Genetic and epigenetic regulation of Catechol-O-methyltransferase in relation to inflammation in chronic fatigue syndrome and Fibromyalgia

BACKGROUND

Catechol-O-methyltransferase (COMT) has been shown to influence clinical pain, descending modulation, and exercise-induced symptom worsening. COMT regulates nociceptive processing and inflammation, key pathophysiological features of Chronic Fatigue Syndrome and Fibromyalgia (CFS/FM). We aimed to determine the interactions between genetic and epigenetic mechanisms regulating COMT and its influence on inflammatory markers and symptoms in patients with CFS/FM.

METHODS

A case-control study with repeated-measures design was used to reduce the chance of false positive and increase the power of our findings. Fifty-four participants (28 patients with CFS/FM and 26 controls) were assessed twice within 4 days. The assessment included clinical questionnaires, neurophysiological assessment (pain thresholds, temporal summation, and conditioned pain modulation), and blood withdrawal in order to assess rs4818, rs4633, and rs4680 COMT polymorphisms and perform haplotype estimation, DNA methylation in the COMT gene (both MB-COMT and S-COMT promoters), and cytokine expression (TNF-α, IFN-γ, IL-6, and TGF-β).

RESULTS

COMT haplotypes were associated with DNA methylation in the S-COMT promoter, TGF-β expression, and symptoms. However, this was not specific for one condition. Significant between-group differences were found for increased DNA methylation in the MB-COMT promoter and decreased IFN-γ expression in patients.

DISCUSSION

Our results are consistent with basic and clinical research, providing interesting insights into genetic-epigenetic regulatory mechanisms. MB-COMT DNA methylation might be an independent factor contributing to the pathophysiology of CFS/FM. Further research on DNA methylation in complex conditions such as CFS/FM is warranted. We recommend future research to employ a repeated-measure design to control for biomarkers variability and within-subject changes.

Role of NR3C1 and SLC6A4 methylation in the HPA axis regulation in burnout

BACKGROUND

Work-related stress and burnout have become major occupational health concerns. Dysregulation of HPA axis is considered one of the central mechanisms and is potentially moderated through epigenetics. In the present study, we aim to investigate epigenetic regulation of the HPA axis in burnout, by focusing on salivary cortisol and cortisone and DNA methylation of the glucocorticoid receptor gene (NR3C1) and the serotonin transporter gene (SLC6A4).

METHODS

We conducted a cross-sectional study with 59 subjects with burnout and 70 healthy controls recruited from the general population. All participants underwent a clinical interview and psychological assessment. Saliva samples were collected at 0, 30 and 60 min after awakening and were used to quantify cortisol and cortisone. Pyrosequencing was performed on whole blood-derived DNA to assess DNA methylation.

RESULTS

There were no between-group differences in cortisol levels, whereas burnout participants had higher levels of cortisone. Job stress was associated with increased cortisol and cortisone. We observed both increased and decreased NR3C1 and SLC6A4 methylation in the burnout group compared to the control group. Some of these methylation changes correlated with burnout symptoms dimensionally. Increased methylation in a specific CpG in the SLC6A4 promoter region moderated the association between job stress and burnout. DNA methylation in this CpG was also associated with increased cortisol. In addition, average methylation of NR3C1 was negatively associated with cortisone levels.

LIMITATIONS

This is a cross-sectional study and therefore no conclusions on causality could be made.

CONCLUSIONS

We provide first evidence of changes in DNA methylation of NR3C1 and SLC6A4 in burnout, which were further associated with cortisol and cortisone. Further, increased cortisol and cortisone seemed to reflect job stress rather than burnout itself.

Interplay of Val66Met and BDNF methylation: effect on reward learning and cognitive performance in major depression

Background

There is a growing interest in the role of brain-derived neurotrophic factor (BDNF) in major depressive disorder (MDD). BDNF potentially exhibits opposite effects in the pathways linked to anhedonia and reward learning on the one hand and cognitive performance, on the other hand. However, the epigenetic mechanisms behind this remain unknown. In the present study, we aimed to investigate the interplay of DNA methylation of different BDNF exons and the common Val66Met polymorphism on anhedonia, reward learning and cognitive performance in MDD.

Methods

We recruited 80 depressed patients and 58 age- and gender-matched healthy controls. Participants underwent clinical assessment including neuropsychological testing and a probabilistic reward task to assess reward learning. Val66Met polymorphism and DNA methylation of BDNF promoters I, IV and exon IX were assessed from whole blood derived DNA, using pyrosequencing.

