Effect of GLP-1 treatment on bone turnover in normal, type 2 diabetic, and insulin-resistant states

Linagliptin-metformin combination: A novel approach to mitigate 4-vinyl cyclohexene di epoxide and dexamethasone-induced osteoporosis in mice

Elevated levels of dipeptidyl-peptidase (DPP-4) enzyme, associated with accelerated bone resorption, are linked to both post-menopausal osteoporosis (PMO) and glucocorticoid-induced osteoporosis (GIO). Consequently, DPP-4 inhibitors, a class of anti-diabetic drugs, emerge as potential candidates for repurposing as anti-osteoporotic agents. In this study, we explored the effect of 4-week treatment with linagliptin (a DPP-4 inhibitor) and its combination with metformin on PMO and GIO in mice. PMO was induced in Balb/c mice by injecting 4-vinyl cyclohexene diepoxide (VCD), 160 mg/kg, ip for 15 days while GIO was induced by administering dexamethasone (DEX) 5 mg/kg, ip for 21 days. A significant improvement in bone architectural parameters and bone mineral density (BMD) was observed following the linagliptin-metformin combination, which was consistent with the altered bone turnover markers i.e., increased ALP, osteocalcin, BMP-2, and reduced serum calcium, TRAP, sclerostin and pro-inflammatory cytokines. Results from bone immunohistochemistry (IHC) demonstrated that the combination led to an increase in immunopositive OPG cells, while RANKL expression was diminished. Linagliptin, however, demonstrated only partial improvement in the PMO model. Conversely, in the GIO model, linagliptin did not show a significant effect except for improved BMD and sclerostin levels. Treatment with metformin did not show significant changes in either model. These findings suggest that the combination of linagliptin with metformin could alleviate the PMO and GIO, possibly through targeting AMPK and Wnt signaling pathway and thereby modulating BMP-2, sclerostin and RANKL/OPG.

The Effects of Glucagon-Like Peptide-1 Agonist Therapy on Risk of Infection, Fracture, and Early Revision in Primary Total Joint Arthroplasty

INTRODUCTION

The purpose of this study was to examine rates of infection, revision, and periprosthetic fracture following total joint arthroplasty in diabetic patients treated with and without glucagon-like peptide-1 (GLP-1) agonist therapy.

METHODS

The TriNetX Global Collaborative Network was queried for patients with diabetes mellitus undergoing primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) from 2005 to 2024. Patients taking GLP-1 agonists within 1 year of surgery were matched to patients without. Cohort matching was done according to race, sex, body mass index nicotine dependence, hemoglobin A1c, and estimated glomerular filtration rate A total of 9,400 TKA procedures and 4,488 THA procedures constituted evenly divided cohorts. Outcomes included infection, revision surgery, and periprosthetic fractures at 3 months and 1 year. Bonferroni correction applied with threshold P < 0.0041.

RESULTS

TKA: periprosthetic infection following TKA was lower in the GLP-1 group compared with the non-GLP-1 group at both 3 months (0.94% vs. 1.45%; P < 0.001) and 1-year (1.21% vs. 2.04%; P < 0.001). Rates of periprosthetic fracture following TKA were higher albeit not markedly in patients prescribed GLP-1 agonists versus patients not receiving GLP-1 agonists at 3-months (0.47% vs. 0.21%; P = 0.034, respectively) and at 1-year (0.70% vs. 0.34%; P = 0.015) postoperatively. THA: No notable differences were observed in rates of infection, revision, or periprosthetic fracture in patients undergoing THA between those prescribed GLP-1s versus patients not receiving GLP-1 agonists at 3-months and 1-year.

CONCLUSION

In this retrospective study of both TKA and THA among diabetic patients, we found that patients using GLP-1 agonists had a lower rate of periprosthetic infection following TKA. The benefits of GLP-1 therapy might limit infection risk, however additional research is needed to understand the effect these medications make on patient nutrition and bone metabolism.

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) for the treatment of type 2 diabetes mellitus: friends or foes to bone health? a narrative review of clinical studies

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a relatively new class of drugs for treatment of Type 2 Diabetes mellitus (T2DM). They have proven to be excellent drugs not only for the results on glycemic control but also for weight loss, cardiovascular protection and several other potential metabolic effects. In contrast, the effects of GLP-1RAs drugs on bone metabolism and bone mineral density (BMD) remain less clearly defined. This narrative review aimed to explore the relationship between GLP-1RAs and bone in T2DM patients by reviewing clinical studies which assessed the effects of GLP-1RAs on BMD, markers of bone turnover and fragility fractures. In vitro and animal studies have demonstrated that GLP-1RAs treatment promotes bone formation and inhibits bone resorption. However, in humans, GLP-1RAs therapy has been shown to primarily stimulate bone resorption, as evidenced by a significant increase in type I collagen C-terminal cross-linked telopeptide levels, while promoting new bone formation to a lesser extent. Clinical studies indicate that GLP-1RAs therapy, in both diabetic and non-diabetic patients, results in a reduction in BMD, which is more pronounced at skeletal sites subjected to higher mechanical loading, such as the femur and tibia, and appears to correlate with the degree of weight loss. Furthermore, in the studies reviewed, parameters related to bone quality and strength, such as Trabecular bone score (TBS), microindentation, High-resolution peripheral Quantitative Computed Tomography (HR-pQCT), and Radiofrequency Echographic Multi Spectrometry (REMS) remain unaffected by GLP-1RAs. Additionally, the incidence of fragility fractures does not increase.

Effects of Anti-Obesity Strategies on Bone Mineral Density: A Comprehensive Meta-Analysis of Randomized Controlled Trials

Background

Although an appropriate weight management strategy is essential for obese individuals, weight loss can have adverse effects on bone mineral density (BMD). We conducted a systematic review of randomized controlled trials to evaluate changes in BMD after the implementation of various weight loss strategies.

Methods

The PubMed, Embase, Web of Science, and Cochrane Library databases were searched to find articles published from database inception until June 2023. Randomized controlled trials of various treatments for obese patients that reported changes in BMD were selected. The primary outcome was BMD of the whole body, lumbar spine, and total hip, measured using dual X-ray absorptiometry.

Results

Eighteen randomized controlled trials involving 2,510 participants with obesity were included in the analysis. At follow-up examination, the BMD of the lumbar spine decreased significantly after metabolic surgery (mean difference [MD]=-0.40 g/cm2; 95% confidence interval [CI], -0.73 to -0.07; I2=0%); lifestyle and pharmacological interventions did not result in a significant decrease in BMD at any location. Metabolic surgery also produced the most substantial difference in weight, with an MD of -3.14 (95% CI, -3.82 to -2.47).

Conclusion

This meta-analysis is the first to examine the effects of all categories of anti-obesity strategies, including the use of anti-obesity medications, on BMD. Bariatric metabolic surgery can have adverse effects on BMD. Moreover, medications can be used as a treatment for weight loss without compromising bone quality.

The "Burden" of Childhood Obesity on Bone Health: A Look at Prevention and Treatment

Childhood obesity represents a multifaceted challenge to bone health, influenced by a combination of endocrine, metabolic, and mechanical factors. Excess body fat correlates with an increase in bone mineral density (BMD) yet paradoxically elevates fracture risk due to compromised bone quality and increased mechanical loading on atypical sites. Additionally, subjects with syndromic obesity, as well as individuals with atypical nutritional patterns, including those with eating disorders, show bone fragility through unique genetic and hormonal dysregulations. Emerging evidence underscores the adverse effects of new pharmacological treatments for severe obesity on bone health. Novel drugs, such as glucagon-like peptide-1 (GLP-1) receptor agonists, and bariatric surgery demonstrate potential in achieving weight loss, though limited evidence is available regarding their short- and long-term impacts on skeletal health. This review provides a comprehensive analysis of the mechanisms underlying the impact of childhood obesity on bone health. It critically appraises evidence from in vitro studies, animal models, and clinical research in children with exogenous obesity, syndromic obesity, and eating disorders. It also explores the effects of emerging pharmacological and surgical treatments for severe obesity on skeletal integrity, highlights prevention strategies, and identifies research gaps.

