Hemoglobin is associated with BMDs and risk of the 10-year probability of fractures in patients with type 2 diabetes mellitus.

Purpose: This study aimed to investigate the associations between hemoglobin (HGB) levels and bone mineral density (BMD) and fracture risk in type 2 diabetes mellitus(T2DM) population of different ages. Method: This cross-sectional study included 641 patients with T2DM (57.9% males). BMD of the femoral neck (FN), total hip (TH), and lumbar spine (LS) were measured using dual-energy X-ray absorptiometry. The 10-year probability of fracture was assessed using a fracture risk assessment tool (FRAX). HGB and other biochemical indices were measured in a certified laboratory at our hospital. Statistical analysis was performed using SPSS 26.0 and R language (R version 4.1.0). Generalized additive models (GAMs) were used to identify the associations between HGB and BMD and fracture risk. Results: Patients with osteoporosis have lower HGB levels than the non-osteoporotic population and lower FN BMD in patients with anemia than in the non-anemic population. In patients with T2DM, there was sex- and age-related variability in the correlation between HGB levels and BMDs and fracture risk. In older men, HGB level was an independent determinant of BMD and was positively correlated with FN and TH BMD. In non-older women, HGB level was an independent determinant of BMD and fracture risk, positively associated with BMDs and negatively associated with 10-year probability of fracture risk. GAMs revealed a positive linear association between HGB level and BMDs in non-older female patients but not in older male patients. Conclusion: Our study provides a new perspective on the association of HGB level and BMDs with fracture risk. Relatively high HGB levels are a protective factor for bone quality in patients with T2DM. However, the bone-protective effect of HGB is influenced by age and sex and persists only in older men and non-older women with T2DM.

The associations between uric acid with BMDs and risk of the 10-year probability of fractures in Chinese patients with T2DM stratified by age and gender.

PURPOSE: Accumulating evidence suggests that serum uric acid (SUA) plays a beneficial role in bone health in the general population through antioxidant mechanisms. However, there is controversy over the association between SUA and bone in patients with type 2 diabetes mellitus (T2DM). We aimed to investigate the association of serum UA with BMDs and future fracture risks and its potential influencing factors in those patients. METHOD: This was a cross-sectional study of 485 patients. BMDs at femoral neck (FN), Troch and the lumbar spine (LS) were measured by DXA. The 10-year probability of fracture risk was assessed using the fracture risk assessment tool (FRAX). SUA level and other biochemical indexes were measured. RESULTS: There were lower SUA concentrations in patients with osteoporosis/osteopenia compared with those in the normal group, which only existed in non-elderly men and elderly women with T2DM. After adjustment for potential confounders, SUA was positively associated with BMD and negatively with 10-year probability of fracture risk only in non-elderly men and elderly women with T2DM. Multiple stepwise regression analysis showed that SUA was an independent determinant of BMD and 10-year probability of fracture risk, which also occurred in the above patients. CONCLUSION: These results implied that relatively high SUA is a protective factor for bone in T2DM patients, but the osteoprotective effect of SUA was mediated by age and gender, and persisted only in non-elderly men and elderly women. Large intervention studies are needed to further confirm the outcomes and provide possible explanations.

BMP9 reduces age-related bone loss in mice by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis.

Age-related osteoporosis is characterized by the accumulation of senescent osteoblastic cells in bone microenvironment and significantly reduced osteogenic differentiation. Clearing of the senescent cells is helpful to improve bone formation in aged mice. Bone morphogenetic protein 9 (BMP9), a multifunctional protein produced and secreted by liver, was reported to improve osteoporosis caused by estrogen withdrawal. However, the mechanism of BMP9 has not been fully elucidated, and its effect on senile osteoporosis has not been reported. This study reveals that BMP9 significantly increases bone mass and improves bone biomechanical properties in aged mice. Furthermore, BMP9 reduces expression of senescent genes in bone microenvironment, accompanied by decreased senescence-associated secretory phenotypes (SASPs) such as Ccl5, Mmp9, Hmgb1, Nfkb1, and Vcam1. In vitro, Bmp9 treatment inhibits osteoblast senescence through activating Smad1, which suppresses the transcriptional activity of Stat1, thereby inhibits P21 expression and SASPs production. Furthermore, inhibiting the Smad1 signal in vivo can reverse the inhibitory effect of BMP9 on Stat1 and downstream senescent genes, which eliminates the protection of BMP9 on age-related osteoporosis. These findings highlight the critical role of BMP9 on reducing age-related bone loss by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis.

