Biology subjects

Vang, C. M.

Publications and source records attributed to Vang, C. M..

4 recordsLinked to original sources

bioRxiv2026

Sulfur amino acid restriction prevents S-adenosylmethionine-driven liver steatosis, hepatocellular carcinoma, and metabolic remodeling in high-fat-fed GNMT-null mice

The expression of glycine N-methyltransferase (GNMT), a critical regulator of S-adenosylmethionine (SAM) levels, is down-regulated in humans with metabolic dysfunction-associated steatotic liver disease (MASLD) and hepatocellular carcinoma (HCC). In low-fat-fed mice, GNMT knockout (KO) induces liver steatosis that progresses to HCC. This is accompanied by increased SAM and a shunting of tricarboxylic acid (TCA) cycle intermediates away from gluconeogenesis to other biosynthetic pathways that support lipid accretion and tumorigenesis. The objective of this study was to test whether this metabolic remodeling persists in GNMT KO mice with diet-induced obesity and to determine if the liver pathophysiology and metabolic dysregulation are dependent on elevated SAM. To accomplish this, GNMT KO mice and wild-type (WT) littermates were fed a high-fat control or high-fat sulfur amino acid restricted (SAAR) diet to mitigate SAM accumulation. 2H/13C isotope infusions in mice quantified in vivo liver glucose and TCA cycle fluxes. Metabolomics, respirometry, and pyruvate tolerance tests were completed to more fully interpret the 2H/13C metabolic flux analyses. KO mice had impaired gluconeogenesis sourced from TCA cycle intermediates. A concurrent elevation in metabolites of pathways that use both SAM and TCA cycle intermediates indicated increased liver polyamine turnover, transsulfuration, and de novo lipogenesis. Importantly, SAAR prevented the increase in SAM, the associated metabolic dysregulation, and the appearance of liver steatosis and HCC. In conclusion, the results of these experiments suggest that the loss of GNMT in mice with diet-induced obesity rewires metabolism in a SAM-dependent manner that precipitates liver steatosis and the transition to HCC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/738958v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@42a108org.highwire.dtl.DTLVardef@5a3b55org.highwire.dtl.DTLVardef@1ed5f2corg.highwire.dtl.DTLVardef@10346cb_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2026

Diet-Dependent Cognitive Benefits of Exogenous Ketone Body Precursor, (R,S)-1,3,-Butanediol, in a Mouse Model of Tauopathy

Alzheimers disease and related tauopathies are escalating public health threats, particularly in the context of obesity and metabolic dysfunction, which accelerate cerebral glucose hypometabolism, tau pathology, neurodegeneration, and cognitive decline. Ketogenic therapies reconfigure systemic fuel metabolism, with emerging evidence for neuroprotection. (R,S)-1,3-butanediol (BD) raises circulating D- and L-{beta}-hydroxybutyrate ({beta}OHB) concentrations. To evaluate whether BD improves cognitive function across dietary contexts, male and female tau-transgenic mice and littermate controls received 10% BD in drinking water for 20 or 30 weeks starting at 6 weeks of age. BD rapidly induced ketosis (1.5-3.0 mM {beta}OHB) in chow-fed mice, with L-{beta}OHB contributing to [~]75% of the circulating {beta}OHB pool. Despite minimal effects of BD on body weight and glucose homeostasis, and no effect on histopathological tau signal, 20-week BD treatment improved memory to control levels in chow-fed female tauopathy mice. Isotope-tracing untargeted metabolomics revealed that BD-treatment differentially affected glucose-derived 13C-enrichment of metabolites in brains of male and female mice. BD-induced cognitive benefits in tau-transgenic mice were abrogated when mice were maintained on BD for 30 weeks on standard chow or when mice were administered BD over 20 weeks while maintained on a high-fat, Western diet, Notably, BD-induced ketosis was blunted in mice consuming Western diet. Moreover, intermittent ketogenic diet-induced ketosis failed to improve cognition in Western diet-fed tauopathy mice. These results suggest BD-induced ketosis extends cognitive benefits in a manner dependent on biological sex and nutritional metabolic status. Taken together, these data contextualize the roles of {beta}OHB as modulators of cognitive resilience in tauopathy.

