The purpose of the present study was to estimate lipid peroxidation expressed as thiobarbituric acid reactive substances (TBARS) and plasma total antioxidant status (TAS) in female and male healthy elderly volunteers. In addition, we explored a possibility that age-related changes in the balance between radical generation and antioxidant potential could vary depending on the sex of elderly volunteers. Forty–four healthy, well-nourished, community-dwelling elderly women (n = 15) and men (n = 29) (over 70 years of age) participated in the study. From each subject, blood samples were taken from the basilic vein after an overnight fast. The venous blood was used to determine concentrations of TAS, TBARS, glucose, total cholesterol, HDL cholesterol and triglycerides. The LDL cholesterol fraction was calculated using Friedewald`s Formula. The glucose levels were significantly lower in women (p<0.05), while TAS and TBARS concentrations in plasma were significantly higher in this group compared to the group of men (p<0.01; p<0.05). No significant differences between the two study groups were found in the triglycerides, LDL-cholesterol, HDL-cholesterol and total cholesterol levels.

Aging is a progressive deterioration in physiological functions and metabolic processes [28]. According to the theory of aging proposed by Harman [7] oxygen free radicals cause injury to long–living molecules such as collagen, as well as to mitochondrial and nuclear DNA, which in turn may lead to the deterioration that occurs with age. Also processes of protein glycosylation intensify resulting in premature aging of cells.

Free radicals are thought to be involved in the etiology of many common diseases in the elderly such as Alzheimer’s disease [15], diabetes [10], atherosclerosis [9], and ischemia/reperfusion injury [4] in which the loss in cellular function appears related to defects in the cellular proteolytic system.

The view that the level of oxidative stress increases with advancing age is well-documented, but it is still not clear whether it is due to the decline of the antioxidant defence system capacity or an increase in the rate of prooxidant production. Research data on different animal species and humans are not consistent in this matter [5, 6].

The purpose of the present study was to estimate lipid peroxidation expressed as thiobarbituric acid reactive substances (TBARS) and plasma total antioxidant status (TAS) in female and male healthy elderly volunteers. In addition, we explored the possibility that age-related changes in the balance between radical generation and antioxidant potential could vary depending on the sex of elderly volunteers.

Forty–four healthy, well nourished, community-dwelling elderly women (n = 15) and men (n = 29) (over 70 years of age) participated in the study. The assessment included data such as age, sex, and body mass. Data concerning health state, dietary habits, alcohol consumption, smoking status and medication was taken using a questionnaire. Patients with inflammatory disorders, recent infections, renal or hepatic insufficiency, active coronary artery disease, diabetes, hypertension (c 160/100 mmHg), heart failure, obvious nutritional deficiencies or using corticosteroids were excluded from the study.

From each subject blood samples were taken from the basilic vein after an overnight fast. The total antioxidant status (TAS) of plasma was measured using a commercially available assay (Randox Laboratorie Ltd., UK), based on the inhibition of oxidation of 2.2’– Azino-di-[3-ethylbenzthiazoline sulphonate] (ABTS). Concentrations of thiobarbituric acid reactive substances (TBARS) in plasma were estimated using a spectrophotometric method with chromogen extraction with n-butanol, as described by Buege and Aust [3]. The venous blood serum was used to determine concentrations of glucose, total cholesterol, HDL cholesterol and triglycerides (all with Cormay tests). LDL cholesterol fraction was calculated using Friedewald`s Formula [2].

All data was expressed as mean ± standard deviation (SD). Comparisons between the groups were performed with the use of Mann-Whitney U-test. Spearman correlations were used to determine the relationships between variables. A two-tailed p value <0.05 was considered significant.

The study got the approval of the Local Committee of Ethics in Scientific Research.

The basic characteristics of the study population are shown in Table 1. The mean age was significantly higher in the elderly women in comparison with the men (p<0.05). Body mass index did not differ significantly between the study groups.

Parameters describing biochemical indices and markers of oxidative stress are given in Table 2. The glucose levels were significantly lower in women (p<0.05) while TAS and TBARS concentrations in plasma were significantly higher in this study group (p<0.01; p<0.05). No significant differences between the two study groups were found in triglycerides, LDL-cholesterol, HDL-cholesterol and total cholesterol.

In the group of women a significant correlation between HDL-cholesterol concentrations and TAS levels (r = 0.376; p<0.05) was observed.

