The Human Obesity Gene Map: The 2004 Update

Umbilical cord DNA methylation is associated with body mass index trajectories from birth to adolescence

BACKGROUND

DNA methylation (DNAm) in cord blood has been associated with various prenatal factors and birth outcomes. This study sought to fill an important knowledge gap: the link of cord DNAm with child postnatal growth trajectories from birth to age 18 years (y).

METHODS

Using data from a US predominantly urban, low-income, multi-ethnic birth cohort (N = 831), we first applied non-parametric methods to identify body-mass-index percentile (BMIPCT) trajectories from birth to age 18 y (the outcome); then, conducted epigenome-wide association study (EWAS) of the outcome, interrogating over 700,000 CpG sites profiled by the Illumina Infinium MethylationEPIC BeadChip. Multivariate linear regression models and likelihood ratio tests (LRT) were applied to examine the DNAm-outcome association in the overall sample and sex strata.

FINDINGS

We identified four distinct patterns of BMIPCT trajectories: normal weight (NW), Early overweight or obesity (OWO), Late OWO, and normal to very late OWO. DNAm at CpG18582997 annotated to TPGS1, CpG15241084 of TLR7, and cg24350936 of RAB31 were associated with BMIPCT at birth-to-3 y, 10 y, and 14 y, respectively (LRT FDR < 0.05 for all).

INTERPRETATION

In this prospective birth cohort study, we identified 4 distinct and robust patterns of growth trajectories from birth to 18 y, which were associated with variations in cord blood DNAm at genes implicated in inflammation induction pathways. These findings, if further replicated, raise the possibility that these DNAm markers along with early assessment of BMIPCT trajectories may help identify young children at high-risk for obesity later in life.

FUNDING

Detailed in the Acknowledgements section.

Comorbidity of Novel CRHR2 Gene Variants in Type 2 Diabetes and Depression

The corticotropin-releasing hormone receptor 2 (CRHR2) gene encodes CRHR2, contributing to the hypothalamic–pituitary–adrenal stress response and to hyperglycemia and insulin resistance. CRHR2−/− mice are hypersensitive to stress, and the CRHR2 locus has been linked to type 2 diabetes and depression. While CRHR2 variants confer risk for mood disorders, MDD, and type 2 diabetes, they have not been investigated in familial T2D and MDD. In 212 Italian families with type 2 diabetes and depression, we tested 17 CRHR2 single nucleotide polymorphisms (SNPs), using two-point parametric-linkage and linkage-disequilibrium (i.e., association) analysis (models: dominant-complete-penetrance-D1, dominant-incomplete-penetrance-D2, recessive-complete-penetrance-R1, recessive-incomplete-penetrance-R2). We detected novel linkage/linkage-disequilibrium/association to/with depression (3 SNPs/D1, 2 SNPs/D2, 3 SNPs/R1, 3 SNPs/R2) and type 2 diabetes (3 SNPs/D1, 2 SNPs/D2, 2 SNPs/R1, 1 SNP/R2). All detected risk variants are novel. Two depression-risk variants within one linkage-disequilibrium block replicate each other. Two independent novel SNPs were comorbid while the most significant conferred either depression- or type 2 diabetes-risk. Although the families were primarily ascertained for type 2 diabetes, depression-risk variants showed higher significance than type 2 diabetes-risk variants, implying CRHR2 has a stronger role in depression-risk than type 2 diabetes-risk. In silico analysis predicted variants’ dysfunction. CRHR2 is for the first time linked to/in linkage-disequilibrium/association with depression-type 2 diabetes comorbidity and may underlie the shared genetic pathogenesis via pleiotropy.

Distribution and effect of ghrelin genotype on plasma lipid and apolipoprotein profiles in obese and nonobese Chinese subjects

PURPOSE

The hormone ghrelin has an important role in a wide range of metabolic and nonmetabolic processes. Ghrelin gene polymorphisms have been reported to influence obesity or lipid abnormalities in some ethnic groups. This study was conducted mainly to examine the possible association of ghrelin - 604 G > A and Leu72Met polymorphisms with obesity and related traits in a Southwest Chinese population.

METHODS

Three hundred and eighty-six Han Chinese individuals (118 obese and 268 normal weight control subjects) in the Chengdu area were studied using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Clinical and biochemical parameters were also analyzed.

RESULTS

The genotype and allele frequencies of ghrelin gene polymorphisms in participants with obesity showed no significant difference compared to those in nonobese controls. However, in the nonobese control group, carriers of genotype Met/Met at the Leu72Met site had higher serum TC and LDL-C concentrations than those of the Leu/Leu genotype (P < 0.05). When nonobese subjects were stratified by sex, the genotype-dependent effects on TC and LDL-C were more evident, although this was observed only in females. In addition, genotype-related effects on these lipid parameters at this site were observed in male obese subjects only.

CONCLUSIONS

The Leu72Met polymorphism of the ghrelin gene is associated with altered plasma TC and LDL-C concentrations, and the effects on TC and LDL-C levels are sex-dependent in both nonobese and obese subjects in the Chinese population of the Chengdu area.

Trefoil Factor Family Member 2: From a High-Fat-Induced Gene to a Potential Obesity Therapy Target

Obesity has its epidemiological patterns continuously increasing. With controlling both diet and exercise being the main approaches to manage the energy metabolism balance, a high-fat (HF) diet is of particular importance. Indeed, lipids have a low satiety potential but a high caloric density. Thus, focusing on pharmacologically targetable pathways remains an approach with promising therapeutic potential. Within this context, trefoil factor family member 2 (Tff2) has been characterized as specifically induced by HF diet rather than low-fat diet. TFF2 has also been linked to diverse neurological mechanisms and metabolic patterns suggesting its role in energy balance. The hypothesis is that TFF2 would be a HF diet-induced signal that regulates metabolism with a focus on lipids. Within this review, we put the spotlight on key findings highlighting this line of thought. Importantly, the hypothetical mechanisms pointed highlight TFF2 as an important contributor to obesity development via increasing lipids intestinal absorption and anabolism. Therefore, an outlook for future experimental activities and evaluation of the therapeutic potential of TFF2 inhibition is given. Indeed, its knockdown or downregulation would contribute to an antiobesity phenotype. We believe this work represents an addition to our understanding of the lipidic molecular implications in obesity, which will contribute to develop therapies aiming to manage the lipidic metabolic pathways including the absorption, storage and metabolism via targeting TFF2-related pathways. We briefly discuss important relevant concepts for both basic and clinical researchers.

