A genome-wide search for linkage of estimated glomerular filtration rate (eGFR) in the Family Investigation of Nephropathy and Diabetes (FIND)

Pathomechanisms of Diabetic Kidney Disease

The worldwide occurrence of diabetic kidney disease (DKD) is swiftly rising, primarily attributed to the growing population of individuals affected by type 2 diabetes. This surge has been transformed into a substantial global concern, placing additional strain on healthcare systems already grappling with significant demands. The pathogenesis of DKD is intricate, originating with hyperglycemia, which triggers various mechanisms and pathways: metabolic, hemodynamic, inflammatory, and fibrotic which ultimately lead to renal damage. Within each pathway, several mediators contribute to the development of renal structural and functional changes. Some of these mediators, such as inflammatory cytokines, reactive oxygen species, and transforming growth factor β are shared among the different pathways, leading to significant overlap and interaction between them. While current treatment options for DKD have shown advancement over previous strategies, their effectiveness remains somewhat constrained as patients still experience residual risk of disease progression. Therefore, a comprehensive grasp of the molecular mechanisms underlying the onset and progression of DKD is imperative for the continued creation of novel and groundbreaking therapies for this condition. In this review, we discuss the current achievements in fundamental research, with a particular emphasis on individual factors and recent developments in DKD treatment.

Cadherin and Wnt signaling pathways as key regulators in diabetic nephropathy

AIM

A recent meta-analysis of genome-wide linkage studies (GWLS) has identified multiple genetic regions suggestive of linkage with DN harboring hundreds of genes. Moving this number of genetic loci forward into biological insight is truly the next step. Here, we approach this challenge with a gene ontology (GO) analysis in order to yield biological and functional role to the genes, an over-representation test to find which GO terms are enriched in the gene list, pathway analysis, as well as protein network analysis.

METHOD

GO analysis was performed using protein analysis through evolutionary relationships (PANTHER) version 14.0 software and P-values less than 0.05 were considered statistically significant. GO analysis was followed by over-representation test for the identification of enriched terms. Statistical significance was calculated by Fisher's exact test and adjusted using the false discovery rate (FDR) for correction of multiple tests. Cytoscape with the relevant plugins was used for the construction of the protein network and clustering analysis.

RESULTS

The GO analysis assign multiple GO terms to the genes regarding the molecular function, the biological process and the cellular component, protein class and pathway analysis. The findings of the over-representation test highlight the contribution of cell adhesion regarding the biological process, integral components of plasma membrane regarding the cellular component, chemokines and cytokines with regard to protein class, while the pathway analysis emphasizes the contribution of Wnt and cadherin signaling pathways.

CONCLUSIONS

Our results suggest that a core feature of the pathogenesis of DN may be a disturbance in Wnt and cadherin signaling pathways, whereas the contribution of chemokines and cytokines need to be studied in additional studies.

Pima Indian Contributions to Our Understanding of Diabetic Kidney Disease

Prospective studies in informative populations are crucial to increasing our knowledge of disease. In this perspective, we describe a half century of studies in an American Indian population that transformed our understanding of kidney disease in type 2 diabetes, now recognized as the leading cause of kidney failure worldwide. Serial examinations conducted for many years that included the collection of data and samples across multiple domains captured an unprecedented volume of clinical, physiologic, morphometric, genomic, and transcriptomic data. This work permitted us to extensively characterize the course and determinants of diabetic kidney disease, its pathophysiologic underpinnings, and important secular trends of urgent concern to populations worldwide, including the emergence of youth-onset type 2 diabetes and its effect on development of diabetic kidney disease in midlife. By combining these data using the tools of integrative biology, we are developing new mechanistic insights into the development and progression of diabetic kidney disease in type 2 diabetes. These insights have already contributed to the identification and successful therapeutic targeting of a novel pathway in DKD. We anticipate that this work will continue to expand our understanding of this complex disease and influence its management in the coming years.

