Candidate-gene association study searching for genetic factors involved in migraine chronification

Influences of Genetic and Environmental Factors on Chronic Migraine: A Narrative Review

PURPOSE OF REVIEW

In this narrative review, we aim to summarize recent insights into the complex interplay between environmental and genetic factors affecting the etiology, development, and progression of chronic migraine (CM).

RECENT FINDINGS

Environmental factors such as stress, sleep dysfunction, fasting, hormonal changes, weather patterns, dietary compounds, and sensory stimuli are critical triggers that can contribute to the evolution of episodic migraine into CM. These triggers are particularly influential in genetically predisposed individuals. Concurrently, genome-wide association studies (GWAS) have revealed over 100 genetic loci linked to migraine, emphasizing a significant genetic basis for migraine susceptibility. In CM, environmental and genetic factors are of equal importance and contribute to the pathophysiology of the condition. Understanding the bidirectional interactions between these elements is crucial for advancing therapeutic approaches and preventive strategies. This balanced perspective encourages continued research into the complex gene-environment nexus to improve our understanding and management of CM.

Genetics of migraine: where are we now?

Migraine is a complex brain disorder explained by the interaction of genetic and environmental factors. In monogenic migraines, including familial hemiplegic migraine and migraine with aura associated with hereditary small-vessel disorders, the identified genes code for proteins expressed in neurons, glial cells, or vessels, all of which increase susceptibility to cortical spreading depression. The study of monogenic migraines has shown that the neurovascular unit plays a prominent role in migraine. Genome-wide association studies have identified numerous susceptibility variants that each result in only a small increase in overall migraine risk. The more than 180 known variants belong to several complex networks of "pro-migraine" molecular abnormalities, which are mainly neuronal or vascular. Genetics has also highlighted the importance of shared genetic factors between migraine and its major co-morbidities, including depression and high blood pressure. Further studies are still needed to map all of the susceptibility loci for migraine and then to understand how these genomic variants lead to migraine cell phenotypes.

Genetic overlap between temporomandibular disorders and primary headaches: A systematic review

Primary headache disorders (PHD), specifically migraine, are strongly associated with temporomandibular disorders (TMD), sharing some patterns of orofacial pain. Both disorders have significant genetic contributions already studied. PRISMA guidelines were followed to conduct this systematic review, which comprehensively summarize and discuss the genetic overlap between TMD and PHD to aid future research in potential therapy targets. This review included eight original articles published between 2015 and 2020, written in English and related to either TMD and/or PHD. The genes simultaneously assessed in PHD and TMD studies were COMT, MTHFR, and ESR1. COMT was proved to play a critical role in TMD pathogenesis, as all studies have concluded about its impact on the occurrence of the disease, although no association with PHD was found. No proof on the impact of MTHFR gene regulation on either TMD or PHD was found. The most robust results are concerning the ESR1 gene, which is present in the genetic profile of both clinical conditions. This novel systematic review highlights not only the need for a clear understanding of the role of ESR1 and COMT genes in pain pathogenesis, but it also evaluates their potential as a promising therapeutic target to treat both pathologies.

Role of CGRP pathway polymorphisms in migraine: a systematic review and impact on CGRP mAbs migraine therapy

Background

the interest of clinical reaseach in polymorphisms and epigenetics in migraine has been growing over the years. Due to the new era of preventative migraine treatment opened by monoclonal antibodies (mAbs) targeting the signaling of the calcitonin-gene related peptide (CGRP), the present systematic review aims at identifying genetic variants occurring along the CGRP pathway and at verifying whether these can affect the clinical features and the course of disease and the responsiveness of patients to therapy.

Methods

the literature search has been conducted consulting the most relevant scientific databases, i.e. PubMed/MEDLINE, Scopus, Web of Science, the Human Genome Epidemiology (HuGE) Published Literature database (Public Health Genomics Knowledge Base) and Clinicaltrials.gov from database inception until April 1, 2021. The process of identification and selection of the studies included in the analysis has followed the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) criteria for systematic reviews and meta-analyses and the guidance from the Human Genome Epidemiology Network for reporting gene-disease associations.

