Dipeptidyl Peptidase Research Articles

Exploring dipeptidyl peptidase-IV inhibitory peptides from Tartary Buckwheat protein: A study of hydrolysis, fractionation, and molecular interactions.

Tartary buckwheat, a protein-rich pseudocereal with anti-diabetic effects, has not yet been fully explored as a source of dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides. This study aims to discover novel DPP-IV inhibitory peptides from tartary buckwheat protein (TBP). Five hydrolysis methods were employed, with simulated gastrointestinal digestion (SGID) releasing the most active DPP-IV inhibitory hydrolysates, showing both the highest degree of hydrolysis (22.66±1.12%) and inhibition activity (41.81±1.52% at 1.25mg/mL). In addition, ultrafiltration enriched the<3 kDa fraction with the highest inhibitory rate, and further purification using reverse-phase high-performance liquid chromatography concentrated the DPP-IV inhibitory peptides in the first fraction (F1). Nano liquid chromatography-tandem mass spectrometry analysis identified 10 new peptides in F1, among which the peptide Leu-His-Ile-Val-Gly-Pro-Asp-Lys (LHIVGPDK) exhibited the strongest inhibitory effect, with an IC50 value of 1.61mM. Kinetic studies revealed that LHIVGPDK acts as a mixed-type inhibitor, and molecular docking indicated that it inhibits DPP-IV by forming stable complexes through five types of interactions, with hydrogen bonds playing a key role. This study underscores TBP's DPP-IV inhibitory potential and anti-diabetic properties, reinforcing the value of tartary buckwheat as a beneficial food for diabetes management. PRACTICAL APPLICATION: This research identified new peptides from Tartary buckwheat protein that effectively inhibit DPP-IV, an enzyme associated with diabetes management. These findings suggest potential applications in developing functional foods to help control hypoglycemia.

Methionine and vitamin E supplementation improve production performance, antioxidant potential, and liver health in aged laying hens

Sulfur metabolites of methionine (Met) and vitamin E (VE) have antioxidant potential and can maintain liver health in chickens. This study explored the underlying mechanisms of Met sources, the ratio of total sulfur amino acids to lysine (TSAA: Lys), and VE levels on production performances, antioxidant potential, and hepatic oxidation in aged laying hens. Eight hundred and sixty-four, Hy-Line Brown laying hens (70-week age) were divided into 12 treatment groups, each having 6 repeats and 12 birds/each repeat. The dietary treatments consisted of DL-Met (DL-Met), DL-2-hydroxy-4-(methylthio)-butanoic acid (OH-Met), 3 ratios of TSAA: Lys (0.90, 0.95, and 1.00), and 2 levels of VE (20 and 40 g/ton). Albumen height and Haugh unit significantly increased at a lower level of VE (P < 0.05). Triglycerides (TG), total cholesterol (TC), low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) in serum and superoxide dismutase (SOD) and catalase activities (CAT) in the liver significantly reduced at 0.95 TSAA: Lys ratio (P < 0.05). Fatty acid synthase (FAS), lipoprotein lipase (LPL), nuclear factor erythroid 2-related factor 2 (Nrf2), and carnitine palmitoyltransferase-1 alpha (CPT-1α) also upregulated at this TSAA: Lys ratio (P < 0.05). Compared with the DL-Met group, the OH-Met group had lower Dipeptidyl Peptidase 4 (DPP4) and higher TC, LDL, and VLDL concentrations (P < 0.05).The expression of FAS,CPT-1α), glutathione (GSH), glutathione disulfide (GSSG), glutathione synthetase (GSS), and Nrf2 were significantly higher in OH-Met compared with the DL-Met group (P < 0.05). OH-Met at 0.95 and DL-Met at 0.90 TSAA: Lys ratio showed higher CAT and lower aspartate aminotransferase (AST) activities. Moreover, OH-Met at 0.90 and DL-Met at 0.95 of the TSAA: Lys ratio had a significant reduction of malondialdehyde (MDA) (P < 0.05). Overall, these results suggest that OH-Met source with a lower level of VE positively influenced production performance and improved liver health in aged laying hens through improved lipid metabolism and hepatic antioxidant function.

Pharmacological PTP1B inhibition rescues motor learning, neuroinflammation, and hyperglycaemia in a mouse model of Alzheimer's disease.

