Dipeptidyl Peptidase-4 Activity Research Articles

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 < 0.01) and females (385 ± 18 vs. 271 ± 27%, P < 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.

Dipeptidyl-peptidase 4 (DPP4) mediates fatty acid uptake inhibition by glucose via TAS1R3 and GLUT-2 in Caco-2 enterocytes

Both high glucose intake with a high-fat meal and inhibition of dipeptidyl peptidase-4 (DPP4) have been associated with plasma lipid-lowering effects, but mechanistic understanding linking glucose and fat absorption is lacking. We here hypothesized that glucose ameliorates intestinal fatty acid uptake via a pathway involving DPP4. A concentration of 50 mM glucose reduced mean DPP4 activity in differentiated Caco-2 enterocytes by 42.5 % and fatty acid uptake by 66.0 % via nutrient sensing by the sweet taste receptor subunit TAS1R3 and glucose transporter GLUT-2. No effect of the DPP4 substrates GLP-1 and GIP or of the cellular energy status on the reduced uptake of fatty acids was seen, but a direct interaction between DPP4 and fatty acid transporters is suggested. Conclusively we identified DPP4 as a regulator of fatty acid absorption in Caco-2 enterocytes that mediates the inhibition of intestinal fatty acid uptake by glucose via an interplay of GLUT-2 and TAS1R3.

Pyrano[2,3-c]pyrazole fused spirooxindole-linked 1,2,3-triazoles as antioxidant agents: Exploring their utility in the development of antidiabetic drugs via inhibition of α-amylase and DPP4 activity

Environment-benign, multicomponent synthetic methodologies are vital in modern pharmaceutical research and facilitates multi-targeted drug development via synergistic approach. Herein, we reported green and efficient synthesis of pyrano[2,3-c]pyrazole fused spirooxindole linked 1,2,3-triazoles using a tea waste supported copper catalyst (TWCu). The synthetic approach involves a one-pot, five-component reaction using N-propargylated isatin, hydrazine hydrate, ethyl acetoacetate, malononitrile/ethyl cyanoacetate and aryl azides as model substrates. Mechanistically, the reaction was found to proceed via in situ pyrazolone formation followed by Knoevenagel condensation, azide alkyne cycloaddition and Michael's addition reactions. The molecules were developed using structure-based drug design. The primary goal is to identifying anti-oxidant molecules with potential ability to modulate α-amylase and DPP4 (dipeptidyl-peptidase 4) activity. The anti-oxidant analysis, as determined via DPPH, suggested that the synthesized compounds, A6 and A10 possessed excellent anti-oxidant potential compared to butylated hydroxytoluene (BHT). In contrast, compounds A3, A5, A8, A9, A13, A15, and A18 were found to possess comparable anti-oxidant potential. Among these, A3 and A13 possessed potential α-amylase inhibitory activity compared to the acarbose, and A3 further emerged as dual inhibitors of both DPP4 and α-amylase with anti-oxidant potential. The relationship of functionalities on their anti-oxidant and enzymatic inhibition was explored in context to their SAR that was further corroborated using in silico techniques and enzyme kinetics.

DPP-4 inhibitors sitagliptin and PF-00734,200 mitigate dopaminergic neurodegeneration, neuroinflammation and behavioral impairment in the rat 6-OHDA model of Parkinson's disease.

