Manganese Supplementation Improves Mineral Density of the Spine and Femur and Serum Osteocalcin in Rats

The effect of manganese (Mn) supplementation on bone mineral density (BMD) and bone metabolism parameters was determined in ovariectomized Sprague-Dawley rats. Rats were divided into four groups (OVX, OVX+Mn, sham, sham+Mn) and fed with different intake levels of manganese (adequate 0.001% Mn, supplementation 0.01% Mn) for 12 weeks. BMD of the lumbar vertebrae, femur, and tibia were significantly lowered in ovariectomized rats compared to the sham group. In addition, BMD of the lumbar vertebrae was significantly increased by Mn supplementation in the sham groups. Serum C-telopeptide cross-links of type I collagen (CTx), bone resorption biomarker, alkaline phosphatase (ALP), and bone formation biomarkers were not significantly different among the four groups. However, serum osteocalcin, a more sensitive bone formation biomarker, was significantly increased by Mn supplementation. To summarize, Mn supplementation resulted in increased BMD and bone formation. Based on our findings, more research is needed to better understand the effects of manganese supplementation on bone formation and resorption.     

Silicon Supplementation Improves the Bone Mineral Density of Calcium-Deficient Ovariectomized Rats by Reducing Bone Resorption

The purpose of this study was to investigate the effect of silicon (Si) supplementation on bone mineral density (BMD) and bone metabolism parameters relative to calcium (Ca) intake levels in ovariectomized rats. A total of 72 female Wistar rats (6 weeks) were ovariectomized (OVX) and divided into six groups, and Si (500 mg of Si per kilogram of feed) was or was not administered with diets containing various levels of Ca (0.1%, 0.5%, and 1.5%) for 10 weeks. The groups were as follows: (1) Ca-deficient group (0.1% Ca), (2) Ca-deficient with Si supplementation group, (3) adequate Ca group (0.5% Ca), (4) adequate Ca with Si supplementation group, (5) high Ca group (1.5% Ca), and (6) high Ca with Si supplementation group. Si supplementation significantly increased the BMD of the femur and tibia in Ca-deficient OVX rats, while no change was observed with Si supplementation in the BMD of the spine, femur, and tibia in the adequate and high Ca groups. Serum alkaline phosphatase and osteocalcin levels were not affected by Si supplementation or Ca intake levels. C-telopeptide type I collagen levels were significantly decreased as a result of Si supplementation in Ca-deficient OVX rats. In summary, Si supplementation produced positive effects on bone mineral density in Ca-deficient OVX rats by reducing bone resorption. Therefore, Si supplementation may also prove to be helpful in preventing osteoporosis in postmenopausal women whose calcium intake is insufficient.     

Zinc-deficient rats have more limited bone recovery during repletion than diet-restricted rats

The objective of this study was to investigate the effects of dietary zinc deficiency and diet restriction on bone development in growing rats, and to determine whether any adverse effects could be reversed by dietary repletion. Weanling rats were fed either a zinc-deficient diet ad libitum (ZD; <1 mg zinc/kg) or nutritionally complete diet (30 mg zinc/kg) either ad libitum (CTL) or pair-fed to the intake of the ZD group (DR; diet-restricted) for 3 weeks (deficiency phase) and then all groups were fed the zinc-adequate diet ad libitum for 3, 7, or 23 days (repletion phase). Excised femurs were analyzed for bone mineral density (BMD) using dual-energy x-ray absorptiometry, and plasma was analyzed for markers of bone formation (osteocalcin) and resorption (Ratlaps). After the deficiency phase, ZD had lower body weight and reduced femur BMD, zinc, and phosphorus concentrations compared with DR; and these parameters were lower in DR compared with CTL. Femur calcium concentrations were unchanged among the groups. Reduced plasma osteocalcin in ZD and elevated plasma Ratlaps in DR suggested that zinc deficiency limits bone formation while diet restriction accelerates bone resorption activity. After 23 days of repletion, femur size, BMD, and zinc concentrations remained lower in ZD compared with DR and CTL. Body weight and femur phosphorus concentrations remained lower in both ZD and DR compared with CTL after repletion. There were no differences in plasma osteocalcin concentrations after the repletion phase, but the plasma Ratlaps concentrations remained elevated in DR compared with CTL. In summary, both ZD and DR lead to osteopenia during rapid growth, but the mechanisms appear to be due to reduced modeling in ZD and higher turnover in DR. Zinc deficiency was associated with a greater impairment in bone development than diet restriction, and both deficiencies limited bone recovery during repletion in growing rats.     

