Cryo-EM structures elucidate the multiligand receptor nature of megalin.

Megalin (low-density lipoprotein receptor-related protein 2) is a giant glycoprotein of about 600 kDa, mediating the endocytosis of more than 60 ligands, including those of proteins, peptides, and drug compounds [S. Goto, M. Hosojima, H. Kabasawa, A. Saito, Int. J. Biochem. Cell Biol. 157, 106393 (2023)]. It is expressed predominantly in renal proximal tubule epithelial cells, as well as in the brain, lungs, eyes, inner ear, thyroid gland, and placenta. Megalin is also known to mediate the endocytosis of toxic compounds, particularly those that cause renal and hearing disorders [Y. Hori et al., J. Am. Soc. Nephrol. 28, 1783-1791 (2017)]. Genetic megalin deficiency causes Donnai-Barrow syndrome/facio-oculo-acoustico-renal syndrome in humans. However, it is not known how megalin interacts with such a wide variety of ligands and plays pathological roles in various organs. In this study, we elucidated the dimeric architecture of megalin, purified from rat kidneys, using cryoelectron microscopy. The maps revealed the densities of endogenous ligands bound to various regions throughout the dimer, elucidating the multiligand receptor nature of megalin. We also determined the structure of megalin in complex with receptor-associated protein, a molecular chaperone for megalin. The results will facilitate further studies on the pathophysiology of megalin-dependent multiligand endocytic pathways in multiple organs and will also be useful for the development of megalin-targeted drugs for renal and hearing disorders, Alzheimer's disease [B. V. Zlokovic et al., Proc. Natl. Acad. Sci. U.S.A. 93, 4229-4234 (1996)], and other illnesses.

Megalin-related mechanism of hemolysis-induced acute kidney injury and the therapeutic strategy.

Hemolysis-induced acute kidney injury (AKI) is attributed to heme-mediated proximal tubule epithelial cell (PTEC) injury and tubular cast formation due to intratubular protein condensation. Megalin is a multiligand endocytic receptor for proteins, peptides, and drugs in PTECs and mediates the uptake of free hemoglobin and the heme-scavenging protein α1-microglobulin. However, understanding of how megalin is involved in the development of hemolysis-induced AKI remains elusive. Here, we investigated the megalin-related pathogenesis of hemolysis-induced AKI and a therapeutic strategy using cilastatin, a megalin blocker. A phenylhydrazine-induced hemolysis model developed in kidney-specific mosaic megalin knockout (MegKO) mice confirmed megalin-dependent PTEC injury revealed by the co-expression of kidney injury molecule-1 (KIM-1). In the hemolysis model in kidney-specific conditional MegKO mice, the uptake of hemoglobin and α1-microglobulin as well as KIM-1 expression in PTECs was suppressed, but tubular cast formation was augmented, likely due to the nonselective inhibition of protein reabsorption in PTECs. Quartz crystal microbalance analysis revealed that cilastatin suppressed the binding of megalin with hemoglobin and α1-microglobulin. Cilastatin also inhibited the specific uptake of fluorescent hemoglobin by megalin-expressing rat yolk sac tumor-derived L2 cells. In a mouse model of hemolysis-induced AKI, repeated cilastatin administration suppressed PTEC injury by inhibiting the uptake of hemoglobin and α1-microglobulin and also prevented cast formation. Hemopexin, another heme-scavenging protein, was also found to be a novel ligand of megalin, and its binding to megalin and uptake by PTECs in the hemolysis model were suppressed by cilastatin. Mass spectrometry-based semiquantitative analysis of urinary proteins in cilastatin-treated C57BL/6J mice indicated that cilastatin suppressed the reabsorption of a limited number of megalin ligands in PTECs, including α1-microglobulin and hemopexin. Collectively, cilastatin-mediated selective megalin blockade is an effective therapeutic strategy to prevent both heme-mediated PTEC injury and cast formation in hemolysis-induced AKI. © 2024 The Pathological Society of Great Britain and Ireland.

The structure of the rat vitamin B12 transporter TC and its complex with glutathionylcobalamin.

