The 482Ser of PPARGC1A and 12Pro of PPARG2 Alleles Are Associated with Reduction of Metabolic Risk Factors Even Obesity in a Mexican-Mestizo Population

The peroxisome proliferator-activated receptor γ coactivator-1 alpha rs8192678 (Gly482Ser) variant and hepatitis B virus clearance

BACKGROUND

Chronic hepatitis B virus (CHB) infection is still incurable a major public health problem. It is yet unclear how host genetic factors influence the development of HBV infection. The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) has been shown to regulate hepatitis B virus (HBV). Several reports found that PPARGC1A variants are involved in a number of distinct liver diseases. Here we investigate whether the PPARGC1A rs8192678 (Gly482Ser) variant is involved in the spontaneous clearance of acute HBV infection and if it participates in chronic disease progression in Moroccan patients.

METHODS

Our study included 292 chronic hepatitis B (CHB) patients and 181 individuals who spontaneously cleared-HBV infection. We genotyped the rs8192678 SNP using a TaqMan allelic discrimination assay and then explored its association with spontaneous HBV clearance and CHB progression.

RESULTS

Our data showed that individuals carrying CT and TT genotypes were more likely to achieve spontaneous clearance (OR = 0.48, 95% CI (0.32-0.73), p = 0.00047; OR = 0.28, 95% CI (0.15-0.53), p = 0.00005, respectively). Subjects carrying the mutant allele T were more likely to achieve spontaneous clearance (OR = 0.51, 95% CI (0.38-0.67), P = 2.68E-06). However, when we investigated the impact of rs8192678 on the progression of liver diseases, we neither observe any influence (p > 0.05) nor found any significant association between ALT, AST, HBV viral loads, and the PPARGC1A rs8192678 genotypes in patients with CHB (p > 0.05).

CONCLUSION

Our result suggests that PPARGC1A rs8192678 may modulate acute HBV infection, and could therefore represent a potential predictive marker in the Moroccan population.

Engineered allele substitution at PPARGC1A rs8192678 alters human white adipocyte differentiation, lipogenesis, and PGC-1α content and turnover

AIMS/HYPOTHESIS

PPARGC1A encodes peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), a central regulator of energy metabolism and mitochondrial function. A common polymorphism in PPARGC1A (rs8192678, C/T, Gly482Ser) has been associated with obesity and related metabolic disorders, but no published functional studies have investigated direct allele-specific effects in adipocyte biology. We examined whether rs8192678 is a causal variant and reveal its biological function in human white adipose cells.

METHODS

We used CRISPR-Cas9 genome editing to perform an allelic switch (C-to-T or T-to-C) at rs8192678 in an isogenic human pre-adipocyte white adipose tissue (hWAs) cell line. Allele-edited single-cell clones were expanded and screened to obtain homozygous T/T (Ser482Ser), C/C (Gly482Gly) and heterozygous C/T (Gly482Ser) isogenic cell populations, followed by functional studies of the allele-dependent effects on white adipocyte differentiation and mitochondrial function.

RESULTS

After differentiation, the C/C adipocytes were visibly less BODIPY-positive than T/T and C/T adipocytes, and had significantly lower triacylglycerol content. The C allele presented a dose-dependent lowering effect on lipogenesis, as well as lower expression of genes critical for adipogenesis, lipid catabolism, lipogenesis and lipolysis. Moreover, C/C adipocytes had decreased oxygen consumption rate (OCR) at basal and maximal respiration, and lower ATP-linked OCR. We determined that these effects were a consequence of a C-allele-driven dysregulation of PGC-1α protein content, turnover rate and transcriptional coactivator activity.

CONCLUSIONS/INTERPRETATION

Our data show allele-specific causal effects of the rs8192678 variant on adipogenic differentiation. The C allele confers lower levels of PPARGC1A mRNA and PGC-1α protein, as well as disrupted dynamics of PGC-1α turnover and activity, with downstream effects on cellular differentiation and mitochondrial function. Our study provides the first experimentally deduced insights on the effects of rs8192678 on adipocyte phenotype.

