Effects of long-term transcutaneous auricular vagus nerve stimulation on circadian vagal activity in people with Prader-Willi Syndrome: A case-series.

BACKGROUND: Prader-Willi Syndrome (PWS) is a genetic neurodevelopmental disorder marked by disruptions in circadian rhythms and autonomic nervous system (ANS) activity, hyperphagia, and episodes of emotional outbursts. Previous trials suggest that both invasive and non-invasive vagus nerve stimulation (VNS) can reduce emotional outbursts in PWS, potentially through its effects on vagal activity. AIM: This case series investigated the effects of transcutaneous auricular VNS (taVNS) on cardiac markers of circadian vagal activity, specifically heart rate variability (HRV) and heart rate (HR), and their potential links to improvements in emotional outbursts. METHODS: Five individuals with PWS (mean age: 26.9 years; 3 males, 2 females) received four hours of daily taVNS for 12 months, followed by one month of two-hour daily sessions. Outcome measures included daily recording of emotional outbursts and every three months 24-h HRV and HR recordings. Mixed cosinor models were applied to analyze changes in circadian rhythms of HRV and HR. A linear mixed model was used to assess the predictive value of cardiac vagal activity on emotional outbursts. RESULTS: Circadian amplitudes of HRV and HR were significantly higher at the end of the treatment compared to baseline (all p's < .01). There was a significant increase in the rhythm-adjusted mean of HRV (p < .01), while the rhythm-adjusted HR mean significantly decreased, both indicating increased cardiac vagal activity. Higher rhythm-adjusted mean HRV predicted a lower number of emotional outbursts. CONCLUSION: The results suggest that taVNS may be effective by targeting ANS activity in individuals with PWS, contributing to improvements in behavioral regulation.

Prader-Willi syndrome: guidance for children and transition into adulthood.

Prader-Willi syndrome (PWS) is a rare orphan disease and complex genetic neurodevelopmental disorder, with a birth incidence of approximately 1 in 10,000-30,000. Management of people with PWS requires a multi-disciplinary approach, ideally through a multi-disciplinary team (MDT) clinic with community support. Hypotonia, poor feeding and faltering growth are characteristic features in the neonatal period, followed by hyperphagia and risk of rapid weight gain later in childhood. Children and adolescents (CA) with PWS usually display developmental delay and mild learning disability and can develop endocrinopathies, scoliosis, respiratory difficulties (both central and obstructive sleep apnoea), challenging behaviours, skin picking, and mental health issues, especially into adulthood. This consensus statement is intended to be a reference document for clinicians managing children and adolescents (up to 18 years of age) with PWS. It considers the bio-psycho-social domains of diagnosis, clinical assessment, and management in the paediatric setting as well as during and after transition to adult services. The guidance has been developed from information gathered from peer-reviewed scientific reports and from the expertise of a range of experienced clinicians in the United Kingdom and Ireland involved in the care of patients with PWS.

Psychotic illness in people with Prader-Willi syndrome: a systematic review of clinical presentation, course and phenomenology.

BACKGROUND: Prader-Willi syndrome (PWS) is a rare and complex neurodevelopmental disorder resulting from absent paternal expression of maternally imprinted genes at chromosomal locus 15q11-13. This absence of expression occurs as a consequence of a deletion on the chromosome 15 of paternal origin (ca. 70%), a chromosome 15 maternal uniparental disomy (mUPD; ca. 25%), or an imprinting centre defect (IC; ca. 1-3%). At birth, individuals with PWS are severely hypotonic and fail to thrive. Hyperphagia and characteristic physical and neuropsychiatric phenotypes become apparent during childhood. The risk for the development of a co-morbid psychotic illness increases during the teenage years, specifically in those with PWS due to the presence of an mUPD. The primary aim of this literature review is to inform clinical practice. To achieve this, we have undertaken a systematic analysis of the clinical research literature on prevalence, presentation, course, characteristics, diagnosis and treatment of psychotic illness in people with PWS. The secondary aim is to identify clinical aspects of psychotic illness in PWS in need of further investigation. METHODS AND FINDINGS: A systematic literature review on psychosis in PWS was conducted on the databases Web of Knowledge, PubMed and Scopus, using the terms "((Prader-Willi syndrome) OR (Prader Willi Syndrome)) AND ((psychosis) OR (psychotic illness))". All articles written in English and reporting original human research were reviewed. In all but three of the 16 cohort studies in which the genetic types were known, the authors reported higher rates of psychosis in people with PWS resulting from an mUPD, compared to those with the deletion subtype of PWS. When psychosis was present the presentation was psychosis similar regardless of genetic type and was usually characterised by an acute onset of hallucinations and delusions accompanied by confusion, anxiety and motor symptoms. CONCLUSIONS: The onset of confusion, an affective cyclical pattern with the presence of abnormal mental beliefs and experiences, usually of rapid onset is suggestive of the development of psychotic illness. Phenomenologically, this psychosis in people with PWS is atypical in comparison to schizophrenia and bipolar disorder in the general population. The relationship to psychosis in the general population and the optimum treatments remain uncertain.

