The effect of metformin versus placebo in combination with insulin analogues on bone mineral density and trabecular bone score in patients with type 2 diabetes mellitus: a randomized placebo-controlled trial

The microbial metabolite imidazole propionate dysregulates bone homeostasis by inhibiting AMP-activated protein kinase (AMPK) signaling

Microbial metabolites provide numerous benefits to the human body but can also contribute to diseases such as obesity, diabetes, cancer, and bone disorders. However, the role of imidazole propionate (ImP), a histidine-derived metabolite produced by the intestinal microbiome, in bone metabolism and the development of osteoporosis is still poorly understood. In this study, we investigated the role of ImP and its underlying mechanisms in regulating bone homeostasis. When ImP was administered to 8-week-old mice for 4 weeks, bone loss was observed, along with a decrease in alkaline phosphatase-positive osteoblast cells. Additionally, bone marrow stromal cells (BMSCs) isolated from ImP-treated mice exhibited reduced osteogenic potential. In BMSCs from control mice, ImP treatment inhibited BMP2-induced osteoblast differentiation while promoting adipocyte differentiation. However, ImP had no effect on RANKL-induced osteoclast differentiation or activity in bone marrow macrophages. Mechanistically, ImP treatment increased p38γ phosphorylation and decreased AMPK (T172) phosphorylation in BMSCs. Suppression of p38γ expression using si-p38γ reversed the inhibitory effects of ImP on osteoblast differentiation, with a concurrent increase in AMPK (T172) phosphorylation. Conversely, ImP stimulated adipocyte differentiation by decreasing AMPK (T172) phosphorylation. Treatment with the AMPK agonist metformin significantly reversed the inhibitory effects of ImP on osteoblast differentiation and the promotion of adipocyte differentiation, along with enhanced AMPK (T172) phosphorylation. These findings suggest that the microbial metabolite ImP may disrupt bone homeostasis by stimulating p38γ phosphorylation and inhibiting the AMPK pathway, presenting a potential therapeutic target for managing metabolic bone diseases.

Effects of Glucagon-Like Peptide-1 Receptor Agonists on Bone Metabolism in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Background

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are an intriguing class of antihyperglycemic drugs for type 2 diabetes mellitus (T2DM). Such drugs not only play a primary role in regulating blood glucose levels but also exhibit additional pleiotropic effects, including potential impacts on bone metabolism and fracture risk. However, the mechanism of such drugs is unclear. The purpose of this study was to evaluate the effect of GLP-1 RAs on bone metabolism in T2DM.

Methods

From database inception to May 1, 2023, the searches were conducted on multiple databases such as Web of Science, Embase, PubMed, CNKI, the Cochrane Library, Wanfang, and VIP. We systematically collected all randomized controlled trials of bone metabolism in patients with T2DM treated with GLP-1 RAs. The quality evaluation was performed according to the Cochrane Handbook for Systematic Reviews of Interventions. Data extraction was analyzed using Review Manager 5.4 software, and funnel plots were drawn to evaluate publication bias.

Results

Twenty-six randomized controlled trials that met the inclusion criteria were included, involving a total of 2268 participants. In this study, compared to other antidiabetic drugs or placebo, GLP-1 RAs were found to significantly increase serum calcium (mean difference (MD) = 0.05, 95% confidence interval (CI) (0.01, 0.09), P = 0.002], bone alkaline phosphatase [standardized MD (SMD) = 0.76, 95% CI (0.29, 1.24), and P = 0.001), and osteocalcin (SMD = 2.04, 95% CI (0.99, 3.08), and P = 0.0001) in T2DM. Specifically, liraglutide increased procollagen type 1 N-terminal propeptide (SMD = 0.45, 95% CI (0.01, 0.89), and P = 0.04). GLP-1 RAs were also associated with a reduction in cross-linked C-terminal telopeptides of type I collagen (SMD = -0.36, 95% CI (-0.70, -0.03), and P = 0.03). In additionally, GLP-1 RAs increased lumbar spine bone mineral density (BMD) (SMD = 1.04, 95% CI (0.60, 1.48), and P < 0.00001) and femoral neck BMD (SMD = 1.29, 95% CI (0.36, 2.23), and P = 0.007).

Conclusions

GLP-1 RAs can not only improve BMD in the lumbar spine and femoral neck of patients with T2DM but also protect bone health by inhibiting bone resorption and promoting bone formation. Systematic Review Registration. PROSPERO, identifier CRD42023418166.

