Combining MK626, a novel DPP-4 inhibitor, and low-dose monoclonal CD3 antibody for stable remission of new-onset diabetes in mice

Effects of incretin-based therapies on β-cell function in type 1 diabetes mellitus: a systematic review and meta-analysis

AIM

To assess the effects of incretin-based therapies on β-cell function in patients with type 1 diabetes mellitus (T1DM).

METHODS

We searched the PubMed, Cochrane Library, Embase, and Web of Knowledge databases for eligible randomized clinical trials published up to July 2021. The inclusion criteria were patients with T1DM or latent autoimmune diabetes in adults, patients treated with dipeptidyl peptidase-4 inhibitors or glucagon like peptide-1 receptor agonists, and outcomes included one of the following: fasting plasma glucose, fasting C-peptide, postprandial C-peptide, C-peptide area under the curve (AUC), homeostasis model assessment for β cell function, and insulin resistance. The effects were analyzed using a random effect model with STATA 11.0.

RESULTS

Eight trials including 427 participants were included in the final analysis. A pooled analysis found no significant difference in fasting plasma glucose, fasting C-peptide, postprandial C-peptide, or C-peptide AUC between patients treated with incretin-based therapies and placebo. The two trials that reported changes in 2-hour postprandial C-peptide and two of the four trials that reported changes in C-peptide AUC reported increases after incretin-based therapies.

CONCLUSION

This meta-analysis showed that incretin-based therapies did not preserve β-cell function in patients with T1DM.

Long-term inhibition of dipeptidyl-peptidase 4 reduces islet infiltration and downregulates IL-1β and IL-12 in NOD mice

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DPP-4 inhibition reduced CD4+T cells infiltration and ameliorated insulitis.

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DPP-4 inhibition downregulated serum IL-1β and IL-12.

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LPS increased CD11b+ cells to infiltrate into islets.

Dipeptidyl-peptidase 4 (DPP-4) inhibitor (sitagliptin) is a novel anti-hyperglycemia drug in the treatment of type 2 diabetes. However, its potential in type 1 diabetes is still unclear. Recent studies show that increased infection, especially respiratory tract infection, is significantly associated with DPP-4 inhibitors. In this study, we aimed to explore the effects of long-term inhibition of DPP- 4 on innate immunity in type 1 diabetes. Forty mice were randomly divided into 4 groups (n = 10 in each group): control group, lipopolysaccharide (LPS) group, sitagliptin group and sitagliptin + LPS group. The concentrations of IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, TNF-α and IFN-γ were measured with Mesco Scale Discovery multiplexed-assay kit. Immunohistochemistry staining of pancreases was performed and insulitis scores for each islet were determined. The results showed that DPP-4 inhibition has no effect on incident rate of diabetes and metabolic parameters in NOD mice. Long-term inhibition of DPP-4 reduced CD4+T cells to infiltrate into islets and ameliorated insulitis in NOD mice. DPP-4 inhibition downregulated serum interleukin IL-1β and IL-12 in NOD mice. However, it had no significant effect on LPS-induced IL-1β, IL-6, IL-10, IL-12, tumor necrosis factor (TNF)-α and interferon (IFN)-γ in NOD mice. In conclusion, Long-term inhibition of DPP-4 exists anti-inflammatory effect in type 1 diabetes probably by reducing CD4+T cells to infiltrate into islets and downregulating L-1β and IL-12 in serum.

DPP-4 Inhibition Leads to Decreased Pancreatic Inflammatory Profile and Increased Frequency of Regulatory T Cells in Experimental Type 1 Diabetes

Sitagliptin is a dipeptidyl peptidase-4 inhibitor (iDPP-4), which has been used for type 2 diabetes treatment. Recently, iDPP-4 has been described as a promising treatment of type 1 diabetes (T1D) but is still necessary to evaluate immune effects of sitagliptin. C57BL/6 mice were induced by multiple low doses of streptozotocin. Diabetes incidence, insulin, glucagon, glucagon-like peptide-1 (GLP-1) serum levels, and inflammatory cytokine levels were quantified in pancreas homogenate after 30 and 90 days of treatment. In addition, frequencies of inflammatory and regulatory T cell subsets were determined in the spleen and in the pancreatic lymph nodes. iDPP-4 decreased blood glucose level while increased GLP-1 and insulin levels. After long-term treatment, treated diabetic mice presented decreased frequency of CD4⁺CD26⁺ T cells and increased percentage of CD4⁺CD25^hiFoxp3⁺ T cells in the spleen. Besides, pancreatic lymph nodes from diabetic mice treated with iDPP-4 presented lower percentage of CD11b⁺ cells and decreased levels of inflammatory cytokines in the pancreas. Treatment of type 1 diabetic mice with iDPP-4 improved metabolic control, decreased inflammatory profile in the pancreatic microenvironment, and increased systemic regulatory T cell frequency. Therefore, we suggest the long-term use of sitagliptin as a feasible and effective therapy for T1D.

