Mild Zinc Deficiency in Human Subjects

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.

Evaluation of genotoxicity of SUNACTIVE Zn-P240 in vitro and in vivo

We evaluated the potential genotoxic effects of the nutrient supplement SUNACTIVE Zn-P240 in vitro and in vivo. Genotoxicity tests were performed at the Korea Testing and Research Institute, a GLP certification institution. A bacterial reverse mutation test was performed using the pre-incubation method, while the in vitro chromosome aberration test was performed using a cultured Chinese hamster lung cell line in the presence or absence of metabolic activation. The in vivo micronucleus test was performed using ICR mice. The bacterial reverse mutation test revealed that SUNACTIVE Zn-P240 did not induce genetic mutations at the tested doses in Salmonella typhimurium (TA98, TA100, TA1535, and TA1537) and Escherichia coli (WP2uvrA) tester strains. Meanwhile, the results of the in vitro chromosomal aberration and in vivo micronucleus tests revealed that SUNACTIVE Zn-P240 did not induce chromosomal aberrations. These results suggest that SUNACTIVE Zn-P240 did not exhibit mutagenic or clastogenic properties in vitro and in vivo.

Zinc and COVID-19: Immunity, Susceptibility, Severity and Intervention

During the coronavirus disease 2019 (COVID-19) pandemic and continuing emergence of viral mutants, there has been a lack of effective treatment methods. Zinc maintains immune function, with direct and indirect antiviral activities. Zinc nutritional status is a critical factor in antiviral immune responses. Importantly, COVID-19 and zinc deficiency overlap in high-risk population. Hence, the potential effect of zinc as a preventive and adjunct therapy for COVID-19 is intriguing. Here, this review summarizes the immune and antiviral function of zinc, the relationship between zinc levels, susceptibility, and severity of COVID-19, and the effect of zinc supplementation on COVID-19. Existing studies have confirmed that zinc deficiency was associated with COVID-19 susceptibility and severity. Zinc supplementation plays a potentially protective role in enhancing immunity, decreasing susceptibility, shortening illness duration, and reducing the severity of COVID-19. We recommend that zinc levels should be monitored, particularly in COVID-19 patients, and zinc as a preventive and adjunct therapy for COVID-19 should be considered for groups at risk of zinc deficiency to reduce susceptibility and disease severity.

Zinc Deficient Intake in Hemodialysis Patients: A Path to a High Mortality Risk

BACKGROUND

Zinc is essential for human nutrition and plays an important role in hemodialysis (HD) patients. The aim of this study is to analyze the relationship between zinc intake and mortality in HD patients.

METHODS

This is a longitudinal, prospective, multicenter study with 582 HD patients from 37 dialysis centers. We recorded clinical and body composition parameters. Dietary intake and physical activity data were obtained using the Food Frequency Questionnaire and International Physical Activity Questionnaire. All statistical tests were performed using SPSS 24.0 software. A P value lower than 0.05 was considered statistically significant.

RESULTS

Patients' mean age was 67.8 ± 17.7 years and median HD vintage was 65 (43-104) months. About 53.6% of the patients presented a deficient daily intake of zinc. Patients with the highest zinc intake were those who had a higher lean tissue index (P = .022), energy (P < .001), and protein (p = .022) intakes. Zinc intake was positively correlated with energy (r = 0.709) and protein intake (r = 0.805) and negatively correlated with the malnutrition screening tool score (r = -0.087). A higher energy, protein, and lower carbohydrates intake, as well as lower HD vintage and higher lean tissue index were predictors of zinc intake. A higher mortality risk was observed in patients with zinc intake below the recommended values, even after the adjustment for age, presence of diabetes, gender, dialysis vintage, albumin, lean tissue index, energy intake/kilogram, and level of physical activity (P = .021).

CONCLUSION

There is a high prevalence of HD patients with an inadequate zinc intake, which is related to worse nutritional and body composition parameters and with a higher mortality risk.

