Clinical and experimental effects of medium-chain-triglyceride-based fat Emulsions—A review

Lipid Emulsion Use in Pediatric Patients Requiring Long-Term Parenteral Nutrition

The ability to deliver nutrients via parenteral nutrition (PN) has markedly improved the prognosis of infants and children with intestinal failure. Technical refinements and advances in knowledge have led to the development of highly sophisticated PN solutions that are tailored to meet the needs of pediatric patients. However, children who require long-term PN have an increased risk of complications such as catheter-related sepsis, liver disease, and bone disease. Although the pathogenesis of intestinal failure associated liver disease (IFALD) is multifactorial, studies have identified a possible link between the dose of lipid emulsions based on soybean oil and cholestasis, shown to occur with a significantly higher frequency in patients receiving >1 g lipids/kg/d. Potential contributing factors include oxidative stress, high ω-6 polyunsaturated fatty acid (PUFA) and phytosterol content, and relatively low α-tocopherol levels. Lipid emulsions containing fish oil offer potential advantages compared with traditional emulsions with a high soybean oil content, such as decreased ω-6 and increased ω-3 PUFA concentrations, high concentrations of α-tocopherol, and reduced phytosterol content. Studies in PN-dependent children at risk for IFALD have shown that lipid emulsions containing fish oil reduce the risk of cholestasis and improve biochemical measures of hepatobiliary function compared with pure soybean oil emulsions. This review summarizes evidence regarding the role of lipid emulsions in the management of pediatric patients with intestinal failure requiring long-term PN, with a particular focus on the prevention and treatment of IFALD.

Exploring the metabolic fate of medium-chain triglycerides in healthy individuals using a stable isotope tracer

BACKGROUND & AIMS

Medium chain triglyceride (MCT) supplementation is often recommended as treatment for patients with long-chain fatty acid β-oxidation (lcFAO) disorders, since they can be utilized as an energy source without the use of the defective enzyme. However, studies in mice and preterm infants suggest that not all medium-chain fatty acids (MCFA) are oxidized and may undergo elongation to long-chain fatty acids (LCFA). In this single blinded study, we explored the metabolic fates of MCT in healthy individuals using a ¹³C-labeled MCT tracer.

METHOD

Three healthy males in rest received on two test days a primed continuous infusion of glyceryl tri[1,2,3,4-¹³C₄]-octanoate with either an isocaloric supplementation of 1) exclusively MCT (MCT-only) or 2) a mixture of MCT, proteins and carbohydrates (MCT-mix). Gas chromatography - combustion - isotope ratio mass spectrometry (GC-C-IRMS) was used to determine ¹³C-enrichment of long-chain fatty acids in plasma and of ¹³CO₂ in exhaled air.

RESULTS

When provided as single energy source, an estimated 42% of administered MCT was converted to CO₂. In combination with carbohydrates and proteins in the diet, oxidation of MCT was higher (62%). In both diets <1% of ¹³C-label was incorporated in LCFA in plasma, indicating that administered MCT underwent chain-elongation to LCT.

CONCLUSIONS

Although the relative MCT oxidation rate was higher when combined with carbohydrates and protein, quantitatively more MCT was oxidized when given an isocaloric meal with solely MCT. As these results were obtained in the resting state opposed to during exercise, it is too early to give a recommendation concerning the use of MCT in lcFAO disorders. The data show that in resting healthy individuals only a very small part of the MCT is traced back as LCFA in plasma, suggesting that MCT treatment does not result in a large LCFA burden, however further research on storage of MCT in tissues is warranted.

REGISTRATION

The study was registered in the Nederlands Trialregister. Protocol ID: Trial NL7417 (NTR7650).

Efficacy, Safety, and Preparation of Standardized Parenteral Nutrition Regimens: Three-Chamber Bags vs Compounded Monobags-A Prospective, Multicenter, Randomized, Single-Blind Clinical Trial

Background: Parenteral nutrition (PN) covering the need for carbohydrates, amino acids, and lipids can either be compounded from single nutrients or purchased as an industrially manufactured ready-to-use regimen. This study compares a commercially available 3-chamber bag (study group) with a conventionally compounded monobag regarding nutrition efficacy, safety, and regimen preparation time. Materials and Methods: This prospective, randomized, single-blind study was conducted at 5 Chinese hospitals from October 2010–October 2011. Postsurgical patients requiring PN for at least 6 days were randomly assigned to receive the study or control regimen. Plasma concentrations of prealbumin and C-reactive protein (CRP), regimen preparation time, length of hospital stay (LOS), 30-day mortality, safety laboratory parameters, and adverse events (AEs) were recorded. Results: In total, 240 patients (121 vs 119 in study and control groups) participated in this study. Changes in prealbumin concentrations during nutrition support (Δ_{Prealb(StudyGroup)} = 2.65 mg/dL, P < .001 vs Δ_{Prealb(ControlGroup)} = 0.27 mg/dL, P = .606) and CRP values were comparable. Regimen preparation time was significantly reduced in the study group by the use of 3-chamber bags (t_(StudyGroup) = 4.90 ± 4.41 minutes vs t_{(ControlGroup)} = 12.13 ± 5.62 minutes, P < .001). No differences were detected for LOS, 30-day mortality, safety laboratory parameters, and postoperative AEs (37 vs 38 in study and control groups). Conclusion: The PN regimen provided by the 3-chamber bag was comparable to the compounded regimen and safe in use. Time savings during regimen preparation indicates that use of 3-chamber bags simplifies the process of regimen preparation.

