Four-month treatment with GLP-2 significantly increases hip BMD: a randomized, placebo-controlled, dose-ranging study in postmenopausal women with low BMD

Bone health in adults with obesity before and after interventions to promote weight loss

Obesity and its associated comorbidities constitute a serious and growing public health burden. Fractures affect a substantial proportion of people with obesity and result from reduced bone strength relative to increased mechanical loading, together with an increased risk of falls. Factors contributing to fractures in people with obesity include adverse effects of adipose tissue on bone and muscle and, in many people, the coexistence of type 2 diabetes. Strategies to reduce weight include calorie-restricted diets, exercise, bariatric surgery, and pharmacological interventions with GLP-1 receptor agonists. However, although weight loss in people with obesity has many health benefits, it can also have adverse skeletal effects, with increased bone loss and fracture risk. Priorities for future research include the development of effective approaches to reduce fracture risk in people with obesity and the investigation of the effects of GLP-1 receptor agonists on bone loss resulting from weight reduction.

Antidiabetic Agents and Bone Quality: A Focus on Glycation End Products and Incretin Pathway Modulations

Diabetes mellitus is associated with inadequate bone health and quality and heightened susceptibility to fractures, even in patients with normal or elevated bone mineral density. Elevated advanced glycation end-products (AGEs) and a suppressed incretin pathway are among the mechanisms through which diabetes affects the bone. Accordingly, the present review aimed to investigate the effects of antidiabetic medications on bone quality, primarily through AGEs and the incretin pathway. Google Scholar, Cochrane Library, and PubMed were used to examine related studies until February 2024. Antidiabetic medications influence AGEs and the incretin pathway directly or indirectly. Certain antidiabetic drugs including metformin, glucagon-like peptide-1 receptor agonists (GLP-1RA), dipeptidyl-peptidase-4 (DDP-4) inhibitors, α-glucosidase inhibitors (AGIs), sodium-glucose co-transporter-2 inhibitors, and thiazolidinediones (TZDs), directly affect AGEs through multiple mechanisms. These mechanisms include decreasing the formation of AGEs and the expression of AGEs receptor (RAGE) in tissue and increasing serum soluble RAGE levels, resulting in the reduced action of AGEs. Similarly, metformin, GLP-1RA, DDP-4 inhibitors, AGIs, and TZDs may enhance incretin hormones directly by increasing their production or suppressing their metabolism. Additionally, these medications could influence AGEs and the incretin pathway indirectly by enhancing glycemic control. In contrast, sulfonylureas have not demonstrated any obvious effects on AGEs or the incretin pathway. Considering their favorable effects on AGEs and the incretin pathway, a suitable selection of antidiabetic drugs may facilitate more protective effects on the bone in diabetic patients.

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.

Targeting the GLP-2 receptor in the management of obesity

Recent advancements in understanding glucagon-like peptide 2 (GLP-2) biology and pharmacology have sparked interest in targeting the GLP-2 receptor (GLP-2R) in the treatment of obesity. GLP-2 is a proglucagon-derived 33-amino acid peptide co-secreted from enteroendocrine L cells along with glucagon-like peptide 1 (GLP-1) and has a range of actions via the GLP-2R, which is particularly expressed in the gastrointestinal tract, the liver, adipose tissue, and the central nervous system (CNS). In humans, GLP-2 evidently induces intestinotrophic effects (i.e., induction of intestinal mucosal proliferation and improved gut barrier function) and promotes mesenteric blood flow. However, GLP-2 does not seem to have appetite or food intake-reducing effects in humans, but its gut barrier-promoting effect may be of interest in the context of obesity. Obesity is associated with reduced gut barrier function, increasing the translocation of proinflammatory gut content to the circulation. This phenomenon constitutes a strong driver of obesity-associated systemic low-grade inflammation, which in turn plays a major role in the development of most obesity-associated complications. Thus, the intestinotrophic and gut barrier-improving effect of GLP-2, which in obese rodent models shows strong anti-inflammatory potential, may, in combination with food intake-reducing strategies, e.g., GLP-1 receptor (GLP-1) agonism, be able to rectify core pathophysiological mechanism of obesity. Here, we provide an overview of GLP-2 physiology in the context of obesity pathophysiology and review the pharmacological potential of GLP-2R activation in the management of obesity and related comorbidities.

Effects of Exogenous GIP and GLP-2 on Bone Turnover in Individuals With Type 2 Diabetes

CONTEXT

Individuals with type 2 diabetes (T2D) have an increased risk of bone fractures despite normal or increased bone mineral density. The underlying causes are not well understood but may include disturbances in the gut-bone axis, in which both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are regulators of bone turnover. Thus, in healthy fasting participants, both exogenous GIP and GLP-2 acutely reduce bone resorption.

OBJECTIVE

The objective of this study was to investigate the acute effects of subcutaneously administered GIP and GLP-2 on bone turnover in individuals with T2D.

METHODS

We included 10 men with T2D. Participants met fasting in the morning on 3 separate test days and were injected subcutaneously with GIP, GLP-2, or placebo in a randomized crossover design. Blood samples were drawn at baseline and regularly after injections. Bone turnover was estimated by circulating levels of collagen type 1 C-terminal telopeptide (CTX), procollagen type 1 N-terminal propeptide (P1NP), sclerostin, and PTH.

RESULTS

GIP and GLP-2 significantly reduced CTX to (mean ± SEM) 66 ± 7.8% and 74 ± 5.9% of baseline, respectively, compared with after placebo (P = .001). In addition, P1NP and sclerostin increased acutely after GIP whereas a decrease in P1NP was seen after GLP-2. PTH levels decreased to 67 ± 2.5% of baseline after GLP-2 and to only 86 ± 3.4% after GIP.

CONCLUSION

Subcutaneous GIP and GLP-2 affect CTX and P1NP in individuals with T2D to the same extent as previously demonstrated in healthy individuals.

Gut hormones and bone homeostasis: potential therapeutic implications

Bone resorption follows a circadian rhythm, with a marked reduction in circulating markers of resorption (such as carboxy-terminal telopeptide region of collagen type I in serum) in the postprandial period. Several gut hormones, including glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP1) and GLP2, have been linked to this effect in humans and rodent models. These hormones are secreted from enteroendocrine cells in the gastrointestinal tract in response to a variety of stimuli and effect a wide range of physiological processes within and outside the gut. Single GLP1, dual GLP1-GIP or GLP1-glucagon and triple GLP1-GIP-glucagon receptor agonists have been developed for the treatment of type 2 diabetes mellitus and obesity. In addition, single GIP, GLP1 and GLP2 analogues have been investigated in preclinical studies as novel therapeutics to improve bone strength in bone fragility disorders. Dual GIP-GLP2 analogues have been developed that show therapeutic promise for bone fragility in preclinical studies and seem to exert considerable activity at the bone material level. This Review summarizes the evidence of the action of gut hormones on bone homeostasis and physiology.

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.

Gut-Derived Peptide Hormone Analogues and Potential Treatment of Bone Disorders in Obesity and Diabetes Mellitus

Obesity and diabetes mellitus are prevalent metabolic disorders that have a detrimental impact on overall health. In this regard, there is now a clear link between these metabolic disorders and compromised bone health. Interestingly, both obesity and diabetes lead to elevated risk of bone fracture which is independent of effects on bone mineral density (BMD). In this regard, gastrointestinal (GIT)-derived peptide hormones and their related long-acting analogues, some of which are already clinically approved for diabetes and/or obesity, also seem to possess positive effects on bone remodelling and microarchitecture to reduce bone fracture risk. Specifically, the incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), as well as glucagon-like peptide-2 (GLP-2), exert key direct and/or indirect benefits on bone metabolism. This review aims to provide an initial appraisal of the relationship between obesity, diabetes and bone, with a focus on the positive impact of these GIT-derived peptide hormones for bone health in obesity/diabetes. Brief discussion of related peptides such as parathyroid hormone, leptin, calcitonin and growth hormone is also included. Taken together, drugs engineered to promote GIP, GLP-1 and GLP-2 receptor signalling may have potential to offer therapeutic promise for improving bone health in obesity and diabetes.

Signs of a Glucose- and Insulin-Independent Gut-Bone Axis and Aberrant Bone Homeostasis in Type 1 Diabetes

CONTEXT

Gut hormones seem to play an important role in postprandial bone turnover, which also may be affected by postprandial plasma glucose excursions and insulin secretion.

