One of the microvascular complications of diabetes is diabetic kidney disease (DKD), often leading to end stage renal disease (ESRD) in which patients require costly dialysis or transplantation. The silent onset and irreversible progression of DKD are characterized by a steady decline of the estimated glomerular filtration rate, with or without concomitant albuminuria. The diabetic milieu allows the complex pathophysiology of DKD to enter a vicious cycle by inducing the synthesis of excessive amounts of reactive oxygen species (ROS) causing oxidative stress, inflammation, and fibrosis. As no cure is available, intensive research is required to develop novel treatments possibilities. This chapter provides an overview of the important pathomechanisms identified in diabetic kidney disease, the currently established therapies, as well as recently developed novel therapeutic strategies in DKD.

Diabetic kidney disease (DKD) is a chronic microvascular complication of diabetes and accounts for 30-40% of all diabetic patients. Patients with DKD experience a progressive and irreversible decline of renal function until dialysis and kidney transplantation become the last line of intervention. Renal loss of function is driven by the diabetic milieu causing an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms. The excessive amounts of ROS, driven either by mitochondria or by NADPH oxidases (NOXs) , cause inflammation and eventually lead to fibrosis and kidney failure. Methods: To address this problem, we cultivated healthy primary human renal cells (renal proximal tubular epithelial cells) under diabetic conditions. The cells were treated either with 5mM normal glucose (NG) , or 25mM high glucose with 10ng/ml TNF-α or TGF-β (HG) for 24h. In addition, a novel mitochondrial complex I modulator (BIM, 250nM) that has been designed to interfere with the ROS production at mitochondrial complex I has been tested in combination with the treatments. We analyzed the gene expression of different oxidative stress, inflammation as well as fibrosis markers. Results: On the transcriptional level, a treatment with BIM resulted in a significant downregulation of the HG treatment-induced expression of the oxidative stress markers SOD2 (by 40%) , NOX4 (by 61%) and NOX5 (by 34%) , the inflammation markers IL1B (by 29%) and TNFA (by 22%) , as well as the fibrosis markers TGFB1 (by 23%) , COL4A1 (by 50%) and CTGF (by 43%) , as determined by a two-way ANOVA and Tukey’s multiple comparison. Conclusion: The reduction of these markers after treatment with the complex I modulator suggests renoprotective properties in vitro. Further in vivo experiments in diabetic db/db mice will reveal whether the novel mitochondrial complex I modulator can attenuate renal injury in DKD. Disclosure A.Aboolian: None. S.Urner: None. M.Roden: Advisory Panel; Eli Lilly and Company, Research Support; Boehringer Ingelheim International GmbH, Nutricia, Speaker's Bureau; Novo Nordisk. K.Jandeleit-dahm: None.

Excessive production of renal reactive oxygen species (ROS) play a major role in diabetic kidney disease (DKD). Here, we provide key novel findings demonstrating the predominant pathological role of the prooxidant enzyme NADPH oxidase-NOX5 in DKD, independent of the previously characterised NOX4 pathway. In diabetic patients, we found increased expression of renal NOX5 in association with enhanced ROS formation and upregulation of ROS-sensitive factors EGR-1 (early growth response 1), PKC-α (protein kinase C- α) and a key metabolic gene involved in redox balance, TXNIP (thioredoxin-interacting protein). In preclinical models of DKD, overexpression of NOX5 in Nox4 deficient mice enhances kidney damage by increasing albuminuria and augmenting renal fibrosis and inflammation via enhanced ROS formation and the modulation of EGR1, TXNIP, ERK1/2, PKC-α and PKC-ε. In addition, the only first in class NOX inhibitor, GKT137831 appears to be ineffective in the presence of NOX5 expression in diabetes. In vitro, silencing of NOX5 in human mesangial cells attenuated high glucose induced upregulation of EGR1, PKC-α, and TXNIP as well as markers of inflammation (TLR4 and MCP-1) and fibrosis (CTGF and collagens I and III) via reduction in ROS formation. Collectively, these findings identify NOX5 as a superior target in human DKD compared to other NOX isoforms such as NOX4 which may have been overinterpreted in previous rodent studies.

