[Consensus recommendations on the diagnosis and treatment of hyponatremia from the Austrian Society for Nephrology 2024]

Hyponatremia is a disorder of water homeostasis. Water balance is maintained by the collaboration of renal function and cerebral structures, which regulate thirst mechanisms and secretion of the antidiuretic hormone. Measurement of serum-osmolality, urine osmolality and urine-sodium concentration help to diagnose the different reasons for hyponatremia. Hyponatremia induces cerebral edema and might lead to severe neurological symptoms, which need acute therapy. Also, mild forms of hyponatremia should be treated causally, or at least symptomatically. An inadequate fast increase of the serum sodium level should be avoided, because it raises the risk of cerebral osmotic demyelination. Basic pathophysiological knowledge is necessary to identify the different reasons for hyponatremia which need different therapeutic procedures.

[Diagnosis and therapy of membranous nephropathy-2023]

Membranous nephropathy (MN) is an immune-complex glomerulonephritis and is one of the most common causes of nephrotic syndrome in adults and is also one of the autoimmune kidney diseases with the highest rate of spontaneous remission. The most common autoantigen (> 70% of cases) is directed against the phospholipase A2 receptor (PLA2-R) and, with its detection and clinical course, allows for excellent diagnostics as well as optimal therapy monitoring. Other autoantigens are constantly being published and will enable an autoantigen-based diagnostic and therapeutic algorithm for MN in the future. In the absence of spontaneous remission, a specific B‑cell-directed therapy, especially with rituximab, is the initial therapy of choice. Calcineurininhibitors or cyclophosphamide should only be used if they are carefully indicated in the respective clinical context and if there are serious clinical consequences both from the nephrotic syndrome and from loss of kidney function. Since immune complexes within the kidney often require a long time to be degraded, proteinuria response can follow the immunological remission after many months. The therapy of MN represents the favorable case of a precision medicine-based therapy in nephrology, whereby new therapeutic B‑cell antibodies for the rare but difficult forms of MN will find their way into clinical routine in the not-too-distant future.

Development of crescentic membranoproliferative glomerulonephritis after COVID-19 vaccination

Membranoproliferative glomerulonephritis (MPGN) comprises a histologic pattern of glomerular injury with different underlying diseases. Here we report on a 47-year-old female with rapidly progressive glomerulonephritis (RPGN) on top of a previously diagnosed idiopathic MPGN after receiving the first dose of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) mRNA vaccine. After aggressive immunosuppression her serum creatinine returned to normal values, along with reduction of proteinuria. Recently, numerous publications have reported an association of glomerular diseases with COVID-19 vaccination. Our case presents to the best of our knowledge the first occurrence of possible association of COVID-19 mRNA vaccination with a crescentic form of MPGN.

FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy

Background

Factor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.

Methods

A total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).

Results

Eight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.

Conclusions

Our observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.

C4 nephritic factor in patients with immune-complex-mediated membranoproliferative glomerulonephritis and C3-glomerulopathy

BACKGROUND

Acquired or genetic abnormalities of the complement alternative pathway are the primary cause of C3glomerulopathy(C3G) but may occur in immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) as well. Less is known about the presence and role of C4nephritic factor(C4NeF) which may stabilize the classical pathway C3-convertase. Our aim was to examine the presence of C4NeF and its connection with clinical features and with other pathogenic factors.

RESULTS

One hunfe IC-MPGN/C3G patients were enrolled in the study. C4NeF activity was determined by hemolytic assay utilizing sensitized sheep erythrocytes. Seventeen patients were positive for C4NeF with lower prevalence of renal impairment and lower C4d level, and higher C3 nephritic factor (C3NeF) prevalence at time of diagnosis compared to C4NeF negative patients. Patients positive for both C3NeF and C4NeF had the lowest C3 levels and highest terminal pathway activation. End-stage renal disease did not develop in any of the C4NeF positive patients during follow-up period. Positivity to other complement autoantibodies (anti-C1q, anti-C3) was also linked to the presence of nephritic factors. Unsupervised, data-driven cluster analysis identified a group of patients with high prevalence of multiple complement autoantibodies, including C4NeF.

