The interaction of zinc and vitamin A in human schistosomiasis

Levels of vitamin A and components of its transport protein complex, retinol binding protein and prealbumin, as well as zinc and its major binding proteins albumin and alpha 2-macroglobulin were measured in plasma of ninety-one male Egyptian patients with active schistosomal infection and thirty-two healthy adult males. Patients were divided into four groups: Group I had active schistosomiasis without associated complications; Group II had schistosomiasis complicated by colonic polyposis; Group III had advanced schistosomiasis, hepatosplenomegaly and/or ascites; and Group IV had chronic salmonella septicaemia in addition to schistosomiasis. Results showed that all patient groups had subnormal levels of plasma vitamin A, retinol binding protein, prealbumin, zinc and albumin (P less than 0.005 for all parameters) but elevated alpha 2-macroglobulin (P less than 0.001) when compared to the control group. Alterations in the vitamin A transport proteins increased with schistosomal complications and were closely correlated to changes in vitamin A (P less than 0.005), but alterations of albumin and alpha 2-macroglobulin were less consistent and did not correlate with changes in zinc levels. There was a highly significant correlation, however, between plasma zinc concentrations and those of vitamin A, retinol binding protein and prealbumin (P less than 0.001 for all correlations) in all groups of patients as well as the control group. These findings indicate that the binding and transport proteins of both zinc and vitamin A were adversely affected by schistosomiasis and its various complications. Deficiencies of both zinc and vitamin A seem to be interrelated in this disease and the vitamin A transport system may be largely dependent on zinc status.