DPP-4 Inhibitors Improve Diabetic Wound Healing via Direct and Indirect Promotion of Epithelial-Mesenchymal Transition and Reduction of Scarring

Incretin-based therapy and the risk of diabetic foot ulcers and related events

AIM

To investigate the effect of dipeptidyl peptidase-4 inhibitors (DPP4-Is) and glucagon-like peptide-1 receptor agonists (GLP1-RAs) on diabetic foot ulcer (DFU) and DFU-related outcomes (lower limb amputation [LLA], DFU-related hospitalization and mortality).

METHODS

We performed a cohort study with data from the Clinical Practice Research Datalink Aurum database with linkage to hospital data. We included people with type 2 diabetes starting treatment with metformin. Then we propensity score matched new users of DPP4-Is and sulphonylureas (N = 98 770), and new users of GLP1-RAs and insulin (N = 25 422). Cox proportional hazards models estimated the hazard ratios (HRs) for the outcomes.

RESULTS

We observed a lower risk of DFU with both DPP4-I use versus sulphonylurea use (HR 0.88, 95% confidence interval [CI]: 0.79-0.97) and GLP1-RA use versus insulin use (HR 0.44, 95% CI: 0.32-0.60) for short-term exposure (≤ 400 days) and HR 0.74 (95% CI: 0.60-0.92) for long-term exposure (>400 days). Furthermore, the risks of hospitalization and mortality were lower with both DPP4-I use and GLP1-RA use. The risk of LLA was lower with GLP1-RA use. The results remained consistent across several sensitivity analyses.

CONCLUSIONS

Incretin-based therapy was associated with a lower risk of DFU and DFU-related outcomes. This suggests benefits for the use of this treatment in people at risk of DFU.

Recent advances in the adjunctive management of diabetic foot ulcer: Focus on noninvasive technologies

Diabetic foot ulcer (DFU) is one of the most costly and serious complications of diabetes. Treatment of DFU is usually challenging and new approaches are required to improve the therapeutic efficiencies. This review aims to update new and upcoming adjunctive therapies with noninvasive characterization for DFU, focusing on bioactive dressings, bioengineered tissues, mesenchymal stem cell (MSC) based therapy, platelet and cytokine-based therapy, topical oxygen therapy, and some repurposed drugs such as hypoglycemic agents, blood pressure medications, phenytoin, vitamins, and magnesium. Although the mentioned therapies may contribute to the improvement of DFU to a certain extent, most of the evidence come from clinical trials with small sample size and inconsistent selections of DFU patients. Further studies with high design quality and adequate sample sizes are necessitated. In addition, no single approach would completely correct the complex pathogenesis of DFU. Reasonable selection and combination of these techniques should be considered.

Exosomal miRNA-26b-5p from PRP suppresses NETs by targeting MMP-8 to promote diabetic wound healing

The utilization of platelet-rich plasma (PRP) has exhibited potential as a therapeutic approach for the management of diabetic foot ulcers (DFUs). However, it is currently not well understood how the diabetic environment may influence PRP-derived exosomes (PRP-Exos) and their potential impact on neutrophil extracellular traps (NETs). This study aims to investigate the effects of the diabetic environment on PRP-Exos, their communication with neutrophils, and the subsequent influence on NETs and wound healing. Through bulk-seq and Western blotting, we confirmed the increased expression of MMP-8 in DFUs. Additionally, we discovered that miRNA-26b-5p plays a significant role in the communication between DFUs and PRP-Exos. In our experiments, we found that PRP-Exos miR-26b-5p effectively improved diabetic wound healing by inhibiting NETs. Further tests validated the inhibitory effect of miR-26b-5p on NETs by targeting MMP-8. Both in vitro and in vivo experiments showed that miRNA-26b-5p from PRP-Exos promoted wound healing by reducing neutrophil infiltration through its targeting of MMP-8. This study establishes the importance of miR-26b-5p in the communication between DFUs and PRP-Exos, disrupting NETs formation in diabetic wounds by targeting MMP-8. These findings provide valuable insights for developing novel therapeutic strategies to enhance wound healing in individuals suffering from DFUs.

Therapeutic Effectiveness of Leukocyte- and Platelet-rich Fibrin for Diabetic Foot Ulcers: A Retrospective Study

OBJECTIVE

Diabetic foot ulcer (DFU) is one of the most serious complications of diabetes. Leukocyte- and platelet-rich fibrin (L-PRF) is a second-generation autologous platelet-rich plasma. This study aims to investigate the clinical effects of L-PRF in patients with diabetes in real clinical practice.

METHODS

Patients with DFU who received L-PRF treatment and standard of care (SOC) from 2018 to 2019 in Tongji Hospital were enrolled. The clinical information including patient characteristics, wound evaluation (area, severity, infection, blood supply), SOC of DFU, and images of ulcers was retrospectively extracted and analyzed. L-PRF treatment was performed every 7±2 days until the ulcer exhibited complete epithelialization or an overall percent volume reduction (PVR) greater than 80%. Therapeutic effectiveness, including overall PVR and the overall and weekly healing rates, was evaluated.

RESULTS

Totally, 26 patients with DFU were enrolled, and they had an ulcer duration of 47.0 (35.0, 72.3) days. The severity and infection of ulcers varied, as indicated by the Site, Ischemia, Neuropathy, Bacterial Infection, and Depth (SINBAD) scores of 2-6, Wagner grades of 1-4, and the Perfusion, Extent, Depth, Infection and Sensation (PEDIS) scores of 2-4. The initial ulcer volume before L-PRF treatment was 4.94 (1.50, 13.83) cm3, and the final ulcer volume was 0.35 (0.03, 1.76) cm3. The median number of L-PRF doses was 3 (2, 5). A total of 11 patients achieved complete epithelialization after the fifth week of treatment, and 19 patients achieved at least an 80% volume reduction after the seventh week. The overall wound-healing rate was 1.47 (0.63, 3.29) cm3/week, and the healing rate was faster in the first 2 weeks than in the remaining weeks. Concurrent treatment did not change the percentage of complete epithelialization or healing rate.

CONCLUSION

Adding L-PRF to SOC significantly improved wound healing in patients with DFU independent of the ankle brachial index, SINBAD score, or Wagner grade, indicating that this method is appropriate for DFU treatment under different clinical conditions.

Total iridoid glycoside extract of Lamiophlomis rotata (Benth) Kudo accelerates diabetic wound healing by the NRF2/COX2 axis

BACKGROUND

Lamiophlomis rotata (Benth.) Kudo (L. rotata), the oral Traditional Tibetan herbal medicine, is adopted for treating knife and gun wounds for a long time. As previously demonstrated, total iridoid glycoside extract of L. rotata (IGLR) induced polarization of M2 macrophage to speed up wound healing. In diabetic wounds, high levels inflammatory and chemotactic factors are usually related to high reactive oxygen species (ROS) levels. As a ROS target gene, nuclear factor erythroid 2-related factor 2 (NRF2), influences the differentiation of monocytes to M1/M2 macrophages. Fortunately, iridoid glycosides are naturally occurring active compounds that can be used as the oxygen radical scavenger. Nevertheless, the influence of IGLR in diabetic wound healing and its associated mechanism is largely unclear.

MATERIALS AND METHODS

With macrophages and dermal fibroblasts in vitro, as well as a thickness excision model of db/db mouse in vivo, the role of IGLR in diabetic wound healing and the probable mechanism of the action were investigated.

RESULTS

Our results showed that IGLR suppressed oxidative distress and inflammation partly through the NRF2/cyclooxygenase2 (COX2) signaling pathway in vitro. The intercellular communication between macrophages and dermal fibroblasts was investigated by the conditioned medium (CM) of IGLR treatment cells. The CM increased the transcription and translation of collagen I (COL1A1) and alpha smooth muscle actin (α-SMA) within fibroblasts. With diabetic wound mice, the data demonstrated IGLR activated the NRF2/KEAP1 signaling and the downstream targets of the pathway, inhibited COX2/PEG2 signaling and decreased the interaction inflammatory targets of the axis, like interleukin-1beta (IL-1β), interleukin 6 (IL-6), apoptosis-associated speck-like protein (ASC), cysteinyl aspartate specific proteinase1 (caspase1) and NOD-like receptor-containing protein 3 (NLRP3).In addition, the deposition of COL1A1, and the level of α-SMA, and Transforming growth factor-β1 (TGF-β1) obviously elevated, whereas that of pro-inflammatory factors reduced in the diabetic wound tissue with IGLR treatment.

CONCLUSION

IGLR suppressed oxidative distress and inflammation mainly through NRF2/COX2 axis, thus promoting paracrine and accelerating wound healing in diabetes mice.

