Betulinic acid inhibits high-fat diet-induced obesity and improves energy balance by activating AMPK

BACKGROUND AND AIM

Metabolic syndromes are prevalent worldwide and result in various complications including obesity, cardiovascular disease and type II diabetes. Betulinic acid (BA) is a naturally occurring triterpenoid that has anti-inflammatory properties. We hypothesized that treatment with BA may result in decreased body weight gain, adiposity and hepatic steatosis in a diet-induced mouse model of obesity.

METHODS AND RESULTS

Mice fed a high-fat diet and treated with BA showed less weight gain and tissue adiposity without any change in calorie intake. Gene expression profiling of mouse tissues and cell lines revealed that BA treatment increased expression of lipid oxidative genes and decreased that of lipogenesis-related genes. This modulation was mediated by increased AMP-activated protein kinase (AMPK) phosphorylation, which facilitates energy expenditure, lipid oxidation and thermogenic capacity and exerts protective effects against obesity and nonalcoholic fatty liver disease. Overall, BA markedly inhibited the development of obesity and nonalcoholic fatty liver disease in mice fed a high-fat diet, and AMPK activation in various tissues and enhanced thermogenesis are two possible mechanisms underlying the antiobesity and antisteatogenic effects of BA.

CONCLUSIONS

The current findings suggest that treatment with BA is a potential dietary strategy for preventing obesity and nonalcoholic fatty liver disease.

Cytotoxic effects of the components in heat-treated mistletoe (Viscum album)

Major cytotoxic components were fractionated from Korean mistletoe and the changes of their cytotoxic effects caused by heat treatment were investigated. The high cytotoxicity of isolated lectin I completely disappeared by heating for 30 min. The fractions of viscotoxins and alkaloids maintained their activities even after heating for 60 and 180 min, respectively. The alkaloid fraction was more cytotoxic to tumor MSV cells than to non-tumor A31 cells and the activity pattern was not changed by heat treatment. The possible contributions of alkaloids and viscotoxins to the activities of heat-treated mistletoe extracts such as tea or decoctions are discussed.

Cytotoxicity of heat-treated Korean mistletoe

The cytotoxic effects of preparations of Korean mistletoe (Viscum album L. var. coloratum Ohwi) on non-tumorigenic A31 cells and tumorigenic MSV cells were investigated. While the aqueous extract from Korean mistletoe (<8 microg/ml) showed strong cytotoxicity on both cell lines, the heat-treated extract was much less cytotoxic with TD50 values of above 300 microg/ml. The heat-treated extract showed a growth-enhancing effect on non-tumorigenic cells and a cytotoxic effect on tumorigenic cells. The alkaloids fraction, which was isolated from the crude extract, was not cytotoxic to non-tumorigenic A31 cells up to 550 microg/ml, but was cytotoxic to tumorigenic MSV cells at 138 microg/ml. Heat treatment did not change the cytotoxic effects of the alkaloids fraction, indicating that the selective cytotoxicity of the heat-treated mistletoe extract on tumorigenic MSV cells might be due to its alkaloids. In order to study the changes in the cytotoxicity of fermented Korean mistletoe, the crude and heat-treated extracts were inoculated with Lactobacillus plantarum. During 7 days of fermentation, the cytotoxicity of the fermented heat-treated extract was increased while that of the fermented crude extract was not changed significantly.