Measurement of bone specific alkaline phosphatase in the horse: a comparison of two techniques

Long-term daily feeding of cannabidiol is well-tolerated by healthy dogs

Cannabidiol (CBD) containing dog food and treats are widely commercially available, mirroring the growing popularity of CBD as a supplement for humans. Despite this, experimental evidence of the safety and efficacy of long-term oral exposure in dogs is lacking. The purpose of this study was to address the gap in knowledge around the longer-term suitability and tolerance of a broad-spectrum CBD (THC-free) distillate in clinically healthy dogs. The study was a randomized, placebo-controlled, and blinded study where one group of twenty dogs received daily CBD capsules at a dose of 4 mg/kg of body weight (BW) for a period of 6 months. The control group of twenty dogs received placebo capsules. A comprehensive suite of physiological health measures was performed throughout the study at baseline, and after 2, 4, 10, 18, and 26 weeks of exposure, followed by 4 weeks of washout. CBD concentrations were measured at the same cadence in plasma, feces and urine. Health measures included biochemistry, hematology, urinalysis, in addition to fortnightly veterinary examinations, twice daily well-being observations, and a daily quality-of-life survey. Biochemistry and hematology showed no clinically significant alterations apart from a transient elevation in alkaline phosphatase (ALP) in just over half of the dogs receiving CBD. This elevation was observed in the absence of concurrent elevations of other liver parameters, and without any adverse effects on health and wellbeing. Furthermore, bone alkaline phosphatase (BALP) was simultaneously elevated with a significant, strong (r > 0.9) positive correlation between the two measures, suggesting that the elevation of total ALP was at least partly due to the bone-derived isoform. This study provides evidence that a once-daily oral dose of 4 mg CBD/kg BW is well tolerated in clinically healthy dogs for a duration of 6-months.

Relationship between serum biomarkers of cartilage and bone metabolism and joint injury in young Thoroughbred racehorses in training

OBJECTIVE

To compare serum concentrations of biomarkers of cartilage and bone metabolism between racehorses with a carpal or metacarpophalangeal or metatarsophalangeal (ie, fetlock) joint injury and matched uninjured control horses, determine changes in biomarker concentrations following joint injury, and establish the biomarkers' diagnostic test performance.

ANIMALS

50 Thoroughbred racehorses with a carpal or fetlock joint injury and 50 matched uninjured horses (control horses).

PROCEDURES

Serum concentrations of 2 cartilage synthesis biomarkers (carboxy-terminal propeptide of type II collagen [CPII] and chondroitin sulfate epitope 846 [CS846]), 2 cartilage degradation biomarkers (neoepitope generated by collagenase cleavage of type II collagen [C2C] and cross-linked carboxy-terminal telopeptide fragments of type II collagen [CTX-II]), and serum activity of a bone formation marker (bone-specific alkaline phosphatase [BAP]) were measured around the time of injury diagnosis and monthly thereafter for as long as possible.

RESULTS

Injured horses as a group and horses specifically with fetlock joint injuries had significantly lower serum CPII concentrations and significantly higher serum BAP activities than matched control horses. Concentrations of CTX-II were decreased between 2 and 4 months following joint injury. Measurement of CPII concentration at baseline could distinguish between injured horses and control horses with a sensitivity of 82% and specificity of 50%.

CONCLUSIONS AND CLINICAL RELEVANCE

Although significant differences in specific biomarker concentrations between horses with carpal and fetlock joint injuries and matched control horses were identified, there was no convincing evidence of the suitability of these biomarkers as diagnostic or prognostic tools in a clinical setting.

Joint dependent concentrations of bone alkaline phosphatase in serum and synovial fluids of horses with osteochondral injury: an analytical and clinical validation

OBJECTIVES

Validate use of a commercially available immunoassay for measurement of bone alkaline phosphatase (BAP) in equine serum and synovial fluid (SF), and investigate the effects of osteochondral (OC) injury in horses on BAP concentrations in serum and SF.