From Molecular Insights to Clinical Perspectives in Drug-Associated Bullous Pemphigoid

Bullous pemphigoid (BP), the most common autoimmune blistering disease, is characterized by the presence of autoantibodies targeting BP180 and BP230 in the basement membrane zone. This leads to the activation of complement-dependent and independent pathways, resulting in proteolytic cleavage at the dermoepidermal junction and an eosinophilic inflammatory response. While numerous drugs have been associated with BP in the literature, causality and pathogenic mechanisms remain elusive in most cases. Dipeptidyl peptidase 4 inhibitors (DPP4i), in particular, are the most frequently reported drugs related to BP and, therefore, have been extensively investigated. They can potentially trigger BP through the impaired proteolytic degradation of BP180, combined with immune dysregulation. DPP4i-associated BP can be categorized into true drug-induced BP and drug-triggered BP, with the latter resembling classic BP. Antineoplastic immunotherapy is increasingly associated with BP, with both B and T cells involved. Other drugs, including biologics, diuretics and cardiovascular and neuropsychiatric agents, present weaker evidence and poorly understood pathogenic mechanisms. Further research is needed due to the growing incidence of BP and the increasing identification of new potential triggers.

Targeting the NOD-Like Receptor Pyrin Domain Containing 3 Inflammasome to Improve Healing of Diabetic Wounds

Significance: Chronic skin wounds are a significant health problem around the world, often leading to amputation and even death. Although persistent inflammation is a hallmark of these poorly healing wounds, few available therapies have been designed to target inflammation. In this review, we summarize available evidence of the role of the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome in impaired wound healing and describe strategies to inhibit the inflammasome to improve wound healing. Recent Advances: The NLRP3 inflammasome plays an important physiological role in skin wound healing, during which transient inflammasome activity contributes to both epidermal and dermal healing. In contrast, sustained activity of the NLRP3 inflammasome leads to impaired epidermal and dermal healing associated with diabetes. Of importance, preclinical studies have demonstrated that inhibiting the NLRP3 inflammasome-induced resolution of inflammation, increased granulation tissue formation and collagen deposition, and accelerated reepithelialization and wound closure. Critical Issues: NLRP3 inflammasome inhibitors have appealing potential for translation into therapies for chronic wounds. Although preclinical studies have shown promising results, there is a need for human/clinical studies to evaluate dosing formulations, potential therapeutic effects, dose-response relationships, and possible side effects. Future Directions: Among strategies to inhibit the NLRP3 inflammasome, glyburide, metformin, peroxisome proliferator-activated receptor agonists, and the dipeptidyl peptidase 4 inhibitor saxagliptin appear to be closest to clinical translation, as these drugs are already Food and Drug Administration approved for other indications. Future clinical studies are needed to develop topical formulations of these drugs, and to assess the safety and efficacy of these inhibitors, to improve healing of chronic wounds.

Targeting cluster of differentiation 26 / dipeptidyl peptidase 4 (CD26/DPP4) in organ fibrosis

Cluster of differentiation 26 (CD26)/dipeptidyl peptidase 4 (DPP4) is an exopeptidase that is expressed as a transmembrane protein in many organs but also present in a circulating soluble form. Beyond its enzymatic and costimulatory activity, CD26/DPP4 is involved in the pathogenesis of chronic fibrotic diseases across many organ types, such as liver cirrhosis, kidney fibrosis and lung fibrosis. Organ fibrosis is associated with a high morbidity and mortality, and there are no causative therapies that can effectively attenuate the progress of the disease. Growing evidence suggests that inhibiting CD26/DPP4 can modulate the profibrotic tissue microenvironment and thus reduce fibrotic changes within affected organs. This review summarizes the role of CD26/DPP4 in fibroproliferative disorders and highlights new opportunities for an antifibrotic treatment by CD26/DPP4 inhibition. As a major advantage, CD26/DPP4 inhibitors have been in safe and routine clinical use in type 2 diabetes for many years and thus qualify for repurposing to repurpose as a promising therapeutic against fibrosis. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Saxagliptin promotes random skin flap survival

BACKGROUND

Flap necrosis is a common issue encountered in clinical flap transplantation surgery. Here, we assessed the effects of saxagliptin, a dipeptidyl peptidase-4 inhibitor, on flap survival and explored the underlying mechanisms.

METHODS

A dorsal McFarlane flap model was established in 36 rats, which were randomly divided into a high-dose saxagliptin (HS) group (saxagliptin, 30 mg/kg/day, n = 12), low-dose saxagliptin (LS) group (saxagliptin, 10 mg/kg/day, n = 12), and control group (n = 12). On day 7, flap survival was examined by eye in six rats from each group, along with determination of blood perfusion by laser Doppler flowmetry and angiogenesis by angiography. The remaining rats were sacrificed for harvesting of flap tissue. The status of the flap tissue was examined histopathologically by staining with hematoxylin and eosin (H&E). Oxidative stress was evaluated by determination of superoxide dismutase (SOD) activity and malonaldehyde (MDA) content. Gasdermin D (GSDMD), vascular endothelial growth factor (VEGF), tumor necrosis factor-α (TNF-α), NOD-like receptor pyrin domain containing 3 (NLRP3), interleukin (IL)-6, IL-18, Toll-like receptor 4 (TLR4), IL-1β, caspase-1, and nuclear factor-κB (NF-κB) expression were detected by immunohistochemical analysis.

RESULTS

The experimental group exhibited a larger area of flap survival, with more blood perfusion and neovascularization and better histopathological status than the control group. The degree of oxidative stress and the levels of NF-κB, TLR4, proinflammatory cytokines, and pyroptosis-associated protein were decreased in the experimental group, while the VEGF level was increased in a saxagliptin dose-dependent manner.

CONCLUSION

Saxagliptin promotes random skin flap survival.

Diabetic foot ulcer: Challenges and future

Diabetic foot ulcers (DFUs) have become one of the important causes of mortality and morbidity in patients with diabetes, and they are also a common cause of hospitalization, which places a heavy burden on patients and society. The prevention and treatment of DFUs requires multidisciplinary management. By controlling various risk factors, such as blood glucose levels, blood pressure, lipid levels and smoking cessation, local management of DFUs should be strengthened, such as debridement, dressing, revascularization, stem cell decompression and oxygen therapy. If necessary, systemic anti-infection treatment should be administered. We reviewed the progress in the clinical practice of treating DFUs in recent years, such as revascularization, wound repair, offloading, stem cell transplantation, and anti-infection treatment. We also summarized and prospectively analyzed some new technologies and measurements used in the treatment of DFUs and noted the future challenges and directions for the development of DFU treatments.

Effects of vildagliptin on wound healing and markers of inflammation in patients with type 2 diabetic foot ulcer: a prospective, randomized, double-blind, placebo-controlled, single-center study

INTRODUCTION

Diabetic foot ulcers (DFU) are one of the leading long-term complications experienced by patients with diabetes. Dipeptidyl Peptidase 4 inhibitors (DPP4is) are a class of antihyperglycemic medications prescribed to patients with diabetes to manage glycaemic control. DPP4is may also have a beneficial effect on DFU healing. This study aimed to determine vildagliptin's effect on inflammatory markers and wound healing.

TRIAL DESIGN

Prospective, randomized, double-blind, placebo-controlled, single-center study.

METHODS

Equal number of participants were randomized into the treatment and placebo groups. The treatment was for 12 weeks, during which the participants had regular visits to the podiatrist, who monitored their DFU sizes using 3D camera, and blood samples were taken at baseline, six weeks, and 12 weeks during the study for measurement of inflammatory markers. In addition, demographic characteristics, co-morbidities, DFU risk factors, and DFU wound parameters were recorded.

RESULTS

50 participants were recruited for the study, with 25 assigned to placebo and 25 to treatment group. Vildagliptin treatment resulted in a statistically significant reduction of HBA1c (p < 0.02) and hematocrit (p < 0.04), total cholesterol (p < 0.02), LDL cholesterol (p < 0.04), and total/HDL cholesterol ratio (P < 0.03) compared to the placebo group. Also, vildagliptin had a protective effect on DFU wound healing, evidenced by the odds ratio (OR) favoring the intervention of 11.2 (95% CI 1.1-113.5; p < 0.04) and the average treatment effect on the treated (ATET) for vildagliptin treatment group showed increased healing by 35% (95%CI; 10-60, p = 0.01) compared to placebo with the model adjusted for microvascular complications, smoking, amputation, dyslipidemia, peripheral vascular disease (PVD) and duration of diabetes.

