Pharmacogenomics: state of the research and perspectives in clinical application

The person-to-person variability of drug response is a major problem in clinical practice and in drug development. It can lead to therapeutic failure or adverse drug reactions (ADRs) in individuals or subpopulation of patients. In addition to the high occurence of ADRs and the associated morbidity and mortality, substantial costs are incurred. Potential risk factors for drug inefficacy or toxicity include drug-drug interactions, the patient's age, renal and liver functions or other disease factors, and lifestyle variables such as smoking and alcohol consumption. In addition, it has become clear in recent years that genetic factors may also significantly modify drug responses or increase the risk for ADRs. Genetic variations in genes (polymorphisms) for drug-metabolizing enzymes, drug receptors, and drug transporters have been associated with individual variability in the efficacy and toxicity of drugs. It is now widely accepted that migraine is a polygenic and multifactorial disorders, thus considered to be a genetic complex disease. Genetic studies on migraine suggested a role of CACNA1A and DRD2 genes as susceptibility genes in this disorder.

Manic-depressive illness: an association study with the inositol polyphosphate 1-phosphatase and serotonin transporter genes

Association studies with candidate genes may contribute towards the understanding of the etiopathogenesis of bipolar disorder. Candidate genes in bipolar disorders are those related to aminergic neurotransmission, which is the target of the effects of antipsychotics and antidepressants, as well as genes related to signal transduction pathways, reporting the target for the mood-stabilizing effects of lithium. Association with such candidate genes may provide clues towards the understanding of the biological components of bipolar disorder. An association study was performed between the 5' regulatory region of the serotonin transporter gene (5-HTTLPR), the inositol polyphosphate 1-phosphatase gene (INPP1) and bipolar disorder using our sample of proband/parent trios. A total of 101 bipolar probands were considered eligible for the study. Since both parents had to be available, mean age at onset of bipolar disorder in probands was relatively young. However, the mean duration of illness and the number of episodes were consistent with a stable diagnosis. In our trios sample, the transmission disequilibrium test revealed no preferential transmission of alleles of the 5-HTTLPR and INPP1 from heterozygous parents to probands. Therefore, additional family-based data are warranted, possibly with a more complete subdivision of 5-HTTLPR alleles, since short and long alleles have recently been divided into four and six kinds of allelic variant, respectively, with significant ethnic differences in allele and genotype distributions.

Association of personal and familial suicide risk with low serum cholesterol concentration in male lithium patients

OBJECTIVE

We sought to establish whether low cholesterol concentration may be associated with a personal history of attempted suicide or a family history of completed suicide in psychiatric out-patients on maintenance lithium treatment, who represent a population at risk for suicide.

METHOD

We retrospectively reviewed charts regarding 783 out-patients consecutively admitted to a lithium clinic from 1976 to 1999. Individual age- and gender-specific quartile of serum cholesterol concentration were correlated against personal lifetime suicide attempts and completed suicide in first-degree relatives.

RESULTS

The proportion of men with a personal lifetime history of attempted suicide, especially if violent, and that of men with history of completed suicide in a first-degree relative were significantly higher among the group with cholesterol concentration in the lowest quartile compared to the group with cholesterol levels above the 25th percentile.

CONCLUSION

Low cholesterol concentration should be studied further as a potential biological/genetic marker of suicide risk.

Family-based association study between bipolar disorder and DRD2, DRD4, DAT, and SERT in Sardinia

Association analysis of candidate genes may represent a strategy for clarifying the genetic components involved in bipolar disorder. Polymorphism at dopamine receptor genes DRD2, DRD4, and dopamine and serotonin transporter genes (DAT, SERT) has been used in previous association studies. Some authors have reported positive association between certain alleles and bipolar disorder, using the case-control design. In this family-based association study of DRD2, DRD4, DAT, and SERT, the distribution of parental nontransmitted alleles was compared with that of alleles transmitted to 53 Sardinian probands suffering from bipolar disorder. The transmission disequilibrium test (TDT) was used to detect any disproportionate transmission of alleles by heterozygous parents to affected children. No differences were found between the allele distribution of polymorphisms at DRD2, DRD4, DAT, and SERT in probands and parental nontransmitted chromosomes. TDT did not reveal any difference between transmitted and nontransmitted alleles. Our results do not support the hypothesis of a role for DRD2, DRD4, DAT, or SERT in bipolar disorder. Previously reported positive associations between DRD2 or SERT and bipolar disorder were conceivably due to stratification dependent on the case-control design, even though our sample might have failed to detect small associations due to limited power.

Suicidal behavior on and off lithium prophylaxis in a group of patients with prior suicide attempts

One hundred patients who had attempted suicide before commencing lithium prophylaxis were followed up. Outcome was analyzed in terms of attempted or completed suicide after a mean of 10 years since admission to the lithium clinics. Of 10 patients who committed suicide, 9 had discontinued adequate lithium prophylaxis for a period ranging from 2 weeks to 7 years before death. Having discontinued lithium therapy was associated with suicide also in the subgroup of patients for whom lithium had not completely prevented episodes during lithium treatment. Suicide risk was 24 times as high during periods off compared with periods on adequate lithium prophylaxis. Incidence of attempting suicide was similar during the periods before receiving or after discontinuing lithium treatment, whereas it was 5 to 6 times lower during prophylaxis. Continuous and adequate lithium prophylaxis should be considered in the presence of high suicide risk, even if the prophylactic effect on the underlying mood disorder may be incomplete.

Carbamazepine augmentation in lithium-refractory bipolar patients: a prospective study on long-term prophlyactic effectiveness

Twenty-two patients affected by bipolar or schizoaffective disorder, in whom carbamazepine was added to lithium after recurrence when on maintenance with lithium alone, were followed up prospectively for 2 to 13 years. The number of episodes, hospitalizations, and cumulative affective morbidity was markedly reduced after carbamazepine augmentation. Seventeen patients presented a better course during combined treatment than during lithium alone, and of these 15 had no further recurrences. Four patients did not appear to improve after carbamazepine augmentation, whereas one featured reemergence of affective episodes after having derived satisfactory benefit from combination for 7 years (delayed tolerance). Carbamazepine augmentation was associated with a reduction of lithium doses in some patients, including a subgroup who had not tolerated lithium at usual therapeutic levels. Carbamazepine significantly reduced serum thyrotropin concentrations, which were abnormally high in approximately one half of patients when on lithium alone. Total serum thyroxine concentrations were also decreased after carbamazepine augmentation, but free thyroid hormone concentrations did not change. Other significant carbamazepine-induced changes in laboratory tests included increases in total cholesterol concentrations and decreases in white blood cell counts.