Molecular genetics of human obesity: A comprehensive review

Development of Obesity: The Driver and the Passenger

Obesity has reached epidemic proportions and is one of the greatest challenges for public health in the twenty-first century. The macronutrient composition of diets, in particular the amount and ratio of carbohydrates, fat and protein, have received considerable attention in recent decades due to its potential relevance to the development of obesity and weight loss. The effects of various macronutrients on body weight regulation are still under debate. High-carbohydrate diets, and particularly high-fat diets, have been blamed for the increase in the prevalence of obesity. This paper shows that neither fat nor carbohydrates are fattening per se. Mixed diets with substantial amounts of fat and high-glycemic carbohydrates, like current WDs, are required to promote weight gain and obesity. High-glycemic carbohydrates are the active partner (the "driver"), which promotes fat storage through its insulinogenic effect, while fat is the passive partner (the "passenger") on the way to obesity. Elevated insulin levels (postprandial, but more importantly due to hypersecretion and hyperinsulinemia) promote fat storage and play a key role in obesogenesis and the obesity epidemic. Furthermore, mixed diets high in high-glycemic carbohydrates and fat promote fetal programming, with long-term adverse impacts on the offspring, including insulin hypersecretion, (childhood) obesity and metabolic diseases. Maternal obesity and high weight gain during pregnancy have also been linked to deleterious effects on fetal programming. As the global obesity epidemic increasingly affects women of reproductive age, a significant percentage of fetuses will experience fetal programming with a tendency towards obesity - a self-reinforcing process that further fuels the epidemic. A change in lifestyle and diet composition is needed to prevent or limit the development of obesity and related diseases.

Obesity: novel and unusual predisposing factors

To tackle the complexity of the global obesity epidemic, it is important to consider the many predisposing factors that underlie progressive and sustained weight gain. Some of the biological drivers for weight gain following initial weight loss include persistent changes in appetite hormones [including ghrelin and postprandial plasma peptide YY (PYY)], and 'persistent metabolic adaptation'. However, many factors within our busy, stressful modern-day environment seem to conspire towards promotion of weight gain. These include the effects of sleep deprivation on appetite regulation, and the effects of modern-day technology on 'attention competition'. These factors, combined with cultural and societal factors can result in a 'mindless' attitude regarding eating-related behaviour that is likely to predispose to weight gain. In addition to the external environment, our internal environment within the gut has also changed radically within the last few decades, resulting from changes in fibre intake, and increased ingestion of highly refined, sterilised and processed foods. Although contentious, these dietary changes have implications for our gut microbiota, and possible downstream effects on control of appetite and metabolism. In this brief review, we consider some of the novel predisposing factors for weight gain within our modern-day 21st century environments (both external and internal), and explore how legal terminology can help to conceptualise the numerous factors that contribute towards weight gain, and, ultimately the global obesity epidemic.

Novel Mutations in Obesity-related Genes in Turkish Children with Non-syndromic Early Onset Severe Obesity: A Multicentre Study

OBJECTIVE

Non syndromic monogenic obesity is a rare cause of early onset severe obesity in the childhood period. This form may not be distinguishable from other forms of severe obesity without genetic analysis, particularly if patients do not exibit any physical abnormalities or developmental delay. The aim of this study was to screen 41 different obesity-related genes in children with non-syndromic early onset severe obesity.

METHODS

Children with severe (body mass index-standard deviation score >3) and early onset (<7 years) obesity were screened by next-generation sequencing based, targeted DNA custom panel for 41 known-obesity-related genes and the results were confirmed by Sanger technique.

RESULTS

Six novel variants were identified in five candidate genes in seven out of 105 children with severe obesity; two in SIM1 (p.W306C and p.Q36X), one in POMC (p.Y160H), one in PCSK1 (p.W130G fs Ter8), two in MC4R (p.D126E) and one in LEPR (p.Q4H). Additionally, two previously known variations in MC4R were identified in four patients (p.R165W in three, and p.V166I in one).

CONCLUSION

We identified six novel and four previously described variants in six obesity-related genes in 11 out of 105 childrens with early onset severe obesity. The prevalence of monogenic obesity was 10.4% in our cohort.

