A new link between skeleton, obesity and insulin resistance: relationships between osteocalcin, leptin and insulin resistance in obese children before and after weight loss

Heat shock response during the resolution of inflammation and its progressive suppression in chronic-degenerative inflammatory diseases

The heat shock response (HSR) is a crucial biochemical pathway that orchestrates the resolution of inflammation, primarily under proteotoxic stress conditions. This process hinges on the upregulation of heat shock proteins (HSPs) and other chaperones, notably the 70 kDa family of heat shock proteins, under the command of the heat shock transcription factor-1. However, in the context of chronic degenerative disorders characterized by persistent low-grade inflammation (such as insulin resistance, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases) a gradual suppression of the HSR does occur. This work delves into the mechanisms behind this phenomenon. It explores how the Western diet and sedentary lifestyle, culminating in the endoplasmic reticulum stress within adipose tissue cells, trigger a cascade of events. This cascade includes the unfolded protein response and activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome, leading to the emergence of the senescence-associated secretory phenotype and the propagation of inflammation throughout the body. Notably, the activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome not only fuels inflammation but also sabotages the HSR by degrading human antigen R, a crucial mRNA-binding protein responsible for maintaining heat shock transcription factor-1 mRNA expression and stability on heat shock gene promoters. This paper underscores the imperative need to comprehend how chronic inflammation stifles the HSR and the clinical significance of evaluating the HSR using cost-effective and accessible tools. Such understanding is pivotal in the development of innovative strategies aimed at the prevention and treatment of these chronic inflammatory ailments, which continue to take a heavy toll on global health and well-being.

Reduction of leptin levels during acute exercise is dependent on fasting but not on caloric restriction during chronic exercise: A systematic review and meta-analysis

BACKGROUND

The importance of leptin in controlling body mass has recently gained more attention. Its levels are directly associated with the amount of fat mass, but not necessarily dependent on it. Exercise has great potential in reducing leptin levels, however the response of exercise to this cytokine is still not well understood.

OBJECTIVE

The objective of the review was to analyze the effects of physical exercise on plasma leptin concentration, either acutely (post-exercise/training session) and/or after a training period (short- or long-term), as well as to investigate the existence of possible moderating variables.

METHODS

The studies included in this systematic review were published between 2005 and May 2023. Only peer-reviewed studies, available in English, performed with humans that evaluated the effects of any form of exercise on leptin levels were included. The search was conducted on May 03, 2023, in Embase (Elsevier), MEDLINE via PubMed®, and Web of Science (Core collection). The risk of bias in the included trials was assessed by the Physiotherapy Evidence Database tool, considering 11 questions regarding the methodology of each study with 10 questions being scored. The data (n, mean, and standard deviation) were extracted from included studies to perform random effects meta-analyses using standardized mean difference between the pre- and post-intervention effects.

RESULTS

Twenty-five studies (acute effect: 262 subjects; short- and long-term effect: 377 subjects) were included in this systematic review and meta-analysis. Short- and long-term physical exercise and caloric restriction plus exercise reduce plasma leptin levels, presenting statistically significant differences (p<0.001); as well as acute effect (p = 0.035), however the latter result was influenced by the pre-exercise meal as shown in the subgroup analysis. In this meta-analysis the effect of moderating factors on leptin reduction, not addressed by past reviews, is verified, such as the relationship with caloric restriction, exercise intensity and pre-exercise meal on acute responses.

CONCLUSION

Both acute and chronic exercise reduce leptin levels, yet the acute effect is dependent on the pre-exercise meal. In addition to having a long-term reduction in leptin levels, the minimum amount of weekly exercise to have a significant reduction in plasma leptin is 180 minutes of moderate-intensity exercise and 120 minutes of high-intensity exercise.

Prenatal Fumonisin Exposure Impairs Bone Development via Disturbances in the OC/Leptin and RANKL/RANK/OPG Systems in Weaned Rat Offspring

The goal of the current study was to examine the effects of prenatal exposure to fumonisins (FBs) on bone properties and metabolism in weaned rat offspring divided into groups intoxicated with FBs at either 0 (the 0 FB group), 60 (the 60 FB group), or 90 mg/kg b.w. 0 (the 90 FB group). Female and male offspring exposed to FBs at a dose of 60 mg/kg b.w. had heavier femora. Mechanical bone parameters changed in a sex and FBs dose-dependent manner. Growth hormone and osteoprotegerin decreased in both sexes, regardless of FBs dose. In males osteocalcin decreased, while receptor activator for nuclear factor kappa-Β ligand increased regardless of FBs dose; while in females changes were dose dependent. Leptin decreased in both male FBs-intoxicated groups, bone alkaline phosphatase decreased only in the 60 FB group. Matrix metalloproteinase-8 protein expression increased in both female FBs-intoxicated groups and decreased in male 90 FB group. Osteoprotegerin and tissue inhibitor of metalloproteinases 2 protein expression decreased in males, regardless of FBs dose, while nuclear factor kappa-Β ligand expression increased only in the 90 FB group. The disturbances in bone metabolic processes seemed to result from imbalances in the RANKL/RANK/OPG and the OC/leptin systems.

Serum Osteocalcin, Sclerostin and Lipocalin-2 Levels in Adolescent Boys with Obesity over a 12-Week Sprint Interval Training

The aim of the study was to examine the effects of supervised cycling sprint interval training (SIT) on serum osteocalcin, lipocalin-2 and sclerostin levels, and bone mineral characteristics among obese adolescent boys. Untrained obese adolescent boys aged 13.4 ± 0.3 were assigned to either a 12-week SIT group (3 sessions/week), or a non-exercising control group who continued with their habitual everyday life. Serum osteocalcin, lipocalin-2 and sclerostin concentrations, and bone mineral values were assessed before and after intervention. After 12-week intervention, where 14 boys in both groups ended the study, there were no significant differences in serum osteokine levels between the groups after 12 weeks, while whole body bone mineral content and lower limb bone mineral density increased in the SIT group (p < 0.05). Change in body mass index was negatively correlated with the change in osteocalcin (r = -0.57; p = 0.034), and positively correlated with the change in lipocalin-2 levels (r = 0.57; p = 0.035) in the SIT group. Supervised 12-week SIT intervention improved bone mineral characteristics, but did not change osteocalcin, lipocalin-2 or sclerostin levels in adolescent boys with obesity.

Identification of bone metabolism disorders in patients with Alström and Bardet-Biedl syndromes based on markers of bone turnover and mandibular atrophy

Objectives

Causative variants in genes responsible for Alström syndrome (ALMS) and Bardet-Biedl syndrome (BBS) cause damage to primary cilia associated with correct functioning of cell signaling pathways in many tissues. Despite differences in genetic background, both syndromes affect multiple organs and numerous clinical manifestations are common including obesity, retinal degeneration, insulin resistance, type 2 diabetes and many others. The aim of the study was to evaluate bone metabolism abnormalities and their relation to metabolic disorders based on bone turnover markers and presence of mandibular atrophy in patients with ALMS and BBS syndromes.

