Sclerostin and its association with insulin resistance in children and adolescents

The role of sclerostin in lipid and glucose metabolism disorders

Lipid and glucose metabolism are critical for human activities, and their disorders can cause diabetes and obesity, two prevalent metabolic diseases. Studies suggest that the bone involved in lipid and glucose metabolism is emerging as an endocrine organ that regulates systemic metabolism through bone-derived molecules. Sclerostin, a protein mainly produced by osteocytes, has been therapeutically targeted by antibodies for treating osteoporosis owing to its ability to inhibit bone formation. Moreover, recent evidence indicates that sclerostin plays a role in lipid and glucose metabolism disorders. Although the effects of sclerostin on bone have been extensively examined and reviewed, its effects on systemic metabolism have not yet been well summarized. In this paper, we provide a systemic review of the effects of sclerostin on lipid and glucose metabolism based on in vitro and in vivo evidence, summarize the research progress on sclerostin, and prospect its potential manipulation for obesity and diabetes treatment.

Antibodies to sclerostin or G-CSF receptor partially eliminate bone or marrow adipocyte loss, respectively, following vertical sleeve gastrectomy

Vertical sleeve gastrectomy (VSG), the most utilized bariatric procedure in clinical practice, greatly reduces body weight and improves a variety of metabolic disorders. However, one of its long-term complications is bone loss and increased risk of fracture. Elevated circulating sclerostin (SOST) and granulocyte-colony stimulating factor (G-CSF) concentrations have been considered as potential contributors to VSG-associated bone loss. To test these possibilities, we administrated antibodies to SOST or G-CSF receptor and investigated alterations to bone and marrow niche following VSG. Neutralizing either SOST or G-CSF receptor did not alter beneficial effects of VSG on adiposity and hepatic steatosis, and anti-SOST treatment provided a further improvement to glucose tolerance. SOST antibodies partially reduced trabecular and cortical bone loss following VSG by increasing bone formation, whereas G-CSF receptor antibodies had no effects on bone mass. The expansion in myeloid cellularity and reductions in bone marrow adiposity seen with VSG were partially eliminated by treatment with Anti-G-CSF receptor. Taken together, these experiments demonstrate that antibodies to SOST or G-CSF receptor may act through independent mechanisms to partially block effects of VSG on bone loss or marrow niche cells, respectively.

New Emerging Biomarkers for Bone Disease: Sclerostin and Dickkopf-1 (DKK1)

A healthy skeleton depends on a continuous renewal and maintenance of the bone tissue. The process of bone remodeling is highly controlled and consists of a fine-tuned balance between bone formation and bone resorption. Biochemical markers of bone turnover are already in use for monitoring diseases and treatment involving the skeletal system, but novel biomarkers reflecting specific biological processes in bone and interacting tissues may prove useful for diagnostic, prognostic, and monitoring purposes. The Wnt-signaling pathway is one of the most important pathways controlling bone metabolism and consequently the action of inhibitors of the pathway such as sclerostin and Dickkopf-related protein 1 (DKK1) have crucial roles in controlling bone formation and resorption. Thus, they might be potential markers for clinical use as they reflect a number of physiological and pathophysiological events in bone and in the cross-talk with other tissues in the human body. This review focuses on the clinical utility of measurements of circulating sclerostin and DKK1 levels based on preanalytical and analytical considerations and on evidence obtained from published clinical studies. While accumulating evidence points to clear associations with a number of disease states for the two markers, and thus, the potential for especially sclerostin as a biochemical marker that may be used clinically, the lack of standardization or harmonization of the assays still hampers the clinical utility of the markers.

