Gut Microbiome and Microbiome-Derived Metabolites in Patients with End-Stage Kidney Disease.

The composition of the gut microbiome is altered in patients with chronic kidney disease (CKD). Dysbiosis leads to decreased levels of stool organic acids (OAs) and systemic inflammation, followed by accumulation of uremic toxins (UTs) and the development of end-stage kidney disease (ESKD). We assessed the relationship between the microbiome and UT levels or the development of ESKD by comparing patients undergoing hemodialysis (HD) and those with normal renal function (NRF). This cross-sectional study recruited 41 patients undergoing HD and 38 sex- and age-matched patients with NRF, and gut microbiome, levels of plasma UTs, inflammatory markers, and stool OAs were compared. The indices of beta-diversity differed significantly between patients with NRF and those undergoing HD, and between patients undergoing HD with and without type 2 diabetes. The levels of stool total OA, inflammatory markers, and UTs differed significantly between the patients with NRF and those undergoing HD. The combined main effects of type 2 diabetes and kidney function status were accumulation of indoxyl sulfate and p-cresyl sulfate. The relative abundances of Negativicutes and Megamonas were associated with development of ESKD and with the levels of UTs, even after adjustment for factors associated with the progression of ESKD. The present study indicates that the gut environment differs between patients with NRF and those undergoing HD and between patients undergoing HD with and without type 2 diabetes. Moreover, ESKD patients with diabetes accumulate more UTs derived from the gut microbiome, which might be associated with cardio-renal diseases and poor prognosis.

Postmortem computed tomography of gas gangrene with aortic gas in a dialysis patient.

Recently, postmortem imaging is sometimes used as an alternative to conventional autopsy. However, there are few case reports of postmortem imaging of dialysis patients. Here, we report a fatal case of gas gangrene involving a 76-year-old man who underwent dialysis. He died suddenly before a diagnosis could be established. Immediately after his death, postmortem computed tomography (PMCT) revealed gas accumulation in his right upper extremity and ascending aorta. Gas gangrene progresses rapidly and may sometimes result in sudden death before it is diagnosed. In this case, PMCT findings were useful to diagnose gas gangrene. Intravascular gas is a common finding on PMCT and is generally caused by cardiopulmonary resuscitation and decomposition. However, the detection of gas in the ascending aorta by PMCT was not described previously. Moreover, Gram stain and culture of the exudate showed anaerobic Gram-positive bacilli which suggested that the gas generation in the blood was caused by Clostridia species. To the best our knowledge, this is the first report of a dialysis patient whose cause of death was determined as gas gangrene using PMCT.

Hemodialysis as a Risk Factor for Ceftriaxone-Associated Pseudolithiasis in Adults.

Ceftriaxone-associated biliary pseudolithiasis is common among children; however, there are only a few reports of pseudolithiasis in adult patients on HD. This retrospective cohort study included 278 adult patients on ceftriaxone therapy from 1 February 2016 to 1 September 2018. Pseudolithiasis was defined as a new development of sludge or stones in the gallbladder within 60 days of ceftriaxone therapy. After excluding patients with preexisting gallstones and a history of cholecystectomy, 113 patients on maintenance HD, and another 98 patients were enrolled as the HD and control group, respectively. Thirteen patients developed pseudolithiasis. Its incidence was significantly higher in the HD group than that in the control group. Multivariate logistic regression analyses showed that development of pseudolithiasis was significantly associated with HD and ceftriaxone dose. Therefore, HD in patients receiving ceftriaxone therapy appears to be associated with a risk of pseudolithiasis. These findings highlight the need for careful follow-up.

Hepcidin-25/erythroferrone ratio predicts improvement of anaemia in haemodialysis patients treated with ferric citrate hydrate.

BACKGROUND/AIMS: Hepcidin-25 (HEP-25) and erythroferrone (ERFE) are key regulators of iron homeostasis. Correlations among serum ferritin, ERFE and HEP-25 levels and improvements in anaemia have not been evaluated after administration of ferric citrate hydrate (FCH). METHODS: This retrospective observational study investigated 24 patients on haemodialysis with both anaemia (haemoglobin (Hb) < 12 g/dL) and hyperphosphatemia (inorganic phosphorus ≥6 mg/dL). The patients who were administered FCH (1500 mg/day) for 12 consecutive weeks and 12 control patients who were administered a phosphate binder other than FCH were included. Correlations among Hb, HEP-25 and ERFE levels were studied. We then stratified the FCH group into two subgroups using the median baseline values of ferritin, HEP-25, ERFE and HEP-25/ERFE ratio to predict whether these markers could serve as prognostic indicators in the treatment of anaemia. RESULTS: In the FCH group, Hb, transferrin saturation, ferritin, HEP-25 and ERFE levels were all significantly increased, while inorganic phosphorus levels, dosage of erythropoietin-stimulating agent, and erythropoietin resistance index were all significantly decreased after drug administration. A significant inverse correlation was apparent between Hb and HEP-25 levels, and a significant positive correlation was seen between Hb and ERFE levels. A significant inverse correlation was found between HEP-25 and serum ERFE levels. Compared with the high HEP-25/ERFE ratio group, only the low HEP-25/ERFE ratio group exhibited significantly increased Hb levels at 12 weeks. CONCLUSION: HEP-25/ERFE ratio could be a novel prognostic marker for increases in Hb levels following FCH administration.

