Associação Do Polimorfismo Htr2a -1438a/g (Rs6311) Com A Preferência Matutina-vespertina Em Uma População De Indivíduos Jovens

Abstract

An individual's circadian preference, also called chronotype, is a phenotypic characteristic that reflects the time of day with the highest level of activity and task performance. Currently, there are different methods and scales that help classify people as “morning” or “evening”. It is suggested that human chronotypes may be influenced by endogenous factors such as the rhythm of body temperature, hormone secretion and genetic mechanisms, as well as exogenous factors such as the daily light/dark cycle (day/night) and social factors. The neurotransmitter serotonin is recognized for its important role in regulating the circadian rhythm, since alterations present in the sleep cycle can be associated with factors such as stress and changes in the individual's mood. Among the genes involved in serotonin metabolism, the rs6311 (-1438G/A) polymorphism in the HTR2A gene was the focus of this study due to its importance for being associated with susceptibility to psychiatric disorders. Given the relevance of serotonin, studies about its influence on the circadian cycle, mainly on chronotypes, can elucidate how much these genotypic variations caninfluence behavior. Thus, the present work aims to investigate the relationship between the rs6311 polymorphism and the morning-evening preference in one of the populations of young individuals. For this, data were collected from 161 male volunteers, aged between 18 and 32 years. To analyze the polymorphism, DNA was extracted from peripheral blood and subsequent genotyping by PCR-RFLP. For the collection of chronotype data, Horne and Ostberg's Questionnaire for the Identification of Morning and Evening Individuals (1976) - MEQ, an instrument usedin the area of neuroscience and in studies with the circadian cycle, was used. Data were analyzed using the following statistical tests: Chi-square for association between genotype and chronotype; and one-way ANOVA for analysis of variances of mean scores in relation to chronotypes per genotype. The results showed that the polymorphism studied in isolation did not influence the morning or afternoon preference of the individuals, due to the chronotype being a complex phenotype and that its determination is up to analysis beyond genetic factors, such as also considering the physiological state, age, gender and environmental factors concerning the individual. Contributing to the following association studies between other polymorphisms of this gene, which shows great potential, since it can present a relationship and contribution in modeling the morning-evening phenotype.