Results

the search has retrieved 800 results, among which only 7 studies have met the eligibility criteria for inclusion in the analysis. The latter are case-control studies of genetic association and an exploratory analysis and two polymorphisms have been detected as the most recurring: the rs3781719 (T > C) of the CALC A gene encoding CGRP and the rs7590387 of the gene encoding the receptor activity-modifying protein (RAMP) 1 (C > G). Only one study assessing the methylation pattern with regard to CGRP pathway has been found from the search. No genetic association studies investigating the possible effect of genetic variants affecting CGRP signaling on the responsiveness to the most recent pharmacological approaches, i.e. anti-CGRP(R) mAbs, gepants and ditans, have been published. According to the Human Genome Epidemiology (HuGE) systematic reviews and meta-analyses risk-of-bias score for genetic association studies, the heterogeneity between and across studies and the small sample size do not allow to draw conclusions and prompt future studies.

Conclusions

adequately powered, good quality genetic association studies are needed to understand the impact of genetic variants affecting the pathway of CGRP on migraine susceptibility and clinical manifestation and to predict the response to therapy in terms of efficacy and safety.

Genetics of migraine

Migraine is a complex brain disorder explained by the interaction of genetic and environmental factors. In monogenic migraines, including familial hemiplegic migraine and migraine with aura associated with hereditary small-vessel disorders, the identified genes encode proteins expressed in neurons, astrocytes or vessels, which all increase the susceptibility to cortical spreading depression. Study of monogenic migraines showed that the neurovascular unit plays a prominent role in migraine. Genome-wide association studies have identified multiple susceptibility variants that only cause a small increase of the global migraine risk. The variants belong to several complex networks of "pro-migraine" molecular abnormalities, which are mainly neuronal or vascular. Genetics has also underscored the importance of genetic factors shared between migraine and its major co-morbidities including depression and high blood pressure. Further studies are still needed to map all of the susceptibility loci for migraine and then to understand how these genomic variants lead to migraine cell phenotypes. Thanks to the advent of new technologies such as induced pluripotent stem cells, genetic data will hopefully finally be able to lead to therapeutic progress.

Chronic migraine: Genetics or environment?

BACKGROUND

The transition from episodic migraine to chronic migraine, migraine chronification, is usually a gradual process, which involves multiple risk factors. To date, studies of the genetic risk factors for chronic migraine have focused primarily on candidate-gene approaches using healthy individuals as controls.

AIMS AND METHODS

In this study, we used a large cohort of migraine families and unrelated migraine patients (n > 2200) with supporting genotype and whole-genome sequencing data. We evaluated whether there are any genetic variants, common or rare, with a specific association to chronic migraine compared with episodic migraine.

RESULTS

We found no aggregation of chronic migraine in families with a clustering of migraine. No specific rare variants gave rise to migraine chronification, and migraine chronification was not associated with a higher polygenic risk score. Migraine chronification was not associated with allelic associations with an odds ratio above 2.65. Assessment of effect sizes with genome-wide significance below an odds ratio of 2.65 requires a genome-wide association study of at least 7500 chronic migraine patients.

CONCLUSION

Our results suggest that migraine chronification is caused by environmental factors rather than genetic factors.

From transformation to chronification of migraine: pathophysiological and clinical aspects

Chronic migraine is a neurological disorder characterized by 15 or more headache days per month of which at least 8 days show typical migraine features. The process that describes the development from episodic migraine into chronic migraine is commonly referred to as migraine transformation or chronification. Ample studies have attempted to identify factors associated with migraine transformation from different perspectives. Understanding CM as a pathological brain state with trigeminovascular participation where biological changes occur, we have completed a comprehensive review on the clinical, epidemiological, genetic, molecular, structural, functional, physiological and preclinical evidence available.

TRPM8 genetic variant is associated with chronic migraine and allodynia

Background

Many single nucleotide polymorphisms (SNPs) have been reported to be associated with migraine susceptibility. However, evidences for their associations with migraine endophenotypes or subtypes are scarce. We aimed to investigate the associations of pre-identified migraine susceptibility loci in Taiwanese with migraine endophenotypes or subtypes, including chronic migraine and allodynia.

Methods

The associations of six SNPs identified from our previous study, including TRPM8 rs10166942, LRP1 rs1172113, DLG2 rs655484, GFRA1 rs3781545, UPP2 rs7565931, and GPR39 rs10803531, and migraine endophenotypes, including chronic migraine and allodynia were tested. Significant associations in the discovery cohort were validated in the replication cohort. The adjusted odds ratios (aOR) were calculated after controlling for confounders.