Genetic variants of VDR and CYP2R1 affect BMI independently of serum vitamin D concentrations

BACKGROUND

Vitamin D metabolism and obesity have been linked by several studies, however the reason for this association is unclear. Our objective was to investigate potential correlations between genetic variants in key enzymes of vitamin D metabolism and the body mass index on a representative and random sample of Hungarian adults.

METHODS

Altogether 462 severely vitamin D deficient individuals were studied at the end of winter in order to decrease environmental and maximize any relevant genetic effect. Furthermore, participants with lifestyle factors known to affect vitamin D homeostasis were also excluded. We selected 23 target SNPs in five genes that encode key proteins of vitamin D metabolism (NADSYN1, GC, CYP24A1, CYP2R1, VDR).

RESULTS

Variants in 2 genetic polymorphisms; rs2853564 (VDR) and rs11023374 (CYP2R1) showed a significant association with participants' BMI. These associations survived further adjustment for total-, free-, or bioactive-25(OH) vitamin D levels, although the variance explained by these 2 SNPS in BMI heterogeneity was only 3.2%.

CONCLUSION

Our results show two novel examples of the relationship between genetics of vitamin D and BMI, highlighting the potential role of vitamin D hormone in the physiology of obesity.

Double Burden of Malnutrition and Nutrition Transition in Asia: A Case Study of 4 Selected Countries with Different Socioeconomic Development

Disease burden and lifestyle patterns have changed rapidly worldwide, especially in some Asian countries over the past 2 decades. However, cross-country comparative research is limited. This study investigated the nutritional status of preschool children and childbearing women in China, India, Nepal, and Pakistan selected based on their socioeconomic status, population size, and urbanization. Nationally representative data were used from the China National Nutrition and Health Surveillance Report, India National Family Health Survey, Nepal Demographic and Health Survey, Pakistan Demographic and Health Survey, the WHO repository, and the World Bank. The prevalence of underweight, overweight, and obesity and some ratios were compared. These rates varied across these 4 countries and were associated with their economic development levels. China's economic status and prevalence of childhood overweight/obesity (11.5%) were highest; India's economic status was higher than that of Nepal and Pakistan, but had higher rates of stunting, wasting, and underweight (38.4%, 21.0%, and 35.7%, respectively) in preschool children. Pakistan had the highest prevalence of overweight/obesity among childbearing women (52.4% in all, 63.0% in urban areas). Nepal had the lowest economic status and overweight/obesity rate in preschool children (1.2%). In general, the prevalence of overweight/obesity was higher in urban than in rural areas, except among childbearing women in China. Nutritional status and health burden are heavily influenced by economic development. The double burden of malnutrition poses prioritization challenges for policymakers and public health efforts. Prevention of obesity is urgently needed, at least in higher-income countries in Asia.

Transcriptomic analysis of left ventricle myocardium in an SHR congenic line with ameliorated cardiac fibrosis

Metabolic syndrome and one of its manifestations, essential hypertension, is an important cause of worldwide morbidity and mortality. Morbidity and mortality associated with hypertension are caused by organ complications. Previously we revealed a decrease of blood pressure and an amelioration of cardiac fibrosis in a congenic line of spontaneously hypertensive rats (SHR), in which a short segment of chromosome 8 (encompassing only 7 genes) was exchanged for a segment of normotensive polydactylous (PD) origin. To unravel the genetic background of this phenotype we compared heart transcriptomes between SHR rat males and this chromosome 8 minimal congenic line (PD5). We found 18 differentially expressed genes, which were further analyzed using annotations from Database for Annotation, Visualization and Integrated Discovery (DAVID). Four of the differentially expressed genes (Per1, Nr4a1, Nr4a3, Kcna5) belong to circadian rhythm pathways, aldosterone synthesis and secretion, PI3K-Akt signaling pathway and potassium homeostasis. We were also able to confirm Nr4a1 2.8x-fold upregulation in PD5 on protein level using Western blotting, thus suggesting a possible role of Nr4a1 in pathogenesis of the metabolic syndrome.

A high-fat diet alters genome-wide DNA methylation and gene expression in SM/J mice

BACKGROUND

While the genetics of obesity has been well defined, the epigenetics of obesity is poorly understood. Here, we used a genome-wide approach to identify genes with differences in both DNA methylation and expression associated with a high-fat diet in mice.

RESULTS

We weaned genetically identical Small (SM/J) mice onto a high-fat or low-fat diet and measured their weights weekly, tested their glucose and insulin tolerance, assessed serum biomarkers, and weighed their organs at necropsy. We measured liver gene expression with RNA-seq (using 21 total libraries, each pooled with 2 mice of the same sex and diet) and DNA methylation with MRE-seq and MeDIP-seq (using 8 total libraries, each pooled with 4 mice of the same sex and diet). There were 4356 genes with expression differences associated with diet, with 184 genes exhibiting a sex-by-diet interaction. Dietary fat dysregulated several pathways, including those involved in cytokine-cytokine receptor interaction, chemokine signaling, and oxidative phosphorylation. Over 7000 genes had differentially methylated regions associated with diet, which occurred in regulatory regions more often than expected by chance. Only 5-10% of differentially methylated regions occurred in differentially expressed genes, however this was more often than expected by chance (p = 2.2 × 10- 8).

CONCLUSIONS

Discovering the gene expression and methylation changes associated with a high-fat diet can help to identify new targets for epigenetic therapies and inform about the physiological changes in obesity. Here, we identified numerous genes with altered expression and methylation that are promising candidates for further study.

Adipose and skeletal muscle thermogenesis: studies from large animals

The balance between energy intake and energy expenditure establishes and preserves a 'set-point' body weight. The latter is comprised of three major components including metabolic rate, physical activity and thermogenesis. Thermogenesis is defined as the cellular dissipation of energy via heat production. This process has been extensively characterised in brown adipose tissue (BAT), wherein uncoupling protein 1 (UCP1) creates a proton leak across the inner mitochondrial membrane, diverting protons away from ATP synthesis and resulting in heat dissipation. In beige adipocytes and skeletal muscle, thermogenesis can occur independent of UCP1. Beige adipocytes have been shown to produce heat via UCP1 as well as via both futile creatine and calcium cycling pathways. On the other hand, the UCP1 homologue UCP3 is abundant in skeletal muscle and post-prandial thermogenesis has been associated with UCP3 and the futile calcium cycling. This review will focus on the differential contributions of adipose tissue and skeletal muscle in determining total thermogenic output and energy expenditure in large mammals. Sheep and pigs do not have a circumscribed brown fat depot but rather possess white fat depots that contain brown and beige adipocytes interspersed amongst white adipose tissue. This is representative of humans, where brown, beige and white adipocytes have been identified in the neck and supraclavicular regions. This review will describe the mechanisms of thermogenesis in pigs and sheep and the relative roles of skeletal muscle and adipose tissue thermogenesis in controlling body weight in larger mammals.

