Decreases in both b-cell function and number can contribute to insulin deficiency in type 2 diabetes. Here, we quantified the b-cell mass in pancreas obtained at autopsy of 57 type 2 diabetic (T2D) and 52 non-diabetic subjects of European origin. Sections from the body and tail were immunostained for insulin. The b-cell mass was calculated from the volume density of b-cells (measured by point-counting methods) and the weight of the pancreas. The pancreatic insulin concentration was measured in some of the subjects. b-cell mass increased only slightly with body mass index (BMI). After matching for BMI, the b-cell mass was 41% (BMI < 25) and 38% (BMI 26-40) lower in T2D compared with non-diabetic subjects, and neither gender nor type of treatment influenced these differences. b-cell mass did not correlate with age at diagnosis but decreased with duration of clinical diabetes (24 and 54% lower than controls in subjects with <5 and >15 years of overt diabetes respectively). Pancreatic insulin concentration was 30% lower in patients. In conclusion, the average b-cell mass is about 39% lower in T2D subjects compared with matched controls. Its decrease with duration of the disease could be a consequence of diabetes that, with further impairment of insulin secretion, contributes to the progressive deterioration of glucose homeostasis. We do not believe that the small difference in b-cell mass observed within 5 years of onset could cause diabetes in the absence of b-cell dysfunction.

Insulin, glucagon, somatostatin and pancreatic polypeptide cells were stained by immunoperoxidase techniques and quantitated morphometrically in sections of pancreases obtained from eight control subjects, four Type 1 (insulin-dependent) and eight Type 2 (non-insulin-dependent) diabetic patients. The whole pancreas was studied to take into consideration the heterogeneous distribution of the different cell types. From the volume density of each cell type, and the weight of each lobe of the pancreas, the total mass of endocrine tissue was calculated. It averaged 1395 mg in control subjects, 413 mg in Type 1 and 1449 mg in Type 2 diabetic patients. The loss of endocrine tissue observed in the Type 1 patients was almost restricted to the lobe poor in pancreatic polypeptide cells. In these patients, B cells were practically absent (at the most seven per section), but the 'atrophic islets' still contained numerous A, D, or pancreatic polypeptide cells. The mass of A, D and pancreatic polypeptide cells and the ratio of D to A cells were not different from those measured in the control subjects. This shows that the disappearance of B cells in Type 1 diabetes has no preferential effect on any other endocrine cell of the pancreas. In Type 2 diabetes, the mass of A cells was increased, whereas that of B, D and pancreatic polypeptide cells was not changed. This hyperplasia of A cells leads to a decrease in the ratio of B to A and of D to A cells. These alterations may enlighten certain aspects of the physiopathology of Type 2 diabetes.

Pig islets encapsulated in a subcutaneous macrodevice can control diabetes up to 6 months without immunosuppression.

Optimal alginate encapsulation significantly prolonged adult pig islet survival into primates for up to 6 months, even in the presence of antibody response.

These results demonstrated that STZ might be used to induce irreversible diabetes in rats and primates. In contrast, the low STZ sensitivity in pigs related to a low expression of GLUT2, higher number of immature beta cells and compensatory beta-cell hypertrophy, renders STZ-induced diabetes inappropriate for studying islet allografts in swine.