The effect of varying ratios of docosahexaenoic acid and arachidonic acid in the prevention and reversal of biochemical essential fatty acid deficiency in a murine model

Erythrocyte fatty acid membrane composition in children on long-term parenteral nutrition enriched with ω-3 fatty acids

BACKGROUND

Composite lipid emulsions containing soybean oil (30%), medium-chain triglycerides (30%), olive oil (25%), and fish oil (15%) (SMOF) are now widely used.

OBJECTIVES

We aimed to evaluate the tolerance, the efficiency, and the erythrocyte fatty acid (FA) profile for children on long-term home parenteral nutrition (HPN) receiving a composite fish oil-based emulsion (FOLE).

METHODS

At baseline, children (n = 46) with severe intestinal failure highly dependent on parenteral nutrition (PN) for ≥1 y were included in the study when they had received the composite FOLE for >6 mo. Out of this baseline group, only 25 children remained highly PN-dependent (SMOF1, n = 25) and could be assessed a second time, 2.4 y later (SMOF2, n = 25). An independent control group ("weaned off PN" group; n = 24) included children who had been weaned off PN for >2 y (median: 4 y). RBC-FA composition was established by GC-MS. Growth parameters, plasma citrulline, conjugated bilirubin, FA profiles, and the Holman ratio (20:3ω-9/20:4ω-6) were compared between groups.

RESULTS

No difference for growth parameters, citrulline, and bilirubin was observed between the SMOF groups after 2.4 y (0.2 < P < 0.8). The weaned-off group did not differ from the SMOF groups for growth parameters (0.2 < P < 0.4) but citrulline was higher (P < 0.0001) and conjugated bilirubin lower (P < 0.01). The composite FOLE induced higher proportions of EPA (20:5n-3) (8.4% ± 2.9%) and DHA (22:6n-3) (11.7% ± 2.2%) than what was observed in weaned-off children (0.8% ± 0.4% and 6.6% ± 2.3%, respectively) but lower proportions of arachidonic acid (20:4n-6). However, the Holman ratio did not vary between groups (P = 0.9), whereas the PUFA concentrations varied widely.

CONCLUSIONS

Long-term use of the composite FOLE was well tolerated in HPN-dependent children. The RBC-FA profile alterations were consistent with the ω-3 PUFA-enriched composition of this emulsion without evidence of essential FA deficiency.

ASPEN lipid injectable emulsion safety recommendations part 2: Neonate and pediatric considerations

Lipid injectable emulsions (ILEs) are complex pharmaceutical formulations intended as a source of energy and fatty acids for parenteral nutrition (PN) therapy. Part 1 of this series addressed issues associated with and safety recommendations pertaining to adult ILE use. Part 2 addresses ILE safety in neonatal and pediatric patients. Considerations for ILE use in the neonatal and pediatric populations differ from those of adults. For example, these patients often require higher doses compared with adult counterparts to support growth, development, and daily metabolic needs. ILE is also frequently administered as a separate infusion as opposed to in a total nutrient admixture owing to compatibility and stability issues and limitations to intravenous access in the neonatal and pediatric populations. ILE is the most frequent PN ingredient associated with PN errors occurring in the administration, prescribing, and transcribing processes. Concerns exist with use of in-line filters and repackaging of commercial products for infusion. ILE use in neonatal and pediatric patients has been associated with both minor and major adverse effects, which most often occur with doses exceeding manufacturer recommendations. Gaps in ILE best practices for neonatal and pediatric patients predispose to errors in the PN use system. This paper describes safe-use considerations for ILE products available in the United States in neonatal and pediatric patients, including indications, prescribing, order review, preparation, administration, and monitoring. This paper has been approved by the American Society for Parenteral and Enteral Nutrition (ASPEN) Board of Directors.

