Improved method for detecting the long and short promoter alleles of the serotonin transporter gene HTT (SLC6A4)

Sometimes It's Good to be Short: The Serotonin Transporter Gene, Positive Parenting, and Adolescent Depression

In threatening environments, the short (S) allele of 5-HTTLPR is proposed to augment risk for depression. However, it is unknown whether 5-HTTLPR variation increases risk for depression in environments of deprivation, lacking positive or nurturant features. Two independent longitudinal studies (n = 681 and 176, respectively) examined whether 5-HTTLPR moderated associations between low levels of positive parenting at 11-13 years and subsequent depression at 17-19 years. In both studies only LL homozygous adolescents were at greater risk for depression with decreasing levels of positive parenting. Thus, while the S allele has previously been identified as a susceptible genotype, these findings suggest that the L allele may also confer sensitivity to depression in the face of specific environmental challenges.

Exploring the multifactorial nature of postoperative nausea and vomiting in women following surgery for breast cancer

BACKGROUND

Postoperative nausea and vomiting (PONV) are two of the most frequent and distressing complications following surgical procedures, with as many as 80% of patients considered to be at risk. Despite recognition of well-established risk factors and the subsequent use of clinical guidelines, 20-30% of women do not respond to antiemetic protocols, indicating that there may be a genetic risk.

OBJECTIVE

The purpose of this pilot study was to describe the incidence and explore the risk factors associated with PONV after surgery in women diagnosed with early stage breast cancer.

METHODS

A prospective cohort design was employed to measure PONV in women recruited prior to surgery. DNA was extracted from saliva samples collected prior to discharge. Polymorphisms for seven candidate genes with a known role in one of the neural pathways associated with PONV were included in this study; serotonin receptor (HTR3A), serotonin transport (SLC6A4), tryptophan (TPH), dopamine receptors (DRD2/ANKK and DRD3), catechol-O-methyltransferase (COMT) and histamine (H1).

RESULTS

Twenty-nine (29.8%) women experienced nausea and 10 (11%) experienced nausea and vomiting while in the PACU despite administration of multiple antiemetic medications. Women who experienced PONV had higher levels of pain and received more opioids than those women who did not experienced PONV. Odds ratios demonstrated that alleles for the COMT, DRD3, and TPH genes were associated with decreased PONV.

CONCLUSION

The understanding of the multifactorial nature of PONV and the recognition of genetic risk will ultimately lead to the development of personalized interventions to manage these frequent and often debilitating symptoms.

Association between serotonin transporter genotype, brain structure and adolescent-onset major depressive disorder: a longitudinal prospective study

The extent to which brain structural abnormalities might serve as neurobiological endophenotypes that mediate the link between the variation in the promoter of the serotonin transporter gene (5-HTTLPR) and depression is currently unknown. We therefore investigated whether variation in hippocampus, amygdala, orbitofrontal cortex (OFC) and anterior cingulate cortex volumes at age 12 years mediated a putative association between 5-HTTLPR genotype and first onset of major depressive disorder (MDD) between age 13-19 years, in a longitudinal study of 174 adolescents (48% males). Increasing copies of S-alleles were found to predict smaller left hippocampal volume, which in turn was associated with increased risk of experiencing a first onset of MDD. Increasing copies of S-alleles also predicted both smaller left and right medial OFC volumes, although neither left nor right medial OFC volumes were prospectively associated with a first episode of MDD during adolescence. The findings therefore suggest that structural abnormalities in the left hippocampus may be present prior to the onset of depression during adolescence and may be partly responsible for an indirect association between 5-HTTLPR genotype and depressive illness. 5-HTTLPR genotype may also impact upon other regions of the brain, such as the OFC, but structural differences in these regions in early adolescence may not necessarily alter the risk for onset of depression during later adolescence.