Body weight, behaviours of concern, and social contact in adults and adolescents with Prader-Willi syndrome in full-time care services: Findings from pooled international archival data.

BACKGROUND: Prader-Willi syndrome (PWS) is a complex genetic neurodevelopmental condition characterised by a range of debilitating and lifelong symptoms. The many physical and behavioural challenges that arise with adults with PWS often necessitate full-time (i.e., 24-hour) professional care support. However, despite the fact that many clinicians regard full-time PWS-specific care to represent best practice, relatively few studies have directly examined the benefits of such services. The purpose of this paper is to use archival data to investigate the impact of full-time care services on people with PWS, and to assemble a large statistical dataset on which robust analyses of improvements in weight, BMI, and behavioural outcomes can be based. METHODS: Information collated by the International PWS Organisation (IPWSO), an international non-profit membership organisation supporting national PWS associations around the world, was combined into a single anonymised dataset for statistical analysis. Data were supplied by service-providers from several countries who provide full-time support to people with PWS. The dataset included details on the specific services provided, basic demographic information on service recipients, including weight, body mass index (BMI), and observational records relating to behaviours of concern (BOC; consisting of temper outbursts, skin-picking, egocentrism, inflexibility, and striving for dominance). RESULTS: A total of 193 people with PWS (ranging in age from < 10 yrs to > 50 yrs; 93% of whom were > 18 yrs), residing in 11 services across 6 countries, were represented in the dataset. On average, people with PWS showed significant reductions in weight and BMI after joining a full-time care service, with improvements within one year of entering, which were cumulative over time and independent of age or initial weight at entry. Similar cumulative improvements over time were seen for BOC within one year and were unrelated to age or severity of BOC at entry. The degree to which services are specialised for residents with PWS appeared to confer particular benefits, with people living in PWS-exclusive services showing the greatest improvements in weight, BMI, and BOC. Reductions in BOC were associated with greater, rather than less, social contact, suggesting that these improvements were not achieved at the expense of broader freedoms, such as the opportunity to meet with families and friends. CONCLUSIONS: We conclude that full-time care services have a high likelihood of enhancing the lives of people with PWS within one year with long-lasting benefits, especially if those services are exclusive and specialised around the particular needs of PWS.

Association of biological sex with clinical outcomes and biomarkers of Alzheimer's disease in adults with Down syndrome.

The study of sex differences in Alzheimer's disease is increasingly recognized as a key priority in research and clinical development. People with Down syndrome represent the largest population with a genetic link to Alzheimer's disease (>90% in the 7th decade). Yet, sex differences in Alzheimer's disease manifestations have not been fully investigated in these individuals, who are key candidates for preventive clinical trials. In this double-centre, cross-sectional study of 628 adults with Down syndrome [46% female, 44.4 (34.6; 50.7) years], we compared Alzheimer's disease prevalence, as well as cognitive outcomes and AT(N) biomarkers across age and sex. Participants were recruited from a population-based health plan in Barcelona, Spain, and from a convenience sample recruited via services for people with intellectual disabilities in England and Scotland. They underwent assessment with the Cambridge Cognitive Examination for Older Adults with Down Syndrome, modified cued recall test and determinations of brain amyloidosis (CSF amyloid-ß 42 / 40 and amyloid-PET), tau pathology (CSF and plasma phosphorylated-tau181) and neurodegeneration biomarkers (CSF and plasma neurofilament light, total-tau, fluorodeoxyglucose-PET and MRI). We used within-group locally estimated scatterplot smoothing models to compare the trajectory of biomarker changes with age in females versus males, as well as by apolipoprotein ɛ4 carriership. Our work revealed similar prevalence, age at diagnosis and Cambridge Cognitive Examination for Older Adults with Down Syndrome scores by sex, but males showed lower modified cued recall test scores from age 45 compared with females. AT(N) biomarkers were comparable in males and females. When considering apolipoprotein ɛ4, female ɛ4 carriers showed a 3-year earlier age at diagnosis compared with female non-carriers (50.5 versus 53.2 years, P = 0.01). This difference was not seen in males (52.2 versus 52.5 years, P = 0.76). Our exploratory analyses considering sex, apolipoprotein ɛ4 and biomarkers showed that female ɛ4 carriers tended to exhibit lower CSF amyloid-ß 42/amyloid-ß 40 ratios and lower hippocampal volume compared with females without this allele, in line with the clinical difference. This work showed that biological sex did not influence clinical and biomarker profiles of Alzheimer's disease in adults with Down syndrome. Consideration of apolipoprotein ɛ4 haplotype, particularly in females, may be important for clinical research and clinical trials that consider this population. Accounting for, reporting and publishing sex-stratified data, even when no sex differences are found, is central to helping advance precision medicine.

