Short-term course of 1,25(OH)2D3 stimulates osteoblasts but not osteoclasts in osteoporosis and osteoarthritis

The Roles of Acidosis in Osteoclast Biology

The adverse effect of acidosis on the skeletal system has been recognized for almost a century. Although the underlying mechanism has not been fully elucidated, it appears that acidosis acts as a general stimulator of osteoclasts derived from bone marrow precursors cells and enhances osteoclastic resorption. Prior work suggests that acidosis plays a significant role in osteoclasts formation and activation via up-regulating various genes responsible for its adhesion, migration, survival and bone matrix degradation. Understanding the role of acidosis in osteoclast biology may lead to development of novel therapeutic approaches for the treatment of diseases related to low bone mass. In this review, we aim to discuss the recent investigations into the effects of acidosis in osteoclast biology and the acid-sensing molecular mechanism.

Bone mineral density loss during adjuvant chemotherapy in pre-menopausal women with early breast cancer: is it dependent on oestrogen deficiency?

Pre-menopausal women given adjuvant chemotherapy for breast cancer experience both premature ovarian failure and loss of bone mineral density (BMD), and this study was designed to see if these observations are causally linked. Chemotherapy was administered to 41 pre-menopausal women with early breast cancer enrolled prospectively in a study of ovarian function and BMD in such women given systemic therapy. After giving written informed consent, all patients underwent baseline and regular on-treatment measurements of BMD by dual-energy X-ray absorptiometry (DXA) scan, bone turnover and ovarian function by analysis of serum hormone levels and self-reported menstrual diaries. Baseline lumbar spine BMD in the 41 women given chemotherapy was higher than the normal population (Z score 0.28 ± 0.14 (mean ± SEM), P = 0.047), and fell significantly over the first 6 months from a mean of 1.05-1.01 g/m(2), P < 0.0001, and similar but smaller changes were demonstrated in hip BMD. This fall was independent of age at diagnosis, type of chemotherapy, development of amenorrhoea or either baseline or on-treatment estradiol concentration. During the 6 months after completion of adjuvant chemotherapy, BMD fell further only in those women with low estradiol or experiencing amenorrhoea during the first 6 months, although all groups showed evidence of increased bone turnover. This study demonstrates loss of both spine and hip BMD in pre-menopausal women during 6 months' adjuvant systemic chemotherapy to be independent of changes in ovarian function. Ovarian function was, however, related to BMD changes after chemotherapy ceased.

Osteocalcin synthesis by human osteoblasts from normal and osteoarthritic bone after vitamin D3 stimulation

Alterations in osteoblast metabolism are involved in the pathogenesis of typical subchondral bone changes in osteoarthritis (OA). Osteocalcin is a specific bone protein, synthesised by the osteoblasts, which can be considered a marker of metabolic activity of these cells. In this study we correlated osteocalcin production from human osteoblasts isolated from healthy and osteoarthritic subjects to the degree of cartilage damage, before and after stimulation with 1,25(OH)2-vitamin D3, the active metabolite of vitamin D3. We isolated human osteoblasts from cancellous bone of healthy subjects and from subchondral bone of osteoarthritic subjects and considered the osteoblasts corresponding to different degrees of cartilage damage as different cell populations. We determined the osteocalcin production in normal and osteoarthritic osteoblasts from maximal and minimal cartilage damage areas both under basal conditions and after vitamin D3 stimulation. Compared to normal osteoblasts, under basal conditions osteocalcin production is significantly greater in osteoarthritic osteoblasts, corresponding both to maximal and minimal damage joint areas. No differences were observed between osteoblasts from maximal and minimal damage areas. The response of osteoblasts to vitamin D3 stimulation appeared to be proportional to the degree of joint damage, as the vitamin D3-induced increase in osteocalcin is proportionally greater in maximally damaged osteoblasts compared to minimally damaged ones. Thus, after vitamin D3 stimulation, a significant increase in osteocalcin production by maximally damaged osteoblasts compared to the minimally damaged ones was observed. This study confirms abnormal osteoarthritic osteoblast behaviour and indicates that osteoblasts from different areas of the same affected joint may be metabolically different, supporting the hypothesis that subchondral osteoblasts may play an essential role in the pathogenesis of OA.

