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Effect of an atherogenic diet on lipoprotein cholesterol profile in the F1B hybrid hamster
ATHEROSCLEROSIS
Atherosclerosis
103 (1993) 291-294
Letter to the Editors
Effect of an atherogenic diet on lipoprotein cholesterol profile in the FIB hybrid hamster E.A.M. de Deckere*, N.J. de Fouw, J. Ritskes-Hoitinga, C.G. Blonk
W.G.L. Van Nielen,
Vnilever Research Laboratorium Vlaardingen, Olivier van Noorrlaan 120, 3133 AT Vlaardingen, The Netherlands
(Received
6 April
1993; revision
received
13 July 1993; accepted
23 July 1993)
Key woruk: Lipoproteins; Cholesterol; Hamster
Dear Editors, The hamster is used as an animal model for human lipoprotein metabolism and atherogenesis. It occurred to us, however, that not all hamster strains respond to an atherogenic diet in a way corresponding to changes seen in man. The Lakeview hamster strain (Charles River) responds to an atherogenic diet with an increase in both low-density and high-density lipoprotein cholesterol concentration (LDL-chol, HDL-chol) [I]. The F,B hybrid Golden Syrian hamster (Bio Breeders Inc., Fitchburg, MA) is therefore an interesting strain as it has been reported by Kowala et al. [2] that this hamster responds to an atherogenic diet by an increase in LDL-chol without an appreciable effect on HDL-chol. The hamsters were fed Purina no. 5001 chow to which
* Corresponding author, Unilever Research Laboratorium Vlaardingen, P.O. Box 114, 3130 AC Vlaardingen, The Netherlands. Fax: (31) IO 460 5383. 0021-9150/93/$06.00 0 1993 Elsevier Scientific SSDI 002 I-91 50(93)05127-Q
Publishers
Ireland
0.05% (w/w) cholesterol and 10% coconut oil were added. After 8 weeks of feeding, HDL-chol had increased slightly (from 58 to 88 mg/dl) and LDL + VLDL-chol had increased strongly (from 58 to 234 mg/dl, mainly LDL-chol). In addition, fatty streaks were present in the aorta. Consequently, the FIB hybrid hamster may be a more suitable model for atherosclerosis in human than other hamster strains. For this reason we have tested this strain under our experimental conditions in an attempt to reproduce the findings of Kowala et al. [2]. Male hamsters of the FIB hybrid strain were obtained from Bio Breeders. At arrival, the hamsters were approximately 3 months old. They were acclimatised for 2 weeks during which they were fed a nonpurified diet (RMH-TM, Hope Farms, Woerden, The Netherlands). They were housed singly, and had free access to food and water. At the end of these 2 weeks, the animals were deprived of food for 18 h after which blood was collected by orbital puncture under ether Ltd. All rights reserved
292
E.A.M.
de Deckere
et al. /Atherosclerosis
103 (1993)
291-294
Table 1 Concentrations of serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-chol) and low-density lipoprotein cholesterol (LDL-chol) before (t = 0 weeks) and after 4 weeks of feeding either a non-atherogenic diet (diet I) or an atherogenic diet (diet 2) Diet
1 2
Separation of lipoprotein fraction?
TC (mgdl)
Apo B prec. UC Apo B prec. UC
139 ?? 4
t = 0
weeks
136 f 4
HDL-chol (mg!dL)
t = 4 weeks
t = 0
135 * 7* 138 175 f 6* 176
75 f 4 (54%)b
weeks
68 f 3 (SOY”)
t = 4 weeks 84 f 5* (62%) 85 (62%) 106 f 5* (61%) 109 (62%)
LDL-chol (mg/dL) t = 4 weeks
32 (23%) 39 (22%)
Mean values f S.E.M., n = 9 or pooled sample values. aHDL-chol was assayed in individual serum samples after precipitation of lipoproteins containing apo B (apo B prec.); HDL-chol and LDL-chol were assayed in pooled serum samples after separation of lipoproteins by density gradient ultracentrifugation (UC). bPercent of TC. ?? P < 0.01, Student’s t-test for unpaired data.
