Association of the Pro12Ala variant in the peroxisome proliferator-activated receptor-gamma2 gene with obesity in two Caucasian populations

Genetic variants in DBC1, SIRT1, UCP2 and ADRB2 as potential biomarkers for severe obesity and metabolic complications

Introduction

Obesity is a multifactorial disease associated with the development of many comorbidities. This disease is associated with several metabolic alterations; however, it has been shown that some individuals with obesity do not exhibit metabolic syndrome. Adipose tissue neutralizes the detrimental effects of circulating fatty acids, ectopic deposition, and inflammation, among others, through its esterification into neutral lipids that are stored in the adipocyte. However, when the adipocyte is overloaded, i.e., its expansion capacity is exceeded, this protection is lost, resulting in fatty acid toxicity with ectopic fat accumulation in peripheral tissues and inflammation. In this line, this study aimed to investigate whether polymorphisms in genes that control adipose tissue fat storage capacity are potential biomarkers for severe obesity susceptibility and also metabolic complications.

Methods

This study enrolled 305 individuals with severe obesity (cases, BMI≥35 kg/m2) and 196 individuals with normal weight (controls, 18.5≤BMI≤24.9 kg/m2). Demographic, anthropometric, biochemical, and blood pressure variables were collected from the participants. Plasma levels of leptin, resistin, MCP1, and PAI1 were measured by Bio-Plex 200 Multiplexing Analyzer System. Genomic DNA was extracted and variants in DBC1 (rs17060940), SIRT1 (rs7895833 and rs1467568), UCP2 (rs660339), PPARG (rs1801282) and ADRB2 (rs1042713 and rs1042714) genes were genotyped by PCR allelic discrimination using TaqMan® assays.

Results

Our findings indicated that SIRT1 rs7895833 polymorphism was a risk factor for severe obesity development in the overdominant model. SIRT1 rs1467568 and UCP2 rs660339 were associated with anthropometric traits. SIRT1 rs1467568 G allele was related to lower medians of body adipose index and hip circumference, while the UCP2 rs660339 AA genotype was associate with increased body mass index. Additionally, DBC1 rs17060940 influenced glycated hemoglobin. Regarding metabolic alterations, 27% of individuals with obesity presented balanced metabolic status in our cohort. Furthermore, SIRT1 rs1467568 AG genotype increased 2.5 times the risk of developing metabolic alterations. No statistically significant results were observed with Peroxisome Proliferator-Activated Receptor Gama and ADRB2 polymorphisms.

Discussion/Conclusion

This study revealed that SIRT1 rs7895833 and rs1467568 are potential biomarkers for severe obesity susceptibility and the development of unbalanced metabolic status in obesity, respectively. UCP2 rs660339 and DBC1 rs17060940 also showed a significant role in obesity related-traits.

Identification and Characteristics of Novel Mutations in Nonsyndromic Monogenic Obesity

Nonsyndromic monogenic obesity (NSMO) is a class of individual obesity that is independent of the environment and caused by a single gene mutation. It is mostly caused by mutations in LEP, LEPR, PCSK1, as well as some rare mutations in UCP3, NR0B2, and PPARG. Among 30 obesity patients, five patients are identified with positive gene detection. For the first time, the c.624C>T mutation associated with PCSK1, and the c.50G>A and c.293_301delinsAC mutations associated with NR0B2, as well as the obesity phenotype mutation (c.284A>G) associated with PPARG is confirmed. Following this, the genotype-clinical phenotype, mutation hotspots, and mutation distributions of each gene are summarized, and the genetic characteristics of NSMO are analyzed. The locations of mutation c.50G>A, and c.284A>G are highly conserved according to the sequencing alignment. According to the findings, the c.624C>T mutation in PCSK1 is a newly discovered synonymous mutation, but it can result in significant early-onset obesity. Additionally, the mutation of c.284A>G(PPARG) can lead to a variety of clinical phenotypes and the mutation of UCP3 and NR0B2 may increase the risk of type 2 diabetes mellitus. This study enriches the human NSMO gene mutation database and provides a scientific basis for clinically accurate diagnosis and treatment.

The Influence of the Differentiation of Genes Encoding Peroxisome Proliferator-Activated Receptors and Their Coactivators on Nutrient and Energy Metabolism

Genetic components may play an important role in the regulation of nutrient and energy metabolism. In the presence of specific genetic variants, metabolic dysregulation may occur, especially in relation to the processes of digestion, assimilation, and the physiological utilization of nutrients supplied to the body, as well as the regulation of various metabolic pathways and the balance of metabolic changes, which may consequently affect the effectiveness of applied reduction diets and weight loss after training. There are many well-documented studies showing that the presence of certain polymorphic variants in some genes can be associated with specific changes in nutrient and energy metabolism, and consequently, with more or less desirable effects of applied caloric reduction and/or exercise intervention. This systematic review focused on the role of genes encoding peroxisome proliferator-activated receptors (PPARs) and their coactivators in nutrient and energy metabolism. The literature review prepared showed that there is a link between the presence of specific alleles described at different polymorphic points in PPAR genes and various human body characteristics that are crucial for the efficacy of nutritional and/or exercise interventions. Genetic analysis can be a valuable element that complements the work of a dietitian or trainer, allowing for the planning of a personalized diet or training that makes the best use of the innate metabolic characteristics of the person who is the subject of their interventions.

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.

Interaction between the dietary indices and PPAR-γ Pro12Ala gene variants on cardiovascular risk factors in patients with type 2 diabetes mellitus

AIMS

We investigated the interaction between peroxisome proliferator-activated receptor gamma (PPAR-γ) Pro12Ala polymorphism and healthy eating index (HEI), Dietary Quality Index-International (DQI-I), and dietary phytochemical index (DPI) on cardiovascular disease (CVD) risk factors in patients with type 2 diabetes mellitus (T2DM).

METHODS

This cross-sectional study was conducted on 393 diabetic patients. PPAR-γ Pro12Ala was genotyped by the PCR-RFLP method. Biochemical markers including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), superoxide dismutase (SOD), C-reactive protein (CRP), total antioxidant capacity (TAC), pentraxin-3 (PTX3), isoprostaneF2α (PGF2α). Interleukin 18 (IL18), leptin, and ghrelin were measured by standard protocol. Food-frequency questionnaires (FFQ) were used for dietary indices (DQI-I, DPI, HEI) calculation.

RESULTS

Homozygous carriers of the rs1801282 C allele showed higher leptin compared G allele carriers (P = .015). The rs1801282-DQI-I interactions were significant on waist circumference (WC) (P = .019). Thus, C-allele carriers in the higher tertile of DQI-I had higher WC compared with GG homozygous. Further, an interaction was observed between PPAR rs1801282 polymorphism and DQI-I on serum IL-18 level (P = .032). Besides, a significant rs1801282-DPI interaction was shown on HDL concentration (P = .041), G allele carriers who were in the highest tertile of DPI, had lower HDL. Moreover, there were significant rs1801282-HEI interactions on serum leptin (P = .021). Individuals with (CC, CG) genotypes in the higher tertile of HEI, had lower leptin concentration.

CONCLUSION

Higher dietary indices (DQI-I, DPI, HEI) may affect the relationship between PPAR-γ Pro12Ala polymorphism and WC, ghrelin, leptin, HDL, and IL-18 concentration in patients with T2DM.

