Insulin Interacts with PPARγ Agonists to Promote Bovine Adipocyte Differentiation

Insulin is a potent adipogenic hormone that triggers a series of transcription factors that regulate the differentiation of preadipocytes into mature adipocytes. Ciglitazone specifically binds to peroxisome proliferator−activated receptor−γ (PPARγ), thereby promoting adipocyte differentiation. As a natural ligand of PPARγ, oleic acid (OA) can promote the translocation of PPARγ into the nucleus, regulate the expression of downstream genes, and promote adipocyte differentiation. We hypothesized that ciglitazone and oleic acid interact with insulin to enhance bovine preadipocyte differentiation. Preadipocytes were cultured 96 h in differentiation medium containing 10 mg/L insulin (I), 10 mg/L insulin + 10 µM cycloglitazone (IC), 10 mg/L insulin + 100 µM oleic acid (IO), or 10 mg/L insulin + 10 µM cycloglitazone+100 µM oleic acid (ICO). Control preadipocytes (CON) were cultured in differentiation medium (containing 5% fetal calf serum). The effects on the differentiation of Yanbian cattle preadipocytes were examined using molecular and transcriptomic techniques, including differentially expressed genes (DEGs) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis. I, IC, IO, and ICO treatments produced higher concentrations of triglycerides (TAG) and lipid droplet accumulation in preadipocytes compared with CON treatment (P < 0.05). Co−treatment of insulin and PPARγ agonists significantly increased the expression of genes involved in regulating adipogenesis and fatty acid synthesis. (P < 0.05). Differential expression analysis identified 1488, 1764, 1974 and 1368 DEGs in the I, IC, IO and ICO groups, respectively. KEGG pathway analysis revealed DEGs mainly enriched in PPAR signalling, FOXO signaling pathway and fatty acid metabolism. These results indicate that OA, as PPARγ agonist, can more effectively promote the expression of bovine lipogenesis genes and the content of TAG and adiponectin when working together with insulin, and stimulate the differentiation of bovine preadipocytes. These findings provide a basis for further screening of relevant genes and transcription factors in intramuscular fat deposition and meat quality to enhance breeding programs.