Effects of pentoxifylline administration on urinary N-acetyl-beta-glucosaminidase excretion in type 2 diabetic patients: a short-term, prospective, randomized study

The effect of a methylxanthine vasodilator: pentoxifylline on the treatment of diabetic nephropathy-a meta-analysis

This meta-analysis aimed to comprehensively evaluate the efficacy and safety of pentoxifylline (PTF) in the treatment of diabetic nephropathy (DN) and to offer fresh perspectives and evidence-based references for this condition. Meta-analysis. Relevant randomized controlled trials (RCTs) were searched from PubMed, Embase, Cochrane Library, China Knowledge Network (CNKI), Wanfang, and China Biomedical Literature Database. All trials were screened for compliance with the inclusion and exclusion criteria, and relevant data were extracted after quality evaluation. Eighteen studies with a total of 1280 patients were finally included. Compared to the control group, high sensitivity C-reactive protein (hsCRP) was improved (MD = - 0.23. 95% CI = [- 0.41, - 0.05], P = 0.01); urinary albumin excretion (UAE) rate was reduced (MD = - 16.50, 95% CI = [- 18.87, - 14.13], P<0.00001); the change of serum creatinine (Scr) from baseline was reduced (MD = - 0.05, 95%CI = [- 0.08, - 0.01], P = 0.009); fasting plasma glucose (FPG) was decreased (MD = - 5.66, 95% CI = [- 9.79, - 1.53], P = 0.007); and the improvement of glomerular filtration rate (eGFR) from baseline was increased (MD = 4.38, 95% CI = [3.28, 5.48], P<0.00001) in the treatment group. No significant difference was observed between the two groups concerning systolic blood pressure, diastolic blood pressure, total cholesterol, and triglycerides. And in terms of safety, the use of PTF was relatively safe with some self-limiting adverse events. FPG was decreased by PTF more effectively, but there was no effect of PTF on glycated hemoglobin (HbA1c). PTF could improve hsCRP, decrease UAE and Scr, and raise eGFR in the treatment of DN.

Antioxidants for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular disease (CVD) and death. Increased oxidative stress in people with CKD has been implicated as a potential causative factor. Antioxidant therapy decreases oxidative stress and may consequently reduce cardiovascular morbidity and death in people with CKD. This is an update of a Cochrane review first published in 2012.

OBJECTIVES

To examine the benefits and harms of antioxidant therapy on death and cardiovascular and kidney endpoints in adults with CKD stages 3 to 5, patients undergoing dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies until 15 November 2022 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials investigating the use of antioxidants, compared with placebo, usual or standard care, no treatment, or other antioxidants, for adults with CKD on cardiovascular and kidney endpoints.

DATA COLLECTION AND ANALYSIS

Titles and abstracts were screened independently by two authors who also performed data extraction using standardised forms. Results were pooled using random effects models and expressed as risk ratios (RR) or mean difference (MD) with 95% confidence intervals (CI). Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 95 studies (10,468 randomised patients) that evaluated antioxidant therapy in adults with non-dialysis-dependent CKD (31 studies, 5342 patients), dialysis-dependent CKD (41 studies, 3444 patients) and kidney transplant recipients (21 studies, 1529 patients). Two studies enrolled dialysis and non-dialysis patients (153 patients). Twenty-one studies assessed the effects of vitamin antioxidants, and 74 assessed the effects of non-vitamin antioxidants. Overall, the quality of included studies was moderate to low or very low due to unclear or high risk of bias for randomisation, allocation concealment, blinding, and loss to follow-up. Compared with placebo, usual care, or no treatment, antioxidant therapy may have little or no effect on cardiovascular death (8 studies, 3813 patients: RR 0.94, 95% CI 0.64 to 1.40; I² = 33%; low certainty of evidence) and probably has little to no effect on death (any cause) (45 studies, 7530 patients: RR 0.95, 95% CI 0.82 to 1.11; I² = 0%; moderate certainty of evidence), CVD (16 studies, 4768 patients: RR 0.79, 95% CI 0.63 to 0.99; I² = 23%; moderate certainty of evidence), or loss of kidney transplant (graft loss) (11 studies, 1053 patients: RR 0.88, 95% CI 0.67 to 1.17; I² = 0%; moderate certainty of evidence). Compared with placebo, usual care, or no treatment, antioxidants had little to no effect on the slope of urinary albumin/creatinine ratio (change in UACR) (7 studies, 1286 patients: MD -0.04 mg/mmol, 95% CI -0.55 to 0.47; I² = 37%; very low certainty of evidence) but the evidence is very uncertain. Antioxidants probably reduced the progression to kidney failure (10 studies, 3201 patients: RR 0.65, 95% CI 0.41 to 1.02; I² = 41%; moderate certainty of evidence), may improve the slope of estimated glomerular filtration rate (change in eGFR) (28 studies, 4128 patients: MD 3.65 mL/min/1.73 m², 95% CI 2.81 to 4.50; I² = 99%; low certainty of evidence), but had uncertain effects on the slope of serum creatinine (change in SCr) (16 studies, 3180 patients: MD -13.35 µmol/L, 95% CI -23.49 to -3.23; I² = 98%; very low certainty of evidence). Possible safety concerns are an observed increase in the risk of infection (14 studies, 3697 patients: RR 1.30, 95% CI 1.14 to 1.50; I² = 3%; moderate certainty of evidence) and heart failure (6 studies, 3733 patients: RR 1.40, 95% CI 1.11 to 1.75; I² = 0; moderate certainty of evidence) among antioxidant users. Results of studies with a low risk of bias or longer follow-ups generally were comparable to the main analyses.

AUTHORS' CONCLUSIONS

We found no evidence that antioxidants reduced death or improved kidney transplant outcomes or proteinuria in patients with CKD. Antioxidants likely reduce cardiovascular events and progression to kidney failure and may improve kidney function. Possible concerns are an increased risk of infections and heart failure among antioxidant users. However, most studies were of suboptimal quality and had limited follow-up, and few included people undergoing dialysis or kidney transplant recipients. Furthermore, the large heterogeneity in interventions hampers drawing conclusions on the efficacy and safety of individual agents.

Diabetic Kidney Disease: From Pathogenesis to Novel Treatment Possibilities

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.

The Differences of N–Acetyl–β–Glucosaminidase and β2 Microglobulin levels in Patients with and without Early Diabetic Nephropathy

Diabetic Nephropathy (DN) is becoming the most serious microvascular complication, which be marked by the presence of persistent albuminuria. N–asetil–β–glucosaminidase is dominant lyzosom enzyme in the renal tubule epitel. β2 microglobulin is low molecular weight protein which produced by major histocompatibility complex class 1 (MHC-1) expressed cell in all nucleated cell. N–asetil–β–glucosaminidase and β2 microglobulin could be new usefull marker for early DN. Analytic observational study with cross sectional approach was conducted in May – July 2019 involving 27 non diabetic patients (K1), 27 diabetic patients without DN (K2) and 27 diabetic patients with early DN (K3) at the Clinical Pathology department of Faculty of Medicine, Diponegoro University and Diabetic Clinic. Data include age, gender, fasting blood glucose, blood preasure and urine albumin creatinine ratio. N–asetil–β–glucosaminidase level between groups were analyzed using Anova, β2 microglobulin level between groups using Kruskal Wallis, p<0.05 were considered significant. There are significant differences in levels of N–asetil–β–glucosaminidase between K1 and K2 (p =0.01), K1 and K3 (p =< 0.01), K2 and K3 (p = 0.03) and β2 microglobulin  between K1 and K2 (p = 0.02), K1 and K3 (p =< 0.01), K2 and K3 (p< 0.01). N-acetyl-β-glucosaminidase and β2 microglobulin levels were higher in K2 compared to K1 and increased higher in K3 compared to K1 and K2. N-acetyl-β-glucosaminidase and β2 microglobulin can be used as an alternative marker for early DN. 

