Familial resemblance of 7-year changes in body mass and adiposity

Genetics of Obesity: What We Have Learned Over Decades of Research

There is a genetic component to human obesity that accounts for 40% to 50% of the variability in body weight status but that is lower among normal weight individuals (about 30%) and substantially higher in the subpopulation of individuals with obesity and severe obesity (about 60%-80%). The appreciation that heritability varies across classes of BMI represents an important advance. After controlling for BMI, ectopic fat and fat distribution traits are characterized by heritability levels ranging from 30% to 55%. Defects in at least 15 genes are the cause of monogenic obesity cases, resulting mostly from deficiencies in the leptin-melanocortin signaling pathway. Approximately two-thirds of the BMI heritability can be imputed to common DNA variants, whereas low-frequency and rare variants explain the remaining fraction. Diminishing allele effect size is observed as the number of obesity-associated variants expands, with most BMI-increasing or -decreasing alleles contributing only a few grams or less to body weight. Obesity-promoting alleles exert minimal effects in normal weight individuals but have larger effects in individuals with a proneness to obesity, suggesting a higher penetrance; however, it is not known whether these larger effect sizes precede obesity or are caused by an obese state. The obesity genetic risk is conditioned by thousands of DNA variants that make genetically based obesity prevention and treatment a major challenge.

Obesity and eating behavior from the perspective of twin and genetic research

Obesity has dramatically increased during the last decades and is currently one of the most serious global health problems. We present a hypothesis that obesity is a neuro-behavioral disease having a strong genetic background mediated largely by eating behavior and is sensitive to the macro-environment; we study this hypothesis from the perspective of genetic research. Genetic family and genome-wide-association studies have shown well that body mass index (BMI, kg/m²) is a highly heritable and polygenic trait. New genetic variation of BMI emerges after early childhood. Candidate genes of BMI notably express in brain tissue, supporting that this new variation is related to behavior. Obesogenic environments at both childhood family and societal levels reinforce the genetic susceptibility to obesity. Genetic factors have a clear influence on macro-nutrient intake and appetite-related eating behavior traits. Results on the gene-by-diet interactions in obesity are mixed, but emerging evidence suggests that eating behavior traits partly mediate the effect of genes on BMI. However, more rigorous prospective study designs controlling for measurement bias are still needed.

Change and Stability in Sibling Resemblance in Obesity Markers: The Portuguese Sibling Study on Growth, Fitness, Lifestyle, and Health

BACKGROUND/OBJECTIVES

Obesity markers evolve over time and these changes are shared within the family orbit and governed by individual and environmental characteristics. Available reports often lack an integrated approach, in contrast to a multilevel framework that considers their concurrent influence. Hence, this study aims to (1) describe mean changes in obesity markers (body fat (%BF), body mass index (BMI), and waist circumference (WC)) across sib-ships; (2) analyze tracking of individuals within their sib-ship in these markers during 2 years of follow-up; (3) probe consistency in sibling resemblance in these markers; and (4) analyze the joint influence of individual and familial characteristics in these markers.

SUBJECTS/METHODS

The sample comprises 168 biological Portuguese siblings (brother-brother (BB), sister-sister (SS), and brother-sister (BS)) aged 9-17 years. %BF, BMI, and WC were measured using standardized protocols, and biological maturation was assessed. Physical activity, diet, screen time, and familial characteristics were obtained by questionnaires. Multilevel models were used to analyze the clustered longitudinal data. Sibling resemblance was estimated with the intraclass correlation.

RESULTS

On average, all sib types increased in BMI and WC over 2 years of follow-up, and SS pairs increased in %BF. Individuals within sib-ships track high in all obesity markers across time. Consistency in siblings' resemblance was also noted, except for BB pairs in %BF which decreased at follow-up. More maturing siblings tend to have higher values in all markers. Greater screen time was associated with higher %BF, whereas those consuming more sugary drinks had lower %BF and BMI values. Siblings whose mothers had less qualified occupations tended to have lower BMI values.

CONCLUSIONS

Longitudinal individual tracking and sibling resemblance for obesity markers were found. Yet, different trajectories were also identified depending on the marker and sib type. Individual and familial characteristics exert different influences on each obesity marker.

Physical Activity, Screen Time, and Dietary Intake in Families: A Cluster-Analysis With Mother-Father-Child Triads

Background: The co-occurrence of multiple health behaviors such as physical activity, diet, and sedentary behavior affects individuals' health. Co-occurence of different health behaviors has been shown in a large number of studies. This study extended this perspective by addressing the co-occurrence of multiple health behaviors in multiple persons. The objective was to examine familial health behavioral patterns by (1) identifying clusters of families with similar behavior patterns and (2) characterizing the clusters by analyzing their correlates.

