Zinc absorption in human small intestine

Supplementation of Micro- and Macronutrients-A Role of Nutritional Status in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a condition in which the pathological cumulation of fat with coexisting inflammation and damage of hepatic cells leads to progressive dysfunctions of the liver. Except for the commonly well-known major causes of NAFLD such as obesity, dyslipidemia, insulin resistance, or diabetes, an unbalanced diet and imbalanced nutritional status should also be taken into consideration. In this narrative review, we summarized the current knowledge regarding the micro- and macronutrient status of patients suffering from NAFLD considering various diets and supplementation of chosen supplements. We aimed to summarize the knowledge indicating which nutritional impairments may be associated with the onset and progression of NAFLD at the same time evaluating the potential therapy targets that could facilitate the healing process. Except for the above-mentioned objectives, one of the most important aspects of this review was to highlight the possible strategies for taking care of NAFLD patients taking into account the challenges and opportunities associated with the micronutrient status of the patients. The current research indicates that a supplementation of chosen vitamins (e.g., vitamin A, B complex, C, or D) as well as chosen elements such as zinc may alleviate the symptoms of NAFLD. However, there is still a lack of sufficient data regarding healthy ranges of dosages; thus, further research is of high importance in this matter.

The nutritional roles of zinc for immune system and COVID-19 patients

Zinc (Zn) is a vital micronutrient that strengthens the immune system, aids cellular activities, and treats infectious diseases. A deficiency in Zn can lead to an imbalance in the immune system. This imbalance is particularly evident in severe deficiency cases, where there is a high susceptibility to various viral infections, including COVID-19 caused by SARS-CoV-2. This review article examines the nutritional roles of Zn in human health, the maintenance of Zn concentration, and Zn uptake. As Zn is an essential trace element that plays a critical role in the immune system and is necessary for immune cell function and cell signaling, the roles of Zn in the human immune system, immune cells, interleukins, and its role in SARS-CoV-2 infection are further discussed. In summary, this review paper encapsulates the nutritional role of Zn in the human immune system, with the hope of providing specific insights into Zn research.

Caseinophosphopeptides Overcome Calcium Phytate Inhibition on Zinc Bioavailability by Retaining Zinc from Coprecipitation as Zinc/Calcium Phytate Nanocomplexes

Caseinophosphopeptides have shown great potential to increase zinc bioavailability from phytate-rich diets, but the mechanism of action remains unclear. Here, caseinophosphopeptides from a sodium caseinate hydrolysate dose-dependently retained zinc in solution against calcium phytate coprecipitation under physiologically relevant conditions. The 3 kDa ultrafiltration separation unveiled no added low-molecular-weight chelates of zinc and calcium by caseinophosphopeptides. Tyndall effect, dynamic light scattering measurements, transmission electron microscopy observation, electron diffraction pattern, X-ray diffraction spectrum, and energy-dispersive X-ray analysis demonstrated the caseinophosphopeptides-mediated formation of single-crystal zinc/calcium phytate nanocomplexes (Zn/CaPA-NCs) with a size and ζ-potential of 10-30 nm and -25 mV, respectively. Caseinophosphopeptides-stabilized Zn/CaPA-NCs were found to deliver bioavailable nanoparticulate zinc in mouse jejunal loop ex vivo model and polarized Caco-2 cells, and the treatments with specific inhibitors revealed that intestinal zinc absorption from Zn/CaPA-NCs invoked macropinocytosis, lysosomal release into the cytosol, and transcytosis. Overall, our study proposes a new paradigm for the benefit of caseinophosphopeptides for zinc bioaccessibility and bioavailability in phytate-rich diets.

Elevated luminal inorganic phosphate suppresses intestinal Zn absorption in 5/6 nephrectomized rats

Zinc (Zn) is an essential trace element in various biological processes. Chronic kidney disease (CKD) often leads to hypozincemia, resulting in further progression of CKD. In CKD, intestinal Zn absorption, the main regulator of systemic Zn metabolism, is often impaired; however, the mechanism underlying Zn malabsorption remains unclear. Here, we evaluated intestinal Zn absorption capacity in a rat model of CKD induced by 5/6 nephrectomy (5/6 Nx). Rats were given Zn and the incremental area under the plasma Zn concentration-time curve (iAUC) was measured as well as the expression of ZIP4, an intestinal Zn transporter. We found that 5/6 Nx rats showed lower iAUC than sham-operated rats, but expression of ZIP4 protein was upregulated. We therefore focused on other Zn absorption regulators to explore the mechanism by which Zn absorption was substantially decreased. Because some phosphate compounds inhibit Zn absorption by coprecipitation and hyperphosphatemia is a common symptom in advanced CKD, we measured inorganic phosphate (Pi) levels. Pi was elevated in not only serum but also the intestinal lumen of 5/6 Nx rats. Furthermore, intestinal intraluminal Pi administration decreased the iAUC in a dose-dependent manner in normal rats. In vitro, increased Pi concentration decreased Zn solubility under physiological conditions. Furthermore, dietary Pi restriction ameliorated hypozincemia in 5/6 Nx rats. We conclude that hyperphosphatemia or excess Pi intake is a factor in Zn malabsorption and hypozincemia in CKD. Appropriate management of hyperphosphatemia will be useful for prevention and treatment of hypozincemia in patients with CKD.NEW & NOTEWORTHY We demonstrated that elevated intestinal luminal Pi concentration can suppress intestinal Zn absorption activity without decreasing the expression of the associated Zn transporter. Increased intestinal luminal Pi led to the formation of an insoluble complex with Zn while dietary Pi restriction or administration of a Pi binder ameliorated hypozincemia in chronic kidney disease model rats. Therefore, modulation of dietary Pi by Pi restriction or a Pi binder might be useful for the treatment of hypozincemia and hyperphosphatemia.

Exploring the potential function of trace elements in human health: a therapeutic perspective

A trace element, known as a minor element, is a chemical element whose concentration is very low. They are divided into essential and non-essential classes. Numerous physiological and metabolic processes in both plants and animals require essential trace elements. These essential trace elements are so directly related to the metabolic and physiologic processes of the organism that either their excess or deficiency can result in severe bodily malfunction or, in the worst situations, death. Elements can be found in nature in various forms and are essential for the body to carry out its varied functions. Trace elements are crucial for biological, chemical, and molecular cell activity. Nutritional deficits can lead to weakened immunity, increased susceptibility to oral and systemic infections, delayed physical and mental development, and lower productivity. Trace element enzymes are involved in many biological and chemical processes. These compounds act as co-factors for a number of enzymes and serve as centers for stabilizing the structures of proteins and enzymes, allowing them to mediate crucial biological processes. Some trace elements control vital biological processes by attaching to molecules on the cell membrane's receptor site or altering the structure of the membrane to prevent specific molecules from entering the cell. Some trace elements are engaged in redox reactions. Trace elements have two purposes. They are required for the regular stability of cellular structures, but when lacking, they might activate alternate routes and induce disorders. Therefore, thoroughly understanding these trace elements is essential for maintaining optimal health and preventing disease.

Role of micronutrients in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an autoimmune intestinal disease that includes ulcerative colitis, Crohn's disease, and indeterminate colitis. Patients with IBD are often at risk for malnutrition, including micronutrient deficiencies, due to dietary restrictions and poor intestinal absorption. Micronutrients, including vitamins and minerals, play an important role in the human body's metabolism and maintenance of tissue functions. This article reviews the role of micronutrients in IBD. Micronutrients can affect the occurrence and progression of IBD by regulating immunity, intestinal flora, oxidative stress, intestinal barrier function, and other aspects. Monitoring and timely supplementation of micronutrients are important to delay progression and improve clinical symptoms in IBD patients.

