New lipids in enteral feeding

Changes in Oxidative Stress and Inflammatory Biomarkers in Fragile Adults over Fifty Years of Age and in Elderly People Exclusively Fed Enteral Nutrition

We aim to evaluate whether exclusive feeding of an enteral formula enriched with n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) affects oxidative stress and the antioxidant defence system and may improve the levels of some relevant inflammatory, and cardiovascular biomarkers in frail adults over fifty years of age and in elderly subjects. Fifty-five patients were divided into two groups and were exclusively fed a newly designed normoproteic and isocaloric enteral formula enriched with eicosapentaenoic (98 mg/d) and docosahexaenoic acids (46 mg/d) (n = 26) or a reference enteral diet (n = 29). Oxidative, inflammatory and cardiovascular risk biomarkers and red blood cell fatty acid profiles were determined at the beginning and after 90 and 180 days of feeding. The n-3 LC-PUFA percentage tended to be higher (P = 0.053) in the experimental group than in the reference group. Administration of the n-3 LC-PUFA diet did not increase oxidative stress or modify plasma antioxidant capacity but decreased antioxidant enzymatic activities. MMP-9 plasma concentration decreased with both formulae, whereas tPAI-1 tended to decrease (P = 0.116) with the administration of the experimental formula. In conclusion, administration of the new n-3 LC-PUFA-enriched product for 6 months did not negatively alter the oxidative status and improved some cardiovascular risk biomarkers.

The optimal lipid formulation in enteral feeding in critical illness: clinical update and review of the literature

Suitable and timely early enteral nutrition is paramount to providing optimal patient care for the critically ill. Lipids serve many essential roles throughout the human body, and are important components of most enteral formulations. This paper reviews lipid structure, function, and optimal utility for this macronutrient in enteral feeds. The use of omega-3 fatty acids has become common in critical care formulations, and their clinical efficacy is outlined separately. Available evidence is reviewed, and future directions are discussed.

Influence of an eicosapentaenoic and docosahexaenoic acid-enriched enteral nutrition formula on plasma fatty acid composition and biomarkers of insulin resistance in the elderly

BACKGROUND & AIMS

n-3 Polyunsaturated fatty acids may improve cardiovascular outcomes in elderly. The aim of this study was to determine the effect of feeding elderly patients exclusively with an n-3 polyunsaturated fatty acid-enriched diet specifically designed for enteral nutrition for 6 months, evaluating modifications in plasma fatty acid profile and some biomarkers of insulin resistance (IR).

METHODS

Thirty-two patients >65 years were fed a new enteral formula (T-Diet Plus) containing 75 mg/l of eicosapentaenoic acid (EPA) and 35 mg/l of docosahexaenoic acid (DHA) and 33 were fed an enteral diet intended for elderly (Jevity). Blood samples were drawn at the beginning and after 3 and 6 months of feeding. Plasma lipids, total plasma and lipid fraction fatty acid profiles, and some IR-associated adipokines were analysed.

RESULTS

Feeding on T-Diet Plus allowed EPA and DHA incorporation into plasma lipids and normalised blood triacylglycerols (TAG) levels after 3 months without major changes in IR, leptin and adiponectin.

CONCLUSIONS

Feeding the elderly exclusively with an enteral formula enriched with EPA and DHA improves their plasma lipid fatty acid profile and lowers TAG, a well known cardiovascular risk biomarker, without affecting IR.

Nutrition support of the traumatically injured warfighter

Major trauma induces metabolic alterations that contribute to the systemic immune suppression in severely injured patients and increase the risk of infection and posttraumatic organ failure. Nutrition modulation of cellular processes has evolved into a high-priority therapy, backed by substantial scientific evidence. The appropriate selection, timing, and dose of nutrients required for metabolic resuscitation must be individualized and goal directed. Ideally, the nutritional interventions for warfighters will be developed strategically based on the extent of injuries and underlying deficiencies and will be designed to provide the nutrients necessary to balance hypermetabolic processes, heal wounds, and promote optimal recovery.

Liposomes: technologies and analytical applications

Liposomes are structurally and functionally some of the most versatile supramolecular assemblies in existence. Since the beginning of active research on lipid vesicles in 1965, the field has progressed enormously and applications are well established in several areas, such as drug and gene delivery. In the analytical sciences, liposomes serve a dual purpose: Either they are analytes, typically in quality-assessment procedures of liposome preparations, or they are functional components in a variety of new analytical systems. Liposome immunoassays, for example, benefit greatly from the amplification provided by encapsulated markers, and nanotube-interconnected liposome networks have emerged as ultrasmall-scale analytical devices. This review provides information about new developments in some of the most actively researched liposome-related topics.

