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Published online before print December 24, 2007, 10.1097/PSY.0b013e31815f66c3
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Psychosomatic Medicine 70:32-39 (2008)
© 2008 American Psychosomatic Society

ORIGINAL ARTICLES

Childhood Socioeconomic Status and Serotonin Transporter Gene Polymorphism Enhance Cardiovascular Reactivity to Mental Stress

Redford B. Williams, MD, Douglas A. Marchuk, PhD, Ilene C. Siegler, PhD, MPH, John C. Barefoot, PhD, Michael J. Helms, MS, Beverly H. Brummett, PhD, Richard S. Surwit, PhD, James D. Lane, PhD, Cynthia M. Kuhn, PhD, Kishore M. Gadde, MD, Allison Ashley-Koch, PhD, Ingrid K. Svenson, BSc and Saul M. Schanberg, MD, PhD

From the Department of Psychiatry and Behavioral Sciences (R.B.W., I.C.S., J.C.B., M.J.H., B.H.B., R.S.S., J.D.L., K.M.G.), Duke University Medical Center; Department of Molecular Genetics and Microbiology (D.A.M., I.K.S.); Duke University Medical Center; Department of Pharmacology and Cancer Biology (C.M.K., S.M.C.), Duke University Medical Center; Department of Medicine (A.A.-K.), Duke University Medical Center, Durham, North Carolina.

Address correspondence and reprint requests to Redford B. Williams, Box 3926, Duke University Medical Center, Durham, NC 27710. E-mail: redfordw{at}duke.edu


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 NOTES
 REFERENCES
 
Objective: To test the hypothesis that low socioeconomic status (SES) and the 5HTTLPR L allele are associated with increased cardiovascular reactivity (CVR) to stress in a larger sample and that SES and 5HTTLPR genotypes interact to enhance CVR to stress. CVR to mental stress has been proposed as one mechanism linking stress to the pathogenesis of cardiovascular disease. The more transcriptionally efficient long (L) allele of a polymorphism of the serotonin transporter gene promoter (5HTTLPR) has been found associated with increased risk of myocardial infarction. We found the long allele associated with larger CVR to mental stress in a preliminary study of 54 normal volunteers.

Methods: Subjects included 165 normal community volunteers stratified for race, gender, and SES, who underwent mental stress testing.

Results: Childhood SES as indexed by Father’s Education Level was associated with larger systolic blood pressure (SBP) (p < .05) and diastolic blood pressure (DBP) (p = .01) responses to mental stress. The L allele was associated with larger SBP (p = .04), DBP (p < .0001), and heart rate (p = .04) responses to mental stress compared with the short (S) allele. Subjects with the SS genotype and high Father’s Education exhibited smaller SBP (5.2 mm Hg) and DBP (2.9 mm Hg) responses than subjects with LL genotype and low Father’s Education (SBP = 13.3 mm Hg, p = .002; DBP = 9.7 mm Hg, p < .0001).

Conclusions: Both the 5HTTLPR long allele and low SES, particularly during childhood, are associated with increased CVR to mental stress, which could account, at least in part, for the increased cardiovascular disease risk associated with these characteristics. If confirmed in further research, these characteristics could be used to identify persons who might benefit from preventive interventions.

Key Words: blood pressure • cardiovascular diseases • genetics • heart rate • environmental stress

Abbreviations: CVD = cardiovascular disease; CVR = cardiovascular reactivity; 5HTTLPR = serotonin transporter promoter polymorphism; SBP = systolic blood pressure; DBP = diastolic blood pressure; HR = heart rate; SES = socioeconomic status; GCRC = General Clinical Research Center; CNS = central nervous system.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 NOTES
 REFERENCES
 
Enhanced cardiovascular reactivity (CVR) to stress is one mechanism whereby psychosocial factors like hostility, depression, job strain, social isolation, and low socioeconomic status (SES) contribute to the development and course of cardiovascular disease (CVD) (1,2). Persons with larger blood pressure (BP) increases from resting levels during a broad range of mental tasks show more rapid progression of carotid atherosclerosis (3), especially among those of low SES (4) or who work in stressful jobs (5). Increased CVR to stress is also associated with increased stroke incidence in middle-aged men (6), increased development of coronary atherosclerosis in cynomolgus monkeys fed a high fat diet (7), increased insulin resistance (8), and increased blood lipid levels (9). In addition to predicting a higher incidence of hypertension (10), a larger BP response to a video game task predicted increased levels of a surrogate marker of atherosclerosis, coronary artery calcification, 13 years later in a large sample of healthy young Black and White men and women (11). Prior research has identified environmental stress factors and candidate genes that are associated with both increased CVD risk and CVR as a potential pathogenic mechanism.

Low SES is an environmental factor that is clearly associated with increased risk of disease and death (12,13). In particular, lower family SES during childhood is associated with increased mortality in adulthood, independently of adult SES, suggesting an enduring impact of adverse social and physical circumstances in childhood on adult health (14). Mechanisms that could account for such an enduring impact include effects of early environment on psychosocial and behavioral risk factors (15) and increased insulin resistance (16) in adulthood. Lower SES is also associated with increased CVR to psychological stress among adolescents and young adults (17,18), and a higher level of parental education buffers the effect of low neighborhood SES to increase CVR in healthy Black adolescents (19).

The role of genetic factors in CVR to stress is documented by twin studies finding moderate to strong heritabilities for systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) responses to various laboratory stressors (20–22). Molecular genetic studies have found associations between increased CVR to mental stress or adrenergic agonists and polymorphisms of several biologically plausible candidate genes, including those encoding for angiotensin-converting enzyme (23), the angiotensin II Type 1 receptor (24), and the β2-adrenergic receptor (25–27).

