Hypoglycemia and Mortality Risk in Incident Hemodialysis Patients.

OBJECTIVE: Hypoglycemia is a frequent occurrence in chronic kidney disease patients due to alterations in glucose and insulin metabolism. However, there are sparse data examining the predictors and clinical implications of hypoglycemia including mortality risk among incident hemodialysis patients. DESIGN AND METHODS: Among 58,304 incident hemodialysis patients receiving care from a large national dialysis organization over 2007-2011, we examined clinical characteristics associated with risk of hypoglycemia, defined as a blood glucose concentration <70 mg/dL, in the first year of dialysis using expanded case-mix + laboratory logistic regression models. We then examined the association between hypoglycemia during the first year of dialysis with all-cause mortality using expanded case-mix + laboratory Cox models. RESULTS: In the first year of dialysis, hypoglycemia was observed among 16.8% of diabetic and 6.9% of nondiabetic incident hemodialysis patients. In adjusted logistic regression models, clinical characteristics associated with hypoglycemia included younger age, female sex, African-American race, presence of a central venous catheter, lower residual renal function, and longer dialysis session length. In the overall cohort, patients who experienced hypoglycemia had a higher risk of all-cause mortality risk (reference: absence of hypoglycemia): adjusted hazard ratio (95% confidence interval) 1.08 (1.04, 1.13). In stratified analyses, hypoglycemia was also associated with higher mortality risk in the diabetic and nondiabetic subgroups: adjusted hazard ratios (95% confidence interval's) 1.08 (1.04-1.13), and 1.17 (0.94-1.45), respectively. CONCLUSIONS: Hypoglycemia was a frequent occurrence among both diabetic and nondiabetic hemodialysis patients and was associated with a higher mortality risk. Further studies are needed to identify approaches that reduce hypoglycemia risk in the hemodialysis population.

Revisiting glomerular hyperfiltration and examining the concept of high dietary protein-related nephropathy in athletes and bodybuilders.

PURPOSE OF REVIEW: High-protein diets (HPDs) are popular but their consequences for kidney health, especially among athletes and bodybuilders who typically maintain a high protein intake for a long time, have not been investigated. This review focused on recent studies of the association of HPD with long-term kidney health and the concept of high dietary protein-related nephropathy. RECENT FINDINGS: Several long-term observational studies including large populations have reinforced the notion that HPDs are associated with a rapid decline of kidney function. An increase in renal blood flow and glomerular hyperfiltration caused by vasodilation, and increased levels of endocrine and paracrine factors (glucagon, IGF-1, prostanoids, and nitric oxide), facilitates the excretion of protein-derived nitrogenous waste. Inhibition of tubule-glomerular feedback and increased proximal tubular Na+ reabsorption after a HPD augment glomerular hyperfiltration and may trigger synthesis of proinflammatory cytokines and receptor for advanced glycation end-products (RAGE). Focal segmental glomerulosclerosis reported in association with anabolic steroid may indeed be a HPD nephropathy given that HPD results in progressive glomerulosclerosis, especially in remnant glomeruli or in diabetic kidney disease but can happen in any high-risk situation, such as solitary kidney and polycystic kidneys. SUMMARY: HPD among athletes and bodybuilders in an extreme way across a long-term period may pose a risk to renal health including high incidence of HPD nephropathy.

Association between exposure to fine particulate matter and kidney function: Results from the Korea National Health and Nutrition Examination Survey.

