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Citation

González JD, Silva-Marrero JI, Metón I, Caballero-Solares A, Viegas I, Fernández F, Mi?arro M, Fàbregas A, Ticó JR, Jones JG & Baanante IV (2016) Chitosan-Mediated shRNA Knockdown of Cytosolic Alanine Aminotransferase Improves Hepatic Carbohydrate Metabolism. Marine Biotechnology, 18 (1), pp. 85-97. https://doi.org/10.1007/s10126-015-9670-8

Abstract
Alanine aminotransferase (ALT) catalyses a transamination reaction that links carbohydrate and amino acid metabolism. In this study, we examined the effect of silencing cytosolic ALT (cALT) expression on the hepatic metabolism in Sparus aurata. A number of siRNA and shRNA designed to down-regulate cALT expression were validated in HEK-293 cells transfected with plasmids expressing S. aurata cALT or mitochondrial ALT (mALT) isoforms: ALT silencing significantly decreased the expression levels of S. aurata mRNA cALT1 to 62 % (siRNA) and 48 % (shRNA) of the values observed in control cells. The effect of cALT silencing was analysed in the liver of S. aurata 72 h after intraperitoneal injection of chitosan-tripolyphosphate (TPP) nanoparticles complexed with a plasmid encoding a shRNA to down-regulate cALT expression (pCpG-si1sh1). In fish fed diets with different ratio of protein to carbohydrate and treated with chitosan-TPP-pCpG-si1sh1, cALT1 and cALT2 mRNA levels significantly decreased irrespective of the diet. Consistently, ALT activity decreased in liver of treated animals. In the liver of S. aurata treated with chitosan-TPP-pCpG-si1sh1 nanoparticles, down-regulation of cALT expression increased the activity of key enzymes in glycolysis (6-phosphofructo-1-kinase and pyruvate kinase) and protein metabolism (glutamate dehydrogenase). Besides showing for the first time that administration of chitosan-TPP-pCpG-si1sh1 nanoparticles silences hepatic cALT expression in vivo, our data support that down-regulation of cALT could improve the use of dietary carbohydrates to obtain energy and spare protein catabolism.

Keywords
Alanine aminotransferase; siRNA; shRNA; Chitosan; Gene therapy; Sparus aurata

Journal
Marine Biotechnology: Volume 18, Issue 1