The goal of this review article,based on a systematic literature search,is to critically assess the state of knowledge and experimental methodologies used to delineate the conversion and metabolism of the 2 methionine...The goal of this review article,based on a systematic literature search,is to critically assess the state of knowledge and experimental methodologies used to delineate the conversion and metabolism of the 2 methionine(Met)sources DL-methionine(DL-Met)and DL-2-hydroxy-4-(methylthio)butanoic acid(HMTBa).The difference in the chemical structures of HMTBa and DL-Met indicates that these molecules are absorbed and metabolized differently in animals.This review explores the methodologies used to describe the 2-step enzymatic conversion of the 3 enantiomers(D-HMTBa,L-HMTBa and D-Met)to L-Met,as well as the site of conversion at the organ and tissue levels.Extensive work was published documenting the conversion of HMTBa and D-Met into L-Met and,consequently,the incorporation into protein using a variety of in vitro techniques,such as tissue homogenates,cell lines,primary cell lines,and everted gut sacs of individual tissues.These studies illustrated the role of the liver,kidney,and intestine in the con-version of Met precursors into L-Met.A combination of in vivo studies using stable isotopes and infusions provided evidence of the wide conversion of HMTBa to L-Met by all tissues and how some tissues are net users of HMTBa,whereas others are net secreters of L-Met derived from HMTBa.Conversion of D-Met to L-Met in organs other than the liver and kidney is poorly documented.The methodology cited in the literature to determine conversion efficiency ranged from measurements of urinary,fecal,and respiratory excretion to plasma concentration and tissue incorporation of isotopes after intraperitoneal and oral in-fusions.Differences observed between these methodologies reflect differences in the metabolism of Met sources rather than differences in conversion efficiency.The factors affecting conversion efficiency are explored in this paper and are mostly associated with extreme dietary conditions,such as noncommercial crystalline diets that are very deficient in total sulfur amino acids with respect to requirements.Impli-cations in the diversion of the 2 Met sources toward transsulfuration over transmethylation pathways are discussed.The strengths and weaknesses of some methodologies used are discussed in this review.From this review,it can be concluded that due to the inherent differences in conversion and metabolism of the 2 Met sources,the experimental methodologies(e.g.,selecting different organs at different time points or using diets severely deficient in Met and cysteine)can impact the conclusions of the study and may explain the apparent divergences of conclusion found in the literature.It is recommended when con-ducting studies or reviewing the literature to properly select the experimental models that allow for differences in how the 2 Met precursors are converted to L-Met and metabolized by the animal to enable a proper comparison of their bioefficacy.展开更多
Given the key role of methionine in biological processes,adequate methionine should be provided to meet the nutritional requirements.DL-2-hydroxy-4-(methylthio)-butanoic acid(DL-HMTBA)has been considered as an importa...Given the key role of methionine in biological processes,adequate methionine should be provided to meet the nutritional requirements.DL-2-hydroxy-4-(methylthio)-butanoic acid(DL-HMTBA)has been considered as an important source of methionine.However,the effects of different sources and levels of methionine on the intestinal health status have not been clarified yet.An experiment was carried out to investigate the effects of different dietary sources and levels of methionine on the intestinal epithelial barrier,inflammatory cytokines expression,ileal morphology,microbiota composition,and cecal short chain fatty acids(SCFA)profiles.For this purpose,720 male Arbor Acre broiler chicks at 1 d old were randomly assigned to a 2×3 factorial arrangement with 2 methionine sources(DL-methionine and DLHMTBA)and 3 total sulfur amino acids(TSAA)levels(80%,100%,and 120%of Arbor Acre recommendation).The results showed that DL-HMTBA supplementation promoted intestinal physical barrier at both gene expression level of claudin-1 and serum diamine oxidase level(P<0.05),and the inflammatory cytokine IL-6 m RNA expression was down-regulated by dietary DL-HMTBA supplementation compared with the DL-methionine group(P<0.05).Meanwhile,an upregulated gene expression of claudin-1 and zonula occluden-1(ZO-1)were observed in the low-TSAA treatment on d 14(P<0.05),whereas this treatment increased the expression of IL-1βand IL-6(P<0.05).Villus height to crypt depth ratio was high(P<0.05)in the middle-level TSAA group.Furthermore,DL-HMTBA supplementation optimized the microbiota of the ileum especially the relative abundance of Lactobacillus,where the digestion and absorption were completed,and elevated the concentrations of SCFA(acetate,propionate,and butyrate)in the cecal content on d 21(P<0.01).In conclusion,dietary DL-HMTBA supplementation improved the intestinal barrier function,immune homeostasis and optimized the microbiota to promote intestinal health status in broiler chickens.展开更多