Osteoarthritis and osteoporosis: clinical and research evidence of inverse relationship

The etiology of osteoporosis (OP) and osteoarthritis (OA) is multifactorial: both constitutional and environmental factors, ranging from genetic susceptibility, endocrine and metabolic status, to mechanical and traumatic injury, are thought to be involved. When interpreting research data, one must bear in mind that pathophysiologic factors, especially in disorders associated with aging, must be regarded as either primary or secondary. Therefore, findings in end-stage pathology are not necessarily the evidence or explanation of the primary cause or event in the diseased tissue. Both aspects of research are important for potentially curative or preventive measures. These considerations, in the case of our topic--the inverse relationship of OP and OA--are of particular importance. Although the inverse relationship between two frequent diseases associated with aging, OA and OP, has been observed and studied for more than 30 years, the topic remains controversial for some and stimulating for many. The anthropometric differences of patients suffering from OA compared with OP are well established. OA cases have stronger body build and are more obese. There is overwhelming evidence that OA cases have increased BMD or BMC at all sites. This increased BMD is related to high peak bone mass, as shown in mother-daughter and twin studies. With aging, the bone loss in OA is lower, except when measured near an affected joint (hand, hip, knee). The lower degree of bone loss with aging is explained by lower bone turnover as measured by bone resorption-formation parameters. OA cases not only have higher apparent and real bone density, but also wider geometrical measures of the skeleton, diameters of long bones and trabeculae, both contributing positively to better strength and fewer fragility fractures. Not only is bone quantity in OA different but also bone quality, compared with controls and OP cases, with increased content of growth factors such as IGF and TGFbeta, factors required for bone repair. Furthermore, in vitro studies of osteoblasts recruited from OA bone have different differentiation patterns and phenotypes. These general bone characteristics of OA bone may explain the inverse relationship OA-OP and why OA cases have fewer fragility fractures. The role of bone, in particular subchondral bone, in the pathophysiology, initiation and progression of OA is not fully elucidated and is still controversial. In 1970, it was hypothesized that an increased number of microfractures lead to an increase in subchondral bone stiffness, which impairs its ability to act as a shock absorber, so that cartilage suffers more. Although subchondral bone is slightly hypomineralized because of local increased turnover, the increase in trabecular number and volume compensates for this, resulting in a stiffer structure. There is also some experimental evidence that osteoblasts themselves release factors such as metalloproteinases directly or indirectly from the matrix, which predispose cartilage to deterioration. Instead, the osteoblast regenerative capacity of bone in OP is compromised compared with OA, as suggested by early cell adhesion differences. The proposition that drugs which suppress bone turnover in OP, such as bisphosphonates, may be beneficial for OA is speculative. Although bone turnover in the subchondral region of established OA is increased, the general bone turnover is reduced. Further reduction of bone turnover, however, may lead to overmineralized (aged) osteons and loss of bone quality, resulting in increased fragility.

Recruitment, augmentation and apoptosis of rat osteoclasts in 1,25-(OH)2D3 response to short-term treatment with 1,25-dihydroxyvitamin D3 in vivo

BACKGROUND

Although much is known about the regulation of osteoclast (OC) formation and activity, little is known about OC senescence. In particular, the fate of of OC seen after 1,25-(OH)2D3 administration in vivo is unclear. There is evidence that the normal fate of OC is to undergo apoptosis (programmed cell death). We have investigated the effect of short-term application of high dose 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on OC apoptosis in an experimental rat model.

METHODS

OC recruitment, augmentation and apoptosis was visualised and quantitated by staining histochemically for tartrate resistant acid phosphatase (TRAP), double staining for TRAP/ED1 or TRAP/DAPI, in situ DNA fragmentation end labelling and histomorphometric analysis.

RESULTS

Short-term treatment with high-dose 1,25-(OH)2D3 increased the recruitment of OC precursors in the bone marrow resulting in a short-lived increase in OC numbers. This was rapidly followed by an increase in the number of apoptotic OC and their subsequent removal. The response of OC to 1,25-(OH)2D3 treatment was dose and site dependent; higher doses producing stronger, more rapid responses and the response in the tibiae being consistently stronger and more rapid than in the vertebrae.

CONCLUSIONS

This study demonstrates that (1) after recruitment, OC are removed from the resorption site by apoptosis (2) the combined use of TRAP and ED1 can be used to identify OC and their precursors in vivo (3) double staining for TRAP and DAPI or in situ DNA fragmentation end labelling can be used to identify apoptotic OC in vivo.