Patients with Alzheimer's Disease (AD) frequently suffer from comorbidities such as type 2 diabetes mellitus (T2DM), accompanied by shared common pathologies such as increased inflammation and impaired glucose homeostasis. Beta-secretase 1 (BACE1), the rate limiting enzyme in AD associated beta-amyloid (Aβ) production, is also implicated in metabolic dysfunction and can increase central and peripheral protein levels of protein tyrosine phosphatase 1B (PTP1B). PTP1B is a validated target in diabetes and obesity, and is a neuroinflammatory regulator involved in degenerative processes. This study investigated the effects of the PTP1B inhibitor, trodusquemine (MSI-1436) on the cognitive and metabolic phenotypes of the neuronal human BACE1 knock-in (PLB4) mouse, a co-morbidity model of AD and T2DM, and their wild-type (PLBWT) controls. Five-month-old male PLB4 and PLBWT mice received PTP1B inhibitor treatment (1mg/kg intraperitoneal injection; 5weeks). Activity and spatial habituation (Phenotyper), motor learning (RotaRod), glucose tolerance, and brain and liver molecular analyses were analysed following treatment. Inhibition of PTP1B improved motor learning alongside glucose tolerance in PLB4 mice, without affecting body weight/adiposity. MSI-1436 treatment led to lower protein levels of amyloid precursor protein (APP), reduced astrogliosis and restoration of the endoplasmic chaperone immunoglobulin heavy chain binding protein (BIP) in the brain, alongside decreased insulin receptor substrate-1 (IRS1) and dipeptidyl peptidase-4 (DPP4) proteins in the liver. We provide evidence that neuronal BACE1 contributes to neuroinflammation and hyperglycaemia in PLB4 mice, and this can be partially rescued by PTP1B inhibition. Targeting PTP1B may therefore offer an attractive therapeutic approach to ameliorate co-morbidity associated pathologies in AD and T2DM.

Effect of Dipeptidyl Peptidase-4 Inhibitors on Renal Outcome in Diabetes Mellitus: A Systematic Review and Meta-analysis

Diabetic nephropathy is a common microvascular consequence, described by a persistent rise in albuminuria or a considerable fall in the predictable estimated glomerular filtration rate (eGFR). Dipeptidyl peptidase-4 (DPP- 4) inhibitors are frequently utilized to treat diabetes mellitus (DM), although it’s unclear how significant these drugs are in terms of specific renal outcomes (RO). This study aims to determine the impact of DPP-4 inhibitors (DPP4-I) on renal consequences in individuals with DM. The relevant studies were searched in PubMed, Google Scholar, and SciHub, and then filtered concurring to the exclusion and inclusion criteria. The preferred reporting item for systematic reviews and meta-analysis criteria were adhered to, and the extracted data were evaluated using the RevMan software. A 95% confidence interval (CI) was calculated in addition to the overall estimate measure. I-squared (I2) statistics were used to assess the studies’ heterogeneity. The qualitative evaluations of publication bias were done using the funnel plot. Ten randomized controlled studies with a total of 39,124 people were eligible for the investigation. At 24 weeks, eGFR in DM patients was not substantially affected by the DPP4-I (mean differences [MD] 4.31; 95% CI −4.93, 13.54; P &lt; 0.00001, heterogeneity I2 = 95%; P = 0.36). Further at 52 weeks also, the changes in eGFR were found non-significant (MD 0.24 [−1.68, 2.16]) as compared to the control group (CG). The changes in urine albumin-creatinine ratio were also found non-significant as compared to the CG. The adverse events in the DPP4-I groups were also found non-significant as compared to the CG which indicates the safety of DPP4-I. Overall, more randomized clinical trials are required to confirm the exact role of DPP4-I on RO in DM.

DiSi Survey: Use of Generic DPP4i-SGLT2i Fixed-dose Combinations in Indian Clinical Practice.

