Stem cell compartmentalization in diabetes and high cardiovascular risk reveals the role of DPP-4 in diabetic stem cell mobilopathy

The impact of diabetes mellitus on hematopoietic stem cell mobilization, a-single center cohort study

BACKGROUND

Factors such as age, underlying hematological disease, chemotherapy and radiotherapy used, and bone marrow infiltration may cause mobilization failure. Several preclinical observed that diabetes mellitus (DM) leads to profound remodeling of the hematopoietic stem cell (HSC) niche, resulting in the impaired release of HSCs. We aim to examine the effect of DM on HSC mobilization and to investigate whether there is a relationship between complications developing in the DM process and drugs used to treat DM and mobilization failure.

METHODS

In Erciyes University Bone Marrow Transplantation Unit, 218 patients who underwent apheresis for stem cell mobilization between 2011 and 2021 were evaluated retrospectively. One hundred and nine patients had a diagnosis of DM, and 109 did not.

RESULTS

Mobilization failure developed in 17 (15.6 %) of the patients in the DM group, while it developed in 7 (6.4 %) patients in the non-DM group (p = 0.03). CD34+ stem cell count was 8.05 (1.3-30.2) × 106/kg in the DM group, while it was 8.2 (1.7-37.3) × 106/kg in the other group (p = 0.55). There was no statistically significant relationship between glucose and hemoglobin A1c levels and the amount of CD34+ cells (p = 0.83 and p = 0.14, respectively). Using sulfonylurea was the only independent predictor of mobilization failure (OR 5.75, 95 % CI: 1.38-24.05, p = 0.02).

CONCLUSION

DM should be considered a risk factor for mobilization failure. Further research is needed fully to understand the mechanisms underlying the mobilization failure effects of sulfonylureas and to develop strategies to improve stem cell mobilization in diabetic patients.

Endothelial progenitor cells as biomarkers of diabetes-related cardiovascular complications

Diabetes mellitus (DM) constitutes a chronic metabolic disease characterized by elevated levels of blood glucose which can also lead to the so-called diabetic vascular complications (DVCs), responsible for most of the morbidity, hospitalizations and death registered in these patients. Currently, different approaches to prevent or reduce DM and its DVCs have focused on reducing blood sugar levels, cholesterol management or even changes in lifestyle habits. However, even the strictest glycaemic control strategies are not always sufficient to prevent the development of DVCs, which reflects the need to identify reliable biomarkers capable of predicting further vascular complications in diabetic patients. Endothelial progenitor cells (EPCs), widely known for their potential applications in cell therapy due to their regenerative properties, may be used as differential markers in DVCs, considering that the number and functionality of these cells are affected under the pathological environments related to DM. Besides, drugs commonly used with DM patients may influence the level or behaviour of EPCs as a pleiotropic effect that could finally be decisive in the prognosis of the disease. In the current review, we have analysed the relationship between diabetes and DVCs, focusing on the potential use of EPCs as biomarkers of diabetes progression towards the development of major vascular complications. Moreover, the effects of different drugs on the number and function of EPCs have been also addressed.

The tyrosine kinase inhibitor Dasatinib reduces cardiac steatosis and fibrosis in obese, type 2 diabetic mice

BACKGROUND

Cardiac steatosis is an early yet overlooked feature of diabetic cardiomyopathy. There is no available therapy to treat this condition. Tyrosine kinase inhibitors (TKIs) are used as first or second-line therapy in different types of cancer. In cancer patients with diabetes mellitus, TKIs reportedly improved glycemic control, allowing insulin discontinuation. They also reduced liver steatosis in a murine model of non-alcoholic fatty liver disease. The present study aimed to determine the therapeutic effect of the second-generation TKI Dasatinib on lipid accumulation and cardiac function in obese, type 2 diabetic mice. We also assessed if the drug impacts extra-cardiac fat tissue depots.

METHODS

Two studies on 21-week-old male obese leptin receptor mutant BKS.Cg-+Leprdb/+Leprdb/OlaHsd (db/db) mice compared the effect of Dasatinib (5 mg/kg) and vehicle (10% DMSO + 90% PEG-300) given via gavage once every three days for a week or once every week for four weeks. Functional and volumetric indices were studied using echocardiography. Post-mortem analyses included the assessment of fat deposits and fibrosis using histology, and senescence using immunohistochemistry and flow cytometry. The anti-adipogenic action of Dasatinib was investigated on human bone marrow (BM)-derived mesenchymal stem cells (MSCs). Unpaired parametric or non-parametric tests were used to compare two and multiple groups as appropriate.

RESULTS

Dasatinib reduced steatosis and fibrosis in the heart of diabetic mice. The drug also reduced BM adiposity but did not affect other fat depots. These structural changes were associated with improved diastolic indexes, specifically the E/A ratio and non-flow time. Moreover, Dasatinib-treated mice had lower levels of p16 in the heart compared with vehicle-treated controls, suggesting an inhibitory impact of the drug on the senescence signalling pathway. In vitro, Dasatinib inhibited human BM-MSC viability and adipogenesis commitment.

CONCLUSIONS

Our findings suggest that Dasatinib opposes heart and BM adiposity and cardiac fibrosis. In the heart, this was associated with favourable functional consequences, namely improvement in an index of diastolic function. Repurposing TKI for cardiac benefit could address the unmet need of diabetic cardiac steatosis.

Impaired haematopoietic stem / progenitor cell traffic and multi-organ damage in diabetes

During antenatal development, hematopoietic stem/progenitor cells (HSPCs) arise from a specialized endothelium and migrate from the extraembryonic mesoderm to the fetal liver before establishing hematopoiesis in the bone marrow (BM). It is still debated whether, in adulthood, HSPCs display such ontologic overlap with vascular cells and capacity for endothelial differentiation. Yet, adult HSPCs retain a prominent migratory activity and traffic in the bloodstream to secondary lymphoid organs and all peripheral tissues, before eventually returning to the BM. While patrolling parenchymatous organs, HSPCs locate close to the vasculature, where they establish local hematopoietic islands and contribute to tissue homeostasis by paracrine signals. Solid evidence shows that diabetes mellitus jeopardizes the traffic of HSPCs from BM to the circulation and peripheral tissues, a condition called “mobilopathy.” A reduction in the levels of circulating HSPCs is the most immediate and apparent consequence, which has been consistently observed in human diabetes, and is strongly associated with future risk for multi-organ damage, including micro- and macro-angiopathy. But the shortage of HSPCs in the blood is only the visible tip of the iceberg. Abnormal HSPC traffic results from a complex interplay among metabolism, innate immunity, and hematopoiesis. Notably, mobilopathy is mechanistically connected with diabetes-induced myelopoiesis. Impaired traffic of HSPCs and enhanced generation of pro-inflammatory cells synergize for tissue damage and impair the resolution of inflammation. We herein summarize the current evidence that diabetes affects HSPC traffic, which are the causes and consequences of such alteration, and how it contributes to the overall disease burden.

Oral 11β-HSD1 inhibitor AZD4017 improves wound healing and skin integrity in adults with type 2 diabetes mellitus: a pilot randomized controlled trial

BACKGROUND

Chronic wounds (e.g. diabetic foot ulcers) reduce the quality of life, yet treatments remain limited. Glucocorticoids (activated by the enzyme 11β-hydroxysteroid dehydrogenase type 1, 11β-HSD1) impair wound healing.

OBJECTIVES

Efficacy, safety, and feasibility of 11β-HSD1 inhibition for skin function and wound healing.

DESIGN

Investigator-initiated, double-blind, randomized, placebo-controlled, parallel-group phase 2b pilot trial.

METHODS

Single-center secondary care setting. Adults with type 2 diabetes mellitus without foot ulcers were administered 400 mg oral 11β-HSD1 inhibitor AZD4017 (n = 14) or placebo (n = 14) bi-daily for 35 days. Participants underwent 3-mm full-thickness punch skin biopsies at baseline and on day 28; wound healing was monitored after 2 and 7 days. Computer-generated 1:1 randomization was pharmacy-administered. Analysis was descriptive and focused on CI estimation. Of the 36 participants screened, 28 were randomized.

RESULTS

Exploratory proof-of-concept efficacy analysis suggested AZD4017 did not inhibit 24-h ex vivoskin 11β-HSD1 activity (primary outcome; difference in percentage conversion per 24 h 1.1% (90% CI: -3.4 to 5.5) but reduced systemic 11β-HSD1 activity by 87% (69-104%). Wound diameter was 34% (7-63%) smaller with AZD4017 at day 2, and 48% (12-85%) smaller after repeat wounding at day 30. AZD4017 improved epidermal integrity but modestly impaired barrier function. Minimal adverse events were comparable to placebo. Recruitment rate, retention, and data completeness were 2.9/month, 27/28, and 95.3%, respectively.

