New advances in the genetics of early onset obesity

Setmelanotide in patients aged 2-5 years with rare MC4R pathway-associated obesity (VENTURE): a 1 year, open-label, multicenter, phase 3 trial

BACKGROUND

Setmelanotide, a melanocortin-4 receptor (MC4R) agonist, has been shown to reduce hunger and weight in patients aged 6 years and older with proopiomelanocortin (POMC) deficiency (including biallelic variants in proprotein convertase subtilisin/kexin type 1 [PCSK1]), leptin receptor (LEPR) deficiency, or Bardet-Biedl syndrome (BBS). No approved therapies for patients younger than 6 years old currently exist. The phase 3, open-label VENTURE trial aimed to evaluate the efficacy and safety of setmelanotide in patients aged 2-5 years with POMC or LEPR deficiency or BBS.

METHODS

This phase 3, open-label, multicentre trial, conducted across six sites in the USA, the UK, Spain, and Australia, enrolled eligible patients aged 2-5 years who had hyperphagia and obesity due to biallelic POMC (including PCSK1) or LEPR variants or genetically confirmed BBS. Open-label subcutaneous setmelanotide was administered once daily for 52 weeks, starting at 0·5 mg with doses increasing every 2 weeks in 0·5 mg increments until reaching the maximum dose based on weight. The co-primary endpoints at week 52 were the percentage of patients reaching a 0·2-point decrease or greater in BMI Z score (a statistical measure used to assess BMI in paediatric patients considering a patient's BMI and comparing it to reference values for the same age and sex) and mean percent change in BMI. Additional endpoints measured safety, hunger, weight-related outcomes, and caregiver burden. The study is registered at ClinicalTrials.gov (NCT04966741) and is complete.

FINDINGS

Between March 8, 2022, and Sept 18, 2023, 13 patients were screened at the six sites, and 12 patients were enrolled in the study (seven with POMC or LEPR and five with BBS); one patient with BBS was excluded as their BMI was not at the 97th percentile or above. Of the 12 patients enrolled, most were male (seven [58%] vs five [42%] for female) and the mean age was 3·6 years (SD 0·9). 11 patients completed the trial. Ten (83%) of the 12 overall participants reached a 0·2-point reduction or more in BMI Z score per WHO methodology at week 52 (95% CI 58·7-99·8). The mean percent change in BMI from baseline at week 52 was -18% (SD 13) in the overall safety population. Mean percent change in BMI at week 52 was -26% (SD 11) in patients with POMC or LEPR deficiency and -10% (9) in patients with BBS. Mean reductions in secondary endpoints of BMI Z score (3·4 [2·5]) and percent of the BMI 95th percentile (32·5 [22·9]) were seen at Week 52. 91% of caregivers reported that patients were less hungry than at baseline. All adverse events were mild or moderate; skin hyperpigmentation, vomiting, nasopharyngitis, upper respiratory tract infection, and injection site reactions were most common. No serious adverse events or adverse events leading to study discontinuation or death were reported.

INTERPRETATION

To our knowledge this is the first trial of setmelanotide in patients younger than 6 years old. These results support the benefit of the drug as an early intervention to manage obesity in this population.

FUNDING

Rhythm Pharmaceuticals.

Genetic Obesity Disorders: Body Mass Index Trajectories and Age of Onset of Obesity Compared with Children with Obesity from the General Population

OBJECTIVE

We sought to assess body mass index trajectories of children with genetic obesity to identify optimal early age of onset of obesity (AoO) cut-offs for genetic screening.

STUDY DESIGN

This longitudinal, observational study included growth measurements from birth onward of children with nonsyndromic and syndromic genetic obesity and control children with obesity from a population-based cohort. Diagnostic performance of AoO was evaluated.

RESULTS

We describe the body mass index trajectories of 62 children with genetic obesity (29 nonsyndromic, 33 syndromic) and 298 controls. Median AoO was 1.2 years in nonsyndromic genetic obesity (0.4 and 0.6 years in biallelic LEPR and MC4R; 1.7 in heterozygous MC4R); 2.0 years in syndromic genetic obesity (0.9, 2.3, 4.3, and 6.8 years in pseudohypoparathyroidism, Bardet-Biedl syndrome, 16p11.2del syndrome, and Temple syndrome, respectively); and 3.8 years in controls. The optimal AoO cut-off was ≤3.9 years (sensitivity, 0.83; specificity, 0.49; area under the curve, 0.79; P < .001) for nonsyndromic and ≤4.7 years (sensitivity, 0.82; specificity, 0.37; area under the curve, 0.68; P = .001) for syndromic genetic obesity.

CONCLUSIONS

Optimal AoO cut-off as single parameter to determine which children should undergo genetic testing was ≤3.9 years. In case of older AoO, additional features indicative of genetic obesity should be present to warrant genetic testing. Optimal cut-offs might differ across different races and ethnicities.

Retrospective analysis of the Special Olympics Health Promotion database for nutrition-specific variables

BACKGROUND

Studies have shown that individuals with intellectual disabilities (ID) exhibit a high prevalence of obesity and poor-quality diet. The population of individuals with ID include athletes that participate in Special Olympics.

AIM

In order to develop appropriate educational programs for the Special Olympics Athletes in Connecticut, a baseline of the various health and nutrition variables needed to be established by examining the existing data in the Special Olympics International's Health Promotion database.

METHODS

A retrospective analysis was performed using data from the Special Olympics International (SOI) Health Promotion database. The study population included athletes at least 20 years of age (n = 47,932) and divided into sub-groups of non-USA, USA and Connecticut (CT). The data was provided by SOI to the research team in a de-identified form covering the time frame of 2014-2019. The existing data was originally collected by trained SO volunteers and included age, height, weight, bone mineral density (BMD), blood pressure (BP) variables and a health habits questionnaire. In addition to basic descriptive statistics, analysis was performed using Chi Squared Analysis and ANOVA with post-hoc. A significance level of p value ≤ 0.05 was used for all analyses.

RESULTS

Results show a high prevalence of obesity, high blood pressure, low bone mineral density and a poor-quality diet across all groups. CT athletes were older and had a more even distribution by gender compared to the non-USA and USA groups. CT athletes had a high prevalence of obesity, HTN, and low BMD, as well as, a poor quality diet reflected by high frequency of consumption of sweetened beverages, fast food and snack food. CT athletes also did not consume the recommended daily servings of calcium containing foods or fruits and vegetables.

CONCLUSION

This data will be used to develop educational programs that will help to improve the overall health of Special Olympics Athletes in Connecticut.

