Insulin-like growth factor binding protein-1 levels are increased in patients with IgA nephropathy

Insulin-Like Growth Factor Binding Proteins in Kidney Disease

The seven members of the insulin-like growth factor (IGF) binding protein family (IGFBPs) were initially considered to be the regulatory proteins of IGFs in the blood circulation, mainly as the subsequent reserve for bidirectional regulation of IGF function during environmental changes. However, in recent years, IGFBPs has been found to have many functions independent of IGFs. The role of IGFBPs in regulating transcription, inducing cell migration and apoptosis is closely related to the occurrence and development of kidney disease. IGFBP-1, IGFBP-3, IGFBP-4 are closely associated with diabetes and diabetic nephropathy. IGFBP-3, IGFBP-4, IGFBP-5, IGFBP-6 are involved in different kidney disease such as diabetes, FSGS and CKD physiological process as apoptosis proteins, IGFBP-7 has been used in clinical practice as a biomarker for early diagnosis and prognosis of AKI. This review focuses on the differential expression and pathogenesis of IGFBPs in kidney disease.

Clinical and Pathological Features of Renal Presentations in Polycythemia Vera

BACKGROUND

Polycythemia vera (PV) is a common type of Philadelphia chromosome-negative chronic myeloproliferative disorder. PV-associated kidney disease is rarely reported and remains poorly understood. It has been observed that chronic kidney disease could be a risk factor for poor prognosis in PV.

METHODS

We retrospectively analyzed the clinicopathological features of renal presentations in eight patients with confirmed PV-associated kidney disease.

RESULTS

The eight patients were 6 males and 2 females, with a mean age of 46.4±16.8 years. Six patients had a history of PV, with a duration range 0.5-16 years. The other two patients were newly diagnosed with PV simultaneously with glomerular disease. Seven patients conducted a JAK2 V617F mutation test, with a positive result in five. Proteinuria and renal dysfunction were the patients' main complaints, with only one having nephrotic syndrome and three having microscopic hematuria. The level of proteinuria ranged from 0.52-10.96 g/day. Three patients had advanced chronic kidney disease (CKD), two in stage 3b and one in stage 4, but only one patient had anemia. Three patients had monoclonal immunoglobulinemia, one patient with immunoglobulin (Ig) G kappa plus light chain lambda, one patient with IgG kappa, and one patient with IgG lambda. Five patients underwent a renal biopsy. The pathological diagnosis was IgA nephropathy in three, non-IgA mesangial proliferative glomerulopathy in one, and glomerular hypertrophy with ischemic renal injury in one patient. Glomerular ischemia, ischemic shrinkage, focal segmental sclerosis, and glomerulomegaly were common pathological features. Glomerular crescents and endocapillary proliferation were also observed. All patients were administered hydroxyurea, and seven were administered renin-angiotensin system inhibitors. During follow-up, one patient with uncontrolled PV developed secondary myelofibrosis and died, three patients were lost to follow-up, and four patients remained alive with CKD.

CONCLUSIONS

Patients with untreated or uncontrolled PV could have massive proteinuria and advanced CKD, pathologically showing ischemic, sclerosing glomerular lesions with hypercellurity, glomerular crescents and endocapillary proliferation. IgA nephropathy was most commonly diagnosed. These findings deserve attention because early screening and effective control of PV may benefit the long-term kidney prognosis.

Integrated bioinformatics analysis reveals novel hub genes closely associated with pathological mechanisms of immunoglobulin A nephropathy

Immunoglobulin A (IgA) nephropathy (IgAN) is the most common glomerular disease. The major pathological changes associated with it affect cell proliferation, fibrosis, apoptosis, inflammation and extracellular matrix (ECM) organization. However, the molecular events underlying IgAN remain to be fully elucidated. In the present study, an integrated bioinformatics analysis was applied to further explore novel potential gene targets for IgAN. The mRNA expression profile datasets GSE93798 and GSE37460 were downloaded from the Gene Expression Omnibus database. After data preprocessing, differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment analysis of DEGs was performed. Protein-protein interaction (PPI) networks of the DEGs were built with the STRING online search tool and visualized by using Cytoscape, and hub genes were identified through the degree of connectivity in the PPI. The hub genes were subjected to Kyoto Encyclopedia of Genes and Genomes pathway analysis, and co-expression analysis was performed. A total of 298 DEGs between IgAN and control groups were identified, and 148 and 150 of these DEGs were upregulated and downregulated, respectively. The DEGs were enriched in distinct GO terms for Biological Process, including cell growth, epithelial cell proliferation, ERK1 and ERK2 cascades, regulation of apoptotic signaling pathway and ECM organization. The top 10 hub genes were then screened from the PPI network by Cytoscape. As novel hub genes, Fos proto-oncogene, AP-1 transcription factor subunit and early growth response 1 were determined to be closely associated with apoptosis and cell proliferation in IgAN. Tumor protein 53, integrin subunit β2 and fibronectin 1 may also be involved in the occurrence and development of IgAN. Co-expression analysis suggested that these hub genes were closely linked with each other. In conclusion, the present integrated bioinformatics analysis provided novel insight into the molecular events and novel candidate gene targets of IgAN.