Increasing variability of body mass and health correlates in Swiss conscripts, a possible role of relaxed natural selection?

BACKGROUND AND OBJECTIVES

The body mass index (BMI) is an established anthropometric index for the development of obesity-related conditions. However, little is known about the distribution of BMI within a population, especially about this distribution's temporal change. Here, we analysed changes in the distribution of height, weight and BMI over the past 140 years based on data of Swiss conscripts and tested for correlations between anthropometric data and standard blood parameters.

METHODS

Height and weight were measured in 59 504 young Swiss males aged 18-19 years during conscription in 1875-79, 1932-36, 1994 and 2010-12. For 65% of conscripts in 2010-12, results of standard blood analysis were available. We calculated descriptive statistics of the distribution of height, weight and BMI over the four time periods and tested for associations between BMI and metabolic parameters.

RESULTS

Average and median body height, body weight and BMI increased over time. Height did no longer increase between 1994 and 2010-12, while weight and BMI still increased over these two decades. Variability ranges of weight and BMI increased over time, while variation of body height remained constant. Elevated levels of metabolic and inflammatory blood parameters were found at both ends of BMI distribution.

CONCLUSIONS AND IMPLICATIONS

Both overweight and underweight subgroups showed similar changes in inflammation parameters, pointing toward related metabolic deficiencies in both conditions. In addition to environmental influences, our results indicate a potential role of relaxed natural selection on genes affecting metabolism and body composition.

Analysis of SNPs of MC4R, GNB3 and FTO gene polymorphism in obese Saudi subjects

Background

The goal of this study was to analyze the association between the FTO rs17817449 (G>T), G protein beta3 subunit (GNB3) C825T and Melanocortin 4 receptor (MC4R) A822G single nucleotide polymorphism (SNP) with obesity in Saudi subjects.

Methods

The subjects were divided into 2 groups according to BMI: Obese (BMI> 29.9) and non- obese control (BMI<24.9). Genotyping of the target genes were determined by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis (RFLP).

Results

We demonstrated the association of the FTO genotype TT with increased weight, BMI and leptin levels in both males and females. However, there was no association of genotype TT with fasting blood glucose, triglycerides and cholesterol levels. Regarding GNB3 rs5443 polymorphism, the likelihood of obesity was linked to the TT genotype which was also associated with increased leptin levels. On the other hand, the SNP of MC4R A822G did not exhibit any significant association with obesity among studied subjects and showed only the presence of homozygous AA genotype.

Conclusion

The polymorphism of FTO gene rs17817449 and GNB3 gene rs5443 (C825T) may be a genetic determinant of obesity in Saudi population whereas impact of MC4R Asn274Ser change could not be detected.

Genetic Determinants of Prepubertal and Pubertal Growth and Development

This article surveys the current general understanding of genetic influences on within- and between-population variation in growth and development in the context of establishing an International Growth Standard for Preadolescent and Adolescent Children. Traditional genetic epidemiologic analysis methods are reviewed, and evidence from family studies for genetic effects on different measures of growth and development is then presented. Findings from linkage and association studies seeking to identify specific genomic locations and allelic variants of genes influencing variation in growth and maturation are then summarized. Special mention is made of the need to study the interactions between genes and environments. At present, specific genes and polymorphisms contributing to variation in growth and maturation are only beginning to be identified. Larger genetic epidemiologic studies are needed in different parts of the world to better explore population differences in gene frequencies and gene—environment interactions. As advances continue to be made in molecular and statistical genetic methods, the genetic architecture of complex processes, including those of growth and development, will become better elucidated. For now, it can only be concluded that although the fundamental genetic underpinnings of the growth and development of children worldwide are likely to be essentially the same, there are also likely to be differences between populations in the frequencies of allelic gene variants that influence growth and maturation and in the nature of gene–environment interactions. This does not necessarily preclude an international growth reference, but it does have important implications for the form that such a reference might ultimately take.

Social Entrepreneurship for Obesity Prevention: What Are the Opportunities?

In recent years, social entrepreneurship has emerged as a new field to address social and public health challenges. Social entrepreneurship, which harnesses traditional business practices and market forces to address social challenges, may produce solutions that are more cost-effective and sustainable than those produced by governmental and nonprofit sectors. In this paper, we discuss whether and how social entrepreneurship can be harnessed for obesity prevention by defining and briefly reviewing the rise of social entrepreneurship in the USA, outlining the threat that obesity poses to US society and offering some examples of how social ventures are addressing the problem of obesity. Additional untapped opportunities are also discussed and recommendations given for how social entrepreneurship might impact obesity prevention in the future.

New targets to treat obesity and the metabolic syndrome

Metabolic syndrome (MetS) is a cluster ofassociated metabolic traits that collectively confer unsurpassed risk for development of cardiovascular disease (CVD) and type 2 diabetes compared to any single CVD risk factor. Truncal obesity plays an exceptionally critical role among all metabolic traits of the MetS. Consequently, the prevalence of the MetS has steadily increased with the growing epidemic of obesity. Pharmacotherapy has been available for obesity for more than one decade, but with little success in improving the metabolic profiles. The serotonergic drugs and inhibitors of pancreatic lipases were among the few drugs that were initially approved to treat obesity. At the present time, only the pancreatic lipase inhibitor orlistat is approved for long-term treatment of obesity. New classes of anti-diabetic drugs, including glucagon-like peptide 1 receptor (GLP-1R) agonists and Dipeptidyl-peptidase IV (DPP-IV) inhibitors, are currently being evaluated for their effects on obesity and metabolic traits. The genetic studies of obesity and metabolic syndrome have identified novel molecules acting on the hunger and satiety peptidergic signaling of the gut-hypothalamus axis or the melanocortin system of the brain and are promising targets for future drug development. The goal is to develop drugs that not only treat obesity, but also favorably impact its associated traits.

SNPs of melanocortin 4 receptor (MC4R) associated with body weight in Beagle dogs

Melanocortin 4 receptor (MC4R), which is associated with inherited human obesity, is involoved in food intake and body weight of mammals. To study the relationships between MC4R gene polymorphism and body weight in Beagle dogs, we detected and compared the nucleotide sequence of the whole coding region and 3'- and 5'- flanking regions of the dog MC4R gene (1214 bp). In 120 Beagle dogs, two SNPs (A420C, C895T) were identified and their relation with body weight was analyzed with RFLP-PCR method. The results showed that the SNP at A420C was significantly associated with canine body weight trait when it changed amino acid 101 of the MC4R protein from asparagine to threonine, while canine body weight variations were significant in female dogs when MC4R nonsense mutation at C895T. It suggested that the two SNPs might affect the MC4R gene's function which was relative to body weight in Beagle dogs. Therefore, MC4R was a candidate gene for selecting different size dogs with the MC4R SNPs (A420C, C895T) being potentially valuable as a genetic marker.

