Repeated oral administration of a cathepsin K inhibitor significantly suppresses bone resorption in exercising horses with evidence of increased bone formation and maintained bone turnover.

Our investigations evaluated the effect of VEL-0230, a highly specific irreversible inhibitor of cathepsin K (CatK). The objectives of our study were to determine whether repeated dosing of a CatK inhibitor (CatKI) produced a desired inhibition of the bone resorption biomarker (CTX-1), and document the effect of repeated dosing on bone homeostasis, structure, and dynamics of bone resorption and formation in horses. Twelve young exercising horses were randomized in a prospective, controlled clinical trial and received 4 weekly doses of a CatKI or vehicle. Baseline and poststudy nuclear scintigraphy, blood sampling and analysis of plasma bone biomarkers (CTX-1 and osteocalcin), poststudy bone fluorescent labeling, and bone biopsy were performed. Bone specimens were further processed for microcomputed tomography and bone histomorphometry. Each dose of this CatKI transiently inhibited plasma CTX-1 (reflecting inhibition of bone collagen resorption) and increased bone plasma osteocalcin concentrations, with no detectable adverse effect on normal bone turnover in the face of exercise. Bone morphology, density, and formation rate were not different between control and treated group. Further investigation of CatK inhibition in abnormal bone turnover is required in animals with bone diseases.

Pasteurella multocida toxin- induced osteoclastogenesis requires mTOR activation.

BACKGROUND: Pasteurella multocida toxin (PMT) is a potent inducer of osteoclast formation. Pigs suffering from an infection with toxigenic Pasteurella multocida strains develop atrophic rhinitis characterised by a loss of turbinate bones and conchae. However, on the molecular level the process of bone loss remains largely uncharacterised. RESULTS: Recently it was found that PMT activates the serine/threonine kinase mammalian target of rapamycin (mTOR) in fibroblasts. Using RAW264.7 macrophages, we investigated the role of the mTOR complex 1 (mTORC1) in PMT-mediated osteoclast formation. PMT induces the differentiation of RAW264.7 macrophages into multinucleated, tartrate resistant acid phosphatase (TRAP) positive osteoclasts that are capable to resorb bone. In the presence of the mTORC1 inhibitor rapamycin, PMT was significantly less able to induce the formation of TRAP-positive osteoclasts. Accordingly, the resulting resorption of bone was strongly reduced. A major target of mTOR is the 70 kDa ribosomal protein S6 kinase 1 (p70 S6K1). Activated p70 S6K1 decreases the expression of programmed cell death protein 4 (PDCD4), a negative transcriptional regulator of osteoclastogenesis, at the protein and gene level. Ultimately this results in the activation of c-Jun, a component of the activator protein 1 (AP-1) complex, which is a major transcription factor for the induction of osteoclast-specific genes. We now demonstrate that c-Jun and its downstream target, the osteoclast-specific bone degrading protease cathepsin K, are upregulated upon PMT treatment in an mTOR-dependent manner. CONCLUSIONS: Activation of mTOR signalling plays a central role in the formation of osteoclasts through the bacterial toxin PMT. On the molecular level, PMT-induced activation of mTOR leads to down regulation of PDCD4, a known repressor of AP-1 complex, culminating in the activation of c-Jun, an essential transcription factor for triggering osteoclastogenesis.

Pharmacokinetics and bone resorption evaluation of a novel Cathepsin K inhibitor (VEL-0230) in healthy adult horses.

Plasma pharmacokinetic (PK) and bone resorption biomarker [carboxy-terminal cross-linking telopeptide of type I collagen (CTX-1)] analyses were performed following single and multiple oral dose protocols of a Cathepsin K inhibitor (VEL-0230) in horses. Outcomes included plasma and urine drug and CTX-1 concentrations. In the dose range study, 2, 4, and 8 mg/kg body weight (b.w.) doses were administered in a Latin square design to three mares and evaluated for 1 week. Based on the PK characteristics of VEL-0230, 4 mg/kg b.w. was selected for the dose interval study in which 3.25 days (d) and 7 days dose intervals were evaluated over three administrations using four exercising horses in a Latin square design. The 3.25 days and 7 days dose intervals provided a rapid inhibition of bone resorption based on plasma CTX-1. CTX-1 inhibition prior to next dose administration was not different from baseline in the 3.25 days and 7 days protocols, and for the first 3 days but the sustained CTX-1 inhibition in the 7 days protocol along with the cost and logistic benefits for weekly administration made the 7 days protocol preferable. Weekly administration of VEL-0230 may provide effective inhibition of bone resorption in young exercising horses that returns to baseline within 7 days after drug withdrawal even after multiple doses.