BACKGROUND: The incidence and prevalence of chronic kidney disease (CKD) are increasing worldwide. Recent studies have shown that air pollution is associated with poorer kidney function. We evaluated the association of long-term exposure to air pollutants with kidney function, and with risk of CKD using data from the seventh Korean National Health and Nutrition Examination Survey (KNHANES). METHODS: KNHANES data from 2016 through 2018 and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation were used to calculate estimated glomerular filtration rates (eGFRs) and define the CKD patients with eGFRs <60 mL/min/1.73 m2. After applying the sampling weights based on the complex survey design, we conducted multivariate linear regression and logistic regression analyses to examine the association of air pollutant exposure with kidney function and CKD risk, after adjusting for covariates, including gender, body mass index, education level, household income, smoking status, alcohol consumption, comorbidities, and serum triglyceride. RESULTS: A total of 15,983 adults aged ≥20 years were included in the analysis. Long-term exposure to PM2.5, PM10, NO2, and CO was associated with decreases in eGFR levels (PM2.5: -4.67, 95% confidence interval (CI): -6.16, -3.18; PM10: -2.19, 95% CI: -2.84, -1.54; NO2: -1.56, 95% CI: -2.16, -0.97; CO: -1.34, 95% CI: -1.96, -0.71). Long-term exposure to PM2.5 (odds ratio (OR): 1.97, 95% CI: 1.14, 3.42) and PM10 (OR: 1.45, 95% CI: 1.10, 1.91) was associated with an increased the risk of CKD. CONCLUSIONS: Annual exposure to PM2.5, PM10, NO2, and CO was significantly associated with decreased eGFR. Long-term exposure to PM2.5 and PM10 was associated with an increased risk of CKD.

Early fluid management affects short-term mortality in patients with end-stage kidney disease undergoing chronic hemodialysis and requiring continuous renal replacement therapy.

BACKGROUND: Early fluid management is considered a key element affecting mortality in critically ill patients requiring continuous renal replacement therapy (CRRT). Most studies have primarily focused on patients with intrinsic acute kidney injury requiring CRRT, although end-stage kidney disease (ESKD) patients generally exhibit greater vulnerability. We investigated the association between fluid balance and short-term mortality outcomes in ESKD patients undergoing chronic hemodialysis and requiring CRRT. METHODS: This retrospective study included 110 chronic hemodialysis patients who received CRRT between 2017 and 2019 at Ewha Womans University Mokdong Hospital. The amounts of daily input and output, and cumulative 3-day and 7-day input and output, were assessed from the initiation of CRRT. The participants were classified into two groups based on 7-day and 14-day mortalities. Cox regression analyses were carried out on the basis of the amounts of daily input and output, cumulative input and output, and cumulative fluid balance. RESULTS: During follow-up, 7-day and 14-day mortalities were observed in 24 (21.8%) and 34 (30.9%) patients. The patients were stratified into two groups (14-day survivors vs. non-survivors), and there were no significant differences in demographic characteristics between the two groups. However, diabetes mellitus was more common among survivors than among non-survivors. Univariate analyses showed that the amounts of daily output at 48, and 72 h, and 3-day cumulative input and output, were significantly associated with 7-day mortality risk regardless of the cumulative fluid balance (HR: 0.28, 95% CI: 0.12-0.70, p = 0.01 for daily output at 48 h; HR: 0.34, 95% CI: 0.13-0.85, p = 0.02 for daily output at 72 h.; HR: 0.72, 95% CI: 0.61-0.86, p = 0.01 for 3-day cumulative input; HR: 0.65, 95% CI: 0.41-0.90, p = 0.01 for 3-day cumulative output). Adjusted multivariate analyses showed that the lower 3-day cumulative output is an independent risk factor for 7-day and 14-day mortality. CONCLUSIONS: In our study, increased cumulative output were significantly associated with reduced short-term mortality risk in chronic hemodialysis patients undergoing CRRT regardless of cumulative fluid balance. Further prospective studies to investigate the association between fluid balance and mortality in ESRD patients requiring CRRT are warranted.

Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Recent data suggested a causative role of uric acid (UA) in the development of renal disease, in which endothelial dysfunction is regarded as the key mechanism. Endothelial-to-mesenchymal transition (EndoMT) and shedding of the glycocalyx are early changes of endothelial dysfunction. We investigated whether UA induced EndoMT in HUVECs and an animal model of hyperuricemia fed with 2% oxonic acid for 4 wk. UA induced EndoMT in HUVECs with a generation of reactive oxygen species via the activation of membranous NADPH oxidase (from 15 min) and mitochondria (from 6 h) along with glycocalyx shedding (from 6 h), which were blocked by probenecid. GM6001, an inhibitor of matrix metalloproteinase, alleviated UA-induced glycocalyx shedding and EndoMT. Antioxidants including N-acetyl cysteine, apocynin, and mitotempo ameliorated EndoMT; however, they did not change glycocalyx shedding in HUVECs. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries (PTCs) was substantially decreased with a de novo expression of α-smooth muscle actin in PTCs. Plasma level of syndecan-1 was increased in hyperuricemic rats, which was ameliorated by allopurinol. UA caused a phenotypic transition of endothelial cells via induction of oxidative stress with glycocalyx shedding, which could be one of the mechanisms of UA-induced endothelial dysfunction and kidney disease.-Ko, J., Kang, H.-J., Kim, D.-A., Kim, M.-J., Ryu, E.-S., Lee, S., Ryu, J.-H., Roncal, C., Johnson, R. J., Kang, D.-H. Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Paricalcitol attenuates TGF-ß1-induced phenotype transition of human peritoneal mesothelial cells (HPMCs) via modulation of oxidative stress and NLRP3 inflammasome.

Phenotype transition of mesothelial cells, such as epithelial-to-mesenchymal transition (EMT), is one of the early mechanisms of peritoneal fibrosis, which is mediated by oxidative stress and inflammation. Nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a multiprotein oligomer that promotes the maturation of IL-1ß and IL-18. Paricalcitol is reported to exert an anti-inflammatory effect; however, there are no studies as to whether paricalcitol modulates the activation of NLRP3 inflammasome. We investigated the role of NLRP3 inflammasome in peritoneal EMT with an exploration of the effect of paricalcitol on oxidative stress, NLRP3 inflammasome, and EMT of mesothelial cells. TGF-ß1-induced EMT in human peritoneal mesothelial cells (HPMCs) was associated with an up-regulation of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and procaspase-1, with an increased production of IL-1ß and IL-18, which was ameliorated by small interfering (si)NLRP3, siASC, caspase inhibitors, or neutralizing antibodies for IL-1ß and IL-18. TGF-ß1 enhanced reactive oxygen species generation with an increase in NADPH oxidase (NOX) activity and mitochondrial NOX4 production. Paricalcitol alleviated TGF-ß1-induced EMT and the NLRP3 inflammasome, which was associated with a down-regulation of NOX activity by interfering with p47phox and p22phox interaction and mitochondrial NOX4 production in HPMCs. Taken together, paricalcitol ameliorated EMT of HPMCs via modulating an NOX-dependent increase in the activity of NLRP3 inflammasome. Paricalcitol could be a novel approach to protect the peritoneum from the development of EMT and peritoneal fibrosis.-Ko, J., Kang, H.-J., Kim, D.-A., Ryu, E.-S., Yu, M., Lee, H., Lee, H. K., Ryu, H.-M., Park, S.-H., Kim, Y.-L., Kang, D.-H. Paricalcitol attenuates TGF-ß1-induced phenotype transition of human peritoneal mesothelial cells (HPMCs) via modulation of oxidative stress and NLRP3 inflammasome.

Eosinophil count and mortality risk in incident hemodialysis patients.

