Activation of the angiotensin II receptor promotes autophagy in renal proximal tubular cells and affords protection from ischemia/reperfusion injury.

Roles of the renin-angiotensin system in autophagy and ischemia/reperfusion (I/R) injury in the kidney have not been fully characterized. Here we examined the hypothesis that modest activation of the angiotensin II (Ang II) receptor upregulates autophagy and increases renal tolerance to I/R injury. Sprague-Dawley rats were assigned to treatment with a vehicle or a non-pressor dose of Ang II (200 ng/kg/min) for 72 h before 30-min renal I/R. LC3-immunohistochemistry showed that Ang II treatment increased autophagosomes in proximal tubular cells by 2.7 fold. In Ang II-pretreated rats, autophagosomes were increased by 2.5 fold compared to those in vehicle-treated rats at 4 h after I/R, when phosphorylation of Akt and S6 was suppressed and ULK1-Ser555 phosphorylation was increased. Serum creatinine and urea nitrogen levels, incidence of oliguria, and histological score of tubular necrosis at 24 h after I/R were attenuated by Ang II-pretreatment. In NRK-52E cells, Ang II induced LC3-II upregulation, which was inhibited by losartan but not by A779. The results indicate that a non-pressor dose of Ang-II promotes autophagy via ULK1-mediated signaling in renal tubular cells and attenuates renal I/R injury. The AT1 receptor, but not the Mas receptor, contributes to Ang-II-induced autophagy and presumably also to the renoprotection.

Involvement of necroptosis in contrast-induced nephropathy in a rat CKD model.

BACKGROUND: The risk of contrast-induced nephropathy (CIN) is high in patients with chronic kidney disease (CKD). However, the mechanism of CIN in CKD is not fully understood. Here, we prepared a clinically relevant model of CIN and examined the role of necroptosis, which potentially cross-talks with autophagy, in CIN. METHODS: In Sprague-Dawley rats, CKD was induced by subtotal nephrectomy (SNx, 5/6 nephrectomy) 4 weeks before induction of CIN. CIN was induced by administration of a contrast medium (CM), iohexol, following administration of indomethacin and N-omega-Nitro-L-arginine methyl ester. Renal function and tissue injuries were assessed 48 h after CM injection. RESULTS: Serum creatinine (s-Cre) and BUN were increased from 0.28 ± 0.01 to 0.52 ± 0.02 mg/dl and from 15.1 ± 0.7 to 29.2 ± 1.2 mg/dl, respectively, after SNx alone. CM further increased s-Cre and BUN to 0.69 ± 0.03 and 37.2 ± 2.1, respectively. In the renal tissue after CM injection, protein levels of receptor-interacting serine/threonine-protein kinase (RIP) 1, RIP3, cleaved caspase 3, and caspase 8 were increased by 64 ~ 212%, while there was reduction in LC3-II and accumulation of p62. Necrostatin-1, an RIP1 inhibitor, administered before and 24 h after CM injection significantly suppressed elevation of s-Cre, BUN and urinary albumin levels, kidney injury molecule-1 expression and infiltration of CD68-positive macrophages in renal tissues after CM injection. CONCLUSION: The results suggest that necroptosis of proximal tubular cells contributes to CIN in CKD and that suppression of protective autophagy by pro-necroptotic signaling may also be involved.

Seasonal variation of serum 25-hydroxyvitamin D level in hemodialysis patients in the northernmost island of Japan.

BACKGROUND: Serum vitamin D level shows a seasonal variation, being lower in winter than in summer in healthy subjects. The aim of this study was to determine whether there is presence of such a seasonal variation in hemodialysis patients. METHODS: A total of 102 patients on hemodialysis were enrolled in February 2017 (winter) for analyses of serum levels of 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] and treatments for chronic kidney disease-mineral and bone disorder (CKD-MBD). The examinations were repeated in August 2017 (summer). After exclusion of patients with malignancy, loss of follow-up and missing data, 78 patients contributed to the analyses. RESULTS: Serum level of 25(OH)D, but not that of 1,25(OH)2D, was significantly lower in winter (14.0 ng/mL) than in summer (15.5 ng/mL), though there was no significant difference in regimen for CKD-MBD treatment including vitamin D receptor activators (VDRAs) between the two seasons. Serum intact parathyroid hormone level tended to be higher and alkaline phosphatase was significantly higher in winter than in summer. Linear mixed-effects model analysis showed that level of 25(OH)D, but not that of 1,25(OH)2D, was significantly associated with season (winter and summer) after adjustment of age, sex, dialysis vintage, albumin level and use of drugs for CKD-MBD. CONCLUSION: Serum 25(OH)D has a seasonal variation, being lower in winter than in summer, independent of CKD-MBD treatment including treatment with VDRAs in Japanese hemodialysis patients. The impact of the seasonal variation on risk of vitamin D deficiency and its effect on prognosis remain to be investigated.

