Association of genetic variation in FTO with risk of obesity and type 2 diabetes with data from 96,551 East and South Asians

Obesity genetics: insights from the Pakistani population

The Pakistani population is extensively diverse, indicating a genetic admixture of European and Central/West Asian migrants with indigenous South Asian gene pools. Pakistanis are organized in different ethnicities/castes based on cultural, linguistic and geographical origin. While Pakistan is facing a rapid nutritional transition, the rising prevalence of obesity is driving a growing burden of health complications and mortality. This represents a unique opportunity for the research community to study the interplay between obesogenic environmental changes and obesity predisposing genes in the time frame of one generation. This review recapitulates the ancestral origins of Pakistani population, the societal determinants of the rise in obesity and its governmental management. We describe the contribution of syndromic, monogenic non-syndromic and polygenic obesity genes identified in the Pakistani population. We then discuss the utility of gene identification approaches based on large consanguineous families and original gene × environment interaction study designs in discovering new obesity genes and causal pathways. Elucidation of the genetic basis of obesity in the Pakistani population may result in improved methods of obesity prevention and treatment globally.

FTO genotype, dietary protein intake, and body weight in a multiethnic population of young adults: a cross-sectional study

BACKGROUND

Variation in the fat mass and obesity-associated gene (FTO) has been associated with susceptibility to obesity, but the association appears to be modified by diet. We investigated whether dietary protein intake modifies the association between FTO variant rs1558902 and body mass index (BMI) and waist circumference in young adults (n = 1491) from the cross-sectional Toronto Nutrigenomics and Health Study.

RESULTS

Lifestyle, genetic, anthropometric, and biochemical data were collected and diet was assessed using a Toronto-modified Willett Food Frequency Questionnaire. General linear models stratified by ethnicity and adjusted for age, sex, and total energy intake were used to examine the association between FTO genotypes and measures of body weight, and whether protein intake modified any of the associations. East Asians who were homozygous for the rs1558902 risk allele (A) had a greater BMI (p = 0.004) and waist circumference (p = 0.03) than T allele carriers. This association was not observed in individuals of Caucasian or South Asian ancestry. Among East Asians, a significant FTO-protein interaction was observed for BMI (p = 0.01) and waist circumference (p = 0.007). Those with low protein intake (≤ 18% total energy intake) who were homozygous for the rs1558902 risk allele (A) had significantly higher BMI (p <  0.0001) and waist circumference (p = 0.0006) compared to carriers of the T allele. These associations were absent in the high protein intake group (> 18% total energy intake). Compared to Caucasians and South Asians, East Asians consumed a significantly higher ratio of animal-to-plant protein (p <  0.05).

CONCLUSIONS

These findings suggest that high dietary protein intake may protect against the effects of risk variants in the FTO gene on BMI and waist circumference.

The interaction of fat mass and obesity associated gene polymorphisms and dietary fiber intake in relation to obesity phenotypes

Controversies surrounding the effectiveness of fiber intake for prevention of obesity can be attributed to differences in the genetic makeup of individuals. This study aims to examining the interaction between dietary fiber intake and common fat mass and obesity–associated (FTO) single-nucleotide polymorphisms (SNPs), in relation to obesity. Subjects of this nested case-control study were selected from among adult participants of the Tehran Lipid and Glucose Study. Cases (n = 627) were individually matched with controls, who had normal weight. Six selected SNPs (rs1421085, rs1121980, rs17817449, rs8050136, rs9939973, and rs3751812) were genotyped by tetra-refractory mutation system-polymerase chain reaction analysis. Genetic risk scores (GRS) were calculated using the weighted method. A significant interaction was observed between total fiber intake and the GRS in relation to obesity (Pinteraction = 0.01); the difference in the risk for obesity was more pronounced in individuals with GRS ≥ 6 who consumed ≥ 14 grams of fiber a day (OR: 2.74, CI: 2.40–3.35 vs Ref.; P trend = 0.0005) than in individuals with GRS < 6 (P trend = 0.34). Dietary fiber intakes modified the association of FTO SNPs and the GRS with general obesity, an effect which was more pronounced in those who consumed high levels of dietary fiber and had a high number of risk alleles.

Common Variations in Perilipin rs1052700 and FTO rs3751812 Gene Variants, and Risk for Obesity and Type-2 Diabetes

BACKGROUND

Perilipins are proteins that coat lipid globules in adipocytes, which are steroid-generating cells that play a central role in lipid storage and breakdown. The FTO gene is associated with type-2 diabetes (T2D) and increased fat mass. In this work the association of perilipin and FTO gene polymorphisms in T2D was investigated.

METHODS

One hundred eighty-three Iranian men and women with T2D, and 174 healthy controls with no known metabolic diseases, participated in the study. The subjects were genotyped using tetra-primer amplification refractory mutation system-polymerase chain reaction (Tetra-ARMS-PCR) and their clinical traits were analyzed.

RESULTS

A significant association was found between the perilipin rs1052700 polymorphism and T2D, and between the FTO rs3751812 polymorphism and obesity (P = 0.03 and 0.003, respectively); however, no significant relationship was found between rs3751812 and T2D.

CONCLUSION

The FTO rs3751812 polymorphism is a major genetic determinant of obesity, but not T2D. The perilipin rs1052700 polymorphism is related to T2D but not obesity.

Genetic association of FTO/IRX region with obesity and overweight in the Polish population

Background/Objectives

Genome-wide association studies (GWAS) have identified many loci associated with body mass index (BMI) in many different populations. Variants in the FTO locus are reported to be one of the strongest genetic predictors of obesity. Recent publications pointed also to a topologically associated domain (TAD) which is identified as a novel region affecting BMI. The TAD area encompasses the IRXB cluster (IRX3, IRX5, IRX6), FTO and RPGRIP1L genes.

Subjects/Methods

In this study, we investigated the relationship between variation of the FTO and IRX genes and obesity in Poles. We presented a case—control association analysis (normal versus overweight and/or obesity group) of Polish adult individuals (N = 5418). We determined whether or not the chromosomal region 16:53 500 000–55 500 000 contains polymorphic variants which are correlated with BMI in Polish population, including sex and age stratified analysis.

Results

The obtained results showed that the problem of weight-height abnormalities differently affects populations of Polish women and men (χ² = 187.1; p<0.0001). From 353 SNPs enrolled to this study, 86 were statistically significant (highest χ² = 15.72; p = 7.35E-05 observed for rs1558902). Linkage disequilibrium (LD) analysis revealed 61 blocks in the tested region of chromosome 16, with 24 SNPs located within the same block (block 8) of approximately 40 kb, in almost complete LD (|D’|>0.98, r²>0.80). We confirmed presence of the genetic susceptibility loci located in intron 1 of the FTO gene, which were correlated with BMI in our study group. For the first time, our analyses revealed strong association of FTO intronic variants (block 8) with overweight in group of men only. We have also identified association of the IRX region with overweight and/or obesity in Polish individuals.

Conclusion

Our study demonstrated how tested SNPs make differential contributions to obesity and overweight risk. We revealed sex dependent differences in the distribution of tested loci which are associated with BMI in the population of Poles.