High Expression Level of PPARγ in CD24 Knockout Mice and Gender-Specific Metabolic Changes: A Model of Insulin-Sensitive Obesity

Background: The heat-stable HSA/CD24 gene encodes a protein that shows high expression levels in adipocyte precursor cells but low levels in terminally differentiated adipocytes. Its high expression in many types of human cancer suggests an association between cancer, diabetes, and obesity, which is currently unclear. In addition, peroxisome proliferator-activated receptor gamma (PPARγ) is a regulator of adipogenesis that plays a role in insulin sensitivity, lipid metabolism, and adipokine expression in adipocytes. Aim: To assess gender-dependent changes in CD24 KO and its association with PPARγ expression. Experimental approach: WT and CD24 KO mice were monitored from birth up to 12 months, and various physiological and molecular characteristics were analysed. Mean body weight and adipose mass were higher in KO mice than in WT mice. Male, but not female, KO mice showed increased insulin sensitivity, glucose uptake, adipocyte size, and PPARγ expression than WT mice. In addition, enteric bacterial populations, assessed through high-throughput sequencing of stool 16S rRNA genes, were significantly different between male KO and WT mice. Conclusions: CD24 may negatively regulate PPARγ expression in male mice. Furthermore, the association between the CD24 and insulin sensitivity suggests a possible mechanism for diabetes as a cancer risk factor. Finally, CD24 KO male mice may serve as a model of obesity and insulin hyper-sensitivity.

Virtual screening of potentially endocrine-disrupting chemicals against nuclear receptors and its application to identify PPARγ-bound fatty acids

Nuclear receptors (NRs) are key regulators of energy homeostasis, body development, and sexual reproduction. Xenobiotics binding to NRs may disrupt natural hormonal systems and induce undesired adverse effects in the body. However, many chemicals of concerns have limited or no experimental data on their potential or lack-of-potential endocrine-disrupting effects. Here, we propose a virtual screening method based on molecular docking for predicting potential endocrine-disrupting chemicals (EDCs) that bind to NRs. For 12 NRs, we systematically analyzed how multiple crystal structures can be used to distinguish actives and inactives found in previous high-throughput experiments. Our method is based on (i) consensus docking scores from multiple structures at a single functional state (agonist-bound or antagonist-bound), (ii) multiple functional states (agonist-bound and antagonist-bound), and (iii) multiple pockets (orthosteric site and alternative sites) of these NRs. We found that the consensus enrichment from multiple structures is better than or comparable to the best enrichment from a single structure. The discriminating power of this consensus strategy was further enhanced by a chemical similarity-weighted scoring scheme, yielding better or comparable enrichment for all studied NRs. Applying this optimized method, we screened 252 fatty acids against peroxisome proliferator-activated receptor gamma (PPARγ) and successfully identified 3 previously unknown fatty acids with Kd = 100-250 μM including two furan fatty acids: furannonanoic acid (FNA) and furanundecanoic acid (FUA), and one cyclopropane fatty acid: phytomonic acid (PTA). These results suggested that the proposed method can be used to rapidly screen and prioritize potential EDCs for further experimental evaluations.

Genetic Background of Hypertension in Connective Tissue Diseases

Peroxisome proliferator-activated receptors (PPAR gamma-2) and beta-3-adrenergic receptors (ADRB3) are involved in the risk of hypertension. But their exact role in blood pressure modulation in patients with connective tissue diseases (CTD) is still not well defined. In this study, 104 patients with CTD and 103 gender- and age-matched controls were genotyped for Pro12Ala and C1431T polymorphisms of the PPAR gamma-2 gene and Trp64Arg polymorphism of the ADRB gene. Anthropometric and biochemical measurements were evaluated, followed by genotyping using TaqMan® SNP genotyping assays and polymerase chain reaction-restriction fragment length polymorphism. The prevalence of analyzed genotypes and alleles was comparable between patients with CTD and the control group, as well as hypertensive and normotensive subjects. Patients with CTD have lower body fat and higher body water amount, serum glucose, and triglyceride (TG) levels. Hypertensive subjects are older and have higher body mass, BMI, waist circumference (WC), body water content, glucose, and TG concentration. The multivariate analysis revealed that hypertensive subjects with Ala12/X or Trp64Trp have higher body mass and WC when compared to normotensive subjects. Trp64Trp polymorphism was also characterized by a higher TG level, while T1431/X subjects had higher WC. The presence of CTD, visceral fat distribution, and increased age are the predictors of hypertension development. Hypertensive patients with CTD and Trp64Trp polymorphism have an increased risk of visceral obesity development and metabolic complications, which in turn affects the value of blood pressure. In addition, either Ala12/X or T1431/X predicts the visceral body fat distribution in hypertensive subjects.

ASSOCIATION OF THE HUMAN PPARγ2 PRO12ALA POLYMORPHISM WITH OBESITY IN A POPULATION FROM TURKEY

BACKGROUND

There have been a number of reports on the relationship between the PPARγ2 Pro12Ala genotype and the development of obesity.

OBJECTIVE

A case-control survey was designed to investigate the potential association between a Pro12Ala polymorphism in the PPARγ2 gene and obesity and/or obesity-related phenotypes in a population from Turkey.

MATERIALS AND METHODS

The polymerase chain reaction and restriction enzyme digestion were used to genotype the Pro12Ala polymorphism of the PPARγ2 gene in 149 unrelated obese and 105 non-obese control subjects from Turkey. The data were analyzed statistically.

RESULTS

We found that the overall minor allele frequency was 0.12 in cases and 0.095 in controls. In terms of genotype distribution and allele frequencies among the cases versus controls in the population studied, only the gender-stratified analysis revealed a significantly higher frequency of Pro/Ala genotype within males. The polymorphism was associated with significantly higher weight, height, waist circumference, central adiposity (waist-to-hip ratio, WHR), lean body weight as well as dry body weight, but not overall adiposity (total body fat percentage, TBF) in cases carrying Ala allele (Pro/Ala or Ala/Ala). However, in the subjects carrying Ala allele of the control group, WHR values were found significantly lower.

CONCLUSION

Our results showed that the Pro12Ala polymorphism in the PPARγ2 gene is associated with obesity in the studied adult population from Turkey. These data suggest that the Pro12Ala polymorphism in PPARγ2 may be a potential genetic risk factor for central obesity.

Effect of the Pro12Ala Polymorphism of the Peroxisome Proliferator-activated Receptor γ2 Gene on Lipid Profile and Adipokines Levels in Obese Subjects

Peroxisome proliferator-activated receptor γ (PPARγ) is a key regulator of metabolism, adipokines production and secretion. The aim of this study was to investigate the association between the PPARγ2 gene Pro12Ala polymorphism in obesity in terms of body mass index (BMI), lipid parameters, homeostasis model assessment of insulin resistance (HOMA-IR), serum lipid, leptin, adiponectin, resistin and chemerin levels. The study included 160 obese and 140 non obese subjects. The Pro12Ala polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum lipid, leptin, adiponectin, resistin and chemerin levels were measured. No association was found between the Pro12Ala polymorphism and BMI. Strikingly, in the study group, obese subjects with the AA genotype had significantly higher triglycerides (p = 0.046) and resistin (p <0.001) levels than those with the wild-type PP and heterozygous PA genotypes. Serum leptin and chemerin levels were significantly associated with Pro-12Ala poymorphism in the obese and non obese groups (p <0.01). In the obese group, subjects with the homozygous AA genotype had significantly lower adiponectin (p = 0.010) activity than the PP genotype. Our results suggest that the PPARγ2 gene Pro12Ala polymorphism has no direct association with obesity but does have significant influences on lipid profiles and adipokines levels.