BACKGROUND: Eosinophils are traditionally known as moderators of allergic reactions; however, they have now emerged as one of the principal immune-regulating cells as well as predictors of vascular disease and mortality in the general population. Although eosinophilia has been demonstrated in hemodialysis (HD) patients, associations of eosinophil count (EOC) and its changes with mortality in HD patients are still unknown. METHODS: In 107 506 incident HD patients treated by a large dialysis organization during 2007-11, we examined the relationships of baseline and time-varying EOC and its changes (ΔEOC) over the first 3 months with all-cause mortality using Cox proportional hazards models with three levels of hierarchical adjustment. RESULTS: Baseline median EOC was 231 (interquartile range 155-339) cells/µL and eosinophilia (>350 cells/µL) was observed in 23.4% of patients. There was a gradual increase in EOC over time after HD initiation with a median ΔEOC of 5.1 (IQR -53-199) cells/µL, which did not parallel the changes in white blood cell count. In fully adjusted models, mortality risk was highest in subjects with lower baseline and time-varying EOC (<100 cells/µL) and was also slightly higher in patients with higher levels (≥550 cells/µL), resulting in a reverse J-shaped relationship. The relationship of ΔEOC with all-cause mortality risk was also a reverse J-shape where both an increase and decrease exhibited a higher mortality risk. CONCLUSIONS: Both lower and higher EOCs and changes in EOC over the first 3 months after HD initiation were associated with higher all-cause mortality in incident HD patients.

The interactive effects of input and output on managing fluid balance in patients with acute kidney injury requiring continuous renal replacement therapy.

BACKGROUND: The interactive effect of cumulative input and output on achieving optimal fluid balance has not been well elucidated in patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT). This study evaluated the interrelation of fluid components with mortality in patients with AKI requiring CRRT. METHODS: This is a retrospective observational study conducted with a total of 258 patients who were treated with CRRT due to AKI between 2016 and 2018 in the intensive care unit of Ewha Womans University Mokdong Hospital. The amounts of fluid input and output were assessed at 24-h and 72-h from the initiation of CRRT. The study endpoints were 7- and 28-day all-cause mortality. RESULTS: The mean patient age was 64.7 ± 15.8 years, and 165 (64.0%) patients were male. During the follow-up, 7- and 28-day mortalities were observed in 120 (46.5%) and 157 (60.9%) cases. The patients were stratified into two groups (28-day survivors vs. non-survivors), and the cumulative fluid balances (CFBs) at 24 h and 72 h were significantly higher in the 28-day non-survivors compared with the survivors. The increase in 24-h and 72-h CFB was significantly associated with an increase in 7- and 28-day mortality risks. To examine the interactive effect of cumulative input or output on the impact of CFB on mortality, we also stratified patients into three groups based on the tertile of 24-h and 72-h cumulative input or output. The increases in 24-h and 72-h CFBs were still significantly related to the increases in 7-day and 28-day mortality, irrespective of the cumulative input. However, we did not find significant associations between increase in 24-h and 72-h CFB and increase in mortality risk in the groups according to cumulative output tertile. CONCLUSIONS: The impact of cumulative fluid balance on mortality might be more dependent on cumulative output. The physicians need to decrease the cumulative fluid balance of CRRT patients as much as possible and consider increasing patient removal.

Fructose and sugar: A major mediator of non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome; its rising prevalence parallels the rise in obesity and diabetes. Historically thought to result from overnutrition and a sedentary lifestyle, recent evidence suggests that diets high in sugar (from sucrose and/or high-fructose corn syrup [HFCS]) not only increase the risk of NAFLD, but also non-alcoholic steatohepatitis (NASH). Herein, we review the experimental and clinical evidence that fructose precipitates fat accumulation in the liver, due to both increased lipogenesis and impaired fat oxidation. Recent evidence suggests that the predisposition to fatty liver is linked to the metabolism of fructose by fructokinase C, which results in ATP consumption, nucleotide turnover and uric acid generation that mediate fat accumulation. Alterations to gut permeability, the microbiome, and associated endotoxemia contribute to the risk of NAFLD and NASH. Early clinical studies suggest that reducing sugary beverages and total fructose intake, especially from added sugars, may have a significant benefit on reducing hepatic fat accumulation. We suggest larger, more definitive trials to determine if lowering sugar/HFCS intake, and/or blocking uric acid generation, may help reduce NAFLD and its downstream complications of cirrhosis and chronic liver disease.

