Possible roles of insulin signaling in osteoblasts

Effects of Metabolic Dysfunction-Associated Steatotic Liver Disease on Bone Density and Fragility Fractures: Associations and Mechanisms

Metabolic dysfunction-associated steatotic liver disease (MASLD) has profound adverse effects on bone health and homeostasis. MASLD appears to be associated with changes in bone mineral density (BMD) and fracture rate. However, the data are ambiguous and conflicting. Although several studies have shown that children and adolescents with MASLD have decreased BMD, the data on the prevalence of fragility fractures among children are scarce. In adults, increasing evidence suggests that MASLD decreases BMD and increases the risk of fragility fractures, which appears to be due to deterioration of bone architecture in addition to a decrease in BMD. Effects of MASLD on bone health may also be age- and race-specific. MASLD does not seem to increase fracture risk in children and adolescents but increases the risk of fractures in elderly men, especially those of Asian origin. From a mechanistic perspective, bone remodeling is a continuous process between osteoblasts (bone-forming) and osteoclasts (bone-resorbing), with any imbalance resulting in metabolic bone disease. In individuals with MASLD, loss of anabolic insulin receptor signaling (insulin resistance) in osteoblasts and increased receptor activator of nuclear factor κB (RANK)/RANK ligand signaling in osteoclasts (proinflammatory cytokines) swings the pendulum toward accelerated bone loss. These processes are further complicated by the concomitant presence of obesity, type 2 diabetes mellitus, or sarcopenia in individuals with MASLD. This study reviews the current literature associated with the effects of MASLD on BMD and fragility fractures in children/adolescents and adults. This review also discusses the pathomechanisms that link MASLD with changes in BMD and fragility fractures.

Sustained Release of Salicylic Acid for Halting Peri-Implantitis Progression in Healthy and Hyperglycemic Systemic Conditions: A Gottingen Minipig Model

To develop a peri-implantitis model in a Gottingen minipig and evaluate the effect of local application of salicylic acid poly(anhydride-ester) (SAPAE) on peri-implantitis progression in healthy, metabolic syndrome (MS), and type-2 diabetes mellitus (T2DM) subjects. Eighteen animals were allocated to three groups: (i) control, (ii) MS (diet for obesity induction), and (iii) T2DM (diet plus streptozotocin for T2DM induction). Maxillary and mandible premolars and first molar were extracted. After 3 months of healing, four implants per side were placed in both jaws of each animal. After 2 months, peri-implantitis was induced by plaque formation using silk ligatures. SAPAE polymer was mixed with mineral oil (3.75 mg/μL) and topically applied biweekly for up to 60 days to halt peri-implantitis progression. Periodontal probing was used to assess pocket depth over time, followed by histomorphologic analysis of harvested samples. The adopted protocol resulted in the onset of peri-implantitis, with healthy minipigs taking twice as long to reach the same level of probing depth relative to MS and T2DM subjects (∼3.0 mm), irrespective of jaw. In a qualitative analysis, SAPAE therapy revealed decreased levels of inflammation in the normoglycemic, MS, and T2DM groups. SAPAE application around implants significantly reduced the progression of peri-implantitis after ∼15 days of therapy, with ∼30% lower probing depth for all systemic conditions and similar rates of probing depth increase per week between the control and SAPAE groups. MS and T2DM conditions presented a faster progression of the peri-implant pocket depth. SAPAE treatment reduced peri-implantitis progression in healthy, MS, and T2DM groups.

Selective Laser Melting of the Porous Ta Scaffold with Mg-Doped Calcium Phosphate Coating for Orthopedic Applications

Addressing the repair of large-scale bone defects has become a hot research topic within the field of orthopedics. This study assessed the feasibility and effectiveness of using porous tantalum scaffolds to treat such defects. These scaffolds, manufactured using the selective laser melting (SLM) technology, possessed biomechanical properties compatible with natural bone tissue. To enhance the osteogenesis bioactivity of these porous Ta scaffolds, we applied calcium phosphate (CaP) and magnesium-doped calcium phosphate (Mg-CaP) coatings to the surface of SLM Ta scaffolds through a hydrothermal method. These degradable coatings released calcium and magnesium ions, demonstrating osteogenic bioactivity. Experimental results indicated that the Mg-CaP group exhibited biocompatibility comparable to that of the Ta group in vivo and in vitro. In terms of osteogenesis, both the CaP group and the Mg-CaP group showed improved outcomes compared to the control group, with the Mg-CaP group demonstrating superior performance. Therefore, both CaP and magnesium-CaP coatings can significantly enhance the osseointegration of three-dimensional-printed porous Ta, thereby increasing the surface bioactivity. Overall, the present study introduces an innovative approach for the biofunctionalization of SLM porous Ta, aiming to enhance its suitability as a bone implant material.

Association of type 2 Diabetes Mellitus and bone mineral density: a two-sample Mendelian randomization study

BACKGROUND

Observational studies have suggested that type 2 Diabetes Mellitus (DM2) is a potentially modifiable risk factor for lower BMD, but the causal relationship is unclear. This study aimed to examine whether the association of DM2 with lower BMD levels was causal by using Mendelian randomization (MR) analyses.

METHODS

We collected genome-wide association study data for DM2 and BMD of total body and different skeletal sites from the IEU database. Subsequently, we performed a two-sample Mendelian randomization analysis using the Two Sample MR package.

RESULTS

We identified a positive association between DM2 risk (61,714 DM2 cases and 596,424 controls) and total BMD, and other skeletal sites BMD, such as femoral neck BMD, ultra-distal forearm BMD and heel BMD. However, non-significant trends were observed for the effects of DM2 on lumbar-spine BMD.

CONCLUSION

In two-sample MR analyses, there was positive causal relationship between DM2 and BMD in both overall samples. In summary, while observational analyses consistently indicate a strong association between DM2 and low BMD, our MR analysis introduces a nuanced perspective. Contrary to the robust association observed in observational studies, our MR analysis suggests a significant link between DM2 and elevated BMD.

The role of non-coding RNAs in diabetes-induced osteoporosis

Diabetes mellitus (DM) and osteoporosis are two major health care problems worldwide. Emerging evidence suggests that DM poses a risk for osteoporosis and can contribute to the development of diabetes-induced osteoporosis (DOP). Interestingly, some epidemiological studies suggest that DOP may be at least partially distinct from those skeletal abnormalities associated with old age or postmenopausal osteoporosis. The increasing number of DM patients who also have DOP calls for a discussion of the pathogenesis of DOP and the investigation of drugs to treat DOP. Recently, non-coding RNAs (ncRNAs) have received more attention due to their significant role in cellular functions and bone formation. It is worth noting that ncRNAs have also been demonstrated to participate in the progression of DOP. Meanwhile, nano-delivery systems are considered a promising strategy to treat DOP because of their cellular targeting, sustained release, and controlled release characteristics. Additionally, the utilization of novel technologies such as the CRISPR system has expanded the scope of available options for treating DOP. Hence, this paper explores the functions and regulatory mechanisms of ncRNAs in DOP and highlights the advantages of employing nanoparticle-based drug delivery techniques to treat DOP. Finally, this paper also explores the potential of ncRNAs as diagnostic DOP biomarkers.

Extract of Artemisia dracunculus L. Modulates Osteoblast Proliferation and Mineralization

Thiazolidinediones (TZD) significantly improve insulin sensitivity via action on adipocytes. Unfortunately, TZDs also degrade bone by inhibiting osteoblasts. An extract of Artemisia dracunculus L., termed PMI5011, improves blood glucose and insulin sensitivity via skeletal muscle, rather than fat, and may therefore spare bone. Here, we examine the effects of PMI5011 and an identified active compound within PMI5011 (2',4'-dihydroxy-4-methoxydihydrochalcone, DMC-2) on pre-osteoblasts. We hypothesized that PMI5011 and DMC-2 will not inhibit osteogenesis. To test our hypothesis, MC3T3-E1 cells were induced in osteogenic media with and without PMI5011 or DMC-2. Cell lysates were probed for osteogenic gene expression and protein content and were stained for osteogenic endpoints. Neither compound had an effect on early stain outcomes for alkaline phosphatase or collagen. Contrary to our hypothesis, PMI5011 at 30 µg/mL significantly increases osteogenic gene expression as early as day 1. Further, osteogenic proteins and cell culture mineralization trend higher for PMI5011-treated wells. Treatment with DMC-2 at 1 µg/mL similarly increased osteogenic gene expression and significantly increased mineralization, although protein content did not trend higher. Our data suggest that PMI5011 and DMC-2 have the potential to promote bone health via improved osteoblast maturation and activity.

