[Management of bone and mineral metabolism disorders before the dialysis stage remains still perfectible. Data from the French Phosphorus and Calcium Survey Photo-Graphe]

Only limited data is available on the management of the chronic kidney disease-associated bone and mineral metabolism disorder (CKD-MBD) in the pre-dialysis stages of CKD in France. A better knowledge of current management habits could lead to an improvement in the implementation of international recommendations (KDIGO). The 3rd version of the French Phosphorus and Calcium Survey Photo-Graphe (Sanofi) included a cohort of CKD stages 4 and 5 patients, whose aim was to examine the prevalence of CKD-MBD and the quality of its management in patients under the care of 62 nephrologists from over 20 geographical regions in France. The study started in October 2011, i.e. one year after patient enrollment. We examined in particular the percentage of patients presenting with laboratory parameter abnormalities indicative of CKD-MBD who were not receiving adequate treatment. A total of 456 patients with CKD stage 4 and 154 with CKD stage 5 were studied. Their mean age was 72.9±14.2 years, and male/female ratio was 58/42. KDIGO targets of serum PTH for CKD stages 4 and 5 were not achieved in respectively 80 and 84% of the patients, for serum calcium in 8 and 22% and for serum phosphate in 12 and 46%. As a potential explanation, insufficient therapy was estimated to account for respectively 45 and 60% of insufficiently controlled secondary hyperparathyroidism, and for 36% of persistent hyperphosphatemia in stage 5. It should be noted that 55.5 and 57.5% of patients were receiving native vitamin D. In this national observatory, the management of CKD-MBD stages 4 and 5 appears suboptimal, especially as regards the control of secondary hyperparathyroidism, which remained untreated in nearly 50% of the patients. Hyperphosphatemia was also common and inadequately controlled in CKD stage 5. To improve the management of CKD-MBD, nephrologists need to be more aware of the importance of aiming for recommended laboratory targets and how this can be achieved.

Effective CKD care in European countries: challenges and opportunities for health policy

Chronic kidney disease (CKD) is an important global public health problem that is associated with adverse health outcomes and high health care costs. Effective and cost-effective treatments are available for slowing the progression of CKD and preventing its complications, including cardiovascular disease. Although wealthy nations have highly structured schemes in place to support the care of people with kidney failure, less consideration has been given to health systems and policy for the much larger population of people with non-dialysis-dependent CKD. Further, how to integrate such strategies with national and international initiatives for control of other chronic noncommunicable diseases (NCDs) merits attention. We synthesized the various approaches to CKD control across 17 European countries and present our findings according to the key domains suggested by the World Health Organization framework for NCD control. This report identifies opportunities to strengthen CKD-relevant health systems and explores potential mechanisms to capitalize on these opportunities. Across the 17 countries studied, we found a number of common barriers to the care of people with non-dialysis-dependent CKD: limited work force capacity, the nearly complete absence of mechanisms for disease surveillance, lack of a coordinated CKD care strategy, poor integration of CKD care with other NCD control initiatives, and low awareness of the significance of CKD. These common challenges faced by diverse health systems reflect the need for international cooperation to strengthen health systems and policies for CKD care.

Serum iPTH, calcium and phosphate, and the risk of mortality in a European haemodialysis population

Background. A number of US observational studies reported an increased mortality risk with higher intact parathyroid hormone (iPTH), calcium and/or phosphate. The existence of such a link in a European haemodialysis population was explored as part of the Analysing Data, Recognising Excellence and Optimising Outcomes (ARO) Chronic Kidney Disease (CKD) Research Initiative.

Methods. The association between the markers of mineral and bone disease and clinical outcomes was examined in 7970 patients treated in European Fresenius Medical Care facilities over a median of 21 months. Baseline and time-dependent (TD) Cox regression were performed using Kidney Disease Outcomes Quality Initiative (KDOQI) target ranges as reference categories, adjusting for demographics, medical history, dialysis parameters, inflammation, medications and laboratory parameters. Fractional polynomial (FP) models were also used.

