Lipid peroxidation of i.v. lipid emulsions in TPN bags: the influence of tocopherols

The Development of Magnolol-Loaded Intravenous Emulsion with Low Hepatotoxic Potential

Intestinal failure-associated liver disease (IFALD) is a severe liver injury occurring due to factors related to intestinal failure and parenteral nutrition administration. Different approaches are studied to reduce the risk or ameliorate the course of IFALD, including providing omega-3 fatty acids instead of soybean oil-based lipid emulsion or administering active compounds that exert a hepatoprotective effect. This study aimed to develop, optimize, and characterize magnolol-loaded intravenous lipid emulsion for parenteral nutrition. The preformulation studies allowed for chosen oils mixture of the highest capacity of magnolol solubilization. Then, magnolol-loaded SMOFlipid was developed using the passive incorporation method. The Box-Behnken design and response surface methodology were used to optimize the entrapment efficiency. The optimal formulation was subjected to short-term stress tests, and its effect on normal human liver cells and erythrocytes was determined using the MTT and hemolysis tests, respectively. The optimized magnolol-loaded SMOFlipid was characterized by the mean droplet diameter of 327.6 ± 2.9 nm with a polydispersity index of 0.12 ± 0.02 and zeta potential of -32.8 ± 1.2 mV. The entrapment efficiency of magnolol was above 98%, and pH and osmolality were sufficient for intravenous administration. The magnolol-loaded SMOFlipid samples showed a significantly lower toxic effect than bare SMOFlipid in the same concentration on THLE-2 cells, and revealed an acceptable hemolytic effect of 8.3%. The developed formulation was characterized by satisfactory stability. The in vitro studies showed the reduced cytotoxic effect of MAG-SMOF applied in high concentrations compared to bare SMOFlipid and the non-hemolytic effect on human blood cells. The magnolol-loaded SMOFlipid is promising for further development of hepatoprotective lipid emulsion for parenteral nutrition.

Narrative Review of n-3 Polyunsaturated Fatty Acid Supplementation upon Immune Functions, Resolution Molecules and Lipid Peroxidation

Fish oil supplementation is commonplace in human nutrition and is being used in both enteral and parenteral formulations during the treatment of patients with a large variety of diseases and immune status. The biological effects of fish oil are believed to result from their content of n-3 polyunsaturated fatty acids (PUFA), particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These fatty acids are known to have numerous effects upon immune functions and are described as immunomodulatory. However, immunomodulatory is a nondescript term that encompasses immunostimulation and immunosuppression. The primary goal of this review is to better describe the immune effects of n-3 PUFA as they relate to immunostimulatory vs. immunosuppressive effects. One mechanism proposed for the immune effects of n-3 PUFA relates to the production of specialized pro-resolving mediators (SPMs). A second goal of this review is to evaluate the effects of n-3 PUFA supplementation upon production of SPMs. Although n-3 PUFA are stated to possess anti-oxidative properties, these molecules are highly oxidizable due to multiple double bonds and may increase oxidative stress. Thus, the third goal of this review is to evaluate the effects of n-3 PUFA upon lipid oxidation. We conclude, based upon current scientific evidence, that n-3 PUFA suppress inflammatory responses and most cellular immune responses such as chemotaxis, transmigration, antigen presentation, and lymphocyte functions and should be considered immunosuppressive. n-3 PUFA induced production of resolution molecules is inconsistent with many resolution molecules failing to respond to n-3 PUFA supplementation. n-3 PUFA supplementation is associated with increased lipid peroxidation in most studies. Vitamin E co-administration is unreliable for prevention of the lipid peroxidation. These effects should be considered when administering n-3 PUFA to patients that may be immunosuppressed or under high oxidative stress due to illness or other treatments.

Composition and Functionality of Lipid Emulsions in Parenteral Nutrition: Examining Evidence in Clinical Applications

Lipid emulsions (LEs), an integral component in parenteral nutrition (PN) feeding, have shifted from the primary aim of delivering non-protein calories and essential fatty acids to defined therapeutic outcomes such as reducing inflammation, and improving metabolic and clinical outcomes. Use of LEs in PN for surgical and critically ill patients is particularly well established, and there is enough literature assigning therapeutic and adverse effects to specific LEs. This narrative review contrarily puts into perspective the fatty acid compositional (FAC) nature of LE formulations, and discusses clinical applications and outcomes according to the biological function and structural functionality of fatty acids and co-factors such as phytosterols, α-tocopherol, emulsifiers and vitamin K. In addition to soybean oil-based LEs, this review covers clinical studies using the alternate LEs that incorporates physical mixtures combining medium- and long-chain triglycerides or structured triglycerides or the unusual olive oil or fish oil. The Jaded score was applied to assess the quality of these studies, and we report outcomes categorized as per immuno-inflammatory, nutritional, clinical, and cellular level FAC changes. It appears that the FAC nature of LEs is the primary determinant of desired clinical outcomes, and we conclude that one type of LE alone cannot be uniformly applied to patient care.

