GWAS meta-analysis reveals key risk loci in essential tremor pathogenesis

Essential tremor (ET) is a prevalent neurological disorder with a largely unknown underlying biology. In this genome-wide association study meta-analysis, comprising 16,480 ET cases and 1,936,173 controls from seven datasets, we identify 12 sequence variants at 11 loci. Evaluating mRNA expression, splicing, plasma protein levels, and coding effects, we highlight seven putative causal genes at these loci, including CA3 and CPLX1. CA3 encodes Carbonic Anhydrase III and carbonic anhydrase inhibitors have been shown to decrease tremors. CPLX1, encoding Complexin-1, regulates neurotransmitter release. Through gene-set enrichment analysis, we identify a significant association with specific cell types, including dopaminergic and GABAergic neurons, as well as biological processes like Rho GTPase signaling. Genetic correlation analyses reveals a positive association between ET and Parkinson's disease, depression, and anxiety-related phenotypes. This research uncovers risk loci, enhancing our knowledge of the complex genetics of this common but poorly understood disorder, and highlights CA3 and CPLX1 as potential therapeutic targets.

Lifestyle and demographic associations with 47 inflammatory and vascular stress biomarkers in 9876 blood donors

BACKGROUND

The emerging use of biomarkers in research and tailored care introduces a need for information about the association between biomarkers and basic demographics and lifestyle factors revealing expectable concentrations in healthy individuals while considering general demographic differences.

METHODS

A selection of 47 biomarkers, including markers of inflammation and vascular stress, were measured in plasma samples from 9876 Danish Blood Donor Study participants. Using regression models, we examined the association between biomarkers and sex, age, Body Mass Index (BMI), and smoking.

RESULTS

Here we show that concentrations of inflammation and vascular stress biomarkers generally increase with higher age, BMI, and smoking. Sex-specific effects are observed for multiple biomarkers.

CONCLUSION

This study provides comprehensive information on concentrations of 47 plasma biomarkers in healthy individuals. The study emphasizes that knowledge about biomarker concentrations in healthy individuals is critical for improved understanding of disease pathology and for tailored care and decision support tools.

A genome-wide association study of social trust in 33,882 Danish blood donors

Social trust is a heritable trait that has been linked with physical health and longevity. In this study, we performed genome-wide association studies of self-reported social trust in n = 33,882 Danish blood donors. We observed genome-wide and local evidence of genetic similarity with other brain-related phenotypes and estimated the single nucleotide polymorphism-based heritability of trust to be 6% (95% confidence interval = (2.1, 9.9)). In our discovery cohort (n = 25,819), we identified one significantly associated locus (lead variant: rs12776883) in an intronic enhancer region of PLPP4, a gene highly expressed in brain, kidneys, and testes. However, we could not replicate the signal in an independent set of donors who were phenotyped a year later (n = 8063). In the subsequent meta-analysis, we found a second significantly associated variant (rs71543507) in an intergenic enhancer region. Overall, our work confirms that social trust is heritable, and provides an initial look into the genetic factors that influence it.

Genetic prediction of 33 blood group phenotypes using an existing genotype dataset

BACKGROUND

Accurate blood type data are essential for blood bank management, but due to costs, few of 43 blood group systems are routinely determined in Danish blood banks. However, a more comprehensive dataset of blood types is useful in scenarios such as rare blood type allocation. We aimed to investigate the viability and accuracy of predicting blood types by leveraging an existing dataset of imputed genotypes for two cohorts of approximately 90,000 each (Danish Blood Donor Study and Copenhagen Biobank) and present a more comprehensive overview of blood types for our Danish donor cohort.

STUDY DESIGN AND METHODS

Blood types were predicted from genome array data using known variant determinants. Prediction accuracy was confirmed by comparing with preexisting serological blood types. The Vel blood group was used to test the viability of using genetic prediction to narrow down the list of candidate donors with rare blood types.

RESULTS

Predicted phenotypes showed a high balanced accuracy >99.5% in most cases: A, B, C/c, Coa /Cob , Doa /Dob , E/e, Jka /Jkb , Kna /Knb , Kpa /Kpb , M/N, S/s, Sda , Se, and Yta /Ytb , while some performed slightly worse: Fya /Fyb , K/k, Lua /Lub , and Vel ~99%-98% and CW and P1 ~96%. Genetic prediction identified 70 potential Vel negatives in our cohort, 64 of whom were confirmed correct using polymerase chain reaction (negative predictive value: 91.5%).

DISCUSSION

High genetic prediction accuracy in most blood groups demonstrated the viability of generating blood types using preexisting genotype data at no cost and successfully narrowed the pool of potential individuals with the rare Vel-negative phenotype from 180,000 to 70.

COVID-19 illness severity and 2-year prevalence of physical symptoms: an observational study in Iceland, Sweden, Norway and Denmark

Background

Although the persistence of physical symptoms after SARS-CoV-2 infection is a major public health concern, evidence from large observational studies beyond one year post diagnosis remain scarce. We aimed to assess the prevalence of physical symptoms in relation to acute illness severity up to more than 2-years after diagnosis of COVID-19.

Methods

This multinational study included 64,880 adult participants from Iceland, Sweden, Denmark, and Norway with self-reported data on COVID-19 and physical symptoms from April 2020 to August 2022. We compared the prevalence of 15 physical symptoms, measured by the Patient Health Questionnaire (PHQ-15), among individuals with or without a confirmed COVID-19 diagnosis, by acute illness severity, and by time since diagnosis. We additionally assessed the change in symptoms in a subset of Swedish adults with repeated measures, before and after COVID-19 diagnosis.

Findings

During up to 27 months of follow-up, 34.5% participants (22,382/64,880) were diagnosed with COVID-19. Individuals who were diagnosed with COVID-19, compared to those not diagnosed, had an overall 37% higher prevalence of severe physical symptom burden (PHQ-15 score ≥15, adjusted prevalence ratio [PR] 1.37 [95% confidence interval [CI] 1.23-1.52]). The prevalence was associated with acute COVID-19 severity: individuals bedridden for seven days or longer presented with the highest prevalence (PR 2.25 [1.85-2.74]), while individuals never bedridden presented with similar prevalence as individuals not diagnosed with COVID-19 (PR 0.92 [0.68-1.24]). The prevalence was statistically significantly elevated among individuals diagnosed with COVID-19 for eight of the fifteen measured symptoms: shortness of breath, chest pain, dizziness, heart racing, headaches, low energy/fatigue, trouble sleeping, and back pain. The analysis of repeated measurements rendered similar results as the main analysis.

Interpretation

These data suggest an elevated prevalence of some, but not all, physical symptoms during up to more than 2 years after diagnosis of COVID-19, particularly among individuals suffering a severe acute illness, highlighting the importance of continued monitoring and alleviation of these targeted core symptoms.

Funding

This work was mainly supported by grants from NordForsk (COVIDMENT, grant number 105668 and 138929) and Horizon 2020 (CoMorMent, 847776). See Acknowledgements for further details on funding.

Rare variants with large effects provide functional insights into the pathology of migraine subtypes, with and without aura

Migraine is a complex neurovascular disease with a range of severity and symptoms, yet mostly studied as one phenotype in genome-wide association studies (GWAS). Here we combine large GWAS datasets from six European populations to study the main migraine subtypes, migraine with aura (MA) and migraine without aura (MO). We identified four new MA-associated variants (in PRRT2, PALMD, ABO and LRRK2) and classified 13 MO-associated variants. Rare variants with large effects highlight three genes. A rare frameshift variant in brain-expressed PRRT2 confers large risk of MA and epilepsy, but not MO. A burden test of rare loss-of-function variants in SCN11A, encoding a neuron-expressed sodium channel with a key role in pain sensation, shows strong protection against migraine. Finally, a rare variant with cis-regulatory effects on KCNK5 confers large protection against migraine and brain aneurysms. Our findings offer new insights with therapeutic potential into the complex biology of migraine and its subtypes.

The differentiating effect of COVID-19-associated stress on the morbidity of blood donors with symptoms of hidradenitis suppurativa, hyperhidrosis, or psoriasis

PURPOSE

The burden of different skin diseases may vary leading individuals to have different sensitivity to stress. Therefore, we compared the health-related quality of life (HRQoL) and stress before and during the universal stress from the severe acute respiratory syndrome coronavirus-2-pandemic in individuals with and without hyperhidrosis, hidradenitis suppurativa, or psoriasis.

METHODS

The study cohort was the Danish Blood Donor Study. Overall, 12,798 participants completed a baseline questionnaire before the pandemic, in 2018-2019, and a follow-up questionnaire during the pandemic, in 2020. Regression determined the association between the skin diseases and outcomes. Outcomes were the physical and mental component summary (MCS, PCS, respectively), which assess the mental and physical HRQoL, and the perceived stress scale, which assesses stress in the past four weeks.

