Hypolipidemic effects of flavonoids extracted from Lomatogonium rotatum

Contained in the Mongolian volumes of Chinese Materia Medica, Lomatogonium rotatum Fries ex Nym. may reduce blood lipid levels and prevent obesity; however, its exact mechanism of action remains unclear. The present study investigated the hypolipidemic and obesity-inhibiting effects of four similarly structured flavonoids extracted from L. rotatum. According to a well-established method, flavonoids such as decussatin were extracted from the whole herb of L. rotatum, and male Wistar rats were subsequently fed a high-fructose diet supplemented with flavonoids (20 mg/kg) for 12 weeks. The levels of total cholesterol, triglyceride (TG), low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol (HDL-C) were detected. In addition, hepatic and epididymal adipose tissues were weighed, and levels of blood glucose, alanine aminotransferase, aspartate aminotransferase, non-esterified fatty acid, insulin and leptin were determined. The mRNA expression levels of fatty acid synthase (FAS) were analyzed using a reverse transcription polymerase chain reaction; whereas FAS, adenosine monophosphate-activated protein kinase (AMPK) and threonine-172 phosphorylated AMPK protein levels were detected by western blotting. The epididymal adipose tissues of rats fed with flavonoids were lighter, as compared with those fed with fructose in the model group. Following a 12-week administration of flavonoids, the serum levels of fasting blood glucose, feeding blood glucose and leptin were decreased. Furthermore, flavonoid treatment reduced TG and cholesterol levels in the blood and increased serum HDL-C levels, as compared with the model group. High-fructose diet administration significantly increased FAS mRNA and protein expression levels, whereas the FAS protein levels of flavonoid-treated rats were markedly reduced. The flavonoid compounds also enhanced threonine-172 phosphorylation of AMPK in the liver lysate, and all flavonoids successfully downregulated leptin levels and the majority decreased the relative weights of epididymal adipose tissue. Therefore, flavonoids may function in a similar way to epigallocatechin gallate, which has previously been shown to inhibit FAS activity by stimulating AMPK in hepatocyte cells via the liver kinase B1 pathway.