Epidemiological studies report an elevated risk of Parkinson's disease (PD) in patients with type 2 diabetes mellitus (T2DM) that is mitigated in those prescribed dipeptidyl peptidase 4 (DPP-4) inhibitors. With an objective to characterize clinically translatable doses of DPP-4 inhibitors (gliptins) in a well-characterized PD rodent model, sitagliptin, PF-00734,200 or vehicle were orally administered to rats initiated either 7-days before or 7-days after unilateral medial forebrain bundle 6-hydroxydopamine (6-OHDA) lesioning. Measures of dopaminergic cell viability, dopamine content, neuroinflammation and neurogenesis were evaluated thereafter in ipsi- and contralateral brain. Plasma and brain incretin and DPP-4 activity levels were quantified. Furthermore, brain incretin receptor levels were age-dependently evaluated in rodents, in 6-OHDA challenged animals and human subjects with/without PD. Cellular studies evaluated neurotrophic/neuroprotective actions of combined incretin administration. Pre-treatment with oral sitagliptin or PF-00734,200 reduced methamphetamine (meth)-induced rotation post-lesioning and dopaminergic degeneration in lesioned substantia nigra pars compacta (SNc) and striatum. Direct intracerebroventricular gliptin administration lacked neuroprotective actions, indicating that systemic incretin-mediated mechanisms underpin gliptin-induced favorable brain effects. Post-treatment with a threefold higher oral gliptin dose, likewise, mitigated meth-induced rotation, dopaminergic neurodegeneration and neuroinflammation, and augmented neurogenesis. These gliptin-induced actions associated with 70-80% plasma and 20-30% brain DPP-4 inhibition, and elevated plasma and brain incretin levels. Brain incretin receptor protein levels were age-dependently maintained in rodents, preserved in rats challenged with 6-OHDA, and in humans with PD. Combined GLP-1 and GIP receptor activation in neuronal cultures resulted in neurotrophic/neuroprotective actions superior to single agonists alone. In conclusion, these studies support further evaluation of the repurposing of clinically approved gliptins as a treatment strategy for PD.

Improvement effect of gemigliptin on salivary gland dysfunction in exogenous methylglyoxal-injected rats

The symptom of hyposalivation associated with hypofunction of the salivary glands is a common feature of diabetes. Inadequate saliva production can cause tissue damage in the mouth, making it susceptible to infections and leading to oral health diseases. Previous studies have highlighted the harmful effects of methylglyoxal (MGO) and MGO-derived advanced glycation end products (AGEs) in diabetes. In this study, we investigated the protective effects of gemigliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, against MGO-induced salivary gland dysfunction. MGO treatment of immortalized human salivary gland acinar cells induced apoptosis via reactive oxygen species (ROS)-mediated pathways, but this effect was mitigated by gemigliptin. In vivo experiments involved the simultaneous administration of MGO (17.25 mg/kg) with aminoguanidine (100 mg/kg) and gemigliptin (10 and 100 mg/kg) daily to rats for two weeks. Gemigliptin increased the saliva volume and amylase levels in MGO-injected rats. Gemigliptin reduced the DPP-4 activity in both the salivary glands and serum of MGO-injected rats. Furthermore, gemigliptin exerted anti-glycation effects by reducing the accumulation of AGEs in the saliva, salivary glands, and serum and suppressing the expression of the receptor for AGEs. These actions protected the salivary gland cells from ROS-mediated apoptosis. Overall, gemigliptin protected the salivary gland cells from ROS-mediated cell death, reduced the accumulation of amylase and mucins in the salivary glands, and enhanced the salivary function by upregulating aquaporin 5 expression, and it exerted protective effects against MGO-induced salivary gland dysfunction by enhancing the anti-glycation, antioxidant, and salivary secretion activities. Our findings suggest gemigliptin as a potential therapeutic for patients with salivary gland dysfunction caused by the complications of diabetes.

Revolutionizing Treatment Strategies for Autoimmune and Inflammatory Disorders: The Impact of Dipeptidyl-Peptidase 4 Inhibitors.

