Dosage Effect of Zinc Glycine Chelate on Zinc Metabolism and Gene Expression of Zinc Transporter in Intestinal Segments on Rat

From zinc homeostasis to disease progression: Unveiling the neurodegenerative puzzle

Zinc is a crucial trace element in the human body, playing a role in various physiological processes such as oxidative stress, neurotransmission, protein synthesis, and DNA repair. The zinc transporters (ZnTs) family members are responsible for exporting intracellular zinc, while Zrt- and Irt-like proteins (ZIPs) are involved in importing extracellular zinc. These processes are essential for maintaining cellular zinc homeostasis. Imbalances in zinc metabolism have been linked to the development of neurodegenerative diseases. Disruptions in zinc levels can impact the survival and activity of neurons, thereby contributing to the progression of neurodegenerative diseases through mechanisms like cell apoptosis regulation, protein phase separation, ferroptosis, oxidative stress, and neuroinflammation. Therefore, conducting a systematic review of the regulatory network of zinc and investigating the relationship between zinc dysmetabolism and neurodegenerative diseases can enhance our understanding of the pathogenesis of these diseases. Additionally, it may offer new insights and approaches for the treatment of neurodegenerative diseases.

The Effect of Dietary Supplementation with Zinc Amino Acids on Immunity, Antioxidant Capacity, and Gut Microbiota Composition in Calves

The aim of this study was to investigate the effect of dietary supplementation with zinc (Zn) amino acids at different concentrations on immunity, antioxidant capacity, and gut microbiota composition in calves. Twenty-four one-month-old healthy Angus calves of comparable body weight were randomly divided into three groups (four males and four females in each group) based on the amount of Zn supplementation added to the feed the animals received: group A, 40 mg/kg DM; group B, 80 mg/kg DM; and group C, 120 mg/kg DM. The experiment ended when calves reached three months of age (weaning period). The increase in dietary Zn amino acid content promoted the growth of calves, and the average daily weight gain increased by 36.58% (p < 0.05) in group C compared with group A. With the increase in the content of dietary Zn amino acids, the indexes of serum immune functions initially increased and then decreased; in particular, the content of immunoglobulin M in group A and group B was higher than that in group C (p < 0.05), whereas the content of interleukin-2 in group B was higher than that in the other two groups (p < 0.05). In addition, the content of superoxide dismutase and total antioxidant capacity in the serum of calves in group B was higher than that in group C (p < 0.05), and the MDA level was lower than in group C (p < 0.05). Moreover, alpha diversity in the gut microbiota of calves in group B was higher than that in group A and group C (p < 0.05); the dominant phyla were Firmicutes and Bacteroidota, whereas the dominant genera were Unclassified-Lachnospiraceae and Ruminococcus. Linear discriminant analysis showed that the relative abundance of Bacteroides in the gut microbiota of calves in group B was higher than that in group A, and the relative abundance of Prevotellaceae-UCG-003 was higher compared to that in experimental group C. Thus, dietary supplementation of 80 mg/kg of Zn amino acids to calves could improve the immune function and antioxidant capacity, as well as enrich and regulate the equilibrium of gut microbiota, thus promoting the healthy growth of calves.

Characteristics of Zn Content and Localization, Cu-Zn SOD, and MT Levels in the Tissues of Marginally Zn-Deficient Mice

Zinc (Zn) is an important trace element in the human body, and Zn deficiency affects the Zn content of major tissues. Marginal Zn deficiency is more common than severe Zn deficiency in humans. The objective of the present study was to compare the content and distribution of Zn and the change in the copper (Cu)-Zn superoxide dismutase (SOD) and metallothionein (MT) levels of soft tissues. Mice were fed with 30 mg/kg (control) or 10 mg/kg (marginally Zn-deficient, MZD) Zn diet for 35 days. We observed that only the Zn contents of serum, bones, and muscles in the control group were higher than those in the MZD group. Autometallography (AMG) was used as a method for staining Zn ions, and the semi-quantitative result indicated that the AMG products of the liver, duodenum, heart, lung, testes, and epididymis in the control group were higher than those in the MZD group. Furthermore, the contents of MT and the activities of Cu-Zn SOD in the testes, brain, duodenum, and liver were higher in the control group than those in the MZD group. However, the AMG products and the activities of Cu-Zn SOD of the kidney in the MZD group were more/higher than those in the control group. These results indicated that a change in the total Zn content of soft tissues may be not obvious and insensitive, and thus, more attention should be given to the distribution and localization of Zn ions. The functional indicators, MT and Cu-Zn SOD, are suitable biomarkers for evaluating zinc nutritional status. The brain, testes, duodenum, and liver are susceptive organs to Zn deficiency.

