Interleukin 4 affects lipid metabolism and the expression of pro-inflammatory factors in mature rat adipocytes

Chronic low-grade inflammation contributes to diseases associated with fat tissue metabolism such as obesity and diabetes by the disturbed production of adipose tissue proteins, both pro- and anti-inflammatory. Interleukin-4 (IL-4) is one of the main inflammatory cytokines that activates Th2-dependent immune response and its increased expression was observed in the course of diseases characterized by chronic low-grade systemic inflammation such as obesity and asthma. We aimed to investigate if IL-4 may influence lipid metabolism and inflammatory responses in primary mature rat adipocytes. Mature adipocytes were isolated from male Wistar rats in incubated with IL-4 at three concentrations. We measured lipogenesis and lipolysis as well as the expression of selected genes using ddCt method was used to calculate relative gene expression. Protein level in tissue was analyzed using Western blot. Protein concentration in cell medium was analyzed using ELISA. Statistical analysis was done using GraphPad Prism 5 software. In primary cell model, we found that IL-4 stimulated lipogenesis and inhibited lipolysis in mature rat adipocytes. It also stimulated the expression of pro-inflammatory cytokines produced by adipocytes and decreased the expression of anti-inflammatory protein, adiponectin. Moreover, we found increased expression of inflammatory cytokines and transcription factors associated with Th2 response. Our observations suggest that low-grade inflammation enhances fat accumulation and significantly alters adipocyte metabolism.