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Effects of a Newly Developed Fat Emulsion Containing Eicosapentaenoic Acid and Docosahexaenoic Acid on Fatty Acid Profiles in Rats
PRELIMINARY REPORT
Nutrition Vol. 14, No. 4, 1998
Effects of a Newly Developed Fat Emulsion Containing Eicosapentaenoic Acid and Docosahexaenoic Acid on Fatty Acid Profiles in Rats TSUGUHIKO TASHIRO, MD, HIDEO YAMAMORI, MD, NAGANORI HAYASHI, MD, TOSHIYUKI SUGIURA, MD, KAZUYA TAKAGI, MD, KATSUNORI FURUKAWA, MD, NOBUYUKI NAKAJIMA, MD, ISAO ITOH, PHD,* TOSHIO WAKABAYASHI, PHD,† SETSUYA OHBA, PHD,† AND NORIKO AKAHANE, BPH From the *First Department of Surgery and Laboratory Animal Center, Chiba University Medical School, Chiba, and †Tsukuba Research Center, SANDOZ Pharmaceutical Co., Tsukuba, Japan Date accepted: 5 September 1997 ABSTRACT
A new fat emulsion of symmetrical triacylglycerols, containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was developed. The effects of this preparation on serum and liver fatty acid composition were investigated. Male Sprague-Dawley rats were fed a fat-free oral diet for 2 wk and were then divided into two groups. Seven rats were infused for 7 d with 1 mL of the new fat emulsion, which accounted for 1% of total caloric intake. The other 7 rats received saline. Both groups of rats received a fat-free diet during the infusion. EPA and DHA decreased to one third to one fifth of normal value after 2 wk on a fat-free diet. EPA and DHA of serum and liver remained at a low level in the control group throughout the study. But in the rats administered with the new fat emulsion, EPA and DHA increased rapidly and exceeded normal values in both serum and liver after 7 d of infusion. Decreased arachidonic acid with increased 20:3n-9 resulted in the rise of the triene/tetraene (T/T) ratio to greater than 0.4, indicating an n-6 essential fatty acid deficiency in the control rats. In the group administered the new fat emulsion, however, 20:3n-9 and total content of monounsaturated fatty acids decreased significantly, and the T/T ratio was less than than 0.4 in both serum and liver. In conclusion, the intravenous use of a newly developed fat emulsion containing EPA and DHA is useful in improving the EPA and DHA status of serum and liver without any harmful effects. Beneficial effects are expected in the modulation of inflammatory and stress response. Nutrition 1998;14:372–375. ©Elsevier Science Inc. 1998 Key words: n-3 and n-6 polyunsaturated fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), fatty acids composition, fat emulsion
INTRODUCTION
Since the epidemiologic studies of populations of coastal Eskimo subjects,1,2 dietary supplementation with n-3 fatty acids has been reported to improve various pathophysiologic states, such as cardiovascular diseases, rheumatoid arthritis,3 psoriasis,4 and inflammatory bowel disease.5 n-3 fatty acids have been revealed to modulate metabolic, inflammatory, and
immunological responses, and is expected for the management of critically ill patients.6 On the basis of these considerations, we have developed a novel lipid emulsion for intravenous use from a structured triacylglycerol containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The present study was undertaken to assess the effects of the new fat emulsion on fatty acid composition when administered intravenously to rats.
Correspondence to: Tsuguhiko Tashiro, MD, First Department of Surgery, Chiba University Medical School, 1-8-1, Inohana, Chuo-ku, Chiba-shi, Chiba-ken, 260, Japan.
Nutrition 14:372–375, 1998 ©Elsevier Science Inc. 1998 Printed in the USA. All rights reserved.
0899-9007/98/$19.00 PII S0899-9007(97)00491-7
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS
373
FIG. 2. Eicosapentaenoic acid (EPA) content in serum and liver. FIG. 1. Symmetrical structured triacylglycerol containing ecosapentanoeic acid (EPA) and docosahexaenoic acid (DHA).
