Abstract
Objective:
Brain-derived neurotrophic factor (BDNF) is associated with the pathophysiology of primary headaches. The present study aimed to investigate interictal and ictal BDNF levels and its association with clinical parameters in patients with primary headaches.
Methods:
Three groups of headache patients enrolled in this study: patients with episodic migraine with and without aura, cluster headaches, and tension-type headaches according to the current criteria of the International Headache Society. In migraine patients and cluster headache patients, venous blood samples were collected twice: outside and during attacks. In patients with tension-type headaches and healthy controls, one single blood sample was taken. The research comprised 120 patients (males and females) suffering from primary headaches. The control group consisted of 30 healthy volunteers.
Results:
This is the first study to show that there is no gender difference BDNF levels in Uzbek patients with primary headaches. Migraine and cluster headache patients revealed significantly higher BDNF serum levels during headache attacks compared with attack-free periods (p < 0.02).
Conclusion:
This reinforces the view that BDNF may be implicated in the pathophysiology of primary headaches.
Introduction
Neurotrophic factors (NF) are a unique group of polypeptides responsible for neuron survival, axon growth, dendrite pruning, and the expression of essential proteins for neuronal functioning. NF are classified in different families according to functional and structural characteristics, such as the glial cell line-derived neurotrophic factor (GNDF) family and the neurotrophin super-family that includes the brain-derived neurotrophic factor (BDNF), the nerve growth factor (NGF), the neurotrophin-3 (NT-3), and the neurotrophin-4/5 (NT-4/5). 1,2 It is known from recent research that these neurotrophic factors are important in the pathogenesis of primary headaches. 3 Neurotrophic factors are involved in the pathophysiology of cluster headaches and migraine. 4 Among neurotrophic factors, BDNF participates in the mechanism of headache formation and regulates pain. 5 In migraine and cluster headache, the amount of BDNF is changes during the attack and attack-free period. 4,6 Changeable levels of BDNF in both episodic and chronic tension-type headaches have been proven in research. 7
However, no research has been conducted in this regard in Uzbekistan. In order to understand the role of BDNF associated with other factors such as gender on headache attacks we aimed to determine whether migraine, cluster headache, and tension-type headaches are correlated with BDNF level and gender.
Methods
Design and patients
One hundred twenty female and male people were selected among the patients suffering from episodic migraine (M) with and without aura, episodic and chronic cluster headache (CH), episodic and chronic tension-type headache (TTH). The diagnosis was done by a certified neurologist and headache specialist according to the current criteria of the International Headache Society (ICHD-3). 8 Thirty healthy people participated in the control group (CG). The sample size was based on the available data. All patients were recruited in outpatient clinic at Tashkent Medical Academy, Tashkent, Uzbekistan and patients were collected from December 2019 to May 2022. The consent in which all the cases were informed was written by all participants and entered into an electronic database. In the patients suffering from episodic migraine (with and without aura) and cluster headache, serum samples were collected twice, either during a headache and headache-free period. Blood analysis was taken once from the two categories of patients with tension-type headache and healthy-control group.
Eligibility criteria
Patients were selected among the people aged from 18 to 45 and suffering from primary headaches. The patients had taken nonsteroidal anti-inflammatory drugs or drug belonging to the triptan group during the last month and the patients having migraine with more than eight headache attacks in 1 month were excluded from the study. We excluded patients with chronic migraine, because of we aimed to learn only episodic migraine with/without aura. Patients who did not take drugs for the prevention therapy of headaches during the last month were selected. Patients who did not yet using preventive therapy were selected and patients who used a preventive therapy the prevention treatment were postponed due to the study. But in chronic CH patients were not interrupted the medications for prophylactic therapy. Furthermore, the patients either who have other secondary diseases, like, cardiovascular system problems, acute infectious-allergic diseases, diabetes, liver diseases, kidney diseases, and various oncological diseases, pregnant and lactating women were not allowed to participate in the research. The patients who has more than one primary headache type, like simultaneous migraine and tension-type headache, were also excluded.
BDNF analysis
Blood samples were taken from the cubital vein of all patients. In patients with M and CH blood tests were taken two times: during the attack and attack-free period. From the patients with TTH and healthy-control (HC) group blood analysis for BDNF was taken once. Obtained blood samples were kept at room temperature for 2 hours and then centrifuged at 1500g for 20 minutes. After centrifugation, blood serum was stored in a refrigerator at −20°C. Serum levels of BDNF were measured by enzyme-linked immunosorbent assay using Elabscience Sandwich ELISA Kit, E-EL-H0010 (USA) reagent. Concentration was expressed as pg/ml. Detection limits were defined as 5 pg/ml for BDNF.
VAS (visual analogic scale) was used to determine the intensity of headaches and identified the correlation with BDNF.
Statistical analysis
The categorical variables were summarized using percentages, and the continuous ones were generally summarized by descriptive statistics (using mean standard deviation values). The data were analyzed with the GraphPad Prism software, version 9.5.1 for Windows. The confidence interval was 95% and the significance level was set at p < 0.05. Categorical data were compared using the Chi-square test. Mann–Whitney was used for the medians comparisons of continuous data. Correlations were evaluated with Pearson test.
Study protocol number (which is registered in clinicaltrials.gov): NCT05760625
The study was approved by the Institute’s Ethical Committee and written informed consent was obtained from each patient prior to enrollment.
