Anti-cancer properties of palm oil have been attributed to the presence of tocotrienols and carotenoids. Studies from various laboratories have shown that tocotrienol-rich fraction (TRF) of palm oil inhibits cell growth and induces apoptosis in both preneoplastic and neoplastic cells. However, the mechanism by which TRF induces apoptosis remains largely unknown. Since several chemopreventive agents have been shown to utilize p53 pathway in negative regulation of cell growth, using human colon carcinoma RKO cells which express wild type p53, we investigated the effect of TRF on components of p53 signaling network. Treatment of cells with TRF resulted in a dose- and time- dependent inhibition of growth and colony formation. Further, TRF treatment of RKO cells resulted in the induction of WAF1/p21 which appears to be independent of cell cycle regulation and is transcriptionally upregulated in p53 dependent fashion. These results were further confirmed by using cells that express luciferase from a p53 responsive promoter where TRF treatment leads to activation of p53 reporter activity. TRF treatment also resulted in alteration in Bax/Bcl2 ratio in favor of apoptosis, which was associated with the release of cytochrome c and induction of apoptotic protease-activating factor-1. This altered expression of Bcl2 family members triggered the activation of initiator caspase-9 followed by activation of effector caspase-3. These signaling cascades lead to condensed chromatin, DNA fragmentation and shrinkage of cell membrane resulting into apoptosis. Our data suggest that TRF-induced apoptosis in colon carcinoma cells is mediated by p53 signaling network which appears to be independent of cell cycle association.
Monthly Archives: February 2004
Dietary antioxidant intake and risk of type 2 diabetes
Montonen J, Knekt P, Järvinen R, Reunanen A.
Diabetes Care. 2004 Feb;27(2):362-6.
Objective: The intake of antioxidants was studied for its ability to predict type 2 diabetes.
Research Design & Methods: A cohort of 2,285 men and 2,019 women 40-69 years of age and free of diabetes at baseline (1967-1972) was studied. Food consumption during the previous year was estimated using a dietary history interview. The intake of vitamin C, four tocopherols, four tocotrienols, and six carotenoids was calculated. During a 23-year follow-up, a total of 164 male and 219 female incident cases occurred.
Results: Vitamin E intake was significantly associated with a reduced risk of type 2 diabetes. The relative risk (RR) of type 2 diabetes between the extreme quartiles of the intake was 0.69 (95% CI 0.51-0.94, P for trend = 0.003). Intakes of alpha-tocopherol, gamma-tocopherol, delta-tocopherol, and beta-tocotrienol were inversely related to a risk of type 2 diabetes. Among single carotenoids, beta-cryptoxanthin intake was significantly associated with a reduced risk of type 2 diabetes (RR 0.58, 95% CI 0.44-0.78, P < 0.001). No association was evident between intake of vitamin C and type 2 diabetes risk.
Conclusion: This study supports the hypothesis that development of type 2 diabetes may be reduced by the intake of antioxidants in the diet.
A simple and reliable method for the simultaneous determination of all eight homologs of Vitamin E in chicken meat is described. All analytes, including the internal standard (alpha-tocopherol acetate), were eluted within 35 min and detected using their native fluorescence (295 nm excitation and 330 nm emission). Chromatography using hexane based eluent on a normal phase silica column included an initial column conditioning step to prevent irreversible adsorption of tocopherols and tocotrienols on silica. Lowest detectable levels of alpha-tocopherol, gamma-tocopherol, alpha-tocotrienol, beta-tocotrienol, gamma-tocotrienol and delta-tocotrienol were 0.73, 0.86, 1.0, 1.2, 1.7 and 1.3 ng, respectively.