Genetic and Epigenetic Studies in Diabetic Kidney Disease

Chronic kidney disease is a worldwide health crisis, while diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease (ESRD). DKD is a microvascular complication and occurs in 30–40% of diabetes patients. Epidemiological investigations and clinical observations on the familial clustering and heritability in DKD have highlighted an underlying genetic susceptibility. Furthermore, DKD is a progressive and long-term diabetic complication, in which epigenetic effects and environmental factors interact with an individual’s genetic background. In recent years, researchers have undertaken genetic and epigenetic studies of DKD in order to better understand its molecular mechanisms. In this review, clinical material, research approaches and experimental designs that have been used for genetic and epigenetic studies of DKD are described. Current information from genetic and epigenetic studies of DKD and ESRD in patients with diabetes, including the approaches of genome-wide association study (GWAS) or epigenome-wide association study (EWAS) and candidate gene association analyses, are summarized. Further investigation of molecular defects in DKD with new approaches such as next generation sequencing analysis and phenome-wide association study (PheWAS) is also discussed.

Inflammation and Immunity Pathways Regulate Genetic Susceptibility to Diabetic Nephropathy

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease worldwide, but its molecular pathogenesis is not well defined, and there are no specific treatments. In humans, there is a strong genetic component determining susceptibility to DN. However, specific genes controlling DN susceptibility in humans have not been identified. In this study, we describe a mouse model combining type 1 diabetes with activation of the renin-angiotensin system (RAS), which develops robust kidney disease with features resembling human DN: heavy albuminuria, hypertension, and glomerulosclerosis. Additionally, there is a powerful effect of genetic background regulating susceptibility to nephropathy; the 129 strain is susceptible to kidney disease, whereas the C57BL/6 strain is resistant. To examine the molecular basis of this differential susceptibility, we analyzed the glomerular transcriptome of young mice early in the course of their disease. We find dramatic differences in regulation of immune and inflammatory pathways, with upregulation of proinflammatory pathways in the susceptible (129) strain and coordinate downregulation in the resistant (C57BL/6) strain. Many of these pathways are also upregulated in rat models and in humans with DN. Our studies suggest that genes controlling inflammatory responses, triggered by hyperglycemia and RAS activation, may be critical early determinants of susceptibility to DN.

Genetic Variation in the H19-IGF2 Cluster Might Confer Risk of Developing Impaired Renal Function

The H19-IGF2 imprinted gene region could be implicated in the risk of developing impaired renal function (IRF). Our aim was to determine the association of several common H19-IGF2 variants and IRF in a cohort of elderly healthy individuals. The study involved 675 individuals >65 years of age, 184 with type 2 diabetes mellitus (T2DM), and 105 with IRF (estimated glomerular filtration rate [eGFR] <60). They were genotyped for two common H19 single nucleotide polymorphisms (SNPs) (rs2839698 and rs10732516), one H19-IGF2 intergenic indel (rs201858505), and one indel in the 3'UTR of the IGF2. For the H19 SNPs, we also determined the allele present in the methylated chromosome through genotyping the DNA digested with a methylation-sensitive endonuclease. None of the four H19-IGF2 variants was associated with IRF in our cohort. We found a significantly higher frequency of the 3'UTR IGF2 deletion (D) in the eGFR <60 group (p = 0.01; odds ratio = 1.16, 95% confidence interval = 1.10-2.51). This association was independent of age and T2DM, two strong predictors of IRF. In conclusion, a common indel variant in the 3'UTR of the IGF2 gene was associated with the risk of IRF. This association could be explained by the role of IGF2 in podocyte survival, through regulation of IGF2 expression by differential binding of miRNAs to the indel sequences. Functional studies should be necessary to clarify this issue.

Genome-Wide Association of CKD Progression: The Chronic Renal Insufficiency Cohort Study

The rate of decline of renal function varies significantly among individuals with CKD. To understand better the contribution of genetics to CKD progression, we performed a genome-wide association study among participants in the Chronic Renal Insufficiency Cohort Study. Our outcome of interest was CKD progression measured as change in eGFR over time among 1331 blacks and 1476 whites with CKD. We stratified all analyses by race and subsequently, diabetes status. Single-nucleotide polymorphisms (SNPs) that surpassed a significance threshold of P<1×10-6 for association with eGFR slope were selected as candidates for follow-up and secondarily tested for association with proteinuria and time to ESRD. We identified 12 such SNPs among black patients and six such SNPs among white patients. We were able to conduct follow-up analyses of three candidate SNPs in similar (replication) cohorts and eight candidate SNPs in phenotype-related (validation) cohorts. Among blacks without diabetes, rs653747 in LINC00923 replicated in the African American Study of Kidney Disease and Hypertension cohort (discovery P=5.42×10-7; replication P=0.039; combined P=7.42×10-9). This SNP also associated with ESRD (hazard ratio, 2.0 (95% confidence interval, 1.5 to 2.7); P=4.90×10-6). Similarly, rs931891 in LINC00923 associated with eGFR decline (P=1.44×10-4) in white patients without diabetes. In summary, SNPs in LINC00923, an RNA gene expressed in the kidney, significantly associated with CKD progression in individuals with nondiabetic CKD. However, the lack of equivalent cohorts hampered replication for most discovery loci. Further replication of our findings in comparable study populations is warranted.

