Age dynamics of strain differences in the morphofunctional state of pancreatic beta- and amylin-producing cells in SHR and Wistar rats

Abstract

Large-scale epidemiological studies have shown that cardiac pathology and progressive atherosclerosis in patients with diabetes mellitus occurred already at the stage of prediabetes. Obesity and insulin resistance affect cardiometabolic health due to pleiotropic effects of insulin. Despite the vast range of research, some aspects remain hidden links in the overall pathogenesis of metabolic and hemodynamic disorders. The aim of the work was to study the morphofunctional state of pancreatic islets (PIs), beta- and amylin-producing cells in male rats of Wistar strain (normotensive) and SHR (with spontaneous development of hypertension) in age dynamics. Materials and methods. The study was carried out using 38 male Wistar rats and SHRs aged 7 and 24 months. Non-invasive blood pressure (BP) detection procedures were done using the BP-2000 Blood Pressure Analysis System. The morphofunctional state of PIs was examined in serial 5-μm thick pancreatic tissue sections. Beta- and amylin-producing cells were detected after histological preprocessing and the use of monoclonal FITC-conjugated antibodies. Image file processing was done via ImageJ software (National Institutes of Health, USA). Levels of glycemia were monitored with a SUPER GLUCOCARD-II glucometer. Results. SHRs were hyperglycemic both at 7 and at 24 months, 8.41 ± 0.15 mmol/l and 8.90 ± 0.14 mmol/l, respectively, with elevated BP, 155 ± 5 / 80 ± 5 mm Hg and 165 ± 5 / 90 ± 5 mm, respectively. Old SHRs developed PI hypertrophy mainly associated with the increased number and percentage of beta-cells, apparently in response to hyperglycemia. Both in the PIs of adult and old SHRs, the number of amylin-producing cells was lower while the content of amylin was higher than those in the age-matched Wistar rats. Conclusions. Male SHRs are characterized by a persistent increase in blood pressure and abnormalities of carbohydrate metabolism already at adult age, one of the manifestations of which is hyperglycemia worsening with age. Chronic hyperglycemia in SHRs due to the higher insulin requirement finds its expression in low content of this hormone in the islets at adult age and decreased its content in beta-cells in old animals.