Results. Hazard ratio (HR) estimates from baseline analysis for iPTH were U-shaped [>600 pg/mL, HR = 2.10, 95% confidence interval (CI) 1.62–2.73; <75 pg/mL, HR = 1.46, 95% CI 1.17–1.83]. TD analysis confirmed the results for iPTH. Baseline analysis showed that calcium >2.75 mmol/L increased risk of death (HR = 1.70, 95% CI 1.19–2.42). TD analysis showed that both low (HR = 1.19, 95% CI 1.04–1.37) and high calcium (HR = 1.74, 95% CI 1.30–2.34) increased risk of death. Baseline analysis for phosphate showed a U-shaped pattern (<1.13 mmol/L, HR = 1.18, 95% CI 1.01–1.37; >1.78 mmol/L, HR = 1.32, 95% CI 1.13–1.55). TD analysis confirmed the results for phosphate <1.13 mmol/L. HR estimates were higher in patients with diabetes versus those without diabetes for baseline analysis only (P-value = 0.014). FP analysis confirmed the results of baseline and TD analyses.

Conclusion. Patients with iPTH, calcium and phosphate levels within the KDOQI target ranges have the lowest risk of mortality compared with those outside the target ranges.

Mineral and bone disease pattern in elderly haemodialysis patients

BACKGROUND

Although many studies have recently addressed the mineral and bone disorder of chronic kidney disease (CKD-MBD), only limited information is available for elderly dialysis patients.

METHODS

We prospectively collected serum phosphorus, calcium, parathyroid hormone (PTH), 25(OH) vitamin D, albumin, C-reactive protein, protein intake and CKD-MBD treatments in 9169 maintenance haemodialysis patients in France in June 2008. We then compared biological and treatment patterns in 3403 patients aged 75 or over to their younger counterparts.

RESULTS

Elderly patients exhibited lower serum phosphorus and parathyroid hormone concentrations (-8 and -18%, respectively) but slightly higher corrected serum calcium levels (+2%) compared to patients aged below 75 years. Elderly patients had higher mean C-reactive protein, lower serum albumin levels and reduced protein intake. Calcium and non-calcium phosphate binders as well as cinacalcet usage and dosage were significantly reduced in elderly patients, with a trend towards lower active vitamin D derivatives usage. Elderly patients were better controlled according to the Kidney Disease Outcome Quality Initiative (K/DOQI) targets compared to patients aged below 75.

CONCLUSION

In this large 2008 cohort of elderly haemodialysis patients, it appears easier to control serum parameters of CKD-MBD as compared to younger dialysis patients. A better control of serum phosphorus was observed, with less phosphate binder and reduced cinacalcet dosage.

Fetuin-A protects against atherosclerotic calcification in CKD

Reduced serum levels of the calcification inhibitor fetuin-A associate with increased cardiovascular mortality in dialysis patients. Fetuin-A-deficient mice display calcification of various tissues but notably not of the vasculature. This absence of vascular calcification may result from the protection of an intact endothelium, which becomes severely compromised in the setting of atherosclerosis. To test this hypothesis, we generated fetuin-A/apolipoprotein E (ApoE)-deficient mice and compared them with ApoE-deficient and wild-type mice with regard to atheroma formation and extraosseous calcification. We assigned mice to three treatment groups for 9 wk: (1) Standard diet, (2) high-phosphate diet, or (3) unilateral nephrectomy (causing chronic kidney disease [CKD]) plus high-phosphate diet. Serum urea, phosphate, and parathyroid hormone levels were similar in all genotypes after the interventions. Fetuin-A deficiency did not affect the extent of aortic lipid deposition, neointima formation, and coronary sclerosis observed with ApoE deficiency, but the combination of fetuin-A deficiency, hyperphosphatemia, and CKD led to a 15-fold increase in vascular calcification in this model of atherosclerosis. Fetuin-A deficiency almost exclusively promoted intimal rather than medial calcification of atheromatous lesions. High-phosphate diet and CKD also led to an increase in valvular calcification and aorta-associated apoptosis, with wild-type mice having the least, ApoE-deficient mice intermediate, and fetuin-A/ApoE-deficient mice the most. In addition, the combination of fetuin-A deficiency, high-phosphate diet, and CKD in ApoE-deficient mice greatly enhanced myocardial calcification, whereas the absence of fetuin-A did not affect the incidence of renal calcification. In conclusion, fetuin-A inhibits pathologic calcification in both the soft tissue and vasculature, even in the setting of atherosclerosis.