Developing Treatments for Chronic Kidney Disease in the 21st Century

Chronic kidney disease (CKD) is a lethal and rapidly increasing burden on society. Despite this, there are relatively few therapies in development for the treatment of CKD. Several recent costly phase 3 trials have failed to provide improved renal outcomes, diminishing interest in pharmaceutical investment. Furthermore, poor patient, physician, and payer awareness of CKD as a diagnosis has contributed to slow trial enrollment and successful implementation of these trials. Nevertheless, several therapeutics remain in development for the treatment of CKD, including mineralocorticoid-receptor antagonists, sodium/glucose cotransporter 2 inhibitors, anti-inflammatory drugs, and drugs that mitigate oxidative injury. Success of future CKD therapeutic trials will depend not only on improved understanding of disease pathogenesis, but also on improved trial enrollment rates, through increasing awareness of this disease by the public, policy makers, and the greater medical community.

Mouse chromosome 2 harbors genetic determinants of resistance to podocyte injury and renal tubulointerstitial fibrosis

Background

Tensin2 deficiency results in alterations in podocytes and subsequent glomerular and tubulointerstitial injuries. However, this pathology is critically dependent on genetic background. While the Tensin2-deficient podocytes of resistant murine strains, including C57BL/6J mice, remain almost intact, susceptible murine strains with Tensin2 deficency, including ICGN mice, develop chronic kidney disease following alterations in the podocyte foot processes. In a previous study, genome-wide linkage analysis was utilized to identify the quantitative trait loci associated with the disease phenotypes on mouse chromosome 2. This study investigated the disease phenotypes of chromosome 2 consomic and subcongenic strains.

Results

ICGN consomic mice introgressed with chromosome 2 from the C57BL/6J mouse were generated and found to exhibit milder renal failure than that in ICGN mice. We developed 6 subcongenic strains that carry C57BL/6J-derived chromosomal segments from the consomic strain. One showed significantly milder albuminuria, another showed significantly milder tubulointerstitial injury, and the both showed significantly milder glomerular injury.

Conclusions

These data indicate that mouse chromosome 2 harbors two major genes associated with the severities of nephropathy induced by Tensin2 deficiency. The proximal region on chromosome 2 contributes to the resistance to tubulointerstitial fibrosis. In contrast, the distal region on chromosome 2 contributes to the resistance to podocyte injury. This study would be helpful to discover the biological mechanism underlying the renal injury, and may lead to the identification of therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0378-1) contains supplementary material, which is available to authorized users.

Genetic Variants in Toll-Like Receptor 4 Gene and Their Association Analysis with Estimated Glomerular Filtration Rate in Mexican American Families

BACKGROUND/AIM

Toll-like receptor 4 (TLR4) is one of the regulators of the innate immune response. Genetic variations in TLR4 have been associated with inflammatory diseases, including type 2 diabetes. However, to our knowledge, there are no reports on the role of variations in TLR4 in chronic kidney disease susceptibility. The objective of this study is to determine whether the genetic variants in TLR4 are associated with the estimated glomerular filtration rate (eGFR), a measure of renal function.

METHODS

To evaluate the association between TLR4 variants and eGFR, we used data obtained from 434 Mexican American participants from the San Antonio Family Diabetes/Gallbladder Study. GFR was estimated using the Modification of Diet in Renal Disease formula. The Asp(299)Gly (rs4986790) and Thr(399)Ile (rs4986791) variants of TLR4 were genotyped using the TaqMan assay. Association analyses between genotypes and eGFR were performed using the measured genotype approach.

