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Visual Abstract, Highlights • Treatment with linagliptin, a DPP-4 inhibitor, alleviates not only EAM but also ICIM. • DPP-4 physically interacts with cathepsin G and enhances its activity. • Linagliptin promotes SerpinA3N activity, thereby suppressing cathepsin G activity. • Cathepsin G aggravates EAM through upregulating angiotensin II. • Linagliptin suppresses oxidative stress in EAM hearts., Summary This study sought to show the mechanism of how to ameliorate experimental autoimmune myocarditis (EAM) by administering dipeptidyl peptidase (DPP)-4 inhibitor linagliptin. The number of RAR-related orphan nuclear receptor gamma–positive Th17 cells infiltrated to the EAM myocardium was significantly attenuated by linagliptin treatment. Tandem mass spectrometry–based analysis demonstrated that DPP-4 binds to cathepsin G in EAM hearts, thereby protecting cathepsin G activity through inhibiting SerpinA3N activity. Linagliptin suppresses oxidative stress in EAM hearts as well. Thus, we found that DPP-4 plays a detrimental role in the progression of EAM by interacting with cathepsin G, which, in turn, suppresses SerpinA3N activity.

Background: The disease course of inflammatory bowel disease (IBD) following treatment with glucagon-like peptide (GLP)-1 based therapies is unclear. Objectives: To examine clinical outcomes of IBD in patients with IBD and type 2 diabetes treated with GLP-1 based therapies compared with treatment with other antidiabetics. Methods: Using nationwide Danish registries, we identified patients with IBD and type 2 diabetes who received antidiabetic treatment between 1 January 2007 and 31 March 2019. The primary outcome was a composite of the need for oral corticosteroids, tumour necrosis factor-α inhibitors, IBD-related hospitalisation, or IBD-related surgery. In the setting of a new-user active comparator design, we used Poisson regression to estimate incidence rate ratios (IRRs) comparing treatment with GLP-1 receptor agonists and dipeptidyl peptidase (DPP)-4 inhibitors with other antidiabetic therapies. The analyses were adjusted for age, sex, calendar year, IBD severity, and metformin use. Results: We identified 3751 patients with a diagnosis of IBD and type 2 diabetes and with a prescription of an antidiabetic drug (GLP-1 receptor agonists/DPP-4 inhibitors: 982 patients; other antidiabetic treatment: 2769 patients). The adjusted IRR of the composite outcome was 0.52 (95% CI: 0.42-0.65) for patients exposed to GLP-1 receptor agonists/DPP-4 inhibitors compared with patients exposed to other antidiabetics. Conclusion: In patients with IBD and type 2 diabetes, treatment with GLP-1 receptor agonists/DPP-4 inhibitors are associated with a lower risk of adverse clinical events compared with treatment with other antidiabetics. Funding Information: The study was funded by the Novo Nordisk Foundation [grant number NNF16OC0022586 and NNF17OC0029768]. Declaration of Interests: None of the authors have any conflicts of interest to disclose. Ethics Approval Statement: The study was approved by the Danish Data Protection Agency, and data were analysed on a secure research server at the Danish Health Data Authority. In Denmark, ethical approval is not required for research using pre-existing, routinely collected data.

Graphical abstract A summarized view of recent findings of host proteins interacting with SARS-CoV-2 and genes containing associated variants with COVID-19 susceptibility and severity. The left side of the figure (A) shows host protein interactors (blue wrote) for SARS-CoV-2 identified through CryoEM or X-ray crystallography and AP-MS or AP-LC-MS/MS studies; the right side (B) depicts host genes (blue wrote) involved in COVID-19 susceptibility and severity discovered by GWAS/TWAS and bioinformatics studies. As shown here, some of the genes that has associated risk variants with COVID-19 belong to the identified protein interactors, for an example, ACE2 is both among the involved proteins and genes in SARS-CoV-2 infection., As of July 2021, the outbreak of coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has led to more than 200 million infections and more than 4.2 million deaths globally. Complications of severe COVID-19 include acute kidney injury, liver dysfunction, cardiomyopathy, and coagulation dysfunction. Thus, there is an urgent need to identify proteins and genetic factors associated with COVID-19 susceptibility and outcome. We comprehensively reviewed recent findings of host-SARS-CoV-2 interactome analyses. To identify genetic variants associated with COVID-19, we focused on the findings from genome and transcriptome wide association studies (GWAS and TWAS) and bioinformatics analysis. We described established human proteins including ACE2, TMPRSS2, 40S ribosomal subunit, ApoA1, TOM70, HLA-A, and PALS1 interacting with SARS-CoV-2 based on cryo–electron microscopy results. Furthermore, we described approximately 1000 human proteins showing evidence of interaction with SARS-CoV-2 and highlighted host cellular processes such as innate immune pathways affected by infection. We summarized the evidence on more than 20 identified candidate genes in COVID-19 severity. Predicted deleterious and disruptive genetic variants with possible effects on COVID-19 infectivity have been also summarized. These findings provide novel insights into SARS-CoV-2 biology and infection as well as potential strategies for development of novel COVID therapeutic targets and drug repurposing.

Porphyromonas gingivalis, an asaccharolytic bacterium, utilizes amino acids as energy and carbon sources. Since amino acids are incorporated into the bacterial cells mainly as di- and tri-peptides, exopeptidases including dipeptidyl-peptidase (DPP) and tripeptidyl-peptidase are considered to be prerequisite components for their metabolism. We recently discovered DPP11, DPP5, and acylpeptidyl oligopeptidase in addition to previously reported DPP4, DPP7, and prolyl tripeptidyl peptidase A. DPP11 is a novel enzyme specific for acidic P1 residues (Asp and Glu) and distributed ubiquitously in eubacteria, while DPP5 is preferential for the hydrophobic P1 residue and the first entity identified in prokaryotes. Recently, acylpeptidyl oligopeptidase with a preference for hydrophobic P1 residues was found to release N-terminally blocked di- and tri-peptides. Furthermore, we also demonstrated that gingipains R and K contribute to P1-basic dipeptide production. These observations implicate that most, if not all, combinations of di- and tri-peptides are produced from extracellular oligopeptides even with an N-terminal modification. Here, we review P. gingivalis exopeptidases mainly in regard to their enzymatic characteristics. These exopeptidases with various substrate specificities benefit P. gingivalis for obtaining energy and carbon sources from the nutritionally limited subgingival environment., Japanese Dental Science Review, 52(1), pp.22-29; 2016