Did you forget your cell sex? An update on the inclusion of sex as a variable in AJP-Cell Physiology.

"I don't know the question, but sex is definitely the answer!," was a Woody Allen quote cited by Fuller and Insel in an Editorial Comment in 2013 on the importance of cell sex in submissions to AJP-Cell Physiology, and in biomedical research in general. The notion that cell sex is important is axiomatic in studies on prostate cancer (LnCAP) or placental physiology (BeWo). Indeed, most researchers are aware that HeLa cells are female cervical derived, and CHO are female hamster ovary cells, yet beyond those well-known examples, it would be fair to assume that the sex of cells derived from kidney, lung, or liver, for example, is given cursory, if any thought. In the end, what possible impact could the presence or absence of a Y chromosome have on protein trafficking in a nonreproductive tissue, such as a pancreatic ß cell? However, this approach to cell, and indeed organismal physiology, seems to be in conflict with accumulating data, that show that far from being irrelevant, genes expressed off sex chromosomes have a broad-ranging impact on cells as diverse as neurons and renal cells. Moreover, it is also the policy of AJP-Cell Physiology that the source of all cells used (species, sex, etc.) should be clearly indicated when submitting an article for publication (https://journals.physiology.org/author-info.manuscript-composition). In 2013, we wrote a review examining how faithfully such requirements were adhered to in submissions to Cell Physiology. Nearly a decade later, it seems fitting to revisit the topic and ask if any improvements have been made in the description of cells and cell lines used in publications submitted to AJP-Cell Physiology.

The transition from pediatric to adult care in individuals with Prader-Willi syndrome.

Prader-Willi syndrome (PWS), the most common form of syndromic obesity, is a complex neurodevelopmental genetic disorder including obesity with hyperphagia, endocrine and metabolic disorders and also psychiatric disorders. The most frequent endocrine disturbances include hypogonadism and growth hormone (GH) deficiency. Hypothyroidism and central adrenal insufficiency can also be observed but are less frequent. The transition of individuals with PWS from adolescence to adult life is challenging because of multiple comorbidities and complex disabilities. Individuals and caregivers face psychological, medical and social issues. This period of profound changes is thus prone to disruptions, and the main risks being the worsening of the medical situation and loss to follow-up of the individuals. Medical care may be poorly adapted to the needs of individuals because of a lack of knowledge concerning the syndrome and also lack of the necessary specific skills. A multidisciplinary panel composed of several experts in PWS met in November 2021 during an European Reference Network on Rare Endocrine Conditions (Endo-ERN) webinar. They presented complementary aspects of PWS from the perspective of the transition including psychiatric, pediatric and adult endocrinological and parent's and patient's points of view and shed light on the best way to approach this pivotal period.

Next Steps in Prader-Willi Syndrome Research: On the Relationship between Genotype and Phenotype.

This article reviews what we know of the phenotype and genotype of Prader-Willi syndrome and hypothesizes two possible paths from phenotype to genotype. It then suggests research that may strengthen the case for one or other of these hypotheses.

Reducing global health inequalities for a rare disorder: evaluating the international Prader-Willi Syndrome Organisation's Echo® programme.

