Intact Osteocalcin Research Articles

Does bone mobilization interfere with energy metabolism in transition cows?

The onset of lactation represents a challenge for both mineral homeostasis and energy metabolism in high-performing dairy cows. It has been shown that subclinical and clinical hypocalcemia increases the risk of ketosis and recent studies suggest that bone-derived endocrine factors could play a role in intermediary metabolism. Therefore, we analyzed serum samples from calculated d −7, calculated d −3, d +1, d +3, and d +7 relative to calving from 15 multiparous cows for total Ca, the bone resorption marker CrossLaps, the bone formation marker intact osteocalcin, undercarboxylated osteocalcin (ucOC), insulin, glucose, nonesterified fatty acids, β-hydroxybutyrate, and insulin-like growth factor 1. Serum concentrations of Ca on d −3 and d +1 were associated with parameters of energy metabolism on d +3 and d +7. As we found large variations for serum concentrations of ucOC already on d −7, we allocated the cows retrospectively to 3 groups: low ucOC, medium ucOC, and high ucOC. These groups differed not only in their ucOC dynamics, but also in insulin sensitivity estimated using the revised quantitative insulin sensitivity index (RQUICKI). High ucOC cows presented with the highest RQUICKI throughout the entire observation period. Our data further support the hypothesis that low serum Ca precedes disturbances of energy metabolism. Furthermore, from our preliminary results it can be assumed that the potential link between mineral homeostasis, bone turnover, and intermediary metabolism should be further investigated.

MO730: Markers of Vitamin K Deficiency in Haemodialysis Patients

Abstract BACKGROUND AND AIMS Vitamin K deficiency is a common feature of CKD, leading to impaired bone quality and an increased risk of vascular calcifications. A method to indirectly measure vitamin K status is measuring the blood level of vitamin K dependent proteins (VKDP)- osteocalcin (OC) and matrix GLA protein (MGP). The aim of this study is to correlate the level of OC and MGP with markers of CKD mineral bone disorder (CKD-MBD). METHOD We conducted a single-centre cross-sectional study that included 45 CKD G5D patients (haemodialysis for 6 months–10 years). All patients have been assessed regarding their dialysis status (medical history), we performed analysis before the dialysis session using standard methods blood biochemistry, complete blood count and intact osteocalcin and matrix GLA protein. RESULTS In the studied haemodialysis patients mean OC was 169.06 ± 128.28 ng/mL, while mean MGP was 3285.93 ± 2092.85 pmol/L. No statistically significant correlation has been found between OC and MGP. We found a strong statistically significant correlation of OC with the markers of CKD-MBD such as: iPTH (r = 0.48, P = 0.0007), serum calcium (r = 0.49, P = 0.0005) and serum phosphorus (r = 0.29, P = 0.04). No statistically significant correlation has been found between MGP and the above- mentioned markers. Only 2 out of 45 patients recorded a past history of bone fractures. Regarding the relationship with the nutritional status of the patients, no statistically significant correlations of the assessed VKDP with BMI and serum albumin have been found. However, a strong indirect statistically significant correlation of OC with abdominal circumference was observed (r = –0.43, P = 0.003). There was also a statistically significant correlation of MGP with markers of inflammation (CRP) (r = 0.55, P = 0.004). No statistically significant differences have been found regarding the level of VKDP between patients with and without a history of diabetes mellitus (13/45), coronary heart disease (18/45) stroke (5/45). The group of patients that are currently under treatment with vitamin K antagonists (13 out of 45) showed significantly higher levels of MGP (5693.0 ± 1728.64 versus 2276.5 ± 1232.54 pmol/L; P < 0.01). Treatment with non-calcium-based phosphate binders (20 patients) was associated to significantly higher levels of MGP compared with treatment with calcium-based phosphate binders (15 patients) (4089.2 ± 2045.79 versus 2134.86 ± 1944.63 pmol/L; P = 0.019). Treatment with vitamin D receptor activator-paricalcitol (20 patients) was associated to significantly increased levels of MGP (4224.55 ± 2162.32 versus 2503.75 ± 1709.31 pmol/L; P = 0.005). CONCLUSION In our study, we found that vitamin K deficiency, measured indirectly using the level of VKDP is associated to CKD-MBD, could be influenced by features of malnutrition-inflammation. The use of medications such as phosphate binders that reduce vitamin K absorbtion, vitamin D that increases vitamin K requirements and also vitamin K antagonists, seems to have an influence on the blood level of VKDPs.