There is also reason to consider the role in CVR of genes involved in the regulation of serotonin function. Serotonin receptors in the central nervous system (CNS) regulate the effects of the sympathetic nervous system (SNS) on cardiovascular (CV) function, with the 5HT1A receptor mediating decreased SNS outflow and the 5HT2 receptor mediating increased SNS outflow in animal models (28). Treatment with selective serotonin reuptake inhibitors (SSRIs) is associated with decreased SNS outflow (29) and decreased CVD risk (30). In contrast, acute CNS serotonin depletion produces increased CVR to mental stress in recovered anxiety disorder patients (31). It has been proposed that dysregulated CNS serotonergic function may enhance the expression of increased CVR to stress, hostility, and other psychosocial risk factors and biobehavioral mechanisms associated with increased CVD risk (1).

A 44 base pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter (5HTT) gene, located on chromosome 17, has received considerable attention as a genetic variant with strong effects—via effects on reuptake—on serotonergic function (32). The common variation in the 5HTT gene linked polymorphic region (5HTTLPR) consists of two alleles, with repeats designated "S" (short) and "L" (long). The S variant is associated with decreased transcriptional efficiency and increased expression of neurotic traits in Caucasian populations (32).

We reported previously an association between the 5HTTLPR L allele and increased mean arterial BP and HR reactivity to a set of laboratory stressors in a sample of 54 healthy volunteers (33), a finding that has been cited, along with serotonin-mediated changes in platelet functions, as one potential mechanism that might account for the observed association between the L allele and increased risk of myocardial infarction in three independent samples (34–36). We have also found that 5HTTLPR genotypes are associated with cerebrospinal fluid (CSF) levels of 5-hydroxyindoleacetic acid (5HIAA), a brain endophenotype that reflects CNS serotonin turnover, but this effect varies as a function of both gender and race, with the S/S genotype being associated with higher CSF 5HIAA levels in women and Blacks, but with lower levels in men and Whites (37). However, other studies have failed to demonstrate clear correlations between 5 HTTLPR genotype and CSF 5 HIAA (38) or serotonin transporter binding in the brain (39). Because these studies did not include African-Americans (38) or test for race or gender moderation of 5HTTLPR effects (38,39), it must be concluded that the relationship between 5 HTTLPR and CNS serotonin function remains to be clearly defined. Rhesus monkeys with the less active S allele of a 5HTTLPR variant analogous to that found in humans have lower levels of CSF 5HIAA, but only if they have been exposed to the early adversity of being separated from the mother for the first 6 months of life and reared with peers (40). This finding provides direct evidence of the importance of early adversity in affecting CNS serotonin function, as well as the moderation of such effects by 5HTTLPR genotype.

Guided by the findings reviewed above and observations that gene-environment (GxE) interactions can play an important role in human biological, cognitive, and emotional responses associated with acute and chronic exposures to current as well as previous stressors (41–43), we hypothesize that a) low SES, especially during childhood, will be associated with increased CVR to mental stress; b) persons carrying the 5HTTLPR L allele will exhibit increased CVR to mental stress; and c) low SES and the presence of the L allele will interact to produce enhanced CVR to mental stress. We tested these hypotheses in a sample of healthy normal community volunteers that we have studied over the past 5 years.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 NOTES
 REFERENCES
 
Subjects were admitted to the General Clinical Research Center (GCRC) at Duke University Medical Center for a 2.5-day protocol that included lumbar puncture to obtain CSF (for assay of monoamine metabolites) (37), followed by randomization to either CNS serotonin enhancement (using tryptophan infusion) or CNS serotonin depletion (using tryptophan depletion) arms, with sham infusion or depletion on the first test day followed by active depletion or infusion on the second test day. Subjects also underwent mental stress testing at the point of expected maximal serotonin enhancement or depletion, with monitoring of cardiovascular function and collection of blood samples to assess neuroendocrine and immune system parameters. Because the focus of this report is on the effect of 5HTTLPR, SES, and their interaction on CVR to stress in the normal state, we report stress response data here only for the first day’s testing in the sham depletion and infusion arms, when CNS serotonin function has not been manipulated. Results relating to the effects of serotonin manipulations on the responses to stress testing will be the subject of subsequent communications.

Subjects were recruited from 1998 to 2003 via advertisements in the public media, inclusion in the community newsletter sent with the county water bill, flyers posted throughout the community, via outreach screening events at civic organizations and other public events, and in paid advertisements such as the back of supermarket tapes. This protocol required that subjects not be at risk due to the study procedures and that subject characteristics not hamper interpretation of the findings, making it important to ensure a sample population in good current health. Therefore, all subjects underwent a comprehensive examination using a modified SCID (by KMG) as well as medical history, physical examination, electrocardiogram, chest radiograph, hemoglobin, hematocrit, white cell count, and blood chemistries to rule out current psychiatric and medical disorders. Use of any prescription drugs, as well as use of illegal drugs (as detected by a urine screen before entry into study) were grounds for exclusion.

As part of the study design, participants were recruited according to their current education and household income levels in order to have approximately equal groups of low and high SES. Thus, two categories of income were used—≤$24,900 and >$24,900, based on the 40th percentile rank of household incomes in Durham County according to the 1990 Census (44). The low SES category includes those who had income of ≤$24,900 and who had less than a college degree. The high SES group included those who had income >$24,900, regardless of education, or those with a college degree. As described in the study by Burroughs et al. (44), the final sample consisted of 165 subjects with 98 high and 67 low SES, 91 male and 74 female, and 94 African-American and 71 Caucasian (based on self-description) subjects, ages 18 to 50 years (mean = 35.1 years). The stringent medical and psychiatric screening requirements made it harder for lower SES and women volunteers to qualify for the study. Included in this final sample are the 54 subjects in whom we found increased CVR among 5HTTLPR L carriers in our earlier, preliminary report (33). With the addition of 111 new subjects, the final sample is more balanced in terms of SES (high versus low), gender, and race and contains three times as many subjects with the SS genotype.

