ABSTRACT
The concept of calcium and 1α, 25-dihydroxy (OH)2-vitamin D3 (calcitriol), which is the active form of vitamin D, modulation of adipocyte and energy metabolism was originally derived from an apparent “antiobesity” effect found in clinical trials, which investigated the effects of high calcium intake for other endpoints (e.g., skeletal and cardiovascular) [1-3]. Subsequently, a number of observational and epidemiological studies [3-8] demonstrated a strong inverse association between calcium intake, vitamin D levels, and relative risk of obesity, suggesting that vitamin D and calcium play a key regulatory role in adipocyte lipid metabolism. These observations are supported by a
8.1 Introduction .......................................................................................................................... 185 8.2 Calcitriol Regulation of Energy Metabolism ........................................................................ 186
8.2.1 Relationship between Dietary Calcium, Vitamin D, and Calcitriol ......................... 186 8.2.2 Vitamin D Status and Obesity .................................................................................. 186 8.2.3 Calcium Paradox ....................................................................................................... 186 8.2.4 Ca2+ Signaling in Adipose Tissue ............................................................................. 187 8.2.5 Role of Adipocyte nVDR .......................................................................................... 187 8.2.6 Regulation of Adipocyte Apoptosis .......................................................................... 188 8.2.7 Modulation of Adipocyte Glucocorticoid Production .............................................. 189 8.2.8 Regulation of Energy Partitioning between Adipocyte and Skeletal Muscle .......... 190
8.3 Calcitriol Regulation of Adipocyte Oxidative Stress and Inammatory Stress ................... 191 8.3.1 Regulation of ROS Production ................................................................................. 191 8.3.2 Regulation of Adipocyte Inammatory Cytokine Production ................................. 192 8.3.3 Calcitriol Regulation of Adipocyte-Macrophage Crosstalk in Inammation .......... 193
8.4 Vitamin D Supplementation and Obesity ............................................................................. 194 8.5 Conclusion ............................................................................................................................ 194 References ...................................................................................................................................... 194
large number of experimental in vitro and in vivo studies that provide a clear mechanistic framework for both genomic and nongenomic actions of calcitriol in regulation of adipocyte function.