Obesity and Pro12Ala Polymorphism of Peroxisome Proliferator-Activated Receptor-Gamma Gene in Healthy Adults: A Systematic Review and Meta-Analysis

BACKGROUND

The aim of this systematic review was to evaluate the relationship between obesity and peroxisome proliferator-activated receptor-gamma (PPARx03B3;) Pro12Ala polymorphism in healthy adults.

SUMMARY

Weighted mean differences (WMDs) of body mass index (BMI) were calculated for different inheritance models and subgroups. Fifty-six studies were eligible for inclusion in the meta-analysis. The result shows that the Ala allele of this polymorphism was associated with increased WMD in mean BMI (WMD = 0.29, 95% CI 0.10-0.48, p = 0.003). The Ala carriers were associated with increased WMD in mean BMI values in both genders and in the Caucasian subgroup. The associations were seen among people with higher levels of BMI (BMI ≥35).

MESSAGE

The Ala allele of the PPARx03B3; Pro12Ala polymorphism in healthy adults was associated with increased BMI under a dominant model of inheritance.

The Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma (PPARG) gene in relation to obesity and metabolic phenotypes in a Taiwanese population

Obesity is considered as an important public health problem in the world. Although the association of a common single nucleotide polymorphism (SNP), rs1801282 (Pro12Ala), in the peroxisome proliferator-activated receptor gamma (PPARG) gene with obesity has been reported in various populations, these data are not conclusive. This study aimed to reassess whether the PPARG rs1801282 SNP is linked with obesity and obesity-related metabolic traits in a Taiwanese population. A total of 674 Taiwanese subjects with general health examinations were genotyped. The rs1801282 genotype was determined by the Taqman SNP genotyping assay. Obesity-related metabolic traits such as triglyceride, waist circumference, systolic and diastolic blood pressure, total cholesterol, and fasting glucose were measured. The PPARG rs1801282 SNP did not exhibit any significant association with obesity among the complete sample population. However, sex-stratified analyses revealed an effect on overweight in female participants where the carriers of the combined CG and GG genotypes had a higher risk to overweight than those with the CC homozygotes (OR=4.05; 95% CI=1.28-12.83; P=0.017). Compared to the carriers of CC homozygotes, BMI was significantly higher for the carriers of the combined CG and GG genotypes in the female subjects (24.4±3.7 vs. 23.5±3.8 kg/m2; P=0.033). In addition, the carriers of the CC homozygotes had a higher total cholesterol level than those with the combined CG and GG genotypes in the female subjects (197.0±37.3 vs. 180.7±33.7 mg/dl; P=0.026). Our study indicates that PPARG rs1801282 may significantly predict overweight, BMI, and total cholesterol in female but not male Taiwanese subjects.

Association between PPAR-γ2 Pro12Ala polymorphism and obesity: a meta-analysis

The peroxisome proliferator-activated receptor-γ2 (PPAR-γ2) gene has been reported in the pathogeny of obesity. However, the results have been inconsistent. The purpose of this meta-analysis was to acquire a more accurate assessment of the association between PPAR-γ2 Pro12Ala polymorphism and obesity. PubMed, Wan Fang (Chinese) databases, Chinese Biomedical Medical databases, and Chinese National Knowledge Infrastructure were searched to identify eligible studies. Finally, 25 studies (6491 cases and 8242 controls) were enrolled in this meta-analysis. The effect summary odds ratio (OR) with 95 % confidence interval (CI) was applied. Random-effects or fixed-effects model was performed based on the heterogeneity. STATA 12.0 was applied for this meta-analysis. The combined results showed that PPAR-γ Pro12Ala polymorphism was associated with the obesity risk (Ala vs. Pro: OR = 1.55, 95 % CI 1.34-1.80; Pro/Ala vs. Pro/Pro: OR = 1.54, 95 % CI 1.31-1.82; Ala/Ala + Pro/Ala vs. Pro/Pro: OR = 1.61, 95 % CI 1.36-1.90). Subgroup analysis by ethnicity showed that there were significant associations between PPAR-γ Pro12Ala polymorphism and obesity risk in Caucasians, Asians, and Mixed population. Subgroup analysis by obesity's cutoff points showed that the associations were found among the patients with the cutoff point of BMI ≥24 and BMI ≥30 but not among the patients with the cutoff point of BMI ≥95th percentile. These results suggested that PPAR-γ Pro12Ala polymorphism might be a risk factor for obesity susceptibility.

Association between Pro12Ala, Pvull, Avall, Sstl and ADIPOQ single-nucleotide polymorphisms with lipid and glycemic profiles of patients with Berardinelli-Seip syndrome

BACKGROUND/AIMS

Berardinelli-Seip syndrome (BSS) is a recessive autosomal genetic disorder characterized by the near loss of adipose tissue with disturbance in lipid metabolism.

METHODS

Biochemical and hormonal parameters and Pro12Ala, Pvull, Avall, Sstl and ADIPOQ polymorphisms in 22 patients with BSS were analyzed and examined for a possible association with lipid profiles.

RESULTS

Parental consanguinity, insulin resistance and diabetes mellitus were observed in 63.6, 81.8 and 59.1% of patients, respectively. All individuals presented high triglyceride levels, and 68.1% of patients showed high cholesterol levels. The Pro/Pro genotype of the Pro12Ala polymorphism of the PPARγ2 gene was found in 86.3% of patients; the Ala/Ala variant was not observed in any patient. The PvuII polymorphism of the LPL gene showed a frequency of 50% for the P1P2 variant. The AvaII polymorphism of the LDLR gene showed a similar frequency of 40.9% for both CT and TT variants. The S1S1 genotype of the Sstl polymorphism of the APOC3 gene had a frequency of 86.3%. The CC allele of the ADIPOQ polymorphism of the adiponectin gene was found in 54.6% of patients.

CONCLUSIONS

No association was found between lipid parameters and the relevant Pvull, Avall and Sstl polymorphisms. However, we did observe an association of the Pro12Ala and ADIPOQ polymorphisms with higher lipid levels, suggesting a close relationship between these factors.

The Pro12Ala Polymorphism of the Peroxisome Proliferator-Activated Receptor Gamma Gene Modifies the Association of Physical Activity and Body Mass Changes in Polish Women

Peroxisome proliferator-activated receptor γ is a key regulator of adipogenesis, responsible for fatty acid storage and maintaining energy balance in the human body. Studies on the functional importance of the PPARG Pro12Ala polymorphic variants indicated that the observed alleles may influence body mass measurements; however, obtained results were inconsistent. We have decided to check if body mass changes observed in physically active participants will be modulated by the PPARG Pro12Ala genotype. The genotype distribution of the PPARG Pro12Ala allele was examined in a group of 201 Polish women measured for selected body mass variables before and after the completion of a 12-week training program. The results of our experiment suggest that PPARG genotype can modulate training-induced body mass measurements changes: after completion of the training program, Pro12/Pro12 homozygotes were characterised by a greater decrease of body fat mass measurements in comparison with 12Ala allele carriers. These results indicate that the PPARG 12Ala variant may impair the training-induced positive effects on body mass measurements; however, the detailed mechanism of such interaction remained unclear and observed correlation between PPARG genotype and body mass differential effects should be interpreted with caution.

