Background: The present study examined the effect of the polyphenol-rich fraction from Thymelaea hirsuta (PRF-Th) in a rat model of streptozotocin (STZ)-diabetes and nitric oxide (NO)-deficient hypertension.
Methods: Diabetes was induced by a single dose of STZ (90 mg/kg, i.p.). To induce NO-deficient hypertension, rats were treated with the NO synthase inhibitor N(G) -nitro-l-arginine methyl ester; l-NAME; 30 mg/kg per day, p.o. for 3 weeks. The effects of 21 days treatment with 80 mg/kg per day PRF-Th in the drinking water were evaluated in diabetic-hypertensive (DH) rats. In all groups (n = 6 in each), glycemia and systolic blood pressure were determined weekly. At the end of the experiment, hepatic glycogen was determined.
Results: Blood glucose levels decreased gradually from baseline until the end of the experiment in untreated DH rats (from 1.92 ± 0.09 to 1.3 ± 0.1 g/L; P < 0.05). Administration of PRF-Th concomitantly with l-NAME prevented the blood pressure increase in rats. After 21 days, blood pressure in PRF-Th + l-NAME- and l-NAME-treated rats was 132 ± 1 and 157 ± 1 mmHg, respectively (P < 0.001). Administration of 2 mL/kg per day PRF-Th to DH rats significantly increased hepatic glycogen levels compared with levels in untreated DH rats (13.65 ± 1.84 vs 6.34 ± 0.75 mg/g tissue, respectively; P < 0.01). Moreover, PRF-Th significantly reduced the amount of glucose absorbed in in situ perfused jejunum segments compared with control (by 33.6%; P <0.001). This effect of PRF-Th was comparable with that of acarbose, an α-glucosidase inhibitor.
Conclusions: The findings of the present study indicate that T. hirsuta has antidiabetic and antihypertensive activity in STZ-diabetic, NO-deficient hypertensive rats. This effect seems to be due to its rich polyphenol content. Therefore, T. hirsuta may be useful as a food supplement for the prevention of type 2 diabetes and hypertension.
© 2012 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd.