Aqueous and methanol extracts of Vernonia amygdalina leaves exert their anti-obesity effects through the modulation of appetite-regulatory hormones

Abstract

Context: Aqueous and methanol extracts of Vernonia amygdalina Del. (Asteraceae) (AEVA and MEVA, respectively) leaves are reported to possess anti-obesity properties, exerted through unknown mechanisms. Objective: This study investigated the effects of AEVA and MEVA on relevant hormones and enzymes in high-fat diet (HFD)-induced obese rats. Materials and methods: Forty-two Wistar rats were placed into seven groups. The test groups received 100 mg/kg.bw AEVA (AEVA100), 500 mg/kg.bw AEVA (AEVA500), 50 mg/kg.bw MEVA (MEVA50) and 200 mg/kg.bw MEVA (MEVA200), respectively. The positive control (PC) group received 20 mg/kg.bw Orlistat, while the negative control (NeC) and normal control (NoC) groups received distilled water. The extracts were given orally daily for 12 weeks. Thereafter, the concentrations/activities of relevant hormones/enzymes in their sera were determined. Results: Insulin concentrations (ng/ml) in the test groups ranged from 1.08 ± 0.01 (AEVA100) to 1.09 ± 0.01 (AEVA500). They were all similar (p >.05) to the NoC and PC controls. Leptin concentrations (pg/ml) in the test rats ranged from 0.02 ± 0.01 (AEVA500) to 0.03 ± 0.00 (MEVA50), and were all similar to the NoC group. The ghrelin concentrations of only the AEVA500 and MEVA200 groups were similar to those of the PC group (0.10 ± 0.01 pg/ml). AEVA100 and MEVA200 resulted in adiponectin concentrations (ng/ml) of the rats (0.27 ± 0.04 and 0.28 ± 0.04 respectively) that were similar to the PC group. The activities of lipoprotein lipase and the concentrations of intestinal amylase in the test rats were similar to values obtained for the control groups. Conclusion: Appetite regulation may be the mechanism through which the weight-loss properties of AEVA and MEVA are expressed.