A targeted proteomics approach for profiling nuclear proteins in insulin resistant adipocytes

Abstract

Insulin resistance (IR) predisposes to type 2 diabetes and cardiovascular diseases. Adipose tissue regulates glucose and lipid metabolism, and adipocyte dysfunction is linked to the development of IR. Transcription factors are the major regulators of adipocyte function, but the profiling of nuclear proteins in IR adipocytes has never been done. Here, we used selective reaction monitoring mass spectrometry to quantitatively measure the expression levels of nuclear proteins relevant to adipocyte function in IR adipocytes and pre‐adipocytes. We used 1) OP9 pre‐ and mature adipocytes treated with or without tumor necrosis factor α to induce IR, and 2) primary adipocytes isolated from IR obese (ob/ob) and C57 control mice. Our results show that IR pre‐and mature adipocytes have unique protein expression profiles, and the profiles obtained from IR primary adipocytes are a mix of these signatures, indicating defects in adipogenesis contribute to the development of IR in vivo. This is also indicated by decreased expression of pro‐adipogenic proteins such as CEBPα, PPARγ, and FAPB4 and increased expression of FLNA which is a negative regulator of PPARγ. Thus, we established a quantitative method to profile nuclear proteins in adipocytes. This approach may help diagnostics or drug screening for IR to prevent the onset of a more severe metabolic disease.