Genotype-by-nutrient interactions assessed in European obese women. A case-only study

Personalized Diets based on the Gut Microbiome as a Target for Health Maintenance: from Current Evidence to Future Possibilities

Recently, the concept of personalized nutrition has been developed, which states that food components do not always lead to the same metabolic responses, but vary from person to person. Although this concept has been studied based on individual genetic backgrounds, researchers have recently explored its potential role in the gut microbiome. The gut microbiota physiologically communicates with humans by forming a bidirectional relationship with the micronutrients, macronutrients, and phytochemicals consumed by the host. Furthermore, the gut microbiota can vary from person to person and can be easily shifted by diet. Therefore, several recent studies have reported the application of personalized nutrition to intestinal microflora. This review provides an overview of the interaction of diet with the gut microbiome and the latest evidence in understanding the inter-individual differences in dietary responsiveness according to individual baseline gut microbiota and microbiome-associated dietary intervention in diseases. The diversity of the gut microbiota and the presence of specific microorganisms can be attributed to physiological differences following dietary intervention. The difference in individual responsiveness based on the gut microbiota has the potential to become an important research approach for personalized nutrition and health management, although further well-designed large-scale studies are warranted.

Contribution of macronutrients to obesity: implications for precision nutrition

The specific metabolic contribution of consuming different energy-yielding macronutrients (namely, carbohydrates, protein and lipids) to obesity is a matter of active debate. In this Review, we summarize the current research concerning associations between the intake of different macronutrients and weight gain and adiposity. We discuss insights into possible differential mechanistic pathways where macronutrients might act on either appetite or adipogenesis to cause weight gain. We also explore the role of dietary macronutrient distribution on thermogenesis or energy expenditure for weight loss and maintenance. On the basis of the data discussed, we describe a novel way to manage excessive body weight; namely, prescribing personalized diets with different macronutrient compositions according to the individual's genotype and/or enterotype. In this context, the interplay of macronutrient consumption with obesity incidence involves mechanisms that affect appetite, thermogenesis and metabolism, and the outcomes of these mechanisms are altered by an individual's genotype and microbiota. Indeed, the interactions of the genetic make-up and/or microbiota features of a person with specific macronutrient intakes or dietary pattern consumption help to explain individualized responses to macronutrients and food patterns, which might represent key factors for comprehensive precision nutrition recommendations and personalized obesity management.

Gene co-expression networks are associated with obesity-related traits in kidney transplant recipients

Background

Obesity is common among kidney transplant recipients; However biological mediators of obesity are not well understood in this population. Because subcutaneous adipose tissue can be easily obtained during kidney transplant surgery, it provides a unique avenue for studying the mechanisms of obesity for this group. Although differential gene expression patterns were previously profiled for kidney transplant patients, gene co-expression patterns can shed light on gene modules not yet explored on the coordinative behaviors of gene transcription in biological and disease processes from a systems perspective.

Methods

In this study, we collected 29 demographic and clinical variables and matching microarray expression data for 26 kidney transplant patients. We conducted Weighted Gene Correlation Network Analysis (WGCNA) for 5758 genes with the highest average expression levels and related gene co-expression to clinical traits.

Results

A total of 35 co-expression modules were detected, two of which showed associations with obesity-related traits, mainly at baseline. Gene Ontology (GO) enrichment was found for these two clinical trait-associated modules. One module consisting of 129 genes was enriched for a variety of processes, including cellular homeostasis and immune responses. The other module consisting of 36 genes was enriched for tissue development processes.

Conclusions

Our study generated gene co-expression modules associated with obesity-related traits in kidney transplant patients and provided new insights regarding the cellular biological processes underlying obesity in this population.

Effect of two different dietary fatty acid profiles and variant rs266729 in ADIPOQ on weight loss and adiponectin concentrations

BACKGROUND

The role of ADIPOQ gene rs266729 variants on weight loss after a dietary intervention are still unclear.

OBJECTIVE

To analyze the effects of the ADIPOQ gene rs266729 variant n weight loss, cardiovascular risk factors, and adiponectin levels after two hypocaloric diets with different dietary fatty profiles.

