Association and interaction of PPARα, δ, and γ gene polymorphisms with low-density lipoprotein-cholesterol in a Chinese Han population

Peroxisome Proliferator-Activated Receptor α and γ Gene Polymorphisms among South Indian Patients with Diabetic Dyslipidaemia

Background

Peroxisome proliferator-activated receptors (PPAR) α and γ genes play an important role in dyslipidaemia of T2DM.

Aims

To estimate the frequency distribution of PPAR α and γ gene polymorphisms in South Indian T2DM patients with dyslipidaemia compared to healthy controls. Normative frequencies of SNPs were established and compared with data for 1000 genome populations.

Methods

Eligible 382 cases and 336 age and sex-matched controls were enrolled. Six SNPs in PPARα [rs1800206 C>G (Leu162Val), rs4253778 G>C, rs135542 T>C] and PPARγ [rs3856806 (C>T), rs10865710 (C>G), rs1805192 C>G (Pro12Ala)] genes were selected for genotyping.

Results

The allele and gene frequencies did not significantly differ between the diabetic dyslipidaemia cases and healthy controls. However, they were significantly different from that of 1000 genome populations except for rs1800206 C>G (Leu162Val) and rs1805192 C>G (Pro12Ala).

Conclusion

The studied polymorphisms in PPARα and PPARγ genes are not associated with diabetic dyslipidaemia among South Indian patients.

Effects of PPARG and PPARGC1A gene polymorphisms on obesity markers

Pediatric obesity presents a multifactorial etiology, which involves genetic traits as well, including single nucleotide polymorphisms. The aim of the study is to investigate the contribution of PPARG gene polymorphisms (namely Pro12Ala rs1801282, His447His rs3856806, and Pro115Gln rs1800571) and PPARGC1A rs8192678 SNP on the anthropometric and metabolic parameters in a population of Romanian children. We conducted a cross-sectional study of 295 Caucasian children, divided according to the body mass index (BMI) z-score into the study (obese and overweight) group of 130 children and the control (normoponderal) group of 165 children. Anthropometric parameters were greater in the obese and overweight population as opposed to controls, with significant differences (p < 0.01) found for the weight (2.77 ± 1.54 SD vs. -0.04 ± 1.15 SD), body mass index (BMI) (2.28 ± 0.97 SD vs. -0.18 ± 1.19 SD), mid-upper arm circumference (MUAC) (4.59 ± 2.28 SD vs. 0.28 ± 3.45 SD), tricipital skin-fold (TSF) (3.31 ± 3.09 SD vs. 0.62 ± 7.28 SD) and waist-to-height ratio (WHtR) (0.61 ± 1.51 SD vs. -0.35 ± 1.35 SD) z-scores. Moreover, triglyceride values were higher in the study group (118.70 ± 71.99 SD vs. 77.09 ± 37.39 SD). No significant difference in the allele and genotype distribution of investigates gene polymorphisms was observed between the studied groups (p > 0.05). PPARG (rs1801282, rs3856806, and rs1800571) were not associated with demographic, anthropometric, and laboratory parameters. However, PPARGC1A rs8192678 CC genotype was associated with TSF z-score (p = 0.03), whereas total and LDL cholesterol levels were significantly higher among TT homozygotes (p < 0.01). Our data suggest that PPARG (rs1801282, rs3856806, and rs1800571) and PPARGC1A (rs8192678) gene polymorphisms were not associated with childhood and adolescence overweight and obesity. The present study identified a significant increase in fasting glucose levels, triglyceride, albumin, and ALT levels in children with excess weight, as well as expected important upward variation of anthropometric parameters (BMI, MUAC, TSF z-scores).

