Replication study for the association of 3 SNP loci identified in a genome-wide association study for diabetic nephropathy in European type 1 diabetes with diabetic nephropathy in Japanese patients with type 2 diabetes

Genetic variants of ERBB4 gene and risk of gestational diabetes mellitus: a susceptibility and diagnostic nomogram study

Introduction

Gestational diabetes (GDM) is one of the common complications of female pregnancy, which seriously affects the health of mothers and their offspring. So far, the etiology has not been fully clarified.

Methods

A case-control study was conducted to clarify the relationship between Erb-b2 receptor tyrosine kinase 4 (ERBB4) functional tag genetic variants (rs1595064, rs1595065, rs1595066 and rs6719645) and the risk of GDM. Associations between variants and GDM risk were evaluated with the odds ratios (ORs) and their corresponding 95% confidence intervals (CIs). Subsequently, the false-positive reporting probability (FPRP), multi-factor dimension reduction (MDR) and bioinformatics analysis were adopted to confirm the significant associations. A nomogram model was constructed to predict the risk of GDM.

Results

Association analysis demonstrated that rs1595066 TT genotype performed a protective effect on GDM risk among all subjects (TT vs. CC: adjusted OR = 0.60, 95% CI = 0.38 - 0.94, P = 0.026; TT vs. CC/CT: adjusted OR = 0.61, 95% CI = 0.40 - 0.95, P = 0.027). Meanwhile, stratified analysis showed that rs1595066 TT can also reduce the GDM risk in age > 30.09 years old, pre-pregnancy BMI > 22.23 Kg/m2, SBP ≤ 110.08 mmHg, etc subgroups. Interactions between rs1595066 and DBP (P interaction = 0.01), FPG (P interaction < 0.001) and HbA1c (P interaction < 0.001) were detected. The FPRP analysis confirmed that association between rs1595066 and GDM risk in subjects of FPG < 4.79 mmol/L (P = 0.199) is true. The MDR analysis showed that rs1595066 was the best single locus model while the 4-loci model was the best multiple factors model to predict GDM risk. Functional prediction revealed that rs1595066 may disturb the stability of miRNA-mRNA binding. The predictive nomogram model has a well consistence and acceptable discriminative ability with a diagnosed AUC of 0.813.

Discussion

ERBB4 variants can change an individual's susceptibility to GDM via the interaction of gene-gene, gene-environment and changes in the regulatory effects of miRNAs on ERBB4 expression.

IGF1 and PPARG polymorphisms are associated with reduced estimated glomerular filtration rate in a cohort of children and adolescents with type 1 diabetes

INTRODUCTION

Several genetic loci have been associated with diabetic nephropathy; however, the underlying genetic mechanisms are still poorly understood, with no robust candidate genes identified yet.

AIM

We aimed to determine whether two polymorphisms, previously associated with renal decline, influence kidney impairment evaluating their association with markers of renal function in a pediatric population with type 1 diabetes (T1D).

MATERIAL AND METHODS

Renal function was evaluated by glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) in a cohort of pediatric subjects with T1D (n = 278). Risk factors for diabetes complications (diabetes duration, blood pressure, HbA1c) were assessed. The IGF1 rs35767 and PPARG rs1801282 SNPs were genotyped by TaqMan RT-PCR system. An additive genetic interaction was calculated. Association analysis between markers of renal function and both SNPs or their additive interaction were performed.

RESULTS

Both SNPs showed a significant association with eGFR: the A allele of rs35767 or the C allele of rs1801282 were associated to reduced eGFR compared to G alleles. Multivariate regression analysis adjusted for age, sex, z-BMI, T1D duration, blood pressure and Hba1c values showed that the additive genetic interaction was independently associated with lower eGFR (β = -3.59 [-6.52 to -0.66], p = 0.017). No associations were detected between SNPs, their additive interaction and ACR.

CONCLUSIONS

These results provide new insight into the genetic predisposition to renal dysfunction, showing that two polymorphisms in IGF1 and PPARG genes can lead to a reduction in renal filtration rate leading these patients to be exposed to a higher risk of early renal complications.

