Association between sensitivity to thyroid hormone indices and osteoporosis in euthyroid patients with type 2 diabetes mellitus.

Background: Thyroid hormones are known to regulate bone metabolism and may influence bone mineral density (BMD), as well as the risk of osteoporosis (OP) and fractures in patients with type 2 diabetes mellitus (T2DM). Recently, sensitivity to thyroid hormone indices has been linked with T2DM and OP independently. However, the relationship between thyroid hormone sensitivity and OP in euthyroid T2DM patients has yet to be investigated. Objectives: The aim of this study was to determine the association between sensitivity to thyroid hormone indices and the risk of OP in euthyroid patients with T2DM. Design: This study employed a retrospective, cross-sectional design and utilized data acquired from the Cangzhou Central Hospital in China between 2019 and 2020. Methods: We retrospectively analyzed the data of 433 patients with T2DM for anthropometric measurements, clinical laboratory test results, and BMD. The thyroid-stimulating hormone index, thyrotroph thyroxine resistance index, and thyroid feedback quantile-based index (TFQI) were calculated to determine thyroid hormone sensitivity. Finally, multivariable logistic regression, generalized additive models, and subgroup analysis were performed to detect the association between sensitivity to thyroid hormone indices and the risk of OP in these patients. Results: We did not observe a statistically significant linear relationship between sensitivity to thyroid hormones indices and OP after covariate adjustment. However, a nonlinear relationship existed between TFQI and the prevalence of OP. The inflection point of the TFQI was at -0.29. The effect sizes (odds ratio) on the left and right of the inflection point were 0.07 [95% confidence interval (CI): 0.01-0.71; p = 0.024] and 2.78 (95% CI: 1.02-7.58; p = 0.046), respectively. This trend was consistent in older female patients with higher body mass index (BMI; 25-30 kg/m2). Conclusion: An approximate U-shaped relationship was observed between sensitivity to thyroid hormone indices and OP risk in euthyroid patients with T2DM with variations in sex, age, and BMI. These findings provide a new perspective to elucidate the role of thyroid hormones in OP, specifically in patients with T2DM.

Development of Machine Learning Models for Predicting Osteoporosis in Patients with Type 2 Diabetes Mellitus-A Preliminary Study.

Purpose: Diagnosing osteoporosis in T2DM based on bone mineral density (BMD) remains challenging. We sought to develop prediction models employing machine learning algorithms for use as screening instruments for osteoporosis in T2DM patients. Patients and Methods: Data were collected from 433 participants and analyzed using nine categorical machine learning algorithms to select features based on demographic and clinical variables. Multiple classification models were compared using the area under the receiver operating characteristic curve (ROC-AUC), accuracy, sensitivity, specificity, the average precision (AP), precision, F1 score, precision-recall curves, calibration plots, and decision curve analysis (DCA) to determine the best model. In addition, 5-fold cross-validation was utilized to optimize the model, followed by an evaluation of feature significance using Shapley Additive exPlanations (SHAP). Using latent class analysis (LCA), distinct subpopulations were identified by constructing several discrete clusters. Results: In this study, nine feature variables were identified to construct predictive models for osteoporosis in individuals with T2DM. The machine learning algorithms achieved an AP range of 0.444-1.000. The XGBoost model was selected as the final prediction model with an AUROC of 0.940 in the training set, 0.772 in the validation set for 5-fold cross-validation, and 0.872 in the test set. Using SHAP methodology, 25(OH)D was identified as the most important risk factor. Additionally, a 3-Class model was constructed using LCA, which categorized individuals into high, medium, and low-risk groups. Conclusion: Our study developed a predictive model with high accuracy and clinical validity for predicting osteoporosis in type 2 diabetes patients. We also identified three subpopulations with varying osteoporosis risk using clustering. However, limited sample size warrants cautious interpretation of results, and validation in larger cohorts is needed.

IRS-1 targets TAZ to inhibit adipogenesis of rat bone marrow mesenchymal stem cells through PI3K-Akt and MEK-ERK pathways.