Glucagon-like Peptide-1 Receptor Agonists and Diabetic Osteopathy: Another Positive Effect of Incretines? A 12 Months Longitudinal Study

Diabetic osteopathy is a frequent complication in patients with type 2 diabetes mellitus (T2DM). The association between T2DM and increased fracture risk has led to study the impact of new antidiabetic drugs on bone metabolism. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are incretin mimetic drugs which have many pleiotropic properties. The relationship between GLP-1RAs and bone is very complex: while in vitro and animal studies have demonstrated a protective effect on bone, human studies are scarce. We led a 12 months longitudinal study evaluating bone changes in 65 patients withT2DM for whom a therapy with GLP-1RAs had been planned. Fifty-four T2DM patients completed the 12-month study period; of them, 30 had been treated with weekly dulaglutide and 24 with weekly semaglutide. One-year therapy with GLP-1RAs resulted in a significant reduction in weight and BMI. Bone mineral density (BMD), bone metabolism, trabecular bone score (TBS), adiponectin, and myostatin were evaluated before and after 12 months of GLP-1RAs therapy. After 12 months of therapy bone turnover markers and adiponectin showed a significant increase, while myostatin values showed a modest but significant reduction. BMD-LS by DXA presented a significant reduction while the reduction in BMD-LS by REMS was not significant and TBS values showed a marginal increase. Both DXA and REMS techniques showed a modest but significant reduction in femoral BMD. In conclusion, the use of GLP-1RAs for 12 months preserves bone quality and reactivates bone turnover. Further studies are needed to confirm whether GLP-1RAs could represent a useful therapeutic option for patients with T2DM and osteoporosis.

Effect of gut hormones on bone metabolism and their possible mechanisms in the treatment of osteoporosis

Bone is a highly dynamic organ that changes with the daily circadian rhythm. During the day, bone resorption is suppressed due to eating, while it increases at night. This circadian rhythm of the skeleton is regulated by gut hormones. Until now, gut hormones that have been found to affect skeletal homeostasis include glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2), glucose-dependent insulinotropic polypeptide (GIP), and peptide YY (PYY), which exerts its effects by binding to its cognate receptors (GLP-1R, GLP-2R, GIPR, and Y1R). Several studies have shown that GLP-1, GLP-2, and GIP all inhibit bone resorption, while GIP also promotes bone formation. Notably, PYY has a strong bone resorption-promoting effect. In addition, gut microbiota (GM) plays an important role in maintaining bone homeostasis. This review outlines the roles of GLP-1, GLP-2, GIP, and PYY in bone metabolism and discusses the roles of gut hormones and the GM in regulating bone homeostasis and their potential mechanisms.

Enhanced bone regeneration via endochondral ossification using Exendin-4-modified mesenchymal stem cells

Nonunions and delayed unions pose significant challenges in orthopedic treatment, with current therapies often proving inadequate. Bone tissue engineering (BTE), particularly through endochondral ossification (ECO), emerges as a promising strategy for addressing critical bone defects. This study introduces mesenchymal stem cells overexpressing Exendin-4 (MSC-E4), designed to modulate bone remodeling via their autocrine and paracrine functions. We established a type I collagen (Col-I) sponge-based in vitro model that effectively recapitulates the ECO pathway. MSC-E4 demonstrated superior chondrogenic and hypertrophic differentiation and enhanced the ECO cell fate in single-cell sequencing analysis. Furthermore, MSC-E4 encapsulated in microscaffold, effectively facilitated bone regeneration in a rat calvarial defect model, underscoring its potential as a therapeutic agent for bone regeneration. Our findings advocate for MSC-E4 within a BTE framework as a novel and potent approach for treating significant bone defects, leveraging the intrinsic ECO process.

Effect of Liraglutide on Osteoporosis in a Rat Model of Type 2 Diabetes Mellitus: A Histological, Immunohistochemical, and Biochemical Study

Diabetic osteoporosis (DOP) is a diabetic complication associated with a significant disability rate. Liraglutide, a glucagon-like peptide-1 receptor agonist, is a promising and innovative drug for type 2 diabetes mellitus (T2DM), with potential therapeutic implications for bone disorders. This investigation examined the impact of liraglutide on osteoporosis in rats with T2DM and studied the influence of vitamin D receptor Bsm1 polymorphism on liraglutide-induced outcomes. Thirty rats were divided into control, T2DM induced by a combination of a high-fat diet and 25 mg/kg streptozotocin, and T2DM-liraglutide (T2DM treated with 0.4 mg/kg/day liraglutide) groups. After 8 weeks of liraglutide treatment, femurs and blood samples were obtained from all rats for subsequent investigations. Diabetes induced a remarkable rise in the serum levels of receptor activator of nuclear factor kappa B ligand (RANKL) and C-telopeptide of type I collagen (CTX-1) associated with a remarkable decline in osteocalcin and osteoprotegerin (OPG). Impaired bone architecture was also demonstrated by light and scanning electron microscopic study. The immune expression of OPG was down-regulated, while RANKL was up-regulated. Interestingly, the administration of liraglutide ameliorated the previous changes induced by diabetes mellitus. In conclusion, liraglutide can prevent DOP, mostly due to liraglutide's ability to increase bone growth, while inhibiting bone resorption.

The associations of gut microbiota, endocrine system and bone metabolism

Gut microbiota is of great importance in human health, and its roles in the maintenance of skeletal homeostasis have long been recognized as the "gut-bone axis." Recent evidence has indicated intercorrelations between gut microbiota, endocrine system and bone metabolism. This review article discussed the complex interactions between gut microbiota and bone metabolism-related hormones, including sex steroids, insulin-like growth factors, 5-hydroxytryptamine, parathyroid hormone, glucagon-like peptides, peptide YY, etc. Although the underlying mechanisms still need further investigation, the regulatory effect of gut microbiota on bone health via interplaying with endocrine system may provide a new paradigm for the better management of musculoskeletal disorders.

Liraglutide in Combination with Insulin Has a Superior Therapeutic Effect to Either Alone on Fracture Healing in Diabetic Rats

Purpose

Fractures in patients with type 2 diabetes mellitus are at a high risk of delayed union or non-union. Previous studies have shown a protective effect of liraglutide on bone. In the present study, we aimed to investigate the effects of a combination of liraglutide and insulin on fracture healing in a rat model of diabetes and the mechanisms involved.

Materials and Methods

Closed femoral mid-shaft fractures were established in male Sprague-Dawley rats with or without diabetes mellitus, and the diabetic rats were administered insulin and/or liraglutide. Six weeks after femoral fracture, the femoral callus was evaluated by immunohistochemistry, histology, and micro-computed tomography. Additionally, the effects of liraglutide on high-glucose-stimulated MC3T3-E1 cells were analyzed by Western blotting.

Results

Micro-computed tomography and safranin O/fast green staining showed that fracture healing was delayed in the diabetic rats, and this was accompanied by much lower expression of osteogenic markers and greater osteoclast activity. However, treatment with insulin and/or liraglutide prevented these changes. Liraglutide in combination with insulin treatment resulted in lower blood glucose concentrations and significantly higher osteocalcin (OCN) and collagen I (Col I) expression six weeks following fracture. Western blot analysis showed that liraglutide prevented the low expression of the bone morphogenetic protein-2, osterix/SP7, OCN, Col I, and β-catenin in high-glucose-stimulated MC3T3-E1 cells.

Conclusion

These results demonstrate that insulin and/or liraglutide promotes bone fracture healing in the DF model. The combination was more effective than either single treatment, which may be because of the two drugs' additive effects on the osteogenic ability of osteoblast precursors.

Linagliptin in Combination With Metformin Ameliorates Diabetic Osteoporosis Through Modulating BMP-2 and Sclerostin in the High-Fat Diet Fed C57BL/6 Mice

BACKGROUND

Diabetic osteoporosis is a poorly managed serious skeletal complication, characterized by high fracture risk, increased bone resorption, reduced bone formation, and disrupted bone architecture. There is a need to investigate drugs that can improve bone health along with managing glycemic control. DPP-4 inhibitors and metformin have proven benefits in improving bone health. Here, we investigated the effects of linagliptin, a DPP inhibitor, and metformin alone and in combination to treat diabetic osteoporosis in high-fat-fed mice.