Methods: Cross-sectional data were collected from 198 families (mother, father, and child). Mothers, fathers, and children completed questionnaires assessing health related behaviors (physical activity, consumption of “healthy” and “unhealthy” foods, and screen time), the perception of Family Health Climate (regarding physical activity and nutrition) and demographics. Twelve variables (four health behaviors of three family members) were included in a cluster analysis conducted with Ward's Method and K-means analysis. Chi-square tests and analyses of variance were performed to characterize the family clusters regarding their demographics and their perception of Family Health Climate.

Results: Three clusters of families with specific behavioral patterns were identified: “healthy behavior families” with levels of physical activity and consumption of healthful foods above average and levels of media use and consumption of sweets below average; “unhealthy behavior families” with low levels of consumption of healthful foods and high levels of screen time; “divergent behavior families” with unhealthier behavioral patterns in parents and healthier screen time and eating behaviors combined with low physical activity levels in children. Family Health Climate differed between family clusters with most positive ratings in “healthy behavior families” and least positive ratings in “unhealthy behavior families.” “Divergent behavior families” rated the nutrition climate nearly as high as “healthy behavior families” while they rated the physical activity climate nearly as low as the “unhealthy behavior families.”

Conclusions: The study shows that co-occurrence of multiple health behaviors occurs on the family level. Therefore, focusing the family as a whole instead of individuals and targeting aspects related to the Family Health Climate in interventions could result in benefits for both children and adults and enhance effectivity of intervention programs.

Body mass index change in gastrointestinal cancer and chronic obstructive pulmonary disease is associated with Dedicator of Cytokinesis 1

BACKGROUND

There have been a number of candidate gene association studies of cancer cachexia-related traits, but no genome-wide association study (GWAS) has been published to date. Cachexia presents in patients with a number of complex traits, including both cancer and COPD. The objective of the current investigation was to search for a shared genetic aetiology for change in body mass index (ΔBMI) among cancer and COPD by using GWAS data in the Framingham Heart Study.

METHODS

A linear mixed effects model accounting for age, sex, and change in smoking status was used to calculate ΔBMI in participants over 40 years of age with three consecutive BMI time points (n = 4162). Four GWAS of ΔBMI using generalized estimating equations were performed among 1085 participants with a cancer diagnosis, 204 with gastrointestinal (GI) cancer, 112 with lung cancer, and 237 with COPD to test for association with 418 365 single-nucleotide polymorphisms (SNPs).

RESULTS

Two SNPs reached a level of genome-wide significance (P < 5 × 10^-8 ) with ΔBMI: (i) rs41526344 within the CNTN4 gene, among COPD cases (β = 0.13, P = 4.3 × 10^-8 ); and (ii) rs4751240 in the gene Dedicator of Cytokinesis 1 (DOCK1) among GI cancer cases (β = 0.10, P = 1.9 × 10^-8 ). The DOCK1 SNP association replicated in the ΔBMI GWAS among COPD cases (β_meta-analyis  = 0.10, P_meta-analyis  = 9.3 × 10^-10 ). The DOCK1 gene codes for the dedicator of cytokinesis 1 protein, which has a role in myoblast fusion.

CONCLUSIONS

In sum, one statistically significant common variant in the DOCK1 gene was associated with ΔBMI in GI cancer and COPD cases providing support for at least partially shared aetiology of ΔBMI in complex diseases.

Evidence update on the treatment of overweight and obesity in children and adolescents

Childhood obesity is associated with increased medical and psychosocial consequences and mortality and effective interventions are urgently needed. Effective interventions are urgently needed. This article reviews the evidence for psychological treatments of overweight and obesity in child and adolescent populations. Studies were identified through searches of online databases and reference sections of relevant review articles and meta-analyses. Treatment efficacy was assessed using established criteria, and treatments were categorized as well-established, probably efficacious, possibly efficacious, experimental, or of questionable efficacy. Well-established treatments included family-based behavioral treatment (FBT) and Parent-Only Behavioral Treatment for children. Possibly efficacious treatments include Parent-Only Behavioral Treatment for adolescents, FBT-Guided Self-Help for children, and Behavioral Weight Loss treatment with family involvement for toddlers, children, and adolescents. Appetite awareness training and regulation of cues treatments are considered experimental. No treatments are considered probably efficacious, or of questionable efficacy. All treatments considered efficacious are multicomponent interventions that include dietary and physical activity modifications and utilize behavioral strategies. Treatment is optimized if family members are specifically targeted in treatment. Research supports the use of multicomponent lifestyle interventions, with FBT and Parent-Only Behavioral Treatment being the most widely supported treatment types. Additional research is needed to test a stepped care model for treatment and to establish the ideal dosage (i.e., number and length of sessions), duration, and intensity of treatments for long-term sustainability of healthy weight management. To improve access to care, the optimal methods to enhance the scalability and implementability of treatments into community and clinical settings need to be established.

