Reduced serum osteocalcin concentrations are associated with type 2 diabetes mellitus and the metabolic syndrome components in postmenopausal women: the crosstalk between bone and energy metabolism

The role of bone in energy metabolism: A focus on osteocalcin

Understanding the mechanisms involved in whole body glucose regulation is key for the discovery of new treatments for type 2 diabetes (T2D). Historically, glucose regulation was largely focused on responses to insulin and glucagon. Impacts of incretin-based therapies, and importance of muscle mass, are also highly relevant. Recently, bone was recognized as an endocrine organ, with several bone proteins, known as osteokines, implicated in glucose metabolism through their effects on the liver, skeletal muscle, and adipose tissue. Research efforts mostly focused on osteocalcin (OC) as a leading example. This review will provide an overview on this role of bone by discussing bone turnover markers (BTMs), the receptor activator of nuclear factor kB ligand (RANKL), osteoprotegerin (OPG), sclerostin (SCL) and lipocalin 2 (LCN2), with a focus on OC. Since 2007, some, but not all, research using mostly OC genetically modified animal models suggested undercarboxylated (uc) OC acts as a hormone involved in energy metabolism. Most data generated from in vivo, ex vivo and in vitro models, indicate that exogenous ucOC administration improves whole-body and skeletal muscle glucose metabolism. Although data in humans are generally supportive, findings are often discordant likely due to methodological differences and observational nature of that research. Overall, evidence supports the concept that bone-derived factors are involved in energy metabolism, some having beneficial effects (ucOC, OPG) others negative (RANKL, SCL), with the role of some (LCN2, other BTMs) remaining unclear. Whether the effect of osteokines on glucose regulation is clinically significant and of therapeutic value for people with insulin resistance and T2D remains to be confirmed.

The effects of exenatide and insulin glargine treatments on bone turnover markers and bone mineral density in postmenopausal patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) related bone fracture. The effects of glucagon-like peptide-1 receptor analogs for the treatment of T2DM on bone are controversial in human studies. This study aimed to compare the effects of GLP-1 receptor analogs exenatide and insulin glargine treatment on bone turnover marker levels and bone mineral density (BMD) in postmenopausal female patients with T2DM. Thirty female patients with T2DM who were naive to insulin and incretin-based treatments, with spontaneous postmenopause, were randomized to exenatide or insulin glargine arms and were followed up for 24 weeks. BMD was evaluated using dual-energy X-ray absorptiometry and bone turnover markers by serum enzyme-linked immunosorbent assay. The body mass index significantly decreased in the exenatide group compared to the glargine group (P < .001). Receptor activator of nuclear factor kappa-B (RANK) and RANK ligand (RANKL) levels were significantly decreased with exenatide treatment (P = .009 and P = .015, respectively). Osteoprotegerin (OPG) level significantly increased with exenatide treatment (P = .02). OPG, RANK, RANKL levels did not change with insulin glargine treatment. No statistically significant difference was found between the pre- and posttreatment BMD, alkaline phosphatase, bone-specific alkaline phosphatase, and type 1 crosslinked N-telopeptide levels in both treatment arms. Despite significant weight loss with exenatide treatment, BMD did not decrease, OPG increased, and the resorption markers of RANK and RANKL decreased, which may reflect early antiresorptive effects of exenatide via the OPG/RANK/RANKL pathway.

Role of gender in explaining metabolic syndrome risk factors in an Iranian rural population using structural equation modelling

Many factors can lead to an increase in the prevalence of metabolic syndrome (MetS) in different populations. Using an advanced structural equation model (SEM), this study is aimed to determine the most important risk factors of MetS, as a continuous latent variable, using a large number of males and females. We also aimed to evaluate the interrelations among the associated factors involved in the development of MetS. This study used data derived from the Fasa PERSIAN cohort study, a branch of the PERSIAN cohort study, for participants aged 35 to 70 years with 10,138 males and females. SEM was used to evaluate the direct and indirect effects, as well as gender effects of influencing factors. Results from the SEM showed that in females most changes in MetS are described by waist circumference (WC), followed by hypertension (HP) and triglyceride (TG), while in males most changes in MetS are described by WC, followed by TG then fasting blood glucose (FBG). Results from the SEM confirmed the gender effects of social status on MetS, mediated by sleep and controlled by age, BMI, ethnicity and physical activity. This study also shows that the integration of TG and WC within genders could be useful as a screening criterion for MetS in our study population.

Diabetes Mellitus Type 2 Patients with Abdominal Obesity Are Prone to Osteodysfunction: A Cross-Sectional Study

Introduction

The interaction between diabetes, obesity, and bone metabolism was drawing increasing public attention. However, the osteometabolic changes in diabetes mellitus type 2 (T2DM) patients with abdominal obesity have not been fully revealed. This study is aimed at investigating the association between abdominal obesity indices and bone turnover markers among T2DM participants.

Methods

4351 subjects were involved in the METAL study. Abdominal obesity indices included neck, waist, and hip circumference, visceral adiposity index (VAI), lipid accumulation product (LAP), waist-to-hip ratio (WHR), and Chinese visceral adiposity index (CVAI). They were applied to elucidate the nexus between β-C-terminal telopeptide (β-CTX), osteocalcin (OC), and intact N-terminal propeptide of type I collagen (P1NP).

Results

Abdominal obesity indices were strongly negatively associated with β-CTX and OC. Among males, five indices were negatively correlated with β-CTX (BMI, WC, LAP, WHR, and CVAI) and OC (BMI, NC, WC, WHR, and CVAI). There were no significant associations with P1NP. Among females, all eight indices were negatively associated with β-CTX. Seven indices were negatively related to OC (BMI, NC, WC, HC, LAP, WHR, and CVAI). The VAI was negatively correlated with P1NP.

Conclusions

The present study demonstrated that in T2DM, abdominal obesity had an obviously negative correlation with bone metabolism. Abdominal obesity indices were significantly negatively associated with skeletal destruction (β-CTX) and formation (OC). In routine clinical practice, these easily obtained indices could be used as a preliminary screening method and relevant factors for osteodysfunction incidence risk at no additional cost and may be of particular value for postmenopausal women in T2DM populations.

Undercarboxylated Osteocalcin: A Promising Target for Early Diagnosis of Cardiovascular and Glycemic Disorders in Patients with Metabolic Syndrome: A Pilot Study

Lifestyle changes are causing an exponential increase in the prevalence of obesity and metabolic syndrome (MetS) worldwide. The most frequent complications of these are the development of diabetes (T2D) and cardiovascular disease (CVD). Accurate tools are needed to classify the cardiovascular risk (CVR) in the MetS population. In recent years, numerous biomarkers of bone metabolism have been associated with CVR. The aim of this study was to determine the levels of undercarboxylated osteocalcin (ucOC) in a cohort of patients with MetS and to analyse its association with MetS parameters and CVR as well as with T2D prevalence. A longitudinal study was conducted in which a MetS population was followed for one year. Weight change, adherence to the Mediterranean diet (MedDiet), ucOC levels, MetS parameters and CVR were analysed and CVR was calculated using different scores. Our results showed a decrease of CVR associated with a better adherence to the MetDiet resulting in higher HDL-C and ucOC levels though the improvement of MetS risk factors. This bone protein appeared as a potential biomarker to classify CVR in the MetS population, especially for MetS patients without prevalent T2D. Furthermore, ucOC serum levels could be good predictors of T2D prevalence.

No Evidence of Association Between Undercarboxylated Osteocalcin and Incident Type 2 Diabetes

Mouse models suggest that undercarboxylated osteocalcin (ucOC), produced by the skeleton, protects against type 2 diabetes development, whereas human studies have been inconclusive. We aimed to determine if ucOC or total OC is associated with incident type 2 diabetes or changes in fasting glucose, insulin resistance (HOMA-IR), or beta-cell function (HOMA-Beta). A subcohort (n = 338; 50% women; 36% black) was identified from participants without diabetes at baseline in the Health, Aging, and Body Composition Study. Cases of incident type 2 diabetes (n = 137) were defined as self-report at an annual follow-up visit, use of diabetes medication, or elevated fasting glucose during 8 years of follow-up. ucOC and total OC were measured in baseline serum. Using a case-cohort design, the association between biomarkers and incident type 2 diabetes was assessed using robust weighted Cox regression. In the subcohort, linear regression models analyzed the associations between biomarkers and changes in fasting glucose, HOMA-IR, and HOMA-Beta over 9 years. Higher levels of ucOC were not statistically associated with increased risk of incident type 2 diabetes (adjusted hazard ratio = 1.06 [95% confidence interval, 0.84-1.34] per 1 standard deviation [SD] increase in ucOC). Results for %ucOC and total OC were similar. Adjusted associations of ucOC, %ucOC, and total OC with changes in fasting glucose, HOMA-IR, and HOMA-Beta were modest and not statistically significant. We did not find evidence of an association of baseline undercarboxylated or total osteocalcin with risk of incident type 2 diabetes or with changes in glucose metabolism in older adults. © 2022 American Society for Bone and Mineral Research (ASBMR).

