The purpose of the present study was to compare the effect of the oral treatment (gavage) with Stevia rebaudiana (Bert.) Bertoni (SRB) and stevioside (STV) on glycaemia and gluconeogenesis of 15-h fasted rats. For this purpose, the rats received SRB (20 mg/kg x day), STV (5.5 mg/kg x day) or an equal volume of water (controls) during 15 days. To measure hepatic gluconeogenesis, liver perfusion and isolated hepatocytes were used. Glycaemia and gluconeogenesis from L-alanine (5 mM), L-glutamine (5 mM) and L-lactate (2 mM) were decreased (P < 0.05) after pre-treatment with SRB. However, the treatment with STV did not influence glycaemia and gluconeogenesis. Moreover, to get further information about the mechanism by which SRB leaves inhibit gluconeogenesis their potential role as a PPARgamma agonist was investigated. The data showed absence of activation of PPARgamma receptors. In summary, our results showed that the reduction of glycaemia promoted by the treatment with SRB leaves was mediated, at least in part, by an inhibition of hepatic gluconeogenesis. However, this effect did not involve stevioside and the activation of PPARgamma receptors.

In this study we investigated the antidiabetic and hypolipidemic potential of dried powdered leaves of Gymnema sylvestre (GS). The acute effect of GS administered by oral gavage on glucose blood level of and lipids in nondiabetic and alloxan-diabetic rats were investigated in the following conditions: a) after a balanced meal; b) after the ingestion of 1000 mg/kg amylose or 1000 mg/kg glucose; c) after the ingestion of a mixture of 12 mL/kg soybean oil + 1% cholesterol (SOC). In addition, the effect of the treatment with GS during two (sub-acute)

RESUMO: "Efeito hipoglicemiante do extrato hidroalcoólico de folhas de Averrhoa carambola L. (Oxalidaceae)". O efeito do tratamento via oral (20 mg/kg x day) com extrato hidroalcoólico de folhas de Averrhoa carambola L. (EHFC) sobre a glicemia de jejum (15 h) foi examinada ao compararmos ratos que receberam veículo (Grupo controle) ou EHFC (Grupo EHFC) durante 15 dias. O grupo EHFC apresentou menor glicemia de jejum (p 0,05). Em contraste, o grupo EHFC apresentou maior (p 0,05) produção hepática glicose a partir de L-alanina (5 mM). Este efeito foi mediado, pelo menos parcialmente, pela ativação do catabolismo da L-alanina, inferido pela maior produção hepática de uréia (p 0,05) e L-lactato (p 0,05). Diferente da L-alanina, a produção hepática de glicose a partir de L-glutamina (5 mM), L-lactato (2 mM) e glicerol (2 mM) no grupo EHFC foi similar ao grupo controle. Adicionalmente, o efeito do tratamento com EHFC sobre a captação de glicose no músculo soleus, inferida pela incorporação de [14 C]-glicose em glicogênio (síntese de glicogênio) e produção de [14 C]-lactato foi investigada, verifi cando-se resultados semelhantes nos dois grupos. Assim, concluiu-se que a redução da glicemia de jejum promovida pelo tratamento com EHFC não foi mediada por inibição da gliconeogenese hepática e/ou aumento da captação muscular de glicose.Unitermos: Averrhoa carambola, Oxalidaceae, carambola, gliconeogenese, plantas antidiabeticas, efeito hipoglicemiante. ABSTRACT:The effect of the oral treatment (20 mg/kg x day) with the hydroalcoholic extract of leaves of Averrhoa carambola L. (HELAC) on fasting glycemia (15 h) was examined. For this purpose, rats that received vehicle (Control group) or HELAC (HELAC group) during 15 days were compared. HELAC group showed lower fasting glycemia (p 0.05). In contrast, livers from HELAC group showed higher (p 0.05) glucose production from L-alanine (5 mM). This effect was mediated, at least part of it, by an activation of the catabolism of L-alanine inferred by the increased hepatic urea (p 0.05) and L-lactate (p 0.05) production. Differently of L-alanine, the glucose production from L-glutamine (5 mM), L-lactate (2 mM) and glycerol (2 mM) was similar (Control group vs. HELAC group). In addition, the HELAC treatment did not change the glucose uptake in soleus muscles, inferred by the incorporation of [ 14 C]-glucose to glycogen (glycogen synthesis) and [14 C]-lactate production. Thus, we can conclude that the reduction of fasting glycemia promoted by the treatment with HELAC was not mediated by an inhibition of hepatic gluconeogenesis and/or an increased glucose uptake by muscles.

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