Association between Biomarkers of Mineral and Bone Metabolism and Removal of Calcium and Phosphate in Hemodialysis

Background: A significant drop of serum phosphate and calcium removal or loading during hemodialysis induce reactions in mineral and bone remodeling that may inversely affect phosphate and calcium removal during dialysis. Objectives: We aimed to analyze the interdependencies between biomarkers of mineral and bone metabolism and removal of phosphate and calcium during hemodialysis, as this complex relationship is not fully understood. Methods: Three subsequent hemodialysis sessions during a 1-week treatment cycle with interdialytic periods of 2–2-3 days were monitored in 25 anuric patients. Calcium and phosphate concentrations were measured in serum before, at 1, 2, and 3 h, at the end, and 45 min after each session and in the outlet dialysate every 30 min. Biomarkers associated with mineral and bone metabolism: parathyroid hormone (PTH 1–34 and PTH 1–84), calcitonin, 25(OH)-vitamin D, fetuin-A, osteopontin, osteocalcin 1–43/49, and intact osteocalcin were assayed once in each patient before the midweek hemodialysis session. Results: Post-dialytic and intra-dialytic serum phosphate of midweek hemodialysis session and phosphate mass removed within 1 week correlated positively with serum PTH (0.40 < rho <0.46, p value <0.05). Higher concentration of serum PTH was associated with an increased level of osteocalcin. Pre-dialytic, post-dialytic, average for treatment time and average weekly concentrations of ionized calcium in serum correlated positively with serum osteocalcin. Serum osteocalcin and osteopontin levels were associated with the masses of total and ionized calcium, respectively, removed during 3 hemodialysis sessions. Conclusions: During hemodialysis, phosphate removal was associated with serum PTH, whereas calcium kinetics was influenced by serum osteocalcin and osteopontin. These results demonstrate that active processes involving biomarkers of mineral and bone metabolism are affected by the phosphate and calcium kinetics already within 4 h hemodialysis sessions.

A meta-analysis of serum osteocalcin level in postmenopausal osteoporotic women compared to controls

BackgroundCirculatory osteocalcin (OC) has been widely used as a biomarker to indicate bone turnover status in postmenopausal osteoporosis (PMO). However, the change of serum OC (sOC) level in PMO cases compared to postmenopausal controls remains controversial.MethodsWe searched the online database of PubMed and Cochrane Library. A meta-analysis of case-control studies was performed to compare the pooled sOC level between PMO patients and postmenopausal controls. Subgroup analysis according to potential confounding factors (different OC molecules and regions of the study population) was also performed.ResultsTen case-control studies with 1577 postmenopausal women were included in this meta analysis. We found no significant difference in the pooled sOC level [mean difference (MD) = 1.84, 95% confidence interval (CI): (− 1.49, 5.16), p = 0.28] between PMO patients and controls. Subgroup analysis also revealed no significant difference in intact OC [MD = 1.76, 95%CI: (− 1.71, 5.23), p = 0.32] or N-terminal mid-fragment of the OC molecule [MD = 0.67, 95%(− 5.83, 7.18), p = 0.84] between groups. For different regions, no significant difference in sOC was found in Asian population between cases and controls [MD = -0.06, 95%(− 6.02, 5.89), p = 0.98], while the pooled sOC level was significantly higher in European PMO cases than controls [MD = 3.15, 95%(0.90, 5.39), p = 0.006].ConclusionsOur analysis revealed no significant difference in sOC level between PMO cases and controls according to all the current eligible studies. OC molecules are quite heterogeneous in the circulation and can be influenced by glucose metabolism. Therefore, sOC is currently not a good indicator for the high bone turnover status in PMO. More trials with standardized methodologies for the evaluation of circulatory OC are awaited to update our current findings.

A INGESTÃO DIETÉTICA DE VITAMINA K ESTÁ ASSOCIADA A PARÂMETROS DE OBESIDADE ENTRE ADOLESCENTES?