RESULTS

Of the two genetic markers examined for association, only the Asp(299)Gly variant of TLR4 exhibited a nominally significant association with eGFR (p = 0.025) after accounting for the covariate effects of age and sex terms, diabetes, duration of diabetes, systolic blood pressure, body mass index, and antihypertensive treatment. Carriers of Gly299 had significantly decreased eGFR values. Although, the Thr(399)Ile variant failed to exhibit a statistically significant association with eGFR, the carriers of Ile399, however, showed a trend towards decrease in eGFR.

CONCLUSION

We show for the first time that Asp(299)Gly variants of TLR4 are associated with decrease in renal function in Mexican Americans.

Molecular disease presentation in diabetic nephropathy

Diabetic nephropathy, as the most prevalent chronic disease of the kidney, has also become the primary cause of end-stage renal disease with the incidence of kidney disease in type 2 diabetics continuously rising. As with most chronic diseases, the pathophysiology is multifactorial with a number of deregulated molecular processes contributing to disease manifestation and progression. Current therapy mainly involves interfering in the renin-angiotensin-aldosterone system using angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers. Better understanding of molecular processes deregulated in the early stages and progression of disease hold the key for development of novel therapeutics addressing this complex disease. With the advent of high-throughput omics technologies, researchers set out to systematically study the disease on a molecular level. Results of the first omics studies were mainly focused on reporting the highest deregulated molecules between diseased and healthy subjects with recent attempts to integrate findings of multiple studies on the level of molecular pathways and processes. In this review, we will outline key omics studies on the genome, transcriptome, proteome and metabolome level in the context of DN. We will also provide concepts on how to integrate findings of these individual studies (i) on the level of functional processes using the gene-ontology vocabulary, (ii) on the level of molecular pathways and (iii) on the level of phenotype molecular models constructed based on protein-protein interaction data.

rs1888747 polymorphism in the FRMD3 gene, gene and protein expression: role in diabetic kidney disease

BACKGROUND

We carried out a case-control study in patients with type 2 diabetes mellitus (T2DM) to evaluate the association between seven single nucleotide polymorphisms (SNPs) previously described to be linked to diabetic kidney disease (DKD) in type 1 diabetes mellitus (T1DM). Additionally, we evaluated gene and protein expression related to the polymorphism associated with DKD.

METHODS

The association study included 1098 T2DM patients (718 with DKD and 380 without DKD). Out of the 13 polymorphisms associated with DKD in a previous study with T1DM, seven were chosen for evaluation in this sample: rs1888747, rs9521445, rs39075, rs451041, rs1041466, rs1411766 and rs6492208. The expression study included 91 patients who underwent nephrectomy. Gene expression was assessed by RT-qPCR and protein expression in kidney samples was quantified by western blot and it localization by immunohistochemistry.

RESULTS

The C/C genotype of rs1888747 SNP was associated with protection for DKD (OR = 0.6, 95 % CI 0.3-0.9; P = 0.022). None of the other SNPs were associated with DKD. rs1888747 is located near FRMD3 gene. Therefore, FRMD3 gene and protein expression were evaluated in human kidney tissue according to rs1888747 genotypes. Gene and protein expression were similar in subjects homozygous for the C allele and in those carrying the G allele.

CONCLUSIONS

Replication of the association between rs1888747 SNP and DKD in a different population suggests that this link is not the result of chance. rs1888747 SNP is located at the FRMD3 gene, which is expressed in human kidney. Therefore, this gene is a candidate gene for DKD. However, in this study, no rs1888747 genotype or specific allele effect on gene and/or protein expression of the FRMD3 gene was demonstrated.

Diabetic Nephropathy: New Risk Factors and Improvements in Diagnosis

Diabetic nephropathy is the leading cause of end-stage renal disease. Patients with diabetic nephropathy have a high cardiovascular risk, comparable to patients with coronary heart disease. Accordingly, identification and management of risk factors for diabetic nephropathy as well as timely diagnosis and prompt management of the condition are of paramount importance for effective treatment. A variety of risk factors promotes the development and progression of diabetic nephropathy, including elevated glucose levels, long duration of diabetes, high blood pressure, obesity, and dyslipidemia. Most of these risk factors are modifiable by antidiabetic, antihypertensive, or lipid-lowering treatment and lifestyle changes. Others such as genetic factors or advanced age cannot be modified. Therefore, the rigorous management of the modifiable risk factors is essential for preventing and delaying the decline in renal function. Early diagnosis of diabetic nephropathy is another essential component in the management of diabetes and its complications such as nephropathy. New markers may allow earlier diagnosis of this common and serious complication, but further studies are needed to clarify their additive predictive value, and to define their cost-benefit ratio. This article reviews the most important risk factors in the development and progression of diabetic nephropathy and summarizes recent developments in the diagnosis of this disease.

