Interactive effects of dietary isoleucine and valine ratios to lysine in response to varying leucine to lysine ratios on jejunal and hepatic protein expression in commercial broilers

Abstract

Valine, leucine, and isoleucine are three essential amino acids, commonly known as branched-chain amino acids (BCAA). Inadequate concentrations of BCAA in poultry diets have been related to the generation of antagonistic effects, and determining optimal dietary ratios is essential to improve broiler growth performance and carcass yields. Therefore, a central composite design (CCD) study was conducted to understand the influence of dietary BCAA ratios on glucose and energy metabolism in the jejunum and amino acid and protein metabolism in the liver of broilers. A total of 2,592 d-old Ross 344 × 708 male broilers were randomly placed in 144 floor pens. Each pen received 1 of 15 dietary treatments in a 23 CCD with 6 center points from 20 to 35 d of age, varying in digestible ratios of isoleucine:lysine (Ile:Lys; 52 to 75), valine:lysine (Val:Lys; 64 to 87), and leucine:lysine (Leu:Lys; 110 to 185). On d 35, 1 bird per pen was selected and both liver and jejunal tissue samples were collected for protein extraction. A proteomic analysis was conducted via data independent acquisition protein sequencing with a timsTOF Pro 2 LC/MS/MS and Spectronaut 15 software. Glycogen synthase kinase-3 beta (GSK3A), dihydrolipoamide acetyltransferase (PDHX), AMP deaminase (AMPD3), succinyl-CoA-Ketoacid-coenzyme A transferase (OXCT1), adipocyte-type fatty acid-binding protein (FABP4), and O-N-acetylglucosamine transferase subunit p110 (OGT) were identified and quantified on the jejunum and dihydrolipoamide acetyltransferase (PDHX), aspartate aminotransferase (GOT2), branched-chain-amino-acid aminotransferase (BCAT1), diphosphomevalonate decarboxylase (MVD), acylamino-acid-releasing enzyme (APEH), and aspartate aminotransferase (GOT1) were identified and quantified on hepatic samples. Protein quantification data were analyzed as a CCD using the RSREG procedure of SAS v. 9.4 with significance declared at P ≤ 0.10. When the individual amino acid effect in the response surface (RS) regression analysis was P ≤ 0.2, raw protein quantification data were analyzed as a 1-way ANOVA and the PDIFF option of SAS set at P ≤ 0.1 using the GLIMMIX procedure. The surface response model for jejunal OGT and hepatic MVD and APEH expression were significant (P ≤ 0.0511; R2 ≤ 0.2451). However, models for the other proteins were not significant (P ≥ 0.1356; R2 ≤ 0.1982). Jejunal GSK3A linear model, PDHX cross product model, and OGT linear and quadratic model were significant (P ≥ 0.0847), as well as hepatic MVD linear model and APEH linear and quadratic models (P ≤ 0.0803). Ile:Lys ratio of 70 resulted in a higher GSK3A jejunal expression compared with 56 if Val:Lys and Leu:Lys are fix at 68 and 170 or 82 and 125 respectively (P ≤ 0.0668). Jejunal PDHX protein expression was higher when Leu:Lys ratio was 125 compared with 170 if Val:Lys was fixed to 68 and Ile:Lys at 56. Treatment where Leu:Lys was 110 had the highest OGT jejunal expression compared with 148 and 185 if Val:Lys and Ile:Lys were fixed to 75 and 63, respectively. MVD increased as Val:Lys ratio increased when Leu:Lys and Ile:Lys were fixed at 148 and 63 or 170 and 70, respectively (P ≤ 0.0926). Low Val:Lys ratio expressed the lowest hepatic APEH expression when Leu:Lys and Ile:Lys ratios were 148 and 63 or 125 and 70, respectively (P ≤ 0.0153). Hepatic MVD expression decreased as Leu:Lys ratio increased when Val:Lys and Ile:Lys were 75 and 63, respectively (P ≤ 0.0044). GOT1 expression was higher with 170 Leu:Lys ratio compared with 125, when Val:Lys and Ile:Lys ratios were 68 and 70, respectably (P ≤ 0.0460). APEH was higher with a low Ile:Lys ratio when Val:Lys and Leu:Lys ratios were 68 and 125, respectively (P ≤ 0.0786). In conclusion, varying concentrations of dietary BCAA and their interactions seem to alter jejunal and hepatic protein expression and may help explain the mechanisms underlying their influence on broiler growth.