Biology subjects

Vergnes, L.

Publications and source records attributed to Vergnes, L..

8 recordsLinked to original sources

bioRxiv2025

Impaired Chylomicron Secretion Results in Reduced Body Fat and Increased Intestinal Fatty Acid Oxidation by Activation of Autophagy

Intestinal absorption of dietary lipid is essential for systemic lipid homeostasis; however, elevated postprandial plasma lipid levels are associated with obesity and increased risk for atherosclerotic cardiovascular disease. In humans and rodents, biological sex impacts dietary triglyceride absorption and males tend to have higher postprandial triglyceride levels compared to females, but the physiological basis for this is not well understood. Here, we show that the gene DENND5B is associated with body composition in humans and mice and that genetic deletion of Dennd5b in mice prevents postprandial plasma triglyceride elevations in both sexes. Our findings establish a role for this protein in intestinal chylomicron secretion and reveal a biological sex-biased differential impact of its deletion on body composition, dietary fatty acid uptake, and intestinal metabolism. Mechanistically, our findings implicate autophagy and mitochondrial beta oxidation in coping with enterocyte lipid accumulation due to impaired chylomicron secretion. This work extends the emerging concept that the intestinal epithelium may play a prominent role in oxidation of diet-derived fatty acids and suggests that this process may contribute to biological sex-based differences in postprandial lipemia and body composition. HighlightsO_LIThe DENND5B gene is required for dietary triglyceride absorption and is associated with metabolic phenotypes in humans and mice. C_LIO_LIDisruption of chylomicron secretion differentially affects body composition, dietary lipid absorption, and intestinal metabolic activity in male and female mice. C_LIO_LIIn mice, genetic disruption of Dennd5b results in lower body fat in both sexes, and increased lean mass only in males. C_LIO_LIMetabolic phenotypes in Dennd5b-deficient mice are driven by reduced absorption of dietary lipid characterized by enterocyte lipid retention and increased fecal lipid excretion. C_LIO_LIImpaired chylomicron secretion in Dennd5b-/- mice induces autophagy-mediated disposal of cellular triglyceride and increased fatty acid oxidation in intestinal tissue. C_LI

physiology↗

bioRxiv2023

A Four "Core Genotypes" rat model to distinguish mechanisms underlying sex-biased phenotypes and diseases

BackgroundPrevious research on Four Core Genotypes and XY* mice has been instrumental in establishing important effects of sex-chromosome complement that cause sex differences in physiology and disease. We have generated rat models using similar modifications of the testis-determining gene Sry, to produce XX and XY rats with the same type of gonad, as well as XO, XXY and XYY rats with varying gonads. The models permit discovery of novel sex-chromosome effects (XX vs. XY) that contribute to sex differences in any rat phenotype, and test for effects of different numbers of X or Y chromosomes. MethodsXY rats were created with an autosomal transgene of Sry, producing XX and XY progeny with testes. In other rats, CRISPR-Cas9 technology was used to remove Y chromosome factors that initiate testis differentiation, producing fertile XY gonadal females. Interbreeding of these lines produced rats with interesting combinations of sex chromosomes and gonads: XO, XX, XY, XXY rats with ovaries; and XO, XX, XY, XXY, and XYY rats with testes. These groups can be compared to detect sex differences caused by sex-chromosome complement (XX vs. XY) and/or by gonadal hormones (rats with testes vs. ovaries). Other comparisons detect the effects of X or Y chromosome number (in gonadal females: XO vs. XX, XX vs. XXY, XO vs. XY, XY vs. XXY; in gonadal males: XY vs. XXY, XY vs. XYY; XX vs. XXY, XO vs. XY). ResultsWe measured numerous phenotypes to characterize these models, including gonadal histology, breeding performance, anogenital distance, levels of reproductive hormones, body and organ weights, and central nervous system sexual dimorphisms. Serum testosterone levels were comparable in adult XX and XY gonadal males. Phenotypes previously known to be sexually differentiated by the action of gonadal hormones were found to be similar in XX and XY rats with the same type of gonad, suggesting that XX and XY rats with the same type of gonad have comparable levels of gonadal hormones at various stages of development. ConclusionThe results establish powerful new models to discriminate sex-chromosome and gonadal hormone effects that cause sexual differences in rat physiology and disease. Plain English SummaryThe Four Core Genotypes and XY* mouse models have been broadly useful for determining if sex differences in any mouse phenotype are caused by gonadal hormones, or by sex-chromosome complement (XX vs. XY), and if sex-chromosome effects are caused by X- or Y-linked mechanisms. Using gene knockout and transgenic methods, we have produced laboratory rat models that offer similar capabilities. The new rat models allow investigators to test with relative ease, for the first time, if a sex difference in a rat trait is caused by effects of XX vs. XY sex chromosomes, not mediated by effects of gonadal hormones, and to narrow the search for X or Y genes that have that role. The models produce XO, XX, XY, and XXY rats with ovaries, and XO, XX, XY, XXY, and XYY rats with testes. The four XX and XY groups represent a Four Core Genotypes rat model, comparison of which tests for sex-chromosome and gonadal hormonal effects that cause female and male rats to have different physiological or disease traits. Moreover, comparison of rats with different numbers of X chromosomes, or of Y chromosomes, but with the same type of gonad, provides evidence regarding the effects of X or Y dosage on rat traits. The new models will improve understanding of the impact of sex chromosomes on diseases or traits that are best modeled in rats. They will also improve understanding of the evolution of functional roles of sex chromosomes. HighlightsIt is advantageous to establish the factors that cause sex differences in diseases, because those factors mitigate or exacerbate diseases. We have produced new laboratory rats that have different types and numbers of sex chromosomes but the same type of gonad, allowing investigation of the role of sex chromosomes in causing sex differences in physiology and disease. The new rat lines allow comparison of XX and XY rats with the same type of gonad, to detect sex differences caused in part by the sex chromosomes. Other comparisons of rats with the same gonad but with different numbers of X chromosomes (XO vs. XX, XY vs XXY) or of Y chromosomes (XO vs. XY, XX vs. XXY, XY vs. XYY) detect effects of X or Y chromosome number. These resources can uncover sex-chromosome effects on any rat phenotype.