Longitudinal follow-up of the relationship between dietary intake and growth and development in the Lifeways cross-generation cohort study 2001-2013

In this paper we will review evidence on the early life and familial influences on childhood growth and development, with particular reference to the Lifeways cross-generation cohort study in the Republic of Ireland. The Lifeways cross-generation cohort study was established in 2001-2013 through two maternity hospitals in the Republic of Ireland and was one of many new cohort studies established worldwide in the millennium period. Mothers were recruited at first booking visit, completing a self-administered questionnaire, which included a 147 item semi-quantitative FFQ. Longitudinal follow-up is ongoing in 2013, with linkage data to hospital and general practice records and examination of children when aged 5 and 9 years. The study is one of very few containing data on grandparents of both lineages with at least one grandparent recruited at baseline. There have been consistent associations between parental and grandparental health status characteristics and children's outcomes, including infant birth-weight, BMI when child was aged 5 years and childhood wheeze or asthma when child was aged 3 and aged 5 years. In conclusion, empirical evidence to date shows consistent familial and cross-generational patterns, particularly in the maternal line.

Parent-child resemblance in weight status and its correlates in the United States

Background

Few studies have examined parent-child resemblance in body weight status using nationally representative data for the US.

Design

We analyzed Body Mass Index (BMI), weight status, and related correlates for 4,846 boys, 4,725 girls, and their parents based on US nationally representative data from the 2006 and 2007 Medical Expenditure Panel Survey (MEPS). Pearson partial correlation coefficients, percent agreement, weighted kappa coefficients, and binary and multinomial logistic regression were used to examine parent-child resemblance, adjusted for complex sampling design.

Results

Pearson partial correlation coefficients between parent and child’s BMI measures were 0.15 for father-son pairs, 0.17 for father-daughter pairs, 0.20 for mother-son pairs, and 0.23 for mother-daughter pairs. The weighted kappa coefficients between BMI quintiles of parent and child ranged from −0.02 to 0.25. Odds ratio analyses found children were 2.1 (95% confidence interval (CI): 1.6, 2.8) times more likely to be obese if only their father was obese, 1.9 (95% CI: 1.5, 2.4) times more likely if only their mother was obese, and 3.2 (95% CI: 2.5, 4.2) times more likely if both parents were obese.

Conclusions

Parent-child resemblance in BMI appears weak and may vary across parent-child dyad types in the US population. However, parental obesity status is associated with children’s obesity status. Use of different measures of parent-child resemblance in body weight status can lead to different conclusions.

Effect of the G-protein β3 subunit 825T allele on the change of body adiposity in obese female

No clinical studies on the lipolytic effect of guanine nucleotide-binding protein β3 subunit gene (GNB3) 825T polymorphism have been performed. This study was a subinvestigation of a 12-week randomized controlled trial (NCT01184560) for the additive effect of orlistat on sibutramine treatment. The analysis involved 101 obese females aged 18-49 years, genotyped at the GNB3 825 locus. To exclude any influence from potential confounders, we used an analysis of covariance model. After the intervention, fat mass proportion in total weight loss was significantly lower in subjects with a T allele than in those without a T allele (p = 0.034). GNB3 825T allele was associated with blunted fat mass reduction in obese females.

Pleiotropic Effects of Genes for Insulin Resistance on Adiposity in Baboons

OBJECTIVE

Previous research has suggested a genetic contribution to the development of insulin resistance and obesity. We hypothesized that the same genes influencing insulin resistance might also contribute to the variation in adiposity.

RESEARCH METHODS AND PROCEDURES

A total of 601 (200 male, 401 female) adult baboons (Papio hamadryas) from nine families with pedigrees ranging in size from 43 to 121 were used in this study. Plasma insulin, glucose, C-peptide, and adiponectin were analyzed, and homeostasis model assessment of insulin resistance (HOMA IR) was calculated. Fat biopsies were collected from omental fat tissue, and triglyceride concentration per gram of fat tissue was determined. Body weight and length were measured, and BMI was derived. Univariate and bivariate quantitative genetic analyses were performed using SOLAR.

RESULTS

Insulin, glucose, C-peptide, and adiponectin levels, HOMA IR, triglyceride concentration of fat tissue, body weight, and BMI were all found to be significantly heritable, with heritabilities ranging from 0.15 to 0.80. Positive genetic correlations (r(G)s) were observed for HOMA IR with C-peptide (r(G) = 0.88 +/- 0.10, p = 0.01), triglyceride concentration in fat tissue (r(G) = 0.86 +/- 0.33, p = 0.02), weight (r(G) = 0.50 +/- 0.20, p = 0.03), and BMI (r(G) = 0.64 +/- 0.22, p = 0.02).

DISCUSSION

These results suggest that a set of genes contributing to insulin resistance also influence general and central adiposity phenotypes. Further genetic research in a larger sample size is needed to identify the common genes that constitute the genetic basis for the development of insulin resistance and obesity.