The effect of starting metformin on bone mineral density among women with type 2 diabetes in the Study of Women's Health Across the Nation (SWAN)

We examined longitudinal changes in BMD among women in the mid-life starting metformin. Study subjects were 57 years old (mean), and 36% were White. Women initiating metformin were similar to noninitiators. During the 3-year follow-up, BMD loss at all anatomic areas was similar between groups and in subgroups including baseline fasting blood glucose.

PURPOSE/INTRODUCTION

Women with type 2 diabetes have higher bone mineral density (BMD), experience slower BMD loss, but have increased fracture risk. Data regarding the effect of metformin on BMD remain discordant. We examined longitudinal changes in BMD among women in the mid-life starting metformin.

METHODS

Participants in the Study of Women's Health Across the Nation (SWAN), a diverse community-based US cohort, with BMD measurements were evaluated. Propensity score matching helped balance baseline characteristics of metformin initiators versus noninitiators. Mixed model regression tested the change in BMD between groups.

RESULTS

Subjects (n = 248) were 57.4 years old (mean), and 35.9% were White. Women initiating metformin (n = 124) were similar to noninitiators (n = 124) in age and race/ethnicity. During the median 3-year follow-up, BMD loss at all anatomic areas was similar between the metformin initiators and nonusers (all p > 0.3). Subgroup analyses including baseline fasting blood glucose showed no between-group differences. Initiation of metformin (vs. not) in peri-menopausal women was not associated with BMD changes.

CONCLUSIONS

Women in the mid-life starting metformin had longitudinal changes in BMD very similar to other women not starting metformin.

Trabecular Bone Score (TBS) in Individuals with Type 2 Diabetes Mellitus: An Updated Review

Bone fragility is a complication of type 2 diabetes mellitus (T2DM) that has been identified in recent decades. Trabecular bone score (TBS) appears to be more accurate than bone mineral density (BMD) in diabetic bone disease, particularly in menopausal women with T2DM, to independently capture the fracture risk. Our purpose was to provide the most recent overview on TBS-associated clinical data in T2DM. The core of this narrative review is based on original studies (PubMed-indexed journals, full-length, English articles). The sample-based analysis (n = 11, N = 4653) confirmed the use of TBS in T2DM particularly in females (females/males ratio of 1.9), with ages varying between 35 and 91 (mean 65.34) years. With concern to the study design, apart from the transversal studies, two others were prospective, while another two were case-control. These early-post-pandemic data included studies of various sample sizes, such as: males and females (N of 245, 361, 511, and 2294), only women (N of 80, 96, 104, 243, 493, and 887), and only men (N = 169). Overall, this 21-month study on published data confirmed the prior profile of BMD-TBS in T2DM, while the issue of whether checking the fracture risk is mandatory in adults with uncontrolled T2DM remains to be proven or whether, on the other hand, a reduced TBS might function as a surrogate marker of complicated/uncontrolled T2DM. The interventional approach with bisphosphonates for treating T2DM-associated osteoporosis remains a standard one (n = 2). One control study on 4 mg zoledronic acid showed after 1 year a statistically significant increase of lumbar BMD in both diabetic and non-diabetic groups (+3.6%, p = 0.01 and +6.2%, p = 0.01, respectively). Further studies will pinpoint additive benefits on glucose status of anti-osteoporotic drugs or will confirm if certain glucose-lowering regimes are supplementarily beneficial for fracture risk reduction. The novelty of this literature research: these insights showed once again that the patients with T2DM often have a lower TBS than those without diabetes or with normal glucose levels. Therefore, the decline in TBS may reflect an early stage of bone health impairment in T2DM. The novelty of the TBS as a handy, non-invasive method that proved to be an index of bone microarchitecture confirms its practicality as an easily applicable tool for assessing bone fragility in T2DM.

Effect of Antidiabetic Drugs on Bone Health in Patients with Normal Renal Function and in Chronic Kidney Disease (CKD): Insight into Clinical Challenges in the Treatment of Type 2 Diabetes