Influence of betahistine repeated administration on a weight gain and selected metabolic parameters in the model of excessive eating in rats

It is important to search for a promising therapeutic target or small molecules that can control excessive eating since limiting the intake of foods, especially tasty ones, could be effective in the treatment or prevention of obesity. Some studies indicate betahistine as an unique drug having the ability to ameliorate, for example, antipsychotic-induced weight gain. This study aimed to determine whether repeated administration of betahistine (histamine H1R agonist and H3R antagonist) could be beneficial in reducing the intake of tasty foods or the body's response to overeating via mechanisms such as by influencing the levels of hormones involved in the regulation of food intake or the levels of selected metabolic parameters. Studies were performed in the excessive eating model in rats, which perfectly illustrates the harmful high-caloric intake from freely available tasty products rich in sugar and fat. Our results indicated that repeated administration of betahistine to rats caused lower gain of body mass compared to the control rats fed palatable feed. Interestingly, betahistine treatment increased the consumption of cheese, which is a source of histamine. Although betahistine did not prevent the development of metabolic disorders, such as reduced glucose tolerance, in test animals, it significantly increased the level of high-density lipoprotein cholesterol, which could certainly be considered beneficial. Further studies should be conducted to investigate the effect of repeated administration of betahistine on satiety, gastrointestinal disorders, and the preference for histamine-containing foods.

Genetic Determinants of Childhood Obesity

Obesity represents a major health burden to both developed and developing countries. Furthermore, the incidence of obesity is increasing in children. Obesity contributes substantially to mortality in the United States by increasing the risk for type 2 diabetes, cardiovascular-related diseases, and other comorbidities. Despite environmental changes over past decades, including increases in high-calorie foods and sedentary lifestyles, there is very clear evidence of a genetic predisposition to obesity risk. Childhood obesity cases can be categorized in one of two ways: syndromic or non-syndromic. Syndromic obesity includes disorders such as Prader-Willi syndrome, Bardet-Biedl syndrome, and Alström syndrome. Non-syndromic cases of obesity can be further separated into rarer instances of monogenic obesity and much more common forms of polygenic obesity. The advent of genome-wide association studies (GWAS) and next-generation sequencing has driven significant advances in our understanding of the genetic contribution to childhood obesity. Many rare and common genetic variants have been shown to contribute to the heritability in obesity, although the molecular mechanisms underlying most of these variants remain unclear. An important caveat of GWAS efforts is that they do not strictly represent gene target discoveries, rather simply the uncovering of robust genetic signals. One clear example of this is with progress in understanding the key obesity signal harbored within an intronic region of the FTO gene. It has been shown that the non-coding region in which the variant actually resides in fact influences the expression of genes distal to FTO instead, specifically IRX3 and IRX5. Such discoveries suggest that associated non-coding variants can be embedded within or next to one gene, but commonly influence the expression of other, more distal effector genes. Advances in genetics and genomics are therefore contributing to a deeper understanding of childhood obesity, allowing for development of clinical tools and therapeutic agents.

Monogenic leptin deficiency in early childhood obesity

BACKGROUND

Early childhood obesity is a public health problem worldwide. It affects different aspects of physical and mental child's health. Identifying the etiologies, especially treatable and preventable causes, can direct health professionals toward proper management. Analysis of serum leptin levels and leptin gene mutations is a rapid and easy step toward the diagnosis of congenital leptin deficiency that is considered an important cause in early childhood obesity.

OBJECTIVES

The aim of this study was to diagnose monogenic leptin deficiency in Egyptian children presenting with early onset obesity (EOO).

METHODS

The current cross-sectional study included 80 children who developed obesity during the first year of life with BMI > 2 SD (for age and sex). The studied population was subjected to history taking, auxological assessment, serum leptin assay, and leptin gene sequencing.

RESULTS

Ten cases had leptin deficiency (12.5%), while 18 cases showed elevated leptin levels (22.5%). Leptin gene variants in the coding region were identified in 30% of the leptin-deficient group: two novel homozygous disease-causing variants (c.104 T > G and c.34 delC) and another previously reported homozygous pathogenic variant (c.313C > T).

CONCLUSION

Leptin deficiency is considered a significant cause of monogenic obesity in Egyptian children with early-onset obesity as the diagnosis of these patients would be a perfect target for recombinant leptin therapy.

How youth cognitive and sociodemographic factors relate to the development of overweight and obesity in the UK and the USA: a prospective cross-cohort study of the National Child Development Study and National Longitudinal Study of Youth 1979

OBJECTIVES

We investigated how youth cognitive and sociodemographic factors are associated with the aetiology of overweight and obesity. We examined both onset (who is at early risk for overweight and obesity) and development (who gains weight and when).

DESIGN

Prospective cohort study.

SETTING

We used data from the US National Longitudinal Study of Youth 1979 (NLSY) and the UK National Child Development Study (NCDS); most of both studies completed a cognitive function test in youth.

PARTICIPANTS

12 686 and 18 558 members of the NLSY and NCDS, respectively, with data on validated measures of youth cognitive function, youth socioeconomic disadvantage (eg, parental occupational class and time spent in school) and educational attainment. Height, weight and income data were available from across adulthood, from individuals' 20s into their 50s.

PRIMARY AND SECONDARY OUTCOME MEASURES

Body mass index (BMI) for four time points in adulthood. We modelled gain in BMI using latent growth curve models to capture linear and quadratic components of change in BMI over time.

RESULTS

Across cohorts, higher cognitive function was associated with lower overall BMI. In the UK, 1 SD higher score in cognitive function was associated with lower BMI (β=-0.20, 95% CI -0.33 to -0.06 kg/m²). In America, this was true only for women (β=-0.53, 95% CI -0.90 to -0.15 kg/m²), for whom higher cognitive function was associated with lower BMI. In British participants only, we found limited evidence for negative and positive associations, respectively, between education (β=-0.15, 95% CI -0.26 to -0.04 kg/m²) and socioeconomic disadvantage (β=0.33, 95% CI 0.23 to 0.43 kg/m²) and higher BMI. Overall, no cognitive or socioeconomic factors in youth were associated with longitudinal changes in BMI.

CONCLUSIONS

While sociodemographic and particularly cognitive factors can explain some patterns in individuals' overall weight levels, differences in who gains weight in adulthood could not be explained by any of these factors.

Whole exome sequencing reveals novel LEPR frameshift mutation in severely obese children from Western India

Background

Obesity, especially early onset of obesity is a serious health concern in both developed and developing countries. This is further associated with serious comorbidities like a fatty liver disease, cardiovascular diseases, type‐2 diabetes, obstructive sleep apnea, renal complications and respiratory problems. Many times early onset of obesity is linked with heritable monogenic, polygenic and syndromic forms. Globally, studies on roles of genes involved in early onset of obesity are limited.

Methods

Here in this study, a consanguineous family of Western Indian origin having four siblings, one unaffected and three affected with severe early onset of obesity was enrolled. Affected siblings also displayed comorbidities like mild to moderate obstructive sleep apnea, raised Renal Resistance Index, oliguria, and severe anemia. Whole Exome Sequencing (WES) of Trio with one affected and unaffected sibling was done. Data analysis was performed to check pathogenic mutation segregation in unaffected parents with affected and unaffected sibling.

Results

WES of trio identified novel frameshift mutation in the LEPR gene resulting in truncated leptin receptor (LEPR). The same mutation was confirmed in other affected siblings and two siblings of distant relatives by Sanger sequencing. The possible effects of truncating mutation in LEPR function by in silico analysis were also studied.

