Dipeptidyl Peptidase-4 Activity Research Articles

Impaired Incretin Homeostasis in Nondiabetic Moderate-to-Severe CKD.

Key Points Total incretin levels and incretin response during oral glucose tolerance testing were significantly higher among patients with moderate-to-severe nondiabetic patients with CKD compared with healthy people.Unlike in healthy individuals, increased incretin response was not correlated with insulin response and coincided with persistently greater glucagon levels to oral glucose tolerance testing in CKD.Disruption in the incretin system and glucagon dynamics may contribute to metabolic complications in moderate-to-severe CKD. Background Incretins are regulators of insulin secretion and glucose homeostasis metabolized by dipeptidyl peptidase-4 (DPP-4). CKD may modify incretin release, metabolism, or response. Methods We performed 2-hour oral glucose tolerance testing in 59 people with nondiabetic CKD (eGFR <60 ml/min per 1.73 m2) and 39 matched controls. We measured total area under the curve and incremental area under the curve (iAUC) of plasma total glucagon-like peptide-1 (GLP-1) and total glucose-dependent insulinotropic polypeptide (GIP). Fasting DPP-4 levels and activity were measured. Linear regression was used to adjust for demographic, body composition, and lifestyle factors. Results Mean (SD) eGFR was 38±13 and 89±17 ml/min per 1.73 m2 in patients with CKD and controls, respectively. GLP-1 total area under the curve and GIP iAUC were higher in patients with CKD than controls with a mean of 1531±1452 versus 1364±1484 pM×min and 62,370±33,453 versus 42,365±25,061 pg×min/ml, respectively. After adjustment, CKD was associated with 15,271 pM×min/ml greater GIP iAUC (95% confidence intervals [CIs], 387 to 30,154) compared with controls. Adjustment for covariates attenuated associations of CKD with higher GLP-1 iAUC (adjusted difference, 122; 95% CI, −619 to 864). Plasma glucagon levels were higher at 30 minutes (mean difference, 1.6; 95% CI, 0.3 to 2.8 mg/dl) and 120 minutes (mean difference, 0.84; 95% CI, 0.2 to 1.5 mg/dl) in patients with CKD compared with controls. There were no differences in insulin levels or plasma DPP-4 activity or levels between groups. Conclusions Overall, incretin response to oral glucose is preserved or augmented in moderate-to-severe CKD, without apparent differences in circulating DPP-4 concentration or activity. However, neither insulin secretion nor glucagon suppression is enhanced.

Population pharmacokinetic and pharmacodynamic model of evogliptin: Severe uremia increases the bioavailability ofevogliptin.

Uremia, a condition characterized by the retention of uremic toxins due to impaired renal function, may affect drug metabolism mediated by CYP3A4 enzymes. Evogliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor diabetic drug that is primarily metabolized by CYP3A4. This study aimed to construct a population pharmacokinetic (PK) and pharmacodynamic (PD) model for evogliptin in patients with varying degrees of renal disease, including end-stage renal disease on hemodialysis. A total of 688 evogliptin concentration and 598 DPP-4 activity data were available from 46 subjects. PK and PD data analyses were performed using a nonlinear mixed-effects model. The PK of evogliptin was optimally described by a two-compartment model with first-order absorption. The significant covariates in the final model included blood amylase and triglyceride on F1 (relative bioavailability). The simulation findings, together with previously reported PK data, provided evidence of a significant inhibition of the first-pass effect of evogliptin in patients with renal impairment. A direct link sigmoidal Emax model was developed to describe the relationship between evogliptin concentration and DPP-4 inhibition. The PD model predicted significant inhibition of DPP-4 at maximum effect (Emax: 88.9%) and a low EC50 value (1.08 μg/L), indicating the high potency and efficacy of evogliptin. The developed PK/PD model accurately predicted exposure and the resulting DPP-4 activity of evogliptin in renal impairment. The findings of this study suggest that renal impairment and associated biochemical changes may impact the bioavailability of CYP3A4-metabolized drugs.

Higher Serum Dipeptidyl Peptidase-4 Activity in Newly Diagnosed Young-Onset Type 2 Diabetes Mellitus.