ESPGHAN Committee on Nutrition Position Paper. Intravenous Lipid Emulsions and Risk of Hepatotoxicity in Infants and Children: a Systematic Review and Meta-analysis

The aim of the present article was to perform a systematic review with meta-analysis of available scientific evidence regarding the role of different intravenous lipid emulsions (ILE) in the pathogenesis of cholestasis and parenteral nutrition-associated liver disease. A systematic review of the literature (up to March 2015) identified 23 randomized controlled trials (RCTs). Of these, 17 were performed in preterm infants or critically ill neonates with a short duration of intervention, 2 in older children with short-term use (following surgery or bone marrow transplantation), 1 in neonates with long-term use, and 3 in infants and children receiving long-term parenteral nutrition (PN). Meta-analysis showed no differences in the rate of cholestasis or bilirubin levels associated with short-term use of different ILEs. Because of high heterogeneity of the long-term studies no meta-analysis could be performed. Available studies found that the use of multicomponent fish oil (FO)-containing ILE compared with pure soya bean oil (SO), ILE-reduced liver enzymes, and bilirubin levels in noncholestatic children on long-term PN and one other RCT found that FO-based ILE-reversed cholestasis in a proportion of patients. The ESPGHAN Committee on Nutrition concludes that there is no evidence of a difference in rates of cholestasis or bilirubin levels between different ILE for short-term use in neonates. The use of multicomponent FO-containing ILE may contribute to a decrease in total bilirubin levels in children with IF on prolonged PN. Well-designed RCTs are, however, lacking and long-term effects have not been determined.

Intestinal failure-associated liver disease: a position paper of the ESPGHAN Working Group of Intestinal Failure and Intestinal Transplantation

Intestinal failure-associated liver disease is the most prevalent complication affecting children with intestinal failure receiving long-term parenteral nutrition. This paper reviews the definition, diagnostic criteria, pathogenesis, and risk factors. The authors discuss the role of enteral nutrition, parenteral nutrition, and its components, especially lipid emulsions. The authors also discuss the surgical treatment, including intestinal transplantation, its indications, technique, and results, and emphasise the importance of specialised intestinal failure centres.

Short-term intravenous fish-oil emulsions in pediatric oncologic patients--effect on liver parameters

Pediatric oncologic patients often need parenteral nutrition (PN) during chemotherapy. Long-term use of soybean-based lipid emulsions is associated with progressive liver disease and cholestasis, whereas fish-oil based emulsions have anticholestatic effects. We studied the potentially hepato-protective effects of short-term use of SMOF lipids in children undergoing chemotherapy. Fifteen pediatric oncologic patients treated with SMOF lipids were retrospectively analyzed in respect to bilirubin and liver parameters and compared to matched-controls who had received soybean-based fat emulsions. For statistics the time-points baseline, Day 14 of PN (PN14), and post (Day+7) were chosen. None of the study patients developed cholestasis. Within the SMOF-lipid group there were no differences in the laboratory parameters between baseline, PN14, and post. In the control group, gamma glutamyltransferase (γGT) levels increased during PN (baseline vs. PN14, 26.43 vs. 63.00 U/l, P < 0.05). Lactate dehydrogenase (LDH) levels showed a significantly different behavior in the 2 groups: In the SMOF lipids group, LDH decreased whereas it increased in the controls (-32.75 U/l vs. + 29.57 U/l, P < 0.05). An advantage of fish oil-based fat emulsions can be shown even after short-term PN. In children undergoing chemotherapy the use of soybean-based fat emulsions but not SMOF lipids led to increased γGT levels.

Lipid Rescue Reverses the Bupivacaine-induced Block of the Fast Na+ Current (INa) in Cardiomyocytes of the Rat Left Ventricle

Background:

Cardiovascular resuscitation upon intoxication with lipophilic ion channel–blocking agents has proven most difficult. Recently, favorable results have been reported when lipid rescue therapy is performed, i.e., the infusion of a triglyceride-rich lipid emulsion during resuscitation. However, the mechanism of action is poorly understood.

Methods:

The authors investigate the effects of a clinically used lipid emulsion (Lipovenös® MCT 20%; Fresenius Kabi AG, Bad Homburg, Germany) on the block of the fast Na+ current (INa) induced by the lipophilic local anesthetic bupivacaine in adult rat left ventricular myocytes by using the whole cell patch clamp technique.

Results:

Bupivacaine at 10 µm decreased INa by 54% (−19.3 ± 1.9 pApF−1vs. −42.3 ± 4.3 pApF−1; n = 17; P &lt; 0.001; VPip = −40 mV, 1 Hz). Addition of 10% lipid emulsion in the presence of bupivacaine produced a 37% increase in INa (−26.4 ± 2.8 pApF−1; n = 17; P &lt; 0.001 vs. bupivacaine alone). To test whether these results could be explained by a reduction in the free bupivacaine concentration by the lipid (lipid-sink effect), the authors removed the lipid phase from the bupivacaine–lipid mixture by ultracentrifugation. Also, the resulting water phase led to an increase in INa (+19%; n = 17; P &lt; 0.001 vs. bupivacaine), demonstrating that part of the bupivacaine had been removed during ultracentrifugation. The substantially less lipophilic mepivacaine (40 µm) reduced INa by 27% (n = 24; P &lt; 0.001). The mepivacaine–lipid mixture caused a significant increase in INa (+17%; n = 24; P &lt; 0.001). For mepivacaine, only a small lipid-sink effect could be demonstrated (+8%; n = 23; P &lt; 0.01), reflecting its poor lipid solubility.