Screening of 31 genes involved in monogenic forms of obesity in 23 Pakistani probands with early-onset childhood obesity: a case report

BACKGROUND

Consanguine families display a high degree of homozygosity which increases the risk of family members suffering from autosomal recessive disorders. Thus, homozygous mutations in monogenic obesity genes may be a more frequent cause of childhood obesity in a consanguineous population.

METHODS

We identified 23 probands from 23 Pakistani families displaying autosomal recessive obesity. We have previously excluded mutations in MC4R, LEP and LEPR in all probands. Using a chip-based, target-region capture array, 31 genes involved in monogenic forms of obesity, were screened in all probands.

RESULTS

We identified 31 rare non-synonymous possibly pathogenic variants (28 missense and three nonsense) within the 31 selected genes. All variants were heterozygous, thus no homozygous pathogenic variants were found. Two of the rare heterozygous nonsense variants identified (p.R75X and p.R481X) were found in BBS9 within one proband, suggesting that obesity is caused by compound heterozygosity. Sequencing of the parents supported the compound heterozygous nature of obesity as each parent was carrying one of the variants. Subsequent clinical investigation strongly indicated that the proband had Bardet-Biedl syndrome.

CONCLUSIONS

Mutation screening in 31 genes among probands with severe early-onset obesity from Pakistani families did not reveal the presence of homozygous obesity causing variants. However, a compound heterozygote carrier of BBS9 mutations was identified, indicating that compound heterozygosity must not be overlooked when investigating the genetic etiology of severe childhood obesity in populations with a high degree of consanguinity.

Genetic screening for MC4R gene identifies three novel mutations associated with severe familiar obesity in a cohort of Spanish individuals

MC4R gene is a hypothalamic satiety control mediator in which mutations cause a monogenic form of obesity. The aim of this study was to perform a genetic screening to identify variations in the entire region of MC4R gene. A total of 236 unrelated and severely obese patients (BMI ≥ 40 kg/m²) with Spanish ancestry and severe overweight familiar history have been enrolled into the study. Seven MC4R gene variants were identified in the heterozygous state in 21 patients. Coding variants p.Thr101Ile and p.Ala259Asp are new and variants p.Ser30Phe, p.Val103Ile and p.Ile251Leu were previously described. Two variants have been also observed in the promoter region of the MC4R gene; the c.-24G>A mutation, described for the first time, and the known c.-178A>C variant. Both in silico and family segregation analysis confirm the correlation between novel identified mutations in MC4R gene and obesity development. The correlation between the four variants (c.-24G>A, p.Thr101Ile, p.Ala259Asp and p.Ser30Phe) and the obesity phenotype, therefore, allows the conclusion that all of the four mutations cause a monogenic form of obesity.

Comprehensive and Systematic Analysis of Gene Expression Patterns Associated with Body Mass Index

Both genetic and environmental factors are suggested to influence overweight and obesity risks. Although individual loci and genes have been frequently shown to be associated with body mass index (BMI), the overall interaction of these genes and their role in BMI remains underexplored. Data were collected in 90 healthy, predominately Caucasian participants (51% female) with a mean age of 26.00 ± 9.02 years. Whole blood samples were assayed by Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. We integrated and analyzed the clinical and microarray gene expression data from those individuals to understand various systematic gene expression patterns underlying BMI. Conventional differential expression analysis identified seven genes RBM20, SEPT12, AX748233, SLC30A3, WTIP, CASP10, and OR12D3 associated with BMI. Weight gene co-expression network analysis among 4,647 expressed genes identified two gene modules associated with BMI. These two modules, with different extents of gene connectivity, are enriched for catabolic and muscle system processes respectively, and tend to be regulated by zinc finger transcription factors. A total of 246 hub genes were converted to non-hub genes, and 286 non-hub genes were converted to hub genes between normal and overweight individuals, revealing the network dynamics underlying BMI. A total of 28 three-way gene interactions were identified, suggesting the existence of high-order gene expression patterns underlying BMI. Our study demonstrated a variety of systematic gene expression patterns associated with BMI and thus provided novel understanding regarding the genetic factors for overweight and obesity risks on system levels.

