Glucose and triglyceride lowering activity of Pterocarpus santaniloides leaf extracts against dexamethasone induced hyperlipidemia and insulin resistance in rats

Abstract

The triglyceride and glucose lowering potential of the leaf extracts of Pterocarpus santalinoides was investigated in dexamethasone induced hyperlipidemia and insulin resistance in rats. Acute toxicity test was performed according to standard methods. An oral glucose tolerance test was carried out in the presence of the extracts in normal rats. Then, graded doses of aqueous and methanol extracts of P. santalinoides (AEPS and MEPS) were administered orally to rats in four groups, respectively, after a 12 h fast followed by subcutaneous administration of dexamethasone (10 mg/kg body wt). Rats in a fifth group received saline (5 ml/kg p.o) followed by dexamethasone (10 mg/kg body wt s.c) and served as positive control while a sixth group served as normal control. The period of extract and dexamethasone administration was 10 days. Acute toxicity test showed that the extract had an oral LD₅₀ > 5000 mg/kg in rats. Graded doses of aqueous and methanol extracts of P. santalinoides to glucose loaded normal rats resulted in significant lowering of blood glucose concentration which started at 90 min post-glucose load when compared with the 60 mine (peak) sample (p < 0.001) and also when compared with the negative control value at 90 min (p < 0.001). Administration of dexamethasone to fasted rats for 10 days resulted in hyperlipidemia and insulin resistance evidenced by the significant increase in mean glucose level (194.50 ± 9.87 mg/dl) and triglyceride level (268.75 ± 21.54 mg/dl) in the positive control when compared with the normal control with mean glucose and triglyceride concentrations of 64.00 ± 3.44 mg/dl and 100.00 ± 15.54 mg, respectively (p < 0.01; p < 0.001). Graded doses of the AEPS and MEPS significantly antagonized dexamethasone induced hyperlipidemia and insulin resistance in rats when compared with the positive control (p < 0.001) and the normal control, respectively (p < 0.05). The antagonistic potency of AEPS was dose dependent while that of the MEPS was not. The leaf extracts of P. santalinoides possess triglyceride and glucose lowering properties in dexamethasone induced hyperlipidemia and insulin resistance and could be of therapeutic value in the management of metabolic syndrome.

Key words: Pterocarpus santalinoides, leaf extracts, glucose tolerance, hyperlipidemia, insulin resistance, glucose, triglyceride, dexamethasone.