Material and methods

In 18 patients (11 with ALMS and 7 with BBS aged 5–29) and in 42 age-matched (p < 0.05) healthy subjects, the following markers of bone turnover were assessed: serum osteocalcin (OC), osteoprotegerin (OPG), s-RANKL and urinary deoxypyridinoline - DPD. In addition, a severity of alveolar atrophy using dental panoramic radiograms was evaluated.

Results

Lower serum OC (p = 0.0004) and urinary DPD levels (p = 0.0056) were observed in the study group compared to controls. In ALMS and BBS patients, serum OC and urinary DPD values negatively correlated with the HOMA-IR index, while a positive correlation between the OC and 25-OHD levels and a negative correlation between s-RANKL and fasting glucose concentrations were found. A significant difference in the incidence of low-grade mandibular atrophy between patients with ALMS and BBS and controls (p < 0.0001) was observed.

Conclusions

The identification of bone metabolism disorders in patients with ALMS and BBS syndromes indicates the necessity to provide them with appropriate diagnosis and treatment of these abnormalities.

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Bone metabolism disorders in Alstrom and Bardet-Biedl syndromes

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Markers of bone turnover in Alstrom and Bardet-Biedl syndromes

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Mandibular atrophy in Alstrom and Bardet-Biedl syndromes

Maternal vitamin D levels correlate with fetal weight and bone metabolism during pregnancy: a materno-neonatal analysis of bone metabolism parameters

OBJECTIVES

Vitamin D plays an essential role in neonatal skeletal development and maternal weight gain during pregnancy. We aim to study the association between vitamin D status, maternal weight, and materno-neonatal bone metabolism parameters.

METHODS

From January to June 2017, we conducted this cross-sectional study among 103 pregnant women (21-42 years old) and their singletons. The levels of serum 25-(OH)D, PTH, P1NP, OC, and CTX were measured for mothers and neonates (cord blood). Serum vitamin D and OC were measured using chemiluminescence and two-site immunoradiometric assay, respectively. Meanwhile, P1NP, CTX, and PTH were measured by ELISA.

RESULTS

The average serum vitamin D levels from mothers were 15.1 ng/mL during pregnancy and 16.2 ng/mL in the umbilical cord. At baseline, vitamin D deficient mothers were more likely to have higher PTH (36.4 vs. 18 pg/mL; p=0.029) and lower P1NP levels (90 vs. 92.5 ng/mL; p=0.026). Also, vitamin D deficient status was associated with lower fetal weight (3,293 vs. 3,358 g; p=0.019). Maternal weight was significantly correlated with P1NP (65.86 vs. 109.35; p=0.001) and OC (14.52 vs. 18.24; p=0.038), as well as cord vitamin D level (13.31 vs. 18.46; p=0.039) among normal vs. overweight women. No significant differences were found for the correlation between maternal weight and fetal parameters except for fetal weight which significantly increased with the increase in maternal weight (overweight vs. obese women=3,280 vs. 3,560; p=0.06).

CONCLUSIONS

Maternal vitamin D status is associated with maternal and neonatal bone metabolism parameters as well as maternal and neonatal weight.

Effects of Dietary Tannic Acid on Obesity and Gut Microbiota in C57BL/6J Mice Fed with High-Fat Diet

Dietary tannic acid, as a natural polyphenolic, has many important biological activities. This study aimed to investigate the effect of dietary tannic acid on obesity and gut microbiota in mice with a high-fat diet. Male C57BL/6J mice fed a high-fat diet were treated with dietary tannic acid for eight weeks. Results showed that dietary tannic acid reduced the body weight gain, regulated glycolipid metabolism, improved the insulin resistance, and attenuated the liver oxidative stress in high-fat diet-fed mice. Moreover, both dietary tannic acid intervention groups repaired the gut barrier damage caused by a high-fat diet, especially in the 50 mg/kg/d dietary tannic acid intervention group. Interestingly, the effect of dietary tannic acid on serum endotoxin lipopolysaccharide (LPS) content was correlated with the abundance of the LPS-producing microbiota. In addition, dietary tannic acid altered the abundance of obesity-related gut microbiota (Firmicutes, Bacteroidetes, Bacteroides, Alistipes, and Odoribacter) in the 150 mg/kg/d dietary tannic acid intervention group, while it was not effective in the 50 mg/kg/d dietary tannic acid intervention group. These findings suggested the potential effect of dietary tannic acid for the prevention and control of obesity.

Crosstalk between bone and other organs

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus, traditionally. Recently, further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body. Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis. Here, we present an overview of the crosstalk between bone and other organs. Furthermore, we describe the factors mediating the crosstalk and review the mechanisms in the development of potential associated diseases. These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

[Epidemiological and clinical characteristics analysis of 681 cases of thoracolumbar osteoporotic vertebral compression fractures]

Objective

To investigate the epidemiological and clinical characteristics of patients with thoracolumbar osteoporotic vertebral compression fracture (OVCF) treated by percutaneous vertebroplasty (PVP).

Methods

The clinical and imaging data of 681 patients with thoracolumbar OVCF treated with PVP between January 2017 and December 2021 were collected. The epidemiological and clinical characteristics of the patients with thoracolumbar OVCF in single center were summarized from the aspects of demographic distribution (mainly including gender, age), fracture characteristic analysis [including pathological segments, bone mineral density, and body mass index (BMI)], and operation related results (including the distribution of unilateral and bilateral puncture and bone cement injection, postoperative effectiveness analysis and refracture).

Results

Of the 681 patients, 134 (19.68%) were male and 547 (80.32%) were female, with a male-to-female ratio of 1∶4.08. The age ranged from 53 to 105 years, with an average of 75.3 years. The age group of 60-90 years old had the largest number of patients (91.04%); the high incidence age group of men was 70-90 years old (13.95%), and that of women was 60-80 years old (72.98%). A total of 836 vertebrae were involved, and the morbidity of thoracolumbar vertebrae (T 11-L 1) was the highest (56.34%, 471/836). The main type of fracture was compression fracture (92.58%, 774/836) and Kümmell disease (7.42%, 62/836). There were 489 cases (71.81%) of osteoporosis, including 66 males and 423 females, with a male-to-female ratio of 1∶6.42. There was significant difference in distribution of bone mineral density between male and female groups ( Z=-5.810, P<0.001). BMI showed 206 cases (30.25%) of underweight, 347 (50.95%) cases of normal, 58 cases (8.52%) of overweight, 42 cases (6.17%) of obese, and 28 cases (4.11%) of extremely obese. The difference in BMI distribution between male and female groups was significant ( Z=-2.220, P=0.026). Of 836 vertebral bodies, 472 (56.46%) were punctured unilaterally and 364 (43.54%) bilaterally. Most of the vertebral bodies (49.88%, 417/836) were injected with 5.0-6.9 mL bone cement, and most of them were distributed in thoracolumbar and lumbar vertebral bodies (T 11-L 3). The visual analogue scale (VAS) score and Oswestry disability index (ODI) of patients with unilateral puncture and bilateral puncture significantly improved at 6 months after operation ( P<0.001), and also the difference was significant between the two groups in the difference of pre- and post-operation ( P<0.001). There were 628 cases (92.22%) with the first occurrence of OVCF, and 53 cases (7.78%) with two or more times of OVCF, all of which were female patients, and 26 cases (49.06%) occurred in the adjacent segment of the previous PVP operation.

