Endurance exercise does not protect the decrease in bone associated with Type 1 diabetes in adult rats

Abstract

Streptozotocin (STZ) induced type 1 diabetes mellitus (T1DM) decreases trabecular bone volume in mice. This study investigated the potential protective effects of endurance training (ET) on bone in STZ‐induced T1DM adult rats. Sixty four 8‐week old Sprague‐Dawley rats were randomly divided into 4 groups of 16: non‐T1DM sedentary (CS) and exercised (CX), T1DM sedentary (DS) and exercised (DX). Blood glucose was maintained at 9–15 mmol/L using subcutaneously implanted insulin pellets (Linplant, Linshin Canada, Inc.). ET was at ~75% VO2max for 1 h/d, 5 d/wk for 10 wk. Areal and volumetric bone mineral density (aBMD and vBMD; excised femur) was measured using dual‐energy x‐ray absorptiometry (DXA; QDR 4500A) and micro computed tomography (μCT; Aloka LCT200); bone strength was estimated using μCT. Two‐way ANOVA was used to test for diabetes and exercise differences; significance was set at P<0.05. T1DM had lower body weight (20.0%), aBMD (8.6%), cortical vBMD (1.6%), and bending (12.4%) and torsional strength (13.4%) vs control (P<0.001) with no differences in trabecular vBMD. Exercise also decreased body weight (4.7%) vs sedentary (P=0.019). These results suggest that 10 wk of ET does not have bone protective effects and T1DM rats have lower aBMD and vBMD than control, which may be secondary to effects on body weight. Funded by CIHR.