The Duke University Medical Center Institutional Review Board (IRB) approved this study, and an IRB-approved form was used to obtain written informed consent from all subjects.

Procedures
Subjects reported to the GCRC during the early afternoon. After completing admission procedures, and without a period of bed rest, lumbar puncture was performed by a Board-certified anesthesiologist. Between 11 AM and noon on the first test day, after the sham depletion or infusion, all subjects underwent a 45-minute mental stress protocol involving a 5-minute baseline rest period followed by oral reading from a neutral text, anger recall (oral report of a recent situation that made you angry), a second neutral text reading, and sadness recall (oral report of a recent situation that made you sad), with 5-minute rest periods between each 5-minute stress period. The reading and anger and sadness recall tasks were performed in the presence of two research assistants, thereby adding an element of public speaking stress.

Measures
Genomic DNA was extracted by standard procedure (Puregene D-50K Isolation Kit, Gentra, Minneapolis, Minnesota) from fresh or frozen samples of peripheral blood collected from the subjects. Polymerase chain reaction amplification to generate a 484- or 528-base pair fragment corresponding to the short (S) and long (L) 5HTTLPR alleles, respectively, was carried out (32). Consistent with other studies (45), allele frequencies varied significantly as a function of ethnicity, with African-Americans having 72% L alleles and 28% S alleles, compared with 60% L and 40% S alleles in Caucasians ({chi}2 = 4.74, 1df, p < .05).

SBP, DBP, and HR were measured (Automatic Vital Signs Monitor, Critikon, Tampa, FL) at 1-minute intervals during the rest and stress periods of the mental stress testing protocol.

Childhood SES was determined by the participant’s recall of parental education. Retrospective data on childhood SES have been shown to be valid in empirical studies (46). Parent’s education was classified as "high" if they had >12 years education and "low" if they had ≤12 years of education. This served as a natural break point in level of education between high school and postsecondary education and provided approximately equal numbers of mothers and fathers with high versus low education levels. The correlations between the subjects’ current SES and their parents’ education levels were only modest (r > .15, p > .07).

Statistical Analyses
Multiple regression in the form of analysis of covariance was used to evaluate baseline adjusted changes in CV measures between mean level across all rest periods and mean of all stress periods as a function of 5HTTLPR genotypes (LL, LS, SS) and SES (both current and childhood, using parents’ education levels). We used mean SBP, DBP, and HR levels across all rest and stress periods in these analyses, because these aggregated indices of CV function provide more reliable assessments (47). The dependent variable was the delta from the mean of all rest periods to the mean of the four stress periods, with the first prestress level as the covariate. To reduce the potential for false-positive results due to population stratification, race was also included as a covariate in all analyses involving the total sample. To test for the possible effects of GxE interactions, categorical variables for SES and gene phenotype, with their interaction, were modeled. When the interactions uniformly proved far from significant, the interactions were dropped from the models to more properly evaluate the main effects of SES and gene. This interaction deletion was done to avoid possible confounding of the main effects tests due to the imperfectly balanced design.

Sample sizes in different analyses vary due to inadequate DNA extraction (n = 1), missing data on mother’s (n = 8) or father’s (n = 20) education. Preliminary analyses showed that arm of study (tryptophan depletion versus enhancement) had no impact on CVR to stress as a function of SES indices or 5HTTLPR genotypes on the first test day, when sham depletion or enhancement was used. In prior research on this sample, we found that the association between 5HTTLPR genotypes and CSF 5HIAA is moderated by both race and gender, with the SS genotype having opposite effects on 5HIAA in men versus women and Blacks versus Whites (37). However, preliminary analyses found no moderation of 5HTTLPR or SES effects on CVR by either gender or race; except for the father’s education x race effect on SBP reactivity (p = .11), all other interactions had p > .37. Therefore, in all analyses, we collapsed the sample across tryptophan arms (day 1) and both race and gender groups.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 NOTES
 REFERENCES
 
We first evaluated associations between current and childhood SES indices and SBP, DBP, and HR reactivity comparing the mean level during the rest periods with the level averaged across the four stress periods. There were no baseline differences as a function of any of the SES measures. As shown in Table 1, in models examining the joint effects of father’s or mother’s education and subject’s current SES, there were no significant associations between current SES and CVR to the stress protocol. In contrast, childhood SES, as indexed by father’s or mother’s education level, showed significant (father’s education) or trend (mother’s education) associations with SBP and DBP changes during the stress protocol. There were no significant interactions between mother’s or father’s education and subject’s SES in predicting CVR. Subjects with lower father’s education levels exhibited SBP and DBP responses that were 25% larger than those with higher father’s education levels. These effects of father’s education on CVR did not vary as a function of race (p = .11–.73) or gender (p = .53–.84).


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  		TABLE 1. Joint Effects of Parent’s Education (Father’s Educ; Mother’s Educ) and Subject’s Current Socioeconomic Status (Subject’s SES) on Mean Cardiovascular Changes (Baseline Adjusted) Across the Four Stress Periods. Separate Models Were Run Testing Father’s Education and Subject’s SES and Mother’s Education and Subject’s SES

 

Because father’s education level was the most robust SES indicator associated with CVR to mental stress, we next evaluated joint effects of father’s education and 5HTTLPR on CVR. Baseline SBP was lower, F (2,139) = 4.27, p = .03, in SS (104 ± 2.8 [SE] mm Hg) subjects than those with LS (111 ± 1.7 mm Hg; p = .03) and LL (112 ± 1.4 mm Hg, p = .01) genotypes. Baseline DBP was lower, F (2,139) = 3.02, p = .05, in SS subjects (63 ± 2.0 mm Hg) than those with LL (68 ± 1.0 mm Hg, p < .05) but not LS (66 ± 1.2 mm Hg, p = .28) genotypes. Baseline HR did not differ as a function of genotype. These effects of 5HTTLPR genotype on baseline SBP and DBP were similar in Blacks and Whites: mean SBP/DBP in Blacks was 103/62 mm Hg for those with SS, 111/65 mm Hg for SL, and 114/68 mm Hg for LL; in Whites, the levels were 103/65 mm Hg for SS, 111/66 mm Hg for SL, and 110/69 mm Hg for LL. Further documenting that the effects of 5HTTLPR on baseline BP values were not due to the presence of more Whites with the SS genotype in the sample (12 versus 7 among Blacks), there were no race differences in baseline SBP (109 mm Hg in Blacks, 108 mm Hg in Whites, p = .73) or DBP (64 mm Hg in Blacks, 67 mm Hg in Whites, p = .22).