Changes in bone turnover after parathyroidectomy in dialysis patients: role of calcitriol administration

BACKGROUND

Available data on changes in serum levels of bone markers after parathyroidectomy (PTx) in dialysis patients are not uniform. Changes are thought to be due to either a reduction in PTH activity per se or to a direct effect of vitamin D therapy on bone cells. We aimed to verify whether treatment with vitamin D modifies serum levels of markers of bone synthesis (alkaline phosphatase (AP), osteocalcin (BGP), procollagen type I C-terminal peptide (PICP)) and resorption (collagen type I C-terminal peptide (ICTP)) within a period of 15 days in haemodialysis patients with severe secondary hyperparathyroidism following PTx.

METHODS

We randomized two groups (A, treatment and B, placebo, 10 patients each) with comparable basal PTH values and measured bone markers 3, 7 and 15 days after surgery. All patients were treated with calcium supplements (i.v. and p.o.), and group A also received calcitriol (2.4+/-1.0 microg/day, p.o.).

RESULTS

In both groups, PTx induced significant changes in all the markers evaluated, except for BGP in group B. Compared to basal values, ICTP decreased from 481+/-152 ng/ml in group A and 277+/-126 ng/ml in group B to 267+/-94 and 185+/-71 ng/ml (M+/-SD) respectively, and PICP increased from 307+/-139 ng/ml in group A and 309+/-200 ng/ml in group B to 1129+/-725 and 1231+/-1267 ng/ml (M+/-SD) respectively, within 3 days of surgery. AP values increased after 15 days from 1115+/-734 mU/ml in group A and 1419+/-1225 mU/ml in group B to 1917+/-1225 and 1867+/-1295 mU/ml (M+/-SD) respectively. On the contrary, mean values of BGP were never different from basal levels after PTx in either group. In the two groups, the pattern of changes of all the bone markers after PTx was almost identical. Group A patients predictably required lower doses of oral calcium supplements to correct hypocalcaemia (16. 9+/-5.7 vs 22.1+/-5.0 g/10 days; M+/-SD, P<0.04).

CONCLUSIONS

The opposite behaviour of serum PICP and ICTP after PTx, in both the treated and untreated groups suggests that quantitative uncoupling between bone synthesis and resorption is responsible for hypocalcaemia. This phenomenon, as reflected by the evaluated bone markers, is unaffected by calcitriol. Based on our data we conclude that immediately after parathyroid surgery, vitamin D therapy does not influence bone cell activity, but improves hypocalcaemia mainly through its known effect on intestinal calcium absorption.

Effects of short-term treatment with prednisolone and calcitriol on bone and mineral metabolism in normal men

To study the effects of treatment with glucocorticoid and calcitriol on biochemical markers of calcium and bone metabolism, 48 normal male volunteers (aged 21-54 years) were randomized to treatment for 7 days with either (A) prednisolone, 10 mg twice daily, (B) prednisolone, 10 mg twice daily, and calcitriol, 1 microg twice daily, (C) calcitriol 1 mg twice daily, or (D) placebo. The study period was 28 days. Renal calcium excretion increased (mean maximal increase +44.7%, p < 0.01) as well as serum parathyroid hormone (PTH) (max. +18.5%, p < 0.01) during prednisolone treatment. Concomitant treatment with calcitriol or calcitriol alone equally enhanced renal calcium excretion (max. +185.2%, p < 0.001) and decreased serum PTH (max. -43.1%, p < 0.001). Prednisolone administration was followed by prompt declines in markers of bone formation [serum osteocalcin (max. -34.7%, p < 0.001) and serum procollagen type I C-terminal propeptide (PICP) (max. -25.9%, p < 0.05)], whereas serum bone alkaline phosphatase (bone AP) remained unchanged. Calcitriol in combination with prednisolone attenuated the decrease in PICP (max. -8.9%, not significant), but it had no effect on osteocalcin (max. -40.1%, p < 0.001), and decreased bone AP (max. -22.2%, p < 0.05). Calcitriol alone increased osteocalcin (max. +37.8%, p < 0.03) and PICP (max. +26.0%, p < 0.05). Among markers of bone degradation, prednisolone suppressed serum C-terminal telopeptide of type I collagen (ICTP) (max. -28.4%, p < 0.001), but not the fasting renal excretion of hydroxyproline (OHP) and collagen type I N-terminal telopeptide (NTx). Calcitriol partially antagonized the decrease in ICTP (max. -17.2%, p < 0.001). Calcitriol alone had no effect on resorptive markers. Extraosseous matrix synthesis was suppressed by prednisolone evaluated by serum procollagen type III N-terminal propeptide (max. -30.8%, p < 0.001) and was not affected by concomitant treatment with calcitriol or calcitriol alone. In conclusion, short-term administration of prednisolone to healthy men leads to fast and protracted suppression of biochemical markers of bone formation and extraosseous connective tissue metabolism. The effect on bone was partially antagonized by simultaneous calcitriol treatment, and points toward a potential role of calcitriol in the prevention of steroid induced osteoporosis.