anaesthesia, and serum total cholesterol (TC) concentration (enzymatic method, Boehringer Mannheim Diagnostica, Mannheim, FRG) determined. The hamsters were then allocated to 2 groups (n = 9) with similar mean serum TC concentration (Table 1, t = 0 weeks) and mean body weight (103 f 5 g), and fed semipurified diets for 4 weeks. One group was fed a non-atherogenic diet (diet 1) and another group was fed an atherogenic diet (diet 2). Both diets contained calcium casein (D.M.V., Veghel, The Netherlands; 14.6 g/MJ, 23% of metabolizable energy (E%)), fat mixture (7.8 g/MJ (29 E%)), starch (Meritena A, N.V. Honig’s Artikelen, Koog a/d Zaan, The Netherlands; 35.2 g/MJ (48 E%)), cellulose (MacheryNagel GmbH, Dtiren-Riilsdorf, FRG; 3.6 g/MJ), mineral mix 0.86 g/MJ [3], vitamin mix 0.2 g/MJ [3]. The non-atherogenic diet contained a fat mixture of sunflowerseed oil (Union N.V., Merksem, Belgium), cocoa butter (Chempri B.V., Raamsdonkveer, The Netherlands), lard (Smilde B.V., Heerenveen, The Netherlands) and hardened coconut oil (Chempri B.V.) with a polyunsaturated fatty acids (P) to saturated fatty acids (S) ratio of 1.42. The P/S ratio of the fat mixture in the atherogenic diet was 0.12. To the atherogenic diet 0.063 g/MJ (0.1% w/w) cholesterol (Merck, Darmstadt, FRG) was added. Before and after feeding
the experimental diets, serum TC concentrations and HDL-chol were determined by using orbital sinus blood. HDL-chol was assayed after lipoproteins containing apo B were precipitated from serum by the phosphotungstate method (Biomerieux, Charbonnieres-les-Bains, France) [4]. In addition, after the experimental feeding period, serum TC concentrations and LDL-chol and HDL-chol were determined in pooled samples. The lipoproteins were separated by density gradient ultracentrifugation [5]. Feeding the atherogenic diet, in comparison with feeding the non-atherogenic diet, increased serum TC concentration by approximately 40 mg/dl, HDL-chol by approximately 22 mg/dl and LDL-chol by approximately 7 mg/dl (Table 1). Thus, under our experimental conditions the FIB hybrid hamster strain responds to an atherogenic diet similar to other hamster strains, namely a small rise in LDL-chol and a large rise in HDLchol. These results are in contradiction to the results reported by Kowala et al. [2]. The reason for this discrepancy in results is not clear. References I
Hayes, K.C., Khosla, P., Kaiser, A., Yeghiazarians, V. and Pronczuk, A., Dietary fat and cholesterol modulate
E.A.M.
de Deckere et al. /Atherosclerosis
IO3 (1993) 291-294
293
the plasma lipoprotein distribution and production of pigment or cholesterol gallstones in hamsters, J. Nutr., 122 (1992) 374. Kowala, MC., Nunnari, J.J., Durham, S.K. and Nicolosi, R.J., Doxazosin and cholestyramine similarly decrease fatty streak formation in the aotic arch of hyperlipidemic hamsters, Atherosclerosis, 91 (1991) 35. De Deckere, E.A.M., Jansen-Verplanke, C., Blank, C.G. and Van Nielen, W.G.L., Effects of type and amount of
4
5
*
dietary fat on rabbit and rat lymphocyte proliferation in vitro, J. Nutr., 118 (1988) 11. Weingand, K.W. and Daggy, B.P., Quantification of highdensity-lipoprotein cholesterol in plasma from hamsters by differential precipitation, Clin. Chem., 36 (1990) 575. Redgrave, T.G., Roberts, D.C.K. and West, C.E., Separation of plasma lipoproteins by density-gradient ultracentrifugation, Anal. B&hem., 65 (1975) 42.
* *
Reply Mark C. Kowala Department
of Pharmacology,
Room Fl.4801,
Bristol-Myers Squibb Pharmaceutical NJ, 08543-4000 USA
Research Institute,
P.O. Box 4000 Princeton
(Received 15 June 1993; revision received 1993; accepted 23 July 1993)
Dear Editors,
In response to the letter of de Deckere et al.: I recently published a study where FIB hamsters were fed chow enriched with 0.05% cholesterol and
10% coconut oil. After several weeks, there was an elevation of plasma low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterol which induced early atherosclerosis in the aortic arch [ 11. Other investigators demonstrated
Table I Plasma lipids in male FIB hamsters fed various diets for 3 weeks” Total cholesterol mg/dl
LDL + VLDL cholesterol mg/dl 57 f 3
HDL cholesterol mg/dl
Total triglycerides mg/dl
52 f 3
132 f 19
Chow
109 f 4
Chow + 0.05% cholesterol 10% coconut oil
192 zt l7*
132 f 17*
60 zt2
417 f 55*
Semipuritied diet + 0.1% cholesterol 10% coconut oil
195 f 14’
121 f 9*
74 f 7*
344 f 47*
Values are mean f S.E.M. Hamsters were 15 weeks old at the start of the study. “Methods for the measurement of plasma lipids are in Kowala et al. [I]. *P < 0.009 compared to the chow group (Mann-Whitney U-test).