Race was entered and then, to control for these baseline differences, baseline levels of SBP, DBP, and HR were entered along with father’s education, subject’s 5HTTLPR genotype, and their interaction in models with changes from averaged rest periods in CV levels averaged across the four stress periods as the dependent variable. As shown in Table 2, independently of 5HTTLPR genotype, subjects with lower father’s education showed larger SBP (32%) and DBP (39%) responses than those with higher father’s education. Independently of father’s education level and despite their higher resting SBP and DBP, subjects with the LL genotype showed larger SBP (58%, p = .02), DBP (100%, p < .0001) and HR (58%, p = .01) responses than those with the SS genotype. LS subjects showed intermediate responses that were significantly different from both LL (p = .04) and SS (p = .003) subjects for DBP and different from SS (p = .02) only and similar to LL for HR. Father’s education by 5HTTLPR interactions were not significant for any CV response parameter. Models substituting mother’s education or subject’s SES for father’s education produced similar patterns of results, but with less robust effects of these SES indicators on CVR when considered jointly with 5HTTLPR genotypes.


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  		TABLE 2. Effects of Father’s Education Level and 5HTTLPR Genotypes on Mean Cardiovascular Changes (Adjusted for Baseline and Race) Across the Four Stress Periods

 

The absence of significant SES x 5HTTLPR interactions using any SES index indicates that effects of both SES and 5HTTLPR genotype on CVR did not vary in a multiplicative way. The finding that both father’s education level and 5HTTLPR genotype were independently associated with SBP and DBP reactivity indicates, however, the presence of a situation in which both the environmental exposure (low childhood SES as indexed by father’s education) and the genotype (5HTTLPR LL genotype) can still have some form of joint effect on disease risk, but with the possibility that their combined effect on risk can be higher or lower than when they occur alone (48). As shown in Figure 1, the combination of low father’s education level and the 5HTTLPR LL genotype is associated with remarkably large additive effects on CVR. The 13.3 mm Hg increase in SBP during stress in those with low father’s education and the LL genotype is significantly larger (p < .05) than all other groups and 2.6 times and 8.1 mm Hg larger (p = .002) than that seen in those with high father’s education and the SS genotype. The low father’s education/LL group’s 9.9 mm Hg DBP response is larger (p < .01) than all the other groups and 3.7 times and 7.2 mm Hg larger (p < .0001) than the DBP response in the high father’s education/SS group. Also noteworthy is that, despite their lower baseline levels, the high father’s education/SS group’s SBP (p = .17–.002) and DBP (p ≤ .05–.0001) reactivity are smaller than all the other groups.


Figure 16
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  		Figure 1. SBP (A) and DBP (B) responses (mean, SE) to stress periods as a function of Father’s Education level and 5HTTLPR genotypes. Race and baseline levels were entered first as covariates. FE = Father’s Education level; SBP = systolic blood pressure; DBP = diastolic blood pressure.

 

Neither race nor gender interacted significantly with SES indices or 5HTTLPR genotypes to influence CVR. As shown in Figure 2, the increasing DBP reactivity as a function of the 5HTTLPR L allele was similar in men and women and in Blacks and Whites, with effects of 5HTTLPR genotype being significant in Blacks, Whites, and males and at the trend level in females.


Figure 26
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  		Figure 2. DBP responses (mean, SE) to stress periods as a function of 5HTTLPR genotypes and gender (A) and race (B). The effect of 5HTTLPR genotype on DBP reactivity was significant in Blacks (p = .004), Whites (p = .007) and males (p = .002) and showed a trend (p = .087) in females. DBP = diastolic blood pressure.

 

Results obtained in analyses in which parental education level was modeled as a continuous variable did not differ in any material way from those reported above using the high/low dichotomy for parental education.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
NOTES
 REFERENCES
 
These findings support our first two hypotheses. The finding of increased SBP and DBP reactivity in persons with low childhood SES as indexed by father’s education is consistent with prior research (17–19) showing increased CVR as a function of low SES, particularly during childhood. The association of the 5HTTLPR LL genotype with increased SBP, DBP, and HR reactivity in a sample that is three times larger and more balanced with respect to race, gender, and 5HTTLPR genotypes than in our preliminary report (33), especially the robustness of the association with DBP reactivity, suggests the presence of an acute, within-subjects GxE effect, such that the influence of genotype on CV function is larger during mental stress than during the rest periods. Considered together with evidence that increased CVR contributes, presumably via more frequent endothelial injury, to the development of CVD (3–11), the parallel between the increased CVR in persons carrying the L allele in this study and the association of the L allele with increased risk of myocardial infarction in three independent studies (34–36) suggests that increased CVR could be one mediator of the association between the L allele and CVD risk. Increased platelet serotonin uptake has also been observed in persons with the 5HTTLPR L allele (49), and could combine with increased CVR to speed atherogenesis and contribute to the precipitation of acute coronary heart disease (CHD) events.

