Abnormal fatty acid composition of biotin-responsive multiple carboxylase deficiency fibroblasts

Clinical and biochemical correlations in the biotin-responsive multiple carboxylase deficiencies have suggested that disordered lipogenesis plays a role in the pathogenesis of the disease. In particular, the activity of biotin-dependent acetyl CoA carboxylase and the de novo synthesis of fatty acids are reduced in mutant fibroblasts. In the present work, we examine the biochemical consequences of these deficiencies, and document and characterize an abnormal fatty acid composition in holocarboxylase synthetase deficiency fibroblasts. Following growth in biotin-restricted medium, the total fatty acid content of mutant cells is reduced. There were significant reductions in the percentage as 16:0, 18:0 and 20:3N9 fatty acids, with the proportion of longer-chain fatty acids either increased or maintained at control levels. The cellular content of 16:0, 16:1, 18:0, 18:1 and 20:3N9 fatty acids was reduced, while that of the longer-chain fatty acids was preserved at control levels in mutant cells deprived of biotin. We speculate that the components of the altered fatty acid pools may be disproportionately incorporated into complex lipids in mutant cells, with pathologic effects on the multiple carboxylase deficiency phenotype.