Sex-specific pathways among tri-allelic serotonin transporter polymorphism, trait neuroticism and generalized anxiety disorder.

Background: Neuroticism personality trait is recognized as an important endophenotypic predictor of generalized anxiety disorder (GAD). Furthermore, endophenotype-based pathway approaches have recently been shown to have greater advantages for gene-finding strategies than traditional case-control studies. In the present study, in addition to conventional case-control methods, we used pathway analyses to test whether the tri-allelic serotonin transporter promoter polymorphism (combining 5-HTTLPR and rs25531) is associated with risk of GAD through its effects on trait neuroticism. Methods: We included 2236 Han Chinese adults in this study, including 736 patients with GAD and 1500 healthy participants. We genotyped the 5-HTTLPR and rs25531 polymorphisms using the polymerase chain reaction restriction fragment length polymorphism method. We used the Neuroticism scale of the Maudsley Personality Inventory (MPI) short version (MPI-Neuroticism) to measure participants' tendency toward neuroticism. Results: Using endophenotype-based path analyses, we found significant indirect effects of the tri-allelic genotype on risk of GAD, mediated by MPI-Neuroticism in both men and women. Compared to women carrying the S'S' genotype, women carrying the L' allele had higher levels of MPI-Neuroticism, which in turn were associated with higher risk of GAD. Men, however, showed the opposite pattern. Using traditional case-control comparisons, we observed that the effect of tri-allelic genotype on GAD was significant, but only in women. Limitations: Participants were restricted to Han Chinese, and we used only 1 questionnaire to assess neuroticism. Conclusion: These findings are the first to show that the triallelic 5-HTTLPR polymorphism is associated with elevated risk of GAD, and that this effect is mediated via increased trait neuroticism, a sex-dependent risk pathway.

Age-dependent association of polymorphisms in the promoter and 5'-untranslated region of the norepinephrine transporter gene with generalized anxiety disorder.

BACKGROUND: Norepinephrine transporter (NET), which regulates synaptic norepinephrine for noradrenergic signaling, is involved in the pathogenesis of anxiety, while expression of the NET gene differs at different ages. Here, we examine whether genetic variants in the NET gene are associated, in an age-specific manner, with increased risk of generalized anxiety disorder (GAD), one of the most disabling anxiety disorders. METHODS: Three common single-nucleotide polymorphisms (SNPs) in the promoter (rs168924: A/G; rs2242446: T/C) and 5'-untranslated region (5'-UTR) (rs2397771: G/C) of the NET gene were genotyped in 2,317 Han-Chinese participants (791 GAD patients and 1,526 controls; age: 20-65). Potential confounding factors, such as gender, stress levels and psychiatric comorbidities, were included as covariates. RESULTS: An interaction between age and NET genotypes and haplotypes was found for the risk of GAD. In the younger participants, rs168924 minor allele G homozygotes had the lowest incidence of GAD; however, older subjects displayed an inverse pattern, with homozygous G/G carriers presenting the highest prevalence of GAD. Additionally, younger individuals carrying 2 copies of the GGT haplotype composed of rs2397771-rs168924-rs2242446 had the lowest rate of GAD. However, those with 2 copies of the same haplotype exhibited the highest risk of GAD in the older groups. LIMITATIONS: Only 3 common SNPs in the promoter and 5'-UTR of the NET gene were analyzed. CONCLUSIONS: Our findings are the first to demonstrate that potentially functional SNPs in the NET promoter and 5'-UTR are associated with an increased risk of GAD, and that such associations are determined in an age-specific way.

BDNF Val66Met polymorphism to generalized anxiety disorder pathways: Indirect effects via attenuated parasympathetic stress-relaxation reactivity.

