Prognostic Biomarkers and AKI: Potential to Enhance the Identification of Post-Operative Patients at Risk of Loss of Renal Function

Acute kidney injury (AKI) is a common complication after surgery and the more complex the surgery, the greater the risk. During surgery, patients are exposed to a combination of factors all of which are associated with the development of AKI. These include hypotension and hypovolaemia, sepsis, systemic inflammation, the use of nephrotoxic agents, tissue injury, the infusion of blood or blood products, ischaemia, oxidative stress and reperfusion injury. Given the risks of AKI, it would seem logical to conclude that early identification of patients at risk of AKI would translate into benefit. The conventional markers of AKI, namely serum creatinine and urine output are the mainstay of defining chronic kidney disease but are less suited to the acute phase. Such concerns are compounded in surgical patients given they often have significantly reduced mobility, suboptimal levels of nutrition and reduced muscle bulk. Many patients may also have misleadingly low serum creatinine and high urine output due to aggressive fluid resuscitation, particularly in intensive care units. Over the last two decades, considerable information has accrued with regard to the performance of what was termed "novel" biomarkers of AKI, and here, we discuss the most examined molecules and performance in surgical settings. We also discuss the application of biomarkers to guide patients' postoperative care.

Longitudinal Analysis of Urinary Cytokines and Biomarkers in COVID-19 Patients with Subclinical Acute Kidney Injury

In hospitalized COVID-19 patients, disease progression leading to acute kidney injury (AKI) may be driven by immune dysregulation. We explored the role of urinary cytokines and their relationship with kidney stress biomarkers in COVID-19 patients before and after the development of AKI. Of 51 patients, 54.9% developed AKI. The principal component analysis indicated that in subclinical AKI, epidermal growth factor (EGF) and interferon (IFN)-α were associated with a lower risk of AKI, while interleukin-12 (IL-12) and macrophage inflammatory protein (MIP)-1β were associated with a higher risk of AKI. After the manifestation of AKI, EGF and IFN-α remained associated with a lower risk of AKI, while IL-1 receptor (IL-1R), granulocyte-colony stimulating factor (G-CSF), interferon-gamma-inducible protein 10 (IP-10) and IL-5 were associated with a higher risk of AKI. EGF had an inverse correlation with kidney stress biomarkers. Subclinical AKI was characterized by a significant up-regulation of kidney stress biomarkers and proinflammatory cytokines. The lack of EGF regenerative effects and IFN-α antiviral activity seemed crucial for renal disease progression. AKI involved a proinflammatory urinary cytokine storm.

Limiting Acute Kidney Injury Progression In Sepsis: Study Protocol and Trial Simulation

OBJECTIVES

To describe study design considerations and to simulate a trial of biomarker-guided sepsis management aimed to reduce acute kidney injury (acute kidney injury). Tissue inhibitor of metalloproteinases-2 and insulin-like growth factor-binding protein 7, urinary biomarkers of cell-cycle arrest, and indicators of kidney stress can detect acute kidney injury before clinical manifestations. We sought to determine the event rates for acute kidney injury as a function of serial measurements of urinary (tissue inhibitor of metalloproteinases-2)•(insulin-like growth factor-binding protein 7) in patients at risk of sepsis-associated acute kidney injury, so that an escalating series of kidney-sparing sepsis bundles based on international guidelines could be applied.

DESIGN

We described the study protocol of "Limiting acute kidney injury Progression In Sepsis," a phase 4, multicenter, adaptive, randomized controlled trial. We performed simulations to estimate the rates for the trial's primary endpoint using patient-level data from two previous studies (Sapphire and Protocolized Care for Early Septic Shock).

SETTING

Academic and community ICUs.

PATIENTS

Critically ill patients with sepsis or septic shock, without evidence of stage 2/3 acute kidney injury at enrollment.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Our primary endpoint is progression of two or more stages of acute kidney injury, death, or dialysis within 72 hours after enrollment. In the Sapphire simulation, 45 of 203 patients (22%) with sepsis met the endpoint. In Protocolized Care for Early Septic Shock, 144 of 607 patients (24%) with septic shock met the endpoint. In both simulations, (tissue inhibitor of metalloproteinases-2)•(insulin-like growth factor-binding protein 7) patterns, suggested by Limiting acute kidney injury Progression In Sepsis protocol, stratified the risk for the endpoint from 6% (three negative tests) to 41% (for patients eligible for the highest level of kidney-sparing sepsis bundle) in Sapphire, and 14% (two negative tests) to 46% (for the highest level of kidney-sparing sepsis bundle) in Protocolized Care for Early Septic Shock.

