The lipoprotein/lipid profile is modulated by a gene–diet interaction effect between polymorphisms in the liver X receptor-α and dietary cholesterol intake in French-Canadians

Genetic and nutritional factors interact together and modulate the plasma lipid profile. We identified variations in the gene encoding the liver X receptor a (LXRa) and investigated their effects on the plasma lipoprotein/lipid profile. We also examined whether the association between cholesterol intake and plasma lipid profile was modulated by LXRa variants. The LXRa gene was sequenced in thirty-five French-Canadian men with high plasma total cholesterol (>5·0 mmol/l) and LDL-cholesterol (>3·5 mmol/l) concentrations. Dietary cholesterol was obtained from a food-frequency questionnaire. The LXRa c.-115G > A, c.-840C > A and c.-1830T > C genotypes were determined by direct sequencing in 732 subjects. Molecular screening of the LXRa gene revealed sixteen variants. Genotypes c.-115G > A, c.-840C > A and c.-1830T > C (rare allele frequency of 14·3 %, 14·2 % and 11·0 %, respectively) were analysed further. Plasma total cholesterol concentrations were higher in carriers of the -115A, -840A and -1830C allele, compared with the -115G/G, -840C/C and -1830T/T homozygotes (P≤0.05). In a model including the c.-115G > A polymorphism, cholesterol intake, the interaction term c.-115G > A X cholesterol intake (mg/d) and covariates, LXRa-115G > A explained 1·8 % and 2·1 % of the variance in total cholesterol and LDL-cholesterol concentrations (P=0·02 and P=0·01), whereas the interaction term explained 2·9% (P=0·002) and 2·8 % (P=0·005), respectively. When subjects were divided into four groups according to the median of cholesterol (290·8 mg) and -115G > A genotypes, high cholesterol intake was associated with higher cholesterol levels in -115A carriers. Similar results were observed for c.-840C > A and c.-1830T > C. These results suggest that cholesterol intake interacts with LXRa variants to modulate the plasma lipid profile.