incretins and Fractures--Bone

The relationship between gut and skeleton is increasingly recognized as part of the integrated physiology of the whole organism. The incretin hormones gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are secreted from the intestine in response to nutrient intake and exhibit several physiological functions including regulation of islet hormone secretion and glucose levels. A number of GLP-1 receptor agonists (GLP-1RAs) are currently used in treatment of type 2 diabetes and obesity. However, GIP and GLP-1 cognate receptors are widely expressed suggesting that incretin hormones mediate effects beyond control of glucose homeostasis, and reports on associations between incretin hormones and bone metabolism have emerged. The aim of this MiniReview was to provide an overview of current knowledge regarding the in vivo and in vitro effects of GIP and GLP-1 on bone metabolism. We identified a total of 30 pre-clinical and clinical investigations of the effects of GIP, GLP-1 and GLP-1RAs on bone turnover markers, bone mineral density (BMD), bone microarchitecture and fracture risk. Studies conducted in cell cultures and rodents demonstrated that GIP and GLP-1 play a role in regulating skeletal homeostasis, with pre-clinical data suggesting that GIP inhibits bone resorption whereas GLP-1 may promote bone formation and enhance bone material properties. These effects are not corroborated by clinical studies. While there is evidence of effects of GIP and GLP-1 on bone metabolism in pre-clinical investigations, clinical trials are needed to clarify whether similar effects are present and clinically relevant in humans.

Topics: Animals; Bone and Bones; Bone Density; Bone Resorption; Diabetes Mellitus, Type 2; Disease Models, Animal; Fractures, Bone; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Incretins; Insulin; Obesity; Osteoblasts; Osteocalcin; Osteoclasts

Bone fractures are common comorbidities of type 2 diabetes mellitus (T2DM). Bone fracture incidence seems to develop due to increased risk of falls, poor bone quality and/or anti-diabetic medications. Previously, a relation between gut hormones and bone has been suspected. Most recent evidences suggest indeed that two gut hormones, namely glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), may control bone remodeling and quality. The GIP receptor is expressed in bone cells and knockout of either GIP or its receptor induces severe bone quality alterations. Similar alterations are also encountered in GLP-1 receptor knock-out animals associated with abnormal osteoclast resorption. Some GLP-1 receptor agonist (GLP-1RA) have been approved for the treatment of type 2 diabetes mellitus and although clinical trials may not have been designed to investigate bone fracture, first results suggest that GLP-1RA may not exacerbate abnormal bone quality observed in T2DM. The recent design of double and triple gut hormone agonists may also represent a suitable alternative for restoring compromised bone quality observed in T2DM. However, although most of these new molecules demonstrated weight loss action, little is known on their bone safety. The present review summarizes the most recent findings on peptide-based incretin therapy and bone physiology.

Topics: Animals; Bone Remodeling; Comorbidity; Diabetes Mellitus, Type 2; Disease Models, Animal; Fractures, Bone; Gastric Inhibitory Polypeptide; Gastrointestinal Hormones; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Incretins; Mice; Mice, Knockout

Older adults with diabetes are at higher risk of fracture and of complications resulting from a fracture. Hence, fracture risk reduction is an important goal in diabetes management. This review is one of a pair discussing the relationship between diabetes, bone and glucose-lowering agents; an accompanying review is provided in this issue of Diabetologia by Beata Lecka-Czernik (DOI 10.1007/s00125-017-4269-4 ). Specifically, this review discusses the challenges of accurate fracture risk assessment in diabetes. Standard tools for risk assessment can be used to predict fracture but clinicians need to be aware of the tendency for the bone mineral density T-score and the fracture risk assessment tool (FRAX) to underestimate risk in those with diabetes. Diabetes duration, complications and poor glycaemic control are useful clinical markers of increased fracture risk. Glucose-lowering agents may also affect fracture risk, independent of their effects on glycaemic control, as seen with the negative skeletal effects of the thiazolidinediones; in this review, the potential effects of glucose-lowering medications on fracture risk are discussed. Finally, the current understanding of effective fracture prevention in older adults with diabetes is reviewed.

