Endocrine control of oleic acid and glucose metabolism in rainbow trout (Oncorhynchus mykiss) muscle cells in culture

The effects of insulin and IGF-I on fatty acid (FA) and glucose metabolism were examined using oleic acid or glucose as tracers in differentiated rainbow trout ( Oncorhynchus mykiss ) myotubes. Insulin and IGF-I significantly reduced the production of CO2 from oleic acid with respect to the control values. IGF-I also significantly reduced the production of acid-soluble products (ASP) and the concentration of FA in the medium, while cellular triacylglycerols (TAG) tended to increase. Only insulin produced a significant accumulation of glycogen inside the cells in glucose distribution experiments. Incubation with catecholamines did not affect oleic acid metabolism. Cells treated with rapamycin [a target of rapamycin (TOR) inhibitor] significantly increased the oxidation of oleic acid to CO2 and ASP, while the accumulation of TAG diminished. Rosiglitazone (a peroxisome proliferator-activated receptor γ agonist) and etomoxir (a CPT-1 inhibitor) produced a severe and significant reduction in the production of CO2 and ASP. Rosiglitazone and etomoxir also produced a significant accumulation of FA outside and inside the cells, respectively. No significant effects of these drugs on glucose distribution were observed. These data indicate that insulin and IGF-I act as anabolic hormones in trout myotubes in both oleic acid and glucose metabolism, although glucose oxidation appears to be less sensitive than FA oxidation to insulin and IGF-I. The use of rapamycin, etomoxir, and rosiglitazone may help us to understand the mechanisms of regulation of lipid metabolism in fish.

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Regulation of proliferation and differentiation of adipocyte precursor cells in rainbow trout (Oncorhynchus mykiss)

Journal of Endocrinology ◽

10.1677/joe-08-0264 ◽

2008 ◽

Vol 198 (3) ◽

pp. 459-469 ◽

Cited By ~ 61

Author(s):

L Bouraoui ◽

J Gutiérrez ◽

I Navarro

Keyword(s):

Cell Proliferation ◽

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Adipocyte Differentiation ◽

Nuclear Antigen ◽

Peroxisome Proliferator ◽

Endocrine Regulation ◽

Endocrine Control ◽

Insulin Growth Factor ◽

Rainbow Trout Oncorhynchus Mykiss

Here, we describe optimal conditions for the culture of rainbow trout (Oncorhynchus mykiss) pre-adipocytes obtained from adipose tissue and their differentiation into mature adipocytes, in order to study the endocrine control of adipogenesis. Pre-adipocytes were isolated by collagenase digestion and cultured on laminin or 1% gelatin substrate. The expression of proliferating cell nuclear antigen was used as a marker of cell proliferation on various days of culture. Insulin growth factor-I stimulated cell proliferation especially on days 5 and 7 of culture. Tumor necrosis factor α (TNFα) slightly enhanced cell proliferation only at a low dose. We verified the differentiation of cells grown in specific medium into mature adipocytes by oil red O (ORO) staining. Quantification of ORO showed an increase in triglycerides throughout culture. Immunofluorescence staining of cells at day 11 revealed the expression of CCAAT/enhancer-binding protein and peroxisome proliferator–activator receptor γ, suggesting that these transcriptional factors are involved in adipocyte differentiation in trout. We also examined the effect of TNFα on the differentiation of these adipocytes in primary culture. TNFα inhibited the differentiation of these cells, as indicated by a decrease in glycerol-3-phosphate dehydrogenase activity, an established marker of adipocyte differentiation. In conclusion, the culture system described here for trout pre-adipocytes is a powerful tool to study the endocrine regulation of adipogenesis in this species.

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Insulin and insulin-like growth factor I signaling pathways in rainbow trout (Oncorhynchus mykiss) during adipogenesis and their implication in glucose uptake

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00457.2009 ◽

2010 ◽

Vol 299 (1) ◽

pp. R33-R41 ◽

Cited By ~ 30

Author(s):

L. Bouraoui ◽

E. Capilla ◽

J. Gutiérrez ◽

I. Navarro

Keyword(s):

