Genome-wide analysis of rare copy number variations reveals PARK2 as a candidate gene for attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurodevelopmental disorder. Genetic loci have not yet been identified by genome-wide association studies. Rare copy number variations (CNVs), such as chromosomal deletions or duplications, have been implicated in ADHD and other neurodevelopmental disorders. To identify rare (frequency ≤1%) CNVs that increase the risk of ADHD, we performed a whole-genome CNV analysis based on 489 young ADHD patients and 1285 adult population-based controls and identified one significantly associated CNV region. In tests for a global burden of large (>500 kb) rare CNVs, we observed a nonsignificant (P=0.271) 1.126-fold enriched rate of subjects carrying at least one such CNV in the group of ADHD cases. Locus-specific tests of association were used to assess if there were more rare CNVs in cases compared with controls. Detected CNVs, which were significantly enriched in the ADHD group, were validated by quantitative (q)PCR. Findings were replicated in an independent sample of 386 young patients with ADHD and 781 young population-based healthy controls. We identified rare CNVs within the parkinson protein 2 gene (PARK2) with a significantly higher prevalence in ADHD patients than in controls (P=2.8 × 10(-4) after empirical correction for genome-wide testing). In total, the PARK2 locus (chr 6: 162 659 756-162 767 019) harboured three deletions and nine duplications in the ADHD patients and two deletions and two duplications in the controls. By qPCR analysis, we validated 11 of the 12 CNVs in ADHD patients (P=1.2 × 10(-3) after empirical correction for genome-wide testing). In the replication sample, CNVs at the PARK2 locus were found in four additional ADHD patients and one additional control (P=4.3 × 10(-2)). Our results suggest that copy number variants at the PARK2 locus contribute to the genetic susceptibility of ADHD. Mutations and CNVs in PARK2 are known to be associated with Parkinson disease.

Comparison of metabolic profiles of acutely ill and short-term weight recovered patients with anorexia nervosa reveals alterations of 33 out of 163 metabolites.

Starvation represents an extreme physiological state and entails numerous endocrine and metabolic adaptations. The large-scale application of metabolomics to patients with acute anorexia nervosa (AN) should lead to the identification of state markers characteristic of starvation in general and of the starvation specifically associated with this eating disorder. Novel metabolomics technology has not yet been applied to this disorder. Using a targeted metabolomics approach, we analysed 163 metabolite concentrations in 29 patients with AN in the acute stage of starvation (T0) and after short-term weight recovery (T1). Of the 163 metabolites of the respective kit, 112 metabolites were quantified within restrictive quality control limits. We hypothesized that concentrations are different in patients in the acute stage of starvation (T0) and after weight gain (T1). Furthermore, we compared all 112 metabolite concentrations of patients at the two time points (T0, T1) with those of 16 age and gender matched healthy controls. Thirty-three of the metabolite serum levels were found significantly different between T0 and T1. At the acute stage of starvation (T0) serum concentrations of 90 metabolites differed significantly from those of healthy controls. Concentrations of controls mostly differed even more strongly from those of AN patients after short-term weight recovery than at the acute stage of starvation. We conclude that AN entails profound and longer lasting alterations of a large number of serum metabolites. Further studies are warranted to distinguish between state and trait related alterations and to establish diagnostic sensitivity and specificity of the thus altered metabolites.

Screening for anorexia nervosa via measurement of serum leptin levels.

Due to their sub-normally low fat mass, leptin levels in patients with acute anorexia nervosa (AN) are well below reference levels for age and sex-matched controls. This hypoleptinemia entails endocrinological and behavioral characteristics observed in AN patients during starvation. We aimed to study the appropriateness of hypoleptinemia as a diagnostic marker for AN by assessing sensitivity, specificity and likelihood ratios for different referral serum leptin levels for predicting anorexia nervosa and healthy leanness. For prediction, we additionally generated a score based on a multivariate logistic model including body mass index (BMI; kg/m²) and leptin level. For this purpose, we measured leptin levels in 74 female patients with acute AN upon admission for inpatient or outpatient treatment. Adolescent and adult patients were recruited according to DSM-IV criteria from two multi-center studies. Additionally, leptin levels were measured in 65 female healthy, lean students. Mean serum leptin level was significantly decreased in patients with AN compared to underweight controls (0.87 ± 0.90 vs. 6.43 ± 3.55 µg/L, p < 0.001). Leptin predicted AN independently of BMI; we confirmed a cutoff value in the range of 2 µg/L as having both high specificity and sensitivity. Hypoleptinemia represents a state marker of acute AN and is useful for a laboratory-based diagnostic screening.

Association study in eating disorders: TPH2 associates with anorexia nervosa and self-induced vomiting.

Twin studies suggest that genetic factors play a substantial role in anorexia nervosa (AN) and self-induced vomiting (SV), a key symptom that is shared among different types of eating disorders (EDs). We investigated the association of 25 single nucleotide polymorphisms (SNPs), capturing 71-91% of the common variance in candidate genes, stathmin (STMN1), serotonin receptor 1D (HTR1D), tryptophan hydroxylase 2 (TPH2) and brain-derived neurotrophic factor (BDNF), with AN and EDs characterized by regular SV. The first allele frequencies of all the SNPs were compared between a Dutch case group (182 AN, 149 EDs characterized by SV) and 607 controls. Associations rendering P-values < 0.05 from this initial study were then tested for replication in a meta-analysis with two additional independent ED case-control samples, together providing 887 AN cases, 306 cases with an ED characterized by SV and 1914 controls. A significant effect for the minor C-allele of tryptophan hydroxylase 2 rs1473473 was observed for both AN [odds ratio (OR) = 1.30, 95% CI 1.08-1.57, P < 0.003] and EDs characterized by SV (OR = 1.52, 95% CI 1.28-2.04, P < 0.006). In the combined case group, a dominant effect was observed for rs1473473 (OR = 1.38, 95% CI 1.16-1.64, P < 0.0003). The meta-analysis revealed that the tryptophan hydroxylase 2 polymorphism rs1473473 was associated with a higher risk for AN, EDs characterized by SV and for the combined group.