Circadian rhythm of bone formation biomarkers in serum of dromedary camels

The circadian rhythm of biomarkers of bone formation including osteocalcin and bone alkaline phosphatase (BAP) was studied in the serum of dromedary camels. Blood samples were collected every 60 min for 24 h from 10 healthy adult female camels. ELISA was used to determine the concentrations of serum osteocalcin and BAP. The results showed a marked fluctuation in the concentration of osteocalcin during the 24 h period with minimum and maximum levels at 13:00 (01:00 pm) and 18:00 (06:00 pm), respectively. Slight fluctuation was observed in the concentration of BAP with minimum and maximum levels at 01:00 am and 12:00 pm, respectively. The correlation between the two biomarkers was weak. It was concluded that it is important to fix the time of blood sampling for analysis of osteocalcin concentrations, but not for BAP.     

Feeding Magnesium Supplement to Foals Reduces Osteochondrosis Prevalence

The influence of supplements containing magnesium on the etiology of osteochondrosis (OC) is unknown. We did two studies to measure the effect of additional minerals (especially magnesium) on OC. In study 1 (five studs, in total 64 mares and foals aged 0 to 5 months, equally divided into two groups), supplementation with minerals and placebo was used. Blood samples were taken from foals at age of 2, 8, and 16 weeks. At the same time, milk samples were taken from the mare. Bone biomarkers (osteocalcin and C-terminal telopeptide [CTx] of type I [CTx-1] collagen) and minerals (calcium, phosphorus, and magnesium) were measured in blood and the same minerals in milk of the mare. At the end of the study, the femoropatellar (knee), tarsocrural (hock), and metacarpophalangeal and/or metatarsophalangeal (fetlock) were radiographed and scored for the presence and grade of osteochondrotic lesions. In study 2 (six studs, 54 foals aged 5 to 12 months, equally divided into two groups), the same was repeated. At the start and end of the study, again blood samples were taken and analyzed on the same parameters as in study 1. Also, the same radiography was done. In study 1 in the mineral supplemented group, 21.9% were diagnosed with osteochondrosis compared with 41.9% in the placebo group. In study 2, there was no change in OC between 5 and 12 months in the placebo group whereas there was a drop of 14.3% in incidence in the supplement group. We concluded that magnesium supplementation reduced OC prevalence.     

Response of plasma bone markers to a single intramuscular administration of calcitriol in dairy cows

To elucidate the effects of an exogenous calcitriol (1,25-dihydroxyvitamin D₃) on plasma bone markers, the formation item osteocalcin (OC), undercarboxylated OC (ucOC) and bone-specific alkaline phosphatase (BALP), and the resorption parameter tartrate-resistant acid phosphatase isoform 5b (TRAP5b) and hydroxyproline (HYP) were measured in conjunction with plasma calcitriol and calcium (Ca) concentrations in dairy cows receiving calcitriol or its vehicle according to a 2 × 2 crossover design. Calcitriol (0.5 μg/kg, i.m.) increased significantly its plasma level during 6 h to day 2 and plasma Ca concentration during 12 h to day 7 compared to the vehicle. Also, plasma OC and ucOC started to rise from day 3 and 1, respectively, and remained elevated until day 7. No change in plasma BALP, TRAP5b or HYP associated with calcitriol treatment was noted. These results demonstrate that exogenous calcitriol stimulates osteoblasts to biosynthesise OC, a determinant of the bone formation in cows.     

A Marine Mineral Supplement Alters Markers of Bone Metabolism in Yearling Arabians

This study tested whether the supplement (Aquacid), high in calcium and other minerals, can alter markers of bone metabolism and mineralization of the equine third metacarpus bone. Radiographs were taken of the left third metacarpus of 14 yearlings. Radiographic bone aluminum equivalence (RBAE) of each cortex was calculated to estimate mineral content. Blood samples were also taken at this time. Horses were ranked according to RBAE and gender, were pair-matched, and randomly assigned to two treatment groups. Each group was provided one of two mineral supplements in addition to their normal diet. The treated group (Aq) received 75 g Aquacid/horse/d, which provided an additional 15 g of calcium. The control group (Co) received 39.5 g of limestone to provide similar amounts of calcium. The study lasted for 112 days, with blood being taken every 28 days. At day 56 and 112, additional radiographs was taken to track changes in RBAE. Blood was analyzed for osteocalcin (a bone formation marker) and serum C-telopeptide crosslaps of type I collagen (a bone resorption marker) to detect alterations in bone metabolism. Using day 0 values as a covariate for bone markers, there was a trend (P = .07) for osteocalcin concentrations to be greater in Aq horses than in Co. Likewise, C-telopeptide crosslaps of type I collagen concentrations were greater (P < .0001) in Aq horses than in Co. There were minimal differences in RBAE values. These findings suggest Aquacid, while not altering bone mass, increases bone turnover and may aid in repairing damaged bone and preventing injuries.     

Serum osteocalcin in dairy cows: age-related changes and periparturient variation

We evaluated age-related changes in serum osteocalcin concentrations in non-periparturient cows and variations in serum osteocalcin concentration in periparturient primiparous and multiparous cows. The serum osteocalcin levels were evaluated in 144 non-periparturient Holstein dairy cows aged 11 days to 10 years; these levels were the highest in the youngest cows, appeared to steadily decrease with age until the time of the first calving, and were subsequently maintained at low levels. Between 14 days before calving and 21 days after calving, the serum osteocalcin levels were significantly higher in the primiparous cows than in the multiparous cows. A comparison between age-matched non-periparturient and periparturient cows showed that serum osteocalcin levels were significantly lowered during late gestation in both primiparous and multiparous cows. These results suggest that serum osteocalcin measurement might be useful for the detection of mineral imbalances at the time of parturition in cows.     