Vitamin B12 (cobalamin or Cbl) functions as a cofactor in two important enzymatic processes in human cells, and life is not sustainable without it. B12 is obtained from food and travels from the stomach, through the intestine, and into the bloodstream by three B12-transporting proteins: salivary haptocorrin (HC), gastric intrinsic factor, and transcobalamin (TC), which all bind B12 with high affinity and require proteolytic degradation to liberate Cbl. After intracellular delivery of dietary B12, Cbl in the aquo/hydroxocobalamin form can coordinate various nucleophiles, for example, GSH, giving rise to glutathionylcobalamin (GSCbl), a naturally occurring form of vitamin B12. Currently, there is no data showing whether GSCbl is recognized and transported in the human body. Our crystallographic data shows for the first time the complex between a vitamin B12 transporter and GSCbl, which compared to aquo/hydroxocobalamin, binds TC equally well. Furthermore, sequence analysis and structural comparisons show that TC recognizes and transports GSCbl and that the residues involved are conserved among TCs from different organisms. Interestingly, haptocorrin and intrinsic factor are not structurally tailored to bind GSCbl. This study provides new insights into the interactions between TC and Cbl.

Defective C3d caused by C3 p.W1034R in inherited atypical hemolytic uremic syndrome.

INTRODUCTION: Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy. Personal genome analyses have revealed numerous aHUS-causing variants, mainly complement-related genes. However, not all aHUS-causing variants have been functionally validated. METHODS: An exome sequence analysis of a Japanese multiplex family composed of three patients diagnosed with aHUS in infancy and showing frequent relapses clustered in a dominant transmission mode was performed. Protein interaction between the C3d and C-terminal domains of factor H was analyzed using a quartz crystal microbalance. RESULTS: Following filtering by heterozygous variants, amino acid substitutions, and allele frequency, the analysis revealed eight rare variants shared by the affected individuals. Variant prioritization listed C3 p.W1034R as the most likely candidate gene mutation in the affected individuals, despite being classified as a variant of uncertain significance. Binding of recombinant C3d harboring 1034R to recombinant short consensus repeats 15 to 20 of factor H was significantly suppressed compared with that of C3 with 1034W. CONCLUSION: C3 p.W1034R results in an inherited form of aHUS that often presents with recurrent episodes, possibly because of impaired interactions between the C3d and C-terminal domains of factor H. Following comprehensive genomic analysis, functional validation of C3 p.W1034R strengthens the molecular basis for aHUS pathophysiology.

Megalin is involved in angiotensinogen-induced, angiotensin II-mediated ERK1/2 signaling to activate Na + -H + exchanger 3 in proximal tubules.

BACKGROUND: Kidney angiotensin (Ang) II is produced mainly from liver-derived, glomerular-filtered angiotensinogen (AGT). Podocyte injury has been reported to increase the kidney Ang II content and induce Na + retention depending on the function of megalin, a proximal tubular endocytosis receptor. However, how megalin regulates the renal content and action of Ang II remains elusive. METHODS: We used a mass spectrometry-based, parallel reaction-monitoring assay to quantitate Ang II in plasma, urine, and kidney homogenate of kidney-specific conditional megalin knockout (MegKO) and control (Ctl) mice. We also evaluated the pathophysiological changes in both mouse genotypes under the basal condition and under the condition of increased glomerular filtration of AGT induced by administration of recombinant mouse AGT (rec-mAGT). RESULTS: Under the basal condition, plasma and kidney Ang II levels were comparable in the two mouse groups. Ang II was detected abundantly in fresh spot urine in conditional MegKO mice. Megalin was also found to mediate the uptake of intravenously administered fluorescent Ang II by PTECs. Administration of rec-mAGT increased kidney Ang II, exerted renal extracellular signal-regulated kinase 1/2 (ERK1/2) signaling, activated proximal tubular Na + -H + exchanger 3 (NHE3), and decreased urinary Na + excretion in Ctl mice, whereas these changes were suppressed but urinary Ang II was increased in conditional MegKO mice. CONCLUSION: Increased glomerular filtration of AGT is likely to augment Ang II production in the proximal tubular lumen. Thus, megalin-dependent Ang II uptake should be involved in the ERK1/2 signaling that activates proximal tubular NHE3 in vivo , thereby causing Na + retention.

The endocytosis receptor megalin: From bench to bedside.

