VANADATE ELEVATES LIPOGENICITY OF STARVED RAT ADIPOSE TISSUE : MECHANISM OF ACTION

We have established an experimental system in rats in which the lipogenic capacity of adipose tissue was decreased in vivo by prolonged fasting, and restored in vitro by glucose together with insulin or vanadate. Incubation of fasted adipose explants for 5 h at 37 C with 2 mm glucose alone did not elevate lipogenic capacity. However, glucose with insulin (17 nm) or vanadate (100 μm), led, respectively, to 2.2- and 8- to 10-fold elevation. Actinomycin D (50μ m) completely blocked this increase, while low concentrations (ED50 = 4.0 ± 0.4 μm) of vanadate potentiated it. Neither insulin nor vanadate elevated fasted adipose explants’ lipogenic capacity in the absence of glucose, or in the presence of the nonmetabolizable glucose analog 3-O-methylglucose. Upon replacing glucose with 2-deoxyglucose (1 mm), a glucose analog that undergoes phosphorylation to 2-deoxyglucose-6-phosphate with no further metabolism, vanadate was nearly as potent as with glucose in elevating lipogenic capacity. Vanadate was superior to...