Decreased thymic output predicts progression of chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is age-related disease, and decreased renal function is associated with the premature aging of T cells and increased incidence of other age-related diseases. However, the relationship between T cell senescence and CKD progression remains unclear. Here, we investigated the relationship between T cell senescence, as indicated by decreased thymic output and increased proportion of highly differentiated CD28- T cells, and CKD progression. RESULTS: A total of 175 patients with non-dialysis-dependent CKD were enrolled in this study. Thymic output was assessed based on the CD45RA+CD31+CD4+ cell (recent thymic emigrant [RTE]) counts (RTEs) (/mm3) and the proportion of RTE among CD4+ T cells (RTE%). Highly differentiated T cells were assessed based on the proportion of CD28- cells among CD4+ T cells (CD28-/CD4+) and CD28- cells among CD8+ T cells (CD28-/CD8+). The primary outcome was estimated glomerular filtration rate (eGFR) decline of ≥40% or initiation of renal replacement therapy. The association between T cell senescence and renal outcomes was examined using Cox proportional hazards models and restricted cubic splines. The median age was 73 years, 33% were women, and the median eGFR was 26 mL/min/1.73 m2. The median RTEs, RTE%, CD28-/CD4+, and CD28-/CD8+ were 97.5/mm3, 16.2, 5.3, and 49.7%, respectively. After a median follow-up of 1.78 years, renal outcomes were observed in 71 patients. After adjusting for age, sex, eGFR, proteinuria, diabetes, and cytomegalovirus seropositivity, decreased RTEs, which corresponded to decreased thymic output, significantly and monotonically increased the risk of poor renal outcome (p = 0.04), and decreased RTE% and increased highly differentiated CD28-/CD4+ T cells also tended to monotonically increase the risk (p = 0.074 and p = 0.056, respectively), but not CD28-/CD8+ T cells. CONCLUSIONS: Decreased thymic output in CKD patients, as well as increased highly differentiated CD4+ T cells, predicted renal outcomes. Thus, the identification of patients prone to CKD progression using T cell senescence, particularly decreased RTE as a biomarker, may help to prevent progression to end-stage kidney disease.

Gitelman syndrome with a novel frameshift variant in SLC12A3 gene accompanied by chronic kidney disease and type 2 diabetes mellitus.

Gitelman syndrome is an autosomal recessive genetic disease caused by pathogenic variants in SLC12A3 resulting in the loss of function of the Na-Cl co-transporter (NCC) in the distal tubules. Hypokalemia and diuretic effects can cause secondary type 2 diabetes and renal function decline. Here, we present the case of a 49-year-old male patient with chronic persistent treatment-resistant hypokalemia for the past 13 years who had been receiving treatment for type 2 diabetes mellitus for 6 years. He was referred to our department due to the presence of urinary protein, impaired renal function, high renin activity, and hyperaldosteronism. Laboratory test results showed hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis. Using next-generation and Sanger sequencing, we identified a novel stop-gain variant (NM_000339.3:c.137del [p.His47fs]) and a missense variant (NM_000339.3:c.2927C > T [p.Ser976Phe]) in the SLC12A3 gene. This novel pathogenic variant was located at the intracellular N-terminus of the NCC. Based on these findings, the patient was diagnosed with Gitelman syndrome. The use of next-generation sequencing facilitated the exclusion of diseases with similar clinical symptoms.

Parathyroid hormone and premature thymus ageing in patients with chronic kidney disease.

