Osteoporosis, postmenopausal form [M81.0]
Dr. rer. nat. Christoph Marschall, Dipl.-Biol. Christine Schack,
Dipl.-Biol. Christina Sofeso
Osteoporosis is characterized by reduction of bone density due to demineralization of the bone. Within the EU, approximately every 8th citizen above the age of 50 suffers a fracture of the vertebral body; every 3rd woman above 80 suffers a femoral neck fracture due to osteoporosis. Family and twin studies showed that up to 80% of the individual bone density is determined genetically, with several genetic factors probably having an impact. In addition, other non-genetic factors such as living and eating habits or hormonal changes influence the bone density significantly as well.
Type I collagen is the main protein component of bones and is encoded by the COL1 gene family. A variant in the regulatory region of COL1A1 seems to have an impact on the bone density and the risk of fracture in postmenopausal women. The COL1A1-S/s polymorphism (frequency of the s allele approx. 20%) leads to increased gene expression which causes an increased synthesis of the α1 chain resulting in an abnormal α1 and α2 collagen chain ratio. The consequence is a decrease in bone density and an increased risk of osteoporotic fractures. Every s allele reduces the bone density and leads to a significant increase in the fracture risk (gene dosage effect). The s allele frequency in patients suffering from osteoporosis and fractures of the vertebral body is nearly twice as high as in the control groups.