Lgr4 promotes aerobic glycolysis and differentiation in osteoblasts via the canonical Wnt/ß-catenin pathway.

Lgr4, a G-protein-coupled receptor, is associated with various physiological and pathological processes including oncogenesis, energy metabolism, and bone remodeling. However, whether Lgr4 is involved in osteoblasts' metabolism is not clear. Here we uncover that in preosteoblast cell line, lacking Lgr4 results in decreased osteogenic function along with reduced glucose consumption, glucose uptake, and lactate production in the presence of abundant oxygen, which is referred to as aerobic glycolysis. Activating canonical Wnt/ß-catenin signaling rescued the glycolytic dysfunction. Lgr4 promotes the expression of pyruvate dehydrogenase kinase 1 (pdk1) and is abolished by interfering canonical Wnt/ß-catenin signaling. Mice lacking Lgr4 specifically in osteoblasts (Lgr4osb-/- ) exhibit decreased bone mass and strength due to reduced bone formation. Additionally, glycolysis of osteoblasts is impaired in Lgr4osb-/- mice. Our study reveals a novel function of Lgr4 in regulating the cellular metabolism of osteoblasts. © 2021 American Society for Bone and Mineral Research (ASBMR).

BMP9 Reduces Bone Loss in Ovariectomized Mice by Dual Regulation of Bone Remodeling.

Bone remodeling is dynamic and is tightly regulated through bone resorption dominated by osteoclasts and bone formation dominated by osteoblasts. Imbalances in this process can cause various pathological conditions, such as osteoporosis. Bone morphogenetic protein 9 (BMP9), a biomolecule produced and secreted by the liver, has many pharmacological effects, including anti-liver fibrosis, antitumor, anti-heart failure, and antidiabetic activities. However, the effects of BMP9 on the regulation of osteoblast and osteoclast functions and the underlying molecular mechanism(s) have not yet been investigated. In this study, BMP9 increased the expression of osteoblastogenic gene markers, such as ALP, Cola1, OCN, RUNX2, and OSX, and ALP activity in MC3T3-E1 cells by upregulating LGR6 and activating the Wnt/ß-catenin pathway. BMP9 also suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation of bone marrow macrophages (BMMs) by inhibiting the Akt-NF-κB-NFATc1 pathway. More importantly, in an ovariectomy (OVX) mouse model, BMP9 attenuated bone loss and improved bone biomechanical properties in vivo by increasing bone-forming activity and suppressing bone resorption activity. Accordingly, our current work highlights the dual regulatory effects that BMP9 exerts on bone remodeling by promoting bone anabolic activity and inhibiting osteoclast differentiation in OVX mice. © 2020 American Society for Bone and Mineral Research.

Follicle-stimulating hormone and estradiol are associated with bone mineral density and risk of fractures in men with type 2 diabetes mellitus.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is associated with a higher fracture risk. Sex hormones are important for maintaining skeletal health. It is not clear which sex hormone(s) contribute(s) to bone mineral density (BMD) and fracture risk in males with T2DM. This study investigated the relationships of these parameters in males with T2DM. METHODS: This study involved 482 men with T2DM. BMDs at the lumbar spine (L2-4), femoral neck (FN), and total hip (TH) were measured by dual-energy X-ray absorptiometry (DXA). The 10-year probability of fractures was assessed using the modified Fracture Risk Algorithm (FRAX) tool. Serum levels of sex hormones were measured. RESULTS: Follicle-stimulating hormone (FSH) and estradiol (E2) were associated with BMDs at L2-4 (FSH, ß = -.162, P < .05; E2, ß = .176, P < .001), and E2 was associated with BMD at FN (ß = .137, P < .05) and TH (ß = .140, P < .05). FSH was associated with major osteoporotic fractures (ß = .288, P < .001) and hip fractures (ß = .235, P < .001). Higher FSH was a risk factor for osteoporosis/osteopenia (odds ratios [OR] = 2.92, 95% CI = 1.66-5.14, P < .001), whereas higher E2 was a protective factor (OR = 0.37, 95% CI = 0.22-0.60, P < .001). Patients in the higher tertile of FSH and lower tertile of E2 had an increased risk of osteoporosis/osteopenia (OR = 5.05, 95% CI = 1.37-18.65, P < .05). CONCLUSIONS: For males with T2DM, FSH and E2 are significantly associated with BMD, osteoporosis/osteopenia, and fracture risk.

