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Kaneko N, Ishikawa T, Nomura K. Effects of the short-term fasting and refeeding on growth-related genes in Japanese eel (Anguilla japonica) larvae. Comp Biochem Physiol B Biochem Mol Biol 2023; 265:110826. [PMID: 36608929 DOI: 10.1016/j.cbpb.2023.110826] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/26/2022] [Accepted: 01/02/2023] [Indexed: 01/05/2023]
Abstract
The Japanese eel (Anguilla japonica) spends a long period as the leptocephalus larval form under current rearing conditions. The duration of the larval stage until metamorphosis is influenced by body size and growth; however, little knowledge exists of the regulatory mechanism of growth in eel larvae. The present study focused on growth hormone (GH), insulin-like growth factors (IGFs), and IGF binding protein (IGFBP) as the central regulators of growth in teleost fishes and transforming growth factor-beta 3 (TGF-β3) as a possible key modulator of muscle growth and body component synthesis. Japanese eel IGFBP-1a and TGF-β3, comprising 264 and 411 amino acids, respectively, were cloned. Short-term (5-day) fasting and refeeding experiments were performed to understand changes in growth-related genes affected by nutritional status. The relative expression of gh increased with fasting and subsequently decreased with refeeding to the basal levels of the fed control. Relative igf-1 and igf-2 expression levels were high in the fasted group. Relative igf-1 was reduced after 2-day refeeding, whereas igf-2 decreased to the basal level after 1-day refeeding, suggesting that IGF-1 and IGF-2 might be regulated independently and contribute to postnatal growth in eel larvae. Relative igfbp-1a expression was sharply increased by fasting, whereas tgf-β3 showed high and low values in the fed and fasted groups, respectively. Relative igfbp-1a and tgf-β3 levels were negatively and positively correlated with body size, respectively. These results suggest that igfbp-1a and tgf-β3 are potential indices of growth for exploring optimal rearing conditions to shorten the larval stage in Japanese eels.
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Affiliation(s)
- Nobuto Kaneko
- Fisheries Technology Institute, Nansei Field Station, Japan Fisheries Research and Education Agency, Minamiise, Mie 516-0193, Japan.
| | - Takashi Ishikawa
- Fisheries Technology Institute, Nansei Field Station, Japan Fisheries Research and Education Agency, Minamiise, Mie 516-0193, Japan
| | - Kazuharu Nomura
- Fisheries Technology Institute, Nansei Field Station, Japan Fisheries Research and Education Agency, Minamiise, Mie 516-0193, Japan
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Cui W, Takahashi E, Morro B, Balseiro P, Albalat A, Pedrosa C, Mackenzie S, Nilsen TO, Sveier H, Ebbesson LO, Handeland SO, Shimizu M. Changes in circulating insulin-like growth factor-1 and its binding proteins in yearling rainbow trout during spring under natural and manipulated photoperiods and their relationships with gill Na +, K +-ATPase and body size. Comp Biochem Physiol A Mol Integr Physiol 2022; 268:111205. [PMID: 35346822 DOI: 10.1016/j.cbpa.2022.111205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 03/10/2022] [Accepted: 03/22/2022] [Indexed: 10/18/2022]
Abstract
Smoltification in salmonids occurs during spring in response to increasing photoperiod to prepare for marine life. Smoltification is associated with increased hypo-osmoregulatory ability and enhanced growth potential, mediated by growth hormone and insulin-like growth factor (IGF)-1. Rainbow trout is uniquely insensitive to the induction of smoltification-associated changes by photoperiod, such as the activation of gill Na+,K+-ATPase (NKA). We measured the circulating IGF-1 and IGF-binding protein (IGFBP)-2b levels in yearling rainbow trout exposed to natural and manipulated photoperiods during spring and correlated these with gill NKA activity and body size. Although the effect of photoperiod manipulation on body size and circulating IGF-1 and IGFBP-2b was negligible, they were positively correlated with gill NKA activity in fish under simulated natural photoperiod. We next pit-tagged yearling rainbow trout and fed them a restricted ration or to satiation under a natural photoperiod. In April, gill NKA activity was higher in the satiation group than in the restricted group and positively correlated with body size and growth rate. In addition, circulating IGFBP-2b was positively correlated with gill NKA, size and growth, whereas circulating IGF-1 was correlated only with size and growth. The relationship between circulating IGF-1 and growth intensified from May to June, suggesting that the IGF-1-growth relationship was disrupted in April when gill NKA was activated. Two additional IGFBPs were related to growth parameters but not to gill NKA activity. The present study suggests that circulating IGFBP-2b and IGF-1 mediate the size-dependent activation of gill NKA in yearling rainbow trout during spring.
