Peroxisome proliferator-activated receptor-γ2 Pro12Ala polymorphism is associated with reduced risk for ischemic stroke with type 2 diabetes

Association between PPAR polymorphisms and neurological functional disability of ischemic stroke

Peroxisome proliferator-activated receptor-γ (PPARγ) plays a protective role against brain injury after stroke in mice. However, the relationship between PPARγ gene polymorphisms and the functional outcome of acute ischemic stroke (AIS) remains unknown. 8822 patients from The Third China National Stroke Registry (CNSR-III) after whole-genome sequencing, two functional single nucleotide polymorphisms(SNPs) in PPARγ, rs1801282 C > G and rs3856806 C > T, were further analysed. The primary outcome was neurological functional disability at three months. Of the 8822 patients, 968 (11.0%) and 3497 (39.6%) were carriers of rs1801282 and rs3856806, respectively. Carriers of rs3856806 showed reduced risks for three-month neurological functional disability (OR, 0.84; 95% CI, 0.73-0.98; p = 0.02) and reduced risks for higher infarct volume (OR 0.90, 95% CI, 0.81-0.99, p = 0.04). They also had a reduced risk of neurological functional disability only in case of lower baseline IL-6 levels (OR 0.64, 95% CI 0.48-0.84, Pinteraction = 0.01). Carriers of rs1801282 had a reduced risk for three-month neurological functional disability (OR 0.77, 95% CI, 0.61-0.99, p = 0.04). Our study suggested that PPARγ polymorphisms are associated with a reduced risk for neurological functional disability and higher infarct volume in AIS. Therefore, PPARγ can be a potential therapeutic target in AIS.

Peroxisome proliferator-activated receptor γ Pro12 ala polymorphism and risk of cerebral stroke in type 2 diabetes mellitus egyptian patients

Objectives

This study aimed to analyze the association of the peroxisome proliferator activated receptor gamma (PPARγ) P12A (rs1801282) polymorphism with development of cerebral stroke in patients with type 2 diabetes mellitus.

Methods

We included 224 patients with diabetes, they were categorized into116 patients with ischemic stroke (IS) and 108 without IS, in addition to 148 healthy controls in this study. respectively. Anthropometric parameters and laboratory tests were measured. The polymorphism was detected by a PCR-RFLP method.

Results

A12 allele and A12 containing genotypes show significant higher percentage in patients with diabetes and IS in comparison to diabetes patients without IS (9.1 vs. 4.2%,16.4 vs7.4%; P = 0.044,0.044) with OR of 2.29 and 2. 449 respectively (95% CI: 1.024-5.115, 1.024-5.856) but does not withstand Bonferroni correction.

Conclusion

A12 containing genotypes and A12 allele are not associated with IR, diabetes and risk of IS development, however, significant higher BMI were observed in A12 allele carriers in the studied patients with diabetes as well as those with IS.

Moderating effect of ppar-γ on the association of c-reactive protein and ischemic stroke in patients younger than 60

AIM

The aim of this study was to evaluate the moderating effect of peroxisome proliferator activated receptor-γ (PPAR-γ) gene variants on the association of serum C-reactive protein level (CRP) and ischemic stroke (IS).

MATERIAL AND METHODS

A total of 114 patients with IS and 135 healthy controls were included.

RESULTS

After adjustment for age, sex, total cholesterol, LDL and HDL cholesterol, triglycerides, hypertension, smoking, body mass index and previous therapy with antihypertensive and/or statins, PPAR-γ had statistically significant moderating effect on association of serum CRP level and IS in patients younger than 60. In participants with PPAR CG or GG genotype level of CRP and IS were not statistically significantly associated (OR = 1.00; 95% CI 0.90-1.10; p = 0.933), but in participants with PPAR CC genotype, the association of serum CRP level and IS was significant (OR = 1.67; 95% CI 1.21-2.31; p = 0.002).

CONCLUSION

In patients with PPAR CC genotype the association of serum CRP level and IS was significant.

Relationship between PPAR-γ gene polymorphisms and ischemic stroke risk: A meta-analysis

BACKGROUND

Published researches have suggested some associations between PPAR-γ and ischemic stroke (IS) development. This meta-analysis was conducted to evaluate the association between PPAR-γ gene polymorphisms and IS risk.