The Effect of a Comprehensive Life-Style Intervention Program of Diet and Exercise on Four Bone-Derived Proteins, FGF-23, Osteopontin, NGAL and Sclerostin, in Overweight or Obese Children and Adolescents

The adipose and bone tissues demonstrate considerable interconnected endocrine function. In the present study, we determined the concentrations of fibroblast growth factor-23 (FGF-23), osteopontin, neutrophil gelatinase-associated lipocalin (NGAL) and sclerostin in 345 children and adolescents who were overweight or obese (mean age ± SD mean: 10.36 ± 0.16 years; 172 males, 173 females; 181 prepubertal; and 164 pubertal) before and after their participation in a comprehensive life-style intervention program of diet and exercise for one year. Following the one-year life-style interventions, there was a significant decrease in BMI (p < 0.01), FGF-23 (p < 0.05), osteopontin (p < 0.01) and NGAL (p < 0.01), and an increase in sclerostin (p < 0.01) concentrations. BMI z-score (b = 0.242, p < 0.05) and fat mass (b = 0.431, p < 0.05) were the best positive predictors and waist-to-height ratio (WHtR) (b = −0.344, p < 0.05) was the best negative predictor of the change of osteopontin. NGAL concentrations correlated positively with HbA1C (b = 0.326, p < 0.05), WHtR (b = 0.439, p < 0.05) and HOMA-IR (b = 0.401, p < 0.05), while BMI (b = 0.264, p < 0.05), fat mass (b = 1.207, p < 0.05), HDL (b = 0.359, p < 0.05) and waist circumference (b = 0.263, p < 0.05) were the best positive predictors of NGAL. These results indicate that FGF-23, osteopontin, NGAL and sclerostin are associated with being overweight or obese and are altered in relation to alterations in BMI. They also indicate a crosstalk between adipose tissue and bone tissue and may play a role as potential biomarkers of glucose metabolism. Further studies are required to delineate the physiological mechanisms underlying this association in children and adolescents.

The role of the Wnt signalling pathway in the energy metabolism of bone remodelling

OBJECTIVES

Bone remodelling is necessary to repair old and impaired bone caused by aging and its effects. Injury in the process of bone remodelling generally leads to the development of various bone diseases. Energy metabolism plays crucial roles in bone cell formation and function, the disorder of which will disrupt the balance between bone formation and bone resorption.

MATERIALS AND METHODS

Here, we review the intrinsic interactions between bone remodelling and energy metabolism and the role of the Wnt signalling pathway.

RESULTS

We found a close interplay between metabolic pathways and bone homeostasis, demonstrating that bone plays an important role in the regulation of energy balance. We also discovered that Wnt signalling is associated with multiple biological processes regulating energy metabolism in bone cells.

CONCLUSIONS

Thus, targeted regulation of Wnt signalling and the recovery of the energy metabolism function of bone cells are key means for the treatment of metabolic bone diseases.

Role of Sclerostin in Cardiovascular Disease

Sclerostin is most recognized for its role in controlling bone formation but is also expressed in the heart, aorta, coronary, and peripheral arteries. This review summarizes research on sclerostin's role in cardiovascular disease. Rodent studies have found sclerostin to be expressed at sites of arterial calcification. In contrast, aortic sclerostin was reported to be downregulated in a mouse model of abdominal aortic aneurysm, and transgenic upregulation or administration of sclerostin was found to prevent abdominal aortic aneurysm and atherosclerosis formation. Sclerostin deficiency was reported to stimulate cardiac rupture in one rodent model. In humans, 7 of 11 studies reported a significant association between high serum sclerostin and high carotid intima media thickness. Ten of 15 studies reported a significant association between high serum sclerostin and severe arterial calcification. Twelve of 14 studies reported a significant association between high serum sclerostin and high arterial stiffness or atherosclerosis severity. Four of 9 studies reported a significant association between high serum sclerostin and high risk of cardiovascular events. A meta-analysis of randomized controlled trials suggested that administration of the sclerostin blocking antibody romosozumab did not significantly increase the risk of major adverse cardiovascular events (risk ratio, 1.14 [95% CI, 0.83-1.57]; P=0.54) or cardiovascular death (risk ratio, 0.92 [95% CI, 0.53-1.59]; P=0.71). Human genetic studies reported variants predisposing to low arterial sclerostin expression were associated with a high risk of cardiovascular events. Overall, past research suggests a cardiovascular protective role of sclerostin but findings have been inconsistent, possibly due to variations in study design, the unique populations and models studied, and the heterogeneous methods used.

