An update of the zinc deficiency theory of schizophrenia. Identification of the sex determining system as the site of action of reproductive zinc deficiency

Marginal Zinc Deficiency during Gestation and Lactation in Rats Affects Oligodendrogenesis, Motor Performance, and Behavior in the Offspring

BACKGROUND

Oligodendrocytes are responsible for myelin production in the central nervous system (CNS). Hypomyelination may slow saltatory nerve signal conduction and affect motor performance and behavior in adults. Gestational marginal zinc deficiency in rats significantly decreases proliferation of neural stem cells (NSCs) in the offspring brain.

OBJECTIVES

Given that NSCs are precursors of oligodendrocytes, this study investigated if marginal zinc deficiency during early development in rats affects oligodendrogenesis in the offspring's CNS.

METHODS

Rat dams were fed an adequate (25 μg zinc/g diet) (C) or a marginal zinc diet (MZD) (10 μg zinc/g diet), from gestation day zero until postnatal day (P) 20, and subsequently all offspring was fed the control diet until P60. Oligodendrogenesis was evaluated in the offspring at P2, P5, P10, P20, and P60, by measuring parameters of oligodendrocyte progenitor cells (OPCs) proliferation, differentiation, maturation, and of myelination.

RESULTS

The expression of 1) proteins that regulate OPC proliferation (Shh, Sox10, Olig2); 2) OPC markers (NG2, PDGFRα); 3) myelin proteins (MBP, MAG, MOG, PLP) were lower in the brain cortex from MZD than C offspring at various stages in development. The amount of myelin after zinc replenishment continued to be low in the MZD young adult at P60. Accordingly, parameters of motor performance and behavior [grip strength, rotarod, elevated T-maze (ETM), and open-field tests] were impaired in the MZD offspring at P60.

CONCLUSIONS

Results support the concept that maternal and early postnatal exposure to MZD affects oligodendrogenesis causing long-lasting effects on myelination and on motor performance in the young adult offspring.

Zinc deficiency as a possible risk factor for increased susceptibility and severe progression of Corona Virus Disease 19

The importance of Zn for human health becomes obvious during Zn deficiency. Even mild insufficiencies of Zn cause alterations in haematopoiesis and immune functions, resulting in a proinflammatory phenotype and a disturbed redox metabolism. Although immune system malfunction has the most obvious effect, the functions of several tissue cell types are disturbed if Zn supply is limiting. Adhesion molecules and tight junction proteins decrease, while cell death increases, generating barrier dysfunction and possibly organ failure. Taken together, Zn deficiency both weakens the resistance of the human body towards pathogens and at the same time increases the danger of an overactive immune response that may cause tissue damage. The case numbers of Corona Virus Disease 19 (COVID-19) are still increasing, which is causing enormous problems for health systems and economies. There is an urgent need to reduce both the number of severe cases and the resulting deaths. While therapeutic options are still under investigation, and first vaccines have been approved, cost-effective ways to reduce the likelihood of or even prevent infection, and the transition from mild symptoms to more serious detrimental disease, are highly desirable. Nutritional supplementation might be an effective option to achieve these aims. In this review, we discuss known Zn deficiency effects in the context of an infection with Severe Acute Respiratory Syndrome-Coronavirus-2 and its currently known pathogenic mechanisms and elaborate on how severe pre-existing Zn deficiency may pre-dispose patients to a severe progression of COVID-19. First published clinical data on the association of Zn homoeostasis with COVID-19 and registered studies in progress are listed.

Trace elements in schizophrenia: a systematic review and meta-analysis of 39 studies (N = 5151 participants)

Context

The pathogenesis of schizophrenia appears to be multifaceted.

Objective

The aim of this meta-analysis of studies that investigated blood and hair concentrations of trace elements in people diagnosed with schizophrenia was to determine whether levels of trace elements in patients with schizophrenia differ from those in healthy individuals.

Data Sources

The PubMed, Scopus, and Web of Science databases were searched to January 2018.

Study Selection

Studies that compared concentrations of trace elements in patients with schizophrenia with those in healthy controls, in patients with schizophrenia under different treatment regimens, or in patients with schizophrenia at different stages of disease were included.