METHODS

SF was collected from 37 joints of 34 Thoroughbred (TB) racehorses undergoing arthroscopic surgery for the removal of OC fragments from either the carpal joints (n=18) or the metacarpo-/metatarsophalangeal (MP) joints (n=19). SF was also obtained from 52 joints of 16 normal TB horses, collected bilaterally from carpal joints of 10 horses (n=40), and MP joints of six horses (n=12). Blood was obtained from all 50 horses. A commercially available immunoassay was validated and subsequently used to determine equine serum and SF BAP concentrations. Correlations to radiographic and arthroscopic scores were assessed.

RESULTS

BAP concentrations were significantly lower in serum from horses with OC injury in their carpal or MP joints than in serum from normal horses. SF BAP concentrations in normal and OC injured carpal joints were significantly higher than MP joints. BAP concentrations were significantly higher in SF from OC injured carpal joints than normal. BAP concentrations were affected by joint sampled, with age having a significant interaction. Concentrations of BAP in the serum (<30U/L), SF (>22U/L) and a ratio of SF to serum > or = 0.5 were predictive of OC injury. Radiographic and arthroscopic scores significantly correlated with serum BAP concentrations, and SF:serum BAP correlated with arthroscopic scores.

CONCLUSIONS

Determination of serum and SF BAP concentrations may be beneficial in the investigation of early joint injury. Joint and injury dependent differences in BAP concentrations allowed the estimation of predictive value for identifying OC injury.

Pharmacological effects of tiludronate in horses after long-term immobilization

INTRODUCTION

Tiludronate, a bisphosphonate, has recently been introduced in veterinary medicine to treat orthopedic conditions in the horse. This study was designed to evaluate its effects on biochemical biomarkers of bone metabolism and on bone density and structure in an experimental model of disuse osteoporosis induced by cast application in horses.

METHODS

Two groups of eight horses were immobilized during 8 weeks. The first group (P-group) received a placebo, and the second group (T-group) received tiludronate 1 mg/kg by slow IV infusion. Both treatments were administered twice, 28 days apart. Immobilization consisted of stall rest with the left forelimb packed in a fiberglass cast. It was followed by a 4-week remobilization period and an 8-week standardized training protocol. One biomarker of bone resorption, the C-telopeptides of type I collagen cross-links (CTX-1) and one biomarker of bone formation, the bone isoenzyme of alkaline phosphatase (bone ALP), were assessed. Metacarpus III (MCIII) bone mineral density (BMD) and speed of sound (SOS) were evaluated respectively by dual energy X-ray absorptiometry (DEXA) and quantitative ultrasonography (QUS). Lameness was regularly assessed during the remobilization and training periods. Group- and time-related effects were tested by analysis of variance on repeated measurements.

RESULTS

A rapid, transient and significant decrease in CTX-1 concentration was seen after each treatment in the T-group only. No significant differences between groups were seen in the evolution of bone ALP activity. At the end of the experiment, the loss of MCIII BMD measured by DEXA in the immobilized limb was significantly less in the T-group than in the P-group. The MCIII SOS measured by QUS did not significantly vary within or between groups throughout the study.

DISCUSSION AND CONCLUSIONS

Tiludronate was found to significantly reduce bone resorption during immobilization, as well as to prevent long-term osteopenia in the immobilized limb. Disuse osteopenia did not affect the lateral superficial cortex of MCIII.

Comparison of rat and human alkaline phosphatase isoenzymes and isoforms using HPLC and electrophoresis

Total activity of alkaline phosphatase (ALP) in serum represents the sum of activities of some isoenzymes and their numerous isoforms derived from various tissues of the organism. The aim of this work was to separate ALP isoenzymes and their isoforms in rat and human serum, compare the properties of serum ALP isoforms in rats and humans, and determine the usefulness of some analytical methods for specific measurements of ALP isoenzyme and isoform activities. Two methods of separation, i.e. high-performance liquid chromatography (HPLC) and agarose gel electrophoresis were chosen. The combination of HPLC with electrophoresis of the eluted fractions and with ALP inhibition methods (urea, l-phenylalanine), inactivation (heat) and precipitation (wheat-germ lectins) enabled the identification of isoenzymes and isoforms of ALP in serum. Using chromatography and a post-column reactor, three isoforms of the intestinal isoenzyme and one bone isoform of a tissue non-specific isoenzyme were detected. Rat serum differs significantly from human as regards activities of intestinal and hepatic isoforms, whereas the properties of the bone isoform are similar in both species. Our HPLC method offers a higher resolution than agarose gel electrophoresis with respect to ALP subfractions in rat serum.

