Impact of the PPAR-gamma2 Pro12Ala polymorphism and ACE inhibitor therapy on new-onset microalbuminuria in type 2 diabetes: evidence from BENEDICT

The impact of PPARγ and ApoE gene polymorphisms on susceptibility to diabetic kidney disease in type 2 diabetes mellitus: a meta-analysis

BACKGROUND

Globally, diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease, imposing substantial social and economic costs. This meta-analysis was designed to provide valuable insights into gene-disease interactions by investigating the potential association between lipid metabolism gene polymorphisms and the risk of DKD.

METHODS

An electronic literature search was conducted on MEDLINE Complete, Web of Science, Embase, and PubMed. A total of 18 studies on the peroxisome proliferator-activated receptor γ (PPARγ) Pro12Ala variant and 20 publications concerning apolipoprotein E (ApoE) gene polymorphism were included in the meta-analysis.

RESULTS

Overall, the PPARγ Pro12Ala polymorphism was found to be significantly associated with a decreased DKD risk (OR = 0.74, 95% CI: 0.62-0.88). In subgroup analysis, Ala carriers were less susceptible to DKD than Pro homozygotes among Asian (OR = 0.73, 95% CI: 0.56-0.95) and Caucasian populations (OR = 0.74, 95% CI: 0.59-0.93). Subgroup analysis stratified by albuminuria categories showed that the PPARγ Pro12Ala polymorphism reduced the risk of both microalbuminuria and macroalbuminuria with corresponding ORs of 0.58 (95% CI: 0.43-0.78) and 0.68 (95% CI: 0.53-0.86). Sensitivity analysis confirmed the robustness of the meta-analysis results. However, publication bias was identified in the subgroup analysis of the Caucasian population. The primary analysis of the ApoE gene polymorphism yielded significant findings, indicating that ApoE ε2/ε2, ApoE ε2/ε3, and ApoE ε2/ε4 genotypes increase the risk of DKD (ε2/ε2 vs. ε3/ε3: OR = 1.93, 95% CI: 1.03-3.61; ε2/ε3 vs. ε3/ε3: OR = 1.63, 95% CI: 1.19-2.25; ε2/ε4 vs. ε3/ε3: OR = 1.87, 95% CI: 1.37-2.55). However, sensitivity analysis suggested that influential and Hardy-Weinberg equilibrium (HWE)-violating studies may impact the overall effect estimates.

CONCLUSIONS

A meta-analysis showed that PPARγ gene polymorphism may be a protective factor for DKD, whereas the ApoE ε2/ε2, ApoE ε2/ε3, and ApoE ε2/ε4 genotypes are associated with an increased risk of DKD. However, the role of ApoE gene polymorphism in susceptibility to DKD is less certain and requires further evaluation.

Immunomodulator FTY720 improves glucose homeostasis and diabetic complications by rejuvenation of β-cell function in nonhuman primate model of diabetes

Inadequate β‐cell mass is essential for the pathogenesis of type 2 diabetes (T2D). Previous report showed that an immunomodulator FTY720, a sphingosine 1‐phosphate (S1P) receptor modulator, sustainably normalized hyperglycemia by stimulating β‐cell in vivo regeneration in db/db mice. We further examined the effects of FTY720 on glucose homeostasis and diabetic complications in a translational nonhuman primate (NHP) model of spontaneously developed diabetes. The male diabetic cynomolgus macaques of 18–19 year old were randomly divided into Vehicle (Purified water, n = 5) and FTY720 (5 mg/kg, n = 7) groups with oral gavage once daily for 10 weeks followed by 10 weeks drug free period. Compared with the Vehicle group, FTY720 effectively lowered HbA1c, blood concentrations of fasting glucose (FBG) and insulin, hence, decreased homeostatic model assessment of insulin resistance (HOMA‐IR); ameliorated glucose intolerance and restored glucose‐stimulated insulin release, indicating rejuvenation of β‐cell function in diabetic NHPs. Importantly, after withdrawal of FTY720, FBG, and HbA1c remained at low level in the drug free period. Echocardiography revealed that FTY720 significantly reduced proteinuria and improved cardiac left ventricular systolic function measured by increased ejection fraction and fractional shortening in the diabetic NHPs. Finally, flow cytometry analysis (FACS) detected that FTY720 significantly reduced CD4 + and CD8 + T lymphocytes as well as increased DC cells in the circulation. Immunomodulator FTY720 improves glucose homeostasis via rejuvenation of β‐cell function, which can be mediated by suppression of cytotoxic CD8 + T lymphocytes to β‐cells, thus, may be a novel immunotherapy to reverse T2D progression and ameliorate the diabetic complications.