CONCLUSION

A phase 2 trial is feasible, and preliminary proof-of-concept data suggests AZD4017 warrants further investigation in conditions of delayed healing, for example in diabetic foot ulcers.

SIGNIFICANCE STATEMENT

Stress hormone activation by the enzyme 11β-HSD type 1 impairs skin function (e.g. integrity) and delays wound healing in animal models of diabetes, but effects in human skin were previously unknown. Skin function was evaluated in response to treatment with a 11β-HSD type 1 inhibitor (AZD4017), or placebo, in people with type 2 diabetes. Importantly, AZD4017 was safe and well tolerated. This first-in-human randomized, controlled, clinical trial found novel evidence that 11β-HSD type 1 regulates skin function in humans, including improved wound healing, epidermal integrity, and increased water loss. Results warrant further studies in conditions of impaired wound healing, for example, diabetic foot ulcers to evaluate 11β-HSD type 1 as a novel therapeutic target forchronic wounds.

Vascular repair and regeneration in cardiometabolic diseases

Chronic cardiometabolic assaults during type 2 diabetes (T2D) and obesity induce a progenitor cell imbalance in the circulation characterized by overproduction and release of pro-inflammatory monocytes and granulocytes from the bone marrow alongside aberrant differentiation and mobilization of pro-vascular progenitor cells that generate downstream progeny for the coordination of blood vessel repair. This imbalance can be detected in the peripheral blood of individuals with established T2D and severe obesity using multiparametric flow cytometry analyses to discern pro-inflammatory vs. pro-angiogenic progenitor cell subsets identified by high aldehyde dehydrogenase activity, a conserved progenitor cell protective function, combined with lineage-restricted cell surface marker analyses. Recent evidence suggests that progenitor cell imbalance can be reversed by treatment with pharmacological agents or surgical interventions that reduce hyperglycaemia or excess adiposity. In this state-of-the-art review, we present current strategies to assess the progression of pro-vascular regenerative cell depletion in peripheral blood samples of individuals with T2D and obesity and we summarize novel clinical data that intervention using sodium-glucose co-transporter 2 inhibition or gastric bypass surgery can efficiently restore cell-mediated vascular repair mechanisms associated with profound cardiovascular benefits in recent outcome trials. Collectively, this thesis generates a compelling argument for early intervention using current pharmacological agents to prevent or restore imbalanced circulating progenitor content and maintain vascular regenerative cell trafficking to sites of ischaemic damage. This conceptual advancement may lead to the design of novel therapeutic approaches to prevent or reverse the devastating cardiovascular comorbidities currently associated with T2D and obesity.

The Fate Status of Stem Cells in Diabetes and its Role in the Occurrence of Diabetic Complications

Diabetes mellitus (DM) is becoming a growing risk factor for public health worldwide. It is a very common disease and is widely known for its susceptibility to multiple complications which do great harm to the life and health of patients, some even lead to death. To date, there are many mechanisms for the complications of diabetes, including the generation of reactive oxygen species (ROS) and the abnormal changes of gas transmitters, which ultimately lead to injuries of cells, tissues and organs. Normally, even if injured, the body can quickly repair and maintain its homeostasis. This is closely associated with the repair and regeneration ability of stem cells. However, many studies have demonstrated that stem cells happen to be damaged under DM, which may be a nonnegligible factor in the occurrence and progression of diabetic complications. Therefore, this review summarizes how diabetes causes the corresponding complications by affecting stem cells from two aspects: stem cells dysfunctions and stem cells quantity alteration. In addition, since mesenchymal stem cells (MSCs), especially bone marrow mesenchymal stem cells (BMMSCs), have the advantages of strong differentiation ability, large quantity and wide application, we mainly focus on the impact of diabetes on them. The review also puts forward the basis of using exogenous stem cells to treat diabetic complications. It is hoped that through this review, researchers can have a clearer understanding of the roles of stem cells in diabetic complications, thus promoting the process of using stem cells to treat diabetic complications.

Fenofibrate increases circulating haematopoietic stem cells in people with diabetic retinopathy: a randomised, placebo-controlled trial

AIM/HYPOTHESIS

In two large RCTs, fenofibrate reduced the progression of diabetic retinopathy. We investigated whether fenofibrate increases circulating haematopoietic stem/progenitor cells (HSPCs), which have vascular properties and have been shown to protect from retinopathy.

METHODS

We conducted a 12 week parallel-group RCT comparing fenofibrate vs placebo. Patients with diabetic retinopathy and without other conditions that would affect HSPCs were enrolled at a tertiary diabetes outpatient clinic and randomised to receive fenofibrate or placebo based on a computer-generated sequence. Patients and study staff assessing the outcomes were blinded to group assignment. The primary endpoint was the change in the levels of circulating HSPCs, defined by expression of the stem cell markers CD34 and/or CD133. Secondary endpoints were the changes in endothelial progenitor cells, lipids, soluble mediators and gene expression. We used historical data on the association between HSPCs and retinopathy outcomes to estimate the effect of fenofibrate on retinopathy progression.

RESULTS

Forty-two participants with diabetic retinopathy were randomised and 41 completed treatment and were analysed (20 in the placebo group and 21 in the fenofibrate group). Mean age was 57.4 years, diabetes duration was 18.2 years and baseline HbA_1c was 60 mmol/mol (7.6%). When compared with placebo, fenofibrate significantly increased levels of HSPCs expressing CD34 and/or CD133. CD34⁺ HSPCs non-significantly declined in the placebo group (mean ± SD -44.2 ± 31.6 cells/10⁶) and significantly increased in the fenofibrate group (53.8 ± 31.1 cells/10⁶). The placebo-subtracted increase in CD34⁺ HSPCs from baseline was 30% (99.3 ± 43.3 cells/10⁶; p = 0.027) which, projected onto the relationship between HSPC levels and retinopathy outcomes, yielded an OR of retinopathy progression of 0.67 for fenofibrate vs placebo. Endothelial differentiation of CD34⁺ cells, estimated by the %KDR (kinase insert domain receptor) expression, was significantly reduced by fenofibrate. Fenofibrate decreased serum triacylglycerols, but the change in triacylglycerols was unrelated to the change in HSPCs. No effect was observed for endothelial progenitor cells, cytokines/chemokines (stromal-cell derived factor-1, vascular endothelial growth factor, monocyte chemoattractant protein-1) and gene expression in peripheral blood mononuclear cells.

CONCLUSIONS/INTERPRETATION

Fenofibrate increased HSPC levels in participants with diabetic retinopathy and this mechanism may explain why fenofibrate reduced retinopathy progression in previous studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01927315.

Current Understanding of Osteoimmunology in Certain Osteoimmune Diseases

The skeletal system and immune system seem to be two independent systems. However, there in fact are extensive and multiple crosstalk between them. The concept of osteoimmunology was created to describe those interdisciplinary events, but it has been constantly updated over time. In this review, we summarize the interactions between the skeletal and immune systems in the co-development of the two systems and the progress of certain typical bone abnormalities and bone regeneration on the cellular and molecular levels according to the mainstream novel study. At the end of the review, we also highlighted the possibility of extending the research scope of osteoimmunology to other systemic diseases. In conclusion, we propose that osteoimmunology is a promising perspective to uncover the mechanism of related diseases; meanwhile, a study from the point of view of osteoimmunology may also provide innovative ideas and resolutions to achieve the balance of internal homeostasis.

Diabetes pharmacotherapy and circulating stem/progenitor cells. State of the art and evidence gaps

Diabetes is burdened with the development of several end-organ complications leading to excess mortality. Though the causes of such organ damage are far from being clarified, diabetes has been redefined as a disease of impaired damage control, wherein ongoing damage is not adequately compensated by activation of repair processes. Bone marrow-derived hematopoietic stem/progenitor cells (HSPCs) and their descendants endothelial progenitor cells (EPCs) have been extensively studied as major players in tissue homeostasis as well as biomarkers of diabetic complication risk. Thus, strategies to raise the levels of circulating HSPCs/EPCs have attracted interest for their potential to modify the future risk of complications. We herein discuss state-of-the-art of the effects exerted by diabetes pharmacotherapy on such cell populations. Further, we highlight which outstanding questions remain to be addressed for a more comprehensive understanding of this topic.

