RESUMO
The Characidae family of fish is composed of commercially important species for which little is known about the regulation of feeding. Fish are ectotherms so that their body temperature fluctuates with the temperature of the surrounding water. Changes in water temperature can thus have major effects on the physiology of fish, in particular their feeding. The mechanisms by which appetite is influenced by changes in temperatures in fish remain unclear. In this study, we examined the effects of temperature on feeding behavior, food intake and the expression of appetite regulators in three characid fish (black tetra, neon tetra and cavefish) by submitting them to four different temperatures for 2 weeks (20°C, 24°C, 28°C, 32°C). In all species, food intake increased with increasing temperature. In neon and black tetras, increasing temperatures decreased expressions of orexin and leptin and increased that of cocaine and amphetamine regulated transcript (CART). In cavefish, temperature had no effect on brain orexin, leptin or CART. In all three species, higher temperatures induced increases in intestine expression of cholecystokinin (CCK), but no effects were seen for intestine ghrelin and peptide YY expressions. Our results show that temperature affects feeding in Characidae fish and induces species-specific changes in the expression of appetite regulators.
Assuntos
Apetite , Characidae , Animais , Apetite/fisiologia , Characidae/fisiologia , Orexinas/metabolismo , Leptina/farmacologia , Temperatura , Neônio/farmacologia , Ingestão de Alimentos , ÁguaRESUMO
Photoperiod can profoundly affect the physiology of teleost fish, including accelerated growth here defined as "fast growth phenotypes". However, molecular regulatory networks (MRNs) and biological processes being affected by continuous illumination and which allow some teleost species evident plasticity to thrive under this condition are not yet clear. Therefore, to provide a broad perspective of such mechanisms, Chirostoma estor fish were raised and sampled for growth under a simulated control (LD) 12 h Light: 12 h Dark or a continuous illumination (LL) 24 h Light: 0 h Dark since fertilization. The experiment lasted 12 weeks after hatching (wah), the time at which fish were sampled for growth, length, and whole-body cortisol levels. Additionally, 3 heads of fish from each treatment were used to perform a de novo transcriptome analysis using Next-Generation Sequencing. Fish in LL developed the fast growth phenotype with significant differences visible at 4 wah and gained 66% more mass by 12 wah than LD fish. Cortisol levels under LL were below basal levels at all times compared to fish in LD, suggesting circadian dysregulation effects. A strong effect of LL was observed in samples with a generalized down-regulation of genes except for Reactive Oxygen Species responses, genome stability, and growth biological processes. To our knowledge, this work is the first study using a transcriptomic approach to understand environmentally sensitive MRNs that mediate phenotypic plasticity in fish submitted to continuous illumination. This study gives new insights into the plasticity mechanisms of teleost fish under constant illumination.
Assuntos
Fenômenos Biológicos , Ritmo Circadiano , Animais , Ritmo Circadiano/fisiologia , Peixes/genética , Hidrocortisona , Luz , Fenótipo , Fotoperíodo , Espécies Reativas de Oxigênio , TranscriptomaRESUMO
Dourado (Salminus brasiliensis) is a large carnivorous fish with high commercial value for which sustainable aquaculture relies on the substitution of expensive dietary animal protein sources in aquafeeds, in particular fish meal (FM), by cheaper plant protein, such as soy protein concentrate (SPC). This study aimed at evaluating feed intake and gene expression of appetite- regulating hormones [orexin, cocaine and amphetamine regulated transcript (CART), leptin, cholecystokinin (CCK) and peptide YY (PYY)] in the intestine, pyloric caeca and hypothalamus of juvenile dourado fed diets containing graded levels of SPC and FM as dietary protein sources for a period of three weeks. Increasing dietary plant protein contents reduced daily feed consumption and the expressions of the anorexigenic hormone CCK in the anterior intestine and in pyloric caeca and PYY in pyloric caeca. No changes were detected in the hypothalamic expression of appetite-regulating hormones, suggesting that gastrointestinal hormones are more involved in the decrease in feeding induced by plant protein diets than central appetite-regulating systems.