DESIGN

A population of 362 obese patients was enrolled in a randomized clinical trial with two diets (Diet M, monounsaturated fat-enriched diet, and Diet P, polyunsaturated-fat enriched diet). Anthropometric measurements, an assessment of nutritional intake, and biochemical tests were performed at baseline and after 12 weeks.

RESULTS

Weight loss was similar with both diets. After Diet M, only subjects with CC genotype showed significant improvements in total cholesterol (CC vs. CG±GG) (-9.0±1.1mU/L vs. -4.5±2.4mg/dL, p=0.01), LDL cholesterol (-6.0±1.1mg/dL vs. -3.0±0.9mg/dL, p=0.03), glucose (-4.7±1.1mg/dL vs. -0.6±0.5mg/dL, p=0.01), and insulin levels (-2.6±1.0mU/L vs. -0.7±0.3mU/L, p=0.02) and in HOMA-IR (-0.5±0.2 units vs. -0.2±0.4 units, p=0.03). The same improvement was reported after Diet P in all parameters, including total cholesterol (CC vs. CG±GG) (-8.0±1.2mU/L vs. -2.1±1.4mg/dL, p=0.02), LDL cholesterol (-7.3±1.2mg/dL vs. -2.1±0.8mg/dL, p=0.02), glucose (-3.2±0.1mg/dL vs. -0.2±0.5mg/dL, p=0.01), and insulin levels (-2.5±1.0mU/L vs. -1±0.6mU/L, p=0.02) and HOMA-IR (-0.5±0.1 units vs. -0.3±0.4 units, p=0.02). Only subjects with CC genotype showed significant increases in adiponectin levels after both diets: (Diet M: 10.3±2.0ng/dL vs. Diet P: 9.3±2.9ng/dL, p=0.43).

CONCLUSION

The CC genotype of ADIPOQ gene rs266729 variant is associated to increased adiponectin levels and decreases in LDL cholesterol, glucose, insulin, and HOMA-IR levels after weight loss.

Adiponectin Gene Variant rs266729 Interacts with Different Macronutrient Distribution of Two Different Hypocaloric Diets

BACKGROUND

The role of ADIPOQ gene variants in weight loss after different dietary fat amounts remains unclear.

OBJECTIVE

Our aim was to analyze the effects of ADIPOQ gene polymorphism rs266729 on metabolic changes after two different amounts of dietary fat in two hypocaloric diets.

DESIGN

A population of 283 obese patients was recruited in a randomized clinical trial with two diets: Diet HF (high-fat diet: 38% carbohydrates, 24% proteins, and 38% fats) versus Diet LF (low-fat diet: 53% carbohydrates, 20% proteins, and 27% fats). Before and after 3 months, an anthropometric evaluation, an assessment of nutritional intake, and a biochemical analysis were carried out. The variant of the ADIPOQgene was assessed by real-time PCR.

RESULTS

Weight loss was similar with both diets in both genotypes (CC vs. CG+GG). After dietary intervention with Diet HF, only subjects with CC genotype showed a significant improvement in insulin levels (-3.3 ± 0.6 vs. -1.8 ± 0.9 mU/L; p = 0.03) and the homeostasis model assessment for insulin resistance (HOMA-IR) (-1.3 ± 0.1 vs. -0.8 ± 0.2 units; p = 0.02). After Diet LF, subjects with CC genotype showed a significant improvement in total cholesterol levels (CC vs. CG+GG) (-15.3 ± 1.4 vs. -6.4 ± 1.3 mg/dL; p = 0.01), LDL cholesterol (-14.6 ± 1.8 vs. -6.4 ± 1.3 mg/dL; p = 0.01), insulin levels (-4.6 ± 1.0 vs. -1.6 ± 0.5 mU/L; p = 0.01), and HOMA-IR (-1.6 ± 0.1 vs. -1.0 ± 0.2 units; p = 0.02). Only subjects with CC genotype showed a significant increase of adiponectin levels after both diets (CC vs. CG+GG): Diet HF (10.6 ± 2.0 vs. 1.8 ± 1.0 ng/dL; p = 0.01) and Diet LF (16.1 ± 2.8 vs. 1.3 ± 1.0 ng/dL: p = 0.03).

