PS9-4. Effects of Duodenal Infusion of Glutamate, Leucine and Lysine on the Expression of Genes Related to Lipid Metabolism in Beef Cattle.

Abstract The utilization of dietary energy from starch is potentially limited in the post-ruminal phase, possibly due to the limited activity of pancreatic α-amylase. Several studies have aimed to increase intestinal starch digestion, and the use of amino acids has shown promise. Furthermore, glucose is an important carbon donor for intramuscular fat synthesis. Therefore, the objective of this study was to evaluate the effects of duodenal infusion of glutamate, leucine, and lysine on the expression of genes involved in lipogenesis in bovine muscle. Five Nellore steers, cannulated in the duodenum, with an initial body weight of 569 ±58.3 kg, were assigned to a 5 × 5 Latin square design. Treatments consisted of duodenal infusion of a solution containing corn starch alone (CON; 1.16 kg DM/day) or combined with lysine (LYS; 44.7 g DM/day), leucine (LEU; 33.1 g DM/day), and glutamate at low (GLU−; 93.7 g DM/day) and high doses (GLU+; 186.9 g DM/day). Infusions were performed continuously using a peristaltic pump, with solution replacement every 12 h and an average infusion rate of 481 ±9.75 mL/h. Each experimental period lasted 9 days, including adaptation and sample collection. Muscle biopsies of the longissimus thoracis were performed on day 9 for gene expression analysis. Gene expression was determined by RT-qPCR. Data were analyzed using PROC MIXED in SAS, with means compared by Tukey’s test and significance declared at P < 0.05. A treatment effect was observed for ACACA expression (Table 1), with lower values in steers receiving LYS and LEU compared to CON. The GLU− treatment showed intermediate values, not differing from CON or the other treatments, whereas GLU+ did not differ from CON. No effects of amino acids were observed for SCD1, CEBPA, SREBF1, FASN, and PPARA expression (P > 0.05). The results indicate that duodenal infusion of lysine and leucine reduced ACACA expression, suggesting a potential effect on the initial step of de novo fatty acid synthesis. However, the lack of response in the other evaluated genes indicates that this effect does not consistently extend to the lipogenic pathway. In conclusion, the post-ruminal supply of lysine and leucine may exert a localized effect on the regulation of lipogenesis under the conditions of this study.Obs: This study was supported by FAPEMIG, CAPES and CNPq For image description, please refer to the figure legend and surrounding text.