Insulin resistance as it occurs in diabetes and obesity is associated with impaired renal function and can lead to end-stage renal disease. In 3 independent studies it was demonstrated that a subphenotype of type 2 diabetes, which is characterized by severe peripheral insulin resistance, demonstrated a particularly high risk for the development and progression of diabetic nephropathy. Therefore, the determination of a panel of metabolic markers, in particular markers of insulin resistance in the initial diagnosis of diabetes, is superior to the measurement of glucose alone and unmasks this subphenotype of diabetes. The patients in the severe insulin-resistant diabetes (SIRD = cluster 3) group already had a reduced estimated glomerular filtration rate (eGFR) and elevated cystatin C values at baseline and demonstrated the highest prevalence for stages 2 and 3 of chronic kidney disease and the highest risk for the development of end-stage renal disease at baseline and after 5 years follow-up despite relatively good metabolic control. These findings support the hypothesis that peripheral insulin resistance and the association with inflammation play an important pathophysiological role in the development and progression of diabetic nephropathy. It can be postulated that the unmasking of high-risk subtypes of type 2 diabetes will enable timely, intensified and tailored treatment as part of a precision medicine approach, to prevent the development and progression of diabetic nephropathy as well as other diabetic complications (neuropathy, retinopathy, fatty liver and liver fibrosis).

Background: The development of anti-inflammatory therapies for renal function loss in patients with diabetes requires identification of specific biomarkers which might differ by diabetes type. This study aimed to investigate associations between a novel panel of biomarkers of inflammation and estimated glomerular filtration rate (eGFR) in patients with type 1 diabetes (T1D) and type 2 diabetes (T2D). Methods: This study was based on 145 participants with T1D (mean age 33.8 years, 60.7% males) and 250 participants with T2D (mean age 55.3 years, 66.4% males) from the observational prospective German Diabetes Study (GDS), which includes adults with a diabetes duration <1 year. A panel of 74 biomarkers of inflammation was measured in serum of fasted participants using the proximity extension assay technology. eGFR was calculated from serum creatinine and cystatin C using the CKD-EPI equation. Associations between each biomarker and eGFR were assessed using multiple linear regression adjusting for age, sex, BMI, HbA1c, diabetes duration, lipids, hypertension and use of NSAIDs and glucose-lowering drugs. Results: Baseline eGFR was higher in T1D compared to T2D (mean (SD) 101.8 (15.3) vs. 89.3 (15.6) mL/min/1.73 m2; P<0.0001). After correction for multiple testing, 6 and 24 biomarkers were inversely associated with eGFR in T1D and T2D, respectively (all P<0.05). TNFB was T1D-specific, while ADA, CD40, CD244, CCL3, CCL20, CCL25, CX3CL1, CXCL9, CSF1, CST5, FGF23, FGF5, IL-15RA, IL12B, MMP10, NT3, SCF, TGFα and uPA were T2D-specific. CCL23, CD5, IL10RB, PDL1 and TNFRSF9 were associated with eGFR in both diabetes types. Conclusion: We identified novel inflammatory biomarkers, independently associated with eGFR in adults with recently diagnosed T1D and T2D. As a next step, these biomarkers shall be evaluated as potential predictors of incident and progressive diabetic nephropathy. Disclosure H. Maalmi: None. C. Herder: Research Support; Self; Sanofi-Aventis. K. Strassburger: None. S. Urner: None. K. Jandeleit-Dahm: None. O.P. Zaharia: None. Y. Karusheva: None. K. Bodis: None. W. Rathmann: Advisory Panel; Self; AstraZeneca. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc. Research Support; Self; Novo Nordisk Inc. Speaker’s Bureau; Self; Eli Lilly and Company, Novo Nordisk Inc. D.F. Markgraf: None. V. Burkart: None. J. Szendroedi: None. M. Roden: Advisory Panel; Self; Servier. Board Member; Self; Poxel SA. Consultant; Self; Eli Lilly and Company, Gilead Sciences, Inc., ProSciento, TARGET PharmaSolutions. Research Support; Self; Boehringer Ingelheim International GmbH, Novartis Pharma K.K., Sanofi US. Speaker’s Bureau; Self; Novo Nordisk A/S.

