Zinc, oxidative stress in the elderly, and implication for inflammation

Essentiality of zinc for humans was only established 50 years ago. Zinc deficiency is now known to affect nearly 2 billion subjects in the developing world. It affects adversely cell-mediated immunity and increases oxidative stress and inflammatory cytokines. In the developed countries, nearly 30% of the elderly are zinc deficient. Many chronic diseases seen in the elderly such as atherosclerosis, diabetes, neurodegenerative disorders, Parkinson's disease, and age-related macular degeneration (AMD) may be due to chronic inflammation and increased oxidative stress. Zinc supplementation studies in the elderly have shown decreased incidence of infections, decreased oxidative stress, and decreased generation of inflammatory cytokines. Decreased incidences of blindness in patients with AMD and increased atheroprotective effect have been observed in the zinc-supplemented elderly. Zinc is a molecular signal for immune cells, and many transcription factors involved in gene expression of inflammatory cytokines and adhesion molecules are regulated by zinc. Zinc is involved in the generation of metallothionein (MT). The major physiological function of this protein is to maintain the homeostasis and function in storage and transport of zinc and Cu in the body. MT is a free radical scavenger and may act as an antioxidant molecule.