Measuring VLDL₁ secretion in humans with an intravenous fat emulsion test

Tracer techniques to assess very-low-density lipoprotein (VLDL) secretion in humans are expensive, are time consuming, and require mathematical models to estimate VLDL kinetics. Here, we describe an alternative, time- and cost-efficient protocol to directly determine VLDL₁ secretion with an intravenous (i.v.) lipid emulsion test that does not require tracers and compartmental modeling. We describe steps for intralipid infusion, blood sampling, and removal of intralipid from plasma samples, followed by density gradient ultracentrifugation to isolate VLDL₁ fraction and measure the secretion rate. For complete details on the use and execution of this protocol, please refer to Bjorkegren et al. (1996),¹ Al-Shayji et al. (2007),² and Metz et al. (2022).³.