Subcutaneous adipose tissue sclerostin is reduced and Wnt signaling is enhanced following 4-weeks of sprint interval training in young men with obesity

Sclerostin is a Wnt/β-catenin antagonist, mainly secreted by osteocytes, and most known for its role in reducing bone formation. Studies in rodents suggest sclerostin can also regulate adipose tissue mass and metabolism, representing bone-adipose tissue crosstalk. Exercise training has been shown to reduce plasma sclerostin levels; but the effects of exercise on sclerostin and Wnt/β-catenin signaling specifically within adipose tissue has yet to be examined. The purpose of this study was to examine subcutaneous WAT (scWAT) sclerostin content and Wnt signaling in response to exercise training in young men with obesity. To this end, 7 male participants (BMI = 35 ± 4; 25 ± 4 years) underwent 4 weeks of sprint interval training (SIT) involving 4 weekly sessions consisting of a 5-min warmup, followed by 8 × 20 s intervals at 170% of work rate at VO_2peak , separated by 10 s of rest. Serum and scWAT were sampled at rest both pre- and post-SIT. Despite no changes in serum sclerostin levels, we found a significant decrease in adipose sclerostin content (-37%, p = 0.04), an increase in total β-catenin (+52%, p = 0.03), and no changes in GSK3β serine 9 phosphorylation. There were also concomitant reductions in serum TNF-α (-0.36 pg/ml, p = 0.03) and IL-6 (-1.44 pg/ml, p = 0.05) as well as an increase in VO_2peak (+5%, p = 0.03) and scWAT COXIV protein content (+95%, p = 0.04). In conclusion, scWAT sclerostin content was reduced and β-catenin content was increased following SIT in young men with excess adiposity, suggesting a role of sclerostin in regulating human adipose tissue in response to exercise training.

The Emerging Role of Bone-Derived Hormones in Diabetes Mellitus and Diabetic Kidney Disease

Diabetic kidney disease (DKD) causes the greatest proportion of end-stage renal disease (ESRD)-related mortality and has become a high concern in patients with diabetes mellitus (DM). Bone is considered an endocrine organ, playing an emerging role in regulating glucose and energy metabolism. Accumulating research has proven that bone-derived hormones are involved in glucose metabolism and the pathogenesis of DM complications, especially DKD. Furthermore, these hormones are considered to be promising predictors and prospective treatment targets for DM and DKD. In this review, we focused on bone-derived hormones, including fibroblast growth factor 23, osteocalcin, sclerostin, and lipocalin 2, and summarized their role in regulating glucose metabolism and DKD.

The enteroendocrine-osseous axis in patients with long-term type 1 diabetes mellitus

INTRODUCTION

The relationship between the gut and skeleton is increasingly recognized as a component of the regulation of carbohydrate metabolism. The aim of our study was to assess the relationship between bone mineral density (BMD), incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), intestinotrophic peptide glucagon-like peptide-2 (GLP-2) and osteocalcin isoforms in patients with long-term type 1 diabetes (T1D) when compared to healthy controls.

METHODS

Eighty two patients with long term T1D, treated in the Department of Metabolic Diseases and 53 healthy controls were recruited to the study. Long term disease duration was defined as lasting for more than 10 years. The control group was selected among age- and sex-matched healthy people. Fasting blood samples were collected to measure levels of incretin hormones (GLP-1, GLP-2, GIP), two forms of osteocalcin (uncarboxylated (ucOC), and carboxylated (cOC)), and additional biochemical parameters associated with glucose and bone metabolism (HbA1c, calcium, phosphorus, 25(OH)D3, PTH).

RESULTS

Patients with T1D had higher BMI than in controls (p = 0.02). There was no difference in BMD at the lumbar spine and the femoral neck between patients with long-term T1D and healthy ones. Z-score values in both groups were within normal ranges. The level of GIP was significantly higher in T1D patients (p = 0.0002) in comparison to the healthy ones. The levels of GLP-1 and GLP-2 did not differ between T1D patients and controls. In the T1D group, strong, positive associations were found between serum levels of GLP-1 and cOC (r = 0.546, p < 0.001) and between GLP-1 and total OC (r = 0.51, p < 0.001), also after adjusting for BMI (p < 0.001 and p < 0.001, respectively). Significant positive associations were also found between serum levels of GLP-2 and cOC (r = 0.27, p = 0.013) and between GLP-2 and total OC (r = 0.25, p = 0.018), also in a multivariate regression (p = 0.009, p = 0,175, respectively). Moreover, in T1D patients, GLP-1 correlated positively with the femoral neck BMD (g/cm²) (r = 0.265, p = 0.016) and this association was statistically significant after adjusting for BMI (p = 0.011). These correlations were not present in the control group. The only significant correlation observed in the control group was between OC and BMD of the neck (p = 0.049 for neck BMD g/cm², and p = 0.041 for neck Z-score).

