Recent studies suggest that point mutation of guanine to thymine at nucleotide position 894 (G894T) in the endothelial nitric oxide synthase (eNOS) gene is associated with incidence of coronary heart disease (CHD). Moreover, the lower frequency of CHD among Mediterranean populations has been related with traditional dietary habits and its effect on oxidation. We evaluated the relationship between Mediterranean diet and oxidized LDL cholesterol levels in eNOS polymorphism (G894T) homozygotes.
During 2001-2002 we conducted a population-based study of 2282 participants. In this work we studied 267 men (18-87 years old) and 327 women (18-89 years old), without any evidence of CHD. Participants were ramdomly selected from the general population according to age-gender distribution of Athens greater area (census 2001). DNA was extracted from peripheral leukocytes. For detection of G894T polymorphism of the eNOS gene, we used primer pairs to amplify a part of the eNOS gene containing exon 7 by polymerase chain reaction (PCR). We defined subjects who adopt the Mediterranean diet using as cut-off points the median values of the monthly food consumption score. MANCOVA was used to examine the associations between the genotypes and oxidized LDL cholesterol levels, by dietary group, after adjusting for several potential confounders.
The distribution of eNOS (G894T) polymorphism was: 10.6% homozygotes (HOM), 40% heterozygotes (HET) and 49.4% normal (NOR), while no association between the distribution of the polymorphism and sex of the participants was observed (p = 0.564). 24% of men and 36% of women were defined closer to the Mediterranean diet. Compared to heterozygotes and normal, homozygotes had higher levels of oxidized LDL-cholesterol levels (HET: 59±20 vs NOR: 61±22 vs HOM: 68±21 mg/dl, p = 0.008), after controlling for age, blood pressure levels, body mass index, smoking habits and physical activity status. However, when we focused on Mediterranean diet group no differences were observed between genotypes and oxidized LDL-cholesterol levels (HET: 60±21 vs NOR: 61±19 vs HOM: 61±23 mg/dl, p = 0.271).
Our findings suggest that the adoption of the Mediterranean diet may moderate oxidation process in G894T polymorphism homozygotes. This could partially explain the protective effect of the Mediterranean diet on human health, even in people at high risk.
Christina Chrysohoou, Demosthenes B. Panagiotakos,
Christos Pitsavos, Christodoulos Stefanadis,
University of Athens, Greece