PGC1α gene Gly482Ser polymorphism predicts improved metabolic, inflammatory and vascular outcomes following bariatric surgery

The Influence of Single Nucleotide Polymorphisms On Body Weight Trajectory After Bariatric Surgery: A Systematic Review

PURPOSE OF REVIEW

To conduct a systematic review to summarize the results of studies on this subject and to identify whether single nucleotide polymorphisms (SNPs) are good prognostic markers for body weight trajectory after bariatric surgery.

RECENT FINDINGS

A considerable number of events can influence the body weight trajectory after bariatric surgery, and in the post-genomic era, genetic factors have been explored. This study is registered with PROSPERO (CRD42021240903). SNPs positively associated with poor weight loss after bariatric surgery were rs17702901, rs9939609, rs1360780, rs1126535, rs1137101, rs17782313, rs490683, and rs659366. Alternatively, SNPs rs2229616, rs5282087, rs490683, rs9819506, rs4771122, rs9939609, rs4846567, rs9930506, rs3813929, rs738409, rs696217, rs660339, rs659366, rs6265, rs1801260, and rs2419621 predicted a higher weight loss after bariatric surgery. Six studies performed with a genetic risk score (GRS) model presented significant associations between GRS and outcomes following bariatric surgery. This systematic review shows that, different SNPs and genetic models could be good predictors for body weight trajectory after bariatric surgery. Based on the results of the selected studies for this Systematic Review is possible to select SNPs and metabolic pathways of interest for the GRS construction to predict the outcome of bariatric surgery to be applied in future studies.

The rs17782313 polymorphism near MC4R gene confers a high risk of obesity and hyperglycemia, while PGC1α rs8192678 polymorphism is weakly correlated with glucometabolic disorder: a systematic review and meta-analysis

Background

The relationships of the rs17782313 polymorphism near melanocortin 4 receptor gene (MC4R) and the rs8192678 polymorphism in peroxisome proliferator-activated receptor gamma coactivator 1 alpha gene (PGC1α) with metabolic abnormalities have been explored in many populations around the world, but the findings were not all consistent and sometimes even a bit contradictory.

Methods

Electronic databases including Medline, Scopus, Embase, Web of Science, CNKI and Google Scholar were checked for studies that met the inclusion criteria. Data were carefully extracted from eligible studies. Standardized mean differences (SMDs) were calculated by using a random-effects model to examine the differences in the indexes of obesity, glucometabolic disorder and dyslipidemia between the genotypes of the rs17782313 and rs8192678 polymorphisms. Cochran's Q-statistic test and Begg's test were employed to identify heterogeneity among studies and publication bias, respectively.

Results

Fifty studies (58,716 subjects) and 51 studies (18,660 subjects) were respectively included in the pooled meta-analyses for the rs17782313 and rs8192678 polymorphisms. The C-allele carriers of the rs17782313 polymorphism had a higher average level of body mass index (SMD = 0.21 kg/m2, 95% confidence interval [95% CI] = 0.12 to 0.29 kg/m2, p < 0.001), waist circumference (SMD = 0.14 cm, 95% CI = 0.06 to 0.23 cm, p < 0.001) and blood glucose (SMD = 0.09 mg/dL, 95% CI = 0.02 to 0.16 mg/dL, p = 0.01) than the TT homozygotes. Regarding the rs8192678 polymorphism, no significant associations with the indexes of obesity, glucometabolic disorder and dyslipidemia were detected. However, significant correlations between the rs8192678 polymorphism and multiple glucometabolic indexes were observed in subgroup analyses stratified by sex, age, ethnicity and health status.

Conclusion

The meta-analysis demonstrates that the C allele of the MC4R rs17782313 polymorphism confers a higher risk of obesity and hyperglycemia, and the PGC1α rs8192678 polymorphism is weakly correlated with glucometabolic disorder. These findings may partly explain the relationships between these variants and diabetes as well as cardiovascular disease.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022373543.

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.