Targeting Inflammation in Diabetic Kidney Disease: Is There a Role for Pentoxifylline?

Diabetic kidney disease (DKD) is the most common cause of ESKD in the United States and worldwide. Current treatment for DKD includes strict glycemic control and normalization of BP with renin-angiotensin-aldosterone system (RAAS) blockade. Although RAAS blockers slow progression of disease, they do not generally prevent ESKD and none of the studies with these agents in DKD included patients who were nonproteinuric, which make up an increasingly large percentage of patients with diabetes now seen in clinical practice. Recent studies with glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter-2 (SGLT2) inhibitors have shown beneficial renal effects, and the benefits of SGLT2 inhibitors likely extend to patients who are nonproteinuric. However, there remains a need to develop new therapies for DKD, particularly in those patients with advanced disease. A role of chronic low-grade inflammation in microvascular complications in patients with diabetes has now been widely accepted. Large clinical trials are being carried out with experimental agents such as bardoxolone and selonsertib that target inflammation and oxidative stress. The Food and Drug Administration–approved, nonspecific phosphodiesterase inhibitor pentoxifylline (PTX) has been shown to have anti-inflammatory effects in both animal and human studies by inhibiting the production of proinflammatory cytokines. Small randomized clinical trials and meta-analyses indicate that PTX may have therapeutic benefits in DKD, raising the possibility that a clinically available drug may be able to be repurposed to treat this disease. A large, multicenter, randomized clinical trial to determine whether this agent can decrease time to ESKD or death is currently being conducted, but results will not be available for several years. At this time, the combination of RAAS blockade plus SGLT2 inhibition is considered standard of care for DKD, but it may be reasonable for clinicians to consider addition of PTX in patients whose disease continues to progress despite optimization of current standard-of-care therapies.

Urinary levels of podocyte-derived microparticles are associated with the progression of chronic kidney disease

Background

Podocyte-derived microparticles (MPs) could be secreted from activated or apoptotic podocytes. An increased number of podocyte-derived MPs in the urine might reflect podocyte injury in renal diseases. This study aimed to observe the change of urinary podocyte-derived MP levels in patients with chronic kidney disease (CKD) and to further explore its correlation with the progression of CKD.

Methods

A prospective, longitudinal study was conducted in eighty patients with biopsy-proven CKD. Podocyte-derived MPs (annexin V and podocalyxin positive) were detected by flow cytometry. The number of urinary podocyte-derived MPs was analyzed to evaluate the association with biochemical measurements and pathological glomerulosclerosis assessment. Patients with idiopathic membranous nephropathy (IMN) were followed up after the six-month treatment of prednisone combined with tacrolimus to evaluate the association of urinary podocyte-derived MP levels and the remission of IMN.

Results

The CKD patients had higher urinary podocyte-derived MP levels compared with healthy controls (HCs). Baseline urinary levels of podocyte-derived MPs were positively correlated with 24-hour proteinuria, while were inversely correlated with the percentage of global glomerulosclerosis. The urinary podocyte-derived MPs levels had good discrimination for glomerulosclerosis [area under curve (AUC), 0.66]. The urinary podocyte-derived MPs levels in IMN patients were significantly decreased accompanied with the recovery of abnormal clinical parameters after six-month treatment.

Conclusions

The urinary levels of podocyte-derived MPs were closely associated with podocyte injury and glomerulosclerosis, which could be useful for monitoring disease activity in CKD patients. Urinary podocyte-derived MPs might be a non-invasive biomarker for the evaluation of early CKD progression.

The Diagnostic Role of Urinary N-Acetyl-β-D-glucosaminidase (NAG) Activity in the Detection of Renal Tubular Impairment

The kidney function can be assessed by a number of methods. The urinary excretion of enzymes, in particular N-acetyl-β-D-glucosaminidase (NAG), is considered a relatively simple, cheap, fast and non-invasive method in the detection and follow-up of renal tubular function under various conditions. The determination of urinary NAG provides a very sensitive and reliable indicator of renal damage, such as injury or dysfunction due to diabetes mellitus, nephrotic syndrome, inflammation, vesicoureteral reflux, urinary tract infection, hypercalciuria, urolithiasis, nephrocalcinosis, perinatal asphyxia, hypoxia, hypertension, heavy metals poisoning, treatment with aminoglycosides, valproate, or other nephrotoxic drugs. This paper gives an overview of the current use of urinary NAG in the detection of renal injury.

Acute Kidney Injury and Progression of Diabetic Kidney Disease

Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.

Oxidative Stress, Apoptosis, and Mitochondrial Function in Diabetic Nephropathy

Diabetic nephropathy (DN) is the second most frequent and prevalent complication of diabetes mellitus (DM). The increase in the production of oxidative stress (OS) is induced by the persistent hyperglycemic state capable of producing oxidative damage to the macromolecules (lipids, carbohydrates, proteins, and nucleic acids). OS favors the production of oxidative damage to the histones of the double-chain DNA and affects expression of the DNA repairer enzyme which leads to cell death from apoptosis. The chronic hyperglycemic state unchains an increase in advanced glycation end-products (AGE) that interact through the cellular receptors to favor activation of the transcription factor NF-κB and the protein kinase C (PKC) system, leading to the appearance of inflammation, growth, and augmentation of synthesis of the extracellular matrix (ECM) in DN. The reactive oxygen species (ROS) play an important role in the pathogenesis of diabetic complications because the production of ROS increases during the persistent hyperglycemia. The primary source of the excessive production of ROS is the mitochondria with the capacity to exceed production of endogenous antioxidants. Due to the fact that the mechanisms involved in the development of DN have not been fully clarified, there are different approaches to specific therapeutic targets or adjuvant management alternatives in the control of glycemia in DN.

Pentoxifylline plus ACEIs/ARBs for proteinuria and kidney function in chronic kidney disease: a meta-analysis

Objective

This meta-analysis aimed to investigate the efficacy and safety of pentoxifylline (PTF) plus angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) for proteinuria and kidney function in chronic kidney disease (CKD).

Methods

CENTRAL, EMBASE, Ovid-MEDLINE, PubMed, and CNKI were searched for relevant, randomized, controlled trials (RCTs). A meta-analysis was performed to review the effect of PTF plus ACEIs/ARBs vs. ACEIs/ARBs alone on proteinuria and kidney function in CKD.

Results

Eleven RCTs including 705 patients were retrieved. PTF plus ACEI/ARB treatment significantly decreased proteinuria in patients with CKD within 6 months (standard mean difference [SMD] −0.52; 95% CI −0.90 to 0.15; I²= 68%) and significantly attenuated a decrease in estimated glomerular filtration rate (eGFR) in patients with stages 3–5 CKD after 6 months of treatment (standard mean difference [SMD] 0.30; confidence limit [Cl] 95% CI 0.06 to 0.54; I²= 0%). PTF plus ACEIs/ARBs for 9 to 12 months significantly reduced albuminuria in patients with CKD (SMD−0.30, 95% CI −0.57 to 0.03; I²= 0%) and alleviated the decline in eGFR in patients with stages 3–5 CKD (SMD 0.51; 95% CI 0.06 to 0.96; I²= 61%).

Conclusion

The combination of an ACEI or ARB and PTF has a protective effect in reducing proteinuria by ameliorating the decline in eGFR in patients with stages 3–5 CKD.

Determination of the serum levels of troponin I and creatinine among Sudanese type 2 diabetes mellitus patients

Background:

Diabetes mellitus (DM) is a significant risk factor for developing cardiac diseases. Hence, we compare the serum levels of cardiac troponin I (CTnI) among type 2 diabetic and healthy patients. We additionally correlated CTnI and creatinine levels with duration of disease.