Context: While inflammation has been associated with kidney function in long-standing diabetes, its possible association in newly diagnosed diabetes is unknown. Objective: To investigate cross-sectional and prospective associations between biomarkers of inflammation and kidney function in recent-onset diabetes. Methods: The study included individuals with type 1 and type 2 diabetes with known diabetes duration of <1 year from the German Diabetes Study. Baseline serum concentrations of 74 biomarkers were measured using proximity extension assay technology and their associations with estimated glomerular filtration rate (eGFR) and kidney function decline over 5 years were tested using multiple linear and logistic regression analysis. Results: The cross-sectional analysis included 165 individuals with type 1 diabetes and 291 with type 2 diabetes. Baseline eGFR was higher in type 1 compared with type 2 diabetes (102 +/- 15 vs 90 +/- 16 mL/min/1.73 m(2); P< 0.0001). After full adjustment for covariates and multiple testing, 7 biomarkers were associated with lower baseline eGFR in type 1 diabetes and 24 were associated with lower baseline eGFR in type 2 diabetes. Among these biomarkers, 6 biomarkers (CD5, CCL23, CST5, IL-10RB, PD-L1, TNFRSF9) were inversely associated with eGFR in both diabetes types. The prospective analysis did not detect associations between inflammatory biomarkers and kidney function decline. No evidence of an interaction between diabetes type and inflammatory biomarkers was found. Conclusion: Several biomarkers of inflammation associate with lower baseline eGFR in recent-onset type 1 and type 2 diabetes, but do not associate with kidney function loss during the first 5 years after the diagnosis of diabetes.

Background: Oxidative stress plays an important role in the pathogenesis of diabetic kidney disease (DKD). Evidences suggest roles for pro-oxidant enzymes Nox4 and Nox5 in animal models of DKD. Nox5 is present in mans but not in mice/rats. It appears that Nox5 could be a main culprit in human DKD. Therefore, we aimed to examine the roles of Nox5 vs. Nox4 and their relative contribution to renal pathology in DKD. Methods: We examined the expression and interaction of Nox5 and Nox4 and ROS formation in human kidney biopsies. In vitro, certain human renal cells being knockdown for Nox4 and Nox5 were exposed to high glucose. In vivo, we examined the effect of Nox5 expression in the absence of Nox4 in STZ- diabetic mice. We developed rabbit models of DKD and Nox5KO rabbits. Results: Increased Nox5 expression and enhanced ROS level was seen in human diabetic kidney biopsies compared to nondiabetic kidney. Nox5 shows the highest upregulation in human renal cells exposed to high glucose in comparison to other Nox isoforms. Nox5 silencing attenuated high glucose induced increased expression of markers of fibrosis, inflammation and putative elements via reduction in ROS formation. Nox5 appears to be upstream of Nox4 and that Nox5 inhibition downregulates Nox4, but not vice versa. In vivo, cell specific expression of Nox5 in both Nox4 KO and GKT137831 (a renal Nox4 inhibitor) treated diabetic mice demonstrated a 30-40% increase in albuminuria, mesangial expansion, renal fibrosis and inflammation as well as enhanced ROS production in comparison to diabetic mice not expressing Nox5. In addition, both high fat feeding and alloxan induced diabetic rabbits showed increased renal Nox5 expression in association with increased renal injury along with upregulation of CTGF, fibronectin and MCP-1 as well as enhanced renal ROS production. Conclusions: These findings provide evidence that Nox5 plays a superior pathogenic role in DKD in comparison to Nox4. Therefore, targeting Nox5 may represent a better approach to treat and prevent DKD in human. Disclosure J.C. Jha: None. S. Urner: None. A. Dai: None. M.E. Cooper: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim International GmbH, Mundipharma International. Research Support; Self; Boehringer Ingelheim International GmbH, Novo Nordisk A/S. Speaker’s Bureau; Self; AstraZeneca, Merck Sharp & Dohme Corp., Novartis AG, Sanofi-Aventis, Servier. M. Roden: Advisory Panel; Self; Servier. Board Member; Self; Poxel SA. Consultant; Self; Eli Lilly and Company, Gilead Sciences, Inc., ProSciento, TARGET PharmaSolutions. Research Support; Self; Boehringer Ingelheim International GmbH, Novartis Pharma K.K., Sanofi US. Speaker’s Bureau; Self; Novo Nordisk A/S. C. Kennedy: None. K. Jandeleit-Dahm: None.