Interactions between a serotonin transporter gene, life events and social support on suicidal ideation in Korean elders

INTRODUCTION

The functional polymorphism in the serotonin transporter gene linked promoter region (5-HTTLPR) may modify associations between environmental stressors and suicidality in adolescents and working-age adults. We investigated whether the 5-HTTLPR s/l polymorphism interacts with stressful life events (SLEs) and social support deficits (SSDs) on late-life suicidal ideation.

METHODS

732 Korean community residents aged 65+ were evaluated and, of 639 without suicidal ideation, 579 (90.6%) were followed two years later. Prevalence and incidence of suicidal ideation was ascertained. Information on SLEs and SSDs were gathered, and covariates included socio-demographic characteristics, depressive symptoms, cognitive function, and disability.

RESULTS

Significant interactions were observed between 5-HTTLPR genotype, SLEs and SSDs on both prevalence and incidence of suicidal ideation after adjustment for covariates. The associations of SLEs and SSDs with suicidal ideation were strengthened in combination with higher numbers of s alleles, and were only significant predictors in those with s/s genotype. A significant three-way interaction between 5-HTTLPR genotype, SLEs and SSDs was also found.

LIMITATIONS

The generalizability of suicidal ideation as a marker of suicidality should be considered.

CONCLUSIONS

Gene-environment interactions on suicidal behavior are therefore identifiable even in old age.

An investigation of associations between alcohol use disorder and polymorphisms on ALDH2, BDNF, 5-HTTLPR, and MTHFR genes in older Korean men

BACKGROUND

This study aimed to investigate the association of alcohol use disorder (AUD) with four candidate genes in older Korean men: aldehyde dehydrogenase 2 (ALDH2, 1/2), brain-derived neurotrophic factor (BDNF, val66met), serotonin transporter gene linked polymorphic region (5-HTTLPR, s/l), and methylenetetrahydrofolate reductase (MTHFR, c.677C > T).

METHODS

A community sample of 300 men aged 65 or over were categorized into 68 subjects with AUD and 232 controls according to clinical examinations and DSM-IV criteria. Genotype distributions and allele frequencies were compared.

RESULTS

Men with AUD had significantly higher ALDH2*1 and BDNF met allele frequencies compared to controls (p-values < 0.05). No significant differences in genotype or allele frequencies were found for 5-HTTLPR or MTHFR (p-values > 0.3).

CONCLUSIONS

AUD was associated with ALDH2*1 and BDNF met alleles in older Korean men. The first is consistent with previous research and likely to be explained by a protective effect of unpleasant symptoms following alcohol consumption associated with ALDH2*2. The second finding is novel and might be accounted for by BDNF-mediated serotonin or dopamine pathways. However, given the relatively small sample size, the results should be regarded as preliminary and requiring independent replication.

Serotonin transporter triallelic genotype and response to citalopram and risperidone in dementia with behavioral symptoms

The risk/benefit ratio of pharmacotherapy for behavioral symptoms of dementia is questionable: second-generation antipsychotics are poorly tolerated, and the efficacy of alternative treatments, for example, selective serotonin-reuptake inhibitors (SSRIs), is uncertain. Biomarkers of treatment response may improve this risk/benefit ratio. The length polymorphism of the serotonin transporter promoter gene (5-HTTLPR/SLC6A4) may moderate tolerability of SSRIs and expression of behavioral symptoms in dementia. We assessed the effect of 5-HTTLPR on tolerability and efficacy of citalopram and risperidone in a 12-week randomized controlled trial, which included nondepressed patients with dementia hospitalized for behavioral or psychotic symptoms. Genotypes including the A/G polymorphism of the L allele (rs25531) were determined in 92 of 103 participants. We used pattern-mixture models to account for dropout. Low-expression alleles (S and Lg) predicted greater early and overall side effects of citalopram and early treatment discontinuation. These results remained unchanged after excluding African-American participants and in covariate analyses. Unexpectedly, low-expression alleles seemed to predict greater early side effects of risperidone (but not early discontinuation) and poorer early response of psychosis symptoms to risperidone. In conclusion, 5-HTTLPR may be a useful biomarker of SSRI intolerance in dementia. Our findings of intolerance of a second-generation antipsychotics and persistence of psychosis in patients with low-expression alleles needs to be replicated.

