305-OR: Short-Term Hyperglycemia Impacts Mouse Skeletal Muscle in a Sex-Specific Manner

Abstract

Cardiorespiratory Fitness (CRF) a universal predictor of cardiovascular and all-cause mortality, is lower in people with diabetes. Skeletal muscle is a key determinant of CRF, in particular mitochondrial content, function and oxygen extraction. Hyperglycemia is implicated in the dysfunction of microvascular blood flow. Our previous work demonstrated lower mitochondrial density/fiber and capillary mean flow velocity (MFV) with 4 weeks of hyperglycemia in males and females. Treadmill running resulted in greater capillary MFV and mitochondrial density in only hyperglycemic females. We hypothesize that along with alterations in mitochondrial density and blood flow, there is a disruption in skeletal muscle mitochondrial function with hyperglycemia, and that these parameters will respond to nitrite (NO2-) treatment in a sex-specific manner. We used a model of short-term hyperglycemia with tamoxifen inducible β-cell deletion of glucokinase. Two weeks after induction, blood flow in the gastrocnemius (gastroc) was measured using intravital microscopy, and the gastroc was collected from male (M) and female (F) mice with blood glucose >400mg/dl (HG) and euglycemic controls (EG). A subset of mice received NO2- treatment for 1-2 weeks prior to gastroc measurements. Immunofluorescence imaging of gastroc were analyzed for expression of COX1 (mitochondrial marker), Dystrophin (muscle fiber sarcolemma boundary), and CD31 (capillary marker). Mitochondrial respiration was measured in gastroc fibers using Oroboros O2k. Mitochondrial respiration was lower in HG compared to EG (p<0.0009), but only respiration in M appeared to respond to NO2- treatment (p=0.0252). No difference was observed in mitochondrial density in EG versus HG. Capillary MFV was greater with HG and mitigated by NO2-treatment. NO2- targets mitochondrial function by improving capillary blood flow, but only in males. Our combined data sets suggest HG-associated mitochondrial defects need to be treated in a sex-specific manner. Disclosure N.A.Hulett: None. L.Knaub: None. G.Pott: None. D.Ramirez: None. A.Johnston: None. R.L.Scalzo: None. J.E.B.Reusch: Advisory Panel; Medtronic. Funding U.S. Department of Veterans Affairs (BX002046, CX001532); National Institutes of Health (P30DK116073, 5T32AG000279-20)