[Influence of microinflammation and oxidative stress on atherosclerosis progression and calcifications in cardiovascular system of hemodialyzed patients during two years follow-up]

Atherosclerosis and calcifications in the cardio-vascular system are the most frequent causes of increased morbidity and mortality in patients with end-stage renal disease treated with hemodialyses. The aim of this study was to estimate the atherosclerosis progression and presence of calcifications in the circulatory system in patients treated with hemodialyses using, non-invasive imaging diagnostic techniques and to search for the relationships between these changes and microinflammation and oxidative stress during two years. The study was performed in 73 patients (36 female and 37 male), aged 25 to 75 years (mean -49.5), treated with hemodialyses, 3 times/week for 12 to 275 months (mean -73.8). In each patient before starting hemodialysis levels of: ox-LDL, Lp (a), procalcitonin, IL-1beta, IL-6, CRP, TGFbeta, TNFalpha, PDGF, AOPP and MPO were determined. Presence of artery calcifications was detected by Multi-Row Spiral Computed Tomography (MSCT) and expressed as coronary artery calcification score (CACS). Ultrasonography was used to evaluate CCA-IMT. During the study CACS increased significantly after 12 and 24 months (p < 0.00001) as compare with baseline. After 12 months, CACS increase significantly correlated with procalcitonin level (r = 0.30 p = 0.01) and after 24 months with CRP (r = 0.46; p = 0.0002) and IL-6 (r = 0.36; p = 0.005). Independent factor of coronary artery calcification progression after 24 months of observation was only CRP (beta = 0.569). CCA-IMT increased during the study and this increase was statistically significant (p < 0.00001). CCA-IMT increase correlated with CACS growth after 12 (r = 0.36; p = 0.003) and 24 months (r = 0.39; p = 0.002). After 12 months significant relationship was noted with procalcitonin (r = 0.29; p = 0.022). After 24 months CCA-IMT correlated with AOPP (r = -0.30; p = 0.017). The independent factor of CCA-IMT progression after 24 months of observation was only CACS (delta CACS beta = 0.49). From the performed study, we can conclude that exacerbation of atherosclerosis and calcification in the circulatory system of patients treated with maintenance hemodialyses depends on microinflammation and oxidative stress. Reasonable tools for diagnostic algorithm estimation of atherosclerosis advancement in this group of patients are non-invasive, visual diagnostic techniques such as MSCT and ultrasonography.

A stable animal model of diet-induced calcium oxalate crystalluria

Twenty male Wistar rats, weighing 150 g, were placed in metabolic cages on a 30% sucrose diet for 7 days, before allocation to two groups: a control group (n = 5) and a lactose group (n = 15). They received respectively a 30% sucrose diet or a 30% lactose diet for 8 weeks, each containing 0.67% calcium and 0.38% phosphorus. After 4 (T1) and 8 (T2) weeks, the serum calcium (Ca) and citrate levels were significantly (P < 0.01) higher in rats fed the lactose diet. Serum alkaline phosphatase activity was increased in the lactose group (P < 0.01) at T1 and T2. The lactose-rich diet induced an increase in urinary Ca excretion at T1 and T2; citrate excretion was only enhanced at T2 (P < 0.001). No difference between the two groups was observed in urinary oxalate (Ox) excretion or creatinine clearance. Crystalluria analysis revealed a marked number (>300/mm3 at T1 and T2) of calcium oxalate dihydrate crystals (COD) in rats fed the lactose-rich diet, whereas no COD crystals were observed in sucrose-fed control rats at any time point. The formation of COD crystals in lactose-fed rats was related to an increase in calcium oxalate (CaOx) product (pCaOx), which was respectively 12.6 vs 3.9 at T1 and 10.5 vs 1.8 at T2, and an increase in CaOx ratio (Ca/Ox), which was 99.1 vs 7.5 and 67.5 vs 18.5 at T1 and T2, respectively. The high pCaOx and Ca/Ox ratios in the lactose group were due to hypercalciuria, in agreement with the number and the type of crystals. The present experimental model confirms that the ingestion of a 30% lactose diet increases urinary Ca excretion without changing urinary Ox excretion and shows for the first time that it induces a stable and marked crystalluria composed of COD. Such a non-nephrotoxic and stable model is of interest for the study of CaOx crystal formation secondary to hypercalciuria, and thus afterwards eventually for CaOx nephrolithiasis.

