Reciprocal regulation of bone and energy metabolism

Renal osteodystrophy: A historical review of its origins and conceptual evolution

Long considered an inert supporting framework, bone studies went neglected until the 17th century when they began as descriptive microscopic studies of structure which over time progressed into that of chemistry and physiology. It was in the mid-19th century that studies evolved into an inquisitive discipline which matured into the experimental investigation of bone in health and disease in the 20th century, and ultimately that of molecular studies now deciphering the genetic language of bone biology. These fundamental studies were catalyzed by increasing clinical interest in bone disease. The first bone disease to be identified was rickets in 1645. Its subsequent connection to albuminuric patients reported in 1883 later became renal osteodystrophy in 1942, launching studies that elucidated the functions of vitamin D and parathyroid hormone and their role in the altered calcium and phosphate metabolism of the disease. Studies in osteoporosis and renal osteodystrophy have driven most recent progress benefitting from technological advances in imaging and the precision of evaluating bone turnover, mineralization, and volume. This review exposes the progress of bone biology from a passive support structure to a dynamically regulated organ with vital homeostatic functions whose understanding has undergone more revisions and paradigm shifts than that of any other organ.

The oxytocin signalling gene pathway contributes to the association between loneliness and cardiometabolic health

Increasing evidence has shown adverse effects of loneliness on cardiometabolic health. The neuromodulator and hormone oxytocin has traditionally been linked with social cognition and behaviour. However, recent implications of the oxytocin system in energy metabolism and the overrepresentation of metabolic issues in psychiatric illness suggests that oxytocin may represent a mechanism bridging mental and somatic traits. To clarify the role of the oxytocin signalling system in the link between cardiometabolic risk factors and loneliness, we calculated the contribution of single nucleotide polymorphisms (SNPs) in the oxytocin signalling pathway gene-set (154 genes) to the polygenic architecture of loneliness and body mass index (BMI). We investigated the associations of these oxytocin signalling pathway polygenic scores with body composition measured using body magnetic resonance imaging (MRI), bone mineral density (BMD), haematological markers, and blood pressure in a sample of just under half a million adults from the UK Biobank (BMD subsample n = 274,457; body MRI subsample n = 9796). Our analysis revealed significant associations of the oxytocin signalling pathway polygenic score for BMI with abdominal subcutaneous fat tissue, HDL cholesterol, lipoprotein(a), triglycerides, and BMD. We also found an association between the oxytocin signalling pathway polygenic score for loneliness and apolipoprotein A1, the major protein component of HDL. Altogether, these results provide additional evidence for the oxytocin signalling pathway's role in energy metabolism, lipid homoeostasis, and bone density, and support oxytocin's complex pleiotropic effects.

Associations of Obesity with Linear Growth and Puberty

BACKGROUND

The prevalence of obesity in childhood has increased dramatically in recent decades with increased risk of developing cardiometabolic and other comorbidities. Childhood adiposity may also influence processes of growth and puberty.

SUMMARY

Growth patterns of obesity during childhood have been shown to be associated with increased linear growth in early childhood, leading to accelerated epiphyseal growth plate (EGP) maturation. Several hormones secreted by the adipose tissue may affect linear growth in the context of obesity, both via the growth hormone IGF-1 axis and via a direct effect on the EGP. The observation that children with obesity tend to mature earlier than lean children has led to the assumption that the degree of body fatness may trigger the neuroendocrine events that lead to pubertal onset. The most probable link between obesity and puberty is leptin and its interaction with the kisspeptin system, which is an important regulator of puberty. However, peripheral action of adipose tissue could also be involved in changes in the onset of puberty. In addition, nutritional factors, epigenetics, and endocrine-disrupting chemicals are potential mediators linking pubertal onset to obesity. In this review, we focused on interactions of obesity with linear growth and pubertal processes, based on basic research and clinical data in humans.

KEY MESSAGE

Children with obesity are subject to accelerated linear growth with risk of impaired adult height and early puberty, with its psychological consequences. The data highlight another important objective in combatting childhood obesity, for the prevention of abnormal growth and pubertal patterns.

Total Flavonoids of Drynariae Rhizoma Improve Glucocorticoid-Induced Osteoporosis of Rats: UHPLC-MS-Based Qualitative Analysis, Network Pharmacology Strategy and Pharmacodynamic Validation

BACKGROUND

Glucocorticoid-induced osteoporosis (GIOP) is a common form of secondary osteoporosis caused by the protracted or a large dosage of glucocorticoids (GCs). Total flavonoids of Drynariae rhizoma (TFDR) have been widely used in treating postmenopausal osteoporosis (POP). However, their therapeutic effects and potential mechanism against GIOP have not been fully elucidated.

METHODS

Ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESIQ-TOF-MS) experiments were performed for qualitative analysis. We performed hematoxylin-eosin (HE) staining and microcomputed tomography (micro-CT) analysis to detect the changes in bone microstructure. The changes in biochemical parameters in the serum samples were determined by performing an enzyme-linked immunosorbent assay (ELISA). The prediction results of network pharmacology were verified via quantitative real-time polymerase chain reaction (qRT-PCR) to elucidate the potential mechanism of TFDR against GIOP.

RESULTS

A total of 191 ingredients were identified in vitro and 48 ingredients in vivo. In the in-vivo experiment, the levels of the serum total cholesterol (TC), the serum triglyceride (TG), Leptin (LEP), osteocalcin (OC), osteoprotegerin (OPG), bone morphogenetic protein-2 (BMP-2), propeptide of type I procollagen (PINP), tartrate-resistant acid phosphatase (TRACP) and type-I collagen carboxy-terminal peptide (CTX-1) in the TFDR group significantly changed compared with those in the GIOP group. Moreover, the TFDR group showed an improvement in bone mineral density and bone microstructure. Based on the results of network pharmacology analysis, 67 core targets were selected to construct the network and perform PPI analysis as well as biological enrichment analysis. Five of the targets with high "degree value" had differential gene expression between groups using qRT-PCR.

CONCLUSION

TFDR, which may play a crucial role between adipose metabolism and bone metabolism, may be a novel remedy for the prevention and clinical treatment of GIOP.

The Role of Sphingolipid Metabolism in Bone Remodeling

Emerging studies of bioactive lipids have made many exciting discoveries in recent years. Sphingolipids and their metabolites perform a wide variety of cellular functions beyond energy metabolism. Emerging evidence based on genetically manipulated mouse models and molecular biology allows us to obtain new insights into the role sphingolipid played on skeletal remodeling. This review summarizes studies or understandings of the crosstalk between sphingomyelin, ceramide, and sphingosine-1-phosphate (S1P) of sphingolipids family and the cells, especially osteoblasts and osteoclasts of the bone through which bone is remodeled during life constantly. This review also shows agonists and antagonists of S1P as possible therapeutic options and opportunities on bone diseases.

Response of Bone Metabolism Markers to Ice Swimming in Regular Practitioners

Objective: Both exercise and cold exposure cause physiological stress and they often occur in combination. However, the effects of exercise during severe cold on variation in bone metabolism in humans have remained elusive. The aim of this study was to investigate the variations in circulating bone metabolism markers after ice swimming (IS).

Methods: Eighty-seven women and men aged 42–84 years old were recruited to perform regular IS activities. Serum parathyroid hormone (PTH), total calcium (Ca²⁺), total phosphorus (Pi), total magnesium (Mg²⁺), N-terminal osteocalcin (N-MID), total propeptide of procollagen 1 (TPINP), and C-terminal telopeptide of type 1 collagen (β-CTX) were measured 30 min before and 30 min after IS. Bone mineral content (BMC) and bone mineral density (BMD) were assessed at lumbar spine 1–4 (L1–L4) and femoral neck (FN). The IS habits were obtained from questionnaires and the 10-year probability of osteoporotic fracture was calculated using the FRAX^® tool with and without a BMD value of the FN.

Results: There were significant increases in PTH (median, 40.120–51.540 pg/mL), Ca²⁺ (median, 2.330–2.400 mmol/L), and Pi (median, 1.100–1.340 mmol/L) and significant decreases in TPINP (median, 38.190–36.610 ng/mL) and β-CTX (median, 0.185–0.171 ng/mL), while there was a trend for increased serum Mg²⁺ (P = 0.058) but no significant change in N-MID (P = 0.933) after IS in all subjects. The increases in the proportions of cases of hyperparathyroidemia, hypercalcemia, and hyperphosphatemia in those performing IS were statistically significant. The baseline levels and the changes of bone metabolism markers had associations with osteoporosis and bone status, but these may be age and sex dependent. Finally, there were significant correlations among the bone metabolism markers.

