Soluble receptor for advanced glycation end-products in Chinese Type 1 Diabetic Patients

Abstract

OBJECTIVES: The receptor for advanced glycation end-products (RAGE) plays an important role in the pathogenesis of diabetic complications. Interfering with the activation of RAGE by using a soluble form of the receptor (sRAGE) ameliorates the vascular complications of diabetes in animal models. sRAGE in the human circulation is partly derived from ectodomain shedding of the membrane-associated receptor. We have investigated the effect of insulin on the generation of sRAGE in vitro and evaluated serum levels of sRAGE in a group of Chinese type 1 diabetic subjects. METHODS: THP-1 cells were incubated with insulin in vitro and sRAGE in the medium measured by Western immunoblot. Cell-surface biotinylation and immunoprecipitation was performed to investigate ectodomain shedding. Serum level of sRAGE in diabetic patients was measured by ELISA. RESULTS: Insulin increased sRAGE in cell conditioned-media in a time- and dose-dependent manner. Pretreatment of THP-1 cells with GM6001, a general metalloproteinase inhibitor which blocked cellular shedding events, significantly reduced the production of sRAGE. This would suggest that the increase in sRAGE upon incubation with insulin was partly due to the shedding of sRAGE by cleavage of full-length cell surface RAGE. In type 1 diabetic patients (n = 120), serum sRAGE was higher compared to a group of age-matched non-diabetic healthy subjects (1021.6 pg/mL [724.8–1212.4.0] vs 812.9 pg/mL [548.0–1202.2.5] respectively, P = 0.004). CONCLUSIONS: Chinese type 1 diabetic patients have higher serum levels of sRAGE and we have shown that insulin can stimulate the ectodomain shedding of cell surface RAGE.