Pinealectomy causes glucose intolerance and decreases adipose cell responsiveness to insulin in rats.

Although the pineal gland influences several physiological systems, only a few studies have investigated its role in the intermediary metabolism. In the present study, male Wistar rats, pinealectomized or sham-operated 6 wk before the experiment, were submitted to both intravenous glucose tolerance tests (IVGTT) and insulin binding as well as glucose transport assays in isolated adipocytes. The insulin receptor tyrosine kinase activity was assessed in liver and muscle. The insulin secretory response during the IVGTT was impaired, particularly in the afternoon, and the glucose transport responsiveness was 33% lower in pinealectomized rats. However, no difference was observed in the insulin receptor number of adipocytes between groups as well as in insulin-stimulated tyrosine kinase activity, indicating that the initial steps in the insulin signaling were well conserved. Conversely, a 40% reduction in adipose tissue GLUT-4 content was detected. In conclusion, pinealectomy is responsible for both impaired insulin secretion and action, emphasizing the influence of the pineal gland on glucose metabolism.

[1]  Natsuko Mori,et al.  ANTI‐GLUCOCORTICOID EFFECTS OF MELATONIN IN YOUNG RATS , 1986, Acta pathologica japonica.

[2]  W. B. Quay,et al.  Effects of pinealectomy and pineal incubation medium and sonicates on insulin release by isolated pancreatic islets in vitro. , 1979, Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme.

[3]  M. Dolnikoff,et al.  The regulation of insulin action in isolated adipocytes. Role of the periodicity of food intake, time of day and melatonin. , 1994, Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas.

[4]  Iain M McIntyre,et al.  Effects of Pinealectomy and Aging on the Serum Corticosterone Circadian Rhythm in Rats , 1984, Journal of pineal research.

[5]  J W Fertig,et al.  A simple method to determine fat cell size and number in four mammalian species. , 1971, The American journal of physiology.

[6]  C. Porro,et al.  Pineal involvement in the alimentary behavior and taste preferences in the rat , 1990, Physiology & Behavior.

[7]  B. Frankel,et al.  Insulin release from isolated mouse islets in vitro: No effect of physiological levels of melatonin or arginine vasotocin , 1991, Journal of pineal research.

[8]  E. Blázquez,et al.  Effect of pinealectomy on plasma glucose, insulin and glucagon levels in the rat. , 1986, Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme.

[9]  R. A. Hoffman,et al.  Rapid pinealectomy in hamsters and other small rodents , 1965, The Anatomical record.

[10]  J. Yudkin,et al.  Diurnal changes in the concentrations of plasma lipids, sugars, insulin and corticosterone in rats fed diets containing various carbohydrates. , 1974, Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme.

[11]  G. Scatchard,et al.  THE ATTRACTIONS OF PROTEINS FOR SMALL MOLECULES AND IONS , 1949 .

[12]  S. Reppert,et al.  The Mel1a Melatonin Receptor Is Coupled to Parallel Signal Transduction Pathways 1. , 1997, Endocrinology.

[13]  F. Halberg,et al.  Perinatal malnutrition, suprachiasmatic nuclear lesioning, and circadian-ultradian aspects of spontaneous behavior of albino rats. , 1987, Progress in clinical and biological research.

[14]  R. Jarrett,et al.  Diurnal variation in insulin sensitivity. , 1972, Lancet.

[15]  H. Towbin,et al.  Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. , 1979, Proceedings of the National Academy of Sciences of the United States of America.

[16]  Quay Wb,et al.  Effects of Pinealectomy and Pineal Incubation Medium and Sonicates on Insulin Release by Isolated Pancreatic Islets In Vitro , 1979, Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme.

[17]  J. Pauly,et al.  Chronobiology: anatomy in time. , 1983, The American journal of anatomy.

[18]  W. Zawalich,et al.  Signal transduction in pancreatic beta-cells: regulation of insulin secretion by information flow in the phospholipase C/protein kinase C pathway. , 1997, Frontiers in bioscience : a journal and virtual library.

[19]  Gagliardino Jj,et al.  Effect of fasting on the circadian rhythm of serum insulin levels. , 1976, Chronobiologia.

[20]  N. Mori,et al.  Melatonin protects rats from injurious effects of a glucocorticoid, dexamethasone. , 1984, The Japanese journal of experimental medicine.

[21]  J. Cipolla-Neto,et al.  Modulation of sympathetic neurotransmission by melatonin. , 1994, European journal of pharmacology.

[22]  H. Keen,et al.  Diurnal Variation in Response to Intravenous Glucose* , 1974, British medical journal.

[23]  L. Bellinger,et al.  Circadian Insulin, GH, Prolactin, Corticosterone and Glucose Rhythms in Fed and Fasted Rats , 1975 .

[24]  L. M. Williams,et al.  Melatonin receptors in red deer fetuses (Cervus elaphus). , 1997, Journal of reproduction and fertility.

[25]  R J Jarrett,et al.  Diurnal Variation in Glucose Tolerance: Associated Changes in Plasma Insulin, Growth Hormone, and Non-esterified , 1974, British medical journal.

[26]  W. Fishbein,et al.  GAMMA-HYDROXYBUTYRATE IN MAMMALIAN BRAIN. REVERSIBLE OXIDATION BY LACTIC DEHYDROGENASE. , 1964, The Journal of biological chemistry.

[27]  M. Rodbell.  METABOLISM OF ISOLATED FAT CELLS. I. EFFECTS OF HORMONES ON GLUCOSE METABOLISM AND LIPOLYSIS. , 1964, The Journal of biological chemistry.

[28]  J. Cipolla-Neto,et al.  Temporal Profile of Superoxide Dismutase Activity in the Pineal Gland and the Liver of Rats , 1991 .

[29]  J. Pauly,et al.  Circadian rhythms in blood glucose and the effect of different lighting schedules, hypophysectomy, adrenal medullectomy and starvation. , 1967, The American journal of anatomy.

[30]  J. Olefsky,et al.  Insulin Induces Progressive Insulin Resistance in Cultured Rat Adipocytes: Sequential Effects at Receptor and Multiple Postreceptor Sites , 1986, Diabetes.