Conclusion

Understanding genetic basis of obesity might provide a clue for better management and treatment in times to come. This work demonstrates identification of novel mutation in LEPR gene resulting into early onset of obesity. Discovery of novel, population‐specific genomics markers will help population screening programs in creating base for possible therapeutic applications and prevention of this disease for next generations.

Congenital Leptin Deficiency and Leptin Gene Missense Mutation Found in Two Colombian Sisters with Severe Obesity

Background: Congenital leptin deficiency is a recessive genetic disorder associated with severe early-onset obesity. It is caused by mutations in the leptin (LEP) gene, which encodes the protein product leptin. These mutations may cause nonsense-mediated mRNA decay, defective secretion or the phenomenon of biologically inactive leptin, but typically lead to an absence of circulating leptin, resulting in a rare type of monogenic extreme obesity with intense hyperphagia, and serious metabolic abnormalities. Methods: We present two severely obese sisters from Colombia, members of the same lineal consanguinity. Their serum leptin was measured by MicroELISA. DNA sequencing was performed on MiSeq equipment (Illumina) of a next-generation sequencing (NGS) panel involving genes related to severe obesity, including LEP. Results: Direct sequencing of the coding region of LEP gene in the sisters revealed a novel homozygous missense mutation in exon 3 [NM_002303.3], C350G>T [p.C117F]. Detailed information and clinical measurements of these sisters were also collected. Their serum leptin levels were undetectable despite their markedly elevated fat mass. Conclusions: The mutation of LEP, absence of detectable leptin, and the severe obesity found in these sisters provide the first evidence of monogenic leptin deficiency reported in the continents of North and South America.

Obesity genetics and cardiometabolic health: Potential for risk prediction

The increasing burden of obesity worldwide and its effect on cardiovascular disease (CVD) risk is an opportunity for evaluation of preventive approaches. Both obesity and CVD have a genetic background and polymorphisms within genes which enhance expression of variant proteins that influence CVD in obesity. Genome-based prediction may therefore be a feasible strategy, but the identification of genetically driven risk factors for CVD manifesting as clinically recognized phenotypes is a major challenge. Clusters of such risk factors include hyperglycaemia, hypertension, ectopic liver fat, and inflammation. All involve multiple genetic pathways having complex interactions with variable environmental influences. The factors that make significant contributions to CVD risk include altered carbohydrate homeostasis, ectopic deposition of fat in muscle and liver, and inflammation, with contributions from the gut microbiome. A futuristic model depends on harnessing the predictive power of plausible genetic variants, phenotype reversibility, and effective therapeutic choices based on genotype-phenotype interactions. Inverting disease phenotypes into ideal cardiovascular health metrics could improve genetic and epigenetic assessment, and form the basis of a future model for risk detection and early intervention.

Remote delivery of weight management for adults with intellectual and developmental disabilities: Rationale and design for a 24 month randomized trial

Adults with intellectual and developmental disabilities (IDD) represent an underserved segment of the US population with a high prevalence of obesity and limited options for weight management. Previous research has demonstrated clinically meaningful weight loss of 7% of total body weight in in adults with IDD using an enhanced Stop Light Diet (eSLD) in combination with monthly at-home face-to-face (FTF) behavioral sessions, and a recommendation for increased physical activity. However, the time and cost associated with FTF delivery (travel + sessions) limits the potential for scaling and implementation and suggests the need for the evaluation of less costly and burdensome strategies for intervention delivery. Therefore, we will conduct a 24-mo. randomized trial to compare a weight management intervention (6 mos. weight loss, 12 mos. maintenance, 6 mos. no-contact follow-up) delivered to 120 overweight/obese adults with IDD in their home, either remotely (RD) using video conferencing on a tablet computer, or during FTF visits. Our primary aim is whether RD is non-inferior to FTF for weight loss (0-6 mos.). Secondarily, we will compare the RD and FTF groups on mean weight loss, the proportion of participants who achieve clinically meaningful weight loss, and changes in quality of life across 24 months. We will also conduct cost analysis, cost-effectiveness, and contingent valuation analyses to compare the RD and FTF groups.

Dietary patterns are not associated with overweight and obesity in a sample of 8900 Chinese preschool children from four cities

Globally, the prevalence of childhood obesity has substantially increased at an alarming rate. This study investigated associations between dietary patterns and overweight/obesity in 3- to 6-year-old children. Recruited children were from four prefecture-level cities in Eastern China. Childhood overweight and obesity were defined according to WHO Child Growth Standards. Individual dietary patterns were assessed by a comprehensive self-administered FFQ using thirty-five food items. Using factor analysis two dietary patterns were derived: the traditional Chinese pattern was characterised by high consumption of cereals, vegetables and fresh juices while the modern pattern was characterised by high consumption of Western fast food, Chinese fast food, sweets/sugary foods and carbonated beverages. The associations of dietary patterns with overweight/obesity were evaluated by logistic regression models. Data of 8900 preschool children from thirty-five kindergartens recruited from March to June 2015 were used in the final analysis. Adherence to the modern dietary pattern was positively associated with children's age while adherence to the traditional dietary pattern was positively associated with maternal education; these associations were statistically significant. After adjustment, we found that being in the highest tertile of any identified dietary patterns was not significantly associated with overweight and obesity. Dietary patterns are not associated with overweight/obesity in Chinese preschool children. Prospective studies are needed to establish a causal link between dietary patterns and childhood obesity.

Genetic obesity: next-generation sequencing results of 1230 patients with obesity

BACKGROUND

Obesity is a global and severe health problem. Due to genetic heterogeneity, the identification of genetic defects in patients with obesity can be time consuming and costly. Therefore, we developed a custom diagnostic targeted next-generation sequencing (NGS)-based analysis to simultaneously identify mutations in 52 obesity-related genes. The aim of this study was to assess the diagnostic yield of this approach in patients with suspected genetic obesity.

METHODS

DNA of 1230 patients with obesity (median BMI adults 43.6 kg/m²; median body mass index-SD children +3.4 SD) was analysed in the genome diagnostics section of the Department of Genetics of the UMC Utrecht (The Netherlands) by targeted analysis of 52 obesity-related genes.

RESULTS

In 48 patients pathogenic mutations confirming the clinical diagnosis were detected. The majority of these were observed in the MC4R gene (18/48). In an additional 67 patients a probable pathogenic mutation was identified, necessitating further analysis to confirm the clinical relevance.

CONCLUSIONS

NGS-based gene panel analysis in patients with obesity led to a definitive diagnosis of a genetic obesity disorder in 3.9% of obese probands, and a possible diagnosis in an additional 5.4% of obese probands. The highest yield was achieved in a selected paediatric subgroup, establishing a definitive diagnosis in 12 out of 164 children with severe early onset obesity (7.3%). These findings give a realistic insight in the diagnostic yield of genetic testing for patients with obesity and could help these patients to receive (future) personalised treatment.

