Insulin modulates norepinephrine-mediated melatonin synthesis in cultured rat pineal gland

Author(s)

Garcia‚ R.A.P. ; Afeche‚ S.C. ; Scialfa‚ J.H. ; do Amaral‚ F.G. ; dos Santos‚ S.H.J. ; Lima‚ F.B. ; Young‚ M.E. ; Cipolla-Neto‚ J.

• Document type: Journal article
• Source: Life Sciences; v. 82, n. 1-2, p. 108-114, 2008.

Abstract

The mammalian pineal gland synthesizes melatonin in a circadian manner, peaking during the dark phase. This synthesis is primarily regulated by sympathetic innervations via noradrenergic fibers, but is also modulated by many peptidergic and hormonal systems. A growing number of studies reveal a complex role for melatonin in influencing various physiological processes, including modulation of insulin secretion and action. In contrast, a role for insulin as a modulator of mclatonin synthesis has not been investigated previously. The aim of the current study was to determine whether insulin modulates norepinephrine (NE)-mediated melatonin synthesis. The results demonstrate that insulin (10(-8)M) potentiated norepinephrine-mediated melatonin synthesis and tryptophan hydroxylase (TPOH) activity in ex vivo incubated pineal glands. When ex vivo incubated pineal glands were synchronized (12h NE-stimulation, followed by 12h incubation in the absence of NE), insulin potentiated NE-mediated melatonin synthesis and arylalkylamine-N-acetyltransferase (AANAT) activity. Insulin did not affect the activity of hydroxyindole-O-methyltranferase (HIOMT), nor the gene expression of tpoh, aanat, or hiomt, under any of the conditions investigated. We conclude that insulin potentiates NE-mediated melatonin synthesis in cultured rat pineal gland, potentially through post-transcriptional events. (C) 2007 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 04/06767-2 - Melatonin and the control of energy metabolism: central and peripheral actions and their interaction with other hormones
• Grantee: José Cipolla Neto
• Support Opportunities: Research Projects - Thematic Grants