Pharmaceutical Aspects of Artificial Nutrition

Artificial nutrition, including enteral (EN) and parenteral (PN) nutrition, is indicated whenever adequate oral nutrition fails to sufficiently supply the necessary nutrients to the body. It is a convenient, efficacious, safe, and well-tolerated form of clinical nutrition in the hospital and home setting. EN is administered via nasogastric tube or ostomies while PN usually requires a central venous access for administration, straight into the blood stream. The infused nutrients can then be taken up directly by the different organs. PN is targeted as a single daily portion formulated as an oil-in-water emulsion providing the necessary substrates for the catabolic and anabolic metabolism including macro- and micronutrients and fluids. PN has a complex pharmaceutical composition-all-in-one admixture-and its compounding or ready-to-use preparation. The use of PN is more challenging and more expensive compare to the use of EN, commercially available as ready-to-use formulations. EN and concomitant medication is highly challenging. Upon incorrect handling and administration, PN is associated with potentially severe or even fatal complications, mostly relating to the central venous access (e.g., catheter-related sepsis) or to a metabolic intolerance (e.g., hyperglycemia, refeeding syndrome) because of inappropriate administration. A correct order of admixing, correct dosing, and administration of the artificial is crucial for safety and efficacy; clinical and biochemical monitoring of the patient and treatment regimen adaption are necessary. The high number of reactive solutes allow only limited stability of a ready-to-use PN admixture. The potential for numerous incompatibilities and interactions renders PN admixtures generally unsuitable as drug vehicle. Laboratory compatibility and stability testing and pharmaceutical expertise are a prerequisite to define the PN composition including nutrients or even drugs admixed to define the appropriate and individualized nutrition and medication regimen. The aim of this narrative review is to present the actual state-of-the-art to deliver best quality artificial nutrition with special regard on pharmaceutical aspects such as instabilities, incompatibilities, and concomitant co-medication.

Parenteral nutrition and oxidant stress in the newborn: A narrative review

There is strong evidence that oxidant molecules from various sources contaminate solutions of parenteral nutrition following interactions between the mixture of nutrients and some of the environmental conditions encountered in clinical practice. The continuous infusion of these organic and nonorganic peroxides provided us with a unique opportunity to study in cells, in vascular and animal models, the mechanisms involved in the deleterious reactions of oxidation in premature infants. Potential clinical impacts of peroxides infused with TPN include: a redox imbalance, vasoactive responses, thrombosis of intravenous catheters, TPN-related hepatobiliary complications, bronchopulmonary dysplasia and mortality. This is a narrative review of published data.

New Parenteral Lipid Emulsions for Clinical Use

Routine use of parenteral lipid emulsions (LE) in clinical practice began in 1961, with the development of soybean oil (SO) - based LE. Although clinically safe, experimental reports indicated that SO-based LE could exert a negative influence on immunological functions. Those findings were related to its absolute and relative excess of omega-6 polyunsaturated fatty acids (PUFA) and the low amount of omega-3 PUFA and also to its high PUFA content with an increased peroxidation risk. This motivated the development of new LE basically designed along the reduction of omega-6 PUFA and the omega-3 PUFA addition in order to obtain balanced levels of the omega-6/omega-3 ratio. The new LE for clinical use (available in Europe and South America) are differentiated by their content in polyunsaturated (omega-6 and omega-3), monounsaturated, and saturated fatty acids (FA), as well as FA source of their origin, including soy, coconut, olive, and fish oil. This article presents the new LE nutrition and energy functions but also its biochemical, metabolic, and immunomodulating aspects, according to their FA content. LE at 20% when infused from 1.0 to 2.0 g/kg body weight/day rates, either alone or in association with amino acids and glucose, are safe and well tolerated in routine clinical practice. LE combining SO with medium-chain triglycerides and/or olive oil have less omega-6 PUFA and are better metabolized, with less inflammatory and immunosuppressive effects than in relation to pure SO-based LE. The omega-3 PUFA used alone or as component of a new and complex LE (soy, MCT, olive and fish oil) has demonstrated anti-inflammatory and immunomodulatory effects.

