A Simplified Intravenous Fat Emulsion. Nagahiko SAKUMA,1,* Yasuhiro HASEGAWA,2 Reiko IKEUCHI,1 Rin CUI,1 Takayoshi ICHIKAWA,1 and Takao FUJINAMII

Size: px

Start display at page:

Download "A Simplified Intravenous Fat Emulsion. Nagahiko SAKUMA,1,* Yasuhiro HASEGAWA,2 Reiko IKEUCHI,1 Rin CUI,1 Takayoshi ICHIKAWA,1 and Takao FUJINAMII"

Alvin Quinn
5 years ago
Views:

1 J. Clin. Biochem. Nutr., 3, , 1987 A Simplified Intravenous Fat Emulsion Tolerance Test Nagahiko SAKUMA,1,* Yasuhiro HASEGAWA,2 Reiko IKEUCHI,1 Rin CUI,1 Takayoshi ICHIKAWA,1 and Takao FUJINAMII Third Department of Internal Medicine, and Department of Physiology, Nagoya City University Medical School, Nagoya 467, Japan (Received April 27, 1987) Summary We developed a simplified intravenous fat emulsion tolerance test (FETT) by administering 0.25 ml/kg body weight of Intralipid (R) 10% fat emulsion in order to study the pathogenesis of hyperlipidemia. The fractional removal rate (K2) of fat emulsion was determined by nephelometry. FETT was performed on male and female normolipidemic subjects and on patients who had primary and secondary hyperlipidemia (except types I and V of W.I.O. classification). The K2 value of normolipidemic subjects ranged from 4.0 to 27.6 % /min, with a mean value of 11.5 ±4.7 (SD) %/min, (n=77). The K2 value of hyperlipidemic patients ranged from 1.8 to 18.6 %/min, and the mean value was 8.2 ± 3.3 (SD) %/min, (n =150). Compared with the data in the literature, the values and range of K2 by this simplified FETT were higher and greater, respectively, than those obtained by the earlier method of administering a higher loading dose such as 1 ml/kg body weight of Intralipid (R) 10% fat emulsion. Good reliability and high reproducibility of K2 by the present FETT were also demonstrated. We suggest that the simplified FETT is a good tool for the study of hyperlipidemia and lipid metabolism. Key Words. intravenous fat emulsion tolerance test, removal rate of fat emulsion, hyperlipidemia Hyperlipidemia has been cited as a risk factor in coronary heart disease [1]. The treatment of hyperlipidemia is important in the prevention of coronary artery sclerosis. A full understanding of a patient's pathologic state is necessary to treat hyperlipidemia effectively. It is desirable to apply a test to assess the patient's pathologic state and the effects of diet, drug treatments, physical training, etc. *To whom correspondence should be addressed. 251