PPARα Targeting GDF11 Inhibits Vascular Endothelial Cell Senescence in an Atherosclerosis Model

Atherosclerosis (AS) is a complex vascular disease that seriously harms the health of the elderly. It is closely related to endothelial cell aging, but the role of senescent cells in atherogenesis remains unclear. Studies have shown that peroxisome proliferator-activated receptor alpha (PPARα) inhibits the development of AS by regulating lipid metabolism. Our previous research showed that PPARα was involved in regulating the repair of damaged vascular endothelial cells. Using molecular biology and cell biology approaches to detect senescent cells in atherosclerosis-prone apolipoprotein E-deficient (Apoe -/-) mice, we found that PPARα delayed atherosclerotic plaque formation by inhibiting vascular endothelial cell senescence, which was achieved by regulating the expression of growth differentiation factor 11 (GDF11). GDF11 levels declined with age in several organs including the myocardium, bone, central nervous system, liver, and spleen in mice and participated in the regulation of aging. Our results showed that PPARα inhibited vascular endothelial cell senescence and apoptosis and promoted vascular endothelial cell proliferation and angiogenesis by increasing GDF11 production. Taken together, these results demonstrated that PPARα inhibited vascular endothelial cell aging by promoting the expression of the aging-related protein GDF11, thereby delaying the occurrence of AS.

Association of PPARG rs3856806 C>T polymorphism with body mass index, glycaemia and lipid parameters in Serbian adolescents

Background/Aim: Peroxisome proliferator-activated receptor gamma (PPARg) belongs to a family of nuclear hormone receptors and ligand-activated transcription factors. PPARG gene is expressed in many tissues including adipose tissue where it plays a crucial role in differentiation of adipocyte, insulin resistance, blood glucose levels and lipid metabolism. The aim of the study was to examine the association of rs3856806 polymorphism with the body mass index (BMI), fasting glucose levels and lipid parameters in Serbian adolescents. Methods: This research included 287 adolescents of both genders (143 boys and 144 girls), 14-15 years of age. Genotype detection was done by polymerase chain reaction-restriction fragment length polymorphism (RFLP) assay. Results: Results showed statistically significant difference in terms of fasting glucose levels among girls (p = 0.013) depending on their genotype. Female carriers of CC genotype had significantly higher level of fasting glucose levels. Also, results showed that in the group of overweight and obese girls, carriers of CT or TT genotype had statistically significant lower values of HDL cholesterol compared to girls - carriers of CC genotype (p = 0.000). However, this result was not confirmed by multiple regression analysis. Statistically significant association of rs3856806 polymorphism was not observed with BMI nor with other lipid parameters. Conclusion: This polymorphism is associated with fasting glucose level and HDL cholesterol among girls. To draw definite conclusions, further research should be conducted including non-genetic factors and other polymorphisms among this gene.

Associations between peroxisome proliferator-activated receptor γ (PPAR-γ) polymorphisms and serum lipids: Two cross-sectional studies of community-dwelling adults

Dyslipidemia is a well-established risk factor for cardiovascular disease. Experimental studies have reported that peroxisome proliferator-activated receptor γ (PPAR-γ) regulates adipocyte differentiation, lipid storage, and glucose metabolism. Therefore, we examined the associations between PPAR-γ polymorphisms (rs1801282, rs3856806, rs12497191, rs1151999, and rs1152003) and serum lipids in two cross-sectional studies. In the Shizuoka area of the Japan Multi-Institutional Collaborative Cohort Study, we examined 4,952 participants (3,356 men and 1,596 women) in a baseline survey and 2,245 participants (1,550 men and 695 women) in a second survey 5 years later. Outcome measures were the prevalence of dyslipidemia (low-density lipoprotein-cholesterol [LDL-C] ≥ 140 mg/dl, high-density lipoprotein-cholesterol < 40 mg/dl, triglycerides ≥ 150 mg/dl, and/or use of cholesterol-lowering drugs) and the prevalence of high LDL-C (LDL-C ≥ 140 mg/dl and/or use of cholesterol-lowering drugs). Multivariate odds ratios (ORs) were estimated by using unconditional logistic regression models. A total of 2,114 and 1,431 individuals (42.7% and 28.9%) had dyslipidemia and high LDL-C in the baseline survey, respectively, as did 933 and 716 (41.6% and 31.9%), respectively, in the second survey. In the baseline study, compared with major allele homozygotes, minor allele homozygotes of rs3856806 and rs12497191 had a 42% (OR, 0.58; 95% confidence interval (CI), 0.39-0.85) and 23% (OR, 0.77; 95% CI, 0.60-0.99) lower risk of dyslipidemia, respectively, after adjustment for potential confounding factors. In addition, minor allele homozygotes of rs3856806 had a 45% (OR, 0.55; 95% CI, 0.35-0.86) lower risk of high LDL-C. Similar risk reductions were found in the second survey. In conclusion, rs3856806 and rs12497191 polymorphisms may be related to a lower risk of dyslipidemia and high LDL-C.