Rac1 in podocytes promotes glomerular repair and limits the formation of sclerosis.

Rac1, a Rho family member, is ubiquitously expressed and participates in various biological processes. Rac1 expression is induced early in podocyte injury, but its role in repair is unclear. To investigate the role of Rac1 expression in podocytes under pathological conditions, we used podocyte-specific Rac1 conditional knock-out (cKO) mice administered adriamycin (ADR), which causes nephrosis and glomerulosclerosis. Larger areas of detached podocytes, more adhesion of the GBM to Bowman's capsule, and a higher ratio of sclerotic glomeruli were observed in Rac1 cKO mice than in control mice, whereas no differences were observed in glomerular podocyte numbers in both groups after ADR treatment. The mammalian target of rapamycin (mTOR) pathway, which regulates the cell size, was more strongly suppressed in the podocytes of Rac1 cKO mice than in those of control mice under pathological conditions. In accordance with this result, the volumes of podocytes in Rac1 cKO mice were significantly reduced compared with those of control mice. Experiments using in vitro ADR-administered Rac1 knockdown podocytes also supported that a reduction in Rac1 suppressed mTOR activity in injured podocytes. Taken together, these data indicate that Rac1-associated mTOR activation in podocytes plays an important role in preventing the kidneys from developing glomerulosclerosis.

Re-expression of Sall1 in podocytes protects against adriamycin-induced nephrosis.

The highly conserved spalt (sal) gene family members encode proteins characterized by multiple double zinc finger motifs of the C2H2 type. Humans and mice each have four known Sal-like genes (SALL1-4 in humans and Sall1-4 in mice). Sall1 is known to have a crucial role in kidney development. To explore the significance of Sall1 in differentiated podocytes, we investigated podocyte-specific Sall1-deficient mice (Sall1 KOp°d°/p°d°) using a podocin-Cre/loxP system and siRNA Sall1 knockdown (Sall1 KD) podocytes. Under physiological conditions, Sall1 KOp°d°/p°d° mice exhibited no proteinuria during their lifetime, but foot-process effacement was detected in some of the podocytes. To elucidate the role of Sall1 in injured podocytes, we used an adriamycin (ADR)-induced model of nephrosis and glomerulosclerosis. Surprisingly, the expression of Sall1 was elevated in control mice on day 14 after ADR injection. On day 28 after ADR injection, Sall1 KOp°d°/p°d° mice exhibited significantly higher levels of proteinuria and higher numbers of sclerotic glomeruli. Differentiated Sall1 KD podocytes showed a loss of synaptopodin, suppressed stress fiber formation, and, ultimately, impaired directed cell migration. In addition, the loss of Sall1 increased the number of apoptotic podocytes following ADR treatment. These results indicated that Sall1 has a protective role in podocytes; thus, we investigated the endoplasmic reticulum stress marker GRP78. GRP78 expression was higher in ADR-treated Sall1 KOp°d°/p°d° mice than in control mice. Sall1 appeared to influence the expression of GRP78 in injured podocytes. These results suggest that Sall1 is associated with actin reorganization, endoplasmic reticulum stress, and apoptosis in injured podocytes. These protective aspects of Sall1 re-expression in injured podocytes may have the potential to reduce apoptosis and possibly glomerulosclerosis.

Podocyte-specific deletion of Rac1 leads to aggravation of renal injury in STZ-induced diabetic mice.

