RESUMEN
Previous studies from our research group have suggested that procyanidins modify glycemia and insulinemia. The aim of this work was to evaluate the effects of procyanidins on ß-cell functionality in a nonpathological system. Four groups of healthy rats were studied. The animals were given daily acute doses of grape seed procyanidin extract (GSPE) for different time periods and at different daily amounts. A ß-cell line (INS-1E) was treated with 25 mg GSPE/L for 24 h to identify possible mechanisms of action for the procyanidins. In vivo experiments showed that different doses of GSPE affected insulinemia in different ways by modifying ß-cell functionality and/or insulin degradation. The islets isolated from rats that were treated with 25 mg GSPE/kg of body weight for 45 days exhibited a limited response to glucose stimulation. In addition, insulin gene expression, insulin synthesis and expression of genes related to insulin secretion were all down-regulated. In vitro studies revealed that GSPE decreased the ability of ß-cells to secrete insulin in response to glucose. GSPE increased glucose uptake in ß-cells under high-glucose conditions but impaired glucose-induced mitochondrial hyperpolarization, decreased adenosine triphosphate (ATP) synthesis and altered cellular membrane potentials. GSPE also modified Glut2, glucokinase and Ucp2 gene expression as well as altered the expression of hepatic insulin-degrading enzyme (Ide), thereby altering insulin degradation. At some doses, procyanidins changed ß-cell functionality by modifying insulin synthesis, secretion and degradation under nonpathological conditions. Membrane potentials and Ide provide putative targets for procyanidins to induce these effects.
Asunto(s)
Células Secretoras de Insulina/efectos de los fármacos , Insulina/metabolismo , Proantocianidinas/farmacología , Adenosina Trifosfato/metabolismo , Animales , Línea Celular , Relación Dosis-Respuesta a Droga , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Glucosa/metabolismo , Glucosa/farmacología , Transportador de Glucosa de Tipo 2/genética , Extracto de Semillas de Uva/farmacología , Proteínas de Homeodominio/genética , Insulina/genética , Secreción de Insulina , Células Secretoras de Insulina/metabolismo , Insulisina/genética , Canales Iónicos/genética , Islotes Pancreáticos/efectos de los fármacos , Islotes Pancreáticos/metabolismo , Potenciales de la Membrana/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Proteínas Mitocondriales/genética , Ratas , Ratas Wistar , Transactivadores/genética , Proteína Desacopladora 2RESUMEN
Natural plant extracts are candidates for the development of new functional foods. Most of them are usually complex mixtures of molecules of uncertain bioavailability that are often partially metabolized before they finally reach the target cells IN VIVO. IN VITRO studies of the bioactivity of these extracts suggest that their direct application to some cell cultures might be a long way from becoming a reality. To overcome this limitation, we seeded Caco-2 cells onto culture inserts and after 21 days, cocultured these with INS-1E on the base of the well. After 24 hours of coculture, TEER (transepithelium electrical resistance) measurements indicated no changes in the permeability of the Caco-2 barrier. We also found no changes in either the ability of Caco-2 cells to metabolize the flavan-3-ol component of a grape-seed procyanidin-rich extract, or in the flavanols' ability to pass through the barrier. However, the expression of the Caco-2 SGLT-1 gene increased due to the coculture. GSIS (glucose stimulated insulin secretion) was maintained in the INS-1E cells with higher levels of insulin secretion despite the fact that the insulin gene expression was unmodified by the cocultivation. Furthermore, we found that in some of the assays requiring several medium changes there was a tendency to lose ß-cells. Neutral red assay showed that seeded cells should only be cocultured for a short time to obtain a higher consistency. In conclusion, four hours coculture with Caco-2 cells and INS-1E is a suitable method for checking the bioactivity of natural plant extracts of unknown bioavailability on ß-cells.
Asunto(s)
Técnicas de Cocultivo , Extracto de Semillas de Uva/farmacología , Células Secretoras de Insulina/efectos de los fármacos , Células CACO-2 , Línea Celular , Expresión Génica , Glucosa/metabolismo , Extracto de Semillas de Uva/química , Humanos , Insulina/metabolismo , Secreción de Insulina , Transportador 1 de Sodio-Glucosa/genética , Transportador 1 de Sodio-Glucosa/metabolismoRESUMEN
The HPLC phenolic profile of virgin olive oils obtained from young olive trees (Arbequina cv.) grown under different deficit irrigation strategies was studied. Deficit irrigation (RDI) did not affect all the phenolic compounds in the same way. Lignans, vanillic acid, vanillin, and the unknown phenolic compound named P24 increased in the oils from the most irrigated treatments. The secoiridoid derivatives and the unknown phenolic compound named P19 increased in the oils from the most stressed irrigation treatments. The period of growth where a water stress significantly affects the phenolic profile of oils was between pit hardening and the first stages of fruit growth and oil accumulation, independently of the water applied during the previous period to harvest. The phenolic profile and those parameters related to phenol content, oxidative stability, and the bitter index were significantly affected only in the most severe RDI strategies. Other strategies produced important savings in irrigation requirements and an increase in the water use efficiency without noticeably affecting the phenolic profile.