Effects of free fatty acids on gene and protein expression and tyrosine phosphorylation of leptin-receptor in rat hepatic cells

Objectives: The effects of free fatty acids on gene and protein expression and tyrosine phosphorylation of leptin receptor in rat hepatic cells were investigated. Methods: Hepatic cells were isolated from new born Sprague Dawley rats. After the rat hepatic cells were incubated with palmitate (0.25 mmol/L) or oleate (0.125 mmol/L) for 12, 24 and 36 hours, Western bolt was used to assess the protein abundance of leptin receptor in rat hepatic 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 incubated with free fatty acids(palmitate and oleate) for 12 and 24 hours, there was no difference of the protein content of leptin receptor among rat hepatic cells treated by palmitate and oleate and the control cells( P 0.05). The protein abundance of leptin receptor in rat hepatic cells was significantly decreased compared with the control after incubated with palmitate and oleate for 36 hours( P 0.05). The RNA content of leptin receptor in rat hepatic cells was similar to the control after incubated with palmitate and oleate for 12 hours( P 0.05),but significantly decreased after 24 or 36 hours( P 0.05).The tyrosine phosphorylation of Leptin receptor was remarkably reduced after incubated with palmitate and oleate for 24 or 36 hours( P 0.05). Conclusions: Free fatty acids(palmitate and oleate) may down regulate leptin receptor gene and protein expression and suppress its tyrosine phosphorylation in rat hepatic cells and may contribute to the occurrence of insulin resistance through inhibiting glucose metabolism and insulin action.