Zinc nutrition and dietary zinc supplements

As the second most abundant trace element in the human body, zinc nutrition is constantly a hot topic. More than one-third population is suffering zinc deficiency, which results in various types of diseases or nutritional deficiencies. Traditional ways of zinc supplementation seem with low absorption rates and significant side effects. Zinc supplements with dietary components are easily accessible and improve zinc utilization rate significantly. Also, mechanisms of maintaining zinc homeostasis are of broad interest. The present review focuses on zinc nutrition in human health in inductive methods. Mainly elaborate on different diseases relating to zinc disorder, highlighting the impact on the immune system and the recent COVID-19. Then raise food-derived zinc-binding compounds, including protein, peptide, polysaccharide, and polyphenol, and also analyze their possibilities to serve as zinc complementary. Finally, illustrate the way to maintain zinc homeostasis and the corresponding mechanisms. The review provides data information for maintaining zinc homeostasis with the food-derived matrix.

Prevalence of Zinc Deficiency in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

Malabsorptive disorders are closely associated with micronutrient deficiencies. In inflammatory bowel disease (IBD), trace element deficiencies pose a clinical burden from disease onset throughout its course, contributing to morbidity and poor quality of life. We aimed to conduct a systematic review and meta-analysis of the prevalence of zinc deficiency in IBD. Literature screening was performed on six electronic databases until 1 May 2022. Two independent investigators assessed the 152 retrieved articles for inclusion criteria, met by only nine, that included 17 prevalence entries for Crohn’s disease (CD) (n = 9) and ulcerative colitis (UC) (n = 8). No exclusion criteria were applied to language, deficiency cut-offs, population age, general health status, country, or study setting (cohort or cross-sectional). The prevalence of zinc deficiency in blood was scored positive if due to a single disease, not cumulative factors. Zinc deficiency prevalence across selected studies showed higher values in CD than in UC. Pooled analyses by the IBD subgroup showed a total population of 1677 with CD, for an overall mean zinc deficiency prevalence of 54% and 95% confidence intervals (CI) ranging from 0.51 to 0.56, versus 41% (95%CI 0.38–0.45) in the UC population (n = 806). The overall prevalence at meta-analysis was estimated at 50% (95%CI 0.48–0.52), but with high heterogeneity, I² = 96%. The funnel plot analysis failed to show any evidence of publication bias. The risk of bias across selected studies was moderate to low. In IBD contexts, one of two patients suffers from zinc deficiency. Mismanagement of micronutrient deficiencies plays a role in inflammation trajectories and related cross-pathways. Clinicians in the field are advised to list zinc among trace elements to be monitored in serum.

Impact of Zinc Transport Mechanisms on Embryonic and Brain Development

The trace element zinc (Zn) binds to over ten percent of proteins in eukaryotic cells. Zn flexible chemistry allows it to regulate the activity of hundreds of enzymes and influence scores of metabolic processes in cells throughout the body. Deficiency of Zn in humans has a profound effect on development and in adults later in life, particularly in the brain, where Zn deficiency is linked to several neurological disorders. In this review, we will summarize the importance of Zn during development through a description of the outcomes of both genetic and early dietary Zn deficiency, focusing on the pathological consequences on the whole body and brain. The epidemiology and the symptomology of Zn deficiency in humans will be described, including the most studied inherited Zn deficiency disease, Acrodermatitis enteropathica. In addition, we will give an overview of the different forms and animal models of Zn deficiency, as well as the 24 Zn transporters, distributed into two families: the ZIPs and the ZnTs, which control the balance of Zn throughout the body. Lastly, we will describe the TRPM7 ion channel, which was recently shown to contribute to intestinal Zn absorption and has its own significant impact on early embryonic development.

Differential Effects of Transition Metals on Growth and Metal Uptake for Two Distinct Lactobacillus Species

Lactobacillus is a genus of Gram-positive bacteria and comprises a major part of the lactic acid bacteria group that converts sugars to lactic acid. Lactobacillus species found in the gut microbiota are considered beneficial to human health and commonly used in probiotic formulations, but their molecular functions remain poorly defined. Microbes require metal ions for growth and function and must acquire them from the surrounding environment. Therefore, lactobacilli need to compete with other gut microbes for these nutrients, although their metal requirements are not well-understood. Indeed, the abundance of lactobacilli in the microbiota is frequently affected by dietary intake of essential metals like zinc, manganese, and iron, but few studies have investigated the role of metals, especially zinc, in the physiology and metabolism of Lactobacillus species. Here, we investigated metal uptake by quantifying total cellular metal contents and compared how transition metals affect the growth of two distinct Lactobacillus species, Lactobacillus plantarum ATCC 14917 and Lactobacillus acidophilus ATCC 4356. When grown in rich or metal-limited medium, both species took up more manganese, zinc, and iron compared with other transition metals measured. Distinct zinc-, manganese- and iron-dependent patterns were observed in the growth kinetics for these species and while certain levels of each metal promoted the growth kinetics of both Lactobacillus species, the effects depend significantly on the culture medium and growth conditions. IMPORTANCE The gastrointestinal tract contains trillions of microorganisms, which are central to human health. Lactobacilli are considered beneficial microbiota members and are often used in probiotics, but their molecular functions, and especially those which are metal-dependent, remain poorly defined. Abundance of lactobacilli in the microbiota is frequently affected by dietary intake of essential metals like manganese, zinc, and iron, but results are complex, sometimes contradictory, and poorly predictable. There is a significant need to understand how host diet and metabolism will affect the microbiota, given that changes in microbiota composition are linked with disease and infection. The significance of our research is in gaining insight to how metals distinctly affect individual Lactobacillus species, which could lead to novel therapeutics and improved medical treatment. Growth kinetics and quantification of metal contents highlights how distinct species can respond differently to varied metal availability and provide a foundation for future molecular and mechanistic studies.

Effects of Zn-Enriched Bifidobacterium longum on the Growth and Reproduction of Rats

Zn is an essential trace element required for maintaining normal growth and development. Zn deficiency can cause growth retardation and reproductive system dysplasia, while Zn supplementation for treating Zn deficiency requires the use of high-quality Zn preparations. In this study, Bifidobacterium longum CCFM1195 was screened for its high Zn enrichment capacity, and the effects of different Zn supplementation regimens and doses on the growth and development of rats after Zn supplementation were investigated by supplementing Zn-deficient rat pups with different doses of various Zn supplements (ZnO, CCFM1195 + ZnO, and Zn-enriched CCFM1195). It was shown that the bioavailability of Zn was positively correlated with indicators of recovery after Zn supplementation, with Zn-enriched CCFM1195 having the best effect, followed by CCFM1195 + ZnO, while ZnO had the worst effect. Significant differences were also observed between the gut microbiota of control, model, and Zn-supplemented rats. Overall, administration of Zn-enriched CCFM1195 was more effective than the other approaches in restoring physical indicators of Zn deficiency after Zn supplementation, and this advantage was more significant at low-dose Zn supplementation.

