The Pro12Ala and C-681G variants of the PPARG locus are associated with opposing growth phenotypes in young schoolchildren

PPARγ2 Pro12Ala Polymorphism is Associated in Children With Traits Related to Susceptibility to Type 2 Diabetes

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear receptor that regulates glucose and lipid metabolism. Pharmacological activators of PPARγ are being used as a treatment of obesity related disorders such as dyslipidaemia and type 2 diabetes, but questions remain open regarding the effects of PPARγ on traits related to the development of type 2 diabetes. In our study, we have analyzed the relationship of the common variant Pro12Ala in the human PPARγ2 gene with the presence of obesity and with insulin, HOMA and lipid profile in a representative sample of 6-to 8-year-old children free from the confounding factors associated with adults. We found that Ala12Ala genotype was significantly more frequent in females with obesity than in those without obesity, with Ala12Ala carriers having significantly higher weight and body mass index (BMI), however the association disappeared when adjusting by leptin concentrations. The Ala12Ala genotype was associated with significantly higher HDL-cholesterol and apoA-I levels in males but not in females, independently of BMI. In a recessive model, in females, leptin levels appeared higher in Ala12Ala carriers. Although no apparent differences were observed in any sex when analyzing insulin levels and HOMA among genotypes without adjusting, lower insulin levels and lower HOMA appeared associated with Ala12Ala carriers when adjusting for BMI and leptin levels. In summary, our data showed that leptin seems to be having an effect on the association between the PPARγ2 Pro12Ala and BMI. Besides, after controlling for BMI and leptin, a protective effect of the Ala12Ala variant of the PPARγ2 Pro12Ala polymorphism on insulin sensitivity is evident already in prepubertal children.

C1431T Variant of PPARγ Is Associated with Preeclampsia in Pregnant Women

Peroxisome proliferator-activated receptor γ (PPARγ) is essential for placental development, whose SNPs have shown increased susceptibility to pregnancy-related diseases, such as preeclampsia. Our aim was to investigate the association between preeclampsia and three PPARγ SNPs (Pro12Ala, C1431T, and C681G), which together with nine clinical factors were used to build a pragmatic model for preeclampsia prediction. Data were collected from 1648 women from the EDEN cohort, of which 35 women had preeclamptic pregnancies, and the remaining 1613 women had normal pregnancies. Univariate analysis comparing preeclamptic patients to the control resulted in the SNP C1431T being the only factor significantly associated with preeclampsia (p < 0.05), with a confidence interval of 95% and odds ratio ranging from 4.90 to 8.75. On the other hand, three methods of multivariate feature selection highlighted seven features that could be potential predictors of preeclampsia: maternal C1431T and C681G variants, obesity, body mass index, number of pregnancies, primiparity, cigarette use, and education. These seven features were further used as input into eight different machine-learning algorithms to create predictive models, whose performances were evaluated based on metrics of accuracy and the area under the receiver operating characteristic curve (AUC). The boost tree-based model performed the best, with respective accuracy and AUC values of 0.971 ± 0.002 and 0.991 ± 0.001 in the training set and 0.951 and 0.701 in the testing set. A flowchart based on the boost tree model was constructed to depict the procedure for preeclampsia prediction. This final decision tree showed that the C1431T variant of PPARγ is significantly associated with susceptibility to preeclampsia. We believe that this final decision tree could be applied in the clinical prediction of preeclampsia in the very early stages of pregnancy.

Analysis of porcine body size variation using re-sequencing data of miniature and large pigs

Background

Domestication has led to substantial phenotypic and genetic variation in domestic animals. In pigs, the size of so called minipigs differs by one order of magnitude compared to breeds of large body size. We used biallelic SNPs identified from re-sequencing data to compare various publicly available wild and domestic populations against two minipig breeds to gain better understanding of the genetic background of the extensive body size variation. We combined two complementary measures, expected heterozygosity and the composite likelihood ratio test implemented in “SweepFinder”, to identify signatures of selection in Minipigs. We intersected these sweep regions with a measure of differentiation, namely F_ST, to remove regions of low variation across pigs. An extraordinary large sweep between 52 and 61 Mb on chromosome X was separately analyzed based on SNP-array data of F₂ individuals from a cross of Goettingen Minipigs and large pigs.

Results

Selective sweep analysis identified putative sweep regions for growth and subsequent gene annotation provided a comprehensive set of putative candidate genes. A long swept haplotype on chromosome X, descending from the Goettingen Minipig founders was associated with a reduction of adult body length by 3% in F₂ cross-breds.

Conclusion

The resulting set of genes in putative sweep regions implies that the genetic background of body size variation in pigs is polygenic rather than mono- or oligogenic. Identified genes suggest alterations in metabolic functions and a possible insulin resistance to contribute to miniaturization. A size QTL located within the sweep on chromosome X, with an estimated effect of 3% on body length, is comparable to the largest known in pigs or other species. The androgen receptor AR, previously known to influence pig performance and carcass traits, is the most obvious potential candidate gene within this region.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5009-y) contains supplementary material, which is available to authorized users.

