Use of structured triacylglycerols containing predominantly stearic and oleic acids to probe early events in metabolic processing of dietary fat

Early events in the metabolic processing of dietary triacylglycerol may hav e an important impact on subsequent development of risk factors for coronar y heart disease, We have used structured triacylglycerols containing predom inantly stearic or oleic acids at the m-2 position to probe aspects of the processing of dietary fatty acids presented to adipose tissue in chylomicro n-triacylglycerol. Studies were conducted on 14 healthy women who were give n meals con; taining 85 g carbohydrate and 60 g of either of the two struct ured triacylglycerols in random order. Systemic concentrations and arterio- venous differences across adipose tissue for plasma triacylglycerol and non -esterified fatty acids were measured, together with analysis of the fatty acid composition of the relevant fractions, The stereo-specific structure o f the ingested triacylglycerol was largely preserved in chylomicron-triacyl glycerol, Systemic concentrations of total and individual nonesterified fat ty acids were not significantly different after ingestion of the two fats, nor were their rates of release across adipose tissue. The composition of n onesterified fatty acids released from adipose tissue changed after the mea l to reflect more closely the composition of the triacylglycerol ingested, but again no significant differences were observed between the two test mea ls. There was no detectable release of monoacylglycerol from adipose tissue after either test: meal.jlr We conclude that the environment for lipoprote in lipase action in adipose tissue in vivo is likely to be highly organized , such that there is no release of monoacylglycerol, nor preferential uptak e or release of fatty acids from chylomicron-triacylglycerol according to t he nature or the position within triacylglycerol of the fatty acid.