Effects of phenytoin and/or vitamin K2 (menatetrenone) on bone mineral density in the tibiae of growing rats

In this study, we investigated 1) whether the administration of phenytoin induced bone loss; and 2) whether menatetrenone could prevent bone loss induced by phenytoin. For this purpose, we previously developed a procedure to measure the bone mineral density using a conventional X-ray absorptiometry method. A long-termed administration of phenytoin (20 mg/kg per day for 5 weeks) produced bone loss in the tibiae of growing rats. The values of bone mineral density (BMD) were significantly decreased in the tibial diaphysis and metaphysis in the phenytoin-treated group. In this period, we measured the serum level of vitamin K-dependent protein, osteocalcin, a marker of bone formation. The serum level of osteocalcin showed a decrease in the phenytoin-treated group compared with the vehicle-treated group. Combined administration of menatetrenone (30 mg/kg in diet per day) with phenytoin for 5 weeks prevented the reduction of BMD, and the level of osteocalcin was slightly increased. Thus, it is suggested that long-termed phenytoin exposure may inhibit bone formation concomitantly with insufficient vitamin K, which, at least in part, contributed to bone loss in rats. Finally, these findings implicated the therapeutic usefulness of menatetrenone on a moderate degree of bone abnormality such as drug-induced osteopenia.     

Treadmill running starting 3 months after orchidectomy restores femoral bone mass in rats

The present study was designed to provide data on the effects on femoral bone of endurance training starting only 3 months after orchidectomy in rats. A total of 70 Wistar male rats were used at 8 weeks of age. On day 0 of the experiment, 10 rats were killed by cervical dislocation to be used as first controls. Among the 60 other animals, half was surgically castrated (CX) or sham operated (SH). On day 90, 10 CX and 10 SH were killed and used as intermediary controls (ICX and ISH). Among the other 20 CX and 20 SH, 10 within each group (CXE, SHE) were selected for treadmill running (60% maximal oxygen uptake, 1 h x day(-1), 5 days x week(-1) for 12 weeks). The 20 other rats were used as sedentary controls (CXR, SHR) and killed (as runners) on day 180. On day 90 femoral bone density (BMD) and mineral content (BMC) were lower in ICX than in ISH. On day 180 total femoral BMD was lower in CXR than in CXE. Simultaneously metaphyseal femoral BMD was lower in CXR than in CXE, SHR or SHE. Furthermore, at that time, no significant difference concerning BMD and BMC was observed between SHR and CXE. This would indicate that treadmill running starting only 3 months after orchidectomy is able to restore BMD and BMC to control values, mainly by inhibiting bone resorption (as shown by decreased urinary deoxypyridinoline excretion in CXE) without decreasing osteoblastic activity (evaluated by plasma osteocalcin concentration).     