Two Novel SNPs of PPARγ Significantly Affect Weaning Growth Traits of Nanyang Cattle

Peroxisome-proliferator-activated receptor gamma (PPARγ) is a key transcription factor that controls adipocyte differentiation and energy in mammals. Therefore, PPARγ is a potential factor influencing animal growth traits. This study primarily evaluates PPARγ as candidate gene for growth traits of cattle and identifies potential molecular marker for cattle breeding. Per previous studies, PPARγ mRNA was mainly expressed at extremely high levels in adipose tissues as shown by quantitative real-time polymerase chain reaction analysis. Three novel SNPs of the bovine PPARγ gene were identified in 514 individuals from six Chinese cattle breeds: SNP1 (AC_000179.1 g.57386668 C > G) in intron 2 and SNP2 (AC_000179.1 g.57431964 C > T) and SNP3 (AC_000179.1 g.57431994 T > C) in exon 7. The present study also investigated genetic characteristics of these SNP loci in six populations. Association analysis showed that SNP1 and SNP3 loci significantly affect weaning growth traits, especially body weight of Nanyang cattle. These results revealed that SNP1 and SNP3 are potential molecular markers for cattle breeding.

A co-association network analysis of the genetic determination of pig conformation, growth and fatness

BACKGROUND

Several QTLs have been identified for major economically relevant traits in livestock, such as growth and meat quality, revealing the complex genetic architecture of these traits. The use of network approaches considering the interactions of multiple molecules and traits provides useful insights into the molecular underpinnings of complex traits. Here, a network based methodology, named Association Weight Matrix, was applied to study gene interactions and pathways affecting pig conformation, growth and fatness traits.

RESULTS

The co-association network analysis underpinned three transcription factors, PPARγ, ELF1, and PRDM16 involved in mesoderm tissue differentiation. Fifty-four genes in the network belonged to growth-related ontologies and 46 of them were common with a similar study for growth in cattle supporting our results. The functional analysis uncovered the lipid metabolism and the corticotrophin and gonadotrophin release hormone pathways among the most important pathways influencing these traits. Our results suggest that the genes and pathways here identified are important determining either the total body weight of the animal and the fat content. For instance, a switch in the mesoderm tissue differentiation may determinate the age-related preferred pathways being in the puberty stage those related with the miogenic and osteogenic lineages; on the contrary, in the maturity stage cells may be more prone to the adipocyte fate. Hence, our results demonstrate that an integrative genomic co-association analysis is a powerful approach for identifying new connections and interactions among genes.

CONCLUSIONS

This work provides insights about pathways and key regulators which may be important determining the animal growth, conformation and body proportions and fatness traits. Molecular information concerning genes and pathways here described may be crucial for the improvement of genetic breeding programs applied to pork meat production.

Polymorphisms in LEPR, PPARG and APM1 genes: associations with energy intake and metabolic traits in young children

OBJECTIVE: To assess the association of single nucleotide polymorphisms (SNPs) in five genes - leptin, leptin receptor (LEPR), adiponectin (APM1), peroxisome proliferator-activated receptor gamma (PPARG) and uncoupling protein 1 - with anthropometric, metabolic, and dietary parameters in a Southern Brazilian cohort of 325 children followed up from birth to 4 years old. MATERIALS AND METHODS: SNPs were analyzed using polymerase chain reaction-based procedures, and their association with phenotypes was evaluated by t-test, analysis of variance, and general linear models. RESULTS: LEPR223Arg allele (rs1137101) was associated with higher daily energy intake at 4 years of age (P = 0.002; Pcorrected = 0.024). PPARG 12Ala-carriers (rs1801282) presented higher glucose levels than Pro/Pro homozygotes (P = 0.007; Pcorrected = 0.042). CONCLUSIONS: Two of the six studied SNPs presented consistent associations, showing that it is already possible to detect the influences of genetic variants on susceptibility to overweight in 4-year-old children.

Association of peroxisome proliferator-activated receptor α/δ/γ with obesity, and gene-gene interaction, in the Chinese Han population

BACKGROUND

We investigated the association of 10 single-nucleotide polymorphisms (SNPs) in the peroxisome proliferator-activated receptors (PPARs) with obesity and the additional role of gene-gene interaction.

METHODS

Participants were recruited within the framework of the Prevention of Multiple Metabolic Disorders and MS in Jiangsu Province cohort population survey of an urban community in China. In total, 820 subjects (513 nonobese adults, 307 obese adults) were randomly selected, and no individuals were consanguineous. Ten SNPs (rs135539, rs4253778, rs1800206, rs2016520, rs9794, rs10865710, rs1805192, rs709158, rs3856806, and rs4684847) were genotyped and analyzed.