Modification effects of genetic polymorphisms in FTO, IL-6, and HSPD1 on the associations of diabetes with breast cancer risk and survival

The contribution of diabetes to breast cancer remains uncertain among Chinese females, which may result from different genetic factors. We evaluated the associations of diabetes, combined with the polymorphisms in the genes of fat mass and obesity-associated gene (FTO), interleukin 6 (IL-6), and heat shock protein 60 (HSPD1), with breast cancer risk and survival in a Chinese Han population. The information on the history of diabetes was collected from 1551 incident breast cancer cases and 1605 age-frequency matched controls in Guangzhou, China. In total, 1168 cases were followed up. Diabetes was associated with both an increased risk of breast cancer [OR (95%CI): 1.67 (1.11, 2.52)] and a poor overall survival and progression free survival for breast cancer patients [HRs (95%CIs): 2.66 (1.10, 6.44) and 2.46 (1.29, 4.70), respectively]. IL-6 rs1800796 and HSPD1 rs2605039 had interactions with diabetes on breast cancer risk. Among women with CC genotype of IL-6 rs1800796 or GG genotype of HSPD1 rs2605039, diabetic individuals had a remarkably increased risk of breast cancer compared to non-diabetic women with ORs and 95%CIs of 2.53 (1.45, 4.41) and 6.40 (2.29, 17.87), respectively. GT/TT genotypes of HSPD1 rs2605039 was also associated with a better progression free survival for breast cancer patients [HR (95%CI): 0.70 (0.49, 0.99)]. Our results suggest that the contribution of diabetes to breast cancer risk might be modified by IL-6 rs1800796 and HSPD1 rs2605039. Diabetes and HSPD1 rs2605039 might also influence breast cancer prognosis.

rs9939609 FTO genotype associations with FTO methylation level influences body mass and telomere length in an Australian rural population

BACKGROUND

The fat mass- and obesity-associated (FTO) gene influences energy homeostasis in humans. Although the obesity-related variant, rs9939609 has been replicated across a number of cohort studies, there remains significant variance and a low to modest association. Telomere length is another commonly reported obesity risk factor. We hypothesize understanding the associations between FTO rs9939609 with FTO methylation and telomere length will provide a more accurate assessment of obesity risk.

METHODS

Overall, 942 participants free of diabetes or pre-diabetes were included in the retrospective study. Leukocyte genomic DNA was analyzed for rs9939609 genotyping, FTO gene methylation and leukocyte telomere length (LTL) measurement.

RESULTS

In general linear models, rs9939609 AA genotypes were associated with increased fat percentage (3.15%, P=0.001), fat mass (4.16 kg, P=0.001), body mass index (BMI) (1.38, P=0.006) and waist circumference (3.35 cm, P=0.006), but not with FTO methylation or LTL in this overall population. However, when participants were stratified into higher and lower FTO methylation groups, the AA genotype possesses a 2.04-fold increased obesity risk in comparison to TT genotype (95%CI, 1.07-3.89, P=0.031) in participants with a higher FTO methylation level, but this association was absent in the lower FTO methylation sub-group. Moreover, AT and AA genotype carriers were associated with shorter LTL compared to TT carriers (P=0.020 and P=0.111, respectively) in the higher FTO methylation level group. However, this association was absent in the lower methylation group. Furthermore, FTO gene methylation level was significantly associated with LTL in the 942 samples (P=0.017).

CONCLUSIONS

FTO rs9939609 is associated with obesity risk and LTL in this study, where this association is only observed at higher, but not lower, FTO methylation levels of participants. Our data suggest association of multiple factors, including FTO methylation level, may be involved in one of several mechanisms underlying the commonly reported obesity risk of this FTO polymorphism.

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.

Recent progress in genetics, epigenetics and metagenomics unveils the pathophysiology of human obesity

In high-, middle- and low-income countries, the rising prevalence of obesity is the underlying cause of numerous health complications and increased mortality. Being a complex and heritable disorder, obesity results from the interplay between genetic susceptibility, epigenetics, metagenomics and the environment. Attempts at understanding the genetic basis of obesity have identified numerous genes associated with syndromic monogenic, non-syndromic monogenic, oligogenic and polygenic obesity. The genetics of leanness are also considered relevant as it mirrors some of obesity's aetiologies. In this report, we summarize ten genetically elucidated obesity syndromes, some of which are involved in ciliary functioning. We comprehensively review 11 monogenic obesity genes identified to date and their role in energy maintenance as part of the leptin-melanocortin pathway. With the emergence of genome-wide association studies over the last decade, 227 genetic variants involved in different biological pathways (central nervous system, food sensing and digestion, adipocyte differentiation, insulin signalling, lipid metabolism, muscle and liver biology, gut microbiota) have been associated with polygenic obesity. Advances in obligatory and facilitated epigenetic variation, and gene-environment interaction studies have partly accounted for the missing heritability of obesity and provided additional insight into its aetiology. The role of gut microbiota in obesity pathophysiology, as well as the 12 genes associated with lipodystrophies is discussed. Furthermore, in an attempt to improve future studies and merge the gap between research and clinical practice, we provide suggestions on how high-throughput '-omic' data can be integrated in order to get closer to the new age of personalized medicine.

Body composition and susceptibility to type 2 diabetes: an evolutionary perspective

Type 2 diabetes is rapidly increasing in prevalence worldwide, in concert with epidemics of obesity and sedentary behavior that are themselves tracking economic development. Within this broad pattern, susceptibility to diabetes varies substantially in association with ethnicity and nutritional exposures through the life-course. An evolutionary perspective may help understand why humans are so prone to this condition in modern environments, and why this risk is unequally distributed. A simple conceptual model treats diabetes risk as the function of two interacting traits, namely 'metabolic capacity' which promotes glucose homeostasis, and 'metabolic load' which challenges glucose homoeostasis. This conceptual model helps understand how long-term and more recent trends in body composition can be considered to have shaped variability in diabetes risk. Hominin evolution appears to have continued a broader trend evident in primates, towards lower levels of muscularity. In addition, hominins developed higher levels of body fatness, especially in females in relative terms. These traits most likely evolved as part of a broader reorganization of human life history traits in response to growing levels of ecological instability, enabling both survival during tough periods and reproduction during bountiful periods. Since the emergence of Homo sapiens, populations have diverged in body composition in association with geographical setting and local ecological stresses. These long-term trends in both metabolic capacity and adiposity help explain the overall susceptibility of humans to diabetes in ways that are similar to, and exacerbated by, the effects of nutritional exposures during the life-course.

Association of KALRN, ADIPOQ, and FTO gene polymorphism in type 2 diabetic patients with coronary artery disease: possible predisposing markers

OBJECTIVES

Recently, several genes have been introduced as potential genetic markers for diabetes mellitus and coronary artery diseases (CAD).

METHODS

In this case-control study, the associations of rs2241766 T/G of ADIPOQ, rs9289231 T/G of KALRN, and rs9939609 A/T of FTO polymorphisms with genetic susceptibility to CAD in type 2 diabetic (T2D) patients were investigated. A total of 224 T2D patients undergoing coronary angiography were randomly recruited into the study. Of the total diabetic patients, 152 were also diagnosed with CAD, whereas the rest were control participants. Genotyping of single-nucleotide polymorphisms was performed by high-resolution melting analysis.

RESULTS

Genotype analysis showed that the minor allele (G) frequency of rs2241766 ADIPOQ was statistically significant in the CAD group compared with the control group [odds ratio (OR), 2.779; 95% confidence interval (CI), 1.403-5.504; P=0.003]. Also, it was found that the minor allele (G) frequency of rs9289231 KALRN was significantly associated with the risk of CAD (OR, 2.098; 95% CI, 1.096-4.017; P=0.025). In addition, no significant association was observed between the minor allele (A) of the FTO rs9939609 polymorphism and CAD (OR, 1.088; 95% CI, 0.578-2.015; P=0.788). It is speculated that the GG genotype and the G allele of the rs9289231 polymorphism of KALRN and the rs224766 polymorphism of ADIPOQ genes may be considered genetic risk factors for CAD in T2D patients and genetic variations of these genes may play a major role in the process of these disorders.

CONCLUSION

Our case-control study in the Iranian population suggested a possible association between the mentioned single-nucleotide polymorphisms and CAD in T2D patients. However, further replication studies and comprehensive meta-analyses are required.