Studies on action of menaquinone-7 in regulation of bone metabolism and its preventive role of osteoporosis

The effect of menaquinone-7 (MK-7) on bone components and bone resorbing factors induced-bone resorption using the femoral-diaphyseal and - metaphyseal tissues obtained from elderly female rats in vitro were examined. Calcium content, alkaline phosphatase activity and deoxyribonucleic acid (DNA) in the diaphyseal and metaphyseal tissues in elderly females rats were significantly decreased as compared with that of young rats, indicating that aging causes a deterioration of bone formation. The presence of MK-7 (10(-6)-10(-5) M) caused a significant prevention of reduction of biochemical components. On the other hand, the bone-resorbing factor, parathyroid hormone (1-34) (PTH; 10(-7) M) and prostaglandin E(2) (PGE(2); 10(-5) M) caused a significant decrease in calcium content in the diaphyseal and metaphyseal tissues. This decreases was completely inhibited in the presence of MK-7 (10(-7)-10(-5) M). In addition, MK-7 (10(-7)-10(-5) M) completely prevented the PTH (10(-7) M) or PGE(2) (10(-5) M) induced increases in medium glucose consumption and lactic acid production by bone tissues, Furthermore, the effect of the prolonged intake of dietary MK-7 on bone loss in ovariectomized rats was investigated. As a result, it was found that the intake of experimental diets containing the fermented soybean (natto) with supplemental MK-7 caused significant elevations of MK-7 and gamma-carboxylated osteocalcin concentration, a bio marker of bone formation, in the serum of both ovariectomized rats and normal subjects, suggesting that MK-7 may play an important role in the prevention of age-related bone loss.     

Long term effects of a single dose of intravenous Ibandronate

For defining the optimal regimen of a treatment of osteoporosis with an intravenous bisphosphonate one needs to know the duration of action of a single dose of the given drug. This allows us to establish the frequency by which a given dose has to be administered for obtaining a sufficient suppression of bone resorption over a longer period. In this study 1 and 2 mg Ibandronate were given as a single i.v. injection to young normal men and to healthy postmenopausal women on a free diet and with no treatment or supplements, and the markers of bone metabolism, as well as BMD, were followed for 6 months. Urinary C-telopeptides decreased by 81-95% 1 week after the injection and remained significantly decreased for 2 weeks after 1 mg Ibandronate, and for 4 months after 2 mg. In men, PTH increased by 80% at one week and remained significantly increased for 2 weeks, after 1mg and 2 mg Ibandronate. Plasma osteocalcin decreased slowly over 2 months in all 3 groups by 22%. Alkaline phosphatase showed similar, but not significant changes. In conclusion, the inhibition of bone resorption induced by 1 mg Ibandronate i.v. does not exceed 1 month and does not allow 3 month intervals in the treatment of osteoporosis, while 2 mg cover 3 months at least.     

Histochemical examination of systemic administration of eldecalcitol combined with guided bone regeneration for bone defect restoration in rats

The aim of this experiment was to elucidate the histological alterations after systemic administration of eldecalcitol (ELD) combined with guided bone regeneration during the restoration of bone defect healing in rats. The femurs of 8-week-old Wister rats were used to generate bone defect models. The defect was covered with a collagen membrane, and ELD group was administrated with eldecalcitol (50 ng/kg body weight) intragastrically once every other day. Femora were harvested at 1, 2, 4 and 8 weeks post-surgery. Decalcify tissue slices were made and used for histological and immunohistochemical examination. Bone biomarkers of RANKL, OPG and osteocalcin (OCN) were detected by western blot. The results revealed that the system administration of ELD could improve new bone formation demonstrated by the increased bone volume/tissue volume ratio and accelerated mineralization. ELD suppressed osteoclastic bone resorption by reducing the number of osteoclasts, decreasing the expression of cathepsin-K and the ratio of RANKL/OPG at the early stage of bone defect restoration (1 and 2 weeks) and upregulating OCN expression at the later stage of bone defect healing (4 and 8 weeks). These data suggested that systemic administration of eldecalcitol accelerated bone formation and promoted bone maturation by decreasing bone resorption and promoting bone mineralization during bone defect restoration.     