genetics↗

bioRxiv2022

The metabolite alpha-ketobutyrate increases health and life spans by activating AMPK

Aging is a complex process that is directly related to human health and disease. The extraordinary finding that aging is malleable, as shown in model organisms whose life and health spans are extended by specific gene mutations or dietary or pharmacological perturbations 1-3, has offered enormous hope for our understanding and treatment of aging and related diseases. Although many molecules have been identified that can extend the lifespan of model organisms, few have been shown to alleviate age-related symptoms or illness in mammals 4. Here we show that supplementation with the endogenous metabolite -ketobutyrate (-KB) increases the lifespan of adult C. elegans. Using Gelfree DARTS-PROTOMAP, we identified microtubule-actin cross-linking factor (MACF1) that was protected against proteolysis in the presence of -KB. MACF1 belongs to the spectraplakin family of giant, evolutionarily conserved proteins with versatile functions 5, but their link to longevity regulation has not been explored. -KBs longevity effect in C. elegans is abrogated by loss-of-function mutation in vab-10, encoding the worm ortholog of mammalian MACF1 6. Like -KB treatment, vab-10 knockdown activates AMP-activated protein kinase (AMPK), and AMPK is required for -KB effects on longevity. The findings suggest a model in which -KB increases longevity by activating AMPK via VAB-10/MACF1 modulation. -KB also delays aging in mammals, increasing the lifespan of aged male mice and the healthspan of both male and female animals. Targeting of broadly expressed scaffolding proteins in connection to cellular energy homeostasis seems to be a clever way that nature has devised for metabolite signals to impinge upon multiple organ and tissue systems, which may have utility for controlling aging and related diseases.

physiology↗

bioRxiv2022

X chromosome dosage drives statin-induced dysglycemia and mitochondrial dysfunction

Statin drugs lower blood cholesterol levels for cardiovascular disease prevention. Women are more likely than men to experience adverse statin effects, particularly new-onset diabetes (NOD) and muscle weakness. We determined that female mice are more susceptible than males to glucose intolerance, fasting hyperglycemia, and muscle weakness after short-term statin treatment. Lipidomic, transcriptomic, and biochemical analyses identified reduced docosahexaenoic acid (DHA) levels, and impaired redox tone and mitochondrial respiration specifically in statin-treated female mice. Statin adverse effects could be prevented in females by complementation with a source of DHA. Statin adverse effects segregated with XX chromosome complement, and specifically dosage of the Kdm5c gene, which regulates fatty acid gene expression and has differential expression levels in females and males. In humans, we found that women experience more severe reductions than men in DHA levels after short-term statin administration, and that DHA reduction was correlated with increases in fasting glucose levels. Furthermore, induced pluripotent stem cells derived from women, but not men, who developed NOD exhibited impaired mitochondrial function when treated with statin. Overall, our studies identify biochemical mechanisms, biomarkers, and a genetic risk factor for susceptibility to statin adverse effects, and point to DHA supplementation as a preventive co-therapy.

