Osteogenic actions of the anti-diabetic drug metformin on osteoblasts in culture

Skeletal Effects of a Prolonged Oral Metformin Treatment in Adult Wistar Rats

INTRODUCTION

We previously showed that a 3-week oral metformin (MET) treatment enhances the osteogenic potential of bone marrow stromal cells (BMSCs) and improves several bone histomorphometric parameters in Wistar rats with metabolic syndrome (MetS). However, the skeletal effects of extended periods of MET need to be completely elucidated. Hence, in this study, the impact of a prolonged (3-month) MET treatment was investigated on bone architecture, histomorphometric and biomechanics variables, and osteogenic potential of BMSCs in Wistar rats with or without MetS.

MATERIALS AND METHODS

Young male Wistar rats (n=36) were randomized into four groups (n=9) that received either 20% fructose (F), MET (MET), F plus MET treatments (FMET), or drinking water alone (Veh). Rats were euthanized, blood was collected, and bones were dissected and processed for peripheral quantitative computed tomography (pQCT) analysis, static and dynamic histomorphometry, and bone biomechanics. In addition, BMSCs were isolated to determine their osteogenic potential.

RESULTS

MET affected trabecular and cortical bone, altering bone architecture and biomechanics. Furthermore, MET increased the pro-resorptive profile of BMSCs. In addition, fructose-induced MetS practically did not affect the the structural or mechanical variables of the skeleton.

CONCLUSION

A 3-month treatment with MET (with or without MetS) affects bone architecture and biomechanical variables in Wistar rats.

Metformin treatment prevents experimental metabolic syndrome-induced femoral bone marrow adiposity in rats

OBJECTIVE.

Motivation for the study. Most research supports a negative association between metabolic syndrome and bone health, although there is an overall lack of consensus. Therefore, there is a need for research in this area to develop a better understanding. Main findings. Metabolic syndrome induced by a fructose-rich diet increases the adipogenic predisposition of bone marrow progenitor cells and femoral medullary adiposity in rats. Furthermore, this can be partially prevented by co-treatment with metformin. Implications. Experimental metabolic syndrome has negative effects on bone tissue and can be prevented by oral treatment with metformin as a normoglycemic drug. To determine the effect of metformin (MET) treatment on adipogenic predisposition of bone marrow progenitor cells (BMPC), bone marrow adiposity and bone biomechanical properties.

MATERIALS AND METHODS.

20 young adult male Wistar rats were sorted into four groups. Each of the groups received the following in drinking water: 100% water (C); 20% fructose (F); metformin 100 mg/kg wt/day (M); or fructose plus metformin (FM). After five weeks the animals were sacrificed. Both humeri were dissected to obtain BMPC, and both femurs were dissected to evaluate medullary adiposity (histomorphometry) and biomechanical properties (3-point bending). BMPC were cultured in vitro in adipogenic medium to evaluate RUNX2, PPAR-γ and RAGE expression by RT-PCR, lipase activity and triglyceride accumulation.

RESULTS.

The fructose-rich diet (group F) caused an increase in both triglycerides in vitro, and medullary adiposity in vivo; being partially or totally prevented by co-treatment with metformin (group FM). No differences were found in femoral biomechanical tests in vivo, nor in lipase activity and RUNX2/PPAR-γ ratio in vitro. DRF increased RAGE expression in BMPC, being prevented by co-treatment with MET.

CONCLUSIONS.

Metabolic syndrome induced by a fructose-rich diet increases femoral medullary adiposity and, in part, the adipogenic predisposition of BMPC. In turn, this can be totally or partially prevented by oral co-treatment with MET.

An epidemiological qualitative/quantitative SWOT-AHP analysis in order to highlight the positive or critical aspects of dental implants: A pilot study

OBJECTIVES

In recent years, dental implants are increasing in popularity due to their high success rate, demonstrated functionality, and aesthetic treatment results. Scientific research is very active in proposing improvements in the quality and survival of implants, taking into consideration various aspects. The objective of this study was to provide a holistic epidemiologic view of the state of dental implants, using a systematic approach based on a multimethod SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis and AHP (analytical hierarchical process) qualitative-quantitative analysis to identify the characteristics that can determine their success or failure.

MATERIALS AND METHODS

The study used the hybrid method of SWOT-AHP.

RESULTS

Analysis of the results showed that among strengths, the skill of the dentist was considered the most important factor, followed by the success of dental implants in the old people; among weaknesses, bruxism and chronic diseases were highlighted; for opportunities, biomechanical behavior, in terms of good mechanical strength and good tribological resistance to chemical and physical agents in the oral cavity, were considered the most important factors; finally, among threats, medical liability and biomechanical problems had equal weight.

CONCLUSIONS

This study applied a multimethod SWOT-AHP approach to bring out favorable or critical evidence on the topic of dental implants. In accordance with the result of the strategic vector identified in the Twisting zone Adjustment type section, showed that implant surgery is a widespread technique but always needs improvement to increase the likelihood of success and reduce the complications that can lead to implant failure.

Applications of Metformin in Dentistry-A review

Metformin is a versatile drug with numerous medical uses. It is known primarily as an anti-hyperglycemic drug that has become the main oral blood-glucose-lowering medication for managing type 2 diabetes mellitus globally. Its use has been reported in a variety of oral conditions and dentistry in general. Recent clinical trials have indicated the effectiveness of adjunct topical application of metformin in improving the periodontal parameters of patients with diabetes and periodontitis. Additionally, studies have suggested that metformin stimulates odontogenic differentiation and mineral synthesis of stem cells in the tooth pulp. Metformin also stimulates osteoblast proliferation, decreases osteoclast activity and exerts regenerative effects on periodontal bone, thus making it a viable candidate for periodontal regeneration. Metformin monotherapy significantly enhances osseointegration of endosseous implants and has been reported to have anti-cancer effects on oral squamous cell carcinoma by impeding tumor progression. Animal studies have indicated that metformin improves orthodontic tooth movement and resists orthodontic appliance corrosion. This narrative review aims to provide a current summary of research highlighting the prospective uses of metformin in dentistry.

Combination of metformin and double antibiotic paste for the regeneration of non-vital immature teeth: a preliminary randomized clinical study

BACKGROUND

The present study aimed to investigate whether incorporating metformin in double antibiotic paste (DAP) can promote the regeneration process of non-vital immature teeth.

METHODS

Out of 32 pediatric patients undergoing regenerative endodontic procedures (REPs), 6 cases with a follow-up period of less than 12 months or lack of documentation were excluded then the remaining 26 were analyzed. 15 cases received DAP, and 11 cases received a DAP + metformin as the intra-canal medicament, kept for an average of 23 days. During 18 months of follow-up, clinical and radiographic examinations were performed to evaluate the treatment outcomes based on the resolution of apical periodontitis, root development, and the occurrence of intracanal calcification. The chi-square test was used for the statistical analysis (P < 0.05).

RESULTS

All patients demonstrated resolution of apical periodontitis; however, complete apical closure was only seen in 50% of the patients. The rate of apical closure and root length was significantly higher in the DAP + metformin group (P = 0.047), although the two groups were not significantly different in terms of root width (P = 0.184). Canal obliteration was seen in 15% of cases, all of which were in the DAP group.

CONCLUSIONS

According to the present findings, metformin could promote root development in the regeneration process when incorporated in DAP.

TRIAL REGISTRATION

This clinical trial was registered on the Iranian Registry of Clinical Trials (IRCT20200120046197N1) on 26.2.2021.

Clinical efficacy of 1% metformin gel around conventionally placed dental implants: A 9-month follow-up study

Aim

The study aimed to compare the clinical and radiographic outcomes of bone volume, density, and crestal bone levels in conventionally placed dental implants with and without local application of 1% metformin (MF) gel using cone-beam computed tomography (CBCT) at 9 months.

Materials and Methods

Twenty implants were placed in 18 individuals, randomly divided into 2 groups where Group A received a local application of 1% MF gel along with implant placement. In contrast, Group B received implant placement alone. After thorough clinical examination and preoperative CBCTs, implants were placed under aseptic conditions. Patients were recalled at 3 and 9 months after surgery. Implants were functionally loaded by the end of 3rd month. Soft-tissue parameters such as modified plaque index and modified sulcular bleeding index were recorded along with CBCT evaluation to assess the crestal bone loss, bone density measurement, and bone volume, postoperatively. Fisher's extract test, independent and paired t-test, and Bonferroni analysis were used to determine statistical significance with P ≤ 0.05.

Results

There was no discernible difference between the groups regarding soft-tissue parameters, bone density, and crestal bone levels. However, comparing bone volume between the test and control groups at 9 months was statistically significant. The test group with 1% MF gel showed increased bone volume around the implant.

