Deletion of SGK1 in Smooth Muscle Cells Induces Sex-specific Differences in Obesity-mediated Metabolic Dysfunction and Adipose Tissue Remodeling

Abstract

Objectives: Obesity, characterized by an excess of adipose tissue, is an important risk factor for the development of metabolic diseases such as type 2 diabetes. In obesity, poor metabolic health is partly due to glucose intolerance, a condition in which whole-body glucose regulation is impaired. Adipose tissue is an endocrine organ central for optimal metabolic health and its expansion by excessive fat intake induces metabolic dysfunction. The molecular mechanisms that promote metabolic dysfunction in obesity are not fully understood. Adipose tissue function is dependent on the presence of new vascular networks capable of supplying nutrients and oxygen during adipose tissue expansion. Thus, pathological vascular remodeling may promote adipose tissue expansion and dysfunction in obesity. In this regard, our previous studies have shown that serum and glucocorticoid-inducible kinase 1 (SGK1) in vascular smooth muscle cells (vSMCs) mediates pathological vascular remodeling in obesity. SGK1 is a serine/threonine kinase that becomes elevated in the vasculature during obesity and is implicated in the development of metabolic syndrome. Therefore, we hypothesize that smooth muscle cell derived-SGK1 promotes pathological adipose tissue remodeling and metabolic dysfunction during obesity by perturbing adipose tissue vascularization. Methods: To test this hypothesis, these studies utilized our novel SMC-specific SGK1 knockout (smSGK1KO) mouse model to study the influence of SMC-derived SGK1 on adipose tissue remodeling and overall metabolic health in vivo. Male and female 8-week-old smSGK1WT and smSGK1KO mice were subjected to either a 10% low-fat diet (LF) or a high-fat diet (HF) for 8 weeks with weekly body weight measurements. Upon completion of respective diets, mice were subjected to glucose tolerance tests (GTT) to assess glucose tolerance and metabolic health. Adipose tissues from the subcutaneous (inguinal) and intra-abdominal (epididymal/gonadal) white adipose tissue (WAT) depots were harvested to assess overall adiposity and vascularization. Results: Our data show sexual dimorphism exists in the way smSGK1KO mice respond to a chronic high-fat diet. When fed a HF diet, female smSGK1KO mice gained approximately 60% more weight than their female smSGK1WT counterparts. In contrast, weight gain was about 50% lower in male smSGK1KO compared to male smSGK1WT mice on the same HF diet. Despite the differences in weight gain, inguinal and epididymal/gonadal WAT were reduced in male and female smSGK1KO mice fed a HF diet. Surprisingly, GTT was similar between female smSGK1KO and smSGK1WT mice, despite the increased weight gain, while male smSGK1KO mice displayed improvement in glucose tolerance in comparison to their wildtype counterparts. Moreover, male smSGK1KO mice appear to have enhanced vascularization in WAT depots as evidenced by increased vascular branching in fat pads. Conclusions: These studies suggest that SGK1 in smooth muscle cells contributes to adipose tissue remodeling and metabolic dysfunction under obesogenic conditions. Additionally, these studies indicate a need to understand the mechanisms by which crosstalk between the vasculature and adipose tissue modulates obesity and overall metabolic health. This research is supported in part by grant number 5U24DK132733-02 from the National Institute of Health, NIH. This research is supported in part by grant number 5T32HL007609-36 from the National Institute of Health, NIH. This research is supported in part by grant number 2100832 from the National Science Foundation, NSF. 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.