Hypothalamic-pituitary-adrenal axis function in Fragile X Syndrome and its relationship to behaviour: A systematic review

Association Between Intellectual Disability and Hair Cortisol Concentration in Adolescents in a Brazilian Population-Based Birth Cohort

OBJECTIVE

Children with intellectual disability (ID) usually exhibit neuroendocrine functioning impairment, such as alterations in the hypothalamic-pituitary-adrenal (HPA) neuroendocrine axis, which can result in glucocorticoid cortisol release alterations. Indeed, many studies showed a positive association between ID and cortisol concentration. However, evidence is lacking on the relationship between child neurodevelopment and cortisol levels during adolescence in population-based studies. We aimed to test the association between ID and hair cortisol concentration (HCC) during adolescence in a prospective population-based cohort.

METHODS

Data from 1770 individuals in the 2004 Pelotas Birth Cohort were used. ID was diagnosed at age 6 through clinical examination. Hair cortisol was measured at age 15. Association was assessed using linear regression models adjusted for sex, socio-economic factors, hair-related variables and corticosteroid use.

RESULTS

Higher HCC were observed in individuals with ID (β: 1.120; 95% CI: 1.012, 1.241) in the analysis adjusted for sex, hair-related variables and corticosteroid use. Compared to the other aetiological groups, this was more evident in idiopathic ID. But this did not remain significant when demographics/socio-economic variables were controlled for.

CONCLUSION

Children with ID, particularly those with idiopathic ID, might exhibit dysfunction in the HPA axis or experience heightened stress levels during adolescence.

The relationship between hair cortisol concentration and autism diagnosis

BACKGROUND

Autistic children are prone to experience heightened levels of distress and physiological reactivity to a range of sensory, social, and emotional stimuli. In line with this, multiple studies have demonstrated that autistic children have higher acute cortisol stress responses to adverse or threatening stimuli and altered cortisol awakening responses. However, few studies have examined whether this sensitivity may relate to heightened levels of chronic stress and persistently elevated hypothalamic-pituitary-adrenal (HPA) axis activity. The measurement of cortisol accumulation in hair is considered a non-invasive biomarker of chronic stress and has been associated with several childhood diseases. Here, we investigated whether hair cortisol concentration in a large sample of autistic children differed from non-autistic children, and after accounting for a range of child, parental and family-level characteristics.

METHODS

Hair cortisol concentration was measured in 307 autistic children and 282 non-autistic controls aged between 2 and 17 years recruited from four Australian states who participated in providing hair samples and demographic data to the Australian Autism Biobank. Independent samples t-test or one-way analysis of variance (ANOVA) were conducted to determine significant differences in the mean hair cortisol concentration (pg/mg) between potential covariates. Primary analysis included multivariable regression modelling of the collapsed sample to identify variables that were significantly associated with hair cortisol concentration after controlling for covariates. We also accounted for the potential interaction of multiple biological (e.g., age, sex, BMI) and psychosocial characteristics at the level of the child, the mother and the father, and the family unit.

RESULTS

Our findings suggest that the diagnosis of autism was not a significant predictor of chronic stress, as measured by hair cortisol concentration. However, findings of the multivariable regression analysis showed that key factors such as area of residence (Queensland vs Victorian state of residence) and decrease in child's age were significantly associated with higher hair cortisol concentration whereas lower family income was significantly associated with higher hair cortisol concentration.

CONCLUSION

To our knowledge, this is the first study to show that socioeconomic factors such as family annual income affect hair cortisol status in autistic children, indicating that the psychosocial environment may be a potential mediator for chronic stress in autistic children just as it has been demonstrated in non-autistic children.

Genetically modified animals as models of neurodevelopmental conditions: A review of systematic review reporting quality

Using genetically modified animals to model neurodevelopmental conditions helps better our understanding of biology underlying these conditions. Animal research has unique characteristics not shared with clinical research, meaning systematic review methods must be adapted to this context. We aim to evaluate the quantity, characteristics, and reporting quality of systematic reviews which synthesise research using genetically modified animals to model neurodevelopmental conditions. On 23 January 2023, we searched PubMed, Embase, and the Web of Science Core Collection to identify systematic reviews of genetic neurodevelopmental condition animal research where the modified gene was one in a list of 102 genes associated with neurodevelopmental conditions identified through large-scale exome sequencing or Fmr1, Mecp2, or Ube3a. Two independent reviewers screened studies based on full text and assessed the reporting quality of relevant reviews using an adapted version of the PRISMA checklist (PRISMA-Pre). Twelve review publications met our criteria. We found mixed levels of reporting: items such as identifying the publication as a systematic review in the title, search strategies, and funding sources being well reported, and others such as protocol registration and data sharing less well reported. We also identified 19 review registrations via PROSPERO, most of which remain unpublished after their anticipated end dates. Systematic reviews are limited by lack of reporting. Increased awareness of reporting guidelines may help authors increase the transparency and reproducibility, and therefore the reliability, of their systematic reviews.

