Functional Exercise Capacity (FEC) , a universal predictor of cardiovascular and all-cause mortality, is lower in adults and youth with diabetes for reasons that are poorly understood. Skeletal muscle is key determinant of FEC. We hypothesized that skeletal muscle capillary and mitochondrial density are lower with hyperglycemia and respond to exercise training. To test this hypothesis we generated a model of short-term hyperglycemia (HG) with inducible beta cell deletion of glucokinase (GKlox/lox;PdxCreER) . Male (M) and female (F) HG mice and euglycemic littermate controls (EG) completed 3 weeks of treadmill training (Ex) or remained sedentary (Sed) . The gastrocnemius was collected 24 hours after the final exercise bout. Expression of COX1 (mitochondrial marker) , Dystrophin (muscle fiber sarcolemma boundary marker) , and CD31 (capillary marker) was detected by immunofluorescence. Sirtuin 3 (SIRT3) , an NAD+ dependent deacetylase (mitochondrial homeostasis) was measured using the JESS system. (Fig 1) Mitochondrial density (mitochondria per fiber as quantified by fluorescence intensity units per fiber [FIU/fiber]) was significantly lower in HG vs. EG (p<0.0001) and differed by sex (p=0.0048 sex x glycemia interaction) . Ex resulted in greater mitochondrial density (p=0.0265) independent of sex and glycemia. Capillary density and SIRT3 were unchanged. Sex-differences in muscle response to HG warrant further investigation.
L.Knaub: None. G.Pott: None. N.A.Hulett: None. S.Hull: None. R.L.Scalzo: None. J.Reusch: Advisory Panel; Medtronic.
VA Merit (BX002046)