Enhancer polymorphism rs10865710 associated with traumatic sepsis is a regulator of PPARG gene expression

Background

Peroxisome proliferator-activated receptor gamma (PPARγ) is a major regulator in sepsis. Our previous study identified the enhancer polymorphism rs10865710C/G to be associated with susceptibility to sepsis in trauma patients. We performed two-stage cohort studies integrating biological experiments of potential functional variants that modify susceptibility to traumatic sepsis.

Methods

Improved multiplex ligation detection reaction (iMLDR) was used to genotype rs10865710 in 797 Han Chinese trauma patients in Chongqing. Clinical relevance was validated in 334 patients in Guizhou. The potential function of rs10865710 in transcriptional regulation was explored through a dual luciferase reporter assay and electrophoretic mobility shift assay (EMSA). Expression of PPARγ was assessed by expression quantitative trait locus (e-QTL) and western blot analyses.

Results

The association results confirmed rs10865710 to be significantly strongly associated with sepsis risk in trauma patients of the Chongqing and Guizhou cohorts (OR = 1.41 (1.11–1.79), P = 0.004 and OR = 1.45 (1.01–2.09), P = 0.046, both for allele-dose effect, respectively). A meta-analysis of both cohorts and a previous study indicated strong evidence for this association (OR = 1.41 (1.17–1.71), P = 0.0004 for the dominant model, OR = 1.78 (1.34–2.36), P < 0.0001 for the recessive model and OR = 1.38 (1.20–1.58), P < 0.0001 for the allelic model). Functional experiments verified that rs10865710 was a causative variant influencing enhancer activity (G vs. C, 0.068 ± 0.004 vs. 0.096 ± 0.002, P = 0.0005) and CREB2 binding. Expression analysis also indicatevd rs10865710 genotypes to be associated with levels of PPARγ expression (P = 9.2 × 10⁻⁵ for dominant effect and P = 0.005 for recessive effect).

Conclusions

Our study provides evidence that the enhancer-region polymorphism rs10865710 might influence transcription factor binding and regulate PPARγ expression, thus conferring susceptibility to traumatic sepsis.

Trial registration

ClinicalTrials.gov, NCT01713205. Registered 18 October 2012, retrospectively registered.

PPARG Polymorphisms Are Associated with Unexplained Mild Vision Loss in Patients with Type 2 Diabetes Mellitus

Objectives

To investigate whether the presence of peroxisome proliferator-activated receptor gamma (PPARG) gene polymorphisms is associated with unexplained mild visual impairment (UMVI) in patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 135 T2DM residents with UMVI and 133 with normal vision (NV; best-corrected visual acuity ≥ 20/25 in both eyes) were enrolled. UMVI was defined as best-corrected visual acuity (BCVA) < 20/25 and ≥ 20/63 in both eyes, with no visual impairment-causing diseases found. Four PPARG gene single-nucleotide polymorphisms (SNPs) (rs3856806, rs1801282, rs709158, and rs10865710) were assessed with the HAPLOVIEW 4.0 software to examine the statistical association of PPARG polymorphisms and UMVI in patients with T2DM.

Results

Four SNPs qualified the Hardy-Weinberg equilibrium (p > 0.05). The frequency of genotype GC at SNP rs10865710 was significantly higher in the UMVI group than in the NV group (p < 0.001; GG + GC versus CC) (OR = 8.94, 95% CI: 4.90-16.31), whereas genotype CC decreased the risk (OR = 0.07, 95% CI: 0.03-0.14). Genotype TT at SNP rs3856806 was strongly associated with UMVI (p < 0.0001, TT + TC versus CC) (OR = 4.74, 95% CI: 2.68-8.54), whereas genotype CC appeared to be protective for UMVI (OR = 0.55, 95% CI: 0.37-0.82).

Conclusions

Susceptibilities of PPARG variants may lead to differences in PPARG transcription, result in early function loss of retinal photoreceptor cells, and eventually cause UMVI.

