The adiponectin rs17300539 G>A variant and nephropathy risk

Meta-analysis of diabetic nephropathy associated genetic variants in inflammation and angiogenesis involved in different biochemical pathways

Background

Diabetes mellitus is the most common chronic endocrine disorder, affecting an estimated population of 382 million people worldwide. It is associated with microvascular and macrovascular complications, including diabetic nephropathy (DN); primary cause of end-stage renal disease. Different inflammatory and angiogenic molecules in various pathways are important modulators in the pathogenesis and progression of diabetic nephropathy. Differential disease risk in DN may be partly attributable to genetic susceptibility. In this meta-analysis, we aimed to determine which of the previously investigated genetic variants in these pathways are significantly associated with the development of DN and to examine the functional role of these genes.

Methods

A systematic search was conducted to collect and analyze all studies published till June 2013; that investigated the association between genetic variants involved in inflammatory cytokines and angiogenesis and diabetic nephropathy. Genetic variants associated with DN were selected and analyzed by using Comprehensive Meta Analysis software. Pathway analysis of the genes with variants showing significant positive association with DN was performed using Genomatix Genome Analyzer (Genomatix, Munich, Germany).

Results

After the inclusion and exclusion criteria for this analysis, 34 studies were included in this meta-analysis. 11 genetic variants showed significant positive association with DN in a random-effects meta-analysis. These included genetic variants within or near VEGFA, CCR5, CCL2, IL-1, MMP9, EPO, IL-8, ADIPOQ and IL-10. rs1800871 (T) genetic variant in IL-10 showed protective effect for DN. Most of these eleven genetic variants were involved in GPCR signaling and receptor binding pathways whereas four were involved in chronic kidney failure. rs833061 [OR 2.08 (95% CI 1.63-2.66)] in the VEGFA gene and rs3917887 [OR 2.04 (95% CI 1.64-2.54)] in the CCL2 gene showed the most significant association with the risk of diabetic nephropathy.

Conclusions

Our results indicate that 11 genetic variants within or near VEGFA, CCR5, CCL2, IL-1, MMP9, EPO, IL-8, ADIPOQ and IL-10 showed significant positive association with diabetic nephropathy. Gene Ontology or pathway analysis showed that these genes may contribute to the pathophysiology of DN. The functional relevance of the variants and their pathways can lead to increased biological insights and development of new therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-014-0103-8) contains supplementary material, which is available to authorized users.

Adiponectin gene polymorphisms and susceptibility to diabetic nephropathy: a meta-analysis

Adiponectin (ADIPOQ) plays an important role in the pathogenesis of diabetic nephropathy (DN) and previous studies regarding the association between ADIPOQ polymorphisms and DN risk reported conflicting results. To derive a more precise estimation of this association, we performed a meta-analysis to assess the association between four ADIPOQ polymorphisms [-11391G > A (rs17300539), -11377C > G (rs266729), +45T > G (rs2241766), and +276G > T (rs1501299)] and risk for DN. Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were pooled to assess the association between four aforementioned polymorphisms and susceptibility to DN. Based on the included criteria, we selected 13 articles, among which 7 studies (cases/controls: 2749/7585) for -11391G > A, 8 studies for -11377C > G (3074/3842), 9 studies for +45T > G (2654/7710), and 10 studies for +276G > T (2812/7821), respectively. Our meta-analysis indicated no evidence heterogeneity among the included studies; thus, the fixed-effects model was used. Overall, there was an association between ADIPOQ -11391A allele with increased DN risk (OR = 1.186, 95% CI: 1.051-1.338, p = 0.006). Subgroup by ethnicity suggested significant association between +45T > G polymorphism and DN risk among Caucasians (OR = 1.122, 95% CI: 1.007-1.250, p = 0.038). Sensitivity analysis suggested exclusion of any single study did not materially alter the overall pooled ORs above. Future studies are needed to validate these findings.

Urinary adiponectin excretion rises with increasing albuminuria in type 1 diabetes

AIM

Urinary adiponectin (u-adiponectin) excretion has been suggested to reflect early glomerular damage. Inspired by this, we studied the levels of u-adiponectin in type 1 diabetic patients with different levels of urinary albumin excretion (UAE).

