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Nobuo Nagano

Publications and source records attributed to Nobuo Nagano.

17 recordsLinked to original sources
PubMed2006

Efficacy of darbepoetin in doxorubicin-induced cardiorenal injury in rats.

This study was intended to elucidate the efficacy of an erythropoietin analog in cardiorenal dysfunction syndrome using a rodent model. Cardiorenal dysfunction was induced using doxorubicin hydrochloride (DXR). Lower doses (3 microg/kg) and higher doses (30 microg/kg) of darbepoetin alfa (DA) were used for intervention. Blood examinations for creatinine, blood urea nitrogen, iron, and hemoglobin were performed until 11 weeks after starting DA administration. Urine collection was performed 10 weeks after starting DA, and protein, iron, and N-acetyl-beta-D-glucosaminidase levels and antioxidation capacity of DA were determined. The dry left ventricular heart weight was measured, when the animals were sacrificed 11 weeks after starting DA administration. Histological analyses were performed for interstitial fibrotic changes and iron deposition in the kidney. Administration of DA markedly improved anemia to the normal control level and significantly alleviated DXR-induced increases of creatinine, blood urea nitrogen, renal interstitial fibrosis, renal iron deposition, and dry left ventricular weight, but serum and urinary iron and urinary protein and N-acetyl-beta-D-glucosaminidase levels were unchanged. The urinary total radical-trapping antioxidant capacity was improved to the normal control level in DA-treated animals. DA reduced the DXR-induced cardiorenal injury. This improvement was achieved, when anemia was corrected to the normal control level.

Acetylglucosaminidase↗
PubMed2006

Direct in vitro evidence of the suppressive effect of cinacalcet HCl on parathyroid hormone secretion in human parathyroid cells with pathologically reduced calcium-sensing receptor levels.

Clinical studies have been performed to determine the effect of cinacalcet HCl (cinacalcet), an allosteric modulator of the calcium-sensing receptor (CaR), on primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism of uremia (SHPT). However, no in vitro studies on human parathyroid cells have been reported to date. In this study, the inhibitory effect of cinacalcet on PTH secretion was analyzed in primary cultured parathyroid cells obtained from patients. The investigation involved three PHPT and three SHPT patients subjected to therapeutic parathyroidectomy. Notably, all SHPT patients were resistant to intravenous vitamin D analogue therapy. Removed parathyroid tumors were used for immunohistochemistry and parathyroid cell primary culture. Immunohistochemical analyses revealed diminished expression of CaR and vitamin D receptor (VDR) in all parathyroid tumors. PTH secretion from cultured parathyroid cells of PHPT and SHPT patients was suppressed by extracellular Ca2+ and cinacalcet in a dose-dependent manner. Rates of suppression of PTH secretion in PHPT and SHPT by cinacalcet (1000 nmol/l) were 61% +/- 21% and 61% +/- 19%, respectively. Cinacalcet demonstrates significant potency in the suppression of PTH secretion in primary cultured human parathyroid cells in vitro, despite reduced levels of the target protein, CaR. Data from this in vitro analysis support the clinical application of cinacalcet in PHPT and SHPT therapy.

Cinacalcet↗
PubMed2005

Sevelamer hydrochloride reverses parathyroid gland enlargement via regression of cell hypertrophy but not apoptosis in rats with chronic renal insufficiency.

BACKGROUND: Dietary phosphate restriction suppresses parathyroid hormone (PTH) secretion, synthesis, and parathyroid cell proliferation in experimental animals with chronic renal insufficiency (CRI), independently of serum calcium and 1,25(OH)2D3 levels. This study was conducted to examine whether sevelamer hydrochloride (sevelamer), a metal-free phosphate binder, could regress an advanced parathyroid gland (PTG) hyperplasia and enlargement in rats with CRI. METHODS: Male Sprague-Dawley rats were fed a diet containing adenine for 6 weeks to establish CRI. Normal rats and adenine-treated rats were sacrificed to obtain the PTG (baseline group). The adenine diet was changed to a normal diet or diet containing 1 or 3% sevelamer for another 4 weeks. Time course changes of serum levels of calcium, phosphorus, and PTH were measured. At the end of the study, the PTG was weighed and examined histologically. RESULTS: Adenine-treated rats developed severe CRI with marked elevation of serum phosphorus and PTH. The PTG weight markedly increased with enlarged cell volume (i.e. cell hypertrophy) at baseline. Sevelamer treatment rapidly lowered serum phosphorus and PTH levels within 6 days, and after 4 weeks, reduced the PTG weight by 38% compared to adenine-treated rats at baseline. The reduction in PTG weight was due to regression of cell hypertrophy, but not to decreased cell number by apoptosis. Decreased expression of calcium receptor in the PTG at baseline was partially recovered by the sevelamer treatment. CONCLUSIONS: The sevelamer treatment can reduce the PTG weight with a reduction in serum PTH levels via regression of cell hypertrophy but not apoptosis in rats with CRI. Reduced PTG function might contribute to the regression of cell hypertrophy.

