Grape Extracts for Type 2 Diabetes Treatment Through Specific Inhibition of α-Glucosidase and Antioxidant Protection

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dc.contributor.authorHogan, Shelly Patriciaen
dc.contributor.committeechairZhou, Kequan Kevinen
dc.contributor.committeememberDuncan, Susan E.en
dc.contributor.committeememberO'Keefe, Sean F.en
dc.contributor.committeememberBevan, David R.en
dc.contributor.committeememberLiu, Dongminen
dc.contributor.departmentFood Science and Technologyen
dc.date.accessioned2014-03-14T20:09:13Zen
dc.date.adate2009-04-30en
dc.date.available2014-03-14T20:09:13Zen
dc.date.issued2009-04-02en
dc.date.rdate2012-03-30en
dc.date.sdate2009-04-09en
dc.description.abstractResearch was conducted to investigate the effect of phenolic compounds derived from inherently rich antioxidant grape extracts (GE) on α-glucosidase inhibitory activity in vitro and in vivo blood glucose control, oxidative stress, and inflammation associated with obesity-induced type 2 diabetes. Because intestinal α-glucosidase plays a key role in the digestion and absorption of complex carbohydrates, the inhibition of this enzyme is a metabolic target for managing diabetes by improving post-prandial blood glucose control. Initially, red Norton wine grape (Vitis aestivalis) and pomace extracts were evaluated and determined to have notable phenolic content and antioxidant properties. Next, grape skin (GSE) and pomace extract (GPE) were tested and both had in vitro yeast and mammalian α-glucosidase inhibitory activity. The GSE was 32-times more potent at inhibiting yeast α-glucosidase than acarbose, a commercial oral hypoglycemic agent. From HPLC and LC-MS analysis, three phenolics from the GSE (resveratrol, ellagic acid, and catechin) were identified as active inhibitory compounds. The acute administration of GPE (400 mg/kg bw) to mice reduced postprandial blood glucose level by 35% following an oral glucose tolerance test compared to the control. The daily supplementation (250 mg/kg bw) of GSE and GPE for 12-weeks to mice affected fasting blood glucose levels, oxidative stress, and inflammatory biomarkers associated with obesity and type 2 diabetes. At the end of the study, the GSE group gained significantly (P < 0.05) more weight (24.6 g) than the control, high fat, or GPE groups (11.2, 20.2, 19.6 g, respectively). Both GSE and GPE groups had lower fasting blood glucose levels (119.3 and 134.2 mg/dL, respectively) compared to the high fat group (144.6 mg/dL). The 12-week supplementation of GSE was associated with a higher plasma oxygen radical absorbance capacity (ORAC), lower liver lipid peroxidation as measure by TBARS, and lower levels of inflammation as measured by plasma C-reactive protein compared to the high fat group. In conclusion, our collective observations from these studies provide insight into the potential effects of antioxidant rich grape extracts on diabetes-related biomarkers through a dual mechanism of antioxidant protection and specific inhibition of intestinal α-glucosidases.en
dc.description.degreePh. D.en
dc.identifier.otheretd-04092009-154109en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-04092009-154109/en
dc.identifier.urihttp://hdl.handle.net/10919/26725en
dc.publisherVirginia Techen
dc.relation.haspartHoganPhD_ETD_2.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectoxidative stressen
dc.subjectdiabetesen
dc.subjectbioactive phenolic compoundsen
dc.subjectα-glucosidaseen
dc.subjectenzyme kineticsen
dc.subjectmacromoleculeen
dc.subjectFunctional foodsen
dc.titleGrape Extracts for Type 2 Diabetes Treatment Through Specific Inhibition of α-Glucosidase and Antioxidant Protectionen
dc.typeDissertationen
thesis.degree.disciplineFood Science and Technologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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