CONCLUSION

CC genotype of ADIPOQgene variantrs266729 was associated with a better metabolic response after both diets. Additionally, Diet LF produced a significant improvement in lipid profile in noncarriers of allele G.

Common Variants in Lipid Metabolism-Related Genes Associate with Fat Mass Changes in Response to Dietary Monounsaturated Fatty Acids in Adults with Abdominal Obesity

BACKGROUND

Different fatty acids (FAs) can vary in their obesogenic effect, and genetic makeup can contribute to fat deposition in response to dietary FA composition. However, the antiobesogenic effects of the interactions between dietary MUFAs and genetics have scarcely been tested in intervention studies.

OBJECTIVE

We evaluated the overall (primary outcome) and genetically modulated (secondary outcome) response in body weight and fat mass to different levels of MUFA consumption.

METHODS

In the Canola Oil Multicenter Intervention Trial II, a randomized, crossover, isocaloric, controlled-feeding multicenter trial, 44 men and 71 women with a mean age of 44 y and an increased waist circumference (men ∼108 cm and women ∼102 cm) consumed each of 3 oils for 6 wk, separated by four 12-wk washout periods. Oils included 2 high-MUFA oils-conventional canola and high-oleic canola (<7% SFAs, >65% MUFAs)-and 1 low-MUFA/high-SFA oil blend (40.2% SFAs, 22.0% MUFAs). Body fat was measured using DXA. Five candidate single-nucleotide polymorphisms (SNPs) were genotyped using qualitative PCR. Data were analyzed using a repeated measures mixed model.

RESULTS

No significant differences were observed in adiposity measures following the consumption of either high-MUFA diet compared with the low-MUFA/high-SFA treatment. However, when stratified by genotype, 3 SNPs within lipoprotein lipase (LPL), adiponectin, and apoE genes influenced, separately, fat mass changes in response to treatment (n = 101). Mainly, the LPL rs13702-CC genotype was associated with lower visceral fat (high-MUFA: -216.2 ± 58.6 g; low-MUFA: 17.2 ± 81.1 g; P = 0.017) and android fat mass (high-MUFA: -267.3 ± 76.4 g; low-MUFA: -21.7 ± 102.2 g; P = 0.037) following average consumption of the 2 high-MUFA diets.

CONCLUSIONS

Common variants in LPL, adiponectin, and apoE genes modulated body fat mass response to dietary MUFAs in an isocaloric diet in adults with abdominal obesity. These findings might eventually help in developing personalized dietary recommendations for weight control. The trial was registered at clinicaltrials.gov as NCT02029833 (https://www.clinicaltrials.gov/ct2/show/NCT02029833?cond=NCT02029833&rank=1).

The contribution of genetics and environment to obesity

BACKGROUND

Obesity is a global health problem mainly attributed to lifestyle changes such as diet, low physical activity or socioeconomics factors. However, several evidences consistently showed that genetics contributes significantly to the weight-gain susceptibility.

SOURCES OF DATA

A systematic literature search of most relevant original, review and meta-analysis, restricted to English was conducted in PubMed, Web of Science and Google scholar up to May 2017 concerning the contribution of genetics and environmental factors to obesity.

AREAS OF AGREEMENT

Several evidences suggest that obesogenic environments contribute to the development of an obese phenotype. However, not every individual from the same population, despite sharing the same obesogenic environment, develop obesity.

AREAS OF CONTROVERSY

After more than 10 years of investigation on the genetics of obesity, the variants found associated with obesity represent only 3% of the estimated BMI-heritability, which is around 47-80%. Moreover, genetic factors per se were unable to explain the rapid spread of obesity prevalence.

GROWING POINTS

The integration of multi-omics data enables scientists having a better picture and to elucidate unknown pathways contributing to obesity.

