Effects Of Different High-fat Diets On Bone Strength And Metabolic Indices Of Different Month-age Ovariectomized Rats

Objective: To observe the effects of different high-fat diets on bone strength and metabolic indices of different month-age ovariectomized rats.Methods:Part 1: 3-month-old female SD rats were randomly divided into sham operated group fed normal chow(SHAM), sham operated group fed high-fat diet(HFD), ovariectomized group fed normal chow(OVX), ovariectomized group treated with high-fat diet(OVX-HFD). The HFD and OVX-HFD group were fed high-fat diet containing 30% fat,0.632% calcium and 0.01% vitamin D3 for 28 weeks. The SHAM and OVX group were fed normal chow. At the end of the experiment, serum fasting blood-glucose(FBG), lipids,estradiol(E2), N-MID osteocalcin(N-MID-OT) and tartrate-resistant acid phosphatase(TRAP) were detected; the bone mineral density(BMD) and bone mineral content(BMC)of rats’ right femurs and lumbar vertebras, the biomechanics of rats’ left femurs and contents of hydroxyproline, calcium and phosphorus of rats’ left femurs were determined.HE staining was used to observe the morphology of rat’s endometrium and trabecula bone in the distal femoral metaphysis.Part 2: 6-month-old female SD rats were randomly divided into sham operated group fed normal chow(SHAM), sham operated group fed high-fat diet(HFD), sham operated group fed high-fat diet deficient in calcium, phosphorus and vitamin D3(HFDD), ovariectomized group fed normal chow(OVX), ovariectomized group treated with high-fat diet(OVX-HFD) and ovariectomized group treated with high-fat diet deficient in calcium,phosphorus and vitamin D3(OVX-HFDD). The HFD and OVX-HFD group were fed high-fat diet containing 30% fat, 0.632% calcium and 0.01% vitamin D3 for 28 weeks. The HFDD and OVX-HFDD group were fed a deficient high-fat diet containing 30% fat for 28 weeks. The SHAM and OVX group were fed normal chow. At the end of the experiment,serum FBG, lipids, E2, N-MID-OT and TRAP were detected; the BMD and BMC of rats’ right femurs and lumbar vertebras, the biomechanics of rats’ left femurs and contents of hydroxyproline, calcium and phosphorus of rats’ left femurs were determined. HE staining was used to observe the morphology of rat’s endometrium and trabecula bone in the distal femoral metaphysis. The protein expression of osteocalcin and MMP9 were assayed by immunohistochemistry(IHC) staining.Results:Part 1: Compared with SHAM group, serum FBG and TRAP levels were significantly higher, while femoral BMD and BMC, bone strength, femoral contents of hydroxyproline and calcium were decreased remarkably in OVX group. Compared with those in SHAM group, the serum levels of FBG, lipids, N-MID-OT and TRAP were increased significantly,and the BMD, BMC of femurs and lumbar vertebras, bone strength, femoral calcium content were increased in HFD group. Compared with OVX group, serum levels of FBG,total cholesterol(TC), the BMD and BMC of femurs and lumbar vertebras, bone strength and femoral calcium content were significantly increased, while serum levels of N-MID-OT and TRAP were increased without obvious differences in OVX-HFD group.Deterioration in femoral trabecula bone and atrophy in endometrium were observed in ovariectomized rats.Part 2: 1.Compared with SHAM group, serum TC and TRAP levels were significantly higher, while femur BMD, content of calcium and expression of osteocalcin protein in femoral trabecula bone were significantly decreased in OVX group. Compared with those in SHAM group, serum FBG, BMD and BMC of femurs and lumbar vertebras and bone strength were significantly increased in HFD group. Moreover, serum FBG and TC were remarkably increased and expression of osteocalcin protein was significantly reduced in HFDD group compared with SHAM group. 2. Compared with OVX group, serum N-MID-OT and femoral calcium content were significantly higher, while serum FBG, TC,TRAP, BMD of femurs and lumbar vertebras, bone strength and expression of osteocalcin protein were increased without significannt difference in OVX-HFD group. Compared with those in OVX group, serum N-MID-OT was sinificantly higher, but BMD and bone strength of femurs were significantly decreased in OVX-HFDD group. 3. Compared with HFD group, serum N-MID-OT and TRAP were sinificantly higher, while BMD of femurs and lumbar vertebras, bone strength and expression of osteocalcin protein were significantly reduced in OVX-HFD group. In HFDD group, BMD and BMC of femurs and lumbar vertebras, bone strength, calcium content and expression of osteocalcin protein were remarkably decreased compared with HFD group. 4. Compared with HFDD group,serum TRAP was sinificantly increased, while BMD, bone strength and calcium content of femurs were sinificantly decreased in OVX-HFDD group. 5. Compared with OVX-HFD group, BMD, bone strength and calcium content of femurs were significantly reduced in OVX-HFDD group. 6. Deterioration in femoral trabecula bone and atrophy in endometrium were observed in all ovariectomized rats, but the bone loss in OVX-HFDD group was severest.Conclusion:(1) The combination of ovariectomy with high-fat diet successfully build a rat model of osteoporosis with obesity and metabolic disturbance in glucose and lipids.(2) The nutritious high-fat diet containing 30% fat could increase the bone mass and bone strength of the 3-month-old normal and ovariectomized rats, which may be due to the enhanced bone formation induced by the balanced diet.(3) The nutritious high-fat diet containing 30% fat increased the femoral calcium content of the 6-month-old ovariectomized rats probably due to the enhanced osteoblast activity.(4) The nutritious high-fat diet containing 30% fat increased the bone mass and bone strength of the 6-month-old normal rats.(5) The deficient high-fat diet containing 30% fat aggravated the bone loss of the6-month-old ovariectomized rats and reduced the bone strength, which may be due to the increased bone turnover induced by the deficiency in calcium, phosphorus and vitamin D3.(6) The deficient high-fat diet containing 30% fat didn’t reduce the bone mass and bone strength of the 6-month-old normal rats, but it weakened the activity of osteoblasts.