Serum microRNAs are altered in various stages of chronic kidney disease: a preliminary study

Circulating miRNAs in Type 2 Diabetic Patients with and without Albuminuria in Malaysia

INTRODUCTION

Diabetic kidney disease (DKD) remains the leading cause of chronic kidney disease. Dysregulation of circulating miRNAs has been reported, suggesting their pathological roles in DKD. This study aimed to investigate differentially expressed miRNAs in the sera of type 2 diabetes mellitus (T2DM) patients with and without albuminuria in a selected Malaysian population.

METHOD

Forty-one T2DM patients on follow-up at a community clinic were divided into normo-(NA), micro-(MIC), and macroalbuminuria (MAC) groups. Differential levels of miRNAs in 12 samples were determined using the pathway-focused (human fibrosis) miScript miRNA qPCR array and was validated in 33 samples, using the miScript custom qPCR array (CMIHS02742) (Qiagen GmbH, Hilden, Germany).

RESULTS

Trends of upregulation of 3 miRNAs in the serum, namely, miR-874-3p, miR-101-3p, and miR-145-5p of T2DM patients with MAC compared to those with NA. Statistically significant upregulation of miR-874-3p (p = 0.04) and miR-101-3p (p = 0.01) was seen in validation cohort. Significant negative correlations between the estimated glomerular filtration rate (eGFR) and miR-874-3p (p = 0.05), miR-101-3p (p = 0.03), and miR-145-5p (p = 0.05) as well as positive correlation between miR-874-3p and age (p = 0.03) were shown by Pearson's correlation coefficient analysis.

CONCLUSION

Upregulation of previously known miRNA, namely, miR-145-5p, and possibly novel ones, namely, miR-874-3p and miR-101-3p in the serum of T2DM patients, was found in this study. There was a significant correlation between the eGFR and these miRNAs. The findings of this study have provided encouraging evidence to further investigate the putative roles of these differentially expressed miRNAs in DKD.

Uremic Toxins: An Alarming Danger Concerning the Cardiovascular System

The kidneys and heart share functions with the common goal of maintaining homeostasis. When kidney injury occurs, many compounds, the so-called "uremic retention solutes" or "uremic toxins," accumulate in the circulation targeting other tissues. The accumulation of uremic toxins such as p-cresyl sulfate, indoxyl sulfate and inorganic phosphate leads to a loss of a substantial number of body functions. Although the concept of uremic toxins is dated to the 1960s, the molecular mechanisms capable of leading to renal and cardiovascular injuries are not yet known. Besides, the greatest toxic effects appear to be induced by compounds that are difficult to remove by dialysis. Considering the close relationship between renal and cardiovascular functions, an understanding of the mechanisms involved in the production, clearance and overall impact of uremic toxins is extremely relevant for the understanding of pathologies of the cardiovascular system. Thus, the present study has as main focus to present an extensive review on the impact of uremic toxins in the cardiovascular system, bringing the state of the art on the subject as well as clinical implications related to patient's therapy affected by chronic kidney disease, which represents high mortality of patients with cardiac comorbidities.

Functional miR143/145 Cluster Variants and Haplotypes Are Associated with Chronic Kidney Disease: a Preliminary Case-Control Study and Computational Analyses

MiR-143/145 cluster is a novel transcriptional target of many signaling pathways, with variations within this cluster contributed to the risk of multiple diseases. To date, no data regarding the link between miR143/145 cluster polymorphisms and the risk of developing chronic kidney disease (CKD) has been reported. Hence, we aimed to examine such association in a population of Iranian ancestry. In this preliminary study, 276 CKD patients and 300 unrelated age and sex-matched healthy controls were recruited. Genotyping was performed by PCR-RFLP and allele-specific-PCR methods. Computational analyses were performed to predict the potential effects of the variants. Our findings indicated that rs41291957, rs12659504, and rs353292 polymorphisms were positively associated with CKD, while rs4705342 and rs4705343 polymorphisms demonstrated a significant negative association with the disease. Moreover, a significant association was observed between CC + TC and TT genotypes and CKD stages. We found that AACTT, AATTC, AATTT, GATTC, GATTT, and GGCTT haplotypes significantly enhanced the risk of CKD compared with the G_rs41291957AA_rs12659504C_rs353292T_rs4705342T_rs4705343 haplotype. Computational analysis showed that rs353292, rs4705342, and rs4705343 might alter the binding of the transcription factors in this gene cluster. We found that miR-143/145 cluster polymorphisms were associated with CKD risk in a sample of the Iranian population. Replicated studies on different ethnicities are necessary to investigate the association between these promoter variants and clinical outcomes.

