Lipid metabolism and m6A RNA methylation are altered in lambs supplemented rumen-protected methionine and lysine in a low-protein diet

Abstract

Abstract Background Methionine or lysine has been reported to influence DNA methylation and fat metabolism, but their combined effects in N6-methyl-adenosine (m 6 A) RNA methylation remain unclarified. The combined effects of rumen-protected methionine and lysine (RML) in a low-protein (LP) diet on lipid metabolism, m 6 A RNA methylation, and fatty acid (FA) profiles in the liver and muscle of lambs were investigated. Sixty-three male lambs were divided into three treatment groups, three pens per group and seven lambs per pen. The lambs were fed a 14.5% crude protein (CP) diet (adequate protein [NP]), 12.5% CP diet (LP), and a LP diet plus RML (LP + RML) for 60 d. Results The results showed that the addition of RML in a LP diet tended to lower the concentrations of plasma leptin ( P = 0.07), triglyceride ( P = 0.05), and non-esterified FA ( P = 0.08). Feeding a LP diet increased the enzyme activity or mRNA expression of lipogenic enzymes and decreased lipolytic enzymes compared with the NP diet. This effect was reversed by supplementation of RML with a LP diet. The inclusion of RML in a LP diet affected the polyunsaturated fatty acids (PUFA), n-3 PUFA, and n-6 PUFA in the liver but not in the muscle, which might be linked with altered expression of FA desaturase-1 ( FADS1 ) and acetyl-CoA carboxylase ( ACC ). A LP diet supplemented with RML increased ( P < 0.05) total m 6 A levels in the liver and muscle and were accompanied by decreased expression of fat mass and obesity-associated protein ( FTO ) and alkB homologue 5 ( ALKBH5 ). The mRNA expressions of methyltransferase-like 3 ( METTL3 ) and methyltransferase-like 14 ( METTL14 ) in the LP + RML diet group were lower than those in the other two groups. Supplementation of RML with a LP diet affected only liver YTH domain family ( YTHDF2 ) proteins ( P < 0.05) and muscle YTHDF3 ( P = 0.09), which can be explained by limited m 6 A-binding proteins that were mediated in mRNA fate. Conclusions Our findings showed that the inclusion of RML in a LP diet could alter fat deposition through modulations of lipogenesis and lipolysis in the liver and muscle. These changes in fat metabolism may be associated with the modification of m 6 A RNA methylation. Graphical abstract A systematic graph illustrates the mechanism of dietary methionine and lysine influence on lipid metabolism and M 6 A. The green arrow with triangular heads indicates as activation and brown-wine arrows with flat heads indicates as suppression.