Impact of atrial fibrillation on the risk of ischemic stroke in patients on hemodialysis: BOREAS-HD3 Study.

BACKGROUND: Atrial fibrillation (AF) is an established risk factor for ischemic stroke in a general population. However, its impact in patients on hemodialysis (HD), a group with a high risk for stroke, is still controversial. Here we examined this issue in a Japanese cohort. METHODS: This study was designed as a multicenter cohort study. HD patients (n = 1,067) were enrolled from 22 institutes in January 2009 and followed up for 3 years. Patients with missing data (n = 196) or kidney transplantation (n = 4) were excluded, and 867 patients contributed to the analysis of the risk of new-onset of ischemic stroke. RESULTS: At baseline, AF was observed in 123 patients (14.2%, AF group) and not in the others (n = 744: 85.8%, non-AF group). During a follow-up period of 31.3 months, the cumulative incidence rate for ischemic stroke was significantly higher in the AF group than in the non-AF group (6.5% vs. 2.9%, p < 0.05). In Cox regression analysis, AF was a significant independent risk factor for new-onset of ischemic stroke after adjustment for age, sex, prior history of ischemic stroke, use of warfarin, dialysis vintage, comorbidity of diabetic nephropathy, and interdialytic weight gain (hazard ratio 2.17-2.68). CONCLUSION: Present analyses using comprehensive adjustment for multiple confounders, including prior history of ischemic stroke, indicated that AF independently increases the risk of new-onset of ischemic stroke by more than twofold in Japanese HD patients.

Significance of urinary fatty acid-binding protein 4 level as a possible biomarker for the identification of minimal change disease in patents with nephrotic-range proteinuria.

BACKGROUND: Fatty acid-binding protein 4 (FABP4), but not FABP1 (liver-type FABP), is ectopically induced in injured glomerular endothelial cells, and urinary FABP4 (U-FABP4) level is associated with proteinuria and renal dysfunction in a general population. METHODS: The clinical significance of U-FABP4 was investigated in 81 patients (male/female: 43/38, age: 57 ± 17 years) who underwent kidney biopsy. RESULTS: U-FABP4 was negatively correlated with estimated glomerular filtration rate (eGFR) (r = - 0.56, P < 0.01) and was positively correlated with age, blood pressure, triglycerides, proteinuria (r = 0.58, P < 0.01), plasma FABP4 and urinary FABP1 (U-FABP1) (r = 0.52, P < 0.01). Multivariable regression analysis showed that eGFR, proteinuria and U-FABP1 were independent predictors of U-FABP4. The level of U-FABP4, but not that of proteinuria, eGFR or U-FABP1, in minimal change nephrotic syndrome (MCNS) was significantly lower than the level in membranous nephropathy (MN) and that in diabetic nephropathy. Receiver operating characteristic curve analysis indicated that U-FABP4 level ≤ 0.78 µg/gCr predicted MCNS in patients who had nephrotic-range proteinuria with a high level of accuracy. When divided by the median value of U-FABP4 at baseline in 33 of the 81 patients who could be followed up, the yearly change (post-pre) in eGFR in the low U-FABP4 group was significantly greater than that in the high U-FABP4 group (median: 11.0 vs. -5.0 mL/min/1.73m2/year). CONCLUSIONS: U-FABP4 level is independently associated with proteinuria and renal dysfunction in patients with glomerular kidney disease. A low U-FABP4 level may predict MCNS in patients with nephrotic syndrome and would be a useful biomarker for differential diagnosis of MCNS and MN, which are common causes of nephrotic syndrome.

Impact of the Number of Anti-Thrombosis Agents in Hemodialysis Patients: BOREAS-HD2 Study.

BACKGROUND/AIMS: Relationships between the number of anti-thrombosis agents, clinical benefits and adverse events in hemodialysis (HD) patients are unclear. METHODS: All patients on HD in 22 institutes (n = 1,071) were enrolled and followed up for 3 years. After exclusion of patients with missing data, kidney transplantation or retraction of consent during the follow-up period (n = 204), mortality rate and ischemic and hemorrhagic events were compared between different regimens of anti-thrombosis agents. RESULTS: The use of dual or triple antiplatelet (AP) agents (HR:2.03, 95% CI:1.01-4.13, p = 0.04) and the combination of an AP agent and warfarin (WF) (HR:4.84, 95%CI 1.96-11.96, p < 0.001) were associated with an increase in hemorrhagic events compared with no use of anti-thrombosis agents. No anti-thrombosis regimen was associated with a significant change in risk of ischemic stroke. The use of dual or triple AP agents, but not WF, was associated with an increase in cardiovascular mortality (HR:2.48, 95% CI:1.24-4.76, p = 0.01). CONCLUSION: A significant increase in hemorrhagic events by the use of dual or more AP agents and by co-administration of an AP agent and WF in patients on HD should be considered in planning their anti-thrombosis regimen.