RESULTS

After covariate adjustment, minor alleles of rs2016520 in PPARδ and rs10865170 in PPARγ were associated with lower BMI (P < 0.01 for all). Generalized multifactor dimensionality reduction analysis showed significant gene-gene interaction among rs2016520, rs9794, and rs10865170 in 3-dimensional models (P = 0.0010); prediction accuracy was 0.6011 and cross-validation consistency was 9/10. It also showed significant gene-gene interaction between rs2016520 and rs10865170 in all 2-dimensional models (P = 0.0010); prediction accuracy was 0.6072 and cross-validation consistency was 9/10.

CONCLUSIONS

rs2016520 and rs10865170 were associated with lower obesity risk. In addition, interaction was identified among rs2016520, rs9794, and rs10865170 in obesity.

Obesity and eating behaviour in children and adolescents: contribution of common gene polymorphisms

The prevalence of childhood obesity is increasing in many countries and confers risks for early type 2 diabetes, cardiovascular disease and metabolic syndrome. In the presence of potent 'obesogenic' environments not all children become obese, indicating the presence of susceptibility and resistance. Taking an energy balance approach, susceptibility could be mediated through a failure of appetite regulation leading to increased energy intake or via diminished energy expenditure. Evidence shows that heritability estimates for BMI and body fat are paralleled by similar coefficients for energy intake and preferences for dietary fat. Twin studies implicate weak satiety and enhanced food responsiveness as factors determining an increase in BMI. Single gene mutations, for example in the leptin receptor gene, that lead to extreme obesity appear to operate through appetite regulating mechanisms and the phenotypic response involves overconsumption and a failure to inhibit eating. Investigations of robustly characterized common gene variants of fat mass and obesity associated (FTO), peroxisome proliferator-activated receptor (PPARG) and melanocortin 4 receptor (MC4R) which contribute to variance in BMI also influence the variance in appetite factors such as measured energy intake, satiety responsiveness and the intake of palatable energy-dense food. A review of the evidence suggests that susceptibility to childhood obesity involving specific allelic variants of certain genes is mediated primarily through food consumption (appetite regulation) rather than through a decrease in activity-related energy expenditure. This conclusion has implications for early detection of susceptibility, and for prevention and management of childhood obesity.

Lack of association of type 2 diabetes susceptibility genotypes and body weight on the development of islet autoimmunity and type 1 diabetes

AIM

To investigate whether type 2 diabetes susceptibility genes and body weight influence the development of islet autoantibodies and the rate of progression to type 1 diabetes.

METHODS

Genotyping for single nucleotide polymorphisms (SNP) of the type 2 diabetes susceptibility genes CDKAL1, CDKN2A/2B, FTO, HHEX-IDE, HMGA2, IGF2BP2, KCNJ11, KCNQ1, MTNR1B, PPARG, SLC30A8 and TCF7L2 was obtained in 1350 children from parents with type 1 diabetes participating in the BABYDIAB study. Children were prospectively followed from birth for islet autoantibodies and type 1 diabetes. Data on weight and height were obtained at 9 months, 2, 5, 8, 11, and 14 years of age.

RESULTS

None of type 2 diabetes risk alleles at the CDKAL1, CDKN2A/2B, FTO, HHEX-IDE, HMGA2, IGF2BP2, KCNJ11, KCNQ1, MTNR1B, PPARG and SLC30A8 loci were associated with the development of islet autoantibodies or diabetes. The type 2 diabetes susceptible genotype of TCF7L2 was associated with a lower risk of islet autoantibodies (7% vs. 12% by age of 10 years, P = 0.015, P(corrected) = 0.18). Overweight children at seroconversion did not progress to diabetes faster than non-overweight children (HR: 1.08; 95% CI: 0.48-2.45, P>0.05).

CONCLUSIONS

These findings do not support an association of type 2 diabetes risk factors with islet autoimmunity or acceleration of diabetes in children with a family history of type 1 diabetes.

Accounting for a quantitative trait locus for plasma triglyceride levels: utilization of variants in multiple genes

Background

For decades, research efforts have tried to uncover the underlying genetic basis of human susceptibility to a variety of diseases. Linkage studies have resulted in highly replicated findings and helped identify quantitative trait loci (QTL) for many complex traits; however identification of specific alleles accounting for linkage remains elusive. The purpose of this study was to determine whether with a sufficient number of variants a linkage signal can be fully explained.

Method

We used comprehensive fine-mapping using a dense set of single nucleotide polymorphisms (SNPs) across the entire quantitative trait locus (QTL) on human chromosome 7q36 linked to plasma triglyceride levels. Analyses included measured genotype and combined linkage association analyses.

