Hypoglycemic activity and constituents analysis of blueberry (<em>Vaccinium corymbosum</em>) fruit extracts

Abstract

BackgroundTo investigate hypoglycemic activity and elucidate the active composition of the fruit blueberry (Vaccinium corymbosum).MethodsMethanol extracts of blueberry (MEB) were separated using a D101 macroporous resin column to yield quinic acid derivative (Fr.1)- and flavonoid (Fr.2)-rich fractions. The effects of the blueberry extracts on mRNA expression of GLUT-2 (glucose transporter type 2) and PPARγ (peroxisome proliferator-activated receptor-γ), as well as on the activities of PPRE (peroxisome proliferator response element) and NF-κB were analyzed in LO2 normal liver cells. Real-time PCR was used to detect the expression of GLUT-2, PPARγ, TNF-α, IL-1β, and IL-6 mRNA. The PPRE and NF-κB activities were detected by a luciferase reporter assay. Western blotting was used to detect the levels of PPARγ, GLUT-2, and p65. The active compositions were isolated using various chromatography columns, and were analyzed by NMR.ResultsmRNA and protein expression of GLUT-2 and PPARγ were significantly increased upon treatment with 400 μg/mL extracts of blueberry (P<0.05). The PPRE activity was also significantly increased in a dose-dependent manner upon administration of MEB (P<0.05). Furthermore, the NF-κB activity induced by lipopolysaccharides was inhibited by MEB (P<0.05). No fraction separated from MEB exhibited PPRE activation or NF-κB inhibition activity. Blueberry extract may execute its hypoglycemic activity by stimulating expression of GLUT-2 and PPARγ, and by inhibiting the inflammatory pathway. Together, quinic acid derivatives and flavonoids may result in a synergistic effect. Fourteen phenolic acids, including eight flavonoids, four quinic acid derivatives, and two other phenolic acids, were isolated and identified, and caffeoylquinic acid derivatives and quercetin glycosides were found to be the major constituents of blueberry.ConclusionBlueberry may have hypoglycemic activity that functions through synergistic effects with caffeoylquinic acid derivatives and quercetin glycosides.

Whole blueberry protects pancreatic beta-cells in diet-induced obese mouse

“…Contrarily, the anti-inflammatory effect was less pronounced in some animal studies and human [21, 36, 37]. New reports indicated that blueberry extracts can significantly inhibit inflammatory and apoptosis via activation of JAK1/STAT3 signaling [38], PPARγ activity [39] or survival PI3K/Akt and MAPK/ERK pathways [40].…”

Select Polyphenol-Rich Berry Consumption to Defer or Deter Diabetes and Diabetes-Related Complications

“…Anthocyanin-enriched diets increased hypoglycemic activity (51%) compared with phenolic-enriched diets (33%) and metformin-treated controls (32%), suggesting that anthocyanins modulated hyperglycemic and hyperlipidemic activities [ 13 ]. The supplementation of BlBE increased the beneficial glucose metabolism involved peroxisome proliferator response element (PPRE) (1.3–1.8%), glucose transporter 2 (GLUT-2) (1.5%), and PPAR-γ (1.4%) activities, and reduced the proinflammatory nuclear factor (NF)-κB activity [ 14 ]. Furthermore, an increase in the intercellular levels of the mRNA of glucose transporter (GLUT4), insulin receptor substrate-1/2 (IRS-1/IRS-2) (insulin response mediators regarding glucose metabolism), and AMP-activated protein kinase (AMPK) (a key regulator of mitochondrial biogenesis and cellular energy homeostasis) were observed in skeletal muscles, indicating increased glucose uptake [ 15 , 16 ].…”

Molecular Mechanism and Health Role of Functional Ingredients in Blueberry for Chronic Disease in Human Beings

“…Blueberry polyphenols prevent heart diseases, which are associated with the reduction of calpain activity and oxidative stress [ 54 ]. Blueberry extract has hypoglycemic activity exerted by promoting the expression of GLUT-2 and PPARγ and controlling the inflammatory pathway; based on interaction between caffeoylquinic acid derivatives and quercetin glycosides [ 132 ]. Blueberry polyphenols and its fermented beverages can inhibit α-amylase and α-glucosidase of starch-degrading for type 2 diabetes management [ 133 ], however polyphenols can regulate the immune function which exists as a mediator role of epigenetic mechanisms [ 134 ].…”