METHODS

C57BL/6 mice were kept on the high-fat diet (HFD) for 22 weeks to induce diabetic osteoporosis. Linagliptin (10mg/Kg), metformin (150mg/Kg), and their combination were orally administered to the diabetic mice from the 18th-22nd week. Femur and tibial bone microarchitecture together with bone mineral density (BMD) were evaluated using µCT and histopathological changes were assessed. Further, bone turnover biomarkers namely bone morphogenetic protein-2 (BMP-2), sclerostin, tartrate-resistant acid phosphatase (TRAP), osteocalcin, alkaline phosphatase (ALP), calcium, and pro-inflammatory cytokines were assessed. Additionally, metabolic parameters including body weight, fasting blood glucose (FBG), glucose & insulin tolerance, lipids profile, and leptin were measured.

RESULTS

HFD feeding resulted in impaired bone microarchitecture, reduced BMD, distorted bone histology, and altered bone turnover biomarkers as indicated by the significant reduction in bone ALP, BMP-2, osteocalcin, and an increase in sclerostin, TRAP, and serum calcium. Interestingly, treatment with linagliptin and its combination with metformin significantly reverted the impaired bone architecture, BMD, and positively modulated bone turnover biomarkers, while metformin alone did not exhibit any significant improvement. Further, HFD induced diabetes and metabolic abnormalities (including an increase in body weight, FBG, impaired glucose and insulin tolerance, leptin, triglycerides, cholesterol), and pro-inflammatory cytokines (TNF-alpha and IL-1β) were successfully reversed by treatment with linagliptin, metformin, and their combination.

CONCLUSION

Linagliptin and its combination with metformin successfully ameliorated diabetic osteoporosis in HFD-fed mice possibly through modulation of BMP-2 and sclerostin. The study provides the first evidence for the possible use of linagliptin and metformin combination for managing diabetic osteoporosis.

Glucagon-like peptide-1 attenuates diabetes-associated osteoporosis in ZDF rat, possibly through the RAGE pathway

Background

Diabetes-associated osteoporosis are partly caused by accumulation of advanced glycation endproducts (AGEs). Glucagon-like peptide-1 (GLP-1) has been shown to regulate bone turnover. Here we explore whether GLP-1 receptor agonist (GLP1RA) can have a beneficial effect on bone in diabetes by ameliorating AGEs.

Methods

In the present study, we evaluated the effects of the GLP-1 receptor agonist liraglutide, insulin and dipeptidyl peptidase-4 inhibitor saxagliptin on Zucker diabetic fatty rats. Meanwhile, we observed the effect of GLP-1 on AGEs-mediated osteoblast proliferation and differentiation and the signal pathway.

Results

Liraglutide prevented the deterioration of trabecular microarchitecture and enhanced bone strength. Moreover, it increased serum Alpl, Ocn and P1NP levels and decreased serum CTX. In vitro we confirmed that GLP-1 could attenuate AGEs-mediated damage in osteogenic proliferation and differentiation. Besides, GLP-1 down-regulated the ROS that caused by AGEs and the mRNA and protein expression of Rage .

Conclusions

Altogether, our findings suggest that GLP-1 receptor agonist promotes osteoblastogenesis and suppresses bone resorption on obese type 2 diabetic rats to a certain degree. The mechanism of these effects may be partly mediated by AGEs-RAGE-ROS pathway via the interaction with GLP-1 receptor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05396-5.

The Multiple Biological Functions of Dipeptidyl Peptidase-4 in Bone Metabolism

Dipeptidyl peptidase-4 (DPP4) is a ubiquitously occurring protease involved in various physiological and pathological processes ranging from glucose homeostasis, immunoregulation, inflammation to tumorigenesis. Recently, the benefits of DPP4 inhibitors as novel hypoglycemic agents on bone metabolism have attracted extensive attraction in many studies, indicating that DPP4 inhibitors may regulate bone homeostasis. The effects of DPP4 on bone metabolism are still unclear. This paper thoroughly reviews the potential mechanisms of DPP4 for interaction with adipokines, bone cells, bone immune cells, and cytokines in skeleton system. This literature review shows that the increased DPP4 activity may indirectly promote bone resorption and inhibit bone formation, increasing the risk of osteoporosis. Thus, bone metabolic balance can be improved by decreasing DPP4 activities. The substantial evidence collected and analyzed in this review supports this implication.

Bariatric Surgery and Osteoporosis

It has been increasingly acknowledged that bariatric surgery adversely affects skeletal health. After bariatric surgery, the extent of high-turnover bone loss is much greater than what would be expected in the absence of a severe skeletal insult. Patients also experience a significant deterioration in bone microarchitecture and strength. There is now a growing body of evidence that suggests an association between bariatric surgery and higher fracture risk. Although the mechanisms underlying the high-turnover bone loss and increase in fracture risk after bariatric surgery are not fully understood, many factors seem to be involved. The usual suspects are nutritional factors and mechanical unloading, and the roles of gut hormones, adipokines, and bone marrow adiposity should be investigated further. Roux-en-Y gastric bypass (RYGB) was once the most commonly performed bariatric procedure worldwide, but sleeve gastrectomy (SG) has now become the predominant bariatric procedure. Accumulating evidence suggests that RYGB is associated with a greater reduction in BMD, a greater increase in markers of bone turnover, and a higher risk of fracture than SG. These findings should be taken into consideration in determining the most appropriate bariatric procedure for patients, especially those at higher fracture risk. Before and after all bariatric procedures, sufficient calcium, vitamin D and protein intake, and adequate physical activity, are needed to counteract negative impacts on bone. There are no studies to date that have evaluated the effect of osteoporosis treatment on high-turnover bone loss after bariatric surgery. However, in patients with a diagnosis of osteoporosis, anti-resorptive agents may be considered.

Sexual dimorphism in the relation between sex hormones and osteoporosis in patients with type 2 diabetes mellitus

INTRODUCTION

To investigate the association between sex hormones and osteoporosis in type 2 diabetic mellitus (T2DM) patients.

MATERIALS AND METHODS

We performed a retrospective study in patients with T2DM. The patients were assigned into three groups (normal bone mineral density, osteopenia, and osteoporosis) in both sexes. The clinical characteristics, bone metabolic markers, and sex hormones were compared. The relationship between the sex hormones and osteoporosis was analyzed by ordinary regression analysis. Statistical analysis was performed using SPSS 26.0.

RESULTS

A total of 795 T2DM patients (446 men ≥ 50 years old and 349 postmenopausal women) were identified and analyzed. The osteoporosis group had the lowest estradiol level in men (P = 0.013) and the highest follicle-stimulating hormone (FSH) level in women (P = 0.042). In the multivariate analysis, men with lower estradiol levels (< 87.96 pmol/L) had a nearly 1.6-fold increased risk for osteoporosis than those with the higher estradiol levels (> 122.82 pmol/L). In addition, women with lower FSH (< 41.17 IU/L) had nearly 0.6-fold for osteoporosis compared to those with higher FSH (> 60.83 IU/L) after adjusting for age, duration of T2DM, body mass index, pulse pressure, creatinine clearance, glycosylated hemoglobin, fasting C-peptide, and estradiol (in FSH) or FSH (in estradiol).

CONCLUSION

In T2DM, the estrogen level was negatively correlated with osteoporosis in men, and the FSH level was positively correlated with the osteoporosis in women.