Tocopherol and tocotrienol homologs in parenteral lipid emulsions

Parenteral lipid emulsions, which are made of oils from plant and fish sources, contain different types of tocopherols and tocotrienols (vitamin E homologs). The amount and types of vitamin E homologs in various lipid emulsions vary considerably and are not completely known. The objective of this analysis was to develop a quantitative method to determine levels of all vitamin E homologs in various lipid emulsions. An HPLC system was used to measure vitamin E homologs using a Pinnacle DB Silica normal phase column and an isocratic, n-hexane:1,4 dioxane (98:2) mobile phase. An optimized protocol was used to report vitamin E homolog concentrations in soybean oil-based (Intralipid®, Ivelip®, Lipofundin® N, Liposyn® III, and Liposyn® II), medium- and long-chain fatty acid-based (Lipofundin®, MCT and Structolipid®), olive oil-based (ClinOleic®), and fish oil-based (Omegaven®) and mixture of these oils-based (SMOFlipid®, Lipidem®) commercial parenteral lipid emulsions. Total content of all vitamin E homologs varied greatly between different emulsions, ranging from 57.9 to 383.9 µg/mL. Tocopherols (α, β, γ, δ) were the predominant vitamin E homologs for all emulsions, with tocotrienol content < 0.3%. In all of the soybean emulsions, except for Lipofundin® N, the predominant vitamin E homolog was γ-tocopherol, which ranged from 57–156 µg/mL. ClinOleic® predominantly contained α-tocopherol (32 µg/mL), whereas α-tocopherol content in Omegaven® was higher than most of the other lipid emulsions (230 µg/mL).

Distribution of Tocopherols and Tocotrienols in Guinea Pig Tissues Following Parenteral Lipid Emulsion Infusion

BACKGROUND

Tocopherols and tocotrienols possess vitamin E activity and function as the major lipid-soluble antioxidants in the human body. Commercial lipid emulsions are composed of different oils and supply different amounts of vitamin E. The objective of this study was to measure all 8 vitamin E homologs within 4 different commercial lipid emulsions and evaluate their distribution in guinea pig tissues.

MATERIALS AND METHODS

The distribution of vitamin E homologs within plasma and guinea pig tissues was determined using a high-performance liquid chromatography (HPLC) system. Lipid hydroperoxides in lipid emulsions were determined using a commercial kit (Cayman Chemical Company, Ann Arbor, MI), and malondialdehyde tissue levels were determined using an HPLC system.

RESULTS

The lipid emulsions contained variable amounts of tocopherols, which were significantly different between emulsions. Tocotrienols were present at very low concentrations (≤0.3%). We found no correlation between the amount of vitamin E present in the lipid emulsions and lipid peroxidation. Hydroperoxides were the lowest with an olive oil-based emulsion and highest with a fish oil emulsion. The predominant vitamin E homolog in guinea pig tissues was α-tocopherol. No tissues had detectable levels of tocotrienols. Vitamin E levels (primarily α-tocopherol and γ-tocopherol) were highly variable among organ tissues. Plasma levels were a poor reflection of most tissue levels.

CONCLUSION

Vitamin E levels within different lipid emulsions and plasma/tissues are highly variable, and no one tissue or plasma sample serves as a good proxy for levels in other tissues. All study emulsions were well tolerated and did not significantly increase systemic lipid peroxidation.

Lipids and liver dysfunction in patients receiving parenteral nutrition

PURPOSE OF REVIEW

Abnormalities of liver function tests are common in patients with intestinal failure receiving parenteral nutrition. Lipid emulsions have been implicated in the development of hepatobiliary disease in patients receiving parenteral nutrition.

RECENT FINDINGS

Lipid emulsions with reduced polyunsaturated fatty acids and specific ω6 : ω3 fatty acid ratios have been shown to have some beneficial effects on liver function, although the studies are small and generally of short duration in paediatric and adult patients.

SUMMARY

There is good evidence to suggest that the parenteral lipid dose should be less than 1 g/kg body weight/day, but this may not apply to all patients. The evidence is presented for the different lipid emulsions and their effect on liver function. The benefit of these emulsions compared with simply giving a lower lipid dose has yet to be studied.

Fish oil emulsions in the management of intestinal failure-associated liver disease

The role of parenteral lipid emulsions in the treatment of intestinal failure-associated liver disease (IFALD) is both topical and controversial. There is strong evidence supporting plant-based (soy, olive) lipid emulsions as a key cause for IFALD, especially in neonates. As a result, alternate lipid formulations, most notably fish oil emulsions (FOE) have come into widespread use despite somewhat limited clinical data on their overall benefit and potential long-term consequences. This review examines putative mechanisms of action of FOE in reversing cholestasis associated with IFALD, and critically reviews published clinical studies of the use of FOE in pediatric patients with IFALD. From these works, it appears the mechanism of action of FOE is most likely related to the reduction of serum phytosterols associated with plant-based lipid emulsions rather than a specific positive benefit of the fish oils themselves. Although the use of FOE seems to correlate with a reduction in cholestasis, their actual individual benefit is not established, and data on long-term outcomes and safety are not yet available.

