DIETARY FISH OIL AND EXPERIMENTAL ATHEROSCLEROSIS DIETARY FISH OIL AND EXPERIMENTAL ATHEROSCLEROSIS Visolie consumptie en experimentele atherosclerose Proefschrift Ter verkrijging van de graad van doctor aan de Erasmus Universiteit Rotterdam op gezag van de rector magnificus Prof. Dr. A.H.G. Rinnooy Kan en volgens besluit van het College van Dekanen De openbare verdediging zal plaats vinden op donderdag 8 juni 1989 om 13.30 uur Johannes Matthijs IJartog geboren te Rotterdam PROMOTIECOMMISSIE PROMOTOREN: Prof. P.G. Hugenholtz Prof. Dr. W.C. Hiilsmann OVERIGE LEDEN: Dr. P.D. Verdouw Dr. J.M.J. Lamers The financial support by the Netherlands Heart Foundation for the publication of this thesis is gratefully acknowledged. Aan mijn vrouw Marie Louise en dochter Suzanne CONTENTS Chapter 1 N-3 polyunsaturated fatty aci!:ls, a literature review 1.1 introduction 1 1.2 cardiovascular effects of dietary n-3 fatty acids 2 1.2.1 the effects of dietary n-3 fatty acids on plasma cholesterol 2 1.2.2 the effects of dietary n-3 fatty acids on plasma triglyceride 6 1.2.3 the effects of dietary n-3 fatty acids on membrane lipid composition 6 1.2.4 the effects of dietary n-3 fatty acids on prostaglandin synthesis 10 1.2.5 the effects of dietary n-3 fatty acids on platelet function 13 1.2.6 the effects of dietary n-3 fatty acids on hemorheology 15 1.2.7 the effects of dietary n-3 fatty acids on hemostasis 15 1.2.8 the effects of dietary n-3 fatty acids on arterial blood pressure 16 1.2.9 the effects of dietary n-3 fatty acids on thrombosis, atherosclerosis and ischemia 16 1.3 adverse effects of dietary n-3 fatty acids 17 Chapter 2 Study objectives 2.1 introduction 29 2.2 chapter outline 29 Chapter 3 Dietary fatty acids and myocardial function J.M.J. Lamers, J.M. Hartog, P.D. Verdouw, W.C. Hiilsmann. Bas. Res. Cardiol. 82(S1): 209-221, 1987. 31 Chapter 4 Comparison of mackerel-oil and lard-fat enriched diets on plasmalipids, cardiac membrane phospholipids, cardiovascular performance, and morphology in young pigs. J.M. Hartog, J.M.J. Lamers, A. Montfoort, A.E. Becker, M. Klompe, H. Morse, L. van der Werf, W.C. Hiilsmann, P.G. Hugenholtz, P.D. Verdouw. Am. J. Clin. Nutr. 46: 258-266, 1987. 45 Chapter 5 Dietary mackerel oil in pigs: Effect on plasmalipids, cardiac sarcolemmal phospholi­ pids and cardiovascular parameters. J.M. Hartog, P.D. Verdouw, M. Klompe, J.M.J. Lamers. J. Nutr. 117, 1371-1378, 1987. 55 Chapter 6 The effects of diets supplemented with lard fat or mackerel oil on plasma lipoprotein lipid concentrations in domestic swine. P.H.E. Groot, J.M. Hartog, M.L. Dubelaar, L.M. Scheek, P.D. Verdouw, J.M.J. Lamers. Atherosclerosis (in press). 63 Chapter 7 The influence of fish oil diet and norepinephrine treatment on fatty acid composition of rat heart phospholipids and the positional fatty acid distribution in phosphatidylethanolamine. A. Montfoort, L. van der Werf, J.M. Hartog, P.G. Hugenholtz, P.D. Verdouw, W.C. HU!smann, J.M.J. Lamers. Basic Res. Cardiol. 81: 289-302, 1986. 71 Chapter 8 The effects of dietary mackerel oil on plasma and cell membrane lipids, on hemo­ dynamics and cardiac arrhythmias during recurrent acute ischemia in the pig. J.M. Hartog, J.MJ. Lamers, P.D. Verdouw. Basic Res. Cardiol. 81: 567-580, 1986. 85 Chapter 9 The effects of dietary mackerel oil on the recovery of cardiac function after acute ischaemic events in the pig. J.M. Hartog, J.M.J. Lamers, P.W. Achterberg, D. van Heuven-Nolsen, F.P. Nijkamp, P.D. Verdouw. Basic Res. Cardiol. 82(S1): 223·234, 1987. 99 Chapter 10 Lipid peroxidation in the normoxic and ischaemic-reperfused heart: A comparative study of fish oil and lard fat fed pigs. J.M.J. Lamers, J.M. Hartog, C. Guarnieri, I. Vaona, P.D. Verdouw, J.F. Koster. J. Mol. Cell. Cardiol. 20: 605-615, 1988. 111 Chapter 11 Does platelet aggregation play a role in the reduction in localized intimal proli­ feration in normolipidemic pigs with a fixed coronary artery stenosis fed dietary fish oil? J.M. Hartog, J.M.J. Lamers, C.E. Essed, W.P. Schalkwijk, P.D. Verdouw. Atherosclerosis 76: 79-88, 1989. 123 Chapter 12 Atherosclerosis, a literature review 12.1 historical notes 133 12.2 risk factors 133 12.3 current views of the pathogenesis of atherosclerosis 134 12.4 possible effects of dietary n-3 PUFA's on atherosclerosis 136 12.5 induction and regression of experimental atherosclerosis 136 12.6 quantification of atherosclerosis 139 Chapter 13 Mackerel oil and atherosclerosis in pigs L.M.A. Sassen, J.M. Hartog, J.M.J. Lamers, M. Klompe, L.J. van Woerkens, P.D. Verdouw. Eur. Heart J. (in press). 