Effect of a bisphosphonate and selective estrogen receptor modulator on bone remodeling in streptozotocin-induced diabetes and ovariectomized rat model

Alpha-lipoic Acid Prevents Bone Loss in Type 2 Diabetes and Postmenopausal Osteoporosis Coexisting Conditions by Modulating the YAP/Glut4 Pathway

This study aims to characterize the bone-protecting effects of Alpha-lipoic acid (ALA), a potent antioxidant, against the detrimental effects of the coexistence of type 2 diabetes mellitus (T2DM) and postmenopausal osteoporosis (POP) and identify the possible mechanisms with particular reference to its modulation of YAP/Glut4 pathway. The T2DM and POP coexisting model was induced in mice by high fat diet (HFD) + Streptozocin (STZ) + ovariectomy (OVX). The mice in the treatment groups were given ALA for 10 weeks. In the in vitro study, MC3T3-E1 cells were induced with 500 μM methylglyoxal for 24 h with or without pretreatment with ALA for 24 h. The oxidative and antioxidative biomarkers, bone microarchitecture, histo-morphology, and related protein expression of apoptosis, osteogenic differentiation and the YAP/Glut4 pathway were detected. The results showed ALA could improve glucose tolerance, inhibit oxidative stress and apoptosis and alleviate bone loss. Further study by siRNA technology revealed that the YAP/Glut4 pathway was implicated in the pathogenesis of bone loss due to the coexistence of T2DM and POP. Taken together, the present study has demonstrated for the first time that ALA exerts potent protective effects against bone loss in T2DM and POP coexisting conditions by modulating the YAP/Glut4 pathway.

Estrogen Facilitates the Healing of Diabetic Wounds via Ameliorating the Function of Bone Marrow Mesenchymal Stem Cells

We inted to elucidate the impacts of estrogen on the bone marrow-originated endothelial progenitor cells (BM-EPC) and mesenchymal stem cells (BM-MSC) as well as on diabetic wound healing. The skin injury models were established using the diabetic mice (db+/db+) and non-diabetic vector mice and then treated with estrogen-based or placebo-based cream. On the 5th day following injury, BM cells were collected for quantification of EPCs and MSCs and colony-forming units along with analysis of wound healing rate and densities of blood vessels and scars following whole-body perfusion. EPCs were identified through staining of VEGFR1 and CD34 by immunohistochemistrical analyses. In contrast to placebo, treatment with estrogen significantly intensified the colony formation of EPC and MSC, and further promoted the viability and proliferation potential of cells. Meanwhile, estrogen-treated mice exhibited increased recruitment of EPC to the diabetic wounds along with increased vascular density. Additionally, on day 6 after injury, estrogen significantly accelerated wound healing, which was mediated by the enhanced collagen deposition through boosting MSC activation and differentiation, resulting in elevated scar density. In conclusion, estrogen prompts wound healing of diabetic mice via ameliorating the function of BM-derived EPC and MSC, so as to accelerate the neovascularization at the sites of wounds in diabetic mice.

Challenges to Improve Bone Healing Under Diabetic Conditions

Diabetes mellitus (DM) can affect bone metabolism and the bone microenvironment, resulting in impaired bone healing. The mechanisms include oxidative stress, inflammation, the production of advanced glycation end products (AGEs), etc. Improving bone healing in diabetic patients has important clinical significance in promoting fracture healing and improving bone integration. In this paper, we reviewed the methods of improving bone healing under diabetic conditions, including drug therapy, biochemical cues, hyperbaric oxygen, ultrasound, laser and pulsed electromagnetic fields, although most studies are in preclinical stages. Meanwhile, we also pointed out some shortcomings and challenges, hoping to provide a potential therapeutic strategy for accelerating bone healing in patients with diabetes.

The Impact of Antiosteoporotic Drugs on Glucose Metabolism and Fracture Risk in Diabetes: Good or Bad News?

