Association of DPP-4 activity with BMD, body composition, and incident hip fracture: the Cardiovascular Health Study

The multiple actions of dipeptidyl peptidase 4 (DPP-4) and its pharmacological inhibition on bone metabolism: a review

BACKGROUND

Dipeptidyl peptidase 4 (DPP-4) plays a crucial role in breaking down various substrates. It also has effects on the insulin signaling pathway, contributing to insulin resistance, and involvement in inflammatory processes like obesity and type 2 diabetes mellitus. Emerging effects of DPP-4 on bone metabolism include an inverse relationship between DPP-4 activity levels and bone mineral density, along with an increased risk of fractures.

MAIN BODY

The influence of DPP-4 on bone metabolism occurs through two axes. The entero-endocrine-osseous axis involves gastrointestinal substrates for DPP-4, including glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptides 1 (GLP-1) and 2 (GLP-2). Studies suggest that supraphysiological doses of exogenous GLP-2 has a significant inhibitory effect on bone resorption, however the specific mechanism by which GLP-2 influences bone metabolism remains unknown. Of these, GIP stands out for its role in bone formation. Other gastrointestinal DPP-4 substrates are pancreatic peptide YY and neuropeptide Y-both bind to the same receptors and appear to increase bone resorption and decrease bone formation. Adipokines (e.g., leptin and adiponectin) are regulated by DPP-4 and may influence bone remodeling and energy metabolism in a paracrine manner. The pancreatic-endocrine-osseous axis involves a potential link between DPP-4, bone, and energy metabolism through the receptor activator of nuclear factor kappa B ligand (RANKL), which induces DPP-4 expression in osteoclasts, leading to decreased GLP-1 levels and increased blood glucose levels. Inhibitors of DPP-4 participate in the pancreatic-endocrine-osseous axis by increasing endogenous GLP-1. In addition to their glycemic effects, DPP-4 inhibitors have the potential to decrease bone resorption, increase bone formation, and reduce the incidence of osteoporosis and fractures. Still, many questions on the interactions between DPP-4 and bone remain unanswered, particularly regarding the effects of DPP-4 inhibition on the skeleton of older individuals.

CONCLUSION

The elucidation of the intricate interactions and impact of DPP-4 on bone is paramount for a proper understanding of the body's mechanisms in regulating bone homeostasis and responses to internal stimuli. This understanding bears significant implications in the investigation of conditions like osteoporosis, in which disruptions to these signaling pathways occur. Further research is essential to uncover the full extent of DPP-4's effects on bone metabolism and energy regulation, paving the way for novel therapeutic interventions targeting these pathways, particularly in older individuals.

Pharmacokinetic/Pharmacodynamic modelling of Saxagliptin and its active metabolite, 5-hydroxy Saxagliptin in rats with Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSES

It is unclear whether the parent Saxagliptin (SAX) in vivo is the same as that in vitro, which is twice that of 5-hydroxy Saxagliptin (5-OH SAX). This study is to construct a Pharmacokinetic-Pharmacodynamic (PK-PD) link model to evaluate the genuine relationship between the concentration of parent SAX in vivo and the effect.

METHODS

First, we established a reliable Ultra Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS/MS) method and DPP-4 inhibition ratio determination method. Then, the T2DM rats were randomly divided into four groups, intravenous injection of 5-OH SAX (0.5 mg/kg) and saline group, intragastric administration of SAX (10 mg/kg) and Sodium carboxymethyl cellulose (CMC-Na) group. Plasma samples were collected at different time points for subsequent testing. Finally, we used the measured concentrations and inhibition ratios to construct a PK-PD link model for 5-OH SAX and parent SAX.