METHODS

U-adiponectin was analysed by ELISA in type 1 diabetic patients: Fifty-eight with normoalbuminuria (<30mg albumin/24h), 43 with persistent microalbuminuria (30-300mg/24h) and 44 with persistent macroalbuminuria (>300mg/24h). For comparison, a control group of 55 healthy individuals was included.

RESULTS

U-adiponectin increased with increasing levels of UAE (p<0.01). U-adiponectin median (interquartile range): Normoalbuminuria 0.38 (0.14-1.31), microalbuminuria 1.12 (0.20-2.68), macroalbuminuria 9.20 (1.10-23.35) and controls 0.09 (0.06-0.24) μg/g creatinine. Levels were unrelated to sex, age, cholesterol, diastolic BP and BMI. U-adiponectin was weakly associated with increasing systolic BP and HbA1c (r(2)<0.1, p<0.05), but strongly related to increasing UAE (r(2)=0.57, p<0.001) and decreasing eGFR (r(2)=0.26, p<0.001). The relationship between UAE and u-adiponectin was significant in all groups and independent of eGFR, BMI, BP and HbA1c. Furthermore, u-adiponectin was associated with markers of tubular damage (p<0.01).

CONCLUSION

U-adiponectin rises with increasing levels of UAE in patients with type 1 diabetes. This is in accordance with the hypothesis that loss of adiponectin may reflect glomerular and/or tubular damage.

Association of the adiponectin rs266729 C>G variant and coronary heart disease in the low risk 'Golden Years' type 1 diabetes cohort

The C-allele of rs266729 is associated with CHD, while the G-allele of rs17300539 is associated with metabolic traits. We examined these in type 1 diabetes. For rs266729, the C-allele was associated with 8-fold increase in CHD. For rs17300539, the G-allele was associated with increases in triglycerides and waist circumference.

Association of ADIPOQ genetic variants and plasma adiponectin isoforms with the risk of incident renal events in type 2 diabetes

BACKGROUND

Adiponectin levels are high in cases of diabetic nephropathy, but it remains unclear whether these high levels are a cause or a consequence of the disease. We investigated the possible association of polymorphisms in the adiponectin gene and baseline adiponectin levels with the incidence of renal events in subjects with type 2 diabetes.

METHODS

We studied three adiponectin polymorphisms (-11391G > A, +45T > G and +276G > T) in 3086 subjects with type 2 diabetes and high levels of albumin excretion from the diabetes, hypertension, microalbuminuria or proteinuria, cardiovascular events and ramipril (DIABHYCAR) trial. Baseline concentrations of total adiponectin and of adiponectin isoforms were determined in cases with incident renal events and in controls matched for sex, age, body mass index (BMI) and adiponectin genotype. We used another cohort of type 2 diabetes patients-the survie, diabète de type 2 et génétique(SURDIAGENE) study (n = 1004)-for the replication of genetic data.

RESULTS

In DIABHYCAR, the -11391A and +45G alleles were associated with a higher incidence of renal events [hazard ratio (HR) = 1.73; 95% confidence interval (CI), 1.10-2.71; and HR = 1.68; 95% CI, 1.14-2.47, respectively]. The haplotype containing susceptibility alleles, -11391A/+45G/+276G, was more frequent in cases with renal events (5.1% vs. 1.9% in those without, P = 0.005). In SURDIAGENE, the -11391A/+45G/+276G haplotype was also associated with renal events (5.6% vs. 1.9% in those without, P = 0.03). In DIABHYCAR, all isoforms were more abundant in subjects carrying the -11391A or +45G alleles. Medium- (MMW) and low-molecular weight (LMW) isoforms were more abundant in cases with renal events.

CONCLUSIONS

In subjects with type 2 diabetes and early renal dysfunction, adiponectin gene variants are determinants of the renal risk. The -11391A and +45G alleles may affect renal risk by leading to high circulating adiponectin concentrations, at least those of MMW and LMW isoforms.