Table 1. Basic characteristics of healthy elderly women and men participating in the study

In our study the intensity of oxidative stress was assessed on the basis of measurements of plasma concentrations of thiobarbitiric acid reactive substances (TBARS). We observed the TBARS concentrations fell within the reference range values in the female and male volunteers (Table 2) (p<0.05). Similar results had been reported by studies of centenarian groups by Kłapcińska et al. [11] and Cals et al. [5] in the elderly population of Paris. In contrast, high concentrations of TBARS in aged subjects were found in the study by Congy et al. [6]. The above mentioned study population, however, consisted of disabled persons, often being hospitalized for a long time. The enhanced lipid peroxidation in these patients most probably resulted from disease processes and akinesis due to their hospital stay. Similar findings were reported by Mezzetti et al. [18] and in older male Fisher rats by Tian et al. [25]. The most recently mentioned study population suggests that accumulation of lipid peroxidation may be minimal in multiple aged tissues. Presumably, oxidativly damaged lipid in healthy human and animals is subject to rapid degradation [8].

We observed significantly higher levels of plasma TBARS (p < 0.05) in female in comparison with male volunteers (Table 2). There is fairly scarce data concerning the effect of aging on sex–dependent differences in TBARS concentrations. Rikans et al. [20] found that MDA concentrations in liver homogenates were lower in male rats than in female rats, and MDA content increased with age in male and decreased with age in female rats. The authors suggest that the most probable explanation for the elevated MDA levels in the livers of old male rats is that MDA oxidation by hepatic aldehyde dehydrogenase decreases with age in male rats. In our study, it is difficult to explain why the TBARS levels are lower in males than in females. It is widely accepted that in premenopausal females concentrations of estrogens may have an impact on the oxidant-antioxidant balance [22], however our female representatives were postmenopausal and estrogen concentrations had no such effect.

Table 2. Comparative analysis of biochemical indices and selected markers of oxidative stress and antioxidant system in healthy elderly women and men

In several studies, an impaired antioxidant defense system was reported in older subjects [18, 24, 25]. In contrast, antioxidant levels in free-living, healthy, well-nourished elderly subjects were found to be similar to those in young adults [5, 14].

The TAS, a composite value based on different contributions from a number of different components including sulphydryl groups (mostly albumin), urate, ascorbate, T-tocopherol and bilirubin [19, 23] has been designed to evaluate the overall performance of the plasma antioxidant system.

In the present study, the indicators of antioxidant status (TAS) in elderly women fell within the reference range values for young adults, but, in contrast, we found a decrease of TAS in the elderly men in comparison with younger individuals. We observed significantly higher TAS levels in women in comparison with the elderly men (Table 2) (p < 0.01). The observed significant age-sex interactions with the TAS suggested age-related decline in male subjects, whereas women showed relative age stability. Similar findings were reported by Wang et al. [26].

A positive correlation between HDL concentrations and TAS levels (r = 0.375; p < 0.05) was also observed. The view that HDL is effective in preventing in vitro oxidative modification of LDL both by transition metal ions and by cells in tissue culture is well-documented [14, 16]. Klimov et al. [14] reported the protective effect of HDL against the oxidative modification of LDL, which was dependent on time of incubation and the concentration of HDL. One in vivo study has shown on antioxidant effect on HDL [13]. The results obtained in our study support the view that a high level of HDL may have a positive impact on the antioxidant potential of women.

On the other hand, there is some evidence that with aging the TAS level is much higher in men than in women. These findings were reported in a study on healthy Finnish population by Alho et al. [1] and Chinese population by Woo [27]. Wang et al. [27] suggested that the high TAS level in male subjects could paradoxically reflect a high oxidative stress level in subjects that had stimulated the compensatory up-regulation of antioxidant.

Our findings have not indicated high levels of oxidative stress expressed as TBARS concentrations in plasma in males subjects, and we suggest that decline of the plasma total antioxidant capacity cannot be entirely attributed to the increase of oxidative stress, and probably various other factors may contribute to this process. It is possible that the significantly higher glucose level in the elderly men in comparison with the women (Table2) (p < 0.05) created the total antioxidant capacity of males. In spite of lack of association of the glucose level with TAS concentrations in our study, a decrease of antioxidant activity was reported in some diabetic populations [17, 21].

Conclusion. The above studies show that lipids oxidative damage expressed as TBARS level is not evident in male and female groups of elderly volunteers. The significantly higher TAS level observed in women as compared to men suggests that the plasma antioxidant system may be sex-dependent.

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