ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 P739

Interleukin-6 is not essential for bone turnover in hypothyroid mice

Janusz Mysliwiec, Robert Zbucki, Maria Winnicka, Boguslaw Sawicki, Agnieszka Nikolajuk, Karol Kaminski, Piotr Mysliwiec, Wlodzimierz Musial, Zofia Bondyra, Jerzy Walecki & Maria Gorska

Medical University, Bialystok, Poland.

Interleukin-6 (IL-6) has been shown to be involved in the pathogenesis of several bone diseases characterized by an imbalance between bone resorption and formation. Lately we have published our data suggesting an important role of IL-6 in thyrotoxicosis-related osteoporosis in mice (Horm Metab Res 2007 39 1–5).

Aim: The aim of the study was to estimate serum markers of bone turnover: osteoclast-derived tartrate-resistant acid phosphatase form 5a (TRACP 5b) and osteocalcin in IL-6-deficient mice to assess the role of IL-6 in bone metabolism in hypothyroidism in mice.

Material and methods: C57BL/6J (wild-type; WT) and C57BL/6JIL6-/-Kopf (IL-6 knock-out; IL6KO) mice randomly divided into 4 groups with 10 in each one: 1/WT mice in hypothyroidism (WT-ht), 2/WT controls, 3/IL6KO mice with hypothyroidism (IL6KO-ht) and 4/IL6KO controls. Experimental model of hypothyroidism was induced by intraperitoneal injection of propylthiouracyl. The serum levels of TRACP 5b and osteocalcin were determined by ELISA.

Results: Serum concentrations of TRACP 5b (median and interquartile ranges) were significantly decreased in both groups of mice with hypothyroidism: WT (3.2 (2.5–4.7) U/l) and IL6KO (2.6 (1.8–3.5) U/l) as compared to the respective controls. Similarly, serum osteocalcin levels were significantly reduced in both groups of mice in experimental hypothyroidism: WT (25.8 (23.0–28.2) ng/ml) and IL6KO (21.5(19.0–24.6) ng/ml) in comparison to the respective controls. There were no significant differences in bone turnover markers between IL6KO and WT mice both in hypothyroid and control animals.

Conclusions: The results of the present study suggest that IL-6 does not play an important role in bone turnover in both euthyroid and hypothyroid mice.