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Studies on bioavailability of quercetin by combined feeding of α-glycosyl-isoquercitrin and soybean fiber, and the protective role against glucose intolerance in rats

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Title: Studies on bioavailability of quercetin by combined feeding of α-glycosyl-isoquercitrin and soybean fiber, and the protective role against glucose intolerance in rats
Other Titles: ラットにおけるα-グルコシルイソクエルシトリンと大豆繊維の共摂取によるケルセチンの生物学的利用能向上とそれによる耐糖能障害の予防に関する研究
Authors: Trakooncharoenvit, Aphichat Browse this author
Issue Date: 24-Sep-2021
Publisher: Hokkaido University
Abstract: Quercetin is a naturally occurring flavonol found abundantly in vegetables and fruits as single- or multi-glycosylated forms. Dietary quercetin and its glycosides reportedly have a promising anti-diabetic effect. Conversely, this beneficial effect was limited due to the poor intestinal absorbability and degradation by commensal bacteria. Improvement of the bioavailability could be valuable to further promote beneficial effects of quercetin on the body. A previous study reported that a non-digestible oligosaccharide promoted intestinal absorption a flavonoid. This raises the possibility that some kinds of dietary fibers improve quercetin bioavailability. Thus, the objective of the study was to investigate the ability of dietary fibers in promotion of quercetin bioavailability, and whether certain combination of quercetin and a dietary fiber improves quercetin bioavailability and glucose tolerance in rats fed with an obesogenic diet. The first experiment aimed to examine the effects of several dietary fibers on the bioavailability of the water-soluble quercetin glycosides, α-glycosyl-isoquercetin (AGIQ). Male Wistar/ST rats were fed a test diet containing 0.7% of AGIQ with or without 5% of each dietary fiber (pectin, soybean fiber, and guar gum) for 9 weeks. The quercetin bioavailability and degradation were evaluated every two weeks by collecting plasma, urine, and feces. At weeks 6 and 8, the soybean fiber supplemented group showed higher concentrations of total quercetin derivatives in plasma and urine, than control. Intestinal degradation of quercetin,calculated from differences between ingestion of aglycone and the sum of excretion in urine and feces, was suppressed by dietary fiber supplementations. From this experiment, soybean fiber showed the best potential to enhance the quercetin bioavailability after a long-term feeding, which may promote the beneficial effects of quercetin. The second experiment aimed to clarify whether the combined feeding of soybean fiber and AGIQ could enhance quercetin bioavailability, subsequently affecting glucose metabolism in a rat model of diet-induced obesity. Male Wistar-ST rats were individually fed an AIN-93G diet as the control, a high-fat high-sucrose (30% fat and 40% sucrose; H) diet, H diet with soybean fiber (HS), H diet with AGIQ (HQ), or H diet with both soybean fiber and AGIQ (HSQ) for 9 weeks. Plasma, urine, feces, and tissue samples were similarly collected as the first experiment. Meal tolerance tests (MTTs) were conducted every 4 weeks in the feeding period to assess postprandial responses of glucose, insulin, and a gastrointestinal hormone glucagon-like peptide-1 (GLP-1). The HSQ group had higher levels of total quercetin derivatives in plasma, urine, feces, and cecal contents than the HQ group at the late period of the experiment. These results demonstrated that the ability on enhancing quercetin bioavailability of soybean fiber under an obesogenic condition, possibly via promotion of cecal fermentation. In addition, the HSQ group had lower postprandial glycemia than the H group, indicating the improvement of glucose tolerance by the combination of quercetin and soybean fiber. Furthermore, a significantly positive correlations were observed between plasma GLP-1 concentrations and plasma quercetin derivative concentrations, suggesting promotive effect of quercetin on GLP-1 secretion. In conclusion, contentious ingestion of soybean fiber can increase quercetin bioavailability in rats, possibly through enhancing intestinal fermentation. The combination of soybean fiber and AGIQ could be beneficial for reducing the risk of glucose intolerance,possibly via enhanced quercetin bioavailability and GLP-1 secretion. These findings might help to establish a new diet composition that combines functional flavonoids with dietary fiber to minimize the risk of diabetes and other related diseases.
Conffering University: 北海道大学
Degree Report Number: 甲第14656号
Degree Level: 博士
Degree Discipline: 農学
Examination Committee Members: (主査) 准教授 比良 徹, 教授 石塚 敏, 教授 園山 慶
Degree Affiliation: 農学院(応用生物科学専攻)
Type: theses (doctoral)
Appears in Collections:課程博士 (Doctorate by way of Advanced Course) > 農学院(Graduate School of Agriculture)
学位論文 (Theses) > 博士 (農学)

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