Biology subjects

Thyfault, J. P.

Publications and source records attributed to Thyfault, J. P..

16 recordsLinked to original sources

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

Brca1 heterozygosity leads to hepatic steatosis in male and female mice despite sexually dimorphic effects on systemic metabolism

Carrying a germline mutation in BRCA1 is associated with an increased risk of several cancers, including breast and ovarian. Our recent work has demonstrated that obesity is associated with elevated levels of DNA damage in breast glands in this high-risk population. BRCA1 is a canonical tumor suppressor gene primarily recognized for its role in DNA damage repair, yet emerging evidence suggests broader functions in metabolic regulation. To determine whether heterozygous loss of Brca1, as seen in individuals who carry a germline mutation, modifies susceptibility to diet-induced metabolic dysfunction in a sex-dependent manner, we subjected wild-type (WT) and Brca1+/- mice of both sexes to a high-fat diet (HFD) and performed longitudinal metabolic phenotyping. Female Brca1+/- mice exhibited pronounced obesity, increased adiposity, hyperinsulinemia, and impaired glucose tolerance. In contrast, male Brca1+/- mice showed modest resistance to HFD-induced weight gain and displayed improved glucose tolerance compared to WT controls. Notably, Brca1 heterozygosity led to more severe hepatic steatosis with HFD, indicating a shared susceptibility to liver lipid accumulation despite divergent systemic outcomes. In females, steatosis was associated with reduced mitochondrial respiratory complex IV activity and transcriptional remodeling that favored lipid storage. Treatment with the dual GLP1/GIP receptor agonist tirzepatide ameliorated systemic metabolic dysfunction and hepatic steatosis in HFD-fed female Brca1+/- mice. These findings identify Brca1 heterozygosity as a modifier of metabolic disease risk, expanding BRCA1 biology beyond tumor suppression. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/708005v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@17f9592org.highwire.dtl.DTLVardef@134c2c2org.highwire.dtl.DTLVardef@de69d8org.highwire.dtl.DTLVardef@1f6f1af_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2026

Hepatocyte Estrogen Receptor α Mediates Estrogen-induced Augmentation of Hepatic 1 Mitochondrial Respiration Following Ovariectomy.

Whole-body estrogen receptor (ER) knockout mice develop hepatic steatosis; however, liver-specific ER knockout (LERKO) mice fail to recapitulate this susceptibility and maintain normal hepatic mitochondrial function. However, estrogen-mediated protection against hepatic steatosis is lost in LERKO mice following ovariectomy (OVX). Here, we tested whether loss of hepatic ER blunts estrogen modulation of hepatic mitochondrial respiratory capacity and mitochondrial proteome following ovariectomy (OVX). Sham or ovariectomy (OVX) surgery was performed in middle-aged female mice (36-40 weeks), followed by AAV injection to generate Control (Con; GFP) or LERKO mice (Cre). All mice were placed on a high-fat diet (HFD) for 10 weeks following surgery. Half of the OVX mice received 17-beta estradiol (E2) replacement (OVX+E2) for the last 4 weeks of HFD. OVX mice had greater body mass and adiposity, which was reversed by E2 replacement in both Con and LERKO mice. While E2 replacement reduced steatosis in both Con and LERKO OVX mice, the LERKO OVX mice maintained greater hepatic triglyceride content. E2 replacement promoted greater basal and ADP-stimulated (State 3) mitochondrial respiration in Con OVX but not in LERKO OVX mice under palmitate-supported conditions. Changes in mitochondrial respiration could not be attributed to altered responses to changes in energy demand (GATP) or to alterations in mitochondrial H2O2 production. Conversely, maximal coupled branched-chain amino acid-supported respiration was universally suppressed by E2 replacement. Proteomics analysis revealed E2-mediated reductions in hepatic mitochondrial energy transduction, with relatively minimal differences between Con and LERKO mice. In conclusion, post-ovariectomy estrogen treatment reduces steatosis in the absence of hepatic ER; however, triglyceride levels remain higher, and mitochondrial respiratory deficits persist despite similar proteomic signatures, suggesting that ER signaling is required for optimal estrogen hepatic responsiveness.

