Intestinal microflora, morphology and enzyme activity in zinc-deficient and Zn-supplemented rats

Abstract

1. Immature, male Wistar rats were given a low-zinc diet (2 mg/kg) for 22-24 d. Control groups received a similar diet supplemented with 58 mg Zn/kg either ad lib., or in amounts matched to the consumption of the Zn-deficient group. Food consumption, rate of growth and food conversion efficiency were markedly lower in the Zn-deficient group of rats compared with controls. Appetite, growth rate and food utilization improved dramatically over a subsequent 4 d period of Zn supplementation. 2.Morphological examination of samples of jejunum and ileum confirmed that Zn deficiency in the rat is accompanied by a reduction in villous dimensions and increase in villous density. After a short period of Zn supplementation, villous density and the basal width and maximum height of individual villi in the jejunum returned to normal. Similar changes occurred in the ileum but to a lesser extent.3. Mucosal alkaline phosphatase (EC 3.1 .3. I ) activity was significantly lower in the small intestine of Zn-deficient rats compared with Zn-supplemented rats. Disaccharidase activities were lower in the Zn-deficient group, compared with their feed-restricted counterparts, but were similar to values for ad lib.-fed controls. Tissue alkaline phosphatase and disaccharidase activitities were consistently higher after a 4 d period of Zn supplementation, compared with non-supplemented animals, but this increase was only significant for alkaline phosphatase.4. Although there were striking similarities in the mucosal characteristics of gnotobiotic and Zn-deficient rats, there was no indication that even severe dietary Zn depletion reduced the numbers of viable bacteria present in either the small or large intestine. Changes in intestinal structure and function resulting from variation in dietary Zn intake appear, therefore, to be unrelated to changes in the intestinal flora.

Small intestinal morphology and bacterial populations in ileal digesta and feces of newly weaned pigs receiving a high dietary level of zinc oxide

“…The present study did not assess coliform population diversity, but CFU counts suggest that ZnO had no effect on the total number of E. coli per gram of ileal digesta or feces. This is in agreement with previous studies (Southon et al 1986;Jensen-Waern et al 1998). Southon et al (1986) reported that severe dietary Zn depletion did not reduce the number of viable bacteria present in either the small or large intestine.…”

“…This is in agreement with previous studies (Southon et al 1986;Jensen-Waern et al 1998). Southon et al (1986) reported that severe dietary Zn depletion did not reduce the number of viable bacteria present in either the small or large intestine. Hence, the mechanism by which supplemented ZnO prevents post-weaning diarrhea remains unclear.…”

“…The bacterial flora in the intestinal lumen also has an important effect on mucosal architecture (Thompson and Trexler 1971), and zinc is an important factor in cell replication and growth for both microorganisms and enterocytes of the villous epithelium. Indeed, the structural and functional characteristics of the small intestine of rats, in the absence of bacteria, were, in many aspects, strikingly similar to those observed in the zinc-deficient rat (Southon et al 1986). The objective of the present study was to investigate the small intestinal morphology of newly weaned pigs supplemented with a high dietary level of ZnO.…”

“…The positive effect of dietary ZnO supplementation on the growth of newly weaned pigs may, therefore, be related to enhanced morphological and functional development of the intestinal mucosa. Southon et al (1986) reported that dietary zinc depletion was associated with morphological and functional changes in the jejunum of rats, which included shortening and narrowing of jejunal villi and a reduction in absorptive surface area. High levels of dietary zinc also prevented an increase in intestinal paracellular permeability in malnourished guinea pigs (Rodrigues et al 1996).…”

Effects of Early Malnutrition on Mental System, Metabolic Syndrome, Immunity and the Gastrointestinal Tract

“…The rates of enterocyte proliferation and migration are affected by a variety of factors. An overt nutrient deficiency, most notably for zinc [80], vitamin A [85], and cyanocobalamin (B12) [95], will affect intestinal physiology. Glutathione is a crucial antioxidant in the gastrointestinal mucosa that is also formed from glutamine [55,72].…”