BACKGROUND: People with rare disorders face significant global health inequalities; the challenge is how to raise awareness and develop a nucleus of experts in a country who are then able to provide guidance to others in that country. The International Prader-Willi Syndrome Organisation (IPWSO) established Project ECHO® with the aim of facilitating the sharing of knowledge and the building of international partnerships to reduce global health inequalities for a particular rare genetically-determined neurodevelopmental disorder, Prader-Willi Syndrome (PWS). Four different ECHO programmes were established for the following groups: (a) Individuals (usually parents) who had taken on a leadership role in their country; (b) health professionals interested in PWS; (c) professional care providers supporting children and adults with PWS; and (d) a Latin American ECHO in Spanish. The programme started in 2020 and an evaluation was undertaken after one year to determine: the extent to which IPWSO had been able to recruit and retain individuals globally; the nature and extent of any benefits gained from the sessions; and examples of how individual involvement in the programme had led to local benefits. The methods included analysing routinely kept process indicators and survey data from the attendees of one component of the programme (the Leadership ECHO), together with a qualitative analysis of survey data and recorded interviews of attendees from countries of differing socio-economic status. RESULTS: We describe the IPWSO ECHO programme and report on the outcomes from the evaluation of one aspect of the programme, the Leadership ECHO. Attendance of the Leadership ECHO sessions was satisfactory, with a mean of 24.7 participants, with participants attending a mean of 5.67 sessions, i.e., 30% of sessions. There was also good global reach, with individuals attending from 34 countries, although there were notable geographic regions with very limited representation. Feedback and interviews demonstrated the positive impact of the programme with some early evidence of positive developments at national level. CONCLUSIONS: Families and professionals from countries with a range of expertise and services offered to people with PWS remained engaged throughout the ECHO programme, established networks of support and fostered the development of good practice.

In vivo neuroimaging evidence of hypothalamic alteration in Prader-Willi syndrome.

Prader-Willi syndrome is a genetic neurodevelopmental disorder with an early phenotype characterized by neonatal hypotonia, failure to thrive, and immature genitalia. The onset of hyperphagia in childhood and developmental, physical and neuropsychiatric characteristics indicate atypical brain development and specifically hypothalamic dysfunction. Whether the latter is a consequence of disruption of hypothalamic pathways for genetic reasons or due to a failure of hypothalamic development remains uncertain. Twenty participants with Prader-Willi syndrome, 40 age-matched controls and 42 obese participants underwent structural MRI scanning. The whole hypothalamus and its subnuclei were segmented from structural acquisitions. The Food-Related Problem Questionnaire was used to provide information relating to eating behaviour. All hypothalamic nuclei were significantly smaller in the Prader-Willi group, compared with age and gender matched controls (P < 0.01) with the exception of the right anterior-inferior nucleus (P = 0.07). Lower whole hypothalamus volume was significantly associated with higher body mass index in Prader-Willi syndrome (P < 0.05). Increased preoccupation with food was associated with lower volumes of the bilateral posterior nuclei and left tubular superior nucleus. The whole hypothalamus and all constituent nuclei were also smaller in Prader-Willi syndrome compared with obese participants (P < 0.001). Connectivity profiles of the hypothalamus revealed that fractional anisotropy was associated with impaired satiety in Prader-Willi syndrome (P < 0.05). We establish that hypothalamic structure is significantly altered in Prader-Willi syndrome, demonstrating that hypothalamic dysfunction linked to eating behaviour is likely neurodevelopmental in nature and furthermore, distinctive compared with obesity in the general population.

Amyloid- ß and tau deposition influences cognitive and functional decline in Down syndrome.

This study investigates whether tau has (i) an independent effect from amyloid-ß on changes in cognitive and functional performance and (ii) a synergistic relationship with amyloid-ß in the exacerbation of decline in aging Down syndrome (DS). 105 participants with DS underwent baseline PET [18F]-AV1451 and PET [11C]PiB scans to quantify tau deposition in Braak regions II-VI and the Striatum and amyloid-ß status respectively. Linear Mixed Effects models were implemented to assess how tau and amyloid-ß deposition are related to change over three time points. Tau was a significant independent predictor of cognitive and functional change. The three-way interaction between time, [11C]PiB status and tau was significant in the models of episodic memory and visuospatial cognition. Baseline tau is a significant predictor of cognitive and functional decline, over and above the effect of amyloid-ß status. Results suggest a synergistic relationship between amyloid-ß status and tau as predictors of change in memory and visuospatial cognition.