The large (∼600 kDa) endocytosis receptor megalin/low-density lipoprotein receptor-related protein 2 is highly expressed at the apical membrane of proximal tubular epithelial cells (PTECs). Megalin plays an important role in the endocytosis of various ligands via interactions with intracellular adaptor proteins, which mediate the trafficking of megalin in PTECs. Megalin mediates the retrieval of essential substances, including carrier-bound vitamins and elements, and impairment of the endocytic process may result in the loss of those substances. In addition, megalin reabsorbs nephrotoxic substances such as antimicrobial (colistin, vancomycin, and gentamicin) or anticancer (cisplatin) drugs and advanced glycation end product-modified or fatty acid-containing albumin. The megalin-mediated uptake of these nephrotoxic ligands causes metabolic overload in PTECs and leads to kidney injury. Blockade or suppression of the megalin-mediated endocytosis of nephrotoxic substances may represent a novel therapeutic strategy for drug-induced nephrotoxicity or metabolic kidney disease. Megalin reabsorbs urinary biomarker proteins such as albumin, α1-microglobulin, ß2-microglobulin, and liver-type fatty acid-binding protein; thus, the above-mentioned megalin-targeted therapy may have an effect on the urinary excretion of these biomarkers. We have previously established a sandwich enzyme-linked immunosorbent assay to measure the ectodomain (A-megalin) and full-length (C-megalin) forms of urinary megalin using monoclonal antibodies against the amino- and carboxyl-terminals of megalin, respectively, and reported their clinical usefulness. In addition, there have been reports of patients with novel pathological anti-brush border autoantibodies targeting megalin in the kidney. Even with these breakthroughs in the characterization of megalin, a large number of issues remain to be addressed in future research.

Urinary A- and C-megalin predict progression of diabetic kidney disease: an exploratory retrospective cohort study.

AIMS: Megalin, a proximal tubular endocytosis receptor, is excreted in urine in two forms: ectodomain (A-megalin) and full-length (C-megalin). We explored whether urinary megalin levels can be used as independent prognostic biomarkers in the progression of diabetic kidney disease (DKD). METHODS: The associations between baseline urinary A-megalin/creatinine (Cr) and/or C-megalin/Cr levels and the subsequent estimated glomerular filtration rate (eGFR) slope were analyzed using a generalized estimating equation. Patients were categorized into higher or lower groups based on the optimal cutoff values, obtained from a receiver operating characteristic curve, of the two forms of urinary megalin. RESULTS: We retrospectively analyzed 188 patients with type 2 diabetes. The eGFR slopes of the higher A-megalin/Cr and higher C-megalin/Cr groups were - 0.904 and -0.749 ml/min/1.73 m2/year steeper than those of the lower groups, respectively. Moreover, the eGFR slope was -1.888 ml/min/1.73 m2/year steeper in the group with both higher A- and higher C-megalin/Cr than in the other group. These results remained significant when adjusted for known urinary biomarkers (albumin, α1-microglobulin, ß2-microglobulin, and N-acetyl-ß-d-glucosaminidase). CONCLUSIONS: Urinary A- and C-megalin/Cr levels are likely to be prognostic biomarkers in the progression of DKD independent of other urinary biomarkers.

Urinary FABP1 is a biomarker for impaired proximal tubular protein reabsorption and is synergistically enhanced by concurrent liver injury.

Urinary fatty acid binding protein 1 (FABP1, also known as liver-type FABP) has been implicated as a biomarker of acute kidney injury (AKI) in humans. However, the precise biological mechanisms underlying its elevation remain elusive. Here, we show that urinary FABP1 primarily reflects impaired protein reabsorption in proximal tubule epithelial cells (PTECs). Bilateral nephrectomy resulted in a marked increase in serum FABP1 levels, suggesting that the kidney is an essential organ for removing serum FABP1. Injected recombinant FABP1 was filtered through the glomeruli and robustly reabsorbed via the apical membrane of PTECs. Urinary FABP1 was significantly elevated in mice devoid of megalin, a giant endocytic receptor for protein reabsorption. Elevation of urinary FABP1 was also observed in patients with Dent disease, a rare genetic disease characterized by defective megalin function in PTECs. Urinary FABP1 levels were exponentially increased following acetaminophen overdose, with both nephrotoxicity and hepatotoxicity observed. FABP1-deficient mice with liver-specific overexpression of FABP1 showed a massive increase in urinary FABP1 levels upon acetaminophen injection, indicating that urinary FABP1 is liver-derived. Lastly, we employed transgenic mice expressing diphtheria toxin receptor (DT-R) either in a hepatocyte- or in a PTEC-specific manner, or both. Upon administration of diphtheria toxin (DT), massive excretion of urinary FABP1 was induced in mice with both kidney and liver injury, while mice with either injury type showed marginal excretion. Collectively, our data demonstrated that intact PTECs have a considerable capacity to reabsorb liver-derived FABP1 through a megalin-mediated mechanism. Thus, urinary FABP1, which is synergistically enhanced by concurrent liver injury, is a biomarker for impaired protein reabsorption in AKI. These findings address the use of urinary FABP1 as a biomarker of histologically injured PTECs that secrete FABP1 into primary urine, and suggest the use of this biomarker to simultaneously monitor impaired tubular reabsorption and liver function. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Combination therapy of cisplatin with cilastatin enables an increased dose of cisplatin, enhancing its antitumor effect by suppression of nephrotoxicity.