Modification by two genes of associations between general somatic health and incident depressive syndrome in older people

OBJECTIVE

To investigate the modifying effects of two candidate genes (serotonin transporter gene linked promoter region (5-HTTLPR) and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms) on the associations between general somatic morbidity and incidence of depression in an East Asian population with high frequencies of potential risk alleles.

METHODS

With a 2-year prospective study of a community sample (N = 521) of older people (aged 65+), information on baseline number of health complaints, diagnosis of moderate/severe depressive syndrome (Geriatric Mental State), and genotypes for 5-HTTLPR and MTHFR C677T polymorphisms were ascertained. Interactions between somatic morbidity and the two genotypes were investigated for incident depression.

RESULTS

Incident depression was present in 63 (12%) and was associated with worse somatic health. Significant interactions between number of somatic complaints and both genotypes were observed. For the 5-HTTLPR genotypes, the association between the number of somatic disorders and depression was significant in s/s homozygotes (chi2 = 8.80 (1 df), p = .003) but not in heterozygotes (chi2 = 0.23, p = .634) or l/l homozygotes (chi2 = 0.04, p = .840). For the MTHFR genotypes, the association between the number of somatic disorders and depression was significant in T/T homozygotes (chi2 = 4.97, p = .026) but not in C/T heterozygotes (chi2 = 1.24, p = .265) or C/C homozygotes (chi2 = 1.04, p = .307).

CONCLUSIONS

These findings suggest that associations between general somatic morbidity and late-life depression are modified by at least two genes, and that elders with particular genotypes are at greater risk for onset of depression in the presence of somatic ill health.

Serotonin transporter binding after recovery from eating disorders

RATIONALE

Several lines of evidence suggest that altered serotonin (5-HT) function persists after recovery from anorexia nervosa (AN) and bulimia nervosa (BN).

OBJECTIVES

We compared 11 subjects who recovered (>1 year normal weight, regular menstrual cycles, no binging or purging) from restricting-type AN (REC RAN), 7 who recovered from bulimia-type AN (REC BAN), 9 who recovered from BN (REC BN), and 10 healthy control women (CW).

MATERIALS AND METHODS

Positron emission tomography (PET) imaging with [11C]McN5652 was used to assess the 5-HT transporter (5-HTT). For [11C]McN5652, distribution volume (DV) values were determined using a two-compartment, three-parameter tracer kinetic model, and specific binding was assessed using the binding potential (BP, BP=DVregion of interest/DVcerebellum-1).

RESULTS

After correction for multiple comparisons, the four groups showed significant (p<0.05) differences for [11C]McN5652 BP values for the dorsal raphe and antero-ventral striatum (AVS). Post-hoc analysis revealed that REC RAN had significantly increased [11C]McN5652 BP compared to REC BAN in these regions.

CONCLUSIONS

Divergent 5-HTT activity in subtypes of eating disorder subjects may provide important insights as to why these groups have differences in affective regulation and impulse control.

Interactions between life stressors and susceptibility genes (5-HTTLPR and BDNF) on depression in Korean elders

BACKGROUND

It has been reported that the functional polymorphism in the serotonin transporter gene linked promoter region (5-HTTLPR) modifies the association between stressful life events (SLEs) and depression in child, adolescent, and adult populations. We sought to replicate this finding in elders and, additionally, to test modifying effects of the brain-derived neurotrophic factor (BDNF) val66met polymorphism.

METHODS

In 732 Korean community residents ages 65+, diagnosis of depression (Geriatric Mental State Schedule), information on SLEs, and genotypes for 5-HTTLPR and BDNF val66met were ascertained. Of those without depression at baseline, 521 (88%) were followed up 2.5 years later. Interactions between SLEs and the two genotypes were investigated for both prevalent depression at baseline and incident depression at follow-up.