Conclusion

Female were more than male in OVCF patients. Thoracolumbar vertebral body has the highest morbidity. Patients with low BMI are more likely to have osteoporosis, and patients with high BMI have a higher risk of compression fracture. The amount of bone cement injected through bilateral puncture was greater than that through unilateral puncture.

The Association of Serum Osteocalcin Levels with Metabolic Parameters and Inflammation in Postmenopausal Women with Metabolic Syndrome

Introduction: Although adipose tissue largely plays a role in the etiopathogenesis of metabolic syndrome (MS), which is an inflammatory process, the skeleton may also contribute to this process through osteocalcin (OC), which is a bone-derived protein. In this study, we aimed to evaluate OC levels in postmenopausal women with MS and to investigate the association of OC levels with the metabolic and inflammatory parameters. Methods: Thirty-five postmenopausal women diagnosed with MS were recruited for the study. Sixteen postmenopausal women without any of the MS criteria formed the control group. Body weight, height, and waist and hip circumference of all of the subjects were measured and body mass indices (BMIs) were calculated. Levels of serum glucose, insulin, C-peptide, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, albumin, creatinine, calcium, phosphorus, total alkaline phosphatase, parathormone, and as inflammatory parameters, erythrocyte sedimentation rate, fibrinogen, and high-sensitive C-reactive protein (hsCRP) were studied from fasting venous blood samples of all the subjects. Homeostatic model assessment for insulin resistance (HOMA-IR) was calculated. Serum total OC levels were studied from all of the subjects. Bone mineral densities were also measured. Results: Serum OC levels of the group with MS median (5.37 ng/mL) were lower than the OC levels of the group without MS (P < 0.01). Serum OC levels significantly and negatively correlated with fasting blood glucose (r = -0.310, P < 0.05), insulin (r = -0.343, P < 0.05), and HOMA-IR (r = -0.384, P < 0.01) values. Serum OC levels showed a significant and negative correlation with body weight (r = -0.293, P < 0.05), BMI (r = -0.333, P < 0.05), and waist-to-hip ratio (r = -0.384, P < 0.05). The inflammatory markers in the patient group were significantly higher than the control group. We found a negative association between serum OC levels and hsCRP levels in all cases (r = -0.283, P < 0.05). Conclusion: In the presence of MS, OC levels are significantly low and display a close association with glucose metabolism and adipose tissue. In addition, OC may play a regulatory role in subclinical systematic inflammatory response.

Bone Response to Weight Loss Following Bariatric Surgery

Obesity is a global health challenge that warrants effective treatments to avoid its multiple comorbidities. Bariatric surgery, a cornerstone treatment to control bodyweight excess and relieve the health-related burdens of obesity, can promote accelerated bone loss and affect skeletal strength, particularly after malabsorptive and mixed surgical procedures, and probably after restrictive surgeries. The increase in bone resorption markers occurs early and persist for up to 12 months or longer after bariatric surgery, while bone formation markers increase but to a lesser extent, suggesting a potential uncoupling process between resorption and formation. The skeletal response to bariatric surgery, as investigated by dual-energy X-ray absorptiometry (DXA), has shown significant loss in bone mineral density (BMD) at the hip with less consistent results for the lumbar spine. Supporting DXA studies, analyses by high-resolution peripheral quantitative computed tomography (HR-pQCT) showed lower cortical density and thickness, higher cortical porosity, and lower trabecular density and number for up to 5 years after bariatric surgery. These alterations translate into an increased risk of fall injury, which contributes to increase the fracture risk in patients who have been subjected to bariatric surgery procedures. As bone deterioration continues for years following bariatric surgery, the fracture risk does not seem to be dependent on acute weight loss but, rather, is a chronic condition with an increasing impact over time. Among the post-bariatric surgery mechanisms that have been claimed to act globally on bone health, there is evidence that micro- and macro-nutrient malabsorptive factors, mechanical unloading and changes in molecules partaking in the crosstalk between adipose tissue, bone and muscle may play a determining role. Given these circumstances, it is conceivable that bone health should be adequately investigated in candidates to bariatric surgery through bone-specific work-up and dedicated postsurgical follow-up. Specific protocols of nutrients supplementation, motor activity, structured rehabilitative programs and, when needed, targeted therapeutic strategies should be deemed as an integral part of post-bariatric surgery clinical support.

The Effect of BMI, Age, Gender, and Pubertal Stage on Bone Turnover Markers in Chinese Children and Adolescents

OBJECTIVES

To ascertain the associations of serum bone turnover markers (BTMs) levels with body mass index (BMI) in Chinese children and adolescents, and whether the influence of BMI, age, pubertal stage on BTMs varied by gender.

METHODS

A total of 500 students (180 controls and 320 children and adolescents with overweight/obesity) aged 9-14 years were randomly selected from the Chinese National Survey on Students Constitution and Health Cohort. Serum levels of BTMs, including bone formation marker bone alkaline phosphatase (BAP), collagen type 1 C-terminal propeptide (CICP), and bone resorption markers C-terminal telopeptide of type-I collagen (CTX) were determined by commercial enzyme-linked immunosorbent assay kits. The associations among BMI, age, gender, pubertal stage, and BTMs were analyzed.

RESULTS

Serum levels of CICP and CTX in overweight/obese children and adolescents were lower than those in controls (p<0.05). Moreover, after subgroup analysis stratified by gender, the decreased serum CICP and CTX levels in overweight/obese children and adolescents were observed only in boys (p<0.05). After adjustment of age and pubertal stage, there was a negative correlation between serum BAP and BMI in both boys and girls (p<0.05). However, the correlations between serum CICP, CTX levels, and BMI were significant in boys but not in girls. Serum BAP and CICP levels were independently correlated with BMI, age, gender, and pubertal stage, while CTX levels were independently correlated with BMI, age, and gender (p<0.05). BAP, CICP, and CTX levels showed a clear age, gender, and pubertal stage dependence with significantly higher values in boys (p<0.05).

CONCLUSIONS

Our findings support the associations between serum BTMs levels and BMI in Chinese children and adolescents, and suggest age, gender, and pubertal stage differences in this relationship that warrant future studies.

The effect of levothyroxine in comparison with placebo on serum osteocalcin levels in patients with subclinical hypothyroidism

BACKGROUND AND OBJECTIVE

Subclinical hypothyroidism can potentially develop to overt hypothyroidism. Thyroid hormones have substantial roles in metabolism and glucose homeostasis and thus are closely related to determinant factors of metabolic syndromes, such as obesity and insulin resistance. Osteocalcin is considered a predictor of metabolic conditions in thyroid diseases. This study aimed to investigate the effect of levothyroxine vs. placebo on serum osteocalcin levels in patients with subclinical hypothyroidism.

METHODS

This randomized clinical trial was performed on 30 patients with subclinical hypothyroidism who were referred to the endocrine clinics of Ghaem and Imam Reza hospitals in Mashhad, Iran. After giving informed consent, patients were randomly divided into intervention (50 µg/day levothyroxine for 2 months) and control (placebo) groups. Serum levels of osteocalcin, thyroid hormones, lipid profile, insulin, and fasting glucose, as well as other clinical and anthropometric data, were measured at baseline and at the end of the study. SPSS was used to analyze the data and P<0.05 was considered significant.

