PERIPHERAL FAT-METABOLISM DURING INFUSION OF AN EXOGENEOUS TRIACYLGLYCEROL EMULSION

OBJECTIVE: To test the hypothesis that intravenous infusion of lipid w ould bring about changes in adipose tissue metabolism, which would ten d to spare net fat mobilization, and to attempt to identify the mediat ors of such responses. DESIGN: The triacylglycerol (TG) emulsion, Intr alipid, was infused and metablic changes in subcutaneous adipose tissu e and forearm muscle were assessed by measurements of arterio-venous d ifferences. SUBJECTS: Six normal male subjects aged 21-37 y, with body mass index (BMI) 23.0-25.9 kg/m(2). RESULTS: Plasma TG and non-esteri fied fatty acid (NEFA) concentrations rose during infusion as expected . The rise in systemic plasma NEFA concentration occurred despite decr eased NEFA release from adipose tissue. Intralipid infusion resulted i n a suppression of intracellular lipolysis in adipose tissue, by mecha nisms which are not clear. Plasma leptin concentrations, measured in a search for the regulator of lipolysis, showed consistent leptin relea se from adipose tissue which did not change significantly with time. C ONCLUSION: The suppression of intracellular lipolysis in adipose tissu e during Intralipid infusion is a new observation and may reflect a no vel mechanism for regulation of fat storage.