Inhibition of Lipoxygenases Showed No Benefit for the Musculoskeletal System in Estrogen Deficient Rats

BACKGROUND

In previous studies, we reported the beneficial impact of two lipoxygenase-inhibitors, Baicalein and Zileuton, on osteoporotic bone in a postmenopausal rat model. Whereas subcutaneous Baicalein predominantly improved cortical bone, Zileuton enhanced vertebral and femoral trabecular bone. In this study, we aimed to reveal whether the oral administration of Baicalein caused similar effects on bone and whether a combined administration of Baicalein and Zileuton could act synergistically to ameliorate the formerly reported effects in the musculoskeletal system.

METHODS

We treated ovariectomized (OVX) female Sprague-Dawley rats either with Baicalein (10mg/kg BW), Zileuton (10mg/kg BW) or a combination of both (each 10mg/kg BW) for 13 weeks and compared with untreated OVX and NON-OVX groups (n=12-16 rats per group). Lumbar vertebral bodies and femora were analyzed. Tibiae were osteotomized, plate-stabilized (at week 8 after OVX) and likewise analyzed by biomechanical, histological, micro-computed tomographical and ashing tests. The skeletal muscle structure was analyzed.

RESULTS

Oral administration of Baicalein did not confirm the reported favorable cortical effects in neither vertebra nor femur. Zileuton showed a beneficial effect on trabecular vertebra, while the femur was negatively affected. Callus formation was enhanced by all treatments; however, its density and biomechanical properties were unaltered. Lipoxygenase inhibition did not show a beneficial effect on skeletal muscle. The combination therapy did not ameliorate OVX-induced osteoporosis but induced even more bone loss.

CONCLUSIONS

The preventive anti-osteoporotic treatments with two lipoxygenase inhibitors applied either alone or in combination showed no benefit for the musculoskeletal system in estrogen deficient rats.

Alkaline Phosphatase, iPTH and Bone Turnover Markers in Chinese Advanced Chronic Kidney Disease Patients

BACKGROUND

Clinicians may use several biochemical markers of bone turnover to assess or guide the care of patients with chronic kidney disease (CKD). The aims of this study are to describe changes and correlations of markers of bone remodeling in patients with different stages of CKD.

METHODS

A total of 317 Chinese patients with advanced CKD (stage 3-5) were enrolled. We measured serum levels of intact-parathyroid hormone (iPTH), N-terminal midfragment (N-MID) osteocalcin, procollagen type 1 amino-terminal propeptide (P1NP), β-isomerized C-terminal telopeptide (β-CTx), total alkaline phosphatase (ALP), and 25-hydroxyvitamin D (25[OH]D).

RESULTS

Levels of iPTH, N-MID osteocalcin, P1NP, and β-CTx and serum phosphorus were significantly different among patients with different stages of CKD. Serum levels of ALP and 25(OH)D were higher in hemodialysis (HD) patients than in peritoneal dialysis (PD) patients. Levels of ALP, osteocalcin, and P1NP were significantly higher in dialysis patients than in non-dialysis patients. Correlations between the levels of iPTH, ALP, N-MID os- teocalcin, P1NP, and β-CTx were statistically significant but weak. There was no correlation between 25(OH)D and iPTH or ALP.

CONCLUSIONS

Our results suggest that measurement of N-MID osteocalcin, P1NP, β-CTx, and iPTH may be useful for assessment of CKD-mineral bone disorder (MBD) in patients with CKD.

A novel function for lysyl oxidase in pluripotent mesenchymal cell proliferation and relevance to inflammation-associated osteopenia

Lysyl oxidase is a multifunctional enzyme required for collagen biosynthesis. Various growth factors regulate lysyl oxidase during osteoblast differentiation, subject to modulation by cytokines such as TNF-α in inflammatory osteopenic disorders including diabetic bone disease. Canonical Wnt signaling promotes osteoblast development. Here we investigated the effect of Wnt3a and TNF-α on lysyl oxidase expression in pluripotent C3H10T1/2 cells, bone marrow stromal cells, and committed osteoblasts. Lysyl oxidase was up-regulated by a transcriptional mechanism 3-fold in C3H10T1/2 cells, and 2.5-fold in bone marrow stromal cells. A putative functional TCF/LEF element was identified in the lysyl oxidase promoter. Interestingly, lysyl oxidase was not up-regulated in committed primary rat calvarial- or MC3T3-E1 osteoblasts. TNF-α down-regulated lysyl oxidase both in Wnt3a-treated and in non-treated C3H10T1/2 cells by a post-transcriptional mechanism mediated by miR203. Non-differentiated cells do not produce a collagen matrix; thus, a novel biological role for lysyl oxidase in pluripotent cells was investigated. Lysyl oxidase shRNAs effectively silenced lysyl oxidase expression, and suppressed the growth of C3H10T1/2 cells by 50%, and blocked osteoblast differentiation. We propose that interference with lysyl oxidase expression under excess inflammatory conditions such as those that occur in diabetes, osteoporosis, or rheumatoid arthritis can result in a diminished pool of pluripotent cells which ultimately contributes to osteopenia.