Pharmacologic PPAR-γ Activation Reprograms Bone Marrow Macrophages and Partially Rescues HSPC Mobilization in Human and Murine Diabetes

Mobilization of hematopoietic stem/progenitor cells (HSPC) from the bone marrow (BM) is impaired in diabetes. Excess oncostatin M (OSM) produced by M1 macrophages in the diabetic BM signals through p66Shc to induce Cxcl12 in stromal cells and retain HSPC. BM adipocytes are another source of CXCL12 that blunts mobilization. We tested a strategy of pharmacologic macrophage reprogramming to rescue HSPC mobilization. In vitro, PPAR-γ activation with pioglitazone switched macrophages from M1 to M2, reduced Osm expression, and prevented transcellular induction of Cxcl12 In diabetic mice, pioglitazone treatment downregulated Osm, p66Shc, and Cxcl12 in the hematopoietic BM, restored the effects of granulocyte-colony stimulation factor (G-CSF), and partially rescued HSPC mobilization, but it increased BM adipocytes. Osm deletion recapitulated the effects of pioglitazone on adipogenesis, which was p66Shc independent, and double knockout of Osm and p66Shc completely rescued HSPC mobilization. In the absence of OSM, BM adipocytes produced less CXCL12, being arguably devoid of HSPC-retaining activity, whereas pioglitazone failed to downregulate Cxcl12 in BM adipocytes. In patients with diabetes on pioglitazone therapy, HSPC mobilization after G-CSF was partially rescued. In summary, pioglitazone reprogrammed BM macrophages and suppressed OSM signaling, but sustained Cxcl12 expression by BM adipocytes could limit full recovery of HSPC mobilization.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Impact of Diabetes Mellitus on Bone Health

Long-term exposure to a diabetic environment leads to changes in bone metabolism and impaired bone micro-architecture through a variety of mechanisms on molecular and structural levels. These changes predispose the bone to an increased fracture risk and impaired osseus healing. In a clinical practice, adequate control of diabetes mellitus is essential for preventing detrimental effects on bone health. Alternative fracture risk assessment tools may be needed to accurately determine fracture risk in patients living with diabetes mellitus. Currently, there is no conclusive model explaining the mechanism of action of diabetes mellitus on bone health, particularly in view of progenitor cells. In this review, the best available literature on the impact of diabetes mellitus on bone health in vitro and in vivo is summarised with an emphasis on future translational research opportunities in this field.

Cytokine-induced hematopoietic stem and progenitor cell mobilization: unraveling interactions between stem cells and their niche

Peripheral blood hematopoietic stem and progenitor cells (HSPCs), mobilized by granulocyte colony‐stimulating factor, are widely used as a source for both autologous and allogeneic stem cell transplantation. The use of mobilized HSPCs has several advantages over traditional bone marrow–derived HSPCs, including a less invasive harvesting process for the donor, higher HSPC yields, and faster hematopoietic reconstitution in the recipient. For years, the mechanisms by which cytokines and other agents mobilize HSPCs from the bone marrow were not fully understood. The field of stem cell mobilization research has advanced significantly over the past decade, with major breakthroughs in the elucidation of the complex mechanisms that underlie stem cell mobilization. In this review, we provide an overview of the events that underlie HSPC mobilization and address the relevant cellular and molecular components of the bone marrow niche. Furthermore, current and future mobilizing agents will be discussed.

Exhaustion of the bone marrow progenitor cell reserve is associated with major events in severe limb ischemia

Lower numbers of progenitor cells (PCs) in peripheral blood (PB) have been associated with cardiovascular events in high-risk populations. Therapies aiming to increase the numbers of PCs in circulation have been developed, but clinical trials did not result in better outcomes. It is currently unknown what causes the reduction in PB PC numbers: whether it is primary depletion of the progenitor cell reserve, or a reduced mobilization of PCs from the bone marrow (BM). In this study, we examine if PB and BM PC numbers predict Amputation-Free Survival (AFS) in patients with Severe Limb Ischemia (SLI). We obtained PB and BM from 160 patients enrolled in a clinical trial investigating BM cell therapy for SLI. Samples were incubated with antibodies against CD34, KDR, CD133, CD184, CD14, CD105, CD140b, and CD31; PC populations were enumerated by flow cytometry. Higher PB CD34⁺ and CD133⁺ PC numbers were related to AFS (Both Hazard Ratio [HR_event] = 0.56, p = 0.003 and p = 0.0007, respectively). AFS was not associated with the other cell populations in PB. BM PC numbers correlated with PB PC numbers and showed similar HRs for AFS. A further subdivision based on relative BM and PB PC numbers showed that BM PC numbers, rather than mobilization, associated with AFS. Both PB and BM PC numbers are associated with AFS independently from traditional risk factor and show very similar risk profiles. Our data suggest that depletion of the progenitor cell reserve, rather than decreased PC mobilization, underlies the association between PB PC numbers and cardiovascular risk.

Neuropathy and inflammation in diabetic bone marrow

Diabetes impairs the bone marrow (BM) architecture and function as well as the mobilization of immature cells into the bloodstream and number of potential regenerative cells. Circadian regulation of bone immature cell migration is regulated by β-adrenergic receptors, which are expressed on haematopoietic stem cells, mesenchymal stem cells, and osteoblasts in the BM. Diabetes is associated with a substantially lower number of sympathetic nerve terminal endings in the BM; thus, diabetic neuropathy plays a critical role in BM dysfunction. Treatment with mesenchymal stem cells, BM mononuclear cells, haematopoietic stem cells, and stromal cells ameliorates the dysfunction of diabetic neuropathy, which occurs, in part, through secreted neurotrophic factors, growth factors, adipokines, and polarizing macrophage M2 cells and inhibiting inflammation. Inflammation may be a therapeutic target for BM stem cells to improve diabetic neuropathy. Given that angiogenic and neurotrophic effects are two major barriers to effective diabetic neuropathy therapy, targeting BM stem cells may provide a novel approach to develop these types of treatments.

Pharmacologic targeting of the diabetic stem cell mobilopathy

Diabetes is a chronic metabolic disease characterized by hyperglycemia and several associated biochemical abnormalities. Diabetes leads to multiorgan complications that collectively reduce life expectancy. Hematopoietic stem cells (HSCs) are nested within bone marrow (BM) niches whence they can be mobilized to the peripheral circulation. Clinically, this is done for HSC collection and autologous or allogenic transplantation. A great amount of data from basic and clinical studies support that diabetic patients are poor HSC mobilizers owing to BM remodeling. Dysfunction of the BM shares pathophysiological features and pathways with typical chronic diabetic complications that affect other issues (e.g. the retina and the kidney). From a clinical perspective, impaired HSC mobilization translates into the failure to collect a minimum number of CD34⁺ cells to achieve a safe engraftment after transplantation. Furthermore, blunted mobilization is associated with reduced steady-state levels of circulating HSCs, which have been consistently described in diabetic patients and associated with increased risk of adverse outcomes, including cardiovascular events and death. In this review, we discuss the most clinically relevant pharmacological options to overcome impaired HSC mobilization in diabetes. These therapeutic strategies may result in an improved outcome of diabetic patients undergoing HSC transplantation and restore circulating HSC levels, thereby protecting from adverse cardiovascular outcomes.

The pleiotropic cardiovascular effects of dipeptidyl peptidase-4 inhibitors

Patients with Type 2 diabetes have an excess risk for cardiovascular disease. One of the several approaches, included in the guidelines for the management of Type 2 diabetes, is based on dipeptidyl peptidase 4 (DPP-4; also termed CD26) inhibitors, also called gliptins. Gliptins inhibit the degradation of glucagon-like peptide-1 (GLP-1): this effect is associated with increased circulating insulin-to-glucagon ratio, and a consequent reduction of HbA1c. In addition to incretin hormones, there are several proteins that may be affected by DPP-4 and its inhibition: among these some are relevant for the cardiovascular system homeostasis such as SDF-1α and its receptor CXCR4, brain natriuretic peptides, neuropeptide Y and peptide YY. In this review, we will discuss the pathophysiological relevance of gliptin pleiotropism and its translational potential.

