The effects of the dopamine and serotonin transporter polymorphisms on clinical features and treatment response in geriatric depression: a pilot study

The 3'UTR VNTR SLC6A3 Genetic Variant and Major Depressive Disorder: A Systematic Review

Major Depressive Disorder (MDD) is a disabling and particularly persistent mental disorder that is considered to be a priority public health problem. The active human dopamine transporter (DAT), which is encoded by the SLC6A3 gene, regulates the dopamine concentration in the synaptic cleft. In this sense, this neurotransmitter is primordial in modulating human emotions. This systematic review aims to verify the SLC6A3 (DAT1) 3'UTR VNTR (rs28363170) gene variant's SS (9R/9R) genotype and S (9R) allele frequency fluctuation and its influence on the modulation of pharmacotherapy in MDD. For this purpose, we searched different databases, and after applying the eligibility criteria, six articles were selected. Studies have shown an association between the SS (9R/9R) genotypic and S (9R) allelic presence with the risk of developing MDD, in addition to influencing the decrease in response to antidepressant therapy. However, despite the findings, disagreements were observed between other studies. For this reason, further studies with the SLC6A3 3'UTR VNTR (rs28363170) variant in different populations are necessary to understand this polymorphism's role in the onset of this disease.

The Role of Pharmacogenetics in Personalizing the Antidepressant and Anxiolytic Therapy

Pharmacotherapy for neuropsychiatric disorders, such as anxiety and depression, has been characterized by significant inter-individual variability in drug response and the development of side effects. Pharmacogenetics, as a key part of personalized medicine, aims to optimize therapy according to a patient's individual genetic signature by targeting genetic variations involved in pharmacokinetic or pharmacodynamic processes. Pharmacokinetic variability refers to variations in a drug's absorption, distribution, metabolism, and elimination, whereas pharmacodynamic variability results from variable interactions of an active drug with its target molecules. Pharmacogenetic research on depression and anxiety has focused on genetic polymorphisms affecting metabolizing cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) enzymes, P-glycoprotein ATP-binding cassette (ABC) transporters, and monoamine and γ-aminobutyric acid (GABA) metabolic enzymes, transporters, and receptors. Recent pharmacogenetic studies have revealed that more efficient and safer treatments with antidepressants and anxiolytics could be achieved through genotype-guided decisions. However, because pharmacogenetics cannot explain all observed heritable variations in drug response, an emerging field of pharmacoepigenetics investigates how epigenetic mechanisms, which modify gene expression without altering the genetic code, might influence individual responses to drugs. By understanding the epi(genetic) variability of a patient's response to pharmacotherapy, clinicians could select more effective drugs while minimizing the likelihood of adverse reactions and therefore improve the quality of treatment.

A Systematic Review of the Current Evidence from Randomised Controlled Trials on the Impact of Medication Optimisation or Pharmacological Interventions on Quantitative Measures of Cognitive Function in Geriatric Patients

Background

Cognitive decline is common in older people. Numerous studies point to the detrimental impact of polypharmacy and inappropriate medication on older people’s cognitive function. Here we aim to systematically review evidence on the impact of medication optimisation and drug interventions on cognitive function in older adults.

Methods

A systematic review was performed using MEDLINE and Web of Science on May 2021. Only randomised controlled trials (RCTs) addressing the impact of medication optimisation or pharmacological interventions on quantitative measures of cognitive function in older adults (aged > 65 years) were included. Single-drug interventions (e.g., on drugs for dementia) were excluded. The quality of the studies was assessed by using the Jadad score.

Results

Thirteen studies met the inclusion criteria. In five studies a positive impact of the intervention on metric measures of cognitive function was observed. Only one study showed a significant improvement of cognitive function by medication optimisation. The remaining four positive studies tested methylphenidate, selective oestrogen receptor modulators, folic acid and antipsychotics. The mean Jadad score was low (2.7).

