Zinc deficiency and supplementation in autism spectrum disorder and Phelan-McDermid syndrome

Exploring potential mechanisms for zinc deficiency to impact in autism spectrum disorder: a narrative review

Autism spectrum disorder (ASD) is a heterogeneous and complex group of life-long neurodevelopmental disorders. How this clinical condition impacts an individual's intellectual, social and emotional capacities, contributing to alterations in the proprioceptive and sensory systems and increasing their selective attitude towards food, is well described in the literature. This complex condition or status exposes individuals with ASD to an increased risk of developing overweight, obesity and non-communicable diseases compared with the neurotypical population. Moreover, individuals with ASD are characterised by higher levels of inflammation, oxidative stress markers and intestinal dysbiosis. All these clinical features may also appear in zinc deficiency (ZD) condition. In fact, zinc is an essential micronutrient for human health, serving as a structural, catalytic and regulatory component in numerous physiological processes. The aim of this narrative review is to explore role of ZD in ASD. Factors affecting zinc absorption, excretion and dietary intake in this vulnerable population are taken into consideration. Starting from this manuscript, the authors encourage future research to investigate the role of ZD in ASD. The perspective is to potentially find another missing piece in the 'ASD clinical puzzle picture' to improve the health status of these individuals.

Differential effectiveness of dietary zinc supplementation with autism-related behaviours in Shank2 knockout mice

The family of SHANK proteins have been shown to be critical in regulating glutamatergic synaptic structure, function and plasticity. SHANK variants are also prevalent in autism spectrum disorders (ASDs), where glutamatergic synaptopathology has been shown to occur in multiple ASD mouse models. Our previous work has shown that dietary zinc in Shank3-/- and Tbr1+/- ASD mouse models can reverse or prevent ASD behavioural and synaptic deficits. Here, we have examined whether dietary zinc can influence behavioural and synaptic function in Shank2-/- mice. Our data show that dietary zinc supplementation can reverse hyperactivity and social preference behaviour in Shank2-/- mice, but it does not alter deficits in working memory. Consistent with this, at the synaptic level, deficits in NMDA/AMPA receptor-mediated transmission are also not rescued by dietary zinc. In contrast to other ASD models examined, we observed that SHANK3 protein was highly expressed at the synapses of Shank2-/- mice and that dietary zinc returned these to wild-type levels. Overall, our data show that dietary zinc has differential effectiveness in altering ASD behaviours and synaptic function across ASD mouse models even within the Shank family. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Postnatal zinc deficiency due to giardiasis disrupts hippocampal and cerebellar development

BACKGROUND

Giardiasis and zinc deficiency have been identified as serious health problems worldwide. Although Zn depletion is known to occur in giardiasis, no work has investigated whether changes occur in brain structures.

METHODS

Three groups of gerbils were used: control (1), orogastrically inoculated on day 3 after birth with trophozoites of two isolates of Giardia intestinalis (HGINV/WB) group (2 and 3). Estimates were made at five ages covering: establishment of infection, Giardia population growth, natural parasite clearance and a post-infection age. QuantiChrome zinc assay kit, cresyl violet staining and TUNEL technique were used.

RESULTS

A significant decrease (p<0.01) in tissue zinc was observed and persisted after infection. Cytoarchitectural changes were observed in 75% of gerbils in the HGINV or WB groups. Ectopic pyramidal neurons were found in the cornus ammonis (CA1-CA3). At 60 and 90 days of age loss of lamination was clearly visible in CA1. In the dentate gyrus (DG), thinning of the dorsal lamina and abnormal thickening of the ventral lamina were observed from 30 days of age. In the cerebellum, we found an increase (p<0.01) in the thickness of the external granular layer (EGL) at 14 days of age that persisted until day 21 (C 3 ± 0.3 μm; HGINV 37 ± 5 μm; WB 28 ± 3 μm); Purkinje cell population estimation showed a significant decrease; a large number of apoptotic somas were observed scattered in the molecular layer; in 60 and 90 days old gerbils we found granular cell heterotopia and Purkinje cell ectopia. The pattern of apoptosis was different in the cerebellum and hippocampus of parasitized gerbils.

CONCLUSION

The morphological changes found suggest that neuronal migration is affected by zinc depletion caused by giardiasis in early postnatal life; for the first time, the link between giardiasis-zinc depletion and damaged brain structures is shown. This damage may explain the psychomotor/cognitive delay associated with giardiasis. These findings are alarming. Alterations in zinc metabolism and signalling are known to be involved in many brain disorders, including autism.

Gastrointestinal Dysfunction in Genetically Defined Neurodevelopmental Disorders

Gastrointestinal symptoms are common in most forms of neurodevelopment disorders (NDDs) such as in autism spectrum disorders (ASD). The current patient-reported outcome measures with validated questionnaires used in the general population of children without NDDS cannot be used in the autistic individuals. We explore here the multifactorial pathophysiology of ASD and the role of genetics and the environment in this disease spectrum and focus instead on possible diagnostics that could provide future objective insight into the connection of the gut-brain-microbiome in this disease entity. We provide our own data from both humans and a zebrafish model of ASD called Phelan-McDermid Syndrome. We hope that this review highlights the gaps in our current knowledge on many of these profound NDDs and that it provides a future framework upon which clinicians and researchers can build and network with other interested multidisciplinary specialties.