Slc39a4 in the small intestine predicts zinc absorption and utilization: a comprehensive analysis of zinc transporter expression in response to diets of varied zinc content in young mice

Zinc homeostasis is primarily maintained by zinc transporters that regulate zinc uptake and efflux in the small intestine; however, the relative contribution of the many zinc transporters identified (Slc39a1-14, Slc30a1-10) to dietary zinc absorption and utilization remains unknown. The objective of this study was to determine the expression of Slc39a1-14 and Slc30a1-10 in the small intestine and their relative contribution to dietary zinc absorption in mice. Five-week-old male C57BL/6J mice were fed modified AIN-93G diets containing <1, 30, or 100ppm zinc (n=15 mice/diet). Following 1 week of feeding, mice were given an oral gavage containing ⁶⁷Zn and liver and plasma isotope appearance was determined 6-h later by ICP-MS. Expression of Slc39a1-14 and Slc30a1-10 was determined in mucosa from duodenum, jejunum, and ileum. Plasma and liver total zinc concentrations were not different after one week of feeding (P>.05). Liver and plasma appearance of ⁶⁷Zn was greater in mice fed <1ppm compared to the 30ppm (P<.0001) and 100ppm (P<.0001) zinc diets. With the exception of Slc39a2, Slc39a12, Slc30a3, and Slc30a8, the remaining zinc transporters were expressed across all diets and intestinal segments. Expression of Slc39a4, Slc39a11, and Slc30a6 changed with diet (P_diet<.05 for all); expression of Slc39a5, Slc39a7, Slc39a11, Slc39a14, Slc30a1, Slc30a2, Slc30a4, Slc30a5, Slc30a7, and Slc30a10 changed by intestinal segment (P_segment<.05 for all). Slc39a4 was the only transporter positively associated with liver (r²=0.316, P<.001) and plasma (r²=0.189, P<.01) ⁶⁷Zn appearance. Although most zinc transporters are expressed in the small intestine, intestinal Slc39a4 predicts fractional zinc absorption and utilization in young mice.

Influence of Dairy Products on Bioavailability of Zinc from Other Food Products: A Review of Complementarity at a Meal Level

In this paper, we reviewed the role of dairy products in dietary zinc absorption. Dairy products can have a reasonable contribution for dietary zinc intake in Western diets, where dairy consumption is high. However, the co-ingestion of dairy products can also improve zinc absorption from other food products. Such improvements have been observed when dairy products (e.g., milk or yoghurt) were ingested together with food such as rice, tortillas or bread products, all of which are considered to be high-phytate foods with low inherent zinc absorption. For foods low in phytate, the co-ingestion of dairy products did not improve zinc absorption. Improved zinc absorption of zinc from high-phytate foods following co-ingestion with dairy products may be related to the beneficial effects of the citrate and phosphopeptides present in dairy products. Considering that the main dietary zinc sources in areas in the world where zinc deficiency is most prevalent are typically high in phytate, the inclusion of dairy products in meals may be a viable dietary strategy to improve zinc absorption.

Zinc as a Drug for Wilson's Disease, Non-Alcoholic Liver Disease and COVID-19-Related Liver Injury

Zinc is the second most abundant trace element in the human body, and it plays a fundamental role in human physiology, being an integral component of hundreds of enzymes and transcription factors. The discovery that zinc atoms may compete with copper for their absorption in the gastrointestinal tract let to introduce zinc in the therapy of Wilson's disease, a congenital disorder of copper metabolism characterized by a systemic copper storage. Nowadays, zinc salts are considered one of the best therapeutic approach in patients affected by Wilson's disease. On the basis of the similarities, at histological level, between Wilson's disease and non-alcoholic liver disease, zinc has been successfully introduced in the therapy of non-alcoholic liver disease, with positive effects both on insulin resistance and oxidative stress. Recently, zinc deficiency has been indicated as a possible factor responsible for the susceptibility of elderly patients to undergo infection by SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic. Here, we present the data correlating zinc deficiency with the insurgence and progression of Covid-19 with low zinc levels associated with severe disease states. Finally, the relevance of zinc supplementation in aged people at risk for SARS-CoV-2 is underlined, with the aim that the zinc-based drug, classically used in the treatment of copper overload, might be recorded as one of the tools reducing the mortality of COVID-19, particularly in elderly people.

Effect of bis-glycinate bound zinc or zinc sulfate on zinc metabolism in growing lambs

To assess the efficacy of bis-glycinate bound Zn, 36 crossbred wethers (34 ± 2 kg) were sorted by body weight into three groups and stagger started on a Zn-deficient diet (18 mg Zn/kg dry matter [DM]; 22.5% neutral detergent fiber [NDF]) for 45 d prior to a 15-d metabolism period (10 d adaptation and 5 d collection). On day 46, lambs were randomly assigned to dietary treatments (four lambs treatment⁻¹group⁻¹): no supplemental Zn (CON) or 15 mg supplemental Zn/kg DM (ZINC) as Zn sulfate (ZS) or bis-glycinate (GLY; Plexomin Zn, Phytobiotics). Blood was collected from all lambs on days 1, 44, 56, and 61. Liver, jejunum, and longissimus dorsi samples were collected after euthanasia on day 61. Gene expression was determined via quantitative real-time polymerase chain reaction. Data were analyzed using ProcMixed of SAS (experimental unit = lamb; fixed effects = treatment, group, and breed) and contrast statements assessed the effects of supplemental Zn concentration (ZINC vs. CON) and source (GLY vs. ZS). After 15 d of Zn supplementation, plasma Zn concentrations were greater for ZINC vs. CON and GLY vs. ZS (P ≤ 0.01); tissue Zn concentrations were unaffected (P ≥ 0.27). Liver Cu concentrations were lesser for ZINC vs. CON (P = 0.03). Longissimus dorsi Mn concentrations were greater for ZINC vs. CON (P = 0.05) and tended to be lesser for GLY vs. ZS (P = 0.09). Digestibility of DM, organic matter (OM), and NDF was lesser for ZINC vs. CON (P ≤ 0.05); acid detergent fiber digestibility tended to be greater for GLY vs. ZS (P = 0.06). Nitrogen retention (g/d) tended to be greater for GLY vs. ZS (P = 0.10), and N apparent absorption was lesser for ZINC vs. CON (P = 0.02). Zinc intake, fecal output, retention, and apparent absorption were greater for ZINC vs. CON (P ≤ 0.01). Apparent absorption of Zn was −5.1%, 12.8%, and 15.0% for CON, ZS, and GLY, respectively. Nitrogen and Zn retention and apparent absorption were not correlated for CON (P ≥ 0.14) but were positively correlated for ZINC (retention: P = 0.02, r = 0.52; apparent absorption: P < 0.01, r = 0.73). Intestinal expression of Zn transporter ZIP4 was lesser for ZINC vs. CON (P = 0.02). Liver expression of metallothionein-1 (MT1) tended to be greater for GLY vs. ZS (P = 0.07). Although Zn apparent absorption did not differ between sources (P = 0.71), differences in post-absorptive metabolism may be responsible for greater plasma Zn concentrations and liver MT1 expression for GLY-supplemented lambs, suggesting improved bioavailability of GLY relative to ZS.

The role of zinc in the prevention and treatment of nonalcoholic fatty liver disease

The zinc element is an essential nutrient for human health. Zinc is involved in the glucose, lipid, and protein metabolism and antioxidant processes in biological pathways. Zinc deficiency can lead to several chronic liver diseases. Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases where zinc deficiency plays a critical role in pathogenesis. Human and animal studies showed that both NAFLD risk factors (i.e., insulin resistance, diabetes mellitus, dyslipidemia, obesity, hypertension) and NAFLD itself are associated with decreased blood levels of zinc. Additionally, endoplasmic reticulum stress and inflammation due to unfolded protein response, inadequate dietary zinc intake, and decreased zinc absorption from the gastrointestinal tract can result in zinc deficiency leading to NAFLD. Herein, we reviewed the mechanistic links between zinc deficiency and NAFLD development and the role of zinc in the prevention and treatment of NAFLD.