Results
Baseline characteristics
Sixty patients with episodic M were taken for the study. Twenty-six of them were diagnosed M with aura and 34 migraines without aura. In all 60 patients, paired blood samples obtained during the attack (before symptomatic medication) and attack-free period were collected. Eight patients with episodic and four with chronic CH were included in the study, among which there were no female patients, cluster headache was observed only in male patients during our study, and paired blood samples were obtained from all of them and BDNF level were compared among two groups of CH. Blood analysis samples were taken once from 48 patients with episodic and chronic TTH, 18 of them were without headache and 30 of them were with headache period. For the study CG, 30 healthy people were taken. Age, gender, smoking, and hormonal contraception did not have significant effects on peripheral BDNF serum levels (data not shown). The sample size was based on the available data. Demographic and clinical data of the subjects included in the study are presented in Table 1.
Clinical and demographic data of patients with primary headache and controls.
When BDNF levels were examined in patients M with aura during attack and attack-free period, it was found that BDNF level was significantly increased during the attack period (p < 0.01). When this indicator was compared between female and male patients, it was found that BDNF increased during the attack in both sexes, but no statistically significant difference was found between males and females (Figure 1). In both male and female patients M without aura, BDNF levels were found to be significantly increased during attacks (p < 0.02), and decreased in both sexes during the attack-free period (Figure 2). Increasing grades of VAS significantly (moderately positive) correlated with BDNF during migraine attacks (r = 0.67) (Figure 3).
Levels of brain-derived neurotrophic factor (BDNF) in migraine with aura during headache attacks and attack-free periods.
Levels of brain-derived neurotrophic factor (BDNF) in migraine without aura during headache attacks and attack-free periods.
Correlation between VAS and BDNF level in migraine.
Increased serum BDNF concentrations in male patients with episodic and chronic CH revealed higher BDNF concentrations during the attack period compared to the attack-free period, but no statistically significant difference was found (p = 0.05) (Figure 4). Serum levels of BDNF were strongly positive correlated with VAS during CH attacks (r = 0.75) (Figure 5).
Levels of brain-derived neurotrophic factor (BDNF) in cluster headache (CH) during headache attacks and attack-free periods.
Correlation between VAS and BDNF level in cluster headache.
The comparison of BDNF serum levels in female and male patients during episodic TTH and chronic TTH periods is shown in Figure 6. When the data were compared, no statistically significant difference was found (p = 0.82). The level of BDNF was not significantly different between controls and patients with TTH (p = 0.83, respectively) (Figure 7 and Table 2). There was no significant difference between VAS and BDNF levels in patients with TTH (p = 0.82).
Levels of brain-derived neurotrophic factor (BDNF) in tension-type of headache (TTH) (F-female, M-male).
BDNF levels in males and females of the healthy-control group.
BDNF levels of female and male patients with primary headaches (during headache attack and attack-free period).
Discussion
In this study, we investigated the levels of BDNF during attacks and attack-free periods in male and female patients with migraine, in male patients with cluster headaches, and in tension-type headache it were examined at once. The relationship between the level of BDNF and pain intensity was compared. To the best of our knowledge, this is the first study in Uzbekistan to show increased levels of BDNF during headache attacks. As a result of our study, it was found that patients with M and CH have higher levels of BDNF during pain attacks. These findings suggest that the level of serum BDNF is an important effect modifier for headache attacks. BDNF levels in the blood plasma of patients with TTH were significantly higher than those of healthy controls (p < 0.05). And during our study we found out that there is no gender difference of BDNF levels in Uzbek patients.
Higher levels of BDNF were correlated with higher VAS results in females and males. The present findings support the notion that BDNF levels may be a neurobiological mechanism underlying the gender-related differences in pain thresholds. 9,10
BDNF is a member of the neurotrophic family and has been recognized as an important modulator of nociceptive pathways. 11 –13 Our results are in line with Fischer et al., who determine that BDNF levels were increased in patients with M and CH during attack period, but they did not conduct investigations in episodic and chronic CH and TTH. 2 Another study investigating neurotrophic factors in primary headaches found the opposite of our results: it found decreased BDNF levels in M (with and without aura) and CH. 3,14 In addition, similar results were obtained in another study conducted in 2015. 15 This may be explained by hypothalamic–pituitary–adrenal (HPA) axis hyperactivity associated with chronic stress in these migraine patients. HPA axis hyperactivity is associated with increased pain sensitivity and reduced BDNF production. These results may be explained by the associated high rates of psychological distress and somatization. 16 In summary, these results support the BDNF role as a pain modulator in patients with M and CH, contributing to trigeminal nociceptive plasticity and pain control in M and CH patients.
However, there were some shortcomings in our research. Firstly, we could not compare BDNF levels in female and male patients with CH, because we did not encounter female patients with CH in our study. Secondly, if we take into account the menstrual migraine (MM) disease that occurs in women of reproductive age, taking into account the specific hormonal background, we did not make a separate group of patients with this type of M in our study, and we could not investigate BDNF changes in MM. Thirdly, in subgroups of CH and TTH there were small size of samples. In our next studies, we will conduct investigations aimed at eliminating these shortcomings.
Conclusion
Neurotrophic factors, in particular BDNF, play an important role in the occurrence of headache attacks. In the course of our research, BDNF was increased during M and CH attacks, and unchangeable BDNF level was in patients with TTH. We were also convinced that there were no gender-specific changes in the amount of BDNF.
Footnotes
Acknowledgments
The authors are grateful to all volunteers for their participation in our study.
Clinical implications
BDNF plays a role in migraine and cluster headaches attacks. Uzbek patients showed a stronger male predominance in cluster headache. During headache attacks, the levels of BDNF are almost equal in both male and female patients with primary headaches. Uzbek patients showed a stronger male predominance in cluster headaches, and female predominance in migraine and tension-type headaches.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Ethical approval
The consent in which all the cases were informed was written by all participants and entered into an electronic database.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by a Junior research grant from the International Headache Society (London).