Free fatty acids act on gene and protein expression and tyrosine phosphorylation of Leptin-receptor in rat skeletal muscle cells

AIM To investigate effect of free fatty acid on gene and protein expression and tyrosine phosphorylation of leptin receptor in rat skeletal muscle cells. METHODS Skeletal muscle cells were isolated from new born Sprague Dawley rats. After rat skeletal muscle cells were incubated with palmitate (0.25 mmol·L -1 ) or oleate (0.125 mmol·L -1 ) for 12 h, 24 h and 36 h, Western bolt was used to assess the protein abundance of Leptin receptor in rat skeletal muscle cells. The RNA expression level of Leptin receptor was revealed by RT PCR. The tyrosine phosphorylation of Leptin receptor was revealed by immuno precipitation. RESULTS After being incubated with free fatty acids (palmitate and oleate) for 12 and 24 h, there was no difference of the protein content of leptin receptor among rat skeletal muscle cells treated by palmitate and oleate and control cells ( P 0.05). The protein abundance of leptin receptor in rat skeletal muscle cells significantly decreased compared with control after incubated with palmitate and oleate for 36 h [palmitate (0.36±0.03) and oleate (0.35±0.04) vs control (0.39±0.05), P 0.05]. The RNA contents of leptin receptor in rat skeletal muscle cells were similar to control after being incubated with palmitate and oleate for 12 h ( P 0.05), but significantly decreased after 24 or 36 h [24 h: palmitate (0.26±0.03) and oleate (0.26±0.04) vs control (0.31±0.03), P 0.05; 36 h: palmitate (0.25±0.04) and oleate (0.23±0.03) vs control (0.29±0.01), P 0.05]. The tyrosine phosphorylation of Leptin receptor remarkably reduced after being incubated with palmitate and oleate for 24 or 36 h [24 h: palmitate (0.17±0.05) and oleate (0.15 ± 0.06) vs control (0.21±0.07), P 0.05; 36 h: palmitate (0.15 ±0.04) and oleate (0.13±0.04) vs control (0.24± 0.06), P 0.05]. CONCLUSION Free fatty acids (palmitate and oleate) may down regulate leptin receptor gene expression and suppress its tyrosine phosphorylation in rat skeletal muscle cells and may contribute to the occurrence of insulin resistance through inhibiting glucose metabolism and insulin action.