Association between Pro12Ala polymorphism and albuminuria in type 2 diabetic nephropathy

AIMS/INTRODUCTION

Diabetic nephropathy (DN) is a complication of diabetes mellitus that is characterized by the gradual loss of kidney function, which results in increased levels of albumin in the urine. The Pro12Ala polymorphism in the peroxisome proliferator-activated receptor-γ2 gene has been confirmed to improve insulin sensitivity, but its association with susceptibility to DN in patients with type 2 diabetes remains inconclusive.

MATERIALS AND METHODS

To examine whether the Pro12Ala polymorphism leads to the development of DN, a case-control study was carried out in 554 patients with type 2 diabetes. The genotypes of Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma 2 gene were analyzed by real-time polymerase chain reaction with TaqMan® probe genotyping assay in all patients.

RESULTS

The mean age of the study population was 57.7 ± 8.8 years, with average diabetes duration of 12.8 ± 6.9 years. The prevalence of albuminuria was 43.5%. The frequency of genotype Pro12Pro, Pro12Ala and Ala12Ala genotype were 92.6%, 7.0%, 0.4% in our study population, and 90.4%, 8.9% and 0.7% in normal urinary albumin-to-creatinine ratio group, respectively. The Ala carriers (Pro12Ala + Ala12Ala) had significantly lower urinary albumin-to-creatinine ratio (15.0 vs 20.5 mg/g, P = 0.001) and better renal function (estimated glomerular filtration rate 81.8 [69.8-97.6] vs 78.7 mL/min/1.73 m2 [61.6-96.2]; P = 0.05) compared with those with the genotype Pro12Pro. After adjustment for age, sex and other confounders, the odds ratio of albuminuria for the Ala12 allele was 0.428 (95% confidence interval 0.195-0.940, P = 0.034]).

CONCLUSIONS

Our results suggest that the peroxisome proliferator-activated receptor gamma 2 Ala12 variant has significant protective effects against albuminuria and DN.

PPARG Pro12Ala Polymorphism with CKD in Asians: A Meta-Analysis Combined with a Case-Control Study-A Key for Reaching Null Association

BACKGROUND

So far, numerous meta-analyses have been published regarding the correlation between peroxisome proliferator-activated receptor gamma (PPARG) proline 12 alanine (Pro12Ala) gene polymorphism and chronic kidney disease (CKD); however, the results appear to be contradictory. Hence, this study is formulated with the objective of using existing meta-analysis data together with our research population to study the correlation between PPARG Pro12Ala gene polymorphism and CKD and evaluate whether an accurate result can be obtained.

METHODS

First, literature related to CKD and PPARG Pro12Ala available on the PubMed and EMBASE databases up to December 2016 was gathered from 20 publications. Then, the gathered results were combined with our case-control study of 1693 enrolled subjects and a trial sequential analysis (TSA) was performed to verify existing evidence and determine whether a firm conclusion can be drawn.

RESULTS

The TSA results showed that the cumulative sample size for the Asian sample was 6078 and was sufficient to support a definite result. The results of this study confirmed that there is no obvious correlation between PPARG Pro12Ala and CKD for Asians (OR = 0.82 (95% CI = 0.66-1.02), I² = 63.1%), but this was not confirmed for Caucasians. Furthermore, the case-control sample in our study was shown to be the key for reaching this conclusion.

CONCLUSIONS

The meta-analysis results of this study suggest no significant correlation between PPARG Pro12Ala gene polymorphism and CKD for Asians after adding our samples, but not for Caucasian.

