Bone Mineral Density And Glucose Uptake In Common Fracture Sites Of Patients With Multiple Sclerosis

Abstract

Patients with Multiple Sclerosis (MS) have been shown to have lower bone mineral densities (BMD), predisposing them to bone fracture. Decreased BMD could be a manifestation of MS directly or from lower physical activity levels. Physical activity is important because bone loading and unloading during exercise stimulates osteoblast activity, maintaining bone health. PURPOSE: To investigate the BMD and glucose uptake (GU) in common fracture sites in patients with MS using Positron Emission Tomography (PET) / Computed Tomography (CT). METHODS: Eight patients (4 men) with MS (aged 44.9 SD 8.6 years) and eight healthy sex matched controls (37.9 SD 8.4 years) walked on a treadmill for 15 min at a self-selected speed, during which ≈ 296 MBq of [18F]-Fluorodeoxyglucose (FDG), a PET glucose analog tracer, was injected. Immediately after walking, PET/CT imaging was performed. FDG uptake was then calculated as the standardized uptake value (SUV), with higher uptake signifying greater metabolic activity in the bone. BMD was assessed using Hounsfield Units (HU). Cortical and trabecular SUV and BMD were determined in the femur spanning from the femoral neck to the proximal end of the lesser trochanter. Trabecular SUV and BMD were calculated at vertebral levels C2 - L5. RESULTS: Patients with MS had lower trabecular BMD than the control group for all (235 SD 43, 288 SD 46, P = 0.02) and individual regions of the spine (P < 0.03), as well as the femoral head (125 SD 18, 153 SD 31, P = 0.03). No differences were detected in cortical BMD in the femur between the MS and control groups (P = 0.42). No significant differences in FDG uptake were identified in the spinal column (MS 1.71 SD 0.26, Con 1.82 SD 0.19, P = 0.45) or femur (MS 0.82 SD 0.26, Con 0.88 SD 0.25, P = 0.64). CONCLUSIONS:Patients with MS had lower trabecular BMD, a finding consistent with previous studies, even though glucose uptake was not different in any region after walking. This suggests that glucose uptake of the bone is not different between patients with MS and healthy controls during walking. Therefore, the reduction in BMD is not explained by metabolic activity. Other factors, such as lower levels of physical activity, may play an important role in bone health. Funded by MS Society (PP 1907) and in part by NIH/NCATS Colorado CTSI # UL1 TR000154.