Differential oxidation of saturated and unsaturated fatty acids in vivo in the rat

The oxidation rates of lauric, myristic, palmitic, stearic, oleic, alpha-linolenic, linoleic, kappa-linolenic, dihomo-gamma-linolenic and arachidonic acids were studied by use of a radioisotope tracer technique in weanling rats at rest in a metabolism chamber over 24 h. Of the saturated fatty acids, lauric acid (12:0) was the most efficient energy substrate: the longer the chain length of the saturated fatty acids, the slower the rate of oxidation. Oleic acid (18:1) was oxidized at a remarkably fast rate, similar to that of lauric acid. Of the omega 6 essential fatty acids studied, linoleic acid (18:2 omega 6) was oxidized at a faster rate than any of its metabolites, with arachidonic acid (20:4 omega 6) being oxidized at the slowest rate. The rate of oxidation of gamma-linolenic acid (18:3 omega 3) was almost as fast as that of lauric and oleic acids.