Alterations of Gut-Derived Melatonin in Neurobehavioral Impairments Caused by Zinc Oxide Nanoparticles

Purpose

The widespread use of zinc oxide nanoparticles (ZnONPs) has raised concerns about its potential toxicity. Melatonin is a neurohormone with tremendous anti-toxic effects. The enterochromaffin cells are an essential source of melatonin in vivo. However, studies on the effects of ZnONPs on endogenous melatonin are minimal. In the present study, we aimed to investigate the effects of ZnONPs exposure on gut-derived melatonin.

Methods

In the present study, 64 adult male mice were randomly and equally divided into four groups, and each group was exposed to ZnONPs (0, 6.5, 13, 26 mg/kg/day) for 30 days. Subsequently, the neurobehavioral changes were observed. The effects of ZnONPs on the expression of melatonin-related genes arylalkylamine N-acetyltransferase (Aanat), melatonin receptor1A (Mt1/Mtnr1a), melatonin receptor1B (Mt2/Mtnr1b), and neuropeptide Y (Npy) on melatonin synthesis and secretion in duodenum, jejunum, ileum and colon during day and night were also assessed.

Results

The results revealed that oral exposure to ZnONPs induced impairments of locomotor activity and anxiety-like behavior in adult mice during the day. The transcriptional analysis of brain tissues revealed that exposure to ZnONPs caused profound effects on genes and transcriptional signaling pathways associated with melatonin synthesis and metabolic processes during the day and night. We also observed that, in the duodenum, jejunum, ileum and colon sites, ZnONPs resulted in a significant reduction in the expression of the gut-derived melatonin rate-limiting enzyme Aanat, the membrane receptors Mt1 and Mt2 and Npy during the day and night.

Conclusion

Taken together, this is the first study shows that oral exposure to ZnONPs interferes with melatonin synthesis and secretion in different intestinal segments of adult mice. These findings will provide novelty insights into the neurotoxic mechanisms of ZnONPs and suggest an alternative strategy for the prevention of ZnONP neurotoxicity.

The Effects of Zinc Methionine on Reproductive and Thyroid Hormones in Rats with Polycystic Ovarian Syndrome

Background

Polycystic ovarian syndrome (PCOS) is an endocrine disorder in fertile women, which seems to be adversely affected by associated thyroid dysfunction. Zinc methionine (ZM) has positive effects on PCOS, but its concerted effects on PCOS and thyroid function have not been investigated. We evaluated the effects of ZM on reproductive and thyroid hormones and the number of follicles in rats with PCOS.

Materials and Methods

This study was conducted on 45 female rats, using sesame oil as control; PCOS animals administered with 0, 25, 75, and 175 mg/kg BW of ZM. Serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid function were investigated. Premature follicles (PMF), primary follicles (PF), preantral follicles (PAF), antral follicles (AF), corpus luteum (CL), and cystic follicles (CF) were assessed.

Results

PCOS decreased the concentrations of FSH and free T4, but increased the levels of LH, TSH, and LH/FSH ratio (ALL P < 0.05). ZM at a dose of 75 and 175 mg increased the level of FSH, free T4, and decreased LH, TSH, and LH/FSH ratio (ALL P < 0.05). Induction of PCOS decreased PMF, PF, PAF, AF, and CL, but increased CF (P < 0.05). PCOS treated groups (75 and 175 mg/kg) increased these follicle numbers and decreased CF compared to ZM 25 mg/kg and PCOS groups (Both P < 0.05).

Conclusions

Although the induction of PCOS had a negative effect on reproductive and thyroid hormones and follicle numbers, ZM treatment (75 and 175 mg/kg) overcame the negative effects. A high dosage of ZM can alleviate the hormonal and cysts disturbances occurring in PCOS.

