Impact of western and mediterranean diets and vitamin D on muscle fibers of sedentary rats

Abstract

Background: The metabolic syndrome is associated with sarcopenia. Decreased serum levels of Vitamin D (VitD) and insulin‐like growth factor (IGF)‐1 and their mutual relationship were also reported. We aimed to evaluate whether different dietary profiles, containing or not VitD, may exert different effects on muscle molecular morphology. Methods: Twenty‐eight male rats were fed for 10 weeks in order to detect early defects induced by different dietary regimens: regular diet (R); regular diet with vitamin D supplementation (R‐DS) and regular diet with vitamin D restriction (R‐DR); high‐fat butter‐based diets (HFB‐DS and HFB‐DR) with 41% energy from fat; high‐fat extra‐virgin olive oil‐based diets (HFEVO‐DS and HFEVO‐DR) with 41% energy from fat. IL‐1β, insulin‐like growth factor (IGF)1, Dickkopf‐1 (DKK‐1), and VitD‐receptor (VDR) expressions were evaluated by immunohistochemistry. Muscle fiber perimeter was measured by histology and morphometric analysis. Results: The muscle fibers of the HEVO‐DS rats were hypertrophic, comparable to those of the R‐DS rats. An inverse correlation existed between the dietary fat content and the perimeter of the muscle fibers (p < 0.01). In the HFB‐DR rats, the muscle fibers appeared hypotrophic with an increase of IL‐1β and a dramatic decrease of IGF‐1 expression. Conclusions: High‐fat western diet could impair muscle metabolism and lay the ground for subsequent muscle damage. VitD associated with a Mediterranean diet showed trophic action on the muscle fibers.