Roles of Zinc in the Pathophysiology of Acute Diarrhea

Dietary zinc supplements: beneficial health effects and application in food, medicine and animals

Zinc, a crucial trace element is vital for the growth and development of humans. It is frequently described as 'the flower of life' and 'the source of intelligence'. Zinc supplements play a pivotal role in addressing zinc deficiency by serving as a vital source of this essential micronutrients, effectively replenishing depleted zinc levels in the body. In this paper, we first described the biological behavior of zinc in the human body and briefly described the physiological phenomena associated with zinc levels. The benefits and drawbacks of various zinc supplement forms are then discussed, with emphasis on the most recent zinc supplement formulations. Finally, the application of zinc supplements in food, medicine, and animal husbandry is further summarized. © 2024 Society of Chemical Industry.

Effect of probiotics plus zinc supplementation on clinical outcomes of infants and children with acute infectious diarrhea: a randomized controlled trial

BACKGROUND

Findings are conflicting regarding the effect of zinc supplementation on disease severity in children with acute gastroenteritis.

PURPOSE

To examine the effects of probiotics and zinc on the clinical outcomes of infants and children with acute infectious diarrhea.

METHODS

In this randomized controlled trial, children with mild or moderate to severe acute gastroenteritis in the Kurdistan Region from November 2021 to June 2022 were diagnosed clinically and randomly assigned to the experimental or control group. The experimental group (n=50) received probiotics and zinc, whereas the control group (n=51) received probiotics alone for 1 week. The product contained live Bifidobacterium infantis, Lactobacillus paracasei, and Lactobacillus rhamnosus (10×106 colony-forming units/day for 7 days). Zinc syrup was administered to the probiotic plus zinc group. Each 5 mL of syrup contained 15 mg of zinc sulfate. Dehydration and disease severity in both groups were measured using the Clinical Dehydration Scale and the Modified Vesikari Scale, respectively. An illness episode was defined as an episode of gastroenteritis with a total score of ≥9 on the Modified Vesikari Scale (range, 0-20).

RESULTS

The probiotic and probiotic plus zinc groups were similar in age (1.79 years vs. 1.69 years, respectively; P= 0.645), sex (male/female ratio: 1.43 and 1.0, respectively; P=0.373), and medical characteristics. The groups had similar mean dehydration and disease severity scores and a similar incidence of dehydration recovery (some dehydration, 3.92% and 4.00%, respectively; P=1.000), and recovery from mild gastroenteritis (0.0% and 2.0%, respectively; P=0.495) at 2 weeks. Significant decreases in mean dehydration severity and disease severity score (1.80 to 0 and 6.66 to 0, respectively; P<0.001) and the development of dehydration (some dehydration, from 94.0% to 4.0%; P<0.001) from baseline to 2 weeks were noted in the probiotics plus zinc group. The probiotics group responded similarly. The development of mild gastroenteritis was significantly reduced from baseline to 2 weeks (90.2% to 0% and 78.0% to 2.0% in the probiotics and probiotics plus zinc groups, respectively; P<0.0001). The probiotics plus zinc group had a shorter mean recovery time (1.34 days vs. 2.00 days, respectively; P<0.001).

CONCLUSION

Taking probiotics plus zinc did not significantly affect disease severity in children with gastroenteritis at 2 weeks. However, the probiotics plus zinc group recovered more quickly than the probiotics group.

Effect of the Source of Zinc on the Tissue Accumulation of Zinc and Jejunal Mucosal Zinc Transporter Expression in Holstein Dairy Calves

Simple Summary

Diarrhea is the main cause of death in newborn calves and is associated with antibiotic use and economic loss for dairy farms. In this study, we evaluated the effects of different sources of the mineral zinc (zinc oxide (ZnO) and zinc methionine (Zn-Met)) on the growth, incidence of diarrhea, tissue zinc accumulation, gene expression of jejunal zinc transporters and serum concentrations of zinc-dependent proteins in newborn Holstein dairy calves. We found that Zn-Met supplementation promoted growth and reduced diarrhea from the second week after birth. It also increased the levels of zinc in the serum and liver, the level of the transporter protein ZIP4 in the jejunal mucosa, as well as the serum alkaline phosphatase and metallothionein concentrations compared to the control group. ZnO supplementation had similar but less marked effects to Zn-Met supplementation. These results suggest that Zn-Met supplementation may be an alternative to antibiotics for the treatment of newborn calf diarrhea.

