Mechanism of cellular uptake of long-chain fatty acids: Do we need cellular proteins?

Defining the mechanism(s) of long-chain fatty acid movement through membranes is vital to understanding whether or not entry of fatty acids into cells can be controlled at the plasma membrane of a typical cell. Is there a protein that acts as gatekeeper, regulating the amount, and possibly the type, of fatty acid that can enter the cell for metabolism? Is the lipid bilayer of the membrane highly permeable to fatty acids, and is the rate of simple diffusion on the time scale of metabolism? We will briefly review efforts to study diffusion in model lipid membranes that are devoid of proteins. We also present new results using dual fluorescence approaches showing that fatty acids diffuse very rapidly across the plasma membrane of the adipocyte.