The Therapeutic Strategies for Uremic Toxins Control in Chronic Kidney Disease.

Uremic toxins (UTs) are mainly produced by protein metabolized by the intestinal microbiota and converted in the liver or by mitochondria or other enzymes. The accumulation of UTs can damage the intestinal barrier integrity and cause vascular damage and progressive kidney damage. Together, these factors lead to metabolic imbalances, which in turn increase oxidative stress and inflammation and then produce uremia that affects many organs and causes diseases including renal fibrosis, vascular disease, and renal osteodystrophy. This article is based on the theory of the intestinal-renal axis, from bench to bedside, and it discusses nonextracorporeal therapies for UTs, which are classified into three categories: medication, diet and supplement therapy, and complementary and alternative medicine (CAM) and other therapies. The effects of medications such as AST-120 and meclofenamate are described. Diet and supplement therapies include plant-based diet, very low-protein diet, probiotics, prebiotics, synbiotics, and nutraceuticals. The research status of Chinese herbal medicine is discussed for CAM and other therapies. This review can provide some treatment recommendations for the reduction of UTs in patients with chronic kidney disease.

Therapeutic Targeting of Aristolochic Acid Induced Uremic Toxin Retention, SMAD 2/3 and JNK/ERK Pathways in Tubulointerstitial Fibrosis: Nephroprotective Role of Propolis in Chronic Kidney Disease.

The nephrotoxicity of aristolochic acids (AAs), p-cresyl sulfate (PCS) and indoxyl sulfate (IS) were well-documented, culminating in tubulointerstitial fibrosis (TIF), advanced chronic kidney disease (CKD) and fatal urothelial cancer. Nonetheless, information regarding the attenuation of AAs-induced nephropathy (AAN) and uremic toxin retention is scarce. Propolis is a versatile natural product, exerting anti-oxidant, anti-cancer and anti-fibrotic properties. We aimed to evaluate nephroprotective effects of propolis extract (PE) in a murine model. AAN was developed to retain circulating PCS and IS using C57BL/6 mice, mimicking human CKD. The kidney sizes/masses, renal function indicators, plasma concentrations of PCS/IS, tissue expressions of TIF, α-SMA, collagen IaI, collagen IV and signaling pathways in transforming growth factor-ß (TGF-ß) family were analyzed among the control, PE, AAN, and AAN-PE groups. PE ameliorated AAN-induced renal atrophy, renal function deterioration, TIF, plasma retention of PCS and IS. PE also suppressed α-SMA expression and deposition of collagen IaI and IV in the fibrotic epithelial-mesenchymal transition. Notably, PE treatment in AAN model inhibited not only SMAD 2/3-dependent pathways but also SMAD-independent JNK/ERK activation in the signaling cascades of TGF-ß family. Through disrupting fibrotic epithelial-mesenchymal transition and TGF-ß signaling transduction pathways, PE improves TIF and thereby facilitates renal excretion of PCS and IS in AAN. In light of multi-faced toxicity of AAs, PE may be capable of developing a new potential drug to treat CKD patients exposed to AAs.

Dietary L-lysine prevents arterial calcification in adenine-induced uremic rats.

Vascular calcification (VC) is a life-threatening complication of CKD. Severe protein restriction causes a shortage of essential amino acids, and exacerbates VC in rats. Therefore, we investigated the effects of dietary l-lysine, the first-limiting amino acid of cereal grains, on VC. Male Sprague-Dawley rats at age 13 weeks were divided randomly into four groups: low-protein (LP) diet (group LP), LP diet+adenine (group Ade), LP diet+adenine+glycine (group Gly) as a control amino acid group, and LP diet+adenine+l-lysine·HCl (group Lys). At age 18 weeks, group LP had no VC, whereas groups Ade and Gly had comparable levels of severe VC. l-Lysine supplementation almost completely ameliorated VC. Physical parameters and serum creatinine, urea nitrogen, and phosphate did not differ among groups Ade, Gly, and Lys. Notably, serum calcium in group Lys was slightly but significantly higher than in groups Ade and Gly. Dietary l-lysine strongly suppressed plasma intact parathyroid hormone in adenine rats and supported a proper bone-vascular axis. The conserved orientation of the femoral apatite in group Lys also evidenced the bone-protective effects of l-lysine. Dietary l-lysine elevated plasma alanine, proline, arginine, and homoarginine but not lysine. Analyses in vitro demonstrated that alanine and proline inhibit apoptosis of cultured vascular smooth muscle cells, and that arginine and homoarginine attenuate mineral precipitations in a supersaturated calcium/phosphate solution. In conclusion, dietary supplementation of l-lysine ameliorated VC by modifying key pathways that exacerbate VC.

