Cellular circadian period length inversely correlates with HbA1c levels in individuals with type 2 diabetes
The circadian system plays an essential role in regulating the timing of human metabolism. Indeed, circadian misalignment is strongly associated with high rates of metabolic disorders. The properties of the circadian oscillator can be measured in cells cultured in vitro and these cellular rhythms are highly informative of the physiological circadian rhythm in vivo. We aimed to discover whether molecular properties of the circadian oscillator are altered as a result of type 2 diabetes.
We assessed molecular clock properties in dermal fibroblasts established from skin biopsies taken from nine obese and eight non-obese individuals with type 2 diabetes and 11 non-diabetic control individuals. Following in vitro synchronisation, primary fibroblast cultures were subjected to continuous assessment of circadian bioluminescence profiles based on lentiviral luciferase reporters.
We observed a significant inverse correlation (ρ = −0.592; p < 0.05) between HbA1c values and circadian period length within cells from the type 2 diabetes group. RNA sequencing analysis conducted on samples from this group revealed that ICAM1, encoding the endothelial adhesion protein, was differentially expressed in fibroblasts from individuals with poorly controlled vs well-controlled type 2 diabetes and its levels correlated with cellular period length. Consistent with this circadian link, the ICAM1 gene also displayed rhythmic binding of the circadian locomotor output cycles kaput (CLOCK) protein that correlated with gene expression.
We provide for the first time a potential molecular link between glycaemic control in individuals with type 2 diabetes and circadian clock machinery. This paves the way for further mechanistic understanding of circadian oscillator changes upon type 2 diabetes development in humans.
RNA sequencing data and clinical phenotypic data have been deposited at the European Genome-phenome Archive (EGA), which is hosted by the European Bioinformatics Institute (EBI) and the Centre for Genomic Regulation (CRG), ega-box-1210, under accession no. EGAS00001003622.
KeywordsCircadian bioluminescence recording Circadian clock HbA1c Humans ICAM1 Type 2 diabetes
Circadian locomotor output cycles kaput
Munich Chronotype Questionnaire
Quantitative real-time PCR
The authors thank I. Wagner, L. Perrin (the Dibner lab), G. Sinyavsky (Florida University, USA), K. Tsutsumi and K. Tamura (Yamaguchi University, Japan) for assistance with the experiments and thank J. M. De Abreu Nunes (Department of Genetics and Evolution, University of Geneva) for help with statistical analyses.
FS, A-MM and CD collected the data and drafted the manuscript. PM, CT and JP recruited and enrolled the volunteers. ZP and AG recruited the volunteers. CH, GR and ETD conducted and analysed RNA sequencing. SAB, CP, JP and CD designed the study. All the authors participated in conception and design of the study and in the drafting and approval of the manuscript. CD is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
This work was funded by the Novartis Foundation for Medical-Biological Research, Jubiläumsstiftung Swiss Life Foundation, Vontobel Foundation and Olga Mayenfisch Foundation (CD) and by SNSF Sinergia grant CRSII3_160741 (SAB, JP, ETD).
Compliance with ethical standards
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
- 18.Benjamini Y, Hochberg Y (1995) Controlling the false discovery rate: a practical and powerful approach to multiple testing. J R Stat Soc Ser B Methodol 57(1):289–300Google Scholar
- 21.Perrin L, Loizides-Mangold U, Chanon S et al (2018) Transcriptomic analyses reveal rhythmic and CLOCK-driven pathways in human skeletal muscle. Elife 7:e34114. https://doi.org/10.7554/eLife.34114