Mitochondria are energy-producing organelles that not only satisfy the high metabolic demands of the kidney but sense and respond to kidney injury-induced oxidative stress and inflammation. Kidneys are rich in mitochondria. Mitochondrial dysfunction plays a critical role in the progression of acute kidney injury and chronic kidney disease. Mitochondrial responses to specific stimuli are highly regulated and synergistically modulated by tightly interconnected processes, including mitochondrial dynamics (fission, fusion) and mitophagy. The counterbalance between these processes is essential in maintaining a healthy network of mitochondria. Recent literature suggests that alterations in mitochondrial dynamics are implicated in kidney injury and the progression of kidney diseases. A decrease in mitochondrial fusion promotes fission-induced mitochondrial fragmentation, but a reduction in mitochondrial fission produces excessive mitochondrial elongation. The removal of dysfunctional mitochondria by mitophagy is crucial for their quality control. Defective mitochondrial function disrupts cellular redox potential and can cause cell death. Mitochondrial DNA derived from damaged cells also act as damage-associated molecular patterns to recruit immune cells and the inflammatory response can further exaggerate kidney injury. This review provides a comprehensive overview of the role of mitochondrial dysfunction in acute kidney injury and chronic kidney disease. We discuss the processes that control mitochondrial stress responses to kidney injury and review recent advances in understanding the role of mitochondrial dysfunction in inflammation and tissue damage through the use of different experimental models of kidney disease. We also describe potential mitochondria-targeted therapeutic approaches.

Acute kidney injury (AKI) in the pediatric population is a relatively common phenomenon. Specifically, AKI has been found in increasing numbers within the pediatric population following cardiac surgery, with up to 43% of pediatric patients developing AKI post-cardiac surgery. However, recent advances have allowed for the identification of risk factors. These can be divided into preoperative, intraoperative, and postoperative factors. Although the majority of pediatric patients developing AKI after cardiac surgery completely recover, this condition is associated with worse outcomes. These include fluid overload and increased mortality and result in longer hospital and intensive care unit stays. Detecting the presence of AKI has advanced; use of relatively novel biomarkers, including neutrophil gelatinase associated lipocalin, has shown promise in detecting more subtle changes in kidney function when compared to conventional methods. While a single, superior treatment has not been elucidated yet, novel functions of medications, including fenoldopam, theophylline and aminophylline, have been shown to have better outcomes for these patients. With the recent advances in identification of risk factors, outcomes, diagnosis, and management, the medical community can further explain the complexities of AKI in the pediatric population post-cardiac surgery.

Diabetes is a leading cause of end-stage renal disease. Therefore, prevention of renal dysfunction is an important treatment goal in the management of diabetes. The data of landmark cardiovascular outcome trials of sodium-glucose cotransporter-2 (SGLT2) inhibitors showed profound reno-protective effects. The Korean Diabetes Association and the Korean Society of Nephrology reviewed clinical trials and performed a meta-analysis to assess the effects of SGLT2 inhibitors on the preservation of estimated glomerular filtration rate (eGFR). We limited the data of SGLT2 inhibitors which can be prescribed in Korea. Both eGFR value and its change from the baseline were significantly more preserved in the SGLT2-inhibitor treatment group compared to the control group after 156 weeks. However, some known adverse events were increased in SGLT2 inhibitor treatment, such as genital infection, diabetic ketoacidosis, and volume depletion. We recommend long-term use of SGLT2 inhibitors in patients with type 2 diabetes mellitus (T2DM) for attenuation of renal function decline. However, we cannot generalize our recommendations due to the lack of long-term clinical trials testing the reno-protective effects of every SGLT2 inhibitor in a broad range of patients with T2DM. This recommendation can be revised and updated after the publication of several large-scale renal outcome trials.

Background: Premature infants are at high risk for acute kidney injury (AKI). Serum creatinine (Cr) has limitations for evaluating kidney function in premature infants. We evaluated whether urine biomarkers could be used to monitor AKI in premature infants.
Methods: A prospective cohort study was conducted among infants born at < 37 weeks. Urine biomarkers and serum Cr were measured on postnatal days 1, 3, 5, 7, 10, and 14. Infants were divided into 3 groups according to gestational age (GA); < 28, 28 to < 32 and 32 to < 37 weeks.
Results: AKI occurred in 17 of 83 (20.5%) recruited infants at a median age of 7 (interquartile range 5-10) days. While the most common cause of AKI was hemodynamically significant patent ductus arteriosus (53.8%) in infants of GA < 28 weeks, necrotizing enterocolitis was the leading cause (50.0%) in infants of GA 28 to < 32 weeks. Urinary levels of neutrophil-gelatinase-associated lipocalin/Cr were higher and epidermal growth factor/Cr were lower in AKI group before the onset of AKI in infants of GA < 28 weeks. In infants of GA 28 to < 32 weeks, urinary interleukin-8/Cr levels were higher in AKI group at approximately the time of AKI onset.
Conclusion: Several urine biomarkers were significantly different between AKI and no AKI groups, and some had changed before the onset of AKI. These groups were distinct according to causative factors of AKI and GA. Urine biomarkers could be useful for monitoring the development of AKI in premature infants.

