Person: Alonso Gómez, Ángel Luis
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First Name
Ángel Luis
Last Name
Alonso Gómez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Biológicas
Department
Genética, Fisiología y Microbiología
Area
Fisiología
Identifiers
8 results
Search Results
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Item Nuclear receptors (PPARs, REV-ERBs, RORs) and clock gene rhythms in goldfish (Carassius auratus) are differently regulated in hypothalamus and liver(Frontiers in Physiology, 2022) Gómez-Boronat, Miguel; Pedro Ormeño, Nuria de; Alonso Gómez, Ángel Luis; Delgado Saavedra, María Jesús; Isorna Alonso, EstherThe circadian system is formed by a network of oscillators located in central and peripheral tissues that are tightly linked to generate rhythms in vertebrates to adapt the organism to the cyclic environmental changes. The nuclear receptors PPARs, REV-ERBs and RORs are transcription factors controlled by the circadian system that regulate, among others, a large number of genes that control metabolic processes for which they have been proposed as key genes that link metabolism and temporal homeostasis. To date it is unclear whether these nuclear receptors show circadian expression and which zeitgebers are important for their synchronization in fish. Therefore, the objective of this study was to investigate whether the two main zeitgebers (light-dark cycle and feeding time) could affect the synchronization of central (hypothalamus) and peripheral (liver) core clocks and nuclear receptors in goldfish. To this aim, three experimental groups were established: fish under a 12 h light-12 h darkness and fed at Zeitgeber Time 2; fish with the same photoperiod but randomly fed; and fish under constant darkness and fed at Circadian Time 2. After one month, clock genes and nuclear receptors expression in hypothalamus and liver and circulating glucose were studied. Clock genes displayed daily rhythms in both tissues of goldfish if the light-dark cycle was present, with shifted-acrophases of negative and positive elements, as expected for proper functioning clocks. In darkness-maintained fish hypothalamic clock genes were fully arrhythmic while the hepatic ones were still rhythmic. Among studied nuclear receptors, in the hypothalamus only nr1d1 was rhythmic and only when the light-dark cycle was present. In the liver all nuclear receptors were rhythmic when both zeitgebers were present, but only nr1d1 when one of them was removed. Plasma glucose levels showed significant rhythms in fish maintained under random fed regimen or constant darkness, with the highest levels at 1-h postprandially in all groups. Altogether these results support that hypothalamus is mainly a light-entrained-oscillator, while the liver is a food-entrained-oscillator. Moreover, nuclear receptors are revealed as clear outputs of the circadian system acting as key elements in the timekeeping of temporal homeostasis, particularly in the liver.Item Ghrelin induces clock gene expression in the liver of goldfish in vitro via protein kinase C and protein kinase A pathways(Journal of Experimental Biology, 2017) Sánchez Bretaño, Aída; Blanco Imperiali, Ayelén M.; Alonso Gómez, Ángel Luis; Delgado Saavedra, María Jesús; Kah, Olivier; Isorna Alonso, EstherThe liver is the most important link between the circadian system and metabolism. As a food-entrainable oscillator, the hepatic clock needs to be entrained by food-related signals. The objective of the present study was to investigate the possible role of ghrelin (an orexigenic peptide mainly synthesized in the gastrointestinal tract) as an endogenous synchronizer of the liver oscillator in teleosts. To achieve this aim, we first examined the presence of ghrelin receptors in the liver of goldfish. Then, the ghrelin regulation of clock gene expression in the goldfish liver was studied. Finally, the possible involvement of the phospholipase C/protein kinase C (PLC/PKC) and adenylate cyclase/protein kinase A (AC/PKA) intracellular signalling pathways was investigated. Ghrelin receptor transcripts, ghs-r1a, are present in the majority of goldfish hepatic cells. Ghrelin induced the mRNA expression of the positive (gbmal1a, gclock1a) and negative (gper genes) elements of the main loop of the molecular clock machinery, as well as grev-erbα (auxiliary loop) in cultured liver. These effects were blocked, at least in part, by a ghrelin antagonist. Incubation of liver with a PLC inhibitor (U73122), a PKC activator (phorbol 12-myristate 13-acetate) and a PKC inhibitor (chelerythrine chloride) demonstrated that the PLC/PKC pathway mediates such ghrelin actions. Experiments with an AC activator (forskolin) and a PKA inhibitor (H89) showed that grev-erbα regulation could be due to activation of PKA. Taken together, the present results show for the first time in vertebrates a direct action of ghrelin on hepatic clock genes and support a role for this hormone as a temporal messenger in the entrainment of liver circadian functions.Item Anatomical distribution and daily profile of gper1b gene expression in brain and peripheral structures of goldfish (Carassius auratus)(Chronobiology International, 2015) Sánchez