MATERIALS AND METHODS
Lipid Emulsion A symmetrical triacylglycerol containing EPA at position 1 and 3 and DHA at position 2 was synthesized (Fig. 1). This triacylglycerol was emulsified by egg yolk lecithin in 2.5% glycerol solution. The purity of the EPA and DHA was more than 95%. The concentration of lipid in the emulsion was 10%. Animals and Experimental Procedures Male Sprague-Dawley rats (Tokyo Orient Co., Tokyo, Japan) weighing 100 –150 g were housed in an environmentally controlled, limited-access room that had a 12-h regulated light– dark cycle at an ambient temperature of 24 –26°C. Tap water and fat-free laboratory chow (Nihon Clea, Tokyo, Japan) were provided ad libitum to 14 rats for 2 wk prior to infusion of the lipid emulsion. Seven rats were infused with 1.0 mL of the new lipid emulsion for 7 d at 09:00 through the tail veins, with the process lasting more than 5 min (group N3, n 5 7). The other 7 rats were infused with the same amount of saline (group control, n 5 7). During the infusions, all rats were fed a fat-free chow. Blood was taken prior to infusion and on the third infusion day. Rats were killed by exanguination under ether anesthesia after 7 d of infusions. Serum was stored at 280°C. Approval to conduct the experiment was granted by the Animal Care Committee of the Chiba University School of Medicine in accordance with guidelines set forth by the Guide for the Care and Use of Laboratory Animals developed by the Institute of Laboratory Animal Resources of the National Research Council.
RESULTS
General Conditions of Animals All rats were healthy and active throughout the study. There was no difference in terms of food intake and body weight gain. Neither hematuria nor a hemorrhagic tendency was observed. Total Fatty Acid Composition of Serum and Liver As published previously,7 the serum levels of EPA in rats of the same age fed normal rat chow was 1.61 6 0.16%. In this experiment, EPA decreased to one third to one quarter of the normal value after 2 wk on a fat-free diet. EPA remained at a low level in the control group throughout the study. In the N3 group, EPA increased rapidly to 7.9 6 1.3% after 7 d of infusion of the new lipid emulsion. Elevation of EPA and DHA levels by administration of this new fat emulsion was also marked in the liver fatty acid composition. The EPA level in liver was 25.9 6 8.3% in the N3 group after 7 d of intravenous new fat emulsion, but it was almost 0 after 3 wk of the fat-free diet in the control group (Fig. 2). Serum DHA of rats fed a normal diet was 4.38 6 0.92%.8 DHA also decreased to one fifth of the normal value after 2 wk of a fat-free diet. In the control group, DHA continued to decrease. In the N3 group, the level of DHA improved to 5.0 6 0.7% after 7 d of infusion of the new lipid emulsion. The level of DHA also increased markedly in the liver to 11.5 6 1.0% after 7 d of intravenous new fat emulsion (Fig. 3).
Analytical Procedures Total lipids were extracted from serum and homogenized liver according to Bligh and Dyer.7 Methylation of the lipid fatty acids was performed by 20% BF3-Methanol. The methyl esters of the fatty acids were recovered and stored at 220°C. Samples were analyzed by gas chromatography (Hewlett Packard 5890 series II, Hewlett Packard, Palo Alto, CA, USA), which was programmed to separate methyl esters ranging from 12:0 to 22:6n-3 using helium as the carrier gas. The split ratio was 1/20 and the column (BPX-70, 25-m, 0.22-mm ID, 0.25-mm film thickness, SGE) and the flow was 12 mL/min. Identifications were made by comparisons with known methyl ester standards (Nu-Chek-Prep, Inc., Eleysian).
FIG. 3. Docosahexaenoic acid (DHA) content in serum and liver.
374
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS
FIG. 4. Arachidonic acid (AA) content in serum and liver. FIG. 6. Triene/tetraene ratio (T/T) in serum and liver.
