Suppression of Lipid Accumulation in Differentiating 3T3-L1 Preadipocytes by a Standardized Commercial Juknyeok

Objectives: Juknyeok (JN) is natural liquor extracted from bamboo stems (Phyllostachys bambusoides) and has been used as a traditional Korean medicine for improving vascular function, blood glucose, and treating stroke. Until now, the JN’s lipid-lowering effect and underlying mechanism in adipocytes are poorly understood. The aim of this study was to scrutinize the effect of a standardized commercial JN on lipid accumulation during the differentiation of 3T3-L1 preadipocytes. Methods: Lipid and triglyceride (TG) accumulation in differentiating 3T3-L1 preadipocytes were measured by Oil Red O staining and AdipoRed assay, respectively. Cell count analysis was used to ascertain 3T3-L1 cytotoxicity. Immunoblotting and Reverse transcription polymerase chain reaction analysis were used to assess protein and messenger RNA (mRNA) expression levels in 3T3-L1 cells, respectively. Results: Treatment with JN at 25 μl/ml after pH calibration with 6.35 significantly reduced lipid and TG accumulation in differentiating 3T3-L1 preadipocytes without significant cytotoxicity. On mechanistic levels, JN markedly suppressed protein expression levels of CCAAT/enhancer-binding protein (C/EBP)-β and fatty acid synthase (FAS) during the differentiation of 3T3-L1 preadipocytes. However, JN did not affect the protein expression levels of C/EBP-α, peroxisome proliferator-activated receptor-β/γ, and phosphorylation levels of signal transducer and activator of transcription-3/5 in differentiating 3T3-L1 preadipocytes. JN also reduced leptin mRNA expression levels in differentiating 3T3-L1 preadipocytes. Conclusions: JN at 25 μl/ml lowers lipid accumulation and TG content in differentiating 3T3-L1 cells, mediated through the reduced expression levels of C/EBP-β and FAS.