Effects of diet and exercise on muscle and liver intracellular lipid contents and insulin sensitivity in type 2 diabetic patients.
ABSTRACT Insulin resistance is associated with the circulating free fatty acid (FFA) level and intracellular lipid content in muscle and liver. We investigated the effect of 2-wk diet and exercise therapy on total adiposity, circulating FFA, intracellular lipid content in muscle and liver, and peripheral insulin sensitivity. Type 2 diabetic patients were divided into a diet group (n = 7) and a diet plus exercise group (n = 7). We performed a hyperinsulinemic-euglycemic clamp study before and after treatment. Intramyocellular lipid (IMCL) in the tibialis anterior muscle and intrahepatic lipid (IHL) were evaluated by (1)H-magnetic resonance spectroscopy. Fasting FFA were not altered, and total body fat showed a slight, but significant, decrease in both groups after treatment. IMCL was decreased by 19%, and the glucose infusion rate was increased by 57% in the diet plus exercise group, whereas neither IMCL nor glucose infusion rate was significantly altered in the diet group. However, IHL showed a significant decrease in both groups. In summary, we found that 2 wk of diet and exercise decreased IMCL and increased muscle insulin-mediated glucose uptake, whereas diet with or without exercise decreased IHL. These effects were evident despite a small decrease in body fat and were observed independently of fasting FFA levels.
Article: Short-term exercise training does not stimulate skeletal muscle ATP synthesis in relatives of humans with type 2 diabetes.[show abstract] [hide abstract]
ABSTRACT: We tested the hypothesis that short-term exercise training improves hereditary insulin resistance by stimulating ATP synthesis and investigated associations with gene polymorphisms. We studied 24 nonobese first-degree relatives of type 2 diabetic patients and 12 control subjects at rest and 48 h after three bouts of exercise. In addition to measurements of oxygen uptake and insulin sensitivity (oral glucose tolerance test), ectopic lipids and mitochondrial ATP synthesis were assessed using(1)H and(31)P magnetic resonance spectroscopy, respectively. They were genotyped for polymorphisms in genes regulating mitochondrial function, PPARGC1A (rs8192678) and NDUFB6 (rs540467). Relatives had slightly lower (P = 0.012) insulin sensitivity than control subjects. In control subjects, ATP synthase flux rose by 18% (P = 0.0001), being 23% higher (P = 0.002) than that in relatives after exercise training. Relatives responding to exercise training with increased ATP synthesis (+19%, P = 0.009) showed improved insulin sensitivity (P = 0.009) compared with those whose insulin sensitivity did not improve. A polymorphism in the NDUFB6 gene from respiratory chain complex I related to ATP synthesis (P = 0.02) and insulin sensitivity response to exercise training (P = 0.05). ATP synthase flux correlated with O(2)uptake and insulin sensitivity. The ability of short-term exercise to stimulate ATP production distinguished individuals with improved insulin sensitivity from those whose insulin sensitivity did not improve. In addition, the NDUFB6 gene polymorphism appeared to modulate this adaptation. This finding suggests that genes involved in mitochondrial function contribute to the response of ATP synthesis to exercise training.Diabetes 04/2009; 58(6):1333-41. · 8.29 Impact Factor
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ABSTRACT: Recent research on the effectiveness of training interventions indicates major alterations of hepatic lipid metabolism and suggests a substantial and beneficial adaptation of the liver to regular physical activity in humans. However, while various' data demonstrate the response of the working skeletal muscle to acute exercise and training, considerably less is known about the molecular events in the liver during and after increased physical activity. Here we discuss recent studies performed in rodents, that elucidate the acute hepatic response to one single bout of exercise with particular emphasis on stress response-related pathways. The acute transcriptional response to one exercise bout comprises three-times more hepatic transcripts than those expressed in soleus muscle, with a significantly more pronounced up- or downregulation of hepatic genes. Evaluation of the affected pathways shows that the liver responds to acute exercise with a rapid activation of the mitogen-activated protein kinase (MAPK) signalling pathway, of the p53 protein, and of interleukin (IL)-6-type cytokine signalling pathways, resulting in a marked transcriptional upregulation of stress response genes (e.g., transcription factors of the Fos/Jun-family, growth arrest and DNA damage (GADD)45gamma, and p53-target genes) and genes typically induced by energy depletion, e.g., insulin-like growth factor binding protein (IGFBP)-1, peroxisome proliferator-activated receptor coactivator (PGC)1alpha. One explanation for the marked differential expression of hepatic genes immediately after exercise is the induction of energetic stress. After non-exhaustive exercise energy depletion predominantly occurs in the liver not as much in the working muscle, and during exercise, the liver is exposed to altered concentrations of insulin and glucagon in the portal vein. Furthermore, lower plasma glucose levels post-exercise are related to increased expression levels of stress response genes. It appears that the unique function of the liver to supply glucose for the working muscle renders this organ especially susceptible for exercise-induced cellular stress that leads to the marked induction of defense adaptations. These results give rise to the question whether these molecular events are linked not only to stress defense but to the metabolic adaptations of the liver to exercise.Exercise immunology review 01/2010; 16:163-83. · 2.79 Impact Factor