CD26 in autoimmune diseases: The other side of "moonlight protein"

Dipeptidyl peptidase 4 (DPP-4) is a serine protease, which has enzymatic activity to selectively clean the N-terminal dipeptide of peptides and proteins with proline or alanine in the second position. DPP-4 inhibitor has been widely used for the treatment of type 2 diabetes by increasing the level of the glucagon-like peptide-1 and decreasing the glucose level. DPP-4, also known as lymphocyte cell surface protein CD26, plays a core role of T cell immunity. Many roles of CD26 in other immune cells have been found. As a "moonlight protein", the effect of CD26 in autoimmune diseases has attracted more and more attention. The paper reviewed the function and potential effect of CD26 in autoimmune diseases, which shows CD26 may be a new target of autoimmune diseases deserved further study.

Pharmacologic adjunctive to insulin therapies in type 1 diabetes: The journey has just begun

Treatment of type 1 diabetes (T1D) is currently based exclusively on insulin replacement therapy. However, there is a need for better glycemic control, lower hypoglycemia rates, more effective weight management, and further reduction of cardiovascular risk in people with T1D. In this context, agents from the pharmaceutical quiver of type 2 diabetes are being tested in clinical trials, as adjunctive to insulin therapies for T1D patients. Despite the limited amount of relevant evidence and the inter-class variability, it can be said that these agents have a role in optimizing metabolic control, assisting weight management and reducing glycemic variability in people with T1D. Specific safety issues, including the increased risk of hypoglycemia and diabetic ketoacidosis, as well as the effects of these treatments on major cardiovascular outcomes should be further assessed by future studies, before these therapeutic choices become widely available for T1D management.

Metabolic Control in Type 1 Diabetes: Is Adjunctive Therapy the Way Forward?

Despite advances in insulin therapies, patients with type 1 diabetes (T1DM) have a shorter life span due to hyperglycaemia-induced vascular disease and hypoglycaemic complications secondary to insulin therapy. Restricting therapy for T1DM to insulin replacement is perhaps an over-simplistic approach, and we focus in this work on reviewing the role of adjuvant therapy in this population. Current data suggest that adding metformin to insulin therapy in T1DM temporarily lowers HbA1c and reduces weight and insulin requirements, but this treatment fails to show a longer-term glycaemic benefit. Agents in the sodium glucose co-transporter-2 inhibitor (SGLT-2) class demonstrate the greatest promise in correcting hyperglycaemia, but there are safety concerns in relation to the risk of diabetic ketoacidosis. Glucagon-like peptide-1 agonists (GLP-1) show a modest effect on glycaemia, if any, but significantly reduce weight, which may make them suitable for use in overweight T1DM patients. Treatment with pramlintide is not widely available worldwide, although there is evidence to indicate that this agent reduces both HbA1c and weight in T1DM. A criticism of adjuvant studies is the heavy reliance on HbA1c as the primary endpoint while generally ignoring other glycaemic parameters. Moreover, vascular risk markers and measures of insulin resistance-important considerations in individuals with a longer T1DM duration-are yet to be fully investigated following adjuvant therapies. Finally, studies to date have made the assumption that T1DM patients are a homogeneous group of individuals who respond similarly to adjuvant therapies, which is unlikely to be the case. Future longer-term adjuvant studies investigating different glycaemic parameters, surrogate vascular markers and harder clinical outcomes will refine our understanding of the roles of such therapies in various subgroups of T1DM patients.