CONCLUSIONS

In conclusion, C4NeF may be a possible cause of complement dysregulation in approximately 10-15% of IC-MPGN/C3G patients.

Validation of distinct pathogenic patterns in a cohort of membranoproliferative glomerulonephritis patients by cluster analysis

Background

A novel data-driven cluster analysis identified distinct pathogenic patterns in C3-glomerulopathies and immune complex-mediated membranoproliferative glomerulonephritis. Our aim was to replicate these observations in an independent cohort and elucidate disease pathophysiology with detailed analysis of functional complement markers.

Methods

A total of 92 patients with clinical, histological, complement and genetic data were involved in the study, and hierarchical cluster analysis was done by Ward method, where four clusters were generated.

Results

High levels of sC5b-9 (soluble membrane attack complex), low serum C3 levels and young age at onset (13 years) were characteristic for Cluster 1 with a high prevalence of likely pathogenic variations (LPVs) and C3 nephritic factor, whereas for Cluster 2—which is not reliable because of the small number of cases—strong immunoglobulin G staining, low C3 levels and high prevalence of nephritic syndrome at disease onset were observed. Low plasma sC5b-9 levels, decreased C3 levels and high prevalence of LPV and sclerotic glomeruli were present in Cluster 3, and patients with late onset of the disease (median: 39.5 years) and near-normal C3 levels in Cluster 4. A significant difference was observed in the incidence of end-stage renal disease during follow-up between the different clusters. Patients in Clusters 3–4 had worse renal survival than patients in Clusters 1–2.

Conclusions

Our results confirm the main findings of the original cluster analysis and indicate that the observed, distinct pathogenic patterns are replicated in our cohort. Further investigations are necessary to analyse the distinct biological and pathogenic processes in these patient groups.

Maternal and Fetal Outcomes of Pregnancies in Women with Atypical Hemolytic Uremic Syndrome

Atypical HUS (aHUS) is a disorder most commonly caused by inherited defects of the alternative pathway of complement, or the proteins that regulate this pathway, and life-threatening episodes of aHUS can be provoked by pregnancy. We retrospectively and prospectively investigated 27 maternal and fetal pregnancy outcomes in 14 women with aHUS from the Vienna Thrombotic Microangiopathy Cohort. Seven pregnancies (26%) were complicated by pregnancy-associated aHUS (p-aHUS), of which three appeared to be provoked by infection, bleeding, and curettage, and three individuals were considered to have preeclampsia/HELLP syndrome before the definitive diagnosis of p-aHUS was made. Mutations in genes that encode the complement alternative pathway proteins or the molecules that regulate this pathway were detected in 71% of the women, with no relationship to pregnancy outcome. Twenty-one pregnancies (78%) resulted in a live birth, two preterm infants were stillborn, and four pregnancies resulted in early spontaneous abortions. Although short-term renal outcome was good in most women, long-term renal outcome was poor; among the 14 women, four had CKD stage 1-4, five had received a renal allograft, and three were dialysis-dependent at study end. We prospectively followed nine pregnancies of four women and treated six of these pregnancies with prophylactic plasma infusions (one pregnancy resulted in p-aHUS, one intrauterine fetal death occurred, and seven pregancies were uneventful). Our study emphasizes the frequency of successful pregnancies in women with aHUS. Close monitoring of such pregnancies for episodes of thrombotic microangiopathy is essential but, the best strategy to prevent these episodes remains unclear.

Elevated uric acid increases the risk for kidney disease

Recent epidemiologic studies suggest that uric acid predicts the development of new-onset kidney disease, but it is unclear whether uric acid is an independent risk factor. In this study, data from 21,475 healthy volunteers who were followed prospectively for a median of 7 yr were analyzed to examine the association between uric acid level and incident kidney disease (estimated GFR [eGFR] <60 ml/min per 1.73 m(2)). After adjustment for baseline eGFR, a slightly elevated uric acid level (7.0 to 8.9 mg/dl) was associated with a nearly doubled risk for incident kidney disease (odds ratio 1.74; 95% confidence interval 1.45 to 2.09), and an elevated uric acid (> or =9.0 mg/dl) was associated with a tripled risk (odds ratio 3.12; 95% confidence interval 2.29 to 4.25). These increases in risk remained significant even after adjustment for baseline eGFR, gender, age, antihypertensive drugs, and components of the metabolic syndrome (waist circumference, HDL cholesterol, blood glucose, triglycerides, and BP). In a fully adjusted spline model, the risk for incident kidney disease increased roughly linearly with uric acid level to a level of approximately 6 to 7 mg/dl in women and 7 to 8 mg/dl in men; above these levels, the associated risk increased rapidly. In conclusion, elevated levels of uric acid independently increase the risk for new-onset kidney disease.