Serum osteocalcin and CTX-MMP concentration in young exercising thoroughbred racehorses

Bone responds to exercise with changes in bone (re-)modelling, which might be monitored non-invasively with biochemical bone markers. The aim of this study was to evaluate the influence of exercise on serum osteocalcin and serum carboxy-terminal cross-linked telopeptide of type I collagen generated by matrix metalloproteinases (CTX-MMP) concentration in young racehorses. Seventy-one 2 to 4-year-old Thoroughbreds were included in this prospective infield study. Blood sampling was performed six times (i.e. six sampling cycles) during a 9-month period. Serum samples were analysed with commercial osteocalcin and CTX-MMP radioimmunoassays. Two-year-old racehorses had higher serum osteocalcin and CTX-MMP values than 3-year-old horses. Gender and training amplitude did not significantly influence serum osteocalcin and CTX-MMP values. Two-year-old horses showed an increase in osteocalcin values between cycles 2 and 3 and an increase in serum CTX-MMP values between cycles 1 and 2. Serum osteocalcin and CTX-MMP concentrations decreased between cycles 4 and 5, and 5 and 6. Three-year-old horses showed an increase in serum osteocalcin levels between cycles 3 and 4 and an increase in serum CTX-MMP concentrations between cycles 1 and 2, and 3 and 4. Serum osteocalcin levels decreased between cycles 5 and 6, whereas serum CTX-MMP levels decreased between cycles 4 and 5, and 5 and 6. Two- and three-year-old horses showed a decreased osteocalcin/CTX-MMP ratio between cycles 1 and 2. Moreover, 2-year-old horses showed an increase in the osteocalcin/CTX-MMP ratio between cycles 2 and 3. Sore shin formation did not significantly influence serum osteocalcin and CTX-MMP values. Serum osteocalcin and CTX-MMP are promising bone markers for monitoring exercise induced changes in equine bone metabolism.

Problems in quantifying bone response to exercise in horses: a review

Detecting changes in bone during growth, training, rest from competition (spelling), and disease in horses requires imaging techniques that have a high level of accuracy and precision. Currently, most imaging techniques used in horses do not possess such characteristics and are more suitable for detecting end-stage disease than subtle changes. Some are incapable of detecting changes in bone size. Non-planar techniques should be used for estimating or determining bone strength. This review outlines available imaging techniques and shows why cross-sectional procedures are required to accurately estimate bone strength. If these can be validated and improved for use in the standing horse, serial examination can be used to show the magnitude of changes in bone strength that occur during training or varying management regimens. Such knowledge can then be used to improve training and spelling regimens for equine athletes, hopefully resulting in a reduction in racing or athletic injury.

A comparison of methods for measuring serum and urinary markers of bone metabolism in cats

