Lipid Emulsion Containing High Amounts of n3 Fatty Acids (Omegaven) as Opposed to n6 Fatty Acids (Intralipid) Preserves Insulin Signaling and Glucose Uptake in Perfused Rat Hearts

BACKGROUND: It is currently unknown whether acute exposure to n3 fatty acid–containing fish oil–based lipid emulsion Omegaven as opposed to the n6 fatty acid–containing soybean oil–based lipid emulsion Intralipid is more favorable in terms of insulin signaling and glucose uptake in the intact beating heart. METHODS: Sprague–Dawley rat hearts were perfused in the working mode for 90 minutes in the presence of 11 mM glucose and 1.2 mM palmitate bound to albumin, the first 30 minutes without insulin followed by 60 minutes with insulin (50 mU/L). Hearts were randomly allocated to 100 µM Intralipid, 100 µM Omegaven, or no emulsion (insulin treatment alone) for 60 minutes. Glycolysis and glycogen synthesis were measured with the radioactive tracer [5-3H]glucose, and glucose uptake was calculated. Phosphorylation of protein phosphatase 2A (PP2A), protein kinase Akt, and phosphofructokinase (PFK)-2 was measured by immunoblotting. Glycolytic metabolites were determined by enzymatic assays. Mass spectrometry was used to establish acylcarnitine profiles. Nuclear factor κB (NFκB) nuclear translocation served as reactive oxygen species (ROS) biosensor. RESULTS: Insulin-mediated glucose uptake was decreased by Intralipid (4.9 ± 0.4 vs 3.7 ± 0.3 μmol/gram dry heart weight [gdw]·min; P = .047) due to both reduced glycolysis and glycogen synthesis. In contrast, Omegaven treatment did not affect insulin-mediated glycolysis or glycogen synthesis and thus preserved glucose uptake (5.1 ± 0.3 vs 4.9 ± 0.4 μmol/gdw·min; P = .94). While Intralipid did not affect PP2A phosphorylation status, Omegaven resulted in significantly enhanced tyrosine phosphorylation and inhibition of PP2A. This was accompanied by increased selective threonine phosphorylation of Akt and the downstream target PFK-2 at S483. PFK-1 activity was increased when compared with Intralipid as measured by the ratio of fructose 1,6-bisphosphate to fructose 6-phosphate (Omegaven 0.60 ± 0.11 versus Intralipid 0.47 ± 0.09; P = .023), consistent with increased formation of fructose 2,6-bisphosphate by PFK2, its main allosteric activator. Omegaven lead to accumulation of acylcarnitines and fostered a prooxidant response as evidenced by NFκB nuclear translocation and activation. CONCLUSIONS: Omegaven as opposed to Intralipid preserves glucose uptake via the PP2A–Akt–PFK pathway in intact beating hearts. n3 fatty acids decelerate β-oxidation causing accumulation of acylcarnitine species and a prooxidant response, which likely inhibits redox-sensitive PP2A and thus preserves insulin signaling and glucose uptake

Diabetic Rat Hearts Show More Favorable Metabolic Adaptation to Omegaven Containing High Amounts of n3 Fatty Acids Than Intralipid Containing n6 Fatty Acids

