Canagliflozin promotes osteoblastic MC3T3-E1 differentiation via AMPK/RUNX2 and improves bone microarchitecture in type 2 diabetic mice

Canagliflozin-Induced Adaptive Metabolism in Bone

Sodium-glucose transporter-2 inhibitor (SGLT2i) drugs are widely used for lowering blood glucose levels independent of insulin. Beyond this, these drugs induce various metabolic changes, including weight loss and impaired bone integrity. A significant gap exists in understanding SGLT2i-induced skeletal changes, as SGLT2 is not expressed in osteoblasts or osteocytes, which use glucose to remodel the bone matrix. We studied the impact of 1, 3, or 6 months of canagliflozin (CANA), an SGLT2i treatment, on the skeleton of 6-month-old genetically heterogeneous UM-HET3 mice. Significant metabolic adaptations to CANA were evident as early as 1.5 months after treatment, specifically in male mice. CANA-treated male mice exhibited notable reductions in body weight and decreased proinflammatory and bone remodeling markers associated with reduced cortical bone remodeling indices. Bone tissue metabolome indicated enrichment in metabolites related to amino acid transport and tryptophan catabolism in CANA-treated male mice. In contrast, CANA-treated female mice showed increases in nucleic acid metabolism. An integrOmics approach of source-matched bone tissue metabolome and bone marrow RNA sequencing indicated a positive correlation between the two omics data sets in male mice. Three clusters of transcripts and metabolites involved in energy metabolism, oxidative stress response, and cellular proliferation and differentiation were reduced in CANA-treated male mice. In conclusion, CANA affects bone metabolism mainly via the "glucose restriction state" it induces and impacts bone cell proliferation and differentiation. These findings underline the effects of SGLT2i on bone health and highlight the need to consider sex-specific responses when developing clinical treatments that alter substrate availability.

ARTICLE HIGHLIGHTS

Effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors, dapagliflozin and canagliflozin, on the musculoskeletal system in an experimental model of diabetes induced by high-fat diet and streptozotocin in rats

The effect of SGLT2 inhibitors, a new group of antidiabetic drugs, on the skeletal system is a matter of debate. There are concerns that they may unfavorably affect bones. The aim of the study was to investigate the effects of dapagliflozin and canagliflozin on musculoskeletal system in an experimental rat model of type 2 diabetes induced by a high-fat diet (HFD) and streptozotocin (STZ). The experiments were carried out on mature female rats. To induce diabetes, STZ was administered 2 weeks after the introduction of HFD. Administration of dapagliflozin (1.4 mg/kg p.o.) or canagliflozin (4.2 mg/kg p.o.) started 1 week after the STZ injection, and lasted 4 weeks. Skeletal muscle mass and strength, serum bone turnover marker concentration and other biochemical parameters, and bone mass, density, histomorphometric parameters and mechanical properties were determined. Diabetes induced decreases in skeletal muscle mass and osteoporotic changes, including decreases in bone density, and worsening of the histomorphometric parameters and cancellous bone mechanical properties. The SGLT2 inhibitors decreased glycemia and other diabetes-induced metabolic changes, and counteracted only some unfavorable effects of diabetes on bones. The effects of dapagliflozin and canagliflozin on metabolic parameters were similar, whereas there were some differences in their effects on the skeletal system. The study demonstrated possibility of differential skeletal effects of different SGLT2 inhibitors in diabetic conditions, indicating the need for caution concerning their use in patients at risk of bone fractures.

Investigating the molecular mechanisms of Jiangu Decoction in treating type 2 diabetic osteoporosis

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetic osteoporosis (T2DOP) is a metabolic bone disease characterized by impaired bone structure and decreased bone strength in diabetic patients. Jiangu Decoction (JGD), a traditional Chinese poly-herbal formulation, has shown efficacy in mitigating osteoporosis (OP) and fractures caused by osteoporosis in diabetic patients in clinical trials. In addition, JGD has been proven to promote the proliferation of osteoblasts. However, the specific mechanisms underlying these effects remain unclear.

