Quercetin Decreases Oxidative Stress, NF-κB Activation, and iNOS Overexpression in Liver of Streptozotocin-Induced Diabetic Rats

Abstract

Increasing evidence in both experimental and clinical studies suggests that oxidative stress is involved in the pathogenesis and progression of diabetic tissue damage. This study investigated the protective effects of quercetin treatment on oxidative stress, nuclear factor (NF)-kappaB activation and expression of inducible nitric oxide synthase (iNOS) in streptozotocin-induced diabetic rats. Male Wistar rats were divided into 4 groups: control rats, control rats treated daily with quercetin (150 micromol/kg, i.p.), untreated diabetic rats, and diabetic rats treated with quercetin. Diabetes was induced by a single i.p. injection of streptozotocin (70 mg/kg). Eight weeks later we measured TBARS and hydroperoxide-initiated chemiluminescence (QL) in liver as markers of oxidative stress, and activities of the antioxidant enzymes catalase, superoxide dismutase (SOD), and glutathione peroxidase, NF-kappaB activation by an electrophoretic mobility shift assay and expression of IkappaB kinases (IKKalpha and IKKbeta), the inhibitor IkappaB (IkappaBalpha and IkappaBbeta), and iNOS by Western blot. The plasma glucose concentration was significantly increased in diabetic rats and was not changed by quercetin. Streptozotocin administration induced significant increases in hepatic TBARS concentration, QL, and SOD and catalase activities that were prevented by quercetin. Activation of NF-kappaB, induction of IKKalpha and iNOS protein levels, and increased degradation of IkappaBalpha were also observed in streptozotocin-treated rats. All of those effects were abolished by quercetin. These findings suggest that quercetin treatment, by abolishing the IKK/NF-kappaB signal transduction pathway, may block the production of noxious mediators involved in the development of early diabetes tissue injury and in the evolution of late complications.

A single HPLC‐PAD‐APCI/MS method for the quantitative comparison of phenolic compounds found in leaf, stem, root and fruit extracts of Vaccinium angustifolium

“…Considering that, in a separate pharmacological study, each extract (leaf, stem, root and fruit) elicited a range of in vitro anti-diabetic activities (Martineau et al, 2006), it is interesting that all the identified classes of phenolic compounds, chlorogenic acid, quercetin derivatives, procyanidins and anthocyanins, have demonstrated anti-diabetic potential in vitro and in vivo (Hemmerle et al, 1997;Rodriguez de Sotillo and Hadley, 2002;Kim et al, 2003;Tsuda et al, 2003;Pinent et al, 2004;Ajay et al, 2005;Coskun et al, 2005;Dias et al, 2005;Jayaprakasam et al, 2006 …”

Preventive Effects of Flavonoids on Alloxan-Induced Diabetes Mellitus in Rats

“…Flavonoids can exert their antioxidant activity by various mechanisms, e.g., by scavenging or quenching free radicals, by chelating metal ions, or by inhibiting enzymatic systems responsible for free radical generation (Bláha et al 2004;Dias et al 2005). …”

Chemical composition, antimicrobial and antioxidant properties of seed oil plants of North-East India: A review

“…Oil producing seeds contain various types of phenolic compounds, such as flavonoids, lignans, lignins, phenolic acids, and tannins. Flavonoids can exert their antioxidant activity via a series of mechanisms, e.g., by chelating metal ions, by scavenging or quenching free-radicals or by inhibiting enzymetic systems responsible for free-radical generation (Dias et al, 2005;Islam, 2009). Flavonoids are the most widely present polyphenolic compounds in many oil seeds (Saikia et al, 2006).…”