The Impact of GLP1 Agonists on Bone Metabolism: A Systematic Review

Background and Objectives: The association between diabetes mellitus and increased risk of bone fractures has led to the investigation of the impact of antidiabetic drugs on bone metabolism. Glucagon-like peptide-1 receptor agonists (GLP1RAs) are a relatively novel and promising class of anti-hyperglycemic drugs. In addition to their blood glucose lowering action, GLP1RAs seem to have additional pleiotropic properties such as a beneficial skeletal effect; although the underlying mechanisms are not completely understood. The present systematic review summarizes current evidence about GLP1RAs and their effects on bone metabolism and fracture. Methods: An extensive literature search was conducted based on electronic databases namely, PubMed, Google Scholar and Cochrane Central Register of Controlled Trials (CENTRAL) through October 2019 to January 2020 for articles related to bone mineral density, diabetes mellitus and GLP1RAs. We included articles published in English. Finally, we included four randomized controlled trials, three meta-analyses, a case-control study and a population-based cohort analysis. Results: Based on the articles included, the animal studies indicated the salutary skeletal effects of GLP1RAs in opposition to what has been commonly observed in human studies, showing that these agents have no impact on bone mineral density (BMD) and the turnover markers. Moreover, it was demonstrated that GLP1 was not associated with fracture risk as compared to other anti-hyperglycemic drugs. Conclusions: Findings from this systematic review have demonstrated the neutral impact of GLP1RAs on BMD. Moreover, further double-blind randomized controlled trials are needed to draw more meaningful and significant conclusions on the efficacy of GLP1RAs on BMD.

Bone Response to Weight Loss Following Bariatric Surgery

Obesity is a global health challenge that warrants effective treatments to avoid its multiple comorbidities. Bariatric surgery, a cornerstone treatment to control bodyweight excess and relieve the health-related burdens of obesity, can promote accelerated bone loss and affect skeletal strength, particularly after malabsorptive and mixed surgical procedures, and probably after restrictive surgeries. The increase in bone resorption markers occurs early and persist for up to 12 months or longer after bariatric surgery, while bone formation markers increase but to a lesser extent, suggesting a potential uncoupling process between resorption and formation. The skeletal response to bariatric surgery, as investigated by dual-energy X-ray absorptiometry (DXA), has shown significant loss in bone mineral density (BMD) at the hip with less consistent results for the lumbar spine. Supporting DXA studies, analyses by high-resolution peripheral quantitative computed tomography (HR-pQCT) showed lower cortical density and thickness, higher cortical porosity, and lower trabecular density and number for up to 5 years after bariatric surgery. These alterations translate into an increased risk of fall injury, which contributes to increase the fracture risk in patients who have been subjected to bariatric surgery procedures. As bone deterioration continues for years following bariatric surgery, the fracture risk does not seem to be dependent on acute weight loss but, rather, is a chronic condition with an increasing impact over time. Among the post-bariatric surgery mechanisms that have been claimed to act globally on bone health, there is evidence that micro- and macro-nutrient malabsorptive factors, mechanical unloading and changes in molecules partaking in the crosstalk between adipose tissue, bone and muscle may play a determining role. Given these circumstances, it is conceivable that bone health should be adequately investigated in candidates to bariatric surgery through bone-specific work-up and dedicated postsurgical follow-up. Specific protocols of nutrients supplementation, motor activity, structured rehabilitative programs and, when needed, targeted therapeutic strategies should be deemed as an integral part of post-bariatric surgery clinical support.

Effects of sleeve gastrectomy on bone mass, microstructure of femurs and bone metabolism associated serum factors in obese rats

BACKGROUND

Sleeve gastrectomy (SG) is a profoundly effective operation for severe obese patients, but is closely associated with bone mass loss. Previous studies have reported changes of various serum factors which may be associated with bone mass loss after SG. However, those results are contradictory. In this study, we assessed the effects of SG on bone mass, microstructure of femurs, and changes in bone turnover markers (BTMs), serum adipokines, inflammatory factors and gastrointestinal hormones after SG in high-fat diet (HFD) induced obese rats.

METHODS

Eight-week-old male Sprague-Dawley (SD) rats were fed with HFD to induce obesity. Then, SG and sham surgery were performed in anesthetized obese rats. SD rats in control group were fed with standard chow. Microstructure of femurs was scanned and analyzed by micro-computed tomography in control group, HFD sham group and HFD SG group. Serum inflammatory factors, adipokines markers, gastrointestinal hormones and BTMs were also measured.

RESULTS

Bone mineral density (BMD) of trabecular bone in both HFD sham group and HFD SG group were remarkably decreased compared with control group. All serum BTMs were significantly higher in HFD SG group than HFD sham group. In the meantime, serum levels of several important inflammatory factors, gastrointestinal hormones and adipokines such as tumor necrosis factor-α (TNF-α), interleukin (IL)-6, monocyte chemoattractant protein-1(MCP-1), ghrelin, insulin and leptin in HFD SG group were remarkably reduced compared with HFD sham group, whereas glucagon-like peptide-1 (GLP-1), adiponectin, fibroblast growth factor (FGF)-19 and FGF-21 were dramatically increased after SG. Protein tyrosine phosphatase 1B (PTP1B) was significantly increased in the HFD sham group than control group. Spearman's correlation analysis indicated that serum osteocalcin (OC) and 25-hydroxy vitamin D₃ (25(OH)D₃) were positively correlated with BMD of trabecular bone, whereas serum PTP1B and TNF-α were negatively related to BMD of trabecular bone.

CONCLUSIONS

SG aggravates bone mass loss and activates bone remodeling in obese rats. Levels of BTMs, adipokines, inflammatory factors, and gastrointestinal hormones could be affected by SG in obese rats. Serum PTP1B level might be associated with abnormal bone mass in obese rats.

Alliances of the gut and bone axis

Gut hormones secreted from enteroendocrine cells following nutrient ingestion modulate metabolic processes including glucose homeostasis and food intake, and several of these gut hormones are involved in the regulation of the energy demanding process of bone remodelling. Here, we review the gut hormones considered or known to be involved in the gut-bone crosstalk and their role in orchestrating adaptions of bone formation and resorption as demonstrated in cellular and physiological experiments and clinical trials. Understanding the physiology and pathophysiology of the gut-bone axis may identify adverse effects of investigational drugs aimed to treat metabolic diseases such as type 2 diabetes and obesity and new therapeutic candidates for the treatment of bone diseases.

Effects of Incretin-Related Diabetes Drugs on Bone Formation and Bone Resorption

Patients with type 2 diabetes have an increased risk of fracture compared to the general population. Glucose absorption is accelerated by incretin hormones, which induce insulin secretion from the pancreas. The level of the incretin hormone, glucagon-like peptide-1 (GLP-1), shows an immediate postprandial increase, and the circulating level of intact GLP-1 is reduced rapidly by dipeptidyl peptidase-4 (DPP-4)-mediated inactivation. Therefore, GLP-1 receptor agonists and DPP-4 inhibitors are effective in the treatment of type 2 diabetes. However, these incretin-related diabetic agents have been reported to affect bone metabolism, including bone formation and resorption. These agents enhance the expression of bone markers, and have been applied to improve bone quality and bone density. In addition, they have been reported to suppress chronic inflammation and reduce the levels of inflammatory cytokine expression. Previously, we reported that these incretin-related agents inhibited both the expression of inflammatory cytokines and inflammation-induced bone resorption. This review presents an overview of current knowledge regarding the effects of incretin-related diabetes drugs on osteoblast differentiation and bone formation as well as osteoclast differentiation and bone resorption. The mechanisms by which incretin-related diabetes drugs regulate bone formation and bone resorption are also discussed.

Critical review of bone health, fracture risk and management of bone fragility in diabetes mellitus

The risk of fracture is increased in both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). However, in contrast to the former, patients with T2DM usually possess higher bone mineral density. Thus, there is a considerable difference in the pathophysiological basis of poor bone health between the two types of diabetes. Impaired bone strength due to poor bone microarchitecture and low bone turnover along with increased risk of fall are among the major factors behind elevated fracture risk. Moreover, some antidiabetic medications further enhance the fragility of the bone. On the other hand, antiosteoporosis medications can affect the glucose homeostasis in these patients. It is also difficult to predict the fracture risk in these patients because conventional tools such as bone mineral density and Fracture Risk Assessment Tool score assessment can underestimate the risk. Evidence-based recommendations for risk evaluation and management of poor bone health in diabetes are sparse in the literature. With the advancement in imaging technology, newer modalities are available to evaluate the bone quality and risk assessment in patients with diabetes. The purpose of this review is to explore the pathophysiology behind poor bone health in diabetic patients. Approach to the fracture risk evaluation in both T1DM and T2DM as well as the pragmatic use and efficacy of the available treatment options have been discussed in depth.