Results

Screening this linkage region, we found an over representation of nominally significant associations in five genes (MLL3, DPP6, PAXIP1, HTR5A, INSIG1). However, no single genetic variant was sufficient to account for the linkage. On the other hand, multiple variants capturing the variation in these five genes did account for the linkage at this locus. Permutation analyses suggested that this reduction in LOD score was unlikely to have occurred by chance (p = 0.008).

Discussion

With recent findings, it has become clear that most complex traits are influenced by a large number of genetic variants each contributing only a small percentage to the overall phenotype. We found that with a sufficient number of variants, the linkage can be fully explained. The results from this analysis suggest that perhaps the failure to identify causal variants for linkage peaks may be due to multiple variants under the linkage peak with small individual effect, rather than a single variant of large effect.

An age-dependent diet-modified effect of the PPARγ Pro12Ala polymorphism in children

Variation in the peroxisome proliferator-activated receptor γ gene alters the risk for adiposity in adults, with evidence of interaction with diet. We investigated the age-related association between the Pro12Ala variant (rs1801282) and diet in obesity-related traits in children. The Pro12Ala variant was assayed in 2102 young children aged 1 to 6 years and in 794 periadolescent children aged 10 to 12 years of Greek origin. In both cohorts, no differences were found in obesity traits between the Ala allele carriers and Pro/Pro homozygotes. Sex-stratified analysis showed that, in periadolescent boys, Ala carriers exhibited lower measures of skinfolds (triceps: 16.9 ± 6.9 vs 19.4 ± 7.9 mm, P = .01; subscapular: 9.6 ± 4.5 vs 11.2 ± 5.4 mm, P = .02). On the other hand, young girls who were Ala carriers presented higher measures of triceps skinfold thickness (10.5 ± 3.0 vs 9.9 ± 2.8 mm, P = .04). Nominal gene-diet interactions were revealed in periadolescents for saturated fatty acid (SFA) intake and skinfolds (P for interaction = .05). In Pro/Pro homozygous young girls, SFA and total fat (TF) intake was positively associated with higher body mass index (BMI) (P = .01), waist circumference (P = .02), and skinfold thickness (triceps-SFA: P = 10⁻⁵, triceps-TF: P = 10⁻⁹, subscapular-SFA: P = 10⁻⁶, subscapular-TF: P = 10⁻⁴). For Pro/Pro homozygotes, unsaturated fat intake was inversely associated with BMI (P = .04) in young girls, and with BMI (P = .03), waist circumference (P = .03), and triceps (P = .02) in periadolescent boys. Our results suggest that adiposity in children is influenced by the Pro12Ala polymorphism in a sex-specific and age-dependent manner. We also demonstrate evidence of an age-dependent gene-diet (SFA, TF) interaction, suggesting that the type of fat intake modifies the effect of the Pro12 allele on obesity-related measures.

BMI at age 8 years is influenced by the type 2 diabetes susceptibility genes HHEX-IDE and CDKAL1

OBJECTIVE

To determine whether HHEX-IDE and CDKAL1 genes, which are associated with birth weight and susceptibility to type 2 diabetes, continue to influence growth during childhood.

RESEARCH DESIGN AND METHODS

BMI, weight, and height at age 8 years expressed as age- and sex-corrected standard deviation scores (SDS) against national reference data and single-nucleotide polymorphism genotyping of HHEX-IDE and CDKAL1 loci were analyzed in 646 prospectively followed children in the German BABYDIAB cohort. All children were singleton full-term births; 386 had mothers with type 1 diabetes, and 260 had fathers with type 1 diabetes and a nondiabetic mother.

RESULTS

Type 2 diabetes risk alleles at the HHEX-IDE locus were associated with reduced BMI-SDS at age 8 years (0.17 SDS per allele; P = 0.004). After stratification for birth weight, both HHEX-IDE and CDKAL1 risk alleles were associated with reduced BMI-SDS (0.45 SDS, P = 0.0002; 0.52 SDS, P = 0.0001) and weight-SDS (0.22 SDS, P = 0.04; 0.56 SDS, P = 0.0002) in children born large for gestational age (>90th percentile) but not children born small or appropriate for gestational age. Within children born large for gestational age, BMI and weight decreased with each additional type 2 diabetes risk allele ( approximately -2 kg per allele; >8 kg overall). Findings were consistent in children of mothers with type 1 diabetes (P < 0.0001) and children of nondiabetic mothers (P = 0.008).

CONCLUSIONS

The type 2 diabetes susceptibility alleles at HHEX-IDE and CDKAL1 loci are associated with low BMI at age 8 years in children who were born large for gestational age.

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.

The role of genetic variation in peroxisome proliferator-activated receptors in the polycystic ovary syndrome (PCOS): an original case-control study followed by systematic review and meta-analysis of existing evidence

OBJECTIVE

To study the association of polymorphisms in the genes encoding peroxisome proliferator-activated receptors (PPARs) with the polycystic ovary syndrome (PCOS).

