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Title: Dietary supplementation with watermelon pomace juice enhances arginine availability and ameliorates the metabolic syndrome in Zucker diabetic fatty rats

Author
item WU, GUOYAO - TEXAS A&M
item COLLINS, JULIE - EOSU, WILBURTON, OK
item Perkins Veazie, Penelope
item SIDDIQ, MUHAMMAD - MICHIGAN STATE UNIV.
item DOLAN, KIRK - MICHIGAN STATE UNIV.
item KELLEY, KATHERINE - TEXAS A&M
item HEAPS, CRISTINE - TEXAS A&M
item MEININGER, CYNTHIA - TEXAS A&M

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2007
Publication Date: 11/20/2007
Citation: Wu, G., Collins, J.K., Perkins Veazie, P.M., Siddiq, M., Dolan, K.D., Kelley, K.A., Heaps, C.L., Meininger, C.J. 2007. Dietary supplementation with watermelon pomace juice enhances arginine availability and ameliorates the metabolic syndrome in Zucker diabetic fatty rats. Journal of Nutrition. 137:2680-2685.

Interpretive Summary: Watermelon contains citrulline, an amino acid that is used to make arginine, which can improve cardiovascular circulation in humans. Watermelon also contains lycopene, a pigment with demonstrated antioxidant activity in cell cultures. This study was done to determine if the residue of watermelon juice (pomace), which is rich in both lycopene and citrulline, had potential for development as a functional food. Diabetic fatty rats were given watermelon pomace, lycopene, or arginine as dietary supplements or a control without a supplement. When provided the watermelon pomace or arginine positive changes were seen in markers that are used to follow cardiovascular disease in animals. These results indicate that pomace may be useful for further study as a functional food, and that the citrulline present in the pomace can affect cardiovascular events in an animal model.

Technical Abstract: Watermelon is rich in L-citrulline, an effective precursor of L-arginine. This study was conducted to determine whether dietary supplementation with watermelon pomace juice could ameliorate the metabolic syndrome in the Zucker diabetic fatty (ZDF) rat, an animal model of noninsulin-dependent diabetes mellitus. Nine-wk-old ZDF rats were assigned randomly to receive drinking water containing 0% (control) or 0.2% L-arginine (as 0.24% L-arginine-HCl), 63% watermelon pomace juice, 0.01% lycopene, or 0.05% citrus pectin (n = 6 per treatment). At the end of the 4-wk supplementation period, blood samples, aortic rings, and hearts were obtained for biochemical and physiological analyses. Feed or energy intakes did not differ among the five groups of rats. However, dietary supplementation with watermelon pomace juice or L-arginine increased serum concentrations of arginine, reduced fat accretion, lowered serum concentrations of glucose, free fatty acids, homocysteine and dimethylarginines, enhanced GTP cyclohydrolase-I activity and tetrahydrobiopterin concentrations in the heart, and improved acetylcholine-induced vascular relaxation. Compared with the control, dietary supplementation with lycopene or citrus pectin did not affect any measured parameter. These results provide the first evidence for a beneficial effect of watermelon pomace juice as a functional food for increasing arginine availability, reducing serum concentrations of cardiovascular risk factors, improving glycemic control, and ameliorating vascular dysfunction in obese animals with type-II diabetes