RESUMO
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).
Assuntos
Desoxiglucose/metabolismo , Frutose/metabolismo , Manose/metabolismo , Proteínas de Transporte de Monossacarídeos/fisiologia , Sequência de Aminoácidos , Animais , Células COS , Humanos , Dados de Sequência Molecular , Proteínas de Transporte de Monossacarídeos/genética , RNA Mensageiro/análise , Transportador 2 de Glucose-SódioRESUMO
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.
Assuntos
Anticolesterolemiantes/farmacologia , Bezafibrato/farmacologia , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Hipolipemiantes/farmacologia , NF-kappa B/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores do Ácido Retinoico/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Gênica , Ativação Transcricional , Western Blotting , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Núcleo Celular/metabolismo , DNA Complementar/metabolismo , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Inibidores Enzimáticos/farmacologia , Ácidos Graxos Monoinsaturados/farmacologia , Fluvastatina , Biblioteca Gênica , Humanos , Indóis/farmacologia , Ligantes , Fígado/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Modelos Biológicos , Músculo Esquelético/metabolismo , Proteínas Nucleares/metabolismo , Estrutura Terciária de Proteína , Piridinas/farmacologia , Quinolinas/farmacologia , Proteínas Recombinantes de Fusão/metabolismo , Receptores X de Retinoides , Análise de Sequência de DNA , Proteína de Ligação a Elemento Regulador de Esterol 1 , Transativadores/metabolismo , TransfecçãoRESUMO
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.