DESIGN

Case-control study and meta-analysis of published evidence.

PATIENTS

One hundred and sixty-one polycystic ovary syndrome patients and 113 non-hyperandrogenic women.

MEASUREMENTS

Genotyping for PPAR-gamma coactivator-1 gene (PPARGC1A) Gly482Ser, PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants and systematic review of the literature using the Entrez-PubMed search engine, followed by meta-analysis whenever possible.

RESULTS

Polycystic ovary syndrome patients carried the Gly482Ser variant in PPARGC1A more frequently than controls (72%vs. 58%, chi(2 )=( )5.54 P = 0.019), whereas carriers of the PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants were distributed similarly among both groups. The interaction between the PPARGC1A Gly482Ser and PPAR-delta-87T/C variants was also associated with PCOS (OR = 1.24, 95% CI 1.05-1.50, P = 0.008). The systematic review identified 31 studies addressing associations between PPARs variants and PCOS; meta-analysis was possible for nine studies focusing on the PPAR-gamma2 Pro12Ala variant. Although the individual studies did not reveal any statistically significant association, meta-analysis uncovered that carrying the PPAR-gamma2 Pro12Ala variant was associated with a reduced probability of having PCOS (OR = 0.77, 95% CI 0.61-0.96, P = 0.025), and that this association may be mediated by an effect on insulin sensitivity.

CONCLUSIONS

Common polymorphisms in the PPARGC1A, PPAR-delta and PPAR-gamma2 loci are associated with PCOS.

PPARG genotype accounts for part of individual variation in body weight reduction in response to calorie restriction

Several studies indicate that expression of the peroxisome proliferator-activated receptor gamma (PPARG) gene is influenced by calorie restriction. The aim of this study was to investigate whether PPARG gene variations are associated with weight reduction and changes in coronary heart disease (CHD) risk factors in response to a 14-week calorie restriction. In total, 95 middle-aged, Japanese women (BMI>or=25 kg/m2) enrolled as subjects for 14 weeks and attended weekly dietary lectures instructing them on how to consume a nutritionally balanced diet of 1,200 kcal/day. Eight single-nucleotide polymorphisms (SNPs) in the PPARG gene (rs1801282 (Pro/Ala), rs2292101, rs2959272, rs1386835, rs709158, rs1175540, rs1175544, and rs1797912) were analyzed. Body weight decreased significantly (-7.7+/-3.1 kg; -11.3+/-4.4%) during the intervention. Six PPARG SNPs (rs2959272, rs1386835, rs709158, rs1175540, rs1175544, and rs1797912) were significantly associated with the weight reduction, with rs1175544 having the strongest association (P=0.004). No differences across the rs1175544 genotypes were observed in any of the blood analyses or in blood pressure. In a multiple regression analysis, the rs1175544 genotypes accounted for 7% of the total weight reduction variance. These data suggest that one SNP of the PPARG genotype accounted for a significant portion of the total body weight reduction variance in response to a short-term intervention consisting of calorie restriction; however, no relationship was found between these SNPs and the changes in CHD risk factors which accompanied weight loss.

A single nucleotide polymorphism on exon-4 of the gene encoding PPARdelta is associated with reduced height in adults and children

CONTEXT

Peroxisome proliferator-activated receptor (PPAR)-delta is a nuclear transcription factor that plays a key role in many metabolic processes, including energy metabolism, and lipid and glucose metabolism. Candidate gene studies have identified a putative functional variant, rs2016520, in the gene encoding PPARdelta (PPARD), which is associated in some studies with metabolic traits. In addition, this single-nucleotide polymorphism was associated with adult height in several whole-genome scans, but this association did not achieve whole genome significance.

OBJECTIVE

This study sought to determine whether PPARD variation influenced height.

DESIGN

Haplotype tagging analysis across PPARD was performed in about 11,000 individuals from the Wellcome Trust U.K. Type 2 Diabetes Case Control Collection (Go-DARTS2).

RESULTS

There was an association between rs2016520 and height in both patients with type 2 diabetes and controls without diabetes (combined P = 5 x 10(-5)). In a metaanalysis using published data from Caucasian cohorts totaling more than 38,000 participants, compelling evidence was found for this locus and its association with height (P = 10(-8)) with an overall effect size of about 0.5 cm per allele. A similar analysis in a group of 2700 prepubescent children also displayed a similar effect size to that seen in the adults.

CONCLUSION

PPARD variation is clearly associated with a phenotype of reduced stature in both adults and children. Because height is an important indicator of metabolic and nutritional status, this provides additional support for a key role for PPARdelta in critical metabolic functions. PPARdelta may affect height through a variety of mechanisms including altered metabolic efficiency or effects on osteoclast function.

