Trajectory of extracellular fluid volume over time and subsequent risks of end-stage kidney disease and mortality in chronic kidney disease: a prospective cohort study.

BACKGROUND: Extracellular fluid volume (ECF) is independently associated with chronic kidney disease (CKD) progression and mortality in patients with CKD, but the prognostic value of the trajectory of ECF over time beyond that of baseline value is unknown. OBJECTIVES: To characterize ECF trajectory and evaluate its association with the risks of end-stage kidney disease (ESKD) and mortality. METHODS: From the prospective tricentric NephroTest cohort, we included 1588 patients with baseline measured glomerular filtration rate (mGFR) ≥15 mL min-1 /1.73 m2 and ECF measurement. ECF and GFR were measured repeatedly using the distribution volume and clearance of 51 Cr-EDTA, respectively. ESKD and mortality were traced through record linkage with the national registries. Adjusted shared random-effect joint models were used to analyse the association between the trajectory of ECF over time and the two competing outcomes. RESULTS: Patients were mean age 58.7 years, 66.7% men, mean mGFR of 43.6 ± 18.6 mL min-1 /1.73 m2 and mean ECF of 16.1 ± 3.6 L. Over a median follow-up of 5.3 [IQR: 3.0;7.4] years, ECF increased by 136 [95%CI 106;167] mL per year on average, whilst diuretic prescription and 24-hour urinary sodium excretion remained stable. ESKD occurred in 324 (20.4%) patients, and 185 (11.6%) patients died before ESKD. A higher current value of ECF was associated with increased hazards of ESKD (adjusted hazard ratio [aHR]: 1.12 [95%CI 1.06;1.18]; P < 0.001 per 1 L increase in ECF), and death before ESKD (aHR: 1.10 [95%CI 1.04;1.17]; P = 0.002). CONCLUSIONS: The current value of ECF was associated with the risks of ESKD and mortality, independent of multiple potential confounders, including kidney function decline. This highlights the need for a close monitoring and adjustment of treatment to avoid fluid overload in CKD patients.

[Chronic metabolic and renal disorders related to lithium salts treatment]. / Complications métaboliques et rénales chroniques du traitement par sels de lithium.

Lithium salts are the main treatment of bipolar disorder, which is characterized by potentially life-threatening maniac and/or depressive episodes. They have proven efficient in the prevention and treatment of acute episodes as well as in the prevention of suicidal risk. However, this efficacy is counterbalanced by a narrow therapeutic range that can lead to potentially harmful overdose, and by adverse long-term events. Nevertheless, they remain first-line treatment, notwithstanding therapeutic alternatives. In this review, we will describe toxic effects of long-term treatment at therapeutic levels of lithium salts. Regarding renal effects, early-impaired urine concentrating ability might lead to polyuria and polydipsia, and even to hypernatremia if free access to water is compromised. Long-term lithium treatment might also lead to chronic kidney disease, characterized by tubulo-interstitial multicystic nephropathy. End-stage renal disease requiring renal replacement therapy is a rare complication. Major extra-renal toxic effects are hypercalcemia and hypothyroidism. Treatment cessation due to these adverse events should be a multidisciplinary and case-by-case decision based on the benefit/risk ratio. Since these toxic effects are mild and display slow progression, treatment cessation is uncommon. However, regular medical and biological check-up is needed in order to prevent these disorders, and patients might be referred to nephrologists and/or endocrinologists once the disorders are established.

Estimated or Measured GFR in Living Kidney Donors Work-up?

