Effects of fasting on circulating IGF-binding proteins, glucose, and cortisol in channel catfish ( Ictalurus punctatus (original) (raw)
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Analysis of the effect of feeding regimen on GH/IGF axis in channel catfish (Ictalurus punctatus)
2012
Channel catfish (Ictalurus punctatus) are the most widely farmed aquatic animal in the United States. Assessing the effect of feeding regimens on their overall growth requires grow-out trials and a subsequent inefficient use of time and money. The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis regulates growth based upon environmental factors such as feed intake in many teleost fish species. In order to increase the efficiency of aquaculture, the components of the GH/IGF-1 axis might be used as endocrine biomarkers to evaluate instantaneous growth rate. The goal of this study was to better understand the effects of feeding regimen on the regulation of growth in channel catfish. Accelerated growth during re-feeding periods after fasting is of particular interest. These periods, termed compensatory growth (CG) periods, have been observed in several teleost fishes. To study this, mRNA expression of GH/IGF-1 axis components was examined in the liver, skeletal muscle and pituitary of channel catfish during two weeks of fasting and one week of re-feeding with a control group of animals fed daily. In addition, hepatosomatic index (HSI) and condition factor (CF) were calculated for each fish. CF data suggests CG after only a week of re-feeding. Fasting induced a significant decrease (P<0.05) in HSI, which returned to normal after re-feeding. Fasting induced a significant increase in muscular ghr-1 (P<0.01) and a significant decrease in muscular igf-1 (P<0.001). Re-feeding induced a significant increase in hepatic igf-1 (P<0.001), igfbp-5a (P<0.01), igfr-1a (P<0.001), and ghr-1 (P<0.01) and in muscular igf-2 (P<0.01), igfbp-1 (P<0.001), igfbp-2 (P<0.01), igfbp-5a (P<0.05), and igfr-1a (P<0.05). Results indicate that the GH/IGF-1 axis is highly sensitive to re-feeding in channel catfish and that CG can be induced.
Comparative Biochemistry and Physiology B-biochemistry & Molecular Biology, 2005
This experiment was conducted to characterize the effect of fasting versus satiety feeding on plasma concentrations of GH, IGF-I, and cortisol over a nychthemeron. Channel catfish fingerlings were acclimated for two weeks under a 12L : 12D photoperiod, then fed or fasted for 21 d. On day 21, blood samples were collected every 2 h for 24 h. Weight of fed fish increased an average of 66.2% and fasted fish lost 21.7% of body weight on average. Average nychthemeral concentrations of plasma GH were not significantly different between fed (24.7 ng/ mL) and fasted (26.8 ng/mL) fish, but average nychthemeral IGF-I concentrations were higher in fed (23.4 ng/mL) versus fasted (17.8 ng/ mL) fish. An increase in plasma IGF-I concentrations was observed in fasted fish 2 h after a peak in plasma GH, but not in fed fish. Average nychthemeral plasma cortisol concentrations were higher in fed (14.5 ng/mL) versus fasted (11.0 ng/mL) fish after 21 d. Significant fluctuations and a postprandial increase in plasma cortisol were observed in fed fish and there was an overall increase in plasma cortisol of both fasted and fed fish during the scotophase. The present experiment indicates little or no effect of 21-d fasting on plasma GH levels but demonstrates fasting-induced suppression of plasma IGF-I and cortisol levels in channel catfish. Published by Elsevier Inc.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2013
Two subtypes of insulin-like growth factor binding protein (IGFBP)-1 are present in salmon blood and they are both up-regulated under catabolic conditions such as stress. The present study examined effects of fasting and re-feeding on IGFBP-1a (28-kDa form) and IGFBP-1b (22-kDa form) both at mRNA and protein levels along with IGF-I and RNA/DNA ratio in yearling masu salmon. Fish were individually tagged and assigned to one of three treatments: Fed, Fasted or Re-fed. Circulating IGF-I levels significantly decreased after fasting for 5 weeks and were positively correlated with individual growth rates. Liver igf-1 mRNA levels were not affected by the treatment. Muscle RNA/DNA ratio did not respond to fasting nor showed correlations with growth rates. Circulating IGFBP-1a and IGFBP-1b increased during fasting and decreased after re-feeding. However, only serum IGFBP-1b levels were inversely correlated with growth rates presumably because IGFBP-1a was less sensitive to mild catabolic conditions. Fasting/re-feeding also affected their mRNA levels in the liver. These results suggest that circulating IGF-I and IGFBP-1b could serve as positive and negative indices of growth, respectively, in masu salmon. Different sensitivities of IGBP-1a and IGFBP-1b may be useful to assess a broad range of catabolic conditions when they are combined.