The Impact of Glucagon-Like Peptide 1 Receptor Agonists on Bone Metabolism and Its Possible Mechanisms in Osteoporosis Treatment

Diabetes mellitus and osteoporosis are closely related and have complex influencing factors. The impact of anti-diabetic drugs on bone metabolism has received more and more attention. Type 2 diabetes mellitus (T2DM) would lead to bone fragility, high risk of fracture, poor bone repair and other bone-related diseases. Furthermore, hypoglycemic drugs used to treat T2DM may have notable detrimental effects on bones. Thus, the clinically therapeutic strategy for T2DM should not only effectively control the patient's glucose levels, but also minimize the complications of bone metabolism diseases. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are novel and promising drug for the treatment of T2DM. Some studies have found that GLP-1RAs may play an anti-osteoporotic effect by controlling blood sugar levels, promoting bone formation and inhibiting bone resorption. However, in clinical practice, the specific effects of GLP-1RA on fracture risk and osteoporosis have not been clearly defined and evidenced. This review summarizes the current research findings by which GLP-1RAs treatment of diabetic osteoporosis, postmenopausal osteoporosis and glucocorticoid-induced osteoporosis and describes possible mechanisms, such as GLP-1R/MAPK signaling pathway, GLP-1R/PI3K/AKT signaling pathway and Wnt/β-catenin pathway, that are associated with GLP-1RAs and osteoporosis. The specific role and related mechanisms of GLP-1RAs in the bone metabolism of patients with different types of osteoporosis need to be further explored and clarified.

Irisin and Incretin Hormones: Similarities, Differences, and Implications in Type 2 Diabetes and Obesity

Incretins are gut hormones that potentiate glucose-stimulated insulin secretion (GSIS) after meals. Glucagon-like peptide-1 (GLP-1) is the most investigated incretin hormone, synthesized mainly by L cells in the lower gut tract. GLP-1 promotes β-cell function and survival and exerts beneficial effects in different organs and tissues. Irisin, a myokine released in response to a high-fat diet and exercise, enhances GSIS. Similar to GLP-1, irisin augments insulin biosynthesis and promotes accrual of β-cell functional mass. In addition, irisin and GLP-1 share comparable pleiotropic effects and activate similar intracellular pathways. The insulinotropic and extra-pancreatic effects of GLP-1 are reduced in type 2 diabetes (T2D) patients but preserved at pharmacological doses. GLP-1 receptor agonists (GLP-1RAs) are therefore among the most widely used antidiabetes drugs, also considered for their cardiovascular benefits and ability to promote weight loss. Irisin levels are lower in T2D patients, and in diabetic and/or obese animal models irisin administration improves glycemic control and promotes weight loss. Interestingly, recent evidence suggests that both GLP-1 and irisin are also synthesized within the pancreatic islets, in α- and β-cells, respectively. This review aims to describe the similarities between GLP-1 and irisin and to propose a new potential axis-involving the gut, muscle, and endocrine pancreas that controls energy homeostasis.

Local administration of high-dose diabetes medicine exendin-4 inhibits orthodontic tooth movement in mice

OBJECTIVES

To investigate the effects of exendin-4 on orthodontic tooth movement distance, root resorption, and expression levels of osteoclast-related cytokines in a mouse model.

MATERIALS AND METHODS

A 10-g NiTi coil spring was placed between the anterior alveolar bone and upper left first molar of 8-week-old male C57BL/6 mice. Twenty microliters of exendin-4 solution (containing 0.2 μg, 4 μg, or 20 μg exendin-4) or phosphate-buffered saline (PBS) were injected on the buccal side of the upper left first molar at 2-day intervals (4 mice per group). Mice were sacrificed on day 12; silicone impressions were taken to record tooth movement distance. The left maxillae of the PBS and 20 μg exendin-4 groups were also excised for histological analysis and quantitative reverse transcription polymerase chain reaction analysis.

RESULTS

Orthodontic tooth movement distance was smaller in the 20 μg exendin-4 group than in the PBS group (P < .01). Compared with the PBS group, the 20 μg exendin-4 group showed lower osteoclast number (P < .05), odontoclast number (P < .05), and root resorption surface percentage (P < .05). Relative to maxillae with PBS injections, maxillae with 20 μg exendin-4 injections had lower receptor activator of nuclear factor kappa-B ligand (RANKL) mRNA expression (P < .05), TNF-α mRNA expression (P < .05), and RANKL/osteoprotegerin (OPG) ratio (P < .01). There were no differences in the expression of OPG mRNA.

CONCLUSIONS

Exendin-4 inhibits orthodontic tooth movement. Therefore, additional attention is needed for orthodontic patients who receive exendin-4 for diabetes treatment. GLP-1 receptor may be a treatment target for patients with severe root resorption.

Barocrinology: The Endocrinology of Obesity from Bench to Bedside

Obesity has reached pandemic proportions. Hormonal and metabolic imbalances are the key factors that lead to obesity. South Asian populations have a unique phenotype, peculiar dietary practices, and a high prevalence of consanguinity. Moreover, many lower middle-income countries lack appropriate resources, super-specialists, and affordability to manage this complex disorder. Of late, there has been a substantial increase in both obesity and diabesity in India. Thus, many more patients are being managed by different types of bariatric procedures today than ever before. These patients have many types of endocrine and metabolic disturbances before and after bariatric surgery. Therefore, these patients should be managed by experts who have knowledge of both bariatric surgery and endocrinology. The authors propose “Barocrinology”, a novel terminology in medical literature, to comprehensively describe the field of obesity medicine highlighting the role of knowing endocrine physiology for understating its evolution, insights into its complications and appreciating the changes in the hormonal milieu following weight loss therapies including bariatric surgery. Barocrinology, coined as a portmanteau of “baro” (weight) and endocrinology, focuses upon the endocrine and metabolic domains of weight physiology and pathology. This review summarizes the key pointers of bariatric management from an endocrine perspective.

Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models

Approx. every third hospitalized patient in Europe suffers from musculoskeletal injuries or diseases. Up to 20% of these patients need costly surgical revisions after delayed or impaired fracture healing. Reasons for this are the severity of the trauma, individual factors, e.g, the patients' age, individual lifestyle, chronic diseases, medication, and, over 70 diseases that negatively affect the bone quality. To investigate the various disease constellations and/or develop new treatment strategies, many in vivo, ex vivo, and in vitro models can be applied. Analyzing these various models more closely, it is obvious that many of them have limits and/or restrictions. Undoubtedly, in vivo models most completely represent the biological situation. Besides possible species-specific differences, ethical concerns may question the use of in vivo models especially for large screening approaches. Challenging whether ex vivo or in vitro bone models can be used as an adequate replacement for such screenings, we here summarize the advantages and challenges of frequently used ex vivo and in vitro bone models to study disturbed bone metabolism and fracture healing. Using own examples, we discuss the common challenge of cell-specific normalization of data obtained from more complex in vitro models as one example of the analytical limits which lower the full potential of these complex model systems.

Update on: effects of anti-diabetic drugs on bone metabolism

INTRODUCTION

Preclinical, clinical, and population-based studies have provided evidence that anti-diabetic drugs affect bone metabolism and may affect the risk of fracture in diabetic patients.

AREAS COVERED

An overview of the skeletal effects of anti-diabetic drugs used in type 2 diabetes is provided. Searches on AdisInsight, PubMed, and Medline databases were conducted up to 1^st July 2020. The latest evidence from randomized clinical trials and population-based studies on the skeletal safety of the most recent drugs (DPP-4i, GLP-1RA, and SGLT-2i) is provided.

