Lipotropes alter casein gene expression in bovine mammary acinar culture.

Lipotropes (methyl group containing nutrients, including methionine and choline, folic acid, and vitamin B(12)) are essential for cell proliferation and differentiation of mammary tissues. Lipotropes interact in the supply and regulation of intracellular methyl group pools, thereby affecting synthesis and methylation of DNA. To determine the effect of lipotropes on milk protein gene expression, acini isolated from mammary tissues of lactating cows were cultured in one of three treatment media: (1) control, (2) lipotrope deficient, and (3) lipotrope supplemented. beta-Casein mRNA was determined by Northern blotting, and milk protein secretion was measured by a pulse-chase method. The level of beta-casein mRNA was lower in cells grown in lipotrope-deficient medium than in cells grown in the lipotrope-supplemented and control media. Acinar cells cultured in lipotrope-deficient medium also had approximately threefold less milk protein secretion than that of cells in either control or lipotrope-supplemented media. Protein secretion did not differ in the control and lipotrope-supplemented groups. The present study indicates that lipotrope deficiency suppresses total protein secretion and beta-casein gene expression in bovine mammary alveolar epithelial cells in culture.