Male Obesity: Epigenetic Origin and Effects in Sperm and Offspring

PURPOSE OF REVIEW

The prevalence of obesity has increased substantially in the current generations of Western countries, and the burden of obesity-related complications has been growing steadily. In men, obesity is not only a major risk factor for serious chronic diseases, concern is growing that the reproductive capacity, and more particularly, their offspring's health may be affected. Obesity-related impaired spermatogenesis is associated with a decrease in microscopic and molecular sperm characteristics and pregnancy success. We hypothesize that epigenetics is an important mediator explaining interactions between an obesogenic environment and sperm/offspring outcomes.

RECENT FINDINGS

Recent studies have explored inter- and transgenerational epigenetic effects in sperm cells and in offspring. Father-to-child effects have been reported in relation to preconceptional nutritional and life-style related factors.

SUMMARY

Here, we summarize the current understanding about obesity and molecular or epigenetic underlying mechanisms in sperm. We identify the obesogenic environment of the father before conception as a potential origin of health or disease in the offspring and include it as part of a new concept, the Paternal Origins of Health and Disease (POHaD).

Early-life exposures predicting onset and resolution of childhood overweight or obesity

OBJECTIVES

To determine which of multiple early-life exposures predict onset or resolution of overweight/obesity during a 9-year period.

METHODS

Design: longitudinal cohort from three harmonised community-based cohorts enriched for overweight and obesity. Early-life exposures: child-gestational age; delivery; birth weight; breast feeding; solids introduction; baseline body mass index (BMI); waist circumference; diet; activity; global, physical and psychosocial health. Mother-baseline BMI; education; age; neighbourhood disadvantage; concern for child's weight. Outcome: change in BMI category. Analyses: adjusted logistic regression.

RESULTS

On average, the 363 children (57% retention) were 6 and 15 years old at baseline and follow-up. Children were classified as 'never' overweight/obese (38%), 'resolving' overweight/obese (15%), 'becoming' overweight/obese (8%) or 'always' overweight/obese (39%). Compared with 'never overweight/obese' children, odds of 'becoming overweight/obese' were greater with higher child (OR 2.33, 95% CI 1.02 to 5.29) and maternal BMI (OR 1.18, CI 1.07 to 1.31), and lower with higher maternal education (OR 0.09, CI 0.02 to 0.34). Compared with 'always overweight/obese' children, odds of 'resolving overweight/obese' were lower with higher maternal BMI (OR 0.87, CI 0.78 to 0.97), and higher with better child physical health (OR 1.06, CI 1.02 to 1.10) and higher maternal age (OR 1.11, CI 1.01 to 1.22) and education (OR 4.07, CI 1.02 to 16.19).

CONCLUSIONS

Readily available baseline information (child/maternal BMI, maternal age, education and child health) were the strongest predictors of both onset and resolution of overweight/obesity between the primary school and adolescent years. Perinatal, breastfeeding and lifestyle exposures were not strongly predictive. Results could stimulate development of algorithms identifying children most in need of targeted prevention or treatment.

Genetics of non-syndromic childhood obesity and the use of high-throughput DNA sequencing technologies

BACKGROUND

Childhood obesity is a serious public health problem associated with the development of several chronic diseases, such as type 2 diabetes mellitus, dyslipidemia, and hypertension. The elevated prevalence of obesity is mostly due to inadequate diet and lifestyle, but it is also influenced by genetic factors.

OBJECTIVES

To review recent advances in the field of the genetics of obesity. We summarize the list of genes associated with the rare non-syndromic forms of obesity, and explain their function. Furthermore, we discuss the technologies that are available for the genetic diagnosis of obesity.

RESULTS

Several studies reported that single gene variants cause Mendelian forms of obesity, determined by mutations of major effect in single genes. Rare, non-syndromic forms of obesity are a result of loss-of-function mutations in genes that act on the development and function of the hypothalamus or the leptin-melanocortin pathway. These variants disrupt enzymes and receptors that play a role in energy homeostasis, resulting in severe early-onset obesity and endocrine dysfunctions. Different approaches and technologies have been used to understand the genetic background of obesity. Currently, whole genome and whole exome sequencing are important diagnostic tools to identify new genes and variants associated with severe obesity, but other approaches are also useful at individual or population levels, such as linkage analysis, candidate gene sequencing, chromosomal microarray analysis, and genome-wide association studies.

CONCLUSIONS

The understanding of the genetic causes of obesity and the usefulness and limitations of the genetic diagnostic approaches can contribute to the development of new personalized therapeutic targets against obesity.

Common Genetic Variant of insig2 Gene rs7566605 Polymorphism Is Associated with Severe Obesity in North India

BACKGROUND

Obesity is a very common disorder resulting from an imbalance between food intake and energy expenditure, and it has a substantial impact on the development of chronic diseases. The aim of this study was to examine the association of INSIG2 (rs7566605) gene polymorphism with obesity and obesity associated phenotypes in North Indian subjects.

METHODS

The variants were investigated for association in 642 obese and non-obese individuals. The genotyping of INSIG2 (rs7566605) single nucleotide polymorphism was analyzed by the TaqMan allelic discrimination protocol.

RESULTS

A significant association was observed for INSIG2 (rs7566605) single nucleotide polymorphism with obesity and obesity-related phenotypes. Furthermore, a significant relationship was found between the rs7566605 and insulin, homeostasis model of assessment-insulin resistance, the percentage of body fat, fat mass, leptin, and adiponectin.

CONCLUSION

The present study observed significant association between INSIG2 (rs7566605) single nucleotide polymorphism and obesity, as well as obesity-associated phenotypes in North Indian population.

Genetics of Obesity

Numerous classical genetic studies have proved that genes are contributory factors for obesity. Genes are directly responsible for obesity associated disorders such as Bardet-Biedl and Prader-Willi syndromes. However, both genes as well as environment are associated with obesity in the general population. Genetic epidemiological approaches, particularly genome-wide association studies, have unraveled many genes which play important roles in human obesity. Elucidation of their biological functions can be very useful for understanding pathobiology of obesity. In the near future, further exploration of obesity genetics may help to develop useful diagnostic and predictive tests for obesity treatment.

Single Gene and Syndromic Causes of Obesity: Illustrative Examples

Obesity is a significant health problem in westernized societies, particularly in the United States where it has reached epidemic proportions in both adults and children. The prevalence of childhood obesity has doubled in the past 30 years. The causation is complex with multiple sources, including an obesity promoting environment with plentiful highly dense food sources and overall decreased physical activity noted for much of the general population, but genetic factors clearly play a role. Advances in genetic technology using candidate gene approaches, genome-wide association studies, structural and expression microarrays, and next generation sequencing have led to the discovery of hundreds of genes recognized as contributing to obesity. Polygenic and monogenic causes of obesity are now recognized including dozens of examples of syndromic obesity with Prader-Willi syndrome, as a classical example and recognized as the most common known cause of life-threatening obesity. Genetic factors playing a role in the causation of obesity will be discussed along with the growing evidence of single genes and the continuum between monogenic and polygenic obesity. The clinical and genetic aspects of four classical but rare obesity-related syndromes (ie, Prader-Willi, Alström, fragile X, and Albright hereditary osteodystrophy) will be described and illustrated in this review of single gene and syndromic causes of obesity.