OBJECTIVE

To investigate the effect of an oral glucose tolerance test (OGTT) and an isoglycemic intravenous glucose infusion (IIGI) on bone resorption and formation markers in individuals with type 1 diabetes and healthy controls.

METHODS

This observational case-control study, conducted at the Center for Clinical Metabolic Research, Gentofte Hospital, Hellerup, Denmark, included 9 individuals with C-peptide negative type 1 diabetes and 8 healthy controls matched for gender, age, and body mass index. Subjects underwent an OGTT and a subsequent IIGI. We analyzed changes in bone resorption assessed by measurements of carboxy-terminal type I collagen crosslinks (CTX) and in bone formation as assessed by procollagen type I N-terminal propeptide (PINP) concentrations.

RESULTS

Baseline CTX and PINP levels were similar in the 2 groups. Both groups exhibited significantly greater suppression of CTX during OGTT than IIGI. PINP levels were unaffected by OGTT and IIGI, respectively, in healthy controls. Participants with type 1 diabetes displayed impaired suppression of CTX-assessed bone resorption and inappropriate suppression of PINP-assessed bone formation during OGTT.

CONCLUSION

Our data suggest the existence of a gut-bone axis reducing bone resorption in response to oral glucose independently of plasma glucose excursions and insulin secretion. Subjects with type 1 diabetes showed impaired suppression of bone resorption and reduced bone formation during OGTT, which may allude to the reduced bone mineral density and increased fracture risk characterizing these individuals.

Post-prandial secretion of glucagon-like peptide-2 (GLP-2) after carbohydrate-, fat- or protein enriched meals in healthy subjects

Glucagon-like peptide 2 (GLP-2) is an important regulator of intestinal growth and function. In adherable mixed meals the macronutrient composition with the best potential for stimulating GLP-2 secretion is not known. We compared the effect of 3 iso-energetic meals, where approximately 60 % of the energy ratio was provided as either carbohydrate, fat, or protein, respectively, on the post-prandial endogenous GLP-2 secretion. The responses were compared to secretion profiles of peptide YY (PYY), and glucose-dependent insulinotropic peptide (GIP). Ten healthy subjects were admitted on three occasions, at least a week apart, after a night of fasting. In an open-label, crossover design, they were randomized to receive a high carbohydrate (HC), high fat (HF) or high protein (HP) meal. The meals were approximately ∼3.9 MJ. Venous blood was collected for 240 min, and plasma concentrations of GLP-2, GIP and PYY were measured with specific radioimmunoassays. Mean GLP-2 levels peaked already at 30 min for the HC meal, however the HP meal induced the highest mean GLP-2 peaking levels, resulting in significantly higher mean GLP-2 area under the curve (AUC) from baseline of 7279 pmol*min/L, 95 %-CI [6081;8477] compared to the HC meal: 4764 pmol*min/L, 95 %-CI [3498;6029], p = 0.020 and the HF meal: 4796 pmol*min/L, [3385;6207], p = 0.011. Findings were similar for the PYY. The HC meal provided a greater AUC for GIP compared to the HP- and HF meals. The HP meal was most effective with respect to stimulation of the postprandial GLP-2 and PYY secretion, whereas the HC meal was more effective for GIP.

Acarbose diminishes postprandial suppression of bone resorption in patients with type 2 diabetes

AIMS

The alpha-glucosidase inhibitor acarbose is an antidiabetic drug delaying assimilation of carbohydrates and, thus, increasing the amount of carbohydrates in the distal parts of the intestines, which in turn increases circulating levels of the gut-derived incretin hormone glucagon-like peptide 1 (GLP-1). As GLP-1 may suppress bone resorption, acarbose has been proposed to potentiate meal-induced suppression of bone resorption. We investigated the effect of acarbose treatment on postprandial bone resorption in patients with type 2 diabetes and used the GLP-1 receptor antagonist exendin(9-39)NH₂ to disclose contributory effect of acarbose-induced GLP-1 secretion.

METHODS

In a randomised, placebo-controlled, double-blind, crossover study, 15 participants with metformin-treated type 2 diabetes (2 women/13 men, age 71 (57-85 years), BMI 29.7 (23.6-34.6 kg/m²), HbA1c 48 (40-74 mmol/mol)/6.5 (5.8-11.6 %) (median and range)) were subjected to two 14-day treatment periods with acarbose and placebo, respectively, separated by a six-week wash-out period. At the end of each period, circulating bone formation and resorption markers were assessed during two randomised 4-h liquid mixed meal tests (MMT) with infusions of exendin(9-39)NH₂ and saline, respectively. Glucagon-like peptide 2 (GLP-2) was also assessed.

RESULTS

Compared to placebo, acarbose impaired the MMT-induced suppression of CTX as assessed by baseline-subtracted area under curve (P = 0.0037) and nadir of CTX (P = 0.0128). During acarbose treatment, exendin(9-39)NH₂ infusion lowered nadir of CTX compared to saline (P = 0.0344). Neither parathyroid hormone or the bone formation marker procollagen 1 intact N-terminal propeptide were affected by acarbose or GLP-1 receptor antagonism. Acarbose treatment induced a greater postprandial GLP-2 response than placebo treatment (P = 0.0479) and exendin(9-39)NH₂ infusion exacerbated this (P = 0.0002).

CONCLUSIONS

In patients with type 2 diabetes, treatment with acarbose reduced postprandial suppression of bone resorption. Acarbose-induced GLP-1 secretion may contribute to this phenomenon as the impairment was partially reversed by GLP-1 receptor antagonism. Also, acarbose-induced reductions in other factors reducing bone resorption, e.g. glucose-dependent insulinotropic polypeptide, may contribute.

Long-acting agonists of human and rodent GLP-2 receptors for studies of the physiology and pharmacological potential of the GLP-2 system

BACKGROUND AND PURPOSE

Glucagon-like peptide-2 (GLP-2) is secreted postprandially from enteroendocrine Lcells and has anabolic action on gut and bone. Short-acting teduglutide is the only approved GLP-2 analog for the treatment of short-bowel syndrome (SBS). To improve the therapeutic effect, we created a series of lipidated GLP-2R agonists.

EXPERIMENTAL APPROACH

Six GLP-2 analogs were studied in vitro for cAMP accumulation, β-arrestin 1 and 2 recruitment, affinity, and internalization. The trophic actions on intestine and bone were examined in vivo in rodents.

KEY RESULTS

Lipidations at lysines introduced at position 12, 16, and 20 of hGLP-2(1-33) were well-tolerated with less than 2.2-fold impaired potency and full efficacy at the hGLP-2R in cAMP accumulation. In contrast, N- and C-terminal (His1 and Lys30) lipidations impaired potency by 4.2- and 45-fold and lowered efficacy to 77% and 85% of hGLP-2, respectively. All variants were similarly active on the rat and mouse GLP-2Rs and the three most active variants displayed increased selectivity for hGLP-2R over hGLP-1R activation, compared to native hGLP-2. Impact on arrestin recruitment and receptor internalization followed that of Gαs-coupling, except for lipidation in position 20, where internalization was more impaired, suggesting desensitization protection. A highly active variant (C16 at position 20) with low internalization and a half-life of 9.5 h in rats showed improved gut and bone tropism with increased weight of small intestine in mice and decreased CTX levels in rats.

CONCLUSION AND IMPLICATION

We present novel hGLP-2 agonists suitable for in vivo studies of the GLP-2 system to uncover its pharmacological potential.

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.

Biased GLP-2 agonist with strong G protein-coupling but impaired arrestin recruitment and receptor desensitization enhances intestinal growth in mice

BACKGROUND AND PURPOSE

Glucagon-like peptide-2 (GLP-2) is secreted postprandially by enteroendocrine L-cells and stimulates growth of the gut and bone. One GLP-2 analogue is approved for short bowel syndrome (SBS). To improve therapeutic efficacy, we developed biased GLP-2 receptor (GLP-2R) agonists through N-terminal modifications.

EXPERIMENTAL APPROACH

Variants with Ala and Trp substitutions of the first seven positions of GLP-2(1-33) were studied in vitro for affinity, G protein activation (cAMP accumulation), recruitment of β-arrestin 1 and 2, and internalization of the human and mouse GLP-2R. The intestinotrophic actions of the most efficacious (cAMP) biased variant were examined in mice.

