Effect of polymorphisms in the PPARGC1A gene on body fat in Asian Indians

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.

Relationships between maternal perfluoroalkyl substance levels, polymorphisms of receptor genes, and adverse birth outcomes in the Hokkaido birth cohort study, Japan

We assessed the associations between perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) levels in third trimester maternal serum, the maternal genotypes of genes encoding nuclear receptors, and birth outcomes. We studied a prospective birth cohort of healthy pregnant Japanese women (n = 372) recruited in Sapporo between July 2002 and October 2005. We analyzed PFOS and PFOA levels using liquid chromatography-tandem mass spectrometry and analyzed 13 single nucleotide polymorphisms (SNPs) of proliferator-activated receptor alpha, gamma, gamma coactivator 1A, delta, constitutive androstane receptor, liver X receptor alpha, and beta (LXRB) using real-time polymerase reaction (PCR). We employed multiple linear regression models to establish the influences of log₁₀-transformed PFOS and PFOA levels and maternal genotypes on birth size. In female infants, we identified interactions between PFOS levels, the maternal genotype of LXRB (rs1405655), and birth weight. The estimated mean changes in birth weight in response to PFOS levels, the maternal genotype LXRB (rs1405655)-TC/CC (compared to TT), and their interactions were -502.9 g (95 % confidence interval [CI] = -247.3, -758.5 g), -526.3 g (95 % CI = -200.7, -852.0 g), and 662.1 g (95 % CI = 221.0, 1,103.2 g; p_int = 0.003), respectively. Interactions between PFOS levels and the maternal genotype of LXRB (rs1405655) also significantly affected birth chest circumference and the Ponderal index (p_int = 0.037 and 0.005, respectively). Thus, interactions between PFOS levels and the maternal genotype of LXRB (rs1405655) affects birth sizes in female infants. We found that certain SNPs modify the effects of PFOS levels on birth size.

Genomic analysis to screen potential genes and mutations in children with non-syndromic early onset severe obesity: a multicentre study in Turkey

BACKGROUND

Obesity is a complex genetic-based pediatric disorder which triggers life-threatening conditions. Therefore, the understanding the molecular mechanisms of obesity has been a significant approach in medicine. Computational methods allow rapid and comprehensive pathway analysis, which is important for generation of diagnosis and treatment of obesity.

METHODS AND RESULTS

Aims of our study are to comprehensively investigate genetic characteristics of obesity in children with non-syndromic, early-onset (< 7 years), and severe obesity (BMI-SDS > 3) through computational approaches. First, the mutational analyses of 41 of obesity-related genes in 126 children with non-syndromic early-onset severe obesity and 76 healthy non-obese controls were performed using the next generation sequencing (NGS) technique, and the NGS data analyzed by using bioinformatics methods. Then, the relationship between pathogenic variants and anthropometric/biochemical parameters was further evaluated. Obtained results demonstrated that the 15 genes (ADIPOQ, ADRB2, ADRB3, IRS1, LEPR, NPY, POMC, PPARG, PPARGC1A, PPARGC1B, PTPN1, SLC22A1, SLC2A4, SREBF1 and UCP1) which directly related to obesity found linked together via biological pathways and/or functions. Among these genes, IRS1, PPARGC1A, and SLC2A4 stand out as the most central ones. Furthermore, 12 of non-synonymous pathogenic variants, including six novels, were detected on ADIPOQ (G90S and D242G), ADRB2 (V87M), PPARGC1A (E680G, A477T, and R656H), UCP1 (Q44R), and IRS1 (R302Q, R301H, R301C, H250P, and H250N) genes.

CONCLUSION

We propose that 12 of non-synonymous pathogenic variations detected on ADIPOQ, ADRB2, PPARGC1A, UCP1, and IRS1 genes might have a cumulative effect on the development and progression of obesity.

Associations between maternal mono-(2-ethylhexyl) phthalate levels, nuclear receptor gene polymorphisms, and fatty acid levels in pregnant Japanese women in the Hokkaido study

