Pei-Ra Ling

Pharmacopeial compliance of fish oil-containing parenteral lipid emulsion mixtures: globule size distribution (GSD) and fatty acid analyses.

Recently, the United States Pharmacopeia (USP) has established Chapter 729 with GSD limits for all lipid emulsions where the mean droplet size (MDS) must be <500 nm and the percent of fat larger than 5 microm (PFAT(5)) must be <0.05%, irrespective of the final lipid concentration. As well, the European Pharmacopeia (EP) Monograph no. 1352 specifies n3-fatty acid (FA) limits (EPA+DHA> or =45%; total n3 or T-n3> or =60%) for fish oil. We assessed compliance with USP physical and EP chemical limits of two fish oil-containing lipid emulsion mixtures. All lipid emulsions passed USP 729 limits. No samples tested had an MDS >302 nm or a PFAT(5) value >0.011%. Only one product met EP limits while the other failed. All emulsions tested were extremely fine dispersions and easily met USP 729 GSD limits. The n3-FAs profiles were lower in one, despite being labeled to contain 50% more fish oil than the other product. This latter finding suggests the n3-FA content of the fish oil source and/or the applied manufacturing processes in these products is different.

Effects of Medium-Chain Triglycerides, Long-Chain Triglycerides, or 2-Monododecanoin on Fatty Acid Composition in the Portal Vein, Intestinal Lymph, and Systemic Circulation in Rats

BACKGROUNDnFatty acid absorption patterns can have a major impact on the fatty acid composition in the portal, intestinal lymph, and systemic circulation. This study sought to determine the effects of long-chain triglycerides (LCT), medium-chain triglycerides (MCT), and 2-monododecanoin (2mono) on intestinal fatty acid composition during continuous feeding over a brief period.nnnMETHODSnThe lipid sources were 100% LCT, 100% MCT, a 50:50 mixture of LCT and MCT (LCT/MCT), and a 50:50 mixture of LCT and 2mono (LCT/2mono). A total of 27 rats were randomly given 1 of the 4 diets at 200 kcal/kg/d, with 30% of total calories from lipids over 3 hours.nnnRESULTSnMCT significantly increased each of the medium-chain fatty acids (C6:0, C8:0, and C10:0) as free fatty acids in the portal vein and about 10%/mol of C10:0 as triglycerides in the lymph compared with the other groups. There was significantly less C10:0 in lymphatic triglycerides with LCT/MCT than with MCT, but more than in the LCT and LCT/2mono diets. MCT also significantly increased the contents of C16:0, C18:0, C18:1, and C20:4 in the lymphatic triglycerides compared with all other groups including LCT/MCT. The amount of linoleic acid (C18:2) in lymphatic triglycerides followed the relative amounts of this fatty acid in the diet, with the greatest in LCT followed by LCT/MCT and LCT/2mono and least in MCT. A so-called structured lipid composed of the medium-chain fatty acid dodecanoic acid on the 2 position and long-chain fatty acids on the 1 and 3 positions appeared to be endogenously synthesized in response to the LCT/2mono diet.nnnCONCLUSIONSnThe original differences in MCT and LCT content in the diets were preserved in the fatty acid composition in the intestinal free fatty acids and triglycerides during feeding. In addition, the duration of lipid administration can play a role in altering fatty acid composition in the intestine.

Hepatic Indicators of Oxidative Stress and Tissue Damage Accompanied by Systemic Inflammation in Rats Following a 24-Hour Infusion of an Unstable Lipid Emulsion Admixture

BACKGROUNDnUse of lipid emulsions in parenteral nutrition therapy is an important source of daily energy in substitution of potentially harmful glucose calories when given in excess in the intensive care unit. When added to parenteral nutrition (PN) admixtures as a total nutrient admixture (TNA), the stability and safety of the emulsion may be compromised. Development of a rat model of a stable vs unstable lipid infusion would enable a study of the potential risk.nnnDESIGNnProspective, randomized, controlled study.nnnMETHODSnSurgical placement of a jugular venous catheter for the administration of TNAs was performed. Two groups were studied: a stable or s-TNA (n = 16) and an unstable or u-TNA (n = 17) as a 24-hour continuous infusion. Stability of TNAs was determined immediately before and after infusion using a laser-based method approved by the United States Pharmacopeia.nnnRESULTSnBlood levels of aspartate aminotransferase, glutathione-S-transferase, and C-reactive protein were significantly elevated in u-TNA vs s-TNA (P < .05). Also, liver tissue concentrations of malondialdehyde were significantly higher in the u-TNA group (P < .05), and triglyceride tissue levels were also higher in u-TNA and approached statistical significance (P = .077).nnnCONCLUSIONSnUnstable lipid infusions over 24 hours produce evidence of hepatic accumulation of fat associated with oxidative stress, liver injury, and a low-level systemic inflammatory response.