Effects of exogenous cortisol on the GH/IGF-I/IGFBP network in channel catfish
Domestic Animal Endocrinology, 2005
Glucocorticoids are known to hinder somatic growth in a number of vertebrate species. In order to better understand the mechanisms through which they may act in channel catfish, we examined the effects of feeding cortisol on the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGFbinding protein (IGFBP) network. Fish (30.6 ± 3.0 g) were fed once daily for 4 weeks and treatments included: (1) High-cortisol (dietary cortisol provided at 400 mg/kg feed), (2) Low-cortisol (dietary cortisol provided at 200 mg/kg feed), and (3) Control (commercial catfish feed). Fish fed diets with cortisol weighed approximately 50% less than Controls. Feed intake was reduced by approximately 30% in both treatments of cortisol fed fish compared to Controls. A ∼20-kDa IGFBP was observed in plasma from High-and Low-treated fish while it was not detected in Control fish plasma. Highcortisol treatment increased pituitary GH mRNA expression approximately 10-fold while liver IGF-I mRNA expression was not different between cortisol-treated fish and Controls. Cortisol treatments decreased plasma levels of IGF-I. These data indicate that feeding cortisol for 4 weeks reduces weight gain, feed intake, and plasma levels of IGF-I and induces a ∼20-kDa IGFBP. One mechanism through which cortisol may impede growth of catfish is through an increase in a low molecular weight IGFBP which may lead to inhibitory effects on the action of IGF-I.
Aquaculture, 2004
A recently developed radioimmunoassay (RIA) for measuring insulin-like growth factor (IGF-I) in a variety of fish species was used to investigate the correlation between growth rate and circulating IGF-I concentrations of barramundi (Lates calcarifer), Atlantic salmon (Salmo salar) and Southern Bluefin tuna (Thunnus maccoyii). Plasma IGF-I concentration significantly increased with increasing ration size in barramundi and IGF-I concentration was positively correlated to growth rates obtained in Atlantic salmon (r 2 =0.67) and barramundi (r 2 =0.65) when fed a variety of diet formulations. IGF-I was also positively correlated to protein concentration (r 2 =0.59). This evidence suggested that measuring IGF-I concentration may provide a useful tool for monitoring fish growth rate and also as a method to rapidly assess different aquaculture diets. However, no such correlation was demonstrated in the tuna study probably due to seasonal cooling of sea surface temperature shortly before blood was sampled. Thus, some recommendations for the 0044-8486/$ -see front matter D Aquaculture 236 (2004) 583 -592 design and sampling strategy of nutritional trials where IGF-I concentrations are measured are discussed. D
General and Comparative Endocrinology, 2003
Vertebrate growth is principally controlled by growth hormone (GH) and, its intermediary, insulin-like growth factor-I (IGF-I). The actions of IGF-I are modulated by high-affinity binding proteins called insulin-like growth factor binding-proteins (IGFBPs). Channel catfish exhibit atypical responses (increased percentage body fat and reduced percentage protein) to GH treatment, despite GH-dependent IGF-I production. Among possible explanations for this atypical response to GH treatment is an unusual regulation of blood IGFBPs. In this species, there has been one report of a single 33-kDa plasma binding protein. To examine the occurrence and regulation of plasma IGFBPs in this species, two strains of channel catfish (Norris and USDA-103) were treated with weekly injections of recombinant bovine GH at different temperatures (21°C versus 26°C). In a separate experiment involving catfish of a different strain, endogenous GH levels were altered via injection of the GH secretogogue, bGHRH 1-29-amide, and held in fresh water or transferred to brackish water (12 ppt). Following these treatments, the type and regulation of plasma IGFBPs in these catfish strains were examined by Western ligand blotting. We have identified five IGFBPs (19, 35, 44, 47, and >80 kDa) in catfish plasma that are differentially altered by experimental treatment and genetic lineage. Levels of the 19-kDa IGFBP were elevated in catfish of Norris and USDA-103 strains that were exposed to a higher environmental temperature (26°C versus 21°C), but was not seen in those animals used for the GH secretogogue/salinity study. In most vertebrates, treatment with GH increases levels of plasma IGFBP-3 ($40-50 kDa). In the USDA-103 and Norris catfish strains, bGH injection reduced plasma levels of the 44-and 47-kDa IGFBPs. Similarly, elevations in plasma GH levels in GH secretogoge-treated and brackish water-adapted catfish resulted in reductions of the 44-and 47-kDa IGFBPs as well as a reduction in presence of a 35-kDa IGFBP that was not detected in the Norris or USDA-103 strains. Reduced levels of the 35, 44, and 47 kDa IGFBPs, seen in the plasma of the GH secretogogue-treated and brackish water-adapted animals, suggests that the atypical response of channel catfish to GH treatment is not attributed to the use of heterologous (bovine) GH. This negative response of the 35-47 kDa IGFBPs to GH has not been reported in any teleost or vertebrate (healthy) and may be partly responsible for the atypical physiological responses of channel catfish to GH treatment.
