Suppression of bank vole pancreatic islet function by proinflammatory cytokines

Eugenol Improves Insulin Secretion and Content of Pancreatic Islets from Male Mouse

Glucose homeostasis is required for control of insulin secretion. Phenolic compounds improved glucose-stimulated insulin secretion (GSIS). Eugenol is a phenolic compound that may increase GSIS. So, it was decided to investigate the effect of eugenol on the insulin secretion and content of pancreatic islets from the male mice. In this experimental study, 3-month-old NMRI mice (20-25 g) were prepared. The pancreatic islets of Langerhans were isolated using the collagenase digestion method and divided into 12 groups: glucose 2.8, 5.6, and 16.7 mM, glucose 2.8 mM + eugenol 50, 100, and 200 µM, glucose 5.6 mM + eugenol 50, 100, and 200 µM, and glucose 16.7 mM + eugenol 50, 100, and 200 µM. The islet's insulin secretion and content were measured after 1 hour and 24 hours incubation at 37°C, respectively, by the ELISA assays method and related commercial kit. Present results showed that all doses of eugenol increased islet's insulin secretion and content in the medium containing glucose concentrations 2.8, 5.6, and 16.7 mM (P < 0.05). In conclusion, eugenol as a phenolic compound increased insulin secretion and content of pancreatic islets. The moderate dose of this compound enhanced insulin secretion during hypo- and hyperglycemic conditions, as well as a high dose of eugenol, increased insulin content. Finally, present research suggested that the administration of eugenol 100 µM was suitable for the early stage of T2DM as well as eugenol 200 µM for the advanced stage of this disease.

Anti-apoptotic Effects of Bone Marrow on Human Islets: A Preliminary Report

Apoptosis is one of the major factors contributing to the failure of human islet transplantation. Contributors to islet apoptosis exist in both the pre-transplantation and post transplantation stages. Factors include the islet isolation process, deterioration in vitro prior to transplantation, and immune rejection post transplantation. Previous studies have demonstrated that co-cultured bone marrow cells with human islets not only significantly enhanced the longevity of human islets but also maintained function. We hypothesized that the protective effects of bone marrow cells on human islets are through mechanisms related to preventing apoptosis. This study observed the levels of inflammatory factors such as interleukin-1β (IL-1β), the release of extracellular ATP in vitro, and expression levels of P2X7 ATP receptor (P2X7R), all of which lead to the occurrence of apoptosis in human islets. When human islets were co-cultured with human bone marrow, there was a reduction in the rate of apoptosis correlated with the reduction in inflammatory factors, extra cellular ATP accumulation, and ATP receptor P2X7R expression versus human islets cultured alone. These results suggest that co-culturing bone marrow cells with human islets inhibits inflammation and reduces apoptosis, thus protecting islets from self-deterioration.

Development of hyperglycemia and diabetes in captive Polish bank voles

Diabetes has been detected in Danish and Swedish bank voles (Myodes glareolus). There are no data, however, concerning the prevalence of diabetes in populations from other geographic regions. We investigated the frequency and physiological effects of glucose metabolism disorders in captive bank voles from Poland. Single measurement of fasting blood glucose concentration performed in the 3-4month old captive-born bank Polish voles without any disease symptoms showed that 8% of individuals (22/284) displayed an impaired fasting glucose (IFG, blood glucose (BG) ≥100mg/dL) and 1% (4/284) showed hyperglycemia (BG ≥126mg/dL) which could suggest diabetes. Next, we analyzed blood glucose in samples taken once a month from an additional cohort of bank voles with (FHD), or without (H), a family history of diabetes. The prevalence of IFG at age six months was 26% (16/62) among bank voles from the H group. In the FHD group the prevalence increased to 49% (43/88), and additional 12% (11/88) became diabetic (DB, BG ≥126mg/dL at two time points). Postnatal stress (three maternal deprivations before weaning) did not affect the risk of developing IFG or DB in H voles, but significantly reduced the frequency of glucose metabolism disorders (IFG and DB combined) in FHD voles. IFG was associated with hyperinsulinemia, but not with other biochemical disturbances. Diabetic animals displayed a progressive malformation and vacuolization of β-cells in the pancreas, without visible leukocytic infiltrations. In summary, our results indicate that Polish captive bank voles can develop diabetes, which shows features of both type 1 and type 2 diabetes in humans. Risk of diabetes is higher in animal with FHD.

Diabetes in Danish bank voles (M. glareolus): survivorship, influence on weight, and evaluation of polydipsia as a screening tool for hyperglycaemia

Background

Previous studies have concluded that the development of polydipsia (PD, a daily water intake ≥21 ml) among captive Danish bank voles, is associated with the development of a type 1 diabetes (T1D), based on findings of hyperglycaemia, glucosuria, ketonuria/-emia, lipemia, destroyed beta cells, and presence of autoantibodies against GAD65, IA-2, and insulin.

Aim and Methods

We retrospectively analysed data from two separate colonies of Danish bank voles in order to 1) estimate survivorship after onset of PD, 2) evaluate whether the weight of PD voles differed from non-PD voles, and, 3), evaluate a state of PD as a practical and non-invasive tool to screen for voles with a high probability of hypeglycaemia. In addition, we discuss regional differences related to the development of diabetes in Scandinavian bank voles and the relevance of the Ljungan virus as proposed etiological agent.

Results

We found that median survival after onset of PD is at least 91 days (lower/upper quartiles = 57/134 days) with a maximum recording of at least 404 days survivorship. The development of PD did not influence the weight of Danish bank voles. The measures of accuracy when using PD as predictor of hyperglycaemia, i.e. sensitivity, specificity, positive predictive value, and negative predictive value, equalled 69%, 97%, 89%, and 89%, respectively.

Conclusion

The relatively long survival of Danish PD bank voles suggests potentials for this model in future studies of the long-term complications of diabetes, of which some observations are mentioned. Data also indicates that diabetes in Danish bank is not associated with a higher body weight. Finally, the method of using measurements of daily water intake to screen for voles with a high probability of hyperglycaemia constitutes a considerable refinement when compared to the usual, invasive, methods.