Effects of bioactive peptide, valyl-prolyl-proline (VPP), and Lactobacillus helveticus fermented milk containing VPP on bone loss in ovariectomized rats

Background: Valyl-prolyl-proline (VPP), a bioactive peptide formed during the fermentation with Lactobacillus helveticus LBK-16H (L. helveticus), has been shown to increase bone formation in vitro. The aim of the study was to determine whether VPP and L. helveticus fermented milk prevent bone loss in ovariectomized (OVX) rats. Methods: During the 12-week intervention study, the OVX rats received VPP in water or L. helveticus fermented milk, containing VPP. Sham-operated rats receiving water acted as controls. The trabecular and cortical bone mineral density were determined by peripheral quantitative computed tomography before the operation and at 4 and 12 weeks. The mechanical testing and ash weight analysis as well as the static and dynamic histomorphometrical parameters were assessed at the end of the intervention. Results: VPP given in water showed no clear effect on bone loss. L. helveticus fermented milk prevented bone loss by decreasing bone turnover and increasing the bone mineral density. Ovariectomy caused a 57% loss in the trabecular bone, which was attenuated by 16% in the L. helveticus group. Conclusions: VPP peptide did not prevent ovariectomy-induced bone loss, which could be due to the poor bioavailability of VPP from water solution. L. helveticus fermented milk prevented bone loss, whether this is due to the VPP peptide cannot be concluded.