Rac1, a GTPase of the Rho subfamily, has a crucial role in cytoskeletal architecture, as well as the regulation of cell migration and growth. However, renal injury in mice with podocyte-specific deletion of Rac1 has yet to be elucidated fully due to conflicting findings. Herein, we identified a possible role for Rac1 in podocytes of streptozotocin- (STZ) induced diabetic mice. The urinary albumin/creatinine ratio (ACR) in the knockout (KO) group was significantly higher than that in the wild type (WT) group at any week of age. A more marked ACR increase was observed in STZ/KO group than STZ/WT group, although ACR did increase with weeks of age in both diabetic groups. The kidney sections from diabetic mice revealed a glomerular hypertrophy with mesangial expansion, but there was no appreciable difference in glomerular findings under a light microscope between STZ/WT and STZ/KO mice. However, an electron microscopy analysis revealed that regardless of the presence or absence of diabetes, both KO (KO and STZ/KO) groups had a higher rate of foot process effacement compared with both WT (WT and STZ/WT) groups. The expression levels of the slit diaphragm protein, podocin, was reduced with the induction of diabetes, and the levels in the STZ/KO group experienced a further reduction compared with the STZ/WT group. The number of WT1-positive cells in the STZ/KO group was more significantly decreased than that in the other three groups. In contrast, the numbers of cleaved caspase 3- and TUNEL-positive cells in the glomeruli of the STZ/KO group were more increased than those in the STZ/WT group. Thus, this study provides evidence that podocyte-specific deletion of Rac1 results in morphological alteration in podocytes, and that the induction of apoptosis or decreased expression of the slit diaphragm proteins by hyperglycemic stimuli are associated with the progression of diabetic nephropathy.

Combination therapy with telmisartan and oxacalcitriol suppresses the progression of murine adriamycin nephropathy.

BACKGROUND: Blockade of the renin-angiotensin system plays a key role in suppressing the progression of renal diseases. It has not been well established whether this therapy provides additional effects when combined with vitamin D or its analog in a model of adriamycin (ADR)-induced nephropathy. METHODS: We evaluated the effect of an angiotensin II subtype 1 receptor blocker (telmisartan) combined with a vitamin D analog (oxacalcitriol) on mice ADR-induced nephropathy (9.5 mg/kg single intravenous injection). We also tested immortalized murine podocytes to examine the effects on podocyte apoptosis. RESULTS: Mice with ADR-induced nephropathy developed progressive albuminuria and glomerulosclerosis within 30 days accompanied by decreased expression of slit diaphragm (SD)-associated proteins (nephrin and podocin), reduced numbers of podocytes, and increased systolic blood pressure. Treatment with telmisartan or oxacalcitriol alone moderately ameliorated kidney injury. The combined treatment most effectively reduced the albuminuria and glomerulosclerosis. These effects were accompanied by the restoration of SD-associated proteins, reduction of podocyte apoptosis, and prevention of podocyte depletion in the glomeruli. Treatment with telmisartan, oxacalcitriol, and the combination therapy resulted in similar reductions in systolic blood pressure. In cultured murine podocytes, ADR stimulated the expression of Bax/Bcl-2 and apoptosis as determined by Hoechst 33342 staining. These changes were effectively inhibited by telmisartan or oxacalcitriol, but the combination treatment most effectively reduced these effects. CONCLUSIONS: These data demonstrated that application of a renin-angiotensin system blocker plus a vitamin D analog effectively prevented renal injury in ADR-induced nephropathy. The observed amelioration of renal injury may be partly attributable to antiapoptotic effects in podocytes.

Significance of urinary full-length megalin in patients with IgA nephropathy.

BACKGROUND AND OBJECTIVES: Megalin is highly expressed at the apical membranes of proximal tubular epithelial cells. A urinary full-length megalin (C-megalin) assay is linked to the severity of diabetic nephropathy in type 2 diabetes. This study examined the relationship between levels of urinary C-megalin and histological findings in adult patients with IgA nephropathy (IgAN). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Urine samples voided in the morning on the day of renal biopsy were obtained from 73 patients with IgAN (29 men and 44 women; mean age, 33 years) and 5 patients with membranous nephropathy (MN). Renal pathologic variables were analyzed using the Oxford classification of IgAN, the Shigematsu classification and the Clinical Guidelines of IgAN in Japan. The levels of urinary C-megalin were measured by sandwich ELISA. RESULTS: Histological analysis based on the Oxford classification revealed that the levels of urinary C-megalin were correlated with mesangial hypercellularity in IgAN patients (OR = 1.76, 95% CI: 1.04-3.27, P<0.05). There was a significant correlation between the levels of urinary C-megalin and the severity of chronic extracapillary abnormalities according to the Shigematsu classification in IgAN patients (ß = 0.33, P = 0.008). The levels of urinary C-megalin were significantly higher in all risk levels of IgAN patients requiring dialysis using the Clinical Guidelines of IgAN in Japan than in the control group. The levels of urinary C-megalin were significantly higher in the high risk and very high risk grades than in the low risk grade (P<0.05). The levels of urinary C-megalin were significantly higher in MN patients compared to the control group. CONCLUSIONS: The levels of urinary C-megalin are associated with histological abnormalities in adult IgAN patients. There is a possibility that urinary C-megalin is an independent predictor of disease progression of IgAN. In addition, our results suggest that urinary C-megalin is a marker of glomerular abnormalities in various glomerular diseases as well as IgAN.