文摘The goal of this review article,based on a systematic literature search,is to critically assess the state of knowledge and experimental methodologies used to delineate the conversion and metabolism of the 2 methionine(Met)sources DL-methionine(DL-Met)and DL-2-hydroxy-4-(methylthio)butanoic acid(HMTBa).The difference in the chemical structures of HMTBa and DL-Met indicates that these molecules are absorbed and metabolized differently in animals.This review explores the methodologies used to describe the 2-step enzymatic conversion of the 3 enantiomers(D-HMTBa,L-HMTBa and D-Met)to L-Met,as well as the site of conversion at the organ and tissue levels.Extensive work was published documenting the conversion of HMTBa and D-Met into L-Met and,consequently,the incorporation into protein using a variety of in vitro techniques,such as tissue homogenates,cell lines,primary cell lines,and everted gut sacs of individual tissues.These studies illustrated the role of the liver,kidney,and intestine in the con-version of Met precursors into L-Met.A combination of in vivo studies using stable isotopes and infusions provided evidence of the wide conversion of HMTBa to L-Met by all tissues and how some tissues are net users of HMTBa,whereas others are net secreters of L-Met derived from HMTBa.Conversion of D-Met to L-Met in organs other than the liver and kidney is poorly documented.The methodology cited in the literature to determine conversion efficiency ranged from measurements of urinary,fecal,and respiratory excretion to plasma concentration and tissue incorporation of isotopes after intraperitoneal and oral in-fusions.Differences observed between these methodologies reflect differences in the metabolism of Met sources rather than differences in conversion efficiency.The factors affecting conversion efficiency are explored in this paper and are mostly associated with extreme dietary conditions,such as noncommercial crystalline diets that are very deficient in total sulfur amino acids with respect to requirements.Impli-cations in the diversion of the 2 Met sources toward transsulfuration over transmethylation pathways are discussed.The strengths and weaknesses of some methodologies used are discussed in this review.From this review,it can be concluded that due to the inherent differences in conversion and metabolism of the 2 Met sources,the experimental methodologies(e.g.,selecting different organs at different time points or using diets severely deficient in Met and cysteine)can impact the conclusions of the study and may explain the apparent divergences of conclusion found in the literature.It is recommended when con-ducting studies or reviewing the literature to properly select the experimental models that allow for differences in how the 2 Met precursors are converted to L-Met and metabolized by the animal to enable a proper comparison of their bioefficacy.
基金This work has been supported by Adisseo France S.A.S(202104810410901)China Agriculture Research System Program(CA RS-41).
文摘Given the key role of methionine in biological processes,adequate methionine should be provided to meet the nutritional requirements.DL-2-hydroxy-4-(methylthio)-butanoic acid(DL-HMTBA)has been considered as an important source of methionine.However,the effects of different sources and levels of methionine on the intestinal health status have not been clarified yet.An experiment was carried out to investigate the effects of different dietary sources and levels of methionine on the intestinal epithelial barrier,inflammatory cytokines expression,ileal morphology,microbiota composition,and cecal short chain fatty acids(SCFA)profiles.For this purpose,720 male Arbor Acre broiler chicks at 1 d old were randomly assigned to a 2×3 factorial arrangement with 2 methionine sources(DL-methionine and DLHMTBA)and 3 total sulfur amino acids(TSAA)levels(80%,100%,and 120%of Arbor Acre recommendation).The results showed that DL-HMTBA supplementation promoted intestinal physical barrier at both gene expression level of claudin-1 and serum diamine oxidase level(P<0.05),and the inflammatory cytokine IL-6 m RNA expression was down-regulated by dietary DL-HMTBA supplementation compared with the DL-methionine group(P<0.05).Meanwhile,an upregulated gene expression of claudin-1 and zonula occluden-1(ZO-1)were observed in the low-TSAA treatment on d 14(P<0.05),whereas this treatment increased the expression of IL-1βand IL-6(P<0.05).Villus height to crypt depth ratio was high(P<0.05)in the middle-level TSAA group.Furthermore,DL-HMTBA supplementation optimized the microbiota of the ileum especially the relative abundance of Lactobacillus,where the digestion and absorption were completed,and elevated the concentrations of SCFA(acetate,propionate,and butyrate)in the cecal content on d 21(P<0.01).In conclusion,dietary DL-HMTBA supplementation improved the intestinal barrier function,immune homeostasis and optimized the microbiota to promote intestinal health status in broiler chickens.
