Plasma calcitonin gene-related peptide (CGRP) in migraine and endometriosis during the menstrual cycle

Untangling the mess of CGRP levels as a migraine biomarker: an in-depth literature review and analysis of our experimental experience

BACKGROUND

Calcitonin gene-related peptide (CGRP) is the most promising candidate to become the first migraine biomarker. However, literature shows clashing results and suggests a methodological source for such discrepancies. We aimed to investigate some of these methodological factors to evaluate the actual role of CGRP as biomarker.

METHODS

Previous to the experimental part, we performed a literature review of articles measuring CGRP in migraine patients. Using our 399 bio-bank sera samples, we performed a series of experiments to test the validity of different ELISA kits employed, time of sample processing, long-term storage, sampling in rest or after moderate exercise. Analysis of in-house data was performed to analyse average levels of the peptide and the effect of sex and age.

RESULTS

Literature review shows the high variability in terms of study design, determination methods, results and conclusions obtained by studies including CGRP determinations in migraine patients. CGRP measurements depends on the method and specific kit employed, also on the isoform detected, showing completely different ranges of concentrations. Alpha-CGRP and beta-CGRP had median with IQR levels of 37.5 (28.2-54.4) and 4.6 (2.4-6.4)pg/mL, respectively. CGRP content is preserved in serum within the 24 first hours when samples are stored at 4°C after clotting and immediate centrifugation. Storages at -80°C of more than 6 months result in a decrease in CGRP levels. Moderate exercise prior to blood extraction does not modulate the concentration of the peptide. Age positively correlates with beta-CGRP content and men have higher alpha-CGRP levels than women.

CONCLUSIONS

We present valuable information for CGRP measurements in serum. ELISA kit suitability should be tested prior to the experiments. Alpha and beta-CGRP levels should be analysed separately as they can show different behaviours even within the same condition. Samples can be processed in a 24-h window if they have been kept in 4°C and should not be stored for more than 6 months at -80°C before assayed. Patients do not need to rest before the blood extraction unless they have performed a high-endurance exercise. For comparative studies, sex and age should be accounted for as these parameters can impact CGRP concentrations.

Calcitonin Gene-Related Peptide Level in Cystic Fibrosis Patients

Calcitonin gene-related peptide (CGRP) has long been implicated in both the physiology and pathophysiology of the respiratory tract. The objective of our study was to determine the serum concentration of alpha CGRP (αCGRP) in cystic fibrosis (CF) that arises from mutations in the gene responsible for encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Currently, there are not many data in the literature about the role of CGRP in CF. The serum level of αCGRP was estimated using the enzyme-linked immunosorbent assay among 64 patients with CF and 31 healthy controls. The αCGRP concentration in the CF group was 62.51 ± 15.45 pg/mL, while in the control group it was 47.43 ± 8.06 pg/mL (p < 0.001). We also compared the level of αCGRP in CF patients according to the type of CFTR mutation. Homozygotes for ΔF508 had higher αCGRP levels than heterozygotes (67.9 ± 10.2 vs. 54.5 ± 18.3 pg/mL, p < 0.01). The level of this neuropeptide was statistically higher in patients with severe disease than in those with mild CF (p = 0.003) when patients were divided into three groups by spirometry results. αCGRP concentration was not correlated with age, sex, clinical parameters, and pulmonary function test results in the study participants. The results of our study suggest a significant increase in the concentration of αCGRP in the serum of patients with CF compared to the control group. This observation opens interesting possibilities for understanding the role of αCGRP in the context of CF pathophysiology.

CGRP neuropeptide levels in patients with endometriosis-related pain treated with dienogest: a comparative study

BACKGROUND AND OBJECTIVE

Endometriosis (EM) involves the peripheral nervous system and causes chronic pain. Sensory nerves innervating endometriotic lesions contribute to chronic pain and influence the growth phenotype by releasing neurotrophic factors and interacting with nearby immune cells. Calcitonin gene-related peptide (CGRP), a pain-signaling neurotransmitter, has a significant role. This study examines the effect of Dienogest (DNG), a hormone therapy used for managing EM -related pain, on serum CGRP levels in EM patients.