Background: While Omegaven, an omega-3 (n3) fatty acid-based lipid emulsion, fosters insulin signaling in healthy hearts, it is unknown whether beneficial metabolic effects occur in insulin-resistant diabetic hearts. Methods: Diabetic hearts from fructose-fed Sprague-Dawley rats were perfused in the working mode for 90 minutes in the presence of 11 mM glucose and 1.2 mM palmitate bound to albumin, the first 30 minutes without insulin followed by 60 minutes with insulin (50 mU/L). Hearts were randomly allocated to Intralipid (25 and 100 µM), Omegaven (25 and 100 µM), or no emulsion (insulin alone) for 60 minutes. Glycolysis, glycogen synthesis, and glucose oxidation were measured with the radioactive tracers [5-H]glucose and [U-C]glucose. Central carbon metabolites, acyl-coenzyme A species (acyl-CoAs), ketoacids, purines, phosphocreatine, acylcarnitines, and acyl composition of phospholipids were measured with mass spectrometry. Results: Diabetic hearts showed no response to insulin with regard to glycolytic flux, consistent with insulin resistance. Addition of either lipid emulsion did not alter this response but unexpectedly increased glucose oxidation (ratio of treatment/baseline, ie, fold change): no insulin 1.3 (0.3) [mean (standard deviation)], insulin alone 1.4 (0.4), insulin + 25 µM Intralipid 1.8 (0.5), insulin + 100 µM Intralipid 2.2 (0.4), P < .001; no insulin 1.3 (0.3), insulin alone 1.4 (0.4), insulin + 25 µM Omegaven 2.3 (0.5) insulin + 100 µM Omegaven 1.9 (0.4), P < .001. Intralipid treatment led to accumulation of acylcarnitines as a result of the released linoleic acid (C18:2-n6) and enhanced its integration into phospholipids, consistent with incomplete or impaired β-oxidation necessitating a compensatory increase in glucose oxidation. Accumulation of acylcarnitines was also associated with a higher nicotinamide adenine dinucleotide reduced/oxidized (NADH/NAD) ratio, which inhibited pyruvate dehydrogenase (PDH), and resulted in excess lactate production. In contrast, Omegaven-treated hearts showed no acylcarnitine accumulation, low malonyl-CoA concentrations consistent with activated β-oxidation, and elevated PDH activity and glucose oxidation, together indicative of a higher metabolic rate possibly by substrate cycling. Conclusions: Omegaven is the preferred lipid emulsion for insulin-resistant diabetic hearts

Quantitative profiling of inflammatory and proresolving lipid mediators in human adolescents and mouse plasma using UHPLC-MS/MS

Objectives Lipid mediators are bioactive lipids which help regulate inflammation. We aimed to develop an ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to quantify 58 pro-inflammatory and pro-resolving lipid mediators in plasma, determine preliminary reference ranges for adolescents, and investigate how total parenteral nutrition (TPN) containing omega-3 polyunsaturated fatty acid (n-3 PUFA) or n-6 PUFA based lipid emulsions influence lipid mediator concentrations in plasma. Methods Lipid mediators were extracted from plasma using SPE and measured using UHPLC-MS/MS. EDTA plasma was collected from healthy adolescents between 13 and 17 years of age to determine preliminary reference ranges and from mice given intravenous TPN for seven days containing either an n-3 PUFA or n-6 PUFA based lipid emulsion. Results We successfully quantified 43 lipid mediators in human plasma with good precision and recovery including several leukotrienes, prostaglandins, resolvins, protectins, maresins, and lipoxins. We found that the addition of methanol to human plasma after blood separation reduces post blood draw increases in 12-hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE), 12S-hydroxyeicosatrienoic acid (12S-HETrE), 14-hydroxydocosahexaenoic acid (14-HDHA) and thromboxane B2 (TXB2). Compared to the n-6 PUFA based TPN, the n-3 PUFA based TPN increased specialized pro-resolving mediators such as maresin 1 (MaR1), MaR2, protectin D1 (PD1), PDX, and resolvin D5 (RvD5), and decreased inflammatory lipid mediators such as leukotriene B4 (LTB4) and prostaglandin D2 (PGD2). Conclusions Our method provides an accurate and sensitive quantification of 58 lipid mediators from plasma samples, which we used to establish a preliminary reference range for lipid mediators in plasma samples of adolescents; and to show that n-3 PUFA, compared to n-6 PUFA rich TPN, leads to a less inflammatory lipid mediator profile in mice.ISSN:1434-6621ISSN:1437-433

Alterations in fatty acid metabolism and sirtuin signaling characterize early type‐2 diabetic hearts of fructose‐fed rats

