Effect of various lipid emulsions on total parenteral nutrition-induced hepatosteatosis in rats

The effect of various lipid emulsions on the development of fatty liver during total parenteral nutrition (TPN) was investigated in rats given TPN for 7 days. Medium-chain triglycerides (MCT), long-chain triglycerides (LCT), chemically defined triglycerides (CDT; structured lipid with a high purity of 94.3%), and a mixture of MCT and LCT (MIX) were prepared as the lipid emulsions. TPN provided 350 kcal/kg/day, with a nonprotein calorie/nitrogen ratio of 160. The TPN-1 group received 10% nonprotein calories and the TPN-2 group received 30% nonprotein calories. MCT TPN was found to have some disadvantages, especially with regard to nitrogen balance and plasma albumin levels. Total cholesterol and phospholipids tended to be high in the MCT TPN group. The hepatic lipid content was higher in the lipid-free TPN and the MCT TPN groups, and lower in the CDT and LCT TPN groups. Histologically, the livers of the MIX, CDT, and LCT TPN groups showed less fatty change than those of the FREE and MCT groups.     

Lipid emulsions and reticuloendothelial system function in healthy and burned guinea pigs

The effect of total parenteral nutrition (TPN) regimens containing various quantities of long-chain triglyceride (LCT) and medium-chain triglyceride (MCT) emulsions on bacterial clearance and organ sequestration was evaluated in healthy and burned guinea pigs. In healthy guinea pigs, increasing the LCT component of TPN to 75% or greater of the nonprotein calories resulted in hepatomegaly, splenomegaly, a significant reduction in the sequestration of intravenously administered Pseudomonas aeruginosa by the liver and spleen, and a markedly increased clearance of bacteria into the lung. In burned guinea pigs, replacement of LCT with MCT emulsions at 75% of the nonprotein caloric intake reduced the sequestration of bacteria in the lung and restored to normal hepatic and splenic uptake. These results suggest that LCT emulsions at 75% of nonprotein calories result in reticuloendothelial system overload and increased bacterial sequestration in the lungs in normal and burned animals. In contrast, administration of MCT emulsions to the burned animal is less likely to result in increased pulmonary sequestration and decreased hepatic or splenic reticuloendothelial system function.     

Brain lipid composition in rabbits after total parenteral nutrition with two different lipid emulsions

ObjectiveTo study the changes occurring in brain lipid composition after the administration of total parenteral nutrition (TPN) by comparing two lipid emulsions, one with long-chain triacylglycerols (LCT) and the other with long-chain and medium-chain triacylglycerols (MCT/LCT 50%/50%).MethodsWe used 21 young New Zealand rabbits divided into three groups of seven animals each. Two groups were subjected to TPN for 7 d, with each group receiving using one of two different lipid emulsions: Intralipid 20% (group LCT) and Lipofundin MCT/LCT 20% (group MCT/LCT). The third control group received an oral diet and underwent the same surgical procedure with the administration of intravenous saline solution. The energy administered in the TPN formulas was non-protein 100 kcal ? kg^?1 ? d^?1, with 40% corresponding to fats.ResultsThere were modest increases in plasma cholesterol and triacylglycerols. In the brain tissue, there was a decrease of phosphatidylcholine in animals with TPN, which was greater in group LCT. There were no significant differences in the overall percentage distribution of brain fatty acids among the groups.ConclusionThe lipid emulsions administered in TPN, especially those prepared exclusively with LCT, cause changes in the brain lipid polar fractions of young rabbits.     

