Depression, antidepressants, and plasma DBH

Association of functional DBH genetic variants with alcohol dependence risk and related depression and suicide attempt phenotypes: results from a large multicenter association study

OBJECTIVE

Dopamine-beta-hydroxylase (DBH) metabolizes the conversion of dopamine to noradrenaline. DBH, located on chromosome 9q34.2 has variants with potential functional consequences which may be related to alterations of neurotransmitter function and several psychiatric phenotypes, including alcohol dependence (AD), depression (MD) and suicidal behavior (SA). The aim of this association study in a large multicenter sample of alcohol-dependent individuals and controls is to investigate the role of DBH SNPs and haplotypes in AD risk and associated phenotypes (AD with MD or SA).

METHOD

1606 inpatient subjects with DSM-IV AD from four addiction treatment centers and 1866 control subjects were included. Characteristics of AD, MD and SA were obtained using standardized structured interviews. After subjects were genotyped for 4 DBH polymorphisms, single SNP case-control and haplotype analyses were conducted.

RESULTS

rs1611115 (near 5') C-allele and related haplotypes were significantly associated with alcohol dependence in females. This association with female alcohol dependence also accounts for the significant relationship between this variant and comorbid conditions and traits.

CONCLUSIONS

This study presents evidence for a potentially functional DBH variant influencing the risk for alcohol dependence while other comorbid conditions are not independently influenced by this SNP. However, the study also supports the possible role of the dopamine system in the etiology of female alcohol dependence.

A functional dopamine-beta-hydroxylase gene promoter polymorphism is associated with impulsive personality styles, but not with affective disorders

Dopamine-beta-hydroxylase (DbetaH) catalyzes the conversion of dopamine to norepinephrine in central noradrenergic and adrenergic neurons and thus is critically involved in the biosynthesis of catecholamines. There are equivocal findings concerning the question whether or not DssH activity levels are altered in affective disorders or in subtypes of affective disorders. Moreover, information about the role of dopamine beta-hydroxylase (DBH) genotype, which explains a large part of the variance of enzymatic activity, in affective disorders and personality dimensions is limited. To resolve these inconsistencies, association tests were performed using four independent samples, healthy volunteers (N = 387), patients with affective disorders (N = 182), adult attention deficit hyperactivity disorder (ADHD) patients (N = 407), and patients with personality disorders (N = 637). In the latter two samples, the revised NEO personality inventory (NEO-PI-R) was administered. All participants were genotyped for a putatively functional single nucleotide polymorphism (C-1021T, rs1611115). No differences in DBH C-1021T genotype distribution were observed between patients with affective disorders and healthy control subjects. Also when the patient sample was divided into uni- and bipolar patients versus controls, no significant differences emerged. Furthermore, no clear-cut association was detected between the TT genotype and personality disorder clusters while there was a significant association with adult ADHD. However, personality disorder patients carrying the DBH TT genotype exhibited higher neuroticism and novelty seeking scores as compared to individuals with the CC or CT genotype. Analyses on the level of the neuroticism and novelty seeking subscales revealed that the DBH TT genotype was primarily associated with personality features related to impulsiveness and aggressive hostility. Also adult ADHD patients carrying the homozygous TT genotypes displayed by significantly increased neuroticism scores; when both personality disorder and adult ADHD patient were analyzed together, TT carriers also displayed by significantly lower conscientiousness levels. Our results thus do not implicate the DBH C-1021T polymorphism in the pathophysiology of depressive disorders or personality disorders, yet homozygosity at this locus appears to increase the risk towards personality traits related to impulsiveness, aggression and related disease states, namely adult ADHD. These data argue for a dimensional rather than categorical effect of genetic variance in DBH activity; accordingly, the inconsistency of previous findings concerning DbetaH levels in affective disorders might be caused by the underlying association of the TT genotype at DBH-1021 with impulsive personality traits.

A quantitative-trait analysis of human plasma-dopamine beta-hydroxylase activity: evidence for a major functional polymorphism at the DBH locus

Dopamine-beta-hydroxylase (D beta H) catalyzes the conversion of dopamine to norepinephrine and is released from sympathetic neurons into the circulation. Plasma-D beta H activity varies widely between individuals, and a subgroup of the population has very low activity levels. Mounting evidence suggests that the DBH structural gene is itself the major quantitative-trait locus (QTL) for plasma-D beta H activity, and a single unidentified polymorphism may account for a majority of the variation in activity levels. Through use of both sequencing-based mutational analysis of extreme phenotypes and genotype/phenotype correlations in samples from African American, European American (EA), and Japanese populations, we have identified a novel polymorphism (--1021C-->T), in the 5' flanking region of the DBH gene, that accounts for 35%--52% of the variation in plasma-D beta H activity in these populations. In EAs, homozygosity at the T allele predicted the very low D beta H-activity trait, and activity values in heterozygotes formed an intermediate distribution, indicating codominant inheritance. Our findings demonstrate that --1021C-->T is a major genetic marker for plasma-D beta H activity and provide new tools for investigation of the role of both D beta H and the DBH gene in human disease.

Decreased dopamine beta-hydroxylase activity in unipolar geriatric delusional depression

BACKGROUND

Decreased dopamine beta-hydroxylase (DBH) activity has been reported in unipolar psychotic depression. DBH comparisons between elderly delusional and nondelusional depressives and controls and determination of whether pretreatment group differences persist have not been reported. Our objective was to compare DBH activity in elderly delusional major depressives with that of nondelusional depressives and normal control subjects before and after hospital treatment.

METHODS

Enzyme activity was assessed after hospital admission. A subsample had predischarge assessments. Treatment was not controlled but accounted for in analyses. Electroconvulsive therapy subjects were medication-free for posttreatment assays.

RESULTS

Baseline and predischarge DBH assays were lower in subjects with delusional depression than in either comparison group. Despite high intraindividual correlation, treatment was associated with significant increases in activity in the clinical groups.

CONCLUSIONS

Patients with late-life delusional depression have lower DBH activity before and after hospital treatment than age-matched nondelusional patients or normal controls.

Serum dopamine-beta-hydroxylase activity in clinical subtypes of depression

Serum dopamine-beta-hydroxylase (DBH) activity was determined in male adult psychiatric patients (n = 280) and age-matched male healthy controls (n = 100). Patients included in the study had no history of previous or current exposure to psychoactive drugs and were diagnosed according to Research Diagnostic Criteria. A significant decrease in serum DBH activity was noted in patients with psychotic major depressive disorder (n = 50) as compared with controls. In acute schizophrenics (n = 100), nonpsychotic major depressives (n = 45) and patients with manic disorder (n = 85), mean DBH activity did not differ significantly from the control values.

Monoamine metabolites as predictors of antidepressant response: a critique

Monoamine metabolite measurements are being increasingly used for making nosological, symptomatological and pharmacological profiles of the affective disorders. A number of unresolved methodological issues question the validity of using baseline metabolite levels for predicting treatment response. Some studies show correlations between baseline metabolite levels and response to treatment with specific antidepressant agents. Effects of antidepressant treatment on metabolite levels may be useful in predicting drug response.