Continuous Activation of Gαq in Osteoblasts Results in Osteopenia through Impaired Osteoblast Differentiation

We explored the role of G alpha(q)-mediated signaling on skeletal homeostasis by selectively expressing a constitutively active G alpha(q) (mutation of Q209L) in osteoblasts. Continuous signaling via G alpha(q) in mouse osteoblastic MC3T3-E1 cells impaired differentiation. Mice that expressed the constitutively active G alpha(q) transgene in cells of the osteoblast lineage exhibited severe osteopenia in cortical and trabecular bones. Osteoblast number, bone volume, and trabecular thickness were reduced in transgenic mice, but the osteoclasts were unaffected. Osteoblasts from transgenic mice showed impaired differentiation and matrix formation. In the presence of a protein kinase C inhibitor GF109203X, this impairment was not seen, indicating mediation by the protein kinase C pathway. We propose that continuous activation of the G alpha(q) signal in osteoblasts plays a crucial, previously unrecognized role in bone formation.

Administration of Cyclooxygenase-2 Inhibitor Reduces Joint Inflammation but Exacerbates Osteopenia in IL-1α Transgenic Mice Due to GM-CSF Overproduction

IL-1alpha transgenic (Tg) mice exhibit chronic inflammatory arthritis and subsequent osteopenia, with IL-1-induced GM-CSF playing an important role in the pathogenesis. This study analyzed the mechanisms underlying osteopenia in Tg mice, and the therapeutic effects of the cyclooxygenase-2 inhibitor celecoxib on such osteopenia. Inhibited osteoclast formation was observed in RANKL-treated bone marrow cell (BMC) cultures from Tg mice and coculture of Tg-derived BMCs and wild-type-derived primary osteoblasts (POBs). FACS analysis indicated that this inhibition was attributable to a decreased number of osteoclast precursors within Tg-derived BMCs. Moreover, in coculture of Tg-derived POBs and either Tg- or wild-type-derived BMCs, osteoclast formation was markedly inhibited because Tg-derived POBs produced abundant GM-CSF, known as a potent inhibitor of osteoclast differentiation. Histomorphometric analysis of Tg mice revealed that both bone formation and resorption were decreased, with bone formation decreased more prominently. Interestingly, administration of celecoxib resulted in further deterioration of osteopenia where bone formation was markedly suppressed, whereas bone resorption remained unchanged. These results were explained by our in vitro observation that celecoxib dose-dependently and dramatically decreased osteogenesis by Tg mouse-derived POBs in culture, whereas mRNA expressions of GM-CSF and M-CSF remained unchanged. Consequently, blockade of PGE(2) may exert positive effects on excessively enhanced bone resorption observed in inflammatory bone disease, whereas negative effects may occur mainly through reduced bone formation, when bone resorption is constitutively down-regulated as seen in Tg mice.

P450 oxidoreductase deficiency: a new form of congenital adrenal hyperplasia

PURPOSE OF REVIEW

P450 oxidoreductase deficiency--a newly described form of congenital adrenal hyperplasia--typically presents a steroid profile suggesting combined deficiencies of steroid 21-hydroxylase and 17alpha-hydroxylase/17,20-lyase activities. These and other enzymes require electron donation from P450 oxidoreductase. The clinical spectrum of P450 oxidoreductase deficiency ranges from severely affected children with ambiguous genitalia, adrenal insufficiency and the Antley-Bixler skeletal malformation syndrome to mildly affected individuals with polycystic ovary syndrome. We review current knowledge of P450 oxidoreductase deficiency and its broader implications.

RECENT FINDINGS

Since the first report in 2004, at least 21 P450 oxidoreductase mutations have been reported in over 40 patients. The often subtle manifestations of P450 oxidoreductase deficiency suggest it may be relatively common. P450 oxidoreductase deficiency, with or without Antley-Bixler syndrome, is autosomal recessive, whereas Antley-Bixler syndrome without disordered steroidogenesis is caused by autosomal dominant fibroblast growth factor receptor 2 mutations. In-vitro assays of P450 oxidoreductase missense mutations based on P450 oxidoreductase-supported P450c17 activities provide excellent genotype/phenotype correlations. The causal connection between P450 oxidoreductase deficiency and disordered bone formation remains unclear.

