Scavenger receptor class B type I (SCARB1) was described as the first high-density lipoprotein receptor. Increasing evidence indicates that SCARB1 plays additional roles particularly in type 2 diabetes mellitus. Our aim was to determine whether the presence of an exon 1 (G-->A) polymorphism at the SCARB1 gene modifies the insulin sensitivity to dietary fat.
Methods: We studied 59 healthy volunteers (30 men and 29 women, 42 G/G homozygous and 17 G/A heterozygous). Subjects consumed three diets for 4 wk each: a saturated fatty acid (SFA)-rich diet (38% fat, 20% SFA), followed by a carbohydrate (CHO)-rich diet (30% fat, 55% CHO) or a monounsaturated fatty acid (MUFA)-rich diet (38% fat, 22% MUFA) after a randomized crossover design. For each diet, we investigated peripheral insulin sensitivity with the insulin suppression test.
Results: Steady-state plasma glucose after the MUFA diet was lower in G/A compared with G/G subjects (P = 0.030). This effect was not observed after CHO and SFA diets (P = 0.177 and 0.957, respectively). Plasma nonesterified free fatty acid values were lower in subjects carrying the A allele for all the diet periods.
Conclusions: Our findings show that carriers of the G/A genotype have significant increases in insulin sensitivity after a MUFA-rich diet compared with G/G individuals.