KEY RESULTS

Ala substitutions had more profound effects than Trp substitutions. For both, alterations at positions 1, 3 and 6 most severely impaired activity. β-arrestin recruitment was more affected than cAMP accumulation. Among Ala substitutions, [H1A], [D3A] and [F6A] impaired potency (EC₅₀ ) for cAMP-accumulation >20-fold and efficacy (E_max ) to 48%-87%, and were unable to recruit arrestins. The Trp substitutions, [A2W], [D3W] and [G4W] were partial agonists (E_max of 46%-59%) with 1.7-12-fold decreased potencies in cAMP and diminished β-arrestin recruitment. The biased variants, [F6A], [F6W] and [S7W] induced less GLP-2R internalization compared with GLP-2, which induced internalization in a partly arrestin-independent manner. In mice, [S7W] enhanced gut trophic actions with increased weight of the small intestine, increased villus height and crypt depth compared with GLP-2.

CONCLUSION AND IMPLICATIONS

G protein-biased GLP-2R agonists with diminished receptor desensitization have superior intestinotrophic effects and may represent improved treatment of intestinal insufficiency including SBS.

N-terminal alterations turn the gut hormone GLP-2 into an antagonist with gradual loss of GLP-2 receptor selectivity towards more GLP-1 receptor interaction

BACKGROUND AND PURPOSE

To fully elucidate the regulatory role of the GLP-2 system in the gut and the bones, potent and selective GLP-2 receptor (GLP-2R) antagonists are needed. Searching for antagonist activity, we performed systematic N-terminal truncations of human GLP-2(1-33).

EXPERIMENTAL APPROACH

COS-7 cells were transfected with the human GLP-2R and assessed for cAMP accumulation or competition binding using ¹²⁵ I-GLP-2(1-33)[M10Y]. To examine selectivity, human GLP-1 or GIP receptor expressing COS-7 cells were assessed for cAMP accumulation.

KEY RESULTS

The affinity for the GLP-2R of the N-terminally truncated GLP-2 peptides decreased with reduced N-terminal peptide length (K_i 6.5-871 nM), while increasing antagonism appeared with inhibitory potencies (IC₅₀ ) values from 79 to 204 nM for truncation up to GLP-2(4-33) and then declined. In contrast, truncation-dependent increases in intrinsic activity were observed from an E_max of only 20% for GLP-(2-33) up to 46% for GLP-2(6-33) at 1 μM, followed by a decline. GLP-2(9-33) had the highest intrinsic efficacy (E_max 65%) and no antagonistic properties. Moreover, with truncations up to GLP-2(8-33) a gradual loss in selectivity for the GLP-2R appeared with increasing GLP-1 receptor (GLP-1R) inhibition (up to 73% at 1 μM). Lipidation of the peptides improved antagonism (IC₅₀ down to 7.9 nM) for both the GLP-2R and the GLP-1R.

CONCLUSION AND IMPLICATIONS

The N-terminus of GLP-2 is crucial for GLP-2R activity and selectivity. Our observations form the basis for the development of tool compounds for further characterization of the GLP-2 system.

GIP and GLP-2 together improve bone turnover in humans supporting GIPR-GLP-2R co-agonists as future osteoporosis treatment

The intestinal hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are key regulators of postprandial bone turnover in humans. We hypothesized that GIP and GLP-2 co-administration would provide stronger effect on bone turnover than administration of the hormones separately, and tested this using subcutaneous injections of GIP and GLP-2 alone or in combination in humans. Guided by these findings, we designed series of GIPR-GLP-2R co-agonists as template for new osteoporosis treatment. The clinical experiment was a randomized cross-over design including 10 healthy men administered subcutaneous injections of GIP and GLP-2 alone or in combination. The GIPR-GLP-2R co-agonists were characterized in terms of binding and activation profiles on human and rodent GIP and GLP-2 receptors, and their pharmacokinetic (PK) profiles were improved by dipeptidyl peptidase-4 protection and site-directed lipidation. Co-administration of GIP and GLP-2 in humans resulted in an additive reduction in bone resorption superior to each hormone individually. The GIPR-GLP-2R co-agonists, designed by combining regions of importance for cognate receptor activation, obtained similar efficacies as the two native hormones and nanomolar potencies on both human receptors. The PK-improved co-agonists maintained receptor activity along with their prolonged half-lives. Finally, we found that the GIPR-GLP-2R co-agonists optimized toward the human receptors for bone remodeling are not feasible for use in rodent models. The successful development of potent and efficacious GIPR-GLP-2R co-agonists, combined with the improved effect on bone metabolism in humans by co-administration, support these co-agonists as a future osteoporosis treatment.

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.

Novel agonist- and antagonist-based radioligands for the GLP-2 receptor - useful tools for studies of basic GLP-2R pharmacology

Background

Glucagon‐like peptide‐2 (GLP‐2) is a pro‐glucagon‐derived hormone secreted from intestinal enteroendocrine L cells with actions on gut and bones. GLP‐2(1–33) is cleaved by DPP‐4, forming GLP‐2(3–33), having low intrinsic activity and competitive antagonism properties at GLP‐2 receptors. We created radioligands based on these two molecules.

Experimental approach

The methionine in position 10 of GLP‐2(1–33) and GLP‐2(3–33) was substituted with tyrosine (M10Y) enabling oxidative iodination, creating [¹²⁵I]‐hGLP‐2(1–33,M10Y) and [¹²⁵I]‐hGLP‐2(3–33,M10Y). Both were characterized by competition binding, on‐and‐off‐rate determination and receptor activation. Receptor expression was determined by target‐tissue autoradiography and immunohistochemistry.

Key results

Both M10Y‐substituted peptides induced cAMP production via the GLP‐2 receptor comparable to the wildtype peptides. GLP‐2(3–33,M10Y) maintained the antagonistic properties of GLP‐2(3–33). However, hGLP‐2(1–33,M10Y) had lower arrestin recruitment than hGLP‐2(1–33). High affinities for the hGLP‐2 receptor were observed using [¹²⁵I]‐hGLP‐2(1–33,M10Y) and [¹²⁵I]‐hGLP‐2(3–33,M10Y) with K_D values of 59.3 and 40.6 nM. The latter (with antagonistic properties) had higher B_max and faster on and off rates compared to the former (full agonist). Both bound the hGLP‐1 receptor with low affinity (K_i of 130 and 330 nM, respectively). Autoradiography in wildtype mice revealed strong labelling of subepithelial myofibroblasts, confirmed by immunohistochemistry using a GLP‐2 receptor specific antibody that in turn was confirmed in GLP‐2 receptor knock‐out mice.

Conclusion and implications

Two new radioligands with different binding kinetics, one a full agonist and the other a weak partial agonist with antagonistic properties were developed and subepithelial myofibroblasts identified as a major site for GLP‐2 receptor expression.

Glucose variability and low bone turnover in people with type 2 diabetes

INTRODUCTION

Type 2 diabetes (T2D) is related to an increased fracture risk and low bone turnover. However, the mechanisms are not elucidated. In the present study we investigate the association between glycemic variability and bone turnover markers.

METHODS

100 participants with T2D and 100 age and gender matched controls were included in this cross-sectional study. All participants with T2D were equipped with a continuous glucose monitoring (CGM) sensor for 3 days (CGMS iPro Continuous Glucose Recorder; Medtronic MiniMed). The dawn glucose levels were defined as a morning period starting 1 h before breakfast ending 1 h post ingestion. On all participants serum (s)-C-terminal cross-linked telopeptide of type-I collagen (CTX), s-procollagen type 1 amino terminal propeptide (P1NP), and s-sclerostin were measured.

RESULTS

Participants with T2D displayed significantly lower levels of the bone resorption marker s-CTX and the bone formation marker s-P1NP compared to controls. S-CTX was significantly negatively associated with the mean amplitude of glycemic excursions (MAGE) and the dawn glucose levels whereas s-P1NP only was significantly negatively associated with the dawn glucose levels while it was borderline significantly associated with MAGE (p = 0.05). S-CTX and s-P1NP were significantly lower among the 50% with the highest dawn glucose levels compared to the 50% lowest dawn glucose levels also after adjustment for age, gender, glycated hemoglobin A1c (HbA1c), and body mass index (BMI).

