Abstract: Objective  To explore the effect of thyroid-stimulating hormone (TSH) on the multisite phosphorylation of hepatic AMP-activated protein kinase (AMPK)α subunit,  and to  reveal the possible mechanism of TSH-regulated AMPKα activity in the liver. Methods  ① In the HepG2 cells stimulated with or without TSH, and the TSH receptor knockout (Tshr-ko) mice and their littermate mice, the expressions of hepatic AMPKα mRNA, total AMPKα protein, phosphorylation of AMPKα Thr 172, AMPKα Ser 173 and acetyl-CoA carboxylase (ACC) Ser 79 were detected by real-time PCR and Western blotting. ② With AICAR (AMPK activator), H89 (PKA inhibitor) or TSH stimulation, AMPKα and ACC phosphorylation were tested in liver cells. Results  Compared to the control group, TSH decreased phosphorylation of AMPKα Thr 172 (P<0.05) in cells, but AMPKα phosphorylation at Ser 173, as well as total AMPKα protein expression, showed no significant change (P>0.05). Compared to WT mice, the expressions of AMPKα mRNA and total protein remained unchanged in Tshr-ko mouse liver. The phosphorylation of AMPKα Thr 172 (P<0.05) and ACC Ser 79 (P<0.01) increased while AMPKα phosphorylation at Ser 173 had no significant difference (P>0.05). AICAR and H89 increased phosphorylation of AMPKα Thr 172 and ACC Ser 79. When H89 was employed, the TSH-induced decrease of AMPKα Thr 172 phosphorylation was partly reversed. Conclusion  TSH regulates the phosphorylation of hepatic AMPKα Thr 172 instead of Ser 173 by acting on thyrotropin receptor.

Key words: Ser 173, AMP-activated protein kinase &alpha, Thyroid-stimulating hormone, Thr 172, Liver, AMP-activated protein kinase &alpha