Rs1520220 and Rs2195239 Polymorphisms of IGF-1 Gene Associated with Histopathological Grades in IgA Nephropathy in Northwestern Chinese Han Population

BACKGROUND/AIMS

Insulin-like growth factor-1 (IGF-1) plays important roles in cellular proliferation, differentiation, and growth. Previous studies showed that single-nucleotide polymorphisms (SNPs) of IGF-1 are associated with various diseases. This case-control study aimed to examine the relationship between IGF-1 polymorphisms and IgA nephropathy (IgAN) risk in a Chinese Han population.

METHODS

We recruited 351 IgAN patients and 310 healthy controls from Northwestern China. Sequenom MassARRAY was utilized to examine the genotypes of two common IGF-1 SNPs (rs1520220 and rs2195239). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by the Chi square test to evaluate the associations between IGF-1 and IgAN.

RESULTS

Our study demonstrated that IGF-1 gene rs1520220 and rs2195239 polymorphisms did not confer susceptibility to IgAN. We found no correlation between gender, blood pressure, proteinuria, eGFR, and IgAN in both SNPs. However, the rs1520220 and rs2195239 variants were correlated with M1 and E1 in patients with IgAN (M0/M1: CC vs. CG+GG: OR = 1.62, P = 0.04; E0/E1: CC vs. CG+GG: OR = 1.95, P = 0.004; GG vs. GC+CC: OR = 1.90, P = 0.004, respectively).

CONCLUSION

These results indicate that IGF-1 gene polymorphisms play crucial roles in the histopathological progression of IgAN in the Chinese Han population.

Role of Receptor Tyrosine Kinase Signaling in Renal Fibrosis

Renal fibrosis can be induced in different renal diseases, but ultimately progresses to end stage renal disease. Although the pathophysiologic process of renal fibrosis have not been fully elucidated, it is characterized by glomerulosclerosis and/or tubular interstitial fibrosis, and is believed to be caused by the proliferation of renal inherent cells, including glomerular epithelial cells, mesangial cells, and endothelial cells, along with defective kidney repair, renal interstitial fibroblasts activation, and extracellular matrix deposition. Receptor tyrosine kinases (RTKs) regulate a variety of cell physiological processes, including metabolism, growth, differentiation, and survival. Many studies from in vitro and animal models have provided evidence that RTKs play important roles in the pathogenic process of renal fibrosis. It is also showed that tyrosine kinases inhibitors (TKIs) have anti-fibrotic effects in basic research and clinical trials. In this review, we summarize the evidence for involvement of specific RTKs in renal fibrosis process and the employment of TKIs as a therapeutic approach for renal fibrosis.

Insulin-like growth factors and kidney disease

Insulin-like growth factors (IGF-1 and IGF-2) are necessary for normal growth and development. They are related structurally to proinsulin and promote cell proliferation, differentiation, and survival, as well as insulin-like metabolic effects, in most cell types and tissues. In particular, IGFs are important for normal pre- and postnatal kidney development. IGF-1 mediates many growth hormone actions, and both growth hormone excess and deficiency are associated with perturbed kidney function. IGFs affect renal hemodynamics both directly and indirectly by interacting with the renin-angiotensin system. In addition to the IGF ligands, the IGF system includes receptors for IGF-1, IGF-2/mannose-6-phosphate, and insulin, and a family of 6 high-affinity IGF-binding proteins that modulate IGF action. Disordered regulation of the IGF system has been implicated in a number of kidney diseases. IGF activity is enhanced in early diabetic nephropathy and polycystic kidneys, whereas IGF resistance is found in chronic kidney failure. IGFs have a potential role in enhancing stem cell repair of kidney injury. Most IGF actions are mediated by the tyrosine kinase IGF-1 receptor, and inhibitors recently have been developed. Further studies are needed to determine the optimal role of IGF-based therapies in kidney disease.

The primary glomerulonephritides: a systems biology approach

Our understanding of the pathogenesis of most primary glomerular diseases, including IgA nephropathy, membranous nephropathy and focal segmental glomerulosclerosis, is limited. Advances in molecular technology now permit genome-wide, high-throughput characterization of genes and gene products from biological samples. Comprehensive examinations of the genome, transcriptome, proteome and metabolome (collectively known as omics analyses), have been applied to the study of IgA nephropathy, membranous nephropathy and focal segmental glomerulosclerosis in both animal models and human patients. However, most omics studies of primary glomerular diseases, with the exception of large genomic studies, have been limited by inadequate sample sizes and the lack of kidney-specific data sets derived from kidney biopsy samples. Collaborative efforts to develop a standardized approach for prospective recruitment of patients, scheduled monitoring of clinical outcomes, and protocols for sampling of kidney tissues will be instrumental in uncovering the mechanisms that drive these diseases. Integration of molecular data sets with the results of clinical and histopathological studies will ultimately enable these diseases to be characterized in a comprehensive and systematic manner, and is expected to improve the diagnosis and treatment of these diseases.