FTO and IRX3 Genes are Not Promising Markers for Obesity in Labrador Retriever Dogs

Obesity is a serious problem in numerous dog breeds, but knowledge of its hereditary background is scarce. On the contrary, numerous DNA polymorphisms associated with human obesity have been identified, with the strongest effect being demonstrated for FTO gene. We used targeted next-generation sequencing (tNGS) to search for polymorphisms in the region harboring FTO and IRX3 in 32 Labrador dogs. Moreover, we investigated the selected regions of FTO and IRX3, orthologous to the human regions associated with obesity, in 165 Labradors. For all dogs, the following information was available: age, sex, gonadal status, body weight, and body conformation score (BCS). The use of tNGS revealed 12,217 polymorphisms, but none of these obtained significance when lean and obese dogs were compared. Study of two SNPs in the 5’-flanking region of FTO in 165 dogs – creating two upstream reading frames (uORFs) – also showed no association with body weight and BCS but suggested the need for improvement in FTO annotation. No polymorphism was found in the 5’UTR of IRX3. Additionally, no differences of CpG islands methylation status between lean and obese dogs were found. Our study suggests that FTO and IRX3 are not useful markers of obesity in Labrador dogs.

DNA methylation markers in obesity, metabolic syndrome, and weight loss

The fact that not all individuals exposed to the same environmental risk factors develop obesity supports the hypothesis of the existence of underlying genetic and epigenetic elements. There is suggestive evidence that environmental stimuli, such as dietary pattern, particularly during pregnancy and early life, but also in adult life, can induce changes in DNA methylation predisposing to obesity and related comorbidities. In this context, the DNA methylation marks of each individual have emerged not only as a promising tool for the prediction, screening, diagnosis, and prognosis of obesity and metabolic syndrome features, but also for the improvement of weight loss therapies in the context of precision nutrition. The main objectives in this field are to understand the mechanisms involved in transgenerational epigenetic inheritance, and featuring the nutritional and lifestyle factors implicated in the epigenetic modifications. Likewise, DNA methylation modulation caused by diet and environment may be a target for newer therapeutic strategies concerning the prevention and treatment of metabolic diseases.

FTO haplotyping underlines high obesity risk for European populations

Background

Fat mass and obesity-associated (FTO) gene has been under close investigation since the discovery of its high impact on the obesity status in 2007 by a range of publications. Recent report on its implication in adipocytes underscored its molecular and functional mechanics in pathology. Still, the population specific features of the locus structure have not been approached in detail.

Methods

We analyzed the population specific haplotype profiles of FTO genomic locus identified by Genome Wide Association Studies (GWAS) for the high obesity risk by examining eighteen 1000G populations from 4 continental groups. The GWAS SNPs cluster is located in the FTO gene intron 1 spanning around 70 kb.

Results

We reconstructed the ancestral state of the locus, which comprised low-risk major allele found in all populations, and two minor risk-associated alleles, each one specific for African and European populations, correspondingly. The locus structure and its allele frequency distribution underscore the high risk allele frequency specifically for the European population. South Asian populations have the second highest frequency of risk alleles, while East Asian populations have the lowest. African population-specific minor allele was only partially risk-associated. All of the GWAS SNPs considered are manifested by low risk alleles as reference (major) ones (p > 0.5) in each of the continental groups. Strikingly, rs1421085, recently reported as a causal SNP, was found to be monomorphic in ancestral (African) populations, implying possible selection sweep in the course of its rapid fixation, as reported previously.

Conclusion

The observations underscore varying FTO -linked risk in the manifestation of population specific epidemiology of genetically bound obesity. The results imply that the FTO locus is one of the major genetic determinants for obesity risk from GWAS SNPs set.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0491-x) contains supplementary material, which is available to authorized users.

Can uterine secretion of modified histones alter blastocyst implantation, embryo nutrition, and transgenerational phenotype?