Release of intact and fragmented osteocalcin molecules from bone matrix during bone resorption in vitro

Osteocalcin detected from serum samples is considered a specific marker of osteoblast activity and bone formation rate. However, osteocalcin embedded in bone matrix must also be released during bone resorption. To understand the contribution of each type of bone cell in circulating osteocalcin levels, we used immunoassays detecting different molecular forms of osteocalcin to monitor bone resorption in vitro. Osteoclasts were obtained from rat long bones and cultured on bovine bone slices using osteocalcin-depleted fetal bovine serum. In addition, human osteoclasts differentiated from peripheral blood mononuclear cells were used. Both rat and human osteoclasts released osteocalcin from bovine bone into medium. The amount of osteocalcin increased in the presence of parathyroid hormone, a stimulator of resorption, and decreased in the presence of bafilomycin A1, an inhibitor of resorption. The amount of osteocalcin in the medium correlated with a well characterized marker of bone resorption, the C-terminal telopeptide of type I collagen (r > 0.9, p < 0.0001). The heterogeneity of released osteocalcin was determined using reverse phase high performance liquid chromatography, and several molecular forms of osteocalcin, including intact molecule, were identified in the culture medium. In conclusion, osteocalcin is released from the bone matrix during bone resorption as intact molecules and fragments. In addition to the conventional use as a marker of bone formation, osteocalcin can be used as a marker of bone resorption in vitro. Furthermore, bone matrix-derived osteocalcin may contribute to circulating osteocalcin levels, suggesting that serum osteocalcin should be considered as a marker of bone turnover rather than bone formation.     

The effects of long-term exposure to extremely low-frequency magnetic fields on bone formation in ovariectomized rats

The effects of long‐term extremely low‐frequency magnetic field (ELF‐MF) exposure on bone formation and biochemical markers were investigated in ovariectomized rats. Sixty mature female Sprague–Dawley rats were randomly divided into four different groups (n = 15): (i) unexposed control (CTL); (ii) ovariectomized only (OVX); (iii) non‐ovariectomized, exposed (SHAM + ELF‐MF); and (iv) ovariectomized, exposed (OVX + ELF‐MF). The third and fourth groups were exposed to 1.5 mT ELF‐MF for 4 h a day for 6 months. Bone mineral density (BMD) was determined using dual energy X‐ray absorption (DEXA) measurements. The formation and resorption of bone were evaluated using bone‐specific alkaline phosphatase (BAP), osteocalcin, osteoprotogerin, and N‐telopeptide. After 6 months of ELF‐MF therapy, BMD values were significantly lower in the OVX group and higher in the OVX + ELF‐MF and SHAM + ELF‐MF groups than they were before therapy (P < 0.001). Although there was no significant difference in BMD values among the groups before therapy, the BMD values increased significantly after 6 months in the OVX + ELF‐MF and SHAM + ELF‐MF groups and were reduced in the OVX group compared to the CTL group (P < 0.001). The concentrations of BAP, osteocalcin, osteoprotogerin, and N‐telopeptide in the three experimental groups also changed in a significant way compared to the CTL group. The results of the present study suggest that osteoporosis can be inhibited by ELF‐MF stimulation treatments. It was also concluded that ELF‐MF may be useful in the prevention of osteoporosis in ovariectomized rats. Bioelectromagnetics 33:543–549, 2012. © 2012 Wiley Periodicals, Inc.     