Variability in the heritability of body mass index: a systematic review and meta-regression

Evidence for a major role of genetic factors in the determination of body mass index (BMI) comes from studies of related individuals. Despite consistent evidence for a heritable component of BMI, estimates of BMI heritability vary widely between studies and the reasons for this remain unclear. While some variation is natural due to differences between populations and settings, study design factors may also explain some of the heterogeneity. We performed a systematic review that identified 88 independent estimates of BMI heritability from twin studies (total 140,525 twins) and 27 estimates from family studies (42,968 family members). BMI heritability estimates from twin studies ranged from 0.47 to 0.90 (5th/50th/95th centiles: 0.58/0.75/0.87) and were generally higher than those from family studies (range: 0.24-0.81; 5th/50th/95th centiles: 0.25/0.46/0.68). Meta-regression of the results from twin studies showed that BMI heritability estimates were 0.07 (P = 0.001) higher in children than in adults; estimates increased with mean age among childhood studies (+0.012/year, P = 0.002), but decreased with mean age in adult studies (-0.002/year, P = 0.002). Heritability estimates derived from AE twin models (which assume no contribution of shared environment) were 0.12 higher than those from ACE models (P < 0.001), whilst lower estimates were associated with self reported versus DNA-based determination of zygosity (-0.04, P = 0.02), and with self reported versus measured BMI (-0.05, P = 0.03). Although the observed differences in heritability according to aspects of study design are relatively small, together, the above factors explained 47% of the heterogeneity in estimates of BMI heritability from twin studies. In summary, while some variation in BMI heritability is expected due to population-level differences, study design factors explained nearly half the heterogeneity reported in twin studies. The genetic contribution to BMI appears to vary with age and may have a greater influence during childhood than adult life.

Counseling and behavior change in pediatric obesity

To effectively intervene with the overweight and obese youth, it is imperative that primary care providers and behavioral interventionists work in concert to help families implement healthy behaviors across socioenvironmental domains. In this article, the authors review current office-based counseling practices and provide evidence-based recommendations for addressing weight status and strategies for encouraging behavior change with children and families, primarily by increasing social support. By providing such collaborative targeted efforts, consistent health messages and support are delivered across children's everyday contexts, thereby helping the youth to achieve successful implementation of eating and activity behaviors and sustainable weight loss outcomes.

A QTL for genotype by sex interaction for anthropometric measurements in Alaskan Eskimos (GOCADAN Study) on chromosome 19q12-13

Variation in anthropometric measurements due to sexual dimorphism can be the result of genotype by sex interactions (G×S). The purpose of this study was to examine the sex-specific genetic architecture in anthropometric measurements in Alaskan Eskimos from the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. Maximum likelihood-based variance components decomposition methods, implemented in SOLAR, were used for G×S analyses. Anthropometric measurements included BMI, waist circumference (WC), waist/height ratio, percent body fat (%BF), and subscapular and triceps skinfolds. Except for WC, mean values of all phenotypes were significantly different in men and women (P < 0.05). All anthropometric measures were significantly heritable (P < 0.001). In a preliminary analysis not allowing for G×S interaction, evidence of linkage was detected between markers D19S414 and D19S220 on chromosome 19 for WC (logarithm of odds (lod) = 3.5), %BF (lod = 1.7), BMI (lod = 2.4), waist/height ratio (lod = 2.5), subscapular (lod = 2.1), and triceps skinfolds (lod = 1.9). In subsequent analyses which allowed for G×S interaction, linkage was again found between these traits and the same two markers on chromosome 19 with significantly improved lod scores for: WC (lod = 4.5), %BF (lod = 3.8), BMI (lod = 3.5), waist/height ratio (lod = 3.2), subscapular (lod = 3.0), and triceps skinfolds (lod = 2.9). These results support the evidence of a G×S interaction in the expression of genetic effects resulting in sexual dimorphism in anthropometric phenotypes and identify the chromosome 19q12-13 region as important for adiposity-related traits in Alaskan Eskimos.

Candidate molecular pathway genes related to appetite regulatory neural network, adipocyte homeostasis and obesity: results from the CARDIA Study

Appetite regulatory neural network and adipocyte homeostasis molecular pathways are critical to long-term weight maintenance. Associations between obesity-related phenotypes and four genes in these pathways - leptin (LEP), leptin receptor (LEPR), neuropeptide Y2 receptor (NPY2R) and peptide YY (PYY) were examined in CARDIA Study participants (aged 18-30 at recruitment in 1985-6). Weight, BMI and waist circumference were measured at baseline and at years 2, 5, 7, 10, 15, and 20. Genotyping was conducted using tag SNPs characterising common genetic variations in these genes. Generalized estimating equation (GEE) models estimated associations between SNPs and repeated anthropometric measurements, controlling for sex and age. False discovery rate was used to adjust for multiple testing. In African-Americans, SNPs across the LEP gene demonstrated significant overall associations with all obesity-related phenotypes. The associations between LEP rs17151919 with weight tended to strengthen with time - the difference in weight associated with each additional minor allele increased from 2.6 kg at baseline to 4.8 kg at year 20 (SNP*time interaction p = 0.0193). NPY2R gene SNPs were associated with waist circumference among African-American men (p = 0.0462). In Caucasians, LEP SNPs also tended to be associated with weight (p = 0.0471), and PYY rs11684664 was associated with obesity-related phenotypes in women only (p = 0.010-0.026). Several LEP, and NPY2R and PYY SNPs were associated with obesity-related phenotypes in young adults, particularly among African-Americans.