Extracellular histones support rodent and human embryo development in at least two ways. First, these molecules in uterine secretions protect embryos from inflammation caused by pathogens that gain access to the reproductive tract. Also, histones in uterine secretions likely support penetration of the uterine epithelium by blastocysts during embryo implantation. Extracellular histones seem to preserve amino acid transport system B0,+ in blastocysts by inhibiting its activity. Preservation of system B0,+ is needed because, at the time of invasion of the uterine epithelium by motile trophoblasts, system B0,+ is likely reactivated to help remove tryptophan from the implantation chamber. If tryptophan is not removed, T-cells proliferate and reject the implanting blastocyst. Epigenetic modification of histones could alter their promotion of normal implantation through, say, incomplete tryptophan removal and, thus, allow partial T-cell rejection of the conceptus. Such partial rejection could impair placental development, embryonal/fetal nutrition, and weight gain prior to birth. Small-for-gestational-age offspring are predisposed to developing metabolic syndrome, obesity, and associated complications as adults. Shifting expression of these phenotypes might contribute to transgenerational variation and evolution. The spectrum of possible extracellular histone targets in early development warrant new research, especially since the effects of epigenetic histone modifications might be transgenerational.

The effect of copy number variations in chromosome 16p on body weight in patients with intellectual disability

Syndromic monogenic obesity is a rare and severe early-onset form of obesity. It is characterized by intellectual disability, congenital malformations, and/or dysmorphic facies. The diagnosis of patients is challenging due to the genetic heterogenicity of this condition. However, the use of microarray technology in combination with public databases has been successful on genotype-phenotype correlations, especially for body mass index (BMI) alteration. In this study, the relationship between copy number variations (CNVs) detected by microarray mapping on 16p region and BMI alterations in syndromic patients were assessed. In order to achieve this goal, 680 unrelated Spanish children with intellectual disability were included. 16p region was characterized by using microarray platforms. All detected variants were classified as: (I) one previously non-described 10-Mb duplication in 16p13.2p12.3 region considered causal of intellectual disability and severe overweight, and (II) eleven 16p11.2 CNVs of low prevalence but with recurrence in syndromic patients with severe BMI alteration (nine proximal and two distal). Proximal 16p11.2 CNVs have a dose-dependent effect: underweight in carriers of duplication and obesity in carriers of deletion. KCTD13 was identified as a possible candidate gene for BMI alteration on proximal syndromes, whereas SH2B1 gene was identified as candidate for distal syndromes. The results shown in this paper suggest that syndromic patients could constitute a reliable model to evaluate hypothalamic satiety and obesity disorders as well as generate a wide expectation for primary prevention of comorbidities. Furthermore, 16p13.2p12.3 showed to be an important region on the regulation of body fatness.

In silico approach to identify non-synonymous SNPs with highest predicted deleterious effect on protein function in human obesity related gene, neuronal growth regulator 1 (NEGR1)

Neuronal growth regulator 1 (NEGR1) is a candidate gene for human obesity, which encodes the neural cell adhesion and growth molecule. The aim of the current study was to recognize the non-synonymous SNPs (nsSNPs) with the highest predicted deleterious effect on protein function of the NEGR1 gene. We have used five computational tools, namely, PolyPhen, SIFT, PROVEAN, MutPred and M-CAP, to predict the deleterious and pathogenic nsSNPs of the NEGR1 gene. Homology modeling approach was used to model the native and mutant NEGR1 protein models. Furthermore, structural validation was performed by the PROCHECK server to interpret the stability of the predicted models. We have predicted four potential deleterious nsSNPs, i.e., rs145524630 (Ala70Thr), rs267598710 (Pro168Leu), rs373419972 (Arg239Cys) and rs375352213 (Leu158Phe), which might be involved in causing obesity phenotypes. The predicted mutant models showed higher root mean square deviation and free energy values under the PyMoL and SWISS-PDB viewer, respectively. Additionally, the FTSite server predicted one nsSNP, i.e., rs145524630 (Ala70Thr) out of four identified nsSNPs found in the NEGR1 protein-binding site. There were four potential deleterious and pathogenic nsSNPs, i.e., rs145524630, rs267598710, rs373419972 and rs375352213, identified from the above-mentioned tools. In future, further functional in vitro and in vivo analysis could lead to better knowledge about these nsSNPs on the influence of the NEGR1 gene in causing human obesity. Hence, the present computational examination suggest that predicated nsSNPs may feasibly be a drug target and play an important role in contributing to human obesity.