Determinants of plasma concentrations of insulin-like growth factor-I and albumin and their hepatic mRNAs: the role of dietary protein content and tumor necrosis factor in malnourished rats.

Protein restriction decreases plasma concentrations of albumin and insulin-like growth factor-I (IGF-I) by reducing their hepatic mRNA levels, whereas protein restriction increases IGF-I binding protein-2 (IGFBP-2) gene expression in the liver. Tumor necrosis factor (TNF), as an inducer of the injury response, decreases plasma albumin concentration and albumin mRNA in the liver. The present study was designed to evaluate the effects of protein repletion and TNF on plasma albumin and IGF-I and their mRNAs and IGFBP-2 mRNA in the liver of protein-restricted rats. After 2 weeks of feeding a 2% casein diet, rats were assigned to four groups according to either being refed with a 2% or 20% casein diet or receiving saline or TNF by intraperitoneal injection (50 microg/kg x d) for 4 days. Plasma IGF-I and albumin were assayed. Hepatic mRNAs of IGF-I, albumin, and IGFBP-2 were determined. Protein repletion increased plasma concentrations of IGF-I and albumin and their mRNA content in the liver, but decreased IGFBP-2 mRNA. TNF did not alter plasma IGF-I concentration but did increase hepatic IGF-I mRNA in protein-repleted animals, and plasma albumin concentration was significantly decreased with unaltered hepatic albumin mRNA. Thus, protein repletion of malnourished rats increased plasma IGF-I and albumin concentrations in association with increased expression of their mRNAs in the liver. However, plasma albumin but not IGF-I decreased following TNF in protein-restricted rats, whereas TNF increased hepatic IGF-I mRNA in protein-repleted rats. Thus, only plasma albumin concentration responds to both principal determinants, diet and injury, in the development of malnutrition.

Fine vs. coarse complete all-in-one admixture infusions over 96 hours in rats: Fat globule size and hepatic function

BACKGROUND & AIMSnThe United States Pharmacopeia (USP) has adopted Chapter <729> that set two globule size limits for all lipid emulsions with the mean droplet size at no >500 nm, while large-diameter fat globules as the percent fat>5 microm or PFAT(5) must be <0.05%. A quantitative risk assessment of toxicity from the intravenous infusion of all-in-one (AIO) admixtures made from a lipid emulsion that meets USP standards (fine) vs. one that does not (coarse), was conducted.nnnMETHODSnTwo separate 96-h infusion studies in rats receiving nutritionally complete AIOs made from a fine (F) vs. a coarse (C) 20% starting lipid emulsion (SLE) with either 18 or 36% as fat calories were performed. The animals were equally divided in each (18% fat, n=18; 36% fat, n=22) to receive AIOs made from F or C lipids. PFAT(5) levels were measured at the outset and every 24h at the change of infusions and blood levels of liver enzymes AST and GST, and serum triglycerides (TG) were measured at the end of study.nnnRESULTSnOn average, the starting PFAT(5) values for infusions of F-AIOs were 0.018+/-0.007 (n=48) vs. C-AIOs at 0.183+/-0.026% (n=48), whereas the 24-h average was 0.234+/-0.211% (n=168) vs. 1.033+/-0.224% (n=180), respectively. No significant differences in the blood-based parameters were noted in rats between F-AIOs and C-AIOs in the studies comparing 18 or 36% of fat calories, respectively. When the data were combined into all F- vs. all C-AIOs, AST was significantly higher in C-AIOs (157+/-41) vs. F-AIOs (130+/-37), p=0.036. TG was lower in C (69+/-37) vs. F (106+/-70), nearly reaching statistical significance (p=0.056) with no differences in GST levels for C (21+/-9) vs. F (17+/-9), p=0.199. When stratified according to a PFAT(5) of 0.4%, C-AIOs were significantly higher than F-AIOs for AST (157+/-41 vs. 130+/-37, p=0.004), and TG was significantly lower in C- vs. F-AIOs (67+/-36 vs. 117+/-71, p=0.022), respectively.nnnCONCLUSIONSnCoarse lipid emulsions that fail pharmacopeial limits produce less stable AIOs and are associated with evidence of worsened hepatic injury.

