Similar Effects of Diets Rich in Stearic Acid or trans -Fatty Acids on Platelet Function and Endothelial Prostacyclin Production in Humans

Abstract

Abstract-The effects of stearic acid (C18:0) and trans-fatty acids (trans-FAs) on measures of platelet function and prostacyclin (PGI 2 ) production are poorly understood in humans. In this controlled dietary study, platelet function and endothelial PGI 2 production were studied in healthy humans after they consumed diets rich in C18:0 or trans-FAs. For 5 weeks, 80 subjects consumed a baseline diet high in saturated FAs and were then switched to a diet containing 9.3% of energy as stearic acid or a diet containing 8.7 energy% as trans-FAs from hydrogenated vegetable oils for another 5 weeks. All diets contained 32.2 to 33.9 energy% fat, 14.6 to 15.8 energy% saturated plus trans-FAs, 12.2 to 12.5 energy% cis-monounsaturated, and 2.9 to 3.5 energy% polyunsaturated FAs. No significant differences between the C18:0 and trans-FA diets were found in the urinary excretion of 2,3-dinor-thromboxane B 2 or 2,3-dinor-6-keto-prostaglandin F 1␣ . In vitro production of thromboxane B 2 by platelets as well as urinary excretion of ␤-thromboglobulin were also similar after both diets. Collagen-induced in vitro aggregation was significantly enhanced after the C18:0 diet compared with the trans-FA diet (Pϭ.02), whereas no differences between the diets were found with ADP. 3,4 although this observation has not been consistent. 5,6 Still, data on the thrombogenic properties of these FAs are mostly based on animal studies or in vitro studies with isolated cells. In rats, trans-FAs have inhibited thromboxane production 7 and either inhibited 8 or had no effect 9 on platelet aggregation.It is apparent that stearic acid has a different cholesterolemic effect than other long-chain saturated FAs. Regarding lipoprotein metabolism, stearic acid has been considered neutral with respect to total cholesterol and LDL cholesterol, although HDL cholesterol has decreased in some studies. 10 -12 Whether stearic acid can also be considered neutral with respect to its thrombotic effects is unclear. Evidence from human epidemiological and animal studies suggests that stearic acid enhances platelet aggregation in vitro, indicating its effects on platelet activity, an important aspect of thrombosis and hemostasis. [13][14][15] In vivo indices of platelet activation have been measured in only one human study, in which thromboxane or prostacyclin synthesis did not change after a diet rich in stearic acid. 16In mixed diets, trans-FAs are mainly substituted for saturated FAs, not for liquid oils. The purpose of our study was therefore to compare the atherogenic and thrombogenic properties of stearic acid and trans-monounsaturated FAs in a strictly controlled way in healthy subjects. The results on lipids and lipoproteins 17 as well as coagulation and fibrinolysis factors 18 have been published previously. This article discusses the effects of stearic acid and trans-FAs, especially those on platelet function, as measured by several in vivo and in vitro parameters as well as those on endothelial cell PGI 2 production. Methods SubjectsAltogether 80 healthy ...

Similar responses in hemostatic factors after consumption of wholemeal rye bread and low-fiber wheat bread

“…In line with previous studies (Wennmalm et al, 1991;Nowak et al, 1987;Barrow et al, 1989), a trend for increased excretion was seen in smokers, whereas the wheat bread and rye bread diets did not differ. Although we could ®nd no differences between the two bread periods, dietary factors, namely dietary fatty acid composition, has been shown to affect excretion of thromboxane metabolites in several studies (Ferretti et al, 1993;Prakash et al, 1994, Turpeinen et al, 1998a.…”

“…The urine was stored in 10 ml tubes at 720 C. The analysis of 2,3-dinor-TXB 2 was carried out from pooled 3-day samples. After sample puri®cation by the method of Berens et al (1984) the samples were analysed for 2,3-dinor-TXB 2 with enzyme immuno assay (EIA) as previously described (Turpeinen et al, 1998a(Turpeinen et al, ,1998b.…”

A stearic acid-rich diet improves thrombogenic and atherogenic risk factor profiles in healthy males

“…To date, the data reported by various authors on the effect of dietary stearic acid on platelet aggregation are con¯icting. It has been demonstrated that, for a particular dietary fatty acid, the aggregatory response to the same agonist can give opposing results (Turpeinen et al, 1998;Kwon et al, 1991), due partly to the medium in which platelets have been assessed. There is argument as to whether whole blood or platelet-rich plasma (PRP) samples are more appropriate for determination of ex vivo aggregation, or as a model to represent the in vivo situation.…”

Short-term diets enriched in stearic or palmitic acids do not alter plasma lipids, platelet aggregation or platelet activation status

“…The data reported by various authors on the effect of dietary stearic acid on platelet aggregation have been conflicting. It has been demonstrated that for a particular dietary fatty acid, the aggregatory response to the same agonist can give opposing results (Kwon et al, 1991;Turpeinen et al, 1998), which may be due partly to the medium in which platelet aggregation has been studied. There is some debate among researchers as to whether in vitro platelet aggregation in whole blood or using platelet-rich plasma is more appropriate.…”