physiology↗

bioRxiv2021

CNTF enhances aerobic glycolysis and anabolic activities in degenerating retinas

Ciliary neurotrophic factor (CNTF) acts as a potent neuroprotective cytokine in multiple models of retinal degeneration. To understand mechanisms underlying its broad neuroprotective effects, we have investigated the influence of CNTF on metabolism in a mouse model of photoreceptor degeneration. CNTF treatment improves the morphology of photoreceptor mitochondria, but also leads to reduced oxygen consumption and suppressed respiratory chain activities. Molecular analyses show elevated glycolytic pathway gene transcripts and active enzymes. Metabolomics analyses detect significantly higher levels of ATP and the energy currency phosphocreatine, elevated glycolytic pathway metabolites, increased TCA cycle metabolites, lipid biosynthetic pathway intermediates, nucleotides, and amino acids. Moreover, CNTF treatment restores the key antioxidant glutathione to the wild type level. Therefore, CNTF significantly impacts the metabolic status of degenerating retinas by promoting aerobic glycolysis and augmenting anabolic activities. These findings reveal cellular mechanisms underlying enhanced neuronal viability and suggest potential therapies for treating retinal degeneration.

neuroscience↗

bioRxiv2020

Integrated analysis of a compendium of RNA-Seq datasets for splicing factors

A vast amount of public RNA-sequencing datasets have been generated and used widely to study transcriptome mechanisms. These data offer precious opportunity for advancing biological research in transcriptome studies such as alternative splicing. We report the first large-scale integrated analysis of RNA-Seq data of splicing factors for systematically identifying key factors in diseases and biological processes. We analyzed 1,321 RNA-Seq libraries of various mouse tissues and cell lines, comprising more than 6.6 TB sequences from 75 independent studies that experimentally manipulated 56 splicing factors. Using these data, RNA splicing signatures and gene expression signatures were computed, and signature comparison analysis identified a list of key splicing factors in Rett syndrome and cold-induced thermogenesis. We show that cold-induced RNA-binding proteins rescue the neurite outgrowth defects in Rett syndrome using neuronal morphology analysis, and we also reveal that SRSF1 and PTBP1 are required for energy expenditure in adipocytes using metabolic flux analysis. Our study provides an integrated analysis for identifying key factors in diseases and biological processes and highlights the importance of public data resources for identifying hypotheses for experimental testing.

bioinformatics↗

bioRxiv2019

Single Cell Analysis Reveals Immune Cell-Adipocyte Crosstalk Regulating the Transcription of Thermogenic Adipocytes

Immune cells are vital constituents of the adipose microenvironment that influence both local and systemic lipid metabolism. Mice lacking IL10 have enhanced thermogenesis, but the roles of specific cell types in the metabolic response to IL10 remain to be defined. We demonstrate here that selective loss of IL10 receptor in adipocytes recapitulates the beneficial effects of global IL10 deletion, and that local crosstalk between IL10-producing immune cells and adipocytes is a determinant of thermogenesis and systemic energy balance. Single Nuclei Adipocyte RNA-sequencing (SNAP-seq) of subcutaneous adipose tissue defined a metabolically-active mature adipocyte subtype characterized by robust expression of genes involved in thermogenesis whose transcriptome was selectively responsive to IL10R deletion. Furthermore, single-cell transcriptomic analysis of adipose stromal populations identified lymphocytes as a key source of IL10 production in response to thermogenic stimuli. These findings implicate adaptive immune cell-adipocyte communication in the maintenance of adipose subtype identity and function.

cell biology↗

bioRxiv2018

Hair regeneration by small molecules that activate autophagy

Hair plays important roles, ranging from the conservation of body heat to the preservation of psychological well-being. Hair loss or alopecia affects millions worldwide and can occur because of aging, hormonal dysfunction, autoimmunity, or as a side effect of cancer treatment (Gilhar et al., 2012; Petukhova et al., 2010). Methods that can be used to regrow hair are highly sought after, but lacking. Here we report that hair regeneration can be stimulated by small molecules that activate autophagy, including the longevity metabolites -ketoglutarate and -ketobutyrate, and the prescription drugs rapamycin and metformin which impinge on TOR and AMPK signaling.

developmental biology↗