MATERIALS AND METHODS

The Visual Analog Scale (VAS) assessed pain in diagnosed EM.

INDIVIDUALS

Serum samples were obtained to measure CGRP concentration. Participants received a 2 mg/day oral dose of DNG for six months as prescribed treatment. Additional serum samples were collected after this period to measure CGRP levels.

RESULTS

In the EM group, 6.7%, 33.3%, and 20% had ovarian EM, ovarian plus uterosacral, and ovarian plus bladder, respectively. The EM group showed higher CGRP serum levels than the control group (80.53 ± 16.13 vs. 58.55 ± 6.93, P < 0.0001). Still, after drug administration, CGRP serum levels significantly decreased compared to pre-treatment levels (69.66 ± 11.53 vs. 80.53 ± 16.13, P < 0.05). The EM group showed higher pain compared to the control group (7.93 ± 1.58 vs. 0.13 ± 0.35, P < 0.0001), but after drug administration, pain significantly decreased compared to pre-treatment levels (1.00 ± 2.00 vs. 7.93 ± 1.58, P < 0.05).

CONCLUSION

DNG administration reduces pain and serum CGRP levels in EM patients, offering the potential for innovative treatments and tailored options. Understanding neurotransmitter roles and drug effects can aid in discovering more effective modulators for these pathways.

Effects of Transcranial Direct Current Stimulation on Clinical Outcomes, Calcitonin Gene-Related Peptide, and Pituitary Adenylate Cyclase-Activating Polypeptide-38 Levels in Menstrual Migraine

OBJECTIVES

Transcranial direct current stimulation (tDCS) has been suggested as an alternative treatment option for migraine. The present study aimed to evaluate the efficacy of tDCS on clinical outcomes in addition to calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating peptide 38 (PACAP-38) levels in individuals with menstrual-related migraine (MRM) for the first time.

MATERIALS AND METHODS

In this parallel study, 58 female patients between the ages of 18 and 45 years, including 36 with MRM and 22 with nonmenstrual migraines (nMM), were recruited. Sessions of 2-mA 20-minute anodal tDCS were administered over the left dorsolateral prefrontal cortex within three consecutive days (1:1 active and sham stimulation). Migraine attack frequency, severity, analgesic usage, CGRP, and PACAP-38 levels of the patients were evaluated before and one month after tDCS.

RESULTS

After tDCS, in the active group compared with the sham group, the frequency (p = 0.031), the severity of attacks (p = 0.003), the number of days with headache (p = 0.004), and the analgesic usage (p = 0.024) were all decreased. In both MRM and nMM groups, the frequency and severity of attacks and analgesic usage were decreased in those receiving active stimulation (p < 0.001 for each). CGRP and PACAP-38 levels were no different in the active group and the sham group after tDCS.

CONCLUSIONS

tDCS was shown to be efficacious in migraine prophylaxis and a valuable option for migraine and MRM treatment. The absence of changes in serum CGRP and PACAP-38 levels suggests that tDCS efficacy may stem from distinct cerebral electrophysiological mechanisms.

An overview and comprehensive analysis of interdisciplinary clinical research in endometriosis based on trial registry

Endometriosis is a chronic multisystem disease associated with immunological, genetic, hormonal, psychological, and neuroscientific factors, leading to a significant socioeconomic impact worldwide. Though multidisciplinary management is the ideal approach, there remains a scarcity of published interdisciplinary clinical trials at present. Here, we have conducted a comprehensive analysis of the characteristics and issues of interdisciplinary trials on endometriosis based on the clinical registration database ClinicalTrials.gov. Among all 387 endometriosis trials, 30% (116) were identified as interdisciplinary, mostly conducted in Europe and North America, and fully funded by non-industrial sources. We documented growth in both patient-centered multidisciplinary comprehensive management and collaboration between fundamental biomedical science and applied medicine. However, compared to traditional obstetric-gynecological trials, interdisciplinary studies exhibited negative characteristics such as less likely to be randomized and less likely to report results. Our study provides insights for future trial investigators and may contribute to fostering greater collaboration in medical research.