Background Dipeptidyl peptidase-4 (DPP4) enzyme inhibition is a therapeutic modality for type 2 diabetes mellitus (T2DM). However, its activity is insufficiently explored yet in youth-onset T2DM. Objective The objective of this study is to measure serum DPP4 enzyme activities in youth-onset T2DM and compare them with those in patients with normal glucose tolerance (NGT). Methods This cross-sectional study comprised 29 young participants with newly diagnosed untreated T2DM (age 24.5±4.5 years, range 13-30 years, 51.7% female) and an equal number of young participants with NGT (age 26.5±2.9 years,48.3% female) screened by a two-sample 75gm oral glucose tolerance test. The relevant history of each participant was obtained, and the waist circumference, waist-hip ratio, blood pressure, and body mass index (BMI) were measured according to the standard procedure and recorded in the data collection sheet. Plasma glucose was measured using the glucose oxidase method, and serum DPP4 activity was measured using the colorimetry method. Results Participants with DM exhibited significantly higher serum DPP4 activity than NGT (DM vs. NGT: 481.4±70.4 pmol/min. vs. 420.3±49.2 pmol/min, mean±SD; p<0.001). A multivariate linear regression model adjusted for age, sex, BMI, and hypertension, found DM as an independent predictor for DPP4 activity (β=0.63.5, 95% CI 28.7-98.4, p=0.022). Conclusion DPP4 activity was significantly elevated in young participants with newly diagnosedT2DM. There might be a pathophysiological implication of DPP4 activity in young-onset T2DM.

Male Sprague Dawley Rats with Type 2 Diabetes Mellitus and Obesity on Body Weight, Body Mass Index, and Fat Content as Affected by Alkaloid Fraction of Litsea Glutinosa Leaves (AFLG)

There were 463 million people living with diabetes around the world, and it is expected to increase by 48% in 2045. Dipeptidyl Peptidase 4 (DPP4) inhibitor is asecond-line anti-diabetic drug, that frequently causes weight gain for long term treatment. Alkaloid fraction of L. glutinosa leaves (AFLG) is able to inhibit DPP4 activity in diabetic rats. Therefore, this study aimed to evaluate the effect of AFLG on body weight (BW), BMI, and fat percentage in male rats with model type 2 diabetes mellitus (T2DM) and obesity. Male Sprague Dawley rats, which weighed 200-250 g, were used in this experimental study. Twelve rats were fed with a high-fat diet for 30 days and then were intraperitoneally injected with 230 and 65 mg/kg BW nicotinamide and streptozotocin, respectively. Those rats were randomly divided into 4 groups, control (C) and three treatment (T1-T3) groups, which were orally given 20, 40, and 80 mg/kg BW/day AFLG for 28 days. Collected data were analyzed using a paired t-test, the one-way ANOVA test. Significant differences in BW in T2 and T3 (p = 0.001), Rohrer index in T2 (p = 0.001) and fat content in C (p = 0.013) were observed between before and after treatments. The average of BW, Lee, Rohrer, and TM indexes and fat content in treatment groups did not significantly differ from the C group after 28 days of treatment (p &gt; 0.005). In conclusion, Alkaloid fraction of L. glutinosa leaves does not influence body weight, nutrition status, or fat content of male rats’ models of T2DM and obesity.

Isospongian Diterpenoids from the Leaves of Amomum tsao-ko Promote GLP-1 Secretion via Ca2+/CaMKII and PKA Pathways and Inhibit DPP-4 Enzyme.

Three uncommon isospongian diterpenoids including a new one, 3-epi-kravanhin A (2), were isolated from the leaves of Amomum tsao-ko. Compounds 2 and 3 dose-dependently promoted GLP-1 secretion on STC-1 cells with promotion ratios of 109.7% and 186.1% (60 μM). Mechanism study demonstrated that the GLP-1 stimulative effects of 2 and 3 were closely related with Ca2+/CaMKII and PKA pathways, but irrelevant to GPBAR1 and GPR119 receptors. Moreover, compound 1 showed moderate DPP-4 inhibitory activity with an IC50 value of 311.0 μM. Molecular docking verified the binding affinity of 1 with DPP-4 by hydrogen bonds between the γ-lactone carbonyl (C-15) and Arg61 residue. Bioinformatics study indicated that compound 1 exerted antidiabetic effects by improving inflammation, oxidative stress and insulin resistance. This study first disclosed the presence of isospongian diterpenoids in A. tsao-ko, which showed antidiabetic potency by promoting GLP-1 secretion and inhibiting DPP-4 activity.

Consumption of a Sourdough-Leavened Croissant Enriched with a Blend of Fibers Influences Fasting Blood Glucose in a Randomized Controlled Trial in Healthy Subjects