India has a high burden of patients with diabetes mellitus (DM). Challenges to managing type 2 diabetes (T2DM) in India are unique. Indian T2DM patients do not just present with DM alone, but with clustering of cardiovascular (CV) risk factors like hypertension (HTN), dyslipidemia, and obesity. Furthermore, Indian patients also have lesser baseline beta-cell function compared to global reference populations. In India, various cost-effective, generic, fixed-dose combinations (FDC) of dipeptidyl peptidase 4 inhibitors (DPP4i) with sodium-glucose cotransporter 2 inhibitors (SGLT2i) are available for the management of T2DM. However, to the best of our knowledge, scant surveys have studied the clinical practice nuances regarding the use of these FDCs in Indian settings. Hence, we designed and conducted a knowledge, attitude, and practice (KAP) survey to study the attitude and practice of Indian physicians with regard to patient population and placement of generic DPP4i-SGLT2i FDCs. Our survey showed that in India, patients often present with a high baseline HbA1c. From a glycaemic control perspective, DPP4i-SGLT2i FDCs are preferred in treatment-naïve patients with HbA1c >8% and those with HbA1c >8.5% despite metformin monotherapy. Also, 85% physicians observed a reduction in SGLT2i associated GUTIs with use of DPP4i-SGLT2i FDCs or concomitant use of these agents. Part of these survey findings were presented at the American Diabetes Association (ADA) 2024 Congress held in Orlando, Florida.

Alogliptin attenuates STZ-induced diabetic nephropathy in rats through the modulation of autophagy, apoptosis, and inflammation pathways: Targeting NF-κB and AMPK/mTOR pathway.

Diabetic nephropathy (DN) is a type of microvascular complication that arises from diabetes mellitus and leads to further health issues. Most importantly, the prevalence of DN is steadily rising in developed countries. This research explored the therapeutic benefits of alogliptin, a dipeptidyl peptidase IV (DPP-4) inhibitor, on streptozotocin (STZ)-induced DN and its underlying mechanisms in rats. Ten rats were allocated to group 1, served as the normal group; and received saline. To develop diabetes, thirty rats were administered a single intraperitoneal dose of STZ (45mg/kg). STZ-induced diabetic rats were randomly assigned to three groups: group 2 diabetic control; was given saline, groups 3 and 4 received alogliptin (10mg/kg) and (20mg/kg), respectively. The treatment began 8weeks after diabetes onset and continued for four weeks. Histopathological alterations in the kidney were detected. Serum was collected to measure blood glucose levels (BGL), renal function, and lactate dehydrogenase (LDH). Tissue samples were collected to detect changes in oxidative stress (OS), inflammation, 5' adenosine monophosphate-activated protein kinase (AMPK), and the mammalian target of Rapamycin (mTOR) signaling pathways in addition to apoptotic and autophagy changes. Alogliptin reduced STZ-induced histological changes in the kidney as well as OS, and inflammation. Alogliptin also ameliorated the AMPK/mTOR signaling pathways, enhanced autophagy, and reduced apoptosis. These results demonstrate that alogliptin ameliorates inflammation and OS and consequently modulates the AMPK/mTOR axis along with targeting autophagy and apoptosis, leading to the alleviation of DN.

Sitagliptin eye drops prevent the impairment of retinal neurovascular unit in the new Trpv2+/− rat model

Impaired function of the retinal neurovascular unit (NVU) is an early event in diabetic retinopathy (DR). It has been previously shown that topical delivery of the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin can protect against diabetes-mediated dysfunction of the retinal NVU in the db/db mouse. The aim of the present study was to examine whether sitagliptin could prevent the DR-like lesions within the NVU of the new non-diabetic model of DR, the Trpv2 knockout rat (Trpv2+/−). For that purpose, at 3 months of age, Trpv2+/− rats were topically treated twice daily for two weeks with sitagliptin or PBS-vehicle eyedrops. Trpv2+/+ rats treated with vehicle served as the control group. Body weight and glycemia were monitored. Optical coherence tomography recordings, fundus images and retinal samples were obtained to evaluate sitagliptin effects. The results revealed that sitagliptin eye drops had no effect on body weight or glycemia. Vehicle-treated Trpv2+/− rats exhibited retinal thinning and larger diameters of major retinal blood vessels, upregulation of inflammatory factors and oxidative markers, glial activation and formation of acellular capillaries. However, topical administration of sitagliptin significantly prevented all these abnormalities. In conclusion, sitagliptin eye drops exert a protective effect against DR-like lesions in Trpv2+/− rats. Our results suggest that sitagliptin eye drops carry significant potential to treat not only early-stages of DR but also other diseases with impairment of the NVU unrelated to diabetes.