RESULTS

Significant interactions of SLEs with both 5-HTTLPR and BDNF genotypes were observed on risk of depression after adjustment for age, gender, education, and disability. A significant three-way interaction between 5-HTTLPR, BDNF, and SLEs was also found. The same findings were observed for predictors of incident depression in the prospective analysis.

CONCLUSIONS

These findings suggest that environmental risk of depression is modified by at least two genes and that gene-environment interactions are found even into old age.

Evaluating associations between 5-HTTLPR polymorphism and Alzheimer's disease for Korean patients

There has been growing evidence that the serotonin (5-HT) system is important in the regulation of memory and thus might be associated with Alzheimer's disease (AD), while research results on this issue have been inconsistent. The 5-HT system has also been suggested to be responsible for a significant portion of the behavioural aspects of AD. This study aimed to investigate the associations of the 5-HT transporter gene linked polymorphic region (5-HTTLPR) polymorphism with AD and delusional/aggressive symptoms of AD in Korean samples of 65 patients and 43 controls. The 5-HTTLPR polymorphism was neither associated with AD nor with delusional/aggressive symptoms of AD. It was suggested that phenotypic expression of the 5-HTTLPR polymorphism might be varied according to ethnic differences.

Effects of serotonin transporter promoter polymorphisms on serotonin function

The serotonin transporter promoter polymorphism (5-HTTLPR) has been associated with vulnerability to stress-induced depressive symptoms and with the speed and rate of response to antidepressant treatment. The goal of the present study was to evaluate the association between the 5-HTTLPR and the functional response of the serotonin system as measured by the neuroendocrine and cerebral metabolic response to intravenous administration of the selective serotonin reuptake inhibitor citalopram in normal control subjects. Genotyping was performed for 5-HTTLPR insertion/deletion polymorphism long (l) and short (s) variant alleles. The ll genotype was compared with the combined sl+ss and with the ss genotype alone. Citalopram plasma concentrations did not differ significantly between groups. The s allele was associated with a less of an increase in prolactin and cortisol than the ll genotype. The s allele was associated with greater decreases in left frontal, precentral and middle temporal gyri compared to the ll genotype. The ll genotype was associated with greater decreases in right frontal, insula and superior temporal gyrus compared to the ss genotype. These findings suggest that 5-HTTLPR is associated with an altered functional response of the serotonin system, which may represent a neurobiologic substrate for the differential response to antidepressant treatment in late life and the emergence of neuropsychiatric symptoms in neurodegenerative disorders.

Allelic variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) and cardiovascular reactivity in young adult male and female twins of European-American descent

OBJECTIVE

To examine the effect of length variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) on individual differences in cardiovascular response to psychological challenge.

METHODS

Heart rate (HR) and systolic and diastolic blood pressure (SBP, DBP) responses to computerized versions of two psychological challenges, the Stroop Color-Word Interference Test and mental arithmetic, were measured among 131 monozygotic (MZ) and 60 dizygotic (DZ) male or female (same-sex) European-American twin pairs. Among the 382 participants, 140 were homozygous for the "long" allele (l/l) at 5-HTTLPR, 61 were homozygous for the "short" allele (s/s), and 181 participants had one long and one short allele (l/s). Association and sib-pair analyses were performed to characterize genetic associations.

RESULTS

In the full sample, 5-HTTLPR was associated with HR reactivity to psychological challenge, albeit in interaction with sex. Task-elicited HR responses of women homozygous for the short allele were significantly greater than among: a) men of the same genotype; and b) women having either one (l/s) or two (l/l) long alleles at 5-HTTLPR. SBP and DBP responsivity was unrelated to genotype. These results were corroborated on reanalysis in two genetically independent subsamples. Variability at 5-HTTLPR also predicted HR reactivity in sib-pair analyses among DZ twins.

CONCLUSIONS

These results suggest that the commonly observed sex difference in HR reactivity may be, in part, genetically mediated and perhaps occur only among individuals homozygous for the short allele at 5-HTTLPR.