biochemistry↗

bioRxiv2025

Adipose Tissue Overexpression of Nicotinamide Phosphoribosyltransferase Prevents Metabolic Dysfunction in Obese Mice

Nicotinamide adenine dinucleotide (NAD+) is a vital coenzyme and a central factor in energy metabolism. Nicotinamide phosphoribosyltransferase (NAMPT) maintains the cellular NAD+ pool by synthesizing the NAD+ precursor, nicotinamide mononucleotide (NMN), and diminished adipocyte NAMPT activity has been implicated in aging- and obesity-related metabolic dysfunction. Herein, we examined the effects of overexpressing or knocking out NAMPT in adipocytes on metabolic dysfunction and interorgan communication in mice. We generated new adipocyte-specific NAMPT overexpressing(ANOV) mice model. Male ANOV mice are protected from diet-induced metabolic dysfunction including adipose tissue inflammation, glucose intolerance, and insulin resistance. In contrast female ANOV mice were less protected from metabolic dysfunction, possibly due to higher endogenous expression of NAMPT in WT female mice. Livers of ANOV mice showed improved insulin signaling, increased NAD content, and reduced steatosis, suggesting that NAMPT regulates interorgan communication between adipocytes and hepatocytes. Extracellular vesicles (EV) isolated from ANOV mice enhanced insulin signaling in HepG2 cells and improved glucose tolerance in WT obese mice. In contrast, EV from ANKO mice suppressed HepG2 insulin signaling and inhibition of EV release improved glucose tolerance in ANKO female mice. Collectively, these data highlight a novel mechanism by which adipocyte NAD+ metabolism regulates systemic metabolic dysfunction via EVs.

physiology↗

bioRxiv2025

Hepatic ketogenic insufficiency blunts exercise-induced energy expenditure and alters mitochondrial proteins in skeletal muscle.

Ketone body (KB) utilization increases during fasting and exercise due to enhanced hepatic fatty acid oxidation and KB production via the rate-limiting mitochondrial enzyme hydroxymethylglutaryl-CoA synthase (HMGCS2). Since KB metabolism intersects with multiple metabolic pathways, and skeletal muscle KB catabolism rises during exercise, we tested the hypothesis that liver-specific HMGCS2 knockouts (KO) would have reduced energy expenditure (EE) and changes in the mitochondrial proteome of skeletal muscle with chronic exercise through voluntary wheel running (VWR), time-restricted feeding (TRF), or both combined to boost hepatic KB production and utilization. Control (CON) and HMGCS2 knockout (KO) mice (n=6-8 per group) underwent sedentary ad libitum feeding (SED+AL), SED+TRF, VWR+AL, and VWR+TRF for 16 weeks, with whole-body EE measured using indirect calorimetry. In CON mice, VWR increased total EE by 19.5% and non-resting EE by 50% under AL conditions, and total EE by 16% and non-resting EE by 47.9% under TRF conditions. However, the EE increases seen with VWR did not occur in KO mice. Proteomic analysis revealed that the loss of liver HMGCS2 significantly impacted proteins involved in metabolic processes within skeletal muscle, including reduced oxidative phosphorylation (OXPHOS) protein expression in SED KO mice compared to sedentary CON. Notably, VWR restored OXPHOS protein expression in the muscle of the liver HMGCS2 KO but did not alter it in the CON. Furthermore, muscle from liver HMGCS2 KO mice had elevated expression glycolytic pathways in sedentary and VWR conditions. These results indicate that hepatic ketogenic deficiency (HMGCS2 KO) diminishes exercise-induced increases in EE and uniquely impacts baseline and exercise-related adaptations in the metabolic and mitochondrial proteome of skeletal muscle.

physiology↗

bioRxiv2025

Endurance exercise drives temporal and sexual dimorphic multi-omic adaptations in liver metabolism-Findings from MoTrPAC.

