Optimal branched-chain amino acid ratio improves cell proliferation and protein metabolism of porcine enterocytesin in vivo and in vitro

Objectives: The aim of this study was to investigate the effects of different branched-chain amino acid (BCAA) ratios on intestinal cell proliferation and protein metabolism. Methods: This in vivo study was conducted in growing pigs (average initial body weight = 9.85 +/- 0.35 kg) exposed to different leucine, isoleucine, and valine (Leu:Ile:Val) ratios (1:1:1, 1:0.75:0.75, 1:0.51:0.63, and 1:0.25:0.25) in 17% crude protein (CP) diets for 45 d to determine intestinal morphology, cell proliferation, and amino acid transporter mRNA expression. This in vitro study was performed in porcine jejunal epithelial cell line to investigate the effects of different BCAA ratios (0, 1:0.25:0.25, 1:0.5:0.5, and 1:1:1) on cell proliferation, AA transporter expression. and protein turnover. Results: Relative to the positive control (Leu:Ile:Val = 1:0.51:0.63, 20% CP), the 1:0.75:0.75 group (17% CP) significantly increased the jejunal villus height, the percentage of proliferating cell nuclear antigen positive cells and decreased the ileal crypt depth (P < 0.05). Moreover, most AA concentrations and AA transporter expression in the jejunal and ileal mucosa in 17% CP diets were increased to the levels similar to those in the positive control. Additionally, this in vitro study showed that the BCAA ratio of 1:0.25:0.25 significantly increased intestinal cell proliferation, mRNA expression of AA transporters, AA concentrations, and protein turnover (P < 0.05). Conclusions: These findings suggest that optimal BCAA ratio (in vivo = 1:0.75:0.75; in vitro = 1:0.25:0.25) would improve intestinal morphology and cell proliferation, increase intestinal AA absorption through mediating expression of intestinal AA transporters, and promote intestinal protein turnover. The findings yield new insights into the use of BCAAs in humans and animals. (C) 2018 Elsevier Inc. All rights reserved.