Results

BDNF promoter I methylation was lower in MDD patients (p = 0.042) and was negatively associated with self-reported anhedonia. In depressed patients, both Val66Met polymorphism and DNA methylation of promoter I were significantly associated with reward bias (p < 0.050 and p = 0.040, respectively), without an interaction effect. On the other hand, methylation of exon IX had a negative impact on executive functioning (p = 0.002) and mediated the effect of Val66Met on this outcome in patients with MDD.

Conclusions

Our results provide the first evidence of Val66Met susceptibility to differential epigenetic regulation of BDNF exons in reward learning and executive functioning in MDD, which needs to be further explored.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01136-z.

The effect of exposure to long working hours on alcohol consumption, risky drinking and alcohol use disorder: A systematic review and meta-analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury

BACKGROUND

The World Health Organization (WHO) and the International Labour Organization (ILO) are developing Joint Estimates of the work-related burden of disease and injury (WHO/ILO Joint Estimates), with contributions from a large network of experts. Evidence from mechanistic data suggests that exposure to long working hours may increase alcohol consumption and cause alcohol use disorder. In this paper, we present a systematic review and meta-analysis of parameters for estimating the number of deaths and disability-adjusted life years from alcohol consumption and alcohol use disorder that are attributable to exposure to long working hours, for the development of the WHO/ILO Joint Estimates.

OBJECTIVES

We aimed to systematically review and meta-analyse estimates of the effect of exposure to long working hours (three categories: 41-48, 49-54 and ≥55 h/week), compared with exposure to standard working hours (35-40 h/week), on alcohol consumption, risky drinking (three outcomes: prevalence, incidence and mortality) and alcohol use disorder (three outcomes: prevalence, incidence and mortality).

DATA SOURCES

We developed and published a protocol, applying the Navigation Guide as an organizing systematic review framework where feasible. We searched electronic bibliographic databases for potentially relevant records from published and unpublished studies, including the WHO International Clinical Trials Register, Ovid MEDLINE, PubMed, Embase, and CISDOC on 30 June 2018. Searches on PubMed were updated on 18 April 2020. We also searched electronic grey literature databases, Internet search engines and organizational websites; hand-searched reference list of previous systematic reviews and included study records; and consulted additional experts.

STUDY ELIGIBILITY AND CRITERIA

We included working-age (≥15 years) workers in the formal and informal economy in any WHO and/or ILO Member State but excluded children (<15 years) and unpaid domestic workers. We considered for inclusion randomized controlled trials, cohort studies, case-control studies and other non-randomized intervention studies with an estimate of the effect of exposure to long working hours (41-48, 49-54 and ≥55 h/week), compared with exposure to standard working hours (35-40 h/week), on alcohol consumption (in g/week), risky drinking, and alcohol use disorder (prevalence, incidence or mortality).

STUDY APPRAISAL AND SYNTHESIS METHODS

At least two review authors independently screened titles and abstracts against the eligibility criteria at a first stage and full texts of potentially eligible records at a second stage, followed by extraction of data from publications related to qualifying studies. Two or more review authors assessed the risk of bias, quality of evidence and strength of evidence, using Navigation Guide and GRADE tools and approaches adapted to this project.

RESULTS

Fourteen cohort studies met the inclusion criteria, comprising a total of 104,599 participants (52,107 females) in six countries of three WHO regions (Americas, South-East Asia, and Europe). The exposure and outcome were assessed with self-reported measures in most studies. Across included studies, risk of bias was generally probably high, with risk judged high or probably high for detection bias and missing data for alcohol consumption and risky drinking. Compared to working 35-40 h/week, exposure to working 41-48 h/week increased alcohol consumption by 10.4 g/week (95% confidence interval (CI) 5.59-15.20; seven studies; 25,904 participants, I2 71%, low quality evidence). Exposure to working 49-54 h/week increased alcohol consumption by 17.69 g/week (95% confidence interval (CI) 9.16-26.22; seven studies, 19,158 participants, I2 82%, low quality evidence). Exposure to working ≥55 h/week increased alcohol consumption by 16.29 g/week (95% confidence interval (CI) 7.93-24.65; seven studies; 19,692 participants; I2 82%, low quality evidence). We are uncertain about the effect of exposure to working 41-48 h/week, compared with working 35-40 h/week on developing risky drinking (relative risk 1.08; 95% CI 0.86-1.36; 12 studies; I2 52%, low certainty evidence). Working 49-54 h/week did not increase the risk of developing risky drinking (relative risk 1.12; 95% CI 0.90-1.39; 12 studies; 3832 participants; I2 24%, moderate certainty evidence), nor working ≥55 h/week (relative risk 1.11; 95% CI 0.95-1.30; 12 studies; 4525 participants; I2 0%, moderate certainty evidence). Subgroup analyses indicated that age may influence the association between long working hours and both alcohol consumption and risky drinking. We did not identify studies for which we had access to results on alcohol use disorder.