Thyroid and bone turnover markers in type 2 diabetes: results from the METAL study

OBJECTIVE

We aimed to evaluate whether thyroid hormones, autoimmune and thyroid homeostasis status were related to bone turnover in type 2 diabetes.

METHODS

The data were obtained from a cross-sectional study, the METAL study. In this study, 4209 participants (2059 men and 2150 postmenopausal women) with type 2 diabetes were enrolled. Thyroid function, thyroid antibodies and three bone turnover markers (BTMs), including a large N-mid fragment of osteocalcin (N-MID osteocalcin), β-C-terminal cross-linked telopeptides of type I collagen (β-CTX) and procollagen type I N-terminal propeptide (P1NP), were measured. Thyroid homeostasis parameters, including the sum activity of step-up deiodinases (SPINA-GD), thyroid secretory capacity (SPINA-GT), Jostel's TSH index (TSHI) and the thyrotroph thyroid hormone resistance index (TTSI), were calculated. The associations of thyroid parameters with BTMs were analyzed using linear regression.

RESULTS

Free and total triiodothyronine were positively associated with N-MID osteocalcin and P1NP in both sexes and positively associated with β-CTX in postmenopausal women. Thyroid-stimulating hormone was negatively associated with β-CTX in postmenopausal women, and free thyroxine was negatively associated with N-MID osteocalcin and P1NP in men. SPINA-GD was positively associated with N-MID osteocalcin and P1NP in both sexes. There was a positive relationship of SPINA-GT with β-CTX, a negative relationship of TTSI with β-CTX, and a negative relationship of TSHI with β-CTX and P1NP in postmenopausal women.

CONCLUSIONS

Among men and postmenopausal women with type 2 diabetes, significant associations were observed between N-MID osteocalcin, β-CTX and P1NP with thyroid function and thyroid homeostasis. Further prospective studies are warranted to understand the causal relationship and underlying mechanism.

The role of osteocalcin in regulation of glycolipid metabolism and muscle function in children with osteogenesis imperfecta

OBJECTIVE

Osteoblasts are discovered to secrete hormones with endocrine effects on metabolism, and osteocalcin (OC) is the most abundant non-collagenous protein in bone. We investigate the relationship between serum OC levels and glycolipid metabolism and muscle function in children with osteogenesis imperfecta (OI).

METHODS

A total of 225 children with OI and 80 healthy controls matched in age and gender were included in this single center study. Serum levels of fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), low- and high-density lipoprotein cholesterol (LDL-C, HDL-C) were measured by automated analyzers. Serum levels of fasting insulin (FINS) were measured using an automated electrochemiluminescence system. Serum levels of OC and undercarboxylated osteocalcin (ucOC) were measured by enzyme-linked immunosorbent assay. Grip strength and timed-up-and-go (TUG) test were measured. Bone mineral density (BMD) and body composition were measured using dual-energy X-ray absorptiometry.

RESULTS

OI patients had significantly higher body mass index (BMI), FBG, and HOMA-IR, but lower HDL-C levels, lower grip strength and longer TUG than control group (all P<0.05). Serum OC, ucOC levels, and ucOC/OC in OI type III patients were significantly lower than those in OI patients with type I and IV. Serum levels of OC, ucOC, and ucOC/OC were negatively correlated to BMI, FBG, insulin levels, and HOMA-IR (all P<0.05). The ratio of ucOC/OC was positively correlated to grip strength (r=0.512, P=0.036), lean mass percentage (%LM) of the total body and limbs, and negatively correlated to fat mass percentage (%FM) of the total body, %FM and fat mass index (FMI) of the trunk (all P<0.05).

CONCLUSIONS

Obesity, glucolipid metabolic abnormalities, and reduced grip strength were common in children with OI. Circulating osteocalcin and ucOC may play an important role in the regulation of glucose metabolism, as well as the muscle function of children with OI.

Osteocalcin Is Independently Associated with C-Reactive Protein during Lifestyle-Induced Weight Loss in Metabolic Syndrome

Bone-derived osteocalcin has been suggested to be a metabolic regulator. To scrutinize the relation between osteocalcin and peripheral insulin sensitivity, we analyzed changes in serum osteocalcin relative to changes in insulin sensitivity, low-grade inflammation, and bone mineral density following lifestyle-induced weight loss in individuals with metabolic syndrome (MetS). Participants with MetS were randomized to a weight loss program or to a control group. Before and after the 6-month intervention period, clinical and laboratory parameters and serum osteocalcin levels were determined. Changes in body composition were analyzed by dual-energy X-ray absorptiometry (DXA). In participants of the intervention group, weight loss resulted in improved insulin sensitivity and amelioration of inflammation. Increased serum levels of osteocalcin correlated inversely with BMI (r = −0.63; p< 0.001), total fat mass (r = −0.58, p < 0.001), total lean mass (r = −0.45, p < 0.001), C-reactive protein (CRP) (r = −0.37; p < 0.01), insulin (r = −0.4; p < 0.001), leptin (r = −0.53; p < 0.001), triglycerides (r = −0.42; p < 0.001), and alanine aminotransferase (ALAT) (r = −0.52; p < 0.001). Regression analysis revealed that osteocalcin was independently associated with changes in CRP but not with changes in insulin concentration, fat mass, or bone mineral density, suggesting that weight loss-induced higher serum osteocalcin is primarily associated with reduced inflammation.

Disentangling the relationship between bone turnover and glucose homeostasis: A prospective, population-based twin study

Background

Biochemical markers of bone turnover are lower in patients with type 2 diabetes, which may be explained by genetic variants being associated with type 2 diabetes and bone turnover as well as environmental factors. We hypothesized that bone turnover markers associate with and predict changes in glucose homeostasis after control for genetics and shared environment.

Methods

1071 healthy, non-diabetic (at baseline, 1997-2000) adult mono- and dizygotic twins participating in the prospective study GEMINAKAR were reassessed between 2010 and 2012 with clinical evaluation, biochemical tests and oral glucose tolerance test. Fasting bone turnover markers (CTX, P1NP and osteocalcin) were measured. The association between bone turnover, glucose homeostasis and the ability of bone turnover markers to predict changes in glucose homeostasis were assessed in cross-sectional and longitudinal analyses. Analyses were performed both at an individual level and adjusted for shared environmental and genetic factors.

Results

Glucose levels increased with age, and 33 (3%) participants had developed type 2 diabetes at follow-up. In women, bone turnover markers increased with age, whereas for men only osteocalcin increased with age. Bone turnover markers were not associated with fasting glucose, insulin, or HOMA-IR at baseline or follow-up before or after adjustment for age, sex, BMI, smoking, and use of medication at baseline. Variation in bone turnover markers was mainly explained by unique environmental factors, 70%, 70% and 55% for CTX, P1NP and osteocalcin, respectively, whereas additive genetic factors explained 7%, 13% and 45% of the variation in CTX, P1NP and osteocalcin.

Conclusions

Bone turnover markers were not associated with baseline plasma glucose levels and did not predict changes in glucose homeostasis. Variation in bone turnover markers is mainly explained by environmental factors, however, compared to CTX and P1NP, genetic factors have a larger impact on osteocalcin levels.

Bone Turnover Markers Do Not Predict Fracture Risk in Type 2 Diabetes

Type 2 diabetes (T2D) is characterized by increased fracture risk despite higher BMD and reduced bone turnover. BMD underestimates fracture risk in T2D, but the predictive role of bone turnover markers (BTMs) on fracture risk in T2D has not been explored. Thus, we sought to determine whether BTMs predict incident fractures in subjects with T2D. For this case-cohort study, we used data from the Health, Aging, and Body Composition (Health ABC) Study of well-functioning older adults, aged 70 to 79 years at baseline (April 1997-June 1998). The case-cohort sample consisted of (i) the cases, composed of all 223 participants who experienced incident fractures of the hip, clinical spine, or distal forearm within the first 9 years of study follow-up; and (ii) the subcohort of 508 randomly sampled participants from three strata at baseline (T2D, prediabetes, and normoglycemia) from the entire Health ABC cohort. A total of 690 subjects (223 cases, of whom 41 were in the subcohort) were included in analyses. BTMs (C-terminal telopeptide of type I collagen [CTX], osteocalcin [OC], and procollagen type 1 N-terminal propeptide [P1NP]) were measured in archived baseline serum. Cox regression with robust variance estimation was used to estimate the adjusted hazard ratio (HR) for fracture per 20% increase in BTMs. In nondiabetes (prediabetes plus normoglycemia), fracture risk was increased with higher CTX (HR 1.10; 95% confidence interval [CI], 1.01 to 1.20 for each 20% increase in CTX). Risk was not increased in T2D (HR 0.92; 95% CI, 0.81 to 1.04; p for interaction .045). Similarly, both OC and P1NP were associated with higher risk of fracture in nondiabetes, but not in T2D, with p for interaction of .078 and .109, respectively. In conclusion, BTMs did not predict incident fracture risk in T2D but were modestly associated with fracture risk in nondiabetes. © 2020 American Society for Bone and Mineral Research.