RESULTS

A two-compartment with additive model showed the pharmacokinetic process of SAX and 5-OH SAX, the concentration-effect relationship was represented by a sigmoidal Emax model and sigmoidal Emax with E0 model for SAX and 5-OH SAX, respectively. Fitting parameters showed SAX was rapidly absorbed after administration (Tmax=0.11 h, t1/2, ka=0.07 h), widely distributed in the body (V ≈ 20 L/kg), plasma exposure reached 3282.06 ng*h/mL, and the elimination half-life was 6.13 h. The maximum plasma dipeptidyl peptidase IV (DPP-4) inhibition ratio of parent SAX was 71.47%. According to the final fitting parameter EC50, EC50, 5-OH SAX=0.46EC50, SAX(parent), it was believed that the inhibitory effect of 5-OH SAX was about half of the parent SAX, which is consistent with the literature.

CONCLUSIONS

The PK-PD link model of the parent SAX established in this study can predict its pharmacokinetic process in T2DM rats and the strength of the inhibitory effect of DPP-4 based on non-clinical data.

Risk of Fracture With Dipeptidyl Peptidase-4 Inhibitors, Glucagon-like Peptide-1 Receptor Agonists, or Sodium-Glucose Cotransporter-2 Inhibitors in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Network Meta-analysis Combining 177 Randomized Controlled Trials With a Median Follow-Up of 26 weeks

Aim: This study aims to investigate the association between the use of dipeptidyl peptidase-4 inhibitors (DPP-4i), glucagon-like peptide-1 receptor agonists (GLP-1 RAs), or sodium-glucose cotransporter-2 inhibitors (SGLT-2i) and the risk of fracture among patients with type 2 diabetes mellitus. Methods: Medline, Embase, Cochrane Library, and Clinical-Trials.gov databases were searched for randomized controlled trials (RCTs). Network meta-analysis was performed for total fracture and a series of secondary outcomes. Results: A total of 177 RCTs (n = 165,081) involving the risk of fracture were identified (a median follow-up of 26 weeks). DPP-4i, GLP-1 RAs, and SGLT-2i did not increase total fracture risk compared with insulin (odds ratio: 0.86, 95% confidence interval: 0.39-1.90; 1.05, 0.54-2.04; 0.88, and 0.39-1.97, respectively), metformin (1.41, 0.48-4.19; 1.72, 0.55-5.38; 1.44, 0.48-4.30), sulfonylureas (0.77, 0.50-1.20; 0.94, 0.55-1.62; 0.79, 0.48-1.31), thiazolidinediones (0.82, 0.27-2.44; 1.00, 0.32-3.10; 0.83, 0.27-2.57), α-glucosidase inhibitor (4.92, 0.23-103.83; 5.99, 0.28-130.37; 5.01, 0.23-107.48), and placebo (1.04, 0.84-1.29; 1.27, 0.88-1.83; 1.06, 0.81-1.39). Conclusions: The use of DPP-4i, GLP-1 RAs, or SGLT-2i is unlikely to increase the risk of fracture among type 2 diabetes mellitus patients.

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.

Efficacy / safety balance of DPP-4 inhibitors versus SGLT2 inhibitors in elderly patients with type 2 diabetes

Dipeptidyl peptidase-4 inhibitors (DPP-4is) and sodium-glucose cotransporter type 2 inhibitors (SGLT2is) offer new options for the oral management of type 2 diabetes mellitus (T2DM), with the advantage in the elderly population to be devoid of a high risk of hypoglycaemia. SGLT2is have also shown benefits regarding cardiovascular (heart failure) and renal protection, including in patients with T2DM aged ≥ 65 years while DPP-4is have only proved cardiovascular and renal safety without superiority compared with placebo. The glucose-lowering efficacy of the two pharmacological classes is almost similar including in older patients with T2DM. However, the tolerance and safety profile may be highly different and overall more favourable with DPP-4is than with SGLT2is. Some adverse events have been reported with SGLT2is which may be more prevalent or severe in older patients than in younger patients. The present comprehensive review focuses on the benefit/risk balance in the elderly population with T2DM by comparing the profile of DPP-4is and SGLT2is regarding the following potential issues: metabolic disorders (hypoglycaemia and diabetic ketoacidosis); cardiac and vascular issues (atheromatous cardiovascular disease, heart failure, volume reduction hypotension, and lower limb amputations); renal endpoints including acute renal injury; risk of infections; digestive disorders; bone and skin adverse events; and cancer risk. Both DPP-4is and SGLT2is have their own advantages and disadvantages. Personalised treatment is recommended based upon the efficacy/safety profile of each drug class and individual patient characteristics that may be markedly different among the heterogeneous population of older individuals with T2DM.