Modeling obesity and its associated disorders in Drosophila

In recent years, obesity has been recognized as a major public health problem due to its increased prevalence in both children and adults and its association with numerous life-threatening complications including diabetes, heart disease, hypertension, and cancer. Obesity is a complex disorder that is the result of the interaction between predisposing genetic and environmental factors. However, the precise nature of these gene-gene and gene-environment interactions remains unclear. Here, we will describe recent studies demonstrating how fruit flies can be used to identify and characterize the mechanisms underlying obesity and to establish models of obesity-associated disorders.

Scientific decision making, policy decisions, and the obesity pandemic

Rising and epidemic rates of obesity in many parts of the world are leading to increased suffering and economic stress from diverting health care resources to treating a variety of serious, but preventable, chronic diseases etiologically linked to obesity, particularly type 2 diabetes mellitus and cardiovascular diseases. Despite decades of research into the causes of the obesity pandemic, we seem to be no nearer to a solution now than when the rise in body weights was first chronicled decades ago. The case is made that impediments to a clear understanding of the nature of the problem occur at many levels. These obstacles begin with defining obesity and include lax application of scientific standards of review, tenuous assumption making, flawed measurement and other methods, constrained discourse limiting examination of alternative explanations of cause, and policies that determine funding priorities. These issues constrain creativity and stifle expansive thinking that could otherwise advance the field in preventing and treating obesity and its complications. Suggestions are made to create a climate of open exchange of ideas and redirection of policies that can remove the barriers that prevent us from making material progress in solving a pressing major public health problem of the early 21st century.

The landscape of host transcriptional response programs commonly perturbed by bacterial pathogens: towards host-oriented broad-spectrum drug targets

BACKGROUND

The emergence of drug-resistant pathogen strains and new infectious agents pose major challenges to public health. A promising approach to combat these problems is to target the host's genes or proteins, especially to discover targets that are effective against multiple pathogens, i.e., host-oriented broad-spectrum (HOBS) drug targets. An important first step in the discovery of such drug targets is the identification of host responses that are commonly perturbed by multiple pathogens.

RESULTS

In this paper, we present a methodology to identify common host responses elicited by multiple pathogens. First, we identified host responses perturbed by each pathogen using a gene set enrichment analysis of publicly available genome-wide transcriptional datasets. Then, we used biclustering to identify groups of host pathways and biological processes that were perturbed only by a subset of the analyzed pathogens. Finally, we tested the enrichment of each bicluster in human genes that are known drug targets, on the basis of which we elicited putative HOBS targets for specific groups of bacterial pathogens. We identified 84 up-regulated and three down-regulated statistically significant biclusters. Each bicluster contained a group of pathogens that commonly dysregulated a group of biological processes. We validated our approach by checking whether these biclusters correspond to known hallmarks of bacterial infection. Indeed, these biclusters contained biological process such as inflammation, activation of dendritic cells, pro- and anti- apoptotic responses and other innate immune responses. Next, we identified biclusters containing pathogens that infected the same tissue. After a literature-based analysis of the drug targets contained in these biclusters, we suggested new uses of the drugs Anakinra, Etanercept, and Infliximab for gastrointestinal pathogens Yersinia enterocolitica, Helicobacter pylori kx2 strain, and enterohemorrhagic Escherichia coli and the drug Simvastatin for hematopoietic pathogen Ehrlichia chaffeensis.

CONCLUSIONS

Using a combination of automated analysis of host-response gene expression data and manual study of the literature, we have been able to suggest host-oriented treatments for specific bacterial infections. The analyses and suggestions made in this study may be utilized to generate concrete hypothesis on which gene sets to probe further in the quest for HOBS drug targets for bacterial infections. All our results are available at the following supplementary website: http://bioinformatics.cs.vt.edu/ murali/supplements/2013-kidane-plos-one.

Overexpression of C10orf116 promotes proliferation, inhibits apoptosis and enhances glucose transport in 3T3-L1 adipocytes

Data from our previous study demonstrated that C10orf116 is an adipocyte lineage-specific nuclear factor, which regulates master adipogenesis transcription factors during early differentiation. However, the precise functional properties of this gene have yet to be identified and further investigation is required. In the present study, we report the effects of C10orf116 expression on cell proliferation and apoptosis in vitro and observed that the overexpression of C10orf116 stimulates proliferation and inhibits apoptosis in preadipocytes. Furthermore, we investigated the effects of C10orf116 on glucose uptake and demonstrated that the ectopic expression of C10orf116 significantly increases insulin-stimulated glucose uptake in adipocytes by increasing glucose transporter type 4 (GLUT4) expression levels. Collectively, these data further support the hypothesis that C10orf116 is important in regulating glucose transport in adipocytes as well as the number of preadipocytes. The results of the present study may also provide insights into the complex mechanisms involved in the development of obesity.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

Association of the common MC4R rs17782313 polymorphism with antipsychotic-related weight gain

Weight gain is a frequent adverse effect of many second-generation antipsychotic (SGA) drugs. Although a number of candidate gene studies have focused on SGA-related weight gain, a clinical benefit for pharmacotherapy has not been achieved as yet. Genome-wide association studies offer great potential of identifying novel candidate genes and help to complete the search for relevant polygenetic risk factors. A polymorphism near the human melanocortin 4 receptor gene (MC4R) was associated with overweight and body mass index in recent studies. Owing to the central role of the MC4R receptor in energy homeostasis, we investigated the influence of the rs17782313 polymorphism on SGA-related weight gain. Three hundred forty-five white inpatients receiving different atypical antipsychotics (clozapine, olanzapine, risperidone, paliperidone, quetiapine, or amisulpride) were included in a naturalistic design. After 4 weeks of treatment, patients homozygous for the rs17782313 C-allele had a significantly higher risk of weight gain and body mass index increase, with a dose effect of the C-allele. In a subpopulation without additional weight gain-inducing comedication, the 106 TT-allele carriers gained on average 1.09% of their baseline weight within the 4 weeks of treatment, whereas the 57 CT-allele carriers and the 9 CC-allele carriers gained 3.28% and 5.47% (P = 0.003). Our findings indicate that the rs17782313 polymorphism could increase the amount of SGA-related weight gain and may influence MC4R expression, which could result in an imbalance of energy homeostasis. Nevertheless, further studies are needed to elucidate the role and mechanism of this polymorphism.