We assessed how the interaction between mono-(2-ethylhexyl) phthalate (MEHP) in maternal sera and the maternal genotypes associated with nuclear receptors affect fatty acid levels in a prospective birth cohort study of pregnant Japanese individuals (n = 437) recruited in Sapporo between 2002 and 2005. We analyzed MEHP and fatty acids using gas chromatography-mass spectrometry. Thirteen single nucleotide polymorphisms of peroxisome proliferator-activated receptor (PPAR) alpha, PPAR gamma (PPARG), PPARG coactivator 1A (PPARGC1A), PPAR delta, constitutive androstane receptor, liver X receptor (LXR) alpha, and LXR beta (LXRB) were analyzed using real-time PCR. Multiple linear regression models were used to confirm the influence of log₁₀-transformed MEHP levels and maternal genotypes on log₁₀-transformed fatty acid levels. When the effects of the interaction between MEHP levels and the maternal PPARGC1A (rs8192678) genotype on oleic acid levels were evaluated, the estimated changes (95 % confidence intervals) in oleic acid levels against MEHP levels, maternal PPARGC1A (rs8192678)-GA/AA genotype, and the interaction between them showed a mean reduction of 0.200 (0.079, 0.322), mean reduction of 0.141 (0.000, 0.283), and mean increase of 0.145 (0.010, 0.281), respectively, after adjusting for the perfluorooctanesulfonate level. The effects of the interaction between MEHP levels and maternal LXRB (rs2303044) genotype on linoleic acid levels was also significant (p_int = 0.010). In conclusion, the interaction between MEHP and the maternal genotypes PPARGC1A (rs8192678) and LXRB (rs2303044) decreased fatty acid levels. Further, the interaction between MEHP and PPARGC1A (rs8192678) may have a greater effect on fatty acid levels than the interaction between PFOS and PPARGC1A.

Pharmacogenomics and Personalized Medicine in Type 2 Diabetes Mellitus: Potential Implications for Clinical Practice

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes, and is rising in incidence with widespread prevalence. Multiple gene variants are associated with glucose homeostasis, complex T2DM pathogenesis, and its complications. Exploring more effective therapeutic strategies for patients with diabetes is crucial. Pharmacogenomics has made precision medicine possible by allowing for individualized drug therapy based on a patient's genetic and genomic information. T2DM is treated with various classes of oral hypoglycemic agents, such as biguanides, sulfonylureas, thiazolidinediones, meglitinides, DPP4 inhibitors, SGLT2 inhibitors, α-glucosidase inhibitors, and GLP1 analogues, which exhibit various pharmacogenetic variants. Although genomic interventions in monogenic diabetes have been implemented in clinical practice, they are still in the early stages for complex polygenic disorders, such as T2DM. Precision DM medicine has the potential to be effective in personalized therapy for those suffering from various forms of DM, such as T2DM. With recent developments in genetic techniques, the application of candidate-gene studies, large-scale genotyping investigations, genome-wide association studies, and "multiomics" studies has begun to produce results that may lead to changes in clinical practice. Enhanced knowledge of the genetic architecture of T2DM presents a bigger translational potential. This review summarizes the genetics and pathophysiology of T2DM, candidate-gene approaches, genome-wide association studies, personalized medicine, clinical relevance of pharmacogenetic variants associated with oral hypoglycemic agents, and paths toward personalized diabetology.

Associations among perfluorooctanesulfonic/perfluorooctanoic acid levels, nuclear receptor gene polymorphisms, and lipid levels in pregnant women in the Hokkaido study

The effect of interactions between perfluorooctanesulfonic (PFOS)/perfluorooctanoic acid (PFOA) levels and nuclear receptor genotypes on fatty acid (FA) levels, including those of triglycerides, is not clear understood. Therefore, in the present study, we aimed to analyse the association of PFOS/PFOA levels and single-nucleotide polymorphisms (SNPs) in nuclear receptors with FA levels in pregnant women. We analysed 504 mothers in a birth cohort between 2002 and 2005 in Japan. Serum PFOS/PFOA and FA levels were measured using liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. Maternal genotypes in PPARA (rs1800234; rs135561), PPARG (rs3856806), PPARGC1A (rs2970847; rs8192678), PPARD (rs1053049; rs2267668), CAR (rs2307424; rs2501873), LXRA (rs2279238) and LXRB (rs1405655; rs2303044; rs4802703) were analysed. When gene-environment interaction was considered, PFOS exposure (log₁₀ scale) decreased palmitic, palmitoleic, and oleic acid levels (log₁₀ scale), with the observed β in the range of - 0.452 to - 0.244; PPARGC1A (rs8192678) and PPARD (rs1053049; rs2267668) genotypes decreased triglyceride, palmitic, palmitoleic, and oleic acid levels, with the observed β in the range of - 0.266 to - 0.176. Interactions between PFOS exposure and SNPs were significant for palmitic acid (P_int = 0.004 to 0.017). In conclusion, the interactions between maternal PFOS levels and PPARGC1A or PPARD may modify maternal FA levels.

Genetic Variants in the Activation of the Brown-Like Adipocyte Pathway and the Risk for Severe Obesity

BACKGROUND

Regular physical activity has an important role in energy expenditure and combats the development of obesity. During exercise, PPARGC1A is overexpressed, stimulating an increase of the expression of FNDC5. This protein is cleaved to release the hormone irisin, which activates a browning process in white adipose tissue through an increase in UCP1 expression. As a result, irisin leads to mitochondrial heat production and energy expenditure.