Conclusion

This systematic review identified a small number of heterogenous RCTs investigating the impact of medication optimisation or pharmacological interventions on cognitive function. Five trials showed a positive impact on at least one aspect of cognitive function, with comprehensive medication optimisation not being more successful than focused drug interventions. More prospective trials are needed to specifically assess ways of limiting the negative impact of certain medication in particular and polypharmacy in general on cognitive function in older patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40266-022-00980-9.

Pharmacogenetic Implications for Antidepressant Pharmacotherapy in Late-Life Depression: A Systematic Review of the Literature for Response, Pharmacokinetics and Adverse Drug Reactions

Affecting up to 15% of older adults, late-life depression (LLD) is characterized by the occurrence of depressive symptoms after the age of 50-65 years and maybe pathophysiologically distinct from depression in younger adults. Therefore, LLD is challenging to treat, and predictive genetic testing might be essential to improve treatment in this vulnerable population. The current review aims to provide a summary of the literature exploring genetic associations with antidepressant treatment outcomes in late-life. We conducted a systematic search of three integrated electronic databases. We identified 29 articles investigating genetic associations with antidepressant treatment outcomes, pharmacokinetic parameters, and adverse drug reactions in older adults. Given the small number of investigations conducted in older adults, it is difficult to conclude the presence or absence of genetic associations with the outcomes of interest. In sum, the most substantial amount of evidence exists for the CYP2D6 metabolizer status, SLC6A4 5-HTTLPR, and BDNF rs6265. These findings are consistent in the literature when not restricting to older adults, suggesting that similar treatment recommendations may be provided for older adults regarding genetic variation, such as those outlined for CYP2D6 by the Clinical Pharmacogenetics Implementation Consortium. Nonetheless, further studies are required in well-characterized samples, including genome-wide data, to validate if similar treatment adjustments are appropriate in older adults, given that there appear to be significant effects of genetic variation on antidepressant treatment factors.

Pharmacogenetic guidelines and decision support tools for depression treatment: application to late-life

Late-life depression (LLD) is a major depressive disorder that affects someone after the age of 60 years. LLD is frequently associated with inadequate response and remission from antidepressants, in addition to polypharmacy. Pharmacogenetics offers a promising approach to improve clinical outcomes in LLD via new discoveries determining the genetic basis of response rates and side effects, as well as the development of tailored pharmacogenetic-based decision support tools. This invited review evaluates the LLD pharmacogenetic evidence base and the extent to which this was incorporated into existing commercial decision support tools and clinical pharmacogenetic guidelines.

Predictors of Response and Remission to Antidepressants in Geriatric Depression: A Systematic Review

BACKGROUND

Geriatric depression is a heterogeneous disorder that increases morbidity and mortality in a population that is already vulnerable. Predicting response and remission to antidepressants could help clinicians to optimize the management of antidepressants and reduce the consequences of depression.

METHOD

The aim of this article is to present results of a systematic review of the literature on predictive factors related to antidepressant response and remission in older adults with depression.

MAIN FINDINGS

We identified sociodemographic, clinical, neuropsychological, neuroimaging, and genetic factors that could be potential predictors of outcomes. Inconsistent findings and methodological differences among studies, however, limit the generalizability and application of these predictors in clinical practice. The results of our review confirm that geriatric depression includes many subgroups of patients with particular endophenotypes that may influence the course of depression.

CONCLUSION

Further studies are needed to characterize depression subgroups in order to better understand the pathophysiology of late life depression and to find specific predictors for each group of patients.

Catecholamine pathway polymorphisms and antidepressant response

INTRODUCTION

Genes that regulate the catecholamine metabolism pathways are potential targets for research in the antidepressant treatment response. This study was intended to determine whether antidepressant responses to selective serotonin reuptake inhibitors (SSRIs) are associated with genetic polymorphisms of the tyrosine or tryptophan gene in Chinese major depressive disorder (MDD) patients.

METHODS

A total of 290 MDD patients were recruited and received a 6-week SSRIs randomized double-blinded treatment. Allele, genotype, and haplotype frequencies were compared between responders and nonresponders in catecholamine genes.