SUMMARY

P450 oxidoreductase mutations cause combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase. Individuals with an Antley-Bixler syndrome-like phenotype presenting with sexual ambiguity or other abnormalities in steroidogenesis should be analyzed for P450 oxidoreductase deficiency.

Serum hyaluronidase aberrations in metabolic and morphogenetic disorders

Hyaluronidases are endo-glycosidases that degrade both hyaluronan (hyaluronic acid) (HA) and chondroitin sulfates. Deficiency of hyaluronidase activity has been predicted to result in a phenotype similar to that observed in mucopolysaccharidosis (MPS). In the present study, we surveyed a variety of patients with phenotypes similar to those observed in MPS, but without significant mucopolysacchariduria to determine if some are based on aberrations in serum hyaluronidase (Hyal-1) activity. The study included patients with well-characterized dysmorphic disorders occurring on genetic basis, as well as those of unkown etiology. The purpose of the study was to establish how wide spread were abnormalities in levels of circulating Hyal-1 activity. A simple and sensitive semi-quantitative zymographic procedure was used for the determination of activity. Levels of both beta-N-acetylglucosaminidase and beta-glucuronidase whose activities contribute to the total breakdown of hyaluronan (HA) were also measured, as well as the concentration of circulating HA. Among 48 patients with bone or connective tissue abnormalities, low levels of Hyal-1 activity were found in six patients compared to levels in 100 healthy donors (2.0-3.2 units/microL vs 6(+/- 1 SE) units/microL). These six patients exhibited a wide spectrum of clinical abnormalities, in particular shortened extremities: they included three patients with unknown causes of clinical symptoms, one patient with Sanfilippo disease, one of the seven patients with achondroplasia, and one with hypophosphotemic rickets. Normal levels of serum Hyal-1 activities were found in patients with Morquio disease, GM1 gangliosidosis, I cell-disease, 6 of the 7 patients with achondroplasia, Marfan's-syndrome and Ehlers-Danlos syndrome. No patient totally lacked serum Hyal-1 activity. Serum HA concentration was elevated in patients with Sanfilippo A and I-cell disease. Determination of serum and leukocyte Hyal-1 and serum HA may be useful to evaluate patients with metabolic and morphogenetic disorders.

Soluble cathepsin-L: a marker of bone resorption and bone density?

We sought to evaluate cathepsin L serum levels in the peripheral blood of patients with low bone density. Blood samples from 60 patients (32 osteoporotic, 28 osteopenic) and 16 healthy controls were taken and quantitative measurements of cathepsin L were performed with the use of a commercially available enzyme-linked immunosorbent assay. Dual x-ray absorptionometry measurements and serum levels of alkaline phosphatase, bone-specific alkaline phosphatase, osteocalcin, parathyroid hormone, sexual hormones, and N -terminal crosslinks of type I collagen were examined. Group comparisons between patients with osteoporosis and controls showed significant differences with respect to cathepsin L ( t = -2.839; df = 29; P =.008). Osteoporosis treatment decreased the serum level of cathespsin L in a statistically significant fashion ( P =.002). These results suggest that the serum level of cathepsin L can serve as a marker of bone resorption and bone density.

[Gaucher's disease: pathogenesis, diagnosis and therapy]

Gaucher's disease is the most common lysosomal storage disorder. Gene defect leads to deficiency or decreased activity of glucocerebrosidase followed by the accumulation of glucosylceramide. Most frequently hepatosplenomegaly, anemia, skeletal and hematological abnormalities are present. Different types are known based on the clinical findings. Recently used enzyme replacement therapy seems to eliminate bone marrow transplantation and has favourable effects on symptoms and outcome. Development of gene therapy (reintroduction of missing DNA sequence) hints the possibility of real causal therapy of the disease.