OBJECTIVES

The aim of this study was to investigate whether genetic variants in genes related to browning are associated with severe obesity and obesity-related features. This case-control study comprised 210 individuals with severe obesity (median body mass index [BMI] 45.6 [range 40.5-52.2]) and 191 normal-weight subjects (BMI 22.8 [21.1-23.9]).

METHODS

Genomic DNA was extracted from peripheral blood and the genotypes of the PPARGC1A(rs8192678, rs3736265, rs2970847, and rs3755863) and UCP1 (rs6536991 and rs12502572) genes were obtained using Taqman® assay. For the FNDC5 gene, screening of exons 3-5 as well as their intron-exon boundaries was performed using automatic sequencing.

RESULTS

Our results demonstrated that PPARGC1Ars2970847 and UCP1rs12502572 are associated with severe obesity. Furthermore, these polymorphisms influence anthropometric traits, such as BMI, body weight, and body adiposity index. Our findings also showed a dose-effect relationship between PPARGC1A rs8192678 and fasting plasma glucose. Finally, 5 rare mutations were identified in FNDC5, and 1 of these is a novel missense mutation.

CONCLUSION

This study shows that genetic variants in the activation of brown-like adipocyte pathway play an important role in the susceptibility to severe obesity.

Peroxisome proliferator-activated receptor gamma coactivator 1α variation: a closer look at obesity onset age and its related metabolic status and body composition

There is a lack of knowledge regarding the effect of polymorphisms of the peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) gene on the age of obesity onset. Hence, 3 polymorphisms of the PGC-1α gene (PGC-1α rs17574213, rs8192678, and rs3755863) were examined in association with obesity onset age. Also, obesity onset age-related metabolic status and body composition were evaluated. This cross-sectional study was conducted with a total of 321 obese participants. Anthropometric and biochemical information, body composition, and PGC-1α gene sequences were analyzed. The rs17574213 polymorphism was associated with obesity onset in children aged <1 years and 10-18 years. The rs8192678 polymorphism was associated with obesity onset in adulthood. Body mass index, body fat percent, and trunk fat were higher in groups whose obesity began at age <1 year or 10-18 years than in other groups. Serum levels of high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol were lowest in the group with obesity onset between the ages of 10 and 18 years. Visceral fat and fasting blood glucose were highest in those whose obesity began in adulthood. In conclusion, 2 polymorphisms of the PGC-1α gene were associated with obesity onset age.

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.

Wider Perioperative Glycemic Fluctuations Increase Risk of Postoperative Acute Kidney Injury: A Prospective Cohort Study

Acute kidney injury (AKI) is a common complication after cardiac surgery. Recent studies have revealed emerging associations between the magnitude of acute glycemic fluctuations and intensive care unit (ICU) mortality rates. However, the effect of acute glycemic fluctuations on the development of postoperative AKI remains unclear. Thus, we aim to investigate the effect of the magnitude of acute perioperative glycemic fluctuations on the incidence of postoperative AKI.We conducted a prospective cohort study by prospectively obtaining data from all patients who underwent elective coronary artery bypass grafting in a tertiary heart institution from 2009 to 2011. The magnitude of the difference between the highest and lowest perioperative glucose levels within 48 hr was calculated as a measure of perioperative glycemic fluctuation. Patients were divided into 4 groups for analysis based on the magnitude of perioperative glycemic fluctuation-A: 0 to 2 mmol/L; B: >2 to 4 mmol/L; C: >4 to 6 mmol/L; and D: >6 mmol/L. We analyzed the incidence of postoperative AKI, ICU mortality and ICU length of stay as primary and secondary outcomes, respectively. Both univariate and multivariate analyses were used.We analyzed data from 1386 patients. The overall incidence of AKI was 29.9% and increased with wider glycemic fluctuation. The incidence of AKI was statistically highest in Group D (38.3%), followed by Groups C (28.6%), B (21.7%), and A (17.4%), respectively (P[REPLACEMENT CHARACTER]=[REPLACEMENT CHARACTER]0.001). A similar trend was observed among both diabetics and nondiabetics (P[REPLACEMENT CHARACTER]=[REPLACEMENT CHARACTER]0.001 and P[REPLACEMENT CHARACTER]=[REPLACEMENT CHARACTER]0.002, respectively). Multivariate logistic regression showed the magnitude of perioperative glycemic fluctuations to be an independent risk factor in the development of AKI (P < 0.001, odds ratio 1.180, 95% confidence interval 1.116-1.247). ICU length of stay was statistically highest in Group D (58.3[REPLACEMENT CHARACTER]hr) compared with Groups C (44.5[REPLACEMENT CHARACTER]hr), B (37.3[REPLACEMENT CHARACTER]hr), and A (32.8[REPLACEMENT CHARACTER]hr, P[REPLACEMENT CHARACTER]=[REPLACEMENT CHARACTER]0.003). ICU mortality rate was comparable among all 4 groups (P[REPLACEMENT CHARACTER]=[REPLACEMENT CHARACTER]0.172).Wide acute perioperative glycemic fluctuations should be avoided as they are associated with a significantly increased risk of AKI and ICU length of stay in both the diabetics and the nondiabetics.

