RESUMEN
The objective of this study was to clarify the relationship between the accumulation of S-adenosylhomocysteine (SAH) and the change in the SAH hydrolase activity in vitamin B6 (B6). Male Wistar rats were fed a control diet (control and pair-fed groups) or B6-free diet (B6-deficient group) for 5 wk. Although the SAH-synthetic activity of SAH hydrolase significantly increased in the B6-deficient group, SAH-hydrolytic activity of SAH hydrolase showed no significant difference in the liver among the three groups. On the other hand, SAH hydrolase mRNA in the liver did not show any significant change. Thus, the accumulation of SAH would be due to the increased SAH-synthetic activity of SAH hydrolase. The disturbed methionine metabolism by B6-deficiency, such as a significant increase of plasma homocysteine, might induce the activation of SAH hydrolase in the direction of SAH synthesis.
Asunto(s)
Adenosilhomocisteinasa/metabolismo , Metionina/metabolismo , S-Adenosilhomocisteína/metabolismo , Deficiencia de Vitamina B/metabolismo , Análisis de Varianza , Animales , Peso Corporal/fisiología , Homocisteína/sangre , Hígado/enzimología , Hígado/metabolismo , Masculino , Distribución Aleatoria , Ratas , Ratas Wistar , Deficiencia de Vitamina B/sangre , Deficiencia de Vitamina B/enzimologíaRESUMEN
The objective of this study was to examine how transient high plasma homocysteine (Hcy) levels affect the metabolism of Hcy, the activity and expression of S-adenosylhomocysteine (SAH) hydrolase which catalyzes both SAH hydrolysis and SAH synthesis. Wistar ST rats (males) were cannulated in the right jugular vein for intravenous infusion of physiological saline or DL-Hcy solutions (15 and 30 mg/mL) for 1 h at 1.1 mL/h/rat. The content of S-adenosylmethionine (SAM), SAH-synthetic activity of SAH hydrolase and the expression of SAH hydrolase mRNA in liver extracts showed no significant difference in the Hcy infused groups as compared to the Control group. On the other hand, the contents of hepatic SAH in the Hcy infused groups were dose-dependent and significantly higher than that of the Control group. Thus, this study showed that hepatic SAH increased without any increase in the SAH-synthetic activity and the expression of SAH hydrolase mRNA under transient high plasma Hcy levels after intravenous infusion of Hcy.
Asunto(s)
Adenosilhomocisteinasa/metabolismo , Homocisteína/sangre , Homocisteína/farmacología , S-Adenosilhomocisteína/metabolismo , Adenosilhomocisteinasa/efectos de los fármacos , Adenosilhomocisteinasa/genética , Análisis de Varianza , Animales , Relación Dosis-Respuesta a Droga , Homocisteína/administración & dosificación , Infusiones Intravenosas/métodos , Hígado/metabolismo , Masculino , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , S-Adenosilmetionina/sangre , Cloruro de Sodio/administración & dosificaciónRESUMEN
Ethyl alpha-D-glucoside (alpha-EG) is normally contained in Sake, which has been taken by Japanese people since ancient times. In this study, the intestinal absorption of alpha-EG was investigated using rat everted intestinal sac. Furthermore, the alpha-EG hydrolytic activity in rat intestine was compared with disaccharides hydrolytic activities, and the effects of alpha-EG on disaccharides hydrolysis were examined using crude enzyme preparation from rat intestinal acetone powder. Glucose liberated from alpha-EG was detected in a serosal solution of everted rat intestinal sac, but it was only less than 4% of absorbed intact alpha-EG. alpha-EG absorption into small intestinal tissue was reduced by elimination of sodium ion from the mucosal solution or under the presence of phlorizin. The hydrolytic activity for alpha-EG was detected in crude enzyme preparation from rat intestinal acetone powder, but it showed a low value as compared to those for disaccharides. alpha-EG showed mixed type inhibition for maltose and sucrose hydrolysis, but inhibitory concentrations of alpha-EG required for 50% inhibition for the maltose and sucrose hydrolysis were higher than those of arabinose and acarbose. In conclusion, a small amount of alpha-EG was hydrolyzed and most of it was absorbed via SGLT1 as an intact form in the rat small intestine, and the inhibitory effect of alpha-EG on disaccharides hydrolysis was weak.
Asunto(s)
Glucósidos/farmacocinética , Absorción Intestinal , Intestinos/enzimología , Animales , Disacáridos/metabolismo , Glucosa/metabolismo , Glucósidos/metabolismo , Glucósidos/farmacología , Hidrólisis/efectos de los fármacos , Cinética , Ratas , Ratas WistarRESUMEN
Ethyl alpha-D-glucoside (alpha-EG) is a peculiar component in sake, a traditional Japanese alcoholic beverage. In this study, morphological changes in kidney and effects on urine excretion by alpha-EG ingestion were investigated. After the rats were fed with pellet diets containing 100% or 20% alpha-EG dietary level, alpha-EG was detected in urine and urine volume showed significant increase (p<0.05). Kidney weights were increased (p<0.05) and renal tubules were dilated in the rats by alpha-EG ingestion, whereas there was no detectable histopathological damage to renal cells. Plasma uric acid and urea levels were not affected. In conclusion, ingested alpha-EG was excreted in urine, increasing urine volume. Increase in kidney weight related to renal tubule dilation was observed with alpha-EG ingestion without deteriorate changes in the renal cells or functions.
