”

• cites [17] Wang Q,, The role of microglia immunometabolism in neurodegeneration: Focus on molecular determinants and metabolic intermediates of metabolic reprogramming. Biomed Pharmacother, 2022. 153: p. 113412. 36076537 sourceSupported
• cites [18] Shippy DC and Ulland TK, Lipid metabolism transcriptomics of murine microglia in Alzheimer’s disease and neuroinflammation. Sci Rep, 2023. 13(1): p. 14800. 37684405 PMC10491618 sourcePartly supported

  The Introduction links increased microglial lipid metabolism to the energy needed for activation, and the Discussion describes lipids as a fuel source for activated microglia. Neither passage establishes that lipids, free fatty acids, or glucose stimulate microglia; the paper supports a link between lipid metabolism and activation, but not the full list of proposed stimuli. Page numbers were not provided in our copy. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [19] Urso CJ and Zhou H, Palmitic Acid Lipotoxicity in Microglia Cells Is Ameliorated by Unsaturated Fatty Acids. Int J Mol Sci, 2021. 22(16). PMC8396597 34445796 sourcePartly supported

  The Introduction (page not provided) says fatty acids may affect microglial function and that studies have examined their effects on microglial immune activation. It does not establish that glucose stimulates microglia. The Discussion (page not provided) says the relationship between microglial metabolic pathways and immune regulation remains to be examined, rather than establishing a link between metabolic reprogramming and activation. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [20] Huang Q,, Glycometabolic Reprogramming of Microglia in Neurodegenerative Diseases: Insights from Neuroinflammation. Aging Dis, 2023. PMC11081147 37611905 sourcePartly supported

  The Abstract (page unavailable) links microglial metabolic reprogramming to immune metabolism and names glucose and fatty acid metabolism. The section “Microglia activation influences glucose metabolism” (page unavailable) describes a close association between metabolism and activation. But the cited passages do not establish that lipids, free fatty acids, or glucose themselves stimulate microglia; they describe increased glucose uptake after activation and activation by inflammatory stimuli or misfolded proteins. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

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

MiR-33 can modulate SREBP1 expression and miR-33 knockout mice are prone to obesity and liver steatosis.

“MiR-33 can modulate SREBP1 expression and miR-33 knockout mice are prone to obesity and liver steatosis [35].”

• cites [35] Horie T,, MicroRNA-33 regulates sterol regulatory element-binding protein 1 expression in mice. Nat Commun, 2013. 4: p. 2883. 24300912 PMC3863899 sourceSupported

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

SREBP2 primarily regulates cholesterol synthesis through increasing HMG-CoA reductase (HMGCR) expression.

“SREBP1a and SREBP1c are responsible for fatty acid metabolism and SREBP2 primarily for cholesterol synthesis through increasing the expression of HMG-CoA reductase (HMGCR) [32].”

• cites [32] Horton JD, Goldstein JL, and Brown MS, SREBPs: activators of the complete program of cholesterol and fatty acid synthesis in the liver. J Clin Invest, 2002. 109(9): p. 1125– 31. 11994399 PMC150968 sourceSupported

May combine two claims.

LDAM have sustained activation, impaired phagocytosis and surveillance, and autophagy dysregulation.

“Among these subsets, LDAM have been given much attention due to their sustained activation, impaired phagocytosis and surveillance, and autophagy dysregulation [26–28].”

• cites [26] Haney MS,, APOE4/4 is linked to damaging lipid droplets in Alzheimer’s microglia. bioRxiv, 2023. PMC10990924 38480892 sourcePartly supported

  In “iMG upregulate ACSL1 and undergo TG lipid synthesis upon fAβ challenge” (page not provided), LD-high microglia show higher inflammatory-cytokine expression, lower homeostasis-marker expression, and dysfunctional phagocytosis. The Discussion (page not provided) links autophagy to lipid-droplet accumulation, but does not establish autophagy dysregulation as a measured LDAM trait. The paper also does not directly establish sustained activation or impaired surveillance. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [27] Victor MB,, Lipid accumulation induced by APOE4 impairs microglial surveillance of neuronal-network activity. Cell Stem Cell, 2022. 29(8): p. 1197– 1212 e8. 35931030 PMC9623845 sourcePartly supported

