Plasma dopamine beta hydroxylase activity in affective disorders

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.

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.

Search for biological/genetic markers in a long-term epidemiological and morbid risk study of affective disorders

A long-term epidemiological genetic study was conducted in which all new patients were evaluated prospectively at the Foundation for Depression and Manic Depression and two Lithium/Affective Disorders clinics at the Columbia-Presbyterian Medical Center between the years of 1972 and 1978. All patients met Feighner, RDC and DSM III criteria for Major Depressive Disorder after initial clinical screening interviews and were further subtyped using the Fieve-Dunner 7-point criteria. All 604 probands and 90% of 2711 first-degree relatives were interviewed blindly by diagnosticians trained in the use of the SADS structured interview. Cumulative morbid risk in parents, siblings and children of 490 bipolar probands was 15.6 +/- 3% and 14.0 +/- 1.7% in the first-degree relatives of 114 unipolar probands. A number of biological and genetic marker studies were simultaneously performed on samples of the overall population. The enzymes catechol O-methyltransferase and dopamine beta-hydroxylase, and the dexamethasone suppression test (SDT) did not show any biological marker value for outpatients even though both enzymes were determined to have hereditability. The HLA system, monoamine oxidase and acetylcholinesterase segregated differently from normal controls in samples of the patient population. The positive association findings with monoamine oxidase and the HLA system conflicted with the positive findings of other investigators, leaving doubtful their biological marker value. Red cell acetylcholinesterase was found to be significantly lower in affective disorder patients than in controls. This positive association finding was recently replicated by Mathews et al. (1982) but needs further confirmation. Using 28 blood group markers, a prior association study between the trait defining susceptibility to affective disorder and the genetic marker was positive for haptoglobin GC, and properdinfactor B, confirming earlier findings. Using the sib-pair method on the remaining 25 blood groups revealed that none other than peptidase A showed significant linkage with affective disorder since one significant finding is expected by chance. We conclude from the overall morbid risk data and segregation analyses that bipolar manic-depressive illness is a spectrum disease inherited through a multifactorial mode of genetic transmission (which is not synonymous with polygenetic inheritance) with possible genetic heterogeneity and find no evidence for X-linkage. Additional studies with acetylcholinesterase, haptoglobin, GC, and properdin-factor B are needed to confirm their positive biological/genetic marker value suggested by our long-term epidemiological study.

Reassessing the bipolar-unipolar dichotomy

This paper is a critical review of the literature on the dichotomous classification of affective disorders into unipolar and bipolar types. The majority of genetic studies show significant overlap in the liability to develop two forms of illness, and the majority of lithium studies show a similar clinical responsiveness of both groups to both acute and maintenance treatment. Biological studies comparing the two groups are difficult to interpret as most have compared manics to depressives without controlling for motor activity, excitement, and other state-dependent clinical variables. Viewed in light of our research findings in a recent genetic study of affective states, we believe these data suggest that the separation of affective disorders by polarity may have been premature, and that the search for heterogeneity should now be carried out using alternative strategies.

Enzymes related to biogenic amine metabolism and personality characteristics in depressed patients

Levels of the activity of enzyme systems involved in the synthesis and metabolism of biogenic amines have been linked in several reports in the literature with various psychopathological conditions and with variations in personality characteristics. In particular, significant negative correlations have been reported between levels of MAO-activity and sensation seeking. In the present study levels of MAO and DBH-activity were investigated in a series of 30 depressed patients, admitted consecutively, who completed a new personality inventory, the KSP, assumed to measure relatively stable personality traits. Our findings appeared to be consistent with those of earlier authors in that the most pronounced significant (negative) correlation occurred between MAO-activity levels and the monotony avoidance subscale of the KSP. This particular subscale is aimed precisely at measuring thrill-seeking and bears a close relation to the Sensation Seeking Scale used by other authors. In addition a weak positive correlation was found between the same subscale and levels of DBH-activity. Finally a weak negative correlation emerged between levels of MAO and the Guilt subscale of the KSP.

Some neuroendocrine parameters in bipolar and unipolar depression

There is mounting evidence showing that some pituitary and hypothalamic hormones play an important role in the affective disorders and may directly affect brain function and behavior. This report briefly reviews some recent endocrinological studies in affective illness with special reference to bipolar and unipolar form of illness. Data on prolactin and growth hormone response to levodopa in bipolar and unipolar illness presented. Preliminary data on plasma dopamine beta hydroxylase activity measured over a 24-h period are illustrated in patients suffering from bipolar and unipolar illnesses as compared to controls. The significance of these results is discussed in relation to biogenic amine dysfunction in the major affective disorders.