Analysis of lipidomics profile of Carya cathayensis nuts and lipid dynamic changes during embryonic development

Hickory (Carya cathayensis) nuts contain higher amount of lipids, and possess high nutritional value and substantial health benefits. However, their lipid composition and dynamic changes during embryogenesis have not been thoroughly investigated. Therefore, lipidomics profile and lipid dynamic changes during embryonic development were analyzed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Totally, 544 kinds of lipids were identified in mature hickory nuts with higher proportions of glycerolipids (59.94%) and glycerophospholipids (38.66%). Notably, diacylglycerols showed gradual uptrends, which corresponded with total glycerolipid and glycerophospholipid at middle and late stage of embryogenesis, suggesting the pivotal role of diacylglycerols in the accumulation of glycerolipids and glycerophospholipids. Moreover, triacylglycerols, diacylglycerols, phosphatidylethanolamines and phosphatidylcholines had high relative content with abundance of unsaturated fatty acids, specifically oleic acid, linoleic acid and linolenic acid, localized mainly at sn-2 lipid position. Together, our study provides innovative perspectives for studying the nutritional benefits of hickory nut lipids.

Intravenous Lipid Emulsions in the NICU

The clinical goals of intravenous lipid emulsions (ILEs) have changed since their initial development. In the past, 100% soybean oil was used to provide energy and prevent an essential fatty acid deficiency. Now, different oil sources are used with the goal of improving nutritional status and preventing common neonatal comorbidities. We now have a better understanding of specific ILE constituents, namely, fatty acids, vitamin E, and phytosterols, and how these components contribute to complications such as intestinal failure-associated liver disease. This review addresses the development and composition of different ILEs and summarizes how individual ILE ingredients affect infant metabolism and health.

Clinical application of fish-oil intravenous lipid emulsion in adult home parenteral nutrition patients

BACKGROUND

High-ω-6 polyunsaturated fatty acids (PUFAs) are noted to contribute to development of intestinal failure-associated liver disease (IFALD) in home parenteral nutrition (HPN). Fish oil (FO) has been added to latest generation of lipid injectable emulsion (ILE) to increase ω-3:ω-6 PUFA ratio; however, appropriate dose of FO to treat IFALD is unknown.

METHODS

After approval of exclusive FO ILE in the US for pediatric patients, we noted 2 adult patients with ongoing IFALD despite transition to mixed-oil (MO) ILE. They were transitioned to off-label FO ILE after review of literature regarding use of FO ILE in adult HPN patients was conducted to guide management.

RESULTS

The first case involves a 40-year-old female receiving HPN with IFALD refractory to MO ILE. MO ILE (with 15% FO) was provided at 50 g/d for 3 d/wk and combined with FO ILE at 50 g/d for 4 d/wk. This combination resulted in improvement in liver studies and allowed for decrease in dextrose calories. The second case involves a 49-year-old male receiving HPN (secondary to complications of necrotizing pancreatitis) who developed IFALD. FO ILE was used as the sole source of lipids and led to improvement in liver function tests. No evidence of essential fatty acid deficiency was found in either case.

CONCLUSIONS

Current case presentations and review of literature support the use of FO ILE to increase ω-3 PUFAs in patients with IFALD refractory to MO ILE. Additional research is necessary to delineate the dose of FO ILE necessary to achieve benefit.

Intravenous Fish Oil Monotherapy as a Source of Calories and Fatty Acids Promotes Age-Appropriate Growth in Pediatric Patients with Intestinal Failure-Associated Liver Disease

OBJECTIVE

To compare growth in children with intestinal failure-associated liver disease (IFALD) who received a fish oil intravenous lipid emulsion (FOLE) to those who received a soybean oil intravenous lipid emulsion (SOLE).