Predictors of new-onset decline in kidney function in a general middle-european population

BACKGROUND

Limited epidemiological data are available on predictors of new-onset kidney disease.

METHODS

In this longitudinal cohort study, 17 375 apparently healthy volunteers of the general Viennese population (46.4% women, age range 20-84 years, men 20-89 years) performed a baseline examination at some time within the study period (1990-2005) and completed a median of two follow-up examinations [interquartile range (IQR) 1 to 4]; the median follow-up period was 7 years (IQR 4 to 11). The outcome of interest was the development of kidney disease, defined as a decrease of the glomerular filtration rate (GFR) <60 ml/min/1.73 m(2) at the follow-up examinations [calculated by the abbreviated modification of diet in renal disease (MDRD) equation]. Logistic generalized estimating equations were used to analyse the relationship between the covariates and the outcome variable.

RESULTS

The following parameters [odds ratios (OR) with 95% confidence intervals] predicted new-onset kidney disease: Age (increase by 5 years), OR = 1.36 (1.34-1.40); National Kidney Foundation-chronic kidney disease (NKF-CKD) stage 1 with proteinuria (+), OR = 1.39 (1.10-1.75); NKF-CKD stage 1 with proteinuria (>/=++), OR = 2.07 (1.11-3.87); NKF-CKD stage 2 with proteinuria (+), OR = 2.71 (2.10-3.51); NKF-CKD stage 2 with proteinuria (>/=++), OR = 3.80 (2.29-6.31); body mass index, OR = 1.04 (1.02-1.06); current-smoker, OR = 1.20 (1.01-1.43); performing no sports, OR = 1.57 (1.27-1.95); uric acid (increase by 2 mg/dl), OR = 1.69 (1.59-1.80); HDL-cholesterol (decrease by 10 mg/dl), OR = 1.12 (1.07-1.17); hypertension stage 1, OR = 1.35 (1.08-1.67); hypertension stage 2, OR = 2.01 (1.62-2.51); diabetes mellitus, OR = 1.44 (1.07-1.93).

CONCLUSIONS

Cardiovascular risk factors as well as NKF-CKD stages 1 and 2 and proteinuria, the more the higher and an entirely novel finding, performing no sports, predicted new-onset kidney disease.

The age-related down-regulation of the growth hormone/insulin-like growth factor-1 axis in the elderly male is reversed considerably by donepezil, a drug for Alzheimer's disease

GH secretion declines by 14%/decade of adult life, leading to the suggestion that people over the age of 60 years are functionally GH deficient. Recently, rivastigmine, a novel cerebral selective cholinesterase-inhibitor (ChEI), was shown to be a powerful drug to enhance GH release to repeated GHRH stimulation in healthy elderly human subjects. The present study was designed as a randomised controlled trial to evaluate long term effects of donepezil, a cerebral selective ChEI, on basal GH and IGF-1 levels and on GH response to GHRH (1 microg/kg i.v., GHRH test) before and after an 8-week donepezil treatment period. Donepezil was given orally 5 mg per day for 4 weeks and 10 mg per day for another 4 weeks. Twenty four healthy male volunteers (n=2 x 12, placebo group vs. donepezil group, age: 61-70 years) were studied. Donepezil treatment group: basal GH levels taken at 08:30 a.m. doubled from 0.4+/-0.3 to 0.8+/-0.4 ng/ml (p=0.008). GHRH-test: GH-AUC was 318+/-227 ng/ml/h and increased by 53% to 485+/-242 ng/ml/h (p=0.009). Total serum IGF-1 levels, taken simultaneously with the basal GH levels, showed a considerable increase, too: the baseline IGF-1 levels increased by 31% from 84+/-19 to 110+/-21 ng/ml (p=0.007). This study demonstrated that the age-related down-regulation of the GH/IGF-1 axis is reversed considerably by donepezil in the elderly male. Future investigation will reveal whether such a new therapeutic intervention can delay the onset or even reverse some manifestations of the somatopause in the long term and evaluate its benefit/risk ratio concerning new treatment implications.

