Zinc-containing yeast extract promotes nonrapid eye movement sleep in mice

Effects of zinc supplementation on sleep quality in humans: A systematic review of randomized controlled trials

Background and Aims

Alternative therapies, such as zinc supplementation, have been explored as potential interventions for sleep disorders. However, the efficacy of zinc supplementation in improving sleep quality remains uncertain. This systematic review aims to examine the impacts of zinc supplementation on sleep quality in humans.

Methods

The Web of Science, Medline, Scopus, and Google Scholar databases were comprehensively searched to find studies investigating the effect of zinc supplementation on sleep quality. After identifying relevant studies by screening, relevant data were extracted from them. The quality assessment was conducted using the Cochrane quality assessment tool.

Results

This systematic review included eight studies. The interventions ranged from 4 to 48 weeks, with a daily dose of zinc supplementation varying between 10 and 73.3 mg. The majority of the evidence examined in this review pointed to the significant improvement effect of zinc supplementation on sleep quality in adults compared to the control groups. Furthermore, zinc supplementation did not have a significant effect on sleep disorders. However, there was no consensus about these findings. Also, the effect of supplementation on sleep duration in nonadults was contradictory.

Conclusions

This systematic review suggests that zinc supplementation may lead to improvements in sleep quality. However, more research, primarily clinical trials, is needed to clarify the beneficial effects of zinc supplementation on sleep quality with consideration of dietary zinc intake and the Recommended Dietary Allowances of zinc (RDA) in the different populations. It is also recommended to investigate the effect of zinc supplementation on sleep quality in people with zinc deficiency in future studies.

Toxicity of zinc oxide nanoparticles: Cellular and behavioural effects

Due to their extensive use, the release of zinc oxide nanoparticles (ZnO NP) into the environment is increasing and may lead to unintended risk to both human health and ecosystems. Access of ZnO NP to the brain has been demonstrated, so their potential toxicity on the nervous system is a matter of particular concern. Although evaluation of ZnO NP toxicity has been reported in several previous studies, the specific effects on the nervous system are not completely understood and, particularly, effects on genetic material and on organism behaviour are poorly addressed. We evaluated the potential toxic effects of ZnO NP in vitro and in vivo, and the role of zinc ions (Zn2+) in these effects. In vitro, the ability of ZnO NP to be internalized by A172 glial cells was verified, and the cytotoxic and genotoxic effects of ZnO NP or the released Zn2+ ions were addressed by means of vital dye exclusion and comet assay, respectively. In vivo, behavioural alterations were evaluated in zebrafish embryos using a total locomotion assay. ZnO NP induced decreases in viability of A172 cells after 24 h of exposure and genetic damage after 3 and 24 h. The involvement of the Zn2+ ions released from the NP in genotoxicity was confirmed. ZnO NP exposure also resulted in decreased locomotor activity of zebrafish embryos, with a clear role of released Zn2+ ions in this effect. These findings support the toxic potential of ZnO NP showing, for the first time, genetic effects on glial cells and proving the intervention of Zn2+ ions.

Novel and safe debranched starch-zinc complexes with endoconcave structure as zinc supplements

Zinc deficiency is a serious risk to human health and growth, especially in children. The development of zinc supplements can effectively reduce this harm. Here, a series of debranched starch‑zinc complexes (DS-Zn) were prepared, whose zinc complexation was inversely proportional to the amylopectin content in the debranched starch (DS). The physicochemical properties of DS-Zn were characterized using the conductivity, XRD, iodine staining and thermogravimetry. Combined with XPS, solid-state 13C NMR and IR, it was elucidated that the structure of DS-Zn is endoconcave structure with 2-O and 3-O of DS on the inner side and 6-O of DS on the outer side, where zinc is located. The DS-Zn exhibits good biosafety including blood, cellular and mutagenicity. In vitro simulations of digestion and zinc-deficient cellular models showed that DS-Zn was more tolerant to the gastrointestinal environment and more effective in zinc supplementation (increased by 33 %) than inorganic zinc supplements. Utilizing the compressibility of starch, DS-Zn was prepared as a more palatable oral cartoon tablet for children. This study will provide important support to advance the development and application of novel starch-based zinc nutritional supplements.

Examining the role of micronutrients on improving long COVID sleep-related symptoms

AIMS AND OBJECTIVES

Long COVID is defined as the continuation of symptoms for four or more weeks after initial contraction of the virus. This review article examines the role of four select micronutrients (zinc, vitamins C, D and polyphenols) for their anti-inflammatory and therapeutic potential to improve sleep-related symptoms in persons with long COVID.

BACKGROUND

Evidence suggests a link between long COVID and increased inflammation. There are currently no therapeutic interventions for common sleep-related symptoms associated with long COVID. Micronutrients, due to their antioxidant and anti-inflammatory properties, may have a role in the treatment of sleep-related symptoms in the context of long COVID.

DESIGN

A narrative literature review was conducted and guided by the PRISMA checklist.