Abstract

Zinc is considered to be an anti-diarrheal agent, and it may therefore reduce the incidence of diarrhea in young calves. In the present study, we aimed to compare the effect of zinc source on growth performance, the incidence of diarrhea, tissue zinc accumulation, the expression of zinc transporters, and the serum concentrations of zinc-dependent proteins in neonatal Holstein dairy calves. Eighteen male newborn Holstein dairy calves were fed milk and starter diet supplemented with or without 80 mg zinc/d in the form of Zn-Met or ZnO for 14 days, and were then euthanized. Zn-Met supplementation improved average daily gain and feed efficiency, and reduced the incidence of diarrhea, compared with control calves (p < 0.05). It also increased the serum and hepatic zinc concentrations and the mRNA expression of the ZIP4 transporter in the jejunal mucosa of the calves (p < 0.05). In addition, the serum alkaline phosphatase activity and metallothionein concentration were higher in Zn-Met-treated calves than in control calves (p < 0.05). ZnO supplementation had similar effects, but these did not reach significance. Thus, Zn-Met supplementation is an effective means of increasing tissue zinc accumulation and jejunal zinc absorption, and can be used as an anti-diarrheal strategy in neonatal calves.

Physiological Concentrations of Zinc Have Dual Effects on P2X Myenteric Receptors of Guinea Pig

We, hereby, characterize the pharmacological effects of physiological concentrations of Zinc on native myenteric P2X receptors from guinea-pig small intestine and on P2X2 isoforms present in most myenteric neurons. This is the first study describing opposite effects of Zinc on these P2X receptors. It was not possible to determine whether both effects were concentration dependent, yet the inhibitory effect was mediated by competitive antagonism and was concentration dependent. The potentiating effect appears to be mediated by allosteric changes induced by Zinc on P2X myenteric channels, which is more frequently observed in myenteric neurons with low zinc concentrations. In P2X2-1 and P2X2-2 variants, the inhibitory effect is more common than in P2X myenteric channels. However, in the variants, the potentiatory effect is of equal magnitude as the inhibitory effect. Inhibitory and potentiatory effects are likely mediated by different binding sites that appear to be present on both P2X2 variants. In conclusion, in myenteric native P2X receptors, Zinc has quantitatively different pharmacological effects compared to those observed on homomeric channels: P2X2-1 and P2X2-2. Potentiatory and inhibitory Zinc effects upon these receptors are mediated by two different binding sites. All our data suggest that myenteric P2X receptors have a more complex pharmacology than those of the recombinant P2X2 receptors, which is likely related to other subunits known to be expressed in myenteric neurons. Because these dual effects occur at Zinc physiological concentrations, we suggest that they could be involved in physiological and pathological processes.

Metallothionein: a Potential Link in the Regulation of Zinc in Nutritional Immunity

Nutritional immunity describes mechanisms for withholding essential transition metals as well as directing the toxicity of these metals against infectious agents. Zinc is one of these transition elements that are essential for both humans and microbial pathogens. At the same time, Zn can be toxic both for man and microbes if its concentration is higher than the tolerance limit. Therefore a "delicate" balance of Zn must be maintained to keep the immune cells surveilling while making the level of Zn either to starve or to intoxicate the pathogens. On the other hand, the invading pathogens will exploit the host Zn pool for its survival and replication. Apparently, different sets of protein in human and bacteria are involved to maintain their Zn need. Metallothionein (MT)-a group of low molecular weight proteins, is well known for its Zn-binding ability and is expected to play an important role in that Zn balance at the time of active infection. However, the differences in structural, functional, and molecular control of biosynthesis between human and bacterial MT might play an important role to determine the proper use of Zn and the winning side. The current review explains the possible involvement of human and bacterial MT at the time of infection to control and exploit Zn for their need.