STUDY DESIGN

This multisite, retrospective study pair-matched FOLE (n = 82) to SOLE recipients (n = 41) using baseline serum direct bilirubin levels and postmenstrual age. Study subjects received open-label FOLE (1 g/kg/day) until IFALD resolved or parenteral nutrition was stopped. Historical control subjects received SOLE (up to 3 g/kg/day). Growth measures (changes in body weight, height/length, and head circumference), prealbumin, triglycerides, and glucose were compared between groups over time using the Wilcoxon rank-sum test.

RESULTS

Although changes in all of the growth measures were similar for both groups (P > .05), FOLE recipients demonstrated an overall improved growth trajectory. After 28 weeks, FOLE recipients had a mean body weight within a z score range of -1 to 1 indicating age-appropriate growth. FOLE recipients consistently had higher prealbumin, lower triglyceride, and more normal glucose concentrations over time compared with SOLE recipients.

CONCLUSIONS

Children with IFALD who received FOLE had similar growth and fewer metabolic abnormalities compared with those who received SOLE.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT00910104 and NCT00738101.

Use of Fish Oil Intravenous Lipid Emulsions as Monotherapy in the Pediatric Intestinal Failure Patient: Beyond the Package Insert

In July 2018, an intravenous lipid emulsion (ILE) composed of 100% fish oil (Omegaven, Fresenius Kabi, Bad Homburg, Germany) received Food and Drug Administration (FDA) approval as a source of fatty acids and calories for infants and children with parenteral nutrition-associated cholestasis. This soy-free fat source is rich in ω-3 fatty acids and α-tocopherol and contains few phytosterols. In comparison to conventional soybean oil ILE, this emulsion appears to be less hepatotoxic. The purpose of this paper is to guide the practitioner on the use of this alternative fat source in clinical practice and augment the material contained in the current package insert. This paper addresses various topics including the identification of which patients would benefit from fish oil ILE, dosing, administration, monitoring, potential adverse effects, and management strategies for fish oil ILE.

Intravenous Fish Oil and Serum Fatty Acid Profiles in Pediatric Patients With Intestinal Failure-Associated Liver Disease

BACKGROUND

Intravenous fish oil (FO) treats pediatric intestinal failure-associated liver disease (IFALD). There are concerns that a lipid emulsion composed of ω-3 fatty acids will cause an essential fatty acid deficiency (EFAD). This study's objective was to quantify the risk for abnormal fatty acid concentrations in children treated with FO.

METHODS

Inclusion criteria for this prospective study were children with intestinal failure. Intravenous soybean oil (SO) was replaced with FO for no longer than 6 months. Serum fatty acids were analyzed using linear and logistic models, and compared with age-based norms to determine the percentage of subjects with low and high concentrations.

RESULTS

Subjects (n = 17) started receiving FO at a median of 3.6 months (interquartile range 2.4-9.6 months). Over time, α-linolenic, linoleic, arachidonic, and Mead acid decreased, whereas docosahexaenoic and eicosapentaenoic acid increased (P < 0.001 for all). Triene-tetraene ratios remained unchanged (P = 1). Although subjects were 1.8 times more likely to develop a low linoleic acid while receiving FO vs SO (95% CI: 1.4-2.3, P < 0.01), there was not a significant risk for low arachidonic acid. Subjects were 1.6 times more likely to develop high docosahexaenoic acid while receiving FO vs SO; however, this was not significant (95% CI: 0.9-2.6, P = 0.08).

CONCLUSION

In this cohort of parenteral nutrition-dependent children, switching from SO to FO led to a decrease in essential fatty acid concentrations, but an EFAD was not evident. Low and high levels of fatty acids developed. Further investigation is needed to clarify if this is clinically significant.

Effects of dietary omega-3 fatty acids on bones of healthy mice

BACKGROUND & AIMS

Altering the lipid component in diets may affect the incidence of metabolic bone disease in patients dependent on parenteral nutrition. Consumption of polyunsaturated fatty acids (PUFA) can impact bone health by modulating calcium metabolism, prostaglandin synthesis, lipid oxidation, osteoblast formation, and osteoclastogenesis. The aim of this study was to evaluate the dietary effects of PUFA on murine bone health.