Peroxisome proliferator‑activated receptor γ polymorphisms as risk factors for dyslipidemia

Peroxisome proliferator‑activated receptor γ (PPARγ) may play an important role in lipid metabolism directly or by inducing the transcription of target genes. The aim of the present study was to investigate the association between common variants at the PPARγ locus (C1431T and Pro12Ala polymorphisms) and lipid serum levels. The studied population consisted of 820 subjects randomly selected from the Prevention of Multiple Metabolic Disorders and Metabolic Syndrome in Jiangsu Province cohort population. All subjects were interviewed and blood samples were obtained for laboratory analysis and DNA extraction. The TaqMan single nucleotide polymorphism genotyping assay was used for polymorphism genotyping. Individual polymorphisms and haplotype data were available for analysis. The 12Ala allele was found to be associated with significantly increased levels of triglyceride (TG) (P<0.01), whilst the 1431T allele was found to be associated with significantly increased levels of TG, total cholesterol (TC) and non‑high‑density lipoprotein (non‑HDL) (P<0.01). When P‑C, the most common haplotype, was used as the reference group, the P‑T, A‑C and A‑T haplotypes were found to be associated with significantly increased levels of TG (P<0.01). In addition, the A‑T haplotype was shown to be associated with significantly increased levels of TC and non‑HDL (P<0.01). In conclusion these results suggest that PPARγ gene variability may increase the risk of dyslipidemia.

Analysis on the association between PPARα/γ polymorphisms and lipoprotein(a) in a Chinese Han population

Lipoprotein(a) [Lp(a)], a low-density lipoprotein-like particle, is recognized as an independent risk factor for atherosclerosis, cardiovascular diseases, and diabetic vascular diseases. Our recent studies revealed that the single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptors (PPARα/δ/γ) gene are involved in the regulation of lipid storage and metabolism. In order to investigate the relationships between the SNPs of PPARα/γ gene and plasma levels of Lp(a), 644 participants were randomly selected from Chinese Han population in the present study. As the results shown, Lp(a) was significantly associated with L162V (rs1800206) in PPARα. Compared with those subjects with widetype (LL), significantly higher Lp(a) concentration was determined in the individuals with mutant (LV + VV) (mean difference: 49.07 mg/l, 95% CI 23.32-74.82 mg/l, p = 0.0002). Moreover, with generalized multifactor dimensionality reduction analysis, our present results indicated that there was a significant association between plasma Lp(a) level and gene-gene interaction among the polymorphisms rs1800206, rs135539 in PPARα and rs10865710, rs1805192, and rs4684847 in PPARγ. Therefore, our presented study indicated that PPARα/γ polymorphisms should be involved in the regulation of plasma Lp(a) in independently and/or in an interactive manner, suggesting that PPARα/γ gene may influence the risk of hypertension, cardiovascular diseases, and dyslipidemia by regulating Lp(a) level.

Epigenetic effects of human breast milk

A current aim of nutrigenetics is to personalize nutritional practices according to genetic variations that influence the way of digestion and metabolism of nutrients introduced with the diet. Nutritional epigenetics concerns knowledge about the effects of nutrients on gene expression. Nutrition in early life or in critical periods of development, may have a role in modulating gene expression, and, therefore, have later effects on health. Human breast milk is well-known for its ability in preventing several acute and chronic diseases. Indeed, breastfed children may have lower risk of neonatal necrotizing enterocolitis, infectious diseases, and also of non-communicable diseases, such as obesity and related-disorders. Beneficial effects of human breast milk on health may be associated in part with its peculiar components, possible also via epigenetic processes. This paper discusses about presumed epigenetic effects of human breast milk and components. While evidence suggests that a direct relationship may exist of some components of human breast milk with epigenetic changes, the mechanisms involved are still unclear. Studies have to be conducted to clarify the actual role of human breast milk on genetic expression, in particular when linked to the risk of non-communicable diseases, to potentially benefit the infant's health and his later life.

The Rate of Decline of Glomerular Filtration Rate May Not Be Associated with Polymorphism of the PPARγ2 Gene in Patients with Type 1 Diabetes and Nephropathy

The aim of the study was to investigate whether a Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma 2 (PPARγ2) gene is associated with the progress of diabetic nephropathy in patients with type 1 diabetes. 197 Caucasian patients with type 1 diabetes and ethnically matched 151 normal healthy controls were genotyped for this polymorphism. Results showed that there were no significant differences in the frequencies of the genotypes and alleles of the polymorphism between groups. Multiple regression analysis in 77 patients demonstrated that the rate of decline in renal function in terms of glomerular filtration rate was significantly correlated to the baseline level of cholesterol (P = 0.0014), mean diastolic blood pressure during follow-up period (P = 0.019), and baseline level of HbA1c (P = 0.022) adjusting for the effect of diabetes duration and gender, but no significant association was found between the polymorphism and the progression of diabetic nephropathy in our studied population. In summary, our results show that the PPARγ2 polymorphism is unlikely to be associated with the development and progression of the diabetic nephropathy in patients with type 1 diabetes. Further studies in different populations may be warranted to confirm our findings as the sample size in our study was relatively small.

Association of PPARγ2 gene variant Pro12Ala polymorphism with hypertension and obesity in the aboriginal Qatari population known for being consanguineous

AIM

The aim of this study was to investigate the association of the Pro12Ala polymorphism of the human peroxisome proliferator-activated receptor gamma 2 (PPARγ2) gene with hypertension and obesity in a highly consanguineous aboriginal Qatari population.

DESIGN

A cross-sectional survey conducted from January 2011-December 2012.

SETTING

Primary health care clinics.

SUBJECTS

A random sample of 1,528 Qatari male and female population older than 20 years of age.

MATERIALS AND METHODS

Data on age, sex, income, level of education, occupation status, body mass index, and blood pressure and lipid profile were obtained. The Pro12Ala in the PPARγ2 gene was detected on the LightCycler® using two specific probes: (Sensor [G] 5'-CTC CTA TTG ACG CAG AAA GCG-FL and PPAR Anchor 5' LC Red 640- TCC TTC ACT GAT ACA CTG TCT GCA AAC ATA TC-PH). Univariate and multivariate logistic regression were performed.

RESULT

Out of a total 1,528 participants, 220 were diagnosed with essential hypertension, and 420 were obese. Participants with consanguinity were significantly higher among hypertensive than normotensive (41.9% versus 30.8%; P=0.001). Altogether, more than three-fourths (89%) of the participants had a wild genotype (Pro12Pro), 9.8% were heterozygous with Pro12Ala, and only 1.2% was homozygous with the Ala12Ala genotype. The frequency of the Pro allele was 94.5% in normotensive versus 90.5% in hypertensive, while the distribution of the Ala allele was 5.5% in normotensive versus 9.5% in the hypertensive group (P=0.001). The odds of hypertension were 1.7 times higher among the participants with the Ala allele as compared to those with the Pro, while adjusting for other potential confounders (adjusted odds ratio 1.69; 95% confidence interval 1.12-2.55; P=0.012). There was no association between the PPARγ2Ala allele and obesity (P=0.740).

CONCLUSION

The current study revealed an association between the PPARγ2Ala allele and hypertension in Qatar's population. On the other hand, this study found no association between the Ala allele and obesity.

The association between the Pro12Ala variant in the PPARγ2 gene and type 2 diabetes mellitus and obesity in a Chinese population

Background

Conflicting results have been reported on the association of the Pro12Ala polymorphism of the PPARγ2 gene with the risk of type 2 diabetes or obesity.

