Different effects of chemically defined structured lipids containing omega3 or omega 6 fatty acids on nitrogen retention and protein metabolism in endotoxemic rats

Alternative lipids like structured triacylglycerols and omega 3 fatty acids were reported to have protein-sparing effects in the hypercatabolic state. The aim of the present study was to determine the effects of chemically de fined structured lipids (SL) with omega 3 fatty acids in position sn-2 (MFM ) compared to SL with omega 6 fatty acids in position sn-2 (MLM) on protein and energy metabolism in a low dose endotoxin (1mg/kgBW/d) rat model. We u sed L-[1-C-14] leucine isotope measurements for the estimation of whole bod y and tissue leucine kinetics. Twenty-four male Sprague Dawley rats were ra ndomly assigned to 4 groups (n=6; MFM, MFM+E, MLM, MLM+E; E:endotoxin) and received 48 h of total parenteral nutrition. Endotoxin infusion resulted in a significant decrease in mean body weight and nitrogen balance in rats of group MLM+E compared with the control group MLM (p<0.05), whereas no signi ficant decrease was observed in rats of group MFM+E. Rats of group MFM+E ha d significantly higher liver weight means and rectus muscle protein content s compared with rats of group MLM+E (p<0.05). This is the first study compa ring effects of structured lipids containing either omega 3 or omega 5 fatt y acids in position sn-2 on protein and nitrogen metabolism in response to sepsis. The results point to a possible protein-sparing effect of the fish oil containing diet that needs to be confirmed, however, by further studies based on a larger number of experimental animals. (C) 2000 Elsevier Scienc e Inc.