Searching for Predictors of Migraine Chronification: a Pilot Study of 1911A>G Polymorphism of TRPV1 Gene in Episodic Versus Chronic Migraine.

Transient receptor potential vanilloid type 1 (TRPV1) receptors activated by heat and capsaicin are expressed in trigeminal nociceptive neurons and implicated in the generation of migraine pain. Genetic studies suggested that single-nucleotide polymorphism (SNP) 1911A>G (rs8065080), leading to amino acid substitution Ile585Val, in the TRPV1 gene affects functional activity of TRPV1 receptors and is involved in different pain conditions. However, this polymorphism has not been tested in migraine patients. The objective of this pilot study was to investigate genetic factors of migraine susceptibility. We evaluated frequency distribution of AA, AG, and GG variants of SNP 1911A>G in the TRPV1 gene in patients with episodic and chronic migraine compared with healthy individuals. The study included 46 patients diagnosed with migraine (27 episodic and 19 chronic) and 50 healthy individuals as a control group. DNA from peripheral blood was used to test TRPV1 SNP using allele-specific PCR combined with gel electrophoresis. The genotype frequency distribution in episodic migraine was comparable with that in controls (AA 33%, AG 56%, GG 11% and AA 34%, AG 46%, GG 20%, respectively). On the contrary, in chronic migraine, the distribution differed significantly (p < 0.05) (AA 68%, AG 32%, GG 0%). This are first indications for a distinctive genotype frequency distribution of TRPV1 1911A>G in chronic migraine patients compared with episodic migraine patients and controls. Our data confirm a different predisposition to chronic pain in migraine and give a prerequisite for a new look at the nature of chronification of migraine, proposing that the absence of GG genotype may be considered as possible risk biomarker of episodic migraine evolution to chronic form.