Gene modification of mesenchymal stem cells (MSCs) offers a promising approach for clinical stem cell therapy. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in MSCs' differentiation. We aim to explore the interaction of insulin receptor substrate-1 (IRS-1) with TAZ to regulate MSCs' adipogenesis in this study. Initially, IRS-1 and TAZ followed similar decreasing expression pattern at the early stage of adipogenesis. And, overexpression of IRS-1 decreased the CCAAT/enhancer binding protein ß (C/EBPß) and peroxi-some proliferator-activated receptor gamma (PPARγ) expression with TAZ upregulation. Accordingly, knockdown of IRS-1 induced the upexpression of C/EBPß and PPARγ with TAZ downregulation. Indeed, IRS-1 targeted TAZ to downregulate the C/EBPß and PPARγ expression, while knockdown of TAZ attenuated the IRS-1 inhibited adipogenesis. Furthermore, both LY294002 (the PI3K-Akt inhibitor) and U0126 (the MEK-ERK inhibitor) blocked the regulation of IRS-1 on TAZ during adipogenesis. Additionally, IRS-1 and TAZ influenced the cell proliferation in the above process. Taken together, this study suggests for the first time that IRS-1 is a key regulator of the MSCs' adipogenesis and may serve as a potential therapeutic target for differential alterations in bone marrow.

Liraglutide Inhibits the Apoptosis of MC3T3-E1 Cells Induced by Serum Deprivation through cAMP/PKA/ß-Catenin and PI3K/AKT/GSK3ß Signaling Pathways.

In recent years, the interest towards the relationship between incretins and bone has been increasing. Previous studies have suggested that glucagon-like peptide-1 (GLP-1) and its receptor agonists exert beneficial anabolic influence on skeletal metabolism, such as promoting proliferation and differentiation of osteoblasts via entero-osseous-axis. However, little is known regarding the effects of GLP-1 on osteoblast apoptosis and the underlying mechanisms involved. Thus, in the present study, we investigated the effects of liraglutide, a glucagon-like peptide-1 receptor agonist, on apoptosis of murine MC3T3-E1 osteoblastic cells. We confirmed the presence of GLP-1 receptor (GLP-1R) in MC3T3-E1 cells. Our data demonstrated that liraglutide inhibited the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation, as detected by Annexin V/PI and Hoechst 33258 staining and ELISA assays. Moreover, liraglutide upregulated Bcl-2 expression and downregulated Bax expression and caspase-3 activity at intermediate concentration (100 nM) for maximum effect. Further study suggested that liraglutide stimulated the phosphorylation of AKT and enhanced cAMP level, along with decreased phosphorylation of GSK3ß, increased ß-catenin phosphorylation at Ser675 site and upregulated nuclear ß-catenin content and transcriptional activity. Pretreatment of cells with the PI3K inhibitor LY294002, PKA inhibitor H89, and siRNAs GLP-1R, ß-catenin abrogated the liraglutide-induced activation of cAMP, AKT, ß-catenin, respectively. In conclusion, these findings illustrate that activation of GLP-1 receptor by liraglutide inhibits the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation through cAMP/PKA/ß-catenin and PI3K/Akt/GSK3ß signaling pathways.

Role of sclerostin and dkk1 in bone remodeling in type 2 diabetic patients.

PURPOSE: This study aimed to investigate the role of sclerostin and dkk1 in the bone metabolism of type 2 diabetic patients. METHODS: This cross-sectional study included 95 inpatients with type 2 diabetes mellitus. We divided the patients into three groups (i.e., the normal bone mineral density (BMD) group, osteopenia group and osteoporosis group) based on their different BMD levels and measured the serum levels of sclerostin, dkk1, 25-hydroxyvitamin D3 (25OHD3), bone turnover markers and other biochemical data in each group. RESULTS: Significantly increased levels of serum sclerostin and dkk1 were found in the osteoporosis group, even when the male and female cohorts were considered separately. Ordinal logistic regression analysis suggested that the levels of serum sclerostin were independently associated with the presence of osteopenia and osteoporosis after adjusting for age, gender and 25OHD3 (sclerostin: OR = 1.02, p = 0.001). The areal BMDs were negatively correlated with the levels of serum sclerostin and dkk1 and positively correlated with 25OHD3. In addition, age, glycosylated hemoglobin and serum sclerostin levels were predictors for N-terminal propeptide of type 1 procollagen and serum dkk1 levels were the only predictors for crosslinked carboxyterminal telopeptide in type 1 collagen. CONCLUSIONS: The sclerostin and dkk1 levels increased in conjunction with the reduction of BMD, confirming that the Wnts, inhibited by sclerostin and dkk1, were potentially responsible for bone fragility in type 2 diabetes patients with osteoporosis. Note that the serum sclerostin levels were predictors for bone formation, while the DKK1 levels predicted bone resorption.