Osteoporosis and diabetes mellitus represent global health problems due to their high, and increasing with aging, prevalence in the general population. Osteoporosis can be successfully treated with both antiresorptive and anabolic drugs. While these drugs are clearly effective in reducing the risk of fracture in patients with postmenopausal and male osteoporosis, it is still unclear whether they may have the same efficacy in patients with diabetic osteopathy. Furthermore, as bone-derived cytokines (osteokines) are able to influence glucose metabolism, it is conceivable that antiosteoporotic drugs may have an effect on glycemic control through their modulation of bone turnover that affects the osteokines’ release. These aspects are addressed in this narrative review by means of an unrestricted computerized literature search in the PubMed database. Our findings indicate a balance between good and bad news. Active bone therapies and their modulation of bone turnover do not appear to play a clinically significant role in glucose metabolism in humans. Moreover, there are insufficient data to clarify whether there are any differences in the efficacy of antiosteoporotic drugs on fracture incidence between diabetic and nondiabetic patients with osteoporosis. Although more studies are required for stronger recommendations to be issued, bisphosphonates appear to be the first-line drug for treatment of osteoporosis in diabetic patients, while denosumab seems preferable for older patients, particularly for those with impaired renal function, and osteoanabolic agents should be reserved for patients with more severe forms of osteoporosis.

The Efficacy of Alendronate Versus Denosumab on Major Osteoporotic Fracture Risk in Elderly Patients With Diabetes Mellitus: A Danish Retrospective Cohort Study

OBJECTIVE

Patients with diabetes mellitus have an increased risk of fractures; however, the underlying mechanism is largely unknown. We aimed to investigate whether the risk of major osteoporotic fractures in diabetes patients differs between subjects initiated with alendronate and denosumab, respectively.

METHODS AND RESEARCH DESIGN

We conducted a retrospective nationwide cohort study through access to all discharge diagnoses (ICD-10 system) from the National Danish Patient Registry along with all redeemed drug prescriptions (ATC classification system) from the Health Service Prescription Registry. We identified all subjects with a diabetes diagnosis between 2000 and 2018 and collected data on the first new prescription of anti-osteoporotic treatment between 2011 and 2018. Exposure was defined as either alendronate or denosumab treatment initiated after diabetes diagnosis. Outcome information was collected by identification of all major osteoporotic fracture (MOF) diagnoses, i.e., hip, spine, forearm, and humerus, from exposure until 2018 or censoring by emigration or death. The risk of fracture was calculated as hazard ratios (HR) using multiply adjusted Cox proportional models with death as a competing risk.

RESULTS

We included 8,745 subjects initiated with either alendronate (n = 8,255) or denosumab (n = 490). The cohort consisted of subjects with a mean age of 73.62 (SD ± 9.27) years, primarily females (69%) and suffering mainly from type 2 diabetes (98.22%) with a median diabetes duration at baseline of 5.45 years (IQR 2.41-9.19). Those in the denosumab group were older (mean 75.60 [SD ± 9.72] versus 73.51 [SD ± 9.23] years), had a higher proportion of women (81% versus 68%, RR 1.18 [95% CI 1.13-1.24], and were more comorbid (mean CCI 2.68 [95% CI 2.47-2.88] versus 1.98 [95% CI 1.93-2.02]) compared to alendronate initiators. In addition, denosumab users had a higher prevalence of previous fractures (64% versus 46%, RR 1.38 [95% CI 1.28-1.48]). The adjusted HR for any MOF after treatment initiation with denosumab was 0.89 (95% CI 0.78-1.02) compared to initiation with alendronate.

CONCLUSION

The risk of incident MOF among subjects with diabetes was similar between those initially treated with alendronate and denosumab. These findings indicate that the two treatment strategies are equally effective in preventing osteoporotic fractures in subjects with diabetes.

Therapeutic effect of the injectable thermosensitive hydrogel loaded with SHP099 on intervertebral disc degeneration

AIMS

Intervertebral disc (IVD) degeneration (IDD), a common musculoskeletal disease with limited self-healing ability, is challenging to treat. The development of innovative therapies to reverse IDD depends on the elucidation of its regulatory mechanisms. Therefore, the role of Src homology region 2-containing protein tyrosine phosphatase 2 (SHP2) in the pathogenesis of IDD and the therapeutic effect of its small-molecule inhibitor, SHP099, were investigated.