CONCLUSIONS

Overall, for alcohol consumption in g/week and for risky drinking, we judged this body of evidence to be of low certainty. Exposure to long working hours may have increased alcohol consumption, but we are uncertain about the effect on risky drinking. We found no eligible studies on the effect on alcohol use disorder. Producing estimates for the burden of alcohol use disorder attributable to exposure to long working hours appears to not be evidence-based at this time. PROTOCOL IDENTIFIER: https://doi.org/10.1016/j.envint.2018.07.025.

PROSPERO REGISTRATION NUMBER

CRD42018084077.

Increased methylation of NR3C1 and SLC6A4 is associated with blunted cortisol reactivity to stress in major depression

Background

Epigenetic changes are considered the main mechanisms behind the interplay of environment and genetic susceptibility in major depressive disorder (MDD). However, studies focusing on epigenetic dysregulation of the HPA axis stress response in MDD are lacking. Our objective was to simultaneously asses DNA methylation of the glucocorticoid receptor gene (NR3C1) and serotonin transporter gene (SLC6A4) and HPA axis response to stress in MDD.

Methods

We recruited 80 depressed inpatients and 58 gender and age matched healthy controls. All participants underwent the Trier Social Stress Test (TSST) and salivary cortisol was repeatedly measured to assess HPA axis reactivity. DNA methylation of the NR3C1 (exon 1 F) and SLC6A4 CpG islands was quantified from whole blood DNA. In the MDD group, clinical assessment was repeated at 8-week follow-up to test the predictive potential of DNA methylation for symptom improvement.

Results

Depressed patients had blunted cortisol reactivity to TSST compared to healthy controls (p = 0.01). In addition, they presented with increased average SLC6A4 (p = 0.003) and NR3C1 methylation (p = 0.03), as well as methylation of two individual NR3C1 CpG loci overlapping with the NGFI-A-binding sites (CpG12 and CpG20). Methylation of one of these two loci (CpG20) predicted lower symptom improvement at the follow-up (p = 0.007). Both, average NR3C1 and SLC6A4 methylation were associated with lower cortisol reactivity in the MDD group and explained about 16% of variability in cortisol response to TSST.

Conclusions

We provide evidence of the role of NR3C1 and SLC6A4 DNA methylation in HPA axis dysregulation in MDD, which needs to be further explored.

Epigenetic perspective on the role of brain-derived neurotrophic factor in burnout

Brain-derived neurotrophic factor (BDNF) plays a potential role in the neurobiology of burnout, but there are no studies investigating the underlying genetic and epigenetic mechanisms. Our aim is to further explore the role of BDNF in burnout, by focusing on the Val66Met polymorphism and methylation patterns of the BDNF gene and serum BDNF (sBDNF) protein expression. We conducted a cross-sectional study by recruiting 129 individuals (59 with burnout and 70 healthy controls). Participants underwent a clinical interview, psychological assessment and blood sample collection. Polymorphism and DNA methylation were measured on DNA from whole blood, using pyrosequencing and sBDNF levels were measured using ELISA. We found significantly increased methylation of promoter I and IV in the burnout group, which also correlated with burnout symptoms. In addition, DNA methylation of promoter I had a significant negative effect on sBDNF. For DNA methylation of exon IX, we did not find a significant difference between the groups, nor associations with sBDNF. The Val66Met polymorphism neither differed between groups, nor was it associated with sBDNF levels. Finally, we did not observe differences in sBDNF level between the groups. Interestingly, we observed a significant negative association between depressive symptoms and sBDNF levels. The current study is the first to show that BDNF DNA methylation changes might play an important role in downregulation of the BDNF protein levels in burnout. The presence of depressive symptoms might have an additional impact on these changes.

DNA Methylation and Brain-Derived Neurotrophic Factor Expression Account for Symptoms and Widespread Hyperalgesia in Patients With Chronic Fatigue Syndrome and Comorbid Fibromyalgia

OBJECTIVE

The epigenetics of neurotrophic factors holds the potential to unravel the mechanisms underlying the pathophysiology of complex conditions such as chronic fatigue syndrome (CFS). This study was undertaken to explore the role of brain-derived neurotrophic factor (BDNF) genetics, epigenetics, and protein expression in patients with both CFS and comorbid fibromyalgia (CFS/FM).

