Exogenous detection of 13C-glucose metabolism in tumor and diet-induced obesity models

Analysis of Exosomal miRNA and Hepatic mRNA Expression in the Dysregulation of Insulin Action in Perimenopausal Mice

Introduction: The aim of present study was to evaluate the impact of perimenopause on insulin resistance. Specifically, insulin sensitivity was assessed in a perimenopausal mouse model treated with 4-vinylcyclohexene diepoxide (VCD), together with the changes in exosomal miRNA and hepatic mRNA expression profiles. Methods: Homeostasis model assessment of insulin resistance (HOMA-IR) was utilized to assess the status of insulin resistance, and insulin action was evaluated during menopausal transition. RNA sequencing (RNA-seq) analysis was used to identify altered expression profiles of exosomal miRNAs and hepatic mRNAs. Differentially expressed miRNA (DEM)-differentially expressed gene (DEG) network analyses were also conducted. Furthermore, altered expression levels of these exosomal miRNAs and genes were validated in plasma exosomes and liver tissue of perimenopausal mice. Results: HOMA-IR in VCD-treated mice was significantly increased, and hepatic glycogen was significantly decreased. Key exosomal miRNAs (miR-17-3p, miR-134-5p, miR-700-5p, and miR-6899-3p) and hepatic genes (G6pdx, Ptpn2, Lepr, Kras, and Braf) may be associated with impaired insulin signaling during perimenopause. Conclusion: The perimenopausal period acts as a potential factor in introducing insulin resistance as evidenced by impaired insulin action and altered expression profiles of exosomal miRNAs and hepatic genes. The present study contributes to the understanding that abnormal cargos carried by plasma exosomes, such as miRNAs, may be related to altered expression of the corresponding genes in the liver and abnormal insulin response.

Metabolic plasticity and obesity-associated changes in diurnal postexercise metabolism in mice

BACKGROUND

Circadian disruption is widespread and increases the risk of obesity. Timing of therapeutic interventions may promote coherent and efficient gating of metabolic processes and restore energy homeostasis.

AIM

To characterize the diurnal postexercise metabolic state in mice and to identify the influence of diet-induced obesity on identified outcomes.

METHODS

C57BL6/NTac male mice (6 wks of age) were fed a standard chow or high-fat diet for 5 weeks. At week 5, mice were subjected to a 60-min (16 m/min, 5 % incline) running bout (or sham) during the early rest (day) or early active (night) phase. Tissue and serum samples were collected immediately post-exercise (n = 6/group). In vivo glucose oxidation was measured after oral administration of 13C-glucose via 13CO2 exhalation analysis in metabolic cages. Basal and isoproterenol-stimulated adipose tissue lipolysis was assessed ex vivo for 1 h following exercise.

RESULTS

Lean mice displayed exercise-timing-specific plasticity in metabolic outcomes, including phase-specificity in systemic glucose metabolism and adipose-tissue-autonomous lipolytic activity depending on time of day. Conversely, obesity impaired temporal postexercise differences in whole-body glucose oxidation, as well as the phase- and exercise-mediated induction of lipolysis in isolated adipose tissue. This obesity-induced alteration in diurnal metabolism, as well as the indistinct response to exercise, was observed concomitant with disruption of core clock gene expression in peripheral tissues.

CONCLUSIONS

Overall, high-fat fed obese mice exhibit metabolic inflexibility, which is also evident in the diurnal exercise response. Our study provides physiological insight into exercise timing-dependent aspects in the dynamic regulation of metabolism and the influence of obesity on this biology.