Exercise improves cardiac function and attenuates insulin resistance in Dahl salt-sensitive rats.

BACKGROUND: The development of heart failure (HF) secondary to hypertension is a complex process related to a series of physiological and molecular factors including glucose dysregulation. The overall objective of this study was to investigate whether exercise training could improve cardiac function and insulin resistance in a rat model of hypertensive HF. METHODS: Seven week old Dahl salt-sensitive rats received either 8% NaCl (n = 30) or 0.3% NaCl (n = 18) diet. After a 5-week diet, animals were randomly assigned to exercise training (treadmill running at 18 m/min, 5% inclination for 60 min, 5 days/week) or kept sedentary for 6 additional weeks. 2D echocardiography was used to calculate left ventricular (LV) dimensions, volumes and global functional parameters. LV global deformation parameters were measured with speckle tracking echocardiography. Insulin resistance was assessed using 1h oral glucose tolerance testing. RESULTS: High salt diet led to cardiac hypertrophy and HF, characterized by increased wall thicknesses and LV volumes as well as reduced deformation parameters. In addition, high salt diet was associated with the development of insulin resistance. Exercise training improved cardiac function, reduced the extent of interstitial fibrosis and reduced insulin levels 60 min post-glucose administration. CONCLUSIONS: Even if not fully reversed, exercise training in HF animals improved cardiac function and insulin resistance. Adjusted modalities of exercise training might offer new insights not only as a preventive strategy, but also as a treatment for HF patients.

Impact of 24 Weeks of Resistance and Endurance Exercise on Glucose Tolerance in Persons with Multiple Sclerosis.

BACKGROUND: Recently, the authors reported an elevated prevalence of impaired glucose tolerance in individuals with multiple sclerosis (MS), compared with matched healthy controls, indicating metabolic defects that may increase comorbidity. MS also leads to a more inactive lifestyle, increasing the likelihood to develop fat accumulation, muscle wasting/weakness, and exercise intolerance. In other populations, these health complications can partly be reversed by physical exercise. OBJECTIVE: The aim of this study was to determine the impact of a mild-to-moderate-intensity exercise program on glucose tolerance, ranging between normal and impaired, in persons with MS. DESIGN: Persons with MS (mean expanded disability status scale, 3.3 ± 0.2; mean age, 48 ± 15 yrs) were randomized to an exercise group (n = 29) or a nonexercise control group (n = 15). Glucose tolerance, as well as muscle strength, exercise tolerance, and body composition to validate the applied exercise program, was determined in both groups at baseline and after 6, 12, and 24 wks of mild-to-moderate-intensity combined endurance and resistance training. RESULTS: No effects on blood glucose and serum insulin were detected. However, 6 mos of exercise improved muscle strength, exercise tolerance, and lean tissue mass within the intervention group as compared with baseline. In the control group, no changes were detected. CONCLUSION: Twenty-four weeks of mild-to-moderate-intensity combined endurance and resistance training was not able to improve glycemic control in this cohort of persons with MS. Future research is warranted to investigate the influence of higher exercise intensities on glucose tolerance, in an attempt to remediate metabolic deficits and to decrease the prevalence of comorbidities in MS.

Exercise training improves insulin release during glucose tolerance testing in stable chronic heart failure patients.

PURPOSE: Chronic heart failure (CHF) patients often present with (pre)diabetes, which negatively influences prognosis. Unlike the proven effect of exercise on glucose regulation in the general population, its effect in CHF is unclear. Therefore, this study aimed at investigating the effect of exercise training on glucose regulation in stable CHF patients. METHODS: Twenty-two CHF patients were randomized into training (EX, n = 15) and control (CON, n = 7) groups. Before and after a 12-week training intervention involving endurance and resistance training, glucose tolerance (2-hour oral glucose tolerance test), exercise tolerance (cardiopulmonary exercise test), muscle strength (isokinetic dynamometer), heart function (echocardiography), glycated hemoglobin, body composition (dual-energy x-ray absorptiometry), and quality of life (EQ5D) were assessed. RESULTS: At baseline, glucose levels 2 hours after glucose intake were elevated in both groups. Whereas area under the glucose curve did not change, area under the insulin curve decreased following training (EX, -13 ± 23% vs CON, +22 ± 33%; P < .05). Changes in the ratio of mitral peak velocity of early filling/early diastolic mitral annular velocity and waist-to-hip fat mass ratio were related to changes in the insulin curve. Exercise training resulted in improved oxygen uptake at the second ventilatory threshold (EX, +10 ± 5% vs CON, -8 ± 5%; P < .05) and isokinetic strength endurance of the upper leg (EX, +25 ± 9% vs CON, -6 ± 5%; P < 0.05). Lean body tissue was increased by 2.2 ± 0.5% in EX versus 0.2 ± 0.6% in CON (P < .05). CONCLUSION: Our data suggest that exercise training attenuates worsening of glucose regulation typically seen in a stable CHF population.