Micro-encapsulation of refined olive oil: influence of capsule wall components and the addition of antioxidant additives on the shelf life and chemical alteration

BACKGROUND

Although refined olive oils (ROOs) exhibit lower quality and less stability toward thermal stress than extra-virgin olive oils, these types of oil are gaining importance in the food industry. The inclusion of ROOs in processed food may alter the oxidative stability of the manufactured products, and therefore having technological alternatives to increase oil stability will be an important achievement. For this reason the main goal of this study was to assess the influence of the micro-encapsulation process on the ROO chemical composition and its oxidative stability. Factors such as microcapsule wall constituents and the addition of the antioxidant butyl hydroxytoluene were investigated in order to establish the most appropriate conditions to ensure no alteration of the refined olive oil chemical characteristics.

RESULTS

The optimised methodology exhibited high encapsulation yield (>98%), with micro-encapsulation efficiency ranging from 35 to 69% according to the nature of the wall components. The encapsulation process slightly altered the chemical composition of the olive oil and protected the oxidative stability for at least 11 months when protein components were included as wall components.

CONCLUSION

It was concluded that the presence of proteins constituents in the microcapsule wall material extended the shelf life of the micro-encapsulated olive oil regardless the use of antioxidant additives.

Lipid peroxidation in all-in-one admixtures for preterm neonates: impact of amount of lipid, type of lipid emulsion and delivery condition

AIM

To evaluate the effect of lipid emulsion composition and delivery condition on lipid peroxidation in typical all-in-one parenteral admixtures for preterm neonates.

METHODS

Malonedialdehyde (MDA) concentrations were assessed in different all-in-one admixtures. We evaluated the effects of fat blend (three lipid emulsions) and the amount of lipids, as well as the effects of protecting bags and/or tubing from ambient light and storage for 72 h. MDA was measured by liquid chromatography/mass spectrometry.

RESULTS

Three hundred and sixty samples were collected from 114 admixtures. Neither the type of lipid (p = 0.43) nor the interaction between light and type of lipid (p = 0.49) had any influence on final MDA concentrations, but the increase in MDA concentration at 24 h (T(24)) was related to light exposure (p < 0.001). The increase in MDA concentration was related to the increase in lipid amount in the admixture at T(0) (r = 0.77) and T(24) (r = 0.86). MDA concentrations in solutions stored for 72 h showed no significant increase, with no difference between the three lipid emulsions (p = 0.69).

CONCLUSION

All-in-one admixtures may be interesting for the parenteral nutrition of preterm neonates. Protection from light and restricting the amount of lipid to what is required for appropriate energy provision are essential to limit lipid peroxidation.

Vitamin E and immunity

Vitamin E is the most important chain-breaking, lipid-soluble antioxidant present in body tissues of all cells and is considered the first line of defense against lipid peroxidation and it is important for normal function of the immune cells. However, vitamin E deficiency is rare in well-nourished healthy subjects and is not a problem, even among people living on relatively poor diets, both T- and B-cell functions are impaired by vitamin E deficiency. While immune cells are particularly enriched in vitamin E because of their high polyunsaturated fatty acid content, this point puts them at especially high risk for oxidative damage. Besides its immunomodulatory effects, vitamin E also plays an important role in carcinogenesis with its antioxidant properties against cancer, and ischemic heart disease with limiting the progression of atherosclerosis. Supplementation of vitamin E significantly enhances both cell mediated and humoral immune functions in humans, especially in the elderly and animals.

Antioxidants: benefits and risks for long-term health

The oxidative modification hypothesis postulates that oxidative stress is one of the major factors in aging and the development of age-related disorders, including cardiovascular diseases. In this scenario, the oxidative modification of lipids, proteins and nucleic acids in vascular walls contributes to the etiology of cardiovascular disease, implying that consumption or therapeutic use of antioxidants could prevent the onset of such pathological disorders. Because of this, a number of studies have been conducted to address the question of whether cardiovascular diseases can be modulated by antioxidant treatment or consumption. Although some of the earliest data, collected in animal studies and epidemiologic studies have shown a measure of success, numerous clinical trials indicate that this approach is of minimal or no benefit. These conclusions represent a challenge to design more sensitive antioxidant trials in order to confirm or alter these conclusions. The focus of this review is on the benefits and disadvantages associated with the use of antioxidants, such as vitamins C and E, polyphenols, or antioxidant therapies, including hormone replacement therapy and iron reduction therapy, on overall vascular health.

