Diabetic Nephropathy: a Tangled Web to Unweave

Examining Structural Patterns and Causality in Diabetic Nephropathy using inter-Glomerular Distance and Bayesian Graphical Models

In diabetic nephropathy (DN), hyperglycemia drives a progressive thickening of glomerular filtration surfaces, increased cell proliferation as well as mesangial expansion and a constriction of capillary lumens. This leads to progressive structural changes inside the Glomeruli. In this work, we make a study of structural glomerular changes in DN from a graph-theoretic standpoint, using features extracted from Minimal Spanning Trees (MSTs) constructed over intercellular distances in order to classify the "packing signatures" of different DN stages. We further investigate the significance of the competing effects of Volume change measured here in 2Dimensional Pixel span area (Area) on one hand and increased cell proliferation on the other in determining the packing patterns. Towards that we formulate the problem as Dynamic Bayesian Network (DBN). From our preliminary results we do postulate that volume expansion caused by internal pressure as capillary lumens constriction has perhaps has a greater effect in the early stages.

Clinical Trials on Diabetic Nephropathy: A Cross-Sectional Analysis

INTRODUCTION

Treatment options and decisions are often based on the results of clinical trials. We have evaluated the public availability of results from completed, registered phase III clinical trials on diabetic nephropathy and current treatment options.

METHODS

This was a cross-sectional analysis in which STrengthening the Reporting of OBservational studies in Epidemiology criteria were applied for design and analysis. In June 2017, 34 completed phase III clinical trials on diabetic nephropathy in the ClinicalTrials. gov registry were identified and matched to publications in the ClinicalTrials.gov registry and to those in the PubMed and Google Scholar databases. If no publication was identified, the principal investigator was contacted. The ratio of published and non-published studies was calculated. Various parameters, including study design, drugs, and comparators provided, were analyzed.

RESULTS

Drugs/supplements belonged to 26 different categories of medications, with the main ones being angiotensin-converting enzyme inhibitors, angiotensin-II receptors blockers, and dipeptidyl-peptidase-4-inhibitors. Among the trials completed before 2016 (n = 32), 22 (69%) were published, and ten (31%) remained unpublished. Thus, data on 11 different interventions and more than 1000 patients remained undisclosed. Mean time to publication was 26.5 months, which is longer than the time constrictions imposed by the U.S. Food and Drug Administration Amendments Act. Most trials only showed weak effects on micro- and macroalbuminuria, with an absolute risk reduction of 1.0 and 0.3%, respectively, and the number needed to treat varied between 91 and 333, without any relevant effect on end-stage-renal disease by intensive glucose-lowering treatment. Comparison of the results, however, was difficult since study design, interventions, and the renal outcome parameters vary greatly between the studies.

CONCLUSION

Despite the financial and human resources involved and the relevance for therapeutic guidelines and clinical decisions, about one-third of phase III clinical trials on diabetic nephropathy remain unpublished. Interventions used in published trials showed a low efficacy on renal outcome.

FUNDING

Deutsche Forschungsgemeinschaft (DFG): SFB 1118.

microRNAs in chronic kidney disease

Chronic kidney disease (CKD) results in high morbidity and mortality worldwide causing a huge socioeconomic burden. MicroRNA (miRNA) exert critical regulatory functions by targeting downstream genes and have been associated with many pathophysiologic processes including CKD. In fact, many studies have shown that the expression of various miRNAs was significantly changed in CKD. Current investigations have focused on revealing the relationship between miRNAs and CKD states including diabetic nephropathy, lupus nephritis, focal segmental glomerulosclerosis and IgA nephropathy. In this review, we summarize the latest advances elucidating miRNA involvement in the progression of CKD and demonstrate that miRNAs have the potential to be effective biomarkers and therapeutic targets for subsequent treatment.