A case of membranous nephropathy secondary to asymptomatic Graves' disease.

Although cases of secondary membranous nephropathy associated with autoimmune thyroid disease (AITD) have been reported, most of them, if not all, present with symptomatic thyroid disease. Here we report an asymptomatic case of AITD complicated with secondary membranous nephropathy. A 16-year-old girl was referred to our institute because of proteinuria found by an annual medical checkup. Urinalysis showed a urinary protein creatinine ratio (UPCR) of 3.0 g/gCre. Blood examination revealed that she had Graves' disease, although she did not have any symptoms of hyperthyroidism such as weight loss, anxiety, tremor, tachycardia, or eye symptoms. In a kidney biopsy, periodic acid silver-methenamine staining showed spike formation in the basement membrane. Electron microscopy showed electron-dense deposits on the epithelial side of the glomerular basement membrane. Immunofluorescent staining showed co-localization of thyroid peroxidase and IgG deposition along the glomerular capillary walls. A diagnosis of membranous nephropathy secondary to asymptomatic Graves' disease was made on the basis of results of the examinations. Treatment with thiamazole added to enalapril improved proteinuria (reduction of UPCR to 0.83 g/gCr) and hypoalbuminemia. Consideration should be given to the possibility of AITD in differential diagnosis of etiologies of membranous nephropathy even when typical symptoms of AITD are lacking.

Fatty liver index is independently associated with deterioration of renal function during a 10-year period in healthy subjects.

A potential link between chronic kidney disease (CKD) and non-alcoholic fatty liver disease (NAFLD) has been suggested. We investigated the relationship between fatty liver index (FLI), a noninvasive and simple predictor of NAFLD, and the development of CKD defined as estimated glomerular filtration rate < 60 mL/min/1.73 m2 or positive for urinary protein during a 10-year follow-up period in subjects who received annual health examinations (n = 28,890). After exclusion of CKD at baseline, a total of 14,163 subjects (male/female: 9077/5086) were recruited. During the 10-year period, 1458 males (16.1%) and 737 females (14.5%) had new onset of CKD. Multivariable Cox proportional hazard models with a restricted cubic spline showed that hazard ratios (HRs) of CKD development increased with a higher FLI at baseline in both males and females after adjustment of confounders. When divided by tertiles of FLI level at baseline (T1 ~ T3), the adjusted risk of CKD development in the T3 group (HR [95% confidence interval], male/female: 1.33 [1.16-1.54]/1.33 [1.08-1.63]) was significantly higher than that in both sexes in the T1 group as the reference. The addition of FLI into traditional risk factors significantly improved the discriminatory capability for predicting CKD. In conclusion, a high level of FLI predicts the development of CKD in both sexes in a general population.

Immunoglobulin A nephropathy secondary to Wilson's disease: a case report and literature review.

Immunoglobulin A nephropathy is the most common primary glomerulonephritis worldwide, and it can be associated with liver disease. However, cases of Immunoglobulin A nephropathy secondary to Wilson's disease are very rare. A 20-year-old Japanese man presented with microscopic hematuria, proteinuria, and renal dysfunction. A renal biopsy showed mesangial cell proliferation, immunoglobulin A deposition, and electron-dense deposit in the mesangial areas, all of which are consistent with Immunoglobulin A nephropathy. Computed tomography of the abdomen showed liver atrophy and splenomegaly, and the diagnosis of Wilson's disease was confirmed with decreased serum ceruloplasmin levels, increased urinary copper excretion, Kayser-Fleischer rings and copper deposition in the liver biopsy. The patient was treated successfully with trientine hydrochloride and zinc acetate and showed improvement in renal manifestations. Wilson's disease is a rare cause of secondary Immunoglobulin A nephropathy. We recommend that Wilson's disease should be considered the cause of secondary Immunoglobulin A nephropathy in juvenile patients with hematuria, proteinuria, and splenomegaly and suggest measuring the serum ceruloplasmin concentrations, urinary copper excretion, and evaluating Kayser-Fleischer rings in these patients.

Tick bite-Erythema migrans.

This manuscript describes the typical presentation of erythema migrans caused by tick bite. The purposes of this article are (i) to encourage physicians to observe patients with tick bite carefully since it may cause fatal encephalitis, and (ii) to facilitate physicians, especially in endemic areas, to consider tick-borne encephalitis virus as one of the causes of encephalitis.