Glomerular endothelial cells versus podocytes as the cellular target in diabetic nephropathy

Angiopoietin-2 and endothelial damage associated with viral load in untreated people living with HIV

BackgroundHIV infection is associated with various types of endothelial damage. Early and accurate diagnosis of endothelial dysfunction may help prevent adverse outcomes. For the first time, this cross-sectional study aims to investigate the effects of increased viral load on endothelial damage and nephrinuria in untreated people living with HIV.MethodsPeople living with HIV not on treatment were included. Laboratory parameters, such as viral load and CD4 count were collected. Participants were divided into three groups according to the tertiles of viral load: low, moderate and high viral load groups. Urinary nephrin, vascular cell adhesion molecule 1 (VCAM-1), angiopoietin-2 and syndecan-1 were quantified by sandwich ELISA assays kits.ResultsA total of 49 patients were examined. The high viral load group (3rd tertile) exhibited a greater frequency of nephrinuria and significantly higher levels of syndecan-1 (58 [48-93] vs 43 [38-65] ng/mL, p = .049) and angiopoietin-2 (2.58 [1.5-3.06] vs 1.34 [0.89-1.76] ng/mL, p = .035). Syndecan-1 levels positively correlated with viral load (rho = 0.452, p = .006), while angiopoietin-2 was positively correlated with viral load (rho = 0.529, p = .001) and inversely correlated with CD4 count (rho = -0.493, p = .003). No significant associations were found for VCAM-1 levels.ConclusionUntreated people living with HIV with elevated viral loads exhibited more pronounced endothelial damage and vascular inflammation, emphasizing the critical importance of early initiation of antiretroviral treatment to mitigate these complications. However, the study's findings should be interpreted with caution due to the small sample size, which may limit the generalizability of the results. Future studies with larger cohorts are needed to confirm these findings.

The circ_0003928/miR-31-5p/MAPK6 cascade affects high glucose-induced inflammatory response, fibrosis and oxidative stress in HK-2 cells

BACKGROUND

Diabetic nephropathy (DN) is a severe diabetic complication disorder. Circular RNAs (circRNAs) actively participate in DN pathogenesis. In this report, we sought to define a new mechanism of circ_0003928 in regulating high glucose (HG)-induced HK-2 cells.

METHODS

To construct a DN cell model, we treated HK-2 cells with HG. Cell viability and apoptosis were detected by CCK-8 and flow cytometry, respectively. The inflammatory cytokines were quantified by ELISA. Protein analysis was performed by immunoblotting, and mRNA expression was detected by quantitative PCR. The circ_0003928/miR-31-5p and miR-31-5p/MAPK6 relationships were validated by RNA pull-down and luciferase assays.

RESULTS

HG promoted HK-2 cell apoptosis, fibrosis and oxidative stress. Circ_0003928 and MAPK6 levels were enhanced and miR-31-5p level was decreased in HK-2 cells after HG treatment. Circ_0003928 disruption promoted cell growth and inhibited apoptosis, inflammatory response, fibrosis and oxidative stress in HG-induced HK-2 cells. Circ_0003928 targeted miR-31-5p, and MAPK6 was a target of miR-31-5p. Circ_0003928 regulated MAPK6 expression through miR-31-5p. The functions of circ_0003928 disruption in HG-induced HK-2 cells were reversed by miR-31-5p downregulation or MAPK6 upregulation.

CONCLUSION

Circ_0003928 exerts regulatory impacts on HG-induced apoptosis, inflammation, fibrosis and oxidative stress in human HK-2 cells by the miR-31-5p/MAPK6 axis.

Dynamics of Endothelial Cell Diversity and Plasticity in Health and Disease

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity.

Roles of Sirt1 and its modulators in diabetic microangiopathy: A review

Diabetic vascular complications include diabetic macroangiopathy and diabetic microangiopathy. Diabetic microangiopathy is characterised by impaired microvascular endothelial function, basement membrane thickening, and microthrombosis, which may promote renal, ocular, cardiac, and peripheral system damage in diabetic patients. Therefore, new preventive and therapeutic strategies are urgently required. Sirt1, a member of the nicotinamide adenine dinucleotide-dependent histone deacetylase class III family, regulates different organ growth and development, oxidative stress, mitochondrial function, metabolism, inflammation, and aging. Sirt1 is downregulated in vascular injury and microangiopathy. Moreover, its expression and distribution in different organs correlate with age and play critical regulatory roles in oxidative stress and inflammation. This review introduces the background of diabetic microangiopathy and the main functions of Sirt1. Then, the relationship between Sirt1 and different diabetic microangiopathies and the regulatory roles mediated by different cells are described. Finally, we summarize the modulators that target Sirt1 to ameliorate diabetic microangiopathy as an essential preventive and therapeutic measure for diabetic microangiopathy. In conclusion, targeting Sirt1 may be a new therapeutic strategy for diabetic microangiopathy.