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Affiliation(s)
- Wenda Cui
- Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Eisuke Takahashi
- Nanae Fresh-Water Station, Field Science Center for Northern Biosphere, Hokkaido University, 2-9-1 Sakura, Nanae, Kameda-gun, Hokkaido 041-1105, Japan
| | - Bernat Morro
- Institute of Aquaculture, University of Stirling, FK9 4LA Stirling, UK
| | - Pablo Balseiro
- NORCE AS, Nygårdsgaten 112, 5008 Bergen, Norway; Department of Biological Sciences, University of Bergen, Thormøhlens gate 53 A/B, 5020 Bergen, Norway
| | - Amaya Albalat
- Institute of Aquaculture, University of Stirling, FK9 4LA Stirling, UK
| | - Cindy Pedrosa
- NORCE AS, Nygårdsgaten 112, 5008 Bergen, Norway; Department of Biological Sciences, University of Bergen, Thormøhlens gate 53 A/B, 5020 Bergen, Norway
| | - Simon Mackenzie
- Institute of Aquaculture, University of Stirling, FK9 4LA Stirling, UK; NORCE AS, Nygårdsgaten 112, 5008 Bergen, Norway
| | - Tom O Nilsen
- NORCE AS, Nygårdsgaten 112, 5008 Bergen, Norway; Department of Biological Sciences, University of Bergen, Thormøhlens gate 53 A/B, 5020 Bergen, Norway
| | - Harald Sveier
- Lerøy Seafood Group ASA, Box 7600, 5020 Bergen, Norway
| | | | - Sigurd O Handeland
- NORCE AS, Nygårdsgaten 112, 5008 Bergen, Norway; Department of Biological Sciences, University of Bergen, Thormøhlens gate 53 A/B, 5020 Bergen, Norway
| | - Munetaka Shimizu
- Section of Aquatic Research, Field Science Center for Northern Biosphere, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
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Izutsu A, Tadokoro D, Habara S, Ugachi Y, Shimizu M. Evaluation of circulating insulin-like growth factor (IGF)-I and IGF-binding proteins as growth indices in rainbow trout (Oncorhynchus mykiss). Gen Comp Endocrinol 2022; 320:114008. [PMID: 35219685 DOI: 10.1016/j.ygcen.2022.114008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 02/20/2022] [Accepted: 02/22/2022] [Indexed: 12/17/2022]
Abstract
Circulating insulin-like growth factor (IGF)-I has been proposed as a growth index in several teleosts, including salmonids, and its level in circulation is stabilized by multiple IGF-binding proteins (IGFBPs). Three IGFBPs, IGFBP-2b, -1a, and -1b, are consistently detected in salmonid blood and are suggested to be indices of positive or negative growth, although their applicability to rainbow trout (Oncorhynchus mykiss) is unclear. The present study examined the usefulness of IGFBPs along with IGF-I as a physiological indicator of growth rate in rainbow trout through a rearing experiment. Two groups of underyearling rainbow trout were pit-tagged and either fed or fasted for 33 days. A third group was fasted for 22 days, followed by refeeding for 11 days. Serum IGF-I levels were reduced after fasting for 22 days, but refeeding did not retore its levels to those of the fed control. Nevertheless, there was a positive relationship between serum IGF-I levels and individual growth rates over 33 days of experimentation, confirming its validity as a growth index. Ligand blotting using labeled human IGF-I revealed two IGFBP bands at 43 and 32 kDa, which corresponded to IGFBP-2b and an unidentified form, respectively. In contrast, bands corresponding to IGFBP-1a and -1b, which usually increase after fasting, were hardly detected, even in the fasted fish. The responses of circulating IGFBP-2b to fasting and refeeding were similar to those of circulating IGF-I and positively correlated with growth rate and IGF-I levels. The intensity of the serum 32-kDa IGFBP band was higher in constantly fed fish than in the fasted fish; however, its correlation with growth rate was weaker than those of IGF-I and IGFBP-2b. The present study shows that IGF-I and IGFBP-2b can be used as growth indices for rainbow trout. In contrast, circulating IGFBP-1a and -1b may not serve as negative growth indices in rainbow trout under regular aquaculture conditions because they are rarely detected by ligand blotting or respond to fasting/refeeding.