RESULTS

Overall, 1168 (9.1%) participants had hyperhidrosis, 363 (2.8%) had hidradenitis suppurativa, and 402 (3.1%) had psoriasis. At follow-up, the participants with hyperhidrosis had worse MCS (coefficient -0.59 [95% confidence interval (CI) -1.05, -0.13]) and higher odds of moderate-to-severe stress (odds ratio 1.37 [95% CI 1.13, 1.65]) and the participants with hidradenitis suppurativa worse PCS (coefficient -0.74 [95% CI -1.21, -0.27]) than the control groups. The associations were independent of baseline HRQoL, stress, the Connor-Davidson Resilience scale, and other covariables. Psoriasis was not associated with the outcomes.

CONCLUSION

Individuals with hyperhidrosis or hidradenitis suppurativa experienced worse mental or physical well-being and individuals with hyperhidrosis also had higher stress during the pandemic compared to healthy individuals. This suggests that individuals with these skin diseases are particularly susceptible to external stress.

Symptoms of attention deficit hyperactivity disorder are associated with Hidradenitis suppurativa in Danish blood donors

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease associated with psychiatric comorbidity. Attention deficit hyperactivity disorder (ADHD) is a mental disorder associated with systemic and skin inflammation such as psoriasis and atopic dermatitis. Whether HS symptoms are associated with ADHD symptoms remains unexplored. Thus, the aim of this study was to explore the possible association between HS and ADHD. Participants in the Danish Blood Donor Study (DBDS) were included in this cross-sectional study during 2015-2017. The participants provided questionnaire data on screening items of HS, ADHD symptoms (ASRS-score), and depressive symptoms, smoking and body mass index (BMI). A logistic regression with HS symptoms as a binary outcome predicted by ADHD adjusted for age, sex, smoking, BMI, and depression was conducted to investigate the association between HS and ADHD. A total of 52,909 Danish blood donors were included in the study. Of these were 1004/52,909 (1.9%) considered participants with HS. Of the participants with HS, 74/996 (7.4%) screened positive of ADHD symptoms, while only 1786/51,129 (3.5%) of the participants without HS screened positive of ADHD. Adjusted for confounders, ADHD was positively associated with HS, odds ratio 1.85 (95% confidence interval: 1.43-2.37). Psychiatric comorbidity of HS is not limited to depression and anxiety. This study shows a positive association between HS and ADHD. Further research on the biological mechanisms behind this association is warranted.

Deficit of homozygosity among 1.52 million individuals and genetic causes of recessive lethality

Genotypes causing pregnancy loss and perinatal mortality are depleted among living individuals and are therefore difficult to find. To explore genetic causes of recessive lethality, we searched for sequence variants with deficit of homozygosity among 1.52 million individuals from six European populations. In this study, we identified 25 genes harboring protein-altering sequence variants with a strong deficit of homozygosity (10% or less of predicted homozygotes). Sequence variants in 12 of the genes cause Mendelian disease under a recessive mode of inheritance, two under a dominant mode, but variants in the remaining 11 have not been reported to cause disease. Sequence variants with a strong deficit of homozygosity are over-represented among genes essential for growth of human cell lines and genes orthologous to mouse genes known to affect viability. The function of these genes gives insight into the genetics of intrauterine lethality. We also identified 1077 genes with homozygous predicted loss-of-function genotypes not previously described, bringing the total set of genes completely knocked out in humans to 4785.

Population-Based Characterization of Menstrual Migraine and Proposed Diagnostic Criteria

Importance

There is a need for better recognition and more extensive research into menstrual migraine (MM) in the general population, and a revision of the diagnostic criteria for MM is warranted to move the field forward. Increased understanding of MM is crucial for improving clinical care, diagnosis, and therapy for MM.

Objectives

To assess the clinical characteristics of MM, including severity and treatment response, and to propose new diagnostic criteria for pure MM and menstrually related migraine.

Design, Setting, and Participants

This is a case-control study of Danish individuals with migraine. All individuals completed a 105-item validated diagnostic migraine questionnaire, sent via the Danish electronic mailing system (e-Boks) between May and August 2020, allowing diagnosis of pure MM and menstrually related migraine by the International Classification of Headache Disorders, Third Edition (ICHD-3). Data analysis was performed from September 2021 to November 2022.

Exposure

Diagnosis of migraine.

Main Outcomes and Measures

Clinical characteristics of women with MM and women with nonmenstrual migraine (non-MM) were compared using the ICHD-3 diagnostic criteria. A simulation of the risk of randomly misclassifying MM was based on number of migraine attacks during 3 menstrual cycles (3 × 28 days), and simulation analyses were performed using 100 000 permutations of random migraine attacks in migraine patients.

Results

A total of 12 618 individuals, including 9184 women, with migraine participated in the study. Among the women with migraine, the prevalence of MM was 16.6% (1532 women), and the prevalence of non-MM was 45.9% (4216 women). The mean (SD) age was 38.7 (8.7) years for women with MM and 37.0 (9.2) years for women with non-MM. Of the 1532 women with MM, 410 (26.8%) fulfilled ICHD-3 diagnostic criteria for pure MM, 1037 (67.7%) fulfilled ICHD-3 diagnostic criteria for menstrually related migraine, and 152 (9.9%) fulfilled proposed diagnostic criteria for rare pure MM. MM was associated with a higher frequency of migraine-accompanying symptoms (odds ratio [OR], 1.98; 95% CI, 1.71-2.29), more frequent (OR, 7.21; 95% CI, 5.77-9.03) and more severe (OR, 1.17; 95% CI, 1.13-1.21) migraine attacks, lower frequency of nonmigraine headache (OR, 0.31; 95% CI, 0.18-0.49), an overall greater response to treatment with triptans (OR, 1.66; 95% CI, 1.24-2.24), better improvement of migraine attacks during late pregnancy (OR, 5.10; 95% CI, 2.17-14.00), and faster reappearance of migraine attacks post partum (OR, 3.19; 95% CI, 2.40-4.25). Hormonal contraceptive-related MM was associated with a higher prevalence of migraine without aura than migraine related to spontaneous menstruation (OR, 1.82; 95% CI, 1.62-2.06). Otherwise, no differences between hormonal and spontaneous MM were observed. The risk of random diagnostic misclassification of ICHD-3 menstrually related migraine in women with high frequency episodic migraine was 43%. This risk was reduced to 3% when applying the proposed criteria for menstrually related migraine.

Conclusions and Relevance

In this case-control study, MM in the general population had clinical characteristics that were quantitively different from those of non-MM. Detailed descriptive data and suggested improved diagnostic criteria for pure MM and menstrually related migraine were provided.

Experience of loneliness during the COVID-19 pandemic: a cross-sectional study of 50 968 adult Danes

OBJECTIVES

To examine the level of loneliness experienced during the COVID-19 pandemic in Denmark and to identify associated behavioural patterns and demographic factors.

DESIGN

Cross-sectional cohort study.

SETTING

Includes Danish active and former blood donors.

PARTICIPANTS

A questionnaire was sent to 124 307 active and former blood donors, of these a total of 50 968 participants completed the study questionnaire (response rate=41%).

PRIMARY AND SECONDARY OUTCOME MEASURES

Subjective experience of loneliness was measured using the 3-item University of California, Los Angeles Loneliness Scale (UCLA-3). Besides the UCLA-3, the respondents answered items on sociodemographic and economic characteristics, items on precautionary measures taken to avoid COVID-19 infection as well as on COVID-19 anxiety.

RESULTS

The participants indicated their experienced level of loneliness both before and during the pandemic. Comparing the two reports yielded a mean increase in loneliness scores of 14.1% (p<0.001). Exploratory factor analysis identified the factor well-being, which comprised three questionnaire items related to emotional heath, physical health and happiness. A high score on the factor well-being was associated with reduced levels of loneliness (coefficient=-0.47, 95% CI -0.49 to -0.46)). Furthermore, women were more likely than men to have experienced increased levels of loneliness during the pandemic (coefficient=0.27, 95% CI 0.25 to 0.29). Furthermore, a negative correlation between higher age and change in loneliness score was observed.

CONCLUSIONS

The findings document an increase in the level of experienced loneliness during the COVID-19 pandemic, particularly affecting individuals with low well-being, women and younger individuals.