Validation by image analysis of a turbidimetric method to study calcium oxalate crystallization

Numerous studies of calcium oxalate crystal formation have been carried out in the past two decades. In the present study, experiments were carried out to validate a turbidimetric method allowing to assess the calcium oxalate crystallization process. This method is quick and reproducible and can be used to quantify the inhibition of calcium oxalate crystal growth by various compounds. An experimental method of validation has been developed, which consisted in filtering solutions pure or containing modifiers at given crystallization times, photographing the filters used on scanning electron microscopy and analyzing the images using mathematical methodology. The results obtained through image analysis, namely crystal density (mean particle number per unit volume) and mean area, were correlated with the turbidimetric parameters. This finding was consistent with the qualitative examination of the photographs. Moreover, the morphological differences in crystals observed on the photographs were confirmed by the calculated length/width ratio. One can therefore assume that inhibition of calcium oxalate crystal growth is at least, partly explained by surface adsorption phenomena, which may add to complex formation.

Stimulation of ileal calcium absorption by sorbitol, L-xylose, or creatine via a decrease in luminal sodium concentration: relation with concomitant changes in enterocyte energy metabolism

Ligated ileal loops, 30 cm in length, of 4-month-old male Wistar rats were instilled with 3 ml of a 10 mM CaCl2 solution (added with 0.25 muCi 45Ca) in the absence (control) or presence of 100mM sorbitol, L-xylose, or creatine. Ileal calcium (Ca) transport, measured by plasma 45Ca appearance, was found to be similar 30 minutes after fluid instillation in all four instances. However, thereafter, 45Ca appearance in plasma did not increase further in control animals whereas it increased twice as much during the subsequent 30 minutes in the presence of sorbitol, L-xylose, or creatine. However, when loops of similar length were instilled with only 1.0 ml of such solutions, the sorbitol effect was already observed during the first 30 minutes. The stimulation of ileal Ca absorption induced by the presence of sorbitol appeared to be due to a cellular effect, associated with a decreased flux across the paracellular pathway, as indicated by 3H-mannitol absorption. The presence of sorbitol in instilled ileal solution induced a significant decrease in luminal Na, K, bicarbonate, and Cl concentrations at each time point studied (30, 60, 120, or 240 minutes after instillation). Thirty minutes after instillation, no difference in soluble Ca concentration was observed between control and experimental rats. After 60 minutes, Ca concentration was dramatically decreased in control rats but it remained nearly constant in experimental animals. Thus, the presence of substances enhancing ileal Ca transport favored the maintenance of soluble Ca in ileal solution during longer time periods than their absence. In the ileal enterocyte, these substances induced a twofold increase of ATP content compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of erythropoietin on DNA synthesis, proto-oncogene expression and phospholipase C activity in rat vascular smooth muscle cells

The administration of recombinant human erythropoietin (rHuEpo) to anemic chronic renal failure patients may be associated with an increase in blood pressure, possibly by direct effects on peripheral blood vessels. The experiments of the present study were designed to explore the hypothesis that rHuEpo might exert mitogenic effects on vascular smooth muscle cells (VSMCs), and that pre-existing hypertension might be a predisposing condition. Cultured aortic VSMCs from spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats were studied for DNA synthesis, phospholipase C activity, and cell growth related proto-oncogene expression in the presence of rHuEpo. In cells from both rat strains, rHuEpo dose-dependently increased DNA synthesis and stimulated phospholipase C activity, as indicated by 3H-thymidine incorporation and inositol phosphate formation, respectively. Exposure of VSMCs to rHuEpo for various periods gradually increased the levels of c-myc and JunB mRNAs and transiently induced c-fos mRNA expression as determined by Northern analysis. The hormone-induced DNA synthesis was markedly enhanced in VSMCs from SHR compared to those from WKY. In contrast, rHuEpo-induced phospholipase C activity and proto-oncogene expression did not differ between the two strains. Taken together, these results suggest that rHuEpo may function as a vascular smooth muscle cell growth promoting factor through activation of the phospholipase C cascade and a modulation of proto-oncogene expression. It could thereby contribute to vascular hypertrophy and arterial hypertension.