Secondary Metabolites, Dietary Fiber and Conjugated Fatty Acids as Functional Food Ingredients against Overweight and Obesity

Obesity is a common serious health problem leading to many serious health disorders. This phenomenon is defined as the over-storage of lipids in adipose tissue that occurs when there is an imbalance between the energy intake and energy used. During obesity, many metabolic alterations occur that can damage several organs, such as vascular or skeletal muscle resulting in the dysfunction of these tissues. In this review, we will discuss molecular genetics and causes of obesity, some of the disorders related to human obesity as well as anti-obesity tool. An interesting solution to the obesity problem is natural substances, revealing anti-obesity activity, as well as functional food enriched with aforementioned substances. Functional foods are products exhibiting a potentially positive effect on health beyond basic nutrition. They contain well-known biologically active natural compounds, which promote optimal health and reduce the risk of many diseases, including obesity.

Phenotype and genotype predictors of BMI variability among European adults

Background/Objective

Obesity is a complex and multifactorial disease resulting from the interactions among genetics, metabolic, behavioral, sociocultural and environmental factors. In this sense, the aim of the present study was to identify phenotype and genotype variables that could be relevant determinants of body mass index (BMI) variability.

Subjects/Methods

In the present study, a total of 1050 subjects (798 females; 76%) were included. Least angle regression (LARS) analysis was used as regression model selection technique, where the dependent variable was BMI and the independent variables were age, sex, energy intake, physical activity level, and 16 polymorphisms previously related to obesity and lipid metabolism.

Results

The LARS analysis obtained the following formula for BMI explanation: (64.7 + 0.10 × age [years] + 0.42 × gender [0, men; 1, women] + −40.6 × physical activity [physical activity level] + 0.004 × energy intake [kcal] + 0.74 × rs9939609 [0 or 1–2 risk alleles] + −0.72 × rs1800206 [0 or 1–2 risk alleles] + −0.86 × rs1801282 [0 or 1–2 risk alleles] + 0.87 × rs429358 [0 or 1–2 risk alleles]. The multivariable regression model accounted for 21% of the phenotypic variance in BMI. The regression model was internally validated by the bootstrap method (r² original data set = 0.208, mean r² bootstrap data sets = 0.210).

Conclusion

In conclusion, age, physical activity, energy intake and polymorphisms in FTO, APOE, PPARG and PPARA genes are significant predictors of the BMI trait.

The gut microbiota and its potential role in obesity

The human GI tract harbors a diverse and dynamic microbial community comprising bacteria, archaea, viruses and eukaryotic microbes, which varies in composition from individual to individual. A healthy microbiota metabolizes various indigestible dietary components of the host, maintains host immune homeostasis and nutrient intake, but, an imbalanced microbiota has been reported to be associated with many diseases, including obesity. Rodent studies have produced evidence in support of the causal role of the gut microbiota in the development of obesity, however, such causal relationship is lacking in humans. The objective of this review is to critically analyze the vast information available on the composition, function and alterations of the gut microbiota in obesity and explore the future prospects of this research area.

Multiple genetic variations confer risks for obesity and type 2 diabetes mellitus in arab descendants from UAE

BACKGROUND

The United Arab Emirates (UAE) is one of the countries most threatened with obesity. Here we investigated associations between hundreds of single-nucleotide polymorphisms (SNPs) and the following obesity indicators: body mass index (BMI), waist circumference (WC), and height. We also investigated the associations between obesity-related genes with type 2 diabetes mellitus (T2DM).