Zinc and Selenium in Inflammatory Bowel Disease: Trace Elements with Key Roles?

Inflammatory bowel disease (IBD) is a chronic inflammatory condition that may emerge at a young age and often lasts for life. It often goes through phases of recurrence and remission and has a devastating effect on quality of life. The exact etiology of the disease is still unclear, but it appears that an inappropriate immune response to intestinal flora bacteria in people with a genetic predisposition may cause the disease. Managing inflammatory bowel disease is still a serious challenge. Oxidative stress and free radicals appear to be involved in the pathogenesis of this disease, and a number of studies have suggested the use of antioxidants as a therapeutic approach. The antioxidant and anti-inflammatory properties of some trace elements have led some of the research to focus on studying these trace elements in inflammatory bowel disease. Zinc and selenium are among the most important trace elements that have significant anti-inflammatory and antioxidant properties. Some studies have shown the importance of these trace elements in inflammatory bowel disease. In this review, we have attempted to provide a comprehensive overview of the findings of these studies and to gather current knowledge about the association of these trace elements with the inflammatory process and inflammatory bowel disease.

Small and Large Intestine (I): Malabsorption of Nutrients

Numerous disorders can alter the physiological mechanisms that guarantee proper digestion and absorption of nutrients (macro- and micronutrients), leading to a wide variety of symptoms and nutritional consequences. Malabsorption can be caused by many diseases of the small intestine, as well as by diseases of the pancreas, liver, biliary tract, and stomach. This article provides an overview of pathophysiologic mechanisms that lead to symptoms or complications of maldigestion (defined as the defective intraluminal hydrolysis of nutrients) or malabsorption (defined as defective mucosal absorption), as well as its clinical consequences, including both gastrointestinal symptoms and extraintestinal manifestations and/or laboratory abnormalities. The normal uptake of nutrients, vitamins, and minerals by the gastrointestinal tract (GI) requires several steps, each of which can be compromised in disease. This article will first describe the mechanisms that lead to poor assimilation of nutrients, and secondly discuss the symptoms and nutritional consequences of each specific disorder. The clinician must be aware that many malabsorptive disorders are manifested by subtle disorders, even without gastrointestinal symptoms (for example, anemia, osteoporosis, or infertility in celiac disease), so the index of suspicion must be high to recognize the underlying diseases in time.

Enterotoxigenic Escherichia coli Heat-Stable Toxin Increases the Rate of Zinc Release from Metallothionein and Is a Zinc- and Iron-Binding Peptide

Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries. Previous studies have identified heat-stable enterotoxin (ST)-producing ETEC as one of the major diarrhea-causing pathogens in children younger than five years. In this study, we examined iron and zinc binding by both human and porcine ST variants and determined how host metallothionein could detoxify ST. We found that ST purified from ETEC culture supernatants eluted as a doublet during C18 reverse-phase chromatography. Leading edge fractions of the ST doublet were found to be devoid of iron, while trailing edge fractions of the ST doublet were found to contain measurable iron. Next, we found that purified ST could be reconstituted with iron under reducing and anaerobic conditions, and iron-bound ST attenuated the induction of cGMP in T84 epithelial cells. Moreover, we demonstrated that supernatants of ETEC 214-4 grown under increasing iron concentrations were only able to induce cGMP at iron concentrations greater than 5 μM. In vitro studies also demonstrated that ST binds zinc, and once bound, zinc removal from ST required denaturing conditions. Zinc-bound ST also failed to induce cGMP. We found that ST contributes disulfide bonds to the perceived oxidized glutathione pool, increases the rate of zinc release from metallothionein, and can be detoxified by metallothionein. Lastly, we showed ST induces transcriptional changes in genes previously shown to be regulated by deferoxamine. These studies demonstrate ST ETEC pathogenesis may be tied intimately to host mucosal metal status.IMPORTANCE Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries, deployed military personnel, and travelers to regions of endemicity. The heat-stable toxin (ST) is a small nonimmunogenic secreted peptide with 3 disulfide bonds. It has been appreciated that dietary disulfides modulate intestinal redox potential and that ST could be detoxified using exogenous reductants. Using biochemical and spectroscopic approaches, we demonstrated that ST can separately bind iron and zinc under reducing conditions, thereby reducing ST toxicity. Moreover, we demonstrated that ST modulates the glutathione (GSH)/oxidized glutathione (GSSG) ratio and that ST should be considered a toxin oxidant. ST can be detoxified by oxidizing zinc-loaded metallothionine, causing free zinc to be released. These studies help lay a foundation to understand how diarrheal pathogens modulate intestinal redox potential and may impact how we design therapeutics and/or vaccines for the pathogens that produce them.

A Guide to Human Zinc Absorption: General Overview and Recent Advances of In Vitro Intestinal Models

Zinc absorption in the small intestine is one of the main mechanisms regulating the systemic homeostasis of this essential trace element. This review summarizes the key aspects of human zinc homeostasis and distribution. In particular, current knowledge on human intestinal zinc absorption and the influence of diet-derived factors on bioaccessibility and bioavailability as well as intrinsic luminal and basolateral factors with an impact on zinc uptake are discussed. Their investigation is increasingly performed using in vitro cellular intestinal models, which are continually being refined and keep gaining importance for studying zinc uptake and transport via the human intestinal epithelium. The vast majority of these models is based on the human intestinal cell line Caco-2 in combination with other relevant components of the intestinal epithelium, such as mucin-secreting goblet cells and in vitro digestion models, and applying improved compositions of apical and basolateral media to mimic the in vivo situation as closely as possible. Particular emphasis is placed on summarizing previous applications as well as key results of these models, comparing their results to data obtained in humans, and discussing their advantages and limitations.

Zinc Deficiency and Clinical Outcome After Infrainguinal Bypass Grafting for Critical Limb Ischemia

Background: The aim of this study was to identify a relationship between zinc (Zn) deficiency and clinical outcome in patients with critical limb ischemia (CLI).

Methods and Results: Forty-five limbs from 44 patients with CLI who underwent de novo infrainguinal bypass grafting (IBG) were retrospectively reviewed. The patients were divided into a Zn deficiency group (ZD group: Zn <60 µg/dL) and a Zn sufficiency group (ZS group: Zn ≥60 µg/dL). Graft patency, limb salvage (LS), amputation-free survival (AFS), and wound healing were compared between the groups. LS and AFS were examined to identify whether Zn deficiency was an independent predictor. The preoperative factors potentially predictive of Zn deficiency were also analyzed. Twenty-four limbs were categorized into the ZD group. Patients in the ZD group were more likely to have undergone hemodialysis (HD) and have lower serum albumin. The surgical procedures were not significantly different between the groups. Patency, LS, AFS, and complete wound healing rates were significantly lower in the ZD group. Zn deficiency was a negative predictor of LS. Age >75 years and HD were identified as predictors of Zn deficiency.

Conclusions: Zn deficiency was associated with poor clinical outcome. Zn supplementation may improve clinical outcomes during IBG for CLI.