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Affiliation(s)
- Ayaka Izutsu
- School of Fisheries Sciences, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan
| | - Daiji Tadokoro
- FRD Japan, Co., Kazusa Kamatari 3-9-13, Kisarazu, Chiba 292-0818, Japan
| | - Shiori Habara
- Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Yuki Ugachi
- Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
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4
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Kaneko N, Nilsen TO, Tanaka H, Hara A, Shimizu M. Intact rather than total circulating insulin-like growth factor binding protein-1a is a negative indicator of growth in masu salmon. Am J Physiol Regul Integr Comp Physiol 2020; 318:R329-R337. [PMID: 31850820 DOI: 10.1152/ajpregu.00099.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Insulin-like growth factor binding protein (IGFBP)-1a is one of three major circulating forms in salmon and induced under catabolic conditions. However, there is currently no immunoassay available for this form because of a lack of standard and specific antibodies. We developed a time-resolved fluoroimmunoassay (TR-FIA) for salmon IGFBP-1a using recombinant protein for labeling, an assay standard, and production of antiserum. The TR-FIA had a low cross-reactivity (3.6%) with IGFBP-1b, another major form in the circulation. Fasting for 4 wk had no effect on serum immunoreactive (total) IGFBP-1a levels in yearling masu salmon, whereas 6-wk fasting significantly increased it. There was a significant, but weak, negative relationship between serum total IGFBP-1a level and individual growth rate (r2 = 0.12, P = 0.01). We next developed a ligand immuno-functional assay (LIFA) using europium-labeled IGF-I to quantify intact IGFBP-1a. In contrast to total IGFBP-1a, serum intact IGFBP-1a levels increased after 4 wk of fasting, and refeeding for 2 wk restored it to levels similar to those of the fed control. Serum intact IGFBP-1a levels showed a significant negative correlation with individual growth rate (r2 = 0.52, P < 0.001), which was as good as that of IGFBP-1b. Our findings using newly developed TR-FIA and LIFA suggest that regulation of intact IGFBP-1a levels has an important effect on growth in salmon and that intact IGFBP-1a is a negative index of salmon growth.
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Affiliation(s)
- Nobuto Kaneko
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan.,Norwegian Research Centre (NORCE) Environment, NORCE Norwegian Research Centre AS, Bergen, Norway
| | - Tom Ole Nilsen
- Norwegian Research Centre (NORCE) Environment, NORCE Norwegian Research Centre AS, Bergen, Norway.,Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Hanae Tanaka
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Akihiko Hara
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, Japan
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Kaneko N, Journey ML, Neville CM, Trudel M, Beckman BR, Shimizu M. Utilization of an endocrine growth index, insulin-like growth factor binding protein (IGFBP)-1b, for postsmolt coho salmon in the Strait of Georgia, British Columbia, Canada. FISH PHYSIOLOGY AND BIOCHEMISTRY 2019; 45:1867-1878. [PMID: 31297680 DOI: 10.1007/s10695-019-00681-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/02/2019] [Indexed: 06/10/2023]
Abstract
Monitoring the growth of salmon during their early marine phase provides insights into prey availability, and growth rates may be linked to risks of size-dependent mortality. However, the measurement of growth rate is challenging for free-living salmon in the ocean. Insulin-like growth factor (IGF)-I is a growth-promoting hormone that is emerging as a useful index of growth in salmon. In addition, laboratory-based studies using coho salmon have shown that one of circulating IGF-binding proteins (IGFBPs), IGFBP-1b, is induced by fasting and thus could be used as an inverse index of growth and/or catabolic state in salmon. However, few studies have measured plasma levels of IGFBP-1b in salmon in the wild. We measured plasma IGFBP-1b levels for postsmolt coho salmon collected in the Strait of Georgia and surrounding waters, British Columbia, Canada, and compared regional differences in IGFBP-1b to ecological information such as seawater temperature and stomach fullness. Plasma IGFBP-1b levels were the highest in fish from Eastern Johnstone Strait and relatively high in Queen Charlotte Strait and Western Johnstone Strait, which was in good agreement with the poor ocean conditions for salmon hypothesized to occur in that region. The molar ratio of plasma IGF-I to IGFBP-1b, a theoretical parameter of IGF-I availability to the receptor, discriminated differences among regions better than IGF-I or IGFBP-1b alone. Our data suggest that plasma IGFBP-1b reflects catabolic status in postsmolt coho salmon, as highlighted in fish in Eastern Johnston Strait, and is a useful tool to monitor negative aspects of salmon growth in the ocean.