Silencing circ_0080425 alleviates high-glucose-induced endothelial cell dysfunction in diabetic nephropathy by targeting miR-140-3p/FN1 axis

BACKGROUND

Hsa_circ_0080425 (circ_0080425) is newly identified to correlate with the progression of diabetic nephropathy (DN). However, its role and mechanism in DN process is not very clear.

METHODS

Cell counting kit-8 assay, flow cytometry, scratch wound assay, and western blotting were performed to measure endothelial cell dysfunction. Expression of circ_0080425, microRNA (miR)-140-3p and fibronectin 1 (FN1) were determined by quantitative real-time PCR and western blotting. The direct interaction was confirmed by dual-luciferase reporter assay.

RESULTS

High-glucose (HG) treatment could induce inhibition of cell proliferation, cell cycle entrance and wound healing rate in human umbilical vein endothelial cells (HRGEC), and enhancement of apoptosis rate. Circ_0080425 expression was upregulated by HG, and exhausting circ_0080425 could attenuate HG-induced above effects in HRGEC. MiR-140-3p was sponged by circ_0080425, and its inhibitor reversed the regulation of circ_0080425 knockdown on HG-induced HRGEC injury. FN1 was targeted by miR-140-3p, and its overexpression also restored the inhibitory effect of miR-140-3p on HC-induced HRGEC injury.

CONCLUSION

Circ_0080425 expression might contribute to HG-induced endothelial cell injury, and circ_0080425/miR-140-3p/FN1 axis was a potential therapeutic approach to interfere DN process.

Changes in Metabolic Parameters in Patients with Diabetic Kidney Disease Depending on the Status of D3

BACKGROUND

Type 2 diabetes is a metabolic disease characterized by hyperglycemia as a result of insulin resistance and decreased insulin secretion. A relatively large number of patients with this type of diabetes have abdominal obesity, which also affects insulin resistance development. Chronic hyperglycemia can lead to damage and dysfunction of various organs, and a striking example is diabetic nephropathy. Diabetic nephropathy is a specific kind of kidney damage that occurs due to complications of diabetes and is accompanied by the formation of diffuse or nodular glomerulosclerosis, which can lead to terminal renal failure and requires immediate substitution through renal therapy or renal transplantation. Diabetic nephropathy is diagnosed with albuminuria and a decrease in the rate of glomerular filtration.

METHODS

This review was based on a literature search for the most important evidence of vitamin D as a possible method of prevention for obesity, type 2 diabetes, and diabetic nephropathy. Collected published articles were summarized according to their overall themes.

RESULTS

In this review, we considered vitamin D as a possible method of treatment for type 2 diabetes, as well as its complications, including diabetic nephropathy.

CONCLUSION

Studies show that vitamin D inhibits the renin-angiotensin-aldosterone system, resulting in improved renal function in diabetic nephropathy. Vitamin D also has antiinflammatory, antiproliferative, and anti-metastatic effects, which improve endothelial function.

Metabolic reprogramming: A novel therapeutic target in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the most common microvascular complications of diabetes mellitus. However, the pathological mechanisms contributing to DKD are multifactorial and poorly understood. Diabetes is characterized by metabolic disorders that can bring about a series of changes in energy metabolism. As the most energy-consuming organs secondary only to the heart, the kidneys must maintain energy homeostasis. Aberrations in energy metabolism can lead to cellular dysfunction or even death. Metabolic reprogramming, a shift from mitochondrial oxidative phosphorylation to glycolysis and its side branches, is thought to play a critical role in the development and progression of DKD. This review focuses on the current knowledge about metabolic reprogramming and the role it plays in DKD development. The underlying etiologies, pathological damages in the involved cells, and potential molecular regulators of metabolic alterations are also discussed. Understanding the role of metabolic reprogramming in DKD may provide novel therapeutic approaches to delay its progression to end-stage renal disease.

