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Effect of zinc supplementation on immune response in Italian old population

Moderate zinc (Zn) deficiency is often associated with ageing, which might arise due to a reduced Zn intake. An inadequate Zn nutriture might be the cause of ageing associated decline in immune function. This study was performed to evaluate whether Zn supplementation could improve the immune response in elderly Italian subjects (70-85 y) in relation to gender and Zn status. The subjects were supplemented for six months with Zn (15mg/day or 30 mg/day) or with placebo using a placebo-controlled, double-blinded design. Lymphocytes, isolated from peripheral whole blood, were cultured in medium containing autologous serum and were unstimulated or stimulated with PHA. Proliferative capacity, measured by 3H-thymidine incorporation and reported as stimulation index (SI: cpm stimulated cells/unstimulated cells), and cytokine production, measured by ELISA, were analysed before and after the supplementation with Zn or placebo. Any significant difference between males and females was found at M0 and at M6.

However, at M6 the lower dose of Zn appeared more effective than the higher one, since the proliferative response of females differed significantly from that of males after 15mg of Zn supplementation. No significant difference of men and women cytokine secretion between M0 and M6 with all doses of Zn supplementation was found. The only exception was a small decrease of IL-8 secretion in males after 15 mg of Zn. At M0 a negative correlation between SI and IL-1b or IL-10 was found. IL-10 appeared also negatively correlated with erythrocyte Zn level in PHA-stimulated lymphocytes in males and with serum Zn unstimulated and PHA-stimulated lymphocytes in females.

At M6 a negative correlation was observed between SI and TNF-a of PHA-stimulated lymphocytes of male supplemented with both the two doses of Zn, and between SI and TNF-a of unstimulated lymphocytes of males after the lower dose of Zn. In males, the TNF-a secreted by PHA-stimulated lymphocytes was negatively associated with Zn intake. In females, the IL-1b and TNF-a of unstimulated lymphocytes were negatively associated with red blood Zn. Moreover, a negative association between TNF-a of stimulated and IL-10 of unstimulated cells with serum Zn was found.

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