Dietary Serine Supplementation Regulates Selenoprotein Transcription and Selenoenzyme Activity in Pigs

The synthesis of selenocysteine and its incorporation into selenoproteins require serine during the action of seryl-tRNA synthetase. In view of this, we conducted this study to explore the effects of dietary serine supplementation on selenoprotein transcription and selenoenzyme activity in pigs. A total of 35 crossbred barrows (28 days old) were randomly assigned to five treatment groups. During the 42-day growth experiment, pigs were fed either a basal diet with no supplemented serine or diets supplemented with 0.25%, 0.5%, 0.75%, or 1% serine. The results showed that serine supplementation had no effect on the selenium content in the serum, skeletal muscle, and kidney of pigs. However, dietary supplementation with 0.5% serine significantly increased the selenium content in the liver. Diets supplemented with different levels of serine significantly increased the gene expression of glutathione peroxidase 1 (Gpx1), Gpx2, thioredoxin reductase 1 (Txnrd1), Txnrd2, and selenoprotein P (Sepp1) in the skeletal muscle and liver of pigs. Moreover, pigs supplemented with 0.5% serine had the highest selenoprotein P concentration and glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) activities in the skeletal muscle, which were significantly higher than those in the control pigs. Additionally, pigs supplemented with 0.25% serine had the highest GPx and TrxR activities in the liver, which were significantly higher than those in the control pigs. In conclusion, dietary serine supplementation could improve selenoprotein transcription and selenoenzyme activity in pigs, with the appropriate concentrations of serine to be included in the diet being 0.25% or 0.5%.

Zinc Supplementation Forms Influenced Zinc Absorption and Accumulation in Piglets

The study aimed at determining the effect of different zinc (Zn) supplementation forms on Zn accumulation, activities of Zn-containing enzymes, gene expression of metallothionein (MT), and Zn transporters in piglets. Eighteen piglets were randomly divided into three groups: (a) a basal diet supplemented with 150 mg/kg Zn from Zn methionine (Zn-Met) in the feed (Zn-Met group), (b) a basal diet supplemented with 150 mg/kg Zn from Zn sulfate (ZnSO₄) in the feed (ZnSO₄, _feed group), and (c) a basal diet supplemented with the same dose of Zn as in ZnSO4,_feed group but in water (ZnSO₄, _water group). The results showed that Zn-Met added in feed and ZnSO₄ dissolved in drinking water significantly improved (p < 0.05) the Zn concentration in liver and jejunum and the apparent digestibility of Zn in comparison with the ZnSO₄ added in feed. In addition, dietary Zn supplementation as Zn-Met significantly increased (p < 0.05) the activity of alkaline phosphatase (AKP) in the jejunum of piglets in comparison with the ZnSO₄, _feed group. Furthermore, the Zn-Met and ZnSO₄, _water groups showed an improved total superoxide dismutase activity (T-SOD) in the ileum as compared to the ZnSO₄, _feed group. Meanwhile, the qPCR and western blot results showed that Zn-Met and ZnSO₄ dissolved in drinking water increased the expression of MT in the jejunum in comparison with the ZnSO₄ added in the piglets' feed. However, different Zn supplementation forms had no effect on the mRNA expressions of Zip4 and ZnT1 transporters. In conclusion, Zn-Met added in feed and ZnSO₄ dissolved in drinking water had higher bioavailability in piglets.

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

Simple Summary

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

Abstract

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

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-containing compounds for personal care applications

It is well-known that zinc ions are widely used in cosmetic products. Their popularity is associated with the multifunctional profile of Zn²⁺ , which is classified as an essential chemical element in the human body. This review examines numerous beneficial biological properties of zinc-containing compounds and classifies the compounds used in cosmetic products according to their functionality profile: antioxidant, sunscreen, anti-inflammatory, anti-pigmentation, anti-ageing, anti-acne, antimicrobial, anti-odour, cleansing or stabilizing activity. It also underlines the significance of zinc in enzymatic processes, which depends on the enzyme type acts as inhibitor or enzymatic stimulator. Moreover, the article describes the chemical nature of the most interesting groups of Zn compounds.