RESULTS

Mean age in the intervention and control groups was 35.07 ± 9.94 and 31.30 ± 4.30, respectively (P=0.20). There was no significant difference between osteocalcin levels before and after the intervention in either of the groups (P=0.54). TSH level was significantly decreased in the levothyroxine group after the intervention (P<0.01). T4 level was significantly increased in the intervention group (P=0.02).

CONCLUSION

Levothyroxine had no significant effect on increasing the levels of serum osteocalcin in patients with subclinical hypothyroidism. We have registered the trial in the Iranian registry of clinical trials (IRCT) with the registration code IRCT20171129037677N1.

Sex differences in the relationship between body composition and biomarkers of bone and fat metabolism in obese boys and girls

Whether a body mass derived from extremes of body weight is beneficial to bone remains controversial. When fat accumulation reaches excessive levels and induces changes in hormonal factors and adipokines, it may affect bone accrual during growth. This study evaluated the relationships between body composition and key biomarkers in relation to bone and fat metabolism in obese Thai boys and girls. Subjects aged 12-14 years were grouped by body mass index (BMI) and percentage of body fat (%Fat). Body composition and heel bone Z-score and speed of sound (SOS) were assessed by bioelectrical impedance analysis and calcaneus bone densitometry, respectively. Serum osteocalcin (OC), adiponectin, leptin, insulin, and 25 hydroxyvitamin D (25(OH)D) were measured by ELISA. Their correlations were analyzed and compared between sexes. The results showed that the obese groups had no differences in mean BMIs and body composition, except that boys had more muscle mass than girls. Boys had lower serum OC and leptin levels than girls. Positive correlations of leptin with %Fat and FM were found in both sexes, while positive associations of %Fat with OC and insulin were found only in boys. Bone Z-score and SOS positively correlated with OC in boys but negatively correlated with 25(OH)D in girls. When classifying the obese group using %Fat ≥25, the positive correlations between %Fat and insulin and the negative associations between %Fat and adiponectin in girls were more pronounced. These results suggest that the associations of body fat and bone parameters with OC, adiponectin, 25(OH)D, and insulin were sex-specific, with greater clarity when %Fat was used instead of BMI to classify obesity.

The effect of exercise training on osteocalcin, adipocytokines, and insulin resistance: a systematic review and meta-analysis of randomized controlled trials

Recently, it has been reported that osteocalcin (OC), in particular its undercarboxylated (ucOC) form, is not only a bone remodeling marker but also an active hormone that intercedes glucose metabolism in humans. This study aimed to determine the impact of an exercise intervention on ucOC, adiponectin, leptin, and insulin resistance (measured by HOMA-IR). PubMed, CINAHL, Medline, Google Scholar, and Scopus databases and reference lists of included studies were searched. Twenty-two randomized controlled trials (RCTs) of exercise training impact in adults were included in the analysis. Results showed an overall significant increase in serum ucOC (MD: 0.15 ng/ml; 95% CI: 0.05 to 0.25) and adiponectin (MD: 2.83 mg/ml; 95% CI: 1.67 to 3.98), a significant decline in leptin (MD: - 4.89 pg/ml; 95% CI: - 6.94 to - 2.84), fasting glucose (MD: - 2.29 mg/dl; 95% CI: - 4.04 to - 0.54), fasting insulin (MD, - 8.90 μIU/ml; 95% CI: - 13.81 to - 3.98), and HOMA-IR (MD: - 1.96; 95% CI: - 3.11 to - 0.80). However, after removal of studies that had prescribed a balanced diet along with exercise intervention, total OC (TOC) levels also increased in the exercise group compared with the control group (MD: 0.36 ng/ml; 95% CI: 0.07 to 0.65). Our findings demonstrate that exercise-induced increases in ucOC are the probable cause of increased adiponectin. Additionally, increases in ucOC itself are probably due to changes in leptin levels and other factors, rather than its direct impact on bone and its osteoblastic activity. Further studies are required to clarify the mechanisms underlying the impact of exercise training on ucOC, adipocytokines, and insulin resistance.

Impact of Type 2 Diabetes Mellitus and Antidiabetic Medications on Bone Metabolism

PURPOSE OF REVIEW

This review focuses on the complex interactions between hyperglycemia and bone fragility and the effects of antidiabetic medications on bone metabolism.

RECENT FINDINGS

Type 2 diabetes (T2D) is associated with increased risk of bone fracture even in those with increased or normal bone mineral density (BMD). The pathophysiology of diabetic bone disease is not completely understood, but it is thought to be multifactorial and associated with complex cross talk among factors such as AGEs, IGF-1, enteric hormones, and pro-inflammatory cytokines. Treatment for T2D may have an impact on bone metabolism. Diabetic bone disease should be considered a serious complication of long-standing T2D.

Children and adolescents with obesity have reduced serum bone turnover markers and 25-hydroxyvitamin D but increased parathyroid hormone concentrations - Results derived from new pediatric reference ranges

BACKGROUND

We aimed to establish age- and gender-specific reference ranges for concentrations of the bone markers osteocalcin (OC), procollagen type 1 N-propeptides (PINP) and carboxy-terminal cross-linking telopeptide of type 1 collagen (CTX-I) as well as for the calciotropic hormones 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) in healthy infants, children and adolescents. In addition, the effect of age, gender, puberty and body mass index (BMI) on bone markers was investigated.

METHODS

2416 healthy subjects (5714 blood withdrawals), aged 3 months to 17 years, were included to estimate the age- and gender-dependence of reference ranges. Subsequently, measured values of the biomarkers were transformed to standard deviation scores (SDS) and their associations with age, gender and puberty were analyzed. Bone marker-SDS values of the reference cohort were compared with an obese cohort (n = 317 and 489 blood withdrawals) to analyze the effect of BMI.

RESULTS

OC, PINP and CTX-I showed a distinct age- and gender-dependence with peak levels at 10 to 11 years (girls, Tanner 3) and 13 years (boys, Tanner 3-4). Children with obesity had significantly lower SDS levels for OC (-0.44), PINP (-0.27), CTX-I (-0.33), 25(OH)D (-0.43) and higher SDS levels for PTH (+0.44) than the reference cohort.

CONCLUSIONS

OC, PINP and CTX-I vary with age, gender and pubertal stage. The body weight status has to be considered in the interpretation of pediatric OC, PINP, CTX-I, 25(OH)D and PTH levels. Consequences of childhood obesity on bone health should be carefully investigated in long-term studies.

Serum osteocalcin levels in overweight children

PURPOSE

Bone plays a role in glucose metabolism through the release of uncarboxylated osteocalcin into the systemic circulation. The identified novel roles for osteocalcin include increasing insulin secretion and sensitivity, energy expenditure, reduction of fat mass, and mitochondrial proliferation and functional enhancement. This study aimed to determine serum osteocalcin levels in overweight children and to investigate the relationships of osteocalcin with glucose metabolism and insulin sensitivity.

