CALORIC RESTRICTION EFFECTS ON SARCOPENIA AND ELECTRON TRANSPORT SYSTEM ABNORMALITIES IN RATS ARE MUSCLE SPECIFIC





Jennifer McGorray, Entela Bua, Judd M. Aiken and Susan H. McKiernan

Animal Health and Biomedical Sciences,
University of Wisconsin,
Madison, WI 53706




Age-related changes were characterized in the soleus and rectus femoris muscles of 18- and 36-month Fisher 344 x Brown Norway F1 hybrid rats to determine the effect of 40% caloric restriction on sarcopenia and mitochondrial electron transport system (ETS) abnormalities. The adult soleus muscle is predominantly comprised of type I fibers (90%) and exhibits moderate sarcopenia with age whereas 97% of fibers in adult rectus femoris are type II and the muscle exhibits severe sarcopenia. Muscles from four 18- and four 36-month ad libitum fed (AL) rats and five 36-month calorically restricted (CR) rats were weighed, cut at midbelly, and frozen in OCT medium. One hundred consecutive 10 um sections were cut from each tissue, mounted on slides, assayed histochemically for succinate dehydrogenase and cytochrome c oxidase activities and immunohistochemically stained for type II myosin. In the soleus, the muscle weight/body weight ratio, muscle cross-sectional area and percent type II fibers decreased significantly between 18- and 36-months in AL rats while aging had no effect on total fiber number or number of ETS abnormal fibers. Caloric restriction preserved 36-month soleus muscle weight/body weight ratio and cross-sectional area to levels characteristic of the 18-month AL rats but did not affect fiber number, percent type II fibers and number of ETS abnormal fibers. In the rectus femoris, the muscle weight/body weight ratio, muscle cross-sectional area, fiber number and percent type II fibers all decreased significantly from 18- to 36-months while the number of ETS abnormal fibers increased with age. Caloric restriction positively impacted 36-month rectus femoris fiber number, muscle weight/body weight ratio, number of ETS abnormal fibers and percent type II fibers but did not affect muscle cross-sectional area in rectus femoris. Caloric restriction attenuates sarcopenic changes in both type I and II muscles differently and decreases the number of ETS abnormal fibers in type II muscles suggesting that the effects of caloric restriction are muscle specific.






Key words: Skeletal muscle, sarcopenia, caloric restriction, ETS abnormalities







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