Insulin in coho salmon (Oncorhynchus kisutch) during the parr to smolt transformation

Plisetskaya, Erika M.; Swanson, Penny; Bernard, Melinda G.; Dickhoff, Walton W.

doi:10.1016/0044-8486(88)90155-x

Cited by 57 publications

(28 citation statements)

References 38 publications

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“…Moreover, rates of hepatic lipid synthesis are greatest in salmon parr (Sheridan et al 1985), when plasma INS levels are at their peak (cf. Plisetskaya et al 1988). Fasting salmon display reduced INS titers when lipogenesis, as indicated by glucose-6-phosphate dehydrogenase activity, tended to be higher, although these results were not conclusive (Sheridan and Mommsen 1991).…”

Section: Discussionmentioning

confidence: 86%

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Insulin stimulates hepatic lipogenesis in rainbow trout, Oncorhynchus mykiss

Cowley

Sheridan

1993

Fish Physiol Biochem

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The effects of the pancreatic hormones, insulin and glucagon, on rates of lipid biosynthesis in liver removed from rainbow trout, Oncorhynchus mykiss, were evaluated in vitro. Livers were removed from animals fasted for 30-36h, cut into ca. 1 mm(3) pieces, and incubated in the presence of various concentrations of salmon insulin (sINS), bovine insulin (bINS), or a combination of BINS and bovine/porcine glucagon (GLU). Lipid synthesis was evaluated by total lipid concentration, (3)H2O incorporation into total lipid, and by fatty acid synthetase activity. Both mammalian and sINS tended to increase tissue total lipid concentration in hepatic tissue incubated for 5h. Insulin also stimulated (3)H2O incorporation into total lipid in a dose-dependent manner. Bovine INS (2 × 10(-6) M) stimulated de novo synthesis nearly 6-fold over control rates; sINS (2 × 10(-6) M) stimulated label incorporation more than 7-fold over control rates. Glucagon inhibited INS-stimulated (3)H2O incorporation; whereas, GLU alone had no effect on lipid synthesis in liver pieces incubated 5h. Lipid class analysis indicated that bINS significantly stimulated (3)H2O incorporation into phospholipids, fatty acids, and triacylglycerols. The greatest accumulation of label was in the triacylglycerol fraction, where incorporation was stimulated 17-fold over control levels. Hepatic enzymatic analysis indicated that bINS also significantly stimulated lipogenic enzyme activity 9-fold above control levels. These results indicate that INS is an important regulator of lipid synthesis in the liver of trout.

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Section: Discussionmentioning

confidence: 86%

“…During salmonid smoltification, development-associated reductions in liver total lipid and triacylglycerol (Sheridan 1989) are coincident with declining plasma INS titers (Plisetskaya et al 1988). Moreover, rates of hepatic lipid synthesis are greatest in salmon parr (Sheridan et al 1985), when plasma INS levels are at their peak (cf.…”

Section: Discussionmentioning

confidence: 99%

Insulin stimulates hepatic lipogenesis in rainbow trout, Oncorhynchus mykiss

Cowley

Sheridan

1993

Fish Physiol Biochem

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“…However, we found that the degree of the insulin increase depends on the feeding history of fish; fish that had been fed daily showed the maximum postprandial insulin response after a meal, whereas the insulin rise was progressively lower in fish fasted for longer periods. This suggests that insulin synthesis decreased, insulin sensitivity increased, or the stimulatory signals for insulin release were somehow reduced in fasted fish (34,51).…”

