Differential Effects of the Polyphenols and Carbohydrates in Dried Plum Account for the Fruit’s Benefits on Bone Health in Estrogen Deficiency

Abstract

Objectives: This study investigated the effects of dried plum’s (DP) polyphenols (PP) and carbohydrates (CHO) on bone mass, microarchitecture, and biomarkers of metabolism over time in an osteopenic model of estrogen deficiency. Methods: A 2 × 2 factorial (factors CHO & PP) embedded within a randomized block design was used with 3-m old C57BL/6 female mice, sham-operated (Sham = 2 groups) and fed AIN-93M control diet (Con) or ovariectomized (OVX = 10 groups) and fed Con or Con diet supplemented with DP (25% w/w), a comparable dose of crude PP extract (CPE), fractionated CHO or PP extract for 5 or 10 wks. At each end-point, dual-energy x-ray absorptiometry scans were performed and bone microarchitecture was assessed at the femur and lumbar vertebra using micro-computed x-ray tomography. Serum biomarkers of osteoblast activity, procollagen type 1 N-terminal propeptide (P1NP), and osteoclast activity, tartrate-resistant acid phosphate (TRAP) were assayed using EIAs. Data was analyzed using SAS with effects of DP and CPE examined using 1-way ANOVA and effects of PP and CHO examined using a 2-way ANOVA. Results: At 5 and 10-wks, mice on the DP and CPE diets had higher (P < 0.05) whole body bone mineral density (BMD), content (BMC), trabecular bone volume (BV/TV) and number (TbN) in the vertebrae and femur compared to the OVX-Con. By 10 wks, improvements in trabecular bone with DP and CPE were greater (P < 0.05) than Sham. Only the CPE significantly improved cortical thickness, a response observed at only 5 wks. DP and CPE had no effect on P1NP, but suppressed OVX-induced increase in TRAP at 5 and 10 wks. PP and CHO increased (P < 0.05) whole body BMD and BMC. CHO significantly improved trabecular BV/TV, TbN, separation, connectivity density, and structure model index at both time points. A similar response occurred in vertebral trabecular bone. In contrast, cortical thickness was increased (P < 0.05) with CHO at 5 wks, but by 10 wks PP alone and in combination with CHO accounted for improved cortical area, thickness and porosity. CHO suppressed TRAP at both time points, but P1NP only at 5 wks. PP did not alter P1NP and only when combined with CHO suppressed TRAP at 5 wks. Conclusions: In the OVX model, both the CHO and PP of DP positively affect BMD, with the CHO fraction enhancing trabecular bone and the PP fraction improving cortical bone.