Effects of Long‐term Voluntary Exercise on the Respiratory Muscles in Young Type 2 Diabetic Rats

Abstract

This study investigated the effects of long‐term voluntary exercise on the respiratory muscles in young type 2 diabetic rats. Twenty‐two Otsuka Long‐Evans Tokushima Fatty (OLETF) rats, a model of type 2 diabetes mellitus, and 18 non‐diabetic control Long‐Evans Tokushima Otsuka (LETO) rats were assigned randomly to sedentary or exercise groups subjected to 20 weeks of voluntary wheel running from 5 weeks of age. A strip of diaphragm was used to measure the contractile properties and the rest was frozen and stored for immunohistochemical analysis. The total running distance did not differ between groups. The voluntary exercise significantly reduced the fasting blood glucose and serum triglyceride in OLETF rats. The mean fiber cross‐sectional area (CSA) was significantly greater in OLETF rats at both 5 and 25 weeks of ages. Type IIb fibers comprised 4–8% in OLETF rats, while little or none was expressed in LETO rats. At 25 weeks of age, muscle force production in OLETF rats was significantly lower than in LETO rats at stimulation frequencies of 1 (OLETF: 6.86 ± 0.96, LETO: 8.16 ± 1.25 N/cm2) and 30 Hz (OLETF: 16.35 ± 0.69, LETO: 18.55 ± 1.56 N/cm2). There was a slight, but non‐significant, tendency for voluntary exercise to increase fiber CSA and force production. Our results indicated that voluntary exercise in the young can improve glucose tolerance and hyperlipidemia, but has little effect on respiratory muscle.This work was supported by grants from the MEXT‐Supported Program for the Strategic Research Foundation at Private Universities (S1101008).