EXPERT OPINION

Diabetic patients present with a higher risk of fracture for a given bone mineral density suggesting a role of bone quality in the etiology of diabetic fracture. Bone quality is difficult to assess in human clinical practice and the use of preclinical models provides valuable information on diabetic bone alterations. As several links have been established between bone and energy homeostasis, it is interesting to study the safety of anti-diabetic drugs on the skeleton. So far, evidence for the newest molecules suggests a neutral fracture risk, but further studies, especially in different types of patient populations (patients at risk or with history of cardiovascular disease, renal impairment, neuropathy) are required to fully appreciate this matter.

Changes in Bone Mineral Density in Patients with Type 2 Diabetes After Different Bariatric Surgery Procedures and the Role of Gastrointestinal Hormones

BACKGROUND

To compare changes in bone mineral density (BMD) in patients with morbid obesity and type 2 diabetes (T2D) a year after being randomized to metabolic gastric bypass (mRYGB), sleeve gastrectomy (SG), and greater curvature plication (GCP). We also analyzed the association of gastrointestinal hormones with skeletal metabolism.

METHODS

Forty-five patients with T2D (mean BMI 39.4 ± 1.9 kg/m²) were randomly assigned to mRYGB, SG, or GCP. Before and 12 months after surgery, anthropometric, body composition, biochemical parameters, fasting plasma glucagon, ghrelin, and PYY as well as GLP-1, GLP-2, and insulin after a standard meal were determined.

RESULTS

After surgery, the decrease at femoral neck (FN) was similar but at lumbar spine (LS), it was greater in the mRYGB group compared with SG and GCP - 7.29 (4.6) vs. - 0.48 (3.9) vs. - 1.2 (2.7)%, p < 0.001. Osteocalcin and alkaline phosphatase increased more after mRYGB. Bone mineral content (BMC) at the LS after surgery correlated with fasting ghrelin (r = - 0.412, p = 0.01) and AUC for GLP-1 (r = - 0.402, p = 0.017). FN BMD at 12 months correlated with post-surgical fasting glucagon (r = 0.498, p = 0.04) and insulin AUC (r = 0.384, p = 0.030) and at LS with the AUC for GLP-1 in the same time period (r = - 0.335, p = 0.049). However, in the multiple regression analysis after adjusting for age, sex, and BMI, the type of surgery (mRYGB) remained the only factor associated with BMD reduction at LS and FN.

CONCLUSIONS

mRYGB induces greater deleterious effects on the bone at LS compared with SG and GCP, and gastrointestinal hormones do not play a major role in bone changes.

Anagliptin stimulates osteoblastic cell differentiation and mineralization

Osteoporosis is a common debilitating bone disease characterized by loss of bone mass and degradation of the bone architecture, which is primarily driven by dysregulated differentiation of mesenchymal stem cells into bone-producing osteoblasts. Osteoblasts contribute to bone formation by secreting various proteins that guide the deposition of bone extracellular matrix, such as alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). The Wnt/β-catenin pathway is widely recognized as a regulator of bone mass and is required to maintain bone homeostasis. Hormones have long been recognized as playing a key role in bone metabolism, and in recent years, growing evidence has shown that diabetes is a risk factor for osteoporosis. In the present study, we investigated the effects of the antidiabetic drug anagliptin on the differentiation and mineralization of osteoblasts induced by osteogenic medium. Anagliptin promotes insulin production via inhibition of dipeptidyl peptidase IV (DPP-4), an enzyme that targets the incretin hormone glucagon-like peptide 1 (GLP-1) for degradation. Our findings show that anagliptin significantly increases the differentiation of MSCs into osteoblasts via activation of RUNX2. Anagliptin significantly increased matrix deposition and mineralization by osteoblasts, as evidenced by elevated levels of ALP, OCN, OPN, and BMP-2. We further demonstrate that anagliptin activates the canonical and noncannonical Wnt signaling pathways and that silencing of Wnt/β-catenin signaling completely abolished the effects of anagliptin. Thus, anagliptin might be a safe, effective therapy for type II diabetes that might show promise as a therapy against osteoporosis.

Long-Term Effects in Bone Mineral Density after Different Bariatric Procedures in Patients with Type 2 Diabetes: Outcomes of a Randomized Clinical Trial

There is scant evidence of the long-term effects of bariatric surgery on bone mineral density (BMD). We compared BMD changes in patients with severe obesity and type 2 diabetes (T2D) 5 years after randomization to metabolic gastric bypass (mRYGB), sleeve gastrectomy (SG) and greater curvature plication (GCP). We studied the influence of first year gastrointestinal hormone changes on final bone outcomes. Forty-five patients, averaging 49.4 (7.8) years old and body mass index (BMI) 39.4 (1.9) kg/m², were included. BMD at lumbar spine (LS) was lower after mRYGB compared to SG and GCP: 0.89 [0.82;0.94] vs. 1.04 [0.91;1.16] vs. 0.99 [0.89;1.12], p = 0.020. A higher percentage of LS osteopenia was present after mRYGB 78.6% vs. 33.3% vs. 50.0%, respectively. BMD reduction was greater in T2D remitters vs. non-remitters. Weight at fifth year predicted BMD changes at the femoral neck (FN) (adjusted R²: 0.3218; p = 0.002), and type of surgery (mRYGB) and menopause predicted BMD changes at LS (adjusted R²: 0.2507; p < 0.015). In conclusion, mRYGB produces higher deleterious effects on bone at LS compared to SG and GCP in the long-term. Women in menopause undergoing mRYGB are at highest risk of bone deterioration. Gastrointestinal hormone changes after surgery do not play a major role in BMD outcomes.

Bone resorption is unchanged by liraglutide in type 2 diabetes patients: A randomised controlled trial

BACKGROUND

Liraglutide, a glucagon-like peptide-1 receptor agonist, has well known beneficial effects on glucose metabolism, and animal studies indicate that liraglutide also affects bone turnover by decreasing bone resorption. The primary objective of the study was to investigate the effect of liraglutide on bone turnover in patients with T2D.

METHODS

The study was a randomized, double-blinded, clinical trial. Sixty participants with T2D were randomized to treatment with liraglutide 1.8 mg daily or placebo for 26 weeks. The primary endpoint was change in p-collagen I cross-linked C-terminal telopeptide (p-CTX).

RESULTS

P-CTX increased in patients treated with liraglutide by 0.07 (0.03; 0.10) μg/L (p < 0.001) and in patients treated with placebo by 0.03 (0.00; 0.06) μg/L (p = 0.04), however, changes were not different between the groups (p = 0.16). Weight decreased in patients treated with liraglutide from baseline to week four (p < 0.001) and remained stable thereafter. P-procollagen type 1 N-terminal propeptide (P1NP) decreased in patients treated with liraglutide from baseline to week four (p < 0.01), increased between weeks 4 and 13 (p = 0.03), and remained elevated thereafter. Weight and p-P1NP did not change in patients treated with placebo. Hip bone mineral density (BMD) decreased in placebo treated patients from baseline to end of study, whereas no changes were seen in patients treated with liraglutide (p = 0.01 difference between groups).

CONCLUSION

Liraglutide treatment for 26 weeks did not affect bone resorption and preserved hip BMD despite weight loss in patients with T2D, suggesting that liraglutide has some antiresorptive effect.

Current molecular aspects in the development and treatment of diabetes

Diabetes mellitus (DM) leads to microvascular, macrovascular, and neurological complications. Less is understood about the mechanisms of this disease that give rise to weak bones. The many molecular mechanisms proposed to explain the damage caused by chronic hyperglycemia are organ and tissue dependent. Since all the different treatments for DM involve therapeutic activity combined with side effects and each patient represents a unique condition, there is no generalized therapy. The alterations stemming from hyperglycemia affect metabolism, osmotic pressure, oxidative stress, and inflammation. In part, hemodynamic modifications are linked to the osmotic potential of the excess of carbohydrates implicated in the disease. The change in osmotic balance increases as the disease progresses because hyperglycemia becomes chronic. The aim of the current contribution is to provide an updated overview of the molecular mechanisms that participate in the development and treatment of diabetes.