The mechanisms by which exercise modulate liver metabolism, a central regulator of systemic metabolism, are poorly understood. Leveraging data from MoTrPAC, we analyzed liver adaptations across 1, 2, 4, and 8 weeks of exercise in male and female rats using multi-omic approaches. Female livers displayed a progressive increase in oxidative phosphorylation (OXPHOS) complexes (at the protein level), while male livers showed an increase in acetylation of OXPHOS, TCA cycle, and fatty acid oxidation enzymes. Exercise also enhanced liver cholesterol and bile acid synthesis, reducing liver lipid metabolites in males after 8 weeks of exercise. Male rats had higher fecal cholesterol and cholic acid levels, indicating a sex-specific mechanism of lipid excretion with exercise. Moreover, 8 weeks of training reduced markers related to hepatic stellate cell activation and fibrosis in both sexes. This study highlights the sexual dimorphic and temporal molecular signatures by which exercise modulates liver metabolism to provide hepatoprotective effects.

physiology↗

bioRxiv2023

Disruption of Hepatic Mitochondrial Pyruvate and Amino Acid Metabolism Impairs Gluconeogenesis and Endurance Exercise Capacity in Mice

Exercise robustly increases the glucose demands of skeletal muscle. This demand is met not only by muscle glycogenolysis, but also by accelerated liver glucose production from hepatic glycogenolysis and gluconeogenesis to fuel mechanical work and prevent hypoglycemia during exercise. Hepatic gluconeogenesis during exercise is dependent on highly coordinated responses within and between muscle and liver. Specifically, exercise increases the rate at which gluconeogenic precursors such as pyruvate/lactate or amino acids are delivered from muscle to the liver, extracted by the liver, and channeled into glucose. Herein, we examined the effects of interrupting gluconeogenic efficiency and capacity on exercise performance by deleting hepatic mitochondrial pyruvate carrier 2 (MPC2) and/or alanine transaminase 2 (ALT2) in mice. We found that deletion of MPC2 or ALT2 alone did not significantly affect time to exhaustion or post-exercise glucose concentrations in treadmill exercise tests, but mice lacking both MPC2 and ALT2 in liver (DKO) reached exhaustion faster and exhibited lower circulating glucose during and after exercise. Use of {superscript 2}H/{superscript 1}3C metabolic flux analyses demonstrated that DKO mice exhibited lower endogenous glucose production owing to decreased glycogenolysis and gluconeogenesis at rest and during exercise. The decreased gluconeogenesis was accompanied by lower anaplerotic, cataplerotic, and TCA cycle fluxes. Collectively, these findings demonstrate that the transition of the liver to the gluconeogenic mode is critical for preventing hypoglycemia and sustaining performance during exercise. The results also illustrate the need for interorgan crosstalk during exercise as described by the Cahill and Cori cycles.

physiology↗

bioRxiv2023

Exposure to early life stress impairs weight loss maintenance success in mice.

Early life stress increases obesity risk, but its impact on weight loss maintenance is unknown. Mice underwent neonatal maternal separation (NMS) from 0-3 weeks and were weaned onto high fat sucrose diet (HFSD) from 3-20 weeks. Calorie-restricted weight loss on a low fat sucrose diet (LFSD) occurred over 2 weeks to induce a 20% loss in body weight, which was maintained for 6 weeks. After weight loss, half the mice received running wheels (EX) the other half remained sedentary (SED). Mice were then fed ad libitum on HFSD or LFSD for 10 weeks and allowed to regain body weight. NMS mice had greater weight regain, total body weight and adiposity compared to naive mice. During the first week of refeeding, NMS mice had increased food intake and were in a greater positive energy balance than naive mice, but total energy expenditure was not affected by NMS. Female mice were more susceptible to NMS-induced effects, including increases in adiposity. NMS and naive females were more susceptible to HFSD-induce weight regain. Exercise was beneficial in the first week of regain in male mice, but long-term only those on LFSD benefited from EX. As expected, HFSD led to greater weight regain than LFSD.

physiology↗

bioRxiv2023

Ketolysis is Required for the Proper Development and Function of the Somatosensory Nervous System.