Materials and Methods:

A cross-sectional study was conducted at Department of Clinical Chemistry, Sudan University of Sciences and Technology, Khartoum, Sudan, from February 2008 to February 2011. 200 patients diagnosed with DM type 2 from Jabir Abulizz Diabetes Centre in Khartoum state, Sudan, and 100 healthy volunteers were included in this study. Blood samples were collected from both groups, and the serum levels of CTnI, creatinine, fasting plasma glucose and glycosylated hemoglobin (HbA1c) levels were measured.

Results:

Significant increase in serum levels of CTnI, glucose, HbA1c, and creatinine was observed in diabetic patients compared to healthy controls. In addition, the significant increase in CTnI and creatinine levels was observed among diabetic patients with ischemic heart disease or hypertension when compared with those without ischemic heart disease or hypertension. Further a strong positive correlation was observed between the duration of diabetes and the serum levels of CTnI and creatinine (r = 0.84, P > 0.01) and (r = 0.72, P > 0.01), respectively.

Conclusion:

The higher levels of CTnI and creatinine may be indicative of progressive cardiovascular disease and nephropathy among diabetic patients.

Urinary enzymatic markers (N-acetyl-beta-D-glucosaminidase) in assessing the tubulointerstitial compartment in chronic glomerulonephritis related to odontogenic foci

Chronic glomerulonephritis is related to focus infection. Odontogenic foci are frequently involved in glomerulonephritis. The relationship with the odontogenic focus infection can be demonstrated by the occurrence or aggravation of the symptoms of glomerulonephritis: proteinuria, haematuria, high blood pressure and oedema. Glomerular impairment in glomerulonephritis occurs together with inflammatory alterations of the tubulointerstitial compartment that can play an important part in the evolution of the disease. Tubular urinary markers can indicate the activation of this compartment during an infection of a focus, an odontogenic focus in our study.The paper aims at demonstrating the relationship between the odontogenic focus infection and tubulointerstitial lesions, assessed by a tubular urinary marker, N-acetyl beta-D glucosaminidase (NAG).We investigated the urinary N-acetyl beta-D glucosaminidase of 20 patients with chronic glomerulonephritis who presented odontogenic focus infections, comparing them with patients with chronic glomerulonephritis without odontogenic foci and of 20 controls, clinically healthy persons.Chronic glomerulonephritis patients with odontogenic focus infection presented clearly increased values as compared to clinically healthy control persons of urinary N-acetyl beta-D glucosaminidase.These patients underwent surgical intervention on the odontogenic focus under antibacterial prophylactic treatment. In 75% cases, the values of N-acetyl beta-D glucosaminidase diminished, indicating the favourable effect of the treatment of the odontogenic focus on the tubulointerstitial compartment in patients with chronic glomerulonephritis. In 25% cases this therapeutic treatment was associated with an increase of the values of urinary N-acetyl beta-D glucosaminidase, expressing its unfavourable effect on chronic glomerulonephritis.Urinary N-acetyl beta-D glucosaminidase indicated an etiopathogenetic relationship between the odontogenic focus and the tubulointerstitial compartment in chronic glomerulonephritis.

Pentoxifylline Decreases Dialysis Risk in Patients With Advanced Chronic Kidney Disease

Few studies evaluated the effects of pentoxifylline on hard endpoints in patients with predialysis stage 5 chronic kidney disease (CKD). Thus, we tried to explore the effects of pentoxifylline and its interaction with renin-angiotensin-aldosterone system (RAAS) blockade on the development of endstage renal disease (ESRD) and mortality. This nationwide cohort study retrospectively included patients who had a serum creatinine level of >6 mg/dL and received erythropoiesis-stimulating agents (ESAs) between 2000 and 2010. We analyzed 7,366 pentoxifylline users and 7,366 propensity score-matched nonusers. Using Cox proportional hazard models, pentoxifylline reduced the risks of ESRD and the composite renal outcome but not that of mortality. In terms of the risks of developing ESRD, pentoxifylline alone exerted a comparable beneficial effect to combined therapy with an RAAS inhibitor and greater renoprotection than RAAS inhibitor monotherapy. This study suggests pentoxifylline is efficacious in slowing progression to ESRD in patients with predialysis stage 5 CKD.

Efficacy and safety of combining pentoxifylline with angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker in diabetic nephropathy: a meta-analysis

OBJECTIVE

Pentoxifylline (PTF) has anti-inflammatory properties, which may be beneficial for diabetic nephropathy (DN). A meta-analysis was conducted to assess the additive effect of pentoxifylline and its safety among patients with type 2 DN under blockade of angiotensin system.

DATA SOURCES

Relevant studies were searched from PubMed, CBM, EMBASE, CENTRAL and Cochrane renal group specialized register.

SELECTION CRITERIA

All RCTs that compared the benefits and harms of pentoxifylline and ACEI/ARB with ACEI/ARB alone for DN were included.

DATA EXTRACTION AND ANALYSIS

Pertinent data were extracted independently by two authors. Meta-analyses were performed when more than one study provided data on a comparable outcome. Standard mean differences (SMDs) for proteinuria and albuminuria, mean differences (MDs) for systolic blood pressure (SBP), diastolic blood pressure (DBP), HbA1c, serum creatinine (Scr), creatinine clearance (CrCl) and urine tumor necrosis factor-alpha (UTNF-α), 95% confidence intervals (CIs) were calculated, and heterogeneity was assessed with the I (2) test. Adverse effects were assessed using descriptive techniques.

RESULTS

Eight studies including 587 patients with a median duration of 5 months were identified. Compared with ACEI/ARB alone, the combination of PTF and ACEI/ARB significantly reduced proteinuria (SMD 0.76, 95% CI 0.52-0.99), albuminuria (SMD 0.36, 95% CI 0.12-0.59) and UTNF-α (MD 1.56 ng/g, 95% CI 0.09-3.03). However, no statistically significant changes were observed for SBP, DBP, HbA1c, Scr and CrCl. The most frequent adverse effects in patients treated with PTF were gastrointestinal symptoms (28/298) and dizziness (7/298), but in most cases, these symptoms were mild, only six participants withdrew due to intractable nausea and vomiting.

CONCLUSIONS

Pentoxifylline can significantly provide additive antiproteinuric effect independent from the decrease in BP or improvement in glycemic control in DN patients under blockade of angiotensin system. Further large, multicenter, high-quality studies with long duration are necessary to prove whether it really has renoprotective effects in this patient population.

Urinary biomarker N-acetyl-β-D-glucosaminidase can predict severity of renal damage in diabetic nephropathy

Background

Diabetic nephropathy is a clinical diagnosis where proteinuria is present in a patient with diabetes. Early intervention can significantly improve the prognosis. However, imprecision of the currently available biomarkers have impaired effective therapies in a timely manner. Urinary N-acetyl-β-D-glucosaminidase (NAG) is excreted in abnormally high amounts in many renal diseases. The aim of this study was to evaluate urinary NAG as an early biomarker in detection of diabetic nephropathy and whether it parallels the severity of kidney damage in different stages of diabetic nephropathy.

Methods

Fifty patients with type 2 DM were classified into 3 groups (normoalbuminurea, microalbuminurea and macroalbuminurea) and 10 healthy subjects served as a control group. Urinary NAG, albumin and creatinine were measured. Blood urea, serum creatinine, serum albumin, total proteins, serum cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), fasting and postprandial blood glucose, HbA1c and creatinine clearance were measured for all subjects.

Results

All diabetic patients had a significantly higher level of urinary NAG compared to control. NAG value increased in parallel with the severity of renal involvement.

Conclusion

Urinary NAG expresses the degree of renal impairment in diabetic nephropathy.