[In vitro effect of citrate and phosphates on calcium transport in the rat ileum]

OBJECTIVES AND METHODS

The effect of the presence of phosphates or citrate on ileal calcium (Ca) absorption was studied by using rat ileum mounted in a Ussing chamber.

RESULTS

Mucosa-to-serosa and serosa-to-mucosa undirectional fluxes were not modified by mucosal addition of 2.8 mM Na phosphate or 2.0 mM Na citrate to Krebs-Ringer-bicarbonate buffer containing 1.25 mM CaCl2. However, 50 mM Na citrate induced a significant and similar increase of both unidirectional Ca fluxes, leading to no modification of net Ca flux. This high citrate concentration was associated with a significant increase of tissue conductance and no alteration of zona adherens and tight junction as observed by electron microscopy.

CONCLUSIONS

Thus in the absence of any Ca gradient along the epithelium, even at high concentration, citrate did not induced modification of ileal Ca absorption.

A new approach to studying inhibitors of calcium oxalate crystal growth

The nucleation and crystal growth of calcium oxalate (CaOx) were studied at pH 5.5 using turbidimetric measurements at 620 nm of suspensions produced by mixing calcium chloride and sodium oxalate (initial conditions: Ca, 3 x 10(-3) M; Ox, 0.5 x 10(-3) M). CaOx crystallization kinetics were defined first by the induction time ti and then by the slope of turbidity as a function of time during the interval corresponding to a correlation coefficient r2 > 0.99. The technique described requires only a small amount of material, is quick, convenient, and can be used to study inhibitors of CaOx crystallization by comparing ti and the rate of crystal growth in the presence and absence of inhibitors. The effects on CaOx crystal growth of several low molecular weight compounds, i.e. di- and tricarboxylic acids, were examined. The majority of these compounds were inhibitors of crystal growth, the greatest effect being seen with citric acid (50% inhibition in the presence of 1.5 x 10(-3) M citric acid), isocitric acid (50% inhibition in the presence of 0.75 x 10(-3) M isocitric acid) and pyrophosphate (30% inhibition in presence of 0.15 x 10(-3) M pyrophosphate). The inhibitors' behaviour regarding the medium was studied without any assumptions about their possible mechanisms of action. Measurements of ionized calcium before and after the reaction, as well as the observation of crystals by scanning electron microscopy, allowed us to formulate the hypothesis that the effect of citric acid and tartaric acid can be attributed mainly to ion pairing, in contrast to that of pyrophosphate and the other carboxylic acids.

[The future of hemodialysis in the adult]

By the year 2000, the perspectives for hemodialysis performed in adults will be oriented towards facilitation of the practice of hemodialysis as a better control of clinical symptoms observed in end stage renal failure treated by hemodialysis. Blood access is the main problem which remains to be solved. The authors describe the advantages and disadvantages of the methods presently used and give the "state of the art" of "blood access" prosthesis. Almost all symptoms encountered in renal failure patients treated by hemodialysis can be efficiently treated. Hypotensive drugs usually reduce hypertension which resists adequate treatment by hemodialysis. Most of the symptoms of osteodystrophy can be avoided by adequate diet associated with the prescription of vitamin D analogs. Nevertheless, the prolongation of hemodialysis treatment duration over 7 years has led to the apparition of destructive arthropathies which are very painful and handicapping. They are related to amyloid deposit of beta 2-microglobulins. Progress in hemodialysis technics and a better control of uremic symptoms allow application of this treatment at all ages of life. The authors examine specific problems concerning school-aged teenagers and aged persons. They show that results already achieved allow a daily treatment of these patients. This is a first step for the generalisation of this procedure to all patients and its advantages are described. Improvement of hemodialysis technics for the year 2000, as can be expected, mainly depends upon progress in knowledge of biocompatibility parameters between materials used in the artificial kidney and patients tissues, mainly blood vessels.