Topics: Adult; Aged; Blood Glucose; Bone and Bones; Bone Density; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Female; Fracture Healing; Fractures, Bone; Humans; Hypoglycemic Agents; Incretins; Male; Middle Aged; Odds Ratio; Risk Assessment; Sodium-Glucose Transporter 2; Thiazolidinediones; Treatment Outcome

The aim of the present study was to estimate the effect of incretins on fracture risk in the real-world situation by meta-analysis of the available population-based cohort data. Pubmed and Embase were searched for original articles investigating use of incretin agents, and fracture risk up to December 2015. Adjusted results were extracted and pooled by use of generic inverse variance methods, assuming a random-effects model. Neither current dipeptidyl peptidase 4-inhibitor use nor current glucagon-like peptide 1 receptor agonist use was associated with a decreased risk of fracture: pooled relative risk (pooled RR [95% confidence interval]: 1.02 [0.91-1.13] and 1.03 [0.87-1.22]), respectively. This meta-analysis demonstrated that current use of incretin agents, was not associated with decreased fracture risk. Our findings show the value of representative real-world populations, and the risks associated with suggesting benefits for medications on the basis of safety reporting in randomized controlled trials.

Topics: Dipeptidyl-Peptidase IV Inhibitors; Fractures, Bone; Glucagon-Like Peptide-1 Receptor; Humans; Hypoglycemic Agents; Incretins; Randomized Controlled Trials as Topic; Risk

Anti-diabetic drugs are widely used and are essential for adequate glycemic control in patients with type 2 diabetes. Recently, marketed anti-diabetic drugs include incretin-based therapies (GLP-1 receptor agonists and DPP-4 inhibitors) and sodium-glucose co-transporter 2 (SGLT2) inhibitors. In contrast to well-known detrimental effects of thiazolidinediones on bone metabolism and fracture risk, clinical data on the safety of incretin-based therapies is limited. Based on meta-analyses of trials investigating the glycemic-lowering effect of GLP-1 receptor agonists and DPP4 inhibitors, it seems that incretin-based therapies are not associated with an increase in fracture risk. Sodium-glucose co-transporter 2 inhibitors may alter calcium and phosphate homeostasis as a result of secondary hyperparathyroidism induced by increased phosphate reabsorption. Although these changes may suggest detrimental effects of SGLT-2 inhibitors on skeletal integrity, treatment-related direct effects on bone metabolism seem unlikely. Observed changes in BMD, however, seem to result from increased bone turnover in the early phase of drug-induced weight loss. Fracture risk, which is observed in older patients with impaired renal function and elevated cardiovascular disease risk treated with SGLT2 inhibitors, seems to be independent of direct effects on bone but more likely to be associated with falls and changes in hydration status secondary to osmotic diuresis.

Topics: Accidental Falls; Bone Density; Bone Remodeling; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Fractures, Bone; Glucagon-Like Peptide-1 Receptor; Humans; Incretins; Risk Factors; Sodium-Glucose Transporter 2 Inhibitors

Patients with type 2 diabetes mellitus (T2DM) have an increased risk of fragility fractures despite increased body weight and normal or higher bone mineral density. The mechanisms by which T2DM increases skeletal fragility are unclear. It is likely that a combination of factors, including a greater risk of falling, regional osteopenia, and impaired bone quality, contributes to the increased fracture risk. Drugs for the treatment of T2DM may also impact on the risk for fractures. For example, thiazolidinediones accelerate bone loss and increase the risk of fractures, particularly in older women. In contrast, metformin and sulfonylureas do not appear to have a negative effect on bone health and may, in fact, protect against fragility fracture. Animal models indicate a potential role for incretin hormones in bone metabolism, but there are only limited data on the impact of dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 agonists on bone health in humans. Animal models also have demonstrated a role for amylin in bone metabolism, but clinical trials in patients with type 1 diabetes with an amylin analog (pramlintide) have not shown a significant impact on bone metabolism. The effects of insulin treatment on fracture risk are inconsistent with some studies showing an increased risk and others showing no effect. Finally, although there is limited information on the latest class of medications for the treatment of T2DM, the sodium-glucose co-transporter-2 inhibitors, these drugs do not seem to increase fracture risk. Because diabetes is an increasingly common chronic condition that can affect patients for many decades, further research into the effects of agents for the treatment of T2DM on bone metabolism is warranted. In this review, the physiological mechanisms and clinical impact of diabetes treatments on bone health and fracture risk in patients with T2DM are described.

Topics: Bone and Bones; Bone Density; Bone Remodeling; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Fractures, Bone; Hip Fractures; Humans; Hypoglycemic Agents; Incretins; Insulin; Islet Amyloid Polypeptide; Metformin; Sulfonylurea Compounds; Thiazolidinediones