Effects of pentoxifylline on proteinuria and glucose control in patients with type 2 diabetes: a prospective randomized double-blind multicenter study

BACKGROUND

Pentoxifylline is a methylxanthine derivative with significant anti-inflammatory, anti-fibrotic, and anti-proliferative properties. Studies have shown that pentoxifylline may have renoprotective effects in patients with diabetic nephropathy. However, most of these studies were limited by small sample sizes. Therefore, we investigated whether pentoxifylline could reduce proteinuria in patients with diabetic nephropathy and residual proteinuria who received an angiotensin-converting enzyme inhibitor (ACEI) or an angiotensin II receptor blocker (ARB). We also studied the effects of pentoxifylline on glycemic control, insulin resistance, and inflammatory parameters.

METHODS

This was a prospective, randomized double-blind, placebo-controlled, multi-center study. A total of 174 patients with type 2 diabetes and albuminuria (>30 mg/g of creatinine) who were taking the recommended dosage of ACEI or ARB for > 6 months and receiving conventional therapy for diabetes were randomly assigned to receive pentoxifylline (1200 mg, daily; n = 87) or a placebo (n = 87) for 6 months. The endpoints were the effects of pentoxifylline on proteinuria, renal function, glucose control, and inflammatory parameters.

RESULTS

The percentage changes in proteinuria from baseline in the pentoxifylline and placebo groups were a decrease of 23 % and 4 %, respectively (p = 0.012). In addition, significant reductions in fasting plasma glucose, glycated hemoglobin, and insulin resistance according to the homeostasis model assessment were observed in the pentoxifylline group compared to those in the placebo group. However there was no significant difference in serum tumor necrosis factor (TNF)-α between the groups.

CONCLUSIONS

Pentoxifylline therapy reduced proteinuria and improved glucose control and insulin resistance without significant change of serum TNF-α in patients with type 2 diabetic nephropathy. Therefore, pentoxifylline is a potential therapeutic alternative for treating diabetes and diabetic nephropathy.

TRIAL REGISTRATION

NCT01382303.

Inflammatory cytokines in diabetic nephropathy

Probably, the most paradigmatic example of diabetic complication is diabetic nephropathy, which is the largest single cause of end-stage renal disease and a medical catastrophe of worldwide dimensions. Metabolic and hemodynamic alterations have been considered as the classical factors involved in the development of renal injury in patients with diabetes mellitus. However, the exact pathogenic mechanisms and the molecular events of diabetic nephropathy remain incompletely understood. Nowadays, there are convincing data that relate the diabetes inflammatory component with the development of renal disease. This review is focused on the inflammatory processes that develop diabetic nephropathy and on the new therapeutic approaches with anti-inflammatory effects for the treatment of chronic kidney disease in the setting of diabetic nephropathy.

TNF receptors: signaling pathways and contribution to renal dysfunction

Tumor necrosis factor (TNF), initially reported to induce tumor cell apoptosis and cachexia, is now considered a central mediator of a broad range of biological activities from cell proliferation, cell death and differentiation to induction of inflammation and immune modulation. TNF exerts its biological responses via interaction with two cell surface receptors: TNFR1 and TNFR2. (TNFRs). These receptors trigger shared and distinct signaling pathways upon TNF binding, which in turn result in cellular outputs that may promote tissue injury on one hand but may also induce protective, beneficial responses. Yet the role of TNF and its receptors specifically in renal disease is still not well understood. This review describes the expression of the TNFRs, the signaling pathways induced by them and the biological responses of TNF and its receptors in various animal models of renal diseases, and discusses the current outcomes from use of TNF biologics and TNF biomarkers in renal disorders.

Inflammation in diabetic kidney disease

Diabetes mellitus entails significant health problems worldwide. The pathogenesis of diabetes is multifactorial, resulting from interactions of both genetic and environmental factors that trigger a complex network of pathophysiological events, with metabolic and hemodynamic alterations. In this context, inflammation has emerged as a key pathophysiology mechanism. New pathogenic pathways will provide targets for prevention or future treatments. This review will focus on the implications of inflammation in diabetes mellitus, with special attention to inflammatory cytokines.

Effect of pentoxifylline on renal function and urinary albumin excretion in patients with diabetic kidney disease: the PREDIAN trial

Diabetic kidney disease (DKD) is the leading cause of ESRD. We conducted an open-label, prospective, randomized trial to determine whether pentoxifylline (PTF), which reduces albuminuria, in addition to renin-angiotensin system (RAS) blockade, can slow progression of renal disease in patients with type 2 diabetes and stages 3-4 CKD. Participants were assigned to receive PTF (1200 mg/d) (n=82) or to a control group (n=87) for 2 years. All patients received similar doses of RAS inhibitors. At study end, eGFR had decreased by a mean±SEM of 2.1±0.4 ml/min per 1.73 m(2) in the PTF group compared with 6.5±0.4 ml/min per 1.73 m(2) in the control group, with a between-group difference of 4.3 ml/min per 1.73 m(2) (95% confidence interval [95% CI], 3.1 to 5.5 ml/min per 1.73 m(2); P<0.001) in favor of PTF. The proportion of patients with a rate of eGFR decline greater than the median rate of decline (0.16 ml/min per 1.73 m(2) per month) was lower in the PTF group than in the control group (33.3% versus 68.2%; P<0.001). Percentage change in urinary albumin excretion was 5.7% (95% CI, -0.3% to 11.1%) in the control group and -14.9% (95% CI, -20.4% to -9.4%) in the PTF group (P=0.001). Urine TNF-α decreased from a median 16 ng/g (interquartile range, 11-20.1 ng/g) to 14.3 ng/g (interquartile range, 9.2-18.4 ng/g) in the PTF group (P<0.01), with no changes in the control group. In this population, addition of PTF to RAS inhibitors resulted in a smaller decrease in eGFR and a greater reduction of residual albuminuria.

Diabetic kidney disease: from physiology to therapeutics

Diabetic kidney disease (DKD) defines the functional, structural and clinical abnormalities of the kidneys that are caused by diabetes. This complication has become the single most frequent cause of end-stage renal disease. The pathophysiology of DKD comprises the interaction of both genetic and environmental determinants that trigger a complex network of pathophysiological events, which leads to the damage of the glomerular filtration barrier, a highly specialized structure formed by the fenestrated endothelium, the glomerular basement membrane and the epithelial podocytes, that permits a highly selective ultrafiltration of the blood plasma. DKD evolves gradually over years through five progressive stages. Briefly they are: reversible glomerular hyperfiltration, normal glomerular filtration and normoalbuminuria, normal glomerular filtration and microalbuminuria, macroalbuminuria, and renal failure. Approximately 20-40% of diabetic patients develop microalbuminuria within 10-15 years of the diagnosis of diabetes, and about 80-90% of those with microalbuminuria progress to more advanced stages. Thus, after 15-20 years, macroalbuminuria occurs approximately in 20-40% of patients, and around half of them will present renal insufficiency within 5 years. The screening and early diagnosis of DKD is based on the measurement of urinary albumin excretion and the detection of microalbuminuria, the first clinical sign of DKD. The management of DKD is based on the general recommendations in the treatment of patients with diabetes, including optimal glycaemic and blood pressure control, adequate lipid management and abolishing smoking, in addition to the lowering of albuminuria.

Pentoxifylline for diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is associated with increased morbidity and mortality, mostly relating to cardiovascular complications. The relevance of inflammation in the pathogenesis of DKD has been investigated in recent years, and it has been shown that inflammatory markers are higher in people with DKD compared with the wider population. Pentoxifylline is a methylxanthine phosphodiesterase inhibitor with favourable anti-inflammatory effects and immunoregulatory properties. The anti-inflammatory effects conferred by pentoxifylline may be beneficial in the management of DKD.