AREAS TIMELY FOR DEVELOPING RESEARCH

New studies based on case-control or gene candidate approach will be important to identify new variants associated with obesity susceptibility and consequently unveiling its genetic architecture. This will lead to an improvement of our understanding about underlying mechanisms involved in development and origin of the actual obesity epidemic. The integration of several omics will also provide insights about the interplay between genes and environments contributing to the obese phenotype.

Genetics of non-alcoholic fatty liver disease: From susceptibility and nutrient interactions to management

Genetics plays an important role in determining the susceptibility of an individual to develop a disease. Complex, multi factorial diseases of modern day (diabetes, cardiovascular disease, hypertension and obesity) are a result of disparity between the type of food consumed and genes, suggesting that food which does not match the host genes is probably one of the major reasons for developing life style diseases. Non-alcoholic fatty liver is becoming a global epidemic leading to substantial morbidity. While various genotyping approaches such as whole exome sequencing using next generation sequencers and genome wide association studies have identified susceptibility loci for non-alcoholic fatty liver disease (NAFLD) including variants in patatin-like phospholipase domain containing 3 and transmembrane 6 superfamily member 2 genes apart from others; nutrient based studies emphasized on a combination of vitamin D, E and omega-3 fatty acids to manage fatty liver disease. However majority of the studies were conducted independent of each other and very few studies explored the interactions between the genetic susceptibility and nutrient interactions. Identifying such interactions will aid in optimizing the nutrition tailor made to an individual's genetic makeup, thereby aiding in delaying the onset of the disease and its progression. The present topic focuses on studies that identified the genetic susceptibility for NAFLD, nutritional recommendations, and their interactions for better management of NAFLD.

Gene-environment interactions and obesity: recent developments and future directions

Obesity, a major public health concern, is a multifactorial disease caused by both environmental and genetic factors. Although recent genome-wide association studies have identified many loci related to obesity or body mass index, the identified variants explain only a small proportion of the heritability of obesity. Better understanding of the interplay between genetic and environmental factors is the basis for developing effective personalized obesity prevention and management strategies. This article reviews recent advances in identifying gene-environment interactions related to obesity and describes epidemiological designs and newly developed statistical approaches to characterizing and discovering gene-environment interactions on obesity risk.

The challenges for molecular nutrition research 1: linking genotype to healthy nutrition

Nutrition science finds itself at a major crossroad. On the one hand we can continue the current path, which has resulted in some substantial advances, but also many conflicting messages which impair the trust of the general population, especially those who are motivated to improve their health through diet. The other road is uncharted and is being built over the many exciting new developments in life sciences. This new era of nutrition recognizes the complex relation between the health of the individual, its genome, and the life-long dietary exposure, and has lead to the realisation that nutrition is essentially a gene-environment interaction science. This review on the relation between genotype, diet and health is the first of a series dealing with the major challenges in molecular nutrition, analyzing the foundations of nutrition research. With the unravelling of the human genome and the linking of its variability to a multitude of phenotypes from "healthy" to an enormously complex range of predispositions, the dietary modulation of these propensities has become an area of active research. Classical genetic approaches applied so far in medical genetics have steered away from incorporating dietary effects in their models and paradoxically, most genetic studies analyzing diet-associated phenotypes and diseases simply ignore diet. Yet, a modest but increasing number of studies are accounting for diet as a modulator of genetic associations. These range from observational cohorts to intervention studies with prospectively selected genotypes. New statistical and bioinformatics approaches are becoming available to aid in design and evaluation of these studies. This review discusses the various approaches used and provides concrete recommendations for future research.

Allelic variants of melanocortin 3 receptor gene (MC3R) and weight loss in obesity: a randomised trial of hypo-energetic high- versus low-fat diets

Introduction

The melanocortin system plays an important role in energy homeostasis. Mice genetically deficient in the melanocortin-3 receptor gene have a normal body weight with increased body fat, mild hypophagia compared to wild-type mice. In humans, Thr6Lys and Val81Ile variants of the melanocortin-3 receptor gene (MC3R) have been associated with childhood obesity, higher BMI Z-score and elevated body fat percentage compared to non-carriers. The aim of this study is to assess the association in adults between allelic variants of MC3R with weight loss induced by energy-restricted diets.