MATERIALS AND METHODS

A systematic search was conducted in PubMed, Embase, Web of Science, China National Knowledge Infrastructure, and WanFang databases. The pooled association of odd ratios (ORs) and its 95% confidence interval (CI) was calculated to assess the IS risk of PPAR-γ rs1801282 C/G and rs3856806 C/T polymorphisms. Furthermore, the heterogeneity test, cumulative analyses, sensitivity analyses, and publication bias were conducted.

RESULT

Sixteen publications with 3786 cases and 5343 controls were identified. Overall findings indicated that rs1801282 C/G polymorphism may be associated with an increased risk for IS (GG vs. CC: OR = 2.17 95%CI = 1.09-4.35, p = .03, I²  = 0%; GG vs. CC+CG: OR = 2.15, 95%CI = 1.07-4.32, p = .03, I²  = 0%). The similar results were also found in the subgroup analysis. In addition, no significant association was observed between rs3856806 C/T polymorphism and IS risk.

CONCLUSION

In conclusion, our study showed that PPAR-γ rs1801282 C/G polymorphism probably plays an important role in IS occurrence. The result should be verified with more studies in the future.

Role of TCF7L2 and PPARG2 Gene Polymorphisms in Renal and Cardiovascular Complications among Patients with Type 2 Diabetes: A Cohort Study

BACKGROUND

The emerging renal and cardiovascular complications of type 2 diabetes (T2DM) genetics involves differently assembled gene variants including transcription factor 7-like 2 (TCF7L2) and peroxisome proliferator-activated receptor gamma 2 (PPARG2) polymorphisms. However, the relevance of these genes for complication prediction has not been extensively tested.

METHODS

We analyzed the SNP rs7903146 variants in TCF7L2 and PPARG2 gene polymorphisms for their contribution to the incidence of chronic kidney disease (CKD) and cardiovascular complications in a prospective cohort study. All T2DM patients were followed up to estimate the glomerular filtration rate and cardiovascular outcomes. Cox proportional hazards regression models were used to estimate the genotype effect on the incidence of CKD and vascular complications.

RESULTS

A total of 422 patients were included. SNP rs7903146 variants in the TCF7L2 gene were classified into 3 groups: CC, 385 patients (91.2%), CT, 32 patients (7.6%), and TT, 5 patients (1.2%), while in the PPARG2 gene they were classified into 2 groups: Pro12Pro, 404 patients (95.7%) and Pro12Ala, 18 patients (4.3%). The prevalence of CKD, cardiovascular disease, and death at the end of the 5-year follow-up was 16.8, 29, and 7.9%, respectively. The Pro12Ala variant of the PPARG2 gene was significantly associated with increased CKD risk at the end of the study (adjusted HR 3.45, 95% CI 1.01-11.77, p = 0.046); it showed a significant association with increased cerebrovascular risk, but not cardiovascular disease and mortality. No genotype effect of rs7903146 in the TCF7L2 gene was apparent on renal and cardiovascular complications, except the TT variant of rs7903146 increased cardiovascular events when compared with the non-TT variant.

CONCLUSION

The findings of our study were that the Pro12Ala variant in the PPARG2 gene was associated with risk of developing CKD and cerebrovascular disease in Asian T2DM subjects in a prospective cohort study. The TCF7L2 polymorphism was not associated with cardiovascular outcomes.

Association between PPARs Gene Functional Polymorphisms and Ischemic Stroke in Chinese Uyghur Population

