Hepatic gene expression profile in persimmon peel extract administrated GK rat. Rattus norvegicus

Persimmon (Diospyros kaki L. f.) is a most popular fruit in Asian countries but its peels are totally wasted despite of containing a plenty of antioxidants such as carotenoids and polyphenols. We prepared a fat-soluble extract from a persimmon peel (PP) fraction and fed type 2 diabetic Goto-Kakizaki (GK) rats with a PP extract-containing AIN-93G diet (PP diet) for 12 weeks. Compared with the control AIN-93G diet, the feeding of the PP diet reduced the plasma glutamic-pyruvate transaminase activity significantly, with accumulation of β-cryptoxanthin in the liver. A DNA microarray analysis revealed that the PP diet altered the hepatic gene expression profiles. In particular, insulin signaling pathway-related genes were significantly enriched in differentially expressed gene sets. Moreover, Western blotting analysis actually showed the promotion of IRβ tyrosine phosphorylation. All these data suggest that the PP extract administration to the GK rats improves their insulin resistance. Overall design: Male GK rats (90–107 g), aged 5 weeks, were purchased from Japan SLC Co. (Hamamatsu, Japan). The rats were maintained in a room at 22 ± 1°C under a 12-h light-dark cycle (lights on at 0800) and administered a commercial diet (AIN-93G, Research Diets, Inc., New Brunswick, NJ, USA) for a week. The rats were allowed free access to diet and water. After one week, they were divided into two groups with similar average body weights. The control group rats (n = 4) were fed on the commercial diet, and the PP group rats (n = 4) on the same diet containing the PP extract. After the 12-week-feeding the liver was excised and analyzed the effect of PP extract administration on hepatic gene expression.