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.

P1446DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS IN PATIENTS UNDERGOING MAINTENANCE HEMODIALYSIS

Background and Aims

Diffuse idiopathic skeletal hyperostosis (DISH) is an idiopathic degenerative disease characterized by ossification of spinal ligaments and entheses, especially in the anterior longitudinal ligament. The ankylosed spine is prone to fracture with minor trauma and may result in spinal cord injury. It is usually asymptomatic and often diagnosed incidentally by computed tomography or other imaging methods. Several reports have revealed DISH as a risk factor for stroke, cardiovascular disease, and metabolic disorders, such as diabetes mellitus, hyperinsulinemia, obesity, dyslipidemia, and hyperuricemia. However, there are few reports of DISH in patients with end stage kidney disease (ESKD) requiring hemodialysis. Epidemiology, etiology and risk factors of DISH in patients with ESKD are unknown. We aimed to examine the prevalence and predictors of DISH in maintenance hemodialysis patients.

Method

This was a case-control study using patients who received maintenance hemodialysis in our hospital in December 2018. The prevalence of DISH at enrollment was evaluated according to Resnick and Niwayama criteria by computed tomography (CT). The criteria is defined as follows: (1) Flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies, (2) Relative preservation of intervertebral disc height in the involved segment, (3) Absence of apophyseal joint bony ankylosis and sacroiliac joint erosion. We excluded patients who could not receive chest CT or with a history of thoracic spine surgery. Fisher exact tests were used to evaluate the relationships between categorical variables, and Kruskal-Wallis or Mann-Whitney U tests were used to evaluate continuous variables. We performed logistic regression analyses to identify variables that had a statistically significant association with DISH, as measured by the estimated odds ratio (OR) with the 95% confidence interval (CI).

Results

A total of 395 consecutive patients were treated with maintenance hemodialysis in our hospital in December 2018. After excluding 4 patients who could not receive chest CT and 2 patients with a history of thoracic spine surgery, the remaining 389 patients were analyzed. The median age was 70 years, and 61.2% of patients were men. One hundred and twenty-three (31.6%) patients were diagnosed with DISH. We assigned them to the DISH group and other 266 patients to the control group. The patients with DISH were significantly more likely to have advanced age, male sex, high body weight, high bone mineral density, prior vertebral fracture, and diabetic nephropathy. Multivariate analysis showed that having DISH was significantly associated with advanced age (OR 1.06, 95%CI 1.03-1.09, P<0.001), high bone mineral density (OR1.02, 95%CI 1.00-1.03, P=0.03), prior vertebral fracture (OR3.22, 95%CI 1.23-8.41, P=0.017), diabetic nephropathy (OR 2.00, 1.03-3.90, P=0.041).

Conclusion

The prevalence of DISH in maintenance hemodialysis patients was high. Advanced age, male sex, high body weight, high bone mineral density, prior vertebral fracture, and diabetic nephropathy were identified as a risk factor for DISH. Physicians involved in hemodialysis treatment should be aware of the existence of DISH as one of the comorbidities in the elderly ESKD patients.

P1335MALNUTRITION, INFLAMMATION, AND ANEMIA SYNERGISTICALLY IMPACT VASCULAR ACCESS FAILURE IN PATIENTS WITH FIRST-TIME ARTERIOVENOUS FISTULA FORMATION

Background and Aims

There are several reports that the initial (within one year) failure of vascular access (VA) is 2–53% in several countries. Malnutrition alone, inflammation alone, and anemia alone are factors that have a well-known relationship to VA failure. We believe that the relationship of these risk factors to VA failure is a complex one. Therefore, we evaluated whether the addition of these factors had a synergistic impact on VA failure.

Method

This longitudinal cohort study sought to confirm the effects of malnutrition, inflammation, and anemia on VA failure. We included 177 patients with chronic kidney disease (CKD) with first-time arteriovenous fistulas who were treated from January 2013 to December 2017. VA failure was defined as a new onset of VA obstruction or the need for percutaneous transluminal angioplasty. Albumin (Alb), C-reactive protein (CRP), and hemoglobin (Hb) were studied as indicators for malnutrition, inflammation, and anemia, respectively. Each highest (CRP) or lowest (Alb and Hb) interquartile range (IQR) group was assigned 1 point (as a risk score). The cumulative VA failure rate was analyzed by the Kaplan-Meier method, which stratified the study cohort into four groups according to the risk scores (0–3). We assessed whether the lowest IQR group of Hb and Alb, and the highest IQR group of CRP were associated with VA failure. To determine this, we used a univariable Cox proportional hazards regression analysis to calculate the hazard ratio (HR) and its 95% confidence interval (CI). A multivariable Cox proportional hazards regression analysis was used to evaluate the association between the risk score and VA failure, with adjustment for age, sex, presence or absence of diabetes mellitus, value of calcium phosphate products, preoperative vein diameter, and intraoperative vascular assessment scores.

Results

The average observational period was 1.6±1.4 years. The incidence of VA failure was 30.5% (54 patients). Cumulative VA failure was significantly higher in patients who had more than two risk scores, as compared to the patients who did not have any risk score (Figure). The univariate Cox regression analysis showed that Alb, CRP, and Hb were significantly associated with VA failure (HR, 2.00; 95% CI, 1.08–3.71 for Alb and HR, 2.21; 95% CI, 1.15–4.13 for CRP and HR, 1.96; 95% CI, 1.02–3.63 for Hb), respectively. The presence of more than two risk scores was significantly associated with VA failure (HR, 4.68; 95% CI, 1.07–18.5 for the patients with two risk scores and HR, 4.72; 95% CI, 1.32–17.2 for the patients with three risk scores).

Conclusion

Malnutrition, inflammation, and anemia independently and synergistically affect VA failure. In clinical settings, we need to be aware of the presence of malnutrition, inflammation, and anemia to better prevent VA failure.

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.

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 KO^p°^d°^/p°^d°) using a podocin-Cre/loxP system and siRNA Sall1 knockdown (Sall1 KD) podocytes. Under physiological conditions, Sall1 KO^p°^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 KO^p°^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 KO^p°^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.

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 (β = 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.

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.