METHODS

Three-weeks-old male (n = 30) and female (n = 30) C57BL/6J mice were randomized into one of three dietary groups. The diets differed only in fat composition: soybean oil (SOY), rich in ω-6 PUFA; docosahexaenoic acid alone (DHA), an ω-3 PUFA; and DHA with arachidonic acid, an ω-6 PUFA, at a 20:1 ratio (DHA/ARA). After 9 weeks of dietary treatment, femurs were harvested for micro-computed tomographic analysis and mechanical testing via 3-point bending. Separate mice from each group were used solely for serial blood draws for measurement of biomarkers of bone formation and resorption.

RESULTS

At the microstructural level, although some parameters in cortical bone reached differences that were statistically significant in female mice, these were too small to be considered biologically relevant. Similarly, trabecular bone parameters in male mice were statistically different in some dietary groups, although the biological interpretation of such subtle changes translate into a lack of effect in favor of any of the experimental diets. No differences were noted at the mechanical level and in blood-based biomarkers of bone metabolism across dietary groups within gender.

CONCLUSIONS

Subtle differences were noted at the bones' microstructural level, however these are likely the result of random effects that do not translate into changes that are biologically relevant. Similarly, differences were not seen at the mechanical level, nor were they reflected in blood-based biomarkers of bone metabolism. Altogether, dietary consumption of PUFA do not seem to affect bone structure or metabolism in a healthy model of growing mice.

Parenteral Soybean Oil Induces Hepatosteatosis Despite Addition of Fish Oil in a Mouse Model of Intestinal Failure-Associated Liver Disease

BACKGROUND

Replacement of parenteral soybean oil (SO) with fish oil (FO) is an effective therapy for intestinal failure-associated liver disease (IFALD) in children. However, practitioners remain concerned about the risk of essential fatty acid deficiency (EFAD) and sometimes treat IFALD with a combination of 50% SO and 50% FO emulsions. The purpose of this study was to determine if mixing 50% SO and 50% FO emulsions would prevent hepatosteatosis in a murine model of parenteral nutrition (PN)-induced hepatosteatosis.

METHODS

C57BL/6 mice were randomized to receive oral PN with parenteral saline, FO, SO, or a mixture of 50% FO and 50% SO for 19 days. Fatty acid analysis, histologic evaluation, Nonalcoholic Steatohepatitis Clinical Research Network (NSCRN) scores, and reverse-transcriptase polymerase chain reaction for key lipogenic genes were performed.

RESULTS

The PN + saline group was the only group with EFAD, with a serum and hepatic triene/tetraene ratio of 0.53. NSCRN scores were highest in the PN + SO group (5.5; 95% confidence interval [CI], 4.9-6.1), followed by the PN + FO/SO (4.5; 95% CI, 3.5-5.5) group, with the lowest score in the PN + FO (2.0; 95% CI, 1.1-2.9) group. Acetyl CoA carboxylase α and acetyl CoA carboxylase β expression was lower in the PN + FO group than in the PN + FO/SO or PN + SO groups.

CONCLUSIONS

Our data demonstrate that a mixed fat emulsion of 50% SO and 50% FO is inferior to 100% FO in reducing hepatosteatosis in this model. These data suggest that use of parenteral SO with parenteral FO, in a 1:1 ratio, may still contribute to liver injury, although it is less hepatotoxic than pure SO.

