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

The Epidemiology, Impact, and Diagnosis of Micronutrient Nutritional Dermatoses Part 1: Zinc, Selenium, Copper, Vitamin A, and Vitamin C

Dermatologists play a critical role in diagnosing and managing nutritional deficiencies as they often present with cutaneous findings. Traditionally, nutritional dermatoses are taught in the context of developing countries, famine, population displacement, and poor healthcare access; however, in the United States, common risk factors include chronic liver disease, alcoholism, psychiatric disease, bariatric surgery, inflammatory bowel disease, and hemodialysis. Additionally, nutritional dermatoses may be underdiagnosed in the United States and result in increased morbidity and utilization of hospital resources. There is a need for providers in developed nations to identify these deficiencies, and this review aims to meet that practice gap and provide relevant context to these diseases for dermatologists. This two-part review series will focus on the epidemiology, impact, appearance, and diagnostic modalities for micronutrient deficiencies, including zinc, selenium, copper, and vitamins A and C in part one. The companion review will focus on the B-complex vitamins.

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.

Current findings support the potential use of bioactive peptides in enhancing zinc absorption in humans

More than two billion people around the world are affected by zinc deficiency, mainly due to the inadequate intake and absorption of zinc. Based on recent research findings, the bioactive peptides could potentially be used to combat zinc deficiency particularly due to their Zinc chelating ability. The main aim of this review was to present current findings, supporting the potential use of bioactive peptides based on their ability to enhance zinc absorption. In-vivo, in-vitro, and ex-vivo studies have demonstrated that zinc chelating peptides can enhance the retention, transportation, and absorption of zinc. Comparative studies on zinc bioavailability from protein hydrolysates and zinc salts have demonstrated that the protein hydrolysates-zinc complexes are more bioavailable than the zinc salts. Data from the structure-function relationship of zinc chelating peptides suggest that the zinc chelating capacities of peptides increase in the following order; the position of zinc chelator > zinc chelator strength > abundance of zinc chelators > net charge > molecular weight. In addition, the transport mechanism of peptide-zinc complex is hypothesized, and the potential use of bioactive peptides based on their safety and taste and limitations to their commercialization are also discussed.

Prevalence of Zinc Deficiency in Healthy 1-3-Year-Old Children from Three Western European Countries

Zinc deficiency (ZnD) has adverse health consequences such as stunted growth. Since young children have an increased risk of developing ZnD, it is important to determine its prevalence and associated factors in this population. However, only a few studies have reported on ZnD prevalence in young children from Western high-income countries. This study evaluated ZnD prevalence and associated factors, including dietary Zn intake, in healthy 1–3-year-old children from Western European, high-income countries. ZnD was defined as serum Zn concentration <9.9 µmol/L. A total of 278 children were included with a median age of 1.7 years (Q1–Q3: 1.2–2.3). The median Zn concentration was 11.0 µmol/L (Q1–Q3: 9.0–12.2), and ZnD prevalence was 31.3%. No significant differences were observed in the socio-economic characteristics between children with and without ZnD. Dietary Zn intake was not associated with ZnD. ZnD is common in healthy 1–3-year-old children from Western European countries. However, the use of currently available cut-off values defining ZnD in young children has its limitations since these are largely based on reference values in older children. Moreover, these values were not evaluated in relation to health consequences, warranting further research.

Content and Nutritional Evaluation of Zinc in PDO and Traditional Italian Cheeses

Zinc is an essential mineral which plays a key role in several important biological processes in the human body. The determination of its level in food matrices can contribute to the food quality characterization and to the adequacy of the diet. Animal food products generally have a higher zinc content compared to vegetables. Among them, dairy products consumption can provide a great contribution to the zinc reference intakes. In this study, different Italian cheeses (38 Protected Denomination of Origin and 9 Traditional) were evaluated for their zinc content. Cow cheeses generally showed the highest zinc content (1.83-7.75 mg/100 g cheese), followed by sheep cheeses (1.34-3.69 mg/100 g), and cheeses from mixed milk (0.39-4.54 mg/100 g). The only cheese from buffalo milk (Mozzarella di Bufala Campana PDO) showed a zinc content of 2.14 mg/100 g. The great variability in the zinc content observed among the samples is the result of the influence of several factors, such as the feeding system, the species (cow, sheep, goat, and buffalo), and the cheese-making. Most of the samples resulted in a great contribution (>10%) to the zinc Daily Reference Intake set by EU (10 mg/day), with only two samples contributing to less than 4%.

Zinc Deficiency, Plasma Fatty Acid Profile and Desaturase Activities in Hemodialysis Patients: Is Supplementation Necessary?