Dipeptidyl peptidase-4(DPP-4) inhibitors: promising new agents for autoimmune diabetes

Dipeptidyl peptidase-4 (DPP-4) inhibitors constitute a novel class of anti-diabetic agents confirmed to improve glycemic control and preserve β-cell function in type 2 diabetes. Three major large-scale studies, EXAMINE, SAVOR-TIMI 53, and TECOS, have confirmed the cardiovascular safety profile of DPP-4 inhibitors. Based on these results, DPP-4 inhibitors have gained widespread use in type 2 diabetes treatment. It is currently unknown, however, whether DPP-4 inhibitors have similar therapeutic efficacy against autoimmune diabetes. Several in vitro and in vivo studies have addressed this issue, but the results remain controversial. In this review, we summarize experimental findings and preliminary clinical trial results, and identify potentially effective immune modulation targets of DPP-4 inhibitors for autoimmune diabetes.

Oral histone deacetylase inhibitor synergises with T cell targeted immunotherapy to preserve beta cell metabolic function and induce stable remission of new-onset autoimmune diabetes in NOD mice

AIM/HYPOTHESIS

Combination therapy targeting the major actors involved in the immune-mediated destruction of pancreatic beta cells appears to be an indispensable approach to treat type 1 diabetes effectively. We hypothesised that the combination of an orally active pan-histone deacetylase inhibitor (HDACi: givinostat) with subtherapeutic doses of CD3 antibodies may provide ideal synergy to treat ongoing autoimmunity.

METHODS

NOD mice transgenic for the human CD3ε (also known as CD3E) chain (NOD-huCD3ε) were treated for recent-onset diabetes with oral givinostat, subtherapeutic doses of humanised CD3 antibodies (otelixizumab, 50 μg/day, 5 days, i.v.) or a combination of both drugs. Disease remission, metabolic profiles and autoreactive T cell responses were analysed in treated mice.

RESULTS

We demonstrated that givinostat synergised with otelixizumab to induce durable remission of diabetes in 80% of recently diabetic NOD-huCD3ε mice. Remission was obtained in only 47% of mice treated with otelixizumab alone. Oral givinostat monotherapy did not reverse established diabetes but reduced the in situ production of inflammatory cytokines (IL-1β, IL-6, TNF-α). Importantly, the otelixizumab + givinostat combination strongly improved the metabolic status of NOD-huCD3ε mice; the mice recovered the capacity to appropriately produce insulin, control hyperglycaemia and sustain glucose tolerance. Finally, diabetes remission induced by the combination therapy was associated with a significant reduction of insulitis and autoantigen-specific CD8⁺ T cell responses.

CONCLUSIONS/INTERPRETATION

HDACi and low-dose CD3 antibodies synergised to abrogate in situ inflammation and thereby improved pancreatic beta cell survival and metabolic function leading to long-lasting diabetes remission. These results support the therapeutic potential of protocols combining these two drugs, both in clinical development, to restore self-tolerance and insulin independence in type 1 diabetes.

DPP-4 Inhibitors as Treatments for Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis

OBJECTIVE

Several clinical studies have reported the application of dipeptidyl peptidase-4 (DPP-4) inhibitors as treatments for type 1 diabetes mellitus (T1DM). This study aims to review the outcomes of these existing studies and to discuss the therapeutic effects of DPP-4 inhibitors on T1DM.

METHODS

We thoroughly searched the Medline, Embase, PubMed, and Cochrane Library databases and ClinicalTrials.gov for studies concerning the use of DPP-4 inhibitors in patients with T1DM.

RESULTS

In preclinical trials, DPP-4 inhibitors improved the pathogenesis of T1DM. However, only a portion of the studies showed potential efficacy regarding clinical glycemic control and other clinical parameters. From this meta-analysis, pooled data from 5 randomized controlled trials revealed that the additional use of DPP-4 inhibitors resulted in a greater decrease in glycated hemoglobin A1c (HbA1c) levels (0.07%, 95% CI (-0.37%-0.23%)) than insulin monotherapy, although the decrease was not significant. A small decrease in postprandial glucose or insulin consumption was confirmed.

CONCLUSION

Although DPP-4 inhibitors may be beneficial for T1DM, existing studies do not strongly support these positive effects in clinical practice. Further optimized clinical trials are needed.

Immunotherapy for Type 1 Diabetes: Why Do Current Protocols Not Halt the Underlying Disease Process?

T cell-directed immunosuppression only transiently delays the loss of β cell function in recent-onset type 1 diabetes. We argue here that the underlying disease process is carried by innate immune reactivity. Inducing a non-polarized functional state of local innate immunity will support regulatory T cell development and β cell proliferation.