FTO Genotype and Type 2 Diabetes Mellitus: Spatial Analysis and Meta-Analysis of 62 Case-Control Studies from Different Regions

Type 2 diabetes mellitus (T2DM) is a global health problem that results from the interaction of environmental factors with genetic variants. Although a number of studies have suggested that genetic polymorphisms in the fat mass and obesity-associated (FTO) gene are associated with T2DM risk, the results have been inconsistent. To investigate whether FTO polymorphisms associate with T2DM risk and whether this association is region-related, we performed this spatial analysis and meta-analysis. More than 60,000 T2DM patients and 90,000 controls from 62 case-control studies were included in this study. Odds ratios (ORs), 95% confidence intervals (CIs) and Moran's I statistic were used to estimate the association between FTO rs9939609, rs8050136, rs1421085, and rs17817499, and T2DM risk in different regions. rs9939609 (OR = 1.15, 95% CI 1.11-1.19) and rs8050136 (OR = 1.14, 95% CI 1.10-1.18) conferred a predisposition to T2DM. After adjustment for body mass index (BMI), the association remained statistically significant for rs9939609 (OR = 1.11, 95% CI 1.05-1.17) and rs8050136 (OR = 1.08, 95% CI 1.03-1.12). In the subgroup analysis of rs9939609 and rs8050136, similar results were observed in East Asia, while no association was found in North America. In South Asia, an association for rs9939609 was revealed but not for rs8050136. In addition, no relationship was found with rs1421085 or rs17817499 regardless of adjustment for BMI. Moran's I statistic showed that significant positive spatial autocorrelations existed in rs9939609 and rs8050136. Studies on rs9939609 and rs8050136 focused on East Asia and South Asia, whereas studies on rs1421085 and rs17817499 were distributed in North America and North Africa. Our data suggest that the associations between FTO rs9939609, rs8050136 and T2DM are region-related, and the two single-nucleotide polymorphisms contribute to an increased risk of T2DM. Future studies should investigate this issue in more regions.

Molecular genetics of human obesity: A comprehensive review

Obesity and its related health complications is a major problem worldwide. Hypothalamus and their signalling molecules play a critical role in the intervening and coordination with energy balance and homeostasis. Genetic factors play a crucial role in determining an individual's predisposition to the weight gain and being obese. In the past few years, several genetic variants were identified as monogenic forms of human obesity having success over common polygenic forms. In the context of molecular genetics, genome-wide association studies (GWAS) approach and their findings signified a number of genetic variants predisposing to obesity. However, the last couple of years, it has also been noticed that alterations in the environmental and epigenetic factors are one of the key causes of obesity. Hence, this review might be helpful in the current scenario of molecular genetics of human obesity, obesity-related health complications (ORHC), and energy homeostasis. Future work based on the clinical discoveries may play a role in the molecular dissection of genetic approaches to find more obesity-susceptible gene loci.

FTO Gene Polymorphism Is Associated with Type 2 Diabetes through Its Effect on Increasing the Maximum BMI in Japanese Men

Aim

Several studies have demonstrated that polymorphisms within the fat-mass and obesity-associated gene (FTO) are associated with type 2 diabetes (T2D). However, whether the effects of the FTO locus on T2D susceptibility are independent of fat-mass increases remains controversial. To investigate this issue, we examined the association of FTO variants with T2D and various aspects of BMI history during adult life in a Japanese population.

Methods

We genotyped SNPs within FTO (rs1121980 and rs1558902) in 760 Japanese patients with T2D who had reached a lifetime maximum BMI (BMI_max) before or at the time of diagnosis and 693 control individuals with information regarding their BMI_max.

Results

The BMI_max showed the strongest association with T2D risk among the BMIs evaluated in this study. In the sex-combined analysis, FTO SNPs were not associated with any of the BMI variables or with T2D, but in sex-stratified analyses, both SNPs were significantly associated with the BMI_max and rs1558902 was associated with T2D in men. The association of the SNPs with T2D remained significant after adjustments for the current BMI and age, whereas the T2D association of the SNP was no longer significant after adjustments for BMI_max and age.

Conclusions

These results suggest that the effects of FTO polymorphisms on T2D susceptibility in Japanese men are mediated through their effect on increasing the BMI_max before or at the time of diagnosis.

Evaluating the transferability of 15 European-derived fasting plasma glucose SNPs in Mexican children and adolescents

Genome wide association studies (GWAS) have identified single-nucleotide polymorphisms (SNPs) that are associated with fasting plasma glucose (FPG) in adult European populations. The contribution of these SNPs to FPG in non-Europeans and children is unclear. We studied the association of 15 GWAS SNPs and a genotype score (GS) with FPG and 7 metabolic traits in 1,421 Mexican children and adolescents from Mexico City. Genotyping of the 15 SNPs was performed using TaqMan Open Array. We used multivariate linear regression models adjusted for age, sex, body mass index standard deviation score, and recruitment center. We identified significant associations between 3 SNPs (G6PC2 (rs560887), GCKR (rs1260326), MTNR1B (rs10830963)), the GS and FPG level. The FPG risk alleles of 11 out of the 15 SNPs (73.3%) displayed significant or non-significant beta values for FPG directionally consistent with those reported in adult European GWAS. The risk allele frequencies for 11 of 15 (73.3%) SNPs differed significantly in Mexican children and adolescents compared to European adults from the 1000G Project, but no significant enrichment in FPG risk alleles was observed in the Mexican population. Our data support a partial transferability of European GWAS FPG association signals in children and adolescents from the admixed Mexican population.

Genetic predisposition to obesity is associated with insulin secretion in Chinese adults: The Cardiometabolic Risk in Chinese (CRC) study

AIMS

The etiological role of obesity in determining diabetes risk among Asians may be different from that among Caucasians. The current study aimed to investigate the association between genetic predisposition to obesity and measures of insulin secretion and resistance in a large Chinese cohort.

METHODS

Study samples were from a community-based health examination survey in central China. A total of 2058 subjects with available biomarkers levels were included in the present study. A genetic risk score (GRS) of obesity was derived on the basis of thirteen Asian-specific body mass index (BMI)-associated variants.

RESULTS

High obesity GRS was significantly associated with increased homeostasis model assessment (HOMA)-B score (β=7.309; P=0.001) but not related to measures of insulin resistance. Adjustment for age, sex, BMI, and levels of lipids did not appreciably change the results. In addition, we found significant interactions between the obesity GRS and measures of body fat distribution including waist circumference (WC; P for interaction=0.004) and neck circumference (NC; P for interaction=0.014) on HOMA-B score.

CONCLUSIONS

Our results suggest that genetic predisposition to obesity may affect beta cell function in Chinese; and body fat distribution may modify the genetic effects.

The Elevated Susceptibility to Diabetes in India: An Evolutionary Perspective

India has rapidly become a "diabetes capital" of the world, despite maintaining high rates of under-nutrition. Indians develop diabetes at younger age and at lower body weights than other populations. Here, we interpret these characteristics in terms of a "capacity-load" model of glucose homeostasis. Specifically, we assume that glycemic control depends on whether the body's "metabolic capacity," referring to traits, such as pancreatic insulin production and muscle glucose clearance, is able to resolve the "metabolic load" generated by high levels of body fat, high dietary glycemic load, and sedentary behavior. We employ data from modern cohorts to support the model and the interpretation that elevated diabetic risk among Indian populations results from the high metabolic load imposed by westernized lifestyles acting on a baseline of low metabolic capacity. We attribute this low metabolic capacity to the low birth weight characteristic of Indian populations, which is associated with short stature and low lean mass in adult life. Using stature as a marker of metabolic capacity, we review archeological and historical evidence to highlight long-term declines in Indian stature associated with adaptation to several ecological stresses. Underlying causes may include increasing population density following the emergence of agriculture, the spread of vegetarian diets, regular famines induced by monsoon failure, and the undermining of agricultural security during the colonial period. The reduced growth and thin physique that characterize Indian populations elevate susceptibility to truncal obesity, and increase the metabolic penalties arising from sedentary behavior and high glycemic diets. Improving metabolic capacity may require multiple generations; in the meantime, efforts to reduce the metabolic load will help ameliorate the situation.