IGFBP5 promotes diabetic kidney disease progression by enhancing PFKFB3-mediated endothelial glycolysis

Renal inflammation is a critical pathophysiological characteristic of diabetic kidney disease (DKD). The mechanism of the inflammatory response is complicated, and there are few effective treatments for renal inflammation that can be used clinically. Insulin-like growth factor-binding protein 5 (IGFBP5) is an important secretory protein that is related to inflammation and fibrosis in several tissues. Studies have shown that the IGFBP5 level is significantly upregulated in DKD. However, the function of IGFBP5 and its mechanism in DKD remain unclear. Here, we showed that IGFBP5 levels were significantly increased in the kidneys of diabetic mice. Ablation of IGFBP5 alleviated kidney inflammation in DKD mice. Mechanistically, IGFBP5 increased glycolysis, which was characterized by increases in lactic acid and the extracellular acidification rate, by activating the transcription factor early growth response 1 (EGR1) and enhancing the expression of PFKFB3 in endothelial cells. Furthermore, a mutation in PFKFB3 attenuated renal inflammation in DKD mice. Taken together, we provided evidence that IGFBP5 enhanced kidney inflammation through metabolic reprogramming of glomerular endothelial cells. Our results provide new mechanistic insights into the effect of IGFBP5 on kidney and highlight potential therapeutic opportunities for IGFBP5 and the metabolic regulators involved in DKD.

Sodium Glucose Cotransporter-2 Inhibitors: Spotlight on Favorable Effects on Clinical Outcomes beyond Diabetes

Sodium glucose transporter type 2 (SGLT2) molecules are found in proximal tubules of the kidney, and perhaps in the brain or intestine, but rarely in any other tissue. However, their inhibitors, intended to improve diabetes compensation, have many more beneficial effects. They improve kidney and cardiovascular outcomes and decrease mortality. These benefits are not limited to diabetics but were also found in non-diabetic individuals. The pathophysiological pathways underlying the treatment success have been investigated in both clinical and experimental studies. There have been numerous excellent reviews, but these were mostly restricted to limited aspects of the knowledge. The aim of this review is to summarize the known experimental and clinical evidence of SGLT2 inhibitors' effects on individual organs (kidney, heart, liver, etc.), as well as the systemic changes that lead to an improvement in clinical outcomes.

Long non-coding RNA TUG1 sponges microRNA-9 to protect podocytes from high glucose-induced apoptosis and mitochondrial dysfunction via SIRT1 upregulation

Podocyte apoptosis and mitochondrial dysfunction serve a major role in diabetic nephropathy progression. The present study revealed a molecular mechanism regulating podocyte apoptosis and mitochondrial dysfunction. In vitro models were established using conditionally immortalized mouse podocyte clonal cells treated with high glucose (HG). Reverse quantitative-transcription PCR were used to detect gene expression, western blotting and immunofluorescence were used to detect protein expression, Cell Counting Kit-8 was used to detect cell viability and flow cytometry was used to detect cell apoptosis. HG treatment in the mouse podocyte clonal cells downregulated taurine-upregulated gene 1 (TUG1) expression and decreased viability in a dose-dependent manner. In addition, TUG1 knockdown (KD) increased HG-induced apoptosis, while TUG1 overexpression (OE) reduced HG-induced apoptosis in podocytes. HG-induced mitochondrial dysfunction was identified in podocytes, with increased reactive oxygen species levels, decreased complex I/III activity and decreased basal/maximal oxygen consumption rate. TUG1 KD worsened HG-induced mitochondrial dysfunction, and TUG1 OE reversed these effects. At the molecular level, TUG1 was revealed to promote sirtuin 1 (SIRT1) expression by sponging microRNA (miR)-9, and SIRT1 OE reversed the HG-induced apoptosis and mitochondrial dysfunction increased by TUG1 KD. The present data indicated that downregulation of TUG1 induced by HG was associated with HG-induced apoptosis and mitochondrial dysfunction in podocytes, and that TUG1 protected HG-induced podocytes by promoting SIRT1 expression via miR-9 inhibition.