[Effects of formestane on the skeletal system in ovariectomized and control rates]

Formestane is an inhibitor of the aromatase enzyme which is uniquely responsible for the generation of estrone and estradiol from androgenic precursors. Formestane is used in the treatment of breast cancer in postmenopausal women. Formestane causes reduction of the estrogen biosynthesis in all tissues where it occurs. Deficiency of estrogens disrypts remodeling of bone tissue. The effect of formestane on bones in not known. The aim of the present study was to investigate the effects of formestane (20 mg/kg s.c. once a week) administered for 4 weeks on the osseous system in bilaterally ovariectomized and non-ovariectomized rats. The experiments were carried out on 4 groups of 3-month-old female Wistar rats:I--Control (non-ovariectomized rats), II--Ovariectomized rats, III--Non-ovariectomized rats + Formestane, IV--Ovariectomized rats + Formestane. In all the groups examined were body weight gain, bone mass, length and diameter, mineral and calcium contents in the tibia and femur, endosteal and periosteal transverse growth, endosteal and periosteal osteoid width transverse cross-section area of the cortical diaphysis and that of the marrow cavity in the tibia, epiphyseal cartilage width, trabeculae width in the epiphysis and metaphysis of the femur. Mechanical properties of the femur were also studied. Bilateral ovariectomy induced osteopenic skeletal changes in female rats. Formestane did not significantly change bone remodeling in non-ovariectomized rats (group III). Formestane administered to the bilaterally ovariectomized rats (group IV) slightly reduced the changes by ovariectomy in the osseus system.

Visualization of bisphosphonate-induced caspase-3 activity in apoptotic osteoclasts in vitro

Bisphosphonates inhibit osteoclast-mediated bone resorption by mechanisms that have only recently become clear. Whereas nitrogen-containing bisphosphonates affect osteoclast function by preventing protein prenylation (especially geranylgeranylation), non-nitrogen-containing bisphosphonates have a different molecular mechanism of action. In this study, we demonstrate that nitrogen-containing bisphosphonates (risedronate, alendronate, pamidronate, and zoledronic acid) and non-nitrogen-containing bisphosphonates (clodronate and etidronate) cause apoptosis of rabbit osteoclasts, human osteoclastoma-derived osteoclasts, and human osteoclast-like cells generated in cultures of bone marrow in vitro. Osteoclast apoptosis was shown to involve characteristic morphological changes, loss of mitochondrial membrane potential, and the activation of caspase-3-like proteases capable of cleaving peptide substrates with the sequence DEVD. Caspase-3-like activity could be visualized in unfixed, dying osteoclasts and osteoclast-like cells using a cell-permeable, fluorogenic substrate. Bisphosphonate-induced osteoclast apoptosis was dependent on caspase activation, because apoptosis resulting from alendronate, clodronate, or zoledronic acid treatment was suppressed by zVAD-fmk, a broad-range caspase inhibitor, or by SB-281277, a specific isatin sulfonamide inhibitor of caspase-3/-7. Furthermore, caspase-3 (but not caspase-6 or caspase-7) activity could be detected and quantitated in lysates from purified rabbit osteoclasts, whereas the p17 fragment of active caspase-3 could be detected in human osteoclast-like cells by immunofluorescence staining. Caspase-3, therefore, appears to be the major effector caspase activated in osteoclasts by bisphosphonate treatment. Caspase activation and apoptosis induced by nitrogen-containing bisphosphonates are likely to be the consequence of the loss of geranylgeranylated rather than farnesylated proteins, because the ability to cause apoptosis and caspase activation was mimicked by GGTI-298, a specific inhibitor of protein geranylgeranylation, whereas FTI-277, a specific inhibitor of protein farnesylation, had no effect on apoptosis or caspase activity.

Bone mineral density and biochemical markers of bone metabolism in late onset rheumatoid arthritis and polymyalgia rheumatica--a prospective study on the influence of glucocorticoid therapy

In the present prospective study, bone metabolism was examined in 51 patients at the time of diagnosis and 6-7 months later: 29 patients had definitive diagnosis of late onset rheumatoid arthritis (LORA) and 22 patients had polymyalgia rheumatica (PMR). At the time of diagnosis, the patients had not received any medication; during the 6-7 months of follow-up they were treated with corticosteroids and nonsteroidal-antirheumatic drugs (NSAIDs). Serum levels of osteocalcin, alkaline phosphatase and ostase, as markers for bone formation, were tested. Bone density was examined by dual x-ray absorption (DEXA) of the lumbar spine and the left ward triangle. At the time of diagnosis, no signs of bone alterations were seen. After 6-7 months, abnormal values of the serum parameters and bone mineral density were found in 16/51 patients (31%): 10/29 patients with LORA and 6/22 with PMR. Thus, our findings suggest that an alteration of bone metabolism could be observed in a minority of patients during the first few months of glucocorticoid medication, but in the majority of patients an osteoprotective effect seems to be worth discussing. The results suggest from a prophylactic and therapeutic point of view that an additional disease-modifying antirheumatic medication should be considered in the early stages of therapy to reduce the osteoporotic risk of a longterm corticoid therapy.