Associations of Polymorphisms in the Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1 Alpha Gene With Subsequent Coronary Heart Disease: An Individual-Level Meta-Analysis

Background: The knowledge of factors influencing disease progression in patients with established coronary heart disease (CHD) is still relatively limited. One potential pathway is related to peroxisome proliferator–activated receptor gamma coactivator-1 alpha (PPARGC1A), a transcription factor linked to energy metabolism which may play a role in the heart function. Thus, its associations with subsequent CHD events remain unclear. We aimed to investigate the effect of three different SNPs in the PPARGC1A gene on the risk of subsequent CHD in a population with established CHD.

Methods: We employed an individual-level meta-analysis using 23 studies from the GENetIcs of sUbSequent Coronary Heart Disease (GENIUS-CHD) consortium, which included participants (n = 80,900) with either acute coronary syndrome, stable CHD, or a mixture of both at baseline. Three variants in the PPARGC1A gene (rs8192678, G482S; rs7672915, intron 2; and rs3755863, T528T) were tested for their associations with subsequent events during the follow-up using a Cox proportional hazards model adjusted for age and sex. The primary outcome was subsequent CHD death or myocardial infarction (CHD death/myocardial infarction). Stratified analyses of the participant or study characteristics as well as additional analyses for secondary outcomes of specific cardiovascular disease diagnoses and all-cause death were also performed.

Results: Meta-analysis revealed no significant association between any of the three variants in the PPARGC1A gene and the primary outcome of CHD death/myocardial infarction among those with established CHD at baseline: rs8192678, hazard ratio (HR): 1.01, 95% confidence interval (CI) 0.98–1.05 and rs7672915, HR: 0.97, 95% CI 0.94–1.00; rs3755863, HR: 1.02, 95% CI 0.99–1.06. Similarly, no significant associations were observed for any of the secondary outcomes. The results from stratified analyses showed null results, except for significant inverse associations between rs7672915 (intron 2) and the primary outcome among 1) individuals aged ≥65, 2) individuals with renal impairment, and 3) antiplatelet users.

Conclusion: We found no clear associations between polymorphisms in the PPARGC1A gene and subsequent CHD events in patients with established CHD at baseline.

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.

Effect of Bariatric Surgery on Serum Inflammatory Factors of Obese Patients: a Systematic Review and Meta-Analysis

Obesity is one of the main causes of inflammation. Previous studies have reported inconclusive results regarding the effect of bariatric surgery on inflammatory markers. This systematic review and meta-analysis is aimed at describing the effect of bariatric surgery on C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α). PubMed/Medline and Scopus were systematically searched for all eligible studies from inception to June 2018. Results are expressed as weighted mean difference (MD) with 95% confidence intervals (CI) using a random effects model. Overall, 116 studies which evaluated serum CRP, IL-6, and TNF-α after bariatric surgery were included. Pooled effect size showed significant reduction in serum CRP (- 5.30 mg/l, 95% CI - 5.46, - 5.15, P < 0.001), IL-6 (- 0.58 pg/ml, 95% CI - 0.64, - 0.53, P < 0.001), and TNF-α (- 0.20 pg/ml, 95% CI - 0.39, - 0.02, P = 0.031) with significant heterogeneity across studies (> 95% for all factors). Bariatric surgery significantly lowered inflammatory factors; however, baseline BMI, follow-up duration and type of surgery could impact the extent of observed effects.

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.

Effects of gastric bypass surgery followed by supervised physical training on inflammation and endothelial function: A randomized controlled trial

BACKGROUND AND AIMS

Obesity and physical inactivity are both associated with low-grade inflammation and endothelial dysfunction. Bariatric surgery improves markers of inflammation and endothelial function, but it is unknown if physical training after bariatric surgery can improve these markers even further. Therefore, we aimed to investigate the effects of Roux-en-Y gastric bypass (RYGB) followed by physical training on markers of low-grade inflammation and endothelial function.