Growth in teleosts is controlled in large part by the activities of the growth hormone (Gh)/insulin-like growth factor (Igf) system. In this study, we initially identified igf-binding protein (bp)1b, -2b, -4, -5a and -6b transcripts in a tilapia EST library. In Mozambique tilapia (Oreochromis mossambicus), tissue expression profiling of igfbps revealed that igfbp1b and -2b had the highest levels of expression in liver while igfbp4, -5a and -6b were expressed at comparable levels in most other tissues. We compared changes in hepatic igfbp1b, -2b and -5a expression during catabolic conditions (28 days of fasting) along with key components of the Gh/Igf system, including plasma Gh and Igf1 and hepatic gh receptor (ghr2), igf1 and igf2 expression. In parallel with elevated plasma Gh and decreased Igf1 levels, we found that hepatic igfbp1b increased substantially in fasted animals. We then tested whether systemic Gh could direct the expression of igfbps in liver. A single intraperitoneal injection of ovine Gh into hypophysectomized tilapia specifically stimulated liver igfbp2b expression along with plasma Igf1 and hepatic ghr2 levels. Our collective data suggest that hepatic endocrine signaling during fasting may involve posttranslational regulation of plasma Igf1 via a shift towards the expression of igfbp1b. Thus, Igfbp1b may operate as a molecular switch to restrict Igf1 signaling in tilapia; furthermore, we provide new details regarding isoform-specific regulation of igfbp expression by Gh.
General and Comparative Endocrinology, 2006
Compensatory growth (CG) is a period of growth that exceeds normal rates after animals are alleviated of certain growth-stunting conditions. Little is known, however, about the endocrine control of CG in teleosts. So, our aim was to induce CG in juvenile hybrid striped bass (HSB, Morone chrysops £ Morone saxatilis) through manipulations in feeding regimen, and then determine whether changes in circulating insulin-like growth factor-I (IGF-I) and hepatic IGF-I gene expression accompany the CG response. A considerable catabolic state was induced in HSB fed a total of two times over 4 weeks (once each in the 2nd and 3rd week). Negative energy balance was evidenced through weight loss (¡3.4% BW) and a signiWcant drop in hepatosomatic index (HSI) from a value of 3.71 to 1.46. Upon realimentation, in which HSB were fed ad libitum 2£/day, a signiWcant CG response was observed over a 4-week period. The CG response was characterized by an elevated speciWc growth rate, hyperphagia, restoration of the HSI and an improvement in feed conversion, all relative to controls that were fed ad libitum 2£/day throughout the experiment. Moreover, the CG response and catabolic state preceding it were marked by a discordant regulation in the expression of hepatic IGF-I mRNA and plasma IGF-I levels, the latter parameter paralleling changes in growth (r 2 D 0.56, P < 001). The catabolic state was accompanied by an 82% increase in hepatic IGF-I mRNA while levels of plasma IGF-I were signiWcantly depressed relative to controls. During the subsequent CG response, however, hepatic IGF-I mRNA decreased by 61% while plasma IGF-I increased by 86%. The underlying mechanisms for this inverse regulation of hepatic IGF-I mRNA and circulating IGF-I are uncertain, but may reXect alterations in hepatic IGF-I mRNA production, stability, and translation such that hepatic IGF-I mRNA is accumulated during periods of catabolism and then rapidly translated and released into circulation when conditions improve. These results suggest that CG can be induced in HSB following a suYcient catabolic state and that systemic IGF-I may be an important mediator of the accelerated growth rate characteristic of CG.