Exploring electrophysiological markers of auditory predictive processes and pathological ageing in adults with Down's syndrome.

Down's syndrome is associated with pathological ageing and a propensity for early-onset Alzheimer's disease. The early symptoms of dementia in people with Down's syndrome may reflect frontal lobe vulnerability to amyloid deposition. Auditory predictive processes rely on the bilateral auditory cortices with the recruitment of frontal cortices and appear to be impaired in pathologies characterized by compromised frontal lobe. Hence, auditory predictive processes were investigated to assess Down's syndrome pathology and its relationship with pathological ageing. An auditory electroencephalography (EEG) global-local paradigm was presented to the participants, in which oddball stimuli could either violate local or higher level global rules. We characterised predictive processes in individuals with Down's syndrome and their relationship with pathological ageing, with a focus on the EEG event-related potential called Mismatch Negativity (MMN) and the P300. In Down's syndrome, we also evaluated the EEG components as predictor of cognitive decline 1 year later. We found that predictive processes of detection of auditory violations are overall preserved in Down's syndrome but also that the amplitude of the MMN to local deviancies decreases with age. However, the 1-year follow-up of Down's syndrome found that none of the ERPs measures predicted subsequent cognitive decline. The present study provides a novel characterization of electrophysiological markers of local and global predictive processes in Down's syndrome.

Neurobehavioral Dimensions of Prader Willi Syndrome: Relationships Between Sleep and Psychosis-Risk Symptoms.

Background: Prader Willi Syndrome (PWS) is a genetic disorder caused by the absence of expression of the paternal copies of maternally imprinted gene(s) located at 15q11-q13. While the physical and medical characteristics of PWS, including short stature, hyperphagia and endocrine dysfunction are well-characterized, systematic investigation of the long-recognized psychiatric manifestations has been recent. Methods: Here, we report on the first remote (web-based) assessment of neurobehavioral traits, including psychosis-risk symptoms (Prodromal Questionnaire-Brief Version; PQ-B) and sleep behaviors (Pittsburgh Sleep Quality Index), in a cohort of 128 participants with PWS, of whom 48% had a paternal deletion, 36% uniparental disomy, 2.4% an imprinting mutation and 13% unknown mutation (mean age 19.3 years ± 8.4; 53.9% female). We aimed to identify the most informative variables that contribute to psychosis-risk symptoms. Multiple domains of cognition (accuracy and speed) were also assessed in a subset of PWS participants (n = 39) using the Penn Computerized Neurocognitive Battery (Penn-CNB). Results: Individuals with PWS reported a range of psychosis-risk symptoms, with over half reporting cognitive disorganization (63.1%) and about one third reporting unusual beliefs (38.6%) and/or suspiciousness (33.3%). Subjectively-reported sleep quality, nap frequency, sleep duration, sleep disturbance, and daytime dysfunction were significant predictors of psychosis-risk symptom frequency and severity (all p's < 0.029). Sleep disturbance ratings were the strongest predictors of psychosis-risk symptoms. Regarding cognition, individuals with PWS showed the most prominent deficits in accuracy on measures of social cognition involving faces, namely Face Memory, Age Differentiation and Emotion Recognition, and greatest slowing on measures of Attention and Emotion Recognition. However, there were no significant differences in psychosis-risk symptoms or cognitive performance as a function of PWS genetic subtype. Conclusions: PWS is associated with a high prevalence of distressing psychosis-risk symptoms, which are associated with sleep disturbance. Findings indicate that self/parent-reported neurobehavioral symptoms and cognition can be assessed remotely in individuals with PWS, which has implications for future large-scale investigations of rare neurogenetic disorders.

Cortical atrophy and amyloid and tau deposition in Down syndrome: A longitudinal study.

Introduction: The Down syndrome population has a high prevalence for dementia, often showing their first clinical symptoms in their 40s. Methods: In a longitudinal cohort, we investigate whether amyloid deposition at time point 1 (TP1) could predict cortical thickness change at time point 2 (TP2). The association between tau burden and cortical thickness was also examined at time point 3 (TP3). Results: Between TP1 and TP2 there was pronounced cortical thinning in temporo-parietal cortices and cortical thickening in the frontal cortex. Baseline amyloid burden was strongly associated to cortical thinning progression, especially in the temporo-parietal regions. At TP3, tau deposition negatively correlated with cortical atrophy in regions where tau usually accumulates at later Braak stages. Discussion: A higher amount of amyloid accumulation triggers a cascade of changes of disease-causing processes that eventually lead to dementia. As expected, we found that regions where tau usually accumulates were those also displaying high levels of cortical atrophy.

