Catechol O-methyltransferase and monoamine oxidase A genotypes, and plasma catecholamine metabolites in bipolar and schizophrenic patients.

Metabolites of dopamine and norepinephrine measured in the plasma have long been associated with symptomatic severity and response to treatment in schizophrenic, bipolar and other psychiatric patients. Plasma concentrations of catecholamine metabolites are genetically regulated. The genes encoding enzymes that are involved in the synthesis and degradation of these monoamines are candidate targets for this genetic regulation. We have studied the relationship between the Val158Met polymorphism in catechol O-methyltransferase gene, variable tandem repeat polymorphisms in the monoamine oxidase A gene promoter, and plasma concentrations of 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid and homovanillic acid in healthy control subjects as well as in untreated schizophrenic and bipolar patients. We found that the Val158Met substitution in catechol O-methyltransferase gene influences the plasma concentrations of homovanillic and 3,4-dihydroxyphenylacetic acids. Although higher concentrations of plasma homovanillic acid were found in the high-activity ValVal genotype, this mutation did not affect the plasma concentration of 3-methoxy-4-hydroxyphenylglycol. 3,4-dihydroxyphenylacetic acid concentrations were higher in the low-activity MetMet genotype. Interestingly, plasma values 3-methoxy-4-hydroxyphenylglycol were greater in schizophrenic patients and in bipolar patients than in healthy controls. Our results are compatible with the previously reported effect of the Val158Met polymorphism on catechol O-methyltransferase enzymatic activity. Thus, our results suggest that this polymorphism, alone or associated with other polymorphisms, could have an important role in the genetic control of monoamine concentration and its metabolites.

GABA and homovanillic acid in the plasma of Schizophrenic and bipolar I patients.

We have determined the plasma (p) concentration of gamma-aminobutyric acid (GABA) and the dopamine metabolite homovanillic acid (HVA), and the pHVA/pGABA ratio in schizophrenic and bipolar patients. The research was undertaken in a geographic area with an ethnically homogeneous population. The HVA plasma concentrations were significantly elevated in the schizophrenic patients compared to the bipolar patients. The levels of pGABA was significantly lower in the two groups of patients compared to the control group, while the pHVA/pGABA ratio was significantly greater in the both groups of patients compared to the controls. As the levels of pHVA and pGABA are partially under genetic control it is better to compare their concentrations within an homogeneous population. The values of the ratio pHVA/pGABA are compatible with the idea of an abnormal dopamine-GABA interaction in schizophrenic and bipolar patients. The pHVA/pGABA ratio may be a good peripheral marker in psychiatric research.

Plasma homovanillic acid and family history of psychotic disorders in bipolar I patients.

It has been suggested that the family history of psychotic disorders is useful in defining homogeneous groups of bipolar patients. The plasma homovanillic acid (pHVA) concentrations have been related to the effect of antipsychotic treatment in psychotic patients. We have studied the influence of a positive family history of psychotic disorders both on the variation of pHVA levels and on the relation between pHVA concentrations and the clinical response to treatment. Clinical status and pHVA levels were assessed in 58 medication free patients before and after 4 weeks of treatment with olanzapine and lithium. Clinical improvement correlated positively with pHVA levels on the 28th day of treatment only in the patients having first degree relatives with psychotic disorders. The pHVA levels did not decrease after 28 days of treatment. Our results reinforce the idea that a positive family history of psychosis in psychotic bipolar disorders may constitute a good basis for sub-grouping these patients.