Premature immune ageing, including thymic atrophy, is observed in patients with chronic kidney disease (CKD). Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23), which are mineral and bone disorder (MBD)-related factors, affect immune cells and possibly cause thymic atrophy. We examined the cross-sectional association between thymic atrophy, evaluated as the number of CD3+CD4+CD45RA+CD31+ cells [recent thymic emigrants (RTE)/µL], and MBD-related factors [(serum PTH, FGF23, and alkaline phosphatase (ALP) level] in 125 patients with non-dialysis dependent CKD. Median estimated glomerular filtration rate (eGFR) was 17 mL/min/1.73 m2. Older age (r = -0.46), male sex (r = -0.34), lower eGFR (r = 0.27), lower serum-corrected calcium (r = 0.27), higher PTH (r = -0.36), and higher ALP level (r = -0.20) were identified as determinants of lower number of RTE. In contrast, serum concentrations of FGF23 and phosphorus were not correlated with RTE. Multivariate non-linear regression analysis indicated a negative association between serum PTH and log-transformed RTE (P = 0.030, P for non-linearity = 0.124). However, the serum levels of FGF23 and ALP were not associated with RTE. In patients with CKD, serum PTH concentrations were related to thymic atrophy which contributes to immune abnormality.

Visualization of kidney fibrosis in diabetic nephropathy by long diffusion tensor imaging MRI with spin-echo sequence.

Renal fibrosis (RF) is an indicator for progression of chronic kidney disease (CKD). Although diabetic nephropathy (DN) is the leading cause of CKD and end-stage renal disease in Western populations, the ability of MRI to evaluate RF in DN patients has not been determined. As a first step to identify possible MRI methods for RF evaluation, we examined the use of diffusion tensor imaging (DTI) MRI to evaluate RF in a rat model of DN (SHR/NDmcr-cp(cp/cp): SHR/ND). The signal-to-noise ratio in DTI MRI was enhanced using a spin-echo sequence, and a special kidney attachment was developed for long-term stabilization. The changes in renal temperature and blood flow during measurement were minimal, suggesting the feasibility of this method. At 38 weeks of age, RF had aggressively accumulated in the outer stripe (OS) of the outer medulla. FA maps showed that this method was successful in visualizing and evaluating fibrosis in the OS of the SHR/ND rat kidney (r = 0.7697, P = 0.0126). Interestingly, in the FA color maps, the directions of water molecule diffusion in RF were random, but distinct from conventional water diffusion in brain neuron fibers. These findings indicate that DTI MRI may be able to evaluate RF in CKD by DN.

Azilsartan Improves Salt Sensitivity by Modulating the Proximal Tubular Na+-H+ Exchanger-3 in Mice.

A potent angiotensin II type-1 receptor blocker, azilsartan, has been reported to reduce blood pressure more effectively than candesartan. Interestingly, azilsartan can also restore the circadian rhythm of blood pressure. We hypothesized that azilsartan could also improve salt sensitivity; thus, we examined the effect of azilsartan on sodium handling in renal tubules. Subtotal nephrectomized C57BL/6 mice received azilsartan (1.0 mg/kg/day), candesartan (0.3 mg/kg/day), or vehicle via the oral route in conjunction with a normal- (0.3%) or high-salt (8.0%) diet. Two weeks later, the azilsartan group showed significantly lower blood pressure during the light period than the candesartan and vehicle groups (azilsartan: 103.1 ± 1.0; candesartan: 111.7 ± 2.7; vehicle: 125.5 ± 2.5 mmHg; P < 0.05; azilsartan or candesartan vs. vehicle). The azilsartan group also showed higher urinary fractional excretion of sodium during the dark period than the candesartan and vehicle groups (azilsartan: 21.37 ± 3.69%; candesartan: 14.17 ± 1.42%; vehicle: 13.85 ± 5.30%; P < 0.05 azilsartan vs. candesartan or vehicle). A pressure-natriuresis curve demonstrated that azilsartan treatment restored salt sensitivity. Immunofluorescence and western blotting showed lower levels of Na+-H+ exchanger-3 (NHE3) protein (the major sodium transporter in renal proximal tubules) in the azilsartan group, but not in the candesartan or vehicle groups. However, azilsartan did not affect NHE3 transcription levels. Interestingly, we did not observe increased expression of downstream sodium transporters, which would have compensated for the increased flow of sodium and water due to non-absorption by NHE3. We also confirmed the mechanism stated above using cultured opossum kidney proximal tubular cells. Results revealed that a proteasomal inhibitor (but not a lysosomal inhibitor) blocked the azilsartan-induced decrease in NHE3 protein expression, suggesting that azilsartan increases NHE3 ubiquitination. In conclusion, azilsartan (but not candesartan) improved salt sensitivity possibly by decreasing NHE3 expression via ubiquitin-proteasomal degradation.