RESULTS

Genotype frequency of the rs1800544 polymorphism in the DRD4 gene was significantly different between responders and nonresponders after false discovery rate correction (P = 0.042). The frequency of the DRD4 rs1800544 CG genotype was significantly higher (P = 0.003) in responders (51.4%) than in nonresponders (35.8%), and patients with the CG genotype showed an 81.7% response rate. In comparison, the response rates were 73.9% and 52.2% in patients with the GG genotype and the CC genotype, respectively. The frequencies of the DRD4 rs1800544 CC and GG genotypes were significantly lower (P = 0.003) in responders (7.7%, 40.9%) than in the nonresponders (19.4%, 44.8%). No significant difference was found between two groups either in genotype or allele frequencies of single nucleotide polymorphisms in the TPH, SLC6A2, SLC6A3, or DRD2 genes. No significant difference was found between two groups in TPH, SLC6A2, SLC6A3, DRD2, orDRD4 gene haplotypes.

DISCUSSION

Polymorphisms of the DRD4 gene appear to be associated with SSRI treatment response in Chinese MDD patients.

Cyr NM, Siddarth P, Baune BT, Lavretsky H. Genomic predictors of remission to antidepressant treatment in geriatric depression using genome-wide expression analyses: a pilot study

OBJECTIVE

This first pilot study of genome-wide expression as predictor of antidepressant response in late-life depression examined genome-wide transcriptional profiles in a randomized placebo-controlled trial of combined methylphenidate and citalopram.

METHODS

Genome-wide transcriptional profiles were examined in peripheral blood leukocytes sampled at baseline and 16 weeks from 35 older adults with major depression, who were randomized to methylphenidate + citalopram, citalopram + placebo, or methylphenidate + placebo. Methylphenidate doses ranged between 10 and 40 mg/day, and citalopram doses ranged between 20 and 60 mg/day. Remission was defined as Hamilton Depression Rating Scale score of 6 or below. Early remission was achieved in the first 4 weeks of treatment. We hypothesized that differential gene expression at baseline can predict antidepressant response.

RESULTS

We analyzed gene expression in 24 remitters and 11 non-remitters. At baseline, we found three genes showing higher expression in all remitters versus non-remitters that satisfied the established level of significance: a fold change of 2 and p-value of 0.05 that included HLA-DRB5, SELENBP1, and LOC388588. Two gene transcripts showed higher expression in early remitters at baseline compared with non-remitters. The first gene was CA1 carbonic anhydrase gene, on chromosome 8 involved in respiratory function (fold change 2.54; p = 0.03). The second gene was the SNCA-α-synuclein gene, implicated, which binds to dopamine transporter (fold change 2.1; p = 0.03).

CONCLUSIONS

Remission to antidepressants in geriatric depression may be associated with a particular gene expression profile in monoaminergic and metabolic pathways and needs to be replicated in a larger sample.

From pharmacogenetics to pharmacogenomics: the way toward the personalization of antidepressant treatment

OBJECTIVE

Major depressive disorder is the most common psychiatric disorder, worldwide, yet response and remission rates are still unsatisfactory. The identification of genetic predictors of antidepressant (AD) response could provide a promising opportunity to improve current AD efficacy through the personalization of treatment. The major steps and findings along this path are reviewed together with their clinical implications and limitations.

METHOD

We systematically reviewed the literature through MEDLINE and Embase database searches, using any word combination of "antidepressant," "gene," "polymorphism," "pharmacogenetics," "genome-wide association study," "GWAS," "response," and "adverse drug reactions." Experimental works and reviews published until March 2012 were collected and compared.

RESULTS

Numerous genes pertaining to several functional systems were associated with AD response. The more robust findings were found for the following genes: solute carrier family 6 (neurotransmitter transporter), member 4; serotonin receptor 1A and 2A; brain-derived neurotrophic factor; and catechol-O-methyltransferase. Genome-wide association studies (GWASs) provided many top markers, even if none of them reached genome-wide significance.