Animals↗
PubMed2005

Pharmacological and clinical properties of calcimimetics: calcium receptor activators that afford an innovative approach to controlling hyperparathyroidism.

Circulating levels of calcium ion (Ca2+) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid gland (PTG) cells. PTG cells can sense small fluctuations in plasma Ca2+ levels by virtue of a cell surface Ca2+ receptor (CaR) that belongs to the superfamily of G protein-coupled receptors (GPCR). Compounds that activate the CaR and inhibit PTH secretion are termed 'calcimimetics' because they mimic or potentiate the effects of extracellular Ca2+ on PTG cell function. Preclinical studies with NPS R-568, a first generation calcimimetic compound that acts as a positive allosteric modulator of the CaR, have demonstrated that oral administration decreases serum levels of PTH and calcium, with a leftward shift in the set-point for calcium-regulated PTH secretion in normal rats. NPS R-568 also suppresses the elevation of serum PTH levels and PTG hyperplasia and can improve bone mineral density (BMD) and strength in rats with chronic renal insufficiency (CRI). Clinical trials with cinacalcet hydrochloride (cinacalcet), a compound with an improved metabolic profile, have shown that long-term treatment continues to suppress the elevation of serum levels of calcium and PTH in patients with primary hyperparathyroidism (1HPT). Furthermore, clinical trials in patients with uncontrolled secondary hyperparathyroidism (2HPT) have demonstrated that cinacalcet not only lowers serum PTH levels, but also the serum phosphorus and calcium x phosphorus product; these are a hallmark of an increased risk of cardiovascular disease and mortality in dialysis patients with end-stage renal disease. Indeed, cinacalcet has already been approved for marketing in several countries. Calcimimetic compounds like cinacalcet have great potential as an innovative medical approach to manage 1HPT and 2HPT.

Aniline Compounds↗
PubMed2005

Functional proteins involved in regulation of intracellular Ca(2+) for drug development: the extracellular calcium receptor and an innovative medical approach to control secondary hyperparathyroidism by calcimimetics.

Circulating levels of calcium ion (Ca(2+)) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid cells. Parathyroid cells can sense small fluctuations in plasma Ca(2+) levels by virtue of a cell surface Ca(2+) receptor (CaR) that belongs to the superfamily of G-protein-coupled receptors. Calcimimetics are positive allosteric modulators that activate the CaR on parathyroid cells and thereby immediately suppress PTH secretion. Pre-clinical studies with NPS R-568, a first generation calcimimetic compound, have demonstrated that daily oral administration inhibits the elevation of plasma PTH levels and parathyroid gland hyperplasia and ameliorates impaired bone qualities in rats with chronic renal insufficiency. The results of clinical trials with cinacalcet hydrochloride, a second generation calcimimetic compound, have shown that calcimimetics possess lowering effects not only on serum PTH levels but also on serum calcium x phosphorus product levels, a hallmark of an increased risk for cardiovascular death in dialysis patients with end-stage renal disease (ESRD). Thus, calcimimetics have considerable potential as an innovative medical approach to manage secondary hyperparathyroidism associated with ESRD. Indeed, cinacalcet hydrochloride has been approved in several countries and is the first positive allosteric modulator of any G protein-coupled receptor to reach the market.

Aniline Compounds↗
PubMed2005

Relationship between parathyroid calcium-sensing receptor expression and potency of the calcimimetic, cinacalcet, in suppressing parathyroid hormone secretion in an in vivo murine model of primary hyperparathyroidism.