Increased body weight in mice with fragile X messenger ribonucleoprotein 1 (Fmr1) gene mutation is associated with hypothalamic dysfunction

Mutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene are linked to Fragile X Syndrome, the most common monogenic cause of intellectual disability and autism. People affected with mutations in FMR1 have higher incidence of obesity, but the mechanisms are largely unknown. In the current study, we determined that male Fmr1 knockout mice (KO, Fmr1-/y), but not female Fmr1-/-, exhibit increased weight when compared to wild-type controls, similarly to humans with FMR1 mutations. No differences in food or water intake were found between groups; however, male Fmr1-/y display lower locomotor activity, especially during their active phase. Moreover, Fmr1-/y have olfactory dysfunction determined by buried food test, although they exhibit increased compulsive behavior, determined by marble burying test. Since olfactory brain regions communicate with hypothalamic regions that regulate food intake, including POMC neurons that also regulate locomotion, we examined POMC neuron innervation and numbers in Fmr1-/y mice. POMC neurons express Fmrp, and POMC neurons in Fmr1-/y have higher inhibitory GABAergic synaptic inputs. Consistent with increased inhibitory innervation, POMC neurons in the Fmr1-/y mice exhibit lower activity, based on cFOS expression. Notably, Fmr1-/y mice have fewer POMC neurons than controls, specifically in the rostral arcuate nucleus, which could contribute to decreased locomotion and increased body weight. These results suggest a role for Fmr1 in the regulation of POMC neuron function and the etiology of Fmr1-linked obesity.

Social Anxiety in Neurodevelopmental Disorders: The Case of Fragile X Syndrome

Despite significant advances in understanding and treating social anxiety in the general population, progress in this area lags behind for individuals with intellectual disability. Fragile X syndrome is the most common cause of inherited intellectual disability and is associated with an elevated prevalence rate of social anxiety. The phenotype of fragile X syndrome encompasses multiple clinically significant characteristics that are posed as risk markers for social anxiety in other populations. Here, evidence is reviewed that points to physiological hyperarousal, sensory sensitivity, emotion dysregulation, cognitive inflexibility, and intolerance of uncertainty as primary candidates for underlying mechanisms of heightened social anxiety in fragile X syndrome. A multilevel model is presented that provides a framework for future research to test associations.

Altered GnRH neuron and ovarian innervation characterize reproductive dysfunction linked to the Fragile X messenger ribonucleoprotein (Fmr1) gene mutation

Introduction

Mutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene cause Fragile X Syndrome, the most common monogenic cause of intellectual disability. Mutations of FMR1 are also associated with reproductive disorders, such as early cessation of reproductive function in females. While progress has been made in understanding the mechanisms of mental impairment, the causes of reproductive disorders are not clear. FMR1-associated reproductive disorders were studied exclusively from the endocrine perspective, while the FMR1 role in neurons that control reproduction was not addressed.

Results

Here, we demonstrate that similar to women with FMR1 mutations, female Fmr1 null mice stop reproducing early. However, young null females display larger litters, more corpora lutea in the ovaries, increased inhibin, progesterone, testosterone, and gonadotropin hormones in the circulation. Ovariectomy reveals both hypothalamic and ovarian contribution to elevated gonadotropins. Altered mRNA and protein levels of several synaptic molecules in the hypothalamus are identified, indicating reasons for hypothalamic dysregulation. Increased vascularization of corpora lutea, higher sympathetic innervation of growing follicles in the ovaries of Fmr1 nulls, and higher numbers of synaptic GABAA receptors in GnRH neurons, which are excitatory for GnRH neurons, contribute to increased FSH and LH, respectively. Unmodified and ovariectomized Fmr1 nulls have increased LH pulse frequency, suggesting that Fmr1 nulls exhibit hyperactive GnRH neurons, regardless of the ovarian feedback.

