Dipeptidyl peptidase 4 (DPP-4)

Overview

Dipeptidyl peptidase 4 (DPP-4), also known as CD26 or adenosine deaminase complexing protein 2, is a serine protease and type II transmembrane glycoprotein expressed across many tissues, including the kidney, liver, intestine, immune cells, and vascular endothelium. It also circulates in a soluble form shed from cell membranes. Its enzymatic function is to cleave dipeptides from the N-terminus of peptides that carry a proline or alanine at the penultimate position, an activity that lets it regulate the availability of numerous bioactive peptides. Most prominently, DPP-4 rapidly inactivates the incretin hormone glucagon-like peptide-1 (GLP-1), truncating it within minutes of its release from intestinal L-cells and thereby blunting its insulinotropic effect on postprandial glucose control. Because of this, elevated or unchecked DPP-4 activity is regarded as an aggravating factor in the progression of type 2 diabetes, and DPP-4 expression and activity are frequently increased in the setting of obesity and insulin resistance.

This substrate-truncating mechanism makes DPP-4 a validated pharmacological target. The "gliptin" class of orally administered inhibitors — including sitagliptin, vildagliptin, saxagliptin, and linagliptin — blocks the enzyme's active site, prolonging endogenous GLP-1 signaling to improve glycemic control in type 2 diabetes, and newer strategies such as PROTAC-mediated targeted degradation aim to achieve more sustained suppression than reversible inhibition allows. Beyond glucose homeostasis, DPP-4 and its inhibition are being examined in a widening range of contexts: coronary microvascular function and cardiovascular disease, bone metabolism and cellular senescence, where DPP-4 has been linked to ferroptosis in bone marrow stromal cells, neurodegenerative and diabetes-associated cognitive pathology, and even primary ovarian failure. These connections reflect the breadth of DPP-4's substrates and its intersections with oxidative stress, inflammatory signaling involving mediators such as TNF-α, and iron-dependent cell death pathways.

Recent Publications Summary

Recent studies have continued to position DPP-4 as a therapeutic target across metabolic, inflammatory, and degenerative disease contexts. In type 2 diabetes, several reports focused on either inhibiting DPP-4 or degrading the protein to achieve more sustained glycemic control. A PROTAC strategy was used to generate a DPP-4 degrader (DeDPP4) that produced dose-dependent DPP-4 depletion in A549 cells and prolonged glucose lowering in vivo, with reduced blood glucose maintained for over 60 hours, sustained GLP-1 elevation, and improved glucose tolerance 41823561Mar. In a related conceptual report, targeted degradation of DPP-4 was proposed as an alternative to conventional competitive inhibition because existing DPP-4 inhibitors may require sustained exposure and can have off-target effects 42260272Jun. Structure-based and peptide-discovery studies also expanded the inhibitor landscape, including de novo-designed dual DPP IV/PTP1B inhibitors with strong docking scores and stability in molecular dynamics simulations 42378400Jun, as well as garlic-derived peptides, walnut-derived peptides, and Lentinula edodes-stem-derived peptides that showed DPP-4 inhibitory activity in computational and experimental assays 41905014Mar41794527Mar41665866Feb.

Beyond diabetes, DPP-4 was investigated as a mechanistic node in several disease models. In intervertebral disc degeneration, sitagliptin, a DPP4 inhibitor, was evaluated as a disease-modifying agent based on Mendelian randomization and experimental validation of macrophage–nucleus pulposus cell crosstalk 41540645Jan. In cardiometabolic disease, linagliptin was studied for its effects on coronary microvascular function and collateralization in a large animal model of cardiometabolic syndrome 42049164Apr. DPP4 also emerged in a gut-heart axis study showing that Bacteroides acidifaciens produces a microbial DPP4 isozyme (BaDPP4) that degrades cardioprotective peptides such as GLP-1 and exacerbates myocardial ischemia/reperfusion injury; pharmacological inhibition of BaDPP4 with daurisoline mitigated cardiac dysfunction 41923637Apr. In addition, a study of hydrolytic drug-metabolizing enzymes quantified DPP4 abundance across liver, intestine, and kidney tissues in humans and several animal species, highlighting intertissue and interspecies variability relevant to translational pharmacology 42342236Jun.

Several publications linked DPP-4 to nontraditional disease mechanisms, including aging, neurodegeneration, and reproductive biology. In senile osteoporosis models, galangin attenuated bone loss and BMSC cellular senescence by inhibiting DPP4 nuclear translocation and disrupting its interaction with NOX1, thereby blocking reactive oxygen species-dependent ferroptosis 42041149Apr. In an Alzheimer’s disease-like rat model, saxagliptin-derived Schiff bases were designed as DPP-IV-related compounds and evaluated for their ability to counter oxidative, amyloidogenic, and cholinergic dysfunction 42178013May. In multiple sclerosis, Mendelian randomization implicated genetically predicted DPP4 activity in disease susceptibility, and experimental autoimmune encephalomyelitis mice exposed to nicotine-derived nitrosamine ketone showed increased DPP4 expression in inflamed CNS regions 41956308Apr. Finally, multi-omics Mendelian randomization and colocalization analyses associated elevated DPP4 expression and protein levels with reduced primary ovarian failure risk, while increased methylation at three DPP4 CpG sites was associated with higher risk 42484070Jul.

What Changes, What Holds

1. DPP-4 degradation strengthens the case for sustained target suppression in diabetes
REINFORCES Targeted degradation does not overturn the established role of DPP-4 in limiting GLP-1 signaling; it extends the therapeutic logic beyond reversible active-site blockade. The new work suggests that deeper and longer-lasting suppression may better match the enzyme’s biology than conventional inhibition alone, while also raising the practical question of whether degradation can improve durability without adding new liabilities. The conceptual report on off-target concerns supports, rather than displaces, the baseline rationale for pursuing more sustained DPP-4 control 41823561Mar42260272Jun.

2. DPP-4 is now implicated in tissue-specific and microbial cardiometabolic mechanisms beyond its classic incretin role
NEW DIRECTION A microbial DPP-4 isozyme that worsens ischemia/reperfusion injury and a coronary microvascular study in cardiometabolic syndrome broaden DPP-4 from a glucose-regulating enzyme into a more general cardiometabolic mediator. The baseline already allows cardiovascular investigation, but it does not cover a gut-derived DPP-4 activity that degrades cardioprotective peptides or the possibility that tissue-specific pharmacology may matter more than systemic inhibition alone. These findings add a new mechanistic layer and complicate translation across organs and species 41923637Apr42342236Jun.

3. DPP-4 is emerging as a node in aging, neurodegeneration, and reproductive risk biology
NEW DIRECTION Work on osteoporosis, Alzheimer-like pathology, multiple sclerosis, and primary ovarian failure pushes DPP-4 into disease domains the Overview did not previously assign to it, especially aging-linked ferroptosis, CNS inflammation, and fertility risk. That does not contradict the known enzyme biology; it expands the map of plausible downstream effects and suggests that DPP-4 expression or activity may be a biomarker or modifier outside metabolic disease. The evidence is still largely associative or preclinical, so these roles remain provisional 42041149Apr42484070Jul.

Overview update candidates: microbial DPP-4 as a cardioprotective peptide-degrading factor in gut-heart signaling; DPP-4 involvement in osteoporosis/ferroptosis; multiple sclerosis; and primary ovarian failure as new disease associations.