title: Antioxidant rich grape pomace extract suppresses postprandial hyperglycemia in diabetic mice by specifically inhibiting alpha-glucosidase.
abstract: BACKGROUND
  Postprandial hyperglycemia is an early defect of type 2 diabetes and one of primary anti-diabetic targets. Treatment of postprandial hyperglycemia can be achieved by inhibiting intestinal α-glucosidase, the key enzyme for oligosaccharide digestion and further glucose absorption. Grape pomace is winemaking byproduct rich in bioactive food compounds such as phenolic antioxidants. This study evaluated the anti-diabetic potential of two specific grape pomace extracts by determining their antioxidant and anti-postprandial hyperglycemic activities in vitro and in vivo.
  
  
  METHODS
  The extracts of red wine grape pomace (Cabernet Franc) and white wine grape pomace (Chardonnay) were prepared in 80% ethanol. An extract of red apple pomace was included as a comparison. The radical scavenging activities and phenolic profiles of the pomace extracts were determined through the measurement of oxygen radical absorbance capacity, DPPH radical scavenging activity, total phenolic content and flavonoids. The inhibitory effects of the pomace extracts on yeast and rat intestinal α-glucosidases were determined. Male 6-week old C57BLKS/6NCr mice were treated with streptozocin to induce diabetes. The diabetic mice were then treated with vehicle or the grape pomace extract to determine whether the oral intake of the extract can suppress postprandial hyperglycemia through the inhibition of intestinal α-glucosidases.
  
  
  RESULTS
  The red grape pomace extract contained significantly higher amounts of flavonoids and phenolic compounds and exerted stronger oxygen radical absorbance capacity than the red apple pomace extract. Both the grape pomace extracts but not the apple pomace extract exerted significant inhibition on intestinal α-glucosidases and the inhibition appears to be specific. In the animal study, the oral intake of the grape pomace extract (400 mg/kg body weight) significantly suppressed the postprandial hyperglycemia by 35% in streptozocin-induced diabetic mice following starch challenge.
  