Bretaño, Aída; Gueguen, Marie-M.; Cano-Nicolau, Joel; Kah, Olivier; Alonso Gómez, Ángel Luis; Delgado Saavedra, María Jesús; Isorna Alonso, EstherThe functional organization of the circadian system and the location of the main circadian oscillators vary through phylogeny. Present study investigates by in situ hybridization the anatomical location of the clock gene gPer1b in forebrain and midbrain, pituitary, and in two peripheral locations, the anterior intestine and liver, in a teleost fish, the goldfish (Carassius auratus). Moreover, the daily expression profiles of this gene were also studied by quantitative Real Time-PCR. Goldfish were maintained under a 12L–12D photoperiod and fed daily at 2 h after lights were switched on. A wide distribution of gPer1b mRNA in goldfish brain and pituitary was found in telencephalon, some hypothalamic nuclei (including the homologous to mammalian SCN), habenular nucleus, optic tectum, cerebellum and torus longitudinalis. Moreover, gPer1b expression was observed, for the first time in teleosts, in the pituitary, liver and anterior intestine. Day/night differences in gper1b mRNA abundance were found by in situ hybridization, with higher signal at nighttime that correlates with the results obtained by RT-PCR, where a rhythmic gPer1b expression was found in all tissues with acrophases at the end of the night. Amplitudes of gper1b rhythms vary among tissues, being higher in liver and intestine than in the brain, maybe because different cues entrain clocks in these locations. These results support the existence of functional clocks in many central and peripheral locations in goldfish coordinated, ticking at the same time.Item Characterization of Ghrelin O-Acyltransferase (GOAT) in goldfish (Carassius auratus)(Plos ONE, 2017) Blanco Imperiali, Ayelén M.; Gómez Boronat, Miguel; Alonso Gómez, Ángel Luis; Yufa, Roman; Unniappan, Suraj; Delgado Saavedra, María Jesús; Valenciano González, Ana IsabelGhrelin is the only known hormone posttranslationally modified with an acylation. This modification is crucial for most of ghrelin’s physiological effects and is catalyzed by the polytopic enzyme ghrelin O-acyltransferase (GOAT). The aim of this study was to characterize GOAT in a teleost model, goldfish (Carassius auratus). First, the full-length cDNA sequence was obtained by RT-PCR and rapid amplification of cDNA ends methods. Two highly homologous cDNAs of 1491 and 1413 bp, respectively, named goat-V1 and goat-V2 were identified. Deduced protein sequences (393 and 367 amino acids, respectively) are predicted to present 11 and 9 transmembrane regions, respectively, and both contain two conserved key residues proposed to be involved in catalysis: asparagine 273 and histidine 304. RT-qPCR revealed that both forms of goat mRNAs show a similar widespread tissue distribution, with the highest expression in the gastrointestinal tract and gonads and less but considerable expression in brain, pituitary, liver and adipose tissue. Immunostaining of intestinal sections showed the presence of GOAT immunoreactive cells in the intestinal mucosa, some of which colocalize with ghrelin. Using an in vitro approach, we observed that acylated ghrelin downregulates GOAT gene and protein levels in cultured intestine in a time-dependent manner. Finally, we found a rhythmic oscillation of goat mRNA expression in the hypothalamus, pituitary and intestinal bulb of goldfish fed at midday, but not at midnight. Together, these findings report novel data characterizing GOAT, and offer new information about the ghrelinergic system in fish.Item Gene characterization of nocturnin paralogues in goldfish: full coding sequences, structure, phylogeny and tissue expression(Internationl Journal of Molecular Sciences, 2024) Madera Sánchez, Diego; Alonso-Gómez, Aitana; Delgado Saavedra, María Jesús; Valenciano González, Ana Isabel; Alonso Gómez, Ángel LuisThe aim of this work is the full characterization of all the nocturnin (noc) paralogues expressed in a teleost, the goldfish. An in silico analysis of the evolutive origin of noc in Osteichthyes is performed, including the splicing variants and new paralogues appearing after teleostean 3R genomic duplication and the cyprinine 4Rc. After sequencing the full-length mRNA of goldfish, we obtained two isoforms for noc-a (noc-aa and noc-ab) with two splice variants (I and II), and only one for noc-b (noc-bb) with two transcripts (II and III). Using the splicing variant II, the prediction of the secondary and tertiary structures renders a well-conserved 3D distribution of four α-helices and nine β-sheets in the three noc isoforms. A synteny analysis based on the localization of noc genes in the patrilineal or matrilineal subgenomes and a phylogenetic tree of protein sequences were accomplished to stablish a classification and a long-lasting nomenclature of noc in goldfish, and valid to be extrapolated to allotetraploid Cyprininae. Finally, both goldfish and zebrafish showed a broad tissue expression of all the noc paralogues. Moreover, the enriched expression of specific paralogues in some tissues argues in favour of neo- or subfunctionalization.Item The liver of goldfish as a component of the circadian system: Integrating a network of signals(General and Comparative Endocrinology, 