Pseudotumor of the craniocervical junction during long-term hemodialysis

A systematic study of the upper cervical spine was performed using magnetic resonance imaging in 25 patients (15 men and 10 women) who had been undergoing hemodialysis for more than 10 years. Seven pseudotumors of the periodontoid soft tissue were disclosed, which were similar to the pannus recently described in rheumatoid arthritis. Bone cystic radiolucencies were observed in association with these pseudotumors in 5 patients. The radiolucencies were located in the atlas (1 in the lateral mass and 1 in the anterior branch) and in the axis (3 in the odontoid process and 1 in the vertebral body). No horizontal or vertical atlantoaxial subluxation was demonstrated. These features were observed only in patients who had amyloid arthropathy. They could be a frequent, yet thus far little-recognized, feature of beta 2-microglobulin amyloidosis.

In vivo T cell preactivation in chronic uremic hemodialyzed and non-hemodialyzed patients

The production and targeting of a major T cell derived lymphokine, Interleukin 2 (IL-2), were studied in 23 uremic patients undergoing regular hemodialysis treatment and 20 uremic patients prior to the onset of renal replacement therapy. In hemodialyzed patients, abnormally increased proportions of circulating T cells spontaneously expressing high affinity IL-2 receptors (IL-2 Rec) were detected: they bound a monoclonal antibody specifically directed to the IL-2 Rec 55 kDa chain (Tac antigen) (mean +/- SEM: 7.12 +/- 0.81% in patients vs. 2.15 +/- 0.39% in normal controls, P less than 0.0001) and significantly proliferated in presence of human recombinant IL-2 alone (mean +/- SEM: 5438 +/- 729 cpm in patients vs. 1647 +/- 244 cpm in normal controls). Hemodialyzed patients also exhibited significantly increased serum levels of soluble IL-2 receptor (mean +/- SEM: 4036 +/- 947 U/ml in patients vs. 253 +/- 29 U/ml in normal controls. P less than 0.001). Moreover, a significantly decreased IL-2 activity was detected in the supernatants of stimulated T cells from hemodialyzed patients (mean +/- SEM: 0.93 +/- 0.12 U/ml in patients vs. 2.49 +/- 0.22 U/ml in normal controls, P less than 0.0001). In nine hemodialyzed patients who were analyzed before and immediately after the hemodialysis session no acute modifications of the various parameters analyzed were detected. Although less profound, a similar pattern of T cell abnormalities was observed in the uremic non-hemodialyzed patients studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of erythropoiesis in dialysis patients receiving recombinant erythropoietin treatment

In eleven patients with uraemia on intermittent haemodialysis treatment, recombinant human erythropoietin (rHuEpo) was used at a dosage schedule of 100 IU/kg bodyweight thrice weekly. Erythrokinetic studies (blood volume, RBC survival and iron kinetics) were performed in nine cases before and after 6 months of treatment. The remaining two patients had only RBC and plasma volume determinations before and after treatment. Although total blood volume remained unchanged, RBC volume was increased in all cases. Red cell loss was not modified, and quantitative improvement of RBC production was noted in all cases. No qualitative defect of erythroid maturation or release was observed in the treated patients. In conclusion, rHuEpo treatment improves the anaemia of haemodialysis patients by normalising circulating RBC volume only through an increase in red cell production.

Hemodialysis-associated amyloidosis and beta-2 microglobulin. Clinical and immunohistochemical study

The beta-2 microglobulin type of amyloidosis was identified in articular and para-articular tissues of 14 patients with non-amyloid nephropathies undergoing long-term hemodialysis. Ten patients had carpal tunnel syndrome, 13 had juxta-articular radiolucent cysts (complicated by spontaneous fractures of the femoral neck in three), and six had destructive arthropathies of the large joints of the limbs. Massive amyloid deposits were found in the synovium, capsule, ligaments, articular cartilage, and/or bone. They were characterized by Congo red-induced green birefringence that was sensitive to potassium permanganate treatment. They reacted with anti-beta-2 microglobulin antiserum, whereas they did not react with antibodies directed against AA protein, prealbumin, or immunoglobulins. These data suggest that the potentially disabling arthropathy of hemodialysis is due to amyloid lesions. The persistently elevated plasma beta-2 microglobulin levels may play a role in the pathogenesis of this recently recognized complication, and if so, this complication should be preventable.

