Thyroid-stimulating hormone decreases insulin receptor substrate 1 expression via stimulating TNF-αsecretion in 3T3-L1 adipocytes / 中华内分泌代谢杂志

ABSTRACT

3T3-L1 adipocytes transfected with TSH receptor (TSHR) shRNA were incubated with bovine TSH.The concentration of tumor necrosis factor (TNF)-α in culture medium was measured by enzyme linked immunosorbent asssy.Protein level of insulin receptor substrate 1 (IRS-1) was quantified by Western blotting.Tyrosine phosphorylation of IRS-1 was measured by immunoprecipitation.The results showed that 1 mIU/ml TSH significantly sitmulated TNF-α release in 3T3-L1 adipocytes [(341.85 ± 12.00 vs 522.67 ± 36.22) ng/L,P＜0.01],along with the decreases in IRS-1 protein expression and its tyrosine phosphorylation (P＜ 0.01).These effects disappeared when TSHR expression was down-regulated with RNA interference in 3T3-L1 adipocytes.In addition,WP9QY,a TNF-α antagonist,blocked TSH-decreased IRS-1 expresssion.These results suggest that TSH downregulates IRS-1 protein expression and its tyrosine phosphorylation through stimulating production of TNF-α,and thus contributes to the development of insulin resistance.