The extract of Cinnamomum cassia twigs inhibits adipocyte differentiation via activation of the insulin signaling pathway in 3T3-L1 preadipocytes.

Context: Obesity is associated with a number of diseases with metabolic abnormalities such as type 2 diabetes (T2D). Medicinal plants have been widely used for the treatment of obesity and related complications. Objective: In this study, we investigated the antidiabetic properties of the extract of twigs of Cinnamomum cassia Blume (Lauraceae) (Cinnamomi Ramulus; CR) in 3T3-L1 murine preadipocytes. Materials and methods: 3T3-L1 cells were differentiated into adipocytes for 3 d in insulin-conditioned medium and then treated with CR extract at concentrations of 100 and 500 mu g/mL for 6 d. Adipocyte differentiation was measured by Oil Red O staining, and the expression of master transcription factors, peroxisome proliferator-activated receptor-gamma (PPAR gamma), CCAAT/enhancer binding protein-alpha (C/EBP alpha), and sterol regulatory element binding protein-1c (SREBP-1c), and lipid metabolism factors were investigated by reverse transcription-polymerase chain reaction (RT-PCR). The activation of the AMP-activated protein kinase (AMPK)/insulin signaling pathway was assessed by western blot analysis. Results: CR extract significantly reduced lipid accumulation and down-regulated the expression of PPAR gamma, C/EBP alpha, and SREBP-1c in 3T3-L1 adipocytes. CR extract also suppressed the expression of fatty acid synthase (FAS), acyl-CoA synthase, and perilipin. Moreover, CR extract markedly up-regulated the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC). In addition, CR extract effectively increased the expression levels of glucose transporter-4 (GLUT-4), phosphatidylinositol 3-kinase (PI3K), and insulin receptor substrate-1 (IRS-1) in 3T3-L1 adipocytes. Discussion and conclusion: These results suggest that CR extract may have therapeutic potential as a natural agent for the improvement of T2D via regulation of the insulin-dependent signaling pathway.