Rainbow Trout ◽

Growth Factor ◽

Oncorhynchus Mykiss ◽

Glucose Uptake ◽

Signaling Pathways ◽

Mapk Phosphorylation ◽

Factor I ◽

Rainbow Trout Oncorhynchus Mykiss ◽

Igf I ◽

Stimulation Of

Primary cultures of rainbow trout ( Oncorhynchus mykiss ) adipocytes were used to examine the main signaling pathways of insulin and insulin-like growth factor I (IGF-I) during adipogenesis. We first determined the presence of IGF-I receptors (IGF-IR) and insulin receptors (IR) in trout preadipocytes ( day 5) and adipocytes ( day 14). IGF-IRs were more abundant and appeared to be in higher levels in differentiated cells than in preadipocytes, whereas IRs were detected in lower but constant levels throughout the culture. The cells were immunoreactive against ERK1/2 MAPK, and AKT/PI3K, components of the two main signal transduction pathways for insulin and IGF-I receptors. Stimulation of MAPK phosphorylation by IGF-I was higher in preadipocytes than in adipocytes, while no effects were observed in MAPK phosphorylation after incubation of cells with insulin. AKT phosphorylation increased in the presence of both insulin and IGF-I, with higher levels of stimulation in adipocytes than in preadipocytes. Activation of both pathways was blocked by the use of specific inhibitors of MAPK (PD98059) and AKT (wortmannin). We describe here, for the first time, the effects of IGF-I and insulin on 2-deoxyglucose uptake in primary culture of trout adipocytes. IGF-I was more potent in stimulating glucose uptake than insulin, and PD98059 and wortmannin inhibited the stimulation of glucose uptake by this growth factor, suggesting that IGF-I plays an important metabolic role in trout adipocytes. Our results suggest that differential activation of the MAPK and AKT pathways are involved in the IGF-I- and insulin-induced effects of trout adipocytes during the various stages of adipogenesis.

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The Influence of Social Status on Hepatic Glucose Metabolism in Rainbow Trout Oncorhynchus mykiss

Physiological and Biochemical Zoology ◽

10.1086/666497 ◽

2012 ◽

Vol 85 (4) ◽

pp. 309-320 ◽

Cited By ~ 16

Author(s):

Kathleen M. Gilmour ◽

Sheryn Kirkpatrick ◽

Andrey Massarsky ◽

Brenda Pearce ◽

Sarah Saliba ◽

...

Keyword(s):

Rainbow Trout ◽

Glucose Metabolism ◽

Oncorhynchus Mykiss ◽

Social Status ◽

Rainbow Trout Oncorhynchus Mykiss ◽

Hepatic Glucose Metabolism ◽

Hepatic Glucose

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Biochemical and functional analysis of a conserved IGF-binding protein isolated from rainbow trout (Oncorhynchus mykiss) hepatoma cells

Journal of Endocrinology ◽

10.1677/joe.0.1700619 ◽

2001 ◽

Vol 170 (3) ◽

pp. 619-628 ◽

Cited By ~ 30

Author(s):

◽

A Garmong ◽

P Swanson ◽

J Moore ◽

M Lin ◽

...

Keyword(s):

Rainbow Trout ◽

Oncorhynchus Mykiss ◽

Hepatoma Cells ◽

Dependent Manner ◽

High Sequence Identity ◽

Concentration Dependent Manner ◽

Igf Binding Proteins ◽

Rainbow Trout Oncorhynchus Mykiss ◽

Igf I ◽

Igf Binding

Rainbow trout (Oncorhynchus mykiss) serum contains several IGF-binding proteins (IGFBPs) that specifically bind to IGFs. The structures of these fish IGFBPs have not been determined and their physiological functions are poorly defined. In this study, we identified a 30 kDa IGFBP present in rainbow trout serum and secreted by cultured trout hepatoma cells. This IGFBP binds to IGFs but not to insulin. This IGFBP was purified to homogeneity using a three-step procedure involving Phenyl-Sepharose chromatography, IGF-I affinity chromatography and reverse-phase HPLC. Affinity cross-linking studies indicated that this IGFBP binds to IGF-I with a higher affinity than to IGF-II. N-terminal sequence analysis of the trout IGFBP suggests that it shares high sequence identity with that of human IGFBP-1 in the N-terminal region. When added to cultured fish and human cells, the trout IGFBP inhibited IGF-I-stimulated DNA synthesis and cell proliferation in a concentration-dependent manner. The inhibitory effect of the fish IGFBP was comparable to those of human IGFBP-1 and -4. These results indicate that the IGFBP molecule is structurally and functionally conserved in evolutionarily ancient vertebrate species such as bony fish.

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