Abstract P3038: Upregulation Of The Mitochondrial Calcium Uniporter Abolishes Mitochondrial Dysfunction Associated With Obesity In Vascular Smooth Muscle Cells

Abstract

Obesity is a growing national epidemic that is associated with an increased prevalence of arterial disease. We found that aortic medial hypertrophy during obesity was accompanied by upregulation of serum and glucocorticoid-inducible kinase 1 (SGK1) and reduced mitochondrial oxidative capacity of vascular smooth muscle cells (VSMC). Interestingly, VSMC-specific deletion of SGK1 attenuated obesity-related aortic remodeling and restored mitochondrial oxidative capacity in VSMC implicating a mediator role for SGK1 in mitochondrial dysfunction during obesity. The mechanistic basis for impaired mitochondrial respiration during obesity in VSMC is unknown. Thus, due to its fundamental role in stimulation of mitochondrial oxidative phosphorylation, the current study will investigate the mitochondrial calcium uniporter (MCU) in obesity-related mitochondrial dysfunction in VSMC. As SGK1 is known to regulate the expression and/or activity of ion channels, we hypothesize that upregulation of SGK1 during obesity negatively regulates MCU expression, mitochondrial oxidative activity, and ATP production. MCU protein levels were assessed by western blot analysis. Mitochondrial oxidative activity and ATP production rate were measured using the Agilent Seahorse XF Cell Mito Stress Test and the ATP Rate Assay, respectively in cultured wildtype and SGK1 knockout aortic VSMC from low-fat (LF) control and high-fat (HF) obese mice. To assess the importance of MCU, both assays were performed in the presence or absence of the MCU inhibitor, Ru360. Obesity caused a significant decrease in MCU abundance, but SGK1 deletion resulted in enrichment of MCU in VSMC. Ru360 treatment reversed the increase in basal mitochondrial respiration. We found that obesity reduced overall ATP production by diminishing ATP production from glycolysis and mitochondrial respiration. However, SGK1 deletion enhanced ATP production from glycolysis and mitochondrial respiration during obesity and this effect was attenuated by Ru360. These findings demonstrate that SGK1 negatively regulates MCU expression and activity and imply that augmentation of MCU-driven mitochondrial oxidative activity may underlie the protective effects of SGK1 inhibition on the vascular during obesity.