CONCLUSIONS

Vildagliptin treatment was effective in healing DFU in addition to controlling the diabetes. Our findings support the use of DPP4is as a preferred option for treating ulcers in patients with diabetes. Further studies on a larger population are warranted to confirm our findings and understand how DPP4is could affect inflammation and DFU healing.

Enhanced Diabetic Wound Healing Using Electrospun Biocompatible PLGA-Based Saxagliptin Fibrous Membranes

Delayed diabetic wound healing is an adverse event that frequently leads to limb disability or loss. A novel and promising vehicle for the treatment of diabetic wounds is required for clinical purposes. The biocompatible and resorbable poly (lactic-co-glycolic acid) (PLGA)-based fibrous membranes prepared by electrospinning that provide a sustained discharge of saxagliptin for diabetic wound healing were fabricated. The concentration of released saxagliptin in Dulbecco’s phosphate-buffered saline was analyzed for 30 days using high-performance liquid chromatography. The effectiveness of the eluted saxagliptin was identified using an endothelial progenitor cell migration assay in vitro and a diabetic wound healing in vivo. Greater hydrophilicity and water storage were shown in the saxagliptin-incorporated PLGA membranes than in the pristine PLGA membranes (both p < 0.001). For diabetic wound healing, the saxagliptin membranes accelerated the wound closure rate, the dermal thickness, and the heme oxygenase-1 level over the follicle areas compared to those in the pristine PLGA group at two weeks post-treatment. The saxagliptin group also had remarkably higher expressions of insulin-like growth factor I expression and transforming growth factor-β1 than the control group (p = 0.009 and p < 0.001, respectively) in diabetic wounds after treatment. The electrospun PLGA-based saxagliptin membranes exhibited excellent biomechanical and biological features that enhanced diabetic wound closure and increased the antioxidant activity, cellular granulation, and functionality.

Insight into the role of DPP-4 in fibrotic wound healing

Wound healing is a complex and long-term process consisting of hemostasis, inflammation, proliferation, and maturation/remodeling. These four stages overlap and influence each other; they affect wound healing in different ways, and if they do not function perfectly, they may cause scarring, proliferative scarring and keloid formation. A therapeutic target affecting wound healing in multiple ways will help the healing process proceed more effectively. DPP-4/CD26 is a multifunctional dimorphic glycoprotein widely distributed on the surface of a variety of cells, including fibroblasts and keratin-forming cells. It has been found to affect periwound inflammation, re-epithelialization, extracellular matrix secretion and skin fibrosis and is a potential target for promoting wound healing and inhibiting scar formation. After presenting a brief introduction of the wound healing process and DPP-4/CD26, this paper summarizes the effects of DPP-4/CD26 on cells involved in different stages of wound healing and discusses the feasibility of DPP-4/CD26 as a multifunctional target for the treatment of wound healing and inhibition of scar formation.

Single-Cell Transcriptomic Atlas of Gingival Mucosa in Type 2 Diabetes

The oral gingival barrier is a constantly stimulated and dynamic environment where homeostasis is often disrupted, resulting in inflammatory periodontal diseases. Type 2 diabetes (T2D) has been reported to be associated with gingival barrier dysfunction, but the effect and underlying mechanism are inconclusive. Herein, we performed single-cell RNA sequencing (scRNA-seq) of gingiva from leptin receptor-deficient mice (db/db) to examine the gingival heterogeneity in the context of T2D. Periodontal health of control mice is characterized by populations of Krt14⁺-expressing epithelial cells and Col1a1⁺-fibroblasts mediating immune homeostasis primarily through the enrichment of innate lymphoid cells. The db/db gingiva exhibited decreased epithelial/stromal ratio and dysfunctional barrier. We further observed stromal, particularly fibroblast immune hyperresponsiveness, linked to the recruitment of myeloid-derived cells at the db/db gingiva. Both scRNA-seq and histological analysis suggested the inflammatory signaling between fibroblasts and neutrophils as a potential driver of diabetes-induced periodontal damage. Notably, the "immune-like" stromal cells were wired toward the induction of gingival γδ T hyperresponsiveness in db/db mice. Our work reveals that the "immune-like" fibroblasts with transcriptional diversity are involved in the innate immune homeostasis at the diabetic gingiva. It highlights a potentially significant role of these cell types in its pathogenesis.

Diabetes complications and extracellular vesicle therapy

Diabetes is a chronic disorder characterized by dysregulated glycemic conditions. Diabetic complications include microvascular and macrovascular abnormalities and account for high morbidity and mortality rates in patients. Current clinical approaches for diabetic complications are limited to symptomatic treatments and tight control of blood sugar levels. Extracellular vesicles (EVs) released by somatic and stem cells have recently emerged as a new class of potent cell-free therapeutic delivery packets with a great potential to treat diabetic complications. EVs contain a mixture of bioactive molecules and can affect underlying pathological processes in favor of tissue healing. In addition, EVs have low immunogenicity and high storage capacity while maintaining nearly the same regenerative and immunomodulatory effects compared to current cell-based therapies. Therefore, EVs have received increasing attention for diabetes-related complications in recent years. In this review, we provide an outlook on diabetic complications and summarizes new knowledge and advances in EV applications. Moreover, we highlight recommendations for future EV-related research.

Advancement in Nanoformulations for the Management of Diabetic Wound Healing

People with diabetes have a very slow tendency for wound healing. Wound healing is a vast process where several factors inhibit the sequence of healing. Nano formulation plays a major role during acute and chronic wound healing. The present manuscript aims to discuss the role of nanoformulation in the treatment of diabetic wound healing. Diabetes is a common disease that has harmful consequences which lead to bad health. During the literature survey, it was observed that nanotechnology has significant advantages in the treatment of diabetic wound healing. The present manuscript summarized the role of nanomaterials in wound healing, challenges in diabetic wound healing, physiology of wound healing, a limitation that comes during wound repair, and treatments available for wound healing. After a comprehensive literature survey, it can be concluded that health worker needs more focus on the area of wound healing in diabetic patients. Medical practitioners, pharmaceutical and biomedical researchers need more attention towards the utilization of nanoformulations for the treatment of wound healing, specifically in the case of diabetes.

Role of Dipeptidyl Dipeptidase 4 Inhibitors in the Management of Diabetic Foot

Background: Patients with diabetes mellitus face difficulties in wound healing. It is important to explore therapeutic options for diabetic complications such as ulcers. This study evaluates the role of dipeptidyl dipeptidase 4 inhibitors (DPP4i) in the management of diabetic foot. Methods: Literature search was conducted in electronic databases (Google Scholar, Ovid, PubMed, Science Direct, and Springer) and studies were selected for inclusion if they reported the incidence rate of diabetic foot ulcer during DPP4i treatment or evaluated the effect of DPP4i on wound healing. Incidence rates of foot ulcer, amputation and peripheral vascular disease were pooled to achieve overall estimates. Meta-analyses of odds ratios were performed to evaluate the risk of foot ulcer, amputation, and peripheral vascular disease with DPP4i, and to examine the effect of DPP4i treatment on ulcer healing. Results: Ten studies (532354 DPP4i and 2092010 non-DPP4i treated diabetes patients) were included. Incidence rates of foot ulcer, amputation, and peripheral vascular disease were 3.80 [95% confidence interval (CI): 0.22, 7.39], 0.82 [95%CI: 0.60, 1.05], and 22.33 [95%CI: 9.14, 35.53] per 1000 person-years respectively in patients treated with DPP4i and 3.60 [95%CI: 1.77, 5.39], 0.76 [95%CI: 0.58, 0.94], and 20.9 [95%CI: 16.04, 25.81] per 1000 person-years respectively in patients treated with non-DPP4i drugs. Risk of ulcer or amputation with DPP4i was not consistent across studies. Odds of non-healing of ulcer were significantly lower with DPP4i in comparison with controls (odds ratio: 0.27 [95%CI: 0.10, 0.71]; p = 0.008). Conclusion: Incidence rates of diabetic foot and amputation are found to be similar with DPP4i and non-DPP4i drugs. DPP4i improved wound healing of diabetic foot in 3-month randomized trials.

IL-25 improves diabetic wound healing through stimulating M2 macrophage polarization and fibroblast activation

BACKGROUND

Persistent chronic inflammation is one of the main pathogenic characteristics of diabetic wounds. The resolution of inflammation is important for wound healing and extracellular matrix (ECM) formation. Interleukin (IL)-25 can modulate the function of macrophage and fibroblast, but its role and mechanism of action in the treatment of diabetic wounds remain largely unclear.

