Increased rates of fatty acid uptake and plasmalemmal fatty acid transporters in obese Zucker rats

Giant vesicles were used to study the rates of uptake of long-chain fatty a cids by heart, skeletal muscle, and adipose tissue of obese and lean Zucker rats. With obesity there was an increase in vesicular fatty acid uptake of 1.8-fold in heart, muscle and adipose tissue. In some tissues only fatty a cid translocase (FAT) mRNA (heart, +37%; adipose, +80%) and fatty acid-bind ing protein (FABPpm) mRNA (heart, +148%; adipose, +196%) were increased. At the protein level FABPpm expression was not changed in any tissues except muscle (+14%), and FAT/CD36 protein content was altered slightly in adipose tissue (+26%). In marked contrast, the plasma membrane FAT/CD36 protein wa s increased in heart (+60%), muscle (+80%), and adipose tissue (+50%). The plasma membrane FABPpm was altered only in heart (+50%) and adipose tissues (+70%). Thus, in obesity, alterations in fatty acid transport in metabolic ally important tissues are not associated with changes in fatty acid transp orter mRNAs or altered fatty acid transport protein expression but with the ir increased abundance at the plasma membrane. We speculate that in obesity fatty acid transporters are relocated from an intracellular pool to the pl asma membrane in heart, muscle, and adipose tissues.