MATERIALS AND METHODS

The expression of SHP2 by nucleus pulposus (NP) cells in IVD was investigated in vitro and in vivo, and its molecular mechanism in IDD was explored using transfection technology. Injectable N-isopropylacrylamide-based thermosensitive hydrogels were synthesized for SHP099 delivery.

KEY FINDINGS

SHP2 was highly expressed in degenerated IVDs, where its overexpression in NP cells inhibited the expression of Sry-related HMG box-9 (Sox9), leading to the decreased expression of key proteins (collagen II and aggrecan) and consequently to IDD. SHP099 reversed the degeneration of NP cells in vitro. Moreover, its administration in rats via the injectable thermosensitive hydrogel had a therapeutic effect on IDD.

SIGNIFICANCE

Our results suggest that SHP2 is a key factor in IDD progression, and SHP099 inhibits both its expression and NP cell degeneration. Therefore, SHP099 delivery via injectable thermosensitive hydrogels is a potential treatment strategy for IDD.

Negligible Effect of Estrogen Deficiency on Development of Skeletal Changes Induced by Type 1 Diabetes in Experimental Rat Models

Although postmenopausal osteoporosis often occurs concurrently with diabetes, little is known about interactions between estrogen deficiency and hyperglycemia in the skeletal system. In the present study, the effects of estrogen deficiency on the development of biochemical, microstructural, and mechanical changes induced by streptozotocin-induced diabetes mellitus (DM) in the rat skeletal system were investigated. The experiments were carried out on nonovariectomized (NOVX) and ovariectomized (OVX) control and diabetic mature female Wistar rats. Serum levels of bone turnover markers (CTX-I and osteocalcin) and 23 cytokines, bone mass and mineralization, histomorphometric parameters, and mechanical properties of cancellous and compact bone were determined. The results were subjected to two-way ANOVA and principal component analysis (PCA). Estrogen deficiency induced osteoporotic changes, with increased bone resorption and formation, and worsening of microstructure (femoral metaphyseal BV/TV decreased by 13.0%) and mechanical properties of cancellous bone (the maximum load in the proximal tibial metaphysis decreased by 34.2%). DM in both the NOVX and OVX rats decreased bone mass, increased bone resorption and decreased bone formation, and worsened cancellous bone microarchitecture (for example, the femoral metaphyseal BV/TV decreased by 17.3% and 18.1%, respectively, in relation to the NOVX controls) and strength (the maximum load in the proximal tibial metaphysis decreased by 35.4% and 48.1%, respectively, in relation to the NOVX controls). Only in the diabetic rats, profound increases in some cytokine levels were noted. In conclusion, the changes induced by DM in female rats were only slightly intensified by estrogen deficiency. Despite similar effects on bone microstructure and strength, the influence of DM on the skeletal system was based on more profound systemic homeostasis changes than those induced by estrogen deficiency.

[Zoledronate regulates osteoclast differentiation and bone resorption in high glucose through p38 MAPK pathway]

OBJECTIVE

To investigate the effect of zoledronate (ZOL) on osteoclast differentiation and bone resorption under high glucose, and the regulation mechanism of p38 mitogen activated kinase (p38 MAPK) signaling pathway in this process.

METHODS

RAW264.7 cells were divided into four groups: low group, high group, low+ZOL group and high+ZOL group after induced into osteoclasts. Cell proliferation activity was determined by MTT assay. The migration of RAW264.7 cells were examined Optical microscopy. Immunofluorescence microscopy was used to observe the cytoskeleton and sealing zones of osteoclasts. After adding group 5: high + ZOL + SB203580 group, trap staining was used to identify the number of positive osteoclasts in each group. The number and area of resorption lacunae were observed by SEM. The mRNA and protein expression of osteoclast related factors were detected by real-time PCR and Western blotting.