Identification of osteoclast-osteoblast coupling factors in humans reveals links between bone and energy metabolism

Bone remodeling consists of resorption by osteoclasts followed by formation by osteoblasts, and osteoclasts are a source of bone formation-stimulating factors. Here we utilize osteoclast ablation by denosumab (DMAb) and RNA-sequencing of bone biopsies from postmenopausal women to identify osteoclast-secreted factors suppressed by DMAb. Based on these analyses, LIF, CREG2, CST3, CCBE1, and DPP4 are likely osteoclast-derived coupling factors in humans. Given the role of Dipeptidyl Peptidase-4 (DPP4) in glucose homeostasis, we further demonstrate that DMAb-treated participants have a significant reduction in circulating DPP4 and increase in Glucagon-like peptide (GLP)-1 levels as compared to the placebo-treated group, and also that type 2 diabetic patients treated with DMAb show significant reductions in HbA1c as compared to patients treated either with bisphosphonates or calcium and vitamin D. Thus, our results identify several coupling factors in humans and uncover osteoclast-derived DPP4 as a potential link between bone remodeling and energy metabolism.

Anti-resorptive bone therapies also inhibit bone formation, as osteoclasts secrete factors that stimulate bone formation by osteoblasts. Here, the authors identify osteoclast-secreted factors that couple bone resorption to bone formation in healthy subjects, and show that osteoclast-derived DPP4 may be a factor coupling bone resorption to energy metabolism.

[Diabetes mellitus and risk of hip fracture. A systematic review]

BACKGROUND AND OBJECTIVES

It has been reported that the risk of fracture is increased in patients with diabetes mellitus (DM). The aim of this study was to investigate the possible relationship between DM and hip fracture, as well as any associated risk factors, by means of a systemic review of the literature.

METHODS

PubMed and SCOPUS databases were used to search for relevant studies published from January 2001 to August 2018. Retrospective and prospective cohort studies were selected in which the estimated risk of hip fracture was demonstrated by comparing groups of diabetic patients with non-diabetics. A search was also made for risk factors independent from the association between DM and hip fracture.

RESULTS

A total of 27 articles that fulfilled the inclusion criteria were included. A clear association was observed in diabetic patients (women and men) compared to non-diabetics patients. Among the risk factors, the most important ones were the fact that diabetes was type 1, probably associated with greater risk to a longer duration of DM, and being a female.

CONCLUSIONS

There is an increased risk of hip fracture in patients diagnosed with DM. This association is more significant in diabetes type 1 and women.

What doesn't kill you makes you stranger: Dipeptidyl peptidase-4 (CD26) proteolysis differentially modulates the activity of many peptide hormones and cytokines generating novel cryptic bioactive ligands

Dipeptidyl peptidase 4 (DPP4) is an exopeptidase found either on cell surfaces where it is highly regulated in terms of its expression and surface availability (CD26) or in a free/circulating soluble constitutively available and intrinsically active form. It is responsible for proteolytic cleavage of many peptide substrates. In this review we discuss the idea that DPP4-cleaved peptides are not necessarily inactivated, but rather can possess either a modified receptor selectivity, modified bioactivity, new antagonistic activity, or even a novel activity relative to the intact parent ligand. We examine in detail five different major DPP4 substrates: glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), peptide tyrosine-tyrosine (PYY), and neuropeptide Y (NPY), and stromal derived factor 1 (SDF-1 aka CXCL12). We note that discussion of the cleaved forms of these five peptides are underrepresented in the research literature, and are both poorly investigated and poorly understood, representing a serious research literature gap. We believe they are understudied and misinterpreted as inactive due to several factors. This includes lack of accurate and specific quantification methods, sample collection techniques that are inherently inaccurate and inappropriate, and a general perception that DPP4 cleavage inactivates its ligand substrates. Increasing evidence points towards many DPP4-cleaved ligands having their own bioactivity. For example, GLP-1 can work through a different receptor than GLP-1R, DPP4-cleaved GIP can function as a GIP receptor antagonist at high doses, and DPP4-cleaved PYY, NPY, and CXCL12 can have different receptor selectivity, or can bind novel, previously unrecognized receptors to their intact ligands, resulting in altered signaling and functionality. We believe that more rigorous research in this area could lead to a better understanding of DPP4's role and the biological importance of the generation of novel cryptic ligands. This will also significantly impact our understanding of the clinical effects and side effects of DPP4-inhibitors as a class of anti-diabetic drugs that potentially have an expanding clinical relevance. This will be specifically relevant in targeting DPP4 substrate ligands involved in a variety of other major clinical acute and chronic injury/disease areas including inflammation, immunology, cardiology, stroke, musculoskeletal disease and injury, as well as cancer biology and tissue maintenance in aging.