Glomerular endothelial cells versus podocytes as the cellular target in diabetic nephropathy

It usually takes several years (in some cases, decades) for predisposed individuals to move from the onset of type 1 or type 2 diabetes to the development of microalbuminuria, the first sign of diabetic nephropathy. This long, complication-free, period represents the best possible moment to start a successful preventive strategy (primary prevention) aimed to avoid or at least to postpone the increase of albumin excretion rate. Prevention is based on understanding and counteracting the initial mechanisms leading to the development of the disease and unfortunately, in case of diabetic nephropathy, most of them remain unclear. Little is also known about which, among endothelial cells and podocytes, represent the first glomerular target of the complication. Selective damage of the endothelium or of the podocyte results, as a common consequence, in an increase of albumin excretion rate. Albuminuria by itself cannot therefore be of help to solve the case. Endothelium and podocytes are involved in a continuous cross-talk and by studying the impact of diabetes on this "communication" process it should be possible to obtain some information regarding the weak component of the glomerular filter. Finally, the careful investigation of the mechanisms leading to the development podocyturia, a recently identified glomerular dysfunction associated to the pathogenesis of diabetic nephropathy, could contribute to shed some more light on the very early stages of this complication.

Searching for Factors Raising the Incidence of Metabolic Syndrome Among 45-60-Year-Old Women

Metabolic syndrome is an increasing health problem, whose pathogenesis may be associated with genetic factors. The main purpose of our study was to assess relationships between MetS and the presence of the FTO rs9939609, the MC4R rs17782313, and the PPAR-γ rs1801282 polymorphisms in 45-60-year-old women. The study included patients from the general population of the Westpomeranian Province (Poland). The mean age was 54.3 ± 4.2 years. The research procedure involved taking structured history, physical examination, anthropometric measurements, and collecting blood for biochemical and genetic analysis. The patients who met the diagnostic criteria for MetS constituted 38.35% of all participants (sample size: 425 patients). The comparison of blood biochemical parameters revealed numerous differences between the women with MetS and those from the control group. Genetic analysis demonstrated that the T allele of the FTO gene was a factor substantially decreasing the incidence of MetS in the study sample (ORT vs. A = 0.734; 95% CI: 0.555 - 0.970; p < 0.05). Other polymorphisms were not directly related to MetS incidence.

CONCLUSIONS

1. MetS-related abnormalities are widespread in the population of 45-60-year-old Polish women. Those most common are the elevated serum total cholesterol and LDL levels, increased insulin resistance and BMI scores, as well as visceral obesity. 2. No direct relationships were demonstrated between MetS and the gene polymorphisms analyzed in our study except for the FTO rs9939609, whose A allele and A/A genotype seemed to predispose to metabolic disorders.

The rs12917707 polymorphism at the UMOD locus and glomerular filtration rate in individuals with type 2 diabetes: evidence of heterogeneity across two different European populations

Background

UMOD variability has been associated at a genome-wide level of statistical significance with glomerular filtration rate (GFR) in Swedish individuals with type 2 diabetes (T2D; n = 4888). Whether this finding is extensible also to diabetic patients from other populations deserves further study. Our aim was to investigate the relationship between UMOD variability and GFR in patients with T2D from Italy.

Methods

Genotyping of the single nucleotide polymorphism (SNP) rs12917707 at the UMOD locus has been carried out in 3087 individuals from four independent Italian cohorts of patients with T2D by TaqMan allele discrimination.

Results

In none of the four study cohorts was rs12917707 significantly associated with GFR (P > 0.05 for all). Similar results were obtained when the four samples were pooled and analyzed together (β = 0.83, P = 0.19). Such effect was strikingly smaller than that previously reported in Swedish patients (P for heterogeneity = 1.21 × 10-7).

Conclusions

The previously reported strong association between rs12917707 and GFR in diabetic patients from Sweden is not observed in Italian diabetic patients, thus clearly pointing to a heterogeneous effect across the two different samples. This suggests that UMOD is a strong genetic determinant of kidney function in patients with T2D in some, but not all, populations.

The PPARγ2 P12A polymorphism is not associated with all-cause mortality in patients with type 2 diabetes mellitus

