Aim: To evaluate the effects of exposure to high glucose (HG) levels and sulphonylurea on isolated human islet-cell function, and to investigate some of the mechanisms that might be involved.
Methods: Islet cells were isolated, using collagenase digestion and gradient purification, from 13 pancreata from non-diabetic multiorgan donors (age: 61.2+/-11.5 years; gender: 7 men/6 women; body mass index: 25.1+/-2.8kg/m(2)). The cells were then cultured for 5 days with normal glucose (NG) concentrations (5.5mmol/L), or NG and HG (16.7mmol/L) levels (alternating every 24h), with or without the addition of therapeutic concentrations of gliclazide (10micromol/L) or glibenclamide (1.0micromol/L). At the end of incubation, functional (glucose-stimulated insulin secretion), morphological (electron microscopy) and molecular (gene and protein expression) studies were performed.
Results: Insulin secretion differed significantly between study groups, with marked decreases in the presence of HG plus glibenclamide. Compared with NG, insulin expression decreased significantly with HG, and increased similarly with gliclazide as with glibenclamide. However, exposure to gliclazide, but not glibenclamide, significantly induced expression (at both gene and protein levels) of PDX-1, a fundamental beta-cell differentiation transcription factor, and Ki67, a marker of proliferation. However, gliclazide and glibenclamide did not differ in terms of effects on gene expression of the antiapoptotic molecule Bcl2 (increased significantly with both) and the proapoptotic molecule Bax (decreased significantly with both).
Conclusion: Gliclazide and glibenclamide have different effects on the changes induced by prolonged exposure of human islet cells to high levels of glucose.