In vivo assessment of bacteriotherapy on acetaminophen-induced uremic rats.

OBJECTIVES: Acetaminophen is a commonly used antipyretic agent which, at high doses, causes renal tubular damage and uremia. Bacteriotherapy affords a promising approach to mitigating uremic intoxication by ingestion of live microbes able to catabolize uremic solutes in the gut. The present study evaluates the nonpathogenic soil-borne urease-positive bacterium Sporosarcina pasteurii (Sp) as a potential urea-targeted component for such an "enteric dialysis" formulation. METHODS: Twenty-four albino male rats were randomly divided into 4 groups: The control group (group NC) received distilled water intraperitoneally for 7 days. The positive control group (group U) received 500 mg/kg acetaminophen intraperitoneally for 7 days. The tested group (group UP) was administered Sp at a dosage of 10(9) cells/day for 5 weeks, after receiving 500 mg/kg per day of acetaminophen intraperitoneally for 7 days. Vehicle control (group VC) received only Sp at a dosage of 10(9) cells/day for 5 weeks without acetaminophen treatment. Blood, kidney, liver and stool samples were collected after scarification, for biochemical (urea, creatinine, malondialdehyde, superoxide dismutase, catalase, glutamate oxaloacetate transaminase [GOT] and glutamate pyruvate transaminase [GPT] of blood, kidney and liver) tests. Limited fecal analysis was performed. RESULTS: Blood urea nitrogen (urea, creatinine) and toxicity indicators (GOT, GPT) were increased, and antioxidant enzymes were decreased in group U. Blood urea nitrogen and toxicity indicators were reduced, and antioxidant enzymes were increased significantly in the group UP (p<0.05) compared with group U. The number of Sp was increased in Sp-treated groups compared with groups NC and U. CONCLUSIONS: The study demonstrated that the bacteria tested reduced blood urea nitrogen levels significantly.

Restoration of bone mineralization by cinacalcet is associated with a significant reduction in calcitriol-induced vascular calcification in uremic rats.

The present study investigated to what extent normalization of bone turnover goes along with a reduction of high-dose calcitriol-induced vascular calcifications in uremic rats. Five groups of male Sprague-Dawley rats were studied: sham-operated controls (n = 7), subtotally nephrectomized (SNX) uremic (CRF) animals (n = 12), CRF + calcitriol (vitD) (0.25 µg/kg/day) (n = 12), CRF + vitD + cinacalcet (CIN) (10 mg/kg/day) (n = 12), and CRF + vitD + parathyroidectomy (PTX) (n = 12). Treatment started 2 weeks after SNX and continued for the next 14 weeks. High-dose calcitriol treatment in hyperparathyroid rats went along with the development of distinct vascular calcification, which was significantly reduced by >50 %, in both CIN-treated and PTX animals. Compared to control animals and those of the CRF group, calcitriol treatment either in combination with CIN or PTX or not was associated with a significant increase in bone area comprising ±50 % of the total tissue area. However, whereas excessive woven bone accompanied by a dramatically increased osteoid width/area was seen in the CRF + vitD group, CIN treatment and PTX resulted in significantly reduced serum PTH level, which was accompanied by a distinct reduction of both the bone formation rate and the amount of osteoid. These data indicate that less efficient calcium and phosphorus incorporation in bone inherent to the severe hyperparathyroidism in vitamin D-treated uremic rats goes along with excessive vascular calcification, a process which is partially reversed by CIN treatment in combination with a more efficacious bone mineralization, thus restricting the availability of calcium and phosphate for being deposited in the vessel wall.

