Disassociation of muscle triglyceride content and insulin sensitivity after exercise training in patients with Type 2 diabetes

AIM/HYPOTHESIS - We determined the effect of exercise training on insulin sensitivity and muscle lipids (triglyceride [TG(m)] and long-chain fatty acyl CoA [LCACoA] concentration) in patients with Type 2 diabetes. METHODS - Seven patients with Type 2 diabetes and six healthy control subjects who were matched for age, BMI, % body fat and VO(2)peak participated in a 3 days per week training program for 8 weeks. Insulin sensitivity was determined pre- and post-training during a 120 min euglycaemic-hyperinsulinaemic clamp and muscle biopsies were obtained before and after each clamp. Oxidative enzyme activities [citrate synthase (CS), beta-hydroxy-acyl-CoA (beta-HAD)] and TG(m) were determined from basal muscle samples pre- and post training, while total LCACoA content was measured in samples obtained before and after insulin-stimulation, pre- and post training. RESULTS - The training-induced increase in VO(2)peak (similar to20%, p < 0.01) was similar in both groups. Compared with control subjects, insulin sensitivity was lower in the diabetic patients before and after training (∼60%; p < 0.05), but was increased to the same extent in both groups with training (similar to30%; p < 0.01). TG(m) was increased in patients with Type 2 diabetes (1.70%; p < 0.05) before, but was normalized to levels observed in control subjects after training. Basal LCACoA content was similar between groups and was unaltered by training. Insulin-stimulation had no detectable effect on LCACoA content. CS and P-HAD activity were increased to the same extent in both groups in response to training (p < 0.001). CONCLUSION/INTERPRETATION - We conclude that the enhanced insulin sensitivity observed after short-term exercise training was associated with a marked decrease in TG(m) content in patients with Type 2 diabetes. However, despite the normalization of TG(m) to levels observed in healthy individuals, insulin resistance was not completely reversed in the diabetic patients