Immunohistochemical expression of pancreatic melatonin receptor (MTNR1B) under experimental sleep disturbance in rats

Sleep amount and quality are important to maintain health, light exposure transported to the pineal gland via suprachiasmatic nucleus pineal pathway, and this affect melatonin synthesis. Melatonin exerts its action by receptors called MT1, MT2 that found in peripheral tissues including pancreas, which affect its endocrine function. In this study we investigate the effect of type of sleep disturbance on the histological structure and the expression of melatonin receptor (MTNR1B) in the pancreas. A sample of 45 adult healthy male rats had free access to water and feeding, divided into 3 groups (15 in each group): the control group had normal 24 h diurnal variation, group A subjected to interruption of sleep by light exposure for 2 h at three intervals, and group B subjected to a reduction in sleep duration by 7 h. This experiment continued for 14 days, animals were scarified by euthanasia by cervical dislocation, pancreatic tissue prepared for paraffin blocks and stained by H&E, and IHC for MTNR1B. Histomorhometric analysis done by image J (V 1.54), immunohistochemical assessment done by Aprioscope image analysis software 12.4.6.5003) mean total positivity of expression was selected, statistical analysis done by SSPS (25 V) and Tukeyꞌs test. Histological evaluation revealed changes in sleep disturbance groups including fat deposition, vascular dilatation, and apoptotic changes for group of cells within islets of Langerhans which showed significant reduction in their count in sleep disturbance groups compared to control, and non-significant change in their area across the groups, but significant reduction in area in sleep deprived group compared to sleep interruption. Immunohistochemical expression of MTNR1B showed it only expressed within the area of islets of Langerhans, with non-significant increase in expression in sleep disturbed groups, being more in sleep deprived group. This study showed that the pancreas is affected by sleep disturbance patterns, mainly its endocrine part (islets of Langerhans), with study expression of melatonin receptor within them. This may suggest a role of melatonin in maintaining pancreatic ꞵ cells.