CONCLUSION

We observed that the amplitude of glycemic excursions and rise in dawn glucose was negatively associated with bone turnover markers. Future research is needed to determine whether reduction of the amplitude of glycemic excursions increase bone turnover markers.

The enteroendocrine-osseous axis in patients with long-term type 1 diabetes mellitus

INTRODUCTION

The relationship between the gut and skeleton is increasingly recognized as a component of the regulation of carbohydrate metabolism. The aim of our study was to assess the relationship between bone mineral density (BMD), incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), intestinotrophic peptide glucagon-like peptide-2 (GLP-2) and osteocalcin isoforms in patients with long-term type 1 diabetes (T1D) when compared to healthy controls.

METHODS

Eighty two patients with long term T1D, treated in the Department of Metabolic Diseases and 53 healthy controls were recruited to the study. Long term disease duration was defined as lasting for more than 10 years. The control group was selected among age- and sex-matched healthy people. Fasting blood samples were collected to measure levels of incretin hormones (GLP-1, GLP-2, GIP), two forms of osteocalcin (uncarboxylated (ucOC), and carboxylated (cOC)), and additional biochemical parameters associated with glucose and bone metabolism (HbA1c, calcium, phosphorus, 25(OH)D3, PTH).

RESULTS

Patients with T1D had higher BMI than in controls (p = 0.02). There was no difference in BMD at the lumbar spine and the femoral neck between patients with long-term T1D and healthy ones. Z-score values in both groups were within normal ranges. The level of GIP was significantly higher in T1D patients (p = 0.0002) in comparison to the healthy ones. The levels of GLP-1 and GLP-2 did not differ between T1D patients and controls. In the T1D group, strong, positive associations were found between serum levels of GLP-1 and cOC (r = 0.546, p < 0.001) and between GLP-1 and total OC (r = 0.51, p < 0.001), also after adjusting for BMI (p < 0.001 and p < 0.001, respectively). Significant positive associations were also found between serum levels of GLP-2 and cOC (r = 0.27, p = 0.013) and between GLP-2 and total OC (r = 0.25, p = 0.018), also in a multivariate regression (p = 0.009, p = 0,175, respectively). Moreover, in T1D patients, GLP-1 correlated positively with the femoral neck BMD (g/cm²) (r = 0.265, p = 0.016) and this association was statistically significant after adjusting for BMI (p = 0.011). These correlations were not present in the control group. The only significant correlation observed in the control group was between OC and BMD of the neck (p = 0.049 for neck BMD g/cm², and p = 0.041 for neck Z-score).

CONCLUSIONS

Our data suggests an effect of gut hormones on bone in long-term T1D, which could be associated with OC activity, however we did not find a direct connection with glucose metabolism. GLP-1 could have a possible, protective role on bone mineral density in patients with T1D. The data from our study suggests that gut hormones could be considered as a new link in the skeleton - pancreatic endocrine loop in patients with T1D.

Subcutaneous GIP and GLP-2 inhibit nightly bone resorption in postmenopausal women: A preliminary study

BACKGROUND

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are gut hormones secreted in response to food ingestion, and they have been suggested to regulate bone turnover. In humans, exogenous GIP and GLP-2 acutely inhibit bone resorption as measured by circulating levels of carboxy-terminal type 1 collagen crosslinks (CTX).

OBJECTIVE

The objective was to study the individual and combined acute effects of GIP and GLP-2 on bone turnover in postmenopausal women during nighttime - a period of increased bone resorption.

METHODS

Using a randomized, placebo-controlled, double-blinded, crossover design, each participant (n = 9) received on four separate study days: GIP, GLP-2, GIP + GLP-2, and placebo (saline) as subcutaneous injections at bedtime. Main outcomes were levels of CTX and procollagen type 1 N-terminal propeptide (P1NP).

RESULTS

Compared with placebo, GIP and GLP-2 alone significantly inhibited bone resorption (measured by CTX). GIP rapidly reduced CTX levels in the period from 45 to 120 min after injection, while GLP-2 had a more delayed effect with reduced CTX levels in the period from 120 to 240 min after injection. Combining GIP and GLP-2 showed complementary effects resulting in a sustained inhibition of CTX with reduced levels from 45 to 240 min after injection. Furthermore, GIP acutely increased bone formation (measured by P1NP).

CONCLUSION

Both GIP and GLP-2 reduced CTX during the night and had complementary effects when combined.

Considerations for understanding protein measurements: Identification of formation, degradation and more pathological relevant epitopes

OBJECTIVES

There is a need for precision medicine and an unspoken promise of an optimal approach for identification of the right patients for value-based medicine based on big data. However, there may be a misconception that measurement of proteins is more valuable than measurement of fewer selected biomarkers. In population-based research, variation may be somewhat eliminated by quantity. However, this fascination of numbers may limit the attention to and understanding of the single. This review highlights that protein measurements (with collagens as examples) may mean different things depending on the targeted epitope - formation or degradation of tissues, and even signaling potential of proteins.

DESIGN AND METHODS

PubMed was searched for collagen, neo-epitope, biomarkers.

RESULTS

Ample examples of assays with specific epitopes, either pathological such as HbA1c, or domain specific such as pro-peptides, which total protein arrays would not have identified were evident.

CONCLUSIONS

We suggest that big data may be considered as the funnel of data points, in which most important parameters will be selected. If the technical precision is low or the biological accuracy is limited, and we include suboptimal quality of biomarkers, disguised as big data, we may not be able to fulfill the promise of helping patients searching for the optimal treatment. Alternatively, if the technical precision of the total protein quantification is high, but we miss the functional domains with the most considerable biological meaning, we miss the most important and valuable information of a given protein. This review highlights that measurements of the same protein in different ways may provide completely different meanings. We need to understand the pathological importance of each epitope quantified to maximize protein measurements.

The Antiresorptive Effect of GIP, But Not GLP-2, Is Preserved in Patients With Hypoparathyroidism-A Randomized Crossover Study

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are gut hormones secreted postprandially. In healthy humans, both hormones decrease bone resorption accompanied by a rapid reduction in parathyroid hormone (PTH). The aim of this study was to investigate whether the changes in bone turnover after meal intake and after GIP- and GLP-2 injections, respectively, are mediated via a reduction in PTH secretion. This was tested in female patients with hypoparathyroidism given a standardized liquid mixed-meal test (n = 7) followed by a peptide injection test (n = 4) using a randomized crossover design. We observed that the meal- and GIP- but not the GLP-2-induced changes in bone turnover markers were preserved in the patients with hypoparathyroidism. To understand the underlying mechanisms, we examined the expression of the GIP receptor (GIPR) and the GLP-2 receptor (GLP-2R) in human osteoblasts and osteoclasts as well as in parathyroid tissue. The GIPR was expressed in both human osteoclasts and osteoblasts, whereas the GLP-2R was absent or only weakly expressed in osteoclasts. Furthermore, both GIPR and GLP-2R were expressed in parathyroid tissue. Our findings suggest that the GIP-induced effect on bone turnover may be mediated directly via GIPR expressed in osteoblasts and osteoclasts and that this may occur independent of PTH. In contrast, the effect of GLP-2 on bone turnover seems to depend on changes in PTH and may be mediated through GLP-2R in the parathyroid gland. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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 a whey protein pre-meal on bone turnover in participants with and without type 2 diabetes-A post hoc analysis of a randomised, controlled, crossover trial

AIMS

Whey protein may improve bone turnover and have anti-osteoporotic effects. The aim of the present randomised, controlled, crossover trial was to evaluate the effects of a whey protein pre-meal on bone turnover in people with type 2 diabetes and controls.

METHODS

Two groups, matched on sex, age and body mass index, comprising 12 participants with and 12 participants without type 2 diabetes were randomly given a pre-meal of whey protein (20 g) or water, which was consumed 15 min before a fat-rich meal or a fat-rich meal supplemented with 20 g whey protein. During a 360-min period, postprandial responses in bone turnover were examined.

RESULTS

Osteocalcin, P-procollagen type 1 amino terminal propeptide (P1NP), C-terminal cross-linked telopeptide of type-I collagen (CTX) and parathyroid hormone (PTH) were lower at baseline and PTH, osteocalcin and P1NP were lower during the entire postprandial phase in participants with type 2 diabetes than in participants without type 2 diabetes. We observed similar postprandial responses in bone turnover markers between persons with and without type 2 diabetes. We observed no effect of the whey protein or the water pre-meal on bone turnover markers. The changes were unrelated to secretion of hormones of the gut-bone axis.

