Testosterone is associated with age-related changes in bone health status, muscle strength and body composition in men.

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.

Modulation of collagen synthesis and its gene expression in human skin fibroblasts by tocotrienol-rich fraction.

INTRODUCTION: 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. MATERIAL AND METHODS: Primary culture of human skin fibroblasts was derived from circumcision foreskin of 9 to 12 year-old boys. Fibroblast cells were divided into 5 different treatment groups: untreated control, hydrogen peroxide (H(2)O(2))-induced oxidative stress (20 µM H(2)O(2) exposure for 2 weeks), TRF treatment, and pre- and post-treatment of TRF to H(2)O(2)-induced oxidative stress. RESULTS: Our results showed that H(2)O(2)-induced oxidative stress decreased the rate of total collagen synthesis and down-regulated COL I and COL III in skin fibroblasts. Pre-treatment of TRF protected against H(2)O(2)-induced oxidative stress as shown by increase in total collagen synthesis and up-regulation of COL I and COL III (p<0.05) genes. However, similar protective effects against H(2)O(2)-induced oxidative stress were not observed in the post-treated fibroblasts. CONCLUSIONS: Tocotrienol-rich fraction protects against H(2)O(2)-induced oxidative stress in human skin fibroblast culture by modulating the expression of COL I and COL III genes with concomitant increase in the rate of total collagen synthesis. These findings may indicate TRF protection against oxidative stress-induced skin aging.

Comparative effects of alpha-tocopherol and gamma-tocotrienol against hydrogen peroxide induced apoptosis on primary-cultured astrocytes.

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.