Insulin-like growth factor-binding protein-1 (IGFBP-1) in goldfish, Carassius auratus: molecular cloning, tissue expression, and mRNA expression responses to periprandial changes and cadmium exposure

Examination of the potential roles of insulin-like peptide receptor in regulating the growth of Manila clam Ruditapes philippinarum

The role of insulin/insulin-like growth factor (IGF) signaling pathway in the growth regulation of marine invertebrates has not been fully studied. In this study, the economically important species Ruditapes philippinarum was sacrificed to clarify the role of IGF system in the growth regulation of R. philippinarum by real-time quantitative PCR. Systematic bioinformatics analysis can identify the major genes of IGF signaling pathway and insulin-like peptide receptor (ILPR) - mediated signaling pathway in R. philippinarum. The expression levels of IGF and its downstream signaling pathway genes in larger clams were significantly higher than those in small clams, indicating that they were involved in the growth regulation of R. philippinarum. These results suggest that IGF signaling pathway and ILPR mediated signaling pathway to regulate the growth of R. philippinarum.

Daily Rhythms in the IGF-1 System in the Liver of Goldfish and Their Synchronization to Light/Dark Cycle and Feeding Time

The relevance of the insulin-like growth factor-1 (IGF-1) system in several physiological processes is well-known in vertebrates, although little information about their temporal organization is available. This work aims to investigate the possible rhythmicity of the different components of the IGF-1 system (igf-1, the igf1ra and igf1rb receptors and the paralogs of its binding proteins IGFBP1 and IGFBP2) in the liver of goldfish. In addition, we also study the influence of two environmental cues, the light/dark cycle and feeding time, as zeitgebers. The hepatic igf-1 expression showed a significant daily rhythm with the acrophase prior to feeding time, which seems to be strongly dependent on both zeitgebers. Only igfbp1a-b and igfbp1b-b paralogs exhibited a robust daily rhythm of expression in the liver that persists in fish held under constant darkness or randomly fed. The hepatic expression of the two receptor subtypes did not show daily rhythms in any of the experimental conditions. Altogether these results point to the igf-1, igfbp1a-b, and igfbp1b-b as clock-controlled genes, supporting their role as putative rhythmic outputs of the hepatic oscillator, and highlight the relevance of mealtime as an external cue for the 24-h rhythmic expression of the IGF-1 system in fish.

Effects of continuous and intermittent cadmium exposure on HPGL axis, GH/IGF axis and circadian rhythm signaling and their consequences on reproduction in female zebrafish: Biomarkers independent of exposure regimes

Typical biomarkers of cadmium (Cd) pollution have well been confirmed in fish from continuous exposure pattern. However, in a natural environment, fish may be exposed to Cd intermittently. In this study, juvenile female zebrafish were exposed for 48 days to 10 μg/L Cd continuously, 20 μg/L for 1 day in every 2 days or 30 μg/L for 1 day in every 3 days. The toxic effects were evaluated using 8 various physiological and biochemical endpoints like specific growth rate (SGR), 17β-estradiol (E2) and vitellogenin (VTG) concentrations in plasma, reproductive parameters (gonadosomatic index (GSI), egg-laying amount, spawning percentage, and hatching and mortality rate of embryos). Transcription of 59 genes related to hypothalamic-pituitary-gonadal-liver (HPGL) axis, circadian rhythm signaling and insulin-like growth factor (IGF) system was examined. SGR, spawning percentage, E2 and VTG levels declined in fish exposed to 10 and 20 μg/L Cd but remained relatively stable in fish exposed to 30 μg/L Cd. Exposure to 10, 20 and 30 μg/L Cd significantly reduced GSI, hatching rate and mortality rate. Similarly, mRNA expression of 27 genes were sensitive to both continuous and intermittent Cd exposure. Among these genes, expression levels of 10 genes had more than 5-fold increase or decrease, including mRNA levels of vtg1, vtg2, vtg3, esr1, igf2a, igf2b, igfbp5b, nr1d1, gnrh3 and gnrhr4. The most sensitive molecular biomarker was vtg3 expression with 1500-3100 fold increase in the liver. The present study, for the first time, provides effective candidate biomarkers for Cd, which are independent of exposure regimes.

