Hepatic activity and transcription of betaine-homocysteine methyltransferase, methionine synthase, and cystathionine synthase in periparturient dairy cows are altered to different extents by supply of methionine and choline

Background: Comparedwith choline,Met enhances milk yield and feed intake, and elicits a better immuno-metabolic status in periparturient cows. It is unknown whether hepatic activity and transcription of betaine-homocysteine methyltransferase (BHMT), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), and cystathionine β-synthase (CBS) are responsive to Met and choline supply. Objective: This study sought to characterize hepatic BHMT, MTR, and CBS transcription and activity in response to Met and choline supplementation. Methods: Fortymultiparous cowswere used in a 2 × 2 factorial design from 221 d through 30 d around parturition to assess effects of dietary rumen-protected Met (0% or 0.08% dry matter basis) or rumen-protected choline (0 or 60 g · cow^-1 ·d^-1). Liver tissue obtained on days -10, 7, 20, and 30 was used for analyses. Results: Met-supplemented cows had greater methionine adenosyltransferase 1A (MAT1A) (0.38 compared with 0.27; SEM = 0.05; P = 0.02) and phosphatidylethanolamine methyltransferase (PEMT) (0.74 compared with 0.58; SEM = 0.08; P = 0.05) expression. Greater S-adenosylhomocysteine hydrolase (SAHH) (0.93 compared with 0.74; SEM = 0.05; P = 0.01) and CBS (1.16 compared with 1.02; SEM = 0.07; P = 0.04), as well as lower MTR activity (23.4 compared with 29.7 nmol product · h^-1 · mg protein^-1; SEM = 2.9; P = 0.04), also were detected in Met- but not choline-supplemented cows. Although BHMT and MTR expression and BHMT enzyme activity did not change (P > 0.05),MTR enzyme activity was lower in choline-supplemented cows (23.5 compared with 29.6 nmol product · h^-1 · mg protein^-1; SEM = 2.9; P = 0.05). Conclusions: These findings indicate that greater synthesis of phosphatidylcholine and antioxidants contribute to the better performance and immuno-metabolic status in Met-supplemented cows. Failure to generate a comparable amount of endogenous Met from choline could be one reason that choline-fed cows fail to achieve comparable performance and health benefits during the periparturient period.