Inflammatory Response of Skeletal Muscles to a High-Fat Diet

Background. The prolonged consumption of a high-fat diet (HFD) leads to abnormal growth of the adipose tissue, development of obesity and low-grade inflammation. However, the data about dietary-induced inflammation in muscles is scarce. Therefore, we estimated the inflammatory response to a HFD of different skeletal muscles in a rat model.Materials and methods. Eight-week-old male Wistar rats were subjected to a high-fat (n = 36) or standard diet (n = 24). After fourteen weeks, tissue samples were collected from twelve animals from each group. To assess the effect of diet duration, twelve of the remaining animals from the experimental group were then subjected to a standard diet, while all the other animals continued with their previous diet for four more weeks. The levels of the pro-inflammatory markers CRP and serum amyloid-A (SAA) and the anti-inflammatory IL-4 were determined by ELISA in tissue homogenates from gastrocnemius, soleus and extensor digitorum longus (EDL) muscles.Results. In general, the HFD elevated slightly muscle levels of the acute phase proteins and its longer duration led to an additional increase, but the increment followed differ-ent pattern, time-dependence and statistical significance in the different skeletal muscles. The gastrocnemius muscle was the most, while the EDL the least responsive. The effect of HFD was more pronounced and faster on CRP than SAA levels. The replacement of the HFD with a standard diet led to restoration of the normal, non-inflammatory pheno-type of the muscles, whereas IL-4 levels were almost unchanged during the experiment.Conclusions. The HFD results in low-grade, chronic inflammation in skeletal muscles which is time-dependent and muscle-specific, but the muscle tissue is less likely to exert control over the development of this process.