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).

Influence of Peroxisome Proliferator-Activated Receptor (PPAR)-gamma Coactivator (PGC)-1 alpha gene rs8192678 polymorphism by gender on different health-related parameters in healthy young adults

This study aimed to analyze the influence of the peroxisome proliferator-activated receptor (PPAR)-gamma coactivator (PGC)-1 alpha (PPARGC1A) gene rs8192678 C>T polymorphism on different health-related parameters in male and female young adults. The PPARGC1A gene rs8192678 polymorphism was ascertained by polymerase chain reaction in 74 healthy adults (28 women; 22.72 ± 4.40 years) from Andalusia (Spain). Health-related variables included cardiometabolic risk, anthropometry and body composition, biochemical parameters, insulin sensitivity (QUICKI and HOMA-IR indexes), blood pressure (BP) at rest and after exercise, diet, basal metabolism, physical activity, maximal fat oxidation, and cardiorespiratory fitness. Our results showed differences by PPARGC1A gene rs8192678 C>T polymorphism in body mass (p = 0.002), body mass index (p = 0.024), lean body mass (p = 0.024), body fat (p = 0.032), waist circumference (p = 0.020), and BP recovery ratio (p < 0.001). The recessive model (CC vs. CT/TT) showed similar results but also with differences in basal metabolism (p = 0.045) and total energy expenditure (p = 0.024). A genotype*sex interaction was found in the QUICKI index (p = 0.016), with differences between CC and CT/TT in men (p = 0.049) and between men and women inside the CT/TT group (p = 0.049). Thus, the PPARGC1A gene rs8192678 C>T polymorphism is associated with body composition, basal metabolism, total energy expenditure, and BP recovery, where the CC genotype confers a protective effect. Moreover, our study highlighted sexual dimorphism in the influence of PPARGC1A gene rs8192678 C>T polymorphism on the QUICKI index.

PPARGC1A rs8192678 G>A polymorphism affects the severity of hepatic histological features and nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease

BACKGROUND

The association between PPARGC1A rs8192678 and nonalcoholic fatty liver disease (NAFLD) requires further confirmation. In addition, it is still unknown whether PPARGC1A rs8192678 is associated with hepatic histological features in NAFLD in the Chinese population.

AIM

To investigate the interaction between PPARGC1A rs8192678 and nonalcoholic steatohepatitis (NASH), and whether this polymorphism is associated with hepatic histological features.

METHODS

Fifty-nine patients with liver biopsy-proven NAFLD and 93 healthy controls were recruited to a cohort representing the Chinese Han population. The SAF (steatosis, activity, and fibrosis) scoring system was used for hepatic histopathological evaluation. The polymorphisms of PPARGC1A rs8192678 and patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 were genotyped. The intrahepatic mRNA expression of PPARGC1A was evaluated by real-time polymerase chain reaction.

RESULTS

Thirty-seven patients with NAFLD had NASH, of which 12 were nonobese. The PPARGC1A rs8192678 risk A allele (carrying GA and AA genotypes) had the lowest P value in the dominant model; the odds ratio (OR) for NAFLD was 2.321 [95% confidence interval (CI): 1.121-4.806]. After adjusting for age, sex, and the PNPLA3 rs738409 risk G allele, the PPARGC1A rs8192678 A allele was a risk factor for NAFLD (OR 2.202, 95%CI: 1.030-4.705, P = 0.042). The genetic analysis showed that patients with NAFLD, moderate-to-severe steatosis (S2-3), and Activity 2-4 (A ≥ 2) were more likely to carry A in PPARGC1A rs8192678 (OR 5.000, 95%CI: 1.343-18.620, P = 0.012; and OR 4.071, 95%CI: 1.076-15.402, P = 0.031). The multivariate logistic regression analysis showed that PPARGC1A rs8192678 risk A allele was also independently associated with S2-3, A ≥ 2, and NASH (OR 6.190, 95%CI: 1.508-25.410, P = 0.011; OR 4.506, 95%CI 1.070-18.978, P = 0.040; and OR 6.337, 95%CI: 1.135-35.392, P = 0.035, respectively) after adjusting for age, sex, body mass index, and PNPLA3 rs738409 risk G allele. The results also showed that this polymorphism was associated with nonobese NASH (OR 22.000, 95%CI: 1.540-314.292, P = 0.021). The intrahepatic expression of PPARGC1A mRNA was significantly lower in the group of patients who carried the risk A allele (P = 0.014).