The lack of a significant statistical (i.e., multiplicative) interaction between SES indices and 5HTTLPR genotype indicates there is not a differential effect of this chronic environmental exposure on CVR as a function of genotype and that effect of genotype does not vary as a function of exposure—indicating that our third hypothesis was not supported by the findings. Nevertheless, the markedly larger SBP and DBP responses to the stress protocol in subjects with LL genotype and low father’s education compared with those with SS genotype and high father’s education (Figure 1) suggests that additive effects of environmental exposure and genotype can be large and likely to have clinically significant effects on risk. It has been reported, for example, that, independently of resting BP, there is a 24% increased odds of having detectable coronary calcium for each 10 mm Hg change in SBP during CVR testing 13 years earlier (11). The 8.1 mm Hg difference in SBP reactivity between subjects with LL genotype and low father’s education and those with SS genotype and high father’s education suggests, therefore, that persons with the LL genotype and low father’s education will exhibit a 19% higher incidence or prevalence of CVD compared with those with SS and high father’s education. It will be possible to test this prediction in extant samples of healthy people or CVD patients with DNA available and among whom father’s education levels are already known or can be readily determined. The higher baseline SBP and DBP we find in those carrying the L allele could add to the effect of the L allele on CVR to stress in potentiating the development of atherosclerosis.

The increased frequency of the 5HTTLPR L allele observed in African-derived populations (45) could be a contributor, via the associated increased CVR to stress, to the increased CVD incidence observed in African-Americans as well, for example, as the increased prevalence of hypertension among Zulus living in South African urban versus rural settings (50). If the L allele is playing such a role to increase stress effects on CVD risk in African-derived populations, the SS genotype should be more frequent, despite its overall rarity (<10%), in those African- Americans who are normotensive or free of other forms of CVD.

In contrast to moderation by both race and gender of the serotonin brain endophenotype indexed by CSF 5HIAA levels we reported previously (37), we find now in the same sample of subjects that the association of the L allele with increased CVR is similar in men and women, Blacks and Whites. We have no ready explanation for this difference between the race and gender moderation of the 5HTTLPR effect on whole brain serotonin turnover as reflected in 5HIAA levels, and the lack of race or gender moderation of CVR to stress. One potential explanation stems from the fact that 5HTTLPR genotype’s influence on serotonergic regulation of sympathetic outflow could occur in the hypothalamus and brain stem, via effects on sympathoinhibitory 5HT1A and sympathostimulatory 5HT2 receptors (28). These brain regions are distant from the site of lumbar puncture, and serotonin turnover at these sites may not be reflected in 5HIAA levels measured in CSF from lumbar puncture.

We recently found (51), in the same sample on which this report is based, that the association between 5HTTLPR genotype and depressive symptoms in those whose fathers had a low education level does vary as a function of gender. In persons whose fathers had >12 years of education, there was no effect of 5HTTLPR genotype on levels of depressive symptoms. In those whose fathers had ≤12 years of education, however, higher levels of depressive symptoms were seen in men with the LL genotype, whereas in women the SS genotype is associated with higher levels of depressive symptoms. Taken together with the findings reported here with respect to CVR to stress, these findings suggest that, among men, the LL genotype may be particularly harmful, because it is associated with both increased CVR to acute stress and increased depressive symptoms in the setting of chronic stress, as indexed by having a father with a low education level. Women with the LL genotype also show increased CVR to acute stress, but seem to be protected against the effect of chronic stress on depressive symptoms.

The present data do not permit us to establish the mechanism responsible for the larger CVR in those with the LL genotype. The effect could be mediated by the aforementioned effects of 5HTTLPR on CNS receptors that influence sympathetic outflow. Alternatively, or in addition to a CNS locus, the larger CVR in LL subjects could be due to effects on peripheral cardiac and/or vascular function. It has been shown, for example, that patients with chronic obstructive pulmonary disease who carry the LL genotype have significantly higher pulmonary artery pressure than those with LS or SS genotype (52).

We are aware of only one other report (53) of effects of 5HTTLPR on CVR to mental stress. In that study, the SS genotype interacted with gender to predict HR reactivity only (there were no effects on SBP and DBP reactivity) to the Stroop Color-Word Test and mental arithmetic in a sample of 131 monozygotic and 60 dizygotic twin pairs. In women, the SS genotype was associated with significantly larger HR reactivity, whereas in men there was a trend to decreased HR reactivity in those with SS genotype. Effects of SES on CVR were not reported. Other than differences between this study and ours in terms of the samples (twins versus a community sample) and stress tasks (cognitive versus emotion-eliciting), we have no ready explanation for the similarity to our results for HR reactivity in men with an opposite effect (larger reactivity in SS) in women. It is possible that the cognitive tasks used in their study elicited primarily a cardiac response that was reflected mainly in HR, whereas the emotion-eliciting tasks in our current study also elicited a stronger vascular response, as reflected in the very robust effects of 5HTTLPR genotype on DBP reactivity. Ultimately, replication studies will be required to determine the effect of 5HTTLPR genotype on CVR to stress and, of equal or greater importance, the development of CVD. We are currently conducting research to address both these questions. In the meanwhile, the congruence between the reported increased platelet serotonin uptake in persons carrying the 5HTTLPR L allele (49), our finding of increased CVR to stress in those carrying the L allele and the finding of increased myocardial infarction risk in those carrying the L allele in three independent studies (34–36) highlights the importance of continuing this line of research.

A limitation in the present study is the small number of subjects—7—with both high father’s education and the SS genotype, which could decrease confidence in the finding of very low CVR in this group. Reducing this concern, however, is the equally significantly higher CVR (Figure 1) in the 40 subjects with low father’s education and the LL genotype. Recent research (54) has demonstrated the existence of a common single base substitution (A->G) within the 5HTTLPR L allele, with the rarer (10% to 15% in Whites, 24% in African-Americans) LG allele showing reduced transcriptional efficiency, comparable to that of the S allele, whereas the LA allele is about twice as transcriptionally efficient as the S or LG alleles. Rather than being responsible for our findings, however, the presence of the less functional LG allele among the LL or LS subjects of our study would dilute the effects of the more active LA allele, making it harder to find CVR differences between SS and LL subjects. The difference in CVR between LL and SS subjects in this study represents, therefore, a conservative estimate of the association of 5HTTLPR genotypes with CVR. Another potential limitation is the potential of the sham tryptophan depletion or infusion to have affected CVR on day 1 of our protocol. We consider this unlikely to account for our findings, however, because a preliminary analysis of our data that included study arm as a covariate showed that study arm did not affect the results.