Among the metabolic changes occurring during the course of type 2 diabetes (T2DM) and diabetic kidney disease (DKD), impaired bone health with consequent increased fracture risk is one of the most complex and multifactorial complications. In subjects with diabetic kidney disease, skeletal abnormalities may develop as a consequence of both conditions. In the attempt to define a holistic approach to diabetes, potential effects of various classes of antidiabetic drugs on the skeleton should be considered in the setting of normal kidney function and in DKD. We reviewed the main evidence on these specific topics. Experimental studies reported potential beneficial and harmful effects on bone by different antidiabetics, with few data available in DKD. Clinical studies specifically designed to evaluate skeletal effects of antidiabetics have not been performed; notwithstanding, data gleaned from randomized controlled trials and intervention studies did not completely confirm observations made by basic research. In the aggregate, evidence from meta-analyses of these studies suggests potential positive effects on fracture risk by metformin and glucagon-like peptide-1 receptor agonists, neutral effects by dipeptidyl peptidase-4 inhibitors, sodium-glucose cotransporter-2 inhibitors, and sulfonylureas, and negative effects by insulin and thiazolidinediones. As no clinical recommendations on the management of antidiabetic drugs currently include fracture risk assessment among the main goal of therapy, we propose an integrated approach with the aim of defining a patient-centered management of diabetes in chronic kidney disease (CKD) and non-CKD patients. Future clinical evidence on the skeletal effects of antidiabetics will help in optimizing the approach to a personalized and more effective therapy of diabetes.

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.

Update on the clinical use of trabecular bone score (TBS) in the management of osteoporosis: results of an expert group meeting organized by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO), and the International Osteoporosis Foundation (IOF) under the auspices of WHO Collaborating Center for Epidemiology of Musculoskeletal Health and Aging

PURPOSE

Trabecular bone score (TBS) is a grey-level textural measurement acquired from dual-energy X-ray absorptiometry lumbar spine images and is a validated index of bone microarchitecture. In 2015, a Working Group of the European Society on Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) published a review of the TBS literature, concluding that TBS predicts hip and major osteoporotic fracture, at least partly independent of bone mineral density (BMD) and clinical risk factors. It was also concluded that TBS is potentially amenable to change as a result of pharmacological therapy. Further evidence on the utility of TBS has since accumulated in both primary and secondary osteoporosis, and the introduction of FRAX and BMD T-score adjustment for TBS has accelerated adoption. This position paper therefore presents a review of the updated scientific literature and provides expert consensus statements and corresponding operational guidelines for the use of TBS.

METHODS

An Expert Working Group was convened by the ESCEO and a systematic review of the evidence undertaken, with defined search strategies for four key topics with respect to the potential use of TBS: (1) fracture prediction in men and women; (2) initiating and monitoring treatment in postmenopausal osteoporosis; (3) fracture prediction in secondary osteoporosis; and (4) treatment monitoring in secondary osteoporosis. Statements to guide the clinical use of TBS were derived from the review and graded by consensus using the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

A total of 96 articles were reviewed and included data on the use of TBS for fracture prediction in men and women, from over 20 countries. The updated evidence shows that TBS enhances fracture risk prediction in both primary and secondary osteoporosis, and can, when taken with BMD and clinical risk factors, inform treatment initiation and the choice of antiosteoporosis treatment. Evidence also indicates that TBS provides useful adjunctive information in monitoring treatment with long-term denosumab and anabolic agents. All expert consensus statements were voted as strongly recommended.

CONCLUSION

The addition of TBS assessment to FRAX and/or BMD enhances fracture risk prediction in primary and secondary osteoporosis, adding useful information for treatment decision-making and monitoring. The expert consensus statements provided in this paper can be used to guide the integration of TBS in clinical practice for the assessment and management of osteoporosis. An example of an operational approach is provided in the appendix. This position paper presents an up-to-date review of the evidence base, synthesised through expert consensus statements, which informs the implementation of Trabecular Bone Score in clinical practice.

The combination of linagliptin and metformin rescues bone loss in type 2 diabetic osteoporosis

To develop an approach to reduce the type 2 diabetic osteoporosis, this study investigated the protective effects of the combination of linagliptin and metformin against osteoporosis. Micro-CT and dynamic biomechanical measurements were used to determine the bone microstructure in the type 2 diabetes mellitus (T2DM) rats. MC3T3-E1 cells were cultured in high glucose environments. In addition, we used qRT-PCR and Western blotting to assess osteogenic markers and p38 and extracellular signal-regulated kinase (ERK) protein expression. The combination of linagliptin and metformin treatment significantly restored bone micro-architecture and femoral mechanical properties in the T2DM rats. In contrast, bone markers including osteocalcin, NH2-terminal propeptide of type I procollagen, COOH-terminal telopeptide of type I collagen and tartrate-resistant acid phosphatase were significantly reduced by the combination of linagliptin and metformin treatment. We used high glucose treated MC3T3-E1 cells to mimic the condition of T2DM. Linagliptin combined with metformin treatment significantly inhibited the phosphorylation of p38 and ERK induced by high glucose treatment. In conclusion, the linagliptin combined with metformin treatment improved the rats' bone mineral density, bone structure, and osteogenic markers. Both p38 and ERK phosphorylation were reduced in high glucose MC3T3-E1 cells. Our findings highlight the potential of linagliptin combined with metformin for the treatment of T2DM-related osteoporosis.