CONCLUSION

Osteocalcin, P1NP, CTX and PTH all decreased following meal ingestion. We observed no convincing effect of a whey protein pre-meal on bone turnover. However, these results confirm that people with type 2 diabetes have low bone turnover and that the decreased bone formation markers are also extend into the postprandial responses.

Preserved postprandial suppression of bone turnover markers, despite increased fasting levels, in postmenopausal women

CONTEXT

Menopause leads to an increased bone turnover associated with a high risk of fractures. Bone turnover is inhibited by meal intake, to some extent mediated by gut hormones, and interventions based on these endocrine changes may have potential in future prevention of osteoporosis.

OBJECTIVE

To investigate whether postmenopausal women exhibit postprandial suppression of bone turnover markers to the same extent as premenopausal women, despite higher fasting levels. Furthermore, to assess whether menopausal differences in bone turnover markers are related to postmenopausal changes in plasma gut hormone levels.

METHODS

A cross-sectional study of 21 premenopausal, 9 perimenopausal, and 24 postmenopausal women between 45 and 60 years of age. Serum/plasma levels of bone turnover markers and gut hormones were investigated during a 120 min oral glucose tolerance test. Bone turnover markers included N-terminal propeptide of type-I procollagen (PINP, bone formation marker) and carboxyterminal collagen I crosslinks (CTX-I, bone resorption marker). Gut hormone secretion was evaluated from responses of glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2) and glucose-dependent insulinotropic polypeptide (GIP).

RESULTS

Fasting levels of s-CTX-I were increased in peri- and postmenopausal women compared to premenopausal women (p = 0.001). Despite higher fasting levels, the relative postprandial s-CTX-I suppression was comparable across menopausal status (p = 0.14). Fasting levels of s-PINP were also increased in postmenopausal women compared to premenopausal women (p < 0.001) with comparable and modest s-PINP suppression over menopause (p = 0.13). Postprandial plasma GLP-1 (p = 0.006) and GLP-2 (p = 0.01) were significantly increased in postmenopausal women compared to premenopausal women while GIP responses were slightly increased in the perimenopausal group (p = 0.02) but comparable between pre- and postmenopausal women. None of the postprandial gut hormone increases predicted postprandial bone turnover suppression in these women.

CONCLUSIONS

Glucose-induced suppression of bone turnover markers is preserved in postmenopausal women, despite significantly higher fasting values, indicating that CTX-I lowering treatments based on these postprandial mechanisms might be a feasible strategy to prevent postmenopausal osteoporosis.

Glucagon-Like Peptide 2 Inhibits Postprandial Gallbladder Emptying in Man: A Randomized, Double-Blinded, Crossover Study

INTRODUCTION:

A recent study in mice points to the gut-derived hormone glucagon-like peptide 2 (GLP-2) as an important regulator of gallbladder motility inducing gallbladder relaxation and refilling. In this study, we evaluated the effect of exogenous GLP-2 on postprandial gallbladder motility in healthy men.

METHODS:

In a randomized, double-blinded, placebo-controlled, crossover study, we evaluated the effect of 4-hour intravenous infusions of high-dose GLP-2 (10 pmol × kg⁻¹ × min⁻¹), low-dose GLP-2 (1 pmol × kg⁻¹ × min⁻¹), and placebo (saline) on postprandial gallbladder motility. A 300-kcal liquid-mixed meal (added 1.5 g of acetaminophen for indirect measurement of gastric emptying) was served 30 minutes after start of intravenous infusions. Gallbladder volume was assessed by ultrasonography.

RESULTS:

Fifteen healthy men, age 24.3 (22.4–26.1) years (mean [95% confidence interval]) and body mass index 22.5 (21.7–23.4) kg × m⁻², were included. Basal plasma GLP-2 concentration was 14 (11–17) pmol/L. During low-dose and high-dose GLP-2 infusions, steady-state postprandial plasma GLP-2 concentrations amounted to 201 (188–214) and 2,658 (2,443–2,873) pmol/L, respectively, compared with maximum postprandial plasma GLP-2 concentration of 34 (25–44) pmol/L during placebo. Gallbladder emptying (assessed as baseline-subtracted area under the curve for gallbladder volume) was reduced by low-dose GLP-2 (−0.8 [0.7–1.9] L × min, P < 0.0001) and nearly abolished by high-dose GLP-2 (1.3 [−1.7 to 0.01] L × min, P = 0.029) compared to placebo (−2.0 [−2.8 to −1.1] L × min). Compared to placebo, gastric emptying was reduced by high-dose GLP-2 (P = 0.0060 and 0.019), whereas low-dose GLP-2 did not affect gastric emptying (P = 0.13 and 0.85).

DISCUSSION:

Exogenous GLP-2 exerts a dose-dependent inhibitory effect on postprandial gallbladder emptying in healthy men.

[Gly²]-GLP-2, But Not Glucagon or [D-Ala²]-GLP-1, Controls Collagen Crosslinking in Murine Osteoblast Cultures

Bone tissue is organized at the molecular level to resist fracture with the minimum of bone material. This implies that several modifications of the extracellular matrix, including enzymatic collagen crosslinking, take place. We previously highlighted the role of several gut hormones in enhancing collagen maturity and bone strength. The present study investigated the effect of proglucagon-derived peptides on osteoblast-mediated collagen post-processing. Briefly, MC3T3-E1 murine osteoblasts were cultured in the presence of glucagon (GCG), [D-Ala²]-glucagon-like peptide-1 ([D-Ala²]-GLP-1), and [Gly²]-glucagon-like peptide-2 ([Gly²]-GLP-2). Gut hormone receptor expression at the mRNA and protein levels were investigated by qPCR and Western blot. Extent of collagen postprocessing was examined by Fourier transform infrared microspectroscopy. GCG and GLP-1 receptors were not evidenced in osteoblast cells at the mRNA and protein levels. However, it is not clear whether the known GLP-2 receptor is expressed. Nevertheless, administration of [Gly²]-GLP-2, but not GCG or [D-Ala²]-GLP-1, led to a dose-dependent increase in collagen maturity and an acceleration of collagen post-processing. This mechanism was dependent on adenylyl cyclase activation. In conclusion, the present study highlighted a direct effect of [Gly²]-GLP-2 to enhance collagen post-processing and crosslinking maturation in murine osteoblast cultures. Whether this effect is translatable to human osteoblasts remains to be elucidated.

Secretion of parathyroid hormone may be coupled to insulin secretion in humans

OBJECTIVE

Parathyroid hormone (PTH) is a key hormone in regulation of calcium homeostasis and its secretion is regulated by calcium. Secretion of PTH is attenuated during intake of nutrients, but the underlying mechanism(s) are unknown. We hypothesized that insulin acts as an acute regulator of PTH secretion.

METHODS

Intact PTH was measured in plasma from patients with T1D and matched healthy individuals during 4-h oral glucose tolerance tests (OGTT) and isoglycemic i.v. glucose infusions on 2 separate days. In addition, expression of insulin receptors on surgical specimens of parathyroid glands was assessed by immunochemistry (IHC) and quantitative PCR (qPCR).

RESULTS

The inhibition of PTH secretion was more pronounced in healthy individuals compared to patients with T1D during an OGTT (decrementalAUC0-240min: -5256 ± 3954 min × ng/L and -2408 ± 1435 min × ng/L, P = 0.030). Insulin levels correlated significantly and inversely with PTH levels, also after adjusting for levels of several gut hormones and BMI (P = 0.002). Expression of insulin receptors in human parathyroid glands was detected by both IHC and qPCR.

CONCLUSION

Our study suggests that insulin may act as an acute regulator of PTH secretion in humans.