  The Discussion (page unavailable) describes LDAM as having reduced phagocytosis and increased secretion of pro-inflammatory cytokines, supporting part of the claim. The Results (page unavailable) link impaired homeostatic surveillance to lipid accumulation in APOE4-derived microglia, but do not establish that finding for LDAM. The passages do not support sustained activation or autophagy dysregulation in LDAM. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [28] Marschallinger J,, Lipid-droplet-accumulating microglia represent a dysfunctional and proinflammatory state in the aging brain. Nat Neurosci, 2020. 23(2): p. 194– 208. 31959936 PMC7595134 sourcePartly supported

  The Results sections on phagocytosis and cytokine release report severe phagocytosis deficits and a primed activation state in LDAM. The paper does not establish sustained activation or impaired surveillance. Its Discussion of lipophagy proposes defective lysosomal degradation as a possibility, rather than demonstrating autophagy dysregulation in LDAM. Page numbers are unavailable in our copy. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

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

SREBP2 can be regulated by miR-185-5p, which alleviates high-fat diet-induced atherosclerosis and lipid accumulation in vivo and in vitro.

“For example, SREBP2 could be regulated by miR-185-5p alleviating high-fat diet-induced atherosclerosis and lipid accumulation in vivo and in vitro [34].”

• cites [34] Tan W,, The elevation of miR-185-5p alleviates high-fat diet-induced atherosclerosis and lipid accumulation in vivo and in vitro via SREBP2 activation. Aging (Albany NY), 2022. 14(4): p. 1729– 1742. 35172278 PMC8908921 sourceSupported

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

Efficacy of statins on neurocognitive impairment has not been as promising in clinical studies.

“Despite the encouraging data from animal studies, the efficacy of statins on neurocognitive impairment has not been as promising in clinical studies [82].”

• cites [82] Bandaru VV,, A lipid storage-like disorder contributes to cognitive decline in HIV-infected subjects. Neurology, 2013. 81(17): p. 1492– 9. 24027056 PMC3888167 sourcePartly supported

  The Results (page not available in our copy) report that, among 19 participants taking a statin at baseline, statin use was not associated with worsening or improvement in cognitive status. This supports a limited lack-of-benefit observation in people with HIV, but the paper does not establish statin efficacy across clinical studies or compare those findings with animal studies. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

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

A number of molecules in lipid metabolism pathways have been identified to regulate NLRP3 inflammasome activation.

“A number of molecules in lipid metabolism pathways have been identified to regulate NLRP3 inflammasome activation [41].”

• cites [41] Hughes MM and O’Neill LAJ, Metabolic regulation of NLRP3. Immunol Rev, 2018. 281(1): p. 88– 98. 29247992 sourceSupported

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

Oxidized low-density lipoprotein (LDL), a cholesterol carrier, can form crystals within lysosomes after internalization.

“Oxidized low-density lipoprotein (LDsL), a cholesterol carrier, can also form crystals within lysosomes after internalization [74].”

• cites [74] Duewell P,, NLRP3 inflammasomes are required for atherogenesis and activated by cholesterol crystals. Nature, 2010. 464(7293): p. 1357– 61. 20428172 PMC2946640 sourceSupported

May combine two claims.

A combination of atorvastatin and SIM decreases proportion of CD16+ monocytes in PBMC cells, which is relevant to HAND since migration of CD16+ cells into CNS accelerates HAND.

“A combination of atorvastatin and SIM decreases the proportion of CD16+ monocytes in PBMC cells, which is relevant to HAND since the migration of CD16+ cells into the CNS accelerate HAND [80, 81].”