The valine66methionine (Val66Met) polymorphism (rs6265) of the brain-derived neurotrophic factor (BDNF) gene has been shown to influence autonomic arousal pathways, which in turn predict elevated syndromal anxiety in healthy humans. We examined whether the BDNF variant is associated with an increased risk of generalized anxiety disorder (GAD), one of the most prevalent anxiety disorders, through altering parasympathetic stress/relaxation reactivity. A total of 2,250 Han Chinese adults (750 GAD patients and 1,500 healthy controls) were included in the genotyping. High-frequency heart rate variability, an index of vagal (parasympathetic) activity, was measured during the supine-standing-supine test (5 min in each position); vagal withdrawal and vagal activation were calculated as baseline supine minus standing and recovery supine minus standing, respectively. Analysis of healthy participants indicated that Val/Val homozygotes displayed significantly blunted vagal withdrawal and vagal activation compared with Met allele carriers. After analyzing the entire sample, these effects remained significant. Furthermore, both attenuated vagal response patterns were found to be significantly associated with a higher incidence of GAD. Lastly, the path analysis identified a significant indirect effect of BDNF on the risk of GAD via diminishing vagal response to either orthostatic stress or supine relaxation. Even when further testing the subsample comprising only comorbidity- and medication-free GAD patients and healthy controls to minimize the confounding bias, the results still remained. Our findings demonstrate that individuals carrying the BDNF Val/Val genotype, compared to Met-carriers, may be at higher risk of GAD due to blunted vagal reactivity in response to both stress and relaxation. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Attenuated vagally-mediated heart rate variability at rest and in response to postural maneuvers in patients with generalized anxiety disorder.

BACKGROUND: Altered heart rate variability (HRV), an index of autonomic nervous system function, has been reported in generalized anxiety disorder (GAD), but the results have been mixed. Thus, the present study, using a large sample size and better methodology, aims to examine whether GAD is associated with impaired HRV, both at rest and in response to posture challenges. METHODS: In total, 1832 participants were recruited in this study, consisting of 682 patients with GAD (including 326 drug- and comorbidity-free GAD patients) and 1150 healthy controls. Short-term HRV was measured during the supine-standing-supine test (5-min per position). Propensity score matching (PSM), a relatively novel method, was used to control for potential confounders. RESULTS: After PSM algorithm, drug- and comorbidity-free GAD patients had reductions in resting (baseline) high-frequency power (HF), an index for parasympathetic modulation, and increases in the low-frequency/HF ratio (LF/HF), an index for sympathovagal balance as compared to matched controls. Furthermore, the responses of HF and LF/HF to posture changes were all attenuated when compared with matched controls. Effect sizes, given by Cohen's d, for resting HF and HF reactivity were 0.42 and 0.36-0.42, respectively. CONCLUSIONS: GAD is associated with altered sympathovagal balance, characterized by attenuation in both resting vagal modulation and vagal reactivity, with an almost medium effect size (Cohen's d ≈ 0.4), regardless of medication use or comorbidity status.

Age-specific associations among functional COMT Val158Met polymorphism, resting parasympathetic nervous control and generalized anxiety disorder.

The functional Val158Met polymorphism (rs4680) of the Catechol-O-Methyltransferase (COMT) gene has been implicated in generalized anxiety disorder (GAD); however, the underlying neural mechanisms remain unexamined. Recent evidence reveals that low resting parasympathetic (vagal) control is an endophenotypic predictor of anxiety, while the effect of COMT rs4680 differs at different ages. Thus, we examined whether the COMT Val158Met variant could increase the risk of GAD through decreased resting parasympathetic nervous control in an age-specific manner. COMT rs4680 polymorphism was genotyped in 1,655 Han Chinese adults (1,142 healthy subjects and 513 patients with GAD; age: 20-65). High-frequency power (HF) of heart rate variability (HRV) was used to measure resting state parasympathetic nervous regulation. Non-genetic factors, such as gender, smoking status, medication use and comorbidity conditions, were treated as covariates. After adjusting for relevant covariates, there was a significant age x COMT genotype interaction on resting HF of HRV. In younger adults, Met allele carriers had a significantly lower HF index; however, older adults exhibited the opposite pattern, with Val/Val homozygotes exhibiting decreased HF values. Moreover, reduced HF-HRV is associated with increased risk of GAD. Finally, pathway analysis revealed a significant indirect effect of COMT on the risk of GAD via reduced resting HF-HRV, in the aforementioned age-dependent manner. Our findings are the first to demonstrate that COMT Val158Met polymorphism is associated with risk of GAD via reduced resting parasympathetic nervous control, an age-specific risk pathway.

Serotonin 2A receptor (5-HT2A) gene promoter variant interacts with chronic perceived stress to modulate resting parasympathetic activity in humans.