Leptin and leptin receptor genetic variants associate with habitual physical activity and the arm body composition response to resistance training

PURPOSE

We investigated the influence of Leptin (LEP) and leptin receptor (LEPR) SNPs on habitual physical activity (PA) and body composition response to a unilateral, upper body resistance training (RT) program.

METHODS

European-derived American volunteers (men=111, women=131, 23.4 ± 5.4 yr, 24.4 ± 4.6 kg·m(-2)) were genotyped for LEP 19 G>A (rs2167270), and LEPR 326 A>G (rs1137100), 668 A>G (rs1137101), 3057 G>A (rs1805096), and 1968 G>C (rs8179183). They completed the Paffenbarger PA Questionnaire. Arm muscle and subcutaneous fat volumes were measured before and after 12 wk of supervised RT with MRI. Multivariate and repeated measures ANCOVA tested differences among phenotypes by genotype and gender with age and body mass index as covariates.

RESULTS

Adults with the LEP 19 GG genotype reported more kcal/wk in vigorous intensity PA (1273.3 ± 176.8, p=0.017) and sports/recreation (1922.8 ± 226.0, p<0.04) than A allele carriers (718.0 ± 147.2, 1328.6 ± 188.2, respectively). Those with the LEP 19 GG genotype spent more h/wk in light intensity PA (39.7 ± 1.6) than A allele carriers (35.0 ± 1.4, p=0.03). In response to RT, adults with the LEPR 668 G allele gained greater arm muscle volume (67,687.05 ± 3186.7 vs. 52,321.87 ± 5125.05 mm(3), p=0.01) and subcutaneous fat volume (10,599.89 ± 3683.57 vs. -5224.73 ± 5923.98 mm(3), p=0.02) than adults with the LEPR 668 AA genotype, respectively.

CONCLUSION

LEP19 G>A and LEPR 668 A>G associated with habitual PA and the body composition response to RT. These LEP and LEPR SNPs are located in coding exons likely influencing LEP and LEPR function. Further investigation is needed to confirm our findings and establish mechanisms for LEP and LEPR genotype and PA and body composition associations we observed.

Obesity genetics: a monopoly game of genes

Obesity is a complex disease that affects all ethnic populations worldwide. The etiology of this disease is based on the interaction of genetic factors, environment and lifestyles indicators. Genetic contribution to the epidemic has gained attention from 2 sources: monogenic syndromes that display severe obesity, and the polygenic model of common obesity. Single mutations can render a syndrome with severe obesity resulting from alteration in central o peripheral appetite control mechanisms. The interaction of several polymorphisms and epigenetic modifications constitute the basic plot for common obesity, molecular ingredients that should not confuse the investigator-they make this riddle even harder to decipher.

Interleukin-1α Polymorphism -889C/T Related to Obesity in Korean Taeumin Women

Interleukin-1 (IL-1), a cytokine produced predominantly by cells from the macrophage lineage, can affect multiple neuroendocrine and metabolic functions. IL-1α production by cultured peripheral blood mononuclear cells from an obese group was significantly elevated in comparison to a control group. The aim of this study was to investigate whether the IL-1α polymorphism and Sasang constitution, a major branch in Korean traditional medicine, were related to obesity. Genotyping was done in 182 healthy females with a marked variation in body mass index (BMI) by a PCR-restriction fragment length polymorphism assay. The T allele was associated with decreased BMI (p = 0.020). In a subgroup with BMI values ranging from 27 ~ 29 kg/m2, the frequency of the T allele was significantly decreased (p = 0.004, odds ratio, OR = 0.141 compared to a subgroup with a BMI values less than 25 Kg/m2). In addition, in Taeumin female subjects, the frequency of the IL-1α T allele was markedly decreased in a subgroup with BMI values in the range of 27 ~ 29 kg/m2compared to a lean group with BMI values less than 25 kg/m2(p = 0.004, OR = 0.139). In Korean women, an association was found between -889C/T polymorphism in the regulatory region of the IL-1α gene and BMI values. In addition, an association was found among IL-1α polymorphism, obesity, and the Sasang constitution.

Mouse obesity network reconstruction with a variational Bayes algorithm to employ aggressive false positive control

BACKGROUND

We propose a novel variational Bayes network reconstruction algorithm to extract the most relevant disease factors from high-throughput genomic data-sets. Our algorithm is the only scalable method for regularized network recovery that employs Bayesian model averaging and that can internally estimate an appropriate level of sparsity to ensure few false positives enter the model without the need for cross-validation or a model selection criterion. We use our algorithm to characterize the effect of genetic markers and liver gene expression traits on mouse obesity related phenotypes, including weight, cholesterol, glucose, and free fatty acid levels, in an experiment previously used for discovery and validation of network connections: an F2 intercross between the C57BL/6 J and C3H/HeJ mouse strains, where apolipoprotein E is null on the background.

RESULTS

We identified eleven genes, Gch1, Zfp69, Dlgap1, Gna14, Yy1, Gabarapl1, Folr2, Fdft1, Cnr2, Slc24a3, and Ccl19, and a quantitative trait locus directly connected to weight, glucose, cholesterol, or free fatty acid levels in our network. None of these genes were identified by other network analyses of this mouse intercross data-set, but all have been previously associated with obesity or related pathologies in independent studies. In addition, through both simulations and data analysis we demonstrate that our algorithm achieves superior performance in terms of power and type I error control than other network recovery algorithms that use the lasso and have bounds on type I error control.

CONCLUSIONS

Our final network contains 118 previously associated and novel genes affecting weight, cholesterol, glucose, and free fatty acid levels that are excellent obesity risk candidates.

Sex distribution of offspring-parents obesity: Angel's hypothesis revisited

This study, which is based on two cross sectional surveys' data, aims to establish any effect of parental obesity sex distribution of offspring and to replicate the results that led to the hypothesis that obesity may be associated with sex-linked recessive lethal gene. A representative sample of 4,064 couples living in Renfrew/Paisley, Scotland was surveyed 1972-1976. A total of 2,338 offspring from 1,477 of the couples screened in 1972-1976, living in Paisley, were surveyed in 1996. In this study, males represented 47.7% among the total offspring of the couples screened in 1972-1976. In the first survey there was a higher male proportion of offspring (53%, p < 0.05) from parents who were both obese, yet this was not significant after adjustment for age of parents. Also, there were no other significant differences in sex distribution of offspring according to body mass index, age, or social class of parents. The conditions of the original 1949 study of Angel ( 1949 ) (which proposed a sex-linked lethal recessive gene) were simulated by selecting couples with at least one obese daughter. In this subset, (n = 409), obesity in fathers and mothers was associated with 26% of offspring being male compared with 19% of offspring from a non-obese father and obese mother. Finally we conclude that families with an obese father have a higher proportion of male offspring. These results do not support the long-established hypotheses of a sex-linked recessive lethal gene in the etiology of obesity.