Genetics of diabetic nephropathy: a long road of discovery

The global prevalence of diabetic nephropathy is rising in parallel with the increasing incidence of diabetes in most countries. Unfortunately, up to 40 % of persons diagnosed with diabetes may develop kidney complications. Diabetic nephropathy is associated with substantially increased risks of cardiovascular disease and premature mortality. An inherited susceptibility to diabetic nephropathy exists, and progress is being made unravelling the genetic basis for nephropathy thanks to international research collaborations, shared biological resources and new analytical approaches. Multiple epidemiological studies have highlighted the clinical heterogeneity of nephropathy and the need for better phenotyping to help define important subgroups for analysis and increase the power of genetic studies. Collaborative genome-wide association studies for nephropathy have reported unique genes, highlighted novel biological pathways and suggested new disease mechanisms, but progress towards clinically relevant risk prediction models for diabetic nephropathy has been slow. This review summarises the current status, recent developments and ongoing challenges elucidating the genetics of diabetic nephropathy.

Spectrum of renal disease in diabetes

The spectrum of renal disease in patients with diabetes encompasses both diabetic kidney disease (including albuminuric and non-albuminuric phenotypes) and non-diabetic kidney disease. Diabetic kidney disease can manifest as varying degrees of renal insufficiency and albuminuria, with heterogeneity in histology reported on renal biopsy. For patients with diabetes and proteinuria, the finding of non-diabetic kidney disease alone or superimposed on the changes of diabetic nephropathy is increasingly reported. It is important to identify non-diabetic kidney disease as some forms are treatable, sometimes leading to remission. Clinical indications for a heightened suspicion of non-diabetic kidney disease and hence consideration for renal biopsy in patients with diabetes and nephropathy include absence of diabetic retinopathy, short duration of diabetes, atypical chronology, presence of haematuria or other systemic disease, and the nephrotic syndrome.

The genetics of diabetic complications

The rising global prevalence of diabetes mellitus is accompanied by an increasing burden of morbidity and mortality that is attributable to the complications of chronic hyperglycaemia. These complications include blindness, renal failure and cardiovascular disease. Current therapeutic options for chronic hyperglycaemia reduce, but do not eradicate, the risk of these complications. Success in defining new preventative and therapeutic strategies hinges on an improved understanding of the molecular processes involved in the development of these complications. This Review explores the role of human genetics in delivering such insights, and describes progress in characterizing the sequence variants that influence individual predisposition to diabetic kidney disease, retinopathy, neuropathy and accelerated cardiovascular disease. Numerous risk variants for microvascular complications of diabetes have been reported, but very few have shown robust replication. Furthermore, only limited evidence exists of a difference in the repertoire of risk variants influencing macrovascular disease between those with and those without diabetes. Here, we outline the challenges associated with the genetic analysis of diabetic complications and highlight ongoing efforts to deliver biological insights that can drive translational benefits.

Evaluation of neurotrophic tyrosine receptor kinase 2 (NTRK2) as a positional candidate gene for variation in estimated glomerular filtration rate (eGFR) in Mexican American participants of San Antonio Family Heart study

Background

The estimated glomerular filtration rate (eGFR) is a well-known measure of kidney function and is commonly used for the diagnosis and management of patients with chronic kidney disease. The inter-individual variation in eGFR has significant genetic component. However, the identification of underlying genetic susceptibility variants has been challenging. In an attempt to identify and characterize susceptibility genetic variant(s) we previously identified the strongest evidence for linkage of eGFR occurring on chromosome 9q21 in the Mexican American participants of San Antonio Family Heart Study (SAFHS). The objective of the present study was to examine whether the common genetic variants in Neurotrophic Tyrosine Receptor Kinase 2 (NTRK2), a positional candidate gene on 9q21, contribute to variation in eGFR.