QbD - A novel approach for design, optimization and evaluation of sitagliptin mucoadhesive microspheres

Quality by Design (QbD) represents a highly systematic approach implementing the Design of Experiment (DoE) for finding the optimal product and process characteristics. Sitagliptin (SIT), a potent and selective dipeptidyl peptidase (DPP) IV inhibitor. Typically, it improves the glycaemic control by increasing the active level of incretin peptides particularly glucagon like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide. A response surface CCD studied by using Design Expert Stat-Ease software. The study includes two factors (independent variable) viz., Sodium alginate (SA) (X1), Carbopol (CA) (X2 ), 2 levels (-1, +1), three response (dependent variables) viz., Particle size (Y1), % EE (Y2), t50 (Y3), 13 runs with 5 center point. The design trials of SIT loaded mucoadhesive microspheres (SIT-MS) were fabricated by ionotropic gelation method. The SIT-MS were characterized for design response and further CCD was applied for studying the influence of factors on response. The optimized formulas generated as per CCD was formulated, characterized and validated with predicted values. FTIR studies showed no interaction between drug and polymers. ANOVA suggest that few model terms are significant (p &lt; 0.05) suggest significant first order linear and quadratic model. The R2 values suggest significant correlation between the factors and response. The quadratic polynomial equations suggest linear and quadratic terms influence on stated response and justified by 2D contour, 3D surface plot. The experimental values of optimized formulations ratified with predicted values. The QbD through CCD results concludes that DoE can be carried out successfully for formulation, characterization and optimization of SIT-MS.

In Silico Molecular Dynamics and 3D‐QSAR Study on Thiazolidinedione Derivatives as Dual Inhibitors of DPP IV and PTP1B (DDPI's) for the Management of T2DM

AbstractSimultaneous inhibition of dipeptidyl peptidase IV and protein tyrosine phosphatase 1B as DDPI's emerged as a therapeutic intervention for the management of T2DM. In the present study, we have employed molecular dynamics simulation in conjugation with the field‐based 3D QSAR studies on a dataset having DDPI activities to identify the spatial fingerprints of target‐specific thiazolidinedione analogs. Separate contours were generated for both DPP IV and PTP1B showing respective pharmacophoric structural requirements for optimal inhibitory activity. These developed 3D QSAR models also showed good statistical measures (DPP IV: r2 = 0.9468; q2 = 0.7173, and PTP1B: r2 = 0.9718; q2 = 0.819) with the excellent predictive ability with PLS‐generated validation constraints. Comparative steric and electrostatic features were elucidated using respective contour maps for selective target‐specific favorable activity. Furthermore, molecular docking was used for elucidating the mode of binding as DDPI's to DPP IV and PTP1B, along with MD simulation (200 ns) analysis such as RMSD, RMSF, Rg, SASA, PCA, and FEL. These studies revealed that all the protein‐ligand docked complexes elicited an overall better stability as compared to reference ligand (vildagliptin or ertiprotafib) complexes. Molecular docking studies revealed that compound 24 (DPP IV: −150.667 kcal/mol; PTP1B: −142.792 kcal/mol) showed maximum affinity toward both the proteins DPP IV and PTP1B, as compared to their respective standard inhibitor, i.e., vildagliptin −99.9843 kcal/mol and ertiprotafib −125.399 kcal/mol, respectively. A comparative study of these developed multitargeted QSAR models along with molecular docking and dynamics study were employed for the optimization of drug candidates as DDPI's. Compound 24 showed most stable behavior in the binding pockets of both the enzymes, as compared to their respective standard inhibitors. This study will be helpful in designing novel DDPIs with appropriately substitute thiazolidinedione for the management of T2DM. The designed compound YSR‐14 exhibited the predicted IC50 values of 0.143 µM in DPP IV and 0.158 µM in PTP1B along with their excellent binding affinity against both targets.

In Silico Hydrolysis of Lupin (Lupinus angustifolius L.) Conglutins with Plant Proteases Releases Antihypertensive and Antidiabetic Peptides That Are Bioavailable, Non-Toxic, and Gastrointestinal Digestion Stable.