Common genetic link between metabolic syndrome components and senile cataract

Relationship between cataract and metabolic syndrome (MetS) is well established, but genetic link remains to be explored. D2S439 at 2q37 linked with QTL controlling visceral fat was investigated for its association with senile cataract. Two hundred and twenty-seven subjects including 119 cataract cases were genotyped for D2S439, tetra nucleotide repeat marker. Statistical tools assessed the association of marker's allele with anthropometric, clinical and oxidation stress parameters. Cases with longer allele ≥ (CTAT)(12) repeats, differed significantly from controls (0.77 vs. 0.58, p < 0.0001). Cases with at least one longer allele had higher waist circumference (50% vs. 15%, p = 0.0090), hyper-triglyceridemia (28% vs. 11%), hypo-HDL cholesterolemia (80% vs. 74%) and high diastolic blood pressure (37% vs. 26%) when compared to cases bearing the shorter allele. Cataract subjects with at least one longer allele had significantly raised lipid peroxidation levels (p = 0.0095) and showed an increased risk for cataract (OR = 5.86, CI(95%) = 1.49-23.11, p = 0.0114) after controlling for dependent variables. This exploratory study suggests that presence of even a single longer allele of D2S439 is associated with both cataract and MetS components in Asian Indians, unraveling the existence of a shared genetic locus.

Association study of apolipoprotein L-I Lys166Glu and Ile244Met gene variants with obesity in Chinese subjects

AIMS

ApoL-I is a newly found component of high-density lipoprotein, and has a potential role in lipid metabolism. This study was mainly to examine the possible association of the ApoL-I gene polymorphism with obesity and plasma lipid levels in the Chinese population.

METHODS

Three hundred nineteen Han Chinese (109 obese and 210 nonobese control subjects) in Chengdu area were studied using polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

The Lys and Glu allele frequencies of the apoL-I gene at the Lys166Glu site in obese and nonobese control groups were 0.830, 0.170 and 0.814, 0.186, respectively. The Ile and Met allele frequencies of the gene at Ile244Met site in the obese and the control groups were 0.844, 0.156 and 0.831, 0.169, respectively. The 166Glu and 244Met allele frequencies of the two polymorphisms in obese subjects were not different from those in the controls, respectively (p>0.05). In the nonobese group, subjects with genotype Lys/Lys at the Lys166Glu site or Ile/Ile at the Ile244Met site had a higher serum mean concentration of triglyceride (TG) as compared with those of corresponding Glu or Met allele carriers (p<0.05). In addition, serum apoC-III and apoE levels were affected by genotypes of Lys166Glu and Ile224Met polymorphisms, respectively, in the control group (all p<0.05).

CONCLUSION

The current study, for the first time, provides evidence that Lys166Glu and Ile244Met polymorphisms in apoL-I gene are associated with TG, apoC-III, and apoE levels in nonobese Chinese. However, these polymorphisms are not associated with obesity in the population.

Cool-1/βPIX functions as a guanine nucleotide exchange factor in the cycling of Cdc42 to regulate insulin secretion

Second-phase insulin release requires the sustained mobilization of insulin granules from internal storage pools to the cell surface for fusion with the plasma membrane. However, the detailed mechanisms underlying this process remain largely unknown. GTP-loading of the small GTPase Cdc42 is the first glucose-specific activation step in the process, although how glucose triggers Cdc42 activation is entirely unknown. In a directed candidate screen for guanine nucleotide exchange factors (GEFs), which directly activate small GTPases, Cool-1/βPix was identified in pancreatic islet beta cells. In support of its role as the beta cell Cdc42 GEF, βPix coimmunoprecipitated with Cdc42 in human islets and MIN6 beta cells in a glucose-dependent manner, peaking just prior to Cdc42 activation. Furthermore, RNAi-mediated βPix reduction by 50% corresponded to full ablation of glucose-induced Cdc42 activation and significant attenuation of basal and glucose-stimulated insulin secretion. Of the two Cdc42 guanine nucleotide dissociation inhibitor (GDI) proteins identified in beta cells, βPix competed selectively with caveolin-1 (Cav-1) but not RhoGDI in coimmunoprecipitation and GST-Cdc42-GDP interaction assays. However, a phospho-deficient Cav-1-Y14F mutant failed to compete with βPix; Cav-1(Tyr14) is an established phosphorylation site for Src kinase. Taken together, these data support a new model, wherein glucose stimulates Cav-1 and induces its dissociation from Cdc42, possibly via Src kinase activation to phosphorylate Cav-1(Tyr14), to promote Cdc42-βPix binding and Cdc42 activation, and to trigger downstream signaling and ultimately sustain insulin release.

Spliceosomal intron insertions in genome compacted ray-finned fishes as evident from phylogeny of MC receptors, also supported by a few other GPCRs

BACKGROUND

Insertions of spliceosomal introns are very rare events during evolution of vertebrates and the mechanisms governing creation of novel intron(s) remain obscure. Largely, gene structures of melanocortin (MC) receptors are characterized by intron-less architecture. However, recently a few exceptions have been reported in some fishes. This warrants a systematic survey of MC receptors for understanding intron insertion events during vertebrate evolution.

METHODOLOGY/PRINCIPAL FINDINGS

We have compiled an extended list of MC receptors from different vertebrate genomes with variations in fishes. Notably, the closely linked MC2Rs and MC5Rs from a group of ray-finned fishes have three and one intron insertion(s), respectively, with conserved positions and intron phase. In both genes, one novel insertion was in the highly conserved DRY motif at the end of helix TM3. Further, the proto-splice site MAG↑R is maintained at intron insertion sites in these two genes. However, the orthologs of these receptors from zebrafish and tetrapods are intron-less, suggesting these introns are simultaneously created in selected fishes. Surprisingly, these novel introns are traceable only in four fish genomes. We found that these fish genomes are severely compacted after the separation from zebrafish. Furthermore, we also report novel intron insertions in P2Y receptors and in CHRM3. Finally, we report ultrasmall introns in MC2R genes from selected fishes.

