RECENT DEVELOPMENTS IN LIPID EMULSIONS - RELEVANCE TO INTENSIVE-CARE

For years, intravenous lipid supply has been considered as a means of providing an efficient fuel to many tissues of the body and of prevent ing or correcting essential fatty acid deficiency. The potential for:l ipid emulsions to modulate cell function via their content of specific fatty acids and of liposoluble vitamins has not received much attenti on yet. Soybean [lung-chain triglycerides (LCT)I emulsions provide a v aluable source of energy, but they are excessively rich in omega-6 ess ential fatty acids (FAs). Their infusion is associated with an accumul ation of linoleate and a reduction of long-chain (greater than or equa l to C20) omega-6 and omega-3 fatty acids in cell membrane phospholipi ds, as well as with a depletion of antioxidant status, associated with a reduction of alpha-tocopherol in plasma lipoproteins. Infusions of the mixed medium-chain triglycerides (MCT)/LCT (50%:50%; wt:wt) largel y bypass these disadvantages. In addition, plasma elimination of MCT/L CT is faster than that of LCT. Recent advances indicate a great potent ial for omega-3 FAs incorporated into membrane phospholipids to modula te cell response to various stimuli and to influence several intracell ular metabolic processes. Furthermore, some of these FA directly influ ence the production and the action of important mediators, the eicosan oids. In practical terms, an increased intake of omega-3 FAs may reduc e inflammatory and thrombotic responses while protecting tissue microp erfusion and immune defenses. Such properties may find interesting app lications in several types of intensive care unit patients, provided t hat omega-3 FA incorporation takes place promptly. We recently had the opportunity to study in vitro and in vivo the metabolism of emulsions made of a mixture of MCT, soybean LCT, and fish oil triglycerides. Pl asma elimination of such preparations appeared to be very fast, and th eir infusion was not associated with a prolonged residence of emulsion particles. In addition, uptake of remnants enriched with omega-3 FAs and liposoluble vitamins was fairly fast and occurred in several types of cells, leading to an efficient incorporation of omega-3 FAs in cel l membranes within a few hours. The understanding that remnant uptake plays a significant role in tie delivery of components included in lip id emulsions opens new areas of investigation and is likely to rind se veral conditions of applications for new types of preparations. (C) El sevier Science Inc. 1997.