Diabetic nephropathy: recent advances in pathophysiology and challenges in dietary management

BACKGROUND

Diabetic nephropathy (DN) or diabetic kidney disease refers to the deterioration of kidney function seen in chronic type 1 and type 2 diabetes mellitus patients. The progression of the disease is known to occur in a series of stages and is linked to glycemic and blood pressure control. However, despite aggressive blood sugar control the prevalence of chronic kidney disease (CKD) in diabetic patients has not witnessed any decrease in the last two decades; which has lead to identification of additional factors in its progression. The nutritional status of patients is an important and modifiable factor that may influence CKD processes and outcome. It directly stems from the traditional dietary choices that patients make due to poor nutritional awareness. Dietary management of DN patients is challenging, as the twin factors of diet overload on kidney function needs to be balanced with malnutrition. Patient education seems to be the key in avoiding overindulgence of carbohydrate and protein-rich foods while favoring inclusion of essential fats in their diet.

CONCLUSION

This review will summarize current advances in staging and molecular pathogenesis of DN. It will highlight recent studies focusing on patient-customized dietary interventions that offer new hope as an effective tool in improving quality of life and delaying disease progression in DN patients.

The role of mass spectrometry in studies of glycation processes and diabetes management

In the last decade, mass spectrometry has been widely employed in the study of diabetes. This was mainly due to the development of new, highly sensitive, and specific methods representing powerful tools to go deep into the biochemical and pathogenetic processes typical of the disease. The aim of this review is to give a panorama of the scientifically valid results obtained in this contest. The recent studies on glycation processes, in particular those devoted to the mechanism of production and to the reactivity of advanced glycation end products (AGEs, AGE peptides, glyoxal, methylglyoxal, dicarbonyl compounds) allowed to obtain a different view on short and long term complications of diabetes. These results have been employed in the research of effective markers and mass spectrometry represented a precious tool allowing the monitoring of diabetic nephropathy, cardiovascular complications, and gestational diabetes. The same approaches have been employed to monitor the non-insulinic diabetes pharmacological treatments, as well as in the discovery and characterization of antidiabetic agents from natural products. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 38:112-146, 2019.

LncRNA ZEB1-AS1 inhibits renal fibrosis in diabetic nephropathy by regulating the miR-217/MAFB axis

Diabetic nephropathy (DN) is a common chronic microvascular complication of diabetes, characterized by the deposition of extracellular matrix (ECM) proteins.

Preventing and treating kidney disease in patients with type 2 diabetes

INTRODUCTION

Chronic kidney disease (CKD) represents a huge burden in patients with type 2 diabetes (T2DM). This review therefore has the aim of assessing the add-on value of new glucose-lowering agents compared or combined with inhibitors of the renin angiotensin aldosterone system (RAAS) on renal outcomes in T2DM patients.

AREAS COVERED

This article first summarizes the results reported with RAAS inhibitors, mainstay of nephroprotection in T2DM with albuminuria. Second, it describes the positive results with glucagon-like peptide-1 receptor agonists (GLP-1RAs) and, even more impressive, sodium-glucose cotransporter type 2 inhibitors (SGLT2is). Third, besides the potential of combined therapies, it briefly considers some new approaches currently in development.

EXPERT OPINION

RAAS inhibitors exert renoprotective effects beyond their blood pressure lowering effects while SGLT2is, and possibly GLP-1RAs, exert nephroprotection independently of their glucose-lowering activity. These effects were demonstrated not only on surrogate endpoints such as albuminuria and estimated glomerular filtration rate decline, but also on hard endpoints, including progression to end-stage renal disease requiring replacement therapy. The underlying mechanisms are different and potentially complementary on glomerular hemodynamics, arguing for combined therapies. Nevertheless, there is still room for new emerging drugs to tackle CKD in T2DM.

Efficacy and renal outcomes of SGLT2 inhibitors in patients with type 2 diabetes and chronic kidney disease

OBJECTIVE

To review glucose-lowering efficacy and changes in renal function associated with sodium-glucose co-transporter 2 (SGLT2) inhibitors among patients with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM).

DATA SOURCES

A literature search of MEDLINE and Cochrane databases was performed from 2000 to August 2018 using search terms: SGLT2 inhibitors, sodium glucose co-transporter 2, canagliflozin, empagliflozin, dapagliflozin, ertugliflozin, and chronic kidney disease. References of identified articles were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

English-language studies investigating glucose-lowering endpoints and/or changes in renal function with one of four U.S. approved SGLT2 inhibitors were included. A total of 10 studies met inclusion criteria and are included in this review.