Spontaneous capital femoral physeal fracture in a cat.

A young neutered male cat was presented with a 1-week history of left hind limb lameness. Pain and crepitus were identified on manipulation of the left coxofemoral joint. Radiographic evaluation led to the diagnosis of physeal dysplasia with slipped capital femoral epiphysis of the left femur, which did not respond to conservative management.

Fracture physaire fémorale proximalespontanée chez un chat. Un jeune chat mâle stérilisé a été présenté avec une anamnèse de 1 semaine de boiterie de la patte arrière gauche. La douleur et la crépitation ont été identifiées à la manipulation de l'articulation coxo-fémorale. L'évaluation radiographique a permis de poser un diagnostic de dysplasie physaire avec un glissement de l'épiphyse fémorale proximale du fémur gauche, qui n'a pas répondu à une gestion conservatrice.(Traduit par Isabelle Vallières).

Clodronate detection and effects on markers of bone resorption are prolonged following a single administration to horses.

BACKGROUND: Clodronate is a potent antiresorptive agent labelled for use in horses over 4 years of age, for the treatment of navicular syndrome. Concerns regarding the extra-label use of clodronate in equine athletes, such as racehorses, have been raised as inhibition of osteoclast activity by clodronate has been postulated to interfere with normal bone healing, which is imperative to the repair of microfractures. The paucity of data describing the long-term pharmacokinetics of clodronate and effects on biomarkers of bone resorption necessitates further study. OBJECTIVES: (1) To determine clodronate concentrations in blood and urine over a 6-month period in horses undergoing treadmill exercise and (2) to assess the effects of clodronate on protein biomarkers of bone remodelling in this same group of horses. STUDY DESIGN: Randomised controlled experimental study. METHODS: Seven exercised Thoroughbred horses received a single im administration of 1.8 mg/kg clodronate and four horses received an equivalent volume of saline. Blood and urine samples were collected prior to, during and for 182 days post drug administration for drug concentration determination using liquid chromatography-tandem mass spectrometry, and determination of protein biomarker (CTX-1 and TRAcP5B) concentrations. RESULTS: Clodronate was detectable in blood for 14-175 days and for up to 175 days in urine. For some horses, concentrations were nondetectable at one time point but detectable at a subsequent time point. The terminal serum half-life ranged from 1.80 to 283.9 days. CTX-1 concentrations were significantly higher, relative to baseline, in both treated and control groups while concentrations of TRAcP5B were significantly lower in the treated group. MAIN LIMITATIONS: Relatively small number of horses studied. CONCLUSIONS: Based on assessment of protein biomarkers, clodronate appears to influence osteoclasts at label doses. Furthermore, results of this study support racing regulations that preclude horses administered bisphosphonates for medical reasons, from racing for a prolonged period of time.

