Effects Of 3-Hydroxybutyrate On Osteoblasts And Rat Osteoporosis Induced By Ovariectomy

Poly-hydroxyalkanoates (PHA), a family of biopolyesters produced by many bacteria, have been recently developed for possible application in tissue engineering because of their good biocompatibility and other properties. In this study, 3-hydroxybutyrate (3HB) was investigated as one of the degredation products of PHAs that may relate to the mechanism of biocompatibility of PHAs. Besides, 3HB is one of the ketone bodies, which has been reported to have numerous potential therapeutic applications. This study evaluated the effect of 3HB on cultured cells and in an experimental model of osteoporosis.Effects of 3HB on the proliferation of some mammalian cells in vitro were studied using MTT assay. Results showed that 3HB in concentrations ranging from 0.005 to 0.1 g/L promoted the proliferation of murine osteoblast MC3T3-E1 cells, rabbit aorta smooth muscle cells (SMCs) and hunman hepatoma HepG2 cells. These results were coincident with our previous work, indicating that 3HB can probably be a growth factor.Further study was mainly focused on the functional effect of 3HB on osteoblast. The effects of 3HB on the differentiation (ALP activity), mineralization, apoptosis and cell cycle of osteoblast MC3T3-E1 cells were evaluated. Results showed that 3HB stimulated the differentiation and mineralization and protected osteoblast MC3T3-E1 cells against apoptosis induced by serum withdrawal, while 3HB had no effect on cell cycle of MC3T3-E1 cells. These results indicated that 3HB could promote the function of osteoblast and induce bone formation, suggesting that 3HB might prevent or cure osteoporosis.On this basis, animal experiment was carried out in a rat model with osteoporosis to tested the idea. Female Wistar rats (3 months old, n = 80) were allocated into normal, sham-operated, ovariectomized (OVX), OVX receiving 3HB at 30, 150, and 750 mg/kg po daily and nilestriol at 1.5 mg/kg po weekly. They were sacrificed 3 months after OVX or the equivalent time for the normal and shams. Serum parameters, bone densitometry, bone biomechanics, and bonehistomorphometry were analyzed.In comparison with normal and sham groups, OVX induced significant body weight gain (58.8%) and uteri shrink (81.4%), and decreased bone mineral density (BMD; by 8.9%), bone histomorphometry and biomechanics. 3HB partly inhibited both the body weight gain and uteri shrink. 3HB also increased serum calcium, decreased osteocalcin, prevented the BMD decrease induced by OVX, enhanced femur maximal load and deformation, and increased the trabicular bone volume (TBV).In summary, 3HB, a degradation product of PHAs, promoted proliferation of the cells studied here, suggesting that 3HB containing PHAs may be useful for tissue regeneration when implanted in vivo. 3HB stimulated the proliferation and differentiation of osteoblasts and protected the cells from cell death triggered by serum withdrawal, which likely explained the protective effects of this ketone in experimental osteoporosis induced by ovariectomy in rats.