Notch2 activation ameliorates nephrosis.

Activation of Notch1 and Notch2 has been recently implicated in human glomerular diseases. Here we show that Notch2 prevents podocyte loss and nephrosis. Administration of a Notch2 agonistic monoclonal antibody ameliorates proteinuria and glomerulosclerosis in a mouse model of nephrosis and focal segmental glomerulosclerosis. In vitro, the specific knockdown of Notch2 increases apoptosis in damaged podocytes, while Notch2 agonistic antibodies enhance activation of Akt and protect damaged podocytes from apoptosis. Treatment with triciribine, an inhibitor of Akt pathway, abolishes the protective effect of the Notch2 agonistic antibody. We find a positive linear correlation between the number of podocytes expressing activated Notch2 and the number of residual podocytes in human nephrotic specimens. Hence, specific activation of Notch2 rescues damaged podocytes and activating Notch2 may represent a novel clinical strategy for the amelioration of nephrosis and glomerulosclerosis.

Translocation of dendrin to the podocyte nucleus in acute glomerular injury in patients with IgA nephropathy.

BACKGROUND: It has been reported that podocytopenia has been occurring with increasing disease severity in patients with IgA nephropathy (IgAN). Dendrin is localized at the slit diaphragm (SD) in podocytes. We showed that dendrin translocates to the nucleus of injured podocytes in experimental nephritis and the nuclear dendrin promotes podocyte apoptosis. It is still unknown whether dendrin translocates from the SD to podocyte nucleus in IgAN. We investigated the presence of nuclear dendrin in patients with IgAN and the association between the translocated dendrin to the podocyte nucleus and disease activity. METHODS: Fourteen adult patients with IgAN were enrolled. The pathological parameters were analyzed. Immunostaining of renal biopsy specimens and urinary sediments from IgAN or minimal change nephrotic syndrome (MCNS) as the control was performed. RESULTS: A positive correlation was observed between an acute extracapillary change and the number of dendrin-positive nuclei. The location of dendrin in the nuclei was found in urinary podocytes of IgAN. The number of dendrin-positive nuclei in urinary podocytes of IgAN was significantly higher than that of MCNS. Urinary podocytes, which expressed the apoptosis marker annexin V, were also detected in IgAN. The translocation of dendrin to the podocyte nucleus as well as strong cathepsin L staining were detected in the glomeruli of IgAN. CONCLUSION: An increasing number of dendrin-positive nuclei in the glomeruli suggest acute glomerular injury in IgAN. Apoptotic podocytes were detectable in the urine of IgAN. It appears that the translocation of dendrin to the podocyte nuclei enhances podocyte apoptosis in acute glomerular injury and leads to podocytopenia in patients with IgAN.

Relationships between levels of urinary podocalyxin, number of urinary podocytes, and histologic injury in adult patients with IgA nephropathy.

BACKGROUND AND OBJECTIVES: Podocalyxin (PCX) is present on the apical cell membrane of podocytes and is shed in urine from injured podocytes. Urinary podocalyxin (u-PCX) is associated with severity of active glomerular injury in patients with glomerular diseases. This study examined the relationship between number of urinary podocytes, levels of u-PCX, and glomerular injury in adults with IgA nephropathy (IgAN). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Urine samples voided in the morning on the day of biopsy were obtained from 51 patients with IgAN (18 men and 33 women; mean age, 31 years). All renal biopsy specimens were analyzed histologically. Pathologic variables of IgAN were analyzed per Shigematsu classification, the Oxford classification of IgAN, and the Clinical Guidelines of IgAN in Japan. Levels of u-PCX were measured by sandwich ELISA. RESULTS: Histologic analysis based on Shigematsu classification revealed a significant correlation between levels of u-PCX and severity of acute extracapillary abnormalities (r=0.72; P<0.001), but levels of urinary protein excretion did not correlate with acute glomerular abnormalities. Levels of urinary protein excretion in patients with segmental sclerosis (n=19) were higher than in patients without (n=22) (0.49 [interquartile range (IQR), 0.20-0.88] g/g creatinine versus 0.20 [IQR, 0.10-0.33] g/g creatinine; P<0.01). The number of urinary podocytes in patients with segmental sclerosis was higher than in patients without (1.05 [IQR, 0.41-1.67] per mg creatinine versus 0.28 [IQR, 0.10-0.66] per mg creatinine; P<0.01). CONCLUSIONS: Levels of u-PCX and the number of urinary podocytes are associated with histologic abnormalities in adults with IgAN.