2015) Sánchez Bretaño, Aída; Alonso Gómez, Ángel Luis; Delgado Saavedra, María Jesús; Isorna Alonso, EstherThe circadian system drives daily physiological and behavioral rhythms that allow animals to anticipate cyclic environmental changes. The discovery of the known as ‘‘clock genes’’, which are very well conserved through vertebrate phylogeny, highlighted the molecular mechanism of circadian oscillators functioning, based on transcription and translation cycles (24 h) of such clock genes. Studies in goldfish have shown that the circadian system in this species is formed by a net of oscillators distributed at central and peripheral locations, as the retina, brain, gut and liver, among others. In this work we review the existing information about the hepatic oscillator in goldfish due to its relevance in metabolism, and its key role as target of a variety of humoral signals. Different input signals modify the molecular clockwork in the liver of goldfish. Among them, there are environmental cues (photocycle and feeding regime) and different encephalic and peripheral endogenous signals (orexin, ghrelin and glucocorticoids). Per clock genes seem to be a common target for different signals. Thus, this genes family might be important for shifting the hepatic oscillator. The physiological relevance of the crosstalking between metabolic and feeding-related hormones and the hepatic clock sets the stage for the hypothesis that these hormones could act as ‘‘internal zeitgebers’’ communicating oscillators in the goldfish circadian system.Item First evidence of nocturnin in fish: two isoforms in goldfish differentially regulated by feeding(American Journal of Physiology, 2018) Blanco Imperiali, Ayelén M.; Gómez-Boronat, Miguel; Madera, Diego; Valenciano González, Ana Isabel; Alonso Gómez, Ángel Luis; Delgado Saavedra, María JesúsNocturnin (NOC) is a unique deadenylase with robust rhythmic expression involved in the regulation of metabolic processes in mammals. Currently, the possible presence of NOC in fish is unknown. This report aimed to identify NOC in a fish model, the goldfish (Carassius auratus), and to study the possible regulation of its expression by feeding. Two partial-length cDNAs of 293 and 223 bp, named nocturnin-a (noc-a) and nocturnin-b (noc-b), were identified and found to be highly conserved among vertebrates. Both mRNAs show a similar widespread distribution in central and peripheral tissues, with higher levels detected for noc-a compared with noc-b. The periprandial expression profile revealed that noc-a mRNAs rise sharply after a meal in hypothalamus, intestinal bulb, and liver, whereas almost no changes were observed for noc-b. Food deprivation was found to exert opposite effects on the expression of both NOCs (generally inhibitory for noc-a, and stimulatory for noc-b) in the three mentioned tissues. A single meal after a 48-h food deprivation period reversed (totally or partially) the fasting-induced decreases in noc-a transcripts in all studied tissues and the increases in noc-b expression in the intestinal bulb. Together, this study offers the first report of NOC in fish and shows a high dependence of its expression on feeding and nutritional status. The differential responses to feeding of the two NOCs raise the possibility that they might be underlying different physiological mechanisms (e.g., food intake, lipid mobilization, energy homeostasis) in fish.Item Interplay between the endocrine and circadian systems in fishes(Journal of Endocrinology, 2017) Isorna Alonso, Esther; Pedro Ormeño, Nuria de; Valenciano González, Ana Isabel; Alonso Gómez, Ángel Luis; Delgado Saavedra, María JesúsThe circadian system is responsible for the temporal organisation of physiological functions which, in part, involves daily cycles of hormonal activity. In this review, we analyse the interplay between the circadian and endocrine systems in fishes. We first describe the current model of fish circadian system organisation and the basis of the molecular clockwork that enables different tissues to act as internal pacemakers. This system consists of a net of central and peripherally located oscillators and can be synchronised by the light–darkness and feeding–fasting cycles. We then focus on two central neuroendocrine transducers (melatonin and orexin) and three peripheral hormones (leptin, ghrelin and cortisol), which are involved in the synchronisation of the circadian system in mammals and/or energy status signalling. We review the role of each of these as overt rhythms (i.e. outputs of the circadian system) and, for the first time, as key internal temporal messengers that act as inputs for other endogenous oscillators. Based on acute changes in clock gene expression, we describe the currently accepted model of endogenous oscillator entrainment by the light–darkness cycle and propose a new model for non-photic (endocrine) entrainment, highlighting the importance of the bidirectional cross-talking between the endocrine and circadian systems in fishes. The flexibility of the fish circadian system combined with the absence of a master clock makes these vertebrates a very attractive model for studying communication among oscillators to drive functionally coordinated outputs.