Lupin (Lupinus angustifolius L.) proteins are potential sources of bioactive peptides (LBPs) that can inhibit dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE-I) activity. However, the capacity of different enzymes to release LBPs, the pharmacokinetic and bioactivities of the peptides released, and their binding affinities with the active sites of DPP-IV and ECA-I are topics scarcely addressed. Therefore, we used in silico hydrolysis (BIOPEP-UWM platform) with various enzymes to predict the release of LBPs. Among the bioactive peptides identified in lupin proteins (n = 4813), 2062 and 1558 had DPP-IV and ACE-I inhibitory activity, respectively. Ficin, bromelain, and papain released the highest proportion of ACE-I (n = 433, 411, and 379, respectively) and DPP-IV (n = 556, 544, and 596, respectively) inhibitory peptides. LBPs with favorable pharmacokinetics and gastrointestinal stability tightly interacted with the active sites of ACE-I (-5.6 to -8.9 kcal/mol) and DPP-IV (-5.4 to -7.6 kcal/mol). Papain generated the most bioavailable LBPs (n = 459) with ACE-I (n = 223) and DPP-IV (n = 412) inhibitory activity. These peptides were non-toxic and gastrointestinal digestion stable. Notably, papain-based hydrolysis released some LBPs (n = 270) that inhibited both ACE-I and DPP-IV. Plant protease-based hydrolysis is a promising approach for producing lupin hydrolysates with ACE-I and DPP-IV inhibitory activities.

Association of Gut Microbiome and Dipeptidyl Peptidase 4 in Immune-Mediated Inflammatory Bowel Disease: A Rapid Literature Review.

Immune-mediated inflammatory diseases (IMIDs) are characterized by dysregulated immune responses and chronic tissue inflammation. In the setting of inflammatory bowel disease (IBD), dipeptidyl peptidase 4 (DPP4) and gut microorganisms have been proved to interplay, potentially influenced by dietary factors. This rapid review aimed to study the DPP4-gut microbiome link in IBD. A search across five databases and two gray literature sources identified seven relevant studies reporting data on DPP4 and gut microbiome in patients with IBD-related IMIDs or in vitro or in vivo models: one cross-sectional, one in vitro, and five in vivo studies. The findings revealed a significant impact of DPP4 and its substrates, i.e., glucagon-like peptide-1/2 (GLP-1/2), on the composition of gut microbiome and on the development of dysbiosis. Increased DPP4 activity is associated with decreased GLP-1/2; increased pathogenic bacterial phyla such as Actinobacteria, Bacteroidetes, Deferribacteres, Firmicutes, Fusobacteriota, Proteobacteria, and Verrucomicrobia; and decreased alpha diversity of beneficial gut microbes, including Clostridiaceae, Lachnospiraceae, and Ruminococcaceae families and short-chain fatty acid-producing bacteria like Odoribacter and Butryvibrio spp., with exacerbation of intestinal inflammation. This overview revealed that understanding the DPP4-gut microbiome association is critical for the development of DPP4-targeted therapeutic strategies to guarantee gut microbiome balance and modulation of immune response in IBD.

Synthesis and Evaluation of Antidiabetic Potential of Gliptin-based Hybrid Scaffolds.

Dipeptidyl peptidase-4 (DPP4) inhibitors are promising therapeutic targets for the treatment of a catastrophic disease, especially diabetes mellitus (DM), which contributed to a massive rate of mortality. This research work succinctly covers the significance and vital role of gliptins in diabetes management and in the potential areas of further antidiabetic research, making it a strong drug candidate for antidiabetic drug development. We illustrated herein molecular docking, synthesis, and biological evaluation of selected potent synthesized molecules. Additionally, all the potent compounds were characterized by means of MASS and NMR spectral analysis, whereas the purity of these molecules were assessed by HPLC method. In order to determine the efficacy and cytotoxicity of synthesized gliptin-based scaffolds, in-vitro anti-oxidant and MTT assays with the implantation of DPPH and THP-1 cell lines, respectively, were performed. The results data disclose the anti-oxidant and biosafety potential of the newly schemed compounds. Based on in-vitro screening outcomes, only a derivative that exhibited potent efficacy was selected and subjected to an in-vivo study. Among them, compounds 6 and 12 are the most potent ones, which exhibited % radical scavenge of 89.38 % and 91.58 % related to standard ascorbic acid (91.58 %). Surprisingly, these compounds also exhibited excellent anti-diabetic efficacy at a dose of 4 mg/kg in an in-vivo animal model. In conclusion, all studies suggested that the titled molecules could be promising lead compounds for the treatment of patients with type 2 diabetes mellitus.

Exploring the Anxiolytic Potential of NPY by a Dipeptidyl Peptidase-IV Inhibitor in an Animal Model of PTSD.