Genetic variation in the peroxisome proliferator-activated receptor (PPAR) and peroxisome proliferator-activated receptor gamma co-activator 1 (PGC1) gene families and type 2 diabetes

We used a two-stage study design to evaluate whether variations in the peroxisome proliferator-activated receptors (PPAR) and the PPAR gamma co-activator 1 (PGC1) gene families (PPARA, PPARG, PPARD, PPARGC1A, and PPARGC1B) are associated with type 2 diabetes (T2D) risk. Stage I used data from a genome-wide association study (GWAS) from Shanghai, China (1019 T2D cases and 1709 controls) and from a meta-analysis of data from the Asian Genetic Epidemiology Network for T2D (AGEN-T2D). Criteria for selection of single nucleotide polymorphisms (SNPs) for stage II were: (1) P < 0.05 in single marker analysis in Shanghai GWAS and P < 0.05 in the meta-analysis or (2) P < 10(-3) in the meta-analysis alone and (3) minor allele frequency ≥ 0.10. Nine SNPs from the PGC1 family were assessed in stage II (an independent set of middle-aged men and women from Shanghai with 1700 T2D cases and 1647 controls). One SNP in PPARGC1B, rs251464, was replicated in stage II (OR = 0.87; 95% CI: 0.77-0.99). Gene-body mass index (BMI) and gene-exercise interactions and T2D risk were evaluated in a combined dataset (Shanghai GWAS and stage II data: 2719 cases and 3356 controls). One SNP in PPARGC1A, rs12640088, had a significant interaction with BMI. No interactions between the PPARGC1B gene and BMI or exercise were observed.

The prevalence of presarcopenia in Asian Indian individuals with and without type 2 diabetes

OBJECTIVE

This study compared the skeletal muscle mass and prevalence of presarcopenia between Asian Indian individuals with and without type 2 diabetes.

SUBJECTS AND METHODS

Participants with type 2 diabetes (n=76) and age- and sex-matched controls without diabetes (n=76) were drawn from the Chennai Urban Rural Epidemiological Study (CURES), which was carried out on a representative sample of Chennai City in South India. Skeletal muscle mass was estimated by dual-energy X-ray absorptiometry, and skeletal muscle mass index (SMI) was calculated by dividing the appendicular skeletal muscle mass by the square of the individual's height in meters and expressed as kg/m(2). Presarcopenia was defined as an SMI of ≤7.26 kg/m(2) for males and ≤5.5 kg/m(2) for females. Biochemical and anthropometric measurements were done using standardized procedures.

RESULTS

The 152 participants included 68 women (44.7%). Mean age was 44±9 years (range, 28-67 years), and the mean body mass index (BMI) was 25.7±3.8 kg/m(2). The prevalence rates of presarcopenia among individuals with and without diabetes were 39.5% and 15.8%, respectively (P=0.001). The mean SMI values were significantly lower in those with diabetes (6.84±1.02 kg/m(2)) compared with participants without diabetes (7.28±1.01 kg/m(2)) (P=0.009). SMI showed a positive correlation with BMI and waist circumference but a negative correlation with age, fasting plasma glucose, glycated hemoglobin, and low-density lipoprotien cholesterol in the total study population. Logistic regression analysis showed that diabetes was independently associated with presarcopenia (P=0.001).

CONCLUSIONS

Prevalence of presarcopenia is higher among Asian Indian subjects with type 2 diabetes compared with age- and sex-matched participants without diabetes.

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

AIMS/HYPOTHESIS

Bariatric surgery is currently employed as an effective approach to treat class III obesity and class II obesity with co-morbidities. Unfortunately, the general anthropometric and metabolic outcomes of the surgery are not homogeneous, and defining the eligibility criteria that allow for a more precise prediction of the outcomes of this invasive procedure will refine the selection of patients. Here we tested the hypothesis that the Gly482Ser polymorphism of the ppargc1a gene would predict different outcomes following bariatric surgery.

METHODS

Fifty-five patients (26 Gly/Gly and 29 Gly/Ser+Ser/Ser) selected for the Roux-en-Y gastric bypass according to the National Institutes of Health Consensus Statement criteria were followed up for 1 year, monitoring their anthropometric, metabolic and inflammatory parameters.

RESULTS

Patients with the Gly482Ser polymorphism had significantly improved reductions in the waist/hip ratio, fasting blood glucose, C-reactive protein, blood leukocyte count, serum interleukin-6 and intima-media thickness of the carotid artery, as compared with Gly/Gly patients.