Results

In total, 1904 patients (mean age 37.5 ± 12.2 years old, female ratio: 77.7%) including 1077 in the discovery cohort and 827 in the replication cohort were recruited. Of them, 584 (30.7%) had chronic migraine. Of the 6 investigated SNPs, TRPM8 rs10166942 T allele-carrying patients were more likely to have chronic migraine than non-T allele carriers in both discovery and replication cohorts and combined samples (33.7% vs. 25.8%, p = 0.004, aOR = 1.62). In addition, T allele carriers reported more allodynic symptoms than non-T allele carriers (3.5 ± 3.7 vs. 2.6 ± 2.8, p < 0.001). However, allodynia severity did not differ between episodic and chronic migraine patients. No further correlations between genetic variants and endophenotypes were noted for the other SNPs.

Conclusions

TRPM8 may contribute to the pathogenesis of chronic migraine. However, our study did not support allodynia as a link between them. The underlying mechanisms deserve further investigations.

Migraine progression in subgroups of migraine based on comorbidities: Results of the CaMEO Study

Objective

To test the hypothesis that statistically defined subgroups of migraine (based on constellations of comorbidities and concomitant conditions; henceforth comorbidities), previously identified using Chronic Migraine Epidemiology and Outcomes (CaMEO) Study data, differ in prognosis, as measured by rates of progression from episodic migraine (EM) to chronic migraine (CM).

Methods

The onset of CM was assessed up to 4 times over 12 months in individuals with EM and ≥1 comorbidity at baseline, based on constellations of comorbidities (comorbidity classes). The “fewest comorbidities” class served as reference. Individuals completing ≥1 follow-up survey from the web-based CaMEO Study were included. Covariates included sociodemographic variables and headache characteristics. Sex, income, cutaneous allodynia, and medication overuse were modeled as binary variables; age, body mass index, headache-related disability (Migraine Disability Assessment [MIDAS]), and Migraine Symptom Severity Scale as continuous variables. CM onset was assessed using discrete time analysis.

Results

In the final sociodemographic model, all comorbidity classes had significantly elevated hazard ratios (HRs) for risk of progression to CM from EM, relative to fewest comorbidities. HRs for CM onset ranged from 5.34 (95% confidence interval [CI] 3.89–7.33; p ≤ 0.001) for most comorbidities to 1.53 (95% CI 1.17–2.01; p < 0.05) for the respiratory class. After adjusting for headache covariates independently, each comorbidity class significantly predicted CM onset, although HRs were attenuated.

Conclusions

Subgroups of migraine identified by comorbidity classes at cross-section predicted progression from EM (with ≥1 comorbidity at baseline) to CM. The relationship of comorbidity group to CM onset remained after adjusting for indicators of migraine severity, such as MIDAS.

Clinicaltrials.gov identifier

NCT01648530.

The Role of Endothelin in the Pathophysiology of Migraine-a Systematic Review

PURPOSE OF REVIEW

Vasoactive peptides play a key role in the attack-initiating cascade of migraine. Recent studies have highlighted a potentially important role for endothelin-1, a potent vasoconstrictor peptide, in migraine pathophysiology. Here, we review the current data on endothelin's involvement in migraine.

RECENT FINDINGS

We identified 23 articles. Nine studies reported on endothelin-1 plasma concentrations in patients with migraine, eight studies investigated relevant genetic associations, five studies investigated endothelin-1 and spreading depression in animals, and one randomized controlled clinical trial tested the efficacy of an endothelin antagonist in the acute treatment of migraine in patients both with and without aura. Elevated endothelin-1 plasma levels have been reported in the early phase of migraine attacks. Genetic abnormalities related to the endothelin type A receptor have been reported in migraineurs. Endothelin-1 potently induces spreading depression in animals, which may explain the connection between endothelial irritation and migraine aura. Endothelin-1 could be a primary factor in the attack-triggering cascade of migraine attacks with and without aura. Additional studies in humans and animal models are needed to further elucidate the role of endothelin-1 in migraine.

A systematic review and critical appraisal of gene polymorphism association studies in medication-overuse headache

Purpose of review

Medication-overuse headache is a secondary chronic headache disorder, evolving from an episodic primary headache type, caused by the frequent and excessive use of headache symptomatic drugs. While gene polymorphisms have been deeply investigated as susceptibility factors for migraine, little attention has been paid to medication-overuse headache genetics. In the present study we conducted a systematic review to identify, appraise and summarize the current findings of gene polymorphism association studies in medication-overuse headache.

Methods

A comprehensive literature search was conducted on PubMed and Web of Knowledge databases of primary studies that met the diagnostic criteria for medication-overuse headache according to the temporally-relevant Classification of Headache Disorder of the International Headache Society.