Despite the fact that skeletal muscle insulin resistance is the hallmark of type-2 diabetes mellitus (T2DM), inflexibility in substrate energy metabolism has been observed in other tissues such as liver, adipose tissue, and heart. In the heart, structural and functional changes ultimately lead to diabetic cardiomyopathy. However, little is known about the early biochemical changes that cause cardiac metabolic dysregulation and dysfunction. We used a dietary model of fructose-induced T2DM (10% fructose in drinking water for 6 weeks) to study cardiac fatty acid metabolism in early T2DM and related signaling events in order to better understand mechanisms of disease. In early type-2 diabetic hearts, flux through the fatty acid oxidation pathway was increased as a result of increased cellular uptake (CD36), mitochondrial uptake (CPT1B), as well as increased b-hydroxyacyl-CoA dehydrogenase and medium-chain acyl-CoA dehydrogenase activities, despite reduced mitochondrial mass. Long-chain acyl-CoA dehydrogenase activity was slightly decreased, resulting in the accumulation of long-chain acylcarnitine species. Cardiac function and overall mitochondrial respiration were unaffected. However, evidence of oxidative stress and subtle changes in cardiolipin content and composition were found in early type-2 diabetic mitochondria. Finally, we observed decreased activity of SIRT1, a pivotal regulator of fatty acid metabolism, despite increased protein levels. This indicates that the heart is no longer capable of further increasing its capacity for fatty acid oxidation. Along with increased oxidative stress, this may represent one of the earliest signs of dysfunction that will ultimately lead to inflammation and remodeling in the diabetic heart

Novel strategies to prevent total parenteral nutrition-induced gut and liver inflammation, and adverse metabolic outcomes

Total parenteral nutrition (TPN) is a life-saving therapy administered to millions of patients. However, it is associated with significant adverse effects, namely liver injury, risk of infections, and metabolic derangements. In this review, we first identify the underlying causes of TPN-associated adverse effects, specifically gut atrophy, dysbiosis of the intestinal microbiome, leakage of the epithelial barrier with bacterial invasion and inflammation. We analyze the role of the bile acid receptors farnesoid X receptor and Takeda G protein-coupled receptor, of pleiotropic hormones and growth factors, and further scrutinize the mechanisms of insulin resistance, namely the lack of insulinotropic and insulinomimetic signaling of gut-originating incretins as well as the administration of potentially toxic phytosterols and pro-inflammatory fatty acids mainly released from soybean oil-based lipid emulsions used for TPN. Finally, we propose novel approaches in the design of next generation lipid delivery systems by modifying the physicochemical properties of lipid emulsions, the use of lipid emulsions generated from sustainable oils with favorable ratios of anti-inflammatory n-3 to pro-inflammatory n-6 fatty acids, beneficial adjuncts to TPN, and concomitant pharmacotherapies to mitigate TPN-associated adverse effects. This article is protected by copyright. All rights reserved

Gut microbiome and circulating bacterial DNA ("blood microbiome") in a mouse model of total parenteral nutrition: Evidence of two distinct separate microbiotic compartments

Background & aims: Total parenteral nutrition (TPN) causes gut atrophy, dysbiosis and leakage of the gut barrier. This study aimed to characterize the gut microbiome in response to different TPNs and tested the hypothesis whether increased gut permeability in TPN would lead to changes in the circulating bacterial DNA ("blood microbiome"). Methods: Male C57BL/6J mice were randomly allocated to the following groups for seven days (1) chow-fed control (C) without jugular vein catheter (JVC, n=6) (2) chow-fed with JVC and infusion of saline (S) (n = 6) (3) Intralipid-based TPN (n-6:n-3 ratio 7:1) (IL, n = 6) (4) Omegaven-based TPN (n-6:n-3 ratio 1:8) (OV, n = 6). Blood was collected by cardiac puncture and feces (stool pellet) were collected from the colon. Blood and stool samples were analyzed by 16S rRNA gene sequencing. Results: TPN administration was associated with a compositional shift in the gut microbial community that involved the expansion of Bacteroidota along with a decrease in gut bacteria belonging to the Firmicutes phylum as compared to chow-fed mice. Gram-negative Verrucomicrobiota and Proteobacteria were also increased in the gut microbiome of mice receiving TPN. Gammaproteobacteria, namely Burkholderiales, were specifically increased in Intralipid-based TPN. On the other hand, Proteobacteria and Actinobacteriota were the dominant taxa in blood samples. The families Comamonadaceae and Burkholderiaceae (both from Burkholderiales order) were increased in the "blood microbiome" of mice with indwelling JVC when compared with chow-fed mice without JVC. The increase in Burkholderiaceae was more pronounced in Intralipid-based TPN. Conclusions: Profound changes in the gut microbiome of mice subjected to TPN occurred, which were not reflected in the "blood microbiome" suggesting that the gut and "blood microbiome" represent two rather distinct separate microbiotic compartments. The parenteral provision of n-3 fatty acids appears to protect against proinflammatory bacteria in the gut and against the increased presence of JVC-associated bacteria as measured by circulating bacterial DNA. Keywords: Blood; Dysbiosis; Gut; Microbiome; Total parenteral nutritio