Conclusion: IS caused significant alterations in bone metabolic markers, specifically, increases in PTH, Ca²⁺ and Pi should raise concerns about potential cardiovascular health risks in severe cold exercise. Additionally, a divergence between PTH elevation and a decline in bone turnover, which shown a special change of bone metabolism after IS and may suggest potential therapeutic implications of cold exercise in PTH and bone metabolic disorders.

Metabolic effects of CoCr-enriched medium on shear-stressed endothelial cell and osteoblasts: A possible mechanism involving a hypoxic condition on bone healing

Cobalt-chromium (CoCr)-based alloys have emerged as an interesting biomaterial within biomedical field, mainly considering their biocompatibility, resistance to corrosion and absence of magnetism; however, its effect on cell metabolism is barely known and this prompted us better evaluating whether CoCr-enriched medium affects the metabolism of both osteoblast and endothelial cells, and also if there is a coupling between them. This is also considered here the already-known effect of Cobalt (Co) as a hypoxic element. Firstly, discs of CoCr [subjecting (W) or not (Wo) to dual acid-etched (DAE)] were incubated into FBS-free cell culture medium up to 24 h (37 °C). This CoCr-enriched medium was further used to treat shear-stressed endothelial cells cultures up to 72 h. Thereafter, the conditioned medium containing metabolites of shear-stressed endothelial cells in response to CoCr-enriched medium was further used to subject osteoblast's cultures, when the samples were properly harvested to allow the analysis of the molecular issues. Our data shows that CoCr-enriched medium contains 1.5 ng-2.0 ng/mL of Co, which was captured by endothelial cells and osteoblasts in about 30% in amount and it seems modulate their metabolic pathways: shear-stressed endothelial cells expressed higher profile of HIF1α, VEGF and nNOS genes, while their global profile of protein carbonylation was lower than the control cultures, suggesting lower oxidative stress commitment. Additionally, osteoblasts responding to metabolites of CoCr-challenged endothelial cells show dynamic expression of marker genes in osteogenic differentiation, with alkaline phosphatase (ALP), osteocalcin, and bone sialoprotein (BSP) genes being significantly increased. Additionally, tensional shear-stress forces decrease the stimulus for ColA1gene expression in osteoblasts responding to endothelial cells metabolites, as well as modifying the extracellular matrix remodeling related genes. Analyzing the activities of matrix metalloproteinases (MMPs), the data shows that shear-stressed endothelial cells metabolites increase the activities of both MMP9 and MMP2 in osteoblasts. Altogether, our data shows for the first time that shear-stressed endothelial metabolites responding to CoCr discs contribute to osteogenic phenotype in vitro, and this predicts an active crosstalk between angiogenesis and osteogenesis during osseointegration of CoCr alloy and bone healing, maybe guided by the Co-induced hypoxic condition.

Leptin Mediated Pathways Stabilize Posttraumatic Insulin and Osteocalcin Patterns after Long Bone Fracture and Concomitant Traumatic Brain Injury and Thus Influence Fracture Healing in a Combined Murine Trauma Model

Recent studies on insulin, leptin, osteocalcin (OCN), and bone remodeling have evoked interest in the interdependence of bone formation and energy household. Accordingly, this study attempts to investigate trauma specific hormone changes in a murine trauma model and its influence on fracture healing. Thereunto 120 female wild type (WT) and leptin-deficient mice underwent either long bone fracture (Fx), traumatic brain injury (TBI), combined trauma (Combined), or neither of it and therefore served as controls (C). Blood samples were taken weekly after trauma and analyzed for insulin and OCN concentrations. Here, WT-mice with Fx and, moreover, with combined trauma showed a greater change in posttraumatic insulin and OCN levels than mice with TBI alone. In the case of leptin-deficiency, insulin changes were still increased after bony lesion, but the posttraumatic OCN was no longer trauma specific. Four weeks after trauma, hormone levels recovered to normal/basal line level in both mouse strains. Thus, WT- and leptin-deficient mice show a trauma specific hyperinsulinaemic stress reaction leading to a reduction in OCN synthesis and release. In WT-mice, this causes a disinhibition and acceleration of fracture healing after combined trauma. In leptin-deficiency, posttraumatic OCN changes are no longer specific and fracture healing is impaired regardless of the preceding trauma.

The endocrine role of bone: Novel functions of bone-derived cytokines

Bone-derived cytokines refer to various proteins and peptides that are released from the skeleton and can distribute in organisms to regulate homeostasis by targeting many organs, such as the pancreas, brain, testicles, and kidneys. In addition to providing support and movement, many studies have disclosed the novel endocrine function of bone, and bone can modulate glucose and energy metabolism as well as phosphate metabolism by versatile bone-derived cytokines. However, this specific exoskeletonfunction of bone-derived cytokines in the regulation of homeostasis and the pathological response caused by skeletal dysfunction are still not very clear, and elucidation of the above mechanisms is of great significance for understanding the pathological processes of metabolic disorders and in the search for novel therapeutic measures for maintaining organ stability and physical fitness.

Effects of Opuntia ficus-indica in the diet of primiparous sows on the metabolic profile during late gestation and lactation and feed intake during lactation

The goal of this study was to evaluate the effects of dietary Opuntia ficus-indica L. (OFI) on the metabolic profile of primiparous sows during late gestation and lactation, and its impact on voluntary feed intake (VFI) during lactation. From day 85 of gestation to weaning, 32 sows were divided into four feeding schemes (n = 8 sows/scheme): Basal diet (BD) without OFI supplementation; Test scheme I, BD during gestation and BD + OFI during lactation; Test scheme II, BD + OFI during both gestation and lactation, and Test scheme III, BD + OFI during gestation and BD during lactation. Blood samples were obtained during gestation (day 85 and 100) and lactation (day 0, 3, 7, 14 and 21) to determine plasma glucose, insulin, triglycerides, leptin, osteocalcin, ghrelin and agouti-related protein (AgRP). VFI was higher (20% higher than that of controls) in sows that received dietary OFI during lactation (p < .05). The concentration of plasma glucose was lower in sows that consumed OFI than sows fed the conventional diet (p < .05). Plasma insulin concentrations were higher in sows that consumed OFI, than in sows that did not (p < .05). Triglyceride concentrations during gestation, farrowing and lactation were also lower in sows that consumed OFI (p < .05). OFI intake caused lower plasma concentrations of leptin during lactation (p < .05). Osteocalcin was higher in sows that consumed OFI versus controls (p < .05): 8.6% and 13.4% during gestation and lactation respectively. From day 3 of lactation, sows that consumed OFI had higher concentrations of ghrelin (p < .05). The concentration of plasma AgRP was higher (p < .05) in sows that consumed OFI versus controls: 3.1% and 14.2% in gestation and lactation respectively. We concluded that OFI intake by primiparous sows during late gestation and lactation favourably modulated the factors that caused insulin resistance and increased sow performance.

Effect of the Inclusion of Different Levels of Dietary Cactus (Opuntia ficus-indica) on Gilts' Biochemical Parameters and Feed Intake during Lactation

Simple Summary

The digestive and metabolic adaptations suffered by sows during the late gestation-lactation transition cause a decrease in the voluntary feed intake. These conditions favor a negative energy balance, forcing the body to mobilize body reserves to meet their nutritional requirements, which represents an obstacle to expressing their reproductive and productive potential. The supplementation of the sows’ diet with cactus (Opuntia ficus-indica L.) improves the feed intake in lactation due to the favorable modulation of biochemical indicators. However, the optimal addition of cactus to the diet of lactating sows is unknown. In the present study, the increase in the inclusion level of cactus did not linearly increase the feed intake in lactation. However, a linear increase in plasma insulin and osteocalcin concentrations were observed, which led to a decrease in the plasma glucose concentrations. We conclude that the inclusion level of cactus (fresh base) in the diet of lactating sows of 1.0% (with respect to the body weight of the sow) could improve the feed intake in lactation and reduce the loss of body weight of the sow at weaning.

Abstract

The regulation of sows’ metabolic state during the gestation-lactation transition is a requirement for a higher feed intake in lactation, an important aspect in improving animal welfare in current swine production systems. The present study aimed to evaluate the effects of the inclusion of different cactus (Opuntia ficus-indica L.) levels in the diet of gilts during late gestation and lactation on their biochemical parameters and voluntary feed intake during lactation. From day 85 of gestation until weaning, 40 gilts were divided into four groups: GNC (group with no cactus) with a basal diet (BD) only, G1C; group with 1% inclusion of cactus plus BD, G2C; group with 1.5% inclusion of cactus plus BD, and G3C; group with 2% inclusion of cactus plus BD. The dietary cactus supplementation increased the gilts’ feed intake (by 1.04 kg/day on average) during lactation and reduced their weight loss (4.3%) at weaning. The glucose concentrations were higher (range 73.0–83.9 mg/dL) in the GNC. The GNC had the highest triglyceride and cholesterol concentrations at day 100 of gestation. G3C had the highest osteocalcin concentration at day 100 of gestation. The highest feed intake and lowest glucose concentration were achieved with a cactus consumption of 1.04% in lactating gilts.