Bone Health in Women With Polycystic Ovary Syndrome: A Narrative Review

Bone as an active connective and endocrine tissue is influenced by hormones, physical activity, inflammatory factors, minerals, dietary components, and body weight. Bone fractures are a major cause of decreased quality of life and mortality in humans. Polycystic ovary syndrome (PCOS), is one of the most common endocrine disorders in women of reproductive age worldwide. PCOS is associated with disturbances in androgen and estrogen levels, insulin resistance (IR), obesity, as well as low-grade chronic inflammation, and gut microbiota (GM) dysbiosis, all of which may negatively or positively affect bone metabolism. However, it has not yet been well clarified whether PCOS is bone-protective or bone-destructive. This study aimed to review the association between bone health and PCOS, and summarize its related factors. PubMed, Scopus, and Web of Science databases were searched to retrieve relevant English publications investigating the relationship between bone health and PCOS. Several disorders associated with PCOS can negatively or positively affect bone metabolism. Despite some positive effects of insulin, androgens, estrogens, and obesity on bone, IR, estrogen deficiency, low-grade chronic inflammation, and GM dysbiosis may adversely affect the bone metabolism in PCOS women. Studies comparing bone mineral density or bone metabolism and the risk of bone fractures in women with PCOS have controversial results. Further studies are required to understand the mechanisms underlying bone metabolism in PCOS subjects. Moreover, prospective studies are needed to estimate the risk of bone fractures and osteoporosis in PCOS subjects.

Research on biochemical indexes of bone metabolism in bipolar disorder: A cross-sectional study with newly diagnosed, drug-naïve patients

BACKGROUND

In recent years, the metabolic abnormalities associated with bipolar disorder (BD) have attracted people's attention. However, clinical studies on bone metabolism in individuals with BD are unavailable. This study was designed to assess biochemical indexes of bone metabolism and related influencing factors.

METHODS

We measured bone turnover markers (BTMs), including procollagen Ⅰ N-terminal propeptide (PⅠNP), osteocalcin (OC) and C-terminal cross-linking telopeptide of type I collagen (CTX-I), and index of calcium and phosphorus metabolism in 100 drug-naïve individuals with BD (DSM-5) and 91 healthy volunteers. Besides, sociodemographic and clinical assessment were collected. Between-group comparisons and within subgroup analysis were performed.

RESULTS

The PⅠNP (t = 3.715, p < 0.001), OC (t = 2.117, p = 0.036), parathyroid hormone (PTH, t = 3.877, p < 0.001), vitamin D (t = 2.065, p = 0.041), insulin (t = 4.208, p < 0.001) and insulin resistance (t = 2.888, p = 0.004) levels in the drug-naive BD group was significantly higher than those in the healthy control (HC) group. The level of calcium (t = -2.124, p = 0.035) in the drug-naive BD group was significantly lower than that of the HC group. But OC and vitamin D loses statistical significance after Bonferroni correction. However, there was no significant difference in the CTX-I level between the two groups. There are gender differences in the level of BMTs in individuals with BD, but this phenomenon was not found in the HC subgroup. It is shown that diagnosed BD, gender, age and BMI may affect the PINP levels through multiple linear regression analysis.

CONCLUSION

The biochemical indexes of bone metabolism in drug-naive individuals with BD were more active than that of the healthy controls in a sample from the Chinese Han nationality. The finding provides new evidence for our understanding of bone metabolism in individuals with BD.

The downregulation of miR-22 and miR-372 may contribute to gestational diabetes mellitus through regulating glucose metabolism via the PI3K/AKT/GLUT4 pathway

Background

Identifying effective regulatory mechanisms will be significant for Gestational diabetes mellitus (GDM) diagnosis and treatment.

Methods

The expressions of miR‐22 and miR‐372 in placenta tissues from 75 pregnant women with GDM and 75 matched healthy controls and HRT8/SVneo cells (a model of insulin resistance) were analyzed by qPCR. The expressions of PI3K, AKT, IRS, and GLUT4 in high glucose‐treated HRT8/SVneo cells transfected with miR‐22 or miR‐372 mimics or inhibitors was assessed by Western blot. A luciferase gene reporter assay was employed to verify miRNAs' target genes.

Results

The expressions of miR‐22 and miR‐372 in placental tissues from GDM patients and HRT8/SVneo cells were significantly decreased compared with the respective controls. The GLUT4 expression was significantly decreased in the placenta tissues of GDM and HRT8/SVneo cells with high glucose transfected with miR‐22 and miR‐372 inhibitors. We confirmed that SLC2A4, the gene encoding GLUT4, was a direct target of miR‐22 and miR‐372. In this study, we report that the lower expressions of miR‐22 and miR‐372 in placental tissue from GDM patients.

Conclusion

Our results further suggested that the downregulations of miR‐22 and miR‐372 may contribute to GDM through regulating the PI3K/GLUT4 pathway.

Bone density in youth with prediabetes: results from the National Health and Nutrition Examination Survey, 2005-2006

Youth with type 2 diabetes might have suboptimal peak bone mass, but it is unknown whether similar effects are evident in youth with prediabetes. Results from this study suggest that diabetes-related effects on peak bone mass likely occur before disease onset, and involve the muscle-bone unit.

INTRODUCTION

Type 2 diabetes might adversely influence bone health around the age of peak bone mass, but it is unknown whether diabetes-related effects on areal bone mineral density (aBMD) are evident in youth with prediabetes. We compared age-related trends in aBMD and associations between lean body mass (LBM) and aBMD between children and adolescents with prediabetes vs. normal glucose regulation.

METHODS

Cross-sectional analysis of data from the National Health and Nutrition Examination Survey (2005-2006) in youth ages 12-20 years (49% female, 34% black) with prediabetes (n = 267) and normal glucose regulation (n = 1664). Whole body aBMD and LBM were assessed via DXA. LBM index (LBMI) and Z-scores for aBMD and LBMI were computed.

RESULTS

Unadjusted between-group comparisons revealed greater mean weight and LBMI Z-scores in youth with prediabetes vs. normal glucose regulation, but similar bone Z-scores between the two groups. While accounting for differences in BMI Z-score, there was a significant interaction between prediabetes status and age with respect to whole body aBMD Z-score (P < 0.05), such that children with prediabetes tended to have increased aBMD but adolescents and young adults with prediabetes tended have lower aBMD. Furthermore, the positive association between LBMI and whole body aBMD was moderated in youth with prediabetes (P < 0.001), who had slightly lower whole body aBMD for a given LBMI (P = 0.068). Lumbar spine bone measures did not differ between the two groups.

CONCLUSIONS

Type 2 diabetes-related threats to peak bone mass might occur prior to disease onset, therefore potentially impacting a considerable proportion of US youth.

Impaired bone fracture healing in type 2 diabetes is caused by defective functions of skeletal progenitor cells

The mechanisms of obesity and type 2 diabetes (T2D)-associated impaired fracture healing are poorly studied. In a murine model of T2D reflecting both hyperinsulinemia induced by high fat diet (HFD) and insulinopenia induced by treatment with streptozotocin (STZ), we examined bone healing in a tibia cortical bone defect. A delayed bone healing was observed during hyperinsulinemia as newly formed bone was reduced by – 28.4±7.7% and was associated with accumulation of marrow adipocytes at the defect site +124.06±38.71%, and increased density of SCA1+ (+74.99± 29.19%) but not Runx2 +osteoprogenitor cells. We also observed increased in reactive oxygen species production (+101.82± 33.05%), senescence gene signature (≈106.66± 34.03%) and LAMIN B1 - senescent cell density (+225.18± 43.15%), suggesting accelerated senescence phenotype. During insulinopenia, a more pronounced delayed bone healing was observed with decreased newly formed bone to -34.9± 6.2% which was inversely correlated with glucose levels (R 2=0.48, p&lt;0.004) and callus adipose tissue area (R 2=0.3711, p&lt;0.01). Finally, to investigate the relevance to human physiology, we observed that sera from obese and T2D subjects had disease state-specific inhibitory effects on osteoblast related gene signatures in human bone marrow stromal cells which resulted in inhibition of osteoblast and enhanced adipocyte differentiation. Our data demonstrate that T2D exerts negative effects on bone healing through inhibition of osteoblast differentiation of skeletal stem cells and induction of accelerated bone senescence and that the hyperglycaemia per se and not just insulin levels is detrimental for bone healing.

Genes and Pathways Associated with Skeletal Sagittal Malocclusions: A Systematic Review

Skeletal class II and III malocclusions are craniofacial disorders that negatively impact people’s quality of life worldwide. Unfortunately, the growth patterns of skeletal malocclusions and their clinical correction prognoses are difficult to predict largely due to lack of knowledge of their precise etiology. Inspired by the strong inheritance pattern of a specific type of skeletal malocclusion, previous genome-wide association studies (GWAS) were reanalyzed, resulting in the identification of 19 skeletal class II malocclusion-associated and 53 skeletal class III malocclusion-associated genes. Functional enrichment of these genes created a signal pathway atlas in which most of the genes were associated with bone and cartilage growth and development, as expected, while some were characterized by functions related to skeletal muscle maturation and construction. Interestingly, several genes and enriched pathways are involved in both skeletal class II and III malocclusions, indicating the key regulatory effects of these genes and pathways in craniofacial development. There is no doubt that further investigation is necessary to validate these recognized genes’ and pathways’ specific function(s) related to maxillary and mandibular development. In summary, this systematic review provides initial insight on developing novel gene-based treatment strategies for skeletal malocclusions and paves the path for precision medicine where dental care providers can make an accurate prediction of the craniofacial growth of an individual patient based on his/her genetic profile.