CONCLUSIONS

Our data suggests an effect of gut hormones on bone in long-term T1D, which could be associated with OC activity, however we did not find a direct connection with glucose metabolism. GLP-1 could have a possible, protective role on bone mineral density in patients with T1D. The data from our study suggests that gut hormones could be considered as a new link in the skeleton - pancreatic endocrine loop in patients with T1D.

Associations between Sclerostin and Anthropometric and Metabolic Parameters in Children and Adolescents

(1) Background: Bone plays an important role in the regulation of the systemic glucose and energy metabolism. Sclerostin, secreted by osteocytes, is an inhibitor of the Wnt/β–catenin bone metabolic pathway, and is involved in osteoporosis and metabolic disease. The aim of this study was to investigate the relationship between sclerostin and anthropometric and metabolic parameters in children and adolescents with obesity or who are overweight. (2) Methods: This study included 63 children and adolescents (20 obese, 11 overweight and 32 healthy control subjects). We evaluated the correlation between serum sclerostin and anthropometric parameters, metabolic parameters related to glucose (homeostasis model assessment of insulin resistance [HOMA–IR]), lipid, and bone metabolism (osteocalcin and 25-hydroxy vitamin D). (3) Results: Sclerostin and osteocalcin levels did not differ between obese and control groups. Sclerostin level was higher in boys than in girls (median 20.7 vs. 18.9 pmol/L, respectively; p = 0.04). In all subjects, sclerostin levels were negatively correlated with fasting insulin (r = −0.26; p = 0.04) and HOMA–IR (r = −0.28; p = 0.03), and positively correlated with serum concentrations of triglycerides (r = 0.29; p = 0.04), alkaline phosphatase (r = 0.41; p = 0.002), and osteocalcin (r = 0.33; p = 0.008). In obese patients, sclerostin levels were correlated negatively with fasting glucose (r = −0.49; p = 0.03) and HOMA–IR (r = −0.48; p = 0.03) and positively correlated with triglyceride levels (r = 0.53; p = 0.02). In the healthy control, sclerostin levels were correlated negatively with fasting insulin levels (r = −0.61; p < 0.001) and HOMA–IR (r = −0.36; p = 0.04). After adjusting for age, sex, and height SDS, a negative correlation between sclerostin and HOMA–IR was found (r = −0.39; p = 0.003) in all of the subjects. This association was more evident in obese patients (r = −0.60; p = 0.01) than in healthy controls (r = −0.39; p = 0.047). (4) Conclusions: Among children and adolescents with obesity, serum sclerostin was negatively correlated with HOMA–IR. Further studies are needed to clarify the mechanisms involved to understand how sclerostin affects the glucose metabolism.

Serum sclerostin concentration is associated with specific adipose, muscle and bone tissue markers in lean adolescent females with increased physical activity

OBJECTIVES

Sclerostin is an important regulator of bone mass involving the Wnt/β-catenin signalling pathway. Relatively few studies have investigated the relationships of circulating sclerostin levels with adiposity-related and muscle-related biochemical factors in individuals with increased energy metabolism. The aim of this study was to investigate the associations of circulating sclerostin with adipokines, myokines, osteokines and body composition values in lean adolescent females with increased physical activity.

METHODS

A total of 73 adolescent females who were physically active and aged 14-18 years old participated in the study. Sclerostin, leptin, resistin, tumour necrosis factor (TNF)-α, interleukin (IL)-6, irisin, osteocalcin, C-terminal telopeptide of type I collagen (CTx), insulin-like growth factor (IGF)-1 and insulin were obtained from fasting blood samples. Body composition was measured by dual-energy X-ray absorptiometry (DXA) and analyzed for body fat mass, lean body mass, bone mineral content and muscle mass.