Cigarette Smoke Extract Modulates Functions of Peroxisome Proliferator-Activated Receptors

Cigarette smoke extract (CSE) contains many toxicants and may derange the physiological processes, such as cholesterol metabolism. We examined the impact of CSE on transcriptional regulation mediated peroxisome proliferator-activated receptors (PPARs) and its interaction with cofactors to elucidate differences in the molecular mechanism between CSE and other agonists of PPARs. We constructed several mutant PPARs (mPPARs) with amino acid substitution in the ligand-binding domain, which according to the molecular modeling, may affect the binding of agonists. In transient expression assays, each wild-type peroxisome proliferator-activated receptor (PPAR) mediated transcription stimulated by CSE was faintly yet significantly elevated compared to the control. The CSE-induced transcriptional activation was abolished in the H323A, H323Y, S342A, and H449A mPPARγs, although the activation elevated by pioglitazone was reserved. In the mPPARγ with Y473A and mPPARβ/δs with H286Y and Y436A, the pioglitazone-induced or L165041-activated transcriptional elevations were decreased and were lower than that of CSE-induced stimulation. These results suggested that CSE activated both mutant PPARs to be selectively different from those ligands. Mammalian two-hybrid assay illustrated that CSE could mildly recruit SRC1 or GRIP1 to the wild-type PPARγ. Representative ingredients, such as acrolein and crotonaldehyde present in CSE, could stimulate PPAR isoforms even at the toxicological concentrations and might possibly contribute to stimulatory effects. CSE mildly regulates the cholesterol metabolism-related genes, such as low density lipoprotein (LDL) receptor and Liver X receptor (LXR)β. In conclusion, these CSE effects the nuclear hormone receptors and their cofactors thereby disturbing metabolic phenomena. Therefore, CSE might be involved in cholesterol metabolism.

PPARγ Pro12Ala and C161T polymorphisms in patients with acne vulgaris: Contribution to lipid and lipoprotein profile

PURPOSE

The aim of present study was to clarify the role of peroxisome proliferator-activated receptor γ (PPARγ) Pro12Ala and C161T variants in the pathogenesis of acne vulgaris (AV) and their influence on lipid and lipoprotein profile.

METHODS

The present case-control study consisted of 393 individuals including 198 patients with AV (mild-, moderate-, and severe-AV) and 195 unrelated age-matched healthy individuals from Western Iran. The PPARγ Pro12Ala and C161T polymorphisms were identified using polymerase chain reaction-restriction length polymorphism method. Also, serum lipid and lipoprotein profile and fasting blood sugar (FBS) were detected in studied individuals.

RESULTS

In women patients with AV significantly higher serum levels of FBS, total cholesterol, low density lipoprotein-cholesterol (LDL-C) and high density lipoprotein-cholesterol compared to healthy women were detected. Neither PPARγ Pro12Ala nor C161T polymorphism was associated with the risk of AV but the Pro allele was a risk factor for AV among all men and women patients ≥20years. The variant genotype of PPARγ CG (Pro/Ala) was associated with significantly higher levels of total cholesterol and triglycerides compared to CC (Pro/Pro) genotype. We detected a significantly lower level of FBS in the presence of CT+TT genotype of PPARγ C161T compared to CC genotype. Also, carriers of PPARγ TT genotype had significantly lower serum level of total cholesterol and LDL-C compared to CC genotype.

CONCLUSIONS

Our results demonstrated the association of PPARγ Pro allele with susceptibility to AV in patients ≥20years and the influence of PPARγ Pro12Ala and C161T polymorphisms on the lipid and lipoprotein profile.

Interactions Between PPARG and AGTR1 Gene Polymorphisms on the Risk of Hypertension in Chinese Han Population

AIMS

To explore the interactions between PPARG and AGTR1 polymorphisms and their associations with hypertension in the Chinese Han population.

METHODS

Seven single nucleotide polymorphisms (SNPs) of the PPARG gene and five SNPs of the AGTR1 gene were selected and genotyped in 1591 unrelated Chinese Han adults. The SNPAssoc package of R was used to analyze the associations between the selected SNPs and hypertension. The potential gene-gene interactions between PPARG and AGTR1 genes were tested by model-based multifactor dimensionality reduction (MB-MDR).