Section: Discussionmentioning

confidence: 99%

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

Shimizu¹,

Cooper²,

Dickhoff³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Fish were initially fasted for 1 day, 1 wk, or 3 wk. Fasted fish were then fed, and blood was collected at 4-h intervals over 26 h. After the various periods of fasting, basal levels of insulin were relatively constant, whereas those of IGF-I, IGFBPs and GH changed in proportion to the duration of the fast. A single meal caused a rapid, large increase in the circulating insulin levels, but the degree of the increase was influenced by the fasting period. IGF-I showed a moderate increase 2 h after the meal but only in the regularly fed fish. Plasma levels of 41-kDa IGFBP were increased in all groups within 6 h after the single meal. The fasting period did not influence the response of 41-kDa IGFBP to the meal. IGFBP-1 and GH decreased after the meal to the same extent among groups regardless of the fasting period. The present study shows that insulin and IGF-I respond differently to long (weeks)-and short (hours)-term nutritional changes in salmon; insulin maintains its basal level but changes acutely in response to food intake, whereas IGF-I adjusts its basal levels to the long-term nutritional status and is less responsive to acute nutritional input. IGFBPs maintain their sensitivity to food intake, even after prolonged fasting, suggesting their critical role in the nutritional regulation of salmon growth.fasting; refeeding; growth; metabolism GROWTH OCCURS WHEN THERE IS a net positive difference between the anabolic and catabolic processes of metabolism. Metabolism rapidly shifts between anabolic and catabolic processes on the order of minutes to hours, depending on current energy intake and expenditures. Growth varies at longer time scales of days to weeks and even months, depending on net energy intake averaged over these same days and weeks. Metabolism directly responds to current stimuli, while changes in growth rate are due not only to current intake but also to nutrient reserves stored over time. Thus growth is integrally connected to metabolism.Regulation of growth and metabolism is among the primary functions of the endocrine system. Both growth and metabolism are mediated and modulated through a myriad of differing factors that include integration and stimulation through the hypothalamic-pituitary axis; however, some primary mediators have been identified in the peripheral circulation (23). Pancreatic hormones such as insulin and glucagon are important regulators of anabolic and catabolic processes, respectively (24, 33). Growth is mediated through the actions of growth hormone (GH)-insulin-like growth factor (IGF)-I system. Interestingly, insulin and IGF-I are structurally related peptides, which arose from gene duplications before the emergence of the Chondrichthyes (8). Endocrine mechanisms have developed such that these structurally similar hormones modulate differing yet linked aspects of the physiology of metabolism and growth.The kinetics of insulin and total IGF-I in the circulation are markedly different. Circulating insulin shows a rapid change in response to a meal and its half-life in the c...

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“…It has been estimated that 7-8% of the lipid loss from maternal somatic tissues is transferred to the ovaries in maturing salmon (Idler and Bitners 1960;Hardy et al 1984). Metabolic changes during smoltification have also been documented from studies of metabolites (Woo et al 1978;Plisetskaya et al 1988), enzymes (Sheridan et al 1985;McCormick et al 1989) and hepatic ultrastructure (Robertson and Bradley 1991).…”

Section: Discussionmentioning

confidence: 99%

Plasma somatolactin levels in coho salmon (Oncorhynchus kisutch) during smoltification and sexual maturation

Rand‐Weaver

Swanson

1993

Fish Physiol Biochem

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Somatolactin (SL) is a novel pituitary hormone recently characterized in several fish species. Structural analyses have shown that SL belongs to the growth hormone/prolactin family, and that it is a highly conserved protein. SL is synthesized by the periodic acid/Schiff-positive cells in the pars intermedia, but has an as yet unidentified function(s). We have recently developed a homologous radioimmunoassay for coho salmon SL and measured plasma levels of SL during two stages of the coho salmon life cycle, smoltification and sexual maturation. During smoltification, plasma levels of SL changed almost in parallel with plasma levels of thyroxine; levels increased as morphological indices of smoltification appeared and decreased as smoltification was completed. Following this period, SL levels remained low until the spring prior to spawning. In a separate study, plasma levels of SL were measured in sexually maturing coho salmon that remained in fresh water throughout their life cycle. During the year of sexual maturation, plasma levels of SL gradually increased from the spring onward, reaching peak levels at the time of spawning in November and December. These data are similar to those previously reported for sexually maturing coho salmon that were maintained in seawater prior to spawning (Rand-Weaver et al. 1992). Therefore, increases in plasma SL levels occurred in sexually maturing fish irrespective of whether they were maintained in fresh water or seawater. Peak levels at spawning were higher than those observed during smoltification. Possible roles for SL in metabolism and reproduction are discussed.

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Insulin in coho salmon (Oncorhynchus kisutch) during the parr to smolt transformation

Cited by 57 publications

References 38 publications

Insulin stimulates hepatic lipogenesis in rainbow trout, Oncorhynchus mykiss

Insulin stimulates hepatic lipogenesis in rainbow trout, Oncorhynchus mykiss

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

Plasma somatolactin levels in coho salmon (Oncorhynchus kisutch) during smoltification and sexual maturation

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