RESULTS

Serum sclerostin (117.9 ± 60.3 pg/mL) was correlated with age, age at menarche, body fat, muscle mass, training activity, leptin, TNF-α, irisin, osteocalcin, CTx and IGF-1. Multivariate linear regression analysis demonstrated that fat mass (β = 0.434; p = 0.001), leptin (β = -0.308; p = 0.015), irisin (β = 0.227; p = 0.024) and CTx (β = 0.290; p = 0.031) were the most important predictors of serum sclerostin concentration.

CONCLUSIONS

Bone-derived sclerostin is associated with specific adipokine, myokine and osteokine values in lean adolescent females with increased physical activity. These results suggest that the interactions between bone, adipose and muscle tissues could also be associated with circulating sclerostin concentrations.

Serum sclerostin is negatively associated with insulin sensitivity in obese but not lean women

OBJECTIVE

The mechanisms underlying the development of peripheral insulin resistance are complex. Several studies have linked sclerostin, an osteocyte-derived inhibitor of the Wnt/β-catenin pathway, to obesity and insulin resistance. The aim of this study was to investigate (1) whether serum sclerostin is associated with insulin sensitivity in lean and/or obese women; and (2) whether hyperinsulinaemia affects serum sclerostin concentrations.

DESIGN

A cross-sectional study.

METHODS

Insulin sensitivity was measured in lean (BMI < 25 kg/m2) and obese (BMI > 30 kg/m2) women using a hyperinsulinaemic-euglycaemic clamp. Serum sclerostin was measured at baseline and during the clamp procedure.

RESULTS

We studied 21 lean and 22 obese women with a median age of 40 and 43 years and a median BMI of 22.4 and 33.5 kg/m2, respectively. Obese women had higher serum sclerostin than lean women (122 ± 33 vs 93 ± 33 nmol/L, P < 0.01). Higher serum sclerostin was associated with lower insulin sensitivity in obese, but not in lean individuals (difference in M-value between highest and lowest quartile: -7.02 mg/kg/min, P = 0.03 and 1.59 mg/kg/min, P = 0.50, respectively). Hyperinsulinaemia did not affect serum sclerostin in lean nor obese women (P > 0.5).

CONCLUSION

Serum sclerostin is negatively associated with insulin sensitivity as measured with the hyperinsulinaemic-euglycaemic clamp in obese, but not lean women. This indicates a potential role of the Wnt/β-catenin pathway in regulating insulin sensitivity particularly in obese individuals. Our findings remain hypothesis-generating and should be confirmed by additional studies.

Plasma sclerostin levels are associated with nutritional status and insulin resistance but not hormonal disturbances in women with polycystic ovary syndrome

Objective

The aim of this study was to evaluate the circulating sclerostin levels with nutritional status, insulin resistance and hormonal disturbances in women with polycystic ovary syndrome (PCOS).

Patients and methods

The cross-sectional study involved 98 PCOS inpatients (20 normal weight, 17 overweight and 61 obese) with stable body mass. Body composition was assessed by bioimpedance method in addition to anthropometric measurements (body mass and height). Serum/plasma concentrations of glucose, insulin (with the calculation of homeostatic model assessment insulin resistance—HOMA-IR), estradiol, total testosterone, sex hormone-binding globulin (SHBG) and sclerostin were measured. Free androgen index (FAI) and estradiol/testosterone index were calculated.

Results

Plasma sclerostin levels were significantly higher in obese [0.61 (interquartile range 0.53–0.77) ng/mL] than in overweight [0.53 (0.49–0.57) ng/mL] and normal weight [0.49 (0.42–0.54) ng/mL] groups. Plasma sclerostin levels were significantly higher in the subgroup with insulin resistance [0.65 (interquartile range 0.53–0.77) vs. 0.52 (0.46–0.58) ng/mL; p < 0.001], while similar concentrations were observed in subgroups with FAI below and above median. Plasma sclerostin levels variability were explained by BMI (r = 0.40), the percentage of body fat (r = 0.40) and HOMA-IR values (r = 0.34) in multivariable models.

