Fatty acid transport in multiple carboxylase deficiency fibroblasts

Holocarboxylase synthetase (HS) and biotinidase deficiencies have been identified as causes of biotin-responsive multiple carboxylase deficiency. Acetyl-CoA carboxylase (ACC) deficiency has been shown to occur in multiple carboxylase deficiency, and HS(-) fibroblasts are being employed to investigate compensatory regulatory responses in cells deficient in ACC. In previous studies, biotin starved HS(-) fibroblasts showed a reduced fatty acid content, an abnormal percentage composition of fatty acids, and a preservation of longer-chain fatty acid contents of cells. We herein ask whether the mutant cells show compensatory increases in the transport of longer-chain fatty acids from the medium into fibroblasts. In the present experiments there was no change in the uptake of arachidonate, palmitate or oleate following growth of mutant and control fibroblasts in (+) or (-) biotin conditions. Differential fatty acid uptake from the medium is therefore not a compensatory mechanism in HS(-) cells, and cannot account for the specific changes in fatty acid composition produced by biotin restriction.