Cellular crosstalk of glomerular endothelial cells and podocytes in diabetic kidney disease

Diabetic kidney disease (DKD) is a serious microvascular complication of diabetes and is the leading cause of end-stage renal disease (ESRD). Persistent proteinuria is an important feature of DKD, which is caused by the destruction of the glomerular filtration barrier (GFB). Glomerular endothelial cells (GECs) and podocytes are important components of the GFB, and their damage can be observed in the early stages of DKD. Recently, studies have found that crosstalk between cells directly affects DKD progression, which has prospective research significance. However, the pathways involved are complex and largely unexplored. Here, we review the literature on cellular crosstalk of GECs and podocytes in the context of DKD, and highlight specific gaps in the field to propose future research directions. Elucidating the intricates of such complex processes will help to further understand the pathogenesis of DKD and develop better prevention and treatment options.

Glomerular Endothelial Cells Are the Coordinator in the Development of Diabetic Nephropathy

The prevalence of diabetes is consistently rising worldwide. Diabetic nephropathy is a leading cause of chronic renal failure. The present study aimed to explore the crosstalk among the different cell types inside diabetic glomeruli, including glomerular endothelial cells, mesangial cells, podocytes, and immune cells, by analyzing an online single-cell RNA profile (GSE131882) of patients with diabetic nephropathy. Differentially expressed genes in the glomeruli were processed by gene enrichment and protein-protein interactions analysis. Glomerular endothelial cells, as well as podocytes, play a critical role in diabetic nephropathy. A subgroup of glomerular endothelial cells possesses characteristic angiogenesis genes, indicating that angiogenesis takes place in the progress of diabetic nephropathy. Immune cells such as macrophages, T lymphocytes, B lymphocytes, and plasma cells also contribute to the disease progression. By using iTALK, the present study reports complicated cellular crosstalk inside glomeruli. Dysfunction of glomerular endothelial cells and immature angiogenesis result from the activation of both paracrine and autocrine signals. The present study reinforces the importance of glomerular endothelial cells in the development of diabetic nephropathy. The exploration of the signaling pathways involved in aberrant angiogenesis reported in the present study shed light on potential therapeutic target(s) for diabetic nephropathy.

High glucose induces Nox4 expression and podocyte apoptosis through the Smad3/ezrin/PKA pathway

Podocytes are the major target in proteinuric kidney diseases such as diabetic nephropathy. The underlying molecular mechanisms by which high glucose (HG) results in podocyte damage remain unclear. This study investigated the regulatory role of Smad3, ezrin, and protein kinase A (PKA) in NADPH oxidase (Nox4) expression, reactive oxidative species (ROS) production, and apoptosis in HG-treated podocytes. A human podocyte cell line was cultured and differentiated, then treated with 30 mM HG. Apoptosis and intracellular ROS levels were assessed using TUNEL and DCF assays, respectively. Expressions of Nox4, phospho-Smad3^Ser423/425, phospho-PKA^Thr197, and phospho-ezrin^Thr567 were evaluated using western blotting. ELISA was used to quantify intracellular cAMP concentration and PKA activity. Knockdown assay was used to inhibit the expressions of Smad3, Nox4, and ezrin by lentiviral shRNA. In HG-treated podocytes, the level of phospho-Smad3^Ser423/425 and phospho-ezrin^Thr567 was increased significantly, which was accompanied by the reduction of cAMP and phospho-PKA^Thr197. HG-induced apoptosis was significantly prevented by the Smad3-inhibitor SIS3 or shRNA-Smad3. In podocytes expressing shRNA-ezrin or shRNA-Nox4, apoptosis was remarkably mitigated following HG treatment. HG-induced upregulation of phospho-ezrin^Thr567 and downregulation of phospho-PKA^Thr197 was significantly prevented by SIS3, shRNA-ezrin or shRNA-Smad3. Forskolin, a PKA activator, significantly inhibited HG-mediated upregulation of Nox4 expression, ROS generation, and apoptosis. Additionally, an increase in the ROS level was prohibited in HG-treated podocytes with the knockdown of Nox4, Smad3, or ezrin. Taken together, our findings provided evidence that Smad3-mediated ezrin activation upregulates Nox4 expression and ROS production, by suppressing PKA activity, which may at least in part contribute to HG-induced podocyte apoptosis.

Summary: The actin-membrane linker protein ezrin-related signaling plays a critical role in podocyte apoptosis through regulation of Nox4 expression and ROS production.