OBJECTIVES

To assess the benefits and harms of pentoxifylline for treating people with DKD.

SEARCH METHODS

We searched the Cochrane Renal Group's specialised register (January 2012), CENTRAL (Issue 12, 2011), MEDLINE, EMBASE and four Chinese biomedical literature databases (CBM-disc, 1979 to July 2009), Chinese Science and Technique Journals Database (VIP, until July 2009), China National Knowledge Infrastructure (CNKI, until July 2009) and WanFang database (until July 2009).

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs studying the benefits and harms of pentoxifylline for DKD.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors. Meta-analyses were performed when more than one study provided data on a comparable outcome in sufficiently similar patients. Results of dichotomous outcomes were expressed as risk ratios (RR) with 95% confidence intervals (CI). Mean differences (MD) were calculated to assess the effects of treatment where outcomes were expressed on continuous scales, and standardised mean differences (SMD) calculated where different scales were used. Data was pooled using the random effects model. Adverse effects were assessed using descriptive techniques and where possible, risk differences (RD) with 95% CI.

MAIN RESULTS

We identified 17 studies that included a total of 991 participants with DKD which met our inclusion criteria. Overall, the methodological quality of included studies was low: 4/17 reported the method of randomisation, 13/17 did not; no study described the method of random allocation; 4/17 studies were considered to be at high risk of bias and 13/17 were considered to have unclear risk for incomplete outcome data reporting; 9/17 studies were at low risk bias and in 8/17 the risk of bias was unclear for selective outcome reporting.Compared with placebo, pentoxifylline significantly reduced serum creatinine (SCr) (MD -0.10 mg/dL, 95% CI -0.17 to -0.03), albuminuria (SMD -2.28, 95% CI -3.85 to -0.70) and overt proteinuria (MD -428.58 µg/min, 95% CI -661.65 to -195.50), but there was no difference in creatinine clearance (CrCl) (MD -5.18 mL/min, 95% CI -15.55 to 5.19). When compared with routine treatment alone, pentoxifylline did not significantly reduce SCr (MD 0.00 mg/dL, 95% CI -0.06 to 0.07) or blood pressure (systolic (SBP): MD -0.28 mm Hg, 95% CI -2.20 to 1.63; diastolic (DBP): MD -0.15 mm Hg, 95% CI -1.44 to 1.14), but did significantly reduce albuminuria (SMD 0.62, 95% CI 0.18 to 1.07) and proteinuria (MD 0.46 g/24 h, 95% CI 0.17 to 0.74). There was no significant difference in SCr (MD 0.00 mg/dL, 95% CI -0.08 to 0.07), albuminuria (MD -8.79 µg/min, 95% CI -27.18 to 9.59), proteinuria (MD -0.01 g/24 h, 95% CI -0.03 to 0.01) or blood pressure (SBP: MD 1.46 mm Hg, 95% CI -0.57 to 3.50; DBP: MD 1.37 mm Hg, 95% CI -0.23 to 2.98) between pentoxifylline and the active comparator (captopril or clonidine/methyldopa) for patients with type 1 and type 2 DKD. CrCl was significantly increased when pentoxifylline was compared to clonidine/methyldopa (MD 10.90 mL/min, 95% CI -1.40 to 20.40) but not with captopril (MD 3.26 mL/min, 95% CI -1.05 to 7.59). No data were available on the incidence of end-stage kidney disease (ESKD), time to ESKD, quality of life, or all-cause mortality. The adverse events of pentoxifylline were mild; no serious adverse events were reported in any of the included studies.

AUTHORS' CONCLUSIONS

From the available evidence, pentoxifylline seems to offer some beneficial effects in renal function improvement and reduction in albuminuria and proteinuria, with no obvious serious adverse effects for patients with DKD. However, most studies were poorly reported, small, and methodologically flawed. Evidence to support the use of pentoxifylline for DKD was insufficient to develop recommendations for its use in this patient population. Rigorously designed, randomised, multicentre, large scale studies of pentoxifylline for DKD are needed to further assess its therapeutic effects.

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.

Pentoxifylline for renoprotection in diabetic nephropathy: the PREDIAN study. Rationale and basal results

STATEMENTS OF THE PROBLEM

Diabetic nephropathy (DN) is the main cause of end-stage renal disease (ESRD). Renin-angiotensin system (RAS) blockade is the standard of care; however, a significant proportion of patients progress to ESRD. Pentoxifylline (PTF) possesses properties suggesting potential renoprotective efficacy. The aim of the Pentoxifylline for Renoprotection in Diabetic Nephropathy (PREDIAN) study is to test the efficacy of PTF addition to RAS blockade on the progression of DN. Here we report the study design and the baseline patient characteristics.

METHODS

This is an investigator-initiated, single-center, prospective, randomized, controlled, clinical trial without any commercial interest, funded by the Spanish Ministry of Science and Innovation. One hundred and sixty-nine type 2 diabetic patients with Stage 3 and 4 chronic kidney disease (CKD) were randomized to a control group (n=87) or an active group (n=82), which will receive PTF (1200 mg/day) for 24 months. The primary outcome measure is the difference in estimated glomerular filtration rate (eGFR) between the groups at the end of the study.

RESULTS

The baseline characteristics of the subjects are as follows: 116 patients (68.6%) with Stage 3 CKD and 53 (31.3%) Stage 4 CKD, age 69±9 years, duration of diabetes 15±3 years, eGFR 37±12 ml/min per 1.73 m(2), albuminuria 1.39±1.16 g/day, blood pressure 142±8/86±8 mmHg. Inflammatory cytokines (tumor necrosis factor-α, interleukin-6, and interleukin-10) and polymorphisms of the coding genes for these molecules are studied.

CONCLUSIONS

The PREDIAN study will provide evidence on the renoprotective benefit of PTF in addition to interventions of proven efficacy (RAS blockade) in DN.

Assessment of novel avian renal disease markers for the detection of experimental nephrotoxicosis in pigeons (Columba livia)

Renal disease is a major cause of illness in captive and wild avian species. Current renal disease markers (e.g., uric acid, blood urea nitrogen, and creatinine) are insensitive. Two endogenous markers, creatine and N-acetyl-beta-D-glucosaminidase (NAG), were selected for study in the pigeon (Columba livia). Representative organs from four pigeons were surveyed to determine those exhibiting the highest level of each marker. In a separate study, NAG and creatine from plasma and urine were assayed before and after gentamicin (50 mg/kg twice daily), administration for up to 9 days. Observer-blinded pathologic scoring (five saline solution controls, 17 treated birds) was used to verify the presence of renal disease that corresponded to marker increases. The first study revealed that kidney tissue had the highest NAG activity (by approximately six times), and pectoral muscle had the most creatine (>900 times). In response to gentamicin, plasma creatine (>five times) and NAG increased (approximately six times), which paralleled uric acid (>10 times). Urine creatine (approximately 60 times) and NAG increased dramatically (approximately 50 times) in response to gentamicin. In conclusion, NAG, especially in the urine, may be of value to noninvasively detect renal toxin exposures and to monitor potentially nephrotoxic drugs, and might be of value to screen free-ranging birds in large exhibits or in the wild by assaying fresh urate samples at feeding stations.

Pathogenic perspectives for the role of inflammation in diabetic nephropathy

Diabetes and its complications have become a public health problem. One of the most important complications is diabetic nephropathy, which is nowadays the main cause of chronic renal failure. In spite of our greater understanding of this complication, the intimate mechanisms leading to the development and progression of renal injury are not well understood. New perspectives in activated innate immunity and inflammation appear to be relevant factors in the pathogenesis of diabetes. Moreover, different inflammatory molecules, including adipokines, Toll-like receptors, chemokines, adhesion molecules and pro-inflammatory cytokines, may be critical factors in the development of microvascular diabetic complications, including nephropathy. This new pathogenic perspective leads to important therapeutic considerations, with new pathogenic pathways becoming important therapeutic targets that can be translated into clinical treatments for diabetic nephropathy.

