L-Carnitine activates calcium signaling in human osteoblasts

Abstract

L-Carnitine (L-C) is a conditionally essential nutrient required for β-oxidation and cell energy production whose unbalanced metabolism is associated with a variety of diseases. L-C increased cell proliferation, differentiation and mineralization of human osteoblast in culture. The present study evaluated the effect of L-C on intracellular calcium signaling, an important modulator of cell proliferation and differentiation in human osteoblasts by means of Fura-2 fluorescence coupled to video imaging technique. 5 mM L-C promoted a calcium influx from the extracellular milieu by depolarizing L-type calcium channels. Moreover, L-C depleted the calcium stores of the mitochondria and of the endoplasmic reticulum through phospholipase C activation. The inhibition of the calcium sensing receptor with 10 µM NPS-2143 prevented the L-C dependent cytosolic calcium increase suggesting that this calcium mobilization is mediated by Calcium Sensing Receptor activation. These results unravel that L-C might be part of a complex nutritional environment which tunes osteoblast activity.

Keywords

• L-Carnitine
• Human primary osteoblast-like cells
• L-VDCC
• PLC sensitive stores
• Mitochondrial calcium stores
• Calcium sensing receptor