The high mortality risk of patients with type 2 diabetes mellitus may well be explained by the several comorbidities and/or complications. Also the intrinsic genetic component predisposing to diabetes might have a role in shaping the risk of diabetes-related mortality. Among type 2 diabetes mellitus SNPs, rs1801282 is of particular interest because (i) it is harbored by peroxisome proliferator-activated receptor-γ2 (PPARγ2), which is the target for thiazolidinediones which are used as antidiabetic drugs, decreasing all-cause mortality in type 2 diabetes mellitus, and (ii) it is associated with insulin resistance and related traits, risk factors for overall mortality in type 2 diabetes mellitus. We investigated the role of PPARγ2 P12A, according to a dominant model (PA + AA vs. PP individuals) on incident all-cause mortality in three cohorts of type 2 diabetes mellitus, comprising a total of 1672 patients (462 deaths) and then performed a meta-analysis of ours and all available published data. In the three cohorts pooled and analyzed together, no association between PPARγ2 P12A and all-cause mortality was observed (HR 1.02, 95 % CI 0.79-1.33). Similar results were observed after adjusting for age, sex, smoking habits, and BMI (HR 1.09, 95 % CI 0.83-1.43). In a meta-analysis of ours and all studies previously published (n = 3241 individuals; 666 events), no association was observed between PPARγ2 P12A and all-cause mortality (HR 1.07, 95 % CI 0.85-1.33). Results from our individual samples as well as from our meta-analysis suggest that the PPARγ2 P12A does not significantly affect all-cause mortality in patients with type 2 diabetes mellitus.

The PPARγ2 Pro12Ala variant is protective against progression of nephropathy in people with type 2 diabetes

Objective

Cross-sectional studies suggest the association between diabetic nephropathy and the PPARγ2 Pro12Ala polymorphism of the peroxisome proliferator-activated receptor γ2 (PPARγ2). Prospective data are limited to microalbuminuria and no information on renal function is available to date. The present study evaluates the association between the Pro12Ala polymorphism of PPARγ2 and the progression of albuminuria and decay in glomerular filtration rate (GFR) in type 2 diabetes.

Patients and measurements

We studied 256 patients with an average 5-year follow-up. Among others, urinary albumin excretion rate (UAER) was measured on spot sample, GFR was estimated with the CKD-EPI Equation.

Results

Baseline UAER and GFR were similar for carriers or non-carriers of the polymorphism. At follow-up no significant changes from baseline were observed for UAER or eGFR in carriers of the Pro12Ala polymorphism whereas a significant increase in UAER [17 (11.3-37.9) versus 24.5 (13.8-49.9) μg/mg, p < 0.006)] and a significant reduction in the eGFR (82.8 ± 14.5 versus 80.3 ± 17.3 ml/min/1.73, m² p = 0.02), were observed in non carriers of the Pro12Ala polymorphism. Progression of nephropathy - defined according to a combined end point of UAER and eGFR- i.e. doubling of baseline UAER to at least 100 μg/mg, or new onset microalbuminuria, or progression from micro to macroalbuminuria, or 25% reduction of eGFR, or annualized eGFR decline >3 ml/min/year - was significantly less frequent in Ala carriers than non carriers (11.4% vs 35.8%; p < 0.01); HR adjusted for baseline age, AER, eGFR, HbA1c, diabetes duration and blood pressure was 0.32 (0.12-0.80).

Conclusions

This study found that among patients with type 2 diabetes, the PPARγ2 Pro12Ala polymorphism is protective against progression of nephropathy and decay of renal function independent of major confounders.

Sequence variants of peroxisome proliferator-activated receptor-gamma gene and the clinical courses of patients with end-stage renal disease

Background. PPAR-γ single nucleotide polymorphisms (SNPs) reportedly play an important role in determining metabolic risk among diverse population. Whether PPAR-γ SNPs affect the clinical courses in ESRD patients is unknown. Methods. From a multicenter cohort, we identified 698 patients with prevalent ESRD between 2002 and 2003, and other 782 healthy subjects as control. Two PPAR-γ SNPs, Pro12Ala (rs1801282) and C161T (rs3856806), were genotyped and their association with ESRD was examined. Both groups were prospectively followed until 2007, and the predictability of genotypes for the long-term survival of ESRD patients was analyzed. Results. After multivariable-adjusted regression, GG genotype of Pro12Ala was significantly more likely to associate with ESRD (P < 0.001) among patients with non-diabetes-related ESRD. Cox's proportional hazard regression showed that both Pro12Ala and C161T polymorphisms were significant predictors of mortality in ESRD patients with DM (Pro12Ala: GG versus other genotypes, hazard ratio [HR] <0.01; P < 0.001; for C161T, CC versus TT genotypes, HR 2.86; P < 0.001; CT versus TT genotypes, HR 1.93; P < 0.001). Conclusion. This is the first and largest study to evaluate PPAR-γ SNPs in ESRD patients. Further mechanistic study is needed to elucidate the role of PPAR-γ among ESRD patients.

