In vivo antioxidant status, DNA damage, mutation and DNA repair capacity in cultured lymphocytes from healthy 75- to 80-year-old humans.

The accumulation of damage to cellular biomolecules, including DNA, over time may play a significant role in the aetiology of the ageing process. We have previously quantified DNA damage and mutation within cultured lymphocytes from healthy human male subjects in three different age groups (35-39, 50-54 and 65-69 years). The results of that study showed an age-related increase in DNA damage and mutations in lymphocytes. In addition, an age-related decrease in the capacity of the lymphocytes to repair H2O2-induced DNA damage was found. In this article, we report the findings of an extension to the earlier study. Thirty-one generally healthy male and female subjects between the ages of 75 and 80 years were recruited. Using a number of bioassays, we were able to determine; basal levels of DNA damage (for 18 subjects) and mutant frequency at the hypoxanthine phosphoribosyltransferase (hprt) gene locus (for 16 subjects) within cultured lymphocytes. In addition, in vivo antioxidant status (for all study subjects) and the capacity of lymphocytes to repair H2O2-induced DNA damage (for 18 subjects) were also assessed. The results obtained showed: that the mean basal level of DNA damage in lymphocytes from subjects in the 75- to 80-year age group (12.6 +/- 4.7%) was similar to that of the 35- to 39-year age group (13.3 +/- 3.3%), p = 0.42 (Mann-Whitney); there was no significant difference between log mean mutant frequency at the hprt gene locus in lymphocytes from the 75- to 80-year age group (0.31 +/- 0.33) compared to that observed in the 35- to 39-year age group (0.24 +/- 0.21; Student's t-test, t = 0.68, p > 0.05). Levels of the antioxidants glutathione peroxidase (GPx EC 1.11.1.9), catalase (CAT; EC 1.11.1.6) and caeruloplasmin (CPL; EC 1.16.3.1) were significantly elevated in the 75- to 80-year age group, compared to the 35- to 39-, 50- to 54- and 65- to 69-year age groups. Levels of bilirubin (BR) were reduced in the 75- to 80-year age group, the decrease being contributed by the female subjects. No differences in levels of superoxide dismutase (SOD; EC 1.15.1.1) or uric acid (UA) were found between the 4 age groups. Following treatment of lymphocytes with H2O2, we did not find any difference in the susceptibility of lymphocytes to DNA damage in the 75- to 80-year age group, compared to the other age groups. The DNA repair capacity in lymphocytes from individuals in the 75- to 80-year age group was similar to that of the 35- to 39-year age group, for all time points assessed. These results highlight the importance of DNA repair processes and antioxidant defence systems for maintaining genomic stability in vivo.

Iron status, blood lipids and endogenous antioxidants in response to dietary iron levels in male and female rats.

The effect of dietary iron levels on iron status, blood lipids and endogenous antioxidants was investigated in male and female rats. Diets low in iron (15 mg/kg Fe; LFe) or high in iron (400 mg/kg Fe; HFe) were given to groups of male (n = 6) and female (n = 6) weanling rats for six weeks. In a second experiment the same dietary iron levels were fed to groups (n = 12) of males and females for seven months, during which colon tumours were induced. Indices of iron status, blood lipid levels and antioxidant enzyme activities were measured in both experiments. In the first experiment, indices of iron status were significantly higher in HFe rats and in females compared with males. Cholesterol and triglycerides were significantly higher in HFe rats and cholesterol was significantly higher in males. Plasma albumin and bilirubin levels and plasma caeruloplasmin activity were significantly higher in female rats. The second experiment confirmed the higher indices of iron status in HFe rats and in female rats, and also showed that plasma cholesterol levels were significantly higher in HFe rats. There were no consistent, significant differences over both experiments in activities of the antioxidant enzymes measured. Results show that higher dietary iron levels are associated with higher cholesterol levels in male and female rats. However cholesterol was found to be higher in male rats while iron status was higher in female rats. This indicates that factors other than iron status are responsible for the differences in cholesterol in male and female rats.