Dietary methionine source and level affect hepatic sulfur amino acid metabolism of broiler breeder hens

Abstract

A study was carried out to investigate the effects of dietary methionine source and level on plasma free amino acids patterns and the expression of genes involved in hepatic methionine metabolism in broiler breeders. A total of 2184 broiler breeders were assigned to 13 dietary treatments, with eight replicates per treatment. The 13 treatments included one control group and 12 additional treatments employing two sources and six levels (0.05, 0.10, 0.15, 0.20, 0.25 and 1.00%). Higher plasma methionine concentration was measured for DL-methionine (DLM) treated hens. Plasma alanine concentration was linearly increased as DLM or 2-hydroxy-4-(methylthio) butanoic acid (HMTBA) supplementation level increased. There was a linear increase in concentrations of tyrosine, valine, glycine and serine as dietary DLM supplementation level increased. Hens treated with DLM had higher relative expression of ADA than those fed HMTBA. The expression of MS, ADA, SAHH and MAT2A changed quadratically as HMTBA supplementation level increased, while the expression of GNMT and SAHH changed quadratically as DLM supplementation level increased. In conclusion, the effects of HMTBA on plasma free amino acid patterns and the expression of hepatic genes involved with methionine are different from DLM.

Keywords: methionine; methionine hydroxyl analogue; plasma free amino acid; sulfur amino acids metabolism.

Figure 1

Effects of methionine source and level on the expression of genes involved in hepatic methyl group metabolism in broiler breeder hens. The expression of MAT1A (A), MAT2A (B), GNMT (C), SAHH (D), ADA (E), ADK (F), BHMT (G), MS (H), MSR (I), MTHFR (J), CBS (K), and PEMT (L) genes was determined by quantitative RT‐PCR. The results are presented as an average relative fold change in the expression of each gene in the livers of hens fed the DL‐methionine (DLM) or 2‐hydroxy‐4‐(methylthio) butanoic acid (HMTBA) supplemental diet relative to that without any DLM or HMTBA, which was assigned a value 1. a–c, Different letters indicate statistical difference at P < 0.05. ADA, adenosine deaminase; BHMT, betaine‐homocysteine methyltransferase; MAT1A, methionine adenosyltransferase 1A; MAT2A, methionine adenosyltransferase 2A; MS, methionine synthase; MTHFR, methyl‐THF reductase; SAHH, S‐adenosylhomocysteine hydrolase; CBS, cystathionine β‐synthase.