Selective inhibition of synthesis of enzymes for de novo fatty acid biosynthesis by an endotoxin-induced mediator from exudate cells.

An endotoxin-induced mediator from exudate cells markedly suppresses the activities of the key enzymes for de novo fatty acid biosynthesis--acetyl-CoA carboxylase [acetyl-CoA:carbon dioxide ligase (ADP-forming), EC 6.4.1.2] and fatty acid synthetase--in differentiating 3T3-L1 murine preadipocytes. The loss in activity, at least in part, appears to be due to a specific effect on the synthesis of the enzymes, as determined by a decreased incorporation of [35S]methionine into immunoadsorbable acetyl-CoA carboxylase and fatty acid synthetase when the cells were exposed to the mediator. During this exposure, the radiolabeling of proteins with [35S]methionine in a particulate fraction was decreased by nearly 50% with little change in the soluble protein fraction. Sodium dodecyl sulfate/polyacrylamide gel analysis of the labeled protein indicated no major disturbances of protein synthesis in general; however, the syntheses of specific proteins in both the soluble and particulate fractions were enhanced or depressed. The present study demonstrates that endotoxin promotes the release of a mediator from exudate cells that regulates key anabolic activities in adipose cells.