METHODS

The mice were categorized into diabetic, diabetic + IL-25 and control groups. Human monocytic THP-1 cell line and human dermal fibroblast (HDF) were stimulated under different IL-25 conditions. Then, flow cytometry, real-time quantitative PCR (RT-qPCR), Western blot (WB), and immunofluorescence (IF) assays were carried out.

RESULTS

The mice in diabetes group (DG) had a slower wound healing rate, more severe inflammation, less blood vessels and more disordered collagen than those in control group (CG). Intradermal injection of IL-25 could improve these conditions. IL-25 promoted M2 macrophage polarization and fibroblast activation in DG and high-glucose environment. The phenomenon, which was dependent on PI3K/AKT/mTOR and TGF-β/SMAD signaling, could be blocked by LY294002 and LY2109761.

CONCLUSION

IL-25 may serve as a therapeutic target to improve wound healing in diabetic mice.

Effect of SGLT2 inhibitors versus DPP4 inhibitors or GLP-1 agonists on diabetic foot-related extremity amputation in patients with T2DM: A meta-analysis

AIM

To compare the contribution of sodium-glucose cotransporter-2 inhibitors (SGLT2is) with that of DPP4i or GLP-1ra toward lower extremity amputation rate.

METHODS

Electronic databases were searched for articles published on the differences between the rates of lower extremity amputation among patients with type 2 diabetes mellitus (T2DM) undergoing SGLT2i treatment and those undergoing other anti-hyperglycemic agent (dipeptidyl peptidase-4 inhibitors [DPP4is], glucagon-like peptide-1 receptor agonist [GLP-1as], or sulfonylurea [SUs]) treatments. Random-effect models were used to generate data if heterogeneity was detected.

RESULTS

Eight studies based on retrospective case-control designs with propensity matching were included. The propensity score-matching method increased credibility. Compared with SGLT2i treatment, DPP4i or GLP-1a treatment tended to result in a higher amputation rate (pooled hazard ratio [HR] = 1.1, 95% confidence interval [CI]: 0.98-1.23), whereas SU treatment resulted in similar amputation rates (pooled HR = 0.92, 95% CI: 0.74-1.13). After excluding the heterogeneous study, the meta-analysis of the remaining studies attained a statistical value (pooled HR = 0.81, 95% CI: 0.65-1.01).

CONCLUSION

The study findings suggest that, with respect to diabetic foot-related limb amputations, SGLT2is are not superior to novel anti-hyperglycemic agents (DPP4is and GLP-1as) or other types of oral hypoglycemic agents (SUs). Therefore, SGLT2is may not have significantly positive effects on the prognosis for T2DM patients with complicated diabetic foot.

Novel topical esmolol hydrochloride improves wound healing in diabetes by inhibiting aldose reductase, generation of advanced glycation end products, and facilitating the migration of fibroblasts

AIMS/OBJECTIVES

Wound healing in people with diabetes is delayed secondary to impaired nitric oxide generation, advanced glycation end products (AGE), and poor migration of epithelial cells. We developed a novel topical esmolol hydrochloride (Galnobax) and assessed its efficacy for wound healing in streptozocin-induced diabetic hairless rat.

METHODS

All experiments were performed at an animal laboratory and tertiary-care research facility. Ex vivo aldose reductase inhibition was assessed from enzymes obtained from a bacterial culture (spectrophotometer), sorbitol content in homogenized red blood cells, and AGE in glucose and bovine serum by fluorometry following the addition of esmolol in varying concentrations. A scratch assay of human fibroblasts, endothelial cells, and keratinocytes was assessed under a high-glucose environment and after esmolol by phase-contrast microscopy. The efficacy evaluation of the topical application of Galnobax (14 and 20%) or vehicle was conducted in streptozotocin-induced diabetic hairless rats, and endogenous nitrite and hydroxyproline from homogenized wound tissue were measured along with pharmacokinetic and dermal toxicity in Hanford miniature swine.

RESULTS

Esmolol inhibited the formation of sorbitol by 59% in erythrocytes in comparison to glucose-induced sorbitol levels. AGE generation in bovine serum albumin was reduced at 1 mM esmolol concentrations (2.6 ± 1.7) compared with control (p < 0.05) and similar to that of diclofenac (2.5 ± 1.3). Esmolol at 1 and 10 µM enhanced the migration of fibroblasts, epithelial cells, and keratinocytes compared with control. The nitric oxide levels (day 7) were 44 and 112% higher with Galnobax (14%) than those of the diabetic group (p < 0.05) and the vehicle control group (p < 0.05), respectively. The days 7 and 14 hydroxyproline in the wound was higher by 22 and 44% following Galnobax (14%) compared with the diabetic and vehicle control groups. The wound area exhibited better reduction with Galnobax at 14% up to day 10 follow-up compared with the controls. The pharmacokinetic and dermal toxicity in miniature swine suggested no significant adverse event with Galnobax.

CONCLUSIONS

Topical esmolol hydrochloride is a novel, safe, and effective treatment modality that acts through pleotropic mechanisms to hasten wound healing in diabetes.

Novel therapeutic targets for diabetes-related wounds or ulcers: an update on preclinical and clinical research

INTRODUCTION

Diabetes-related wounds, particularly diabetes-related foot ulcers, are mainly caused by lack of foot sensation and high plantar tissue stress secondary to peripheral neuropathy, ischemia secondary to peripheral artery disease, and dysfunctional wound healing. Current management of diabetes-related wounds involves the offloading of high foot pressures and the treatment of ischemia through revascularization. Despite these treatments, the global burden of diabetes-related wounds is growing, and thus, novel therapies are needed. The normal wound healing process is a coordinated remodeling process orchestrated by fibroblasts, endothelial cells, phagocytes, and platelets, controlled by an array of growth factors. In diabetes-related wounds, these coordinated processes are dysfunctional. The past animal model and human research suggest that prolonged wound inflammation, failure to adequately correct ischemia, and impaired wound maturation are key therapeutic targets to improve diabetes-related wound healing.

AREAS COVERED

This review summarizes recent preclinical and clinical research on novel diabetes-related wound treatments. Animal models of diabetes-related wounds and recent studies testing novel therapeutic agents in these models are described. Findings from clinical trials are also discussed. Finally, challenges to identifying and implementing novel therapies are described.

EXPERT OPINION

Given the growing volume of promising drug therapies currently under investigation, it is expected within the next decade, that diabetes-related wound treatment will be transformed.

Pleiotropic Benefits of DPP-4 Inhibitors Beyond Glycemic Control

Dipeptidyl peptidase (DPP)-4 inhibitors are oral anti-diabetic medications that block the activity of the ubiquitous enzyme DPP-4. Inhibition of this enzyme increases the level of circulating active glucagon-like peptide (GLP)-1 secreted from L-cells in the small intestine. GLP-1 increases the glucose level, dependent on insulin secretion from pancreatic β-cells; it also decreases the abnormally increased level of glucagon, eventually decreasing the blood glucose level in patients with type 2 diabetes. DPP-4 is involved in many physiological processes other than the degradation of GLP-1. Therefore, the inhibition of DPP-4 may have numerous effects beyond glucose control. In this article, we review the pleiotropic effects of DPP-4 inhibitors beyond glucose control, including their strong beneficial effects on the stress induced accelerated senescence of vascular cells, and the possible clinical implications of these effects.

Influence of Dipeptidyl Peptidase-4 (DPP4) on Mesenchymal Stem-Cell (MSC) Biology: Implications for Regenerative Medicine - Review

Dipeptidyl peptidase IV (DPP4) is a ubiquitous protease that can be found in membrane-anchored or soluble form. Incretins are one of the main DPP4 substrates. These hormones regulate glucose levels, by stimulating insulin secretion and decreasing glucagon production. Because DPP4 levels are high in diabetes, DPP4 inhibitor (DPP4i) drugs derived from gliptin are widespread used as hypoglycemic agents for its treatment. However, as DPP4 recognizes other substrates such as chemokines, growth factors and neuropeptides, pleiotropic effects have been observed in patients treated with DPP4i. Several of these substrates are part of the stem-cell niche. Thus, they may affect different physiological aspects of mesenchymal stem-cells (MSC). They include viability, differentiation, mobilization and immune response. MSC are involved in tissue homeostasis and regeneration under both physiological and pathological conditions. Therefore, such cells and their secretomes have a high clinical potential in regenerative medicine. In this context, DPP4 activity may modulate different aspects of MSC regenerative capacity. Therefore, the aim of this review is to analyze the effect of different DPP4 substrates on MSC. Likewise, how the regulation of DPP4 activity by DPP4i can be applied in regenerative medicine. That includes treatment of cardiovascular and bone pathologies, cutaneous ulcers, organ transplantation and pancreatic beta-cell regeneration, among others. Thus, DPP4i has an important clinical potential as a complement to therapeutic strategies in regenerative medicine. They involve enhancing the differentiation, immunomodulation and mobilization capacity of MSC for regenerative purposes.

