Aalborg Universitet Catechol-O-Methyltransferase Val158Met Polymorphism Is Associated with Anxiety, Depression, and Widespread Pressure Pain Sensitivity in Women with Chronic, but Not Episodic, Migraine

Citation for published version (APA): Fernández-de-Las-Peñas, C., Ambite-Quesada, S., Florencio, L. L., Palacios-Ceña, M., Ordás-Bandera, C., & Arendt-Nielsen, L. (2019). Catechol-O-Methyltransferase Val158Met Polymorphism Is Associated with Anxiety, Depression, and Widespread Pressure Pain Sensitivity in Women with Chronic, but Not Episodic, Migraine. Pain Medicine, 20(7), 1409-1417. https://doi.org/10.1093/pm/pny237

Migraine is a primary headache disorder with a worldwide prevalence of 11.6% 84 (13.8% females/6.9% males) (1). In the last Global Burden of Disease Study, migraine 85 and tension-type headache were found to be the second most prevalent pain conditions 86 in the world (2). In fact, general costs of headaches in Europe (€13.8 billion) mainly 87 account for migraine and tension type headache (3). 88 It is accepted that the pathophysiology of migraine is associated with abnormal 89 neuronal excitability leading to cortical spreading depression and to central sensitization 90 of trigemino-vascular pathways (4). There are several factors that could affect the pain 91 processing. One of these factors is genetics. Different genetic epidemiological studies 92 have investigated the familial aggregation in migraine and it seems that an hereditary 93 component can be present in some migraine types, i.e. hemiplegic migraine (5,6). 94 The catechol-O-methyltransferase (COMT) gene is one of the potential genetic 95 determinants in chronic pain (7). The COMT is an enzyme involved in the metabolic 96 degradation of several neurotransmitters, e.g., dopamine, norepinephrine, or epinephrine 97 (8). The activity of the COMT gene can be affected by different polymorphisms such as 98 rs4680, rs6269, rs4633, or rs4818. It seems that the rs4680 genetic polymorphism due to 99 a G→A substitution at codon 158 of this gene, leading to a valine (Val) to methionine 100 (Met) substitution, will result in differences within COMT gene activity related to pain 101 sensitivity. In fact, a valine (Val) allele at codon 158 results in a high-activity variant 102 (Val/Val) whereas a methionine (Met) at this codon position (Val/Met, Met/Met) results 103 in low-activity variants (9). It has been found that subjects with the Met/Met genotype 104 exhibit higher pain sensitivity, that is, lower pain thresholds to different stimuli (10,11), 105 and different brain responses to painful stimuli (12) than those subjects with the Val/Val 106 genotype, supporting a role of this gene in nociceptive pain processing. 107 There are several studies investigating the role of Val158Met polymorphisms in 108 migraine; although the results are inconsistent. The most recent meta-analysis did not 109 observe a significant association between the Val158Met polymorphism and migraine 110 (13). Similarly, a recent study, not included in the abovementioned meta-analysis, did 111 not also reveal differences in Val158Met polymorphism distribution between subjects 112 with migraine and healthy controls (14). Based on current evidence, it would seem that 113 Val158Met polymorphism (rs4680) is not associated to a higher risk of suffering from 114 migraine. However, it should be noted that most studies did not differentiate between 115 episodic and chronic migraine. Similarly, another study including subjects with chronic 116 migraine did not also find an association of the rs4680 Val158Met polymorphism with 117 this subgroup (15). including location, quality of pain, years with disease, frequency and intensity of pain 142 attacks, family history, and medication intake were collected. To be included, subjects 143 had to describe typical pain features of migraine pain (unilateral location, pulsating 144 pain, high intensity, and aggravation during physical activity) and associated symptoms 145 including photophobia, phonophobia, mild nausea or vomiting (19). 146 Participants were excluded if they presented any of the following: 1) other primary 147 or secondary headache, including medication overuse headache; 2) history of cervical or 148 head trauma; 3) pregnancy; 4) history of cervical herniated disk or cervical osteoarthritis 149 on medical records; 5) any systemic medical disease, e.g., rheumatoid arthritis, lupus 150 erythematous; 6) comorbid fibromyalgia syndrome; 7) had received treatment including 151 anesthetic blocks, botulinum toxin or physical therapy within the previous 6 months; or, 152 8) male gender. All participants were carefully interviewed for assesing their medical 153 history. Further a medical exam, including neuro-imaging examination (MRI or CT) of 154 the head, was performed in all patients in order to identify any exclusion criteria. 155 Age-matched healthy women without history of headache diagnosis and without 156 reporting a headache pain attack during the previous year were also included. Exclusion 157 criteria for the control group were the same as for the headache groups. All participants 158 signed the informed consent form before their inclusion in the study. The local Ethics 159 Committee of Hospital Rey Juan Carlos, Spain (HRJ 07/14) approved the study design. 160

