1.
Effects of beta-carotene supplements on cancer prevention: meta-analysis of randomized controlled trials.
Jeon, YJ, Myung, SK, Lee, EH, Kim, Y, Chang, YJ, Ju, W, Cho, HJ, Seo, HG, Huh, BY
Nutrition and cancer. 2011;(8):1196-207
Abstract
This meta-analysis aimed to investigate the effects of beta-carotene supplements alone on cancer prevention as reported by randomized controlled trials (RCTs). We searched PubMed, EMBASE, and CENTRAL. Among the 848 articles searched, 6 randomized controlled trials, including 40,544 total participants, 20,290 in beta-carotene supplement groups, and 20,254 in placebo groups, were included in the final analysis. In a meta-analysis of 6 RCTs, beta-carotene supplements had no preventive effect on either cancer incidence [relative risk (RR) = 1.08, 95% confidence interval (CI) = 0.99-1.18] or cancer mortality (RR = 1.00, 95% CI = 0.87-1.15). Similar findings were observed in both primary prevention trials and secondary prevention trials. Subgroup analyses by various factors revealed no preventive effect of beta-carotene supplementation on cancer prevention and that it significantly increased the risk of urothelial cancer, especially bladder cancer (RR = 1.52, 95% CI = 1.03-2.24) and marginally increased the risk of cancer among current smokers (RR = 1.07, 95% CI = 0.99-1.17). The current meta-analysis of RCTs indicated that there is no clinical evidence to support the overall primary or secondary preventive effect of beta-carotene supplements on cancer. The potential effects, either beneficial or harmful, of beta-carotene supplementation on cancer should not be overemphasized.
2.
β-Carotene and lutein inhibit hydrogen peroxide-induced activation of NF-κB and IL-8 expression in gastric epithelial AGS cells.
Kim, Y, Seo, JH, Kim, H
Journal of nutritional science and vitaminology. 2011;(3):216-23
Abstract
Reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)) are involved in the pathogenesis of gastric inflammation. Interleukin-8 (IL-8) is a potent mediator of the inflammatory response by activating and recruiting neutrophils to the site of infection. Oxidant-sensitive transcription factor NF-κB regulates the expression of IL-8 in the immune and inflammatory events. Carotenoids (carotenes and oxygenated carotenoids) show antioxidant and anti-inflammatory activities. Low intake of β-carotene leads to high risk of gastric cancer. Oxygenated carotenoid lutein inhibited NF-κB activation in experimental uveitis. The present study aims to investigate whether β-carotene and lutein inhibit H(2)O(2)-induced activation of NF-κB and expression of IL-8 in gastric epithelial AGS cells. The cells were treated with carotenoids 2 h prior to the treatment of H(2)O(2). mRNA expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and real time RT-PCR analyses. IL-8 level in the medium was determined by enzyme-linked immunosorbent assay. NF-κB activation was assessed by electrophoretic mobility shift assay. ROS levels of the cells were detected by confocal microscopic analysis for fluorescent dichlorofluorescein. As a result, H(2)O(2 )induced the activation of NF-κB and expression of IL-8 in AGS cells time-dependently. β-Carotene and lutein showed inhibitory effects on H(2)O(2)-induced increase in intracellular ROS levels, activation of NF-κB, and IL-8 expression in AGS cells. In conclusion, supplementation of carotenoids such as β-carotene and lutein may be beneficial for the treatment of oxidative stress-mediated gastric inflammation.