Subjects and Methods

This research is based on the NUGENOB study, a trial conducted to assess weight loss during a 10-week dietary intervention involving two different hypo-energetic (high-fat and low-fat) diets. A total of 760 obese patients were genotyped for 10 single nucleotide polymorphisms covering the single exon of MC3R gene and its flanking regions, including the missense variants Thr6Lys and Val81Ile. Linear mixed models and haplotype-based analysis were carried out to assess the potential association between genetic polymorphisms and differential weight loss, fat mass loss, waist change and resting energy expenditure changes.

Results

No differences in drop-out rate were found by MC3R genotypes. The rs6014646 polymorphism was significantly associated with weight loss using co-dominant (p = 0.04) and dominant models (p = 0.03). These p-values were not statistically significant after strict control for multiple testing. Haplotype-based multivariate analysis using permutations showed that rs3827103–rs1543873 (p = 0.06), rs6014646–rs6024730 (p = 0.05) and rs3746619–rs3827103 (p = 0.10) displayed near-statistical significant results in relation to weight loss. No other significant associations or gene*diet interactions were detected for weight loss, fat mass loss, waist change and resting energy expenditure changes.

Conclusion

The study provided overall sufficient evidence to support that there is no major effect of genetic variants of MC3R and differential weight loss after a 10-week dietary intervention with hypo-energetic diets in obese Europeans.

Association of the CYBA, PPARGC1A, PPARG3, and PPARD gene variants with coronary artery disease and metabolic risk factors of coronary atherosclerosis in a Russian population

Abnormalities in lipid metabolism and enhanced oxidative stress are considered as major risk factors for coronary atherosclerosis. Functional genetic variations in genes whose products are involved in lipid metabolism and antioxidant defense could therefore modulate risk of coronary artery disease (CAD). In this study, we evaluate whether the PPARGC1A Gly482Ser, PPARG3 (-681)C/G, PPARD +294T/C, and CYBA +242C/T gene variants confer the risk of CAD in a Russian population. A total of 313 CAD patients and 132 controls with no clinical sign of CAD were studied. The polymorphic markers were tested using a TaqMan assay. Allele and genotype frequencies in CAD patients and controls were compared using the Yates chi(2) test. Association of the genetic markers with metabolic risk factors of arterial atherosclerosis was studied using the analysis of variance test and then adjusted for conventional risk factors in the multiple regression analysis. For CYBA +242C/T, both the allele T and genotype T/T showed significant association with higher risk of CAD (odds ratio =1.49 and 3.89, respectively). The allele C and genotype C/C of the +294T/C marker of PPARD were associated with increased risk of CAD providing an odds ratio of 2.12 and 2.78, respectively. The risk variants of CYBA +242C/T and PPARD +294T/C markers were associated with higher low-density lipoprotein cholesterol and increased total serum cholesterol, respectively. In conclusion, the CYBA +242C/T and PPARD +294T/C variants modulate risk of CAD through their associations with atherogenic serum lipid profiles.

Gene-nutrient interactions in the metabolic syndrome: single nucleotide polymorphisms in ADIPOQ and ADIPOR1 interact with plasma saturated fatty acids to modulate insulin resistance

BACKGROUND

Progression of the metabolic syndrome (MetS) is determined by genetic and environmental factors. Gene-environment interactions may be important in modulating the susceptibility to the development of MetS traits.

OBJECTIVE

Gene-nutrient interactions were examined in MetS subjects to determine interactions between single nucleotide polymorphisms (SNPs) in the adiponectin gene (ADIPOQ) and its receptors (ADIPOR1 and ADIPOR2) and plasma fatty acid composition and their effects on MetS characteristics.

DESIGN

Plasma fatty acid composition, insulin sensitivity, plasma adiponectin and lipid concentrations, and ADIPOQ, ADIPOR1, and ADIPOR2 SNP genotypes were determined in a cross-sectional analysis of 451 subjects with the MetS who participated in the LIPGENE (Diet, Genomics, and the Metabolic Syndrome: an Integrated Nutrition, Agro-food, Social, and Economic Analysis) dietary intervention study and were repeated in 1754 subjects from the LIPGENE-SU.VI.MAX (SUpplementation en VItamines et Minéraux AntioXydants) case-control study (http://www.ucd.ie/lipgene).

