New molecular insights in diabetic nephropathy

Epidermal Growth Factor Protects Against High Glucose-Induced Podocyte Injury Possibly via Modulation of Autophagy and PI3K/AKT/mTOR Signaling Pathway Through DNA Methylation

AIM

Diabetic nephropathy (DN) is a serious health problem worldwide. Epidermal growth factor (EGF) has suggested as a potential biomarker for the progression of chronic kidney disease. In this study, we examined the effects of EGF on the high glucose (HG)-induced podocyte injury and explored the underlying molecular mechanisms.

METHODS

The cell proliferation, toxicity, and cell apoptosis of podocytes were determined by CCK-8 assay, lactate dehydrogenase release assay, and flow cytometry, respectively, and protein levels in the podocytes were determined by Western blot assay. Mechanistically, DNA methylation analysis, bioinformatic analysis, methylation‑specific PCR and quantitative real-time PCR were used to analyze functional pathways in differentially methylated genes and the expression of the key methylated genes in the podocytes after different interventions.

RESULTS

EGF treatment significantly increased the protein expression level of LC3 and decreased the protein level of P62 in HG-stimulated podocytes, which was attenuated by autophagy inhibitor, 3-methyladenine. EGF increased the cell proliferation and the protein expression levels of nephrin and synaptopodin, but reduced cell toxicity and cell apoptosis and protein expression level of cleaved caspase-3, which was partially antagonized by 3-methyladenine. DNA methylation expression profiles revealed the differential hypermethylation sites and hypomethylation sites among podocytes treated with normal glucose, HG and HG+EGF. GO enrichment analysis showed that DNA methylation was significantly enriched in negative regulation of phosphorylation, cell-cell junction and GTPase binding. KEGG pathway analysis showed that these genes were mainly enriched in PI3K-Akt, Hippo and autophagy pathways. Further validation studies revealed that six hub genes (ITGB1, GRB2, FN1, ITGB3, FZD10 and FGFR1) may be associated with the protective effects of EGF on the HG-induced podocyte injury.

CONCLUSION

In summary, our results demonstrated that EGF exerted protective effects on HG-induced podocytes injury via enhancing cell proliferation and inhibiting cell apoptosis. Further mechanistic studies implied that EGF-mediated protective effects in HG-stimulated podocytes may be associated with modulation of autophagy and PI3K/AKT/mTOR signaling pathway.

Eriodictyol inhibits high glucose-induced extracellular matrix accumulation, oxidative stress, and inflammation in human glomerular mesangial cells

Diabetic nephropathy (DN) is one of the major complications of diabetes mellitus. The progression of DN has been found to be associated with high glucose (HG)-induced oxidative stress and inflammation in diabetes mellitus. Eriodictyol is a flavonoid that possesses antioxidant and anti-inflammatory effects. However, the effect of eriodictyol on DN remains unknown. In the present study, we evaluated the role of eriodictyol in mesangial cells (MCs) in response to HG condition. The results showed that eriodictyol repressed cell proliferation of HG-stimulated MCs. Treatment with eriodictyol attenuated oxidative stress, which was evidenced by increased superoxide dismutase activity as well as decreased production of reactive oxygen species (ROS) and malondialdehyde. Besides, eriodictyol suppressed the expressions of two NADPH oxidase (NOX) isoforms, NOX2 and NOX4, which are responsible for the generation of ROS. Eriodictyol suppressed the production of extracellular matrix proteins including fibronectin and Collagen IV, as well as the secretion of inflammatory cytokines including TNF-α, IL-1β, and IL-6 in HG-induced MCs. Moreover, the HG-induced activation of Akt/NF-κB pathway was mitigated by eriodictyol. In conclusion, eriodictyol protected MCs from HG stimulation though inhibition of Akt/NF-κB pathway.

New Areas of Interest: Is There a Role for Omega-3 Fatty Acid Supplementation in Patients With Diabetes and Cardiovascular Disease?