Prevention of Zinc Precipitation with Calcium Phosphate by Casein Hydrolysate Improves Zinc Absorption in Mouse Small Intestine ex Vivo via a Nanoparticle-Mediated Mechanism

Casein phosphopeptides are known to enhance zinc absorption, but the underlying mechanism remains unclear. Here, a gastrointestinal casein hydrolysate (CH) was found to keep zinc in solution despite heavy precipitation of calcium and phosphate, the omnipresent mineral nutrients that could co-precipitate zinc out of solution instantly and almost completely under physiologically relevant conditions. Dynamic light scattering, transmission electron microscopy, and energy-dispersive X-ray analysis displayed the CH-mediated formation of zinc/calcium phosphate (Zn/CaP) nanocomplexes aggregated from rather small nanoclusters. The ex vivo mouse ileal loop experiments revealed enhanced intestinal zinc absorption by CH's prevention of zinc co-precipitation with CaP, and the treatments with specific inhibitors unveiled the involvement of macropinocytic internalization, lysosomal degradation, and transcytosis in the intestinal uptake of zinc from Zn/CaP nanocomplexes. A low calcium-to-phosphorus ratio adversely affected CH's efficiency to enhance zinc solubility and absorption. Overall, our study provides a new paradigm for casein phosphopeptides to improve zinc bioavailability.

Trace Elements in Human Nutrition (II) - An Update

The dietary requirement for an essential trace element is an intake level which meets a specified criterion for adequacy and thereby minimizes risk of nutrient deficiency or excess. Disturbances in trace element homeostasis may result in the development of pathologic states and diseases. This article is an update of a review article “Trace Elements in Human Nutrition-A Review” previously published in 2013. The previous review was updated to emphasis in detail the importance of known trace elements so far in humans’ physiology and nutrition and also to implement the detailed information for practical and effective management of trace elements’ status in clinical diagnosis and health care situations. Although various classifications for trace elements have been proposed and may be controversial, this review will use World Health Organization( WHO) classification as previously done. For this review a traditional integrated review format was chosen and many recent medical and scientific literatures for the new findings on bioavailability, functions, and state of excess/deficiency of trace elements were assessed. The results indicated that for the known essential elements, essentiality and toxicity are unrelated and toxicity is a matter of dose or exposure. Little is known about the essentiality of some of the probably essential elements. In regard to toxic heavy metals, a toxic element may nevertheless be essential. In addition, the early pathological manifestations of trace elements deficiency or excess are difficult to detect until more specific pathologically relevant indicators become available. Discoveries and many refinements in the development of new techniques and continual improvement in laboratory methods have enabled researchers to detect the early pathological consequences of deficiency or excess of trace elements. They all are promises to fulfill the gaps in the present and future research and clinical diagnosis of trace elements deficiencies or intoxications. However, further investigations are needed to complete the important gaps in our knowledge on trace elements, especially probably essential trace elements’ role in health and disease status.

Micronutrient Absorption and Related Outcomes in People with Inflammatory Bowel Disease: A Review

Inflammatory Bowel Disease (IBD) is a chronic disorder associated with immune dysregulation and chronic inflammation of the digestive tract. While it is poorly understood, the role of nutrition and nutrient status in the etiology of IBD and its associated outcomes has led to increased research relating to micronutrient deficiency. This review offers an overview of recent literature related to micronutrient absorption and outcomes in adults with IBD. Although the absorption and IBD-related outcomes of some micronutrients (e.g., vitamin D and iron) are well understood, other micronutrients (e.g., vitamin A) require further research. Increased research and clinician knowledge of the relationship between micronutrients and IBD may manifest in improved nutrient screening, monitoring, treatment, and outcomes for people living with IBD.

Transition metals and host-microbe interactions in the inflamed intestine

Host-associated microbial communities provide critical functions for their hosts. Transition metals are essential for both the mammalian host and the majority of commensal bacteria. As such, access to transition metals is an important component of host-microbe interactions in the gastrointestinal tract. In mammals, transition metal ions are often sequestered by metal binding proteins to limit microbial access under homeostatic conditions. In response to invading pathogens, the mammalian host further decreases availability of these micronutrients by regulating their trafficking or releasing high-affinity metal chelating proteins, a process termed nutritional immunity. Bacterial pathogens have evolved several mechanisms to subvert nutritional immunity. Here, we provide an overview on how metal ion availability shapes host-microbe interactions in the gut with a particular focus on intestinal inflammatory diseases.

Titanium dioxide nanoparticle exposure alters metabolic homeostasis in a cell culture model of the intestinal epithelium and Drosophila melanogaster

Nanosized titanium dioxide (TiO₂) is a common additive in food and cosmetic products. The goal of this study was to investigate if TiO₂ nanoparticles affect intestinal epithelial tissues, normal intestinal function, or metabolic homeostasis using in vitro and in vivo methods. An in vitro model of intestinal epithelial tissue was created by seeding co-cultures of Caco-2 and HT29-MTX cells on a Transwell permeable support. These experiments were repeated with monolayers that had been cultured with the beneficial commensal bacteria Lactobacillus rhamnosus GG (L. rhamnosus). Glucose uptake and transport in the presence of TiO₂ nanoparticles was assessed using fluorescent glucose analog 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). When the cell monolayers were exposed to physiologically relevant doses of TiO₂, a statistically significant reduction in glucose transport was observed. These differences in glucose absorption were eliminated in the presence of beneficial bacteria. The decrease in glucose absorption was caused by damage to intestinal microvilli, which decreased the surface area available for absorption. Damage to microvilli was ameliorated in the presence of L. rhamnosus. Complimentary studies in Drosophila melanogaster showed that TiO₂ ingestion resulted in decreased body size and glucose content. The results suggest that TiO₂ nanoparticles alter glucose transport across the intestinal epithelium, and that TiO₂ nanoparticle ingestion may have physiological consequences.

Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands

Aqueous solubility of zinc phytate (K_sp = (2.6 ± 0.2) × 10^-47 mol⁷/L⁷), essential for zinc bioavailability from plant foods, was found to decrease with increasing temperature corresponding to ΔH_dis of -301 ± 22 kJ/mol and ΔS_dis of -1901 ± 72 J/(mol K). Binding of zinc to phytate was found to be exothermic for the stronger binding site and endothermic for the weaker binding site. The solubility of the slightly soluble zinc citrate and insoluble zinc phytate was found to be considerably enhanced by the food components with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving force for the enhanced solubility is mainly due to the complex formation between zinc and the investigated food components rather than ligand exchange and ternary complex formation as revealed by quantum mechanical calculations and isothermal titration calorimetry. Histidine and citrate are promising ligands for improving zinc absorption from phytate-rich foods.

Characterization of zinc amino acid complexes for zinc delivery in vitro using Caco-2 cells and enterocytes from hiPSC

Zn is essential for growth and development. The bioavailability of Zn is affected by several factors such as other food components. It is therefore of interest, to understand uptake mechanisms of Zn delivering compounds to identify ways to bypass the inhibitory effects of these factors. Here, we studied the effect of Zn amino acid conjugates (ZnAAs) on the bioavailabilty of Zn. We used Caco-2 cells and enterocytes differentiated from human induced pluripotent stem cells from a control and Acrodermatitis enteropathica (AE) patient, and performed fluorescence based assays, protein biochemistry and atomic absorption spectrometry to characterize cellular uptake and absorption of ZnAAs. The results show that ZnAAs are taken up by AA transporters, leading to an intracellular enrichment of Zn mostly uninhibited by Zn uptake antagonists. Enterocytes from AE patients were unable to gain significant Zn through exposure to ZnCl₂ but did not show differences with respect to ZnAAs. We conclude that ZnAAs may possess an advantage over classical Zn supplements such as Zn salts, as they may be able to increase bioavailability of Zn, and may be more efficient in patients with AE.