RESULTS

In patients with T2DM and CKD, SGLT2 inhibitors are modestly effective in lowering hemoglobin A1C and fasting plasma glucose compared to placebo. Small reductions in eGFR are seen shortly after initiating therapy with SGLT2 inhibitors, but return to baseline levels after discontinuation. SGLT2 inhibitors are associated with a substantial reduction in albuminuria and reduced risk of progression to albuminuria.

CONCLUSIONS

In patients with T2DM and CKD, SGLT2 inhibitors have a decreased glucose-lowering effect compared to patients without CKD. Renal benefits among patients with CKD are similar to those without CKD and include a significant reduction in albuminuria and reduced incidence of worsening albuminuria. Given that CKD and T2DM are both associated with increased cardiovascular risk, we believe these agents should considered as preferred add-on agents in most patients with uncontrolled T2DM and eGFR >30 ml/min/1.73 m². Ongoing studies will provide additional information as to whether these agents should be added to the current standard of care for CKD patients, with and without T2DM.

A review of the anti-inflammatory properties of antidiabetic agents providing protective effects against vascular complications in diabetes

The global prevalence of Type 2 diabetes mellitus and its associated complications are growing rapidly. Although the role of hyperglycemia is well recognized in the pathophysiology of diabetic complications, its exact underlying mechanisms are not fully understood. In this regard, accumulating evidence suggests that the role of inflammation appears pivotal, with studies showing that most diabetic complications are associated with an inflammatory response. Several classes of antidiabetic agents have been introduced for controlling glycemia, with evidence that these pharmacological agents may have modulatory effects on inflammation beyond their glucose-lowering activity. Here we review the latest evidence on the anti-inflammatory effects of commonly used antidiabetic medications and discuss the relevance of these effects on preventing diabetic complications.

Dysregulation of lncRNAs GM5524 and GM15645 involved in high‑glucose‑induced podocyte apoptosis and autophagy in diabetic nephropathy

Diabetic nephropathy (DN) is an important microvascular complication of diabetes, and one of the leading causes of end‑stage kidney disease. However, the mechanism of the DN pathogenic process remains unclear. Recently, long non‑coding (lnc)RNA dysregulation has been regarded to cause the occurrence and development of various human diseases, although the functions of lncRNAs in human DN are poorly understood. The authors' previous study using microarray analysis identified hundreds of dysregulated lncRNAs in DN, although the functions of these lncRNAs were not demonstrated. Out of those dysregulated lncRNAs, Gm5524 was significantly upregulated in response to DN, while Gm15645 was significantly downregulated in response to DN. In the present study, this result was further validated by reverse transcription‑quantitative polymerase chain reaction assays, and downregulating or overexpressing Gm5524 and Gm15645 in mouse podocytes. Notably, knockdown of Gm5524 and overexpression of Gm15645 induced mouse podocyte apoptosis and decreased cell autophagy in high‑glucose culture conditions. In conclusion, the results of the present study revealed the roles of lncRNAs Gm5524 and Gm15645 in high‑glucose induced podocyte apoptosis and autophagy during DN, which may further the understanding of the involvement of lncRNAs in DN, and provide a potential novel therapeutic target for this disease.

Effect of linagliptin on oxidative stress markers in patients with type 2 diabetes: a pilot study

Background

Dipeptidyl peptidase-4 (DPP-4) inhibitors are commonly used for the treatment of type 2 diabetes and have been previously shown to prevent diabetic renal injury via various mechanisms, including the attenuation of oxidative stress. Therefore, we hypothesized that linagliptin, a DPP-4 inhibitor, attenuates oxidized stress and diabetic renal injury.

Methods

In total, 30 patients with type 2 diabetes who were undergoing treatment with linagliptin (5 mg) during the 3-month study period were enrolled. Oxidative stress markers [serum malondialdehyde-modified LDL (MDA-LDL) and urinary 8-hydroxydeoxyguanosine (8-OHdG)], an inflammatory marker (high-sensitive CRP), urinary albumin excretion, estimated GFR, and a urinary tubulointerstitial injury marker [urinary liver-type fatty acid-binding protein (L-FABP)] were evaluated at baseline and after 3 months of treatment.

