Exercise training favors increased insulin-stimulated glucose uptake in skeletal muscle in contrast to adipose tissue: A randomized study using FDG PET imaging

Physical exercise increases peripheral insulin sensitivity, but regional differences are poorly elucidated in humans. We investigated the effect of aerobic exercise training on insulin-stimulated glucose uptake in five individual femoral muscle groups and four different adipose tissue regions using dynamic (femoral region) and static (abdominal region) 2-deoxy-2-(18F)fluoro-D-glucose (FDG) PET/CT methodology during steady state insulin infusion (40 mU*m-2*min-1). Body composition was measured by Dual X-ray Absorptiometry and MRI. Sixty-one healthy, sedentary (VO2max: 36(5) ml*kg-1*min-1)(mean(SD)), moderately overweight (BMI: 28.1(1.8)), young (age: 30(6) years) men were randomized to sedentary living (CON; n=17 completers), moderate (MOD; 300 kcal/day, n=18) or high (HIGH; 600 kcal/day, n=18) dose physical exercise for 11 weeks. At baseline, insulin-stimulated glucose uptake was highest in femoral skeletal muscle followed by intraperitoneal visceral adipose tissue (VAT), retroperitoneal VAT, abdominal (anterior+posterior) subcutaneous adipose tissue (SAT) and femoral SAT (P<0.0001 between tissues). Metabolic rate of glucose increased similarly (~30%) in the two exercise groups in femoral skeletal muscle (MOD: 24[9; 39] µmol*kg-1*min-1, P=0.004; HIGH: 22[9; 35] µmol*kg-1*min-1, P=0.003) (mean[95% CI]) and in five individual femoral muscle groups but not in femoral SAT. Standardized Uptake Value of FDG decreased ~24% in anterior abdominal SAT and ~20% in posterior abdominal SAT when compared to CON but not in either intra- or retroperitoneal VAT. Total adipose tissue mass decreased in both exercise groups and the decrease was distributed equally among subcutaneous and intraabdominal depots. In conclusion, aerobic exercise training increases insulin-stimulated glucose uptake in skeletal muscle but not in adipose tissue, which demonstrates some interregional differences.