The effect of increasing levels of fish oil-containing structured triglycerides on protein metabolism in parenterally fed rats stressed by burn plus endotoxin

Structured Triglyceride Emulsions in Parenteral Nutrition

Over the past 3 decades, various concepts for IV fat emulsions (IVFE) have been developed. A randomized, structured-lipid emulsion based on an old technology has recently become available. This structured-lipid emulsion is produced by mixing medium-chain triglycerides and long-chain triglycerides, then allowing hydrolysis to form free fatty acids, followed by random transesterification of the fatty acids into mixed triglyceride molecules. Studies in animals have shown an improvement in nitrogen balance with the use of these lipid emulsions. Only 8 human clinical studies with these products have been performed. The results of these human clinical studies have been less promising than the animal studies; however, an improvement in nitrogen balance and lipid metabolism exceeds results associated with infusion of long-chain triglycerides (LCT) or a physical mixture of long-chain triglycerides and medium-chain triglycerides (LCT-MCT). Structured-lipid emulsion seems to induce less elevation in serum liver function values compared with standard IVFEs. In addition, structured-lipid emulsions have no detrimental effect on the reticuloendothelial system. Further studies are necessary in order to recommend the use of structured-lipid emulsions. The clinical community hopes that chemically defined structured triglycerides will make it possible to determine the distribution of specific fatty acids on a specific position on the glycerol core and therefore obtain specific activity for a specific clinical situation.

Malnutrition, nutritional indices, and early enteral feeding in critically ill children

We measured the incidences of protein and fat depletions and the frequencies of acute and chronic protein-energy malnutrition during stress states in children and investigated the influence of early enteral feeding on nutrition indices and acute-phase proteins. Seventy-one, consecutively enrolled, critically ill children received early enteral feeding (energy intakes equal to 0.50, 1, 1.25, 1.5, and 1.5 of the predicted basal metabolic rates on days 1 through 5, respectively) through nasogastric tubes. On the first day of the study, 16.7% of the patients already were depleted of protein and 31% of fat stores. Overall, 16.9% were at risk for chronic protein-energy malnutrition and 21.1% for acute protein-energy malnutrition, whereas 4.2% and 5.6% already had chronic and acute, respectively protein-energy malnutrition. Only 22.7% of patients without protein deficiencies versus 37% of those at risk or already deficient developed multiple-organ system failure. Transferrin and prealbumin levels improved at the end of the period of early enteral feeding (187 +/- 6.6 versus 233 +/- 7 mg/dL, P < 0.0001; 15.1 +/- 2 versus 21.9 +/- 2.9 mg/dL, P < 0.0001; respectively); survivors had higher prealbumin levels than non-survivors (22.3 versus 15.5 mg/dL). With logistic regression analysis, only repleted energy, not anthropometric or nutrition indices, was independently associated with survival (P = 0.05). These results reinforce the observation that critically ill children are at risk for fat or protein depletion and development of malnutrition, which is associated with increased morbidity and mortality. We conclude that early enteral nutrition improves nutrition indices and outcomes.

Structured lipids improve fat absorption in normal and malabsorbing rats

The presence of medium-chain fatty acids in dietary fatty acid as well as the triacylglycerol structure may influence the absorption and lymphatic transport of fatty acids. We compared the lymphatic transport and recovery of fatty acids from four intragastrically administered fats based on rapeseed oil and decanoic acid in two rat models of normal absorption and malabsorption, respectively. The fats were: 1) a fat with a regiospecific structure, 2) a similar fat but with a random distribution of fatty acids in the triacylglycerol molecule, 3) a physical mixture of tridecanoin and rapeseed oil and 4) rapeseed oil as control. Lymph samples were collected for 24 h. Significantly higher recoveries were observed of total fatty acids, oleic acid, linoleic acid and linolenic acid from the specific oil in malabsorbing rats and of linoleic acid in normal rats fed specific oil compared with those fed rapeseed oil. Furthermore, the recoveries of oleic acid and linolenic acid from the specific oil in normal rats were higher than those from the other oils. In malabsorbing rats, the transport of all fats was approximately 90% less than that of normal rats. The present study demonstrates improved hydrolysis and absorption of the specific oil compared with the other oils examined both in rats with normal absorption and in rats with malabsorption.

Formulation of enteral diets

The number of enteral diets has increased from a handful in the 1970s to over 100 at present. These can be classified as polymeric, chemically defined, disease-specific, and specialized diets, as well as oral dietary supplements. The properties, indications, pros and cons for the use of these diets are outlined in an effort to assist clinicians in their selection.

Medium-chain triglyceride and n-3 polyunsaturated fatty acid-containing emulsions in intravenous nutrition

Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions as a physical mixture have attracted increasing interest for use in parenteral nutrition and may play an important role in the development of structured triglycerides in a future generation of new lipids. Over the past two decades, the clinical use of intravenous emulsion for the nutritional support of hospitalized patients has relied exclusively on long-chain triglycerides providing both a safe, calorically dense alternative to dextrose and a source of essential fatty acids needed for biological membranes and maintenance of the immune function. During the past decade, the development of new triglycerides (medium- and long-chain triglyceride emulsions and structured triglyceride emulsions) for parenteral use have provided useful advances and opportunities to enhance nutritional and metabolic support. Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions possess unique physical, chemical, and metabolic properties that make them theoretically advantageous over the conventional long-chain triglycerides. The physical mixture of medium- and long-chain triglycerides have been used clinically in patients with critical illness, liver disease, immunosuppression, pulmonary disease, and in premature infants, with good tolerance and the avoidance of some of the problems encountered with long-chain triglycerides alone.