Arachidonic acid decreased to one half of the normal value after 2 wk of a fat-free diet and continued to decrease gradually in both groups. In the liver, total fatty acid profile, arachidonic acid was lower in the N3 group when compared with the control group (Fig. 4). The novel fatty acid 20:3n-9, which cannot be detected in normal animals, increased significantly in both serum and the liver. The T/T ratio exceeded 0.4, indicating an n-6 essential fatty acid deficiency. In the N3 group, however, 20:3n-9 decreased significantly and the 20:3n-9/C20:4n-6 (T/T) ratio was less than 0.4 in both the serum and the liver (Figs. 5 and 6). The total content of monounsaturated fatty acids increased continuously in control rats, but it decreased significantly when administering the new lipid emulsion in both serum and the liver (Fig. 7). DISCUSSION
In 1982, Holman et al.9 reported a human linolenic acid deficiency involving neurologic abnormality after long-term total parenteral nutrition with safflower oil emulsion, which is rich in linoleic acid and low in a-linolenic acid, demonstrating the nutritional importance of n-3 polyunsaturated fatty acids (PUFA) in addition to n-6 PUFA. Since 1991, we have developed an intravenous fat emulsion containing soybean oil (85%) and fish oil (15%). We have observed safety measures and at the same time have attempted to improve the EPA and DHA status by intravenous administration of this solution not only to experimental animals but also to humans.8,10 For this purpose, we developed a
FIG. 5. 20:3n9 in serum and liver.
novel lipid emulsion from a structured triacylglycerol containing only EPA and DHA. Intravenous supplementation has several merits. Oral or enteral nutritional supplementation should sometimes be avoided due to the problems of alimentary tract or gut dysfunction in critically ill patients. A prompt effect of drugs is expected when they are administered intravenously.11 An intravenous preparation containing only EPA and DHA may be convenient in clinical practice for the following reasons. The total fat intake may be excessive in critically ill patients or patients with liver dysfunction when fish oil or a mixture of fish oil and soybean oil is used in an attempt to meet EPA or DHA requirements. Doses of EPA and DHA can be easily changed according to the pathophysiology and severity of the patient condition when a preparation containing only EPA and DHA is used. The present study was undertaken to assess the effects of a new fat emulsion on the composition of fatty acids when administered intravenously to the rats. The dose of lipid from the new fat emulsion was 100 mg/d, which accounted for 1% of the energy intake and is considered to be the optimal dose for rats. After administration of the new fat emulsion for 7 d, serum EPA and DHA increased rapidly and reached or exceeded normal values. Food intake and body weight gain were not influenced by the intravenous administration of new fat emul-
FIG. 7. Monounsaturated fatty acids in serum and liver.
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS sion. Thus, it was shown that rapid alteration of fatty acid composition without harmful effects could be obtained by the intravenous administration of this new preparation. In this experiment, no other fat component except for EPA and DHA was supplied. In mammals, 20:3n-9 is synthesized from oleic acid (18:1n-9) in the absence of n-6 essential fatty acids, and the ratio of the T/T ratio is an indicator of n-6 essential fatty acid deficiency.12 In this experiment, 20:3n-9 was shown to decrease significantly not by administering n-6 PUFA but with the n-3 PUFAs, EPA, and DHA. Supplementation of fatty acids, not specifically EPA and DHA, might have suppressed fatty acids synthesis in animals fed a fat-deprived diet13 as evidenced by significantly decreased levels of monounsaturated fatty acids. But the fact that the rate of decrease in 20:3n-9 was more than the increase in monounsaturated fatty acids may indicate the suppression of desaturase activity by EPA and DHA to produce 20:3n-9. Furthermore, decreased 20:3n-9 easily led to a decreased T/T ratio, less than 0.4. To evaluate whether this reduction of T/T ratio means the im-
375 provement of n-6 essential fatty acid deficiency, further investigation is necessary. In the past few years, particular attention has been given to the potential value of n-3 PUFA in critical illness, as evidenced by the improved metabolic and immunologic responses of burned guinea pigs fed an enteral regimen containing fish oil.6 The new fat emulsion containing only EPA and DHA is expected to have beneficial effects for the treatment of critical illness, such as extended burn injury, multiple trauma, sepsis, or organ failure. In conclusion, a newly developed symmetrical-triacylglycerol fat emulsion containing only EPA and DHA was infused without any harmful effects to the experimental animals. A rapid improvement of EPA and DHA status in serum and the liver tissue level was obtained by the intravenous infusion of this preparation. Reduced 20:3n9, together with a decreased T/T ratio, was also obtained. It is further expected that intravenous administration of this new fat emulsion may improve stress response and modulate the immune status of critically ill patients.