Conclusion

The data obtained were strong enough to suggest that 1% MF gel administered locally can increase peri-implant bone volume, possibly due to its additional property favoring osteoblastic stimulation and proliferation.

Injectable periodontal ligament stem cell-metformin-calcium phosphate scaffold for bone regeneration and vascularization in rats

OBJECTIVES

Injectable and self-setting calcium phosphate cement scaffold (CPC) capable of encapsulating and delivering stem cells and bioactive agents would be highly beneficial for dental and craniofacial repairs. The objectives of this study were to: (1) develop a novel injectable CPC scaffold encapsulating human periodontal ligament stem cells (hPDLSCs) and metformin (Met) for bone engineering; (2) test bone regeneration efficacy in vitro and in vivo.

METHODS

hPDLSCs were encapsulated in degradable alginate fibers, which were then mixed into CPC paste. Five groups were tested: (1) CPC control; (2) CPC + hPDLSC-fibers + 0% Met (CPC + hPDLSCs + 0%Met); (3) CPC + hPDLSC-fibers + 0.1% Met (CPC + hPDLSCs + 0.1%Met); (4) CPC + hPDLSC-fibers + 0.2% Met (CPC + hPDLSCs + 0.2%Met); (5) CPC + hPDLSC-fibers + 0.4% Met (CPC + hPDLSCs + 0.4%Met). The injectability, mechanical properties, metformin release, and hPDLSC osteogenic differentiation and bone mineral were determined in vitro. A rat cranial defect model was used to evaluate new bone formation.

RESULTS

The novel construct had good injectability and physical properties. Alginate fibers degraded in 7 days and released hPDLSCs, with 5-fold increase of proliferation (p＜0.05). The ALP activity and mineral synthesis of hPDLSCs were increased by Met delivery (p＜0.05). Among all groups, CPC+hPDLSCs+ 0.1%Met showed the greatest cell mineralization and osteogenesis, which were 1.5-10 folds those without Met (p＜0.05). Compared to CPC control, CPC+hPDLSCs+ 0.1%Met enhanced bone regeneration in rats by 9 folds, and increased vascularization by 3 folds (p＜0.05).

CONCLUSIONS

The novel injectable construct with hPDLSC and Met encapsulation demonstrated excellent efficacy for bone regeneration and vascularization in vivo in an animal model. CPC+hPDLSCs+ 0.1%Met is highly promising for dental and craniofacial applications.

Effects of metformin on human gingival fibroblasts: an in vitro study

OBJECTIVE

To investigate the effects of metformin (MF) treatment on the matrix metalloproteinases (MMPs) and proinflammatory cytokines production from lipopolysaccharide (LPS) - stimulated human gingival fibroblasts (HGFs).

METHODS

HGFs were obtained from subcultures of biopsies from clinically healthy gingival tissues of patients undergoing oral surgeries. Cell cytotoxicity assay was used to determine the effect of different concentrations of MF on viability of HGFs. HGFs were then incubated and treated with different concentrations of MF and Porphyromonas gingivais (Pg) LPS. MMP-1, MMP-2, MMP-8, MMP-9, IL-1β, and IL-8 expression analysis was performed using xMAP technology (Luminex 200, Luminex, Austin, TX, USA). Student's t-test for a single sample was used to compare the mean values of the study groups with the control value. A p-value of <0.05 and 95% confidence intervals were used to report the statistical significance and precision of mean values.

RESULTS

Concentrations of 0.5, 1- and 2-mM MF had a minimal non-significant cytotoxic effect on the HGFs and caused statistically significant reduction of MMP-1, MMP-2, MMP-8 and IL-8 expressed by the LPS-stimulated HGFs.

CONCLUSION

The results of the present study confirm that MF suppresses MMP-1, MMP-2, MMP-8 and IL-8 in LPS-stimulated HGFs suggesting an anti-inflammatory effect of MF and potential adjunct therapeutic role in the treatment of periodontal diseases.

Comparison of the Effects of Metformin and Thiazolidinediones on Bone Metabolism: A Systematic Review and Meta-Analysis

OBJECTIVES

Studies have shown that people with diabetes have a high risk of osteoporosis and fractures. The effect of diabetic medications on bone disease cannot be ignored. This meta-analysis aimed to compare the effects of two types of glucose-lowering drugs, metformin and thiazolidinediones (TZD), on bone mineral density and bone metabolism in patients with diabetes mellitus.

METHODS

This systematic review and meta-analysis were prospectively registered on PROSPERO, and the registration number is CRD42022320884. Embase, PubMed, and Cochrane Library databases were searched to identify clinical trials comparing the effects of metformin and thiazolidinediones on bone metabolism in patients with diabetes. The literature was screened by inclusion and exclusion criteria. Two assessors independently assessed the quality of the identified studies and extracted relevant data.

RESULTS

Seven studies involving 1656 patients were finally included. Our results showed that the metformin group had a 2.77% (SMD = 2.77, 95%CI [2.11, 3.43]; p < 0.00001) higher bone mineral density (BMD) than the thiazolidinedione group until 52 weeks; however, between 52 and 76 weeks, the metformin group had a 0.83% (SMD = -0.83, 95%CI: [-3.56, -0.45]; p = 0.01) lower BMD. The C-terminal telopeptide of type I collagen (CTX) and procollagen type I N-terminal propeptide (PINP) were decreased by 18.46% (MD = -18.46, 95%CI: [-27.98, -8.94], p = 0.0001) and 9.94% (MD = -9.94, 95%CI: [-16.92, -2.96], p = 0.005) in the metformin group compared with the TZD group.

Pleiotropic Effects of Metformin in Osteoarthritis

The involvement of the knee joint is the most common localization of the pathological process in osteoarthritis (OA), which is associated with obesity in over 50% of the patients and is mediated by mechanical, inflammatory, and metabolic mechanisms. Obesity and the associated conditions (hyperglycemia, dyslipidemia, and hypertension) have been found to be risk factors for the development of knee OA, which has led to the emerging concept of the existence of a distinct phenotype, i.e., metabolic knee OA. Combined assessment of markers derived from dysfunctional adipose tissue, markers of bone and cartilage metabolism, as well as high-sensitivity inflammatory markers and imaging, might reveal prognostic signs for metabolic knee OA. Interestingly, it has been suggested that drugs used for the treatment of other components of the metabolic syndrome may also affect the clinical course and retard the progression of metabolic-associated knee OA. In this regard, significant amounts of new data are accumulating about the role of metformin-a drug, commonly used in clinical practice with suggested multiple pleiotropic effects. The aim of the current review is to analyze the current views about the potential pleiotropic effects of metformin in OA. Upon the analysis of the different effects of metformin, major mechanisms that might be involved in OA are the influence of inflammation, oxidative stress, autophagy, adipokine levels, and microbiome modulation. There is an increasing amount of evidence from in vitro studies, animal models, and clinical trials that metformin can slow OA progression by modulating inflammatory and metabolic factors that are summarized in the current up-to-date review. Considering the contemporary concept about the existence of metabolic type knee OA, in which the accompanying obesity and systemic low-grade inflammation are suggested to influence disease course, metformin could be considered as a useful and safe component of the personalized therapeutic approach in knee OA patients with accompanying type II diabetes or obesity.

Impact of Metformin on Periodontal and Peri-Implant Soft and Hard Tissue

Periodontal and peri-implant soft and hard tissue in diabetic patients have always been a topic of interest for researchers and clinicians alike. Among which, a subtopic that has attracted more attention is the beneficial effect of metformin (MF) on periodontal and peri-implant soft and hard tissue. This review aimed to assess the impact of MF on the periodontal and peri-implant soft- and hard-tissue healing among diabetic patients. Research was conducted using the keywords 'metformin', 'diabetes', 'periodontitis', 'implant', and 'peri-implantitis' via the Medline (PubMed) and Google Scholar databases. Selected articles were reviewed. A total of 21 articles, discussing the impact on periodontal health (six animal studies, seven clinical studies, and three systematic reviews) and five studies on peri-implant health (four animal studies and one clinical study) were included. All have reported a positive impact of MF on decreasing the inflammatory response, oxidative stress, and ultimate bone loss. Similarly, human studies reported a positive effect of MF on clinical and radiographic parameters compared with controls. Despite systematic reviews reporting heterogeneity among the included studies, MF has shown a positive impact on periodontal health. In animal, clinical studies, and systematic reviews, MF showed a protective impact on periodontal and peri-implant health.

