Diabetes associated cell stress and dysfunction: role of mitochondrial and non-mitochondrial ROS production and activity.

It is now widely accepted, given the current weight of experimental evidence, that reactive oxygen species (ROS) contribute to cell and tissue dysfunction and damage caused by glucolipotoxicity in diabetes. The source of ROS in the insulin secreting pancreatic beta-cells and in the cells which are targets for insulin action has been considered to be the mitochondrial electron transport chain. While this source is undoubtably important, we provide additional information and evidence for NADPH oxidase-dependent generation of ROS both in pancreatic beta-cells and in insulin sensitive cells. While mitochondrial ROS generation may be important for regulation of mitochondrial uncoupling protein (UCP) activity and thus disruption of cellular energy metabolism, the NADPH oxidase associated ROS may alter parameters of signal transduction, insulin secretion, insulin action and cell proliferation or cell death. Thus NADPH oxidase may be a useful target for intervention strategies based on reversing the negative impact of glucolipotoxicity in diabetes.

Pleiotropic effects of fatty acids on pancreatic beta-cells.

Hyperlipidemia is frequently associated with insulin resistance states as found in type 2 diabetes and obesity. Effects of free fatty acids (FFA) on pancreatic beta-cells have long been recognized. Acute exposure of the pancreatic beta-cell to FFA results in an increase of insulin release, whereas a chronic exposure results in desensitization and suppression of secretion. We recently showed that palmitate augments insulin release in the presence of non-stimulatory concentrations of glucose. Reduction of plasma FFA levels in fasted rats or humans severely impairs glucose-induced insulin release. These results imply that physiological plasma levels of FFA are important for beta-cell function. Although, it has been accepted that fatty acid oxidation is necessary for its stimulation of insulin secretion, the possible mechanisms by which fatty acids (FA) affect insulin secretion are discussed in this review. Long-chain acyl-CoA (LC-CoA) controls several aspects of the beta-cell function including activation of certain types of protein kinase C (PKC), modulation of ion channels, protein acylation, ceramide- and/or nitric oxide (NO)-mediated apoptosis, and binding to nuclear transcriptional factors. The present review also describes the possible effects of FA on insulin signaling. We showed for the first time that acute exposure of islets to palmitate upregulates the intracellular insulin-signaling pathway in pancreatic islets. Another aspect considered in this review is the source of FA for pancreatic islets. In addition to be exported to the medium, lipids can be transferred from leukocytes (macrophages) to pancreatic islets in co-culture. This process consists an additional source of FA that may plays a significant role to regulate insulin secretion.

Comparison of ion chromatography and neutron activation analysis for the microdetermination of Na+ and K+ in muscle.

The simultaneous determination of Na+ and K+ in small tissue samples by means of neutron activation (NAA) and ion chromatography (IC) is described. A 5 X 10(11) n cm-2 s-1 neutron flux was used for Na+ analysis and the induced 24Na and 42K activities were measured without chemical separation with a Ge(Li) detector coupled to a 4096 channel analyzer. A minicomputer on line with the analyzer was employed for the interpretation of gamma spectra. When IC was used, the sample and the standard were dissolved in the solutions before injection into the ion chromatograph. The ion concentration in the effluent solution was measured by electric conductivity. The two methods were compared in terms of time required, sensitivity, accuracy, precision, simplicity and operational cost of the analysis. Both techniques proved to be excellent from the point of view of the reliability of the results, and can be used for the determination of Na+ and K+ in biological samples.