Background: Desaturation and elongation are critical processes in endogenous metabolic fatty acid pathways. Zinc (Zn) is a cofactor for desaturases and elongases enzymes. There is limited evidence regarding the relationships between biomarkers of Zn status, nutritional intake, plasma phospholipid fatty acid profile and clinical outcomes among patients undergoing hemodialysis (HD). Objective: To examine the relationships between dietary and serum levels of Zn and Cu/Zn ratio and to explore associations of these micronutrients with PUFA profile and estimated desaturase and elongase enzyme activities in serum phospholipids among HD patients. Methods: This study included 40 adult patients undergoing hemodialysis treatment. Repeated 24-h recalls were applied for dietary intake assessment. Serum concentration of Zn and Cu were determined using inductively coupled plasma mass spectrometry and fatty acid composition by gas-liquid chromatography. Desaturase and elongase activities were calculated from product-precursor fatty acid ratios. Results: Inadequate dietary Zn intake was found in 55% of HD patients. They all had serum Zn concentration below the reference value of 60 μg/dL (mean 38.8 ± 7.72 μg/dL). Adequate zinc intake was accompanied with significantly higher intake of energy, total fats, SFA, MUFA and proteins. There was no correlation between Zn serum status and Zn intake estimates. Serum Cu/Zn ratio was high, (2.76 ± 0.68), directly and significantly associated with HD period, CRP, BMI, VFA, and inversely with Kt/V, albumin, iron, and iPTH. The n-6/n-3 ratio in plasma phospholipids was elevated (12.25 ± 3.45) and patients with inadequate Zn intake had lower n-3 PUFA intake and status compared to those with adequate intake. Serum Zn concentrations were inversely correlated with linoleic/dihomo-γ-linolenic acid ratio (LA/DGLA) (p = 0.037), related to D6-desaturase activity (p = 0.033) and directly with DGLA relative abundances (p = 0.024). Cu status was inversely associated with EPA level (p = 0.03) and estimates of elongase activity (p = 0.001). Furthermore, positive relationship was found between the Cu/Zn ratio and determined elongase value (p = 0.01). Conclusion: Findings of this study underpin the high prevalence of Zn deficiency and inadequate n-3 PUFA intake and status among subjects undergoing HD. The results obtained indicate that the assessment of Zn status should be a standard parameter of nutritional status screening in HD patients while emphasizing the importance of Cu/Zn determination. Although further research is warranted, Zn and-n-3 PUFA supplementation in HD patients might be beneficial for the prevention and attenuation of adverse health outcomes.

Zinc Status Index (ZSI) for Quantification of Zinc Physiological Status

Zinc (Zn) deficiency is estimated to affect over one billion (17%) of the world’s population. Zn plays a key role in various cellular processes such as differentiation, apoptosis, and proliferation, and is used for vital biochemical and structural processes in the body. Widely used biomarkers of Zn status include plasma, whole blood, and urine Zn, which decrease in severe Zn deficiency; however, accurate assessment of Zn status, especially in mild to moderate deficiency, is difficult, as studies with these biomarkers are often contradictory and inconsistent. Thus, sensitive and specific biological markers of Zn physiological status are still needed. In this communication, we provide the Zn status index (ZSI) concept, which consists of a three-pillar formula: (1) the LA:DGLA ratio, (2) mRNA gene expression of Zn-related proteins, and (3) gut microbiome profiling to provide a clear assessment of Zn physiological status and degree of Zn deficiency with respect to assessing dietary Zn manipulation. Analysis of five selected studies found that with lower dietary Zn intake, erythrocyte LA:DGLA ratio increased, mRNA gene expression of Zn-related proteins in duodenal and liver tissues was altered, and gut microbiota populations differed, where the ZSI, a statistical model trained on data from these studies, was built to give an accurate estimation of Zn physiological status. However, the ZSI needs to be tested and refined further to determine its full potential.

The Interplay between Non-Esterified Fatty Acids and Plasma Zinc and Its Influence on Thrombotic Risk in Obesity and Type 2 Diabetes

Thrombosis is a major comorbidity of obesity and type-2 diabetes mellitus (T2DM). Despite the development of numerous effective treatments and preventative strategies to address thrombotic disease in such individuals, the incidence of thrombotic complications remains high. This suggests that not all the pathophysiological mechanisms underlying these events have been identified or targeted. Non-esterified fatty acids (NEFAs) are increasingly regarded as a nexus between obesity, insulin resistance, and vascular disease. Notably, plasma NEFA levels are consistently elevated in obesity and T2DM and may impact hemostasis in several ways. A potentially unrecognized route of NEFA-mediated thrombotic activity is their ability to disturb Zn²⁺ speciation in the plasma. Zn²⁺ is a potent regulator of coagulation and its availability in the plasma is monitored carefully through buffering by human serum albumin (HSA). The binding of long-chain NEFAs such as palmitate and stearate, however, trigger a conformational change in HSA that reduces its ability to bind Zn²⁺, thus increasing the ion’s availability to bind and activate coagulation proteins. NEFA-mediated perturbation of HSA-Zn²⁺ binding is thus predicted to contribute to the prothrombotic milieu in obesity and T2DM, representing a novel targetable disease mechanism in these disorders.

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.

Theoretical Three-Dimensional Zinc Complexes with Glutathione, Amino Acids and Flavonoids

Zinc plays an important role in the regulation of many cellular functions; it is a signaling molecule involved in the transduction of several cascades in response to intra and extracellular stimuli. Labile zinc is a small fraction of total intracellular zinc, that is loosely bound to proteins and is easily interchangeable. At the cellular level, several molecules can bind labile zinc and promote its passage across lipophilic membranes. Such molecules are known as ionophores. Several of these compounds are known in the scientific literature, but most of them can be harmful to human health and are therefore not allowed for medical use. We here performed a theoretical three-dimensional study of known zinc ionophores, together with a computational energetic study and propose that some dietary flavonoids, glutathione and amino acids could form zinc complexes and facilitate the transport of zinc, with the possible biological implications and potential health benefits of these natural compounds. The study is based on obtaining a molecular conformational structure of the zinc complexes with the lowest possible energy content. The discovery of novel substances that act as zinc ionophores is an attractive research topic that offers exciting opportunities in medicinal chemistry. We propose that these novel complexes could be promising candidates for drug design to provide new solutions for conditions and diseases related to zinc deficiency or impairment derived from the dysregulation of this important metal.

