Peripheral fat metabolism during infusion of an exogenous triacylglycerol emulsion.

OBJECTIVE

To test the hypothesis that intravenous infusion of lipid would bring about changes in adipose tissue metabolism, which would tend to spare net fat mobilization, and to attempt to identify the mediators of such responses.

DESIGN

The triacylglycerol (TG) emulsion, Intralipid, was infused and metabolic changes in subcutaneous adipose tissue and forearm muscle were assessed by measurements of arterio-venous differences.

SUBJECTS

Six normal male subjects aged 21-37 y, with body mass index (BMI) 23.0-25.9 kg/m2.

RESULTS

Plasma TG and non-esterified fatty acid (NEFA) concentrations rose during infusion as expected. The rise in systemic plasma NEFA concentration occurred despite decreased NEFA release from adipose tissue. Intralipid infusion resulted in a suppression of intracellular lipolysis in adipose tissue, by mechanisms which are not clear. Plasma leptin concentrations, measured in a search for the regulator of lipolysis, showed consistent leptin release from adipose tissue which did not change significantly with time.

CONCLUSION

The suppression of intracellular lipolysis in adipose tissue during Intralipid infusion is a new observation and may reflect a novel mechanism for regulation of fat storage.