• cites [80] Yadav A, Betts MR, and Collman RG, Statin modulation of monocyte phenotype and function: implications for HIV-1-associated neurocognitive disorders. J Neurovirol, 2016. 22(5): p. 584– 596. 27021071 PMC5040617 sourcePartly supported

  The Results and Discussion (page not provided) report that simvastatin and atorvastatin each reduced the proportion of CD16+ monocytes in PBMC cultures and link these cells’ migration into the CNS to HAND pathogenesis. The Methods specify treatment with simvastatin or atorvastatin, not a combination of the two, so the claimed effect of combined treatment is unsupported. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [81] Williams DW,, Monocyte maturation, HIV susceptibility, and transmigration across the blood brain barrier are critical in HIV neuropathogenesis. J Leukoc Biol, 2012. 91(3): p. 401– 15. 22227964 PMC3289493 sourcePartly supported

  The Concluding Remarks state that CD14+CD16+ monocytes transmigrate into the CNS and are believed to promote events leading to neurocognitive impairment. The paper does not support the claim that a combination of atorvastatin and SIM decreases their proportion in PBMCs; searches for the drug combination found no such result in our copy. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

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

Drug-drug interactions between antiretrovirals and statin might be a potential problem.

“The drug-drug interactions between antiretrovirals and statin might be a potential problem [83].”

• cites [83] Chastain DB, Stover KR, and Riche DM, Evidence-based review of statin use in patients with HIV on antiretroviral therapy. J Clin Transl Endocrinol, 2017. 8: p. 6– 14. 29067253 PMC5651339 sourceSupported

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

Microglia has sex-dependent immune response and sex-dependent regulation on microglia also exists in HIV infection.

“Since microglia has sex-dependent immune response [85] and sex-dependent regulation on microglia also exists in HIV infection [86]”

• cites [85] Berkiks I,, The sex differences of the behavior response to early Life immune stimulation: Microglia and astrocytes involvement. Physiol Behav, 2019. 199: p. 386– 394. 30529512 sourceSupported
• cites [86] Wilson ME,, Immune modulation by estrogens: role in CNS HIV-1 infection. Endocrine, 2006. 29(2): p. 289– 97. 16785604 sourceNot checked — no full text of the source

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

NADPH oxidase 4, responsible for fatty acid oxidation, activates NLRP3 inflammasome in macrophage.

“NADPH oxidase 4, responsible for fatty acid oxidation, activates the NLRP3 inflammasome in macrophage [71].”

• cites [71] Moon JS,, NOX4-dependent fatty acid oxidation promotes NLRP3 inflammasome activation in macrophages. Nat Med, 2016. 22(9): p. 1002– 12. 27455510 PMC5204248 sourceSupported

May combine two claims.

Palmitic acid and other saturated fatty acids can crystallize in macrophages causing lysosomal membrane rupture, a known signal 2 for NLRP3 inflammasome assemble.

“Palmitic acid and other saturated fatty acids can be crystallized in macrophages causing lysosomal membrane rupture, a known signal 2 for NLRP3 inflammasome assemble [72].”

• cites [72] Karasawa T,, Saturated Fatty Acids Undergo Intracellular Crystallization and Activate the NLRP3 Inflammasome in Macrophages. Arterioscler Thromb Vasc Biol, 2018. 38(4): p. 744– 756. 29437575 sourceSupported

May combine two claims.

SIM has marginal effects on LDs formation and microglial activation in HPs of control mice but significantly inhibits LDs numbers and microglial activation in HIV-iTAT mice.

“SIM has marginal effects on LDs formation and microglial activation in the HPs of control mice but significantly inhibit LDs numbers and microglial activation in HIV-iTAT mice (sFigs. 4A – 4C, * P < 0.05 vs. control mice + veh, # P < 0.05, HIV-iTAT mice + SIM vs. HIV-iTAT mice + veh).”

May combine two claims.

SIM pretreatment inhibits astrocyte activation and restores PSD95 levels in HPs of HIV-iTAT mice.

“SIM pretreatment also inhibit astrocyte activation and restore PSD95 levels in the HPs of HIV-iTAT mice (sFigs. 5A – 5D, * P < 0.05 vs. control mice + veh, # P < 0.05, HIV-iTAT mice + SIM vs. HIV-iTAT mice + veh).”

May combine two claims.

In the three detected brain regions of HIV-iTAT mice, the co-localization ratios of LDs with microglia and astrocytes are 73% vs. 7% in the HP; 55% vs. 10% in the PFc, and 55% vs. 15% in the striatum.