Titanium Dioxide Nanoparticle Ingestion Alters Nutrient Absorption in an In Vitro Model of the Small Intestine

Ingestion of titanium dioxide (TiO₂) nanoparticles from products such as agricultural chemicals, processed food, and nutritional supplements is nearly unavoidable. The gastrointestinal tract serves as a critical interface between the body and the external environment, and is the site of essential nutrient absorption. The goal of this study was to examine the effects of ingesting the 30 nm TiO₂ nanoparticles with an in vitro cell culture model of the small intestinal epithelium, and to determine how acute or chronic exposure to nano-TiO₂ influences intestinal barrier function, reactive oxygen species generation, proinflammatory signaling, nutrient absorption (iron, zinc, fatty acids), and brush border membrane enzyme function (intestinal alkaline phosphatase). A Caco-2/HT29-MTX cell culture model was exposed to physiologically relevant doses of TiO₂ nanoparticles for acute (four hours) or chronic (five days) time periods. Exposure to TiO₂ nanoparticles significantly decreased intestinal barrier function following chronic exposure. Reactive oxygen species (ROS) generation, proinflammatory signaling, and intestinal alkaline phosphatase activity all showed increases in response to nano-TiO₂. Iron, zinc, and fatty acid transport were significantly decreased following exposure to TiO₂ nanoparticles. This is because nanoparticle exposure induced a decrease in absorptive microvilli in the intestinal epithelial cells. Nutrient transporter protein gene expression was also altered, suggesting that cells are working to regulate the transport mechanisms disturbed by nanoparticle ingestion. Overall, these results show that intestinal epithelial cells are affected at a functional level by physiologically relevant exposure to nanoparticles commonly ingested from food.

Risk of Malnutrition, Trace Metal, and Vitamin Deficiency Post Roux-en-Y Gastric Bypass--a Prospective Study of 20 Patients with BMI < 35 kg/m²

BACKGROUND

Due to its reliable effects on type 2 diabetes mellitus (T2DM) remission, Roux-en-Y gastric bypass (RYGB) has recently been investigated as a treatment option for nonseverely obese patients with T2DM (body mass index (BMI) <35 kg/m(2)). The purpose of this study was to investigate whether RGYB induces malnutrition of macro- and micronutrients within 24 months in these patients.

METHODS

A prospective cohort of 20 patients with longstanding, insulin-dependent T2DM and a BMI of 25-35 kg/m(2) were treated with RYGB. The patients were supplemented with over-the-counter, multivitamin, and micronutrient supplements. Serum concentrations of albumin, vitamins, and trace elements, hemoglobin, and bone density were measured preoperatively and over a 24-month period (DRKS00004605).

RESULTS

RYGB did not result in underweight or protein malnutrition. No new onset of deficiencies of water- or fat-soluble vitamins developed over the study period. However, serum selenium, zinc, and ferritin decreased significantly (selenium, 1.17 ± 0.13 to 0.89 ± 0.11 μmol/l, p = 0.018; zinc, 13.9 ± 0.5 to 10.8 ± 0.5 μmol/l, p = 0.012; ferritin, 171.7 ± 26.9 to 31.8 ± 11.2 μg/l, p = 0.018). Hemoglobin remained stable. Vitamin D (13.7 ± 1.8 to 19.1 ± 1.1 ng/ml, p = 0.017) and osteocalcin (15.3 ± 1.7 to 25.4 ± 2.7 ng/ml, p = 0.025) rose significantly, whereas the parathyroid hormone remained stable. Despite increased bone formation, bone density decreased (T score hip, 0.15 ± 0.25 to -0.71 ± 0.34, p = 0.005) resulting in a significant increase in osteopenia rates (18 to 50 %, p = 0.046).

CONCLUSIONS

This is the first prospective cohort to investigate malnutrition after RYGB in nonseverely obese patients. These patients are at risk of developing iron, selenium, and zinc deficiencies within 24 months, as well as osteopenia despite an increase in bone formation.

Zinc in gut-brain interaction in autism and neurological disorders

A growing amount of research indicates that abnormalities in the gastrointestinal (GI) system during development might be a common factor in multiple neurological disorders and might be responsible for some of the shared comorbidities seen among these diseases. For example, many patients with Autism Spectrum Disorder (ASD) have symptoms associated with GI disorders. Maternal zinc status may be an important factor given the multifaceted effect of zinc on gut development and morphology in the offspring. Zinc status influences and is influenced by multiple factors and an interdependence of prenatal and early life stress, immune system abnormalities, impaired GI functions, and zinc deficiency can be hypothesized. In line with this, systemic inflammatory events and prenatal stress have been reported to increase the risk for ASD. Thus, here, we will review the current literature on the role of zinc in gut formation, a possible link between gut and brain development in ASD and other neurological disorders with shared comorbidities, and tie in possible effects on the immune system. Based on these data, we present a novel model outlining how alterations in the maternal zinc status might pathologically impact the offspring leading to impairments in brain functions later in life.

The relevance of the colon to zinc nutrition

Globally, zinc deficiency is widespread, despite decades of research highlighting its negative effects on health, and in particular upon child health in low-income countries. Apart from inadequate dietary intake of bioavailable zinc, other significant contributors to zinc deficiency include the excessive intestinal loss of endogenously secreted zinc and impairment in small intestinal absorptive function. Such changes are likely to occur in children suffering from environmental (or tropical) enteropathy (EE)—an almost universal condition among inhabitants of developing countries characterized by morphologic and functional changes in the small intestine. Changes to the proximal gut in environmental enteropathy will likely influence the nature and amount of zinc delivered into the large intestine. Consequently, we reviewed the current literature to determine if colonic absorption of endogenous or exogenous (dietary) zinc could contribute to overall zinc nutriture. Whilst we found evidence that significant zinc absorption occurs in the rodent colon, and is favoured when microbially-fermentable carbohydrates (specifically resistant starch) are consumed, it is unclear whether this process occur in humans and/or to what degree. Constraints in study design in the few available studies may well have masked a possible colonic contribution to zinc nutrition. Furthermore these few available human studies have failed to include the actual target population that would benefit, namely infants affected by EE where zinc delivery to the colon may be increased and who are also at risk of zinc deficiency. In conducting this review we have not been able to confirm a colonic contribution to zinc absorption in humans. However, given the observations in rodents and that feeding resistant starch to children is feasible, definitive studies utilising the dual stable isotope method in children with EE should be undertaken.

Zinc deficiency in children with environmental enteropathy-development of new strategies: report from an expert workshop

Zinc deficiency is a major cause of childhood morbidity and mortality. The WHO/UNICEF strategy for zinc supplementation as adjunctive therapy for diarrhea is poorly implemented. A conference of experts in zinc nutrition and gastrointestinal disorders was convened to consider approaches that might complement the current recommendation and what research was needed to develop these approaches. Several key points were identified. The design of novel zinc interventions would be facilitated by a better understanding of how disturbed gut function, such as environmental (or tropical) enteropathy, affects zinc absorption, losses, and homeostasis. Because only 10% of zinc stores are able to be rapidly turned over, and appear to be rapidly depleted by acute intestinal illness, they are probably best maintained by complementary regular supplementation in a primary prevention strategy rather than secondary prevention triggered by acute diarrhea. The assessment of zinc status is challenging and complex without simple, validated measures to facilitate field testing of novel interventions. Zinc bioavailability may be a crucial factor in the success of primary prevention strategies, and a range of options, all still inadequately explored, might be valuable in improving zinc nutrition. Some therapeutic actions of zinc on diarrhea seem attributable to pharmacologic effects, whereas others are related to the reversal of deficiency (ie, nutritional). The distinction between these 2 mechanisms cannot be clarified given the insensitivity of serum zinc to identify subclinical deficiency states. Why zinc seems to be less effective than expected at all ages, and ineffective for secondary prevention of diarrhea in children <12 mo of age, remains unclear. It was concluded that a reframing of the current recommendation is warranted with consideration of how to better optimize and deliver zinc and whether to provide a complementary public health primary prevention zinc strategy. This requires careful consideration of the zinc product to be used as well as strategies for its delivery.