Introdução: Na adolescência, fase em que ocorrem muitas mudanças na composição corporal, torna-se útil investigar a ingestão de micronutrientes como a vitamina K, que podem estar indiretamente relacionados à obesidade nesses indivíduos. Assim, o objetivo deste estudo foi investigar a relação entre a ingestão de vitamina K, o estado nutricional e as concentrações séricas de osteocalcina, leptina e adiponectina em adolescentes. Metodologia: Estudo transversal realizado com 129 adolescentes de ambos os sexos, com idade entre 14 e 18 anos, participantes do Inquérito de Saúde no Município de São Paulo 2008 (ISA-Capital 2008). Amostras de sangue venoso periférico foram coletadas para determinar as concentrações séricas de osteocalcina total (tOC), osteocalcina não carboxilada (ucOC), leptina e adiponectina. Foram realizadas correlação de Spearman e regressão linear múltipla para avaliar as associações entre o consumo de vitamina K e as variáveis antropométricas e bioquímicas. Resultados: Em indivíduos com peso normal, a ingestão de vitamina K apresentou correlação positiva com a idade (r = 0,2489; p = 0,0174) e correlação negativa com o peso (r = -0,2335; p = 0,0259). Na amostra total, a ingestão de vitamina K não se correlacionou com peso (r = -0,0856; p = 0,3442), IMC (r = 0,0669; p = 0,4621), leptina (r = 0,1291; p = 0,1530), adiponectina (r = - 0,0682; p = 0,4517), tOC (r = 0,0442; p = 0,6256) e ucOC (r = -0,1136; p = 0,2110). Conclusões: Em indivíduos com peso normal, observou-se correlação negativa entre a ingestão de vitamina K e peso corporal. Ainda não está bem elucidado quais as vias metabólicas envolvidas na relação entre a ingestão de vitamina K e a composição corporal.DOI: 10.12957/demetra.2019.39079

Increased risk of osteoporotic fracture in community-dwelling elderly men 20 or more years after gastrectomy: The Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) Cohort Study.

Many studies have reported that patients with a history of gastrectomy (gastrectomized patients) have lower areal bone mineral density (aBMD) and higher fracture risk than those without. However, population-based studies on this topic are scarce, and little is known regarding the bone metabolic status of gastrectomized patients in the long-term. This study aimed to clarify the association of gastrectomy with aBMD, bone metabolism markers, and fracture risk in community-dwelling elderly Japanese men. A total of 1992 men aged ≥65 years completed baseline measurements including aBMD at the spine and hip, serum levels of intact parathyroid hormone (PTH), intact osteocalcin (OC), tartrate-resistant acid phosphatase isoenzyme 5b (TRACP5b), and undercarboxylated OC (ucOC), and an interview regarding past medical history including gastrectomy. Osteoporotic fractures (OPFs) that occurred during the 5-year follow-up period were determined through structured interviews. After excluding participants with type 1 diabetes mellitus and those with missing values, 1985 men, including 132 gastrectomized men, were analyzed. Gastrectomized men had significantly higher PTH, TRACP5b, and ucOC levels, and lower aBMD, than non-gastrectomized men. Gastrectomy was associated with a significantly higher risk of OPF after adjusting for confounding variables (hazard ratio (HR): 2.55, 95% confidence interval (CI): 1.17, 5.55), and the risk was no longer significant when further adjusted for PTH and aBMD. Even in this model, however, increase in OPF risk was significant in gastrectomized men who survived 20 years or more after the surgery (HR: 3.56, 95% CI: 1.33, 9.52). History of gastrectomy was associated with elevated bone resorption, decreased aBMD, and increased fracture risk in community-dwelling elderly Japanese men. This increase in fracture risk was more prominent long after gastrectomy.

Osteocalcin and carotid-femoral pulse wave velocity in patients on peritoneal dialysis.

Objective:Vascular calcification is a cardiovascular risk factor in dialysis patients. Vascular calcification involves a complex process of biomineralization resembling osteogenesis, which leads to arterial stiffness. Osteocalcin is the most abundant noncollagenous protein in the bone matrix. It is synthesized in the bone by osteoblasts and reflects the rate of bone formation. The aim of this study was to evaluate the relationship between serum osteocalcin levels and the carotid–femoral pulse wave velocity (cfPWV) in peritoneal dialysis (PD) patients.Materials and Methods:Serum intact osteocalcin and cfPWV were measured in 62 PD patients. Those with CfPWV values >10 m/s were defined as the high central arterial stiffness group, while those with values ≤10 m/s were regarded as the low central arterial stiffness group, according to the European Society of Hypertension and of the European Society of Cardiology guidelines.Results:Seventeen of the 62 PD patients (27.4%) were in the high central arterial stiffness group. The high central arterial stiffness group were older (P = 0.002), had a longer PD vintage (P = 0.018), and had higher serum osteocalcin levels (P = 0.001) than those in the low group. Multivariate logistic regression analysis showed that the osteocalcin level (odds ratio: 1.069, 95% confidence interval (CI): 1.005–1.137, P = 0.035), PD vintage (odds ratio: 1.028, 95% CI: 1.010–1.048, P = 0.003), and age (odds ratio: 1.081, 95% CI: 1.005–1.162, P = 0.035) were independently associated with central arterial stiffness in PD patients. Among these patients, cfPWV (β: 0.216, P = 0.001) values and log-transformed intact parathyroid hormone (β: −’0.447, P < 0.001) levels were independently associated with the osteocalcin level in PD patients after multivariate forward stepwise linear regression analysis.Conclusion:Older PD patients with a longer PD vintage and higher serum osteocalcin levels had higher central arterial stiffness as measured by cfPWV. The serum osteocalcin level is an independent marker of central arterial stiffness in PD patients.