Atherosclerosis
103 (1993) 291-294
Letter to the Editors
Effect of an atherogenic diet on lipoprotein cholesterol profile in the FIB hybrid hamster E.A.M. de Deckere*, N.J. de Fouw, J. Ritskes-Hoitinga, C.G. Blonk
W.G.L. Van Nielen,
Vnilever Research Laboratorium Vlaardingen, Olivier van Noorrlaan 120, 3133 AT Vlaardingen, The Netherlands
(Received
6 April
1993; revision
received
13 July 1993; accepted
23 July 1993)
Key woruk: Lipoproteins; Cholesterol; Hamster
Dear Editors, The hamster is used as an animal model for human lipoprotein metabolism and atherogenesis. It occurred to us, however, that not all hamster strains respond to an atherogenic diet in a way corresponding to changes seen in man. The Lakeview hamster strain (Charles River) responds to an atherogenic diet with an increase in both low-density and high-density lipoprotein cholesterol concentration (LDL-chol, HDL-chol) [I]. The F,B hybrid Golden Syrian hamster (Bio Breeders Inc., Fitchburg, MA) is therefore an interesting strain as it has been reported by Kowala et al. [2] that this hamster responds to an atherogenic diet by an increase in LDL-chol without an appreciable effect on HDL-chol. The hamsters were fed Purina no. 5001 chow to which
* Corresponding author, Unilever Research Laboratorium Vlaardingen, P.O. Box 114, 3130 AC Vlaardingen, The Netherlands. Fax: (31) IO 460 5383. 0021-9150/93/$06.00 0 1993 Elsevier Scientific SSDI 002 I-91 50(93)05127-Q
Publishers
Ireland
0.05% (w/w) cholesterol and 10% coconut oil were added. After 8 weeks of feeding, HDL-chol had increased slightly (from 58 to 88 mg/dl) and LDL + VLDL-chol had increased strongly (from 58 to 234 mg/dl, mainly LDL-chol). In addition, fatty streaks were present in the aorta. Consequently, the FIB hybrid hamster may be a more suitable model for atherosclerosis in human than other hamster strains. For this reason we have tested this strain under our experimental conditions in an attempt to reproduce the findings of Kowala et al. [2]. Male hamsters of the FIB hybrid strain were obtained from Bio Breeders. At arrival, the hamsters were approximately 3 months old. They were acclimatised for 2 weeks during which they were fed a nonpurified diet (RMH-TM, Hope Farms, Woerden, The Netherlands). They were housed singly, and had free access to food and water. At the end of these 2 weeks, the animals were deprived of food for 18 h after which blood was collected by orbital puncture under ether Ltd. All rights reserved
292
E.A.M.
de Deckere
et al. /Atherosclerosis
103 (1993)
291-294
Table 1 Concentrations of serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-chol) and low-density lipoprotein cholesterol (LDL-chol) before (t = 0 weeks) and after 4 weeks of feeding either a non-atherogenic diet (diet I) or an atherogenic diet (diet 2) Diet
1 2
Separation of lipoprotein fraction?
TC (mgdl)
Apo B prec. UC Apo B prec. UC
139 ?? 4
t = 0
weeks
136 f 4
HDL-chol (mg!dL)
t = 4 weeks
t = 0
135 * 7* 138 175 f 6* 176
75 f 4 (54%)b
weeks
68 f 3 (SOY”)
t = 4 weeks 84 f 5* (62%) 85 (62%) 106 f 5* (61%) 109 (62%)
LDL-chol (mg/dL) t = 4 weeks
32 (23%) 39 (22%)
Mean values f S.E.M., n = 9 or pooled sample values. aHDL-chol was assayed in individual serum samples after precipitation of lipoproteins containing apo B (apo B prec.); HDL-chol and LDL-chol were assayed in pooled serum samples after separation of lipoproteins by density gradient ultracentrifugation (UC). bPercent of TC. ?? P < 0.01, Student’s t-test for unpaired data.