CONTEXTO: Clodronato é um agente antirreabsortivo potente e recomendado para o uso em cavalos com mais de 4 anos de idade, para o tratamento da síndrome do navicular. Há preocupação com o uso indiscriminado de clodronato em equinos atletas, como cavalos de corrida, já que a inibição da atividade dos osteoclastos pelo clodronato tem sido postulada em interferir na cicatrização óssea normal, o que é essencial para a cicatrização de microfraturas. A escassez de informação quanto às ações prolongadas do uso de clodronato e seus efeitos nos biomarcadores de reabsorção óssea requere mais estudos. OBJETIVOS: (1) Determinar a concentração de clodronato no sangue e urina por um período de 6 meses em cavalos submetidos ao exercício em esteira e (2) acessar os efeitos de clodronato nos biomarcadores de remodelação óssea no mesmo grupo de cavalos. DELINEAMENTO DO ESTUDO: Estudo controlado randomizado. METODOLOGIA: Sete cavalos Puro-Sangue Inglês em exercício receberam uma única dose im de 1.8 mg/kg de clodronato e 4 cavalos receberam um volume equivalente de solução fisiológica. Amostras de sangue e urina foram coletadas antes, durante e por 182 dias após a administração de clodronato. Valores de concentração da droga foram determinados utilizando cromatografia líquida-espectrometria de massa (LC-MS/MS), e determinação da concentração de biomarcadores (CTX-1 e TRAcP5B) também foi realizada. RESULTADOS: Clodronato foi detectado no sangue por 14-175 dias e por até 175 dias na urina. Para alguns equinos, a concentração foi não-detectável em um momento, mas detectável no próximo momento. O valor terminal da vida-média em soro foi 1.80-283.9 dias. A concentração de CTX-1 foi significativamente elevada, relativo às amostras iniciais, em ambos os grupos (tratamento e controle), enquanto as concentrações de TRAcP5B foram significativamente menores no grupo de cavalos tratados. PRINCIPAIS LIMITAÇÕES: Número relativamente pequenos de cavalos no estudo. CONCLUSÕES: Baseado nos resultados dos biomarcadores, clodronato parece influencia osteoclastos na dose recomendada. Além disso, os resultados deste estudo suportam o regulamento de cavalos de corrida que impedem que cavalos que receberam bifosfonatos por razão médica de competir por um período de tempo prolongado.

Review of the Mechanism of Action and Use of Bisphosphonates in Horses.

Bisphosphonates are a group of drugs that can reduce bone resorption by incorporating into the crystal structure of exposed hydroxyapatite where they are taken up by osteoclasts. Bisphosphonates have several other mechanisms of action including reducing pain and inflammation and altering macrophage function. There are two types of bisphosphonates-nitrogenous and non-nitrogenous, the latter of which is used in horses. This article provides a literature-based review of the proposed mechanisms of action and therapeutic uses of bisphosphonates including a brief review of bone response to disease. A review of the literature available in horses including safety data and current rules and regulations is also provided.

An in vitro model for discovery of osteoclast specific biomarkers towards identification of racehorses at risk for catastrophic fractures.

BACKGROUND: Focal bone microcracks with osteoclast recruitment and bone lysis, may reduce fracture resistance in racehorses. As current imaging does not detect all horses at risk for fracture, the discovery of novel serum biomarkers of bone resorption or osteoclast activity could potentially address this unmet clinical need. The biology of equine osteoclasts on their natural substrate, equine bone, has never been studied in vitro and may permit identification of specific biomarkers of their activity. OBJECTIVES: (1) Establish osteoclast cultures on equine bone, (2) Measure biomarkers (tartrate resistant acid phosphatase isoform 5b [TRACP-5b] and C-terminal telopeptide of type I collagen [CTX-I]) in vitro and (3) Study the effects of inflammation. STUDY DESIGN: In vitro experiments. METHODS: Haematopoietic stem cells, from five equine sternal bone marrow aspirates, were differentiated into osteoclasts and cultured either alone or on equine bone slices, with or without a pro-inflammatory stimulus (IL-1ß or LPS). CTX-I and TRACP-5b were immunoassayed in the media. Osteoclast numbers and bone resorption area were assessed. RESULTS: TRACP-5b increased over time in osteoclast cultures without bone (p < 0.0001) and correlated with osteoclast number (r = 0.63, p < 0.001). CTX-I and TRACP-5b increased with time for cultures with bone (p = 0.002; p = 0.02 respectively), correlated with each other (r = 0.64, p < 0.002) and correlated with bone resorption (r = 0.85, p < 0.001; r = 0.82, p < 0.001 respectively). Inflammation had no measurable effects. MAIN LIMITATIONS: Specimen numbers limited. CONCLUSIONS: Equine osteoclasts were successfully cultured on equine bone slices and their bone resorption quantified. TRACP-5b was shown to be a biomarker of equine osteoclast number and bone resorption for the first time; CTX-I was also confirmed to be a biomarker of equine bone resorption in vitro. This robust equine specific in vitro assay will help the study of osteoclast biology.

Bone resorption markers and dual-energy x-ray absorptiometry in dogs with avascular necrosis, degenerative joint disease, and trauma of the coxofemoral joint.

