Insulin isolated islets

The pioneering work of Nerup and co-workers provided the initial evidence suggesting that local fluctuations of cytokine concentrations may influence insulin secretion by islets. The effects of IL-1)8 on insulin secretion have been confirmed and extended to show that lL-l/3-induced inhibition of glucose stimulated insulin secretion by isolated islets is both time- and concentration-depen-dent as shown in Fig. 1 (Spinas et al., 1986 Comens et al., 1987 McDaniel et al., 1988a Palmer etal., 1989). Treatment of islets for short periods of time with high concentrations of IL-lj8 (1-10 U/ml) or for longer periods of time with... 

Effects of IL-1 on glucose-stimulated insulin secretion Concentration and time dependence. The ability of IL-1 to modulate insulin secretion by isolated rat islets is illustrated. Short exposures of islets to high concentrations of lL-1 [2 nM as shown here, or 5 U/ml (5 pM) as used in other studies], or prolonged exposure to low concentrations of lL-1 (0.5 pM or 0.5 U/ml) result in a stimulation of glucose-induced insulin secretion. Incubation of islets for 18 hr with 2 nM (or 5 U/ml) IL-1 results in a potent and reversible inhibition of glucose stimulated insulin secretion. Islet destruction is observed when islets are treated for 4 to 6 days with 2 nM (or 5 U/ml) lL-1. Reproduced with permission from Diabetes (McDaniel et al, 1988), by the American Diabetes Association, Inc. 

Hoa, N.K., D.V. Phan, N.D. Thuan,and C.G. Ostenson. 2004. Insulin secretion is stimulated by ethanol extract of Anemarrhena aspk)-deloides in isolated islet of healthy Wistar and diabetic Goto-Kakizaki rats. Exp. Clin. Endocrinol. Diabetes 112(9) 520-525. 

Hannan, J.M., L. Marenah, L. Ali, et al. 2007. Insulin secretory actions of extracts of Asparagus racemosus root in perfused pancreas, isolated islets and clonal pancreatic beta-cells. /. Endocrinol. 192 (1) 159-168. 

Many ions have been shown to alter the release of insulin (K+, Mg++, Ca-H-, Na+, Ba-H- and Li+). Their effects are believed to be related to electrical potentials across cell raembranes j S. Changes in potentials across isolated islets have been measured and found to correlate with the release of insulin. 

Flavones and flavonols, especially quercetin, have been reported to possess antidiabetic activity. A cohort study that predicted the effects of flavonoids on chronic diseases showed that a trend toward a reduction in risk of type 2 diabetes was associated with higher quercetin and myricetin intakes. Vessal et al. reported that quercetin brings about the regeneration of pancreatic islets and increases insulin release in streptozotocin-induced diabetic rats [133]. Also in another study, Hif and Howell reported that quercetin stimulates insulin release and enhances Ca " uptake from isolated islet cells which suggest a place for flavonoids in non-insulin-dependent diabetes [134, 135]. 

Lopez et al. reported the isolation of three quinolizidine alkaloids such as lupanine (30), 13-a-hydroxylupanine (31), and 17-oxo-lupanine (32) from Lupinus perennis Wild, (family Fabaceae) all these three isolates were found to have potent activity in enhancing glucose-induced insulin release from isolated rat islet cells in a glucose concentration-dependent manner. While the synthetic compound 2-thionosparteine... 

---