Dietary and Physiological Effects of Zinc on the Immune System

Evidence for the importance of zinc for all immune cells and for mounting an efficient and balanced immune response to various environmental stressors has been accumulating in recent years. This article describes the role of zinc in fundamental biological processes and summarizes our current knowledge of zinc's effect on hematopoiesis, including differentiation into immune cell subtypes. In addition, the important role of zinc during activation and function of immune cells is detailed and associated with the specific immune responses to bacteria, parasites, and viruses. The association of zinc with autoimmune reactions and cancers as diseases with increased or decreased immune responses is also discussed. This article provides a broad overview of the manifold roles that zinc, or its deficiency, plays in physiology and during various diseases. Consequently, we discuss why zinc supplementation should be considered, especially for people at risk of deficiency. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Assessment of the In Vivo Release and Biocompatibility of Novel Vesicles Containing Zinc in Rats

This paper is focused on the in vivo release and biocompatibility evaluation in rats of some novel systems entrapping zinc chloride in lipid vesicles. The particles were prepared by zinc chloride immobilization inside lipid vesicles made using phosphatidylcholine, stabilized with 0.5% chitosan solution, and dialyzed for 10 h to achieve a neutral pH. The submicrometric systems were physico-chemically characterized. White Wistar rats, assigned into four groups of six animals each, were treated orally with a single dose, as follows: Group I (control): deionized water 0.3 mL/100 g body weight; Group II (Zn): 2 mg/kg body weight (kbw) zinc chloride; Group III (LV-Zn): 2 mg/kbw zinc chloride in vesicles; Group IV (LVC-Zn): 2 mg/kbw zinc chloride in vesicles stabilized with chitosan. Haematological, biochemical, and immune parameters were assessed after 24 h and 7 days, and then liver fragments were collected for histopathological examination. The use of zinc submicrometric particles-especially those stabilized with chitosan-showed a delayed zinc release in rats. No substantial changes to blood parameters, plasma biochemical tests, serum complement activity, or peripheral neutrophils phagocytic capacity were noted; moreover, the tested substances did not induce liver architectural disturbances. The obtained systems provided a delayed release of zinc, and showed good biocompatibility in rats.

Zinc absorption and zinc status are reduced after either sleeve gastrectomy or Roux-en-Y gastric bypass in premenopausal women with severe obesity studied prospectively over 24 postoperative months

BACKGROUND

Roux-en-Y gastric bypass (RYGBP) is known to reduce zinc absorption; the effects of vertical sleeve gastrectomy (SG) and its long-term implications on zinc absorption have not yet been studied.

OBJECTIVE

The aim was to evaluate the effects of SG and RYGBP on zinc absorption and zinc status in premenopausal women with severe obesity up to 24 mo after surgery.

METHODS

Twenty-six premenopausal women undergoing SG [BMI (in kg/m2): 37.3 ± 3.2] and 32 undergoing RYGBP (BMI: 42.0 ± 4.2) were studied. A series of anthropometric, dietary, and zinc status parameters (plasma and hair zinc), and the size of the exchangeable zinc pool (EZP), as well as percentage zinc absorption from a standardized dose using a stable isotope methodology were evaluated in the patients before the surgical procedure and at 12 and 24 mo after SG or RYGBP. SG patients received 15 mg and RYGBP received 25 mg of supplemental Zn/d.

RESULTS

In premenopausal women, zinc absorption was decreased by 71.9% and 52.0% in SG and RYGBP, respectively, 24 mo postsurgery, compared with initial values. According to 2-factor repeated-measures ANOVA, time effect was significant (P = <0.0001), but not time × group interaction (P = 0.470). Plasma zinc below the cutoff point of 70 µg/dL increased from 0 to 15.4% and 38.1% in SG and RYGBP, respectively. Mean EZP was significantly reduced 24 mo after surgery, although no time × group interactions were observed. Hair zinc did not change across time or between groups.

CONCLUSIONS

Both SG and RYGBP have profound effects on zinc absorption capacity, which are not compensated for after 24 mo. Although zinc absorption reduction was similar in both types of surgeries, plasma zinc was more affected in RYGBP than SG, despite greater zinc supplementation in RYGBP.This trial was registered at http://www.isrctn.com as ISRCTN31937503.