Conclusion:

The authors demonstrate lipid rescue on the single-cell level and provide evidence for a lipid-sink mechanism.

Fat absorption and deposition in Japanese quail (Coturnix coturnix japonica) fed a high fat diet

Dietary fat contributes significantly to the energy requirements of poultry. Not all species are able to increase their absorptive capacity for fats in response to a high fat diet. The effects of a high fat diet (10% canola oil) on the lipid absorption and deposition in the liver, breast and thigh muscles of male and female Japanese quail were investigated. Thirty-eight Japanese quail (Coturnix coturnix japonica) were randomly divided into a high fat diet (HFD) and a standard diet (STD) group. The birds were fed the diets for seven weeks after which half of the birds were subjected to oral fat loading tests (OFLT) with plant oils containing long-chain and medium-chain triglycerides. The remaining birds were included for the lipid deposition measurements. Thereafter the birds were euthanised, blood samples were collected and liver, breast and thigh muscle lipid deposition was determined. Female quail on both diets had significantly higher plasma triglyceride concentrations (p 0.05) compared with their male counterparts. No significant differences in plasma triglyceride concentrations were observed after the OFLTs. Female quail had significantly heavier liver masses compared with the males but there was no significant difference in the liver lipid content per gram liver mass. Female quail on the HFD had higher lipid content (p 0.05) in the breast muscle compared with their male counterparts whilst male quail on the HFD had higher lipid content (p 0.05) in the thigh muscle in comparison with both males and females on the standard diet. Dietary supplementation with 10% canola oil did not alter gastrointestinal tract lipid absorption, but it caused differences between the sexes in muscle lipid accumulation, the physiological significance of which requires further investigation.

Development of clinical application for a nutritional prescription support system for total parenteral/enteral nutrition

One of the important roles of pharmacists as members of a nutrition support team is nutritional prescription support. We developed a nutritional prescription support system (NPSS) that facilitates prescription support and analysis and evaluated its usefulness in nutritional therapy. An NPSS for prescription support and the management of patient information was created. With this NPSS, the nutritional status was assessed, and, on the basis of the results, such variables as the total energy expenditure were calculated. This system allows prescription support for parenteral nutrition (PN) therapy, enteral nutrition (EN) therapy, and the transition period between them. This system was used for 2 representative patients and evaluated. In a malnourished patient receiving oral warfarin, EN solutions were compared by means of the NPSS, and an appropriate EN solution was selected. In addition, the prothrombin time-international normalized ratio was monitored, and favorable results were obtained regarding the adjustment of the warfarin dose and nutritional management. In a patient with aspiration pneumonia, continuous nutritional management to EN from PN therapy was straightforwardly performed with the NPSS. This NPSS allows rapid, comprehensive nutritional management during the transition period to EN from PN therapy, despite these therapies being considered separately in conventional nutritional management. The NPSS is useful for simplifying prescription support and facilitating information sharing among members of a nutrition support team.

Medium-chain fatty acids improve cognitive function in intensively treated type 1 diabetic patients and support in vitro synaptic transmission during acute hypoglycemia

OBJECTIVE

We examined whether ingestion of medium-chain triglycerides could improve cognition during hypoglycemia in subjects with intensively treated type 1 diabetes and assessed potential underlying mechanisms by testing the effect of beta-hydroxybutyrate and octanoate on rat hippocampal synaptic transmission during exposure to low glucose.

RESEARCH DESIGN AND METHODS

A total of 11 intensively treated type 1 diabetic subjects participated in stepped hyperinsulinemic- (2 mU x kg(-1) x min(-1)) euglycemic- (glucose approximately 5.5 mmol/l) hypoglycemic (glucose approximately 2.8 mmol/l) clamp studies. During two separate sessions, they randomly received either medium-chain triglycerides or placebo drinks and performed a battery of cognitive tests. In vitro rat hippocampal slice preparations were used to assess the ability of beta-hydroxybutyrate and octanoate to support neuronal activity when glucose levels are reduced.

RESULTS

Hypoglycemia impaired cognitive performance in tests of verbal memory, digit symbol coding, digit span backwards, and map searching. Ingestion of medium-chain triglycerides reversed these effects. Medium-chain triglycerides also produced higher free fatty acids and beta-hydroxybutyrate levels compared with placebo. However, the increase in catecholamines and symptoms during hypoglycemia was not altered. In hippocampal slices beta-hydroxybutyrate supported synaptic transmission under low-glucose conditions, whereas octanoate could not. Nevertheless, octanoate improved the rate of recovery of synaptic function upon restoration of control glucose concentrations.

CONCLUSIONS

Medium-chain triglyceride ingestion improves cognition without adversely affecting adrenergic or symptomatic responses to hypoglycemia in intensively treated type 1 diabetic subjects. Medium-chain triglycerides offer the therapeutic advantage of preserving brain function under hypoglycemic conditions without causing deleterious hyperglycemia.