The reduced release of GH by GHRH in 8 subjects aged 65-69 years is augmented considerably by rivastigmine, a drug for Alzheimer's disease

BACKGROUND

The growth hormone (GH) secretion declines by 14% with each decade of adult life. Several attempts have been made to reverse the manifestations of the senile GH deficiency, termed somatopause, but GH substitution treatment in old age has not yet developed an established regimen. Cholinesterase inhibitors like pyridostigmine are able to elicit GH secretion when administered alone and to enhance the GH response to growth hormone releasing hormone (GHRH), but its clinical use is limited due to the strong peripheral cholinergic side effects.

OBJECTIVE

The aims of our experiments were to find out whether the GH response to GHRH can be augmented by rivastigmine, a new orally applicable and well-tolerated selective inhibitor of cerebral acetylchoinesterase.

METHODS

Eight healthy volunteers (age range 65-69 years) were studied. After an overnight fast, GHRH tests were done: 1 microg/kg GHRH was injected as an intravenous bolus. Blood samples for an immunoradiometric GH assay were taken at the time of GHRH injection (time 0) and after 15, 30, 45, 60, and 120 min. First, the baseline experiment was done: it consisted of two subsequent GHRH tests which were carried out within an interval of 120 min. Four weeks later the rivastigmine experiment was done identically, but 60 min before performing the second GHRH test, rivastigmine (4.5 mg) was administered orally. The GH secretory responses were expressed as areas under the curve (AUC; median, interquartile range), Wilcoxon's signed-rank test was used for statistical comparisons.

RESULTS

Baseline experiment: The GH AUC of the first GHRH test was 1040 (range 420-1250) ng/ml/h. The repeated GHRH stimulation after 120 min (second GHRH test) showed a 13-fold decrease to 80 (range 60-130) ng/ml/h. Rivastigmine experiment: The GH AUC of the first GHRH test was 950 (range 540-1430) ng/ml/h and, therefore, similar to that of the baseline experiment. 60 min after ingestion of the single oral dose of rivastigmine (4.5 mg), the following GHRH stimulation (second GHRH test) nearly doubled the GH AUC to 1580 (range 860-3330) ng/ml/h. Comparing the DeltaGH AUC values (DeltaGH AUC = GH AUC of the first GHRH test minus GH AUC of the second GHRH test), baseline experiment versus rivastigmine experiment, there was a 20-fold (p = 0.018) increase in GH AUC after rivastigmine pretreatment.

CONCLUSIONS

Rivastigmine is a powerful drug to enhance GH release to repeated GHRH stimulation in healthy elderly human subjects. Future investigations are necessary to find out whether rivastigmine can restore the senile decline of the circadian GH secretion in the long term and, therefore, has new implications for patient treatment.

Glycoprotein Ib polymorphisms influence platelet plug formation under high shear rates

Platelet polymorphisms (Kozak, VNTR and HPA-2) within glycoprotein (GP)Ib alpha may be associated with an increased risk of arterial thrombosis. However, the functional role of these polymorphisms has not been clarified. Their influence on platelet plug formation under high shear rates was, therefore, examined in 233 healthy individuals. Collagen-adrenaline-induced closure time was shorter in carriers of the C/D versus C/C VNTR allele and in homozygotes with the (-5)T/T versus (-5)C/T Kozak genotype as determined by novel polymerase chain reaction methods. The HPA-2 genotype had no effects, and the density of GPIb alpha molecules was not influenced by GPIb alpha genotypes.

Point of care measurement of lepirudin and heparin anticoagulation during systemic inflammation

BACKGROUND

The number of indications for recombinant human hirudin lepirudin therapy has increased in recent years, and now includes acute coronary syndromes and heparin-induced thrombocytopenia. Hence, point of care monitoring appears desirable for therapy with lepirudin. As CoaguChek Plus (CCP) provides a rapid bedside test to monitor therapy with other anticoagulants, we aimed to determine its suitability for lepirudin therapy.

