Possible metabolic impact of Ramadan fasting in healthy men

Turkish Journal of Medical Sciences Turk J Med Sci (2014) 44: 1010-1020 © TÜBİTAK doi:10.3906/sag-1308-30 http://journals.tubitak.gov.tr/medical/ Research Article Possible metabolic impact of Ramadan fasting in healthy men 1,2 2 1, Mustafa Cumhur VARDARLI , Hans-Peter HAMMES , İrfan VARDARLI * 1 Bad Lauterberg Diabetes Center, Bad Lauterberg, Germany 2 Fifth Medical Department, Mannheim Faculty of Medicine, University of Heidelberg, Mannheim, Germany Received: 08.08.2013 Accepted: 24.03.2014 Published Online: 24.10.2014 Printed: 21.11.2014 Background/aim: Insulin sensitivity and β-cell function during Ramadan fasting in healthy male subjects have not been investigated so far. We assessed the changes of these and other metabolic parameters to judge the potential metabolic benefits of Ramadan fasting. Materials and methods: Twenty-four healthy males of Turkish origin living in Germany, with normal glucose tolerance, participated in this study during Ramadan of 2009; 19 who completed fasting were analyzed. Blood was drawn at sunset after a period of fasting lasting approximately 15 h on days 0, 16, and 30 of Ramadan, as well as 7 and 28 days later. Insulin sensitivity (Homeostasis Model Assessment, HOMA), β-cell function, and other parameters were assessed. Results: Ramadan fasting was associated with a significant reduction (–) or increment (+) for the following variables: insulin sensitivity (–20%; P = 0.04), β-cell function (+10%; P = 0.049), high-density lipoprotein cholesterol (–23%; P = 0.0003), low-density lipoprotein cholesterol (+14%; P = 0.007), nonesterified fatty acids (–62%; P < 0.0001), resistin (–20%; P = 0.01), adiponectin (+16%; P = 0.003), and glucagon (–21%; P = 0.01). C-peptide, insulin, leptin, triglyceride, and very low-density lipoprotein cholesterol concentrations were not significantly changed. Conclusion: Ramadan fasting is associated with transiently impaired insulin sensitivity, compensated for by an increased β-cell function. However, the pattern of insulin resistance-mediating adipocytokines suggests a potentially beneficial metabolic effect of Ramadan fasting. Key words: Insulin sensitivity, β-cell function, adiponectin, leptin, resistin, Ramadan fasting 1. Introduction Many efforts have been undertaken to elucidate the changes of metabolic parameters during Ramadan fasting in healthy subjects, including the following: 1) Regarding blood glucose, significant reductions (1,2) or no significant changes (3,4) have been reported. 2) Insulin was not changed (3,5). 3) For high-density lipoprotein (HDL) as well as low-density lipoprotein (LDL) cholesterol concentrations, conflicting data have been published, (6,7), and no significant changes were described for very low-density lipoprotein (VLDL) cholesterol (4,7,8). 4) Concerning triglycerides, conflicting data have been presented (3,4,6,7). 5) Regarding thyroid parameters, Fadail et al. reported a significant rise in total thyroxin and a reduction in triiodothyronine (5), and Sajid et al. showed a significant increment in thyrotropin (9). 6) For cortisol, Al-Hadramy et al. reported a reduction and Bahijri et al. reported an increase in concentrations (10,11). 7) With respect to renal parameters, conflicting urea concentrations have been reported (2,3,7), and Maislos * Correspondence: 1010 et al. found no significant changes regarding creatinine concentrations (7). Several studies showed a reduction (3,8,12), and other studies no change, in body weight or body mass index (BMI) (4,13) during Ramadan fasting. 8) Blood pressure during Ramadan fasting has been found unchanged (14), or systolic as well as diastolic blood pressures were reported decreased (15). Adlouni et al. reported an increase (6) and Bouhlel et al. a significant decrease (3) in total calorie intake during Ramadan fasting. All adult Muslims, with some exceptions (e.g., illness, gestation, menstruation, and travel), are requested to fast 30 days from early dawn until sunset during the ninth lunar calendar every year. Metabolic parameters are usually determined in the morning. However, in studies during Ramadan the parameters are obtained before sunset in the evening. The equivalence/comparability of fasting parameters obtained in the morning and in the evening, respectively, has not been investigated so far. VARDARLI et al. / Turk J Med Sci To our knowledge, insulin sensitivity, β-cell function, glucagon, nonesterified fatty acids, and adipocytokines (adiponectin, leptin, and resistin) have not been examined during and after Ramadan fasting in healthy subjects with normal glucose tolerance so far. Therefore, in the present study we investigated the changes in insulin sensitivity, β-cell function, and other metabolic factors during and after Ramadan fasting in healthy men with normal glucose tolerance. 2. Materials and methods 2.1. Protocol The study protocol was approved by the ethics committee of the Georg-August University of Göttingen (registration number 23/1/09) on 18 May 2009, and the study was carried out in accordance with the Declaration of Helsinki. 2.2. Subjects We recruited 24 healthy male migrants of Turkish origin in Germany who had decided to participate in Ramadan fasting independent from our study. Inclusion criteria: Healthy male subject with normal oral glucose tolerance, aged 18–75 years. Exclusion criteria: BMI of <18.5 or ≥35 kg/m2, any type of diabetes, impaired glucose tolerance, impaired fasting glucose , endocrine disorders influencing glucose metabolism, treatment with drugs with influence on glucose metabolism (e.g., hydrochlorothiazide, β-blockers, diazoxide, interferon-alpha, cyclosporine, glucocorticoids, nicotinic acid, statins, and fibrates), any interruption of Ramadan fasting, renal insufficiency at screening [estimated glomerular filtration rate (eGFR) of <60 mL/min], and overt hyper- or hypothyroidism. 2.3. Procedures The volunteers participated at the following visits: Visit 1, screening in the morning, 0800–0900 hours (between 5 June and 19 August 2009), after a period of at least 12 h without nutrient intake. Visit 2 (day 0), beginning of Ramadan fasting [20 August 2009, 1940–2040 hours, at sunset (“iftar”)] (to enable the participants to take their meal at sunset on the first day of Ramadan fasting (21 August 2009) together with their families at home, we started the fasting 1 day earlier than usual). Visit 3 (day 16), in the middle of the Ramadan fasting period (5 September 2009, 1905–2005 hours). Visit 4 (day 30), end of Ramadan fasting (19 September 2009, 1835–1935 hours). Visit 5 (day 37), 7 days after the end of Ramadan fasting (26 September 2009, 1820–1920 hours). Visit 6 (day 58), 28 days after the end of Ramadan fasting (17 October 2009, 1730–1830 hours). During Ramadan fasting and thereafter the examinations were at sunset after a fasting period. The duration of the fasting period was from 0440 to 2040 hours on day 0, and thereafter it shifted with the exact timing of (...truncated)