Apolipoprotein E polymorphism in the Tunisian population: Frequency and effect on lipid parameters

Objectives: We determined the frequencies of apolipoprotein E (apo E) gene alleles and examined the association between apo E polymorphism and lipid parameters in a sample of the Tunisian population. Design and methods: Apo E polymorphism was investigated using PCR, and plasma lipid parameters were measured in 122 men and 111 women aged 35 to 87 years. Results: The allele frequencies were ε2: 7.3%, ε3: 84.6%, and ε4: 8.1%. Apo E polymorphism was associated with significant differences (P < 0.001) in total cholesterol, apo B and LDL cholesterol in both men and women. ε2 carriers had the lowest mean total cholesterol, apo B and LDL-C concentrations, and subjects with the ε4 allele had the highest levels. Triglycerides levels increased with the ε4 allele, but this did not reach statistical significance. These results remained unchanged after adjustment for age, body mass index, sex, hypertension, diabetes and smoking. However, in obese subjects (BMI > 30 kg/m2), TG concentrations were significantly lower in individuals homozygous for the ε3 allele compared to those with the alleles ε2 or ε4. Conclusion: In this sample of the Tunisian population, the distribution of apo E gene alleles is similar to that observed in Southern European populations with low prevalence of the ε4 allele. Variations in the apo E gene play a role in determining plasma lipid levels. These data also suggest that effects of apo E alleles on lipids levels are partly dependent on environmental variables such as BMI. These findings highlight the importance of the gene/environment interaction on the deleterious effect of obesity on cardiovascular risk factors.