Screening of breast cancer stem cell inhibitors using a protein kinase inhibitor library.

BACKGROUND: Cancer stem cells (CSCs), a subpopulation in tumors, are known to cause drug resistance, tumor recurrence and metastasis. Based on the characteristic formation of mammospheres in in vitro conditions, the mammosphere formation assay has become an essential tool for quantifying CSC activity in breast cancer research. However, manual counting of mammospheres is a time-consuming process that is not amenable to high-throughput screening, and there are occasional inaccuracies in the process of determining the mammosphere diameter. In this study, we proposed a novel automated counting method of mammosphere using the National Institute of Standards and Technology (NIST)'s Integrated Colony Enumerator (NICE) with a screening of protein kinase library. METHODS: Human breast cancer cell line MCF-7 was used for evaluation of tumor sphere efficiency, migration, and phenotype transition. Cell viability was assessed using MTT assay, and CSCs were identified by an analysis of CD44 expression and ALDEFLUOR assay using flow cytometry. Automated counting of mammosphere using NICE program was performed with a comparison to the result of manual counting. After identification of inhibitors to ameliorate CSC formation by screening a library of 79 protein kinase inhibitors using automated counting in primary, secondary and tertiary mammosphere assay, the effect of selected kinase inhibitors on migration, colony formation and epithelial-to-mesenchymal transition (EMT) of MCF-7 cells was investigated. RESULTS: Automated counting of mammosphere using NICE program was an easy and less time-consuming process (<1 min for reading 6-well plate) which provided a comparable result with manual counting. Inhibition of calcium/calmodulin-dependent protein kinase II (CaMKII), Janus kinase-3 (JAK-3), and IκB kinase (IKK) were identified to decrease the formation of MCF-7-derived CSCs in primary, secondary and tertiary mammosphere assay. These protein kinase inhibitors alleviated TGF-ß1-induced migration, colony formation and EMT of MCF-7 cells. CONCLUSIONS: We have developed a novel automated cell-based screening method which provided an easy, accurate and reproducible way for mammosphere quantification. This study is the first to show the efficacy of an automated medium-throughput mammosphere-counting method in CSC-related research with an identification of protein kinase inhibitors to ameliorate CSC formation.

Dementia is a risk factor for major adverse cardiac and cerebrovascular events in elderly Korean patients initiating hemodialysis: a Korean national population-based study.

BACKGROUND: Dementia is common in end-stage renal disease (ESRD) patients on hemodialysis (HD) and is associated with worse outcomes. This study aimed to investigate the risk of major adverse cardiac and cerebrovascular event (MACCE) in elderly patients with dementia initiating HD. METHODS: Using the database from the Health Insurance Review & Assessment Service, we analyzed 10,171 patients aged 65 years or older who had initiated dialysis from 2005 to 2008. MACCE was defined as a composite outcome of all-cause mortality, nonfatal acute myocardial infarction, target vessel revascularization, and nonfatal ischemic and hemorrhagic stroke. The Kaplan-Meier method and Cox proportional hazards model were used, and further comparisons using propensity-score matching at 1:2 ratio were also performed. RESULTS: A total of 303 elderly patients (3.0%) had dementia at initiating HD. During follow-up, dementia was a significant predictor of MACCE after adjustment for confounding variables. In addition, further analyzed in the propensity-score matched groups, dementia was an independent predictor of both nonfatal ischemic stroke and all-cause mortality. CONCLUSIONS: Dementia is an independent risk factor for mortality and ischemic stroke in elderly ESRD patients initiating HD. Patients with dementia who start dialysis should be closely monitored to reduce the risk of mortality and ischemic stroke.

Aging-associated renal disease in mice is fructokinase dependent.

