Transcription factor HBP1 functions as a regulator of adipocyte differentiation

Abstract

Adipocyte differentiation is a complex process, involving many transcription factors. The transcription factor HBP1, a cell cycle inhibitor, is highly expressed in the adipose tissue in rat, but its role in adipocyte differentiation is not clear. The objective of the current study is to determine HBP1 as a regulator of adipocyte differentiation. We found that HBP1 expression was not increased until the late stage in 3T3‐L1 differentiation. HBP1 knockdown with either HBP1 siRNA or shRNA in 3T3‐L1 cells accelerated cell growth in the Mitotic Clonal Expansion (MCE) stage, but impaired adipogenesis, suggesting that increased HBP1 expression in the terminal differentiation stage is needed for full adipogenesis. We then hypothesized HBP1 as a potential PPAR£^target during the terminal differentiation stage. GW9662 (PPAR£^antagonist) inhibited HBP1 promoter activity and decreased HBP1 mRNA expression, whereas TZD (PPAR£^agonist) activated HBP1 promoter. Taken together, HBP1 seems to function as a stage‐specific regulator during adipocyte differentiation. These findings will help characterize HBP1 as a novel biomarker for adipocyte differentiation and a potential biological target in obesity intervention.Grant Funding Source: CMU95‐206