232. Effect of Amino Acid Derivatives and Polyphenol Supplementation on Skeletal Muscle In Vitro and In Vivo.

Abstract The lack of approved growth promoters, such as anabolic implants for sheep, has contributed to a significant decline in US lamb production. Satellite cells (SC) are the building blocks of muscle growth; hence, they play a crucial role in muscle fiber hypertrophy. We hypothesized that guanidinoacetic acid (GAA) and 5-hydroxytryptophan (5-HTP), along with quercetin, would alter skeletal muscle growth in vitro and in vivo, thereby improving lamb production. The objectives of this study were to: 1) investigate the effect of quercetin, GAA, and 5-HTP on satellite cell proliferation and differentiation in vitro, and 2) examine the effect of GAA and 5-HTP on muscle growth in sheep. SC were previously isolated and cultured (45,000/well) with 5-HTP, GAA, or quercetin at different concentrations (0, 12.5, 25, and 50 μmol/L). We visualized and quantified SC proliferation on d 1 using Hoechst dye and on d 4 using 5-ethynyl-2-deoxyuridine (EDU) staining; whereas immunohistochemistry was used to assess SC differentiation on d 4. For the in vivo study, 15 Texel lambs were used (n = 5/trt; 33 kg + 6 kg BW) and randomly assigned to one of three treatments: control, GAA, or 5-HTP for 28 d. Supplements were administered sublingually at a dose of 2.5 mg/kg BW before feeding. Skeletal muscle biopsies of the longissimus muscles were performed, and RNA was extracted, followed by RNA sequencing. Liquid chromatography (LC) - mass spectrometry (MS) was used to analyze GAA and 5-HTP in the blood plasma sampled on d 26. SC proliferation was altered by 25 μmol/L 5-HTP and 12.5 μmol/L quercetin supplementation (P < 0.05), while 12.5 μmol/L and 25 μmol/L of GAA supplementation altered the percentage of satellite cell differentiation (P < 0.05). For lamb performance, GAA or 5-HTP did not influence (P > 0.05) average daily gain or dry matter intake. There was a difference (P < 0.01) in ribeye area pre- and post-supplementation for all treatment groups. RNA sequencing showed that GAA supplementation altered gene expression (Padj< 0.05) compared to the control or 5-HTP, showing that GAA enriched valine, leucine, and isoleucine biosynthesis, as well as glycine, serine, and threonine metabolism. However, 5-HTP did not affect (P > 0.05) gene expression compared to the control. LC-MS also showed that 5-HIAA levels differed (P < 0.05) and were elevated in the 5-HTP group. These data suggest that amino acid derivatives and polyphenols can influence SC proliferation or differentiation in vitro, suggesting an increase in muscle mass accretion. Short-term supplementation of GAA or 5-HTP to finishing lambs did not alter growth performance; however, GAA supplementation altered genes associated with amino acid metabolism, which is commonly linked to muscle growth through muscle protein synthesis.