Multi-level block permutation

Under weak and reasonable assumptions, mainly that data are exchangeable under the null hypothesis, permutation tests can provide exact control of false positives and allow the use of various non-standard statistics. There are, however, various common examples in which global exchangeability can be violated, including paired tests, tests that involve repeated measurements, tests in which subjects are relatives (members of pedigrees) - any dataset with known dependence among observations. In these cases, some permutations, if performed, would create data that would not possess the original dependence structure, and thus, should not be used to construct the reference (null) distribution. To allow permutation inference in such cases, we test the null hypothesis using only a subset of all otherwise possible permutations, i.e., using only the rearrangements of the data that respect exchangeability, thus retaining the original joint distribution unaltered. In a previous study, we defined exchangeability for blocks of data, as opposed to each datum individually, then allowing permutations to happen within block, or the blocks as a whole to be permuted. Here we extend that notion to allow blocks to be nested, in a hierarchical, multi-level definition. We do not explicitly model the degree of dependence between observations, only the lack of independence; the dependence is implicitly accounted for by the hierarchy and by the permutation scheme. The strategy is compatible with heteroscedasticity and variance groups, and can be used with permutations, sign flippings, or both combined. We evaluate the method for various dependence structures, apply it to real data from the Human Connectome Project (HCP) as an example application, show that false positives can be avoided in such cases, and provide a software implementation of the proposed approach.

The Effectiveness of a Weight Maintenance Intervention for Adults with Intellectual Disabilities and Obesity: A Single Stranded Study

BACKGROUND

The evidence base for weight management programmes incorporating a weight loss and a weight maintenance phase for adults with intellectual disabilities (ID) is limited. This study describes the weight maintenance phase of a multicomponent weight management programme for adults with intellectual disability and obesity (TAKE 5).

MATERIALS AND METHODS

Thirty-one participants who had completed the 16 week TAKE five weight loss intervention (Phase I) were invited to participate in a 12 month weight maintenance intervention (Phase II). Content included recommendations of the National Weight Control Registry.

RESULTS

Twenty-eight participants completed Phase II with 50.4% maintaining their weight (mean weight change -0.5 kg, SD 2.2), 28.7% gaining weight (mean weight gain 5.4 kg, SD 2.2) and 21.6% losing weight (mean weight loss -8.0 kg, SD 3.0) at 12 months.

CONCLUSION

Further research is justified to investigate the efficacy of weight loss maintenance interventions in adults with intellectual disability and obesity, using controlled study designs.

Genes and the hypothalamic control of metabolism in humans

Heritability of obesity and body weight variation is high. Molecular genetic studies have led to the identification of mutations in a few genes, with a major effect on obesity (major genes and monogenic forms). Analyses of these genes have helped to unravel important pathways and have created a more profound understanding of body weight regulation. For most individuals, a polygenic basis is relevant for the genetic predisposition to obesity. Small effect sizes are conveyed by the polygenic variants. Hence, only if a number of these variants is harboured, a sizeable phenotypic effect is detectable. Most, if not all, of the genes relevant to weight regulation are expressed in the hypothalamus. This underscores the major role of this region of the brain in body weight regulation.

Effect of GAS6 and AXL Gene Polymorphisms on Adiposity, Systemic Inflammation, and Insulin Resistance in Adolescents

The present study was designed to explore the effects of GAS6 and AXL gene polymorphisms on adiposity, systemic inflammation, and insulin resistance in adolescents. After multistage sampling from the data of the Taipei Children Heart Study-III, we collected 358 boys and 369 girls with an average age of 13.3 years. We genotyped the adolescents' GAS6 rs8191973, GAS6 rs8191974, AXL rs4802113, and AXL rs2304232 polymorphisms. Significantly higher body mass index (BMI), waist circumference (WC), and hsCRP levels were found in boys with the GG genotype of GAS6 rs8191974 than A allele carriers; higher IL-6 and insulin levels and increased HOMA-IR were found in boys with the GG genotype of AXL rs2304232 than the A allele carriers. There was a significant difference in hsCRP levels of boys with the TT, TC, and CC genotypes of AXL rs4802113. Boys with both the GG genotype of GAS6 rs8191973 and the GG genotype of GAS6 rs8191974 exhibited higher BMI, WC, IL-6, and hsCRP levels than the boys carrying both the C allele of the GAS6 rs8191973 and the A allele of the GAS6 rs8191974. In conclusion, GAS6 and AXL polymorphisms are associated with adiposity, systemic inflammation, and insulin resistance in adolescents, especially in boys.

The genetics of human obesity

It has long been known that there is a genetic component to obesity, and that characterizing this underlying factor would likely offer the possibility of better intervention in the future. Monogenic obesity has proved to be relatively straightforward, with a combination of linkage analysis and mouse models facilitating the identification of multiple genes. In contrast, genome-wide association studies have successfully revealed a variety of genetic loci associated with the more common form of obesity, allowing for very strong consensus on the underlying genetic architecture of the phenotype for the first time. Although a number of significant findings have been made, it appears that very little of the apparent heritability of body mass index has actually been explained to date. New approaches for data analyses and advances in technology will be required to uncover the elusive missing heritability, and to aid in the identification of the key causative genetic underpinnings of obesity.

Genetic determinants of cardiometabolic risk: a proposed model for phenotype association and interaction

This review provides a translational and unifying summary of metabolic syndrome genetics and highlights evidence that genetic studies are starting to unravel and untangle origins of the complex and challenging cluster of disease phenotypes. The associated genes effectively express in the brain, liver, kidney, arterial endothelium, adipocytes, myocytes, and β cells. Progression of syndrome traits has been associated with ectopic lipid accumulation in the arterial wall, visceral adipocytes, myocytes, and liver. Thus, it follows that the genetics of dyslipidemia, obesity, and nonalcoholic fatty liver disease are central in triggering progression of the syndrome to overt expression of disease traits and have become a key focus of interest for early detection and for designing prevention and treatments. To support the "birds' eye view" approach, we provide a road-map depicting commonality and interrelationships between the traits and their genetic and environmental determinants based on known risk factors, metabolic pathways, pharmacologic targets, treatment responses, gene networks, pleiotropy, and association with circadian rhythm. Although only a small portion of the known heritability is accounted for and there is insufficient support for clinical application of gene-based prediction models, there is direction and encouraging progress in a rapidly moving field that is beginning to show clinical relevance.

Childhood obesity for pediatric gastroenterologists

Obesity in childhood is one of the major health issues in pediatric health care today. As expected, the prevalence of obesity-related comorbidities has risen in parallel with that of obesity. Consultation regarding these concomitant diseases and subsequent management by subspecialists, including pediatric gastroenterologists, is now common and has resulted in obesity being recognized as a chronic disease requiring coordination of care. Although medications and even surgery may provide effective, though often temporary, treatments for obesity and its comorbidities, behavioral interventions addressing healthy dietary and physical activity habits remain a mainstay in the obesity treatment paradigm. Therefore, the issue of weight management must be addressed by both general practitioner and subspecialist alike. In this report, we review select aspects of pediatric obesity and obesity-related management issues because it relates in particular to the field of pediatric gastroenterology and hepatology.

