The essentiality of dietary myo-inositol to oriental river prawn (Macrobrachium nipponense): Evidence in growth performance, lipid metabolism and mitochondrial function

Abstract

The essentiality of dietary myo-inositol to aquatic animals is species-dependent. Meanwhile, the mechanisms underlying its beneficial effects on the growth performance and intermediary metabolism are still poorly understood. This dose-response study was designed to investigate the optimum myo-inositol demand of oriental river prawn (Macrobrachium nipponense). In addition, the potential effects on lipid metabolism and mitochondrial function were also characterized to elucidate how myo-inositol benefits the growth performance and physiological functions of aquatic animals. Prawns (average body weight 0.17 g) were randomly divided into 6 groups, and fed six diets with graded myo-inositol levels (1700, 2160, 3120, 3970, 5350 and 6000 mg/kg). After the 10-week feeding trial, the survival rate, feed intake, hemolymph high-density lipoprotein cholesterol content and mitochondrial complex II activity all showed no statistical difference. However, the specific growth rate, weight gain, protein efficiency ratio, hemolymph cholesterol content, and the hepatopancreas activities of complex III and IV all increased remarkably as dietary myo-inositol levels increased up to 5350 mg/kg, while an opposite was result was noted in the feed conversion ratio. In addition, hemolymph triglyceride content and hepatopancreas complex V activity both exhibited distinct linear effects peaking at the 3120 mg/kg group. The moderate doses of myo-inositol markedly up-regulated the transcriptions of fatty acid binding protein, acyl-CoA binding protein, scavenger receptor class B type I, carnitine palmitoyltransferase I, cytochrome c oxidase 1 and 2 and AMP-activated protein kinase α, but down-regulated those of acetyl-CoA carboxylase, fatty acid synthase and cytochrome b. Overall, dietary supplementation of 2787.00-5484.87 mg/kg myo-inositol ameliorated the growth performance and mitochondrial function of oriental river prawn coupled with the enhanced lipid transport, lipolysis and fatty acid β-oxidation.