METHODS

After overnight fasting, serum osteocalcin levels were measured in overweight (n=50) children between 6.0 and 12.9 years of age and nonoverweight controls (n=60). Height, weight, fasting serum glucose, insulin, alkaline phosphatase, total cholesterol, and 25 hydroxy vitamin D3 (25(OH)VitD3) were also measured in all subjects.

RESULTS

There were significant differences in serum osteocalcin levels between the overweight and control groups (64.00±20.44 vs. 89.56±28.63, P&lt;0.001). Serum osteocalcin levels were inversely correlated with body mass index (BMI) (r=-0.283, P=0.003), weight standard deviation score (SDS) (r=-0.222, P=0.020), BMI SDS (r=-0.297, P=0.002), insulin (r=-0.313, P=0.001), and homeostasis model assessment of insulin resistance (HOMA-IR) index (r=-0.268, P=0.005). In the subsequent multiple regression analyses, BMI, HOMA-IR, and age were determined to be independent predicting factors for serum osteocalcin.

CONCLUSION

Our findings showed associations of serum osteocalcin with glucose metabolism and insulin sensitivity in overweight children, but we could not establish a causal relationship.

Bone mass development is sensitive to insulin resistance in adolescent boys

PURPOSE

Insulin resistance may exert a negative influence on bone mass in childhood and adolescence. The objective was to assess the association between insulin resistance and total body less head (TBLH) bone mineral content (BMC) and to investigate whether body composition, physical activity or osteocalcin levels may influence this association.

METHODS

A longitudinal study with follow-up over more than 6 years was performed and included 562 apparently healthy participants with a mean age of 9.6 years at baseline. Participants underwent DXA scanning at baseline. At the two follow-ups, participants had performed another DXA scanning, had blood samples taken for fasting insulin, glucose and osteocalcin and had physical activity measured with an accelerometer. HOMA-IR was calculated as an index of insulin resistance.

RESULTS

HOMA-IR was negatively associated with TBLH BMC in boys at follow-ups (β = -31.4, p < 0.001) after adjustment for maturity, height, bone area, and baseline level of TBLH BMC. The negative association remained almost unchanged after further adjustments for body composition and physical activity. No association between HOMA-IR and TBLH BMC was found in girls.

CONCLUSION

Insulin resistance may be detrimental for bone development through puberty in boys independent of body composition and the level of physical activity.

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 of Serum Total Osteocalcin Concentrations With Endogenous Glucocorticoids and Insulin Sensitivity Markers in 12-Year-Old Children: A Cross-Sectional Study

Background: Osteocalcin (OC) is an osteoblast-derived marker of bone turnover that has recently been linked to glucose metabolism, glucocorticoid action, and cardiovascular risk. Objective: We determined whether serum total OC (tOC) is associated with cardiometabolic factors, such as insulin sensitivity (IS) markers and endogenous glucocorticoids in 12-year-old children. In addition, we assessed whether low birth weight or exposure to maternal preeclampsia affect tOC concentrations. Methods: In this cross-sectional study, 192 children (109 girls) were studied at 12 years of age. Seventy of them had been born small (SGA), 78 appropriate for gestational age (AGA), and 44 from preeclamptic pregnancies (PRE) as AGA. Blood pressure was measured, and fasting blood samples were collected for markers of glucose metabolism, osteoblast, adipocyte, and adrenocortical function. IS was estimated by Quantitative Insulin Sensitivity Check Index (QUICKI). Free cortisol index (FCI) was calculated as serum cortisol/corticosteroid binding globulin. Results: The highest tOC concentrations were detected in midpubertal children (Tanner B/G stage 3). The children in the highest tOC quartile (n = 48) had lower body mass index (BMI), waist-to-height ratio, diastolic blood pressure, leptin, cortisol/cortisone ratio and FCI, and higher insulin-like growth factor I (IGF-I), IGF-binding protein-1 (IGFBP-1), IGFBP-3, and alkaline phosphatase (ALP) than those in the lower tOC quartiles (p < 0.02 for all). QUICKI was similar in these subgroups. In logistic regression analysis, pubertal developmental stages 2 and 3, high ALP, IGF-I, and low FCI and BMI (p < 0.02 for all) were associated independently with higher tOC. The means of serum tOC and IS markers were similar in the SGA, AGA, and PRE subgroups. Conclusions: In both sexes, the highest tOC levels were detected in midpubertal children reflecting the fast pubertal growth phase. Higher tOC levels were associated with lower BMI and FCI, whereas no association was found with IS. Birth weight or exposure to preeclampsia had no effect on tOC concentrations.

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.

Inflammation Markers in Type 2 Diabetes and the Metabolic Syndrome in the Pediatric Population

PURPOSE OF REVIEW

Chronic inflammation, adipokines, and hepatokines have been identified as basis of insulin resistance and β cell failure in animal models. We present our current knowledge concerning the potential relationship between these cytokines, inflammation, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM) in the pediatric population.

RECENT FINDINGS

Pro-inflammatory cytokines related to insulin resistance and MetS in children are tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-1β, interferon gamma, pigment epithelium-derived factor, chemerin, vaspin, and fetuin A. Anti-inflammatory cytokines associated with insulin resistance and MetS in children are leptin, adiponectin, omentin, fibroblast growth factor (FGF)-21, osteocalcin, and irisin. These anti-inflammatory cytokines are decreased (adiponectin, omentin, and osteocalcin) or increased (leptin, FGF-21, and irisin) in obesity suggesting a resistance state. TNF-α, fetuin A, and FGF-21 are altered in obese children with T2DM suggesting an involvement in β cell failure. These cytokines, adipokines, and hepatokines may be able to predict development of MetS and T2DM and have a potential therapeutic target ameliorating insulin resistance.

The associations between the changes in serum inflammatory markers and bone mineral accrual in boys with overweight and obesity during pubertal maturation: a 3-year longitudinal study in Estonian boys

Adipose tissue produces different inflammatory cytokines which compromise bone mineral accrual during puberty. Vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), interleukin (IL)-8, and interferon-gamma (IFN-γ) are significantly related to bone mineral accrual during pubertal maturation in boys with different BMI values.

INTRODUCTION

This longitudinal study aims to identify the inflammatory markers that most strongly associate with pubertal bone mineral density (BMD) increment in boys with overweight and obesity (OWB).

METHODS

Twenty-six OWB and 29 normal-weight boys were followed yearly for 3 years to measure changes in 12 serum inflammatory markers, BMD (by DXA), and apparent volumetric BMD. The OWB group was further divided into two subgroups according to their BMI gain during the 3-year period. Data through time points presented as slopes were used to calculate correlation coefficients to explore the possible relationships between variables of interest. In the whole study group, linear mixed effects (LME) models were also used.

RESULTS

Increment in serum VEGF concentration was inversely associated with an increase in total body (TB) BMD (r = - 0.82, P = 0.02) and TB bone mineral content (BMC)/height (r = - 0.82, P = 0.02) in those OWB whose BMI gain was higher during pubertal years. In the whole study group, the LME model confirmed the inverse association between VEGF and TB BMC/height (P < 0.05). EGF was inversely associated with LS BMD and LS BMAD (P < 0.05), whereas there was a positive association between IL-8 and TB BMAD and between IFN-γ and LS BMD (P < 0.05).