Association of peroxisome proliferator-activated receptor γ Pro12Ala gene polymorphism with type 2 diabetic nephropathy risk in Caucasian population

Association of peroxisome proliferator-activated receptor gamma (PPARγ) Pro12Ala gene polymorphism with type 2 diabetic nephropathy (T2DN) risk in Caucasians is still not clear. This investigation was conducted to assess if there was an association between the PPARγ Pro12Ala gene polymorphism and T2DN risk in Caucasians using meta-analysis. The relevant literatures were identified from PubMed, and Cochrane Library on 10 October 2013, and eligible studies were included and synthesized. Six reports including eight studies were recruited into this meta-analysis for the association of the PPARγ Pro12Ala gene polymorphism with T2DN risk in Caucasians. The Pro/Pro genotype was shown to be associated with T2DN risk in Caucasians. However, the Ala/Ala genotype and Ala allele were not associated with T2DN risk in Caucasians. In the sensitivity analysis, according to the control source from hospital, the control source from population, the genotyping methods using PCR-RFLP, Taqman, sample size of case <100, the association of the PPARγ Pro12Ala gene polymorphism with T2DN risk was similar to those in non-sensitivity analysis. In conclusion, the PPARγ Pro/Pro genotype was associated with T2DN risk in Caucasians, but the Ala/Ala genotype and Ala allele not. However, additional studies are required to firmly establish a correlation between the PPARγ Pro12Ala gene polymorphism and T2DN risk in Caucasians.

ADAMTS13 predicts renal and cardiovascular events in type 2 diabetic patients and response to therapy

In patients with diabetes, impaired ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) proteolysis of highly thrombogenic von Willebrand factor (VWF) multimers may accelerate renal and cardiovascular complications. Restoring physiological VWF handling might contribute to ACE inhibitors' (ACEi) reno- and cardioprotective effects. To assess how Pro618Ala ADAMTS13 variants and related proteolytic activity interact with ACEi therapy in predicting renal and cardiovascular complications, we genotyped 1,163 normoalbuminuric type 2 diabetic patients from BErgamo NEphrologic DIabetes Complications Trial (BENEDICT). Interaction between Pro618Ala and ACEi was significant in predicting both renal and combined renal and cardiovascular events. The risk for renal or combined events versus reference Ala carriers on ACEi progressively increased from Pro/Pro homozygotes on ACEi (hazard ratio 2.80 [95% CI 0.849-9.216] and 1.58 [0.737-3.379], respectively) to Pro/Pro homozygotes on non-ACEi (4.77 [1.484-15.357] and 1.99 [0.944-4.187]) to Ala carriers on non-ACEi (8.50 [2.416-29.962] and 4.00 [1.739-9.207]). In a substudy, serum ADAMTS13 activity was significantly lower in Ala carriers than in Pro/Pro homozygotes and in case subjects with renal, cardiovascular, or combined events than in diabetic control subjects without events. ADAMTS13 activity significantly and negatively correlated with all outcomes. In patients with diabetes, ADAMTS13 618Ala variant associated with less proteolytic activity, higher risk of chronic complications, and better response to ACEi therapy. Screening for Pro618Ala polymorphism may help identify patients with diabetes at highest risk who may benefit the most from early reno- and cardioprotective therapy.

The association between the PPARγ2 Pro12Ala polymorphism and nephropathy susceptibility in type 2 diabetes: a meta-analysis based on 9,176 subjects

Background

The polymorphism Pro12Ala in peroxisome proliferator-activated receptor­γ2 gene (PPARγ2) has been reported to be associated with diabetic nephropathy (DN) in some studies, though the results remain inconclusive. To explore this relationship between PPARγ2 Pro12Ala polymorphism and the susceptibility for DN, a cumulative meta-analysis was performed in this study.

Method

PubMed, Medline, Embase and Web of Science databases have been systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

Results

18 studies were included in this meta-analysis, involving 3,361 cases and 5,815 controls. The PPARγ2 Ala12 allele was significantly associated with decreased risk of DN based on dominant model (OR=0.778; 95%CI=0.618–0.981; P_{heterogeneity}=0.008; P=0.034). In the stratified analysis by ethnicity, significantly decreased risks were found among Caucasians for dominant model (OR=0.674; 95%CI=0.500–0.909; P_{heterogeneity}=0.079; P=0.010), while there was no significant association was found in Asians.

