Elsevier

Physiology & Behavior

Volume 123, 17 January 2014, Pages 231-235
Physiology & Behavior

Daily profile in two circadian markers “melatonin and cortisol” and associations with metabolic syndrome components

https://doi.org/10.1016/j.physbeh.2012.06.005Get rights and content

Abstract

Objective

The aim of the present work was to investigate associations in circadian markers, melatonin (MT) and cortisol, with metabolic syndrome (MetS) parameters, and with leptin, adiponectin and ghrelin plasma values.

Methods

The study was conducted in 70 women (mean age: 41 ± 10 years) that were classified without MetS (n = 30) and with MetS (n = 40). Blood collection, plasma separation and processing, and biochemical analyses for plasma lipids were performed. For measuring salivary melatonin, participants collected two samples. The first simple was obtained before lunch (at 14:00 p.m.) and the second sample was taken at night (3:00 a.m.). On a random working day, participants delivered repeated salivary cortisol samples. The first sample was obtained in the morning (09:00 a.m.), then before lunch at (14:00 p.m.), and finally just before bedtime (23:00 p.m.).

Results

Significant differences were found between the MT measurements taken at night in women without and with MetS. With respect to cortisol, significant differences were found in the different times cortisol levels toward a more flattened pattern among MetS women. Both parameters were positive correlated between them. Of note MT and cortisol night/morning ratios were associated with MetS score and metabolic syndrome components.

Conclusion

The findings indicate that diminished daily amplitude in MT and cortisol circadian patterns was associated with metabolic disturbances in blood pressure, glucose and plasma lipids regulation, ghrelin and adipocyte-secreted hormones such as leptin and adiponectin.

Highlights

► Investigate associations in circadian markers with metabolic syndrome. ► Women with MetS had less melatonin values at night than women without MetS. ► Cortisol levels toward a more flattened pattern among MetS women. ► Melatonin and cortisol amplitudes were associated with MetS score and components. ► Melatonin and cortisol circadian patterns were associated with metabolic disturbances.

Introduction

Obesity and some of the metabolic syndrome (MetS) features could be explained as a fault in the circadian system, as a pathology associated with “chronodisruption” [1], [2]. In the circadian orchestra, different biological rhythms are the output of rhythmic activity of organs and physiological systems driven by the central pacemaker, the suparachiasmatic nuclei (SCN) [2], [3]. Thus, for example, melatonin (MT) peaks during the night in response to nocturnal activation by SCN of the limitant enzyme AANAT (arylalkylamine N-acetyltransferase) in the pineal gland, while cortisol peak should occur in the morning in response to suprarenal activation by ACTH (adrenocorticotropic hormone), which in turn, is under SCN control [4]. When the orchestra is out of tune within our body, we talk about chronodisruption.

Different studies performed in hibernating animals have shown that characteristic seasonal changes in fat stores depend on the photoperiod through the nocturnal release of MT. This ability to manipulate energy balance through photoperiod of MT provides new opportunities to discover new control mechanisms involved in the central control of energy homeostasis and body weight regulation [5].

The pineal hormone, MT, is a messenger of the light–dark alternation in our environment and is thought to serve as synchronizer for circadian rhythms and seasonal variations. Its circadian periodicity may be understood as a coordinating signal for other biological rhythmicities, or as an “endogenous synchronizer [6]. Plasma MT levels have been shown to be a good biomarker of circadian dysregulation and have been associated with shift work and exposure to light-at-night in both laboratory-based and field studies. Among other circadian markers, rhythms (such as core body temperature) remain comparatively robust in the presence of various external influences [7].

Interestingly, MT is not stored in the pineal gland and thus the plasma concentrations directly reflect its synthesis and secretion. Moreover, MT concentrations in saliva parallel those in plasma and are comparable in their circadian timing, but in lower concentration [8].

It is noteworthy that MT exerts a modulatory effect on several endocrine functions [9]. Due to the effect of the pineal gland on the pituitary–adrenocortical axis (PAA) [10], [11], the study of MT circadian profiles seems to be particularly important in pathological situations such as obesity, where alterations of the PAA function can occur [12].

An important marker of PAA function is cortisol. This hormone is also considered as another relevant circadian marker rhythm. Cortisol amplitude, obtained as the difference between morning and evening values, has been previously associated with obesity, and more specifically with abdominal obesity [13]. Salivary cortisol response to waking has been also identified as a marker of neuroendocrine regulation that may be influenced by psychological stress and other factors [14], [15].

Previous studies have demonstrated the relationship between MT secretion and the PAA i.e. cortisol secretion [16].

The aim of the present work was to investigate associations in circadian markers, MT and cortisol, with metabolic syndrome parameters, and with leptin, adiponectin and ghrelin plasma values.

Section snippets

Subjects

The study was conducted in 70 women, with no other (endocrine, renal, hepatic, or severe psychiatric) disorders and who were not using prescribed drugs or other pharmacologic treatment, no one of them had obstructive sleep apnoea disorders. Patients with missing data or technical problems in collecting nocturnal saliva samples were excluded from the study. All procedures were in accordance with good clinical practice and was performed in accordance with the Helsinki Declaration of Human Studies

Subject characteristics

The anthropometric characteristics, circadian markers and MetS component data of the participants are listed in Table 1.

MT values (after lunch and at night) in women without and with MetS are represented in Fig. 1a. Significant differences were found between the MT measurements taken at night in women without and with MetS, while significance was lost among “before lunch” measurements between both groups of women without MetS. Fig. 1b, illustrates the time course of salivary cortisol

Discussion

The present study confirms an important role of both circadian marker rhythms MT and cortisol of the circadian homeostatic system on metabolic syndrome (MetS) in women. Indeed, MT and cortisol rhythmicity was flattened in women suffering from MetS. In the following section we will discuss the impact on the different factors.

When comparing daily MT measurements, data showed significant differences in MT night measurements attending to MetS, toward decreased values among the MetS women group.

Acknowledgements

This work was supported by The Spanish Government of Science and Innovation (projects BFU2011-24720), the SENECA Foundation (project 15123/PI/10) and the Tomás Pascual and Pilar Gómez-Cuétara Foundations.

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