The present study examined whether high-fat diet (HFD) consumption for 20 weeks had a temperature-specific effect on the contractile performance and regional thermal sensitivity of isolated mouse soleus and diaphragm muscle. Four-week-old female CD-1 mice were randomly selected to consume either a standard laboratory diet or a standard laboratory diet in conjunction with a HFD for 20 weeks. Peripheral soleus and core diaphragm were isolated from each animal and maximal isometric force and work loop power were assessed at 20, 28, 35 and 40°C. Increasing temperature to 35°C resulted in greater isometric stress, lower activation and relaxation time, and higher work loop power in both muscles. A further increase in temperature to 40°C did not affect isometric force but increased work loop power output of the soleus. Conversely, isometric force of the diaphragm was reduced and work loop power maintained when temperature was increased to 40°C. HFD consumption resulted in greater isometric force and absolute work loop power of the soleus and reduced isometric stress of the diaphragm, effects that were less apparent at lower temperatures. When the relationship between temperature and each measure of contractile function was examined by linear regression, there was no difference in slope between the control or HFD groups for either the soleus or diaphragm. These results indicate that whilst contractile function initially increases with temperature, the temperature to elicit maximal performance is muscle and contractile mode specific. Furthermore, HFD effects on contractile function are temperature specific, but HFD does not influence the relationship between temperature and performance.
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