AIM OF THE STUDY

This study aimed to elucidate the molecular mechanisms underlying the therapeutic effects of JGD in treating T2DOP.

MATERIALS AND METHODS

Liquid chromatography-mass spectrometry (LC-MS) was utilized to elucidate the chemical profile of JGD. A T2DOP mouse model (C57BL/6) was established by combining a high-fat diet with streptozotocin (STZ). Micro-computed tomography (micro-CT) imaging, three-point bending tests, and histological staining were utilized to assess alterations in bone mass, bone quality, and bone strength in mice. Mouse Calvaria 3T3-E1 (MC3T3-E1) cells were treated with 33 mmol/L D-glucose (HG), and the protective effect of JGD on the high glucose injury model was observed. Western blotting and qRT-PCR were employed to analyze alterations in biomarkers associated with the Keap1/Nrf2/HO-1 signaling pathway, both in vivo and in vitro.

RESULTS

A total of 909 compounds were identified in JGD using LC-MS. Subsequently, the function of JGD was evaluated both in vitro and in vivo. The findings indicated that JGD promoted bone formation, enhanced bone microstructure, and ameliorated diabetic symptoms in T2DOP mice. Additionally, JGD increased alkaline phosphatase (ALP) activity, facilitated bone mineralization, and upregulated the expression levels of osteogenic marker genes such as runt-related transcription factor 2 (Runx2), osteocalcin (Ocn), and collagen type 1 alpha (Col1a1). Importantly, JGD reduced oxidative stress levels and decreased the accumulation of reactive oxygen species by modulating the Keap1/Nrf2/HO-1 axis both in vivo and in vitro.

CONCLUSION

Our study suggests that JGD could alleviate T2DOP impairment, closely linked to the Keap1/Nrf2/HO-1 signaling pathway.

PRKD2 as a novel target for targeting the diabetes-osteoporosis nexus

Diabetes mellitus (DM) and osteoporosis (OP) co-morbidity (DMOP) pose major health challenges owing to their complex pathophysiological interactions. The aim of this study was to identify and validate key genes implicated in the pathogenesis of both conditions. By employing the Mfuzz time-series gene clustering method combined with transcriptome sequencing of patient serum, we systematically delineated gene expression patterns during the transition from a healthy state through DM to DMOP. These findings were further validated using external datasets, and a series of functional enrichment analyses, gene set enrichment analyses, and immune cell infiltration studies were conducted. Our analyses revealed a distinct progression pattern from a normal state through DM to DMOP, characterized by dynamic gene expression changes. Notably, PRKD2 emerged as a significantly downregulated gene in DMOP, highlighting its crucial role in disease pathogenesis. Further analyses revealed the involvement of PRKD2 in key signaling pathways, especially the Wnt and IL-18 pathways, which are critical for bone and glucose metabolism. Validation in cellular and animal models confirmed the role of PRKD2 in apoptosis and bone metabolism, emphasizing its therapeutic potential. In conclusion, our findings establish PRKD2 as a pivotal molecule in DMOP, offering fresh insights into its mechanisms and affirming its value as a therapeutic target.

In Vitro Engineered ECM-incorporated Hydrogels for Osteochondral Tissue Repair: A Cell-Free Approach