DPP4 (Dipeptidyl-peptidase 4) a versatile protease, emerges as a prominent player in soluble and membrane-bound forms. Its heightened expression has been intimately linked to the initiation and severity of diverse autoimmune diseases, spanning rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis (SSc), inflammatory bowel disease, autoimmune diabetes, and even SARS-CoV-2 infection. Operating as a co-stimulator of T cell activity, DPP4 propels T cell proliferation by binding adenosine deaminase (ADA), thereby augmenting the breakdown of adenosine-an influential inhibitor of T cell proliferation. However, the discovery of a wide range of DPP4 inhibitors has shown promise in alleviating these diseases' signs, symptoms, and severity. The available DPP4 inhibitors have demonstrated significant effectiveness in blocking DPP4 activity. Based on the characterization of their binding mechanisms, three distinct groups of DPP4 inhibitors have been identified: saxagliptin, alogliptin, and sitagliptin, each representing a different class. Elevated levels of angiotensin-converting enzyme 2 (ACE2) expression are associated with producing various coronavirus peptidases. With its anti-inflammatory properties, Sitagliptin may assist COVID-19 patients in preventing and managing cytokine storms. This comprehensive review delves into the burgeoning realm of DPP4 inhibitors as therapeutic interventions for diverse autoimmune diseases. With a discerning focus on their efficacy, the investigation sheds light on their remarkable capacity to alleviate the burdensome signs and symptoms intricately linked to these conditions.

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.

A Review of Dipeptidyl Peptidase-4 (DPP-4) and its potential synthetic derivatives in the management of Diabetes Mellitus

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a type of oral medication used to treat type 2 diabetes mellitus (T2DM). They have become increasingly popular due to their effectiveness and safety in managing the condition. DPP-4 inhibitors function by inhibiting the enzyme that breaks down the incretin hormones, namely glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). These medicines efficiently raise the levels of active GLP-1 and GIP by blocking DPP-4 activity. As a result, there is an increase in the production of insulin, a decrease in the release of glucagon, and a lowering of glucose levels after a meal. Multiple clinical trials have conclusively shown that DPP-4 inhibitors effectively lower glycated hemoglobin (HbA1c) levels. Certain studies have even proved their equivalent efficacy to other anti-diabetic medications such as metformin or sulfonylureas. Furthermore, DPP-4 inhibitors possess the benefit of being weight-neutral and exhibiting a little risk of hypoglycemia. These qualities render them a compelling option for patients with type 2 diabetes mellitus who are overweight or susceptible to hypoglycemia episodes. In general, DPP-4 inhibitors are a promising therapeutic choice for the management of type 2 diabetes mellitus (T2DM), offering effective regulation of blood sugar levels with a minimal likelihood of adverse effects. Nevertheless, it is important to acknowledge some restrictions and factors to take into account, including the possibility of heightened susceptibility to pancreatitis, nasopharyngitis, and certain drug-drug combinations. Additional investigation is necessary to completely clarify the long-term safety and potential supplementary advantages of DPP-4 inhibitors.

Research Progress on the Effect and Mechanism of Tea Products with Different Fermentation Degrees in Regulating Type 2 Diabetes Mellitus.

A popular non-alcoholic beverage worldwide, tea can regulate blood glucose levels, lipid levels, and blood pressure, and may even prevent type 2 diabetes mellitus (T2DM). Different tea fermentation levels impact these effects. Tea products with different fermentation degrees containing different functional ingredients can lower post-meal blood glucose levels and may prevent T2DM. There are seven critical factors that shed light on how teas with different fermentation levels affect blood glucose regulation in humans. These factors include the inhibition of digestive enzymes, enhancement of cellular glucose uptake, suppression of gluconeogenesis-related enzymes, reduction in the formation of advanced glycation end products (AGEs), inhibition of dipeptidyl peptidase-4 (DPP-4) activity, modulation of gut flora, and the alleviation of inflammation associated with oxidative stress. Fermented teas can be used to lower post-meal blood glucose levels and can help consumers make more informed tea selections.

Study on the Mechanism of Interaction between Dipeptidyl Peptidase 4 and Inhibitory Peptides Based on Gaussian Accelerated Molecular Dynamic Simulation.