REFERENCES 1. Bang HO, Dyerberg J, Nielsen AB. Plasma lipid and lipoprotein pattern in Greenlandic west-coast Eskimos. Lancet 1971;1:1143 2. Kromann N, Green A. Epidemiologic studies in the Upernavic district, Greenland: incidence of some chronic diseases 1950 –1974. Acta Med Scand 1980;208:401 3. Kremer JM, Lawrence DA, Petrillo GF, et al. Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal antiinflammatory drugs: clinical and immune correlates. Arthritis Rheum 1995;38:1107 4. Soyland E, Lea T, Sandstad B, et al. Dietary supplementation with very long-chain n-3 fatty acids in man decreases expression of the interleukin-2 receptor (CD25) on mitogen-stimulated lymphocytes from patients with inflammatory skin disease. Eur J Clin Invest 1994;24:236 5. Ross E. The role of marine fish oil in the treatment of ulcerative colitis. Nutr Rev 1993;51:47 6. Alexander JW, Saito H, Ogle C, et al. The importance of lipid type in the diet after burn injury. Ann Surg 1986;204:1 7. Bligh EG, Dyer WJ. A rapid method of total lipid extraction and purification. Can J Biochem Physiol 1959;37:911
8. Misawa H, Mashima Y, Tashiro T, et al. Studies on intravenous administration of n-3 essential fatty acids in total parenteral nutrition. Jpn J Surg Metab Nutr 1991;25:167 9. Holman RT, Lohnson SB, Hatch TF. A case of human linolenic acid deficiency involving neurological abnormalities. Am J Clin Nutr 1982;35:617 10. Misawa H, Mashima Y, Tashiro T, et al. Serum fatty acid composition in essential fatty acid deficiency rats following intravenous administration of fat emulsion made from soybean oil and fish oil. Jpn J Surg Metab Nutr 1992;26:107 11. Hamazaki T, Urakaze M, Yano S, et al. Injection of tridocosahexaenoyl-glycerol emulsion and fatty acid composition of blood cells. Lipids 1987;22:1031 12. Holman RT. The ratio of trienoic-tetraenoic acids in tissue lipids as a measure of essential fatty acid requirement. J Nutr 1960;70:405 13. Hill R, Linazasoro JM, Chevallier F, et al. Regulation of hepatic lipogenesis: the influence of dietary fats. J Biol Chem 1958;233: 305
Nutrition Vol. 14, No. 4, 1998
Effects of a Newly Developed Fat Emulsion Containing Eicosapentaenoic Acid and Docosahexaenoic Acid on Fatty Acid Profiles in Rats TSUGUHIKO TASHIRO, MD, HIDEO YAMAMORI, MD, NAGANORI HAYASHI, MD, TOSHIYUKI SUGIURA, MD, KAZUYA TAKAGI, MD, KATSUNORI FURUKAWA, MD, NOBUYUKI NAKAJIMA, MD, ISAO ITOH, PHD,* TOSHIO WAKABAYASHI, PHD,† SETSUYA OHBA, PHD,† AND NORIKO AKAHANE, BPH From the *First Department of Surgery and Laboratory Animal Center, Chiba University Medical School, Chiba, and †Tsukuba Research Center, SANDOZ Pharmaceutical Co., Tsukuba, Japan Date accepted: 5 September 1997 ABSTRACT
A new fat emulsion of symmetrical triacylglycerols, containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was developed. The effects of this preparation on serum and liver fatty acid composition were investigated. Male Sprague-Dawley rats were fed a fat-free oral diet for 2 wk and were then divided into two groups. Seven rats were infused for 7 d with 1 mL of the new fat emulsion, which accounted for 1% of total caloric intake. The other 7 rats received saline. Both groups of rats received a fat-free diet during the infusion. EPA and DHA decreased to one third to one fifth of normal value after 2 wk on a fat-free diet. EPA and DHA of serum and liver remained at a low level in the control group throughout the study. But in the rats administered with the new fat emulsion, EPA and DHA increased rapidly and exceeded normal values in both serum and liver after 7 d of infusion. Decreased arachidonic acid with increased 20:3n-9 resulted in the rise of the triene/tetraene (T/T) ratio to greater than 0.4, indicating an n-6 essential fatty acid deficiency in the control rats. In the group administered the new fat emulsion, however, 20:3n-9 and total content of monounsaturated fatty acids decreased significantly, and the T/T ratio was less than than 0.4 in both serum and liver. In conclusion, the intravenous use of a newly developed fat emulsion containing EPA and DHA is useful in improving the EPA and DHA status of serum and liver without any harmful effects. Beneficial effects are expected in the modulation of inflammatory and stress response. Nutrition 1998;14:372–375. ©Elsevier Science Inc. 1998 Key words: n-3 and n-6 polyunsaturated fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), fatty acids composition, fat emulsion
INTRODUCTION
Since the epidemiologic studies of populations of coastal Eskimo subjects,1,2 dietary supplementation with n-3 fatty acids has been reported to improve various pathophysiologic states, such as cardiovascular diseases, rheumatoid arthritis,3 psoriasis,4 and inflammatory bowel disease.5 n-3 fatty acids have been revealed to modulate metabolic, inflammatory, and
immunological responses, and is expected for the management of critically ill patients.6 On the basis of these considerations, we have developed a novel lipid emulsion for intravenous use from a structured triacylglycerol containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The present study was undertaken to assess the effects of the new fat emulsion on fatty acid composition when administered intravenously to rats.