Renal dysfunction and podocyturia in pre-eclampsia may be explained by increased urinary VEGF

BACKGROUND

Preeclampsia has a major impact on renal function as shown by the development of proteinuria and podocyturia. How the systemic, Fms-like tyrosine kinase-1 (sFlt-1)-driven inhibition of vascular endothelial growth factor (VEGF) activity detected in preeclampsia directly affects renal function remains unknown. Aim of the study was to clarify whether a non-canonical, renal centered escape from VEGF inhibition in case of preeclamptic pregnancy might have a direct impact on the renal function.

METHODS

We evaluated plasma and urinary VEGF and placental growth factor (PlGF), plasma sFlt-1 and carbonic anhydrase IX (CAIX), albuminuria and podocyturia in 18 women with uncomplicated pregnancy, 21 with preeclampsia and 18 non pregnant. The three groups were matched for age and the pregnant groups also for gestational age at enrollment.

RESULTS

Plasma VEGF was reduced in uncomplicated (p = 0.001) and preeclamptic (p = 0.0003) pregnancies when compared to controls. In uncomplicated pregnancy the dysfunction was balanced by an increase (p = 0.009) of plasma PlGF. Increased (p = 0.0001) plasma CAIX in preeclampsia was in line with hypoxia. Preeclampsia resulted in a paradoxical increase (p = 0.0004) of urinary excretion of VEGF. Urinary concentrations of VEGF and podocytes were correlated to each other (r2 = 0.48, p < 0.0005) but also to plasma sFlt-1 (r2 = 0.56, p < 0.0001 and r2 = 0.23, p = 0.03 respectively).

CONCLUSIONS

In case of preeclampsia, the systemic VEGF inhibition brings the kidney, possibly the podocyte, to increase the VEGF synthesis. The mechanisms leading to local VEGF overproduction or the overproduced VEGF itself are reasonably involved in the pathogenesis of podocyturia and, as a consequence, of renal dysfunction in preeclampsia.

Glucose-responsive hydrogel enhances the preventive effect of insulin and liraglutide on diabetic nephropathy of rats

Diabetic nephropathy (DN) is one of the most serious complications of diabetes mellitus. The combination of insulin (Ins) with liraglutide (Lir) has a greater potential for preventing DN than monotherapy. However, the renal protective effect of the combined Ins/Lir therapy is largely compromised due to their short half-lives after subcutaneous injection. Herein, a glucose-responsive hydrogel was designed in situ forming the dynamic boronic esters bonds between phenylboronic acid-grafted γ-Polyglutamic acid (PBA-PGA) and konjac glucomannan (KGM). It was hypothesized that the KGM/PBA-PGA hydrogel as the delivery vehicle of Ins/Lir would enhance the combinational effect of the latter on preventing the DN progress. Scan electronic microscopy and rheological studies showed that KGM/PBA-PGA hydrogel displayed good glucose-responsive property. Besides, the glucose-sensitive release profile of either Ins or Lir from KGM/PBA-PGA hydrogel was uniformly displayed at hyperglycemic level. Furthermore, the preventive efficacy of KGM/PBA-PGA hydrogel incorporating insulin and liraglutide (Ins/Lir-H) on DN progress was evaluated on streptozotocin-induced rats with diabetic mellitus (DM). At 6 weeks after subcutaneous injection of Ins/Lir-H, not only the morphology of kidneys was obviously recovered as shown by ultrasonography, but also the renal hemodynamics was significantly improved. Meanwhile, the 24-h urinary protein and albumin/creatinine ratio were well modulated. Inflammation and fibrosis were also largely inhibited. Besides, the glomerular NPHS-2 was obviously elevated after treatment with Ins/Lir-H. The therapeutic mechanism of Ins/Lir-H was highly associated with the alleviation of oxidative stress and activation of autophagy. Conclusively, the better preventive effect of the combined Ins/Lir via KGM/PBA-PGA hydrogel on DN progress was demonstrated as compared with their mixed solution, suggesting KGM/PBA-PGA hydrogel might be a potential vehicle of Ins/Lir to combat the progression of DN.