[Alkaline phosphatase level and bone density in Scheuermann's disease and in adolescent idiopathic scoliosis]

Authors made a comparison between 167 suffers from Scheuermann's disease (SD), 70 adolescence idiopathic scoliosis (AIS) and 132 age, sex, height, weight, pubertal developmental stages (Tanner stages) matched controls. The height percentile in 130 cases was also determined. The bone mineral density (BMD) was measured by pQCT on the non dominate sided radial bone. The alkaline phosphatase (AP) level increased at the beginning of puberty and in the puberty in SD. In SD the trabecular Z-score of BMD was significantly decreased in Tanner stage 1 to 4 in both boys and girls. It was not found any significance difference, however, in Tanner stage 5, while in AIS girl no significance decrease of BMD was found. In SD good correlation could be demonstrated between increase in AP and decrease in trabecular Z score r = 0.2, while did not correlate with height percentile. The AP level's increase, and radiomorphometric data of SD severity (intervertebral space narrowing and antero-posterior diameter increase of vertebral body) shows a significant correlation with decreased trabecular Z-score in the period of prepuberty.

Tartrate-resistant acid phosphatase forms complexes with alpha2-macroglobulin in serum

Tartrate-resistant acid phosphatase (TRAP) is a standard histochemical marker of differentiated osteoclasts and has been proposed as a serum/plasma marker for osteoclast activity. Enzyme assays have been described that show elevated TRAP enzyme activity in the serum or plasma of patient groups known to have increased bone metabolism. However, the poor stability of the enzyme and potential contribution from nonosteoclastic sources make it problematic to measure in patient samples. Immunoassays developed to measure TRAP in serum and plasma have yielded widely varying TRAP levels in both normal and disease states. It is not clear if this variability is caused by differences in assay calibration, antibody specificity, and/or TRAP instability. In this paper, we report that purified TRAP spiked into serum forms high molecular weight complexes. Complex formation results in greatly decreased TRAP enzyme activity and immunoreactivity. The complexing protein in serum has been identified as alpha2-macroglobulin (alpha2M). Similar complexes are observed in stored patient samples. In vitro studies with purified components show that TRAP binds to alpha2M primarily through noncovalent ionic interactions. Our results demonstrate that one mechanism of TRAP instability in serum is complex formation with alpha2M and suggest further that current TRAP enzyme and immunoassays may not accurately measure the circulating level of TRAP.

Otological findings in idiopathic hyperphosphatasia

A 17-year-old male patient was admitted because of progressive hearing loss since the age of six. His former blood and radiology investigation had revealed idiopathic hyperphosphatasia. On ENT examination bilateral thickened tympanic membranes with severe mixed-type hearing loss was diagnosed. Computerized tomography (CT) demonstrated expansion of the calvarial bones, including the temporal bones, except for the otic capsule. Middle-ear exploration revealed thickened middle-ear mucosa and a stone hard, immobile bony mass instead of the normal ossicular chain at the posterior superior part of the mesotympanum. No ossicular reconstruction could be attempted and the patient was rehabilitated with a hearing aid.

Tartrate-resistant acid phosphate activity as osteoclastic marker: sensitivity of cytochemical assessment and serum assay in comparison with standardized osteoclast histomorphometry

Tartrate-resistant acid phosphatase (TRAP) activity is regarded as an important cytochemical marker of osteoclasts; its concentration in serum is utilized as a biochemical marker of osteoclast function and degree of bone resorption. This study was carried out to assess the sensitivity of TRAP activity both as a cytochemical marker in histological sections and as a biochemical marker in serum in comparison with the standardized histomorphometric variables of osteoclasts. To this end we investigated 24 patients (21 women, 3 men; 60 +/- 17 years of age) affected with various metabolic bone diseases. Osteoclast surface (OcS/BS) and osteoclast number (OcN/BS) were evaluated by standardized histomorphometry in iliac crest biopsies. On the basis of TRAP cytochemical activity, TRAP-positive osteoclast surface (TRAP + OcS/BS) and number (TRAP + OcN/BS) were measured. TRAP-positive cells adjacent to bone and showing one nucleus or no nuclei at all in the plane of section were included in the counts as osteoclasts. Serum TRAP activity was determined by spectrophotometric assay. Values of OcS/BS and OcN/BS were much lower than those of TRAP + OcS/BS (-50%) and TRAP + OcN/BS (-60%), respectively. Correlations between OcS/BS and TRAP + OcS/BS, and between OcN/BS and TRAP + OcN/BS, were highly significant. Serum TRAP was significantly correlated with OcS/BS, OcN/BS, and TRAP + OcN/BS. These correlations, however, were rather low. Moreover, serum TRAP did not correlate with TRAP + OcS/BS. From these results, the conclusion can be drawn that while TRAP activity is confirmed as a valid cytochemical marker for identification of osteoclasts, serum TRAP activity is an osteoclastic marker of weak sensitivity. This may be due to known factors, such as synthesis of the enzyme not being unique to osteoclasts, enzyme instability, and the presence of inhibitors in serum. Mononucleated osteoclasts do not significantly influence the serum enzyme levels.

