Sex-specific association between nerve growth factor polymorphism and cardiac vagal modulation

Heart rate variability: Evaluating a potential biomarker of anxiety disorders

Establishing quantifiable biological markers associated with anxiety will increase the objectivity of phenotyping and enhance genetic research of anxiety disorders. Heart rate variability (HRV) is a physiological measure reflecting the dynamic relationship between the sympathetic and parasympathetic nervous systems, and is a promising target for further investigation. This review summarizes evidence evaluating HRV as a potential physiological biomarker of anxiety disorders by highlighting literature related to anxiety and HRV combined with investigations of endophenotypes, neuroimaging, treatment response, and genetics. Deficient HRV shows promise as an endophenotype of pathological anxiety and may serve as a noninvasive index of prefrontal cortical control over the amygdala, and potentially aid with treatment outcome prediction. We propose that the genetics of HRV can be used to enhance the understanding of the genetics of pathological anxiety for etiological investigations and treatment prediction. Given the anxiety-HRV link, strategies are offered to advance genetic analytical approaches, including the use of polygenic methods, wearable devices, and pharmacogenetic study designs. Overall, HRV shows promising support as a physiological biomarker of pathological anxiety, potentially in a transdiagnostic manner, with the heart-brain entwinement providing a novel approach to advance anxiety treatment development.

Serum NGF and BDNF in Long-COVID-19 Adolescents: A Pilot Study

COVID-19 (COronaVIrus Disease 19) is an infectious disease also known as an acute respiratory syndrome caused by the SARS-CoV-2. Although in children and adolescents SARS-CoV-2 infection produces mostly mild or moderate symptoms, in a certain percentage of recovered young people a condition of malaise, defined as long-COVID-19, remains. To date, the risk factors for the development of long-COVID-19 are not completely elucidated. Neurotrophins such as NGF (Nerve Growth Factor) and BDNF (Brain-Derived Neurotrophic Factor) are known to regulate not only neuronal growth, survival and plasticity, but also to influence cardiovascular, immune, and endocrine systems in physiological and/or pathological conditions; to date only a few papers have discussed their potential role in COVID-19. In the present pilot study, we aimed to identify NGF and BDNF changes in the serum of a small cohort of male and female adolescents that contracted the infection during the second wave of the pandemic (between September and October 2020), notably in the absence of available vaccines. Blood withdrawal was carried out when the recruited adolescents tested negative for the SARS-CoV-2 (“post-infected COVID-19”), 30 to 35 days after the last molecular test. According to their COVID-19 related outcomes, the recruited individuals were divided into three groups: asymptomatics, acute symptomatics and symptomatics that over time developed long-COVID-19 symptoms (“future long-COVID-19”). As a control group, we analyzed the serum of age-matched healthy controls that did not contract the infection. Inflammatory biomarkers (TNF-α, TGF-β), MCP-1, IL-1α, IL-2, IL-6, IL-10, IL-12) were also analyzed with the free oxygen radicals’ presence as an oxidative stress index. We showed that NGF serum content was lower in post-infected-COVID-19 individuals when compared to healthy controls; BDNF levels were found to be higher compared to healthy individuals only in post-infected-COVID-19 symptomatic and future long-COVID-19 girls, leaving the BDNF levels unchanged in asymptomatic individuals if compared to controls. Oxidative stress and inflammatory biomarkers were unchanged in male and female adolescents, except for TGF-β that, similarly to BDNF, was higher in post-infected-COVID-19 symptomatic and future long-COVID-19 girls. We predicted that NGF and/or BDNF could be used as early biomarkers of COVID-19 morbidity in adolescents.

No Association of Polymorphisms in Nav1.7 or Nerve Growth Factor Receptor Genes with Trigeminal Neuralgia

OBJECTIVE

Trigeminal neuralgia is defined as a sudden severe shock-like pain within the distribution of the trigeminal nerve. Pain is a subjective experience that is influenced by gender, culture, environment, psychological traits, and genes. Sodium channels and nerve growth factor play important roles in the transmission of nociceptive signals and pain. The aim of this study was to investigate the occurrence of Nav1.7 sodium channel and nerve growth factor receptor TrkA gene polymorphisms (SCN9A/rs6746030 and NTRK1/rs633, respectively) in trigeminal neuralgia patients.

