Abstract
BackgroundData 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.ObjectiveThis study aimed to clarify whether calcium supplementation alleviated bone loss caused by calcium restriction combined with estrogen deficiency in rats.MethodsForty-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.ResultsThe 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 β-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.ConclusionsThe 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.
Highlights
Osteoporosis is a disease characterized by a decrease in bone mineral density and the destruction of the bone microstructure, which eventually leads to increased bone fragility and fracture [1,2,3]
The results clearly indicated that calcium supplementation was beneficial for decreasing bone loss in Ovariectomized rats fed a low calcium diet (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
Summary
Osteoporosis is a disease characterized by a decrease in bone mineral density and the destruction of the bone microstructure, which eventually leads to increased bone fragility and fracture [1,2,3]. With the aging of the population, osteoporosis has become a common disease that endangers the health of elderly individuals worldwide and has imposed heavy economic and social burdens [4]. Osteoporosis is mainly caused by estrogen deficiency. The 2010– 2012 Chinese National Nutrition and Health Survey showed that the daily Ca intake of Chinese residents was 366.1 mg/d, which was only half of the recommended Ca intake, and the Ca intake of 96.6% of Chinese residents was lower than the estimated average requirement for Ca [12]. The vast majority of postmenopausal women in China are present with dual deficiencies in Ca and estrogen. 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
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