The effect of apolipoprotein B xbaI polymorphism on plasma lipid response to dietary fat

Lipid response to dietary fat and cholesterol is, to a large extent, genetically controlled. Apolipoprotein B (apo B) plays a dominant role in cholesterol homeostasis. Several polymorphic sites within or adjacent to the gene locus for apo B have been detected. The X+ allele of the XbaI restriction fragment polymorphism of the apo B gene has been found to be associated with higher serum cholesterol and/or triglyceride levels. In order to study the influence of this mutation on the plasma lipid response in diets of varying fat content, 72 healthy male subjects were studied, 21 X- X- (X-) and 51 X+ (X+ X- or X+ X+).

These subjects followed three consecutive 28-day diet periods: one rich in saturated fats (SAT diet; 38% fat, 20% saturated); a National Cholesterol Education Program type I diet (NCEP-I diet) (28% fats, < 10% saturated); and a third monounsaturated (MUFA diet) (38% fats, 22% monounsaturated). The different genotypes can be observed to have significant effects on total and LDL cholesterol concentrations (P < 0.017). X+ individuals had higher levels of total and LDL cholesterol after the consumption of a SAT diet (P < 0.012; P < 0.006, respectively), NCEP diet (P < 0.060; P < 0.054, respectively) and MUFA diet (P < 0.022; P < 0.042, respectively) in comparison with X- individuals. A significant interaction between genotypes and dietary effects was observed for diet-induced changes in plasma triglycerides (P < 0.032). Significant decreases in the absolute values of triglyceride concentrations (-0.18 mmol L(-1), P < 0.024) were noted in the X- subjects after the high intake of a MUFA diet, while no significant differences were observed in the X+ individuals (0.006 mmol L(-1), P < 0.858).

Our results suggest that the total triglyceride response to diet is influenced by the apo B XbaI polymorphism.