Differential Modulation of Cancellous and Cortical Distal Femur by Fructose and Natural Mineral-Rich Water Consumption in Ovariectomized Female Sprague Dawley Rats

Bone mineral density (BMD) and microstructure depend on estrogens and diet. We assessed the impact of natural mineral-rich water ingestion on distal femur of fructose-fed estrogen-deficient female Sprague Dawley rats. Ovariectomized rats drank tap or mineral-rich waters, with or without 10%-fructose, for 10 weeks. A sham-operated group drinking tap water was included (n = 6/group). Cancellous and cortical bone compartments were analyzed by microcomputed tomography. Circulating bone metabolism markers were measured by enzyme immunoassay/enzyme-linked immunosorbent assay or multiplex bead assay. Ovariectomy significantly worsened cancellous but not cortical bone, significantly increased circulating degradation products from C-terminal telopeptides of type I collagen and receptor activator of nuclear factor-kappaB ligand (RANKL), and significantly decreased circulating osteoprotegerin and osteoprotegerin/RANKL ratio. In ovariectomized rats, in cancellous bone, significant water effect was observed for all microstructural properties, except for the degree of anisotropy, and BMD (neither a significant fructose effect nor a significant interaction between water and fructose ingestion effects were observed). In cortical bone, it was observed a significant (a) water effect for medullary volume and cortical endosteal perimeter; (b) fructose effect for cortical thickness, medullary volume, cross-sectional thickness and cortical endosteal and periosteal perimeters; and (c) interaction effect for mean eccentricity. In blood, significant fructose and interaction effects were found for osteoprotegerin (no significant water effect was seen). For the first time in ovariectomized rats, the positive modulation of cortical but not of cancellous bone by fructose ingestion and of both bone locations by natural mineral-rich water ingestion is described.

Effects of metformin and alogliptin on body composition in people with type 2 diabetes

AIMS/INTRODUCTION

The aim of the present study was to investigate the effects of metformin and a dipeptidyl peptidase-4 inhibitor, alogliptin, on body composition in a 12-week randomized add-on trial in Japanese participants with type 2 diabetes.

MATERIALS AND METHODS

A total of 84 participants with poorly controlled type 2 diabetes undergoing antidiabetic therapy were randomly assigned to receive alogliptin (25 mg, once daily) or metformin (1,000 mg, twice daily) for 12 weeks. The primary efficacy end-point was body composition. The secondary end-points included factors associated with decreased bodyweight.

RESULTS

Compared with the baseline values, alogliptin significantly increased bodyweight (66.5 ± 19.2 to 67.6 ± 19.3 kg), body mass index (BMI; 25.4 ± 6.1 to 25.8 ± 6.3 kg/m2 ) and fat mass (20.3 ± 12.8 to 21.8 ± 14.5 kg), whereas metformin had no significant effect on body composition. Alogliptin was inferior to metformin in reducing bodyweight (0.84 ± 1.57 vs -0.35 ± 1.53 kg, P = 0.002), BMI (0.34 ± 0.69 to -0.15 ± 0.56 kg/m2 , P = 0.002) and fat mass (1.49 ± 5.06 vs -0.04 ± 1.81 kg, P = 0.042). BMI at baseline was associated with changes in bodyweight negatively in the metformin group and positively in the alogliptin group.

CONCLUSIONS

Metformin and alogliptin exert opposite effects on bodyweight in type 2 diabetes patients who are overweight. The higher the BMI, the more metformin reduces bodyweight and alogliptin increases weight.

Exenatide ameliorates inflammatory response in human rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease of unknown etiology characterized by degradation of cartilage and bone, accompanied by unimpeded proliferation of synoviocytes of altered phenotype. In the present study, we investigated the involvement of the glucagon-like peptide 1 (GLP-1) receptor on human fibroblast-like synoviocytes (FLS) in the pathogenesis of RA using the selective GLP-1 agonist exenatide, a licensed drug used for the treatment of type 2 diabetes. Our results indicate that exenatide may play a role in regulating tumor necrosis factor-α-induced mitochondrial dysfunction by increasing mitochondrial membrane potential, oxidative stress by reducing the production of reactive oxygen species, the expression of NADPH oxidase 4, expression of matrix metalloproteinase (MMP)-3 and MMP-13, release of proinflammatory cytokines including interleukin-1β (IL-1β), IL-6, monocyte chemoattractant protein-1, and high-mobility group protein 1, as well as activation of the p38/nuclear factor of κ light polypeptide gene enhancer in B-cells inhibitor, α/nuclear factor κB signaling pathway in primary human RA FLS. These positive results indicate that exenatide may have potential as a therapeutic agent for the treatment and prevention of RA. © 2019 IUBMB Life, 9999(9999):1-9, 2019.

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.

Gut Hormones and Their Effect on Bone Metabolism. Potential Drug Therapies in Future Osteoporosis Treatment

Bone homeostasis displays a circadian rhythm with increased resorption during the night time as compared to day time, a difference that seems-at least partly-to be caused by food intake during the day. Thus, ingestion of a meal results in a decrease in bone resorption, but people suffering from short bowel syndrome lack this response. Gut hormones, released in response to a meal, contribute to this link between the gut and bone metabolism. The responsible hormones appear to include glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), known as incretin hormones due to their role in regulating glucose homeostasis by enhancing insulin release in response to food intake. They interact with their cognate receptors (GIPR and GLP-1R), which are both members of the class B G protein-coupled receptors (GPCRs), and already recognized as targets for treatment of metabolic diseases, such as type 2 diabetes mellitus (T2DM) and obesity. Glucagon-like peptide-2 (GLP-2), secreted concomitantly with GLP-1, acting via another class B receptor (GLP-2R), is also part of this gut-bone axis. Several studies, including human studies, have indicated that these three hormones inhibit bone resorption and, moreover, that GIP increases bone formation. Another hormone, peptide YY (PYY), is also secreted from the enteroendocrine L-cells (together with GLP-1 and GLP-2), and acts mainly via interaction with the class A GPCR NPY-R2. PYY is best known for its effect on appetite regulation, but recent studies have also shown an effect of PYY on bone metabolism. The aim of this review is to summarize the current knowledge of the actions of GIP, GLP-1, GLP-2, and PYY on bone metabolism, and to discuss future therapies targeting these receptors for the treatment of osteoporosis.

Diabetes pharmacotherapy and effects on the musculoskeletal system

Persons with type 1 or type 2 diabetes have a significantly higher fracture risk than age-matched persons without diabetes, attributed to disease-specific deficits in the microarchitecture and material properties of bone tissue. Therefore, independent effects of diabetes drugs on skeletal integrity are vitally important. Studies of incretin-based therapies have shown divergent effects of different agents on fracture risk, including detrimental, beneficial, and neutral effects. The sulfonylurea class of drugs, owing to its hypoglycemic potential, is thought to amplify the risk of fall-related fractures, particularly in the elderly. Other agents such as the biguanides may, in fact, be osteo-anabolic. In contrast, despite similarly expected anabolic properties of insulin, data suggests that insulin pharmacotherapy itself, particularly in type 2 diabetes, may be a risk factor for fracture, negatively associated with determinants of bone quality and bone strength. Finally, sodium-dependent glucose co-transporter 2 inhibitors have been associated with an increased risk of atypical fractures in select populations, and possibly with an increase in lower extremity amputation with specific SGLT2I drugs. The role of skeletal muscle, as a potential mediator and determinant of bone quality, is also a relevant area of exploration. Currently, data regarding the impact of glucose lowering medications on diabetes-related muscle atrophy is more limited, although preclinical studies suggest that various hypoglycemic agents may have either aggravating (sulfonylureas, glinides) or repairing (thiazolidinediones, biguanides, incretins) effects on skeletal muscle atrophy, thereby influencing bone quality. Hence, the therapeutic efficacy of each hypoglycemic agent must also be evaluated in light of its impact, alone or in combination, on musculoskeletal health, when determining an individualized treatment approach. Moreover, the effect of newer medications (potentially seeking expanded clinical indication into the pediatric age range) on the growing skeleton is largely unknown. Herein, we review the available literature regarding effects of diabetes pharmacotherapy, by drug class and/or by clinical indication, on the musculoskeletal health of persons with diabetes.