Epidermal Growth Factor Receptor: A Potential Therapeutic Target for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease worldwide and the major cause of renal failure among patients on hemodialysis. Numerous studies have demonstrated that transient activation of epidermal growth factor receptor (EGFR) pathway is required for promoting kidney recovery from acute injury whereas its persistent activation is involved in the progression of various chronic kidney diseases including DKD. EGFR-mediated pathogenesis of DKD is involved in hemodynamic alteration, metabolic disturbance, inflammatory response and parenchymal cellular dysfunction. Therapeutic intervention of this receptor has been available in the oncology setting. Targeting EGFR might also hold a therapeutic potential for DKD. Here we review the functional role of EGFR in the development of DKD, mechanisms involved and the perspective about use of EGFR inhibitors as a treatment for DKD.

Astragalus mongholicus Bunge and Panax notoginseng (Burkill) F.H. Chen Formula for Renal Injury in Diabetic Nephropathy-In Vivo and In Vitro Evidence for Autophagy Regulation

Background

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus (DM) with limited treatment options. DN leads to progressive renal failure and accelerates rapidly into end-stage renal disease. Astragalus mongholicus Bunge and Panax notoginseng (Burkill) F.H. Chen formula (APF) is a traditional Chinese medicine (TCM) formula widely used to treat chronic kidney diseases (CKD) in the clinic in the southwest of China. The aim of this study is to explore how APF and its related TCM theory work on DN and whether mTOR/PINK1/Parkin signaling plays a part in this process.

Methods

HPLC was used for preliminary chemical analysis and quantitative analysis of the five components of APF. An in vivo autophagy deficiency model was established in C57BL/6 mice by streptozocin (STZ) combined with a high-fat and high-sugar diet, while the in vitro autophagy deficiency model was induced with high glucose (HG) in renal mesangial cells (RMCs). Renal histopathology staining was performed to investigate the extents of inflammation and injury. Real time-PCR and Western blotting techniques were utilized to assess autophagy-related proteins.

Results

APF significantly ameliorated renal injury in DN mice, specifically restoring blood urea nitrogen, serum creatinine, and 24-hour albuminuria. APF also reduced the mRNA and protein expressions of TNFα, IL-1β, and IL-6 in STZ-induced DN mice. Furthermore, APF improved the autophagy deficiency induced by STZ in vivo or HG in vitro, as revealed by changes in the expressions of mTOR, PINK1, Parkin, Beclin 1, p62, and LC3B. Notably, inhibition of autophagy with 3-methyladenine in APF-treated RMCs aggravated cellular damage and altered mTOR/PINK1/Parkin signaling, indicating that APF rescued HG damage through promoting autophagy.

Conclusion

APF may protect the kidneys from inflammation injuries in DN by upregulating autophagy via suppressing mTOR and activating PINK1/Parkin signaling. This experimental evidence strongly supports APF as a potential option for the prevention and treatment of DN.

SGLT2 Inhibitor Empagliflozin and DPP4 Inhibitor Linagliptin Reactivate Glomerular Autophagy in db/db Mice, a Model of Type 2 Diabetes

Recent data have indicated the emerging role of glomerular autophagy in diabetic kidney disease. We aimed to assess the effect of the SGLT2 inhibitor empagliflozin, the DPP4 inhibitor linagliptin, and their combination, on glomerular autophagy in a model of type 2 diabetes. Eight-week-old male db/db mice were randomly assigned to treatment with empagliflozin, linagliptin, empagliflozin-linagliptin or vehicle for 8 weeks. Age-matched non-diabetic db/+ mice acted as controls. To estimate glomerular autophagy, immunohistochemistry for beclin-1 and LAMP-1 was performed. Podocyte autophagy was assessed by counting the volume density (Vv) of autophagosomes, lysosomes and autolysosomes by transmission electron microscopy. LC3B and LAMP-1, autophagy markers, and caspase-3 and Bcl-2, apoptotic markers, were evaluated in renal cortex by western blot. Vehicle-treated db/db mice had weak glomerular staining for beclin-1 and LAMP-1 and reduced Vv of autophagosomes, autolysosomes and lysosomes in podocytes. Empagliflozin and linagliptin, both as monotherapy and in combination, enhanced the areas of glomerular staining for beclin-1 and LAMP-1 and increased Vv of autophagosomes and autolysosomes in podocytes. Renal LC3B and Bcl-2 were restored in actively treated animals. LAMP-1 expression was enhanced in the empagliflozin group; caspase-3 expression decreased in the empagliflozin-linagliptin group only. Mesangial expansion, podocyte foot process effacement and urinary albumin excretion were mitigated by both agents. The data provide further explanation for the mechanism of the renoprotective effect of SGLT2 inhibitors and DPP4 inhibitors in diabetes.