Effects of metformin on bone mineral density and bone turnover markers: a systematic review and meta-analysis

OBJECTIVES

Metformin is associated with osteoblastogenesis and osteoclastogenesis. This study aims to investigate the impacts of metformin therapy on bone mineral density (BMD) and bone turnover markers.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

METHODS

Searches were carried out in PubMed, EMBASE, Web of science, Cochrane library, ClinicalTrials.gov from database inception to 26 September 2022. Two review authors assessed trial eligibility in accordance with established inclusion criteria. The risk of bias was assessed using the Cochrane Risk of Bias tool (RoB V.2.0). Data analysis was conducted with Stata Statistical Software V.16.0 and Review Manager Software V.5.3.

RESULTS

A total of 15 studies with 3394 participants were identified for the present meta-analysis. Our pooled results indicated that metformin had no statistically significant effects on BMD at lumbar spine (SMD=-0.05, 95% CI=-0.19 to 0.09, p=0.47, participants=810; studies=7), at femoral (MD=-0.01 g/cm2, 95% CI=-0.04 to 0.01 g/cm2, p=0.25, participants=601; studies=3) and at hip (MD=0.01 g/cm2, 95% CI=-0.02 to 0.03 g/cm2, p=0.56, participants=634; studies=4). Metformin did not lead to significant change in osteocalcin, osteoprotegerin and bone alkaline phosphatase. Metformin induced decreases in N-terminal propeptide of type I procollagen (MD=-6.09 µg/L, 95% CI=-9.38 to -2.81 µg/L, p=0.0003, participants=2316; studies=7) and C-terminal telopeptide of type I collagen (MD=-55.80 ng/L, 95% CI=-97.33 to -14.26 ng/L, p=0.008, participants=2325; studies=7).

CONCLUSION

This meta-analysis indicated that metformin had no significant effect on BMD. Metformin decreased some bone turnover markers as N-terminal propeptide of type I procollagen and C-terminal telopeptide of type I collagen. But the outcomes should be interpreted with caution due to several limitations.

mTOR Signaling Pathway in Bone Diseases Associated with Hyperglycemia

The interplay between bone and glucose metabolism has highlighted hyperglycemia as a potential risk factor for bone diseases. With the increasing prevalence of diabetes mellitus worldwide and its subsequent socioeconomic burden, there is a pressing need to develop a better understanding of the molecular mechanisms involved in hyperglycemia-mediated bone metabolism. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that senses extracellular and intracellular signals to regulate numerous biological processes, including cell growth, proliferation, and differentiation. As mounting evidence suggests the involvement of mTOR in diabetic bone disease, we provide a comprehensive review of its effects on bone diseases associated with hyperglycemia. This review summarizes key findings from basic and clinical studies regarding mTOR's roles in regulating bone formation, bone resorption, inflammatory responses, and bone vascularity in hyperglycemia. It also provides valuable insights into future research directions aimed at developing mTOR-targeted therapies for combating diabetic bone diseases.

Bone parameters in T1D and T2D assessed by DXA and HR-pQCT - A cross-sectional study: The DIAFALL study

INTRODUCTION/AIM

People with type 1 diabetes(T1D) and type 2 diabetes(T2D) have an increased risk of fractures due to skeletal fragility. We aimed to compare areal bone mineral density(aBMD), volumetric BMD(vBMD), cortical and trabecular measures, and bone strength parameters in participants with diabetes vs. controls.

METHODS

In a cross-sectional study, we included participants with T1D(n = 111), T2D(n = 106) and controls(n = 328). The study comprised of whole-body DXA and HR-pQCT scans, biochemistry, handgrip strength(HGS), Timed Up and GO(TUG), vibration perception threshold (VPT), questionnaires, medical histories, alcohol use, and previous fractures. Group comparisons were performed after adjustment for sex, age, BMI, diabetes duration, HbA1c, alcohol, smoking, previous fractures, postmenopausal, HGS, TUG, and VPT.