Conclusions

Circulating sclerostin levels in women with PCOS are related to nutritional status and insulin resistance, but not to sex hormone disturbances.

Roles of bone-derived hormones in type 2 diabetes and cardiovascular pathophysiology

Background

Emerging evidence demonstrates that bone is an endocrine organ capable of influencing multiple physiological and pathological processes through the secretion of hormones. Recent research suggests complex crosstalk between the bone and other metabolic and cardiovascular tissues. It was uncovered that three of these bone-derived hormones—osteocalcin, lipocalin 2, and sclerostin—are involved in the endocrine regulations of cardiometabolic health and play vital roles in the pathophysiological process of developing cardiometabolic syndromes such as type 2 diabetes and cardiovascular disease. Chronic low-grade inflammation is one of the hallmarks of cardiometabolic diseases and a major contributor to disease progression. Novel evidence also implicates important roles of bone-derived hormones in the regulation of chronic inflammation.

Scope of review

In this review, we provide a detailed overview of the physiological and pathological roles of osteocalcin, lipocalin 2, and sclerostin in cardiometabolic health regulation and disease development, with a focus on the modulation of chronic inflammation.

Major conclusions

Evidence supports that osteocalcin has a protective role in cardiometabolic health, and an increase of lipocalin 2 contributes to the development of cardiometabolic diseases partly via pro-inflammatory effects. The roles of sclerostin appear to be complicated: It exerts pro-adiposity and pro-insulin resistance effects in type 2 diabetes and has an anti-calcification effect during cardiovascular disease. A better understanding of the actions of these bone-derived hormones in the pathophysiology of cardiometabolic diseases will provide crucial insights to help further research develop new therapeutic strategies to treat these diseases.

Relationship between Insulin Resistance (HOMA-IR), Trabecular Bone Score (TBS), and Three-Dimensional Dual-Energy X-ray Absorptiometry (3D-DXA) in Non-Diabetic Postmenopausal Women

BACKGROUND

Insulin may play a key role in bone metabolism, where the anabolic effect predominates. This study aims to analyze the relationship between insulin resistance and bone quality using the trabecular bone score (TBS) and three-dimensional dual-energy X-ray absorptiometry (3D-DXA) in non-diabetic postmenopausal women by determining cortical and trabecular compartments.

METHODS

A cross-sectional study was conducted in non-diabetic postmenopausal women with suspected or diagnosed osteoporosis. The inclusion criteria were no menstruation for more than 12 months and low bone mass or osteoporosis as defined by DXA. Glucose was calculated using a Hitachi 917 auto-analyzer. Insulin was determined using an enzyme-linked immunosorbent assay (EIA). Insulin resistance was estimated using a homeostasis model assessment of insulin resistance (HOMA-IR). DXA, 3D-DXA, and TBS were thus collected. Moreover, we examined bone parameters according to quartile of insulin, hemoglobin A1C (HbA1c), and HOMA-IR.

RESULTS

In this study, we included 381 postmenopausal women. Women located in quartile 4 (Q4) of HOMA-IR had higher values of volumetric bone mineral density (vBMD) but not TBS. The increase was higher in the trabecular compartment (16.4%) than in the cortical compartment (6.4%). Similar results were obtained for insulin. Analysis of the quartiles by HbA1c showed no differences in densitometry values, however women in Q4 had lower levels of TBS. After adjusting for BMI, statistical significance was maintained for TBS, insulin, HOMA-IR, and HbA1c.

CONCLUSIONS

In non-diabetic postmenopausal women there was a direct relationship between insulin resistance and vBMD, whose effect is directly related to greater weight. TBS had an inverse relationship with HbA1c, insulin, and insulin resistance unrelated to weight. This might be explained by the formation of advanced glycosylation products (AGEs) in the bone matrix, which reduces bone deformation capacity and resistance, as well as increases fragility.