CONCLUSIONS/INTERPRETATION

Thus, the Gly482Ser polymorphism may predict a more favorable metabolic and inflammatory outcome for obese patients submitted to bariatric surgery, leading to a reduced atherosclerotic risk.

GLUT4 gene polymorphisms and their association with type 2 diabetes in south Indians

BACKGROUND AND OBJECTIVES

The GLUT4 gene, which encodes glucose transporter 4, is a candidate gene for type 2 diabetes mellitus (T2DM). The aim of this study was to screen the GLUT4 gene for polymorphisms and to study association of such polymorphisms with T2DM in an Asian Indian population in southern India.

METHODS

The GLUT4 gene was sequenced in 25 normal glucose tolerance (NGT) and 25 T2DM subjects, and the variants found were then genotyped by polymerase chain reaction-restriction fragment length polymorphism in a pilot study population of 552 NGT and 643 T2DM subjects, randomly selected from the Chennai Urban Rural Epidemiology Study. Two of the variants (rs5435 and the novel variant), which showed significantly higher minor allele frequency in T2DM compared with NGT individuals in the pilot study population, were then retested with an additional 465 NGT and 363 T2DM subjects, giving a final sample size of 1,017 NGT and 1,006 T2DM subjects.

RESULTS

Sequencing of the GLUT4 gene revealed three known polymorphisms (rs5418, rs5421, and rs5435) and one novel T→G variant in the 3' untranslated region (UTR) at nucleotide position 6787483. The rs5418 and rs5421 polymorphisms did not show any association with diabetes. The rs5435 [Asn130Asn(C→T)] polymorphism was found to be associated with diabetes, with the odds ratio for the CT+TT genotype being 1.26 (95% confidence interval, 1.00-1.57; P=0.043) when the CC genotype was taken as reference. The frequency of the TG genotype of the novel 3'UTR T→G variant was significantly higher in diabetes subjects (1%) compared with NGT subjects (0.2%) (P=0.021). There was a significant difference in the proportion of the ACGT haplotype of the rs5418(A→G), rs5435(C→T), rs5421(C→G), and the T→G 3'UTR variant between the NGT (7.5%) and diabetes (5%) groups (P=0.003).

CONCLUSION

The rs5435 (C→T) polymorphism of the GLUT4 gene is associated with type 2 diabetes in this south Indian population.

Association of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) gene polymorphisms and type 2 diabetes mellitus: a meta-analysis

BACKGROUND

The association between peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) polymorphisms and type 2 diabetes mellitus (T2DM) has been investigated in several studies, but these studies yielded contradictory results. We conducted a meta-analysis to assess the association between three polymorphisms (Gly482Ser, Thr394Thr and Thr612Met) in PPARGC1A and T2DM.

METHODS

A literature-based search was conducted to collect data. The additive model was chosen to investigate the association between the three polymorphisms and T2DM. The random effects model was used if there was heterogeneity between studies. In addition, subgroup meta-analyses were made according to the ethnic groups.

RESULTS

Twenty-three studies were enrolled in this meta-analysis (7539 cases and 9562 controls for Gly482Ser, 1818 cases and 2376 controls for Thr394Thr, 2042 cases and 1289 controls for Thr612Met). In the combined analysis of all eligible studies, a significant association was found between Gly482Ser, Thr394Thr and T2DM with pooled odds ratios 1.19 [95% confidence interval (CI) 1.05-1.34] and 1.33 (95% CI 1.04-1.70), respectively, but great heterogeneity was found between studies. In the subgroup meta-analyses, we found that Gly482Ser and Thr394Thr polymorphisms were associated with the risk of T2DM, and the pooled odds ratios were 1.66 (95% CI 1.28-2.15) and 1.72 (95% CI 1.45-2.03), respectively, in the Indian population; no significant evidence was found in the Caucasian and East Asian populations.

CONCLUSIONS

This meta-analysis indicated that Gly482Ser and Thr394Thr polymorphisms of PPARGC1A gene were significantly associated with the risk of T2DM, especially in the Indian population. No relationship was found between the Thr612Met and risk of T2DM.

Testing the thrifty gene hypothesis: the Gly482Ser variant in PPARGC1A is associated with BMI in Tongans

Background

The thrifty gene hypothesis posits that, in populations that experienced periods of feast and famine, natural selection favoured individuals carrying thrifty alleles that promote the storage of fat and energy. Polynesians likely experienced long periods of cold stress and starvation during their settlement of the Pacific and today have high rates of obesity and type 2 diabetes (T2DM), possibly due to past positive selection for thrifty alleles. Alternatively, T2DM risk alleles may simply have drifted to high frequency in Polynesians. To identify thrifty alleles in Polynesians, we previously examined evidence of positive selection on T2DM-associated SNPs and identified a T2DM risk allele at unusually high frequency in Polynesians. We suggested that the risk allele of the Gly482Ser variant in the PPARGC1A gene was driven to high frequency in Polynesians by positive selection and therefore possibly represented a thrifty allele in the Pacific.