METHODS

Ninety-six subjects from pain specialty centers in the southeastern region of Brazil were divided into 2 groups: 48 with classical trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated using the visual analog scale and multidimensional McGill Pain Questionnaire. Genomic DNA was obtained from oral swabs in all individuals and was analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed between evaluated polymorphisms and trigeminal neuralgia. For allele analyses, patients and controls had similar frequencies for both genes. Genotype distribution or allele frequencies of polymorphisms analyzed here did not correlate to pain scores.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia diagnosis or pain severity was observed, our data do not exclude the possibility that other genotypes affecting the expression of Nav1.7 or TrkA are associated with the disease. Further studies should investigate distinct genetic polymorphisms and epigenetic factors that may be important in expression of these molecules.

Effect of gender-related depression on heart rate variability during an autonomic nervous test

Patients with depression have lower heart rate variability (HRV) compared with controls. However, studies have indicated HRV difference between male and female controls. The gender effect might be interactive with the depression effect on the HRV, resulting in a low accuracy of recognising the patients with depression from the controls. Our study explores the effect of gender-related depression on HRV. Four ANS tests including resting, deep breathing, Valsalva, and orthostatic test are employed as stimuli. HRV were collected from 182 subjects comprising 91 depressive patients (33 females/58 males) and 91 controls (33 females/58 males) in the four tests. Time and frequency domains and nonlinear parameters are employed to quantify HRV. Two-way ANOVA is applied to evaluate the effect of gender-related depression. Most HRV parameters of the patients significantly differ from those of the controls, but some parameters indicate different depression effect between the males and females in the deep breathing and Valsalva test. Some HRV parameters illustrate significant difference between the male and female controls. Therefore, the effect of depression on HRV of each gender should be investigated.

NGF gene polymorphisms are not associated with heroin dependence in a Taiwanese male population

BACKGROUND AND OBJECTIVES

Heroin dependence (HD) is a chronic relapsing brain illness with substantial heritability. Nerve growth factor (NGF) is a crucial modulator in the neurodevelopment, and may be a key mediator of reward processes in HD. The purpose of this genetic study was to investigate whether NGF gene polymorphisms associate with the occurrence of HD and the specific personality traits of patients with HD.

METHODS

We selected a homogeneous Han Chinese male population to overcome possible confounding effects of population and gender. For the study, 272 HD patients and 141 controls completed the Tridimensional Personality Questionnaire to evaluate their personality traits. In addition, a further sample 303 HD patients and 204 controls was added (with totally 920 participants) for the gene association and genotype-phenotype interaction studies.

RESULTS

Patients with HD had higher novelty seeking (NS) and harm avoidance (HA) scores than healthy subjects. Nonetheless, NGF gene polymorphisms did not associate with specific personality traits in HD patients and controls. There is no significant difference in NGF gene polymorphisms between patients with HD and controls.

DISCUSSION AND CONCLUSIONS

The NGF gene may neither contribute to the risk of development of HD, nor mediate the relationship between specific personality traits and HD in Han Chinese male population.

SCIENTIFIC SIGNIFICANCE

Patients with HD had higher novelty seeking (NS) and harm avoidance (HA) scores than healthy subjects. However, none of the polymorphisms in the NGF gene affected the NS and HA scores in both patients and healthy subjects. (Am J Addict 2018;27:516-523).

Serotonin receptor 1A promoter polymorphism, rs6295, modulates human anxiety levels via altering parasympathetic nervous activity

OBJECTIVE

The G-allele of the -1019C/G (rs6295) promoter polymorphism of the serotonin receptor 1A (HTR1A) gene has been implicated in anxiety; however, the underlying neurophysiological processes are still not fully understood. Recent evidence indicates that low parasympathetic (vagal) tone is predictive of anxiety. We thus conducted a structural equation model (SEM) to examine whether the HTR1A rs6295 variant can affect anxiety by altering parasympathetic nervous activity.

