Circadian clocks, clock networks, arylalkylamine N-acetyltransferase, and melatonin in the retina

Iuvone, P. Michael; Tosini, Gianluca; Pozdeyev, Nikita; Haque, Rashidul; Klein, David C.; Chaurasia, Shyam S.

doi:10.1016/j.preteyeres.2005.01.003

Cited by 307 publications

(295 citation statements)

References 241 publications

Supporting

Mentioning

277

Contrasting

Unclassified

Order By: Relevance

“…It explains why there is actually a very modest daily variation in AANAT mRNA levels in humans, but a prominent rhythm of protein levels and activity. Moreover, PKA phosphorylates the transcription factor cAMP-responsive element binding protein, which activates transcription of AANAT; this process is particularly effective in rodents, in which, at night, there is an approximately 100-fold increase in pineal gland levels of AANAT mRNA [16]. Furthermore, AANAT is itself subject to phosphorylation by PKA, which enhances its activity [15].…”

Section: Pineal Secretion Of Melatoninmentioning

confidence: 99%

See 1 more Smart Citation

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

et al. 2009

View full text Add to dashboard Cite

Melatonin is a circulating hormone that is primarily released from the pineal gland. It is best known as a regulator of seasonal and circadian rhythms; its levels are high during the night and low during the day. Interestingly, insulin levels also exhibit a nocturnal drop, which has previously been suggested to be controlled, at least in part, by melatonin. This regulation can be explained by the proposed inhibitory action of melatonin on insulin release. Indeed, both melatonin receptor 1A (MTNR1A) and MTNR1B are expressed in pancreatic islets. The role of melatonin in the regulation of glucose homeostasis has been highlighted by three independent publications based on genome-wide association studies of traits connected with type 2 diabetes, such as elevated fasting glucose, and, subsequently, of the disease itself. The studies demonstrate a link between variations in the MTNR1B gene, hyperglycaemia, impaired early phase insulin secretion and beta cell function. The risk genotype predicts the future development of type 2 diabetes. Carriers of the risk genotype exhibit increased expression of MTNR1B in islets. This suggests that these individuals may be more sensitive to the actions of melatonin, leading to impaired insulin secretion. Blocking the inhibition of insulin secretion by melatonin may be a novel therapeutic avenue for type 2 diabetes.

show abstract

Section: Pineal Secretion Of Melatoninmentioning

confidence: 99%

“…1) for how melatonin is released from the pineal gland [16,[20][21][22]: the circadian clock in the suprachiasmatic nucleus is more active during the day than at night. The neurons in the suprachiasmatic nucleus release γ-aminobutyric acid (GABA) to inhibit the activity of neurons in the paraventricular nucleus.…”

Section: Pineal Secretion Of Melatoninmentioning

confidence: 99%

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

et al. 2009

View full text Add to dashboard Cite

show abstract

“…A highly conserved feature in vertebrates is the daily rhythmic pattern of MEL synthesis, which is determined by rhythms in AANAT activity, protein amount and, in some cases, gene expression, resulting in a nocturnal increase of this neurohormone (Iuvone et al, 2005, Klein, 2007. Pineal and retinal expression of Aanats has been reported in several teleost adults Zilberman-Peled et al, 2004;2006) and in photoreceptive organs of embryos of chum salmon (Shi et al, 2004), turbot (Vuilleumier et al, 2007) and in the sole (Isorna et al, 2009), and a species-dependent expression pattern has been evidenced.…”

Section: Introductionmentioning

confidence: 99%

MELATONIN-SYNTHESIZING ENZYMES IN PINEAL, RETINA, LIVER, AND GUT OF THE GOLDFISH (CARASSIUS): mRNA EXPRESSION PATTERN AND REGULATION OF DAILY RHYTHMS BY LIGHTING CONDITIONS