Practical handling of AIO admixtures - Guidelines on Parenteral Nutrition, Chapter 10

All-in-one admixtures (AIO-admixtures) provide safe, effective and low-risk PN (parenteral nutrition) for practically all indications and applications. Water, energy (carbohydrates and lipids), amino acids, vitamins and trace elements are infused together with PN either as industrially-manufactured AIO admixtures provided as two- or three-chamber bags (shelf life usually more than 12 months) completed with electrolytes and micronutrients where appropriate or as individually compounded ready-to-use AIO admixtures (compounding, usually prepared by a pharmacy on either a daily or weekly basis and stored at 2–8°C). Physico-chemical and microbial stability of an AIO admixture is essential for the safety and effectiveness of patient-specific PN, and its assurance requires specialist pharmaceutical knowledge. The stability should be documented for an application period of 24 (–48) hours. It is advisable to offer a limited selection of different PN regimes in each hospital. For reasons of drug and medication safety, PN admixtures prepared for individual patients must be correctly labelled and specifications for storage conditions must also be followed during transport. Monitoring is required where applicable. Micronutrients are usually administered separately to AIO admixtures. In case compatibility and stability have been well documented trace elements and/or combination preparations including water-soluble or water-soluble/fat soluble vitamin supplements can be added to PN admixtures under strict aseptic conditions. AIO admixtures are usually not used as vehicles for drugs (incompatibilities).

Immune modulation by parenteral lipid emulsions

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

Improved fatty acid and leukotriene pattern with a novel lipid emulsion in surgical patients

OBJECTIVE

We assessed the effects of a novel lipid emulsion with reduced content of n-6 fatty acids (FA), increased share of MUFA and n-3 FA and supplemental vitamin E on fatty acid and leukotriene pattern in surgical patients.

METHODS

In a double-blind, randomized study 33 patients received isonitrogenous, isocaloric TPN over 5 postoperative days following major abdominal surgery. 19 patients received the new SMOFlipid 20% and 14 patients a standard soybean oil emulsion (Lipovenoes 20%, both Fresenius Kabi), each 1.5 g fat/kg body weight (BW)/d. Routine lipid biochemistry, plasma tocopherol, fatty acid pattern in plasma phospholipids, as well as leukotriene (LT) release in leukocytes were assessed. Additionally, fatty acid pattern in leukocyte and platelet phospholipids were analysed, but results are not presented.

RESULTS

On day 6, plasma alpha-tocopherol (34.2 +/- 10.3 vs. 17.6 +/- 2.9 micromol/L) and, in plasma PL, total n-3 FA were higher (11.1 +/- 1.9 vs. 4.9 +/- 0.9 mol%; p < 0.05) and total n-6 FA lower (23.8 +/- 2.2 vs. 31.8 +/- 1.7 mol%; P < 0.05); the ratio n-3/n-6 FA being elevated (0.5 +/- 0.1 vs. 0.2 +/- 0.0 p < 0.05) with SMOFlipid compared to the soybean oil emulsion. The shares of EPA (3.3+/-1.0 vs. 0.4+/-0.2 mol%; p<0.05) and DHA (6.9 +/- 1.8 vs. 3.7 +/- 0.8 mol%; p < 0.05) were highly increased but that of arachidonic acid (AA) was unchanged with SMOFlipid while the ratio EPA/AA was increased (0.7 +/- 0.2 vs. 0.1 +/- 0.0 p < 0.05). LTB(5) release was enhanced on day 6 (8.1 +/- 5.3 vs. 1.8 +/- 3.8 pmol/10(7) PMN, p < 0.05) and liberation of LTB(4) was lowered, yet not significantly with SMOFlipid (124.0 +/- 51.2 vs. 152.1 +/- 68.8 pmol/10(7) PMN). Length of hospital stay was significantly shorter with SMOFlipid (13.4 +/- 2.0 vs. 20.4 +/- 10.0 days, p < 0.05).

CONCLUSION

Treatment with the new emulsion SMOFlipid is well tolerated and modulates FA and leukotriene pattern suggesting favourable anti-inflammatory effects and further clinical benefits.

Peroxidation potential of lipid emulsions after compounding in all-in-one solutions

OBJECTIVES

We investigated the peroxidation potential of fat emulsions in all-in-one solutions (AIOs).

METHODS

Three 20% emulsions were compared: soybean oil (SO; 60% polyunsaturated fatty acids [PUFAs], alpha-tocopherol:PUFAs = 0.44), soybean plus medium-chain triacylglycerol (SO-MCT; 31% PUFAs, alpha-tocopherol:PUFAs = 0.35), and olive oil (OO; 21% PUFAs, alpha-tocopherol:PUFAs = 1.42). For each emulsion, six AIO solutions were prepared by adding 250 mL of emulsion to a lipid-free solution. Lipid peroxide (LPX) and malondialdehyde (MDA) concentrations were evaluated in fat emulsions, lipid-free solutions, and AIOs immediately (T0) and 24 h (T24) after lipid addition. Statistical analysis was done with analysis of variance.