METHOD

A sample of 1141 drug-free healthy Han Chinese was recruited for HTR1A genotyping. Autonomic nervous function was assessed by short-term spectral analysis of heart rate variability (HRV). Anxiety and stress levels were evaluated by the Beck Anxiety Inventory (BAI) and the Perceived Stress Scale (PSS) respectively.

RESULTS

The number of the HTR1A G allele was inversely correlated with high-frequency power (HF), a parasympathetic index of HRV. The HF index was negatively associated with BAI scores. Furthermore, the good-fitting SEM, adjusting for confounding variables (e.g., age and PSS levels), revealed a significant pathway linking rs6295 variant to BAI scores via HF index modulation.

CONCLUSION

These results are the first to show that HTR1A -1019C/G polymorphism influences anxiety levels by modulating parasympathetic tone, providing a neurophysiological insight into the role of HTR1A in human anxiety.

The genetics of anxiety-related negative valence system traits

NIMH's Research Domain Criteria (RDoC) domain of negative valence systems (NVS) captures constructs of negative affect such as fear and distress traditionally subsumed under the various internalizing disorders. Through its aims to capture dimensional measures that cut across diagnostic categories and are linked to underlying neurobiological systems, a large number of phenotypic constructs have been proposed as potential research targets. Since "genes" represent a central "unit of analysis" in the RDoC matrix, it is important for studies going forward to apply what is known about the genetics of these phenotypes as well as fill in the gaps of existing knowledge. This article reviews the extant genetic epidemiological data (twin studies, heritability) and molecular genetic association findings for a broad range of putative NVS phenotypic measures. We find that scant genetic epidemiological data is available for experimentally derived measures such as attentional bias, peripheral physiology, or brain-based measures of threat response. The molecular genetic basis of NVS phenotypes is in its infancy, since most studies have focused on a small number of candidate genes selected for putative association to anxiety disorders (ADs). Thus, more research is required to provide a firm understanding of the genetic aspects of anxiety-related NVS constructs. © 2016 Wiley Periodicals, Inc.

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.

Reduced cardiac autonomic response to deep breathing: A heritable vulnerability trait in patients with schizophrenia and their healthy first-degree relatives

Reduced resting heart rate variability (HRV) has been observed in patients with schizophrenia and their relatives, suggesting genetic predispositions. However, findings have not been consistent. We assessed cardiac autonomic response to deep breathing in first-degree relatives of patients with schizophrenia (n=45; 26 female; aged 39.69±14.82 years). Data were compared to healthy controls (n=45; 26 female; aged 38.27±9.79 years) matched for age, gender, body mass index and physical activity as well as to unmedicated patients with acute schizophrenia (n=45; 25 female; aged 37.31±12.65 years). Electrocardiograms were recorded under supine resting and deep-breathing conditions (10-12breaths/min). We measured HRV components including variance, low-frequency (LF) power, which may reflect baroreflex function, high-frequency (HF) power, which reflects cardiac parasympathetic activity, and LF/HF ratio, which may reflect sympatho-vagal balance. Patients rather than relatives exhibited lower resting-state HRV (variance, LF, and HF) than controls. As expected, deep breathing induced an increase in variance and HF-HRV in controls. However, such a response was significantly reduced in both patients and their relatives. In conclusion, the diminished cardiac autonomic reactivity to deep breathing seen in patients and their unaffected relatives indicates that this pattern of cardiac autonomic dysregulation may be regarded as a genetic trait marker for schizophrenia.

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.

Linking an Anxiety-Related Personality Trait to Cardiac Autonomic Regulation in Well-Defined Healthy Adults: Harm Avoidance and Resting Heart Rate Variability

OBJECTIVE

Anxiety trait, anxiety and depression states have all been reported to increase risks for cardiovascular disease (CVD), possibly through altering cardiac autonomic regulation. Our aim was to investigate whether the relationship between harm avoidance (HA, an anxiety-related personality trait) and cardiac autonomic regulation is independent of anxiety and depression states in healthy adults.

