Abstract
This study investigated the effects of resveratrol on the growth performance, energy sensing, glycolipid metabolism and glucose and insulin load of blunt snout bream Megalobrama amblycephala fed high-carbohydrate diets. Fish (39.44 ± 0.06 g) were randomly fed three diets: a control diet (30% carbohydrate), a high-carbohydrate diet (HC, 41% carbohydrate), and the HC diet supplemented with 0.04% resveratrol (HCR) for 12 weeks. Fish fed the HC diet had significantly high values of nitrogen and energy retention efficiency, hepatosomatic index, intraperitoneal fat ratio, whole-body lipid content and intraperitoneal fat glycogen and lipid contents compared to the control group, but showed little difference with the HCR treatment. Liver and muscle lipid contents and plasma levels of glucose, glycated serum protein, advanced glycation end products and total cholesterol of fish fed the HC diet were significantly higher than those of the control group, whereas the opposite was found with resveratrol supplementation. Fish fed the HC diet obtained significantly low values of plasma insulin levels and hepatic adenosine monophosphate (AMP) contents and NAD+/NADH ratio compared to HCR treatment, but showed little difference with the control group. The opposite was found for hepatic adenosine triphosphate (ATP) contents and the ATP/AMP ratio. In addition, fish fed the HC diet showed significantly high transcriptions of glucose transporter 2 (GLUT2), glucose-6-phosphate dehydrogenase, glycogen synthase, fatty acid synthetase (FAS), acetyl-CoA carboxylase α (ACCα), peroxisome proliferator-activated receptor γ and PPARα compared to the control group, whereas the opposite was found for protein levels of AMP-activated protein kinase α (t-AMPKα), phosphorylated AMP-activated protein kinase α (p-AMPKα), sirtuin-1 (SIRT1), and p-AMPKα/t-AMPKα ratio as well as the transcriptions of AMPKα1, AMPKα2, SIRT1, PPARγ coactivator-1α (PGC-1α), phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphatase, carnitine palmitoyl transferase I (CPT I) and acyl-CoA oxidase. Resveratrol supplementation significantly up-regulated the protein levels of t-AMPK, p-AMPK, and SIRT1, p-AMPK/t-AMPK ratio as well as the transcriptions of AMPKα1, AMPKα2, SIRT1, PGC-1α, GLUT2, FBPase, and CPT I compared to HC group, while the opposite was found for sterol regulatory element-binding protein-1, FAS and ACCα. Furthermore, resveratrol improved glucose and insulin tolerance of fish fed the HC diet after glucose and insulin load.
Highlights
Carbohydrates are generally deemed to the most economical energy source in fishery, because of their relatively low cost and protein-sparing effect (Shiau and Lin, 2001; Watanabe, 2002)
This could not have negative effects on the growth performance of fish, since as a herbivorous fish blunt snout bream has a high tolerance for cellulose than most of the carnivorous and omnivorous species (Li et al, 2013; Zhou C.P. et al, 2013)
According to a previous study, resveratrol could enhance the glucose-stimulated insulin secretion by improving the functions of pancreatic usually lead to the dephosphorylation of glycogen phosphorylase beta-cells, up-regulating Glycogen Synthase (GS) expression of mammals (GPase) and glutamine synthetase (GSase) by inhibiting the (Vetterli et al, 2011)
Summary
Carbohydrates are generally deemed to the most economical energy source in fishery, because of their relatively low cost and protein-sparing effect (namely spare protein from being catabolized for energy, and decrease the ammonia emission into aquatic environment) (Shiau and Lin, 2001; Watanabe, 2002). The omnivorous and herbivorous fish are capable to utilize much higher levels of carbohydrates than carnivorous ones (Wilson, 1994). The metabolic differences in carbohydrate utilization among fish species are not still fully understood. Some studies have shown that the low utilization of carbohydrates by fish might be partly due to the poor postprandial supervision of certain energy metabolic sensors, which are closely involved in glucose metabolism (Magnoni et al, 2012; Polakof et al, 2012; Condesieira and Soengas, 2017; Kamalam et al, 2017). Some studies have shown that the intermediary metabolism of fish could be regulated by these energy sensors that control intracellular glucose use (Lu et al, 2018; Xu et al, 2018). The molecular investigations of these energy sensors might promote our understanding of the carbohydrate utilization by fish
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