Oxidative stress is thought to be one of the factors that cause neurodegeneration and that this can be inhibited by antioxidants. Since astrocytes support the survival of central nervous system (CNS) neurons, we compared the effect of alpha-tocopherol and gamma-tocotrienol in minimizing the cytotoxic damage induced by H(2)O(2), a pro-oxidant. Primary astrocyte cultures were pretreated with either alpha-tocopherol or gamma-tocotrienol for 1 h before incubation with 100 microM H(2)O(2) for 24 h. Cell viability was then assessed using the MTS assay while apoptosis was determined using a commercial ELISA kit as well as by fluorescent staining of live and apoptotic cells. The uptake of alpha-tocopherol and gamma-tocotrienol by astrocytes were also determined using HPLC. Results showed that gamma-tocotrienol is toxic at concentrations >200 microM but protects against H(2)O(2) induced cell loss and apoptosis in a dose dependent manner up to 100 microM. alpha-Tocopherol was not cytotoxic in the concentration range tested (up to 750 microM), reduced apoptosis to the same degree as that of gamma-tocotrienol but was less effective in maintaining the viable cell number. Since the uptake of alpha-tocopherol and gamma-tocotrienol by astrocytes is similar, this may reflect the roles of these 2 vitamin E subfamilies in inhibiting apoptosis and stimulating proliferation in astrocytes.
Skin aging may occur as a result of increased free radicals in the body. Vitamin E, the major chain-breaking antioxidant, prevents propagation of oxidative stress, especially in biological membranes. In this study, the molecular mechanism of tocotrienol-rich fraction (TRF) in preventing oxidative stress-induced skin aging was evaluated by determining the rate of total collagen synthesis and its gene expression in human skin fibroblasts.
OBJECTIVE: Variations in testosterone levels are associated with several outcomes of aging. The present study aimed to examine the relationship between age-related decline of testosterone levels and changes in bone health status, handgrip strength, body fat percentage and fat-free mass.
MATERIALS AND METHODS: A total of 335 Malaysian Chinese and Malay men aged 40 years and above were recruited for this study. Their body compositions, calcaneal speed of sound and handgrip strength were measured and their blood was collected. Linear regression analysis was done to examine the relationship among age, testosterone levels and outcomes of aging.
RESULTS: The results indicated significant changes in all testosterone measurements, sex hormone binding globulin level, calcaneal speed of sound, handgrip strength, body fat percentage and fat-free mass with age (p < 0.05). Age-dependent decline in bioavailable and free testosterone levels were significantly associated with reduction in calcaneal speed of sound, fat-free mass and handgrip strength (p < 0.05). Age-dependent decline in the total testosterone level was significantly associated with an increase in body fat percentage among the elderly men (p < 0.05).
CONCLUSION: Testosterone levels are associated with changes in outcome of aging such as bone health status, muscle strength and body composition, and the relationships are age-dependent.