Degradable hydrogel fibers encapsulate and deliver metformin and periodontal ligament stem cells for dental and periodontal regeneration

Human periodontal ligament stem cells (hPDLSCs) are promising cells for dental and periodontal regeneration. This study aimed to develop novel alginate-fibrin fibers that encapsulates hPDLSCs and metformin, to investigate the effect of metformin on the osteogenic differentiation of hPDLSCs, and to determine the regulatory role of the Shh/Gli1 signaling pathway in the metformin-induced osteogenic differentiation of hPDLSCs for the first time. CCK8 assay was used to evaluate hPDLSCs. Alkaline phosphatase (ALP) staining, alizarin red S staining, and the expression of osteogenic genes were evaluated. Metformin and hPDLSCs were encapsulated in alginate-fibrinogen solutions, which were injected to form alginate-fibrin fibers. The activation of Shh/Gli1 signaling pathway was examined using qRT-PCR and western blot. A mechanistic study was conducted by inhibiting the Shh/Gli1 pathway using GANT61. The administration of 50 μM metformin resulted in a significant upregulation of osteogenic gene expression in hPDLSCs by 1.4-fold compared to the osteogenic induction group (P < 0.01), including ALP and runt-related transcription factor-2 (RUNX2). Furthermore, metformin increased ALP activity by 1.7-fold and bone mineral nodule formation by 2.6-fold (P<0.001). We observed that hPDLSCs proliferated with the degradation of alginate-fibrin fibers, and metformin induced their differentiation into the osteogenic lineage. Metformin also promoted the osteogenic differentiation of hPDLSCs by upregulating the Shh/Gli1 signaling pathway by 3- to 6- fold compared to the osteogenic induction group (P<0.001). The osteogenic differentiation ability of hPDLSCs were decreased 1.3- to 1.6-fold when the Shh/Gli1 pathway was inhibited, according to ALP staining and alizarin red S staining (P<0.01). Metformin enhanced the osteogenic differentiation of hPDLSCs via the Shh/Gli1 signaling pathway. Degradable alginate-fibrin hydrogel fibers encapsulating hPDLSCs and metformin have significant potential for use in dental and periodontal tissue engineering applications. Alginate-fibrin fibers encapsulating hPDLSCs and metformin have a great potential for use in the treatment of maxillofacial bone defects caused by trauma, tumors, and tooth extraction. Additionally, they may facilitate the regeneration of periodontal tissue in patients with periodontitis.

A blast from the past: To tame time with metformin

The strong evidence of metformin use in subjects affected by type 2 diabetes (T2DM) on health outcomes, together with data from pre-clinical studies, has led the gerontological research to study the therapeutic potential of such a drug as a slow-aging strategy. However, despite clinical use for over fifty years as an anti-diabetic drug, the mechanisms of action beyond glycemic control remain unclear. In this review, we have deeply examined the literature, doing a narrative review from the metformin story, through mechanisms of action to slow down aging potential, from lower organisms to humans. Based on the available evidence, we conclude that metformin, as shown in lower organisms and mice, may be effective in humans' longevity. A complete analysis and follow-up of ongoing clinical trials may provide more definitive answers as to whether metformin should be promoted beyond its use to treat T2DM as a drug that enhances both healthspan and lifespan.

Metformin suppresses Oxidative Stress induced by High Glucose via Activation of the Nrf2/HO-1 Signaling Pathway in Type 2 Diabetic Osteoporosis

BACKGROUND

Metformin (MET) is widely used as a first-line hypoglycemic agent for the treatment of type 2 diabetes mellitus (T2DM) and was also confirmed to have a therapeutic effect on type 2 diabetic osteoporosis (T2DOP). However, the potential mechanisms of MET in the treatment of T2DOP are unclear.

OBJECTIVE

To clarify the effect of MET in T2DOP and to explore the potential mechanism of MET in the treatment of T2DOP.

METHODS

In vitro, we used MC3T3-E1 cells to study the effects of MET on osteogenic differentiation and anti-oxidative stress injury in a high glucose (Glucose 25 mM) environment. In vivo, we directly used db/db mice as a T2DOP model and assessed the osteoprotective effects of MET by Micro CT and histological analysis.

RESULTS

In vitro, we found that MET increased ALP activity in MC3T3-E1 cells in a high-glucose environment, promoted the formation of bone mineralized nodules, and upregulated the expression of the osteogenesis-related transcription factors RUNX2, Osterix, and COL1A1-related genes. In addition, MET was able to reduce high glucose-induced reactive oxygen species (ROS) production. In studies on the underlying mechanisms, we found that MET activated the Nrf2/HO-1 signaling pathway and alleviated high-glucose-induced oxidative stress injury. In vivo results showed that MET reduced bone loss and bone microarchitecture destruction in db/db mice.

CONCLUSION

Our results suggest that MET can activate the Nrf2/HO-1 signaling pathway to regulate the inhibition of osteogenic differentiation induced by high glucose thereby protecting T2DOP.

Risk of fracture caused by anti-diabetic drugs in individuals with type 2 diabetes: A network meta-analysis

AIMS

Diabetes is associated with increased risk of fracture. This study aims to evaluate the correlation between anti-diabetic agents and fracture risk in patients with type 2 diabetes.

METHODS

Literature research was conducted using PubMed, Embase, and ClinicalTrials.gov. Search-term included "type 2 diabetes," "fracture," "randomized controlled trial," and seven kinds of anti-diabetic agents. Random-effect models established fractures in the follow-up period as the primary outcome. A network meta-analysis was performed to compare available treatments within a single Bayesian analytical framework.

RESULTS

A total of 191,361 patients were included in 161 studies, with 2916 fractures. DPP-4i (risk ratio [RR] 1.76 [95 % confidence interval (CI) 1.21-2.55]), SGLT-2i (RR 1.5 [95 % CI 1.05-2.16]) and placebo (RR 1.44 [95 % CI 1.04-1.98]) increased fracture risk when compared to GLP1-RA. GLP1-RA (RR 0.5 [95 % CI 0.31-0.79]) and SU (RR 0.56 [95 % CI 0.41-0.77]) provided greater protection against fracture than TZD. DPP-4i increased fracture risk when compared to SU (RR 1.55 [95 % CI 1.08-2.22]), and was comparable in effect to TZD.

CONCLUSIONS

GLP1-RA offered better protection against fracture than placebo. Insulin and SU had effects comparable with GLP1-RA. SU offered greater protection against fractures than TZD and DPP-4i. SGLT-2i increased risk of fracture when compared to GLP1-RA.

Preparation, characterization, and osteogenic activity mechanism of casein phosphopeptide-calcium chelate

Casein phosphopeptides (CPPs) are good at calcium-binding and intestinal calcium absorption, but there are few studies on the osteogenic activity of CPPs. In this study, the preparation of casein phosphopeptide calcium chelate (CPP-Ca) was optimized on the basis of previous studies, and its peptide-calcium chelating activity was characterized. Subsequently, the effects of CPP-Ca on the proliferation, differentiation, and mineralization of MC3T3-E1 cells were studied, and the differentiation mechanism of CPP-Ca on MC3T3-E1 cells was further elucidated by RNA sequencing (RNA-seq). The results showed that the calcium chelation rate of CPPs was 23.37%, and the calcium content of CPP-Ca reached 2.64 × 10⁵ mg/kg. The test results of Ultraviolet–Visible absorption spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR) indicated that carboxyl oxygen and amino nitrogen atoms of CPPs might be chelated with calcium during the chelation. Compared with the control group, the proliferation of MC3T3-E1 cells treated with 250 μg/mL of CPP-Ca increased by 21.65%, 26.43%, and 28.43% at 24, 48, and 72 h, respectively, and the alkaline phosphatase (ALP) activity and mineralized calcium nodules of MC3T3-E1 cells were notably increased by 55% and 72%. RNA-seq results showed that 321 differentially expressed genes (DEGs) were found in MC3T3-E1 cells treated with CPP-Ca, including 121 upregulated and 200 downregulated genes. Gene ontology (GO) revealed that the DEGs mainly played important roles in the regulation of cellular components. The enrichment of the Kyoto Encyclopedia of Genes and Genomes Database (KEGG) pathway indicated that the AMPK, PI3K-Akt, MAPK, and Wnt signaling pathways were involved in the differentiation of MC3T3-E1 cells. The results of a quantitative real-time PCR (qRT-PCR) showed that compared with the blank control group, the mRNA expressions of Apolipoprotein D (APOD), Osteoglycin (OGN), and Insulin-like growth factor (IGF1) were significantly increased by 2.6, 2.0 and 3.0 times, respectively, while the mRNA levels of NOTUM, WIF1, and LRP4 notably decreased to 2.3, 2.1, and 4.2 times, respectively, which were consistent both in GO functional and KEGG enrichment pathway analysis. This study provided a theoretical basis for CPP-Ca as a nutritional additive in the treatment and prevention of osteoporosis.