Decreased resting vagal (parasympathetic) tone is implicated in the development of stress-related disorders, including anxiety and depression. Chronic stress elevates the expression of serotonin 2A receptors (5-HT2A), while activation of 5-HT2A leads to inhibition of parasympathetic synaptic transmission. The T allele of the promoter variant, rs6311 (C>T), of the 5-HT2A gene has been shown to increase the 5-HT2A expression in vitro and to be associated with anxiety and depressive disorders. We thus hypothesized that the 5-HT2A functional polymorphism may influence resting vagal activity among persons with chronically high levels of perceived stress. A total of 1138 well-defined healthy, medication-free Han Chinese were included for 5-HT2A genotyping. The Perceived Stress Scale (PSS) was used to measure the level of perceived stress during the last month and participants were divided into low and high PSS groups. Resting-state heart rate variability (HRV) was used to assess autonomic function. No significant between-genotype difference was found in any HRV variable in the low PSS group (n=610). However, in the high PSS group (n=528), high frequency power and root mean square of successive heartbeat interval differences (both HRV indices of parasympathetic activity) were significantly reduced in T/T genotype carriers compared to C/C homozygotes. Our findings are the first to show that individuals homozygous for the high-expressing 5-HT2A (T) allele exhibit diminished resting vagal tone-an index of stress vulnerability-when experiencing chronically elevated levels of perceived stress. The present results may advance our understanding of the genetic mechanism underlying individual differences in susceptibility to stress.

Gender-specific association between serotonin transporter polymorphisms (5-HTTLPR and rs25531) and neuroticism, anxiety and depression in well-defined healthy Han Chinese.

BACKGROUND: A tri-allelic serotonin transporter promoter polymorphism (5-HTTLPR/rs25531) more effectively determines the levels of transcriptional efficacy than that with the bi-allelic 5-HTTLPR polymorphism in vitro. Both are reportedly associated with personality traits of negative emotionality, but with conflicting findings. One explanation for this is that a gender difference may play a role in genetic contribution. Here, we hypothesized that the tri-allelic genotype of the serotonin transporter is more closely linked to neuroticism, an anxiety- and depression-related trait, than the bi-allelic variation, particularly in a gender-dependent way. METHODS: The genotypes of the 5-HTTLPR and rs25531 loci were determined in 1139 well-defined physically and mentally healthy Han Chinese (550 men, 589 women; mean age 38.3±10.3 years). All participants completed the neuroticism measure of the short-form Maudsley Personality Inventory (MPI). The levels of anxiety and depression were assessed by the Beck Anxiety Inventory (BAI) and the Beck Depression Inventory (BDI), respectively. RESULTS: A significant tri-allelic genotype-by-gender interaction effect was found in the MPI-neuroticism measure. S'S' homozygotes were associated with higher neuroticism than L' allele carriers in men. Also, both the BAI and BDI scores were higher in the S'S' homozygotic men. In the bi-allelic analyses, however, there was only an association between SS genotype and MPI-neuroticism in men. LIMITATIONS: Sub-analyses by gender-stratification may reduce the statistical power. CONCLUSIONS: Our findings confirm that gender differences exist in the genetic contributions of the serotonin transporter in human neuroticism, and anxiety/depression. Our data provide further support for rs25531, strengthening the effects of 5-HTTLPR.

Association of neuropeptide Y promoter polymorphism (rs16147) with perceived stress and cardiac vagal outflow in humans.

Neuropeptide Y (NPY) is involved in resilience to stress, and higher vagal (parasympathetic) activity has been associated with greater stress resilience. Thus, we examined whether rs16147, a functional promoter polymorphism (C>T) of the NPY gene, could influence vagal tone during chronic high stress levels. NPY genotyping, chronic psychological stress level measurement (using the Perceived Stress Scale [PSS]), cardiac autonomic function assessment (using short-term heart rate variability [HRV]) were performed in 1123 healthy, drug-free Han Chinese participants who were divided into low- and high-PSS groups. In the high-PSS group (n = 522), the root mean square of successive heartbeat interval differences and high frequency power (both HRV indices of parasympathetic activity) were significantly increased in T/T homozygotes compared to C/C homozygotes. However, no significant between-genotype difference was found in any HRV variable in the low-PSS group (n = 601). Our results are the first to demonstrate that functional NPY variation alters chronic stress-related vagal control, suggesting a potential parasympathetic role for NPY gene in stress regulation.