Effects of flavonoids on insulin secretion and 45Ca2+ handling in rat islets of Langerhans

Abstract

The effects of some flavonoids, a group of naturally occurring pigments one of which has been claimed to possess antidiabetic activities, on insulin release and 45Ca2+ handling have been studied in isolated rat islets of Langerhans. Insulin release was enhanced by approximately 44-70% when islets were exposed to either (-)epicatechin (0.8 mmol/l) or quercetin (0.01-0.1 mmol/l); others such as naringenin (0.1 mmol/l) and chrysin (0.08 mmol/l) inhibited hormone release by approximately 40-60%. These effects were observed only in the presence of 20 mmol glucose/l. Quercetin (0.01 mmol/l) and (-)epicatechin (0.8 mmol/l) both inhibited 45Ca2+ efflux in the presence and absence of extracellular Ca2+. In the presence of 20 mmol glucose/l both the short-term (5 min) and steady-state (30 min) uptake of 45Ca2+ were significantly increased by either quercetin or (-)epicatechin. These results suggest that the stimulatory compounds such as quercetin and (-)epicatechin may, at least in part, exert their effects on insulin release via changes in Ca2+ metabolism.

Use of dark chocolate for diabetic patients: a review of the literature and current evidence

“…In in vivo studies, diabetic rat models confirmed the insulin-sensitizing effect of dark chocolate. In two such studies, epicatechin increased insulin secretion and regenerated pancreatic β-cells [13–15]. Similarly, supplementation of diabetic rats with cocoa extract for four weeks was dose-dependently associated with reduced serum glucose, post-prandial hyperglycemia, atherogenic lipid levels, insulin resistance, and 8-isoprostane, a biomarker of oxidative stress [14–17].…”

Effect of quercetin nanoparticles on the kidney of the streptozotocin-induced diabetes in male rats: A histological study and serum biochemical alterations

“…Vessal et al (2003) reported that supplementation has proven to be beneficial in decreasing the concentration of blood glucose, promoting the pancreatic islets regeneration and increasing release of insulin in STZ treated diabetic rats; thus exerting its beneficial antidiabetic effects (Formica and Regelson 1995). This is supported by the previous literature reports where these types of flavonoids enhance release of insulin up to 70% by its effect on function of islet at least in part, metabolism of cyclic nucleotide, and via alteration in Ca +2 fluxes (Yen et al, 2009;Hii and Howell, 1985a;Hii and Howell, 1985b). Blood glucose levels were significantly increased after 72 h following STZ injection compared to control group, while all QUE treatment groups had significantly decreased blood glucose concentrations compared to the diabetic group after 30 days (Elbe et al, 2015).…”

Antioxidant and Antihyperglycemic Effects of Ferula drudeana and Ferula huber-morathii in Experimental Diabetic Rats

“…Flavonoids are reported to possess antidiabetic activity as they can preserve β-cell function and prevent diabetes induced ROS formation (Aslan et al, 2007). Moreover, Hii and Howell (1985) mentioned that certain flavonoids enhanced insulin release from the isolated rat islets. Thus, the hypoglycemic effect of F. drudeana and F. huber-morathii may be due to the presence of flavonoids.…”