Aging-associated kidney disease is usually considered a degenerative process associated with aging. Recently, it has been shown that animals can produce fructose endogenously, and that this can be a mechanism for causing kidney damage in diabetic nephropathy and in association with recurrent dehydration. We therefore hypothesized that low-level metabolism of endogenous fructose might play a role in aging-associated kidney disease. Wild-type and fructokinase knockout mice were fed a normal diet for 2 yr that had minimal (<5%) fructose content. At the end of 2 yr, wild-type mice showed elevations in systolic blood pressure, mild albuminuria, and glomerular changes with mesangial matrix expansion, variable mesangiolysis, and segmental thrombi. The renal injury was amplified by provision of high-salt diet for 3 wk, as noted by the presence of glomerular hypertrophy, mesangial matrix expansion, and alpha smooth muscle actin expression, and with segmental thrombi. Fructokinase knockout mice were protected from renal injury both at baseline and after high salt intake (3 wk) compared with wild-type mice. This was associated with higher levels of active (phosphorylated serine 1177) endothelial nitric oxide synthase in their kidneys. These studies suggest that aging-associated renal disease might be due to activation of specific metabolic pathways that could theoretically be targeted therapeutically, and raise the hypothesis that aging-associated renal injury may represent a disease process as opposed to normal age-related degeneration.

Restoring multidrug resistance-associated protein 3 attenuates cell proliferation in the polycystic kidney.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by abnormal proliferation of renal tubular epithelial cells, resulting in the loss of renal function. Despite identification of the genes responsible for ADPKD, few effective drugs are currently available for the disease. Thus finding additional effective drug targets is necessary. The functions of multidrug- resistance-associated protein 3 (MRP3) have been reported only in the field of drug resistance, and the renal functions of MRP3 are mostly unknown. In this study, we found that MRP3 was significantly downregulated in kidneys of human patients with ADPKD and polycystic kidney disease (PKD) mouse models. Our results suggest that downregulated MRP3 stimulated renal epithelial cell proliferation through the B-Raf/MEK/ERK signaling pathway. In contrast, we found that restoring MRP3 reduced cell proliferation and cystogenesis in vitro. These results suggest that the renal function of MRP3 is related to renal cell proliferation and cyst formation and that restoring MRP3 may be an effective therapeutic approach for PKD.

Endoplasmic reticulum stress as a novel target to ameliorate epithelial-to-mesenchymal transition and apoptosis of human peritoneal mesothelial cells.

Epithelial-to-mesenchymal transition (EMT) and apoptosis of peritoneal mesothelial cells are known to be the earliest mechanisms of peritoneal fibrosis in peritoneal dialysis (PD). Endoplasmic reticulum (ER) stress with an unfolded protein response is regarded to have a role in the development of organ fibrosis. To investigate the potential role of ER stress as a target to prevent and/or delay the development of peritoneal fibrosis, we examined the effect of ER stress on EMT or apoptosis of human peritoneal mesothelial cells (HPMCs) and elucidated the mechanisms underlying the protective effect of ER stress preconditioning on TGF-ß1-induced EMT. ER stress inducers, tunicamycin (TM) and thapsigargin (TG), induced EMT with Smad2/3 phosphorylation, an increased nuclear translocation of ß-catenin and Snail expression. Low concentrations of TM and TG did not induce apoptosis within 48 h; however, high concentrations of TM- (>1 ng/ml) and TG- (>1 nM) induced apoptosis at 12 h with a persistent increase in C/EBP homologous protein. TGF-ß1 induced EMT and apoptosis in HPMCs, which was ameliorated by taurine-conjugated ursodeoxycholic acid, an ER stress blocker. Interestingly, pre-treatment with TM or TG for 4 h also protected the cells from TGF-ß1-induced EMT and apoptosis, demonstrating the role of ER stress as an adaptive response to protect HPMCs from EMT and apoptosis. Peritoneal mesothelial cells isolated from PD patients displayed an increase in GRP78/94, which was correlated with the degree of EMT. These findings suggest that the modulation of ER stress in HPMCs could serve as a novel approach to ameliorate peritoneal damage in PD patients.