What is the function of osteocalcin?

BACKGROUND

Osteocalcin is the most abundant non-collagenous protein in bone and is specifically expressed in osteoblasts. Previous studies using osteocalcin-deficient (Ocn^-/-) mice demonstrated that osteocalcin inhibits bone formation, and serum uncarboxylated osteocalcin functions as a hormone that improves glucose metabolism, induces testosterone synthesis in the testes, and maintains muscle mass. Furthermore, the relationship between serum osteocalcin and glucose metabolism or cardiovascular risk in humans has been reported. However, new Ocn^-/- mice exhibited different phenotypes.

HIGHLIGHT

Bone volume, formation, and resorption were normal in the new Ocn^-/- mice. The orientation of collagen fibers was parallel to the bone longitudinal direction and the size of apatite crystals was normal, but the c-axis of apatite crystals was random and bone strength was reduced in new Ocn^-/- mice. Glucose metabolism, testosterone synthesis, and muscle mass were normal in new Ocn^-/- mice. Exercise improved glucose metabolism and increased bone formation, leading to an increase in the serum osteocalcin level, which is a marker for bone formation.

CONCLUSION

Contrary to previous findings, new Ocn^-/- mice revealed that osteocalcin has no function in the regulation of bone quantity, but instead, functions to direct the parallel alignment of the c-axis of apatite crystals with collagen fibrils. Moreover, it has no physiological function as a hormone that regulates glucose metabolism, testosterone synthesis, or muscle mass. These controversial phenotypes require further investigation. The relationship of serum osteocalcin with glucose metabolism or cardiovascular risk suggests the importance of exercise for their improvement.

Osteocalcin is necessary for the alignment of apatite crystallites, but not glucose metabolism, testosterone synthesis, or muscle mass

The strength of bone depends on bone quantity and quality. Osteocalcin (Ocn) is the most abundant noncollagenous protein in bone and is produced by osteoblasts. It has been previously claimed that Ocn inhibits bone formation and also functions as a hormone to regulate insulin secretion in the pancreas, testosterone synthesis in the testes, and muscle mass. We generated Ocn-deficient (Ocn^–/–) mice by deleting Bglap and Bglap2. Analysis of Ocn^–/–mice revealed that Ocn is not involved in the regulation of bone quantity, glucose metabolism, testosterone synthesis, or muscle mass. The orientation degree of collagen fibrils and size of biological apatite (BAp) crystallites in the c-axis were normal in the Ocn^–/–bone. However, the crystallographic orientation of the BAp c-axis, which is normally parallel to collagen fibrils, was severely disrupted, resulting in reduced bone strength. These results demonstrate that Ocn is required for bone quality and strength by adjusting the alignment of BAp crystallites parallel to collagen fibrils; but it does not function as a hormone.

The strength of bone depends on both its quantity and quality. Osteocalcin (Ocn) is the most abundant non-collagenous protein in bone, but its function remains unclear. Earlier studies by other investigators have suggested that Ocn decreases the quantity of bone by decreasing bone formation; and in addition it works as a hormone to regulate glucose metabolism, testosterone synthesis, and muscle mass in distant tissues. We have generated Ocn-deficient mice and show herein that Ocn is not required for bone formation. It is, however, required for optimal bone quality and strength. Specifically, we show that in the Ocn-deficient mice collagen fibers align normally, but apatite crystallites align randomly against collagen, resulting in disorganized mineralization and reduced bone strength. Furthermore, we show that glucose metabolism, testosterone synthesis, and muscle mass are normal in the Ocn-deficient mice. We conclude that Ocn acts in bone to optimize its quality and strength, but not quantity. And, in contrast to earlier claims, it does not work as a hormone to control glucose metabolism, testosterone synthesis, and muscle mass.

Circulating Undercarboxylated Osteocalcin as Estimator of Cardiovascular and Type 2 Diabetes Risk in Metabolic Syndrome Patients

Undercarboxylated osteocalcin (ucOC) could be a biomarker of glucose disturbances and cardiovascular risk. Our study aimed to determine the association between serum levels of ucOC and cardiovascular risk in metabolic syndrome (MetS) patients and to analyse its potential role as estimator of type 2 diabetes (T2D) risk in this population. This cross-sectional study included 235 patients with MetS, 53.2% women, aged 55–75 years. Circulating ucOC levels were measured by ELISA. Cardiovascular risk was determined as Z-score of the diagnostic criteria for MetS (CV-ZS). Linear regression model was performed to analyse the association between circulating ucOC and CV-ZS. A receiver operating curve (ROC) was performed to analyse the usefulness of ucOC as T2D risk estimator. Patients above the CV-ZS median showed significant lower ucOC levels. We found an inverse association between ucOC levels and CV-ZS in MetS patients without T2D. Patients with ucOC levels below the 25^th percentile showed worse cardiometabolic profile and higher cardiovascular and T2D risk. The area under the curve performed better when ucOC levels were included along with the classic T2D risk factors. The measurement of circulating ucOC could be a useful tool to identify increased cardiovascular and T2D risk in MetS patients without T2D.

Bone health in diabetes and prediabetes

Bone fragility has been recognized as a complication of diabetes, both type 1 diabetes (T1D) and type 2 diabetes (T2D), whereas the relationship between prediabetes and fracture risk is less clear. Fractures can deeply impact a diabetic patient's quality of life. However, the mechanisms underlying bone fragility in diabetes are complex and have not been fully elucidated. Patients with T1D generally exhibit low bone mineral density (BMD), although the relatively small reduction in BMD does not entirely explain the increase in fracture risk. On the contrary, patients with T2D or prediabetes have normal or even higher BMD as compared with healthy subjects. These observations suggest that factors other than bone mass may influence fracture risk. Some of these factors have been identified, including disease duration, poor glycemic control, presence of diabetes complications, and certain antidiabetic drugs. Nevertheless, currently available tools for the prediction of risk inadequately capture diabetic patients at increased risk of fracture. Aim of this review is to provide a comprehensive overview of bone health and the mechanisms responsible for increased susceptibility to fracture across the spectrum of glycemic status, spanning from insulin resistance to overt forms of diabetes. The management of bone fragility in diabetic patient is also discussed.

Prevalence of metabolic syndrome in Iran: A meta-analysis of 69 studies

AIMS

Metabolic syndrome increases the risk of chronic diseases including cardiovascular diseases and diabetes. The present study investigated the prevalence of metabolic syndrome in Iran.

MATERIALS AND METHODS

Published articles in English and Persian during 2000-2016 identified using keywords of prevalence, metabolic syndrome, and Iran in the following databases: Web of Science, PubMed, Scopus, Google scholar, SID and Magiran. Random effect model used to calculate the pooled estimates. Heterogeneity of studies assessed using Q statistic, and geographical distribution of metabolic syndrome demonstrated via GIS map. Data were analyzed by STATA-11.

RESULTS

The overall prevalence of metabolic syndrome was 30.4% (95%CI: 28.3-32.6) with no significant heterogeneity by diagnostic criteria. The lowest frequency was reported in Sistan and Baluchestan Province [18.3% (95% CI: 12.9-25.8)] compared to the highest in Bushehr [57.8% (95% CI: 41.8-80.0)]. It was significantly more prevalent in women [(34.8% (95%CI: 31.2-38.8)] compared to men [25.7% (95%CI: 23.4-28.3)] (P = 0.001)]. A significant increasing trend (P = 0.001) was observed in different age groups, as metabolic syndrome increased from 12.1% (95% CI: 9.37-15.6) in 20-29 years-old age group to 51.7% (95%CI: 47.4-56.4) in the over 60 years-old age group.

CONCLUSIONS

Approximately one-third of Iranian adults have metabolic syndrome which varied by regions, age and gender. Then, appropriate intervention based on behavioral patterns of inhabitants and local conditions may help to reduce the burden of disease.