Correlation between endometriosis and migraine features: Results from a prospective case-control study

BACKGROUND

Endometriosis and migraine frequently coexist, but only a limited number of studies have focused on their mutual association. The aim of our study was to investigate, in untreated women with comorbid endometriosis/adenomyosis and migraine, the correlation between headache features and endometriotic subtypes and their possible relationship with pain severity and disease disability.

METHODS

Fifty women affected by endometriosis/adenomyosis and migraine matched (1:2) with 100 patients with endometriosis alone and 100 patients with only migraine were recruited and underwent pelvic ultrasound imaging and neurological examination.

RESULTS

Severe adenomyosis, posterior and anterior deep infiltrating endometriosis (p = 0.027, p = 0.0031 and p = 0.029, respectively) occurred more frequently in women with migraine. Dysmenorrhea was the most commonly reported symptom in women with endometriosis and migraine and the mean VAS scores of all typical endometriotic symptoms were significantly higher in the presence of comorbidity. Women with both migraine and endometriosis reported significant higher pain intensity (p = 0.004), higher monthly migraine days (p = 0.042) and increased HIT 6-scores (p = 0.01), compared with those without endometriosis.

CONCLUSIONS

Our results demonstrated that the co-occurrence of migraine in untreated women with endometriosis is associated with more severe gynecological infiltrations and correlated with increased pain intensity and disease disability.Trial Registration: Protocol number 119/21.

Adverse event reporting of four anti-Calcitonin gene-related peptide monoclonal antibodies for migraine prevention: a real-world study based on the FDA adverse event reporting system

Background: Anti-Calcitonin gene-related peptide monoclonal antibodies (anti-CGRP mAbs) have shown significant efficacy in preventing migraine. However, there have been limited reports of adverse events (AEs) after marketing, particularly for eptinezumab launched in 2020. The study aimed to mine and analyze the AE signals with four anti-CGRP mAbs from the United States Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) database to gain insights into the safety profile of these medications post-marketing. Methods: All AE reports on the four anti-CGRP mAbs (erenumab, galcanezumab, fremanezumab, and eptinezumab) were retrieved from the FAERS database from the first quarter (Q1) of 2018 to Q1 of 2023. Disproportionality analysis was measured by reporting odd ratio (ROR) and Bayesian confidence propagation neural network (BCPNN) to identify potential AE signals. Comparisons were made between the four drugs in terms of AEs. Results: A total of 38,515 reports of erenumab, 19,485 reports of galcanezumab, 5,332 reports of fremanezumab, and 2,460 reports of eptinezumab were obtained, mostly reported in the second to third year after launch in the market. The common AEs to erenumab included constipation (17.93%), injection site pain (14.08%), and alopecia (7.23%). The AEs that occurred more frequently with galcanezumab included injection site pain (24.37%), injection site erythema (5.35%), and injection site haemorrhage (4.97%). Common AEs related to fremanezumab were injection site pain (13.10%), injection site erythema (7.02%), and injection site pruritus (5.47%). Fatigue (13.54%), throat irritation (9.02%), and pruritus (8.20%) were the most common AEs with eptinezumab. In addition, there are new AEs that were not listed in the drug instructions but occurred concurrently with multiple drugs, such as Raynaud's phenomenon, weight increase, menstrual disorders, throat tightness, and paraesthesia oral. Conclusion: Common AE signals of the four anti-CGRP mAbs and new AE signals were found to provide a reference for clinical drug selection in clinical practice.

Calcitonin/PAC1 receptor splice variants: a blind spot in migraine research

The neuropeptides calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) and their receptors are linked to migraine neurobiology. Recent antimigraine therapeutics targeting the signaling of these neuropeptides are effective; however, some patients respond suboptimally, indicating an incomplete understanding of migraine pathophysiology. The CGRP- and PACAP-responsive receptors can be differentially spliced. It is known that receptor splice variants can have different pathophysiological effects in other receptor-mediated pain pathways. Despite considerable knowledge on the structural and pharmacological differences of the CGRP- and PACAP-responsive receptor splice variants and their expression in migraine-relevant tissues, their role in migraine is rarely considered. Here we shine a spotlight on the calcitonin and PACAP (PAC1) receptor splice variants and examine what implications they may have for drug activity and design.

