Estrogen Receptor 1 Gene Polymorphism Frequency in Fibromyalgia Syndrome

Objective: The fact that fibromyalgia and migraine are more common in women of reproductive age and their incidence are higher than other populations suggests that these three diseases may have a common genetic basis. Therefore, we aimed to investigate whether there is a relationship between ESR-1 594G> A (rs2228480), ESR-1 325C> G (rs2295190) polymorphisms and fibromyalgia disease.

Introduction: Fibromyalgia syndrome (FMS), diffuse body pain, chronic musculoskeletal disease with increased fatigue and tenderness and sleep disorder in specific anatomical regions . The FMS diagnosis is based on American College of Rheumatology(ACR) 1990 classification criteria. FM frequently affects women between 30 and 50 years of age and its prevalence is between 1% and 4% of the whole population, 0-4% in men and 2.5-10.5% in women. Researchers have found that the strong familial tendency in FM has a risk of developing FM in first-degree relatives of patients with FM, 8 times more than in the general population. Family members of FM patients are more susceptible to pain and are more likely to develop conditions such as irritable bowel syndrome (IBS), temporomandibular disorder (TMD), headache-migraine, restless leg syndrome, and other regional pain syndromes . Several studies have been conducted to demonstrate specific genetic polymorphism in FM. To date, polymorphisms in the serotonin receptor, serotonin transporter, dopamine D4 receptor and catechol-O-methyltransferase genes have been found to be high . All these identified polymorphisms are responsible for the metabolism and transport of monoamines; These are compounds that play a critical role in the human stress response.

The more frequent occurrence of FMS in women is observed in young adults, indicating the effect of sex hormones on the pathophysiology of this condition. However, the mechanism of action of these hormonal effects is still unknown and is a matter of debate. Steroid hormones, in particular estrogen, affect both peripheral and central nervous system (CNS) receptors (Estrogen Receptor-1; estrogen receptor-a [Era] and Estrogen Receptor-2;estrogen receptor-b [ERb]), the inflammatory process and the transmission of central pain. For example, estrogen may directly affect monocytes and macrophages to regulate the production of cytokines (eg, Interleukin-1 [IL-1], IL-6 and tumor necrosis factor-a [TNF-a]).

Migraine is a neurological disorder characterized by episodes of hemicranial pain characterized by attacks. one-year prevalence of migraine in the general population in Turkey 16.4%, while the proportion of patients with FM were significantly lower (9). The incidence of headache increased in patients with fibromyalgia syndrome. Migraine and non-migraine headaches have been reported in patients with FM between 28% and 58% . Similarly, in a study conducted on 33 FM patients, the current migraine was present at 45% and the lifetime migraine history was 55% . The prevalence of migraine has been reported to be approximately 2-fold (reproductive period) and the severity of migraine attacks in women compared to men . Studies investigating the relationship between sex hormone levels and polymorphisms due to more frequent reproductive states have shown that they are associated with estrogen receptor-alpha (ERa 594G> A (rs2228480), ERa 325C> G (rs2295190) polymorphisms.

Methods: Establishment of study groups: 100 patients diagnosed as Fibromyalgia syndrome according to the criteria of ACR 1990, 18-65 years old, and having similar sociodemographic characteristics. 100 control patients will be taken. As the inclusion criteria for the patients; Being between 18 and 60 years of age, taking the diagnosis of primary FMS according to ACR 1990 diagnostic criteria, accepting to participate in the study, lack of any sex hormone disease. The control group will be composed of volunteers with similar age and gender characteristics. The volunteers taken into the control group will have no sex hormone. The participants will be informed about the subject before being taken into the study and the necessary permits will be taken.

Semi-structured sociodemographic information form prepared by us will be used in accordance with the clinical experience and the information obtained from the scanned sources and the aims of the study (ANNEX-1) Age, gender, education level, marital status, BMI, family history of fibromyalgia diseases and accompanying symptoms. Accompanied by the symptoms; TMD symptoms such as migraine type headache, jaw pain and locking, sleep disorder, dry mouth, dry eyes, irritable bowel symptoms, restless leg symptoms, soft tissue swelling, fatigue, depressive symptoms or depression history will be questioned. Patients with headache will be evaluated by a neurologist in terms of the diagnosis of migraine. Pain evaluation of the cases will be done by Visual Analog Scale (VAS). A 10 cm ruler will be used for this. Patients will be evaluated once and the appropriate amount of blood samples will be collected from the patients after the evaluation.

Collection of Blood Samples: 5 mL blood samples from the control and patient groups will be taken into sterile, citrate tubes. The blood in the tubes will be stored at -80 ° C until isolation of the DNA.

Isolation of Genomic DNA: Genomic DNA will be isolated from the blood using a DNA isolation kit. DNA purity will be determined by spectrophotometric method.

Genotyping: Genotyping of ESR-1 325 C> G and 594 G> A polymorphisms in the study group will be performed by using single nucleotide polymorphism analysis kit and sequence-specific double-dye hydrolysis probes and allelic segregation analysis in real-time polimerase chain reaction (RT-PCR) using primers. Genotyping of each patient and control will be repeated 3 times to ensure the reliability of the analysis results.

Statistical methods: The number of individuals to be included in the study was determined by Statistical Power Analysis. In this study, when α = 0.05, β = 0.10, 1- β = 0.90, it was decided to take 100 individuals to each patient and control groups, and the strength of the test was found to be p = 0.9072. All data obtained from the study will be evaluated with SPSS 18 program. The χ2 test and Student-t and Mann-Whitney tests will be used to evaluate the suitability of nominal and continuous variables.