Glucagon and insulin response to dietary carbohydrate in rainbow trout (Oncorhynchus mykiss)

Insulin regulates the expression of several metabolism-related genes in the liver and primary hepatocytes of rainbow trout (Oncorhynchus mykiss)

“…Indeed, plasma glucose levels were so drastically reduced 6 h after intraperitoneal administration of insulin (1.78±0.18 mmol l -1 ) that the expected effect of insulin was counteracted by the inhibitory effect of the very low glucose level. These results are in agreement with the previous demonstration that GK gene expression was only enhanced when rainbow trout were fed with a single meal of glucose or a carbohydrate-rich diet (Panserat et al, 2000b;Panserat et al, 2001c) whereas insulin secretion was similar in trout fed with high or low carbohydrate diets (Capilla et al, 2004b;del sol Novoa et al, 2004). The regulation of the second glycolytic enzyme that we studied -PK, the last enzyme of glycolysis (Towle et al, 1997) exhibited a different response under insulin stimulation in in vivo and in vitro studies.…”

“…This suggests a direct effect of insulin on the transcription of these genes that probably involves the activation of FoxO1 and PGC1α transcription factors, as has been described in mammals (Puigserver et al, 2003). However, the effects of insulin on the regulation of gluconeogenic gene expression were studied in animals that presented plasma glucose levels (1.78±0.18 mmol l -1 ) far below those normally measured in fasted animals (4.10±0.40 mmol l -1 ) or even in rainbow trout fed with 28% carbohydrates (12.2 mmol l -1 ) (del sol Novoa et al, 2004). In this context, we also analyzed the effects of insulin on target gene expression in primary hepatocytes in relation to glucose concentrations corresponding to plasma glucose levels of fasted and carbohydrate-fed trout, respectively.…”

“…For gene expression analysis, 48 h-cultured cells were exposed for an additional 24 h to 4ϫ10 -9 mol l -1 bovine insulin in the presence of 3 or 20 mmol l -1 glucose, the mean glucose concentrations measured in fasted trout and trout fed the carbohydrate-rich diet, respectively (Bergot, 1979;del sol Novoa et al, 2004;Hemre et al, 2002;Panserat et al, 2001c). Osmotic pressures of insulin-glucose-supplemented cell culture media were verified before each treatment and calibrated to 300 mosmol l -1 using a K7400 osmometer (Knauer, Berlin, Germany).…”

“…Oral or intravenous administration of glucose and a carbohydrate-rich diet result in persistent hyperglycemia in various fish species, including rainbow trout (Bergot, 1979;del sol Novoa et al, 2004;Legate et al, 2001;Palmer and Ryman, 1972;Parrizas et al, 1994b), and are also associated with an increase in insulin levels. The magnitude of the insulin response is very fish-species dependent and less than that in mammals (Furuichi and Yone, 1981).…”

Hepatic fatty acid biosynthesis is more responsive to protein than carbohydrate in rainbow trout during acute stimulations

“…Ϫ9 mol/l of bovine insulin (Sigma) corresponding to the postprandial level of insulin (17,51), low or high level of glucose (3 mM, low Glu; or 20 mM, high Glu) (57,75), and a low or high level of amino acids [one-fold (low AA) or four-fold (high AA) concentrated amino acids]. In the second in vitro experiment, 48-h cultured hepatocytes were stimulated with glucose (3 mM), low or high level of insulin [1ϫ10 Ϫ9 mol/l, low insulin or 4ϫ10 Ϫ9 mol/l, high insulin, corresponding to the 2-wk fasted or postprandial insulin levels (51, 59)], and low or high levels of amino acids (low AA or high AA).…”