Improvement of Insulin Sensitivity by Short-term Exercise Training in Hypertensive African American Women

Abstract

Abstract African American women have a high prevalence of insulin resistance, non–insulin-dependent diabetes mellitus, obesity, and hypertension that may be linked to low levels of physical activity. We sought to determine whether 7 days of aerobic exercise improved glucose and insulin metabolism in 12 obese (body fat >35%), hypertensive (systolic blood pressure ≥140 and/or diastolic blood pressure ≥90 mmHg) African American women (mean age 51±8 years). Insulin-assisted frequently-sampled intravenous glucose tolerance tests were performed at baseline and 14 to 18 hours after the 7th exercise session. There was no significant change in maximal oxygen consumption, body composition, or body weight after the 7 days of aerobic exercise. The insulin sensitivity index increased (2.68±0.45 · 10 −5 to 4.23±0.10 · 10 −5 [min −1 /pmol/L], P =.02). Fasting (73±9 to 50±9 pmol/L, P =.02) and glucose-stimulated (332±58 to 261±45 pmol/L, P =.05) plasma insulin levels decreased. Additional measures related to the insulin resistance syndrome also changed with the 7 days of exercise: basal plasma norepinephrine concentrations were reduced (2.46±0.27 to 1.81±0.27 nmol/L, P =.02) and sodium excretion rate increased from 100±13 to 137±7 mmol/d ( P =.03); however, there was no change in potassium excretion or 24-hour ambulatory blood pressure. We conclude that a short-term aerobic exercise program improves insulin sensitivity in African American hypertensive women independent of changes in fitness levels, body composition, or body weight. The present study indicates that short-term exercise can improve insulin resistance in hypertensive, obese, sedentary African American women and confirms previous reports that a portion of the exercise-induced improvements in glucose and insulin metabolism may be the result of recent exercise.