Conclusions

The results from the present meta-analysis indicated that the Pro12Ala polymorphism in PPARγ2 gene is not a risk factor for DN in type 2 diabetes (T2D). Further large and well-designed studies are needed to confirm this conclusion.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7491348341027320.

Antihypertensive agents for preventing diabetic kidney disease

BACKGROUND

Various blood pressure-lowering agents, and particularly inhibitors of the renin-angiotensin system (RAS), are widely used for people with diabetes to prevent the onset of diabetic kidney disease (DKD) and adverse cardiovascular outcomes. This is an update of a Cochrane review first published in 2003 and updated in 2005.

OBJECTIVES

This systematic review aimed to assess the benefits and harms of blood pressure lowering agents in people with diabetes mellitus and a normal amount of albumin in the urine (normoalbuminuria).

SEARCH METHODS

In January 2011 we searched the Cochrane Renal Group's Specialised Register through contact with the Trials Search Co-ordinator.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any antihypertensive agent with placebo or another agent in hypertensive or normotensive patients with diabetes and no kidney disease (albumin excretion rate < 30 mg/d) were included.

DATA COLLECTION AND ANALYSIS

Two investigators independently extracted data on kidney and other patient-relevant outcomes (all-cause mortality and serious cardiovascular events), and assessed study quality. Analysis was by a random effects model was applied to analyse results which were expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

We identified 26 studies that enrolling 61,264 participants. Angiotensin-converting enzyme inhibitors (ACEi) reduced the risk of new onset of microalbuminuria, macroalbuminuria or both when compared to placebo (8 studies, 11,906 patients: RR 0.71, 95% CI 0.56 to 0.89), with similar benefits in people with and without hypertension (P = 0.74), and when compared to calcium channel blockers (5 studies, 1253 participants: RR 0.60, 95% CI 0.42 to 0.85). ACEi reduced the risk of death when compared to placebo (6 studies, 11,350 participants: RR 0.84, 95% CI 0.73 to 0.97). No effect was observed for angiotensin receptor blockers (ARB) when compared to placebo for new microalbuminuria, macroalbuminuria or both (5 studies, 7653 participants: RR 0.90, 95% CI 0.68 to 1.19) or death (5 studies, 7653 participants: RR 1.12, 95% CI 0.88 to 1.41); however, meta-regression suggested possible benefits from ARB for preventing kidney disease in high risk patients. There was a trend towards benefit from use of combined ACEi and ARB for prevention of DKD compared with ACEi alone (2 studies, 4171 participants: RR 0.88, 95% CI 0.78 to 1.00).The risk of cough was significantly increased with ACEi when compared to placebo (6 studies, 11,791 patients: RR 1.84, 95% CI 1.24 to 2.72), however there was no significant difference in the risk of headache or hyperkalaemia. There was no significant difference in the risk of cough, headache or hyperkalaemia when ARB was to placebo. On average risk of bias was judged to be either low (27% to 69%) or unclear (i.e. no information available) (8% to 73%). Blinding of participants, incomplete outcome data and selective reporting were judged to be high in 23%, 31% and 31% of studies, respectively.

AUTHORS' CONCLUSIONS

ACEi were found to prevent new onset DKD and death in normoalbuminuric people with diabetes, and could therefore be used in this population. More data are needed to clarify the role of ARB and other drug classes in preventing DKD.

Role of insulin resistance in kidney dysfunction: insights into the mechanism and epidemiological evidence

