Hypertriglyceridemia induced by short-term lipid infusions causes redistribution of neutral lipid components between endogenous lipoproteins and emulsion particles. To determine whether such redistribution occurs over a long-term infusion period and affects lipoprotein pattern, we studied seven patients with inflammatory bowel disease who received cyclic home parenteral nutrition for two consecutive periods of 3 months with two different lipid emulsions. During each period, they received in random order either an emulsion composed exclusively of soy-derived long-chain triglycerides (LCTs) or another emulsion containing an equal weight:weight mixture of long- and medium-chain triglycerides (MCTs/LCTs). Both emulsions contained 20 triglycerides (TGs) and 1.2 phospholipids. Lipids provided 50 of nonprotein energy. Blood samples were taken once a week, 1 hour before the end of infusion (during) and again after a 6- to 8-h lipid-free interval (baseline). During infusion, there was a moderate increase of plasma TGs and phospholipids and a slight decrease of plasma esterified cholesterol (CE) and free cholesterol. Most of the plasma TGs increase occurred in the very-low-density lipoprotein fraction (containing both emulsion particles and the endogenous very-low-density lipoprotein), but there was also an increase of TGs content in low-density lipoprotein (LDL) and high-density lipoprotein (HDL) that was more pronounced with MCTs/LCTs. Acquisition by exogenous particles of CE transferred from LDL and HDL was significant for the LCT emulsion only. Although no change was observed in plasma lipid concentration of baseline samples during 3 months of home parenteral nutrition, some modifications were observed in the composition of lipoprotein fractions demonstrating a redistribution of lipid components.(ABSTRACT TRUNCATED AT 250 WORDS)