The effects of increasing serum calcitriol on energy and fat metabolism and gene expression

Abstract

Objective: Evidence from a number of investigations indicates that calcium intake could be inversely related to body weight through alterations in the 1,25-OH2-D3 metabolism. The objective of this study was to test whether energy and substrate metabolism and adipose tissue enzyme mRNA expression can be altered by changes in serum 1,25-OH2-D3 through oral cholecalciferol supplementation in non-obese human subjects. Research Methods and Procedures: An intervention study was used with a treatment period of 7 days. During this intervention, energy expenditure (EE) and substrate metabolism were measured using indirect calorimetry at t = 0, 1, 3, and 7 days, and blood samples were obtained at t = -1, 0, 1, 2, 3, 5 and 7 days. Fat biopsies were obtained at t = 0 and 7 days for determination of expression of genes involved in lipolytic and lipogenic pathways. Subjects from the general community were studied in an ambulatory setting at a university hospital. Ten healthy young men (age, 28 ± 3 years; BMI, 25.5 ± 0.5 kg/m 2) were recruited by local announcement, and all completed the study. All subjects received 2000 IU cholecalciferol/d for 7 days, and they were instructed to consume a low-cholecalciferol, low-calcium diet. EE, fat oxidation, and adipose tissue enzyme mRNA were the main outcome measures. Results: Despite a significant increase in serum 1,25-OH2-D 3 concentration at t = 5 and 7 days, no significant differences in substrate and energy metabolism nor mRNA concentrations of different lipid metabolism-related proteins were observed. Discussion: Seven-day supplementation with 2000 IU cholecalciferol/d together with a decrease in dietary calcium intake does not affect EE or substrate metabolism nor gene expression of proteins related to fat metabolism, despite a significant increase in serum 1,25-OH2-D3 concentration. Copyright © 2006 NAASO.