Correspondence to: Tsuguhiko Tashiro, MD, First Department of Surgery, Chiba University Medical School, 1-8-1, Inohana, Chuo-ku, Chiba-shi, Chiba-ken, 260, Japan.
Nutrition 14:372–375, 1998 ©Elsevier Science Inc. 1998 Printed in the USA. All rights reserved.
0899-9007/98/$19.00 PII S0899-9007(97)00491-7
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS
373
FIG. 2. Eicosapentaenoic acid (EPA) content in serum and liver. FIG. 1. Symmetrical structured triacylglycerol containing ecosapentanoeic acid (EPA) and docosahexaenoic acid (DHA).
MATERIALS AND METHODS
Lipid Emulsion A symmetrical triacylglycerol containing EPA at position 1 and 3 and DHA at position 2 was synthesized (Fig. 1). This triacylglycerol was emulsified by egg yolk lecithin in 2.5% glycerol solution. The purity of the EPA and DHA was more than 95%. The concentration of lipid in the emulsion was 10%. Animals and Experimental Procedures Male Sprague-Dawley rats (Tokyo Orient Co., Tokyo, Japan) weighing 100 –150 g were housed in an environmentally controlled, limited-access room that had a 12-h regulated light– dark cycle at an ambient temperature of 24 –26°C. Tap water and fat-free laboratory chow (Nihon Clea, Tokyo, Japan) were provided ad libitum to 14 rats for 2 wk prior to infusion of the lipid emulsion. Seven rats were infused with 1.0 mL of the new lipid emulsion for 7 d at 09:00 through the tail veins, with the process lasting more than 5 min (group N3, n 5 7). The other 7 rats were infused with the same amount of saline (group control, n 5 7). During the infusions, all rats were fed a fat-free chow. Blood was taken prior to infusion and on the third infusion day. Rats were killed by exanguination under ether anesthesia after 7 d of infusions. Serum was stored at 280°C. Approval to conduct the experiment was granted by the Animal Care Committee of the Chiba University School of Medicine in accordance with guidelines set forth by the Guide for the Care and Use of Laboratory Animals developed by the Institute of Laboratory Animal Resources of the National Research Council.
RESULTS
General Conditions of Animals All rats were healthy and active throughout the study. There was no difference in terms of food intake and body weight gain. Neither hematuria nor a hemorrhagic tendency was observed. Total Fatty Acid Composition of Serum and Liver As published previously,7 the serum levels of EPA in rats of the same age fed normal rat chow was 1.61 6 0.16%. In this experiment, EPA decreased to one third to one quarter of the normal value after 2 wk on a fat-free diet. EPA remained at a low level in the control group throughout the study. In the N3 group, EPA increased rapidly to 7.9 6 1.3% after 7 d of infusion of the new lipid emulsion. Elevation of EPA and DHA levels by administration of this new fat emulsion was also marked in the liver fatty acid composition. The EPA level in liver was 25.9 6 8.3% in the N3 group after 7 d of intravenous new fat emulsion, but it was almost 0 after 3 wk of the fat-free diet in the control group (Fig. 2). Serum DHA of rats fed a normal diet was 4.38 6 0.92%.8 DHA also decreased to one fifth of the normal value after 2 wk of a fat-free diet. In the control group, DHA continued to decrease. In the N3 group, the level of DHA improved to 5.0 6 0.7% after 7 d of infusion of the new lipid emulsion. The level of DHA also increased markedly in the liver to 11.5 6 1.0% after 7 d of intravenous new fat emulsion (Fig. 3).