Background: Proteinuria is a significant risk factor for progression of IgA nephropathy (IgAN) and has a positive correlation with severity of foot process effacement (FPE). We evaluated the relationship of FPE with proteinuria and histologic characteristics, including the Oxford classification.
Methods: Patients who underwent renal biopsy and were diagnosed with IgAN at a single center were retrospectively reviewed. Patients aged less than 18 years and those with the possibility of secondary causes were excluded from the study. Subsequently, we evaluated the association between degree of proteinuria, severity of FPE, and histologic characteristics, including the Oxford classification and other immunofluorescence stains.
Results: A total of 805 cases of renal biopsy was performed at our institution, and 327 patients were diagnosed with IgAN. Among them, 82 patients were excluded. Severity of FPE had an impact on the degree of proteinuria. Notably, the group with diffuse FPE had more than about 1.3 g/day of urine protein compared to those with rare FPE. Among the histologic characteristics, M1 score and immune deposition of IgG affected severity of FPE (hazard ratios [95% confidence interval], 1.90 [1.10 to 3.26], and 3.77 [1.66 to 8.54], respectively).
Conclusion: Severity of FPE had an impact on the degree of proteinuria and may be associated with the pathogenesis of IgAN.

Background: Chronic kidney disease (CKD) patients have poor cardiorespiratory fitness. Although cardiopulmonary exercise testing (CPET) is a universal assessment of cardiorespiratory fitness, values taken at 'peak' effort are strongly influenced by motivation and the choice of test endpoint. The oxygen uptake efficiency slope (OUES) integrates cardiovascular, musculoskeletal, and respiratory function into a single index to provide a more pragmatic and safer alternative to maximal testing. No research has explored whether exercise can improve the OUES in CKD patients.
Methods: Thirty-two patients with non-dialysis CKD were recruited into a 12-week exercise program consisting of mixed aerobic and resistance training three times a week. CPET was conducted at baseline, and then, following a 6-week control period, at pre- and post-exercise intervention. Direct measurements of oxygen consumption (V̇O2) and ventilatory parameters were collected. The OUES was calculated as the relationship between V̇O2 and the log10 of minute ventilation (V̇E).
Results: No changes were observed in any variable during the control period, although modest increases in V̇O2peak were observed. No meaningful changes were observed as a result of exercise in any cardiorespiratory value obtained. The OUES calculated at 100%, 90%, 75%, and 50% of exercise duration did not change significantly after 12 weeks of exercise training.
Conclusion: Our results show that 12 weeks of exercise training had no beneficial effects on the OUES, which supports the modest change observed in V̇O2peak. The lack of change in the OUES and other parameters could indicate a dysfunctional cardiorespiratory response to exercise in patients with CKD, likely mediated by dysfunctional peripheral metabolic mechanisms.

Background: We explored the association of anemia severity in patients with chronic kidney disease (CKD) and anemia treatment with work productivity in China.
Methods: Cross-sectional survey data from Chinese physicians and their CKD patients were collected in 2015. Physicians recorded demographics, disease characteristics, and treatment. Patients completed the Work Productivity and Activity Impairment questionnaire. Data were stratified by dialysis-dependence, hemoglobin (Hb) level, and anemia treatment.
Results: Based on data from 1,052 patients (704 non-dialysis-dependent [NDD] and 348 dialysis-dependent [DD] patients), prescribed anemia treatment differed significantly across Hb levels (P < 0.001). In NDD patients, anemia treatment also differed significantly by on-treatment Hb level (P < 0.001). In treated NDD patients with Hb < 10 g/ dL, Hb 10 to 12 g/dL, and Hb > 12 g/dL, 31%, 59%, and 38% of patients, respectively, were prescribed oral iron, and 34%, 19%, and 0% of patients, respectively, were prescribed oral iron with erythropoiesis-stimulating agents (ESA). NDD patients were less likely to be prescribed any anemia treatment, and ESA specifically, than DD patients. When treated, 67% and 45% of NDD and DD patients, respectively, had Hb ≥ 10 g/dL (P < 0.001). Overall work and activity impairment differed significantly across Hb levels in NDD and DD patients, with the least impairment observed at the highest Hb level.
Conclusion: Approximately 40% of NDD patients and 60% of DD patients receiving anemia treatment had Hb < 10 g/ dL. Compared with mild anemia patients, severe anemia patients were more likely to be treated for anemia and have impaired work productivity. Chinese CKD patients could benefit from improved anemia treatment.