Prevalence of osteoarthritis has been increasing in aging populations, which has necessitated the use of advanced biomedical treatments. These involve grafts or delivering drug molecules entrapped in scaffolds. However, such treatments often show suboptimal therapeutic effects due to poor half-life and off-target effects of drug molecules. As a countermeasure, a 3D printable robust hydrogel-based tissue-repair platform is developed containing decellularized extracellular matrix (dECM) from differentiated mammalian cells as the therapeutic cargo. Here, pre-osteoblastic and pre-chondrogenic murine cells are differentiated in vitro, decellularized, and incorporated into methacrylated gelatin (GelMA) solutions to form osteogenic (GelO) and chondrogenic (GelC) hydrogels, respectively. Integrating the bioactive dECM from differentiated cell sources allows GelO and GelC to induce differentiation in human adipose-derived stem cells (hASCs) toward osteogenic and chondrogenic lineages. Further, GelO and GelC can be covalently adhered using a carbodiimide coupling reaction, forming a multi-layered hydrogel with potential application as a bioactive osteochondral plug. The designed multi-layered hydrogel can also induce differentiation of hASCs in vitro. In conclusion, the bioactive dECM carrying 3D printed robust hydrogel offers a promising new drug and cell-free therapeutic strategy for bone and cartilage repair and future osteoarthritis management.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Unveiling the Role of Sik1 in Osteoblast Differentiation: Implications for Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative disease characterized by subchondral osteosclerosis, mainly due to osteoblast activity. This research investigates the function of Sik1, a member of the AMP-activated protein kinase family, in OA. Proteomic analysis was conducted on clinical samples from 30 OA patients, revealing a negative correlation between Sik1 expression and OA. In vitro experiments utilized BMSCs to examine the effect of Sik1 on osteogenic differentiation. BMSCs were cultured and induced toward osteogenesis with specific media. Sik1 overexpression was achieved through lentiviral transfection, followed by analysis of osteogenesis-associated proteins using Western blotting, RT-qPCR, and alkaline phosphate staining. In vivo experiments involved destabilizing the medial meniscus in mice to establish an OA model, assessing the therapeutic potential of Sik1. The CT scans and histological staining were used to analyze subchondral bone alterations and cartilage damage. The findings show that Sik1 downregulation correlates with advanced OA and heightened osteogenic differentiation in BMSCs. Sik1 overexpression inhibits osteogenesis-related markers in vitro and reduces cartilage damage and subchondral osteosclerosis in vivo. Mechanistically, Sik1 modulates osteogenesis and subchondral bone changes through Runx2 activity regulation. The research emphasizes Sik1 as a promising target for treating OA, suggesting its involvement in controlling bone formation and changes in the subchondral osteosclerosis.

Recent advances in understanding the mechanisms in skeletal muscle of interaction between exercise and frontline antihyperglycemic drugs

Regular exercise and antihyperglycemic drugs are front-line treatments for type-2 diabetes and related metabolic disorders. Leading drugs are metformin, sodium-glucose cotransporter-2 inhibitors, and glucagon-like peptide 1 receptor agonists. Each class has strong individual efficacy to treat hyperglycemia, yet the combination with exercise can yield varied results, some of which include blunting of expected metabolic benefits. Skeletal muscle insulin resistance contributes to the development of type-2 diabetes while improvements in skeletal muscle insulin signaling are among key adaptations to exercise training. The current review identifies recent advances into the mechanisms, with an emphasis on skeletal muscle, of the interaction between exercise and these common antihyperglycemic drugs. The review is written toward researchers and thus highlights specific gaps in knowledge and considerations for future study directions.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.

Cardiovascular Calcification Heterogeneity in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) exhibit tremendously elevated risk for cardiovascular disease, particularly ischemic heart disease, due to premature vascular and cardiac aging and accelerated ectopic calcification. The presence of cardiovascular calcification associates with increased risk in patients with CKD. Disturbed mineral homeostasis and diverse comorbidities in these patients drive increased systemic cardiovascular calcification in different manifestations with diverse clinical consequences, like plaque instability, vessel stiffening, and aortic stenosis. This review outlines the heterogeneity in calcification patterning, including mineral type and location and potential implications on clinical outcomes. The advent of therapeutics currently in clinical trials may reduce CKD-associated morbidity. Development of therapeutics for cardiovascular calcification begins with the premise that less mineral is better. While restoring diseased tissues to a noncalcified homeostasis remains the ultimate goal, in some cases, calcific mineral may play a protective role, such as in atherosclerotic plaques. Therefore, developing treatments for ectopic calcification may require a nuanced approach that considers individual patient risk factors. Here, we discuss the most common cardiac and vascular calcification pathologies observed in CKD, how mineral in these tissues affects function, and the potential outcomes and considerations for therapeutic strategies that seek to disrupt the nucleation and growth of mineral. Finally, we discuss future patient-specific considerations for treating cardiac and vascular calcification in patients with CKD-a population in need of anticalcification therapies.