The aim of the current study was to investigate the regulatory effect of sericin on the hepatic insulin-phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in a type 2 diabetes rat model. Male Sprague Dawley rats were randomly divided into four groups: Control group, diabetic model group, high-dose sericin group and low-dose sericin group, with 12 rats in each group. Fasting blood glucose was detected by the glucose oxidase method, and hepatic glycogen was determined by periodic acid-Schiff staining. The morphology of the liver was observed by hematoxylin and eosin staining. Immunohistochemical staining, western blotting and reverse transcription-quantitative polymerase chain reaction were used to determine the protein and mRNA expression levels of insulin receptor (IR), IR substrate-1 (IRS-1), PI3K and AKT. Compared with the control group, the blood glucose of the diabetic model group was significantly increased (P<0.05). The glycogen content and the expression levels of IR, IRS-1, PI3K and AKT in the diabetic model group were significantly lower (P<0.05), and the liver morphological structure of the diabetic model group exhibited obvious pathological changes compared with the control group. Compared with the diabetic model group, the blood glucose of the high- and low-dose sericin groups was significantly reduced, while the glycogen content and the expression levels of IR, IRS-1, PI3K and AKT in the sericin treatment groups were significantly increased (P<0.05). Additionally, the liver pathological changes of high-dose and low-dose sericin groups were markedly reduced. Sericin may enhance the signaling transduction effect of insulin by upregulating the expression levels of key factors (IR, IRS-1, PI3K and AKT) in the liver insulin-PI3K/AKT signaling pathway, thus promoting glucose transport and liver glycogen synthesis, and further reducing blood glucose.
Keywords: insulin; liver; phosphoinositide 3-kinase/protein kinase B signaling pathway; sericin; type 2 diabetes mellitus.