Two Novel Human Leukocyte Antigen Alleles Are Associated with Decreased Risk of Onychomycosis in a Large Cohort of Danish Blood Donors

<b><i>Introduction:</i></b> Antigen presentation and antimicrobial immune responses involve the human leukocyte antigen (HLA) system. Onychomycosis is primarily caused by dermatophytes and affects around 5.5% of the population worldwide. Yet, only limited data exist on the associations between the HLA system and onychomycosis. Thus, the objective of the study was to investigate if there is an association between HLA alleles and onychomycosis. <b><i>Methods:</i></b> Participants in the Danish Blood Donor Study were defined as cases of onychomycosis and controls based on antifungal prescriptions in the national prescription registry. Associations were investigated using logistic regressions adjusted for confounders and were Bonferroni corrected for multiple tests. <b><i>Results:</i></b> A total of 3,665 participants were considered onychomycosis cases, and 24,144 participants were considered controls. We found two protective HLA alleles of onychomycosis: DQB1*06:04, odds ratios (OR) 0.80 (95% confidence interval (CI) 0.71–0.90), and DRB1*13:02, OR 0.79 (95% CI: 0.71–0.89). <b><i>Conclusion:</i></b> The finding of two novel protective alleles of onychomycosis indicates that certain HLA alleles have certain antigen presentation properties affecting the risk of fungal infection. These findings may provide the basis for future research identifying immunologically relevant antigens of fungi causing onychomycosis, which could ultimately lead to targets of new drugs with antifungal effects.

A large cohort study of the effects of Lewis, ABO, 13 other blood groups, and secretor status on COVID-19 susceptibility, severity, and long COVID-19

BACKGROUND

Previous studies have reported Blood type O to confer a lower risk of SARS-CoV-2 infection, while secretor status and other blood groups have been suspected to have a similar effect as well.

STUDY DESIGN AND METHODS

To determine whether any other blood groups influence testing positive for SARS-CoV-2, COVID-19 severity, or prolonged COVID-19, we used a large cohort of 650,156 Danish blood donors with varying available data for secretor status and blood groups ABO, Rh, Colton, Duffy, Diego, Dombrock, Kell, Kidd, Knops, Lewis, Lutheran, MNS, P1PK, Vel, and Yt. Of these, 36,068 tested positive for SARS-CoV-2 whereas 614,088 tested negative between 2020-02-17 and 2021-08-04. Associations between infection and blood groups were assessed using logistic regression models with sex and age as covariates.

RESULTS

The Lewis blood group antigen Le^a displayed strongly reduced SARS-CoV-2 susceptibility OR 0.85 CI[0.79-0.93] p < .001. Compared to blood type O, the blood types B, A, and AB were found more susceptible toward infection with ORs 1.1 CI[1.06-1.14] p < .001, 1.17 CI[1.14-1.2] p < .001, and 1.2 CI[1.14-1.26] p < .001, respectively. No susceptibility associations were found for the other 13 blood groups investigated. There was no association between any blood groups and COVID-19 hospitalization or long COVID-19. No secretor status associations were found.

DISCUSSION

This study uncovers a new association to reduced SARS-CoV-2 susceptibility for Lewis type Le^a and confirms the previous link to blood group O. The new association to Le^a could be explained by a link between mucosal microbiome and SARS-CoV-2.

Prevalence of major depressive disorder in 51,658 otherwise healthy adult Danes: Sex differences in symptomatology and prediction of future anti-depressive medication

Major Depressive Disorder (MDD) is a heterogeneous disease, which displays sex differences in symptomatology. This study aimed to assess point prevalence of MDD in undiagnosed, healthy adults as well as sex differences in symptomatology and clarify if specific symptoms increased the later need for anti-depressive medication. The study included 51,658 blood donors. Depressive symptoms were assessed according to ICD-10 using the Major Depression Inventory. Demographics, previous MDD, anti-depressive medication were collected from questionnaires and population registers. Descriptive, Logistic and Cox regression analyses were conducted. In total, 1.15% participants met the criteria for MDD. Women were significantly more likely to experience "increased appetite" and less likely to experience "a feeling of life not worth living", compared to men. MDD significantly associated with an increased hazard of later receiving a prescription for anti-depressive medication. The risk increased proportionally with increasing MDD severity. The two symptoms, "feeling that life is not worth living" and "trouble sleeping" were the strongest individual predictive symptoms of future anti-depressive medication in women and men, respectively. The results confirm findings in MDD patient groups. The diagnostic and prognostic value should be investigated further to address their potential as part of the clinical assessment.

Human leukocyte antigen system associations in Malassezia-related skin diseases

BACKGROUND

The human leukocyte antigen system (HLA) is divided into two classes involved in antigen presentation: class I presenting intracellular antigens and class II presenting extracellular antigens. While susceptibility to infections is correlated with the HLA system, data on associations between HLA genotypes and Malassezia-related skin diseases (MRSD) are lacking. Thus, the objective of this study was to investigate associations between HLA alleles and MRSD.

MATERIALS AND METHODS

Participants in The Danish Blood Donor Study (2010-2018) provided questionnaire data on life style, anthropometric measures, and registry data on filled prescriptions. Genotyping was done using Illumina Infinium Global Screening Array, and HLA alleles were imputed using the HIBAG algorithm. Cases and controls were defined using filled prescriptions on topical ketoconazole 2% as a proxy of MRSD. Logistic regressions assessed associations between HLA alleles and MRSD adjusted for confounders and Bonferroni corrected for multiple tests.

RESULTS

A total of 9455 participants were considered MRSD cases and 24,144 participants as controls. We identified four risk alleles B*57:01, OR 1.19 (95% CI: 1.09-1.31), C*01:02, OR 1.19 (95% CI: 1.08-1.32), C*06:02, OR 1.14 (95% CI: 1.08-1.22), and DRB1*01:01, OR 1.10 (95% CI: 1.04-1.17), and two protective alleles, DQB1*02:01, OR 0.89 (95% CI: 0.85-0.94), and DRB1*03:01, OR 0.89 (95% CI: 0.85-0.94).

CONCLUSION

Five novel associations between HLA alleles and MRSD were identified in our cohort, and one previous association was confirmed. Future studies should assess the correlation between Malassezia antigens and antigen-binding properties of the associated HLA alleles.

Investigating the inflammation marker neutrophil-to-lymphocyte ratio in Danish blood donors with restless legs syndrome

Background

Restless Legs Syndrome (RLS) is a neurological sensorimotor disorder that occurs in the evening and night, thereby impacting quality of sleep in sufferers. The pathophysiology of RLS is poorly understood but inflammation has been proposed as possibly being involved. The neutrophil-to-lymphocyte ratio (NLR) can be used as an inflammation marker but results from small studies have been inconclusive in determining whether NLR is associated with RLS. We aimed to assess whether an association between NLR and RLS exists in a large cohort of healthy individuals.

Methods

Neutrophils and lymphocytes were measured in blood samples of 13,055 individuals from the Danish Blood Donor Study, all of whom completed the validated Cambridge-Hopkins RLS-questionnaire for RLS assessment.

Results

In the sample, 661 individuals were determined as current RLS cases (5.1%). A higher proportion of individuals with RLS were females (62.5% vs 47.5%; P<0.001) and RLS cases were older than controls (P<0.001), but no differences in body mass index (BMI), smoking or alcohol consumption were found between the two groups. An increased NLR was observed in RLS cases compared to controls (median NLR: 1.80 vs 1.72; P = 0.033). In an unadjusted logistic regression model, increased NLR was associated with RLS (OR = 1.10 per NLR unit increase [95%CI:1.01–1.20]; P = 0.032); however, the association was not significant in multivariate models adjusting for sex and age (P = 0.094) or sex, age, alcohol consumption, smoking status and BMI (P = 0.107).

Conclusion

We found no association between RLS and NLR among Danish blood donors after adjusting for sex, age, alcohol consumption, smoking status and BMI. Further studies are needed to determine whether inflammation is a risk factor for RLS.

No association between plasma hepcidin levels and restless legs syndrome - results from the Danish Blood Donor Study

BACKGROUND

Restless Legs Syndrome (RLS) is a neurological sensorimotor disorder that occurs in the evening and night, thereby often impacting quality of sleep in sufferers. The aetiology of RLS is not completely understood although iron dysregulation has been suggested as a likely pathway. The relationship between RLS and the iron regulatory protein hepcidin has not been studied in large cohorts. We aimed to assess whether an association between plasma hepcidin variation and RLS exists in a large cohort of healthy individuals.

METHODS

Plasma hepcidin levels were measured in 9708 Danish blood donors from the Danish Blood Donor Study all of whom correctly completed the validated Cambridge-Hopkins RLS-questionnaire for RLS assessment.

RESULTS

A total of 466 blood donors were determined as current RLS cases in the sample (4.8%). RLS cases had a significantly higher proportion of females (56.7% vs 46.7%; P < 0.001) and were older (median age [IQR] 40.6 years vs 38.0 years; P = 0.010) than controls. RLS cases were also more frequent smokers (P = 0.004). No significant differences were found in body mass index (BMI), alcohol consumption, time of donation and donation history between cases and controls. No difference in plasma hepcidin levels was observed between RLS cases and controls (median concentration [IQR]: 10.5 ng/ml [6.3-16.4] in RLS cases vs 10.5 ng/ml [6.0-16.5] in controls). Using a logistic regression model, we found that hepcidin levels were not associated with RLS after adjusting for age, sex, alcohol consumption, smoking status, donation time and donation history (OR = 1.00 [0.99-1.02] per 1 ng/ml increase of hepcidin; P = 0.429).