The insulin-like growth factor system in kidney disease and hypertension

PURPOSE OF REVIEW

The insulin-like growth factor system plays an important role in renal physiology and it is perturbed in a range of kidney diseases.

RECENT FINDINGS

Some insulin-like growth factor (IGF) actions in the kidney are mediated by nitric oxide. Growth hormone and IGF-binding proteins may contribute to renal diseases via effects on podocytes and proximal tubule cells. In contrast, growth hormone and IGF-I may counteract the catabolic consequences of end-stage renal disease. Polymorphisms in the IGF system are associated with hypertension.

SUMMARY

Further studies are needed to determine whether modulating the IGF system may have a role in treating kidney diseases and/or hypertension.

High serum thioredoxin levels are reduced after tonsillectomy in patients with IgA nephropathy

OBJECTIVE

The role of oxidative stress in IgA nephropathy (IgAN), the most common type of primary glomerulonephritis, is unknown. We evaluated the clinical significance of serum levels of oxidative stress markers, thioredoxin (TRX) and manganese superoxide dismutase (MnSOD), in patients with IgAN.

METHODS

Forty-eight patients with histologically confirmed IgAN and 14 healthy subjects were enrolled in this study. Serum samples from 14 IgAN patients were obtained after tonsillectomy, a procedure hypothesized to be an effective treatment for IgAN.

RESULTS

Serum TRX levels were significantly higher in patients with IgAN than in healthy subjects (mean [ng/mL]; 49.5 vs.14.4, p<0.001). Serum TRX levels are positively correlated with blood urea nitrogen, serum uric acid and proteinuria, and negatively with estimated glomerular filtration rate (eGFR). In addition, serum TRX levels gradually increased as the severity of renal histology increased. High levels of serum TRX were significantly decreased after tonsillectomy in patients with IgAN (mean [ng/mL]; 55.5 to 41.1, p=0.02). In contrast, serum MnSOD levels did not differ between IgAN patients and healthy subjects, and these levels did not change after tonsillectomy in IgAN patients.

CONCLUSION

Serum TRX is associated with IgAN, and tonsillectomy may decrease oxidative stress in IgAN patients, leading to clinical improvement.

Change of MAX interactor 1 expression in an anti-Thy1 nephritis model and its effect on mesangial cell proliferation

BACKGROUND/AIMS

During the disease process of mesangial proliferative glomerulonephritis, the expression of various factors that influence mesangial proliferation is altered. MAX interactor 1 (Mxi1) antagonizes the transcription factor Myc and is believed to be a tumor suppressor. However, no studies have investigated its effect on mesangial cell proliferation.

METHODS

To investigate the effect of Mxi1 on renal mesangial cell proliferation, we established a classic rat anti-Thy1 mesangial proliferative glomerulonephritis model. Mesangial proliferation was estimated by immunohistochemical analysis of Ki67. Mxi1 expression at each time point was assessed by real-time RT-PCR and Western blot analyses. Furthermore, we altered the expression level of Mxi1 by a plasmid and siRNA to detect its effect on rat mesangial cell proliferation in vitro.

RESULTS

Mxi1 expression decreased significantly during the proliferative period of anti-Thy1 nephritis model and then gradually increased as proliferation declined, indicating that Mxi1 may be linked to mesangial cell proliferation. Upregulation of Mxi1 expression via plasmid transfection in vitro reduced the expression of the positive-acting cell cycle regulatory proteins cyclin B1, cyclin D1, cyclin E, CDC2 and CDK2; significantly reduced mesangial cell proliferation; reduced the percentage of S phase cells; and increased the percentage of G2/M phase cells. Inhibition of Mxi1 expression by siRNA in vitro produced the opposite effects: increased expression of cyclin B1, cyclin D1, cyclin E, CDC2 and CDK2; markedly increased cell proliferation; higher percentage of S phase cells; and dramatically lower percentage of G2/M phase cells. Transcription factor c-myc protein expression showed no obvious difference after Mxi1 plasmid and siRNA transfection. The expressions of cell cycle regulatory proteins mentioned above were negative correlated with Mxi1 expression in anti-Thy1 nephritis model.

CONCLUSION

These results suggest that Mxi1 expression levels were inversely correlated with proliferation in anti-Thy1 nephritis rats and it may influence cell cycle progression and thus the rate of mesangial cell proliferation by regulating the expression of c-myc target cell cycle regulatory proteins.