MiR-335, an adipogenesis-related microRNA, is involved in adipose tissue inflammation

During the development of obesity, adipose tissue releases a host of different adipokines and inflammatory cytokines, such as leptin, resistin, tumor necrosis factor α (TNF-α), Interleukin-6 (IL-6), and adiponectin, which mediate insulin resistance. Recently, some microRNAs (miRNAs) regulated by adiponectin were identified as novel targets for controlling adipose tissue inflammation. Therefore, the relationship between adipokines and miRNA is worth studying. MiR-335 is an adipogenesis-related miRNA and implicated in both fatty acid metabolism and lipogenesis. In this study, we focused on the association of miR-335 and adipokines, and examined the expression trend of miR-335 during human adipocyte differentiation. Our results showed that miR-335 is significantly upregulated with treatment of leptin, resistin, TNF-α, and IL-6 in human mature adipocytes, and its expression elevated in the process of adipocyte differentiation. Interestingly, the transcriptional regulation of miR-335 by these adipokines seems independent of its host gene (mesoderm-specific transcript homolog, MEST). Thus, we cloned and identified potential promoter of miR-335 within the intron of MEST. As a result, a fragment about 600-bp length upstream sequences of miR-335 had apparent transcription activity. These findings indicated a novel role for miR-335 in adipose tissue inflammation, and miR-335 might play an important role in the process of obesity complications via its own transcription mechanism.