Short-term treatment of rats with high dose 1,25-dihydroxyvitamin D3 stimulates bone formation and increases the number of osteoblast precursor cells in bone marrow

Using an experimental rat model, this study was undertaken to assess the effects of a short-term application of high dose 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] on calcium homeostasis, cancellous bone formation, and numbers of osteoblast precursors in ex vivo bone marrow cultures. For Exp 1 and 2, 6-month-old female rats were sc injected with either 0.2 microg 1,25-(OH)2D3/kg x day or vehicle on days 1, 2, and 3 of the studies. Serum calcium and urinary excretion of calcium were monitored for 12 days in Exp 1. In Exp 2, the rats were ip labeled with five different fluorochromes on days 0, 5, 10, 15, and 20, respectively. Half of the rats in each group were killed on day 7, the rest of the rats were killed on day 24, and the first lumbar vertebrae were processed for histomorphometry. In Exp 3, 0.2 microg 1,25-(OH)2D3/kg BW or vehicle was sc administered to 6-month-old male rats on days 1, 2, and 3, and the number of colony-forming units with the ability to express alkaline phosphatase, to calcify, and/or to synthesize collagen were enumerated sequentially on days 4, 6, 8, 10, 12, and 14 in bone marrow cultures. Short-term 1,25-(OH)2D3 treatment resulted in increased values for serum and urinary calcium during the treatment phase in Exp 1, depressed osteoclast numbers and strongly elevated osteoblast perimeter by day 7, and stimulated mineral apposition rate and bone formation rate in the interval between days 5-15 of Exp 2. Moreover, 1,25-(OH)2D3 administration to rats significantly enhanced the number of mesenchymal precursor cells in bone marrow with the ability to differentiate into an osteoblastic phenotype in ex vivo bone marrow cultures on day 4 of Exp 3. These studies provide evidence that short-term 1,25-(OH)2D3 treatment creates new bone remodeling units and augments osteoblast recruitment and osteoblast team performance in rat cancellous bone.

1-alpha-Hydroxyvitamin D3 treatment decreases bone turnover and modulates calcium-regulating hormones in early postmenopausal women

50 Japanese women within 10 years after menopause (mean age 52.5 years) were studied to determine the effects of 0.75 microgram of 1-alpha-hydroxyvitamin D3 [1-alpha-(OH)D3] with calcium (150 mg/day) (treated group: N = 25) and calcium only (control group: N = 25) for 12 months on bone mass and metabolism. Their L2-4 BMD measurements were 1.5 SD below the mean value of Japanese young, normal women. L2-4 BMDs increased significantly in the treated group (+2.1%; p < 0.01), but decreased significantly in controls (-2.1%; p < 0.01). Although serum calcium and creatinine remained unchanged in both groups, phosphorus levels increased significantly in the treated group (p < 0.01). Urinary calcium/creatinine (Cr) increased in both groups. Urinary pyridinoline/Cr and deoxypyridinoline/Cr decreased significantly in the treated group (p < 0.05), but not in the control group. Serum osteocalcin levels remained unchanged in both groups. Intact parathyroid hormone levels decreased significantly (p < 0.05) and calcitonin levels significantly increased in the treated group (p < 0.05), but these changes were not observed in the control group. These data clearly demonstrate that 0.75 microgram of 1-alpha-(OH)D3 maintained bone mass by reducing bone resorption by modulation of calcium-regulating hormones. Temporarily increased urinary calcium excretion was observed in control group, but did not appear to be effective in modulating bone turnover.