RESULTS

We found decreased aBMD in participants with T1D at the femoral neck(p = 0.028), whereas T2D had significantly higher aBMD at peripheral sites(legs, arms, p < 0.01) vs. controls. In T1D we found higher vBMD(p < 0.001), cortical vBMD (p < 0.001), cortical area(p = 0.002) and thickness(p < 0.001), lower cortical porosity(p = 0.008), higher stiffness(p = 0.002) and failure load(p = 0.003) at radius and higher vBMD(p = 0.003), cortical vBMD(p < 0.001), bone stiffness(p = 0.023) and failure load(p = 0.044) at the tibia than controls. In T2D we found higher vBMD(p < 0.001), cortical vBMD(p < 0.001), trabecular vBMD(p < 0.001), cortical area (p < 0.001) and thickness (p < 0.001), trabecular number (p = 0.024), lower separation(p = 0.010), higher stiffness (p < 0.001) and failure load (p < 0.001) at the radius and higher total vBMD(p < 0.001), cortical vBMD(p < 0.011), trabecular vBMD(p = 0.001), cortical area(p = 0.002) and thickness(p = 0.021), lower trabecular separation(p = 0.039), higher stiffness(p < 0.001) and failure load(p = 0.034) at tibia compared with controls.

CONCLUSION

aBMD measures were as expected but favorable bone microarchitecture and strength parameters were seen at the tibia and radius for T1D and T2D.

The assessment value of pathological condition of serum adiponectin and amylin in primary osteoporosis and its correlation analysis with bone metabolism indexes

Background

This paper explores the assessment value of pathological condition of serum adiponectin (APN) and amylin in primary osteoporosis (POP) and their correlation with bone metabolism indexes.

Methods

From January 2019 to June 2021, 79 cases of POP patients were selected as the research objects. A test of the patients' bone density was conducted, and clinical grading of POP was via T value (normal, mild, moderate, severe). The analysis of the assessment value of pathological condition of serum APN and amylin for POP and their association with bone metabolism indexes in patients was performed.

Results

APN and amylin in patients were declined with POP's aggravation. APN of 5.15 μg/mL or less and amylin of 15.38 pmol/L or less were risk factors influencing the aggravation of pathological condition of POP (P< 0 .0 5). The area under the curve (AUC) of combined detection of APN and amylin to assess the severity of POP was elevated vs. alone test of amylin (P< 0.05). 25-hydroxyvitamin D (25-(OH) D) and total type 1 procollagen amino-terminal propeptide (t-PINP) in patients were descended with the aggravation of pathological condition of osteoporosis (P < 0.05). At the same time, no distinct differences were presented in the three groups of type I collagen hydroxyl terminal peptide b degradation product (β-CTX) and N-terminal osteocalcin (N-MID) (P> 0.05). APN, amylin, 25-(OH)D, β-CTX, and t-PINP were negatively linked with POP clinical grade (P< 0.05). APN and amylin were associated with 25-(OH) D, β-CTX, t-PINP (P< 0.05), and APN and amylin were not linked with N-MID (P> 0.05).

Conclusions

Serum APN and amylin are provided with evaluation values for the severity of POP and are associated with bone metabolism in patients.

A narrative review of diabetic bone disease: Characteristics, pathogenesis, and treatment

Recently, the increasing prevalence of diabetes mellitus has made it a major chronic illness which poses a substantial threat to human health. The prevalence of osteoporosis among patients with diabetes mellitus has grown considerably. Diabetic bone disease is a secondary osteoporosis induced by diabetes mellitus. Patients with diabetic bone disease exhibit variable degrees of bone loss, low bone mineral density, bone microarchitecture degradation, and increased bone fragility with continued diabetes mellitus, increasing their risk of fracture and impairing their ability to heal after fractures. At present, there is extensive research interest in diabetic bone disease and many significant outcomes have been reported. However, there are no comprehensive review is reported. This review elaborates on diabetic bone disease in the aspects of characteristics, pathogenesis, and treatment.

Association of metformin use with fracture risk in type 2 diabetes: A systematic review and meta-analysis of observational studies

AIMS

Increasing evidence suggests that metformin can affect bone metabolism beyond its hypoglycemic effects in diabetic patients. However, the effects of metformin on fracture risk in type 2 diabetes mellitus (T2DM) patients remain unclear. A systematic review and meta-analysis were performed in this study to evaluate the association between metformin application and fracture risk in T2DM patients based on previous studies published until June 2021.