Fat supplementation, health, and endurance performance

Pre-exercise fat ingestion (i.e., long chain triacylglycerol ingestion 1 to 4 h before exercise), medium-chain triacylglycerols, fish oil, and conjugated linoleic acid have been suggested to alter metabolism to achieve weight loss, alter lipid profiles, or improve performance. However, studies have demonstrated that ingestion of meals with long-chain triacylglycerols before exercise has little or no effect on metabolism and does not alter subsequent exercise performance. Also, medium-chain triacylglycerol supplementation before or during exercise has not been shown to be ergogenic, although this could be related to the small amounts of medium-chain triacylglycerol that can be ingested before gastrointestinal discomfort occurs. Fish oil may improve red blood cell deformability, but these effects are likely to be small and do not seem to influence maximum oxygen delivery or exercise performance. Conjugated linoleic acid has been implicated in weight loss, but based on the results of human studies it must be concluded that the effects of conjugated linoleic acid on body weight loss are far less clear than those observed in animal studies. Most studies have not found any evidence for a beneficial effect of conjugated linoleic acid.

Nitrogen sparing effect of structured triglycerides containing both medium-and long-chain fatty acids in critically ill patients; a double blind randomized controlled trial

BACKGROUND AND AIMS

Patients with sepsis and trauma are characterised by hypermetabolism, insulin resistance and protein catabolism. Fat emulsions containing medium chain triglycerides have been suggested to be beneficial for these patients since medium chain fatty acids are a more readily available source of energy when compared to long chain fatty acids. The aim of this study was to compare a medium and long chain triglyceride emulsion consisting of structured triglycerides (ST) with a long chain triglyceride (LCT) emulsion in terms of effects on nitrogen balance, energy metabolism and safety.

METHODS

30 ICU patients with sepsis or multiple injury received a fat emulsion with ST or 20% LCT (1.5 g triglycerides/kg body weight/day) as a component of total parenteral nutrition (TPN), for 5 days in a double blind randomised parallel group design. The main analysis was made on the 3 day per protocol population due to lack of patients at day 5.

RESULTS

There were no differences in baseline characteristics of the two groups receiving either the LCT or the ST emulsion. The efficacy analysis was performed on the per protocol population (n=9 ST, n=11 LCT). There was a significant difference between the two treatments regarding daily nitrogen balances when the first 3 days were analysed P=0.0038). This resulted in an amelioration of the nitrogen balance on day 3 in the group on ST as compared to those on LCT (0.1+/-2.4 g vs -9.9+/-2.1 g P=0.01). The 3 day cumulative nitrogen balance was significantly better in the group receiving ST compared to those on LCT (-0.7+/-6.0 vs -16.7+/-3.9 P=0.03). This better cumulative nitrogen balance on day 3 was also preserved as a tendency (P=0.061) in the analysis of the intention to treat population, but on day 5 there was no significant difference (P=0.08). The ST emulsion was well tolerated and no difference was found compared to the LCT emulsion regarding respiratory quotient, energy expenditure, glucose or triglyceride levels during infusion.

CONCLUSION

Administration of a structured triglyceride emulsion resulted in an amelioration of nitrogen balance despite no effect on energy expenditure in short term administration over 3 days to ICU patients when compared to a long chain triglyceride emulsion. No side effects linked to medium chain triglycerides were noted.

Review of the toxicologic properties of medium-chain triglycerides

Medium chain triglycerides (MCTs) are a family of triglycerides, containing predominantly, caprylic (C(8)) and capric (C(10)) fatty acids with lesser amounts of caproic (C(6)) and lauric (C(12)) fatty acids. MCTs are widely used for parenteral nutrition in individuals requiring supplemental nutrition and are being more widely used in foods, drugs and cosmetics. MCTs are essentially non-toxic in acute toxicity tests conducted in several species of animals. In ocular and dermal irritation testing MCTs exhibit virtually no potential as ocular or dermal irritants, even with prolonged eye or skin exposure. MCTs exhibit no capacity for induction of hypersensitivity. Ninety-day toxicity tests did not result in notable toxicity, whether the product was administered in the diet up to 9375mg/kg body weight/day or by intramuscular (im) injection (up to 0. 5ml/kg/day, rabbits). There was no evidence that intravenous (iv) or dietary administration of MCTs adversely affected the reproductive performance of rats or resulted in maternal toxicity, foetal toxicity or teratogenic effects at doses up to 4.28g/kg body weight/day (iv) or 12,500mg/kg body weight/day (dietary). There was no evidence that dietary administration of MCTs adversely affected the reproductive performance of pigs or resulted in maternal toxicity, foetal toxicity or teratogenic effects at doses up to 4000mg/kg body weight/day in the diet. In rabbits, following iv administration, the maternal and foetal no-observed-adverse-effect levels (NOAELs) were between 1.0 and 4.28g/kg body weight/ day. A 2-year study in rats, conducted with a closely related compound (tricaprylin, a triglyceride with C(8) fatty acids), provided no evidence of a carcinogenic effect when the material was administered by oral gavage at levels up to 10ml/kg (9.54g/kg) per day. Although tricaprylin was found to be positive in one of five strains of Salmonella typhimurium in the presence of metabolic activation in an Ames mutagenicity assay, the results of the carcinogenicity test with tricaprylin and mutagenicity tests with caprylic acid indicate that MCTs do not have the potential to be carcinogenic or mutagenic. The safety of human dietary consumption of MCTs, up to levels of 1g/kg, has been confirmed in several clinical trials.