Genetic epidemiology of BMI and body mass change from adolescence to young adulthood

The complex interplay between genes and environment affecting body mass gain over lifecycle periods of risk is not well understood. We use longitudinal sibling cohort data to examine the role of shared household environment, additive genetic, and shared genetic effects on BMI and BMI change. In the National Longitudinal Study of Adolescent Health, siblings and twin pairs sharing households for > or =10 years as adolescents (N = 5,524; mean = 16.5 +/- 1.7 years) were followed into young adulthood (N = 4,368; mean = 22.4 +/- 1.8 years). Using a variance component approach, we quantified genetic and household effects on BMI in siblings and nonsiblings sharing household environments over time. Adjusting for race, age, sex, and age-by-sex interaction, we detected a heritability of 0.43 +/- 0.05 for BMI change. Significant household effects were noted during the young adulthood period only (0.11 +/- 0.06). We find evidence for shared genetic effects between BMI and BMI change during adolescence (genetic correlation (rho(G)) = 0.61 +/- 0.03) and young adulthood (rho(G) = 0.23 +/- 0.06). Our findings support a complex etiology of BMI and BMI change.

Genetic variations in regulatory pathways of fatty acid and glucose metabolism are associated with obesity phenotypes: a population-based cohort study

BACKGROUND

As nuclear receptors and transcription factors have an important regulatory function in adipocyte differentiation and fat storage, genetic variation in these key regulators and downstream pathways may be involved in the onset of obesity.

OBJECTIVE

To explore associations between single nucleotide polymorphisms (SNPs) in candidate genes from regulatory pathways that control fatty acid and glucose metabolism, and repeated measurements of body mass index (BMI) and waist circumference in a large Dutch study population.

METHODS

Data of 327 SNPs across 239 genes were analyzed for 3575 participants of the Doetinchem cohort, who were examined three times during 11 years, using the Illumina Golden Gate assay. Adjusted random coefficient models were used to analyze the relationship between SNPS and obesity phenotypes. False discovery rate q-values were calculated to account for multiple testing. Significance of the associations was defined as a q-value < or = 0.20.

RESULTS

Two SNPs (in NR1H4 and SMARCA2 in women only) were significantly associated with both BMI and waist circumference. In addition, two SNPs (in SIRT1 and SCAP in women only) were associated with BMI alone. A functional SNP, in IL6, was strongly associated with waist.

CONCLUSION

In this explorative study among participants of a large population-based cohort, five SNPs, mainly located in transcription mediator genes, were strongly associated with obesity phenotypes. The results from whole genome and candidate gene studies support the potential role of NR1H4, SIRT1, SMARCA2 and IL6 in obesity. Although replication of our findings and further research on the functionality of these SNPs and underlying mechanism is necessary, our data indirectly suggest a role of GATA transcription factors in weight control.

Genetic and environmental influences on factors associated with cardiovascular disease and the metabolic syndrome

The relative influence of genetics and the environment on factors associated with cardiovascular disease (CVD) and metabolic syndrome (MetS) remains unclear. We performed model-fitting analyses to quantify genetic, common environmental, and unique environmental variance components of factors associated with CVD and MetS [waist circumference, blood pressure, fasting plasma glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and fasting plasma lipids] in adult male and female monozygotic twins reared apart or together. We also investigated whether MetS components share common influences. Plasma cholesterol and triglyceride concentrations were highly heritable (56-77%, statistically significant). Waist circumference, plasma glucose and insulin, HOMA-IR, and blood pressure were moderately heritable (43-57%, statistically significant). Unique environmental factors contributed to the variance of all variables (20-38%, perforce statistically significant). Common environmental factors contributed 23, 30, and 42% (statistically significant) of the variance of waist circumference, systolic blood pressure, and plasma glucose, respectively. Two shared factors influenced MetS components; one influenced all components except HDL cholesterol, another influenced only lipid (triglyceride and HDL cholesterol) concentrations. These results suggest that genetic variance has a dominant influence on total variance of factors associated with CVD and MetS and support the proposal of one or more underlying pathologies of MetS.