  
  CONCLUSIONS
  This is the first report that the grape pomace extracts selectively and significantly inhibits intestinal α-glucosidase and suppresses postprandial hyperglycemia in diabetic mice. The antioxidant and anti-postprandial hyperglycemic activities demonstrated on the tested grape pomace extract therefore suggest a potential for utilizing grape pomace-derived bioactive compounds in management of diabetes.
authors.affiliation: Department of Nutrition and Food Science, Wayne State University, Detroit, MI, 48202, USA. kzhou@wayne.edu.
authors.forename: Shelly
authors.initials: S
authors.lastname: Hogan
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Jianrong
authors.initials: J
authors.lastname: Li
authors.forename: Shi
authors.initials: S
authors.lastname: Sun
authors.forename: Corene
authors.initials: C
authors.lastname: Canning
authors.forename: Kequan
authors.initials: K
authors.lastname: Zhou
references.citation: J Nutr. 1995 Jun;125(6):1554-62
references.pmid: 7782910
references.citation: Lancet. 2002 Jun 15;359(9323):2072-7
references.pmid: 12086760
references.citation: J Med Food. 2003 Winter;6(4):291-9
references.pmid: 14977436
references.citation: Biosci Biotechnol Biochem. 2007 Jan;71(1):69-76
references.pmid: 17213665
references.citation: Br J Nutr. 2004 Mar;91(3):357-65
references.pmid: 15005821
references.citation: Life Sci. 2002 Aug 9;71(12):1405-15
references.pmid: 12127161
references.citation: Bioresour Technol. 2008 Nov;99(17):8413-20
references.pmid: 18445523
references.citation: Bioresour Technol. 2008 May;99(8):2981-8
references.pmid: 17706416
references.citation: Gastroenterology. 1986 Jul;91(1):41-8
references.pmid: 2423408
references.citation: South Med J. 2001 Aug;94(8):804-9
references.pmid: 11549192
references.citation: Diabetes Obes Metab. 2001 Aug;3(4):240-8
references.pmid: 11520303
references.citation: J Agric Food Chem. 2004 Jan 28;52(2):234-8
references.pmid: 14733501
references.citation: Br J Nutr. 2007 Oct;98(4):702-10
references.pmid: 17537288
references.citation: Am J Clin Nutr. 2004 May;79(5):727-47
references.pmid: 15113710
references.citation: Metabolism. 2006 Jun;55(6):832-41
references.pmid: 16713445
references.citation: J Agric Food Chem. 2007 Jan 10;55(1):99-105
references.pmid: 17199319
references.citation: Biofactors. 2005;23(4):189-95
references.pmid: 16498205
references.citation: Am J Clin Nutr. 2002 Jul;76(1):266S-73S
references.pmid: 12081850
references.citation: J Agric Food Chem. 2004 Jul 14;52(14):4360-7
references.pmid: 15237937
references.citation: J Agric Food Chem. 2007 Feb 7;55(3):992-1002
references.pmid: 17263504
references.citation: J Agric Food Chem. 2007 May 2;55(9):3729-36
references.pmid: 17411070
references.citation: J Ethnopharmacol. 2005 Mar 21;97(3):497-501
references.pmid: 15740886
references.citation: J Cardiovasc Pharmacol. 2007 Oct;50(4):434-40
references.pmid: 18049312
references.citation: J Agric Food Chem. 1999 Feb;47(2):550-3
references.pmid: 10563931
references.citation: Menopause Int. 2007 Dec;13(4):165-9
references.pmid: 18088528
references.citation: Br J Biomed Sci. 1999;56(2):109-13
references.pmid: 10695051
references.citation: Diabetes Care. 2005 Jan;28(1):154-63
references.pmid: 15616251
references.citation: J Agric Food Chem. 2004 Oct 6;52(20):6108-14
references.pmid: 15453674
references.citation: Eur J Clin Invest. 1994 Aug;24 Suppl 3:3-10
references.pmid: 8001624
references.citation: Phytother Res. 2007 Aug;21(8):796-9
references.pmid: 17533638
references.citation: J Agric Food Chem. 2008 Sep 10;56(17):7781-9
references.pmid: 18690694
references.citation: Bioresour Technol. 2004 Apr;92(2):201-8
references.pmid: 14693454
references.citation: J Agric Food Chem. 2004 Nov 3;52(22):6779-86
references.pmid: 15506816
references.citation: Crit Rev Food Sci Nutr. 1995 Jul;35(4):341-71
references.pmid: 7576162
references.citation: Clin Exp Pharmacol Physiol. 2006 Apr;33(4):351-7
references.pmid: 16620300
references.citation: Poult Sci. 2008 Feb;87(2):307-16
references.pmid: 18212374
references.citation: J Agric Food Chem. 2007 Dec 12;55(25):10200-7
references.pmid: 17999462
references.citation: Med Hypotheses. 2005;65(1):152-4
references.pmid: 15893133
references.citation: J Biol Chem. 1995 Nov 10;270(45):26778-81
references.pmid: 7592915
references.citation: Nutrition. 2005 Jun;21(6):756-61
references.pmid: 15925302
references.citation: J Nutr. 1989 Dec;119(12):2023-9
references.pmid: 2695605
references.citation: Diabetes Res Clin Pract. 2007 Jul;77(1):41-6
references.pmid: 17098323
references.citation: Waste Manag. 2008;28(2):372-80
references.pmid: 17433659
references.citation: J Pediatr Endocrinol Metab. 2003 Jan;16(1):5-22
references.pmid: 12585335
references.citation: J Org Chem. 2008 Apr 18;73(8):3070-7
references.pmid: 18345685
references.citation: J Biol Chem. 1997 Jan 17;272(3):1601-7
references.pmid: 8999834
references.citation: Mayo Clin Proc. 1987 Apr;62(4):249-55
references.pmid: 2436011
references.citation: J Agric Food Chem. 2002 Oct 9;50(21):5909-14
references.pmid: 12358458
references.citation: J Anim Physiol Anim Nutr (Berl). 2007 Aug;91(7-8):289-96
references.pmid: 17614999
references.citation: J Enzyme Inhib Med Chem. 2009 Feb;24(1):65-9
references.pmid: 18615280
references.citation: J Nutr. 2000 Aug;130(8S Suppl):2073S-85S
references.pmid: 10917926
references.citation: Carcinogenesis. 2006 Jul;27(7):1445-53
references.pmid: 16474170