Adipose tissue labelling in man, using a structurally-labelled fatty acid as tracer.

Three healthy male subjects had their adipose tissue enriched with a structurally-labelled fatty acid, 13-methyltetradecanoic acid (13-MTD), occurring naturally only in trace amounts. Needle biopsies from femoral, gluteal and abdominal adipose tissue were obtained at several intervals during a 6-week 13-MTD ingestion period and also along an 11-week period following the cessation of the label intake. Fatty acid composition was analysed by gas-liquid chromatography. Using this method, it was possible to show that different adipose tissues had various responsiveness to labelling (with abdominal fat having the highest one) and hence had different turnover rates. Incorporation and particularly disappearance rates were slow, half-lifes for label incorporation ranged from 2 to 12 weeks and that for label mobilization ranged from 4 to 10 months, thus confirming few other published results. The unexpected observation that incorporation of the label did not cease at the end of the 13-MTD feeding period, but did continue for at least a fortnight, might indicate that existence of a buffer pool where fatty acids may be momentarily stored before their definite incorporation into adipose tissue, as suggested in few other studies.