DNA polymorphisms around the apo AI gene in normal and hyperlipidaemic individuals selected for a twin study.

We have investigated the allele frequencies, in a Norwegian population, of two restriction fragment length polymorphisms (RFLPs) in the apolipoprotein (apo) AI-CIII-AIV gene region. The study group consisted of clinically well twins and their unrelated spouses. In the normotriglyceridaemic individuals tested, the frequency of the rare allele (S2) of the RFLP detected using the restriction enzyme Sst I was 0.17; for the RFLP detected with the enzyme Xmn I, the rare allele (X2) frequency was 0.06. The frequency of the S2 allele was lower in individuals with serum triglyceride levels above 1.7 mmol l-1, but this was not statistically significant. Conversely, the frequency of the X2 allele was higher in individuals with raised serum triglyceride levels, but similarly, did not reach statistical significance. Taken together with the data from our previous study on UK individuals, these results support the suggestion that inherited variations in this apolipoprotein gene cluster are involved in the determination of serum triglyceride levels.