Cinnamon extract and polyphenols affect the expression of tristetraprolin, insulin receptor, and glucose transporter 4 in mouse 3T3-L1 adipocytes

Cinnamon improves glucose and lipid profiles of people with type 2 diabetes. Water-soluble cinnamon extract (CE) and HPLC-purified cinnamon polyphenols (CP) with doubly linked procyanidin type-A polymers display insulin-like activity. The objective of this study was to investigate the effects of cinnamon on the protein and mRNA levels of insulin receptor (IR), glucose transporter 4 (GLUT4), and tristetraprolin (TTP/ZFP36) in mouse 3T3-L1 adipocytes. Immunoblotting showed that CP increased IRβ levels and that both CE and CP increased GLUT4 and TTP levels in the adipocytes. Quantitative real-time PCR indicated that CE (100 μg/ml) rapidly increased TTP mRNA levels by approximately 6-fold in the adipocytes. CE at higher concentrations decreased IRβ protein and IR mRNA levels, and its effect on GLUT4 mRNA levels exhibited a biphasic pattern in the adipocytes. These results suggest that cinnamon exhibits the potential to increase the amount of proteins involved in insulin signaling, glucose transport, and anti-inflammatory/anti-angiogenesis response.