Medium-chain triglycerides inhibit growth of Malassezia: implications for prevention of systemic infection

OBJECTIVE

Lipophilic Malassezia species may induce catheter-associated sepsis in newborns and immunocompromised patients receiving parenteral lipids. Therefore, we tested whether M. furfur and six other Malassezia species can use commercially available infusions as a lipid source.

DESIGN

Prospective in vitro study.

SETTING

Research laboratory in a university hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

With the exception of M. restricta, all Malassezia species grow on lipid infusions. There are no substantial differences among the different brands. The most rapid growth is shown by M. furfur, which grows better on agar containing a 20% rather than a 10% lipid infusion. Growth of M. furdur and M. sympodialis can be reduced by infusions containing medium-chain triglycerides. Incubated in triglycerides, M. furfur is strongly suppressed by 50% medium-chain triglycerides and M. sympodialis by 8% medium-chain triglycerides. When medium-chain free fatty acids are added to triglycerides, both species can be suppressed by about 1% free fatty acids.

CONCLUSION

Medium-chain triglycerides and medium-chain free fatty acids are toxic for Malassezia species. Commercially available infusions containing medium-chain triglycerides might be used to prevent systemic Malassezia infections.

Structure and metabolic fate of triacylglycerol- and phospholipid-rich particles of commercial parenteral fat emulsions

The lipid emulsions used in parenteral nutrition are constituted of particles rich in triacylglycerols (TAG) called artificial chylomicrons (200-500 nm in diameter; monolayer of phospholipids [PL] enveloping a TAG core) and PL-rich particles called liposomes (diameter inferior to 80 nm; bilayer of PL around an aqueous phase), which represent the excess emulsifier. Introduced into the circulation, the two populations of particles come into contact with circulating lipoproteins and cell membranes and experience the same overall fate: exchanges and transfers of lipids and apolipoproteins, enzymatic hydrolysis of TAG and PL, and internalization by different tissues. The relative importance of these different metabolic processes varies depending on the type of particle. The artificial chylomicrons undergo a hydrolysis of their TAG by lipoprotein lipase, with a release of fatty acids and formation of smaller particles of remnants, which are rapidly removed by the liver. In delivering fatty acids to the tissue, artificial chylomicrons fulfill an energy transport function similar to the natural chylomicrons. The liposomes hold little energy interest, and they also have deleterious effects when infused in excess. They inhibit the lipolysis of artificial chylomicrons and, by actively capturing endogenous cholesterol, they stimulate tissue cholesterogenesis and accumulate in the blood as lipoprotein-X, a long-lived abnormal lipoprotein. To limit as much as possible the metabolic perturbations due to the intravenous administration of exogenous PL, the emulsion has to be infused at a low rate, and should contain the minimal amount of excess PL.

Nutritional support in malnourished paediatric patients

An imbalance between a person's energy requirements and his or her dietary protein and caloric supply is the source of protein energy malnutrition (PEM), which compounds the problems of any underlying disease. Malnutrition may occur quite rapidly in critically ill patients, particularly those suffering from sepsis, setting up a vicious cycle with worsening of the PEM. This chapter examines the main consequences of PEM, the means whereby appropriate nutrition may be provided, and risks for severely malnourished paediatric patients in hospital. If the gastrointestinal tract can be used for refeeding, it should be used. When the gastrointestinal tract is unable to meet the protein and energy requirements, parenteral nutrition (PN) is required. PN is efficient but carries a high risk of metabolic complications known as the refeeding syndrome and directly related to the homeostatic changes secondary to severe PEM. Catch-up growth may be achieved by using appropriate nutritional support. Changes in body composition have to be assessed during the course of renutrition.

Mixture experiments with the oil phase of parenteral emulsions

The effects of the oil phase as a mixture (binary, ternary) on the emulsion droplet size were investigated. The binary trials were performed with the aid of simplex lattice design with constraints. Droplet diameter was evaluated in terms of the oil phase viscosity and the interfacial tension between oil phase and the aqueous phase. As a result it could be shown that increasing the oil phase viscosity as a function of castor oil concentration led to a greater increase in particle size. At the same time, decreasing the interfacial tension of the oil phase as a function of oleic acid or oleic alcohol was shown to have a negligible effect on the particle size of the dispersed phase. A further aim was to find out a formulation by using a ternary oil phase resulting in a stable emulsion which could pass the autoclaving process. It was ascertained that oleic acid as a part of the oil phase led to proper formulation showing a satisfactory stability.

Antitumor effect of medium-chain triglyceride and its influence on the self-defense system of the body

Medium-chain triglyceride (MCT), long-chain triglyceride (LCT), and their mixture were compared in reference to both cytotoxic effect against human tumor cells and influence on the immune system. MCT showed more potent cytotoxicity than LCT. Continuous contact with MCT also inhibited the cytotoxic effect of lymphokine-activated killer (LAK) cells much more strongly than LCT. However, there is a discrepancy between the concentration of MCT, or the mixture, that could suppress the growth of tumor cells and the concentration that inhibited the cytotoxicity of LAK cells. Moreover, no damage was observed in PBL or LAK cells or in their cytotoxicity when the cells were incubated with TG for 2 h a day. Thus, short-term contact with TG could inhibit tumor growth while immune system was maintained within normal range. Clinically fine control of the concentration of injected triglycerides, especially MCT, can be expected to provide potent antitumor effect and maintenance of normal immune system.

