Role of Proton-Coupled Oligopeptide Transporters in Small Peptide Absorption and Disposition.

Proton-coupled oligopeptide transporters (POTs) (i.e., PEPT1, PEPT2, PHT1 and PHT2) translocate various small peptide/mimetic across the biological membrane. The first part of this dissertation focuses on investigating the transport properties of carnosine in kidney using SKPT cell cultures as a model of proximal tubular transport. Results demonstrated that carnosine is expected to have a substantial cellular accumulation in kidney due to its high influx clearance across apical membranes by PEPT2, but minimal tubular reabsorption into blood because of very low efflux clearance across basolateral membranes. Although the role of PEPT1 in intestinal absorption of small peptide/mimetics has been demonstrated previously by in vitro models, its relative importance during in vivo intestinal absorption is unknown. Therefore, the objective of the second part of this dissertation is to delineate the relative importance of PEPT1 in intestinal absorption and disposition of small peptides/mimetics using wild-type and PEPT1 deficient mice, and glycylsarcosine (GlySar) as a model dipeptide substrate. In situ intestinal perfusions and in vivo absorption models in mice were used in our investigations. The results from our in situ studies show that PEPT1 is responsible for at least 90% of GlySar uptake in the small intestine and the transport protein exhibits low-affinity kinetics. However, during in vivo conditions, the extent of reduction in absorption, due to the absence of PEPT1, was lower than that of the in situ model. Specifically, the extent of GlySar absorption was reduced by about 50% due to the absence of PEPT1 transporter during in vivo condition. When partial AUC0-120 min was used as an indicator of the rate of absorption, there was a 60% reduction in the rate of GlySar absorption in PEPT1 deficient mice compared to the wild-type animals. With the exception of small intestine, PEPT1 had little effect on the tissue distribution of GlySar. In conclusion, the present studies demonstrate, using both in situ and in vivo models, that PEPT1 ablation significantly reduces both the rate and extent of oral absorption of small peptide/mimetic substrates (i.e., GlySar). These studies suggest that variability in intestinal PEPT1 (expression and/or activity) should exert a similar fate on peptide-like drugs.Ph.D.Pharmaceutical SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64610/1/djappar_1.pd

Research progress on extraction, purification, structure and biological activity of Dendrobium officinale polysaccharides

Dendrobium officinale Kimura et Migo (D. officinale) is a traditional medicinal and food homologous plant that has been used for thousands of years in folk medicine and nutritious food. Recent studies have shown that polysaccharide is one of the main biologically active components in D. officinale. D. officinale polysaccharides possess several biological activities, such as anti-oxidant, heptatoprotective, immunomodulatory, gastrointestinal protection, hypoglycemic, and anti-tumor activities. In the past decade, polysaccharides have been isolated from D. officinale by physical and enzymatic methods and have been subjected to structural characterization and activity studies. Progress in extraction, purification, structural characterization, bioactivity, structure-activity relationship, and possible bioactivity mechanism of polysaccharides D. officinale were reviewed. In order to provide reference for the in-depth study of D. officinale polysaccharides and the application in functional food and biomedical research

Urinary proteome and metabolome in dogs (Canis lupus familiaris): The effect of chronic kidney disease

Chronic kidney disease (CKD) is a progressive and irreversible disease. Although urine is an ideal biological sample for proteomics and metabolomics studies, sensitive and specific biomarkers are currently lacking in dogs. This study characterised dog urine proteome and metabolome aiming to identify and possibly quantify putative biomarkers of CKD in dogs. Twenty-two healthy dogs and 28 dogs with spontaneous CKD were selected and urine samples were collected. Urinary proteome was separated by SDS-PAGE and analysed by mass spectrometry, while urinary metabolome was analysed in protein-depleted samples by 1D 1H NMR spectra. The most abundant proteins in urine samples from healthy dogs were uromodulin, albumin and, in entire male dogs, arginine esterase. In urine samples from CKD dogs, the concentrations of uromodulin and albumin were significantly lower and higher, respectively, than in healthy dogs. In addition, these samples were characterised by a more complex protein pattern indicating mixed glomerular (protein bands ≥65 kDa) and tubular (protein bands <65 kDa) proteinuria. Urine spectra acquired by NMR allowed the identification of 86 metabolites in healthy dogs, belonging to 49 different pathways mainly involved in amino acid metabolism, purine and aminoacyl-tRNA biosynthesis or tricarboxylic acid cycle. Seventeen metabolites showed significantly different concentrations when comparing healthy and CKD dogs. In particular, carnosine, trigonelline, and cis-aconitate, might be suggested as putative biomarkers of CKD in dogsinfo:eu-repo/semantics/acceptedVersio