The zinc sensing receptor, ZnR/GPR39, triggers metabotropic calcium signalling in colonocytes and regulates occludin recovery in experimental colitis

Impaired epithelial barrier function is a hallmark of inflammatory bowel diseases, such as colitis, contributing to diarrhoea and perpetuating inflammation. We show that the zinc sensing receptor, ZnR/GPR39, triggers intracellular Ca(2+) signalling in colonocytes thereby inducing occludin expression. Moreover, ZnR/GPR39 is essential for epithelial barrier recovery in the dextran sodium sulfate (DSS) ulcerative colitis model. Loss of ZnR/GPR39 results in increased susceptibility to DSS-induced inflammation, owing to low expression of the tight junction protein occludin and impaired epithelial barrier. Recovery of wild-type (WT) mice from the DSS insult was faster than that of ZnR/GPR39 knockout (KO) mice. Enhanced recovery of the epithelial layer and increased crypt regeneration were observed in WT mice compared with ZnR/GPR39 KO, suggesting that ZnR/GPR39 is promoting epithelial barrier integrity following DSS insult. Indeed, cell proliferation and apical expression of occludin, following the DSS-induced epithelial erosion, were increased in WT tissue but not in ZnR/GPR39 KO tissue. Importantly, survival following DSS treatment was higher in WT mice compared with ZnR/GPR39 KO mice. Our results support a direct role for ZnR/GPR39 in promoting epithelial renewal and barrier function following DSS treatment, thereby affecting the severity of the disease. We suggest ZnR/GPR39 as a novel therapeutic target that can improve epithelial barrier function in colitis.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

Drug-development concepts as guides for optimizing clinical trials of supplemental zinc for populations at risk of deficiency or diarrhea

Studies on the efficacy of zinc supplementation for treatment or prevention of diarrhea have shown an inconsistent effect in populations at risk for zinc deficiency. Unlike drugs, which have no preexisting presence in the body, endogenous zinc must be assessed pharmacokinetically by isotope tracer studies. Although such methods have produced much data, very few studies have estimated the dose and the timing of dosing of zinc supplementation. This review examines drug kinetics used to establish the best dose, the timing of such doses, and the mechanism of action through pharmacodynamic markers and applies them, where possible, to zinc supplements. The findings reveal that little is known, especially in children at highest risk of zinc deficiency. Key data missing to inform proper dosing, whether for treatment of disease or for preventive nutrient supplementation, are noted. Addressing these uncertainties could improve study design, leading to future studies of zinc supplements that might be of greater benefit.

The Zn2+-sensing receptor, ZnR/GPR39, upregulates colonocytic Cl- absorption, via basolateral KCC1, and reduces fluid loss

Administration of zinc, as a complement to oral rehydration solutions, effectively diminishes duration and severity of diarrhea, but it is not known whether it merely fulfills a nutritional deficiency, or if zinc has a direct role of regulating solute absorption. We show that Zn2+ acts via a specific receptor, ZnR/GPR39, to reduce fluid loss. Intestinal fluid secretion triggered by cholera toxin (CTx) was lower in WT mice compared to ZnR/GPR39 KO. In the absence of dietary Zn2+ we observed similar fluid accumulation in WT and ZnR/GPR39 KO mice, indicating that Zn2+ and ZnR/GPR39 are both required for a beneficial effect of Zn2+ in diarrhea. In primary colonocytes and in Caco-2 colonocytic cells, activation of ZnR/GPR39 enhanced Cl- transport, a critical factor in diarrhea, by upregulating K+/Cl- cotransporter (KCC1) activity. Importantly, we show basolateral expression of KCC1 in mouse and human colonocytes, thus identifying a novel Cl- absorption pathway. Finally, inhibition of KCC-dependent Cl- transport enhanced CTx-induced fluid loss. Altogether, our data indicate that Zn2+ acting via ZnR/GPR39 has a direct role in controlling Cl- absorption via upregulation of basolateral KCC1 in the colon. Moreover, colonocytic ZnR/GPR39 and KCC1 reduce water loss during diarrhea and may therefore serve as effective drug targets.

The effectiveness and safety of treatments used for acute diarrhea and acute gastroenteritis in children: protocol for a systematic review and network meta-analysis

BACKGROUND

Acute diarrhea and acute gastroenteritis (AD/AGE) are common among children in low- and middle-income countries (LMIC) and high-income countries (HIC). Supportive therapy including maintaining feeding, prevention of dehydration, and use of oral rehydration solution (ORS), is the mainstay of treatment in all children. Several additional treatments aiming to reduce the episode duration have been compared to placebo, but the differences in effectiveness among them are unknown.