Effect of a fish oil structured lipid-based diet on prostaglandin release from mononuclear cells in cancer patients after surgery

BACKGROUND

The authors compared the effect on eicosanoid production (prostaglandin E2 [PGE2], 6-keto PGF 1 alpha, and thromboxane B2) from peripheral blood mononuclear cells (PBMC) of feeding an enteral diet containing a fish oil/medium-chain triglyceride structured lipid (FOSL-HN) vs an isonitrogenous, isocaloric formula (O-HN) in patients undergoing major abdominal surgery for upper gastrointestinal malignancies. A previous study, which used the same formulas and experimental design, suggested improved renal and liver function as well as a reduced number of gastrointestinal and infectious complications with the use of fish oil structured lipids. This study sought to investigate the potential mechanism for these effects by assessing eicosanoid production from PBMC with the two diets.

METHODS

This prospective, blinded, randomized trial was conducted in 20 patients who were jejunally fed either FOSL-HN or O-HN for 7 days. Serum chemistries, hematology, urinalysis, gastrointestinal complications, liver and renal function, and eicosanoid production from isolated PBMC, either unstimulated or stimulated with endotoxin, were measured at endotoxin baseline and on day 7. Comparisons were made in 10 and 8 evaluable patients based a priori on the ability to reach a tube feeding rate of > 40 mL/h.

RESULTS

Patients receiving FOSL-HN experienced no untoward side effects compared with patients given O-HN and demonstrated the same general trend toward improved hepatic, renal and immune function found in the previous study. There was a significant reduction in PGE2 (p < .03) and 6-keto PGF 1 alpha (p < .01) production from PBMC with endotoxin stimulation in patients receiving FOSL-HN.

CONCLUSIONS

The results of early enteral feeding with FOSL-HN after surgery in this follow-up study provide further support to claims of safety, tolerance, and improved physiologic function. There was an associated reduction in eicosanoid production from PBMCs, which is presumed to be the principal mechanism for these effects.

Early enteral feeding in postsurgical cancer patients. Fish oil structured lipid-based polymeric formula versus a standard polymeric formula

OBJECTIVES

The authors compared the safety, gastrointestinal tolerance, and clinical efficacy of feeding an enteral diet containing a fish oil/medium-chain triglyceride structured lipid (FOSL-HN) versus an isonitrogenous, isocaloric formula (O-HN) in patients undergoing major abdominal surgery for upper gastrointestinal malignancies.

SUMMARY BACKGROUND DATA

Previous studies suggest that feeding with n-3 fatty acids from fish oil can alter eicosanoid and cytokine production, yielding an improved immunocompetence and a reduced inflammatory response to injury. The use of n-3 fatty acids as a structured lipid can improve long-chain fatty acid absorption.

METHODS

This prospective, blinded, randomized trial was conducted in 50 adult patients who were jejunally fed either FOSL-HN or O-HN for 7 days. Serum chemistries, hematology, urinalysis, gastrointestinal complications, liver and renal function, plasma and erythrocyte fatty acid analysis, urinary prostaglandins, and outcome parameters were measured at baseline and on day 7. Comparisons were made in 18 and 17 evaluable patients based a priori on the ability to reach a tube feeding rate of 40 mL/hour.

RESULTS

Patients receiving FOSL-HN experienced no untoward side effects, significant incorporation of eicosapentaenoic acid into plasma and erythrocyte phospholipids, and a 50% decline in the total number of gastrointestinal complications and infections compared with patients given O-HN. The data strongly suggest improved liver and renal function during the postoperative period in the FOSL-HN group.

CONCLUSION

Early enteral feeding with FOSL-HN was safe and well tolerated. Results suggest that the use of such a formula during the postoperative period may reduce the number of infections and gastrointestinal complications per patient, as well as improve renal and liver function through modulation of urinary prostaglandin levels. Additional clinical trials to fully quantify clinical benefits and optimize nutritional support with FOSL-HN should be undertaken.

Effects of chemically defined structured lipid emulsions on reticuloendothelial system function and morphology of liver and lung in a continuous low-dose endotoxin rat model

BACKGROUND

This study was undertaken to determine the effect of chemically defined structured lipids on nonspecific host defense and on histologic patterns of liver and lungs compared with a physical mixture of long-chain triglycerides and medium-chain triglycerides in a continuous low-dose endotoxin rat model.

METHODS

Forty male Sprague-Dawley rats, divided into four feeding groups (structured lipids, structured lipids+endotoxin, physical mixture, physical mixture+endotoxin), received total parenteral nutrition for 48 hours. During the first part of the study, 24 animals were given an injection of live Escherichia coli labeled with radioactive iron (59Fe) to investigate the function of the reticuloendothelial system. During the second part of the study, the liver and lungs of 16 animals were histologically examined using light and electron microscopy.

RESULTS

Despite the similar values in the control groups, the animals receiving structured lipids+endotoxin sequestered a significantly greater percentage of bacteria in the liver and spleen (p < or = .01) and a significantly lesser percentage in the lung (p < or = .05) compared with the animals given physical mixture+endotoxin as part of their diet. Moreover, rats in the physical mixture+endotoxin group showed a microscopically evaluated higher fatty infiltration in the liver than did the structured lipids+endotoxin group.

CONCLUSIONS

The results of this study indicate that chemically defined structured lipids reduce fatty infiltration of the liver compared with a physical mixture of the same compounds in an animal model of metabolic stress. They were accompanied by a better function of the reticuloendothelial system and a lesser bacterial sequestration in the lungs.