Nutraceutical Supplementation Ameliorates Visual Function, Retinal Degeneration, and Redox Status in rd10 Mice

Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies characterized by progressive degeneration of photoreceptor cells. Ocular redox status is altered in RP suggesting oxidative stress could contribute to their progression. In this study, we investigated the effect of a mixture of nutraceuticals with antioxidant properties (NUT) on retinal degeneration in rd10 mice, a model of RP. NUT was orally administered to rd10 mice from postnatal day (PD) 9 to PD18. At PD18 retinal function and morphology were examined by electroretinography (ERG) and histology including TUNEL assay, immunolabeling of microglia, Müller cells, and poly ADP ribose polymers. Retinal redox status was determined by measuring the activity of antioxidant enzymes and some oxidative stress markers. Gene expression of the cytokines IL-6, TNFα, and IL-1β was assessed by real-time PCR. NUT treatment delayed the loss of photoreceptors in rd10 mice partially preserving their electrical responses to light stimuli. Moreover, it ameliorated redox status and reduced inflammation including microglia activation, upregulation of cytokines, reactive gliosis, and PARP overactivation. NUT ameliorated retinal functionality and morphology at early stages of RP in rd10 mice. This formulation could be useful as a neuroprotective approach for patients with RP in the future.

The Safety of a Vegan Diet During Pregnancy

There is an increasing number of people who go vegetarian. Some young parents also switch to this diet. The safety of vegetarian diets, especially vegan diets, is very important, especially during pregnancy. Unfortunately, reference publications do not provide coherent data on the safety of vegetarian diets during pregnancy. On the one hand, the vegan diet has advantages because it reduces the risk of heart disease and gestational diabetes. On the other hand, vegetarians/vegans should be aware of potential deficiencies of some nutrients (iron, zinc, vitamin B12, vitamin D, omega-3 fatty acids, calcium, iodine) and the clinical consequences for the fetus. For example, iron deficiency may affect cognitive abilities, behavior, intelligence and increase the risk of preterm birth and low birth weight of infants. Plant food contains non-haem iron with variable absorption. Therefore, the vegan diet should include nutrients increasing the bioavailability of iron, e.g. ascorbic acid, carotene and retinol. Due to the fact that animal food is the main source of vitamin B12, vegans are at a very high risk of vitamin B12 deficiency, which will affect the infant’s weight at birth. Low level of vitamin D, which is prevalent in animal food, is the most common deficiency among vegans and lacto-ovo vegetarians. This vitamin prevents gestational diabetes, reduces insulin resistance and guarantees normal function of the musculoskeletal system. Zinc deficiency during pregnancy may lead to preterm birth, neural tube defects or even miscarriage. In view of the clinical consequences of potential deficiencies of nutrients, the vegetarian/vegan diet should be well balanced.

Associations Between Serum Zinc Levels and Alanine Aminotransferase Elevation in Adults

Recent findings showed that zinc might be linked to alanine aminotransferase (ALT) elevation. This analysis aimed to explore the association between serum zinc levels and ALT elevation in adults. Data on serum zinc and ALT levels from adults aged 20 years and older who participated in the 2011-2016 National Health and Nutrition Examination Surveys were analyzed (N = 4138). Individuals with excessive alcohol consumption and hepatitis B or C infection were excluded. ALT elevation was defined as any value above normal of ALT (> 33 IU/L for males and > 25 IU/L for females). The multivariate logistic model and restricted cubic splines were adopted to assess the non-linear relationship. In a fully adjusted model, the odds ratio and 95% confidence interval of ALT elevation for quartile 4 (Q4) vs. quartile 1 (Q1) of serum zinc levels were 1.68 and 1.29-2.20 (per quartile: 1.20 (1.10-1.31)). In subgroup analysis, the association between serum zinc levels and ALT elevation was found in females (Q4 vs Q1: 1.95 (1.20-3.15)), obese individuals (Q4 vs Q1: 1.80 (1.19-2.74)), and young adults (Q4 vs Q1: 1.72 (1.09-2.72)), while the association was not evident in males, non-obese individuals, and adults older than 50 years old. A linear dose-response relationship between serum zinc levels and ALT elevation was found (P_{for non-linearity} = 0.77). In conclusion, serum zinc was positively associated with ALT elevation in adults, and the association was mainly observed in females, obese individuals, and young adults.

Dysphagia, texture modification, the elderly and micronutrient deficiency: a review

Dysphagia is an underlying symptom of many health issues affecting a person's ability to swallow. Being unable to swallow correctly may limit food intake and subsequently micronutrient status. The elderly may be the most at risk group of suffering dysphagia as well as most likely to be deficient in micronutrients. The use of texture-modified meals is a common approach to increasing dysphagia sufferer's food intake. The modification of food may affect the micronutrient content and currently there is a limited number of studies focusing on micronutrient content of texture-modified meals. This review considers the prevalence of dysphagia within the elderly UK community whilst assessing selected micronutrients. Vitamin B₁₂, C, D, folate, zinc and iron, which are suggested to be most likely deficient in the general elderly UK population, were reviewed. Each micronutrient is considered in terms of prevalence of deficiency, metabolic function, food source and processing stability to provide an overview with respect to elderly dysphagia sufferers.

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.