PPARγ and PPARα belong to a receptor family of ligand-activated transcription factors involved in the regulation of inflammation, cellular glucose uptake, protection against atherosclerosis and endothelial cell function. Through these effects, they might be involved with the ischemic stroke (IS). We recruited 100 IS patients diagnosed by CTs or/and magnetic resonance imaging (MRI) and 100 normal healthy controls from Chinese Uyghur Population to assess the nature of the functional polymorphisms of PPARs and any links with IS in this unique population which has 60% European ancestry and 40% East Asian ancestry. We found that the Ala allele of the PPARγ Pro12Ala polymorphism was more common in controls than IS subjects (P = 0.008, corrected for multiple testing) in the Uyghur Population. Pro/Ala carriage may be associated with a decreased risk of IS in Uyghurs (OR 0.542, 95% CI 0.346-0.850). Additionally, the 162Val allele frequency at the DNA-binding region of PPARα was extremely rare in Chinese Uguhur IS patients and controls. Our population and ethnic-based study demonstrates that the 162Val allele frequency was extremely low in the Chinese Uyghur Population different from Some European and African populations and the PPARγ 12 Pro/Ala resulting in an amino acid exchange in N-terminal sequence may be an independent protective factor for IS in the Chinese Uyghur Population.

Association between PPARG genetic polymorphisms and ischemic stroke risk in a northern Chinese Han population: a case-control study

Two common polymorphisms of the peroxisome proliferator-activated receptor gamma (PPARG) gene, rs1801282 and rs3856806, may be important candidate gene loci affecting the susceptibility to ischemic stroke. This case-control study sought to identify the relationship between these two single-nucleotide polymorphisms and ischemic stroke risk in a northern Chinese Han population. A total of 910 ischemic stroke participants were recruited from the First Hospital of China Medical University, Shenyang, China as a case group, of whom 895 completed the study. The 883 healthy controls were recruited from the Health Check Center of the First Hospital of China Medical University, Shenyang, China. All participants or family members provided informed consent. The study protocol was approved by the Ethics Committee of the First Hospital of China Medical University, China on February 20, 2012 (approval No. 2012-38-1). The protocol was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559). Plasma genomic DNA was extracted from all participants and analyzed for rs1801282 and rs3856806 single nucleotide polymorphisms using a SNaPshot Multiplex sequencing assay. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression to estimate the association between ischemic stroke and a particular genotype. Results demonstrated that the G allele frequency of the PPARG gene rs1801282 locus was significantly higher in the case group than in the control group (P < 0.001). Individuals carrying the G allele had a 1.844 fold increased risk of ischemic stroke (OR = 1.844, 95% CI: 1.286-2.645, P < 0.001). Individuals carrying the rs3856806 T allele had a 1.366 fold increased risk of ischemic stroke (OR = 1.366, 95% CI: 1.077-1.733, P = 0.010). The distribution frequencies of the PPARG gene haplotypes rs1801282-rs3856806 in the control and case groups were determined. The frequency of distribution in the G-T haplotype case group was significantly higher than that in the control group. The risk of ischemic stroke increased to 2.953 times in individuals carrying the G-T haplotype (OR = 2.953, 95% CI: 2.082-4.190, P < 0.001). The rs1801282 G allele and rs3856806 T allele had a multiplicative interaction (OR = 3.404, 95% CI: 1.631-7.102, P < 0.001) and additive interaction (RERI = 41.705, 95% CI: 14.586-68.824, AP = 0.860; 95% CI: 0.779-0.940; S = 8.170, 95% CI: 3.772-17.697) on ischemic stroke risk, showing a synergistic effect. Of all ischemic stroke cases, 86% were attributed to the interaction of the G allele of rs1801282 and the T allele of rs3856806. The effect of the PPARG rs1801282 G allele on ischemic stroke risk was enhanced in the presence of the rs3856806 T allele (OR = 8.001 vs. 1.844). The effect of the rs3856806 T allele on ischemic stroke risk was also enhanced in the presence of the rs1801282 G allele (OR = 2.546 vs. 1.366). Our results confirmed that the G allele of the PPARG gene rs1801282 locus and the T allele of the rs3856806 locus may be independent risk factors for ischemic stroke in the Han population of northern China, with a synergistic effect between the two alleles.

Association between PRO12ALA polymorphism of the PPAR-γ2 gene and type 2 diabetes mellitus in Iranian patients

BACKGROUND:

Peroxisome proliferator-activated receptor (PPARs) have been identified as ligand-activated transcription factors that belong to the nuclear receptor superfamily. It has been shown that an association exists between Proline 12 alanine (Pro12Ala) polymorphism of PPAR-GAMMA2 (PPAR-γ2) gene and increased risk of type 2 diabetes mellitus (T2DM) in different populations. Therefore, the present study was designed to investigate the association between Pro12Ala polymorphism of PPAR-γ2 gene and T2DM in an Iranian population.