The regulatory neuropeptide Y (NPY) is implicated in anxiety and post-traumatic stress disorder (PTSD)-related behaviors. NPY exerts its effects through 5 receptor subtypes, with Y1 and Y2 receptors being predominantly expressed in the rat brain. Activation of Y1 by full-length NPY1-36 induces anxiolytic effects, whereas Y2 binds truncated peptides, eliciting region-specific anxiogenic responses. Dipeptidyl peptidase-IV (DPP-IV) cleaves NPY, thereby modulating its functionality. Sitagliptin, a DPP-IV inhibitor (DPP-IV-I), inhibits the degradation of various vasoactive peptides, including cerebral NPY. As such, the therapeutic potential of DPP-IV-I following a traumatic event remains inconclusive. We assessed the effects of a highly selective DPP-IV-I, administered either shortly after the stressor or intermittently over 3 days, on behavioral outcomes using the predator scent stress (PSS) model of PTSD. Rats exposed to PSS or sham-PSS received a single dose of sitagliptin (10 or 30mg/kg) or saline 1 hour post-exposure, or repeated doses over 3 days (20mg/kg). Behavioral outcomes were evaluated using the elevated plus maze and acoustic startle response at 7 days post-exposure. Additionally, rats exposed to PSS or sham-PSS were treated with sitagliptin (30mg/kg) or saline, and their brains were prepared for immunofluorescence and enzyme-linked immunosorbent assay (ELISA). Sitagliptin did not attenuate anxiety-related behaviors or PTSD-related behavior prevalence compared to saline. Notably, the 30mg/kg dose increased NPY levels in several brain regions without affecting NPY-Y1 levels. The findings suggest that sitagliptin-induced upregulation of NPY levels shortly after PSS is insufficient to prevent the development of post-traumatic responses. The effectiveness of NPY signaling may be influenced by factors beyond peptide concentration alone, potentially limiting its therapeutic efficacy. Activation of NPY-Y1 receptors, rather than merely increasing NPY levels, appears to be crucial for modulating anti-anxiety and post-traumatic responses.

Neurological Sequelae of Post-COVID-19 Fatigue: A Narrative Review of Dipeptidyl Peptidase IV-Mediated Cerebrovascular Complications.

Coronavirus disease 2019 (COVID-19) has been a global pandemic affecting millions of people's lives, which has led to 'post-COVID-19 fatigue'. Alarmingly, severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) not only infects the lungs but also influences the heart and brain. Endothelial cell dysfunction and hypercoagulation, which we know occur with this infection, lead to thrombo-inflammation that can manifest as many myriad cardio-cerebrovascular disorders, such as brain fog, fatigue, cognitive dysfunction, etc. Additionally, SARS-CoV-2 has been associated with oxidative stress, protein aggregation, cytokine storm, and mitochondrial dysfunction in neurodegenerative diseases. Accordingly, the identification of molecular targets involved in these actions could provide strategies for preventing and treating this disease. In particular, the very common enzyme dipeptidyl peptidase IV (DPPIV) has recently been identified as a candidate co-receptor for the cell entry of the SARS-CoV-2 virus with its involvement in infection. In addition, DPPIV has been reported as a co-receptor for some viruses such as Middle East respiratory syndrome-coronavirus (MERS-CoV). It mediates immunologic reactions and diseases such as type 2 diabetes mellitus, obesity, and hypertension, which have been considered the prime risk factors for stroke among other types of cardio-cerebrovascular diseases. Unlike angiotensin-converting enzyme 2 (ACE2), DPPIV has been implicated in aggravating the course of infection due to its disruptive effect on inflammatory signaling networks and the neuro-glia-vascular unit. Regarding the neurological, physiological, and molecular grounds governing post-COVID-19 fatigue, this review focuses on DPPIV as one of such reasons that progressively establishes cerebrovascular grievances following SARS-CoV infection.

An Interdisciplinary Approach Provides Insights into the Pronounced Selectivity of Compound 42 for DPP9.