CONCLUSIONS

Lower increment in BMD in OWB with higher BMI gain is associated with increasing serum VEGF concentration during pubertal maturation. VEGF, EGF, IL-8, and IFN-γ are significantly associated with BMD during pubertal maturation in boys with different BMI values.

The effect of weight loss on body composition, serum bone markers, and adipokines in prepubertal obese children after 1-year intervention

Purpose/Aim: The influence of weight loss on bone turnover and bone quality in childhood remains controversial, but it may implicate interactions between adiposity and bone metabolism. Therefore, we studied the relationships between bone markers and adipokines during weight loss in obese children.

MATERIALS AND METHODS

We determined serum leptin, soluble leptin receptor, adiponectin, bone alkaline phosphatase (BALP), C-terminal telopeptide of type I collagen (CTX-I), osteocalcin (OC), carboxylated-OC (Gla-OC), undercarboxylated-OC (Glu-OC), sclerostin, body composition, and bone mineral density (BMD) in 40 obese prepubertal children before and after therapy. The control group, matched for sex and age, consisted of 40 non-obese children.

RESULTS

We found that values of the total body less head-bone mineral content (TBLH-BMC) and TBLH-BMD were significantly increased, but TBLH-BMD Z-score was decreased by 25% (p = 0.002) in obese children with weight loss after therapy. We observed increases of CTX-I to OC ratio (p = 0.009), and Gla-OC concentrations (p = 0.049). Changes in TBLH-BMD Z-score in patients were positively correlated with changes in BMI Z-score (p = 0.001), percentage of fat mass (p = 0.004), and BALP activity (p = 0.01). Changes in BALP activity were negatively correlated (p < 0.001) with changes in adiponectin concentrations, while changes in sclerostin levels were positively correlated (p = 0.001) with leptin changes.

CONCLUSIONS

We suggest that alterations in adipokines metabolism were associated with a lower rate of bone mineral accrual as a result of decreased bone formation rather than increased bone resorption. The lower rate of bone mass accrual in weight losing children may be an effect of reduced BALP levels related to increase in adiponectin levels.

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.

Osteocalcin-A Versatile Bone-Derived Hormone

Bone has long been regarded as a static organ, simply providing protection and support. However, this mindset has changed radically in recent years and bone is becoming increasingly recognized for its endocrine function of secreting several hormones, thereby controlling various physiological pathways. One of the factors released by the skeleton is osteocalcin. Importantly, osteocalcin is secreted solely by osteoblasts but only has minor effects on bone mineralization and density. Instead, it has been reported to control several physiological processes in an endocrine manner, such as glucose homeostasis and exercise capacity, brain development, cognition, and male fertility. The aim of this review is to provide an overview of the currently known roles of osteocalcin and their underlying mechanisms. At present, one of the major goals in this field is translating basic research into therapeutic applications, therefore ongoing efforts to bring these findings to the clinics will also be discussed.

Bone Health is Maintained, While Fat Mass is Reduced in Pre-pubertal Children with Obesity Participating in a 1-Year Family-Centered Lifestyle Intervention

Diet and physical activity (PA) influence bone health in children. This study tested whether increasing milk and milk products and weight-bearing types of PA favorably changed bone outcomes assessed by dual-energy X-ray absorptiometry (DXA) and bone biomarkers in children with obesity participating in a 1-year family-centered lifestyle intervention. Children were randomized to one of three groups: Control (Ctrl; no intervention), Standard treatment (StnTx: two servings milk and milk products/day; meet PA guidelines plus weight-bearing PA three times/week), or Modified treatment (ModTx: four servings milk and milk products/day; meet PA guidelines plus daily weight-bearing PA). Baseline and 12-month measurements included DXA scans for whole body (WB), lumbar spine (LS), lumbar lateral spine (LLS), and ultra-distal (UD) ulna + radius for bone mineral content (BMC), areal bone mineral density (aBMD) and BMD z-scores. Fat mass index (FMI), fat-free mass index (FFMI), and biomarkers of bone metabolism were assessed. Seventy-eight children 6-8 years old were recruited (mean body mass index for-age z-score: 3.3 ± 1.2). Compared to baseline, all groups increased BMC of WB, LS, and LLS (p < 0.001), whereas only StnTx increased UD ulna + radius BMC at 12 months (p < 0.05). At 12 months, WB-BMD z-scores were significantly lower in Ctrl (p < 0.05), whereas WB and LLS aBMD increased in StnTx and ModTx (p < 0.001) but not in Ctrl. All groups increased FFMI (p < 0.001), while only Ctrl increased FMI (p < 0.001). Bone biomarkers did not change over time. Participating in a family-centered lifestyle intervention based on Canadian diet and PA guidelines maintained bone health in obese children.

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.

[Osteocalcin and glucose metabolism: assessment of human studies]

Osteocalcin, a protein secreted by osteoblasts, is recognized as a biomarker of bone mineralization. Besides, animal experimental studies have shown that osteocalcin could play an important role in glucose metabolism. Over the course of the last decade, this theory has been investigated in several human studies. Most of the results obtained from these reports support a positive correlation between total and undercarboxylated osteocalcin and insulin secretion/sensitivity. Studies also corroborate a reverse association with glycemic parameters such as fasting glucose and glycated hemoglobin. Nevertheless, because most of the studies published are observational, it is not possible to yet confirm a direct cause-effect relationship. Research in the field will surely contribute to the development of new pharmacological strategies for the treatment of endocrine diseases.

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.

Osteocalcin as a potential risk biomarker for cardiovascular and metabolic diseases

Clear evidence supports a role for circulating and locally-produced osteocalcin (OC) in the pathophysiology of cardiovascular (CV) lesions and CV risk, also in combination with metabolic changes, including type 2 diabetes mellitus (T2DM). Reduced plasma OC levels are associated with greater incidence of pathological CV changes, like arterial and valvular calcification, coronary and carotid atherosclerosis and increased carotid intima-media thickness. The actual relationship between OC levels and incidence of major CV events is, however, still unclear. Moreover, reduced circulating OC levels have been mostly associated with insulin resistance, metabolic syndrome or T2DM, indicating relevant OC actions on pancreatic β-cells and insulin secretion and activity. Based on these observations, this review article will attempt to summarize the current evidence on the potential usefulness of circulating OC as a biomarker for CV and metabolic risk, also evaluating the currently open issues in this area of research.

Associations among osteocalcin, leptin and metabolic health in children ages 9-13 years in the United States

Background

This study aimed to investigate the relationships among osteocalcin, leptin and metabolic health outcomes in children ages 9–13 years.

Methods

This was a cross-sectional analysis of baseline data from 161 boys and 157 girls (ages 9–13 years) who previously participated in a double-blinded randomized placebo controlled trial of vitamin D supplementation. Relationships among fasting serum total osteocalcin (tOC), undercarboxylated osteocalcin (ucOC), leptin, and metabolic health outcomes were analyzed.