CONCLUSIONS/SIGNIFICANCE

The current repository of MC receptors illustrates that fishes have no MC3R ortholog. MC2R, MC5R, P2Y receptors and CHRM3 have novel intron insertions only in ray-finned fishes that underwent genome compaction. These receptors share one intron at an identical position suggestive of being inserted contemporaneously. In addition to repetitive elements, genome compaction is now believed to be a new hallmark that promotes intron insertions, as it requires rapid DNA breakage and subsequent repair processes to gain back normal functionality.

The profile of the Greek ‘XXL’ family

Objective

To identify Greek families in which all members were overweight or obese (XXL families) and to describe their profile with regard to their socio-economic status and their eating behaviours and practices.

Design

A prospective cohort study.

Setting

The metropolitan area of Kavala.

Subjects

We recruited children aged 11 and 12 years from twelve primary schools, and their parents, from volunteers. Auxologic measurements of the children included height and weight. A structured questionnaire pertaining to information on the socio-economic status of the family, anthropometric values and educational status of parents, dietary habits and the availability of various food products and beverages at home, as well as dietary intake, physical activity, time spent sleeping and time spent watching television, was filled in by one of the parents of each child. A total of 331 families finally participated.

Results

In sixty-one families (18·43 %) both parents and child were either overweight or obese (XXL family), and in seven of these families all members were obese. Only twenty-eight families (8·46 %) had all members with a normal BMI. The XXL family was associated with lower educational status of both parents, whereas a higher percentage of XXL families resided in rural areas and had lower income. Skipping breakfast and spending more than 3 h in front of a screen every day were more frequently observed in XXL families. With regard to the availability of various food products and beverages at home, no significant differences were observed between XXL families and the rest of the studied families.

Conclusions

Greek XXL families have lower educational status and lower annual income.

AMPK as Target for Intervention in Childhood and Adolescent Obesity

Childhood obesity is a major worldwide health problem. Intervention programs to ameliorate the rate of obesity have been designed and implemented; yet the epidemic has no end near in sight. AMP-activated protein kinase (AMPK) has become one of the most important key elements in energy control, appetite regulation, myogenesis, adipocyte differentiation, and cellular stress management. Obesity is a multifactorial disease, which has a very strong genetic component, especially epigenetic factors. The intrauterine milieu has a determinant impact on adult life, since the measures taken for survival are kept throughout life thanks to epigenetic modification. Nutrigenomics studies the influence of certain food molecules on the metabolome profile, raising the question of an individualized obesity therapy according to metabolic (and probably) genetic features. Metformin, an insulin sensitizing agent, its known to lower insulin resistance and enhance metabolic profile, with an additional weight reduction capacity, via activation of AMPK. Exercise is coadjutant for lifestyle modifications, which also activates AMPK in several ways contributing to glucose and fat oxidation. The following review examines AMPK's role in obesity, applying its use as a tool for childhood and adolescent obesity.

Abundant variations of MC4R gene revealed by Phylogenies of Yak (Bos grunniens) and other mammals

MC4R gene was proved to play important roles in body weight regulation in many mammals and exhibit higher homology among different species. The mutations MC4R significantly correlated to the restricted feeding weight, fat deposition and energy balance. In this work, ORF sequences of MC4R gene of Bos grunniens were cloned and phylogenetic relationships of yak and other mammals were analyzed on the basis of MC4R genes. Totally 290 variable sites were examined in 25 sequences from 22 different mammals, and 23 haplotypes were defined with a haplotype diversity of 0.9900. All the sequences were clustered into phylogenetic clades representing different orders or families. The individuals of Bos grunniens, Bos taurus and Ovis aries which belonged to the family of Bovidae were more divergent from the other orders or families and bovid animals may have branched out from the phylogenetic tree earlier than other mammals analyzed during 450 million years of vertebrate evolution. Amino acid sequences inferred from MC4R genes exhibited 54 variable sites, while high conservation of MC4R was observed within the same order or family. We concluded that coding region of MC4R gene displayed abundant variations among different mammal phylogenetic clades, whereas, the conservation of MC4R within order or family could be explained that MC4R gene may have been subjected to substantial constraints or strong purifying selection during several million years of mammal evolution.

Spatial organization of transmembrane receptor signalling

The spatial organization of transmembrane receptors is a critical step in signal transduction and receptor trafficking in cells. Transmembrane receptors engage in lateral homotypic and heterotypic cis-interactions as well as intercellular trans-interactions that result in the formation of signalling foci for the initiation of different signalling networks. Several aspects of ligand-induced receptor clustering and association with signalling proteins are also influenced by the lipid composition of membranes. Thus, lipid microdomains have a function in tuning the activity of many transmembrane receptors by positively or negatively affecting receptor clustering and signal transduction. We review the current knowledge about the functions of clustering of transmembrane receptors and lipid-protein interactions important for the spatial organization of signalling at the membrane.

Association of lifestyle factors, polymorphisms in adiponectin, perilipin and hormone sensitive lipase, and clinical markers in Japanese males

According to recent genome-wide association studies, a number of single nucleotide polymorphisms is reported to be associated with diseases or several clinical markers. Among them, adiponectin (ADIPOQ) and perilipin (PLIN) polymorphisms are major factors of obesity. However, the association between lifestyle factor, these polymorphisms and obesity-related clinical markers in Japanese is not well researched. Therefore, the aim of present study is to investigate the association between lifestyle factor, polymorphisms of lipid metabolic genes, and clinical markers in 148 middle-aged Japanese males. The study revealed that ADIPOQ 45 T>G and ADIPOQ 276 G>T genotypes were significantly associated with triglyceride, total cholesterol, hemoglobin A1c (HbA1c) in blood and body mass index (BMI). PLIN4 11482 G>A and hormone sensitive lipase (LIPE)-60 C>G genotypes were respectively associated with BMI and serum triglyceride. Not only genetic factors but also lifestyle factors influence several clinical markers. The BMI of subjects who like sweets and have the GG allele in ADIPOQ 276 G>T was higher than that of subjects who don't like sweets. The habit of eating fruits and fish affected low-density lipoprotein-cholesterol of the GT allele and HbA1c of the TT allele in ADIPOQ 276 G>T. Those findings indicate improvement and conservation of lifestyle depending on genetic predisposition in ADIPOQ, PLIN and LIPE should be encouraged.

