monascin and Hyperglycemia

Methylglyoxal (MG) is a toxic-glucose metabolite and a major precursor of advanced glycation endproducts (AGEs). MG has been reported to result in inflammation by activating receptor for AGEs (RAGE). We recently found that Monascus-fermented metabolite monascin acts as a novel natural peroxisome proliferator-activated receptor-γ (PPARγ) agonist that improves insulin sensitivity. We investigated the metabolic, biochemical, and molecular abnormalities characteristic of type 2 diabetes in MG-treated Wistar rats treated with oral administration of monascin or rosiglitazone. Monascin (a novel PPARγ agonist) activated nuclear factor-erythroid 2-related factor 2 (Nrf2) and down-regulated hyperinsulinmia in oral glucose tolerance test (OGTT). Monascin was able to elevate glyoxalase-1 expression via activation of hepatic Nrf2, hence, resulting in MG metabolism to d-lactic acid and protected from AGEs production in MG-treated rats. Rosiglitazone did not activate Nrf2 nor glyoxalase expression to lower serum and hepatic AGEs levels. Monascin acts as a novel natural Nrf2 activator with PPARγ-agonist activity were confirmed by Nrf2 and PPARγ reporter assays in Hep G2 cells. These findings suggest that monascin acts as an anti-diabetic and anti-oxidative stress agent to a greater degree than rosiglitazone and thus may have therapeutic potential for the prevention of diabetes.

Topics: Animals; Dose-Response Relationship, Drug; Hep G2 Cells; Heterocyclic Compounds, 3-Ring; Humans; Hyperglycemia; Male; NF-E2-Related Factor 2; PPAR gamma; Pyruvaldehyde; Rats; Rats, Wistar

Several lines of evidence have implicated high levels of advanced glycation endproducts (AGEs) in diabetes. Pancreas impairment caused by AGEs has been found in recent studies. Monascin (MS) and monacolin K (MK) are active compounds identified from Monascus-fermented products, which have been reported to inhibit inflammation and improve insulin resistance. In order to confirm the protective effects of MS and MK on pancreatic function, BALB/c mice were treated with AGEs via intraperitoneal injection for 22 weeks to induce hyperglycemia, and the pancreas-protecting mechanism of MS and MK from AGE-induced damage was investigated. We found that the expression of pancreatic and duodenal homeobox-1 (PDX-1) and glucose transporter 2 (GLUT2) was recovered by MS or MK administration to AGE-treated mice. In addition, MS strongly improved performance in the oral glucose tolerance test (OGTT) and the insulin tolerance test (ITT), suggesting that MS sensitized to insulin in AGE-treated mice. Both MS and MK elevated pancreatic insulin expression when compared to the AGE-treated group, suggesting that MS and MK attenuated AGE-induced pancreatic dysfunction. Histopathology studies showed that intraperitoneal injection of AGEs did not result in pancreas damage. These findings confirm that the potential mechanism of AGEs on pancreatic dysfunction involves the induction of inflammation and the suppression of PDX-1 and GLUT2 expression. Taken together, MS and MK may be developed as an anti-diabetic agent in the future.

Topics: Animals; Diabetes Mellitus; Female; Fermentation; Glucose Tolerance Test; Glycation End Products, Advanced; Heterocyclic Compounds, 3-Ring; Humans; Hyperglycemia; Hypoglycemic Agents; Insulin; Insulin Resistance; Lovastatin; Male; Mice; Mice, Inbred BALB C; Monascus; Oryza; Pancreas