Bone mineral density in patients with apolipoprotein E type 2/2 and 4/4 genotype

The peak bone mass and the rate of bone loss are in part genetically determ ined. It has been suggested that bone mineral density (BMD) may be related to allelic variation in the apolipoprotein E (ApoE) gene locus. ApoE is imp ortant in the receptor-mediated clearance of chylomicron particles from the plasma, Apo E4 having the highest and Apo E2 the lowest receptor affinity. Chylomicrons are the main carrier of vitamin K in the plasma; vitamin K pl ays an important role in the carboxylation of osteocalcin. We have tested t he hypothesis that persons with E4 variant would have lower BMD and increas ed bone turnover than those with E2 variant. A total of 18 ApoE 2/2 and Apo E 4/4 homozygotes were selected from 873 patients who were examined for the ApoE genotype. BMD in lumbar vertebral, femoral neck and distal forearm wa s measured and plasma concentrations of osteocalcin and C-terminal fragment s of collagen (CTx) were determined. BMD values (expressed as T-score) at t he three specified sites were -0.12+/-1.72, -0.52+/-1.32 and -0.52+/-0.81 i n ApoE 2/2 group and -0.24+/-1.22, 0.00+/-0.84 and -0.17+/-1.07 in the ApoE 4/4 group. Plasma osteocalcin and CTx were within normal limits in both gr oups. In conclusion, we did not observe any association of ApoE genotype wi th BMD and biochemical markers of bone metabolism in ApoE 2/2 and ApoE 4/4 homozygotes.