Occupational kidney disease among Chinese herbalists exposed to herbs containing aristolochic acids.

OBJECTIVE: Many Chinese herbs contain aristolochic acids (ALAs) which are nephrotoxic and carcinogenic. The objective of this study was to identify whether exposure to herbs containing ALAs increased the risk of kidney disease among Chinese herbalists. METHODS: A nested case-control study was carried out on 6538 Chinese herbalists registered between 1985 and 1998. All incident cases of chronic renal failure reported to the Database of Catastrophic Illness of the National Health Insurance Bureau between 1995 and 2000 were defined as the case group. Up to four controls without renal failure were randomly matched to each case by sex and year of birth. A structured questionnaire survey was administered between November and December 2002. The Mantel-Haenszel method and conditional logistic regression were used to estimate the risks. RESULTS: 40 cases and 98 matched controls were included in the final analysis. After adjusting for age, frequent analgesic use, and habitual consumption of alcohol, fermented or smoked food, we found manufacturing and selling Chinese herbal medicine (OR 3.43, 95% CI 1.16 to 10.19), processing, selling or dispensing herbal medicines containing Fangji (OR 4.17, 95% CI 1.36 to 12.81), living in the workplace (OR 3.14, 95% CI 1.11 to 8.84) and a history of taking of herbal medicines containing Fangji (frequently or occasionally) (OR 5.42, 95% CI 1.18 to 24.96) were significantly associated with renal failure. CONCLUSION: Occupational exposure to and consumption of herbs containing ALAs increases the risk of renal failure in Chinese herbalists.

Mutant FGF23 prevents the progression of chronic kidney disease but aggravates renal osteodystrophy in uremic rats.

Phosphorus is one of the important factors that accelerate the progression of chronic kidney disease. Phosphorus restriction or phosphate binders have been reported to have the ability to prevent the progression of chronic kidney disease. FGF23 is a circulating factor that regulates renal phosphorus reabsorption and 1 alpha-hydroxylase activity. We focused on the phosphaturic activity of FGF23 and investigated whether a pharmacological dose of FGF23 is beneficial to the progression of renal insufficiency in uremic rats. To this end, we administered one of the mutant FGF23 expression plasmids into irreversible Thy1 rats. Chronic renal failure rats were established by intravenous injection of anti-rat CD90 (Thy1.1) monoclonal antibody to unilaterally nephrectomized Wistar rats. The rats were then intravenously injected every 2 wk with a naked DNA solution containing 10 microg of MOCK vector or a mutant FGF23 expression plasmid for 13 wk. Renal function was assessed biochemically and histopathologically. Mutant FGF23 significantly decreased serum creatinine and serum urea nitrogen. The marked glomerular sclerosis observed in uremic rats receiving the MOCK vector was ameliorated in rats treated with mutant FGF23. However, mutant FGF23 not only significantly decreased serum 1,25(OH)(2)D and calcium but also aggravated high-turnover renal osteodystrophy from extremely high levels of PTH. These results might be a result of the mechanisms of FGF23 such as phosphaturic activity and lowering the level of 1,25(OH)(2)D. In conclusion, mutant FGF23 prevented the progression of chronic renal failure by regulating serum phosphorus but aggravated renal osteodystrophy from the lowered levels of 1,25(OH)(2)D.

Intravenous iron, inflammation, and oxidative stress: is iron a friend or an enemy of uremic patients?

