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Effects of Watermelon Powder and l-arginine Supplementation on Azoxymethane-Induced Colon Carcinogenesis in Rats

Glenn, Keith, Klarich, DawnKylee S, Kalaba, Milica, Figueroa, Arturo, Hooshmand, Shirin, Kern, Mark, Hong, Mee Young
Nutrition and cancer 2018 v.70 no.6 pp. 938-945
DNA, DNA damage, DNA repair, animal models, arginine, azoxymethane, body weight, carcinogenesis, citrulline, colon, colorectal neoplasms, dietary supplements, fruits, gene expression, gene expression regulation, inflammation, laboratory animals, males, methyltransferases, nitric oxide, nutrition risk assessment, rats, risk reduction, vegetables, watermelons
Diets high in fruits and vegetables may help prevent colorectal cancer (CRC). Watermelon consumption may reduce CRC risk due to its concentration of l-citrulline and its role in endothelial nitric oxide (NO) production. Research suggests that increased NO levels have tumoricidal effects. The purpose of this study was to determine the effects of watermelon powder supplementation on aberrant crypt foci (ACF) formation, precancerous lesions, and expression of genes associated with colon carcinogenesis. Thirty-two male Sprague-Dawley rats were assigned into three groups: control, 0.36% l-arginine, or 0.5% watermelon powder and injected with azoxymethane (15 mg/kg body weight). Both l-arginine and watermelon powder groups exhibited lower total numbers of ACF and high multiplicity ACF (P < 0.01). The watermelon powder group exhibited higher NO levels and lower 8-hydroxyguanosine DNA damage (P < 0.05). Watermelon powder and l-arginine downregulated 8-oxoguanine DNA glycosylase gene expression and upregulated O⁶-methylguanine DNA methyltransferase gene expression (P < 0.05). Cyclooxgenase-2 gene expression was lower for rats fed with watermelon powder (P < 0.05). These results suggest that watermelon powder or l-arginine supplementation may reduce the risk of colon cancer by suppressing ACF formation through lowering oxidative DNA damage and inflammation, modulating DNA repair enzyme expression, and/or enhancing NO production.