Liraglutide Enhances the Efficacy of Human Mesenchymal Stem Cells in Preserving Islet β-cell Function in Severe Non-obese Diabetic Mice

Glucagon-like peptide 1 (GLP-1) can promote islet β-cell replication and function, and mesenchymal stem cells (MSCs) can inhibit T cell autoimmunity. This study aimed at testing the dynamic distribution of infused human MSCs and therapeutic effect of combined MSCs and Liraglutide, a long-acting GLP-1 analogue, on preserving β-cell function in severe non-obese diabetic (NOD) mice. We found that infused MSCs accumulated in the pancreas at 4 weeks post infusion, which was not affected by Liraglutide treatment. Liraglutide significantly enhanced the function of MSCs to preserve islet β-cells by reducing glucose level at 30 minutes post glucose challenge and increasing the contents and secretion of insulin by islet β-cells in severe diabetic NOD mice. Infusion with MSCs significantly reduced insulitis scores, but increased the frequency of splenic Tregs, accompanied by reducing the levels of plasma IFN-γ and TNF-α and elevating the levels of plasma IL-10 and transforming growth factor-β1 (TGF-β1) in NOD mice. Although Liraglutide mitigated MSC-mediated changes in the frequency of Tregs and the levels of plasma IL-10, Liraglutide significantly increased the levels of plasma TGF-β1 in severe diabetic NOD mice. Therefore, our findings suggest that Liraglutide may enhance the therapeutic efficacy of MSCs in treatment of severe type 1 diabetes.

CD26/DPPIV inhibition alters the expression of immune response-related genes in the thymi of NOD mice

The transmembrane glycoprotein CD26 or dipeptidyl peptidase IV (DPPIV) is a multifunctional protein. In immune system, CD26 plays a role in T-cell function and is also involved in thymic maturation and emigration patterns. In preclinical studies, treatment with DPPIV inhibitors reduces insulitis and delays or even reverses the new -onset of type 1 diabetes (T1D) in non-obese diabetic (NOD) mice. However, the specific mechanisms involved in these effects remain unknown. The aim of the present study was to investigate how DPPIV inhibition modifies the expression of genes in the thymus of NOD mice by microarray analysis. Changes in the gene expression of β-cell autoantigens and Aire in thymic epithelial cells (TECs) were also evaluated by using qRT-PCR. A DPPIV inhibitor, MK626, was orally administered in the diet for 4 and 6 weeks starting at 6-8 weeks of age. Thymic glands from treated and control mice were obtained for each study checkpoint. Thymus transcriptome analysis revealed that 58 genes were significantly over-expressed in MK626-treated mice after 6 weeks of treatment. Changes in gene expression in the thymus were confined mainly to the immune system, including innate immunity, chemotaxis, antigen presentation and immunoregulation. Most of the genes are implicated in central tolerance mechanisms through several pathways. No differences were observed in the expression of Aire and β-cell autoantigens in TECs. In the current study, we demonstrate that treatment with the DPPIV inhibitor MK626 in NOD mice alters the expression of the immune response-related genes in the thymus, especially those related to immunological central tolerance, and may contribute to the prevention of T1D.

Dipeptidyl peptidase-4 inhibitor MK-626 restores insulin secretion through enhancing autophagy in high fat diet-induced mice

Autophagy is cellular machinery for maintenance of β-cell function and mass. The current study aimed to investigate the regulatory effects of MK-626, a dipeptidyl peptidase-4 inhibitor, on insulin secretion through the activation of autophagy in high fat diet-induced obese mice. C57BL/6 mice were fed with a rodent diet containing 45 kcal% fat for 16 weeks to induce obesity and then were received either vehicle or MK-626 (3 mg/kg/day) orally during the final 4 weeks. Mouse islets were isolated. Phosphorylation of serine/threonine-protein kinase mTOR and levels of light chain 3B I (LC3B I), LC3B II, sequestosome-1 (SQSTM1/p62) and autophagy-related protein-7 (Atg7) were examined by Western blotting. Glucagon like-peptide-1 (GLP-1) level and insulin secretion were measured by ELISA. GLP-1 level in plasma was decreased in obese mice, which was elevated by dipeptidyl peptidase-4 inhibitor MK-626. In the islets of obese mice, phosphorylation of mTOR, ratio of LC3B I and LC3B II, and level of p62 were elevated and the expression of Atg7 and insulin secretion were reduced compared to those of C57BL/6 mice. However, such effects were reversed by MK-626. Autophagy activator rapamycin stimulated insulin secretion in obese mice but autophagy inhibitor chloroquine treatment inhibited insulin secretion in obese mice administrated by MK-626. Furthermore, the beneficial effects of MK-626 were inhibited by GLP-1 receptor antagonist exendin 9-39. The present study reveals the activation of autophagy to mediate the anti-diabetic effect of GLP-1.