Assuntos
Apetite , Caraciformes , Ração Animal/análise , Animais , Apetite/genética , Caraciformes/genética , Colecistocinina/genética , Colecistocinina/metabolismo , Dieta/veterinária , Ingestão de Alimentos/fisiologia , Expressão Gênica , Proteínas de SojaRESUMO
The dourado, Salminus brasiliensis (Cuvier, 1816) is a freshwater piscivorous Characin native to South American rivers. Owing to the high quality of its flesh and its fast growth, it is the object of both capture fisheries and fish farming. However, very little is known about the endocrine regulation of feeding and metabolism of dourado. In this study, cDNAs for orexin, CART and CCK were isolated in dourado, and their mRNA tissue distributions examined. In order to assess the role of these peptides in the regulation of feeding of dourado, the effects of fasting and feeding on mRNA expression levels of orexin, CART and CCK in the brain as well as CCK in the intestine were assessed. Whereas orexin and CCK have widespread mRNA distributions in the brain and peripheral organs, CART seems to be mostly limited to the brain. Orexin brain expression increased with fasting and displayed periprandial changes, suggesting it is involved in both long- and short-term regulation of feeding and appetite. CART and CCK hypothalamic expressions were not affected by fasting, but displayed periprandial changes with post-feeding decreases, suggesting roles in short-term satiation. CCK expression in the anterior intestine was not affected by fasting and did not display periprandial changes. Overall, our results suggest that orexin, CART and CCK are involved in the physiology of feeding of dourado.
Assuntos
Apetite/fisiologia , Characidae/genética , Characidae/fisiologia , DNA Complementar/genética , Jejum/fisiologia , Comportamento Alimentar/fisiologia , Regulação da Expressão Gênica , Animais , Colecistocinina/genética , Colecistocinina/metabolismo , Clonagem Molecular , DNA Complementar/metabolismo , Perfilação da Expressão Gênica , Hipotálamo/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Orexinas/genética , Orexinas/metabolismo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Distribuição TecidualRESUMO
The effects of intraperitoneal injections of cholecystokinin (CCK), apelin, ghrelin, and orexin on food intake were examined in the blind cavefish Astyanax fasciatus mexicanus. CCK (50ng/g) induced a decrease in food intake whereas apelin (100ng/g), orexin (100ng/g), and ghrelin (100ng/g) induced an increase in food intake as compared to saline-injected control fish. In order to better understand the central mechanism by which these hormones act, we examined the effects of injections on the brain mRNA expression of two metabolic enzymes, tyrosine hydroxylase (TH), and mechanistic target of rapamycin (mTOR), and of appetite-regulating peptides, CCK, orexin, apelin and cocaine and amphetamine regulated transcript (CART). CCK injections induced a decrease in brain apelin injections, apelin injections induced an increase in TH, mTOR, and orexin brain expressions, orexin treatment increased brain TH expression and ghrelin injections induced an increase in mTOR and orexin brain expressions. CART expression was not affected by any of the injection treatments. Our results suggest that the enzymes TH and mTOR and the hormones CCK, apelin, orexin, and ghrelin all regulate food intake in cavefish through a complex network of interactions.
Assuntos
Apetite/fisiologia , Encéfalo/efeitos dos fármacos , Colecistocinina/administração & dosagem , Ingestão de Alimentos/efeitos dos fármacos , Grelina/administração & dosagem , Hormônios/farmacologia , Peptídeos e Proteínas de Sinalização Intracelular/administração & dosagem , Neuropeptídeos/administração & dosagem , Sirolimo/farmacologia , Tirosina 3-Mono-Oxigenase/metabolismo , Animais , Encéfalo/enzimologia , Characidae , Quimiocinas/administração & dosagem , Colagogos e Coleréticos/administração & dosagem , Imunossupressores/farmacologia , Neurotransmissores/administração & dosagem , Orexinas , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Tirosina 3-Mono-Oxigenase/antagonistas & inibidores , Tirosina 3-Mono-Oxigenase/genéticaRESUMO
The effects of fasting and feeding on the brain expression of orexin (OX), tyrosine hydroxylase (TH), peptide Y (PY) and cholecystokinin (CCK) were examined in the blind cavefish Astyanax fasciatus mexicanus. A 10-days fasting period induced increases in both OX and TH brain mRNA expression but had no effect on PYY and CCK expression. Periprandial changes in expression were seen for OX, TH and PYY but not for CCK. OX brain expression peaked 1h prior to a scheduled meal and decreased 1h post feeding in fed fish. A peak in TH expression was seen 1h post feeding in unfed fish whereas a peak in PYY expression was seen 1h post feeding in fed fish. Our result indicates that brain OX, TH and PYY might be involved in the central regulation of feeding of blind cavefish.