Effect of Medium-Chain Triglyceride Emulsion in Total Parenteral Nutrition on Experimental Hepatic Metastasis in the Rat

Background: This study evaluated the effect of total parenteral nutrition (TPN) regimens containing a medium-chain triglyceride (MCT) emulsion on tumor metastasis. Methods: Tumor metastasis development was assessed by the number of metastatic foci on the liver surface in rats inoculated with ACL-15 tumor cells via the portal vein. Rats received one of the following TPN regimens: TPN containing an MCT emulsion (group M), in which tricaprylin emulsion served as the MCT and comprised 50% of nonprotein calories (NPC); TPN containing a long-chain triglyceride (LCT) emulsion (group L), in which soybean oil served as the LCT and comprised 50% of NPC; and TPN without lipid emulsion (group G), in which dextrose comprised 100% of NPC. Results: The number of metastatic foci was greatest in rats receiving TPN containing the MCT emulsion on day 11 after tumor cell inoculation and either 11 days of TPN or 2 days of TPN followed by 9 days standard rat chow. Conclusions: TPN containing MCT emulsion increases liver metastasis early in its administration. (Journal of Parenteral and Enteral Nutrition 21:220–223, 1997)     

Clinical and metabolic effects of two lipid emulsions on the parenteral nutrition of septic patients

OBJECTIVE: We compared the metabolic and clinical effects of two lipid emulsions, long-chain triacylglycerols (LCT) and a mixture of medium- and long-chain triacylglycerols (MCT/LCT), in septic patients. METHODS: Both groups received total parenteral nutrition (TPN) with a solution enriched with branched-chain amino acids (BCAA). Seventy-two septic patients received TPN with MCT/LCT (group 1) or LCT (group 2). Before starting TPN (basal) and 10 d after (final), various parameters were evaluated. RESULTS: Twenty-six subjects in each group completed the study. Both groups showed an increase in cholestasis enzymes, with no significant changes in lipid parameters. The rise of retinol-binding protein and the recovery of nitrogen balance were significantly greater in group 1. A multivariate analysis of nutritional markers and catabolic parameters showed a better evolution in group 1 (P = 0.002). The MCT/LCT group exhibited a significant increase of insulin levels. Overall mortality and length of stay in the intensive care unit were not affected by the lipid emulsion. CONCLUSIONS: In septic patients who received TPN with a solution enriched with BCAAs, the use of an emulsion containing MCT provided them with a greater recovery of their nutrition status than the traditional LCT formula, without influencing the outcome.     

Lipid and lipid-free total parenteral nutrition: differential effects on macrophage phagocytosis in rats

Lipid emulsions provided with total parenteral nutrition (TPN) have been associated with mononuclear phagocytic system functional changes. The aim of the present investigation was to assess the influence of TPN with added lipid emulsions on macrophage (M phi) phagocytosis. Wistar rats (n = 70) with external jugular vein cannulation were randomized into seven groups. The rats received an oral diet or six different isocaloric (1.16 kcal/mL), isonitrogenous (1.5 g/mL), and isolipidic (30% non-protein calories) TPN regimens: (a) an oral diet with intravenous infusion of saline (OS); (b) non-lipid TPN (glucose); (c) TPN with 10% long chain triacylglycerol emulsions (LCT); (d) TPN with 90% LCT and 10% fish oil (FO) emulsion; (e) TPN with 50% LCT and 50% FO; (f) TPN with 10% lipid emulsion with 50% medium chain triacylglycerol (MCT) and 50% LCT; and (g) TPN with 45% MCT, 45% LCT, and 10% FO. After 96 h of TPN or saline infusion, colloidal carbon (Pelikan, Germany) was injected intravenously at 1.0 mL/kg body weight, and the rats were killed after 3 h. Liver, spleen, and lung were weighed and prepared by immunohistochemistry analyses with the HAM-56 anti-M phi antibody. Under light microscopy, the total M phi number (MT) and the colloidal carbon phagocytic M phi number (MP) were established, and the phagocytic index was calculated as MP/MT x 100. There were no statistical (P < 0.05) differences in liver, spleen, or lung weights among the seven groups in comparison with the OS group. Non-lipid TPN inhibited spleen and lung M phi phagocytosis when compared with the OS and lipid-TPN groups. Lipid TPN supplemented with fish oil emulsion increased total liver and lung M phi number and phagocytosis. These results indicate that TPN supplemented with fish oil increases M phi phagocytosis in rats.     

Comparison of effects of long-chain and medium-chain triglyceride emulsions during hepatic regeneration in rats.

