ABSTRACT
We isolated a cDNA clone of SLC5A9/SGLT4 from human small intestinal full-length cDNA libraries, and functionally characterized it in vitro. The messenger RNA encoding SGLT4 was mainly expressed in the small intestine and kidney, among the human tissues tested. COS-7 cells transiently expressing SGLT4 exhibited Na(+)-dependent alpha-methyl-D-glucopyranoside (AMG) transport activity with an apparent K(m) of 2.6 mM, suggesting that SGLT4 is a low affinity-type transporter. The rank order of naturally occurring sugar analogs for the inhibition of AMG transport was: D-mannose (Man) >> D-glucose (Glc) > D-fructose (Fru) = 1,5-anhydro-D-glucitol (1,5AG) > D-galactose (Gal). Recognition of Man as a substrate was confirmed by direct uptake of Man into the cell. COS-7 cells expressing a putative murine SGLT4 ortholog showed similar Na(+)-dependent AMG transport activity and a similar deduced substrate specificity. These results suggest that SGLT4 would have unique physiological functions (i.e., absorption and/or reabsorption of Man, 1,5AG, and Fru, in addition to Glc).
Subject(s)
Deoxyglucose/metabolism , Fructose/metabolism , Mannose/metabolism , Monosaccharide Transport Proteins/physiology , Amino Acid Sequence , Animals , COS Cells , Humans , Molecular Sequence Data , Monosaccharide Transport Proteins/genetics , RNA, Messenger/analysis , Sodium-Glucose Transporter 2ABSTRACT
In this study, we used a coactivator-dependent receptor-ligand interaction assay (CARLA), which is a semifunctional in vitro assay, to determine whether hypolipidemic drugs are ligands for the three peroxisome proliferator-activated receptor isotypes (PPARalpha, delta, and gamma). We also evaluated the transcriptional activities of the three PPAR isotypes by transient transfection assays. We found that bezafibrate was a ligand for PPARalpha, delta, and gamma in the CARLA and that bezafibrate induced transcriptional activation of PPARalpha/RXRalpha, PPARdelta/RXRalpha, and PPARgamma/RXRalpha. Although the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors cerivastatin, fluvastatin, and pitavastatin were not ligands for these three nuclear receptors in the CARLA, they induced transcriptional activation of PPARalpha/RXRalpha, PPARdelta/RXRalpha, and PPARgamma2/RXRalpha. Moreover, cerivastatin, fluvastatin, and pitavastatin synergistically and dose-dependently increased the transcriptional activation of PPARalpha/RXRalpha induced by bezafibrate. In addition, the cerivastatin-induced transcriptional activation of PPARalpha/RXRalpha was decreased by addition of mevalonate, farnesol, geranylgeraniol, or cholesterol and by co-transfection with sterol regulatory element-binding protein-1 (SREBP-1). Moreover, concomitant administration of statins and fibrates also decreased the transactivation of nuclear factor kappaB (NFkappaB) and the activation of NFkappaB by mitogen-activated protein kinase kinase kinase (MEKK) also decreased the transactivation of PPARalpha/RXRalpha.
Subject(s)
Anticholesteremic Agents/pharmacology , Bezafibrate/pharmacology , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Hypolipidemic Agents/pharmacology , NF-kappa B/metabolism , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Retinoic Acid/metabolism , Transcription Factors/metabolism , Transcription, Genetic , Transcriptional Activation , Blotting, Western , CCAAT-Enhancer-Binding Proteins/metabolism , Cell Nucleus/metabolism , DNA, Complementary/metabolism , DNA-Binding Proteins/metabolism , Dose-Response Relationship, Drug , Drug Synergism , Enzyme Inhibitors/pharmacology , Fatty Acids, Monounsaturated/pharmacology , Fluvastatin , Gene Library , Humans , Indoles/pharmacology , Ligands , Liver/metabolism , Mitogen-Activated Protein Kinase Kinases/metabolism , Models, Biological , Muscle, Skeletal/metabolism , Nuclear Proteins/metabolism , Protein Structure, Tertiary , Pyridines/pharmacology , Quinolines/pharmacology , Recombinant Fusion Proteins/metabolism , Retinoid X Receptors , Sequence Analysis, DNA , Sterol Regulatory Element Binding Protein 1 , Trans-Activators/metabolism , TransfectionABSTRACT
KDR-5169, 4-amino-5-chloro-N-[1-(3-fluoro-4-methoxybenzyl)piperidin-4-yl]-2-(2-hydroxyethoxy)benzamide hydrochloride dihydrate, is a new prokinetic with a dual action, i.e., stimulation of the 5-HT4 receptor and antagonism of the dopamine D2 receptor. In this study, we determined in vitro activities of KDR-5169 towards both receptors and demonstrated the effect of the compound on gastrointestinal motor activity in conscious dogs and rats. In dogs, intravenous KDR-5169 stimulated upper gastrointestinal motility in the fasting state and also eliminated the depressive effect of 3,4-dihydroxyphenylalanine (L-DOPA) on this motility in the postprandial state. The effect of KDR-5169 on gastric emptying was further characterized by the use of three rat gastroparesis models (dopamine D2 receptor agonist (quinpirol)-, abdominal surgery-, or combined-situation-induced). Domperidone (a dopamine D2 receptor antagonist) was effective in the quinpirol-delay and combination-delay models, and cisapride and mosapride (5-HT4 receptor agonists) were effective in the surgery-delay model. Only KDR-5169 eliminated the delay of gastric emptying in all three models. In addition, KDR-5169 accelerated emptying to above the normal level in the combination-delay model. These results suggest that KDR-5169 would be effective in various types of gastric ileus caused by different mechanisms.