Emerging therapeutic targets for osteoporosis

Introduction: Osteoporosis is a chronic, skeletal disorder characterized by compromised bone strength and increased fracture risk; it affects 50% of women and 20% of men. In the past two decades, there have been substantial improvements in the pharmacotherapy of osteoporosis which have yielded potent inhibitors of bone resorption or stimulators of bone formation.Areas covered: This review discusses newly identified targets and pathways and conceptual approaches to the prevention of multiple age-related disorders. Furthermore, it summarizes existing therapeutic strategies for osteoporosis.Expert opinion: Our enhanced understanding of bone biology and the reciprocal interactions between bone and other tissues have allowed the identification of new targets that may facilitate the development of novel drugs. These drugs will hopefully achieve the uncoupling of bone formation from resorption and possibly exert a dual anabolic and antiresorptive effect on bone. Alas, limitations regarding adherence, efficacy on nonvertebral fracture prevention and the long-term adverse events still exist for currently available therapeutics. Moreover, the efficacy of most agents is limited by the tight coupling of osteoblasts and osteoclasts; hence the reduction of bone resorption invariably reduces bone formation, and vice versa. This field is very much 'a work in progress.'

GLP-2 administration in ovariectomized mice enhances collagen maturity but did not improve bone strength

Osteoporosis and bone fragility are progressing worldwide. Previous published literature reported a possible beneficial role of gut hormones, and especially glucagon-like peptide-2 (GLP-2), in modulating bone remodeling. As now (Gly²)GLP-2 is approved in the treatment of short bowel syndrome, we thought to investigate whether such molecule could be beneficial in bone fragility.

MC3T3 and Raw 264.7 were cultured in presence of ascending concentrations of (Gly²)GLP-2. Collagen crosslinks, maturity, lysyl oxidase activity and osteoclastogenesis were then analyzed. Furthermore, (Gly²)GLP-2, at the clinical approved dose of 50 μg/kg/day, was also administered to ovariectomized Balb/c mice for 8 weeks. Hundred μg/kg zoledronic acid (once iv) was also used as a positive comparator. Bone strength, microarchitectures and bone tissue composition were analyzed by 3-point bending, compression test, microCT and Fourier transform infrared imaging, respectively.

In vitro, (Gly²)GLP-2 was potent in enhancing bone matrix gene expression but also to dose-dependently enhanced collagen maturation and post-processing. (Gly²)GLP-2 was also capable of reducing dose-dependently the number of newly generated osteoclasts. However, in vivo, (Gly²)GLP-2 was not capable of improving neither bone strength, at the femur diaphysis or lumbar vertebrae, nor bone microarchitecture. On the other hand, at the tissue material level, (Gly²)GLP-2 significantly enhances collagen maturity and reduce phosphate/amide ratio.

Overall, this study highlights that despite modification of bone tissue composition, (Gly²)GLP-2, at the clinical approved dose of 50 μg/kg/day, did not provide real beneficial effects in improving bone strength in a mouse model of bone fragility. Further studies are recommended to validate the best dose and regimen of administration to significantly enhance bone strength.

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In vitro, (Gly²)GLP-2 enhances dose-dependently bone matrix deposition and quality.

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In vitro, (Gly²)GLP-2 reduces dose-dependently osteoclast formation.

•

In vivo, (Gly²)GLP-2 failed to improve bone strength in ovariectomy-induced bone loss.

•

In vivo, (Gly²)GLP-2 failed to improve bone microarchitecture.

•

In vivo, (Gly²)GLP-2 increased collagen maturity and phosphate/amide ratios.

Biomarkers of Osteoporosis: An Update

Background:

Osteoporosis, characterized by compromised bone quality and strength is associated with bone fragility and fracture risk. Biomarkers are crucial for the diagnosis or prognosis of a disease as well as elucidating the mechanism of drug action and improve decision making.

Objective:

An exhaustive description of traditional markers including bone mineral density, vitamin D, alkaline phosphatase, along with potential markers such as microarchitectural determination, trabecular bone score, osteocalcin, etc. is provided in the current piece of work. This review provides insight into novel pathways such as the Wnt signaling pathway, neuro-osseous control, adipogenic hormonal imbalance, gut-bone axis, genetic markers and the role of inflammation that has been recently implicated in osteoporosis.

Methods:

We extensively reviewed articles from the following databases: PubMed, Medline and Science direct. The primary search was conducted using a combination of the following keywords: osteoporosis, bone, biomarkers, bone turnover markers, diagnosis, density, architecture, genetics, inflammation.

Conclusion:

Early diagnosis and intervention delay the development of disease and improve treatment outcome. Therefore, probing for novel biomarkers that are able to recognize people at high risk for developing osteoporosis is an effective way to improve the quality of life of patients and to understand the pathomechanism of the disease in a better way.

Glucagon-like peptide 1 and Glucagon-like peptide 2 in relation to osteoporosis in non-diabetic postmenopausal women

Osteoporosis results from an imbalance in bone remodeling, which is known to follow a circadian rhythm determined by a functional relationship between intestine and bone tissue. Specific intestinal peptides have been identified as mediators. Glucagon-like peptide 1 and glucagon-like peptide 2, have been associated with bone health. Our main objective was to determine whether postprandial plasma levels of glucagon-like peptide 1, glucagon-like peptide 2 and dipeptidyl-peptidase 4 activity, are associated with osteoporosis in non-diabetic postmenopausal women. We studied non-diabetic postmenopausal women with osteoporosis diagnosed by dual-energy X-ray absorptiometry (cases, n = 43) and age-matched (±1 yr) controls without osteoporosis or a history of osteoporotic fracture (n = 43). We measured postprandial plasma levels of glucagon-like peptide 1, glucagon-like peptide 2, and dipeptidyl-peptidase 4 activity, bone mineral density, and baseline levels of bone remodeling markers and analyzed the food intake using a food-frequency questionnaire. Postprandial glucagon-like peptide 1 values were lower (p < 0.001) in cases, μ (SEM) = 116.25 (2.68), than in controls, μ (SEM) = 126.79 (2.68). Glucagon-like peptide 1 was associated with reduced osteoporosis risk in the crude logistic regression analysis [OR (95% CI) = 0.724 (0.53-0.97), p = 0.031] and adjusted analysis [OR = 0.603 (0.38-0.94), p = 0.027]. We found no association of glucagon-like peptide 2, or dipeptidyl-peptidase 4 activity with osteoporosis. Postprandial glucagon-like peptide 1 levels are related to osteoporosis and osteoporosis risk in non-diabetic postmenopausal women. Further studies are required to verify these findings.

Effect of Dipeptidyl Peptidase-4 Inhibitors on the Risk of Bone Fractures in a Korean Population

BACKGROUND

There have been equivocal results in studies of the effects of dipeptidyl peptidase-4 inhibitors (DPP-4i) on fractures. In this study, we analyzed the effect of DPP-4i on bone fracture risk in a Korean population.

METHODS

We extracted subjects (n = 11,164) aged 50 years or older from the National Health Insurance Service-National Sample Cohort 2.0 from 2009 to 2014. Our control group included subjects without diabetes (n = 5,582), and our treatment groups with diabetes included DPP-4i users (n = 1,410) and DPP-4i non-users (n = 4,172). The primary endpoint was the incidence of a composite outcome consisting of osteoporosis diagnosis, osteoporotic fractures, vertebral fractures, non-vertebral fractures, and femoral fractures. The secondary endpoint was the incidence of each individual component of the composite outcome. Survival analysis was performed with adjustment for age, gender, diabetes complications severity index, Charlson comorbidity index, hypertension medication, and dyslipidemia treatment.

RESULTS

The incidence of the composite outcome per 1,000 person-years was 0.089 in DPP-4i users, 0.099 in DPP-4i non-users, and 0.095 in controls. There was no significant difference in fracture risk between DPP-4i users and DPP-4i non-users or controls after the adjustments (P > 0.05). The incidences of osteoporosis diagnosis, osteoporotic fractures, vertebral fractures, non-vertebral fractures, and femoral fractures were not significantly different between DPP-4i users and non-users. The results of subgroup analyses by gender and age were consistent.

CONCLUSION

DPP-4i had no significant effect on the risk of fractures in a Korean population.

GLP-2 and GIP exert separate effects on bone turnover: A randomized, placebo-controlled, crossover study in healthy young men

BACKGROUND

Glucagon-like peptide-2 (GLP-2) and glucose-dependent insulinotropic polypeptide (GIP) both inhibit bone resorption in humans but the underlying mechanisms are poorly understood. In vitro, GLP-2 activates the GIP-receptor (GIPR).

OBJECTIVE

Based on in vitro studies, we hypothesized that the antiresorptive effect of GLP-2 was mediated through the GIPR. This was tested using the selective GIPR-antagonist GIP(3-30)NH₂.

