Project description:The relationship between loss of hypothalamic function and onset of diabetes mellitus remains elusive. Therefore, we generated a targeted oxidative-stress murine model utilizing conditional knockout of selenocysteine-tRNA (Trsp) using rat insulin promoter-driven-Cre (RIP-Cre). These Trsp-knockout (TrspRIPKO) mice exhibit deletion of Trsp in both hypothalamic cells and pancreatic β-cells leading to increased hypothalamic oxidative stress and severe insulin resistance. Leptin signals were suppressed and numbers of proopiomelanocortin-positive neurons in the hypothalamus were decreased. In contrast, a Trsp-knockout mouse (TrspIns1KO) expressing Cre specifically in pancreatic β-cells, but not in the hypothalamus, did not display insulin and leptin resistance, demonstrating a critical role of the hypothalamus in the onset of diabetes mellitus. Nrf2 (NF-E2-related-factor-2) regulates antioxidant gene expression. Gene-driven increase in Nrf2 signaling suppressed hypothalamic oxidative stress and improved insulin and leptin resistance in TrspRIPKO mice. Thus, Nrf2 harbors the potential to prevent the onset of diabetic mellitus by reducing hypothalamic oxidative damage.
Project description:The relationship between loss of hypothalamic function and onset of diabetes mellitus remains elusive. Therefore, we generated a targeted oxidative-stress murine model utilizing conditional knockout of selenocysteine-tRNA (Trsp) using rat insulin promoter-driven-Cre (RIP-Cre). These Trsp-knockout (TrspRIPKO) mice exhibit deletion of Trsp in both hypothalamic cells and pancreatic β-cells leading to increased hypothalamic oxidative stress and severe insulin resistance. Leptin signals were suppressed and numbers of proopiomelanocortin-positive neurons in the hypothalamus were decreased. In contrast, a Trsp-knockout mouse (TrspIns1KO) expressing Cre specifically in pancreatic β-cells, but not in the hypothalamus, did not display insulin and leptin resistance, demonstrating a critical role of the hypothalamus in the onset of diabetes mellitus. Nrf2 (NF-E2-related-factor-2) regulates antioxidant gene expression. Gene-driven increase in Nrf2 signaling suppressed hypothalamic oxidative stress and improved insulin and leptin resistance in TrspRIPKO mice. Thus, Nrf2 harbors the potential to prevent the onset of diabetic mellitus by reducing hypothalamic oxidative damage.
Project description:Obesity is characterized by central leptin resistance. Celastrol has been identified to reduce leptin resistance in diet-induced obese and leptin resistant mice. Current microarray data provide the hypothalamic gene expression profiles from mice treated with Celastrol or Withaferin A.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Mitochondrial dysfunction has been reported in obesity and insulin resistance, but primary genetic mitochondrial dysfunction is generally not associated with these, arguing against a straightforward causal relationship. A rare exception, recently identified in humans, is a syndrome of lower body adipose loss, leptin-deficient severe upper body adipose overgrowth, and insulin resistance caused by the p.Arg707Trp mutation in MFN2, encoding mitofusin-2. How this selective perturbation of mitochondrial function leads to tissue- and adipose depot-specific growth abnormalities and systemic biochemical perturbation is unknown. To address this, Mfn2R707W/R707W knock-in mice were generated and phenotyped on chow and high fat diets. Electron microscopy revealed adipose-specific mitochondrial morphological abnormalities. Oxidative phosphorylation by isolated mitochondria was unperturbed, but the cellular integrated stress response was activated in adipose tissue. Fat mass and distribution, body weight, and systemic glucose and lipid metabolism were unchanged, however serum leptin and adiponectin concentrations, and their secretion from adipose explants were reduced. Pharmacological induction of the integrated stress response in wild-type adipocytes also reduced secretion of leptin and adiponectin, suggesting an explanation for the in vivo findings. These data suggest that the p.Arg707Trp MFN2 mutation perturbs mitochondrial morphology and activates the integrated stress response selectively in adipose tissue. In mice, this does not disrupt most adipocyte functions or systemic metabolism, whereas in humans it is associated with pathological adipose remodelling and metabolic disease. In both species, disproportionate effects on leptin secretion may relate to cell autonomous induction of the integrated stress response.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.