Immunomodulatory diet in pediatric age

In the last few decades, the importance of a functioning immune system and health status has become more evident. Multiple factors are able to influence the development of chronic diseases and diet is one of the most important environmental factors. Evidence demonstrates that dietary patterns high in fat and low in fiber are associated with the development of non-communicable diseases. Moreover, optimal nutritional status can modulate immune maturation and response to inflammation. During inflammatory conditions, nutritional deficiencies may occur, establishing a vicious circle, consequently a balanced nutritional status is essential to prevent and counteract infections. Dietary diversity can prevent allergic diseases and nutrients such as DHA, arginine, vitamins and trace elements have an impact on physical barriers (such as gut mucosal barrier and skin), on the immune system response and on microbiome modulation. Protein deficiencies can compromise innate and adaptive immune functions; arginine availability can affect the immune response in injured states and other disease processes; EPA and DHA can modulate both innate and adaptive immunity; prebiotics have a beneficial effect on the functioning of the immune system. Zinc, copper, selenium and iron are involved in the correct development and function of the immune system. Vitamins D, E, A, B and C have a role on immune system through different mechanisms of action. Since a complex interplay exists between diet, microbiome and epigenetic factors which determine nutrient-induced changes on the immune function, the effect of each single nutrient may be difficult to study. Well-designed intervention studies, investigating the effects of whole dietary pattern, should be performed to clarify impact of foods on the immune function and disease risk.

Zinc supplementation as an adjunct therapy for COVID-19: Challenges and opportunities

An outbreak of a novel coronavirus (COVID‐19 or 2019‐CoV) infection has posed significant threats to international health and the economy. Patients with COVID‐19 are at risk of cytokine storm, acute respiratory distress syndrome (ARDS), reduced blood oxygenation, mechanical ventilation, and a high death rate. Although recent studies have shown remdesivir and dexamethasone as treatment options, there is an urgent need to find a treatment to inhibit virus replication and to control the progression of the disease. Essential biometal zinc has generated a lot of excitement as one of the promising candidates to reduce the severity of COVID‐19 infection. Several published observations outlined in the review are the reasons why there is a global enthusiasm that zinc therapy could be a possible therapeutic option. However, the biggest challenge in realising the therapeutic value of zinc is lack of optimal treatment modalities such as dose, duration of zinc supplementation and the mode of delivery. In this review, we discuss the regulatory mechanism that hinges upon the bioavailability of zinc. Finally, we propose that intravenous zinc could circumvent the confounding factors affecting the bioavailability of zinc and allow zinc to achieve its therapeutic potential. If successful, due to advantages such as lack of toxicity, low cost and ease of availability, intravenous zinc could be rapidly implemented clinically.

Interactions of zinc- and redox-signaling pathways

Zinc and cellular oxidants such as reactive oxygen species (ROS) each participate in a multitude of physiological functions. There is considerable overlap between the affected events, including signal transduction. While there is no obvious direct connection between zinc and ROS, mainly because the bivalent cation zinc does not change its oxidation state in biological systems, these are linked by their interaction with sulfur, forming the remarkable triad of zinc, ROS, and protein thiols. First, zinc binds to reduced thiols and can be released upon oxidation. Thereby, redox signals are translated into changes in the free zinc concentration, which can act as zinc signals. Second, zinc affects oxidation of thiols in several ways, directly as well as indirectly. A protein incorporating many of these interactions is metallothionein (MT), which is rich in cysteine and capable of binding up to seven zinc ions in its fully reduced state. Zinc binding is diminished after (partial) oxidation, while thiols show increased reactivity in the absence of bound metal ions. Adding still more complexity, the MT promoter is controlled by zinc (via metal regulatory transcription factor 1 (MTF-1)) as well as redox (via nuclear factor erythroid 2-related factor 2 (NRF2)). Many signaling cascades that are important for cell proliferation or apoptosis contain protein thiols, acting as centers for crosstalk between zinc- and redox-signaling. A prominent example for shared molecular targets for zinc and ROS are active site cysteine thiols in protein tyrosine phosphatases (PTP), their activity being downregulated by oxidation as well as zinc binding. Because zinc binding also protects PTP thiols form irreversible oxidation, there is a multi-faceted reciprocal interaction, illustrating that zinc- and redox-signaling are intricately linked on multiple levels.

The Safety of TheVegan Diet During Pregnancy

There is an increasing number of people who go vegetarian. Some young parents also switch to this diet. The safety of vegetarian diets, especially ve-gan diets, is very important, especially during pregnancy. Unfortunately, reference publications do not provide coherent data on the safety of vegetar-ian diets during pregnancy. On the one hand, the vegan diet has advantages because it reduces the risk of heart disease and gestational diabetes. On the other hand, vegetarians/vegans should be aware of potential deficiencies of some nutrients (iron, zinc, vitamin B12, vitamin D, omega-3 fatty acids, cal-cium, iodine) and the clinical consequences for the foetus. For example, iron deficiency may affect cognitive abilities, behaviour, intelligence and increase the risk of preterm birth and low birth weight of infants. Plant food contains non-haem iron with variable absorption. Therefore, the vegan diet should include nutrients increasing the bioavailability of iron, e.g. ascorbic acid, carotene and retinol. Due to the fact that animal food is the main source of vitamin B12, vegans are at very high risk of vitamin B12 deficiency, which will affect the infant’s weight at birth. Low level of vitamin D, which is prevalent in animal food, is the most common deficiency among vegans and lacto-ovo vegetarians. This vitamin prevents gestational diabetes, reduces insulin resistance and guarantees normal function of the musculoskeletal system. Zinc deficiency during pregnancy may lead to preterm birth, neural tube defects or even miscarriage. In view of the clinical consequences of po-tential deficiencies of nutrients, the vegetarian/vegan diet should be well balanced.

