Bone-origin alkaline phosphatase in plasma by wheat-germ lectin methods in bone disease

Mouse Red Blood Cell-Mediated Rare Xenobiotic Phosphorylation of a Drug Molecule Not Intended to Be a Kinase Substrate

Phosphorylation of xenobiotics is rare, probably owing to a strong evolutionary pressure against it. This rarity may have attracted more attention recently as a result of intentionally designed kinase-substrate analogs that depend on kinase-catalyzed activation to form phosphorylated active drugs. We report a rare phosphorylated metabolite observed unexpectedly in mouse plasma samples after an oral dose of a Tankyrase inhibitor that was not intended to be a kinase substrate, i.e., (S)-2-(4-(6-(3,4-dimethylpiperazin-1-yl)-4-methylpyridin-3-yl)phenyl)-8-(hydroxymethyl)quinazolin-4(3H)-one (AZ2381). The phosphorylated metabolite was not generated in mouse hepatocytes. In vitro experiments showed that the phosphorylation of AZ2381 occurred in mouse whole blood with heparin as anticoagulant but not in mouse plasma. The phosphorylated metabolite was also produced in rat, dog, and human blood, albeit at lower yields than in mouse. Divalent metal ions are required for the phosphorylation since the reaction is inhibited by the metal chelator EDTA. Further investigations with different cellular fractions of mouse blood revealed that the phosphorylation of AZ2381 was mediated by erythrocytes but did not occur with leukocytes. The levels of ¹⁸O incorporation into the phosphorylated metabolite when inorganic ¹⁸O₄-phosphate and γ-¹⁸O₄-ATP were added to the mouse blood incubations separately suggested that the phosphoryl transfer was from inorganic phosphate rather than ATP. It remains unclear which enzyme present in red blood cells is responsible for this rare phosphorylation.

Online assay of bone specific alkaline phosphatase with a flow injection-bead injection system

Alkaline phosphatase (ALP) has been used as one of the biomarkers for bone resorption and liver diseases. Normally, total alkaline phosphatase is quantified along with other symptoms to determine the releasing source of the alkaline phosphatase. A semi-automated flow injection-bead injection system was proposed to conveniently and selectively assay bone alkaline phosphatase (BALP) based on its specific binding to wheat germ coated beads. Amount of BALP in serum was determined from the intensity of the yellow product produced from bound BALP on the retained beads and its substrate pNPP. The used beads were discarded and the fresh ones were introduced for the next analysis. The reaction cell was designed to be opened and closed using a computer controlled solenoid valve for a precise incubation time. The performance of the proposed system was evaluated by using it to assay BALP in human serum. The results were compared to those obtained by using a commercial ELISA kit. The system is proposed to be an easy and cost effective system for quantification of BALP as an alternative to batch wise wheat germ specific binding technique.

Pediatric reference intervals for bone markers

Bone markers are specific bone-derived molecules that reflect bone remodeling activity and can be classified into two categories: bone formation and bone resorption markers. Children have significantly elevated bone marker levels due to high skeletal growth velocity and rapid bone turnover during childhood growth. Many physiological and pathological processes may influence bone metabolism and bone marker concentrations during childhood growth. Measurements of bone markers may be useful in investigating skeletal diseases in children and monitoring the response to treatment. This review documents recent advances in analytical methods, preanalytical considerations related to each marker and particularly highlights the most valuable bone formation markers, bone alkaline phosphatase and osteocalcin, and bone resorption markers, pyridinium cross-links and cross-linked telopeptides. Age- and sex-specific pediatric reference intervals and their limitations in clinical application are also discussed.

Paget's disease of bone (osteitis deformans)

Paget's disease of bone is important in geriatric populations because it is the second most common bone disorder after osteoporosis. In older people, it may be responsible for chronic back pain and joint pain, skeletal deformities, hearing loss, and cranial nerve compression. Paget's disease can reduce both function and mobility in the older people. In addition to newer tests for assessing the activity of Paget's disease, effective therapy is available in the form of salmon calcitonin for nasal administration and new third generation bisphosphonates. Frequently, treatment can reverse the course of the disease. For these reasons, it is feasible for the physician to adopt an aggressive approach to diagnosis and treatment. The objective should be to relieve pain, improve mobility, and forestall debilitating complications. This review will focus on the manifestations and clinical management of Paget's disease. Two cases are presented that illustrate common management problems in older patients.