Results

Twelve tagging single nucleotide polymorphisms (SNPs) across the NTRK2 gene region were selected (r2 ≥ 0.80, minor allele frequency of ≥ 0.05) from the Hapmap database. SNPs were genotyped by TaqMan assay in the 848 Mexican American subjects participated in the SAFHS. Association analysis between the genotypes and eGFR (estimated by the Modification of Diet in Renal Disease equation) were performed by measured genotype approach as implemented in the program SOLAR. Of the 12 common genetic variants examined, the rs1036915 (located in 3′UTR) and rs1187274 (located in intron-14), present in perfect linkage disequilibrium, exhibited an association (P = 0.017) with eGFR after accounting for the effects of age, sex, diabetes, diabetes duration, systolic blood pressure and blood pressure medication. The carriers of minor allele of rs1036915 (G; 38%) had increased eGFR (104 ± 25 ml/min/1.73 m²) in comparison to the carriers of major allele A (98 ± 25 ml/min/1.73 m²).

Conclusion

Together, our results suggest for the first time that the genetic variants in NTRK2 may regulate eGFR.

Hispanic Americans living in the United States and their risk for obesity, diabetes and kidney disease: Genetic and environmental considerations

The Hispanic American, the largest minority population in the United States, is at increased risk for obesity, diabetes and end-stage renal disease. Here we review genetic and environmental factors that might account for their increased risk for these conditions. Whereas many environmental and genetic factors have important roles in driving the increased risk for obesity and kidney disease in this population, a case is made that excessive intake of sugary beverages is a contributory cause. Studies focusing on decreasing intake of sugary beverages among the Hispanic American could potentially reduce renal and cardiovascular complications in this population.

Biomarkers of vascular complications in type 2 diabetes

People with T2D are at substantially increased risk of developing severe complications, (coronary heart disease, stroke, retinopathy and nephropathy). Clinicians have an important responsibility to identify those patients who, because they are at high risk, will benefit more from a preventive program or intensified therapy. However, due to the limited accuracy of the predictive tests, and limited effectiveness of preventive measures, clinicians and their patients show a suboptimal compliance to such programs. An improved risk assessment will positively impact cost/benefit ratios, opening the door for new intervention. Research involving human genetic or genomic information becomes increasingly powerful and, in conjunction with other novel biomarkers, together with personal or health data, will offer new tools for harnessing risk factors underlying complex (multi-factorial) diseases such as T2D and its complications. Altogether, there is a rationale to develop early biomarkers with improved predictive value for vascular complications of T2D by integrating patients' genetic information with traditional and emerging biomarkers.

Genetic and epigenetic factors influencing chronic kidney disease

Chronic kidney disease (CKD) has become a serious public health problem because of its associated morbidity, premature mortality, and attendant healthcare costs. The rising number of persons with CKD is linked with the aging population structure and an increased prevalence of diabetes, hypertension, and obesity. There is an inherited risk associated with developing CKD, as evidenced by familial clustering and differing prevalence rates across ethnic groups. Previous studies to determine the inherited risk factors for CKD rarely identified genetic variants that were robustly replicated. However, improvements in genotyping technologies and analytic methods are now helping to identify promising genetic loci aided by international collaboration and multiconsortia efforts. More recently, epigenetic modifications have been proposed to play a role in both the inherited susceptibility to CKD and, importantly, to explain how the environment dynamically interacts with the genome to alter an individual's disease risk. Genome-wide, epigenome-wide, and whole transcriptome studies have been performed, and optimal approaches for integrative analysis are being developed. This review summarizes recent research and the current status of genetic and epigenetic risk factors influencing CKD using population-based information.

Genetic and epigenetic risk factors for diabetic kidney disease

Diabetes is increasing at daunting rates worldwide, and approximately 40% of affected individuals will develop kidney complications. Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease, and there are significant healthcare costs providing appropriate renal replacement therapies to affected individuals. For several decades, investigators have sought to discover inherited risk factors and biomarkers for DKD. In recent years, advances in high-throughput laboratory techniques and computational analyses, coupled with the establishment of multicenter consortia, have helped to identify genetic loci that are replicated across multiple populations. Several genome-wide association studies (GWAS) have been conducted for DKD with further meta-analysis of GWAS and comprehensive "single gene" meta-analyses now published. Despite these efforts, much of the inherited predisposition to DKD remains unexplained. Meta-analyses and integrated-omics pathway studies are being used to help elucidate underlying genetic risks. Epigenetic phenomena are increasingly recognized as important drivers of disease risk, and several epigenome-wide association studies have now been completed. This review describes key findings and ongoing genetic and epigenetic initiatives for DKD.