Pharmacogenetics and mood stabilization in bipolar disorder

Hospital treatment, mortality and healthcare costs in relation to socioeconomic status among people with bipolar affective disorder

BACKGROUND

Evidence regarding the relationships between the socioeconomic status and long-term outcomes of individuals with bipolar affective disorder (BPD) is lacking.

AIMS

We aimed to estimate the effects of baseline socioeconomic status on longitudinal outcomes.

METHOD

A national cohort of adult participants with newly diagnosed BPD was identified in 2008. The effects of personal and household socioeconomic status were explored on outcomes of hospital treatment, mortality and healthcare costs, over a 3-year follow-up period (2008-2011).

RESULTS

A total of 7987 participants were recruited. The relative risks of hospital treatment and mortality were found elevated for the ones from low-income households who also had higher healthcare costs. Low premium levels did not correlate with future healthcare costs.

CONCLUSIONS

Socioeconomic deprivation is associated with poorer outcome and higher healthcare costs in BPD patients. Special care should be given to those with lower socioeconomic status to improve outcomes with potential benefits of cost savings in the following years.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© 2016 The Royal College of Psychiatrists. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

A genetic network model of cellular responses to lithium treatment and cocaine abuse in bipolar disorder

Background

Lithium is an effective treatment for Bipolar Disorder (BD) and significantly reduces suicide risk, though the molecular basis of lithium's effectiveness is not well understood. We seek to improve our understanding of this effectiveness by posing hypotheses based on new experimental data as well as published data, testing these hypotheses in silico, and posing new hypotheses for validation in future studies. We initially hypothesized a gene-by-environment interaction where lithium, acting as an environmental influence, impacts signal transduction pathways leading to differential expression of genes important in the etiology of BD mania.

Results

Using microarray and rt-QPCR assays, we identified candidate genes that are differentially expressed with lithium treatment. We used a systems biology approach to identify interactions among these candidate genes and develop a network of genes that interact with the differentially expressed candidates. Notably, we also identified cocaine as having a potential influence on the network, consistent with the observed high rate of comorbidity for BD and cocaine abuse. The resulting network represents a novel hypothesis on how multiple genetic influences on bipolar disorder are impacted by both lithium treatment and cocaine use. Testing this network for association with BD and related phenotypes, we find that it is significantly over-represented for genes that participate in signal transduction, consistent with our hypothesized-gene-by environment interaction. In addition, it models related pharmacogenomic, psychiatric, and chemical dependence phenotypes.

Conclusions

We offer a network model of gene-by-environment interaction associated with lithium's effectiveness in treating BD mania, as well as the observed high rate of comorbidity of BD and cocaine abuse. We identified drug targets within this network that represent immediate candidates for therapeutic drug testing. Posing novel hypotheses for validation in future work, we prioritized SNPs near genes in the network based on functional annotation. We also developed a "concept signature" for the genes in the network and identified additional candidate genes that may influence the system because they are significantly associated with the signature.

Lithium: a key to the genetics of bipolar disorder

Since the 1950s, lithium salts have been the main line of treatment for bipolar disorder (BD), both as a prophylactic and as an episodic treatment agent. Like many psychiatric conditions, BD is genetically and phenotypically heterogeneous, but evidence suggests that individuals who respond well to lithium treatment have more homogeneous clinical and molecular profiles. Response to lithium seems to cluster in families and can be used as a predictor for recurrence of BD symptoms. While molecular studies have provided important information about possible genes involved in BD predisposition or in lithium response, neither the mechanism of action of this drug nor the genetic profile of bipolar disorder is, as yet, completely understood.

Lithium: updated human knowledge using an evidence-based approach. Part II: Clinical pharmacology and therapeutic monitoring

After a single dose, lithium, usually given as carbonate, reaches a peak plasma concentration at 1.0-2.0 hours for standard-release dosage forms, and 4-5 hours for sustained-release forms. Its bioavailability is 80-100%, its total clearance 10-40 mL/min and its elimination half-life is 18-36 hours. Use of the sustained-release formulation results in 30-50% reductions in peak plasma concentrations without major changes in the area under the plasma concentration curve. Lithium distribution to the brain, evaluated using 7Li magnetic resonance spectroscopy, showed brain concentrations to be approximately half those in serum, occasionally increasing to 75-80%. Brain concentrations were weakly correlated with serum concentrations. Lithium is almost exclusively excreted via the kidney as a free ion and lithium clearance is considered to decrease with aging. No gender- or race-related differences in kinetics have been demonstrated. Renal insufficiency is associated with a considerable reduction in renal clearance of lithium and is considered a contraindication to its use, especially if a sodium-poor diet is required. During the last months of pregnancy, lithium clearance increases by 30-50% as a result of an increase in glomerular filtration rate. Lithium also passes freely from maternal plasma into breast milk. Numerous kinetic interactions have been described for lithium, usually involving a decrease in the drug's clearance and therefore increasing its potential toxicity. Clinical pharmacology studies performed in healthy volunteers have investigated a possible effect of lithium on cognitive functions. Most of these studies reported a slight, negative effect on vigilance, alertness, learning and short-term memory after long-term administration only. Because of the narrow therapeutic range of lithium, therapeutic monitoring is the basis for optimal use and administration of this drug. Lithium dosages should be adjusted on the basis of the serum concentration drawn (optimally) 12 hours after the last dose. In patients receiving once-daily administration, the serum concentration at 24 hours should serve as the control value. The efficacy of lithium is clearly dose-dependent and reliably correlates with serum concentrations. It is now generally accepted that concentrations should be maintained between 0.6 and 0.8 mmol/L, although some authors still favour 0.8-1.2 mmol/L. With sustained-release preparations, and because of the later peak of serum lithium concentration, it is advised to keep serum concentrations within the upper range (0.8-1 mmol/L), rather than 0.6-0.8 mmol/L for standard formulations. It is controversial whether a reduced concentration is required in elderly people. The usual maintenance daily dose is 25-35 mmol (lithium carbonate 925-1300 mg) for patients aged <40 years; 20-25 mmol (740-925 mg) for those aged 40-60 years; and 15-20 mmol (550-740 mg) for patients aged >60 years. The initial recommended dose is usually 12-24 mmol (450-900 mg) per day, depending on age and bodyweight. The classical administration schedule is two or three times daily, although there is no strong evidence in favour of a three-times-daily schedule, and compliance with the midday dose is questionable. With a modern sustained-release preparation, the twice-daily schedule is well established, although one single evening dose is being recommended by a number of expert panels.

Effect of the dysbindin gene on antimanic agents in patients with bipolar I disorder

OBJECTIVE

We previously reported an association between dysbindin gene (DTNBP1) variants and bipolar I disorder (BID). This paper expands upon previous findings suggesting that DTNBP1 variants may play a role in the response to acute mood stabilizer treatment.

METHODS

A total of 45 BID patients were treated with antimanic agents (lithium, valproate, or carbamazepine) for an average of 36.52 (+/-19.87) days. After treatment, the patients were evaluated using the Clinical Global Impression (CGI) scale and the Young Mania Rating Scale (YMRS) and genotyped for their DTNBP1 variants (rs3213207 A/G, rs1011313 C/T, rs2005976 G/A, rs760761 C/T and rs2619522 A/C).

RESULTS

There was no association between the variants investigated and response to mood stabilizer treatment, even after considering possible stratification factors.

CONCLUSION

Although the small number of subjects is an important limitation in our study, DTNBP1 does not seem to be involved in acute antimanic efficacy.