Leptin-adiposity relationship changes, plus behavioral and parental factors, are involved in the development of body weight in a Dutch children cohort

BACKGROUND

The development of body weight is determined by different factors, namely genetic, behavioral, parental and physiological.

OBJECTIVE

To investigate whether genetic, behavioral, parental and physiological factors are involved and the extent of involvement in the development of body weight at ages 12 and 13 y in a Dutch children cohort.

METHODS

In a Dutch cohort of 94 children at ages 12 and 13 y, we determined anthropometric measurements, body composition, leptin concentrations, TFEQ scores, physical activity, as well as 3 polymorphisms, and in the parents we determined anthropometric measurements and TFEQ scores.

RESULTS

11% of the children in the cohort were classified as overweight. The genotype frequency distributions of the PPARy2, GRL and CNTF genes at ages 12 and 13 y were not significantly different for the overweight children compared to the lean children. Overweight children showed higher dietary restraint and disinhibition scores. Overweight children's parents had a higher BMI, dietary restraint and disinhibition scores, compared to lean children's parents. A peak in leptin concentrations between 7 and 13 y was shown at 12 y. In lean boys, the decrease in leptin concentrations between 12 and 13 y was related to an increase in fat free mass. At the age of 12 y predominantly the physiological factors were predictors for body weight, and at the age of 13 y both the physiological and behavioral factors were predictors for body weight.

CONCLUSION

We conclude from this longitudinal study, that leptin appeared to play an important role in the development of body weight during puberty, in addition to behavioral and parental factors.

Association of the peroxisome proliferator-activated receptor-gamma2 Pro12Ala but not the C1431T gene variants with lower body mass index in Type 2 diabetes

The peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor involved in lipid metabolism, adipocyte differentiation and regulation of insulin sensitivity, and is associated with Type 2 diabetes (T2DM). The association of the C1431T silent mutation and the Pro12Ala missense transversion within the PPARgamma gene with the development of T2DM or obesity has often yielded contradictory results. We examined the association of the PPARgamma Pro12Ala and C1431T gene variants and their haplotypes with the susceptibility to T2DM. This was a retrospective study involving 491 T2DM patients and 400 age- and gender-matched controls. Pro12Ala and C1431T genotyping was done by PCR-RFLP analysis. Comparable frequencies of the mutant 12Ala (0.07 vs 0.08, p=0.216) and 1431T (0.12 vs 0.10, p=0.189) alleles, and Pro12Ala (p=0.218) and C1431T (p=0.421) genotypes were seen between patients and in nondiabetic control subjects. While no difference was noted in the distribution of Pro12Ala- C1431T haplotypes and genotypes between patients and controls, the PPARgamma 12Ala, but not 1431T, allele was significantly associated with lower body mass index (BMI) (< or =25.0) among patients. Regression analysis confirmed the association of the Pro12Ala (odds ratio =5.340; 95% confidence interval =1.044-27.311) with normal (BMI<25.0) but not with overweight/obesity among T2DM patients. Despite its association with lower BMI among T2DM patients, the PPARgamma gene does not appear to markedly influence Type 2 diabetes among Tunisian subjects.

Variants of the peroxisome proliferator-activated receptor gamma- and beta-adrenergic receptor genes are associated with measures of compensatory eating behaviors in young children

BACKGROUND

Young children can regulate energy precisely in the short term, showing the potential for an innate compensation mechanism of eating behavior. However, data suggest that precise compensation is attenuated as a function of increasing adiposity, parental feeding style, and age. Common variation in candidate obesity genes may account for some of the individual variation observed in short-term energy compensation. Polymorphisms in the peroxisome proliferator-activated receptor gamma (PPARG) and beta-adrenergic receptor (ADRB3) genes have been linked to increased body mass index (BMI; in kg/m(2)), obesity, and more recently dietary nutrients and preferences. In addition, common variation in ADRB3 interacts with PPARG to modulate adult body weight.

OBJECTIVE

This study investigated whether variants in these genes were associated with measurable effects on child eating behavior.

DESIGN

Children (n=84) aged 4-10 y were prospectively selected for variants of the PPARG locus (Pro12Ala, C1431T). Heights and weights were measured. Energy intake from a test meal was measured 90 min after ingestion of a no-energy (NE), low-energy (LE), or high-energy (HE) preload, and the compensation index (COMPX) was calculated.

RESULTS

BMI differed significantly by gene model, whereby Pro12Ala was associated with a lower BMI. Poor COMPX was associated with the PPARG T1431 allele (P=0.009). There was a significant interaction between COMPX and the ADRB3 Trp64Arg variant in modulating compensation (P=0.003), whereas the Arg64 allele was associated with good compensation (P=0.001).

CONCLUSIONS

This is the first study to suggest that a genetic interaction involving ADRB3 and PPARG variants influences eating behavior in children.

