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The initial enthusiasm for the advent of a potentially nonnephrotoxic immunosuppressant has been muted by data unmasking nephrotoxicity of mammalian target of rapamycin inhibitors, including renal podocyte injury resulting in proteinuria. Adverse reactions, including anemia, thrombocytopenia, hyperlipidemia, and especially diabetogenesis, have limited its use to niche indications such as prevention or amelioration of malignancy in organ transplant. The class seems to be best used to address malignancy in organ allograft recipients and as a first-line therapy in lymphangioleiomyomatosis.
Transforming growth factor-β (TGF-β) and phosphatidylinositol-3-kinase (PI3 K) isoforms contribute to glomerular disease. Finer and colleagues define a temporal and selective role for the p110γ catalytic isoform of PI3 K, normally expressed by hematopoietic cells, and TGF-β in adriamycin-mediated glomerular injury. Early ectopic upregulation of p110γ by podocytes drives initial injury and proteinuria, whereas late upregulation of TGF-β drives fibrogenesis. Thus, proteinuria and renal fibrogenesis involve distinct signaling activated by p110γ and TGF-β, respectively.
PURPOSE OF REVIEW - Expanding rates of acute kidney injury (AKI) coupled with increasing awareness of its short-term and long-term sequelae have focused efforts to identify patients at risk for this disease and its complications. This review details the recent attempts to identify novel risk factors for AKI, describes further refinements in the diagnostic and prognostic approach using biological markers of injury, and highlights the features of AKI that independently predict poor long-term outcomes.
RECENT FINDINGS - The presence of proteinuria predicts the development of AKI independently of estimated glomerular filtration rate. Initial results from a large prospective study of AKI biomarkers in cardiac surgery indicate lower agreement with serum creatinine as an AKI standard than observed in early studies. AKI severity and duration are important predictors of chronic kidney disease and long-term mortality. A minority of patients surviving AKI with decreased kidney function is seen by a nephrologist.
SUMMARY - Although the pathophysiologic link is unclear, proteinuria is an easily measurable risk factor for AKI worth considering before anticipated procedures or medication exposures carrying nephrologic risk. Investigation extending beyond agreement with serum creatinine is needed to fully understand the diagnostic and prognostic value of AKI biomarkers. Severity and duration are components of AKI that can help risk-stratify survivors in need of monitoring or nephrology referral.
Induction of hemeoxygenase-1 (HO-1) lowers blood pressure and reduces organ damage in hypertensive animal models; however, a potential protective role for HO-1 induction against diabetic-induced glomerular injury remains unclear. We hypothesize that HO-1 induction will protect against diabetes-induced glomerular injury by maintaining glomerular integrity and inhibiting renal apoptosis, inflammation, and oxidative stress. Diabetes was induced with streptozotocin in spontaneously hypertensive rats (SHR) as a model where the coexistence of hypertension and diabetes aggravates the progression of diabetic renal injury. Control and diabetic SHR were randomized to receive vehicle or the HO-1 inducer cobalt protoporphyrin (CoPP). Glomerular albumin permeability was significantly greater in diabetic SHR compared with control, consistent with an increase in apoptosis and decreased glomerular nephrin and α(3)β(1)-integrin protein expression in diabetic SHR. CoPP significantly reduced albumin permeability and apoptosis and restored nephrin and α(3)β(1)-integrin protein expression levels in diabetic SHR. Glomerular injury in diabetic SHR was also associated with increases in NF-κB-induced inflammation and oxidative stress relative to vehicle-treated SHR, and CoPP significantly blunted diabetes-induced increases in glomerular inflammation and oxidative stress in diabetic SHR. These effects were specific to exogenous stimulation of HO-1, since incubation with the HO inhibitor stannous mesoporphyrin alone did not alter glomerular inflammatory markers or oxidative stress yet was able to prevent CoPP-mediated decreases in these parameters. These data suggest that induction of HO-1 reduces diabetic induced-glomerular injury and apoptosis and these effects are associated with decreased NF-κB-induced inflammation and oxidative stress.