ALOX12 polymorphisms are associated with fat mass but not peak bone mineral density in Chinese nuclear families

OBJECTIVE

Arachidonate 12-lipoxygenase (ALOX12) is a member of the lipoxygenase superfamily, which catalyzes the incorporation of molecular oxygen into polyunsaturated fatty acids. The products of ALOX12 reactions serve as endogenous ligands for peroxisome proliferator-activated receptor γ (PPARG). The activation of the PPARG pathway in marrow-derived mesenchymal progenitors stimulates adipogenesis and inhibits osteoblastogenesis. Our objective was to determine whether polymorphisms in the ALOX12 gene were associated with variations in peak bone mineral density (BMD) and obesity phenotypes in young Chinese men.

METHODS

All six tagging single-nucleotide polymorphisms (SNPs) in the ALOX12 gene were genotyped in a total of 1215 subjects from 400 Chinese nuclear families by allele-specific polymerase chain reaction. The BMD at the lumbar spine and hip, total fat mass (TFM) and total lean mass (TLM) were measured using dual-energy X-ray absorptiometry. The pairwise linkage disequilibrium among SNPs was measured, and the haplotype blocks were inferred. Both the individual SNP markers and the haplotypes were tested for an association with the peak BMD, body mass index, TFM, TLM and percentage fat mass (PFM) using the quantitative transmission disequilibrium test (QTDT).

RESULTS

Using the QTDT, significant within-family association was found between the rs2073438 polymorphism in the ALOX12 gene and the TFM and PFM (P=0.007 and 0.012, respectively). Haplotype analyses were combined with our individual SNP results and remained significant even after correction for multiple testing. However, we failed to find significant within-family associations between ALOX12 SNPs and the BMD at any bone site in young Chinese men.

CONCLUSIONS

Our present results suggest that the rs2073438 polymorphism of ALOX12 contributes to the variation of obesity phenotypes in young Chinese men, although we failed to replicate the association with the peak BMD variation in this sample. Further independent studies are needed to confirm our findings.

Endocannabinoid Pro129Thr FAAH functional polymorphism but not 1359G/A CNR1 polymorphism is associated with antipsychotic-induced weight gain

Several candidate genes have been associated with antipsychotic-induced body weight (BW) gain. Because the endocannabinoid system is deeply involved in BW regulation, endocannabinoid genes may have a role in the antipsychotic-induced weight gain. Therefore, we investigated the 1359 G/A (rs1049353) single nucleotide polymorphisms (SNP) of the cannabinoid receptor 1 (CNR1) gene, which codes the endocannabinoid CB1 receptor, and the complementary DNA (cDNA) 385C/A (rs324420) SNP of the FAAH gene, which codes the endocannabinoid degrading enzyme, for their role in BW changes induced by antipsychotic drugs. Eighty-three white psychotic patients who underwent a naturalistic treatment with different antipsychotics (clozapine, olanzapine, risperidone, quetiapine, and haloperidol) and completed a 24-week treatment period were included into the study together with 80 age- and sex-matched white healthy controls. At the 24th week of treatment, 41 patients gained more than 7% of their baseline BW. No significant differences between patients and controls emerged in genotype and allele frequencies of both SNPs. Genotype and allele frequencies of the FAAH cDNA 385C/A SNP but not of the CNR1 1359 G/A SNP significantly differed between subjects who gained more than 7% of BW and those who did not, with both AC and AA genotypes and the A allele being significantly more frequent in patients who gained more than 7% of their baseline BW. Present findings, although obtained in a small population and in a naturalistic setting, suggest that the cDNA 385C/A SNP of the FAAH gene may predispose subjects to get a clinically meaningful weight gain after antipsychotic exposure.

Family and population-based studies of variation within the ghrelin receptor locus in relation to measures of obesity

BACKGROUND

The growth hormone secretagogue receptor (GHSR) is mediating hunger sensation when stimulated by its natural ligand ghrelin. In the present study, we tested the hypothesis that common and rare variation in the GHSR locus are related to increased prevalence of obesity and overweight among Whites.

METHODOLOGY/PRINCIPAL FINDINGS

In a population-based study sample of 15,854 unrelated, middle-aged Danes, seven variants were genotyped to capture common variation in an 11 kbp region including GHSR. These were investigated for their individual and haplotypic association with obesity. None of these analyses revealed consistent association with measures of obesity. A -151C/T promoter mutation in the GHSR was found in two unrelated obese patients. One family presented with complete co-segregation, but the other with incomplete co-segregation. The mutation resulted in an increased transcriptional activity (p<0.02) and introduction of a specific binding for Sp-1-like nuclear extracts relative to the wild type. The -151C/T mutation was genotyped in the 15,854 Danes with a minor allele frequency of 0.01%. No association with obesity in carriers (mean BMI: 27+/-4 kg/m(2)) versus non-carriers (mean BMI: 28+/-5 kg/m(2)) (p>0.05) could be shown.

CONCLUSIONS/SIGNIFICANCE

In a population-based study sample of 15,854 Danes no association between GHSR genotypes and measures of obesity and overweight was found. Also, analyses of GHSR haplotypes lack consistent associations with obesity related traits. A rare functional GHSR promoter mutation variant was identified, yet there was no consistent relationship with obesity in neither family- nor population-based studies.

Transcriptional profiling of hypothalamus during development of adiposity in genetically selected fat and lean chickens

The hypothalamus integrates peripheral signals to regulate food intake, energy metabolism, and ultimately growth rate and body composition in vertebrates. Deviations in hypothalamic regulatory controls can lead to accumulation of excess body fat. Many regulatory genes involved in this process remain unidentified, and comparative studies may be helpful to unravel evolutionarily conserved mechanisms controlling body weight and food intake. In the present study, divergently selected fat (FL) and lean (LL) lines of chickens were used to characterize differences in hypothalamic gene expression in these unique genetic lines that develop differences in adiposity without differences in food intake or body weight. Hypothalamic transcriptional profiles were defined with cDNA microarrays before and during divergence of adiposity between the two lines. Six differentially expressed genes identified in chickens are related to genes associated with control of body fat in transgenic or knockout mice, supporting the importance of these genes across species. We identified differences in expression of nine genes involved in glucose metabolism, suggesting that alterations in hypothalamic glycolysis might contribute to differences in levels of body fat between genotypes. Expression of the sweet taste receptor (TAS1R1), which in mammals is involved in glucose sensing and energy uptake, was also higher in FL chickens, suggesting that early differences in glucose sensing might alter the set point for subsequent body composition. Differences in expression of genes associated with tumor necrosis factor (TNF) signaling were also noted. In summary, we identified alterations in transcriptional and metabolic processes within the hypothalamus that could contribute to excessive accumulation of body fat in FL chickens in the absence of differences in food intake, thereby contributing to the genetic basis for obesity in this avian model.