The value of estimated glomerular filtration rate (eGFR) in living kidney donors screening is unclear. A recently published web-based application derived from large cohorts, but not living donors, calculates the probability of a measured GFR (mGFR) lower than a determined threshold. Our objectives were to validate the clinical utility of this tool in a cohort of living donors and to test two other strategies based on chronic kidney disease epidemiology collaboration (CKD-EPI) and on MDRD-eGFR. GFR was measured using 51 Cr- ethylene-diamine tetraacetic acid urinary clearance in 311 potential living kidney donors (178 women, mean age 50 ± 11.6 years). The web-based tool was used to predict those with mGFR < 80 mL/min/1.73 m2 . Inputs to the application were sex, age, ethnicity, and plasma creatinine. In our cohort, a web-based probability of mGFR <90 mL/min/1.73 m2 higher than 2% had 100% sensitivity for detection of actual mGFR <80 mL/min/1.73 m2 . The positive predictive value was 0.19. A CKD-EPI-eGFR threshold of 104 mL/min/1.73 m2 and an MDRD-eGFR threshold of 100 mL/min/1.73 m2 had 100% sensitivity to detect donors with actual mGFR <80 mL/min/1.73 m2 . We obtained similar results in an external cohort of 354 living donors. We confirm the usefulness of the web-based application to identify potential donors who should benefit from GFR measurement.

Therapeutic mTOR inhibition in autosomal dominant polycystic kidney disease: What is the appropriate serum level?

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disease, and sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to significantly retard cyst expansion in animal models. The optimal therapeutic dose of sirolimus is not yet defined. Here, we report the history of a previously unknown ADPKD deceased donor whose kidneys were engrafted in two different recipients. One of the two received an immunosuppressive regimen based on sirolimus for 5 years while the other did not. After transplantation, both patients developed severe transplant cystic disease. Donor DNA sequence identified a new hypomorphic mutation in PKD1. The rate of cyst growth was identical in the two patients regardless of the treatment. While sirolimus treatment reduced the activation of mTOR in peripheral blood mononuclear cells, it failed to prevent mTOR activation in kidney tubular cells, this could account for the inefficiency of treatment on cyst growth. Together, our results suggest that the dose of sirolimus required to inhibit mTOR varies according to the tissue.

[Kimura's disease associated with extracapillary glomerulonephritis]. / Maladie de Kimura associée à une glomérulonéphrite extra-capillaire nécrosante.

BACKGROUND: Kimura's disease is a rare and benign chronic inflammatory soft-tissue disorder of unknown origin. Most cases involve young Asian males. The typical presentation consists of painless papules or nodules with a predilection for the head and neck region, associated with lymphadenopathy, parotid gland involvement, peripheral blood eosinophilia and raised immunoglobulin E. PATIENTS AND METHODS: A 49-year-old Mauritian man was hospitalized for nephrotic syndrome. Examination revealed a painless 3 cm nodule in the left pre-auricular region and multiple enlarged left cervical lymph nodes. Histopathologic examination of a nodule confirmed the diagnosis of Kimura's disease, which was associated with necrotic extracapillary glomerulonephritis. Corticosteroids were initiated, resulting in rapid improvement of renal function and partial regression of the patient's cutaneous nodules and lymph node disorder. DISCUSSION: Renal manifestations are the only visceral localization of Kimura's disease, and proteinuria is seen in 12% of cases, of which 50% are accompanied by nephrotic syndrome. Many different histologic types of renal involvement may be observed with potentially severe lesions. To our knowledge, this is the first case of Kimura's disease associated with extracapillary glomerulonephritis.

Vasculitis with mesangial IgA deposits complicating relapsing polychondritis.

The authors report the case of a patient presenting with cutaneous, renal and neurologic vasculitis in the course of relapsing polychondritis (RPC). A 78-year-old man presented with a palpable purpura of the lower limbs, high fever arthralgias, delirium, and nephrotic syndrome. He had a history of relapsing polychondritis treated by corticosteroids. Renal biopsy showed diffuse endo- and extracapillary proliferative glomerulonephritis with mesangial IgA deposits. A spectacular regression of the symptoms was observed in response to pulse intravenous methylprednisolone. Relapsing polychondritis is complicated by vasculitis in 25% of the cases. This vasculitis is characterized by cutaneous, neurologic and renal manifestations, usually occurring in elderly patients. Renal involvement is characterized by segmental and focal or diffuse necrotizing glomerulonephritis. The mesangial IgA deposits observed in our patient are rarely present in the course of RPC. Renal manifestations identify severe forms of RPC, justifying systematic screening for renal complications.

