Title

Interferon-γ-induced Regulation of Peroxisome Proliferator-activated Receptor γ and STATs in Adipocytes

Document Type

Article

Publication Date

3-9-2001

Abstract

Interferon-γ (IFN-γ) is known primarily for its roles in immunological responses but also has been shown to affect fat metabolism and adipocyte gene expression. To further investigate the effects of IFN-γ on fat cells, we examined the effects of this cytokine on the expression of adipocyte transcription factors in 3T3-L1 adipocytes. Although IFN-γ regulated the expression of several adipocyte transcription factors, IFN-γ treatment resulted in a rapid reduction of both peroxisome proliferator-activated receptor (PPAR) protein and mRNA. A 48-h exposure to IFN-γ also resulted in a decrease of both CCAAT/enhancer-binding α and sterol regulatory element binding protein (SREBP-1) expression. The short half-life of both the PPARγ mRNA and protein likely contributed to the rapid decline of both cytosolic and nuclear PPARγ in the presence of IFN-γ. Our studies clearly demonstrated that the IFN-γ-induced loss of PPARγ protein is partially inhibited in the presence of two distinct proteasome inhibitors. Moreover, IFN-γ also inhibited the transcription of PPARγ, which was accompanied by a decrease in PPARγ mRNA accumulation. In addition, exposure to IFN-γ resulted in a substantial increase in STAT I expression and a small increase in STAT 3 expression. IFN-γ treatment of 3T3-L1 adipocytes (48-96 h) resulted in a substantial inhibition of insulin-sensitive glucose uptake. These data clearly demonstrate that IFN-γ treatment results in the development of insulin resistance, which is accompanied by the regulation of various adipocyte transcription factors, in particular the synthesis and degradation of PPARγ.

Publication Source (Journal or Book title)

Journal of Biological Chemistry

First Page

7062

Last Page

7068

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