Association of body mass index and waist circumference with osteocalcin and C-terminal telopeptide in Iranian elderly: results from a cross-sectional study

There is no agreement on the role of obesity as a protection or unfavorable factor on bone. In the present study, the association of body mass index (BMI) and waist circumference (WC) with osteocalcin, C-terminal telopeptide of type 1 collagen (CTX-I), highly sensitive C-reactive protein (hs-CRP), parathormon (PTH) and 25-hydroxyvitamin D (25(OH)D) in elderly people was investigated. This cross-sectional study was conducted on 178 elderly residents in Tehran, with a mean age of 67.04 (60-83). Serum osteocalcin, hs-CRP, 25(OH) D, PTH and urine CTX-I were measured for all participants. Waist circumference, weight and height were measured and BMI was calculated. Linear regression and Pearson correlation were performed to evaluate the relation of BMI and waist circumference with other variables. A significant inverse association was found between BMI with osteocalcin (β = - 0.171, p = 0.027) after control for covariates. In addition, there were a significant relation of BMI and WC with hs-CRP (β = 0.246, p = 0.002 and β = 0.219, p = 0.006, respectively) and PTH (β = 0.1169, p = 0.040 and β = 0.200, p = 0.018), respectively. The present study did not show a significant relation of BMI and WC with urine CTX-I even after adjustment for potential confounders (β = - 0.143, p = 0.065 and β = - 0.104, p = 0.183, respectively). The present study has concluded that obesity is an undesirable factor for bone metabolism by reducing serum osteocalcin and by increasing hs-CRP and PTH which contribute to bone resorption.

Metformin; an old antidiabetic drug with new potentials in bone disorders

The prevalence of diabetes mellitus especially type 2 diabetes mellitus is increasing all over the world. In addition to cardiomyopathy and nephropathy, diabetics are at higher risk of mortality and morbidity due to greater risk of bone fractures and skeletal abnormalities. Patients with diabetes mellitus have lower bone quality in comparison to their non-diabetic counterparts mainly because of hyperglycemia, toxic effects of advanced glycosylation end-products (AGEs) on bone tissue, and impaired bone microvascular system. AGEs may also contribute to the development of osteoarthritis further to osteoporosis. Therefore, glycemic control in diabetic patients is vital for bone health. Metformin, a widely used antidiabetic drug, has been shown to improve bone quality and decrease the risk of fractures in patients with diabetes in addition to glycemic control and improving insulin sensitivity. AMP activated protein kinase (AMPK), the key molecule in metformin antidiabetic mechanism of action, is also effective in signaling pathways involved in bone physiology. This review, discusses the molecules linking diabetes and bone turnover, role of AMPK in bone metabolism, and the effect of metformin as an activator of AMPK on bone disorders and malignancies.

The prevalence of metabolic syndrome in postmenopausal women: A systematic review and meta-analysis in Iran

Metabolic syndrome is a set of cardiovascular risk factors that increase the risk of cardiovascular disease, diabetes and mortality. Women are at risk of developing metabolic syndrome as they enter the postmenopausal period. The present systematic review and meta-analysis was conducted to estimate the prevalence of metabolic syndrome in Iranian postmenopausal women. In this systematic review and meta-analysis, 16 national articles published in Persian and English were gathered without time limit. National databases such as SIDs, IranMedex and MagIran, and international databases such as Web of Science, Google Scholar, PubMed and Scopus were used to search the relevant studies. We searched for articles using the keywords "menopause", "postmenopausal", "metabolic syndrome", "MetSyn", and their combinations. Data were analyzed using the meta-analysis method and the random effects model. Analysis of 16 selected articles with a sample size of 5893 people showed that the prevalence of metabolic syndrome in Iranian postmenopausal women was 51.6% (95% CI: 43-60). The prevalence of metabolic syndrome based on ATP III and IDF criteria was 54% (95% CI: 59-63) and 50% (95% CI: 45-56), respectively. Based on the results of univariate meta-regression analysis, the increase in the mean age of postmenopausal women (p = 0.001) and sample size (p = 0.029), the prevalence of metabolic syndrome increased significantly. More than half of postmenopausal women in Iran suffer from metabolic syndrome. Providing training programs for postmenopausal women to prevent and control cardiovascular disease and its complications seems to be necessary.

Assessment of bone quality in patients with diabetes mellitus

Substantial evidence exists that diabetes mellitus is associated with an increased risk of osteoporotic fractures. Low bone strength as well as bone extrinsic factors are probably contributing to the increased bone fragility in diabetes. Bone density and quality are important determinants of bone strength. Although bone mineral density (BMD) and the fracture risk assessment tool (FRAX) are very useful clinical tools in assessing bone strength, they may underestimate the fracture risk in diabetes mellitus. Through advances in new technologies such as trabecular bone score (TBS) and peripheral quantitative computed tomography (pQCT), we can better assess the bone quality and fracture risk of patients with diabetes mellitus. Invasive assessments such as microindentation and histomorphometry have been great complement to the existing bone analysis techniques. Bone turnover markers have been found to be altered in diabetes mellitus patients and may be associated with fractures. This review will give a brief summary of the current development and clinical uses of these assessments.

Undercarboxylated Osteocalcin: Experimental and Human Evidence for a Role in Glucose Homeostasis and Muscle Regulation of Insulin Sensitivity

Recent advances have indicated that osteocalcin, and in particular its undercarboxylated form (ucOC), is not only a nutritional biomarker reflective of vitamin K status and an indicator of bone health but also an active hormone that mediates glucose metabolism in experimental studies. This work has been supported by the putative identification of G protein-coupled receptor, class C, group 6, member A (GPRC6A) as a cell surface receptor for ucOC. Of note, ucOC has been associated with diabetes and with cardiovascular risk in epidemiological studies, consistent with a pathophysiological role for ucOC in vivo. Limitations of existing knowledge include uncertainty regarding the underlying mechanisms by which ucOC interacts with GPRC6A to modulate metabolic and cardiovascular outcomes, technical issues with commonly used assays for ucOC in serum, and a paucity of clinical trials to prove causation and illuminate the scope for novel health interventions. A key emerging area of research is the role of ucOC in relation to expression of GPRC6A in muscle, and whether exercise interventions may modulate metabolic outcomes favorably in part via ucOC. Further research is warranted to clarify potential direct and indirect roles for ucOC in human health and cardiometabolic diseases.

Glycemic Control and Bone Turnover in Older Mexican Americans with Type 2 Diabetes

Altered bone quality, caused by underlying metabolic changes of type 2 diabetes (T2D), has been hypothesized to cause altered bone strength and turnover leading to increased fracture risk in T2D patients. Current understanding about changes in bone turnover markers in T2D patients is mainly based on studies focused on Caucasian men and women. However, Hispanic populations have the highest prevalence of both T2D and osteoporosis in the US. We investigated associations of glycemic control (in terms of glycated hemoglobin [HbA1c]) and bone turnover rate in 69 older (≥50 years) Mexican American Cameron County Hispanic Cohort (CCHC) participants with T2D. Multivariable analyses were conducted to assess the associations between HbA1c (%), serum osteocalcin (OC), and serum sclerostin. In agreement with published reports from other racial/ethnic populations, our study found that lower bone turnover (indicated by lower serum OC) occurred in Mexican American men with T2D who had poorer glycemic control. For the women in our study, we found no significant association between glycemic control and OC. In contrast, HbA1c was positively associated with sclerostin for women, with near significance (p = 0.07), while no association was found in men. We recommend screening Mexican American individuals with T2D, specifically those with poor glycemic control, for bone loss and fracture risk.

Insulin resistance and bone: a biological partnership

Despite a clear association between type 2 diabetes (T2D) and fracture risk, the pathogenesis of bone fragility in T2D has not been clearly elucidated. Insulin resistance is the primary defect in T2D. Insulin signalling regulates both bone formation and bone resorption, but whether insulin resistance can affect bone has not been established. On the other hand, evidence exists that bone might play a role in the regulation of glucose metabolism. This article reviews the available experimental and clinical evidence on the interplay between bone and insulin resistance. Interestingly, a bilateral relationship between bone and insulin resistance seems to exist that unites them in a biological partnership.

Biochemical relationships between bone turnover markers and blood glucose in patients with type 2 diabetes mellitus

INTRODUCTION

Patients with type 2 diabetes mellitus develop many complications including osteopenia, which is associated with high fracture risk. Osteocalcin is a non collagenous protein derived from the osteoblasts. Recently, it was found that osteocalcin enhances the pancreatic beta cell proliferation, insulin secretion and protection against type 2 diabetes.