METHODS

All articles were screened from PubMed, ScienceDirect, NCBI or Google Scholar and were limited to human studies. The following keywords were used: 'COVID-19', 'sleep symptoms', 'zinc', 'vitamin C', 'vitamin D', 'polyphenols' and 'micronutrients'.

RESULTS

There are currently no studies that examine the usage of micronutrients and its impacts on long-term, sleep-related symptoms post-COVID-19 infection. We focussed our review on prior studies that examined micronutrients in the context of sleep symptoms and inflammation, while exploring the potential for micronutrients to help improve sleep-related symptoms associated with long COVID.

CONCLUSIONS

There is evidence to suggest that sleep-related symptoms associated with long COVID, such as fatigue and poor sleep quality, are associated with inflammation. Zinc, vitamins C, D and polyphenols all have the potential to improve both inflammation and sleep quality to alleviate symptoms. Future research should further examine these micronutrients in the context of long COVID to improve sleep and quality of life.

RELEVANCE TO CLINICAL PRACTICE

This article provides implications for clinicians to be at the forefront of research on the usage of micronutrients to improve sleep-related symptoms in persons with long COVID.

Effect of zinc supplement on sleep quality in older adults: A randomized clinical trial study

Introduction/Aim: The use of macronutrient and micronutrient foods is associated with the duration of sleep. This study aimed to determine the effect of zinc supplements on the sleep quality of older adults. Methods: The current parallel randomized clinical trial study was performed using a convenience sampling method. One hundred and fifty older adults who met the inclusion criteria were assigned to intervention and control group. The participants in the intervention group received a daily dose of 30 mg zinc supplementation pill for 70 days and the control group did not receive any supplement. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). Serum zinc level in both groups was measured through the auto-analysis method. The questionnaire was completed and the serum level of zinc was measured twice, before the intervention and 70 days after the intervention. Results: Both groups were homogeneous in terms of demographic variables, sleep quality, and serum zinc level before the intervention. Of all, 73.3% of older adults in the intervention group and 74.7% of older adults in the control group had poor sleep quality. Sleep quality in the intervention group, as compared with the control group, significantly improved after the intervention. Furthermore, serum zinc levels in older adults in the intervention group, as compared with the control group, significantly increased after the intervention. Conclusion: Based on the results of this study, it is recommended to utilize zinc supplementation as a new therapeutic approach for improving sleep quality in older adults.

Wheel-Running Behavior Is Negatively Impacted by Zinc Administration in a Novel Dual Transgenic Mouse Model of AD

Alzheimer's disease (AD) is a neurocognitive disorder that impacts both the brain and behavior. Metal ions, including zinc (Zn), have been seen to play an important role in AD-related pathology. In this study, we show alterations in wheel-running behavior both early and late in disease progression in a novel dual Tg mouse model of AD. This mouse includes both amyloid and tau pathology through its cross with the J20 (hAPP) and P301L (Tau) parentage. Animals were given either lab water or water that had been supplemented with 10 ppm Zn. Wheel running was assessed through individually housing mice and measuring wheel-running activity in both the light and dark cycles. Dual Tg mice showed significantly less activity in the first part of the dark cycle than WT mice at both 3.5 and 7 months of age (p < 0.05). Dual Tg mice given Zn water showed less activity compared to dual Tg mice on lab water, tau mice on Zn water, or WT mice given either lab or Zn water (p < 0.05) at 7 months. Female mice in this study consistently showed higher activity compared to male mice in all groups whereas Zn led to reduced activity. Daily activity rhythm was altered in both the tau and dual Tg mice, and Zn impacted this alteration through effects on amyloid, tau, and through circadian pathways.

Low energy intake and dietary quality are associated with low objective sleep quality in young Japanese women

Literature reports suggest that subjective sleep quality is associated with nutrient intake in elderly people and workers. However, few studies have suggested an association between objective sleep quality and dietary intake in adolescents and young women. We hypothesized that objective sleep quality is associated with dietary intake in adolescents and young women. We evaluated the association between energy and nutrient intake and objective sleep quality in adolescents and young Japanese women. In a cross-sectional study of 80 women aged 18-27 years, dietary intake was assessed using the self-administered diet history questionnaire. Objective sleep quality was assessed by actigraphy. Lifestyle characteristics, dietary habits, and mental health were assessed using specific questionnaires. Subjects were classified into 3 groups according to sleep efficiency (SE <80%, 80%-85%, and ≥85%), and the relationships between dietary intake and objective sleep quality were statistically evaluated. No significant differences occurred in lifestyle characteristics, physical activity levels, eating behavior, and mental health status among the 3 SE groups. Energy intake was significantly lower in the low-SE group than in the middle- (P = .004) and high- (P = .015) SE groups. Protein intake was significantly lower in the low-SE group than in the high-SE group (P = .034). The mean energy-adjusted intakes of vitamin K, vitamin B₂, potassium, magnesium, iron, zinc, copper, and tryptophan were significantly lower in the low-SE group than in the high-SE group. Adequate energy intake and a high-quality diet including vitamins, minerals, and tryptophan may result in high sleep quality and help prevent sleep problems.

