Exercise and diet reduce muscle insulin resistance in obese Zucker rat

Abstract

Two treatments that increase skeletal muscle insulin action are exercise training and high-carbohydrate diet. The purpose of the present study was to determine whether exercise training and a diet high in carbohydrates could function synergistically to reduce the muscle insulin resistance in the obese Zucker rat. Obese rats 4 wk of age were randomly assigned to an exercise or sedentary group. Each group was subdivided by diet with one-half of the rats fed a high-carbohydrate diet and one-half fed a high-fat diet. Lean Zucker rats fed the high-fat diet were used as controls. Muscle insulin resistance was assessed during hindlimb perfusion with a submaximally stimulating concentration of insulin. Exercise training and the high-carbohydrate diet increased the rate of muscle glucose uptake in the obese rat by 46 and 53%, respectively. More importantly, the combined effect of exercise training and high-carbohydrate diet was greater than the sum of their individual effects. Glycogen synthesis paralleled glucose uptake and was the major pathway for intracellular glucose disposal. Muscle glucose uptake for exercise-trained, high-carbohydrate fed obese rats was comparable with that of lean controls. It is concluded that exercise training and the high-carbohydrate diet functioned synergistically to reduce the muscle insulin resistance in the obese rat.

Increased Fatty Acid Uptake and Altered Fatty Acid Metabolism in Insulin-Resistant Muscle of Obese Zucker Rats

“…However, because muscle FA uptake was higher in obese Zucker rats, total muscle FA oxidation was also found to be higher. These results agree with some but not all previously reported data (2,6). In incubated soleus muscle, basal glucose oxidation was found to be lower in obese Zucker rats compared with their lean counterparts, leading to the conclusion that muscle FA oxidation was reciprocally higher in obese rats (2).…”

“…In incubated soleus muscle, basal glucose oxidation was found to be lower in obese Zucker rats compared with their lean counterparts, leading to the conclusion that muscle FA oxidation was reciprocally higher in obese rats (2). Conversely, in perfused hindlimbs, insulin-stimulated glucose oxidation was found to be higher in obese than in lean Zucker rats; this suggests that FA oxidation was lower rather than higher in the muscles of the obese rats (6). However, it is important to remember that our data, like those of Crettaz et al (2), were collected under basal conditions and thus reflect the inherent ability of the insulin-resistant muscle.…”

“…Although defects in glucose metabolism have been well documented in this model of insulin resistance, changes in FA metabolism have only been inferred from changes in carbohydrate metabolism, thus leading to equivocal conclusions (2,6,7). Some researchers have suggested that muscle FA oxidation was increased (2,7) in obese Zucker rats, whereas others have suggested that muscle FA oxidation was decreased (6).…”

Mediation of ?-endorphin in exercise-induced improvement in insulin resistance in obese Zucker rats

“…These symptoms are similar to those observed in human type 2 diabetes, making these rats useful as an animal model for the study of this malady [12]. Insulin resistance in this animal is responsive to exercise training [13]. Thus, these rats served as a suitable model system for the present study.…”

Metformin and exercise reduce muscle FAT/CD36 and lipid accumulation and blunt the progression of high-fat diet-induced hyperglycemia

“…Exercise training has been shown to improve insulin-stimulated glucose transport in obese Zucker rats (11,28) up to 7 days after the last exercise bout (11). In the current study, the development of skeletal muscle insulin resistance was blunted, as indicated by improved insulin-stimulated glucose transport, as well as whole muscle and plasma membrane-associated GLUT4 protein expression.…”