Efeito do extrato do quiabo (Abelmoschus esculentus L.) lipossomal sobre homeostase glicêmica e estresse oxidativo em ratos pré-diabéticos

Abstract

Glucocorticoids are widely used in clinical medicine; however, its chronic use has been associated with the development of insulin resistance. On the other hand, bioactive compounds, and functional foods such as okra (Abelmoschus esculentus L.) appear as promising in the fight against type 2 diabetes mellitus. Our study aimed to perform a physicochemical characterization of liposomes containing okra, and to test their hypoglycemic effect in insulin resistant rats induced by synthetic glucocorticoid dexamethasone (DEX). At 60 days-old, male and female Wistar rats underwent a daily injection of dexamethasone (DEX; 1mg/kg body weight, bw) for 10 days, while control rats received saline solution (NaCl, 0.9% i.p., CONT group). At 65 days-old, a batch of DEX rats were treated, via gavage for five consecutive days, with a liposome containing okra (1.5 mg/kg bw, DEX-LipoQ group) or okra extract in the free form (200 mg/kg of pc, DEX-ExtrL), as negative control, DEX rats received white liposome (without okra, DEX-LipoB). During treatment, baseline blood glucose, body mass, water and food intake were evaluated. At the end, glycemic homeostasis through glucose, insulin and pyruvate tolerance tests was evaluated. The physicochemical characterization of the developed liposomes shows a structure with an average diameter of 280 nm, zeta potential –31.46±1.48 and 6.8 as pH. In relation to CONT rats, DEX rats, in both sexes, were hyperglycemic, glucose intolerant and insulin resistant (P<0.05), as well as reduced pyruvate response at pyruvate tolerance test. Similarly, DEX-LipoB rats, in both sexes, were hyperglycemic, glucose and pyruvate intolerant, and insulin resistant compared to CONT rats (P<0.05) but did not statistically different of the DEX rats (P>0.05). DEXLipoQ and DEX-ExtrL rats, in both sexes, presented basal glycemia, glucose tolerance and inulin responsiveness like those observed in CONT rats (P>0.05), but significantly different of those observed in DEX rats (P<0.05). Regarding sexual dimorphism, glycemic homeostasis of males was more vulnerable to the effect of dexamethasone, as well as showing a more prominent improvement to the effect of okra; on the other hand, peripheral insulin sensitivity in females improved with magnitude around of 40-fold greater than in males. In summary, the treatment with okra, even in a smaller concentration, was effective on reversing glucose and intolerance and insulin resistance, and improving pyruvate responsiveness which was also observed in rats treated with okra in a free form, but only by using a higher okra-extract concentration. Furthermore, considering the applied dose, liposomes containing okra was more effective in promoting glycemic control in hyperglycemic animals, in both sexes, than it was using okra-extract in free form.