Lower melatonin concentrations and sleep quality in patients with type 2 diabetes and obesity

Abstract

Introduction: There is a close relationship between melatonin as a circadian regulator and insulin, glucagon and somatostatin production. This study aimed to describe subgroups of type 2 diabetes mellitus (T2DM) patients that may benefit from melatonin clock-targeting properties. Materials and methods: The study involved 38 participants: 26 type 2 diabetes patients, and 12 participants without diabetes in the control group. The study involved 20 women and 18 men aged 26 to 86 years. The doctors of the enrolled patients were asked to complete a questionnaire on their patients´ diabetes and co-morbidity treatment. Each participant was asked to complete two questionnaires. The first questionnaire consisted of questions regarding history of diabetes and lifestyle factors: dietary, smoking, alcohol and caffeine-containing beverage intake habits. Each participant also completed the questionnaire of Pittsburgh Sleep Quality Index (PSQI). PSQI is an effective tool for assessing sleep quality in adults. The "good” and "poor” quality of sleep is determined by evaluating the seven components. Standard biochemical venous sample testing was performed. In addition, one sample of saliva was collected for melatonin testing immediately after awakening (6:00 to 6:30 AM). Following sampling, the sample was refrigerated within 30 minutes, and frozen at -20 ° C within 4 hours. On the day of testing, samples were defrozen and centrifuged at 1500 x g for 15 minutes, then the samples were brought on an analyte plate within 30 minutes. Testing was performed with The Salimetrics® Melatonin Enzyme Immunoassay Kit in accordance with the manufacturer´s instructions (Salimetrics: Melatonin ELISA Kit (Saliva) -Salimetrics Assays The data were processed and analyzed using Microsoft Excel and IBM SPSS 20. Non-parametric statistical methods were employed. The results are shown as median (interquartile range). Continuous variable differences between the two groups were analyzed with Mann-Whitney test, and Spearman´s rank correlation coefficient was used for correlation testing. Results: This study showed a trend of higher PSQI score correlation with a lower melatonin concentration. Subjects with PSQI score ≥ 5 had a median melatonin concentration of 6.6 pg/ml vs those with PSQI score < 5 :14.6. The overall BMI of the study population was 31.5 kg/m2. Patients with DM had a significantly higher BMI than the control group: 36.1 kg/m2 vs 23.2 kg/m2, respectively. Melatonin concentration in participants without obesity (BMI < 30 kg/m2) was significantly higher than that in obese participants. Obese participants had a significantly higher PSQI score than non-obese subjects. When analyzing concentration of melatonin in T2DM patients and participants without the condition, a significantly higher concentration was observed in the control group. Conclusions: The current study evaluated melatonin levels and sleep quality in T2DM and obese patients. We showed that both T2DM and obesity were associated with lower melatonin levels. Furthermore, obesity was also associated with poor sleep quality according to the PSQI score. Acknowledgements: The publication was supported in part by grant No. 2014.10-4/VPP- 1.1.2 and -5.1.2 in the framework of the Latvian National Program.