BDH1 acetylation at K116 modulates milk fat production in dairy goats

Goat milk is increasingly recognized for high digestibility and a distinctive compositional profile. Protein acetylation, an important post-translational modification, regulates biosynthetic and metabolic pathways. This study aimed to identify critical acetylated proteins and specific modification sites involved in milk production and component synthesis in dairy goats, thereby elucidating the molecular mechanisms of lactation. We performed a comparative TMT-based acetylomic and proteomic analysis of mammary tissues from Saanen dairy goats during peak lactation and the dry period using LC-MS/MS. A candidate acetylation site was further investigated in goat mammary epithelial cells (GMECs) through site-directed mutagenesis and lipid metabolic assays, establishing functional links between acetylation and mammary lipid metabolism and providing a foundation for molecular strategies to improve milk quality and yield.

We established a comprehensive mammary acetylome, identifying 862 significantly acetylated proteins and 2,028 modification sites across the two physiological phases. Differentially acetylated proteins were predominantly localized to the cytoplasm (39.98%). From these, 54 key acetylated proteins, including MTOR, BCAT2, QARS1, GOT1, GOT2, BDH1, ACSS1, STAT5B, FABP5, and GPAM were prioritized as candidates involved in milk protein synthesis, milk fat synthesis, lactose synthesis, and other lactation-related processes. Among them, β-hydroxybutyrate dehydrogenase 1 (BDH1) acetylation was characterized in detail. Members of the HDAC family were identified as primary regulators mediating BDH1 deacetylation. BDH1 acetylation promoted lipid droplet formation and triglyceride synthesis in GMECs. At the transcriptional level, BDH1 acetylation upregulated LXRα, ACSL1 and SCD1, whereas deacetylation downregulated SCD1, FASN, and ACSL1. Notably, BDH1 acetylation/deacetylation significantly reduced SREBP1 expression, linking this modification to coordinated control of lipogenic gene networks.

This study established, for the first time, the comprehensive acetylome of mammary gland tissues in dairy goats, revealing a substantial number of differentially acetylated proteins and modification sites. We demonstrate that acetylation of BDH1 regulated by HDACs promotes lipid droplet biogenesis and triglyceride synthesis in GMECs through transcriptional modulation of key lipogenic genes and suppression of SREBP1. These findings provide mechanistic insights into the post-translational regulation of mammary lipid metabolism and offer molecular targets for future genetic and nutritional strategies aimed at enhancing milk quality and yield in dairy goats.