Bone density and local growth factors in generalized osteoarthritis

Osteoarthritis is usually considered to be a primary disorder of chondrocyte function with secondary changes in bones. However, a defect in the subchondral bone resulting in loss of its shock absorbing capacity could transfer the stress of loading directly to the articular cartilage with secondary changes in the cartilage. Review of histomorphometric and bone densitometric studies at sites of osteoarthritis at the hip or knee revealed that cartilage fibrillation could not be dissociated from bony changes even in the earliest stages of osteoarthritis and that subchondral trabeculae are thickened and more spaced in osteoarthritis. Microfractures of subchondral trabecular bone were less frequently seen in osteoarthritis compared to controls. Changes of the tidemark were found to be multiform and metabolically active in the osteoarthritic process. Endochondral ossification depletes the calcified cartilage at the cartilage/bone interface and the tidemark has been thought of as a calcification front advancing in the direction of non-calcified cartilage. Duplication of the tidemark is cited as evidence of this advancement. In the few experimental animal studies of subchondral bone in osteoarthritis, thicker trabeculae which were closer together were found in guinea pigs already when only mild cartilage changes were present. In the dog, with cruciate ligament transection, changes in bone were later than in the cartilage, but the changes in bone could still contribute to the progression of osteoarthritis. To study if bone changes may precede injury to the cartilage and if metabolic and systemic influences can also alter the subchondral bone, rendering it less able to withstand normal mechanical stresses, bone at different sites in the body has been studied extensively by the authors. Epidemiological and case control studies have revealed that osteoarthritis cases have more bone at all sites than expected and that bone in cases with generalized osteoarthritis shows both quantitative and qualitative differences, including increased contents of growth factors and hypermineralization. These findings suggest that a more generalized bone alteration may be the basis of the pathogenesis of osteoarthritis.

Dose-response effect of short-term calcitriol treatment on bone and mineral metabolism in normal males

To evaluate the effects of short-term treatment with calcitriol on biochemical markers of calcium and bone metabolism, 36 normal male volunteers (aged 21-54 years) were randomized to oral treatment for 7 days with either (A) calcitriol, 1 microgram twice daily, (B) calcitriol, 0.5 microgram twice daily, or (C) placebo twice daily. Serum calcium increased slightly in a dose-dependent manner (maximal increase 2.5%, p < 0.05) followed by a heavy increase in both 24 h (max. 156.1%, p < 0.001) and fasting urinary calcium excretion (max. 123.1%, p < 0.001), and a striking reduction in serum PTH (max. -43.1%, p < 0.001). Biochemical markers of osteoblast activity and bone formation increased immediately in a dose-dependent manner [serum osteocalcin (max. 37.8%, p < 0.03) and serum procollagen type I C-terminal propeptide (PICP) (max. 26.0%, p < 0.05)], whereas there was no effect on serum bone alkaline phosphatase. Calcitriol treatment had no effect on biochemical markers of bone resorption [serum C-terminal telopeptide of type I collagen (ICTP) and fasting urinary excretion of hydroxyproline/creatinine (OHP)]. Extraosseous collagen matrix synthesis was not affected evaluated by serum procollagen type III N-terminal propeptide (PIIINP). In the follow-up period (15 weeks) no unequivocal changes were observed. The fast and protracted increase in biochemical markers of osteoblast activity and bone formation, without affecting bone resorption and extraosseous connective tissue metabolism points toward a selective effect of calcitriol on bone matrix formation.

Calcium and vitamin D enriched diets increase and preserve vertebral mineral content in aging laboratory rats

To assess the long-term effect of vitamin D or calcium supplementation on the skeletal metabolism of aging laboratory rodents, 1.5-month-old female Wistar rats were fed with diets containing twice the concentration of vitamin D (group 2) and of calcium (group 3) as in the usual rat chow. Follow-up to 24 months of age did not show significant differences between the enriched-diet groups and the controls (group 1) in terms of the vertebral body weight and protein content. Significantly higher bone mineral contents were found in groups 2 and 3 than were found in controls, as revealed by an increased bone mineral density (BMD: +62%, group 2; +48%, group 3) and vertebral calcium content (+73%, group 2; +84%, group 3). The vertebral alkaline phosphatase enzymatic activity was significantly lower in the enriched diet groups than in controls (-47%, group 2; -45%, group 3). The ratio alkaline phosphatase/acid phosphatase activity was markedly reduced in groups 2 and 3 (-57% and -59%, respectively), which might indicate a diminished rate of bone turnover. The trabecular bone volume (BV/TV) decreased in all groups during senescence, being significantly elevated in group 3 as compared to controls. Vitamin D and calcium dietary supplementations increase the axial mineral bone content in laboratory rats and might reduce the bone turnover. Their influence on the trabecular bone volume has yet to be examined.