Biomarkers of obesity and subsequent cardiovascular events

Obesity is a major risk factor for cardiovascular diseases, but the mechanisms for increased cardiovascular risk in obesity are still unclear. Inflammation and increased oxidative stress are two potential mechanisms proposed to play a major role in the morbidity associated with obesity. Studies that investigate these mechanisms rely on biomarkers, but validated biomarkers for obesity-related cardiovascular outcomes are lacking. By finding optimal biomarkers, diagnostic criteria for cardiovascular diseases can be refined in the obese beyond "traditional" risk factors to identify early pathologic processes. The objective of this review is to identify potential early biomarkers resulting from obesity and associated with cardiovascular disease. Studies were initially identified through the search engine PubMed by using the keywords "obesity" and "biomarker." Subsequently, combinations of the keywords "obesity," "biomarker," "cardiovascular risk," "adipose tissue," "adipokine," "adipocytokine," and "oxidative stress" were used. The SOURCE database and Online Mendelian Inheritance in Man (OMIM) were used to obtain more information on the biomarkers. Results of the searches yielded a large number of potential biomarkers that occur in obesity and which either correlate with traditional cardiovascular risk factors or predict subsequent cardiovascular events. Several biomarkers are promising regarding their biologic properties, but they require further validation in humans.

PPARgamma in human and mouse physiology

The peroxisome proliferator activated receptor gamma (PPARgamma) is a member in the nuclear receptor superfamily which mediates part of the regulatory effects of dietary fatty acids on gene expression. As PPARgamma also coordinates adipocyte differentiation, it is an important component in storing the excess nutritional energy as fat. Our genes have evolved into maximizing energy storage, and PPARgamma has a central role in the mismatch between our genes and our affluent western society which results in a broad range of metabolic disturbances, collectively known as the metabolic syndrome. A flurry of human and mouse studies has shed new light on the mechanisms how the commonly used insulin sensitizer drugs and PPARgamma activators, thiazolidinediones, act, and which of their physiological effects are dependent of PPARgamma. It is now evident that the full activation of PPARgamma is less advantageous than targeted modulation of its activity. Furthermore, new roles for PPARgamma signaling have been discovered in inflammation, bone morphogenesis, endothelial function, cancer, longevity, and atherosclerosis, to mention a few. Here we draw together and discuss these recent advances in the research into PPARgamma biology.

PPARG locus haplotype variation and exacerbations in asthma

The peroxisome proliferator-activated receptor gamma (PPARgamma) regulates inflammation and may play a role in asthma. Using mouthwash-derived DNA and clinical interviews and measurements, we investigated the association of previously characterized single-nucleotide polymorphisms in the PPARG gene (Pro12Ala, C1431T, and C-681G) with asthma exacerbations in patients aged 3-22 years (n=569). The common homozygous haplotype combination of the Pro12 and C1431 alleles was associated with increased risk for asthma exacerbations (ProC, odds ratio (OR) 1.87, 95% confidence interval 1.25-2.79; P=0.002). The ProC genotype was associated with increased school absences (OR 1.82, 95% confidence interval 1.21-2.76; P=0.004) and hospital admissions (OR 2.32, 95% confidence interval 1.18-4.58; P=0.015) over the preceding 6 months. The population-attributable risk of this genotype was 33%. Common genetic variation at the PPARG locus may play an important role in modulating the long-term control of asthma in children and young adults.

Cues to overeat: psychological factors influencing overconsumption

Human food intake is driven by necessity, but modern industrialized societies are characterized by food surfeit and an increasingly ‘obesogenic’ environment. This environment tends to discourage energy expenditure and to facilitate energy intake. The amount eaten in any given eating episode depends less on internal need state and more on environmental contextual factors such as the availability of highly-palatable energy-dense foods. In addition, the process of satiation can easily be disrupted by the introduction within a meal of different foods (variety effect), the presence of others (social context) and competing tasks (distraction). Properties of ingestants such as alcohol promote food intake and characteristics of individuals make them more or less susceptible to situational cues to overeat. In the present review the role of each of these environmental factors in promoting overconsumption are considered and the extent to which these factors might contribute to long-term weight regulation is discussed.

Determinants of overweight in a cohort of Dutch children

BACKGROUND

To improve the effective prevention and treatment of obesity, it is important to focus on body weight (BW) development and its determinants during childhood.

OBJECTIVE

The aim of the present study was to investigate the effects of early development, parental and genetic variables, and behavioral determinants on overweight at 12 y.

DESIGN

In a Dutch cohort of 105 children, anthropometric measurements were conducted from birth until age 7 y. At age 12 y, anthropometric measurements were obtained again, as were measurements of body composition, leptin concentration, 3 polymorphisms, and physical activity, and the Three-Factor Eating Questionnaire was conducted. In addition, parental body mass indexes (BMIs, in kg/m2) and Three-Factor Eating Questionnaire scores were determined.