奶牛骨钙素基因的克隆与原核表达

以奶牛骨组织提取的RNA为模板，利用RT—PCR技术扩增出奶牛骨钙素全长cDNA，然后将扩增产物重组到PMD-18T载体中，测定了全基因的核苷酸序列。序列分析表明，奶牛骨钙素全长cDNA为303bp，编码100个氨基酸，与GenBank中的X53699的序列完全相同。通过加端PCR技术连接单链DNA片段人工定点同义突变，将奶牛骨钙素成熟蛋白基因中的大肠杆菌稀有密码子同义突变为大肠杆菌常用密码子并亚克隆至PET-32a表达载体．转化到宿主菌BL21（DE3）中，经IPTG诱导后，成功表达出奶牛骨钙素融合蛋白。     

Research progress in regulation of glucose metabolism by osteocalcin

Osteocalcin (OCN) is a non-collagenous protein, which is synthesized and secreted by osteoblasts and closely associated with bone metabolism. Previously, blood circulation-derived OCN has been confirmed to promote β-cell proliferation, enhance insulin secretion, and improve insulin sensitivity by increasing the expression of adiponectin. Recent studies indicate that insulin signaling in the regulation of OCN activity mediated by osteoblasts is through the enterococcal surface protein (ESP) gene to increase the expression of OCN gene and enhance OCN activity by favoring bone resorption. Meanwhile, adiponectin may also behave as a kind of insulin secretagogue potentially. Intense researches on the specific mechanism concerning the effects of insulin signaling and adiponectin during the process of glucose homeostasis by OCN may provide new therapeutic targets for treating diabetes and its related complications.     

成骨生长肽对体外培养奶牛成骨细胞碱性磷酸酶和骨钙素的影响初探

体外培养奶牛成骨细胞,用10^-12mol／L、10^-11mol／L、10^-10mol／L、10^-9mol／L和10^-8mol／L成骨生长肽（OGP）干预5d后．紫外分光光度法检测细胞上清液中碱性磷酸酶（ALP）活性,以放射免疫法检测细胞上清液中骨钙素（OC）含量。结果显示：成骨生长肽对细胞上清液中ALP活性起抑制作用,其中在10^-10mol／L时抑制作用最为显著（P〈0．01）;对细胞上清液中OC亦起抑制作用,且该抑制呈现剂量双向性．在10^-10mol／L时抑制作用显著。结论：成骨生长肽对体外培养奶牛成骨细胞碱性磷酸酶和骨钙素起轻微抑制作用而且呈双向性。     

Improvement of insulin sensitivity by osteocalcin inhibits inflammation in the adipose tissue of obese mice

AIM: To explore the improving effect of osteocalcin on obesity-related insulin resistance and inflammation in the adipose tissue of obese mice.METHODS: The C57BL/6 mice were fed with high-fat diet for 12 weeks to obtain obese mice. Osteocalcin (30 ng/kg or 3 ng/kg) and saline solution (control) were intraperitoneally injected for other 4 weeks. The fat mass, body weight, serum triglycerides and serum free fatty acid were analyzed. Intraperitoneal glucose tolerance test and insulin tolerance test were carried out. Macrophage infiltration degree in the adipose tissue was observed by immunohistochemical staining. The mRNA expression of monocyte chemotactic protein-1 (MCP-1) and CD68 was detected by real-time fluorescence quantitative PCR.RESULTS: Osteocalcin (30 ng/kg or 3 ng/kg) treatment for 4 weeks significantly reduced the body weight, fat mass and insulin level, and improved abnormal glucose tolerance and insulin resistance in the obese mice. Moreover, the macrophage infiltration decreased, and the mRNA expression of MCP-1 and CD68 was down-regulated in the adipose tissue of obese mice treated with osteocalcin at 30 ng/kg.CONCLUSION: Osteocalcin at 30 ng/kg significantly reduces body weight and fat mass, and attenuates the severity of insulin resistance through down-regulating the mRNA expression of MCP-1 and CD68 and inbihiting macrophage infiltration in the adipose tissue of obese mice induced by high-fat diet.     

The efficacy of the bone markers osteocalcin and the carboxyterminal cross-linked telopeptide of type-I collagen in evaluating osteogenesis in a canine crural lengthening model

The aim of the present study was to determine the efficacy of the bone markers osteocalcin (OC) and carboxyterminal cross-linked telopeptide of type-I collagen (ICTP) in evaluating new bone formation in the dog, using commercially available immunoassay kits. Dogs were randomly divided into three groups and a circular external skeletal fixation system (CESF) was mounted on the tibia. In the first group a distraction osteogenesis procedure of the crus was performed. The second group received an osteotomy without crural lengthening, whereas the third group served as a sham-operated control. Bone formation was assessed using densitometric image analysis of crural radiographs. Despite significant differences in the amount of newly formed bone, this finding was not reflected in the plasma levels of OC and ICTP. In conclusion, OC and ICTP were not efficacious as markers of bone formation and resorption during osteogenesis in this canine model.