2 252 N. SAKUMA et al. on the metabolism of serum lipids. For this reason, Lewis et al. had developed intravenous fat tolerance test [2]. Their method uses fat emulsion Intralipid (Vitrum AB, Stockholm), which is similar to chylomicrons in chemical composition and in mode of catabolism in the early stage in the blood after intravenous administration, as a tracer [3]. From the fractional removal rate of fat emulsion obtained in this test, the metabolism of triglyceride rich lipoprotein (chylomicrons, very low density lipoprotein) can be indirectly determined [4, 5]. However, the quantity of fat emulsion loaded in their method is so large (1 ml/kg body weight) and it takes long time (40 min) to complete the test. Therefore, we developed a simplified fat emulsion tolerance test (FETT) to reduce the quantity of fat emulsion to be loaded and shorten the test time [6]. In the present study, we investigated the value and range of the fractional removal rate (K2) of fat emulsion obtained by the simplified FETT in normolipidemic subjects and hyperlipidemic patients. The reliability and reproducibility of K2 obtained by this method were also assessed. MATERIALS AND METHODS Subjects. Two hundred twenty-seven subjects were used in the study, including male and female normolipidemic subjects and patients with primary and secondary hyperlipidemia (except types I and V of WHO. classification) [7]. The age of the 50 male and 27 female normolipidemic subjects ranged from 20 to 76 years, with the mean age of 39.8± 15.1 (SD) years. Their body weight index (weight (kg)/height (cm)- 100) ranged between 0.73 and 1.57 (mean ± SD, 0.96± 0.18; n =77). The ages of the 92 male and 58 female hyperlipidemic patients ranged from 19 to 76 years, with the mean age of (SD) years. Their body weight index ranged between 0.74 and 1.77 (1.04 ± 0.18; n =150). FETT. Subjects were kept at rest in a supine position after fasting for 14 h. A winged needle with a polyethylene cannula filled with physiological saline solution was inserted into an antebrachial veins on each arm, one for blood sampling and the other for intravenous injection. Before fat loading, blood sample was drawn and then Intralipid 10% emulsion at 0.25 ml per kg body weight was injected intravenously over 90-s periods. The midpoint of intravenous injection, 45 s, was taken as time zero and thereafter blood samples were drawn at 5, 7, 9, 11, 14, 17, and 20 min. Each blood sample was centrifuged at 4 C and 1,800 x g for 30 min to separate the serum. Serum obtained at each time was divided in half, each sample of which was diluted 100-fold with physiological saline solution. The light scattering index (LSI) was then determined by a nephelometer (Nephelotek DN 2110, Kyoto Daiichi Kagaku, Kyoto) to obtain the mean value. The wavelength of this nephelometer is 610 nm or greater. The LSI is expressed in terms of the specially made optical glass standard equipped with this instrument. Using the logarithmic value of the mean LSI of samples at each time minus the mean LSI of samples before fat emulsion loading, we calculated the regression coefficient J. Clin. Biochem. Nutr.

3 FAT EMULSION TOLERANCE TEST 253 (- b) of a successively declining curve of LSI by the method of least squares. The fractional removal rate (K2) of fat emulsion (10% Intralipid ) is expressed as b. As an index of the reliability of b, the t value is obtained from b/sb, where Sb is the standard error of b [8]. To study the reproducibility of K2, twenty-one subjects were selected randomly from among all 227 subjects. FETT was performed at 1-week intervals under a constant daily total food calorie intake to compare K2 obtained in the first FETT with K2 obtained in the second FETT. RESULTS The K2 value of normolipidemic subjects ranged from 4.0 to 27.6 //min, with a mean value of I- 4.7 (SD) %/min, (11=77). The K2 value of hyperlipid- Fig. 1. Fractional removal rate (K2) of normolipidemic subjects and hyperlipidemic patients. Each data point represents one case. The horizontal lines indicate the mean + SD. Fig. 2. Frequency distribution of Student's t value of K2 elimination (b / Sb) obtained by intravenous fat emulsion tolerance test (FETT) in 227 subjects. Vol. 3, No. 3, 1987

4 254 N. SAKUMA et al. Fig. 3. Correlation coefficient between K2 in the first and second FETT. Correlation coefficient : 0.85 (p <0.001). emic patients ranged from L8 to 18.6 %/min, with a mean value of 8.2± 3.3 (SD) /min, (n=150) (Fig. 1). The t value of K2 obtained by FETT in all 227 cases ranged from 5 to 72 (Fig. 2). K2 obtained in the first FETT correlated significantly with K2 obtained in the second FETT (r =0.8 5, p <0.001, n =21, Fig. 3). DISCUSSION Intralipid and chylomicrons have similar enzyme kinetic behavior when incubated in vitro [9], and the kinetics for elimination of Intralipid from blood are identical to those of chylomicrons [3]. These findings together with studies demonstrating that the K2 value of earlier intravenous fat tolerance test is well correlated with the fractional removal rates of triglyceride or apolipoprotein B of very low density lipoprotein [4, 5], indicate that Intralipid can be used as a model emulsion in the study of triglyceride metabolism. To design an intravenous FETT that is readily usable clinically, it is desirable to reduce the quantity of emulsion to be loaded to prevent such side effects as nausea, vomiting, chest oppression, etc., caused by rapid intravenous injection. Since the dose of fat emulsion was low in our simplified FETT, there was no side effect caused by rapid intravenous injection in any subject in the present study. Hallberg stated that, when fat emulsion (Intralipid ) is administered intravenously to a man or dog, zero-order kinetics are present in which fat emulsion disappears linearly from the blood at more than a certain concentration (critical concentration) [3]. The same author defined the slope as the maximal removal rate, expressed as Kl (mmol/liter of plasma/min). Further, below the critical concentration (C), fat emulsion decreased rapidly, approximately linearly on a semilogarithmic scale, and from the slope the fractional removal rate, K2 (%/min), J. Clin. Biochem. Nutr.