BackgroundAn incorrect lifestyle, including diet, is responsible for the worldwide dramatic increase in obesity and type 2 diabetes. Increasing dietary fiber consumption may lead to health benefits, and reformulation of bakery products may be a strategy to globally improve the diet. ObjectivesThis study aimed to assess the impact of a 2-wk breakfast consumption with a sourdough-leavened croissant containing a blend of dietary fiber from 10 sources (4.8 g/100 g, croissant enriched with dietary fibers [FIBCRO]), compared with a control croissant (dietary fibers 1.3 g/100 g, CONCRO) on daily energy intake, appetite, metabolic variables, and the gut microbiome. MethodsThirty-two healthy participants were randomly allocated to 2 groups consuming FIBCRO or CONCRO. Participants self-recorded their diet and appetite through 7-d weighted food diaries and visual analog scales every day over the 2 wk. At baseline and after the intervention, fasting blood and urine samples, and fecal samples were collected beside blood pressure, anthropometry, and body composition. Serum glucose, lipids, C-reactive protein, and insulin according to the official methods and serum dipeptidyl peptidase-4 (DPPIV) activity by photometric method were measured. Polyphenols and urolithins in urines were analyzed by Liquid chromatography–tandem mass spectrometry (LC/MS/MS), whereas gut microbiome in feces by shotgun metagenomics. ResultsFIBCRO consumption improved fasting blood glucose compared with CONCRO (mean changes from baseline −2.0 mg/dL in FIBCRO compared with +3.1 mg/dL in CONCRO, P = 0.022), also reducing serum DPPIV activity by 1.7 IU/L (P = 0.01) and increasing urinary excretion of urolithin A-sulfate by 6.9 ng/mg creatinine (P = 0.04) compared with baseline. No further changes in any of the monitored variables or in the gut microbiome were detected. ConclusionsResults suggested that a 2-wk consumption of a sourdough croissant claimed as “source of dietary fiber” improved fasting glycemia compared with a conventional sourdough croissant in healthy subjects. The reduced serum DPPIV activity and increased bioavailability of urolithin likely contributed to determine that effect independently from gut microbiome changes.This trial was registered at clinicaltrials.gov as NCT04999280.

Detection and Evaluation of Procalcitonin Variants As Diagnostic Tools in Systemic Inflammation

BACKGROUND: Procalcitonin is an indicator of systemic inflammation associated with major surgery or sepsis. Procalcitonin exists in a full-length and truncated variant as a result of dipeptidylpeptidase-4 (DPP4)-cleavage. We recently identified differential biological activity of both variants. Here, we present an immunoassay-based method for the separate detection of procalcitonin variants and correlation to clinical data in patients with severe systemic inflammation. METHODS: Rabbits were immunized with peptides of N-terminal sequences of both human procalcitonin variants and polyclonal antibodies purified from rabbit plasma. Antibodies were used for the detection of procalcitonin variants in an indirect sandwich enzyme-linked immunosorbent assay (ELISA) using a commercially available monoclonal anti-procalcitonin antibody as capture. Serum was collected from 19 septic patients exhibiting hyperprocalcitonemia as part of a cross-sectional study; clinical data were analyzed and correlated with procalcitonin variant measurements. DPP4 activity was determined by a DPP4 activity assay. RESULTS: Purified antibodies allowed for the separate detection of both procalcitonin variants in all patients. Levels of truncated procalcitonin (truncPCT) correlated with DPP4-activity (Pearson’s R = 0.85, P &lt; .001) and negatively correlated with patients’ Sequential Organ Failure Score (SOFA) scores (Pearson’s R = –0.56, P = .013). In contrast, the correlation between full-length procalcitonin (fullPCT) and SOFA scores was positive (Pearson’s R = 0.56, P = .013). Separation of the patient collective into groups with higher amounts of fullPCT versus truncPCT revealed higher SOFA scores in patients with fullPCT &gt; truncPCT (mean ± standard error of the mean; 11. 3 ± 0.8 vs 6. 1 ± 1.5, P = .003). Patients with fullPCT &gt; truncPCT showed a tendency towards higher doses of vasopressor (0. 2 ± 0.1 vs 0. 1 ± 0.03 µg/kg/min norepinephrine within the first 24 hours after sepsis diagnosis, P = .062) and exhibited higher creatinine (2. 0 ± 0.2 vs 1. 4 ± 0.3mg/dL, P = .019) and leukocyte levels (31. 0 ± 5.4 vs 12. 8 ± 1.9cells/µL, P = .012). In addition, patients with fullPCT &gt; truncPCT were more often subjected to treatment with hydrocortisone (49.0 vs 0%, P = .018). CONCLUSIONS: Polyclonal antibodies generated using procalcitonin N-terminal variant peptides as immunogens are suitable for procalcitonin variant assessment. The separate detection of procalcitonin variants may offer additional diagnostic value and can be correlated with organ dysfunction and clinical outcomes in patients with systemic inflammation.

Roseburia intestinalis-derived extracellular vesicles ameliorate colitis by modulating intestinal barrier, microbiome, and inflammatory responses.