Relationship between the location of osteoblastic alkaline phosphatase activity and bone formation in human iliac crest bone

It is not feasible to use in vivo tetracycline double labeling to study bone formation in biopsies taken during the emergency fixation of fractures. We therefore compared the trabecular localization and extent of osteoblastic alkaline phosphatase (AP) perimeters with tetracycline and osteoid perimeters in iliac crest biopsies from 7 women with postmenopausal osteoporosis and 13 women without metabolic bone disease. Fresh biopsies were chilled to -70 degrees C, and triplicate serial unfixed undecalcified cryostat sections were cut and reacted for AP, stained for osteoid, or mounted unstained. At individual remodeling sites, the mineralizing perimeter (M.Pm) was measured as the extent of a double or single label accompanied by greater than or equal to 1 lamella of osteoid and greater than or equal to 1 lamella of mineralized matrix between the mineralization front and the adjacent label. Osteoid perimeters (O.Pm) and AP perimeters (AP.Pm) were also measured. In each biopsy there was good agreement between the location of AP and bone formation (kappa statistic, range 0.71-1.0). The overall sensitivity and specificity of AP as an indicator of the location of bone formation were 0.963 and 0.902, respectively. At the level of the basic multicellular unit, in those samples in which greater than 3 active BMUs were found, there was (1) significant positive correlation between the M.Pm and both AP.Pm and AP-positive O.Pm (except 1 patient) and (2) no significant difference between the M.Pm and AP-positive O.Pm (17 of 18 patients and 18 of 18 patients at the tissue level).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical usefulness of serum tartrate-resistant acid phosphatase activity determination to evaluate bone turnover

The study was carried out to evaluate the clinical validity and usefulness of serum tartrate-resistant acid phosphatase (TRAP) activity determined using an improved spectrophotometric assay. Enzyme activity was measured in 84 normal subjects and in 109 patients with common metabolic bone diseases. Mean values of serum TRAP activity in male subjects (n = 19; 10.4 +/- 2.15 U l-1) were not significantly different from those found in female subjects (n = 65; 10.8 +/- 1.8 U l-1). In the latter group mean values were significantly raised in post-menopausal subjects (10.5 +/- 2.0 U l-1; p less than 0.01) compared with mean values in pre-menopausal women (8.45 +/- 1.8 U l-1). We found a significant inverse correlation between serum TRAP activity values and bone mineral density (BMD) measured both at an ultradistal radial point (n = 33, r = -0.506; p less than 0.01), and at the lumbar spine (n = 57, r = -0.261; p less than 0.05). Mean serum TRAP activity values in patients with metabolic bone diseases were: primary hyperparathyroidism, n = 30: 14.2 +/- 4.89 U l-1, p less than 0.001 vs normal subjects; chronic maintenance haemodialysis, n = 19: 17.4 +/- 6.7, p less than 0.001; metastatic cancer, n = 13: 21.2 +/- 6.3, p less than 0.001; post-surgical hypoparathyroidism, n = 10: 9.9 +/- 1.8, NS; involutional osteoporosis, n = 20: 12.5 +/- 2.3 p less than 0.001; Paget's disease, n = 10: 16.8 +/- 3.5, p less than 0.001; osteomalacia, n = 7: 19.5 +/- 3.31, p less than 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical markers of bone metabolism

Bone metabolic homeostasis is regulated by a number of hormones and local modulators, and the study of these factors has been of major help in our understanding of bone disease. However, these parameters do not, in a strict sense reflect the metabolic and biochemical changes in the diseased bone tissue. Thus, there is a great interest in the study of biochemical specific "markers" of bone metabolic processes, namely of bone formation and bone resorption. Alkaline phosphatase, osteocalcin, osteonectin, and procollagen type I propeptides are the currently known markers of bone formation, whereas urinary hydroxyproline and hydroxylysine glycosides, plasma tartrate resistant acid phosphatase, and urinary hydroxy-pyridinium crosslinks of collagen are considered markers of bone resorption. In this paper, we review the background work on each of these markers, and subsequently give an overview of the currently available data on their usefulness in metabolic bone diseases, namely in Paget's disease of bone, primary hyperparathyroidism, osteoporosis, and renal osteodystrophy.