CONCLUSION

Our study in Danish blood donors did not find an association between RLS and plasma hepcidin levels. Our findings suggest that plasma hepcidin's role as a potential diagnostic biomarker of RLS is inadequate.

A life course approach to understanding associations between natural environments and mental well-being for the Danish blood donor cohort

Natural environments have been associated with mental health benefits, but globally access to these benefits is threatened by urban development and densification. However, it remains unclear how natural environments relate to mental health and how consistent the association is across populations. Here we use a life-course approach with a population consisting of 66 194 individuals from the Danish Blood Donor Study (DBDS) to investigate the association between green and blue space (e.g. parks and lakes) and self-evaluated mental well-being. Green and blue space was identified from remotely-sensed images from the Landsat program, while mental well-being was based on the mental component score (MCS) calculated using the 12-item short form health survey. We use multivariate linear regression models and logistic regression models to quantify the associations. We adjust for additional environmental (urbanization, and air pollution) and lifestyle factors (smoking, body mass index, socioeconomic status, and physical activity) and specifically evaluate the role of physical activity and air pollution as possible mediating factors. We found a positive association between the MCS and current and childhood green space, and a non-significant association for current and childhood blue space. Adjusting for environmental and the other factors attenuated the effect sizes indicating that a broad range of factors determine mental well-being. Physical activity and air pollution were both associated with the MCS as possible mediators of green space associations. In addition, the odds for successfully completing tasks', seeing others, and feeling less downhearted increased with higher levels of green space, and the odds of feeling calm increased with higher levels of blue space. In conclusion, we found support for an association between green and, to less degree, blue space and mental well-being throughout different life stages. In addition, we found a positive association with individual indicators of mental well-being such as being productive, feeling less downhearted and calmer, and being social. The healthy blood donor effect and the bias towards urban residency may explain why we found smaller effect sizes between green and blue space and mental well-being for this generally healthy and resourceful cohort compared to previous studies.

Hyperhidrosis and the risk of being treated for skin infections

BACKGROUND

A few studies have described an increased prevalence of skin infections in individuals with hyperhidrosis compared to others. However, it remains uncertain whether hyperhidrosis is an independent risk factor for skin infections.

OBJECTIVE

To compare the risk of skin infections in individuals with and without hyperhidrosis.

METHODS

In this retrospective cohort study, data on hyperhidrosis were collected from the Danish Blood Donor Study. Blood donors included in 2010-2019 were followed from inclusion until December 2019. Data on redeemed prescriptions against skin infections were collected from the National Prescription Register. The intensity of prescription-use by hyperhidrosis status was assessed in Andersen-Gill models.

RESULTS

Overall, 4,176 (9.6%) of 43,477 blood donors had self-reported hyperhidrosis and 437 (0.34%) of 127,823 blood donors had hospital diagnosed hyperhidrosis. Self-reported hyperhidrosis was associated with the use of antibiotic prescriptions (adjusted hazard ratio = 1.21; 95% confidence interval 1.00-1.45, p = 0.047). Hospital diagnosed hyperhidrosis was associated with the use of antibiotic (adjusted hazard ratio = 1.33; 95% confidence interval 1.03-1.68, p = 0.028) and topical antifungal prescriptions (adjusted hazard ratio = 1.43; 95% confidence interval 1.04-1.97, p = 0.027).

CONCLUSIONS

Hyperhidrosis is associated with the use of prescriptions for antibiotics and topical antifungals. This suggests a clinically relevant association between hyperhidrosis and skin infections.

Association of proton pump inhibitor and histamine H2-receptor antagonists with restless legs syndrome

Restless legs syndrome (RLS) is a common sensorimotor disorder, which can disrupt sleep and is thought to be caused in part by low cellular iron stores. Proton pump inhibitors (PPI) and histamine H₂-receptor antagonists (H₂A) are among the most commonly used drugs worldwide and show evidence of causing iron deficiency. We conducted a case/non-case observational study of blood donors in the United States (N = 13,403; REDS-III) and Denmark (N = 50,323; Danish Blood Donor Study, DBDS), both of which had complete blood count measures and a completed RLS assessment via the Cambridge–Hopkins RLS questionnaire. After adjusting for age, sex, race, BMI, blood donation frequency, smoking, hormone use, and iron supplement use, PPI/H₂A use was associated with RLS (odds ratio [OR] = 1.41; 95% confidence interval [CI], 1.13–1.76; p = 0.002) in REDS-III for both PPI (OR = 1.43; CI, 1.03–1.95; p = 0.03) and H₂A (OR = 1.56; CI, 1.10–2.16; p = 0.01). DBDS exhibited a similar association with PPIs/H₂As (OR = 1.29; CI, 1.20–1.40; p < 0.001), and for PPIs alone (OR = 1.27; CI, 1.17–1.38; p < 0.001), but not H₂As alone (OR = 1.18; CI, 0.92–1.53; p = 0.2). We found no evidence of blood iron stores mediating this association. The association of PPI, and possibly H₂A, consumption with RLS independent of blood iron status and other factors which contribute to RLS risk suggest the need to re-evaluate use of PPI/H₂A in populations at particular risk for RLS.

The impact of health-related quality of life and depressive symptoms on blood donor career-Results from the Danish blood donor study

BACKGROUND

Blood donors report better health-related quality of life (HRQL) than non-donors. Likewise, donors reporting good health are less likely to stop donating and have a higher donation frequency. This is evidence of the healthy donor effect (HDE). This study is the first to investigate the impact of HRQL and depressive symptoms on subsequent donor career.

STUDY DESIGN AND METHODS

Prospective cohort study includes 102,065 participants from the Danish Blood Donor Study applying the 12-item short-form health survey (SF-12) measuring a mental (MCS) and a physical component score (PCS) and the Major Depression Inventory (MDI). Poisson and Cox regression models were used to assess the effect of SF-12 and MDI scores on donation frequency and donor cessation. Higher MCS/PCS scores indicate good HRQL, while higher MDI score indicates higher experience of depressive symptoms.

RESULTS

For both sexes, MCS was positively correlated with donation frequency for up to 5 years, and similarly for PCS among women. A negative correlation between MDI score and donation frequency in the year following assessment was observed only among men. No correlation was observed among women. An increase in both MCS and PCS was associated with a lower risk of donation cessation in both sexes, while an increase in MDI score was only associated with an increased risk of donation cessation in men.

CONCLUSION

MCS, PCS, and MDI score affect donor career. Thus, adjusting for donation frequency may reduce HDE-bias in donor health research. However, because of the small effect sizes, other ways of quantifying HDE may be beneficial.

Large genome-wide association study identifies three novel risk variants for restless legs syndrome

Restless legs syndrome (RLS) is a common neurological sensorimotor disorder often described as an unpleasant sensation associated with an urge to move the legs. Here we report findings from a meta-analysis of genome-wide association studies of RLS including 480,982 Caucasians (cases = 10,257) and a follow up sample of 24,977 (cases = 6,651). We confirm 19 of the 20 previously reported RLS sequence variants at 19 loci and report three novel RLS associations; rs112716420-G (OR = 1.25, P = 1.5 × 10-18), rs10068599-T (OR = 1.09, P = 6.9 × 10-10) and rs10769894-A (OR = 0.90, P = 9.4 × 10-14). At four of the 22 RLS loci, cis-eQTL analysis indicates a causal impact on gene expression. Through polygenic risk score for RLS we extended prior epidemiological findings implicating obesity, smoking and high alcohol intake as risk factors for RLS. To improve our understanding, with the purpose of seeking better treatments, more genetics studies yielding deeper insights into the disease biology are needed.

SARS-CoV-2 infection fatality rate among elderly retired Danish blood donors - A cross-sectional study

BACKGROUND

Despite the vast majority of individuals succumbing to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are elderly, infection fatality rate (IFR) estimates for the age group 70 years older are still scarce. To this end we assessed SARS-CoV-2 seroprevalence among retired blood donors and combined it with national COVID-19 survey data to provide reliable population-based IFR estimates for this age group.

METHODS

We identified 60,926 retired blood donors age 70 years or older in the rosters of three region-wide Danish blood banks and invited them to fill in a questionnaire on COVID-19 related symptoms and behaviours. Among 24,861 (40.8%) responders, we invited a random sample of 3,200 individuals for blood testing. Overall, 1,201 (37.5%) individuals were tested for SARS-CoV-2 antibodies (Wantai) and compared to 1,110 active blood donors age 17-69 years. Seroprevalence 95% confidence intervals (CI) were adjusted for assay sensitivity and specificity.