Genetics of tracking of body mass index from birth to late middle age: evidence from twin and family studies

The persistence of obesity from early childhood to late middle age is well known. We reviewed the results from existing genetic studies on tracking of BMI to discover how much genetic and environmental factors contribute to this tracking of obesity. In total, we found 5 genetic longitudinal studies on childhood obesity and 8 on obesity in adulthood. One was an adoption study, 3 were family studies, and 9 were twin studies. All were based on Caucasian populations, and one included genetic level information (the FTO gene). Strong genetic continuity in BMI was found from early childhood to onset of adulthood. Although new genetic factors started to affect BMI during the growth period, genetic correlations remained high. Evidence of the effect of common environment on the tracking of BMI during childhood was also found. The heritability estimates reported in twin studies ranged from 0.57 to 0.86 for the trend of BMI from early adulthood to late middle age. The three family studies gave lower estimates. Important unresolved questions are the genetics of BMI change in old age, the genetics of body composition change, the genetic architecture of tracking of obesity in ethnic groups other than Caucasians, and the interplay between genes and environment underlying the development and tracking of obesity.

Genetic influences on growth traits of BMI: a longitudinal study of adult twins

OBJECTIVE

To investigate the interplay between genetic factors influencing baseline level and changes in BMI in adulthood.

METHODS AND PROCEDURES

A longitudinal twin study of the cohort of Finnish twins (N = 10,556 twin individuals) aged 20-46 years at baseline was conducted and followed up 15 years. Data on weight and height were obtained from mailed surveys in 1975, 1981, and 1990.

RESULTS

Latent growth models revealed a substantial genetic influence on BMI level at baseline in males and females (heritability (h(2)) 80% (95% confidence interval 0.79-0.80) for males and h(2) = 82% (0.81, 0.84) for females) and a moderate-to-high influence on rate of change in BMI (h(2) = 58% (0.50, 0.69) for males and h(2) = 64% (0.58, 0.69) for females). Only very weak evidence for genetic pleiotropy was observed; the genetic correlation between baseline and rate of change in BMI was very modest (-0.070 (-0.13, -0.068) for males and 0.04 (0.00, 0.08) for females.

DISCUSSION

Our population-based results provide a basis for identifying genetic variants for change in BMI, in particular weight gain. Furthermore, they demonstrate for the first time that such genetic variants for change in BMI are likely to be different from those affecting level of BMI.

Associations between long-term physical activity, waist circumference and weight gain: a 30-year longitudinal twin study

BACKGROUND AND OBJECTIVE

Physical activity level and obesity are both partly determined by genes and childhood environment. To determine the associations between long-term leisure-time physical activity, weight gain and waist circumference and whether these are independent of genes and childhood effects.

DESIGN AND SUBJECTS

The study design is a 30-year follow-up twin study in Finland. For this study, 146 twin pairs were comprehensively identified from the large Finnish Twin Cohort. These twin pairs were discordant for both intensity and volume of leisure physical activity in 1975 and 1981 and were healthy in 1981. At follow-up in 2005, both members of 89 pairs were alive and participated in a structured telephone interview. In the interview self-measured weight and waist circumference, and physical activity level for the whole follow-up were assessed. Paired tests were used in the statistical analyses.

MAIN OUTCOME MEASURES

Waist circumference at 30-year follow-up (2005) and change in weight from 1975 to 2005.

RESULTS

In the 42 twin pairs discordant for physical activity at all time points during the 30-year period, the mean weight gain from 1975 through 2005 was 5.4 kg (95% confidence interval (CI) 2.0-8.9) less in the active compared to inactive co-twins (paired t-test, P=0.003). In 2005, the mean waist circumference was 8.4 cm (95% CI 4.0-12.7) less in the active compared with inactive co-twins (P<0.001). These trends were similar for both monozygotic and dizygotic twin pairs. Pairwise differences in weight gain and waist circumference were not seen in the 47 twin pairs, who were not consistently discordant for physical activity.

CONCLUSION

Persistent participation in leisure-time physical activity is associated with decreased rate of weight gain and with a smaller waist circumference to a clinically significant extent even after partially controlling for genetic liability and childhood environment.

Age-related changes in echocardiographic measurements: association with variation in the estrogen receptor-alpha gene

Left ventricular (LV) mass and other LV measures have been shown to be heritable. In this study we hypothesized that functional variation in the gene coding for estrogen receptor-alpha (ESR1), known for mediating the effect of estrogens on myocardium, is associated with age-related changes in LV structure. Four genetic markers (ESR1 TA repeat; rs2077647, or +30T>C; rs2234693, or PvuII; and rs9340799, or XbaI) were genotyped in 847 unrelated individuals (488 women) from the Framingham Offspring Study, who attended 2 examination cycles 16 years apart (mean ages at first examination: 43+/-9 years; at follow-up: 59+/-9 years). ANCOVA was used to assess the association of polymorphisms and their haplotypes with cross-sectional measurements and longitudinal changes in LV mass, wall thickness, end-diastolic and end-systolic internal diameter, and fractional shortening after adjustment for factors known to influence these variables. Changes over time were detected for all of the LV measurements (P ranging from <0.0001 to 0.02), except for fractional shortening in men. The SS genotype of the ESR1 TA repeat polymorphism in the promoter region was associated with longitudinal changes in LV mass and LV wall thickness (P ranging from 0.0006 to 0.01). Moreover, the TA[S]-+30[T]-PvuII[T]-XbaI[A] haplotype (frequency: 47.5%) was associated with greater LV changes as compared with the TA[L]-+30[C]-PvuII[C]-XbaI[G] haplotype (frequency: 31.8%). Our results are consistent with the hypothesis that common ESR1 polymorphisms are significantly associated with age-related changes in LV structure. Understanding the mechanisms predisposing to unfavorable LV remodeling of the heart with advancing age may aid in the discovery of new therapeutic targets for the prevention of heart failure.