Tumor necrosis factor-alpha as a therapeutic target for diabetic nephropathy

Activation of innate immunity with the subsequent development of a chronic low-grade inflammatory response is now recognized as a critical factor in the pathogenesis of diabetes mellitus and diabetic complications, including diabetic nephropathy. In the setting of diabetic nephropathy, there is now evidence of the relevant contribution of pro-inflammatory cytokines, with special participation of tumor necrosis factor-alpha (TNF-alpha). This new pathogenic perspective leads to new therapeutic implications derived from modulation of inflammation and inflammatory cytokines. Experimental studies have shown the beneficial renal actions derived from TNF-alpha inhibition with the use of soluble TNF-alpha receptor fusion proteins, chimeric monoclonal antibodies and pentoxifylline (PTF). Clinical application of this strategy is nowadays limited to PTF administration, which has demonstrated significant beneficial effects in patients with diabetic nephropathy. Overall, these studies indicate that inhibition of TNF-alpha might be an efficacious treatment for renal disease secondary to diabetes mellitus.

Effect of pentoxifylline on GFR decline in CKD: a pilot, double-blind, randomized, placebo-controlled trial

BACKGROUND

Pentoxifylline is a nonspecific phosphodiesterase inhibitor with anti-inflammatory properties. It reduces proteinuria in patients with glomerular disease, although its impact on glomerular filtration rate (GFR) is unknown. We hypothesized that pentoxifylline would slow the estimated GFR decrease in patients with chronic kidney disease at high risk of progression.

STUDY DESIGN

Pilot randomized double-blind placebo-controlled trial.

SETTING & PARTICIPANTS

40 outpatients with decreased GFR, hypertension, and proteinuria greater than 1 g/24 h currently treated with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or the combination and followed up in a nephrology clinic at a tertiary medical care facility.

INTERVENTION

Pentoxifylline, 400 mg twice daily, or matching placebo.

OUTCOMES

Difference in rates of estimated GFR change during the 1-year study period between the 2 groups.

MEASUREMENTS

Estimated GFR (4-variable Modification of Diet in Renal Disease Study equation) and proteinuria by 24-hour urine collection were assessed at baseline and 6 and 12 months after enrollment.

RESULTS

Baseline characteristics were similar between the 2 groups. At 1 year, the mean estimated GFR decrease was significantly less in the pentoxifylline group than the placebo group (-1.2 +/- 7.0 versus -7.2 +/- 8.2 mL/min/1.73 m2/y; mean difference, -6.0 mL/min/1.73 m2/y; 95% confidence interval, -11.4 to -0.6; P = 0.03). For pentoxifylline-treated participants, the mean estimated GFR decrease during treatment was slower compared with the year before study enrollment (-9.6 +/- 11.9 mL/min/1.73 m2/y; mean difference, -8.4 mL/min/1.73 m2/y; 95% confidence interval, -14.8 to -2.1; P = 0.01). Proteinuria was not different between the pentoxifylline and placebo groups at baseline, 6 months, or 1 year.

LIMITATIONS

Small sample size and incomplete follow-up.

CONCLUSIONS

Pentoxifylline may slow the estimated GFR decrease in high-risk patients. This may be independent of its antiproteinuric properties and warrants further investigation.

The effect of pentoxifylline on proteinuria in diabetic kidney disease: a meta-analysis

BACKGROUND

Pentoxifylline is a potential therapeutic agent for diabetic kidney disease because it has anti-inflammatory, antifibrotic, and hemorheological properties.

STUDY DESIGN

Systematic review and meta-analysis of randomized controlled trials.

SETTING, POPULATION, & INTERVENTION

Adult patients with diabetic kidney disease who received oral pentoxifylline.

SELECTION CRITERIA FOR STUDIES

We searched bibliographic databases for trials involving pentoxifylline that reported proteinuria, glomerular filtration rate, or blood pressure.

OUTCOMES

The primary outcome measure was the effect of pentoxifylline on proteinuria stratified by whether pentoxifylline was compared with renin-angiotensin system blockade.

RESULTS

10 studies including a total of 476 participants with a median duration of 6 months were identified. Pentoxifylline significantly decreased proteinuria (weighted mean difference, -278 mg/d of protein; 95% confidence interval [CI], -398 to -159; P < 0.001) compared with placebo or usual care. Compared with captopril, the decrease in proteinuria with pentoxifylline was similar (weighted mean difference, 0 mg/d of protein; 95% CI, -17 to 18; P = 0.9). Secondary analysis showed that patients with microalbuminuria had a nonsignificant decrease in protein excretion (weighted mean difference, -87 mg/d; 95% CI, -201 to 27; P = 0.1), whereas those with overt proteinuria (protein > 300 mg/d) had a significant decrease (weighted mean difference, -502 mg/d; 95% CI, -805 to -198; P = 0.001). No significant changes in systolic or diastolic blood pressure or glomerular filtration rate were found.

LIMITATIONS

Quality scores of studies were low, and there was significant heterogeneity.

CONCLUSIONS

Available evidence suggests that pentoxifylline may decrease proteinuria in patients with diabetic nephropathy. To confirm these findings, large high-quality studies are required.

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.

Effect of Pentoxifylline on inflammatory burden, oxidative stress and platelet aggregability in hypertensive type 2 diabetes mellitus patients

OBJECTIVES

Inflammation and oxidative stress are main culprits behind atherosclerosis in diabetes mellitus. This study explores the effect of add-on Pentoxifylline on inflammatory burden and oxidative stress in hypertensive diabetic patients.

RESEARCH DESIGN AND METHODS

60 hypertensive type 2 diabetic, aged > or = 45 years were evaluated for anthropometry, clinical parameters, C-reactive protein, total leukocyte count, erythrocyte sedimentation rate, serum albumin, plasma malondialdehyde, blood reduced glutathione, platelet aggregation and clot retraction profile. With informed consent and randomization, Pentoxifylline (400 mg) was prescribed to 30 patients orally twice daily with meals as add-on therapy to the standard therapeutic regimen for one month. The particular parameters were repeated in 26 patients in control group and 25 patients in Pentoxifylline group who completed the follow up. The study was a randomized, open, add-on clinical trial with parallel controls.

RESULTS

At one-month follow-up, in the Pentoxifylline group, there was 20.9% decrease (p<0.001) in C-reactive protein, 18% reduction (p<0.001) in erythrocyte sedimentation rate, 11.1% reduction (p<0.001) in total leukocyte count and 5.8% increase (p=0.003) in serum albumin. Pentoxifylline showed 20.2% reduction in plasma malondialdehyde and 4.6% increase in blood reduced glutathione level. In therapeutic dose range, Pentoxifylline exerted a significant anti-aggregatory effect and a dose dependent decrease in clot retraction in-vitro but there was no significant change in ex-vivo clot retraction. The control group showed no statistically significant change in parameters assessed.

CONCLUSION

This study reveals improvements in inflammatory markers, oxidative stress and platelet-aggregation by Pentoxifylline, thus preventing atherosclerosis in diabetes mellitus.

Renal pro-inflammatory cytokine gene expression in diabetic nephropathy: effect of angiotensin-converting enzyme inhibition and pentoxifylline administration

BACKGROUND

Recent studies have shown a role for inflammation in the pathogenesis of diabetic nephropathy (DN). Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 and IL-6 are cytokines with a prevalent pro-inflammatory activity. Our objective was to study the renal gene expression of TNF-alpha, IL-1 and IL-6 in DN and their relationship with renal damage assessed by urinary albumin excretion (UAE). In addition, we also investigated the effect of angiotensin-converting enzyme inhibition and pentoxifylline (PTF) administration on these parameters.

