The Negative Impact of Selective Activation of Retinoic Acid Receptors on Bone Metabolism and Bone Mechanical Properties in Rats.

BACKGROUND: Drug-induced osteoporosis is a significant health problem, as many drugs have deleterious effects on bone metabolism. Data from several studies concerning the influence of retinol on bone homeostasis are inconsistent. OBJECTIVES: The purpose of this study was to investigate the influence of tazarotene, a selective agonist of the retinoic acid receptor (RAR), on bone metabolism and bone mechanical properties in rats. MATERIAL AND METHODS: Sixteen male Wistar rats were assigned either to the group receiving tazarotene or to the control group. Serum biochemical markers of bone turnover (osteocalcin: OC, tartrate resistant acid phosphatase 5: TRACP5b, and osteoprotegerin: OPG) and the mechanical properties of bones were analyzed. RESULTS: The mean Young's modulus was 24% higher (p < 0.05) in the control group than in the group receiving tazarotene. The stiffness of femur bones was 25% lower (p < 0.05) in rats receiving tazarotene. Flexural yield stress was slightly (2%) decreased in the tazarotene group, but the difference was not statistically significant. In the tazarotene group significantly lower serum concentration of bone turnover markers were obeserved (TRACP5b: 0.86 ± 0.30 ng/mL vs. 2.17 ± 0.67 ng/mL, OC: 7.77 ± 2.28 ng/mL vs. 13.04 ± 3.54 ng/mL and OPG: 0.09 ± 0.04 ng/mL vs. 0.27 ± 0.10) than in the control group. CONCLUSIONS: Tazarotene worsened bone mechanical properties and inhibited bone turnover in rats. These results suggest that tazarotene has a negative impact on bone metabolism and that it exerts osteoporotic activity.