Methods and Findings

A total of 3146 subjects with 1145 cases of type 2 diabetes and 2001 healthy controls were included in the study. Genomic DNA was obtained from blood samples and the screening for the gene polymorphisms was done using an allelic discrimination assay-by-design TaqMan method. Overall, the Ala allele frequency was 5.6% in control subjects and 3.9% in diabetes subjects (P = 0.023). We found a statistically significant association of carriers of the Ala allele with greater homoeostasis model assessment of beta cell function index in all subjects (P = 0.046). After controlling for confounders, carriers of the Ala allele had a decreased risk of diabetes compared with noncarriers [odds ratio (OR) 0.64, 95% confidence interval (CI) 0.49–0.83; P = 0.001]. A beneficial effect of the Ala allele was also observed for obesity (OR 0.64, 95% CI 0.42–0.96; P = 0.030).

Conclusion

Our results suggested that the presence of the Ala allele may contribute to improved insulin secretory capacity and may confer protection from type 2 diabetes and obesity in the Chinese population.

Association between the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma gene and strength athlete status

Background

The 12Ala allele of the Peroxisome Proliferator-Activated Receptor gamma gene (PPARG) Pro12Ala polymorphism produces a decreased binding affinity of the PPARγ2 protein, resulting in low activation of the target genes. The 12Ala allele carriers display a significantly improved insulin sensitivity that may result in better glucose utilisation in working skeletal muscles. We hypothesise that the PPARG 12Ala allele could be associated with strength athlete status in Polish athletes.

Methodology

The genotype distribution of PPARG Pro12Ala was examined in 660 Polish athletes. The athletes were stratified into four subgroups: endurance, strength-endurance, sprint-strength and strength. Control samples were prepared from 684 unrelated sedentary volunteers. A χ² test was used to compare the PPARG Pro12Ala allele and genotype frequencies between the different groups of athletes and control subjects. Bonferroni’s correction for multiple testing was applied.

Results

A statistically significant higher frequency of PPARG 12Ala alleles was observed in the subgroup of strength athletes performing short-term and very intense exertion characterised by predominant anaerobic energy production (13.2% vs. 7.5% in controls; P = 0.0007).

Conclusion

The PPARG 12Ala allele may be a relevant genetic factor favouring strength abilities in professional athletes, especially in terms of insulin-dependent metabolism, a shift of the energy balance towards glucose utilisation and the development of a favourable weight-to-strength ratio.

ACE I/D and MTHFR C677T polymorphisms are significantly associated with type 2 diabetes in Arab ethnicity: a meta-analysis

In this meta-analysis study, SNPs were investigated for their association with type 2 diabetes (T2D) in both Arab and Caucasian ethnicities. A total of 55 SNPs were analyzed, of which 11 fulfilled the selection criteria, and were used for analysis. It was found that TCF7L2 rs7903146 was significantly associated with a pooled OR of 1.155 (95%C.I.=1.059-1.259), p<0.0001 and I(2)=78.30% among the Arab population, whereas among Caucasians, the pooled OR was 1.45 (95%C.I.=1.386-1.516), p<0.0001 and I(2)=77.20%. KCNJ11 rs5219 was significantly associated in both the populations with a pooled OR of 1.176(1.092-1.268), p<0.0001 and I(2)=32.40% in Caucasians and a pooled OR of 1.28(1.111-1.475), p=0.001 among Arabs. The ACE I/D polymorphism was found to be significantly associated with a pooled OR of 1.992 (95%C.I.=1.774-2.236), p<0.0001 and I(2)=83.20% among the Arab population, whereas among Caucasians, the pooled OR was 1.078 (95%C.I.=0.993-1.17), p=0.073 and I(2)=0%. Similarly, MTHFR C677T polymorphism was also found to be significantly associated among Arabs with a pooled OR of 1.924 (95%C.I.=1.606-2.304), p<0.0001 and I(2)=27.20%, whereas among Caucasians, the pooled OR was 0.986 (95%C.I.=0.868-1.122), p=0.835 and I(2)=0%. Meanwhile PPARG-2 Pro12Ala, CDKN2A/2B rs10811661, IGF2BP2 rs4402960, HHEX rs7923837, CDKAL1 rs7754840, EXT2 rs1113132 and SLC30A8 rs13266634 were found to have no significant association with T2D among Arabs. In conclusion, it seems from this study that both Arabs and Caucasians have different SNPs associated with T2D. Moreover, this study sheds light on the profound necessity for further investigations addressing the question of the genetic components of T2D in Arabs.

Inference of cross-level interaction between genes and contextual factors in a matched case-control metabolic syndrome study: a Bayesian approach

Genes, environment, and the interaction between them are each known to play an important role in the risk for developing complex diseases such as metabolic syndrome. For environmental factors, most studies focused on the measurements observed at the individual level, and therefore can only consider the gene-environment interaction at the same individual scale. Indeed the group-level (called contextual) environmental variables, such as community factors and the degree of local area development, may modify the genetic effect as well. To examine such cross-level interaction between genes and contextual factors, a flexible statistical model quantifying the variability of the genetic effects across different categories of the contextual variable is in need. With a Bayesian generalized linear mixed-effects model with an unconditional likelihood, we investigate whether the individual genetic effect is modified by the group-level residential environment factor in a matched case-control metabolic syndrome study. Such cross-level interaction is evaluated by examining the heterogeneity in allelic effects under various contextual categories, based on posterior samples from Markov chain Monte Carlo methods. The Bayesian analysis indicates that the effect of rs1801282 on metabolic syndrome development is modified by the contextual environmental factor. That is, even among individuals with the same genetic component of PPARG_Pro12Ala, living in a residential area with low availability of exercise facilities may result in higher risk. The modification of the group-level environment factors on the individual genetic attributes can be essential, and this Bayesian model is able to provide a quantitative assessment for such cross-level interaction. The Bayesian inference based on the full likelihood is flexible with any phenotype, and easy to implement computationally. This model has a wide applicability and may help unravel the complexity in development of complex diseases.

Correlation of peroxisome proliferator-activated receptor (PPAR-γ) mRNA expression with Pro12Ala polymorphism in obesity

Our study aimed to analyze whether the expression of PPARγ mRNA in subcutaneous adipocyte tissue correlates with Pro12Ala PPARγ2 polymorphism in the obesity context. We found that mRNA expression of PPARγ in subcutaneous adipose tissue was greater in obese subjects (P < 0.05) than in the nonobese control group. Concurrently, genotyping of the Pro12Ala polymorphism showed that obese subjects possess a significantly higher frequency of the Pro/Pro genotype than nonobese controls (90.5 vs 79.5%; P = 0.03), suggesting that this genotype is involved in an increased risk of obesity in the Tunisian population. Taken together, our results demonstrate that the Pro12 allele is accompanied by an overexpression of PPARγ mRNA in subcutaneous adipocyte tissue, suggesting that the PPARγ Pro12Ala variant may contribute to the observed variability in PPARγ mRNA expression and consequently in body mass index and insulin sensitivity in the general population.