Updates in Diabetic Wound Healing, Inflammation, and Scarring

Diabetic patients can sustain wounds either as a sequelae of their disease process or postoperatively. Wound healing is a complex process that proceeds through phases of inflammation, proliferation, and remodeling. Diabetes results in several pathological changes that impair almost all of these healing processes. Diabetic wounds are often characterized by excessive inflammation and reduced angiogenesis. Due to these changes, diabetic patients are at a higher risk for postoperative wound healing complications. There is significant evidence in the literature that diabetic patients are at a higher risk for increased wound infections, wound dehiscence, and pathological scarring. Factors such as nutritional status and glycemic control also significantly influence diabetic wound outcomes. There are a variety of treatments available for addressing diabetic wounds.

Targeting Dermal Fibroblast Subtypes in Antifibrotic Therapy: Surface Marker as a Cellular Identity or a Functional Entity?

Fibroblasts are the chief effector cells in fibrotic diseases and have been discovered to be highly heterogeneous. Recently, fibroblast heterogeneity in human skin has been studied extensively and several surface markers for dermal fibroblast subtypes have been identified, holding promise for future antifibrotic therapies. However, it has yet to be confirmed whether surface markers should be looked upon as merely lineage landmarks or as functional entities of fibroblast subtypes, which may further complicate the interpretation of cellular function of these fibroblast subtypes. This review aims to provide an update on current evidence on fibroblast surface markers in fibrotic disorders of skin as well as of other organ systems. Specifically, studies where surface markers were treated as lineage markers and manipulated as functional membrane proteins are both evaluated in parallel, hoping to reveal the underlying mechanism behind the pathogenesis of tissue fibrosis contributed by various fibroblast subtypes from multiple angles, shedding lights on future translational researches.

Dedicator of Cytokinesis 5 Regulates Keratinocyte Function and Promotes Diabetic Wound Healing

Cutaneous wound healing is a fundamental biologic and coordinated process, and failure to maintain this process contributes to the dysfunction of tissue homeostasis, increasing the global burden of diabetic foot ulcerations. However, the factors that mediate this process are not fully understood. Here, we identify the pivotal role of dedicator of cytokinesis 5 (Dock5) in keratinocyte functions contributing to the process of skin wound healing. Specifically, Dock5 is highly upregulated during the proliferative phase of wound repair and is predominantly expressed in epidermal keratinocytes. It regulates keratinocyte adhesion, migration, and proliferation and influences the functions of extracellular matrix (ECM) deposition by facilitating the ubiquitination of transcription factor ZEB1 to activate laminin-332/integrin signaling. Genetic ablation of Dock5 in mice leads to attenuated reepithelialization and granulation tissue formation, and Dock5 overexpression-improved skin repair can be abrogated by LAMA3 knockdown. Importantly, Dock5 expression in the skin edge is reduced in patients and animal models of diabetes, further suggesting a direct correlation between its abundance and healing capability. The rescue of Dock5 expression in diabetic mice causes a significant improvement in reepithelialization, collagen deposition, ECM production, and granulation. Our study provides a potential therapeutic target for wound healing impairment during diabetes.

Regulatory Role of Nrf2 Signaling Pathway in Wound Healing Process

Wound healing involves a series of cellular events in damaged cells and tissues initiated with hemostasis and finally culminating with the formation of a fibrin clot. However, delay in the normal wound healing process during pathological conditions due to reactive oxygen species, inflammation and immune suppression at the wound site represents a medical challenge. So far, many therapeutic strategies have been developed to improve cellular homeostasis and chronic wounds in order to accelerate wound repair. In this context, the role of Nuclear factor erythroid 2-related factor 2 (Nrf2) during the wound healing process has been a stimulating research topic for therapeutic perspectives. Nrf2 is the main regulator of intracellular redox homeostasis. It increases cytoprotective gene expression and the antioxidant capacity of mammalian cells. It has been reported that some bioactive compounds attenuate cellular stress and thus accelerate cell proliferation, neovascularization and repair of damaged tissues by promoting Nrf2 activation. This review highlights the importance of the Nrf2 signaling pathway in wound healing strategies and the role of bioactive compounds that support wound repair through the modulation of this crucial transcription factor.

Keratinocytes Migration Promotion, Proliferation Induction, and Free Radical Injury Prevention by 3-Hydroxytirosol

3-hydroxytyrosol (HT) is the main phenolic compound found in olive oil with known antioxidant, anti-inflammatory, and antimicrobial properties in several dermatological conditions, both when taken in the form of olive oil or pure in cosmeceutical formulations. To date, its direct effect on the wound healing process and the molecular mechanisms involved have not yet been elucidated. Thus, in the present study, we aimed to explore its effects in vitro in epidermal keratinocyte cultures focusing on the molecular mechanism implied. HT was able to induce keratinocyte proliferation in the low micromolar range, increasing the expression of cyclin dependent kinases fundamental for cell cycle progression such as CDK2 and CDK6. Furthermore, it increased cell migration through the activation of tissue remodeling factors such as matrix metalloproteinase-9 (MMP-9) protein. Then, we evaluated whether HT also showed antioxidant activity at this concentration range, protecting from H₂O₂-induced cytotoxicity. The HT prevented the activation of ATM serine/threonine kinase (ATM), Checkpoint kinase 1 (Chk1), Checkpoint kinase 2 (Chk2), and p53, reducing the number of apoptotic cells. Our study highlighted novel pharmacological properties of HT, providing the first evidence of its capability to induce keratinocyte migration and proliferation required for healing processes and re-epithelialization.

CD26 Identifies a Subpopulation of Fibroblasts that Produce the Majority of Collagen during Wound Healing in Human Skin

Fibroblasts produce collagens and other proteins that form the bulk of the extracellular matrix (ECM) in connective tissues. Emerging data point to functional heterogeneity of fibroblasts. However, the lack of subtype-specific markers hinders our understanding of the different roles of fibroblasts in ECM biology, wound healing, diseases, and aging. We have investigated the utility of the cell surface protein CD26 to identify functionally distinct fibroblast subpopulations in human skin. Using flow cytometry and immunohistology, we found that CD26, in combination with the cell surface glycoprotein CD90, identifies a distinct subpopulation of cells, which express relatively high levels of COL1A1, a hallmark of fibroblasts. Importantly, the population of CD26+ fibroblasts is selectively increased after wounding of human skin. These cells account for the majority of COL1A1 expression during the ECM remodeling phase of healing. The proportion of CD26+ fibroblasts in the skin of young and aged individuals is similar, indicating that the loss of collagen production during aging does not involve selective reduction of CD26+ fibroblasts. In culture, the majority of freshly isolated CD26- fibroblasts gain expression of CD26+. Taken together, these data provide a foundation for targeting CD26+ fibroblasts to modulate wound healing in human skin.

Ganoderma lucidum Ethanol Extracts Enhance Re-Epithelialization and Prevent Keratinocytes from Free-Radical Injury

Ganoderma lucidum or Reishi is recognized as the most potent adaptogen present in nature, and its anti-inflammatory, antioxidant, immunomodulatory and anticancer activities are well known. Moreover, lately, there has been an increasing interest from pharmaceutical companies in antiaging G. lucidum-extract-based formulations. Nevertheless, the pharmacological mechanisms of such adaptogenic and regenerative actions remain unclear. The present investigation aimed to explore its molecular and cellular effects in vitro in epidermal keratinocyte cultures by applying liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LCMS-IT-TOF) for analysis of ethanol extracts using ganoderic acid-A as a reference compound. The G. lucidum extract showed a keratinocyte proliferation induction accompanied by an increase of cyclic kinase protein expressions, such as CDK2 and CDK6. Furthermore, a noteworthy migration rate increase and activation of tissue remodelling factors, such as matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), were observed. Finally, the extract showed an antioxidant effect, protecting from H₂O₂-induced cytotoxicity; preventing activation of AKT (protein kinase B), ERK (extracellular signal-regulated kinase), p53 and p21; and reducing the number of apoptotic cells. Our study paves the path for elucidating pharmacological properties of G. lucidum and its potential development as cosmeceutical skin products, providing the first evidence of its capability to accelerate the healing processes enhancing re-epithelialization and to protect cells from free-radical action.

