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Metabolites are small molecules involved in cellular metabolism where they act as reaction substrates or products. The term ‘metabolomics’ refers to the comprehensive study of these molecules. The concentrations of metabolites in biological tissues are under genetic control, but this is limited by environmental factors such as diet. In adult mono- and dizygotic twin pairs, we estimated the contribution of genetic and shared environmental influences on metabolite levels by structural equation modeling and tested whether the familial resemblance for metabolite levels is mainly explained by genetic or by environmental factors that are shared by family members. Metabolites were measured across three platforms: two based on proton nuclear magnetic resonance techniques and one employing mass spectrometry. These three platforms comprised 237 single metabolic traits of several chemical classes. For the three platforms, metabolites were assessed in 1407, 1037 and 1116 twin pairs, respectively. We carried out power calculations to establish what percentage of shared environmental variance could be detected given these sample sizes. Our study did not find evidence for a systematic contribution of shared environment, defined as the influence of growing up together in the same household, on metabolites assessed in adulthood. Significant heritability was observed for nearly all 237 metabolites; significant contribution of the shared environment was limited to 6 metabolites. The top quartile of the heritability distribution was populated by 5 of the 11 investigated chemical classes. In this quartile, metabolites of the class lipoprotein were significantly overrepresented, whereas metabolites of classes glycerophospholipids and glycerolipids were significantly underrepresented.
Objective: Alexithymia refers to an ineffective regulation and expression of emotions. It constitutes a major risk factor for a range of medical and psychiatric problems, including chronic pain, somatisation, anxiety and depression. Alexithymia is a multi-faceted concept, described in terms of cognitive and affective aspects. From a neuropsychological perspective, alexithymia can be defined as a disturbance in affective information processing and social cognition. As the growing literature on brain structures involved in alexithymia is fragmented and sometimes even contradictory, the aim of this article was to review findings on neural substrates with regard to their convergence.
Methods: A narrative review was performed, including both early neuropsychological and more recent imaging studies, in order to achieve a better understanding of the aetiology of alexithymia.
Results: Corpus callosum, cingulate cortex and insula are clearly involved in alexithymia. The amygdala and the orbitofrontal part of the cortex appear to be implicated as mediators, because of their broader involvement in emotional processing and executive control.
Conclusion: Notwithstanding the diffuse neural representation, the alexithymia construct can be usefully applied in the clinical and empirical studies of social cognition, particularly when adopting a dimensional neuropsychological approach.
Neurosyphilis is caused by dissemination into the central nervous system of Treponema pallidum. Although the incidence of syphilis in the Netherlands has declined since the mid-1980s, syphilis has re-emerged, mainly in the urban centres. It is not known whether this also holds true for neurosyphilis.
The epidemiology of neurosyphilis in Dutch general hospitals in the period 1999–2010 was studied in a retrospective cohort study. Data from the Dutch sexually transmitted infection (STI) clinics were used to analyse the number of patients diagnosed with syphilis in this period.
An incidence of neurosyphilis of 0.47 per 100 000 adults was calculated, corresponding with about 60 new cases per year. This incidence was higher in the western (urbanised) part of the Netherlands, as compared with the more rural areas (0.6 and 0.4, respectively). The number of patients diagnosed with syphilis in STI clinics increased from 150 to 700 cases in 2004 and decreased to 500 new cases in 2010. The sex ratio was in favour of men, yielding a percentage of 90% of the syphilis cases and of 75% of the neurosyphilitic cases. The incidence of neurosyphilis was highest in men aged 35–65 years, and in women aged 75 years and above. The most frequently reported clinical manifestation of neurosyphilis was tabes dorsalis. In this study, 15% of the patients were HIV seropositive.
The incidence of neurosyphilis in a mixed urban–rural community such as the Netherlands is comparable to that in other European countries. Most patients are young, urban and men, and given the frequent atypical manifestations of the disease reintroduction of screening for neurosyphilis has to be considered.
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