An analysis of genotype effects and their interactions by using the apolipoprotein E polymorphism and longitudinal data

We investigate the interaction between the apolipoprotein E polymorphism and changes in weight and height as they affect the longitudinal profile of total cholesterol, triglyceride, beta lipoprotein, and glucose levels. Data were available on a sample of 466 individuals in 158 nuclear families from Nancy, France. Longitudinal data analyses were carried out on 128 unrelated adults and 56 unrelated children. We estimate the relative frequencies of the epsilon 2, epsilon 3, and epsilon 4 apolipoprotein E alleles in this population to be .120, .764, and .116, respectively. There is no significant evidence from these data that supports an effect of the apolipoprotein E polymorphism on the longitudinal profile of any of the variables considered. There is a significant interaction between the effects of this gene and weight change on the longitudinal change of serum triglyceride and beta lipoprotein levels in adults. In conjunction with weight gain, individuals with an epsilon 4 allele are expected to show a larger increase in triglyceride levels (0.15 +/- 0.03 mmol/L/kg) compared with individuals with no epsilon 4 allele. An increased production of very-low-density lipoprotein (VLDL) as one gains weight, along with retarded VLDL clearance attributable to the effects of the epsilon 4 allele, may account for this results. The significant interaction between the apolipoprotein E polymorphism and changes in weight on the longitudinal change in triglyceride levels corroborates epidemiological studies reporting that the epsilon 4 allele increases the risk of hypertriglyceridemia among obese individuals.