We examined the effect of long-chain triglyceride (LCT) and medium-chain triglyceride (MCT) emulsions on hepatic regeneration. After approximately 70% hepatectomy, Sprague-Dawley rats were maintained for 96 hours on total parenteral nutrition (TPN) (250 kcal/kg per day; nonprotein calories-nitrogen 160:1) with LCT or MCT as 30% of nonprotein calories. There were no significant differences in the body weight, cumulative nitrogen balance, urinary 3-methylhistidine excretion, or changes in the energy stores between the two groups; but the fatty acid composition of the phospholipid fraction of the regenerating liver differed significantly between the LCT and the MCT groups. The extent of hepatic regeneration by weight was 88.7 +/- 10.5% in the MCT group and 99.1 +/- 10.6% in the LCT group by 96 hours after hepatectomy. Furthermore, the incorporation of 3H-orotic acid into DNA and RNA of regenerating liver cells in the LCT group was higher than in the MCT group 24 hours after hepatectomy. These observations indicate that essential fatty acids--components of the cell membrane and precursors as functional mediators--are very important to hepatic regeneration.     

Medium- and long-chain triglycerides have different effects on the synthesis of tumor necrosis factor by human mononuclear cells in patients under total parenteral nutrition.

Lipid emulsions containing both long- and medium-chain triglycerides (LCT/MCT) have been used in total parenteral nutrition (TPN) regimens and seem to have certain advantages for seriously ill patients. The aim of the present study was to investigate the effect of lipid emulsions containing 100% LCT or 50% LCT/50% MCT on tumor necrosis factor (TNF) production by human mononuclear cells.

This was a prospective study, in which 20 malnourished patients were randomly allocated to receive either 100% LCT or 50% LCT/50% MCT for > 30 days. We measured TNF synthesis before initiation of TPN, as well as at 15 and 30 days during TPN.

Departments of Medicine and Surgery, Patras University Medical School, Patras, Greece.

Members of the staff of the Departments of Medicine and Surgery, Patras University Medical School.

We found that TNF production was significantly (p < 0.01) elevated at 30 days in the LCT group, while no significant differences were detected in the LCT/MCT group.

It is concluded that long-term TPN formulas, where LCT have been partially replaced by MCT, do not change TNF synthesis by peripheral blood mononuclear cells, and this may be beneficial in seriously ill, cachectic patients.     

Effect of structured lipids as energy substrate after hepatectomy in rats with streptozocin-induced diabetes.

The suitability of energy substrates for use by the remnant liver after 70% hepatectomy was studied in relation to the hepatic energy status in diabetic rats. Rats with streptozocin-induced diabetes underwent 70% hepatectomy and were divided into five groups receiving total parenteral nutrition (TPN) for 24 h. One group received standard TPN without fat, and four groups respectively received standard TPN with long-chain triglycerides (LCTs), medium-chain triglycerides (MCTs), mixed triglycerides (MIX), or structured lipids (SLs) as a 10% lipid emulsion. The latter groups received 60% of nonprotein calories per day with fat emulsion (LCT, MCT, MIX, or SL), and the remaining 40% with glucose. The group that received 100% of nonprotein calories per day with glucose was defined as the TPN group. All rats in the TPN group died from nonketotic hyperosmolarity within 24 h. The blood ketone body ratio (acetoacetate/beta-hydroxybutyrate), the energy charge level of the remnant liver, and the cumulative excretion of 14CO2 in expired breath during 6 h after [14C]glucose administration were all significantly higher in the SL group than in the other groups 24 h after hepatectomy. These findings suggest that SL may be a superior energy substrate to other triglyceride preparations during the immediate posthepatectomy phase in diabetic patients.     