The Mulberry (Morus alba L.) Fruit-A Review of Characteristic Components and Health Benefits

Mulberry (Morus alba L.) fruit has a high yield in one fruiting season in many countries, especially in Asia, and a long history of use as an edible fruit and traditional medicine. A great diversity of nutritive compounds such as fatty acids, amino acids, vitamins, minerals, and bioactive compounds, including anthocyanins, rutin, quercetin, chlorogenic acid, and polysaccharides have been found in mulberry fruit depending on the cultivars and maturity stages. Furthermore, the extracts and active components of mulberry fruit have demonstrated numerous biological activities, including antioxidant, neuroprotective, antiatherosclerosis, immunomodulative, antitumor, antihyperglycemic, and hypolipidemic activities in in vitro and in vivo studies, and they have received increasing interest from researchers and pharmaceutical companies. Although some mechanistic studies further substantiate these potential health benefits of mulberry fruit, a need exists to make a better understanding of the roles of these compounds in traditional medicine and the diet. This review provides recent findings regarding the chemical constituents and biological activities of mulberry fruit, which may be useful for stimulating deep research of mulberry fruit and for predicting their uses as important and safe contributors to benefit human health.

Redefining essential fatty acids in the era of novel intravenous lipid emulsions

The essentiality of fatty acids was determined by the Burrs in the 1920s. It is commonly accepted that provision of linoleic (LA) and alpha-linolenic acids (ALA) prevents and reverses essential fatty acid deficiency (EFAD). Development of alternative injectable lipid emulsions (ILE) low in LA and ALA has raised concern about their ability to prevent EFAD. This review provides biochemical evidence coupled with observations from animal and human studies that aim to characterize which fatty acids are truly essential to prevent EFAD. Retroconversion pathways and mobilization from body stores suggest that arachidonic and docosahexaenoic acids (ARA and DHA - the main derivatives of LA and ALA, respectively) also prevent EFAD. Our group first proposed the essentiality of ARA and DHA by feeding mice exclusively these fatty acids and proving that they prevent EFAD. Survival for 5 generations on this diet provides additional evidence that growth and reproductive capabilities are maintained. Moreover, the use of fish oil-based ILE, with minimal LA and ALA and abundant DHA and ARA, for treatment of intestinal failure-associated liver disease, does not result in EFAD. These findings challenge the essentiality of LA and ALA in the presence of ARA and DHA. Evidence discussed in this review supports the idea that ARA and DHA can independently fulfill dietary essential fatty acid requirements. The imminent introduction of new ILE rich in ARA and DHA in the United States highlights the importance of understanding their essentiality, especially when provision of ALA and LA is below the established daily minimum requirement.

Intravenous Fat Emulsion Formulations for the Adult and Pediatric Patient: Understanding the Differences

Intravenous fat emulsions (IVFEs) provide essential fatty acids (EFAs) and are a dense source of energy in parenteral nutrition (PN). Parenterally administered lipid was introduced in the 17th century but plagued with side effects. The formulation of IVFEs later on made it a relatively safe component for administration to patients. Many ingredients are common to all IVFEs, yet the oil source(s) and its (their) percentage(s) makes them different from each other. The oil used dictates how IVFEs are metabolized and cleared from the body. The fatty acids (FAs) present in each type of oil provide unique beneficial and detrimental properties. This review provides an overview of IVFEs and discusses factors that would help clinicians choose the optimal product for their patients.

Phenotypic divergence in two lines of L-Fabp-/- mice reflects substrain differences and environmental modifiers