PURPOSE OF REVIEW

Summarize studies on omega-3 fatty acids in prevention of albuminuria in subjects with diabetes.

RECENT FINDINGS

Several small, short-term trials suggested benefit on albuminuria in subjects with diabetes; however, results were not definitive. Welty et al. showed that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 1 year slowed progression of early-stage albuminuria in subjects with diabetes with clinical coronary artery disease on an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker, the majority of whom had an albumin/creatinine ratio (ACR) < 30 μg/mg. Moreover, significantly more (3-fold) subjects on EPA and DHA had a decrease in ACR compared to control, and three on EPA and DHA had a change in category from > 30 μg/mg to < 30 μg/mg, whereas no controls did. Potential mechanisms for benefit are discussed. These results suggest that there is benefit and perhaps even reversal of albuminuria with EPA and DHA at an early stage of disease in those with ACR < 30 μg/mg and those with microalbuminuria (ACR > 30).

Evaluation of endocan and endoglin levels in chronic kidney disease due to diabetes mellitus

INTRODUCTION

Endocan and endoglin have been shown to play a role in angiogenesis. Aberrant excessive angiogenesis is a main factor in the development of diabetic nephropathy. In this study we evaluated endocan and endoglin levels in diabetes patients with and without albuminuria and compared them with healthy subjects. Therefore we aimed at gaining a better understanding of the role of angiogenesis in diabetic nephropathy and to assess the predictive role of endocan and endoglin as markers of diabetic nephropathy progression.

MATERIAL AND METHODS

Ninety-six type 2 diabetes patients were classified according to their 24-hour urinary albumin excretion rate. Forty type 2 diabetes patients with normoalbuminuria (urinary albumin excretion < 30 mg/day), 56 type 2 diabetes patients with diabetic nephropathy (with a urinary albumin excretion ≥ 30 mg/day) and 35 healthy non-diabetic control subjects were included. Their anthropometric features, arterial blood pressures, fasting glucose, glycated hemoglobin, urea, creatinine, lipids, endocan and endoglin levels were measured and compared to each other.

RESULTS

Endocan and endoglin levels of diabetics patients were higher than those of the controls. In comparison of endocan and endoglin levels of diabetic nephropathy patients with controls, p-values were < 0.001 and 0.002 respectively. In comparison of normoalbuminuric diabetic patients with controls, p-values were 0.001 and 0.017 respectively. Endocan levels of diabetic nephropathy cases were higher than those of normoalbuminuric patients (p = 0.011) but there was no statistically significant difference in endoglin levels between them (p = 0.822).

CONCLUSIONS

Endocan might be a more reliable marker of diabetic nephropathy development than endoglin.

Supersonic Shear Wave Ultrasonography for Assessing Tissue Stiffness in Native Kidney

Recent years have brought shear wave elastography to the attention of nephrologists as a non-invasive method for detecting kidney fibrosis and, therefore, as a potential tool for reducing the need for kidney biopsy. Few studies are performed on native kidney. We aimed to compare cortical stiffness, assessed by measuring Young's modulus (YM, kPa) with SuperSonic Imaging technology, in patients with various degrees of chronic kidney disease (CKD) compared with healthy individuals. Cortical stiffness was measured by two operators, in different sessions, in 32 patients with CKD stages 3-5 and 20 healthy individuals. Comparison between mean YM values in CKD and those in controls and also between the different stages of CKD was our primary objective. The influence of other possible confounders on YM readings was also investigated and analyzed. Mean YM was significantly greater in CKD patients than in controls. Estimated YM was not able to differentiate the stages of CKD, except stage 5. Intra-subject variability was greater in CKD than in controls. Body mass index was the most important confounder in multiple analyses, in both the CKD and control groups. Our results highlight a positive correlation between increased cortical stiffness and presence of CKD. Further studies are needed to validate this method for implementation in daily clinical practice.