METHODS

A systematic search was performed to collect publications on metformin application in T2DM patients based on PubMed, Embase, Cochran, and Web of Science databases. Meta-analysis was performed by using a random-effects model to estimate the summary relative risks (RRs) with 95% confidence intervals (CIs). Subgroup analyses based on cohort/case-control and ethnicity and sensitivity analyses were also performed.

RESULTS

Eleven studies were included in the meta-analysis. Results demonstrated metformin use was not significantly associated with a decreased risk of fracture (RR, 0.91; 95% CI, 0.81-1.02; I^{2 =} 96.8%). Moreover, metformin use also demonstrated similar results in subgroup analyses of seven cohort studies and four case-control studies, respectively (RR, 0.90; 95% CI, 0.76-1.07; I^{2 =} 98.0%; RR, 0.96; 96% CI, 0.89-1.03; I^{2 =} 53.7%). Sensitivity analysis revealed that there was no publication bias.

CONCLUSION

There was no significant correlation between fracture risk and metformin application in T2DM patients. Due to a limited number of existing studies, further research is needed to make a definite conclusion for clinical consensus.

Fracture Patterns in Type 1 and Type 2 Diabetes Mellitus: A Narrative Review of Recent Literature

PURPOSE OF REVIEW

In this narrative review, we have summarized the literature on fracture risk in T1DM and T2DM with a special focus on fracture site, time patterns, glucose-lowering drugs, and micro- and macrovascular complications.

RECENT FINDINGS

T1DM and T2DM were associated with an overall increased fracture risk, with preferent locations at the hip, vertebrae, humerus, and ankle in T1DM and at the hip, vertebrae, and likely humerus, distal forearm, and foot in T2DM. Fracture risk was higher with longer diabetes duration and the presence of micro- and macrovascular complications. In T2DM, fracture risk was higher with use of insulin, sulfonylurea, and thiazolidinediones and lower with metformin use. The increased fracture risk in T1DM and T2DM concerns specific fracture sites, and is higher in subjects with longer diabetes duration, vascular complications, and in T2DM with the use of specific glucose-lowering medication.

Osteosarcopenia and trabecular bone score in patients with type 2 diabetes mellitus

OBJECTIVE

To evaluate the prevalence of osteosarcopenia and the association of osteosarcopenia with trabecular bone score (TBS) in a group of patients with type 2 diabetes mellitus(T2DMG) compared with a paired control group (CG).

METHODS

Cross-sectional study with men and women ≥ 50 years recruited by convenience. Patients in both groups answered questionnaires and underwent evaluation of bone mineral density (BMD), handgrip strength (HGS), and TBS. The T2DMG also underwent a gait speed (GS) test. Sarcopenia was defined as low lean mass plus low HGS or GS according to the Foundation for the National Institute of Health Sarcopenia Project, and osteosarcopenia was deemed present when sarcopenia was associated with osteopenia, osteoporosis, or low-energy trauma fractures.

RESULTS

The T2DMG (n = 177) and CG (n = 146) had, respectively, mean ages of 65.1 ± 8.2 years and 68.8 ± 11.0 years and 114 (64.4%) and 80 (54.7%) women. T2DMG versus the CG had higher rates of osteosarcopenia (11.9% versus 2.14%, respectively, p = 0.010), sarcopenia (12.9% versus 5.4%, respectively, p < 0.030), and fractures (29.9% versus 18.5%, respectively, p = 0.019), and lower HGS values (24.4 ± 10.3 kg versus 30.9 ± 9.15 kg, respectively, p < 0.001), but comparable BMD values. Mean TBS values were 1.272 ± 0.11 and 1.320 ± 0.12, respectively (p = 0.001). On multivariate analysis, age, greater waist circumference, fractures, and osteoporosis increased the risk of degraded TBS. Osteosarcopenia was associated with diabetes complications (p = 0.03), calcium and vitamin D supplementation (p = 0.01), and all components of osteosarcopenia diagnosis (p < 0.05).

CONCLUSION

Compared with the CG, the T2DMG had a higher prevalence of osteosarcopenia, sarcopenia, and fractures and lower bone quality assessed by TBS.