anaesthesia, and serum total cholesterol (TC) concentration (enzymatic method, Boehringer Mannheim Diagnostica, Mannheim, FRG) determined. The hamsters were then allocated to 2 groups (n = 9) with similar mean serum TC concentration (Table 1, t = 0 weeks) and mean body weight (103 f 5 g), and fed semipurified diets for 4 weeks. One group was fed a non-atherogenic diet (diet 1) and another group was fed an atherogenic diet (diet 2). Both diets contained calcium casein (D.M.V., Veghel, The Netherlands; 14.6 g/MJ, 23% of metabolizable energy (E%)), fat mixture (7.8 g/MJ (29 E%)), starch (Meritena A, N.V. Honig’s Artikelen, Koog a/d Zaan, The Netherlands; 35.2 g/MJ (48 E%)), cellulose (MacheryNagel GmbH, Dtiren-Riilsdorf, FRG; 3.6 g/MJ), mineral mix 0.86 g/MJ [3], vitamin mix 0.2 g/MJ [3]. The non-atherogenic diet contained a fat mixture of sunflowerseed oil (Union N.V., Merksem, Belgium), cocoa butter (Chempri B.V., Raamsdonkveer, The Netherlands), lard (Smilde B.V., Heerenveen, The Netherlands) and hardened coconut oil (Chempri B.V.) with a polyunsaturated fatty acids (P) to saturated fatty acids (S) ratio of 1.42. The P/S ratio of the fat mixture in the atherogenic diet was 0.12. To the atherogenic diet 0.063 g/MJ (0.1% w/w) cholesterol (Merck, Darmstadt, FRG) was added. Before and after feeding
the experimental diets, serum TC concentrations and HDL-chol were determined by using orbital sinus blood. HDL-chol was assayed after lipoproteins containing apo B were precipitated from serum by the phosphotungstate method (Biomerieux, Charbonnieres-les-Bains, France) [4]. In addition, after the experimental feeding period, serum TC concentrations and LDL-chol and HDL-chol were determined in pooled samples. The lipoproteins were separated by density gradient ultracentrifugation [5]. Feeding the atherogenic diet, in comparison with feeding the non-atherogenic diet, increased serum TC concentration by approximately 40 mg/dl, HDL-chol by approximately 22 mg/dl and LDL-chol by approximately 7 mg/dl (Table 1). Thus, under our experimental conditions the FIB hybrid hamster strain responds to an atherogenic diet similar to other hamster strains, namely a small rise in LDL-chol and a large rise in HDLchol. These results are in contradiction to the results reported by Kowala et al. [2]. The reason for this discrepancy in results is not clear. References I
Hayes, K.C., Khosla, P., Kaiser, A., Yeghiazarians, V. and Pronczuk, A., Dietary fat and cholesterol modulate
E.A.M.
de Deckere et al. /Atherosclerosis
IO3 (1993) 291-294
293
the plasma lipoprotein distribution and production of pigment or cholesterol gallstones in hamsters, J. Nutr., 122 (1992) 374. Kowala, MC., Nunnari, J.J., Durham, S.K. and Nicolosi, R.J., Doxazosin and cholestyramine similarly decrease fatty streak formation in the aotic arch of hyperlipidemic hamsters, Atherosclerosis, 91 (1991) 35. De Deckere, E.A.M., Jansen-Verplanke, C., Blank, C.G. and Van Nielen, W.G.L., Effects of type and amount of
4
5
*
dietary fat on rabbit and rat lymphocyte proliferation in vitro, J. Nutr., 118 (1988) 11. Weingand, K.W. and Daggy, B.P., Quantification of highdensity-lipoprotein cholesterol in plasma from hamsters by differential precipitation, Clin. Chem., 36 (1990) 575. Redgrave, T.G., Roberts, D.C.K. and West, C.E., Separation of plasma lipoproteins by density-gradient ultracentrifugation, Anal. B&hem., 65 (1975) 42.
* *
Reply Mark C. Kowala Department
of Pharmacology,
Room Fl.4801,
Bristol-Myers Squibb Pharmaceutical NJ, 08543-4000 USA
Research Institute,
P.O. Box 4000 Princeton
(Received 15 June 1993; revision received 1993; accepted 23 July 1993)
Dear Editors,
In response to the letter of de Deckere et al.: I recently published a study where FIB hamsters were fed chow enriched with 0.05% cholesterol and
10% coconut oil. After several weeks, there was an elevation of plasma low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterol which induced early atherosclerosis in the aortic arch [ 11. Other investigators demonstrated
Table I Plasma lipids in male FIB hamsters fed various diets for 3 weeks” Total cholesterol mg/dl
LDL + VLDL cholesterol mg/dl 57 f 3
HDL cholesterol mg/dl
Total triglycerides mg/dl
52 f 3
132 f 19
Chow
109 f 4
Chow + 0.05% cholesterol 10% coconut oil
192 zt l7*
132 f 17*
60 zt2
417 f 55*
Semipuritied diet + 0.1% cholesterol 10% coconut oil
195 f 14’
121 f 9*
74 f 7*
344 f 47*
Values are mean f S.E.M. Hamsters were 15 weeks old at the start of the study. “Methods for the measurement of plasma lipids are in Kowala et al. [I]. *P < 0.009 compared to the chow group (Mann-Whitney U-test).