Anti-obesity and lipid-lowering effects of mountain caviar extract and its principal saponin momordin Ic via delayed gastric emptying and GLP-1 secretion independent of energy expenditure

The fruit of Bassia scoparia (L.) A. J. Scott [syn. Kochia scoparia (L.) Schrad.], commonly known as mountain caviar, are traditionally consumed as both food and medicine. Oral administration of 65% aqueous ethanol mountain caviar extract (MCE, 125-250 mg/kg) significantly suppressed postprandial plasma triglyceride (TG) elevation in olive oil-loaded mice. Among isolated saponins, the principal saponin momordin Ic exhibited significant antihyperlipidemic effect at 20 mg/kg. HPLC quantitative analysis using charged aerosol detector revealed that momordin Ic accounted for 12.6% of the MCE. Mechanistic studies demonstrated that momordin Ic markedly delayed gastric emptying (GE) without inhibiting pancreatic lipase activity. Moreover, momordin Ic significantly enhanced plasma glucagon-like peptide-1 (GLP-1) levels. In a high-fat diet-fed (HFD) mice model, 14-day administration of MCE suppressed body weight gain. Similarly, momordin Ic (20 mg/kg/day) significantly reduced visceral fat accumulation, liver cholesterol content, and plasma low-density lipoprotein/very low-density lipoprotein (LDL/VLDL) cholesterol levels, with a tendency to decrease plasma TG and total cholesterol. Notably, total energy expenditure measured using the doubly labeled water method was not significantly altered by MCE. These findings indicate that MCE and momordin Ic exert anti-obesity and lipid-lowering effects primarily through the suppression of dietary fat absorption and partly delayed GE, rather than by enhancing energy expenditure.