Obesity/Metabolic Syndrome and Diabetes Mellitus on Peri-implantitis

Literature has reported that up to 50% of dental implants may be affected by peri-implantitis, a bacteria-induced chronic inflammatory process, which promotes osteoclast-mediated bone resorption and inhibits bone formation, leading to progressive bone loss around implants. Current evidence points toward an increased risk for the development of peri-implantitis in both obesity/metabolic syndrome (MetS) and diabetes mellitus (DM) conditions relative to the healthy population. Currently, there is no effective treatment for peri-implantitis and the 50% prevalence in MetS and DM, along with its predicted increase in the worldwide population, presents a major concern in implant dentistry as hyperglycemic conditions are associated with bone-healing impairment; this may be through dysfunction of osteocalcin-induced glucose metabolism. The MetS/DM proinflammatory systemic condition and altered immune/microbiome response affect both catabolic and anabolic events of bone-healing that include increased osteoclastogenesis and compromised osteoblast activity, which could be explained by the dysfunction of insulin receptor that led to activation of signals related with osteoblast differentiation. Furthermore, chronic hyperglycemia along with associated micro- and macro-vascular ailments leads to delayed/impaired wound healing due to activation of pathways that are particularly important in initiating events linked to inflammation, oxidative stress, and cell apoptosis; this may be through deactivation of AKT/PKB protein, which possesses a pivotal role in drive survival and eNOS signaling. This review presents an overview of the local and systemic mechanisms synergistically affecting bone-healing impairment in MetS/DM individuals, as well as a rationale for hierarchical animal model selection, in an effort to characterize peri-implantitis disease and treatment.

Lipids in the Bone Marrow: An Evolving Perspective

Because of heavy energy demands to maintain bone homeostasis, the skeletal system is closely tied to whole-body metabolism via neuronal and hormonal mediators. Glucose, amino acids, and fatty acids are the chief fuel sources for bone resident cells during its remodeling. Lipids, which can be mobilized from intracellular depots in the bone marrow, can be a potent source of fatty acids. Thus, while it has been suggested that adipocytes in the bone marrow act as "filler" and are detrimental to skeletal homeostasis, we propose that marrow lipids are, in fact, essential for proper bone functioning. As such, we examine the prevailing evidence regarding the storage, use, and export of lipids within the skeletal niche, including from both in vitro and in vivo model systems. We also highlight the numerous challenges that remain to fully appreciate the relationship of lipid turnover to skeletal homeostasis.

The effect of adolescent inhalant abuse on energy balance and growth

The abuse of volatile solvents such as toluene is a significant public health concern, predominantly affecting adolescents. To date, inhalant abuse research has primarily focused on the central nervous system; however, inhalants also exert effects on other organ systems and processes, including metabolic function and energy balance. Adolescent inhalant abuse is characterized by a negative energy balance phenotype, with the peak period of abuse overlapping with the adolescent growth spurt. There are multiple components within the central and peripheral regulation of energy balance that may be affected by adolescent inhalant abuse, such as impaired metabolic signaling, decreased food intake, altered dietary preferences, disrupted glucose tolerance and insulin release, reduced adiposity and skeletal density, and adrenal hypertrophy. These effects may persist into abstinence and adulthood, and the long-term consequences of inhalant-induced metabolic dysfunction are currently unknown. The signs and symptoms resulting from chronic adolescent inhalant abuse may result in a propensity for the development of adult-onset metabolic disorders such as type 2 diabetes, however, further research investigating the long-term effects of inhalant abuse upon energy balance and metabolism are needed. This review addresses several aspects of the short- and long-term effects of inhalant abuse relating to energy and metabolic processes, including energy balance, intake and expenditure; dietary preferences and glycemic control; and the dysfunction of metabolic homeostasis through altered adipose tissue, bone, and hypothalamic-pituitary-adrenal axis function.

Sclerostin and its association with insulin resistance in children and adolescents

INTRODUCTION

Recent studies have shown that sclerostin, which is mainly known as a negative regulator of bone formation, could play an important role in the crosstalk between bone and glucose metabolism. The aim of this study was to investigate the relationship between sclerostin, other bone and fat related factors as osteocalcin (OC), Receptor Activator of Nuclear Factor NF-қB ligand (RANKL), leptin and adiponectin with glucose metabolism and insulin action in children and adolescents with obesity compared with healthy children and adolescents.

METHODS

Fifty-five obese children and adolescents, a mean age of 13.2 ± 3.4 yrs., BMI 28.89 ± 5.5 kg/m², and 26 healthy controls (mean age 13.0 ± 4.3 yrs., BMI 19.96 ± 3.1 kg/m²), sex-, and Tanner stage-matched were included into the study. Fasting blood samples for measurement of sclerostin, glucose, lipid profile, HbA1c, C-peptide, OC, RANKL, leptin and adiponectin, and vitamin D were taken at 8.00 AM.

RESULTS

Sclerostin, osteocalcin, RANKL, and adiponectin levels did not differ between obese patients and the control group. Leptin and fasting insulin levels were significantly higher in obese subjects compared with controls (p < 0.01, p = 0.01, respectively). A positive correlation between sclerostin and OC (r = 0.417, p = 0.027) and negative correlations between sclerostin and HOMA-IR and between sclerostin and age (r = -0.24, p = 0.045, r = -0.23, p = 0.037, respectively) were found in all of the subjects. Sclerostin did not correlate with HbA1c, lipids, RANKL and fat-derived leptin and adiponectin. Partial correlation analysis adjusted for age, SDS-BMI and Tanner staging only revealed a negative correlation between sclerostin and HOMA-IR (r = -0.3, p = 0.01). In obese patients this correlation was stronger than in the whole group (r = -0.39, p = 0.005). Moreover, a negative correlation between sclerostin and insulin was found in obese patients (r = -0.39, p = 0.006). In the healthy cohort, sclerostin had a negative correlation only with C-peptide (r = -0.79, p = 0.02).

CONCLUSIONS

Sclerostin could play an important role in the regulation of glucose metabolism in children and adolescents, regardless of other fat and bone-derived factors. In obese young patients it's action could be associated with decreasing insulin resistance.

Sclerostin and its significance for children and adolescents with type 1 diabetes mellitus (T1D)

INTRODUCTION

Recent studies have shown that sclerostin, which is a negative regulator of bone formation, could play an important role in the crosstalk between bone and glucose metabolism. The role of sclerostin and its link with glucose homeostasis in type 1 diabetes mellitus (T1D) has not been yet studied extensively in children. The aim of this study was to assess sclerostin and its relationship between other bone and fat related factors as well as glucose metabolism in children and adolescents with T1D in comparison to their healthy peers.

METHODS

Forty patients with T1D, 18 girls, mean age 12.3 ± 4.7 yrs, and 28 healthy as controls (13.1 ± 4.2 yrs), sex and Tanner stage-matched were included into the study. Fasting blood samples for measurement of sclerostin, osteocalcin (OC), leptin, adiponectin, vitamin D, fasting glucose, lipid profile, HbA1c, and C-peptide were taken at 8.00 AM.

RESULTS

Sclerostin levels were significantly higher in patients with T1D than in the control group (p = 0.04) without significant differences between genders. Pearson correlation coefficients revealed a positive association between serum sclerostin levels and leptin OC (r = 0.59, p < 0.001) and a negative correlation between serum sclerostin levels and leptin (r = -0.32, p = 0.02) in all of the subjects and no significant correlations between sclerostin and adiponectin, 25(OH)D3, nor lipids. In the group of T1D patients a strong positive association between serum sclerostin levels and OC (r = 0.62, p < 0.001), and a negative association between serum sclerostin levels and HbA1c and leptin levels (r = -0.33, p = 0.04; r = -0.33, p = 0.03, respectively) were found. These associations were significant also after adjusting the analysis to the age, SDS-BMI and Tanner staging. In the healthy group after adjustment to age, SDS-BMI and Tanner stage, a negative correlation between sclerostin and C-peptide (r = -0.79, p = 0.02) was found.