Oral 1,25-dihydroxyvitamin D administration in osteoporotic women: effects of estrogen therapy

Estrogen has been shown to modify calcium and skeletal homeostasis. In this study, we tested the ability of estrogen to influence the effects of short-term 1,25(OH)2D administration on biochemical indices of bone formation and resorption in a cross-sectional analysis of untreated (n = 10) and estrogen-treated (n = 14) osteoporotic women. Patients were given oral 1,25(OH)2D (Rocaltrol) 0.5 microgram twice a day for 5 days. Serum and urine were sampled at baseline and then 1 h after the first daily Rocaltrol dose for the 5 days of the study. 1,25(OH)2D levels rose similarly in both groups with plateaus reached by the third day of the investigation. Serum PTH levels decreased by the first sampling period (1 h after first Rocaltrol dose; p < 0.008 both groups) and continued to fall gradually in both groups. There were no changes in serum calcium but serum phosphorus rose by the second day (p < 0.05 both groups) and remained elevated throughout the remainder of the protocol. Serum bone Gla protein increased approximately 40% (p < 0.05) with no group differences. In contrast, total alkaline phosphatase and carboxy-terminal propeptide of type I collagen did not increase in either group. Furthermore, there were no significant increments in any bone resorption indicators, including serum tartrate-resistant acid phosphatase and cross-linked carboxy-terminal telopeptide of type I collagen, as well as urine hydroxyproline and pyridinoline. Serum IGF-1 levels also remained unchanged in both groups. We conclude that oral 1,25(OH)2D administration decreased 1-84PTH levels, probably due to a suppression of parathyroid production, and did not stimulate bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

High-dose glucocorticoids in multiple sclerosis patients exert direct effects on the kidney and skeleton

The effects of acute pharmacologic steroid treatment on skeletal and mineral metabolism were assessed in 56 multiple sclerosis patients who were to receive 1 g intravenous methylprednisolone for 10 days, followed by a 4 day intravenous and 28 day oral glucocorticoid taper. Serum and urine samples were obtained at baseline and then within 3 days, 1, 2, and 3 weeks after beginning steroids. A subset of patients (n = 11) had sampling throughout the 6 weeks of steroid administration and up to 8 weeks afterward. All mean basal biochemistries were normal except 25(OH)D, which was in the "insufficient" range (25-50 nM) at 10 nM. During and after steroid administration, there were no changes in ionized calcium, 25(OH)D, urinary hydroxyproline, or pyridinoline. There was an increase in 1,25(OH)2D and a decrease in serum phosphorus, accompanied by an increase in urinary phosphate clearance, within 3 days of administration (p < 0.006). Serum osteocalcin (BGP) decreased to below assay sensitivity limits within 3 days of steroid administration (p < 0.0002), increasing thereafter but remaining at 50% of baseline by the third week. PTH(1-84) increased to a peak at week 2 (p < 0.02), after both the 1,25(OH)2D peak and the serum phosphorus nadir. Tartrate-resistant acid phosphatase, urinary calcium, and urinary cyclic AMP all increased above baseline (p < 0.05) with a pattern similar to that of PTH. To investigate further the immediate effects of steroid administration, serum samples were obtained at the same four times on both the day before and the day after the first intravenous methylprednisolone dose in a randomly chosen subset of patients (n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

A novel synthetic vitamin D analogue, 2 beta-(3-hydroxypropoxy)1 alpha, 25-dihydroxyvitamin D3 (ED-71), increases bone mass by stimulating the bone formation in normal and ovariectomized rats