METHODS

A repeated-measures study was conducted in 54 participants (28 patients with CFS/FM and 26 matched healthy controls). Participants underwent a comprehensive assessment, including questionnaires, sensory testing, and blood withdrawal. Serum BDNF (sBDNF) protein levels were measured using enzyme-linked immunosorbent assay, while polymorphism and DNA methylation were measured in blood using pyrosequencing technology. To assess the temporal stability of the measures, participants underwent the same assessment twice within 4 days.

RESULTS

Repeated-measures mixed linear models were used for between-group analysis, with mean differences and 95% confidence intervals (95% CIs) shown. Compared to controls, serum BNDF was higher in patients with CFS/FM (F = 15.703; mean difference 3.31 ng/ml [95% CI 1.65, 4.96]; P = 0.001), whereas BDNF DNA methylation in exon 9 was lower (F = 7.543; mean difference -2.16% [95% CI -3.93, -0.83]; P = 0.007). BDNF DNA methylation was mediated by the Val66Met (rs6265) polymorphism. Lower methylation in the same region predicted higher sBDNF levels (F = 7.137, β = -0.408 [95% CI -0.711, -0.105]; P = 0.009), which in turn predicted participants' symptoms (F = 14.410, β = 3.747 [95% CI 1.79, 5.71]; P = 0.001) and widespread hyperalgesia (F = 4.147, β = 0.04 [95% CI 0.01, 0.08]; P = 0.044).

CONCLUSION

Our findings indicate that sBDNF levels are elevated in patients with CFS/FM and that BDNF methylation in exon 9 accounts for the regulation of protein expression. Altered BDNF levels might represent a key mechanism explaining CFS/FM pathophysiology.

Glucocorticoid receptor DNA methylation and childhood trauma in chronic fatigue syndrome patients

OBJECTIVE

Although the precise mechanisms are not yet understood, previous studies have suggested that chronic fatigue syndrome (CFS) is associated with hypothalamic-pituitary-adrenal (HPA) axis dysregulation and trauma in early childhood. Consistent with findings suggesting that early life stress-induced DNA methylation changes may underlie dysregulation of the HPA axis, we previously found evidence for the involvement of glucocorticoid receptor (GR) gene (NR3C1) methylation in whole blood of CFS patients.

METHODS

In the current study, we assessed NR3C1-1F region DNA methylation status in peripheral blood from a new and independent sample of 80 female CFS patients and 91 female controls. In CFS patients, history of childhood trauma subtypes was evaluated using the Childhood Trauma Questionnaire short form (CTQ-SF).

RESULTS

Although absolute methylation differences were small, the present study confirms our previous findings of NR3C1-1F DNA hypomethylation at several CpG sites in CFS patients as compared to controls. Following multiple testing correction, only CpG_8 remained significant (DNA methylation difference: 1.3% versus 1.5%, p<0.001). In addition, we found associations between DNA methylation and severity of fatigue as well as with childhood emotional abuse in CFS patients, although these findings were not significant after correction for multiple testing.

CONCLUSIONS

In conclusion, we replicated findings of NR3C1-1F DNA hypomethylation in CFS patients versus controls. Our results support the hypothesis of HPA axis dysregulation and enhanced GR sensitivity in CFS.

Stress, burnout and depression: A systematic review on DNA methylation mechanisms

Despite that burnout presents a serious burden for modern society, there are no diagnostic criteria. Additional difficulty is the differential diagnosis with depression. Consequently, there is a need to dispose of a burnout biomarker. Epigenetic studies suggest that DNA methylation is a possible mediator linking individual response to stress and psychopathology and could be considered as a potential biomarker of stress-related mental disorders. Thus, the aim of this review is to provide an overview of DNA methylation mechanisms in stress, burnout and depression. In addition to state-of-the-art overview, the goal of this review is to provide a scientific base for burnout biomarker research. We performed a systematic literature search and identified 25 pertinent articles. Among these, 15 focused on depression, 7 on chronic stress and only 3 on work stress/burnout. Three epigenome-wide studies were identified and the majority of studies used the candidate-gene approach, assessing 12 different genes. The glucocorticoid receptor gene (NR3C1) displayed different methylation patterns in chronic stress and depression. The serotonin transporter gene (SLC6A4) methylation was similarly affected in stress, depression and burnout. Work-related stress and depressive symptoms were associated with different methylation patterns of the brain derived neurotrophic factor gene (BDNF) in the same human sample. The tyrosine hydroxylase (TH) methylation was correlated with work stress in a single study. Additional, thoroughly designed longitudinal studies are necessary for revealing the cause-effect relationship of work stress, epigenetics and burnout, including its overlap with depression.