An update on therapies for the treatment of diabetes-induced osteoporosis

Introduction: Currently, 424 million people aged between 20 and 79 years worldwide are diabetic. More than 25% of adults aged over 65 years in North America have Type 2 diabetes mellitus (DM). Diabetes-induced osteoporosis (DM-OS) is caused by chronic hyperglycemia, advanced glycated end products and oxidative stress. The increase in the prevalence of DM-OS has prompted researchers to develop new biological therapies for the management of DM-OS. Areas covered: This review covered the current and novel biological agents used in the management of DM-OS. Data were retrieved from PubMed, Scopus, American Diabetes Association and International Osteoporosis Foundation websites, and ClinicalTrials.gov. The keywords for the search included: DM, osteoporosis, and management. Expert opinion: Several biological molecules have been examined in order to find efficient drugs for the treatment of DM-OS. These biological agents include anti-osteoporosis drugs: net anabolics (parathyroid hormone/analogs, androgens, calcilytics, anti-sclerostin antibody), net anti-resorptive osteoporosis drugs (calcitonin, estrogen, selective estrogen receptor modulators, bisphosphonates, RANKL antibody) and anti-diabetic drugs (alpha glucosidase inhibitors, sulfonylureas, biguanides, meglitinides, thiazolidinediones, GLP-1 receptor agonists, dipeptidylpeptidase-4 inhibitors, sodium glucose co-transporter-2 inhibitors, insulin). Biological medications that effectively decrease hyperglycemia and, at the same time, maintain bone health would be an ideal drug/drug combination for the treatment of DM-OS.

Diabetes pharmacotherapy and effects on the musculoskeletal system

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

Soluble Dipeptidyl Peptidase-4 Levels Are Associated with Decreased Renal Function in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) is strongly expressed in the kidney, and soluble levels of this protein are used as a marker in various chronic inflammatory diseases, including diabetes, coronary artery disease, and cancer. This study examined the association between the serum soluble DPP-4 levels and renal function or cardiovascular risk in patients with type 2 diabetes mellitus.

METHODS

In this retrospective analysis, soluble DPP-4 levels were measured in preserved sera from 140 patients with type 2 diabetes mellitus who had participated in our previous coronary artery calcium (CAC) score study.

RESULTS

The mean±standard deviation soluble DPP-4 levels in our study sample were 645±152 ng/mL. Univariate analyses revealed significant correlations of soluble DPP-4 levels with the total cholesterol (r=0.214, P=0.019) and serum creatinine levels (r=-0.315, P<0.001) and the estimated glomerular filtration rate (eGFR; estimated using the modification of diet in renal disease equation) (r=0.303, P=0.001). The associations of soluble DPP-4 levels with serum creatinine and GFR remained significant after adjusting for age, body mass index, and duration of diabetes. However, no associations were observed between soluble DPP-4 levels and the body mass index, waist circumference, or CAC score.

CONCLUSION

These data suggest the potential use of serum soluble DPP-4 levels as a future biomarker of deteriorated renal function in patients with type 2 diabetes mellitus.