Results

Approximately 52% of study participants were obese based on percent body fat cutoffs (>25% for boys and >32% for girls) and about 5% had fasting serum glucose within the prediabetic range (i.e. 100 to 125 mg/dL). Serum tOC was not correlated with leptin, glucose, insulin, HOMA-IR, or HOMA-β after adjusting for percent body fat. However, serum ucOC negatively correlated with leptin (partial r = −0.16; p = 0.04) and glucose (partial r = −0.16; p = 0.04) after adjustment for percent body fat. Leptin was a positive predictor of insulin, glucose, HOMA-IR, and HOMA-β after adjusting for age, sex and percent body fat (all p < 0.001).

Conclusions

These data depict an inverse relationship between leptin and various metabolic health outcomes in children. However, the notion that tOC or ucOC link fat with energy metabolism in healthy children was not supported.

Clinical trial registration number

NCT00931580.

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.

Molecular Mechanisms of Obesity-Induced Osteoporosis and Muscle Atrophy

Obesity and osteoporosis are two alarming health disorders prominent among middle and old age populations, and the numbers of those affected by these two disorders are increasing. It is estimated that more than 600 million adults are obese and over 200 million people have osteoporosis worldwide. Interestingly, both of these abnormalities share some common features including a genetic predisposition, and a common origin: bone marrow mesenchymal stromal cells. Obesity is characterized by the expression of leptin, adiponectin, interleukin 6 (IL-6), interleukin 10 (IL-10), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), macrophage colony stimulating factor (M-CSF), growth hormone (GH), parathyroid hormone (PTH), angiotensin II (Ang II), 5-hydroxy-tryptamine (5-HT), Advance glycation end products (AGE), and myostatin, which exert their effects by modulating the signaling pathways within bone and muscle. Chemical messengers (e.g., TNF-α, IL-6, AGE, leptins) that are upregulated or downregulated as a result of obesity have been shown to act as negative regulators of osteoblasts, osteocytes and muscles, as well as positive regulators of osteoclasts. These additive effects of obesity ultimately increase the risk for osteoporosis and muscle atrophy. The aim of this review is to identify the potential cellular mechanisms through which obesity may facilitate osteoporosis, muscle atrophy and bone fractures.

Different osteocalcin forms, markers of metabolic syndrome and anthropometric measures in children within the IDEFICS cohort

OBJECTIVE

Osteocalcin (OC), an aboundant non-collagenous bone protein, is inversely associated with parameters of glucose metabolism. Interactions between bone tissue and energy metabolism have not been thoroughly investigated during childhood. This study investigated OC, metabolic parameters and anthropometric characteristics in normal weight and overweight/obese children.

METHODS

This study comprised 108 (46 normal weight/62 overweight/obese) Swedish 2-9year old children. Anthropometric data, insulin, glucose, glycosylated haemoglobin (HbA1c), HOMA index, vitamin D, adiponectin, total OC, carboxylated OC (cOC) and undercarboxylated OC (ucOC) were analysed.

RESULTS

No difference was found for total OC between the normal and overweight/obese groups, with a mean (±SD) value of 82.6 (±2.8) ng/mL and 77.0 (±2.4) ng/mL, (P=0.11), respectively. Overweight children had lower cOC levels, mean 69.1 (±2.2) ng/mL, vs. normal weight children, mean 75.6 (±2.5) ng/mL (P=0.03). The mean ucOC levels of 7.9 (±0.4) ng/mL in overweight children did not differ vs. normal weight children, mean level 7.0 (±0.4) ng/mL, (P=0.067). None of the three OC forms correlated with any of the measured parameters.

CONCLUSIONS

The cOC levels were lower in overweight children. There was no correlation between the three OC forms and any of the measured anthropometric or metabolic parameters. OC has been suggested to have a possible metabolic role, but in general the current study in prepubertal children does not support the hypothesis of an association between OC and a positive metabolic profile.

Carboxylated and intact osteocalcin predict adiponectin concentration in hemodialyzed patients

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

New insights into the biology of osteocalcin

Osteocalcin is among the most abundant proteins in bone and is produced exclusively by osteoblasts. Initially believed to be an inhibitor of bone mineralization, recent studies suggest a broader role for osteocalcin that extends to the regulation of whole body metabolism, reproduction, and cognition. Circulating undercarboxylated osteocalcin, which is regulated by insulin, acts in a feed-forward loop to increase β-cell proliferation as well as insulin production and secretion, while skeletal muscle and adipose tissue respond to osteocalcin by increasing their sensitivity to insulin. Osteocalcin also acts in the brain to increase neurotransmitter production and in the testes to stimulate testosterone production. At least one putative receptor for osteocalcin, Gprc6a, is expressed by adipose, skeletal muscle, and the Leydig cells of the testes and appears to mediate osteocalcin's effects in these tissues. In this review, we summarize these new discoveries, which suggest that the ability of osteocalcin to function both locally in bone and as a hormone depends on a novel post-translational mechanism that alters osteocalcin's affinity for the bone matrix and bioavailability. This article is part of a Special Issue entitled Bone and diabetes.

Metabolic Syndrome in Children and Adolescents: a Critical Approach Considering the Interaction between Pubertal Stage and Insulin Resistance

Pediatricians increasingly diagnose the metabolic syndrome (MetS) in recent years to describe cardiovascular risk and to guide management of the obese child. However, there is an ongoing discussion about how to define the MetS in childhood and adolescence. Since insulin resistance-the major driver of MetS-is influenced by pubertal stage, it is questionable to use definitions for MetS in children and adolescents that do not take into account pubertal status. A metabolic healthy status in prepubertal stage does not predict a metabolic healthy status during puberty. Furthermore, cardiovascular risk factors improve at the end of puberty without treatment. However, having a uniform internationally accepted definition of the MetS for children and adolescents would be very helpful for the description of populations in different studies. Therefore, the concept of MetS has to be revisited under the influence of puberty stage.

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.

Bone-adiposity cross-talk: implications for pediatric obesity. A narrative review of literature

The rising prevalence of overweight and obesity among pediatric populations has become a major global concern. The objective of this review is to demonstrate potential interactions between the products released by fat tissue and the hormonal production of bone tissue in obese children and adolescents. Advancing the understanding of the complex interactions between adipocyte and osteocyte activities may contribute to the mechanistic understanding of the body's responses to weight loss during adolescence. This knowledge could also reveal any side effects encountered with these interventions. Currently, the concept of bone-adiposity crosstalk has not been fully elucidated, and the mechanisms remain controversial. Understanding the local interactions between the released products by fat tissue and hormones produced in bone tissue requires further investigations.

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.

Osteocalcin and type 2 diabetes risk in Latinos: a life course approach

OBJECTIVE

To examine associations between circulating levels of the bone-derived protein osteocalcin (OC) and type 2 diabetes (T2D) risk in Latino children and adults.

METHODS

Serum OC was measured in 136 children and 531 adults who had the following T2D risk factors assessed, body mass index (BMI), Hemoglobin A1c (HbA1c), fasting and 2-hour glucose during an oral glucose tolerance test.