BACKGROUND - Previous studies have shown that patients with chronic kidney disease, including those with diabetic nephropathy, are more likely to die of cardiovascular disease than reach end-stage renal disease (ESRD). This analysis was conducted to determine whether ESRD is a more common outcome than cardiovascular death in patients with type 2 diabetic nephropathy, significant proteinuria, and decreased kidney function who were selected for participation in a clinical trial.
STUDY DESIGN - Retrospective analysis of the DIAMETRIC (Diabetes Mellitus Treatment for Renal Insufficiency Consortium) database derived from 2 prospective randomized controlled clinical trials (IDNT [Irbesartan Diabetic Nephropathy Trial] and RENAAL [Reduction of Endpoints in Non-Insulin-dependent Diabetes With the Angiotensin II Antagonist Losartan]).
SETTING & PARTICIPANTS - 3,228 adult patients with type 2 diabetic nephropathy from IDNT and RENAAL were combined to establish the DIAMETRIC database. This is the largest global source of clinical information for patients with type 2 diabetic nephropathy who have decreased kidney function and significant proteinuria.
INTERVENTION - Angiotensin receptor blocker versus non-angiotensin receptor blocker therapy to slow the progression of type 2 diabetic nephropathy (in the prospective trials).
OUTCOMES & MEASUREMENTS - Incidence rates of ESRD, cardiovascular death, and all-cause mortality.
RESULTS - Mean follow-up was 2.8 years; 19.5% of patients developed ESRD, approximately 2.5 times the incidence of cardiovascular death and 1.5 times the incidence of all-cause mortality. ESRD was more common than cardiovascular death in all subgroups analyzed with the exception of participants with low levels of albuminuria (albumin excretion <1.0 g/g) and well-preserved levels of kidney function (estimated glomerular filtration rate >45 mL/min/1.73 m(2)) at baseline.
LIMITATIONS - All participants were included in a prospective clinical trial.
CONCLUSIONS - Patients with type 2 diabetic nephropathy, characterized by decreased kidney function and significant proteinuria, are more likely to reach ESRD than die during 3 years' mean follow-up. Given the rapidly increasing number of cases of type 2 diabetes worldwide, this has implications for predicting future renal replacement therapy requirements.
Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
Pyridoxamine dihydrochloride (Pyridorin, NephroGenex) inhibits formation of advanced glycation end products and scavenges reactive oxygen species and toxic carbonyls, but whether these actions translate into renoprotective effects is unknown. In this double-blind, randomized, placebo-controlled trial, we randomly assigned 317 patients with proteinuric type 2 diabetic nephropathy to twice-daily placebo; Pyridorin, 150 mg twice daily; or Pyridorin, 300 mg twice daily, for 52 weeks. At baseline, the mean age ± SD was 63.9±9.5 years, and the mean duration of diabetes was 17.6±8.5 years; the mean serum creatinine level was 2.2±0.6 mg/dl, and the mean protein-to-creatinine ratio was 2973±1932 mg/g. Regarding the primary end point, a statistically significant change in serum creatinine from baseline to 52 weeks was not evident in either Pyridorin group compared with placebo. However, analysis of covariance suggested that the magnitude of the treatment effect differed by baseline renal function. Among patients in the lowest tertile of baseline serum creatinine concentration, treatment with Pyridorin associated with a lower average change in serum creatinine concentration at 52 weeks (0.28, 0.07, and 0.14 mg/dl for placebo, Pyridorin 150 mg, and Pyridorin 300 mg, respectively; P=0.05 for either Pyridorin dose versus placebo); there was no evidence of a significant treatment effect in the middle or upper tertiles. In conclusion, this trial failed to detect an effect of Pyridorin on the progression of serum creatinine at 1 year, although it suggests that patients with less renal impairment might benefit.
BACKGROUND - Peroxisome proliferator-activated receptor gamma (PPARγ) agonists have beneficial effects on renal structure and function in models of diabetes and chronic kidney diseases. However, the increased incidence of weight gain and edema potentially limits their usefulness. We studied an acute minimal-change disease-like nephrotic syndrome model to assess effects of PPARγ agonist on acute podocyte injury and effects on fluid homeostasis.