Baicalin and baicalein inhibit transforming growth factor-ß1-mediated epithelial-mesenchymal transition in human breast epithelial cells.

Since the epithelial-mesenchymal transition (EMT) is involved in many crucial functions of cancer cells, we set out to identify a natural compound capable of inhibiting EMT processes. TGF-ß1 treatment induces EMT among normal mammary epithelial cells (MCF10A cells), as reflected by characteristic morphological changes into the fibroblastic phenotype, reduced expression of E-cadherin. Interestingly, butanol extracts of Scutellaria baicalensis Georgi significantly reduced the TGF-ß1-mediated EMT of MCF10A cells. Further analysis revealed that baicalin and baicalein, the major flavones of these butanol extracts, inhibited TGF-ß1-mediated EMT by reducing the expression level of the EMT-related transcription factor, Slug via the NF-κB pathway, and subsequently increased migration in MCF10A cells. Finally, both compounds reduced the TGF-ß1-mediated EMT, anchorage-independent growth and cell migration of human breast cancer cells (MDA-MB-231 cells). Taken together, these results suggest that baicalin and baicalein of Scutellaria baicalensis Georgi may suppress the EMT of breast epithelial cells and the tumorigenic activity of breast cancer cells. Thus, these compounds could have potential as therapeutic or supplementary agents for the treatment of breast cancer.

Uric acid induces endothelial dysfunction by vascular insulin resistance associated with the impairment of nitric oxide synthesis.

Endothelial dysfunction is defined as impairment of the balance between endothelium-dependent vasodilation and constriction. Despite evidence of uric acid-induced endothelial dysfunction, a relationship with insulin resistance has not been clearly established. In this study, we investigated the role of vascular insulin resistance in uric acid-induced endothelial dysfunction. Uric acid inhibited insulin-induced endothelial nitric oxide synthase (eNOS) phosphorylation and NO production more substantially than endothelin-1 expression in HUVECs, with IC50 of 51.0, 73.6, and 184.2, respectively. Suppression of eNOS phosphorylation and NO production by uric acid was PI3K/Akt-dependent, as verified by the transfection with p110. Treatment of rats with the uricase inhibitor allantoxanamide induced mild hyperuricemia and increased mean arterial pressure by 25%. While hyperuricemic rats did not show systemic insulin resistance, they showed impaired vasorelaxation induced by insulin by 56%. A compromised insulin response in terms of the Akt/eNOS pathway was observed in the aortic ring of hyperuricemic rats. Coadministration with allopurinol reduced serum uric acid levels and blood pressure and restored the effect of insulin on Akt-eNOS pathway and vasorelaxation. Taken together, uric acid induced endothelial dysfunction by contributing to vascular insulin resistance in terms of insulin-induced NO production, potentially leading to the development of hypertension.-Choi, Y.-J., Yoon, Y., Lee, K.-Y., Hien, T. T., Kang, K. W., Kim, K.-C., Lee, J., Lee, M.-Y., Lee, S. M., Kang, D.-H., Lee, B.-H. Uric acid induces endothelial dysfunction by vascular insulin resistance associated with the impairment of nitric oxide synthesis.

Inactivation of max-interacting protein 1 induces renal cilia disassembly through reduction in levels of intraflagellar transport 20 in polycystic kidney.