METHODS

We tested 87, 58, and 586 SNPs in a previous genome-wide significance level for associations with BMI (n = 880), WC (n = 455), and height (n = 897), respectively. For each trait, we used normally transformed Z scores and tested them with SNPs using linear regression models that incorporated age and gender as covariates. The weighted polygenic risk scores for significant SNPs for each trait were tested with the corresponding Z scores using linear regression models with the same covariates. We further tested 145 obesity loci with T2DM (464 cases, 415 controls) using a logistic regression model including age, gender, and BMI Z scores as covariates.

RESULTS

The Mean BMI was 29.39 kg/m², and mean WC was 103.66 cm. Hypertension and dyslipidemia were common obesity comorbidities (>60%). The best associations for BMI was in FTO, LOC284260 and USP37, and for WC in RFX7 and MYEOV. For height, the best association was in NSD1 followed by MFAP2 and seven other loci. The polygenic scores revealed stronger associations for each trait than individual SNPs; although they could only explain <1% of the traits' Z scores variations. For T2DM, the strongest associations were with the TCF7L2 and MC4R loci (P < 0.01, OR ~1.70), with novel associations detected with KCNK3 and RARB.

CONCLUSIONS

In this first study of Arab descendants, we confirmed several known obesity (FTO, USP37, and RFX7), height (NSD1, MFAP2), and T2DM (TCF7L2, MC4R) associations; and report novel associations, like KCNK3 and RARB for T2DM.

Lipid regulatory genes polymorphism in children with and without obesity and cardiometabolic risk factors: The CASPIAN-III study

Background:

Genetically, predisposed children are considered as at-risk individuals for cardiovascular disease. In this study, we aimed to compare the frequency of four-lipid regulatory polymorphism in obese and normal-weight children with and without cardiometabolic risk factors.

Materials and Methods:

In this nested case–control study, 600 samples of four groups of participants consisted of those with normal weight with and without cardiometabolic risk factors and obese with and without cardiometabolic risk factors. Allelic and genotypic frequencies of GCKR (rs780094), GCKR (rs1260333), MLXIPL (rs3812316), and FADS (rs174547) polymorphisms were compared in the four studied groups.

Results:

Data of 528 samples were complete and included in this study. The mean (standard deviation) age of participants was 15.01 (2.21) years. Frequency of tt allele (minor allele) of GCKR (rs1260333) polymorphism was significantly lower in normal weight metabolically healthy participants than metabolically unhealthy normal weight (MUHNW) and obese children with and without cardiometabolic risk factor (P = 0.01). Frequency of ga allele of GCKR (rs780094) polymorphism was significantly higher in normal weight children with cardiometabolic risk factor than in their obese counterparts with cardiometabolic risk factor (P = 0.04). Frequency of cg and gg alleles (minor type) of MLXIPL (rs3812316) polymorphism in normal weight metabolically healthy participants was significantly higher than MUHNW (P = 0.04) and metabolically healthy obese children (P = 0.04).

Conclusion:

The findings of our study indicated that the minor allele of GCKR (rs1260333) single nucleotide polymorphisms (SNPs) could have pathogenic effect for obesity and cardiometabolic risk factors. Ga allele of GCKR (rs780094) SNPs had a protective effect on obesity. Minor alleles of MLXIPL (rs3812316) could have a protective effect for obesity and cardiometabolic risk factors.

Preliminary evidence for genetic overlap between body mass index and striatal reward response

The reward-processing network is implicated in the aetiology of obesity. Several lines of evidence suggest obesity-linked genetic risk loci (such as DRD2 and FTO) may influence individual variation in body mass index (BMI) through neuropsychological processes reflected in alterations in activation of the striatum during reward processing. However, no study has tested the broader hypotheses that (a) the relationship between BMI and reward-related brain activation (measured through the blood oxygenation-dependent (BOLD) signal) may be observed in a large population study and (b) the overall genetic architecture of these phenotypes overlap, an assumption critical for the progression of imaging genetic studies in obesity research. Using data from the Human Connectome Project (N = 1055 healthy, young individuals: average BMI = 26.4), we first establish a phenotypic relationship between BMI and ventral striatal (VS) BOLD during the processing of rewarding (monetary) stimuli (β = 0.44, P = 0.013), accounting for potential confounds. BMI and VS BOLD were both significantly influenced by additive genetic factors (H2r = 0.57; 0.12, respectively). Further decomposition of this variance suggested that the relationship was driven by shared genetic (ρ g = 0.47, P = 0.011), but not environmental (ρ E = -0.07, P = 0.29) factors. To validate the assumption of genetic pleiotropy between BMI and VS BOLD, we further show that polygenic risk for higher BMI is also associated with increased VS BOLD response to appetitive stimuli (calorically high food images), in an independent sample (N = 81; P FWE-ROI < 0.005). Together, these observations suggest that the genetic factors link risk to obesity to alterations within key nodes of the brain's reward circuity. These observations provide a basis for future work exploring the mechanistic role of genetic loci that confer risk for obesity using the imaging genetics approach.

