Paper Title
Melatonin Levels in Saudi Female with Type 2 Diabetes Mellitus

Abstract
Melatonin functioning in diabetes mellitus has been investigated, researchers have recorded a decline in plasma melatonin concentrations in diabetes. The current study aimed to assess melatonin levels and investigate their correlation with glucose levels in female patients with type 2 diabetes mellitus.A case-control study was conducted between January 2017 to January 2019 with 100 diabetic participants and 100 healthy participants from Taibah University. Our study enrolled 100 type 2 diabetic mellitus (DM) female patients, aged 30–55 years, and 100 age-matched healthy female control subjects. After overnight fasting, glucose, glycated hemoglobin (HbA1c), melatonin, insulin levels, and lipid profile were analyzed to determine the association between melatonin levels and glucose intolerance and lipid profile in females with type 2 DM. Data processing was performed using GraphPad Prism 7. Quantitative data were expressed as mean [SD]. The student’s t-test was applied to compare the continuous baseline characteristics of the study groups. Daytime melatonin levels decreased considerably in the diabetic group compared to the non-diabetic group (P =.003) and were lower in the diabetic retinopathy group than in the non-retinopathy groups (P = .02). There was a significantly evident and negative correlation between the decreasing melatonin levels and glucose levels (r = −0.531, P = .001). Also, there were significant negative correlations between the decreasing melatonin levels and the increase in insulin levels and insulin resistance (IR) (r = −0.421, P = .02, r = −0.634, P = .002).The melatonin level decreased in patients with diabetes and was negatively associated with increased IR. The alteration of melatonin levels may accelerate the additional incidence of complications in diabetic patients, especially retinopathy. Keywords - Circadian Rhythm; Diabetic Retinopathy; Melatonin; Type 2 Diabetes; Glucose Metabolism; Glycemia.