Pancreas deficiency modifies bone development in the ovine fetus near term

Hormones have an important role in the regulation of fetal growth and development, especially in response to nutrient availability in utero. Using micro-CT and an electromagnetic three-point bend test, this study examined the effect of pancreas removal at 0.8 fraction of gestation on the developing bone structure and mechanical strength in fetal sheep. When fetuses were studied at 10 and 25 days after surgery, pancreatectomy caused hypoinsulinaemia, hyperglycaemia and growth retardation which was associated with low plasma concentrations of leptin and a marker of osteoclast activity and collagen degradation. In pancreatectomized fetuses compared to control fetuses, limb lengths were shorter, and trabecular (Tb) bone in the metatarsi showed greater bone volume fraction, Tb thickness, degree of anisotropy and porosity, and lower fractional bone surface area and Tb spacing. Mechanical strength testing showed that pancreas deficiency was associated with increased stiffness and a greater maximal weight load at fracture in a subset of fetuses studied near term. Overall, pancreas deficiency in utero slowed the growth of the fetal skeleton and adapted the developing bone to generate a more compact and connected structure. Maintenance of bone strength in growth-retarded limbs is especially important in a precocial species in preparation for skeletal loading and locomotion at birth.

Hexokinase 2-mediated glycolysis promotes receptor activator of NF-κB ligand expression in Porphyromonas gingivalis lipopolysaccharide-treated osteoblasts

BACKGROUND

Glucose metabolism plays a pivotal role in sustaining the inflammatory response to microbial stimulation by providing sufficient energy in immune cells. The main purpose of our study was to explore whether hexokinase 2 (HK2)-mediated glycolysis affected the expression of receptor activator of NF-κB Ligand (RANKL) in Porphyromonas gingivalis lipopolysaccharide (P. gingivalis-LPS)-treated osteoblasts and evaluate the potential involvement of the AKT/PI3K pathway activation during HK2-mediated glycolysis.

METHODS

Primary mice osteoblasts were treated with P. gingivalis-LPS, whereas the HK2 inhibitor (Lonidamine, LND) and small interference RNA were used to restrain HK2 expression. Conditioned medium from osteoblasts was utilized for culturing osteoclast precursors. The mRNA and protein levels of genes involved in glycolysis and bone metabolism including RANKL and osteoprotegerin (OPG) were detected by real-time PCR and western blotting. HK2 and lactate levels were detected by ELISA. Tartrate-resistant acid phosphatase (TRAP) staining was utilized to assess osteoclast formation. The involvement of the AKT/PI3K pathway in osteoblasts was explored by Western blotting.

RESULTS

P. gingivalis-LPS enhanced HK2 expression along with rising glycolysis in osteoblasts. LND and HK2-knockdown decreased RANKL expression and the RANKL/OPG ratio in osteoblasts, leading to less osteoclast formation from osteoclast precursors as evidenced by TRAP staining, while the osteogenic potential and proliferation of osteoblasts were not affected by HK2-knockdown. Moreover, P. gingivalis-LPS activated the AKT/PI3K pathway, which could regulate HK2 and RANKL expression in osteoblasts.

CONCLUSIONS

HK2-mediated glycolysis promoted RANKL in osteoblasts and enhanced osteoclast differentiation. Targeting glycolysis may provide novel therapeutic methods for reducing alveolar bone loss.

Strontium-incorporated titanium implant surfaces treated by hydrothermal treatment enhance rapid osseointegration in diabetes: A preclinical vivo experimental study

OBJECTIVES

The aim of the current study was to explore effects of strontium-incorporated titanium implant surfaces by hydrothermal treatment on osseointegration in diabetic rats.

MATERIALS AND METHODS

The surface characteristics of SLA and SLA-Sr surfaces were detected by related instruments. Thirty-six male Sprague-Dawley rats were induced into diabetes, and thirty-six rats were normal. SLA and SLA-Sr implants were, respectively, inserted into bilateral tibial metaphysis of each rat. Percentage of bone-to-implant contact (BIC%) and percentage of bone area (BA%) were analyzed at 4 and 8 weeks after implantation. Immunohistochemistry of osteoprotegerin (OPG) and Wnt5a were conducted at 1 and 4 weeks. Gene expression levels of inflammatory cytokines and related signaling molecules in peri-implant bone tissue were detected at 3 and 7 days.

RESULTS

Strontium was uniformly distributed on SLA-Sr surfaces, and it was released in an effective concentration range. SLA-Sr surfaces showed significantly higher BIC% in diabetic rats at 4 (p < .05) and 8 weeks (p < .05). Besides, it displayed higher BIC% at 4 weeks (p < .05) in normal rats. Also, SLA-Sr surfaces upregulated expression of OPG at 4 weeks (p < .05) in diabetic rats. What's more, SLA-Sr surfaces downregulated inflammation (TNF-α, IL-1β, and IL-6; p < .01) in diabetic rats at 3 days. In addition, expression of Wnt5a and ROR2 was upregulated (p < .05) at 7 days after implantation under diabetes.

CONCLUSION

It is suggested that strontium-incorporated titanium implant surfaces by hydrothermal treatment could enhance implant osseointegration as compared with SLA implant surfaces in diabetic rats.

Comparative Proteomic and Metabolomic Analysis of Human Osteoblasts, Differentiated from Dental Pulp Stem Cells, Hinted Crucial Signaling Pathways Promoting Osteogenesis

Population aging has been a global trend for the last decades, which increases the pressure to develop new cell-based or drug-based therapies, including those that may cure bone diseases. To understand molecular processes that underlie bone development and turnover, we followed osteogenic differentiation of human dental pulp stem cells (DPSCs) using a specific induction medium. The differentiation process imitating in vivo osteogenesis is triggered by various signaling pathways and is associated with massive proteome and metabolome changes. Proteome was profiled by ultrahigh-performance liquid chromatography and comprehensively quantified by ion mobility-enhanced mass spectrometry. From 2667 reproducibly quantified and identified proteins, 432 were differentially abundant by strict statistic criteria. Metabolome profiling was carried out by nuclear magnetic resonance. From 27 detected metabolites, 8 were differentially accumulated. KEGG and MetaboAnalyst hinted metabolic pathways that may be involved in the osteogenic process. Enrichment analysis of differentially abundant proteins highlighted PPAR, FoxO, JAK-STAT, IL-17 signaling pathways, biosynthesis of thyroid hormones and steroids, mineral absorption, and fatty acid metabolism as processes with prominent impact on osteoinduction. In parallel, metabolomic data showed that aminoacyl-tRNA biosynthesis, as well as specific amino acids, likely promote osteodifferentiation. Targeted immunoassays validated and complemented omic results. Our data underlined the complexity of the osteogenic mechanism. Finally, we proposed promising targets for future validation in patient samples, a step toward the treatment of bone defects.

Mechanisms of altered bone remodeling in children with type 1 diabetes

Bone loss associated with type 1 diabetes mellitus (T1DM) begins at the onset of the disease, already in childhood, determining a lower bone mass peak and hence a greater risk of osteoporosis and fractures later in life. The mechanisms underlying diabetic bone fragility are not yet completely understood. Hyperglycemia and insulin deficiency can affect the bone cells functions, as well as the bone marrow fat, thus impairing the bone strength, geometry, and microarchitecture. Several factors, like insulin and growth hormone/insulin-like growth factor 1, can control bone marrow mesenchymal stem cell commitment, and the receptor activator of nuclear factor-κB ligand/osteoprotegerin and Wnt-b catenin pathways can impair bone turnover. Some myokines may have a key role in regulating metabolic control and improving bone mass in T1DM subjects. The aim of this review is to provide an overview of the current knowledge of the mechanisms underlying altered bone remodeling in children affected by T1DM.

Endocrine role of bone in the regulation of energy metabolism

Bone mainly functions as a supportive framework for the whole body and is the major regulator of calcium homeostasis and hematopoietic function. Recently, an increasing number of studies have characterized the significance of bone as an endocrine organ, suggesting that bone-derived factors regulate local bone metabolism and metabolic functions. In addition, these factors can regulate global energy homeostasis by altering insulin sensitivity, feeding behavior, and adipocyte commitment. These findings may provide a new pathological mechanism for related metabolic diseases or be used in the diagnosis, treatment, and prevention of metabolic diseases such as osteoporosis, obesity, and diabetes mellitus. In this review, we summarize the regulatory effect of bone and bone-derived factors on energy metabolism and discuss directions for future research.

