ABSTRACT
The pineal hormone melatonin is known to influence insulin secretion via the G-protein-coupled receptor isoforms MT1 and MT2. The present study was aimed to further elucide the impact of melatonin on blood glucose regulation. To this end, mouse lines were used, in which one of the two or both melatonin receptors were deleted. In comparison with wild-type mice of the same age (8-12 months old), increased plasma insulin and melatonin levels and decreased blood glucose levels and body weights were detected in the MT1- and double-knockout lines. The elimination of melatonin receptor signalling also altered blood glucose concentrations, body weight and melatonin and insulin levels when comparing wild-type and receptor knockout mice of different ages (6 wk and 8-12 months old); such changes, however, were dependent on the type of receptor deleted. Furthermore, reverse transcription polymerase chain reaction results provided evidence that melatonin receptor deficiency has an impact on transcript levels of pancreatic islet hormones as well as on pancreatic and hepatic glucose transporters (Glut1 and 2). Under stimulated insulin secretion in the presence of melatonin in the rat insulinoma ß-cells INS-1, the Glut1 transcript level was decreased. In conclusion, the present findings demonstrate that melatonin receptor knockout types affect blood glucose levels, body weight, plasma levels of melatonin and insulin, as well as pancreatic hormone and Glut1 expression in significantly different manners.
Subject(s)
Blood Glucose/metabolism , Receptor, Melatonin, MT1/metabolism , Receptor, Melatonin, MT2/metabolism , Analysis of Variance , Animals , Blood Glucose/genetics , Body Weight/genetics , Cell Line, Tumor , Female , Glucagon/analysis , Glucagon/genetics , Glucagon/metabolism , Glucose Transporter Type 1/analysis , Glucose Transporter Type 1/genetics , Glucose Transporter Type 1/metabolism , Insulin/blood , Male , Melatonin/blood , Mice , Mice, Knockout , Organ Specificity , RNA, Messenger/analysis , RNA, Messenger/genetics , Receptor, Melatonin, MT1/genetics , Receptor, Melatonin, MT2/genetics , Somatostatin/analysis , Somatostatin/genetics , Somatostatin/metabolismABSTRACT
Cochlear implantation has become a standard therapy for children with bilateral profound hearing loss, resulting in substantial and sustainable benefits for the development of expressive and receptive and expressive language skills and cognition. During the last few years, audiologic and otologic criteria for cochlear implantation have been expanded. Recently, patients with profound single-sided deafness with or without tinnitus have received cochlear implants despite normal to near-normal hearing on the contralateral side. This indication, however, has thus far been restricted to adult patients. Although it is known that unilateral hearing has an impact on social-emotional development in children, otologic surgeons have been reluctant to treat children with single-sided deafness with a cochlear implant. We report here on a case of successful cochlear implantation in an 8-year-old boy with acute single-sided deafness due to a lateral skull-base fracture, after an MRI showed signs of imminent fibrosis of the inner ear with possible prevention of cochlear implantation at a later stage. There was normal hearing in the contralateral ear. The child showed rapid development of speech discrimination in the implanted ear, improvements in sound localization and speech perception in noise, and a high degree of patient satisfaction. This experience may encourage using this therapeutic approach in children with chronic profound single-sided deafness.