METHODS

After streptozotocin-induced diabetes, rats received either no treatment or therapy with enalapril (EN) or PTF for 8 weeks. Renal expression of pro-inflammatory cytokines was evaluated by real-time polymerase chain reaction. Urinary cytokine excretion and albuminuria were also evaluated.

RESULTS

Renal cortical mRNA expression for TNF-alpha, IL-1 and IL-6 in untreated diabetic rats was 2.4-, 1.2- and 3.4-fold higher than in non-diabetic rats. Kidney weight and UAE were significantly associated with renal mRNA expression of TNF-alpha and IL-6. Both EN and PTF administration virtually abrogated the overexpression of TNF-alpha, IL-1 and IL-6, which was associated with a reduction in kidney weight and urinary albumin excretion.

CONCLUSION

The renal expression of the main pro-inflammatory cytokines TNF-alpha, IL-1 and IL-6 is increased in DN, which is significantly associated with UAE. EN and PTF administration prevented this enhanced expression, leading to a decrease in urinary cytokine excretion and a reduction in albuminuria. These findings provide novel insight into the pathogenic mechanisms of DN, supporting the hypothesis that inflammatory mechanisms play a role in the renal injury secondary to diabetes mellitus.

Inflammation and diabetic nephropathy

Diabetic nephropathy has become the main cause of renal failure, but unfortunately the intimate mechanisms leading to the development and progression of renal injury are not yet fully known. Activated innate immunity and inflammation are relevant factors in the pathogenesis of diabetes. Moreover, different inflammatory molecules, including chemokines, adhesion molecules, and proinflammatory cytokines, may be critical factors in the development of microvascular diabetic complications, including nephropathy. This new pathogenic perspective leads to important therapeutic considerations, with new pathogenic pathways becoming important therapeutic targets that can be translated into clinical treatments for diabetic nephropathy.

Pentoxifylline ameliorates proteinuria through suppression of renal monocyte chemoattractant protein-1 in patients with proteinuric primary glomerular diseases

Proteinuria (albuminuria) reflects dysfunction of the glomerular permeability barrier in which inflammatory cytokines play a key role. Pentoxifylline (PTX) is a phosphodiesterase inhibitor that possesses potent anti-inflammatory and immunomudulatory effects. This study evaluated the effectiveness of PTX to reduce proteinuria and inflammatory mediators in patients with proteinuric primary glomerular diseases. Seventeen patients with primary glomerular diseases, a persistent spot proteinuria exceeding 1.5 g/g creatinine (Cr) and a glomerular filtration rate between 24 and 115 ml/min/1.73 m(2) were treated with PTX 400 mg twice daily for 6 months. Before and after the treatment, serum Cr, plasma renin activity and aldosterone concentrations, plasma and urinary tumor necrosis factor (TNF)-alpha, interleukin-1beta and monocyte chemoattractant protein (MCP)-1, as well as urinary protein and Cr were measured. PTX significantly reduced urinary protein excretion, along with an increase of serum albumin. A significant correlation existed between the basal urinary protein/Cr and the basal urinary MCP-1/Cr ratios. PTX lowered the urinary MCP-1/Cr ratio, and the percent reduction of urinary protein/Cr ratio correlated directly with the precent decrease of urinary MCP-1/Cr ratio after PTX treatment. There was no significant change in blood pressure, renal function, biochemical parameters, plasma renin activity and aldosterone concentrations, or plasma TNF-alpha and MCP-1 levels during the study. In conclusion, administration of PTX 800 mg per day is safe and effective for reducing proteinuria in patients with proteinuric primary glomerular diseases. This beneficial effect occurs in close association with a reduction of urinary MCP-1 excretion.

Processing Advanced Glycation End Product-Modified Albumin by the Renal Proximal Tubule and the Early Pathogenesis of Diabetic Nephropathy

Diabetes is characterized by increased quantities of circulating proteins modified by advanced glycation end products (AGEs). Proteins filtered at the glomerulus and presented to the renal proximal tubule are likely to be highly modified by AGEs. The proximal tubule binds, takes up, and catabolizes AGE-modified albumin by pathways different from those of unmodified albumin. These differences were examined in polarized, electrically resistant proximal tubular cells grown in monolayer culture. In patients with type 1 diabetes, urinary excretion of a lysosomal enzyme predicted the development of nephropathy.

Short Term Change of Urinary N-Acetyl-.BETA.-D-Glucosaminidase in Reduced Kidney Mass with Renal Artery Ligation

The aim of the present study was to evaluate short term urinary NAG levels in a model of reduced kidney mass. The half and quarter kidney mass were made from ligation of the renal artery. Both groups decreased in the level of excreted NAG on day 1 and 2 after operation. On day 5 after operation, both groups achieved urinary enzyme levels comparable to that of the sham-operated group. The remaining compensated nephrons held normal range of excreted urinary NAG levels, although reduced number of nephrons resulted in a decline in urinary NAG levels.

Progression of chronic kidney disease: can it be prevented or arrested?

Chronic kidney disease constitutes a highly prevalent health problem worldwide. Left untreated, it progresses inexorably to greater levels of severity at variable rates. The morbid impact of chronic kidney disease is heightened by its role as risk factor for cardiovascular disease. In the past two decades, considerable gains have been realized in retarding progression of chronic kidney disease by emphasizing blood pressure control and blockade of the renin-angiotensin system. Notwithstanding, the therapeutic goal of preventing or arresting chronic kidney disease progression remains unfulfilled. Currently attainable rates of decrease in glomerular filtration rate remain at 2 to 8 mL/min/y depending on the underlying disease. It is now believed that to achieve optimal therapeutic targets (proteinuria of <500 mg/day and decrease in glomerular filtration rate of 1 mL/min/y, the average age-related decline) we must introduce novel strategies and a multifaceted approach to treatment that interrupts multiple mechanisms of progression. To this end, and wherever relevant, new approaches to cause-specific treatment must be applied, such as targeted immunosuppression, intensive glycemic control, gene therapy, and enzyme replacement therapy. Furthermore, in all chronic kidney disease, we must interfere more effectively with the multitude of common mechanisms of progression. Established or putative, such approaches include aggressive blood pressure control; advanced renin-angiotensin system blockade; cytokine modulation and antifibrotic therapy; aldosterone blockade; endothelin blockade, nitric oxide modulation and vasopeptidase inhibition; antioxidant therapy; statin therapy; glycosaminoglycan therapy; anemia therapy; dietary restrictions; lifestyle changes; and pharmacogenomic profiling. Such a concerted, multifaceted approach to management might indeed prevent or arrest progression of chronic kidney disease, or even achieve regression of chronic kidney disease.

Candesartan Reduces Urinary Fatty Acid-Binding Protein Excretion in Patients with Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Free fatty acids (FFAs) bound to albumin are overloaded in renal proximal tubules and exacerbate tubulointerstitial damage. Liver-type fatty acid-binding protein (L-FABP) is an intracellular carrier protein of FFAs that is expressed in renal proximal tubules in humans. Urinary L-FABP reflects the clinical prognosis of chronic glomerulonephritis. The aim of the present study was to determine whether urinary L-FABP excretion is altered in patients with autosomal dominant polycystic kidney disease (ADPKD) and whether candesartan cilexetil, an angiotensin II receptor antagonist, affects these levels.

METHODS

Subjects comprised 20 normotensive ADPKD patients (8 men and 12 women, mean age 42.6 years) and 20 age-matched healthy volunteers (8 men and 12 women, mean age 44.0 years). The 20 ADPKD patients participated in a randomized double-blind placebo-controlled study of candesartan cilexetil for 6 months. Urinary L-FABP levels were measured by a newly established ELISA method.