Significance: Oxidative stress plays a critical role in the development and progression of serious micro- and macrovascular complications of diabetes. Nicotinamide adenine dinucleotide phosphate oxidase (NOX)-derived reactive oxygen species (ROS) significantly contribute to oxidative stress-associated inflammatory pathways that lead to tissue damage of different organs, including the kidneys, retina, brain, nerves, and the cardiovascular system. Recent Advances: Preclinical studies, including genetic-modified mouse models or cell culture models, have revealed the role of specific NOX isoforms in different diabetic complications, and suggested them as a promising target for the treatment of these diseases. Critical Issues: In this review, we provide an overview of the role of ROS and oxidative stress in macrovascular complications, such as stroke, myocardial infarction, coronary artery disease, and peripheral vascular disease that are all mainly driven by atherosclerosis, as well as microvascular complications, such as diabetic retinopathy, nephropathy, and neuropathy. We summarize conducted genetic deletion studies of different Nox isoforms as well as pharmacological intervention studies using NOX inhibitors in the context of preclinical as well as clinical research on diabetic complications. Future Directions: We outline the isoforms that are most promising for future clinical trials in the context of micro- and macrovascular complications of diabetes.

Insulinresistenz bei Adipositas und Diabetes ist mit Nierenfunktionsstörungen assoziiert, die zum terminalen Nierenversagen führen können. In 3 unabhängigen Studien wurde gezeigt, dass ein Subphänotyp des Typ-2-Diabetes, der durch eine starke periphere Insulinresistenz charakterisiert ist, ein besonders hohes Risiko für die Entwicklung und Progression einer diabetischen Nephropathie aufweist. Die Bestimmung einer Gruppe von metabolischen Parametern, insbesondere der Insulinresistenz bei Erstdiagnose des Diabetes, ist der alleinigen Bestimmung von Glukose überlegen und demaskiert diesen Subphänotypen des Diabetes. Die Patienten der schwer insulinresistenten Gruppe (SIRD = Cluster 3) hatten bereits zu Beginn eine erniedrigte eGFR („estimated glomerular filtration rate“) und erhöhte Cystatin-C-Werte, zeigten die höchste Prävalenz des Stadiums 2 und 3 der Niereninsuffizienz und das höchste Risiko für die Entwicklung eines terminalen Nierenversagens bei Erstdiagnose und nach 5 Jahren Verlaufskontrolle trotz relativ guter metabolischer Kontrolle. Diese Befunde sind ein weiterer Beweis dafür, dass der peripheren Insulinresistenz und ihrer Assoziation mit Inflammation eine wichtige pathophysiologische Rolle bei der Entstehung und Progression der diabetischen Nephropathie zukommt. Es kann postuliert werden, dass die Demaskierung der Hochrisikosubtypen bei Typ-2-Diabetes eine frühzeitige, intensivierte und maßgeschneiderte Therapie im Sinne einer Präzisionstherapie erlaubt, um das Auftreten und Fortschreiten der diabetischen Nephropathie sowie weiterer diabetischer Komplikationen (Neuropathie, Retinopathie, aber auch Fettleber und Fibrose) zu vermeiden.