Influence of nutrients on the bioaccessibility and transepithelial transport of polybrominated diphenyl ethers measured using an in vitro method and Caco-2 cell monolayers

Previous research has shown the absorption of polybrominated diphenyl ethers (PBDEs) in the human gastrointestinal tract, but limited attention has been given to the influence of nutrients on PBDE absorption from food matrices. We investigated the effects of nutrients (oil, starch, protein, and dietary fiber) on the absorption and transport of PBDEs in a Caco-2 cell model and bioaccessibility of PBDEs by an in vitro gastrointestinal digestion method. The results showed that the accumulation ratios of PBDE congeners in Caco-2 cells were higher in the nutrient addition groups (oil: 26.7-50.6%, starch: 27.0-58.7%, protein: 12.1-44.1%, and dietary fiber: 28.2-55.1%) than the control group (7.17-36.1%), whereas the transport ratios were lower (oil: 2.30-7.20%, starch: 1.55-9.15%, protein: 1.04-8.78%, and dietary fiber: 0.85-7.04%) than control group (3.78-11.1%). Additionally, the PBDE bioaccessibility could be increased by adding the nutrients, particularly oil and starch. This study clarified the differences in PBDE absorption in the presence of nutrients using the in vitro digestion and Caco-2 cell model. The findings showed that nutrients were an important factor that promoted PBDE absorption in the gastrointestinal tract. Therefore, it is important to focus on a novel dietary strategy of food consumption with contaminant compounds to protect human health.

Antioxidant supplements in age-related macular degeneration: are they actually beneficial?

Age-related macular degeneration (ARMD) is one of the prominent causes of central visual loss in the older age group in the urbanized, industrialized world. In recent years, many epidemiological studies and clinical trials have evaluated the role of antioxidants and micronutrients to prevent the progression of ARMD. In this article, we review some of these major studies. In addition, we review the absorption and bioavailability and possible undesirable effects of these nutrients after ingestion. The role of genotypes and inappropriate use of these supplements are also discussed. From all the above evidence, we conclude that it may not be prudent to prescribe these formulations without a proper assessment of the individual's health and dietary status. The effectiveness of all the components in antioxidant formulations is controversial. Thus, these supplements should not be prescribed just for the purpose of providing patients some kind of therapy, which may give a false sense of mental satisfaction.

Synthesis of an unprecedented H-stitched binuclear crystal structure based on selective fluorescence recognition of Zn2+ in newly synthesized Schiff base ligand with DFT and imaging application in living cells

Single hydrogen atom stitched giant binuclear crystal.

Biofortification and bioavailability of Zn, Fe and Se in wheat: present status and future prospects

Knowledge of genetic variation, genetics, physiology/molecular basis and breeding (including biotechnological approaches) for biofortification and bioavailability for Zn, Fe and Se will help in developing nutritionally improved wheat. Biofortification of wheat cultivars for micronutrients is a priority research area for wheat geneticists and breeders. It is known that during breeding of wheat cultivars for productivity and quality, a loss of grain micronutrient contents occurred, leading to decline in nutritional quality of wheat grain. Keeping this in view, major efforts have been made during the last two decades for achieving biofortification and bioavailability of wheat grain for micronutrients including Zn, Fe and Se. The studies conducted so far included evaluation of gene pools for contents of not only grain micronutrients as above, but also for phytic acid (PA) or phytate and phytase, so that, while breeding for the micronutrients, bioavailability is also improved. For this purpose, QTL interval mapping and GWAS were carried out to identify QTLs/genes and associated markers that were subsequently used for marker-assisted selection (MAS) during breeding for biofortification. Studies have also been conducted to understand the physiology and molecular basis of biofortification, which also allowed identification of genes for uptake, transport and storage of micronutrients. Transgenics using transgenes have also been produced. The breeding efforts led to the development of at least a dozen cultivars with improved contents of grain micronutrients, although land area occupied by these biofortified cultivars is still marginal. In this review, the available information on different aspects of biofortification and bioavailability of micronutrients including Zn, Fe and Se in wheat has been reviewed for the benefit of those, who plan to start work or already conducting research in this area.

Time- and Zinc-Related Changes in Biomechanical Properties of Human Colorectal Cancer Cells Examined by Atomic Force Microscopy

Simple Summary

We aimed to study how cellular zinc status (adequate vs. deficiency), closely related to colorectal cancer, does affect the nanomechanical properties of cell lines HT-29 and HT-29-MTX during their early proliferation (24–96 h). These properties and their variations can be characterized by means of Atomic Force Microscopy (AFM), a technique that allows perpendicular indentation of cells with a sharp nanometric tip, under controlled speed and load, while recording the real time variation of tip-to-cell interacting forces on approach, contact, and retraction segments. From each of these sections, complete information about the respective elastic modulus, relaxation behavior, and adhesion is extracted, thus identifying cell line- and zinc-related nanomechanical fingerprints. Our results show how the impact of zinc deficiency on the mechanical response of the cells underlines the relevance of monitoring the nutritional zinc status of tumor samples when analyzing cancerous tissues or single cells with AFM, particularly regarding the development and validation of biomechanical fingerprints as diagnostic markers for cancer.