Development of an in house ELISA for human intact osteocalcin and its utility in diagnosis and management of osteoporosis

BackgroundSerum Osteocalcin (OC) is a biomarker for evaluating bone turnover in humans. Commercial kits of OC in India are imported, hence the associated high cost prohibits their use in routine screening of osteoporosis. The present study describes the development, validation of human OC ELISA and establishes cut off values for its use in screening and management of women at risk for osteoporosis. MethodsA sandwich OC ELISA was developed using immuno-reagents prepared indigenously and validated for analytical sensitivity, specificity, accuracy and compared with commercial kit using Bland-Altman method. The utility of OC assay was evaluated by ROC analysis. ResultsThe new ELISA was sufficiently precise, accurate, matrix-free, sensitive and cost effective. The levels of OC were significantly different in women with osteopenia and osteoporosis (ANOVA, p < .0001) compared to women with normal BMD. ROC analysis demonstrated the cut off values of OC >11.9 ng/mL for osteopenia and > 14.9 ng/mL for osteoporosis. The OC levels had maximum AUC of 0.831 in osteopenia and 0.932 in osteoporosis. Further, OC levels showed significant changes within 3 months in women monitored on therapy. ConclusionThe developed OC ELISA has great potential to be used as a biomarker for routine screening and management of osteoporosis in Indian women.

Effects of Biliopancreatic Diversion on Bone Turnover Markers and Association with Hormonal Factors in Patients with Severe Obesity.

This study evaluated early and medium-term changes in bone turnover markers, and their associations with weight loss, total bone mineral density (BMD), and hormonal changes after biliopancreatic diversion (BPD). Ancillary study from a one-year prospective cohort of 16 individuals assessed before, 3days, 3 and 12months after BPD. Bone turnover markers (C-terminal telopeptide (CTX), intact osteocalcin (OC), sclerostin, and osteoprotegerin (OPG)) and several hormones were measured at each visit. Total BMD by DXA was assessed at baseline, 3 and 12months after BPD. Three participants were lost to follow-up. CTX increased significantly at 3days (+ 66%), 3months (+ 219%), and 12months (+ 295%). OC decreased at 3days (- 19%) then increased at 3months (+ 69%) and 12months (+ 164%). Change in sclerostin was only significant between 3days and 3months (+ 13%), while change in OPG was significant between baseline and 3days (+ 48%) and baseline and 12months (+ 45%). CTX increase correlated negatively with weight loss at 3 (r = - 0.63, p = 0.009) and 12months (r = - 0.58, p = 0.039), and total BMD decrease (r = - 0.67, p = 0.033) at 12months. Change in insulin and adiponectin correlated with changes in bone turnover markers independently of weight loss. BPD causes an earlier and greater increase in bone resorption over bone formation markers and a decrease in total BMD. Sclerostin did not increase as expected following extensive weight loss. Changes in insulin and adiponectin seem to play a role in the activation of bone remodeling after BPD.

Significant Bone Loss in Obese Patients with Acanthosis Nigricans after LSG—One-Year Follow-Up Study