Methods

Here we examine whether PPARGC1A is a thrifty gene in Pacific populations by testing for an association between Gly482Ser genotypes and BMI in two Pacific populations (Maori and Tongans) and by evaluating the frequency of the risk allele of the Gly482Ser variant in a sample of worldwide populations.

Results

We find that the Gly482Ser variant is associated with BMI in Tongans but not in Maori. In a sample of 58 populations worldwide, we also show that the 482Ser risk allele reaches its highest frequency in the Pacific.

Conclusion

The association between Gly482Ser genotypes and BMI in Tongans together with the worldwide frequency distribution of the Gly482Ser risk allele suggests that PPARGC1A remains a candidate thrifty gene in Pacific populations.

A haplotype at the UCP1 gene locus contributes to genetic risk for type 2 diabetes in Asian Indians (CURES-72)

BACKGROUND

The gene encoding for uncoupling protein-1 (UCP1) is considered to be a candidate gene for type 2 diabetes because of its role in thermogenesis and energy expenditure. The objective of the study was to examine whether genetic variations in the UCP1 gene are associated with type 2 diabetes and its related traits in Asian Indians.

METHODS

The study subjects, 810 type 2 diabetic subjects and 990 normal glucose tolerant (NGT) subjects, were chosen from the Chennai Urban Rural Epidemiological Study (CURES), an ongoing population-based study in southern India. The polymorphisms were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Linkage disequilibrium (LD) was estimated from the estimates of haplotypic frequencies.

RESULTS

The three polymorphisms, namely -3826A-->G, an A-->C transition in the 5'-untranslated region (UTR) and Met229Leu, were not associated with type 2 diabetes. However, the frequency of the A-C-Met (-3826A-->G-5'UTR A-->C-Met229Leu) haplotype was significantly higher among the type 2 diabetic subjects (2.67%) compared with the NGT subjects (1.45%, P < 0.01). The odds ratio for type 2 diabetes for the individuals carrying the haplotype A-C-Met was 1.82 (95% confidence interval, 1.29-2.78, P = 0.009).

CONCLUSIONS

The haplotype, A-C-Met, in the UCP1 gene is significantly associated with the increased genetic risk for developing type 2 diabetes in Asian Indians.

Association and interaction of PPAR-complex gene variants with latent traits of left ventricular diastolic function

Background

Abnormalities in myocardial metabolism and/or regulatory genes have been implicated in left ventricular systolic dysfunction. However, the extent to which these modulate left ventricular diastolic function (LVDF) is uncertain.

Methods

Independent component analysis was applied to extract latent LVDF traits from 14 measured echocardiography-derived endophenotypes of LVDF in 403 Caucasians. Genetic association was assessed between measured and latent LVDF traits and 64 single nucleotide polymorphisms (SNPs) in three peroxisome proliferator-activated receptor (PPAR)-complex genes involved in the transcriptional regulation of fatty acid metabolism.

Results

By linear regression analysis, 7 SNPs (4 in PPARA, 2 in PPARGC1A, 1 in PPARG) were significantly associated with the latent LVDF trait, whereas a range of 0-4 SNPs were associated with each of the 14 measured echocardiography-derived endophenotypes. Frequency distribution of P values showed a greater proportion of significant associations with the latent LVDF trait than for the measured endophenotypes, suggesting that analyses of the latent trait improved detection of the genetic underpinnings of LVDF. Ridge regression was applied to investigate within-gene and gene-gene interactions. In the within-gene analysis, there were five significant pair-wise interactions in PPARGC1A and none in PPARA or PPARG. In the gene-gene analysis, significant interactions were found between rs4253655 in PPARA and rs1873532 (p = 0.02) and rs7672915 (p = 0.02), both in PPARGC1A, and between rs1151996 in PPARG and rs4697046 in PPARGC1A (p = 0.01).

Conclusions

Myocardial metabolism PPAR-complex genes, including within and between genes interactions, may play an important role modulating left ventricular diastolic function.