Effect of gallium nitrate in vitro and in normal rats

Gallium nitrate (GN) is an inhibitor of bone resorption and thereby may result in a change in coupled bone formation. In the present investigation the effects of GN on bone formation were studied in the rat osteosarcoma (ROS) 17/2.8 cell line and normal diploid rat osteoblasts (ROB) in vitro and the femur of rats treated in vivo, measuring mRNA levels for two osteoblast parameters, type I collagen, a marker of matrix formation, and osteocalcin, a bone specific protein and also histone H₄, a marker of cell proliferation. GN, at 50 μM for 3 h, increased type I collagen mRNA levels by 132% in ROS 17/2.8 cells and by 122% in proliferating ROB cells. Osteocalcin (OC) mRNA levels were decreased by 61% in ROS 17/2.8 cells and by 97% in differentiated ROB cells. These changes occurred in the absence of any effects on cell proliferation. Seventy-day-old female rats were then treated with GN, 0.5 mg/kg/day, for 3 weeks. As previously reported, GN decreased serum calcium levels, but had no effect on lumbar or femoral bone density. In contrast to the in vitro effects, GN had no effect on type I collagen steady-state mRNA levels in the femur; however, it decreased OC steady-state mRNA levels in the femur by 58%. These results suggest that GN has similar in vitro effects in transformed and normal osteoblasts, while the collagen-stimulatory effects observed in vitro cannot be extrapolated to in vivo models. The consistent inhibition of osteocalcin in vitro and in vivo suggests a more specific target for GN that may relate to its effects in inhibiting bone resorption in normal rats.     

Circadian rhythms in serum bone markers and their relation to the effect of etidronate in rats

Circadian rhythmicity is an essential feature of bone metabolism. The present study was undertaken to (Aoshima et al., [1998]) determine the changes in bone resorption and formation in rats over 24h, (Black et al., [1999]) evaluate the effect of the consecutive administration of etidronate on circadian rhythms of serum bone markers, and (Blumsohn et al., [1994]) determine whether the effect of etidronate on bone metabolism is circadian time-dependent. One hundred twenty male Wistar rats, which had been adapted to a 12/12h light/dark cycle, were injected subcutaneously once daily with either 0.5 mgP/kg etidronate or 0.9% NaCl (control group) at 0090, 1300, 1700, 2100, 0100, or 0500h for 10d. Serum was collected and tibiae were dissected 24h after the last injection. Serum pyridinoline (Pyd), tartrate-resistant acid phosphatase (TRAP), osteocalcin (OC), alkaline phosphatase (ALP), calcium (Ca), phosphorus (Pi), calcitonin (CT), and parathyroid hormone (PTH) were determined. Bone mineral density (BMD) in the proximal tibia, and the rate of formation of longitudinal trabecular bone over the past 48h were also determined using a chronological labeling method with NTA-Pb. The results showed characteristic circadian rhythms in serum bone markers in rats, with peaks in both bone resorption and bone formation during the animals' rest span. The administration of etidronate at the different times of the day decreased the level of bone-resorption markers (Pyd and TRAP) without affecting the circadian patterns of markers of bone formation (OC and ALP). However, the magnitude of the decrease due to etidronate was not uniform throughout the day, and was greatest during the daytime. Etidronate increased the BMD in the tibial metaphysis in all of the time-treatment groups, but the magnitude of the increase did not vary with the time of etidronate administration. The present data provide a physiological basis for future studies on bone metabolism and may be important in the design of future experiments and in the interpretation of experimental data.     

Effect of melatonin on bone metabolism in ovariectomized rats.

To assess the effect of pharmacological dose of melatonin on bone metabolism in ovariectomized rats, urinary deoxypyridinoline (a marker of bone resorption) and calcium excretion, circulating levels of calcium, phosphorus and bone alkaline phosphatase activity (a marker of bone formation), and bone mineral density (BMD), mineral content (BMC) and bone area (BA) of total body, were measured in adult rats for up to 60 days after surgery. Rats received melatonin in the drinking water (25 microg/ml water) or drinking water alone. Urinary deoxypyridinoline increased significantly after ovariectomy by 51% (30 days after surgery) and by 47% (60 days after surgery). The increase in urinary deoxypyridinoline found 30 days after ovariectomy was not observed in melatonin-treated rats. Urinary calcium concentration was similar in the 4 experimental groups studied, as was the circulating calcium concentration at every time interval examined. Fifteen days after surgery, a significant increase in serum phosphorus and bone alkaline phosphatase levels occurred in ovariectomized rats receiving melatonin as compared to their controls. Sixty days after surgery BMD, BMC and BA decreased significantly in ovariectomized rats, an effect not modified by melatonin. Serum estradiol decreased significantly by 30 days after ovariectomy to attain values close to the limit of detection of the assay by 60 days after ovariectomy. The results support the conclusion that a pharmacological amount of melatonin modifies bone remodeling after ovariectomy and that the effect may need adequate concentrations of estradiol.     

