PREVENTIVE EFFECTS OF CLITORIA TERNATEA EXTRACT ON METHYLGLYOXAL-INDUCED PROTEIN GLYCATION, OXIDATIVE DNA DAMAGE AND ADIPOGENESIS

Abstract

This study was aimed to determine the inhibitory effects of Clitoria ternatea extract (CTE) on glycation of BSA, oxidative DNA damage, and adipogenesis mediated by methylglyoxal (MG). The results showed that polyphenols in CTE identified by LC-MS/MS were ternatins, delphinidin derivatives, quercetin-3-rutinoside, apigenin-7-O-neohesperidoside , Kaemferol-3-O-rutinoside, (+)-catechin-7-O-b-glucoside, and syringetin-3-O-glucoside. CTE (250-1,000 µg/mL) significantly inhibited fructose- and MG-induced formation of fluorescent, non-fluorescent AGEs, fructosamine, amyloid cross β structure, protein carbonyl content and preventing free thiol depletion in BSA system. CTE (250-1,000 µg/mL) suppressed oxidative DNA strand breakage through inhibition of superoxide anion and hydroxyl radical production in 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH) and MG/lysine system. The mechanisms of anti-glycation of CTE are a direct carbonyl trapping ability and free radical scavenging activity. In early phase, CTE (500-1,000 µg/mL) inhibited MG-mediated adipogenesis through suppression of cell proliferation related to Akt and ERK1/2 signaling pathway in 3T3-L1 preadipocytes. In late stage of adipogenesis, CTE inhibited MG-induced expression of adipogenic transcription factors including PPARγ and C/EBPα and subsequently down-regulation of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC), causing the reduction of TG accumulation in mature adipocytes. When the cells were incubated without MG, CTE (500-1,000 µg/mL) treatment markedly decreased cell differentiation through Akt and ERK1/2 signaling pathway in the early stage of adipogenesis together with suppression of mRNA expression of adipogenic genes (PPARγ and C/EBPα) in late stage of adipogenesis. Furthermore, CTE could enhance lipolysis in mature adipocytes. The inhibition of MG-induced adipogenesis by CTE was due to its effects on the regulation of Akt and ERK1/2 signaling pathway and adipogenic transcription factors and the direct MG trapping ability. This study indicates that CTE can be a potential candidate for the prevention of protein glycation and adipogenesis.