RESUMO
In this study we examined the acute in vivo effect and short- and long-term in vitro effects of samples from native and commercial Ilex paraguariensis on glucose homeostasis. Also, the potential effect of I. paraguariensis on serum insulin secretion was investigated. The chemical identification and quantification of methyl xanthines and polyphenols in CH2Cl2, EtOAc and n-BuOH fractions of native I. paraguariensis as well as infusions of green and roasted I. paraguariensis from a commercial source was verified by high-performance liquid chromatography. The results for the serum glucose-lowering indicated that both fractions and both infusions were able to improve significantly the oral glucose tolerance curve. Additionally, both the EtOAc and n-BuOH fractions induced-insulin secretion, but EtOAc induced an early (at 15 min) and late (at 60 min) biphasic peak of insulin secretion similar to glipizide stimulatory effect. Both fractions increased liver glycogen content compared with fasted normal rats. Also, EtOAc and n-BuOH fractions inhibited in vitro disaccharidases activities after an acute treatment. The maximum inhibitory effect of the EtOAc and n-BuOH fractions on maltase activity (at 5 min) was around 35%. The evident reduction of protein glycation by glucose or fructose with EtOAc and n-BuOH fractions increased from 7 to 28 days of in vitro incubation. Inhibition of bovine serum albumin glycation by glucose and fructose, by around 50% and 90%, respectively, was observed. Additionally, the green and roasted mate infusions reduced the formation of AGEs in a characteristic long-term effect. In conclusion, this study shows that I. paraguariensis has an anti-hyperglycemic potential role able to improve the diabetic status and is probably a source of multiple hypoglycemic compounds.
Assuntos
Glicemia/metabolismo , Hipoglicemiantes/farmacologia , Ilex paraguariensis/química , Insulina/sangue , Extratos Vegetais/farmacologia , Polifenóis/farmacologia , Xantinas/farmacologia , Animais , Bebidas , Brasil , Bovinos , Cromatografia Líquida de Alta Pressão , Comércio , Dissacaridases/metabolismo , Inibidores Enzimáticos/farmacologia , Frutose/metabolismo , Glipizida/farmacologia , Teste de Tolerância a Glucose , Produtos Finais de Glicação Avançada/metabolismo , Glicogênio/metabolismo , Glicosilação , Homeostase/efeitos dos fármacos , Hipoglicemiantes/análise , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Extratos Vegetais/química , Polifenóis/análise , Proteínas/metabolismo , Ratos , Ratos Wistar , Valores de Referência , Albumina Sérica/metabolismo , Tempo , Xantinas/análise , alfa-Glucosidases/metabolismoRESUMO
We investigated the involvement of protein synthesis in the stimulatory action of thyroid hormones on amino acid accumulation and characterized K(+) currents involved in the hyperpolarizing effect of thyroxine (T(4)) on Sertoli cells. Immature rat testes were incubated in Krebs Ringer-bicarbonate buffer (KRb) in the presence of [(14)C]methylaminoisobutyric acid with and without T(4), 3,5,3'-l-triiodothyronine (T(3)) and/or cycloheximide. Sertoli cells were monitored by intracellular recording in a chamber perfused with KRb with and without T(4), T(3) and/or blockers, and the membrane potential was monitored. T(4) and T(3) stimulated amino acid accumulation and protein synthesis. Treatment with cycloheximide diminished T(3) stimulatory actions on amino acid accumulation but had no effect on T(4) action. Both hormones elicited a hyperpolarization of the Sertoli cell membrane potential which involved K(+) channels, since TEA and apamin abolished this effect. These findings on rapid membrane actions of thyroid hormone in the testis suggest that some effects of T(4) are modulated by non-genomic mechanisms.