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.

Overview of paediatric obesity for the paediatric mental health provider

Childhood obesity represents a significant challenge for paediatric healthcare delivery. As obesity rates increase, obese children and adolescents are at significant risk for the development of a myriad of medical and surgical problems as well as mental health problems. Moreover, children with mental health problems are increasingly presenting to their psychiatrists with obesity. Treatment of paediatric obesity requires a multidisciplinary approach with incorporation of the family into the treatment plan although still typically only offering suboptimal results. Paediatric providers from all disciplines should focus efforts primarily on obesity prevention and encouragement of healthy lifestyles, while incorporating treatment for obesity when such efforts fail. The goals of this article are to provide an overview of the epidemiology, pathophysiology, genetics, clinical features and treatment strategies for paediatric obesity.

The A-allele of the common FTO gene variant rs9939609 complicates weight maintenance in severe obese patients

OBJECTIVE

The A-allele of the fat mass and obesity-associated (FTO) gene variant rs9939609 has been associated with increased body weight, whereas no effect on weight loss during weight reduction programs has been observed. We questioned whether the AA-genotype interferes with weight stabilization after weight loss.

DESIGN

We conducted a monocentric, longitudinal study involving obese individuals. The FTO gene variant rs9939609 was genotyped in participants attending a weight reduction program that was divided into two phases: a weight reduction period with formula diet (12 weeks) and a weight maintenance phase (40 weeks). Body weight, body mass index (BMI), blood pressure and concentrations of blood glucose, total cholesterol, low-density lipoprotein, high-density lipoprotein and triglycerides were determined in week 0 (T(0)), after 12 weeks (T(1)) and at the end in week 52 (T(2)).

SUBJECTS

A total of 193 obese subjects aged between 18 and 72 years (129 female, 64 male; initial body weight: 122.4±22.3 kg, initial BMI: 41.8±6.7 kg m(-2)) were included.

RESULTS

Genotyping revealed 32.1% TT-, 39.4% AT- and 28.5% AA-genotype carriers. At T (0), carriers of the AA-genotype had significantly higher body weight (P=0.04) and BMI (P=0.005) than carriers of the TT-genotype. Of the 193 participants, 68 discontinued and 125 completed the program. Dropout rate was not influenced by genotype (P=0.33). Completers with AA-genotype showed significantly lower additional weight loss during the weight maintenance phase than TT-genotype carriers (P=0.02). Furthermore, among participants facing weight regain during weight maintenance (n=52), more subjects were carrying the AA-genotype (P=0.006). No influence of genotype on weight reduction under formula diet was observed (P=0.32).

CONCLUSION

In this program, the AA-genotype of rs9939609 was associated with a higher initial body weight and did influence success of weight stabilization. Thus, emphasizing the maintenance phase during a weight reduction program might result in better success for AA-genotype carriers.

Melanocortin signalling and the regulation of blood pressure in human obesity

Obesity has reached epidemic proportions worldwide. Sympathetic nervous system activation has been shown to play a major role linking obesity to the development of associated metabolic complications, such as hypertension. Recent evidence has implicated central melanocortin signalling in the regulation of blood pressure in rodents and humans. The importance of sympathetic neural activity in mediating this association has been highlighted. Humans with loss-of-function mutations in the melanocortin 4 receptor (MC4R) are an ideal group of subjects in whom the importance of melanocortin signalling in linking obesity to hypertension can be studied. Consistent with rodent studies, it was recently demonstrated that humans with MC4R deficiency have lower blood pressure, less hypertension, lower 24-h urinary catecholamine excretion, lower resting heart rate and attenuated insulin-mediated sympathetic activation compared to equally-obese humans. In overweight and obese humans without MC4R mutations, the infusion of a highly-selective MC4R agonist led to dose-dependent increases in blood pressure and heart rate. All effects were independent of insulin. This evidence supports the notion that the melanocortin system regulates blood pressure and sympathetic neural function. The results obtained in rodent and human studies, in relation to blood pressure and sympathetic function, may limit the use of MC4R agonists for the treatment of obesity. Future studies will determine whether MC4R deficiency is associated with protection from development of the detrimental cardiovascular consequences that accompany obesity.

Genetics of childhood obesity

Obesity is a major health problem and an immense economic burden on the health care systems both in the United States and the rest of the world. The prevalence of obesity in children and adults in the United States has increased dramatically over the past decade. Besides environmental factors, genetic factors are known to play an important role in the pathogenesis of obesity. Genome-wide association studies (GWAS) have revealed strongly associated genomic variants associated with most common disorders; indeed there is general consensus on these findings from generally positive replication outcomes by independent groups. To date, there have been only a few GWAS-related reports for childhood obesity specifically, with studies primarily uncovering loci in the adult setting instead. It is clear that a number of loci previously reported from GWAS analyses of adult BMI and/or obesity also play a role in childhood obesity.

A genome-wide study reveals copy number variants exclusive to childhood obesity cases

The prevalence of obesity in children and adults in the United States has increased dramatically over the past decade. Genomic copy number variations (CNVs) have been strongly implicated in subjects with extreme obesity and coexisting developmental delay. To complement these previous studies, we addressed CNVs in common childhood obesity by examining children with a BMI in the upper 5(th) percentile but excluding any subject greater than three standard deviations from the mean in order to reduce severe cases in the cohort. We performed a whole-genome CNV survey of our cohort of 1080 defined European American (EA) childhood obesity cases and 2500 lean controls (< 50(th) percentile BMI) who were genotyped with 550,000 SNP markers. Positive findings were evaluated in an independent African American (AA) cohort of 1479 childhood obesity cases and 1575 lean controls. We identified 17 CNV loci that were unique to at least three EA cases and were both previously unreported in the public domain and validated via quantitative PCR. Eight of these loci (47.1%) also replicated exclusively in AA cases (six deletions and two duplications). Replicated deletion loci consisted of EDIL3, S1PR5, FOXP2, TBCA, ABCB5, and ZPLD1, whereas replicated duplication loci consisted of KIF2B and ARL15. We also observed evidence for a deletion at the EPHA6-UNQ6114 locus when the AA cohort was investigated as a discovery set. Although these variants may be individually rare, our results indicate that CNVs contribute to the genetic susceptibility of common childhood obesity in subjects of both European and African ancestry.

High-fat diet-induced obesity in animal models

Epidemiological studies have shown a positive relationship between dietary fat intake and obesity. Since rats and mice show a similar relationship, they are considered an appropriate model for studying dietary obesity. The present paper describes the history of using high-fat diets to induce obesity in animals, aims to clarify the consequences of changing the amount and type of dietary fats on weight gain, body composition and adipose tissue cellularity, and explores the contribution of genetics and sex, as well as the biochemical basis and the roles of hormones such as leptin, insulin and ghrelin in animal models of dietary obesity. The major factors that contribute to dietary obesity - hyperphagia, energy density and post-ingestive effects of the dietary fat - are discussed. Other factors that affect dietary obesity including feeding rhythmicity, social factors and stress are highlighted. Finally, we comment on the reversibility of high-fat diet-induced obesity.

