Endocrine Abstracts

In addition to its central role in the control of thyrocyte growth and function, the TSHR is expressed during the differentiation of mesenchymal precursors. To explore further, we have developed an in vitro model in which TSHR activation is achieved by introducing constitutively active (M453T, L629F) TSHR, using retroviral vectors.

We aimed to investigate the effect of TSHR activation on body composition, via the production of TNFα and expression of its receptor, TNFαR1, in preadipocyte and osteoblast-like cell lines.

Preadipocyte (NIH3T3LI,WAT; PAZ6, BAT) and osteoblast-like (MG63) cell lines, non-modified or stably expressing the WT, L629F or M453T TSHR were cultured in DMEM supplemented with FCS. NIH3T3LI were also cultured in medium to induce differentiation. TNFα released into the medium was measured by ELISA. RNA was extracted; reverse transcribed and transcripts for TNFαR1 and a housekeeping gene measured with Sybr green and a Stratagene MX3000.

Results: Number of cells required to produce 1 pg/ml TNFα in 18 hours.

In NIH3T3LI, TSHR activation induces a 4–5 fold decrease in TNFα and a 10 fold increase in TNFαR1 expression. Differentiation induces a 5 fold increase in TNFα which is increased 3 fold further by TSHR activation. In PAZ6, TSHR activation induces 2–3 and 10 fold decreases in TNFα and TNFαR1 respectively. In MG63, TSHR activation induces 2–3 and 2–8 fold increases in TNFα and TNFαR1 respectively. TSHR activation has opposing effects on the production of TNFα and on the potential to respond to this ligand in pre-adipocytes and osteoblast-like cells. Since TNFα inhibits adipogenesis but promotes osteogenesis, TSHR activation may impact body composition. It may also provide a mechanism for the increased inflammation of Graves’ disease.