Alfacalcidol restores cancellous bone in ovariectomized rats

Active vitamin D metabolites have been demonstrated to reduce vertebral and hip fractures in elderly patients. A number of in vitro and in vivo pre-clinical studies have suggested that vitamin D may effectively stimulate osteoblastic activity and exert an anabolic effect on bone. The current study was designed to further explore the ability of an active vitamin D analog to restore bone in a skeletal site with established osteopenia in ovariectomized (OVX) rats. Female Sprague Dawley rats at five months of age and 8 weeks after sham ovariectomy or ovariectomy were randomly divided into 7 groups with 10 per group. At the beginning of the treatments, one group of sham-operated rats and one group of OVX rats were sacrificed to serve as baseline controls. Another group of sham-operated rats and one group of OVX rats were treated with vehicle for 4 weeks. The OVX rats in the remaining groups were treated with alfacalcidol at 0.05, 0.1 or 0.2 microg/kg/d by daily oral gavage, 5 days/week for 4 weeks. As expected, estrogen depletion caused high bone turnover and cancellous bone loss in lumbar vertebra of OVX rats. Alfacalcidol treatment at 0.1 or 0.2 but not 0.05 microg/kg/d increased serum calcium and phosphorus in OVX rats as compared with vehicle treatment. In addition, serum parathyroid hormone was suppressed, whereas serum osteocalcin was increased by alfacalcidol at all dose levels. Furthermore, histomorphometric data of 2nd lumbar vertebral body revealed that cancellous bone volume in OVX rats treated with alfacalcidol at 0.1 or 0.2 microg/kg/d was increased to the level of sham-operated rats treated with vehicle. This increment in cancellous bone mass was accompanied by increases in trabecular number and thickness and a decrease in trabecular separation. Moreover, osteoclast surface and number were significantly decreased, whereas bone formation variables such as mineralizing surface and bone formation rate were significantly increased in alfacalcidol- treated OVX rats compared with those of vehicle-treated OVX rats. Finally, a linear regression analysis showed that alfacalcidol treatment dose-dependently altered most of the variables measured in the current study. In conclusion, alfacalcidol completely restores cancellous bone by stimulating bone formation and suppressing bone resorption in lumbar vertebra of OVX rats when the treatment is started at an early phase of osteopenia. The evidence of increased bone formation by alfacalcidol treatments further supports the notion that active vitamin D metabolites or their analogs may exert anabolic effects on bone.     

Osteoporosis in experimental postmenopausal polyarthritis: the relative contributions of estrogen deficiency and inflammation

Generalized osteoporosis in postmenopausal rheumatoid arthritis (RA) is caused both by estrogen deficiency and by the inflammatory disease. The relative importance of each of these factors is unknown. The aim of this study was to establish a murine model of osteoporosis in postmenopausal RA, and to evaluate the relative importance and mechanisms of menopause and arthritis-related osteoporosis. To mimic postmenopausal RA, DBA/1 mice were ovariectomized, followed by the induction of type II collagen-induced arthritis. After the mice had been killed, paws were collected for histology, one femur for bone mineral density (BMD) and sera for analyses of markers of bone resorption (RatLaps; type I collagen cross-links, bone formation (osteocalcin) and cartilage destruction (cartilage oligomeric matrix protein), and for the evaluation of antigen-specific and innate immune responsiveness. Ovariectomized mice displayed more severe arthritis than sham-operated controls. At termination of the experiment, arthritic control mice and non-arthritic ovariectomized mice displayed trabecular bone losses of 26% and 22%, respectively. Ovariectomized mice with arthritis had as much as 58% decrease in trabecular BMD. Interestingly, cortical BMD was decreased by arthritis but was not affected by hormonal status. In addition, markers of bone resorption and cartilage destruction were increased in arthritic mice, whereas markers of bone formation were increased in ovariectomized mice. This study demonstrates that the loss of endogenous estrogen and inflammation contribute additively and equally to osteoporosis in experimental postmenopausal polyarthritis. Markers of bone remodeling and bone marrow lymphocyte phenotypes indicate different mechanisms for the development of osteoporosis caused by ovariectomy and arthritis in this model.     

