ABSTRACT
BACKGROUND: Data from the 2010-2012 Chinese National Nutrition and Health Survey showed that the vast majority of postmenopausal women in China had dual deficiencies in calcium and estrogen. OBJECTIVE: This study aimed to clarify whether calcium supplementation alleviated bone loss caused by calcium restriction combined with estrogen deficiency in rats. METHODS: Forty-eight female rats aged 9 weeks were assigned to 4 groups and fed a low-calcium diet: sham-operated (SHAM-LC), ovariectomized (OVX-LC), and ovariectomized rats treated with 750 mg/kg (OVX-LC-M) or 2800 mg/kg CaCO3 (OVX-LC-H). CaCO3 or distilled water was administered orally for 13 weeks. Bone mineral density (BMD) and histomorphometry of the femur, serum biochemical parameters, and serum metabolites were analyzed. RESULTS: The OVX-LC rats showed a significant increase in body weight and serum levels of lipid markers, a significant decrease in serum estradiol, calcium, phosphorus, and 25(OH)D levels, and deterioration of the femur. At 750 mg/kg and 2800 mg/kg, CaCO3 reduced the deterioration of trabecular bone and increased the trabecular area percentage (Tb.Ar %) and BMD of the femur. Serum estradiol levels increased in a dose-dependent manner after CaCO3 supplementation (p < 0.01). The administration of 2800 mg/kg CaCO3 decreased serum triglyceride and high-density lipoprotein levels (p < 0.05) and decreased the levels of the bone turnover markers osteocalcin, N-telopeptide of type I collagen and ß-crosslaps. The results of the metabolomics analysis showed that the glycerophospholipid metabolism pathway was closely related to calcium supplementation, and more DG (44:6 n3), LysoPC (22:2) and PE (P-34:3) and less Cer (d43:0) and PE-NMe2 (46:3) were produced. CONCLUSIONS: The results clearly indicated that calcium supplementation was beneficial for decreasing bone loss in OVX-LC rats. The present study is the first to show that calcium supplementation increased the estradiol content in OVX-LC rats, and the effect of calcium on bone loss may be partially attributed to the increase in the estrogen level that subsequently induced the changes in metabolite levels, eventually increasing the bone mineral density to a relatively higher level to reduce bone deterioration.
ABSTRACT
OBJECTIVE: To study the effect of calcium content on bone mineral density and intestinal microbiota in ovariectomized rats. METHODS: A total of 30 Wistar rats were randomly divided into 3 groups, namely the sham operation group, the model group and the calcium carbonate supplement group. Postmenopausal osteoporosis rats were established by ovariectomy(OVX). After the first week of modeling, each group was intragastric separately. The calcium carbonate solution was given to the calcium carbonate supplement group, and the same amount of sterile water was given to the other two groups. The animals were executed at the end of the 12 weeks. Left femur was taken and bone mineral density(BMD) was detected by dual-energy X-ray absorptiometry. The total DNA of fecal samples was aseptically extracted and the Illumina Miseq platform was to carry out high-throughput sequencing. RESULTS: Compared with the sham operation group, the body mass increment of rats in the model group was significantly increased, the level of BMD was significantly reduced(P<0. 05), the intestinal microbiota diversity was not significantly changed, the Firmicutes abundance was decreased, and the Bacteroidetes abundance was increased. Compared with the model group, the body mass increment of rats in the calcium carbonate supplementation group was significantly reduced and BMD was significantly increased(P<0. 05). There was no significant change in the intestinal microbiota diversity, Firmicutes were increased, and Bacteroidetes were decreased. CONCLUSION: Calcium supplementation can improve bone mineral density and inhibit the increase of body mass during the experiment period, and its mechanism may be related to regulating the structure of intestinal microbiota.