The micronutrient zinc inhibits EAEC strain 042 adherence, biofilm formation, virulence gene expression, and epithelial cytokine responses benefiting the infected host

Enteroaggregative Escherichia coli (EAEC) is a major pathogen worldwide, associated with diarrheal disease in both children and adults, suggesting the need for new preventive and therapeutic treatments. We investigated the role of the micronutrient zinc in the pathogenesis of an E. coli strain associated with human disease. A variety of bacterial characteristics-growth in vitro, biofilm formation, adherence to IEC-6 epithelial cells, gene expression of putative EAEC virulence factors as well as EAEC-induced cytokine expression by HCT-8 cells-were quantified. At concentrations (≤ 0.05 mM) that did not alter EAEC growth (strain 042) but that are physiologic in serum, zinc markedly decreased the organism's ability to form biofilm (P<0.001), adhere to IEC-6 epithelial cells (P<0.01), and express putative EAEC virulence factors (aggR, aap, aatA, virK) (P<0.03). After exposure of the organism to zinc, the effect on virulence factor generation was prolonged (> 3 h). Further, EAEC-induced IL-8 mRNA and protein secretion by HCT-8 epithelial cells were significantly reduced by 0.05 mM zinc (P<0.03). Using an in vivo murine model of diet-induced zinc-deficiency, oral zinc supplementation (0.4 µg/mouse daily) administered after EAEC challenge (10 (10) CFU/mouse) significantly abrogated growth shortfalls (by>90%; P<0.01); furthermore, stool shedding was reduced (days 9-11) but tissue burden of organisms in the intestine was unchanged. These findings suggest several potential mechanisms whereby physiological levels of zinc alter pathogenetic events in the bacterium (reducing biofilm formation, adherence to epithelium, virulence factor expression) as well as the bacterium's effect on the epithelium (cytokine response to exposure to EAEC) to alter EAEC pathogenesis in vitro and in vivo. These effects may help explain and extend the benefits of zinc in childhood diarrhea and malnutrition.

Zinc and copper serum levels of morbidly obese patients before and after biliopancreatic diversion: 4 years of follow-up

BACKGROUND

Zinc and copper are two essential trace elements. However, few studies have been conducted specifically to investigate these deficiencies in patients who underwent bariatric surgery. The aim of our work was to describe the influence of biliopancreatic diversion (BPD) on serum copper and zinc levels during 4 years.

METHODS

We have analyzed a consecutive series of 65 patients who have been followed-up for 4 years after undergoing open BPD.

RESULTS

The final (4 years) initial excess weight percent loss was 63.5%. A significant improvement of BMI, weight, waist circumference, and fat mass was detected. The preoperative average zinc (42.2 ± 53.2 μg/dl) and copper (61.3 ± 58.6 μg/dl) levels are under the lower limit of the normal values. These data show a deficient micronutrient status in morbidly obese patients, 73.8% of patients had low basal zinc values and 67.8% low basal copper values. Values of both micronutrients at different times (6 months, 1, 2, 3, and 4 years) were lower than basal value.

CONCLUSION

BPD is an effective method of sustainable weight loss. Otherwise, a high prevalence of zinc and copper basal deficiencies in morbidly obese seeking bariatric surgery was detected. These deficiencies of copper and zinc increased during the 4 years of follow-up after BDP.

Copper and zinc serum levels after derivative bariatric surgery: differences between Roux-en-Y Gastric bypass and biliopancreatic diversion

BACKGROUND

There are limited data on the prevalence of copper and zinc deficiency in the long term after bariatric surgery.

METHODS

We analysed copper and zinc serum levels in a cohort of 141 patients, 52 who underwent Roux-en-Y gastric bypass (RYGB) and 89 biliopancreatic diversion (BPD), with a follow-up of 5 years.

RESULTS

Mean copper level was significantly lower in the BPD group (P < 0.0001 vs. RYGB). Forty-five (50.6%) BPD patients had, at least once, a low copper level, and half of them, 27 (30.3%) patients, had repeatedly low levels. In this group, serum copper level correlated positively with total leukocyte and granulocyte count (r = 0.14, P = 0.002, and r = 0.17, P < 0.001, respectively). However, no patient had clinical evidence of haematological or neurological disorders. Only two RYGB patients (3.8%) had copper deficiency. Mean zinc level was also significantly lower in the BPD group (P < 0.0001). All but one BPD patient had hypozincaemia at least once, and the percentage of patients with hypozincaemia ranged from 44.9% to 74.2%. In RYGB patients, zinc deficiency peaked at 48 and 60 months (15.4% and 21.2%, respectively). The zinc level was determined by the alimentary limb length in this group, but the common channel length had no influence on copper and zinc levels in the BPD group.

CONCLUSIONS

Hypocupremia, and especially hypozincaemia, are frequent findings in BPD patients, but rarely found in patients who underwent RYGB, particularly short RYGB. Our data also suggest that a long-standing and severe hypocupremia is required to develop neurological and haematological disorders after bariatric surgery.

Altered plasma response to zinc and iron tolerance test after Roux-en-Y gastric bypass

BACKGROUND

The duodenum and proximal jejunum are excluded after Roux-en-Y gastric bypass but these intestinal sites are where iron and zinc are most absorbed. Therefore, they are among the nutrients whose digestive and absorptive process can be impaired after surgery. The aim of the present study was to investigate the iron and zinc plasma response to a tolerance test before and after bariatric surgery. The study was performed at São Paulo University School of Medicine of Ribeirão Preto, Brazil.

METHODS

In a longitudinal paired study, 9 morbidly obese women (body mass index ≥40 kg/m(2)) underwent an iron and zinc tolerance test before and 3 months after surgery. The iron and zinc levels were determined at 0, 1, 2, 3, and 4 hours after a physiologic unique oral dose. The mineral concentrations in the plasma and 24-hour urine sample were assayed using an atomic absorption spectrophotometer. The anthropometric measurements and 3-day food record were also evaluated. A linear mixed model was used to compare the plasma concentration versus interval after the oral dose, before and after surgery.

RESULTS

The pre- and postoperative test results revealed a significantly lower plasma zinc response (P <.01) and a delayed response to iron intake after surgery. The total plasma iron concentration area, during the 4 hours, was not different after surgery (P >.05). The 24-hour urinary iron and zinc excretion did not differ between the pre- and postoperative phases.

CONCLUSION

The present data showed a compromised response to the zinc tolerance test after gastric bypass surgery, suggesting an impaired absorption of zinc. More attention must be devoted to zinc nutritional status after surgery.

Does promoter methylation of the SLC30A5 (ZnT5) zinc transporter gene contribute to the ageing-related decline in zinc status?

A decline in Zn status with ageing may contribute to the development of frailty, including impaired immune function, and increased incidence of age-related degenerative diseases. This decline may be a result of reduced dietary Zn intake and/or impaired Zn absorption in the gut. The Zn transporter ZnT5 may play a key role in the absorption of dietary Zn. The corresponding gene (SLC30A5) has a CpG island in its promoter region, so could be regulated by epigenetic mechanisms. It is hypothesised that methylation of the SLC30A5 promoter region is increased with age and that a resulting reduction in ZnT5 expression contributes to the decline in Zn status observed with ageing. This hypothesis has been addressed through (1) studies of effects of SLC30A5 promoter methylation on gene expression in vitro and (2) in vivo measurements of the DNA methylation status of this gene domain. It has been established in vitro that methylation of the human SLC30A5 promoter region results in reduced expression of an associated reporter gene. Second, this gene region shows variable levels of methylation in vivo. Correlation between the level of methylation at this locus and age would support the hypothesis that age-related hypermethylation of this region has the potential to modulate dietary Zn absorption. This premise is being investigated by analysis of additional samples from a human adult cohort to test the hypothesis that methylation of the SLC30A5 promoter region contributes to the age-related decline in Zn status.

