Relative Metabolic Stability, but Disrupted Circadian Cortisol Secretion during the Fasting Month of Ramadan

Chronic feeding and sleep schedule disturbances are stressors that exert damaging effects on the organism. Practicing Muslims in Saudi Arabia go through strict Ramadan fasting from dawn till sunset for one month yearly. Modern era Ramadan practices in Saudi Arabia are associated with disturbed feeding and sleep patterns, namely abstaining from food and water and increasing daytime sleep, and staying awake and receiving food and water till dawn.

Strict Ramadan practices in Saudi Arabia may influence metabolism, sleep and circadian cortisol secretion.

Young, male Ramadan practitioners were evaluated before and two weeks into the Ramadan. Blood samples were collected at 9.00 am and 9.00 pm for measurements of metabolic parameters and cortisol. Saliva was collected serially during the day for cortisol determinations.

Ramadan practitioners had relative metabolic stability or changes expected by the pattern of feeding. However, the cortisol circadian rhythm was abolished and circulating insulin levels and HOMA index were increased during this period.

The flattening of the cortisol rhythm is typical of conditions associated with chronic stress or endogenous hypercortisolism and associated with insulin resistance.

Modern Ramadan practices in Saudi Arabia are associated with evening hypercortisolism and increased insulin resistance. These changes might contribute to the high prevalence of chronic stress-related conditions, such as central obesity, hypertension, metabolic syndrome and diabetes mellitus type 2, and their cardiovascular sequelae observed in the Kingdom.

Citation: Bahijri S, Borai A, Ajabnoor G, Abdul Khaliq A, AlQassas I, Al-Shehri D, et al. (2013) Relative Metabolic Stability, but Disrupted Circadian Cortisol Secretion during the Fasting Month of Ramadan. PLoS ONE 8(4): e60917. https://doi.org/10.1371/journal.pone.0060917

Editor: Harpal Singh Randeva, University of Warwick – Medical School, United Kingdom

Received: December 6, 2012; Accepted: March 4, 2013; Published: April 18, 2013

Copyright: © 2013 Bahijri et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This study was supported by the deanship of research at King Abdulaziz University – Jeddah- Kingdom of Saudi Arabia under grant number (HiCi/1432-6-2) as part of a main research project conducted by “Saudi Diabetes Study Research Group”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Disruption of feeding and sleep schedules have adverse effects on affect and metabolism [1], [2], [3], [4]. Both conditions are stressors that influence the stress system and the secretion of its mediators, including corticotropin-releasing hormone, the catecholamines norepinephrine and epinephrine and cortisol, through which they exert damaging effects [5]. The chronicity of these stressors is key, as stress hormones are meant to act as homeostatic mediators in a time-limited fashion, allowing tissue repair and functionality once they no longer exist [6].

The Muslims represent roughly 1/4th of humanity [7]. The religious fasting of the Ramadan takes place once a year and lasts one month, i.e. accounts for about 8 percent of a practicing adult Muslim's life. During Ramadan, there is no food or water taken up from dawn to sunset. Instead, all feeding and water uptake take place from sunset to dawn. Traditional fasting practices in the past did not affect daily routine dramatically. However with modernization and availability of electricity, lifestyle changed dramatically, especially in the gulf countries. Staying up till dawn became a common practice among all age groups and socioeconomic classes, curtailing the duration of sleep and disturbing its quality. These stressful changes during the Ramadan are accentuated when it takes place in the summer, when the daylight hours are increased.

This study examined the effect of Ramadan fasting and disturbance of sleep patternson markers of metabolism and circadian cortisol secretion of practicing healthy young Saudi Arabian men and women.

Studying the same subjects at different times helps to avoid variability between groups at base time, and allows for smaller sample number. Based on laboratory quality control data, and reference ranges for intended measurements, sample size was calculated to avoid type II statistical error [8]. Since serum cortisol showed the greatest variability, and its analytical method had the highest coefficient of variation, a difference of 20% in its mean was adopted to calculate the required sample size, which was found to be 18.7. This was increased further to account for drop-outs, and the total number of recruited subjects was 25. The protocol was approved by the Committee on the Ethics of Human Research at the “Faculty of Medicine- King Abdulaziz University”. Twenty-fourvolunteer healthy subjects (19 males, 5 females), aged 18–42 years, were recruited and completedthe study. Written informed consent was obtained in all cases. Volunteers were studied twice, during their regular life before, and again 10–15 days into the Ramadan (fasting) period. They were instructed to have meals as usual on the day of testing, and to record their usual sleeping and waking times for the previous three days. Anthropometric and blood pressure measurements were obtained by a team of two trained observers using calibrated tools.

Blood samples were drawn twice daily at 9 am (±1 hour) and again twelve hours later. Thus, sample one and three were obtained while fasting (at least 10 hours for sample one and 6–7 hours for sample 3), and samples two and four were obtained 2–5 hours after meals as shown in Figure 1.

https://doi.org/10.1371/journal.pone.0060917.g001

The subjects were also given salivettes (SARSTEDT) to collect saliva every 4 hours for 24 hours, except when asleep, during both days of blood sampling. Salivary samples were collected using the salivette tubes and cotton swabs saturated with citric acid (SARSTEDT, Cat. 51.1534.001). Salivettes are specially designed for cortisol determination in saliva (recovery ∼100% after swab centrifugation). Salivettes were stored in the refrigerator during collection time, and brought to the laboratory for storage in the next morning. Separated serum samples, as well as centrifuged saliva samples, were stored at −80°C until measurements were performed.

Serum biochemical and endocrine parameters were assayed in the accredited Clinical Chemistry laboratories of the “National Guard Hospital” in Jeddah. Serum glucose and lipids (cholesterol, triglycerides and high density lipoprotein (HDL-C) were assayed on ABBOTT Architect c16000 auto-analyzer, which was also employed for the quantitative determination of electrolytes (Sodium, Potassium and Chloride) in serum using the principle of Integrated Chip Technology (ICT). Low density lipoprotein- cholesterol (LDL-C) was calculated using the Friedewald equation [9]. Insulin was measured by a chemiluminescent microparticle immunoassay (CMIA) on ABBOTT Architect i1000 auto-analyzer. Insulin and glucose values were used to calculate homeostasis model assessment (HOMA-IR) insulin resistance equation [10]. Serum cortisol was determined by achemiluminescence immunoassay using Immulite1000. All tests were kindly donated by Abbott Medi-Serve (Saudi Arabia).

Salivary cortisol was assayed at the “Nutrition Research Unit” at King Fahd Medical Research Centre by IBL-AMERICA Salivary Cortisol HSELISA kit using Thermo Labsystems Ultra Wash Plus microplate washer and Multilabel Counter VICTOR model 1420 plate reader from PerkinElmer, UK. The assay is a solid phase enzyme-linked immunosorbent assay (ELISA), based on the principle of competitive binding with a maximum intra- and inter-assay coefficient of variation (CV) of 9.1 % and 11.9%, respectively, and analytical sensitivity of 0.012 ng/mL.

Analyses were performed using SPSS statistical package version 16. Descriptive statistics, such as mean ± SEM, were calculated for all estimated parameters. Paired Student t-test, and the Mann Whitney-U test were employed for comparison of normally distributed and non-normally distributed parameters, respectively. Linear regression analysis was carried out for Shaaban and Ramadan separately with salivary cortisol concentrations being the dependent variables and time being the independent variable. Significance was assigned at p