RESULTS

The frequencies of the C allele of rs3856806 and the G allele of rs13433696 in the PPARG gene were significantly lower in hypertensive subjects, whereas the A allele of rs9817428 in the PPARG gene was much higher in hypertensives. In addition, individuals with T allele of rs2933249 in the AGTR1 gene displayed a significantly decreased risk of hypertension. MB-MDR analyses suggested that the two-locus model (rs9817428 and rs2933249) and the three-locus model (rs9817428, rs3856806, and rs2933249) were significantly associated with a decreased risk of hypertension. Moreover, among the eight SNPs not individually associated with hypertension (rs12631819, rs2920502, rs1175543, and rs2972164 in the PPARG gene, and rs2638360, rs1492100, rs5182, and rs275646 in the AGTR1 gene), the two-locus model involving rs12631819 and rs5182 demonstrated increased susceptibility to hypertension, and the five-locus model involving rs12631819, rs2920502, rs2972164, rs5182, and rs2638360 demonstrated a significantly decreased risk of hypertension.

CONCLUSION

Polymorphisms in both the PPARG and AGTR1 genes were found to be significantly associated with hypertension. Moreover, there were significant gene-gene interactions identified between the PPARG and AGTR1 genes in relation to hypertension susceptibility in the Chinese Han population.

Peroxisome proliferator-activated receptors in cardiac energy metabolism and cardiovascular disease

Cardiomyocytes mainly depend on energy produced from the oxidation of fatty acids and mitochondrial oxidative phosphorylation. Shortage of energy or excessive fat accumulation can lead to cardiac disorders. High saturated fat intake and a sedentary life style have a major influence in the development of cardiovascular disease (CVD). Peroxisome proliferator-activated receptors (PPARs), one of the nuclear receptor super family members, play critical role in the metabolism of lipids by regulating their oxidation and storage. Furthermore, they are involved in glucose homeostasis as well. PPARs, mainly alpha (α) and beta/delta (β/δ), have a significant effect on the lipid metabolism and anti-inflammation in endothelial cells (ECs), vascular smooth muscle cells, and also in cardiomyocytes. Pro-inflammatory cytokines, mainly tumour necrosis factor-α, released at the site of inflammation in the sub-ECs of coronary arteries can inactivate the PPARs which can eventually lead to decreased energy production in the myocardium. Various synthetic ligands of PPAR-α and β/δ have many favourable effects in modulating the vascular diseases and heart failure. Despite the adverse effects from therapy using PPAR- gamma ligands, several laboratories are now focused on synthesizing partial activators which may combine their beneficial effects with lowering of undesirable side effects. This review discusses the role of isoforms of PPAR in the cardiomyocytes energy balance and CVD. The knowledge will help in the synthesis of ligands for their partial activation in order to render energy balance and protection from CVD.

Genetic determinants of inherited susceptibility to hypercholesterolemia - a comprehensive literature review

Hypercholesterolemia is a strong determinant of mortality and morbidity associated with cardiovascular diseases and a major contributor to the global disease burden. Mutations in four genes (LDLR, APOB, PCSK9 and LDLRAP1) account for the majority of cases with familial hypercholesterolemia. However, a substantial proportion of adults with hypercholesterolemia do not have a mutation in any of these four genes. This indicates the probability of having other genes with a causative or contributory role in the pathogenesis of hypercholesterolemia and suggests a polygenic inheritance of this condition. Here in, we review the recent evidence of association of the genetic variants with hypercholesterolemia and the three lipid traits; total cholesterol (TC), HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C), their biological pathways and the associated pathogenetic mechanisms. Nearly 80 genes involved in lipid metabolism (encoding structural components of lipoproteins, lipoprotein receptors and related proteins, enzymes, lipid transporters, lipid transfer proteins, and activators or inhibitors of protein function and gene transcription) with single nucleotide variants (SNVs) that are recognized to be associated with hypercholesterolemia and serum lipid traits in genome-wide association studies and candidate gene studies were identified. In addition, genome-wide association studies in different populations have identified SNVs associated with TC, HDL-C and LDL-C in nearly 120 genes within or in the vicinity of the genes that are not known to be involved in lipid metabolism. Over 90% of the SNVs in both these groups are located outside the coding regions of the genes. These findings indicates that there might be a considerable number of unrecognized processes and mechanisms of lipid homeostasis, which when disrupted, would lead to hypercholesterolemia. Knowledge of these molecular pathways will enable the discovery of novel treatment and preventive methods as well as identify the biochemical and molecular markers for the risk prediction and early detection of this common, yet potentially debilitating condition.