RESULTS

Fat emulsion LPX in SO-MCT was lower than that in SO (P = 0.015) and OO (P = 0.024); LPX in SO was greater than that in OO (P = 0.013); MDA in SO was greater than that in SO-MCT (P = 0.001) and OO (P = 0.013); and MDA in SO-MCT was greater than that in OO (P = 0.001). In comparison with MDA at AIO-T0, MDA at AIO-T24 increased in SO (P = 0.005) and SO-MCT (P < 0.001) and decreased in OO (P = 0.003); at AIO-T24, LPX was greater in SO, but not significantly.

CONCLUSIONS

In AIO bags, LPX occurred within 24 h after the addition of the lipid emulsion and seemed to be directly related to the PUFA content and inversely related to the alpha-tocopherol:PUFA ratio of the emulsion.

Tocopherol isoforms in parenteral lipid emulsions and neutrophil activation

BACKGROUND AND AIMS

Tocopherol is a lipid-soluble anti-oxidant that exists in several isoforms. Patients on total parenteral nutrition depend on lipid emulsions for their tocopherol intake. In the present study, we analysed the content of tocopherol isoforms in various lipid emulsions. We also tested the hypothesis that immune-modulating effects of lipid emulsions could be attributed to different concentrations of alpha-tocopherol (alpha-toc) or peroxidation products.

METHOD

alpha-, beta-, gamma- and delta-toc were measured in emulsions containing long-chain triglycerides (LCT), mixed long- and medium-chain triglycerides (LCT/MCT), structured lipids (SL), olive oil (OO) or fish oil (FO). As a measure for cellular activation, neutrophil membrane adhesion markers were assessed after exposure to two LCT/MCT emulsions that differ only in alpha-toc content.

RESULTS

Various emulsions differed widely in tocopherol contents, especially with respect to the alpha- isoform. The latter isomer also was subject to considerable degradation despite adequate storage conditions. The previously observed activation of neutrophils by LCT/MCT was not influenced by the increased concentration of alpha-toc or the decreased concentration of lipid peroxidation products in a new LCT/MCT emulsion.

CONCLUSIONS

Tocopherol supplementation by parenteral lipid emulsions strongly depends on the lipid source and the storage lifetime of the emulsion. The effects of LCT/MCT on the immune system are not modulated by alpha-toc or by lipid peroxidation products.

Prospective survey of parenteral nutrition in Switzerland: a three-year nation-wide survey

BACKGROUND AND AIMS

The goals of this national survey were to determine the current PN practices and admixture formulations used in Switzerland.

METHODS

During three years, an annual questionnaire was sent to all heads of Swiss hospital pharmacies.

RESULTS

92% of Swiss hospitals with a full-time pharmacist participated. Different PN systems were commonly used for adult patients: 2 commercial formulas in 2 or 3 compartments bags, 2 commercial formulas with/without lipid, 3 formulas compounded by the hospital pharmacy. For hospitalized adults, 83% of PN bags were administered as commercial multicompartment bags. The compounding of individualized PN admixtures takes place primarily in pharmacies of medium to large size hospitals. For pediatric PN, hospital compounding is routine because of individualized PN compositions and absence of commercially available standardized admixtures. Long-term home-PN was mostly delivered by hospital pharmacies (57%) or by private nutrition support home delivery services (37%). Most PN formula compositions complied with European guidelines and represented 2.6+/-2.0% of the hospital drug budget. Multi-disciplinary nutritional support teams were present in 52% of hospitals.

CONCLUSION

In Switzerland, most PN for hospitalized adults were administered as commercial multi-compartment bags. The compounding of individualized PN admixtures were still important for pediatric patients and long-term home-PN.

Phagocytosis and killing of Candida albicans by human neutrophils after exposure to structurally different lipid emulsions

BACKGROUND

To test the hypothesis that structurally different lipid emulsions have distinct immune-modulating properties, we analyzed the elimination of Candida albicans by neutrophils after exposure to various emulsions.

METHODS

Neutrophils from 8 volunteers were incubated in physiologic 5 mmol/L emulsions containing long-chain- (LCT), medium-chain- (MCT), mixed LCT/MCT-, alpha-tocopherol-enriched LCT/MCT (LCT/MCT-E), or structured lipids (SL). After washing, the neutrophils were incubated with C. albicans. Phagocytosis was measured as the number of yeast-associated neutrophils relative to the total neutrophil count. Killing was expressed as the percentage of Candida survival relative to the initial yeast cell count.