RESULTS

The children's mean (+/-SD) BMI at 12 y was 19.0 +/- 2.6, and 15.2% were classified as overweight. From the first year of life, BMI tracked significantly with BMI at age 12 y (r = 0.24, P < 0.05). Linear regression analyses showed that a rapid increase in BW during the first year of life, a high BMI of the father, and a high dietary restraint score of the mother were significantly associated with overweight at age 12 y (P < 0.05). No significant genetic relation was observed. In addition, overweight was positively associated with dietary restraint of the child, and percentage body fat was negatively associated with the child's activity score (P < 0.05).

CONCLUSIONS

In this homogeneous cohort of normal-weight to moderately overweight children, tracking of BMI during childhood took place from the first year of life. Overweight at age 12 y was predicted by an early rapid increase in BW and parental influences. Overweight during childhood may be maintained or even promoted by a high dietary restraint score and low physical activity.

Patterns of association between PPARgamma genetic variation and indices of adiposity and insulin action in African-Americans and whites: the CARDIA Study

We performed a combination of single-variant- and haplotype-based analyses to investigate the association of peroxisome-proliferator-activated receptor gamma (PPARgamma) gene sequence variation with indices of adiposity, including body mass index (BMI) and waist girth, as well as insulin action, including fasting blood glucose and insulin levels. Nine polymorphisms, selected based on race-specific pairwise linkage disequilibrium relations and/or potential functional relevance, were assayed in 3,875 African-American and white young adults from the Coronary Artery Risk Development in Young Adults Study. These polymorphisms were C25819G (C-681G), C65746G (Pro12Ala), G67222A, A69208G, G81556T, T95872C, T115432G, C127599T, and C148157T (C1431T). They defined seven and six common haplotypes in African-Americans and whites, respectively. Patterns of associations of PPARgamma genetic variation with the metabolic traits differed between the two racial groups, with some exceptions. Haplotype CCGGCTCC was associated with a significant reduction in glucose levels in both racial groups (P<0.001 in each group), and the G69208 allele was associated with lower glucose levels in lean African-Americans and in whites (both P=0.02). Two haplotypes, relatively unique to whites, were associated with measures of adiposity and glucose levels. Two haplotypes, relatively unique to African-Americans, were associated with glucose levels. There were no significant effects of PPARgamma haplotypes on measures of body size in this racial group, but a novel polymorphism, G67222A, significantly modulated the relation between BMI and glucose levels (P interaction, 0.003). This study provides evidence that variants, other than Pro12Ala, influence variation in body size and indices of insulin action. It underscores the role of genetic and environmental contexts in shaping the patterns of associations of PPARgamma sequence variants with metabolic traits in human populations.

Energy balance and food intake: the role of PPARgamma gene polymorphisms

Mechanisms regulating energy balance involve complex interactions between genetic, environmental and behavioural (learnt and intrinsic) factors. Genotype may drive the partitioning of energy metabolism and predispose to site-specific adiposity, culminating in a state of energy imbalance. One candidate gene with a direct link to adiposity is the peroxisome proliferator-activated receptor gamma (PPARG) gene. PPARG is a cell nuclear receptor expressed almost exclusively in adipose tissue that regulates adipocyte differentiation, lipid metabolism and insulin sensitivity. PPARgamma appears to be a key regulator of energy balance, with polymorphisms on the PPARG gene linked to obesity and effects on body composition. Our research has confirmed an association between the pro12ala allele and reduced incidence of obesity in pre-pubertal children and there are strong associations between genetic variation at the PPARG locus and percentage body fat. Moreover, our evidence suggests that PPARG C-681G and pro12ala polymorphisms display opposing effects in terms of growth phenotype, with pro12Ala associated with deficient energy utilisation, leading to reduced growth and the G-681 variant associated with accelerated growth compared with wildtypes. Common differences in this gene have also been associated with variations in body weight in response to dietary macronutrients. Preliminary evidence suggests that PPARG variants may even be involved in the control of short term energy compensation. Taken together these data suggest that the role of PPARG is varied and complex, influencing fat deposition and growth velocity early in life, with potential impact in the control of energy intake and appetite regulation, and could provide a key target for future research and anti-obesity agents.

Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis

Atopic disease, including atopic dermatitis (eczema), allergy and asthma, has increased in frequency in recent decades and now affects approximately 20% of the population in the developed world. Twin and family studies have shown that predisposition to atopic disease is highly heritable. Although most genetic studies have focused on immunological mechanisms, a primary epithelial barrier defect has been anticipated. Filaggrin is a key protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Here we show that two independent loss-of-function genetic variants (R510X and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis. These variants are carried by approximately 9% of people of European origin. These variants also show highly significant association with asthma occurring in the context of atopic dermatitis. This work establishes a key role for impaired skin barrier function in the development of atopic disease.