Sex-specific differences in Type 2 Diabetes Mellitus and dyslipidemia therapy: PPAR agonists

The influence of sex on the development of obesity, Type 2 Diabetes Mellitus (T2DM), and dyslipidemia is well documented, although the molecular mechanism underlying those differences reminds elusive. Ligands of peroxisome proliferator-activated receptors (PPARs) are used as oral antidiabetics (PPARgamma agonists: thiazolidinediones, TZDs), or for the treatment of dyslipidemia and cardiovascular diseases, due to their lipid-lowering properties (PPARalpha agonists: fibrates), as PPARs control transcription of a set of genes involved in the regulation of lipid and carbohydrate metabolism. Given a high prevalence of those metabolic disorders, and thus a broad use of PPAR agonists, the present review will discuss distinct aspects of sex-specific differences in antiobesity treatment using those groups of PPAR ligands.

Association of MTHFR and PPARγ2 gene polymorphisms in relation to type 2 diabetes mellitus cases among north Indian population

BACKGROUND

Type 2 diabetes mellitus is a multifactorial and polygenic disease, which is considered as a major life threatening problem all over the world. There has been a worldwide effort in the identification of susceptibility genes for type 2 diabetes mellitus and its complications. At present, adequate data is not available dealing with MTHFR (rs1801133) and PPARγ2 (rs1801282) gene polymorphisms and its association with type 2 diabetes mellitus cases among north Indian populations. Thus, we conceived the need for further studies to investigate MTHFR and PPARγ2 gene polymorphisms and their susceptibility to type 2 diabetes mellitus in north Indian population.

MATERIALS AND METHODS

In this study, a total 175 subjects including 87 type 2 diabetes mellitus cases and 88 controls were enrolled. MTHFR and PPARγ2 gene polymorphisms in the cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The MTHFR gene CC, CT, TT genotype frequencies obtained were 40%, 43%, and 17% in type 2 diabetes mellitus cases and 56%, 29%, and 15% in healthy controls respectively. The OR for CC was 0.54 (95%CI 0.29-0.98, P=0.041, χ(2)=4.18, power=0.98), for CT 1.76 (95%CI 0.94-3.30, P=0.07, χ(2)=3.2, power=0.96), and for TT 1.2 (95%CI 0.53-2.70, P=0.66, χ(2)=0.198, power=0.76). The PPARγ2 gene GG CG, CC genotype frequencies obtained were 28%, 41%, and 31% in cases and 40%, 39%, and 21% in healthy controls respectively. OR for GG was 0.58 (95%CI 0.30-1.09, P=0.08, χ(2)=2.9, power=0.96), for CG 1.12 (95%CI 0.61-2.05, P=0.71, χ(2)=0.137, power=0.778), and for CC 1.63 (95%CI 0.82-3.23, P=0.156, χ(2)=2.01, power=0.92).

CONCLUSION

It might be recommended that MTHFR CC genotype seems to be a good marker for the early identification of population at risk of type 2 diabetes mellitus. While we have detected significant difference in allelic frequencies of PPARγ2 C (Proline) and G (Alanine), but at genotypic level significant difference was not detected in this case-control study. Further study with larger groups may be required to validate the study.

The Obesity Pandemic: Where Have We Been and Where Are We Going?

Obesity, a new pandemic, is associated with an increased risk of death, morbidity, and accelerated aging. The multiple therapeutic modalities used to promote weight loss are outlined with caution, especially for patients who are very young or old. Except for very rare single gene defects, the inheritance of obesity is complex and still poorly understood, despite active investigations. Recent advances that have shed light on the pathophysiology of obesity are the recognition that 1) excess fat is deposited in liver, muscle, and pancreatic islets; 2) fat tissue secretes a large number of active signaling molecules including leptin, adiponectin, and resistin, as well as free fatty acids; and 3) activated macrophages colonize the adipose tissue. Other candidates for key roles in the causes and consequences of obesity include 1) metabolic programming, where food acts as a developmental regulator; 2) the constellation of defects known as the "metabolic syndrome;" 3) cortisol overproduction in the adipose tissue; and especially, 4) insulin resistance. The possible etiologies of insulin resistance include cytokine excess, elevated free fatty acids, and hyperinsulinemia itself, as with transgenic overproduction of insulin in mice.

Ala/Ala genotype of Pro12Ala polymorphism in the peroxisome proliferator-activated receptor-γ2 gene is associated with obesity and insulin resistance in Asian Indians

AIM

We determined the association of the Pro12Ala polymorphism of the peroxisome proliferator activated receptor (PPAR)-γ2 gene with obesity, insulin resistance (IR), and lipids in Asian Indians without diabetes in north India.

SUBJECTS AND METHODS

In this cross-sectional study (n = 495; 279 males and 216 females, 18-60 years of age), anthropometric (body mass index, waist and hip circumferences, and skinfold thickness) and biochemical (fasting glucose, lipid profile, fasting insulin, leptin, and adiponectin) parameters were assessed. Polymerase chain reaction-restriction fragment length polymorphism analysis was used for identification of individual genotypes.

RESULTS

Frequencies of the Pro and Ala alleles were 0.89 and 0.11, respectively. The genotype frequencies (%) of Pro/Pro, Pro/Ala, and Ala/Ala were 82.6, 14.7, and 2.7, respectively, without any gender differences. The frequency of the Ala/Ala genotype was higher in obese than in nonobese subjects (4.9% vs. 1.5%, P = 0.06). The Ala/Ala genotype was associated with higher values of hip circumference, subscapular skinfold thickness, and sum of four skinfold thickness than the Pro/Pro and Pro/Ala genotypes (P<0.05). Using a multivariate logistic regression model after adjusting for age, sex, and insulin, subjects with the Ala/Ala genotype showed a high risk of obesity (odds ratio [OR], 3.2, 95% confidence interval [CI] 1.2-12.9) and IR (OR, 3.6, 95% CI: 1.04-12.4).

CONCLUSION

The Ala/Ala genotype of the PPAR-γ2 gene is associated with obesity and IR in Asian Indians without diabetes living in north India.

Association between PPARγ2 Pro12Ala polymorphism and myocardial infarction and obesity in Han Chinese in Hohhot, China

Activation of the peroxisome proliferator-activated receptor g (PPARg) improves insulin sensitivity and inhibits atherosclerosis. Whether PPARg2 Pro12Ala polymorphism affects myocardial infarction is not clearly understood. We investigated a possible association of PPARg2 Pro12Ala polymorphism with obesity and myocardial infarction in Han Chinese in Hohhot, Inner Mongolia, China. We included 121 subjects with myocardial infarction and 137 healthy controls in our study. Triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were measured. The following information was recorded for each subject: age, gender, body height, body weight, systolic blood pressure, and diastolic blood pressure; the body mass index was calculated. PCR-RFLP was used to examine Pro12Ala polymorphism. There were significant differences in clinical characteristics between myocardial infarction patients and healthy controls, except for diastolic blood pressure and triglycerides. The PP, PA/AA genotype frequencies were 88.4 and 11.6% in myocardial infarction patients and 95.6 and 4.4% in controls, respectively (P = 0.031). Individuals with the A allele had a significantly higher risk of myocardial infarction. The A allele was not an independent risk factor for obesity. We conclude that PPARg2 Pro12Ala polymorphisms are associated with increased risk for myocardial infarction in Han Chinese in Hohhot.

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.

Association of PPAR-γ gene polymorphisms with obesity and obesity-associated phenotypes in North Indian population

OBJECTIVES

The worldwide increasing prevalence of obesity is considered as a major health problem. Peroxisome proliferator-activated receptor gamma (PPAR-γ) controls adipocyte differentiation and regulates a number of genes associated with energy homeostasis. In this study, we investigated the association of PPAR-γ gene Pro12Ala (rs1801282) and C1431T (rs3856806) polymorphisms with morbid obesity and related phenotypes, in north Indian population.