Cisplatin, one of the most active anticancer agents, is widely used in standard chemotherapy for various cancers. Cisplatin is more poorly tolerated than other chemotherapeutic drugs, and the main dose-limiting toxicity of cisplatin is its nephrotoxicity, which is dose-dependent. Although less toxic methods of cisplatin administration have been established, cisplatin-induced nephrotoxicity remains an unsolved problem. Megalin is an endocytic receptor expressed at the apical membrane of proximal tubules. We previously demonstrated that nephrotoxic drugs, including cisplatin, are reabsorbed through megalin and cause proximal tubular cell injury. We further found that cilastatin blocked the binding of cisplatin to megalin in vitro. In this study, we investigated whether cilastatin could reduce cisplatin-induced nephrotoxicity without influencing the antitumor effects of cisplatin. Nephrotoxicity was decreased or absent in mice treated with cisplatin and cilastatin, as determined by kidney injury molecule-1 staining and the blood urea nitrogen content. Combined with cilastatin, a twofold dose of cisplatin was used to successfully treat the mice, which enhanced the antitumor effects of cisplatin but reduced its nephrotoxicity. These findings suggest that we can increase the dose of cisplatin when combined with cilastatin and improve the outcome of cancer patients.

Low bone mineral density due to secondary hyperparathyroidism in the GlatmTg(CAG-A4GALT) mouse model of Fabry disease.

Low bone mineral density (BMD)-diagnosed as osteoporosis or osteopenia-has been reported as a new characteristic feature of Fabry disease; however, the mechanism underlying the development of low BMD is unknown. We previously revealed that a mouse model of Fabry disease [GlatmTg(CAG-A4GALT)] exhibits impaired functioning of medullary thick ascending limb (mTAL), leading to insufficient Ca2+ reabsorption and hypercalciuria. Here, we investigated bone metabolism in GlatmTg(CAG-A4GALT) mice without marked glomerular or proximal tubular damage. Low BMD was detected by 20 weeks of age via micro-X-ray-computed tomography. Bone histomorphometry revealed that low BMD results by accelerated bone resorption and osteomalacia. Plasma parathyroid hormone levels increased in response to low blood Ca2+-not plasma fibroblast growth factor 23 (FGF-23) elevation-by 5 weeks of age and showed progressively increased phosphaturic action. Secondary hyperparathyroidism developed by 20 weeks of age and caused hyperphosphatemia, which increased plasma FGF-23 levels with phosphaturic action. The expression of 1α-hydroxylase [synthesis of 1α,25(OH)2D3] in the kidney did not decrease, but that of 24-hydroxylase [degradation of 1α,25(OH)2D3] decreased. Vitamin D deficiency was ruled out as the cause of osteomalacia, as plasma 1α,25(OH)2D3 and 25(OH)D3 levels were maintained. Results demonstrate that secondary hyperparathyroidism due to mTAL impairment causes accelerated bone resorption and osteomalacia due to hyperphosphaturia and hypercalciuria, leading to low BMD in Fabry model mice.

Rice Endosperm Protein Administration to Juvenile Mice Regulates Gut Microbiota and Suppresses the Development of High-Fat Diet-Induced Obesity and Related Disorders in Adulthood.

