Juan F. Navarro-González

The Role of Inflammatory Cytokines in Diabetic Nephropathy

Cytokines act as pleiotropic polypeptides regulating inflammatory and immune responses through actions on cells. They provide important signals in the pathophysiology of a range of diseases, including diabetes mellitus. Chronic low-grade inflammation and activation of the innate immune system are closely involved in the pathogenesis of diabetes and its microvascular complications. Inflammatory cytokines, mainly IL-1, IL-6, and IL-18, as well as TNF-alpha, are involved in the development and progression of diabetic nephropathy. In this context, cytokine genetics is of special interest to combinatorial polymorphisms among cytokine genes, their functional variations, and general susceptibility to diabetic nephropathy. Finally, the recognition of these molecules as significant pathogenic mediators in diabetic nephropathy leaves open the possibility of new potential therapeutic targets.

Beyond proteinuria: VDR activation reduces renal inflammation in experimental diabetic nephropathy

Local inflammation is thought to contribute to the progression of diabetic nephropathy. The vitamin D receptor (VDR) activator paricalcitol has an antiproteinuric effect in human diabetic nephropathy at high doses. We have explored potential anti-inflammatory effects of VDR activator doses that do not modulate proteinuria in an experimental model of diabetic nephropathy to gain insights into potential benefits of VDR activators in those patients whose proteinuria is not decreased by this therapy. The effect of calcitriol and paricalcitol on renal function, albuminuria, and renal inflammation was explored in a rat experimental model of diabetes induced by streptozotocin. Modulation of the expression of mediators of inflammation by these drugs was explored in cultured podocytes. At the doses used, neither calcitriol nor paricalcitol significantly modified renal function or reduced albuminuria in experimental diabetes. However, both drugs reduced the total kidney mRNA expression of IL-6, monocyte chemoattractant protein (MCP)-1, and IL-18. Immunohistochemistry showed that calcitriol and paricalcitol reduced MCP-1 and IL-6 in podocytes and tubular cells as well as glomerular infiltration by macrophages, glomerular cell NF-κB activation, apoptosis, and extracellular matrix deposition. In cultured podocytes, paricalcitol and calcitriol at concentrations in the physiological and clinically significant range prevented the increase in MCP-1, IL-6, renin, and fibronectin mRNA expression and the secretion of MCP-1 to the culture media induced by high glucose. In conclusion, in experimental diabetic nephropathy VDR activation has local renal anti-inflammatory effects that can be observed even when proteinuria is not decreased. This may be ascribed to decreased inflammatory responses of intrinsic renal cells, including podocytes, to high glucose.

Pathophysiological role and therapeutic implications of inflammation in diabetic nephropathy

Diabetes mellitus and its complications are becoming one of the most important health problems in the world. Diabetic nephropathy is now the main cause of end-stage renal disease. The mechanisms leading to the development and progression of renal injury are not well known. Therefore, it is very important to find new pathogenic pathways to provide opportunities for early diagnosis and targets for novel treatments. At the present time, we know that activation of innate immunity with development of a chronic low grade inflammatory response is a recognized factor in the pathogenesis of diabetic nephropathy. Numerous experimental and clinical studies have shown the participation of different inflammatory molecules and pathways in the pathophysiology of this complication.

Baseline characteristics of patients with chronic kidney disease stage 3 and stage 4 in spain: the MERENA observational cohort study

BackgroundTo obtain information on cardiovascular morbidity, hypertension control, anemia and mineral metabolism based on the analysis of the baseline characteristics of a large cohort of Spanish patients enrolled in an ongoing prospective, observational, multicenter study of patients with stages 3 and 4 chronic kidney diseases (CKD).MethodsMulticenter study from Spanish government hospital-based Nephrology outpatient clinics involving 1129 patients with CKD stages 3 (n = 434) and 4 (n = 695) defined by GFR calculated by the MDRD formula. Additional analysis was performed with GFR calculated using the CKD-EPI and Cockcroft-Gault formula.ResultsIn the cohort as a whole, median age 70.9 years, morbidity from all cardiovascular disease (CVD) was very high (39.1%). In CKD stage 4, CVD prevalence was higher than in stage 3 (42.2 vs 35.6% p < 0.024). Subdividing stage 3 in 3a and 3b and after adjusting for age, CVD increased with declining GFR with the hierarchy (stage 3a < stage 3b < stage 4) when calculated by CKD-EPI (31.8, 35.4, 42.1%, p 0.039) and Cockcroft-Gault formula (30.9, 35.6, 43.4%, p 0.010) and MDRD formula (32.5, 36.2, 42.2%,) but with the latter, it did not reach statistical significance (p 0.882). Hypertension was almost universal among those with stages 3 and 4 CKD (91.2% and 94.1%, respectively) despite the use of more than 3 anti-hypertensive agents including widespread use of RAS blockers. Proteinuria (> 300 mg/day) was present in more than 60% of patients and there was no significant differences between stages 3 and 4 CKD (1.2 ± 1.8 and 1.3 ± 1.8 g/day, respectively). A majority of the patients had hemoglobin levels greater than 11 g/dL (91.1 and 85.5% in stages 3 and 4 CKD respectively p < 0.001) while the use of erythropoiesis-stimulating agents (ESA) was limited to 16 and 34.1% in stages 3 and 4 CKD respectively. Intact parathyroid hormone (i-PTH) was elevated in stage 3 and stage 4 CKD patients (121 ± 99 and 166 ± 125 pg/mL p 0.001) despite good control of calcium-phosphorus levels.ConclusionThis study provides an overview of key clinical parameters in patients with CKD Stages 3 and 4 where delivery or care was largely by nephrologists working in a network of hospital-based clinics of the Spanish National Healthcare System.