The Treatment of Impaired Wound Healing in Diabetes: Looking among Old Drugs

Chronic wounds often occur in patients with diabetes mellitus due to the impairment of wound healing. This has negative consequences for both the patient and the medical system and considering the growing prevalence of diabetes, it will be a significant medical, social, and economic burden in the near future. Hence, the need for therapeutic alternatives to the current available treatments that, although various, do not guarantee a rapid and definite reparative process, appears necessary. We here analyzed current treatments for wound healing, but mainly focused the attention on few classes of drugs that are already in the market with different indications, but that have shown in preclinical and few clinical trials the potentiality to be used in the treatment of impaired wound healing. In particular, repurposing of the antiglycemic agents dipeptidylpeptidase 4 (DPP4) inhibitors and metformin, but also, statins and phenyotin have been analyzed. All show encouraging results in the treatment of chronic wounds, but additional, well designed studies are needed to allow these drugs access to the clinics in the therapy of impaired wound healing.

Dipeptidyl Peptidase-4 at the Interface Between Inflammation and Metabolism

Dipeptidyl peptidase-4 (DPP4) is a serine protease that rapidly inactivates the incretin peptides, glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptide to modulate postprandial islet hormone secretion and glycemia. Dipeptidyl peptidase-4 also has nonglycemic effects by controlling the progression of inflammation, which may be mediated more through direct protein-protein interactions than catalytic activity in the context of nonalcoholic fatty liver disease (NAFLD), obesity, and type 2 diabetes (T2D). Failure to resolve inflammation resulting in chronic subclinical activation of the immune system may influence the development of metabolic dysregulation. Thus, through both its cleavage and regulation of the bioactivity of peptide hormones and its influence on inflammation, DPP4 exhibits a diverse array of effects that can influence the progression of metabolic disease. Here, we highlight our current understanding of the complex biology of DPP4 at the intersection of inflammation, obesity, T2D, and NAFLD. We compare and review new mechanisms identified in basic laboratory and clinical studies, which may have therapeutic application and relevance to the pathogenesis of obesity and T2D.

DPP4 Inhibition, NPY1-36, PYY1-36, SDF-1α, and a Hypertensive Genetic Background Conspire to Augment Cell Proliferation and Collagen Production: Effects That Are Abolished by Low Concentrations of 2-Methoxyestradiol

By reducing their metabolism, dipeptidyl peptidase 4 inhibition (DPP4I) enhances the effects of numerous peptides including neuropeptide Y_1–36 (NPY_1–36), peptide YY_1–36 (PYY_1–36), and SDF-1α. Studies show that separately NPY_1–36, PYY_1–36 and SDF-1α stimulate proliferation of, and collagen production by, cardiac fibroblasts (CFs), preglomerular vascular smooth muscle cells (PGVSMCs), and glomerular mesangial cells (GMCs), particularly in cells isolated from genetically hypertensive rats. Whether certain combinations of these factors, in the absence or presence of DPP4I, are more profibrotic than others is unknown. Here we contrasted 24 different combinations of conditions (DPP4I, hypertensive genotype and physiologic levels [3 nM] of NPY_1–36, PYY_1–36, or SDF-1α) on proliferation of, and [³H]-proline incorporation by, CFs, PGVSMCs, and GMCs. In all three cell types, the various treatment conditions differentially increased proliferation and [³H]-proline incorporation, with a hypertensive genotype + DPP4I + NPY_1–36 + SDF-1α being the most efficacious combination. Although the effects of this four-way combination were similar in male versus female CFs, physiologic (1 nM) concentrations of 2-methoxyestradiol (2ME; nonestrogenic metabolite of 17β-estradiol), abolished the effects of this combination in both male and female CFs. In conclusion, this study demonstrates that CFs, PGVSMCs, and GMCs are differentially activated by various combinations of NPY_1–36, PYY_1–36, SDF-1α, a hypertensive genetic background and DPP4I. We hypothesize that as these progrowth conditions accumulate, a tipping point would be reached that manifests in the long term as organ fibrosis and that 2ME would obviate any profibrotic effects of DPP4I, even under the most profibrotic conditions (i.e., hypertensive genotype with high NPY_1–36 + SDF-1α levels and low 2ME levels).

Tissue repair brakes: A common paradigm in the biology of regeneration

To date, most attention on tissue regeneration has focused on the exploration of positive cues promoting or allowing the engagement of natural cellular restoration upon injury. In contrast, the signals fostering cell identity maintenance in the vertebrate body have been poorly investigated; yet they are crucial, for their counteraction could become a powerful method to induce and modulate regeneration. Here we review the mechanisms inhibiting pro-regenerative spontaneous adaptive cell responses in different model organisms and organs. The pharmacological or genetic/epigenetic modulation of such regenerative brakes could release a dormant but innate adaptive competence of certain cell types and therefore boost tissue regeneration in different situations.

An Efficient and Practical Method for the Synthesis of Saxagliptin Intermediate 2-(3-Hydroxy-1-adamantane)-2-oxoacetic Acid and Its Optimization

A mild and relatively simple way for preparation of 2-(3-hydroxy-1-adamantane)-2-oxoacetic acid (I) was reported. It was prepared from 1-adamantanecarboxylic acid (II) via sulfuric acid/nitric acid to get 3-hydroxy-1-adamantanecarboxylic acid (III); treated with the one-pot method through acylation, condensation, and decarboxylation to obtain 3-hydroxy-1-acetyladamantane (IV); and finally oxidized by potassium permanganate (KMnO4) to get the target compound (I). The overall yield was about 60%, which provides a new idea for commercial production of saxagliptin intermediate.

Heat shock transcription factor 1 affects kidney tubular cell migration by regulating the TGF‑β1‑Smad2/3 signaling pathway

Cell migration is important for renal recovery from tubular cell injury. Heat shock transcription factor 1 (HSF1) is a well‑studied regulatory factor that is active during acute kidney injury. HSF1 is also involved in the migration process during tumor metastasis. Therefore, we hypothesized that HSF1 may promote the recovery of renal function by affecting kidney tubular cell migration. A wound healing assay was used to examine the cell migration rate. The results demonstrated that the migration of rat kidney proximal tubular cells (RPTCs) was increased following knockdown of HSF1. In addition, the invasion ability of HSF1 knockdown RPTCs was also significantly upregulated. The present study also identified that transforming growth factor‑β1 (TGF‑β1) was highly expressed at the edge of the wound in control cells, and its expression was further increased upon knockdown of HSF1. Inhibition of TGF‑β1 signaling prevented RPTC HSF1 knockdown cell migration, suggesting that HSF1‑regulated RPTC cell migration was dependent on the TGF‑β1 signaling pathway. Furthermore, phosphorylation of TGF‑β1 and Smad2/3 was induced in HSF1 knockdown cells. Together, these results suggest that HSF1 may suppress RPTC migration by inhibiting the activation of the TGF‑β1‑Smad2/3 signaling pathway.

Regulation of Wound Healing by the NRF2 Transcription Factor-More Than Cytoprotection

The nuclear factor-erythroid 2-related factor 2 (NRF2) transcription factor plays a central role in mediating the cellular stress response. Due to their antioxidant properties, compounds activating NRF2 have received much attention as potential medications for disease prevention, or even for therapy. Accumulating evidence suggests that activation of the NRF2 pathway also has a major impact on wound healing and may be beneficial in the treatment of chronic wounds, which remain a considerable health and economic burden. While NRF2 activation indeed shows promise, important considerations need to be made in light of corresponding evidence that also points towards pro-tumorigenic effects of NRF2. In this review, we discuss the evidence to date, highlighting recent advances using gain- and loss-of-function animal models and how these data fit with observations in humans.

Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid

Bullous pemphigoid (BP) is an organ-specific autoantibody-mediated blistering skin disease that mainly affects the elderly. Typical clinical features include the widespread blisters, often preceded by and/or associated with itchy urticarial or eczema-like lesions. BP patients have circulating autoantibodies against BP180 and/or the plakin family protein BP230 both of which are components of hemidesmosomes in basal keratinocytes. Most BP autoantibodies particularly target the epitopes within the non-collagenous NC16A domain of BP180. Clinical findings and murine models of BP have provided evidence of a pathogenic role of anti-NC16A autoantibodies. However, it is largely unknown what triggers the breakage of immunotolerance against BP180 in elderly individuals. The incidence of BP has been increased over the past two decades in several countries. Aside from aging populations, the factors behind this phenomenon are still not fully understood. Neurodegenerative diseases such as multiple sclerosis, Parkinson's disease, and certain dementias are independent risk factors for BP. Recently several case reports have described BP in patients with diabetes mellitus (DM) patients who have been treated with dipeptidyl peptidase-4 inhibitors (DPP-4i or gliptins), which are a widely used class of anti-DM drugs. The association between the use of DPP-4is, particularly vildagliptin, and BP risk has been confirmed by several epidemiological studies. Evidence suggests that cases of gliptin-associated BP in Japan display certain features that set them apart from cases of “regular” BP. These include a “non-inflammatory” phenotype, targeting by antibodies of different immunodominant BP180 epitopes, and a specific association with the human leukocyte antigen (HLA) types. However, recent studies in European populations have found no major differences between the clinical and immunological characteristics of gliptin-associated BP and “regular” BP. The DPP-4 protein (also known as CD26) is ubiquitously expressed and has multiple functions in various cell types. The different effects of the inhibition of DPP-4/CD26 activity include, for example, tissue modeling and regulation of inflammatory cells such as T lymphocytes. Although the pathomechanism of gliptin-associated BP is currently largely unknown, investigation of the unique effect of gliptins in the induction of BP may provide a novel route to better understanding of how immunotolerance against BP180 breaks down in BP.