CONCLUSIONS

AD pharmacogenetics have not produced any knowledge applicable to routine clinical practice yet, as results were mainly inconsistent across studies. Despite this, the rising awareness about methodological deficits of past studies could allow for the identication of more suitable strategies, such as the integration of the GWAS approach with the candidate gene approach, and innovative methodologies, such as pathway analysis and study of depressive endophenotypes.

Clinical validity of cytochrome P450 metabolism and serotonin gene variants in psychiatric pharmacotherapy

Adverse events, response failures and medication non-compliance are common in patients receiving medications for the treatment of mental illnesses. A systematic literature review assessed whether pharmacokinetic (PK) or pharmacodynamic (PD) responses to 26 commonly prescribed antipsychotic and antidepressant medications, including efficacy or side effects, are associated with nucleotide polymorphisms in eight commonly studied genes in psychiatric pharmacotherapy: CYP2D6, CYP2C19, CYP2C9, CYP1A2, CYP3A4, HTR2C, HTR2A, and SLC6A4. Of the 294 publications included in this review, 168 (57%) showed significant associations between gene variants and PK or PD outcomes. Other studies that showed no association often had insufficient control for confounding variables, such as co-medication use, or analysis of medications not substrates of the target gene. The strongest gene-outcome associations were for the PK profiles of CYP2C19 and CYP2D6 (93% and 90%, respectively), for the PD associations between HTR2C and weight gain (57%), and for SLC6A4 and clinical response (54%), with stronger SLC6A4 response associations for specific drug classes (60-83%). The preponderance of evidence supports the validity of analyzing nucleotide polymorphisms in CYP and pharmacodynamic genes to predict the metabolism, safety, or therapeutic efficacy of psychotropic medications commonly used for the treatment of depression, schizophrenia, and bipolar illness.

Pharmacogenetics of antidepressant drugs: an update after almost 20 years of research

Major depressive disorder (MDD) is an emergent cause of personal and socio-economic burden, both for the high prevalence of the disorder and the unsatisfying response rate of the available antidepressant treatments. No reliable predictor of treatment efficacy and tolerance in the single patient is available, thus drug choice is based on a trial and error principle with poor clinical efficiency. Among modulators of treatment outcome, genetic polymorphisms are thought to explain a significant share of the inter-individual variability. The present review collected the main pharmacogenetic findings primarily about antidepressant response and secondly about antidepressant induced side effects, and discussed the main strengths and limits of both candidate and genome-wide association studies and the most promising methodological opportunities and challenges of the field. Despite clinical applications of antidepressant pharmacogenetics are not available yet, previous findings suggest that genotyping may be applied in the clinical practice. In order to reach this objective, further rigorous pharmacogenetic studies (adequate sample size, study of better defined clinical subtypes of MDD, adequate covering of the genetic variability), their combination with the results obtained through complementary methodologies (e.g., pathway analysis, epigenetics, transcriptomics, and proteomics), and finally cost-effectiveness trials are required.

The interaction between cerebrovascular disease and neuroticism in late-life depression: a cross-sectional study

OBJECTIVE

Vascular disease and neuroticism are both risk factors for late-life depression. In this study we examined the interaction between vascular disease and neuroticism as determinants of clinically relevant depressive symptoms (CRDS) in late-life.

METHODS

Multivariate logistic regression in a survey of 1396 population-dwelling people aged ≥70 years. CRDS were defined as scoring ≥16 on the CES-D. Vascular disease was categorised into four levels: none, ≥2 vascular risk factors, cardiac disease or stroke.

RESULTS

Neuroticism was strongly associated with CRDS in women (OR: 1.6, 95% CI: 1.4-1.8). In men vascular disease interacted negatively but significantly with neuroticism (cardiac disease by neuroticism: OR: 0.8, 95% CI: 0.6-0.9; stroke by neuroticism: OR: 0.8, 95% CI: 0.6-0.96) when predicting CRDS.

