Original articleAdministration of phytosterols isolated from Aloe vera gel reduce visceral fat mass and improve hyperglycemia in Zucker diabetic fatty (ZDF) rats
Introduction
Aloe is a kind of traditional medical plant belonging to the family Liliaceae. Among 360 aloe species, Aloe barbadensis Miller (Aloe vera) is the most widely used in manufacture of food and drink products, pharmaceuticals, and cosmetics [1]. Aloe species have been used for their anti-tumor, anti-inflammatory, antioxidant, and laxative effects [2], [3], [4]. The anti-diabetic effects of Aloe have been also studied. There are some reports showed hypoglycemic effects of Aloe vera gel on streptozotocin-induced diabetic animals [5], [6]. In the clinical trial, a research group of Mahidol University demonstrated the anti-diabetic activity of Aloe vera juice [7], [8].
In our previous study, we demonstrated the anti-hyperglycemic effect of Aloe vera gel and identified five phytosterols, i.e., lophenol, 24-methyl-lophenol, 24-ethyl-lophenol, cycloartanol and 24-methylene-cycloartanol, as anti-diabetic compounds [9]. However, the effects of these compounds on the lipid metabolism have not been clear. Zucker diabetic fatty (ZDF; ZDF/Crl-Leprfa(fa/fa)) rats are used as type II diabetes model, and have a mutation in their leptin receptor and spontaneously develop obese, hyperglycemia, hyperinsulinemia and hyperlipidemia [10]. In this study, we administered two kinds of phytosterols (lophenol and cycloartanol) derived from Aloe vera gel to ZDF rats, in order to assess improving effects on hyperglycemia and hyperlipidemia.
Section snippets
Reagents
Lophenol (4-methylcholest-7-en-3-ol) and cycloartanol (9,19-cyclolanostan-3-ol) were isolated from Aloe vera gel (Fig. 1) [9]. These two compounds are dissolved in DMSO (Sigma–Aldrich, Tokyo, Japan) and the concentration was adjusted to 10 μg/ml with distilled water for the treatment sample. The final DMSO concentration was adjusted to 0.1%.
Animals
Six-week-old male Zucker diabetic fatty (ZDF/Crl-Leprfa(fa/fa)) rats and their lean littermates were purchased from Charles River Laboratories (Wilmington,
Hypoglycemic effects of Lo and Cy
Fig. 2 shows the changes in random blood glucose (A) during the treatments and the HbA1c (B) levels on the 36th day in each group. In the lean animals, the blood glucose concentrations were kept in normal levels during the experiments. In contrast, untreated ZDF rats already showed mild hyperglycemia (levels of 200 mg/dl) at the beginning of the experiment and slowly progressed. Compared to the ZDF-control group, the random blood glucose concentrations were suppressed in the rats treated with Lo
Discussion
In our previous report, we identified five minor phytosterols isolated from Aloe vera gel as the anti-diabetic compounds [9]. However, it was not clear the effects of these phytosterols on lipid metabolism. In the present study, to investigate the effects of these Aloe vera-derived phytosterols on both anti-diabetes and anti-hyperlipidemia, we administered Lo and Cy to male ZDF rats consecutively.
We observed that the random blood glucose levels and the HbA1c levels were significantly suppressed
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