OBJECTIVES: To compare the ability of N-terminal telopeptide (NTx) assays and dual-energy x-ray absorptiometry (DEXA) to detect bone resorption in dogs with nonneoplastic bone lysis and evaluate the correlation between these diagnostic tools. STUDY DESIGN: Prospective, cross-sectional clinical study. ANIMALS: Dogs (n = 35; 39 femoral heads) that had femoral head and neck ostectomy and 6 cadaver specimens from healthy immature small dogs. METHODS: Small dogs with avascular necrosis (n = 12), a reference group of small dogs (7), large dogs with degenerative joint disease (DJD; 10), and large dogs with trauma (10) were studied in addition to 6 femoral heads harvested from 6 small immature and healthy dogs euthanatized for reasons unrelated to this study. Densitometric measurements of femoral heads, urine NTx excretion, and serum NTx concentration were compared between groups. RESULTS: Avascular necrosis resulted in a decrease in bone mineral density (BMD) (0.18 ± 0.01 g/cm(2;) P < .01) of the femoral head and elevation of serum NTx (159.3 ± 59.4 nM; P = .03) compared to small dog controls (0.28 ± 0.02 g/cm(2) ; 18.7 ± 1.83 nM, respectively), but did not seem to affect urine NTx. DJD in large dogs did not seem to affect any of the densitometric parameters evaluated. BMD (P = .03) and serum NTx (P = .04) were lower in small compared to large dogs. Serum NTx and densitometric measurements correlate inversely with each other (P = .001) but neither test correlated with urine NTx (P = .8-.9). CONCLUSION: Serum NTx levels vary with dog size but seem to correlate better with BMD better than urine NTx excretion in dogs with nonneoplastic bone resorption.

Effect of Weight Change on Markers of Bone Turnover and Phosphorus Excretion.

There is little information about how weight change in horses impacts bone turnover and the metabolism of minerals associated with bone. This study evaluated weight change in mature horses as a factor that could alter bone turnover and fecal P output. Fifteen horses (555 ± 8 kg) were assigned to three treatments: weight loss (LO; n = 5), weight maintenance (MA; n = 5), and weight gain (GA; n = 5). Diets contained 75%, 100%, and 145% of maintenance digestible energy requirements for the three treatments, respectively, but contained similar amounts of protein and minerals. At the end of the weight change period (27 ± 6 d), blood samples were analyzed for bone biomarkers and a 5-day total fecal collection was conducted to measure fecal mineral output. Horses fed the MA diet had an average daily weight change that was not different from either the GA or LO treatments, while weight change was different between the GA group and the LO group (0.49 kg/d vs. -1.16 kg/d; P = .017). Weight change was negatively correlated with cross-linking C-terminal telopeptides of type-I collagen, a biomarker of bone resorption (r = -0.62; P = .014) and tended to be positively correlated with bone alkaline phosphatase, a biomarker of bone formation (r = 0.48; P = .068). Also, fecal P output tended to be lower in GA than in LO horses (P = .085), while MA was intermediate and not different, suggesting that weight loss was increasing bone resorption, resulting in a tendency for higher P loss from the body. Weight change in horses can influence bone metabolism as well as mineral excretion.

Aster saponin A2 inhibits osteoclastogenesis through mitogen-activated protein kinase-c-Fos-NFATc1 signaling pathway.

BACKGROUND: In lipopolysaccharide-induced RAW264.7 cells, Aster tataricus (AT) inhibits the nuclear factor kappa-light-chain-enhancer of activated B cells and MAPKs pathways and critical pathways of osteoclast development and bone resorption. OBJECTIVES: This study examined how aster saponin A2 (AS-A2) isolated from AT affects the processes and function of osteoclastogenesis induced by receptor activator of nuclear factor kappa-B ligand (RANKL) in RAW264.7 cells and bone marrow macrophages (BMMs). METHODS: The cell viability, tartrate-resistant acid phosphatase staining, pit formation assay, polymerase chain reaction, and western blot were carried out to determine the effects of AS-A2 on osteoclastogenesis. RESULTS: In RAW264.7 and BMMs, AS-A2 decreased RANKL-initiated osteoclast differentiation in a concentration-dependent manner. In AS-A2-treated cells, the phosphorylation of ERK1/2, JNK, and p38 protein expression were reduced considerably compared to the control cells. In RAW264.7 cells, AS-A2 suppressed the RANKL-induced activation of osteoclast-related genes. During osteoclast differentiation, AS-A2 suppressed the transcriptional and translational expression of NFATc1 and c-Fos. AS-A2 inhibited osteoclast development, reducing the size of the bone resorption pit area. CONCLUSION: AS-A2 isolated from AT appears to be a viable therapeutic therapy for osteolytic illnesses, such as osteoporosis, Paget's disease, and osteogenesis imperfecta.