CONCLUSION

The PPARGC1A rs8192678 risk A allele is associated with NAFLD, and with S2-3, A ≥ 2 and NASH in NAFLD patients, independent of PNPLA3 rs738409, and may be associated with nonobese NASH.

Influence of pre-pregnancy body mass index (p-BMI) and gestational weight gain (GWG) on DNA methylation and protein expression of obesogenic genes in umbilical vein

Understanding the regulatory mechanisms that affect obesogenic genes expression in newborns is essential for early prevention efforts, but they remain unclear. Our study aimed to explore whether the maternal p-BMI and GWG were associated with regulatory single-locus DNA methylation in selected obesogenic genes. For this purpose, DNA methylation was assayed by Methylation-Sensitive High Resolution Melting (MS-HRM) technique and Sanger allele-bisulfite sequencing in fifty samples of umbilical vein to evaluate glucosamine-6-phosphate deaminase 2 (GNPDA2), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), and leptin receptor (LEPR) genes. Correlations between DNA methylation levels and indicators of maternal nutritional status were carried out. Western blotting was used to evaluate protein expression in extracts of the same samples. Results indicated that GNPDA2 and PGC1α genes have the same level of DNA methylation in all samples; however, a differential DNA methylation of LEPR gene promoter was found, correlating it with GWG and this correlation is unaffected by maternal age or unhealthy habits. Furthermore, leptin receptor (Lep-Rb) was upregulated in samples that showed the lowest levels of DNA methylation. This study highlights the association between poor GWG and adjustments on obesogenic genes expression in newborn tissues with potential consequences for development of obesity in the future.

Meta-analysis demonstrates Gly482Ser variant of PPARGC1A is associated with components of metabolic syndrome within Asian populations

AIM

To determine the association of peroxisome proliferator activated receptor gamma coactivator 1 Gly482Ser variant with components of metabolic syndrome.

MATERIALS AND METHODS

A systematic search was carried out using Web of Science, PubMed, EMBASE and the Cochrane library using the key words: Peroxisome proliferator activator receptor gamma coactivator 1, PPARGC1A, PGC-1, PGC-1alpha, and PGC1alpha alone or with polymorphism, Gly482Ser and rs8192678.

RESULTS

Data from 19 articles generated 28 separate data sets. Under the recessive model fasting plasma glucose was significantly lower in AA genotypes when compared to GG + GA in the total sample group and in non-Asian group (p < .001). The AA genotype showed significantly lower levels of total cholesterol compared to GG + GA genotype using the recessive model with the non-Asian group (p < .05). Under the dominant model, body mass index of the GG genotype was significantly higher in Asian subgroups (p < .05).

CONCLUSION

PPARGC1A Gly482Ser variant impacts differently in Asian population groups.