If further research demonstrates the predicted increase in CVD prevalence or incidence among persons with the LL genotype and a low father’s education, such persons could be targeted for behavioral and/or drug interventions with the potential to reduce CVR to stress. β blockers would be one obvious pharmacologic approach to reduce CVR to stress. The use of selective serotonin reuptake inhibitors has been reported in an observational study to reduce the risk of myocardial infarction (30), suggesting that these agents also deserve consideration as a means of reducing CVD risk associated with the L allele. There is also preliminary evidence from research in CHD patients that behavioral training in stress coping skills has the potential to reduce CVR to stress (55). The stronger impact of childhood SES, as indexed by father’s education level, on CVR suggests that such interventions could be more effective if instituted during childhood or adolescence.

In conclusion, our findings show that SBP, DBP, and HR reactivity to a set of emotion-eliciting mental stressors are larger in a sample of healthy adults who are carriers of the 5HTTLPR L allele or whose childhood environment was of lower SES. Participants with the combination of the LL genotype and lower childhood SES showed marked elevations of CVR. These data support the hypothesis that increased CVR to mental stress could partially explain the increased CVD risk that has been associated with the L allele in three independent studies. If the combination of lower childhood SES and the LL genotype is found associated with increased coronary atherosclerosis and/or to predict the prevalence and incidence of clinical CVD in future research, it would indicate that persons carrying the LL genotype and whose childhood environment was of lower SES could be targeted for trials of interventions aimed at preventing the development of CVD.


   NOTES
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 NOTES
REFERENCES
 
Received for publication May 24, 2007; revision received July 27, 2007.

This study was funded by Grant P01HL36587 from the National Heart, Lung, and Blood Institute (R.B.W.), Clinical Research Unit Grant M01RR30, and the Duke University Behavioral Medicine Research Center.

Disclosures: Redford Williams has a patent pending on the use of 5HTTLPR L allele as a marker of increased CVD risk due to stress. He is a founder and major stockholder in Williams LifeSkills, Inc.