Fish Physiology and Biochemistry, 1993
Un dosage des somatomédines (IGF) plasmatiques de téléostéens a été mise au point, en utilisant une protéine du sérum de truite qui lie spécifiquement les IGF humains (Niu and Le Bail 1993). Pour éliminer les risques d'interférence dues aux protéines de liaison (IGF-BP), l'activité IGF des différents échantillons a été extraite à l'aide de SP Sephadex C-25 en condition acide. La contamination en IGF-BP de ces extraits est estimée à 5% par dosage de la liaison et n'est pas détectable en western ligand blot. L'IGF-I humain a été utilisée comme standard et comme traceur. La sensibilité du dosage est de 0.15–0.40 ng/ml (ED90) et l'ED50 varie entre 1 et 3 ng/ml. L'IGF-II humain est reconnue partiellement mais aucune réaction croisée n'est observée avec de l'insuline de différentes espèces ni avec les autres hormones testées. Les courbes d'inhibition obtenues avec les sera de mammifères et de téléostéens sont parallèles à la courbe standard. Ces résultats montrent que le dosage par protéine de liaison est capable de quantifier une activité de type IGF dans le sérum des téléostéen, et que le site de liaison des IGF est resté bien conservé au cours de l'évolution des vertébrés. En utilisant ce dosage, nous avons mesuré l'activité IGF et les niveaux d'hormone de croissance (GH) dans des plasmas de jeunes truites arc-en-ciel abattues toutes les heures et demie durant 24h. Les profils nycthémér-aux des deux hormones, qui sont de type pulsatile, apparaissent similaires. Une corrélation significative est observée entre les niveaux de GH et les activités IGF circulant une heure et demie plus tard. Des observations analogues ont été faites chez des truites adultes cathétérisées. Cependant, les niveaux plasmatiques de GH sont très différents d'un animal à l'autre, alors que les variations de l'activité IGF sont moins prononcées. Dans une troisième expérience, des truites ont été réparties en trois groupes: un groupe contrôle, un groupe traité avec de la GH bovine et un groupe soumis à un jeûne prolongé. Chez les animaux à jeun, les niveaux de GH augmentent alors que les activités IGF diminuent. Chez les animaux injectés avec de la GH, les activités IGF sont significativement plus élevées que chez les animaux témoins. Ces résultats suggèrent que, comme chez les mammifères, la sécrétion des IGF plasmatiques est contrôlée par les niveaux circulants de GH et que les variations de la réceptivité tissulaire à la GH dépendent de l'état nutritionnel des animaux. Using rainbow trout plasma protein (IGF-BP) which specifically binds human insulin-like growth factor (IGF) (Niu and Le Bail 1993), we have developed an assay to measure plasma IGF-like levels in different teleost species. Before the assay and to prevent interference by IGF-BP, IGF-like was extracted from all samples, using SP Sephadex C-25 in acidic conditions. After this treatment, contamination of the IGF fraction by IGF-BP which was estimated by binding assay, was approximately 5%, and was not detectable by western ligand blot. Human IGF-I was used as standard and labelled hormone. Sensitivity of the assay was 0.15–0.40 ng/ml (ED90) and ED50 was 1–3 ng/ml. hIGF-II crossreaction was partial and no significant displacement was observed with Insulin from different species or with other hormones. Inhibition curves were obtained with plasma IGF fractions (but not with tissue extracts) from teleost and mammals and are parallel to the standard curve. These results suggest that the protein binding assay can quantify an IGF-like factor in the plasma of teleost and that the binding sites of IGF are well conserved during vertebrate evolution. Using this IGF binding assay, IGF-like was measured in parallel with growth hormone (GH) in plasma from young rainbow trout killed every 1.5h throughout one day. The daily profiles for both hormones, which appear pulsatile, are similar. A significant correlation was observed between GH levels and IGF-like levels with a 1.5h delay. Analogous observations were obtained in individual catheterized adult rainbow trout. Although plasma GH levels differ greatly between fish, less variability is found with IGF-like. In a third experiment, rainbow trout were starved or submitted to bovine GH treatment for four weeks. Starved fish, in which plasma GH levels increased, had plasma IGF-like level significantly lower than in fed fish. In bGH injected fish, plasma IGF-like level was significantly higher than in non-injected fish. These results suggest that, as in mammals, IGF-like secretion depends on plasma GH level and could be modulated by the nutritional status of fish.
AFRICAN JOURNAL OF BIOTECHNOLOGY
This study aimed to show the difference in compensatory growth (CG) with different starvation and feeding periods replications, depending on the IGF-I hormone level in the blood. There were 4 treatments in 3 replications. Other indexes like food coefficient ratio (FCR), specific growth rate (SGR) and daily food intake were also examined during the experiment. Fish were fed twice a day ad libitum as follows during the 65 days. Treatment A (TA): control treatment, continues feeding. Treatment B (TB): 4 weeks of starvation and 5 weeks of re-feeding. Treatment C (TC): 3 weeks of starvation and 5 weeks of re-feeding. Treatment D (TD): 2 weeks of starvation and 5 weeks of re-feeding. Each tank contained 23 fishes in each unit with an initial mean weight (SD) of 47.19 ± 0.42 (g). Blood was sampled in IGF-I hormone concentration at the beginning of the experiment, at the end of the starvation period and every 12 days in re-feeding periods. There was no significant difference between the tre...