EFFECT OF ORAL ZINC SUPPLEMENTATION ON METALLOTHIONEIN AND SUPEROXIDE-DISMUTASE CONCENTRATIONS IN PATIENTS WITH INFLAMMATORY BOWEL-DISEASE

Oxygen-derived free radicals may contribute to intestinal tissue damag e in inflammatory bowel disease. The concentrations of metallothionein and superoxide dismutase, two copper and zinc containing proteins inv olved in the scavenging of free radicals, were previously found to be decreased in the intestinal mucosa of patients with this disorder. The plasma zinc concentration is often decreased also in these patients. Since zinc is reported to be an efficient inducer of metallothionein s ynthesis, and probably of superoxide dismutase, we evaluated the effec t of oral zinc supplementation on metallothionein and superoxide dismu tase levels in patients with inflammatory bowel disease. Fourteen pati ents with inactive to moderately active inflammatory bowel disease rec eived oral zinc supplementation (300 mg zinc aspartate, equal to 60 mg elemental zinc per day) for 4 weeks in a placebo-controlled double-bl ind cross-over trial. The plasma zinc concentration of these patients was low at the start of the study (12.2+/-1.7 mu mol/L, P < 0.05), whe n compared to that of 22 healthy controls (13.6+/-2.3 mu mol/L), but i ncreased (P < 0.05) towards the levels of controls during the suppleme ntation period (13.3+/-2.5 mu mol/L). The concentrations of metallothi onein and superoxide dismutase in plasma and in erythrocytes did not c hange in relation to the supplementation. The metallothionein concentr ation in both inflamed and non-inflamed intestinal mucosa was slightly higher after zinc supplementation but the superoxide dismutase concen tration in the tissue was nor altered. The histological inflammation s core of intestinal biopsies, plasma albumin levels, and the disease ac tivity index of the patients did not change during the study. Thus, al though zinc supplementation therapy increased plasma zinc concentratio ns, there was no effect on the plasma, erythrocyte and mucosal metallo protein levels in inactive to moderately active patients with inflamma tory bowel disease.