Conclusion

These results reveal Fmr1 function in the regulation of GnRH neuron secretion, and point to the role of GnRH neurons, in addition to the ovarian innervation, in the etiology of Fmr1-mediated reproductive disorders.

Alteration of peripheral cortisol and autism spectrum disorder: A meta-analysis

Cortisol is the main HPA axis hormone secreted by the adrenal cortex, and influences metabolism, cognition, and behavior. Recently, a plethora of studies have tried to confirm the correlation between peripheral cortisol and autism spectrum disorder (ASD). However, the results were controversial. We assessed the effects of peripheral cortisol on ASD in this study. The included studies were identified according to the inclusion and exclusion criteria. The pooled Hedges' g and its 95% confidence interval were selected to evaluate the association between peripheral cortisol and ASD. Subgroup analyses, sensitivity analyses, meta-regression, and publication bias tests were also undertaken based on the obtained information. There were a total of twelve studies with 375 ASD patients and 335 controls included in our meta-analysis. Obvious heterogeneity across studies was found in the overall analysis. Peripheral cortisol levels were significantly elevated in ASD patients compared with controls in the absence of obvious heterogeneity. A single study did not influence the overall comparison results. Meta-regression analyses revealed that age and gender of the included subjects, sample size, and publication year did not moderate effects on the present results. These findings may provide us some targeted strategies to the diagnosis and treatment of ASD.

Anxiety in Angelman Syndrome

Angelman Syndrome (AS) is a neurodevelopmental disorder most commonly caused by the impaired expression of the maternal UBE3A gene on chromosome 15. Though anxiety has been identified as a frequently present characteristic in AS, there are limited studies examining anxiety in this population. Studies of anxiety in other neurodevelopmental disorders have found disorder specific symptoms of anxiety and age specific displays of anxiety symptoms. However, there is a consistent challenge in identifying anxiety in people with neurodevelopmental disorders given the lack of measurement instruments specifically designed for this population. Given the limited information about AS and anxiety, the aims of the current project were to (a) examine symptoms of anxiety in children with AS and (b) determine the correlates of anxiety in children with AS. Participants included 42 adult caregivers of youth with AS in the AS Natural History study who completed the Developmental Behavior Checklist (DBC). The results found that 26% of the sample demonstrated elevated symptoms of anxiety and established a relationship between elevated anxiety in youth with AS and higher levels of irritability, hyperactivity, self-absorbed behaviors, and disruptive/antisocial behaviors. Findings from this research provide a foundation for tailoring evidence-based assessments and treatments for youth with AS and anxiety.

Circulating leptin, cortisol and gender differences associated with anorexia or obesity in depression

Objectives: To assess the role of circulating cortisol and leptin in depression associated with anorexia or obesity.Methods: Two hundred and fifty depressed patients presenting to the outpatient clinic of a psychiatric hospital and 250 non-depressed healthy volunteers were included in the study. The subjects of both groups were sub-grouped based upon their gender and BMI. Serum cortisol and leptin were determined by using respective ELISA kits.Results: The number of depressed than non-depressed subjects was three-fold higher in obese BMI groups of both genders. There were more depressed than non-depressed subjects in the underweight male BMI groups and in the overweight female BMI groups. There was a BMI-related increase in serum leptin and a decrease in serum cortisol in both genders. Depression in underweight BMI groups of both genders was associated with a decrease in serum leptin and an increase in cortisol. Higher serum leptin in obese BMI group was associated with a decrease in serum cortisol.Conclusions: Obesity is a risk factor for depression. The shift from typical to atypical depression is due to an inhibitory effect of higher circulating leptin on HPA axis activity and subsequent decrease in the lipolytic effects of cortisol.

Feasibility of a Complex Setting for Assessing Sleep and Circadian Rhythmicity in a Fragile X Cohort

INTRODUCTION

Sleep, circadian rhythms, (mental) health, and development are assumed to be intertwined. However, differentiated and reliable parameters of sleep and circadian rhythms are particularly difficult to assess for Fragile X (FXS) individuals. As those parameters need to be observed in complex settings, the feasibility of measurements for people with FXS was to be proven. Findings from this pilot study can inform further research and help to estimate sample sizes for future studies on FXS patients.