OBJECTIVE

Investigation of the association of serum osteocalcin and other bone turnover markers with blood glucose level and diabetes mellitus duration in type 2 diabetic patients.

SUBJECTS AND METHODS

Twenty diagnosed type 2 diabetic patients together with 20 healthy controls were enrolled in this study. Serum osteocalcin, alkaline phosphatase activity and calcium concentrations were measured by commercial ELISA kits.

RESULTS

The results showed that type 2 diabetic patients exhibited a significantly lower serum osteocalcin and calcium (p=0.0001 and 0.002 respectively) and a higher alkaline phosphatase (p=0.008) compared to the controls. Multiple linear regression analysis revealed that serum osteocalcin was inversely associated with fasting blood glucose and Diabetes Mellitus duration (β=- 0.018; p=0.007 and β=- 0.085; p=0.014 respectively) in Type 2 diabetic patients. In addition, alkaline phosphatase was positively associated (β=0.828; p=0.015) while serum calcium was negatively associated (β=- 0.046; p=0.048) with Diabetes Mellitus duration.

CONCLUSION

These results refer to the strong association between diabetes and bone turnover markers and call for monitoring of diabetes-associated osteopenia in type 2 diabetic patients.

Prevalence of metabolic syndrome in Iran: A meta-analysis

Background

Metabolic syndrome) MetS( is a complex risk factor which increases the risk of cardiovascular diseases and type 2 diabetes. There are many studies with various populations and results about the prevalence of MetS in Iran; in order to authenticate these studies and have an overall estimation of its prevalence in Iran, performing a meta-analysis seems to be necessary.

Objective

This study aimed to investigate the prevalence of MetS and its components in Iran via meta-analysis method.

Methods

All associated published papers in national and international journals of PubMed, Scopus, Web of Science, Magiran, Iranmedex, Science Direct, Medlib, and SID databases were searched from January, 2000 to October, 2016. All types of studies, including local and national surveys that reported the prevalence of MetS among healthy populations in Iran were reviewed. The effects of age, sample size and publication date as possible sources of heterogeneity among the study findings was examined by meta-regression. P-values less than 0.05 were considered as significant in heterogeneity tests. All analysis was done by R Ver. 3.2.1 and STATA (version 10).

Results

Seventy eligible studies were selected for meta-analysis. The overall estimation of MetS prevalence was 25% (95% CI: 22-29%) based on the Adult Treatment Panel III (ATP III) criteria, 30% (95% CI: 25-36%) according to the International Diabetes Federation (IDF), and 39% (95% CI: 26-52%) based on the Joint Interim Societies (JIS) criteria. The prevalence of MetS was lower in men than in women (26.9% versus 35.7%). The prevalence of various MetS components including High TG (triglyceride), Low HDL-C, High BP and High FBS (fasting blood sugar) was 43%, 54%, 38% and 22% among the adult population.

Conclusion

Findings from the present meta-analyses study displayed a high prevalence of metabolic syndrome in Iran, especially in women, which increases with age in both sexes. It alerts health care providers and policy makers to find solutions in order to take action to reduce MetS risk in society.

Bone Metabolism and Fracture Risk in Diabetes Mellitus

Individuals with Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are at increased risk for fragility fractures. Bone mineral density (BMD) is decreased in T1DM but often normal or even elevated in T2DM when compared with age-matched non-DM populations. However, bone turnover is decreased in both T1DM and T2DM. The pathophysiologic mechanisms leading to bone fragility is multifactorial, and potentially leads to reduced bone formation, altered bone microstructure and decreased bone strength. Interestingly, different antidiabetic treatments may influence fracture risk due to effects on glycemic control, triggering of hypoglycemic events or osteoblastogenesis.

Association between serum osteocalcin and body mass index: a systematic review and meta-analysis

PURPOSE

Osteocalcin is considered as a bone-derived hormone affecting on the body fat distribution and body mass index. Several cross-sectional studies have investigated the association between serum osteocalcin and body mass index. The aim of this study was to summarize the evidence on the relationship between serum osteocalcin and body mass index.

METHODS

We conducted a complete search up to November 2016 in PubMed and SCOPUS and reviewed reference list of all relevant articles and reviews. The DerSimonian-Laird method were used to pool effect sizes of eligible studies. The potential sources of heterogeneity were assessed using the standard χ ² test.To find possible the sources of between-study heterogeneity, we carried out subgroup analyses based on sex, and type of study population.

RESULTS

There was a significant inverse association in the overall result of this study between serum osteocalcin levels and BMI(r = -0.161; 95% CI: -0.197, -0.124, p < 0.000). In the subgroup analysis to find the sources of significant heterogeneity between-study, we observed that the type of the study population may be the source of between-study heterogeneity and the most correlation was seen in metabolic syndrome studies (r = -0.265; p = 0.000).

CONCLUSION

Findings from the available data indicated an overall significant inverse association between serum osteocalcin and body mass index. Further studies based on the type of study population are needed to better clarify these associations.

Association between osteocalcin gamma-carboxylation and insulin resistance in overweight and obese postmenopausal women

AIM

In mice, osteocalcin (OCN) acts as a bone-derived hormone promoting insulin sensitivity and glucose tolerance. In that species, OCN endocrine action is inhibited when its first glutamic acid residue (Glu13) is γ-carboxylated (Gla). The importance of this posttranslational modification for OCN function in human is still unclear. Our objectives were to identify an assay to assess γ-carboxylation of human OCN on its first Glu residue (Glu17) and to test its association with insulin resistance and inflammation profile in overweight women.

METHODS

Several ELISAs were tested to determine their specificity toward various forms of human OCN. Associations between OCN γ-carboxylation and determinants of glucose tolerance, insulin sensitivity, liver function and subclinical inflammation were then investigated in 129 non-diabetic overweight and obese postmenopausal women.

RESULTS

We identified assays allowing the measurement of total OCN (tOCN) and the ratio of Gla17/tOCN. Circulating Gla17/tOCN levels correlated negatively with insulin sensitivity assessed by hyperinsulinemic-euglyceamic clamp (P=0.02) or insulin sensitivity index derived from oral glucose tolerance test (P=0.00003), and positively with insulin resistance assessed by HOMA-IR (P=0.0005) and with markers of subclinical inflammation and liver enzymes, including C-reactive protein (CRP; P=0.007) and aspartate aminotransferase (AST; P=0.009).

CONCLUSIONS

γ-carboxylation of OCN on Glu17 residue correlates with insulin resistance and subclinical inflammation, suggesting that γ-carboxylation of OCN negatively regulates its endocrine action in humans.

MECHANISMS IN ENDOCRINOLOGY: Diabetes mellitus, a state of low bone turnover - a systematic review and meta-analysis

OBJECTIVE

To investigate the differences in bone turnover between diabetic patients and controls.

DESIGN

A systematic review and meta-analysis.

METHODS

A literature search was conducted using the databases Medline at PubMed and EMBASE. The free text search terms 'diabetes mellitus' and 'bone turnover', 'sclerostin', 'RANKL', 'osteoprotegerin', 'tartrate-resistant acid' and 'TRAP' were used. Studies were eligible if they investigated bone turnover markers in patients with diabetes compared with controls. Data were extracted by two reviewers.

RESULTS

A total of 2881 papers were identified of which 66 studies were included. Serum levels of the bone resorption marker C-terminal cross-linked telopeptide (-0.10 ng/mL (-0.12, -0.08)) and the bone formation markers osteocalcin (-2.51 ng/mL (-3.01, -2.01)) and procollagen type 1 amino terminal propeptide (-10.80 ng/mL (-12.83, -8.77)) were all lower in patients with diabetes compared with controls. Furthermore, s-tartrate-resistant acid phosphatase was decreased in patients with type 2 diabetes (-0.31 U/L (-0.56, -0.05)) compared with controls. S-sclerostin was significantly higher in patients with type 2 diabetes (14.92 pmol/L (3.12, 26.72)) and patients with type 1 diabetes (3.24 pmol/L (1.52, 4.96)) compared with controls. Also, s-osteoprotegerin was increased among patients with diabetes compared with controls (2.67 pmol/L (0.21, 5.14)).

CONCLUSIONS

Markers of both bone formation and bone resorption are decreased in patients with diabetes. This suggests that diabetes mellitus is a state of low bone turnover, which in turn may lead to more fragile bone. Altered levels of sclerostin and osteoprotegerin may be responsible for this.

Is Diabetic Skeletal Fragility Associated with Microvascular Complications in Bone?

