Effects of short-acting exenatide added three times daily to insulin therapy on bone metabolism in type 1 diabetes

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 Glucagon-Like Peptide-1 Receptor Agonist on Bone Mineral Density and Bone Turnover Markers: A Meta-Analysis

AIMS

Glucagon-like peptide-1 receptor agonist (GLP-1RA) may promote bone formation, but conversely, they could also weaken bones due to the reduction in mechanical load associated with weight loss. However, the clinical effects in humans have not been clearly demonstrated. This meta-analysis aimed to evaluate whether GLP-1RAs affect BMD and bone turnover markers.

MATERIAL AND METHODS

PubMed, Embase, and Scopus were searched on June 13, 2024. The eligibility criteria were: (1) human studies, (2) receiving a GLP-1RA for more than 4 weeks, (3) an untreated control group or a placebo group, (4) reporting of at least one BMD or bone turnover marker, and (5) an RCT design. The risk of bias was assessed using the Cochrane risk of bias 2 tool. Fixed- or random-effects meta-analysis was performed according to heterogeneity.

RESULTS

Seven studies were included in the meta-analysis. GLP-1RAs did not significantly change BMD in the femoral neck (mean difference [MD], 0.01 g/cm2; 95% CI, -0.01-0.04 g/cm2), in the total hip (MD, -0.01 g/cm2; 95% CI, -0.02-0.01 g/cm2), and in the lumbar spine (MD, 0 g/cm2; 95% CI, -0.02-0.02 g/cm2). C-terminal telopeptide of type 1 collagen (CTX), a bone resorption marker, significantly increased after GLP-1RA treatment (MD, 0.04 μg/L; 95% CI, 0.01-0.07 μg/L). GLP-1RAs did not significantly change bone formation markers such as procollagen type 1 N-terminal propeptide, bone-specific alkaline phosphatase, osteocalcin.

CONCLUSIONS

GLP-1RA did not affect BMD and bone formation markers. However, GLP-1RAs led to a significant increase in CTX.

Mechanistic Pathways and Clinical Implications of GLP-1 Receptor Agonists in Type 1 Diabetes Management

GLP-1 receptor agonists, which were initially intended to treat type 2 diabetes patients, have demonstrated promise as an adjuvant therapy for type 1 diabetes (T1D). These medications can manage T1D by improving β-cell function, reducing glucose fluctuation, and providing cardioprotective effects. Recent research suggests that boosting cell proliferation and lowering apoptosis can help maintain the bulk of β-cells. Furthermore, GLP-1 receptor agonists have potent anti-inflammatory characteristics, improving immunological control and lowering systemic inflammation, both of which are critical for reducing autoimmune damage in T1D. Beyond glucose control, these agonists have neuroprotective qualities and aid in weight management. Combining these medications with insulin could significantly change how T1D is managed. The clinical data and biological mechanisms discussed in this review support the potential use of GLP-1 receptor agonists in T1D.

Gut hormone analogues and skeletal health in diabetes and obesity: Evidence from preclinical models

Diabetes mellitus and obesity are rapidly growing worldwide. Aside from metabolic disturbances, these two disorders also affect bone with a higher prevalence of bone fractures. In the last decade, a growing body of evidence suggested that several gut hormones, including ghrelin, gastrin, glucose-dependent insulinotropic polypeptide (GIP), glucagon, and glucagon-like peptide-1 and 2 (GLP-1 and GLP-2, respectively) may affect bone physiology. Several gut hormone analogues have been developed for the treatment of type 2 diabetes and obesity, and could represent a new alternative in the therapeutic arsenal against bone fragility. In the present review, a summary of the physiological roles of these gut hormones and their analogues is presented at the cellular level but also in several preclinical models of bone fragility disorders including type 2 diabetes mellitus, especially on bone mineral density, microarchitecture and bone material properties. The present review also summarizes the impact of GLP-1 receptor agonists approved for the treatment of type 2 diabetes mellitus and the more recent dual or triple analogue on bone physiology and strength.