A metabolic comparison of a pure long-chain triglyceride lipid emulsion (LCT) and various medium-chain triglyceride (MCT)-LCT combination emulsions in dogs

Two 20% lipid emulsions containing mixtures of long-(LCT) and medium-chain triglycerides (MCT) were compared with a 20% LCT lipid emulsion. Beagles were infused with emulsions containing either 100% LCT, 75% LCT-25% MCT, or 50% LCT-50% MCT. The emulsions were part of a total parenteral nutrition (TPN) regimen that included 10% dextrose and 5.5% amino acids. Basic nutritional parameters as well as elimination kinetics were monitored. Plasma linoleic acid, ketone, lactate, pyruvate, insulin, glucose, and carnitine were analyzed. The 75% LCT-25% MCT emulsion offers little advantage over 100% LCT as a metabolic substrate. The 50% LCT-50% MCT combination proved to be a potentially better caloric source due to rapid elimination kinetics, increased ketone production, lack of deposition, and no interference with linoleic acid metabolism.     

Dietary fat level as determinant of protein-sparing actions of structured triglycerides.

This study assessed the effects of total parenteral nutrition (TPN) containing long-chain triglycerides (LCTs), an equimolar physical mixture of LCT and medium-chain triglycerides (MCTs), and a structured triglyceride synthesized from equimolar amounts of MCT and LCT on energy and protein metabolism after thermal injury (25% body surface area full-thickness scald burn). Male Sprague-Dawley rats (245-271 g) received isovolemic diets intravenously that supplied 250 kcal.kg-1.day-1, 2 g amino acid nitrogen.kg-1.day-1, and 50% of nonprotein calories as lipid and 50% as dextrose for 3 days. Whole-body and tissue leucine kinetics were estimated by a 4-h continuous infusion of L-[1-14C]leucine on day 3. Nitrogen balance, plasma albumin, plasma glucose, energy expenditure, and whole-body and liver and rectus muscle protein kinetic parameters were determined. No significant differences were noted in any of the parameters measured. This study suggests that the unique protein-sparing actions usually associated with structured triglyceride administration are not seen when they are provided as 50% of nonprotein calories. In addition, the ratio of MCT to LCT in the starting mixture from which the structured triglycerides are synthesized may be an important determinant of the protein-sparing actions attributed to these lipids.     

脂肪乳剂对完全胃肠外营养大鼠血清游离脂肪酸谱的影响

为研究脂肪乳剂对机体脂肪代谢的影响，用气相色谱法观测了完全胃肠外营养（ＴＰＮ）大鼠血清游离脂肪酸（ＦＦＡ）谱的变化。将４０只雄性Ｗｉｓｔａｒ大鼠随机分成５组，每组８只：（１）ＳＨ（Ｓｈａｍｏｐｅｒａｔｉｏｎ）组，仅进行颈外静脉结扎，正常饲养；（２）ＮＳ（Ｎｏｔｍａｌｓａｌｉｎｅ）组：正常饲养，输入生理盐水；（３）ＧＳ（Ｇｌｕｃｏｓｅ）组：全部能量由葡萄糖提供，即不含脂肪乳剂ＴＰＮ组；（４）ＬＣＴ（Ｌｏｎｇｃｈａｉｎｔｒｉｇｌｙｃｅｒｉｄｅ）组：含１０％Ｉｎｔｒａｌｉｐｉｄ脂肪轧的ＴＰＮ组；（５）ＭＣＴ（Ｍｅｄｉｕｍｃｈａｉｎｔｒｉｇｌｙｃｅｒｉｄｅ）组：含１０％Ｌｉｐｏｆｕｎｄｉｎ脂肪乳ＴＰＮ组。ＴＰＮ各组大鼠等能量等氮量等液量匀速连续输入“生合一”营养液（即将所有营养物混合在一个溶器内）。于第７天取血标本进行血清ＦＦＡ测定。结果表明：不含脂肪乳的ＴＰＮ大鼠血清各种ＦＦＡ下降，并出现必需脂肪酸缺乏（ＥＦＡＤ）症状，如精神不振活动少，毛发无光泽、脱落等；脂肪乳剂的使用，使大鼠血清各种ＦＦＡ升高，对机体的代谢和功能有着不同的生理、药理作用。     

