Mechanisms of Cinnamon Extract-Induced Suppression of the Intestinal Overproduction of Apolipoprotein B48-Containing Lipoproteins in Insulin Resistant High-Fructose Fed Animals.

We have reported previously that cinnamon extract (CE) prevents high-fructose (HF) feeding-induced whole-body insulin resistance by enhancing insulin signaling in skeletal muscle. In this study, we investigated whether intestinal apolipoprotein overproduction is inhibited by CE in this insulin-resistant animal model. After 2-hour acute CE oral treatment (50mg/kg body weigh), CE significantly inhibited total serum and triglyceride rich lipoprotein (TRL)-apoB48 in fasted HF-fed rats. In an olive oil-loading study, we also found that acute CE oral treatment inhibited the serum triglyceride levels in HF-fed rats but did not affect cholesterol or HDL levels. In a Triton-WR-1339 study, our results indicated that acute CE oral administration inhibited the overproduction of total serum and TRL-apoB48. In ex vivo pulse-chase labeling studies, the significant decreases were also observed in apoB48 secretion into media in freshly isolated enterocytes from HF-fed hamsters, together with increased apoB degradation. CE decreased the phosphorylation of p38 and ERK in normal hamster primary enterocytes, and increased the impaired phosphorylation of p38 and ERK in HF-fed hamster enterocytes. CE also decreased the protein mass of intestinal microsomal triglyceride Wansfer protein (MTP) in CE treated HF-hamster enterocytes. In summary, these data suggest that the overproduction of apoB48 can be acutely inhibited by CE treatment in a process involving p38, ERK phosphorylation and MTP expression. [ABSTRACT FROM AUTHOR]