MATERIALS AND METHODS:

Two hundred unrelated people, including 100 healthy controls and 100 diabetic patients were recruited diagnosed based on American Diabetes Association criteria. Blood samples were used for isolation of genomic deoxyribonucleic acid (DNA). Having extracted the genomic DNA from human blood leukocytes by means of High Pure polymerase chain reaction (PCR) Template preparation kit, we carried out polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) on each blood sample. Then, Genomic DNA was digested by BstU-I restriction enzyme. Thereafter, restriction products were analyzed by means of Polyacrylamide gel electrophoresis and stained by Ethidium Bromide.

RESULTS:

We found that the frequency of Ala allele in healthy subjects was significantly higher than in diabetic subjects (P = 0003). Moreover, the genotype frequency of Ala/Ala in healthy subjects was significantly higher than in diabetic subjects (P < 0.001). However, the genotype frequency of Ala/Pro in diabetic subjects was significantly higher than in healthy subjects (P < 0.001).

CONCLUSION:

The present study suggests that polymorphism of PPAR-γ2 gene is associated with T2DM. Furthermore, Ala allele is significantly found in non-diabetic individual’s Iranian population.

Genetic determinants of obesity and related vascular diseases

Obesity is one of the major risk factors of vascular diseases, and its prevalence is increasing worldwide. In the past decade, progress has been made in the understanding of genetic determinants of obesity and obesity-associated diseases. Genome-wide association studies identified a number of genetic variants associated with obesity. In addition to common variants, FTO and MC4R, new loci, such as TMEM18, KCTD15, GNPDA2, SH2B1, MTCH2, and NEGR1 have been detected. In the past years, abdominal obesity has been shown to be a more important vascular risk factor than the body mass index. In the context of vascular risk assessment, identification of genetic polymorphisms associated with accumulation of visceral fat is of special importance. Some polymorphisms associated with abdominal obesity, such as variants of gene encoding microsomal triglyceride transfer protein, have been already discovered. In this chapter, we provide a review of genetic determinants of obesity and discuss their role in obesity-related vascular diseases.

Role of PPARg2 transcription factor in thiazolidinedione-induced insulin sensitization

OBJECTIVES

Adipose tissue is the key regulator of energy balance, playing an active role in lipid storage and metabolism and may be a dynamic buffer to control fatty acid flux. Peroxisome proliferator-activated receptor gamma isoform-2 (PPARg2), an isoform of the nuclear hormone receptor superfamily, has been implicated in almost all aspects of human metabolic alterations such as obesity, insulin resistance, type-2 diabetes and dyslipidaemia. The PPARg2 isoform is highly present in adipose tissue where it functions as a thrifty phenotype, which promotes adipocyte differentiation and triglyceride storage. Thiazolidinediones, antidiabetic drugs, induce insulin sensitivity by controlling adipokines. The thiazolidinediones bind with PPARg2 in adipocytes and exert an agonist effect by enhancing adipogenesis and fatty acid uptake. Thiazolidinediones stimulate PPARg2, by which they down-regulate tumour necrosis factor-α, leptin, interleukin-6 and plasminogen and also enhance insulin sensitivity. The aim of this work is to define role of PPARg2 transcription factor in thiazolidinedione-induced insulin sensitization.

KEY FINDINGS

The PPARg2 alters the transcription of the target gene. This altered gene transcription results in the up-regulation of insulin-sensitizing factors and down-regulation of insulin-resistant factors. The variant Pro12Ala of the PPARg2 gene is an important modulator in metabolic control in the body. Thiazolidinediones stimulate PPARg2 transcription factor by which PPARg2 binds to responsive elements located in the promoter regions of many genes and modulates their transcriptive activity. There is a strong mutual relationship between receptor binding and agonism, which is evidence of the insulin-sensitizing target of thiazolidinediones in PPARg2. This evidently increases the biological potency of the glucose-lowering effect of thiazolidinediones in vivo as well as their antidiabetic activity.