Nutrition support and the chronic critical illness syndrome

Critical illness can be viewed as consisting of 4 distinct stages: (1) acute critical illness (ACI), (2) prolonged acute critical illness, (3) chronic critical illness, and (4) recovery. ACI represents the evolutionarily programmed response to a stressor. In ACI, substrate is shunted away from anabolism and toward vital organ support and inflammatory proteins. Nutrition support in this stage is unproven and may ultimately prove detrimental. As critical illness progresses, there is no evolutionary precedent, and man owes his life to modern critical care medicine. It is at this point that nutrition and metabolic support become integral to the care of the patient. This paper (1) delineates and develops the 4 stages of critical illness using current evidence, clinical experience, and new hypotheses; (2) defines the chronic critical illness syndrome (CCIS); and (3) details an approach to the metabolic and nutrition support of the chronically critically ill patient using the metabolic model of critical illness as a guide. It is our hope that this clinical model can generate testable hypotheses that can improve the outcome of this unique population of patients.

Inflammation as the key interface of the medical and nutrition universes: a provocative examination of the future of clinical nutrition and medicine

There has been tremendous interest in inflammation by researchers, the medical community, and the lay public. Modulation of injury response is felt to represent a tenuous balance of pro- and anti-inflammatory cytokines. Adverse outcomes may result from severe, sustained, or repeated bouts of inflammation. A critical observation is that nutrition support alone is inadequate to prevent muscle loss during active inflammation. It is necessary to take inflammation into consideration in conducting appropriate nutrition assessment, intervention, and monitoring. A host of medical conditions are actually inflammatory states that have important implications for nutrition care. Multifaceted interventions that may include anti-inflammatory diets, glycemic control, physical activity, appetite stimulants, anabolic agents, anti-inflammatory agents, anticytokines, and probiotics, will be necessary to blunt undesirable aspects of inflammatory response to preserve body cell mass and vital organ functions. Nutrition practitioners can seize this opportunity to be a part of the future medical team that brings highly individualized patient care to the bedside.

Short-chain fatty acids: ready for prime time?

The concept of colonic health has become a major target for the development of functional foods such as probiotics, prebiotics, and synbiotics. These bioactive agents have a profound effect on the composition of the microflora, as well as on the physiology of the colon, and display distinct health benefits. Dietary carbohydrates escaping digestion/absorption in the small bowel and prebiotics undergo fermentation in the colon and give rise to short-chain fatty acids (SCFA). As the main anions of the colon and the major source of energy for colonocytes, SCFA are rapidly absorbed by nonionic diffusion mostly but also by active transport mediated by a sodium-coupled transporter, thereby fostering the absorption of sodium and water. SCFA in general and butyrate in particular enhance the growth of lactobacilli and bifidobacteria and play a central role on the physiology and metabolism of the colon. The effect of prebiotics on cell proliferation, differentiation, apoptosis, mucin production, immune function, mineral absorption, lipid metabolism, and gastrointestinal (GI) peptides has been well documented experimentally. These effects seem to be largely mediated by SCFA, but evidence from human studies remains inconsistent. The food industry is making a leap of faith in their efforts to commercialize prebiotics and exploit potential health benefits. The future lies with the design of studies to further explore basic mechanisms, and gene expression in particular, but emphasis should be placed on human intervention trials.

An update on parenteral lipids and immune function: only smoke, or is there any fire?

PURPOSE OF REVIEW

This paper synthesizes information from recent studies on the modulation of immune responses by lipid emulsions that are applied as part of parenteral nutrition. This issue is especially relevant in light of the high rate of infectious complications and disturbed inflammatory responses in patients receiving this form of nutritional support.

RECENT FINDINGS

Studies reporting on novel emulsions based on olive and fish oils, structured lipids or mixed-type emulsions in which various lipid species replace conventional long-chain triglycerides indicate that these lipids are generally well tolerated. While long-chain triglycerides may promote inflammation due to conversion of n-6 polyunsaturated fatty acids into arachidonic acid-derived eicosanoids, structured lipids and olive oil emulsions appear more immune-neutral. Leukocyte-activating effects of medium-chain triglycerides in experimental studies await further characterization in vivo. A body of evidence shows that immune modulation by fish oil emulsions is essentially anti-inflammatory in nature. This is in line with the observation that n-3 polyunsaturated fatty acids in fish oil replace arachidonic acid in cell membranes as an eicosanoid substrate, resulting in a decreased production of pro-inflammatory mediators. Importantly, recent investigations indicate beneficial effects of parenteral fish oil on relevant clinical outcome measures.

SUMMARY

The characteristics of, and mechanisms behind, the effects of various parenteral lipids on immune function are becoming increasingly well understood. The practical relevance of many of these findings is not immediately clear, however, and will have to be substantiated in adequately powered trials before we can translate these findings into a tailored approach for specific clinical situations.

Increased immune response in mice consuming rice bran oil

BACKGROUND

Polyunsaturated fatty acids play a key role in a number of biological functions. Rice bran oil (RBO) is rich in linoleic acid, an essential n-6 fatty acid. n-6 fatty acids are said to have proinflammatory effects as a result of an increase in n-6 fatty acid-derived eicosanoids. RBO is also rich in gamma-oryzanol, a compound from the unsaponifiable fraction, with antioxidant properties.