The aim of the study was to investigate the longitudinal bone mineral density(BMD) and bone metabolic related markers changes in obese patients with acanthosis nigricans (AN) and without AN(OB) after Laroscopic Sleeve Gastrectomy (LSG). 41 obese patients (AN group:n=29,OB group:n=12) were recruited in this study. Areal BMD (aBMD) and lumbar spine volumetric BMD (vBMD)were measured by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). Insulin and markers of bone metabolism including 25-OHD, calcium, intact parathyroid hormone (iPTH), osteocalcin (OC), and type I collagen cross-linked C-terminal telopeptide (CTX) ] were assessed; Insulin area under the curve(AUCins) and HOMA-IR were computed. Results showed that the AN group had a higher fasting serum insulin (42.80±28.52 vs. 22.55±8.94mU/L,p=0.006), AUCins (522.42±280.32 vs. 263.87±195.75mU/L,p=0.008)and BMI(40.6±5.1 vs. 36.7±4.1kg/m2,p=0.024) compared to the OB group at baseline. The both groups did a obvious decrease in HOMA-IR after LSG; In AN group, there was a significant decrease in Lumbar vBMD(-4.4%,p=0.011), pelvic aBMD (-6.48%,p&amp;lt;0.001) and femoral neck aBMD (-6.7%,p=0.045) after LSG compared with baseline, whereas no detectable BMD changes in the OB group. CTX and OC increased in both AN (97.69%,79.65%,respectively)and OB(115.21%,62.28%,respectively) groups; No significant alteration of 25-OHD, serum calcium, or iPTH was observed. In conclusion, Insulin resistance was improved, and bone turnover was activated one year after LSG in both groups, but the bone loss was more likely to occur in the obese patients with acanthosis nigricans. Disclosure Y. Zhang: None. Z. Zhang: None. C. Zhu: None. S. Sun: None. Y. Yin: None. R. Cui: None. H. Sheng: None. S. Qu: None.

Low serum osteocalcin concentration is associated with incident type 2 diabetes mellitus in Japanese women.

Increasing evidence suggests that osteocalcin is involved in the regulation of glucose homeostasis. However, the relationship between serum osteocalcin levels and risk of incident type 2 diabetes mellitus is not clear. The objective of this study is to investigate whether serum osteocalcin levels are associated with the risk of incident type 2 diabetes mellitus. This study included 1691 Japanese postmenopausal women, 61 incident diabetes cases, and 1630 non-diabetic control subjects in the observation period. Baseline concentrations of intact osteocalcin, HbA1c, bone-specific alkaline phosphatase, adiponectin, leptin, urinary N-telopeptides were assessed. Serum osteocalcin levels were significantly correlated with HbA1c levels among 1691 Japanese postmenopausal women (R=-0.12, P<0.0001). In receiver operating characteristic curve analysis, the optimal cut-off levels for serum osteocalcin to predict the development of type 2 diabetes mellitus was 6.1ng/mL. The group with baseline osteocalcin levels <6.1ng/mL showed a significantly higher risk for developing diabetes than the group with baseline osteocalcin levels >6.1ng/mL (log-rank test, P < 0.0001) during the mean observation period (7.6±6.1years; mean±SD). In multiple Cox proportional hazard analysis, osteocalcin levels were significantly associated with development of type 2 diabetes mellitus during the observation period. Our results indicate that a decrease in serum osteocalcin levels is associated with future development of type 2 diabetes mellitus independent of conventional risk factors in Japanese postmenopausal women.

Renal osteodystrophy in the obesity era: Is metabolic syndrome relevant?

BackgroundObservational studies have shown a beneficial effect of obesity on bone health; however, most of those studies were not based on bone biopsies. Metabolic syndrome (MetS) could have an effect on bone remodeling. However, there are no data on the effects of MetS in the presence of renal osteodystrophy.ObjectiveThe aim of this study was to investigate associations between MetS and renal osteodystrophy using the bone histomorphometric turnover-mineralization-volume (TMV) classification.Design, setting, participants & measurementsThis observational cross-sectional study included 55 hemodialysis patients (28 women/27 men) who were evaluated for MetS and bone histomorphometry. Biochemical parameters included calcium, phosphorus, alkaline phosphatase, intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, free serum leptin, fibroblast growth factor 23 (FGF23), intact osteocalcin, sclerostin (Scl), glucose, insulin, and thyroid hormones. Robust models of multivariate linear regressions were used for the statistical analyses.ResultsFemales had higher iPTH levels (1,143 vs. 358, p = 0.02). Patients with normal bone volume (BV/TV) had a higher prevalence of MetS (73.6% vs. 41.7%, p = 0.02) and higher serum phosphorus, C-terminal FGF23 and insulin levels. The multivariate regression analysis showed that low-density lipoprotein cholesterol (LDL) was positively correlated with bone formation rate (BFR/BS) and negatively associated with mineralization lag time. Bone volume was negatively associated with age but positively associated with MetS. Body mass index (BMI) was not correlated with any of the bone histomorphometric parameters.ConclusionOur results suggest that MetS is not a risk factor for low bone volume in hemodialysis patients. Furthermore, BMI alone was not related to bone volume in this population.