CONCLUSIONS

Our data suggest a possible relationship between sclerostin and glucose metabolism in children and adolescents with T1D. It would be worth to investigate if an increase in sclerostin levels could present as a potential cause of the reduction of bone formation in T1D. Both bone-derived OC as well as fat-derived leptin seems to possibly modulate the participation of sclerostin in metabolic regulation in T1D.

Association between undercarboxylated osteocalcin, bone mineral density, and metabolic parameters in postmenopausal women

OBJECTIVE

Osteocalcin has been associated with several effects on energy and glucose metabolism. However, the physiological role of undercarboxylated osteocalcin (U-osc; the hormonally active isoform of osteocalcin) is still controversial. To correlate the serum levels of U-osc with bone mineral density (BMD) values and metabolic parameters in postmenopausal women.

SUBJECTS AND METHODS

Cross-sectional study including 105 postmenopausal women (age 56.5 ± 6.1 years, body mass index [BMI] 28.2 ± 4.9 kg/m2) grouped based on the presence of three or less, four, or five criteria of metabolic syndrome according to the International Diabetes Federation (IDF). The subjects underwent dualenergy x-ray absorptiometry (DXA) for the assessment of body composition and BMD and blood tests for the measurement of U-osc and bone-specific alkaline phosphatase (BSAP) levels.

RESULTS

The mean U-osc level was 3.1 ± 3.4 ng/mL (median 2.3 ng/mL, range 0.0-18.4 ng/mL) and the mean BSAP level was 12.9 ± 4.0 ng/mL (median 12.1 ng/mL, range 73-24.4 ng/mL). There were no associations between U-osc and BSAP levels with serum metabolic parameters. Lower fasting glucose levels were observed in participants with increased values of U-osc/femoral BMD ratio (3.61 ± 4 ng/mL versus 10.2 ± 1.6 ng/mL, p = 0.036). When the participants were stratified into tertiles according to the U-osc/ femoral BMD and U-osc/lumbar BMD ratios, lower fasting glucose levels correlated with increased ratios (p = 0.029 and p = 0.042, respectively).

CONCLUSION

Based on the ratio of U-osc to BMD, our study demonstrated an association between U-osc and glucose metabolism. However, no association was observed between U-osc and metabolic parameters.The U-osc/BMD ratio is an innovative way to correct the U-osc value for bone mass.

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.

Longitudinal changes in bone-testis axis and their associations with insulin resistance in 11- to 12-year-old boys

PURPOSE

Associations between osteocalcin (OCN), an osteoblast-specific hormone, and different markers of energy metabolism and insulin resistance have been reported in adults, but few studies have investigated this in children. The aim of the current study was to investigate serum OCN levels during pubertal development in normal weight (NW) and overweight (OW) boys, and to evaluate possible associations of OCN with body composition, testosterone, insulin resistance and adipocytokine values during puberty.

METHODS

Ninety 11- to 12-year-old boys were investigated at 12-month intervals over the next 2years. Boys were divided by their BMI into NW (n=60) and OW (n=30) groups. Serum OCN, testosterone, leptin, adiponectin, insulin, HOMA-IR score, and body composition were measured.

RESULTS

Pubertal development over the 2-year period was similar in both groups. Serum OCN was not different at the beginning of the study and increased similarly in both groups. However, at the end of the study, NW had higher OCN than OW (142.9±5.2 vs. 124.0±7.4ng/ml; p<0.05). OW had higher leptin, insulin and HOMA-IR compared to NW, and these differences remained significant through the 2-year period. Testosterone, insulin and HOMA-IR increased through the study period in both groups. In multiple regression analyses increment in OCN was associated with the increase in testosterone in NW (p<0.001) and OW (p=0.049) boys. Increment in OCN was also associated with the increase in insulin (p=0.019) and HOMA-IR (p=0.012) over the 2-year period in NW boys.

CONCLUSION

Serum OCN concentration increases in puberty and the increment is positively associated with the rise in testosterone level in both NW and OW boys. The positive association between the rise in OCN and insulin in NW boys would suggest that OCN may have a role in the development of insulin resistance.

The effects of resistance training volume on osteosarcopenic obesity in older women

The aim of this study was to analyze the effects of resistance training (RT) performed with 1 or 3 sets per exercise on osteosarcopenic obesity (OSO) syndrome parameters in older women. Sixty-two older women (68.0 ± 4.3 years, 26.8 ± 4.4 kg/m²) participated in a 12-week RT program. Participants were randomly assigned into one of the three groups: two training groups that performed either 1 set (G1S, n = 21) or 3 sets (G3S, n = 20) 3 times weekly, or a control group (CG, n = 21). Body composition was assessed by dual X-ray absorptiometry, strength was evaluated by 1 repetition maximum testing. The G3S presented significantly higher strength changes than G1S. The changes for percentage of body fat were higher for G3S compared to G1S. There was no difference in skeletal muscle mass between G3S and G1S, however both training groups displayed greater increases in this outcome compared to CG. There was no effect for bone mineral density. The overall analysis indicated higher (P < 0.05) positive changes for G3S than G1S (composed Z-score: G3S = 0.62 ± 0.40; G1S = 0.11 ± 0.48). The results suggest that a 12-week RT period is effective to improve the risk factors of OSO, and that 3 sets induce higher improvements than a single set.

Relationship between plasma osteocalcin, glycaemic control and components of metabolic syndrome in adult Nigerians with type 2 diabetes mellitus

AIMS

To determine the levels of plasma osteocalcin (OC) in Nigerians with type 2 diabetes mellitus (DM) and compare these to levels in non-diabetic controls (NDM). To assess the relationship of OC to glycaemic control and parameters of metabolic syndrome (MetS) and compare its levels in Nigerians with and without MetS.

METHODS

The waist circumference (WC), body mass index (BMI) and blood pressure of 200 study participants were taken. Plasma osteocalcin, fasting glucose (FPG), glycated haemoglobin (HbA1c), high density lipoprotein cholesterol (HDL-c) and triglyceride (TG) levels were determined. Metabolic syndrome was defined by the International Diabetes Federation criteria. Statistical significance was set at 0.05.

RESULTS

Osteocalcin levels were lower in the DM group (p=0.002) and inversely related to FPG (r=-0.198, p=0.003), HbA1c (r=-0.313, p<0.001), BMI (r=-0.331, p<0.001), WC (r=-0.339, p<0.001) and TG (r=-0.145, p=0.040), but directly related to HDL-c levels (r=0.166, p=0.019). Osteocalcin was higher in participants without MetS (Median 8.75ng/mL IQR[5.48-12.68]ng/mL) than in those with MetS (Median 4.74ng/Ml, IQR[2.80-9.12]ng/mL), p<0.001.

CONCLUSIONS

Plasma osteocalcin levels are inversely associated with good glycaemic control and components of MetS and are lower in individuals with DM and in those with MetS. These findings support a vital role of the bone, in the regulation of glucose and energy metabolism, in Nigerians. Further extensive studies are required to explore the potentials of OC in the management of DM and MetS.

Aging human body: changes in bone, muscle and body fat with consequent changes in nutrient intake

Aging affects almost all physiological processes, but changes in body composition and body phenotype are most observable. In this review, we focus on these changes, including loss of bone and muscle and increase in body fat or redistribution of the latter, possibly leading to osteosarcopenic obesity syndrome. We also address low-grade chronic inflammation, prevalent in aging adults and a cause of many disorders including those associated with body composition. Changes in dietary intake and nutritional requirements of older individuals, that all may lead to some disturbances on tissue and organ levels, are discussed as well. Finally, we discuss the hormonal changes in the aging body, considering each of the tissues, bone, muscle and fat as separate endocrine organs, but yet in the continuous interface and communication with each other. Although there are still many unanswered questions in this field, this review will enable the readers to better understand the aging human body and measures needing to be implemented toward reducing impaired health and disability in older individuals.

Resveratrol suppresses thyroid hormone‑induced osteocalcin synthesis in osteoblasts

Resveratrol, a polyphenolic compound that is present in grape skins, berries and red wine, may be beneficial for human health through its anti‑inflammatory and anti‑oxidant effects. It has been previously demonstrated that resveratrol exerts its biological effects primarily via sirtuin 1 (SIRT1) activation. We previously reported that triiodothyronine (T3) induces osteocalcin synthesis in osteoblast‑like MC3T3‑E1 cells, and that p38 mitogen‑activated protein (MAP) kinase mediates the T3‑stimulated synthesis of osteocalcin. The present study investigated the effect of resveratrol on T3‑induced osteocalcin synthesis and its underlying mechanism in MC3T3‑E1 cells. Cultured cells were stimulated with T3, and osteocalcin release from MC3T3‑E1 cells was measured by ELISA and phosphorylation of p38 MAP kinase was analyzed by western blotting. Resveratrol significantly suppressed the release of osteocalcin stimulated by T3, and SRT1720, a SIRT1 activator, significantly reduced T3‑induced osteocalcin release. The expression level of osteocalcin mRNA stimulated by T3 was significantly attenuated by resveratrol and T3‑induced transactivation activity of the thyroid hormone‑responsive element was significantly diminished by resveratrol. However, only limited effects of resveratrol on the T3‑induced phosphorylation of p38 MAP kinase were observed. The results of the present study demonstrated that resveratrol suppresses T3‑stimulated osteocalcin synthesis at a point upstream of transcription in osteoblasts, and that the inhibitory effect of resveratrol is mediated, at least partially, through SIRT1 activation. These results indicate that there may be a novel role for the polyphenol in the modulation of bone metabolism.

Connecting Bone and Fat: The Potential Role for Sclerostin

Sclerostin (SOST), a protein secreted from mature osteocytes in response to mechanical unloading and other stimuli, inhibits the osteogenic Wnt/β-catenin pathway in mesenchymal stem cells (MSCs) impeding their ability to differentiate into mineralizing osteoblasts.

PURPOSE

This review summarizes the crosstalk between adipose tissue and bone. It also reviews the origin, regulation, and role of SOST in osteogenesis and brings attention to an emerging role of this protein in the regulation of adipogenesis.

RECENT FINDINGS

Bone-derived molecules that drive MSC adipogenesis have not previously been identified, but recent findings suggest that SOST signaling may induce adipogenesis. In vivo SOST acts locally to induce changes in bone and, in vitro, increases adipogenesis in 3T3-L1 preadipocytes.

SUMMARY

SOST is able to induce adipogenesis in certain preadipocytes, however bone-specific studies are needed to determine the effect of local SOST concentrations in healthy and disease models on bone marrow adipose tissue.

Whole-Body Vibration Mimics the Metabolic Effects of Exercise in Male Leptin Receptor-Deficient Mice

Whole-body vibration (WBV) has gained attention as a potential exercise mimetic, but direct comparisons with the metabolic effects of exercise are scarce. To determine whether WBV recapitulates the metabolic and osteogenic effects of physical activity, we exposed male wild-type (WT) and leptin receptor-deficient (db/db) mice to daily treadmill exercise (TE) or WBV for 3 months. Body weights were analyzed and compared with WT and db/db mice that remained sedentary. Glucose and insulin tolerance testing revealed comparable attenuation of hyperglycemia and insulin resistance in db/db mice following TE or WBV. Both interventions reduced body weight in db/db mice and normalized muscle fiber diameter. TE or WBV also attenuated adipocyte hypertrophy in visceral adipose tissue and reduced hepatic lipid content in db/db mice. Although the effects of leptin receptor deficiency on cortical bone structure were not eliminated by either intervention, exercise and WBV increased circulating levels of osteocalcin in db/db mice. In the context of increased serum osteocalcin, the modest effects of TE and WBV on bone geometry, mineralization, and biomechanics may reflect subtle increases in osteoblast activity in multiple areas of the skeleton. Taken together, these observations indicate that WBV recapitulates the effects of exercise on metabolism in type 2 diabetes.

Bone Cell Bioenergetics and Skeletal Energy Homeostasis

The rising incidence of metabolic diseases worldwide has prompted renewed interest in the study of intermediary metabolism and cellular bioenergetics. The application of modern biochemical methods for quantitating fuel substrate metabolism with advanced mouse genetic approaches has greatly increased understanding of the mechanisms that integrate energy metabolism in the whole organism. Examination of the intermediary metabolism of skeletal cells has been sparked by a series of unanticipated observations in genetically modified mice that suggest the existence of novel endocrine pathways through which bone cells communicate their energy status to other centers of metabolic control. The recognition of this expanded role of the skeleton has in turn led to new lines of inquiry directed at defining the fuel requirements and bioenergetic properties of bone cells. This article provides a comprehensive review of historical and contemporary studies on the metabolic properties of bone cells and the mechanisms that control energy substrate utilization and bioenergetics. Special attention is devoted to identifying gaps in our current understanding of this new area of skeletal biology that will require additional research to better define the physiological significance of skeletal cell bioenergetics in human health and disease.

Do metabolic syndrome and its components have an impact on bone mineral density in adolescents?

In recent years, there has been growing concern about the occurrence of metabolic syndrome (MetS) at an early age and its effects on bone mass in adolescents. Adolescence is considered a critical period for bone mass gain. Impaired bone acquisition during this phase can lead to “suboptimal” peak bone mass and increase the risk of osteopenia/osteoporosis and fractures in old age. The objective of this review was to perform a critical analysis of articles that specifically focus on this age group, evaluating the influence of MetS and its components on bone mineral density in adolescents. A possible relationship between this syndrome and bone mass has been demonstrated, but the number of studies addressing this topic in adolescents is small. Despite the scarcity of evidence, the results of those studies show that Metabolic Syndrome is negatively correlated with bone mass and also that some components of MetS are negatively correlated with bone mineral density in adolescents. However, the associations between MetS and bone mass development need to be further explored in the age group corresponding to adolescence. Further good-quality studies are necessary to complement the understanding of this relationship.

Attenuation by incretins of thyroid hormone-stimulated osteocalcin synthesis in osteoblasts

Incretins, the polypeptide hormone glucose- dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) secreted from the small intestine after nutrient ingestion, are generally known to stimulate insulin secretion from pancreatic β-cells. We previously demonstrated that triiodothyronine (T₃) stimulates osteocalcin synthesis at least in part through p38 mitogen-activated protein kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effects of GIP and GLP-1 on T₃-stimulated osteocalcin synthesis and the mechanism of action involved in MC3T3-E1 cells. GIP and GLP-1 markedly suppressed the T₃-stimulated osteocalcin release. GIP and GLP-1 significantly attenuated the expression levels of osteocalcin mRNA induced by T₃. The T₃-stimulated transactivation activity of the thyroid hormone-responsive element was reduced by GIP and GLP-1. These results suggest that incretins repressed the T₃-stimulated osteocalcin synthesis in osteoblast-like MC3T3-E1 cells, and the suppressive effect of incretins was mediated through transcriptional levels.

Suppressed bone remodeling in black bears conserves energy and bone mass during hibernation

Decreased physical activity in mammals increases bone turnover and uncouples bone formation from bone resorption, leading to hypercalcemia, hypercalcuria, bone loss and increased fracture risk. Black bears, however, are physically inactive for up to 6 months annually during hibernation without losing cortical or trabecular bone mass. Bears have been shown to preserve trabecular bone volume and architectural parameters and cortical bone strength, porosity and geometrical properties during hibernation. The mechanisms that prevent disuse osteoporosis in bears are unclear as previous studies using histological and serum markers of bone remodeling show conflicting results. However, previous studies used serum markers of bone remodeling that are known to accumulate with decreased renal function, which bears have during hibernation. Therefore, we measured serum bone remodeling markers (BSALP and TRACP) that do not accumulate with decreased renal function, in addition to the concentrations of serum calcium and hormones involved in regulating bone remodeling in hibernating and active bears. Bone resorption and formation markers were decreased during hibernation compared with when bears were physically active, and these findings were supported by histomorphometric analyses of bone biopsies. The serum concentration of cocaine and amphetamine regulated transcript (CART), a hormone known to reduce bone resorption, was 15-fold higher during hibernation. Serum calcium concentration was unchanged between hibernation and non-hibernation seasons. Suppressed and balanced bone resorption and formation in hibernating bears contributes to energy conservation, eucalcemia and the preservation of bone mass and strength, allowing bears to survive prolonged periods of extreme environmental conditions, nutritional deprivation and anuria.