Bone-invasive oral squamous cell carcinoma in cats: pathology and expression of parathyroid hormone-related protein.

Feline oral squamous cell carcinoma (OSCC) is the most common oral tumor in cats. There is no effective treatment, and the average duration of survival after diagnosis is only 2 months. Feline OSCC is frequently associated with osteolysis; however, the mechanisms responsible are unknown. The objective of this study was to characterize the epidemiology and pathology of bone-invasive OSCC in cats and to determine the expression of select bone resorption agonists. In sum, 451 cases of feline OSCC were evaluated. There was no sex or breed predisposition, although there were more intact cats in the OSCC group compared to the control group. Gingiva was the most common site, followed by the sublingual region and tongue. Cats with lingual OSCC were younger (mean, 11.9 years) compared to cats with gingival OSCC (mean, 13.6 years). In addition to osteolysis, there was periosteal new bone formation, osseous metaplasia of tumor stroma, and direct apposition of OSCC to fragments of bone, suggestive of bone-binding behavior. Eighty-two cases were selected for immunohistochemical detection of parathyroid hormone-related protein (PTHrP). Specimens with osteolysis had increased PTHrP expression and nuclear localization, compared to OSCC without osteolysis. Thirty-eight biopsies of OSCC with osteolysis were evaluated for tumor necrosis factor α expression, and only 4 biopsies had such expression in a small proportion of tumor cells. Increased tumor expression of PTHrP and increased localization of PTHrP to the nucleus were associated with osteolysis and may play an important role in bone resorption and tumor invasion in cats with OSCC.

Formulating diets based on digestible calcium instead of total calcium does not affect growth performance or carcass characteristics, but microbial phytase ameliorates bone resorption caused by low calcium in diets fed to pigs from 11 to 130 kg.

An experiment was conducted to test the hypothesis that the requirement for Ca expressed as a ratio between standardized total tract digestible (STTD) Ca and STTD P obtained in short-term experiments may be applied to pigs fed diets without or with microbial phytase from 11 to 130 kg. In a 5-phase program, 160 pigs (body weight: 11.2 ± 1.8 kg) were randomly allotted to 32 pens and 4 corn-soybean meal-based diets in a 2 × 2 factorial design with 2 diet formulation principles (total Ca or STTD Ca), and 2 phytase inclusion levels (0 or 500 units/kg of feed) assuming phytase released 0.11% STTD P and 0.16% total Ca. The STTD Ca:STTD P ratios were 1.40:1, 1.35:1, 1.25:1, 1.18:1, and 1.10:1 for phases 1 to 5, and STTD P was at the requirement. Weights of pigs and feed left in feeders were recorded at the end of each phase. At the conclusion of phase 1 (day 24), 1 pig per pen was euthanized and a blood sample and the right femur were collected. At the end of phases 2 to 5, a blood sample was collected from the same pig in each pen. At the conclusion of the experiment (day 126), the right femur of 1 pig per pen was collected and carcass characteristics from this pig were measured. No interactions were observed between diet formulation principle and phytase inclusion for growth performance in any phase and no differences among treatments were observed for overall growth performance. Plasma Ca and P and bone ash at the end of phase 1 were also not influenced by dietary treatments. However, on day 126, pigs fed nonphytase diets formulated based on total Ca had greater bone ash than pigs fed STTD Ca-based diets, but if phytase was used, no differences were observed between the 2 formulation principles (interaction P < 0.05). At the end of phases 2 and 3, pigs fed diets without phytase had greater (P < 0.05) plasma P than pigs fed diets with phytase, but no differences were observed at the end of phases 4 and 5. A negative quadratic effect (P < 0.05) of phase (2 to 5) on the concentration of plasma Ca was observed, whereas plasma P increased (quadratic; P < 0.05) from phases 2 to 5. However, there was no interaction or effect of diet formulation principle or phytase inclusion on any carcass characteristics measured. In conclusion, STTD Ca to STTD P ratios can be used in diet formulation for growing-finishing pigs without affecting growth performance or carcass characteristics and phytase inclusion ameliorates bone resorption caused by low dietary Ca and P.