Effects of Incretin Therapy on Skeletal Health in Type 2 Diabetes-A Systematic Review

Diabetes poses a significant risk to bone health, with Type 1 diabetes (T1D) having a more detrimental impact than Type 2 diabetes (T2D). The group of hormones known as incretins, which includes gastric inhibitory peptide (GIP) and glucagon-like peptide 1 (GLP-1), play a role in regulating bowel function and insulin secretion during feeding. GLP-1 receptor agonists (GLP-1 RAs) are emerging as the primary treatment choice in T2D, particularly when atherosclerotic cardiovascular disease is present. Dipeptidyl peptidase 4 inhibitors (DPP-4is), although less potent than GLP-1 RAs, can also be used. Additionally, GLP-1 RAs, either alone or in combination with GIP, may be employed to address overweight and obesity. Since feeding influences bone turnover, a relationship has been established between incretins and bone health. To explore this relationship, we conducted a systematic literature review following the PRISMA guidelines. While some studies on cells and animals have suggested positive effects of incretins on bone cells, turnover, and bone density, human studies have yielded either no or limited and conflicting results regarding their impact on bone mineral density (BMD) and fracture risk. The effect on fracture risk may vary depending on the choice of comparison drug and the duration of follow-up, which was often limited in several studies. Nevertheless, GLP-1 RAs may hold promise for people with T2D who have multiple fracture risk factors and poor metabolic control. Furthermore, a potential new area of interest is the use of GLP-1 RAs in fracture prevention among overweight and obese people. Based on this systematic review, existing evidence remains insufficient to support a positive or a superior effect on bone health to reduce fracture risk in people with T2D. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The effects of exenatide and insulin glargine treatments on bone turnover markers and bone mineral density in postmenopausal patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) related bone fracture. The effects of glucagon-like peptide-1 receptor analogs for the treatment of T2DM on bone are controversial in human studies. This study aimed to compare the effects of GLP-1 receptor analogs exenatide and insulin glargine treatment on bone turnover marker levels and bone mineral density (BMD) in postmenopausal female patients with T2DM. Thirty female patients with T2DM who were naive to insulin and incretin-based treatments, with spontaneous postmenopause, were randomized to exenatide or insulin glargine arms and were followed up for 24 weeks. BMD was evaluated using dual-energy X-ray absorptiometry and bone turnover markers by serum enzyme-linked immunosorbent assay. The body mass index significantly decreased in the exenatide group compared to the glargine group (P < .001). Receptor activator of nuclear factor kappa-B (RANK) and RANK ligand (RANKL) levels were significantly decreased with exenatide treatment (P = .009 and P = .015, respectively). Osteoprotegerin (OPG) level significantly increased with exenatide treatment (P = .02). OPG, RANK, RANKL levels did not change with insulin glargine treatment. No statistically significant difference was found between the pre- and posttreatment BMD, alkaline phosphatase, bone-specific alkaline phosphatase, and type 1 crosslinked N-telopeptide levels in both treatment arms. Despite significant weight loss with exenatide treatment, BMD did not decrease, OPG increased, and the resorption markers of RANK and RANKL decreased, which may reflect early antiresorptive effects of exenatide via the OPG/RANK/RANKL pathway.

The Gut-Bone Axis in Diabetes

PURPOSE OF REVIEW

To describe recent advances in the understanding of how gut-derived hormones regulate bone homeostasis in humans with emphasis on pathophysiological and therapeutic perspectives in diabetes.

RECENT FINDINGS

The gut-derived incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is important for postprandial suppression of bone resorption. The other incretin hormone, glucagon-like peptide 1 (GLP-1), as well as the intestinotrophic glucagon-like peptide 2 (GLP-2) has been shown to suppress bone resorption in pharmacological concentrations, but the role of the endogenous hormones in bone homeostasis is uncertain. For ambiguous reasons, both patients with type 1 and type 2 diabetes have increased fracture risk. In diabetes, the suppressive effect of endogenous GIP on bone resorption seems preserved, while the effect of GLP-2 remains unexplored both pharmacologically and physiologically. GLP-1 receptor agonists, used for the treatment of type 2 diabetes and obesity, may reduce bone loss, but results are inconsistent. GIP is an important physiological suppressor of postprandial bone resorption, while GLP-1 and GLP-2 may also exert bone-preserving effects when used pharmacologically. A better understanding of the actions of these gut hormones on bone homeostasis in patients with diabetes may lead to new strategies for the prevention and treatment of skeletal frailty related to diabetes.