Contribution of several candidate gene polymorphisms in the determination of adiposity changes: results from the Québec Family Study

BACKGROUND

Several candidate genes have been associated with obesity, but very few studies have tested more than one gene simultaneously.

METHODS

In this study, 15 polymorphisms in 10 candidate genes of obesity were tested for association with changes in adiposity measured over a period of 6-10 years in a maximum of 332 adult subjects with a wide range of adiposity (17.5<body mass index (BMI)<55.6 kg/m2) from the Québec Family Study. Stepwise regression models were used to identify the combination of genes explaining changes in adiposity after adjustment for age (initial value), gender, initial value of the adiposity variable and duration of follow-up. Analyses were carried out in the whole sample and repeated while stratifying on age (<40 and>or=40 years).

RESULTS

In the whole sample, the variance in age-related adiposity changes explained by the candidate gene polymorphisms ranged from 3.1% (BMI, P<0.05) to 8.5% (fat mass (FM), P<or=0.0005). The genes retained in the prediction model for changes in FM were leptin (P<or=0.05), guanine nucleotide binding protein beta3 (P<or=0.05), adrenergic receptor beta3 (P<or=0.05), neuromedin beta (P<or=0.05) and peroxisome proliferator-activated receptor-gamma2 (P<or=0.10). The effects of the genes were significant in both age groups, but the genes contributing to adiposity changes were different and their effects were stronger in the younger than in the older age group.

CONCLUSION

This study suggests that models including genetic information from several candidate gene polymorphisms can significantly contribute to the changes in adiposity over time, that different genes may act at different ages and that genetic information could be useful for the identification of individuals at high risk for gaining body fat over time.

Anthropometric relationships between parents and children throughout childhood: the Fleurbaix-Laventie Ville Santé Study

BACKGROUND

The study of parent-child anthropometric relationships and their evolution over time may help to better understand familial risk factors for childhood obesity.

METHODS

In a population-based cohort of 124 nuclear families (Fleurbaix-Laventie Ville Santé Study (FLVS) I and II), various anthropometric parameters were measured in both parents and their children, first when the children were prepubescent and again at the end of puberty. Troncular adiposity repartition was estimated by calculating troncular to peripheral skinfolds ratio and waist-to-hip circumferences ratio. Birth and infancy heights and weights were also obtained from the children's health booklets. Parent-child correlations were estimated in infancy, before and at the end of the child's puberty. A prospective analysis was performed to predict the changes in the children's measurements over puberty according to their parents' corresponding baseline values.

RESULTS

BMI and weight correlations at birth were high (>0.30) with the mother and low (<0.10) with the father, then they converged to an intermediate level at 2 y and remained between 0.2 and 0.3 thereafter. Correlations for waist circumference were already present at the prepubertal period and persisted on the same level at the postpubertal period, whereas correlations for subcutaneous adiposity - measured by four skinfolds - and for adiposity distribution - measured by ratios - were higher at the postpubertal period. Moreover, the prospective approach showed that mother's BMI predicted the evolution of her children's BMI over puberty, whereas this relationship was observed more specifically with the father concerning adiposity distribution parameters.

CONCLUSION

Maternal adiposity may act early in life on the adiposity of the child. Maternal and paternal adiposities seem to have quite distinct effects at two key periods of the child's adiposity development such as the prenatal and pubertal periods.

Interaction of Body Mass Index and Framingham Risk Score in Predicting Incident Coronary Disease in Families

Background— Siblings of individuals with premature coronary heart disease (CHD) have a marked excess risk of CHD risk factors and premature CHD. The impact of body mass index (BMI) on incident CHD in these families and the extent to which it may be mediated by associated risk factors are unknown. The aim of this study was to examine the effect of high BMI on incident CHD in white and black families with premature CHD and to estimate the heritability of BMI.

