Differential effects of docoosahexaenoic and arachidonic acid on fatty acid composition and myosin heavy chain-related genes of slow- and fast-twitch skeletal muscle tissues.

Myosin heavy chain (MHC) mediates the metabolic and contractile responses of skeletal muscles. MHC displays different isoforms, each of which has different characteristics. To better understand the effect of polyunsaturated fatty acids in skeletal muscles, rats were fed with control-, docosahexaenoic acid (DHA)-, and arachidonic acid (ARA)-oil, and the effects on plasma and muscular fatty acid profile, oxidative stress, mRNA levels of myosin heavy chain isoforms MHC1 of slow-twitch muscle (SO) and MHC2A, MHC2X, and MHCB isoforms of extensor digitorum longus (EDL) of fast-twitch muscle were evaluated. Concomitantly, mRNA levels of anti-oxidative enzymes, such as, catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD were determined. The expressions of MHC1, MHC2A, MHC2X, and MHC2B were lower in the SO of the DHA-fed rats. In the EDL muscles of DHA-fed rats, the expressions of MHC1 and MHC2A increased; however, the expressions of MHC2X increased and that of the MHC2 were not altered. Oxidative stress, as indicated by the levels of LPO, was significantly higher in the plasma of the ARA-fed rats, when compared with that of the DHA-fed rats. The LPO levels were higher both in the SO and EDL muscles of ARA-fed rats. Compared with ARA oil intake, DHA oil showed higher mRNA levels of GPx and SOD. Catalase expression was higher only in the EDL but not in the SO-type muscles. Our studies finally indicate that DHA and ARA differentially affect the regulation of contractile and metabolic properties of slow- and fast-twitch skeletal muscles.