Oleic acid, independent of insulin, promotes differentiation of goat primary preadipocytes in vitro

Context. Oleic acid together with insulin is widely used to induce preadipocyte differentiation in humans and mammals, and is also used alone in chicken preadipocytes from abdominal adipose tissue. However, it is not clear whether oleic acid alone promotes goat primary intramuscular preadipocyte differentiation. Aims. The aim of the present study was to identify the role of oleic acid in regulating primary preadipocyte differentiation in goats. Methods. Three healthy, 7-day-old Jianzhou goats were randomly selected. After slaughter, the longissimus dorsi tissues were collected from each goat under sterile procedures and mixed equally. The primary preadipocytes were then prepared using collagenase type I digestion, and treated with 5 mg/L insulin or different concentrations of oleic acid, including 0 mu M, 50 mu M, 100 mu M, 150 mu M and 300 mu M. The results were determined using microscopy and Oil Red O staining. The expression of genes related to preadipocyte differentiation were determined by real-time fluorescence quantitative polymerase chain reaction. Results. Lower concentrations of oleic acid (50 mu M, 100 mu M and 150 mu M) did not affect the cell morphology and cell growth, whereas 300 mu M oleic acid led to severe cytotoxicity compared with the control (0 mu M). The treatment of oleic acid (100 mu M) enhanced cellular accumulation and lipid droplets deposition significantly, which was not affected by supplementary insulin. In addition, insulin alone treatment did not alter cellular adipogenesis in goat intramuscular preadipocytes. Treatment with oleic acid significantly increased the expression of peroxisome proliferator-activated receptor gamma, CCAAT enhancer-binding protein alpha and fatty acid binding protein 4, and decreased the expression of lipoprotein esterase on Day 2 after cell differentiation, all of which decreased continually on Day 4 and Day 6. Expression of all genes increased significantly on Day 8 after oleic acid treatment in goat intramuscular preadipocytes. Conclusion. The results underscore the role of oleic acid independent of insulin in promoting intramuscular preadipocytes in goats, and probably via the control of peroxisome proliferator-activated receptor gamma and CCAAT enhancer-binding protein alpha. Implications. These data provide insight into the mechanism underlying preadipocyte differentiation.