Metformin treatment is associated with an increase in bone mineral density in type 2 diabetes mellitus patients in China: a retrospective single center study

AIMS

- To investigate the association between metformin and bone mineral density (BMD) in a large cohort of Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

- A total of 11,458 T2DM patients aged ≥ 40 years were included. Information on demographic, anthropometric and clinical characteristics was collected from medical records. BMD at lumbar spine (LS), femoral neck (FN), and total hip(TH) was assessed by dual-energy X-ray absorptiometry.

RESULTS

- Overall prevalence of osteopenia and osteoporosis was 37.4% and 10.3%, and was lower in patients on metformin (34.6% vs 38.3% and 7.1% vs 11.3%, both P < 0.001). Patients who had a lower BMI, older age, and lower estimated glomerular filtration rate (eGFR), had more osteoporosis, lower BMD (osteoporosis or osteopenia), and a lower T-score at LS, FN and TH. Metformin use and male sex was associated with a higher BMD. Metformin treatment was also independently associated with higher T-score at LS, FN and TH (β values of 0.120, 0.082 and 0.108; all P < 0.001), and lower odds ratio of osteoporosis (OR = 0.779, 95%CI: 0.648-0.937, P = 0.008) or low BMD (OR = 0.834, 95%CI: 0.752 - 0.925, P = 0.001). However, when analyzed by sex, this association of a lower odds ratio for osteoporosis with metformin was only significant in women (OR= 0.775, 95% CI: 0.633-0.948; P = 0.013).

CONCLUSIONS

- Metformin treatment was associated with a higher T-score and a lower odds ratio of osteopenia and osteoporosis, especially in the female population, independent of age, BMI, and eGFR.

The Function of Metformin in Aging-Related Musculoskeletal Disorders

Metformin is a widely accepted first-line hypoglycemic agent in current clinical practice, and it has been applied to the clinic for more than 60 years. Recently, researchers have identified that metformin not only has an efficient capacity to lower glucose but also exerts anti-aging effects by regulating intracellular signaling molecules. With the accelerating aging process and mankind’s desire for a long and healthy life, studies on aging have witnessed an unprecedented boom. Osteoporosis, sarcopenia, degenerative osteoarthropathy, and frailty are age-related diseases of the musculoskeletal system. The decline in motor function is a problem that many elderly people have to face, and in serious cases, they may even fail to self-care, and their quality of life will be seriously reduced. Therefore, exploring potential treatments to effectively prevent or delay the progression of aging-related diseases is essential to promote healthy aging. In this review, we first briefly describe the origin of metformin and the aging of the movement system, and next review the evidence associated with its ability to extend lifespan. Furthermore, we discuss the mechanisms related to the modulation of aging in the musculoskeletal system by metformin, mainly its contribution to bone homeostasis, muscle aging, and joint degeneration. Finally, we analyze the protective benefits of metformin in aging-related diseases of the musculoskeletal system.

New Therapeutics Targeting Arterial Media Calcification: Friend or Foe for Bone Mineralization?

The presence of arterial media calcification, a highly complex and multifactorial disease, puts patients at high risk for developing serious cardiovascular consequences and mortality. Despite the numerous insights into the mechanisms underlying this pathological mineralization process, there is still a lack of effective treatment therapies interfering with the calcification process in the vessel wall. Current anti-calcifying therapeutics may induce detrimental side effects at the level of the bone, as arterial media calcification is regulated in a molecular and cellular similar way as physiological bone mineralization. This especially is a complication in patients with chronic kidney disease and diabetes, who are the prime targets of this pathology, as they already suffer from a disturbed mineral and bone metabolism. This review outlines recent treatment strategies tackling arterial calcification, underlining their potential to influence the bone mineralization process, including targeting vascular cell transdifferentiation, calcification inhibitors and stimulators, vascular smooth muscle cell (VSMC) death and oxidative stress: are they a friend or foe? Furthermore, this review highlights nutritional additives and a targeted, local approach as alternative strategies to combat arterial media calcification. Paving a way for the development of effective and more precise therapeutic approaches without inducing osseous side effects is crucial for this highly prevalent and mortal disease.

Unmasking Fracture Risk in Type 2 Diabetes: The Association of Longitudinal Glycemic Hemoglobin Level and Medications

CONTEXT

Fracture risk is underestimated in people with type 2 diabetes (T2D).

OBJECTIVE

To investigate the longitudinal relationship of glycated hemoglobin (HbA1c) and common medications on fracture risk in people with T2D.

METHODS

This retrospective population-based cohort study was conducted using de-identified claims and electronic health record data obtained from the OptumLabs Data Warehouse for the period January 1, 2007, to September 30, 2015. For each individual, the study was conducted within a 2-year HbA1c observation period and a 2-year fracture follow-up period. A cohort of 157 439 individuals with T2D [age ≥ 55 years with mean HbA1c value ≥ 6%] were selected from 4 018 250 US Medicare Advantage/Commercial enrollees with a T2D diagnosis. All fractures and fragility fractures were measured.

RESULTS

With covariates adjusted, poor glycemic control in T2D individuals was associated with an 29% increase of all fracture risk, compared with T2D individuals who had adequate glycemic control (HR: 1.29; 95% CI, 1.22-1.36). Treatment with metformin (HR: 0.88; 95% CI, 0.85-0.92) and DPP4 inhibitors (HR: 0.93; 95% CI, 0.88-0.98) was associated with a reduced all fracture risk, while insulin (HR: 1.26; 95% CI, 1.21-1.32), thiazolidinediones (HR: 1.23; 95% CI, 1.18-1.29), and meglitinides (HR: 1.12; 95% CI, 1.00-1.26) were associated with an increased all fracture risk (All P value < 0.05). Bisphosphonates were associated similarly with increased fracture risk in the T2D and nondiabetic groups.

CONCLUSION

Longitudinal 2-year HbA1c is independently associated with elevated all fracture risk in T2D individuals during a 2-year follow-up period. Metformin and DPP4 inhibitors can be used for management of T2D fracture risk.

Efficacy of 1.5% metformin gel as an adjuvant to scaling, root planing, and curettage for the treatment of infrabony defects in chronic periodontitis patients

Context:

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Results:

Conclusions:

The antidiabetic drug metformin acts on the bone microenvironment to promote myeloma cell adhesion to preosteoblasts and increase myeloma tumour burden in vivo

Multiple myeloma is a haematological malignancy that is dependent upon interactions within the bone microenvironment to drive tumour growth and osteolytic bone disease. Metformin is an anti-diabetic drug that has attracted attention due to its direct antitumor effects, including anti-myeloma properties. However, the impact of the bone microenvironment on the response to metformin in myeloma is unknown. We have employed in vitro and in vivo models to dissect out the direct effects of metformin in bone and the subsequent indirect myeloma response. We demonstrate how metformin treatment of preosteoblasts increases myeloma cell attachment. Metformin-treated preosteoblasts increased osteopontin (OPN) expression that upon silencing, reduced subsequent myeloma cell adherence. Proliferation markers were reduced in myeloma cells cocultured with metformin-treated preosteoblasts. In vivo, mice were treated with metformin for 4 weeks prior to inoculation of 5TGM1 myeloma cells. Metformin-pretreated mice had an increase in tumour burden, associated with an increase in osteolytic bone lesions and elevated OPN expression in the bone marrow. Collectively, we show that metformin increases OPN expression in preosteoblasts, increasing myeloma cell adherence. In vivo, this translates to an unexpected indirect pro-tumourigenic effect of metformin, highlighting the importance of the interdependence between myeloma cells and cells of the bone microenvironment.

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.

Human dental pulp stem cells and hormesis

This paper represents the first assessment of hormetic dose responses by human dental pulp stem cells (hDPSCs) with particular emphasis on cell renewal (proliferation) and differentiation. Hormetic dose responses were commonly reported in this model, encompassing a broad range of chemicals, including principally pharmaceuticals (e.g., metformin and artemisinin), dietary supplements/extracts from medicinal plants (e.g., berberine, N-acetyl-L-cysteine, and ginsenoside Rg1) and endogenous agents (e.g., ATP, TNF-α). The paper assesses mechanistic foundations of the hDPSCs hormetic dose responses for both cell proliferation and cell differentiation, study design considerations, and therapeutic implications.