Methods and Results— Risk factors, BMI, and Framingham Risk Score (FRS) were assessed at baseline and incident CHD was determined prospectively in 827 apparently healthy siblings of probands with premature CHD aged <60 years. During a mean follow-up of 8.7 years, 13.3% of siblings had incident CHD events. Event rates were higher in obese and overweight siblings than in those with normal weight (15.3% and 16.0% versus 8.1%, respectively; P =0.01). Multivariable Cox proportional hazards analyses demonstrated the independent prognostic value of BMI when added to FRS ( P =0.02). A marked interaction between obesity (BMI ≥30 kg/m 2 ) and high FRS (>20%) was seen for incident CHD ( P for interaction=0.008), with an adjusted hazard ratio compared with low-FRS/normal-weight siblings of 14.63 (95% CI, 6.40 to 33.44; P <0.0001). BMI heritability (h 2 ) was moderate for whites and low for blacks (52% and 29%, respectively).

Conclusions— High BMI contributed independently and significantly to incident CHD, beginning in the overweight range, and was most notable for obese siblings with a high-risk FRS.

Predictors of body mass index and associations with cardiovascular risk factors in Australian children: a prospective cohort study

OBJECTIVE

To examine predictors of body mass index (BMI) at the age of 8 y in a prospective study of Australian children.

DESIGN

Longitudinal survey of a cohort of Australian children followed from the 16th week of gestation to 8 y.

SUBJECTS

In total, 741 boys and 689 girls who attended the survey as 8 y olds.

MEASUREMENTS

Weight and height, blood pressure measured by automated oscillometry, fasting blood lipids and glucose. Questionnaire assessment of activity and diet.

RESULTS

Proportions of overweight including obesity in boys and girls were, respectively, 22 and 25% at 1 y, 14 and 14% at 3 y, 13 and 18% at 5 y and 15 and 20% at 8 y. At the age of 1, 3, 6 and 8 y, children with overweight including obesity showed significantly more adverse cardiovascular risk factors. Blood pressure (BP) was significantly higher by 2/3 mmHg (systolic/diastolic) at 1 y, 3/2 mmHg at 3 y, 4/2 mmHg at 5 y and 6/2 mmHg at 8 y; HDL was significantly lower (P=0.002) by 8% and triglycerides were significantly higher by 27% (P<0.001). In multivariate regression, BMI at the age of 8 y was significantly predicted positively by birth weight, mother's BMI and hours spent in watching television at the time of the survey of 6 y olds. Mothers being ex-smokers or non smokers and children being 'slightly active' and 'active' negatively predicted BMI in 8 y olds. In a subset of 298 children with information about fathers, paternal BMI was an additional independent predictor. Maternal or paternal overweight including obesity each independently increased risk of overweight including obesity at the age of 8 y three-fold. A food factor with consumption of cereals and breads as the major components derived from a Food Frequency Questionnaire in a subset of 340 children was also an independent negative predictor of BMI in multivariate models.

CONCLUSION

The increasing rate of overweight including obesity, particularly in girls, is associated with an increase in cardiovascular risk factors very early in life. Improvement of health-related behaviours within the family and a focus on promotion of activity in children should be priorities in achieving weight control.

Genómica de la regulación del peso corporal: mecanismos moleculares que predisponen a la obesidad

Obesity has become a worldwide public health problem which affects millions of people. Substantial progress has been made in elucidating the pathogenesis of energy homeostasis over the past few years. The fact that obesity is under strong genetic control has been well established. Twin, adoption and family studies have shown that genetic factors play a significant role in the pathogenesis of obesity. Human monogenic obesity is rare in large populations. The most common form of obesity is considered to be a polygenic disorder. New treatments are currently required for this common metabolic disease and type 2 diabetes. The identification of physiological and biochemical factors that underlie the metabolic disturbances observed in obesity is a key step in developing better therapeutic outcomes. The discovery of new genes and pathways involved in the pathogenesis of such a disease is critical to this process. However, identification of genes that contribute to the risk of developing the disease represents a significant challenge since obesity is a complex disease with many genetic and environmental causes. A number of diverse approaches have been used to discover and validate potential new genes for obesity. To date, DNA-based approaches using candidate genes and genome-wide linkage analysis have not had a great success in identifying genomic regions or genes involved in the development of these diseases. Recent advances in the ability to evaluate linkage analysis data from large family pedigrees (using variance components-based linkage analysis) show great promise in robustly identifying genomic regions associated with the development of obesity. Studying rare mutations in humans and animal models has provided fundamental insight into a complex physiological process, and has complemented population-based studies that seek to reveal primary causes. Remarkable progress has been made in both fronts and the pace of advance is likely to accelerate as functional genomics and the human genome project expand and mature. Approaches based on Mendelian and quantitative genetics may well converge, and ultimately lead to more rational and selective therapies.

[Genetics of obesity and metabolic complications in the Quebec Family Study]

Considerable progress has been accomplished over the past 10 years in the understanding of the genetic basis of obesity and its related metabolic complications. It is now well established that obesity aggregates within families and that genes are partly responsible for this familial aggregation. The number of genes potentially involved in obesity continues to grow. This review summarizes the evidence accumulated so for regarding the contribution of genetic factors in obesity and the number of gene and loci linked to obesity in the Quebec Family Study.