Intravenous iron supplementation is a recognized therapy for anemia in chronic hemodialysis patients, especially in those treated with erythropoietin. The vast majority of patients with chronic kidney disease (CKD) seem to be iron-deficient, as evaluated by the usual parameters and by iron staining on bone marrow biopsy, because of multiple forms of interference with all phases of iron metabolism. The need for iron supplementation in CKD patients becomes obvious. Intravenous iron was demonstrated to be superior to oral iron in hemodialysis patients. There is also evidence for the superiority of intravenous iron in peritoneal dialysis and in nondialysis-dependent CKD patients. On the other hand, intravenous iron could promote cytotoxicity and tissue injury, and exacerbate oxidative stress and thus endothelial dysfunction, as well as inflammation and the progression of both CKD and cardiovascular disease. Nevertheless, correction of anemia is effective in reducing oxidative stress and, consequently, cardiovascular risk. The overall risk-benefit ratio favors the use of intravenous iron alone or with an erythropoietic stimulating agent in the management of renal anemia. Clinical judgment is necessary in each individual case to diagnose iron deficiency and effectively use intravenous iron.

Administration of oral charcoal adsorbent (AST-120) suppresses low-turnover bone progression in uraemic rats.

BACKGROUND: Using a rat model of renal failure with normal parathyroid hormone levels, we had demonstrated previously that bone formation decreased depending on the degree of renal dysfunction, and hypothesized that uraemic toxins (UTx) are associated with the development of low-turnover bone development, complicating renal failure. In this study, focusing on indoxyl sulphate (IS) as a representative UTx, we analysed the effect of an oral charcoal adsorbent AST-120, which removes uraemic toxins and their precursors from the gastrointestinal tract, on bone turnover. METHODS: AST-120 or vehicle was administered orally to model rats with uraemia and low turnover bone. Bone turnover was analysed by histomorphometry. Expression of osteoblast-related genes and oat-3 gene was analysed by reverse transcription polymerase chain reaction. RESULTS: In rats treated with vehicle, serum IS level increased with time after renal dysfunction, while bone formation decreased accompanied by down-regulation of the parathyroid/parathyroid-related peptide hormone receptor, alkaline phosphatase and osteocalcin genes. Administration of AST-120 inhibited the accumulation of IS in blood and ameliorated bone formation. Bone formation rate was 2.4 +/- 1.7 microm(3)/m(2)/year in controls given vehicle and was 11.7 +/- 2.4 microm(3)/m(2)/year in rats administered with AST-120 (P < 0.05). AST-120 treatment also reversed the down-regulation of osteoblast-related genes. Gene expression of oat-3 was detected in the tibia of rats. CONCLUSION: Administration of the oral charcoal adsorbent AST-120 decreases the osteoblast cytotoxicity of UTx including IS, and suppresses progression of low bone turnover in uraemic rats.

Hypocalcemia and azotemia associated with zoledronic acid and interferon alfa.

OBJECTIVE: To describe severe hypocalcemia and acute renal failure associated with zoledronic acid and interferon alfa in a patient with metastatic carcinoid tumors. CASE SUMMARY: A 39-year-old white man with metastatic carcinoid tumor tolerated treatment with subcutaneous long-acting octreotide monthly and interferon alfa 6 million units 3 times weekly for 6 months. Due to multiple bony metastases, zoledronic acid was prescribed as a monthly 4-mg intravenous infusion over 30 minutes to prevent skeletal-related events. Although the first infusion went well, the patient developed severe hypocalcemia and acute renal failure after the second zoledronic infusion. DISCUSSION: Bisphosphonates may infrequently cause symptomatic hypocalcemia, especially among patients who have vitamin D deficiency or hypoparathyroidism or receive treatment with an aminoglycoside. Our literature review suggests that zoledronic acid and interferon alfa may exert additive effects on the inhibition of osteoclasts, thus potentially precipitating hypocalcemia. Renal dysfunction may not be a direct consequence of interferon alfa. However, altered mental function due to hypocalcemia may lead to dehydration and further exacerbate renal dysfunction, a known adverse effect of zoledronic acid. Since therapeutic indications of both interferon alfa and zoledronic acid continue to expand, clinicians should be aware of these serious adverse reactions and potential interaction. Supportive treatment with hydration, calcium supplement, and oral calcitriol resulted in resolution of hypocalcemia, but only partial improvement of azotemia. CONCLUSIONS: In our patient with metastatic carcinoid tumor, treatment with zoledronic acid and interferon alfa was associated with symptomatic hypocalcemia and acute renal failure.