Have dipeptidyl peptidase-4 inhibitors ameliorated the vascular complications of type 2 diabetes in large-scale trials? The potential confounding effect of stem-cell chemokines

Drugs that inhibit dipeptidyl peptidase-4 (DPP-4) are conventionally regarded as incretin-based agents that signal through the glucagon-like peptide-1 (GLP-1) receptor. However, inhibition of DPP-4 also potentiates the stem cell chemokine, stromal cell-derived factor-1 (SDF-1), which can promote inflammation, proliferative responses and neovascularization. In large-scale cardiovascular outcome trials, enhanced GLP-1 signaling has reduced the risk of atherosclerotic ischemic events, potentially because GLP-1 retards the growth and increases the stability of atherosclerotic plaques. However, DPP-4 inhibitors have not reduced the risk of major adverse cardiovascular events, possibly because potentiation of SDF-1 enhances plaque growth and instability, activates deleterious neurohormonal mechanisms, and promotes cardiac inflammation and fibrosis. Similarly, trials with GLP-1 agonists and sodium-glucose cotransporter 2 inhibitors have reported favorable effects on renal function, even after only 3-4 years of treatment. In contrast, no benefits on the rate of decline in glomerular filtration rate have been seen in trials of DPP-4 inhibitors, perhaps because the renal actions of DPP-4 inhibitors are primarily mediated by potentiation of SDF-1, not GLP-1. Experimentally, SDF-1 can promote podocyte injury and glomerulosclerosis. Furthermore, the natriuretic action of SDF-1 occurs primarily in the distal tubules, where it cannot utilize tubuloglomerular feedback to modulate the deleterious effects of glomerular hyperfiltration. Potentiation of SDF-1 in experimental models may also exacerbate both retinopathy and neuropathy. Therefore, although DPP-4 inhibitors have attractive clinical features, the benefits that might be expected from GLP-1 signaling may be undermined by their actions to enhance SDF-1.

Diabetes mellitus as a poor mobilizer condition

Hematopoietic stem cell (HSC) transplantation in an effective and curative therapy for numerous hematological malignancies. Mobilization of HSCs from bone marrow (BM) to peripheral blood (PB) followed by apheresis is the gold standard for obtaining HSCs for both autologous and allogeneic stem cell transplantation. After administration of granulocyte-colony stimulating factor (G-CSF), up to 30% of patients fail to mobilize "optimal" numbers of HSCs required for engraftment. This review summarizes the current experimental and clinical evidence that diabetes mellitus is a risk factor for poor mobilization. Diabetes causes a profound remodeling of the HSC niche, resulting in impaired release of HSCs. Experimental studies indicate that hyperglycemia hampers regulation of CXCL12 and clinical studies suggest that diabetes impairs HSC mobilization especially in response to G-CSF, but less to plerixafor. Understanding further the biochemical alterations in the diabetic BM will provide insights into future therapeutic strategies to reverse the so-called "diabetic stem cell mobilopathy".

Hematopoietic stem/progenitor involvement in retinal microvascular repair during diabetes: Implications for bone marrow rejuvenation

The widespread nature of diabetes affects all organ systems of an individual including the bone marrow. Long-term damage to the cellular and extracellular components of the bone marrow leads to a rapid decline in the bone marrow-hematopoietic stem/progenitor cells (HS/PCs) compartment. This review will highlight the importance of bone marrow microenvironment in maintaining bone marrow HS/PC populations and the contribution of these key populations in microvascular repair during the natural history of diabetes. The autonomic nervous system can initiate and propagate bone marrow dysfunction in diabetes. Systemic pharmacological strategies designed to protect the bone marrow-HS/PC population from diabetes induced-oxidative stress and advanced glycation end product accumulation represent a new approach to target diabetic retinopathy progression. Protecting HS/PCs ensures their participation in vascular repair and reduces the risk of vasogdegeneration occurring in the retina.

Chronic Psychological Stress Accelerates Vascular Senescence and Impairs Ischemia-Induced Neovascularization: The Role of Dipeptidyl Peptidase-4/Glucagon-Like Peptide-1-Adiponectin Axis

BACKGROUND

Exposure to psychosocial stress is a risk factor for cardiovascular disease, including vascular aging and regeneration. Given that dipeptidyl peptidase-4 (DPP4) regulates several intracellular signaling pathways associated with the glucagon-like peptide-1 (GLP-1) metabolism, we investigated the role of DPP4/GLP-1 axis in vascular senescence and ischemia-induced neovascularization in mice under chronic stress, with a special focus on adiponectin -mediated peroxisome proliferator activated receptor-γ/its co-activator 1α (PGC-1α) activation.

METHODS AND RESULTS

Seven-week-old mice subjected to restraint stress for 4 weeks underwent ischemic surgery and were kept under immobilization stress conditions. Mice that underwent ischemic surgery alone served as controls. We demonstrated that stress impaired the recovery of the ischemic/normal blood-flow ratio throughout the follow-up period and capillary formation. On postoperative day 4, stressed mice showed the following: increased levels of plasma and ischemic muscle DPP4 and decreased levels of GLP-1 and adiponectin in plasma and phospho-AMP-activated protein kinase α (p-AMPKα), vascular endothelial growth factor, peroxisome proliferator activated receptor-γ, PGC-1α, and Sirt1 proteins and insulin receptor 1 and glucose transporter 4 genes in the ischemic tissues, vessels, and/or adipose tissues and numbers of circulating endothelial CD31+/c-Kit+ progenitor cells. Chronic stress accelerated aortic senescence and impaired aortic endothelial sprouting. DPP4 inhibition and GLP-1 receptor activation improved these changes; these benefits were abrogated by adiponectin blocking and genetic depletion.

CONCLUSIONS

These results indicate that the DPP4/GLP-1-adiponectin axis is a novel therapeutic target for the treatment of vascular aging and cardiovascular disease under chronic stress conditions.

Dipeptidyl Peptidase-IV Inhibition for the Treatment of Cardiovascular Disease - Recent Insights Focusing on Angiogenesis and Neovascularization

Dipeptidyl peptidase IV (DPP-IV) is a complex enzyme that acts as a membrane-anchored cell surface exopeptidase and transmits intracellular signals through a small intracellular tail. DPP-IV exists in human blood in a soluble form, and truncates a large number of peptide hormones, chemokines, cytokines, and growth factors in vitro and in vivo. DPP-IV has gained considerable interest as a therapeutic target, and a variety of DPP-IV inhibitors that prolong the insulinotropic effects of glucagon-like peptide-1 (GLP-1) are widely used in clinical settings as antidiabetic drugs. Indeed, DPP-IV is upregulated in proinflammatory states, including obesity and cardiovascular disease with and without diabetes mellitus. Consistent with this maladaptive role, DPP-IV inhibitors seem to exert a protective role in cardiovascular disease. In addition to their GLP-1-dependent vascular protective actions, DPP-IV inhibitors exhibit GLP-1-independent beneficial effects on angiogenesis/neovascularization via several signaling pathways (e.g., stromal cell-derived factor-1α/C-X-C chemokine receptor type-4, vascular endothelial growth factor-A/endothelial nitric oxide synthase, etc.). This review focuses on recent findings in this field, highlighting the role of DPP-IV in therapeutic angiogenesis/neovascularization in ischemic heart disease and peripheral artery disease.

Concise Review: Perspectives and Clinical Implications of Bone Marrow and Circulating Stem Cell Defects in Diabetes

Diabetes mellitus is a complex systemic disease characterized by severe morbidity and excess mortality. The burden of its multiorgan complications relies on an imbalance between hyperglycemic cell damage and defective endogenous reparative mechanisms. Inflammation and abnormalities in several hematopoietic components are typically found in diabetes. The discovery that diabetes reduces circulating stem/progenitor cells and impairs their function has opened an entire new field of study where diabetology comes into contact with hematology and regenerative medicine. It is being progressively recognized that such rare circulating cell populations mirror finely regulated processes involved in hematopoiesis, immunosurveillance, and peripheral tissue homeostasis. From a clinical perspective, pauperization of circulating stem cells predicts adverse outcomes and death. Furthermore, studies in murine models and humans have identified the bone marrow (BM) as a previously neglected site of diabetic end-organ damage, characterized by microangiopathy, neuropathy, fat deposition, and inflammation. As a result, diabetes impairs the mobilization of BM stem/progenitor cells, a defect known as mobilopathy or myelokathexis, with negative consequences for physiologic hematopoiesis, immune regulation, and tissue regeneration. A better understanding of the molecular and cellular processes that govern the BM stem cell niche, cell mobilization, and kinetics in peripheral tissues may uncover new therapeutic strategies for patients with diabetes. This concise review summarizes the current knowledge on the interplay between the BM, circulating stem cells, and diabetes, and sets the stages for future developments in the field. Stem Cells 2017;35:106-116.

