(LB03-03-24) Intestinal Zinc Homeostasis Upon Dietary Zinc Variations in Mice

Objectives: Zinc is an essential micronutrient vital for various physiological processes, yet excessive intake can lead to toxicity. The small intestine plays a pivotal role in maintaining zinc homeostasis by regulating both zinc absorption into the body and its secretion into the intestinal lumen. This regulation involves intricate mechanisms influenced by the status of zinc and other metals within the intestinal epithelium. To elucidate the dynamics of intestinal zinc homeostasis under fluctuating dietary zinc intakes, this study aimed to examine the impact of varying zinc levels in diets on the intestinal status of zinc and other minerals in mice.

Methods: Male C57BL/6 mice (8 wks old) were assigned to five zinc-diet groups: zinc-deficient (ZD; 0 mg/kg), marginal deficient (MZD; 6 mg/kg), adequate (ZA; 30 mg/kg), supplemented (ZS; 60 mg/kg), and high-dose supplemented (HZS; 300 mg/kg) diets based on the egg whites-modified AIN-93 diets. After 3 and 6 wks of feeding, small intestines (duodenum, jejunum, and ileum) were collected post-overnight fasting for mineral analyses using inductively coupled plasma-optical emission spectrometry.

Results: At 3 wks of feeding, only the duodenum exhibited significant zinc status differences among diet groups, with lower zinc levels in ZD and MZD groups and higher levels in the HZS group compared to ZA. After 6 wks, both ZS and HZS diets showed elevated duodenal zinc levels compared to ZA, with only the HZS diet’s effect observed in the jejunum and ileum. Despite the shared roles of transporters and binding proteins in regulating zinc, copper, and iron in the intestines, the dietary zinc interventions did not exert marked effects on the concentrations of copper and iron within the tissues.

Conclusions: The duodenum emerged as the most responsive segment to dietary zinc variations at both 3 and 6 wks, while the jejunum and ileum exhibited increased zinc levels only with HZS diets. Notably, supplementation of 30 mg/kg zinc to ZA diets, representative of typical 50 mg zinc supplements in non-zinc deficient humans, did not significantly alter intestinal zinc status, suggesting a stable fractional zinc absorption capacity. These findings underscore the intricate regulation of intestinal zinc homeostasis and lay the groundwork for future zinc intervention studies.

Funding Sources: USDA-NIFA-AFRI