TBC1D1 Ser237 phosphorylation, but not insulin sensitivity, is higher following a bout of high-intensity interval exercise in healthy males as compared with females

Abstract

Interval training has been found to lower glucose concentrations and increase insulin sensitivity in males but not in females, which may be due to inherent sex-based differences in metabolism. Twenty-four (12/sex) participants completed a bout of high-intensity interval exercise (HIIE, 10 × 1 min at 90% HR_max) to evaluate whether sex influenced the physiological effects of HIIE on postexercise glycemic control during an oral glucose tolerance test (OGTT). Given that body anthropometrics influence postprandial glucose, data were also expressed as a function of the normalized glucose dose. In addition, we examined whether sex differences in postexercise glycemic control were related to sex differences in muscle metabolism and/or insulin signaling proteins. HIIE increased insulin sensitivity in both sexes as characterized by the Matsuda (P = 0.03, η_p²= 0.20) and HOMA-IR (P = 0.047, η_p² = 0.17) indices. HIIE also lowered insulin concentration during the OGTT (P = 0.04, η_p² = 0.18) as compared with control. When normalized for glucose dose relative to lean mass, glucose area under the curve (AUC) was lower in females than in males (P ≤ 0.001, η_p² = 0.47). TBC1D1 Ser²³⁷ phosphorylation increased in males, but not in females, postexercise (P = 0.03, η_p² = 0.19). There was no difference in total insulin signaling protein content, muscle glycogen utilization, or AMPK activation during exercise between the sexes. These findings indicate that when the glucose dose is normalized for differences in body composition glycemic handling is better in females and that an acute bout of HIIE improves insulin sensitivity equally in healthy males and females.

Keywords: TBC1D1; high-intensity interval exercise; insulin sensitivity; muscle metabolism; sex-based differences.