Ketogenic diets are emerging as protective interventions in preclinical and clinical models of somatosensory nervous system disorders. Additionally, dysregulation of succinyl-CoA 3-oxoacid CoA-transferase 1 (SCOT, encoded by Oxct1), the fate-committing enzyme in mitochondrial ketolysis, has recently been described in Friedreichs ataxia and amyotrophic lateral sclerosis. However, the contribution of ketone metabolism in the normal development and function of the somatosensory nervous system remains poorly characterized. We generated sensory neuron-specific, Advillin-Cre knockout of SCOT (Adv-KO-SCOT) mice and characterized the structure and function of their somatosensory system. We used histological techniques to assess sensory neuronal populations, myelination, and skin and spinal dorsal horn innervation. We also examined cutaneous and proprioceptive sensory behaviors with the von Frey test, radiant heat assay, rotarod, and grid-walk tests. Adv-KO-SCOT mice exhibited myelination deficits, altered morphology of putative A{delta} soma from the dorsal root ganglion, reduced cutaneous innervation, and abnormal innervation of the spinal dorsal horn compared to wildtype mice. Synapsin 1-Cre-driven knockout of Oxct1 confirmed deficits in epidermal innervation following a loss of ketone oxidation. Loss of peripheral axonal ketolysis was further associated with proprioceptive deficits, yet Adv-KO-SCOT mice did not exhibit drastically altered cutaneous mechanical and thermal thresholds. Knockout of Oxct1 in peripheral sensory neurons resulted in histological abnormalities and severe proprioceptive deficits in mice. We conclude that ketone metabolism is essential for the development of the somatosensory nervous system. These findings also suggest that decreased ketone oxidation in the somatosensory nervous system may explain the neurological symptoms of Friedreichs ataxia.

neuroscience↗

bioRxiv2022

Early life stress exposure increases susceptibility to high fat/high sucrose diet in female mice

Exposure to stress early in life has been associated with adult-onset co-morbidities such as chronic pain, metabolic dysregulation, obesity, and inactivity. We have established an early life stress model using neonatal maternal separation (NMS) in mice, which displays evidence of increased body weight and adiposity, widespread mechanical allodynia, and hypothalamic-pituitary-adrenal axis dysregulation in male mice. Early life stress and consumption of a western style diet contribute to the development of obesity, however, relatively few pre-clinical studies have been performed in female rodents, which are known to be protected against diet induced obesity and metabolic dysfunction. In this study we gave naive and NMS female mice access to a high-fat/high-sucrose (HFS) diet beginning at 4 weeks of age. Robust increases in body weight and fat were observed in HFS-fed NMS mice during the first 10 weeks on the diet, driven partly by increased food intake. Female NMS mice on a HFS diet showed widespread mechanical hypersensitivity compared to either naive mice on a HFS diet or NMS mice on a control diet. HFS diet-fed NMS mice also had impaired glucose tolerance and fasting hyperinsulinemia. Strikingly, female NMS mice on a HFS diet showed evidence of hepatic steatosis with increased triglyceride levels and altered glucocorticoid receptor levels and phosphorylation state. They also exhibited increased energy expenditure as observed via indirect calorimetry and expression of pro-inflammatory markers in perigonadal adipose. Altogether, our data suggest that early life stress exposure increased the susceptibility of female mice to develop diet-induced metabolic dysfunction and pain-like behaviors.

physiology↗

bioRxiv2020

Reduced Liver-Specific PGC1a Increases Susceptibility for Short-Term Diet-induced Weight Gain in Male Mice