Non-invasive magnetic resonance imaging in rats for prediction of the fate of grafted kidneys from cardiac death donors.

The main objective of this study was to assess cardiac death (CD) kidney grafts before transplantation to determine whether blood oxygen level-dependent (BOLD) and diffusion MRI techniques can predict damage to these grafts after transplantation. We assessed CD kidney tissue by BOLD and diffusion MRI. We also examined pathological and gene expression changes in CD kidney grafts before and after transplantation. Although there was significantly more red cell congestion (RCC) in the inner stripe of the outer medulla (IS) in both 1 h after cardiac death (CD1h) and CD2h kidneys destined for grafts before transplantation compared with CD0h (p<0.05), CD2h, but not CD1h, kidney grafts had significantly different RCC in the IS 2 days after transplantation (p<0.05). Consistent with these pathological findings, tissue plasminogen activator (tPA) gene expression was increased only in the cortex and medulla of CD2h kidney grafts after transplantation. BOLD MRI successfully and non-invasively imaged and quantified RCC in the IS in both CD1h and CD2h kidney grafts (p<0.05). Diffusion MRI also non-invasively assessed increased the apparent diffusion coefficient in the IS and decreased it in the outer stripe (OS) of CD2h grafts, in concordance with interstitial edema in the IS and tubule cellular edema in the OS. These two types of edema in the outer medulla could explain the prolonged RCC in the IS only of CD2h kidney grafts, creating part of a vicious cycle inhibiting red cells coming out of capillary vessels in the IS. Perfusion with University of Wisconsin solution before MRI measurements did not diminish the difference in tissue damage between CD1h and CD2h kidney grafts. BOLD and diffusion MRI, which are readily available non-invasive tools for evaluating CD kidney grafts tissue damage, can predict prolonged organ damage, and therefore the outcome, of transplanted CD kidney grafts.

Renal transplantations from parents to siblings with autosomal recessive Alport syndrome caused by a rearrangement in an intronic antisense Alu element in the COL4A3 gene led to different outcomes.

Two siblings with autosomal recessive Alport syndrome (ARAS) obtained renal transplants from their consanguineous parents. Their COL4A3 mRNA transcripts were disrupted by a 139 bp intronic sequence between exon 48 and 49, which was derived from an antisense Alu element in this intron. The new amino acid sequence from the cryptic exon was terminated by a stop codon at the 1511th codon, resulting in the loss of 76 % α3(IV)NC1. This is the first case report of kidney transplantations between ARAS-homozygous siblings and their heterozygous parents. The brother experienced acute rejection just after transplantation and post-transplantation anti-glomerular basement membrane (GBM) nephritis, whereas the sister has experienced no problems to date. The anti-GBM nephritis could have resulted from the acute rejection. The COL4A3 gene heterozygous mutated parents, who are possibly at risk for thin basement membrane disease, have maintained their renal functions without urinary abnormalities after renal transplantation to date.

[Clinical characteristics of five elderly patients with severe hypokalemia induced by glycyrrhizin derivatives].