Evaluation of bone turnover markers and serum minerals variations for predicting fracture healing versus non-union processes in adult sheep as a model for orthopedic research

Bone turnover markers (BTMs) have been considered as an auxiliary method of following the fracture healing process and for early prediction of impaired bone healing. A better understanding of the potential of BTMs in this application could allow for earlier interventions and improved patient care. The aim of this study with a large animal experimental model was to assess the variation of bone formation markers − namely the total alkaline phosphatase (ALP) and its bone-specific isoform (BALP), serum concentration of intact osteocalcin (OC), N-terminal propeptide type III procollagen (PIIINP) and of bone resorption markers – namely tartrate resistant acid phosphatase (TRAP) and deoxypyridinoline crosslink (DPD) during the first stages of a normal fracture healing process and of a segmental critical size defect (CSD), which progresses to a non-union process. Thirty healthy female sheep (Portuguese Churra-da-Terra-Quente breed), approximately 4-years-old, were enrolled in this study. Jugular venous blood samples were collected pre-operatively and at 1, 2, 3, 4, 6, 8, 10 and 12 post-operative weeks. The animals of the CSD group showed significant lower serum levels of BALP, OC and significant higher serum PIIINP levels at early stages of the fracture healing process, compared with animals that progressed in a normal fracture healing process. Serum BALP, OC and PIIINP levels could be useful as non-invasive auxiliary tools with other complementary methods for predicting the outcome of traumatic bone fractures.

Predicting bone mineral acquisition during puberty: data from a 3-year follow-up study in Hamamatsu, Japan.

Although most adult bone mass is acquired before adolescence, only a few studies have assessed bone turnover markers in children. Thus, the utility of bone markers to evaluate and predict bone mineral accrual in children is unclear. The present study assessed the association between serum bone markers at 11years of age and subsequent changes in bone gain. Information on bone minerals and bone markers at baseline and at the 3-year follow-up were obtained from 121 children who registered as fifth-grade students in 2010, in Hamamatsu, Japan. Whole-body bone mineral content (WBBMC) and whole-body bone mineral density (WBBMD) were measured using dual-energy X-ray absorptiometry. Boys showed significant (P<0.05) positive relationships between intact osteocalcin at baseline and WBBMC at follow-up (β=0.24), between tartrate-resistant acid phosphatase isoenzyme 5b (TRAP5b) and WBBMC (β=0.34), and between TRAP5b and WBBMD (β=0.34), after adjusting for potential confounding factors. In girls, adjusted means of 3-year gain in both WBBMC and WBBMD significantly increased from the lowest to highest quartiles of type 1 collagen cross-linked C-terminal telopeptide. In boys, adjusted means of 3-year gain in both WBBMC and WBBMD significantly increased from the lowest to highest quartiles of TRAP5b. Children with a high concentration of bone turnover markers tended to exhibit substantial accrual of bone minerals. These results suggest that serum levels of circulating biomarkers at age 11 predict subsequent bone mineral accrual.

Carboxylated and intact osteocalcin predict adiponectin concentration in hemodialyzed patients

Purpose Disrupted bone metabolism in patients with chronic kidney disease (CKD) is associated with elevated concentrations of biochemical bone markers. Recently, animal studies show the role of osteocalcin in energy metabolism, which is partially confirmed in humans. The aim of our study was to evaluate the relationships between serum concentrations of bone markers and indices of energy metabolism in CKD patients on maintenance hemodialysis; in particular, the relationship between various forms of osteocalcin and adiponectin. Patients and methods The cross-sectional study included 155 hemodialyzed stage 5 CKD patients. Serum concentrations of glucose, insulin, adiponectin, bone alkaline phosphatase (bALP), tartrate resistant acid phosphatase (TRAP), carboxylated (cOC), undercarboxylated (ucOC), and intact osteocalcin (OC) were determined. Results In total cohort, bALP, TRAP, cOC, and ucOC negatively correlated with BMI. All analyzed bone markers positively correlated with adiponectin in total cohort and in men. In multiple linear regression analysis including all patients, log(cOC) and log(intact OC) were the only bone markers that predicted log(adiponectin) (beta = 0.22; p = 0.016 and beta = 0.26; p = 0.010) independently of sex, dialysis vintage, CRP, insulin, iPTH concentrations, BMI, and age. Conclusions Our data confirm the positive association between cOC, intact OC, and adiponectin concentrations in CKD patients on maintenance hemodialysis.