Manipulation of tissue fatty acid profile by intravenous lipids in dogs

This study was undertaken to determine the effects on the fatty acid (FA) composition of various dog tissues of 4 different lipid emulsions (a 100% long-chain triacylglycerol (LCT) derived from soya bean oil emulsion, a mixed 50% medium-chain triacylglycerol (MCT)/50% LCT emulsion as well as both these emulsions supplemented with 10% fish oil (FO) triacylglycerols), when daily infused over 15 days as a substantial component of total parenteral nutrition. Lipids represented 55% of the non-protein energy. Blood samples as well as biopsies from liver, muscle and adipose tissue were taken 15 days before, and again immediately after TPN. In addition, the spleen was also removed immediately after TPN. Tissue FA composition was analysed by gas liquid chromatography of each lipid component after separation by thin layer chromatography. No differences in either safety or tolerance were detected between the different TPN preparations. In particular, infusion over 2 weeks of fat emulsions containing 10% fish oil was tolerated as well as conventional LCT and MCT/LCT emulsions. Relative linoleate content of tissue triacylglycerol (TG) was markedly increased in animals that received the LCT emulsions (e.g. from 22.6 +/- 2.5% to 32.2 +/- 0.6% in the liver), this effect being markedly reduced with MCT/LCT preparations. n-3FA were slightly incorporated into liver TG (from 0.0 +/- 0.0% to 2.3 +/- 0.7% and 1.2 +/- 0.4% for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) respectively, with LCT + FO), but remained undetectable in extrahepatic tissue TG. Of interest, medium chain FA were found in tissue TG after infusion of the mixed MCT/LCT emulsions. As expected, changes of tissue phospholipid (PL) composition involved only long-chain FA. Infusion of soya bean oil emulsion was associated with an increased content of linoleate in liver PL (from 13.6 +/- 0.4% to 17.7 +/- 0.4%), but not in other tissues. MCT/LCT did not markedly affect PL/FA pattern in any tissue. Supplementation with fish oil was associated with an efficient incorporation of n-3FA into tissue PL, particularly in the liver (from 0.4 +/- 0.1% to 2.5 +/- 0.3% for EPA and from 3.9 +/- 0.8% to 9.1 +/- 0.4% for DHA, with the LCT + FO emulsion).     

Effect of tracer and intravenous fat emulsion on the measurement of reticuloendothelial system function

Since the addition of lipid to intravenous feeding formulas, animal and human studies have shown impairment of the reticuloendothelial system (RES) due to slow rates of clearance and gradual accumulation of long chain triglycerides (LCT) in the liver. Medium chain triglycerides (MCT) accumulate only minimally in the liver and do not impair the RES. However, results from animal studies using technetium sulfur colloid (TSC) to assess RES function have been inconclusive. The present study reevaluates RES function after lipid infusion in guinea pigs as measured by organ distribution of TSC. Guinea pigs were fed 300 kcal/kg/day of total parenteral nutrition (TPN) for 2.5 days, with 50% of nonprotein calories as fat in the form of LCT or MCT, then injected intravenously with 2.5 or 25 microCi of TSC, and uptake by liver, spleen, and lungs was determined. Liver, lungs, and spleen all increased in size after TPN with LCT or MCT. Liver TSC uptake was significantly affected by the dose of TSC (p less than 0.05), with the high dose probably inducing an increased capacity of the liver to clear TSC from the blood. Liver uptake was not influenced by diet, but feeding MCT did significantly stimulate lung uptake of TSC (p less than 0.0001). This suggests that the hepatic TSC uptake system is not saturable, and may not be an appropriate measure of Kupffer cell function since the colloid is not phagocytosed. However, TSC blood clearance remains an excellent prognostic indicator for bacteremia and mortality in humans, and is useful for measuring global RES function.     

Changes of hepatic morphology during parenteral nutrition with lipid emulsions containing LCT or MCT/LCT quantified by ultrasound.