Metabolic and Endocrine Consequences of Bariatric Surgery

Obesity is one of the most serious worldwide epidemics of the twenty-first century according to the World Health Organization. Frequently associated with a number of comorbidities, obesity threatens and compromises individual health and quality of life. Bariatric surgery (BS) has been demonstrated to be an effective treatment to achieve not only sustained weight loss but also significant metabolic improvement that goes beyond mere weight loss. The beneficial effects of BS on metabolic traits are so widely recognized that some authors have proposed BS as metabolic surgery that could be prescribed even for moderate obesity. However, most of the BS procedures imply malabsorption and/or gastric acid reduction which lead to nutrient deficiency and, consequently, further complications could be developed in the long term. In fact, BS not only affects metabolic homeostasis but also has pronounced effects on endocrine systems other than those exclusively involved in metabolic function. The somatotropic, corticotropic, and gonadal axes as well as bone health have also been shown to be affected by the various BS procedures. Accordingly, further consequences and complications of BS in the long term in systems other than metabolic system need to be addressed in large cohorts, taking into account each bariatric procedure before making generalized recommendations for BS. In this review, current data regarding these issues are summarized, paying special attention to the somatotropic, corticotropic, gonadal axes, and bone post-operative health.

The effects of diabetes therapy on bone: A clinical perspective

The effects of diabetes and diabetes therapy on bone are less known among clinicians. Traditionally, the emphasis of diabetes therapy has been on reducing cardiovascular risk by facilitating reductions in weight, blood pressure, blood sugar, systemic inflammation, and lipid levels. Now, with ample research demonstrating that patients with diabetes are more susceptible to bone fractures relative to controls, there has been a greater or renewed interest in studying the effects of diabetes therapy on bone. Interestingly, the majority of antidiabetic agents positively affect bone, but a few have detrimental effects. Specifically, although insulin has been demonstrated to be anabolic to bone, the rate of hypoglycemic episodes are increased with exogenous infusion; consequently, there is an increased fall and fracture frequency. Other agents such as thiazolidinediones have more direct negative effects on bone through transcriptional regulation. Even metabolic surgery, to a varying operation-dependent extent, exacerbates bone strength and may heighten fracture rate. The remaining diabetes agents seem to have neutral or positive effects on bone. With the increasing incidence of diabetes, it is more pertinent than ever to fully comprehend the effects of diabetes-related therapeutic modalities.

Exenatide preserves trabecular bone microarchitecture in experimental ovariectomized rat model

PURPOSE

The aim of this study is to investigate effects of exenatide (Glucagon-Like Peptide Agonist) replacement on bone mineral density (BMD) and microarchitecture in a surgical menopause-induced osteoporosis model in rats.

METHODS

In this study, 24 female Sprague-Dawley albino mature rats were used. Rats were assigned either to the group ovariectomized administered exenatide or to the control group. Bone Mineral Density (BMD), plasma cytokine levels and histomorphometric analysis were measured.

RESULTS

Ovariectomized rats showed significant decrease BMD values, trabecular counts, trabecular thickness and trabecular area. Also, significant increase trabecular separation and plasma TNF-α (Tumor Necrosis Factor) and IL-6 (Interleukin) levels. Exenatide treatment reversed these changes and it showed a considerable protective effect on trabecular bone microarchitecture.

CONCLUSIONS

Exenatide may be a candidate for use in the treatment of postmenopausal osteoporosis and anti-inflammatory properties can be attributed this effects.

The effects of Exendin-4 on bone marrow-derived mesenchymal cells

PURPOSE

GLP-1 receptor agonists are antidiabetic drugs currently used in the therapy of type 2 diabetes. Despite several in vitro and in vivo animal studies suggesting a beneficial effect of GLP-1 analogues on bone, in humans their skeletal effects are not clear and clinical studies report conflicting results.

METHODS

We differentiated human mesenchymal stromal cells (hMSC) toward the adipogenic and the osteoblastic lineages, analysing the effect of Exendin-4 (EXE) before, during and after specific differentiations.

RESULTS

We showed EXE ability to act selectively on a sub-population of hMSC characterised by a more stem potential, shifting them from G1 to S/M phase of cell cycle. We observed that EXE pre-treatment promotes both adipogenic and osteoblastic differentiations, possibly determined by an increased number of uncommitted progenitors. In fully differentiated cells, EXE affects mature adipocytes by increasing lipolysis, otherwise not altering osteoblasts metabolic activity. Moreover, the increased expression of osteoprotegerin, a modulator of the RANK/RANKL system, observed during osteogenic induction in presence of EXE, could negatively modulate osteoclastogenesis.

CONCLUSIONS

Our data suggest a complex action of EXE on bone, targeting the proliferation of mesenchymal progenitors, the metabolism of mature adipocytes and the modulation of osteoclastogenesis. Thus, an overall positive effect of this molecule on bone quality might be hypothesised.

Liraglutide exerts a bone-protective effect in ovariectomized rats with streptozotocin-induced diabetes by inhibiting osteoclastogenesis

Liraglutide, a glucagon-like peptide-1 receptor agonist, is an anti-diabetic medicine associated with a reduced risk of fracture in diabetic patients. In the present study, rats with streptozotocin (STZ)-induced diabetes and/or bilateral ovariectomy (OVX) were treated with liraglutide for eight weeks. Liraglutide treatment increased insulin secretion and managed blood glucose levels in the rats following STZ-induced diabetes. In addition, STZ- and OVX-induced reduction of femoral bone mineral density and destruction of bone microarchitecture were alleviated by liraglutide. STZ decreased, whereas OVX increased, serum osteocalcin (OC) level (a bone formation marker) and osteoblast counts in the trabecular bone. OVX, however not STZ, markedly increased the level of serum c-terminal telopeptide of type 1 collagen (CTX-1, a bone resorption marker) and osteoclast counts in the trabecular area. Liraglutide treatment significantly increased serum OC levels in all three osteoporotic models, however had minimal effects on osteoblast counts. Furthermore, liraglutide significantly decreased serum CTX-1 level and osteoclast numbers in OVX and STZ+OVX rats. Furthermore, the present study examined the mRNA expression and serum concentrations of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL), and liraglutide significantly decreased the RANKL/OPG ratio compared with the untreated rats, indicating that osteoclastogenesis was inhibited by liraglutide. In summary, the results suggested that liraglutide ameliorates STZ+OVX-induced bone deterioration in the rat model, primarily through the inhibition of osteoclastogenesis. These preliminary findings propose a potentially beneficial effect of liraglutide on the bone health of postmenopausal diabetic patients.

The Glucagon-Like Peptide-1 Receptor Agonist Exendin-4 Inhibits Lipopolysaccharide-Induced Osteoclast Formation and Bone Resorption via Inhibition of TNF-α Expression in Macrophages

Glucagon-like peptide-1 (GLP-1) receptor agonists are an effective treatment approach for type 2 diabetes. Recently, anti-inflammatory effects of GLP-1 receptor agonists have also been reported. Lipopolysaccharide (LPS) induces inflammation and osteoclast formation. In this study, we investigated the effect of exendin-4, a widely used GLP-1 receptor agonist, in LPS-induced osteoclast formation and bone resorption. LPS with or without exendin-4 was administered on mouse calvariae by daily subcutaneous injection. The number of osteoclasts, the ratio of bone resorption pits, and the level of C-terminal cross-linked telopeptide of type I collagen (CTX) were significantly lower in LPS- and exendin-4-coadministered mice than in mice administered with LPS alone. RANKL and TNF-α mRNA expression levels were lower in the exendin-4- and LPS-coadministered group than in the LPS-administered group. Our in vitro results showed no direct effects of exendin-4 on RANKL-induced osteoclast formation, TNF-α-induced osteoclast formation, or LPS-induced RANKL expression in stromal cells. Conversely, TNF-α mRNA expression was inhibited in the exendin-4- and LPS-cotreated macrophages compared with cells treated with LPS alone. These results indicate that the GLP-1 receptor agonist exendin-4 may inhibit LPS-induced osteoclast formation and bone resorption by inhibiting LPS-induced TNF-α production in macrophages.