Neuregulin4 Acts on Hypothalamic ErBb4 to Excite Oxytocin Neurons and Preserve Metabolic Homeostasis

Neuregulin 4 (Nrg4) is an adipose tissue-enriched secreted factor that modulates glucose and lipid metabolism. Nrg4 is closely associated with obesity and preserves diet-induced metabolic disorders. However, the specific mechanisms via which Nrg4 regulates metabolic homeostasis remain incompletely understood. Here, this work finds that the Nrg4 receptor, ErbB4, is highly expressed in the hypothalamus, and the phosphorylation of hypothalamic ErbB4 is reduced in diet-induced obesity (DIO) mice. Peripheral Nrg4 can act on ErbB4 via blood circulation and excite neurons in the paraventricular nucleus of hypothalamus (PVN). Central administration of recombinant Nrg4 protein (rNrg4) reduces obesity and related metabolic disorders by influencing energy expenditure and intake. Overexpression of ErbB4 in the PVN protects against obesity, whereas its knock down in oxytocin (Oxt) neuron accelerates obesity. Furthermore, Nrg4-ErbB4 signaling excites Oxt release, and ablation of Oxt neuron considerably attenuates the effect of Nrg4 on energy balance. These data suggest that the hypothalamus is a key target of Nrg4, which partially explains the multifaceted roles of Nrg4 in metabolism.

The rs705708 A allele of the ERBB3 gene is associated with lower prevalence of diabetic retinopathy and arterial hypertension and with improved renal function in type 1 diabetic patients

INTRODUCTION

The Erb-b2 receptor tyrosine kinase 3 (ERBB3) is involved in autoimmune processes related to type 1 diabetes mellitus (T1DM) pathogenesis. Accordingly, some studies have suggested that single nucleotide polymorphisms (SNPs) in the ERBB3 gene confer risk for T1DM. Proliferation-associated protein 2G4 (PA2G4) is another candidate gene for this disease because it regulates cell proliferation and adaptive immunity. Moreover, PA2G4 regulates ERBB3. To date, no study has evaluated the association of PA2G4 SNPs and T1DM.

AIM

To evaluate the association of ERBB3 rs705708 (G/A) and PA2G4 rs773120 (C/T) SNPs with T1DM and its clinical and laboratory characteristics.

METHODS

This case-control study included 976 white subjects from Southern Brazil, categorized into 501 cases with T1DM and 475 non-diabetic controls. The ERBB3 and PA2G4 SNPs were genotyped by allelic discrimination-real-time PCR.

RESULTS

ERBB3 rs705708 and PA2G4 rs773120 SNPs were not associated with T1DM considering different inheritance models and also when controlling for covariables. However, T1DM patients carrying the ERBB3 rs705708 A allele developed T1DM at an earlier age vs. G/G patients. Interestingly, in the T1DM group, the rs705708 A allele was associated with lower prevalence of diabetic retinopathy and arterial hypertension as well as with improved renal function (higher estimated glomerular filtration rate and lower urinary albumin excretion levels) compared to G/G patients.

CONCLUSIONS

Although no association was observed between the ERBB3 rs705708 and PA2G4 rs773120 SNPs and T1DM, the rs705708 A allele was associated, for the first time in literature, with lower prevalence of diabetic retinopathy and arterial hypertension. Additionally, this SNP was associated with improved renal function.

Mechanism and effects of artesunate on the liver function of rats with type 1 diabetic periodontitis

Periodontitis is an inflammatory disease of the gums. Periodontitis in patients with diabetes can aggravate insulin resistance, but its molecular and biological mechanism remains unclear. This study aimed to explore the effects of diabetic periodontitis on liver function and determine the mechanism by which artesunate improves liver function. Rats with streptozotocin-induced diabetes were divided into five groups, i.e., normal control group (NC group), diabetic periodontitis group (DM+PD group), artesunate intervention group (ART group), insulin intervention group (INS group), and combined medication intervention group (ART+INS group). Drug interventions were then administered to the rats in each group as follows: 50 mg/kg artesunate to the ART group, 6 U/kg insulin to the INS group, and 50 mg/kg artesunate + 6 U/kg insulin to the ART+INS group. Blood samples, liver tissues, and the maxillary alveolar bone were collected post-sacrifice. ART was found to significantly ameliorate hyperglycemia, blood lipid levels, and liver function. The levels of inflammatory factors reduced; the effect was more pronounced in the ART+INS group. Artesunate presumably inhibits the TLR4/NF-κB signaling pathway and expression of downstream inflammatory factors, thereby exerting a protective effect on diabetes-related liver function. This offers a fresh approach to treat diabetes mellitus.

Diabetic kidney disease: Are the reported associations with single-nucleotide polymorphisms disease-specific?