Anti-CD3/Anti-CXCL10 Antibody Combination Therapy Induces a Persistent Remission of Type 1 Diabetes in Two Mouse Models

Anti-CD3 therapy of type 1 diabetes results in a temporary halt of its pathogenesis but does not constitute a permanent cure. One problem is the reinfiltration of islets of Langerhans with regenerated, autoaggressive lymphocytes. We aimed at blocking such a reentry by neutralizing the key chemokine CXCL10. Combination therapy of diabetic RIP-LCMV and NOD mice with anti-CD3 and anti-CXCL10 antibodies caused a substantial remission of diabetes and was superior to monotherapy with anti-CD3 or anti-CXCL10 alone. The combination therapy prevented islet-specific T cells from reentering the islets of Langerhans and thereby blocked the autodestructive process. In addition, the local immune balance in the pancreas was shifted toward a regulatory phenotype. A sequential temporal inactivation of T cells and blockade of T-cell migration might constitute a novel therapy for patients with type 1 diabetes.

Type 1 Diabetes Prevention in NOD Mice by Targeting DPPIV/CD26 Is Associated with Changes in CD8⁺T Effector Memory Subset

CD26 is a T cell activation marker consisting in a type II transmembrane glycoprotein with dipeptidyl peptidase IV (DPPIV) activity in its extracellular domain. It has been described that DPPIV inhibition delays the onset of type 1 diabetes and reverses the disease in non-obese diabetic (NOD) mice. The aim of the present study was to assess the effect of MK626, a DPPIV inhibitor, in type 1 diabetes incidence and in T lymphocyte subsets at central and peripheral compartments. Pre-diabetic NOD mice were treated with MK626. Diabetes incidence, insulitis score, and phenotyping of T lymphocytes in the thymus, spleen and pancreatic lymph nodes were determined after 4 and 6 weeks of treatment, as well as alterations in the expression of genes encoding β-cell autoantigens in the islets. The effect of MK626 was also assessed in two in vitro assays to determine proliferative and immunosuppressive effects. Results show that MK626 treatment reduces type 1 diabetes incidence and after 6 weeks of treatment reduces insulitis. No differences were observed in the percentage of T lymphocyte subsets from central and peripheral compartments between treated and control mice. MK626 increased the expression of CD26 in CD8+ T effector memory (TEM) from spleen and pancreatic lymph nodes and in CD8+ T cells from islet infiltration. CD8+TEM cells showed an increased proliferation rate and cytokine secretion in the presence of MK626. Moreover, the combination of CD8+ TEM cells and MK626 induces an immunosuppressive response. In conclusion, treatment with the DPPIV inhibitor MK626 prevents experimental type 1 diabetes in association to increase expression of CD26 in the CD8+ TEM lymphocyte subset. In vitro assays suggest an immunoregulatory role of CD8+ TEM cells that may be involved in the protection against autoimmunity to β pancreatic islets associated to DPPIV inhibitor treatment.

The CXCR1/2 Pathway: Involvement in Diabetes Pathophysiology and Potential Target for T1D Interventions

Although numerous chemokine/chemokine receptor pathways have been described to be implicated in the pathogenesis of type 1 diabetes (T1D), the CXCR1/2 axis has recently been proved to be crucial for leucocyte recruitment involved in insulitis and β cell damage. Multiple strategies blocking the CXCR1/2 pathway are available such as neutralizing antibodies, small molecules and peptide-derived inhibitors. They were firstly and widely used in cancer thanks to their anti-tumorigenic activity and only recently they were tested as a new interventional approach for T1D. As well, CXCR1/2 inhibition has been demonstrated to prevent inflammation- and autoimmunity-mediated damage of the pancreatic islets through inhibiting the migration of CXCR1/2-expressing cells. Among them, neutrophils, macrophages, and, although to a smaller extent, lymphoid cells are the main CXCR1/2-expressing cells. These results supported the active role of the innate immunity in the autoimmune process and opened new interventional approaches for the management of T1D.