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

Abstract

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), β-hydroxy-acyl-CoA (β-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 insulinstimulation, pre-and post training. Results. The training-induced increase in VO 2 peak (~20%, 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 (~30%; p<0.01). TG m was increased in patients with Type 2 diabetes (170%; 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 β-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. Type 2 diabetes is characterized by skeletal muscle insulin resistance and impaired glucose metabolism. In addition to disturbances in glucose homeostasis, individuals with Type 2 diabetes have an impaired lipid metabolism, reflected by increased circulating free fatty acids [1], reduced rates of whole body fat oxidation [2] and excessive deposition of lipids in various tissues including skeletal muscle [3]. With regard to muscle lipid status, there is evidence in humans that increased trigacylglycerol (TG m ) concentration [3,4,5,6,7] and increased long-chain fatty acyl CoA (LCACoA) content are negatively associated with whole body insulin action [8]. Considering the rela-

Acute exercise increases insulin sensitivity in adult sheep: a new preclinical model

“…Importantly, exercise increased insulin sensitivity despite the ewes in the present study gaining significant body weight between preexercise and postexercise tests. This is consistent with the fact that exercise training increases insulin sensitivity before weight is lost in humans (6).…”

Leisure-time physical activity and type 2 diabetes during a 28 year follow-up in twins

“…More specifically, physical activity or exercise training has been shown to reduce visceral fat [33], improve skeletal muscle insulin sensitivity [37,38] and increase the oxidative capacity of skeletal muscle, which correlates with insulin sensitivity [39], and also leads to increased/modified fat oxidation, which is most likely to prevent lipid-mediated insulin resistance [40].…”

Adaptations to exercise training within skeletal muscle in adults with type 2 diabetes or impaired glucose tolerance: a systematic review

“…ES for each of the controlled trials was interpreted according to the method of Cohen [16]. from 18 studies including 3 randomized controlled trials reported in 9 publications [17][18][19][20][21][22][23][24][25] (2 trials reported in 8 publications with resistance training [17][18][19][20][21][22][23][24] and 1 with aerobic training [25]), 2 non-randomized controlled trials [26,27] (with aerobic training [26,27]) and 13 uncontrolled trials reported in 15 publications [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] (11 trials reported in 13 publications with aerobic training [28,[30][31][32][33][34][35][36][37][38]…”

“…In the randomized controlled trials and non-randomized controlled trials, all studies consisted of mixed gender cohorts [17][18][19][20][21][22][23][24][25][26][27]; in the uncontrolled trials, five studies published in six papers were in male cohorts [31,32,34,37,38,42], seven studies published in eight papers were in mixed cohorts [28][29][30]33,35,36,39,41] and one study did not report gender [40].…”

“…Except for one uncontrolled trial [33], all other studies of type 2 diabetes [17-24,27-29,31,32,34-36, 38-40,42] reported the subjects' diabetic medications. Among these studies, two trials reported in five papers included some or all subjects with insulin treatment [17][18][19][20]42]; subjects in the other 10 studies reported in 15 publications [21][22][23][24][27][28][29]31,32,[34][35][36][38][39][40] were treated only with oral agents or did not take diabetic medications. In studies including type 2 diabetes, 18% of subjects took insulin, 81% took oral agents, and 16% did not take diabetic medications.…”