In this study, 177 cases (patients who suffered myocardial infarction [MI] or sudden coronary death within 10 years of follow-up) were selected from the PROCAM (Prospective Cardiovascular Muenster) study population. Each case was matched to two controls (n=354) from PROCAM based on age, gender, smoking status and date of investigation. Phytosterol concentrations, including sitosterol, were measured in samples collected at baseline in order to determine an association between phytosterol blood levels and increased risk for future coronary events.
Results from the study, which was funded in part by Merck/Schering-Plough
Pharmaceuticals, showed that levels of sitosterol were higher in patients who suffered coronary events compared to the matched controls (5.03 ± 3.44 µmol/L vs. 4.31 ± 2.38 µmol/L, p=0.003).
In addition, results from this preliminary study showed that study patients with modestly elevated (5) levels of sitosterol (>5.25µmol/L) and high LDL cholesterol (LDL-C) (=4.14 mmol/L) were at nearly double the risk of a major coronary event compared to those with high LDL-C and sitosterol in the lower ranges (=5.25µmol/L; p=0.025). Men considered at high risk for coronary events (>20 percent in 10 years as calculated using the PROCAM algorithm), who also had modestly elevated levels of sitosterol were at an estimated three-fold increased risk compared to those with sitosterol in the lower ranges (p=0.032).
"The results seen in these patients would suggest that sitosterol absorbed from the intestine may lead to modest elevations of sitosterol in the blood, which in turn may be associated with an increased risk for coronary events. However, nested case-control studies are preliminary by nature and results from studies of this kind should be viewed very cautiously," said Gerd Assmann, M.D., professor, University of Muenster, Germany. "Further studies will certainly be needed to determine if sitosterol might play a role as a marker for increased risk of heart disease."
This nested, case-control study was conducted among participants in the Prospective Cardiovascular Muenster (PROCAM) study, a large, prospective, employment-based, epidemiological study of men and women in Muenster, Germany. The study enrolled 20,060 individuals between 1979 and 1985.
1. Sitosterol is one of the most abundant plant sterols and belongs to the larger group known as phytosterols (which include plant sterols and the less abundant plant stanols).
2. Hubacek JA, Berge KE, Cohen JC, Hobbs HH. Mutations in ATP-cassette binding proteins G5 (ABCG5) and G8 (ABCG8) causing sitosterolemia. Hum.Mutat. 2001;18:359-60.
3. Bhattacharyya AK, Connor, WE: ß-sitosterolemia and xanthomatosis. A newly described lipid disease in two sisters. J. Clin Invest 1974;68: 1033-1043.
4. Beta-sitosterolemia. National Heart Lung and Blood Institute 2001 Rare Diseases Report.
5. Modestly elevated sitosterol is defined in the study as those patients in the top quartile (>5.25µmol/L) for sitosterol in this study population compared to those in the lower three quartiles (=5.25µmol/L).
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