Beekman K, et al. - In this study, raloxifene was tested for impact on marrow adipose tissue (MAT) and, the link between MAT and bone turnover was elucidated in patients with osteoporosis. Treatment with raloxifene exerted no impact on marrow adipose tissue but tended to increase adipocyte number compared to placebo. At baseline, associations of MAT volume and adipocyte size with bone resorption and, adipocyte size with osteoid surface, were indicative of an interaction between bone marrow adipocytes and bone turnover. Furthermore, in postmenopausal women with osteoporosis, the association of high MAT volume and larger adipocyte size with prevalent vertebral fractures suggested an impact of adipocyte size on bone quality, independent of bone volume.

Methods

• An analysis was performed of bone biopsies from the MORE trial.
• In the MORE trial, the impacts of raloxifene 60 or 120 mg per day versus placebo on bone metabolism and fracture incidence were assessed in patients with postmenopausal osteoporosis.
• Researchers quantified MAT in iliac crest biopsies obtained at baseline and after 2 years of treatment (n = 53; age 68.2 ± 6.2 years).

Results

• Findings demonstrated that raloxifene neither influenced the change in MAT volume after 2 years compared to baseline (placebo: 1.89 ± 10.84%, raloxifene 60 mg: 6.31 ± 7.22%, raloxifene 120 mg: -0.77 ± 10.72%), nor affected change in mean adipocyte size (placebo: 1.45(4.45)μm, raloxifene 60 mg: 1.45(4.35)μm, raloxifene 120 mg: 0.81(5.21)μm).
• Researchers observed that following placebo treatment, adipocyte number tended to decrease (-9.92(42.88 cells/mm²) and, tended to increase during raloxifene 60 mg treatment (13.27 (66.14) cells/mm²) while adipocyte number remained unchanged in the raloxifene 120 mg group, compared to placebo (3.06 (39.80) cells/mm², Kruskal-Wallis p = 0.055, post hoc: placebo vs raloxifene 60 mg p = 0.017).
• Data also indicated a negative association of MAT volume and adipocyte size with osteoclast number at baseline (R² = 0.123, p = 0.006 and R² = 0.098, p = 0.016 respectively).
• Furthermore, it was found that adipocyte size was negatively related to osteoid surface (R² = 0.067, p = 0.049).
• Finally, higher MAT volume (50.82 (8.80)%) and larger adipocytes (55.75 (3.14)μm) were observed in patients with vertebral fractures, compared to patients without fractures (45.58(12.72)% p = 0.032, 52.77(3.73) μm p0.004 respectively).