LNK deficiency aggravates palmitate-induced preadipocyte apoptosis

Abstract

LNK (SH2B3) is an intracellular adaptor protein that negatively regulates cellular proliferation or self-renewal of hematopoietic stem cells and some other progenitor cells. LNK is also recognized as a key regulator of insulin resistance and inflammatory responses in several tissues and organs. The function of LNK in adipose tissue is unknown. We previously demonstrated that type 2 diabetes mellitus (T2DM) mouse model had elevated serum free fatty acids (FFAs) levels and increased preadipocyte apoptosis in visceral fat tissue, showing the occurrence of lipotoxicity. Herein, when compared to control mice, the protein expression of LNK decreased in epididymal fat tissue from the high-sucrose/fat diet, low-dose streptozotocin induced T2DM mouse model. We thus investigated whether LNK could regulate palmitate-induced preadipocyte apoptosis in an in vitro apoptotic model in 3T3-L1 preadipocytes. LNK specific siRNA exacerbated palmitate-induced apoptosis and increased pro-apoptotic protein levels of cleaved caspase-3, Bax and cytochrome C; while overexpression of LNK cDNA exhibited significant anti-apoptotic effects. Consistently, LNK specific siRNA further decreased the Akt Ser-473 phosphorylation reduced by palmitate and located on upstream of Bax and cytochrome C. The siRNA-mediated LNK knockdown exacerbated mitochondrial membrane depolarization and mitochondrial-derived reactive oxygen species production induced by palmitate, whereas overexpression of LNK attenuated that. These results indicated that LNK plays a regulatory role in the palmitate-related preadipocyte apoptosis and might be involved in adipose tissue dysfunction.