OBJECTIVE

The aim of this work is to examine the effect of RBO-and/or gamma-oryzanol-enriched diets on the regulation of the immune response.

METHODS

4 week-old Balb/C mice were fed diets enriched with either RBO or high oleic-sunflower oil (HOSO), for one month. Serum samples, bone marrow-derived macrophages and lymphocytes from the spleen were collected.

RESULTS

Compared to HOSO, our results show that RBO modulates the immune system by enhancing B-lymphocyte proliferation (6842 +/- 2959 vs 10073 +/- 4186 cpm; HOSO vs RBO; n = 10 per group) and TH1-type cytokines such as IL-2 (55.85 +/- 18.2 vs 101.7 +/- 21.6 pg/ml) or TNF-alpha (49.12 +/- 18.6 vs 184.9 +/- 46.2 pg/ml; HOSO vs RBO) in a significant way (n = 10 per group). Moreover, the reduction found in the TH2 cytokine IL-4 (7.59 +/- 2.3 vs 4.48 +/- 1.6 pg/ml) and IgE (56.9 +/- 39.2 vs 42.4 +/- 35.2 ng/ ml; HOSO vs RBO, n = 10 per group) levels suggests RBO may have antiallergenic properties. To elucidate the role of gamma-oryzanol, a similar study was also carried out including diets enriched with refined RBO or HOSO containing gamma-oryzanol (2 %). Our results suggest that although gamma-oryzanol may modulate the immune system, it is not responsible for the overall immunostimulation effect seen for RBO.

CONCLUSIONS

RBO-enriched diets could be useful in situations where a potentiation of the immune response was required. The fatty acids composition, more than the unsaponifiable fraction, might be responsible for this effect.

Lipid vesicles in capillary electrophoretic techniques: characterization of structural properties and associated membrane-molecule interactions

This paper reviews the use of lipid vesicles as model membranes in capillary electrophoresis (CE). The history and utility of CE in the characterization of microparticles is summarized, focusing on the application of colloidal electromigration theories to lipid vesicles. For instance, CE experiments have been used to characterize the size, surface properties, enclosed volumes, and electrophoretic mobilities of lipid vesicles and of lipoprotein particles. Several techniques involving small molecules or macromolecules separated in the presence of lipid vesicles are discussed. Interactions between the analytes and the lipid vesicles - acting as a pseudostationary phase or coated stationary phase in electrokinetic chromatography (EKC) - can be used to obtain additional information on the characteristics of the vesicles and analytes, and to study the biophysical properties of membrane-molecule interactions in lipid vesicles and lipoproteins. Different methods of determining binding constants by EKC are reviewed, along with the relevant binding constant calculations and a discussion of the application and limitations of these techniques as they apply to lipid vesicle systems.

Lipids in the nutritional support of the critically ill patients

PURPOSE OF REVIEW

This review reports recent findings on lipid use in artificial nutrition in patients with acute respiratory failure or severe sepsis or undergoing major surgery. It examines current knowledge of fatty acid safety, biologic effects, and the impact on patients' morbidity and mortality. The newly emerging area of genotypic influence and timing of immunonutrition is also discussed.

RECENT FINDINGS

In acute respiratory distress syndrome, the debate concerning the use of long-chain fatty acids as opposed to physical mixtures of medium- and long-chain fatty acids, specifically regarding their effects on gas exchange and pulmonary hemodynamics, still remains unresolved. By contrast, providing fish oil fatty acids (mainly eicosapentaenoic and docosahexaenoic acids) and/or gamma-linolenic acid, seems to decrease harmful excessive inflammatory/immune activation and to improve clinical outcome. Similar effects, although not conclusively demonstrated, have been reported for n-3 fatty acid-enriched lipid emulsions in patients with sepsis. Few recent studies examined the impact of n-3 fatty acid-enriched enteral formulas on patients undergoing major surgery. Most studies focused on intravenous fish oil and suggest beneficial effects both on inflammatory/immune parameters and patient outcome. Studies suggest that lipid use in critically ill patients may be improved by increased knowledge of genetic determinants of severity of injury and response to therapeutic agents as well as by the development of tools that allow better timing of immunonutritional intervention.

SUMMARY

Overall, lipids, in particular n-3 fatty acids, emerge as powerful nutrients with pharmacologic properties potentially improving prognosis in critically ill patients. However, heterogeneity in study design makes the interpretation of available studies difficult. Consequently, larger prospective, randomized, double-blind trials with comparable methodologies are necessary for detailed evaluation of the pharmacologic impact of lipids. In addition, a better knowledge of the influence of genotypic variation and postinjury inflammatory/immune temporal patterns may improve our current therapeutic use of various fatty acids.