$We reported earlier that the fractional removal rate of fat emulsion increased if the fat emulsion dose was decreased below the critical concentration [6].$

5 FAT EMULSION TOLERANCE TEST 255 was calculated. A relational formula K1 =K2 C has been proposed. We reported earlier that the fractional removal rate of fat emulsion increased if the fat emulsion dose was decreased below the critical concentration [6]. In our previous study, the fractional removal rate of fat emulsion by administration of Intralipid 10 emulsion at 0.25 ml per kg body weight (mean + SD, //min) was significantly higher than by administering Intralipid 10% emulsion at 1 ml per kg body weight (4.4± 1.8 %/min) to the same 15 subjects [6]. In the present study, the K2 (mean -I- SD; 11.5±4.7 //min, n=77) of normolipidemic subjects by the simplified FETT was higher than the level (mean + SD; 4.4±2.0 //min, n=35) reported by Ericsson and Rossner, who used a larger amount of fat emulsion for the loading (1 ml of 10% Intralipid /kg body weight) [10]. Also, K2 value by the present FETT of hyperlipidemic patients was higher than with the earlier method [4]. When fat emulsion Intralipid enters the circulation, it does not contain the small molecular weight apolipoprotein C, among which apo C-II is probably the sole activator of lipoprotein lipase [11], which hydrolyzes circulating triglyceride. Havel et a!. demonstrated that Intralipid acquires C-peptides from HDL, and thereby becomes a suitable substrate for lipoprotein lipase [12]. Ultra-histochemical studies have shown that, as is the case with chylomicrons, the triglyceride of Intralipid is hydrolyzed at the surface of endotherial cells in capillaries [13, 14]. Weinberg and Scanu indicated that Intralipid exhibits in vitro the net transfer of cholesterol esters from HDL to Intralipid, with reciprocal net transfer of triglyceride to HDL [15]. It is supposed that as the present FETT uses a smaller amount of fat emulsion than that of earlier method, it takes shorter time for fat emulsion administered in FETT to be catabolized in bloodstream by the abovementioned reaction [12-15]. It seems likely that this yields a larger K2 of the present FETT (the range of K2, /min) as compared with the earlier method ( //min) [4]. It is supposed that the greater range in K2 values yielded by this FETT serves better to distinguish patients with a different pathogenesis of hyperlipidemia. Since the time constant of the decay curve of LSI in FETT is small, the rate of decrease of fat emulsion can be fully investigated over an examination time of 20 min. The reliability of K2 can be determined from the t value. If the t value of K2 is greater than 5, it is estimated that the confidence interval of K2 is small. The t value of K2 was distributed between 5 and 72. This high t value indicates the high reliability of K2. The high correlation coefficient of 0.85 (p <0.001) between K2 In the first and the second FETT corroborates the high reproducibility of K2 (Fig. 3). Because of this good reproducibility, FETT can be readily used to study the effects of diet and drug treatments, physical training, etc. on the metabolism of serum lipids. The authors are indebted to Dr. John J. Albers, Research Professor of Medicine, University of Washington School of Medicine, U.S.A., for his review of manuscript. Vol. 3, No. 3, 1987