Hyperhomocysteinemia, low folate status, homozygous C677T mutation of the methylene tetrahydrofolate reductase and renal arterial thrombosis.

We report a renal artery thrombosis in a 42-year-old man. Fasting homocysteinemia was at 23 micromol/l 3 months later and at 33 pmol/l 5 months after the vascular event. A homozygous C677T MTHFR was found with low folate status. Active smoking may also have contributed to the pathogenesis of renal arterial thrombosis. The other causes of thrombophilia were ruled out. Homocysteine lowering treament was started: homocysteine normalized at 10.6 micromol/l. There was no recurrence of vascular event within 18 months. We propose mild or moderate hyperhomocysteinemia triggered by low folate status in patients with homozygous C677T MTHFR as a cause of renal arterial thrombosis.

[Sclerosing peritonitis]. / Péritonite sclérosante.

The case presented in this study illustrates the peritoneal changes observed in long-term peritoneal dialysis (PD) patients. This male patient was on peritoneal dialysis (CAPD) for seven months before and 86 months after renal transplantation. Two episodes of peritonitis occurred during that time. The patient developed symptoms (ascites, gastro-intestinal disturbances, deteriorating general condition, inflammatory syndrome) four months after starting hemodialysis, one month after ablation of the PD catheter. Other potential causes (infection, malignancy, hepatitis, etc.) of these symptoms were ruled out following an exhaustive etiological work-up. A final diagnosis of sclerosing peritonitis was made, and the patient was started on corticosteroid therapy. Both morphological and functional alterations of the peritoneal membrane associated with long term PD and the detection of such alterations in everyday practice are reviewed here, along with possible etiological factors and therapeutic measures discussed in the literature. A better understanding of the pathophysiological mecHanisms underlying these alterations would make it possible to develop preventive measures, such as more biocompatible dialysates.

[Inhibitors of HMG CoA reductase: new modes of action, new indications?]. / Les inhibiteurs de l'HMG Co A réductase: nouveaux modes d'action, nouvelles indications?

3-hydroxy-3-methylglutaryl Coenzyme A reductase inhibitors, or statins, are hypocholesterolaemic agents used in the treatment of hypercholesterolaemia and cardiovascular diseases. Their hypocholesterolaemic action results from the inhibition of the intracellular synthesis of cholesterol via the mevalonate pathway. Recent studies have demonstrated that cholesterol is not the only intracellular target of statins. Indeed, statins have been shown to inhibit protein isoprenylation, a post-translational modification involved in membrane localization and protein activity. By inhibiting isoprenylation of Ras protein, statins induce the inhibition of the Ras-AP1 pathway and the decrease in cell proliferation. Similarly, inhibition of Rho protein insoprenylation leads to the disorganization of the cytoskeleton and the induction of the fibrinolytic system. All these effects need to be confirmed in vivo and in the human, and open new areas for these therapeutics agents.

Effects of atorvastatin on dyslipidaemia in uraemic patients on peritoneal dialysis.