The Role of FTO and Vitamin D for the Weight Loss Effect of Roux-en-Y Gastric Bypass Surgery in Obese Patients

BACKGROUND

A recent study in children demonstrated that the rs9939609 single-nucleotide polymorphism in the fat mass and obesity (FTO) gene influences prospective weight gain, however, only in those who were vitamin D-deficient. If this might also be the case for Roux-en-Y gastric bypass (RYGB), surgery-induced weight loss is however unknown. The objective of this study is to examine if the magnitude of RYGB surgery-induced weight loss after 2 years depends on patients' FTO rs9939609 genotype (i.e., TT, AT, and AA) and presurgery vitamin D status (<50 nmol/L equals deficiency).

METHODS

Before and at 24 months after RYGB surgery, BMI was measured in 210 obese patients (mean BMI 45 kg/m(2), 72 % females). Serum 25-hydroxyvitamin D3 levels were also repeatedly measured. Following surgery, vitamin D was supplemented. Possible weight loss differences between genotypes were tested with multiple linear regressions.

RESULTS

The per-allele effect of each FTO A-allele on excessive BMI loss (EBMIL) was 3 % (P = 0.02). When split by baseline status, the EBMIL of vitamin D-deficient patients carrying AA exceeded that of vitamin D-deficient patients carrying TT by ~14 % (P = 0.03). No such genotypic differences were found in patients without presurgery vitamin D deficiency. Post-surgery serum levels of vitamin D did not differ between groups.

CONCLUSIONS

Our data suggest that presurgery vitamin D levels influence the size of genotype effects of FTO rs9939609 on RYGB surgery-induced weight loss in obese patients.

Interaction between FTO gene variants and lifestyle factors on metabolic traits in an Asian Indian population

Background

Lifestyle factors such as diet and physical activity have been shown to modify the association between fat mass and obesity–associated (FTO) gene variants and metabolic traits in several populations; however, there are no gene-lifestyle interaction studies, to date, among Asian Indians living in India. In this study, we examined whether dietary factors and physical activity modified the association between two FTO single nucleotide polymorphisms (rs8050136 and rs11076023) (SNPs) and obesity traits and type 2 diabetes (T2D).

Methods

The study included 734 unrelated T2D and 884 normal glucose-tolerant (NGT) participants randomly selected from the urban component of the Chennai Urban Rural Epidemiology Study (CURES). Dietary intakes were assessed using a validated interviewer administered semi-quantitative food frequency questionnaire (FFQ). Physical activity was based upon the self-report. Interaction analyses were performed by including the interaction terms in the linear/logistic regression model.

Results

There was a significant interaction between SNP rs8050136 and carbohydrate intake (% energy) (P_interaction = 0.04), where the ‘A’ allele carriers had 2.46 times increased risk of obesity than those with ‘CC’ genotype (P = 3.0 × 10⁻⁵) among individuals in the highest tertile of carbohydrate intake (% energy, 71 %). A significant interaction was also observed between SNP rs11076023 and dietary fibre intake (P_interaction = 0.0008), where individuals with AA genotype who are in the 3^rd tertile of dietary fibre intake had 1.62 cm lower waist circumference than those with ‘T’ allele carriers (P = 0.02). Furthermore, among those who were physically inactive, the ‘A’ allele carriers of the SNP rs8050136 had 1.89 times increased risk of obesity than those with ‘CC’ genotype (P = 4.0 × 10⁻⁵).

Conclusions

This is the first study to provide evidence for a gene-diet and gene-physical activity interaction on obesity and T2D in an Asian Indian population. Our findings suggest that the association between FTO SNPs and obesity might be influenced by carbohydrate and dietary fibre intake and physical inactivity. Further understanding of how FTO gene influences obesity and T2D through dietary and exercise interventions is warranted to advance the development of behavioral intervention and personalised lifestyle strategies, which could reduce the risk of metabolic diseases in this Asian Indian population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0098-6) contains supplementary material, which is available to authorized users.

Investigation of Genetic Variation Underlying Central Obesity amongst South Asians

South Asians are 1/4 of the world's population and have increased susceptibility to central obesity and related cardiometabolic disease. Knowledge of genetic variants affecting risk of central obesity is largely based on genome-wide association studies of common SNPs in Europeans. To evaluate the contribution of DNA sequence variation to the higher levels of central obesity (defined as waist hip ratio adjusted for body mass index, WHR) among South Asians compared to Europeans we carried out: i) a genome-wide association analysis of >6M genetic variants in 10,318 South Asians with focused analysis of population-specific SNPs; ii) an exome-wide association analysis of ~250K SNPs in protein-coding regions in 2,637 South Asians; iii) a comparison of risk allele frequencies and effect sizes of 48 known WHR SNPs in 12,240 South Asians compared to Europeans. In genome-wide analyses, we found no novel associations between common genetic variants and WHR in South Asians at P<5x10-8; variants showing equivocal association with WHR (P<1x10-5) did not replicate at P<0.05 in an independent cohort of South Asians (N = 1,922) or in published, predominantly European meta-analysis data. In the targeted analyses of 122,391 population-specific SNPs we also found no associations with WHR in South Asians at P<0.05 after multiple testing correction. Exome-wide analyses showed no new associations between genetic variants and WHR in South Asians, either individually at P<1.5x10-6 or grouped by gene locus at P<2.5x10-6. At known WHR loci, risk allele frequencies were not higher in South Asians compared to Europeans (P = 0.77), while effect sizes were unexpectedly smaller in South Asians than Europeans (P<5.0x10-8). Our findings argue against an important contribution for population-specific or cosmopolitan genetic variants underlying the increased risk of central obesity in South Asians compared to Europeans.

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.

Association of FTO and near MC4R variants with obesity measures in urban and rural dwelling Sri Lankans

OBJECTIVES

To investigate the association between the fat mass and obesity related (FTO) gene rs9939609 and near melanocortin-4-receptor (MC4R) gene rs17782313 polymorphisms with obesity measures and metabolic parameters in urban and rural dwelling Sri Lankans.

METHODS

535 subjects (60.9% female) from the general adult population (ages 18-70 years) representative of both urban (28.4%) and rural areas of residence were recruited by multi-stage random sampling. Body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) was obtained by standard methods. DNA extracted from whole blood was genotyped using real-time PCR.

RESULTS

The FTO risk genotypes (AA+AT) were associated with higher BMI (p=0.03) and WC (p=0.05) measures as well as categorical obesity (BMI ≥27.5kgm^-2 definition) (OR 1.69 95% CI 1.11-2.56, p=0.01). The near MC4R risk genotypes (CC+CT) were associated with greater BMI (p=0.03) as well as categorical obesity (BMI ≥25kgm^-2 definition) (OR 1.57 95% CI 1.11-2.22, p=0.01). In addition the MC4R risk genotype carriers (CC+CT) had significantly higher fasting blood sugar (FBS) levels compared to the 'TT' genotype carriers independent of BMI (p=0.05). Urban living was associated with significantly greater BMI values for FTO risk genotypes compared to rural living (p=0.02).

CONCLUSIONS

FTO and near MC4R variants are associated with obesity measures in Sri Lankan populations whilst urban living accentuates the obesogenic effect of the FTO polymorphism.

