Common variant within the FTO gene, rs9939609, obesity and type 2 diabetes in population of Karachi, Pakistan

Single nucleotide polymorphisms (SNPs) that are associated with obesity and type 2 diabetes among Asians: a systematic review and meta-analysis

Single nucleotide polymorphisms (SNPs) could increase the susceptibility of individuals to develop obesity and type 2 diabetes (T2DM). Obesity and T2DM are closely related pathophysiologically, thus similar SNPs could mediate both these diseases, but this is rarely reported. Furthermore, limited studies have been performed to summarize SNP data in the Asian population compared to the Western population. In this study, we aimed to summarize SNPs that are associated with the development of obesity and T2DM among Asian populations. We searched six literature databases and Review Manager (RevMan) was used for meta-analysis. The pooled odds ratios (ORs) and 95% CIs were calculated with a random effects model for the heterogeneity among studies. The pooled analysis showed that rs9939609 (FTO gene) and rs17782313 and rs571312 (MC4R gene) are associated with obesity with an odd ratio (OR) of 1.37, 1.36 and 1.29 respectively. For T2DM, five SNPs, rs7903146 and rs12255372 (TCF7L2 gene), rs13266634 and rs11558471 (SLC30A8 gene) and rs2283228 (KCNQ1 gene) have also shown strong associations with T2DM at OR of 1.64, 1.61, 1.22, 1.29 and 1.60 respectively. This data could be used to develop a gene screening panel for assessing obesity and T2DM susceptibility.

FTO gene variants (rs9939609, rs8050136 and rs17817449) and type 2 diabetes mellitus risk: A Meta-Analysis

BACKGROUND AND AIMS

There is tremendous increase in type 2 diabetes mellitus (T2DM) worldwide. The impact of FTO gene polymorphisms on the risk of T2DM is not yet clear because of the controversial results of studies. This meta-analysis aimed to better clarify the association between three FTO gene polymorphisms SNPs (rs9939609, rs8050136 and rs17817449) and T2DM in a larger combined population worldwide.

MATERIAL AND METHODS

A comprehensive search on the PubMed, Science Direct, and Web of Science databases was conducted to identify investigations in relationship between different FTO gene polymorphisms (rs9939609, rs8050136 and rs17817449) and T2DM globally. Published papers from January 2007 to May 2023 were collected. Inclusion criteria are limited to human case-control studies published in English and peer-reviewed, which provided data on the genotype distributions of FTO gene polymorphisms and T2DM risk. Odds ratios (OR) and 95% confidence intervals (CI) were calculated to express the results of the meta-analysis. Potential sources of bias and heterogeneity using Egger's regression analysis were also assessed.

RESULTS

Of 234695 identified articles, forty-eight studies were selected including 36,051 patients with T2DM and 51,266 control subjects. Overall, we found a significant increased risk of T2DM susceptibility and rs9939609 FTO gene polymorphism in the Allele contrast (A vs. T: OR = 1,30, 95% CI = 1.14; 1.48, P < 0,05, I2 = 0,94), Recessive model (AA vs. AT + TT: OR = 1,54, 95% CI = 1.19; 2.00, P < 0,05, I2 = 0,94), Dominant model (AA + AT vs. TT: OR = 1,26, 95% CI = 1.10; 1.45, P < 0,05, I2 = 0,89), homozygote model (AA vs. TT: OR = 1,60, 95% CI = 1.26; 2.03, P < 0,05, I2 = 0,90), and heterozygote model (AA vs. AT: OR = 1,43, 95% CI = 1.09; 1.88, P = 0,008, I2 = 0,93). we also found a significantly increased risk of T2DM susceptibility and rs8050136 FTO gene polymorphism under all models. For rs17817449 we did not find any association between with T2DM.

CONCLUSION

The present meta-analysis confirms that rs9939609 and rs8050136 in the FTO gene are significantly associated with T2DM, while rs17817449 does not show any association.

FTO: a critical role in obesity and obesity-related diseases

In recent years, obesity is a growing pandemic in the world and has likely contributed to increasing the incidence of obesity-related diseases. Fat mass and obesity-associated gene (FTO) is the first gene discovered which has a close connection with fat. Recent studies suggested that FTO gene has played an important role in the molecular mechanisms of many diseases. Obesity is considered to be a hereditary disease and can evoke many kinds of diseases, including polycystic ovary syndrome (PCOS), type 2 diabetes mellitus (T2DM), cancer, etc., whose exact possible molecular mechanisms responsible for the effect of FTO on obesity and obesity-related diseases remain largely unknown. In this review, we comprehensively discuss the correlation between FTO gene and obesity, cancer, PCOS, T2DM, as well as the molecular mechanism involved in these diseases.