The RUNX2 Transcription Factor Negatively Regulates SIRT6 Expression to Alter Glucose Metabolism in Breast Cancer Cells

Activation of genes promoting aerobic glycolysis and suppression of mitochondrial oxidative phosphorylation is one of the hallmarks of cancer. The RUNX2 transcription factor mediates breast cancer (BC) metastasis to bone and is regulated by glucose availability. But, the mechanisms by which it regulates glucose metabolism and promotes an oncogenic phenotype are not known. RUNX2 expression in luminal BC cells correlated with lower estrogen receptor-α (ERα) levels, anchorage-independent growth, expression of glycolytic genes, increased glucose uptake, and sensitivity to glucose starvation, but not to inhibitors of oxidative phosphorylation. Conversely, RUNX2 knockdown in triple-negative BC cells inhibited mammosphere formation and glucose dependence. RUNX2 knockdown resulted in lower LDHA, HK2, and GLUT1 glycolytic gene expression, but upregulation of pyruvate dehydrogenase-A1 (PDHA1) mRNA and enzymatic activity, which was consistent with lower glycolytic potential. The NAD-dependent histone deacetylase, SIRT6, a known tumor suppressor, was a critical regulator of these RUNX2-mediated metabolic changes. RUNX2 expression resulted in elevated pAkt, HK2, and PDHK1 glycolytic protein levels that were reduced by ectopic expression of SIRT6. RUNX2 also repressed mitochondrial oxygen consumption rates (OCR), a measure of oxidative phosphorylation (respiration). Overexpression of SIRT6 increased respiration in RUNX2-positive cells, but knockdown of SIRT6 in cells expressing low RUNX2 decreased respiration. RUNX2 repressed SIRT6 expression at both the transcriptional and post-translational levels and endogenous SIRT6 expression was lower in malignant BC tissues or cell lines that expressed high levels of RUNX2. These results support a hypothesis whereby RUNX2-mediated repression of the SIRT6 tumor suppressor regulates metabolic pathways that promote BC progression.

Histological and radiographic study of human edentulous and dentulous maxilla

Data on the bone trabecular structure and density of the edentulous regions of the first upper molars are important for designing successful dental treatments, especially dental implants. However, no detailed defined morphometric properties on the human maxilla are available at the immunohistochemical and radiographic levels. Cone-beam computed tomography analysis and immunohistochemical observation were applied to the maxillary first molar region of 91 cadavers (46 males and 45 females). The edentulous maxilla can be classified into the following three forms: fully edentulous (FE), partially edentulous (PE), and immediately edentulous (IE). Compared with the first molar dentulous (FMD) specimens, significant differences in cortical bone structure and bone density exist among IE, PE, and FE in maxilla (P < 0.001). According to histochemical observations, the positive CD31 reaction clearly described a large vessel of the PE and small vessels of FMD and IE in maxillary sinus connective tissue. These structural issues were clearly related to tooth extraction. These morphological and radiographic data describing the edentulous region of the maxillary first molar might be useful for improving dental treatments.

Association of lipid parameters and insulin resistance with bone health in South Korean adolescents

This study investigated the association between lipid profiles and insulin resistance and bone mineral content (BMC) in Korean adolescents and found that BMC was inversely associated with triglyceride (TG) and homeostasis model assessment of insulin resistance (HOMA-IR). This association did not differ according to obesity status in either boys or girls.

INTRODUCTION

To prevent future osteoporosis, it is important to identify factors that affect bone health in adolescents as well as adults. This study aimed to examine the association between lipid profiles and insulin resistance and BMC in Korean adolescents.

METHODS

Data from 706 boys and 621 girls, who participated in the Korea National Health and Nutrition Examination Survey from 2008 to 2011, were analyzed. Lipid profiles were measured, and HOMA-IR was calculated to assess insulin resistance. BMC was measured for the total femur, femur neck, and lumbar spine by using whole-body dual-energy X-ray absorptiometry (DXA).

RESULTS

TG level and HOMA-IR were negatively correlated with BMC at all three sites in boys. In girls, TG level showed a negative correlation with BMC at the femur neck and lumbar spine, and HOMA-IR was negatively associated with BMC at the femur neck only. These inverse associations did not differ according to obesity status in either sex. Adjusted means of BMC at the three sites in boys tended to decrease in the higher tertile groups of TG and HOMA-IR, and the adjusted means of BMC for the total femur in girls tended to decrease in the higher tertile groups of TG and HOMA-IR.

CONCLUSIONS

BMC was inversely associated with TG and HOMA-IR in Korean adolescents, and this association was more pronounced in boys. This association did not differ according to obesity status in either sex.

Low osteocalcin level is a risk factor for impaired glucose metabolism in a Chinese male population

AIMS/INTRODUCTION

This study was to assess the association between serum osteocalcin level and glucose metabolism in a Chinese male population.

MATERIALS AND METHODS

We carried out a cross-sectional study with a cohort of participants from the Fangchenggang Area Male Health and Examination Survey. The cross-sectional study was carried out among 2,353 men, including 2,139 participants with normal glucose tolerance, 148 with impaired fasting glucose and 66 with type 2 diabetes. A subsample of 1,109 men with measurement of osteocalcin was observed in the cohort. After a 4-year follow-up period, 1,049 non-diabetic and 983 participants with normal glucose tolerance who submitted the available information were enrolled in the cohort. Participants were divided into group-H (≥23.33 ng/mL) and group-L (<23.33 ng/mL) by osteocalcin level.

RESULTS

In the cross-sectional study, osteocalcin levels were highest in participants with normal glucose tolerance, followed by those with impaired fasting glucose and type 2 diabetes (P < 0.001). In partial correlation analysis adjusted for age, serum osteocalcin level was related to glucose level (r = -0.082, P < 0.001), insulin level (r = -0.079, P < 0.001) and insulin resistance (r = -0.065, P = 0.002). Compared with group-H, group-L was associated with an increased risk of type 2 diabetes (odds ratio 2.107, 95% confidence interval 1.123-3.955), impaired fasting glucose (odds ratio 2.106; 95% CI 1.528-2.902), and insulin resistance (odds ratio 1.359, 95% confidence interval 1.080-1.710) adjusted for age, education levels, cigarette smoking and lipid profiles. In the cohort study, the increased risk of impaired fasting glucose was significant in group-L vs group-H (3.3% vs 1.2%, P = 0.026).

CONCLUSIONS

Low serum osteocalcin level was a risk factor for impaired glucose metabolism and subsequent type 2 diabetes.

Maternal serum osteocalcin at 11-14 weeks of gestation in gestational diabetes mellitus

BACKGROUND

Recent studies support that osteocalcin (OC), apart from its skeletal role, is implicated in glucose homoeostasis. Aims of this study were to examine the first-trimester maternal serum concentrations of OC in pregnancies that developed gestational diabetes mellitus (GDM) and to create a first-trimester prediction model for GDM.

DESIGN

Case-control study in a prospective cohort of pregnant women. Maternal serum levels of OC were measured in 40 cases that developed GDM and 94 unaffected controls. First-trimester biophysical parameters, biochemical indices, maternal-pregnancy characteristics, and OC concentrations were assessed in relation to GDM occurrence.

RESULTS

In the GDM group, first-trimester OC serum levels were increased compared to the control group (mean = 8·81 ng/mL, SD = 2·59 vs. mean = 7·34 ng/ml, SD = 3·04, P = 0·0058). Osteocalcin was independent of first-trimester biophysical and biochemical indices. Osteocalcin alone (OR = 1·21, CI: 1·02-1·43, P = 0·023) was a significant predictor of GDM [Model R(2) = 0·04, area under the curve (AUC) = 0·61, CI: 0·55-0·72, P < 0·001]. The combination of maternal and pregnancy characteristics with OC resulted in an improved prediction model for GDM (Model R(2) = 0·21, AUC = 0·80, CI: 0·71-0·88, P < 0·001). The combined model yields a sensitivity of 72·2% for 25% false-positive rate.

CONCLUSIONS

First-trimester maternal serum levels of OC are increased in GDM pregnancies. Osteocalcin combined with maternal and pregnancy characteristics provides an effective screening for GDM at 11-14 weeks.

Coronary artery calcification is associated with high serum concentration of undercarboxylated osteocalcin in asymptomatic Korean men

CONTEXT

Osteocalcin is associated with energy metabolism and atherosclerosis, besides bone metabolism. However, the association between osteocalcin or its undercarboxylated form (ucOC) and coronary artery calcification is controversial.

OBJECTIVE

To evaluate the relationship between coronary artery calcium score (CACS) and the concentration of serum osteocalcin and ucOC.

DESIGN

Cross-sectional.

PATIENTS

A total of 162 subjects (114 men and 48 women) with no angina symptom.

MEASUREMENTS

Serum analyses included glucose, insulin and lipid profiles as well as osteocalcin and ucOC. Bone mineral density (BMD) was measured by dual X-ray absorptiometry. CACS was measured using multidetector computed tomography and categorized into CACS = 0 and CACS > 0.

RESULTS

The mean osteocalcin concentration in men was 15·6 ± 4·2 for CACS = 0 group and 14·1 ± 4·0 for CACS > 0 group, respectively (P = 0·050). In women, the osteocalcin concentration, ucOC concentration and ucOC to osteocalcin ratio (OCR) were not different between the CACS groups. However, the concentrations of osteocalcin and ucOC were significantly lower in women with hypertension or diabetes than those without, respectively. In the multivariate logistic regression models adjusted for medical history, body mass index, lipid profiles, insulin resistance and BMD in men, the higher concentration of ucOC and higher OCR showed significant association with coronary calcification (CACS > 0).