Dipeptidyl peptidase 8 (DPP8) and 9 (DPP9) are proteases gaining significant attention for their role in health and disease. Distinctive studies of these proteases are hampered by their close homology. Furthermore, designing selective compounds is a major challenge due to the highly conserved catalytic site. Here, we provide mechanistic insights underlying the DPP9-over-DPP8 selectivity of the semi-selective inhibitor "Compound 42". We performed enhanced sampling molecular dynamics simulations to investigate the binding pose of "Compound 42", which enabled the design of various DPP9 mutants that were characterized through a combination of biochemical (Ki determinations) and in silico approaches. Our findings show that DPP9 residue F253 is an important selectivity-determining factor. This work marks the discovery and validation of a structural feature that can be exploited for the design of DPP8 or DPP9 selective inhibitors.

Multi-targeted olink proteomics analyses of cerebrospinal fluid from patients with aneurysmal subarachnoid hemorrhage

BackgroundThe complexity of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH) may require the simultaneous analysis of variant types of protein biomarkers to describe it more accurately. In this study, we analyzed for the first time the alterations of cerebrospinal fluid (CSF) proteins in patients with aSAH by multi-targeted Olink proteomics, aiming to reveal the pathophysiology of DCI and provide insights into the diagnosis and treatment of aSAH.MethodsSix aSAH patients and six control patients were selected, and CSF samples were analyzed by Olink Proteomics (including 96-neurology panel and 96-inflammation panel) based on Proximity Extension Assay (PEA). Differentially expressed proteins (DEPs) were acquired and bioinformatics analysis was performed.ResultsPCA analysis revealed better intra- and inter-group reproducibility of CSF samples in the control and aSAH groups. 23 neurology-related and 31 inflammation-relevant differential proteins were identified. In the neurology panel, compared to controls, the up-regulated proteins in the CSF of SAH patients predominantly included macrophage scavenger receptor 1 (MSR1), siglec-1, siglec-9, cathepsin C (CTSC), cathepsin S (CTSS), etc. Meanwhile, in the inflammation group, the incremental proteins mainly contained interleukin-6 (IL-6), MCP-1, CXCL10, CXCL-9, TRAIL, etc. Cluster analysis exhibited significant differences in differential proteins between the two groups. GO function enrichment analysis hinted that the differential proteins pertinent to neurology in the CSF of SAH patients were mainly involved in the regulation of defense response, vesicle-mediated transport and regulation of immune response; while the differential proteins related to inflammation were largely connected with the cellular response to chemokine, response to chemokine and chemokine-mediated signaling pathway. Additionally, in the neurology panel, KEGG enrichment analysis indicated that the differential proteins were significantly enriched in the phagosome, apoptosis and microRNAs in cancer pathway. And in the inflammation panel, the differential proteins were mainly enriched in the chemokine signaling pathway, viral protein interaction with cytokine and cytokine receptor and toll-like receptor signaling pathway.ConclusionsThese identified differential proteins reveal unique pathophysiological characteristics secondary to aSAH. Further characterization of these proteins and aberrant pathways in future research could enable their application as potential therapeutic targets and biomarkers for DCI after aSAH.

Vitamin D Supplementation as a Therapeutic Strategy in Autoimmune Diabetes: Insights and Implications for LADA Management.

Latent autoimmune diabetes of adults (LADA) is the most prevalent form of autoimmune diabetes (AI-D) in adulthood; however, its accurate diagnosis and optimal treatment remain challenging. Vitamin D deficiency (VDD) is commonly observed in LADA patients, while increased vitamin D exposure through supplementation and dietary intake is associated with a reduced incidence of LADA. Although limited, case reports, case-control studies, and randomized clinical trials have examined the effects of vitamin D supplementation-alone or combined with dipeptidyl peptidase-4 inhibitors (DPP4-is)-on glucose regulation, residual β-cell function, and glutamic acid decarboxylase antibody (GADA65) levels. Findings, while preliminary, indicate that vitamin D supplementation may enhance glycemic control, preserve β-cell function, and reduce autoimmune activity. Given its accessibility, affordability, and relative safety, vitamin D supplementation presents an attractive adjunct treatment option for LADA patients. This narrative review discusses current evidence on the potential therapeutic benefits of vitamin D supplementation in patients with AI-D, including LADA, who are also vitamin D deficient. Beginning with an exploration of the epidemiological patterns, clinical presentation, and diagnostic framework essential for understanding and identifying LADA, this review then examines the proposed mechanisms through which vitamin D may influence autoimmune modulation of pancreatic β-cells, integrating recent data pertinent to LADA pathology. By distilling and consolidating existing research, we aim to provide a platform for advancing targeted investigations within this distinct patient population.