Dipeptidyl peptidase-4 plays a pathogenic role in BSA-induced kidney injury in diabetic mice

Diabetic kidney disease (DKD) is appeared to be higher risk of declining kidney function compared to non-diabetic kidney disease with same magnitude of albuminuria. Epithelial-mesenchymal transition (EMT) program of tubular epithelial cells (TECs) could be important for the production of the extracellular matrix in the kidney. Caveolin-1 (CAV1), dipeptidyl peptidase-4 (DPP-4) and integrin β1 have shown to be involved in EMT program. Here, we found diabetic kidney is prone for albuminuria-induced TECs damage and DPP-4 plays a vital role in such parenchymal damages in diabetic mice. The bovine serum albumin (BSA) injection induced severe TECs damage and altered expression levels of DPP-4, integrin β1, CAV1, and EMT programs including relevant microRNAs in type 1 diabetic CD-1 mice when compared to non-diabetic mice; teneligliptin (TENE) ameliorated these alterations. TENE suppressed the close proximity among DPP-4, integrin β1 and CAV1 in a culture of HK-2 cells. These findings suggest that DPP-4 inhibition can be relevant for combating proteinuric DKD by targeting the EMT program induced by the crosstalk among DPP-4, integrin β1 and CAV1.

Advancing pharmacotherapy for diabetic foot ulcers

INTRODUCTION

Standard treatment for diabetic foot ulcers (DFUs) includes off-loading, debridement, moisture balance, management of infection and peripheral arterial disease (PAD) as well as adequate glycemic control. The outcomes so far are unsatisfactory.

AREAS COVERED

Herein, the authors provide an outline of newer pharmacological agents for the management of DFUs and give their expert perspectives on future treatment strategies.

EXPERT OPINION

Evidence-based healthcare calls for high quality evidence from large RCTs before the implementation of new guidelines for the management of DFUs. Empagliflozin and liraglutide can be recommended for glucose control in patients with DFUs and PAD, while intensive lipid lowering therapy with evolocumab when primary cholesterol goals are not met could be offered to patients with DFUs. Further clinical studies are warranted to develop a structured algorithm for the treatment of DFUs that fail to heal after four weeks of current standard of care. Sucrose octasulfate dressings, becaplermin gel, and platelet-rich plasma (PRP) could also be considered as advanced treatment options for the management of hard to heal DFUs.

Alteration of gut microbiota induced by DPP-4i treatment improves glucose homeostasis

Background

Increasing evidence indicates that the gut microbiota contributes to the occurrence and development of metabolic diseases. However, little is known about the effects of commonly used antidiabetic agents on the gut microbiota. In this study, we investigated the roles of dipeptidyl peptidase-4 inhibitors (DPP-4i) and α-glucosidase inhibitor in modulating the gut microbiota.

Methods

16S-rDNA sequencing was performed to analyse the effects of DPP-4i and acarbose on the gut microbiota in mice fed a high-fat diet (HFD). Fecal microbiota transplantation (FMT) from type 2 diabetes patients to germ-free mice was performed to investigate the contribution of the altered microbiome to antidiabetic effects of the drugs. Fecal metabolomics was also analysed by untargeted and targeted GC–MS systems.

Findings

Although DPP-4i and α-glucosidase inhibitor both altered the gut microbial composition, only the microbiome modulation of DPP-4i contributed to its hypoglycemic effect. Specifically, the changes of 68.6% genera induced by HFD were rescued by DPP-4i. FMT showed that the DPP-4i-altered microbiome improved glucose tolerance in colonized mice, while acarbose did not. Moreover, DPP-4i increased the abundance of Bacteroidetes, and also promoted a functional shift in the gut microbiome, especially increasing the production of succinate.

Interpretation

Our findings demonstrate an important effect of DPP-4i on the gut microbiota, revealing a new hypoglycemic mechanism and an additional benefit of it. Furthermore, modulating the microbial composition, and the functional shift arising from changes in the microbiome, might be a potential strategy for improving glucose homeostasis.

Fund

This work was supported by grants from the National Natural Science Foundation of China (No. 81700757, No. 81471039, No. 81700714 and No. 81770434), the National Key R&D Program of China (No. 2017YFC1309602, No. 2016YFC1101100, No. 2017YFD0500503 and No. 2017YFD0501001), and the Natural Science Foundation of Chongqing (No. cstc2014jcyjjq10006, No. cstc2016jcyjA0093 and No. cstc2016jcyjA0518).

Inhibition of Dipeptidyl Peptidase-4 Accelerates Epithelial-Mesenchymal Transition and Breast Cancer Metastasis via the CXCL12/CXCR4/mTOR Axis

Dipeptidyl peptidase (DPP)-4 is a multifunctional glycoprotein involved in various biological and pathologic processes. DPP-4 has been widely recognized as a therapeutic target for type 2 diabetes mellitus but is also implicated in the development of human malignancies. Here, we show that inhibition of DPP-4 accelerates breast cancer metastasis via induction of CXCL12/CXCR4, which activates mTOR to promote epithelial-mesenchymal transition (EMT). In cultured cells, DPP-4 knockdown induced EMT and cell migration. Treatment with the DPP-4 inhibitor KR62436 (KR) promoted primary tumor growth and lung metastasis in a 4T1 tumor allograft mouse model; DPP-4 knockdown in 4T1 cells displayed similar phenotypes in vivo and in vitro. KR treatment enhanced the levels of CXCL12/CXCR4 and phosphorylated mTOR, which were associated with the induction of EMT in metastatic cancer cells. KR-induced EMT in cancer cells was inhibited by treatment with the CXCR4 inhibitor AMD3100 or the mTOR inhibitor rapamycin, and AMD3100 suppressed KR-induced metastasis in vivo. Our findings suggest that DPP-4 plays a significant role in cancer biology and that inhibition of DPP-4 promotes cancer metastasis via induction of the CXCL12/CXCR4/mTOR/EMT axis. SIGNIFICANCE: These findings reveal that inhibition of DPP-4 increases the metastatic potential of breast cancer. This is especially important given the potential use of DPP-4 inhibition as a therapeutic strategy for type 2 diabetes.

Incretin-based therapy for diabetic ulcers: from bench to bedside

INTRODUCTION

Diabetic foot ulcers are a serious complication of diabetes and are associated with pain, disability, and poor quality of life. Incretin-based therapy is available for type-2 diabetes. Aside from glucose control, such treatment can impart numerous beneficial effects.

AREAS COVERED

This review summarizes the preclinical and clinical evidence supporting incretin-based treatment approaches for diabetic ulcers.

EXPERT OPINION

Incretin-based therapy may have a role in the treatment of diabetic foot ulcers; the benefits of such treatment arise from attenuation of inflammatory response, improvement of keratinocyte migration, induction of angiogenesis, and the enhancement of tissue remodeling. Large-scale clinical trials are required to determine the advantages of GLP-1 receptor agonists and DPP4 inhibitors. Future research on the topical application of incretin-based therapy is necessary. Such therapeutic approaches may provide new hope in improving the treatment of impaired diabetic foot ulcers.