Patients with diabetes are at greater risk of fractures mostly due to not only to extraskeletal factors, such as propensity to fall, but also to bone quality alteration, which reduces bone strength. In people with diabetes, insulin deficiency and hyperglycaemia seem to play a role in determining bone formation alteration by advanced glycation end product (AGE) accumulation or AGE/RAGE (receptors for AGE) axis imbalance, which directly influence osteoblast activity. Moreover, hyperglycaemia and oxidative stress are able to negatively influence osteocalcin production and the Wnt signalling pathways with an imbalance of osteoblast/osteoclast activity leading to bone quality reduction as global effect. In addition, other factors such as insulin growth factors and peroxisome proliferator-activated receptor-γ pathways seem to have an important role in the pathophysiology of osteoporosis in diabetes. Although there are conflicting data in literature, adequate glycaemic control with hypoglycaemic treatment may be an important element in preventing bone tissue alterations in both type 1 and type 2 diabetes. Attention should be paid to the use of thiazolidinediones, especially in older women, because the direct negative effect on bone could exceed the positive effect of glycaemic control. Finally, preliminary data on animals and in humans suggest the hypothesis that incretins and dipeptidyl peptidase-4 inhibitors could have a positive effect on bone metabolism by a direct effect on bone cells; however, such issue needs further investigations.

Topics: Aging; Animals; Bone Density; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Female; Fractures, Bone; Glycation End Products, Advanced; Humans; Hypoglycemic Agents; Incretins; Male; Metformin; Osteocalcin; Osteoporosis; PPAR gamma; Risk Factors; Signal Transduction; Thiazolidinediones; Wnt Proteins

Novel incretin-based drugs, such as glucagon-like peptide-1 receptor agonists (GLP-1 RA) and dipeptidyl peptidase-4 inhibitors (DPP-4i), have been last introduced in the pharmacological treatment of type 2 diabetes. In the last few years, the interest on the relationship of gut hormones with bone metabolism in diabetes has been increasing. The aim of present paper is to examine in vitro and in vivo evidence on the connections between incretin hormones and bone metabolism. We also discuss results of clinical trials and metaanalysis, explore the effects of incretin drugs in vitro on osteogenic cells and osteoclasts, and speculate on the possibility of different effects of GLP-1 RA and DPP-4i on the risk of bone fractures risk in humans. Although existing preliminary evidence suggests a protective effect on the bone, at least for DPP-4i, further controlled, long-term studies with measurement of bone markers, bone density, and clinical fractures rates are needed to substantiate and confirm those findings.

Topics: Animals; Bone and Bones; Bone Resorption; Clinical Trials as Topic; Dipeptidyl-Peptidase IV Inhibitors; Female; Fractures, Bone; Glucagon-Like Peptide-1 Receptor; Hormones; Humans; Incretins; Male; Models, Biological; Osteoclasts; Osteogenesis; Protease Inhibitors; Receptors, Glucagon

Postmenopausal individuals with type 2 diabetes are susceptible to fractures due to the interaction of elevated blood glucose levels and a deficiency of the hormone estrogen. Despite continued concerns of fracture risks associated with sodium-glucose cotransporter 2 inhibitors (SGLT2i), existing evidence in this high-risk population is lacking.. To assess the risk of fractures associated with SGLT2i vs incretin-based drugs of dipeptidyl-peptidase 4 inhibitors (DPP4i) and glucagon-like peptide 1 receptor agonists (GLP1RA), separately, in postmenopausal individuals with type 2 diabetes.. This active-comparator, new-user cohort study used nationwide claims data of Korea and took place from January 1, 2013, to December 31, 2020. Postmenopausal individuals (aged ≥45 years) with type 2 diabetes were included.. New users of SGLT2i or comparator drugs.. The primary outcome was overall fractures, comprising vertebral, hip, humerus, and distal radius fractures. Patients were followed up from the day after drug initiation until the earliest of outcome occurrence, drug discontinuation (90-day grace period) or switch, death, or end of the study period. After propensity score fine stratification, hazard ratios (HRs) with 95% CIs were estimated using weighted Cox models.. Among 37 530 (mean [SD] age, 60.6 [9.7] years) and 332 004 (mean [SD] age, 60.6 [9.9] years) new users of SGLT2i and DPP4i, respectively, a lower rate of incident overall fractures was presented with SGLT2i vs DPP4i (weighted HR, 0.78; 95% CI, 0.72-0.84). Among 111 835 (mean [SD] age, 61.4 [9.8] years) and 8177 (mean [SD] age, 61.1 [10.3] years) new users of SGLT2i and GLP1RA, respectively, no association with an increased risk of overall fractures was presented with SGLT2i vs GLP1RA (weighted HR, 0.92; 95% CI, 0.68-1.24). Results from several subgroup and sensitivity analyses presented consistent results from main analysis.. This population-based cohort study suggests that SGLT2i was not associated with an increased rate of incident fractures compared with DPP4i and GLP1RA, separately, among postmenopausal individuals with type 2 diabetes.

Topics: Aged; Cohort Studies; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Fractures, Bone; Humans; Incretins; Middle Aged; Sodium-Glucose Transporter 2 Inhibitors