SIRT2 deficiency prevents age-related bone loss in rats by inhibiting osteoclastogenesis.

Sirtuin 2 (SIRT2) is a deacetylase that belongs to class III family of histone deacetylases (HDACs). Although it is the most abundantly expressed member of HDAC-III in human bone tissues, it is unclear whether SIRT2 plays a role in bone metabolism. In this study, the role of SIRT2 in bone metabolism, and the underlying mechanism were investigated. In in vivo experiments, micro-CT analysis revealed that there were no differences in bone microstructures between SIRT2-KO and WT rats at 12 weeks of age. However, in 36-week-old rats, increased Tb. BMD, bone volume fraction (BV/TV) and trabecular number (Tb. N) of distal femurs were observed in SIRT2-KO rats, when compared with those of WT rats. Moreover, reduced serum ß-CTX was identified in the 36-week old rats. In in vitro studies, inhibition of SIRT2 with its specific inhibitor, AGK2, suppressed the differentiation of bone marrow-derived mononuclear cells (BMMs) into osteoclasts via reduction of the expressions of c-Fos and NFATc1. These results suggest that SIRT2 plays a role in age-related bone loss, probably by regulating osteoclastogenesis.

Associations of serum sex hormone binding globulin with bone mineral densities and higher 10-year probability of fractures in postmenopausal women with type 2 diabetes mellitus.

BACKGROUND: Postmenopause and type 2 diabetes mellitus (T2DM) are associated with higher fracture risk. Sex hormones are important in maintaining woman skeleton health. The relationships of sex hormone(s) with bone mineral density (BMD) and fracture risk are still unclear in diabetic-postmenopausal women. This study aimed to investigate the relationships of sex hormones with BMDs and fracture risk in postmenopausal women with T2DM. METHODS: Two hundred and fourteen postmenopausal women with T2DM were included. BMDs at lumbar spine (L2-4), femoral neck (FN) and total hip (TH) were measured by dual-energy X-ray absorptiometry (DXA). The 10-year probability of fractures was accessed by modified fracture risk algorithm (FRAX) tool. Serum concentrations of sex hormones were measured. RESULTS: Sex hormone binding globulin (SHBG) was a determinant of BMDs at L2-4 (ß=-0.199, P<0.05), TH (ß=-0.233, P<0.05), major osteoporotic fracture (MOF) (ß=0.253, P<0.001) and hip fracture (HF) (ß=0.262, P<0.001). Per SD increase in SHBG caused a 2% increase in the risk of osteoporosis/osteopenia. SHBG in quartile-4 was associated with 4.21 higher risk of osteoporosis/osteopenia compared with SHBG in quartile-1. CONCLUSIONS: In postmenopausal women with T2DM, higher serum SHBG tended to be associated with lower BMDs, and increased the risk of osteoporosis/osteopenia and the fracture risk.

LGR6 promotes osteogenesis by activating the Wnt/ß-catenin signaling pathway.