Several lines of evidence suggest a pathogenic role of insulin resistance on kidney dysfunction. Potential mechanisms are mostly due to the effect of single abnormalities related to insulin resistance and clustering into the metabolic syndrome. Hyperinsulinemia, which is inevitably associated to insulin resistance in non diabetic states, also appears to play a role on kidney function by inducing glomerular hyperfiltration and increased vascular permeability. More recently, adipocytokine which are linked to insulin resistance, low grade inflammation, endothelial dysfunction and vascular damage have been proposed as additional molecules able to modulate kidney function. In addition, recent evidences point also to a role of insulin resistance at the level of the podocyte, an important player in early phases of diabetic kidney damage, thus suggesting a new mechanism through which a reduction of insulin action can affect kidney function. In fact, mouse models not expressing the podocyte insulin receptor develop podocytes apoptosis, effacement of its foot processes along with thickening of the glomerular basement membrane, increased glomerulosclerosis and albuminuria. A great number of epidemiological studies have repeatedly reported the association between insulin resistance and kidney dysfunction in both non diabetic and diabetic subjects. Among these, studies addressing the impact of insulin resistance genes on kidney dysfunction have played the important role to help establish a cause-effect relationship between these two traits. Finally, numerous independent intervention studies have shown that a favourable modulation of insulin resistance has a positive effect also on urinary albumin and total protein excretion. In conclusion, several data of different nature consistently support the role of insulin resistance and related abnormalities on kidney dysfunction. Intervention trials designed to investigate whether treating insulin resistance ameliorates also hard renal end-points are both timely and needed.

Measurable urinary albumin predicts cardiovascular risk among normoalbuminuric patients with type 2 diabetes

Micro- or macroalbuminuria is associated with increased cardiovascular risk factors among patients with type 2 diabetes, but whether albuminuria within the normal range predicts long-term cardiovascular risk is unknown. We evaluated the relationships between albuminuria and cardiovascular events in 1208 hypertensive, normoalbuminuric patients with type 2 diabetes from the BErgamo NEphrologic Diabetes Complication Trial (BENEDICT), all of whom received angiotensin-converting enzyme inhibitor (ACEI) therapy at the end of the trial and were followed for a median of 9.2 years. The main outcome was time to the first of fatal or nonfatal myocardial infarction; stroke; coronary, carotid, or peripheral artery revascularization; or hospitalization for heart failure. Overall, 189 (15.6%) of the patients experienced a main outcome event (2.14 events/100 patient-years); 24 events were fatal. Albuminuria independently predicted events (hazard ratio [HR], 1.05; 95% confidence interval [CI], 1.02-1.08). Second-degree polynomial multivariable analysis showed a continuous nonlinear relationship between albuminuria and events without thresholds. Considering the entire study population, even albuminuria at 1-2 μg/min was significantly associated with increased risk compared with albuminuria <1 μg/min (HR, 1.04; 95% CI, 1.02-1.07). This relationship was similar in the subgroup originally randomly assigned to non-ACEI therapy. Among those originally receiving ACEI therapy, however, the event rate was uniformly low and was not significantly associated with albuminuria. Taken together, among normoalbuminuric patients with type 2 diabetes, any degree of measurable albuminuria bears significant cardiovascular risk. The association with risk is continuous but is lost with early ACEI therapy.

Peroxisome proliferator-activated receptor γ polymorphism Pro12Ala Is associated with nephropathy in type 2 diabetes: evidence from meta-analysis of 18 studies

OBJECTIVE

Insulin resistance plays a part in diabetic nephropathy (DN). The association between the peroxisome proliferator-activated receptor γ Pro to Ala alteration at codon 12 (Pro12Ala) polymorphism and the risk of insulin resistance has been confirmed. The association between the polymorphism and DN risk has also been widely studied recently, but no consensus was available up to now.

RESEARCH DESIGN AND METHODS

A systematic search of electronic databases (MEDLINE, Embase, and China National Knowledge Infrastructure) and reference lists of relevant articles was carried out, and then 18 case-control studies involving 3,361 DN cases and 5,825 control subjects were identified.

RESULTS

In the overall analysis, the Ala12 variant was observed to be significantly associated with decreased DN risk (odds ratio 0.76 [95% CI 0.61-0.93]). Some evidence of heterogeneity among the included studies was detected, which could be explained by the difference of ethnicity and stage of DN. Subgroup analyses stratified by ethnicity and stage of DN were performed, and results indicated the Pro12Ala polymorphism was associated with the risk of DN in Caucasians but no similar association was observed in Asians. Additionally, we observed that Ala12 was associated with decreased risk of albuminuria. With only a few of subjects were available, we failed to detect statistically significant association between the polymorphism and end-stage renal disease (ESRD).

CONCLUSIONS

Our results indicated that the Ala12 variant is a significantly protective factor for DN. Future research should focus on the effect of Pro12Ala polymorphism on ESRD and gathering data of Africans.

Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers for treatment of ischemic heart disease: Future research needs prioritization

BACKGROUND

A recent review evaluated the comparative effectiveness of angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin II receptor blockers (ARBs) in patients with or at high risk for stable ischemic heart disease (IHD). The prioritization of future research needs has customarily been an informal process that is not responsive to the needs of all relevant stakeholders.

METHODS

As part of the Agency for Healthcare Research and Quality Effective Healthcare Program, the Duke Evidence-Based Practice Center engaged a diverse stakeholder group in 3 exercises designed to prioritize future research needs pertaining to the comparative effectiveness of ACE-I/ARB in patients with stable IHD.

RESULTS

Our stakeholders prioritized the following areas of research pertaining to the comparative effectiveness of ACE-I/ARB in stable IHD: (1) strategies to enhance greater evidence-based use, (2) impact of adherence on effectiveness or harms, (3) impact of comorbidities on effectiveness or harms, (4) medication impact on patient quality of life, (5) impact of demographic differences on effectiveness or harms, and (6) medication impact on incidence of new diagnoses. This project also yielded suggestions regarding potential study designs to address these future research needs.

CONCLUSIONS

Our stakeholders prioritized research designed to facilitate (1) tailored ACE-I/ARB treatment based on individual patient characteristics and (2) implementation of ACE-I/ARB use among patients most likely to benefit. With respect to suggested study designs, it was felt that analysis of existing data would sufficiently address many of the top-tier future research needs (FRNs).

Glitazones in chronic kidney disease: potential and concerns

AIMS

Glitazones rank now among the most used hypoglycemic agents in patients with type-2 diabetes. This systematic review focuses on the cardiovascular and renal outcomes in chronic kidney disease (CKD) patients treated with these drugs.

DATA SYNTHESIS

Data from randomized clinical trials and a meta-analysis indicate that glitazones (particularly rosiglitazone) may increase the risk of myocardial infarction, heart failure and cardiovascular death in type-2 diabetics. Observational studies looking at survival and cardiovascular outcomes in diabetic patients with kidney failure show controversial results. Studies in experimental models and clinical studies suggest that glitazones may have favorable effects on renal disease progression, because these drugs coherently reduce urinary albumin excretion and proteinuria in diabetic and non-diabetic nephropathies. No clinical trial based on clinical end-points like kidney failure has until now tested the effect of glitazones on the evolution of chronic renal failure in these patients.

CONCLUSIONS

Whether the use of glitazones has a positive or a negative impact upon major cardiovascular and renal outcomes in diabetic patients remains an open, unanswered question. Specific studies are needed to assess the efficacy and safety of glitazones in a high risk population like type-2 diabetics with chronic kidney disease.

PPARγ2 P12A polymorphism and albuminuria in patients with type 2 diabetes: a meta-analysis of case-control studies

BACKGROUND

Insulin resistance has a role in diabetic nephropathy. The A12 variant of the PPARγ2 P121A polymorphism has been firmly associated with reduced risk of insulin resistance, while its role on the risk of albuminuria in patients with type 2 diabetes is uncertain. This study investigated whether the PPARγ2 P12A polymorphism modulates the risk of albuminuria in these patients.

METHODS

We tested the association between the A12 variant and albuminuria in three new case-control studies in diabetic patients from Italy (n = 841, n = 623 and n = 714 patients, respectively) and then performed a meta-analysis of all studies available to date. The nine studies we meta-analysed (six previously published and three presented here) comprised a total of 2376 cases and 4188 controls.

RESULTS

In none of the three new studies was a significant association observed with odds ratio (OR) [95% confidence intervals (95% CI)] being 1.115, 0.799 and 0.849 (P = 0.603, 0.358 and 0.518, respectively). At meta-analysis, the overall OR (95% CI) for association between A12 and albuminuria was 0.694 (0.528-0.912). A significant heterogeneity of the genetic effect was observed (P = 0.026), which was totally explained by the different method of urine collection and albuminuria definition utilized across the studies. In fact, most of the effect was observed in the four studies determining albumin excretion rate rather than in those using albumin concentration in a single spot (OR, 95% CI: 0.529, 0.397-0.706, P = 0.0000164 and 0.919, 0.733-1.153, P = 0.47, respectively).

CONCLUSION

The present study shows that the PPARγ2 Ala12 variant is significantly associated with a reduced risk of albuminuria among patients with type 2 diabetes.