Abstract

Monitoring biomechanics of cells or tissue biopsies employing atomic force microscopy (AFM) offers great potential to identify diagnostic biomarkers for diseases, such as colorectal cancer (CRC). Data on the mechanical properties of CRC cells, however, are still scarce. There is strong evidence that the individual zinc status is related to CRC risk. Thus, this study investigates the impact of differing zinc supply on the mechanical response of the in vitro CRC cell lines HT-29 and HT-29-MTX during their early proliferation (24–96 h) by measuring elastic modulus, relaxation behavior, and adhesion factors using AFM. The differing zinc supply severely altered the proliferation of these cells and markedly affected their mechanical properties. Accordingly, zinc deficiency led to softer cells, quantitatively described by 20–30% lower Young’s modulus, which was also reflected by relevant changes in adhesion and rupture event distribution compared to those measured for the respective zinc-adequate cultured cells. These results demonstrate that the nutritional zinc supply severely affects the nanomechanical response of CRC cell lines and highlights the relevance of monitoring the zinc content of cancerous cells or biopsies when studying their biomechanics with AFM in the future.

Relationship between serum zinc, HOMA2 parameters and glycemic status in a regional Australian hospital population

BACKGROUND: Previous studies demonstrated lower serum zinc among prediabetics and diabetics, compared to normoglycemics, however no current data is available for regional Australia. OBJECTIVE: We aimed to determine the relationship between serum zinc, glycemic status and Homeostasis Model Assessment (HOMA2) parameters in a regional Australian hospital population. METHODS: Retrospective review of patients presenting to a regional Australian hospital between June-2004 and April-2017 was conducted. Patients ordered for fasting blood glucose (FBG)+serum zinc; or FBG+serum insulin; or FBG+serum zinc+serum insulin were included. Serum zinc, FBG, serum insulin, lipid profile, vitamin-D and demographic information were collected. β-cell function, insulin resistance and insulin sensitivity were calculated by HOMA2 calculator. RESULTS: Three hundred and thirteen patient records were retrieved: 75% normoglycemic, 19% prediabetic, 6% diabetic. Serum zinc was lowest in diabetics and lower in prediabetics than normoglycemics. In simple linear regression among all participants, higher serum zinc associated with increased insulin sensitivity, decreased insulin resistance and decreased β-cell function. CONCLUSIONS: The low serum zinc status exhibited in diabetic and prediabetic individuals may play a role in insulin resistance pathogenesis. Higher zinc levels associated with greater insulin sensitivity and lower insulin resistance signifying the importance of investigating zinc supplementation in prediabetics to prevent or delay diabetes in future studies.

Opportunities for plant-derived enhancers for iron, zinc, and calcium bioavailability: A review

Understanding of the mechanism of interactions between dietary elements, their salts, and complexing/binding ligands is vital to manage both deficiency and toxicity associated with essential element bioavailability. Numerous mineral ligands are found in both animal and plant foods and are known to exert bioactivity via element chelation resulting in modulation of antioxidant capacity or micobiome metabolism among other physiological outcomes. However, little is explored in the context of dietary mineral ligands and element bioavailability enhancement, particularly with respect to ligands from plant-derived food sources. This review highlights a novel perspective to consider various plant macro/micronutrients as prospective bioavailability enhancing ligands of three essential elements (Fe, Zn, and Ca). We also delineate the molecular mechanisms of the ligand-binding interactions underlying mineral bioaccessibility at the luminal level. We conclude that despite current understandings of some of the structure-activity relationships associated with strong mineral-ligand binding, the physiological links between ligands as element carriers and uptake at targeted sites throughout the gastrointestinal (GI) tract still require more research. The binding behavior of potential ligands in the human diet should be further elucidated and validated using pharmacokinetic approaches and GI models.

Zinc Deficiency Disturbs Mucin Expression, O-Glycosylation and Secretion by Intestinal Goblet Cells

Approximately 1 billion people worldwide suffer from zinc deficiency, with severe consequences for their well-being, such as critically impaired intestinal health. In addition to an extreme degeneration of the intestinal epithelium, the intestinal mucus is seriously disturbed in zinc-deficient (ZD) animals. The underlying cellular processes as well as the relevance of zinc for the mucin-producing goblet cells, however, remain unknown. To this end, this study examines the impact of zinc deficiency on the synthesis, production, and secretion of intestinal mucins as well as on the zinc homeostasis of goblet cells using the in vitro goblet cell model HT-29-MTX. Zinc deprivation reduced their cellular zinc content, changed expression of the intestinal zinc transporters ZIP-4, ZIP-5, and ZnT1 and increased their zinc absorption ability, outlining the regulatory mechanisms of zinc homeostasis in goblet cells. Synthesis and secretion of mucins were severely disturbed during zinc deficiency, affecting both MUC2 and MUC5AC mRNA expression with ongoing cell differentiation. A lack of zinc perturbed mucin synthesis predominantly on the post-translational level, as ZD cells produced shorter O-glycans and the main O-glycan pattern was shifted in favor of core-3-based mucins. The expression of glycosyltransferases that determine the formation of core 1-4 O-glycans was altered in zinc deficiency. In particular, B3GNT6 mRNA catalyzing core 3 formation was elevated and C2GNT1 and C2GNT3 elongating core 1 were downregulated in ZD cells. These novel insights into the molecular mechanisms impairing intestinal mucus stability during zinc deficiency demonstrate the essentiality of zinc for the formation and maintenance of this physical barrier.