We performed dosing experiments to evaluate the bone mass increasing action of a novel, synthetic vitamin D derivative, 2 beta-(3-hydroxypropoxy)-1 alpha,25(OH)2D3 (ED-71), in normal and estrogen-deficient rats. The first experiment consisted of 31 Sprague-Dawley rats, 28 weeks of age. The second experiment consisted of 44 animals who were ovariectomized (OVX) or sham operated at the age of 12 weeks. ED-71 was given twice a week for the duration of 12 weeks. At the end of the experiments, serum chemistries were examined and lumbar vertebrae were assessed histomorphometrically. Serum alkaline-phosphatase levels tended to decrease by ED-71 administration in the first experiment and their elevated values after ovariectomy were also depressed by ED-71 in the second experiment. Serum osteocalcin levels, however, increased by the agent. In the first experiment, cancellous bone volume (BV/TV) increased dose dependently. Bone formation rates (BFR/BS) also increased. In the second experiment, BV/TV significantly decreased by ovariectomy and it increased in ED-71-treated groups, but not in 1 alpha-(OH)D3-treated group. BFR/BS increased by ED-71. Activation frequency did not decrease by ED-71 in either experiment. These data clearly demonstrated that ED-71 administration was capable of increasing the bone mass by stimulating bone formation in normal and estrogen-deficient rats.

Generalized osteoarthritis associated with increased insulin-like growth factor types I and II and transforming growth factor beta in cortical bone from the iliac crest. Possible mechanism of increased bone density and protection against osteoporosis

OBJECTIVE

To investigate whether growth factors stored in bone might explain the increased bone density and resistance to osteoporosis in generalized osteoarthritis.

METHODS

Levels of insulin-like growth factor (IGF) types I and II and transforming growth factor beta (TGF beta) were measured in extracts of cortical bone from the iliac crest obtained at necropsy from subjects with or without osteoarthritis of the hands.

RESULTS

Concentrations of IGF-I, IGF-II, and TGF beta were significantly higher in extracts of bone powder from subjects in the osteoarthritis group than in extracts from subjects in the control group.

CONCLUSION

The results suggest that the increased bone density and resistance to osteoporosis in patients with osteoarthritis may be associated with increased skeletal concentrations of IGF-I, IGF-II, and TGF beta and may reflect a generally increased biosynthetic activity of osteoblasts in these patients.

Osteoarthritis protects against femoral neck fracture: the MEDOS study experience

The relationship between osteoarthritis and osteoporosis (hip fracture) was studied using the data from the MEDOS study, a large prospective epidemiological study of femoral neck fracture patients and age-matched controls in the Mediterranean area. Osteoarthritis was found to be protective against hip fracture in both men and women, with a significant reduction of the relative risk factor for osteoporosis (relative risk = 0.48 and 0.68, respectively, p < 0.001). The age-adjusted relative risk factor for osteoporosis remains even after adjustment for body mass index, indicating that body mass index and osteoarthritis are independent relative risk factors for hip fracture. The mean age of the group with co-existent osteoarthritis and hip fracture was significantly higher for both men and women, compared to the group with osteoporosis alone. This indicates that if osteoarthritic subjects develop osteoporotic fracture, they do so at a later age. The osteoarthritic cases compared to controls and hip fracture cases were significantly smaller in stature in both sexes, and women had a significantly higher body weight and body mass index. Extra-capsular hip fracture was significantly more frequent in cases with concomitant osteoarthritis. These findings confirm earlier observations that osteoarthritis and osteoporosis are two distinct diseases and not phenomena related solely to aging.

Prevention of post-menopausal bone loss with 1 alpha-hydroxy vitamin D3. A three-year prospective study

An open and controlled prospective study was used to assess the preventive efficiency of 1 alpha-hydroxy vitamin D3 (1 alpha (OH) Vit. D3) on post-menopausal vertebral bone loss. Of the 36 patients included in the study, 25 completed two years of treatment with 1 microgram/day of 1 alpha (OH) Vit. D3 and 500 mg of calcium. The vertebral bone mineral density measured by dual photon absorptiometry did not vary in the treated group, whereas it decreased significantly in the control group at the end of the 2 years. At two years, withdrawal of treatment led to a significant bone loss, whereas bone mass remained stable in a subgroup of patients who underwent a third year of treatment with 1 alpha (OH) Vit. D3. Overall, tolerance was satisfactory. However, urinary calcium increased significantly during treatment and one third of the patients developed hypercalciuria > or = 7.5 mmoles/24 h. No variation in either serum calcium or creatinine levels was noted. These results indicate that 1 alpha (OH) Vit. D3 could be useful in preventing post-menopausal bone loss provided it was complemented by regular monitoring of urinary calcium excretion.