Gly482Ser polymorphism in the peroxisome proliferator-activated receptor gamma coactivator-1alpha gene is associated with oxidative stress and abdominal obesity

The objective of the study was to o investigate the relationship of the Gly482Ser (G482S) polymorphism in the peroxisome proliferator-activated receptor gamma coactivator-1alpha (PPARGC1A) gene and type 2 diabetes mellitus (T2DM), obesity, and oxidative status in Chinese adults. We enrolled 276 T2DM patients and 1049 nondiabetic subjects aged at least 35 years. The G482S variant was detected using polymerase chain reaction and restriction enzyme digestion. The levels of thiobarbituric acid reactive substance, an indicator of lipid peroxidation, were measured in plasma samples. The homeostasis model assessment-estimated insulin resistance (HOMA-IR) index was determined for nondiabetic subjects. P values were adjusted for age, sex, and body mass index by using a generalized linear model. In this series, there was no association between G482S polymorphism and T2DM and obesity (body mass index >25 kg/m(2)). However, the plasma fasting insulin levels and HOMA-IR indices were significantly higher in nondiabetic subjects harboring the variant (S/S) genotype than in those with the heterozygous (G/S) genotype. With regard to the effect of the different genotypes on body fat distribution, overweight nondiabetic subjects harboring the S/S or G/S genotype had a significantly higher waist-to-hip ratio than those with the wild-type (G/G) genotype. Furthermore, subjects with the S/S genotype had significantly higher serum thiobarbituric acid reactive substance levels than those with the G/G genotype; the diabetic group mainly contributed to this significant association (P < .001). In overweight, nondiabetic Chinese adults, G482S polymorphism in the PPARGC1A gene is associated with hyperinsulinemia, HOMA-IR indices, and abdominal obesity. Furthermore, in hyperglycemia, the S482 allele is related to increased oxidative stress.

The PPARGC1A Gly482Ser polymorphism is associated with left ventricular diastolic dysfunction in men

Background

The Gly482Ser polymorphism in peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PPARGC1A) has been demonstrated to be associated with diabetes, obesity and hypertension, all of which are important risk factors for left ventricular diastolic dysfunction.

Methods

The PPARGC1A Gly482Ser polymorphism was genotyped in a community-based cohort of 499 men and 533 women, who also underwent an echocardiographic examination to determine their left ventricular diastolic function. The association between the polymorphism and the presence of diastolic dysfunction was evaluated using logistic regression models.

Results

The Ser allele of the PPARGC1A Gly482Ser polymorphism was significantly associated with a lower risk of diastolic dysfunction in men, but not in women. In a model adjusting for potential confounders (age, body mass index, leisure time physical activity, hypertension and diabetes) the results were still significant and substantial (odds ratio 0.13, 95% confidence interval 0.03–0.54, p for trend = 0.004). The results were consistent in a series of models, and they imply a multiplicative, protective effect of the Ser allele, with lower risk of diastolic dysfunction for each copy of the allele.

Conclusion

The Ser allele of the PPARGC1A Gly482Ser polymorphism was associated with decreased risk of diastolic left ventricular dysfunction in men, but not in women, in our large community-based sample. It was associated with a substantially decreased risk, even after adjustment for potential confounders. The clinical importance of the findings has to be established in further studies.

Association between PPARGC1A gene polymorphisms and coronary artery disease in a Chinese population

Peroxisome proliferrator-activated receptor gamma coactivator-1alpha (PGC-1alpha; PPARGC1A) is a coactivator of the nuclear hormone receptor family that participates in the transcriptional programme of lipid metabolism and oxidative stress implicated in atherogenesis. Therefore, in the present study, we investigated PPARGC1A polymorphisms in the prevalence of coronary artery disease (CAD). A case-control study comprising 342 patients with CAD and 334 controls was performed in a Chinese population. Two single nucleotide polymorphisms (Gly482Ser and Thr394Thr) in the PPARGC1A gene were genotyped and compared using the polymerase chain reaction-restriction fragment length polymorphism method. The XA (GA + AA) genotype of Gly482Ser displayed a higher frequency in CAD patients than that in control subjects (P = 0.019; adjusted odds ratio = 1.53; 95% confidence interval 1.06-2.20). No significant difference in Thr394Thr genotype distribution or in Gly482Ser-Thr394Thr haplotype combinations was found between CAD patients and controls. Furthermore, we found that the significantly increased risk of CAD associated with the XA genotypes of Gly482Ser was more evident among subjects who were younger than 64 years of age, female, overweight and with hypertension. The results indicate that the PPARGC1A Gly482Ser polymorphism may contribute to the risk of CAD in the Chinese population investigated.

Candidate genes for obesity revealed from a C57BL/6J x 129S1/SvImJ intercross

OBJECTIVE

To identify the genes controlling body fat, we carried out a quantitative trait locus (QTL) analysis using C57BL/6J (B6) and 129S1/SvImJ (129) mice, which differ in obesity susceptibility after consuming an atherogenic diet.

METHODS

Mice were fed chow until 8 weeks and an atherogenic diet from 8 to 16 weeks; body fatness was measured by X-ray absorptiometry in 528 (B6 x 129) F(2) at 8 and 16 weeks. A high-density genome scan was performed using 508 polymorphic markers. After identifying the genetic loci, we narrowed the QTL using comparative genomics and bioinformatics.

