Kidney-specific genetic deletion of both AMPK α-subunits causes salt and water wasting.

AMP-activated kinase (AMPK) controls cell energy homeostasis by modulating ATP synthesis and expenditure. In vitro studies have suggested AMPK may also control key elements of renal epithelial electrolyte transport but in vivo physiological confirmation is still insufficient. We studied sodium renal handling and extracellular volume regulation in mice with genetic deletion of AMPK catalytic subunits. AMPKα1 knockout (KO) mice exhibit normal renal sodium handling and a moderate antidiuretic state. This is accompanied by higher urinary aldosterone excretion rates and reduced blood pressure. Plasma volume, however, was found to be increased compared with wild-type mice. Thus blood volume is preserved despite a significantly lower hematocrit. The lack of a defect in renal function in AMPKα1 KO mice could be explained by a compensatory upregulation in AMPK α2-subunit. Therefore, we used the Cre-loxP system to knock down AMPKα2 expression in renal epithelial cells. Combining this approach with the systemic deletion of AMPKα1 we achieved reduced renal AMPK activity, accompanied by a shift to a moderate water- and salt-wasting phenotype. Thus we confirm the physiologically relevant role of AMPK in the kidney. Furthermore, our results indicate that in vivo AMPK activity stimulates renal sodium and water reabsorption.

Advanced Kidney Models In Vitro Using the Established Cell Line Renal Proximal Tubular Epithelial/Telomerase Reverse Transcriptase1 for Nephrotoxicity Assays.

Nephrotoxicity stands as one of the most limiting effects in the development and validation of new drugs. The kidney, among the organs evaluated in toxicity assessments, has a higher susceptibility, with nephrotoxic potential frequently evading detection until late in clinical trials. Traditional cell culture, which has been widely used for decades, does not recapitulate the structure and complexity of the native tissue, which can affect cell function, and the response to cytotoxins does not resemble what occurs in the kidney. In the current study, we aimed to address these challenges by creating in vitro kidney models that faithfully biomimic the dynamics of the renal proximal tubule, using the well-established RPTEC/TERT1 cell line. For doing so, two models were developed, one recreating tubule-like structures (2.5D model) and the other using microfluidic technology (kidney-on-a-chip). The 2.5D model allowed tubular structures to be generated in the absence of hydrogels, and the kidney-on-a-chip model allowed shear stress to be applied to the cell culture, which is a physiological stimulus in the renal tissue. After characterization of both models, different nephrotoxic compounds such as cisplatin, tacrolimus, and daunorubicin were used to study cell responses after treatment. The developed models in our study could be a valuable tool for pre-clinical nephrotoxic testing of drugs and new compounds.

Elevated urinary kidney injury molecule 1 at discharge strongly predicts early mortality following an episode of acute decompensated heart failure.

INTRODUCTION: Hospitalization for acute decompensation of heart failure (ADHF) is a frequent event associated with long­term adverse effects. Prognosis is even worse if acute kidney injury (AKI) occurs during hospitalization. OBJECTIVES: The study aimed to determine whether kidney damage biomarkers neutrophil gelatinase­associatedlipocalin (NGAL), kidney injury molecule 1 (KIM­1), and interleukin18 (IL­18) might predict AKI and have prognostic value in ADHF. PATIENTS AND METHODS: Serum NGAL on admission and urine NGAL, KIM­1, and IL­18 on discharge were determined in 187 ADHF patients enrolled in a prospective, observational, unblinded study. AKI was diagnosed using the Kidney Disease: Improving Global Outcomes criteria. Patients were followedfor 12 months to record all­cause mortality. RESULTS: A total of 22% patients died during the follow­up, with 52.5% dying within 4 months after discharge. Serum NGAL (P <0.001), urine NGAL (P = 0.047), and urinary KIM­1 (P = 0.014) levels were significantly higher in the deceased patients at discharge. After adjustment for estimated glomerular filtration rate (eGFR), only urinary KIM­1 independently predicted mortality at month 4 (hazard ratio [HR], 3.166; 95% CI, 1.203-8.334; P = 0.020) and month 12 (HR, 1.969; 95% CI, 1.123-3.454; P = 0.018) in Cox regression models. In receiver operating characteristic (ROC) analysis urinary KIM­1 (area under the ROC curve [AUC] = 0.830) outperformed other markers of renal function. The Kaplan-Meier survival analysis showed KIM­1 predictive value as additive to that of AKI incidence and admission eGFR. Admission serum NGAL was higher in AKI patients (P ≤0.001) with a modest diagnostic performance (AUC = 0.667), below that of urea (AUC = 0.732), creatinine (AUC = 0.696), or cystatin C (AUC = 0.676). CONCLUSIONS: Discharge urinary KIM­1 was a strong and independent predictor of mortality, particularly during the most vulnerable period shortly after hospitalization. Admission serum NGAL was inferior to conventional renal function parameters in predicting AKI during ADHF.