Insulin Signaling in Arthritis

Inflammatory arthritis is burdened by an increased risk of metabolic disorders. Cytokines and other mediators in inflammatory diseases lead to insulin resistance, diabetes and hyperlipidemia. Accumulating evidence in the field of immunometabolism suggests that the cause-effect relationship between arthritis and metabolic abnormalities might be bidirectional. Indeed, the immune response can be modulated by various factors such as environmental agents, bacterial products and hormones. Insulin is produced by pancreatic cells and regulates glucose, fat metabolism and cell growth. The action of insulin is mediated through the insulin receptor (IR), localized on the cellular membrane of hepatocytes, myocytes and adipocytes but also on the surface of T cells, macrophages, and dendritic cells. In murine models, the absence of IR in T-cells coincided with reduced cytokine production, proliferation, and migration. In macrophages, defective insulin signaling resulted in enhanced glycolysis affecting the responses to pathogens. In this review, we focalize on the bidirectional cause-effect relationship between impaired insulin signaling and arthritis analyzing how insulin signaling may be involved in the aberrant immune response implicated in arthritis and how inflammatory mediators affect insulin signaling. Finally, the effect of glucose-lowering agents on arthritis was summarized.

JAK2 Inhibition by Fedratinib Reduces Osteoblast Differentiation and Mineralisation of Human Mesenchymal Stem Cells

Several signalling pathways, including the JAK/STAT signalling pathway, have been identified to regulate the differentiation of human bone marrow skeletal (mesenchymal) stem cells (hBMSCs) into bone-forming osteoblasts. Members of the JAK family mediate the intracellular signalling of various of cytokines and growth factors, leading to the regulation of cell proliferation and differentiation into bone-forming osteoblastic cells. Inhibition of JAK2 leads to decoupling of its downstream mediator, STAT3, and the subsequent inhibition of JAK/STAT signalling. However, the crucial role of JAK2 in hBMSCs biology has not been studied in detail. A JAK2 inhibitor, Fedratinib, was identified during a chemical biology screen of a small molecule library for effects on the osteoblastic differentiation of hMSC-TERT cells. Alkaline phosphatase activity and staining assays were conducted as indicators of osteoblastic differentiation, while Alizarin red staining was used as an indicator of in vitro mineralised matrix formation. Changes in gene expression were assessed using quantitative real-time polymerase chain reaction. Fedratinib exerted significant inhibitory effects on the osteoblastic differentiation of hMSC-TERT cells, as demonstrated by reduced ALP activity, in vitro mineralised matrix formation and downregulation of osteoblast-related gene expression, including ALP, ON, OC, RUNX2, OPN, and COL1A1. To identify the underlying molecular mechanisms, we examined the effects of Fedratinib on a molecular signature of several target genes known to affect hMSC-TERT differentiation into osteoblasts. Fedratinib inhibited the expression of LIF, SOCS3, RRAD, NOTCH3, TNF, COMP, THBS2, and IL6, which are associated with various signalling pathways, including TGFβ signalling, insulin signalling, focal adhesion, Notch Signalling, IL-6 signalling, endochondral ossification, TNF-α, and cytokines and inflammatory response. We identified a JAK2 inhibitor (Fedratinib) as a powerful inhibitor of the osteoblastic differentiation of hMSC-TERT cells, which may be useful as a therapeutic option for treating conditions associated with ectopic bone formation or osteosclerotic metastases.

Berberine promotes peri-implant osteogenesis in diabetic rats by ROS-mediated IRS-1 pathway

Accompanying with diabetes mellitus-induced osteoporosis (DM-OS), diabetic patients show poor peri-implant osteogenesis after implantation for dentition defect. Berberine (BBR), a candidate oral hypoglycemic agent, is a promising agent for treating DM-OS. In this study, BBR was applied on DM rats and high-glucose-cultured bone mesenchymal stem cells (BMSCs) to investigate its therapeutic mechanism on DM-OS, thus laying a theoretical basis for the future application of BBR in implant restoration. Phenotypes were assessed in the DM rats after 4 w of gavage with BBR. Furthermore, BMSCs were cultured with high glucose and BBR. Cell Counting Kit-8, 2',7'-dichlorofluorescin diacetate (H2 DCF-DA), quantitative real-time PCR (qRT-PCR), and western blot were performed to estimate the cell proliferation, oxidative stress, and osteogenic differentiation. Moreover, the DM rats treated with BBR and insulin receptor substrate-1 anti-sense oligonucleotide (IRS-1-ASO) underwent a 4-w implant-healing period and then micro computed tomography (Micro-CT) and histology were performed to verify the mechanism. Results showed that the 4-w administration of BBR markedly improved the glucose metabolism and bone metabolism in the DM rats. in vitro experiments revealed that BBR alleviated high-glucose-inhibited osteogenesis of the BMSCs by upregulating reactive oxygen species (ROS)-mediated IRS-1 signaling. Besides, injection of IRS-1-ASO abolished the BBR promotion of implant osseointegration in the DM rats. In conclusion, targeting ROS-mediated IRS-1 signaling, BBR acted as an efficient agent to advance osseointegration in DM, which indicated that BBR use is a good strategy for future implants restoration in diabetic patients.

The seed of Litchi chinensis fraction ameliorates hippocampal neuronal injury in an Aβ25-35-induced Alzheimer's disease rat model via the AKT/GSK-3β pathway

Context: The seed of Litchi chinensis Sonn., a famous traditional Chinese medicine, was recently reported to enhance cognitive function by inhibiting neuronal apoptosis in rats.Objective: We determined whether the seed of Litchi chinensis fraction (SLF) can ameliorate hippocampal neuronal injury via the AKT/GSK-3β pathway.Materials and methods: We established Alzheimer's disease (AD) model by infusing Aβ_25-35 into the lateral ventricle of Sprague-Dawley (SD) rats and randomly divided into five groups (n = 10): sham, donepezil and SLF (120, 240 and 480 mg/kg/d). Rats were treated by intragastric administration for 28 consecutive days. Spatial learning and memory were evaluated with Morris water maze, while protein expression of AKT, GSK-3β and tau in the hippocampal neurons was measured by Western blotting and immunohistochemistry.Results: On the fifth day, escape latency of the AD model group was 45.78 ± 2.52 s and that of the sham operative group was 15.98 ± 2.32 s. SLF could improve cognitive functions by increasing the number of rats that crossed the platform (p < 0.01), and their platform quadrant dwell time (p < 0.05). The protein expression level of AKT was upregulated (p < 0.001), while that of GSK-3β and tau (p < 0.01) was remarkably downregulated in the hippocampal CA1 area.Discussion and conclusions: To our knowledge, the present study is the first to show that SLF may exert neuroprotective effect in AD rats via the AKT/GSK-3β signalling pathway, thereby serving as evidence for the potential utility of SLF as an effective drug against AD.

Tankyrase inhibitor XAV-939 enhances osteoblastogenesis and mineralization of human skeletal (mesenchymal) stem cells

Tankyrase is part of poly (ADP-ribose) polymerase superfamily required for numerous cellular and molecular processes. Tankyrase inhibition negatively regulates Wnt pathway. Thus, Tankyrase inhibitors have been extensively investigated for the treatment of clinical conditions associated with activated Wnt signaling such as cancer and fibrotic diseases. Moreover, Tankyrase inhibition has been recently reported to upregulate osteogenesis through the accumulation of SH3 domain-binding protein 2, an adaptor protein required for bone metabolism. In this study, we investigated the effect of Tankyrase inhibition in osteoblast differentiation of human skeletal (mesenchymal) stem cells (hMSCs). A Tankyrase inhibitor, XAV-939, identified during a functional library screening of small molecules. Alkaline phosphatase activity and Alizarin red staining were employed as markers for osteoblastic differentiation and in vitro mineralized matrix formation, respectively. Global gene expression profiling was performed using the Agilent microarray platform. XAV-939, a Tankyrase inhibitor, enhanced osteoblast differentiation of hBMSCs as evidenced by increased ALP activity, in vitro mineralized matrix formation, and upregulation of osteoblast-related gene expression. Global gene expression profiling of XAV-939-treated cells identified 847 upregulated and 614 downregulated mRNA transcripts, compared to vehicle-treated control cells. It also points towards possible changes in multiple signaling pathways, including TGFβ, insulin signaling, focal adhesion, estrogen metabolism, oxidative stress, RANK-RANKL (receptor activator of nuclear factor κB ligand) signaling, Vitamin D synthesis, IL6, and cytokines and inflammatory responses. Further bioinformatic analysis, employing Ingenuity Pathway Analysis identified significant enrichment in XAV-939-treated cells of functional categories and networks involved in TNF, NFκB, and STAT signaling. We identified a Tankyrase inhibitor (XAV-939) as a powerful enhancer of osteoblastic differentiation of hBMSC that may be useful as a therapeutic option for treating conditions associated with low bone formation.