Cinacalcet HCl, an allosteric modulator of the calcium-sensing receptor (CaR), has recently been approved for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease on dialysis, due to its suppressive effect on parathyroid hormone (PTH) secretion. Although cinacalcet's effects in patients with primary and secondary hyperparathyroidism have been reported, the crucial relationship between the effect of calcimimetics and CaR expression on the parathyroid glands requires better understanding. To investigate its suppressive effect on PTH secretion in primary hyperparathyroidism, in which hypercalcemia may already have stimulated considerable CaR activity, we investigated the effect of cinacalcet HCl on PTH-cyclin D1 transgenic mice (PC2 mice), a model of primary hyperparathyroidism with hypo-expression of CaR on their parathyroid glands. A single administration of 30 mg/kg body weight (BW) of cinacalcet HCl significantly suppressed serum calcium (Ca) levels 2 h after administration in 65- to 85-week-old PC2 mice with chronic biochemical hyperparathyroidism. The percentage reduction in serum PTH was significantly correlated with CaR hypo-expression in the parathyroid glands. In older PC2 mice (93-99 weeks old) with advanced hyperparathyroidism, serum Ca and PTH levels were not suppressed by 30 mg cinacalcet HCl/kg. However, serum Ca and PTH levels were significantly suppressed by 100 mg/kg of cinacalcet HCl, suggesting that higher doses of this compound could overcome severe hyperparathyroidism. To conclude, cinacalcet HCl demonstrated potency in a murine model of primary hyperparathyroidism in spite of any presumed endogenous CaR activation by hypercalcemia and hypo-expression of CaR in the parathyroid glands.

Aging↗
PubMed2005

[Drugs inhibiting parathyroid hormone (PTH) secretion by control of the calcium receptor (calcimimetics)--effect on the set point of calcium-regulated PTH secretion].

Calcimimetics are positive allosteric modulators that activate the parathyroid calcium receptor (CaR) and thereby immediately suppress parathyroid hormone (PTH) secretion. Preclinical studies have demonstrated that calcimimetics inhibit PTH secretion and parathyroid gland hyperplasia and ameliorates bone qualities in rats with chronic renal insufficiency. Clinical trials with cinacalcet hydrochloride, a calcimimetic compound, have shown that calcimimetics possess lowering effects not only on serum PTH levels but also on serum phosphorus levels in dialysis patients with secondary hyperparathyroidism (2HPT). Thus, calcimimetics have considerable potential as an innovative medical approach to manage 2HPT. In this review, the similarities are extrapolated between the pharmacological effect of calcimimetics on the set point of Ca-regulated PTH secretion and clinical observations in affected subjects with activating CaR mutations.

Animals↗
PubMed2005

[The calcium receptor and magnesium metabolism].

The calcium receptor (CaR), which regulates Ca(2+) homeostasis, senses Mg(2+) and participates in Mg(2+) metabolism mainly at the parathyroid gland and kidney as well as Ca(2+) metabolism. In the parathyroid gland, Mg(2+) suppresses parathyroid hormone (PTH) secretion by the activation of CaR, and regulates the sensitivity of CaR by its unique effect. In the kidney, the activation of CaR inhibits Mg(2+) reabsorption directly or indirectly, mainly at the downstream of loop of Henle.

Animals↗
PubMed2005

[Effects of intermittent treatment with sevelamer hydrochloride on parathyroid hyperplasia and vascular calcification in rats with chronic kidney disease].

Phosphorus directly controls parathyroid hormone (PTH) synthesis and secretion. Serum levels of the novel phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), are positively correlated with hyperphosphatemia in patients with chronic kidney disease (CKD). Rats were fed a diet containing adenine for 4 weeks to establish CKD. Animals were then offered a diet containing sevelamer hydrochloride (sevelamer) or a normal diet for alternating 2 week periods over 8 weeks. Adenine-treated rats showed marked elevations of serum phosphorus, PTH and FGF23 levels associated with parathyroid hyperplasia and aortic calcification. Serum phosphorus, PTH and FGF23 levels decreased rapidly when sevelamer treatments commenced and recovered rapidly once they were discontinued. However, intermittent treatment with sevelamer successfully inhibited parathyroid hyperplasia and aortic calcification. In conclusion, phosphate-binder treatment can effectively inhibit the elevation of serum FGF23 levels, as well as PTH levels, under conditions of CKD. Setting up a period of reduced serum phosphorus levels, even if it is intermittent, is worthwhile for the inhibition of the development of parathyroid hyperplasia and aortic calcification.

Adenine↗
PubMed2004

[Sevelamer hydrochloride prevents ectopic calcification of blood vessels].

Sevelamer hydrochloride is a non-absorbed calcium- and metal-free phosphate binder that lowers the serum phosphorus levels in hemodialysis patients. Sevelamer contains multiple amines, which are partially protonated and interact with phosphate molecules through ionic and hydrogen bonding. We show the in vitro phosphate binding assay data and the efficacy of sevelamer to lower the serum phosphorus and calcium phosphorus product in several animal models. Furthermore, we indicate the vivid data that sevelamer prevented the ectopic calcification of aorta in adenine induced renal failure model, which represent severe hyperphosphatemia and the related dialysis complications.