Biochemical markers of bone cell activity have recently been shown to be useful for monitoring skeletal health in domestic animals, including dogs and horses. The aim of this study was to evaluate a number of biochemical assays, originally developed for use in humans, for their ability to measure indicators of bone cell activity in serum and urine of normal cats over a range of ages. Bone alkaline phosphatase (BAP), a marker of bone formation, was measured in serum using wheatgerm lectin precipitation (WGL) and by ELISA. The curve derived from serial dilution of feline serum was parallel with the ELISA standard curve, indicating species cross-reactivity, and there was a significant relationship between assays (rs = 0.97, P < 0.001). Deoxypyridinoline (DPD), a marker of bone resorption, was measured in its total form in urine by HPLC and ELISA, and in its free form in serum and urine by ELISA. The dilution curve for free DPD in urine showed parallelism with the assay standard curve; however, the curves for total DPD in urine and serum did not. A significant relationship was established between total urinary DPD (HPLC) with total serum DPD (rs = 0.69, P < 0.001), and with free urinary DPD (rs = 0.95, P < 0.001) concentrations. Carboxy-terminal telopeptide of type I collagen (CTX) concentration, another marker of bone resorption, was measured in serum and urine by ELISA, and there was a significant relationship between assays (rs = 0.82, P < 0.001). CTX could not be measured reliably using an auto-analysis method. A significant relationship was established between total urinary DPD (HPLC) with serum CTX (rs = 0.59, P < 0.05), and urinary CTX (rs = 0.65, P < 0.001) concentrations. BAP (ELISA and WGL), total urinary DPD (HPLC), urinary CTX (ELISA), and serum CTX (ELISA) concentrations were significantly inversely correlated with age (rs = -0.66, -0.88, -0.61, -0.70, and -0.51, P < 0.05 respectively). Cats under two years of age had significantly higher BAP, total urinary DPD (HPLC), and urinary CTX concentrations compared to older cats. In conclusion, this study has shown that a number of commercially available assays provide reliable methods for non-invasively monitoring bone cell activity in cats and has shown that bone turnover decreases within the first two years of life, until complete skeletal maturity is attained. Future studies can now be directed at evaluating the potential clinical application of these methods.

Biochemical markers of bone metabolism in animals: uses and limitations

Routine assessment of the skeleton's response to disease and injury traditionally has consisted of plain-film radiography supplemented with advanced imaging techniques, such as computed tomography, magnetic resonance imaging, nuclear scintigraphy, and bone densitometry. Although these techniques provide increased sensitivity as compared with radiography, they still are limited by the fact that they can only document the net results of past skeletal activity. In contrast, serum and urinary biomarkers of bone formation and resorption provide near real-time information about bone cell activity. In this review, I describe the scientific rationale behind the use of these markers in humans and detail the efforts that have been made to adapt this technology to veterinary medicine and animal research. Commercial assay kits that are applicable to different animal species are described, and the potential limitations of the technology are discussed. The goal of this review is to provide clinical pathologists and researchers with the information needed to decide whether the use of bone markers is likely to be helpful and to select the most appropriate marker (or panel of markers) to answer a particular question.

Evaluation of serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I associated with treadmill exercise in young horses

OBJECTIVE

To evaluate changes in serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I (IGF-I) associated with treadmill exercise in young horses.

ANIMALS

12 two-year-old Thoroughbred mares.

PROCEDURE

During a 20-week study period, 6 horses were exercised on a treadmill 3 times a week (exercise group) and 6 horses received walking exercise 6 days a week (controls). Serum concentrations or activity of biochemical markers and IGF-I were assessed biweekly. Bone mineral density and content of the first phalanx were measured by dual-energy X-ray absorbiometry (DEXA) on completion of the study.

RESULTS

Compared with values in controls, bone mineral density and content were higher and serum concentrations of osteocalcin (a marker of bone formation) and the carboxy-terminal telopeptide of type I collagen (a marker of bone resorption; ICTP) were lower in exercised horses. Serum concentration and activity of the bone formation markers carboxy-terminal propeptide of type I collagen and bone-specific alkaline phosphatase (BAP) were not different between the 2 groups. Serum IGF-I concentration was lower in the exercise group, compared with control values; there was a significant correlation between change in IGF-I values and changes in osteocalcin, ICTP, and BAP values at the end of the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Treadmill exercise over 20 weeks induced adaptive changes in bones of 2-year-old Thoroughbreds; training appears to increase bone mineral density, thereby enhancing mechanical strength of bone, but decreases bone turnover. Results indicated an association between changes in serum IGF-I concentration and bone cell activity in horses.