Presence of preactivated T cells in hemodialyzed patients: their possible role in altered immunity

Interleukin 2 (IL-2) and B-cell growth factors I and II (BCGF I and BCGF II) are lymphokines produced by T cells that play a major role in T- and B-cell cooperation. Peripheral blood lymphocytes from 12 uremic patients undergoing intermittent hemodialysis were tested for their capacity to produce IL-2 and BCGFs and to respond to these soluble mediators. IL-2 and BCGF activities were determined by means of two biological assays (proliferation of IL-2-dependent cytotoxic T-cell line CTLL-2 and of anti-human IgM (mu chain)-stimulated normal B cells, respectively) in the supernatants of phytohemagglutinin A-stimulated T-cell cultures. IL-2 activity was significantly decreased in patients as compared to normal controls (mean +/- SEM, 0.28 +/- 0.09 unit per ml) in hemodialyzed patients versus 1.02 +/- 0.16 units per ml in normal controls). This profound abnormality contrasted with the normal activity of the BCGFs that was invariably observed in the same supernatants. A similar dissociation was detected when analyzing the sensitivity of uremic B and T cells to exogenous purified lymphokines. Anti-IgM (mu chain)-stimulated uremic B cells exhibited a normal response to recombinant IL-2 and to chromatography-purified BCGF I and BCGF II. Resting B cells did not show any increased reactivity to these lymphokines. In contrast, whereas in normal controls recombinant IL-2 exclusively induced the proliferation of T cells that had been previously activated by a mitogen, resting T cells from uremic patients were highly responsive to exogenous IL-2. This abnormal response was paralleled by significantly increased proportions of peripheral T cells recognized by the anti-Tac monoclonal antibody that specifically binds to the IL-2 receptor. These data clearly show the existence in hemodialyzed patients of abnormally high proportions of T cells presenting phenotypic and functional signs of preactivation. This increased T-cell IL-2 receptor expression may offer an explanation to the deficient IL-2 activity observed in patients' supernatants (by inducing increased absorption of the lymphokine). The potential relevance of these preactivated T cells to the depressed cell-mediated immunity observed in hemodialyzed patients is outlined.

Correction by insulin of disturbed TG-rich LP metabolism in rats with chronic renal failure

To define the role of insulin in lipid disturbances of chronic renal failure, chronically uremic rats (U+) were supplemented by continuous insulin infusion over a 35-day experimental period and compared with control ad libitum-fed rats (C) and uremic rats without insulin (U). Uremic rats were characterized by hypoinsulinemia, an increase in both circulating very low-density lipoprotein (VLDL) and their cholesterol concentration, a normal hepatic triglyceride secretion rate (TGSR) determined with Triton WR 1339, and a low adipose tissue lipoprotein lipase (LPL) activity. Chronic insulin infusion at low rate (0.5 IU/24 h) to U+ rats normalized serum insulin (from 17.0 +/- 0.6 mU/l in U rats to 23.4 +/- 1.7 mU/l in U+ rats), serum VLDL triglycerides (from 804 +/- 65 to 410 +/- 36 mg/l), and serum VLDL cholesterol (from 43 +/- 8 to 16 +/- 3 mg/l). Hepatic TGSR decreased significantly after insulin treatment (from 0.58 +/- 0.03 to 0.44 +/- 0.03 mumol/min). Moreover, adipose tissue LPL was restored to normal by insulin supplementation (from 460 +/- 60 to 860 +/- 150 mU per total epididymal fat in U and U+ rats, respectively). Correction of the disturbed VLDL metabolism was associated with multiple actions of insulin including 1) a decrease of peripheral lipolysis, 2) a decrease of hepatic TGSR, and 3) an increase of adipose tissue LPL activity. Because cholesterol-rich VLDL are potentially atherogenic, their normalization with insulin treatment in this animal model suggests a viable area of investigation for the prevention of accelerated atherogenesis in chronic renal failure.