6 256 N. SAKUMA et al. REFERENCES 1. Lippel, K., Tyroler, H., Eder, H., Gotto, A., Jr., and Vahouny, G. (1981) : Relationship of hypertriglyceridemia to atherosclerosis. Arteriosclerosis, 1, Lewis, B., Boberg, J., Mancini, M., and Carlson, L.A. (1972): Determination of the intravenous fat tolerance test with Intralipid (R) by Nephelometry. Atherosclerosis, 15, Hallberg, D. (1964) : On the kinetics of the elimination of intravenous fat emulsion from the blood stream in dog and man. Nutr. Dieta., 6, Rossner, S. (1974) : Studies on an intravenous fat tolerance test : methodological, experimental and clinical experiences with intralipid. Acta Med. Scand. Suppl., 564, Nicoll, A., Sigurdsson, G., March, A., and Lewis, B. (1977) : Intraveous fat tolerance, correlation with very low density lipoprotein apoprotein B kinetics in man. Atherosclerosis, 26, Sakuma, N., Tabe, R., Ichikawa, T., Lin, C., Kawaguchi, M., Hasegawa, Y., Hokama, M., and Fujinami, T. (1985) : Study on a simplified fat emulsion tolerance test-influence of administered amount of fat emulsion on fractional removal rate. J. Jpn. Atheroscler. Soc., 13, Beaumont, J.L., Carlson, L.A., Cooper, G.R., Fej ar, Z., Fredrickson, D.S., and Strasser, T. (1970) : Classification of hyperlipidaemias and hyperlipoproteinaemias. Bull. WHO., 43, Snedector, G.S., and Cochran, W.G. (1967): Statistical Methods, 6th ed., The Iowa State University Press, Iowa. 9. Boberg, J., and Carlson, L.A. (1964) : Determination of heparin-induced lipoprotein lipase activity in human plasma. Clin. Chim. Acta, 10, Ericsson, M., and Rossner, S. (1979) : Correlations between intravenous fat tolerance and serum lipoproteins in normal and atherosclerotic subjects. Atherosclerosis, 33, Havel, R.J., Fielding, C.J., Olivecrona, T., Shore, V.G., Fielding, P.E., and Egelrud, T. (1973) : Cofactor activity of protein components of human very low density lipoproteins in the hydrolysis of triglycerides by lipoprotein lipase from different sources. Biochemistry, 12, Havel, R.J., Kane, J.P., and Kashyap, M.L. (1973) : Interchange of apoproteins between chylomicrons and high density lipoproteins during alimentary lipemia in man. J. Clin. Invest., 52, Scow, R.O., Hamosch, M., Blanchette-Mackie, E.J., and Evans, A.J. (1972) : Uptake of blood triglyceride by various tissues. Lipids, 7, Blanchette-Mackie, E.J., and Scow, R.O. (1971) : Sites of lipoprotein lipase activity in adipose tissue perfused with chylomicrons. Electron microscope cytochemical study. J. Cell Biol., 51, Weinberg, R.B., and Scanu, A.M. (1982): In vitro reciprocal exchange of apoprotein and nonpolar lipids between human high density lipoproteins and artificial triglyceride-phospholipids emulsion (intralipid). Atherosclerosis, 44, J. Clin. Biochem. Nutr.

Kinetics of an Intravenously Injected Fat Emulsion Reflect Postheparin Plasma Lipoprotein Lipase Mass and Activity

J. Clin. Biochem. Nut:, 31, 37-43, 2002 Kinetics of an Intravenously Injected Fat Emulsion Reflect Postheparin Plasma Lipoprotein Lipase Mass and Activity Nagahiko SAKUMA,* Reiko IKEUCHI, Takeshi HIBINO,