Serum cross-linked N-telopeptide of type I collagen across the canine life span: An investigation in intact and neutered male and female dogs.

In this study, we conducted study to explore the association between serum cross-linked N-telopeptide of type I collagen (NTx), a marker of bone resorption, and age, body weight, and blood biochemical parameters as well as the neutered and intact status in male and female dogs. We targeted 145 healthy dogs (aged 0.33-18.33 years); 70 were males (38 intact, 32 castrated), and 75 were females (31 intact, 44 ovariohysterectomized). We found that the NTx levels were significantly higher in dogs aged ≤2 years than in older dogs. NTx concentration tended to decrease with age in dogs aged ≤2 years, but not significantly, and remained constant in dogs aged >2 years. Accordingly, we investigated sex/sterilization status in two age cohorts (juvenile-to-young-adult, ≤2 years of age; adult-to-geriatric, >2 years of age). In the adult-to-geriatric cohort, NTx concentration was highest in intact males, followed by neutered males, neutered females, and intact females. The intact vs. neutered difference was significant in males, but not in females. Our results suggested that estradiol deficiency may not affect bone metabolism in female dogs, but androgen deficiency may affect bone metabolism in male dogs. Furthermore, age did not affect bone metabolism after 2 years. NTx concentrations were significantly higher in the juvenile-to-young-adult cohort than in the adult-to-geriatric cohort and tended to decrease with age, similar to young humans. This study unveils novel sex differences in canine serum NTx concentrations and suggests the effect of neutering on bone metabolism, showing that serum NTx concentrations change with age.

Eimeria challenge adversely affected long bone attributes linked to increased resorption in 14-day-old broiler chickens.

There is limited information on the effects of enteric pathogen on bone quality in rapidly growing broiler chicks. We examined tibia and femur attributes (length, diameter, relative weight of ash content [AC] to the BW, ash concentration [AP]) and serum bone-turnover markers including receptor activator of nuclear factor kappa-B ligand (RANKL) for resorption, alkaline phosphatase (ALP) for mineralization, and selected serum metabolites in 14-day-old broilers challenged with Eimeria. A total of 160 (80 males and 80 females) 1-day-old Ross × Ross 708 chicks were used. Based on BW, birds were placed within sex in cages (5 birds per cage) and fed chick starter diets to day 9 of age. On day 9, half of the cages were orally gavaged with 1 mL of Eimeria culture (100,000 oocysts of E. acervulina and 25,000 oocysts of E. maxima) and the other half (unchallenged control) received 1 mL 0.9% saline in distilled water. On day 14, 2 birds were randomly selected and necropsied for intestinal lesion score, blood, tibia, and femur samples. Data were analyzed in a 2 (challenged vs. unchallenged) × 2 (males vs. females) factorial arrangement. There was no interaction (P > 0.05) between Eimeria and sex on any measurement. Whereas there were no intestinal lesions in unchallenged birds, Eimeria resulted in lesion score (0 to 4) of 3.35, 2.59 and 0.11 in duodenum, jejunum and ileum, respectively. Eimeria challenge decreased (P < 0.05) tibia AC and AP by 10 and 8.2%, respectively but had no (P > 0.10) effect on femur attributes. Generally, males showed (P < 0.05) longer and wider bones with more AC compared with the female. Circulating serum RANKL concentration increased (P = 0.017) in response to Eimeria challenge and was negatively correlated with tibia AC (-0.731; P = 0.021). Our findings showed that Eimeria damage to the intestinal physiology had adverse effects on long bone attributes linked to increased resorption.

Bone resorption in dogs with calcium oxalate urolithiasis and idiopathic hypercalciuria.