The ERK pathway involves positive and negative regulations of HT-29 colorectal cancer cell growth by extracellular zinc

Dietary zinc is an important trace element in the body and is related to both cell proliferation and growth arrest. A recent study found that extracellular zinc-sensing receptors trigger intracellular signal transduction in HT-29 human colorectal cancer cells. However, the signaling mechanism causing this growth regulation by extracellular zinc is not clearly understood. At 10- and 100-microM levels of ZnCl2 treatment, HT-29 cell growth and proliferation increased and decreased, respectively, in a minimally serum-starved medium (MSSM). A lack of significant increase in intracellular zinc levels after zinc treatment suggested that this differential growth regulation of HT-29 cells by extracellular zinc is acquired by receptor-mediated signal transduction. Moreover, this zinc-induced growth regulation was differentially affected by PD-98059, suggesting the involvement of the ERK pathway. Transient ERK activation and subsequent cyclin D1 induction were observed on adding 10 microM ZnCl2 in MSSM in the presence of cell proliferation. On the other hand, prolonged ERK activity was observed with a subsequent increase of cyclin D1 and p21(Cip/WAF1) on adding 100 microM ZnCl2 in MSSM, and this was associated with nonproliferation. Moreover, this ERK activation and cyclin D1 and p21(Cip/WAF1) induction were abolished by PD-98059 pretreatment. The differential regulations of cell growth, ERK activities, and cyclin D1 and p21(Cip/WAF1) inductions were also observed in serum-enriched medium containing higher zinc concentrations. Therefore, differential cell cycle regulator induction occurs by a common ERK pathway in the differential growth regulation of HT-29 cells by extracellular zinc.

Nutritive metal uptake in teleost fish

Transition metals are essential for health, forming integral components of proteins involved in all aspects of biological function. However, in excess these metals are potentially toxic, and to maintain metal homeostasis organisms must tightly coordinate metal acquisition and excretion. The diet is the main source for essential metals, but in aquatic organisms an alternative uptake route is available from the water. This review will assess physiological, pharmacological and recent molecular evidence to outline possible uptake pathways in the gills and intestine of teleost fish involved in the acquisition of three of the most abundant transition metals necessary for life; iron, copper, and zinc.

Extracellular zinc stimulates ERK-dependent activation of p21(Cip/WAF1) and inhibits proliferation of colorectal cancer cells

Zinc is an important trace element in the body and is involved in both the proliferation and growth arrest of many kinds of cells including colorectal epithelial cells. The aim of this study was to identify the molecular mechanism of the growth regulation of colorectal cancer cells by extracellular zinc. Zinc-stimulated activation of the mitogen-activated protein kinase (MAPK) cascade was measured by immunoblotting and Elk-1 dependent trans-reporter gene expression, and zinc-stimulated p21(Cip/WAF1) activation by immunoblotting, Northern blot analysis and immunochemistry. Cell proliferation was measured by thymidine and bromodeoxyuridine (BrdU) incorporation. By treating colorectal cancer cells with 100 microM ZnCl2, MAPKs were activated in two different phases, the initial weak activation occurred within 5 min and this was followed by a stronger and more prolonged activation. Zinc concomitantly activated Raf-1-MEK-MAPK kinases, and induced Elk-1 dependent trans-reporter gene expression. Prolonged activation of MAPKs by 100 microM of ZnCl2 resulted in the induction and nuclear localization of p21(Cip/WAF1) and was related to the inhibition of both thymidine and BrdU incorporations. These results not only suggest the presence of a mechanism for p21(Cip/WAF1) dependent negative regulation of colorectal cancer cell growth by zinc but also suggest potential usage of zinc to control the growth of colorectal cancer cells.

Development of a compartmental model of human zinc metabolism: identifiability and multiple studies analyses

A compartmental model of zinc metabolism has been developed from stable isotope tracer studies of five healthy adults. Multiple isotope tracers were administered orally and intravenously, and the resulting enrichment was measured in plasma, erythrocytes, urine, and feces for as long as 3 wk. Data from total zinc measurements and model-independent calculations of various steady-state parameters were also modeled with the kinetic data. A structure comprised of 14 compartments and as many as 25 unknown kinetic parameters was developed to adequately model the data from each of the individual studies. The structural identifiability of the model was established using the GLOBI2 identifiability analysis software. Numerical identifiability of parameter estimates was evaluated using statistical data provided by SAAM. A majority of the model parameters was estimated with sufficient statistical certainty to be considered well determined. After the fitting of the model and data from the individual studies using SAAM/CONSAM, results were submitted to SAAM extended multiple studies analysis for aggregation into a single set of population parameters and statistics. The model was judged to be valid based on criteria described elsewhere.

Use of the InteliSite capsule to study ranitidine absorption from various sites within the human intestinal tract

PURPOSE

The purpose of this study was to evaluate the extent of ranitidine absorption from an externally activated drug-delivery system in two distinct regions of the intestine (jejunum and ileum) in healthy human volunteers. This investigation also was designed to evaluate the utility of the InteliSite capsule for studying regional intestinal drug absorption in humans.

METHODS

The intestinal absorption of ranitidine from the jejunum and ileum was compared in eight, healthy volunteers in this open-label, two-way crossover study. In two of the eight volunteers, absorption from the colon also was studied. Subjects swallowed the capsule containing ranitidine solution (121 mg) and 100 microCi of 99mTc-DTPA. The endcap of the capsule contained 20 microCi of (111)In-DTPA. At the desired intestinal site, the capsule was activated by the application of an external RF magnetic signal (6.78 MHz operating frequency) and the ranitidine solution was released. Blood samples were collected from a forearm vein for 12 hours after capsule activation.

RESULTS

The capsule released the ranitidine solution when activated in the jejunum, ileum and colon (visualized by the gamma camera). There was no difference in the extent of ranitidine absorption or ranitidine pharmacokinetics when the capsule was activated in the jejunum or ileum.

CONCLUSIONS

This study demonstrates the utility of a novel, externally activated drug-delivery system to assess site-specific intestinal drug absorption in humans. Results indicate that use of the InteliSite capsule method to evaluate site-specific intestinal ranitidine absorption in humans yields data similar to that obtained previously by means of oral intubation studies.

Effect of zinc on L-threonine transport across the jejunum of rabbit

Zinc is an essential trace element for life. Many metalloenzymes involved in the metabolism of carbohydrates, lipids, protein, and nucleic acids require zinc for their functions. The aim of this study was to characterize how zinc acts on the intestinal amino acid absorption in rabbit. Results obtained show that zinc inhibits both L-threonine accumulation in the jejunum tissue, and mucosal-to-serosal transepithelial flux of this amino acid in a dose-dependent way. The inhibition does not increase by a 10-min previous intestinal exposure of the mucosa to the heavy metal, and is not reversed by washing the intestinal tissue with saline solution or 10mM EDTA, but is appreciably reversed with 10mM dithioerythritol. Zinc seems not to modify amino acid diffusion across the intestinal epithelium. The inhibition of intestinal amino acid transport by zinc seems to be of a competitive type, and appears to be a result of impairment of the active transport that is altered by its binding to proteins (prevailing to thiol groups) of the brush-border membrane of enterocytes.