Biochemical markers of bone metabolism in growing thoroughbreds: a longitudinal study

This study describes longitudinal changes in serum levels of biochemical markers of bone cell activity in a group of 24 thoroughbred foals from birth to 18 months of age. The markers of bone formation included the type I collagen carboxy-terminal propeptide (PICP), the bone-specific isoenzyme of alkaline phosphatase (BAP), and osteocalcin (OC). Levels of the cross-linked telopeptide of type I collagen (ICTP), a marker of bone resorption, and the N-terminal propeptide of type III collagen (PNIIIP), a marker of soft tissue turnover, were also measured. Levels of all markers fell significantly between birth and 18 months of age (70-80 per cent); this decrease being most marked between 0 and 6 months. However, a transient increase in levels of the markers then occurred between 6 and 14 months of age. The timing of this increase was specific for each parameter. ICTP and OC concentrations increased between October and December. PICP concentrations increased between December and April whereas the increase in PIIINP was coincident with the peak in weight gain between April and June. Changes in BAP concentration were less distinct at this time. Season was shown to have significant effects on the biochemical markers independent from the effect of age. Concentrations of all markers decreased with increasing body weight and at any given age heavier horses had lower marker levels. These results show that biochemical markers of bone cell activity and soft tissue turnover follow characteristic patterns of change in growing thoroughbreds influenced by age, season and bodyweight. The demonstration that the reference ranges for the biochemical markers change from month to month means that single samples from individuals are of little value for monitoring bone cell activity in growing thoroughbreds.

Cross-sectional comparison of synovial fluid biochemical markers in equine osteoarthritis and the correlation of these markers with articular cartilage damage

OBJECTIVE

To investigate the relationship between biochemical markers in the synovial fluid of osteoarthritic and contralateral equine joints and gross articular cartilage pathology.

DESIGN

Twenty-two horses underwent bilateral arthroscopy of their carpal or metacarpophalangeal joints following recent onset lameness. The degree of cartilage damage in each joint was scored and synovial fluid, from both the clinically affected and the contralateral joint, was collected. Bone specific alkaline phosphatase (BAP), 5D4 epitope of keratan sulphate (KS), total glycosaminoglycans (GAG) and hyaluronan (HA) were measured.

RESULTS

The mean age of the horses was 4.1 years and the maximum duration of lameness was three months. Joints examined were midcarpal, antebrachiocarpal and metacarpophalangeal. The median concentration (semi-interquartile range) of BAP was significantly higher in the clinically active joint than in the contralateral joint, 21.75 (6.22) vs. 12.35 (4.07) units, while the other biomarkers measured were significantly lower in the clinically active joint than in the contralateral joint, i.e. KS 8.79 (1.96) microg/ml vs. 16.39 (5.65) microg/ml, KS:GAG ratio 0.19 (0.04) vs. 0.31 (0.10) and HA 741.6 (222) microg/ml vs. 1061.75 (325) microg/ml. BAP was positively (R=0.57), and KS (R=-0.57) and KS:GAG ratio (R=-0.49) were negatively correlated to the degree of cartilage damage within the joint.

CONCLUSION

The correlation between articular cartilage damage and synovial fluid BAP and KS imparts validity to their potential use as non-invasive diagnostic aids in equine osteoarthritis (OA). The positive correlation between BAP and cartilage damage suggests that there is a link between bone turnover and cartilage damage in OA.

Non-invasive assessment of equine bone: an update

This paper summarizes traditional and current methods of non-invasive assessment of bone in the horse. The description and potential clinical utility of two non-invasive technologies with major development in the last decade are presented, namely, (1) serum biochemical markers for bone turnover and (2) quantitative ultrasound. Serum biochemical markers of bone formation valid in horses are osteocalcin, carboxy-terminal peptide of type I procollagen and bone-specific alkaline phosphatase. The cross-linked carboxy-terminal telopeptide of type 1 collagen c-telopeptides of type I collagen and total deoxypyridinoline are the serum markers for bone degradation. These markers respond more rapidly to skeletal changes than other bone assessment techniques, but ideally each horse needs to be compared with itself. Quantitative ultrasound is radiation free and is a well-tolerated technique for measuring bone properties in horses. This device allows bone speed of sound measurements at various sites using the axial transmission mode along the cortex and gives information about stiffness, architecture, porosity and bone mass.A combination of different non-invasive assessment techniques is recommended for the evaluation of bone biphasic modelling-remodelling activity and the mineral phase with its architecture. The potential clinical and research use of these techniques is considered.

