Effect of training on insulin sensitivity of glucose uptake and lipolysis in human adipose tissue

Training increases insulin sensitivity of both whole body and muscle in hum ans. To investigate whether training also increases insulin sensitivity of adipose tissue, we performed a three-step hyperinsulinemic, euglycemic clam p in eight endurance-trained (T) and eight sedentary (S) young men [insulin infusion rates: 10,000 (step I), 20,000 (step II), and 150,000 (step III) mu U . min(-1) . m(-2)]. Glucose and glycerol concentrations were measured in arterial blood and also by microdialysis in interstitial fluid in perium bilical, subcutaneous adipose tissue and in quadriceps femoris muscle (gluc ose only). Adipose tissue blood flow was measured by Xe-133 washout. In the basal state, adipose tissue blood flow tended to be higher in T compared w ith S subjects, and in both groups blood flow was constant during the clamp . The change from basal in arterial-interstitial glucose concentration diff erence was increased in T during the clamp but not in S subjects in both ad ipose tissue and muscle [adipose tissue: step I (n = 8), 0.48 +/- 0.18 mM ( T), 0.23 +/- 0.11 mM (S); step II (n = 8), 0.19 +/- 0.09 (T), -0.09 +/- 0.2 4 (S); step III (n = 5), 0.47 +/- 0.24 (T), 0.06 +/- 0.28 (S); (T: P < 0.00 1, S: P > 0.05); muscle: step I (n = 4), 1.40 +/- 0.46 (T), 0.31 +/- 0.21 ( S); step II (n = 4), 1.14 +/- 0.54 (T), -0.08 +/- 0.14 (S); step III (n = 4 ), 1.23 +/- 0.34 (T), 0.24 +/- 0.09 (S); (T: P < 0.01, S: P > 0.05)]. Inter stitial glycerol concentration decreased faster in T than in S subjects [ha lf-time: T, 44 +/- 9 min (n = 7); S, 102 +/- 23 min (n = 5); P < 0.05]. In conclusion, training enhances insulin sensitivity of glucose uptake in subc utaneous adipose tissue and in skeletal muscle. Furthermore, interstitial g lycerol data suggest that training also increases insulin sensitivity of li polysis in subcutaneous adipose tissue. Insulin per se does not influence s ubcutaneous adipose tissue blood flow.