Expression of Circulating MicroRNAs Linked to Bone Metabolism in Chronic Kidney Disease-Mineral and Bone Disorder

The pathophysiology of chronic kidney disease-mineral and bone disorder (CKD-MBD) is complex and multifactorial. Recent studies have identified a link between microRNAs (miRNAs) and bone loss. In this study, we investigated the expression of miRNAs in CKD-MBD. In this case-control study, we included thirty patients with CKD-MBD (cases) and 30 age- and gender-matched healthy individuals (controls). Bone mineral density (BMD) and trabecular bone score (TBS) evaluation was performed with dual X-ray absorptiometry. The selected panel of miRNAs included: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3; hsa-miRNA-124-3p; hsa-miRNA-2861. The majority of cases had low BMD values. The relative expression of miRNA-21-5p was 15 times lower [fold regulation (FR): -14.7 ± 8.1, p = 0.034), miRNA-124-3p, 6 times lower (FR: -5.9 ± 4, p = 0.005), and miRNA-23a-3p, 4 times lower (FR: -3.8 ± 2.0, p = 0.036) in cases compared to controls. MiRNA-23a-3p was significantly and inversely correlated with TBS, adjusted for calcium metabolism and BMD values (beta = -0.221, p = 0.003, 95% CI -0.360, -0,081) in cases. In a receiver operating characteristic (ROC) analysis, expression of miRNA-124-3p demonstrated 78% sensitivity and 83% specificity in identifying CKD patents with osteoporosis. Serum expression of miRNAs related to osteoblasts (miRNA-23a-3p) and osteoclasts (miRNA-21-5p, miRNA-124-3p) is significantly altered in patients with CKD-MBD.

Inflammation, Senescence and MicroRNAs in Chronic Kidney Disease

Background

Patients with chronic kidney disease (CKD) show a chronic microinflammatory state that promotes premature aging of the vascular system. Currently, there is a growth interest in the search of novel biomarkers related to vascular aging to identify CKD patients at risk to develop cardiovascular complications.

Methods

Forty-five CKD patients were divided into three groups according to CKD-stages [predialysis (CKD4-5), hemodialysis (HD) and kidney transplantation (KT)]. In all these patients, we evaluated the quantitative changes in microRNAs (miRNAs), CD14+C16++ monocytes number, and microvesicles (MV) concentration [both total MV, and monocytes derived MV (CD14+Annexin V+CD16+)]. To understand the molecular mechanism involved in senescence and osteogenic transdifferentation of vascular smooth muscle cells (VSMC), these cells were stimulated with MV isolated from THP-1 monocytes treated with uremic toxins (txMV).

Results

A miRNA array was used to investigate serum miRNAs profile in CKD patients. Reduced expression levels of miRNAs-126-3p, -191-5p and -223-3p were observed in CKD4-5 and HD patients as compared to KT. This down-regulation disappeared after KT, even when lower glomerular filtration rates (eGFR) persisted. Moreover, HD patients had higher percentage of proinflammatory monocytes (CD14+CD16++) and MV derived of proinflammatory monocytes (CD14+Annexin V+CD16+) than the other groups. In vitro studies showed increased expression of osteogenic markers (BMP2 and miRNA-223-3p), expression of cyclin D1, β-galactosidase activity and VSMC size in those cells treated with txMV.

Conclusion

CKD patients present a specific circulating miRNAs expression profile associated with the microinflammatory state. Furthermore, microvesicles generated by monocytes treated with uremic toxins induce early senescence and osteogenic markers (BMP2 and miRNA-223-3p) in VSMC.

Circulating microRNAs as potential biomarkers of chronic kidney disease

Chronic kidney disease (CKD) is a supra - nosological term that reflects the progressive nature of chronic kidney diseases, which are based on the mechanisms of nephrosclerosis. Diagnosis of CKD at the earliest stages is of great importance, because it allows, by using therapeutic agents, to slow the progression of renal dysfunction and the development of cardiovascular complications. However, the currently available methods for diagnosing renal function impairment, including the determination of endogenous creatinine clearance, can detect renal dysfunction too late, when around 40-50% of the renal parenchyma is already reversibly or irreversibly damaged. In this regard, there is an active search for new, more sensitive and specific biomarkers for early diagnosis of CKD. Recent studies in cellular and animal models of CKD have demonstrated the important role of microRNA, a new class of posttranscriptional regulators of gene expression, in physiology and pathophysiology of kidneys. In particular, it has been shown that their expression profile in blood or urine can reflect changes in cells involved in a particular pathological process, since these cells can secrete a specific population of microRNAs, for example, through secretion of microRNA-containing exosomes. This gave grounds for considering increased or decreased expression of individual microRNAs in renal tissue or biological fluids (including urine) as new biomarkers for the diagnosis and monitoring of CKD. This review presents the results of recent experimental and clinical studies on these issues.