Bone metabolism in patients with primary hyperparathyroidism before and after surgery

Primary hyperparathyroidism (PHPT) is accompanied with a reduced bone mineral density (BMD) and an increased risk of fracture. Surgery is the only option for cure. It is hypothesized that in patients with PHPT bone metabolism normalizes after parathyroidectomy (PTX) and that BMD gradually increases. Fifty-two patients with PHPT who underwent surgery were prospectively followed for 1 year. Biochemical analyses were performed at baseline and 1, 4, 7 days; 6 weeks; and 3, 6, and 12 months, and BMD before and one year after surgery. Parathyroid hormone (PTH), calcium, and the bone resorption marker dropped immediately, but transiently after PTX, bone formation decreased more slowly. Osteoprotegerin (OPG) as well as cathepsin K did not show significant changes. BMD of the lumbar spine, but not of the femoral neck, increased significantly within one year after surgery. Moderate correlations existed between the changes of total calcium, ionized calcium, as well as bone-specific alkaline phosphatase and changes of the lumbar BMD. Patients who needed postoperative supplementation with calcium and vitamin D had significantly higher PTH levels. Some gender-specific differences in patients with PHPT were observed. In patients with PHPT, males appear to be more severely affected than females. Within the first year after PTX, bone metabolism normalized, and BMD of the lumbar spine increased. Patients who needed a supplementation with calcium and vitamin D after PTX preoperatively had higher serum levels of PTH.     

Effects of chronic NH4Cl dosage and swimming exercise on bone metabolic turnover in rats

To determine the effects of ammonium chloride (NH4Cl) dosage and swimming exercise training during 4 weeks on bone metabolic turnover in rats, seven-week-old female 24 Wister-Kyoto (WKY) rats were investigated by bone status including bone mineral density (BMD) and biomechanical markers from blood and urine. Twenty-four rats (initial weight: 191.2+/-7.6 g) were randomly divided into four groups: baseline (8 weeks old) control group (n=6, BC), 4-week control group (n=6, Con), 4-week swimming exercise loading group (n=6, Swim) and 4-week chronic NH4Cl dosage group (n=6, Acid). All rats were fed an AIN93M diet (Ca: 0.5%, P: 0.3%), and both Con and Swim groups were pair-fed by feeding volume of the NH4Cl dosage group. The acid group only received 0.25 M NH4Cl distilled water ad libitum. At the end of the experimental period, rats were sacrificed with blood drawn and femur and tibia were removed for analysis of bone mineral density (BMD) by dual energy X-ray absorptiometry (DEXA). In the Swim group, 24-hour urinary deoxypiridinoline (Dpd) excretion, reflecting bone resorption, was significantly increased (p<0.05) with a tendency towards decrease of BMD (N.S.), and body weight and abdominal fat weight were decreased in approximately 7% (p<0.05) and 58% (p<0.001), as compared with age matched Con rats. In the Acid group, 24-hour urinary calcium (Ca) and phosphorus (P) excretion were increased approximately 2.1-fold (p<0.05) and 2.0-fold (p<0.01), respectively, with increase of kidney weight as much as in the Con groups. Serum Ca and P concentration, as well as urinary Dpd excretion were, however, not significantly changed. These results suggest that blood Ca and P concentrations in the chronic acidosis condition during the 4-weeks might be maintained by hypercalciuria and hyperphosphaturia with kidney disorder, and swimming exercise training leads to decrease in BMD with stimulation of bone resorption and reduction of body fat.     