BACKGROUND: Our purpose was to evaluate the efficacy and safety of atorvastatin, a potent cholesterol- and triglyceride-lowering agent, in peritoneal dialysis patients with dyslipidaemia. METHODS: Peritoneal dialysis patients with hypercholesterolaemia were treated for 4 months with atorvastatin at a starting dose of 10 mg. The dose could be increased to 20 or 40 mg in order to achieve the following targets: plasma LDL-cholesterol of 130 mg/dl for primary prevention of coronary heart disease, plasma LDL cholesterol of 100 mg/dl for secondary prevention, and plasma triglycerides of 200 mg/dl. Plasma lipid profile and liver and muscle enzyme levels were assessed at baseline and then monthly during treatment. RESULTS: Thirty-one patients with hypercholesterolaemia were included (16 males and 15 females; mean age 57+/-16 years; mean duration of peritoneal dialysis 27+/-17 months). Nineteen of the patients also had hypertriglyceridaemia and seven had diabetes. Twenty patients had no coronary history (primary prevention), whereas nine had experienced a coronary event (secondary prevention). In the primary and the secondary prevention patients, mean LDL-cholesterol levels (mg/dl) decreased significantly by 42 and 46% from 204+/-23 to 119+/-27 (P<0. 001) and 198+/-37 to 104+/-21 (P<0.001), and mean triglyceride levels (mg/dl) decreased by 37 and 26% from 289+/-132 to 186+/-92 (P<0.001) and 201+/-62 to 150+/-54 (P<0.001 respectively). Nineteen primary prevention and seven secondary prevention patients achieved the LDL-cholesterol target. The triglyceride target was achieved by 15 of the 19 hypertriglyceridaemic patients. Two patients stopped treatment (one because of gastrointestinal disturbances, the other because of an allergic skin reaction). After 4 months, there were no changes in enzyme levels. CONCLUSION: Atorvastatin is an effective and safe lipid-lowering agent for peritoneal dialysis patients with mixed dyslipidaemia.

Renal tubular cells cultured from genetically modified animals.

The culture of renal tubular cells from genetically modified animals opens the opportunity of biochemical, cell biology and physiological studies under strictly controlled conditions. Either primary cultures or cell lines can be used. Through two examples of primary cultures of proximal tubular cells obtained from knock-out mice, important information about the function of proteins were obtained. Mice lacking vimentin, an intermediate filament normally reexpressed in tubular cells during regeneration and culture, have a normal tubular function under basal conditions. Proximal cells grown from these animals exhibit a defect in sodium-glucose cotransport activity, most likely related to alterations in the dimer/monomer ratio of the transporter in the apical membranes. These alterations may be important in terms of tubular function during the recovery phase following acute tubular necrosis. The situation is strikingly different with regard to mice lacking HNF-1, a transactivator involved in the transcription of multiple genes. These animals suffer from severe Fanconi syndrome related to decreased expression of proximal transporters including isoforms of sodium-glucose (SGLT2) and sodium-phosphate (NPT1) cotransporters. Whereas transport defects are observed in isolated tubules, they are no longer apparent in cultured proximal cells because the expression of these isoforms is suppressed under culture conditions. These observations illustrate the interest and limits of the in vitro models for studying renal function in transgenic animals.

Mutational analysis in murine models for myeloma-associated Fanconi's syndrome or cast myeloma nephropathy.

We have designed an in vivo model in which murine hybridoma cell clones producing human Ig light chains (LC) are administered to mice. Depending on which monoclonal LC is expressed, this model mimics either cast myeloma nephropathy or the pathological condition defined as myeloma-associated Fanconi's syndrome (FS) with LC crystallization. Morphological alterations of the kidney cells are thus obtained in mice. All studied LC are closely related human monoclonal VkappaI proteins, which differ by a limited number of substitutions within the variable region. In the case of an FS monoclonal LC, we show that limited changes introduced through site-directed mutagenesis in the variable domain may suppress formation of intracellular crystals within tubular cells. We also show that multiple peculiarities of the variable region are simultaneously needed to allow LC crystallization; this property thus likely results from a unique LC tridimensional conformation imposed by concomitant somatic mutations of a specific germinally encoded framework.

Effect of lipid-lowering strategies on tubular cell biology.

