Ionic mechanisms and Ca2+ dynamics underlying the glucose response of pancreatic ß cells: a simulation study.

To clarify the mechanisms underlying the pancreatic ß-cell response to varying glucose concentrations ([G]), electrophysiological findings were integrated into a mathematical cell model. The Ca(2+) dynamics of the endoplasmic reticulum (ER) were also improved. The model was validated by demonstrating quiescent potential, burst-interburst electrical events accompanied by Ca(2+) transients, and continuous firing of action potentials over [G] ranges of 0-6, 7-18, and >19 mM, respectively. These responses to glucose were completely reversible. The action potential, input impedance, and Ca(2+) transients were in good agreement with experimental measurements. The ionic mechanisms underlying the burst-interburst rhythm were investigated by lead potential analysis, which quantified the contributions of individual current components. This analysis demonstrated that slow potential changes during the interburst period were attributable to modifications of ion channels or transporters by intracellular ions and/or metabolites to different degrees depending on [G]. The predominant role of adenosine triphosphate-sensitive K(+) current in switching on and off the repetitive firing of action potentials at 8 mM [G] was taken over at a higher [G] by Ca(2+)- or Na(+)-dependent currents, which were generated by the plasma membrane Ca(2+) pump, Na(+)/K(+) pump, Na(+)/Ca(2+) exchanger, and TRPM channel. Accumulation and release of Ca(2+) by the ER also had a strong influence on the slow electrical rhythm. We conclude that the present mathematical model is useful for quantifying the role of individual functional components in the whole cell responses based on experimental findings.

Pitavastatin reduces elevated IL-18 levels in Japanese subjects with hypercholesterolemia: sub-analysis of Kansai investigation of statin for hyperlipidemic intervention in metabolism and endocrinology (KISHIMEN).

AIM: Pitavastatin significantly improved lipid profiles and reduced serum high-sensitivity C-reactive protein (hs-CRP) levels in a multi-center and prospective study. The aim of this study was to explore the effect of pitavastatin on serum levels of another inflammatory biomarker, interleukin-18 (IL-18), in a sub-analysis of the previous multi-center prospective study. METHODS: The subjects were 83 patients derived from the KISHIMEN study. Pitavastatin (1-2 mg/day) was administered for 12 months. Serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), remnant-like particle cholesterol (RLP-C), triglycerides (TG), IL-18, and high sensitivity C-reactive protein (hs-CRP) levels were measured. RESULTS: TC, LDL-C, and RLP-C levels were significantly reduced by 18.3%, 30.1%, and 21.0% (mean values) at 12 months after pitavastatin administration. TG levels were decreased by 9.8% in subjects whose basal TG levels were above 150 mg/dL. HDL-C levels were significantly increased at 6 months (11.9%). Pitavastatin did not significantly alter IL-18 levels in overall subjects, but reduced IL-18 levels in the highest quartile by 24.5% (median value) at 12 months. Pitavastatin significantly reduced hs-CRP levels by 28.6% in overall subjects and by 62.4% in the highest quartile at 12 months. There was a significant correlation between IL-18 and hs-CRP at baseline after both values were transformed into logarithms (Pearson's correlation coefficient, r = 0.259, p = 0.0181); however, percent changes in these levels were not significantly correlated. CONCLUSION: Pitavastatin significantly improves lipid profiles, and reduces enhanced inflammation monitored by IL-18, as well as by hs-CRP, in hypercholesterolemic subjects.