Phenotypic divergence in diet-induced obesity (DIO) and hepatic steatosis has been reported in two independently generated lines of L-Fabp(-/-) mice [New Jersey (NJ) L-Fabp(-/-) vs. Washington University (WU) L-Fabp(-/-) mice]. We performed side-by-side studies to examine differences between the lines and investigate the role of genetic background, intestinal microbiota, sex, and diet in the divergent phenotypes. Fasting-induced steatosis was attenuated in both L-Fabp(-/-) lines compared with C57BL/6J controls, with restoration of hepatic triglyceride levels following adenoviral L-Fabp rescue. Both lines were protected against DIO after high-saturated-fat diet feeding. Hepatic steatosis was attenuated in WU but not NJ L-Fabp(-/-) mice, although this difference between the lines disappeared upon antibiotic treatment and cohousing. In contrast, there was phenotypic divergence in L-Fabp(-/-) mice fed a high cocoa butter fat diet, with WU L-Fabp(-/-) mice, but not NJ L-Fabp(-/-) mice, showing protection against both DIO and hepatic steatosis, with some sex-dependent (female > male) differences. Dense mapping revealed no evidence of unintended targeting, duplications, or deletions surrounding the Fabp1 locus in either line and only minor differences in mRNA expression of genes located near the targeted allele. However, a C57BL/6 substrain screen showed that the NJ L-Fabp(-/-) line contains ∼40% C57BL/6N genomic DNA, despite reports that these mice were backcrossed six generations. Overall, these findings suggest that some of the phenotypic divergence between the two L-Fabp(-/-) lines may reflect unanticipated differences in genetic background, underscoring the importance of genetic background in phenotypic characterization.

Intravenous Lipid Emulsions in Parenteral Nutrition

Fat is an important macronutrient in the human diet. For patients with intestinal failure who are unable to absorb nutrients via the enteral route, intravenous lipid emulsions play a critical role in providing an energy-dense source of calories and supplying the essential fatty acids that cannot be endogenously synthesized. Over the last 50 y, lipid emulsions have been an important component of parenteral nutrition (PN), and over the last 10-15 y many new lipid emulsions have been manufactured with the goal of improving safety and efficacy profiles and achieving physiologically optimal formulations. The purpose of this review is to provide a background on the components of lipid emulsions, their role in PN, and to discuss the lipid emulsions available for intravenous use. Finally, the role of parenteral fat emulsions in the pathogenesis and management of PN-associated liver disease in PN-dependent pediatric patients is reviewed.

Potential role of dietary lipids in the prophylaxis of some clinical conditions

An imbalance of dietary lipids may potentially have a significant role in the pathobiology of some chronic diseases. Public health dietary fat recommendations have emphasized that low saturated fat, high monounsaturated fat, and high polyunsaturated fat with a lower ω-6 to ω-3 fatty acid ratio intake are necessary for normal health. However, such universal recommendations are likely to be hazardous, since the outcome of recommended lipid intake may depend on the consumption of other important dietary constituents that have an important role in the metabolism of lipids. In addition, consumption of fatty acids as per the individually tailored specific requirements in the context of other nutritional factors may have the potential to stabilize hormones, mood and sleep, and minimize adverse events. In support of this proposal, we review various factors that influence fatty acid metabolism, which need to be taken into consideration for appropriate utilization and consequently prevention of various diseases.

Targeted lipidomic strategies for oxygenated metabolites of polyunsaturated fatty acids

Oxidation of polyunsaturated fatty acids (PUFA) through enzymatic or non-enzymatic free radical-mediated reactions can yield an array of lipid metabolites including eicosanoids, octadecanoids, docosanoids and related species. In mammals, these oxygenated PUFA mediators play prominent roles in the physiological and pathological regulation of many key biological processes in the cardiovascular, renal, reproductive and other systems including their pivotal contribution to inflammation. Mass spectrometry-based technology platforms have revolutionized our ability to analyze the complex mixture of lipid mediators found in biological samples, with increased numbers of metabolites that can be simultaneously quantified from a single sample in few analytical steps. The recent development of high-sensitivity and high-throughput analytical tools for lipid mediators affords a broader view of these oxygenated PUFA species, and facilitates research into their role in health and disease. In this review, we illustrate current analytical approaches for a high-throughput lipidomic analysis of eicosanoids and related mediators in biological samples. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance."

The effect of docosahexaenoic acid on bone microstructure in young mice and bone fracture in neonates

BACKGROUND

As low bone mineral density is a risk factor for fracture in childhood, optimizing age appropriate bone mass is recommended and might lower the impact of bone loss related to age. Consumption of omega-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic and docosahexaenoic (DHA) acids have been shown to beneficially modulate bone metabolism. The objective of this study was to determine the incidence of fracture in neonates receiving a fish compared with soybean oil-based intravenous lipid emulsion and evaluate the effect of varying dietary omega-3 PUFA consumption on growing bone in young mice.