CONCLUSIONS

PPARg2 transcription factor plays an important role in treatment of type-2 diabetes with thiazolidindiones. The variant Pro12Ala of the PPARg2 gene promotes the activity of thiazolidinediones in minimizing insulin resistance. Transcriptional activity of Pro12Ala variant improves the activity of insulin. Thus thiazolidinediones promote the phosphorylation of PPARg2 to induce insulin sensitivity.

Evaluation of the obesity genes FTO and MC4R and the type 2 diabetes mellitus gene TCF7L2 for contribution to stroke risk: The Mannheim-Heidelberg Stroke Study

OBJECTIVE

Studies evaluating genetic markers for vascular risk and risk of stroke are limited, and none of them evaluated obesity genes. The objective was to investigate the genetic markers related to obesity genes FTO and MC4R and the gene of type 2 diabetes mellitus TCF7L2 for their contribution to risk of stroke and transient ischemic attacks (TIA).

METHODS

We recruited 379 consecutive patients with stroke/TIA and 379 healthy population-based controls. The single-nucleotide polymorphisms (SNPs) rs9937053 (FTO), rs2229616 (MC4R V103I), rs17782313 (188kb downstream of MC4R), and rs7903146 (TCF7L2) were evaluated for association with stroke using logistic regression analyses.

RESULTS

The odds ratios for stroke/TIA were 1.14 (95%CI 0.91-1.42) for rs9937053/FTO, 1.11 (95%CI 0.49-2.51) for rs2229616/MC4R, 1.05 (95%CI 0.82-1.3) for rs17782313/MC4R, and 0.99 (95%CI 0.78-1.25) for rs7903146/TCF7L2. Further exploration revealed that male patients with the T allele of rs7903146/TCF7L2 had a worse clinical outcome compared with male patients carrying the C allele.

CONCLUSION

The observed trends of obesity risk alleles for risk of stroke/TIA as well as the possible sex-specific differences in clinical outcomes found for the TCF7L2 (rs7903146) require replication in future studies. Our study demonstrates that candidate gene studies for common stroke may benefit from focusing on polymorphisms that predispose to vascular risk.

Significant synergistic effect of peroxisome proliferator-activated receptor gamma C-2821T and diabetes on the risk of ischemic stroke

OBJECTIVE

To explore the relationship between the genetic polymorphisms of PPARgamma (Pro12Ala, C1431T, and C-2821T) and the risk of ischemic stroke and to investigate whether these genetic polymorphisms of PPARgamma would modify the risk of ischemic stroke among patients with hypertension or diabetes.

RESEARCH DESIGN AND METHODS

The case-control study was conducted with 537 ischemic stroke patients and 537 control subjects. A structured questionnaire was used to collect information on conventional cardiovascular risk factors and laboratory results. The genetic polymorphisms of PPARgamma were determined by PCR-restriction fragment-length polymorphism.

RESULTS

A significant interaction was seen between the -2821C allele and diabetes but not between this allele and hypertension. A markedly elevated risk of ischemic stroke (odds ratio 9.7) was found in the subjects with diabetes and the -2821C allele compared with that in those without these two risk factors.

CONCLUSIONS

The -2821C allele of PPARgamma was a strong predictor of ischemic stroke for diabetic patients.

Influence of the Pro12Ala polymorphism of PPAR-gamma on age at onset and sRAGE levels in Alzheimer's disease

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) has been described to have a role in the modulation of various genes involved in Abeta homeostasis, inflammation, and energy metabolism, making it a candidate gene for risk of Alzheimer's disease (AD). A functional polymorphism in exon 2 of the PPAR-gamma gene has been related to AD, but the effects are inconsistent across studies. To determine the role of PPAR-gamma in genetic susceptibility to AD in a representative Chinese sample, we genotyped 362 AD patients and 370 healthy controls for PPAR-gamma Pro12Ala polymorphism by polymerase chain reaction-restriction fragment length polymorphism method. We also examined the potential impact of this polymorphism on plasma level of soluble receptor for advanced glycation end products (sRAGE), a decoy receptor whose reduction has been associated with a higher risk of AD. Our results suggest that PPAR-gamma Pro12Ala polymorphism was not associated with an increased risk of AD in the overall sample. Stratification analysis revealed that the PPAR-gamma Pro/Ala genotype may be associated with the development of early-onset AD in the individuals without APOE epsilon4 allele (OR=3.76, 95% CI=1.10-12.84; p=0.03), but this association became insignificant after Bonferroni correction (p (corr)=0.10). Moreover, in the subgroup of APOE epsilon4 noncarriers, Kaplan-Meier survival analyses indicated that AD patients with the Pro/Ala genotype presented with disease onset 4.6 years earlier than carriers of Pro/Pro genotype. Further investigation revealed that AD patients carrying Pro/Ala genotype had significantly lower plasma sRAGE levels than patients with Pro/Pro genotype. These findings suggest that the functional PPAR-gamma Pro12Ala polymorphism may modify the age at onset of AD.