People with calcium oxalate (CaOx) urolithiasis and idiopathic hypercalciuria (IH) often have evidence of increased bone resorption, but bone turnover has not previously been investigated in dogs with these conditions. The aim of this study was to determine whether a marker of bone resorption, ß-crosslaps, differs between dogs with CaOx urolithiasis and IH compared to controls. This retrospective, cross-sectional study used a canine specific ELISA to measure ß-crosslaps concentrations in stored frozen serum samples from 20 dogs with CaOx urolithiasis and IH and 20 breed-, sex-, and age-matched stone-free controls (18 Miniature Schnauzers, 14 Bichons Frise, and 8 Shih Tzus). Dogs with CaOx urolithiasis and IH had lower ß-crosslaps concentrations relative to controls (P = .0043), and ß-crosslaps had a moderate negative correlation with urinary calcium-to-creatinine ratios (r = -0.44, P = .0044). Miniature Schnauzers had lower ß-crosslaps concentrations than the other two breeds (P = .0035). The ELISA had acceptable intra-assay precision, but concentrations decreased when samples were repeatedly assayed over time. Assay recovery rates were also below acceptance criteria. In conclusion, Miniature Schnauzers, Bichons Frise, and Shih Tzus with CaOx urolithiasis and IH have evidence of decreased bone resorption compared to stone-free controls. This suggests that other causes of IH, such as intestinal hyperabsorption of calcium, underlie risk for CaOx urolithiasis in these breeds. Results should be confirmed in larger populations and with other ß-crosslaps assays and additional biomarkers of bone turnover. The stability of canine serum ß-crosslaps after freeze-thaw cycles and storage at various temperatures requires investigation.

Polar bears (Ursus maritimus), the most evolutionary advanced hibernators, avoid significant bone loss during hibernation.

Some hibernating animals are known to reduce muscle and bone loss associated with mechanical unloading during prolonged immobilisation,compared to humans. However, here we show that wild pregnant polar bears (Ursus maritimus) are the first known animals to avoid significant bone loss altogether, despite six months of continuous hibernation. Using serum biochemical markers of bone turnover, we showed that concentrations for bone resorption are not significantly increased as a consequence of hibernation in wild polar bears. This is in sharp contrast to previous studies on other hibernating species, where for example, black bears (Ursus americanus), show a 3-4 fold increase in serum bone resorption concentrations posthibernation,and must compensate for this loss through rapid bone recovery on remobilisation, to avoid the risk of fracture. In further contrast to black bears, serum concentrations of bone formation markers were highly significantly increased in pregnant female polar bears compared to non-pregnant,thus non-hibernating females both prior to and after hibernation. However, bone formation concentrations in new mothers were significantly reduced compared to pre-hibernation concentrations. The de-coupling of bone turnover in favour of bone formation prior to hibernation, suggests that wild polar bears may posses a unique physiological mechanism for building bone in protective preparation against expected osteopenia associated with disuse,starvation, and hormonal drives to mobilise calcium for reproduction, during hibernation. Understanding this physiological mechanism could have profound implications for a natural solution for the prevention of osteoporosis in animals subjected to captivity with inadequate space for exercise,humans subjected to prolonged bed rest while recovering from illness, or astronauts exposed to antigravity during spaceflight.© 2008 Elsevier Inc. All rights reserved.

Basidiomycosis: Schizophyllum commune osteomyelitis in a dog.

A six-year-old female Labrador retriever dog was suffering from osteomyelitis in her hindlimb. A puncture wound caused by a rotted bamboo stick was presumed as the source of infection. The dog suffered from pre-existing aortic stenosis, but otherwise exhibited no significant abnormality in her systemic conditions excluding claudication of the left hindlimb. The results of cytology and pathological examinations of biopsy samples revealed the diagnosis of mycotic osteomyelitis in this dog. Mycological and DNA tests showed the pathogen as the mushroom Schizophyllum commune. Antibiotic sensitivity testing also revealed susceptibility to itraconazole, which was used to successfully treat the dog. This is a rare case of canine basidiomycosis with S. commune as the etiologic agent.

Preliminary investigation of urine N-telopeptide concentration as a biomarker of bone resorption in dogs receiving glucocorticoids.

