Regulation Of Muscle Growth By Long Chain Omega-3 Polyunsaturated Fatty Acids In Rats.

Abstract

INTRODUCTION: Numerous studies have reported the metabolic health benefits of consuming a diet rich in the long chain omega-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA; C20:5 n-3) and docosahexaenoic acid (DHA; C22:6 n-3), including an improvement in insulin sensitivity. While muscle mass provides an important component of glucose and insulin regulation, the direct effects of PUFA on skeletal muscle size or morphology are not known. In vitro data from our laboratory have shown that DHA prevented atrophy and altered morphology in C2C12 muscle cells that were exposed to high levels of the saturated fatty acid palmitate. However, it is not known if PUFAs will directly alter muscle growth or myogenic signaling in vivo. PURPOSE: The objective of this study was to determine if dietary PUFA regulates skeletal muscle size and myogenic signaling in rat hindlimb muscles in a fiber type specific fashion.. METHODS: Young (28 d) female Sprague-Dawley rats (n=5/group) were individually housed in metabolic cages, and pair-fed (14.75g ± 0.75g) high fat diets (12% by weight) for 8 weeks. The diets consisted of corn, flax, menhaden, krill, salmon or tuna oil as the lipid source. After 8 weeks, the soleus and plantaris muscles and medial and lateral heads of the gastrocnemius from each limb were blotted dry, immediately weighed and flash frozen. RESULTS: Animal bodyweights did not differ among groups. However, the wet weight and muscle weight to bodyweight of the lateral head of the left gastrocnemius muscle was significantly greater in rats that consumed menhaden as compared with krill, tuna, and salmon. There was also a significant difference among groups for the medial head of the left gastrocnemius with rats consuming tuna having the highest mean weight. No other differences among groups were observed. Myogenic gene regulation and apoptotic signaling may provide a partial explanation for the differences in muscle wet weight that was observed in rats that consumed diets with different PUFA concentrations. CONCLUSIONS: These data suggest that dietary PUFA may regulate, at least in part, muscle growth in the fast contracting gastrocnemius muscle of young rats.