RESULTS

OC was significantly higher in children than adults (209.0 ± 12.1 vs. 41.0 ± 0.9 ng/ml, p<0.0001). In adults, OC was inversely associated (all p<0.001) with BMI (r=-0.2), HbA1c (r=-0.2), fasting glucose (r=-0.16), and 2-hour glucose (r=-0.21), while there were no significant associations in children. There was a stepwise decrease in OC with increasing dysglycemia in adults, normoglycemic (44.1 ± 1.3 ng/ml), prediabetic (39.3 ± 1.3 ng/ml), and T2D (31.8 ± 1.2 ng/ml), (p<0.0001), whereas there were no differences between normal and prediabetic youth (195.7 ± 16.1 vs. 194.7 ± 25.8 ng/ml, p=0.3).

CONCLUSIONS

OC was inversely associated with T2D risk in Latino adults; however, this pattern was not observed in children.

Bone Mineral Content as a Driver of Energy Expenditure in Prepubertal and Early Pubertal Boys

OBJECTIVE

To examine the associations of bone and bone-secreted factors with measures of energy metabolism in prepubertal and early pubertal boys.

STUDY DESIGN

Participants in this cross-sectional, observational study included 37 (69% black, 31% white) boys, aged 7-12 years (Tanner stage <III). Dual-energy X-ray absorptiometry was used to measure bone mineral content (BMC) and percent body fat. Indirect calorimetry was used to assess resting energy expenditure (REE). Fasting blood levels of osteocalcin (OCN), fibroblast growth factor 23 (FGF23), insulin, glucose, precursor product of type I collagen (N-terminal pro-peptide) and type I collagen, and C-terminal cross-linked telopeptide were measured. Pearson correlations were performed to evaluate relationships among BMC, OCN, FGF23, fasting insulin and glucose, and REE. Multiple linear regression models were used to test associations between OCN and BMC (independent variables) with fasting insulin and glucose and with REE, adjusting for bone turnover markers and further adjusted for percent body fat.

RESULTS

BMC was correlated with REE and insulin. OCN was correlated with glucose in blacks only (r = 0.45, P < .05). FGF23 was not correlated with any markers of energy metabolism. BMC was associated with insulin level in blacks (β = 0.95, P = .001), which was attenuated by percent body fat (β = 0.47, P = .081). BMC was associated with REE in whites (β = 0.496.7, P < .05) and blacks (β = 619.5, P < .0001); but accounting for percent body fat attenuated the association in whites (β = 413.2, P = .078).

CONCLUSION

Our findings suggest that BMC is a determinant of fasting insulin and REE, and that the contribution of body fat appears to be race-specific. Endocrine effects of FGF23 and OCN on energy metabolism were not apparent.

TRIAL REGISTRATION

Registered with ClinicalTrials.gov: NCT02040740, NCT02040727, and NCT01410643.

Reduced serum total osteocalcin is associated with central obesity in Korean children

BACKGROUND

Recently, osteocalcin (OC), an osteoblast-derived hormone, has been suggested as a new link between obesity and insulin resistance in humans. However, few studies regarding the relationship between OC and obesity in Asian children have been published. We investigated the association of OC with adiposity, insulin resistance and metabolic syndrome (MetS) in Korean children.

METHODS

Two hundred and nine (100 boys, 109 girls) children (age: 9.78 ± 1.05 years, body mass index (BMI): 22.27 ± 5.34 kg/m(2)) participated in this cross-sectional study. Anthropometric parameters, insulin resistance, lipid profiles, total OC, and an inflammatory marker, C-reactive protein (CRP), were measured. MetS phenotype was also determined.

RESULTS

Serum total OC levels were significantly lower in overweight or obese children (76.96 ± 27.08 ng/ml vs. 66.91 ± 21.39 ng/ml, p = 0.020) and it was negatively associated with body fat after controlling for age, gender and BMI. Serum total OC concentrations were significantly lower in participants with central obesity or at least two components of MetS driven by waist circumference than they were in those with none. Stepwise linear regression results also showed that serum total OC was partially explained by age, gender, waist-to-hip ratio, and fasting glucose.

CONCLUSIONS

This study supported a negative association between serum total OC and adiposity in children. OC may be associated with childhood central obesity; however, further research using more accurate measurements is needed to identify the association between these variables.

Phylloquinone supplementation improves glycemic status independent of the effects of adiponectin levels in premonopause women with prediabetes: a double-blind randomized controlled clinical trial

BACKGROUND

Vitamin K, as a cofactor in the gamma carboxylation of certain glutamic acid (Gla) residues, has been related to glucose metabolism and insulin sensitivity. Osteocalcin, also known as bone γ-carboxyglutamic acid, increases β-cell proliferation as well as insulin and adiponectin secretion, which improve glucose tolerance and insulin sensitivity. Thus, the purpose of the present study was to examine the possible role of adiponectin as a mediator of glucose homeostasis following phylloquinone supplementation in premonopause women with prediabetes.

METHODS

Eighty two women were randomized to consume vitamin k1 supplement (n = 39) or placebo (n = 43) for four weeks. Participants in vitamin K1 treatment group received one pearl softgel capsule containing 1000 micrograms phylloquinone while the placebo group received one placebo capsules daily for four weeks. The Blood samples were collected at baseline and after a four-week intervention to quantify osteocalcin, adiponectin, leptin and relevant variables.

RESULTS

Phylloquinone supplementation significantly increased serum adiponectin concentration (1.24 ± 1.90 compared with -0.27 ± 1.08 μg/ml), and did not alter total osteocalcin (0.50 ± 4.11 compared with 0.13 ± 1.85 ng/ml) and leptin (-0.29 ± 8.23 compared with -1.15 ± 5.25 ng/ml) compared with placebo. Adjustments for total osteocalcin and adiponectin using analysis of covariance (ANCOVA) did not affect the association of glycemic status with related variables.

CONCLUSIONS

In conclusion our study demonstrated that phylloquinone supplementation improved glycemic status in premonopausal prediabetic women independent of adiponectin.

TRIAL REGISTRATION

This trial was registered in Iranian Registry of Clinical Trials with ID number of IRCT2013120915724N1.

Bone Regulates Glucose Metabolism as an Endocrine Organ through Osteocalcin

Skeleton was considered as a dynamic connective tissue, which was essential for mobility, calcium homeostasis, and hematopoietic niche. However more and more evidences indicate that skeleton works not only as a structural scaffold but also as an endocrine organ, which regulates several metabolic processes. Besides osteoprotegerin (OPG), sclerostin (SOST), and Dickopf (DKK) which play essential roles in bone formation, modelling, remodelling, and homeostasis, bone can also secret hormones, such as osteocalcin (OCN), which promotes proliferation of β cells, insulin secretion, and insulin sensitivity. Additionally OCN can also regulate the fat cells and male gonad endocrine activity and be regulated by insulin and the neural system. In summary, skeleton has endocrine function via OCN and plays an important role in energy metabolism, especially in glucose metabolism.

Skeleton and glucose metabolism: a bone-pancreas loop

Bone has been considered a structure essential for mobility, calcium homeostasis, and hematopoietic function. Recent advances in bone biology have highlighted the importance of skeleton as an endocrine organ which regulates some metabolic pathways, in particular, insulin signaling and glucose tolerance. This review will point out the role of bone as an endocrine "gland" and, specifically, of bone-specific proteins, as the osteocalcin (Ocn), and proteins involved in bone remodeling, as osteoprotegerin, in the regulation of insulin function and glucose metabolism.

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.