Selected Candidate Genes and Obesity Among Ghanaian Adults: A Case Control Study at the Korle-Bu Teaching Hospital (Dietherapy Unit) Accra

Abstract

Obesity is a complex, heterogeneous group of disorders that is determined by genes, environmental factors and interaction between genes and environment. Several studies have all established associations of certain candidate genes to obesity and their variations with respect to race, geographical location/country of origin. A study of this nature to investigate the relationship between some of these selected genes and obesity has not yet been conducted in Ghana. Aim: The aim of this study was to investigate the relationship between single nucleotide polymorphisms (SNPS) in selected candidate genes (β3-adrenergic receptors (ADRB3), leptin receptor (LEPR), and peroxisome proliferator activator γ receptor (PPARγ)) and obesity among Ghanaian adults. Methods: This was a case-control study. The cases were newly diagnosed obese (BMI ≥ 30 kg/m2)male and female Ghanaian adults (18 and 60 years) who visited the Dietherapy Unit (KBTH) for dietary counselling. Controls were students of the School of Allied Health Sciences and various staff members of Korle bu Teaching Hospital. A validated questionnaire was used to collect data on demographic characteristics, feeding habits, dietary history and anthropometric measures. Dietary intake was assessed using a food frequency questionnaire. DNA was extracted from mouth rinse water samples and SNPS in the ADRB3, LEPR and PPARγ genes were determined by polymerase chain reaction restriction fragment length polymorphism (PCR –RFLP). Results: A total of 56 subjects (71.4% females), consisting of 24 cases (41.63 ± 11.50 years) and 32 controls (26.42 ± 5.48 years), were recruited for the study. All the subjects were non-smokers, with 80.3% not consuming alcohol. There were statistically significant differences in BMI, waist to hip ration (WHR) and mid-upper arm circumference (MUAC) measurements between cases and controls (all ps˂ 0.0001)

There was no statistically significant difference (p = 0.3032) between the mean energy intakes of the cases and controls. DNA fragments for the PPARγ gene was amplified in 55 out of the 56 respondents. Only the presence of CC (Pro12Pro) genotype was detected after the RFLP. No relationship was observed between PPARγ gene polymorphism and BMI, MUAC and WHR among the participants. For LEPR, amplification was successful in 15 cases and 14 controls. However, only amplicons of six cases, all in the OBClass 1 to OBClass 3 range, after RFLP indicated the presence of the Gln223Arg genotype. A significant difference (all ps <0.05) emerged for the LEPR gene Gln223Arg genotype polymorphism frequencies between the cases and the controls for BMI, MUAC and WHR. For ADRB3, amplification was successful in 19 cases and 24 controls. RFLP indicated the presence of the Trp64Trp and the Trp64Arg genotypes. No significant difference (all ps >0.05) emerged for the ADRB3 gene Try64Arg genotype polymorphism frequencies between the cases and the controls for BMI, MUAC and WHR. Conclusions: No relationships were observed between ADRB3 and PPARγ genotype polymorphisms and BMI, MUAC and WHR. However, LEPR gene Gln223Arg genotype polymorphism was statistically associated with BMI, MUAC and WHR. A larger sample size would have to be considered in order to establish any potential associations between LEPR and obesity in the Ghanaian population.