The safety of gliptins : updated data in 2018

INTRODUCTION

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are generally considered as glucose-lowering agents with a safe profile in type 2 diabetes.

AREAS COVERED

An updated review of recent safety data from randomised controlled trials, observational studies, meta-analyses, pharmacovigilance reports regarding alogliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin, with a special focus on risks of hypoglycemia, pancreatitis and pancreatic cancer, major cardiovascular events, hospitalisation for heart failure and other new safety issues, such as bone fractures and arthralgia. The safety of DPP-4i use in special populations, elderly patients, patients with renal impairment, liver disease or heart failure, will also be discussed.

EXPERT OPINION

The good tolerance/safety profile of DPP-4is has been largely confirmed, including in more fragile populations, with no gastrointestinal adverse effects and a minimal risk of hypoglycemia. DPP-4is appear to be associated with a small increased incidence of acute pancreatitis in placebo-controlled trials, although most observational studies are reassuring. Most recent studies with DPP-4is do not confirm the increased risk of hospitalisation for heart failure reported with saxagliptin in SAVOR-TIMI 53, but further post-marketing surveillance is still recommended. New adverse events have been reported such as arthralgia, yet a causal relationship remains unclear.

Effect of Dipeptidyl Peptidase-4 Inhibitors on Bone Metabolism and the Possible Underlying Mechanisms

Diabetes mellitus has been demonstrated to be closely associated with osteoporosis. Accordingly, hypoglycemic therapy is considered effective in treating metabolic bone disease. Recently, the effects of dipeptidyl peptidase-4 (DPP-4) inhibitors, a new type of antidiabetic drug, on bone metabolism have been widely studied. This review mainly describes the effects of DPP-4 inhibitors on bone metabolism, including their effects on bone mineral density, bone quality, and fracture risk. In addition, the potential underlying mechanisms are discussed. Based on the current progress in this research field, DPP-4 inhibitors have been proved to reduce fracture risk. In addition, sitagliptin, a strong and highly selective DPP-4 inhibitor, showed its beneficial effects on bone metabolism by improving bone mineral density, bone quality, and bone markers. With regard to the potential underlying mechanisms, DPP-4 inhibitors may promote bone formation and reduce bone resorption through DPP-4 substrates and DPP-4-related energy metabolism. Vitamin D and other related signaling pathways also play a role in affecting bone metabolism. Although these assumptions are controversial, they provide a translational pharmacology approach for the clinical use of DPP-4 inhibitors in the treatment of metabolic diseases. Prior to the use of these drugs in clinic, further studies should be conducted to determine the appropriate type of DPP-4 inhibitor, the people who would benefit the most from this therapy, appropriate dose and duration, and the effects of the treatment.

Dipeptidyl Peptidase-4 and Adolescent Idiopathic Scoliosis: Expression in Osteoblasts

It has been proposed that girls with adolescent idiopathic scoliosis (AIS) tend to have a taller stature and a lower body mass index. Energy homeostasis, that is known to affect bone growth, could contribute to these characteristics. In circulation, dipeptidyl peptidase-4 (DPP-4) inactivates glucagon-like peptide-1 (GLP-1), an incretin that promotes insulin secretion and sensitivity. Our objectives were to investigate DPP-4 status in plasma and in osteoblasts of AIS subjects and controls and to evaluate the regulatory role of metabolic effectors on DPP-4 expression. DPP-4 activity was assessed in plasma of 113 girls and 62 age-matched controls. Osteoblasts were isolated from bone specimens of AIS patients and controls. Human cells were incubated with glucose, insulin, GLP-1 and butyrate. Gene and protein expressions were evaluated by RT-qPCR and Western blot. Our results showed 14% inferior plasma DPP-4 activity in AIS patients when compared to healthy controls (P = 0.0357). Similarly, osteoblasts derived from AIS subjects had lower DPP-4 gene and protein expression than controls by 90.5% and 57.1% respectively (P < 0.009). DPP-4 expression was regulated in a different manner in osteoblasts isolated from AIS participants compared to controls. Our results suggest a role for incretins in AIS development and severity.