The effects of type 1 IGF receptor inhibition in a mouse model of diabetic kidney disease

Human umbilical cord mesenchymal stem cells attenuate diabetic nephropathy through the IGF1R-CHK2-p53 signalling axis in male rats with type 2 diabetes mellitus

Diabetes mellitus (DM) is a disease syndrome characterized by chronic hyperglycaemia. A long-term high-glucose environment leads to reactive oxygen species (ROS) production and nuclear DNA damage. Human umbilical cord mesenchymal stem cell (HUcMSC) infusion induces significant antidiabetic effects in type 2 diabetes mellitus (T2DM) rats. Insulin-like growth factor 1 (IGF1) receptor (IGF1R) is important in promoting glucose metabolism in diabetes; however, the mechanism by which HUcMSC can treat diabetes through IGF1R and DNA damage repair remains unclear. In this study, a DM rat model was induced with high-fat diet feeding and streptozotocin (STZ) administration and rats were infused four times with HUcMSC. Blood glucose, interleukin-6 (IL-6), IL-10, glomerular basement membrane, and renal function were examined. Proteins that interacted with IGF1R were determined through coimmunoprecipitation assays. The expression of IGF1R, phosphorylated checkpoint kinase 2 (p-CHK2), and phosphorylated protein 53 (p-p53) was examined using immunohistochemistry (IHC) and western blot analysis. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of 8-hydroxydeoxyguanosine (8-OHdG). Flow cytometry experiments were used to detect the surface markers of HUcMSC. The identification of the morphology and phenotype of HUcMSC was performed by way of oil red "O" staining and Alizarin red staining. DM rats exhibited abnormal blood glucose and IL-6/10 levels and renal function changes in the glomerular basement membrane, increased the expression of IGF1 and IGF1R. IGF1R interacted with CHK2, and the expression of p-CHK2 was significantly decreased in IGF1R-knockdown cells. When cisplatin was used to induce DNA damage, the expression of p-CHK2 was higher than that in the IGF1R-knockdown group without cisplatin treatment. HUcMSC infusion ameliorated abnormalities and preserved kidney structure and function in DM rats. The expression of IGF1, IGF1R, p-CHK2, and p-p53, and the level of 8-OHdG in the DM group increased significantly compared with those in the control group, and decreased after HUcMSC treatment. Our results suggested that IGF1R could interact with CHK2 and mediate DNA damage. HUcMSC infusion protected against kidney injury in DM rats. The underlying mechanisms may include HUcMSC-mediated enhancement of diabetes treatment via the IGF1R-CHK2-p53 signalling pathway.

IGF-1/IGF-1R blockade ameliorates diabetic kidney disease through normalizing Snail1 expression in a mouse model

This study investigated the role of insulin-like growth factor-1/insulin-like growth factor-1 receptor (IGF-1/IGF-1R) in the genesis and progression of diabetic kidney disease (DKD) in a streptozotocin (STZ)-induced mouse diabetes model. We showed elevated IGF-1 expression in the DKD kidneys after 16 wk of diabetic onset. Intraperitoneal administration of IGF-1R inhibitor (glycogen synthase kinase-3β, GSK4529) from week 8 to week 16 postdiabetes induction ameliorated urinary albumin excretion and kidney histological changes due to diabetes, including amelioration of glomerulomegaly, inflammatory infiltration, and tubulointerstitial fibrosis. The GSK4529 treatment also attenuated alterations in renal tubular expression of E-cad and matrix protein fibronectin. Moreover, renal fibrosis in DKD (without treatment) was associated with Snail1 overexpression that was effectively prevented by IGF-1R inhibition. Further experiments in cultured renal epithelial cells (NRK) showed that IGF-1 silencing reproduced in vivo effects of IGF-1R inhibition with markedly attenuated Snail1 expression and near normalization of the Ecad1 and fibronectin expression pattern. Further Snail1 silencing prevented high-glucose-induced changes without affecting IGF-1 expression, consistent with Snail1 acting downstream to IGF-1. The antifibrotic effects were also shown with benazepril or insulin treatment but to a much lesser degree. In summary, in STZ-induced diabetic mice, activation of IGF-1 in diabetic kidneys induces fibrogenesis through Snail1 upregulation. The diabetes-related histological and functional changes, as well as fibrogenesis, can be attenuated by IGF-1/IGF-1R inhibition.