In Vivo and Computational Studies on Sitagliptin's Neuroprotective Role in Type 2 Diabetes Mellitus: Implications for Alzheimer's Disease.

Diabetes mellitus (DM), a widespread endocrine disorder characterized by chronic hyperglycemia, can cause nerve damage and increase the risk of neurodegenerative diseases such as Alzheimer's disease (AD). Effective blood glucose management is essential, and sitagliptin (SITG), a dipeptidyl peptidase-4 (DPP-4) inhibitor, may offer neuroprotective benefits in type 2 diabetes mellitus (T2DM). T2DM was induced in rats using nicotinamide (NICO) and streptozotocin (STZ), and biomarkers of AD and DM-linked enzymes, inflammation, oxidative stress, and apoptosis were evaluated in the brain. Computational studies supported the in vivo findings. SITG significantly reduced the brain enzyme levels of acetylcholinesterase (AChE), beta-secretase-1 (BACE-1), DPP-4, and glycogen synthase kinase-3β (GSK-3β) in T2DM-induced rats. It also reduced inflammation by lowering cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and nuclear factor-κB (NF-κB). Additionally, SITG improved oxidative stress markers by reducing malondialdehyde (MDA) and enhancing glutathione (GSH). It increased anti-apoptotic B-cell lymphoma protein-2 (Bcl-2) while reducing pro-apoptotic markers such as Bcl-2-associated X (BAX) and Caspace-3. SITG also lowered blood glucose levels and improved plasma insulin levels. To explore potential molecular level mechanisms, docking was performed on AChE, COX-2, GSK-3β, BACE-1, and Caspace-3. The potential binding affinity of SITG for the above-mentioned target enzymes were 10.8, 8.0, 9.7, 7.7, and 7.9 kcal/mol, respectively, comparable to co-crystallized ligands. Further binding mode analysis of the lowest energy conformation revealed interactions with the critical residues. These findings highlight SITG's neuroprotective molecular targets in T2DM-associated neurodegeneration and its potential as a therapeutic approach for AD, warranting further clinical investigations.

Potent and Protease Resistant Azapeptide Agonists of the GLP-1 and GIP Receptors.

The gut-derived peptide hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) play important physiological roles including glucose homeostasis and appetite suppression. Stabilized agonists of the GLP-1 receptor (GLP-1R) and dual agonists of GLP-1R and GIP receptor (GIPR) for the management of type 2 diabetes and obesity have generated widespread enthusiasm and have become blockbuster drugs. These therapeutics are refractory to the action of dipeptidyl peptidase-4 (DPP4), that catalyzes rapid removal of the two N-terminal residues of the native peptides, in turn severely diminishing their activity profiles. Here we report that a single atom change from carbon to nitrogen in the backbone of the entire peptide makes them refractory to DPP4 action while still retaining full potency and efficacy at their respective receptors. This was accomplished by use of aza-amino acids, that are bioisosteric replacements for α-amino acids that perturb the structural backbone and local side chain conformations. Molecular dynamics simulations reveal that aza-amino acid can populate the same conformational space that GLP-1 adopts when bound to the GLP-1R. The insertion of an aza-amino acid at the second position from the N-terminus in semaglutide and in a dual agonist of GLP-1R and GIPR further demonstrates its capability as a viable alternative to current DPP4 resistance strategies while offering additional structural variation that may influence downstream signaling.

Metabolic Consequences of Glucagon-Like Peptide-1 Receptor Agonist Shortage: Deterioration of Glycemic Control in Type 2 Diabetes.

In the context of a global shortage of glucagon-like peptide-1 (GLP-1) receptor agonists, we assessed the impact of discontinuing dulaglutide on metabolic control in individuals with type 2 diabetes. Our analysis included data from 69 individuals and revealed a significant deterioration in glycemic control following the discontinuation. Specifically, the average hemoglobin A1c level increased from 7.0%±0.9% to 8.1%±1.4% (P<0.001), and fasting glucose levels rose from 129±31 to 156±50 mg/dL (P<0.001) within 3 months after stopping the medication. Alternative treatments such as dipeptidyl peptidase-4 inhibitors and sodium glucose cotransporter- 2 inhibitors were insufficient substitutes, highlighting the essential role of continuous GLP-1 receptor agonist therapy in maintaining metabolic health.