Results

A total of 17 candidate gene association studies focusing on medication-overuse headache were finally included in the qualitative review. Among these, 12 studies investigated the role of common gene polymorphisms as risk factors for medication-overuse headache susceptibility, six studies focused on the relationship with clinical features of medication-overuse headache patients, and four studies evaluated their role as determinants of clinical outcomes in medication-overuse headache patients.

Conclusion

Results of single studies show a potential role of polymorphic variants of the dopaminergic gene system or of other genes related to drug-dependence pathways as susceptibility factors for disease or as determinants of monthly drug consumption, respectively. In this systematic review, we summarize the findings of gene polymorphism association studies in medication-overuse headache and discuss the methodological issues that need to be addressed in the design of future studies.

Chronic Migraine: An Update on Physiology, Imaging, and the Mechanism of Action of Two Available Pharmacologic Therapies

Several lines of research support the hypothesis that migraine is a spectrum of illness, with clinical symptoms that vary along a continuum from episodic migraine to chronic migraine. Physiologic changes may result in episodic migraine evolving into chronic migraine over months to years in susceptible individuals. With chronification, headache frequency increases, becoming more disabling and less responsive to therapy. Neurophysiologic and functional imaging research has reported that chronic migraine may be associated with severity‐specific metabolic, functional, and structural abnormalities in the brainstem. Without longitudinal studies, it is unclear whether these changes may represent a continuum of individual progression and/or are reversible. Furthermore, chronic migraine is associated with larger impairments in cortical processing of sensory stimuli when compared with episodic migraine, possibly caused by more pronounced cortical hyperexcitability.

Progressive changes in nociceptive thresholds and subsequent central sensitization due to recurrent migraine attacks in vulnerable individuals contribute to the chronic migraine state. This may result in changes to baseline neurologic function between headache attacks, evident in both electrophysiological and functional imaging research. Patients experiencing migraine chronification may report increased non‐headache pain, fatigue, psychiatric disorders (eg, depression, anxiety), gastrointestinal complaints, and other somatic conditions associated with their long‐term experience with migraine pain.

Recent research provides a foundation for differentiating episodic and chronic migraine based on neurophysiologic and neuroimaging tools. In this literature review, we consider these findings in the context of models designed to explain the physiology and progression of episodic migraine into chronic migraine, and consider treatment of chronic migraine in susceptible individuals. Advances in pharmacotherapy provide treatment options for chronic migraine. Of the currently available treatment options, only onabotulinumtoxinA and topiramate have received regulatory approval and have demonstrated efficacy in patients with chronic migraine, although the exact mechanisms of action are not fully elucidated.

Diagnosis and Management of Childhood Headache

Headache is one of the most common chief complaints seen in the pediatrician's office. Oftentimes, identifying the etiology of headache and differentiating primary and secondary causes can present a diagnostic conundrum. Understanding the most common causes of primary and secondary headache is vital to making a correct diagnosis. Here we review the typical presentations of the most common primary headache disorders and the approach to evaluation of the pediatric patient presenting with headache. Diagnostic workup, including the key features to elicit on physical examination, when to order head imaging, and the use of other ancillary tests, is discussed. Current treatment modalities and their indications are reviewed. We will also describe some of the new, emerging therapies that may alter the way we manage headache in the pediatric population. Headache can, at times, be a frustrating symptom seen in the pediatrician's office, but here we hope to better elucidate the approach to evaluation, management, and treatment as well as provide some hope in regards to more effective upcoming therapies.

Neural Plasticity in Common Forms of Chronic Headaches

Headaches are universal experiences and among the most common disorders. While headache may be physiological in the acute setting, it can become a pathological and persistent condition. The mechanisms underlying the transition from episodic to chronic pain have been the subject of intense study. Using physiological and imaging methods, researchers have identified a number of different forms of neural plasticity associated with migraine and other headaches, including peripheral and central sensitization, and alterations in the endogenous mechanisms of pain modulation. While these changes have been proposed to contribute to headache and pain chronification, some findings are likely the results of repetitive noxious stimulation, such as atrophy of brain areas involved in pain perception and modulation. In this review, we provide a narrative overview of recent advances on the neuroimaging, electrophysiological and genetic aspects of neural plasticity associated with the most common forms of chronic headaches, including migraine, cluster headache, tension-type headache, and medication overuse headache.