【Naringin】Main Citrus Flavonoids with Antidiabetic Effects
Naringin is a flavanone-7-O-glycoside located between the flavanone naringenin and the disaccharide neohesperidose. It occurs naturally in citrus fruits, predominantly in grapefruits. Similarly to naringenin, Naringin is widely sold as a food supplement because of its cardioprotective, neuroprotective, and immunomodulatory properties . When ingested by humans, Naringin is metabolized by Naringinase in the liver, so the main product of this metabolism is naringenin, which seems to be responsible, at least in part, for the biological effects attributed to this biomolecule. Naringin showed beneficial effects in acute and chronic models, such as those of diabetic neuropathy, pleurisy, asthma, cancer, behavioral deficits, Alzheimer’s disease, and chronic fatigue, and in experimental models for inflammation and oxidative stress induced by cisplatin.
Mahmoud et al. conducted two studies, in 2012 and 2015, to evaluate the antidiabetic potential of Naringin. According to the authors, Naringin attenuated hyperglycemia-mediated oxidative stress parameters (MDA and NO) and pro-inflammatory cytokine (TNF-α and IL-6) secretion and production in HFD/STZ-induced type 2 diabetic rats. The authors confirmed that the oral administration of Naringin normalized the activities of important enzymes in hepatic glycolytic metabolism, such as G6Pase, glycogen phosphorylase, and fructose-1,6-bisphosphatase. In addition, Naringin increased the release of insulin from isolated islets in the presence of IL-1β and decreased intestinal glucose absorption. Its antioxidant effects were also verified due to the reduction of NO in isolated pancreatic islets. The mechanism of the action responsible for the effects of Naringin may be related to the increased expression of GLUT4 in adipose tissue, which aids in the uptake of free circulating glucose from the blood to peripheral tissues.
Malakul, Pengnet, Kumchoom, and Tunsophon investigated the effect of Naringin on fructose-induced endothelial dysfunction in rats and its fundamental mechanisms. Rats that had consumed fructose in drinking water showed significantly increased levels of blood glucose, TC, TG, and LDL C. Consequently, Naringin treatment significantly brought these parameters back to near normal. Fructose impaired endothelial function, but vascular smooth muscle function was unaffected by fructose treatment. Interestingly, Naringin restored endothelial function in the aortic rings, confirming a vasoprotective effect. In addition, Naringin improved serum nitrate/nitrite (NOx), eNOS, and phosphorylated eNOS (p-eNOS) protein expression. Therefore, the authors concluded that the vascular potential of Naringin was moderately attributed to improving NO bioavailability, increasing eNOS activity, and obstructing the accumulation of peroxynitrite in the aortae.
In summary, the results of these studies demonstrate the related curative potential of Naringin in attenuating oxidative damage and inflammatory cascades. Moreover, it exhibits a unique preserving effect on endothelial dysfunction, an important factor in the development of diabetic complications, especially atherosclerosis and cardiovascular diseases.