Adsorption↗
PubMed2003

Sevelamer hydrochloride prevents ectopic calcification and renal osteodystrophy in chronic renal failure rats.

BACKGROUND: Hyperphosphatemia is associated with severe complications, including ectopic calcification of soft tissues, secondary hyperparathyroidism, and renal osteodystrophy (ROD). Sevelamer hydrochloride is a nonabsorbed calcium- and metal-free phosphate binder that lowers serum phosphorus levels in hemodialysis patients. This study examined the efficacy of sevelamer in preventing ectopic calcification of soft tissues and ROD in adenine-induced renal failure rats. METHODS: Male, 12-week-old Wistar-Jcl rats were freely fed an adenine diet (0.75 g adenine in 100 g normal diet) for four weeks. After three weeks of the adenine diet, when serum phosphorus levels had significantly increased, the rats were freely fed a normal diet that contained 1% or 2% of sevelamer for another five weeks. Time course changes of serum levels of phosphorus, calcium, and parathyroid hormone (PTH) were measured. At the end of the study, calcium and phosphorus levels in the heart and aorta were measured, and the calcification of kidney, heart, aorta, and stomach were histopathologically examined. The severity of ROD was evaluated by a histopathologic and morphometric analysis of the femurs. RESULTS: Compared with the adenine controls (N = 10), the sevelamer-treated (1%, N = 6; and 2%, N = 10) groups of adenine-induced renal failure rats had reduced serum phosphorus, serum calcium x phosphorus product, and serum PTH levels. Moreover, in the treatment groups, sevelamer suppressed calcification of the aorta media, and also the osteoid volume, fibrosis volume, and porosity ratio of femurs. CONCLUSION: These results suggest that sevelamer treatment might contribute to the suppression of ectopic calcification and ROD.

Animals↗
PubMed2003

Control of parathyroid cell growth by calcimimetics.

Parathyroid cell hyperplasia is commonly observed in patients with chronic renal insufficiency and largely accounts for refractory secondary hyperparathyroidism. Calcimimetics are newly synthesized compounds that activate a calcium receptor on the parathyroid cell and can suppress parathyroid hormone secretion. The calcimimetic compound AMG 073 has been examined in clinical trials, and the data obtained so far demonstrate that the compound can lower the circulating levels of parathyroid hormone and calcium-phosphorus product in patients with secondary hyperparathyroidism. Furthermore, experimental evidence indicates that calcimimetics have the potential to inhibit parathyroid cell proliferation and block the progression of parathyroid hyperplasia. These beneficial effects, especially the potential to control parathyroid cell proliferation, would place calcimimetics among the essential therapeutic agents for treating secondary hyperparathyroidism.

Animals↗
PubMed2003

Sevelamer hydrochloride, a calcium-free phosphate binder, inhibits parathyroid cell proliferation in partially nephrectomized rats.

BACKGROUND: Secondary hyperparathyroidism characterized by hyperplasia of the parathyroid gland (PTG) is a consequence of chronic renal insufficiency (CRI). Dietary phosphate restriction and sevelamer hydrochloride, a calcium-free phosphate binder, suppress parathyroid hormone (PTH) secretion and PTG hyperplasia in experimental animals with CRI, independently of serum calcium and 1,25(OH)(2)D(3) concentrations. In the present study, the effect of sevelamer on PTG cell proliferation in rats with CRI was investigated. METHODS: Seven weeks after a 5/6 nephrectomy, rats were fed a diet containing 0, 1 or 3% sevelamer for 4 weeks, and sham-operated rats were fed a normal diet. Serum calcium, phosphorus, PTH and 1,25(OH)(2)D(3) concentrations were measured. The number of cells positive for proliferating cell nuclear antigen (PCNA) in the maximal two-dimensional PTG area was counted at the end of study. RESULTS: Sevelamer inhibited increases in serum phosphorus, calcium-phosphorus product and PTH concentrations without affecting serum calcium or 1,25(OH)(2)D(3). Sevelamer also suppressed the maximal PTG area and PCNA-positive cells. There was also a strong correlation between the maximal PTG area and serum PTH concentration, and between PCNA-positive cells and the maximal PTG area, as well as between serum phosphorus concentration and PCNA-positive cells. CONCLUSIONS: These results indicate that sevelamer treatment reduces serum phosphorus concentration and could inhibit PTG cell proliferation and prevent PTG hyperplasia.

Animals↗
PubMed2003

Sevelamer hydrochloride, a phosphate binder, protects against deterioration of renal function in rats with progressive chronic renal insufficiency.