CONCLUSIONS

In men vascular disease attenuates the predictive value of neuroticism in CRDS, which might be mediated by apathy caused by cerebrovascular disease.

Pharmacogenetics of antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

Pharmacogenomic implications of variants of monoaminergic-related genes in geriatric psychiatry

Response to psychiatric medications in later life is highly heterogeneous and complex. Monoaminergic-related polymorphisms may influence medication response and susceptibility to side effects in elderly individuals. Individuals with the lower function short (S) allele of the serotonin transporter gene (SLC6A4) insertion/deletion (indel) promoter polymorphism (5-HTTLPR) have both increased the likelihood of adverse drug events and increased the need for higher antidepressant concentrations to obtain maximum antidepressant response. By contrast, carriers of the higher expression homozygous long allele (L/L) genotype may respond at lower concentrations. The differential role of these polymorphisms appears at early stages of treatment rather than in the final antidepressant outcome. Research findings suggest that the rs25531 SNP may influence functional expression of the L allele. Similarly, a variable number of tandem repeats in the second intron of the serotonin transporter gene may influence the expression of SLC6A4 and the implications of these variants may be influenced by aging. Two polymorphisms, rs2242466 (-182T/C) and rs5569 (1287G/A), in the norepinephrine transporter gene (SLC6A2 or NET) have been associated with antidepressant response. Studies in dopamine-related polymorphisms have focused on associations with neuroleptic-induced movement disorders. The rs1800497 variant (Taq1A) of the dopamine receptor D2 (DRD2) gene located in a noncoding 3´ region may regulate expression of D2 receptors. The rs6280 variant (Ser9Gly) of the dopamine receptor 3 (DRD3) gene may influence the binding affinity of D3 receptors as a result of serine to glycine substitution of the receptor protein. A multicenter collaborative research effort would be an effective strategy to increase sample sizes to further investigate how gene variants impact the pharmacodynamics and pharmacokinetics of psychotropic drugs in elderly persons.

Methylphenidate for the treatment of depressive symptoms, including fatigue and apathy, in medically ill older adults and terminally ill adults

BACKGROUND

Depressive symptoms, fatigue, and apathy are common symptoms among medically ill older adults and patients with advanced disease, and have been associated with morbidity and mortality. Methylphenidate has been used to treat these symptoms because of its rapid effect. Despite the long history of methylphenidate use for the treatment of depressive symptoms, fatigue, and apathy, there is little definitive evidence to support its use.

OBJECTIVE

The aim of this paper was to review the efficacy and tolerability of methylphenidate in the treatment of depressive symptoms, fatigue, and apathy in medically ill older adults and adults receiving palliative care.

METHODS

English-language articles presenting systematic reviews, clinical trials, or case series describing the use of methylphenidate for the treatment of depressive symptoms, fatigue, or apathy in medically ill older adults or adults receiving palliative care were identified. The key words methylphenidate and either depressive, depression, fatigue, or apathy were used to search the Cochrane Database, MEDLINE, PsycINFO, and International Pharmaceutical Abstracts. Included articles addressed depressive symptoms, fatigue, or apathy in (1) older adults (generally, age > or =65 years), particularly those with comorbid medical illness; (2) adults receiving palliative care; and (3) adults with other chronic illnesses. I excluded articles regarding treatment of depression in healthy young adults; bipolar disorder and attention-deficit/hyperactivity disorder; and narcolepsy, chronic fatigue syndrome, and related disorders.

RESULTS

A total of 19 controlled trials of methylphenidate in medically ill older adults or patients in palliative care were identified. Unfortunately, their conflicting results, small sample sizes, and poor methodologic quality limited the ability to draw inferences regarding the efficacy of methylphenidate, although evidence of tolerability was stronger. The available evidence suggests possible effectiveness of methylphenidate for depressive symptoms, fatigue, and apathy in various medically ill populations.

CONCLUSION

In the absence of definitive evidence of effectiveness, trials of low-dose methylphenidate in medically ill adults with depression, fatigue, or apathy, with monitoring for response and adverse effects, are appropriate.