METHODS AND SAMPLE

Nine individuals (male and female) with full mutation of the FMR1 gene were integrated in the study and underwent a complex measurement including actigraphy, sleep log, and 24-h saliva sampling in order to examine profiles of melatonin and cortisol, and a polysomnography.

RESULTS

Seven actigraphy profiles, eight sleep logs, eight saliva profiles and seven polysomnographic data sets were collected. Complete data were analyzed for six individuals [mean age 14.87 years (SD 4.12), mean BMI 25.90 (SD 4.44)] were collected. No drop outs due to the constraints of the assessment were registered.

DISCUSSION

All assessments and the setting in total were tolerated well by participants and caregivers. Procedures were adapted to individual needs of the participants.

CONCLUSION

All its components and the setting in total are absolutely feasible in the specific population of FXS individuals. Losses during consenting and recruiting have to be planned as well as high amounts of interindividual variances have to be taken into account.

Biobehavioral composite of social aspects of anxiety in young adults with fragile X syndrome contrasted to autism spectrum disorder

Social anxiety is a common disorder that has negative impacts across multiple domains of function. Several clinical groups are at elevated risk for social anxiety, including those with fragile X syndrome and those with autism spectrum disorder. Measuring social anxiety in these clinical subgroups is fraught with challenge, however, given the complexity of social anxiety and measurement limitations that are particularly acute in persons with neurodevelopmental disorders. The over-arching aim of this study was to contribute to our understanding of the nature of social anxiety in fragile X syndrome and its association with autism spectrum disorder. To address this aim, we created a multi-faceted composite representing behavioral and biological aspects of social anxiety and examined differences in two adolescent and young adult-aged groups: 59 males with fragile X syndrome and 18 males with autism spectrum disorder. Results indicated a lower score on the multivariate composite for the males with fragile X syndrome relative to autism spectrum disorder but with evidence that traits of autism and social anxiety overlap. We conclude that measuring anxiety and autism traits in fragile X syndrome and autism spectrum disorder is complex with features that overlap and interact in a dynamic manner.

Cortisol profiles differentiated in adolescents and young adult males with fragile X syndrome versus autism spectrum disorder

BACKGROUND

Fragile X syndrome (FXS) and non-syndromic autism spectrum disorder (ASD) are distinct disorders with overlapping behavioral features. Both disorders are also highly associated with anxiety with abnormal physiological regulation implied mechanistically. Some reports suggest atypical hypothalamus-pituitary-adrenal (HPA) axis function, indexed via aberrant cortisol reactivity, in both FXS and non-syndromic ASD. However, no study has compared cortisol reactivity across these two disorders, or its relationship to ASD symptom severity.

METHODS

Cortisol reactivity (prior to and following a day of assessments) was measured in 54 adolescent/young adult males with FXS contrasted to 15 males with non-syndromic ASD who had low cognitive abilities.

RESULTS

Greater ASD symptom severity was related to increased cortisol reactivity and higher levels at the end of the day, but only in the non-syndromic ASD group. Elevated anxiety was associated with increased HPA activation in the group with FXS alone.

CONCLUSIONS

Taken together, findings suggest a unique neuroendocrine profile that distinguishes adolescent/young adult males with FXS from those with non-syndromic ASD. Severity of ASD symptoms appears to be related to cortisol reactivity in the non-syndromic ASD sample, but not in FXS; while anxiety symptoms are associated with HPA activation in the FXS sample, but not in ASD despite a high prevalence of ASD, anxiety and physiological dysregulation characteristic in both populations.

Fragile X syndrome

Fragile X syndrome (FXS) is the leading inherited form of intellectual disability and autism spectrum disorder, and patients can present with severe behavioural alterations, including hyperactivity, impulsivity and anxiety, in addition to poor language development and seizures. FXS is a trinucleotide repeat disorder, in which >200 repeats of the CGG motif in FMR1 leads to silencing of the gene and the consequent loss of its product, fragile X mental retardation 1 protein (FMRP). FMRP has a central role in gene expression and regulates the translation of potentially hundreds of mRNAs, many of which are involved in the development and maintenance of neuronal synaptic connections. Indeed, disturbances in neuroplasticity is a key finding in FXS animal models, and an imbalance in inhibitory and excitatory neuronal circuits is believed to underlie many of the clinical manifestations of this disorder. Our knowledge of the proteins that are regulated by FMRP is rapidly growing, and this has led to the identification of multiple targets for therapeutic intervention, some of which have already moved into clinical trials or clinical practice.