Tocotrienol-rich fraction prevents cellular aging by modulating cell proliferation signaling pathways.

BACKGROUND AND OBJECTIVE: Vitamin E has been suggested as nutritional intervention for the prevention of degenerative and age-related diseases. In this study, we aimed to elucidate the underlying mechanism of tocotrienol-rich fraction (TRF) in delaying cellular aging by targeting the proliferation signaling pathways in human diploid fibroblasts (HDFs). MATERIALS AND METHODS: Tocotrienol-rich fraction was used to treat different stages of cellular aging of primary human diploid fibroblasts viz. young (passage 6), pre-senescent (passage 15) and senescent (passage 30). Several selected targets involved in the downstream of PI3K/AKT and RAF/MEK/ERK pathways were compared in total RNA and protein. RESULTS: Different transcriptional profiles were observed in young, pre-senescent and senescent HDFs, in which cellular aging increased AKT, FOXO3, CDKN1A and RSK1 mRNA expression level, but decreased ELK1, FOS and SIRT1 mRNA expression level. With tocotrienol-rich fraction treatment, gene expression of AKT, FOXO3, ERK and RSK1 mRNA was decreased in senescent cells, but not in young cells. The three down-regulated mRNA in cellular aging, ELK1, FOS and SIRT1, were increased with tocotrienol-rich fraction treatment. Expression of FOXO3 and P21Cip1 proteins showed up-regulation in senescent cells but tocotrienol-rich fraction only decreased P21Cip1 protein expression in senescent cells. CONCLUSIONS: Tocotrienol-rich fraction exerts gene modulating properties that might be responsible in promoting cell cycle progression during cellular aging.

Comparable down-regulation of TYR, TYRP1 and TYRP2 genes and inhibition of melanogenesis by tyrostat, tocotrienol-rich fraction and tocopherol in human skin melanocytes improves skin pigmentation.

BACKGROUND AND OBJECTIVE: Antioxidant has been recognized to inhibit UV-induced melanogenesis. This study aimed to elucidate the molecular mechanism of tyrostat, tocopherol and tocotrienol-rich fraction in inhibiting melanogenesis in human skin melanocytes. MATERIALS AND METHODS: Primary culture of melanocytes was exposed to repeated doses of 0.6 J/cm2 UVA for 6 days and treated with tyrostat, tocotrienol-rich fraction or tocopherol alone or in combination. RESULTS: UVA irradiation increased melanin content and tyrosinase activity and up-regulated TYR, TYRP1 and TYRP2 genes. Treatment with tyrostat, tocotrienol-rich fraction or tocopherol decreased melanin content and down-regulated TYR, TYRP1 and TYRP2 genes with decreased tyrosinase activity. Combined treatment exerted better effects as compared to treatment with single compound in decreasing the melanin content and down-regulating TYR, TYRP1 and TYRP2 genes. These findings indicated that tyrostat, tocotrienol-rich fraction and tocopherol inhibit melanogenesis by modulating the expression of genes involved in the regulation of melanin synthesis and inhibiting tyrosinase activity. CONCLUSIONS: Tyrostat, tocopherol and tocotrienol-rich fraction possessed anti-melanogenic properties and might be useful in improving skin pigmentation caused by UVA exposure.

Simultaneous determination of retinol and α-tocopherol by high pressure liquid chromatography in micro-volumes of serum.

The lack of biochemical data to indicate the prevalence of marginal vitamin A deficiency (VAD) in the country is largely because of the difficulty of obtaining enough serum for analysis, especially from malnourished children. Efforts were therefore made to establish a high-pressure liquid chromatography system (HPLC) for the determination of retinol in micro-volumes of serum. Since our previous studies showed that tocopherol could be simultaneously determined in the same system, studies have been carried out for the determination of both vitamins using retinol acetate and -tocopherol acetate as internal standards. Trials were carried out to determine the most suitable sample treatment procedures and chromatographic system including composition of the mobile phase for handling 20 ml of serum. The HPLC system proposed enables successful separation and quantitation of retinol and α-tocopherol and their respective internal standards, retinol acetate and -tocopherol in less than 14 minutes. Reproducibility studies carried out with pooled sera showed a within day and between day variation of less than 8% and 13% respectively for retinol, whilst variations for α-tocopherol were higher, ranging from 8-16%. The proposed method is currently being applied to the determination of retinol and α-tocopherol in a group of malnourished children under six years of age.

Carotenoid composition and content of legumes, tubers and roots by HPLC.

As part of a series of studies on the analytical and nutritional aspects of carotenoids and retinoids in foods, seventeen types of legumes and their products and 9 tubers and starchy roots were studied for their carotenoid composition and content by HPLC. All samples were saponified and subsequently chromatographed using a reverse-phase HPLC method previously developed in this laboratory in which carotenoids were separated isocratically on an octadecylsilane (C18) column using a ternary mixture of acetonitrile, methanol and ethyl acetate (88:10:2) as the mobile phase. Carotenoid peaks obtained were tentatively identified using 6 reference standards similarly chromatographed. The HPLC method used enabled the separation and quantitation of the major carotenoids present, namely, lutein, cryptoxanthin, lycopene, g-, a- and b-carotenes. For most of the legumes, the major carotenoids detected were b-carotene, lutein and cryptoxanthin. Lutein was found in all the legumes studied, and was clearly the major carotenoid in most of the legumes, followed by unidentified carotenoids, b-carotene and cryptoxanthi. The other carotenoids were encountered infrequently and at low levels. The starchy roots and tubers gave a different carotenoid composition from those obtained for the legumes: lycopene and b-carotene were detected in all the samples except in sago. There was no clear pattern of carotenoids present in the samples studied. Compared with the vegetables and fruits, the carotenoid concentration in legumes, tubers and roots were found to be much lower. None of the items studied can be said to be good sources of vitamin A. Nevertheless, they are still of nutritional import flee, if consumed in significant amounts.