Bone Mass and Density in Youth With Type 2 Diabetes, Obesity, and Healthy Weight

OBJECTIVE

Youth-onset type 2 diabetes is an aggressive condition with increasing incidence. Adults with type 2 diabetes have increased fracture risk despite normal areal bone mineral density (aBMD), but the influence of diabetes on the growing skeleton is unknown. We compared bone health in youth with type 2 diabetes to control patients with obesity or healthy weight.

RESEARCH DESIGN AND METHODS

Cross-sectional study of youth (56% African American, 67% female) ages 10-23 years with type 2 diabetes (n = 180), obesity (BMI >95th; n = 226), or healthy weight (BMI <85th; n = 238). Whole-body (less head) aBMD and lean mass as well as abdominal visceral fat were assessed via DXA. Lean BMI (LBMI) and aBMD SD scores (z scores) were computed using published reference data.

RESULTS

We observed age-dependent differences in aBMD and LBMI z scores between the healthy weight, obese, and type 2 diabetes groups. In children, aBMD and LBMI z scores were greater in the type 2 diabetes group versus the obese group, but in adolescents and young adults, aBMD and LBMI z scores were lower in the type 2 diabetes group versus the obese group (age interactions P < 0.05). In the type 2 diabetes group and the obese group, aBMD was about 0.5 SDs lower for a given LBMI z score compared with healthy weight control patients (P < 0.05). Further, aBMD was lower in those with greater visceral fat (β = -0.121, P = 0.047).

CONCLUSIONS

These results suggest that type 2 diabetes may be detrimental to bone density around the age of peak bone mass. Given the increased fracture risk in adults with type 2 diabetes, there is a pressing need for longitudinal studies aimed at understanding the influence of diabetes on the growing skeleton.

Local delivery of insulin/IGF-1 for bone regeneration: carriers, strategies, and effects

Bone defects caused by trauma, tumor resection, congenital malformation and infection are still a major challenge for clinicians. Biomimetic bone materials have attracted more and more attention in science and industry. Insulin and insulin-like growth factor-1 (IGF-1) have been increasingly recognized as an inducible factor for osteogenesis and angiogenesis. Spatiotemporal release of insulin may serve as the promising strategy. Considering the successful application of nanoparticles in drug loading, various insulin delivery systems have been developed, including (poly (lactic-co-glycolic acid), PLGA), hydroxyapatite (HA), gelatin, chitosan, alginate, and (γ-glutamic acid)/β-tricalcium phosphate, γ-PGA/β-TCP). Here, we have reviewed the progress on nanoparticles carrying insulin/IGF for bone regeneration. In addition, the key regulatory mechanism of insulin in bone regeneration is also summarized. The future application strategies and the challenges in bone regeneration are also discussed.

Impact of diabetes mellitus simulations on bone cell behavior through in vitro models

Diabetes mellitus (DM) is related to impaired bone healing and an increased risk of bone fractures. While it is recognized that osteogenic differentiation and the function of osteoblasts are suppressed in DM, the influence of DM on osteoclasts is still unclear. Hyperglycemia and inflammatory environment are the hallmark of DM that causes dysregulation of various pro-inflammatory cytokines and alternated gene expression in periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. A methodological review on conceptual and practical implications of in vitro study models is used for DM simulation on bone cells. Several major databases were screened to find literature related to the study objective. Published literature within last 20 years that used in vitro DM-simulated models to study how DM affects the cellular behavior of bone cells were selected for this review. Studies utilizing high glucose and serum acquired from diabetic animals are the mainly used methods to simulate the diabetic condition. The combination with various simulating factors such as lipopolysaccharide (LPS), hydrogen peroxide (H₂O₂), and advanced glycation end products (AGEs) have been reported in diabetic situations in vitro, as well. Through screening procedure, it was evident DM-simulated conditions exerted negative impact on bone-related cells. However, inconsistent results were found among different reported studies, which could be due to variation in culture conditions, concentrations of the stimulating factors and cell lineage, etc. This manuscript has concisely reviewed currently existing DM-simulated in vitro models and provides valuable insights of detailed components in simulating DM conditions in vitro. Studies using DM-simulated microenvironment revealed that in vitro simulation negatively impacted periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. Contrarily, studies also indicated beneficial influence on bone-related cells when such conditions are reversed.

Obesity/Metabolic Syndrome and Diabetes Mellitus on Peri-implantitis

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

miR-26a Attenuated Bone-Specific Insulin Resistance and Bone Quality in Diabetic Mice

Diabetes mellitus is a prevalent disease result in several complications, including bone problems. Previous studies have shown that microRNA (miR)-26a regulates glucose metabolism and plays a protective role in diabetes. However, whether miR-26a also affects bone quality in diabetes remains unknown. In the present study, we evaluated the potential effects of miR-26a on bone in diabetic mice. We administrated miR-26a in streptozotocin-induced diabetic mice. The metabolic parameters, bone quality, osteoblast and osteoclast markers, and insulin signaling activation were measured. miR-26a ameliorated insulin resistance and glucose tolerance, improved bone microarchitecture and quality, increased osteoblasts and bone formation, decreased osteoclasts, and promoted the insulin signaling pathway in diabetic mice. These effects were abolished in insulin receptor-compromised Col1a1-Insr^+/- mice. In conclusion, miR-26a could ameliorate bone-specific insulin resistance and bone quality in diabetic mice, which depended on the insulin receptors on osteoblasts. Our findings highlight the potential of miR-26a as a therapeutic target for diabetes mellitus-related bone metabolism and diseases.

APPL1 negatively regulates bone mass, possibly by controlling the fate of bone marrow mesenchymal progenitor cells

Adiponectin is an adipokine that can exert a regulatory function on bone metabolism. However, there are many contradictions between clinical and pre-clinical studies on adiponectin. APPL1 is an adaptor protein that can interact with adiponectin receptors. In the current study, we found that knockout of the Appl1 gene in male mice was associated with higher bone volume and numbers of trabeculae than in females or controls. The trabecular thickness, cortical thickness, ratio of bone volume/trabecular volume, cross-sectional bone area, and mean polar moment of inertia increased in Appl1 KO mice compared with wild-type mice. The number of osteoblasts increased but the number of adipocytes decreased in Appl1 KO mice. Knockdown of Appl1 impaired adipogenesis in bone marrow-derived mesenchymal stem cells. Mineralization was increased by knockdown of Appl1 during osteoblast differentiation. Data from differentiation-related genes showed results consistent with the in vivo effects. In summary, this study provides further clarification of the effect of the adiponectin signaling pathway on bone metabolism.

Phosphoproteomic profiling reveals a defined genetic program for osteoblastic lineage commitment of human bone marrow-derived stromal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) differentiate into osteoblasts upon stimulation by signals present in their niche. Because the global signaling cascades involved in the early phases of MSCs osteoblast (OB) differentiation are not well-defined, we used quantitative mass spectrometry to delineate changes in human MSCs proteome and phosphoproteome during the first 24 h of their OB lineage commitment. The temporal profiles of 6252 proteins and 15,059 phosphorylation sites suggested at least two distinct signaling waves: one peaking within 30 to 60 min after stimulation and a second upsurge after 24 h. In addition to providing a comprehensive view of the proteome and phosphoproteome dynamics during early MSCs differentiation, our analyses identified a key role of serine/threonine protein kinase D1 (PRKD1) in OB commitment. At the onset of OB differentiation, PRKD1 initiates activation of the pro-osteogenic transcription factor RUNX2 by triggering phosphorylation and nuclear exclusion of the histone deacetylase HDAC7.

Uniform-sized insulin-loaded PLGA microspheres for improved early-stage peri-implant bone regeneration

Poor initial stability at the first four weeks after surgery is becoming the major causes for metal implant failure. Previous attempts neglected the control release of insulin for the bone regeneration among nondiabetic subjects. The major reason may lie in the adverse effects, such as attenuated bone formation, hypoglycemia or hyperinsulinemia, that caused by the excessive insulin. Thus, spatiotemporal release of insulin may serve as the promising strategy. To address this, through solvent extraction (EMS), solvent evaporation (SMS) and cosolvent methods (CMS), we prepared three types of PLGA microspheres with various internal structures, but similar size distribution. The effects of the preparation methods on the properties of the microspheres, such as their release behavior, degradation of molecular weight, and structural evolution, were investigated. Human bone marrow mesenchymal stromal cells (BMSCs) and rabbit implant models were used to test the bioactivity of the microspheres in vitro and in vivo, respectively. The result demonstrated that these three preparation methods did not influence the polymer degradation but instead affected the internal structural evolution, which plays a crucial role in the release behavior, osteogenesis and peri-implant bone regeneration. Compared with EMS and CMS microspheres, SMS microspheres exhibited a relatively steady release rate in the first four weeks, which evidently stimulated the osteogenic differentiation of the stem cells and peri-implant bone regeneration. Meanwhile, SMS microspheres significantly enhanced the stability of the implant at Week 4, which is promising to reduce early failure rate of the implant without inducing adverse effects on the serum biochemical indices.