RESULTS

Among retired (age 70 years or older) and active (age 17-69 years) blood donors, adjusted seroprevalences were 1.4% (95% CI: 0.3%-2.5%) and 2.5% (95% CI: 1.3%-3.8%), respectively. Using available population data on COVID-19 related fatalities, IFRs for patients age 70 years or older and for 17-69 years were estimated at 5.4% (95% CI: 2.7%-6.4%) and 0.083% (95% CI: 0.054%-0.18%), respectively. Only 52.4% of SARS-CoV-2 seropositive retired blood donors reported having been sick since the start of the pandemic.

CONCLUSION

COVID-19 IFR in the age group above 69 years is estimated to be 65 times as high as the IFR for people age 18-69 years.

Genetic factors influencing hemoglobin levels in 15,567 blood donors: results from the Danish Blood Donor Study

BACKGROUND

Blood donors have an increased risk of low hemoglobin (Hb) levels due to iron deficiency. Therefore, knowledge of genetic variants associated with low Hb could facilitate individualized donation intervals. We have previously reported three specific single-nucleotide polymorphisms that were associated with ferritin levels in blood donors. In this study, we investigated the effect of these single-nucleotide polymorphisms on Hb levels in 15,567 Danish blood donors.

STUDY DESIGN AND METHODS

We studied 15,567 participants in the Danish Blood Donor Study. The examined genes and single-nucleotide polymorphisms were 1) TMPRSS6, involved in regulation of hepcidin: rs855791; 2) HFE, associated with hemochromatosis: rs1800562 and rs1799945; 3) BTBD9, associated with restless leg syndrome: rs9357271; and 4) TF, encoding transferrin: rs2280673 and rs1830084. Associations with Hb levels and risk of Hb deferral were assessed in multivariable linear and logistic regression models.

RESULTS

The HFE,rs1800562 G-allele and the HFE rs1799945 C-allele were associated with lower Hb levels in men and women, and with an increased risk of Hb below 7.8 mmol/L (12.5 g/dL) in women. Only the rs1799945 C-allele increased the risk of Hb below 8.4 mmol/L (13.5 g/dL) in men. In TMPRSS6, the rs855791 T-allele was associated with lower Hb levels in both men and women, and with an increased risk of low Hb among women.

CONCLUSION

With this study we demonstrate that HFE and TMPRSS6 are associated with Hb levels and risk of Hb below the limit of deferral. Thus, genetic testing may be useful in a future assay for personalized donation intervals.

Epidemiology of chronic red-cell transfusion recipients in Sweden and Denmark-a 10 year follow-up study

BACKGROUND AND OBJECTIVES

Chronic red-cell transfusions may be an indispensable part of patient treatment and may require early intervention to avoid adverse transfusion effects. The population of chronic transfusion recipients including common diagnoses and survival remains poorly characterised. Thus, the objective was to examine the complete range of chronic transfusion recipients, including demographic and patient characteristics and survival.

MATERIALS AND METHODS

All patients who received their first transfusion in Sweden or Denmark from January 1, 2002 to December 31, 2010 were followed up for subsequent transfusion episodes until December 31, 2012. Data on patient characteristics at time of the first and subsequent transfusions were retrieved from the national registers. We estimated the proportion of transfused patients who experienced 20 or more red-cell transfusion episodes (with an episode defined as all transfusions received 4 days or less apart) and characterised this patient population with respect to diagnoses, demographics and survival.

RESULTS

Among 893 117 first time red-cell transfusion recipients, 6157 (0·7%) experienced 20 or more episodes in total. The most common diagnoses among these patients were haematologic malignancies followed by non-haematologic malignancies and non-malignant blood and immune system related diseases. On average, chronically transfused patients had a median survival of less than 1 year following their 20th transfusion episode.

CONCLUSION

This study provides an overview of patient characteristics related to repeat red-cell transfusions and of the amount of red-cell transfusion episodes administered during a 10-year period in two countries. Patients who become chronically transfused suffer from diseases with poor prognosis.

Restless legs syndrome is associated with increased risk of migraine

Migraine and restless legs syndrome (RLS) are common disorders that are associated with a high level of individual suffering and major comorbidities. The aetiologies of the disorders are largely unknown, although both migraine and RLS have been linked to disturbances in the dopaminergic system and sleep issues, suggesting a relationship between the disorders. This study examines the association between RLS and migraine in a large population of otherwise healthy adults who are not taking medication. Cross-sectional study that included 20,938 participants enrolled in the Danish Blood Donor Study from 1 May 2015 to 1 February 2017. The study included complete information on migraines, the Cambridge-Hopkins RLS questionnaire, the Major Depression Inventory Scale, sex, age, body mass index (BMI), educational level, smoking status and alcohol consumption. Associations between RLS and migraine, with and without aura, were examined using multivariable logistic regression analysis. Among the participants, 4827 were self-reported migraine sufferers and 1091 were classified as suffering from RLS. Individuals with RLS had an increased risk of migraine compared to non-RLS sufferers, with an odds ratio (OR) = 1.52 (95% confidence interval: 1.33–1.73). For the investigated subtypes of migraine, this association was found to be OR = 1.55 (1.31–1.83) for migraines with aura and OR = 1.29 (1.09–1.52) for migraines without aura. We found a significantly increased occurrence of migraine in individuals with RLS. This risk was independent of sex, age, BMI, educational level, smoking status, alcohol consumption and depressive disorder. Our findings suggest that RLS and migraine may have a common aetiology.

The association of IgA deficiency on infection rate, self-perceived health, and levels of C-reactive protein in healthy blood donors

The clinical importance of immunoglobulin A (IgA) deficiency in otherwise healthy individuals is not well described. We aimed to investigate the self-reported mental and physical health and the risk of infection in IgA-deficient blood donors compared to healthy control blood donors. Infectious events, recorded in public health registries either as prescriptions filled of any antimicrobial medicine or as hospital infections, were compared between 177 IgA-deficient blood donors and 1770 control blood donors. A subset of the IgA-deficient donors were further characterized by self-reported health (Short Form-12, n = 28) and circulating C-reactive protein (CRP) (n = 10). IgA-deficient individuals had lower self-reported mental health (p = 0.01) and higher CRP (p < 0.05). A strong trend was found regarding prescription of antimicrobial medicine (hazard ratio = 1.19, p = 0.05). No association was found with hospital infections (hazard ratio = 1.02, p = 0.95) or self-reported physical health (p = 0.86). IgA-deficient blood donors have impaired self-reported mental health, enhanced inflammation and possibly an increased risk of infection. Despite these findings, this study does not provide sufficient evidence to warrant specific health precautions for donors with IgA deficiency.

Restless legs syndrome is associated with major comorbidities in a population of Danish blood donors

BACKGROUND

Restless Legs Syndrome (RLS) is characterized by uncomfortable nocturnal sensations in the legs making sedentary activities and sleep difficult, and is thus linked with psychosocial distress. Due to the symptomatology and neurobiology of RLS (disrupting brain iron and dopamine) it is likely that RLS associates with poorer health-related quality of life (HRQL) and depressive disorder. The objective of this study was to investigate the RLS-HRQL and the RLS-depressive disorder links in a generally healthy population that is not biased by medications.

METHODS

Complete data, including the Cambridge-Hopkins RLS questionnaire, the 12-item short-form standardized health survey (SF-12), the Major Depression Inventory (MDI), body mass index, smoking status, alcohol consumption, and education were available for 24,707 participants enrolled in the Danish Blood Donor Study from May 1, 2015 to February 1, 2017. Information on quality of sleep was available for all RLS cases. T-tests and multivariable logistic regression models were applied to examine the associations of RLS and MDI scores, and the physical and mental component scores (PCS and MCS) of SF-12, respectively. Analyses were conducted separately for men and women.

RESULTS

RLS associated with poorer MCS and poorer PCS. Moreover, Participants with RLS were more likely to classify with depressive disorder. Poor quality of sleep was associated with depressive disorder and poorer MCS among RLS cases, and with poorer PCS in female RLS cases.

CONCLUSION

Thus, we demonstrated that RLS is associated with a significantly lower HRQL and a higher prevalence of depressive disorder among otherwise healthy individuals.

Oxidative stress-driven parvalbumin interneuron impairment as a common mechanism in models of schizophrenia

Parvalbumin inhibitory interneurons (PVIs) are crucial for maintaining proper excitatory/inhibitory balance and high-frequency neuronal synchronization. Their activity supports critical developmental trajectories, sensory and cognitive processing, and social behavior. Despite heterogeneity in the etiology across schizophrenia and autism spectrum disorder, PVI circuits are altered in these psychiatric disorders. Identifying mechanism(s) underlying PVI deficits is essential to establish treatments targeting in particular cognition. On the basis of published and new data, we propose oxidative stress as a common pathological mechanism leading to PVI impairment in schizophrenia and some forms of autism. A series of animal models carrying genetic and/or environmental risks relevant to diverse etiological aspects of these disorders show PVI deficits to be all accompanied by oxidative stress in the anterior cingulate cortex. Specifically, oxidative stress is negatively correlated with the integrity of PVIs and the extracellular perineuronal net enwrapping these interneurons. Oxidative stress may result from dysregulation of systems typically affected in schizophrenia, including glutamatergic, dopaminergic, immune and antioxidant signaling. As convergent end point, redox dysregulation has successfully been targeted to protect PVIs with antioxidants/redox regulators across several animal models. This opens up new perspectives for the use of antioxidant treatments to be applied to at-risk individuals, in close temporal proximity to environmental impacts known to induce oxidative stress.