RESULTS

Single SNP effects were detected in the cohort. Triacylglycerols, nonesterified fatty acids, and waist circumference were significantly different between genotypes for 2 SNPs (rs266729 in ADIPOQ and rs10920533 in ADIPOR1). Minor allele homozygotes for both of these SNPs were identified as having degrees of insulin resistance, as measured by the homeostasis model assessment of insulin resistance, that were highly responsive to differences in plasma saturated fatty acids (SFAs). The SFA-dependent association between ADIPOR1 rs10920533 and insulin resistance was replicated in cases with MetS from a separate independent study, which was an association not present in controls.

CONCLUSIONS

A reduction in plasma SFAs could be expected to lower insulin resistance in MetS subjects who are minor allele carriers of rs266729 in ADIPOQ and rs10920533 in ADIPOR1. Personalized dietary advice to decrease SFA consumption in these individuals may be recommended as a possible therapeutic measure to improve insulin sensitivity. This trial was registered at clinicaltrials.gov as NCT00429195.

Distribution of plasma levels of adiponectin and leptin in an adult Caucasian population

OBJECTIVES

Little is known regarding the distribution and the determinants of leptin and adiponectin levels in the general population.

DESIGN

Cross-sectional study.

PATIENTS

Women (3004) and men (2552) aged 35-74 living in Lausanne, Switzerland.

MEASUREMENTS

Plasma levels of leptin and adiponectin (ELISA measurement).

RESULTS

Women had higher leptin and adiponectin levels than men. In both genders, leptin and adiponectin levels increased with age. After adjusting for fat mass, leptin levels were significantly and negatively associated with age in women: 18.1 +/- 0.3, 17.1 +/- 0.3, 16.7 +/- 0.3 and 15.5 +/- 0.4 ng/ml (adjusted mean +/- SE) for age groups [35-44], [45-54], [55-64] and [65-75], respectively, P < 0.001. A similar but nonsignificant trend was also found in men. Conversely, the age-related increase of adiponectin was unrelated to body fat in both genders. Post-menopausal women had higher leptin and adiponectin levels than premenopausal women, independently of hormone replacement therapy. Although body fat mass was associated with leptin and adiponectin, the associations were stronger with body mass index (BMI), waist and hip in both genders. Finally, after adjusting for age and anthropometry, no relationships were found between leptin or adiponectin levels with alcohol, caffeine consumption and physical activity, whereas smoking and diabetes decreased leptin and adiponectin levels in women only.

CONCLUSIONS

The age-related increase in leptin levels is attributable to changes in fat mass in women and probably also in men. Leptin and adiponectin levels are more related to BMI than to body fat mass. The effects of smoking and diabetes appear to be gender-specific.

Genotype x nutrient association of common polymorphisms in obesity-related genes with food preferences and time structure of energy intake

Personal food preferences can either enhance or suppress the development of obesity and the selection and proportion of macronutrients in the diet seem to have a heritable component. In the present study, we therefore focused on dietary composition as a specific trait related to obesity and we determined whether genetic variations in leptin (LEP), LEP receptor (LEPR), adiponectin (ADIPOQ), IL-6 and pro-opiomelanocortin (POMC) underlie specific native food preferences and obesity-related anthropometric parameters. The total of 409 individuals of Czech Caucasian origin were enrolled into the present study and 7 d food records were obtained from the study subjects along with selected anthropometric measurements. In a subset of study subjects, plasma levels of ADIPOQ, LEP and soluble LEPR were measured. Independently of the BMI of the individuals, common variations in LEP and LEPR genes were associated with specific eating patterns, mainly with respect to timing of eating. The LEP + 19A/G polymorphism served as an independent predictor for BMI, percentage of body fat and skinfold thickness and significantly affected the time structure of the daily energy intake. The POMC RsaI polymorphism was associated with percentage of body fat. The ADIPOQ 45 T/G polymorphism was associated with the thickness of the subscapular skinfold. The LEPR Gln223Arg polymorphism was associated with multiple parameters, including diastolic blood pressure, meal sizes during the day and plasma ADIPOQ levels. In a separate analysis, soluble leptin receptor (sObR) plasma levels and LEP:sObR ratio were significantly correlated with systolic blood pressure (beta = - 0.66, P = 0.002; beta = - 1.23, P = 0.02) and sObR plasma levels also served as an independent predictor for diastolic blood pressure (beta = - 0.50; P = 0.04). To conclude, we report common allelic variants associated with specific feeding behaviour and obesity-related anthropometric traits. Moreover, we identified allelic variants that significantly influence the time structure of food intake during the day.