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Affiliation(s)
- Nobuto Kaneko
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan
| | - Meredith L Journey
- Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, 2725 Montlake Boulevard East, Seattle, WA, 98112, USA
| | - Chrys M Neville
- Fisheries and Oceans Canada, St Andrews Biological Station, St Andrews, New Brunswick, Canada
| | - Marc Trudel
- Fisheries and Oceans Canada, St Andrews Biological Station, St Andrews, New Brunswick, Canada
| | - Brian R Beckman
- Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, 2725 Montlake Boulevard East, Seattle, WA, 98112, USA
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan.
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Kaneko N, Torao M, Koshino Y, Fujiwara M, Miyakoshi Y, Shimizu M. Evaluation of growth status using endocrine growth indices, insulin-like growth factor (IGF)-I and IGF-binding protein-1b, in out-migrating juvenile chum salmon. Gen Comp Endocrinol 2019; 274:50-59. [PMID: 30611815 DOI: 10.1016/j.ygcen.2019.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 11/21/2018] [Accepted: 01/02/2019] [Indexed: 11/29/2022]
Abstract
This study aimed to utilize circulating insulin-like growth factor binding protein (IGFBP)-1b as a negative index of growth to evaluate the growth status of juvenile chum salmon (Oncorhynchus keta) in the ocean. First, rearing experiments using PIT-tagged juveniles were conducted to examine the relationship of circulating IGFBP-1b with growth rate of the fish in May and in June. The serum IGFBP-1b level negatively correlated with fish growth rate in both months, suggesting its utility as a negative index of growth. Next, the growth status of out-migrating juveniles in northeastern Hokkaido, Japan, was monitored for 3 years using the growth indices. Serum levels of IGF-I, a positive index of growth, in fish collected from the nearshore zone were low in May and high in June of all years. Levels of serum IGFBP-1b showed a trend opposite to that of serum IGF-I. However, the IGF-I/IGFBP-1b molar ratios well reflected the seasonal and regional trends. These findings suggest that the juveniles in June left the nearshore area under better growth conditions. The present study also suggests that the use of multiple growth indices would improve the sensitivity and accuracy to evaluate the current growth status of out-migrating juvenile chum salmon.
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Affiliation(s)
- Nobuto Kaneko
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan
| | - Mitsuru Torao
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, 3-373 Kitakashiwagi, Eniwa, Hokkaido 061-1433, Japan
| | - Yousuke Koshino
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, 3-373 Kitakashiwagi, Eniwa, Hokkaido 061-1433, Japan
| | - Makoto Fujiwara
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, 3-373 Kitakashiwagi, Eniwa, Hokkaido 061-1433, Japan
| | - Yasuyuki Miyakoshi
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, 3-373 Kitakashiwagi, Eniwa, Hokkaido 061-1433, Japan
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
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Hack NL, Strobel JS, Journey ML, Beckman BR, Lema SC. Response of the insulin-like growth factor-1 (Igf1) system to nutritional status and growth rate variation in olive rockfish (Sebastes serranoides). Comp Biochem Physiol A Mol Integr Physiol 2018; 224:42-52. [DOI: 10.1016/j.cbpa.2018.05.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 05/28/2018] [Accepted: 05/30/2018] [Indexed: 12/20/2022]
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Balseiro P, Moe Ø, Gamlem I, Shimizu M, Sveier H, Nilsen TO, Kaneko N, Ebbesson L, Pedrosa C, Tronci V, Nylund A, Handeland SO. Comparison between Atlantic salmon Salmo salar post-smolts reared in open sea cages and in the Preline raceway semi-closed containment aquaculture system. JOURNAL OF FISH BIOLOGY 2018; 93:567-579. [PMID: 29952001 DOI: 10.1111/jfb.13659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 05/06/2018] [Indexed: 06/08/2023]
Abstract
The use of closed containment (CCS) or semi-closed containment systems (S-CCS) for Atlantic salmon Salmo salar aquaculture is under evaluation in Norway. One such system is the Preline S-CCS, a floating raceway system that pumps water from 35 m depth creating a constant current through the system. Exposing fish to moderate water currents is considered aerobic exercise and it is often perceived as positive for fish welfare, growth, food utilization, muscle development and cardiac health. The present study compared fish reared in the Preline S-CCS and in a reference open pen. Samples were taken in fresh water before being transferred to the seawater systems and after 1, 2 and 4 months in seawater and analysed for growth, mortality, muscle development and plasma insulin-like growth factor I (IGF-I) levels. Moreover, gene transcription were determined in the skeletal muscle [igf-I, insulin-like growth factor 1 receptor a (igf1ra) and insulin-like growth factor 1 binding protein 1a (igf1bp1a)] and cardiac transcription factors [myocyte-specific enhancer factor 2C (mef2c), gata4 and vascular endothelial growth factor (vegf)]. While the results suggest that post-smolts in Preline S-CCS were smaller than reference fish, fish from Preline S-CCS have less accumulated mortality at the end of the experiment and showed 2.44 times more small muscle fibres than the reference group fish after 4 months in seawater. These results confirmed what was previously observed in the second generation of Preline. Similar levels of big muscle fibres between Preline S-CCS and reference suggest a similar hypertrophy of muscle fibres even with lower IGF-I expression in the Preline S-CCS. Cardiac gene transcription suggests cardiac hypertrophy was observed after 4 months in seawater in the Preline S-CCS group. Altogether, Preline S-CCS is a promising technology able to produce more robust S. salar with a faster growth and lower mortality in the subsequent standard open cage system growth period.