Although hypokalemia is a common clinical problem, symptoms generally do not become manifest unless the serum potassium (K) falls rapidly. We encountered five cases with symptomatic severe hypokalemia (K<2.0 mEq/L) hospitalized for the past 15 months at our hospital. We examined the clinical characteristics and treatment of these patients. All five patients were women, and their mean age was 77.8 (73-82)years. They suffered from hypertension. Mean K level at admission was 1.66 (1.4-1.9) mEq/L and HCO3(-) was 48.3 (33.6-56.1) mmol/L. Plasma aldosterone level was low and plasma rennin activity was suppressed. All patients developed progressive muscle weakness with elevated creatinine phosphokinase. Three of the patients had received Chinese medicine which contained licorice, one received glycyrrhizin and the other one had received both. We diagnosed these cases as pseudoaldosteronism induced by glycyrrhizin. With discontinuation of the drugs and intravenous as well as oral K supplementation, serum K were normalized and clinical symptoms improved within 12 days. For one patient who developed cardiac dysfunction, concentrated K solution (230 mEq/L) was infused into the central vein. These findings show that glycyrrhizin ingestion should be kept in mind as a cause of an extreme degree of an hypokalemia, especially in elderly patients.

[Plasma B-type natriuretic peptide level predicts the renal outcome in patients with chronic kidney disease].

PURPOSE: Elevation of the plasma level of B-type natriuretic peptide (BNP) is commonly seen in patients with chronic kidney disease (CKD), but its significance remains unclarified. We conducted a prospective study to evaluate the role of plasma BNP level as a predictive marker of renal outcome. METHODS: 237 patients with CKD stage 3, 4 not on dialysis were prospectively enrolled as a hospital cohort from August 2004 to December 2008. Combined renal endpoint was doubling of baseline serum creatinine or end-stage renal disease requiring dialysis. Endpoint free renal survival was calculated by Kaplan Meier analysis and compared by the log-rank test. We used Cox proportional hazards analysis to determine the independent predictor for renal outcome among the clinical data at the time of referral to a nephrologist. ROC analysis was used to determine the best cut-off value of plasma BNP level to predict the renal outcome. RESULTS: The mean follow-up period was 2.5 +/- 1.1 years. Median age was 65 years. Of the subjects, 65.8% were men and 37.9% had diabetes mellitus. Median serum creatinine level was 2.7 mg/dL. Plasma BNP level was significantly higher among 147 patients who reached the combined renal endpoint compared with 90 patients who did not (116.0 pg/mL vs 54.5 pg/mL, p<0.001). After adjustment with other established predictive factors of renal outcome, plasma BNP level was selected to be the strongest predictive marker for renal endpoint (Hazard ratio 1.173, 95%CI 1.000-1.376). The optimal cut-off value of plasma BNP level suggested by ROC analysis was 69.5 pg/mL. Patients with a plasma BNP level above the cut-off point revealed a significantly poor renal outcome compared with those with a plasma BNP level below the cut-off point. CONCLUSIONS: The present study suggests that the plasma BNP level might be a predictive marker for renal outcome and a guide for management of cardio-renal interaction.

[Case of scleroderma with rapid progressive glomerulonephritis associated with both MPO-ANCA and anti-GBM antibodies].

A 66-year-old male with scleroderma developed rapidly progressive glomerulonephritis (RPGN). Renal pathology revealed crescentic glomerulonephritis with interstitial inflammation and fibrosis. Immunofluorescent micrography showed linear deposition of IgG along the glomerular capillary wall. Both anti-glomerular basement membrane antibody (anti-GBM Ab), and myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) were detected by an enzyme-linked immunosorbent assay (ELISA). These findings were compatible with ANCA-related vasculitis and anti-GBM Ab nephritis. Laboratory findings showed rapid elevation of the serum creatinine level (5.9 mg/dL), and a high titer of MPO-ANCA (530 EU) and anti-GBM Ab (21 EU). He was started on methylprednisolone pulse therapy and temporary hemodialysis. Since the immunosuppressive therapy lowered both antibody titers steadily and improved renal function, hemodialysis was discontinued 4 weeks after the therapy. It has been reported that some scleroderma patients developed rapid progressive glomerulonephritis due to ANCA-associated vasculitis in addition to the typical scleroderma renal crisis. There have been few reports of a scleroderma patient associated with RPGN, in whom both MPO-ANCA and anti GBM antibodies were detected.