Objective: To elucidate cellular mechanisms of insulin resistance induced by high free fatty acids, and study the protein
abundance of insulin
receptor, insulin receptor substrate 1(IRS 1) and their tyrosine phosphorylation in palmitate or oleate treated rats skeletal muscle cells in vitro . Methods: The skeletal muscle cells were isolated from Wistar rat. When the cells differentiated to confluent and auto contraction, the media were replaced by 199 with palmitate (0.25 mmol·L -1 ) or oleate (0.125 mmol·L -1 ) then cells were incubated for 6, 12 and 24 hours. The
abundance of insulin receptor and IRS 1 was assessed by Western blot. The tyrosine phosphorylation of insulin receptor β subunit and IRS 1 was measured using immunoprecipitation and immunobloting with anti phosphor tyrosine antibodies. Results: (1)There was no change of insulin receptor levels in both fatty acids treated muscle cells. (2)The protein abundance of IRS 1 in palmitate and oleate treated muscle cells was decreased compared with control groups. (3)The insulin was less effective in stimulating tyrosine phospholation of insulin receptor and IRS 1 in fatty acids treated muscle cells. Conclusion: Decrease of IRS 1 protein abundance and tyrosine phosphorylation of insulin receptor β subunit and IRS 1 contributed significantly to the muscle insulin resistance induced by fatty acids.