Ultrastructural Characterization of Proteinuric Patients Predicts Clinical Outcomes

BACKGROUND

The analysis and reporting of glomerular features ascertained by electron microscopy are limited to few parameters with minimal predictive value, despite some contributions to disease diagnoses.

METHODS

We investigated the prognostic value of 12 electron microscopy histologic and ultrastructural changes (descriptors) from the Nephrotic Syndrome Study Network (NEPTUNE) Digital Pathology Scoring System. Study pathologists scored 12 descriptors in NEPTUNE renal biopsies from 242 patients with minimal change disease or FSGS, with duplicate readings to evaluate reproducibility. We performed consensus clustering of patients to identify unique electron microscopy profiles. For both individual descriptors and clusters, we used Cox regression models to assess associations with time from biopsy to proteinuria remission and time to a composite progression outcome (≥40% decline in eGFR, with eGFR<60 ml/min per 1.73 m², or ESKD), and linear mixed models for longitudinal eGFR measures.

RESULTS

Intrarater and interrater reproducibility was >0.60 for 12 out of 12 and seven out of 12 descriptors, respectively. Individual podocyte descriptors such as effacement and microvillous transformation were associated with complete remission, whereas endothelial cell and glomerular basement membrane abnormalities were associated with progression. We identified six descriptor-based clusters with distinct electron microscopy profiles and clinical outcomes. Patients in a cluster with more prominent foot process effacement and microvillous transformation had the highest rates of complete proteinuria remission, whereas patients in clusters with extensive loss of primary processes and endothelial cell damage had the highest rates of the composite progression outcome.

CONCLUSIONS

Systematic analysis of electron microscopic findings reveals clusters of findings associated with either proteinuria remission or disease progression.

SHIPping out diabetes-Metformin, an old friend among new SHIP2 inhibitors

SHIP2 (Src homology 2 domain‐containing inositol 5′‐phosphatase 2) belongs to the family of 5′‐phosphatases. It regulates the phosphoinositide 3‐kinase (PI3K)‐mediated insulin signalling cascade by dephosphorylating the 5′‐position of PtdIns(3,4,5)P3 to generate PtdIns(3,4)P2, suppressing the activity of the pathway. SHIP2 mouse models and genetic studies in human propose that increased expression or activity of SHIP2 contributes to the pathogenesis of the metabolic syndrome, hypertension and type 2 diabetes. This has raised great interest to identify SHIP2 inhibitors that could be used to design new treatments for metabolic diseases. This review summarizes the central mechanisms associated with the development of diabetic kidney disease, including the role of insulin resistance, and then moves on to describe the function of SHIP2 as a regulator of metabolism in mouse models. Finally, the identification of SHIP2 inhibitors and their effects on metabolic processes in vitro and in vivo are outlined. One of the newly identified SHIP2 inhibitors is metformin, the first‐line medication prescribed to patients with type 2 diabetes, further boosting the attraction of SHIP2 as a treatment target to ameliorate metabolic disorders.

Risk factors and urinary biomarkers of non-albuminuric and albuminuric chronic kidney disease in patients with type 2 diabetes

BACKGROUND

A number of recent studies indicate a transformation in the natural course of chronic kidney disease (CKD) in type 2 diabetes (T2D) patients: an increasing prevalence of declined renal function without proceeding to the accompanying elevation of albuminuria. It has been suggested that albuminuric and non-albuminuric CKD patterns could be different in their phenotypes and pathogenic mechanisms.

AIM

To identify the risk factors and biomarkers of albuminuric and non-albuminuric patterns of CKD in patients with T2D.

METHODS

Three hundred sixty patients with T2D duration ≥ 10 years were included in this observational cross-sectional study. The associations of a panel of demographic and clinical characteristics, complications, comorbidities, and metabolic and hematology parameters with albuminuric and non-albuminuric CKD patterns were analyzed. The urinary excretion of nephrin and podocin, two podocyte-specific markers, and WAP-four-disulfide core domain protein 2 (WFDC-2), a marker of tubulointerstitial fibrosis, was determined by ELISA in comparison with healthy controls.