Elemental zinc to zinc nanoparticles: is ZnO NPs crucial for life? Synthesis, toxicological, and environmental concerns

The semi-conducting material zinc is one of the essential trace elements for humans, is a co-factor of more than 300 enzymes, and plays an important role in maintaining vital cellular functions. Deficiency of zinc may lead to cancer initiation; however, a high concentration also has toxic effects that might be life threatening. The toxicity can be addressed by the disequilibrium of zinc-mediated proteins and oxidative stress that produce nascent oxygen, hydroxyl radicals, and other reactive oxygen species. Zinc-based nanoparticles (NPs) are among the most important and multifunctional compounds. Zinc oxide (ZnO) NPs exhibit attractive antimicrobial and photocatalytic properties due to the smaller particle size and increased particle surface reactivity. Further, these are more biocompatible compared to other metallic NPs, easily synthesizable, and have high selectivity, enhanced cytotoxicity, and are a promising anticancer agent. However, some of the pertinent concerns regarding nano-zinc still needs to be clarified. Current research also demonstrates their usage in wastewater treatment, textile, medicine, etc. This review covers the importance of zinc for living systems and its NPs, with more emphasis on ZnO NPs. A comprehensive overview of ZnO NPs, their synthesis, characterization techniques, crystal structure, properties, and brief industrial applications are presented.

Anosmia after Intranasal Zinc Gluconate Use

Background

Zinc is an essential mineral. Beneficial zinc absorption takes place via enteral, parenteral, or cutaneous routes. However, direct application to the olfactory epithelium has been reported to cause loss of smell. Recently, intranasal zinc gluconate has been recommended as a treatment for the common cold. Severe posttreatment hyposmia and anosmia have been observed.

Methods

The case report of a typical patient is presented and analyzed in detail, followed by a series of patients with severe hyposmia or anosmia after the use of intranasal zinc gluconate.

Results

Although interindividual variation in drug response and drug effect is apparent, the severe hyposmia or anosmia appears to be long lasting or permanent in some cases. The mechanism of olfactory loss is thought to be the direct action of the divalent zinc ion on the olfactory receptor cell.

Conclusions

Zinc ions are toxic to olfactory epithelium. Reports of severe hyposmia with parosmia or anosmia have occurred after intranasal use of zinc gluconate.

Genomic instability related to zinc deficiency and excess in an in vitro model: is the upper estimate of the physiological requirements recommended for children safe?

Micronutrients are important for the prevention of degenerative diseases due to their role in maintaining genomic stability. Therefore, there is international concern about the need to redefine the optimal mineral and vitamin requirements to prevent DNA damage. We analyzed the cytostatic, cytotoxic, and genotoxic effect of in vitro zinc supplementation to determine the effects of zinc deficiency and excess and whether the upper estimate of the physiological requirement recommended for children is safe. To achieve zinc deficiency, DMEM/Ham's F12 medium (HF12) was chelated (HF12Q). Lymphocytes were isolated from healthy female donors (age range, 5-10 yr) and cultured for 7 d as follows: negative control (HF12, 60 μg/dl ZnSO₄); deficient (HF12Q, 12 μg/dl ZnSO₄); lower level (HF12Q + 80 μg/dl ZnSO₄); average level (HF12Q + 180 μg/dl ZnSO₄); upper limit (HF12Q + 280 μg/dl ZnSO₄); and excess (HF12Q + 380 μg/dl ZnSO₄). The comet (quantitative analysis) and cytokinesis-block micronucleus cytome assays were used. Differences were evaluated with Kruskal-Wallis and ANOVA (p < 0.05). Olive tail moment, tail length, micronuclei frequency, and apoptotic and necrotic percentages were significantly higher in the deficient, upper limit, and excess cultures compared with the negative control, lower, and average limit ones. In vitro zinc supplementation at the lower and average limit (80 and 180 μg/dl ZnSO₄) of the physiological requirement recommended for children proved to be the most beneficial in avoiding genomic instability, whereas the deficient, upper limit, and excess (12, 280, and 380 μg/dl) cultures increased DNA and chromosomal damage and apoptotic and necrotic frequencies.