The Association of Fat Mass and Obesity-Associated Gene Polymorphism (rs9939609) on the Body Composition of Older People: Systematic Review

BACKGROUND

Population aging is growing faster than any other age group. Associated with aging, the prevalence of overweight and obesity is a potential risk factor for the development and aggravation of numerous pathologies. A genetic factor often associated with obesity is the Fat mass and obesity associated (FTO) (rs9939609) gene polymorphism, which has been extensively investigated in children, young, and adults. However, few studies have been carried out with the older population. This review aimed to verify the influence of the FTO (rs9939609) gene polymorphism on the body composition of the older population.

METHODS

We conducted a systematic review and Meta-analysis of PubMed, Scielo, and LILACS databases. Statistical analysis for meta-analysis was performed using mean values of Body Mass Index (BMI) and standard deviations.

RESULTS

The results did not show significant differences between FTO genotypes and BMI values (-0.32, 95%CI -0.45 to -0.19, I2 = 0%, p = 0.52). However, 59% of the studies identified some influence on body composition, obesity, or comorbidities.

CONCLUSION

Few publications verify FTO polymorphism effects on specific groups of the older, suggesting a reduction in the influence of this gene in the BMI with advancing age. However, we believe that more controlled studies in older populations should be performed.

Relationship between the FTO Genotype and Early Chronic Kidney Disease in Type 2 Diabetes: The Mediating Role of Central Obesity, Hypertension, and High Albuminuria

INTRODUCTION

Single nucleotide polymorphisms (SNP) in the fat mass and obesity-associated (FTO) gene have been associated with type 2 diabetes (T2D) and its complications. The aim of the present research was to investigate which and how (directly or indirectly) clinical and metabolic variables mediate the association between fat mass and the FTO gene and early chronic kidney disease (CKD) in individuals with T2D.

METHODS

This cross-sectional study was conducted in a sample of 236 participants with T2D (53.4% women, mean age 60 ± 10 years). DNA samples were genotyped for the rs7204609 polymorphism (C/T) in the FTO gene. Clinical, anthropometric, and metabolic data were collected. Path analysis was used to evaluate the associations.

RESULTS

Of the sample, 78 individuals with T2D had CKD (33%). Presence of the risk allele (C) was higher among participants with CKD (21.8 vs. 10.8%; p = 0.023). This polymorphism was positively associated with higher waist circumference, which in turn was associated with higher glycated hemoglobin and higher blood pressure. A higher blood-pressure level was associated with higher urinary albumin excretion (UAE) and as expected, higher UAE was associated with CKD. Path analysis showed an indirect relationship between the FTO gene and early CKD, mediated by waist circumference, blood-pressure levels, and UAE.

CONCLUSIONS

These findings suggest that the C allele may contribute to genetic susceptibility to CKD in individuals with T2D through the presence of central obesity, hypertension, and high albuminuria.

Fat mass and obesity-associated (FTO) and leptin receptor (LEPR) gene polymorphisms in Egyptian obese subjects

BACKGROUND

Several studies addressed the contribution of fat mass and obesity-associated (FTO) and leptin receptor (LEPR) polymorphisms for the susceptibility to obesity among different ethnic subjects. The main purpose of this work is to evaluate the association of these polymorph\isms with obesity among Egyptian subjects.

SUBJECTS AND METHODS

This case-control study was carried out on 110 unrelated obese Egyptian subjects who were compared with 122 controls. Their genomic DNA was genotyped using the PCR technique.

RESULTS

The allelic frequencies of FTO rs9939609 (A) and LEPR rs1137101 (223R) were significantly higher in obese subjects compared with non-obese controls (p < .001). Comparing different phenotype frequencies including clinical, anthropometric, and biochemical parameters in obese subjects revealed no significant difference in relation to their genotype frequencies (p> .05).

CONCLUSIONS

This study designates a strong association for FTO and LEPR variants with the risk of obesity among Egyptian subjects.

Association and interaction of the FTO rs1421085 with overweight/obesity in a sample of Pakistani individuals

PURPOSE

Genetic variants determine the predisposition of an individual to obesity in a given environment. The present study was conducted to seek an association of the FTO variant rs1421085 with overweight/obesity and related traits in 612 Pakistani subjects in a case-control manner (overweight/obese = 306 and non-obese = 306). Moreover, interaction effects of the rs1421085 and overweight/obesity on multiple metabolic traits were also investigated, which were never explored before in Pakistani as well as in any other population.