Asunto(s)
Glucósidos/efectos adversos , Riñón/anatomía & histología , Riñón/efectos de los fármacos , Orina , Bebidas Alcohólicas/análisis , Animales , Dilatación Patológica/inducido químicamente , Glucósidos/farmacología , Glucósidos/orina , Túbulos Renales/efectos de los fármacos , Túbulos Renales/patología , Masculino , Tamaño de los Órganos/efectos de los fármacos , Ratas , Ratas WistarRESUMEN
OBJECTIVE: Ethyl alpha-D-glucoside (alpha-EG) is a peculiar component in sake. We investigated how alpha-EG was absorbed, hydrolyzed, and excreted in urine when it was ingested orally by rats. METHODS: Hydrolyzing activity for alpha-EG was determined by incubating it with crude enzyme solutions prepared from several rat organs, and absorption activity for alpha-EG was determined by incubating rat small intestinal everted sac in sodium or potassium Krebs-Ringer buffer that contained alpha-EG. alpha-EG solution was fed to rats, and urine volume and plasma alpha-EG, glucose and insulin and urinary alpha-EG were determined. RESULTS: alpha-EG was hydrolyzed by crude enzyme solutions prepared from rat small intestinal mucosa and kidney, and these hydrolyzing activities were lower than those for maltose. alpha-EG absorbed into everted rat intestinal sacs in potassium Krebs-Ringer buffer reduced almost completely compared with that in sodium Krebs-Ringer buffer. When alpha-EG was ingested orally by rats, it was absorbed into the bloodstream and more than 60% was excreted in urine, and urine volume increased. CONCLUSIONS: In rats, alpha-EG was absorbed in small intestine and excreted intact in urine without affecting blood glucose and insulin and thus was a diuretic, insulin-independent, and low-nutritive glucoside that could be safely applicable to food.
Asunto(s)
Glucósidos/farmacocinética , Glucósidos/orina , Absorción Intestinal/fisiología , Intestino Delgado/metabolismo , Análisis de Varianza , Animales , Glucemia/efectos de los fármacos , Peso Corporal/efectos de los fármacos , Cromatografía Líquida de Alta Presión/métodos , Ingestión de Líquidos/efectos de los fármacos , Alimentos , Glucósidos/química , Técnicas In Vitro , Insulina/sangre , Maltosa/farmacocinética , Ratas , Ratas WistarRESUMEN
The distribution of theanine-degrading activity in Wistar rats was examined and this activity was detected only in the kidney. Judging from polyacrylamide gel electrophoresis, theanine-degrading enzyme from rat kidney was purified almost to homogeneity. Theanine-degrading activity was co-purified with glutaminase activity, and the relative activity for theanine was about 85% of that for L-glutamine throughout purification. Substrate specificity of purified enzyme preparation coincided well with the data of phosphate-independent glutaminase [EC 3.5.1.2], which had been previously reported. It was very curious that gamma-glutamyl methyl and ethyl esters were more effectively hydrolyzed than theanine and L-glutamine, in view of relative activity and K(m) value. It was suggested that gamma-glutamyl moiety in theanine molecule was transferred to form gamma-glutamylglycylglycine with relative ease in the presence of glycylglycine. On the other hand, purified phosphate-dependent glutaminase did not show theanine-degrading activity at all. Thus, it was concluded that theanine was hydrolyzed by phosphate-independent glutaminase in kidney and suggested that, as for the metabolic fate of theanine, its glutamyl moiety might be transferred by means of gamma-glutamyl transpeptidase reaction to other peptides in vivo.
Asunto(s)
Glutamatos/metabolismo , Glutaminasa/metabolismo , Riñón/enzimología , Animales , Cromatografía en Capa Delgada , Electroforesis en Gel de Poliacrilamida , Etilaminas/metabolismo , Ácido Glutámico/metabolismo , Glutaminasa/química , Glutaminasa/aislamiento & purificación , Glicilglicina , Isoenzimas/metabolismo , Fosfatos/química , Ratas , Ratas Wistar , Especificidad por Sustrato , gamma-Glutamiltransferasa/metabolismoRESUMEN
Recently we reported that the supplementation of vitamin B6 to low vitamin B6 diet caused suppression in colon tumorigenesis and cell proliferation of azoxymethane-treated mice in a dose-dependent manner among 1, 7, and 14 mg pyridoxine HCl/kg diet (J. Nutr. 131: 2204-2207, 2001). To examine the mechanism of the anticolon tumor effect of vitamin B6, male ICR mice were fed the diet containing 1, 7, 14, and 35 mg pyridoxine HCl/kg diet for 22 wk and simultaneously given a weekly injection of azoxymethane for an initial 10 wk. The supplementation of vitamin B6 to a low vitamin B6 diet (1 mg pyridoxine HCl/kg) suppressed the levels of colonic 8-hydroxyguanosine and 4-hydroxynonenal and inducible nitric oxide synthase protein. The results suggest that the preventive effect of vitamin B6 against colon tumorigenesis is at least in part mediated by reducing oxidative stress and nitric oxide production.