Analytical Procedures Total lipids were extracted from serum and homogenized liver according to Bligh and Dyer.7 Methylation of the lipid fatty acids was performed by 20% BF3-Methanol. The methyl esters of the fatty acids were recovered and stored at 220°C. Samples were analyzed by gas chromatography (Hewlett Packard 5890 series II, Hewlett Packard, Palo Alto, CA, USA), which was programmed to separate methyl esters ranging from 12:0 to 22:6n-3 using helium as the carrier gas. The split ratio was 1/20 and the column (BPX-70, 25-m, 0.22-mm ID, 0.25-mm film thickness, SGE) and the flow was 12 mL/min. Identifications were made by comparisons with known methyl ester standards (Nu-Chek-Prep, Inc., Eleysian).
FIG. 3. Docosahexaenoic acid (DHA) content in serum and liver.
374
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS
FIG. 4. Arachidonic acid (AA) content in serum and liver. FIG. 6. Triene/tetraene ratio (T/T) in serum and liver.
Arachidonic acid decreased to one half of the normal value after 2 wk of a fat-free diet and continued to decrease gradually in both groups. In the liver, total fatty acid profile, arachidonic acid was lower in the N3 group when compared with the control group (Fig. 4). The novel fatty acid 20:3n-9, which cannot be detected in normal animals, increased significantly in both serum and the liver. The T/T ratio exceeded 0.4, indicating an n-6 essential fatty acid deficiency. In the N3 group, however, 20:3n-9 decreased significantly and the 20:3n-9/C20:4n-6 (T/T) ratio was less than 0.4 in both the serum and the liver (Figs. 5 and 6). The total content of monounsaturated fatty acids increased continuously in control rats, but it decreased significantly when administering the new lipid emulsion in both serum and the liver (Fig. 7). DISCUSSION
In 1982, Holman et al.9 reported a human linolenic acid deficiency involving neurologic abnormality after long-term total parenteral nutrition with safflower oil emulsion, which is rich in linoleic acid and low in a-linolenic acid, demonstrating the nutritional importance of n-3 polyunsaturated fatty acids (PUFA) in addition to n-6 PUFA. Since 1991, we have developed an intravenous fat emulsion containing soybean oil (85%) and fish oil (15%). We have observed safety measures and at the same time have attempted to improve the EPA and DHA status by intravenous administration of this solution not only to experimental animals but also to humans.8,10 For this purpose, we developed a
FIG. 5. 20:3n9 in serum and liver.
novel lipid emulsion from a structured triacylglycerol containing only EPA and DHA. Intravenous supplementation has several merits. Oral or enteral nutritional supplementation should sometimes be avoided due to the problems of alimentary tract or gut dysfunction in critically ill patients. A prompt effect of drugs is expected when they are administered intravenously.11 An intravenous preparation containing only EPA and DHA may be convenient in clinical practice for the following reasons. The total fat intake may be excessive in critically ill patients or patients with liver dysfunction when fish oil or a mixture of fish oil and soybean oil is used in an attempt to meet EPA or DHA requirements. Doses of EPA and DHA can be easily changed according to the pathophysiology and severity of the patient condition when a preparation containing only EPA and DHA is used. The present study was undertaken to assess the effects of a new fat emulsion on the composition of fatty acids when administered intravenously to the rats. The dose of lipid from the new fat emulsion was 100 mg/d, which accounted for 1% of the energy intake and is considered to be the optimal dose for rats. After administration of the new fat emulsion for 7 d, serum EPA and DHA increased rapidly and reached or exceeded normal values. Food intake and body weight gain were not influenced by the intravenous administration of new fat emul-
FIG. 7. Monounsaturated fatty acids in serum and liver.