Vegetarian and Vegan Weaning of the Infant: How Common and How Evidence-Based? A Population-Based Survey and Narrative Review

Background: Vegetarian and vegan weaning have increasing popularity among parents and families. However, if not correctly managed, they may lead to wrong feeding regimens, causing severe nutritional deficiencies requiring specific nutritional support or even the need for hospitalization. Aim: To assess the prevalence of vegetarian and vegan weaning among Italian families and to provide an up-to-date narrative review of supporting evidence. Materials and methods: We investigated 360 Italian families using a 40-item questionnaire. The narrative review was conducted searching scientific databases for articles reporting on vegetarian and vegan weaning. Results: 8.6% of mothers follow an alternative feeding regimen and 9.2% of infants were weaned according to a vegetarian or vegan diet. The breastfeeding duration was longer in vegetarian/vegan infants (15.8 vs. 9.7 months; p < 0.0001). Almost half of parents (45.2%) claim that their pediatrician was unable to provide sufficient information and adequate indications regarding unconventional weaning and 77.4% of parents reported the pediatrician’s resistance towards alternative weaning methods. Nine studies were suitable for the review process. The vast majority of authors agree on the fact that vegetarian and vegan weaning may cause severe nutritional deficiencies, whose detrimental effects are particularly significant in the early stages of life. Discussion and conclusion: Our results show that alternative weaning methods are followed by a significant number of families; in half of the cases, the family pediatrician was not perceived as an appropriate guide in this delicate process. To date, consistent findings to support both the safety and feasibility of alternative weaning methods are still lacking. Since the risk of nutritional deficiencies in the early stages of life is high, pediatricians have a pivotal role in guiding parents and advising them on the most appropriate and complete diet regimen during childhood. Efforts should be made to enhance nutritional understanding among pediatricians as an unsupervised vegetarian or vegan diet can cause severe nutritional deficiencies with possible detrimental long-term effects.

Zinc Oxide Exerts Anti-Inflammatory Properties on Human Placental Cells

Background: An aberrant and persistent inflammatory state at the fetal-maternal interface is considered as a key contributor in compromised pregnancies. Decidual endothelial cells (DECs) play a pivotal role in the control of the local decidual inflammation. The aim of the current study was to determine whether dietary supplement with zinc oxide (ZnO), due to its very low adverse effects, may be useful for modulating the inflammatory response in the first trimester of pregnancy. Methods: The anti-inflammatory properties of ZnO in pregnancy were evaluated by in vitro tests on endothelial cells isolated from normal deciduas and on a trophoblast cell line (HTR8/Svneo). The effects of this treatment were analyzed in terms of adhesion molecule expression and inflammatory cytokine secretion, by real time-quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). Results: Our data showed that ZnO was able to reduce the inflammatory response of DECs, in terms of vascular cell adhesion molecule-1 (VCAM-1), interleukin (IL)-8, IL-6, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) expression induced by TNF-α stimulation. This compound exerted no effect on intracellular adhesion molecule-1 (ICAM-1) exocytosis induced by TNF-α on stimulated trophoblast cells, but significantly reduced their IL-6 expression. Conclusion: According to these results, it can be suggested that the ZnO supplement, through its modulation of the pro-inflammatory response of DECs, can be used in pregnancy for the prevention of local decidual inflammation.

Zinc as a Therapeutic Agent in Bone Regeneration

Zinc is an essential mineral that is required for normal skeletal growth and bone homeostasis. Furthermore, zinc appears to be able to promote bone regeneration. However, the cellular and molecular pathways through which zinc promotes bone growth, homeostasis, and regeneration are poorly understood. Zinc can positively affect chondrocyte and osteoblast functions, while inhibiting osteoclast activity, consistent with a beneficial role for zinc in bone homeostasis and regeneration. Based on the effects of zinc on skeletal cell populations and the role of zinc in skeletal growth, therapeutic approaches using zinc to improve bone regeneration are being developed. This review focuses on the role of zinc in bone growth, homeostasis, and regeneration while providing an overview of the existing studies that use zinc as a bone regeneration therapeutic.

Revised D-A-CH-reference values for the intake of zinc

BACKGROUND

The Nutrition Societies of Germany, Austria and Switzerland as the joint editors of the 'D-A-CH reference values for nutrient intake' have revised the reference values for zinc in July 2019.

METHODS

For infants aged 0 to under 4 months, an estimated value was set based on the zinc intake via breast feeding. For all other age groups, the reference values were calculated using the factorial method considering endogenous zinc losses via intestinal losses, urine, faeces, skin and sweat, semen in men and the additional zinc requirements to build up body weight in children and adolescents as well as in pregnant women. Due to the strong influence of phytate intake on zinc absorption, the recommendations for the intake of zinc for adults are derived depending on low (0.5 mmol/day, corresponding to 330 mg/day), moderate (1.0 mmol/day, corresponding to 660 mg/day) and high (1.5 mmol/day, corresponding to 990 mg/day) phytate intake. The reference values for lactating women take into account the zinc loss via breast milk.

RESULTS AND CONCLUSION

For adults, pregnant and lactating women, the recommended intake values for zinc range from 7 mg/day to 16 mg/day, depending on sex and dietary phytate intake.