Oxidative stress and bone mineral density in elderly men: Antioxidant activity of alpha-tocopherol a b s t r a c t a r t i c l e i n f o Oxidative stress has recently been identified as a pivotal pathogenetic factor of bone loss in mice, but its importance in humans is not clear. We aimed to investigate the association between urinary 8-iso-PGF 2α levels, a major F 2 -isoprostane and a reliable in vivo biomarker of oxidative stress, and bone mineral density (BMD), and to study whether vitamin E in the form of serum α-tocopherol, a scavenger of peroxyl radicals, modifies the association. In 405 men, urinary 8-iso-PGF 2α and serum α-tocopherol were measured at age 77 years and BMD at age 82 years. One SD increase in 8-iso-PGF 2α corresponded to an approximately 2-4% decrease in average adjusted BMD values of total body, lumbar spine, and proximal femur (all P b 0.001). Serum α-tocopherol levels seemed to modify the association between urinary 8-iso-PGF 2α and BMD. Men with α-tocopherol levels below the median combined with high oxidative stress, i.e., 8-iso-PGF 2α above the median, had 7% (95% CI 3-11%) lower BMD at the lumbar spine and 5% (95% CI 2-9%) lower BMD at the proximal femur. In elderly men high oxidative stress is associated with reduced BMD, which is more pronounced in individuals with low serum levels of the antioxidant vitamin E.

The aim of the study was to investigate the distribution of lactate in plasma, whole blood, erythrocytes, and capillary finger blood, before and during submaximal exercise. Ten healthy male subjects performed submaximal graded cycle ergometer exercise for 20-25 min. Venous blood samples and capillary finger blood samples were taken before exercise and every 5th min during exercise for lactate determination. The plasma lactate concentration was significantly higher (P less than 0.001, approximately 50%) than in the erythrocytes. This difference was not altered by the venous blood lactate concentration or exercise intensity. A significant difference (P less than 0.01) in lactate concentration was also found between capillary whole blood and venous whole blood. It was concluded that direct comparisons between lactate in capillary finger blood, venous whole blood and plasma could not be made.

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