Effect of increasing acetate, butyrate, and beta-hydroxy butyrate on expression of lipogenic genes in bovine mammary epithelial cell culture

Acetate and butyrate are the main lipogenic short-chain fatty acids (SCFA). β-hydroxybutyrate (BHB) is synthesized primarily from butyrate and can also serve as a substrate for mammary de novo fatty acid synthesis. Acetate supplementation in vivo increases milk fat yield, but the direct effect of SCFA and BHB on transcriptional regulation of lipid synthesis in mammary epithelial cells remains unclear. This study was designed to specifically evaluate the direct effects of increasing sodium butyrate, sodium acetate, and BHB on lipogenic gene expression in mammary epithelial cells (MAC-T). Cells were treated for 24 h with 0, 4, 8, or 12 mM of each and expression of ACSS2 , ACACA , FASN , SCD1 , INSIG1 , and SREBF1C genes were analyzed. Butyrate increased lipogenic genes to the greatest extent, with a dramatic increase in SREBF1c (>14-fold at 12 mM), FASN , ACACA , and SCD1 . Sodium acetate had modest effects, increasing ACSS2 and SCD1 expression without broad activation of other lipogenic genes. However, BHB increased FASN (∼16-fold at 8 mM) but had minimal effects on SREBF1c , INSIG1 , or SCD1 . BHB also increased PPARG and FABP3 , which was not observed with acetate or butyrate. In summary, butyrate strongly increased expression of mammary lipogenic genes, consistent with both its role as a preferred primer for fatty acid synthesis and reported HDAC-inhibitory activity. Acetate and BHB exerted more limited, pathway-specific responses, underscoring potentially distinct mechanisms of SCFA-mediated regulation of expression of lipid metabolism enzymes in the mammary gland. Future work will be needed to determine the functional roles on the rate of lipid synthesis.