Renal bone disease 1990: an unmet challenge for the nephrologist

24,25-dihydroxy vitamin D3 treatment inhibits parathyroid-stimulated adenylate cyclase in iliac crest biopsies from uremic patients

Renal osteodystrophy with increased bone resorption is a major clinical problem in patients with chronic renal failure. Previous reports have shown that treatment with 24,25-dihydroxy vitamin D3 (24,25(OH)2D3) may result in decreased bone resorption. The present study addresses basic mechanisms for the action of 24,25(OH)2D3 in bone of patients with elevated serum parathyroid hormone (PTH) levels due to chronic renal disease. Twenty-four patients 56 +/- 17 years old (mean +/- SE) with chronic kidney disease in the predialytic state (serum creatinine > 150 mumol/l) and elevated serum midregion PTH > 1.2 micrograms/l were randomly assigned to oral treatment with either 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) (0.25-0.50 microgram/day), 24,25(OH)2D3 (daily dose of 15 micrograms), or a combination of the two vitamin D3 analogs. The control group received calcium carbonate (maximal dosage of 1 g x 3). Selected variables in serum and urine as well as hormone sensitive adenylate cyclase (AC) in iliac crest biopsies were assessed before treatment and during follow-up after two and six months. Serum levels of 1,25(OH)2D3 and 24,25(OH)2D3 were significantly (P < 0.05) increased after two and six months in the respective treatment groups. Net bone PTH-enhanced AC (PTH-AC) fell abruptly (P < 0.01) after two months of treatment and was nearly abolished (P < 0.01) after six months with 24,25(OH)2D3 given alone or in combination with 1,25(OH)2D3. An inverse relationship (r = -0.57, P < 0.05, n = 48) between net PTH-AC in bone and serum levels of 24,25(OH)2D3 was demonstrated. In all groups, serum total calcium (s-Ca) was maintained within normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporin A-induced transient rise in plasma alkaline phosphatase in kidney transplant patients

In 1981 cyclosporin A (CyA) became available and replaced azathioprine (Aza) as the immunosuppressive agent in kidney transplantation at the University Hospitals in Basel, Switzerland. Patients on CyA and prednisone (CyA/p) therapy frequently demonstrated an isolated rise in bone-derived serum alkaline phosphatase (aP) concentration, but patients on Aza and prednisone (Aza/p) therapy did not. On the basis of long-term aP concentration and using noninvasive means, the present retrospective study was designed to investigate biochemical markers and radiographic signs of bone disease after successful kidney transplantation in patients on Cya/p treatment. Similar investigations were performed in patients on Aza/p and the results were compared. Follow-up examinations included clinical examination, radiography of the hand, and biochemical analysis of serum and urine. In 139 renal transplant patients on CyA/p, aP increased transiently after successful grafting (at transplantation 84 +/- 43 U/l; on day 90, 112 +/- 82 U/l). In 50 patients aP levels were higher at the time of transplantation (120 +/- 80 U/l) and aP peaked after 8 +/- 6 months, at a mean concentration of 242 +/- 103 U/l. In these patients aP concentrations exceeded the normal range for 16 +/- 10 months. None of the patients on CyA/p showed symptoms of bone disease when aP was increased. Radiological surveys revealed more pronounced osteodystrophy in patients at the time of transplantation, which increased aP to above the normal range after transplantation. Despite this rise in aP, over the long term bone lesions improved radiographically while bone mass remained stable.(ABSTRACT TRUNCATED AT 250 WORDS)

The spectrum of bone disease in end-stage renal failure--an evolving disorder

We have assessed the bone histology in 259 chronic dialysis patients, all of whom were in the same dialysis program. All patients had bone biopsies with quantitative histomorphometry, intact parathyroid hormone (PTH) measurements, basal and deferoxamine stimulated serum aluminum levels. Results demonstrate the increased incidence of the recently described aplastic bone lesion, particularly in patients treated with peritoneal dialysis (PD). Aluminum-related bone disease is much less common than previously described, perhaps in relation to the declining use of aluminum as a phosphate binder. A different pattern of bone lesions is seen in PD as compared with hemodialysis (HD), with low turnover disorders comprising 66% of the lesions seen in PD and high turnover lesions accounting for 62% of the bone histologic findings in HD. The difference in these patterns may relate to alterations in PTH levels, as mean PTH levels in HD patients were 2-1/2 times the levels found in PD patients (P < 0.0005), while older age, higher prevalence of diabetes and a shorter duration of dialysis may also have contributed to the findings in the PD patients. We suggest that PD, perhaps by maintaining calcium at higher levels, may more effectively suppress the parathyroid gland.