Levels of Circulating Progenitor Cells, Cardiovascular Outcomes and Death

Rationale:

Circulating progenitor cells (CPCs), including endothelial progenitor cells (EPCs) are biologically related to many aspects of cardiovascular disease, as they promote angiogenesis and vascular repair.

Objective:

We herein aimed to meta-analyze studies reporting the prognostic role of the CPC/EPC measure on cardiovascular outcomes and death.

Methods and Results:

We screened the English-language literature for longitudinal studies reporting the association between baseline CPC/EPC levels, future cardiovascular events, and death. We retrieved 28 studies, 21 of which contained poolable data and entered the meta-analysis, for a total of 4155 patients, mostly with a high baseline cardiovascular risk. Sixty percent of the studies met at least 11 of 16 items of quality assessment. Overall, reduced CPC/EPC levels were associated with a ≈2-fold increased risk of future cardiovascular events and cardiovascular death. The most predictive phenotype was CD34 + CD133 + : low versus high levels predicted cardiovascular events, restenosis after endovascular intervention, cardiovascular death, and all-cause mortality. Heterogeneity among studies and according to the CPC/EPC phenotype was generally high. Excluding studies for which the risk estimate had to be extrapolated or limiting the analyses to higher quality studies still indicated a significant risk for future cardiovascular events and death in patients with low versus high progenitor cell counts.

Conclusions:

This meta-analysis shows that a reduction in the levels of circulating cells putatively provided with vasculoregenerative properties represents a risk factor for adverse cardiovascular outcomes and death.

Plerixafor improves the endothelial health balance. The effect of diabetes analysed by polychromatic flow cytometry

BACKGROUND AND AIMS

Diabetes damages the endothelium and reduces the availability of bone marrow (BM)-derived endothelial progenitor cells (EPCs). The mobilization of hematopoietic stem cells (HSCs) and EPCs in response to G-CSF is impaired by diabetes, owing to CXCL12 dysregulation. We have previously shown that the CXCR4/CXCL12 disruptor plerixafor rescues HSC and EPC mobilization in diabetes. We herein explored the effects of plerixafor on HSCs, EPCs, and circulating endothelial cells (CECs) in patients with and without diabetes.

METHODS

We re-analysed data gathered in the NCT02056210 trial, wherein patients with (n = 10) and without diabetes (n = 10) received plerixafor to test stem/progenitor cell mobilization. We applied a novel and very specific polychromatic flow cytometry (PFC) approach to identify and quantify HSCs, EPCs, and CECs.

RESULTS

We found that 7-AAD(-)Syto16(+)CD34(+)CD45(dim) HSC levels determined by PFC strongly correlated to the traditional enumeration of CD34(+) cells, whereas 7-AAD(-)Syto16(+)CD34(+)CD45(neg)KDR(+) EPCs were unrelated to the traditional enumeration of CD34(+)KDR(+) cells. Using PFC, we confirmed that plerixafor induces rapid mobilization of HSCs and EPCs in both groups, with a marginally significant defect in patients with diabetes. Plerixafor reduced live (7-AAD(-)) and dead (7-AAD(+)) Syto16(+)CD34(bright)CD45(neg)CD146(+) CECs more in patients without than in those with diabetes. The EPC/CEC ratio, a measure of the vascular health balance, was increased by plerixafor, but less prominently in patients with that in those without diabetes.

CONCLUSIONS

In addition to rescuing defective mobilization associated with diabetes, plerixafor improves the balance between EPCs and CECs, but the latter effect is blunted in patients with diabetes.

Bone Marrow-Derived Stem Cells: a Mixed Blessing in the Multifaceted World of Diabetic Complications

Diabetes is one of the main economic burdens in health care, which threatens to worsen dramatically if prevalence forecasts are correct. What makes diabetes harmful is the multi-organ distribution of its microvascular and macrovascular complications. Regenerative medicine with cellular therapy could be the dam against life-threatening or life-altering complications. Bone marrow-derived stem cells are putative candidates to achieve this goal. Unfortunately, the bone marrow itself is affected by diabetes, as it can develop a microangiopathy and neuropathy similar to other body tissues. Neuropathy leads to impaired stem cell mobilization from marrow, the so-called mobilopathy. Here, we review the role of bone marrow-derived stem cells in diabetes: how they are affected by compromised bone marrow integrity, how they contribute to other diabetic complications, and how they can be used as a treatment for these. Eventually, we suggest new tactics to optimize stem cell therapy.

Efficacy of CD34+ Stem Cell Therapy in Nonischemic Dilated Cardiomyopathy Is Absent in Patients With Diabetes but Preserved in Patients With Insulin Resistance

We evaluated the association of diabetes and insulin resistance with the response to cell therapy in patients with nonischemic dilated cardiomyopathy (DCM). A total of 45 outpatients with DCM received granulocyte colony-stimulating factor for 5 days. CD34(+) cells were then collected by apheresis and injected transendocardially. Twelve patients had diabetes mellitus (DM group), 17 had insulin resistance (IR group), and 16 displayed normal glucose metabolism (no-IR group). After stimulation, we found higher numbers of CD34(+) cells in the IR group (94 ± 73 × 10(6) cells per liter) than in the no-IR group (54 ± 35 × 10(6) cells per liter) or DM group (31 ± 20 × 10(6) cells per liter; p = .005). Similarly, apheresis yielded the highest numbers of CD34(+) cells in the IR group (IR group, 216 ± 110 × 10(6) cells; no-IR group, 127 ± 82 × 10(6) cells; DM group, 77 ± 83 × 10(6) cells; p = .002). Six months after cell therapy, we found an increase in left ventricular ejection fraction in the IR group (+5.6% ± 6.9%) and the no-IR group (+4.4% ± 7.2%) but not in the DM group (-0.9% ± 5.4%; p = .035). The N-terminal pro-brain natriuretic peptide levels decreased in the IR and no-IR groups, but not in the DM group (-606 ± 850 pg/ml; -698 ± 1,105 pg/ml; and +238 ± 963 pg/ml, respectively; p = .034). Transendocardial CD34(+) cell therapy appears to be ineffective in DCM patients with diabetes. IR was associated with improved CD34(+) stem cell mobilization and a preserved clinical response to cell therapy.

SIGNIFICANCE

The present study is the first clinical study directly evaluating the effects of altered glucose metabolism on the efficacy of CD34(+) stem cell therapy in patients with nonischemic dilated cardiomyopathy. The results offer critical insights into the physiology of stem cell mobilization in heart failure and possibly an explanation for the often conflicting results obtained with stem cell therapy for heart failure. These results demonstrate that patients with dilated cardiomyopathy and diabetes do not benefit from autologous CD34(+) cell therapy. This finding could serve as a useful tool when selecting heart failure patients for future clinical studies in the field of stem cell therapy.

Increased Proportion of Hematopoietic Stem and Progenitor Cell Population in Cord Blood of Neonates Born to Mothers with Gestational Diabetes Mellitus

We assessed the hematopoietic stem and progenitor cell (HSPC) population in the cord blood of neonates born to mothers with gestational diabetes mellitus (GDM) in a hypothesis generating pilot study, due to that, neonatal polycythemia may be the consequence of GDM pregnancy. Forty-five pregnant women with GDM (last trimester mean HbA1C = 33.9 mmol/mol) and 42 (nondiabetic) control pregnant women were enrolled after their routine 75 g oral glucose tolerance test (OGTT) between the 24th and 28th gestational week (with expected differences in their mean routine clinical characteristics: plasma glucose at OGTT: 0′ = 5.07 vs. 4.62 mM, 120′ = 8.9 vs. 5.76 mM, age = 35.07 vs. 31.66 years, prepregnancy body mass index = 27.9 vs. 23.9 kg/m², GDM vs. control, respectively) on a voluntary basis after signing the informed consent. EDTA-treated cord blood samples were analyzed by flow cytometry and the software Kaluza1.2 using CD45 and CD34-specific fluorescent antibodies to identify the HSPC population (CD34⁺ cells within the CD45^dim blast gate). The proportion of CD34⁺CD45^dim HSPCs among the nucleated cells was significantly (P < 0.05, statistical power = 60.8%) higher in the cord blood samples of neonates born to mothers with GDM (median 0.38%) compared to neonates born to nondiabetic mothers (median 0.32%) and according to treatment types (P < 0.05) median: control 0.32%, GDM-diet only 0.37%, GDM-on insulin 0.45%; control versus GDM on insulin (P < 0.05). The increased proportion of circulating CD34⁺CD45^dim cells in the cord blood may possibly be related to altered fetal stem cell mobilization in GDM pregnancy, yet these results should be interpreted only as preliminary due to the small sample sizes.