Genetic susceptibility to pre diabetes mellitus and related association with obesity and physical fitness components in Mexican-Mestizos

Pre diabetes mellitus (pre-DM) is considered an early-reversible condition that can progress to Type 2 diabetes mellitus (T2DM) which is the main cause of death for adult Mexican population. Gene variants influencing fasting glucose levels may constitute helpful tool for prevention purposes in pre-DM condition. Physically active Mexican-Mestizo adults (n=565) were genotyped for 6 single nucleotide polymorphisms (SNPs) (ADIPOQ rs2241766, ACSL1 rs9997745, LIPC rs1800588, PPARA rs1800206, PPARG rs1801282 and PPARGC1A rs8192678) related to lipid and carbohydrate metabolism. Fasting glucose was measured and values classified as pre-DM (≥100mg/dL) or normal fasting glucose. Logistic models were used to test associations between pre-DM condition and SNPs, and interaction with Body Mass Index (BMI) and physical fitness components. The A allele of ASCL1 rs9997745 conferred increased risk (OR=3.39, p=0.001) of pre-DM which is modulated by BMI. The A allele of the PPARGC1A rs8192678 showed significant SNP*BMI (OR=1.10, p=0.008) interaction effect for pre-DM risk, meaning that obese subjects showed higher pre-DM risk but normal weight subjects showed lower risk. The effect increased with age and was attenuated by higher cardiorespiratory values. We found that both ACSL1 rs9997745 and PPARGC1A rs8192678 are associated with pre-DM, and that BMI significantly modified their association.

Association of common polymorphisms in the VEGFA and SIRT1 genes with type 2 diabetes-related traits in Mexicans

INTRODUCTION

Genetic variants have been replicated for association with type 2 diabetes mellitus (T2D) and many of them with diabetes-related traits. Because T2D is highly prevalent in Mexico, this study aimed to test the association of CDKN2A/B, PPARGC1A, VEGFA, SIRT1 and UCP2 gene polymorphisms (rs10811661, rs8192678, rs2010963, rs7896005 and rs659366 respectively) with metabolic traits in 415 unrelated Mexican mestizos with T2D under three models of inheritance.

MATERIAL AND METHODS

A total of 415 unrelated Mexican mestizos were genotyped by TaqMan assays. Triglycerides, cholesterol, glucose, high-density lipoprotein cholesterol (HDL-C), insulin and anthropometric measurements were determined and the HOMA-IR was calculated. Association studies were tested by the Kruskal-Wallis test, linear regression, statistical power analysis, Bonferroni correction, paired SNP analysis, and physical interaction by GeneMANIA.

RESULTS

All polymorphisms were in Hardy-Weinberg equilibrium, and the association by genotype with T2D-related traits displayed nominal significance for rs8192678 with glucose (p = 0.023) and triglycerides (p = 0.013); rs2010963 with diastolic blood pressure (DBP) (p = 0.012) and cholesterol (p = 0.013); rs7896005 with DBP (p = 0.012) and insulin (p = 0.011); and rs659366 with cholesterol (p = 0.034), glucose (p = 0.031) and triglycerides (p = 0.028); and the association of rs2010963 with HDL-C (p = 0.0007) was significant. Linear regression performed with three models of inheritance, adjusted by age + sex + BMI and corrected with Bonferroni, showed a significant association of rs2010963 with HDL-C in an additive model (p = 0.007); and rs7896005 was significantly associated with DBP in the recessive model (p = 0.006).

CONCLUSIONS

Rigorous analysis evidenced the association of VEGFA rs2010963 and SIRT1 rs7896005 with HDL-C and DBP respectively; these traits are known predictors of cardiovascular complications, which increase the risk of cardiovascular diseases in this population.

Central obesity and body fat, but not body mass index, are associated with the Pro12Ala polymorphism in the peroxisome proliferator-activated receptor γ gene in a population with a high consumption of saturated and trans-fatty acids