Dipeptidyl peptidase 4 (DPP4) inhibitors can effectively inhibit the activity of DPP4, increasing the concentrations of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which allows for them to effectively contribute to the reduction of blood sugar levels. Leu-Pro-Ala-Val-Thr-Ile-Arg (LPAVTIR) and Leu-Pro-Pro-Glu-His-Asp-Trp-Arg (LPPEHDWR) were the two peptides with the strongest inhibitory activity against DPP4 selected from silkworm pupa proteins. In this study, four systems were established: Apo (ligand-free DPP4), IPI (IPI-bound DPP4), LPAVTIR (LPAVTIR-bound DPP4), LPPEHDWR (LPPEHDWR-bound DPP4), and Gaussian accelerated molecular dynamic (GaMD) simulation was conducted to investigate the mechanism of action of two inhibitory peptides binding to DPP4. Our study revealed that the LPAVTIR peptide possessed a more stable structure and exhibited a tighter binding to the Ser630 active site in DPP4, thus exhibiting a favorable competitive inhibition effect. In contrast, the LPPEHDWR peptide caused the horizontal α-helix (residues 201-215) composed of Glu205 and Glu206 residues in DPP4 to disappear. The spatial arrangement of active sites Ser630 relative to Glu205 and Glu206 was disrupted, resulting in enzyme inactivation. Moreover, the size of the substrate channel and cavity volume was significantly reduced after the binding of the inhibitory peptide to the protein, which was an important factor in the inhibition of the enzyme activity. A similar effect was also found from IPI (our positive control). By stabilizing the active site of DPP4, the IPI peptide induced the disappearance of the horizontal α-helix and a notable reduction in the active cavity volume. In conclusion, our study provided a solid theoretical foundation for the inhibitory mechanisms of IPI, LPAVTIR, and LPPEHDWR on DPP4, offering valuable insights for advancing the development of drug targets for type 2 diabetes.

DPP-4 inhibition by linagliptin ameliorates age-related mild cognitive impairment by regulating microglia polarization in mice

Extensive preclinical evidence demonstrates a causative link between insulin signaling dysfunction and the pathogenesis of Alzheimer's disease (AD), and diabetic drugs may represent a promising approach to fighting AD. However, it remains to be determined which antidiabetic drugs are more effective in preventing cognitive impairment. Thus, the present study investigated the effect of dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin on cognitive impairment in middle-aged mice by comparing it with the effect of metformin. We found that DPP-4 activity increased in the hippocampus of middle-aged mice, and DPP-4 was mainly expressed by microglia rather than astrocytes and oligodendrocytes. DPP-4 directly regulated M1/M2 microglia polarization following LPS or IL-4 stimulation, while DPP-4 inhibitor, linagliptin, suppressed M1-polarized activation and induced M2-polarized activation. Both linagliptin and metformin enhanced cognitive ability, increased hippocampal synaptic plasticity and neurogenesis, and decreased age-related oxidative stress and inflammation by regulating microglia polarization in the hippocampus of middle-aged mice. The combination of linagliptin and metformin showed a maximum protective effect compared to the individual drugs alone. Loss of macrophage inflammatory protein-1α (MIP-1α), a DPP-4 substrate, abrogated the cognitive protection and anti-inflammation effects of linagliptin. Therefore, the current investigation exhibits a potential utility for DPP-4 inhibition in attenuating microglia-mediated inflammation and preventing mild cognitive impairment (MCI) in middle-aged mice, and the effect was partly mediated by MIP-1α.

Decreased circulating dipeptidyl peptidase-4 activity after short-term intensive insulin therapy predicts clinical outcomes in patients with newly diagnosed type 2 diabetes.

This study aims to investigate the changes in circulating dipeptidyl peptidase-4 (DPP-4) activity following short-term intensive insulin therapy (SIIT) in newly diagnosed type 2 diabetes (T2D) patients and to assess its potential in predicting long-term remission. Ninety-five patients underwent SIIT for 2-3 weeks to attain and sustain near-normal glycemia. Insulin was then discontinued, and patients were followed for a year to evaluate glycemic outcomes. Biochemical tests, serum DPP-4 activity, and mixed meal tolerance tests were conducted at baseline, post-SIIT, and the 3-month follow-up. DPP-4 activity decreased from 44.08 ± 9.58 to 40.53 ± 8.83 nmol/min/mL after SIIT (P<0.001). After three months post-SIIT, DPP-4 activity remained stable in the remission group (39.63 ± 8.53 nmol/L) but increased in the non-remission group (42.34 ± 6.64 nmol/L). This resulted in a more pronounced decrease in DPP-4 activity from baseline in the remission group (-3.39 ± 8.90 vs.-1.10 ± 8.95, P = 0.035). Logistic regression analyses showed that patients with greater DPP-4 activity reduction had a higher likelihood of 1-year remission (70% vs. 51.1%, OR: 7.939 [1.829, 34.467], P = 0.006 in the fully adjusted model). A non-linear relationship between △DPP-4 and 1-year remission rate was observed, with a clear threshold and saturation effect. Circulating DPP-4 activity significantly decreases after SIIT. The change in circulating DPP-4 activity during the 3-month post-treatment phase has the potential to predict long-term remission.

