ABCD1 and X-linked adrenoleukodystrophy: Because both acyl chain length and retention time of D31-16:0-CoA are close to those of 17:0-CoA rather than 26:0-CoA, these results indicate that the amounts of VLCFA-CoA species with fewer number of double bonds in their acyl chain moiety were underestimated in this study, and the amount of 26:1-CoA may be much higher than that of 18:1-CoA in both X-ALD fibroblasts and ABCD1-deficient HeLa cells.