Effects of 3 diets with various calcium contents on 24-h energy expenditure, fat oxidation, and adipose tissue message RNA expression of lipid metabolism-related proteins

Background: Evidence from molecular and animal research and epidemiologic investigations indicates that calcium intake may be inversely related to body weight, possibly through alterations in 1,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3] metabolism. Objective: We tested whether energy and substrate metabolism and adipose tissue enzyme messenger RNA (mRNA) expression can be altered by dietary calcium intake in healthy, nonobese, human volunteers consuming an isocaloric diet. Design: Twelve healthy men [age: 28 +/- 2 y; body mass index (BMI; in kg/m(2)) : 25.2 +/- 06] received 3 isocaloric diets [high calcium (1259 +/- 9 mg/d), high dairy (high/high); high calcium (1259 +/- 9 mg/d), low dairy (high/low); and low calcium (349 +/- 8 mg/d), low dairy (low/low)] in a randomized crossover design. At the end of the 7-d dietary periods, 24-h energy expenditure and substrate metabolism were measured, and fat biopsy specimens were obtained to determine mRNA expression in genes involved in the lipolytic and lipogenic pathways. Results: The 24-h energy expenditure was 11.8 +/- 0.3, 11.6 +/- 0.3, and 11.7 +/- 0.3 MJ/24 h in the high/high, high/low, and low/low conditions, respectively. Fat oxidation in these conditions was 108 +/- 7, 105 +/- 9, and 100 +/- 6 g/24 h. These differences were not statistically significant. mRNA concentrations of UCP2, FAS, GPDH2, HSL, and PPARG did not differ significantly. Serum 1,25(OH)(2)D-3 concentrations changed from 175 +/- 16 to 138 +/- 15, 181 +/- 23 to 159 +/- 19, and 164 +/- 13 to 198 +/- 19 pmol/L in the high/high, high/low, and low/low conditions, respectively, and was significantly different between the high/high and low/low conditions (P < 0.05). Conclusion: Altering the dietary calcium content for 7 d does not influence substrate metabolism, energy metabolism, or gene expression in proteins related to fat metabolism, despite significant changes in 1,25(OH)(2)D-3 concentrations.