Nutrition support in hospitalised adults at nutritional risk

BACKGROUND

The prevalence of disease-related malnutrition in Western European hospitals is estimated to be about 30%. There is no consensus whether poor nutritional status causes poorer clinical outcome or if it is merely associated with it. The intention with all forms of nutrition support is to increase uptake of essential nutrients and improve clinical outcome. Previous reviews have shown conflicting results with regard to the effects of nutrition support.

OBJECTIVES

To assess the benefits and harms of nutrition support versus no intervention, treatment as usual, or placebo in hospitalised adults at nutritional risk.

SEARCH METHODS

We searched Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (Ovid SP), Embase (Ovid SP), LILACS (BIREME), and Science Citation Index Expanded (Web of Science). We also searched the World Health Organization International Clinical Trials Registry Platform (www.who.int/ictrp); ClinicalTrials.gov; Turning Research Into Practice (TRIP); Google Scholar; and BIOSIS, as well as relevant bibliographies of review articles and personal files. All searches are current to February 2016.

SELECTION CRITERIA

We include randomised clinical trials, irrespective of publication type, publication date, and language, comparing nutrition support versus control in hospitalised adults at nutritional risk. We exclude trials assessing non-standard nutrition support.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane and the Cochrane Hepato-Biliary Group. We used trial domains to assess the risks of systematic error (bias). We conducted Trial Sequential Analyses to control for the risks of random errors. We considered a P value of 0.025 or less as statistically significant. We used GRADE methodology. Our primary outcomes were all-cause mortality, serious adverse events, and health-related quality of life.

MAIN RESULTS

We included 244 randomised clinical trials with 28,619 participants that met our inclusion criteria. We considered all trials to be at high risk of bias. Two trials accounted for one-third of all included participants. The included participants were heterogenous with regard to disease (20 different medical specialties). The experimental interventions were parenteral nutrition (86 trials); enteral nutrition (tube-feeding) (80 trials); oral nutrition support (55 trials); mixed experimental intervention (12 trials); general nutrition support (9 trials); and fortified food (2 trials). The control interventions were treatment as usual (122 trials); no intervention (107 trials); and placebo (15 trials). In 204/244 trials, the intervention lasted three days or more.We found no evidence of a difference between nutrition support and control for short-term mortality (end of intervention). The absolute risk was 8.3% across the control groups compared with 7.8% (7.1% to 8.5%) in the intervention groups, based on the risk ratio (RR) of 0.94 (95% confidence interval (CI) 0.86 to 1.03, P = 0.16, 21,758 participants, 114 trials, low quality of evidence). We found no evidence of a difference between nutrition support and control for long-term mortality (maximum follow-up). The absolute risk was 13.2% in the control group compared with 12.2% (11.6% to 13%) following nutritional interventions based on a RR of 0.93 (95% CI 0.88 to 0.99, P = 0.03, 23,170 participants, 127 trials, low quality of evidence). Trial Sequential Analysis showed we only had enough information to assess a risk ratio reduction of approximately 10% or more. A risk ratio reduction of 10% or more could be rejected.We found no evidence of a difference between nutrition support and control for short-term serious adverse events. The absolute risk was 9.9% in the control groups versus 9.2% (8.5% to 10%), with nutrition based on the RR of 0.93 (95% CI 0.86 to 1.01, P = 0.07, 22,087 participants, 123 trials, low quality of evidence). At long-term follow-up, the reduction in the risk of serious adverse events was 1.5%, from 15.2% in control groups to 13.8% (12.9% to 14.7%) following nutritional support (RR 0.91, 95% CI 0.85 to 0.97, P = 0.004, 23,413 participants, 137 trials, low quality of evidence). However, the Trial Sequential Analysis showed we only had enough information to assess a risk ratio reduction of approximately 10% or more. A risk ratio reduction of 10% or more could be rejected.Trial Sequential Analysis of enteral nutrition alone showed that enteral nutrition might reduce serious adverse events at maximum follow-up in people with different diseases. We could find no beneficial effect of oral nutrition support or parenteral nutrition support on all-cause mortality and serious adverse events in any subgroup.Only 16 trials assessed health-related quality of life. We performed a meta-analysis of two trials reporting EuroQoL utility score at long-term follow-up and found very low quality of evidence for effects of nutritional support on quality of life (mean difference (MD) -0.01, 95% CI -0.03 to 0.01; 3961 participants, two trials). Trial Sequential Analyses showed that we did not have enough information to confirm or reject clinically relevant intervention effects on quality of life.Nutrition support may increase weight at short-term follow-up (MD 1.32 kg, 95% CI 0.65 to 2.00, 5445 participants, 68 trials, very low quality of evidence).

AUTHORS' CONCLUSIONS

There is low-quality evidence for the effects of nutrition support on mortality and serious adverse events. Based on the results of our review, it does not appear to lead to a risk ratio reduction of approximately 10% or more in either all-cause mortality or serious adverse events at short-term and long-term follow-up.There is very low-quality evidence for an increase in weight with nutrition support at the end of treatment in hospitalised adults determined to be at nutritional risk. The effects of nutrition support on all remaining outcomes are unclear.Despite the clinically heterogenous population and the high risk of bias of all included trials, our analyses showed limited signs of statistical heterogeneity. Further trials may be warranted, assessing enteral nutrition (tube-feeding) for different patient groups. Future trials ought to be conducted with low risks of systematic errors and low risks of random errors, and they also ought to assess health-related quality of life.

The translationally relevant mouse model of the 15q13.3 microdeletion syndrome reveals deficits in neuronal spike firing matching clinical neurophysiological biomarkers seen in schizophrenia

Aim

To date, the understanding and development of novel treatments for mental illness is hampered by inadequate animal models. For instance, it is unclear to what extent commonly used behavioural tests in animals can inform us on the mental and affective aspects of schizophrenia.

Methods

To link pathophysiological processes in an animal model to clinical findings, we have here utilized the recently developed Df(h15q13)/+ mouse model for detailed investigations of cortical neuronal engagement during pre‐attentive processing of auditory information from two back‐translational auditory paradigms. We also investigate if compromised putative fast‐spiking interneurone (FSI) function can be restored through pharmacological intervention using the Kv3.1 channel opener RE1. Chronic multi‐array electrodes in primary auditory cortex were used to record single cell firing from putative pyramidal and FSI in awake animals during processing of auditory sensory information.

Results

We find a decreased amplitude in the response to auditory stimuli and reduced recruitment of neurones to fast steady‐state gamma oscillatory activity. These results resemble encephalography recordings in patients with schizophrenia. Furthermore, the probability of interneurones to fire with low interspike intervals during 80 Hz auditory stimulation was reduced in Df(h15q13)/+ mice, an effect that was partially reversed by the Kv3.1 channel modulator, RE1.

Conclusion

This study offers insight into the consequences on a neuronal level of carrying the 15q13.3 microdeletion. Furthermore, it points to deficient functioning of interneurones as a potential pathophysiological mechanism in schizophrenia and suggests a therapeutic potential of Kv3.1 channel openers.

Associations between social cognition, skills, and function and subclinical negative and positive symptoms in 22q11.2 deletion syndrome

Background

Identification of the early signs of schizophrenia would be a major achievement for the early intervention and prevention strategies in psychiatry. Social impairments are defining features of schizophrenia. Impairments of individual layers of social competencies are frequently described in individuals with 22q11.2 deletion syndrome (22q11.2DS), who have high risk of schizophrenia. It is unclear whether and to what extent social impairments associate with subclinical negative and positive symptoms in 22q11.2DS, and which layer of social impairments are more correlated with schizophrenia-related symptoms. The aims of this study were to conduct a comprehensive investigation of social impairments at three different levels (function, skill, and cognition) and their interrelationship and to determine to what degree the social impairments correlate to subclinical levels of negative and positive symptoms, respectively, in a young cohort of 22q11.2DS not diagnosed with schizophrenia.

Methods

The level of social impairment was addressed using questionnaires and objective measures of social functioning (The Adaptive Behavior Assessment System), skills (Social Responsiveness Scale), and cognition (The Awareness of Social Inference Test and CANTAB Emotional Recognition Task), and the presence of subclinical symptoms of schizophrenia were evaluated using the Structured Interview for Prodromal Syndromes in a cross-sectional case-control study of 29 cases and 29 controls, aged 12 to 25 years. Association between social impairment and negative and positive symptoms levels was examined in cases only.