METHODS

The study was a randomized, single-blinded, placebo-controlled, crossover study conducted at Hvidovre University Hospital, Denmark. Eight healthy young men were included and studied on four study days: GIP (200 μg), GLP-2 (800 μg), GIP(3-30)NH₂ (800 pmol/kg/min) + GLP-2 (800 μg), and placebo. The main outcomes were bone resorption measured as collagen type 1 C-terminal telopeptide (CTX) and bone formation measured as procollagen type 1 N-terminal propeptide (P1NP).

RESULTS

CTX (mean ± SEM) significantly decreased after both GIP (to 55.3 ± 6.3% of baseline at t = 90 min) and GLP-2 (to 60.5 ± 5.0% of baseline at t = 180 min). The maximal reduction in CTX after GIP(3-30)NH₂ + GLP-2 (to 63.2 ± 3.1% of baseline) did not differ from GLP-2 alone (p = 0.95) nor did net AUC_0-240 (-6801 ± 879%*min vs -6027 ± 648%*min, p = 0.56). At t = 30 min, GIP significantly (p < 0.0001) increased P1NP to 115.1 ± 2.2% of baseline compared with 103.1 ± 1.5% after placebo. Both GLP-2 and GIP(3-30)NH₂ + GLP-2 significantly (p < 0.0001) decreased P1NP to 91.3 ± 1.1% and 88.1 ± 3.0% of baseline, respectively (at t = 45 min) compared with placebo.

CONCLUSIONS

GIPR antagonism did not inhibit the GLP-2-induced reduction in bone resorption (CTX) in healthy young men. In contrast to GLP-2, GIP increased P1NP despite decreasing CTX indicating an uncoupling of bone resorption from formation. Thus, GLP-2 and GIP seem to exert separate effects on bone turnover in humans.

CLINICAL TRIALS INFORMATION

ClinicalTrials.gov (NCT03159741).

Glucagon like peptide 2 has a positive impact on osteoporosis in ovariectomized rats

AIMS

In this study, we evaluate the effects of glucagon-like peptide 2 (GLP-2) on bone microarchitecture, bone turnover markers (BTMs) and inflammation markers in ovariectomized (OVX) rats.

MATERIAL AND METHODS

In total, 31 Sprague-Dawley rats were divided into the following three groups: sham (control sham-operated with vehicle, n = 7), OV (OVX with vehicle, n = 12), and GLP-2 (OVX with GLP-2, n = 12). Intervention began at the 12th week after surgery and lasted for 4 weeks. The dosage of the GLP-2 was 160 μg/kg/d through subcutaneous injections, and normal saline was used as the vehicle agent. After 4 weeks of treatment, serum BTM and inflammation marker levels were measured by ELISA, and femora samples were analyzed by qRT-PCR, micro-CT, histology and histomorphometry.

KEY FINDINGS

After 4 weeks of treatment, serum TRAcP-5b and RANKL levels as well as the CTX-1/P1NP ratio in the GLP-2 group decreased, and ALP activity, P1NP level, and OPG/RANKL ratio increased significantly; qRT-PCR analysis showed that mRNA levels of RANKL decreased, and Runx2, ALP, and Col-1 levels as well as the OPG/RANKL ratio increased significantly in the GLP-2 group compared with the OV group. In bone histology analysis, GLP-2 significantly decreased the AV/MV, Oc.N and Oc.S but increased the Ob.N, BFR and MAR. Analysis with μ-CT showed that the BMD, BV/TV, Tb.N and Conn.D increased significantly in the GLP-2 group compared with the OV group. The levels of serum inflammation markers TNF-α, IL-1β and IL-6 decreased, and TGF-β levels increased in the GLP-2 group compared with the OV group.

SIGNIFICANCE

GLP-2 may have a positive impact on osteoporosis by promoting bone formation, inhibiting bone resorption and decreasing circulatory inflammation in ovariectomized rats.

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.

Increased Body Weight and Fat Mass After Subchronic GIP Receptor Antagonist, but Not GLP-2 Receptor Antagonist, Administration in Rats

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are hormones secreted from the enteroendocrine cells after a meal. They exert their actions through activation of G protein-coupled receptors (R), the GIPR and GLP-2R, respectively. Both have been reported to influence metabolism. The purpose of the study was to investigate the role of the hormones in the regulation of lipid and bone homeostasis by subchronic treatment with novel GIPR and GLP-2R antagonists. Rats were injected once daily with vehicle, GIPR, or GLP-2R antagonists for 3 weeks. Body weight, food intake, body composition, plasma lipoprotein lipase (LPL), adipokines, triglycerides and the marker of bone resorption carboxy-terminal collagen crosslinks (CTX), were examined. In rats, subchronic treatment with GIPR antagonist, rat GIP (3-30)NH₂, did not modify food intake and bone resorption, but significantly increased body weight, body fat mass, triglycerides, LPL, and leptin levels compared with vehicle treated rats. Subchronic (Pro3)GIP (a partial GIPR agonist), GLP-2(11-33), and GLP-2(3-33) (GLP-2R antagonists) treatment did not affect any parameter. The present results would be consistent with a role for GIP, but not GLP-2, in the maintenance of lipid homeostasis in rats, while neither GIPR nor GLP-2R antagonism appeared to influence bone resorption in rats.

Type 1 Diabetes and Bone Fragility: Links and Risks

Type 1 diabetes (T1D) is associated with an increased fracture risk, which is present at young and old age. Reductions in bone mineral density do not explain the increased fracture risk. Novel scanning modalities suggest that structural deficits may contribute to the increased fracture risk. Furthermore, T1D may due to insulinopenia be a state of low bone turnover. However, diabetes complications and comorbidities may influence fracture risk. Patients with T1D are fearful of falls. The diabetes related complications, hypoglycemic events, and antihypertensive treatment may all lead to falls. Thus, the increased fracture risk in T1D seems to be multifactorial, and earlier intervention with antiosteoporotic medication and focus on fall prevention is needed. This systematic review addresses the epidemiology of fractures and osteoporosis in patients with T1D and the factors that influence fracture risk.

The effect of meals on bone turnover - a systematic review with focus on diabetic bone disease

INTRODUCTION

Type 2 diabetes is associated with an increased risk of bone fractures. Bone mineral density (BMD) is increased and bone turnover is low in type 2 diabetes and the increased BMD does not explain the increased fracture risk. However, the low bone turnover may lead to insufficient bone renewal with unrepaired micro-cracks and thus increase fracture risk. Ingestion of food acutely decreases bone resorption markers and the macronutrient composition of meals and meal frequency may influence bone metabolism adversely in subjects with unhealthy eating patterns, e.g., patients with type 2 diabetes.

AREAS COVERED

The treatment strategy of bone disease in type 2 diabetics is covered in this review. The current management of diabetic bone disease consists of anti-osteoporotic treatment. However, anti-resorptives may further reduce an already low bone turnover with uncertain effects. Furthermore, the acute and long-term effects of meal ingestion, weight loss alone and in combination with exercise as well as the possible underlying mechanisms are covered in this systematic review.

EXPERT COMMENTARY

Current management of diabetic bone disease is based on principles of anti-osteoporotic treatment in non-diabetic subjects. However, studies are urged to investigate whether anti-resorptives are equally beneficial in type 2 diabetes as in non-diabetic individuals.

Diabetes management before, during, and after bariatric and metabolic surgery

Metabolic surgery is unrivaled by other therapeutic modalities due to its ability to foster diabetes remission. Metabolic surgery is an integral therapeutic modality in obese and morbidly obese populations because pharmacological and behavioral therapy often fail to effectively manage type II diabetes. However, given the invasiveness of the metabolic surgery relative to behavioral therapy and the need to conform to preparatory and discharge guidelines, patients must adhere to strict nutritional and diabetes management protocols. Also, the pharmacological regimen that is instituted upon discharge is distinct from the preoperative regimen. Oftentimes, the dose for insulin and oral medications are significantly decreased or withdrawn. As time elapses and depending on several factors (e.g., exercise adherence), diabetes control becomes tenuous in a small portion of the patients because there is weight regain and on-going beta cell failure. At this time interval, intensification of diabetes therapy becomes prudent. Indeed, pharmacotherapy from the preoperative to the postoperative phase is labile and may be complex. Therefore, by discussing pharmacology options during the preoperative, perioperative, and postoperative period, the goal is to guide clinician-driven care.