Transcriptome analysis of grass carp (Ctenopharyngodon idella) between fast- and slow-growing fish

Grass carp is one of the most important freshwater aquaculture species in China. However, the mechanisms underlying the growth of muscle tissue in the fish are unclear. High-throughput RNA-Seq was used to analyze the transcriptome of grass carp muscle tissue between fast- and slow-growing fish family groups. Twenty-four individuals each from 4 fast-growing families and 4 slow-growing families were used to reduce background noise. 71 up-regulated and 35 down-regulated genes were identified in the differentially expressed genes (DEGs). GO and KEGG enrichment analyses revealed the DEGs were involved in the GH/IGF axis, calcium metabolism, protein and glycogen synthesis, oxygen transport, cytoskeletal and myofibrillar components. IGFBP1 was up-regulated in big fish while GHR2 was down-regulated. Glutamic pyruvate transaminase 2, an indicator of liver tissue damage, was down-regulated in big grass carp, which indicates that the fish was better adapted to an artificially formulated diet. GAPDH, the rate-limiting enzyme in glycolytic flux was highly expressed in fast-growing grass carp, reflecting enhanced carbohydrate metabolism. Higher expression of ALAS2 and myoglobin 1 in big grass carp, related to oxygen transport might promote aerobic exercise along with food intake and muscle growth. Genes for cytoskeletal and myofibrillar components such as tropomyosin, meromyosin, and troponin I were also up-regulated in big grass carp. These results provide valuable information about the key genes for use as biomarkers of growth in selective breeding programs for grass carp and contribute to our understanding of the molecular mechanisms and regulative pathways regulating growth in fish.

Molecular identification of grouper Igfbp1 and its mRNA expression in primary hepatocytes under Gh and insulin

The insulin-like growth factor (IGF) system plays a pivotal role in the regulation of growth, and IGF binding proteins (IGFBPs) are important regulatory factors in the IGF system. Generally, IGFBPs inhibit IGF actions by preventing its binding to receptors. Under some conditions, the IGFBPs can also enhance IGF actions. IGFBP1 is generally inhibitory to IGFI. In this study, the grouper (Epinephelus coioides) igfbp1 (MK621003) gene was cloned from the liver. The sequence of igfbp1 cDNA was 1055 bp and contained a 5'UTR of 127 bp and a 3'UTR of 247 bp, and the ORF of grouper igfbp1 was 741 bp, encoding 246 amino acids. The tissue distribution results showed that igfbp1 has a higher expression in the liver. In the nutritional status experiment, igfbp1 expression was significantly increased in the liver after 7 days of fasting and was markedly decreased after refeeding. In in vitro experiments, igfbp1 expression in grouper primary hepatocytes was significantly inhibited by recombinant grouper Gh (growth hormone) in a dose-dependent manner. Additionally, igfbp1 expression decreased in grouper primary hepatocytes upon incubation with insulin. This is the first report describing grouper igfbp1, and these findings contribute to understanding the roles of IGFBP1 in metabolism and growth in grouper.

Molecular cloning and expression profiles of IGFBP-1a in common carp (Cyprinus carpio) and its expression regulation by growth hormone in hepatocytes

In this study, we cloned and determined IGFBP-1a cDNA from common carp (Cyprinus carpio) liver. The 1655 bp full-length cDNA consisted of a 96 bp 5-untranslated region (UTR), a 789 bp open reading frame encoding 262 amino acid residues and a 770 bp 3-UTR containing seven mRNA instability motifs. Northern blot revealed a 1.8 kb IGFBP-1a transcript. IGFBP-1a mRNA was widely distributed in all tissues examined and predominantly expressed in the liver. During embryogenesis, IGFBP-1a mRNA was firstly observed in blastula stage, and significant increases were observed in body segment stage, lens formation stage and blood cycling stage. After hatching, its expression increased more than twenty times. Furthermore, hypoxia could significantly up-regulate IGFBP-1a expression in the liver and brain. IGFBP-1a expression increased with ovarian maturation and decreased at regressed stage. In testis, IGFBP-1a mRNA maintained relatively higher levels at recrudescing and matured stages, while it sharply declined at regressed stage. In primary cultured hepatocytes, IGFBP-1a gene was greatly down-regulated by growth hormone via the MAPK and PI3 kinase signaling pathways. These results suggest that IGFBP-1a may be involved in the IGF system regulating growth, development and reproduction in common carp.

Insulin-Like Growth Factor-Binding Proteins of Teleost Fishes

The insulin-like growth factor (Igf) binding protein (Igfbp) family has a broad range of physiological functions and a fascinating evolutionary history. This review focuses on the Igfbps of teleost fishes, where genome duplication events have diversified gene repertoire, function, and physiological regulation-with six core Igfbps expanded into a family of over twenty genes in some lineages. In addition to briefly summarizing the current state of knowledge on teleost Igfbp evolution, function, and expression-level regulation, we highlight gaps in our understanding and promising areas for future work.