PPARs as new therapeutic targets for the treatment of cerebral ischemia/reperfusion injury

Stroke is a leading cause of death and long-term disability in industrialized countries. Despite advances in understanding its pathophysiology, little progress has been made in the treatment of stroke. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signaling proteins which could be exploited to design novel therapeutic modalities. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that control lipid and glucose metabolism. PPARs regulate gene expression by binding with the retinoid X receptor (RXR) as a heterodimeric partner to specific DNA sequences, termed PPAR response elements. In addition, PPARs may modulate gene transcription also by directly interfering with other transcription factor pathways in a DNA-binding independent manner. To date, three different PPAR isoforms, designated alpha, beta/delta, and gamma, have been identified. Recently, they have been found to play an important role for the pathogenesis of various disorders of the central nervous system and accumulating data suggest that PPARs may serve as potential targets for treating ischemic stroke. Activation of all PPAR isoforms, but especially of PPARgamma, was shown to prevent post-ischemic inflammation and neuronal damage in several in vitro and in vivo models, negatively regulating the expression of genes induced by ischemia/ reperfusion (I/R). This paper reviews the evidence and recent developments relating to the potential therapeutic effects of PPAR-agonists in the treatment of cerebral I/R injury.

Peroxisome proliferator-activated receptor gamma-2 P12A polymorphism and risk of acute myocardial infarction, coronary heart disease and ischemic stroke: a case-cohort study and meta-analyses

Background

The alanine allele of P12A polymorphism in PPARG gene in a few studies has been associated with a reduced or increased risk of acute myocardial infarction (AMI). Yet, the risk relation has not been confi rmed, and data on ischemic stroke (IS) is scarce. We therefore investigated the role of this polymorphism on occurrence of AMI, coronary heart disease (CHD) and IS.

Methods and fi ndings

We performed a case-cohort study in 15,236 initially healthy Dutch women and applied a Cox proportional hazards model to study the relation of the P12A polymorphism and AMI (n = 71), CHD (n = 211), and IS (n = 49) under different inheritance models. In addition, meta-analyses of published studies were performed. Under the dominant inheritance model, carriers of the alanine allele compared with those with the more common genotype were not at increased or decreased risk of CHD (hazard ratio [HR] = 0.82; 95% confi dence interval [CI], 0.58 to 1.17) and of IS (HR = 1.03; 95% CI, 0.14 to 7.74). In addition no relations were found under the recessive and additive models. Our meta-analyses corroborated these fi ndings by showing no signifi cant association. For AMI we found a borderline signifi cant association under dominant (HR = 0.49; 95% CI, 0.26 to 0.94), and additive (HR = 0.51; 95% CI, 0.26 to 1.00) models which could be due to chance, because of small cases in this subgroup. The meta-analysis did not show any association between the polymorphism and risk of AMI under the different genetic models.

Conclusions

Our study in healthy Dutch women in combination with the meta-analyses of previous reports does not provide support for a role of P12A polymorphism in PPARG gene in MI and CHD risk. Also our study shows that the polymorphism has no association with IS risk.