Metformin-loaded β-TCP/CTS/SBA-15 composite scaffolds promote alveolar bone regeneration in a rat model of periodontitis

Periodontitis is a progressive infectious inflammatory disease, which leads to alveolar bone resorption and loss of periodontal attachment. It is imperative for us to develop a therapeutic scaffold to repair the alveolar bone defect of periodontitis. In this study, we designed a new composite scaffold loading metformin (MET) by using the freeze-drying method, which was composed of β-tricalcium phosphate (β-TCP), chitosan (CTS) and the mesoporous silica (SBA-15). The scaffolds were expected to combine the excellent biocompatibility of CTS, the good bioactivity of β-TCP, and the anti-inflammatory properties of MET. The MET-loaded β-TCP/CTS/SBA-15 scaffolds showed improved cell adhesion, appropriate porosity and good biocompatibility in vitro. This MET composite scaffold was implanted in the alveolar bone defects area of rats with periodontitis. After 12 weeks, Micro-CT and histological analysis were performed to evaluate different degrees of healing and mineralization. Results showed that the MET-loaded β-TCP/CTS/SBA-15 scaffolds promoted alveolar bone regeneration in a rat model of periodontitis. To our knowledge, this is the first report that MET-loaded β-TCP/CTS/SBA-15 scaffolds have a positive effect on alveolar bone regeneration in periodontitis. Our findings might provide a new and promising strategy for repairing alveolar bone defects under the condition of periodontitis.

Lower Prevalence of Osteoporosis in Patients with COPD Taking Anti-Inflammatory Compounds for the Treatment of Diabetes: Results from COSYCONET

Background

Patients with chronic obstructive pulmonary disease (COPD) often have osteoporosis and diabetes as comorbid conditions. Anti-diabetic medication, including metformin, has protective effects on osteoporosis in experimental studies. We therefore studied whether patients with COPD receiving anti-diabetic medication had a lower osteoporosis prevalence in a large COPD cohort, COSYCONET.

Methods

Assessment of osteoporosis was based on patients’ reports of physician-based diagnoses and the presence of disease-specific medication. The predictive value of physical characteristics, lung function, comorbidities, cardiovascular medication, and the use of anti-inflammatory diabetes medication, including metformin, sulfonylureas, glinides or DPP4I, was evaluated using logistic regression analysis. ClinicalTrials.gov: NCT01245933.

Results

In total, 2222 patients were eligible for analysis (863 [39%] female, mean age 65 y), 515 of whom had higher symptoms and exacerbations (Global Initiative for Chronic Obstructive Lung Disease group D). Osteoporosis was present in 15.8% of the overall cohort, and in 24.1% of GOLD D patients. Regression analyses identified the following as associated with osteoporosis (p < 0.05): female sex, higher age, lower body-mass index, asthma, higher air trapping, oral steroids, and cardiovascular medication. Although oral anti-diabetic medication was overall not associated with a lower prevalence of osteoporosis (p = 0.131), anti-inflammatory anti-diabetic medication (p = 0.009) and metformin-containing therapy (p = 0.039) were. This was driven by GOLD D patients.

Conclusion

In a large COPD cohort, anti-inflammatory diabetes therapy, including metformin, was associated with a lower prevalence of osteoporosis, especially in patients with higher symptoms and exacerbations. These findings suggest a protective effect of common anti-diabetic medication on osteoporosis, possibly as a result of attenuated systemic inflammation.

Osteoprotective Effects of ‘Anti-Diabetic’ Polyherbal Mixture in Type 1 Diabetic Rats

Bone loss leading to osteopenia and osteoporosis is a frequent secondary complication of diabetes. This study aimed to evaluate the value of a traditionally used ‘anti-diabetic’ polyherbal mixture as a possible remedy for the prevention of this complication. Diabetes was induced in Wistar female rats with a single intraperitoneal injection of alloxan monohydrate. The animals with blood glucose higher than 20 mmol/L for 14 consecutive days were considered diabetic. For the next 14 days, animals were treated with two concentrations of the polyherbal mixture (10 and 20 g of dry plant material/ kg). Bone histopathology was evaluated using the H&E and Masson’s trichrome staining. Alloxan-induced diabetes triggered bone histological changes characteristic for the development of osteopenia and osteoporosis and treatment with the polyherbal decoction restored these histopathological changes of the bones to the healthy animal level. At the same time, treatment with these tested doses has shown no adverse effects. These findings suggest that this mixture might be used as a remedy for the prevention of diabetic bone loss.

Clinico-radiographic comparative evaluation of 1% metformin gel plus platelet-rich fibrin over platelet-rich fibrin alone in treatment of Grade II furcation defects: A randomized controlled double-blind clinical trial

BACKGROUND

The present study was aimed to evaluate and compare the effects of 1% MF plus PRF over PRF alone in treatment of Grade II furcation defects, clinically and radiographically by using cone-beam computed tomography.

METHODS

This split-mouth clinical trial randomly allotted 21 patients with 42 bilateral Grade II furcation defects into two groups. Group I was treated with PRF alone while Group II with 1% MF gel and PRF. The primary outcome parameters were clinical attachment level (CAL) and horizontal probing depth (HPD) while the secondary outcome parameters were probing depth (PD) and defect volume (DV). The clinical parameters were evaluated at 3, 6, and 12 months and the radiographic parameters at 12 months.

RESULTS

Both the study groups yielded improvements in assessed parameters; however, significantly greater mean reduction of PD, HPD, and CAL gain was observed in Group II (3.90 ± 0.78 mm, 2.94 ± 0.80 mm, and 3.42 ± 0.93 mm) in comparison with Group I (3.23 ± 0.90 mm, 1.96 ± 0.80 mm, and 2.67 ± 0.88 mm) at 12 months, respectively. A significant reduction of DV was exhibited radiographically in Group II (12.61 ± 4.01 mm³ ) as compared with Group I (9.14 ± 4.31 mm³ ) at the end of 12 months.

CONCLUSIONS

Better clinical and radiographic findings in terms of reduction in PD, HPD, CAL gain, and significant reduction in DV in Group II patients indicated that the combination therapy of 1% MF + PRF promotes regenerative ability within the periodontal tissues in Grade II furcation defects to a greater extent.

Pharmaceutical Drugs and Natural Therapeutic Products for the Treatment of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is the most widespread form of diabetes, characterized by chronic hyperglycaemia, insulin resistance, and inefficient insulin secretion and action. Primary care in T2DM is pharmacological, using drugs of several groups that include insulin sensitisers (e.g., biguanides, thiazolidinediones), insulin secretagogues (e.g., sulphonylureas, meglinides), alpha-glucosidase inhibitors, and the newest incretin-based therapies and sodium-glucose co-transporter 2 inhibitors. However, their long-term application can cause many harmful side effects, emphasising the importance of the using natural therapeutic products. Natural health substances including non-flavonoid polyphenols (e.g., resveratrol, curcumin, tannins, and lignans), flavonoids (e.g., anthocyanins, epigallocatechin gallate, quercetin, naringin, rutin, and kaempferol), plant fruits, vegetables and other products (e.g., garlic, green tea, blackcurrant, rowanberry, bilberry, strawberry, cornelian cherry, olive oil, sesame oil, and carrot) may be a safer alternative to primary pharmacological therapy. They are recommended as food supplements to prevent and/or ameliorate T2DM-related complications. In the advanced stage of T2DM, the combination therapy of synthetic agents and natural compounds with synergistic interactions makes the treatment more efficient. In this review, both pharmaceutical drugs and selected natural products, as well as combination therapies, are characterized. Mechanisms of their action and possible negative side effects are also provided.

Metformin reverses the effects of high glucose on human dermal fibroblasts of aged skin via downregulating RELA/p65 expression

Metformin has been successfully used as an anti-aging agent but exact molecular mechanisms of metformin in anti-aging remain unknown. Hyperglycemia during skin aging not only causes oxidative damage to cellular macromolecules, like dermal collagen, but also modulates the activation of transcription factor nuclear factor kappa B (NF-kB). We aimed to investigate in vitro effects of high glucose (HG) and metformin treatment on proliferation and apoptosis of human primary dermal fibroblasts (HDFs), and the expression of COL1A1, COL3A1, and RELA/p65 genes. Effects of normal glucose (5.5 mM) and HG concentration (50 mM HG) on HDFs, with two doses of metformin (50 μM and 500 μM), were investigated by immunostaining. Apoptotic levels were analyzed by flow cytometry. Expression of COL1A1, COL3A1, and RELA/p65 genes was measured by quantitative real-time PCR. The proliferation of HDFs was decreased significantly (P < 0.01) and expression of COL1A1 was downregulated by HG without metformin, whereas proliferation was elevated and expression was upregulated with 500 μM metformin + HG compared to 5.5 mM glucose (P < 0.05). The expression of COL3A1 and RELA/p65 were upregulated (P < 0.01 for COL3A1), and percentage of late apoptotic cells increased significantly by HG without metformin (P < 0.001) while it decreased in two concentrations of metformin dramatically compared with 5.5 mM glucose (P < 0.01 for expressions and < 0.001 for apoptosis). Metformin not only significantly downregulated RELA/p65 expression, but also inhibited the apoptosis of HDFs from aged human skin at toxic glucose concentrations which could be inversely mediated via COL1A1 and COL3A1 expression.