BACKGROUND: Interstitial fibrosis and the development of renal cysts are crucial phenomena in renal disease progression. While 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has been shown to reduce the progression of several experimental nephropathies, the mechanism of their potential protective effect remaines unclear. METHODS: The antiproliferative, apoptotic, and fibrinolytic effects of HMG-CoA reductase inhibitors were assessed in primary cultured rat (rPTCs) and mouse proximal tubule cells (mPTCs), in isolated rat proximal tubules, and in vivo in 5/6 nephrectomized rats (Nx). RESULTS: In vitro, lovastatin inhibited rPTC proliferation in a manner selectively prevented by mevalonate, farnesyl-, or geranylgeranyl-pyrophosphate (FPP or GGPP). Lovastatin reduced membrane-bound p21ras and fetal calf serum-induced c-fos and c-jun protein expression. Gel shift assay showed that lovastatin reduced activated protein-1 (AP-1) binding activity. In vivo, lovastatin inhibited tubular cell proliferation after Nx, as measured by proliferative cell nuclear antigen staining. Lovastatin-treated mPTCs displayed nucleus cleavage and DNA ladder formation, which were prevented by GGPP. Like C3 exoenzyme, lovastatin induced actin filament disruption, which preceded evidence of apoptosis. Lovastatin increased tissue-type plasminogen activator (PA) and decreased PA inhibitor activities and antigens; these effects were prevented by mevalonate and GGPP but not FPP, and were reproduced by C3 exoenzyme in a manner insensitive to GGPP. CONCLUSIONS: HMG-CoA reductase inhibitors decreased proliferation, increased apoptosis, and enhanced fibrinolytic activity of renal tubular cells via modulation of different isoprenylated proteins. These effects could participate to reduce the progression of renal diseases.

Severe cutaneous hypersensitivity requiring permanent icodextrin withdrawal in a CAPD patient.

We report a case of severe cutaneous hypersensitivity to icodextrin occurring in a CAPD diabetic patient. Icodextrin withdrawal was necessary to achieve cutaneous recovery. Although rare, this adverse event should be kept in mind.

Lovastatin modulates in vivo and in vitro the plasminogen activator/plasmin system of rat proximal tubular cells: role of geranylgeranylation and Rho proteins.

Interstitial fibrosis is one of the most deleterious events during the progression of renal deterioration after renal mass reduction. In vivo, hydroxymethylglutaryl CoA reductase inhibitors (HRI) were shown to reduce progression of glomerulosclerosis, but the mechanisms are still unclear. The present study investigates, in vivo, whether lovastatin, a potent HRI, was able to modulate the plasminogen-plasmin pathway, one of the most efficient systems involved in extracellular matrix remodeling, and characterizes in vitro the cellular mechanisms of these effects. Proximal tubules freshly isolated from rats treated for 2 d with lovastatin (4 mg/kg per d) showed increased tissue-type plasminogen activator (tPA) and urokinase (uPA) activities and antigens. Incubation with lovastatin (5 microM) of proximal tubules isolated from untreated rats induced an increase in tPA and uPA and a decrease in plasminogen activator inhibitor-1 (PAI-1) activities. In vitro, supernatants, cytosols, and membranes of renal proximal tubular cells in primary cultures had no detectable uPA activity, and lovastatin (0.1 to 10 microM) induced an increase in tPA and a decrease in PAI-1 activities and antigens. These effects were reversed by mevalonate and geranylgeranyl-pyrophosphate (GGPP) but not by farnesyl-pyrophosphate or LDL cholesterol. C3 exoenzyme, an inhibitor of the geranylgeranylated-activated Rho protein, reproduced the effect of lovastatin on tPA and PAI- activity and blocked its reversion by GGPP. The effect of lovastatin was associated with a disruption of cellular actin stress fibers, which was reversed by GGPP and reproduced by C3 exoenzyme. In conclusion, HRI can modify the fibrinolytic potential of proximal tubules, most likely via inhibition of geranylgeranylated Rho protein and disruption of the cytoskeleton. The resulting increase of proteolytic activity of tubular cells may serve to prevent extracellular matrix deposition and renal interstitial fibrosis.

Renal thrombotic microangiopathy in systemic lupus erythematosus: clinical correlations and long-term renal survival.

