Clinical Relevance and Predictive Value of Damage Biomarkers of Drug-Induced Kidney Injury

Nephrotoxin exposure accounts for up to one-fourth of acute kidney injury episodes in hospitalized patients, and the associated consequences are as severe as acute kidney injury due to other etiologies. As the use of nephrotoxic agents represents one of the few modifiable risk factors for acute kidney injury, clinicians must be able to identify patients at high risk for drug-induced kidney injury rapidly. Recently, significant advancements have been made in the field of biomarker utilization for the prediction and detection of acute kidney injury. Such biomarkers may have a role both for detection of drug-induced kidney disease and implementation of preventative and therapeutic strategies designed to mitigate injury. In this article, basic principles of renal biomarker use in practice are summarized, and the existing evidence for six markers specifically used to detect drug-induced kidney injury are outlined, including liver-type fatty acid binding protein, neutrophil gelatinase-associated lipocalin, tissue inhibitor of metalloproteinase-2 times insulin-like growth factor-binding protein 7 ([TIMP-2]·[IGFBP7]), kidney injury molecule-1 and N-acetyl-β-D-glucosaminidase. The results of the literature search for these six kidney damage biomarkers identified 29 unique articles with none detected for liver-type fatty acid binding protein and [TIMP-2]·[IGFBP7]. For three biomarkers, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin and N-acetyl-β-D-glucosaminidase, the majority of the studies suggest utility in clinical practice. While many questions need to be answered to clearly articulate the use of biomarkers to predict drug-induced kidney disease, current data are promising.

N-acteyl-ß-D-glucosaminidase and kidney injury molecule-1: New predictors for long-term progression of chronic kidney disease in patients with heart failure

AIM

Patients with chronic heart failure (CHF) are often characterized by the cardiorenal syndrome (CRS). The aim of the present study was to assess whether novel markers of kidney injury are able to predict progression of chronic kidney disease (CKD) in patients with CHF.

METHODS

New renal biomarkers, N-acteyl-ß-D-glucosaminidase (NAG), kidney injury molecule-1 (KIM-1) and Neutrophil Gelatinase-Associated Lipocalin (NGAL), were assessed from urine samples of 149 patients with chronic heart failure. During a 5-year-follow-up, renal function was assessed by creatinine and estimated glomerular filtration rate (eGFR CKD EPI) and was available for 138 patients. Further, data regarding all-cause mortality was obtained.

RESULTS

Twenty-six patients (18.8%) developed a progression of CKD during the follow-up period, as defined by decline in eGFR category accompanied by a ≥25% drop in eGFR form baseline. No difference regarding age, sex, body mass index, hypertension, diabetes or EF was present between patients with and without CKD progression (each P = n.s.). At baseline, creatinine concentrations and eGFR were significantly different between both groups (sCr: 1.50 ± 0.67 vs 1.04 ± 0.37, P = < 0.001; eGFR: 47.8 ± 12.3 vs. 77.3 ± 23.5 mL/min per 1.73m(2) , each P < 0.001). In a Kaplan-Meier-analysis, KIM-1 and NAG were significant predictors for CKD progression (both P < 0.05). In Cox regression analysis, NAG > median (OR 3.25,P = 0.013), initial eGFR (OR 0.94, P < 0.001) and diuretic use (OR 3.92, P = 0.001) were independent predictors of CKD progression. Further, KIM-1 and NAG were also independent predictors of a combined endpoint of CKD progression and all-cause mortality by Cox regression analysis (each P < 0.05). The combination of both markers showed additive value regarding both endpoints. NGAL showed no association with CKD progression.

CONCLUSIONS

During long-term follow-up chronic heart failure patients with CKD show a relevant disease progression. The current study emphasizes a strong association of the tubular biomarkers NAG and KIM-1 with CKD progression in chronic heart failure and suggests their usefulness as cardiorenal markers.

Role of biomarkers of nephrotoxic acute kidney injury in deliberate poisoning and envenomation in less developed countries

Acute kidney injury (AKI) has diverse causes and is associated with increased mortality and morbidity. In less developed countries (LDC), nephrotoxic AKI (ToxAKI) is common and mainly due to deliberate ingestion of nephrotoxic pesticides, toxic plants or to snake envenomation. ToxAKI shares some pathophysiological pathways with the much more intensively studied ischaemic AKI, but in contrast to ischaemic AKI, most victims are young, previously healthy adults. Diagnosis of AKI is currently based on a rise in serum creatinine. However this may delay diagnosis because of the kinetics of creatinine. Baseline creatinine values are also rarely available in LDC. Novel renal injury biomarkers offer a way forward because they usually increase more rapidly in AKI and are normally regarded as absent or very low in concentration, thereby reducing the need for a baseline estimate. This should increase sensitivity and speed of diagnosis. Specificity should also be increased for urine biomarkers since many originate from the renal tubular epithelium. Earlier diagnosis of ToxAKI should allow earlier initiation of appropriate therapy. However, translation of novel biomarkers of ToxAKI into clinical practice requires better understanding of non-renal factors in poisoning that alter biomarkers and the influence of dose of nephrotoxin on biomarker performance. Further issues are establishing LDC population-based normal ranges and assessing sampling and analytical parameters for low resource settings. The potential role of renal biomarkers in exploring ToxAKI aetiologies for chronic kidney disease of unknown origin (CKDu) is a high research priority in LDC. Therefore, developing more sensitive biomarkers for early diagnosis of nephrotoxicity is a critical step to making progress against AKI and CKDu in the developing world.

Aminoglycoside toxicity in neonates: something to worry about?

Toxicity has limited the use of aminoglycosides and adult studies report high rates of both ototoxicity and nephrotoxicity. Conversely paediatric studies have shown lower rates and extended interval dosing may have reduced toxicity further. We review the animal and human evidence for aminoglycoside toxicity in neonates including mechanisms, measurement and rates of toxicity; and differences between aminoglycosides and dosing regimens. We discuss genetic susceptibility and the impact of other synergistic effects.

Urinary Activities of Proximal Tubule Enzymes in Neonates Treated with Gentamicin

In order to determine the nephrotoxicity of gentamicin, an aminoglycoside antibiotic, activity of the enzymes dominantly localized in proximal tubules, i.e. alanine aminopeptidase (AAP), γ-glutamyl transferase (GGT) and N-acetylβ-D-glucosaminidase (NAG) was examined. Determinations were performed in 12-h urine samples of 30 neonates i.v. receiving gentamicin against Gram negative infections in daily doses of 5.0 mg/kg body mass for 10 consecutive days. The activities of the same enzymes were measured in 12-h urine samples of 30 examinées of the control group. The groups consisted of neonates of both sexes. The pretreatment period lasted for 5 days. On day 8 of gentamicin application, statistically significant differences in the activity of AAP and GGT expressed in U/mmol creatinine between the gentamicin-receiving and control group (p<0.01) were found. No significant differences in NAG activity of the gentamicin-treated group in comparison with the control were recorded during the 10-day gentamicin therapy. It can be concluded that 10-day treatment of neonates with usually prescribed gentamicin doses results in mild nephrotoxic changes close to the end of the therapy accompanied by increased activity of both urinary AAP and GGT, known as very sensitive indicators of nephrotoxicity. During the same treatment period no changes in NAG activity were observed, meaning that the antibiotic causes no severe injuries to proximal tubule cells at the level of cellular organelles.