Support vector machine learning and diffusion-derived structural networks predict amyloid quantity and cognition in adults with Down's syndrome.

Down's syndrome results from trisomy of chromosome 21, a genetic change which also confers a probable 100% risk for the development of Alzheimer's disease neuropathology (amyloid plaque and neurofibrillary tangle formation) in later life. We aimed to assess the effectiveness of diffusion-weighted imaging and connectomic modelling for predicting brain amyloid plaque burden, baseline cognition and longitudinal cognitive change using support vector regression. Ninety-five participants with Down's syndrome successfully completed a full Pittsburgh Compound B (PiB) PET-MR protocol and memory assessment at two timepoints. Our findings indicate that graph theory metrics of node degree and strength based on the structural connectome are effective predictors of global amyloid deposition. We also show that connection density of the structural network at baseline is a promising predictor of current cognitive performance. Directionality of effects were mainly significant reductions in the white matter connectivity in relation to both PiB+ status and greater rate of cognitive decline. Taken together, these results demonstrate the integral role of the white matter during neuropathological progression and the utility of machine learning methodology for non-invasively evaluating Alzheimer's disease prognosis.

The paradox of Prader-Willi syndrome revisited: Making sense of the phenotype.

Prader-Willi syndrome arises as a consequence of absent paternal copies of maternally imprinted genes at 15q11-13. Such gender-of-origin imprinted genes are expressed in the brain and also in mammalian placenta where paternally expressed imprinted genes drive foetal nutritional demand. We hypothesise that the PWS phenotype is the result of the genotype impacting two pathways: first, directly on brain development and secondly, on placental nutritional pathways that results in its down-regulation and relative foetal starvation. The early PWS phenotype establishes the basis for the later characteristic phenotype. Hyperphagia. and other phenotypic characteristics arise as a consequence of impaired hypothalamic development. Hypothalamic feeding pathways become set in a state indicative of starvation, with a high satiety threshold and a dysfunctional neurophysiological state due to incorrect representations of reward needs, based on inputs that indicate a false requirement for food. Our hypotheses, if confirmed, would lead to novel and effective interventions.

t-VNS to treat disorders of behaviour in Prader-Willi Syndrome and in people with other neurodevelopmental conditions.

This paper proposes that tVNS has the potential to be a new treatment for some of the behaviour difficulties that may affect people with intellectual disabilities and/or autism, particularly those people born with specific neurodevelopmental syndromes. Behaviours, such as emotional outbursts, physical aggression, and self-injury are a relative common occurrence in these groups and have a significant impact on wellbeing and quality of life for the individuals and their families. Such behaviours have generally been understood through the lens of learning theory, the likelihood of their occurrence being shaped and reinforced by the responses of others. However, when vagus nerve stimulation has been used to treat epilepsy improvements in cognition, behaviour, and general wellbeing have been noted suggesting that with these behaviours other causal mechanisms are also important. More recently incidental findings from a proof of concept study where vagus nerve stimulation was given, using an implanted device, to people with the genetically determined neurodevelopmental disorder, Prader-Willi Syndrome (PWS), findings of benefit supported the above view. A second study, this time using tVNS, reported a similar result. In this paper we review the evidence for the use of tVNS for behavioural problems, consider the challenges when conducting trials in this population, and reflect on what the preliminary observations in people with PWS tell us about the possible mechanisms that underpin such behaviours.

Interplay of Ferritin Accumulation and Ferroportin Loss in Ageing Brain: Implication for Protein Aggregation in Down Syndrome Dementia, Alzheimer's, and Parkinson's Diseases.