Ketodiet, physiological calcium intake and native vitamin D improve renal osteodystrophy

The effects of a very low-protein diet (VLPD) supplemented with amino acids and ketoanalogues (KA) and with 1 g of calcium carbonate and 1000 IU of vitamin D2, were studied in 17 patients with advanced renal failure (GFR < or = 20 ml/min) over a period of one year. The protein intake was 0.3 g protein/kg body wt/day. Daily phosphorus and calcium intake were respectively 1,500 mg and 300 mg. Sequential bone densitometry was performed and bone histomorphometry after double tetracycline labeling was evaluated, before and after one year of diet. Calcium and phosphate metabolism parameters were monitored every two months. In spite of a significant decrease of GFR, phosphorus, parathyroid hormone (1-84) and osteocalcin plasma levels decreased significantly, while low plasma bicarbonate normalized, and calcitriol and calcium levels remained respectively low and normal. Before the diet, histological study disclosed four cases of mixed osteopathy: osteomalacia associated with osteitis fibrosa (OM/OF), nine pure osteitis fibrosa (OF) and four with normal bone remodeling (NB). After one year of diet, the OM component of OM/OF disappeared, as evidenced by a normalization of the mineral apposition rate and osteoid thickness. In the patients presenting pure OF, a significant decrease in osteoblastic and osteoclastic surfaces, in the number of osteoclasts, and in the bone formation rate (BFR) were found. Vertebral mineral density measured by quantitative computerized tomodensitometry did not change significantly. In conclusion, this study not only confirms the beneficial effects of VLPD + KA + calcium on uremic hyperparathyroid bone disease in advanced renal failure assessed using static bone histomorphometry, but also shows a correction of histodynamic bone parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone lead measurements in patients with chronic renal disease studied over time

Results of longitudinal studies that involved the measurement of lead by different methodologies are presented for two groups of patients with chronic renal disease. Methodologies for all patients included x-ray fluorescence measurements of finger-bone lead. These measurements were conducted 5 y apart for one group of patients (n = 15). Initial measurements for the other group (n = 15) were supplemented by bone lead levels obtained either from skull at craniotomy or from skull, and sometimes rib, at autopsy. Most subjects also underwent ethylenediaminetetraacetic acid (specifically CaNa2 EDTA) lead-mobilization testing. A correlation between rate of decrease in finger-bone lead and immunoreactive parathormone levels was suggested. Renal patients were compared with age-matched controls, and their bone half-lives did not differ. The data are discussed and related to other results obtained from clinical and nonclinical populations in which trabecular and cortical bones were studied, and our results were consistent with evidence that more rapid turnover of lead occurs in trabecular bone than in cortical bone. No support was found for the hypothesis that patients who undergo renal dialysis accumulate lead in bone.

Some commonly unrecognized manifestations of metabolic arthropathies

The metabolic arthropathies are characterized by the deposition of abnormal substances in or around joints. Certain features of some of these arthropathies and their significance have only recently been recognized and others have been insufficiently emphasized. An important group of conditions are the arthropathies related to renal failure and its treatment, namely, aluminum toxicity, periarticular calcification and crystal deposition, hyperparathyroidism, and dialysis-related amyloidosis. Crystal deposition diseases, specifically, gouty arthritis, calcium pyrophosphate deposition, and calcium hydroxyapatite deposition, are also reviewed.

Unusual feature of soft-tissue calcification in chronic renal failure: tumoral calcification

Two cases of massive calcification in dialysed patients are described with computerized tomography correlation: one in the abdominal/pelvic cavity, which is a rare location, and the other in the abdominal wall. The cause of these calcified deposits is multifactorial and complex. Usually painless, they may cause restriction of joint movement by virtue of their bulky size.

Scintigraphy in the clinical evaluation of disorders of mineral and skeletal metabolism in renal failure

In patients with renal bone disease skeletal and extra-skeletal abnormalities can be visualised using conventional bone scintigraphy. Some of these abnormalities are associated with characteristic scintigraphic appearances, which are reviewed in detail, and the possible mechanisms involved are discussed. Specific imaging with iodine 123 serum amyloid P component and iodine 131 beta 2-microglobulin is also discussed in the diagnosis of beta 2-microglobulin amyloidosis specific to patients on dialysis. In the light of available evidence, it appears that bone scintigraphy plays, so far, a limited role in the clinical evaluation of skeletal and extra-skeletal abnormalities in chronic renal failure. The potential role of bone scintigraphy in identifying patients with aluminium-related bone disease needs to be investigated further, and in this respect special attention must be given to the problem of high soft-tissue activity associated with impaired renal function. Timing haemodialysis sessions before scintigraphic imaging deserves wider recognition as it reduces high soft-tissue activity, thereby allowing bone uptake to be assessed more accurately. Specific imaging of amyloidosis resulting from beta 2-microglobulin deposition is a promising technique, but the relative value of the two proposed radiopharmaceuticals needs further clarification.

