The uptake and intracellular metabolism of 4-(1-pyrene)butanoic
acid (P4), 10-(1-pyrene)decanoic
acid (P10) and
12-(1-pyrene)dodecanoic acid (P12) were investigated in cultured lymphoid cell lines from normal individuals and from a patient with multisystemic
lipid storage myopathy (MLSM). The cellular uptake was shown to be dependent on the
fatty-acid chain length, but no significant difference in the uptake of
pyrene fatty acids was observed between MLSM and control lymphoid cells. After incubation for 1 h the distribution of fluorescent
fatty acids taken up by the lymphoid cell lines also differed with the chain length, most of the fluorescence being associated with
phospholipid and
triacylglycerols. In contrast with P10 and P12, P4 was not incorporated into neutral
lipids. When the cells were incubated for 24 h with the
pyrene fatty acids, the amount of fluorescent
lipids synthesized by the cells was proportional to the
fatty acid concentration in the culture medium. After a 24 h incubation in the presence of P10 or P12, at any concentration, the fluorescent
triacylglycerol content of MLSM cells was 2-5-fold higher than that of control cells. Concentrations of
pyrene fatty acids higher than 40 microM seemed to be more toxic for mutant cells than for control cells. This cytotoxicity was dependent on the fluorescent-
fatty-acid chain length (P12 greater than P10 greater than P4). Pulse-chase experiments permitted one to demonstrate the defect in the degradation of endogenously biosynthesized
triacylglycerols in MLSM cells (residual activity was around 10-25% of controls on the basis of half-lives and initial rates of P10- or P12-labelled-
triacylglycerol catabolism); MLSM lymphoid cells exhibited a mild phenotypic expression of the
lipid storage (less severe than that observed in fibroblasts). P4 was not utilized in the synthesis of
triacylglycerols, and thus did not accumulate in MLSM cells: this suggests that natural
short-chain fatty acids might induce a lesser
lipid storage in this disease.