METHODS

Forty-four healthy volunteers received a 2 ng/kg endotoxin infusion (to induce coagulation) together with clinically relevant doses of lepirudin or heparin in a prospective, placebo-controlled, randomised fashion. Measurements of CCP-partial thromboplastin time (aPTT) were compared to laboratory STA-aPTT.

RESULTS

As expected, baseline values of CCP-aPTT were shorter than STA-aPTT. Lepirudin increased CCP-aPTT 3-fold, and STA-aPTT 2-fold 1 h after bolus infusion. During lepirudin infusion, the correlation between CCP-aPTT and STA-aPTT was excellent (r=0.86-0.92). Both methods were equally sensitive to over-anticoagulation with heparin. Acute systemic inflammation had little effects on CCP-aPTT.

CONCLUSION

CCP-aPTT is suitable for longitudinal point of care monitoring of lepirudin therapy. As baseline values of CCP-aPTT are shorter than STA-aPTT, it is recommended not to indiscriminately change between methods in the follow-up of individual patients.

Effects of anticoagulation on thrombopoietin release during endotoxemia

Several lines of evidence suggest that coagulation may induce the release of thrombopoietin (TPO) into plasma and that TPO levels are higher in disseminated intravascular coagulation. Therefore we set out to illuminate the mechanism of TPO release in the setting of experimental endotoxemia, which induces activation of coagulation and platelets. Endotoxin (lipopolysachharide [LPS], 2 ng/kg) was infused into a total of 54 healthy men in two subsequent studies. Volunteers received infusions of unfractionated heparin, low-molecular-weight heparin, lepirudin, or placebo in a randomized, placebo-controlled fashion after bolus injection of LPS. TPO levels increased on average by 27% to 38% in all groups at 6 hours (P <.05 vs baseline), although all active drugs effectively blocked coagulation. Platelet counts dropped by about 15% at 1 hour after LPS infusion, recovered after 2 days, and exceeded baseline values by 8% to 18% after 7 days (P <.001 vs baseline for all groups). Yet lepirudin blunted the LPS-induced increase in circulating P-selectin by one half (P <.005 vs placebo), whereas both heparins did not diminish the increase in this platelet or endothelial activation marker as compared with placebo. Endotoxemia enhances TPO plasma levels independent of the degree of coagulation induction, which eventually results in increased platelet numbers. Of potential clinical interest is the observation that the direct thrombin inhibitor lepirudin, in contrast to heparins, mitigated LPS-induced platelet activation.

Heparin blunts endotoxin-induced coagulation activation

BACKGROUND

Lipopolysaccharide (LPS) is a major trigger of sepsis-induced disseminated intravascular coagulation (DIC) via the tissue factor (TF)/factor VIIa-dependent pathway of coagulation. Experimental endotoxemia has been used repeatedly to explore this complex pathophysiology, but little is known about the effects of clinically used anticoagulants in this setting. Therefore, we compared with placebo the effects of unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) on LPS-induced coagulation.

METHODS AND RESULTS

In a randomized, double-blind, placebo-controlled trial, 30 healthy male volunteers received LPS 2 ng/kg IV followed by a bolus-primed continuous infusion of UFH, LMWH, or placebo. In the placebo group, activation of coagulation caused marked increases in plasma levels of prothrombin fragment F(1+2) (P<0.01) and polymerized soluble fibrin, termed thrombus precursor protein (TpP; P<0.01); TF-positive monocytes doubled in response to LPS, whereas levels of activated factor VII slightly decreased and levels of TF pathway inhibitor remained unchanged. UFH and LMWH markedly decreased activation of coagulation caused by LPS, as F(1+2) and TpP levels only slightly increased; TF expression on monocytes was also markedly reduced by UFH. TF pathway inhibitor values increased after either heparin infusion (P<0.01). Concomitantly, factor VIIa levels dropped by >50% at 50 minutes after initiation of either heparin infusion (P<0.01).

CONCLUSIONS

This experimental model proved the anticoagulatory potency of UFH and LMWH in the initial phase of experimental LPS-induced coagulation. Successful inhibition of thrombin generation also translates into blunted activation of coagulation factors upstream and downstream of thrombin.