Cilia in ciliated cells consist of protruding structures that sense mechanical and chemical signals from the extracellular environment. Cilia are assembled with variety molecules via a process known as intraflagellar transport (IFT). What controls the length of cilia in ciliated cells is critical to understand ciliary disease such as autosomal dominant polycystic kidney disease, which involves abnormally short cilia. But this control mechanism is not well understood. Previously, multiple tubular cysts have been observed in the kidneys of max-interacting protein 1 (Mxi1)-deficient mice aged 6 months or more. Here, we clarified the relationship between Mxi1 inactivation and cilia disassembly. Cilia phenotypes were observed in kidneys of Mxi1-deficient mice using scanning electron microscopy to elucidate the effect of Mxi1 on renal cilia phenotype, and cilia disassembly was observed in Mxi1-deficient kidney. In addition, genes related to cilia were validated in vitro and in vivo using quantitative PCR, and Ift20 was selected as a candidate gene in this study. The length of cilium decreased, and p-ERK level induced by a cilia defect increased in kidneys of Mxi1-deficient mice. Ciliogenesis of Mxi1-deficient mouse embryonic fibroblasts (MEFs) decreased, and this abnormality was restored by Mxi1 transfection in Mxi1-deficient MEFs. We confirmed that ciliogenesis and Ift20 expression were regulated by Mxi1 in vitro. We also determined that Mxi1 regulates Ift20 promoter activity via Ets-1 binding to the Ift20 promoter. These results indicate that inactivating Mxi1 induces ciliary defects in polycystic kidney.

Renoprotective effect of red ginseng in gentamicin-induced acute kidney injury.

Aminoglycoside-induced nephrotoxicity is one of the prevalent causes of acute kidney injury (AKI). Oxidative stress-mediated apoptosis of renal tubular cells is known to be a major mechanism of renal injury. Red ginseng extract (RGE) has been reported to possess antioxidant and immune-modulatory activities. We investigated the effect of RGE on gentamicin (GM)-induced apoptosis and oxidative stress in cultured renal tubular cells and animal model of GM-induced AKI. GM induced the generation of reactive oxygen species (ROS) with an increase in NADPH oxidase (NOX) activity and mitochondrial oxidation in NRK-52E cells that were ameliorated with RGE. GM-induced apoptosis of NRK-52E cells, which was associated with an increased expression of mitochondrial Bax, cytosolic cytochrome c, and cleaved caspase-9 and -3, along with a decrease in bcl-2 expression, was also blocked by RGE. In an animal model of GM-induced AKI, RGE treatment significantly attenuated renal dysfunction, cell apoptosis, and tubular damage. RGE ameliorated ROS production in rats with GM-induced AKI, as demonstrated by an increase in the reduced form of glutathione in renal cortex and a decrease in urinary excretion of 8-hydroxy-2'-deoxyguanosine. Our results suggest that RGE protects the kidney from GM-induced AKI via the mechanism of modulation of oxidative stress.

Uric acid induces fat accumulation via generation of endoplasmic reticulum stress and SREBP-1c activation in hepatocytes.

Non-alcoholic fatty liver disease (NAFLD) is currently one of the most common types of chronic liver injury. Elevated serum uric acid is a strong predictor of the development of fatty liver as well as metabolic syndrome. Here we demonstrate that uric acid induces triglyceride accumulation by SREBP-1c activation via induction of endoplasmic reticulum (ER) stress in hepatocytes. Uric acid-induced ER stress resulted in an increase of glucose-regulated protein (GRP78/94), splicing of the X-box-binding protein-1 (XBP-1), the phosphorylation of protein kinase RNA-like ER kinase (PERK), and eukaryotic translation initiation factor-2α (eIF-2α) in cultured hepatocytes. Uric acid promoted hepatic lipogenesis through overexpression of the lipogenic enzyme, acetyl-CoA carboxylase 1 (ACC1), fatty acid synthase (FAS), and stearoyl-CoA desaturase 1 (SCD1) via activation of SREBP-1c, which was blocked by probenecid, an organic anion transport blocker in HepG2 cells and primary hepatocytes. A blocker of ER stress, tauroursodeoxycholic acid (TUDCA), and an inhibitor of SREBP-1c, metformin, blocked hepatic fat accumulation, suggesting that uric acid promoted fat synthesis in hepatocytes via ER stress-induced activation of SREBP-1c. Uric acid-induced activation of NADPH oxidase preceded ER stress, which further induced mitochondrial ROS production in hepatocytes. These studies provide new insights into the mechanisms by which uric acid stimulates fat accumulation in the liver.