OBJECTIVES: The influence of glucocorticoid therapy on bone resorption in dogs using a urine N-telopeptide assay was investigated. MATERIALS AND METHODS: Thirty-one dogs receiving oral glucocorticoids and 31 age-matched healthy control dogs were enrolled. Urine N-telopeptide concentration was measured using a commercially available immunoassay and results were expressed as a ratio against urinary creatinine concentration. Dogs receiving glucocorticoids were divided into three subgroups based on daily glucocorticoid dose and three subgroups based on treatment duration. Urine N-telopeptide concentration was then compared between groups. RESULTS: Urine N-telopeptide concentration was significantly higher in dogs receiving glucocorticoids compared to the control group. CLINICAL SIGNIFICANCE: This preliminary study demonstrates significant increase in urine N-telopeptide concentration in dogs receiving glucocorticoid therapy compared to control dogs. Further studies are needed to assess whether this increase in urine N-telopeptide concentration correlates with decreases in bone mineral density as has been identified in humans.

Biochemical markers of bone metabolism and risk of dorsal metacarpal disease in 2-year-old Thoroughbreds.

REASONS FOR PERFORMING STUDY: Dorsal metacarpal disease (DMD) is a common problem in 2-year-old racehorses and results in loss of a significant number of days from training. Biochemical markers of bone cell activity measured early in the training season could have value for identifying 2-year-old Thoroughbred racehorses that develop DMD. OBJECTIVES: To determine the association between serum concentrations of osteocalcin, the carboxyterminal propeptide of type I collagen (PICP) and the carboxyterminal cross-linked telopeptide of type I collagen (ICTP) measured early in the training season and the risk of DMD. METHODS: Blood samples were collected from 165 two-year-old Thoroughbreds during late November/early December. Osteocalcin and PICP were measured as markers of bone formation, and ICTP as a marker of bone resorption. Training and veterinary records for each horse were monitored over the following training/racing season (10 months). Cases were defined as an episode where signs of DMD were sufficiently severe for a horse to miss at least 5 consecutive days of training. Classification tree and logistic regression analysis were used to identify the most important factors suitable for prediction of DMD risk. RESULTS: There were 24 cases of DMD during the season (14.6% cumulative incidence), with an average time to recognition of approximately 6 months (May). The earliest recognised case was in February and the latest in September. Osteocalcin and ICTP concentrations in the early stages of the training season were significantly higher in horses that subsequently developed DMD (P = 0.017 and 0.019, respectively). DMD cases were also significantly older compared to noncases (21.04 vs. 20.44 months, P = 0.023). Using a multivariable logistic regression model, it was possible to postulate a set of diagnostic rules to predict the likelihood of DMD injury during the season. This suggested that horses with ICTP concentrations above 12365 ug/l and older than 20.5 months are 2.6 times more likely to develop DMD. CONCLUSIONS: The measurement of the bone resorption marker ICTP could be useful for identification of 2-year-olds at increased risk of developing DMD. POTENTIAL RELEVANCE: These findings, together with other strategies such as modification of training regimens, e.g. early introduction of short distances of high-speed exercise into the training programme, could help reduce the days lost to training as a result of DMD.

Evaluation of intravenous pamidronate administration in 33 cancer-bearing dogs with primary or secondary bone involvement.

The purpose of this study was to evaluate the clinical safety of pamidronate when administered at a mean dosage of 1.0 mg/kg IV q28d in 33 tumor-bearing dogs. Biochemical tests of renal function were evaluated before each successive pamidronate treatment. Of 33 dogs treated with pamidronate, 1 dog had clinically relevant increases in serum creatinine and blood urea nitrogen concentrations. The biologic activity of IV pamidronate was assessed prospectively in 10 dogs with appendicular osteosarcoma and was assessed on reductions in urine N-telopeptide excretion (P = .042) and enhanced bone mineral density of the primary tumor measured with dual-energy x-ray absorptiometry (P = .024). Additionally, in these 10 dogs, pamidronate's therapeutic activity was supported by subjective improvement in pain control in 4 of the 10 dogs treated. IV pamidronate appears clinically safe in tumor-bearing dogs and may possess modest biologic activity for managing neoplastic complications associated with pathologic bone resorption.