Exercise Reverses Peripheral Insulin Resistance in Trained L-NAME–Hypertensive Rats

Abstract

Abstract-Several studies have demonstrated an increase in peripheral resistance to insulin associated with hypertension. To assess the hemodynamic and metabolic effects of exercise training, normotensive and N -nitro-L-arginine methyl ester (L-NAME)-hypertensive male Wistar rats were submitted to low-intensity treadmill exercise training for 10 weeks and compared with their sedentary controls. Blood pressure signals were obtained and processed with a data acquisition system (CODAS, 1 kHz) to evaluate mean arterial pressure, heart rate, autonomic control of heart rate, and baroreflex sensitivity. Exercise training induced a nonsignificant 6.5-mm Hg decrease in mean arterial pressure in trained hypertensive rats (163Ϯ9 mm Hg) compared with sedentary hypertensive rats (169.5Ϯ5.5 mm Hg). The hypertensive groups showed impairment of baroreflex function in response to changes in arterial pressure compared with sedentary controls. Furthermore, exercise training improved the tachycardic response to decreasing arterial pressure and reduced intrinsic heart rate in trained control rats compared with all other groups. Sedentary hypertensive rats presented a decrease in body weight compared with normotensive animals. Basal evaluation of the glucose/insulin ratio showed increased insulin resistance in sedentary (28.4Ϯ3) and trained (23.5Ϯ2.7) hypertensive rats compared with sedentary control rats (40.5Ϯ3). However, the glucose/insulin ratio evaluated during the exercise session in trained rats showed an improvement in insulin resistance (54.5Ϯ5 for control rats and 44Ϯ9 for hypertensive rats). In conclusion, L-NAME-induced hypertension is accompanied by an increase in insulin resistance in rats. The improvement in peripheral insulin sensitivity during exercise and the body weight gain observed in trained hypertensive rats may support the positive role of physical activity in the management of hypertension. Key Words: insulin resistance Ⅲ hypertension Ⅲ exercise Ⅲ autonomic nervous system Ⅲ baroreceptors H ypertension is a multifaceted medical and health problem related to morphological and functional changes in the cardiovascular system and autonomic control in humans and animals. 1 There is now convincing evidence that nitric oxide (NO) is an important molecular messenger that plays a critical role in vascular relaxation, neuronal transmission, and immune modulation. 2 The importance of NO for cardiovascular homeostasis is demonstrated by acute 3-5 and chronic 6 inhibition of NO synthase by N -nitro-L-arginine methyl ester (L-NAME), which leads to arterial hypertension. Changes in autonomic mechanisms 7,8 and baroreflex sensitivity 9,10 involved in cardiovascular control in hypertension induced by NO blockade have been observed. Moreover, several studies have suggested that NO blockade is frequently associated with changes in peripheral resistance to insulin action. 11-13 Previous studies have demonstrated that abrogation of NO release by an NO synthase inhibitor prevents the action of insulin involved in increasing blood fl...

Effect of exercise training on resistance arteries in rats with chronic NOS inhibition

“…Values are means Ϯ SE; n ϭ 6 -9 animals per group. 4-AP, 4-aminopyridine; L-NAME, N -nitro-l-arginine methyl ester; NE, norepinephrine; ODQ, 1H- (1,2,4) On the other hand, the responses to ACh were almost equally attenuated in all groups with the ODQ protocol (Fig. 4C).…”

“…The effect of exercise on NOS-blockage hypertension has not been investigated in detail, and limited data are available regarding this issue. In a study performed by d'Avila et al (4), a nonsignificant decrease in systolic blood pressure was observed in exercising rats under chronic NOS inhibition. The main focus of this study was investigation of insulin sensitivity in exercising rats with chronic NOS blockage.…”

Dynamic Aerobic Exercise Induces Baroreflex Improvement in Diabetic Rats

“…Regarding BRS, it is well known that exercise training improves baroreflex control of circulation in normotensive and diabetic in animals and humans [11–14, 25–28]. Figueiroa et al [29] have demonstrated that endurance exercise training reduced blood pressure without changes in heart rate variability (HRV) and BRS at rest, but training increased HRV and BRS during the recovery of acute endurance exercise, indicating an improved postexercise autonomic modulation of HR, which was similar in obese women with and without type 2 diabetes.…”

Habitual low-intensity exercise does not protect against myocardial dysfunction after ischemia in rats

“…Chronic treadmill exercise by rats at 55% VO 2 max is known to result in decreased sympathetic drive to the heart, lower blood pressure in hypertensive animals, and decreased insulin resistance [2][3][4]. Similarly, in humans this exercise intensity results in lower blood pressure and heart rate, improved lipid profile, decreased beta-adrenergic tone, improved insulin sensitivity, and decreased obesity [1].…”

“…Benefits arise from changes, both intrinsic and extrinsic, to the heart. Extrinsic changes observed in human and animal models include neural, hormonal, humoral, and obesity factors [1][2][3][4], while intrinsic changes include improved ability to tolerate acute stresses. Several investigators have reported that habitual exercise attenuates myocardial ischemia-reperfusion injury in rats [5][6][7][8][9][10][11][12][13][14][15].…”