X-linked hypophosphatemia: normal renal function despite medullary nephrocalcinosis 25 years after transient vitamin D2-induced renal azotemia.

Nephrocalcinosis (NC) detected by ultrasound is a recognized abnormality for some patients with X-linked hypophosphatemia (XLH) who received vitamin D2 and inorganic phosphate therapy, but is commonly observed in XLH patients treated with 1,25-dihydroxyvitamin D3 and inorganic phosphate supplementation. Nevertheless, long-term follow-up of kidney function in XLH patients with NC detected ultrasonographically has not been reported. We investigated two women with XLH, ages 31 (patient 1) and 39 (patient 2) years, each of whom had suffered at least one documented episode of vitamin D2-induced hypercalcemia and renal azotemia during childhood. Patient 2 had also been treated with inorganic phosphate. No medications for XLH had been taken during adulthood. Renal ultrasonography at our institution demonstrated marked bilateral medullary NC in both women. No other explanation was found for their NC that apparently occurred several decades earlier from medical therapy for XLH. Detailed studies (including creatinine clearance, beta2-microglobulin excretion, and fasting urinary osmolality and acidification) revealed no impairment of kidney function in either patient. Our findings indicate that subradiographic medullary NC acquired during medical therapy for XLH may persist for decades, but with no adverse renal sequelae. Definitive (long-term) assessment of kidney function in the XLH population with NC, however, will be necessary to fully understand the risk of current medical treatment for this most common heritable form of rickets.

[The hypoazotemic and diuretic action of lespeflan in acute kidney failure]. / Gipoazotemicheskoe i dureticheskoe deistvie lespefalana pri ostroi pochechnoi nedostatochnosti.

Hypoazotemic and diuretic effects of a new bioflavonoid drug lespephlan made in Russia have been tested in a dose 2 ml/kg to treat acute renal failure induced by mercury bichloride solution (a dose 2 mg/kg). The data were obtained on lespephlan ability to reduce blood levels of urea, creatinine and activate their renal elimination, to enhance diuresis, sodium clearance, glomerular filtration. Water and electrolyte release were also changeable by angiotensin aldosterone system. Mechanism of lespephlan hypoazotemic action is related to hepatic arginase inhibited activity as this enzyme plays a key role in detoxication of nitrous products urea and creatinine.

In vivo effect of cyanate on serum and eye lens in rat.

Supplementation of cyanate in rats caused a significant decrease in serum GSH and increase in calcium and phosphate level both in serum and lens. Consequently, these changes led to induce acidosis uremia in serum and hypercalcemia and hyperphosphatemia in lens which may be possible causing factor for cataract.

Renal effects of continuous infusion of recombinant interleukin-2 in children.

Recombinant interleukin-2 (rIL-2) is a new promising treatment for cancer, but is associated with severe renal toxicity. This study is the first to analyse the renal effects of rIL-2 in children. Twenty-one cycles of continuous rIL-2 infusion were studied in 15 patients; mean age was 6.9 years and average weight 18.9 kg. Interstitial fluid retention and oliguria (baseline, 1.7 ml/kg per hour; nadir, 0.5 mg/kg per hour) were associated with hypotension (baseline, 101/56 mm Hg; nadir, 85/43 mm Hg) and decreased intravascular volume (plasma renin activity increased x 10). Weight gain (+7.9%) was observed in 13 cycles whereas weight loss (-6.3%) was shown in 8 cycles because of digestive and cutaneous losses, mainly in the youngest patients. This prerenal azotaemia was characterized by a decrease in creatinine clearance (from 101 to 36 ml/min per 1.73 m2) and a low fractional excretion of sodium (FENa) (from 0.70% to 0.09%). Hypotension and hypovolaemia needed vascular filling (n = 12), dopamine (n = 7) and interruption of rIL-2 (n = 2). Most abnormalities occurred as early as day 2 of therapy and were always reversible after a short period with sodium leakage (diuresis = 2.2 ml/kg per hour, FENa = 2.01%). Hypophosphataemia was associated with low urinary excretion of phosphorus, suggesting an increased uptake of inorganic phosphorus by rapidly proliferating lymphoid cells.

