Hepatic noradrenergic innervation acts via CREB/CRTC2 to activate gluconeogenesis during cold

Abstract

Background and aim: Although it is well established that hormones like glucagon stimulates gluconeogenesis via the PKA-mediated phosphorylation of CREB and dephosphorylation of the cAMP-regulated CREB coactivators CRTC2, the role of neural signals in the regulation of gluconeogenesis remains uncertain.

Methods and results: Here, we characterize the noradrenergic bundle architecture in mouse liver; we show that the sympathoexcitation induced by acute cold exposure promotes hyperglycemia and upregulation of gluconeogenesis via triggering of the CREB/CRTC2 pathway. Following its induction by dephosphorylation, CRTC2 translocates to the nucleus and drives the transcription of key gluconeogenic genes. Rodents submitted to different models of sympathectomy or knockout of CRTC2 do not activate gluconeogenesis in response to cold. Norepinephrine directly acts in hepatocytes mainly through a Ca²⁺-dependent pathway that stimulates CREB/CRTC2, leading to activation of the gluconeogenic program.

Conclusion: Our data demonstrate the importance of the CREB/CRTC2 pathway in mediating effects of hepatic sympathetic inputs on glucose homeostasis, providing new insights into the role of norepinephrine in health and disease.

Keywords: Calcium pathway; Hepatic glucose production; Liver; Noradrenaline; Sympathetic nervous system.