Effect of Dipeptidyl Peptidase-4 Inhibitors on Bone Health in Patients with Type 2 Diabetes Mellitus

Patients with type 2 diabetes (T2DM) have a higher risk of bone fracture even when bone mineral density (BMD) values are normal. The trabecular bone score (TBS) was recently developed and used for evaluating bone strength in various diseases. We investigated the effect of DPP-4 inhibitors on bone health using TBS in patients with T2DM. This was a single-center, retrospective case-control study of 200 patients with T2DM. Patients were divided into two groups according to whether they were administered a DPP-4 inhibitor (DPP-4 inhibitor group vs. control group). Parameters related to bone health, including BMD, TBS, and serum markers of calcium homeostasis, were assessed at baseline and after one year of treatment. We found TBS values increased in the DPP-4 group and decreased in the control, indicating a significant difference in delta change between them. The BMD increased in both groups, with no significant differences in delta change between the two groups observed. Serum calcium and 25-hydroxy vitamin D3 increased only in the DPP-4 inhibitor group, while other glycemic parameters did not show significant differences between the two groups. Treatment with DPP-4 inhibitors was associated with favorable effects on bone health evaluated by TBS in patients with T2DM.

Effect of metformin and insulin vs. placebo and insulin on whole body composition in overweight patients with type 2 diabetes: a randomized placebo-controlled trial

Some studies indicate potential beneficial effects of metformin on body composition and bone. This trial compared metformin + insulin vs placebo + insulin. Metformin treatment had a small but positive effect on bone quality in the peripheral skeleton, reduced weight gain, and resulted in a more beneficial body composition compared with placebo in insulin-treated patients with type 2 diabetes.

INTRODUCTION

Glucose-lowering medications affect body composition. We assessed the long-term effects of metformin compared with placebo on whole body bone and body composition measures in patients with type 2 diabetes mellitus.

METHODS

This was a sub-study of the Copenhagen Insulin and Metformin Therapy trial, which was a double-blinded randomized placebo-controlled trial assessing 18-month treatment with metformin compared with placebo, in combination with different insulin regimens in patients with type 2 diabetes mellitus (T2DM). The sub-study evaluates the effects on bone mineral content (BMC), density (BMD), and body composition from whole body dual-energy X-ray absorptiometry (DXA) scans which were assessed at baseline and after 18 months.

RESULTS

Metformin had a small, but positive, (p < 0.05) effect on subtotal, appendicular, and legs BMC and BMD compared with placebo. After adjustment for sex, age, vitamin D, smoking, BMI, T2DM duration, HbA1c, and insulin dose, the effects on appendicular BMC and BMD persisted (p < 0.05 for both). The changes in appendicular BMC and BMD corresponded approximately to a 0.7% and 0.5% increase in the metformin group and 0.4% and 0.4% decrease in the placebo group, respectively. These effects were mostly driven by an increase in BMC and BMD in the legs and a loss of BMC and BMD in the arms. During 18 months, all participants increased in weight, fat mass (FM), FM%, and lean mass (LM), but decreased in LM%. The metformin group increased less in weight (subtotal weight (weight-head) - 2.4 [- 3.5, - 1.4] kg, p value < 0.001) and FM (- 1.5 [- 2.3, - 0.8] kg, p value < 0.001) and decreased less in LM% (0.6 [0.2, 1.1] %, p value < 0.001) compared with the placebo group.

CONCLUSION

Metformin treatment had a small positive effect on BMC and BMD in the peripheral skeleton and reduced weight gain compared with placebo in insulin-treated patients with T2DM.

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.

Glycemic Control and Insulin Treatment Alter Fracture Risk in Older Men With Type 2 Diabetes Mellitus

Diabetes mellitus among older men has been associated with increased bone mineral density but paradoxically increased fracture risk. Given the interactions among medication treatment, glycemic control, and diabetes-associated comorbidities, the relative effects of each factor remains unclear. This retrospective study includes 652,901 male veterans aged ≥65 years with diabetes and baseline hemoglobin A1c (HbA1c) value. All subjects received primary care in the Veterans Health Administration (VHA) from 2000 to 2010. Administrative data included ICD9 diagnoses and pharmacy records and was linked to Medicare fee-for-service data. Hazard ratios (HR) for any clinical fracture and hip fracture were calculated using competing risk hazards models, adjusted for fracture risk factors including age, race/ethnicity, body mass index (BMI), alcohol and tobacco use, rheumatoid arthritis, corticosteroid use, as well as diabetes-related comorbidities including cardiovascular disease, chronic kidney disease, and peripheral neuropathy. HbA1c <6.5% was associated with a higher risk of any clinical fracture (HR = 1.08, 95% confidence interval [CI] 1.06-1.11) compared with the reference HbA1c of 7.5% to 8.5%. Fracture risk was not increased among those with A1c ≥8.5%, nor among those with A1c 6.5% to 7.5%. Use of insulin was independently associated with greater risk of fracture (HR = 1.10, 95% CI 1.07-1.12). There was a significant interaction between insulin use and HbA1c level, (p < 0.001), such that those using insulin with HbA1c <6.5% had HR = 1.23 and those with HbA1c 6.5% to 7.5% had HR = 1.15. Metformin use was associated with decreased fracture risk (HR = 0.88, 95% CI 0.87-0.90). We conclude that among older men with diabetes, those with HbA1c lower than 6.5% are at increased risk for any clinical and hip fracture. Insulin use is associated with higher fracture risk, especially among those with tight glycemic control. Our findings demonstrate the importance of the treatment regimen and avoiding hypoglycemia for fracture prevention in older men with diabetes. © 2019 American Society for Bone and Mineral Research.