Comment on "Bone Regulates Glucose Metabolism as an Endocrine Organ through Osteocalcin".

While reading the insightful review of Shao et al. [1] on the effect of osteocalcin (OC) on glucose homeostasis, we came across a few lacunas which we want to fill up so as to generalise the osteocalcin concept. Firstly, Shao et al. reported that the concentration of uncarboxylated osteocalcin (ucOC) is controlled by decarboxylation of carboxylated osteocalcin (cOC), which is not true; it has been reported in the literature that during the bone resorption process initially a small fraction of intact OC is released in the acidic environment created by osteoclasts, which undergoes enzymatic proteolysis and subsequently excretion of OC fragments in urine. In the same research, researchers also prove that incubation of cOC in simulated osteoclastic lacuna medium (pH 4.8, 37°C) for 48 hours did not result in decarboxylation process and it requires heating of cOC at 110°C for 3 hours in HCl (50 mmol/L) to cause its decarboxylation [2]. Clearly, such conditions are not available in a physiological environment; therefore, the concept of decarboxylation from our point of view requires further investigation. Secondly, it is still a questionable fact that impairment in OC (any form) levels causes disturbance in glucose homeostasis because hyperglycemia, both in vitro [3] and clinically [4], is reported to cause impaired osteoblastic activity too. Therefore, whether OC imbalance causes impaired glucose homeostasis or vice versa is a matter of research. Thirdly, if as mentioned by Shao et al. ucOC is the only active form of OC, then supplementation of Vitamin K or various antiresorptive therapies (raloxifene, alendronate, and strontium) should theoretically increase risk of Type 2 Diabetes because they decrease the level of circulating OC (ucOC) but it is not the case [5–9]; rather, they are reported to decrease the risk of Type 2 Diabetes. Therefore, which form of osteocalcin is responsible for benefit in glucose homeostasis is not clear till now. Moreover, the presence of γ-glutamate carboxylase has been reported on osteoblasts [10], absence of which results in impaired glucose homeostasis, clearly indicating the protective role of Vitamin K (cofactor of γ-glutamate carboxylase) in maintaining glucose balance. Lastly, Shao et al. did not list the major difference in OC physiology in mice and humans, while extrapolating the benefits; for example, mice have three genes for OC while humans have only one gene and Vitamin D3 downregulates the OC expression in mice while it causes the opposite in humans [11, 12]. We appreciate the work of Shao et al., for their efforts to compile such a controversial topic, and we are looking forward to further research on this topic.

Osteocalcin and bone-specific alkaline phosphatase in Asian elephants (Elephas maximus) at different ages

Bone turnover markers could offer a potential alternative means for the early diagnosis of metabolic bone disease in young growing elephants although the baseline of bone turnover markers in elephant is not well established. The aim of this study was to determine any relationship between the age of captive Asian elephants (Elephas maximus) and markers of bone formation.Serum samples from 24 female Asian elephants were collected to evaluate levels of two bone formation markers, namely, osteocalcin (OC) and bone-specific alkaline phosphatase (BAP). Both intact and N-terminal midfragment OC and BAP were negatively correlated with age. The findings demonstrate that younger elephants have a higher rate of bone turnover than older elephants. Use of these and additional bone markers could lead to the establishment of validated protocols for the monitoring of bone disease in elephants.

Increased undercarboxylated osteocalcin/intact osteocalcin ratio in patients undergoing hemodialysis.

Serum undercarboxylated osteocalcin (ucOC)/intact osteocalcin (iOC) ratio increased >1.0 in the patients undergoing hemodialysis, particularly in those with high bone turnover state. Consequently, serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in hemodialysis patients. Serum intact osteocalcin (iOC), undercarboxylated OC (ucOC), and the ucOC/iOC ratio are considered clinically relevant indices in pre-dialysis chronic kidney disease (CKD) and hemodialysis (HD) patients, despite their accumulation in uremic serum. Serum iOC and ucOC were measured along with serum intact parathyroid hormone (iPTH), bone alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase (TRACP)-5b in 89 pre-dialysis CKD and 189 HD patients. Serum iOC and ucOC showed significantly negative correlations with estimated glomerular filtration rate in pre-dialysis CKD patients, although serum ucOC/iOC ratio did not correlate. Serum ucOC was significantly greater in HD patients than in pre-dialysis CKD patients, while serum iOC did not differ significantly, resulting in serum ucOC/iOC ratio >1.0 in 135 (71.4%) out of 189 HD patients. HD patients with high serum ucOC/iOC ratio (>1.0) had a significantly younger age and significantly higher values of body mass index, serum creatinine, albumin, phosphate, iPTH, and TRACP-5b than those with low ucOC/iOC ratio (≤ 1.0). The baseline iPTH and P1NP correlated with the changes of the ucOC/iOC ratio during the 2 days of the inter-dialytic period. Multivariate analysis showed that log [ucOC/iOC] in HD patients was significantly associated with log [iPTH], log [BAP], or log [TRACP-5b]. Serum ucOC/iOC ratio >1.0 was observed in as high as 71.4% of HD patients, preferentially with high bone turnover state, in comparison with pre-dialysis CKD patients. These data suggested that serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in HD patients.