Liraglutide, a glucagon-like peptide-1 receptor agonist, facilitates osteogenic proliferation and differentiation in MC3T3-E1 cells through phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT), extracellular signal-related kinase (ERK)1/2, and cAMP/protein kinase A (PKA) signaling pathways involving ß-catenin.

Previous studies have proven that glucagon-like peptide-1 (GLP-1) and its receptor agonist exert favorable anabolic effects on skeletal metabolism. However, whether GLP-1 could directly impact osteoblast-mediated bone formation is still controversial, and the underlying molecular mechanism remains to be elucidated. Thus in this paper, we investigated the effects of liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, on murine MC3T3-E1 preosteoblasts proliferation and differentiation and explored the potential cellular basis. Our study confirmed the presence of GLP-1R in MC3T3-E1, and demonstrated that liraglutide promotes osteoblasts proliferation at an intermediate concentration (100nM) and time (48h), upregulated the expression of osteoblastogenic biomarkers at various stages, and stimulated osteoblastic mineralization. Liraglutide also elevated the intracellular cAMP level and phosphorylation of AKT, ERK and ß-catenin simultaneously with increased nuclear ß-catenin content and transcriptional activity. Pretreatment of cells with the inhibitors LY294002, PD98059, H89 and GLP-1R and ß-catenin siRNA partially blocked the liraglutide-induced signaling activation and attenuated the facilitating effect of liraglutide on MC3T3-E1 cells. Collectively, liraglutide was capable of acting upon osteoblasts directly through GLP-1R by activating PI3K/AKT, ERK1/2, cAMP/PKA/ß-cat-Ser675 signaling to promote bone formation via GLP-1R. Thus, GLP-1 analogues may be potential therapeutic strategy for the treatment of osteoporosis in diabetics.

Associations between fat distribution and volumetric bone mineral density in Chinese adults.

The aim of this study was to explore the association between fat distribution and volumetric bone mineral density (vBMD) in Chinese Adults. Using a cross-sectional investigation of 867 participants including 521 women and 346 men from China, vBMD and subcutaneous adipose tissue (SCAT) or visceral adipose tissue (VAT) were measured accordingly by quantitative computed tomography. The peak vBMD values of the spine were observed at ages 30-39 years in women and at ages 20-29 years in men. In women, the peak values of VAT and SCAT were observed, respectively, at ages ≥ 70 years and at the age range of 60-69 years. In men, the peak values of VAT and SCAT were observed, respectively, at ages ≥ 70 years and at ages 30-39 years. Using the correlation tests, there was no correlation between SCAT and vBMD in both genders. Most relationships between VAT and BMD were negative (r = -0.204, P < 0.01, in premenopausal women; r = -0.150, P < 0.05, in postmenopausal women; and r = -0.181, P < 0.05, in middle-aged men). After multiple linear regression analysis, no correlations were observed. There appears to be no correlation between fat distribution and vBMD in Chinese adults, and further studies are needed to explore associations between fat distribution and vBMD.

IGF1 promotes osteogenic differentiation of mesenchymal stem cells derived from rat bone marrow by increasing TAZ expression.

Whether insulin-like growth factor 1 (IGF1) inhibits or promotes the osteogenic differentiation in vitro remains controversial. Moreover, the biological mechanisms and signaling pathways by which IGF1 affects osteogenic differentiation remain obscure. Transcriptional coactivator with PDZ-binding motif (TAZ) plays a vital role in the osteogenic differentiation of mesenchymal stem cells (MSCs), and strongly activates runt related transcription factor 2 (RUNX2)-driven genes during the terminal osteogenic differentiation. In the present study, we found that IGF1 increased the ALP activities and calcium depositions of MSCs derived from rat bone marrow dose-dependently, with a peak at 100-200ng/ml. IGF1 increased TAZ and RUNX2 expression mainly at the early stage of osteogenic differentiation, but increased OCN expression at the late stage. Our data further demonstrated that down-regulation of TAZ expression by siRNA inhibited the IGF1 induced increase in osteogenic differentiation. Moreover, UO126 (the MEK-ERK inhibitor), not LY294002 (the PI3K-Akt inhibitor), inhibited the IGF1 induced increase in TAZ expression. Taken together, we provide evidence to demonstrate that IGF1 promotes the osteogenic differentiation of rat MSCs by increasing TAZ expression, and that the increased TAZ expression induced by IGF1 is mostly mediated by the MEK-ERK pathway.