Effect of parenteral medium- and long-chain triglycerides on lymphocytes subpopulations and functions in patients with acquired immunodeficiency syndrome: a prospective study

BACKGROUND

Total parenteral nutrition (TPN) may offer significant clinical benefit in malnourished patients with acquired immunodeficiency syndrome (AIDS). However, the immunologic effect of parenteral lipids remains unknown in these severely immunodepressed patients.

METHODS

We undertook a prospective randomized double-blind multicenter study comparing the effects of two i.v. lipid emulsions used during TPN: long-chain triglycerides (LCT) or balanced emulsion of long-and medium-chain triglycerides (LCT/MCT). Thirty-three AIDS patients requiring TPN for wasting and reduced oral intake were allocated randomly to receive a ternary TPN mixture consisting of 1.5 g/kg/d proteins, 18 kcal/kg/d lipids, and 12 Kcal/kg/d carbohydrates for 6 days. The following tests were performed at days 0 and 7: immunoglobulins, complement fractions, lymphocyte subpopulations count, and lymphocyte proliferation with mitogens.

RESULTS

Patients were all severely malnourished (weight loss: -14.0 +/- 1.3 kg). No clinical or biological differences were observed between the groups at baseline. At day 7, both groups reported a significant increase in weight. Patients in the LCT group exhibited a significant decrease in phytohemagglutinin A response (p = .04) compared with baseline. Patients in the LCT/MCT group exhibited a lower level of IgM (p = .03) and significant increase in C3 fraction (p = .03) compared with baseline. They also showed a tendency to have a higher CD4/CD8 lymphocyte ratio (p = .07), whereas other immunological parameters remained unchanged

CONCLUSIONS

Parenteral ternary mixture containing LCT or LCT/MCT are clinically well tolerated in AIDS patients over 6 days. With 2 g/kg/d of lipids, LCT seems to induce significant abnormalities in lymphocyte function. Such abnormalities are not observed with LCT/MCT.

Use of a mixture of medium-chain triglycerides and longchain triglycerides versus long-chain triglycerides in critically ill surgical patients: a randomized prospective double-blind study

Twenty critically-ill surgical patients who needed total parenteral nutrition were randomly enrolled in a double-blind study comparing two intravenous fat emulsions: one containing a mixture of 50% medium-chain triglycerides and 50% long-chain triglycerides and another containing 100% longchain triglycerides. The purpose of this study was to investigate metabolic and biochemical differences between both emulsions with special reference to liver enzymes. After a baseline period of 24 h with only glucose and NaCl infusion, the lipid emulsion was added continuously during 24 h over 5 days. The parenteral nutrition was administered in mixture bags containing amino-acids, glucose and lipids together. Two-thirds of the non-protein calories were administered as glucose 40% and one third as either long-chain triglycerides or a mixture of medium-chain triglycerides and long-chain triglycerides. The total amount of non-protein calories received was the measured energy expenditure during the baseline period plus 10% and was fixed during the study. Plasma substrate concentrations, energy expenditure, and nitrogen balance were determined and arterial blood samples were taken. No toxic effects or complications attributable to one of the two emulsions were observed. There was no significant difference in energy expenditure, nitrogen balance, liver function tests, carnitine, transferrin, pre-albumin, albumin, cholesterol, triglycerides and free fatty acids. The only parameter that showed a different pattern of reaction between the two emulsions was serum bilirubin concentration. In this study no evidence of any advantageous effect of a mixture of medium-chain triglycerides and long-chain triglycerides was seen.

Comparative hemodynamic effects of three different parenterally administered lipid emulsions in conscious dogs

OBJECTIVE

To compare the hemodynamic side effects of three structurally different lipid emulsions.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

University research laboratory.

SUBJECTS

Six chronically instrumented mongrel dogs.

INTERVENTIONS

On separate days, all animals were submitted to three different treatments, in a randomized order. After baseline measurements, either a long-chain triglyceride emulsion (treatment 1), a mixed medium-chain triglyceride/long-chain triglyceride emulsion (treatment 2), or an omega3 polyunsaturated fatty acid long-chain triglyceride (PUFA) emulsion (treatment 3) was administered intravenously over 30 mins.

MEASUREMENTS AND MAIN RESULTS

Global and regional hemodynamics (sonomicrometry) were recorded for 2 hrs after baseline measurements. Arterial blood gases and plasma concentrations of hemoglobin, triglycerides, total protein, and glucose were recorded for 2 hrs. Long-chain triglycerides did not affect the cardiovascular performance in awake animals. However, medium-chain triglycerides/long-chain triglycerides and omega3 PUFA caused marked increases in systemic vascular resistance (from 1833 +/- 154 to 3277 +/- 163 mm Hg/dynexsec5, p < .05), heart rate (from 89 +/- 6 to 158 +/- 10 beats/min, p < .05), and depressed ventricular performance (wall-thickening fraction [as percentage from baseline] decreased to 53 +/- 9%, p < .05).

CONCLUSIONS

Commercially available lipid emulsions can cause profound cardiovascular side effects at high doses, depending on their composition. Whereas long-chain triglyceride emulsions have virtually no effects on hemodynamics in normal dogs, medium-chain triglyceride/long-chain triglyceride, and omega3 PUFA emulsions should be used with caution in critically ill patients with compromised cardiovascular function.