CONCLUSIONS

Findings of our Limiting acute kidney injury Progression In Sepsis trial simulation confirmed that (tissue inhibitor of metalloproteinases-2)•(insulin-like growth factor-binding protein 7) could identify patients with different rates of progression to moderate/severe acute kidney injury, death, or dialysis in 72 hours. The Limiting acute kidney injury Progression In Sepsis protocol algorithm is therefore feasible in terms of identifying suitably high-risk individuals for kidney-sparing sepsis bundle.

Use of Biomarkers to Identify Acute Kidney Injury to Help Detect Sepsis in Patients With Infection

OBJECTIVES

Although early recognition of sepsis is vital to improving outcomes, the diagnosis may be missed or delayed in many patients. Acute kidney injury is one of the most common organ failures in patients with sepsis but may not be apparent on presentation. Novel biomarkers for acute kidney injury might improve organ failure recognition and facilitate earlier sepsis care.

DESIGN

Retrospective, international, Sapphire study.

SETTING

Academic Medical Center.

PATIENTS

Adults admitted to the ICU without evidence of acute kidney injury at time of enrollment.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We stratified patients enrolled in the Sapphire study into three groups-those with a clinical diagnosis of sepsis (n = 216), those with infection without sepsis (n = 120), and those without infection (n = 387) at enrollment. We then examined 30-day mortality stratified by acute kidney injury within each group. Finally, we determined the operating characteristics for kidney stress markers (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) for prediction of acute kidney injury as a sepsis-defining organ failure in patients with infection without a clinical diagnosis of sepsis at enrollment. Combining all groups, 30-day mortality was 23% for patients who developed stage 2-3 acute kidney injury within the first 3 days compared with 14% without stage 2-3 acute kidney injury. However, this difference was greatest in the infection without sepsis group (34% vs 11%; odds ratio, 4.09; 95% CI, 1.53-11.12; p = 0.005). Using a (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) cutoff of 2.0 units, 14 patients (11.7%), in the infection/no sepsis group, tested positive of which 10 (71.4%) developed stage 2-3 acute kidney injury. The positive test result occurred a median of 19 hours (interquartile range, 0.8-34.0 hr) before acute kidney injury manifested by serum creatinine or urine output. Similar results were obtained using a cutoff of 1.0 for any stage of acute kidney injury.

CONCLUSIONS

Use of the urinary (tissue inhibitor of metalloproteinases-2) × (insulin-like growth factor binding protein 7) test could identify acute kidney injury in patients with infection, possibly helping to detect sepsis, nearly a day before acute kidney injury is apparent by clinical criteria.

The MMP-2/TIMP-2 System in Alzheimer Disease

Alzheimer Disease (AD) is the most prevalent type of dementia. Pathological changes in the AD brain include Amyloid β-protein (Aβ) plaques and Neurofibrillary Tangles (NFTs), as well as extensive neuronal and synaptic loss. Matrix Metalloproteinase-2 (MMP-2) is a neutral, zinc-dependent protease that primarily targets extracellular matrix proteins. MMP-2 activity is strictly controlled, and its dysregulation has been implicated in a variety of pathologies, including AD. In this brief review, we discussed the contributions of dysregulated MMP-2 activity and an imbalanced interaction between MMP-2 and its endogenous inhibitor, Tissue Inhibitors of Metalloproteinase-2 (TIMP-2), to AD. We also described the underlying mechanisms of the effects of MMP-2/TIMP-2, both beneficial and detrimental, on AD, including: (1) MMP-2 directly degrades Aβ resulting in the clearance of Aβ deposits. Conversely, Aβ-induced MMP-2 may contribute to brain parenchymal destruction. (2) MMP-2 induces breakdown of BBB, and this deleterious effect could be reversed by TIMP-2. (3) MMP-2 disrupts oxidative homeostasis in AD. (4) MMP-2 has both proinflammatory/pro-angiogenetic and antiinflammatory/ anti-angiogenetic effects on AD. Besides, we discuss the clinical utility of MMP- 2/TIMP-2 as therapeutic targets for AD.

Role of matrix metalloproteinases and their inhibitors in the development of cervical metastases in papillary thyroid cancer

OBJECTIVE

To investigate the role of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in the development of cervical metastases in papillary thyroid cancer. Our hypothesis is that level of expression of MMPs and TIMPs is associated with the development of cervical metastases and the pattern of metastatic process in papillary thyroid cancer.

DESIGN

This research retrospectively investigates the expression of MMP-1, -2 and -9 as well as TIMP-1 and -2 in papillary thyroid carcinoma tissue. Tissue specimens were immunohistochemically treated with primary monoclonal antibodies against MMP-1, MMP-2, MMP-9, TIMP-1 and TIMP-2.

SETTING

Single-centre study.