MATERIALS AND METHODS

Eligibility criteria for the clinical study included gestational age ≤37 wk and parenteral nutrition-dependence for ≥4 wk. Radiographs were reviewed after lipid initiation to identify radiologic bone fracture. The animal study evaluated female C57/Bl6 mice randomized into one of five groups from age 3-12 wk, at which time femurs were harvested for micro-computed tomography and light microscopy analysis.

RESULTS

A lower incidence of bone fracture was found in neonates maintained on fish compared with soybean oil. In the animal study, findings suggest the DHA diet provides the best protection against trabecular bone loss as evidenced by increased bone volume fraction, increased trabecular number, and decreased trabecular separation on micro-computed tomography. These protective effects appeared to affect the bone microstructure alone.

CONCLUSIONS

The lower fracture risk observed in fish oil fed neonates in combination with the protective effects of DHA observed in the femurs of young C57/BL6 mice suggest an important role for omega-3 PUFAs on bone growth.

The Pex1-G844D mouse: a model for mild human Zellweger spectrum disorder

Zellweger spectrum disorder (ZSD) is a disease continuum that results from inherited defects in PEX genes essential for normal peroxisome assembly. These autosomal recessive disorders impact brain development and also cause postnatal liver, adrenal, and kidney dysfunction, as well as loss of vision and hearing. The hypomorphic PEX1-G843D missense allele, observed in approximately 30% of ZSD patients, is associated with milder clinical and biochemical phenotypes, with some homozygous individuals surviving into early adulthood. Nonetheless, affected children with the PEX1-G843D allele have intellectual disability, failure to thrive, and significant sensory deficits. To enhance our ability to test candidate therapies that improve human PEX1-G843D function, we created the novel Pex1-G844D knock-in mouse model that represents the murine equivalent of the common human mutation. We show that Pex1-G844D homozygous mice recapitulate many classic features of mild ZSD cases, including growth retardation and fatty livers with cholestasis. In addition, electrophysiology, histology, and gene expression studies provide evidence that these animals develop a retinopathy similar to that observed in human patients, with evidence of cone photoreceptor cell death. Similar to skin fibroblasts obtained from ZSD patients with a PEX1-G843D allele, we demonstrate that murine cells homozygous for the Pex1-G844D allele respond to chaperone-like compounds, which normalizes peroxisomal β-oxidation. Thus, the Pex1-G844D mouse provides a powerful model system for testing candidate therapies that address the most common genetic cause of ZSD. In addition, this murine model will enhance studies focused on mechanisms of pathogenesis.

Is there an optimal dose for dietary linoleic acid? Lessons from essential fatty acid deficiency supplementation and adipocyte functions in rats

Differential effects of n-3 and n-6 polyunsaturated fatty acids (PUFAs) have been demonstrated on adipose tissue physiology. Facing to the widely recognized beneficial effects of n-3 PUFAs, the n-6 PUFA effects remain controversial. Thus, we further analyzed the linoleic acid (LA) influence on adipocyte functions. To this aim, we treated by LA supplementation at three distinct doses (1, 2.5, or 5% of energy intake) rats with essential fatty acids deficiency (EFAD). PUFA composition was determined in blood and white adipose tissue (WAT), while lipolytic and lipogenic activities were measured in isolated adipocytes. EFAD rats exhibited reduced WAT mass and increased EFAD biomarkers. WAT mass was completely recovered after supplementation, irrespective of LA dose. However, neither body mass nor EFAD biomarkers returned to control with 1% LA, while LA abundance doubled in adipocytes from rats supplemented with 5% LA. Regarding lipolysis, 2.5% LA normalized the EFAD-induced alterations. A trend to decrease the maximal stimulation of lipolysis was observed with 1 and 5% LA. Regarding lipogenesis, the lower and higher LA doses increased basal activity and hampered insulin to further stimulate glucose incorporation into lipids whereas 2.5% LA normalized the basal or insulin-stimulated levels. Our results show that dietary linoleate at 2.5% restored anatomical, biochemical, and functional disturbances induced by EFAD. At higher dose, LA tended to reduce triacylglycerol breakdown, to increase triacylglycerol assembly, and to provoke insulin resistance. Therefore, LA influence on adipocyte functions does not appear to follow a typical dose-response relationship, adding further complexity to the definition of its dietary requirement.

