Melatonin Levels and Obesity

Background: Melatonin is a neurohormone that regulates the circadian rhythm by translating photoperiodic information from the eyes to the brain. MTNR1B , is one of melatonin receptors which is expressed in the retina, in the brain and in pancreatic tissue. In Genome Wide Association studies a SNP in the intronic variant in MTNR1B was found to be to in association with elevated fasting plasma glucose and with increased risk of T2DM among lean and obese adults and children.

Working hypothesis and aims: There is a possible link between circadian rhythm regulation and glucose homeostasis through melatonin pathways. We aim to examine the relation between melatonin levels and degree of obesity and the metabolic syndrome, in children and adolescents in different pubertal stages.

Methods: The study group will include twenty-four children and adolescents in various stages of pubertal development. Participants will be categorized into three groups: 1) normal-weight, 2) obese subjects with metabolic syndrome, 3) obese without metabolic syndrome. Melatonin levels will be measured using saliva during the night. Each child will be measured for height, weight, waist circumference and blood pressure. Fasting insulin, glucose and lipid profile will be taken. Each child will fill out questionnaires about depression, sleep quality and television usage.

Expected results: We expect to find a relation between melatonin levels to the metrics of metabolic syndrome, sleep duration, number of television viewing hours and sense of depression. We expect to find lower levels of melatonin in the group of obese children with metabolic syndrome during night time. We expect that children with lower levels of melatonin should report on fewer hours of sleep, more hours of watching television and feeling more depressed.

Importance: Childhood obesity is recognized as a major medical and public health problem and is strongly associated with many serious medical complications including the metabolic syndrome and Type 2 diabetes (T2DM). It is important to understand mechanisms involved in the development of obesity and hyperinsulinemia.