Rapid assay of stem cell functionality and potency using electric cell-substrate impedance sensing

Regenerative medicine studies using autologous bone marrow mononuclear cells (BM-MNCs) have shown improved clinical outcomes that correlate to in vitro BM-MNC invasive capacity. The current Boyden-chamber assay for testing invasive capacity is labor-intensive, provides only a single time point, and takes 36 hours to collect data and results, which is not practical from a clinical cell delivery perspective. To develop a rapid, sensitive and reproducible invasion assay, we employed Electric Cell-substrate Impedance Sensing (ECIS) technology. Chemokine-directed BM-MNC cell invasion across a Matrigel-coated Transwell filter was measurable within minutes using the ECIS system we developed. This ECIS-Transwell chamber system provides a rapid and sensitive test of stem and progenitor cell invasive capacity for evaluation of stem cell functionality to provide timely clinical data for selection of patients likely to realize clinical benefit in regenerative medicine treatments. This device could also supply robust unambiguous, reproducible and cost effective data as a potency assay for cell product release and regulatory strategies.

Diabetes Limits Stem Cell Mobilization Following G-CSF but Not Plerixafor

Previous studies suggest that diabetes impairs hematopoietic stem cell (HSC) mobilization in response to granulocyte colony-stimulating factor (G-CSF). In this study, we tested whether the CXCR4 antagonist plerixafor, differently from G-CSF, is effective in mobilizing HSCs in patients with diabetes. In a prospective study, individuals with and without diabetes (n = 10/group) were administered plerixafor to compare CD34(+) HSC mobilization; plerixafor was equally able to mobilize CD34(+) HSCs in the two groups, whereas in historical data, G-CSF was less effective in patients with diabetes. In a retrospective autologous transplantation study conducted on 706 patients, diabetes was associated with poorer mobilization in patients who received G-CSF with/without chemotherapy, whereas it was not in patients who received G-CSF plus plerixafor. Similarly in an allogeneic transplantation study (n = 335), diabetes was associated with poorer mobilization in patients who received G-CSF. Patients with diabetes who received G-CSF without plerixafor had a lower probability of reaching >50/μL CD34(+) HSCs, independent from confounding variables. In conclusion, diabetes negatively impacted HSC mobilization after G-CSF with or without chemotherapy but had no effect on mobilization induced by G-CSF with plerixafor. This finding has major implications for the care of patients with diabetes undergoing stem cell mobilization and transplantation and for the vascular regenerative potential of bone marrow stem cells.

Bone Marrow Macrophages Contribute to Diabetic Stem Cell Mobilopathy by Producing Oncostatin M

Diabetes affects bone marrow (BM) structure and impairs mobilization of stem cells (SCs) into peripheral blood (PB). This amplifies multiorgan complications because BMSCs promote vascular repair. Because diabetes skews macrophage phenotypes and BM macrophages (BMMΦ) prevent SC mobilization, we hypothesized that excess BMMΦ contribute to diabetic SC mobilopathy. We show that patients with diabetes have increased M1 macrophages, whereas diabetic mice have increased CD169(+) BMMΦ with SC-retaining activity. Depletion of BMMΦ restored SC mobilization in diabetic mice. We found that CD169 labels M1 macrophages and that conditioned medium (CM) from M1 macrophages, but not from M0 and M2 macrophages, induced chemokine (C-X-C motif) ligand 12 (CXCL12) expression by mesenchymal stem/stromal cells. In silico data mining and in vitro validation identified oncostatin M (OSM) as the soluble mediator contained in M1 CM that induces CXCL12 expression via a mitogen-activated protein kinase kinase-p38-signal transducer and activator of a transcription 3-dependent pathway. In diabetic mice, OSM neutralization prevented CXCL12 induction and improved granulocyte-colony stimulating factor and ischemia-induced mobilization, SC homing to ischemic muscles, and vascular recovery. In patients with diabetes, BM plasma OSM levels were higher and correlated with the BM-to-PB SC ratio. In conclusion, BMMΦ prevent SC mobilization by OSM secretion, and OSM antagonism is a strategy to restore BM function in diabetes, which can translate into protection mediated by BMSCs.

Circulating Progenitor Cell Count Predicts Microvascular Outcomes in Type 2 Diabetic Patients

CONTEXT

Diabetes reduces the levels of circulating progenitor cells (CPCs) and endothelial progenitor cells (EPCs), which promote vascular repair and are inversely correlated with cardiovascular risk.

OBJECTIVE

The objective of the study was to test whether CPC/EPC levels predict onset/progression of microangiopathy in a cohort of type 2 diabetic (T2D) patients.

DESIGN

This was a pseudoprospective study with a 3.9-year follow-up.

SETTING

The study was conducted at a tertial referral diabetes outpatient clinic.

PATIENTS

A total of 187 T2D patients having a baseline determination of CPCs/EPCs participated in the study.

INTERVENTION

Baseline data on demographics, anthropometrics, concomitant risk factors, diabetic complications, and medications were collected.

MAIN OUTCOME MEASURE

Onset or progression of microangiopathy was assessed at follow-up compared with baseline.

RESULTS

New onset or progression of microalbuminuria, chronic kidney disease, retinopathy, and neuropathy occurred in 70 patients (9.5%/y). After controlling the false discovery rate, baseline CD34(+) CPCs and EPCs were significantly lower in patients with onset/progression of microalbuminuria and any microangiopathy. Patients with baseline CD34(+) CPC or CD133(+)/kinase insert domain-containing receptor(+)/EPC levels below the median were more likely to experience worsening microangiopathy than those with high cell levels. Independently from confounders, including age, sex, glycated hemoglobin, and diabetes duration, CD34(+) cells predicted onset/progression of microalbuminuria, retinopathy, and any microangiopathy in false discovery rate-adjusted analyses. A low CD34(+) cell count limited the beneficial effects of renin-angiotensin system blockers on microalbuminuria progression.

CONCLUSIONS

Levels of circulating (endothelial) progenitor cells predict microvascular outcomes in T2D. Together with previous studies showing an association with cardiovascular events, these data indicate that CPCs/EPCs represent biomarkers of the global complication burden in diabetes.

Anti-atherosclerotic effects of the glucagon-like peptide-1 (GLP-1) based therapies in patients with type 2 Diabetes Mellitus: A meta-analysis

This study assessed the effect of GLP-1 based therapies on atherosclerotic markers in type 2 diabetes patients. 31 studies were selected to obtain data after multiple database searches and following inclusion and exclusion criteria. Age and BMI of the participants of longitudinal studies were 59.8 ± 8.3 years and 29.2 ± 5.7 kg/m² (Mean±SD). Average duration of GLP-1 based therapies was 20.5 weeks. Percent flow-mediated diameter (%FMD) did not change from baseline significantly but when compared to controls, %FMD increased non-significantly following GLP-1-based therapies (1.65 [−0.89, 4.18]; P = 0.2; REM) in longitudinal studies and increased significantly in cross sectional studies (2.58 [1.68, 3.53]; P < 0.00001). Intima media thickness decreased statistically non-significantly by the GLP-1 based therapies. GLP-1 based therapies led to statistically significant reductions in the serum levels of brain natriuretic peptide (−40.16 [−51.50, −28.81]; P < 0.0001; REM), high sensitivity c-reactive protein (−0.27 [−0.48, −0.07]; P = 0.009), plasminogen activator inhibitor-1 (−12.90 [−25.98, 0.18]; P=0.05), total cholesterol (−5.47 [−9.55, −1.39]; P = 0.009), LDL-cholesterol (−3.70 [−7.39, −0.00]; P = 0.05) and triglycerides (−16.44 [−25.64, −7.23]; P = 0.0005) when mean differences with 95% CI in the changes from baselines were meta-analyzed. In conclusion, GLP-1-based therapies appear to provide beneficial effects against atherosclerosis. More randomized data will be required to arrive at conclusive evidence.

Reduced levels of circulating progenitor cells in juvenile idiopathic arthritis are counteracted by anti TNF-α therapy

Background

Endothelial progenitor cells (EPC) promote angiogenesis and vascular repair. Though reduced EPC levels have been shown in rheumatoid arthritis, no study has so far evaluated EPCs in children with juvenile idiopathic arthritis (JIA). We aimed to study circulating EPCs in children with JIA, their relation to disease activity, and effects of anti TNF-α treatment.