Metformin: Is It the Well Wisher of Bone Beyond Glycemic Control in Diabetes Mellitus?

Both diabetes mellitus and osteoporosis constitute a notable burden in terms of quality of life and healthcare costs. Diabetes mellitus affecting the skeletal system has been gaining attention in recent years and is now getting recognized as yet another complication of the disease, known as diabetic bone disease. As this condition with weaker bone strength increases fracture risk and reduces the quality of life, so much attention is being paid to investigate the molecular pathways through which both diabetes and its therapy are affecting bone metabolism. Out of many therapeutic agents currently available for managing diabetes mellitus, metformin is one of the most widely accepted first choices worldwide. The purpose of this review is to describe the effects of biguanide-metformin on bone metabolism in type 2 diabetes mellitus including its plausible mechanisms of action on the skeleton. In vitro studies suggest that metformin directly stimulates osteoblasts differentiation and may inhibit osteoclastogenesis by increasing osteoprotegerin expression, both through activation of the AMPK signaling pathway. Several studies in both preclinical and clinical settings report the favorable effects of metformin on bone microarchitecture, bone mineral density, bone turnover markers, and fracture risk. However, animal studies were not specific in terms of the diabetic models used and clinical studies were associated with several confounders. The review highlights some of these limitations and provide future recommendations for research in this area which is necessary to better understand the role of metformin on skeletal outcomes in diabetes.

Trelagliptin stimulates osteoblastic differentiation by increasing runt-related transcription factor 2 (RUNX2): a therapeutic implication in osteoporosis

Osteoporosis, an aging-associated bone metabolic disease, is affecting millions of people worldwide. The deregulated process of osteoblastic differentiation has been linked with the progression of osteoporosis. Trelagliptin is a long-acting inhibitor of DPP-4 used for the management of type 2 diabetes mellitus. However, it is unknown whether Trelagliptin possesses a beneficial effect in osteoblastic differentiation. Interestingly, we found that treatment with Trelagliptin enhanced differentiation and promoted the mineralization of MC3T3-E1 cells. Firstly, Trelagliptin increased the activity of alkaline phosphatase (ALP) and promoted osteoblastic calcium deposition. Additionally, treatment with Trelagliptin upregulated ALP, osteocalcin (OCN), osteopontin (OPN), and bone morphogenetic protein-2 (BMP-2). Notably, Trelagliptin increased RUNX2, a major regulator of osteoblastic differentiation. Mechanistically, Trelagliptin upregulated the levels of p-AMPKα. Blockage of AMPK with compound C abolished the effects of Trelagliptin in RUNX2 and osteoblastic differentiation, suggesting the involvement of AMPK. Our findings suggest that Trelagliptin might possess a potential for the treatment of osteoporosis.

Effects of metformin on the osteogenesis of alveolar BMSCs from diabetic patients and implant osseointegration in rats

OBJECTIVES

This study aimed to explore the effects of metformin on osteogenic differentiation of alveolar bone marrow mesenchymal stem cells (BMSCs) from type-2 diabetes mellitus (T2DM) patients (DM-BMSCs) and implant osseointegration in rats, screen the optimal concentration, and investigate whether metformin could protect against the adverse impact of T2DM on BMSC osteogenic capacity.

SUBJECTS AND METHODS

Different concentrations of metformin were administered to human-derived BMSCs and Wistar rats receiving implants. ALP detection, alizarin red staining, real-time RT-PCR and Western blotting were performed to detect osteogenesis and investigate the mechanism. Toluidine blue staining was performed to analyse bone-implant contact in rats.

RESULTS

Metformin increased implant osseointegration in a rat model and promoted the osteogenic capacity of DM-BMSCs via the AMPK/BMP/Smad signalling pathway, and 125 μM was the optimal concentration; however, concentrations over 200 µM, metformin showed an inhibitory effect on DM-BMSCs. Additionally, metformin at the optimal concentration (125 µM) identified in this study could compensate for the negative impacts of T2DM on the osteogenic differentiation of BMSCs.

CONCLUSIONS

Metformin can promote the osteogenesis of BMSCs from T2DM patients and osseointegration in rats, and it might be an effective drug for increasing the success rate of T2DM-associated implants.

Antidiabetic Treatment, Level of Glycemic Control, and Risk of Fracture in Type 2 Diabetes: a Nested, Case-Control Study

CONTEXT

Patients with type 2 diabetes mellitus (T2DM) have an increased risk of low-trauma fractures. However, the effect of antidiabetic medication in relation to glycemic control on the risk of fracture is poorly understood.

OBJECTIVE

This work aimed to evaluate the association between the level of glycemic control, use of antidiabetic medication, and risk of low-trauma fractures in patients with newly diagnosed T2DM.

METHODS

We conducted a nested case-control analysis among individuals registered in the Clinical Practice Research Datalink. The base population consisted of patients with newly diagnosed T2DM from 1995 to 2017. Cases were patients with a low-trauma fracture after T2DM diagnosis. We matched 4 controls to each case. Exposures of interest were glycemic control (last glycated hemoglobin [HbA1c] level before fracture) and type of diabetes treatment. We conducted conditional logistic regression analyses adjusted for several confounders.

RESULTS

We identified 8809 cases and 35 219 controls. Patients with current metformin use and HbA1c levels of less than 7.0% and between 7.0-8.0% had a reduced risk of fractures (adjusted odds ratio 0.89; 95% CI, 0.83-0.96 and 0.81; 95% CI, 0.73-0.90, respectively) compared with untreated patients. However, in patients receiving metformin plus 1 or 2 other antidiabetic drugs, or insulin (alone or in addition to other antidiabetic medication), the level of glycemic control was not associated with the risk of fracture compared with untreated patients.

CONCLUSIONS

While patients with good or medium glycemic control receiving current metformin monotherapy had a lower risk of fracture compared with untreated patients, glycemic control in patients receiving treatment other than metformin was not associated with risk of fracture.

Metformin-Induced MicroRNA-34a-3p Downregulation Alleviates Senescence in Human Dental Pulp Stem Cells by Targeting CAB39 through the AMPK/mTOR Signaling Pathway

Dental pulp stem cells (DPSCs) are ideal seed cells for the regeneration of dental tissues. However, DPSC senescence restricts its clinical applications. Metformin (Met), a common prescription drug for type 2 diabetes, is thought to influence the aging process. This study is aimed at determining the effects of metformin on DPSC senescence. Young and aging DPSCs were isolated from freshly extracted human teeth. Flow cytometry confirmed that DPSCs expressed characteristic surface antigen markers of mesenchymal stem cells (MSCs). Cell Counting Kit-8 (CCK-8) assay showed that a concentration of 100 μM metformin produced the highest increase in the proliferation of DPSCs. Metformin inhibited senescence in DPSCs as evidenced by senescence-associated β-galactosidase (SA-β-gal) staining and the expression levels of senescence-associated proteins. Additionally, metformin significantly suppressed microRNA-34a-3p (miR-34a-3p) expression, elevated calcium-binding protein 39 (CAB39) expression, and activated the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway. Dual-luciferase reporter assay confirmed that CAB39 is a direct target for miR-34a-3p. Furthermore, transfection of miR-34a-3p mimics promoted the senescence of DPSCs, while metformin treatment or Lenti-CAB39 transfection inhibited cellular senescence. In conclusion, these results indicated that metformin could alleviate the senescence of DPSCs by downregulating miR-34a-3p and upregulating CAB39 through the AMPK/mTOR signaling pathway. This study elucidates on the inhibitory effect of metformin on DPSC senescence and its potential as a therapeutic target for senescence treatment.

