Testing of Fat Emulsions for Toxicity

Experimental Investigation of a New Iodinated Lipid Emulsion for Computed Tomography of the Liver

Iodinated lipid emulsions are highly efficient macrophage imaging agents. Nevertheless, none of them has been accepted for clinical use because of adverse reactions. We have tested a new iodinated lipid emulsion, Intraiodol. The size and surface properties of the particles of this emulsion are similar to those of Intralipid which in turn closely resemble the naturally occurring chylomicrons. Using computed tomography (CT) of the rabbit liver as well as vital microscopy and electron microscopy of the rat liver we found that Intraiodol has low efficiency as a liver-specific contrast medium because its particles are predominantly taken up by the hepatocytes and to a less extent by the Kupffer cells, as is Intralipid. The low efficiency of Intraiodol could be fully compensated by an increase in dosage without any significant effect on sinusoidal blood flow. This in turn suggests that the likelihood of release of toxic mediators (and thereby related adverse reactions from activated macrophages) is reduced. We believe that this new way of delivering iodinated lipid particles to the liver represents an important advance in the search for a non-toxic lipid emulsion for CT of the liver.

In vitro investigation of the effect of various isotonic substances in parenteral emulsions on human erythrocytes

The hemolytic behaviour of human erythrocytes in parenteral emulsions containing various isotonizing substances (xylitol, sorbitol and glycerol) was studied. It was found that complete hemolysis of human erythrocytes occurred in parenteral emulsions with isotonic or isosmotic concentration of glycerol after 5 min, whereas emulsions which contained an isotonic concentration of xylitol or sorbitol did not show any hemolysis after 40 min. Conversely, formulations with different concentrations of glycerol in an isotonic solution of sorbitol did not show any hemolytic behaviour after 40 min. It appeared that all the hemolytic phenomena encountered in glycerol were of an isotonic character since hemolysis was totally prevented by the inclusion of an isotonic concentration of sorbitol. According to these in vitro results it seems that glycerol, a commonly used substance in commercial parenteral emulsions, may not be the best isotonizing substance.

Biochemical and ultra-structural reactions to parenteral nutrition with two different fat emulsions in rats

OBJECTIVE

To compare the effects on fat metabolism and Kupffer cell morphology by total parenteral nutrition (TPN) with two different fat emulsions.

DESIGN

Thirty-two male Sprague-Dawley rats, divided into three groups, were investigated. Rats fed orally were used as a reference group, and a group of rats receiving TPN with fat emulsions containing pure long-chain triglycerides (LCT) was compared to a group of rats receiving fat emulsions containing both long-chain triglycerides and medium-chain triglycerides (MCT/LCT). The TPN regimens were equicaloric and administered continuously via a jugular catheter for 10 days.

INTERVENTIONS

After suffocation, blood of the rats was collected for the determination of serum lipids. Epididymal fat and heart were collected for the analysis of lipoprotein lipase (LPL) activities, and liver specimens were saved for analyses of hepatic triglyceride concentration, as well as activities of hepatic lipase (HL) and lysosomal enzymes. Light and electron microscopy were used for examination of the Kupffer cell reaction.

RESULTS

Directly after termination of parenteral feeding, the levels of serum triglycerides and high density lipoprotein (HDL) triglycerides were higher in the MCT/LCT group than in the LCT group, while no differences concerning cholesterol and phospholipid concentrations were found. No significant difference in liver steatosis was found between the two TPN groups. Comparison of the TPN groups showed that the MCT/ LCT group had significantly decreased LPL activity in adipose tissue, while the LCT group had significantly increased LPL activity in the heart. The activity of HL was low in both groups, but significantly lower in the LCT group. Lipid accumulation and an increased number of lysosomes were found in all Kupffer cell when TPN with LCTemulsions was used. Moreover, TPN induced a pronounced increase in various liver lysosomal enzyme activities, but there was no notable difference between LCT and MCT/LCT effects.

CONCLUSIONS

Compared to treatment with pure LCTemulsions, treatment with MCT/LCT emulsions evoked weaker biochemical reactions in terms of lower activity of lipoprotein lipase in fat and heart together with higher serum and HDL triglyceride levels. Morphological signs of increased Kupffer cell activity such as the appearance of multiple lysosomes and fat vacuoles in the cytoplasm followed treatment with pure LCT emulsions. However, both TPN groups showed a marked increase in activities of liver lysosomal enzymes.

