Human pancreatic islet function at the onset of Type 1 (insulin-dependent) diabetes mellitus

Abstract

Summary. Viable human pancreatic islets isolated from a recent-onset Type 1 (insulin-dependent) diabetic patient were used to perform in vitro studies. Pre-proinsulin mRNA and insulin content, as well as insulin response were analyse d . Insulin response to glucose and forskolin was completely absent in diabetic islets, as compared to control islets. Insulin content was reduced to only one-third of control values (395.0 + 3.5 vs 989.0 _+ 46.3 gU/islet) and 20.7 + 3.9 % of islets from the diabetic pancreas contained insulin-positive cells in immunofluorescence studies. Northern blot analysis revealed a severe reduction in the content of pre-proinsulin mRNA in diabetic pancreatic tissue. Our results indicate that although markedly decreased, beta cells in human pancreatic islets at the onset of Type 1 diabetes are still present. Nevertheless, pancreatic islet function is disproportionately impaired with a complete absence of an insulin response. Key words:Human islets, islet function, onset of Type 1 (insulin-dependent) diabetes mellitus.Type i (insulin-dependent) diabetes mellitus is an autoimmune disease caused by the selective destruction of islet beta cells. Attempts have been made to define the immunopathological aspects of this destruction. This has shown that pancreatic tissue from newly-diagnosed Type i diabetic patients presents several distinct features including: severely reduced beta-cell mass, various degrees of expression of MHC class I and class II antigens in islet cells and lymphocytic infiltrates [1][2][3]. However, the beta-cell secretory function of this clinical entity has only been evaluated in in vivo studies [4].We report here the first study in which viable human pancreatic islets were isolated from a recent-onset Type 1 diabetic patient and thus were used to perform in vitro functional studies. Subjects and methodsAfter obtaining the family's informed consent and with the approval of the Hospital Ethics Committee, human pancreatic islets were isolated from the pancreas of a islet cell antibody positive 18-year-old woman who had died 6 h after her admission because of diabetic ketoacidosis. She had been asymptomatic up to 2 days prior to admission when polydipsia, polyuria and polyphagia were observed. Islets were obtained following a modification of Ricordi's automatic digestion technique [5]. The pancreas from the diabetic patient was treated in the same manner as the pancreata obtained from the control cadaveric organ donors with a similar time period between death and pancreas removal. Briefly, after the pancreatic duct was cannulated, Hanks' balanced salt solution (HBSS) at 37 ~ containing 1% newborn calf serum (NCS; Gibco, Paisley, UK), 2.5 mg/ml collagenase (Type P; Boehringer Mannheim, Mannheim, FRG) and 0.04mg/ml deoxyribonuclease (DNAseI; Sigma, St.Louis, Mo., USA) was injected. The pancreas was loaded into a digestion chamber and was connected to a closed circuit with recircularization of the medium and continuously shaken. Samples were taken every 3 min, stained with dithizone ...

The Cytokine Interleukin-1β Reduces the Docking and Fusion of Insulin Granules in Pancreatic β-Cells, Preferentially Decreasing the First Phase of Exocytosis

“…There are already subtle changes in ␤-cell function during this period, including both disproportionately elevated proinsulin/insulin levels (4, 5) and a preferential loss of the first phase insulin secretion in response to an intravenous glucose challenge (6 -9). Of note, ␤-cell suppression precedes ␤-cell death in T1D, as suggested by results obtained in islets isolated from prediabetic non-obese diabetic mice (10,11) or from a patient who died immediately after diagnosis of T1D (12). This initial ␤-cell functional suppression might be due to exposure to cytokines.…”

Islet inflammation in human type 1 diabetes mellitus

“…A second patient (18 years) who was studied immediately after disease diagnosis also retained insulin‐positive islets which could be harvested following isolation; however, in this case, no insulin secretory response to glucose (or forskolin) was evident, leading the authors to conclude that islet function was ‘disproportionately impaired’ . The third patient was a girl of 14 years who died 8 months after diagnosis of T1DM and whose insulin‐containing islets were harvested and then studied after various periods of tissue culture .…”

Tumour necrosis factor-α-induced glucose-stimulated insulin secretion inhibition in INS-1 cells is ascribed to a reduction of the glucose-stimulated Ca2+ influx

“…The inhibition of GSIS as a functional defect of pancreatic b-cells was reported to be a characteristic of the pre-diabetic stage in autoimmune type 1 diabetic subjects (Conget et al 1993, Sherry et al 2005, but this inhibition could be restored in in vitro cultures (Strandell et al 1990). …”