Evaluation of the association of dietary components with brain-derived neurotrophic factor val66met polymorphism in obese adults

Obesity is defined as a multifactorial disease characterized by increased fat tissue as a result of the imbalance between energy intake and energy expenditure, and caused by the influence of genetic and environmental factors. In recent years, the concept of individualized dietary approach has gained importance in the treatment of obesity, and the relationship between obesity-related genes and diet has started to be investigated. The brain-derived neurotrophic factor (BDNF) gene is associated with both monogenic and polygenic obesity and the Val66Met polymorphism in this gene is the most common and most studied genetic variant. The aim of this study is to evaluate the relationship between brain-derived neurotrophic factor Val66Met polymorphism and dietary components in obese adults. The sample of the study consisted of 260 individuals [134 obese (Female:81, Male:53) and 126 normal body weight (Female:76, Male:50)], aged between 20-50 years, who applied to Amasya University Sabuncuoğlu Şerefeddin Training and Research Hospital Internal Medicine Department Polyclinic for examination and control. Research data was collected through face-to-face interviews and a survey form. The survey form consisted of nine sections: general information, eating habits, anthropometric measurements, food consumption record, Mediterranean Diet Adherence Screener and International Physical Activity Questionnaire (short form), some routinely checked biochemical parameters, blood pressure and gene analyses. Within the scope of the study, genotype distribution in BDNF Val66Met polymorphism was determined by Real Time-Polymerase Chain Reaction using blood samples taken from individuals. The average age of individuals is 38.0±8.7 years. 83.6% of obese individuals and 78.2% of normal body weight individuals have the G allele (p>0.05). 68.6% of obese individuals are GG, 29.9% are AG and 1.5% are AA, 61.9% of individuals with normal body weight are GG, 32.5% are AG and 5% are AA, 6 of them were in AA genotype (p>0.05). In obese individuals, the daily amount of carbohydrates intake in the diet was higher in GG genotype carriers than in individuals with AG+AA genotype, and the percentage of energy coming from polyunsaturated fatty acids (PUFA) was found to be lower (p<0.05). Analyses by gender showed that obese women with GG genotype had higher dietary carbohydrate intake (p<0.05), while obese men with GG genotype had lower dietary intake of FFA, percentage of energy from FFA and n-6 fatty acids (p<0.05). It was found that the total score of the Healthy Eating Index-2015 and the scores of seafood and vegetable proteins among its subcomponents were lower in obese individuals with the GG genotype compared to AA+AG carriers (p<0.05). In individuals with genotype GG, as the percentage of energy coming from carbohydrate increased, waist hip ratio increased; as the percentage coming from protein increased, body mass index, waist circumference and waist hip ratio decreased; as the percentage coming from fat increased, body fat mass ratio increased (p<0.05). The risk of high LDL, high total cholesterol and low vitamin D was increased in individuals with genotype GG (p<0.05). In conclusion, in this study, it was determined that BDNF Val66Met polymorphism may affect obesity indicators in relation to diet and other lifestyle factors.