Exercise-induced increase in skeletal muscle vasodilatory responses in obese Zucker rats

Abstract

The purpose of this study was to test the hypothesis that exercise training improves microvascular function in obese Zucker rats, a model of obesity and type II diabetes. Animals were divided into four age-matched groups: lean sedentary (LS), lean exercise (LE), obese sedentary (OS), and obese exercise (OE). The exercise groups were treadmill-exercised from 5 to 11 wk of age, including a 2-wk acclimation period. Mean arterial pressure (MAP) was not significantly different between any of the groups. The OS had significantly higher mean body weight, blood glucose, insulin, IL-6, and leptin levels compared with the LS, whereas the OE had significantly lower blood glucose, insulin, and IL-6 levels compared with the OS. Functional hyperemia and endothelial-dependent vasodilation were tested in the spinotrapezius muscle using intravital microscopy. Functional hyperemia and acetylcholine (0.1 microM, 1 microM, and 10 microM) responses were significantly attenuated in OS compared with the LS, while the contraction and ACh-induced (1 microM and 10 microM) vasodilation were significantly increased in both LE and OE compared with the sedentary animals. These results suggest that exercise training can improve vascular function in this model of type II diabetes. Moreover, the impaired vasodilation observed in 11-wk-old OZR suggests that the microvascular dysfunction is not likely due to an elevated blood pressure.

Exercise reduces oxidative stress but does not alleviate hyperinsulinemia or renal dopamine D1receptor dysfunction in obese rats

“…Furthermore, even in studies reporting an improvement in insulin sensitivity, there were no reductions in fasting plasma insulin concentrations (18,36,71). While our study involved 8 wk of exercise at 10 m/min, Xiang et al (74) exercised the rats for 4-5 wk at 24 m/min. However, the difference in intensity of exercise may not be responsible for the difference in the effect on insulin levels.…”

“…In a clinical trial involving children 8-14 yr of age, Reinehr et al (56) have reported that plasma leptin concentrations are a predictor of overweight reduction with a lifestyle intervention. Although we did not measure leptin levels, others (50,74) have reported that exercise does not reduce leptin levels in these rats.…”

“…This might have been responsible for the apparent lower blood pressures in both the lean and obese exercised groups. Xiang et al (74) have reported a decrease in insulin levels with exercise. However, a number of other studies have reported no reductions in plasma insulin levels with exercise in obese rats (11,14,19,33,35,63) as well as humans (64).…”

Exercise and the cytokines-interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α): A review

“…However, Xiang et al 19 showed that obese Zucker rats subjected to regular moderate exercise had lower IL-6 levels compared to obese sedentary rats. They also showed acetylcholineinduced vasodilatation was much more pronounced in the former group of rats.…”

Preserved coronary arteriolar dilatation in patients with type 2 diabetes mellitus: Implications for reactive oxygen species

“…Before the morphological changes take place [18,19,26,45,57], vasomotor dysfunction of microvessels may occur, which is considered to be one of the early alterations that occur in several cardiovascular diseases, as outlined by many recent reviews [9,11,12,29,32,44]. In humans with diabetes mellitus, impaired vasomotor function of the large conductance arteries is established [14].…”