[Efficacy and side effects of differential calcium and phosphate administration in prevention of osteopenia in premature infants]

The prevention of osteopenia and frequency of renal and intestinal side effects of mineral supplementation was studied in 24 preterm infants with birth weight under 1,500 g, prospectively (gestational age 26-34 weeks). Calcium intake varied from 2.5 vs. 3.75 vs. 5 mmol/kg/day, phosphate was offered in dose of 2.5 mmol/kg/day. At the expected birth date 40% of infants with low calcium dose showed an activity of serum alkaline phosphatase greater than five times the maximum adult normal value which is defined as a reliable marker; for osteopenia no infant with medium or high calcium intake reached this critical value (p = 0.03). Medium and high calcium doses resulted in an increased risk for hypercalcuria (25 vs. 50%) (p = 0.03). Half of these infants developed typical signs of nephrocalcinosis on ultrasound examination. No significant difference of fecal fat content was observed with increased calcium intake; but more episodes of abdominal distension occurred during the first days of high calcium supplementation (p = 0.03). We conclude, that a calcium intake of 3.75 mmol/kg/day in combination with phosphate 2.5 mmol/kg/day is sufficient for adequate bone mineralization on a low level of side effects. Calcium excretion in urine has to be observed for early diagnosis of nephrocalcinosis.

High alkaline phosphatase activity and growth in preterm neonates

In a study on 857 infants born preterm, high peak plasma alkaline phosphatase activity was independently related to slower growth rate in the neonatal period, and to a highly significant reduction in attained length at 9 months and 18 months post term. At 18 months the deficit in body length associated with peak neonatal plasma alkaline phosphase activity of 1200 IU/l or more was 1.6 cm (95% confidence interval 0.9 to 2.3 cm) after adjusting for confounding factors. The strength and magnitude of this association between high plasma alkaline phosphase activity and body length was greater than that for any other factor identified, including the infant's sex and the presence of fetal growth retardation. Data are presented that support the view that the high plasma alkaline phosphatase activity reflected early bone mineral substrate deficiency resulting in metabolic bone disease. We speculate that even silent early bone disease may interfere with the control of subsequent linear growth and emphasise the potential importance of providing preterm infants, especially those fed human milk, with adequate substrate for bone mineralisation.

[The effect of osteopenia prevention in very small premature infants on hormonal parameters of calcium metabolism and bone mineralization]

In 23 very low birth weight infants the influence of mineral supplementation with 0.4 mmol calciumgluconate and 0.2 mmol glucose-1-phosphate/dl human milk on concentrations of 25-OH-D3, parathyroid hormone, calcitonine, calcium, phosphorus and activity of alkaline phosphatase was studied on days 3, 8, 28 and 56. On days 28 and 56 respectively, degree of bone mineralisation was classified. 8 preterm infants received supplementation before day 28, 7 infants after day 28, 8 infants had no supplementation. All preterm infants received beginning with day 7 vitamin D3 1000 IU/day. In all preterms mean concentrations of 25-OH-D3 were normal and increasing with age. Concentrations of parathyroid hormone and calcitonine were first of all increased and decreased with age, especially in supplemented infants. Light metabolic bone disease without fractures occurred in 4 infants of supplemented groups. Non-supplemented group contains 5 infants with severe metabolic bone disease without fractures. Results indicate intact metabolism and secretion of 25-OH-D3, parathyroid hormone and calcitonine. Decrease of calcitonine concentration in mineral supplemented preterms is a reference to a better mineral supply. Mineral supplementation is followed by an increase in bone mineralisation with prevention of severe metabolic bone disease.

