Effects of exercise training intensity on pancreatic beta-cell function.

OBJECTIVE: Insulin resistance and beta-cell dysfunction both are important contributors to the pathogenesis of type 2 diabetes. Exercise training improves insulin sensitivity, but its effects on beta-cell function are less well studied. RESEARCH DESIGN AND METHODS: Sedentary, overweight adults were randomized to control or one of three 8-month exercise programs: 1) low amount/moderate intensity, 2) low amount/vigorous intensity, or 3) high amount/vigorous intensity. Of 387 randomized, 260 completed the study and 237 had complete data. Insulin sensitivity (S(i)), acute insulin response to glucose (AIRg), and the disposition index (DI = S(i) x AIRg) were modeled from an intravenous glucose tolerance test. RESULTS: Compared with control subjects, all three training programs led to increases in DI. However, the moderate-intensity group experienced a significantly larger increase in DI than either of the vigorous-intensity groups and through a different mechanism. The high-amount/vigorous-intensity group improved S(i) and had a compensatory reduction in AIRg, whereas the moderate-intensity group had a similar improvement in S(i) but almost no reduction in AIRg. Importantly, the inactive control group experienced a significant increase in fasting glucose. CONCLUSIONS: To the extent that the DI accurately reflects beta-cell function, we observed that both moderate- and vigorous-intensity exercise training improved beta-cell function, albeit through distinct mechanisms. It is not clear which of these mechanisms is preferable for maintenance of metabolic health. While moderate-intensity exercise led to a larger improvement in DI, which may reflect a transition toward a more normal DI, longer-term investigations would be necessary to determine which was more effective at reducing diabetes risk.

Duke Scholars

Author William Erle Kraus Medicine, Cardiology

Author Kim Marie Huffman Medicine, Rheumatology and Immunology