Freeze-Dried Watermelon Supplementation Has Modest Effects on Bone and Lipid Parameters of Ovariectomized Mice

This study investigated the effects of two doses of freeze-dried watermelon (WM) on bone and lipid parameters in ovariectomized (OVX) mice, a model of post-menopausal osteoporosis. Three-month-old C57BL/6 female mice (n=46) were sham-operated (SHAM) or OVX and randomly assigned to the control or WM diets for 12 weeks: SHAM-control, OVX-control, OVX+1%, or 10% (wt/wt) freeze-dried WM. All diets were isocaloric and isonitrogenous, and had the same calcium and phosphorus concentrations. Freeze-dried WM supplementation was not able to prevent the decrease in whole body, tibial, and lumbar bone mineral density due to estrogen deficiency. Micro-computed tomography analyses showed that WM was also not able to modulate changes in tibial trabecular and cortical bone microarchitecture due to ovariectomy. However, the lumbar trabecular micro-architecture analyses revealed that the WM-10% group had a similar connectivity density, trabecular number, trabecular separation, and structure model index as the SHAM group. Supplementation with 10% WM reduced plasma cholesterol and total liver lipids to the level of the SHAM group but was still similar to that of the OVX-control group. Supplementation with 10% WM increased liver catalase (CAT) mRNA levels but had no effects on mRNA levels of glutathione peroxidase (GPX) and the pro-inflammatory cytokine interleukin-6. There were no differences in plasma activity of the antioxidant enzymes GPX and CAT between all treatment groups. Our findings demonstrate some positive effects of watermelon for modulating lipids and attenuating lumbar vertebral bone loss arising from ovarian hormone deficiency.