METHODS

A total of 6,42 subjects, 309, obese and 333 nonobese individuals were included in this case-control study. Insulin, adiponectin, glucose, and lipid levels were estimated using standard protocols. All subjects were genotyped by PCR restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

The ProAla+AlaAla genotypes of PPAR-γ Pro12Ala were significantly associated with higher risk of obesity while C1431T polymorphism did not show any significant association. None of the haplotypes showed association with morbid obesity. However, a strong association of variant genotypes was observed with higher levels of insulin, HOMA-IR, and lower serum adiponectin concentrations.

CONCLUSION

PPAR-γ gene polymorphisms influence obesity and obesity phenotype in a complex manner, probably involving insulin resistance in north Indian population.

PPARγ2 gene Pro12Ala and PPARα gene Leu162Val single nucleotide polymorphisms interact with dietary intake of fat in determination of plasma lipid concentrations

BACKGROUND/AIMS

The peroxisome proliferator-activated receptors (PPARs) are transcriptional regulators of lipid metabolism, activated by unsaturated fatty acids. We investigated independent and interactive effects of PPARγ2 gene PPARG Pro12Ala (rs1801282) andPPARαgene PPARA Leu162Val (rs1800206) genotypes with dietary intake of fatty acids on concentrations of plasma lipids in subjects of whom 47.5% had metabolic syndrome.

METHODS

The RISCK study is a parallel design, randomised controlled trial. Plasma lipids were quantified at baseline after a 4-week high saturated fatty acids diet and after three parallel 24-week interventions with reference (high saturated fatty acids), high monounsaturated fatty acids and low-fat diets. Single nucleotide polymorphisms were genotyped in 466 subjects.

RESULTS

At baseline, the PPARG Ala12allele was associated with increased plasma total cholesterol (n = 378; p = 0.04), LDL cholesterol (p = 0.05) and apoB (p =0.05) after adjustment for age, gender and ethnicity. At baseline, PPARA Leu162Val × PPARG Pro12Ala genotype interaction did not significantly influence plasma lipid concentrations. After dietary intervention, gene-gene interaction significantly influenced LDL cholesterol (p =0.0002) and small dense LDL as a proportion of LDL (p = 0.005) after adjustments.

CONCLUSIONS

Interaction between PPARG Pro12Ala and PPARA Leu162Val genotypes may influence plasma LDL cholesterol concentration and the proportion as small dense LDL after a high monounsaturated fatty acids diet.

Cardiovascular risk factors related to the PPARγ Pro12Ala polymorphism in patients with type 2 diabetes are gender dependent

The interaction of the PPARγ Pro12Ala polymorphism with diabetes and cardiovascular risk is controversial. We studied 173 women and 309 men in the observational CARDIPP trial in which determination of left ventricular mass, carotid intima-media thickness (IMT) and pulse wave velocity (PWV) were performed. Blood pressures were measured with 24-h ambulatory technique (ABP). Heterozygotes and homozygotes of Ala were defined as Ala in the analyses. Men with Ala-isoform displayed higher waist circumference (Ala: 107 ± 14 cm, Pro: 104 ± 11 cm, p = 0.045) and body weight (Ala: 95.7 ± 18 kg, Pro: 91.6 ± 14 kg, p = 0.042) than Pro-homozygotes. Men with ALA-isoform also showed higher systolic ABP levels (Ala: 134 ± 15 mmHg, Pro: 130 ± 14 mmHg, p = 0.004), whereas left ventricular mass index, IMT and PWV were unrelated to isoforms. In contrast, carotid-radial PWV was lower in women with the Ala-isoform (Ala: 7.9 ± 1.0 m/s, Pro: 8.5 ± 1.3 m/s, p = 0.01) and levels of apolipoprotein A1 were higher (Ala: 1.43 ± 0.27 g/l, Pro: 1.35 ± 0.17 g/l, p = 0.03). In conclusion, we found that men with type 2 diabetes having the Ala-isoform of PPARγ Pro12Ala had an unfavorable cardiovascular risk profile, whereas women with this isoform had lower carotid-radial PWV and higher apolipoprotein A1 levels suggesting a beneficial prognosis. These differences according to gender of the ALA isoform in type 2 diabetes deserve further attention.

'Striking the Right Balance' in Targeting PPARgamma in the Metabolic Syndrome: Novel Insights from Human Genetic Studies

At a time when the twin epidemics of obesity and type 2 diabetes threaten to engulf even the most well-resourced Western healthcare systems, the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) has emerged as a bona fide therapeutic target for treating human metabolic disease. The novel insulin-sensitizing antidiabetic thiazolidinediones (TZDs, e.g., rosiglitazone, pioglitazone), which are licensed for use in the treatment of type 2 diabetes, are high-affinity PPARγ ligands, whose beneficial effects extend beyond improvement in glycaemic control to include amelioration of dyslipidaemia, lowering of blood pressure, and favourable modulation of macrophage lipid handling and inflammatory responses. However, a major drawback to the clinical use of exisiting TZDs is weight gain, reflecting both enhanced adipogenesis and fluid retention, neither of which is desirable in a population that is already overweight and prone to cardiovascular disease. Accordingly, the “search is on” to identify the next generation of PPARγ modulators that will promote maximal clinical benefit by targeting specific facets of the metabolic syndrome (glucose intolerance/diabetes, dyslipidaemia, and hypertension), while simultaneously avoiding undesirable side effects of PPARγ activation (e.g., weight gain). This paper outlines the important clinical and laboratory observations made in human subjects harboring genetic variations in PPARγ that support such a therapeutic strategy.

PPAR Gamma: Coordinating Metabolic and Immune Contributions to Female Fertility

Peroxisome proliferator-activated receptor gamma (PPARG) regulates cellular functions such as adipogenesis and immune cell activation. However, new information has indicated additional roles of PPARG directing the cyclic changes that occur within ovarian tissue of female mammals, including those that facilitate the release of oocytes each estrous cycle. In addition to ovarian PPARG expression and function, many PPARG actions within adipocytes and macrophages have additional direct and indirect implications for ovarian function and female fertility. This encompasses the regulation of lipid uptake and transport, insulin sensitivity, glucose metabolism, and the regulation of inflammatory mediator synthesis and release. This review discusses the developing links between PPARG activity and female reproductive function, and highlights several mechanisms that may facilitate such a relationship.

PPAR Action in Human Placental Development and Pregnancy and Its Complications

During pregnancy crucial anatomic, physiologic, and metabolic changes challenge the mother and the fetus. The placenta is a remarkable organ that allows the mother and the fetus to adapt to the new metabolic, immunologic, and angiogenic environment imposed by gestation. One of the physiologic systems that appears to have evolved to sustain this metabolic regulation is mediated by peroxisome proliferator-activated receptors (PPARs). In clinical pregnancy-specific disorders, including preeclampsia, gestational diabetes, and intrauterine growth restriction, aberrant regulation of components of the PPAR system parallels dysregulation of metabolism, inflammation and angiogenesis. This review summarizes current knowledge on the role of PPARs in regulating human trophoblast invasion, early placental development, and also in the physiology of clinical pregnancy and its complications. As increasingly indicated in the literature, pregnancy disorders, such as preeclampsia and gestational diabetes, represent potential targets for treatment with PPAR ligands. With the advent of more specific PPAR agonists that exhibit efficacy in ameliorating metabolic, inflammatory, and angiogenic disturbances, further studies of their application in pregnancy-related diseases are warranted.