RESULTS

Urinary L-FABP levels were significantly higher in ADPKD patients (154.5 +/- 110.6 microg/g Cr) than in healthy subjects (5.5 +/- 3.8 microg/g Cr) (P < 0.001). Candesartan cilexetil reduced urinary L-FABP levels from 168.5 +/- 104.5 microg/g Cr to 98.5 +/- 68.5 microg/g Cr after 3 months (P < 0.01) and to 44.6 +/- 30.8 microg/g Cr after 6 months (P < 0.001). Placebo had no effect on L-FABP levels (before, 140.5 +/- 100.5 microg/g Cr; at 3 months, 148.5 +/- 108.5 microg/g Cr; at 6 months, 150.5 +/- 110.8 microg/g Cr). During the 6 months, serum creatinine, blood urea nitrogen, 24-hour creatinine clearance and blood pressure showed little change in either group.

CONCLUSIONS

Increased urinary L-FABP levels may be associated with the development of ADPKD, and candesartan cilexetil has a beneficial effect on reducing these levels.

Effects of polymyxin B immobilized fiber on urinary N-acetyl-beta-glucosaminidase in patients with severe sepsis

Severe sepsis is known to cause multiple organ failure, including renal dysfunction. During sepsis, endotoxin targets the renal proximal tubular cells, the function of which can be evaluated on the basis of urinary N-acetyl-beta-glucosaminidase (NAG). We investigated whether urinary NAG activity is altered in patients with severe sepsis and whether treatment with polymyxin B immobilized fibers (PMX-F) affects this activity. Subjects of this study were 120 patients with severe sepsis and 60 healthy volunteers matched for age and gender. Patients were randomly assigned to one of two treatments: PMX-F treatment (n = 70) or conventional treatment (n = 50). The plasma endotoxin level was significantly reduced, from 34.6 +/- 10.2 to 6.8 +/- 2.4 pg/ml (p < 0.01) in patients treated with PMX-F, and the urinary NAG/creatinine ratio was reduced from 46.5 +/- 26.8 U/gm to 18.6 +/- 13.6 U/gm (p < 0.01). The plasma endotoxin level and urinary NAG/creatinine ratio were unchanged in patients who received conventional treatment. The increased urinary NAG/creatinine ratio in patients with severe sepsis may reflect proximal tubular dysfunction. PMX-F is effective in reducing proximal tubular dysfunction, in part owing to reduced plasma endotoxin levels.

Pentoxifylline Attenuates Tubulointerstitial Fibrosis by Blocking Smad3/4-Activated Transcription and Profibrogenic Effects of Connective Tissue Growth Factor

Pentoxifylline (PTX) is a potent inhibitor of connective tissue growth factor (CTGF), but its underlying mechanism is poorly understood. Here, it was demonstrated that PTX inhibited not only TGF-beta1-induced CTGF expression but also CTGF-induced collagen I (alpha1) [Col I (alpha1)] expression in normal rat kidney fibroblasts (NRK-49F) and alpha-smooth muscle actin expression in normal rat kidney proximal tubular epithelial cells (NRK-52E). Furthermore, PTX attenuated tubulointerstitial fibrosis, myofibroblasts accumulation, and expression of CTGF and Col I (alpha1) in unilateral ureteral obstruction kidneys. The mechanism by which PTX reduced CTGF in NRK-49F and NRK-52E was investigated. Activation of Smad3/4 was essential for TGF-beta1-induced CTGF transcription, but PTX did not interfere with TGF-beta1 signaling to Smad2/3 activation and association with Smad4 and their nuclear translocation. However, PTX was capable of blocking activation of TGF-beta1-induced Smad3/4-dependent reporter as well as CTGF promoter, suggesting that PTX affects a factor that acts cooperatively with Smad3/4 to execute transcriptional activation. It was found that PTX increased intracellular cAMP and caused cAMP response element binding protein phosphorylation. The protein kinase A antagonist H89 abolished the inhibitory effect of PTX on Smad3/4-dependent CTGF transcription, whereas dibutyryl cAMP and forskolin recapitulated the inhibitory effect. In conclusion, these results indicate that PTX inhibits CTGF expression by interfering with Smad3/4-dependent CTGF transcription through protein kinase A and blocks the profibrogenic effects of CTGF on renal cells. Because of the dual blockade, PTX potently attenuates the tubulointerstitial fibrosis in unilateral ureteral obstruction kidneys.

Additive antiproteinuric effect of pentoxifylline in patients with type 2 diabetes under angiotensin II receptor blockade: a short-term, randomized, controlled trial

Despite the beneficial effects of blockade of the renin-angiotensin system in diabetic nephropathy (DN), albuminuria and progression of renal disease are not completely halted by these agents. Therefore, it is necessary to explore potential antiproteinuric and renoprotective effects of innovative therapeutic approaches. This study tested the hypothesis that the combination of pentoxifylline (PTF) with angiotensin II receptor blockers in normotensive patients with type 2 diabetes produces an additive antiproteinuric effect. Sixty-one patients with DN and residual albuminuria despite treatment with the recommended doses of ARB for >1 yr were randomly assigned to receive the addition of 1200 mg of PTF daily (n = 30) or to a control group (n = 31). Baseline characteristics were similar between groups, and correlation analysis showed a significant association between urinary albumin excretion (UAE) and urinary TNF-alpha (R = 0.53, P < 0.001). After 4 mo, albuminuria showed a significant decrease in patients who received PTF, from 900 mg/24 h (466 to 1542 mg/d) to 791 mg/24 h (309 to 1400 mg/d; P < 0.001), whereas no significant changes were observed in the control group: 920 mg/24 h (450 to 1489 mg/d) at baseline, and 900 mg/24 h (428 to 1800 mg/d) at the end of the study. The mean percentage variation of UAE in the treatment and control groups was -16.7 and 5.5%, respectively (between-group comparison, P < 0.001). This additive antiproteinuric effect was not dependent on changes in BP or metabolic control. However, both serum and urinary levels of TNF-alpha also decreased in patients who received PTF, from 6.4 pg/ml (2.1 to 9.7) and 16 pg/mg (8 to 29) at baseline to 4.6 pg/ml (0.4 to 9) and 14.2 pg/mg (3 to 26) at the end of the study, respectively (P < 0.01), without significant variations in control patients. Moreover, regression analysis at the end of the study showed a correlation between the change in UAE and the change in urinary TNF-alpha in patients who were treated with PTF (R = 0.49, P < 0.001). In conclusion, administration of PTF to patients who have type 2 diabetes and are under long-term treatment with an ARB produces a significant additive antiproteinuric effect associated with a reduction of urinary TNF-alpha excretion.

The renoprotective potential of pentoxifylline in chronic kidney disease

Current interventions with proven efficacy, such as glycemic and blood pressure control, dietary protein restriction, and angiotensin II blockade, slow the progression of chronic kidney disease (CKD); however, whether long-term cessation of CKD progression is possible remains unclear. Because of the pathogenetic complexity of this condition, multidrug interventions with the least adverse effects should be investigated as the next step in attempts to stop CKD progression. Pentoxifylline, a non-selective phosphodiesterase inhibitor with indiscernible toxicity, exerts potent inhibitory effects against cell proliferation, inflammation, and extracellular matrix accumulation, all of which play important roles in CKD progression. Pentoxifylline monotherapy markedly reduces proteinuria in patients with membranous nephropathy. Moreover, limited human studies have proven pentoxifylline efficacy in reducing proteinuria in patients with diabetes receiving angiotensin-converting enzyme inhibitors, and in patients with nephrotic syndrome secondary to lupus nephritis despite immunosuppressive therapy. Further clinical trials are necessary to examine whether pentoxifylline can improve renal outcomes in patients receiving interventions of proven efficacy.