Early-life determinants of overweight and obesity: a review of systematic reviews

The aim of this paper was to review the evidence for early-life (from conception to 5 years of age) determinants of obesity. The design is review of published systematic reviews. Data sources included Medline, Embase, Web of Science, Cochrane Library, CINAHL, PsycINFO. Identification of 22 eligible reviews from a database of 12,021 independent publications. Quality of selected reviews assessed using the Assessment of Multiple Systematic Reviews score. Articles published after the reviews were used to confirm results. No review was classified as high quality, 11 as moderate and 11 as low. Factors associated with later overweight and obesity: maternal diabetes, maternal smoking, rapid infant growth, no or short breastfeeding, obesity in infancy, short sleep duration, <30 min of daily physical activity, consumption of sugar-sweetened beverages. Other factors were identified as potentially relevant, although the size of their effect is difficult to estimate. Maternal smoking, breastfeeding, infant size and growth, short sleep duration and television viewing are supported by better-quality reviews. It is difficult to establish a causal association between possible determinants and obesity, and the relative importance of each determinant. Future research should focus on early-life interventions to confirm the role of protective and risk factors and to tackle the high burden obesity represents for present and future generations.

Associations between severity of obesity in childhood and adolescence, obesity onset and parental BMI: a longitudinal cohort study

OBJECTIVE

To explore the relationship between severity of obesity at age 7 and age 15, age at onset of obesity, and parental body mass index (BMI) in obese children and adolescents.

DESIGN

Longitudinal cohort study.

SUBJECTS

Obese children (n = 231) and their parents (n = 462) from the Swedish National Childhood Obesity Centre.

METHODS

Multivariate regression analyses were applied with severity of obesity (BMI standard deviation score (BMI SDS)) and onset of obesity as dependent variables. The effect of parental BMI was evaluated and in the final models adjusted for gender, parental education, age at onset of obesity, severity of obesity at age 7 and obesity treatment.

RESULTS

For severity of obesity at age 7, a positive correlation with maternal BMI was indicated (P = 0.05). Severity of obesity at this age also showed a strong negative correlation with the age at onset of obesity. Severity of obesity at age 15 was significantly correlated with both maternal and paternal BMI (P < 0.01). In addition, BMI SDS at age 15 differed by gender (higher for boys) and was positively correlated with severity of obesity at age 7 and negatively correlated with treatment. Also, a negative correlation was indicated at this age for parental education. No correlation with age at onset was found at age 15. For age at onset of obesity there was no relevant correlation with parental BMI. Children within the highest tertile of the BMI SDS range were more likely to have two obese parents.

CONCLUSION

The impact of parental BMI on the severity of obesity in children is strengthened as the child grows into adolescence, whereas the age at onset is probably of less importance than previously thought. The influence of parental relative weight primarily affects the severity of childhood obesity and not the timing.

Diet-induced obesity alters behavior as well as serum levels of corticosterone in F344 rats

Obesity is an increasing socio-economic health problem. Diet-induced obese (DIO) rodents are widely used as a model of obesity in humans. However, there is no comprehensive data about the behavioral phenotype of DIO rodents. Therefore, the aim of the present study was to determine whether a high-fat-diet changes behavioral patterns of DIO Fischer 344 (F344) rats in comparison with lean littermates. The behavioral tests (homecage, holeboard, social interaction, and hotplate) were performed in 28 normal-weight and 28 male DIO F344 rats (mean age: 16 weeks) and revealed a significantly higher level of anxiety- and aggression-related parameters in obese rats, whereas their pain threshold was significantly lower. Fitting to a different behavioral response, basal corticosterone levels (measured by RIA) of obese animals were significantly elevated (16.0ng/ml vs. 12.5ng/ml; p<0.01). We conclude that obese rats differ in various aspects from their lean littermates. The altered behavioral characteristics displayed by DIO F344 rats have to be considered in further experiments involving DIO rodents.

Changes in the transcriptome of abdominal subcutaneous adipose tissue in response to short-term overfeeding in lean and obese men

BACKGROUND

Obesity is caused by the excessive accumulation of adipose tissue as a result of a chronic energy surplus. Little is known regarding the molecular mechanisms involved in the response to an energy surplus in human adipose tissue at the genomic level.

OBJECTIVE

The objective was to investigate changes in the transcriptome of abdominal subcutaneous adipose tissue after a positive energy challenge induced by overfeeding in both lean and obese subjects to identify novel obesity candidate genes.

DESIGN

A total of 26 men were recruited and classified on the basis of percentage body fat (measured by dual-energy X-ray absorptiometry) as lean (<20%) or obese (>25%) to participate in the baseline comparison. Sixteen men participated in the overfeeding study (8 lean and 8 obese). Adipose tissue biopsy samples were collected from all subjects at the subumbilical region. Global gene expression profiles were determined at baseline and after a 7-d hypercaloric diet at 40% above normal energy requirements by using whole human genome DNA microarrays.

RESULTS

Overfeeding induced differential expression in 45 genes. Six genes displayed a significant interaction effect between adiposity status and overfeeding treatment, including transferrin (TF), stearoyl-CoA desaturase (SCD), transaldolase 1 (TALDO1), cathepsin C (CTSC), insulin receptor substrate 2 (IRS2), and pyruvate dehydrogenase kinase, isozyme 4 (PDK4). Overfeeding resulted in changes in expression of these genes in lean subjects, whereas no significant changes were evident in obese subjects.

CONCLUSIONS

Differential expression of these 6 genes may represent a protective mechanism at the molecular level in lean subjects in response to an energy surplus. These genes represent valuable candidates for downstream studies related to obesity.

Relevance of animal models to human eating disorders and obesity

BACKGROUND AND RATIONALE

This review addresses the role animal models play in contributing to our knowledge about the eating disorders anorexia nervosa (AN) and bulimia nervosa (BN) and obesity.

OBJECTIVES

Explore the usefulness of animal models in complex biobehavioral familial conditions, such as AN, BN, and obesity, that involve interactions among genetic, physiologic, psychological, and cultural factors.

RESULTS AND CONCLUSIONS

The most promising animal model to mimic AN is the activity-based anorexia rodent model leading to pathological weight loss. The paradigm incorporates reward elements of the drive for activity in the presence of an appetite and allows the use of genetically modified animals. For BN, the sham-feeding preparation in rodents equipped with a gastric fistula appears to be best suited to reproduce the postprandial emesis and the defects in satiety. Animal models that incorporate genes linked to behavior and mood may clarify biobehavioral processes underlying AN and BN. By contrast, a relative abundance of animal models has contributed to our understanding of human obesity. Both environmental and genetic determinants of obesity have been modeled in rodents. Here, we consider single gene mutant obesity models, along with models of obesigenic environmental conditions. The contributions of animal models to obesity research are illustrated by their utility for identifying genes linked to human obesity, for elucidating the pathways that regulate body weight and for the identification of potential therapeutic targets. The utility of these models may be further improved by exploring the impact of experimental manipulations on the behavioral determinants of energy balance.

