ABSTRACT
The present study was designed to determine the effects of pineal glandderived melatonin on obesity by employing a rat pinealectomy (Pnx) model. After 10 weeks of a highfat diet, rats received sham or Pnx surgery followed by a normal chow diet for 10 weeks. Reverse transcriptionquantitative PCR, western blotting analysis, immunohistochemistry and ELISA were used to determine the effects of Pnx. Pnx decreased the expression of melatonin receptor (MTNR)1A and MTNR1B, in brown adipose tissues (BAT) and white adipose tissues (WAT). Pnx rats showed increased insulin sensitivity compared with those that received sham surgery. Leptin levels were significantly decreased in the serum of the Pnx group. In addition, Pnx stimulated thermogenic genes in BAT and attenuated lipogenic genes in both WAT and the liver. Histological analyses revealed a marked decrease in the size of lipid droplets and increased expression of uncoupling protein 1 in BAT. In the liver of the Pnx group, the size and number of lipid droplets had also decreased. In conclusion, the results presented in the current study suggested that Pnx increases thermogenesis in BAT and decreases lipogenesis in WAT and the liver.
Subject(s)
Lipogenesis , Obesity/metabolism , Pinealectomy/methods , Thermogenesis , Adipose Tissue, Brown/metabolism , Adipose Tissue, White/metabolism , Animals , Disease Models, Animal , Down-Regulation , Gene Expression Regulation , Insulin Resistance , Leptin/blood , Liver/metabolism , Male , Obesity/etiology , Obesity/genetics , Rats , Receptor, Melatonin, MT1/genetics , Receptor, Melatonin, MT1/metabolismABSTRACT
Pinealectomy can cause a disturbance in emotional status and circadian rhythms of the endocrine and metabolic functions in the body. Endurance training is considered a part of the complex therapy of dysfunctions driven by changes in circadian dynamics of many physiological indicators. In the present study, we aimed to study the effect of endurance training on depressive behavior induced by pinealectomy in rat. We tested the hypothesis that endurance training can have a beneficial impact on depressive behavior induced by pinealectomy in rat via correction of desynchronized circadian rhythms of corticosterone secretion in plasma and brain-derived neurothrophic factor (BDNF) in the hippocampus. The continuous exercise program attenuated depressive responses characterized by the disrupted diurnal rhythm of home-cage motor activity, anhedonia in the sucrose preference test, decreased grooming in the splash test, and despair-like behavior in the forced swimming test of rats with pinealectomy to values resembling those of sham-treated controls. Parallel to the observed positive effect on the emotional status, exercise training diminished total plasma corticosterone levels and corrected its flattened pattern. While the melatonin deficiency did not affect the fluctuations of the BDNF levels, the exercise program induced a considerable and time-dependent increase in its level. These findings suggest that the antidepressant-like effect of endurance training might be mediated via correction of the disturbed circadian rhythm of corticosterone release and enhancement of hippocampal BDNF levels in rats with pinealectomy. Therefore, this alternative mode might have a potential therapeutic application in a subpopulation of people characterized by a melatonin deficiency.
Subject(s)
Brain-Derived Neurotrophic Factor/metabolism , Circadian Rhythm/physiology , Corticosterone/metabolism , Depression/metabolism , Endurance Training/methods , Pinealectomy/methods , Animals , Depression/psychology , Depression/therapy , Endurance Training/psychology , Exercise Test/methods , Exercise Test/psychology , Male , Motor Activity/physiology , Physical Conditioning, Animal/methods , Physical Conditioning, Animal/psychology , Pineal Gland/metabolism , Pineal Gland/surgery , Pinealectomy/psychology , Rats , Rats, Wistar , Time FactorsABSTRACT
Melatonin, a neuroendocrine hormone synthesized by the pineal gland and cholangiocytes, decreases biliary hyperplasia and liver fibrosis during cholestasis-induced biliary injury via melatonin-dependent autocrine signaling through increased biliary arylalkylamine N-acetyltransferase (AANAT) expression and melatonin secretion, downregulation of miR-200b and specific circadian clock genes. Melatonin synthesis is decreased by pinealectomy (PINX) or chronic exposure to light. We evaluated the effect of PINX or prolonged light exposure on melatonin-dependent modulation of biliary damage/ductular reaction/liver fibrosis. Studies were performed in male rats with/without BDL for 1â¯week with 12:12â¯h dark/light cycles, continuous light or after 1â¯week of PINX. The expression of AANAT and melatonin levels in serum and cholangiocyte supernatant were increased in BDL rats, while decreased in BDL rats following PINX or continuous light exposure. BDL-induced increase in serum chemistry, ductular reaction, liver fibrosis, inflammation, angiogenesis and ROS generation were significantly enhanced by PINX or light exposure. Concomitant with enhanced liver fibrosis, we observed increased biliary senescence and enhanced clock genes and miR-200b expression in total liver and cholangiocytes. In vitro, the expression of AANAT, clock genes and miR-200b was increased in PSC human cholangiocyte cell lines (hPSCL). The proliferation and activation of HHStecs (human hepatic stellate cell lines) were increased after stimulating with BDL cholangiocyte supernatant and further enhanced when stimulated with BDL rats following PINX or continuous light exposure cholangiocyte supernatant via intracellular ROS generation. Conclusion: Melatonin plays an important role in the protection of liver against cholestasis-induced damage and ductular reaction.
Subject(s)
Arylalkylamine N-Acetyltransferase/genetics , CLOCK Proteins/genetics , Cholestasis/genetics , Liver Cirrhosis/genetics , Melatonin/biosynthesis , MicroRNAs/genetics , Animals , Arylalkylamine N-Acetyltransferase/metabolism , Bile Ducts, Intrahepatic/metabolism , Bile Ducts, Intrahepatic/pathology , Bile Ducts, Intrahepatic/surgery , CLOCK Proteins/metabolism , Cell Line , Cell Proliferation/radiation effects , Cholestasis/metabolism , Cholestasis/pathology , Epithelial Cells/metabolism , Epithelial Cells/radiation effects , Gene Expression Regulation , Hepatic Stellate Cells/metabolism , Hepatic Stellate Cells/radiation effects , Humans , Kupffer Cells/metabolism , Kupffer Cells/radiation effects , Light , Liver/metabolism , Liver/pathology , Liver/surgery , Liver Cirrhosis/metabolism , Liver Cirrhosis/pathology , Male , MicroRNAs/metabolism , Pineal Gland/metabolism , Pineal Gland/radiation effects , Pineal Gland/surgery , Pinealectomy/methods , Primary Cell Culture , Rats , Rats, Inbred F344 , Signal TransductionABSTRACT
To determine the role of the pineal gland and its secretory product melatonin on various aspects of the functioning of the organism, the gland can be easily surgically removed in rats within 18 hours after birth. We performed pinealectomy in rats in a state of deep hypothermia under an operating microscope, using a micro-suction device of our own construction. The rats were induced into a state of suspended animation by placing them in the freezing compartment at minus 20 Celsius degrees. The cessation of respiration and heart beat lasted for about 15 minutes. During that time the pinealectomy was performed. In some cases there was minor hemorrhage that was easily controlled. There were no major side effects or mortality following surgery. All rats recovered within 15 minutes after the end of the procedure. The pinealectomy procedure described in this study is simple, rapid, effective and safe, and can be easily performed with instruments commonly available in most laboratories.
