ECTS2013 Poster Presentations Other diseases of bone and mineral metabolism (48 abstracts)
Osteocyte metabolism on post-menopausal bone loss and role of hormone replacement therapy
Ana Maria Silva 1, , Ana Carolina Moreira 1, , Maria Sancha Santos 1, , Anabela Albuquerque 3 , Izilda Ferreira 3 , Paulo Gil 3 , Jorge Isidoro 3 , Romeu Videira 4 , Rui Carvalho 1, & Vilma Sardão 1
1CNC – Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; 2Department of Life Sciences, University of Coimbra, Coimbra, Portugal; 3SMN-CHUC – Serviço de Medicina Nuclear do Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal; 4CECAV – Animal and Veterinary Research Centre, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal.
Introduction: Osteocytes play a major role in the bone remodelling unit (BRU). Thus, we hypothesize that mitochondrial bioenergetics impairment and mitochondrial/peroxisomal fatty acid β-oxidation unbalance is a cause of osteocytes metabolic decline during 17β-estradiol (E2) reduction. E2 and a phytochemical substitute, coumestrol (COU) were used (30 mg/kg during 24 h in ovariectomized rats in order to compare bone loss with sham-operated animals.
Methods: Four groups of 12-week-old female Wistar–Han rats were used: i) controls; ii) ovariectomized animals, OVX; iii) OVX+E2; and iv) OVX+COU. Animals were sacrificed four weeks after ovariectomy and estrogens levels in blood serum were evaluated. Left and right posterior limbs were surgically removed and freeze-clamped. For each animal, one limb was used to extract metabolites from the femur and tibia bone-embedded osteocytes and to measure mineral content; the paired limb was used to measure bone mineral density (BMD) by Dual-energy X-ray absorptiometry (DXA). Methanol/water extracted metabolites were analyzed by high resolution 600 MHz 1H nuclear magnetic resonance (NMR) spectroscopy. Total lipids were trans-methylated to fatty acyl methyl esters (FAMES) and analyzed by gas chromatography coupled to a mass spectrometer (GC–MS).
Results: All experimental groups did not show differences regarding mineral content, despite OVX group presented a slight decrease on BMD. Higher lactate/alanine and acetate/alanine ratios in the OVX group, and specially in the E2 group, were observed when compared with the control. Fatty acid content of osteocytes was also measured. Fatty acid profile was altered in the E2 group, with increased content in palmitic acid, α/γ-linolenic acids and arachidonic acid, and in the OVX group, presenting a 62% decrease in tetradecenoylcarnitine and a 2.5-fold increase in indocosanoic acid, when compared with the control group.
Conclusions: Although no major alterations were observed in terms of BMD, the results suggest metabolic alterations in osteocytes, which are associated with the decline in estrogens. The methodology here described is promising in evaluating the cellular metabolites and lipid content in osteocytes and in understanding how modulation of estrogen levels impact bone metabolism and homeostasis.
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Bone Abstracts
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