RESULTS

The cells in the 5 groups showed similar proliferative activity. High glucose promoted the migration of RAW264.7 cells (P < 0.05), inhibited the clarity of cytoskeleton and the formation of sealing zones in the osteoclasts. Exposure to high glucose significantly lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP, and inhibited osteoclast differentiation and bone absorption (P < 0.05). Treatment with ZOL obviously suppressed the migration ability of RAW264.7 cells, further reduced the clarity of the cytoskeleton, inhibited the formation of sealing zones of the osteoclasts, lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK, and TRAP (P < 0.05), and inhibited osteoclast differentiation and bone absorption. Treatment with SB203580 obviously inhibited osteoclast differentiation and bone resorption and the expressions of P38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP (P < 0.05).

CONCLUSIONS

High glucose inhibits osteoclast differentiation and bone resorption. ZOL inhibits osteoclast differentiation and bone resorption in high-glucose conditions by regulating p38 MAPK pathway, which can be a new pathway for ZOL to regulate diabetic osteoporosis.

Combination of Red Clover and Hops Extract Improved Menopause Symptoms in an Ovariectomized Rat Model

Red clover and hops are already known for their alternative menopausal therapies; however, their combination has not yet been studied. This study aimed to evaluate the efficacy of the combination of red clover and hops extract (RHEC) for treating menopausal symptoms for the first time. A high-performance liquid chromatography (HPLC) method for RHEC was developed and validated for the analysis of biochanin A in red clover extract and xanthohumol in hops extract. An in vivo study was conducted using an ovariectomized rat model treated with RHEC (125, 250, and 500 mg/kg, p.o.) for a 12-week test period. Changes in body weight, tail skin temperature (TST), serum lipid profile, bone metabolism, antioxidants, and markers of vasorelaxation and uterus endometrium were evaluated. RHEC significantly inhibited body weight gain and decreased fat weight. Changes in TST associated with flashes were significantly inhibited in the RHEC groups. Other markers related to menopausal symptoms, such as blood lipid profile (total cholesterol and low-density-lipoprotein cholesterol), bone metabolism (serum alkaline phosphatase, osteocalcin, and c-terminal telopeptide type 1), antioxidants (superoxide dismutase and malondialdehyde), and vasorelaxants (endothelin-1 and nitric oxide), were significantly improved after the administration of RHEC. We also confirmed the safety of RHEC through histopathological observation of the endometrium. Our findings demonstrate that RHEC appears to have high potential for comprehensively improving various symptoms of menopause.

Raloxifene retards cartilage degradation and improves subchondral bone micro-architecture in ovariectomized rats with patella baja-induced - patellofemoral joint osteoarthritis

OBJECTIVE

Abnormal remodeling of subchondral bone (SB) induced by estrogen deficiency has been shown to be involved in osteoarthritis (OA). Raloxifene (RAL) is commonly used to treat postmenopausal osteoporosis (OP). However, little is known about its effects on OA combined with estrogen deficiency. This study was performed to evaluate the efficacy of RAL on patella baja-induced patellofemoral joint OA (PFJOA) in an ovariectomized rat model.

DESIGN

Patellar ligament shortening (PLS) and ovariectomy (OVX) were performed simultaneously in 3-month-old female Sprague-Dawley rats, which were treated with RAL (10 mg/kg/day) or vehicle at 72 h postoperatively for 10 weeks. PFJOA was assessed by immunohistochemistry (IHC), real-time polymerase chain reaction (PCR), tartrate-resistant acid phosphatase (TRAP) staining, enzyme-linked immunosorbent assay (ELISA), micro-computed tomography (μCT), histomorphology and behavioral analyses.

RESULTS

X-ray examinations showed that patella baja was successfully established by PLS. Histomorphological analysis revealed that PFJOA was significantly exacerbated by OVX and markedly alleviated by RAL. Moreover, RAL improved cartilage metabolism by decreasing MMP-13, ADAMTS-4, and caspase-3 and increasing Col-II and aggrecan at both the protein and mRNA levels. Furthermore, RAL markedly improved bone mass and SB microarchitecture and reduced osteoclast numbers and the serum osteocalcin and CTX-I levels. Although RAL showed a trend toward reducing pain sensitivity based on mechanical allodynia testing, this result was not statistically significant.

CONCLUSION

These findings demonstrate that RAL treatment retards PFJOA progression in an ovariectomized rat model, suggesting that it may be a potential candidate for amelioration of the progression of PFJOA accompanied by postmenopausal OP.