Spontaneous hypoparathyroidism: clinical, biochemical and radiological features

The clinical, biochemical and radiological features of spontaneously occurring hypoparathyroidism in 13 patients (mean age 9 years, range 4 months to 20 years) are highlighted. Nine patients presented with a history of generalised seizures and 2 were in acute hypocalcemic crisis at the time of admission. Ocular involvement (corneal opacities, cataract) was present in 3 patients and vitiligo in 1 patient. The serum calcium level was low (mean 5.46 mg/dl, range 5.0-7.2) and serum phosphorus level was high (mean 8.49 mg/dl, range 6-14 mg/dl) in all the patients. Six patients had elevated serum alkaline phosphatase (greater than 20 KAU). Radiological examination revealed osteopenia in 3 patients. Nine patients underwent a head CT scan; 5 had evidence of basal ganglia calcification. The findings of elevated serum alkaline phosphatase and osteopenia are at variance with existing literature and may possibly reflect pre-existing vitamin D deficiency.

Correlation between alkaline and acid phosphatase activities and age-related osteopenia in murine vertebrae

Lumbar vertebrae (L4) from CW-1 female mice were examined for age-related changes in alkaline and acid phosphatase activities from young to old age. Histochemically, both enzymes were encountered along the bony surfaces of both trabecular and cortical bones with no significant age-related changes in their distribution. Biochemical determinations of bone alkaline phosphatase (Alk'ase) activity revealed that for a given unit level of bone or the bone as a whole no significant changes took place, whereas acid phosphatase (Acid'ase) activity was found to have increased significantly with age. A high positive correlative relationship was noted between the calcium content and the trabecular bone volume of the same vertebrae. It may, therefore, be proposed that age-related bone loss in mice could be attributed to an enhanced resorption rather than to a substantial reduction in the formative potential of bone cells.

Concurrent assays of circulating bone Gla-protein and bone alkaline phosphatase: effects of sex, age, and metabolic bone disease

We measured the serum concentrations of 2 biochemical markers of bone formation, bone Gla-protein (BGP) and bone alkaline phosphatase (BAP), in 164 normal subjects and 164 patients with metabolic bone disorders. The data were reported as Z scores (deviation in SDs from the sex-specific age regression in normal subjects). Both serum BGP and BAP distinguished abnormalities well (mean Z scores for BGP and BAP, respectively) and gave concordant results in patients with hypoparathyroidism (-1.7, -1.4), hyperthyroidism (+1.1, +1.8), primary hyperparathyroidism (+3.6, +2.5), acromegaly (+1.2, +2.8), and postmenopausal osteoporosis (+0.4, +1.9). The 2 markers gave discordant results, however, in patients with glucocorticoid excess (-2.4, +0.9), Paget's disease (+1.8, +41.8), chronic renal failure (+16.3, +0.4), and osteolytic metastases (-1.4, +5.9). These discrepancies may have occurred because serum BGP and BAP concentrations reflect different aspects of osteoblast function or because there are differences in their clearance from the circulation. Consequently, more information is derived about the level of bone formation across the wide range of metabolic bone disorders when both biochemical markers are assayed.

Characterization and assay of tartrate-resistant acid phosphatase activity in serum: potential use to assess bone resorption

We improved the spectrophotometric assay of tartrate-resistant acid phosphatase (TrACP; EC 3.1.3.2) activity in serum. During development of the assay we found that human serum contains a dialyzable, mixed-type noncompetitive inhibitor(s) of TrACP activity, the effects of which on the assay were substantially lessened by diluting the serum sample with water before assay and increasing the substrate concentration. Hemolysis releases into serum a significant amount of TrACP activity from erythrocytes, which can be inactivated by incubating the serum at 37 degrees C for 1 h before assay. Our improved assay was reproducible (CV = 5%), and measured within 10% of the amount of added bovine skeletal TrACP activity. Preliminary application of the assay revealed that the amount of serum TrACP activity in patients with skeletal diseases differed from normal values and changed in the same direction as the expected change in bone turnover, suggesting that TrACP activity in serum could be useful clinically as a marker of bone metabolism, possibly of bone resorption.

Neurovisceral and skeletal GM1-gangliosidosis in dogs with beta-galactosidase deficiency

Beta-galactosidase-deficient siblings in two litters of English springer spaniel puppies showed a progressive neurological impairment, dwarfism, orbital hypertelorism, and dysostosis multiplex. An excess of GM1-ganglioside was found in the brain. Three abnormal oligosaccharides were present in samples of urine, brain, liver, and cartilage. Light microscopy of selected tissue specimens revealed cytoplasmic vacuoles in neurons, circulating blood cells, macrophages, and chondrocytes. Ultrastructural studies demonstrated that these membrane-bound vacuoles were of two types--one containing lamellated membranes and the other, finely granular material. These clinical and pathological findings are similar to those observed in human patients affected by the infantile form of GM1-gangliosidosis.