Glycated fetal calf serum affects the viability of an insulin-secreting cell line in vitro

Abstract

The purpose of the present study was to evaluate the direct effects of advanced glycation end products (AGEs) on β-cells by their exposure to a glycated serum to estimate the cellular viability and the related insulin secretion. Glycation of fetal calf serum was obtained by incubation with 50 mol/L ribose at 37°C for 7 days; at the end of this incubation period, the pentosidine content ranged between 15 and 16 × 10 5 pmol/L. HIT-T15 cells, a pancreatic islet cell line, were grown and cultured for 5 days in Roswell Park Memorial Institute (RPMI) medium containing either not glycated (NGS) or glycated (GS) fetal calf serum. Cellular oxidative stress (ie, thiobarbituric acid-reactive substances) was assessed by high-performance liquid chromatography. Cellular viability was evaluated by detection of proliferation, cell necrosis, and cell apoptosis rate. The insulin secretion and the related intracellular content were evaluated by enzyme-linked immunosorbent assay. The present study reported, after 5 days of exposure to the glycation environment, a moderately reduced cellular proliferation (−20.44% ± 2.92%) with a corresponding increase of cell necrosis (+67.7% ± 1.56%) and cell apoptosis (+39.83% ± 2.92%) rate in comparison with the untreated cells. Oxidative intracellular stress was higher in GS conditions compared with the NGS ones (+293.3% ± 87.53%). Insulin release from GS-treated HIT-T15 cells was lower than that of NGS-treated cells both when cells were stimulated with low glucose concentration (2.8 mmol/L, −30.3% ± 4.91%) or when they were challenged with high glucose concentration (16.7 mmol/L, −29.2% ± 5.82%). Incubation of HIT-T15 cells with glycated serum also caused a significant decrease of insulin intracellular content (−44.47% ± 9.98%). Thus, AGEs were shown to exert toxic effects on insulin-secreting cells. Chronically high intracellular oxidative stress, due to accumulation of AGEs, affects the insulin secretion machinery. The present data suggest a pivotal role of the non-enzymatic glycation process in the onset and progression of diabetes during aging and a direct adverse effect of a glycated environment on the pancreatic islet cells.