Results

Subjects with 22q11.2DS were highly impaired in social function, social skills, and social cognition (p ≤ 6.2 × 10⁻⁹) relative to control peers and presented with more negative (p = 5.8 × 10⁻¹¹) and positive (p = 7.5 × 10⁻⁴) symptoms. In particular, social functional and skill levels were highly associated with notably subclinical negative symptoms levels.

Conclusions

This study shows strong correlations between levels of social impairments and subclinical negative and positive symptoms. However, longitudinal studies are required to show if social impairments represent early disease manifestations. If parental or self-reporting suggests severe social impairment, it should advocate for clinical awareness not only to social deficits per se but also of potential subclinical psychosis symptoms.

Genome-wide study of association and interaction with maternal cytomegalovirus infection suggests new schizophrenia loci

Genetic and environmental components as well as their interaction contribute to the risk of schizophrenia, making it highly relevant to include environmental factors in genetic studies of schizophrenia. This study comprises genome-wide association (GWA) and follow-up analyses of all individuals born in Denmark since 1981 and diagnosed with schizophrenia as well as controls from the same birth cohort. Furthermore, we present the first genome-wide interaction survey of single nucleotide polymorphisms (SNPs) and maternal cytomegalovirus (CMV) infection. The GWA analysis included 888 cases and 882 controls, and the follow-up investigation of the top GWA results was performed in independent Danish (1396 cases and 1803 controls) and German-Dutch (1169 cases, 3714 controls) samples. The SNPs most strongly associated in the single-marker analysis of the combined Danish samples were rs4757144 in ARNTL (P=3.78 × 10(-6)) and rs8057927 in CDH13 (P=1.39 × 10(-5)). Both genes have previously been linked to schizophrenia or other psychiatric disorders. The strongest associated SNP in the combined analysis, including Danish and German-Dutch samples, was rs12922317 in RUNDC2A (P=9.04 × 10(-7)). A region-based analysis summarizing independent signals in segments of 100 kb identified a new region-based genome-wide significant locus overlapping the gene ZEB1 (P=7.0 × 10(-7)). This signal was replicated in the follow-up analysis (P=2.3 × 10(-2)). Significant interaction with maternal CMV infection was found for rs7902091 (P(SNP × CMV)=7.3 × 10(-7)) in CTNNA3, a gene not previously implicated in schizophrenia, stressing the importance of including environmental factors in genetic studies.

Performance of male C57BL/6J mice and Wistar rats in the water maze following various schedules of phencyclidine treatment

In order to establish an animal model of cognitive impairments relevant to schizophrenia, we set out to obtain an optimal treatment protocol with phencyclidine (PCP) that would lead to robust cognitive impairment with minimal PCP-related adverse effects. Effects of various doses (0.63-5 mg/kg), pre-treatment period (0, 3, 7 and 10 days before the beginning of acquisition) and treatment schedules (before the first or immediately after the last trial on each day) of PCP on the performance of male C57BL/6J mice and Wistar rats in the spatial version of the water maze were studied. In mice, a 10-day pre-treatment period was required to prevent PCP-induced motor impairments, whereas a 3-day pre-treatment was sufficient in rats. PCP impaired spatial learning in both rats and mice, if animals were administered PCP prior to the first trial. The optimal dose was 2.5 mg/kg. In contrast, animals given PCP immediately after the daily training sessions performed as well as controls. Thus, PCP impairs spatial learning in the water maze only when present in the organism. It can be concluded that PCP interferes with learning, and perhaps retrieval, but not consolidation of newly acquired information.

Effects of the 5-HT(6) receptor antagonist, SB-271046, in animal models for schizophrenia

The 5-HT(6) receptor is targeted by several new antipsychotics such as clozapine, olanzapine, and sertindole. We studied the effect of SB-271046 [5-chloro-N-(4-methoxy-3-piperazin-1-yl-phenyl)-3-methyl-2-benzothiophenesulfonamide], a specific 5-HT(6) receptor antagonist, in three models for the positive symptoms of schizophrenia---D-amphetamine-induced hyperactivity, and D-amphetamine- or phencyclidine (PCP)-disrupted prepulse inhibition (PPI). We also tested this compound in a model for the negative symptoms of schizophrenia, PCP-disrupted social interaction (SIT) in rats. Induction of side effects by this compound was evaluated by testing its potency to reduce spontaneous motility, and to induce catalepsy in rats. The effect of SB-271046 was compared to clozapine in all models tested. This study showed that SB-271046 had no beneficial effect in PCP-disrupted SIT. However, SB-271046 dose-dependently normalised D-amphetamine-disrupted PPI, but did not reverse PCP-disrupted PPI. In addition, SB-271046 did not antagonise D-amphetamine-induced hyperactivity. Thus, this specific 5-HT(6) receptor antagonist was associated with a clear positive outcome in only one model for the positive symptoms of schizophrenia, and had no beneficial effect in the model for negative symptoms. Consequently, it is clear that SB-271046 is not expected to have an antipsychotic efficacy, at least when given as monotherapy.

Effects of the 5-HT(7) receptor antagonist SB-258741 in animal models for schizophrenia

The 5-HT(7) receptor is targeted by several new antipsychotics such as clozapine and risperidone. We studied the effect of R-(+)-1-(toluene-3-sulfonyl)-2-[2-(4-methylpiperidin-1-yl)ethyl]-pyrrolidine (SB-258741), a specific 5-HT(7) receptor antagonist, in three models for positive symptoms, D-amphetamine-induced hyperactivity and D-amphetamine- and phencyclidine (PCP)-disrupted prepulse inhibition (PPI) in rats, with the aim of investigating the role of this receptor in the clinical effect of antipsychotics. We also tested this compound in a model for negative symptoms, PCP-disrupted social interaction (SIT) in rats. Induction of side effects by this compound was evaluated by testing its potency to reduce spontaneous motility and to induce catalepsy in rats. The effect of SB-258741 was compared to risperidone in all models. This study showed that SB-258741 had no beneficial effect on PCP-disrupted SIT. SB-258741 did not reverse D-amphetamine-disrupted PPI; however, it dose-dependently normalised PCP-disrupted PPI. SB-258741 antagonised D-amphetamine-induced hyperactivity but reduced motility of rats at similar doses. Thus, this specific 5-HT(7) receptor antagonist brought a clear positive outcome in only one model for positive symptoms of schizophrenia and had no beneficial effect in the model for negative symptoms. Consequently, it is clear that SB-258741 affects the PPI phenomenon but is not expected to have an antipsychotic effect on its own in clinic.

Induction of tolerance to the suppressant effect of the neurotensin analogue NT69L on amphetamine-induced hyperactivity

Although several studies have indicated that neurotensin administered acutely has several pharmacological properties common with those of antipsychotic drugs, the effects of repeated exposure to neurotensin receptor agonism have been less well characterised. Here, we investigated the effect of the novel neurotensin-(8-13) analogue NT69L [(N-methyl-Arg), Lys, Pro, L-neo-Trp, tert-Leu, Leu] in animal models sensitive to central neurotensin receptor stimulation as well as in predictive models for antipsychotic activity and motor side-effect liability. Acute injection of NT69L (0.19-6.1 micromol/kg, s.c./i.p.) caused hypothermia (>2.5 degrees C) and reduction in spontaneous locomotor activity but failed to induce catalepsy. Furthermore, NT69L (0.10 micromol/kg, s.c.) counteracted the hyperlocomotion elicited by amphetamine (0.5 mg/kg, s.c.). However, repeated injections of NT69L (0.19 micromol/kg, s.c. for 6 days, twice daily) significantly reduced its effect on spontaneous locomotor activity and completely abolished its effect on amphetamine-elicited hyperactivity. Our data obtained after single injections of NT69L indicate that this drug stimulates central neurotensin receptors after peripheral administration and collectively support the notion that neurotensin receptor agonism is associated with an attractive pre-clinical profile as regards both antipsychotic activity and motor side-effect liability. However, the present results also indicate that repeated neurotensin receptor stimulation may cause a desensitisation of neurotensin receptor mediated effects.