Effects of n-3 and n-6 fatty acids on plasma eicosanoids and liver antioxidant enzymes in rats receiving total parenteral nutrition

The effect of total parenteral nutrition (TPN) enriched with n-3 or n-6 fatty acids on the concentration of plasma eicosanoids was evaluated in rats. Rats were divided into three groups: the control group (n = 6) was fed a chow diet and infused with saline only. Two experimental groups (n = 11, 13) received TPN solutions at an energy level of 30 kcal/100g body weight with 40% energy provided as fat. The experimental groups were maintained on TPN for a period of 7 d. The basal TPN solutions were isonitrogenous and identical in nutrient composition except for differences in lipid source. One experimental group received a safflower oil emulsion, whereas the other group received a fish oil emulsion. At the end of the experimental period, plasma 6-keto prostaglandin F1 alpha, thromboxane B2, bleeding time, lipid peroxidation products, and antioxidant enzymes of liver were analyzed. The results demonstrated that the fish oil group had lower 6-keto prostaglandin F1 alpha concentration than the safflower oil group. Also, plasma thromboxane B2 was the lowest in the fish oil group among the three groups. There was no difference in bleeding time among the groups. With regard to liver lipid peroxidation products, malondialdehyde concentration was not higher in the fish oil group, whereas superoxide dismutase and glutathione peroxidase activities were lower in the fish oil group compared with the control and safflower oil groups. The results suggest that TPN prepared with fish oil fat emulsion causes less accumulation of lipid peroxidation products in the liver of rats, and may be beneficial in preventing platelet aggregation.

Lipid deposition in Kupffer cells after parenteral fat nutrition in rats: a biochemical and ultrastructural study

OBJECTIVE

To study fat metabolism and evaluate lipid deposition in hepatocytes and Kupffer cells during parenteral nutrition (PN) with or without fat.

DESIGN

20 male Sprague-Dawley rats, divided into four groups, were investigated. Rats fed orally were used as a reference group and compared to three groups of rats receiving PN either without fat or with 33% of non-protein energy as fat or with 66% of non-protein energy as fat. The PN regimens were equicaloric and administered continuously via a jugular catheter for 7 days.

INTERVENTIONS

After suffocation, blood was collected for determination of serum lipids. Epididymal fat and heart were collected for analysis of lipoprotein lipase activities, and pieces of liver were saved for analyses of liver triglyceride concentration and hepatic lipase activity. Light and electron microscopy were used for examination of lipid deposition in Kupffer cells.

RESULTS

Directly after termination of parenteral feeding, the serum levels of triglycerides were similar in all PN groups, while the levels of non-high-density lipoprotein (HDL) cholesterol and non-HDL phospholipids were significantly increased in parallel with increased doses of fat. Lipid-free PN resulted in significantly less liver steatosis than high-fat PN. Lipid PN also resulted in downregulated hepatic lipase activity, signs of lipid accumulation in Kupffer cells and hepatocytes and an increased number of phagosomes in Kupffer cells.

CONCLUSIONS

Fat vacuoles were found in Kupffer cells after lipid PN, although serum levels of triglycerides were not elevated and lipoprotein lipase activity were not depressed. The cells were distended by fat vacuoles after administration of PN solutions with a high fat concentration. Morphological signs of increased Kupffer cell activity were also found, suggesting that intravenous fat emulsions may activate macrophages.

Effects of fish oil and safflower oil emulsions on diet-inducedhepatic steatosis in rats receiving total parenteral nutrition

This study was conducted to investigate the effects of fish oil and safflower oil emulsions in total parenteral nutrition (TPN) solutions on diet-induced hepatic steatosis. Rats were divided into a control group (C, n = 6) and four experimental groups (A, B, S, F, n = 11 approximately 14). The control group was fed a chow diet whereas the experimental groups received a high fat (15%, w/w) diet containing 0.1% (w/w) cholesterol. Group A received the high fat diet for 4 weeks, and was killed at the end of the fourth week to ensure that hepatic steatosis had occurred. Groups S and group F received TPN with safflower oil or fish oil emulsions, respectively, for 1 week following experimental diet feeding for 4 weeks. Group B was fed a limited amount of the high fat diet, without cholesterol, for 1 week following 4 weeks of experimental diet in order to maintain the same body weight and cholesterol intake as the TPN groups. Diet-induced hepatic steatosis was observed in the experimental groups. Fat deposition was reversed when the total caloric and cholesterol intake was reduced. Fish oil infusion ameliorated the severity of hepatic steatosis, whereas safflower oil had no effect on liver fat deposition. These results suggest that TPN with fish oil emulsions may be beneficial to patients with diet-induced hepatic steatosis.

