Dietary zinc and metallothionein on small intestinal disaccharidases activity in mice

AIM: To examine the effect of increasing dietary zinc (Zn) intake and the lack of metallothionein (MT) expression on activity of small intestinal disaccharidases. METHODS: MT- I and II knockout (MT-/-) and wild-type (MT+/+) female mice at 3.5 wk of age were randomly fed with a diet containing 2 (2 Zn), 15 (15 Zn) or 50 (50 Zn) mg Zn/kg (n = 8/group/genotype) for 5 wk. Small intestinal segments (duodenum, jejunum and ileum) were collected and either fixed in 10% formalin for histological analysis or snap frozen in liquid nitrogen for sucrase, lactase and maltase activity analyses. RESULTS: Plasma Zn was significantly (P < 0.05) lower (33%) in MT-/- compared with MT+/+ mice fed the 2 Zn diet. Villus height and crypt depth were increased by approximately 15% in MT+/+ mice compared with MT-/- mice. Duodenal disaccharidase activities were significantly higher in MT+/+ compared with MT-/- mice particularly in those fed the 2 Zn diet. For the 50 Zn diet, jejunal sucrase and lactase activities were significantly higher in MT-/- (13313 +/- 2314; 4107 +/- 364 mu mol glucose/well/min/g tissue, respectively) compared with MT+/+ mice (7054 +/- 608; 1818 +/- 174). Similarly, ileal lactase activities were higher in MT-/- (1480 +/- 192) compared with MT+/+ (629 +/- 353) mice particularly those fed the 2 Zn diet. CONCLUSION: Increasing dietary Zn has little effect on disaccharidases activity in MT wild-type mice. The presence of MT may enhance morphological and functional development of the gut. (C) 2011 Baishideng. All rights reserved.