Omega‐3 fatty acid supplementation does not attenuate declines in skeletal muscle mitochondrial area in young, healthy females during immobilization

Mitochondrial subcellular area influences function. Muscle disuse reduces mitochondrial content; however, its effect on mitochondrial subcellular location is unclear. Omega-3 fatty acid (n-3) attenuates declines in muscle mass and mitochondrial function during disuse; however, whether n-3 supplementation prevents the decline in mitochondrial content has not been examined. We investigated the effects of 2 weeks of leg immobilization followed by 2 weeks of remobilization on skeletal muscle mitochondrial content and subcellular localization with and without n-3 supplementation. Twenty healthy females supplemented with n-3 (2.97 g EPA and 2.03 g DHA) or control (isoenergetic sunflower oil) during 2 weeks of unilateral leg immobilization and 2 weeks of remobilization. Vastus lateralis biopsies were taken for electron microscopic analysis of mitochondrial content. Subsarcolemmal (SS) mitochondrial content decreased during immobilization (control: -9%, n-3: -66%, p = 0.009) and remained lower following recovery (control: -41%, n-3: -42%, p = 0.005). This effect was driven by the n-3 group (p < 0.02). Intermyofibrillar (IMF) mitochondrial content did not decline during immobilization, but was lower than baseline following recovery in the central (p = 0.01) IMF. The effects of leg immobilization on mitochondrial content differ by location, are not reversed with short-term recovery, and are influenced by n-3 supplementation.