METHODS AND ANALYSIS

We will conduct a systematic review of all randomized controlled trials evaluating the use of zinc, vitamin A, probiotics, prebiotics, synbiotics, racecadotril, smectite, and fermented and lactose-free milk/formula for AD/AGE treatment in children. The primary outcomes are diarrhea duration and mortality. Secondary outcomes are diarrhea lasting 3 or 7 days, stool frequency, treatment failure, hospitalizations, and adverse events. We will search MEDLINE, Ovid EMBASE, CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL), and LILACS through Ovid, as well as grey literature resources. Two reviewers will independently screen titles and abstracts, review full texts, extract information, and assess the risk of bias (ROB) and the confidence in the estimate (with the grading of recommendations, assessment, development, and evaluation [GRADE] approach). Results will be summarized narratively and statistically. Subgroup analysis according to HIC vs. LMIC, age, nutrition status, and ROB is planned. We will perform a Bayesian network meta-analysis to combine the pooled direct and indirect treatment effect estimates for each outcome, if adequate data is available.

DISCUSSION

This is the first systematic review and network meta-analysis that aims to determine the relative effectiveness of pharmacological and nutritional treatments for reducing the duration of AD/AGE in children. The results will help to reduce the uncertainty of the effectiveness of the interventions, find knowledge gaps, and/or encourage further research for other therapeutic options.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42015023778.

Zinc for Acute Diarrhea and Amoxicillin for Pneumonia, Do They Work? : Delivered at the AIIMS, IJP Excellence Award for the year 2013 on 7th September 2014

Acute diarrhea and pneumonia are the two largest killers of under-five children in the world. Zinc, used in management of acute diarrhea and Amoxicillin, used in community acquired pneumonia, feature in the list of 13 Life Saving Commodities for Women's and Children Health by the UN Commission. Zinc has caught wide scientific attention for the conceptual promise it has to offer for prevention, control and treatment of acute diarrhea. This presentation focuses on author's research on the mechanisms by which zinc might contribute to the pathogenesis of acute diarrhea and the degree of success achieved in diarrhea control and treatment by zinc supplementation including its impact on mortality. However, emerging evidence in terms of controlled studies in humans beckons a more complete understanding of the mechanistic basis for zinc supplementation. Current evidence indicates that studies specifically addressing the variability in response to zinc supplementation need to be undertaken to better comprehend these mechanisms. Similarly, the author presented her research that examined the role of oral amoxicillin in community management of severe pneumonia in children and the need to assess its universal efficacy in all children with severe pneumonia.

Zinc deficiency in infants and children: a review of its complex and synergistic interactions

Zinc deficiency is estimated to contribute to over half a million deaths per year in infants and children under 5 years of age. This paper reviews the features of mild-to-moderate zinc deficiency, which include growth faltering, deficits in immune function and altered integrity and function of the gastro-intestinal tract. Sub-clinical features include oxidative stress and a pro-inflammatory state. The homeostatic response to low dietary zinc intake by increasing absorption is limited, especially if the source of zinc is of poor bioavailability, and conservation of endogenous intestinal losses is a critical component of adaptation. Owing to low zinc intakes, older breastfed infants, especially those of low birthweight, are predictably at risk of zinc deficiency if complementary food choices are unfortified and/or low in zinc. Host factors such as young age, poor intra-uterine zinc accretion owing to poor maternal status and/or prematurity, and gastro-intestinal dysfunction also potently predispose to zinc deficiency. Environmental enteropathy, which is prevalent in low-resource settings, may substantially impair zinc absorption and/or increase endogenous losses, and thus lead to relatively high zinc requirements. Emerging evidence highlights common features between chronic inflammation and zinc deficiency, and each may exacerbate the other. More investigations of zinc homeostasis in populations in low-resource settings are needed to better quantify absorption capacity and losses. Effective preventive strategies must address potentially higher zinc requirements as well as the underlying context that perpetuates a vicious cycle of zinc deficiency and multiple adverse outcomes.