Action of green tea catechin on bone metabolic disorder in chronic cadmium-poisoned rats

The purpose of this study was to investigate the effects of green tea catechin on bone metabolic disorders and its mechanism in chronic cadmium-poisoned rats. Sprague-Dawley male rats weighing 100+/-10 g were randomly assigned to one control group and three cadmium-poisoned groups. The cadmium groups included a catechin free diet (Cd-0C) group, a 0.25% catechin diet (Cd-0.25C) group and a 0.5% catechin diet (Cd-0.5C) group according to their respective levels of catechin supplement. After 20 weeks, the deoxypyridinoline and crosslink values measured in urine were significantly increased in the Cd-0C group. Cadmium intoxication seemed to lead to an increase in bone resorption. In the catechin supplemented group (Cd-0.5C group), these urinary bone resorption marks, were decreased. The serum osteocalcin content in the cadmium-poisoned group was significantly increased as compared with the control group. In the catechin supplemented group serum osteocalcin content values were lower than the control group. The cadmium-intoxicated group (Cd-0C group), had lower bone mineral density than the control group (total body, vertebra, pelvis, tibia and femur). The catechin supplement increased bone mineral density to about the same as the control group. Bone mineral content showed a similar trend to total bone mineral density. Therefore, the bone mineral content of the Cd-0C group at the 20th week was significantly lower than the control group. The catechin supplemented group (Cd-0.5C group) was about the same as the control group. The cause of decreasing bone mineral density and bone mineral content by cadmium poisoning was due to the fast bone turnover rate, where bone resorption occurred at a higher rate than bone formation. The green tea catechin aided in normalizing bone metabolic disorders in bone mineral density, bone mineral content and bone calcium content caused by chronic cadmium intoxication.     

Increased osteoblastogenesis and decreased bone resorption protect against ovariectomy-induced bone loss in thrombospondin-2-null mice.

Although bone is composed primarily of extracellular matrix (ECM), the dynamic role that the ECM plays in regulating bone remodeling secondary to estrogen loss is relatively unexplored. Previous studies have shown that mice deficient in the matricellular protein thrombospondin-2 (TSP2-null) form excess endocortical bone; thus, we postulated that enhanced bone formation in TSP2-null mice could protect against ovariectomy (OVX)-induced bone loss. Wild-type (WT) OVX mice showed a significant loss of both midfemoral endocortical and proximal tibial trabecular bone, but OVX did not significantly alter TSP2-null bone. TSP2-null mice showed an increase in bone formation, as indicated by a 70% increase in serum osteocalcin two weeks post OVX and a two-fold increase in bone formation rate (BFR) five weeks post OVX as measured by dynamic histomorphometry. WT animals showed only a 20% increase in serum osteocalcin at two weeks and no change in BFR at five weeks. This increase in bone formation in TSP2-null OVX mice was accompanied by a three-fold increase in osteoprogenitor number. Although these results provide a partial explanation for the maintenance of bone geometry post-OVX, TSP2-null mice five weeks post-OVX also showed a significantly lower level of bone resorption than OVX WT mice, as determined by serum levels of the amino-terminal telopeptide of type I collagen (NTx). We conclude that the absence of TSP2 protects against OVX-induced bone loss by two complementary processes: increased formation and decreased resorption.     

Dietary iron deficiency decreases serum osteocalcin concentration and bone mineral density in rats

We investigated the effects of dietary iron deficiency on bone metabolism by measuring markers of bone turnover in rats. Twelve 3-week-old male Wistar-strain rats were fed a control diet or an iron-deficient diet for 4 weeks. Dietary iron deficiency decreased hemoglobin concentration and increased heart weight. Serum osteocalcin concentration, bone mineral content, bone mineral density, and mechanical strength of the femur were significantly lower in the iron-deficient group than in the control group. These results suggested that dietary iron deficiency affected bone, which might have been due to a decrease in bone formation in rats.