RESULTS

No significant differences in yeast-neutrophil association could be demonstrated after neutrophil incubation in various lipid emulsions or medium, after correction for non-specific adhesion. However, although Candida survival after 1 hour incubation with non-lipid-exposed neutrophils amounted to 53% +/- 11% and was not influenced by LCT (60% +/- 11%), LCT/MCT (78% +/- 7%), LCT/MCT-E (72% +/- 12%), and SL (67% +/- 6%), pure MCT (70% +/- 13%) significantly impaired the killing capacity of neutrophils.

CONCLUSIONS

The decreased killing capacity of neutrophils after exposure to medium-chain fatty acid-containing emulsions and the absence of this effect with LCT suggest that lipid emulsions influence the elimination of C. albicans depending on the triglyceride chain length.

Effects of structurally different lipid emulsions on human neutrophil migration

AIM

To test the hypothesis that structurally different lipid emulsions have distinct immunomodulatory properties, we analysed neutrophil migration in the presence of various lipid emulsions.

METHOD

Neutrophils of 8 volunteers were pre-incubated in medium or physiological 2.5 mM emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, alpha -tocopherol-enriched LCT/MCT (LCT/MCT-E) or structured triglycerides (SL). Thereafter, the cells were put on top of 3 microm-pore-sized cell culture filters and incubated for one hour in the presence or absence of a chemo-attractant. Neutrophil migration was measured as the percentage of cells that had passed the filter in the presence (chemotaxis) or absence (random migration) of a chemotactic factor.

RESULTS

Compared to lipid-free incubation (19+/-1%) random neutrophil migration significantly decreased with LCT/MCT (11+/-2%), LCT/MCT-E (12+/-2) and MCT (5+/-2%), while LCT (18+/-3%) and SL (20+/-1%) had no effect. N-formyl-methionyl-leucyl-phenylalanine- (fMLP, 10(-8)M) or zymosan-activated-serum-induced (ZAS, 10%) filter passage under lipid-free conditions amounted to 61+/-14% and 70+/-13%, respectively. These values decreased with LCT/MCT to 11+/-9% and 15+/-7%; with LCT/MCT-E to 18+/-10% and 28+/-12%; with SL to 39+/-18% and 57+/-14%, and with MCT to 5+/-2% and 10+/-6%, (all P<0.01), while LCT had no effect. Compared to LCT/MCT, the alpha -tocopherol-enriched formulation significantly increased ZAS- and fMLP-induced chemotaxis. fMLP-induced chemotaxis decreased in direct proportion to LCT/MCT triglyceride concentration.

CONCLUSIONS

Human neutrophil migration is distinctively inhibited by structurally different lipid emulsions, depending on triglyceride chain-length and concentration as well as alpha -tocopherol content.

Antioxidant status of surgical patients receiving TPN with an omega-3-fatty acid-containing lipid emulsion supplemented with alpha-tocopherol

BACKGROUND

LCT lipid emulsions and even more fish oil-containing lipid emulsions are under debate regarding their tocopherol and PUFA content as well as their effect on the antioxidative status especially in patients with oxidative stress.

METHODS

Thirty-three patients undergoing major abdominal surgery were randomly assigned to receive either an alpha-tocopherol-supplemented (562 micromol/l) MCT/LCT/omega-3-acid triglycerides (MLF, 5/4/1 w/w/w, 20%) emulsion or a soybean oil-based LCT emulsion (20%). The TPN regimen continuously provided 1.4 g fat kg bw(-1)d(-1)over 5 days.

RESULTS

Plasma antioxidant concentrations were strongly reduced by surgical treatment. Following 5 days of TPN with the MLF emulsion, mean plasma alpha-tocopherol increased by 20.0 micromol/l (1.98 micromol/mmol lipid), while nearly no change was observed in the LCT emulsion group. In both groups, plasma concentrations of all non-supplemented antioxidants (vitamin C, carotenoids, selenium) as well as serum total antioxidant capacity further decreased during TPN. The concentrations of plasma cholesterol oxidation products as a measure of in vivo lipid peroxidation revealed no changes over the TPN period in either group.

CONCLUSION

In contrast to the LCT emulsion, administration of the a-tocopherol supplemented MLF lipid emulsion normalized a-tocopherol plasma concentrations. Despite its high long-chain PUFA content, no hint for increased lipid peroxidation was found.