“In the three detected brain regions of HIV-iTAT mice, the co-localization ratios of LDs with microglia and astrocytes are 73% vs. 7% in the HP; 55% vs. 10% in the PFc, and 55% vs. 15% in the striatum.”

May combine two claims.

Cotransfection of wild-type luciferase plasmids and miR-124 significantly decreases luciferase intensity, but not mutant plasmid.

“only cotransfection of WT luciferase plasmids and miR-124 could significantly decreases the luciferase intensity but not for mutant plasmid (Fig. 5F, * P < 0.05, miR-124 + WT plasmids vs. miR-C + WT; # P < 0.05, miR-124 + mutant plasmid vs. miR-124 + WT plasmid).”

May combine two claims.

After 10-day SIM administration, neuromuscular strength is significantly improved in HIV-iTAT mice (SIM vs vehicle), with no significant difference between SIM and vehicle in control mice.

“while there is no significant difference on neuromuscular strength between on groups of control mice (SIM vs. vehicle), the neuromuscular strength is significant improved in HIV-iTAT mice (SIM vs. vehicle) (Fig. 7C, two-way ANNOVA, interaction (genetic X SIM): F (1, 13) = 10.35, P = 0.0067; SIM: F (1. 36) = 6.54, P = 0.02; genetic: F (1, 36) = 5.67, P = 0.03).”

May combine two claims.

Most LDs in HIV-iTAT mouse brain are co-localized with microglia (73% in HP, 55% in PFc, 55% in striatum) but not with astrocytes (7% in HP, 10% in PFc, 15% in striatum).

“Interestingly, the colocalization analysis show that most of LDs are co-localized with microglia (73% in the HP, 55% in the PFc, and 55% in the striatum) but not with astrocyte (7% in the HP, 10% in the PFc, 15% in the striatum) (Fig. 2F).”

May combine two claims.

HIV-iTAT mice have dysregulated lipid profiles and increased LDs in the brain.

“Our results show HIV-iTAT mice have dysregulated lipid profiles and increased LDs in the brain.”

May combine two claims.

Levels of SREBP2 are significantly increased in TAT(+) microglia compared to TAT(-) microglia, and miR-124 levels show the opposite direction.

“Interestingly, the levels of SREBP2 are significantly increased in TAT (+) microglia comparing to TAT (−) microglia and the levels of miR-124 show the opposite direction (Fig. 5D, * P < 0.05).”

May combine two claims.

In HIV-iTAT mouse hippocampus, IL1β and IL6 expression are upregulated (1.66-fold and 1.34-fold, respectively).

“There is an increase in the neuroinflammation levels in HIV-TAT HPs (IL1β, 1.66 folds; IL6, 1.34 folds upregulation) (Fig. 1E, supplementary Fig. 1).”

May combine two claims.

SIM treatment significantly increases time spent on novel object in HIV-iTAT mice but not in HIV-TAT(-) mice.

“SIM treatment significantly increased the time spent on novel object from HIV-iTAT mice but not from HIV-TAT (−) mice.”

May combine two claims.

HIV-TAT upregulates levels of il1β, il6, tnfα, ccl2 in microglia, and SIM reverses such upregulation.

“while HIV-TAT upregulates the levels of these four pro-inflammatory mediators, SIM could reverse such upregulation effects in microglia (Figs. 7E – 7H, * P < 0.05, HIV-iTAT + veh vs. HIV-iTAT + SIM; # P < 0.05, HIV-iTAT + veh vs. TAT (−) + veh).”

May combine two claims.

SIM decreases neuroinflammation and restores behavioral deficiency in HIV-iTAT mice.

“Our results also show that cholesteral inhibtion (SIM) could decrease neuroinflamation, restore the behavioral deficiency in HIV-iTAT mice.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Microglia are very sensitive to surrounding changes and vigilant on the presence of HIV proteins such as TAT even at lower concentrations.

“Microglia are very sensitive to the surrounding changes. Therefore, microglia are very vigilant on the presence of HIV proteins such as TAT even at lower concentrations.”

Classified as probably not a substantial claim.

The purity of microglial cultures was evaluated by Iba1 immunostaining.