Increased Thyroid DPP4 Expression Is Associated With Inflammatory Process in Patients With Hashimoto Thyroiditis.

Dipeptidyl peptidase-4 (DPP4) is originally described as a surface protein in lymphocytes. Lymphocyte infiltration and subsequent destruction of thyroid tissue have been considered as the central pathological mechanism in Hashimoto thyroiditis (HT). The present study aimed to investigate DPP4 expression in peripheral blood and thyroid tissue in HT patients, and explore the role of DPP4 in the pathophysiological process of HT. This case-control study recruited 40 drug-naive HT patients and 81 control individuals. Peripheral blood and thyroid specimens were collected for assessing the expression and activity of DPP4. Moreover, single-cell RNA sequencing (scRNA-seq) analysis of 6 "para-tumor tissues" samples from scRNA-seq data set GSE184362 and in vitro cell experiments were also conducted. The HT patients had similar DPP4 serum concentration and activity as the controls. However, the expression and activity of DPP4 was significantly increased in the thyroid of the HT group than in the control group. The scRNA-seq analysis showed that DPP4 expression was significantly increased in the HT group, and mainly expressed in T cells. Further in vitro studies showed that inhibition of lymphocyte DPP4 activity with sitagliptin downregulated the production of inflammatory factors in co-cultured thyroid cells. DPP4 expression was significantly increased in the thyroid of the HT group compared with the control group, and was mainly localized in the lymphocytes. Inhibition of lymphocyte DPP4 activity reduced the production of inflammatory factors in co-cultured thyroid cells. Therefore, inhibition of DPP4 may have a beneficial effect by alleviating inflammatory reactions in HT patients.

CHARACTERISTICS OF SOME ENZYMES IN BLOOD PLASMA OF DIABETIC HUMANS

Тhe enzymes adenosine deaminase (ADA), dipeptidyl peptidase 4 (DPP4) and glutaminase (GL) are involved in the development of both the type 1 (T1DM) and type 2 diabetes mellitus (T2DM). They can be considered as targets in the prevention and/or treatment of these diseases. The autoimmune response of the body is caused by the post-translational protein modifications, one of which is protein citrullination, when arginine residue transforms to citrulline. This work compares the ADA, DPP4, GL enzymes and protein citrullination in blood plasma from T1DM, T2DM patients and relatively healthy individuals. The enzymes were isolated and purified from the blood samples. We found that DPP4 activity was significantly higher in the plasma of patients compared to controls, particularly in T1DM. Currently the medicines based on DPP4 inhibitors are used in the treatment of T2DM. Our results indicate that this treatment strategy can be recommended in the T1DM treatment as well.