BACKGROUND: Renal thrombotic microangiopathy (TMA) is an uncommon vascular complication of systemic lupus erythematosus (SLE). Its clinical symptoms and impact on renal survival remain unclear. METHODS: Eight patients aged 25 +/- 6 years with biopsy-proven renal TMA and at least four ARA criteria for the diagnosis of SLE were retrospectively studied over a 7-year period. RESULTS: All patients presented with renal failure (creatinine 3.3 +/- 2.1 mg/dl), six had proteinuria (2.5 +/- 1.3 g/day) with microscopic haematuria in four cases. Six patients had hypertension, which was severe in five cases. Renal histology disclosed arterial and/or arteriolar thrombosis with parietal thickening without angeitis (8 patients), glomerular microthrombi (3 patients), and vascular fibrin deposits (5/6 patients). In two cases, vascular lesions were associated with a mesangial or a proliferative glomerulonephritis. Thrombocytopenia was present in four patients with haemolytic microangiopathic anaemia in one case. Lupus anticoagulant (LA) was detected in five of eight patients, who also had anticardiolipin antibodies (3/7 patients) and/or were positive for VDRL (3/6 patients). Four patients with LA experienced arterial thrombosis and/or repeated spontaneous abortions. Treatment consisted of corticosteroids (8 patients), cytotoxic drugs (4 patients), plasma exchanges and/or intravenous immunoglobulins (4 patients) and antiplatelet and/or anticoagulant therapy (3 patients). Two patients recovered normal renal function and five had persistent renal insufficiency. One patient started haemodialysis on admission and died of sepsis 2 months later. CONCLUSIONS: TMA may be the sole renal complication in SLE and is not usually associated with haemolytic microangiopathic anaemia. In our series renal survival was influenced by the extent and severity of vascular lesions. Despite a frequent association with antiphospholipid antibodies, pathophysiological mechanisms of renal TMA in SLE remain unknown. Renal histology is mandatory for the diagnosis and the prognostic evaluation of renal vasculopathy in SLE.

HMG-CoA reductase inhibitors induce apoptosis in mouse proximal tubular cells in primary culture.

Renal cyst formation in polycystic diseases or after nephron reduction is attributed to enhanced tubular cell proliferation with unbalanced cell death. The induction of tubular cell death could be effective to reduce renal cyst formation. In this study, we examined the effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors on apoptosis in mouse proximal tubular (MPT) cells in primary culture. After treatment with HMG-CoA reductase inhibitors, the extracted DNA was analyzed by gel-electrophoresis under ultraviolet light. Apoptosis was evaluated quantitatively by estimating the ratio of fragmented DNA over intact DNA. For morphologic studies, cells were stained with Hoechst 33,258. DNA ladder pattern of 200 kDa typical of apoptosis and significant increase in DNA fragmentation were seen after 24 hours of treatment with lovastatin, a HMG-CoA reductase inhibitor. Staining with the Hoechst dye revealed cleavage of nucleus into pieces under the same condition. Geranylgeranylpyrophosphate (20 microM) and mevalonate (500 microM) completely reversed the effect of lovastatin, while farnesylpyrophosphate (20 microM) partially reversed it. Other products of HMG-CoA pathway such as cholesterol, ubiquinone, dolichol, and isopentenyladenine had no effect. Perillic acid and alpha-hydoxyfarnesylphosphonic acid, isoprenylation inhibitors, induced apoptosis of the cells. A treatment with lovastatin caused actin filament disruption. Cytochalasin D, an inhibitor of actin polymerization, induced apoptosis. Interleukin-1 beta-converting enzyme inhibitor II, a protease inhibitor, had no effect on the apoptosis induced by either HRI or cytochalasin D. The present study suggests that in mouse proximal tubules, HMG-CoA reductase inhibitors induce apoptosis via inhibition of isoprenoid production, and disruption of actin filaments may play a role in the apoptosis induction.