DOI:10.1097/PSY.0b013e31815f66c3


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 NOTES
 REFERENCES
 

  1. Williams RB. Hostility (and other psychosocial risk factors): effects on health and the potential for successful behavioral approaches to prevention and treatment. In: Baum A, Revenson TR, Singer JE, editors. Handbook of Psychology and Health. Hillsdale, NJ: Lawrence Erlbaum Associates; 2000.
  2. Treiber FA, Kamarck T, Schneiderman N, Sheffield D, Kapuku G, Taylor T. Cardiovascular reactivity and development of preclinical and clinical disease states. Psychosom Med 2003;65:46–62.[Abstract/Free Full Text]
  3. Barnett PA, Spence JD, Manuck SB, Jennings JR. Psychological stress and the progression of carotid artery disease. J Hypertens 1997;15:49–55.[CrossRef][Medline]
  4. Lynch JW, Everson SA, Kaplan GA, Salonen R, Salonen JT. Does low socioeconomic status potentiate the effects of heightened cardiovascular response to stress on the progression of carotid atherosclerosis? Am J Public Health 1998;88:389–94.[Abstract/Free Full Text]
  5. Everson SA, Lynch JW, Chesney MA, Kaplan GA, Goldberg DE, Shade SB, Cohen RD, Salonen R, Salonen JT. Interaction of workplace demands and cardiovascular reactivity in progression of carotid atherosclerosis: a population based study. BMJ 1997;314:553–61.[Abstract/Free Full Text]
  6. Everson SA, Lynch JW, Kaplan GA, Lakka TA, Sivenius J, Salonen JT. Stress-induced blood pressure reactivity and incident stroke in middle-aged men. Stroke 2001;32:1263–70.[Abstract/Free Full Text]
  7. Manuck SB, Kaplan JR, Clarkson TB. Behaviorally induced heart rate reactivity and atherosclerosis in cynomolgus monkeys. Psychosom Med 1983;45:95–108.[Abstract/Free Full Text]
  8. Moan A, Nordby G, Rostrup M, Eide I, Kjeldsen SE. Insulin sensitivity, sympathetic activity, and cardiovascular reactivity in young men. Am J Hypertens 1995;8:268–75.[CrossRef][Medline]
  9. Burker EJ, Fredrikson M, Rifai N, Siegel W, Blumenthal JA. Serum lipids, neuroendocrine, and cardiovascular responses to stress in men and women with mild hypertension. Behav Med 1994;19:155–61.[Medline]
  10. Matthews KA, Katholi CR, McCreath H, Whooley MA, Williams DR, Zhu S, Markovitz JH. Blood pressure reactivity to psychological stress predicts hypertension in the CARDIA study. Circulation 2004;110:74–8.[Abstract/Free Full Text]
  11. Matthews KA, Zhu S, Tucker DC, Whooley MA. Blood pressure reactivity to psychological stress and coronary calcification in the coronary artery risk development in young adults study. Hypertension 2006;47:391–5.[Abstract/Free Full Text]
  12. Adler NE, Boyce WT, Chesney MA, Folkman S, Syme SL. Socioeconomic inequalities in health: no easy solution. JAMA 1993;269:3140–5.[Abstract/Free Full Text]
  13. Marmot MG, Kogevinas M, Elston MA. Social/economic status and disease. Annu Rev Public Health 1987;8:111–35.[CrossRef][Medline]
  14. Smith GD, Hart C, Blane D, Hole D. Adverse socioeconomic conditions in childhood and cause-specific adult mortality: prospective observational study. BMJ 1998;316:1631–5.[Abstract/Free Full Text]
  15. Lynch JW, Kaplan GA, Salonen JT. Why do poor people behave poorly? Variation in adult health behaviours and psychosocial characteristics by stages of the socioeconomic lifecourse. Soc Sci Med 1997;44:809–19.[CrossRef][Medline]
  16. Lawlor DA, Ebrahim S, Davey Smith G. Socioeconomic position in childhood and adulthood and insulin resistance: cross sectional survey using data from British women’s heart and health study. BMJ 2002;325:805–7.[Abstract/Free Full Text]
  17. Kapuku GL, Treiber JC, Davis HC. Relationships among socioeconomic status, stress induced changes in cortisol, and blood pressure in African American males. Ann Behav Med 2002;24:320–5.[CrossRef][Medline]
  18. Merritt MM, Bennett GG, Williams RB, Sollers JJ 3rd, Thayer JF. Low educational attainment, John Henryism, and cardiovascular reactivity to and recovery from personally relevant stress. Psychosom Med 2004;66:49–55.[Abstract/Free Full Text]
  19. Wilson DK, Kliewer W, Plybon L, Sica DA. Socioeconomic status and blood pressure reactivity in healthy black adolescents. Hypertension 2000;35:496–500.[Abstract/Free Full Text]
  20. Boomsma DI, Snieder H, de Geus EJ, van Doomen LJ. Heritability of blood pressure increases during mental stress. Twin Res 1998;1:15–24.[Medline]
  21. Cheng LS-C, Carmelli D, Hunt SC, Williams RR. Segregation analysis of cardiovascular reactivity to laboratory stressors. Genet Epidemiol 1997;14:35–49.[CrossRef][Medline]
  22. Smith TW, Turner CW, Ford MH, Hunt SC, Barlow GK, Stults BM, Williams RR. Blood pressure reactivity in adult male twins. Health Psychol 1987;6:209–20.[CrossRef][Medline]
  23. Uemura K, Kohara K, Nakura J, Miki T. Deletion polymorphism of the ACE gene is associated with higher blood pressure after hospitalization in normotensive subjects. Hypertens Res 2000;23:201–5.[Medline]
  24. Henrion D, Amant C, Benessiano J, Philip I, Plantefeve G, Chatel D, Hwas U, Desmont JM, Durand G, Amouyel P, Levy BI. Antiotensin II type I receptor gene polymorphism is associated with an increased vascular reactivity in the human mammary artery in vitro. J Vasc Res 1998;35:356–62.[CrossRef][Medline]
  25. Cockcroft JR, Gazis AG, Cross DJ, Wheatley A, Dewar J, Hall IP, Noon JP. Beta(2)-adrenoreceptor polymorphism determines vascular reactivity in humans. Hypertension 2000;36:371–5.[Abstract/Free Full Text]
  26. Gratze G, Fortin J, Labugger R, Binder A, Kotanko P, Timmermann B, Luft FC, Hoehe MR, Skrabal F. Beta-2 adrenergic receptor variants affect resting blood pressure and agonist-induced vasodilatation in young adult Caucasians. Hypertension 1999;33:1425–30.[Abstract/Free Full Text]
  27. Li GH, Faulhaber HD, Rosenthal M, Schuster H, Jordan J, Timmermann B, Hoehe MR, Luft FC, Busjahn A. Beta-2 adrenergic receptor gene variations and blood pressure under stress in normal twins. Psychophysiology 2001;38:485–9.[CrossRef][Medline]
  28. Ramage AG. Central cardiovascular regulation and 5-hydroxytryptamine receptors. Brain Res Bull 2001;56:425–39.[CrossRef][Medline]
  29. Shores MM, Pasculaly M, Lewis NL, Flatness D, Veith RC. Short-term sertraline treatment suppresses sympathetic nervous system activity in healthy human subjects. Psychoneuroendocrinol 2001;26:433–9.[CrossRef][Medline]
  30. Sauer WH, Berlin JA, Kimmel SE. Selective serotonin reuptake inhibitors and myocardial infarction. Circulation 2001;104:1894–8.[Abstract/Free Full Text]