Zinc as a potential coadjuvant in therapy for type 2 diabetes

BACKGROUND

Type 2 diabetes is highly prevalent in populations having high rates of overweight and obesity. It is a chronic condition responsible for long-term severe dysfunction of several organs, including the kidneys, heart, blood vessels, and eyes. Although there are a number of pharmacologic products in the market to treat insulin resistance and impaired insulin secretion--the most prominent features of this disease--interventions directed at preserving the integrity and function of beta-cells in the long term are less available. The use of some nutrients with important cellular protective roles that may lead to a preservation of beta-cells has not been fully tested; among these, zinc may be an interesting candidate.

OBJECTIVE

To assess the potential of zinc supplementation as coadjuvant to diabetes therapy.

METHODS

This article reviews the available information on the use of zinc as part of diabetes therapy.

RESULTS

Cellular and animal models provide information on the insulin mimetic action of zinc, as well as its role as a regulator of oxidative stress, inflammation, apoptosis, and insulin secretion. Zinc supplementation studies in humans are limited, although some positive effects have been reported; mainly, a modest but significant reduction in fasting glucose and a trend to decreased glycated hemoglobin (HbA1c).

CONCLUSIONS

Zinc supplementation may have beneficial effects on glycemic control. Nevertheless, among the studies considered, the vast majority lasted for 6 months or less, suggesting the importance of conducting long-duration studies given the characteristics of type 2 diabetes as a chronic disease.

Zinc supplementation does not affect growth, morbidity, or motor development of US term breastfed infants at 4-10 mo of age

BACKGROUND

It has been documented that growth patterns differ between breastfed and formula-fed infants. Some investigators have suggested that these differences may be related to differences in zinc nutriture.

OBJECTIVE

The objective of this study was to examine the effect of zinc supplementation on growth, morbidity, and motor development in healthy, term, breastfed infants.

DESIGN

We conducted a randomized double-blind intervention comparing zinc supplementation (5 mg/d as zinc sulfate) with placebo in breastfed infants aged 4-10 mo. Growth and indexes of body composition and gross motor development were measured monthly from 3 to 10 mo. Morbidity data were collected weekly.

RESULTS

Eighty-five infants were enrolled, and 70 completed the study. The baseline characteristics, attained weight or length at 10 mo, growth velocity, gross motor development, and morbidity did not differ significantly between groups, even after control for potentially confounding variables.

CONCLUSIONS

The dietary zinc intake of these breastfed infants appeared to be adequate, given that zinc supplementation did not affect growth, development, or risk of infection (although sample size for detection of differences in development or infection was limited). Previously described differences in growth between breastfed and formula-fed infants in such populations do not appear to be due to differences in zinc nutriture.

Effects of oral zinc supplementation on serum leptin levels in Ache males of eastern Paraguay

Significant population variation has been demonstrated in serum leptin levels, independent of adiposity. Included within these populations, Ache males have significantly lower leptin levels compared to American subjects with comparable adiposity. The underlying causes of these differences are not understood but zinc has been shown to be an important regulator of leptin in humans and rodents. Zinc deficiency is associated with somatic wasting and significant declines in circulating leptin levels. Zinc deficiency is common in underdeveloped regions and may therefore contribute to low leptin levels among Ache men. To ascertain the potential role of zinc on Ache male leptin profiles, zinc supplementation was conducted to observe leptin responsiveness. Ache males were given daily oral zinc supplementation (50mg zinc gluconate) (n = 8) or placebo (n = 6) for 10 days. Serum leptin levels were measured on the first and last days of the treatment/placebo period. Despite supplementation exceeding triple the USDA recommended daily requirements, serum leptin levels did not change in the zinc-supplemented group (P = 0.61) and were not significantly different from males receiving placebo (P = 0.72). It is concluded that zinc is not likely to be a contributing factor in male Ache leptin profiles and that other sources of variation such as chronic energetic stresses affecting leptin production and perhaps receptor number or sensitivity should be considered.

Interrelationships of key variables of human zinc homeostasis: relevance to dietary zinc requirements

Currently, estimates of human zinc requirements depend primarily on a factorial approach. The availability of tracer techniques employing zinc stable isotopes has facilitated the acquisition of data on major variables of zinc homeostasis in addition to those that can be measured with careful metabolic balance techniques. These data have promising potential to facilitate and improve the factorial approach. The thesis proposed in this paper is that realistic estimations of dietary zinc requirements by a factorial approach require attention to the dynamic interrelationships between major variables of zinc homeostasis. This applies especially to the positive relationship between endogenous fecal zinc and total absorbed zinc, which is the essential starting point in estimating physiologic and, from there, dietary requirements.