Physical activity attenuates genetic effects on BMI: Results from a study of Chinese adult twins

OBJECTIVE

This study aimed to examine the gene-environment interaction of physical activity and body mass index (BMI) using the Chinese National Twin Registry (CNTR).

METHODS

A total of 19,308 same-sex adult twins from CNTR were included in the analysis. Twin zygosity was determined by self-reported questionnaire. Height and weight were measured using self-reported questionnaire. The vigorous physical activity was defined as greater or equal to five times a week of at least 30 min moderate- or high-intensity physical activity. A twin structural equation model was used to analyze the gene-environment interaction of vigorous exercise with BMI among 13,506 monozygotic twins and 5,802 dizygotic twins.

RESULTS

A structural equation model adjusting for age and sex found vigorous exercise significantly moderated the additive genetic effects (P < 0.001) and shared environmental effects (P < 0.001) on BMI. The genetic contributions to BMI were significantly lower for people who adopted a physically active lifestyle [h(2) = 40%, 95% confidence interval (CI): 35%-46%] than those who were relative sedentary (h(2) = 59%, 95% CI: 52%-66%). The observed gene-physical activity interaction was more pronounced in men than women.

CONCLUSIONS

Our results suggested that adopting a physically active lifestyle may help to reduce the genetic influence on BMI among the Chinese population.

Role of a common variant of Fat Mass and Obesity associated (FTO) gene in obesity and coronary artery disease in subjects from Punjab, Pakistan: a case control study

BACKGROUND

The FTO gene has recently become one of the most extensively investigated genes associated with body mass and has been shown to play a role in cardiovascular diseases as well. The aim of the current study was to investigate the effect of a common variant of FTO gene, rs9939609 in obese and coronary heart disease (CHD) patients of Pakistan and investigate whether it has any influence on the serum biochemical parameters.

METHODS

A total of 970 samples (295 obese, 425 CHD and 250 controls) were genotyped using TaqMan allelic discrimination assay. Serum total cholesterol, HDL-C and triglycerides were measured using spectrophotometric methods. LDL-C was calculated by Friedwalds equation. Statistical analysis was done by SPSS version 22.

RESULTS

Results showed moderately high minor allele frequency (MAF) in obese and CHD cases as compared to controls (obese = 0.381 CAD = 0.361 and controls = 0.286). The variant was significantly associated with obesity and CAD (obesity odds ratio (OR) = 1.54, confidence interval (CI) = 1.07-2.21, p = 0.0009; CHD OR = 1.43, CI = 1.02-2.01, p = 0.004) in Pakistan. The risk allele did not show a significant association with any of the lipid trait tested (p > 0.05) but a strong association was observed with plasma glucose levels (obese p = 0.001, CAD p = 0.014, controls p = 0.019).

CONCLUSION

In conclusion, the variant was associated with obesity and CAD in the studied subjects and its possible effect may involve the blood sugar metabolism but not serum lipid chemistry.

Effects of Obesity Related Genetic Variations on Visceral and Subcutaneous Fat Distribution in a Chinese Population

Genome-wide association studies (GWAS) have uncovered numerous variants associated with body mass index (BMI), waist circumference, and waist-to-hip ratio. Our study aims to investigate how these variants are linked to fat distribution. We genotyped 56 validated variants of BMI, waist circumference, and waist-to-hip ratio in 2958 subjects from Chinese community-based populations and performed linear regression analyses to determine the association with visceral fat area (VFA) and subcutaneous fat area (SFA) imaged by magnetic resonance imaging (MRI). We found rs671 in ALDH2 exhibited the significant associations with VFA and the VFA-SFA ratio in all subjects (P = 9.64 × 10⁻⁵ and 6.54 × 10⁻⁴). rs17782313 near MC4R for VFA and rs4846567 near LYPLAL1 for SFA were found in females only (P = 2.93 × 10⁻⁴ and 0.0015), whereas rs671 in ALDH2 for VFA and the VFA-SFA ratio was restricted to males (P = 1.75 × 10⁻⁸ and 4.43 × 10⁻⁸). Given the robust association of rs671 with alcohol consumption, we next demonstrated the primary effects of rs671 on VFA and the VFA-SFA ratio were restricted to drinkers (P = 1.45 × 10⁻⁴ and 4.65 × 10⁻³). Our data implied that variants of MC4R and LYPLAL1 modulated body fat distribution with sexual dimorphism and that alcohol consumption may mediate the impact of the ALDH2 locus on visceral fat in a Chinese population.

Combined effects of FTO rs9939609 and MC4R rs17782313 on elevated nocturnal blood pressure in the Chinese Han population

AIM

In this study we investigated the association of FTO rs9939609 and MC4R rs17782313 with elevated blood pressure in the Chinese Han population, and analysed the relationship between the rs9939609 and rs17782313 variants.

METHODS

We tested the rs9939609 and rs17782313 variants with the sequence-retrieval method.

RESULTS

The increase in odds ratios of the A allele of rs9939609 and the C allele of rs17782313 for nocturnal blood pressure were 1.37 and 1.69. The nocturnal blood pressure of participants simultaneously carrying the A and C alleles was significantly higher than the blood pressure of those carrying neither FTO nor MC4R risk alleles (p < 0.05), and that of the controls carrying only the A or C alleles (p < 0.05). No association between the FTO or MC4R genes with daytime hypertension was found in this Chinese population (p > 0.05).

CONCLUSION

Our data suggest that the rs9939609 and rs17782313 variants may be significantly associated with nocturnal but not daytime blood pressure levels and their combined effects were significant in this Chinese Han population.

Insights into the Genetic Susceptibility to Type 2 Diabetes from Genome-Wide Association Studies of Obesity-Related Traits

Obesity and type 2 diabetes (T2D) are common and complex metabolic diseases, which are caused by an interchange between environmental and genetic factors. Recently, a number of large-scale genome-wide association studies (GWAS) have improved our knowledge of the genetic architecture and biological mechanisms of these diseases. Currently, more than ~250 genetic loci have been found for monogenic, syndromic, or common forms of T2D and/or obesity-related traits. In this review, we discuss the implications of these GWAS for obesity and T2D, and investigate the overlap of loci for obesity-related traits and T2D, highlighting potential mechanisms that affect T2D susceptibility.

Characterizing the genetic risk for Type 2 diabetes in a Malaysian multi-ethnic cohort

AIMS

To characterize the association with Type 2 diabetes of known Type 2 diabetes risk variants in people in Malaysia of Malay, Chinese and Indian ancestry who participated in the Malaysian Cohort project.

METHODS

We genotyped 1604 people of Malay ancestry (722 cases, 882 controls), 1654 of Chinese ancestry (819 cases, 835 controls) and 1728 of Indian ancestry (851 cases, 877 controls). First, 62 candidate single-nucleotide polymorphisms previously associated with Type 2 diabetes were assessed for association via logistic regression within ancestral groups and then across ancestral groups using a meta-analysis. Second, estimated odds ratios were assessed for excess directional concordance with previously studied populations. Third, a genetic risk score aggregating allele dosage across the candidate single-nucleotide polymorphisms was tested for association within and across ancestral groups.

RESULTS

After Bonferroni correction, seven individual single-nucleotide polymorphisms were associated with Type 2 diabetes in the combined Malaysian sample. We observed a highly significant excess in concordance of effect directions between Malaysian and previously studied populations. The genetic risk score was strongly associated with Type 2 diabetes in all Malaysian groups, explaining from 1.0 to 1.7% of total Type 2 diabetes risk variance.

CONCLUSION

This study suggests there is substantial overlap of the genetic risk alleles underlying Type 2 diabetes in Malaysian and other populations.