Effects of 22-oxa-calcitriol on podocyte injury in adriamycin-induced nephrosis.

BACKGROUND: In various animal studies, vitamin D has been shown to have a significant effect on reduction of proteinuria and the progression of kidney disease. However, little is known on its renoprotective effect in adriamycin (ADR)-induced nephrosis mice. The present study was intended to determine the therapeutic benefit of 22-oxa-calcitriol (OCT), a vitamin D analog, in reducing proteinuria and its renoprotective effect, i.e. preventing podocyte injury on ADR-induced nephrosis mice. METHODS: Three experimental groups were used as follows: (1) nephrosis mice, established by a single intravenous injection of ADR; (2) ADR+OCT mice, nephrosis mice treated with OCT, and (3) mice treated only with OCT as the control group. Podocyte injury was assessed by podocyte apoptosis using the TUNEL assay, podocyte counting, podocyte-specific expressed protein by immunofluorescence and Western blot analysis, and foot process effacement using electron microscopy. RESULTS: Lower proteinuria was observed in ADR+OCT mice. Improvement in glomerulosclerosis and interstitial fibrosis, and prevention of glomerular hyperfiltration were observed in ADR+OCT mice. Immunofluorescence and Western blot analyses showed restoration of downregulated expression of nephrin, CD2AP and podocin. Nevertheless, dendrin expression was not restored. An insignificant reduction in podocyte numbers was found in ADR+OCT mice. Complete foot process effacement was partially prevented in ADR+OCT mice. CONCLUSIONS: The results indicate that OCT reduces podocyte injury and has renoprotective effects in ADR nephrosis mice.

Dendrin location in podocytes is associated with disease progression in animal and human glomerulopathy.

BACKGROUND: Adriamycin (ADR) nephrosis in mice has been extensively studied and has enabled a greater understanding of the processes underlying the progression of renal injury. Dendrin is a novel component of the slit diaphragm with proapoptotic signaling properties, and it accumulates in the podocyte nucleus in response to glomerular injury in mice. The present study re-evaluated chronic progressive nephropathy in ADR mice and the localization of dendrin in mice and in human glomerulopathy. METHODS: To investigate the localization of dendrin, a mouse model of nephrosis and glomerulosclerosis was used, in which ADR was injected once. WT-1-positive cells and apoptotic cells were counted in vivo and in vitro. To check the expression of dendrin in ADR mice, immunostaining and Western blot were performed. A survey of dendrin staining was performed on human kidney biopsy specimens. RESULTS: The injection of ADR induced proteinuria, podocyte loss and glomerulosclerosis. It also caused the relocation of dendrin from the slit diaphragm to the podocyte nucleus. We demonstrated the location of dendrin to podocyte nuclei in several cases of human glomerulopathy. The mean occurrence of dendrin-positive nucleus per glomerulus increased in several cases of human glomerulopathy. CONCLUSIONS: These findings suggest that the relocation of dendrin to the podocyte nuclei is useful as a novel marker of podocyte injury in human glomerulopathy.

[A case report of segmental arterial mediolysis].

We report a case of 58-year-old woman with a ruptured dissecting aneurysm of the middle colic artery (MCA). Her initial manifestation was sudden and severe right-sided abdominal pain, followed by hemorrhagic shock and acute anemia. Abdominal CT showed a right retroperitoneal hemorrhage. Emergency catheter angiography and therapeutic coil embolization of the middle colic artery were performed and micro aneurysms were enhanced in the jejunal branch. Immunological tests showed nothing abnormal. Follow-up angiography after 3 months showed that the micro aneurysms had disappeared. The patient was diagnosed as having segmental arterial mediolysis (SAM), because no definitive evidence of atherosclerosis and polyarteritis nodosa were observed. SAM is a rare disease of unknown etiology. The arterial lesions developing in elderly patients are characterized by segmental lysis of the abdominal splanchnic arteries resulting in aneurysms, and acute bleeding in a skip pattern. Multiple aneurysms and abdominal pain due to the rupture of these lesions in SAM resemble the clinical findings in polyarteritis nodosa. Differential diagnosis of the two diseases is important because steroid therapy is not beneficial for SAM.