Inflammatory bowel disease (IBD) is a chronic disorder characterized by recurrent gastrointestinal inflammation, lacking a precise aetiology and definitive cure. The gut microbiome is vital in preventing and treating IBD due to its various physiological functions. In the interplay between the gut microbiome and human health, extracellular vesicles secreted by gut bacteria (BEVs) are key mediators. Herein, we explore the role of Roseburia intestinalis (R)-derived EVs (R-EVs) as potent anti-inflammatory mediators in treating dextran sulfate sodium-induced colitis. R was selected as an optimal BEV producer for IBD treatment through ANCOM analysis. R-EVs with a 76nm diameter were isolated from R using a tangential flow filtration system. Orally administered R-EVs effectively accumulated in inflamed colonic tissues and increased the abundance of Bifidobacterium on microbial changes, inhibiting colonic inflammation and prompting intestinal recovery. Due to the presence of Ile-Pro-Ile in the vesicular structure, R-EVs reduced the DPP4 activity in inflamed colonic tissue and increased the active GLP-1, thereby downregulating the NFκB and STAT3 via the PI3K pathway. Our results shed light on the impact of BEVs on intestinal recovery and gut microbiome alteration in treating IBD.

IL-10 Enhances the Inhibitory Effect of Adipose-Derived Stromal Cells on Insulin Resistance/Liver Gluconeogenesis by Treg Cell Induction.

The modulation of cellular phenotypes within adipose tissue provides a potential means for therapeutic intervention for diabetes. Endogenous interleukin-10 (IL-10) protects against diet-induced insulin resistance. We examined the effects and mechanisms of action of IL-10-treated adipose-derived stromal cells on diabetes-induced insulin resistance and liver gluconeogenesis. We harvested stromal vascular fractions (SVFs) from the adipose tissue of diabetic (Leprdb/db) mice and treated them with IL-10 in vitro. SVFs treated with 10 or 100 ng of IL-10 were injected into the inguinal adipose tissue of Leprdb/db mice. IL-10 treatment suppressed the mRNA expression of IL-6, IL-33, CCL2, TNF-α, and IL-1β. Additionally, it suppressed the protein expression of IL-6, pmTOR, pJNK, and pNF-κB but enhanced Foxp3 mRNA expression in SVFs from diabetic mice. Meanwhile, IL-10 treatment repressed CCL2 and PDGFRα expression in adipose tissue macrophages (ATMs) and IL-6 expression in non-ATMs but increased the Foxp3 and IL-10 mRNA expression of ATMs from diabetic mice. Injection of IL-10-treated SVFs decreased the IL-6, IL-33, CCL2, IL-1β, and CCL2 but enhanced the Foxp3 and IL-10 mRNA expression of adipose tissue from Leprdb/db mice. Furthermore, injection of IL-10-treated SVFs increased CD4+ regulatory T cells (Tregs) in SVFs and adipose IL-10 levels and suppressed plasma adiponectin levels and DPP4 activity in diabetic mice. Injection of IL-10-treated SVFs decreased hepatic G6PC and PCK1 mRNA expression and increased Akt activation, STAT3 phosphorylation in the liver, and glucose tolerance in diabetic mice. Our data suggest that IL-10 treatment decreases inflammation in adipose SVFs of diabetic mice. Injection of IL-10-treated SVFs into the adipose tissue decreased diabetes-induced gluconeogenesis gene expression, DPP4 activity, and insulin resistance by enhancing Treg cells in diabetic mice. These data suggest that IL-10-treated adipose stromal vascular cells could be a promising therapeutic strategy for diabetes mellitus.

Fabrication of a Near-Infrared-Emissive Probe for Detecting Dipeptidyl Peptidase 4 in the Liver of Diabetic Mice and Clinical Serum.

Dipeptidyl peptidase 4 (DPP4) plays a key role in glucose metabolism, which has been a close target for diabetes pathology and treatment. It is significant for the evaluation of cellular DPP4 activity in various biological systems. Fluorescence imaging technology is currently a popular method for detecting enzymes in living cells due to its advantages of high selectivity, high sensitivity, high spatiotemporal resolution, and real-time visualization. Herein, a near-infrared (NIR)-emissive probe NEDP with a large Stokes shift (153 nm) was developed for the assay of DPP4 activity. Upon addition of DPP4, NEDP can emit a significant turn-on NIR fluorescence signal (673 nm) with high sensitivity and specificity. Moreover, NEDP can successfully be used for imaging of intracellular DPP4, confirming the regulation of DPP4 expression in hyperglucose and its treatment in living cells. Most importantly, NEDP can not only monitor the changes of DPP4 in vivo but also show that DPP4 in diabetes is mainly up-regulated in the liver, and the level of DPP4 is positively correlated with the pathological damage of the liver. In addition, NEDP can identify the serum of diabetic patients from healthy people through the fluorescence response to DPP4. These results demonstrated that the designed probe NEDP provides a prospective visual tool to explore the relationship between DPP4 and diabetes and would be applied for detecting serum of diabetes in the clinic.

