Differences in leptin, ghrelin, and glucagon-like peptide-1 levels between religious fasting and normal fasting

Turkish Journal of Medical Sciences Turk J Med Sci (2017) 47: 1152-1156 © TÜBİTAK doi:10.3906/sag-1603-32 http://journals.tubitak.gov.tr/medical/ Research Article Differences in leptin, ghrelin, and glucagon-like peptide-1 levels between religious fasting and normal fasting 1, 2 3 3 3 1 Özge TELCİ ÇAKLILI *, Banu İŞBİLEN , Gülcan YAVUZ , Selcan TÜLÜ , Banu MESÇİ , Aytekin OĞUZ 1 Department of Internal Medicine, Kocaeli State Hospital, Kocaeli, Turkey 2 Department of Biochemistry, Faculty of Engineering and Natural Sciences, İstanbul Medeniyet University, İstanbul, Turkey 3 Department Internal Medicine, Faculty of Medicine, İstanbul Medeniyet University, İstanbul, Turkey Received: 03.03.2016 Accepted/Published Online: 21.02.2017 Final Version: 23.08.2017 Background/aim: Leptin, ghrelin, and glucagon-like peptide-1 (GLP-1) affect hunger, satiety feelings, and food intake. We hypothesized that during Ramadan, if the brain knows that the body will be hungry until sunset, there may be differences between leptin, ghrelin, and GLP-1 levels in Ramadan and non-Ramadan fasting. Materials and methods: This study had two phases. In the first phase, the participants were asked to skip the dawn meal of Ramadan (suhur), so that 12 h of fasting could be achieved. Participants ceased food intake at midnight, and at noon blood was drawn. Eight participants were selected as a subgroup. These participants gave blood three times a day to detect hormonal changes during Ramadan. Six months later, in the second phase, blood samples were obtained at noon from participants after 12 h of fasting. Results: Analysis was conducted on 30 patients [19 males (63.3%) and 11 females (36.7%)]. There was a significant difference in leptin, ghrelin, and GLP-1 levels between Ramadan fasting and non-Ramadan fasting (P = 0.04, P = 0.02, and P < 0.001, respectively). In the subgroup analysis, there was no statistically significant difference in leptin, ghrelin, and GLP-1 levels over time. Conclusion: The results of this study suggest that the nervous and gastrointestinal systems may behave differently in religious fasting than in nonreligious fasting. Key words: Leptin, ghrelin, glucagon-like peptide-1, fasting 1. Introduction It is a known fact that there is a link between the central nervous system and the gastrointestinal system. In recent years, this link has been further elucidated, especially with the discovery of new molecules affecting both brain and gut. One of these molecules is leptin, also known as the ‘satiety’ hormone. It is produced mostly by adipose tissue (1) and inhibits hunger in the hypothalamus (2). Another molecule interacting with appetite is ghrelin. Ghrelin is produced in the gastrointestinal tract, and its main purpose is to stimulate hunger in the brain (3). It acts on the hypothalamus and increases hunger and gastric secretions (4). Glucagon-like peptide-1 (GLP-1) is a gut peptide, an incretin that is produced mainly from intestinal L cells in the gastrointestinal system (5) and from the solitary tract nucleus of the brain (6). In modern practice, although its analogs are used for treatment of type 2 diabetes, its functions include lessening the motivational effects of * Correspondence: 1152 eating and decreasing the quantity and frequency of food consumption, leading to an early ‘fullness’ feeling (7). Ramadan is a unique month in the Islamic calendar. During Ramadan, Muslims fast from sunrise to sunset. When they wake up, they know that they will be hungry for the rest of the day. We hypothesized that if the brain knows that the body will be hungry until sunset, the aforementioned appetite-related hormone levels may be different than in normal fasting. In this regard, we aimed to identify the differences between leptin, ghrelin, and GLP-1 levels in Ramadan and non-Ramadan fasting. 2. Materials and methods 2.1. Study design Ethics committee approval for this study was obtained from the relevant ethics board (Decision No. 2013/0024). The study consisted of two phases: the first phase was in the month of Ramadan in 2013 (July) and the second phase was 6 months later (January 2014). In the first phase, TELCİ ÇAKLILI et al. / Turk J Med Sci healthy volunteers were recruited by hospital staff and blood samples were collected in the last week of Ramadan. In the second phase, blood samples were obtained 6 months later from the same participants. 2.2. Participants Power analysis was conducted to determine the sample size needed. Thirty participants were recruited according to the power analysis, and five more were included in the study to compensate for possible drop-outs. The study protocol was explained to each screened candidate. Inclusion criteria of the participants consisted of being ≥18 years old, fasting for the whole month, and giving consent. Exclusion criteria consisted of having a medical disorder or using any medical agent, pregnancy, and not fasting for the whole month. To adjust the neurological and gastroenterological system to fasting, we recruited patients who fasted the whole month and we collected the blood samples in the last week of Ramadan. 2.3. Protocol 2.3.1. First phase Participants were asked to skip the dawn meal of Ramadan (suhur) so that 12 h of fasting could be achieved. They ceased food intake at midnight and blood was drawn at noon. Eight participants were selected as a subgroup. We collected blood samples from the subgroup patients three times (0900, 1200, and 1700 hours) to detect hormonal changes during the day in Ramadan. The remaining participants gave blood only at noon (1200 hours). 2.3.2. Second phase To ensure that participants were free of the influence of Ramadan, the study protocol was repeated 6 months later. If the participant had a different BMI or waist circumference value from the first phase’s results, they were excluded from the analysis. Participants were asked to cease food intake again at midnight, and after 12 h of fasting, blood samples were obtained at noon. No subgroup was formed in the second phase. 2.4. Biochemical measurements 2.4.1. Blood samples Venous blood samples were collected into two different blood tubes: a plain blood tube to obtain a serum sample for measuring glucose, insulin, and leptin, and a prechilled BD P800 blood collection tube (Becton, Dickinson and Company, NJ, USA), which contained spray-dried K2EDTA anticoagulant and proprietary additives to collect and preserve plasma for measuring metabolic markers, including GLP-1 and ghrelin. After the collection of blood, serum and plasma samples were immediately separated by cold centrifugation and stored at –80 °C until further analysis. 2.4.2. Analytical methods All the samples were measured together centrally to prevent interassay variation. Serum glucose was measured by hexokinase method, using an Architect c8000 biochemistry analyzer (Abbott Laboratories, Abbott Park, IL, USA). Serum insulin levels were measured using a chemiluminescent immu (...truncated)