Prevalence of and Risk Factors for Type 2 Diabetes Mellitus in Vietnam: A Systematic Review

This systematic review examined trends in the prevalence of type 2 diabetes mellitus (T2DM) and identified its risk factors among adults in Vietnam. PubMed, Web of Science, Wiley Online Library, and Scopus databases were searched to identify relevant literature. The search yielded 10 studies, including 2 national surveys and 8 regional investigations. National prevalence estimates of T2DM were 2.7% in 2002 and 5.4% in 2012. The estimates for the northern region were 1.4% in 1994 and 3.7% in 2012 and those for the southern region were 3.8% in 2004, 7.0% in 2008, and 12.4% in 2010. The major determinants of T2DM included older age, urban residence, high levels of body and abdominal fat, physical inactivity, sedentary lifestyle, genetic factors, and hypertension. The prevalence rate by gender was variable in both national and regional studies. There was insufficient information available on some potentially important risk factors such as smoking, dietary intake, income, and educational level. Our review signifies a rapidly growing prevalence of T2DM in Vietnam and suggests that extra effort is required to prevent and control this disease.

The obesity-related FTO gene variant associates with the risk of recurrent miscarriage

OBJECTIVE

To investigate the association of the fat mass and obesity associated gene (FTO) rs9939609 single nucleotide polymorphism with recurrent miscarriage.

DESIGN

Candidate gene association study.

SETTING

Human Genetics Unit, Colombo, Sri Lanka.

POPULATION

A total of 202 Sinhalese women with two or more first-trimester miscarriages and no living children (cases) and 202 age- and ethnicity-matched women with no history of miscarriage and having two or more living children (controls).

METHODS

Peripheral blood was collected from the participants and DNA was extracted. Genotyping was performed at the Australian genome Research Facility using the Sequenom MassARRAY system. Genotype and allele frequencies of cases were compared with controls using chi-squared testing.

MAIN OUTCOME MEASURES

The prevalence of the single nucleotide polymorphism in cases and controls.

RESULTS

The mean age of the women in the recurrent miscarriage group was 31.9 ± 0.4 years and that of the control group was 32.3 ± 0.3 years. Of the women in the recurrent miscarriage group, 140 (69.3%) had experienced three or more first-trimester miscarriages. The prevalence of the AA genotype [p = 0.0002, odds ratio (95% CI) = 3.8 (1.8-8.0)] and A allele [p = 0.002, odds ratio (95% CI) = 1.6 (1.2-2.2)] of the FTO rs9939609 single nucleotide polymorphism were increased in women in the recurrent miscarriage group compared with the control group.

CONCLUSION

The obesity-related FTO rs9939609 single nucleotide polymorphism associates with recurrent miscarriage. This finding warrants further investigation with controlling for important factors such as body mass index, diabetes and cardiovascular disease status. The single nucleotide polymorphism may be useful in predicting the risk of recurrent miscarriage.

The obesity-risk variant of FTO is inversely related with the So-Eum constitutional type: genome-wide association and replication analyses

Background

Body constitutional types described in the traditional Korean medicine system, Sasang constitutional medicine, are heritable, as has been revealed by twin and family studies. Thus, individuals with the same constitution type usually have similar pathophysiological and psychological traits. In several recent genome-wide association (GWA) analyses performed to identify constitution-associated variants, the association signals were not replicated due to small sample size and dissimilar, non-objective methods for classification of the constitutional types.

Methods

We conducted GWA analysis and followed replication analysis in two large populations (5,490 subjects: 3,810 subjects at discovery stage and 1,680 subjects at replication stage) to identify the replicable constitution-associated variants, wherein subjects with the highest tertile of constitution probability values versus the reference with the lowest tertile of the values obtained from a recently developed constitution analysis tool were compared.

Results

We found that the obesity-risk variant in intron 1 of the fat mass and obesity–associated (FTO) gene was replicably inversely associated with the So-Eum (SE) type, characterized by reduced appetite, slim body, and cautious personality (rs7193144 in combined samples: odds ratio = 0.729, p = 1.47 × 10⁻⁷), and substantial association signal remained after controlling for body mass index (BMI). In contrast, the association of the variant with the Tae-Eum type, characterized by high body mass, disappeared after controlling BMI.

Conclusions

In summary, the obesity-risk variant in FTO intron 1 was inversely associated with the SE type, independent of BMI, which corresponded well with the characteristics of the SE type, such as the lowest body mass and lowest susceptibility to metabolic disorders among the constitutional types. Therefore, the obesity-risk variant of FTO associated with body mass increase might be involved in the determination of body constitution type.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-015-0609-4) contains supplementary material, which is available to authorized users.

Is the adiposity-associated FTO gene variant related to all-cause mortality independent of adiposity? Meta-analysis of data from 169,551 Caucasian adults

Previously, a single nucleotide polymorphism (SNP), rs9939609, in the FTO gene showed a much stronger association with all-cause mortality than expected from its association with body mass index (BMI), body fat mass index (FMI) and waist circumference (WC). This finding implies that the SNP has strong pleiotropic effects on adiposity and adiposity-independent pathological pathways that leads to increased mortality. To investigate this further, we conducted a meta-analysis of similar data from 34 longitudinal studies including 169,551 adult Caucasians among whom 27,100 died during follow-up. Linear regression showed that the minor allele of the FTO SNP was associated with greater BMI (n = 169,551; 0.32 kg m(-2) ; 95% CI 0.28-0.32, P < 1 × 10(-32) ), WC (n = 152,631; 0.76 cm; 0.68-0.84, P < 1 × 10(-32) ) and FMI (n = 48,192; 0.17 kg m(-2) ; 0.13-0.22, P = 1.0 × 10(-13) ). Cox proportional hazard regression analyses for mortality showed that the hazards ratio (HR) for the minor allele of the FTO SNPs was 1.02 (1.00-1.04, P = 0.097), but the apparent excess risk was eliminated after adjustment for BMI and WC (HR: 1.00; 0.98-1.03, P = 0.662) and for FMI (HR: 1.00; 0.96-1.04, P = 0.932). In conclusion, this study does not support that the FTO SNP is associated with all-cause mortality independently of the adiposity phenotypes.

Ghrelin

BACKGROUND

The gastrointestinal peptide hormone ghrelin was discovered in 1999 as the endogenous ligand of the growth hormone secretagogue receptor. Increasing evidence supports more complicated and nuanced roles for the hormone, which go beyond the regulation of systemic energy metabolism.

SCOPE OF REVIEW

In this review, we discuss the diverse biological functions of ghrelin, the regulation of its secretion, and address questions that still remain 15 years after its discovery.

MAJOR CONCLUSIONS

In recent years, ghrelin has been found to have a plethora of central and peripheral actions in distinct areas including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation and glucose metabolism.

Obesity and genomics: role of technology in unraveling the complex genetic architecture of obesity

Obesity is a complex and multifactorial disease that occurs as a result of the interaction between "obesogenic" environmental factors and genetic components. Although the genetic component of obesity is clear from the heritability studies, the genetic basis remains largely elusive. Successes have been achieved in identifying the causal genes for monogenic obesity using animal models and linkage studies, but these approaches are not fruitful for polygenic obesity. The developments of genome-wide association approach have brought breakthrough discovery of genetic variants for polygenic obesity where tens of new susceptibility loci were identified. However, the common SNPs only accounted for a proportion of heritability. The arrival of NGS technologies and completion of 1000 Genomes Project have brought other new methods to dissect the genetic architecture of obesity, for example, the use of exome genotyping arrays and deep sequencing of candidate loci identified from GWAS to study rare variants. In this review, we summarize and discuss the developments of these genetic approaches in human obesity.