Data Extraction

Data on study and sample characteristics and measures of trace elements were extracted.

Results

Thirty-nine studies with a total of 5151 participants were included. Meta-analysis of combined plasma and serum data showed higher levels of copper, lower levels of iron, and lower levels of zinc among patients with schizophrenia vs controls without schizophrenia. Subgroup analyses confirmed the following: higher levels of copper in plasma, in users of typical antipsychotic drugs, and in males; lower levels of zinc in serum, in patients in Asia, in drug-naive/drug-free patients, and in inpatients; lower levels of iron in serum, in patients in Asia, in drug-naive/drug-free patients, in patients on antipsychotic drugs, in inpatients, in patients with acute or newly diagnosed schizophrenia, in patients with chronic or previously diagnosed schizophrenia, and in males; and lower levels of manganese in plasma and in patients with chronic or previously diagnosed schizophrenia.

Conclusions

This meta-analysis provides evidence of an excess of copper, along with deficiencies of zinc, iron, and manganese, in patients with schizophrenia.

Zinc and the ERK kinases in the developing brain

This article reviews evidence in support of the hypothesis that impaired activation of the extracellular signal-regulated kinases (ERK1/2) contributes to the disruptions in neurodevelopment associated with zinc deficiency. These kinases are implicated in major events of brain development, including proliferation of progenitor cells, neuronal migration, differentiation, and apoptotic cell death. In humans, mutations in ERK1/2 genes have been associated with neuro-cardio-facial-cutaneous syndromes. ERK1/2 deficits in mice have revealed impaired neurogenesis, altered cellularity, and behavioral abnormalities. Zinc is an important modulator of ERK1/2 signaling. Conditions of both zinc deficiency and excess affect ERK1/2 phosphorylation in fetal and adult brains. Hypophosphorylation of ERK1/2, associated with decreased zinc availability in cell cultures, is accompanied by decreased proliferation and an arrest of the cell cycle at the G0/G1 phase. Zinc and ERK1/2 have both been shown to modulate neural progenitor cell proliferation and cell death in the brain. Furthermore, behavioral deficits resulting from developmental zinc deficiency are similar to those observed in mice with decreased ERK1/2 signaling. For example, impaired performance on behavioral tests of learning and memory; such as the Morris water maze, fear conditioning, and the radial arm maze; has been reported in both animals exposed to developmental zinc deficiency and transgenic mice with decreased ERK signaling. Future study should clarify the mechanisms through which a dysregulation of ERK1/2 may contribute to altered brain development associated with dietary zinc deficiency and with conditions that limit zinc availability.

Neurobiological plausibility of prenatal nutritional deprivation as a risk factor for schizophrenia

Emerging evidence indicates that schizophrenia may in some cases be a neurodevelopmental disorder, resulting in part from the effects of prenatal exposures. Studies by our group have focused attention on the potential role of prenatal nutritional deficiency as a potential etiological factor. Therefore, we sought to examine the biological plausibility of prenatal nutritional deprivation in the etiopathogenesis of schizophrenia. We conducted a review of the pertinent literature. Four lines of evidence support prenatal nutritional deficiencies as a plausible set of risk factors for schizophrenia: a) their effects are not incompatible with the epidemiology of schizophrenia; b) they have adverse effects on brain development; c) general malnutrition results in neuropathological anomalies of brain regions implicated in schizophrenia; and d) prenatal malnutrition affects maternal systems critical to the developing fetal nervous system. There is sufficient evidence to warrant further studies of prenatal nutritional deficits as risk factors for schizophrenia. A strategy for testing these hypotheses is outlined.

Sunspots and the recency theory of schizophrenia

Schizophrenia, a disorder with a high, fairly uniform, global distribution, can occur with or without an accompanying family history of mental disorder. Given the preponderance of sporadic cases and the low fertility of genetic cases, this combination suggests that the disorder might be caused by a globally active teratogen. It has recently been shown that some factor associated with high sunspot activity acts transgenerationally to reduce lifespan. The following article discusses the relevance of that finding to changes in the incidence of schizophrenia and suggests that schizophrenia is caused by some factor associated with sunspots.