DNA Collection and COMT Genotyping 161
Non-stimulated whole saliva samples were collected into collection tubes (passive 162 drooling technique) according to standardized procedures. Saliva collections were made 163 when participants were headache-free, or with a migraine intensity of less than 3 points 164 (in those patients with high frequency of attacks). Immediately after collection, samples 165 were centrifuged at 3000 rpm for 15min to obtain the cell sediment and they were stored 166 at -20º C until the analysis. We prefer to use saliva instead of blood sampling because 167 salivary collection is a non-invasive, stress-free and ethic suitable assessment method.

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One hundred and twenty (n=120) consecutive women presenting with headache 257 were screened for eligibility criteria. Twenty (17%) were excluded for the following 258 reasons: co-morbid headaches (n=7); previous head or neck trauma (n=6); receiving 259 anaesthetic block in the past 3 months (n=5) or pregnancy (n=2). Finally, 50 women 260 with chronic migraine (age: 43±12 years), 50 with episodic migraine (age: 42±13 years) 261 satisfied all criteria, signed the informed consent, and agreed to participate. Further, 50 262 age-matched women without headache (age: 43±11 years) were also included. Table 1  263 summarizes clinical, psychological and pain sensitivity data of the sample. Women with 264 chronic migraine exhibited significant higher headache frequency (P<0.001) and higher 265 migraine-related disability (P=0.04) than those with episodic migraine. Further, women 266 with episodic or chronic migraine exhibited higher widespread pressure pain sensitivity 267 (P<0.001) than healthy women, without differences between them (P>0.9). 268

Distribution of Val158Met Polymorphism in migraine 269
The genotype distributions in women with and without migraine did not deviate

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The current study found no differences in the genotype distribution and allele 306 frequency of the Val158Met polymorphism between those women with migraine, either 307 episodic or chronic, and healthy women. Further, the presence of the Met/Met genotype 308 was associated to higher levels of anxiety, depression, disability and greater widespread 309 pressure hyperalgesia, in women with the chronic, but not episodic, form of the disease. 310

Val158Met polymorphism and migraine 311
We did not observe significant differences in the distribution of the Val158Met 312 polymorphism between women with episodic or chronic migraine and healthy women, 313 supporting the assumption that this polymorphism is not involved in a predisposition to 314 suffer from migraine. Our results agree with a recent systematic review concluding that 315 the Val158Met polymorphism was not associated with migraine risk (13). Additionally, 316 Takigawa et al did not also observe differences in the presence of other haplotypes of 317 the COMT gene, e.g., rs4633, rs6267, rs6270 between individuals with migraine and 318 healthy people (14). Nevertheless, since the rs4680 Val158Met polymorphism has been 319 associated, in some studies, to different conditions, e.g., fibromyalgia syndrome (33) or 320 temporomandibular pain (34), it is possible that it could be associated to some particular 321 pain conditions rather than to chronic pain in general. Furthermore, since migraine is 322 comorbid with other chronic pain syndromes, i.e. fibromyalgia (35) Our study is the first reporting an association between the Val158Met polymorphism 355 and widespread pressure pain sensitivity in chronic migraine. Several mechanisms could 356 explain this association. For instance, a reduction within COMT gene activity associated 357 with the Met allele at codon 158 of the Val158Met leads to a reduction in the content of 358 enkephalins in some regions of the central nervous system associated with pain (9). This 359 hypothesis would correlate with the presence of hyper-excitability of the central nervous 360 system and of endogenous inhibitory pain pathways previously observed in adults with 361 chronic migraine (44). In fact, migraine has been associated with a non-physiological 362 production of some neuromodulators (45). Therefore, another potential mechanism may 363 be an increase of catecholamine levels, which will promote stimulation of b2-adrenergic 364 receptors in the central nervous system, associated with a reduced COMT gene activity 365 (46). Since individuals with migraine exhibit hyper-excitability of the central nervous 366 system, it is possible that the presence of the Met/Met genotype, in some predisposed 367 subjects, could contribute to this process. In fact, this hypothesis is also suggested in 368 subjects with fibromyalgia (47). 369

Limitations 370
Although the results of this study are informative, potential limitations should be 371 considered. First, we included women with migraine and derived from a specialized 372 tertiary hospital center. Therefore, our results should be not extrapolated to men and to 373 other primary headaches such as tension-type headache. Second, it is possible that the 374 study was underpowered for other outcomes different than PPTs. Therefore, a greater 375 sample size including patients from the general population would be needed to further