Plasma Protein Oxidation and Antioxidant Defense During Aging

Background: Oxidative stress is an important process that occurs in vivo during aging and is considered one of the main causes of molecular damage to cellular and tissue structures. These changes can accumulate in biological structures during aging. Objective: The aim of this work is to evaluate plasma protein oxidative damage, measured as carbonyl groups content, and the concentration of some antioxidant molecules (vitamins and carotenoids) in 122 healthy volunteers (50 males and 72 females), 25 to 89 years old. Results: Total plasma proteins slightly decreased with age, but the level of carbonyl groups was similar in the adult (< 65 years) and in the old, and was similar in both sexes. Plasma concentration of antioxidant molecules such as a-tocopherol, b-carotene and other carotenoids, increased with age and correlated with the level of lipoproteins; plasma total cholesterol and triglycerides were significantly correlated with age as well. Conclusions: The surprisingly normal level of plasma protein carbonyl groups in our older subjects suggests two possibilities: a) the older people in our study are healthy and free from pathologies because of better protection against oxidative injury during their lifetimes, i.e., they maintained low-level oxidative damage on plasma proteins; or b) the level of carbonyl groups is normal because of the high turnover in plasma: the oxidized circulating proteins are preferentially and quickly removed; in this case oxidative damage is not discernible in plasma proteins but may proceed silently in other tissues.