Obesity and related disorders, which are increasing in adults worldwide, are closely linked to childhood diet and are associated with chronic inflammation. Rice endosperm protein (REP) intake during adulthood has been reported to improve lipid metabolism and suppress the progression of diabetic kidney disease in animal models. However, the effects of REP intake during childhood on adulthood health are unclear. Therefore, we used a mouse model to experimentally investigate the preconditioning effects of REP intake during childhood on the development of obesity and related disorders in adulthood. Male C57BL/6J mice were pair-fed a normal-fat diet containing casein or REP during the juvenile period and then a high-fat diet (HFD) containing casein or REP during adulthood. Mice fed REP during the juvenile period showed better body weight, blood pressure, serum lipid profiles, lipopolysaccharide (LPS)-binding protein levels, and glucose tolerance in adulthood than those fed casein during the juvenile period. HFD-induced renal tubulo-glomerular alterations and hepatic microvesicular steatosis were less evident in REP-fed mice than in casein-fed ones. REP intake during the juvenile period improved HFD-induced dysbiosis (i.e., Escherichia genus proliferation and reduced gut microbiota diversity), thereby suppressing endotoxin-related chronic inflammation. Indeed, REP-derived peptides showed antibacterial activity against Escherichia coli, a major producer of LPS. In conclusion, REP supplementation during the juvenile period may regulate the gut microbiota and thus suppress the development of obesity and related disorders in adulthood in mice.

Exocytosis-Mediated Urinary Full-Length Megalin Excretion Is Linked With the Pathogenesis of Diabetic Nephropathy.

Efficient biomarkers for diabetic nephropathy (DN) have not been established. Using ELISA, we found previously that urinary levels of full-length megalin (C-megalin), a multiligand endocytic receptor in proximal tubules, was positively correlated with DN progression in patients with type 2 diabetes mellitus (T2DM). Here, we found that urinary extracellular vesicle (UEV) excretion and C-megalin content in UEVs or in their exosomal fraction increased along with the progression of the albuminuric stages in patients with T2DM. Cultured immortalized rat proximal tubule cells (IRPTCs) treated with fatty acid-free BSA or advanced glycation end product-modified BSA (AGE-BSA), endocytic ligands of megalin, increased EV excretion, and their C-megalin content. C-megalin excretion from IRPTCs via extracellular vesicles was significantly blocked by an exosome-specific inhibitor, GW4869, indicating that this excretion is mainly exocytosis-mediated. AGE-BSA treatment of IRPTCs caused apparent lysosomal dysfunction, which stimulated multivesicular body formation, resulting in increased exosomal C-megalin excretion. In a high-fat diet-induced, megalin-mediated kidney injury model in mice, urinary C-megalin excretion also increased via UEVs. Collectively, exocytosis-mediated urinary C-megalin excretion is associated with the development and progression of DN in patients with T2DM, particularly due to megalin-mediated lysosomal dysfunction in proximal tubules, and hence it could be a candidate biomarker linked with DN pathogenesis.

Megalin Blockade with Cilastatin Suppresses Drug-Induced Nephrotoxicity.

Nephrotoxicity induced by antimicrobial or anticancer drugs is a serious clinical problem. Megalin, an endocytic receptor expressed at the apical membranes of proximal tubules, mediates the nephrotoxicity of aminoglycosides and colistin, key antimicrobials for multidrug-resistant organisms. The mechanisms underlying the nephrotoxicity induced by vancomycin, an antimicrobial for methicillin-resistant Staphylococcus aureus, and cisplatin, an important anticancer drug, are unknown, although the nephrotoxicity of these drugs and gentamicin, an aminoglycoside, is suppressed experimentally with cilastatin. In the clinical setting, cilastatin has been used safely to suppress dehydropeptidase-I-mediated renal metabolism of imipenem, a carbapenem antimicrobial, and thereby limit tubular injury. Here, we tested the hypothesis that cilastatin also blocks megalin-mediated uptake of vancomycin, cisplatin, colistin, and aminoglycosides, thereby limiting the nephrotoxicity of these drugs. Quartz crystal microbalance analysis showed that megalin also binds vancomycin and cisplatin and that cilastatin competes with megalin for binding to gentamicin, colistin, vancomycin, and cisplatin. In kidney-specific mosaic megalin knockout mice treated with colistin, vancomycin, or cisplatin, the megalin-replete proximal tubule epithelial cells exhibited signs of injury, whereas the megalin-deficient cells did not. Furthermore, concomitant cilastatin administration suppressed colistin-induced nephrotoxicity in C57BL/6J mice. Notably, cilastatin did not inhibit the antibacterial activity of gentamicin, colistin, or vancomycin in vitro, just as cilastatin did not affect the anticancer activity of cisplatin in previous studies. In conclusion, megalin blockade with cilastatin efficiently suppresses the nephrotoxicity induced by gentamicin, colistin, vancomycin, or cisplatin. Cilastatin may be a promising agent for inhibiting various forms of drug-induced nephrotoxicity mediated via megalin in the clinical setting.