Hedgehog Signaling Inhibition by Smoothened Antagonist BMS-833923 Reduces Osteoblast Differentiation and Ectopic Bone Formation of Human Skeletal (Mesenchymal) Stem Cells

Background

Hedgehog (Hh) signaling is essential for osteoblast differentiation of mesenchymal progenitors during endochondral bone formation. However, the critical role of Hh signaling during adult bone remodeling remains to be elucidated.

Methods

A Smoothened (SMO) antagonist/Hedgehog inhibitor, BMS-833923, identified during a functional screening of a stem cell signaling small molecule library, was investigated for its effects on the osteoblast differentiation of human skeletal (mesenchymal) stem cells (hMSC). Alkaline phosphatase (ALP) activity and Alizarin red staining were employed as markers for osteoblast differentiation and in vitro mineralization capacity, respectively. Global gene expression profiling was performed using the Agilent® microarray platform. Effects on in vivo ectopic bone formation were assessed by implanting hMSC mixed with hydroxyapatite-tricalcium phosphate granules subcutaneously in 8-week-old female nude mice, and the amount of bone formed was assessed using quantitative histology.

Results

BMS-833923, a SMO antagonist/Hedgehog inhibitor, exhibited significant inhibitory effects on osteoblast differentiation of hMSCs reflected by decreased ALP activity, in vitro mineralization, and downregulation of osteoblast-related gene expression. Similarly, we observed decreased in vivo ectopic bone formation. Global gene expression profiling of BMS-833923-treated compared to vehicle-treated control cells, identified 348 upregulated and 540 downregulated genes with significant effects on multiple signaling pathways, including GPCR, endochondral ossification, RANK-RANKL, insulin, TNF alpha, IL6, and inflammatory response. Further bioinformatic analysis employing Ingenuity Pathway Analysis revealed significant enrichment in BMS-833923-treated cells for a number of functional categories and networks involved in connective and skeletal tissue development and disorders, e.g., NFκB and STAT signaling.

Conclusions

We identified SMO/Hedgehog antagonist (BMS-833923) as a powerful inhibitor of osteoblastic differentiation of hMSC that may be useful as a therapeutic option for treating conditions associated with high heterotopic bone formation and mineralization.

Notch Signaling Inhibition by LY411575 Attenuates Osteoblast Differentiation and Decreased Ectopic Bone Formation Capacity of Human Skeletal (Mesenchymal) Stem Cells

Background

Chemical biology approaches using small molecule inhibitors targeting specific signaling pathways are useful tools to dissect the molecular mechanisms governing stem cell differentiation and for their possible use in therapeutic interventions.

Methods

Stem cell signaling small molecule library functional screen was performed employing human bone marrow skeletal (mesenchymal) stem cells (hBMSCs). Alkaline phosphatase (ALP) activity and formation of mineralized matrix visualized by Alizarin red staining were employed as markers for osteoblastic differentiation. Global gene expression profiling was conducted using the Agilent microarray platform, and data normalization and bioinformatics were performed using GeneSpring software. Pathway analyses were conducted using the Ingenuity Pathway Analysis (IPA) tool. In vivo ectopic bone formation was performed using hBMSC mixed with hydroxyapatite–tricalcium phosphate granules that were implanted subcutaneously in 8-week-old female nude mice. Hematoxylin and eosin staining and Sirius red staining were performed to identify bone formation in vivo.

Results

Among the tested molecules, LY411575, a potent γ-secretase and Notch signaling inhibitor, exhibited significant inhibitory effects on osteoblastic differentiation of hBMSCs manifested by reduced ALP activity, mineralized matrix formation, and decreased osteoblast-specific gene expression as well as in vivo ectopic bone formation. Global gene expression profiling of LY411575-treated cells revealed changes in multiple signaling pathways, including focal adhesion, insulin, TGFβ, IL6, and Notch signaling, and decreased the expression of genes associated with functional categories of tissue development. Among the affected signaling networks were TGFβ1, SPP1, and ERK regulatory networks.

Conclusions

We identified γ-secretase inhibitor (LY411575) as a potent regulator of osteoblastic differentiation of hBMSC that may be useful as a therapeutic option for treating conditions associated with ectopic bone formation.

Bone health in diabetes and prediabetes

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

Association Study between BGLAP Gene HindIII Polymorphism and Type 2 Diabetes Mellitus Development in Ukrainian Population

Type 2 diabetes mellitus (T2DM) belongs to the diseases with hereditary predisposition, so both environmental and genetic factors contribute to its development. Recent studies have demonstrated that the skeleton realizes systemic regulation of energy metabolism through the secretion of osteocalcin (OCN). Thus, the association analysis between HindIII single nucleotide polymorphism of OCN gene (BGLAP) promoter region and T2DM development in Ukrainian population was carried out. 153 individuals diagnosed with T2DM and 311 control individuals were enrolled in the study. The genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The lack of association between BGLAP HindIII single nucleotide polymorphism (SNP) and T2DM development among Ukrainians was found. Further studies with extended groups of comparison are needed to confirm the obtained results.

Red (635 nm), Near-Infrared (808 nm) and Violet-Blue (405 nm) Photobiomodulation Potentiality on Human Osteoblasts and Mesenchymal Stromal Cells: A Morphological and Molecular In Vitro Study

Photobiomodulation (PBM) has been used for bone regenerative purposes in different fields of medicine and dentistry, but contradictory results demand a skeptical look for its potential benefits. This in vitro study compared PBM potentiality by red (635 ± 5 nm) or near-infrared (NIR, 808 ± 10 nm) diode lasers and violet-blue (405 ± 5 nm) light-emitting diode operating in a continuous wave with a 0.4 J/cm² energy density, on human osteoblast and mesenchymal stromal cell (hMSC) viability, proliferation, adhesion and osteogenic differentiation. PBM treatments did not alter viability (PI/Syto16 and MTS assays). Confocal immunofluorescence and RT-PCR analyses indicated that red PBM (i) on both cell types increased vinculin-rich clusters, osteogenic markers expression (Runx-2, alkaline phosphatase, osteopontin) and mineralized bone-like nodule structure deposition and (ii) on hMSCs induced stress fiber formation and upregulated the expression of proliferation marker Ki67. Interestingly, osteoblast responses to red light were mediated by Akt signaling activation, which seems to positively modulate reactive oxygen species levels. Violet-blue light-irradiated cells behaved essentially as untreated ones and NIR irradiated ones displayed modifications of cytoskeleton assembly, Runx-2 expression and mineralization pattern. Although within the limitations of an in vitro experimentation, this study may suggest PBM with 635 nm laser as potential effective option for promoting/improving bone regeneration.

Higher dietary glycemic index and glycemic load values increase the risk of osteoporotic fracture in the PREvención con DIeta MEDiterránea (PREDIMED)-Reus trial

Background

High glucose and insulin concentrations seem to have a negative impact on bone health. However, the relation between the dietary glycemic index (DGI) and the dietary glycemic load (DGL), which has proved to be effective at modulating blood glucose concentrations after carbohydrate consumption, has yet to be explored in relation to bone health.

Objective

The aim of the study was to examine the associations between the DGI or DGL and the risk of osteoporotic-related fractures in an elderly Mediterranean population.

Design

The study was conducted in 870 subjects aged 55-80 y at high cardiovascular disease risk participating in the PREvención con DIeta MEDiterránea (PREDIMED)-Reus study. The DGI and DGL were estimated from validated food-frequency questionnaires with the use of the international glycemic index and glycemic load values, with glucose as reference. Data on osteoporotic fractures were acquired from a systematic review of medical records. We used Cox proportional hazard models to assess the risk of osteoporotic fracture according to tertiles of average DGI and DGL.

Results

A total of 114 new cases of osteoporotic-related fractures were documented after a mean follow-up of 8.9 y. Participants in the highest tertile of DGI and DGL had a significantly higher risk of osteoporotic fractures than those in the lowest tertile after adjusting for potential confounders (HR: 1.80; 95% CI: 1.03, 3.15 and HR: 3.20; 95% CI: 1.25, 8.18, respectively).

Conclusions

A high DGI and DGL are associated with a higher risk of osteoporosis-related fractures in an elderly Mediterranean population at high cardiovascular disease risk. This trial was registered at isrctn.com as ISRCTN35739639.