Role of parenteral lipid emulsions in the preterm infant

Parenteral nutrition (PN) is necessary for infants unable to receive adequate calories enterally due to prematurity, decreased bowel length, or functional intestinal disorders. While PN can be life saving, its use is associated with significant risks of sepsis from catheter-associated infections and progressive liver dysfunction from prolonged use. The preterm infant population is at highest risk for these complications due to the presence of multiple comorbidities and immaturity of the biliary system. Strong data has implicated parenteral lipids in the multifactorial pathogenesis of PN-associated liver disease (PNALD). However, lipids are essential in early infant development, particularly in the neurocognitive development of preterm infants. Substitution of the lipid source from soybean oil to fish oil has emerged as a safe and efficacious treatment of PNALD, with marked improvements in morbidity and mortality. Knowledge of the developmental needs and physiologic limitations of preterm infants is crucial to optimizing parenteral lipid administration to nurture growth, and minimize and treat associated complications. The purpose of this review is to provide an overview of lipid requirements of the preterm infant and discuss the role of parenteral lipid emulsions in the management of PNALD and other diseases of prematurity.

Ω-3 fatty acids prevent hepatic steatosis, independent of PPAR-α activity, in a murine model of parenteral nutrition-associated liver disease

OBJECTIVES

ω-3 Fatty acids (FAs), natural ligands for the peroxisome proliferator-activated receptor-α (PPAR-α), attenuate parenteral nutrition-associated liver disease (PNALD). However, the mechanisms underlying the protective role of ω-3 FAs are still unknown. The aim of this study was to determine the effects of ω-3 FAs on hepatic triglyceride (TG) accumulation in a murine model of PNALD and to investigate the role of PPAR-α and microsomal triglyceride transfer protein (MTP) in this experimental setting.

METHODS

129S1/SvImJ wild-type or 129S4/SvJaePparatm/Gonz/J PPAR-α knockout mice were fed chow and water (controls); oral, fat-free PN solution only (PN-O); PN-O plus intraperitoneal (IP) ω-6 FA-predominant supplements (PN-ω-6); or PN-O plus IP ω-3 FA (PN-ω-3). Control and PN-O groups received sham IP injections of 0.9% NaCl. Hepatic histology, TG and cholesterol, MTP activity, and PPAR-α messenger RNA were assessed after 19 days.

RESULTS

In all experimental groups, PN feeding increased hepatic TG and MTP activity compared with controls. Both PN-O and PN-ω-6 groups accumulated significantly greater amounts of TG when compared with PN-ω-3 mice. Studies in PPAR-α null animals showed that PN feeding increases hepatic TG as in wild-type mice. PPAR-α null mice in the PN-O and PN-ω-6 groups demonstrated variable degrees of hepatic steatosis, whereas no evidence of hepatic fat accumulation was found after 19 days of oral PN plus IP ω-3 FAs.

CONCLUSIONS

PN induces TG accumulation (steatosis) in wild-type and PPAR-α null mice. In PN-fed wild-type and PPAR-α null mice given IP ω-3 FAs, reduced hepatic TG accumulation and absent steatosis are found. Prevention of steatosis by ω-3 FAs results from PPAR-α-independent pathways.