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Affiliation(s)
- Pablo Balseiro
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | - Øyvind Moe
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | - Ingrid Gamlem
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan
| | | | - Tom O Nilsen
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | - Nobuto Kaneko
- Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan
| | - Lars Ebbesson
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | - Cindy Pedrosa
- Uni Research Environment, Uni Research AS, Bergen, Norway
| | | | - Are Nylund
- Department of Biology, University of Bergen, Bergen, Norway
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Taniyama N, Kaneko N, Inatani Y, Miyakoshi Y, Shimizu M. Effects of seawater transfer and fasting on the endocrine and biochemical growth indices in juvenile chum salmon (Oncorhynchus keta). Gen Comp Endocrinol 2016; 236:146-156. [PMID: 27444127 DOI: 10.1016/j.ygcen.2016.07.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/14/2016] [Accepted: 07/16/2016] [Indexed: 01/23/2023]
Abstract
Insulin-like growth factor (IGF)-I, IGF-binding protein (IGFBP)-1 and RNA/DNA ratio are endocrine and biochemical parameters used as growth indices in fish, however, they are subjected to environmental modulation. Chum salmon (Oncorhynchus keta) migrate from freshwater (FW) to seawater (SW) at fry/juvenile stage weighing around 1g and suffer growth-dependent mortality during the early phase of their marine life. In order to reveal environmental modulation of the IGF/IGFBP system and establish a reliable growth index for juvenile chum salmon, we examined effects of SW transfer and fasting on IGF-I, IGFBP-1 and RNA/DNA ratio, and correlated them to individual growth rate. Among serum IGF-I, liver and muscle igf-1, igfbp-1a, igfbp-1b and RNA/DNA ratio examined, muscle RNA/DNA ratio and muscle igfbp-1a responded to SW transfer. Serum IGF-I, liver igf-1 and liver RNA/DNA ratio were sensitive to nutritional change by being reduced in 1week in both FW and SW while muscle igf-1 was reduced 2weeks after fasting. In contrast, igfbp-1a in both tissues was increased by 2weeks of fasting and igfbp-1b in the liver of SW fish was increased in 1week. These results suggest that the sensitivity of igf-1 and igfbp-1s to fasting differs between tissues and subtypes, respectively. When chum salmon juveniles in SW were marked and subjected to feeding or fasting, serum IGF-I showed the highest correlation with individual growth rate. Liver igfbp-1a and -1b, and muscle igf-1 exhibited moderate correlation coefficients with growth rate. These results show that serum IGF-I is superior to the other parameters as a growth index in juvenile chum salmon in term of its stability to salinity change, high sensitivity to fasting and strong relationship with growth rate. On the one hand, when collecting blood from chum salmon fry/juveniles is not practical, measuring liver igfbp-1a and -1b, or/and muscle igf-1 is an alternative.
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Affiliation(s)
- Natsumi Taniyama
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan
| | - Nobuto Kaneko
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan
| | - Yu Inatani
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan
| | - Yasuyuki Miyakoshi
- Salmon and Freshwater Fisheries Research Institute, Hokkaido Research Organization, 3-373 Kitakashiwagi, Eniwa, Hokkaido 061-1433, Japan
| | - Munetaka Shimizu
- Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
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