Exercise-induced lipid peroxidation: Implications for deoxyribonucleic acid damage and systemic free radical generation.

Exercise-induced deoxyribonucleic acid (DNA) damage is often associated with an increase in free radicals; however, there is a lack of evidence examining the two in parallel. This study tested the hypothesis that high-intensity exercise has the ability to produce free radicals that may be capable of causing DNA damage. Twelve apparently healthy male subjects (age: 23 ± 4 years; stature: 181 ± 8 cm; body mass: 80 ± 9 kg; and VO(2max) : 49 ± 5 ml/kg/min) performed three 5 min consecutive and incremental stages (40, 70, and 100% of VO(2max) ) of aerobic exercise with a 15-min period separating each stage. Blood was drawn after each bout of exercise for the determination of ex vivo free radicals, DNA damage, protein carbonyls, lipid hydroperoxide (LOOH) concentration, and a range of lipid-soluble antioxidants. Lipid-derived oxygen-centered free radicals (hyperfine coupling constants a(Nitrogen) = 13.7 Gauss (G) and aß(Hydrogen) = 1.8 G) increased as a result of acute moderate and high-intensity exercise (P < 0.05), while DNA damage was also increased (P < 0.05). Systemic changes were observed in LOOH and for lipid-soluble antioxidants throughout exercise (P < 0.05); however, there was no observed change in protein carbonyl concentration (P > 0.05). These findings identify lipid-derived free radical species as possible contributors to peripheral mononuclear cell DNA damage in the human exercising model. This damage occurs in the presence of lipid oxidation but in the absence of any change to protein carbonyl concentration. The significance of these findings may have relevance in terms of immune function, the aging process, and the pathology of carcinogenesis.

The validity of androgen assays.

Problems in the measurement of androgens and in interpreting results have been reviewed and classified as follows: PREANALYTICAL FACTORS: The exact sampling conditions in relation to circadian and seasonal variations, diet, alcohol, physical activity and posture. PHYSIOLOGICAL AND MEDICAL FACTORS: Androgen levels vary according to the patient's general health, stress, sexual activity and smoking habits. Analytical variables. Sample preservation and storage variables are often unknown. The different androgen assays used have widely differing accuracy and precision and are subject to large inter-laboratory variation, which especially in women and children can render the results of routinely available direct immunoassays meaningless. INTERPRETATION OF RESULTS: Laboratory reference ranges vary widely, largely independent of methodology, and fail to take into account the log-normal distribution of androgen values, causing errors in clinical diagnosis and treatment. Other unknowns are antagonists such as SHBG, estrogens, catecholamines, cortisol, and anti-androgens. As well as age, androgen receptor polymorphisms play a major role in regulating androgen levels and resistance to their action. CONCLUSIONS: Though laboratory assays can support a diagnosis of androgen deficiency in men, they should not be used to exclude it. It is suggested that there needs to be greater reliance on the history and clinical features, together with careful evaluation of the symptomatology, and where necessary a therapeutic trial of androgen treatment given.