Trophic enteral nutrition increases hepatic glutathione and protects against peroxidative damage after exposure to endotoxin.

BACKGROUNDnDuring total parenteral nutrition (TPN), hepatic concentration of the important intracellular antioxidant glutathione (GSH) is decreased. This study sought to determine whether enteral trophic (small quantity) feeding of GSH precursors would increase hepatic GSH levels during TPN and result in decreased peroxidative injury after endotoxin exposure.nnnMETHODSnSprague-Dawley rats received full TPN for 7 days with postpyloric infusions of either (1) amino acid GSH precursors (cysteine, 60 mg/d; glycine, 86 mg/d; glutamate, 31 mg/d; F1); (2) iso-nitrogenous alanine (132 mg/d; F2); or (3) normal saline (SA). Hepatic GSH concentration was measured by gas chromatography/mass spectrometry. In a parallel study, animals were given TPN and either F1 or SA for 7 days, and endotoxin was administered intravenously before death. Hepatic lipid peroxidation and histology were assessed.nnnRESULTSnHepatic GSH concentration measured 11.7 +/- 0.6 micromol/g in F1. This was significantly higher (P <.001) than in F2 (7.0 +/- 0.8 micromol/g) or SA (5.0 +/- 0.4 micromol/g). F2 and SA were not significantly different. Hepatic malondialdehyde concentration after exposure to endotoxin was significantly higher in SA (10.36 micromol/g +/- 0.65) than in F1 (7.38 micromol/g +/- 0.77; P <.01). All SA animals had histologic evidence of hepatic necrosis, whereas none of the F1 group showed these changes.nnnCONCLUSIONSnTargeted trophic feeding of GSH amino acid precursors during parenteral nutrition markedly increased hepatic GSH concentration. This was associated with decreased lipid peroxidation and enhanced hepatocellular protection after endotoxin challenge. Thus, targeted trophic feedings may aid in the prevention of TPN-related liver disease.

Effect of continuous enteral medium-chain fatty acid infusion on lipid metabolism in rats

This study compared (i) the relative effects of long-chain triglycerides (LCT) and medium-chain triglycerides (MCT), (ii) the influence of amount of MCT, and (iii) the impact of medium-chain fatty acid position, on plasma and lymphatic triglycerides and portal vein free fatty acids. The animals were fed approximately at 250 kcal/kg · day for 20h. The lymph from lymphatic duct and blood from portal vein and systemic circulation were collected. The results showed that feeding 100% MCT for 20h was sufficiently long to reduce significantly the level of linoleic acid in portal vein fatty acids and plasma and lymph triglycerides. However, this alteration induced by MCT feeding was partially prevented by adding LCT to the diet. The level of arachidonic acid was significantly reduced in plasma triglycerides by any of the diets containing medium-chain fatty acids compared to 100% LCT. When feeding MCT only, palmitoleic acid, presumably reflecting de novo lipogenesis, was increased in lymphatic triglycerides and portal vein fatty acids. Total saturated fatty acids as a total percentage of total fatty acids were also significantly increased in plasma and lymphatic triglycerides and portal vein fatty acids. Thus, when linoleic acid is limiting, the conversion of MCT into long-chain fatty acids by de novo lipogenesis is likely to be an important metabolic route. Providing LCT with MCT or 2-monodecanoin appears to limit this pathway.

Nutrition and IGF Proteins in Chronic Malnutrition and Critical Illness

The systemic inflammatory response found in severe stress, or its persistence as seen in chronic diseases, can cause a rapid or prolonged catabolic hypermetabolic condition leading to accelerated energy and nitrogen loss that cannot be compensated by dietary intake and results in protein energy malnutrition. n n nThe catabolic response to systemic inflammation is the consequence of multiple factors including increased levels of proinflammatory cytokines and catabolic hormones, decreased concentrations of anabolic hormones and growth factors such as IGFs, as well as tissue resistance to their effects. Although nutritional therapy has beneficial effects, adequate nutrition support alone cannot overcome the catabolic effects induced by severe illness. n n nCytokines reduce the levels of IGF-I and impair the action of IGF-I directly, as well as indirectly, by altering the IGFBPs. n n nThe most effective nutrition support for patients with conditions of acute or chronic systemic inflammation is actively being studied. Specific amino acids, omega-3-fatty acids, and antioxidant vitamins are examples of anabolic nutrition therapies that may, with anabolic hormone therapy, be effective in the management of disease-related malnutrition.