New developments in total parenteral nutrition for children

The field of parenteral nutrition continues to evolve along two major paths: prevention of complications and refining of nutritional needs. Parenteral nutrition-associated liver disease remains a vexing problem. No single factor is to blame; rather, it requires a number of "hits." In the infant, the liver disease primarily appears to be related to prematurity of bile flow and production, infection, lack of enteral feedings, and most recently appreciated, perhaps free radicals. We are able to meet the nutritional needs of our patients, but our knowledge of actual nutritional requirements remains incomplete. Future studies need to define better appropriate intakes and to rigorously test the utility of proposed nutrients such as glutamine.

Lipid peroxidation of intravenous lipid emulsions and all-in-one admixtures in total parenteral nutrition bags: the influence of trace elements

An iodometric titration was used to assess the influence of a daily portion of trace elements on lipid peroxidation of pure lipid emulsions and lipid-containing all-in-one (AIO) admixtures by measuring the peroxide value (PV; mmol peroxides/L). A pure lipid emulsion (Intralipid 20%; Pharmacia & Upjohn, Dubendorf, Switzerland) was stored in ethylvinylacetate bags under light protection (LP) at 40 degrees C with and without trace elements. In absence of trace elements the PV of Intralipid 20% was significantly lower (day 14: 2.77 vs 18.04; p < .001). After the same time period with the same storage conditions the drop in pH was two times higher in presence of trace elements (1.54 vs 0.77). In an AIO admixture with LP stored at 2 degrees C to 8 degrees C, trace elements increased the PV from 0.04 to 0.19 mmol/L (day 29; p < .01). The drop in pH was 0.01 and 0.02 units, respectively. When stored at 20 degrees C to 30 degrees C and exposed to daylight, the PV of the AIO admixture containing trace elements reached 1.92 compared with 0.52 in their absence (day 19; p < .001) with a pH drop of 0.03 and 0.11, respectively (day 29). Although trace elements led to a much higher drop in pH in pure lipid emulsions, no obvious influence on the pH of AIO admixtures was demonstrated. To minimize lipid peroxidation, AIO admixtures should be stored light-protected and refrigerated without trace elements. The latter should be added immediately before administration or should be given separately.

Phagocyte-induced lipid peroxidation of different intravenous fat emulsions and counteractive effect of vitamin E

Unsaturated fatty acids, a major component of fat emulsions used in parenteral nutrition, are prone to peroxidation which is an important feature of oxygen-associated tissue damage. We used the nitroblue tetrazolium (NBT) reduction test to measure the production of superoxide radicals by stimulated polymorphonuclear neutrophils (PMN) in the presence of different fat emulsions: Intralipid (containing 100% long-chain triacylglycerols, LCT), Vasolipid (a physical mixture of 50% LCT and 50% medium-chain triacylglycerols, MCT) and Structolipid (structured triacylglycerols containing 63% LCT and 37% MCT). We measured the amount of malonaldehyde (MDA) and 4-hydroxyalkenal to determine the lipid peroxidation of the three fat emulsions in the presence of stimulated neutrophils. Further, we investigated the role of vitamin E (alpha-tocopherol) in preventing lipid peroxidation in vitro. The results showed that the values of NBT reduction of PMN were significantly decreased in each of the three fat emulsions and that increasing concentrations of fat emulsions were associated with decreased values of NBT reductions, in a dose-dependent way (P<0.001). There were, however, no statistically significant differences between the values of the three different types of fat emulsions (P>0.05). Lipid peroxidation increased significantly in the presence of all three types of fat emulsions, and was more pronounced for Intralipid than for Vasolipid and Structolipid after 1 and 2 h of incubation with resting as well as with stimulated phagocytes. The increased lipid peroxidation of the fat emulsions was markedly reduced by vitamin E, and the inhibition was concentration dependent. In conclusion, lipid peroxidation in vitro is more pronounced when PMNs are incubated with fat emulsions. This increase in lipid peroxidation can be reduced by adding vitamin E to the fat emulsions.

Top ten considerations in the development of parenteral emulsions

The development of parenteral emulsions continues to play an important role in the formulation and delivery of many drugs. In addition to solubilization and stabilization applications, appropriately designed parenteral emulsions are effective delivery systems for sustained release and targeting of drugs. Control of the strict requirements of globule size and surface charge is important in the design and ultimate stability of the formulation. This review highlights the important issues and suggests strategies to assist the scientist in the development, manufacture and stability of this essential dosage form.

Clinical use of lipid emulsions

Substantial progress has been made in the understanding of the metabolism of intravenous lipid emulsions and the delivery of their various components to specific tissues or cells. Lipid emulsions should be considered not only as a means of providing energy substrates but also specific compounds that participate in the regulation of key metabolic functions. Such improved knowledge should find applications in the metabolic care of different types of patients.