Effects of Dipeptidyl Peptidase-4 Inhibitor and Angiotensin-Converting Enzyme Inhibitor on Experimental Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease in the United States and worldwide. Proteinuria is a major marker of the severity of injury. Dipeptidyl peptidase-4 inhibitor (DPP-4I) increases incretin-related insulin production and is, therefore, used to treat diabetes. We investigated whether DPP4I could have direct effect on kidney independent of its hypoglycemic activity. We, therefore, tested the effects of DPP4I with or without angiotensin-converting enzyme inhibitor (ACEI) on the progression of diabetic nephropathy and albuminuria in a murine model of DKD. eNOS−/−db/db mice were randomized to the following groups at age 10 weeks and treated until sacrifice: baseline (sacrificed at week 10), untreated control, ACEI, DPP4I, and combination of DPP4I and ACEI (Combo, sacrificed at week 18). Systemic parameters and urine albumin–creatinine ratio were assessed at baseline, weeks 14, and 18. Kidney morphology, glomerular filtration rate (GFR), WT-1, a marker for differentiated podocytes, podoplanin, a marker of foot process integrity, glomerular collagen IV, and alpha-smooth muscle actin were assessed at the end of the study. All mice had hyperglycemia and proteinuria at study entry at week 10. Untreated control mice had increased albuminuria, progression of glomerular injury, and reduced GFR at week 18 compared with baseline. DPP4I alone reduced blood glucose and kidney DPP-4 activity but failed to protect against kidney injury compared with untreated control. ACEI alone and combination groups showed significantly reduced albuminuria and glomerular injury, and maintained GFR and WT-1+ cells. Only the combination group had significantly less glomerular collagen IV deposition and more podoplanin preservation than the untreated control. DPP-4I alone does not decrease the progression of kidney injury in the eNOS−/−db/db mouse model, suggesting that targeting only hyperglycemia is not an optimal treatment strategy for DKD. Combined DPP-4I with ACEI added more benefit to reducing the glomerular matrix.

Structure-based molecular docking and molecular dynamics simulations study for the identification of dipeptidyl peptidase 4 inhibitors in type 2 diabetes

Inhibition of dipeptidyl peptidase-4 (DPP4) activity has emerged as a promising therapeutic approach for the treatment of type 2 diabetes mellitus (T2DM). Bioinformatics-driven approaches have emerged as crucial tools in drug discovery. Molecular docking and molecular dynamics (MD) simulations are effective tools in drug discovery, as they reduce the time and cost associated with experimental screening. In this study, we employed structure-assisted in-silico methods, including molecular docking and MD simulations, to identify SRT2183, a small molecule that may potentially inhibit the activity of DPP4 enzyme. The interaction between the small molecule "SRT2183" and DPP4 exhibited a binding affinity of −9.9 Kcal/Mol, leading to the formation of hydrogen bonds with the amino acid residues MET348, SER376, and THR351 of DPP4. The MD simulations over a period of 100 ns indicated stable protein-ligand interactions, with no significant conformational rearrangements observed within the simulated timeframe. In conclusion, our results suggest that the small molecule SRT2183 may have the potential to inhibit the DPP4 enzyme and pave the way for the therapeutics of T2DM. Communicated by Ramaswamy H. Sarma

Diabetic individuals with COVID-19 exhibit reduced efficacy of gliptins in inhibiting dipeptidyl peptidase 4 (DPP4). A suggested explanation for increased COVID-19 susceptibility in patients with type 2 diabetes mellitus (T2DM)

AimsDipeptidyl peptidase 4 (DPP4) has been proposed as a coreceptor for SARS-CoV-2 cellular entry. Considering that type 2 diabetes mellitus (T2DM) has been identified as the most important risk factor for SARS-CoV-2, and that gliptins (DPP4 inhibitors) are a prescribed diabetic treatment, this study aims to unravel the impact of DPP4 in the intersection of T2DM/COVID-19. Materials and methodsWe analyzed 189 serum human samples, divided into six clinical groups (controls, T2DM, T2DM + gliptins, COVID-19, COVID-19 + T2DM, and COVID-19 + T2DM + gliptins), measuring DPP4 protein concentration and activity by Western blot, ELISA, and commercial activity kits. The obtained results were verified in Huh-7 cellular models. Key findingsBoth DPP4 concentration and activity were decreased in COVID-19 patients, and as in T2DM patients, compared to controls. Despite these lower levels, the ratio of DPP4 activity/concentration in COVID-19 sera was the highest (0.782 ± 0.289 μU/ng vs. 0.547 ± 0.050 μU/ng in controls, p < 0.0001), suggesting a compensating mechanism in these patients. Supernatants of Huh-7 cells incubated with COVID-19 serum showed a consistent and significantly lower DPP4 concentration and activity. Furthermore, COVID-19 + T2DM + gliptins patients showed a higher serum DPP4 concentration and activity than T2DM + gliptin subjects (p < 0.05), indicating that sera from COVID-19 convalescents interfere with gliptins. SignificanceEither SARS-CoV-2 or some metabolites present in the sera of COVID-19-convalescent patients interact with soluble DPP4 or even gliptins themselves since the inhibitory effect of gliptins on DPP4 activity is being prevented. The interactions between DPP4, gliptins, and SARS-CoV-2 should be further elucidated to reveal the mechanism of action for these interesting observations.