METHODS

Sixty patients approved for RYGB underwent examinations pre-surgery, 6, 12, and 24 months post-surgery. Six months post-surgery, they were randomized 1:1 to an intervention group or a control group. The interventions consisted of two weekly sessions of supervised moderate intensity physical training for a period of 26 weeks. Fasting blood samples were analyzed for concentrations of interleukin 6 (IL-6), C-reactive protein (CRP), intercellular adhesion molecule 1 (ICAM-1), tissue-type plasminogen activator antigen (t-PA:Ag) and von Willebrand factor (vWF).

RESULTS

RYGB markedly improved markers of inflammation (IL-6, CRP) (p < 0.001) and endothelial function (ICAM-1, t-PA:Ag, vWF) (p < 0.05), and the improvements were sustained 24 months post-surgery (p < 0.01), except for the effects on vWF. We found no correlations between the changes in weight or BMI and the changes in markers of inflammation and endothelial function, except that the change in vWF was found to be inversely correlated with the changes in weight and BMI. We observed no effects of supervised physical training on markers on inflammation or endothelial function (p>0.1 for all).

CONCLUSIONS

RYGB causes substantial and sustained favorable effects on markers of inflammation and endothelial function. Supervised physical training after RYGB did not cause additional improvements.

Human catalase gene promoter haplotype and cardiometabolic improvement after bariatric surgery

Although its powerful impact on most co-morbidities has been widely demonstrated, the metabolic outcomes of bariatric surgery (BS) show a great heterogeneity among patients. Haplotypes of one of the major antioxidant enzyme, catalase (CAT), are associated with hypertension, dyslipidemia, and diabetes. The haplotype referred to as CAT1 includes homozygous carriers of CATH1 [-844G,-89A,-20T], whereas CAT2 haplotype includes heterozygous carriers (CATH1/CATH2) and CATH2 homozygous [-844A,-89T,-20C]. The aim of our study was to evaluate the impact of CAT1 and CAT2 haplotypes on traditional cardiovascular and metabolic markers one year after BS in a women population. The 294 women with a body mass index (BMI) >35 kg/m2 were followed-up for one year after BS, monitoring their anthropometric, metabolic and inflammatory parameters. CAT1 patients had significantly improved diastolic blood pressure (DBP) and Creactive protein (CRP) levels compared to CAT2 one year after BS. In untreated women at baseline, the change of CRP one year after BS was higher in CAT1 patients. In the population of women receiving at least one anti-lipidic, anti-hypertensive or anti-diabetic treatment at baseline, DBP and fat mass were lower one year after BS in CAT1 patients and the greater change of fat mass was associated with a higher change of adiponectin. The results highlight the beneficial impact of the CAT1 haplotype on traditional cardiovascular and metabolic parameters after BS. Our findings suggest that the CAT1 haplotype could be implicated in the level of metabolic and cardiovascular improvement after BS.

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.

Resistance to high-fat diet-induced obesity in male heterozygous Pprc1 knockout mice

Peroxisome proliferator-activated receptor gamma, co-activator-related 1 (Pprc1) is the third member of the Pgc1 family. Other than the well-characterized Pgc1a and Pgc1b that act as regulators of mitochondrial biogenesis and oxidative metabolism, the function of Pprc1 in vivo is rarely reported, due to embryonic lethality of whole-body Pprc1 knockout mice. To investigate the biological and physiological function of Pprc1 in metabolic processes, male Pprc1(+/-) mice fed with a high fat diet (HFD) showed resistance to diet-induced obesity with a decrease of adipose tissue in Pprc1(+/-) mice, which was a result of elevated energy expenditure. In skeletal muscle of Pprc1(+/-) mice, Pprc1 level showed haplo-insufficiency with down-regulation of Pgc1b and Pgc1a, whereas in adipose tissue, Pprc1 expression remained normal, with significant compensatory increase of other Pgc1 family members to induce an up-regulation of respiratory chain genes. Taken together, as the first report on the metabolic roles of Pprc1 in vivo, these results indicated an elevated basal metabolic rate and lipid metabolic alteration of male Pprc1(+/-) mice on HFD, suggesting the significant role of Pprc1 in controlling mitochondrial gene expression and energy metabolic processes, synergistically with Pgc1a and Pgc1b.

