SerpinA3N in Leptin Receptor Neurons Regulates Metabolic and Glucose Homeostasis

Abstract

Obesity and associated conditions such as type 2 diabetes are among the most concerning issues for health in the U.S. Leptin receptor signaling in the brain plays a pivotal role in the regulation of food intake and energy expenditure. High fat diet induces inflammation within the hypothalamus, leading to leptin insensitivity which contribute to obesity. Previous studies have shown that a novel gene SerpinA3N, a serine protease inhibitor, which is highly expressed in the arcuate nucleus of the hypothalamus, where the leptin receptor is also highly expressed, is upregulated in diet-induced obesity and by leptin stimulation. However, the role of SerpinA3N in the leptin receptor expressing cells in the control of body weight and glucose homeostasis remain unknown. RNAseq analysis showed that SerpinA3N mRNA levels were significantly upregulated in the hypothalamus of mice fed high fat high sucrose diet (HFHSD) for 12 weeks. Upregulation of hypothalamic SerpinA3N in HFHSD fed mice was confirmed by Western blot. This increase in hypothalamic SerpinA3N appears to be caused by excess of nutrient as we found that exposure to fatty acid significantly increased SerpeinA3N promoter activity in mouse hypothalamic N39 cells. Using immunofluorescence staining, we confirmed that SerpinA3N is expressed the leptin receptor positive cells of the hypothalamus. Next, we investigated whether loss of SerpinA3N in leptin receptor expressing neurons affects metabolic and glucose homeostasis. For this, we crossed mice harboring floxed alleles of the SerpinA3N gene (SerpinA3Nfl/fl) with mice expressing Cre recombinase in leptin receptor cells (LepRCre). We found that female, but not male, conditional knockout (CKO, LepRCre/SerpinA3Nfl/fl) mice have significantly lower body weight when fed normal chow or HFHSD. This lower body weight was due to decreased fat mass, measured by NMR. However, no alteration in food intake was observed between female CKO mice and controls, indicating that increased energy expenditure may account for the lower body weight in female CKO mice. Interestingly, CKO mice displayed exaggerated weight loss and anorectic response following leptin treatment (1 mg/g, twice daily, IP), indicating that loss of SerpinA3N enhances leptin sensitivity. Female CKO mice fed normal chow diet also exhibited enhanced insulin sensitivity compared to control animals. On the other hand, male CKO mice displayed significantly improved glucose handling, but not change in insulin sensitivity, only when fed HFHSD. Finally, insulin-induced phosphorylation of AKT was elevated in skeletal muscle, but not in liver and white adipose tissue, of CKO mice relative to controls. These results demonstrate that SerpinA3N in leptin receptor-expressing neurons regulate body weight and glucose homeostasis in a sex-dependent manner. NIH and VA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.