Severe obesity is associated with novel single nucleotide polymorphisms of the ESR1 and PPARgamma locus in Han Chinese

BACKGROUND

A large number of potential obesity loci have been reported. At least 18 genes have been replicated in a minimum of 5 studies on obesity-related phenotypes. Fourteen additional genes have been associated with obesity in Asians.

OBJECTIVES

Our objectives were to examine how many common variants of these candidate genes are associated with severe obesity in Han Chinese and how they are combined to exert their effects.

DESIGN

In total, 304 severely obese patients [body mass index (BMI; in kg/m(2)) > or =39] and 304 control subjects (BMI < or = 24) participated in a 2-staged association study. Subsequently, 220 additional severely obese patients (BMI > or = 35) and 338 controls (BMI < or = 24) were recruited to replicate the results. All of the controls were age-, sex-, education- and residence-matched. Finally, a pooled analysis was carried out based on all 514 cases and 606 controls with complete information.

RESULTS

The first-stage association analysis in 94 cases and 94 controls found 18 potentially associated single nucleotide polymorphisms (SNPs) (P = 0.01-0.1). The significance of 3 novel common SNPs, 1 on ESR1 and 2 on PPARgamma, were confirmed in the second stage and replicated further with odds ratios ranging from 1.89 to 2.24. The combined effect of these 3 genes was stronger (odds ratio: 5.27; 95% CI: 2.25, 12.32) than that from any individual gene.

CONCLUSIONS

Severe obesity in Han Chinese was associated with 3 novel common SNPs for ESR1 and PPARgamma. These 2 genes collectively result in a >5-fold risk of severe obesity. This information may contribute to the assessment of risk of severe obesity.

Effect of ID ACE gene polymorphism on dietary composition and obesity-related anthropometric parameters in the Czech adult population

The aim of this study was to investigate the possible associations between insertion/deletion (ID) polymorphism in angiotensin-converting enzyme (ACE) (dbSNP rs 4646994) with the food intake and body composition in the Czech non-obese, obese and extremely obese populations. A total of 453 various-weighted individuals were enrolled in the study and were according to their BMI assigned into following subgroups, such as obese (30 </= BMI < 40), morbidly obese (BMI >/=40) and non-obese (20 < BMI < 30) subjects. Both the obese cases and the non-obese controls underwent the identical subset of standardized examinations (BMI, % body fat, waist-to-hip ratio, skin fold thickness, native dietary composition examined by 7-day food records, etc.). No significant case-control differences in genotype distributions or allelic frequencies were observed. There were no differences in genotype frequencies between males and females either. The prevalence of obesity was significantly higher among subjects with the II genotype (42 %) when compared with those with DD (36%) and those with ID (37%) genotypes (P = 0.04). When compared with carbohydrate intake in the whole studied cohort, the odds ratios of carrying the DD allele in the morbidly obese cohort were 0.84 (95% CI 0.34, 2.10, P = 0.17), 0.27 (0.07, 0.98, P = 0.02), and 4.25 (1.44, 12.51, P = 0.005) in those individuals consuming <210, 210-260, and >260 g of carbohydrates/day, respectively. Based on our findings, the ID ACE polymorphism could represent a gene modulator of carbohydrate intake in morbidly obese Czech population; the strong significant effect of DD genotype was observed in the phenotypes of extreme obesity with the highest carbohydrate intake.