“The purity of microglial cultures was evaluated by Iba1 immunostaining (Wako Pure Chemical Industries, 019-19741).”

May combine two claims.

SIM reduces neuroinflammation through inhibiting microglia and astrocyte and restores neuronal plasticity, which underlie therapeutic effects on HIV-TAT mediated behavioral deficiency.

“These results indicate that SIM can reduce neuroinflammation levels through both inhibiting microglia and astrocyte and restore neuronal plasticity which underlie the therapeutic effects on HIV-TAT mediated behavioral deficiency.”

May combine two claims.

HIV-TAT can dysregulate lipid metabolism and increase microglial LDs formation through SREBP2/miR-124 axis in vitro.

“HIV-TAT can dysregulate lipid metabolism and increase microglial LDs formation through SREBP2/miR-124 axis in vitro.”

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

All procedures were conducted in accordance with the National Institutes of Health's Guide for the Care and Use of Experimental Animals and were approved by VHS Institutional Animal Care and Use Committee (protocol number: 23-009).

“All procedures were conducted in accordance with the National Institutes of Health’s Guide for the Care and Use of Experimental Animals and were approved by VHS Institutional Animal Care and Use Committee (protocol number: 23-009).”

May combine two claims.

Inhibition of LDs formation mitigates behavioral deficiency and neuroinflammation in HIV-iTAT mice.

“Inhibition on LDs formation could mitigate the behavioral deficiency and neuroinflammation in HIV-iTAT mice.”

May combine two claims.

Inhibition of lipid/cholesterol synthesis mitigates TAT-mediated LDs formation, NLRP3 inflammasome activity, and microglial activation.

“Taken all together, inhibition on lipid/cholesterol synthesis could mitigate TAT-mediated LDs formation, NLRP3 inflammasome activity, and microglial activation.”

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

Astrocytes are the main resource of cholesterol for neurons and lipids and cholesterols are easily exported for neuronal absorption.

“Astrocytes are the main resource of cholesterol for neurons and the lipids and cholesterols are easily exported for neuronal absorption [62].”

• cites [62] Pfrieger FW, Outsourcing in the brain: do neurons depend on cholesterol delivery by astrocytes? Bioessays, 2003. 25(1): p. 72– 8. 12508285 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

Accumulation on LDAM might be different between male and female HIV-iTAT mice.

“the accumulation on LDAM might be different between male and female HIV-iTAT mice.”

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

The study only employed male HIV-iTAT and control mice throughout.

“we only employed male HIV-iTAT and control mice througout the study.”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

Since there are substantive investigations supporting neuroprotective roles of cholesterol and lipid regulation in Alzheimer's, Parkinson's, Multiple Sclerosis and strokes, the same mechanisms might also apply for HAND treatment.

“Since there are substantive investigations supporting the neuroprotective roles of cholesterol and lipid regulation in Alzheimer’s, Parkinson’s, Multiple Sclerosis and strokes, the same mechanisms might also apply for HAND treatment [84].”

• cites [84] van der Most PJ,, Statins: mechanisms of neuroprotection. Prog Neurobiol, 2009. 88(1): p. 64– 75. 19428962 sourceNot checked — no full text of the source

May combine two claims.

UCP2, a driver for fatty acid synthesis, activates NLRP3 inflammasome.

“the uncoupling protein 2, a driver for fatty acid synthesis, activates NLRP3 inflammasome [70].”

• cites [70] Moon JS,, UCP2-induced fatty acid synthase promotes NLRP3 inflammasome activation during sepsis. J Clin Invest, 2015. 125(2): p. 665– 80. 25574840 PMC4319445 sourceNot checked — no full text of the source

May combine two claims.

miR-124 directly regulates SREBP2 activity and affects LDs formation.

“All these data together demonstrate that miR-124 could direclty regulate SREBP2 activity and affect LDs formation.”

May combine two claims.

HIV-iTAT mice exhibit heightened LDAM in the brain, with TAT contributing to increased LDs formation through SREBP2/miR124 axis.

“our study highlihgts that HIV-iTAT mice exhibit heightened LDAM in the brain, with TAT contributing to the increased LDs formation through SREBP2/miR124 axis.”