Significance of a common variant in the CDKAL1 gene with susceptibility to type 2 diabetes mellitus in Iranian population

Background:

Type 2 diabetes mellitus (T2DM) is a worldwide problem that threatens the public health and economies of all countries. A multifactorial etiology and interaction between environmental factors and genetic components are responsible for triggering and progression of T2DM. Recently, rs7754840 single nucleotide polymorphism (SNP) in the CDKAL1 gene was reported to be associated with T2DM in various populations. However, due to inconsistent results in various populations about the association of rs7754840 with T2DM, and lack of information in the Iranian population, we have evaluated its association with T2DM in a subset of the Iranian population from Isfahan province, central part of Iran.

Materials and Methods:

The study included 140 patients and 140 controls selected based on the World Health Organization guidelines. Genomic DNA was extracted from blood samples and the rs7754840 SNP was genotyped using a polymerase chain reaction-restriction fragment length polymorphism assay with specific primers and restriction enzyme (Ac1I).

Results:

The frequency of the C allele in the cases was higher than that in the controls (72.9% vs. 65%; P = 0.045). Using logistic regression analysis, we found a significant risk association of CC genotype with T2DM susceptibility (OR = 2.319, 95% CI = 1.436-3.744, P = 0.001). Furthermore, compared with the CC genotype, individuals with the GC genotype had a lower risk (protective association) of developing T2DM (OR = 0.332, 95% CI = 0.202-0.547, P < 0.001).

Conclusions:

We confirmed that there is a significant risk association between rs7754840 polymorphism and development of T2DM in a subset of the Iranian population from Isfahan province.

The fat mass and obesity-associated (FTO) gene variant rs9939609 predicts long-term incidence of cardiovascular disease and related death independent of the traditional risk factors

OBJECTIVE AND METHODS

The impact of the rs9939609 FTO variant on cardiovascular events was investigated in the 19-year follow-up of subjects recruited to the OPERA study.

RESULTS

A total of 212 cardiovascular disease (CVD) and 152 coronary heart disease (CHD) events or deaths occurred during follow-up. The logistic regression analysis revealed that among the AA genotype the incidence of CHD (OR 1.905; 95% CI 1.250-2.903, p = 0.001) and CVD (OR 1.849; 1.265-2.702, p = 0.003) events or death was significantly higher when adjusted for age, sex, and study group. After further adjustment with BMI, smoking status, systolic blood pressure, and low-density lipoprotein cholesterol, the higher incidence of CHD and CVD events or death among subjects with the AA genotype remained significant (OR 1.895; p = 0.002 and p = 0.004, respectively). In Cox regression analysis, the AA genotype displayed a higher rate of CVD and CHD death when the model was adjusted for sex, age, and study group (p = 0.006 and p = 0.046). FTO rs9939609 AA genotype improved the C-index of the final predictive model from 0.709 to 0.715. In reclassification analyses, the integrated discrimination index was significant 0.011 (p = 0.010).

CONCLUSION

The AA genotype of FTO rs9939609 seems to be associated with a higher risk of CVD, and this phenomenon seems to be independent of the traditional risk factors for atherosclerosis.

Advancement in genetic variants conferring obesity susceptibility from genome-wide association studies

Obesity prevalence has increased in recent years. Lifestyle change fuels obesity, but genetic factors cause more than 50% of average variations in obesity. The advent of genome-wide association studies (GWAS) has hastened the progress of polygenic obesity research. As of this writing, more than 73 obesity susceptibility loci have been identified in ethnic groups through GWAS. The identified loci explain only 2% to 4% of obesity heritability, thereby indicating that a large proportion of loci remain undiscovered. Thus, the next step is to identify and confirm novel loci, which may exhibit smaller effects and lower allele frequencies than established loci. However, achieving these tasks has been difficult for researchers. GWAS help researchers discover the causal loci. Moreover, numerous biological studies have been performed on the polygenic effects on obesity, such as studies on fat mass- and obesity-associated gene (FTO), but the role of these polygenic effects in the mechanism of obesity remains unclear. Thus, obesity-causing variations should be identified, and insights into the biology of polygenic effects on obesity are needed.

Association of Glutathione-S-Transferase (GSTM1 and GSTT1) and FTO Gene Polymorphisms with Type 2 Diabetes Mellitus Cases in Northern India

Type 2 diabetes mellitus (T2DM) is growing in an epidemic manner across the world and India has the world's largest number of diabetic subjects. The present study was carried out to investigate the association of glutathione-S-transferase (GSTM1, GSTT1) and fat mass and obesity associated (FTO) gene polymorphisms with T2DM patients and controls, and its role in increasing the susceptibility to T2DM. A total of 198 subjects (101 T2DM patients and 97 controls) participated in this study. GSTM1, GSTT1 and FTO gene polymorphisms in the patients and controls were evaluated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). We observed significant association of GSTM1 positive (p = 0.046) and GSTM1 null (p = 0.046) genotypes with T2DM, while no significant association was found with the FTO gene polymorphism in our study. It seems that the GSTM1 gene polymorphism can be a predictive marker for early identification of a population at risk of T2DM. The potential role of GST and FTO gene polymorphisms as a marker of susceptibility to T2DM needs further studies in a larger number of patients.

Association between maternal single nucleotide polymorphisms in genes regulating glucose metabolism and risk for neural tube defects in offspring

BACKGROUND

Maternal pregestational hyperglycemia, diabetes, and obesity are well-established risk factors for neural tube defects (NTDs). As a common underlying mechanism, the imbalance of glucose homeostasis is directly related to the development of NTDs. Polymorphisms in genes regulating glucose metabolism in women may impact their chance of having an NTD-affected pregnancy.

METHODS

We conducted a two-stage case-control study to investigate the association between maternal genetic variants in genes regulating glucose metabolism and risk for NTDs. The cases were 547 women who gave birth to a child with an NTD (anencephaly, spina bifida, or encephalocele); the controls were 543 women who gave birth to a full-term healthy infant. In the first stage, 12 single nucleotide polymorphisms were genotyped in 160 cases and 162 controls. In the second stage, five single nucleotide polymorphisms found in the first stage and potentially associated with NTD risk were genotyped for validation, in an additional 387 cases and 381 controls.

RESULTS

Combined analysis of data from the two stages showed an association between maternal AA genotype of GCKR rs780094 and increased risk for total NTDs [odds ratio, 1.73; 95% confidence interval, 1.16-2.59) and spina bifida subtype [odds ratio, 1.83; 95% confidence interval, 1.16-2.88). No association was found between the other four single nucleotide polymorphisms (LEPR rs1137100, HK1 rs748235, HHEX rs5015480, KCNQ1 rs2237892) and NTD risk.

CONCLUSION

The AA genotype in maternal GCKR rs780094 is associated with an increased risk for NTDs and spina bifida in the Chinese population.

FTO rs9939609 polymorphism is associated with metabolic disturbances and response to HCV therapy in HIV/HCV-coinfected patients

BACKGROUND

The Fat Mass and Obesity-Associated Protein (FTO) gene rs9939609 single nucleotide polymorphism (SNP) has been associated with obesity, metabolic syndrome, insulin resistance (IR), and type 2 diabetes mellitus in the general population. The aim of our study was to examine for the first time the association of the rs9939609 polymorphism with metabolic disturbances, liver disease and virologic response to hepatitis C virus (HCV) therapy with pegylated-interferon-alpha plus ribavirin (pegIFNα/RBV) in human immunodeficiency virus (HIV)/HCV coinfected patients.

METHODS

We carried out a cross-sectional study in 261 patients, of whom 178 were subsequently treated with pegIFNα/RBV therapy. FTO rs9939609 and IFNL3 rs12980275 polymorphisms were genotyped by GoldenGate®. The main outcomes were: 1) metabolic disturbances: insulin resistance (homeostatic model assessment (HOMA-IR)) and overweight (body mass index (BMI)); 2) liver disease (Metavir score): significant fibrosis (F ≥2) and steatosis (>10% fatty hepatocytes); and 3) virologic response to HCV treatment: sustained virologic response (SVR).