Novel Strategies to Prevent Total Parenteral Nutrition‐Induced Gut and Liver Inflammation, and Adverse Metabolic Outcomes

Total parenteral nutrition (TPN) is a life‐saving therapy administered to millions of patients. However, it is associated with significant adverse effects, namely liver injury, risk of infections, and metabolic derangements. In this review, the underlying causes of TPN‐associated adverse effects, specifically gut atrophy, dysbiosis of the intestinal microbiome, leakage of the epithelial barrier with bacterial invasion, and inflammation are first described. The role of the bile acid receptors farnesoid X receptor and Takeda G protein‐coupled receptor, of pleiotropic hormones, and growth factors is highlighted, and the mechanisms of insulin resistance, namely the lack of insulinotropic and insulinomimetic signaling of gut‐originating incretins as well as the potentially toxicity of phytosterols and pro‐inflammatory fatty acids mainly released from soybean oil‐based lipid emulsions, are discussed. Finally, novel approaches in the design of next generation lipid delivery systems are proposed. Propositions include modifying the physicochemical properties of lipid emulsions, the use of lipid emulsions generated from sustainable oils with favorable ratios of anti‐inflammatory n‐3 to pro‐inflammatory n‐6 fatty acids, beneficial adjuncts to TPN, and concomitant pharmacotherapies to mitigate TPN‐associated adverse effects.ISSN:1613-4125ISSN:1613-413

Choice of Lipid Emulsion Determines Inflammation of the Gut-Liver Axis, Incretin Profile, and Insulin Signaling in a Murine Model of Total Parenteral Nutrition

SCOPE The aim of this study is to test whether the choice of the lipid emulsion in total parenteral nutrition (TPN), that is, n-3 fatty acid-based Omegaven versus n-6 fatty acid-based Intralipid, determines inflammation in the liver, the incretin profile, and insulin resistance. METHODS AND RESULTS Jugular vein catheters (JVC) are placed in C57BL/6 mice and used for TPN for 7 days. Mice are randomized into a saline group (saline infusion with oral chow), an Intralipid group (IL-TPN, no chow), an Omegaven group (OV-TPN, no chow), or a chow only group (without JVC). Both TPN elicite higher abundance of lipopolysaccharide binding protein in the liver, but only IL-TPN increases interleukin-6 and interferon-γ, while OV-TPN reduces interleukin-4, monocyte chemoattractant protein-1, and interleukin-1α. Insulin plasma concentrations are higher in both TPN, while glucagon and glucagon-like peptide-1 (GLP-1) were higher in IL-TPN. Gluconeogenesis is increased in IL-TPN and the nuclear profile of key metabolic transcription factors shows a liver-protective phenotype in OV-TPN. OV-TPN increases insulin sensitivity in the liver and skeletal muscle. CONCLUSION OV-TPN as opposed to IL-TPN mitigates inflammation in the liver and reduces the negative metabolic effects of hyperinsulinemia and hyperglucagonemia by "re-sensitizing" the liver and skeletal muscle to insulin