Independent Associated SNPs at SORCS3 and Its Protein Interactors for Multiple Brain-Related Disorders and Traits

Sortilin-related vacuolar protein sorting 10 (VPS10) domain containing receptor 3 (SORCS3) is a neuron-specific transmembrane protein involved in the trafficking of proteins between intracellular vesicles and the plasma membrane. Genetic variation at SORCS3 is associated with multiple neuropsychiatric disorders and behavioural phenotypes. Here, we undertake a systematic search of published genome-wide association studies to identify and catalogue associations between SORCS3 and brain-related disorders and traits. We also generate a SORCS3 gene-set based on protein-protein interactions and investigate the contribution of this gene-set to the heritability of these phenotypes and its overlap with synaptic biology. Analysis of association signals at SORSC3 showed individual SNPs to be associated with multiple neuropsychiatric and neurodevelopmental brain-related disorders and traits that have an impact on the experience of feeling, emotion or mood or cognitive function, while multiple LD-independent SNPs were associated with the same phenotypes. Across these SNPs, alleles associated with the more favourable outcomes for each phenotype (e.g., decreased risk of neuropsychiatric illness) were associated with increased expression of the SORCS3 gene. The SORCS3 gene-set was enriched for heritability contributing to schizophrenia (SCZ), bipolar disorder (BPD), intelligence (IQ) and education attainment (EA). Eleven genes from the SORCS3 gene-set were associated with more than one of these phenotypes at the genome-wide level, with RBFOX1 associated with SCZ, IQ and EA. Functional annotation revealed that the SORCS3 gene-set is enriched for multiple ontologies related to the structure and function of synapses. Overall, we find many independent association signals at SORCS3 with brain-related disorders and traits, with the effect possibly mediated by reduced gene expression, resulting in a negative impact on synaptic function.

Assessment of the Roles of Magnesium and Zinc in Clinical Disorders

The ability and facility of magnesium (Mg2+) and zinc (Zn2+) to interact with phosphate ions confer them the characteristics of essential trace elements. Trace elements are extremely necessary for the basic nucleic acid chemistry of cells of all known living organisms. More than 300 enzymes require zinc and magnesium ions for their catalytic actions, including all the enzymes involved in the synthesis of ATP. In addition, enzymes such as isomerases, oxidoreductases, lyases, transferases, ligases and hydrolases that use other nucleotides to synthesize DNA and RNA require magnesium and zinc. These nucleotides may trigger oxidative damage or important changes against free radicals. In the same way, nucleotides may play an important role in the pathophysiology of degenerative diseases, including in some clinical disorders, where vascular risk factors, oxidative stress and inflammation work to destabilize the patients` homeostatic equilibrium. Indeed, reduced levels of zinc and magnesium may lead to inadequate amount of antioxidant enzymes, and thus, acts as an important contributing factor for the induction of oxidative stress leading to cellular or tissue dysfunction. Hence, the development of zinc or magnesium enzyme inhibitors could be a novel opportunity for the treatment of some human disorders. Therefore, the objective of the present work was to assess the clinical benefits of zinc and magnesium in human health and their effects in some clinical disorders.

Experiences surrounding the diagnostic process and care among parents of children diagnosed with Phelan-McDermid syndrome: A qualitative study

AIM

To explore the experience of parents of children diagnosed with Phelan-McDermid syndrome (PMS) with regard to the diagnostic process, treatment, and medical care.

METHOD

A qualitative descriptive study was conducted. Participants were recruited using non-probabilistic purposeful sampling. In total, 32 parents with children with PMS were included. In-depth interviews and researcher field notes were used. An inductive thematic analysis was performed.

RESULTS

Five themes were identified: (1) the 'diagnostic process' describes the diagnostic process and how it is communicated to the parents; (2) 'treatment and expectations' describes the expectations and hopes placed on future treatment; (3) 'family planning' describes how parents deal with genetic counselling when planning to have more children after a diagnosis of PMS; (4) 'the world of disability' describes the entry of parents into an environment of dependency and disability after the diagnosis; (5) 'family's financial situation' highlights the financial difficulties due to the high cost of therapies and daily care products.

INTERPRETATION

Our results provide insight on how a diagnosis of PMS and its consequences are experienced by parents of children with PMS. These results can be used by health professionals to help and support parents.

Identification of a Novel SHANK2 Pathogenic Variant in a Patient with a Neurodevelopmental Disorder

Genetic defects in the SHANK2 gene, encoding for synaptic scaffolding protein, are associated with a variety of neurodevelopmental conditions, including autism spectrum disorders and mild to moderate intellectual disability. Until now, limited patient clinical descriptions have been published. Only 13 unrelated patients with SHANK2 pathogenic variations or microdeletions have been reported worldwide. By Exome Sequencing, we identified a de novo stop-gain variant, c.334C>T, p.(Gln112*), in an Italian patient with a neurodevelopmental disorder. The patient (9 years old) presented the following facial features: a flat profile, thick eyebrows, long eyelashes, a bulbous nasal tip and a prominent columella, retracted ears, dental anomalies. The patient showed speech delay and mild neuromotor delay but not autism spectrum disorder. In conclusion, this patient with a novel pathogenic variant in SHANK2 enlarges the phenotypic spectrum of SHANK2-mutated patients and demonstrates that the severity of SHANK2-associated disorders is highly variable.