Diurnal changes of biochemical metabolic markers in healthy young males – the Bispebjerg study of diurnal variations

Abstract

Background. To examine whether time of the day has an effect on the circulating levels of metabolism parameters. Methods. Venous blood samples were obtained under standardized conditions from 24 healthy young men every third hour through 24 hours. The metabolic markers and melatonin were examined at each time-point and data were analyzed by rhythmometric statistical methods. Results. The normal 24-h rhythms of the participants were confirmed by significant oscillation of melatonin (p < 0.0001). Cosinor analysis revealed significant diurnal 24-h rhythms of five of the seven examined markers: Total cholesterol (p = 0.01, amplitude (amp) = 0.18 mmol/L) peaking in the early afternoon, Glucose (p < 0.0001, amp = 0.35 mmol/L) peaking around midnight, C-peptide (p < 0.001, amp = 360 pmol/L), triglyceride (p < 0.0001, amp = 0.37 mmol/L) peaking in the afternoon and low-density lipoprotein cholesterol (p = 0.003, amp = 0.16 mmol/L) peaking in the morning. C-peptide, triglyceride, and glucose had the highest 24-h oscillations in proportion to the reference ranges of the parameters for healthy young men. Glycated haemoglobin (HbA1c) (p = 0.07, amp = 0.57 mmol/L) and high-density lipoprotein (p = 0.09, amp = 0.06 mmol/L) did not show significant oscillations. Conclusions. When diagnosing and monitoring metabolic disorders compensation for the 24-h variation of the biochemical metabolic markers is needed especially C-peptide, triglyceride and glucose. Furthermore, the stable HbA1c level through 24 h makes it an accurate diagnostic test for diabetes mellitus.

Key Words::

• Biological clocks
• circadian clocks
• circadian rhythm
• chronobiology disorders
• diabetes mellitus
• lipids
• metabolic syndrome X

Acknowledgements

Jens Peter Goetze's help with the planning and conducting of the study is thankfully appreciated. The skillful technical assistance of the laboratory technicians of the department, in particular Anne-Louise Smidt Hansen, Lone Hellstrøm, Jannik Pedersen and Anita Hansen, is gratefully acknowledged.

Funding

The study was supported by the Danish Biotechnology Center for Cellular Communication. All the authors were independent of the funder. The study sponsor had no influence on the study design, collection, analysis and interpretation of data and the writing of the article and the decision to submit it for publication.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.