Calcium deficiency decreases bone mass without affecting adiposity in ovariectomized rats fed a high-fat diet

Authors: Cao, Jay; Gregoire, Brian

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2024
Publication Date: 2/7/2024
Citation: Cao, J.J., Gregoire, B.R. 2024. Calcium deficiency decreases bone mass without affecting adiposity in ovariectomized rats fed a high-fat diet. Nutrients. 16(4). Article 478. https://doi.org/10.3390/nu16040478.
DOI: https://doi.org/10.3390/nu16040478

Interpretive Summary: Among many dietary macro- and micro-nutrients, calcium is likely the most important nutrient affecting bone health and osteoporosis risk. Existing evidence demonstrates that obesity is a risk factor for low bone mass and osteoporosis. Limited data suggest that dietary calcium may also regulate energy metabolism and obesity risk. In this study, we investigated if calcium deficiency further decreases bone mass and increases fat mass in high-fat diet fed ovariectomized rats, a model for postmenopausal bone loss. We found that the both high-fat diet and calcium deficiency decreased bone mass and dietary calcium content did not affect body weight, fat mass, lean mass, food intake, energy intake, and serum cytokines. Our results suggest that inadequate calcium intake and high-fat diet have independent negative impact on bone.

Technical Abstract: Background: Obesity induced by a high-fat (HF) diet increases bone resorption and/or decreases bone formation resulting in reduced bone mass and strength in various animal models. Inadequate Ca intake is a modifiable risk factor for osteoporosis and bone fracture. Objective: This study investigated whether Ca deficiency exacerbates bone structure and affects adiposity in ovariectomized (OVX) rats fed a HF diet. We hypothesized that Ca deficiency further decreases bone mass and increases fat mass in HF-fed OVX rats. Methods: Forty-seven OVX at 6-mo-old were purchased and randomly assigned to four groups in a 2x2 factorial design: normal-fat (NF, 10% fat as energy) diet or HF (45% fat as energy) diet with either low Ca (LC, 1 g/4,057 kcal) or normal Ca (NC, 6 g/4,057 kcal). In addition, 12 sham-operated rats at 6-mo-old were fed a NFNC diet as a control for OVX procedure. Rats were fed the respective diet for 4 mos. Food intake, body composition, tibial bone structure, femoral mineral content, and serum bone-related cytokines were measured. The main effects of dietary fat and Ca of OVX groups and their interactions were analyzed using 2-factor ANOVA. A pre-planned contrast, or a priori contrast, was written to test whether the mean of the four OVX groups differed from the Sham. Results: Dietary Ca content did not affect body weight, fat mass, lean mass, food intake, energy intake, and serum cytokines. Compared to NC, LC resulted in lower bone volume/total volume (BV/TV, P < 0.01), Connectivity Density (P < 0.01), trabecular number (Tb.N, P = 0.01), BMD (P < 0.01), femur weight (P < 0.01), femur content of Ca (P < 0.01), Cu (P = 0.03), Zn (P < 0.01), and higher trabecular separation (Tb.Sp, P < 0.01) at proximal tibia indicating bone structure deterioration. Compared to rats on NF diet, animals fed the HF had lower BV/TV (P = 0.03) and Tb.N (P < 0.01) with higher body weight (P < 0.01), fat mass (P < 0.01), Tb.Sp (P = 0.01), and serum leptin (P < 0.01). There were no significant interactions between Ca and fat for all endpoint measurements. Compared to Sham, OVX resulted in higher body weight and fat mass. Trabecular bone structure, but not cortical bone, of tibia was significantly impaired by OVX procedure. Conclusions: These data indicate that inadequate Ca intake and high-fat diet have independent negative effects on bone structure and Ca deficiency does not affect adiposity in OVX rats.