PARTICIPANTS

In total, samples of 159 patients were analysed. In all patients, total thyroidectomy was performed, whereas 102 patients underwent selective neck dissection of either central (level VI) or lateral neck (level II-V). Subjects were divided into four groups.

MAIN OUTCOME MEASURES

Matrix metalloproteinases and TIMPs expression values were analysed in each group, and groups were compared to each other.

RESULTS

Total number of patients was 159, of which 125 were women and 34 men. Comparing expression levels of MMPs and TIMPs in metastatic (study groups) and non-metastatic (control group), papillary thyroid carcinomas yielded significant differences in MMP-1 and TIMP-1 expression levels, where the highest expression values were found in the group with metastasis in lateral neck. Expression levels of MMP-2, MMP-9 and TIMP-2 did not differ statistically significant among the groups.

CONCLUSION

Elevated expression of MMP-1 and TIMP-1 in tumour tissue can be considered a predictive factor for the development of metastases.

Urinary Tissue Inhibitor of Metalloproteinases-2 and Insulin-Like Growth Factor-Binding Protein 7 Do Not Correlate With Disease Severity in ADPKD Patients

Introduction

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation and variable renal function decline that frequently leads to end-stage renal failure. With the advent of renoprotective treatment, there is renewed interest in noninvasive biomarkers to help identify patients at risk of rapid disease progression at early stages. Urinary tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) have been validated as early markers of acute kidney injury. Because these markers are associated with tubular damage, we studied the performance of both markers in a cohort with chronic tubular pathology. We investigated whether these biomarkers may be useful to evaluate disease severity in ADPKD.

Methods

In a cross-sectional analysis, we measured TIMP-2 and IGFBP7 in stored spot urine samples of patients with ADPKD with various stages of chronic kidney disease (CKD) and healthy controls by enzyme-linked immunosorbent assay. Renal function was estimated using the CKD-Epidemiology Collaboration equation. Patients were stratified according to the Kidney Disease Outcomes Quality Initiative classification for CKD. In a subset of patients, total kidney volume (TKV; using magnetic resonance imaging [MRI]) was measured.

Results

In 296 patients with ADPKD (45.5 ± 11.5 years, 51.0% female, serum creatinine 106 [85-147] μmol/l), urine levels of TIMP-2 and IGFBP7 were not increased or tended to be lower as compared with 71 healthy controls (46.5 ± 18.5 years, 72.6% female). The levels did not differ across CKD stages, which remained so after correcting for urine creatinine or osmolality, and for age, sex, and urine protein in multivariable analyses.

Conclusions

Urinary levels of TIMP-2 and IGFBP7 were not higher in patients with ADPKD, and did not correlate with disease severity.

Urinary TIMP2⋅IGFBP7 for the prediction of platinum-induced acute renal injury

Introduction

Platinum-based chemotherapy (PBC) is a potent antineoplastic treatment, but cisplatin nephrotoxicity is often the limiting factor. Identifying the patients who are at risk for developing platinum-induced renal injury is an important issue. We tested urinary TIMP2·IGFBP7, a new US Food and Drug Administration (FDA)-cleared test to assess the risk of acute kidney injury (AKI), in a cohort of patients with malignant neoplastic disease receiving PBC.

Patients and methods

A total of 58 patients with malignant neoplastic disease were enrolled in this study, of whom 32 patients had both urine samples and subsequent serum creatinine values available for detecting AKI within 72 hours. Urine samples were collected within 6 hours prior to PBC application and within 12 hours after the end of chemotherapy administration. We examined the predictive ability of TIMP2·IGFBP7 for the development of AKI as defined by KDIGO (Kidney Disease: Improving Global Outcomes) criteria within 72 hours after the administration of chemotherapy. Operating characteristics were determined for the previously validated TIMP2·IGFBP7 cutoff of 0.3 (ng/mL)²/1000.

Results

Four (12.5%) patients developed AKI within 72 hours. Primary disease was lymphoma in 13 patients (40.6%) and solid tumors in 19 patients (59.4%). Eight patients (25.0%) received carboplatin and 24 (75.0%) cisplatin. TIMP2·IGFBP7 after PBC administration discriminated for the risk of AKI with an area under the receiver operating characteristic curve (AUC; 95% confidence interval) of 0.92 (0.80–1.00). At the cutoff of 0.3 for TIMP2·IGFBP7, sensitivity was 50%, specificity was 87%, negative predictive value was 95% and positive predictive value was 25% for the prediction of AKI within 72 hours.

Conclusion

Urinary TIMP2·IGFBP7 measured in specimens gathered after PBC may be a useful tool to early identify patients who are at risk for developing platinum-induced AKI.