Iron accumulates in the ageing brain and in brains with neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and Down syndrome (DS) dementia. However, the mechanisms of iron deposition and regional selectivity in the brain are ill-understood. The identification of several proteins that are involved in iron homeostasis, transport, and regulation suggests avenues to explore their function in neurodegenerative diseases. To uncover the molecular mechanisms underlying this association, we investigated the distribution and expression of these key iron proteins in brain tissues of patients with AD, DS, PD, and compared them with age-matched controls. Ferritin is an iron storage protein that is deposited in senile plaques in the AD and DS brain, as well as in neuromelanin-containing neurons in the Lewy bodies in PD brain. The transporter of ferrous iron, Divalent metal protein 1 (DMT1), was observed solely in the capillary endothelium and in astrocytes close to the ventricles with unchanged expression in PD. The principal iron transporter, ferroportin, is strikingly reduced in the AD brain compared to age-matched controls. Extensive blood vessel damage in the basal ganglia and deposition of punctate ferritin heavy chain (FTH) and hepcidin were found in the caudate and putamen within striosomes/matrix in both PD and DS brains. We suggest that downregulation of ferroportin could be a key reason for iron mismanagement through disruption of cellular entry and exit pathways of the endothelium. Membrane damage and subsequent impairment of ferroportin and hepcidin causes oxidative stress that contributes to neurodegeneration seen in DS, AD, and in PD subjects. We further propose that a lack of ferritin contributes to neurodegeneration as a consequence of failure to export toxic metals from the cortex in AD/DS and from the substantia nigra and caudate/putamen in PD brain.

A Systematic Review of Unexplained Early Regression in Adolescents and Adults with Down Syndrome.

A proportion of young people with Down syndrome (DS) experience unexplained regression that severely impacts on their daily lives. While this condition has been recognised by clinicians, there is a limited understanding of causation and an inconsistent approach to diagnosis and treatment. Varied symptomology and little knowledge of the cause of this regression have impacted on clinician's ability to prevent or manage this condition. The purpose of this review was to examine the current evidence surrounding unexplained regression in adolescents and young adults, and to establish patterns that may be of use to clinicians, as well as raising awareness of this condition. Four areas were specifically reviewed, (1) terminology used to refer to this condition, (2) the symptoms reported, (3) potential trigger events and, (4) treatments and prognosis. A variety of terminology is used for this condition, which has constrained past attempts to identify patterns. An extensive number of symptoms were reported, however sleep impairment, loss of language and distinct changes in personality and behaviour, such as disinterest and withdrawal, were among the most frequently seen. Life events that were tentatively associated with the onset of a regressive period included a significant change in environmental circumstances or a transition, such as moving home or leaving school. Prognosis for this condition is relatively positive with the majority of individuals making at least a partial recovery. However, few patients were found to make a full recovery to their previous level of functioning and serious adverse effects could persist in those who have made a partial recovery. This is an under-researched condition with significant impacts on people with DS and their families. There are no established treatments for this condition and there is relatively little recognition in the research community. Further studies that focus on the prevention and treatment of this condition with controlled treatment trials are needed.

Impaired Iron Homeostasis and Haematopoiesis Impacts Inflammation in the Ageing Process in Down Syndrome Dementia.

Down syndrome (DS) subjects are more likely to develop the clinical features of Alzheimer's disease (AD) very early in the disease process due to the additional impact of neuroinflammation and because of activation of innate immunity. Many factors involved in the neuropathology of AD in DS, including epigenetic factors, innate immunity and impaired haematopoiesis, contribute significantly towards the pathophysiology and the enhanced ageing processes seen in DS and as a consequence of the triplication of genes RUNX1, S100ß and OLIG2, together with the influence of proteins that collectively protect from cellular defects and inflammation, which include hepcidin, ferritin, IL-6 and TREM2. This study is aimed at determining whether genetic variants and inflammatory proteins are involved in haematopoiesis and cellular processes in DS compared with age-matched control participants, particularly with respect to neuroinflammation and accelerated ageing. Serum protein levels from DS, AD and control participants were measured by enzyme-linked immunosorbent assay (ELISA). Blood smears and post-mortem brain samples from AD and DS subjects were analysed by immunohistochemistry. RUNX1 mRNA expression was analysed by RT-PCR and in situ hybridisation in mouse tissues. Our results suggest that hepcidin, S100ß and TREM2 play a critical role in survival and proliferation of glial cells through a common shared pathway. Blood smear analysis showed the presence of RUNX1 in megakaryocytes and platelets, implying participation in myeloid cell development. In contrast, hepcidin was expressed in erythrocytes and in platelets, suggesting a means of possible entry into the brain parenchyma via the choroid plexus (CP). The gene product of RUNX1 and hepcidin both play a critical role in haematopoiesis in DS. We propose that soluble TREM2, S100ß and hepcidin can migrate from the periphery via the CP, modulate the blood-brain immune axis in DS and could form an important and hitherto neglected avenue for possible therapeutic interventions to reduce plaque formation.