Endosteal surfaces in hyperparathyroidism: an enzyme cytochemical study on low-temperature-processed, glycol-methacrylate-embedded bone biopsies

Alkaline phosphatase (AlP) and tartrate-resistant acid phosphatase (TRAP) activities have been studied comparatively in needle biopsies of the iliac crest of four cases of secondary hyperparathyroidism (renal osteodystrophy). AlP activity was associated with the plasma membrane of osteoblasts and their processes, of reticular cells of bone marrow and of young osteocytes of osteoid borders and woven bone. Moreover, it was detected in the fibroblast-like cells of the endosteal "fibrosis". These cells were orderly in arrangement and were parallel to the endosteal surfaces near zones of bone formation. They were disorderly near zones of bone resorption. A strong TRAP-positive reaction was present in osteoclasts and mononuclear cells of endosteal "fibrosis" and in osteocytes located near active osteoclasts and in woven bone. These results suggest that the so-called fibrosis of hyperparathyroidism, rather than representing reparative, inert tissue, consists of osteoblast-like cells, probably precursors of osteoblasts derived by parathormone-stimulated proliferation of AlP-positive stromal cells of bone marrow, and of TRAP-positive, mononuclear cells, probably preosteoclasts. Moreover, they show that TRAP activity can be present in osteocytes, probably under stimulation by the same factors which stimulate osteoclast activity. The histochemical demonstration of AlP and TRAP facilitates the morphological diagnosis of metabolic bone disease and may improve knowledge of bone physiopathology.

Effects of systemic aluminum on the resolution of a uremic and dietary phosphorus-dependent model of uremic osteomalacia in rats

We have developed a model of osteomalacia that is dependent on both uremia and the feeding of a diet low in phosphorus and that can be reversed by subsequent dietary phosphorus repletion. The objectives for this study were to use this model to investigate the role of aluminum (Al) in both the induction and resolution of osteomalacia. Adult male Sprague-Dawley rats were five-sixths nephrectomized and fed either low or normal dietary phosphorus, both with and without intraperitoneal Al injections. Uremic rats fed low phosphorus developed osteomalacia characterized by increased osteoid surface, volume, and thickness and osteoid maturation time and decreased mineralizing surface. Al-treated uremic rats fed low phosphorus were similarly affected, developing increased osteoid volume and thickness and osteoid maturation time and decreased osteoblastic surface, mineralizing surface, and bone formation rate. In addition, they had a significantly increased Al-positive surface. Al-treated uremic rats fed normal phosphorus had only increased osteoid thickness and aluminum-positive surface and decreased osteoblastic surface. Osteomalacic rats continuously treated with Al during the induction and phosphorus repletion stages had increased growth plate thickness, osteoid volume and thickness, and Al-positive surface and decreased osteoblastic and mineralizing surface. Mineralization in these rats was impaired to such a degree that no detectable double labels were present. Osteomalacic rats treated with Al during the induction phase but not during phosphorus repletion had increased osteoid surface and volume and Al-positive surface and decreased osteoblastic and mineralizing surface. Double labels were not detectable in these rats, either.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of parathyroid hormone synthesis in chronic renal failure in rats

To clarify the mechanism of secondary hyperparathyroidism in chronic renal failure at the parathyroid hormone (PTH) synthesis level, we measured PTH messenger RNA (mRNA) levels in parathyroid glands in a rat model of chronic renal failure. Four weeks after 7/8 nephrectomy, hyperplasia of parathyroid glands was evident and serum PTH levels were elevated. Serum concentration of calcium, inorganic phosphate, and 1,25-dihydroxyvitamin D (1,25(OH)2D) of rats with chronic renal failure were not detectably different from those of sham-operated rats. In chronic renal failure rats, PTH mRNA levels were elevated both per RNA and per DNA of parathyroid cells, suggesting increased PTH mRNA levels per cell. The elevated levels of PTH mRNA were returned to normal levels by achieving supraphysiological concentrations of 1,25(OH)2D3 given i.p. twice at 24 and 48 hours before sacrifice, although this was attended by slight hypercalcemia. A synthetic analogue of vitamin D, 22-oxa-1,25(OH)2D3, also suppressed PTH mRNA to normal levels, but without hypercalcemia. These data suggest that secondary hyperparathyroidism in early chronic renal failure may be due in part to the resistance of parathyroid cells to the physiological concentration of 1,25(OH)2D in circulation on PTH synthesis and that 22-oxa-1,25(OH)2D3 may be useful in the management of secondary hyperparathyroidism of chronic renal failure.