Methods

Circulating EPCs were quantified by flow cytometry based on CD34, CD133 and KDR expression in peripheral blood of 22 patients with oligoarticular JIA and 29 age-matched controls. EPCs were re-assessed in children with methotrexate-resistant oligo-extended JIA before and up to 12 month after initiation of anti-TNF-alpha therapy. Plasma concentrations of inflammatory and EPC-regulating factors were measured using a multiplex array. Confocal immunofluorescence was used to demonstrate EPCs in synovial tissues.

Results

Children with active JIA showed a significant reduction of relative and absolute counts of circulating progenitor cells and EPCs compared to age-matched healthy controls. CD34⁺ cell levels were modestly and inversely correlated to disease activity. A strong inverse correlation was found between serum TNF-α and EPC levels. In 8 patients treated with anti TNF-α agents, the number of EPCs rose to values similar to healthy controls. CD34⁺KDR⁺ EPCs were found in the synovial tissue of JIA children, but not in control.

Conclusions

Children with JIA have reduced levels of the vasculoprotective and proangiogenic EPCs. While EPCs may contribute to synovial tissue remodelling, EPC pauperization may indicate an excess cardiovascular risk if projected later in life.

Cord serum dipeptidyl-peptidase 4 activity in gestational diabetes

BACKGROUND

Tissue-specific dipeptidyl-peptidase 4 (DPP4) dysregulation has been described in adults with diabetes mellitus. The DPP4 -incretin system has not been studied in foetal life. In this study, DPP4 activity and glucagon-like peptide-1 (GLP-1) levels were assessed in cord blood of neonates born to women with gestational diabetes mellitus (GDM) and nondiabetic controls.

MATERIAL AND METHODS

This study has been conducted in two Hungarian and one Austrian centres.

PATIENTS

A total of 568 pregnant women were enrolled in the study after their OGTT between the 24th and 28th gestational week. Cord blood samplings with DPP4 activity and GLP-1 level measurements were possible in 270 (DPP4: 159 control, 111 GDM) and 112 (GLP-1: 72 control, 40 GDM) cases. OGTT (24-28th gestational week) and cord blood sampling at delivery were performed. Cord serum DPP4 activity was determined in a continuous monitoring microplate-based kinetic assay, and cord plasma GLP-1 was measured using a fluorescence ELISA method.

RESULTS

Cord serum DPP4 activity was lower in GDM [mean (95% CI): 28.07 U/L (26.32-29.82 U/L)] than in controls [31.61 U/L (29.93-33.29 U/L), MWU P = 0.0015]. Cord plasma active GLP-1 levels were close to the lower detection limit and were not altered in GDM (control: mean = 3.43 pM, 95% CI: 3.04-3.82 pM, GDM: mean = 3.61 pM, 95% CI: 2.96-4.28 pM - MWU test P = 0.6).

CONCLUSIONS

Decreased cord serum DPP4 activity in gestational diabetes mellitus might be the result of an adaptive foetal response or an early dysregulation in the entero-insular axis with consequences beyond the incretin system. Cord plasma GLP-1 levels may reflect the missing oral intake with a limited glucose sensing of L cells via the circulation in foetal life.

Gliptin and GLP-1 analog treatment improves survival and vascular inflammation/dysfunction in animals with lipopolysaccharide-induced endotoxemia

Dipeptidyl peptidase (DPP)-4 inhibitors are used to treat hyperglycemia by increasing the incretin glucagon-like peptide-1 (GLP-1). Previous studies showed anti-inflammatory and antiatherosclerotic effects of DPP-4 inhibitors. Here, we compared the effects of linagliptin versus sitagliptin and liraglutide on survival and vascular function in animal models of endotoxic shock by prophylactic therapy and treatment after lipopolysaccharide (LPS) injection. Gliptins were administered either orally or subcutaneously: linagliptin (5 mg/kg/day), sitagliptin (50 mg/kg/day) or liraglutide (200 µg/kg/day). Endotoxic shock was induced by LPS injection (mice 17.5-20 mg/kg i.p., rats 10 mg/kg/day). Linagliptin and liraglutide treatment or DPP-4 knockout improved the survival of endotoxemic mice, while sitagliptin was ineffective. Linagliptin, liraglutide and sitagliptin ameliorated LPS-induced hypotension and vascular dysfunction in endotoxemic rats, suppressed inflammatory parameters such as whole blood nitrosyl-iron hemoglobin (leukocyte-inducible nitric oxide synthase activity) or aortic mRNA expression of markers of inflammation as well as whole blood and aortic reactive oxygen species formation. Hemostasis (tail bleeding time, activated partial thromboplastin time) was impaired in endotoxemic rats and recovered under cotreatment with linagliptin and liraglutide. Finally, the beneficial effects of linagliptin on vascular function and inflammatory parameters in endotoxemic mice were impaired in AMP-activated kinase (alpha1) knockout mice. The improved survival of endotoxemic animals and other data shown here may warrant further clinical evaluation of these drugs in patients with septic shock beyond the potential improvement of inflammatory complications in diabetic individuals with special emphasis on the role of AMP-activated kinase (alpha1) in the DPP-4/GLP-1 cascade.

Pharmacology, physiology, and mechanisms of action of dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 (DPP4) is a widely expressed enzyme transducing actions through an anchored transmembrane molecule and a soluble circulating protein. Both membrane-associated and soluble DPP4 exert catalytic activity, cleaving proteins containing a position 2 alanine or proline. DPP4-mediated enzymatic cleavage alternatively inactivates peptides or generates new bioactive moieties that may exert competing or novel activities. The widespread use of selective DPP4 inhibitors for the treatment of type 2 diabetes has heightened interest in the molecular mechanisms through which DPP4 inhibitors exert their pleiotropic actions. Here we review the biology of DPP4 with a focus on: 1) identification of pharmacological vs physiological DPP4 substrates; and 2) elucidation of mechanisms of actions of DPP4 in studies employing genetic elimination or chemical reduction of DPP4 activity. We review data identifying the roles of key DPP4 substrates in transducing the glucoregulatory, anti-inflammatory, and cardiometabolic actions of DPP4 inhibitors in both preclinical and clinical studies. Finally, we highlight experimental pitfalls and technical challenges encountered in studies designed to understand the mechanisms of action and downstream targets activated by inhibition of DPP4.

The effects of dipeptidyl peptidase-4 inhibition on microvascular diabetes complications

We performed a review of the literature to determine whether the dipeptidyl peptidase-4 inhibitors (DPP4-I) may have the capability to directly and positively influence diabetic microvascular complications. The literature was scanned to identify experimental and clinical evidence that DPP4-I can ameliorate diabetic microangiopathy. We retrieved articles published between 1 January 1980 and 1 March 2014 in English-language peer-reviewed journals using the following terms: ("diabetes" OR "diabetic") AND ("retinopathy" OR "retinal" OR "nephropathy" OR "renal" OR "albuminuria" OR "microalbuminuria" OR "neuropathy" OR "ulcer" OR "wound" OR "bone marrow"); ("dipeptidyl peptidase-4" OR "dipeptidyl peptidase-IV" OR "DPP-4" OR "DPP-IV"); and ("inhibition" OR "inhibitor"). Experimentally, DPP4-I appears to improve inflammation, endothelial function, blood pressure, lipid metabolism, and bone marrow function. Several experimental studies report direct potential beneficial effects of DPP4-I on all microvascular diabetes-related complications. These drugs have the ability to act either directly or indirectly via improved glucose control, GLP-1 bioavailability, and modifying nonincretin substrates. Although preliminary clinical data support that DPP4-I therapy can protect from microangiopathy, insufficient evidence is available to conclude that this class of drugs directly prevents or decreases microangiopathy in humans independently from improved glucose control. Experimental findings and preliminary clinical data suggest that DPP4-I, in addition to improving metabolic control, have the potential to interfere with the onset and progression of diabetic microangiopathy. Further evidence is needed to confirm these effects in patients with diabetes.