All-trans retinoic acid induces nerve regeneration and increases serum and nerve contents of neural growth factor in experimental diabetic neuropathy

Local diminution of the neural growth factor (NGF) contributes to the apparition of diabetic neuropathy. All-trans retinoic acid (RA) increases the expression of neural growth factor and its receptor participating in translation pathways. This study evaluates RA as a treatment of diabetic neuropathy: 120 mice were assigned randomly to 4 groups. Group A (n = 30) was taken as control; group B (n = 30) received 50 mg/kg intraperitoneal streptozotocin (STZ); group C (n = 30) received STZ, and after diabetic neuropathy developed, they were treated with subcutaneous RA 20 mg/kg daily during 60 days; and group D (n = 30) only received RA. Plasma glucose, thermosensitive tests, serum, and the nerve contents of NGF were measured in all animals. Evaluation by electron microscopy was performed in search of morphologic changes secondary to neuropathy and nerve regeneration. Diabetic mice had an increased threshold to pain. Treatment with RA in diabetic mice reverted changes in sensitivity as compared with diabetic mice that received placebo (P < 0.001). No differences in pain threshold among controls, RA, and diabetes mellitus (DM) + RA groups were found. Glucose levels were not affected by the treatment with RA. NGF diminished significantly in the sciatic nerve in diabetic mice as compared with controls and with the RA group. Animals with DM + RA had a significant increase of NGF in nerves as compared with the other groups. RA also regressed the ultrastructural changes induced by diabetes that showed increased neural regeneration. RA can revert functional and ultrastructural changes and induce neural regeneration after the establishment of diabetic neuropathy, possibly because of the increased of NGF concentrations in nerve terminals.

Single gene contributions: genetic variants of peroxisome proliferator-activated receptor (isoforms alpha, beta/delta and gamma) and mechanisms of dyslipidemias

PURPOSE OF REVIEW

Polymorphisms in peroxisome proliferator-activated receptor isoforms may be among the most important single-gene contributors to dyslipidemias, insulin resistance, and maturity-onset diabetes.

RECENT FINDINGS

Familial partial lipodystrophy is a rare but characteristic phenotype associated with carriers of peroxisome proliferator-activated receptor-gamma missense mutations. Mutant receptors are transcriptionally defective, exhibit aberrant affinity for co-regulator molecules, and can exert dominant-negative or haplo-insufficiency effects on normal peroxisome proliferator-activated receptor-gamma function. The P12A variant of isoform gamma is estimated to reduce diabetes risk by 19% in many populations, and has a large attributable risk because of high prevalence of the normal allele. Variants L162V and V227A of isoform alpha (common in white and Oriental populations, respectively) are associated with sexually dimorphic perturbations of lipid metabolism and cardiovascular risk. Polymorphisms in isoforms alpha and beta/delta are reported to influence lipid and glucose utilization. Apart from lipodystrophic syndromes, metabolic and cardiovascular risk in peroxisome proliferator-activated receptor variants is apparently modulated by dietary and exercise interventions, and interactions with polymorphisms in other genetic loci.

SUMMARY

Polymorphisms in peroxisome proliferator-activated receptors are critical susceptibility risk factors for dyslipidemias and diabetes. They provide attractive targets for gene-environment interventions to reduce the burden of metabolic disease.

Drug insight: effects mediated by peroxisome proliferator-activated receptor-gamma in CNS disorders

The finding that activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) suppresses inflammation in peripheral macrophages and in models of human autoimmune disease instigated the evaluation of this salutary action for the treatment of CNS disorders with an inflammatory component. The fact that NSAIDs delay the onset of and reduce the risk of developing Alzheimer's disease (AD), while also binding to and activating PPARgamma, led to the hypothesis that one dimension of NSAID protection in AD is mediated by PPARgamma. Several lines of evidence from experiments using AD-related transgenic cellular and animal models have supported this hypothesis. The capacity of PPARgamma agonists to elicit anti-inflammatory, anti-amyloidogenic and insulin-sensitizing effects might account for their observed protective effects. Several clinical trials employing PPARgamma agonists have yielded promising results, and further trials are in preparation. Positive outcomes following PPARgamma administration have been obtained in animal models of other neurodegenerative diseases, including Parkinson's disease and amyotrophic lateral sclerosis, both of which are associated with a considerable degree of neuroinflammation. Finally, activation of PPARgamma has been found to be protective in several models of multiple sclerosis. The verification of these findings in human cells prompted the initiation of clinical studies evaluating PPARgamma activation in patients with multiple sclerosis.