Improved Sp1 and Betaine Homocysteine-S-Methyltransferase Expression and Homocysteine Clearance Are Involved in the Effects of Zinc on Oxidative Stress in High-Fat-Diet-Pretreated Mice

Zinc plays a role in alleviating oxidative stress. However, the related mechanisms remain to be further elucidated. The present study was conducted to investigate whether the recovery of oxidative stress in high-fat-diet (HFD)-pretreated mice was affected by zinc. Male mice received either an HFD or a low-fat-diet (LFD) for 8 weeks. Then, the mice fed with HFD and LFD were both assigned to either a control diet (30 mg zinc, ZD) or a no-added zinc diet (NZD) for an additional 4 weeks. The results showed that after feeding with NZD for 4 weeks, the HFD-pretreated mice had the highest plasma glucose and insulin concentrations, while had the lowest CuZn-SOD and glutathione concentrations. Moreover, after feeding with NZD for 4 weeks, the HFD-pretreated mice had the highest hepatic ROS and homocysteine concentrations, while had the lowest glutathione and methionine concentrations. Furthermore, the HFD-pretreated mice fed with NZD for 4 weeks had the lowest gene and protein expression of betaine homocysteine-S-methyltransferase (BHMT), cystathionine β-synthase, and Sp1. The results suggested that zinc was critical for oxidative stress alleviation and homocysteine clearance in HFD-pretreated mice. It was further elucidated that improved Sp1 and BHMT expression are involved in the effects of zinc on oxidative stress.

Melatonin Improves Laying Performance by Enhancing Intestinal Amino Acids Transport in Hens

The high concentration of melatonin (MEL) in the intestinal mucosa suggests that it has a special physiological function in intestine. In hens, previous studies have shown that MEL treatment promoted egg-laying performance. Considering the importance of amino acids (AA) for egg formation, we hypothesized that MEL may enhance the intestinal absorption of AA from the feed, thus promoting egg laying performance. In this study, we supplemented the hens with MEL for two consecutive weeks. The results showed that, compared with control group, feeding with 0.625 mg MEL/kg diets gave rise to higher egg laying rate (by 4.3%, P = 0.016), increased eggshell thickness (by 16.9%, P < 0.01) and albumen height (by 4.5%, P = 0.042). Meanwhile, feeding with 0.625 and 2.5 mg MEL/kg diets could significantly increase serum levels of aspartic acid, threonine, serine, glutamic acid, glycine, alanine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, and proline. Furthermore, a 0.625 mg MEL/kg diets could significantly increase the expression of PepT1 (by 3949.9%), B⁰AT (by 6045.9%), b^{0, +}AT (by 603.5%), and EAAT3 (by 412.7%) in the jejunum. Additionally, in the cultured intestinal crypt "organoids," treatment with 0.5 μM MEL could significantly enhance the expression of PepT1, b^{0, +}AT and EAAT3 mRNAs by 35.4%, 110.0%, and 160.1%, respectively. Detection of MEL concentration in serum and intestinal fluid suggested that lower dosage of MEL feeding was mainly acted on intestine locally, and further increased intestinal antioxidases (GPx-3, SOD-1 or PRDX-3) mRNA expression. Taken together, we demonstrated that MEL feeding in laying hens could locally promote the expression and function of AA transporter in small intestine by up-regulating antioxidases expression, and finally elevate laying performance.

Effects of dietary supplementation with tribasic zinc sulfate or zinc sulfate on growth performance, zinc content and expression of zinc transporters in young pigs

An experiment was conducted to compare the effects of zinc sulfate (ZS) and tribasic zinc sulfate (TBZ) as sources of supplemental zinc on growth performance, serum zinc (Zn) content and messenger RNA (mRNA) expression of Zn transporters (ZnT1/ZnT2/ZnT5/ZIP4/DMT1) of young growing pigs. A total of 96 Duroc × Landrace × Yorkshire pigs were randomly allotted to two treatments and were fed a basal diet supplemented with 100 mg/kg Zn from either ZS or TBZ for 28 days. Feed : gain ratio in pigs fed TBZ were lower (P < 0.05) than pigs fed ZS, and average daily weight gain tended to increase (0.05 ≤ P ≤ 0.10) in pigs fed TBZ. Compared with pigs fed ZS, pigs fed TBZ had a higher CuZn-superoxide dismutase and Zn content in serum (P < 0.05) while they had a lower Zn content in feces (P < 0.05). In addition, ZIP4 mRNA expression of zinc transporter in either duodenum or jejunum of pigs fed TBZ were higher (P < 0.05) than pigs fed ZS. These results indicate that TBZ is more effective in serum Zn accumulation and intestinal Zn absorption, and might be a potential substitute for ZS in young growing pigs.