Abnormal sensitivity to glucose of human islets cultured in a high glucose medium: partial reversibility after an additional culture in a normal glucose medium

Prolonged exposure of human pancreatic islets to high glucose concentrations in vitro impairs the beta-cell function

The aim of the present study was to clarify whether prolonged in vitro exposure of human pancreatic islets to high glucose concentrations impairs the function of these cells. For this purpose, islets isolated from adult cadaveric organ donors were cultured for seven days in RPMI 1640 medium supplemented with 10% fetal calf serum and containing either 5.6, 11, or 28 mM glucose. There was no glucose-induced decrease in islet DNA content or signs of morphological damage. However, islets cultured at 11 or 28 mM glucose showed a 45 or 60% decrease in insulin content, as compared to islets cultured at 5.6 mM glucose. Moreover, when such islets were submitted to a 60-min stimulation with a low (1.7 mM) followed by a high (16.7 mM) concentration of glucose, the islets cultured at 5.6 mM glucose showed a higher insulin response to glucose than those of the two other groups. Islets cultured at the two higher glucose concentrations showed increased rates of insulin release in the presence of low glucose, and a failure to enhance further the release in response to an elevated glucose level. Islets cultured at 28 mM glucose showed an absolute decrease in insulin release after stimulation with 16.7 mM glucose, as compared to islets cultured at 5.6 mM glucose. The rates of glucose oxidation, proinsulin biosynthesis, and total protein biosynthesis were similar in islets cultured at 5.6 or 11 mM glucose, but they were decreased in islets cultured at 28 mM glucose. These combined results suggest that lasting exposure to high glucose concentrations impairs the function of human pancreatic islets.

Gene expression of type I phospholipase A2 in pancreatic beta cells. Regulation of mRNA levels by starvation or glucose excess

Messenger RNA from intact rat pancreatic islets, or from transformed hamster beta (HIT) cells, hybridized with the cDNA probe for type I (but not type II) phospholipase A2. The levels of phospholipase A2 mRNA increased in islets from fasted rats; they decreased in islets cultured in a high glucose concentration (control values at 5.5 mM glucose = 150 +/- 6% of those at 22 mM) which impaired subsequent insulin secretion (reduction in second-phase release = 70 +/- 11%). These studies uniquely demonstrate that type I phospholipase A2 is expressed specifically in beta cells and that nutrient availability modulates transcript levels, an effect which could that nutrient availability modulates transcript levels, an effect which could contribute to the detrimental influence of prolonged hyperglycemia on islet function.

Fresh human islet transplantation to replace pancreatic endocrine function in type 1 diabetic patients. Report of six cases

The aim of this study was to evaluate the feasibility of islet allografts in patients with type 1 diabetes mellitus. Six patients received human islets from either one or two donors via the portal vein, after (n = 4) or simultaneously with (n = 2) a kidney graft. The patients with functioning kidney grafts (nos. 1-4) were already on triple immunosuppressive therapy (cyclosporine A, azathioprine, prednisone). Prednisone was increased to 60 mg/day for 15 days after the islet transplant in patient 1. Patients 2-4 and the patients who underwent a simultaneous kidney-islets graft (nos. 5, 6) also received antilymphocyte globulin. Intravenous insulin was given for the first 15 days to maintain blood glucose concentrations within the normal range. Patient 1 rejected the islets within 15 days of islet transplantation. In patient 2, a 25% reduction in insulin requirement was observed and 12 months after transplantation post-prandial serum C-peptide was 1.5 ng/ml. In patient 3, the insulin requirement decreased from 40 to 8 units/day with a post-prandial serum C-peptide of 4.1 ng/ml 12 months after islet transplantation. In patient 4 the post-prandial secretion of C-peptide increased to 6.4 ng/ml. Six months after the islet infusion, insulin therapy was discontinued and HbA1c, 24-h metabolic profile and oral glucose tolerance test remained within the normal range. He had remained off insulin for 5 months until recently, when foot gangrene paralleled a worsening of post-prandial glycaemic control. Twelve months after transplantation he is receiving 8 units insulin/day.(ABSTRACT TRUNCATED AT 250 WORDS)