BACKGROUND

The genetic backgrounds of diabetic kidney disease (DKD) and end-stage kidney disease (ESKD) have not been fully elucidated.

AIM

To examine the individual and cumulative effects of single-nucleotide polymorphisms (SNPs) previously associated with DKD on the risk for ESKD of diabetic etiology and to determine if any associations observed were specific for DKD.

METHODS

Fourteen SNPs were genotyped in hemodialyzed 136 patients with diabetic ESKD (DKD group) and 121 patients with non-diabetic ESKD (NDKD group). Patients were also re-classified on the basis of the primary cause of chronic kidney disease (CKD). The distribution of alleles was compared between diabetic and non-diabetic groups as well as between different sub-phenotypes. The weighted multilocus genetic risk score (GRS) was calculated to estimate the cumulative risk conferred by all SNPs. The GRS distribution was then compared between the DKD and NDKD groups as well as in the groups according to the primary cause of CKD.

RESULTS

One SNP (rs841853; SLC2A1) showed a nominal association with DKD (P = 0.048; P > 0.05 after Bonferroni correction). The GRS was higher in the DKD group (0.615 ± 0.260) than in the NDKD group (0.590 ± 0.253), but the difference was not significant (P = 0.46). The analysis of associations between GRS and individual factors did not show any significant correlation. However, the GRS was significantly higher in patients with glomerular disease than in those with tubulointerstitial disease (P = 0.014) and in those with a combined group (tubulointerstitial, vascular, and cystic and congenital disease) (P = 0.018).

CONCLUSION

Our results suggest that selected SNPs that were previously associated with DKD may not be specific for DKD and may confer risk for CKD of different etiology, particularly those affecting renal glomeruli.

Leptin Receptor-Deficient db/db Mice Show Significant Heterogeneity in Response to High Non-heme Iron Diet

Recent studies have shown an association between iron homeostasis, obesity and diabetes. In this work, we investigated the differences in the metabolic status and inflammation in liver, pancreas and visceral adipose tissue of leptin receptor-deficient db/db mice dependent on high iron concentration diet. 3-month-old male BKS-Leprdb/db/JOrlRj (db/db) mice were divided into two groups, which were fed with different diets containing high iron (29 g/kg, n = 57) or standard iron (0.178 g/kg; n = 42) concentrations for 4 months. As anticipated, standard iron-fed db/db mice developed obesity and diabetes. However, high iron-fed mice exhibited a wide heterogeneity. By dividing into two subgroups at the diabetes level, non-diabetic subgroup 1 (<13.5 mmol/l, n = 30) significantly differed from diabetic subgroup two (>13.5 mmol/l, n = 27). Blood glucose concentration, HbA1c value, inflammation markers interleukin six and tumor necrosis factor α and heme oxygenase one in visceral adipose tissue were reduced in subgroup one compared to subgroup two. In contrast, body weight, C-peptide, serum insulin and serum iron concentrations, pancreatic islet and signal ratio as well as cholesterol, LDL and HDL levels were enhanced in subgroup one. While these significant differences require further studies and explanation, our results might also explain the often-contradictory results of the metabolic studies with db/db mice.

Multi-Omics Data Analysis Uncovers Molecular Networks and Gene Regulators for Metabolic Biomarkers

The insulin-like growth factors (IGFs)/insulin resistance (IR) axis is the major metabolic hormonal pathway mediating the biologic mechanism of several complex human diseases, including type 2 diabetes (T2DM) and cancers. The genomewide association study (GWAS)-based approach has neither fully characterized the phenotype variation nor provided a comprehensive understanding of the regulatory biologic mechanisms. We applied systematic genomics to integrate our previous GWAS data for IGF-I and IR with multi-omics datasets, e.g., whole-blood expression quantitative loci, molecular pathways, and gene network, to capture the full range of genetic functionalities associated with IGF-I/IR and key drivers (KDs) in gene-regulatory networks. We identified both shared (e.g., T2DM, lipid metabolism, and estimated glomerular filtration signaling) and IR-specific (e.g., mechanistic target of rapamycin, phosphoinositide 3-kinases, and erb-b2 receptor tyrosine kinase 4 signaling) molecular biologic processes of IGF-I/IR axis regulation. Next, by using tissue-specific gene–gene interaction networks, we identified both well-established (e.g., IRS1 and IGF1R) and novel (e.g., AKT1, HRAS, and JAK1) KDs in the IGF-I/IR-associated subnetworks. Our results, if validated in additional genomic studies, may provide robust, comprehensive insights into the mechanisms of IGF-I/IR regulation and highlight potential novel genetic targets as preventive and therapeutic strategies for the associated diseases, e.g., T2DM and cancers.