animal behavior and cognition↗

bioRxiv2026

Hepatic ketogenesis supports liver lipid homeostasis during acute exercise but is not required for exercise training to mitigate liver steatosis in mice

The acceleration of hepatic lipid disposal during acute exercise has been proposed as a contributor to the anti-steatotic effects of exercise training. Ketogenesis, which produces acetoacetate (AcAc) and {beta}-hydroxybutyrate ({beta}OHB) from fatty acids, is among the lipid disposal pathways stimulated by exercise. This study tested the hypothesis that hepatic ketogenesis is necessary for exercise training to lower liver lipids. Liver-specific 3-hydroxymethylglutaryl-CoA synthase 2 knockout (HMGCS2 KO) mice and wild type (WT) littermates underwent sedentary, acute exercise, and exercise training protocols. Liver ketone bodies and lipids were determined via mass spectrometry platforms. Stable isotope infusions in conscious, unrestrained mice defined mitochondrial oxidative fluxes at rest and during exercise. Loss of hepatic HMGCS2 decreased liver AcAc and {beta}OHB concentrations and impaired their increase during exercise. Liver triacylglycerides (TAGs) were comparable between genotypes at rest (i.e., ad libitum fed and short fasted conditions). In contrast, liver TAGs were elevated in HMGCS2 KO mice following acute, non-exhaustive exercise. Liver TCA cycle flux was higher in KO mice at rest. During exercise, TCA cycle flux increased in both WT and KO mice but was not different between genotypes with greater exercise duration. This suggests that enhanced disposal of lipids via the TCA cycle may prevent liver lipid accumulation in HMGCS2 KO mice under sedentary conditions, but not during exercise. Unexpectedly, exercise training decreased liver TAGs similarly in both HMGCS2 KO and WT mice. In conclusion, hepatic ketogenesis supports liver lipid homeostasis during acute exercise, but is not required for exercise training to lower liver lipids. NEW & NOTEWORTHYExercise training has been proposed to mitigate liver steatosis partly through enhanced hepatic lipid disposal. During acute exercise, the disposal of fatty acids to ketone bodies is stimulated. This study tested the hypothesis that hepatic ketogenesis was required for exercise training to reduce liver fat in mice. The results show that hepatic ketogenesis is needed to prevent lipid accumulation during acute exercise, but is not necessary for exercise training to lower liver lipids.

physiology↗

bioRxiv2025

Dietary sulfur amino acid restriction improves glucose homeostasis through hepatic de novo serine synthesis

Dietary sulfur amino acid restriction (SAAR) improves whole-body glucose homeostasis, elevates liver insulin action, and lowers liver triglycerides. These adaptations are associated with an increased expression of hepatic de novo serine synthesis enzymes, phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1). This study tested the hypothesis that enhanced hepatic serine synthesis is necessary for glucose and lipid adaptations to SAAR. Hepatocyte-specific PSAT1 knockout (KO) mice and wild type (WT) littermates were fed a high-fat control or SAAR diet. In WT mice, SAAR increased liver PSAT1 protein ([~]70-fold), serine concentration ([~]2-fold), and 13C-serine ([~]20-fold) following an intravenous infusion of [U-13C]glucose. The elevated liver serine and partitioning of circulating glucose to liver serine by SAAR were attenuated in KO mice. This was accompanied by a blunted improvement in glucose tolerance in KO mice fed a SAAR diet. Interestingly, SAAR decreased liver lysine lactoylation, a SAA-supported post-translational modification known to inhibit PHGDH enzymatic activity. This suggests dietary SAAR may increase serine synthesis, in part, by lowering lysine lactoylation. Beyond glucose metabolism, dietary SAAR reduced body weight, adiposity, and liver triglycerides similarly in WT and KO mice. Collectively, these results demonstrate that hepatic PSAT1 is necessary for glucose, but not lipid, adaptations to SAAR. Graphical AbstractSchematic representation of liver glucose adaptations to SAAR O_FIG O_LINKSMALLFIG WIDTH=132 HEIGHT=200 SRC="FIGDIR/small/682938v2_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@dcda30org.highwire.dtl.DTLVardef@1789003org.highwire.dtl.DTLVardef@36cd4eorg.highwire.dtl.DTLVardef@1e0c640_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