Thyroid-Stimulating Hormone Inhibits Insulin Receptor Substrate-1 Expression and Tyrosyl Phosphorylation in 3T3-L1 Adipocytes by Increasing NF-κB DNA-Binding Activity.

Yaoyao Bian,Yajing Zhang,Ling Feng

doi:10.1155/2022/7553670

Abstract

Background Abundant evidence indicates that thyroid-stimulating hormone (TSH) levels are associated with insulin resistance in adipocytes. However, the potential mechanism of the association remains uncertain. The objective of this study was to determine the potential role of TSH in the suppression of insulin receptor substrate-1 (IRS-1) expression and IRS-1 tyrosyl phosphorylation, which might contribute to insulin resistance. Methods Mouse 3T3-L1 preadipocytes were differentiated into adipocytes. After treatment with 0.01, 0.1, and 1.0 mIU/ml bovine TSH, the TNF-α concentration in the medium was determined by enzyme-linked immunosorbent assay (ELISA). Nuclear factor-kappa B (NF-κB) DNA-binding activity was quantified by electrophoretic mobility shift assay (EMSA). IRS-1 levels in adipocytes were quantified by Western blotting, and tyrosine phosphorylation was measured by immunoprecipitation. Results TSH induced TNF-α secretion in a dose-dependent manner. There was a significant positive correlation between NF-κB DNA-binding activity and TNF-α secretion. This effect and correlation were weakened by BAY 11-7082 (a nuclear NF-κB inhibitor) and H89 (an inhibitor of cyclic adenosine monophosphate- (cAMP-) dependent protein kinase A (PKA)). Treatment of cultured adipocytes with TSH inhibited insulin-stimulated IRS-1 tyrosyl phosphorylation but promoted TSH-dependent secretion of TNF-α and activation of NF-κB DNA-binding activity. The effects of TSH were significantly inhibited by BAY 11-7082 and H89 and were completely blocked by the TNF-α antagonist WP9QY. Conclusion TSH inhibited IRS-1 protein expression and tyrosyl phosphorylation in 3T3-L1 adipocytes by stimulating TNF-α production via promotion of NF-κB DNA-binding activity. TSH might play a pivotal role in the development of insulin resistance.

Highlights

Diabetes mellitus (DM) is a major chronic disease affecting humans
It was found that NF-κB DNA-binding activity was significantly and dose-dependently upregulated in cells treated with different concentrations of thyroid-stimulating hormone (TSH) (0.01, 0.1, and 1 mIU/ml) compared with control cells, especially in cells stimulated with 0.1 mIU/ml and 1 mIU/ml TSH (P < 0:01) (Figures 1(a) and 1(b))
These results indicated that TSH increased NF-κB DNA-binding activity in adipocytes

Summary

Introduction

Diabetes mellitus (DM) is a major chronic disease affecting humans. More than 95% of all cases of diabetes are type 2 DM (T2DM) [1]. It has been reported that TNF-α is the key mediator of insulin resistance in obesity because it suppresses insulin activity [5] by potently inhibiting the expression and tyrosyl phosphorylation of insulin receptor substrate-1 (IRS-1, the major insulin-like growth factor-I receptor), which might reduce the ability of IRS-1 to transduce signals in the insulin signaling system [6]. There was a significant positive correlation between NF-κB DNA-binding activity and TNF-α secretion This effect and correlation were weakened by BAY 11-7082 (a nuclear NF-κB inhibitor) and H89 (an inhibitor of cyclic adenosine monophosphate- (cAMP-) dependent protein kinase A (PKA)). Treatment of cultured adipocytes with TSH inhibited insulin-stimulated IRS-1 tyrosyl phosphorylation but promoted TSH-dependent secretion of TNF-α and activation of NF-κB DNA-binding activity. TSH inhibited IRS-1 protein expression and tyrosyl phosphorylation in 3T3-L1 adipocytes by stimulating TNF-α production via promotion of NF-κB DNA-binding activity. TSH might play a pivotal role in the development of insulin resistance

Objectives

Methods

Results

Conclusion