The novel coding region SNPs of PPARGC1A gene and their associations with growth traits in Chinese native cattle

The peroxisome proliferator-activated receptor gamma coactivator-1 alpha protein, encoded by the PPARGC1A gene, is a metabolic switch, which transcriptionally activates a complex pathway of mitochondrial biogenesis, lipid and glucose metabolism. Three SNPs (exon 3 c.396G>A, intron 9 c.1892 + 19C>T and exon 10 c.1971C>T) were found and identified in three Chinese native cattle breeds by PCR-SSCP, PCR-RFLP and DNA sequencing methods. All three populations had a low genetic diversity at SNP396 locus (PIC <0.25) while possessed a moderate genetic diversity at SNP1892 locus (0.25 < PIC < 0.5). Association study indicated that the synonymous mutation c.396G>A significantly associated with body weight and average daily gain in Nanyang cattle at the adult age (P < 0.05). Our investigation will not only extend the spectrum of genetic variation of bovine PPARGC1A gene, but also provide useful information for the marker assisted selection in beef cattle breeding program.

Polymorphisms in the Promoter Region of the Chinese Bovine PPARGC1A Gene

The peroxisome proliferator-activated receptor gamma coactivator-1 alpha protein, encoded by the PPARGC1A gene, plays an important role in energy homeostasis. The genetic variations within the PPARGC1A gene promoter region were scanned in 808 Chinese native bovines belonging to three cattle breeds and yaks. A total of 6 SNPs and one 4 bp insertion variation in the promoter region of the bovine PPARGC1A gene were identified: SNP -259 T>A, -301_-298insCTTT, -915 A>G, -1175 T>G, -1590 C>T, -1665 C>T and -1690 G>A, which are in the binding sites of some important transcription factors: sex-determining region Y (SRY), myeloid-specific zinc finger-1 (MZF-1) and octamer factor 1(Oct-1). It is expected that these polymorphisms may regulate PPARGC1A gene transcription and might have consequences at a regulatory level.

Defective regulation of adipose tissue autophagy in obesity

OBJECTIVES

Autophagy is a highly regulated process that has an important role in the control of a wide range of cellular functions, such as organelle recycling, nutrient availability and tissue differentiation. A recent study has shown an increased autophagic activity in the adipose tissue of obese subjects, and a role for autophagy in obesity-associated insulin resistance was proposed. Body mass reduction is the most efficient approach to tackle insulin resistance in over-weight subjects; however, the impact of weight loss in adipose tissue autophagy is unknown.

SUBJECTS

Adipose tissue autophagy was evaluated in mice and humans.

RESULTS

First, a mouse model of diet-induced obesity and diabetes was maintained on a 15-day, 40% caloric restriction. At baseline, markers of autophagy were increased in obese mice as compared with lean controls. Upon caloric restriction, autophagy increased in the lean mice, whereas it decreased in the obese mice. The reintroduction of ad libitum feeding was sufficient to rapidly reduce autophagy in the lean mice and increase autophagy in the obese mice. In the second part of the study, autophagy was evaluated in the subcutaneous adipose tissue of nine obese-non-diabetic and six obese-diabetic subjects undergoing bariatric surgery for body mass reduction. Specimens were collected during the surgery and approximately 1 year later. Markers of systemic inflammation, such as tumor necrosis factor-1α, interleukin (IL)-6 and IL-1β were evaluated. As in the mouse model, human obesity was associated with increased autophagy, and body mass reduction led to an attenuation of autophagy in the adipose tissue.

CONCLUSION

Obesity and caloric overfeeding are associated with the defective regulation of autophagy in the adipose tissue. The studies in obese-diabetic subjects undergoing improved metabolic control following calorie restriction suggest that autophagy and inflammation are regulated independently.