Fatty infiltration of the liver with cholestasis is one of the complications of total parenteral nutrition (TPN). The cause has not yet been determined. It seems probable, however, that these alterations could be prevented when a mixture of medium- and long-chain triglycerides (MCT/LCT) is used as a fat component instead of the application of long-chain emulsions (LCT) alone. To determine whether this could also be demonstrated morphologically in man, 14 patients needing TPN (25 kcal/kg BW x day, carbohydrate 45%, fat 35%, protein 20%) were examined by ultrasound in order to compare liver size and gray-scale value before and after 7 days of TPN. Seven of the patients were randomly administered a MCT/LCT emulsion as their fat intake, the other seven were exclusively given LCT. There were no changes in liver size and gray-scale value in the MCT/LCT-group, whereas both parameters showed a significant rise in the patients with LCT (size: 10.4 +/- 1.4 to 11.5 +/- 1.4 cm; gray-scale value: 9.3 +/- 1.0 to 11.6 +/- 0.7). These data suggest that TPN, administered with a mixture of MCT/LCT emulsions as fat components, could reduce the risk of hepatic dysfunction such as cholestasis and fatty infiltration of the liver.     

Energy expenditure in rats maintained with intravenous or intragastric infusion of total parenteral nutrition solutions containing medium- or long-chain triglyceride emulsions.

Energy expenditure was determined in male Fischer 344 rats (235-246 g) fed by intravenous (IV) or intragastric (IG) infusion with total parenteral nutrition solutions providing 65% of nonprotein energy as fat from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions. Respiratory gas exchange and somatomotor activity were assessed continuously for 24 h during d 5 and 11 of infusion feeding. The MCT infusion resulted in one-third the weight gain noted with LCT infusion (MCT, 10 +/- 2 g/14 d; LCT, 32 +/- 4 g/14 d; P less than 0.0001). Insulin concentration was 60% higher with IV than with IG infusion and approximately 100% higher with IV-MCT than with IG-MCT or LCT infusion (P less than 0.05). Rats receiving IV infusion of MCT displayed similar levels of motor activity but 8-13% greater daily energy expenditure (kJ.kg-0.75.kJ intake-1) than rats receiving IG-MCT or LCT infusion (P less than 0.05). The MCT infusion also resulted in an elevation in respiratory quotient after cessation of nutrient infusion (MCT, 0.87-0.92; LCT, 0.83-0.85; P less than 0.05). Total and resting energy expenditure decreased approximately 13% from 5 to 11 d of infusion feeding. The lower weight gain and greater energy expenditure seen with MCT- compared with LCT-supplemented total parenteral nutrition may be mediated by higher insulin concentrations.     

Different effects of long-chain and medium-chain triglycerides on glucose oxidation during total parenteral nutrition.

This study was undertaken to clarify differences in the effects of lipid emulsions containing either long-chain or medium-chain triglycerides (MCT) on glucose metabolism during total parenteral nutrition (TPN). Glucose kinetics were assessed in beagle dogs using primed, constant infusions of [14C]- and [6-3H]glucose. The rate of appearance of glucose, the percent of VCO2 derived from the oxidation of glucose, the rate of glucose oxidation, and the percent of glucose uptake oxidized were measured at the end of 72 hours of each of the two TPN regimens, ie, TPN in which soybean oil served as long-chain triglyceride comprising 40% of nonprotein calories (L-TPN), and TPN in which tricaprylin emulsion served as MCT (M-TPN). Glucose intake was 5.9 +/- 0.5 mg/kg per minute in L-TPN and 5.8 +/- 0.2 mg/kg per minute in M-TPN. There was no significant difference in the rate of glucose appearance between L-TPN and M-TPN. The rate of glucose oxidation was higher with M-TPN than with L-TPN (p < .05). Not only the percent of VCO2 derived from the oxidation of glucose but also the percent of glucose uptake oxidized tended to be higher during M-TPN than during L-TPN. These findings suggest that the glucose metabolism of dogs receiving L-TPN is different from that of dogs receiving M-TPN.     