The Interplay Between Bone and Glucose Metabolism

The multiple endocrine functions of bone other than those related to mineral metabolism, such as regulation of insulin sensitivity, glucose homeostasis, and energy metabolism, have recently been discovered. In vitro and murine studies investigated the impact of several molecules derived from osteoblasts and osteocytes on glucose metabolism. In addition, the effect of glucose on bone cells suggested a mutual cross-talk between bone and glucose homeostasis. In humans, these mechanisms are the pivotal determinant of the skeletal fragility associated with both type 1 and type 2 diabetes. Metabolic abnormalities associated with diabetes, such as increase in adipose tissue, reduction of lean mass, effects of hyperglycemia per se, production of the advanced glycation end products, diabetes-associated chronic kidney disease, and perturbation of the calcium-PTH-vitamin D metabolism, are the main mechanisms involved. Finally, there have been multiple reports of antidiabetic drugs affecting the skeleton, with differences among basic and clinical research data, as well as of anti-osteoporosis medication influencing glucose metabolism. This review focuses on the aspects linking glucose and bone metabolism by offering insight into the most recent evidence in humans.

Assessment of Sclerostin and Interleukin 6 Levels and Selected Anthropometric Parameters in Patients Receiving Hemodialysis Replacement Therapy-Pilot Study

Background and Objectives: Chronic kidney disease (CKD) is an important public health problem associated with, e.g., progressive renal insufficiency, bone mineral disorders, and increased inflammatory marker levels. The objective of this study was to compare selected biochemical parameters and to evaluate potential correlations between selected anthropometric parameters and levels of sclerostin and interleukin 6 (IL-6) in blood plasma. Materials and Methods: The study group consisted of 34 patients aged 59.8 ± 9.8 years, receiving hemodialysis therapy. The control group consisted of 31 individuals aged 55.4 ± 9.37 years, presenting with GFR (glomerular filtration rate) of more than 60 mL/min/1.73 m2. Selected anthropometric and biochemical parameters were assessed at baseline, as well as 3 and 6 months into the study. Statistical analyses were performed using the Statistica 2014 software package (StatSoft, Inc.Tulsa, OK, USA). Analyses included descriptive statistics, intergroup comparisons using the Mann-Whitney U-test or the Kruskal-Wallis test, and Spearman's correlation analysis. The significance level was set at p ≤ 0.005. Results: At all measurement time points, i.e., at baseline, at month 3, and at month 6, the IL-6 levels in the study group were significantly higher than those in the control group. No correlations were observed in the study group between SCL or IL-6 levels and anthropometric parameters such as body weight, body mass index (BMI), or waist circumference. Conclusions: Patients receiving hemodialysis replacement therapy present with significantly higher levels of IL-6 in their blood. Anthropometric parameters (body weight, BMI, and waist circumference) have no impact on sclerostin and IL-6 levels in patients undergoing hemodialysis therapy. The results obtained are satisfactory, and the research will be continued.

Lrp4 expression by adipocytes and osteoblasts differentially impacts sclerostin's endocrine effects on body composition and glucose metabolism

Sclerostin exerts profound local control over bone acquisition and also mediates endocrine communication between fat and bone. In bone, sclerostin's anti-osteoanabolic activity is enhanced by low-density lipoprotein receptor-related protein 4 (Lrp4), which facilitates its interaction with the Lrp5 and Lrp6 Wnt co-receptors. To determine whether Lrp4 similarly affects sclerostin's endocrine function, we examined body composition as well as glucose and fatty acid metabolism in mice rendered deficient of Lrp4 in the adipocyte (AdΔLrp4) or the osteoblast (ObΔLrp4). AdΔLrp4 mice exhibit a reduction in adipocyte hypertrophy and improved glucose and lipid homeostasis, marked by increased glucose and insulin tolerance and reduced serum fatty acids, and mirror the effect of sclerostin deficiency on whole-body metabolism. Indeed, epistasis studies place adipocyte-expressed Lrp4 and sclerostin in the same genetic cascade that regulates adipocyte function. Intriguingly, ObΔLrp4 mice, which exhibit dramatic increases in serum sclerostin, accumulate body fat and develop impairments in glucose tolerance and insulin sensitivity despite development of a high bone mass phenotype. These data indicate that expression of Lrp4 by both the adipocyte and osteoblast is required for normal sclerostin endocrine function and that the impact of sclerostin deficiency on adipocyte physiology is distinct from the effect on osteoblast function.

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.