A Novel Classification of Endometriosis Based on Clusters of Comorbidities

Endometriosis is a heterogeneous, complex, and still challenging disease, due to its epidemiological, etiological and pathogenic, diagnostic, therapeutic, and prognosis characteristics. The classification of endometriosis is contentious, and existing therapies show significant variability in their effectiveness. This study aims to capture and describe clusters of women with endometriosis based on their comorbidity. With data extracted from electronic records of primary care, this study performs a hierarchical clustering with the Ward method of women with endometriosis with a subsequent analysis of the distribution of comorbidities. Data were available for 4055 women with endometriosis, and six clusters of women were identified: cluster 1 (less comorbidity), cluster 2 (anxiety and musculoskeletal disorders), cluster 3 (type 1 allergy or immediate hypersensitivity); cluster 4 (multiple morbidities); cluster 5 (anemia and infertility); and cluster 6 (headache and migraine). Clustering aggregates similar units into similar clusters, partitioning dissimilar objects into other clusters at a progressively finer granularity-in this case, groups of women with similarities in their comorbidities. Clusters may provide a deeper insight into the multidimensionality of endometriosis and may represent diverse "endometriosis trajectories" which may be associated with specific molecular and biochemical mechanisms. Comorbidity-based clusters may be important to the scientific study of endometriosis, contributing to the clarification of its clinical complexity and variability. An awareness of those comorbidities may help elucidate the etiopathogenesis and facilitate the accurate earlier diagnosis and initiation of treatments targeted toward particular subgroups.

Sex Hormones and Calcitonin Gene-Related Peptide in Women With Migraine: A Cross-sectional, Matched Cohort Study

BACKGROUND AND OBJECTIVES

Sex hormones may modulate calcitonin gene-related peptide (CGRP) release in the trigeminovascular system. We studied CGRP concentrations in plasma and tear fluid in female participants with episodic migraine (EM) and a regular menstrual cycle (RMC), female participants with EM and combined oral contraception (COC), and female participants with EM in the postmenopause. For control, we analyzed 3 corresponding groups of age-matched female participants without EM.

METHODS

Participants with an RMC had 2 visits: during menstruation on menstrual cycle day 2 ± 2 and in the periovulatory period on day 13 ± 2. Participants with COC were examined at day 4 ± 2 of the hormone-free interval (HFI) and between days 7 and 14 of hormone intake (HI). Postmenopausal participants were assessed once at a random time point. Plasma and tear fluid samples were collected at each visit for determination of CGRP levels with an ELISA.

RESULTS

A total of 180 female participants (n = 30 per group) completed the study. Participants with migraine and an RMC showed statistically significantly higher CGRP concentrations in plasma and tear fluid during menstruation compared with female participants without migraine (plasma: 5.95 pg/mL [IQR 4.37-10.44] vs 4.61 pg/mL [IQR 2.83-6.92], p = 0.020 [Mann-Whitney U test]; tear fluid: 1.20 ng/mL [IQR 0.36-2.52] vs 0.4 ng/mL [IQR 0.14-1.22], p = 0.005 [Mann-Whitney U test]). In contrast, female participants with COC and in the postmenopause had similar CGRP levels in the migraine and the control groups. In migraine participants with an RMC, tear fluid but not plasma CGRP concentrations during menstruation were statistically significantly higher compared with migraine participants under COC (p = 0.015 vs HFI and p = 0.029 vs HI, Mann-Whitney U test).

DISCUSSION

Different sex hormone profiles may influence CGRP concentrations in people, with current or past capacity to menstruate, with migraine. Measurement of CGRP in tear fluid was feasible and warrants further investigation.