A Multicenter, Randomized, Double-Blind, Placebo-Controlled, and Dose-Increasing Study on the Safety, Tolerability and PK/PD of Multiple Doses of HSK7653 by Oral Administration in Patients with Type 2 Diabetes Mellitus in China.

This study assessed the safety, tolerability, and PK/PD of HSK7653 tablets in Chinese patients with type 2 diabetes mellitus (T2DM). This was a Phase IIa, multicenter, randomized, double-blind, placebo-controlled, and dose-increasing study with 48 Chinese diabetes patients. Subjects were randomly assigned to placebo and 10/25/50mg dose groups, and they received oral administration once every two weeks for a total of six times. Safety and tolerability were assessed throughout this study, and PK/PD parameters were analyzed using non-compartment model with WinNonlin. The three doses of HSK7653 were well tolerated, and the incidence of TEAE and ADR was not significantly increased compared with the placebo group. Cmax increased linearly with the increasing dose, and the mean t1/2 was 64.0-87.0h. The first dose and last dose PK parameters were similar. After oral administration of 10-50mg HSK7653 every two weeks, the average Rac_Cmax and Rac_AUC were 0.9-1.0 and 1.0-1.1 respectively; therefore, HSK7653 was not accumulated in vivo. All three doses significantly inhibited DPP-4 activity and increased plasma GLP-1 level and serum insulin levels. When the plasma concentration of HSK7653 was ≥ 20.0ng/mL, the DPP-4 inhibition rate in all subjects was maintained at > 80.0%. In 10 and 25mg dose groups, the HbA1c levels maintained a downward trend compared with the placebo group. HSK7653 showed desirable pharmacokinetic and pharmacodynamic properties with good safety and tolerability in Chinese T2DM patients. DPP-4 inhibition rate and plasma GLP-1 levels were higher in each dose group than in placebo group. CTR20182505 (Drug Clinical Trial Registration and Information Disclosure Platform, www.chinadrugtrials.org.cn ).

Differential Modulation of Saliva-Derived Microcosm Biofilms by Antimicrobial Peptide LL-31 and D-LL-31.

Microbiome modulation, aiming to restore a health-compatible microbiota, is a novel strategy to treat periodontitis. This study evaluated the modulation effects of antimicrobial peptide LL-31 and its D-enantiomer (D-LL-31) on saliva-derived microcosm biofilms, spiked with or without Porphyromonas gingivalis. To this end, one-day-old biofilms were incubated for 24 h with biofilm medium alone, or medium containing 40 µM LL-31 or D-LL-31, after which biofilms were grown for 5 days. Biofilms were assessed at 1 day and 5 days after intervention for the total viable cell counts, dipeptidyl peptidase IV (DPP4) activity, P. gingivalis amount (by qPCR) and microbial composition (by sequencing). The results showed that D-LL-31, not LL-31, significantly reduced the total viable cell counts, the P. gingivalis amount, and the DPP4 activity of the biofilms spiked with P. gingivalis, but only at 1 day after intervention. In the biofilms spiked with P. gingivalis, D-LL-31 tended to reduce the α-diversity and the compositional shift of the biofilms in time as compared to the control and LL-31 groups. In conclusion, D-LL-31 showed a better performance than LL-31 in biofilm modulation. The biofilm modulation function of the peptides could be impaired when the biofilms were in a severely dysbiotic state.