METHODS

We recruited 535 physically and mentally healthy volunteers. Participants completed the Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI) and Tri-dimensional Personality Questionnaire. Participants were divided into high or low HA groups as discriminated by the quartile value. Cardiac autonomic function was evaluated by measuring heart rate variability (HRV). We obtained the time and frequency-domain indices of HRV including variance (total HRV), the low-frequency power (LF; 0.05-0.15 Hz), which may reflect baroreflex function, the high-frequency power (HF; 0.15-0.40 Hz), which reflects cardiac parasympathetic activity, as well as the LF/HF ratio.

RESULTS

The BDI and HA scores showed associations with HRV parameters. After adjustment for the BDI scores and other control variables, HA is still associated with reduced variance, LF and HF power. Compared with the participants with low HA, those with high HA displayed significant reductions in variance, LF and HF power and a significant increase in their LF/HF ratio.

CONCLUSION

This study highlights the independent role of HA in contributing to decreased autonomic cardiac regulation in healthy adults and provides a potential underlying mechanism for anxiety trait to confer increased risk for CVD.

Distinguishing bipolar II depression from unipolar major depressive disorder: Differences in heart rate variability

OBJECTIVES

Bipolar II (BPII) depression is commonly misdiagnosed as unipolar depression (UD); however, an objective and reliable tool to differentiate between these disorders is lacking. Whether cardiac autonomic function can be used as a biomarker to distinguish BPII from UD is unknown.

METHODS

We recruited 116 and 591 physically healthy patients with BPII depression and UD, respectively, and 421 healthy volunteers aged 20-65 years. Interviewer and self-reported measures of depression/anxiety severity were obtained. Cardiac autonomic function was evaluated by heart rate variability (HRV) and frequency-domain indices of HRV.

RESULTS

Patients with BPII depression exhibited significantly lower mean R-R intervals, variance (total HRV), low frequency (LF)-HRV, and high frequency (HF)-HRV but higher LF/HF ratio compared to those with UD. The significant differences remained after adjusting for age. Compared to the controls, the patients with BPII depression showed cardiac sympathetic excitation with reciprocal vagal impairment, whereas the UD patients showed only vagal impairment. Depression severity independently contributed to decreased HRV and vagal tone in both the patients with BPII depression and UD, but increased sympathetic tone only in those with BPII depression.

CONCLUSIONS

HRV may aid in the differential diagnosis of BPII depression and UD as an adjunct to diagnostic interviews.

Sex differences in healthy human heart rate variability: A meta-analysis

The present meta-analysis aimed to quantify current evidence on sex differences in the autonomic control of the heart, indexed by measures of heart rate variability (HRV) in healthy human subjects. An extensive search of the literature yielded 2020 titles and abstracts, of which 172 provided sufficient reporting of sex difference in HRV. Data from 63,612 participants (31,970 females) were available for analysis. Meta-analysis yielded a total of 1154 effect size estimates (k) across 50 different measures of HRV in a cumulated total of 296,247 participants. Females showed a significantly lower mean RR interval and standard deviation of RR intervals (SDNN). The power spectral density of HRV in females is characterized by significantly less total power that contains significantly greater high- (HF) and less low-frequency (LF) power. This is further reflected by a lower LF/HF ratio. Meta-regression revealed significant effects of age, respiration control and the length of recording available for analysis. Although women showed greater mean heart rate, they showed greater vagal activity indexed by HF power of HRV. Underlying mechanisms of these findings are discussed.

Heart rate variability in major depressive disorder and after antidepressant treatment with agomelatine and paroxetine: Findings from the Taiwan Study of Depression and Anxiety (TAISDA)