Distinct but complementary contributions of PPAR isotypes to energy homeostasis

Peroxisome proliferator-activated receptors (PPARs) regulate energy metabolism and hence are therapeutic targets in metabolic diseases such as type 2 diabetes and non-alcoholic fatty liver disease. While they share anti-inflammatory activities, the PPAR isotypes distinguish themselves by differential actions on lipid and glucose homeostasis. In this Review we discuss the complementary and distinct metabolic effects of the PPAR isotypes together with the underlying cellular and molecular mechanisms, as well as the synthetic PPAR ligands that are used in the clinic or under development. We highlight the potential of new PPAR ligands with improved efficacy and safety profiles in the treatment of complex metabolic disorders.

Interaction between peroxisome proliferator-activated receptor gamma polymorphism and obesity on type 2 diabetes in a Chinese Han population

AIMS

The aim of this study was to investigate the association of four single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptor gamma (PPARG) with type 2 diabetes mellitus (T2DM) risk and additional role of gene-obesity interaction.

METHODS

Four SNPs were selected for genotyping in the case-control study: rs1805192, rs709158, rs3856806 and rs4684847. Generalized multifactor dimensionality reduction (GMDR) model and logistic regression was used to examine the interaction between SNP and obesity on T2DM, odds ratio (OR) and 95% confident interval (95% CI) were calculated.

RESULTS

T2DM risk was significantly higher in individuals with rs1805192-G allele (p < 0.05). The carriers of G allele of the rs1805192 polymorphism revealed increased T2DM risk than those with CC variants (CG + GG versus CC, adjusted OR (95% CI) 1.76 (1.45-2.06), p < 0.001). T2DM risk was also significantly higher in individuals with rs3856806-T allele (p < 0.05). The carriers of T allele of the rs3856806 polymorphism revealed increased T2DM risk than those with CC variants (CT + TT versus CC, adjusted OR (95% CI) 1.25 (1.17-1.76), p < 0.001). There was a significant two-locus model (p = 0.0107) involving rs1805192 and obesity. Obese subjects with CG or GG genotype have the highest T2DM risk, compared to subjects with CC genotype and normal BMI (OR 2.40, 95% CI 1.68-3.63).

CONCLUSIONS

Our results support an important association between rs1805192 and rs3856806 minor allele (G allele) of PPARG and increased T2DM risk, the interaction analysis shown a combined effect of G- obesity interaction between rs1805192 and obesity on increased T2DM risk.

Appropriate LDL-C-to-HDL-C Ratio Cutoffs for Categorization of Cardiovascular Disease Risk Factors among Uygur Adults in Xinjiang, China

Elevated LDL-C/HDL-C ratio has been shown to be a marker of lipid metabolism as well as a good predictor of coronary artery disease (CAD). Thus, the aim of this study was to investigate whether the LDL-C/HDL-C ratio is useful for detecting cardiovascular disease (CVD) risk factors in general healthy Uygur adults in Xinjiang. A total of 4047 Uygur subjects aged ≥35 years were selected from the Cardiovascular Risk Survey (CRS) study which was carried out from October 2007 to March 2010. Anthropometric data, blood pressure, lipid profile and fasting glucose were measured in all participants. The prevalence, sensitivity, specificity and distance on the receiver operating characteristic (ROC) curve of each LDL-C/HDL-C ratio were calculated. The prevalence of high LDL-C and low HDL-C cholesterol was high and positively correlated with higher LDL-C/HDL-C ratio in the Uygur population. In both men and women, we detected a slight apparent trend of high prevalence of hypertension and hypercholesterolemia with higher LDL-C/HDL-C ratio. Our study also demonstrated that the discriminatory power of the LDL-C/HDL-C ratio for CVD risk factors was slightly stronger in men than in women. Analysis of the shortest distance in the ROC curves for hypertension, dyslipidemia, diabetes, or ≥two of these risk factors suggested a LDL-C/HDL-C ratio cutoff of 2.5 for both men and women. The results of this study showed that a LDL-C/HDL-C ratio cut-off of 2.5 might be used as the predictive marker to detect CVD risk factors among Uygur adults in Xinjiang.