Concise review: diabetes, the bone marrow niche, and impaired vascular regeneration

Diabetes mellitus is a global health problem that results in multiorgan complications leading to high morbidity and mortality. Until recently, the effects of diabetes and hyperglycemia on the bone marrow microenvironment-a site where multiple organ systems converge and communicate-have been underappreciated. However, several new studies in mice, rats, and humans reveal that diabetes leads to multiple bone marrow microenvironmental defects, such as small vessel disease (microangiopathy), nerve terminal pauperization (neuropathy), and impaired stem cell mobilization (mobilopathy). The discovery that diabetes involves bone marrow-derived progenitors implicated in maintaining cardiovascular homeostasis has been proposed as a bridging mechanism between micro- and macroangiopathy in distant organs. Herein, we review the physiological and molecular bone marrow abnormalities associated with diabetes and discuss how bone marrow dysfunction represents a potential root for the development of the multiorgan failure characteristic of advanced diabetes. The notion of diabetes as a bone marrow and stem cell disease opens new avenues for therapeutic interventions ultimately aimed at improving the outcome of diabetic patients.

The dipeptidyl peptidase-4 inhibitor saxagliptin improves function of circulating pro-angiogenic cells from type 2 diabetic patients

BACKGROUND

Type 2 diabetes (T2D) is associated with reduction and dysfunction of circulating pro-angiogenic cells (PACs). DPP-4 inhibitors, a class of oral agents for T2D, might possess pleiotropic vasculoprotective activities. Herein, we tested whether DPP-4 inhibition with Saxagliptin affects the function of circulating PACs from T2D and healthy subjects.

METHODS

PACs were isolated from T2D (n = 20) and healthy (n = 20) subjects. Gene expression, clonogenesis, proliferation, adhesion, migration and tubulisation were assessed in vitro by incubating PACs with or without Saxagliptin and SDF-1α. Stimulation of angiogenesis by circulating cells from T2D patients treated with Saxagliptin or other non-incretinergic drugs was assessed in vivo using animal models.

RESULTS

Soluble DPP-4 activity was predominant over cellular activity and was successfully inhibited by Saxagliptin. At baseline, T2D compared to healthy PACs contained less acLDL(+)Lectin(+) cells, and showed altered expression of genes related to adhesion and cell cycle regulation. This was reflected by impaired adhesion and clonogenesis/proliferative response of T2D PACs. Saxagliptin + SDF-1α improved adhesion and tube sustaining capacity of PACs from T2D patients. CD14+ PACs were more responsive to Saxagliptin than CD14- PACs. While Saxagliptin modestly reduced angiogenesis by mature endothelial cells, circulating PACs-progeny cells from T2D patients on Saxagliptin treatment displayed higher growth factor-inducible in vivo angiogenetic activity, compared to cells from T2D patients on non-incretinergic regimen.

CONCLUSIONS

Saxagliptin reverses PACs dysfunction associated with T2D in vitro and improves inducible angiogenesis by circulating cells in vivo. These data add knowledge to the potential pleiotropic cardiovascular effects of DPP-4 inhibition.

Advanced age impairs cardioprotective function of mesenchymal stem cell transplantation from patients to myocardially infarcted rats

OBJECTIVES

Mesenchymal stem cells (MSCs) have limited clinical therapeutic effects in older myocardial infarction (MI) patients. Thus, whether younger MSCs might confer greater protection is worth investigating.

METHODS

Human MSCs (hMSCs) were isolated before coronary artery bypass graft surgery and growth characteristics of hMSCs at passage 3 were observed. Vascular endothelial growth factor (VEGF) and Bcl-2 mRNA and protein expression from hMSCs were measured. In vivo, 45 adult male rats with MI were randomized to receive one of three treatments: old hMSCs, young hMSCs or culture medium (control) transplanted into infarcted myocardium. Echocardiography, TUNEL, immunohistochemistry and Western blot were used to assess results.

RESULTS

hMSC proliferation in the old group was significantly lower than the young group. VEGF decreased 35% and Bcl-2 decreased more than 60% at the mRNA level; VEGF and Bcl-2 protein were decreased in the old versus the young group. hMSC transplantation may improve cardiac function, but MSC source may affect therapeutic efficacy. Similar data were obtained from TUNEL, immunohistochemistry and Western blot.

CONCLUSION

Transplantation of hMSCs improves heart function, but proliferative ability and myocardial protection decrease with older MSCs, likely due to differences between VEGF and Bcl-2 expression and reduced anti-apoptosis.

Diabetes causes bone marrow autonomic neuropathy and impairs stem cell mobilization via dysregulated p66Shc and Sirt1

Diabetes compromises the bone marrow (BM) microenvironment and reduces the number of circulating CD34(+) cells. Diabetic autonomic neuropathy (DAN) may impact the BM, because the sympathetic nervous system is prominently involved in BM stem cell trafficking. We hypothesize that neuropathy of the BM affects stem cell mobilization and vascular recovery after ischemia in patients with diabetes. We report that, in patients, cardiovascular DAN was associated with fewer circulating CD34(+) cells. Experimental diabetes (streptozotocin-induced and ob/ob mice) or chemical sympathectomy in mice resulted in BM autonomic neuropathy, impaired Lin(-)cKit(+)Sca1(+) (LKS) cell and endothelial progenitor cell (EPC; CD34(+)Flk1(+)) mobilization, and vascular recovery after ischemia. DAN increased the expression of the 66-kDa protein from the src homology and collagen homology domain (p66Shc) and reduced the expression of sirtuin 1 (Sirt1) in mice and humans. p66Shc knockout (KO) in diabetic mice prevented DAN in the BM, and rescued defective LKS cell and EPC mobilization. Hematopoietic Sirt1 KO mimicked the diabetic mobilization defect, whereas hematopoietic Sirt1 overexpression in diabetes rescued defective mobilization and vascular repair. Through p66Shc and Sirt1, diabetes and sympathectomy elevated the expression of various adhesion molecules, including CD62L. CD62L KO partially rescued the defective stem/progenitor cell mobilization. In conclusion, autonomic neuropathy in the BM impairs stem cell mobilization in diabetes with dysregulation of the life-span regulators p66Shc and Sirt1.

The emerging role of dipeptidyl peptidase-4 inhibitors in cardiovascular protection: current position and perspectives

Dipeptidyl peptidase-4 (DPP-4 or CD26) inhibitors, a new class of oral anti-hyperglycemic agents that prolong the bioavailability of the endogenously secreted incretin hormone glucagon-like peptide-1 (GLP-1) and the glucose-dependent insulinotropic polypeptide (GIP), are effective in the treatment of diabetes. Accumulating data have indicated that DPP-4 inhibitors play important protective roles in the cardiovascular system. DPP-4 inhibitors act to decrease myocardial infarct size, stabilize the cardiac electrophysiological state during myocardial ischemia, reduce ischemia/reperfusion injury, and prevent left ventricular remodeling after myocardial infarction. Moreover, DPP-4 inhibitors can mobilize stem/progenitor cells to move to sites of cardiovascular injury, thus further promoting tissue repair. In addition, DPP-4 inhibitors not only improve myocardial metabolism but also regulate cardioactive peptides. DPP-4 inhibitors can also protect the vasculature through their anti-inflammatory and anti-atherosclerotic effects and through the ability of the inhibitors to promote vascular relaxation. Finally, the potential effects of DPP-4 inhibitors on blood pressure and lipid metabolism have also been investigated. However, some reports on the cardioprotective activities of DPP-4 inhibitors are controversial. Herein, we summarize the available data on cardiovascular protection by DPP-4 inhibitors that have emerged in recent years and discuss current position and future perspectives concerning the use of DPP-4 inhibitors in cardiovascular medicine.

A reappraisal of the role of circulating (progenitor) cells in the pathobiology of diabetic complications

Traditionally, the development of diabetic complications has been attributed to the biochemical pathways driving hyperglycaemic cell damage, while reparatory mechanisms have been long overlooked. A more comprehensive view of the balance between damage and repair suggests that an impaired regenerative capacity of bone marrow (BM)-derived cells strongly contributes to defective re-endothelisation and neoangiogenesis in diabetes. Although recent technological advances have redefined the biology and function of endothelial progenitor cells (EPCs), interest in BM-derived vasculotropic cells in the setting of diabetes and its complications remains high. Several circulating cell types of haematopoietic and non-haematopoietic origin are affected by diabetes and are potentially involved in the pathobiology of chronic complications. In addition to classical EPCs, these include circulating (pro-)angiogenic cells, polarised monocytes/macrophages (M1 and M2), myeloid calcifying cells and smooth muscle progenitor cells, having disparate roles in vascular biology. In parallel with the study of elusive progenitor cell phenotypes, it has been recognised that diabetes induces a profound remodelling of the BM stem cell niche. The alteration of circulating (progenitor) cells in the BM is now believed to be the link among distant end-organ complications. The field is rapidly evolving and interest is shifting from specific cell populations to the complex network of interactions that orchestrate trafficking of circulating vasculotropic cells.