Comparison of bone marrow toxicity of medium-chain and long-chain triglyceride emulsions: an in vitro study in humans

BACKGROUND

In this study, we evaluated the in vitro bone marrow toxicity of two lipid emulsions containing either long-chain triglycerides (LCT) or a mixture of medium-chain triglycerides (MCT) and LCT.

METHODS

Bone marrow cells were obtained from six healthy subjects and were cultured for 14 days after a 24-hour preincubation with various concentrations (from 0 to 10 mg/mL) of LCT- and LCT/MCT-based lipid emulsions.

RESULTS

Compared with controls (no preincubation with lipid emulsion), both lipid emulsions significantly inhibited by 50% to 70% colony formation of all the human bone marrow cells cultured from a triglyceride concentration of 0.5 mg/mL (p < .05). Erythroid burst-forming unit (BFU-E) formation was significantly more inhibited with LCT/MCT emulsion than with LCT emulsion (p < .05). The inhibition of granulocyte-macrophage colony-forming unit (GM-CFU) and mixed granulocyte-erythrocyte-monocyte-megakaryocyte colony-forming unit (GEMM-CFU) formation did not significantly differ with the two emulsions.

CONCLUSIONS

Both LCT- and LCT/MCT-based lipid emulsions strongly inhibit colony formation by human bone marrow cells. BFU-E colony formation is more sensitive to LCT/MCT inhibition than to LCT.

Fat emulsions based on structured lipids (1,3-specific triglycerides): an investigation of the in vitro interaction with plasma proteins

Structured lipids (1,3-specific triglycerides) are new chemical entities made by enzymatic transesterification of the fatty acids in the 1,3-positions of the triglyceride. The purpose of this study was to investigate the in vitro interaction of fat emulsions based on either structured lipids or vegetable oils with human plasma proteins employing two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The structured lipids are triglycerides of the SLS and MLM types, where S is short-chain fatty acids (C4), M is medium-chain fatty acids (C8-10) and L is long-chain fatty acids (C16-18). The vegetable oil-based fat emulsions were the commercially available product, Intralipid, and a soybean oil (LLL) emulsion made de novo identically as the emulsions containing structured lipids. The SLS emulsion was found to adsorb a different protein pattern than the MLM and LLL emulsions. The protein pattern of the SLS emulsion was similar to the protein pattern of Intralipid. These findings might explain the in vivo difference in elimination found in another study, where the emulsion based on structured lipids with short-chain fatty acids in the 1,3-positions was removed more slowly from the general blood circulation compared to emulsions based on lipids with long-chain fatty acids in the 1,3-positions (LLL).

The effect of intravenous lipids on gastric emptying in rats subjected to total parenteral nutrition

Total parenteral nutrition (TPN) is indicated in a number of clinical situations involving obstructive disorders of the gastrointestinal tract or when total bowel rest is required. However, little is known of its effects upon the physiology of gastric storage and emptying. A study of the effects of lipid nutrient content of TPN on the gastric emptying of a non-energy liquid test meal in male and female conscious rats (250-280 g) was undertaken. Five experimental groups were set up according to the percentage of total non-protein energy administered in the form of different lipids: A (lipid-free: 100% of non-protein energy as glucose); B (5% long-chain triglycerides (LCT), 95% glucose); C (40% LCT, 60% glucose); D (5% LCT and medium-chain triglycerides (MCT) in 1:1 proportion, 95% glucose); and E (40% LCT and medium-chain triglycerides (MCT) in 1:1 proportion, 60% glucose). Animals were maintained on TPN for 24 h and for 3 and 4 days, after which gastric emptying was measured by the phenol red method. 40% lipid TPN was found to accelerate gastric emptying as infusion was prolonged, although the type of lipid had no effect.

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).

Infusion of long-chain or medium-chain triglycerides inhibits peripheral glucose metabolism in men

To investigate whether increased availability of lipids affects glucose metabolism in healthy postabsorptive men when lipid and glucose are infused in amounts used in parenteral nutrition, we infused glucose (4 mg/kg.min-1) for 6 hours and clamped plasma glucose at basal level during the first 3 hours. After 3 hours, either long-chain triglycerides (LCTs) (0.07 g/kg.h-1) (n = 7) or a mixture of LCTs and medium-chain triglycerides (MCTs) (MCTs/LCTs, 50/50%, 0.07 g/kg.h-1) (n = 7) was administered, and the infusion rates of glucose and insulin were unchanged compared with the first 3 hours. In a control study, glucose was infused for a period of 6 hours without the lipid infusion (n = 5). After 6 hours, the plasma glucose concentration and glucose tissue uptake were not affected by LCT or MCT/LCT infusion. Nonetheless, glucose oxidation decreased in the LCT group (from 6.42 +/- 1.04 to 2.31 +/- 0.85 mumol/kg.min-1, p < .001) and in the MCT/LCT group (from 7.62 +/- 1.50 to 5.50 +/- 0.76 mumol/kg.min-1, p < .01) but not in the control group. Concentrations of the glucoregulatory hormones were not different among the three groups. In conclusion, MCTs/LCTs administered concomitantly with glucose infusion, in amounts similar to those used in total parenteral nutrition, inhibit glucose oxidation without affecting glucose tissue uptake, just as LCTs do.