Preventative effects of metformin on glucocorticoid-induced osteoporosis in rats

This study evaluated the preventative effects of metformin (Met) on glucocorticoid (GC)-induced osteoporosis in a rat model, compared with alendronate (Aln). Twenty-eight 3-month-old female Sprague-Dawley rats were randomly assigned into four groups: normal control (Ctr), methylprednisolone (MP, 13 mg/kg/day, sc, 5 days per week), MP plus Aln orally (1 mg/kg/day), and MP plus Met orally (200 mg/kg/day). After 9 weeks, serum bone metabolic biochemistry, bone densitometry and histomorphometry were performed. The GC-induced osteoporosis model was characterized by decreased osteocalcin, increased tartrate-resistant acid phosphatase-5b (TRAP-5b), and decreased bone mineral density (BMD) in the femur and fifth lumbar vertebra (L5). Histomorphometrically, MP significantly decreased trabecular bone volume, decreased bone formation and increased bone resorption in proximal metaphysis, compared with the controls. Aln and Met increased the BMDs of femur (0.305 ± 0.011 vs. 0.280 ± 0.012, P < 0.05; 0.304 ± 0.019 vs. 0.280 ± 0.012, P < 0.05) and L5 (0.399 ± 0.029 vs. 0.358 ± 0.022, P < 0.05; 0.397 ± 0.022 vs. 0.358 ± 0.022, P < 0.05), compared with the model group. Met increased osteocalcin and decreased TRAP-5b, but Aln only decreased TRAP-5b, compared with model group. In histomorphometry of tibial proximal metaphysis, Aln and Met increased trabecular bone volume (39.21 ± 2.46 vs. 30.98 ± 5.83, P < 0.05; 38.97 ± 5.56 vs. 30.98 ± 5.83, P < 0.05), while Met increased the bone formation dynamic parameters and decreased bone resorption dynamic parameters, but Aln just decreased bone resorption dynamic parameters, compared with model group significantly. These findings suggest that metformin prevents GC-induced bone loss by suppressing bone resorption and stimulating bone formation in trabecular bone. The action mode of metformin was different from alendronate, which only suppressed bone resorption.

Metformin: Mechanisms in Human Obesity and Weight Loss

PURPOSE OF REVIEW

Metformin has multiple benefits for health beyond its anti-hyperglycemic properties. The purpose of this manuscript is to review the mechanisms that underlie metformin's effects on obesity.

RECENT FINDINGS

Metformin is a first-line therapy for type 2 diabetes. Large cohort studies have shown weight loss benefits associated with metformin therapy. Metabolic consequences were traditionally thought to underlie this effect, including reduction in hepatic gluconeogenesis and reduction in insulin production. Emerging evidence suggests that metformin-associated weight loss is due to modulation of hypothalamic appetite regulatory centers, alteration in the gut microbiome, and reversal of consequences of aging. Metformin is also being explored in the management of obesity's sequelae such as hepatic steatosis, obstructive sleep apnea, and osteoarthritis. Multiple mechanisms underlie the weight loss-inducing and health-promoting effects of metformin. Further exploration of these pathways may be important in identifying new pharmacologic targets for obesity and other aging-associated metabolic diseases.

Update on the impact of type 2 diabetes mellitus on bone metabolism and material properties

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40-70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must account for increased bone fragility. This review summarizes the current knowledge on the complex effects of T2DM on bone including effects on bone cells, bone material properties and other endocrine systems that subsequently affect bone, discusses the effects of T2DM medications on bone and concludes with a model identifying factors that may contribute to poor bone quality and increased bone fragility in T2DM.