Effects of gamma-glutamyl carboxylase gene polymorphism (R325Q) on the association between dietary vitamin K intake and gamma-carboxylation of osteocalcin in young adults.

It has been demonstrated that single nucleotide polymorphism (SNP) (R325Q, 974G>A) in the gamma-glutamyl carboxylase (GGCX) gene is associated with the bone mineral density (BMD). In the present study, we investigated the effect of GGCX polymorphism (974G>A) on the correlations among the vitamin K in-take, level of serum vitamin K, and ratio of undercarboxylated osteocalcin (ucOC) to intact osteocalcin (OC) in healthy young Japanese subjects. Healthy young adult subjects (n=189) were genotyped for the poly-morphism, and we measured the levels of serum vitamin K, intact OC, ucOC, and dietary nutrient intakes. Dietary vitamin K intake from vegetables was significantly correlated with the level of serum phylloquinone (PK), and vitamin K intake from fermented beans, natto, was also significantly correlated with the level of serum menaquinone-7 (MK-7). Moreover, the total dietary vitamin K intake showed a significant negative correlation with the ratio of ucOC to intact OC. Interestingly, on grouping by the GGCX genotype, there was a significant interaction between the ratio of ucOC to intact OC with vitamin K intake in homozygotes (GG-type) and heterozygotes (GA-type) (p<0.001). These results suggest that an adequate nutritional strategy is necessary for people with high-risk genotypes (GG- or GA-type). We demonstrated the effects of SNP (974G>A) in the GGCX gene on the correlation between dietary vitamin K intake and gamma-carboxylation of serum OC. Our data may be useful for planning strategies to prevent osteoporosis.

Low-dose hydrocortisone replacement therapy is associated with improved bone remodelling balance in hypopituitary male patients

Glucocorticoid (GC) therapy is associated with adverse effects on bone metabolism, yet the effects of different GC physiological replacement regimens in hypopituitarism are not well characterised. We aimed to assess the effect of three hydrocortisone (HC) replacement dose regimens on bone turnover. An open cross-over study randomising ten hypopituitary men with severe acth deficiency to three commonly used HC dose regimens: dose A (20 mg mane and 10 mg tarde), dose B (10 mg mane and 10 mg tarde) and dose C (10 mg mane and 5 mg tarde). Following 6 weeks of each regimen, the participants underwent 24-h serum cortisol sampling and measurement of bone turnover markers: bone-specific alkaline phosphatase, procollagen type I N-propeptide (PINP), intact osteocalcin (OC(1-49)), C-terminal cross-linking telopeptide (CTX-I) and tartrate-resistant acid phosphatase 5b (TRACP5b). Bone remodelling balance was estimated as an absolute ratio (PINP:CTX-I) and as an index using standardised scores derived from the matched controls. There were significant increases in the concentrations of the formation markers PINP (P=0.045) and OC(1-49) (P=0.006) and in the PINP:CTX-I ratio (P=0.015), and a more positive bone remodelling balance index (P=0.03) was observed in patients on the lowest dose C than in those on the highest dose A. Mean 24-h cortisol concentrations correlated negatively with CTX-I (r=-0.66 and P=0.04) and TRACP5b (r=-0.74 and P=0.01) in patients on dose B and with OC(1-49) (r=-0.66 and P=0.04) and CTX-I (r=-0.81 and P<0.01) in patients on dose C. In patients receiving the lower-dose regimen, trough cortisol concentrations correlated with increased bone formation and resorption. Low-dose HC replacement (10 mg mane and 5 mg tarde) is associated with increased bone formation and a positive bone remodelling balance. This may have a long-term beneficial effect on bone health.