Parenteral (glucose or glucose-lipid) vs enteral repletion in malnourished primates: a controlled crossover study

Nutritional repletion with glucose-based total parenteral nutrition (TPN), mixed-substrate (58% lipid, 42% glucose) TPN, and mixed-substrate total enteral nutrition (TEN) was studied in four adult male chair-adapted primates using a crossover design. After 10 d nutritional depletion animals were repleted for 10 d with one of three isocaloric isonitrogenous diets. TPN Diets I and II were identical except that I provided all nonprotein calories as glucose while II provided 58% nonprotein calories as lipid and 42% as glucose. Animals were randomized to I or II as their first repletion treatment. The 20-d depletion-repletion cycle was repeated with the other TPN diet after a 30-d rest period of caged free-feeding. After another 30-d rest period, animals underwent a third 10-d depletion and were repleted with 10 d of TEN (Diet III, identical to II in composition). The three diets resulted in similar weight gain, positive nitrogen balance and fluid balance, and increase in total iron-binding capacity.     

Parenteral infusion of long- and medium-chain triglycerides and reticuloendothelial system function in man

Previous study demonstrated that patients who received total parenteral nutrition (TPN) with standard intermittent infusion of long chain triglyceride (LCT) at 0.13 g kg-1hr-1 over 10 hr for each of three days showed a significant decline in 99Tc-sulfur colloid (TSC) clearance rate by the reticuloendothelial system (RES). The present studies evaluated eight patients who received the same total lipid dose of LCT infused continuously as in a three-in-one admixture, and another nine patients receiving the same amount of fat as a medium chain triglyceride (MCT)/LCT (75%/25%) emulsion intermittently over 10 hr at 0.13 g kg-1hr-1 for three consecutive days. Patients were given continuous total parenteral nutrition (TPN) comprised of protein, 1.5 g kg-1day-1, and dextrose, 4.5 g kg-1day-1. RES function was examined by measuring the clearance rates of intravenously injected TSC while receiving TPN containing only protein and dextrose, and again after three days of fat infusion. Mean (+/- SEM) clearance rate constants before and after continuous LCT infusion were 0.38 +/- 0.09 and 0.41 +/- 0.08 min-1, respectively, while those before and after intermittent MCT/LCT infusion were 0.50 +/- 0.18 and 0.73 +/- 0.24 min-1, respectively. In contrast to intermittent LCT infusion, the administration of continuous LCT or an intermittent MCT/LCT mixture does not impair TSC clearance by the RES. These findings suggest that condensing the daily period of LCT infusion at standard dosage may exceed the rate of metabolic utilization, resulting in increased fat removal and diminished TSC uptake by the RES.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lipid infusion with different triglyceride cores (long-chain vs medium-chain/long-chain triglycerides): effect on plasma lipids and bilirubin binding in premature infants.

The possible beneficial effects of infusing a lipid emulsion containing 50% by weight of medium-chain triglycerides (MCT) compared with a standard long-chain triglyceride (LCT) emulsion were studied in 18 premature neonates (gestational age less than 34 weeks) requiring parenteral nutrition. The infants were assigned in a double-blind manner to receive one of the two lipid emulsions over 17 hours a day as a supplemental regimen for total parenteral nutrition. A lipid load of 1 g/kg per day was initiated on the third day of life and was increased at the rate of 1 g/kg per day until a maximal dose of 3 g/kg per day was obtained on the fifth day of life and maintained thereafter. Both bound and unbound bilirubin decreased with both infusion regimens during the study period. Despite a marked increase in plasma free fatty acid levels (260% in the MCT/LCT group compared with 210% in the LCT group), the fraction of unbound (free) bilirubin was significantly lower in the MCT/LCT group (34% vs 13%). Free fatty acid levels, corrected to albumin, were positively correlated to the percentage of free bilirubin only for the LCT lipid infusion. The finding of a significant elevation of plasma cholesterol levels only in the MCT/LCT group is now under investigation. Use of the MCT-containing emulsion was not associated with a higher frequency of adverse effects than the commonly used LCT-containing emulsion.(ABSTRACT TRUNCATED AT 250 WORDS)