Evidence from previous studies suggests that heart rate variability (HRV) is reduced in major depressive disorder (MDD). However, whether this reduction is attributable to the disorder per se or to medication, since antidepressants may also affect HRV, is still debated. There is a dearth of information regarding the effects of agomelatine, a novel antidepressant, on HRV. Here, we investigated whether HRV is reduced in MDD and compared the effects of agomelatine and paroxetine on HRV. We recruited 618 physically healthy unmedicated patients with MDD and 506 healthy volunteers aged 20-65 years. Frequency-domain measures of resting HRV were obtained at the time of enrollment for all participants. For patients with MDD, these measures were obtained again after 6 weeks of either agomelatine or paroxetine monotherapy. Compared with healthy subjects, unmedicated patients with MDD exhibited significantly lower variance (total HRV), low frequency (LF), and high frequency (HF) HRV, and a higher LF/HF ratio. Depression severity independently contributed to decreased HRV and vagal tone. Fifty-six patients completed the open-label trial (n=29 for agomelatine, n=27 for paroxetine). Between-group analyses showed a significant group-by-time interaction for LF-HRV and HF-HRV, driven by increases in LF-HRV and HF-HRV only after agomelatine treatment. Within the paroxetine-treated group, there were no significant changes in mean R-R intervals or any HRV indices. We therefore concluded that MDD is associated with reduced HRV, which is inversely related to depression severity. Compared with paroxetine, agomelatine has a more vagotonic effect, suggesting greater cardiovascular safety. Clinicians should consider HRV effects while selecting antidepressants especially for depressed patients who already have decreased cardiac vagal tone.

Harm avoidance involved in mediating the association between nerve growth factor (NGF) gene polymorphisms and antidepressant efficacy in patients with major depressive disorder

BACKGROUND

Antidepressants have variable efficacies in subjects with major depressive disorder (MDD). Nerve growth factor (NGF) has been suggested to play an important role in the pathogenesis of depressive symptoms and the response to antidepressant therapy. The aim of this study was to examine whether NGF gene polymorphisms are associated with the antidepressant therapeutic efficacy in subjects with MDD.

METHODS

A naturalistic follow-up study was carried out on 557 subjects with MDD. Of the enrolled patients, 304 completed the 8-week open-label antidepressant treatment. Seven single-nucleotide polymorphisms (SNPs) of the NGF gene were genotyped. The 21-item Hamilton Depression Rating Scale was used to assess depressive severity from baseline to endpoint. Tridimensional Personality Questionnaire was used to assess baseline personality traits. Single marker and haplotype analyses were conducted. Binary logistic regression was used to calculate odds ratios of remission. Structural equation modeling was used to analyze the predicted mediation effect.

RESULTS

A significant difference in genotype frequencies between remitters and non-remitters was observed in three NGF SNPs (rs12760036, rs7523654, and rs17033692). The haplotype analysis revealed that the CCC haplotype (rs2254527-rs6678788-rs12760036) was associated with a higher remission rate, while the CCA haplotype was associated with a lower remission rate. The harm avoidance psychological factor partially mediated the effect of NGF variants on antidepressant efficacy.

LIMITATIONS

The selected SNPs may not cover whole NGF gene.

CONCLUSIONS

NGF variants are associated with remission rates after 8-week antidepressant treatment, and harm avoidance partially mediated the effect of NGF variants on treatment outcomes.

Functional Ser205Leu polymorphism of the nerve growth factor receptor (NGFR) gene is associated with vagal autonomic dysregulation in humans

Evidence indicates that reduced cardiac vagal (parasympathetic) tone, a robust cardiovascular risk factor, is a trait vulnerability marker of major depressive disorder (MDD). The Ser205/Ser205 genotype of the functional polymorphism (Ser205Leu) of the nerve growth factor receptor (NGFR), also called p75 neurotrophin receptor (p75^NTR), gene is reported to increase the risk of MDD. Here, we hypothesized that the NGFR Ser205Leu polymorphism may have an effect on vagal control. A sample of 810 healthy, drug-free, unrelated Han Chinese (413 males, 397 females; mean age 35.17 ± 8.53 years) was included in the NGFR genotyping. Short-term heart rate variability (HRV) was used to assess vagus-mediated autonomic function. Potential HRV covariates, such as mood/anxiety status and serum metabolic parameters, were assessed. Homozygotes of the Ser205 allele had significantly lower high frequency power and root mean square of successive heartbeat interval differences, both HRV indices of vagal modulation, compared to Leu205 allele carriers. Even after adjusting for relevant confounders, these associations remained significant. Further stratification by sex revealed that the associations were observed only in males. Our results implicate that decreased parasympathetic activity is associated with the NGFR Ser205/Ser205 genotype in a gender-specific manner, suggesting a potential role of NGFR polymorphism in modulating cardiac autonomic function.