Normal and
hepatoma bearing rats were fed a low level of
methyl 2-hexadecynoate in a
low fat diet for one month. The effect of the
acetylenic acid on lipid metabolism as derived from mass analysis of
lipid classes,
fatty acids and positional monoene isomers isolated from the major
lipid classes of liver and
hepatoma has been assessed.
Methyl 2-hexadecynoate caused a 25% decrease in
body weight and the appearance of essential
fatty acid deficiency symptoms within one week. Non-
tumor-bearing animals contained a seven-fold increase in all neutral
lipid classes, except
cholesterol, while host animals did not contain fatty livers. The apparent protective effect of the host animal by the
hepatoma also resulted in only marginal changes in the
fatty acid and positional monoene isomers from host liver and
hepatoma lipids. In contrast to host liver and
hepatoma,
methyl 2-hexadecynoate caused a massive accumulation of
palmitate and hexadecenoates with a concomitant decrease in
stearate and octadecenoates in most of the
lipid classes from non-
tumor-bearing animals. These changes were accompanied by a shift from the higher molecular weight
triglycerides to lower molecular weights corresponding to
carbon number 48. The high concentrations of hexadecenoates consisted predominantly of the delta 9 isomer. Despite the high concentrations of cis delta 9 hexadecenoate, precursor of cis delta 11 octadecenoate (vaccenate), total vaccenate levels of the five major
lipid classes were lower than control values. All of these data strongly suggest that long-chain 2-ynoic
acids inhibit elongation of saturated and monoene
fatty acids.