Zinc and the gene

A significant portion of cellular zinc is found in the nucleus where it appears to be critically involved in maintaining genetic stability and in the process of gene expression. With regard to gene expression zinc functions mechanistically at several levels but recent interest has focussed especially on the involvement of zinc in DNA transcription through the activity of transcription factors which contain specific zinc-finger regions which bind to DNA and, in conjunction with other families of transcription factors, control cell proliferation, differentiation and cell death. Because of the central importance of zinc in cell division and growth, considerable attention is paid to zinc as an essential trace element and much has been written concerning dietary sources of zinc and recommended dietary intakes of the metal.

Short-term zinc deficiency affects nuclear factor-kappab nuclear binding activity in rat testes

We reported previously that feeding zinc-deficient diets for 14 d altered the oxidant defense system in the testes of young male rats and increased levels of lipid, protein and DNA oxidation in this tissue. In this study, we investigated the early involvement of oxidative stress in zinc deficiency-induced testicular pathology. Weanling male rats (17 d old) were given free access to a control (25 microg Zn/g) or a zinc-deficient (0.5 microg Zn/g) diet, or restricted access to the control diet at a level of intake similar to that of rats fed the 0.5 microg Zn/g diet (restricted group) for 7 d. Rats fed the low zinc diet were characterized by low testes zinc and alkaline phosphatase activity compared with ad libitum and restricted controls. Testes protein and lipid oxidation variables did not differ among the groups. Higher than normal (P < 0.05) activities of CuZn (CuZnSOD) and Mn (MnSOD) superoxide dismutases were observed in the low zinc group. Glutathione peroxidase and glutathione reductase activities did not differ among the groups. Total glutathione concentrations were lower in the low zinc and restricted groups than in the control group (P < 0.05). The testes nuclear binding activities of two transcription factors sensitive to oxidants [nuclear factor (NF)-kappaB and AP-1] were assessed. AP-1 nuclear binding activity did not differ among the groups, but NF-kappaB nuclear binding activity was lower in the low zinc group than in the control groups (P < 0.05). We suggest that the reduction in NF-kappaB binding reflects an early response to zinc deficiency-induced oxidative stress.

Zinc deficiency in an exclusively breast-fed preterm infant

A formerly premature, exclusively breast-fed infant with severe zinc deficiency syndrome is presented. He showed the characteristic erosive skin changes, including alopecia, as seen in acrodermatitis enteropathica. In addition, he manifested a failure to thrive and irritability. The diagnosis was confirmed by reduced serum levels of zinc (2.3 mumol/l) and alkaline phosphatase (45 U/l). We consider the reduced zinc supply in the breast milk (5.7 mumol/l) as the most likely cause of the disease. Therapy consisted of oral zinc supplements (50 mumol/kg/day) for a period of 30 weeks. Symptoms and laboratory values normalized completely and did not recur on a normal diet.

CONCLUSION

A diet of breast milk can, in rare circumstances, cause insufficient zinc intake resulting in severe zinc deficiency syndrome with characteristic dermatological features. Therapy consists of temporary oral zinc supplementation at a daily dose of 50 mumol/kg.

Intrinsic labelling of different foods with stable isotope of zinc (67Zn) for use in bioavailability studies

Intrinsically-labelled foods are required to validate extrinsic-labelling techniques used to study the bioavailability of trace elements. Wheat (Triticum aestivum), peas (Pisum sativum), goat's milk, human milk, eggs and chicken meat were selected for intrinsic-labelling studies with 67Zn. Peas were grown hydroponically in enriched nutrient solution and wheat was grown in sand and watered with enriched nutrient solution. Some of the wheat plants were also given stem injections of 67Zn solution. Eggs and chicken meat were prepared by administering 67Zn intravenously to chickens, and human milk was collected after an oral dose of 67Zn in a cola drink. All the foods investigated were sufficiently enriched with 67Zn for Zn absorption studies except wheat prepared by the sand and water-culture method.