BACKGROUND: Dietary phosphate restriction prevents renal function deterioration in animal models. This study examined whether sevelamer hydrochloride (Renagel(R); 'sevelamer' hereafter), a non-calcaemic phosphate binder could slow deterioration of renal function in rats with progressive renal insufficiency. METHODS: Wistar Kyoto male rats were singly injected with normal rabbit serum or rabbit anti-rat glomerular basement membrane serum. Three days later, rats were fed a powder diet containing 0, 1 or 3% sevelamer for 58 days. Time course changes of serum levels of blood urea nitrogen (BUN), creatinine, calcium, phosphorus and parathyroid hormone (PTH) were measured throughout, and creatinine clearance (CCr), kidney calcium content and renal histology examined at the end of the study. RESULTS: Sevelamer partially inhibited elevation of BUN and serum creatinine, and completely inhibited increases in serum phosphorus, PTH and calcium xphosphorus product. Sevelamer significantly prevented the decrease in CCr and kidney calcium content elevation. Kidney calcium content and BUN and serum creatinine were strongly positively correlated, and kidney calcium content and CCr strongly negatively correlated. Kidney calcium content correlated well with serum phosphorus, serum calcium x phosphorus product and PTH, but not serum calcium. Sevelamer treatment partly prevented histological deterioration of both glomerular and tubulointerstitial lesions of the kidney. CONCLUSIONS: The results suggest that sevelamer protects against renal function deterioration by maintaining kidney calcium at a low level as a result of reducing serum phosphorus and PTH.

Animals↗
PubMed2003

[Pharmacological and clinical trial data on a novel phosphate-binding polymer (sevelamer hydrochloride), a medicine for hyperphosphatemia in hemodialysis patients].

Hyperphosphatemia is one of the major complications of hemodialysis patients and plays a key role in the pathogenesis of cardiovascular calcification and secondary hyperparathyroidism. Dietary phosphate restriction and removal of phosphate by dialysis are insufficient to control hyperphosphatemia. Therefore, almost all patients undergoing hemodialysis should take oral phosphate binders. Sevelamer hydrochloride (sevelamer) is a novel phosphate-binding polymer that contains neither aluminum nor calcium, and it is not absorbed from the gastrointestinal tract. In rat models with progressive chronic renal insufficiency, in addition to lowering effects on serum levels of phosphorus, calcium x phosphorus product, and parathyroid hormone, dietary treatment of sevelamer can prevent parathyroid hyperplasia, vascular calcification, high turnover bone lesion, and renal functional deterioration. In clinical studies with hemodialysis patients, sevelamer lowers serum phosphorus and calcium x phosphorus product without any incidence of hypercalcemia. Switching calcium-containing phosphate binders to sevelamer can decrease the percentage of hypoparathyroidism and hyperparathyroidism by negative calcium balance and increased dosage of vitamin D, respectively. Sevelamer also decreases serum low-density lipoprotein cholesterol levels by its bile acid-binding capacity. A long-term clinical study has demonstrated that the progression of coronary and aortic calcification in hemodialysis patients is attenuated by sevelamer. Thus, sevelamer offers the promise of impacting cardiac calcification and thereby reducing morbidity and mortality of hemodialysis patients.

Animals↗
PubMed2000

Activation of the calcium receptor by a calcimimetic compound halts the progression of secondary hyperparathyroidism in uremic rats.

The secondary hyperparathyroidism that develops in rats with chronic renal insufficiency (CRI) can be totally prevented by activation of the parathyroid Ca(2+) receptor with a calcimimetic compound, when treatment is initiated before parathyroid cell hyperplasia and increased circulating parathyroid hormone levels develop. In clinical practice, however, secondary hyperparathyroidism is usually manifest by the time CRI is diagnosed. This study examined the effects of daily oral gavage or continuous subcutaneous infusion for 8 wk of the calcimimetic NPS R-568 on the progression of established mild or moderate-to-severe secondary hyperparathyroidism in rats with CRI induced by 5/6 nephrectomy. Both oral and infused NPS R-568 completely prevented further hyperplasia but did not reduce total parathyroid cell number below that present at the initiation of treatment. This prevention of cellular proliferation occurred despite increases in plasma phosphate and decreases in Ca(2+) and 1, 25-dihydroxyvitamin D levels, and supports the view that the Ca(2+) receptor is the dominant regulator of parathyroid cell hyperplasia in addition to parathyroid hormone secretion. The clinical implications of these findings suggest that controlling Ca(2+) receptor activity with calcimimetic compounds could be sufficient to manage secondary hyperparathyroidism in CRI.

Analysis of Variance↗