Endocrine Abstracts (2015) 38 P6 | DOI: 10.1530/endoabs.38.P6

Increased circulating sclerostin levels in type 2 diabetic rats are not associated with changes in bone sclerostin production

Marie Pereira1, Stephanie Gohin1, Nina Lund1, Anne Hvid1, Peter Smitham2, Michael Oddy3, Ines Reichert4 & Chantal Chenu1

1Royal Veterinary College, London, UK; 2Institute of Orthopaedics & Musculoskeletal Science, Stanmore, UK; 3University College London, London, UK; 4Kings College, London, UK.

Type 2 Diabetes Mellitus (T2DM) is associated with decreased bone quality and a higher prevalence of fractures. Sclerostin is an inhibitor of bone formation produced by osteocytes and its expression is elevated in serum of diabetic patients. We examined the effect of T2DM on bone architecture and sclerostin levels in a rat model of T2DM and the influence of hyperglycaemia on sclerostin production by bone cells in vitro. Bone architecture was measured by microCT in 14 weeks-old Zucker diabetic fatty (ZDF) and control Zucker lean male rats (n=6/group). Sclerostin expression was quantified in serum at 9, 11 and 13 weeks using ELISA and in rat femurs using qPCR. The number of osteocytic empty lacunae was measured on tibia sections of ZDF and control rats. Osteoblast-like UMR106 cells were cultured with increasing concentrations of glucose and sclerostin mRNA expression and protein release determined by qPCR and ELISA, respectively. Our results showed that ZDF rats have lower trabecular bone mass and mineral density compared to controls, due to decreases in bone volume and thickness. They also exhibit impaired bone connectivity and cortical bone geometry. Serum sclerostin levels were higher in ZDF compared to lean rats at 9 weeks (+40%, P<0.01), but this difference disappeared after 11 weeks. Bone sclerostin mRNA levels were similar in ZDF and lean rats. The number of osteocytic empty lacunae in bones of ZDF and lean rats was comparable. Glucose dose-dependently stimulated sclerostin mRNA levels and protein release in UMR106 cells. Altogether, our data indicate that sclerostin production is increased by hyperglycemia in vitro and in serum of ZDF rats at onset of diabetes, but bone sclerostin levels and the number of apoptotic osteocytes are not elevated in diabetic rats. Further studies are required to determine whether sclerostin contributes to the deleterious effect of T2DM on bone.

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