Association analysis of the FTO gene with obesity in children of Caucasian and African ancestry reveals a common tagging SNP

Recently an association was demonstrated between the single nucleotide polymorphism (SNP), rs9939609, within the FTO locus and obesity as a consequence of a genome wide association (GWA) study of type 2 diabetes in adults. We examined the effects of two perfect surrogates for this SNP plus 11 other SNPs at this locus with respect to our childhood obesity cohort, consisting of both Caucasians and African Americans (AA). Utilizing data from our ongoing GWA study in our cohort of 418 Caucasian obese children (BMI>or=95th percentile), 2,270 Caucasian controls (BMI<95th percentile), 578 AA obese children and 1,424 AA controls, we investigated the association of the previously reported variation at the FTO locus with the childhood form of this disease in both ethnicities. The minor allele frequencies (MAF) of rs8050136 and rs3751812 (perfect surrogates for rs9939609 i.e. both r(2) = 1) in the Caucasian cases were 0.448 and 0.443 respectively while they were 0.391 and 0.386 in Caucasian controls respectively, yielding for both an odds ratio (OR) of 1.27 (95% CI 1.08-1.47; P = 0.0022). Furthermore, the MAFs of rs8050136 and rs3751812 in the AA cases were 0.449 and 0.115 respectively while they were 0.436 and 0.090 in AA controls respectively, yielding an OR of 1.05 (95% CI 0.91-1.21; P = 0.49) and of 1.31 (95% CI 1.050-1.643; P = 0.017) respectively. Investigating all 13 SNPs present on the Illumina HumanHap550 BeadChip in this region of linkage disequilibrium, rs3751812 was the only SNP conferring significant risk in AA. We have therefore replicated and refined the association in an AA cohort and distilled a tag-SNP, rs3751812, which captures the ancestral origin of the actual mutation. As such, variants in the FTO gene confer a similar magnitude of risk of obesity to children as to their adult counterparts and appear to have a global impact.

Regulation of fetal growth: consequences and impact of being born small

The first trimester of pregnancy is the time during which organogenesis takes place and tissue patterns and organ systems are established. In the second trimester the fetus undergoes major cellular adaptation and an increase in body size, and in the third trimester organ systems mature ready for extrauterine life. In addition, during that very last period of intrauterine life there is a significant increase in body weight. In contrast to the postnatal endocrine control of growth, where the principal hormones directly influencing growth are growth hormone (GH) and the insulin-like growth factors (IGFs) via the GH-IGF axis, fetal growth throughout gestation is constrained by maternal factors and placental function and is coordinated by growth factors. In general, growth disorders only become apparent postnatally, but they may well be related to fetal life. Thus, fetal growth always needs to be considered in the overall picture of human growth as well as in its metabolic development.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

Gene-diet interactions in childhood obesity: paucity of evidence as the epidemic of childhood obesity continues to rise

Childhood obesity is growing rapidly worldwide. Although there have been enormous advances in the genetic underpinnings of obesity in recent years, the pathways that lead to obesity are still not completely understood. One of the ongoing challenges is the lack of a comprehensive definition of the obese phenotype that encompasses intermediary phenotypic expressions of biological and behavioral nature. Interactions between genetic and environmental factors, including nutrient exposures and dietary behaviors, can influence the development of the obese phenotype. Specifically, genes play a decisive role in the etiology of childhood obesity under the permissive circumstances of an obesogenic environment (increase in energy intake with a decrease in physical activity). Like many diseases, the causes of obesity are complex and their investigation requires novel approaches. Given the many contributors to obesity (weight gain, weight loss, weight maintenance, variability in body composition), as well as the dynamic nature of this issue, genomic tools must continue to be employed to evaluate all dimensions of the obesity phenotype, such as biochemical characteristics, susceptibility markers, nutrient intake, feeding practices and gene-environment interactions. Fundamental knowledge of the types of genes involved and available gene-diet interaction studies in children's obesity are reviewed. Although there is a paucity of existing literature in this specific domain of childhood obesity, ongoing investigations utilizing large cohorts have potential for providing the knowledge needed for targeted interventions in the future.

Earlier mother's age at menarche predicts rapid infancy growth and childhood obesity

BACKGROUND

Early menarche tends to be preceded by rapid infancy weight gain and is associated with increased childhood and adult obesity risk. As age at menarche is a heritable trait, we hypothesised that age at menarche in the mother may in turn predict her children's early growth and obesity risk.

METHODS AND FINDINGS

We tested associations between mother's age at menarche, mother's adult body size and obesity risk, and her children's growth and obesity risk in 6,009 children from the UK population-based Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort who had growth and fat mass at age 9 y measured by dual-energy X-ray absorptiometry. A subgroup of 914 children also had detailed infancy and childhood growth data. In the mothers, earlier menarche was associated with shorter adult height (by 0.64 cm/y), increased weight (0.92 kg/y), and body mass index (BMI, 0.51 kg/m2/y; all p < 0.001). In contrast, in her children, earlier mother's menarche predicted taller height at 9 y (by 0.41 cm/y) and greater weight (0.80 kg/y), BMI (0.29 kg/m2/y), and fat mass index (0.22 kg/m2/year; all p < 0.001). Children in the earliest mother's menarche quintile (< or =11 y) were more obese than the oldest quintile (> or =15 y) (OR, 2.15, 95% CI 1.46 to 3.17; p < 0.001, adjusted for mother's education and BMI). In the subgroup, children in the earliest quintile showed faster gains in weight (p < 0.001) and height (p < 0.001) only from birth to 2 y, but not from 2 to 9 y (p = 0.3-0.8).

CONCLUSIONS

Earlier age at menarche may be a transgenerational marker of a faster growth tempo, characterised by rapid weight gain and growth, particularly during infancy, and leading to taller childhood stature, but likely earlier maturation and therefore shorter adult stature. This growth pattern confers increased childhood and adult obesity risks.

Diet, obesity and diabetes: a current update

The prevalence of obesity has been increasing at a rapid rate over the last few decades. Although the primary defect can be attributed to an imbalance of energy intake over energy expenditure, the regulation of energy balance is now recognized to be complex. Adipose-tissue factors play a central role in the control of energy balance and whole-body fuel homoeostasis. The regulation of adipose-tissue function, in particular its secretion of adipokines, is impaired by increases in adipose mass associated with obesity, and with the development of insulin resistance and Type 2 diabetes. This review analyses adipose-regulated energy input and expenditure, together with the impact of dietary macronutrient composition on energy balance in relation to susceptibility to the development of obesity and Type 2 diabetes, and how these metabolic conditions may be exacerbated by the consequences of abnormal adipose function. By gaining a greater understanding of how energy balance is controlled in normal, and in obese and diabetic states, a more practical approach can be employed to prevent and better treat obesity and metabolic disorders.