PURPOSE OF REVIEW

The objective of this literature review is to determine whether there are indications that microvascular complications occur in diabetic bone. Evidence definitively linking diabetic skeletal fragility with microvascular complications in bone remains elusive.

RECENT FINDINGS

Circumstantial evidence, some recent and some lost to time, suggests that atherosclerotic vascular diseases such as peripheral arterial disease cause poor blood perfusion of bone and subsequent hypoxia and contribute to low bone density and high cortical porosity, patterns similar to some recently observed in diabetic subjects. Evidence also exists to suggest that potentially anti-angiogenic conditions, such as impaired vascular endothelial growth factor (VEGF) signaling, predominate in diabetic bone. Microvascular complications may contribute, in part, to diabetic skeletal fragility but data supporting this interpretation are primarily circumstantial at this time. This review highlights gaps in our knowledge and hopefully spurs further discussions and research on this topic.

Osteopontin: Relation between Adipose Tissue and Bone Homeostasis

Osteopontin (OPN) is a multifunctional protein mainly associated with bone metabolism and remodeling. Besides its physiological functions, OPN is implicated in the pathogenesis of a variety of disease states, such as obesity and osteoporosis. Importantly, during the last decades obesity and osteoporosis have become among the main threats to health worldwide. Because OPN is a protein principally expressed in cells with multifaceted effects on bone morphogenesis and remodeling and because it seems to be one of the most overexpressed genes in the adipose tissue of the obese contributing to osteoporosis, this mini review will highlight recent insights about relation between adipose tissue and bone homeostasis.

Lower serum osteocalcin concentrations are associated with brain microstructural changes and worse cognitive performance

OBJECTIVE

Rodent models have found that osteocalcin crosses the blood-brain barrier and regulates behaviour. No data are available on osteocalcin's effects on brain microstructure and cognitive performance in humans. We evaluated the association between serum osteocalcin concentrations and (i) brain microstructural changes on magnetic resonance imaging (MRI) and (ii) neuropsychological performance.

DESIGN, PATIENTS AND MEASUREMENTS

We studied 24 consecutive obese subjects (13 women; age, 49·8 ± 8·1 years; body mass index [BMI], 43·9 ± 4·54 kg/m(2) ) and 20 healthy volunteers (10 women; age, 48·8 ± 9·5 years; BMI, 24·3 ± 3·54 kg/m(2) ) in a cross-sectional study within the multicentre FLORINASH Project. FLAIR signal intensity and DTI-metrics (primary (λ1 ), secondary (λ2 ) and tertiary (λ3 ) eigenvalues; fractional anisotropy (FA); and mean diffusivity) in the caudate, hypothalamus, thalamus and putamen, and in subcortical white matter were assessed. Cognitive performance evaluated by neuropsychological test battery.

RESULTS

Lower osteocalcin concentrations were associated with BMI, higher λ1, λ2 and λ3 values at the caudate and lower FLAIR signal intensity at the caudate and putamen. Obese patients with lower osteocalcin concentrations had higher FA at putamen and thalamus. Lower osteocalcin concentrations were associated with higher Iowa Gambling Task (IGT) scores. FLAIR signal intensity at the caudate <601·832 yielded 85·7% sensitivity, 64·3% specificity, 70·6% negative predictive value and 81·8% positive predictive value for IGT score. Lower osteocalcin was an independent predictor of worse cognitive performance on multivariate analysis (F = 3·551, P = 0·01343; R(2) = 0·103). Bayesian information criterion demonstrated that osteocalcin had the predominant role in predicting IGT score.

CONCLUSIONS

Lower serum osteocalcin concentrations are associated with brain microstructural changes and worse cognitive performance.

Differences in biochemical bone markers by diabetes type and the impact of glucose

BACKGROUND

Diabetes mellitus is associated with an increased fracture risk, however the fracture risk is 7 fold increased in patients with type 1 diabetes (T1D) and 1.4 fold increased in patients with type 2 diabetes (T2D) with decreased and increased bone mineral density, respectively. Oral ingestion of glucose causes an acute decrease in bone turnover markers, and thus glucose levels may affect bone turnover in diabetes.

OBJECTIVE

The aim was to examine disparities in bone turnover markers between patients with T1D and T2D and evaluate the effect of glucose on bone turnover.

METHODS

A cross-sectional study was conducted. Patients diagnosed with T1D (n=98) or T2D (n=96) were included from the outpatient clinics at two University Hospitals. All individuals had normal renal function. Glucose and bone turnover markers were measured in non-fasting blood samples.

RESULTS

P-procollagen type 1 amino terminal propeptide (P1NP), p-osteocalcin (OC), and s-Receptor Activator of Nuclear factor Kappa beta Ligand (RANKL) were lower in patients with T2D compared to T1D, and s-osteoprotegerin (OPG) was higher in T2D. P-C-terminal cross-linked telopeptide of type-I collagen (CTX), p-fibroblast growth factor-23 (FGF-23), p-sclerostin, and p-undercarboxylated osteocalcin (ucOC) were similar in between the two groups of patients. Increasing non-fasting glucose levels were inversely related to p-CTX, p-P1NP, p-OC, and p-ucOC and directly related to s-OPG in simple linear and multiple linear regressions adjusted for factors influencing bone turnover markers including HbA1c.

CONCLUSION

Bone turnover markers were lower in patients with T2D compared to T1D. Acute blood glucose alterations may change bone turnover mediated by OPG and have detrimental effects on bone health in diabetes.

TRIAL REGISTRATION NUMBER

ClinicalTrials.govNCT01870557.

Biochemical bone turnover markers in diabetes mellitus - A systematic review

BACKGROUND

Diabetes mellitus is associated with an increased risk of fractures, which is not explained by bone mineral density. Other markers as bone turnover markers (BTMs) may be useful.

AIM

To assess the relationship between BTMs, diabetes, and fractures.

METHODS

A systematic literature search was conducted in August 2014. The databases searched were Medline at Pubmed and Embase. Medline at Pubmed was searched by "Diabetes Mellitus" (MESH) and "bone turnover markers" and Embase was searched using the Emtree by "Diabetes Mellitus" and "bone turnover", resulting in 611 studies. The eligibility criteria for the studies were to assess BTM in either type 1 diabetes (T1D) or type 2 diabetes (T2D) patients.

RESULTS

Of the 611 eligible studies, removal of duplicates and screening by title and abstract lead to 114 potential studies for full-text review. All these studies were full-text screened for eligibility and 45 studies were included. Two additional studies were added from other sources. Among the 47 studies included there were 1 meta-analysis, 29 cross-sectional studies, 13 randomized controlled trials, and 4 longitudinal studies. Both T1D and T2D were studied. Most studies reported fasting BTM and excluded renal disease.

CONCLUSION

Markers of bone resorption and formation seem to be lower in diabetes patients. Bone specific alkaline phosphatase is normal or increased, which suggests that the matrix becomes hypermineralized in diabetes patients. The BTMs: C-terminal cross-link of collagen, insulin-like growth factor-1, and sclerostin may potentially predict fractures, but longitudinal trials are needed. This article is part of a Special Issue entitled Bone and diabetes.

Osteocalcin carboxylation is not associated with body weight or percent fat changes during weight loss in post-menopausal women

Osteocalcin (OC) is a vitamin K-dependent bone protein used as a marker of bone formation. Mouse models have demonstrated a role for the uncarboxylated form of OC (ucOC) in energy metabolism, including energy expenditure and adiposity, but human data are equivocal. The purpose of this study was to determine the associations between changes in measures of OC and changes in body weight and percent body fat in obese, but otherwise healthy post-menopausal women undergoing a 20-week weight loss program. All participants received supplemental vitamins K and D and calcium. Body weight and body fat percentage (%BF) were assessed before and after the intervention. Serum OC [(total (tOC), ucOC, percent uncarboxylated (%ucOC)], and procollagen type 1N-terminal propeptide (P1NP; a measure of bone formation) were measured. Women lost an average of 10.9 ± 3.9 kg and 4 %BF. Serum concentrations of tOC, ucOC, %ucOC, and P1NP did not significantly change over the twenty-week intervention, nor were these measures associated with changes in weight (all p > 0.27) or %BF (all p > 0.54). Our data do not support an association between any serum measure of OC and weight or %BF loss in post-menopausal women supplemented with nutrients implicated in bone health.

Inverse relationship between serum osteocalcin levels and nonalcoholic fatty liver disease in postmenopausal Chinese women with normal blood glucose levels

AIM

Osteocalcin is involved in the progression of nonalcoholic fatty liver disease (NAFLD) in animal models and humans. In this study we investigated the relationship between serum osteocalcin levels and NAFLD in postmenopausal Chinese women.