Diagnosis of anomalous origin and course of coronary arteries using non-contrast cardiac CT scan and detection features

10.1016/j.jcct.2012.06.005Journal of Cardiovascular Computed Tomography65335-34

Derivatization-independent cholesterol analysis in crude lipid extracts by liquid chromatography/mass spectrometry: Applications to a rabbit model for atherosclerosis

10.1016/j.chroma.2011.05.011Journal of Chromatography A1218284357-4365JCRA

An updated meta-analysis on the clinical outcomes of percutaneous left atrial appendage closure versus direct oral anticoagulation in patients with atrial fibrillation

The availability of direct oral anticoagulants (DOACs) with known lower bleeding risk compared with warfarin have raised questions about the role of left atrial appendage closure (LAAC). We aimed to perform a meta-analysis to compare the clinical outcomes for LAAC versus DOACs. All studies directly comparing LAAC with DOACs up to January 2023 were included. The outcomes studied included the combined major adverse cardiovascular (CV) events outcomes, ischemic stroke and thromboembolic events, major bleeding, CV mortality, and all-cause mortality. Hazard ratios (HRs) and their 95% confidence interval were extracted or estimated from the data and pooled together with a random-effects model. A total of 7 studies (1 randomized controlled trial, 6 propensity-matched observational studies) were finally included, with a pooled population of 4,383 patients who underwent LAAC and 4,554 patients on DOACs. There were no significant differences between patients who underwent LAAC and patients on DOACs in terms of baseline age (75.0 vs 74.7, p = 0.27), CHA2DS2-VASc score (5.1 vs 5.1, p = 0.33), or HAS-BLED score (3.3 vs 3.3, p = 0.36). After a mean weighted follow-up of 22.0 months, LAAC was associated with significantly lower rates of combined major adverse CV event outcomes (HR 0.73 [0.56 to 0.95], p = 0.02), all-cause mortality (HR 0.68 [0.54 to 0.86], p = 0.02), and CV mortality (HR 0.55 [0.41 to 0.72], p<0.01). There were no significant differences in the rates of ischemic stroke or systemic embolism (HR 1.12 [0.92 to 1.35], p = 0.25), major bleeding (HR 0.94 [0.67 to 1.32], p = 0.71), or hemorrhagic stroke (HR 1.07 [0.74 to 1.54], p = 0.74) between LAAC and DOAC. In conclusion, percutaneous LAAC was found to be as efficacious as DOACs for stroke prevention, with lower all-cause and CV mortality. The rates of major bleeding and hemorrhagic stroke were similar. LAAC has a potential role to play in stroke prevention in patients with atrial fibrillation in the era of DOACs, but further randomized data are needed

Significance and Regional Dependency of Peptide Transporter (PEPT) 1 in the Intestinal Permeability of Glycylsarcosine: In Situ Single-Pass Perfusion Studies in Wild-Type and Pept1 Knockout Mice

The purpose of this study was to evaluate the role, relevance, and regional dependence of peptide transporter (PEPT) 1 expression and function in mouse intestines using the model dipeptide glycylsarcosine (GlySar). After isolating specific intestinal segments, in situ single-pass perfusions were performed in wild-type and Pept1 knockout mice. The permeability of [3H]GlySar was measured as a function of perfusate pH, dipeptide concentration, potential inhibitors, and intestinal segment, along with PEPT1 mRNA and protein. We found the permeability of GlySar to be saturable (Km = 5.7 mM), pH-dependent (maximal value at pH 5.5), and specific for PEPT1; other peptide transporters, such as PHT1 and PHT2, were not involved, as judged by the lack of GlySar inhibition by excess concentrations of histidine. GlySar permeabilities were comparable in the duodenum and jejunum of wild-type mice but were much larger than that in ileum (approximately 2-fold). A PEPT1-mediated permeability was not observed for GlySar in the colon of wild-type mice (<10% residual uptake compared to proximal small intestine). Moreover, GlySar permeabilities were very low and not different in the duodenum, jejunum, ileum, and colon of Pept1 knockout mice. Functional activity of intestinal PEPT1 was confirmed by real-time polymerase chain reaction and immunoblot analyses. Our findings suggest that a loss of PEPT1 activity (e.g., due to polymorphisms, disease, or drug interactions) should have a major effect in reducing the intestinal absorption of di-/tripeptides, peptidomimetics, and peptide-like drugs