Bone mineral mass is associated with interleukin 1 receptor autoantigen and TNF-alpha gene polymorphisms in post-menopausal Mediterranean women.

Abstract

Bone mass is known to be under genetic control. Interleukin-1 (IL-1), interleukin-6 (IL-6) and TNF-alpha are strong inductors of bone resorption. The estrogenic deficiency that occurs during menopause leads to an increase in the production of these cytokines. We analyzed the genetic susceptibility of several polymorphisms of the interleukin-1 receptor antagonist (IL-1ra), IL-6 and TNF-alpha genes in lumbar spine and hip bone mass in a sample of post-menopausal Caucasian Mediterranean women with osteoporosis. 104 post-menopausal osteoporotic women (58.6+/-4.8 yr) and 51 post-menopausal women without osteoporosis as the control group (57.2+/-4.5 yr) were studied. The osteoporotic group was in turn sub-classified into severe and non-severe osteoporosis. The variable number of tandem repeats IL1-ra, IL-6 SfaNI and TNF-alpha NcoI genetic polymorphisms were studied. Biochemical markers of bone turnover were measured in blood and urine. Women carrying the A2 allele (A2+) of the IL-1ra gene showed greater BMD in the lumbar spine (p=0.02) and hip (p=0.006), compared to those not carrying the allele (A2-). The IL-6 polymorphism studied in its 5' flanking region did not show any association with BMD values. The TNF-alpha gene G allele was associated with a greater bone mass in the non-severe osteoporotic subgroup, both in the lumbar spine (p=0.0007) and in the hip (p=0.02). Likewise, genotype combination A2+GG was associated to a greater hip BMD at the femoral neck and Ward triangle levels (p=0.02). We conclude that both IL-1ra and TNF-alpha can be candidate loci to be studied in the susceptibility to develop post-menopausal osteoporosis.