Altered contractile properties of fast and slow skeletal muscles from db/db mice (1102.16)

Abstract

In the db/db mouse, leptin receptor mutation results in a model of metabolic syndrome. Initial hyperinsulinemia brought on by hyperphagia is followed by peripheral insulin resistance, elevated blood glucose and increased body weight. The purpose of this study was to determine the skeletal muscle contractile properties in the BKS.Cg‐Dock7m +/+Leprdb/J mouse model of metabolic syndrome (i.e. db/db mouse). Muscle contractile properties were determined ex vivo in the fast extensor digitorum longus (EDL) muscle and the slow soleus muscle in 17 week old mice. Body weight was 43% greater in db/db mice compared to wild type control mice. Soleus muscle mass was 49% lower and EDL muscle mass was 55% lower in the db/db mouse. EDL twitch force was 58% lower than control with an associated 20% longer contraction time and 25% longer 1/2 relaxation time. There were no differences in soleus twitch force. However, contraction time was 1.7‐fold longer and 1/2 relaxation time was 1.6‐fold longer than control. The force‐frequency relationship in the soleus muscle was significantly shifted to the left toward lower stimulation frequencies, with no differences in the EDL. The rate of force loss with repeated contractions was also consistent with a less oxidative profile in both muscle types. Collectively, these data demonstrate the effects of risk factors for metabolic syndrome on muscle contractile properties in the db/db mouse.