Vitamin D and bone mineral density

Bone mineral density (BMD) at the lumbar spine and the neck of femur and serum concentrations of 25-hydroxyvitamin D (25OHD), intact parathyroid hormone (PTH), alkaline phosphatase, calcium, albumin, creatinine and phosphate were measured in a group of 166 postmenopausal women (30-79 years) attending a bone clinic for bone density measurements. Four subjects with suspected primary hyperparathyroidism were excluded from analysis. BMD at the lumbar spine was correlated with body mass index (BMI) (r = 0.278, p = 0.0003), age (r = -0.194, p = 0.0134) and serum 25OHD (r = 0.188, p = 0.0167). BMD at the neck of femur correlated with BMI (r = 0.391, p < 0.0001), age (r = -0.356, p < 0.0001), PTH (r = -0.156, p = 0.047) and serum 25OHD (r = 0.231, p = 0.0031). Stepwise multiple regression analysis showed that age, BMI and serum 25OHD contributed to the variation in BMD at lumbar spine. At the neck of femur, PTH was an additional contributor. We conclude that serum 25OHD makes a contribution to BMD a lumbar spine and neck of femur.

Separation and quantification of corticosteroid-induced, bone and liver alkaline phosphatase isoenzymes in canine serum

Quantifying alkaline phosphatase (ALP) isoenzymes in canine serum would provide a useful index in a clinical laboratory. To achieve this goal, we tested a semi-automatic assay combining wheat germ lectin (WGL) precipitation and chemical inhibition of isoenzymes of the TNS gene with levamisole to quantify bone ALP (BALP) and corticosteroid-induced ALP (CALP), respectively. The liver ALP (LALP) isoenzyme was then calculated from the equation: TALP = BALP + LALP + CALP BALP, LALP and CALP standards from serum of puppies, bile-duct ligated dogs and dogs on 4.4 mg/kg/day prednisolone for 30 days, respectively, were used. The suitability of standard sera was tested by affinity electrophoresis. Levamisole (4.2 mM) inhibits 98% of BALP and LALP but only 42% CALP. Multiplying measured CALP by 1.8 gives the total CALP value in serum. WGL precipitated 92.3% BALP, 23.3% LALP and 26.8% heated CALP standards. These values were used to adjust precipitated ALP to obtain the exact levels of BALP. WGL was then tested on pooled serum standards in which the relative proportions of all the ALPs were known and controlled. BALP was adequately quantified except when LALP and CALP levels were extremely high. The assay was also applicable under conditions resulting in high ALP. Therefore, combining WGL and levamisole inhibition provides an adequate separation and quantification of canine ALP isoenzymes. The method has great potential for diagnostic use and should be tested further for routine implementation.

Biological variation in bone-derived biochemical markers in serum

Analytical, within-subject and between-subject components of variation have been determined for total alkaline phosphatase (ALP) and its bone isoform, osteocalcin, and tartrate-resistant acid phosphatase (TR-ACP) in serum specimens from a cohort of 10 healthy subjects over a 1-month period. From these data, we have calculated the desirable analytical imprecisions, the indices of individuality, the critical differences for significant change detection, and the number of specimens required to estimate the homeostatic setpoint of an individual. For total ALP and its bone isoform, most of the observed variability was biologic, whereas osteocalcin and TR-ACP also had relatively high analytical variability. Total and bone ALP were also the parameters showing the lowest within-subject variability, whereas TR-ACP showed the lowest interindividual fluctuation. Osteocalcin and bone ALP had marked individuality, showing that the use of population-based reference limits is inadequate for their interpretation. The applicable differences required for two results to be significantly different (p < or = 0.05) are bone ALP: 20%; osteocalcin: 29%; and TR-ACP: 35%. The results demonstrate that the biochemical markers of bone turnover studied are of limited use to screen for metabolic bone disorders, but can be useful adjuncts for monitoring groups of patients in longitudinal studies.

Milk consumption decreases activity of human serum alkaline phosphatase: a cross-sectional study

Since the Japanese have not reached the recommended daily allowance (RDA) for calcium (600 mg), milk is recommended as a Ca-rich food to increase Ca intake and prevent osteoporosis in Japan. To determine whether milk consumption influences Ca/bone metabolism in the Ca-deficient population, relationships between milk consumption and serum alkaline phosphatase (Al-P) activity were analyzed in 3,098 premenopausal and 1,182 postmenopausal women and 13,141 men aged 30 to 69 years. Milk consumption was classified into no/yes groups by a self-administered questionnaire that asked "Do you drink a glass of milk (180 to 200 mL) or more everyday?". Regardless of age or sex, the "yes" group had a lower activity of serum Al-P than the "no" group. Milk consumption decreased the activity to a greater degree in women, especially perimenopausal/postmenopausal women, than in men. These results were confirmed in a multivariate analysis considering age, body mass index (BMI), and smoking and drinking habits as confounding factors. Although menopause obviously increased serum Al-P activity in perimenopausal women, it could not influence the effects of milk consumption on the activity. These results suggest that milk has osteostatic effects on humans via a mechanism different from that of estrogens. Milk consumption, even one glass per day, may be an easy and effective strategy for prevention of osteoporosis in the Ca-deficient population, especially perimenopausal/postmenopausal women.