Urinary markers of type I collagen degradation in the dog

Urinary assays for type I collagen metabolites provide a non invasive index of bone resorption in humans, and are widely used in the management of patients with metabolic bone diseases. The specific aims of this study were to investigate the feasibility of using commercial human assay kits for quantifying the urinary excretion of type I collagen metabolites in dogs of different ages. Urine and serum samples were collected from 35 beagle dogs in five age groups (0 to 1 years; 1 to 2 years; 2 to 3 years; 3 to 7 years; > 8 years old). Urinary concentrations of pyridinoline (Pyd), deoxypyridinoline (Dpd), and the carboxy- and amino-terminal cross-linked telopeptides of type I collagen (CTx and NTx, respectively) were measured with commercial enzyme-linked immunoassay kits. Serum concentrations of another type I collagen metabolite, the carboxy-terminal cross-linked teloptide of type I collagen (ICTP), were measured with a commercial radioimmunoassay. Dilutional studies indicated that the four urinary assays show specific cross-reactivity with canine urine. Age-related differences in urinary marker excretion were identified, with young dogs excreting the highest concentrations of Pyd, Dpd, NTx and CTx. The correlation between the individual urinary markers was excellent (r = 0.87 to 0.98), while the correlation between serum ICTP and individual urinary markers was weaker (r = 0.52 to 0.64). These results validate the usefulness of the commercial assay kits in monitoring type I collagen metabolism in dogs. Histomorphometric studies have confirmed the relationship between collagen degradation and bone resorption in humans, and similar studies are now needed in dogs.

A comparison of two techniques for the determination of serum bone-specific alkaline phosphatase activity in dogs

Bone-specific alkaline phosphatase (BALP) shows potential as a marker of bone formation in the dog. Recent studies have indicated that serum BALP may provide a useful, non-invasive indicator of skeletal health in dogs, and as a diagnostic and prognostic marker in the management of dogs with musculoskeletal or metabolic disorders. Two assay techniques (one based on wheatgerm lectin precipitation followed by a simple enzymatic reaction, the second on a specific enzyme-linked immunoassay) were used to measure serum levels of BALP in 35 dogs of different ages. As expected, BALP concentrations decreased with age. For the enzymatic assay, mean (+/-SD) serum concentrations of BALP activities were 100.3 (+/-11.6) U/liter in dogs under 1 year of age, 25.3 (+/-6.8) U/L in dogs 1 to 2 years of age, 16.5 (+/-7.3) U/L in dogs 2 to 3 years of age, 14.3 (+/-5.6) U/L in dogs 3 to 7 years of age, and 12.3 (+/-4.8) U/L in dogs aged 8 years and older. Corresponding results from the immunoassay were 56.3 (+/-9.8) U/L, 10.7 (+/-4.5) U/L, 7.0 (+/-2.5) U/L, 6.7 (+/-3.6) U/L and 7.0 (+/-2.9) U/L. There was excellent correlation between the results from the two assay techniques (r = 0. 96; P < 0.0001). The correlation between BALP and total ALP activities was poor (r = 0.20 for enzymatic BALP, r = 0.31 for immunoreactive BALP), indicating that total ALP should be considered unreliable as an indicator of BALP activity in canine serum. The immunoassay demonstrated acceptable (13 per cent) cross-reactivity with the liver isoform of ALP. The commercial immunoassay kit is simple and provides fast results. Although the wheatgerm lectin/enzymatic technique is preferred in situations where the activities of all three isoforms of ALP are required, the immunoassay should be considered whenever the activity of BALP is the focus of interest.