Steps in discovery of alogliptin

Alogliptin was initially approved to treat T2DM in Japan in 2010 and then approved by FDA and by EMA in 2013. Alogliptin, a highly potent and selective, noncovalent inhibitor of DPP-4. Inhibition of DPP-4 activity, alogliptin slows the inactivation of incretin hormones, glucagon-like peptide-1 (GLP-1). In terms of drug safety alogliptin is generally well-tolerated, with a low risk of hypoglycemia, weight gain, acute pancreatitis, and hepatotoxicity. Alogliptin has been effectively combined with Metformin or Pioglitazone to provide better glycaemic control. The drug can be used in mild hepatic or renal impairment with appropriate dosage adjustment. Treatment with alogliptin has shown less weight gain compared with sulfonylureas. Alogliptin and FDC of Alogliptin + Metformin approved and available in India with brand name Aloja &amp; Aloja M/Forte, with well documented safety and efficacy through phase IV study conducted in India.

Excessive accumulation of epicardial adipose tissue promotes microvascular obstruction formation after myocardial ischemia/reperfusion through modulating macrophages polarization

BackgroundOwing to its unique location and multifaceted metabolic functions, epicardial adipose tissue (EAT) is gradually emerging as a new metabolic target for coronary artery disease risk stratification. Microvascular obstruction (MVO) has been recognized as an independent risk factor for unfavorable prognosis in acute myocardial infarction patients. However, the concrete role of EAT in the pathogenesis of MVO formation in individuals with ST-segment elevation myocardial infarction (STEMI) remains unclear. The objective of the study is to evaluate the correlation between EAT accumulation and MVO formation measured by cardiac magnetic resonance (CMR) in STEMI patients and clarify the underlying mechanisms involved in this relationship.MethodsFirstly, we utilized CMR technique to explore the association of EAT distribution and quantity with MVO formation in patients with STEMI. Then we utilized a mouse model with EAT depletion to explore how EAT affected MVO formation under the circumstances of myocardial ischemia/reperfusion (I/R) injury. We further investigated the immunomodulatory effect of EAT on macrophages through co-culture experiments. Finally, we searched for new therapeutic strategies targeting EAT to prevent MVO formation.ResultsThe increase of left atrioventricular EAT mass index was independently associated with MVO formation. We also found that increased circulating levels of DPP4 and high DPP4 activity seemed to be associated with EAT increase. EAT accumulation acted as a pro-inflammatory mediator boosting the transition of macrophages towards inflammatory phenotype in myocardial I/R injury through secreting inflammatory EVs. Furthermore, our study declared the potential therapeutic effects of GLP-1 receptor agonist and GLP-1/GLP-2 receptor dual agonist for MVO prevention were at least partially ascribed to its impact on EAT modulation.ConclusionsOur work for the first time demonstrated that excessive accumulation of EAT promoted MVO formation by promoting the polarization state of cardiac macrophages towards an inflammatory phenotype. Furthermore, this study identified a very promising therapeutic strategy, GLP-1/GLP-2 receptor dual agonist, targeting EAT for MVO prevention following myocardial I/R injury.

Dipotassium glycyrrhizate prevents oral dysbiosis caused by Porphyromonas gingivalis in an in vitro saliva-derived polymicrobial biofilm model

ObjectivesOral microbiome dysbiosis prevention is important to avoid the onset and progression of periodontal disease. Dipotassium glycyrrhizate (GK2) is a licorice root extract with anti-inflammatory effects, and its associated mechanisms have been well-reported. However, their effects on the oral microbiome have not been investigated. This study aimed to elucidate the effects of GK2 on the oral microbiome using an in vitro polymicrobial biofilm model. MethodsAn in vitro saliva-derived polymicrobial biofilm model was used to evaluate the effects of GK2 on the oral microbiome. One-week anaerobic culture was performed, in which GK2 was added to the medium. Subsequently, microbiome analysis was performed based on the V1–V2 region of the 16 S rRNA gene, and pathogenicity indices were assessed. We investigated the effects of GK2 on various bacterial monocultures by evaluating its inhibitory effects on cell growth, based on culture turbidity. ResultsGK2 treatment altered the microbiome structure and decreased the relative abundance of periodontal pathogenic bacteria, including Porphyromonas. Moreover, GK2 treatment reduced the DPP4 activity —a pathogenicity index of periodontal disease. Specifically, GK2 exhibited selective antibacterial activity against periodontal pathogenic bacteria. ConclusionsThese findings suggest that GK2 has a selective antibacterial effect against periodontal pathogenic bacteria; thus, preventing oral microbiome dysbiosis. Therefore, GK2 is expected to contribute to periodontal disease prevention by modulating the oral microbiome toward a state with low inflammatory potential, thereby utilizing its anti-inflammatory properties on the host.