Effects of fat emulsions with different fatty acid composition on plasma and hepatic lipids in rats receiving total parenteral nutrition

Effects of different fatty acids on the development of hepatic steatosis were studied in rats receiving total parenteral nutrition (TPN). 65 rats, with internal jugular catheters, were divided into one control group (n = 8), and four experimental groups (n = 13-15 each). The control group was fed a chow diet and all experimental groups received TPN. TPN provided 300 kcal/kg/day with 40% of the non-protein energy provided as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fatty acid composition of the fat emulsion. Four kinds of fat emulsions rich in: 1) medium chain fatty acids (C8:0,C10:0), 2) oleic acid (C18:1 n-9), 3) linoleic acid (C18:2 n-6), 4) eicosapentaenoic acid (C20:5 n-3)/docosahexaenoic acid (C22:6 n-3), were used. These fat emulsions were prepared with: 1) a mixture of medium chain triglycerides (MCT) and soybean oil (9:1), 2) olive oil, 3) safflower oil, 4) fish oil, respectively. The results of the study demonstrated a higher hepatic lipid content in the olive oil and safflower oil groups than in the control group, whereas no significant difference was seen between the MCT and control groups. Also, no difference was observed between the fish oil and control groups. With regard to the plasma lipids, the MCT group and olive oil group produced hyperlipidaemia. The plasma of the safflower oil and fish oil groups, however, had a low lipid concentration comparable to the control group. These results suggest that TPN with a fat emulsion prepared with fish oil does not cause hyperlipidaemia nor induce hepatic steatosis in normal rats.

Efficacy evaluation of a novel submicron miconazole emulsion in a murine cryptococcosis model

Submicron emulsions of miconazole were stabilized by using a combination of three emulsifiers comprising phospholipids, poloxamer, and deoxycholic acid (DCA). The presence of DCA was vital for prolonged emulsion stability owing to its contribution to the elevated zeta potential of the emulsion. Further, the results by the phospholipid surface labelling colorimetric technique clearly suggested that poloxamer molecules interacted with phospholipid polar-head groups of the mixed DCA-phospholipid interfacial film, resulting in the stabilization of the emulsion by a steric enthalpic entropic mechanism. The plain emulsion vehicle was well tolerated up to a dose of 0.6 ml injected i.v. to BALB/c mice. The maximum tolerated dose of miconazole was 80 and 250 mg/kg in Daktarin i.v. (a marketed product) and emulsion, respectively, showing an improved safety ratio of 1 to 3 in favor of the emulsion. These results tended to confirm that the adverse effects associated with Daktarin i.v. injection should be associated with the vehicle rather than with the miconazole itself. In a murine cryptococcosis model, only one mouse out of ten remained alive by day 15 in the infected group treated with Daktarin i.v., while in the miconazole emulsion treated group, mice began to die from day 16 up to day 25 post inoculation. Thus, the multiple-dose treatment with the miconazole emulsions improved the protection offered to the infected mice. However, the therapeutic levels of miconazole that were reached in the target organ (brain) were lower than those required for complete eradication of Cryptococcus neoformans, which is known to multiply preferentially in the brain.

Odd-numbered medium-chain triglycerides (trinonanoin) in total parenteral nutrition: effects on parameters of fat metabolism in rabbits

Odd-numbered medium-chain triglycerides (MCTs) might combine the advantages of "usual" MCTs applied in clinical nutrition with lower ketogenic action and the release of three carbon units. To test subacute toxicity, trinonanoin/long-chain triglyceride (LCT) (7/3 wt/wt) fat emulsions were given to rabbits (n = 8) for 11 days (7 h/d) within a total parenteral nutrition regimen at a dose of 46.5% of total daily energy. Comparisons were made with rabbits receiving equicaloric amounts of MCT/LCT (7/3, wt/wt) or pure LCT fat emulsions, as well as with orally fed controls. The trinonanoin/LCT emulsion was well tolerated by all animals. Body weight changes showed no statistically significant differences between groups. The enzymatic determination of triglycerides, non-esterified fatty acids, and free glycerol concentrations in plasma samples revealed similar results for both MCT groups. However, ketone body concentrations (3-hydroxybutyrate) were significantly lower after trinonanoin/LCT emulsion administration. In the trinonanoin/LCT group, the plasma concentrations of propionic acid as well as of other short-chain fatty acids continuously increased; on days 10 and 11, elevated amounts of propionic acid were also detected in the urine. The histologic examination of the gut mucosa revealed no distinct differences between groups. On the basis of the presented data, the trinonanoin/LCT emulsion showed no inferiority to "usual" MCT/LCT emulsions. The lower ketogenic effect as well as the marked increase in plasma short-chain fatty acid concentrations may encourage further testing of this substrate for total parenteral nutrition.

