Abstract
BackgroundAs the extend of low‐protein diets in many countries including China, more researches of amino acid nutrition (AA) have been carried out. But the ideal AA pattern, especially the reasonable proportion of amino acids such as the desired methionine (Met): cystine (Cys) ratios are not yet clear.ObjectivesIn this article, the experiments of low‐protein diet with varying ratios of Met:Cys (low ratio of 1:3, medium ratio of 1:1, and high ratio of 3:1) were conducted to investigate the effect on mice growth and reproductive performance.ResultsThe result indicated that the lower Met:Cys ratio improves reproductive performance in male mice, but the growth performance were no change in all groups. Meanwhile, the abnormality rate of sperm increased as the ratio of methionine and cystine increased. Quantitative analysis showed that the low Met:Cys ratio has obviously decreased the expression of Bax protein and the concentrations of testosterone in male serum, but Prm2, Pgk2, Bcl‐2, Bak1, and AR gene were made no difference. Furthermore, different Met:Cys ratios have significant effects on the modulated methionine cycle by increasing the expressions of MAT2B, GNMT, and BHMT in low Met:Cys ratio. On the other hand, it was also found that there were increases in GSH‐Px enzyme activities and decreases in MDA levels in male serum.ConclusionsOverall, the present study showed that a dietary lower Met:Cys ratio in a low‐protein diet had a positive influence on the reproductive performance of male animal through obviously improving sperm quality and antioxidant capacity, and inhibiting apoptosis. And the study provided new pieces of evidence to re‐evaluate the role of precise sulfur amino acid nutrition in a low‐protein diet.
Highlights
In livestock production, the investment cost depends on the content of dietary protein
It remains to be clarified whether the Met:Cys ratio alters the supplement of methyl donor and affects the methylation of related genes and proteins, which may further affect the processes of growth, development and nutrition metabolism in animals
This study showed for the first time that lower Met:Cys ratios were beneficial for reproduction performances in litter size and sperm quality
Summary
The investment cost depends on the content of dietary protein. SAM is a primary methyl donor molecule synthesized directly from the essential amino acid methionine, utilized in cellular methylation reactions such as methylations of DNA, RNA, and protein (Fontecave, Atta, & Mulliez, 2004) to regulate genetic expressions. There is a dynamic balance between the substrates and the metabolites, and their ratio affects the changes of the metabolic intermediate, such as the supply of methyl donors It remains to be clarified whether the Met:Cys ratio alters the supplement of methyl donor and affects the methylation of related genes and proteins, which may further affect the processes of growth, development and nutrition metabolism in animals. | 2867 to investigate the effect of different Met:Cys ratios on the reproductive performance of mice in a low‐protein diet and re‐evaluate the precise requirements of sulfur amino acids on animal nutrition, production, and reproduction
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