Gut microbiota DPP4-like enzymes are increased in type-2 diabetes and contribute to incretin inactivation

BackgroundThe gut microbiota controls broad aspects of human metabolism and feeding behavior, but the basis for this control remains largely unclear. Given the key role of human dipeptidyl peptidase 4 (DPP4) in host metabolism, we investigate whether microbiota DPP4-like counterparts perform the same function.ResultsWe identify novel functional homologs of human DPP4 in several bacterial species inhabiting the human gut, and specific associations between Parabacteroides and Porphyromonas DPP4-like genes and type 2 diabetes (T2D). We also find that the DPP4-like enzyme from the gut symbiont Parabacteroides merdae mimics the proteolytic activity of the human enzyme on peptide YY, neuropeptide Y, gastric inhibitory polypeptide (GIP), and glucagon-like peptide 1 (GLP-1) hormones in vitro. Importantly, administration of E. coli overexpressing the P. merdae DPP4-like enzyme to lipopolysaccharide-treated mice with impaired gut barrier function reduces active GIP and GLP-1 levels, which is attributed to increased DPP4 activity in the portal circulation and the cecal content. Finally, we observe that linagliptin, saxagliptin, sitagliptin, and vildagliptin, antidiabetic drugs with DPP4 inhibitory activity, differentially inhibit the activity of the DPP4-like enzyme from P. merdae.ConclusionsOur findings confirm that proteolytic enzymes produced by the gut microbiota are likely to contribute to the glucose metabolic dysfunction that underlies T2D by inactivating incretins, which might inspire the development of improved antidiabetic therapies.

Soluble CD26: From Suggested Biomarker for Cancer Diagnosis to Plausible Marker for Dynamic Monitoring of Immunotherapy.

Soluble CD26 (sCD26), a glycoprotein with dipeptidyl peptidase (DPP4) enzymatic activity, can contribute to early diagnosis of colorectal cancer and advanced adenomas and has been studied, including for prognostic purposes, across various other types of cancer and disease. The latest research in this field has confirmed that most, though not all, serum/plasma sCD26 is related to inflammation. The shedding and/or secretion of sCD26 from different immune cells are being investigated, and blood DPP4 activity levels do not correlate very strongly with protein titers. Some of the main substrates of this enzyme are key chemokines involved in immune cell migration, and both soluble and cell-surface CD26 can bind adenosine deaminase (ADA), an enzyme involved in the metabolism of immunosuppressor extracellular adenosine. Of note, there are T cells enriched in CD26 expression and, in mice tumor models, tumor infiltrating lymphocytes exhibited heightened percentages of CD26+ correlating with tumor regression. We employed sCD26 as a biomarker in the follow-up after curative resection of colorectal cancer for the early detection of tumor recurrence. Changes after treatment with different biological disease-modifying antirheumatic drugs, including Ig-CTLA4, were also observed in rheumatoid arthritis. Serum soluble CD26/DPP4 titer variation has recently been proposed as a potential prognostic biomarker after a phase I trial in cancer immunotherapy with a humanized anti-CD26 antibody. We propose that dynamic monitoring of sCD26/DPP4 changes, in addition to well-known inflammatory biomarkers such as CRP already in use as informative for immune checkpoint immunotherapy, may indicate resistance or response during the successive steps of the treatment. As tumor cells expressing CD26 can also produce sCD26, the possibility of sorting immune- from non-immune-system-originated sCD26 is discussed.

Epigallocatechin gallate alleviates non-alcoholic fatty liver disease through the inhibition of the expression and activity of Dipeptide kinase 4

BackgroundNon-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent glocal cause of chronic hepatic disease, with incidence rates that continue to rise steadily. Treatment options for affected patients are currently limited to dietary changes and exercise interventions, with no drugs having been licensed for the treatment of this disease. There is thus a pressing need for the development of novel therapeutic strategies. Work from our group suggests that the primary bioactive ingredient in green tea, epigallocatechin gallate (EGCG), may help reduce liver fat content and protect against hepatic injury through the inhibition of dipeptidyl peptidase 4 (DPP4) expression and activity. The study investigated the potential pathways by which EGCG may improve NAFLD, identified the sites of interaction between EGCG and DPP4, and proposed novel clinical treatment strategies. MethodsA clinical randomized controlled trial was conducted to investigate the potential efficacy of EGCG in NAFLD patients. The study compared relevant indices before and after EGCG administration. Animal models of NAFLD were constructed using male C57BL/6J mice fed a high-fat diet to observe the ameliorative effects of EGCG on the livers of the model mice and to investigate the potential pathways by which EGCG alleviates NAFLD. The interaction mechanism between EGCG and DPP4 was investigated using oleic acid and palmitic acid-treated HepG2 cell lines. Plasmids in which different sites had been disrupted were used to identify the effective interaction sites. ResultsECGC was found to suppress the accumulation of lipids, inhibit inflammation, remediate dysregulated lipid metabolism, and improve the pathogenesis of NAFLD via the inhibition of the expression and activity of DPP4. ConclusionsThe study results indicate that EGCG has a positive impact on improving NAFLD. These results highlight promising new opportunities to safely and effectively treat NAFLD in the clinic. Study id numberChiCTR2300076741; https://www.chictr.org.cn/