RESULTS

The percentage of body fat was significantly linked to loci on chromosomes (Chr) 1 (22, 68 and 173 Mb), 4 (74 Mb), 5 (73 Mb), 7 (88 Mb), 8 (43 and 80 Mb), 9 (55 Mb), 11 (115 Mb) and 12 (32 Mb); three suggestive loci on Chrs 6 (76 Mb), 9 (30 Mb) and 16 (26 Mb) and two pairs of interacting loci (Chr 2 at 99.8 Mb with Chr 7; Chr 1 at 68 Mb with Chr 11). Comparative genomics narrowed the QTL intervals by 20-57% depending on the chromosome; in most cases, haplotype analysis further narrowed them by about 90%.

CONCLUSIONS

Our analysis identified 15 QTL for percentage of body fat. We narrowed the QTL using comparative genomics and haplotype analysis and suggest several candidate genes: Apcs on Chr 1, Ppargc1a on Chr 5, Ucp1 on Chr 8, Angptl6 on Chr 9 and Lpin1 on Chr 12.

Is there an association between PPARGC1A genotypes and endurance capacity in Chinese men?

Our purpose was to determine the possible association between genotypes of three polymorphisms (Gly482Ser, Thr394Thr and A2962G) of the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) gene, on one hand, and both the pre- (baseline) and post-training levels of maximal (i.e., maximal oxygen uptake [VO2max]) and submaximal human endurance capacity (i.e., running economy [RE]). We studied 102 young males (physically active, non-athletes; age: 19+/-1 yrs) from Northern China (of Han origin) who underwent a 18-week endurance training (running) program and were tested on a treadmill (for VO2max and RE determination) before and after training. None of the VO2max and RE related traits were associated with the Gly482Ser and Thr394Thr polymorphisms at baseline or after training. The A2962G polymorphism was however associated with VO2max at baseline, as carriers of the G allele (AG+GG genotypes; n=49) had higher levels of VO2max than the AA group (n=53) (58.2+/-4.3 vs 56.3+/-3.9 mL/kg/min; P=0.017). Our results do not support previous data on Caucasians showing an association between the Gly482Ser variant and VO2max but suggest the potential role of another polymorphism (A2962G) to explain individual VO2max differences in Chinese men.

Medical sequencing at the extremes of human body mass

Body weight is a quantitative trait with significant heritability in humans. To identify potential genetic contributors to this phenotype, we resequenced the coding exons and splice junctions of 58 genes in 379 obese and 378 lean individuals. Our 96-Mb survey included 21 genes associated with monogenic forms of obesity in humans or mice, as well as 37 genes that function in body weight-related pathways. We found that the monogenic obesity-associated gene group was enriched for rare nonsynonymous variants unique to the obese population compared with the lean population. In addition, computational analysis predicted a greater fraction of deleterious variants within the obese cohort. Together, these data suggest that multiple rare alleles contribute to obesity in the population and provide a medical sequencing-based approach to detect them.

Polymorphisms of the peroxisome proliferator-activated receptor-γ coactivator-1α gene are associated with hypertrophic cardiomyopathy and not with hypertension hypertrophy

BACKGROUND

The clinical phenotype of both hypertrophic cardiomyopathy (HCM) and left ventricular hypertrophy (LVH) induced by hypertension is heterogeneous. Genetic factors may contribute to this heterogeneity. Evidence is accumulating that the peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) gene plays a role in cardiac hypertrophy. The aim of our study was to identify the association between PGC-1alpha gene polymorphisms and cardiac hypertrophy.

METHODS

A total of 270 consecutive HCM patients and 2486 hypertensive patients, comprising 1180 with LVH and 1306 without LVH, as well as 894 healthy controls, were successfully investigated. Polymorphisms of the PGC-1alpha gene were genotyped by PCR-restriction fragment length polymorphism and confirmed by sequencing.

RESULTS

The Ser482 allele (rs8192678 G>A and A>A) and CC genotype of Thr394Thr (rs2970847) conferred increased risk for HCM [odds ratio (OR) 1.52, 95% confidence interval (CI) 1.11-2.11; OR 1.49, 95% CI 1.15-1.98, respectively]. The maximum ventricular thickness was greater in HCM patients carrying the Ser482 risk allele than in carriers of the non-risk allele (20.7+/-4.1 vs. 19.1+/-4.3 mm, p<0.05) and for the CC Thr394Thr genotype (20.9+/-4.6 vs. 19.0+/-4.2 mm, p<0.05). No association was found between PGC-1alpha polymorphism and hypertension with or without LVH.

CONCLUSIONS

Our data indicate that variants of the PGC-1alpha gene are correlated with increased risk for HCM.