Dried Plum Enhances Recovery of Bone Following Hindlimb Unloading in Female Rats

Abstract

Recent studies have shown dried plum to prevent and reverse bone loss in animal models of osteoporosis. The objectives of this study were to determine if dried plums could enhance bone recovery following hindlimb unloading (HLU); to determine the most effective dose (5%, 15%, or 25%; w/w) of dried plum; and to determine how the effects of dried plum on bone compare to the anabolic effects of parathyroid hormone (PTH). Six month old female virgin Sprague-Dawley rats were either HLU (HLU=6 groups of 8-12 rats) to induce bone loss or remained ambulatory (AMB=2 groups of 8-12 rats) for 3 weeks. Following the HLU period, two groups (i.e. one HLU and one AMB) were necropsied and bone evaluated to characterize the bone loss. The remaining groups were randomly assigned to the following treatments for 90 days: standard semi-purified AIN (control) diet with either LD=5%, MD=15% or HD=25% (w/w) dried plum added or control diet plus parathyroid hormone administration (80 g PTH/kg bw; 3 x wk Bachem, Inc). Tibial bone mineral content (BMC) and density (BMD) were enhanced significantly by the HD compared to animals on the control diet, although, not to the level of the PTH group. Compared to controls, recovery of vertebral BMD was significantly greater in the MD and HD groups, and the HD group was comparable to PTH. Evaluation of the distal femur using micro-computed tomography (Scanco Medical CT 40) indicated that bone volume (BV/TV) in the HD group was similar to the PTH group and significantly higher than the control group. Trabecular thickness (TbTh) of the vertebra increased in the MD and HD dried plum groups, although not to the level of PTH. Trabecular separation (TbSp) and number (TbN) in the distal femur and TbN within the vertebra were unchanged by both dried plum and PTH. Bone formation as indicated by serum alkaline phosphatase (ALP) was significantly higher in the HD group, but bone resorption was unaltered. These findings indicate that bone recovery following HLU is enhanced by dried plum up-regulating bone formation and has somewhat similar effects to PTH.