Velarde

Cerdá‐Reverter

Alonso-Gómez

et al. 2010

Chronobiology International

View full text Add to dashboard Cite

(MAX 350 WORDS)Melatonin is currently proposed to be synthesized in non-photosensitive organs of vertebrates, besides its well-known sites of synthesis, the pineal gland and the retina.However, very few studies have demonstrated gene expression of MEL synthesizing enzymes in extrapineal and extraretinal locations. In the present study, present study focuses on the circadian expression of the two key enzymes of the melatoninergic pathway, the AANAT and the HIOMT in central and peripheral locations of the goldfish we give report of the full-length cloning of the two enzymes catalyzing the final steps of melatonin biosynthesis, the arylalkylamine N-acetyltransferase (AANAT) and the hydroxyindole-Omethyltransferase (HIOMT), in a teleosts fish, the goldfish (Carassius auratus). Both enzymes showed high similarity with other teleost sequences, corresponding to the goldfish AANAT-2 and HIOMT-2. Two forms of AANATs were widely known to exist in teleosts, but this is the first time that two isoforms of HIOMT are deduced from a phylogenetic analysis.Both enzymes were detected in several peripheral locations, including liver and gut, being present results the first to find HIOMT in non-photosensitive structures of a fish species. No studies exist on transcriptional regulation of the expression of MEL biosynthesis enzymes in non photosensitive structures in fish The daily expression pattern of both genes in pineal gland, retina, liver and gut was investigated using quantitative real time RT-PCR and cosinor analysis. This is the first time that a rhythmic expression of AANAT and HIOMT are found in digestive tissues of a vertebrate species, supporting a functional melatonin synthesis pathway in liver and gut of the goldfish. Besides, the transcriptional regulation of Aanat-2 in pineal and peripheral locations of goldfish maintained under different lighting conditions was investigated expression of gAANAT-2 is analyzed under different lighting conditions including continuous light and darkness, revealing, as expected, light-dependent rhythms in pineal gland and retina, but also in liver. Nevertheless, the persistence in hindgut of these Aanat-2 rhythms in constant conditions suggests that the expression of this transcript is under circadian clock and entrained by non-photic cues. Our results reinforce the existence of melatonin synthesis in gut and liver of the goldfish, while the rhythmic expression profiles reported point to a regulation of both genes in gut and liver by peripheral oscillators entrainable to non-photic cues.

show abstract

“…Melatonin is at the core of the vertebrate circadian system; nonetheless it also fulfils several other paracrine roles many of which still need to be studied (Beyer et al, 1998;Falcon et al, 2003;Barrenetxe et al, 2004;Iuvone et al, 2005;Hardeland et al, 2006). Typically, melatonin is produced at night in two main sites: the pineal gland and the retina.…”

Section: Introductionmentioning

confidence: 99%

“…Melatonin produced by the pineal gland in response to the daynight rhythm is released into the bloodstream and cerebrospinal fluid (Tricoire et al, 2002) and to act as a "zeitgeber" (endocrine role) to other processes. In the retina, melatonin has been suggested to play a paracrine role such as protecting the tissue through detoxification (Falcon et al, 2003;Klein, 2004;Iuvone et al, 2005;Siu et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Retinal light input is required to sustain plasma melatonin rhythms in Nile tilapia Oreochromis niloticus niloticus

Martinez-Chavez

Migaud

2009

Brain Research

View full text Add to dashboard Cite

The aim of this work was to confirm previous findings suggesting that the eyes are required for night-time melatonin production in Nile tilapia and further characterise this divergent circadian organisation. To do so, melatonin levels were firstly measured in eyecups and plasma to determine circadian patterns of melatonin production.Secondly, the effect of partial ophthalmectomy on the suppression of melatonin production was determined in vivo as well as ex vivo pineal light/dark sensitivity.Finally, to investigate whether such findings could be related to post-surgery stress, melatonin analyses were performed in the subsequent 24 h and 7 days postophthalmectomy with cortisol levels assessed as an indicator of stress. Our results showed an inverse pattern of melatonin production in the eye cups of tilapia compared to blood circulating levels, suggesting different roles played by melatonin in these two tissues. Results then demonstrated that total or partial ophthalmectomy resulted in the suppression of night-time melatonin production. Furthermore, although pineals in culture were shown to be photosensitive, night-time melatonin levels were much lower than seen in other species. Finally, when performing sampling immediately or one week post-surgery, no difference in the melatonin profiles were observed. It is therefore unlikely that post-surgery stress would explain such suppression in melatonin production although all fish displayed high cortisol levels most probably due to social and handling stress. Taken together, these results provide further evidence of a new type of circadian organisation in a teleost species where the eyes are required to sustain night time melatonin levels. Section: Regulatory systems

show abstract

Circadian clocks, clock networks, arylalkylamine N-acetyltransferase, and melatonin in the retina

Cited by 307 publications

References 241 publications

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

MELATONIN-SYNTHESIZING ENZYMES IN PINEAL, RETINA, LIVER, AND GUT OF THE GOLDFISH (CARASSIUS): mRNA EXPRESSION PATTERN AND REGULATION OF DAILY RHYTHMS BY LIGHTING CONDITIONS

Retinal light input is required to sustain plasma melatonin rhythms in Nile tilapia Oreochromis niloticus niloticus

Contact Info

Product

Resources

About