Mechanism of holocarboxylase synthetase and biotin supplementation in promoting adipose development

Pig back fat (BF) thickness is a key indicator for evaluating lipid deposition in pigs. Consuming pork belly with thick BF can increase cholesterol intake and negatively impact human health. Holocarboxylase synthetase (HLCS) is a crucial ligase that binds biotin to carboxylases, affecting the function of biotin-dependent carboxylases. The relationship between single-nucleotide polymorphisms (SNPs) in <italic>HLCS</italic> and BF in pigs, along with the direct effects of <italic>HLCS</italic> on adipocyte development, remains unclear. While biotin is used to treat HLCS deficiency, its role in adipocyte development is not well understood. This study identified two <italic>HLCS</italic> SNPs associated with 100-kg BF in 592 Duroc pigs. In 3T3-L1 cells, <italic>HLCS</italic> interference reduced cell proliferation and decreased protein levels of phosphorylated p38 (p-p38) and phosphorylated signal-regulated kinase1/2 (p-ERK1/2) in the MAPK signaling pathway. Exogenous biotin promoted <italic>HLCS</italic> expression and alleviated the inhibitory effects of <italic>HLCS</italic> interference on lipogenesis-related genes, lipolysis-related genes, glycolysis-related genes, and p-ERK1/2 and p-p38 protein expression in adipocytes. In conclusion, <italic>HLCS</italic> is a significant candidate gene for pig BF development, with its interference adversely affecting adipocyte growth. Exogenous biotin not only stimulated HLCS expression but also influenced lipid metabolism by regulating carboxylase activity, glycolysis, and lipid synthesis/degradation through the MAPK pathway. This study provides new insights into HLCS function and the therapeutic role of biotin in HLCS deficiency, offering a theoretical foundation for molecular breeding of pigs with reduced BF.