The relationship between bone mineral density and levels of RANKL, osteoprotegerin and cathepsin-K in patients with rheumatoid arthritis

Objectives: The aim of this study was to evaluate the levels of osteoprotegerin (OPG), nuclear factor kappa B receptor activator ligand (RANKL), cathepsin K in patients with rheumatoid arthritis (RA) and the relation between these parameters and bone mineral density (BMD). Materials and methods: Totally 90 cases including 30 postmenopausal and healthy women, 30 with postmenopausal osteoporosis and 30 with postmenopause RA were enrolled in the study. The serum RANKL, OPG and cathepsin K were measured by ELISA method. Results: The levels of serum RANKL and OPG in the patients with postmenopausal RA were found significantly higher compared to the postmenopausal healthy women whereas the rate of serum OPG/RANKL was found significantly lower. In addition, the rate of OPG and OPG/RANKL were significantly lower in patients with postmenopausal RA compared to the postmenopausal osteoporosis, whereas the level of serum RANKL was significantly higher. Positive correlation was detected between bone densities of lumbar spine (LS), femur neck (FN) and the rate of OPG/RANKL in patients with postmenopausal RA. Also negative correlation was detected between LS and FN bone densities and RANKL levels. Conclusions: The system of RANKL/RANK/OPG may have a role in osteoporosis and RA pathogenesis and the rate of OPG/RANKL might be a significant determiner of bone density

Amaç: Bu çalışmanın amacı Romatoid Artrit’li (RA) hastalarda Osteoprotegerin (OPG), Nükleer faktör kappa B reseptör aktivatörü ligandı (RANKL), katepsin-K düzeylerini ve ayrıca bu parametrelerin kemik mineral yoğunluğu (BMD) ile ilişkisini araştırmaktır. Gereç ve yöntem: Çalışmaya postmenopozal sağlıklı (n=30), postmenopozal osteoporozlu (n=30) ve postmenopoz RA’lı (n=30) toplam 90 olgu alındı. Serum RANKL, OPG ve katepsin-K ELİSA yöntemiyle çalışıldı. Bulgular: Postmenopozal RA’ lı hastalarda serum RANKL ve OPG seviyeleri postmenopozal sağlıklı kontrollere kıyasla anlamlı yüksekken, serum OPG/RANKL oranı anlamlı düşük bulundu. Bununla birlikte postmenopozal RA’lı hastalarda, postmenopozal osteoporozlu hastalara göre serum OPG ve OPG/RANKL oranı anlamlı düşük iken, serum RANKL seviyesi anlamlı yüksekti. Postmenopozal RA’lı hastalarda lomber spine (LS) ve femur neck (FN) kemik mineral dansiteleri (BMD) ile OPG/RANKL oranı arasında pozitif korelasyon saptanırken; RANKL düzeyleri ile negatif korelasyon bulundu. Sonuç: RANKL/RANK/OPG sistemi osteoporoz ve RA patogenezinde rol alabilmektedir ve OPG/RANKL oranı kemik dansitesinin önemli bir belirleyicisi olabilir.