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.

Bone Turnover Markers in Patients With Nonalcoholic Fatty Liver Disease and/or Type 2 Diabetes During Oral Glucose and Isoglycemic Intravenous Glucose

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes (T2D) and vice versa, and both conditions are associated with an increased risk of fractures and altered bone turnover. Although patients with NAFLD typically suffer from decreased bone mineral density (BMD), T2D is associated with normal to high BMD. The pathophysiology is uncertain but may involve the gut-bone axis.

OBJECTIVE

We investigated the influence of the gut on glucose-induced changes in plasma bone turnover markers in healthy controls and patients with T2D and/or biopsy-verified NAFLD.

DESIGN

Cross-sectional cohort study.

PATIENTS

Patients with NAFLD with normal glucose tolerance, patients with NAFLD and T2D, patients with T2D without liver disease, and healthy controls.

INTERVENTIONS

Four-hour 50-g oral glucose tolerance test (OGTT) and an isoglycemic intravenous glucose infusion (IIGI).

MAIN OUTCOME MEASURES

Collagen type 1 C-telopeptide (CTX), osteocalcin, procollagen type 1 N-terminal propeptide (P1NP), and parathyroid hormone.

RESULTS

Plasma glucose levels achieved during OGTTs were successfully matched on corresponding IIGI days. Patients with NAFLD and T2D exhibited similar CTX suppression during the two glucose challenges (P = 0.46) and pronounced suppression of P1NP during IIGI compared with OGTT. Conversely, remaining groups showed greater (P < 0.05) CTX suppression during OGTT and similar suppression of bone formation markers during IIGI and OGTT.

CONCLUSIONS

OGTT-induced CTX suppression seems to be impaired in patients with NAFLD and T2D, but preserved in patients with either NAFLD or T2D, suggesting that coexistence of T2D and NAFLD may affect gut-bone axis.

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 risk of fragility fractures in new users of dipeptidyl peptidase-4 inhibitors compared to sulfonylureas and other anti-diabetic drugs: A cohort study

AIMS

Mixed evidence exists for the effect of incretin-based therapies on osteoporosis in type-2 diabetes. Therefore, we conducted a cohort study to determine the association between dipeptidyl peptidase-4 (DPP-4) inhibitors and common osteoporotic "fragility fractures" (upper extremity, hip, spine).

METHODS

The UK-based Clinical Practice Research Datalink was used to identify adults without prior fractures receiving a new anti-diabetic drug or a new type-2 diabetes diagnosis between 2007 and 2016. The primary aim was to compare new-users of DPP-4 inhibitors versus new-users of sulfonylureas (SU). The association between DPP-4 inhibitors and incident fractures was estimated using Cox proportional hazards models. Deciles of high-dimensional propensity scores and other anti-diabetic drugs were used as covariates.

RESULTS

We identified 7993 and 26,636 new-users of DPP-4 inhibitors and SUs, respectively. At cohort entry, the mean age was 58.8, 40% were female, mean diabetes duration was 1.3 years, and 42% had A1c > 9%. Over 9 years (mean follow-up = 1.2 years), the incident rate of fragility fractures was lower among DPP-4 versus SU users (3.0/1000 vs. 5.2/1000 person-years; P-value = 0.007). After adjustment, there was no statistically significant difference in fracture risk (hazard ratio adjusted, aHR = 0.80, 95%CI 0.51-1.24; P-value = 0.3125). In a secondary analysis, DPP-4 inhibitors were not associated with a difference in fracture risk compared to insulin (aHR = 0.91, 95%CI 0.40-2.09); however were associated with a lower fracture risk versus thiazolidinediones (aHR = 0.47, 95%CI 0.26-0.83). Sensitivity analyses supported findings.

CONCLUSIONS

DPP-4 inhibitors are not associated with an increased risk of fragility fractures compared with SUs or insulin; however, are associated with a lower risk versus thiazolidinediones.

Postprandial GLP-2 Levels Are Increased After Biliopancreatic Diversion in Diabetic Individuals with Class I Obesity: a Prospective Study

BACKGROUND

Biliopancreatic diversion (BPD) is a predominantly malabsorptive procedure. Glucagon-like peptide 2 (GLP-2) plays predominantly trophic effects on the gut. A significant increase in GLP-2 after BPD in rats was previously observed, but there are no studies investigating the effect of BPD in GLP-2 levels in humans.

OBJECTIVE

The aim of this study is to evaluate the influence of BPD on the release of GLP-2.

METHODS

This is a prospective cohort study that evaluated diabetic individuals with class I obesity which underwent BPD (Scopinaro operation) and were followed up for 12 months. Of 12 individuals, four did not comply with the proposed follow-up and were excluded from the analysis. GLP-2 levels were determined by means of an enzyme-linked immunosorbent assay (ELISA), and we collected serial lab samples through a standard meal tolerance test (MTT) in the immediate preoperative period and 12 months after surgery.

RESULTS

During standard MTT, we observed significant increases of GLP-2 levels from 15 to 60 min (respectively, at 15 min, 5.7 ± 3.4 versus 12.4 ± 4.3, p = 0.029; 30 min, 6 ± 3.5 versus 14.6 ± 3.9; p = 0.004; 45 min, 5.6 ± 4.1 versus 12.6 ± 5.2, p = 0.013; 60 min, 5.8 ± 2.9 versus 10.6 ± 5.6, p = 0.022); then it began to gradually decrease to levels close to the basal.

DISCUSSION

Our findings have confirmed that there is a significant increase in GLP-2 levels after BPD in humans. GLP-2 plays a number of roles which may be adaptive, compensatory, and beneficial in the context of BPD. The clinical implications of this finding remain to be completely understood.

Role of Incretin Axis in Inflammatory Bowel Disease

The inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory conditions of the gastrointestinal tract and involve a complicated reciprocity of environmental, genetic, and immunologic factors. Despite substantial advances in the foundational understanding of the immunological pathogenesis of IBD, the detailed mechanism of the pathological progression in IBD remains unknown. In addition to Th1/Th2 cells, whose role in IBD has been previously well defined, recent evidence indicates that Th17 cells and Tregs also play a crucial role in the development of IBD. Diets which contain excess sugars, salt, and fat may also be important actors in the pathogenesis of IBD, which may be the cause of high IBD incidence in western developed and industrialized countries. Up until now, the reason for the variance in prevalence of IBD between developed and developing countries has been unknown. This is partly due to the increasing popularity of western diets in developing countries, which makes the data harder to interpret. The enterocrinins glucagon-like peptides (GLPs), including GLP-1 and GLP-2, exhibit notable benefits on lipid metabolism, atherosclerosis formation, plasma glucose levels, and maintenance of gastric mucosa integrity. In addition to the regulation of nutrient metabolism, the emerging role of GLPs and their degrading enzyme dipeptidyl peptidase-4 (DPP-4) in gastrointestinal diseases has gained increasing attention. Therefore, here we review the function of the DPP-4/GLP axis in IBD.

Review article: effects of type 2 diabetes therapies on bone metabolism

Diabetes complications and osteoporotic fractures are two of the most important causes of morbidity and mortality in older patients, and they share many features, including genetic susceptibility, molecular mechanisms, and environmental factors. Type 2 diabetes mellitus (T2DM) compromises bone microarchitecture by inducing abnormal bone cell function and matrix structure with increased osteoblast apoptosis, diminished osteoblast differentiation, and enhanced osteoclast-mediated bone resorption. The linkage between these two chronic diseases creates a possibility that certain antidiabetic therapies may affect bone function. The treatment of T2DM has been improved in the past two decades with the development of new therapeutic drugs. Each class has a pathophysiologic target related to the regulation of the energy metabolism and insulin secretion. However, both glycemic homeostasis and bone homeostasis are under the control of common regulatory factors. This background allows the individual pharmacological targets of antidiabetic therapies to affect bone quality due to their indirect effects on bone cell differentiation and the bone remodeling process. With a greater number of diabetic patients and antidiabetic agents being launched, it is critical to highlight the consequences of this disease and its pharmacological agents on bone health and fracture risk. Currently, there is little scientific knowledge approaching the impact of most anti-diabetic treatments on bone quality and fracture risk. Thus, this review aims to explore the pros and cons of the available pharmacologic treatments for T2DM on bone mineral density and risk fractures in humans.