ENRICHMENT OF SELECTED SERUM FATTY-ACIDS AFTER A SMALL ORAL DOSAGE OF(1-C-13)TRIOLEIN AND (8-C-13)TRIOLEIN IN HUMAN VOLUNTEERS ANALYZED BYGAS-CHROMATOGRAPHY COMBUSTION ISOTOPE RATIO MASS-SPECTROMETRY

In this study the fate of 100 mg orally administered (1-C-13)- and (8- C-13)triolein was traced in the serum lipids of four healthy human sub jects. After an overnight fast the subjects consumed hourly meals of a liquid formula diet over 12 h. Ninety minutes after the first meal in the first study (1-C-13)triolein was given and in the repeat study th e same subject received (8-C-13)triolein. Triacylglycerol (TG), phosph olipid (PL) and cholesterol ester (CE) were isolated from serum sample d prior to and in intervals after isotope administration. Fatty acid c omposition of serum lipids was measured using gas chromatography/mass spectrometry. C-13 enrichment in palmitic, stearic, oleic and linoleic acids of these fractions was determined by gas chromatography/isotope ratio mass spectrometry. With (8-C-13)triolein a significantly higher enrichment (peak + 17.1 +/- 14.3 parts per thousand delta(13)C) was f ound in the oleic acid of TG fraction than with (1-C-13)triolein (peak -7.1 +/- 4.2 parts per thousand), which may be due to a faster elimin ation of (1-C-13)oleic acid from serum TG. C-13 enrichments in the oth er fatty acids of the TG fraction as well as of PL and CE fractions we re in the range of natural(13)C abundance (-25 to -32 parts per thousa nd).