CONCLUSION

Higher ucOC concentration was associated with coronary artery calcification independent of conventional cardiovascular risk factors and BMD in men.

Higher daily physical activity is associated with higher osteocalcin levels in adolescents

BACKGROUND

Exercise stimulates bone remodeling and improves insulin sensitivity (Si), even without associated weight loss. Osteocalcin (OCN), a bone-derived protein, is associated with improved Si.

PURPOSE

We examined how daily physical activity is associated with OCN and Si.

METHODS

Physical activity was measured through questionnaires completed in Minneapolis from 2010-2012. A physical activity score (PAQsum) was calculated to quantify physical activity (range 1-5). OCN and bone specific alkaline phosphatase (BAP) were measured by ELISA. Si was measured by the insulin modified frequently sampled IV glucose tolerance test.

RESULTS

The mean PAQsum value was 2.4±0.8 in 47 participants (12-17.9 years old). PAQsum was positively associated with OCN (p= 0.006). Participants with PAQsum<2 had significantly lower OCN levels compared to participants with PAQsum>2 (p<0.02). Obesity did not modify the association between PAQsum and OCN. There was no statistically significant association between PAQsum and Si or between OCN and Si, even after adjustment for percent body fat.

CONCLUSIONS

OCN is higher in more physically active individuals. More research is needed to clarify the relationship between OCN, physical activity and Si.

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.

Osteocalcin, but not deoxypyridinoline, increases in response to isoflurane-induced anaesthesia in young female guinea pigs

The effect of the inhaled anaesthetic isoflurane was investigated on bone biomarkers, both during maturation and on minerals and glucose postpartum. Female guinea pigs (n = 10) were anaesthetized during maturation (5 and 9 weeks) and postpartum (26 weeks of age) with isoflurane during dual-energy X-ray absorptiometry scanning. Blood collection was performed at all ages before and after anaesthesia for measurement of plasma osteocalcin (OC), total deoxypyridinoline (tDPD), and cortisol. Postpartum measurements also included: blood ions, acid-base parameters and glucose, plasma minerals, total alkaline phosphatase (tALP), and albumin. Plasma OC concentration almost doubled after exposure to isoflurane at 5 weeks (30.1 ± 5.0-57.9 ± 11.2 nmol/L, p < 0.001) and at 9 weeks (29.1 ± 7.5-62.9 ± 15.9 nmol/L, p < 0.001), but did not change postpartum (3.7 ± 3.3-4.3 ± 3.9 nmol/L, p = 0.88). There was no effect of isoflurane exposure on plasma tDPD at any age. Plasma cortisol increased after exposure to isoflurane at 9 weeks (1859.6 ± 383.2-2748.0 ± 235.3 nmol/L, p < 0.01) and postpartum (3376.7 ± 322.2-4091.6 ± 195.6 nmol/L, p < 0.001) but not at 5 weeks (2088.3 ± 326.4-2464.1 ± 538.0 nmol/L, p > 0.05). Blood ionized Ca(2+), Na(+) and plasma total Ca did not change, whereas plasma albumin decreased, and inorganic phosphate (PO4) and Cl(-) increased upon exposure to isoflurane. Isoflurane decreased tALP (43.2 ± 6.6-40.2 ± 5.9 IU/L, p = 0.01) and increased glucose (7.5 ± 0.6-10.9 ± 1.7 mmol/L, p < 0.0001) postpartum. Isoflurane inflates the assessment of a bone-derived biomarker, OC, during rapid growth, but not following pregnancy when formation is very low. Measurements prior to anaesthesia are recommended to reflect normal metabolism.

Effects of moderate amounts of barley in late pregnancy on growth, glucose metabolism and osteoarticular status of pre-weaning horses

In stud management, broodmares are commonly fed concentrates in late pregnancy. This practice, however, was shown to correlate with an increased incidence of osteochondrosis in foals, which may be related to insulin sensitivity. We hypothesized that supplementation of the mare with barley in the last trimester of pregnancy alters the pre-weaning foal growth, glucose metabolism and osteoarticular status. Here, pregnant multiparous saddlebred mares were fed forage only (group F, n=13) or both forage and cracked barley (group B, n=12) from the 7th month of pregnancy until term, as calculated to cover nutritional needs of broodmares. Diets were given in two daily meals. All mares and foals returned to pasture after parturition. Post-natal growth, glucose metabolism and osteoarticular status were investigated in pre-weaning foals. B mares maintained an optimal body condition score (>3.5), whereas that of F mares decreased and remained low (<2.5) up to 3 months of lactation, with a significantly lower bodyweight (-7%) than B mares throughout the last 2 months of pregnancy. B mares had increased plasma glucose and insulin after the first meal and after the second meal to a lesser extent, which was not observed in F mares. B mares also had increased insulin secretion during an intravenous glucose tolerance test (IVGTT). Plasma NEFA and leptin were only temporarily affected by diet in mares during pregnancy or in early lactation. Neonatal B foals had increased serum osteocalcin and slightly increased glucose increments and clearance after glucose injection, but these effects had vanished at weaning. Body measurements, plasma IGF-1, T4, T3, NEFA and leptin concentrations, insulin secretion during IVGTT, as well as glucose metabolism rate during euglycemic hyperinsulinemic clamps after weaning, did not differ between groups. Radiographic examination of joints indicated increased osteochondrosis relative risk in B foals, but this was not significant. These data demonstrate that B or F maternal nutrition has very few effects on foal growth, endocrinology and glucose homeostasis until weaning, but may induce cartilage lesions.

Deletion of the nuclear localization sequence and C-terminus of parathyroid hormone-related protein decreases osteogenesis and chondrogenesis but increases adipogenesis and myogenesis in murine bone marrow stromal cells

The N-terminus of parathyroid hormone-related protein regulates bone marrow stromal cell differentiation. We hypothesized that the nuclear localization sequence and C-terminus are involved. MicroRNA and gene expression analyses were performed on bone marrow stromal cells from mice lacking the nuclear localization sequence and C-terminus (PthrpΔ/Δ ) and age-matched controls. Differentiation assays with microRNA, cytochemical/histologic/morphologic, protein, and gene expression analyses were performed. PthrpΔ/Δ bone marrow stromal cells are anti-osteochondrogenic, pro-adipogenic, and pro-myogenic, expressing more Klf4, Gsk-3β, Lif, Ct-1, and microRNA-434 but less β-catenin, Igf-1, Taz, Osm, and microRNA-22 (p ⩽ 0.024). PthrpΔ/Δ osteoblasts had less mineralization, osteocalcin, Runx2, Osx, Igf-1, and leptin (p ⩽ 0.029). PthrpΔ/Δ produced more adipocytes, Pparγ, and aP2, but less Lpl (p ⩽ 0.042). PthrpΔ/Δ cartilage pellets were smaller with less Sox9 and Pth1r, but greater Col2a1 (p ⩽ 0.024). PthrpΔ/Δ produced more myocytes, Des, and Myog (p ⩽ 0.021). MicroRNA changes supported these findings. In conclusion, the nuclear localization sequence and C-terminus are pro-osteochondrogenic, anti-adipogenic, and anti-myogenic.

Changes in Bone Biomarkers, BMC, and Insulin Resistance Following a 10-Week Whole Body Vibration Exercise Program in Overweight Latino Boys

PURPOSE

With the childhood obesity epidemic, efficient methods of exercise are sought to improve health. We tested whether whole body vibration (WBV) exercise can positively affect bone metabolism and improve insulin/glucose dynamics in sedentary overweight Latino boys.

METHODS

Twenty Latino boys 8-10 years of age were randomly assigned to either a control (CON) or 3 days/wk WBV exercise (VIB) for 10-wk.

RESULTS

Significant increases in BMC (4.5 ± 3.2%; p=0.01) and BMD (1.3 ± 1.3%; p<0.01) were observed for the VIB group when compared to baseline values. For the CON group BMC significantly increased (2.0 ± 2.2%; p=0.02), with no change in BMD (0.8 ± 1.3%; p=0.11). There were no significant between group changes in BMC or BMD. No significant change was observed for osteocalcin and (collagen type I C-telopeptide) CTx for the VIB group. However, osteocalcin showed a decreasing trend (p=0.09) and CTx significantly increased (p<0.03) for the CON group. This increase in CTx was significantly different between groups (p<0.02) and the effect size of between-group difference in change was large (-1.09). There were no significant correlations between osteocalcin and measures of fat mass or insulin resistance for collapsed data.