Fat emulsions for parenteral nutrition II: Characterisation and physical long-term stability of Lipofundin MCTLCT

Lipofundin MCT LCT emulsions for parenteral nutrition were characterized in terms of particle size (bulk population), presence of large particles ( 1 mum) and droplet charge (zeta potential as measure of electrostatic stabilization). Photon Correlation Spectroscopy (PCS), microscopy and Laser Diffractometry (LD) were employed as sizing techniques and compared to each other. Zeta potentials were determined by Laser Doppler Anemometry (LDA). The characterization data showed a good batch-to-batch reproducibility. The physical stability of Lipofundin MCT LCT was monitored over a period of 2 years. The mean diameter of the bulk droplet population did not increase. No formation of larger droplets was found by microscopy and LD. A negligible coalescence could only be detected by the very sensitive PCS measurements (two time window analysis). The zeta potential stayed above -45 mV providing sufficient electrostatic stabilization during the whole storage period.

Efficacy evaluation of a novel submicron amphotericin B emulsion in murine candidiasis

A submicron amphotericin B (AmB) sterile emulsion with a mean droplet size of approximately 100 nm was prepared. The emulsion was stable at 4 degrees C over a period of 4 months. The acute toxicity results showed that the maximum tolerated dose of the AmB emulsion was 2.0 mg kg-1 as compared to 0.5 mg kg-1 for a commercial deoxycholate suspension, Fungizone. Efficacy evaluations of submicron AmB emulsion compared to Fungizone were performed in a murine candidiasis model using either a single or a multiple daily dose administration of 0.4 mg kg-1. Survival (100%) was observed up to 15-18 days post-infection in mice treated with AmB emulsion or Fungizone, while all control non-treated animals had died after 9 days in both single and multi-treatment experiments. Survival (50%) was obtained after 35 days in the single treatment, and 40 days in the multi-treatment, experiment with AmB emulsion, while treatment with Fungizone gave 50% survival after 15 and 20 days, respectively. The overall results indicate that in murine candidiasis, treatment with AmB submicron emulsion was more effective than Fungizone, suggesting a potential therapeutic application.

Fat emulsions for parenteral nutrition. I: Evaluation of microscopic and laser light scattering methods for the determination of the physical stability

Droplet size distribution was studied as a measure of the physical stability of fat emulsions. Test emulsions with increasing fractions of larger particles were prepared and investigated by conventional light microscopy and laser light scattering techniques (Photon Correlation Spectroscopy (PCS), Laser Diffractometer). Light microscopy proved to be most sensitive for detecting a few single large particles. All the techniques placed the test emulsions in the same order of increasing content of larger droplets. The application of a two time window analysis for PCS markedly improved the ability to differentiate between emulsions which were very similar in size distribution. In contrast to the applied semi-quantitative microscopic method, the laser techniques characterise the emulsion in absolute figures. Additional zeta potential measurements by Laser Doppler Anemometry (LDA) can quantify reduced electrostatic repulsion as a possible cause for increased formation of larger droplets.

The effect of infused fat emulsions on reticuloendothelial function in the rabbit

The effect of the infusion of different fat emulsions (Intralipid and MCT/LCT mixtures) on the reticuloendothelial function of the rabbit has been investigated. Emulsions containing 20% dispersed triglyceride were administered over 6 h to a total of 3 g/kg body weight. The extent of blockade of the reticuloendothelial system was measured using a labelled probe in the form of technetium-99m labelled albumin microspheres. Scintigraphic and blood and organ level determinations demonstrated that all emulsions caused an impairment of reticuloendoethlial function, but this was small.

Effects of repeated intravenous infusions of the plasticizer di-(2-ethylhexyl) phthalate in young male rats

The effects of six iv infusions of an emulsion containing the plasticizer di(2-ethylhexyl) phthalate (DEHP) on the liver and testes were investigated in 40-day-old rats. Groups of five to six animals received the emulsion every other day in doses of 0, 5, 50 or 500 mg DEHP/kg body weight. Liver effects were studied by histological examination and by measuring bromosulfophthalein clearance, peroxisomal proliferation and certain enzymes in serum. Testicular effects were evaluated by light and electron microscopy. To investigate the possibility of an age-related effect on the testis, five 25-day-old rats were given six infusions of 500 mg DEHP/kg. Compared with control animals, the high-dose group showed a 36% increase in relative liver weight and a 41% increase in the number of peroxisomes. In Epon-embedded testicular material from animals given the highest dose, which is about 100 times the highest estimated human exposure, some altered Sertoli cells and some degenerated primary spermatocytes were observed. No age-related effect on the testis similar to that found following oral administration of DEHP was observed in this study.