The Theoretical Substantiation of the Targeted Search for New DPP4 Inhibitors. Computational Studies of Potential Candidates

Growing evidence suggests that dipeptidyl peptidase 4 (DPP4) inhibitors, in addition to their role in improving glycemic control, help to reduce endothelial dysfunction and have hypolipidemic, anti-atherosclerotic, antitumor, antiviral, and neurotropic properties. This multi-target property may be one of the reasons for repurposing therapeutic treatment strategies with existing agents and the basis for finding new agents to inhibit this target. Based on the structural prerequisites and the evolutionary path of creating DPP4 inhibitors, an inhibitory (R)-β-aminoamide base was used as the basis for constructing potential candidates. It contained a substituted piperazine-2-one derivative and (S)-pyrrolidine-2-carbonitrile fragment, as well as phenyl and diphenyl rings, which were additionally saturated with substituents of various electronic structures, in position 4 of the β-aminoamide chain. The construction of the molecules was carried out taking into account the correspondence of chiral centers to combinations of chiral chains at the DPP4 binding site to possibly prevent a decrease in the inhibitory activity. In silico assessment of the “drug-likeness” and pharmacokinetic profile of the group of compounds studied showed that it had favorable characteristics and could be recommended for further molecular docking in order to predict the likely inhibition of the catalytic activity of DPP4. According to the results of docking, molecules with a moderate and high affinity were found. A detailed analysis of the resulting complexes showed that only nine compounds had a binding mode similar to classical inhibitors. According to the calculated array of values and analysis of the results of docking among the derivatives tested, a hit compound was found as a promising DPP4 inhibitor.

Effects of dipeptidyl peptidase-4 inhibition in vivo: Dipeptidyl peptidase-4 inhibitor/gut microbiome crosstalk suggests novel therapeutic options for diabetes management.

Wang etal. report that clinical dipeptidyl peptidase-4 (DPP-4) inhibitors show little effect on microbial DPP-4 produced by Bacteroidesgenus. Furthermore, oral administration of microbial DPP-4 to high-fat diet-fed mice was found to reduce plasma active glucagon-like peptide-1 levels through an increase in extraluminal intestinal tissular DPP-4 activity, resulting in reduced glucose-induced insulin levels and exacerbated glucose tolerance.

Deletion of dipeptidyl peptidase 4 attenuates angiotensin II-induced blood pressure rise and enhances NHE3 phosphorylation at serine 552 in the kidneys of male and female mice

Dipeptidyl peptidase 4 (DPP4) physically associates with the Na+/H+ exchanger isoform3 (NHE3), and DPP4 inhibitors reduce NHE3-dependent sodium reabsorption in the renal proximal tubule. Angiotensin II (Ang II) is a key mediator of sodium and water retention by the kidneys, partly through the activation of proximal tubule NHE3. Recent studies from our group reveled that Ang II activates DPP4 by, both in vivo and in vitro, and that inhibition of several canonical and non-canonical pathways can suppress this activation. However, the impact of this interaction on renal sodium handling and blood pressure remains unclear. This study aimed to test the hypothesis that DPP4 deletion mitigates the blood pressure elevation induced by Ang II in male and female mice, at least partly due to the downregulation of NHE3 in the renal proximal tubule. Male and female mice with global DPP4 deletion or wild-type controls were acutely administered either a pressor dose of Ang II (1000 ng/kg/minute) or saline. Blood pressure was measured before and one hour after the administration of Ang II or saline by tail-cuff plethysmography. Kidneys were subsequently collected for protein homogenate preparation. Increased DPP4 activity was observed in response to acute Ang II stimulation in both male and female wild-type mice, with female mice exhibiting higher basal DPP4 activity. As expected, DPP4 knockout mice exhibited minimal DPP4 activity. Baseline blood pressure did not differ significantly between male wild-type and DPP4 knockout mice or between females. In line with our hypothesis, both male and female DPP4 knockout mice displayed a reduced increase in blood pressure in response to acute Ang II administration compared to their wild-type counterparts. Furthermore, the phosphorylation of NHE3 at serine 552 (pS552-NHE3), a surrogate marker of NHE3 inhibition, was higher in wild-type females than males. Interestingly, pS552-NHE3 was fivefold higher in male DPP4 knockout mice and threefold higher in female DPP4 knockout mice compared to their wild-type counterparts. Additionally, the increase in pS552-NHE3 one hour after Ang II administration was higher in males (1208 ± 119 vs. 544 ± 54 %, P &lt; 0.01) and females (385 ± 18 vs. 271 ± 27%, P &lt; 0.01) DPP4 knockout mice compared to wild-type animals. Moreover, ERK, a well-known effector of the AT1R signaling cascade, was phosphorylated in a similar manner as NHE3 in response to Ang II in males but not in females. In conclusion, our data demonstrate that the absence of DPP4 reduces the rise in blood pressure induced by acute Ang II stimulation, possibly through Ang II/AT1R signaling pathways influencing phosphorylation of downstream effectors such as NHE3. Furthermore, we observe significant sex differences in Ang II effects on DPP4 activity, and AT1R signaling cascades. FAPESP 2021/14524-3 NIDDKD - K08DK115886. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Global Deletion of DPP4 Prevents the Development of Salt-sensitive Hypertension in Obese Mice via Regulation of Sodium and Water Excretion