Odd-numbered medium-chain triglycerides (trinonanoin) in total parenteral nutrition: effects on parameters of fat metabolism in rabbits

Odd-numbered medium-chain triglycerides (MCTs) might combine the advantages of "usual" MCTs applied in clinical nutrition with lower ketogenic action and the release of three carbon units. To test subacute toxicity, trinonanoin/long-chain triglyceride (LCT) (7/3 wt/wt) fat emulsions were given to rabbits (n = 8) for 11 days (7 h/d) within a total parenteral nutrition regimen at a dose of 46.5% of total daily energy. Comparisons were made with rabbits receiving equicaloric amounts of MCT/LCT (7/3, wt/wt) or pure LCT fat emulsions, as well as with orally fed controls. The trinonanoin/LCT emulsion was well tolerated by all animals. Body weight changes showed no statistically significant differences between groups. The enzymatic determination of triglycerides, non-esterified fatty acids, and free glycerol concentrations in plasma samples revealed similar results for both MCT groups. However, ketone body concentrations (3-hydroxybutyrate) were significantly lower after trinonanoin/LCT emulsion administration. In the trinonanoin/LCT group, the plasma concentrations of propionic acid as well as of other short-chain fatty acids continuously increased; on days 10 and 11, elevated amounts of propionic acid were also detected in the urine. The histologic examination of the gut mucosa revealed no distinct differences between groups. On the basis of the presented data, the trinonanoin/LCT emulsion showed no inferiority to "usual" MCT/LCT emulsions. The lower ketogenic effect as well as the marked increase in plasma short-chain fatty acid concentrations may encourage further testing of this substrate for total parenteral nutrition.

Isocaloric feeding and medium chain triglycerides fail to improve liver function tests in a patient with Crohn's disease and a high output stoma

A patient with Crohn's disease complicated by multiple fistulae to the skin and bladder and a high-output stoma following previous multiple short bowel resections developed liver dysfunction during total parenteral nutrition. Isocaloric feeding based on calorimetry and changing from a long chain triglyceride emulsion to a mixture of medium and long chain triglyceride emulsion failed to improve liver function. Surgical removal of the affected small bowel resulted in a rapid improvement of the liver function despite continuation of total parenteral nutrition.

Effects of D-beta-hydroxybutyrate and long- and medium-chain triglycerides on leucine metabolism in humans

Ketone bodies and/or fatty acids might play a protein-sparing role during prolonged fasting or parenteral nutrition. To assess this problem, we studied whole body leucine metabolism, using L-[1-13C]leucine in normal postabsorptive volunteers who received either long-chain triglycerides (LCT, 0.15 g.kg-1.h-1, 6 subjects), a 50-50 mixture of medium-chain triglycerides (MCT) and LCT (0.15 g.kg-1.h-1, 6 subjects), D-beta-hydroxybutyrate (540 mumol.kg-1.h-1, 6 subjects), or saline (4 subjects). Leucine concentration decreased only with MCT-LCT. Leucine flux decreased by 10-20% from basal in all groups. Leucine oxidation, which was corrected for the contribution to 13CO2 of the 13C natural abundance of the infused substrates, decreased during LCT infusion (0.31 +/- 0.02 to 0.24 +/- 0.01 mumol.kg-1.min-1, P less than 0.01), but was unaffected by MCT-LCT (despite plasma free fatty acid levels similar to those obtained with LCT), D-beta-hydroxybutyrate, or saline infusion. Therefore, 1) the effect of fatty acids on amino acid oxidation is not mediated by ketone bodies, 2) it depends on the fatty acid chain length, 3) long-chain fatty acids but not medium-chain fatty acids could play a protein-sparing role during parenteral nutrition.

Effect of medium- and long-chain triglyceride infusion on lipoprotein and hepatic lipase in healthy subjects

Plasma lipolytic activity and hydrolysis of intravenous fat were studied in six healthy subjects during infusion of a long-chain triglyceride (LCT) fat emulsion (Intralipid 20%) or of a medium-chain triglyceride (MCT)/LCT emulsion (Lipofundin MCT 20%). The fat emulsions were infused continuously at a rate of 0.17 g triglyceride kg-1 body weight (BW)h-1 for 6 h in random order at 7-day intervals. A continuous infusion of glucose (0.18 g kg-1 BW h-1) was administered for a period of 7 h and was started 1 h before the lipid infusion. Infusions of both types of fat increased plasma triglyceride (TG), free fatty acid (FFA) and lipoprotein lipase (LPL) levels and steady-state values were present during the 3rd to 5th h of infusion. MCT/LCT infusion resulted in higher plasma levels at steady-state of TG (3.63 +/- 0.45 [SEM] vs 2.73 +/- 0.45 mmol l-1; P less than 0.05), FFA (1.05 +/- 0.08 vs 0.54 +/- 0.04 mmol l-1; P less than 0.01) and LPL (4.6 +/- 0.6 vs 2.6 +/- 0.5 mU ml-1; P less than 0.05) in comparison with LCT administration. There was a positive correlation between plasma LPL activity and TG concentration (r = 0.77; P less than 0.001) when data for the two infusions were combined. Although the same amount of fat was infused on a weight basis, the molar infusion rate was 40% higher with MCT/LCT than with LCT infusion, due to differences in molecular weights (634 vs 885 Da).(ABSTRACT TRUNCATED AT 250 WORDS)