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

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.

Fish Oil Enriched Intravenous Lipid Emulsions Reduce Triglyceride Levels in Non-Critically Ill Patients with TPN and Type 2 Diabetes. A Post-Hoc Analysis of the INSUPAR Study

There are no studies that have specifically assessed the role of intravenous lipid emulsions (ILE) enriched with fish oil in people with diabetes receiving total parenteral nutrition (TPN). The objective of this study was to assess the metabolic control (glycemic and lipid) and in-hospital complications that occurred in non-critically ill inpatients with TPN and type 2 diabetes with regard to the use of fish oil emulsions compared with other ILEs. We performed a post-hoc analysis of the Insulin in Parenteral Nutrition (INSUPAR) trial that included patients who started with TPN for any cause and that would predictably continue with TPN for at least five days. The study included 161 patients who started with TPN for any cause. There were 80 patients (49.7%) on fish oil enriched ILEs and 81 patients (50.3%) on other ILEs. We found significant decreases in triglyceride levels in the fish oil group compared to the other patients. We did not find any differences in glucose metabolic control: mean capillary glucose, glycemic variability, and insulin dose, except in the number of mild hypoglycemic events that was significantly higher in the fish oil group. We did not observe any differences in other metabolic, liver or infectious complications, in-hospital length of stay or mortality.

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.

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.