The relationship of the Pro12Ala polymorphism in the peroxisome proliferator-activated receptor γ (PPARγ) gene with obesity and its modulation by dietary fat has been proposed, but the few studies addressing this issue have yielded controversial results. In a Mexican population characterized by high-fat consumption, we hypothesized that the Pro12Ala PPARγ genotype is related to obesity and this relationship is modulated by intake of saturated fatty acids (SFAs) and trans-fatty acids (TFAs). We recruited 69 adults for this cross-sectional study. The Pro12Ala PPARγ polymorphism was determined from blood genomic DNA by using real-time polymerase chain reaction. Univariate and multivariate logistic regression analyses were performed. Pro12Ala showed a positive association with central obesity (adjusted odds ratio, 7.38; 95% confidence interval, 1.19-45.77; P = .032) and percentage of body fat (%BF; adjusted odds ratio, 1.08; 95% confidence interval, 1.00-1.17; P = .048), suggesting that Pro12Ala carriers are more likely to have central obesity and a higher %BF than Pro12Pro carriers. A modifying effect was observed for the SFAs strata: we found a significant association between the Pro12Ala polymorphism and %BF in the high-SFA-intake stratum (P < .04), but not in the low-intake stratum (P > .7). No modifying effect was observed for the TFAs strata. In addition, the impact of total energy intake on obesity in Pro12Ala carriers seemed to be stronger than that in the wild-type genotype carriers. As hypothesized, our data demonstrated a relationship between the Pro12Ala PPARγ polymorphism and the presence of obesity, which is modulated by SFA intake but not TFA intake.

Linking Metabolic Disease With the PGC-1α Gly482Ser Polymorphism

Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is a highly conserved transcriptional coactivator enriched in metabolically active tissues including liver, adipose, pancreas, and muscle. It plays a role in regulating whole body energy metabolism and its deregulation has been implicated in type 2 diabetes (T2D). A single nucleotide variant of the PPARGC1A gene (rs8192678) is associated with T2D susceptibility, relative risk of obesity and insulin resistance, and lower indices of β cell function. This common polymorphism is within a highly conserved region of the bioactive protein and leads to a single amino acid substitution (glycine 482 to serine). Its prevalence and effects on metabolic parameters appear to vary depending on factors including ethnicity and sex, suggesting important interactions between genetics and cultural/environmental factors and associated disease risk. Interestingly, carriers of the serine allele respond better to some T2D interventions, illustrating the importance of understanding functional impacts of genetic variance on PGC-1α when targeting this pathway for personalized medicine. This review summarizes a growing body of literature surrounding possible links between the PGC-1α Gly482Ser single nucleotide polymorphism and diabetes, with focus on key clinical findings, affected metabolic systems, potential molecular mechanisms, and the influence of geographical or ethnic background on associated risk.

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.

THE PPARGC1A - GLY482SER POLYMORPHISM (RS8192678) AND THE METABOLIC SYNDROME IN A CENTRAL ROMANIAN POPULATION

Background

The peroxisome proliferator-activated receptor-γ co-activator 1-α (PPARGC1A), a key transcription factor involved in the control of metabolism and energy homeostasis, is an important biological and positional candidate of the metabolic syndrome. Association studies of its polymorphisms, however, yielded inconsistent sometimes conflicting results, pointing to important ethnic differences, which call for replication in various populations.

Objective

In order to study its most common - potentially functional - polymorphism Gly482Ser (rs8192678), we carried out a case-control study in a central Romanian population.

Material and methods

Two hundred and ninety six patients affected by the metabolic syndrome diagnosed according to the International Diabetes Federation proposed criteria and 166 middle-aged control subjects have been investigated. Genotyping was done by PCR-RFLP, using the restriction enzyme MspI.

Results

While the G(Gly)/A(Ser) allele frequencies (66.89/33.11 vs. 71.68/28.31 %) and GG/GA/AA genotype distribution (45.27-43.24-11.48 vs. 54.21-34.93-10.84 %) differed in the metabolic syndrome and control group, the risk of developing the metabolic syndrome did not reach the limit of statistical significance (OR=1.43; p=0.06, CI 95%: 0.97-2.09). Metabolic parameters in the two study groups did not show significant differences according to the genotype (p>0.05).

Conclusion

rs8192678 could be a functional polymorphism contributing to the development of the metabolic syndrome, but probably its effect is minor, and might depend on gene-gene and gene-environment interactions. Clarification of very small effects would require larger sample sizes.