The effects on beagles of long-term administration of 20% Travamulsion fat emulsion

The tolerance of 20% Travamulsion intravenous fat emulsion (Travenol Laboratories, Inc., Deerfield, IL) was studied using male beagle dogs. Physiologic (0.9%) saline, USP, was used as the control, and 10% Travamulsion Intravenous fat emulsion (Travenol Laboratories) as the reference article. The 20 and 10% emulsions were administered intravenously to each of eight animals for 91 days at 20 and 40 ml/kg/day, respectively. These dosages were administered over 4 hr and they correspond to approximately 4 g of lipid as soybean oil per kilogram of body weight. The saline was administered to eight animals at 40 ml/kg/day. On day 92, one-half of the animals in each group were necropsied. The remaining dogs were observed and necropsied on day 122. Toxicity was assessed on animal survival; changes in body weight, urinalysis, and hematologic, and serum biochemical analyses; ophthalmologic examination; gross pathology; and histopathology. The results obtained for the 20% Travamulsion fat emulsion correlated well with those for the 10% Travamulsion fat emulsion. The emulsions were well tolerated and all animals survived and gained weight. The 20% Travamulsion fat emulsion administered provided about 45% of the total caloric requirement of the dog, which is equal to an often used clinical dose. However, caloric administration in the form of lipid emulsion in relation to total energy required was performed at three to six times the indicated clinical rate. In addition to demonstrating that it is safe for prolonged administration, the 20% Travamulsion fat emulsion offers an advantage over the 10% Travamulsion fat emulsion in providing the same amount of calories because it produces lower serum levels of phospholipid, cholesterol, and triglyceride, and the volume of emulsion required is reduced.

Studies of the toxicity of an intravenous fat emulsion. II. Blood chemical changes after administration of a soybean oil (FE-S15) in beagles

Biochemical changes were monitored during fat infusion as part of an evaluation of the toxicity that accompanies the intravenous administration of a new soybean oil emulsion in dogs. Beagles were given FE-S15 at 9 and 4 g/kg/day for 28 days via a central venous catheter. The total serum lipid, triglyceride, and phospholipid concentrations of the animals receiving fat in high doses increased 3 to 4 times in comparison to that of the control group; cholesterol increased 5 times. The rise of serum lipid fractions was proportionally smaller in animals receiving the low dose fat infusion. All values returned to the control range 2 wks after termination of the infusion. The serum protein level fell from 6.5 to 5.1 g/dl in animals given 9 g/kg/day fat while animals receiving 4 g/kg/day had a significant increase to 8.4 g/dl (day 27). In comparison with the control groups, the animals receiving low dose fat infusion also had a significant rise in serum albumin and, to a lesser degree, in alpha and beta globulins. A rise in alkaline phosphatase activity was observed in all dogs receiving fat infusion, but was significantly different from the controls only in animals on high dose fat infusion. None of the other monitored biochemical serum values were affected by the administered fat and there was no evidence of disturbance in liver function.

Contrasting effects on plasma lipoproteins of intravenous versus oral administration of a triglyceride-phospholipid emulsion

The effect of fat on plasma lipoproteins was compared when administered by the oral and intravenous routes to healthy control subjects on a low fat diet for 5-6 weeks. During this time each subject underwent two 5 day periods of fat supplementation with a soya bean triglyceride-egg yolk phospholipid emulsion (Intralipid), once via intragastric tube, once intravenously. Changes in plasma lipoproteins were assessed by measurement of their lipid and protein content. Intragastric fat administration significantly decreased the level of very low density lipoprotein (VLDL), whereas intravenous fat administration caused a significant rise in low density lipoprotein (LDL). Morphological evidence of persistence of exogenous phospholipid in plasma following intravenous fat administration was confirmed by alterations in the fatty acid composition of lecithin in the d 1.006-1.063 fraction of plasma. In vitro studies showed that exchange readily occurred between Intralipid and LDL lecithin, causing the latter to assume a more saturated pattern. It is concluded that the occurrence of similar changes in vivo could explain the rise in low density lipoprotein following intravenous fat, possibly by influencing the catabolic rate of the apoprotein. Hydrolysis of ingested phospholipids during absorption presumably explains why none of these changes occurred after oral fat supplementation, and would seem to be an important regulatory function of the small intestine in relation to plasma lipoprotein metabolism.