Differences in the adsorption of nafamostat mesilate between polyester-polymer alloy and polysulfone membranes.

We previously experienced severe clot formation in a polyester-polymer alloy (PEPA) dialyzer and hemodialysis (HD) circuit with nafamostat mesilate (NM) as an anticoagulant. The possibility of NM adsorption to the PEPA membrane was taken into consideration, but there was not enough information. In the present study, we evaluated differences in the adsorption of NM between a PEPA membrane (FDX-120 GW, Nikkiso, Tokyo, Japan) and two different polysulfone membranes (FX-140, Fresenius Medical Care, Tokyo, Japan; NV-15U, Toray Medical, Tokyo, Japan). We calculated the NM concentration by measuring absorbance at 241 nm using a spectrometer. NM adsorption was evaluated in three ways. First, we evaluated NM adsorption to hollow fibers. Then, we passed an NM solution through dialyzers and evaluated its adsorption in a single-pass examination. Finally, we circulated an NM solution in an HD circuit using a blood pump and evaluated NM adsorption. In all the experiments, NM adsorption to the PEPA membrane was greater than that to the polysulfone membranes examined. In the blood pump experiment, the estimated adsorption quantities of NM to the PEPA membrane and the FX-140 and NV-15U polysulfone membranes were 12.0 ± 0.1, 1.0 ± 0.1, and 4.1 ± 0.4 mg/m2, respectively. NM adsorption was confirmed, especially in the early phase, and the PEPA membrane adsorbed greater amounts of NM than the polysulfone membranes. We should pay attention to the choice of dialyzer as well as the appropriate dose of NM administration during the preparation of HD circuits.

[A case of rapidly progressive glomerulonephritis exhibiting granulomatosis with polyangiitis (GPA) and extremely high level of PR3-ANCA with improvement of renal dysfunction after plasma exchange therapy].

A 68-year-old Japanese man was diagnosed with left otitis media with effusion and left uveitis more than 5 months before admission. He was urgently admitted to our hospital for progressive deterioration of his renal function [serum creatinine(Cr) 7.59 mg/dL] with proteinuria and urinary red blood cell casts, inflammation, and anemia. Additionally, his serum proteinase 3 antinuclear antibody (PR3-ANCA) level, determined by using the chemiluminescence enzyme immunoassay method, had increased to more than 3,500 U/mL. Hemodialysis (HD) was initiated on the third day after admission and renal biopsy was performed on the eighth day. The histological findings showed necrotic cellar crescents, hence, he was diagnosed as granulomatosis with polyangiitis on the basis of the clinical criteria. Methylprednisolone pulse therapy was administered from the 11th day. Thereafter, the administration of oral prednisolone (PSL) was started, and plasma exchange was initiated for the purpose of RP3-ANCA removal. In his clinical course, PSL was tapered as soon as possible because of the development of steroid psychosis, and we started intravenous cyclophosphamide on the 25th day instead of tapering the PSL. Subsequently, his renal function improved even without HD, and he was discharged on the 49th day. Although his PR3-ANCA level was still high after discharge, the administration of azathioprine led to a decrease in the PR-3 ANCA levels. About 2 years after discharge, the PR3-ANCA level decreased to 10.0 U/mL, and there has been no sign of GPA recurrence.

Non-Classic Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency that Developed into Symptomatic Severe Hyponatremia.

A 78-year-old woman diagnosed with non-classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency had been under glucocorticoid replacement therapy since the age of 17 years. After several weeks of suffering from gastroenteritis with vomiting, she presented with disturbance of consciousness, hypotension, dehydration, and severe hyponatremia (108 mEq/L) and a markedly increased serum vasopressin concentration (45.5 pg/mL). She regained consciousness after correcting her body-fluid balance with hypertonic saline and intravenous hydrocortisone sodium therapy. Her hyponatremia was likely caused by extra-renal sodium loss and impaired water excretion induced by an increase of serum vasopressin due to volume depletion and glucocorticoid deficiency.

