Follicle-stimulating hormone enhances hepatic gluconeogenesis by GRK2-mediated AMPK hyperphosphorylation at Ser485 in mice
Increased serum follicle-stimulating hormone (FSH) is correlated with fasting hyperglycaemia. However, the underlying mechanism remains unclear. Because excessive hepatic gluconeogenesis is a major cause of fasting hyperglycaemia the present study investigated whether FSH increases hepatic gluconeogenesis in mice.
Ovariectomised mice supplemented with oestradiol (E2) to maintain normal levels of serum E2 (OVX+E2 mice) were injected with low or high doses of FSH. We knocked out Crtc2, a crucial factor in gluconeogenesis, and Fshr to discern their involvement in FSH signalling. To evaluate the role of the G-protein-coupled receptor (GPCR) kinase 2 (GRK2), which could affect glucose metabolism and interact directly with non-GPCR components, a specific GRK2 inhibitor was used. The pyruvate tolerance test (PTT), quantification of PEPCK and glucose-6-phosphatase (G6Pase), key enzymes of gluconeogenesis, GRK2 and phosphorylation of AMP-activated protein kinase (AMPK) were examined to evaluate the level of gluconeogenesis in the liver. A nonphosphorylatable mutant of AMPK Ser485 (AMPK S485A) was transfected into HepG2 cells to evaluate the role of AMPK Ser485 phosphorylation.
FSH increased fasting glucose (OVX+E2+high-dose FSH 8.18 ± 0.60 mmol/l vs OVX+E2 6.23 ± 1.33 mmol/l), the PTT results, and the transcription of Pepck (also known as Pck1; 2.0-fold increase) and G6pase (also known as G6pc; 2.5-fold increase) in OVX+E2 mice. FSH also enhanced the promoter luciferase activities of the two enzymes in HepG2 cells. FSH promoted the membrane translocation of GRK2, which is associated with increased AMPK Ser485 and decreased AMPK Thr172 phosphorylation, and enhanced the nuclear translocation of cyclic AMP-regulated transcriptional coactivator 2 (CRTC2). GRK2 could bind with AMPK and induce Ser485 hyperphosphorylation. Furthermore, either the GRK2 inhibitor or AMPK S485A blocked FSH-regulated AMPK Thr172 dephosphorylation and gluconeogenesis. Additionally, the deletion of Crtc2 or Fshr abolished the function of FSH in OVX+E2 mice.
The results indicate that FSH enhances CRTC2-mediated gluconeogenesis dependent on AMPK Ser485 phosphorylation via GRK2 in the liver, suggesting an essential role of FSH in the pathogenesis of fasting hyperglycaemia.
KeywordsAMPK CRTC2 FSH Gluconeogenesis GRK2 Liver
AMP-activated protein kinase
Calcium/calmodulin-dependent protein kinase
Cyclic AMP response element
Cyclic AMP response element-binding protein
Cyclic AMP-regulated transcriptional coactivator 2
Follicle-stimulating hormone receptor
GPCR kinase 2
Glycogen synthase kinase 3β
Haematoxylin and eosin
Insulin tolerance test
Insulin sensitivity index
Liver kinase B1
Mitogen-activated protein kinase
Protein kinase A
Pyruvate tolerance test
We thank Y. Wang (School of Life Sciences, Tsinghua University, China) for providing mice; H. Choi (School of Biological Sciences and Technology, Chonnam National University, Republic of Korea), J. Staňková (Department of Paediatrics, University of Sherbrooke, Canada), F. Mayor (Department of Molecular Biology, Universidad Autónoma de Madrid, Spain) and J. L. Benovic (Department of Biochemistry and Molecular Biology, Thomas Jefferson University, USA) for providing plasmids.
JZ and LG designed and supervised the project. JZ, LG, CY, YS, YG and XQ designed the experiments. XQ, YG and DK performed the experiments. XQ analysed the data and wrote the manuscript. CY, DK, LF and LZ participated in analysis and interpretation of data. All authors revised the manuscript critically and approved the final version for publication. LG is the guarantor of this work.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
- 31.Taguchi K, Matsumoto T, Kamata K, Kobayashi T (2012) Inhibitor of G protein-coupled receptor kinase 2 normalizes vascular endothelial function in type 2 diabetic mice by improving beta-arrestin 2 translocation and ameliorating Akt/eNOS signal dysfunction. Endocrinology 153:2985–2996CrossRefPubMedGoogle Scholar