Endocrine Biomarkers of Growth and Applications to Aquaculture: A Minireview of Growth Hormone, Insulin‐Like Growth Factor (IGF)‐I, and IGF‐Binding Proteins as Potential Growth Indicators in Fish

Abstract

Growth in fish and other vertebrates is under endocrine control, particularly through the growth hormone (GH)-insulin-like growth factor (IGF) axis. For this reason, it has been of interest to aquaculture researchers and the industry to establish endocrine biomarkers that can both reflect and predict growth rates in fish subject to various biotic and abiotic manipulations. Ultimately, by understanding the hormones that control growth and utilizing them as biomarkers, we hope to achieve optimal growth conditions in the aquaculture environment with less need for lengthy and costly grow-out trials. While the most appropriate endocrine biomarkers for growth can be both species and situation specific, IGF-I may be the most promising candidate for measuring instantaneous growth in fish. This is based on the direct contributions of IGF-I in regulating cell proliferation and ultimately somatic growth, along with its previously established correlations with the specific growth rate in fish under various conditions that alter growth. However, other endocrine indices, such as GH and IGF-binding proteins (IGFBPs), are also important contributors and may in some instances prove a strong corollary to growth rate. This review discusses the potential utility of GH, IGF-I, and IGFBPs as growth biomarkers for those manipulations most relevant to the aquaculture industry, namely, feeding regimen, diet composition, temperature, photoperiod, and stress.

Postprandial changes in plasma growth hormone, insulin, insulin-like growth factor (IGF)-I, and IGF-binding proteins in coho salmon fasted for varying periods

“…The present study was undertaken as part of a validation of the use of circulating IGF-I as a growth index in fish. Increasing evidence in teleosts suggests that circulating IGF-I levels positively correlate with growth rates of individuals and could be used to evaluate growth performance of fish for aquaculture and stock assessment (3,30). The present study expands our knowledge of the efficacy of IGF-I as a growth indicator, as the effect of recent feeding history was examined.…”

“…Multiple IGFBPs are also present in the circulation of fish species. Western ligand blotting of fish plasma/serum typically reveals three IGFBP bands at [20][21][22][23][24][25][25][26][27][28][29][30][40][41][42][43][44][45][46][47][48][49][50]. The 20 -30-kDa and 40 -50-kDa IGFBPs are believed to be fish homologs of mammalian IGFBP-1 and -3, respectively.…”

Differential regulation of Igf1 and Igf2 mRNA levels in tilapia hepatocytes: effects of insulin and cortisol on GH sensitivity

“…If endocrine Igf2 is a somatomedin in fishes, then both Igfs should be taken into account in applications of growth endocrinology in fisheries management, conservation, and aquaculture. Plasma levels of both Igfs may be useful indicators of growth status in wild and captive fishes (Picha et al 2008a). Plasma levels of both Igfs may provide information on energetic status to neuroendocrine systems that regulate major life history transitions, such as smolting and reproductive maturation (Dickhoff et al 1997, Luckenbach et al 2010.…”

Chronic cortisol and the regulation of food intake and the endocrine growth axis in rainbow trout

“…Since glucocorticoids promote the mobilization and redistribution of energy, the effects of chronic stress on growth in fish have generally been attributed to the actions of cortisol (Pickering 1992, Pankhurst & Van Der Kraak 1997, Small et al 2008. Although studies using exogenous cortisol have previously linked the growth-suppressing effects of cortisol in fish to its actions on food intake, intermediary metabolism and muscle mass regulation (reviewed by Mommsen et al (1999), Bernier (2006) and Picha et al (2008)), the precise mechanisms by which cortisol affects these complex systems are far from clear.…”