In vivo muscarinic cholinergic mediated effects of Lu 25-109, a M1 agonist and M2/M3 antagonist in vitro

Lu 25-109 [5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine] , has M agonistic and M2/M3 antagonistic effects at muscarinic receptors in vitro; a pharmacological profile that may be beneficial in treatment of Alzheimer's disease. In the present study, we compare functional in vivo effects of Lu 25-109 and reference compounds in animal models of muscarinic cholinergic function. Lu 25-109 substituted completely for the discriminative stimulus effects of (-)-7-methyl-3-(2-propynyloxy)-4,5,6,7-tetrahydroisothiazolo -[4, 5-c]pyridine (Lu 26-046), a partial M1/M2 agonist, but only weakly for the effects of the non-selective M1/M2/M3 agonist 3-methoxy-4,5,6,7-tetrahydro-isoxazolo[4, 5-c] pyridine (O-Me-THPO). Lu 25-109 did not reverse O-Me-THPO-induced discriminative stimulus. Tacrine did not substitute for any of the training drugs. Lu 25-109 did not substitute in (-)-nicotine trained rats. Lu 25-109 did not antagonize oxotremorine-induced hypothermia, tremor and salivation in mice and antagonized physostigmine-induced lethality with low potency. Unlike non-selective muscarinic agonists and acetylcholinesterase inhibitors, Lu 25-109 did not induce hypothermia, tremor or salivation in mice. Spontaneous locomotor activity and motor co-ordination were inhibited only at high doses. Lu 25-109 had no effect on mean blood pressure in anaesthetized rats. Lu 25-109 and O-Me-THPO produced a significant increase in heart rate. The maximum increase was 37%. In anaesthetized cats, increasing i.v. doses of Lu 25-109 were without effect on the mean blood pressure, except for a short lasting (<2 min) depressor effect following the IV injection. Furthermore, Lu 25-109 did not attenuate the reflex mechanisms restoring blood pressure following orthostasis in cats. In conclusion, the drug discrimination studies suggest a unique activity profile of Lu 25-109, and the in vivo profile suggests none or a very low frequency of unwanted cholinergic mediated effects.

Excitatory amino acid receptor ligands: resolution, absolute stereochemistry, and enantiopharmacology of 2-amino-3-(4-butyl-3-hydroxyisoxazol-5-yl)propionic acid

(RS)-2-Amino-3-(4-butyl-3-hydroxyisoxazol-5-yl)propionic acid (Bu-HIBO, 6) has previously been shown to be an agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors and an inhibitor of CaCl2-dependent [3H]-(S)-glutamic acid binding (J. Med. Chem. 1992, 35, 3512-3519). To elucidate the pharmacological significance of this latter binding affinity, which is also shown by quisqualic acid (3) but not by AMPA, we have now resolved Bu-HIBO via diastereomeric salt formation using the diprotected Bu-HIBO derivative 11 and the enantiomers of 1-phenylethylamine (PEA). The absolute stereochemistry of (S)-Bu-HIBO (7) (ee = 99.0%) and (R)-Bu-HIBO (8) (ee > 99.6%) were established by an X-ray crystallographic analysis of compound 15, a salt of (R)-PEA, and diprotected 8. Circular dichroism spectra of 7 and 8 were recorded. Whereas 7 (IC50 = 0.64 microM) and 8 (IC50 = 0.57 microM) were equipotent as inhibitors of CaCl2-dependent [3H]-(S)-glutamic acid binding, neither enantiomer showed significant affinity for the synaptosomal (S)-glutamic acid uptake system(s). AMPA receptor affinity (IC50 = 0.48 microM) and agonism (EC50 = 17 microM) were shown to reside exclusively in the S-enantiomer, 7. Compounds 7 and 8 did not interact detectably with kainic acid or N-methyl-D-aspartic acid (NMDA) receptor sites. Neither 7 nor 8 affected the function of the metabotropic (S)-glutamic acid receptors mGlu2 and mGlu4a, expressed in CHO cells. Compound 8 was shown also to be inactive at mGlu1 alpha, whereas 7 was determined to be a moderately potent antagonist at mGlu1 alpha (Ki = 110 microM) and mGlu5a (Ki = 97 microM). Using the rat cortical wedge preparation, the AMPA receptor agonist effect of 7 was markedly potentiated by coadministration of 8 at 21 degrees C, but not at 2-4 degrees C. These observations together indicate that the potentiation of the AMPA receptor agonism of 7 by 8 is not mediated by metabotropic (S)-glutamate receptors but rather by the CaCl2-dependent (S)-glutamic acid binding system, which shows the characteristics of a transport mechanism. After intravenous administration in mice, 7 (ED50 = 44 mumol/kg) was slightly more potent than AMPA (1) (ED50 = 55 mumol/kg) and twice as potent as Bu-HIBO (6) (ED50 = 94 mumol/kg) as a convulsant, whereas 8 was inactive. After subcutaneous administration in mice, Bu-HIBO (ED50 = 110 mumol/kg) was twice as potent as AMPA (ED50 = 220 mumol/kg) as a convulsant. Since 7 and Bu-HIBO (EC50 = 37 microM) are much weaker than AMPA (EC50 = 3.5 microM) as AMPA receptor agonists in vitro, the presence of a butyl group in the molecules of Bu-HIBO and 7 seems to facilitate the penetration of these compounds through the blood-brain barrier.

AMPA receptor agonists: synthesis, protolytic properties, and pharmacology of 3-isothiazolol bioisosteres of glutamic acid

A number of 3-isothiazolol bioisosteres of glutamic acid (1) and analogs of the AMPA receptor agonist, (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA, 2a), including (RS)-2-amino-3-(3-hydroxy-5-methylisothiazol-4-yl)propionic acid (thio-AMPA, 2b), were synthesized. Comparative in vitro pharmacological studies on this series of 3-isothiazolol and the corresponding 3-isoxazolol amino acids were performed using a series of receptor binding assays (IC50 values) and the electrophysiological rat cortical slice model (EC50 values). Whereas 2a (IC50 = 0.04 +/- 0.005 microM, EC50 = 3.5 +/- 0.2 microM) is markedly more potent than the tert-butyl analog ATPA (3a) (IC50 = 2.1 +/- 0.16 microM, EC50 = 34 +/- 2.4 microM) in [3H]AMPA binding and electrophysiological studies, 2b (IC50 = 1.8 +/- 0.13 microM, EC50 = 15.0 +/- 2.4 microM) was approximately equipotent with thio-ATPA (3b) (IC50 = 0.63 +/- 0.07 microM, EC50 = 14 +/- 1.3 microM). (RS)-2-Amino-3-(3-hydroxyisoxazol-5-yl)propionic acid (HIBO, 4a) was approximately equipotent with its thio analog 4b, whereas 4-Br-HIBO (5a) (IC50 = 0.65 +/- 0.12 microM, EC50 = 22 +/- 0.6 microM) turned out to be much more potent than the corresponding 3-isothiazolol 5b (IC50 = 17 +/- 2.2 microM, EC50 = 500 +/- 23 microM). 2b (ED50 = 130 mumol/kg) was more potent than 2a (220 mumol/kg) as a convulsant after subcutaneous administration in mice. The protolytic properties of 2a,b-4a,b were determined using 13C NMR spectroscopy. For each pair of compounds, the alpha-amino acid groups showed similar protolytic properties, whereas the 3-isoxazolol moieties typically showed pKa values 2 units lower than those of the 3-isothiazolols. Accordingly, calculations of ionic species distributions revealed pronounced differences between 3-isoxazolol and 3-isothiazolol amino acids. No simple correlation between activity as AMPA agonists in vitro and pKa values of these compounds was apparent. On the other hand, the relative potencies of AMPA (2a) and thio-AMPA (2b) in vitro and in vivo may reflect that these compounds predominantly penetrate the blood-brain barrier as net uncharged diprotonated ionic species.

Effects of antipsychotics on cognitive behaviour in rats using the delayed non-match to position paradigm

The acute effects of the dopamine D1 receptor antagonist SCH 23390 [(R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepi n-7-ol d hemimaleat, the dopamine D2 receptor antagonists raclopride and haloperidol, the compounds with mixed receptor profiles clozapine, risperidone and sertindole, the alpha 1-adrenoceptor antagonist prazosin and scopolamine were investigated in a delay-response task, a test for working memory, for rats. SCH 23390 induced a delay-dependent impairment of the performance. Raclopride, haloperidol, clozapine, and risperidone induced a delay-independent impairment. Sertindole was without effect. The specific (delay-dependent) and unspecific (delay-independent) effects on working memory of the dopamine D1 and D2 receptor antagonists, respectively, were associated with the dominance of dopamine D1 receptors in the prefrontal cortex and of dopamine D2 receptors in the basal structures of the brain. Prazosin did not affect working memory; however, a reduction in intertrial responses was found. Scopolamine induced a delay-independent impairment. It is concluded that the compounds have different activity profiles in this cognitive task. This finding may have important implications for the development of antipsychotics with a lower propensity for cognitive side effects.

The effect of risperidone on schedule-induced polydipsia

The effects of risperidone on the acquisition of schedule-induced polydipsia in rats were investigated in a chronic dose regime followed by seven days of withdrawal. Risperidone dose-dependently suppressed water intake and number of panel pushes. Drinking efficiency and free water intake in home cages were unchanged. By comparing the effects of risperidone in the present paper with the effects of different-neuroleptics in the same procedure from an earlier study, it appears that the effect of risperidone is intermediary to that of the 'typical' and 'atypical' neuroleptics. It may be concluded that risperidone acts as an atypical neuroleptic compound; however, increasing the dose only two-fold will cause EPS.