Leucine-rich repeat containing G-protein-coupled receptor 6 (LGR6) is a member of the rhodopsin-like 7-transmembrane domain receptor superfamily and has high homology to LGR4 and LGR5. LGR6 is highly expressed in osteoblastic progenitors, and LGR6-deficient mice show nail and bone regeneration defect. However, the effect of LGR6 on the osteogenic differentiation of osteoblastic progenitors and its underlying mechanisms are largely unknown. In this study, we overexpressed and knockdown LGR6 with lentivirus in the preosteoblastic cell MC3T3-E1 to observe the effect of LGR6 on osteogenic differentiation and explore its possible molecular mechanism. LGR6 overexpression promoted osteogenic differentiation and mineralization by stabilizing ß-catenin to potentiate the Wnt/ß-catenin signaling pathway in MC3T3-E1 cells. Conversely, LGR6 knockdown inhibited osteogenic differentiation and mineralization by enhancing ß-catenin degradation to inactivate the Wnt/ß-catenin signaling pathway. These results reveal that LGR6 is highly expressed in osteoblastic progenitors, and promotes osteogenesis by enhancing ß-catenin stability to strengthen the Wnt signaling pathway. This study provides an important reference into the exact mechanisms of osteogenic differentiation.

Rapamycin ameliorates immune-mediated aplastic anemia by inhibiting the proliferation and metabolism of T cells.

Aplastic anemia (AA) is a serious blood system disease that threatens human health. At present, the main cause of this disease is believed to be immune hyperfunction. However, the specific metabolic mode involved in the occurrence of lymphocytes in AA is still unknown. In addition, whether rapamycin, a specific blocker of the mTOR signaling pathway, plays a therapeutic role by inhibiting lymphocyte metabolism remains unclear. We induced an AA mouse model through the classical immune-mediated pathway and simultaneously administered rapamycin intervention therapy. First, the AA-associated phenotypic changes and the efficacy of rapamycin in the treatment of AA were discussed. Second, the proliferation and metabolic pathway of bone marrow (BM) lymphocytes in AA and the effect of rapamycin on this process were determined. Finally, the expression levels of mTOR pathway-related proteins were analyzed. By inhibiting the mTOR signaling pathway, rapamycin could ameliorate the phenotype of the immune-mediated AA model and inhibit the proliferation of T cells by preventing cell cycle transition from G0 to G1 phase. Moreover, we found that mitochondrial oxidative phosphorylation is involved in the metabolic reprogramming of T cells in AA and that rapamycin can inhibit this process. We confirmed that mitochondrial oxidative phosphorylation is involved in the metabolic reprogramming of T cells in AA and further extended the mechanism of rapamycin in treating AA by inhibiting the mTOR signaling pathway. This viewpoint may provide a new therapeutic idea for clinical applications.

Hypercholesterolaemia increases the risk of high­turnover osteoporosis in men.

As the incidence of osteoporosis (OP) and hypercholesterolaemia in men has increased, male OP has drawn more attention from clinicians worldwide. The present study sought to investigate the effects of cholesterol on male bone. Between July 2015 and October 2015, 216 men (aged ≥18 years) were recruited for this cross­sectional study. To test our clinical hypothesis, we designed two male animal models: Exogenous hypercholesterolaemia induced by a high­cholesterol diet (HCD) and endogenous hypercholesterolaemia induced by apolipoprotein E (ApoE) knockout. Finally, the direct effects of cholesterol on osteoblasts were observed in cell experiments. In our clinical studies, men with hypercholesterolaemia displayed a lower bone mineral density (BMD) and increased beta collagen cross­linking (beta­CTX) and type I anterior collagen amino terminal peptide (PINP) levels compared to those of the control subjects. Serum cholesterol levels were a significant independent predictor of BMD, beta­CTX and PINP and were negatively correlated with BMD and positively correlated with beta­CTX and PINP levels. Our animal experimental results validated our clinical results, as they also indicated that hypercholesterolaemia damages bone microstructure and reduces bone strength. Cholesterol directly increased osteoblast functional gene expression in vitro. Hypercholesterolaemia increases the risk of high­turnover osteoporosis in men at least in part by excessively promoting the activity of the remodelling pathway. In addition, hypercholesterolaemia damages the bone microstructure, resulting in osteopenia or OP and reduced bone strength, leading to a higher risk of fracture in men. We emphasize the importance of preventing and treating hypercholesterolaemia as well as monitoring bone metabolic markers and BMD in men with hypercholesterolemia for the effective prevention of bone loss and subsequent fracture. In addition, our findings provide a theoretical basis for the development of treatments for high cholesterol­induced osteoporosis in men.