METHODS

A total of 733 postmenopausal women (age range: 41-78 years) with normal blood glucose levels were enrolled in this cross-sectional study. Women taking lipid-lowering or anti-hypertensive drugs were excluded. Serum osteocalcin levels were assessed using an electrochemiluminescence immunoassay. The degree of NAFLD progression for each subject was assessed through ultrasonography. The fatty liver index (FLI) of each subject was calculated to quantify the degree of liver steatosis.

RESULTS

The median level of serum osteocalcin for all subjects enrolled was 21.99 ng/mL (interquartile range: 17.84-26.55 ng/mL). Subjects with NAFLD had significantly lower serum osteocalcin levels (18.39 ng/mL; range: 16.03-23.64 ng/mL) compared with those without NAFLD (22.31 ng/mL; range: 18.55-27.06 ng/mL; P<0.01). Serum osteocalcin levels decreased with incremental changes in the FLI value divided by the quartile (P-value for trend<0.01). The serum osteocalcin levels showed a negative correlation with the FLI values, even after adjusting for confounding factors (standardized β=-0.124; P<0.01). Binary logistic regression analysis identified an individual's serum osteocalcin level as an independent risk factor for NAFLD (odds ratio: 0.951; 95% confidence interval: 0.911-0.992; P=0.02).

CONCLUSION

Serum osteocalcin levels are inversely correlated with NAFLD in postmenopausal Chinese women with normal blood glucose levels.

Prevalence of Metabolic Syndrome and Its Components in the Iranian Adult Population: A Systematic Review and Meta-Analysis

CONTEXT

Metabolic syndrome (MetS) increases the risk of most non-communicable diseases; gathering information about its prevalence can be very effective in formulating preventive strategies for metabolic diseases. There are many different studies about the prevalence of MetS in Iran, but the results and the study populations of these studies are very different; therefore, it is very important to have an overall estimation of its prevalence in Iran.

OBJECTIVES

This study systematically reviewed the findings of all available studies on MetS in the adult Iranian population and estimated the overall prevalence of MetS in this population.

DATA SOURCES

International databases (Scopus, ISI Web of Science, and PubMed) were searched for papers published from January, 2000 to December, 2013 using medical subject headings (MeSH), Emtree, and related keywords (metabolic syndrome, dysmetabolic syndrome, cardiovascular syndrome, and insulin resistance syndrome) combined with the words "prevalence" and "Iran." The Farsi equivalent of these terms and all probable combinations were used to search Persian national databases (IranMedex, Magiran, SID, and Irandoc).

STUDY SELECTION

All population-based studies and national surveys that reported the prevalence of MetS in healthy Iranian adults were included.

DATA EXTRACTION

After quality assessment, data were extracted according to a standard protocol. Because of between-study heterogeneity, data were analyzed by the random effect method.

RESULTS

We recruited the data of 27 local studies and one national study. The overall estimation of MetS prevalence was 36.9% (95% CI: 32.7 - 41.2%) based on the Adult Treatment Panel III (ATP III) criteria, 34.6% (95% CI: 31.7 - 37.6%) according to the International Diabetes Federation (IDF), and 41.5% (95% CI: 29.8 - 53.2%) based on the Joint Interim Societies (JIS) criteria. The prevalence of MetS determined by JIS was significantly higher than those determined by ATP III and IDF. The prevalence of MetS was 15.4% lower in men than in women (27.7% versus 43.1%) based on the ATP III criteria, and it was 11.3% lower in men based on the IDF criteria; however according to the JIS criteria, it was 8.4% more prevalent in men.

CONCLUSIONS

There is a high prevalence of MetS in the Iranian adult population, with large variations based on different measurement criteria. Therefore, prevention and control of MetS should be considered a priority.

Association between osteocalcin and glucose metabolism: a meta-analysis

This meta-analysis aimed to investigate the associations between osteocalcin (Ocn) and fasting plasma glucose (FPG) and glycated hemoglobin A1c (HbA1c). It was revealed that both total Ocn and undercarboxylated Ocn (unOcn) were negatively related with FPG and HbA1c, and the association of unOcn with FPG was more pronounced in men.

INTRODUCTION

The aim of this study was to investigate the strength of associations between Ocn and FPG and HbA1c using a meta-analysis approach.

METHODS

A search was carried out using the databases of PubMed, ISI Web of Science, and the Cochrane library from 2007 to 2014 to identify related studies. A pooled effect size with 95 % confidence intervals (CI) was derived.

RESULTS

The meta-analysis included 39 studies involving 23,381 participants. The overall correlation was -0.16 (95 % CI, -0.19 to -0.14) between total Ocn (tOcn) and FPG and -0.15 (95 % CI, -0.20 to -0.11) between undercarboxylated Ocn (unOcn) and FPG. In the analysis of the association between Ocn and HbA1c, the pooled correlation was -0.16 (95 % CI, -0.18 to -0.14) for tOcn and -0.16 (95 % CI, -0.23 to -0.08) for unOcn. The magnitude of the correlation between unOcn and FPG is significantly higher in men than in women (r = -0.18, 95 % CI, -0.21 to -0.14; r = -0.09, 95 % CI, -0. 13 to -0.05, respectively; P for interaction < 0.05). Similar trend was also found between unOcn and HbA1c but without significance (for men, r = -0.19, 95 % CI, -0.24 to -0.14; for women, r = -0.09, 95 % CI, -0.22 to 0.04, respectively; P for interaction > 0.05). No indication of significant publication bias was found in any method.

CONCLUSIONS

This meta-analysis demonstrated that both unOcn and tOcn were similarly and negatively correlated with FPG and HbA1c in humans. The negative correlations between unOcn and glucose metabolism appear to be more pronounced in men than in women.

Uncarboxylated osteocalcin inhibits high glucose-induced ROS production and stimulates osteoblastic differentiation by preventing the activation of PI3K/Akt in MC3T3-E1 cells

Uncarboxylated osteocalcin, an osteoblast-derived protein, plays an important role in the regulation of glucose metabolism. It has previously been demonstrated that high glucose levels inhibit osteoblast proliferation and differentiation. However, the mechanisms through which uncarboxylated osteocalcin regulates osteoblast proliferation and differentiation under high glucose conditions remain unclear. Thus, in the present study, we aimed to examine the effects of uncarboxylated osteocalcin on the proliferation and differentiation of MC3T3-E1 cells under high glucose conditions. We demonstrated that high glucose levels induced the production of reactive oxygen species (ROS) in MC3T3-E1 cells, and this production was inhibited by treatment with uncarboxylated osteocalcin and N-acetyl-L-cysteine (NAC), a ROS scavenger. In addition, we found that uncarboxylated osteocalcin reduced high glucose‑induced oxidative stress and increased the mRNA expression of the osteogenic markers, runt-related transcription factor 2 (Runx2), osterix and osteocalcin, as well as the formation of mineralized nodules; it also inhibited adipogenic differentiation, as shown by a decrease in the mRNA expression of the adipogenic markers, peroxisome proliferator‑activated receptor γ (PPARγ), adipocyte fatty acid-binding protein (adipocyte protein 2; aP2) and fatty acid synthase (FAS), and reduced lipid drop accumulation. Furthermore, we found that uncarboxylated osteocalcin inhibited PI3K/Akt signaling which was induced by ROS and facilitated the osteogenic differentiation of MC3T3-E1 cells under high glucose conditions. Taken together and to the best of ou knowledge, our results demonstrate for the first time that uncarboxylated osteocalcin inhibits high glucose-induced ROS production and stimulates osteoblastic differentiation by inhibiting the activation of PI3K/Akt in MC3T3-E1 cells. Therefore, we suggest that uncarboxylated osteocalcin may be a potential therapeutic agent for diabetes-related osteoporosis.

Association between serum osteocalcin level and visceral obesity in Chinese postmenopausal women

BACKGROUND

A low serum osteocalcin level, visceral obesity and postmenopausal status are recognized risk factors for cardiovascular disease.

OBJECTIVE

We investigated the relationship between the serum osteocalcin level and visceral fat content in a population of Chinese postmenopausal women.

DESIGN AND PATIENTS

In total, 1481 postmenopausal women (mean age ± standard deviation, 57·1 ± 4·8 years) were selected from the Shanghai Obesity Study.

MEASUREMENTS

Abdominal fat accumulation was quantified using magnetic resonance imaging. Subjects with a visceral fat area (VFA) of ≥80 cm(2) were classified as abdominally obese. The total serum osteocalcin level was measured by electrochemiluminescence immunoassay.