Zinc deficiency causes delayed ATP clearance and adenosine generation in rats and cell culture models

Zinc deficiency causes myriad pathophysiological symptoms, but why distinct phenotypes are generated by zinc deficiency remains unclear. Considering that several ectoenzymes involved in purinergic signaling through extracellular adenine-nucleotide hydrolysis possess zinc ions in their active sites, and disorders in purinergic signaling result in diverse diseases that are frequently similar to those caused by zinc deficiency, herein we examine whether zinc deficiency affects extracellular adenine-nucleotide metabolism. Zinc deficiency severely impairs the activities of major ectoenzymes (ENPP1, ENPP3, NT5E/CD73, and TNAP), and also strongly suppresses adenine-nucleotide hydrolysis in cell-membrane preparations or rat plasma, thereby increasing ATP and ADP levels and decreasing adenosine levels. Thus, zinc deficiency delays both extracellular ATP clearance and adenosine generation, and zinc modulates extracellular adenine-nucleotide metabolism. Since the finely tuned balance between extracellular adenine nucleotides and adenosine is critical for purinergic signaling, these findings provide a novel insight into why zinc deficiency results in diverse symptoms.

Taka-aki Takeda et al. find that zinc deficiency impairs adenine nucleotide metabolism in both cell and rat models leading to delays in extracellular ATP clearance and adenosine generation. The results show that zinc deficiency affects purinergic signaling and may explain why zinc deficiency in humans results in diverse symptoms.

Dietary Zinc Acts as a Sleep Modulator

While zinc is known to be important for many biological processes in animals at a molecular and physiological level, new evidence indicates that it may also be involved in the regulation of sleep. Recent research has concluded that zinc serum concentration varies with the amount of sleep, while orally administered zinc increases the amount and the quality of sleep in mice and humans. In this review, we provide an exhaustive study of the literature connecting zinc and sleep, and try to evaluate which molecular mechanism is likely to be involved in this phenomenon. A better understanding should provide critical information not only about the way zinc is related to sleep but also about how sleep itself works and what its real function is.

Metals and Circadian Rhythms

Circadian rhythms describe the behavioral and physiological changes that occur in living organisms in order to attune to a 24 hour cycle of day and night. The most striking aspect of circadian function is the sleep-wake cycle, however many other physiological processes are regulated in 24 hour oscillations, including blood pressure, body temperature, appetite, urine production, and the transcription and translation of thousands of circadian dependent genes. Circadian disruption and sleep disorders are strongly connected to neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, and Huntington's disease as well as others. Metal exposures have been implicated in neurodegenerative diseases, in some cases involving metals that are essential micronutrients but are toxic at high levels of exposure (such as manganese, copper, and zinc), and in other cases involving metals that have no biological role but are toxic to living systems (such as lead, mercury, and aluminum). In this review, we examine the evidence for circadian and sleep disorders with exposures to these metals and review the literature for possible mechanisms. We suggest that giving the aging population, the prevalence of environmental exposures to metals, and the increasing prevalence of neurodegenerative disease in the aged, more research into the mechanisms of circadian disruption subsequent to metal exposures is warranted.

Oral administration of Japanese sake yeast (Saccharomyces cerevisiae sake) promotes non-rapid eye movement sleep in mice via adenosine A2A receptors

We have demonstrated previously that Japanese sake yeast improves sleep quality in humans. In the present study, we examined the molecular mechanisms of sake yeast to induce sleep by monitoring locomotor activity, electromyogram and electroencephalogram in mice. Oral administration of Japanese sake yeast (100, 200, and 300 mg kg^-1 ) decreased the locomotor activity by 18, 46 and 59% and increased the amount of non-rapid eye movement (NREM) sleep by 1.5-, 2.3- and 2.4-fold (to 37 ± 6, 57 ± 8, and 60 ± 4 min from 25 ± 6 min in the vehicle-administered group, respectively) in a dose-dependent manner for 4 h after oral administration. However, Japanese sake yeast did not change the amount of rapid eye movement (REM) sleep, the electroencephalogram power density during NREM sleep or show any adverse effects, such as rebound of insomnia, during 24 h postadministration and on the next day. An intraperitoneal pretreatment with an adenosine A_2A receptor-selective antagonist, ZM241385 (15 mg kg^-1 ), reduced the amount of NREM sleep of sake yeast-administered mice to the basal level, without changing basal amount of sleep. Conversely, an A₁ receptor-selective antagonist, 8-cyclopentyltheophylline (10 mg kg^-1 ), did not affect the sleep-promoting effect of Japanese sake yeast. Thus, Japanese sake yeast promotes NREM sleep via activation of adenosine A_2A but not A₁ receptors.