Pro12Ala polymorphism in human peroxisome proliferator activated receptor gamma is associated with hyperlipidaemia in obstructive sleep apnoea hypopnoea syndrome

Objective:

Peroxisome proliferator activated receptor gamma is a ligand-dependent transcription factor with an important role in insulin resistance and obesity. We investigated the associations between the Pro12Ala polymorphism of this receptor, obstructive sleep apnoea hypopnoea syndrome and hyperlipidaemia risk factors, in a Chinese cohort.

Subjects and methods:

We recruited 420 obstructive sleep apnoea hypopnoea syndrome patients and 190 healthy controls. Genetic analysis was conducted by restriction fragment length polymorphism. The hyperlipidaemia risk in both the study and control groups was analysed.

Results:

Comparison of genotype and allele frequencies revealed no significant differences between patients and controls (p > 0.05). In patients, there was no correlation between genotype and clinical parameters (p > 0.05), apart from a significant association between the Ala12 allele and hyperlipidaemia (odds ratio = 2.181; p = 0.017; 95 per cent confidence interval = 1.133–4.198).

Conclusion:

In this Chinese cohort, the Pro12Ala polymorphism of peroxisome proliferator activated receptor gamma was not associated with obstructive sleep apnoea hypopnoea syndrome, but was associated with increased hyperlipidaemia risk.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

PPARγ2 C1431T genotype increases metabolic syndrome risk in young men with low cardiorespiratory fitness

The peroxisome proliferator-activated receptor gamma 2 (PPARγ2) genotypes are related to obesity and the metabolic syndrome (MetS). A low level of cardiorespiratory fitness is also a strong determining factor in the development of MetS. This cross-sectional study was performed to investigate the influence of the interaction between the PPARγ2 genotype and cardiorespiratory fitness on the risk of MetS. Healthy Japanese men ( n = 211) and women ( n = 505) participated in this study. All subjects were divided into 8 groups according to sex, fitness level (high and low fitness groups), and age (younger, age < 40 yr; middle-aged/older, age ≥ 40 yr). The PPARγ2 genotypes (Pro12Ala and C1431T) were analyzed by real-time PCR with Taq-Man probes. Two-way ANCOVA with adjustment for age as a covariate indicated that fitness and the CC genotype of C1431T in the PPARγ2 gene interacted to produce a significant effect on MetS risk in younger men and that the risk of MetS in the CC genotype group with low cardiorespiratory fitness was significantly higher than that in the corresponding CT+TT genotypes or in the high fitness groups. There was no significant interaction between fitness and genotype in determining MetS risk in middle-aged/older men or in women in any group. With regard to the Pro12Ala genotype of the PPARγ2 gene, there were no significant differences in fitness or genotype effects nor were there any interactions between measurement variables. We concluded that the CC genotype of C1431T in the PPARγ2 gene together with low cardiorespiratory fitness may increase the risk of MetS in younger men (age < 40 yr), even with adjustment for age.

Evidences on three relevant obesogenes: MC4R, FTO and PPARγ. Approaches for personalized nutrition

Obesity is a complex disease that results from the interaction between lifestyle (dietary patterns and sedentary habits) and genetic factors. The recognition of a genetic basis for human obesity has driven to identify putative causal genes to understand the pathways that control body mass and fat deposition in humans as well as to provide personalized treatments and prevention strategies to fight against obesity. More than 120 candidate genes have been associated with obesity-related traits. Genome-wide association study has so far identified over 20 novel loci convincingly associated with adiposity. This review is specifically focused on the study of the effects of melanocortin 4 receptor, Peroxisome proliferator-activated receptor γ and fat mass and obesity associated (FTO) gene variants and their interactions with dietary intake, physical activity or drug administration on body weight control. The advances in this field are expected to open new ways in genome-customized diets for obesity prevention and therapy following personalized approaches.

Peroxisome proliferator-activated receptor gamma polymorphism and periodontitis in pregnant Japanese women

BACKGROUND

Recent studies suggest an association between maternal periodontitis and preterm birth, although the association remains controversial. It was suggested that mechanisms such as a genetic predisposition for a hyperinflammatory response cause periodontitis and preterm births. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear hormone receptor and ligand-dependent transcription factor. PPARgamma inhibits the transcriptional activity of the genes that produce proinflammatory mediators and repress periodontitis. Recently, a common polymorphism, proline(PRO)-to-alanine(ALA) mutation at codon12 in exonB (Pro12Ala: rs 1801282) PPARgamma, was reported to reduce the ability to transactivate responsive promoters. In this study, we tested whether the PPARgammaPro12Ala polymorphism was associated with maternal periodontitis and/or preterm birth.

METHODS

Genomic DNA was isolated from the venous blood of pregnant Japanese women (term birth: n = 72; preterm birth: n = 58). The PPARgammaPro12Ala genotype was determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism. Within 5 days after labor, clinical periodontal parameters were evaluated, and periodontopathic bacteria from the subgingival plaque were detected by species-specific PCR.

RESULTS

The mean clinical attachment level (P = 0.012), mean probing depth (P = 0.031), mean gingival index (P = 0.037), and percentages of sites with bleeding on probing (P = 0.041) in women with the PPARgammaPro12Ala genotype were significantly higher than in women with the PPARgammaPro12Pro genotype. However, there was no association between preterm birth and periodontitis.

CONCLUSION

We suggest that the PPARgammaPro12Ala polymorphism may represent a genetic susceptibility factor for the clinical measurements of periodontitis in a limited number of pregnant Japanese women, but it probably cannot influence the relationship between periodontitis and preterm birth.

The Ala allele in the PPAR-gamma2 gene is associated with reduced risk of type 2 diabetes mellitus in Caucasians and improved insulin sensitivity in overweight subjects

The purpose of the present study was to identify the association of the Pro12Ala polymorphism in the PPAR-gamma2 gene with diabetes, insulinaemia and insulin resistance. A meta-analysis study was carried out based on studies conducted in the last 10 years, using the databases PubMed, ISI Web of Knowledge, High Wire Press and Scielo, and the reference lists of the obtained articles. We included original studies that showed the relationship between the Pro12Ala polymorphism in the PPAR-gamma2 gene and type 2 diabetes mellitus (T2DM), insulinaemia and insulin resistance. Statistical analyses were conducted using the program RevMAn 5.0. The Mantel-Haenszel test was used to estimate the OR and the 95 % CI of the dichotomous variable, while the standardised effect size was used to estimate the average standardised mean difference and 95 % CI of continuous variables. The studies were subgrouped by ethnicity and overweight status. Forty-one studies were analysed, including a global sample of 30 612 subjects. We found a significant association of the Ala allele with the lowest risk of T2DM in Caucasians (OR 0.80; 95 % CI 0.65, 0.98), lower serum insulin (standardised effect size: - 0.05; 95 % CI - 0.09, - 0.00; P = 0.04), and greater sensitivity to insulin in overweight individuals (homeostasis model assessment of insulin resistance standardised effect size: - 0.07; 95 % CI - 0.13, - 0.01; P = 0.02). Considering that the Pro12Ala polymorphism in the PPAR-gamma2 gene is one of the factors related to insulin sensitivity, the present study demonstrated a significant effect of the Ala allele on lower development of T2DM in Caucasians and greater sensitivity to insulin in overweight subjects.