MATERIALS AND METHODS

Anthropometric traits were measured by standard procedures, while metabolic parameters were determined by biochemical assays. Genotyping of the rs1421085 was carried out by TaqMan allelic discrimination assay. The data were analysed using SPSS software version 19.

RESULTS

The study revealed a significant association of the rs1421085 with overweight/obese phenotype with respect to over-dominant model indicated by h-index. The CT genotype of the rs1421085 was observed to increase the risk of being overweight/obese by 1.583 times (95% CI 1.147-2.185, p = 0.005). The CT genotype was also found to be associated with higher values of all anthropometric variables (except height and waist-to-hip ratio). Moreover, the interaction between the CT genotype of the rs1421085 and overweight/obesity was found to influence several metabolic parameters (raised blood pressure, product of triglyceride and glucose index, triglyceride levels, LDL-C, VLDL-C, coronary risk index, atherogenic index, and triglyceride-to-HDL-C ratio).

CONCLUSION

In conclusion, the rs1421085 was found to be associated with overweight/obesity and related anthropometric traits independent of age and gender in Pakistani population. Moreover, this variant was found to influence various metabolic traits in the presence of overweight/obesity.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

Determination of individual type 2 diabetes risk profile in the North East Indian population & its association with anthropometric parameters

Background & objectives:

Diabetes genomics research has illuminated single nucleotide polymorphism (SNP) in several genes including, fat mass and obesity associated (FTO) (rs9939609 and rs9926289), potassium voltage-gated channel subfamily J member 11 (rs5219), SLC30A8 (rs13266634) and peroxisome proliferator-activated receptor gamma 2 (rs1805192). The present study was conducted to investigate the involvement of these polymorphisms in conferring susceptibility to type 2 diabetes (T2D) in the North East Indian population, and also to establish their association with anthropometric parameters.

Methods:

DNA was extracted from blood samples of 155 patients with T2D and 100 controls. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing. To confirm the association between the inheritance of SNP and T2D development, logistic regression analysis was performed.

Results:

For the rs9939609 variant (FTO), the dominant model AA/(AT+TT) revealed significant association with T2D [odds ratio (OR)=2.03, P=0.021], but was non-significant post correction for multiple testing (P=0.002). For the rs13266634 variant (SLC30A8), there was considerable but non-significant difference in the distribution pattern of genotypic polymorphisms between the patients and the controls (P=0.004). Significant association was observed in case of the recessive model (CC+CT)/TT (OR=4.56 P=0.001), after adjusting for age, gender and body mass index. In addition, a significant association (P=0.001) of low-density lipoprotein (mg/dl) could be established with the FTO (rs9926289) polymorphism assuming dominant model.

Interpretation & conclusions:

The current study demonstrated a modest but significant effect of SLC30A8 (rs13266634) polymorphisms on T2D predisposition. Considering the burgeoning prevalence of T2D in the Indian population, the contribution of these genetic variants studied, to the ever-increasing number of T2D cases, appears to be relatively low. This study may serve as a foundation for performing future genome-wide association studies (GWAS) involving larger populations.

Associations between obesity candidate gene polymorphisms (fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), leptin (LEP) and leptin receptor (LEPR)) and dietary intake in pregnant women

Genetic variants associated with dietary intake may be important as factors underlying the development of obesity. We investigated the associations between the obesity candidate genes (fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), leptin (LEP) and leptin receptor) and total energy intake and percentage of energy from macronutrients and ultra-processed foods before and during pregnancy. A sample of 149 pregnant women was followed up in a prospective cohort in Rio de Janeiro, Brazil. A FFQ was administered at 5-13 and 30-36 weeks of gestation. Genotyping was performed using real-time PCR. Associations between polymorphisms and the outcomes were investigated through multiple linear regression and ANCOVA having pre-pregnancy dietary intake as a covariate. The A-allele of FTO-rs9939609 was associated with a -6·5 % (95 % CI -12·3, -0·4) decrease in the percentage of energy from protein and positively associated with the percentage of energy from carbohydrates before pregnancy (β=2·6; 95 % CI 0·5, 4·8) and with a 13·3 % (95 % CI 0·7, 27·5) increase in the total energy intake during pregnancy. The C-allele of MC4R-rs17782313 was associated with a -7·6 % (95 % CI -13·8, -1·0) decrease in the percentage of energy from protein, and positively associated with the percentage of energy from ultra-processed foods (β=5·4; 95 % CI 1·1, 9·8) during pregnancy. ANCOVA results revealed changes in dietary intake from pre-pregnancy to pregnancy for FTO-rs9939609 (percentage of energy from ultra-processed foods, P=0·03), MC4R-rs17782313 (total energy intake, P=0·02) and LEP-rs7799039 (total energy intake, P=0·04; percentage of energy from protein, P=0·04). These findings suggest significant associations between FTO-rs9939609, MC4R-rs17782313 and LEP-rs7799039 genes and the components of dietary intake in pregnant women.