RESULTS

Non-albuminuric CKD was associated with age ≥ 65 years (P = 0.0001), female sex (P = 0.04), diabetes duration ≥ 15 years (P = 0.0009), and the use of diuretics (P = 0.0005). Male sex (P = 0.01), smoking (P = 0.01), waist-to-hip ratio >1.0 (P = 0.01) and hemoglobin A1c (HbA1c) > 8.0% (P = 0.005) were risk factors for elevated albuminuria not accompanied by a decrease in estimated glomerular filtration rate (eGFR). Duration of diabetes ≥ 15 years and the use of calcium channel blockers were risk factors for albuminuria with decreased eGFR (both P = 0.01). In multivariate logistic regression analysis, age, HbA1c, female sex and diuretics were significant predictors for reduced eGFR, while waist-to-hip ratio, HbA1c and male sex were associated with elevated urinary albumin-to-creatinine ratio (UACR). Excretion of nephrin and podocin was increased in patients with albuminuria, regardless of decline in renal function (P < 0.001), correlating positively with UACR. The urinary excretion of WFDC-2 was markedly higher in men than in women (P < 0.000001). Men with T2D demonstrated increased WFDC-2 levels independently of the CKD pattern (all P < 0.05). In T2D women, WFDC-2 excretion was increased in those with reduced renal function (P ≤ 0.01), correlating negatively with eGFR.

CONCLUSION

The data provide further evidence that albuminuric and non-albuminuric CKD phenotypes correspond to different pathways of diabetic kidney disease progression.

Role of Vitamin D Status in Diabetic Patients with Renal Disease

Diabetes mellitus (DM) poses a major public health problem worldwide, with ever-increasing incidence and prevalence in recent years. The Institute for Alternative Futures (IAF) expects that the total number of people with type 1 and type 2 DM in the United States will increase by 54%, from 19,629,000 to 54,913,000 people, between 2015 and 2030. Diabetic Nephropathy (DN) affects about one-third of patients with DM and currently ranks as the first cause of end-stage kidney disease in the Western world. The complexity of interactions of Vitamin D is directly related with progressive long-term changes implicated in the worsening of renal function. These changes result in a dysregulation of the vitamin D-dependent pathways. Various studies demonstrated a pivotal role of Vitamin D supplementation in regression of albuminuria and glomerulosclerosis, contrasting the increase of glomerular basement membrane thickening and podocyte effacement, with better renal and cardiovascular outcomes. The homeostasis and regulation of the nephron's function are absolutely dependent from the cross-talk between endothelium and podocytes. Even if growing evidence proves that vitamin D may have antiproteinuric, anti-inflammatory and renoprotective effects in patients with DN, it is still worth investigating these aspects with both more in vitro studies and randomized controlled trials in larger patient series and with adequate follow-up to confirm the effects of long-term vitamin D analogue supplementation in DN and to evaluate the effectiveness of this therapy and the appropriate dosage.

SMAD3-dependent and -independent pathways in glomerular injury associated with experimental glomerulonephritis

Glomerulonephritis (GN) is a common cause of end-stage kidney disease and is characterized by glomerular inflammation, hematuria, proteinuria, and progressive renal dysfunction. Transforming growth factor (TGF)-β is involved in glomerulosclerosis and interstitial fibrosis. TGF-β activates multiple signaling pathways, including the canonical SMAD pathway. We evaluated the role of SMAD signaling in renal injury and proteinuria in a murine model of GN. SMAD3^+/+ or SMAD3^-/- mice received anti-glomerular basement membrane antibodies to induce GN. We confirmed previous reports that demonstrated that SMAD3 is an important mediator of glomerulosclerosis and renal interstitial fibrosis. Proteinuria was highly SMAD3 dependent. We found differential effects of SMAD3 deletion on podocytes and glomerular endothelial cells. GN led to podocyte injury, including foot process effacement and loss of podocyte-specific markers. Interestingly, these changes were not SMAD3 dependent. Furthermore, there were significant changes to glomerular endothelial cells, including loss of fenestrations, swelling, and basement membrane reduplication, which were SMAD3 dependent. Despite ongoing markers of podocyte injury in SMAD3^-/- mice, proteinuria was transient. Renal injury in the setting of GN involves TGF-β and SMAD3 signaling. Cell populations within the glomerulus respond differently to SMAD3 deletion. Proteinuria correlated more with endothelial cell changes as opposed to podocyte injury in this model.