Anti-inflammatory and pro-healing impacts of exendin-4 treatment in Zucker diabetic rats: Effects on skin wound fibroblasts

Using male Zucker diabetic fatty (ZDF) rats implanted subcutaneously with polyethylene mesh pieces stimulating granulation tissue development, we investigated the effects of the in vivo and in vitro treatment with exendin-4, a glucagon-like peptide-1 agonist displaying a variety of antidiabetic actions, on the markers of metabolism, inflammation, and healing in addition to skin wound fibroblast/myofibroblast activities. Exendin-4 at increasing doses of 3-10 μg/kg or 0.9% saline was injected daily to ZDF rats pre-implanted with the mesh for 3 weeks. Then, fibroblasts/myofibroblasts isolated from the granulation tissue in both groups were further exposed in vitro to exendin-4 at concentrations of 0-100 nmol/l. After a 3-week administration period, cumulative food and water intake and body weight were reduced significantly. The serum and fibroblast culture medium C-reactive protein (CRP) concentrations and matrix metalloprotease-9/tissue matrix metalloproteinase inhibitor-1 (MMP-9/TIMP-1) ratio in the fibroblast culture medium were diminished significantly in the exendin-4 pretreated group, indicating the increased expression of anti-inflammatory and pro-healing biomarkers. In vivo exendin-4 treatment also increased the number of living fibroblasts/myofibroblasts in cell cultures. The subsequent in vitro exposure to exendin-4 significantly increased metabolic activity and total collagen content in fibroblast/myofibroblast colonies derived from exendin-4-pretreated rats but reduced the number of viable cells. A cytotoxic effect was noted at the highest exendin-4 concentrations used. To conclude, the treatment of diabetic rats with exendin-4 had beneficial effects on systemic and tissue metabolic, inflammatory, and healing markers and on fibroblast functions crucial for wound repair but showed some cytotoxicity on these cells.

The Impact of Liraglutide on Diabetes-Related Foot Ulceration and Associated Complications in Patients With Type 2 Diabetes at High Risk for Cardiovascular Events: Results From the LEADER Trial

OBJECTIVE

Diabetes-related foot ulcers (DFUs) and their sequelae result in large patient and societal burdens. Long-term data determining the efficacy of individual glucose-lowering agents on DFUs are lacking. Using existing data from the Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results (LEADER) trial, we conducted post hoc analyses assessing the impact of liraglutide versus placebo in people with type 2 diabetes and at high risk of cardiovascular (CV) events on the incidence of DFUs and their sequelae.

RESEARCH DESIGN AND METHODS

The LEADER trial (NCT01179048) was a randomized, double-blind, multicenter, CV outcomes trial assessing liraglutide (1.8 mg/day) versus placebo, in addition to standard of care, for up to 5 years. Information on DFUs was collected systematically during the trial, and DFU complications were assessed post hoc through reviewing case narratives.

RESULTS

During a median of 3.8 years' follow-up, similar proportions of patients reported at least one episode of DFU in the liraglutide and placebo groups (3.8% [176/4,668] versus 4.1% [191/4,672], respectively; hazard ratio [HR] 0.92 [95% CI 0.75, 1.13; P = 0.41]). Analysis of DFU-related complications demonstrated a significant reduction in amputations with liraglutide versus placebo (HR 0.65 [95% CI 0.45, 0.95; P = 0.03]). However, no differences were found for foot infections, involvement of underlying structures, or peripheral revascularization in the main analysis.

CONCLUSIONS

Treatment with liraglutide in patients with type 2 diabetes and at high risk of CV events in the LEADER trial did not increase the risk of DFU events and was associated with a significantly lower risk of DFU-related amputations compared with placebo. This association, possibly due to chance, needs further investigation.

Use of Some Asteraceae Plants for the Treatment of Wounds: From Ethnopharmacological Studies to Scientific Evidences

Severe wounds result in large lesions and/or loss of function of the affected areas. The treatment of wounds has challenged health professionals due to its complexity, especially in patients with chronic diseases (such as diabetes), and the presence of pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa. Taking this into consideration, the development of new therapies for wound healing requires immediate attention. Ethnopharmacological studies performed in different countries have shown the use of several plants from the Asteraceae family as wound-healing agents. Evidences gained from the traditional medicine have opened new ways for the development of novel and more efficient therapies based on the pharmacological properties of these plants. In this article, we discuss the literature data on the use of Asteraceae plants for the treatment of wounds, based on the ethnopharmacological relevance of each plant. Special attention was given to studies showing the mechanisms of action of Asteraceae-derived compounds and clinical trials. Ageratina pichinchensis (Kunth) R.M. King and H. Rob. and Calendula officinalis L. preparations/compounds were found to show good efficacy when assessed in clinical trials of complicated wounds, including venous leg ulcers and foot ulcers of diabetic patients. The compounds silibinin [from Silybum marianum (L.) Gaertn.] and jaceosidin (from Artemisia princeps Pamp.) were identified as promising compounds for the treatment of wounds. Overall, we suggest that Asteraceae plants represent important sources of compounds that may act as new and efficient healing products.

The efficacy and safety of once-weekly DPP-4 inhibitor omarigliptin in patients with type 2 diabetes mellitus: A systemic review and meta-analysis

BACKGROUND

The efficacy and safety of once-weekly dipeptidyl peptidase-4 inhibitor (DPP-4i) omarigliptin as monotherapy or add on to other antihyperglycemic agents (AHAs) in patients with type 2 diabetes mellitus (T2DM) is unclear.

METHODS

PubMed, EMBASE, Cochrane library, and ClinicalTrials.gov were searched from the inception to January 24, 2018. Randomized controlled trials comparing omarigliptin with placebo or other AHAs in T2DM patients were included in our meta-analysis. Risk ratio (RR) and mean difference (MD) were used to evaluate the outcomes.

RESULTS

Totally, 11 trials involving 8276 patients were satisfied with our inclusion criteria. Compared with control group, omarigliptin was associated with a significantly stronger reduction in hemoglobin A1c (HbA1c) (MD 0.38%, 95% confidence interval [CI] [0.18, 0.58], P = .0002) and fasting plasma glucose (MD 0.48 mmol/L, 95% CI [0.14 mmol/L, 0.82 mmol/L], P = .006). Omarigliptin increased the number of participants who achieved HbA1c < 7.0% compared with control group (RR 2.03, 95% CI [1.38, 2.98], P = .0003). No significant difference was found in the aspect of adverse events (RR 1.00, 95% CI [0.97, 1.03], P = .99), serious adverse events (RR 1.02, 95% CI [0.91, 1.13], P = .75), hypoglycemic events (RR 0.86, 95% CI [0.48, 1.54], P = .61) between omarigliptin and control group. Omarigliptin has a homologous efficacy and safety background to other AHAs according to the results of subgroup analysis.

CONCLUSIONS

This review revealed that omarigliptin had a favorable efficacy and safety as monotherapy or add on to other AHAs in treating T2DM patients. It is a superior choice for T2DM patients who have a poor adherence to daily AHAs.

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.

Coadministration of DPP-4 inhibitor and insulin therapy does not further reduce the risk of cardiovascular events compared with DPP-4 inhibitor therapy in diabetic foot patients: a nationwide population-based study

BACKGROUND

The effect of combined insulin and dipeptidyl peptidase-4 inhibitor (DPP4i) therapy on major adverse cardiovascular events (MACEs) in patients with diabetic foot is unclear.

METHODS

We conducted this nationwide cohort study using longitudinal claims data obtained from the Taiwan National Health Insurance program and included 19,791 patients with diabetic foot from 2007 to 2014. Patients receiving DPP4i-based therapy and/or insulin-based therapy after a diagnosis of diabetic foot were categorized into combined, DPP4i- or insulin-based groups, respectively. The risk of MACEs including nonfatal myocardial infarction, nonfatal stroke, cardiac death, and heart failure was assessed using Cox proportional hazards analysis and propensity score matching.

RESULTS

Among the 19,791 patients with diabetic foot (mean age, 58.8 years [SD, 12.5]; men, 51.2%), 6466 received DPP4i-based therapy, 1925 received insulin-based therapy, and 11,400 received combined DPP4i and insulin therapy. The DPP4i-based and insulin-based groups had a lower risk of MACEs (HR 0.53, 95% CI 0.50-0.57 DPP4i only; HR 0.89, 95% CI 0.81-0.97 insulin only) than the combined group. After propensity score matching, the incidence of all complications in the DPP4i-based group was still significantly lower than that in the combined group (HR 0.55, 95% CI 0.51-0.59 for MACEs; HR 0.32, 95% CI 0.24-0.42 for nonfatal myocardial infarction; HR 0.70, 95% CI 0.63-0.78 for nonfatal stroke; HR 0.22, 95% CI 0.13-0.38 for cardiac death; HR 0.22, 95% CI 0.19-0.25 for any death; HR 0.16, 95% CI 0.13-0.20 for amputation). In the diabetic foot patients with end-stage renal disease (ESRD), the benefit of a lower incidence of MACEs in the DPP4i-based group disappeared (HR 0.77, 95% CI 0.58-1.08).

CONCLUSIONS

This study demonstrated that the patients with diabetic foot receiving DPP4i-based therapy had a lower risk of MACEs than those receiving combined therapy with DPP4i and insulin, but that the effect disappeared in those with concurrent ESRD.