Soy Protein Isolate Suppresses Bone Resorption and Improves Trabecular Microarchitecture in Spontaneously Hyperphagic, Rapidly Growing Male OLETF Rats

BACKGROUND

Traditionally, milk proteins have been recommended for skeletal health; recently, soy proteins have emerged as popular alternatives. Excess adiposity appears detrimental to skeletal health, as obese adolescents have increased fracture rates compared with healthy controls. However, soy protein effects on skeletal health during excess adiposity remain unknown.

OBJECTIVE

The study objective was to examine the effects of isocaloric diets containing milk protein isolate (MPI), soy protein isolate (SPI), or a 50/50 combination (MIX) as the sole protein source on metabolic health indicators and bone outcomes in rapidly growing, hyperphagic, male Otsuka Long Evans Tokushima Fatty (OLETF) rats.

METHODS

OLETF rats, aged 4 wk, were randomly assigned to 3 treatment groups (MPI, SPI, or MIX, n = 20 per group) and provided with access to experimental diets ad libitum for 16 wk.

RESULTS

Body mass did not differ between the groups, but SPI had lower percentage body fat than MPI (P = 0.026). Insulin was lower in MPI than in MIX (P = 0.033) or SPI (P = 0.044), but fasting blood glucose was not different between the groups. SPI significantly reduced serum cholesterol compared with MPI (P = 0.001) and MIX (P = 0.002). N-terminal propeptide of type I collagen (P1NP) was higher in MIX than MPI (P = 0.05); C-terminal telopeptide of type 1 collagen (CTx) was higher in MPI than SPI (P < 0.001) and MIX (P < 0.001); the P1NP to CTx ratio was significantly higher in SPI and MIX than in MPI (P < 0.001). Trabecular separation was reduced in SPI compared with MPI (P = 0.030) and MIX (P = 0.008); trabecular number was increased in SPI compared with MIX (P = 0.038). No differences were seen in cortical geometry and biomechanical properties.

CONCLUSIONS

In the context of excess adiposity, soy- and milk-based proteins have comparable effects on cortical bone geometry and biomechanical properties, whereas soy-based proteins favorably affect the trabecular microarchitecture, and the combination of both proteins may offer additional benefits to bone remodeling in rapidly growing male OLETF rats.

Maternal obesity increases insulin resistance, low-grade inflammation and osteochondrosis lesions in foals and yearlings until 18 months of age

INTRODUCTION

Obesity is a growing concern in horses. The effects of maternal obesity on maternal metabolism and low-grade inflammation during pregnancy, as well as offspring growth, metabolism, low-grade inflammation, testicular maturation and osteochondrotic lesions until 18 months of age were investigated.

MATERIAL AND METHODS

Twenty-four mares were used and separated into two groups at insemination according to body condition score (BCS): Normal (N, n = 10, BCS ≤4) and Obese (O, n = 14, BCS ≥4.25). BCS and plasma glucose, insulin, triglyceride, urea, non-esterified fatty acid, serum amyloid A (SAA), leptin and adiponectin concentrations were monitored throughout gestation. At 300 days of gestation, a Frequently Sampled Intravenous Glucose Tolerance Test (FSIGT) was performed. After parturition, foals' weight and size were monitored until 18 months of age with plasma SAA, leptin, adiponectin, triiodothyronine (T3), thyroxine (T4) and cortisol concentrations measured at regular intervals. At 6, 12 and 18 months of age, FSIGT and osteoarticular examinations were performed. Males were gelded at one year and expression of genes involved in testicular maturation analysed by RT-qPCR.

RESULTS

Throughout the experiment, maternal BCS was higher in O versus N mares. During gestation, plasma urea and adiponectin were decreased and SAA and leptin increased in O versus N mares. O mares were also more insulin resistant than N mares with a higher glucose effectiveness. Postnatally, there was no difference in offspring growth between groups. Nevertheless, plasma SAA concentrations were increased in O versus N foals until 6 months, with O foals being consistently more insulin resistant with a higher glucose effectiveness. At 12 months of age, O foals were significantly more affected by osteochondrosis than N foals. All other parameters were not different between groups.

CONCLUSION

In conclusion, maternal obesity altered metabolism and increased low-grade inflammation in both dams and foals. The risk of developing osteochondrosis at 12 months of age was also higher in foals born to obese dams.

Bone Density in Patients With Berardinelli-Seip Congenital Lipodystrophy Is Higher in Trabecular Sites and in Type 2 Patients

Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare autosomal recessive syndrome characterized by a difficulty storing lipid in adipocytes, low body fat, hypoleptinemia, and hyperinsulinemia. We report here laboratory, bone mineral density (BMD), and bone mineral content findings of 21 patients (24.1 ± 8.4 yr old, 14 females, 18 diabetics, 5.3% total body fat) with BSCL. The mean leptin was very low (0.91 ± 0.42 ng/mL), and the mean values of the Z-scores for all studied sites were positive, except for the 33% radius (Z-score -0.5 standard deviation [SD]). Twelve patients (57.1%) had a BMD Z-score higher than +2.5 SD in at least 1 site. There was no significant difference in the Z-scores between males and females. None of type 1 (AGPAT2) patients had Z-scores higher than +2.5 SD, and these patients had a smaller Z-score of BMD total body (0.26 SD vs 1.90 SD, p = 0.022) and of bone mineral content (1.59 SD vs 3.3 SD, p = 0.032) than type 2 (seipin) patients. Insulin, as well as HOMA_IR (homeostasis model assessment), correlated positively with the BMD of all sites, except for the 33% radius. Z-Scores on this site (33% radius) were the smallest of all. More than half of our patients with BSCL have BMD Z-scores higher than +2.5 SD on at least 1 site, and this increase is more pronounced in the trabecular sites and in type 2 patients.

Enhanced bone regeneration using an insulin-loaded nano-hydroxyapatite/collagen/PLGA composite scaffold

Insulin is widely considered as a classical hormone and drug in maintaining energy and glucose homeostasis. Recently, insulin has been increasingly recognized as an indispensable factor for osteogenesis and bone turnover, but its applications in bone regeneration have been restricted because of the short periods of activity and uncontrolled release. In this study, we incorporated insulin-loaded poly lactic-co-glycolic-acid (PLGA) nanospheres into nano-hydroxyapatite/collagen (nHAC) scaffolds and investigated the bioactivity of the composite scaffolds in vitro and in vivo. Bioactive insulin was successfully released from the nanospheres within the scaffold, and the release kinetics of insulin could be efficiently controlled by uniform-sized nanospheres. The physical characterizations of the composite scaffolds demonstrated that incorporation of nanospheres in nHAC scaffolds using this method did not significantly change the porosity, pore diameters, and compressive strengths of nHAC. In vitro, the insulin-loaded nHAC/PLGA composite scaffolds possessed favorable biological function for bone marrow mesenchymal stem cells adhesion and proliferation, as well as the differentiation into osteoblasts. In vivo, the optimized bone regenerative capability of this composite scaffold was confirmed in rabbit mandible critical size defects. These results demonstrated successful development of a functional insulin-PLGA-nHAC composite scaffold that enhances the bone regeneration capability of nHAC.

Long Noncoding RNA H19 Inhibits Cell Viability, Migration, and Invasion Via Downregulation of IRS-1 in Thyroid Cancer Cells

Thyroid cancer is a common endocrine gland malignancy which exhibited rapid increased incidence worldwide in recent decades. This study was aimed to investigate the role of long noncoding RNA H19 in thyroid cancer. Long noncoding RNA H19 was overexpressed or knockdown in thyroid cancer cells SW579 and TPC-1, and the expression of long noncoding RNA H19 was detected by real-time polymerase chain reaction. The cell viability, migration, and invasion were determined by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide assay, Transwell assay, and wound healing assay, respectively. Furthermore, cell apoptosis was analyzed by flow cytometry, and expressions of some factors that were related to phosphatidyl inositide 3-kinases/protein kinase B and nuclear factor κB signal pathway were measured by Western blotting. This study revealed that cell viability and migration/invasion of SW579 and TPC-1 were significantly decreased by long noncoding RNA H19 overexpression compared with the control group (P < .05), whereas cell apoptosis was statistically increased (P < .001). Meanwhile, cell viability and migration/invasion were significantly increased after long noncoding RNA H19 knockdown (P < .05). Furthermore, long noncoding RNA H19 negatively regulated the expression of insulin receptor substrate 1 and thus effect on cell proliferation and apoptosis. Insulin receptor substrate 1 regulated the activation of phosphatidyl inositide 3-kinases/AKT and nuclear factor κB signal pathways. In conclusion, long noncoding RNA H19 could suppress cell viability, migration, and invasion via downregulation of insulin receptor substrate 1 in SW579 and TPC-1 cells. These results suggested the important role of long noncoding RNA H19 in thyroid cancer, and long noncoding RNA H19 might be a potential target of thyroid cancer treatment.