Digitalis toxicity at Duke Hospital, 1973 to 1984.

In a review of the records of 81 patients with the discharge diagnosis of digitalis toxicity, I found a preponderance of very old patients, many of whom had anorexia, nausea, and prerenal azotemia. Arrhythmias were common (93%) and reflected enhanced automaticity, enhanced AV block, or both. Atrial fibrillation with complete heart block and a regular junctional rhythm should particularly elicit suspicion of digitalis toxicity. Atrial tachycardia with block is less specific and less frequent.

Sequential chemotherapy of advanced colorectal cancer with standard or high-dose methotrexate followed by 5-fluorouracil.

Thirty patients with advanced measurable colorectal cancer were randomized to receive either methotrexate (MTX) 200 mg/m2 or 40 mg/m2, followed in four hours by 5-fluorouracil (5-FU) 600 mg/m2. Patients receiving the higher dose MTX were given leucovorin rescue 24 hours later. Eight of 13 patients treated with 200 mg/m2 MTX + 5-FU developed severe hematologic toxicity, leading to two toxic deaths. In addition, 9/13 developed mild azotemia, and three patients had severe gastrointestinal toxicity. No patients with prior chemotherapy responded to either regimen. Among those without prior chemotherapy, there were two of six and three of eight partial responses, respectively, in the 200 mg/m2 and 40 mg/m2 MTX regimens. Sequential 200 mg/m2 MTX followed by 5-FU after four hours has unacceptable toxicity. Sequential treatment with standard dose MTX + 5-FU is tolerable and merits further study.

Intravascular haemolysis and renal impairment after blood transfusion in two patients on long-term 5-fluorouracil and mitomycin-C.

In a multicentre trial of adjuvant chemotherapy in gastric adenocarcinoma, a number of patients developed chronic haemolysis and renal failure following long-term treatment with 5-fluorouracil and mitomycin-C. This was exacerbated by blood transfusion, leading to an acute intravascular haemolytic state accompanied by rapid decline in renal function. One patient investigated extensively was treated with antiplatelet drugs, steroids, and fresh frozen plasma without success. At necropsy this patient and another had renal changes typical of the haemolytic-uraemic syndrome and no evidence of tumour recurrence. Long-term treatment with this drug combination is potentially dangerous, and routine monitoring of renal function is recommended.

Chronic uremia syndrome in dogs induced with uranyl nitrate.

11 adult female dogs were given periodic intravenous injections of uranyl nitrate [UO2(NO3)2 . 6H2O] to create a syndrome of chronic uremia. Initially, dogs usually received 2.0 mg/kg of uranyl nitrate; subsequent doses were generally less. After the initial injection, there was an abrupt fall in creatinine clearance and rise in plasma urea nitrogen. Low and relatively constant creatinine clearances (10.2 +/- SD 2.7 ml/min) were easily maintained with further injections. Dogs developed proteinuria, aminoaciduria, weight loss, and plasma amino acid levels similar to those of chronically uremic humans and rats. With creatinine clearances of 4 ml/min or less, dogs became listless and lethargic, and daily activity and food intake decreased. Repeated injections of uranyl nitrate appear to be an easy and reliable method for creating a model of chronic uremia in dogs.