Metformin-Loaded PCL/PVA Fibrous Scaffold Preseeded with Human Endometrial Stem Cells for Effective Guided Bone Regeneration Membranes

Many studies have been devoted to investigating the potential of guided bone regeneration (GBR) membranes for bone defect reconstruction. Regardless of approaches for treating damaged bone tissues, a beneficial therapeutic strategy has remained a challenge. In this study, a novel GBR membrane with polycaprolactone (PCL) and poly(vinyl alcohol) (PVA) containing different concentrations of metformin (Met) for improving osteogenic properties was developed. The membranes were evaluated for their hydrophilicity, degradation rate, swelling ratio, drug release, mechanical properties, and biological responses. The results showed a significant increase in hydrophilicity, swelling ratio, and degradation rate and no significant changes in mechanical properties of PCL/PVA membranes with Met concentration enhancement. A decrease in cell viability cultured on the surface of the PCL/PVA membrane was seen when the amount of Met was changed from 10 to 15 wt %. The results of the in vitro quantitative real-time polymerase chain reaction (qRT-PCR) also confirmed the higher secretion of osteogenic-related genes in a PCL/PVA/Cell/10 wt % Met scaffold than in the PCL/PVA/Cell sample. Therefore, further in vivo studies were conducted using the electrospun PCL/PVA membrane containing human endometrial stem cells (hEnSCs) and 10% Met. Histopathological and histomorphometric results confirmed that PCL/PVA/hEnSCs/10 wt % Met has excellent potential to differentiate hEnSCs into osteogenic lineages and bone regeneration in calvarial defects of rats. The results of this study confirm the high potential of the PCL/PVA/10 wt % Met fibrous membrane preseeded with hEnSCs in GBR applications.

Effects of metformin on the prevention of bisphosphonate-related osteonecrosis of the jaw-like lesions in rats

PURPOSE

In this study, we aimed to investigate the effect of glucose metabolism on bone healing after tooth extraction in an osteoporosis rat model administered zoledronic acid (ZA) and dexamethasone (DX).

METHODS

In total, 24 male Wistar rats (4 weeks old) were randomly assigned to four groups: Control (subcutaneous physiological saline), ZD (subcutaneous ZA and DX twice a week), Ins+ZD (subcutaneous insulin followed by ZD treatment), and Met+ZD (oral metformin followed by ZD treatment). Blood was collected every two weeks . Two weeks after treatment initiation, the first molar tooth on the right maxilla was extracted from all rats. Four weeks later, the rats were sacrificed, and bone healing was assessed. Maxillae samples were fixed and scanned using micro-computed tomography for quantifying areas of bone defects. Hematoxylin-eosin and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate bone apoptosis and osteoclast number.

RESULTS

In all experimental groups, body weight was statistically lower than that in the Control group, with no changes observed in uncarboxylated osteocalcin concentrations. The radiological analysis revealed that insulin or metformin administration improved healing in the tooth extraction socket (p < 0.01). Histological examination revealed that the osteonecrosis area was reduced in the Ins+ZD and Met+ZD groups (p < 0.01). TRAP staining presented increased osteoclast numbers in the ZD group when compared with that observed in the Control.

CONCLUSIONS

Tooth extraction with long-term ZA and DX administration inhibited bone remodeling and induced bisphosphonate-related osteonecrosis of the jaw-like lesions. Metformin exerted protective effects ag ainst osteonecrosis of the jaw.

Metformin promotes the osseointegration of titanium implants under osteoporotic conditions by regulating BMSCs autophagy, and osteogenic differentiation

Osteoporosis is a common bone disorder with adverse effects on oral osseointegration, and the effects of metformin on bone metabolism have received increasing attention. The aim of the present study was to test the hypothesis that metformin promoted osteogenesis of bone mesenchymal stem cells (BMSCs) and osseointegration of titanium implants. BMSCs were treated with metformin to assess autophagic capacity, reactive oxygen species (ROS) production, anti-aging ability, and osteogenic differentiation. To determine its potential application in peri-implant of the maxilla, metformin was injected around the implant each day, immediately after the implant was embedded into the tooth socket. The results showed that metformin increased the autophagic capacity and decreased ROS production of osteoporotic BMSCs under hypoxia and serum deprivation (H/SD) culturing conditions. Metformin treatment significantly enhanced stemness properties and mineralized nodule formation, and increased the expression of osteogenic markers, including runt related transcription factor 2 (Runx2), osteocalcin (OCN), and alkaline phosphatase (ALP). Moreover, metformin substantially accelerated the formation of new bone, ameliorated the bone microarchitecture and promoted osseointegration of the dental implant. Collectively, metformin induces an osteogenic effect around the implant. Considering the widespread use of metformin, the results of the present study might promote a novel understanding of the positive effects of local metformin delivery on alveolar ridge defect, and have potential clinical application for the acceleration of osseointegration.

The effects of metformin on the bone filling ration around of TiAl6Va4 implants in non diabetic rats

Objectives

In this research it was aimed to that evaluation of the effects of systemic metformin administration on the periimplant bone tissue response of TiAl₆Va₄ implants in experimental rat model.

Materials and method

Firstly TiAl₆Va₄ implants were inserted surgically in the metaphyseal part of the tibial bone and after, the rats were randomly separated into two groups: Controls (CNT) (n = 10) and Metformin group (M) (n = 10). No additional treatment was applied to the controls during the 4-week experimental period. Rats received 40 mg/kg metformin in every day during the four week experimental period in M group. At the end of the 28-day follow-up period, the TiAl₆Va₄ implants with surrounding bone were used for the histopathologic analysis. To analysis of the datas between M and CNT Student-T Test was used.

Result

Periimplant bone tissue filling ratios (%) were detected higher in M group compared with the CNT (P < 0.05).

Conclusion

Systemic administration of metformin may increases titanium implant osseointegration in non-diabetic rats.

Metformin promotes cell proliferation and osteogenesis under high glucose condition by regulating the ROS‑AKT‑mTOR axis

Metformin, a cost-effective and safe orally administered antidiabetic drug used by millions of patients, has exhibited great interest for its potential osteogenic-promoting properties in different types of cells, including mesenchymal stem cells (MSCs). Diabetic osteopathy is a common comorbidity of diabetes mellitus; however, the underlying molecular mechanisms of metformin on the physiological processes of MSCs, under high glucose condition, remain unknown. To determine the effects of metformin on the regulatory roles of proliferation and differentiation in MSCs, under high glucose conditions, osteogenesis after metformin treatment was detected with Alizarin Red S and ALP staining. The results demonstrated that high glucose levels significantly inhibited cell proliferation and osteogenic differentiation under high glucose conditions. Notably, addition of metformin reversed the inhibitory effects induced by high glucose levels on cell proliferation and osteogenesis. Furthermore, high glucose levels significantly decreased mitochondrial membrane potential (MMP), whereas treatment with metformin helped maintain MMP. Further analysis of mitochondrial function revealed that metformin significantly promoted ATP synthesis, mitochondrial DNA mass and mitochondrial transcriptional activity, which were inhibited by high glucose culture. Furthermore, metformin significantly scavenged reactive oxygen species (ROS) induced by high glucose levels, and regulated the ROS-AKT-mTOR axis inhibited by high glucose levels, suggesting the protective effects of metformin against high glucose levels via regulation of the ROS-AKT-mTOR axis. Taken together, the results of the present study demonstrated the protective role of metformin on the physiological processes of MSCs, under high glucose condition and highlighted the potential molecular mechanism underlying the effect of metformin in promoting cell proliferation and osteogenesis under high glucose condition.

Chitosan Coating of TiO2 Nanotube Arrays for Improved Metformin Release and Osteoblast Differentiation

Background

Ineffective integration has been recognized as one of the major causes of early orthopedic failure of titanium-based implants. One strategy to address this problem is to develop modified titanium surfaces that promote osteoblast differentiation. This study explored titanium surfaces modified with TiO2 nanotubes (TiO2 NTs) capable of localized drug delivery into bone and enhanced osteoblast cell differentiation.

Materials and Methods

Briefly, TiO2 NTs were subjected to anodic oxidation and loaded with Metformin, a widely used diabetes drug. To create surfaces with sustainable drug-eluting characteristics, TiO2 NTs were spin coated with a thin layer of chitosan. The surfaces were characterized via scanning electron microscopy, atomic force microscopy, and contact angle measurements. The surfaces were then exposed to mesenchymal bone marrow stem cells (MSCs) to evaluate cell adhesion, growth, differentiation, and morphology on the modified surfaces.

Results

A noticeable increase in drug release time (3 days vs 20 days) and a decrease in burst release characteristics (85% to 7%) was observed in coated samples as compared to uncoated samples, respectively. Chitosan-coated TiO2 NTs exhibited a considerable enhancement in cell adhesion, proliferation, and genetic expression of type I collagen, and alkaline phosphatase activity as compared to uncoated TiO2 NTs.

Conclusion

TiO2 NT surfaces with a chitosan coating are capable of delivering Metformin to a bone site over a sustained period of time with the potential to enhance MSCs cell attachment, proliferation, and differentiation.

