2-Hydroxy-4-(methylthio)butyric acid

2-Hydroxy-4-(methylthio)butyric acid (2-Hydroxy-4-(Methylthio)-Butanoic Acid) is an orally active source of methionine. 2-Hydroxy-4-(methylthio)butyric acid reduces the expression of multiple mRNAs (BHMT, MTR, MAT1A, SAHH, and PCK1). 2-Hydroxy-4-(methylthio)butyric acid increases milk production in periparturient cows^{[1][2][3][4][5]}. In Vitro:2-Hydroxy-4-(methylthio)butyric acid (10-60 μM; 24 h) linearly decreases the mRNA expression of BHMT, MTR, MAT1A, and PCK1, linearly decreases SAHH and G6PC mRNA expression, and has no significant effect on CPT1a mRNA expression in primary hepatocytes isolated from Holstein calves^[5]. In Vivo:2-Hydroxy-4-(methylthio)butyric acid (0.1% of diet; p.o. via diet; twice daily; 16 wk) has no significant effects on milk yield, milk composition, and nitrogen efficiency in Holstein cows^[2].
2-Hydroxy-4-(methylthio)butyric acid (prepartum: 0.09%, 0.18% of diet DM; postpartum: 0.13%, 0.20% of diet DM; p.o. via diet; from 21 d prepartum to 84 d postpartum) increases milk yield quadratically, with the highest yield in the 0.09% (prepartum) and 0.13% (postpartum) groups, but does not improve hepatic lipid metabolism in periparturient Holstein cows^[4].