RESULTS

The median serum osteocalcin level was 20·66 μg/l (interquartile range, 16·88-25·42 μg/l). The overall prevalence of abdominal obesity was 49·1% (n = 727). Abdominally obese subjects had lower serum osteocalcin levels than did nonabdominally obese subjects [19·14 (16·02-23·82) vs 21·97 (18·14-26·77) μg/l, respectively; P < 0·001]. Partial correlation analysis showed that the serum osteocalcin level was still negatively correlated with VFA after adjusting for age, years since menopause and body mass index (P < 0·01). Moreover, VFA was independently associated with the serum osteocalcin level after adjustment for confounding factors (P < 0·05). A low serum osteocalcin level was an independent risk factor for abdominal obesity (odds ratio, 0·972; 95% confidence interval, 0·953-0·991; P = 0·004).

CONCLUSION

The serum osteocalcin level was inversely correlated with the visceral fat content in these Chinese postmenopausal women.

Association of serum total osteocalcin with type 2 diabetes and intermediate metabolic phenotypes: systematic review and meta-analysis of observational evidence

Serum total osteocalcin, a marker of bone formation, may regulate glucose metabolism and influence the risk of developing adverse metabolic outcomes. We conducted a systematic review and meta-analysis of published observational evidence, to assess and quantify the associations of serum total osteocalcin with type 2 diabetes and intermediate metabolic phenotypes [e.g., metabolic syndrome (MetS)]. Relevant studies were identified in a literature search of MEDLINE, EMBASE, Web of Science, and reference lists of relevant studies to May 2015. Mean differences and risk estimates (odds ratios or relative risks) with 95% CIs were aggregated using random-effects models. Fifty-two observational (38 cross-sectional, eight cohort, five case-control, and one both cross-sectional and cohort) studies with data on 46,998 non-overlapping participants were included. Baseline serum total osteocalcin levels were significantly lower in type 2 diabetes compared with non-type 2 diabetes and in MetS compared with non-MetS in pooled analysis of cross-sectional evidence. Pooled risk estimates (95% CIs) for type 2 diabetes in a comparison of extreme fourths of total osteocalcin levels were 0.23 (95% CI 0.12, 0.46) and 0.89 (95% CI 0.78, 1.01) for cross-sectional and cohort studies respectively. The corresponding estimate was 0.39 (0.27, 0.56) for MetS from cross-sectional evidence. In both cross-sectional and cohort studies, a unit increase in serum total osteocalcin levels was associated with a significant mean increase in HOMA-B and mean reduction in HbA1c; with significant mean reductions in fasting plasma glucose levels, HOMA-IR, and body mass index in only cross-sectional studies. Available evidence--mainly from cross-sectional studies, supports inverse associations of serum total osteocalcin with risk of adverse metabolic outcomes. Large-scale prospective studies are needed to establish whether serum total osteocalcin may be useful in the prevention of adverse metabolic outcomes such as type 2 diabetes.

Relationship between serum osteocalcin level and carotid intima-media thickness in a metabolically healthy Chinese population

Background

The relationship between osteocalcin and atherosclerosis remains unclear. This might be due to different degrees of confounding from factors that are associated with serum osteocalcin level, such as metabolic-related variables. This study aimed to investigate the relationship between serum osteocalcin level and carotid intima-media thickness (C-IMT) in a metabolically healthy population.

Methods

A total of 476 subjects with normal values for weight, glucose tolerance, blood pressure, and lipids (age range, 20–75 years; 155 men, 201 premenopausal women, 120 postmenopausal women) from the Shanghai Obesity Study were recruited for this cross-sectional study. Subjects with a history of cardiovascular disease or carotid plaque were excluded. C-IMT was measured by ultrasonography. Serum osteocalcin level was assessed by an electrochemiluminescence immunoassay.

Results

Median C-IMT in the entire study population was 0.55 mm with an interquartile range of 0.50–0.60 mm. C-IMT in premenopausal women was significantly lower than that in men and postmenopausal women (all P < 0.001). The median (interquartile range) of serum osteocalcin level in the entire population was 17.02 (13.31–21.47) ng/mL. Serum osteocalcin level in postmenopausal women was significantly higher than that in men and premenopausal women (all P < 0.001), while the level of serum osteocalcin in men was also significantly higher than that in premenopausal women (P < 0.001). No significant correlation was found between C-IMT and serum osteocalcin level in either men or postmenopausal women. There was a significant, inverse correlations between C-IMT and serum osteocalcin level in premenopausal women after adjustment of age, but this association was eliminated after adjustment for other confounding factors.

Conclusions

Serum osteocalcin level was not independently associated with C-IMT in a metabolically healthy Chinese population.

Bone as an endocrine organ relevant to diabetes

There are well-established associations between diabetes and fracture risk and yet the mechanism underlying these associations are controversial. Guided by a series of mouse studies, a specific form of the bone protein, osteocalcin, was proposed to be the mechanistic link between these two chronic diseases. Translation to humans initially appeared elusive in part because serum concentrations of osteocalcin are a biomarker of bone turnover and not necessarily specific to the biology of this protein. The suitability of the mouse model for the study of osteocalcin as a therapeutic target also appears ambiguous. With greater discrimination of the different forms of osteocalcin present in circulation and inclusion of multiple measures of bone turnover, evidence currently does not support osteocalcin as a protein critical to the diabetes and fracture association in humans.

Serum ferritin levels are positively associated with bone mineral density in elderly Korean men: the 2008-2010 Korea National Health and Nutrition Examination Surveys

A possible negative effect of iron overload on bone metabolism has been suggested by the fact that patients with hemochromatosis, thalassemia, and sickle cell anemia have lower bone mineral density than the general population. However, the influence of iron overload on bone health in the general population is uncertain. The aim of this study was to investigate the relationship between serum ferritin levels and bone mineral density (BMD) in elderly Koreans. A total of 2,943 subjects aged 65 years and over who participated in the 2008-2010 Korea National Health and Nutrition Examination Surveys were included in this study. Age, physical activity, current smoking status, alcohol consumption, education level, household income, and dietary assessment were surveyed by a face-to-face interview. BMD was measured at the lumbar spine and femur by dual-energy X-ray absorptiometry, and other biochemical markers, including serum ferritin, 25-hydroxyvitamin D3, serum alkaline phosphatase, and parathyroid hormone, were assayed. After adjusting for age and body mass index, we found an association between BMD of the total lumbar spine, total femur, and femur neck and levels of alkaline phosphatase, parathyroid hormone, vitamin D3, and daily intake of calcium and protein. Serum ferritin levels were positively associated with BMD of the total lumbar spine, total femur, and femur neck after adjusting for all covariates in men, but not in women. This study suggests a positive association between serum ferritin levels and BMD in elderly South Korean men without hematologic disorders. Further study is warranted to verify the effects of iron on bone metabolism.

The effects of improved metabolic risk factors on bone turnover markers after 12 weeks of simvastatin treatment with or without exercise

OBJECTIVE

Emerging evidence supports an association between metabolic risk factors and bone turnover. Statins and exercise independently improve metabolic risk factors; however whether improvements in metabolic risk factor affects bone turnover is unknown. The purpose of the present study was to: 1) evaluate the relationship between metabolic risk factors and bone turnover; and 2) determine if improvements in metabolic risk factors after 12 weeks of statin treatment, exercise or the combination affect bone turnover.

METHODS

Fifty participants with ≥2 metabolic syndrome defining characteristics were randomly assigned to one of three groups: statin (STAT: simvastatin, 40 mg/day), exercise (EX: brisk walking and/or slow jogging, 45 minutes/day, 5 days/week), or the combination (STAT+EX). Body composition and whole body bone mineral density were measured with dual energy X-ray absorptiometry. Serum markers of bone formation (bone specific alkaline phosphatase, BAP; osteocalcin, OC), resorption (C-terminal peptide of type I collagen, CTX) and metabolic risk factors were determined. Two-factor (time, group) repeated-measures ANCOVA was used to examine changes of metabolic risk factors and bone turnover. General linear models were used to determine the effect of pre-treatment metabolic risk factors on post-treatment bone turnover marker outcomes.

RESULTS

Participants with ≥4 metabolic syndrome defining characteristics had lower pre-treatment OC than those with 3 or fewer. OC was negatively correlated with glucose, and CTX was positively correlated with cholesterol. STAT or STAT+EX lowered total and LDL cholesterol. The OC to CTX ratio decreased in all groups with no other significant changes in bone turnover. Higher pre-treatment insulin or body fat predicted a greater CTX reduction and a greater BAP/CTX increase.

CONCLUSION

Metabolic risk factors were negatively associated with bone turnover markers. Short-term statin treatment with or without exercise lowered cholesterol and all treatments had a small effect on bone turnover.