Zinc supplementation in the elderly subjects: Effect on oxidized protein degradation and repair systems in peripheral blood lymphocytes

Aging has been associated with zinc deficiency, leading to chronic inflammation and subsequent oxidative stress, especially in the immune system. The increased oxidative stress provokes the accumulation of oxidized proteins, raising the problem of the efficacy of intracellular protein maintenance systems responsible for the elimination of oxidatively modified proteins. Our objective was to analyse the effect of zinc supplementation in the elderly on protein maintenance in peripheral blood lymphocytes. The status of the proteasome, which is in charge of oxidized protein degradation and the repair enzymes peptide methionine sulfoxide reductases, which can reverse methionine oxidation in proteins, were analysed on peripheral blood lymphocytes collected from 20 elderly subjects (age range between 59 and 85 years old) before and after zinc supplementation (10 mg of zinc per day for 48 ± 2 days). A decrease of oxidized protein content in zinc supplemented subjects was observed and was associated with an increase of expression levels and/or activities of proteasome and methionine sulfoxide reductases. Our results indicate that zinc treatment could enhance the anti-oxidative defences of peripheral blood lymphocytes by increasing the activities of protein maintenance systems responsible for the elimination of oxidatively modified proteins.