147 Chapter 14 Epicrisis 163 Samenvatting 173 Dankwoord 175 Curriculum Vitae 177 List of publications 179 I j j j j j j j j j j j j j j j j j j j j j j j j j j j j j j CHAPTER 1 N-3 POLYUNSATURATED FATTY ACIDS, A LITERATURE REVIEW 1.1 Introduction In the last decades the interest in the role of n-3 fatty acids in several diseases has grown. Low incidences of ischemic heart disease, diabetes, cancer, rheumatism and multiple sclerosis have been found in Arctic populations [1-8]. Fish consuming communities in Japan [9, 10], The Netherlands [11] and United States [12, 13] show also a lower incidence of ischemic heart disease. Several investigators have postulated that dietary n-3 polyunsaturated fatty acids (PUFA's), which are present in the fat of sea fish, may cause the lower incidence of ischemic heart disease [14-17]. Many experimental and human studies have been carried out with purified marine oils [18-32], but the reported results are often difficult to compare because of differences in doses and ratios of eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) used. In this chapter the results of human studies are reviewed. An attempt has been made to clarify some of the differences by ranging the studies according to doses of EPA used. For a review of animal data the reader is referred to references 19, 20, 23, 24, 32. PUFA's can be divided in two major families: those of the n-6 and those of the n- 3 type. The n-6 PUFA's have their first double bond on the sixth carbon atom counting from the methyl end of the fatty acid. The n-3 PUFA's start with their first double bond at the third carbon atom (figure 1). Vegetable oils contain PUFA's of the n-6 type (linoleic acid; LA, 18:2 n-6), and of n-3 type (alpha-linolenic acid, a-LNA, 18:3 n-3). Some vegetable oils, like primrose oil, are relatively rich in dihomo-gamma-linolenic acid (20:3 n-6, g-LNA). Animal fats often contain some PUFA's of the n-6 type (LA and arachidonic acid; AA 20:4 n-6) and the n-3 type (a-LNA). Fish oils mainly contain PUFA's of the n-3 type (EPA, DHA and docosapentaenoic acid; DPA 22:5 n-3). Fish do not synthesize the n-3 PUFA's themselves, but they derive their dietary n-3 PUFA's from the consumption of plankton. The marine phytoplankton and zooplankton n-3 PUFA contents depend on the water temperature. The colder the water the more n-3 PUFA's are synthesized by the plankton. It will be clear that there is a wide variation of n-3 PUFA content of fish depending on marine, terrestrial and seasonal circumstances. Another rich source of n-3 fatty acids are, except for fish, the large quantities of fish consuming animals, such as seals. 2 PLANKTONPLANTS c::J:'~ -i 3 ' LINOLEIC ACID (18:2 n-6) a-LINOLENIC ACID 08:3 n-3) PLANTS I ! PLANKTON._. DIHOMO-y-LINOLENIC ACID (20: 3 n-6) EICOSAPENTAENOIC ACID C20:5 n-3) ! ARACHIDONIC ACID (20:4 n-6) OOCOSAPENTAENOICc::::::::J. ACID (22:5 n-3) DOCOSAPENTAENOIC ACID (22:5 n-6} DOCOSAHEXAENOIC ACID (22:6 n-3) Figure 1. Chemical structures of the polyunsaturated fatty acids of the n-6 and n-3 family. 1.2 Cardiovascular effects of dietary n-3 fatty acids The American cardiologist Nelson already prescribed a diet with 3 fish meals a week to a large number of post infarction patients 25 years before the epidemiological studies among Eskimos [17], Japanese fishermen [9, 10] and citizens of Zutphen [11] became known. Nelson noted that the incidence of myocardial infarction was decreased among these individuals during the follow up period stretching beyond 16 years [33]. These findings of Nelson did not receive much attention, in contrast with the high interest in later studies. In the following years, various actions of dietary n-3 PUPA's on cardiovascular risk factors have since been described. In the next paragraphs the effects of dietary fish oil on these factors are summarized. 1.2.1 The effects of dietary n-3 fatty acids on plasma cholesterol There is evidence that the n-3 PUPA's decrease the synthesis of the triglyceride-rich very low density lipoproteins (VLDL) [34, 35]. As VLDL is a precursor particle for low density lipoprotein (LDL) and its surface fragments are incorporated in the high density lipoprotein (HDL), a decrease in VLDL level will be reflected on the plasma levels of LDL and HDL [36-43].