Urinary [TIMP-2] × [IGFBP7] for risk prediction of acute kidney injury in decompensated heart failure

BACKGROUND

In acute decompensated heart failure (ADHF) the risk of acute kidney injury (AKI) is high. Early detection of patients at risk for AKI is important. We tested urinary [TIMP-2] × [IGFBP7], a new US Food and Drug Administration-cleared test to assess AKI risk, in a cohort of hospitalized ADHF patients.

HYPOTHESIS

In patients with ADHF, urinary [TIMP-2] × [IGFBP7] is associated with moderate to severe AKI and related to increased mortality.

METHODS

We enrolled 400 patients in the emergency department at Robert-Bosch Hospital, Stuttgart, Germany. We examined the predictive ability of urinary [TIMP-2] × [IGFBP7] (units: [ng/mL]² /1000) for development of AKI stage 2 or 3 within 24 hours of sample collection in patients with ADHF. Operating characteristics were determined for the validated cutoffs of 0.3 and 2.0.

RESULTS

Forty patients had ADHF upon presentation and sufficient data for AKI staging. 27.5% developed AKI stage 2-3 within 7 days. Urinary [TIMP-2] × [IGFBP7] discriminated for AKI stage 2-3 over the first day with an area under the ROC curve of 0.84 (95% confidence interval: 0.72-0.93) and over 7 days with an AUC of 0.77 (95% confidence interval: 0.65-0.88). For the first day, sensitivity was 86% at the 0.3 cutoff and specificity was 95% at the 2.0 cutoff for prediction of AKI stage 2-3. There was a trend (P = 0.08) for higher mortality in patients with urinary [TIMP-2] × [IGFBP7] >2.0 and AKI 2-3.

CONCLUSIONS

Urinary [TIMP-2] × [IGFBP7] is a promising marker for AKI risk assessment in patients with ADHF.

Clinical adjudication in acute kidney injury studies: findings from the pivotal TIMP-2*IGFBP7 biomarker study

Background

The NEPROCHECK test (Astute Medical, San Diego, CA, USA) combines urinary tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) to identify patients at high risk for acute kidney injury (AKI). In a US Food and Drug Administration registration trial (NCT01573962), AKI was determined by a three-member clinical adjudication committee. The objectives were to examine agreement among adjudicators as well as between adjudicators and consensus criteria for AKI and to determine the relationship of biomarker concentrations and adjudicator agreement.

Methods

Subjects were classified as AKI 3/3, 2/3, 1/3 or 0/3 according to the proportion of adjudicators classifying the case as AKI. Subjects were classified as Kidney Disease: Improving Global Outcomes (KDIGO) AKI(+) when stage 2 or 3 AKI criteria were met.

Results

Concordance between adjudicators and between adjudicators and KDIGO criteria were lower for AKI than non-AKI subjects [78.9 versus 97.3% (P < 0.001) and 91.5 versus 97.9% (P = 0.01)]. Subjects who were AKI 3/3 or 2/3 but KDIGO AKI(−) had higher median [TIMP-2]•[IGFBP7] compared with those who were AKI-1/3 or 0/3 but KDIGO AKI(+) {2.78 [interquartile range (IQR) 2.33–3.56] versus 0.52 [IQR 0.26–1.64]; P = 0.008}. [TIMP-2]•[IGFBP7] levels were highest in patients with AKI 3/3 and lowest in AKI 0/3, whereas AKI 2/3 and 1/3 exhibited intermediate values.

Conclusions

In this analysis, urine [TIMP-2]•[IGFBP7] levels correlated to clinically adjudicated AKI better than to KDIGO criteria. Furthermore, in difficult cases where adjudicators overruled KDIGO criteria, the biomarker test discriminated well. This study highlights the importance of clinical adjudication of AKI for biomarker studies and lends further support for the value of urine [TIMP-2]•[IGFBP7].

Cell-cycle arrest and acute kidney injury: the light and the dark sides

Acute kidney injury (AKI) is a common consequence of systemic illness or injury and it complicates several forms of major surgery. Two major difficulties have hampered progress in AKI research and clinical management. AKI is difficult to detect early and its pathogenesis is still poorly understood. We recently reported results from multi-center studies where two urinary markers of cell-cycle arrest, tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) were validated for development of AKI well ahead of clinical manifestations—azotemia and oliguria. Cell-cycle arrest is known to be involved in the pathogenesis of AKI and this ‘dark side’ may also involve progression to chronic kidney disease. However, cell-cycle arrest has a ‘light side’ as well, since this mechanism can protect cells from the disastrous consequences of entering cell division with damaged DNA or insufficient bioenergetic resources during injury or stress. Whether we can use the light side to help prevent AKI remains to be seen, but there is already evidence that cell-cycle arrest biomarkers are indicators of both sides of this complex physiology.