  31. Davies SJ, Hood SD, Argyropoulos SV, Morris K, Bell C, Witchel HJ, Jackson PR, Nutt DJ, Potokar JP. Depleting serotonin enhances both cardiovascular and psychological stress reactivity in recovered patients with anxiety disorders. J Clin Psychopharmacol 2006;26:414–8.[CrossRef][Medline]
  32. Lesch KP, Bengel D, Heils A, Sabol SZ, Greenberg BD, Petri S, Benjamin J, Muller CR, Hamer DH, Murphy DL. Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 1996;274:1527–31.[Abstract/Free Full Text]
  33. Williams RB, Marchuk DA, Gadde KM, Barefoot JC, Grichnik K, Helms MJ, Kuhn CM, Lewis JG, Schanberg SM, Stafford-Smith M, Suarez EC, Clary GL, Svenson IK, Siegler IC. Central nervous system serotonin function and cardiovascular responses to stress. Psychosom Med 2001;63:300–5.[Abstract/Free Full Text]
  34. Arinami T, Ohtsuki T, Yamakawa-Kobayashi JR, Amemiya H, Fujiwara H, Kawata K, Ishiguro H, Hamaguchi H. A synergistic effect of serotonin transporter gene polymorphism and smoking in association with CHD. Thromb Haemost 1999;81:853–6.[Medline]
  35. Fumeron F. Betoulle D, Nicaud V, Evans A, Kee F, Ruidavets J-B, Arveiler D, Luc G, Cambien F. Serotonin transporter gene polymorphism and myocardial infarction. Circulation 2002;105:2943–5.[Abstract/Free Full Text]
  36. Coto E, Reguero JR, Alvarez V, Morales B, Batalla A, Gonzalez P, Martin M, Garcia-Castro M, Iglesias-Cubero G, Cortina A. 5-Hytroxytrptamine 5-HT2A receptor and 5-hydroxytryptamine transporter polymorphisms in acute myocardial infarction. Clin Sci 2003;104:241–5.[CrossRef][Medline]
  37. Williams RB, Marchuk DA, Gadde KM, Barefoot JC, Grichnik K, Helms MJ, Kuhn CM, Lewis JG, Schanberg SM, Stafford-Smith M, Suarez EC, Clary GL, Svenson IK, Siegler IC. Serotonin-related gene polymorphisms and central nervous system serotonin function. Neuropsychopharmacology 2003;28:533–41.[CrossRef][Medline]
  38. Zalsman G, Huang Y, Oquendo MA, Burke AK, Hu X, Brent DA, Ellis SP, Goldman D, Mann JJ. Association of a triallaelic serotonin transporter gene promoter region (5-HTTLPR) polymorphism with stressful life events and severity of depression. Am J Psychiatry 2006;163:1588–93.[Abstract/Free Full Text]
  39. Mann JJ, Huang YY, Underwood MD, Kassir SA, Oppenheim S, Kelly TM, Dwork AJ, Arango V. A serotonin transporter gene promoter polymorphism (5-HTTLPR) and prefrontal cortical binding in major depression and suicide. Arch Gen Psychiatry 2000;57:729–38.[Abstract/Free Full Text]
  40. Bennett AJ, Lesch KP, Heils A, Long JC, Lorenz JG, Shoaf SE, Champoux M, Suomi SJ, Linnoila MV, Higley JD. Early experience and serotonin transporter gene variation interact to influence primate CNS function. Mol Psychiatry 2002;7:118–22.[CrossRef][Medline]
  41. Caspi A, McClay J, Moffitt TE, Mill J, Martin J, Craig IW, Taylor A, Poulton R. Role of genotype in the cycle of violence in maltreated children. Science 2002;297:851–4.[Abstract/Free Full Text]
  42. Caspi A, Sugden K, Moffitt TE, Taylor A, Craig IW, Harrington HL, McClay J, Mill J, Martin J, Braithwaite A, Poulton R. Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene. Science 2003;301:386–9.[Abstract/Free Full Text]
  43. Moffitt TE, Caspi A, Rutter M. Strategy for investigating interactions between measured genes and measured environments. Arch Gen Psychiatry 2005;62:473–81.[Abstract/Free Full Text]
  44. Burroughs AR, Visscher WA, Haney T, Efland JR, Barefoot JC, Williams RB, Siegler I. Community recruitment process by race, gender and SES gradient: lessons learned from the community health and stress evaluation (CHASE) study experience. J Community Health 2003;28:421–37.[CrossRef][Medline]
  45. Gelernter J, Cubells JF, Kidd JR, Pakstis AJ, Kidd KK. Population studies of polymorphisms of the serotonin transporter gene. Am J Med Genet 1999;88:61–6.[CrossRef][Medline]
  46. Krieger N, Okamoto A, Selby JV. Adult female twins’ recall of childhood social class and father’s education: a validation study for public health research. Am J Epidemiol 1998;147:704–8.[Abstract/Free Full Text]
  47. Kamarck TW, Jennings JR, Debski TT, Glickman-Weiss E, Johnson PS, Eddy MJ, Manuck SB. Reliable measures of behaviorally-evoked cardiovascular reactivity: reactivity from a PC-based test battery: results from student and community samples. Psychophysiology 1992;29:17–28.[Medline]
  48. Ottman R. Gene-environment interaction: definitions and study designs. Prev Med 1996;25:764–70.[CrossRef][Medline]
  49. Greenberg BD, Tolliver TJ, Huang SJ, Li Q, Bengel D, Murphy DL. Genetic variation in the serotonin transporter promoter region affects serotonin uptake in human blood platelets. Am J Med Genet 1999;88:83–7.[CrossRef][Medline]
  50. Seedat YK, Seedat MA, Hackland DB. Prevalence of hypertension in the urban and rural Zulu. J Epidemiol Community Health 1982;36:256–61.[Abstract/Free Full Text]
  51. Brummett BH, Boyle SH, Siegler IC, Kuhn CM, Ashley-Koch AE, Jonassaint CR, Zuchner S, Collins A, Williams RB. Effects of environmental stress and gender on associations among symptoms of depression and the serotonin transporter gene linked polymorphic region (5HTTLPR). Behavior Genetics 2007 Oct 23; [Epub ahead of print].
  52. Eddahibi S, Chaouat A, Morrell N, Fadel E, Fuhrman C, Bugnet A-S, Dartevelle P, Housset B, Hamon M, Weitzenblum E. Polymorphism of the serotonin transporter gene and pulmonary hypertension in chronic obstructive pulmonary disease. Circulation 2003;108:1839–44.[Abstract/Free Full Text]
  53. McCaffery JM, Bleil M, Pogue-Geile MF, Ferrell RE, Manuck SB. Allelic variation in the serotonin transporter gene-linked polymorphism region (5HTTLPR) and cardiovascular reactivity in young male and female twins of European-American descent. Psychosom Med 2003;65:721–8.[Abstract/Free Full Text]
  54. Hu XZ, Lipsky RH, Zhu G, Akhtar LA, Taubman J, Greenberg BD, Xu K, Arnold PD, Richter MA, Kennedy JL, Murphy DL, Goldman D. Serotonin transporter promoter gain-of-function genotypes are linked to obsessive-compulsive disorder. Am J Hum Genet 2006;78:815–26.[CrossRef][Medline]
  55. Bishop GC, Kaur D, Tan VLM. Effects of a psychosocial skills training workshop on psychophysiological and psychological risk in patients undergoing coronary artery bypass grafting. Am Heart J 2005;150:602–9.[CrossRef][Medline]




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