ADIPOQ polymorphisms, monounsaturated fatty acids, and obesity risk: the GOLDN study

Serum adiponectin levels have been positively associated with insulin sensitivity and are decreased in type 2 diabetes (T2D) and obesity. Genetic and environmental factors influence serum adiponectin and may contribute to risk of metabolic syndrome and T2D. Therefore, we investigated the effect of ADIPOQ single-nucleotide polymorphisms (SNPs), -11377C>G and -11391G>A, on metabolic-related traits, and their modulation by dietary fat in white Americans. Data were collected from 1,083 subjects participating in the Genetics of Lipid Lowering Drugs and Diet Network study. Mean serum adiponectin concentration was higher for carriers of the -11391A allele (P = 0.001) but lower for the -11377G allele carriers (P = 0.017). Moreover, we found a significant association with obesity traits for the -11391G>A SNP. Carriers of the -11391A allele had significantly lower weight (P = 0.029), BMI (P = 0.019), waist (P = 0.003), and hip circumferences (P = 0.004) compared to noncarriers. Interestingly, the associations of the -11391G>A with BMI and obesity risk were modified by monounsaturated fatty acids (MUFAs) intake (P-interaction = 0.021 and 0.034 for BMI and obesity risk, respectively). In subjects with MUFA intake above the median (> or =13% of energy intake), -11391A carriers had lower BMI (27.1 kg/m(2) for GA+AA vs. 29.1 kg/m(2) for GG, P = 0.002) and decreased obesity risk (odds ratio for -11391A = 0.52, 95% confidence interval (CI); 0.28-0.96; P = 0.031). However, we did not detect genotype-related differences for BMI or obesity in subjects with MUFA intake <13%. Our findings support a significant association between the -11391G>A SNPs and obesity-related traits and the potential to moderate such effects using dietary modification.

ZAG, a lipid mobilizing adipokine, is downregulated in human obesity

The main goal of this study was to compare the expression of Zinc-alpha2-glycoprotein (ZAG), a recently described adipokine, in obese and lean subjects. ZAG expression was determined by Real-time PCR analysis in subcutaneous abdominal adipose tissue of eighteen young men, 9 lean (BMI = 23.1 +/- 0.4 kg/m2) and 9 obese (34.7 +/- 1.2 kg/m2) with a similar habitual dietary intake of fat and physical activity, which were assessed by validated methods. Our data revealed that ZAG gene was downregulated (-70%; p < 0.05) in subcutaneous adipose tissue of obese compared to lean subjects. Moreover, statistically significant positive correlations between ZAG gene expression and serum adiponectin (r = 0.89; p < 0.01) and a negative correlation with the plasma levels of leptin (r = -0.82; p < 0.05) and waist circumference (r = -0.64; p < 0.05) were found in obese subjects. Our data suggest that this novel adipokine could play a role in human susceptibility to obesity related disorders and that upregulation of ZAG could be a promising therapeutic target for metabolic syndrome treatment.

Why study gene-environment interactions?

PURPOSE OF REVIEW

We examine the reasons for investigating gene-environment interactions and address recent reports evaluating interactions between genes and environmental modulators in relation to cardiovascular disease and its common risk factors.

RECENT FINDINGS

Studies focusing on smoking, physical activity, and alcohol and coffee consumption are observational and include relatively large sample sizes. They tend to examine single genes, however, and fail to address interactions with other genes and other correlated environmental factors. Studies examining gene-diet interactions include both observational and interventional designs. These studies are smaller, especially those including dietary interventions. Among the reported gene-diet interactions, it is important to highlight the strengthened position of APOA5 as a major gene that is involved in triglyceride metabolism and modulated by dietary factors, and the identification of APOA2 as a modulator of food intake and obesity risk.

SUMMARY

The study of gene-environment interactions is an active and much needed area of research. Although technical barriers of genetic studies are rapidly being overcome, inclusion of comprehensive and reliable environmental information represents a significant shortcoming of genetics studies. Progress in this area requires inclusion of larger populations but also more comprehensive, standardized, and precise approaches to capturing environmental information.