Salt-sensitivity of hypertension (HTN) occurs in up to 50% of hypertensive patients and is more common in the older population, Blacks and the obesity/diabetes/hypertension subsets. The renin-angiotensin aldosterone system (RAAS), in particular Angiotensin II (Ang II) and aldosterone known to regulate the Na+/H+ exchanger isoform 3 (NHE3) and ENaC respectively, is thought to be activated in the obesity/diabetes/hypertension subsets and thereby plays an important role in salt-sensitive HTN. RAAS blockade is an acceptable treatment for salt-sensitive HTN along with the use of diuretics. However, not every patient can tolerate RAAS blockade. Recently, dipeptidyl peptidase 4 (DPP4) has been shown to bind to NHE3, colocalizes to the microvillar fractions with active NHE3 and DPP4 inhibition reduces sodium uptake into proximal tubule cells and isolated rat proximal tubules. In addition, DPP4 may act on more distal transporters. Furthermore, data from our lab has revealed that DPP4 knockout (DPP4KO) mice have a lower sodium balance both under conditions of high salt (1.23%) and low salt (0.02%) ingestion suggesting that DPP4 regulates sodium transport and/or balance under physiological conditions. However, whether DPP4 has any effects on salt-sensitive HTN and the underlying mechanisms remain unknown. Therefore, we hypothesized that the absence of DPP4 could mitigate the development of salt-sensitive HTN in an obesity model, by improving the natriuretic and diuretic response mediated by NHE3 and/or distal mechanisms. To this end, 6-8wk old DPP4KO and C57Bl/6 littermate wild-type (WT) mice were fed a control (CD) or Western diet (WD, high in refined fats and sugars) to induce obesity. Circulating (175%) and kidney (125%) DPP4 activity were both elevated in the obese WT mice compared to the CD-fed WT mice (100%) and DPP4KO mice had minimal DPP4 activity as expected. The lack of DPP4 prevented the increase in systolic blood pressure (~15 mmHg) in the obese animals, and the absence of the development of cardiac hypertrophy in this group corroborated the pressure effect. The development of salt-sensitive HTN in the obese WT mice was associated with a lower natriuretic and diuretic response assessed by the salt overload experiment, suggesting higher tubular reabsorption of sodium and water by the nephrons. In turn, the lack of DPP4 prevented the lowering of natriuretic and diuretic response in obese mice, indicating that the beneficial effect of the absence of DPP4 on the development of salt-sensitive HTN is closely related to effects on renal tubule transport. Importantly, a high salt diet increased sodium balance and blood pressure in the obese WT mice and DPP4 deletion mitigated this increase. Furthermore, on low salt diet, the absence of DPP4 led to “salt wasting” in the obese mice similar to the CD-fed mice. Surprisingly, gene and protein expression measurements showed involvement of distal tubule sodium transporters and aquaporins and not NHE3. In contrast, assessment of the DPP4 interactome in obese mice showed binding to Myosin 6 and APN, which may regulate proximal tubule transporters and hypertension. Transdermal measurements showed no changes in the glomerular filtration rate. In conclusion, deletion of DPP4 protects against the development of salt-sensitive hypertension in obese mice by improving the natriuretic and diuretic response likely via regulation of sodium and water transporters. FAPESP, Brazil NIH K08DK115886, USA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.