Central integration of peripheral neural signals is one mechanism by which systemic energy homeostasis is regulated. Previous work described increased acute food intake following chemical reduction of hepatic fatty acid oxidation and ATP levels, which was prevented by common hepatic branch vagotomy (HBV). However, possible offsite actions of the chemical compounds confound the precise role of liver energy metabolism. Herein, we used a liver-specific PGC1a heterozygous (LPGC1a) mouse model, with associated reductions in mitochondrial fatty acid oxidation and respiratory capacity, to assess the role of liver energy metabolism in systemic energy homeostasis. LPGC1a male mice have 70% greater high-fat/high-sucrose (HFHS) diet-induced weight gain and 35% greater positive energy balance compared to wildtype (WT) (p<0.05). The greater energy balance was associated with altered feeding behavior and lower activity energy expenditure during HFHS in LPGC1a males. Importantly, no differences in HFHS-induced weight gain or energy metabolism was observed between female WT and LPGC1a mice. WT and LPGC1a mice underwent sham or HBV to assess whether vagal signaling was involved in HFHS-induced weight gain of male LPGC1a mice. HBV increased HFHS-induced weight gain (85%, p<0.05) in male WT, but not LPGC1a mice. As above, sham LPGC1a males gain 70% more weight during short-term HFHS feeding than sham WT (p<0.05). These data demonstrate a sexspecific role of reduced liver energy metabolism in acute diet-induced weight gain, and the need of more nuanced assessment of the role of vagal signaling in short-term diet-induced weight gain. Key Points SummaryO_LIReduced liver PGC1a expression results in reduced mitochondrial fatty acid oxidation and respiratory capacity in male mice. C_LIO_LIMale mice with reduced liver PGC1a expression (LPGC1a) demonstrate greater short-term high-fat/high-sucrose diet-induced weight gain compared to wildtype. C_LIO_LIGreater positive energy balance during HFHS feeding in male LPGC1a mice is associated with altered food intake patterns and reduced activity energy expenditure. C_LIO_LIFemale LPGC1a mice do not have differences in short-term HFHS-induced body weight gain or energy metabolism compared to wildtype. C_LIO_LIDisruption of vagal signaling through common hepatic branch vagotomy increases short-term HFHS-induced weight gain in male wildtype mice, but does not alter male LPGC1a weight gain. C_LI

physiology↗

bioRxiv2020

A high fat anti-inflammatory diet improves widespread allodynia despite worsening metabolic outcomes in adult mice exposed to neonatal maternal separation

Inflammation plays a key role in the progression and maintenance of chronic pain, which impacts the lives of millions of Americans. Despite growing evidence that chronic pain can be improved by treating underlying inflammation, successful treatments are lacking and pharmaceutical interventions are limited due to drug side effects. Here we are testing whether an anti-inflammatory diet (AID) containing a combination of key anti-inflammatory compounds, at clinically relevant doses, improves pain-like behaviors in a preclinical model of chronic widespread hypersensitivity induced by neonatal maternal separation (NMS). Our results demonstrate a benefit of the AID on pain-like behaviors, despite the diet being high in fat, which led to increased caloric intake, adiposity, and weight gain. The AID specifically increased measures of metabolic syndrome and inflammation in female mice, compared to an isocaloric, macronutrient-matched diet lacking the anti-inflammatory compounds. Male mice, especially those exposed to NMS, were equally susceptible to both diets worsening metabolic measures. This work highlights important sexual dimorphic outcomes related to early life stress exposure and dietary interventions, as well as a potential disconnect between improvements in pain-like behaviors and metabolic measures.

physiology↗

bioRxiv2020

Early life stress reduces voluntary exercise and its prevention of diet-induced obesity and metabolic dysfunction in mice