Anti‐Inflammatory Profile of Paricalcitol in Hemodialysis Patients: A Prospective, Open‐Label, Pilot Study

Inflammation is a strong predictor of increased morbidity and mortality in hemodialysis (HD) patients. Paricalcitol, a selective vitamin D receptor activator used for prevention and treatment of secondary hyperparathyroidism, has shown anti‐inflammatory properties in experimental studies, although clinical data are scarce. In an open‐label, prospective, single center, pilot study, 25 stable HD patients, previously receiving calcitriol, completed 12 weeks of therapy with oral paricalcitol. Serum and peripheral blood mononuclear cell (PBMC) expression profiles of inflammatory cytokines were analyzed. Serum interleukin (IL)‐1, IL‐10, and IL‐18 did not change, unlike high‐sensitivity C‐reactive protein (hs‐CRP), tumor necrosis factor‐α (TNF‐α), and IL‐6, which experienced a significant mean percent decrease of 14.3%, 4.7%, and 5%, respectively. There was a significant reduction in the TNF‐α/IL‐10 and the IL‐6/IL‐10 ratios (P < .05). Serum intact parathyroid hormone concentration experienced a mild but significant reduction. In addition, expression levels of TNF‐α and IL‐6 decreased by 19.1% (P < .01) and 17.5% (P < .001), respectively, whereas expression of IL‐10 increased by 17.7% (P < .01) after treatment. In conclusion, paricalcitol administration to HD patients is associated with a beneficial effect on the inflammatory cytokine serum and gene expression profile of PBMC. This effect may contribute to the survival benefits of paricalcitol observed in clinical studies.

Diabetic nephropathy is an independent factor associated to severe subclinical atheromatous disease

BACKGROUND Atheromatous disease (AD) is a risk factor for death in renal patients. Traditional CV risk factors do not predict the presence of AD in this population. The aim of this study is to analyze whether the etiology of the primary renal disease influences in the risk of having silent AD. STUDY DESIGN Observational cross-sectional study in chronic kidney disease patients without previous cardiovascular events. SETTINGS AND PARTICIPANTS 2436 CKD subjects without any previous CV event included in the prospective Spanish multicenter NEFRONA study. Patients were classified according to primary renal disease: diabetic nephropathy (n = 347), vascular nephropathy (n = 476), systemic/glomerular disease (n = 447), tubulointerstitial and drug toxicity nephropathy (n = 320), polycystic kidney disease (n = 238), non-filiated nephropathy (n = 406) and other causes (n = 202). PREDICTORS B-mode and Doppler ultrasonography analysis of the carotid arteries were performed to measure intima media thickness (IMT) and the presence of plaques. Clinical and laboratory parameters related to CV risk were also determined. OUTCOMES AD was scored according with the ultrasonography findings and the ankle-brachial index into two large groups: absence or incipient AD and severe AD. RESULTS In multivariate regression analysis, older age (OR 1.09/year [1.088-1.108]), smoking habit (OR 2.10 [1.61-2.74]), male gender (OR 1.33 [1.09-1.64]), grade-5D of CKD (OR 2.19 [1.74-2.74]), and diabetic nephropathy (OR 2.59 [1.93-3.48]) are independent risk factors for severe AD. The prevalence of silent AD was highest for diabetic nephropathy with grade-5D of CKD (82.2%) and lowest with stages 2-3 CKD systemic/glomerular disease (36.6%). LIMITATIONS Observational study with the potential for confounding. CONCLUSION In CKD patients without any CV event in the background clinical history, diabetic nephropathy as primary renal disease is the most significant factor associated to severe silent AD. Furthermore, this difference was independent of other conventional risk factors for atherosclerosis and CV events.

Effects of Pentoxifylline on Soluble Klotho Concentrations and Renal Tubular Cell Expression in Diabetic Kidney Disease

OBJECTIVE The effect of pentoxifylline on Klotho levels in patients with type 2 diabetes mellitus with chronic kidney disease (CKD) was assessed in a post hoc analysis of the Pentoxifylline for Renoprotection in Diabetic Nephropathy (PREDIAN) trial. RESEARCH DESIGN AND METHODS Circulating and urinary tumor necrosis factor-α (TNF-α) and Klotho were measured before and after 1 year of pentoxifylline. The effect on Klotho expression was assessed in cultured renal tubular cells. RESULTS Pentoxifylline administration resulted in decreased serum and urinary TNF-α, whereas serum and urinary Klotho increased significantly. Changes in urinary Klotho, urinary TNF-α, and phosphorus were associated with changes in serum Klotho; changes in estimated glomerular filtration rate, urinary TNF-α, and albuminuria were related to urinary Klotho variation. In renal tubular cells, pentoxifylline prevented the decrease in Klotho expression induced by inflammatory cytokines or albumin. CONCLUSIONS Pentoxifylline increased Klotho levels in patients with diabetes with stage 3–4 CKD and prevented reduced Klotho expression in vitro. This beneficial effect may be related to anti-inflammatory and antialbuminuric activity.