239 Impaired Myoblast Function and Poor Muscle Growth in Intrauterine Growth-Restricted Fetal Sheep Is Improved By the Anti-Inflammatory Nutraceutical, Eicosapentaenoic Acid

Abstract

Abstract Chronic heat stress during pregnancy causes low birthweight due to intrauterine growth restriction (IUGR) of the fetus. Recent findings indicate that IUGR fetal programming includes enhanced inflammatory sensitivity that disproportionally affects skeletal muscle. Thus, our objective was to determine if 5-d intravenous fetal infusion of the anti-inflammatory ω-3 polyunsaturated fatty acid, eicosapentaenoic acid (EPA) improved growth metrics and ex vivo myoblast (i.e., muscle stem cell) function in heat stress-induced IUGR fetal sheep. Maternal heat stress (40°C, 35% humidity, THI = 85) from d 40 to 95 of gestation was used to produce IUGR fetuses. Saline or EPA (25 mg/d) was infused via fetal femoral catheter from d 118 to 122 of gestation. At 122 d gestation, IUGR fetuses (n = 10; 2.31 ± 0.16 kg) were 26% lighter (P < 0.05) than control fetuses (n = 10; 3.10 ± 0.15 kg). Body mass of EPA-infused IUGR fetuses (n = 9; 2.70 ± 0.16 kg) were intermediate between controls and IUGR fetuses. Likewise, IUGR fetuses had lighter (P < 0.05) hindlimbs (28%), semitendinosus (30%), longissimus muscle (28%), flexor digitorum superficialis (30%), and soleus (31%) than controls. EPA infusion partially recovered (P < 0.05) hindlimb and longissimus muscle mass and fully recovered (P < 0.05) flexor digitorum superficialis and soleus mass but did not improve semitendinosus mass. Primary myoblasts were isolated at necropsy and incubated in proliferation media (DMEM + 20% fetal bovine serum) for 2 h or differentiation media (DMEM + 2% fetal bovine serum) for 96 h. Proliferation rates (determined by EdU incorporation over 2 h) were less (P < 0.05) for myoblasts from IUGR fetuses (38 ± 2% EdU+) and EPA-infused IUGR fetuses (39 ± 2% EdU+) than controls (44 ± 1% EdU+). Differentiation rates (determined by myogenin expression after 96 h) were less (P < 0.05) for myoblasts from IUGR fetuses (9 ± 1% myogenin+) but not EPA-infused IUGR fetuses (13±1% myogenin+) compared with controls (12 ± 1% myogenin+). IUGR fetuses had lighter (P < 0.05) heart (19%) and brain (11%) mass than controls, but heart/fetal mass and brain/fetal mass were greater (P < 0.05) than controls, which indicates tissue sparing for these organs. EPA infusion did not affect heart or brain mass but reduced (P < 0.05) heart/fetal mass and brain/fetal mass. Together, these findings demonstrate that skeletal muscle growth is disproportionately restricted compared with whole-body, brain, heart, or liver growth, and that this is facilitated by intrinsic impairment of myoblast function. Moreover, prolonged fetal infusion of the anti-inflammatory nutraceutical, EPA, partially recovered myoblast function and muscle growth in IUGR fetal sheep.