Dietary amylose/amylopectin ratio influences the expression of amino acid transporters and enzyme activities for amino acid metabolism in the gastrointestinal tract of goats

Abstract

Abstract This study was designed to investigate the effects of dietary starch structure on muscle protein synthesis and gastrointestinal amino acid (AA) transport and metabolism of goats. Twenty-seven Xiangdong black female goats (average body weight = 9.00 ± 1.12 kg) were randomly assigned to three treatments, i.e., fed a T1 (normal corn 100%, high amylose corn 0%), T2 (normal corn 50%, high amylose corn 50%) and T3 (normal corn 0%, high amylose corn 100%) diet for 35 days, respectively. All amino acids in the ileal mucosa were decreased linearly as amylose/amylopectin increased in diets (P<0.05). The plasma valine (linear, P=0.03), leucine (linear, P=0.04), and total amino acids content (linear, P=0.03) increased linearly with the increase in the ratio of amylose in the diet. The relative mRNA levels of SLC38A1 (linear, P=0.01), SLC3A2 (linear, P=0.02), and SLC38A9 (linear, P=0.02) in the ileum increased linearly with the increase in the ratio of amylose in the diet. With the increase in the ratio of amylose/amylopectin in the diet, the mRNA levels of ACADSB (linear, P=0.04), BCAT1 (linear, P=0.02), and BCKDHB (linear, P=0.01) in the ileum decreased linearly. Our results revealed that the protein abundances of p-mTOR (P<0.001), p-4EBP1 (P<0.001), and p-S6K1 (P<0.001) of T2 and T3 were significantly higher than that of T1. In general, a diet with a high amylose ratio could reduce the consumption of amino acids in the intestine, allowing more amino acids to enter the blood to maintain higher muscle protein synthesis through the mTOR pathway.