METHODS - Acute podocyte injury and nephrotic syndrome were induced by puromycin aminonucleoside (PAN) injection in rats.
RESULTS - PPARγ agonist, given at the time or after, but not before PAN, reduced proteinuria, restored synaptopodin, decreased desmin and trended to improve foot process effacement. There was no significant difference in glomerular filtration, effective circulating volume, blood pressure or fractional sodium excretion. PAN-injured podocytes had decreased PPARγ, less nephrin and α-actinin-4, more apoptosis and reduced phosphorylated Akt. In PAN-injured cultured podocytes, PPARγ agonist also reversed abnormalities only when given simultaneously or after injury.
CONCLUSIONS - These results show that PPARγ agonist has protective effects on podocytes in acute nephrotic syndrome without deleterious effects on fluid homeostasis. PPARγ agonist-induced decrease in proteinuria in acute nephrotic syndrome is dependent at least partially on regulation of peroxisome proliferator-response element-sensitive gene expression such as α-actinin-4 and nephrin and the restoration of podocyte structure.
Type 2 diabetic nephropathy (type 2 DN) patients traditionally develop significant proteinuria prior to the development of renal impairment. However, this clinical paradigm, based on observations prior to the widespread usage of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB), has recently been questioned. 2,303 patients enrolled in the Sulodexide Overt Nephropathy Study (OVERT) were analyzed. Prior therapy with ACEi and/or ARB at the time of screening was recorded in 951 patients. 22% of patients had significant renal impairment with a PCR at screening of <500 mg/g. Therapy with ACEi and/or ARB at the time of screening was recorded in 94%, where prior medication data was available. In patients with type 2 DN and advanced renal impairment, levels of proteinuria below that which traditionally defines overt diabetic nephropathy, are found in more than one fifth of patients. We suggest that the high prevalence of ACEi and ARB usage in patients with type 2 DN may be effecting the traditional clinical paradigm of type 2 DN.
Copyright © 2011 S. Karger AG, Basel.
BACKGROUND - Few studies have examined the association between obesity and markers of kidney injury in a chronic kidney disease population. We hypothesized that obesity is independently associated with proteinuria, a marker of chronic kidney disease progression.
STUDY DESIGN - Observational cross-sectional analysis.
SETTING & PARTICIPANTS - Post hoc analysis of baseline data for 652 participants in the African American Study of Kidney Disease (AASK).
PREDICTORS - Obesity, determined using body mass index (BMI).
MEASUREMENTS & OUTCOMES - Urine total protein-creatinine ratio and albumin-creatinine ratio measured in 24-hour urine collections.
RESULTS - AASK participants had a mean age of 60.2 ± 10.2 years and serum creatinine level of 2.3 ± 1.5 mg/dL; 61.3% were men. Mean BMI was 31.4 ± 7.0 kg/m(2). Approximately 70% of participants had a daily urine total protein excretion rate <300 mg/d. In linear regression analyses adjusted for sex, each 2-kg/m(2) increase in BMI was associated with a 6.7% (95% CI, 3.2-10.4) and 9.4% (95% CI, 4.9-14.1) increase in urine total protein-creatinine and urine albumin-creatinine ratios, respectively. In multivariable models adjusting for age, sex, systolic blood pressure, serum glucose level, uric acid level, and creatinine level, each 2-kg/m(2) increase in BMI was associated with a 3.5% (95% CI, 0.4-6.7) and 5.6% (95% CI, 1.5-9.9) increase in proteinuria and albuminuria, respectively. The interaction between older age and BMI was statistically significant, indicating that this relationship was driven by younger AASK participants.
LIMITATIONS - May not generalize to other populations; cross-sectional analysis precludes statements regarding causality.
CONCLUSIONS - BMI is associated independently with urine total protein and albumin excretion in African Americans with hypertensive nephrosclerosis, particularly in younger patients.
Copyright © 2010 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.