Protector Role of Cx30.2 in Pancreatic ß-Cell against Glucotoxicity-Induced Apoptosis.

Glucotoxicity may exert its deleterious effects on pancreatic ß-cell function via a myriad of mechanisms, leading to impaired insulin secretion and, eventually, type 2 diabetes. ß-cell communication requires gap junction channels to be present among these cells. Gap junctions are constituted by transmembrane proteins of the connexins (Cxs) family. Two Cx genes have been identified in ß cells, Cx36 and Cx30.2. We have found evidence that the glucose concentration on its own is sufficient to regulate Cx30.2 gene expression in mouse islets. In this work, we examine the involvement of the Cx30.2 protein in the survival of ß cells (RIN-m5F). METHODS: RIN-m5F cells were cultured in 5 mM D-glucose (normal) or 30 mM D-glucose (high glucose) for 24 h. Cx30.2 siRNAs was used to downregulate Cx30.2 expression. Apoptosis was measured by means of TUNEL, an annexin V staining method, and the cleaved form of the caspase-3 protein was determined using Western blot. RESULTS: High glucose did not induce apoptosis in RIN-m5F ß cells after 24 h; interestingly, high glucose increased the Cx30.2 total protein levels. Moreover, this work found that the downregulation of Cx30.2 expression in high glucose promoted apoptosis in RIN-m5F cells. CONCLUSION: The data suggest that the upregulation of Cx30.2 protects ß cells from hyperglycemia-induced apoptosis. Furthermore, Cx30.2 may be a promising avenue of therapeutic investigation for the treatment of glucose metabolic disorders.

Chronic consumption of imbalance diets high in sucrose or fat induces abdominal obesity with different pattern of metabolic disturbances and lost in Langerhans cells population.

AIM: Obesity is a worldwide health issue, associated with development of type 2 Diabetes Mellitus. The aim of this study is to analyze the effect of consumption of two hypercaloric diets on metabolic disturbance and beta cells damage. MAIN METHODS: Male Wistar rats were subjected to twelve months consumption of three diets: a Control balanced diet (CTD, carbohydrates 58 %, proteins 29 %, lipids 13 %) and two hypercaloric diets, high in sucrose (HSD, carbohydrates 68 %, proteins 22 %, lipids 10 %) or high in fat (HFD, carbohydrates 31 %, proteins 14 %, lipids 55 %). Serum levels of glucose, triglycerides and free fatty acids were measured after zoometric parameters determination. Antioxidant enzymes activity and oxidative stress-marker were measured in pancreas tissue among histological analysis of Langerhans islets. KEY FINDINGS: Although diets were hypercaloric, the amount of food consumed by rats decreased, resulting in an equal caloric consumption. The HSD induced hypertriglyceridemia and hyperglycemia with higher levels in free fatty acids (FFA, lipotoxicity); whereas HFD did not increased neither the triglycerides nor FFA, nevertheless the loss of islets' cell was larger. Both diets induced obesity with hyperglycemia and significant reduction in Langerhans islets size. SIGNIFICANCE: Our results demonstrate that consumption of HSD induces more significant metabolic disturbances that HFD, although both generated pancreas damage; as well hypercaloric diet consumption is not indispensable to becoming obese; the chronic consumption of unbalanced diets (rich in carbohydrates or lipids) may lead to abdominal obesity with metabolic and functional disturbances, although the total amount of calories are similar.

Sobrevida de los islotes β pancreáticos y uso de hipoglucemiantes orales: un gran reto para el médico actual / Survival of pancreatic islet β and use of oral hypoglycemic agents: a challenge for the current doctor

La célula β no sólo es capaz de fabricar y secretar la insulina, sino además, hace que dicha secreción sea en el momento justo y en la cantidad adecuada. Las elevaciones postprandiales de glucosa generan una respuesta secretora aguda en la célula β, pero en ciertas patologías como la diabética, el escenario cambia radicalmente, resultando en una disfunción caracterizada por un proceso secretor alterado y múltiples cambios fenotípicos. En estos, los nutrientes, glucosa y ácidos grasos, están elevados de forma crónica, convirtiéndose en sustancias tóxicas que pueden llevar a la muerte de la propia célula β. Por lo tanto, cualquier aproximación terapéutica a la cura de esta enfermedad debe afrontar la necesidad de reemplazar o evitar esta disminución celular, siendo imperativo mencionar el papel de los hipoglucemiantes orales como los inhibidores de la DPP-4 y los análogos de la GLP-1 en la protección contra el fracaso de la masa de células β.

The beta cell is not only able to produce and secrete insulin, but also makes this secretion is at the right time and in the right amount. Postprandial glucose elevations produce an acute secretory response in the beta cell, but in certain diseases such as diabetes mellitus, the scene changes dramatically, resulting in dysfunction, characterized by an altered secretion process and multiple phenotypic changes. In these, nutrients like glucose and fatty acids are chronically elevated, becoming toxic substances that can lead to death of the beta cell itself. Therefore, any therapeutic approach to cure this disease must face the need to replace or avoid this cell decline, it is imperative to mention the role of oral hypoglycemic agents as inhibitors of DPP-4 and analogs of the GLP-1 in protection against failure of the β cell mass.