Hepatic gene expression of the insulin signaling pathway is altered by administration of persimmon peel extract: a DNA microarray study using type 2 diabetic Goto-Kakizaki rats

Persimmon (Diospyros kaki) is a very popular fruit in East Asian countries, but its peels are not consumed despite the fact that they contain many antioxidants such as carotenoids and polyphenols. We prepared a fat-soluble extract from persimmon peel (PP) and fed type 2 diabetic Goto-Kakizaki (GK) rats an AIN-93G rodent diet supplemented with persimmon peel extract (PP diet) for 12 weeks. Compared with the control AIN-93G diet, the PP diet significantly reduced plasma glutamic-pyruvate transaminase activity, with accumulation of β-cryptoxanthin in the liver. DNA microarray analysis revealed that the PP diet altered hepatic gene expression profiles. In particular, expression of insulin signaling pathway-related genes was significantly enriched in differentially expressed gene sets. Moreover, Western blotting analysis showed an increase in insulin receptor beta tyrosine phosphorylation in rats fed the PP diet. These data suggest that the PP diet improves insulin resistance in GK rats.