Sarcoplasmic Proteome Changes in Response to Aging and Diet

Abstract

We seek to establish the change in the sarcoplasmic proteome the rat medial gastrocnemius (MG), as a function of age and dietary fish oil enriched diet. Physiological and behavioral measures were acquired in conjunction with quantitative two‐dimensional gel electrophoresis (2D PAGE) and immunoblotting (IB) of muscle sarcoplasm extracts. Significant proteomic changes were observed across experimental groups: young adult (8–9 months) and aged (22–23 months) S‐D rats assigned to control (Ctl) or Fish oil‐supplemented (FO) diets for 8 weeks (7 adult; 6 aged rats/group).Forelimb grip strength was assessed before & after the 8‐week diet. In situ twitch and tetanic (100 Hz) forces were assessed at completion. MG samples were extracted and the sarcoplasmic protein fraction analyzed by 2D PAGE and the integrated spot intensity analyzed. Spots showing significant changes (± ≥ 2.00, p < 0.05) were identified by HPLC/MS. For IB, PVDF blots were probed with primary antibody, then stripped and reprobed for GAPDH (loading control). Animal use and all procedures were approved by the Ohio Univ IACUC, and the “Principles of Laboratory Animal Care” (NIH Pub No. 86‐23, rev 1985), were followed throughout the study. Data were analyzed by 2 × 2 ANOVA (age × dietary group), except for grip strength, which was assessed using a repeated measures ANOVA, with time as the repeated factor.Body mass was reduced with age, but food intake did not differ across groups. Based on food disappearance, rats in the FO group ingested ~1.12 g/kg FO, with no age‐difference. There was an overall trend (P = 0.089) for FO maintaining greater grip strength vs. Ctl over time. Aged animals exhibited comparable significant reduction in MG mass and twitch & tetanic (15–20%). FO diet significantly increased tetanic (P = 0.046) but not twitch force (P = 0.262), despite having no effect on muscle mass. Twitch and tetanic force, when normalized to MG anatomical cross‐sectional area, exhibited a significant diet × age interaction (P = 0.027) and a strong trend (P = 0.051) for an effect of diet, respectively. Protein changes were classified into meta‐KOG groupings: Metabolic: 54%, Oxidative Stress: 20%, Cytoskeletal: 13% and Misc: 13%. Overall, Age × Diet interactions influenced energy metabolism proteins: CKM ‐ muscle creatine kinase; TPI 1 ‐ isoform 1 ‐ triose phosphate isomerase; DJ1 ‐ a protein deglycase; PKM ‐ muscle pyruvate kinase; BE ‐ beta enolase; NADHD ‐ NADH dehydrogenase. In Ctl conditions, CKM, NADHD and PKM were elevated in the old vs. young; BE was reduced and DJ1 and TPI1 were not different; In response to dietary FO, CKM and NADHD increased for the young and decreased for the old; BE decreased in the young only; TPI increased in the young only; DJ1 decreased in the young and increased in the old and PKM decreased in the old only.An 8‐week FO diet produced some mass‐independent improvements in muscle function and performance in young and aged rats. FO affected the expression of several proteins in young and aged MG muscle, predominantly ones related to energy metabolism.Support or Funding InformationSmith Coll Blakeslee Fund and SURF, and Ohio Univ Coll Health Sci and Professions Res Dean's Innovation ChallengeThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.