Impact of short-term exercise training intensity on β-cell function in older obese adults with prediabetes.

The effect of work-matched exercise intensity on β-cell function is unknown in people with prediabetes before clinical weight loss. We determined if short-term moderate continuous (CONT) vs. high-intensity interval (INT) exercise increased β-cell function. Thirty-one subjects (age: 61.4 ± 2.5 yr; body mass index: 32.1 ± 1.0 kg/m2) with prediabetes [American Diabetes Association criteria, 75-g oral glucose tolerance test (OGTT)] were randomized to work-matched CONT (70% HRpeak) or INT (3 min 90% HRpeak and 3 min 50% HRpeak) exercise for 60 min/day over 2 wk. A 75-g 2-h OGTT was conducted after an overnight fast, and plasma glucose, insulin, C-peptide, and free fatty acids were determined for calculations of skeletal muscle [oral minimal model (OMM)], hepatic (homeostatic model of insulin resistance), and adipose (Adipose-IR) insulin sensitivity. β-Cell function was defined from glucose-stimulated insulin secretion (GSIS, deconvolution modeling) and the disposition index (DI). Glucagon-like polypeptide-1 [GLP-1(active)] and glucose-dependent insulinotropic polypeptide (GIP) were also measured during the OGTT, along with peak oxygen consumption and body composition. CONT and INT increased skeletal muscle- but not hepatic- or adipose-derived DI ( P < 0.05). Although both treatments tended to reduce fasting GLP-1(active) ( P = 0.08), early phase GLP-1(active) increased post-CONT and INT training ( P < 0.001). Interestingly, CONT exercise increased fasting GIP compared with decreases in INT ( P = 0.02). Early and total-phase skeletal muscle DI correlated with decreased total glucose area under the curve ( r = -0.52, P = 0.002 and r = -0.50, P = 0.003, respectively). Independent of intensity, short-term training increased pancreatic function adjusted to skeletal muscle in relation to improved glucose tolerance in adults with prediabetes. Exercise also uniquely affected GIP and GLP-1(active). Further work is needed to elucidate the dose-dependent mechanism(s) by which exercise impacts glycemia. NEW & NOTEWORTHY Exercise is cornerstone for reducing blood glucose, but whether high-intensity interval training is better than moderate continuous exercise is unclear in people with prediabetes before weight loss. We show that 2 wk of exercise training, independent of intensity, increased pancreatic function in relation to elevated glucagon-like polypeptide-1 secretion. Furthermore, β-cell function, but not insulin sensitivity, was also correlated with improved glucose tolerance. These data suggest that β-cell function is a strong predictor of glycemia regardless of exercise intensity.