The development of obesity-related metabolic syndrome (MetS) involves a complex interaction of genetic and environmental factors. One environmental factor found to be significantly associated with MetS is early life stress (ELS). We have previously reported on our mouse model of ELS, induced by neonatal maternal separation (NMS), that displays altered regulation of the hypothalamic-pituitary-adrenal (HPA) axis and increased sensitivity in the urogenital organs, which was attenuated by voluntary wheel running. Here, we are using our NMS model to determine if ELS-induced changes in the HPA axis also influence weight gain and MetS. Naive (non-stressed) and NMS male mice were given free access to a running wheel and a low-fat control diet at 4-weeks of age. At 16-weeks of age, half of the mice were transitioned to a high fat/sucrose (HFS) diet to investigate if NMS influences the effectiveness of voluntary exercise to prevent diet-induced obesity and MetS. Overall, we observed a greater impact of voluntary exercise on prevention of HFS diet-induced outcomes in naive mice, compared to NMS mice. Although body weight and fat mass were still significantly higher, exercise attenuated fasting insulin levels and mRNA levels of inflammatory markers in epididymal adipose tissue in HFS diet-fed naive mice. Only moderate changes were observed in exercised NMS mice on a HFS diet, although this could partially be explained by reduced running distance within this group. Interestingly, sedentary NMS mice on a control diet displayed impaired glucose homeostasis and moderately increased pro-inflammatory mRNA levels in epididymal adipose, suggesting that early life stress alone impairs metabolic function and negatively impacts the therapeutic effect of voluntary exercise.

physiology↗

bioRxiv2019

Divergent Energy Expenditure Impacts Mouse Metabolic Adaptation to Acute High-Fat/High-Sucrose Diet Producing Sexually Dimorphic Weight Gain Patterns

ObjectiveLong-term weight gain can result from cumulative small weight increases due to short-term excess caloric intake during weekends and holidays. Increased physical activity may mediate weight gain through increases in energy expenditure (EE) and reductions in energy balance. Current methods for modulating mouse EE (e.g. - exercise, chemical uncouplers, etc.) have confounding effects. However, it is known that mouse EE linearly increases as housing temperature decreases below the thermoneutral zone. MethodsTo determine how robust differences in baseline EE impact 7-day changes in weight and body composition on low-fat and high-fat, high-sucrose (HFHS) diets, we performed indirect calorimetry measurements in male and female mice housed at divergent temperatures (20{degrees}C vs. 30{degrees}C). ResultsAs expected, mice housed at 30{degrees}C have [~]40% lower total EE and energy intake compared to 20{degrees}C mice regardless of diet or sex. Energy balance was increased with HFHS in all groups, with [~]30% greater increases observed in 30{degrees}C versus 20{degrees}C mice. HFHS increased weight gain regardless of temperature or sex. Interestingly, no HFHS-induced weight gain differences were observed between females at different temperatures. In contrast, 30{degrees}C male mice on HFHS gained [~]50% more weight than 20{degrees}C males, and [~]80% more weight compared to 30{degrees}C females. HFHS increased fat mass across all groups but 2-fold higher gains occurred in 30{degrees}C mice compared to 20{degrees}C mice. Females gained [~]35% less fat mass than males at both temperatures. ConclusionsTogether, these data reveal an interaction between divergent ambient temperature-induced EE and sex that impacted diet-induced patterns of short-term weight gain and body composition. HighlightsO_LIUtilized ambient temperature differences as an experimental tool to study the impact of divergent baseline energy expenditure on metabolic adaptation to high-fat, high-sucrose diet. C_LIO_LIBaseline energy expenditure and sex interact to impact diet-induced changes in body composition and weight gain. C_LIO_LIThe energy expenditure and sex interaction is a result of an inverse relationship between fat mass gain and weight-adjusted total energy expenditure, as well as, diet-induced non-shivering thermogenesis. C_LIO_LIThese data support that the hypothesis that higher energy expenditure amplifies the coupling of energy intake to energy expenditure during energy dense feeding, resulting in reduced positive energy balance and reduced gains in weight and adiposity. C_LIO_LIFirst evidence that energy expenditure level plays a role in the composition of weight gained by female mice during acute HFHS feeding. C_LIO_LIThis study further highlights issues with obesity/energy metabolism research performed in mice at sub-thermoneutral housing temperatures, particularly with sex comparisons. C_LI GRAPHIC ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/840702v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@39eb69org.highwire.dtl.DTLVardef@8e564forg.highwire.dtl.DTLVardef@c46714org.highwire.dtl.DTLVardef@4b5898_HPS_FORMAT_FIGEXP M_FIG Legend: Male and female mice housed at 30{degrees}C had lower energy expenditure (EE) & energy intake (EI), while having greater energy balance (EB), during 7-day high-fat/high-sucrose (HFHS) feeding compared to male and female mice, respectively, housed at 20{degrees}C. However, female mice had lower EB compared to males at both housing temperature. Female mice housed at 30{degrees}C gained less weight than 30{degrees}C males but gained the same relative amount of fat mass during acute HFHS feeding. Interestingly, 20{degrees}C females gained the same amount of weight as 20{degrees}C males but gained primarily fat-free mass, while the males gained the same proportion of fat as 30{degrees}C males and females. C_FIG