The association between insulin use and volumetric bone mineral density, bone micro-architecture and bone strength of the distal radius in patients with type 2 diabetes - The Maastricht study

Type 2 diabetes mellitus (T2DM) has been associated with an increased risk of fractures, despite normal to increased bone mineral density (BMD). Insulin use is one of the factors linked to this increased fracture risk. However, direct negative effects of insulin on bone quality are not expected since insulin is thought to be anabolic to bone. In this cross-sectional study the association between insulin use and volumetric BMD (vBMD), bone micro-architecture and bone strength of the distal radius, as measured with HR-pQCT, was examined. Data from 50 participants with T2DM of The Maastricht Study (mean age 62±7.5years, 44% women) was used. Participants were classified as insulin user (n=13) or non-insulin user (n=37) based on prescription data. Linear regression analysis was used to estimate the association between current insulin use and HR-pQCT derived parameters. After adjustment for age, sex, body mass index, glycated hemoglobin A1c and T2DM duration, insulin use was associated with lower total vBMD (standardized beta (β):-0.56 (95% CI:-0.89 to -0.24)), trabecular vBMD (β:-0.58 (95% CI:-0.87 to -0.30)), trabecular thickness (β:-0.55 (95% CI:-0.87 to -0.23)), cortical thickness (β:-0.41 (95% CI:-0.74 to -0.08)), log cortical pore volume (β:-0.43 (95% CI:-0.73 to -0.13)), bone stiffness (β:-0.39 (95% CI:-0.62 to -0.17)) and failure load (β:-0.39 (95% CI:-0.60 to -0.17)) when compared to the non-insulin users. Insulin use was not associated with cortical vBMD, trabecular number, trabecular separation, cortical porosity and cortical pore diameter. This study indicates that insulin use is negatively associated with bone density, bone micro-architectural and bone strength parameters. These findings may partly explain the previously observed increased fracture risk in insulin users, although there may be residual confounding by other factors related to disease severity in insulin users.

Insulin Resistance and the IGF-I-Cortical Bone Relationship in Children Ages 9 to 13 Years

IGF-I is a pivotal hormone in pediatric musculoskeletal development. Although recent data suggest that the role of IGF-I in total body lean mass and total body bone mass accrual may be compromised in children with insulin resistance, cortical bone geometric outcomes have not been studied in this context. Therefore, we explored the influence of insulin resistance on the relationship between IGF-I and cortical bone in children. A secondary aim was to examine the influence of insulin resistance on the lean mass-dependent relationship between IGF-I and cortical bone. Children were otherwise healthy, early adolescent black and white boys and girls (ages 9 to 13 years) and were classified as having high (n = 147) or normal (n = 168) insulin resistance based on the homeostasis model assessment of insulin resistance (HOMA-IR). Cortical bone at the tibia diaphysis (66% site) and total body fat-free soft tissue mass (FFST) were measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), respectively. IGF-I, insulin, and glucose were measured in fasting sera and HOMA-IR was calculated. Children with high HOMA-IR had greater unadjusted IGF-I (p < 0.001). HOMA-IR was a negative predictor of cortical bone mineral content, cortical bone area (Ct.Ar), and polar strength strain index (pSSI; all p ≤ 0.01) after adjusting for race, sex, age, maturation, fat mass, and FFST. IGF-I was a positive predictor of most musculoskeletal endpoints (all p < 0.05) after adjusting for race, sex, age, and maturation. However, these relationships were moderated by HOMA-IR (p_Interaction  < 0.05). FFST positively correlated with most cortical bone outcomes (all p < 0.05). Path analyses demonstrated a positive relationship between IGF-I and Ct.Ar via FFST in the total cohort (β_{Indirect Effect} = 0.321, p < 0.001). However, this relationship was moderated in the children with high (β_{Indirect Effect} = 0.200, p < 0.001) versus normal (β_{Indirect Effect} = 0.408, p < 0.001) HOMA-IR. These data implicate insulin resistance as a potential suppressor of IGF-I-dependent cortical bone development, though prospective studies are needed. © 2017 American Society for Bone and Mineral Research.

Porous Nanohydroxyapatite/Collagen Scaffolds Loading Insulin PLGA Particles for Restoration of Critical Size Bone Defect

Insulin is considered to be a classical central regulator of energy homeostasis. Recently, the effect of insulin on bone has gained a lot of attention, but little attention has been paid to the application in bone tissue engineering. In this study, porous nanohydroxyapatite/collagen (nHAC) scaffolds incorporating poly lactic-co-glycolic acid (PLGA) particles were successfully developed as an insulin delivery platform for bone regeneration. Bioactive insulin was successfully released from the PLGA particles within the scaffold, and the size of the particles as well as the release kinetics of the insulin could be efficiently controlled through Shirasu porous glass premix membrane emulsification technology. It was indicated that the nHAC/PLGA composite scaffolds possessed favorable mechanical and structural properties for cell adhesion and proliferation, as well as the differentiation into osteoblasts. It was also demonstrated that the nHAC/PLGA scaffolds implanted into a rabbit critical-size mandible defect possessed tissue compatibility and higher bone restoration capacity compared with the defects that were filled with or without nHAC scaffolds. Furthermore, the in vivo results showed that the nHAC/PLGA scaffolds which incorporated insulin-loaded microspheres with a size of 1.61 μm significantly accelerated bone healing compared with two other composite scaffolds. Our study indicated that the local insulin released at the optimal time could substantially and reproducibly improve bone repair.

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.

Kuei-Lu-Er-Xian-Jiao extract enhances BMP-2 production in osteoblasts

Osteoporosis is a common skeletal disorder, resulting from an imbalance in bone resorption relative to formation. Bone morphogenetic protein (BMP) is a key regulator in bone formation and osteoblastic differentiation. Hence, compounds that promote BMP expression may be suitable candidates for osteoporosis treatment. This study examined the effects of the traditional Chinese medicinal agent, Kuei-Lu-Er-Xian-Jiao (KLEXJ), on BMP-2 production in osteoblasts. We found that KLEXJ extract promoted osteoblastic differentiation marker ALP activity and increased BMP-2 production; pretreatment with PI3K and Akt inhibitors, or small interfering RNA (siRNA), reduced these effects. KLEXJ also enhanced PI3K and Akt phosphorylation. Treatment of osteoblastic cells with NF-κB inhibitors (TPCK or PDTC) markedly inhibited KLEXJ-enhancement of ALP activity and BMP-2 production. KLEXJ also significantly promoted p65 phosphorylation, while treatment with PI3K and Akt inhibitors antagonized KLEXJ-enhanced p65 phosphorylation. Thus, KLEXJ enhances ALP activity and BMP-2 production of osteoblasts through the PI3K/Akt/ NF-κB signaling pathway and hence may be suitable in the treatment of osteoporosis.

Lychee Seed Saponins Improve Cognitive Function and Prevent Neuronal Injury via Inhibiting Neuronal Apoptosis in a Rat Model of Alzheimer's Disease

Lychee seed is a traditional Chinese medicine and possesses many activities, including hypoglycemia, liver protection, antioxidation, antivirus, and antitumor. However, its effect on neuroprotection is still unclear. The present study investigated the effects of lychee seed saponins (LSS) on neuroprotection and associated mechanisms. We established a rat model of Alzheimer’s disease (AD) by injecting Aβ_25–35 into the lateral ventricle of rats and evaluated the effect of LSS on spatial learning and memory ability via the Morris water maze. Neuronal apoptosis was analyzed by hematoxylin and eosin stain and terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP nick-end labeling analysis, and mRNA expression of caspase-3 and protein expressions of Bax and Bcl-2 by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The results showed that LSS remarkably improved cognitive function and alleviated neuronal injury by inhibiting apoptosis in the hippocampus of AD rats. Furthermore, the mRNA expression of caspase-3 and the protein expression of Bax were downregulated, while the protein expression of Bcl-2 and the ratio of Bcl-2/Bax were increased by LSS. We demonstrate that LSS significantly improves cognitive function and prevent neuronal injury in the AD rats via regulation of the apoptosis pathway. Therefore, LSS may be developed as a nutritional supplement and sold as a drug for AD prevention and/or treatment.

Conversations between insulin and bone: Potential mechanism of high bone density in patients with Berardinelli-Seip Congenital Lipodystrophy

Berardinelli-Seip Congenital Lipodystrophy (BSCL) is a rare autosomal recessive syndrome characterized by a difficulty storing lipid in adipocytes, low body fat, hypertriglyceridemia, and fat liver. The serum leptin is usually very low, and serum insulin, as well as HOMA_IR (homeostasis model assessment), is very high and correlated positively with bone mineral density (BMD). Despite deficiency/insufficiency of vitamin D, low body mass index, low daily calcium intake, physical inactivity, and menarche at a later age, BSCL patients usually have normal or even high BMD. We hypothesize that low leptin and high insulin may play a role in this outcome. Understanding the potential pathophysiological mechanism of these bone abnormalities will help to clarify the effects of extreme insulin resistance in the bone.