Factors affecting cerebral oxygenation in hemodialysis patients: cerebral oxygenation associates with pH, hemodialysis duration, serum albumin concentration, and diabetes mellitus.

BACKGROUND: Patients undergoing hemodialysis (HD) often develop cerebral disease complications. Furthermore, cerebral regional saturation of oxygen (rSO2) was previously reported to be significantly lower in HD patients than in healthy subjects. We aimed to identify the factors affecting the cerebral rSO2 in HD patients. METHODS: Fifty-four HD patients (38 men and 16 women; mean age, 67.7 ± 1.2 years, HD duration, 6.5 ± 1.9 years) were recruited. Cerebral rSO2 was monitored at the forehead before HD using an INVOS 5100C (Covidien Japan, Tokyo, Japan). RESULTS: The rSO2 levels were significantly lower in HD patients compared with healthy controls (49.5 ± 1.7% vs. 68.9 ± 1.6%, p <0.001). Multiple regression analysis showed that cerebral rSO2 independently associated with pH (standardized coefficient: -0.35), HD duration (standardized coefficient: -0.33), and serum albumin concentration (standardized coefficient: 0.28). Furthermore, the rSO2 was significantly lower in HD patients with diabetes mellitus (DM), compared with patients without DM (46.8 ± 1.7% vs. 52.1 ± 1.8%, p <0.05). CONCLUSIONS: In HD patients, cerebral rSO2 was affected by multiple factors, including pH, HD duration, and serum albumin concentration. Furthermore, this is the first report describing significantly lower levels of rSO2 in HD patients with DM than in those without DM.

A Higher Cardiothoracic Ratio Is Associated with 2-Year Mortality after Hemodialysis Initiation.

UNLABELLED: A high cardiothoracic ratio (CTR) is indicative of a cardiac disorder. However, few reports have revealed an association between the CTR and mortality in patients starting hemodialysis (HD). METHODS: Patients with HD initiation (n = 387; mean age, 66.7 ± 12.7 years) were divided into the following three groups according to their CTR at HD initiation: CTR <50%, 50% ≤ CTR < 55%, and CTR ≥55%. Kaplan-Meier analysis was performed to compare 2-year all-cause mortality among these groups. Furthermore, we investigated the factors affecting their 2-year mortality using a Cox proportional hazard regression analysis. RESULTS: Sixty-five patients (17%) died within 2 years after HD initiation. Kaplan-Meier analysis showed that patients with CTR ≥55% had a higher mortality rate than those in the other groups. Cox proportional hazard regression analysis was performed using parameters with p values <0.1 among these three groups [sex, age, presence or absence of ischemic heart disease, hemoglobin levels, serum albumin levels, CTR, body mass index (BMI)] and confounding factors [presence or absence of diabetes mellitus, and estimated glomerular filtration rate (eGFR)]. Age, eGFR, BMI, and CTR ≥55% at HD initiation were identified as factors influencing 2-year mortality. CONCLUSION: CTR >55% is one of the most important independent factors to affect 2-year all-cause mortality. Thus, confirming the cardiac condition of patients at HD initiation with a CTR >55% may improve their survival.

Effectiveness of plasma exchange for acquired type A hemophilia.

An 80-year-old man was treated at our hospital for chronic kidney disease, diabetes mellitus and hypertension. He presented a bleeding tendency over the past several weeks. When he was admitted to our hospital with a consciousness disturbance, he had irregular 10-20 cm patches of subcutaneous bleeding. Laboratory findings showed prolonged activated partial thromboplastin time (APTT) but normal platelet count and prothrombin time. The administration of fresh frozen plasma did not control the bleeding tendency and the result of APTT cross-mixing test suggested the presence of factor VIII inhibitor. The diagnosis of acquired hemophilia A was made by a marked decrease in factor VIII activity levels (<1 %) and a high titer of factor VIII inhibitor (11 Bethesda units). To remove the factor VIII inhibitor and suppress its production, plasma exchange was performed and methylprednisolone was administered. Thereafter, the bleeding tendency could be controlled with APTT measurement normalization. Plasma exchange does not have a first priority in the treatment but our case findings suggested that plasma exchange is an effective method for eliminating factor VIII inhibitor and alleviating acquired hemophilia A severity.