physiology↗

bioRxiv2019

Mutational mimics of allosteric effectors: a genome editing design to validate allosteric drug targets

Development of drugs that allosterically regulate enzyme functions to treat disease is a costly venture. Screening mutations that mimic allosteric effectors in vitro will identify therapeutic regulatory targets enhancing the likelihood of developing a disease treatment at a reasonable cost. We demonstrate the potential of this approach utilizing human liver pyruvate kinase (hLPYK) as a model. Inhibition of hLPYK was the first desired outcome of our screen. We identified individual point mutations that: 1) mimicked allosteric inhibition by alanine, 2) mimicked inhibition by protein phosphorylation, and 3) prevented binding of fructose-1,6-bisphosphate (Fru-1,6-BP). Our second desired screening outcome was activation of hLPYK. We identified individual point mutations that: 1) prevented hLPYK from binding alanine, the allosteric inhibitor, 2) prevented inhibitory protein phosphorylation, or 3) mimicked allosteric activation by Fru-1,6-BP. Combining the three activating point mutations produced a constitutively activated enzyme that was unresponsive to regulators. Expression of a mutant hLPYK transgene containing these three mutations in a mouse model was not lethal. Thus, mutational mimics of allosteric effectors will be useful to confirm whether allosteric activation of hLPYK will control glycolytic flux in the diabetic liver to reduce hepatic glucose production and, in turn, reduce or prevent hyperglycemia.

biochemistry↗

bioRxiv2018

Hepatocyte-Specific Hepatocyte Nuclear Factor 4 alpha (HNF4α) Deletion Decreases Resting Energy Expenditure By Disrupting Lipid and Carbohydrate Homeostasis

Hepatocyte Nuclear Factor 4 alpha (HNF4) is required for hepatocyte differentiation and regulates expression of genes involved in lipid and carbohydrate metabolism including those that control VLDL secretion and gluconeogenesis. Whereas previous studies have focused on specific genes regulated by HNF4 in metabolism, its overall role in whole body energy utilization has not been studied. In this study, we used indirect calorimetry to determine the effect of hepatocyte-specific HNF4 deletion (HNF4-KO) in mice on whole body energy expenditure (EE) and substrate utilization in fed, fasted, and high fat diet (HFD) conditions. HNF4-KO had reduced resting EE during fed conditions and higher rates of carbohydrate oxidation with fasting. HNF4-KO mice exhibited decreased body mass caused by fat mass depletion despite no change in energy intake and evidence of positive energy balance. HNF4-KO mice were able to upregulate lipid oxidation during HFD suggesting that their metabolic flexibility was intact. However, only hepatocyte specific HNF4-KO mice exhibited significant reduction in basal metabolic rate and spontaneous activity during HFD. Consistent with previous studies, hepatic gene expression in HNF4-KO supports decreased gluconeogenesis and decreased VLDL export and hepatic {beta}-oxidation in HNF4-KO livers across all feeding conditions. Together, our data suggest deletion of hepatic HNF4 increases dependence on dietary carbohydrates and endogenous lipids for energy during fed and fasted conditions by inhibiting hepatic gluconeogenesis, hepatic lipid export, and intestinal lipid absorption resulting in decreased whole body energy expenditure. These data clarify the role of hepatic HNF4 on systemic metabolism and energy homeostasis.

physiology↗