EFFECTS OF NEW FAT EMULSION ON FATTY ACIDS sion. Thus, it was shown that rapid alteration of fatty acid composition without harmful effects could be obtained by the intravenous administration of this new preparation. In this experiment, no other fat component except for EPA and DHA was supplied. In mammals, 20:3n-9 is synthesized from oleic acid (18:1n-9) in the absence of n-6 essential fatty acids, and the ratio of the T/T ratio is an indicator of n-6 essential fatty acid deficiency.12 In this experiment, 20:3n-9 was shown to decrease significantly not by administering n-6 PUFA but with the n-3 PUFAs, EPA, and DHA. Supplementation of fatty acids, not specifically EPA and DHA, might have suppressed fatty acids synthesis in animals fed a fat-deprived diet13 as evidenced by significantly decreased levels of monounsaturated fatty acids. But the fact that the rate of decrease in 20:3n-9 was more than the increase in monounsaturated fatty acids may indicate the suppression of desaturase activity by EPA and DHA to produce 20:3n-9. Furthermore, decreased 20:3n-9 easily led to a decreased T/T ratio, less than 0.4. To evaluate whether this reduction of T/T ratio means the im-
375 provement of n-6 essential fatty acid deficiency, further investigation is necessary. In the past few years, particular attention has been given to the potential value of n-3 PUFA in critical illness, as evidenced by the improved metabolic and immunologic responses of burned guinea pigs fed an enteral regimen containing fish oil.6 The new fat emulsion containing only EPA and DHA is expected to have beneficial effects for the treatment of critical illness, such as extended burn injury, multiple trauma, sepsis, or organ failure. In conclusion, a newly developed symmetrical-triacylglycerol fat emulsion containing only EPA and DHA was infused without any harmful effects to the experimental animals. A rapid improvement of EPA and DHA status in serum and the liver tissue level was obtained by the intravenous infusion of this preparation. Reduced 20:3n9, together with a decreased T/T ratio, was also obtained. It is further expected that intravenous administration of this new fat emulsion may improve stress response and modulate the immune status of critically ill patients.
REFERENCES 1. Bang HO, Dyerberg J, Nielsen AB. Plasma lipid and lipoprotein pattern in Greenlandic west-coast Eskimos. Lancet 1971;1:1143 2. Kromann N, Green A. Epidemiologic studies in the Upernavic district, Greenland: incidence of some chronic diseases 1950 –1974. Acta Med Scand 1980;208:401 3. Kremer JM, Lawrence DA, Petrillo GF, et al. Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal antiinflammatory drugs: clinical and immune correlates. Arthritis Rheum 1995;38:1107 4. Soyland E, Lea T, Sandstad B, et al. Dietary supplementation with very long-chain n-3 fatty acids in man decreases expression of the interleukin-2 receptor (CD25) on mitogen-stimulated lymphocytes from patients with inflammatory skin disease. Eur J Clin Invest 1994;24:236 5. Ross E. The role of marine fish oil in the treatment of ulcerative colitis. Nutr Rev 1993;51:47 6. Alexander JW, Saito H, Ogle C, et al. The importance of lipid type in the diet after burn injury. Ann Surg 1986;204:1 7. Bligh EG, Dyer WJ. A rapid method of total lipid extraction and purification. Can J Biochem Physiol 1959;37:911
8. Misawa H, Mashima Y, Tashiro T, et al. Studies on intravenous administration of n-3 essential fatty acids in total parenteral nutrition. Jpn J Surg Metab Nutr 1991;25:167 9. Holman RT, Lohnson SB, Hatch TF. A case of human linolenic acid deficiency involving neurological abnormalities. Am J Clin Nutr 1982;35:617 10. Misawa H, Mashima Y, Tashiro T, et al. Serum fatty acid composition in essential fatty acid deficiency rats following intravenous administration of fat emulsion made from soybean oil and fish oil. Jpn J Surg Metab Nutr 1992;26:107 11. Hamazaki T, Urakaze M, Yano S, et al. Injection of tridocosahexaenoyl-glycerol emulsion and fatty acid composition of blood cells. Lipids 1987;22:1031 12. Holman RT. The ratio of trienoic-tetraenoic acids in tissue lipids as a measure of essential fatty acid requirement. J Nutr 1960;70:405 13. Hill R, Linazasoro JM, Chevallier F, et al. Regulation of hepatic lipogenesis: the influence of dietary fats. J Biol Chem 1958;233: 305