CONCLUSION

Although bone metabolism was altered by WBV training, no associations were apparent between osteocalcin and insulin resistance. These findings suggest WBV exercise may positively increase BMC and BMD by decreasing bone resorption in overweight Latino boys.

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.

Genetic association analyses of fast plasma glucose level in pre-menopausal Chinese women: potential interaction between osteocalcin and oestrogen receptor α

BACKGROUND

Fasting plasma glucose (FPG) levels are usually tightly regulated within a narrow physiologic range. Variation of FPG levels is clinically important and is strongly heritable. Several lines of evidence suggest the importance of the oestrogen receptor α (ER-α) and osteocalcin (also known as BGP, for bone Gla protein) in determining FPG; however, whether their polymorphisms are associated with FPG variation is not well understood.

AIM

To investigate whether ER-a PvuII and BGP HindIII genetic polymorphisms and their potential interaction are associated with FPG variation.

SUBJECTS AND METHODS

The study subjects were 328 unrelated pre-menopausal Chinese women aged 21 years and over (mean age ± SD, 33.2 ± 5.9 years), with an average FPG of 4.92 (SD = 0.81). All subjects were genotyped at the ER-α PvuII and BGP HindIII loci using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP).

RESULTS

The ER-α PvuII genotypes were significantly associated with FPG (p = 0.007). In addition, a significant interaction was observed of the ER-α PvuII polymorphism with BGP HindIII polymorphism on FPG variation (p = 0.013), although the BGP HindIII polymorphism was not shown to be individually associated with FPG.

CONCLUSION

The PvuII polymorphism of the ER-α gene and its potential interaction with the HindIII polymorphism of the BGP gene were associated with FPG in pre-menopausal Chinese women.

Up-regulation of cyclinD1 and Bcl2A1 by insulin is involved in osteoclast proliferation

AIMS

Insulin receptor signaling in osteoblasts has been well established, but the effects of insulin on osteoclast proliferation are poorly explored. The objective of this study was to investigate the roles and the mechanisms of insulin on osteoclast proliferation.

MAIN METHODS

After insulin treatment to primary osteoclast precursors, BrdU incorporation assay was performed and the expression of cell cycle- and apoptosis-related genes was determined by real-time PCR and immunoblotting. Apoptosis was analyzed using a FACScan flow cytometer.

KEY FINDINGS

Insulin activated insulin receptor and promoted the proliferation of osteoclast precursors in time- and dose-dependent manners. However, the expression of insulin receptor was not changed by it during that time. Insulin remarkably induced the expression of cyclinD1, a cell cycle marker, and Bcl2A1, an anti-apoptotic oncogene, whereas cdk1 and cdk4 were not affected by it. The expression of Bcl2l11 and Bax, both apoptotic markers, was reduced or not changed in osteoclast precursors. Bcl2A1/Bax ratio was also increased in protein levels. Treatment with obatoclax, a Bcl2 family inhibitor, significantly induced the apoptosis of osteoclast precursors in the presence of insulin. These results demonstrate that insulin promotes osteoclast proliferation by increasing cell cycle and suppressing apoptosis through specific gene regulation.

SIGNIFICANCE

These data provide a basis for understanding and ultimately treating several bone-related metabolic diseases.

Endocrine crosstalk between muscle and bone

The musculoskeletal system is a complex organ comprised of the skeletal bones, skeletal muscles, tendons, ligaments, cartilage, joints, and other connective tissue that physically and mechanically interact to provide animals and humans with the essential ability of locomotion. This mechanical interaction is undoubtedly essential for much of the diverse shape and forms observed in vertebrates and even in invertebrates with rudimentary musculoskeletal systems such as fish. It makes sense from a historical point of view that the mechanical theories of musculoskeletal development have had tremendous influence of our understanding of biology, because these relationships are clear and palpable. Less visible to the naked eye or even to the microscope is the biochemical interaction among the individual players of the musculoskeletal system. It was only in recent years that we have begun to appreciate that beyond this mechanical coupling of muscle and bones, these 2 tissues function at a higher level through crosstalk signaling mechanisms that are important for the function of the concomitant tissue. Our brief review attempts to present some of the key concepts of these new concepts and is outline to present muscles and bones as secretory/endocrine organs, the evidence for mutual genetic and tissue interactions, pathophysiological examples of crosstalk, and the exciting new directions for this promising field of research aimed at understanding the biochemical/molecular coupling of these 2 intimately associated tissues.

Interrelationship among muscle, fat, and bone: connecting the dots on cellular, hormonal, and whole body levels

While sarcopenia and sarcopenic obesity have been recognized in the last decade, a combined concept to include decreased muscle mass and strength, as well as decreased bone mass with coexistence of adiposity is discussed here. We introduce a new term, osteopenic obesity, and operationalize its meaning within the context of osteopenia and obesity. Next, we consolidate osteopenic obesity with the already existing and more familiar term, sarcopenic obesity, and delineate the resulting combined condition assigning it the term osteosarcopenic obesity. Identification and possible diagnosis of each condition are discussed, as well as the interactions of muscle, fat and bone tissues on cellular level, considering their endocrine features. Special emphasis is placed on the mesenchymal stem cell commitment into osteoblastogenic, adipogenic and myogenic lineages and causes of its deregulation. Based on the presented evidence and as expounded within the text, it is reasonable to say that under certain conditions, osteoporosis and sarcopenia could be the obesity of bone and muscle, respectively, with the term osteosarcopenic obesity as an encompassment for all.

Effects of correction of vitamin D insufficiency on serum osteocalcin and glucose metabolism in obese children

OBJECTIVES

Osteocalcin (OCN) and vitamin D insufficiency (VDI) have been shown to be associated with abnormal glucose metabolism (GluMet). Whether correction of VDI affects serum OCN is unknown. This study evaluated the effects of correction of VDI on OCN and GluMet, and determined the associations of OCN with 25-hydroxyvitamin D (25-OHD) and GluMet.

DESIGN, PATIENTS AND MEASUREMENTS

This study involved 230 obese children in a cross-sectional part and 72 participants in a prospective part in which children with VDI were treated with vitamin D2 at a dose of 20 000 IU daily for 28 days. All 230 children underwent an oral glucose tolerance test and had their serum total and undercarboxylated OCNs and 25-OHD measured. Forty of 72 children were reassessed for the GluMet and serum total and undercarboxylated OCNs and 25-OHD after the vitamin D2 treatment.

RESULTS

In the prospective part, correction of VDI by raising mean (SD) 25-OHD of 51·5 (12·3) to 141·8 (40·8) nmol/l resulted in an improvement of their GluMet and increase in their whole-body insulin sensitivity index with no changes in their OCN measures. In the cross-sectional part, after adjustments for age, sex and puberty, the total (β = 0·322) and undercarboxylated OCNs (β = 0·315) were positively associated with insulinogenic index, which is an index of insulin secretion (P = 0·034 and 0·037, respectively) in the group of prediabetic and diabetic children.

CONCLUSIONS

Correction of VDI increased insulin sensitivity and improved GluMet, but had no effect on serum OCN measures. OCN was associated with increased insulin secretion in children with abnormal GluMet.

Insulin is inversely associated with bone mass, especially in the insulin-resistant population: the Korea and US National Health and Nutrition Examination Surveys

BACKGROUND

Insulin is an important osteotropic hormone but may be negatively associated with bone mass after adjustment for body mass index in adolescent populations. However, the association between insulin and bone mass in adults remains unclear.

OBJECTIVE

The objective of the study was to investigate whether insulin was associated with bone mass in adults and, if so, whether the association was positive or negative.

DESIGN

This study had a cross-sectional design, using data from the Fourth Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2009 and the US National Health and Nutrition Examination Survey (NHANES) 1999-2006.

SETTING

The setting for the study was the Korean and US population.

PARTICIPANTS

A total of 7271 KNHANES and 3399 NHANES participants were included.

MAIN OUTCOME MEASURES

Anthropometric parameters and bone mass data, fasting glucose and insulin, height, weight, and markers related to insulin resistance were measured.

RESULTS

After adjusting for confounding factors, there was an inverse relationship between insulin and total body bone mineral content in the KNHANES and NHANES subjects. In a stratified analysis, an association between insulin and bone mass was apparent, especially in the highest homeostatic model of assessment of insulin resistance quartile in the Korean subjects. However, this association was seen only in men in the US subjects.

CONCLUSIONS

There is an inverse relationship between insulin and total body bone mineral content after adjustment for confounding factors in Korean and US subjects, especially in the insulin-resistant population. This strongly suggests that the adverse influence of insulin on bone mass likely reflects the effects of other factors associated with insulin resistance rather than being a direct action of insulin itself.