Metabolomics reveals citric acid secretion in mechanically?stimulated osteocytes is inhibited by high glucose.

Abstract

Osteocytes are the main cells of bone tissue and play a crucial role in bone formation and resorption. Recent studies have indicated that Diabetes Mellitus (DM) afects bone mass and potentially causes higher bone fracture risk. Previous work on osteocyte cell cultures has demonstrated that mechanotransduction is impaired after culture under diabetic pre-conditioning with high glucose (HG), specifcally osteoclast recruitment and diferentiation. The aim of this study was to analyze the extracellular metabolic changes of osteocytes regarding two conditions: pre-conditioning to either basal levels of glucose (B), mannitol (M) or HG cell media, and mechanical stimulation by fuid fow (FF) in contrast to static condition (SC). Secretomes were analyzed using Liquid Chromatography and Capillary Electrophoresis both coupled to Mass Spectrometry (LC-MS and CE-MS, respectively). Results showed the osteocyte profle was very similar under SC, regardless of their pre-conditioning treatment, while, after FF stimulation, secretomes followed diferent metabolic signatures depending on the preconditioning treatment. An important increment of citrate pointed out that osteocytes release citrate outside of the cell to induce osteoblast activation, while HG environment impaired FF efect. This study demonstrates for the frst time that osteocytes increase citrate excretion under mechanical stimulation, and that HG environment impaired this efect.