Association of the Val66Met Polymorphism of the BDNF Gene with the Depression in a Mexican Population with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, autoimmune pathology that affects the nervous system. It is characterized by inflammatory lesions that cause axonal damage with neurodegeneration. The signs and symptoms present in this pathology include among others, psychiatric disorders. In MS, depression is the most frequent psychiatric disorder, with prevalence levels of 40 to 60%; to date, the cause is unknown. The brain-derived neurotrophic factor (BDNF) is a neurotrophin related to neuroplasticity. The single-nucleotide polymorphism Val66Met, encoded by the BDNF gene, has been associated with various effects, including the presence of neuropsychiatric disorders. The purpose of our study was to evaluate the association between the BDNF Val66Met polymorphism and depression in MS patients. Methods: Study design, cases, and controls: Mexican mestizo MS patients. Cases: Patients diagnosed with depression. Controls: Patients without depression diagnosis. Measurements: For depression, the Beck Depression Inventory; for polymorphism, real-time PCR. Results: No statistically significant differences were found in sociodemographic and disease variables between the case and control groups. qPCR analysis showed that 68% of the participants were Val/Val wild-type homozygotes, 29% were Val/Met polymorphism heterozygotes, and 3% were Met/Met polymorphism homozygotes. The presence of the BDNF gene rs6265 polymorphism was associated with a 5.6-fold increase in the probability of depression in the cases compared to the controls. Conclusions: The BDNF Val66Met Polymorphism is associated with depression in Mexican mestizo patients diagnosed with MS.