Complex Relationship between Obesity and the Fat Mass and Obesity Locus

In the 21st century, obesity has become a serious problem because of increasing obese patients and numerous metabolic complications. The primary reasons for this situation are environmental and genetic factors. In 2007, FTO (fat mass and obesity associated) was the first gene identified through a genome-wide association study (GWAS) associated with obesity in humans. Subsequently, a cluster of single nucleotide polymorphisms (SNPs) in the first intron of the FTO gene was discovered to be associated with BMI and body composition. Various studies have explored the mechanistic basis behind this association. Thus, emerging evidence showed that FTO plays a key role regulating adipose tissue development and functions in body size and composition. Recent prevalent research topic concentrated in the three neighboring genes of FTO: RPGRIP1L, IRX3 and IRX5, as having a functional link between obesity-associated common variants within FTO and the observed human phenotypes. The purpose of this review is to present a comprehensive picture of the impact of FTO on obesity susceptibility and to illuminate these new studies of FTO function in adipose tissue.

Evaluation of the Causes of Erectile Dysfunction in Patients Undergoing Penile Doppler Ultrasonography in Pakistan

PURPOSE

In patients with erectile dysfunction, it is important to differentiate psychogenic from organic causes. Penile Doppler ultrasonography is a relatively inexpensive and minimally invasive tool for this purpose. This study was conducted to evaluate the causes of erectile dysfunction in an adult male population, using penile Doppler ultrasonography.

MATERIALS AND METHODS

A retrospective study was conducted in a single center. All patients who presented with complaints of erectile dysfunction and underwent penile Doppler ultrasonography between July 2014 and June 2016 were included in this study. All examinations were performed using GE Voluson S6 and GE Logiq P5 devices. Following baseline scans, an intracavernosal injection of 20 μg of prostaglandin E1 was given. Peak systolic and end diastolic velocities were measured in each cavernosal artery. Patients with a peak systolic velocity of <25 cm/s were considered to have arterial insufficiency, while an end diastolic velocity of >5 cm/s was considered to indicate venous incompetence.

RESULTS

Out of 97 patients (mean age, 37.09±11.59 years; range, 19~69 years), 50 patients (51.5%) had normal findings, 24 patients (24.7%) had arterial insufficiency, 15 patients (15.5%) had a venous leak, and 8 patients (8.2%) patients had arterial insufficiency with a venous leak. Psychogenic erectile dysfunction was significantly higher among patients aged ≤40 years, while arterial insufficiency with or without a venous leak was significantly higher among patients aged >40 years (p=0.022).

CONCLUSIONS

A majority of the studied individuals demonstrated no organic cause of erectile dysfunction, thus confirming a high prevalence of the psychogenic etiology, particularly in relatively young individuals.

Association of FTO rs9939609 SNP with Obesity and Obesity- Associated Phenotypes in a North Indian Population

OBJECTIVES

Obesity is a common disorder that has a significant impact on morbidity and mortality. Twin and adoption studies support the genetic influence on variation of obesity, and the estimates of the heritability of body mass index (BMI) is significantly high (30 to 70%). Variants in the fat mass and obesity-associated (FTO) gene have been associated with obesity and obesity-related phenotypes in different populations. The aim of this study was to examine the association of FTO rs9939609 with obesity and related phenotypes in North Indian subjects.  .

METHODS

Gene variants were investigated for association with obesity in 309 obese and 333 non-obese patients. Genotyping of the FTO rs9939609 single nucleotide polymorphism (SNP) was analyzed using Restriction Fragment Length Polymorphism Analysis of PCR-Amplified Fragments. We also measured participants fasting glucose and insulin levels, lipid profile, percentage body fat, fat mass and fat free mass.  .

RESULTS

Waist to hip ratio, systolic blood pressure, diastolic blood pressure, percentage body fat, fat mass, insulin concentration, and homeostasis model assessment index (HOMA-Index) showed a significant difference between the study groups. Significant associations were found for FTO rs9939609 SNP with obesity and obesity-related phenotypes. The significant associations were observed between the rs9939609 SNP and blood pressure, fat mass, insulin, and HOMA-index under a different model.  .

CONCLUSION

This study presents significant association between FTO rs9939609 and obesity defined by BMI and also established the strong association with several measures of obesity in North Indian population.