Association between polymorphisms in SLC15A1 and PLA2G16 genes and development of obesity in Chinese subjects

INTRODUCTION

The small peptide transporter 1 (PepT-1) and adipose phospholipase A2 (AdPLA) play a key role in the development of obesity. However, there are no data assessing the impact of PepT-1 (SLC15A1) and AdPLA (PLA2G16) variants on obesity susceptibility. Therefore, we assessed the contribution of 9 single-nucleotide polymorphisms (SNPs) between these two genes on obesity susceptibility in Chinese subjects.

MATERIALS AND METHODS

A total of 611 participants were enrolled in the study, and 9 SNPs in the SLC15A1 and PLA2G16 genes were selected. Blood samples were collected for genotyping. Overweight and obesity were established by body mass index. Regression analyses were performed to test for any association of genetic polymorphisms with weight abnormality.

RESULTS

The genotype frequencies (P=0.04 for rs9557029, P=0.027 for rs1289389) were significantly different between obese or overweight subjects and healthy controls. However, no significant difference in allele was found between these three groups (P>0.05). Further logistic regression analyses adjusted for age and sex also failed to reveal significant associations between overweight, obesity, and the selected SNPs (P>0.05).

CONCLUSION

Data indicate that the selected 9 SNPs in SLC15A1 and PLA2G16 genes were not related to obesity susceptibility in the Han Chinese population.

Obesity in International Migrant Populations

PURPOSE OF REVIEW

This review examines the risk of obesity in migrant groups-specifically migrants from countries with lower prevalence of obesity to countries with higher prevalence of obesity. We examine obesity prevalence within migrant groups compared with native populations and the evidence on factors that might shape obesity risk in these migrant groups.

RECENT FINDINGS

Migrants may arrive in new countries with a health advantage including generally a healthier body weight. Genetic and epi-genetic factors, as well as body size preference, socio-economic factors, and stress exposure, may play a role in increasing unhealthy weight gain in migrant populations. This unhealthy weight gain leads to similar or greater obesity risk in migrant populations compared with native populations 10-15 years after migration. Meeting the challenge of prevention and treatment of obesity in diverse populations will require greater attention to minority groups in research in the future.

Is bisphenol A an environmental obesogen?

Bisphenol A (BPA) is an endocrine disruptor with an oestrogenic activity that is widely produced for the manufacture of polycarbonate plastic, epoxy resin, and thermal paper. Its ubiquitous presence in the environment contributes to broad and continuous human exposure, which has been associated with deleterious health effects. Despite numerous controversial discussions and a lack of consensus about BPA's safety, growing evidence indicates that BPA exposure positively correlates with an increased risk of developing obesity. An updated analysis of the epidemiological, in vivo, and in vitro studies indicates that BPA should be considered an obesogenic environmental compound. Precisely, BPA exposure during all life stages correlates with increased body weight and/or body mass index. Developmental periods that include prenatal, infancy, and childhood appear to be critical windows with increased sensitivity to BPA effects. Finally, blood analysis and in vitro data clearly demonstrate that BPA promotes adipogenesis, lipid and glucose dysregulation, and adipose tissue inflammation, thus contributing to the pathophysiology of obesity. Future prevention efforts should now be employed to avoid BPA exposure, and more research to determine in depth the critical time windows, doses, and impact of long-term exposure of BPA is warranted in order to clarify its risk assessment.

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.