Abstract

BACKGROUND
It has been reported that a decrease in the beta-cell mass, may play a major role in the development of type 2 diabetes. Some stimuli that cause beta-cell loss can stimulate neogenesis from precursors as well as replication of matured beta-cells. In an animal-based studies reported that alpha-cells can also be produced in the course of alpha-cell neogenesis, after being treated with streptozotocin. Through this research, we attempted to determine the change of beta-cell mass according to the changes in alpha-cell mass and to characterize the size of the beta-cell nucleus observed in type 2 diabetes. METHOD: To estimate the relative fraction of alpha- and beta-cell mass in the pancreas, we counted beta-cells and alpha-cells by point count method. We also performed a double immunohistochemical staining with glucagon and insulin antibodies to calculate the ratio between these two cells area in the pancreas (A/B ratio). In order to measure the size of the beta-cell nucleus, an immunofluorescence staining of the nucleus and insulin was carried out. Data were gathered from type 2 diabetic subjects (n=19) and normal controls (n=8). RESULTS: Although there was no statistical difference, we observed the tendency of decrease of beta-cell mass and increase of alpha-cell mass in the pancreas of type 2 diabetic patients. The ratio of alpha-to beta-cell area in islet (A/B ratio) increased to 0.81+/-0.76 in diabetic patients compared to control with 0.26+/-0.25 (p<0.01). The mean of the A/B ratios of the islets more than 22,000 micro m2 was 1.64+/-1.10, whereas that of the islets less than 22,000 micro m2 was 0.73+/-0.67 in type 2 diabetic patients (p<0.01). The size of the beta-cell nucleus in both diabetic subjects and normal controls was bigger than that of exocrine cells (p<0.05) and 2.9% of beta-cells in type 2 diabetic subjects showed substantially enlarged nuclei more than M+5SD (M and SD means the average and standard deviation of nucleus size of exocrine cells, respectively) whereas this type of nucleus was found in only 0.5% of beta-cells in normal controls (p<0.05). CONCLUSION: The islet pathology in type 2 diabetes could be characterized by an expansion of alpha-cells associated with the selective loss of beta-cells. Some beta-cells found in diabetes showed a significant increase in size of the nucleus. Through the results from this study, we postulate that enlarged beta-cell nucleus and reverse of A/B ratio in the islets could be a marker of early senescence of beta-cells in patients with type 2 diabetes mellitus.

• Keywords: Selective beta cell loss;Expanded alpha cell mass;A/B ratio;Enlarged nuclei;Cell senescence