Current and Emerging Pharmacotherapy for Menstrual Migraine: A Narrative Review

INTRODUCTION

In this article, we discuss menstrual migraine (MM), which can be categorized as menstrually related migraine (MRM) or pure menstrual migraine (PMM). MM attacks are often longer, more severe, and harder to treat than other migraine attacks. Appropriate treatment strategies include acute treatment, short term preventive treatment, and daily preventive treatment, depending on the patient's pattern of migraine and occurrence of migraine outside the menstrual period.

AREAS COVERED

A PubMed, Cochrane Library, Medline, and Ovid search from inception to October 2022 provided articles relating to MM pathophysiology and treatment.

EXPERT OPINION

In patients for whom standard acute therapy is inadequate, short term or daily preventive treatment should be considered. Patients with PMM may be adequately managed with short term preventive treatment started 2 days prior to the onset of migraine and continued for 5-6 days. Frovatriptan is the mainstay of short-term prevention. Patients who experience additional attacks outside the menstrual period may benefit from daily preventive treatment. Estrogen-containing contraceptive treatment may be effective in appropriately selected patients. Emerging research on the pathophysiology of MM indicates that oxytocin agonists and CGRP antagonists may prove to be effective treatment options.

Change of CGRP Plasma Concentrations in Migraine after Discontinuation of CGRP-(Receptor) Monoclonal Antibodies

Discontinuation of treatment with monoclonal antibodies (mAb) targeting the Calcitonin Gene-Related Peptide (CGRP) pathway leads to an increase in migraine frequency. We aimed to assess changes in free and total CGRP plasma concentrations after the discontinuation of CGRP(-receptor) mAbs. This prospective analysis included 59 patients with migraine (n = 25 erenumab, n = 25 galcanezumab, n = 9 fremanezumab) who discontinued mAbs after ≥8 months of treatment. Patients were visited at the time of the last mAb injection (V1) and 16 weeks later (V2). For control, 30 migraine patients without preventive drug therapy were included. We measured free CGRP plasma concentrations in the erenumab and fremanezumab group and total CGRP concentrations in the galcanezumab group. Free CGRP plasma concentrations did not change after treatment discontinuation [erenumab: V1 31.2 pg/mL (IQR 25.8−45.6), V2 30.3 pg/mL (IQR 22.9−47.6), p = 0.65; fremanezumab V1 29.4 pg/mL (IQR 16.4−61.9), V2 34.4 (19.2−62.0), p = 0.86]. Controls had similar CGRP values of 32.6 pg/mL (IQR 21.3−44.6). Total CGRP concentrations in the galcanezumab group were 5439.3 pg/mL (2412.7−6338.1) at V1, and decreased to 1853.2 pg/mL (1136.5−3297.0) at V2 (p < 0.001). Cessation of treatment with CGRP(-R) mAbs did not have an impact on the free-circulating CGRP concentrations. Total CGRP decreased significantly after three months of treatment discontinuation.

Is calcitonin gene-related peptide a reliable biochemical marker of migraine?

PURPOSE OF REVIEW

The aim of this study was to provide an overview of clinical studies on calcitonin gene-related peptide (CGRP) measurements in body fluids of migraine patients and to discuss the validity of CGRP measurement as a clinical biomarker of migraine.

RECENT FINDINGS

Several studies have reported increased CGRP levels in venous blood, saliva and tear fluid of migraine patients compared with healthy controls and in migraine patients during attacks compared with the interictal state, suggesting that CGRP may be a feasible biomarker of migraine. However, the findings of studies investigating CGRP levels in migraine patients are generally conflicting and measurements of CGRP levels are challenged by several methodological issues. Reported differences in CGRP levels between patients with chronic migraine relative to episodic migraine have also been inconsistent. There is also a well documented involvement of CGRP in several nonmigraine pain disorders, including cluster headache and common pain conditions such as osteoarthritis.

SUMMARY

Current evidence does not justify the usage of CGRP levels as a biomarker for diagnosing migraine or for determining the severity of the disease in individual patients. However, CGRP measurements could prove useful in the future as clinically relevant biomarkers for predicting the response to therapy, including anti-CGRP migraine drugs.