Angiocrine signals derived from endothelial cells are an important component of intercellular communication and have a key role in organ growth, regeneration and disease 1 – 4 . These signals have been identified and studied in multiple organs, including the liver, pancreas, lung, heart, bone, bone marrow, central nervous system, retina and some cancers 1 – 4 . Here we use the developing liver as a model organ to study angiocrine signals 5 , 6 , and show that the growth rate of the liver correlates both spatially and temporally with blood perfusion to this organ. By manipulating blood flow through the liver vasculature, we demonstrate that vessel perfusion activates β1 integrin and vascular endothelial growth factor receptor 3 (VEGFR3). Notably, both β1 integrin and VEGFR3 are strictly required for normal production of hepatocyte growth factor, survival of hepatocytes and liver growth. Ex vivo perfusion of adult mouse liver and in vitro mechanical stretching of human hepatic endothelial cells illustrate that mechanotransduction alone is sufficient to turn on angiocrine signals. When the endothelial cells are mechanically stretched, angiocrine signals trigger in vitro proliferation and survival of primary human hepatocytes. Our findings uncover a signalling pathway in vascular endothelial cells that translates blood perfusion and mechanotransduction into organ growth and maintenance.

Vascular endothelial growth factor receptor‐3 (VEGFR3) signalling promotes lymphangiogenesis. While there are many reported mechanisms of VEGFR3 activation, there is little understanding of how VEGFR3 signalling is attenuated to prevent lymphatic vascular overgrowth and ensure proper lymph vessel development. Here, we show that endothelial cell‐specific depletion of integrin‐linked kinase (ILK) in mouse embryos hyper‐activates VEGFR3 signalling and leads to overgrowth of the jugular lymph sacs/primordial thoracic ducts, oedema and embryonic lethality. Lymphatic endothelial cell (LEC)‐specific deletion of Ilk in adult mice initiates lymphatic vascular expansion in different organs, including cornea, skin and myocardium. Knockdown of ILK in human LECs triggers VEGFR3 tyrosine phosphorylation and proliferation. ILK is further found to impede interactions between VEGFR3 and β1 integrin in vitro and in vivo, and endothelial cell‐specific deletion of an Itgb1 allele rescues the excessive lymphatic vascular growth observed upon ILK depletion. Finally, mechanical stimulation disrupts the assembly of ILK and β1 integrin, releasing the integrin to enable its interaction with VEGFR3. Our data suggest that ILK facilitates mechanically regulated VEGFR3 signalling via controlling its interaction with β1 integrin and thus ensures proper development of lymphatic vessels. Tight regulation of VEGFR3 signaling, which ensures proper lymph vessel development, has been studied mostly at the level of VEGFR3 activation. This study identifies integrin‐linked kinase (ILK) as mechanosensitive negative regulator of VEFGR3 signaling, which acts by perturbing the interaction between β1 integrin and VEGFR3. Lymphatic endothelial cell‐specific depletion of integrin‐linked kinase (ILK) in mice identifies it as mechanosensitive regulator of physiological lymph vessel expansion.

The blood and lymphatic vasculatures are hierarchical networks of vessels, which constantly transport fluids and, therefore, are exposed to a variety of mechanical forces. Considering the role of mechanotransduction is key for fully understanding how these vascular systems develop, function, and how vascular pathologies evolve. During embryonic development, for example, initiation of blood flow is essential for early vascular remodeling, and increased interstitial fluid pressure as well as initiation of lymph flow is needed for proper development and maturation of the lymphatic vasculature. In this review, we introduce specific mechanical forces that affect both the blood and lymphatic vasculatures, including longitudinal and circumferential stretch, as well as shear stress. In addition, we provide an overview of the role of mechanotransduction during atherosclerosis and secondary lymphedema, which both trigger tissue fibrosis.