The effect of the rate and route of nutrient delivery on total body and organ composition in rats

To assess the effects of administering increasing rates of total parenteral nutrition (TPN) on total-body and organ composition, infusion catheters were implanted aseptically into the right jugular vein of Sprague-Dawley rats. Animals received 14 d of either a high (H), medium (M), or low (L) rate of TPN infusion (1.22, 1.49, 1.74 MJ · kg−1BW · d−1 and 1.74, 1.48, 1.22 gN · kg−1BW · d−1, respectively; 1:1 lipid:glucose energy), or the TPN solution orally (O TPN group). Weight-matched (w) chow-fed (c) animals were sacrificed at the same final weight as the L TPN and O TPN groups (190 g, LWC group), or the M and H TPN groups (250 g, HWC group). There were 5 animals in each group. The rates of body weight increase of the M TPN, H TPN, and HWC groups were similar (p> 0.05) and greater than the L TPN and O TPN groups (p < 0.001). The L TPN and O TPN groups who received similar amounts of nutrients had similar rates of weight gain. Total body lipid expressed as a percentage of body weight was significantly greater (p < 0.01) in the L, M, and H TPN groups compared to the orally fed groups. The proportion of water and protein in the fat-free wet weight were similar for all groups (p> 0.05). The lipid content of the liver as a percentage of its weight was greater (p < 0.05) in the orally fed groups. There was no significant difference in the percentage of water or protein of individual organs or the total viscera between any group. These finding indicate that: (a) TPN administration can maintain similar rates of protein and water deposition compared to normal growth-maintaining oral diets; (b) there is an effect of route of TPN administration on lipid deposition in adipose tissues; and (c) infusion of a glucose/lipid TPN regimen at rates in excess of requirements for growth in rats promotes lipid deposition in adipose tissues rather than visceral tissues.