AMP-activated protein kinase (AMPK) regulates autophagy, inflammation and immunity and contributes to osteoclast differentiation and functionabs

Osteoclasts are multinucleated giant cells, responsible for bone resorption. Osteoclast differentiation and function requires a series of cytokines to remove the old bone, which coordinates with the induction of bone remodelling by osteoblast-mediated bone formation. Studies have demonstrated that AMP-activated protein kinase (AMPK) play a negative regulatory role in osteoclast differentiation and function. Research involving AMPK, a nutrient and energy sensor, has primarily focused on osteoclast differentiation and function; thus, its role in autophagy, inflammation and immunity remains poorly understood. Autophagy is a conservative homoeostatic mechanism of eukaryotic cells, and response to osteoclast differentiation and function; however, how it interacts with inflammation remains unclear. Additionally, based on the regulatory function of different AMPK subunits for osteoclast differentiation and function, its activation is regulated by upstream factors to perform bone metabolism. This review summarises the critical role of AMPK-mediated autophagy, inflammation and immunity by upstream and downstream signalling during receptor activator of nuclear factor kappa-B ligand-induced osteoclast differentiation and function. This pathway may provide therapeutic targets for bone-related diseases, as well as function as a biomarker for bone homoeostasis.

Metformin therapy and hip fracture risk among patients with type II diabetes mellitus: A population-based cohort study

BACKGROUND

This study aimed to investigate the potential association of exposure to metformin therapy with the risk of hip fracture in adult patients with type II diabetes. We included patients with diabetes who were registered in the 2010 sample cohort database of the National Health Insurance Service in South Korea.

METHODS

The patients who had been prescribed continuous oral metformin therapy for a 1-year period in 2010 were defined as the metformin group, while those who were not prescribed metformin during the same period were classified as the control group. The primary endpoint of this study was the development of hip fracture between January 2011 and December 2015.

RESULTS

A total of 64,878 patients (31,300 patients in the metformin group and 32,439 patients in the control group) were included in this study. Among those, 1655 patients (2.6%) had experienced a hip fracture. After a propensity score matching, a total of 37,378 patients (18,689 patients in each group) were included in the analysis. Using a time-dependent Cox regression analysis on the propensity score-matched cohort, the exposure to metformin was not significantly associated with the development of hip fracture compared to the control group (hazard ratio: 1.00, 95% confidence interval: 0.86 to 1.16; P = 0.985). Similar results were observed using sensitivity analysis of a multivariable time-dependent Cox regression model of the entire cohort (hazard ratio: 0.78, 95% confidence interval: 0.36 to 1.69; P = 0.525).

CONCLUSIONS

This population-based cohort study in South Korea showed that there was no significant association between the exposure to metformin therapy and hip fracture in patients with type II diabetes mellitus.

Metformin: Sentinel of the Epigenetic Landscapes That Underlie Cell Fate and Identity

The biguanide metformin is the first drug to be tested as a gerotherapeutic in the clinical trial TAME (Targeting Aging with Metformin). The current consensus is that metformin exerts indirect pleiotropy on core metabolic hallmarks of aging, such as the insulin/insulin-like growth factor 1 and AMP-activated protein kinase/mammalian Target Of Rapamycin signaling pathways, downstream of its primary inhibitory effect on mitochondrial respiratory complex I. Alternatively, but not mutually exclusive, metformin can exert regulatory effects on components of the biologic machinery of aging itself such as chromatin-modifying enzymes. An integrative metabolo-epigenetic outlook supports a new model whereby metformin operates as a guardian of cell identity, capable of retarding cellular aging by preventing the loss of the information-theoretic nature of the epigenome. The ultimate anti-aging mechanism of metformin might involve the global preservation of the epigenome architecture, thereby ensuring cell fate commitment and phenotypic outcomes despite the challenging effects of aging noise. Metformin might therefore inspire the development of new gerotherapeutics capable of preserving the epigenome architecture for cell identity. Such gerotherapeutics should replicate the ability of metformin to halt the erosion of the epigenetic landscape, mitigate the loss of cell fate commitment, delay stochastic/environmental DNA methylation drifts, and alleviate cellular senescence. Yet, it remains a challenge to confirm if regulatory changes in higher-order genomic organizers can connect the capacity of metformin to dynamically regulate the three-dimensional nature of epigenetic landscapes with the 4th dimension, the aging time.

Effects of Targeted Delivery of Metformin and Dental Pulp Stem Cells on Osteogenesis via Demineralized Dentin Matrix under High Glucose Conditions

High glucose condition inhibited osteoblast differentiation could be a main mechanism contributing to the decreased bone repair associated with diabetes. Metformin, a widely prescribed antidiabetic drug, was shown to have osteogenic properties in our previous study. Transplanted mesenchymal stromal cells (MSCs) may differentiate into osteoblasts and promote bone regeneration. Our study aimed to combine the benefits of metformin and MSCs transplantation on osteogenesis in high glucose conditions. We developed demineralized dentin matrix (DDM) as a carrier to target deliver metformin and dental pulp-derived MSCs (DPSCs). We collected clinically discarded teeth, isolated DPSCs from the dental pulp, and prepared the DDM from the dentin. The DDM was observed by scanning electron microscopy and was found to have well-distributed tubes. Then, metformin was loaded into the DDM to form the DDM-Met complex (DDM-Met); DDM-Met released metformin at a favorable concentration. The DPSCs seeded with the DDM-Met in a high glucose medium showed satisfactory attachment and viability together with increased mineralization and upregulated osteogenesis-related genes, including alkaline phosphatase (ALP), osteocalcin (OCN), runt-related transcription factor 2 (Runx2), and osteopontin (OPN). A possible mechanism of the enhanced osteogenic differentiation of DPSCs was explored, and the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway was found to play a role in the enhancement of osteogenesis. DDM-Met appeared to be a successful metformin and DPSC carrier that allowed for the local delivery of metformin and DPSCs in high glucose conditions. DDM-Met-DPSC construct has promising prospects to promote osteogenesis and enhance the much-needed diabetic bone regeneration.

The Effects of Diabetes and Diabetic Medications on Bone Health

The incidence and prevalence of diabetes continues to increase, and proper understanding of the adverse effects on bone metabolism is important. This review attempts to discuss the pathophysiology of the effects of diabetes and diabetic medications on bone metabolism and bone health. In addition, this review will address the mechanisms resulting in increased fracture risk and delayed bone healing to better treat and manage diabetic patients in the orthopedic clinical setting.

Diabetes Mellitus and Osteoporosis Correlation: Challenges and Hopes

Diabetes and osteoporosis are two common diseases with different complications. Despite different therapeutic strategies, managing these diseases and reducing their burden have not been satisfactory, especially when they appear one after the other. In this review, we aimed to clarify the similarity, common etiology and possible common adjunctive therapies of these two major diseases and designate the known molecular pattern observed in them. Based on different experimental findings, we want to illuminate that interestingly similar pathways lead to diabetes and osteoporosis. Meanwhile, there are a few drugs involved in the treatment of both diseases, which most of the time act in the same line but sometimes with opposing results. Considering the correlation between diabetes and osteoporosis, more efficient management of both diseases, in conditions of concomitant incidence or cause and effect condition, is required.

Metformin facilitates the proliferation, migration, and osteogenic differentiation of periodontal ligament stem cells in vitro

Periodontitis is one of the main causes of tooth loss and has been confirmed as the sixth complication of diabetes. Metformin promotes the osteogenic differentiation of stem cells. Periodontal ligament stem cells (PDLSCs) are the best candidate stem cells for periodontal tissue regeneration. Herein, we aimed to identify the effects of metformin on the proliferation, migration, and osteogenic differentiation of PDLSCs in vitro. PDLSCs were isolated by limiting dilution, and their characteristics were assessed by colony formation assay and flow cytometry. Cell counting and migration assays were used to investigate the effects of metformin on proliferation and migration. The osteogenic differentiation ability of PDLSCs was detected by alkaline phosphatase (ALP) activity and Alizarin Red S staining. Gene and protein levels of osteogenesis-related markers were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis, respectively. Metformin treatment at 10 μM did not affect PDLSC proliferation, while at 50 and 100 μM, metformin time-dependently enhanced PDLSC proliferation and significantly increased cell numbers after 5 and 7 days of stimulation (P <  0.05). In addition, 50 μM metformin exhibited a maximal effect on migration, ALP activity, and mineral deposition (P <  0.05). Furthermore, 50 μM metformin significantly upregulated the gene expression levels of ALP, BSP, OPN, OCN, and Runx2 and the protein expression of ALP and Runx2 (P <  0.05). In summary, our study confirms that metformin facilitates the proliferation, migration, and osteogenic differentiation of PDLSCs in vitro and could be used as a new strategy for periodontal tissue regeneration.