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.

ErbB4 deletion predisposes to development of metabolic syndrome in mice

ErbB4, a member of the EGF receptor family, plays a variety of roles in physiological and pathological states. Genetic studies have indicated a link between ErbB4 and type 2 diabetes and obesity, but its role in metabolic syndrome (MetS) has not been reported. In the current study we found that mice with ErbB4 deletion developed MetS after 24 wk on a medium-fat diet (MFD), as indicated by development of obesity, dyslipidemia, hepatic steatosis, hyperglycemia, hyperinsulinemia, and insulin resistance, compared with wild-type mice. ErbB4 deletion mice also exhibited increased amounts of subcutaneous and visceral fat, with increased serum leptin levels, compared with wild-type mice, whereas levels of adiponectin were not significantly different. Histologically, severe inflammation, indicated by F4/80 immunostaining and M1 macrophage polarization, was detected in inguinal and epididymal white adipose tissue in ErbB4 deletion mice. ErbB4 expression decreased during 3T3-L1 preadipocyte differentiation. Administration of neuroregulin 4, a specific ligand for ErbB4, to 3T3-L1 adipocytes had no effect on adipogenesis and lipolysis but significantly inhibited lipogenesis, promoted browning, induced GLUT4 redistribution to the cell membrane, and increased glucose uptake. Neuroregulin 4 also significantly increased glucose uptake in adipocytes isolated from wild-type mice, while these effects were significantly decreased in adipocytes isolated from ErbB4 deletion mice. In conclusion, our results indicate that ErbB4 may play an important role in glucose homeostasis and lipogenesis. ErbB4 deficiency-related obesity and adipose tissue inflammation may contribute to the development of MetS.

ErbB4 deletion accelerates renal fibrosis following renal injury

Tubulointerstitial fibrosis (TIF) is a prominent factor in the progression of chronic kidney disease regardless of etiology. Avian erythroblastic leukemia viral oncogene homolog 4 (ErbB4) expression levels were inversely correlated to renal fibrosis in human fibrotic kidneys. In both unilateral ureteral obstruction (UUO) and ischemia-reperfusion injury followed by uninephrectomy (IRI/UNx) mouse models, expression levels of ErbB4 were elevated in the early stage of renal injury. Using mice with global ErbB4 deletion except for transgenic rescue in cardiac tissue ( ErbB4-/-ht+), we determined that UUO induced similar injury in proximal tubules compared with wild-type mice but more severe injury in distal nephrons. TIF was apparent earlier and was more pronounced following UUO in ErbB4-/-ht+ mice. With ErbB4 deletion, UUO injury inhibited protein kinase B phosphorylation and increased the percentage of cells in G2/M arrest. There was also increased nuclear immunostaining of yes-associated protein and increased expression of phospho-Mothers against decapentaplegic homolog 3, snail1, and vimentin. These results indicate that ErbB4 deletion accelerates the development and progression of renal fibrosis in obstructive nephropathy. Similar results were found in a mouse IRI/UNx model. In conclusion, increased expression of ErbB4 in the early stages of renal injury may reflect a compensatory effect to lessen tubulointerstitial injury.

Genetics of cardiovascular and renal complications in diabetes

The development of debilitating complications represents a major heathcare burden associated with the treatment of diabetes. Despite advances in new therapies for controlling hyperglycemia, the burden associated with diabetic complications remains high, especially in relation to cardiovascular and renal complications. Furthermore, an increasing proportion of patients develop type 2 diabetes at a younger age, putting them at higher risk of developing complications as a result of the increased exposure to hyperglycemia. Diabetes has become the main contributing cause to end‐stage renal disease in most countries. Although there has been important breakthroughs in our understanding of the genetics of type 1 and type 2 diabetes, bringing important insights towards the pathogenesis of diabetes, there has been comparatively less progress in our understanding of the genetic basis of diabetic complications. Genome‐wide association studies are beginning to expand our understanding of the genetic architecture relating to diabetic complications. Improved understanding of the genetic basis of diabetic cardiorenal complications might provide an opportunity for improved risk prediction, as well as the development of new therapies.

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.