RESULTS

The rs9939609 AA genotype was associated with higher values of BMI (adjusted arithmetic mean ratio (aAMR) = 1.08; 95% confidence interval (95%CI) = 1.03 to 1.14; P = 0.002) and HOMA-IR (aAMR = 1.32; 95%CI = 1.03 to 1.69; P = 0.027). Patients with an rs9939609 AA genotype had higher likelihoods of achieving values of BMI ≥27.5 kg/m2 (adjusted odds ratio (aOR) = 3.46; 95%CI =1.17 to 10.21; P = 0.024), HOMA-IR ≥2.5 (aOR = 2.09; 95%CI = 1.02 to 4.32; P = 0.045), significant fibrosis (aOR = 2.34; 95%CI =1.02 to 5.36; P = 0.045) and steatosis (aOR = 3.65; 95%CI = 1.29 to 10.36; P = 0.015). The rs9939609 AT/AA genotype decreased the likelihood of achieving SVR (aOR = 0.58; 95%CI = 0.34 to 0.99; P = 0.044). A decision tree was performed with the genotypes of HCV, IFNL3 and FTO. The incorporation of rs9939609 significantly improves the prediction of SVR (P <0.05). The overall accuracy was 68.2%.

CONCLUSIONS

Patients carrying the unfavourable AT/AA genotype of rs9939609 polymorphism had higher odds of metabolic disturbances and a lower likelihood of achieving successful virologic response to HCV therapy.

Associations of genetic variants in/near body mass index-associated genes with type 2 diabetes: a systematic meta-analysis

OBJECTIVE

Genome-wide association studies have identified many obesity/body mass index (BMI)-associated loci in Europeans and East Asians. Since then, a large number of studies have investigated the role of BMI-associated loci in the development of type 2 diabetes (T2D). However, the results have been inconsistent. The objective of this study was to investigate the associations of eleven obesity/BMI loci with T2D risk and explore how BMI influences this risk.

METHODS

We retrieved published literature from PubMed and Embase. The pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated using fixed- or random-effect models.

RESULTS

In the meta-analysis of 42 studies for 11 obesity/BMI-associated loci, we observed a statistically significant association of the FTO rs9939609 polymorphism (66 425 T2D cases/239 689 normoglycaemic subjects; P = 1·00 × 10(-41) ) and six other variants with T2D risk (17 915 T2D cases/27 531 normoglycaemic individuals: n = 40 629-130 001; all P < 0·001 for SH2B1 rs7498665, FAIM2 rs7138803, TMEM18 rs7561317, GNPDA2 rs10938397, BDNF rs925946 and NEGR1 rs2568958). After adjustment for BMI, the association remained statistically significant for four of the seven variants (all P < 0·05 for FTO rs9939609, SH2B1 rs7498665, FAIM2 rs7138803, GNPDA2 rs10938397). Subgroup analysis by ethnicity demonstrated similar results.

CONCLUSIONS

This meta-analysis indicates that several BMI-associated variants are significantly associated with T2D risk. Some variants increase the T2D risk independent of obesity, while others mediate this risk through obesity.

Association of genetic predisposition to obesity with type 2 diabetes risk in Han Chinese individuals

AIMS/HYPOTHESIS

Obesity is a major risk factor for type 2 diabetes, but little is known about the contribution of BMI-associated loci to type 2 diabetes risk in East Asian populations.

METHODS

In this study, 30 known BMI-associated variants and a genetic risk score (GRS) calculated by summing the BMI-increasing alleles of these variants were tested for associations with type 2 diabetes and related glycaemic traits in 1,873 cases of type 2 diabetes and 1,839 controls in Han Chinese individuals. Logistic and linear regression analyses were performed to determine the association with type 2 diabetes risk or related glycaemic traits, respectively, under an additive model with or without adjustment for BMI.

RESULTS

The GRS was significantly associated with increased BMI (β [SE] 0.070 [0.016]; p = 1.33 × 0(-5)) in the overall population. Each additional BMI-increasing allele in the GRS increased type 2 diabetes risk by 1.029-fold (95% CI 1.008, 1.050; p = 0.0056) without adjustment for BMI, and the association was slightly attenuated after adjustment for BMI (OR 1.022; 95% CI 1.002, 1.043; p = 0.035). In non-diabetic controls, the GRS was also associated with HOMA of beta cell function (HOMA-B) with adjustment for BMI (β [SE] -0.876 [0.345]; p = 0.011). Notably, the association of GRS with type 2 diabetes was abolished after adjusting for HOMA-B (OR 1.012; 95% CI 0.986, 1.039; p = 0.380).

CONCLUSIONS/INTERPRETATION

Our results suggested that genetic predisposition to obesity leads to increased risk of type 2 diabetes, independent of BMI and partly through impaired beta cell function.

Metabolically healthy and unhealthy obese--the 2013 Stock Conference report

Obesity is closely associated with cardiovascular diseases and type 2 diabetes, but some obese individuals, despite having excessive body fat, exhibit metabolic health that is comparable with that of lean individuals. The 'healthy obese' phenotype was described in the 1980s, but major advancements in its characterization were only made in the past five years. During this time, several new mechanisms that may be involved in health preservation in obesity were proposed through the use of transgenic animal models, use of sophisticated imaging techniques and in vivo measurements of insulin sensitivity. However, the main obstacle in advancing our understanding of the metabolically healthy obese phenotype and its related long-term health risks is the lack of a standardized definition. Here, we summarize the proceedings of the 13th Stock Conference of the International Association of the Study of Obesity. We describe the current research and highlight the unanswered questions and gaps in the field. Better understanding of metabolic health in obesity will assist in therapeutic decision-making and help identify therapeutic targets to improve metabolic health in obesity.

The effects of genetic variation in FTO rs9939609 on obesity and dietary preferences in Chinese Han children and adolescents

The association of the rs9939609 single nucleotide polymorphism in FTO gene with obesity has been extensively investigated in studies of populations of European, African, and Asian ancestry. However, inconsistent results have been reported in Asian populations, and the relationship of FTO variation and dietary behaviors has only rarely been examined in Chinese children and adolescents. The aim of this study was to assess the association of rs9939609 with obesity and dietary preferences in childhood in a Chinese population. Epidemiological data including dietary preferences were collected in interviews using survey questionnaires, and rs9939609 genotype was determined by real-time PCR. The associations of rs9939609 genotypes with obesity and dietary preferences were analyzed by multivariate logistic regression using both additive and dominant models. The results showed that subjects with a TA or AA genotype had an increased risk of obesity compared with the TT participants; the odds ratios (ORs) were 1.47 (95% CI: 1.25–1.71, P = 1.73×10⁻⁶), and 3.32 (95% CI: 2.01–5.47, P = 2.68×10⁻⁶), respectively. After adjusting for age and gender, body mass index, waist circumference, hip circumference, systolic blood pressure, diastolic blood pressure, fasting blood glucose, triglycerides, and low-density lipoprotein cholesterol were higher, and high-density lipoprotein cholesterol was lower in TA and AA participants than in those with the TT genotype. After additionally controlling for body mass index, the association remained significant only for systolic blood pressure (P = 0.005). Compared with TT participants, those with the AA genotype were more likely to prefer a meat-based diet (OR = 2.81, 95% CI: 1.52–5.21). The combined OR for obesity in participants with TA/AA genotypes and preference for a meat-based diet was 4.04 (95% CI: 2.8–5.81) compared with the TT participants who preferred a plant-based diet. These findings indicate the genetic variation of rs9939609 is associated with obesity and dietary preferences in Chinese children and adolescents.