Circadian Clock, Diurnal Glucose Metabolic Rhythm, and Dawn Phenomenon

Authors

Fei Peng
Xin Li
Fang Xiao
Ruxing Zhao
Zheng Sun

Publication Date

6-1-2022

Journal

Trends Neuroscience

DOI

10.1016/j.tins.2022.03.010

PMID

35466006

PMCID

PMC9117496

PubMedCentral® Posted Date

6-1-2023

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes

Keywords

Circadian Clocks, Circadian Rhythm, Diabetes Mellitus, Type 2, Glucose, Humans, Hyperglycemia, Suprachiasmatic Nucleus, circadian rhythm, metabolism, diabetes, SCN, GABA, neuron

Abstract

The circadian clock provides cue-independent anticipatory signals for diurnal rhythms of baseline glucose levels and glucose tolerance. The central circadian clock is located in the hypothalamic suprachiasmatic nucleus (SCN), which comprises primarily GABAergic neurons. The SCN clock regulates physiological diurnal rhythms of endogenous glucose production (EGP) and hepatic insulin sensitivity through neurohumoral mechanisms. Disruption of the molecular circadian clock is associated with the extended dawn phenomenon (DP) in type 2 diabetes (T2D), referring to hyperglycemia in the early morning without nocturnal hypoglycemia. The DP affects nearly half of patients with diabetes, with poorly defined etiology and a lack of targeted therapy. Here we review neural and secreted factors in physiological diurnal rhythms of glucose metabolism and their pathological implications for the DP.