Results

Following linagliptin treatment, serum MDA-LDL, serum HbA1c, and urinary L-FABP levels significantly decreased, while urinary 8-OHdG tended to decrease. In contrast, 1,5-AG levels increased, and high-sensitive CRP and urinary albumin excretion remained unchanged.

Conclusion

In this study, we demonstrated that linagliptin partially attenuated oxidative stress. We also demonstrated that linagliptin treatment reduced urinary L-FABP excretion, suggesting that renal tubule-interstitial injury may be attenuated by linagliptin (UMIN 000015308).

Genistein and Myd88 Activate Autophagy in High Glucose-Induced Renal Podocytes In Vitro

BACKGROUND Renal podocyte damage plays a crucial role in the development of diabetic nephropathy. Genistein is derived from a leguminous plant, and MyD88 and TRIF are adaptor molecules in the Toll-like receptor (TLR) signaling pathway, which may play a role in autophagy. In this study, we utilized an in vitro high glucose (HG)-treated podocyte model to investigate the effects and underlying mechanisms of Genistein and MyD88 or TRIF siRNA induced autophagy and renal protection. MATERIAL AND METHODS An immortalized mouse podocyte cell line was treated with HG, Genistein, chloroquine, and/or transfected with specific Myd88 and TRIF siRNAs. The formation of autophagosomes and related autophagic vacuoles were monitored by transmission electron microscopy. The expression of autophagy-related factors and podocyte structure and functional markers, including LC3, p62, p-mTOR, synaptopodin, and nephrin, were measured by Western blot, and LC3 and p-mTOR expression were also assessed by immunofluorescence. RESULTS We showed that HG transiently (after 6-h exposure) induced expression of the autophagy activation marker LC3-II in podocytes. Genistein treatment induced autophagy in both normal and HG-treated podocytes through inactivating mTOR signaling. Moreover, Genistein protected podocytes against chloroquine in HG-cultured conditions in vitro by maintaining the level of autophagy-related proteins. In addition, MyD88 siRNA downregulated expression of autophagy-related proteins, whereas Genistein treatment reversed these effects. CONCLUSIONS This study demonstrated that Genistein-induced autophagy could be a potential treatment strategy for glomerular diseases.

Prevention of the progression of renal injury in diabetic rodent models with preexisting renal disease with chronic endothelin A receptor blockade

The endothelin (ET) system has emerged as a therapeutic target for the treatment of diabetic nephropathy (DN). The present study examined whether chronic endothelin A (ET_A) receptor blockade with atrasentan prevents the progression of renal injury in two models of DN with preexisting renal disease that exhibit an increased renal ET-1 system compared with nondiabetic rats: streptozotocin-treated Dahl salt-sensitive (STZ-SS) and type 2 diabetic nephropathy (T2DN) rats. Nine week-old SS rats were treated with (STZ; 50 mg/kg ip) to induce diabetes. After 3 wk of diabetes, proteinuria increased to 353 ± 34 mg/day. The rats were then separated into two groups: 1) vehicle and 2) atrasentan (5 mg·kg^-1·day^-1) via drinking water. After 6 wk of treatment with atrasentan, mean arterial pressure (MAP) and proteinuria decreased by 12 and 40%, respectively, in STZ-SS rats. The degree of glomerulosclerosis and renal fibrosis was significantly reduced in the kidneys of atrasentan-treated STZ-SS rats compared with vehicle STZ-SS rats. Interestingly, treatment with atrasentan did not affect GFR but significantly increased renal blood flow by 33% and prevented the elevations in filtration fraction and renal vascular resistance by 23 and 20%, respectively, in STZ-SS rats. In contrast to the STZ-SS study, atrasentan had no effect on MAP or proteinuria in T2DN rats. However, treatment with atrasentan significantly decreased glomerular injury and renal fibrosis and prevented the decline in renal function in T2DN rats. These data indicate that chronic ET_A blockade produces advantageous changes in renal hemodynamics that slow the progression of renal disease and also reduces renal histopathology in the absence of reducing arterial pressure and proteinuria.