A 70% Ethanol Extract of Mistletoe Rich in Betulin, Betulinic Acid, and Oleanolic Acid Potentiated β-Cell Function and Mass and Enhanced Hepatic Insulin Sensitivity

Figure 5

Insulin-stimulated glucose uptake in 3T3-L1 adipocytes and PPAR-γ activity by betulin, betulinic acid, and oleanolic acid. 3T3-L1 adipocytes were treated with low (0.5 μg/mL) or high (5 μg/mL) doses of vehicle (DMSO) or low (5 μM) or high (50 μM) doses of betulin, betulinic acid, and oleanolic acid for 16 hours. At the end of the incubation, insulin (0.2 nM) was administered for 30 minutes to determine insulin-stimulated glucose uptake, which would represent insulin-sensitizing activities. Vehicle and 10 nM insulin treatments were used as negative and positive controls, respectively. The data are presented as ³H-deoxyglucose content per mg of protein in the cells, which indicates the degree of glucose uptake (). After 16 hours of treatment with betulin, betulinic acid, or oleanolic acid, the cells were immediately lysed with a lysis buffer, and the phosphorylation and expression levels of Akt, GSK-1β, and AMPK were determined by immunoblotting with specific antibodies (b). Values on the bars with different superscripts were significantly different in a Tukey post hoc test at a significance of .

(a)

(b)