MicroRNA-375 inhibits esophageal squamous cell carcinoma proliferation through direct targeting of SP1

Several studies have shown that microRNA-375 (miR-375) is frequently downregulated in several types of human cancer including gastric cancer, colorectal cancer and oral squamous cell carcinoma. However, the role of miR-375 in human esophageal cancer remains unknown. In the current study, the expression level of miR-375 was analyzed in 43 esophageal squamous cell carcinoma (ESCC) tissue and matched adjacent normal tissue samples from patients with ESCC by reverse transcription-quantitative polymerase chain reaction. In addition, the expression level of miR-375 was analyzed in ESCC cell lines (KYSE450 and KYSE150) and the human esophageal epithelial cell line Het-1A by the same method. The expression level of miR-375 was significantly downregulated in ESCC tissue samples and cell lines compared with adjacent normal tissue samples and the human esophageal epithelial cell line, respectively. The effect of miR-375 on ESCC cell proliferation was detected by cell counting kit-8 (CCK-8) and colony formation assays. miR-375 overexpression significantly decreased ESCC cell proliferation and colony formation. Bioinformatics analysis was used to predict specificity protein 1 (SP1) as a target gene of miR-375 in ESCC, and this was verified by dual-luciferase assay. The present study demonstrated that SP1 regulates ESCC cell proliferation and colony formation through direct interaction with miR-375. In addition, the overall survival of patients with ESCC was analyzed using the Kaplan-Meier method and log-rank test. The results indicated that patients with ESCC with high miR-375 expression had a better survival rate compared with patients with ESCC with low miR-375 expression. Taken together, these results suggest that downregulated miR-375 promotes ESCC cell proliferation and colony formation via direct targeting of SP1, and this association may contribute to ESCC progression.

MicroRNAs as biomarkers for clinical studies

The development of better diagnostic and prognostic non-invasive biomarkers holds an enormous potential to improve the ability to diagnose and individualize treatment of a great number of human diseases and substantially reduce health care cost. The discovery of a fundamental role of microRNAs in the disease pathogenesis and their presence and stability in biological fluids has led to extensive investigation of the role of microRNAs as potential non-invasive biomarkers for disease diagnosis and prognosis. The result of this research has suggested that alterations of microRNAs may be sensitive indicators of various pathologies; however, despite the indisputable progress in this field, the diagnostic promise of microRNAs has remained a work in progress, and circulating microRNAs have not entered the field of clinical medicine yet. Commonly reported microRNAs as disease biomarkers are largely not disease-specific and the results are often contradicting in independent studies. This review summarizes the current knowledge on the role of microRNAs as disease indicators and emphasizes the current gaps, challenges, and questions that need to be addressed in future well-designed and well-controlled studies for a successful translation of microRNA profiling into clinically meaningful tests. Impact statement This review summarizes the current knowledge on the role of circulating miRNAs as clinical diagnostic biomarkers and highlights the challenges that need to be addressed in future studies for a successful translation of circulating miRNAs into a novel diagnostic tool.

Circulating miRNAs as biomarkers of kidney disease

Interest in microRNAs (miRNAs) has dramatically increased in recent years not only because they regulate mRNA expression, and thus many physiological or pathophysiological processes, but also because they could serve as biomarkers. Next to analysis of tissue miRNA expression, measurement in body fluids such as blood or urine is attractive because miRNA in microvesicles or bound to protein is very stable. Currently it is unclear whether these circulating miRNAs are tissue and disease specific or represent more general pathologies like inflammation. In addition pre-analytical sample handling and variable analysis techniques affect the results and thus much more work needs to be done before one can draw a final conclusion about their clinical utility.

Direct visualization of sub-femtomolar circulating microRNAs in serum based on the duplex-specific nuclease-amplified oriented assembly of gold nanoparticle dimers

The combination of DSNSA and oriented assembly of AuNPs was used for direct visualization of sub-femtomolar circulating microRNAs in serum.