Dietary glutamine, glutamate, and aspartate supplementation improves hepatic lipid metabolism in post-weaning piglets

A previous study has demonstrated that early weaning significantly suppressed hepatic glucose metabolism in piglets. Glutamate (Glu), aspartate (Asp) and glutamine (Gln) are major metabolic fuels for the small intestine and can alleviate weaning stress, and therefore might improve hepatic energy metabolism. The objective of this study was to investigate the effects of administration of Glu, Asp and Gln on the expression of hepatic genes and proteins involved in lipid metabolism in post-weaning piglets. Thirty-six weaned piglets were assigned to the following treatments: control diet (Control; basal diet + 15.90 g/kg alanine); Asp, Gln and Glu-supplemented diet (Control + AA; basal diet + 1.00 g/kg Asp + 5.00 g/kg Glu + 10.00 g/kg Gln); and the energy-restricted diet supplemented with Asp, Gln and Glu (Energy− + AA; energy deficient diet + 1.00 g/kg Asp + 5.00 g/kg Glu + 10.00 g/kg Gln). Liver samples were obtained on d 5 and 21 post-weaning. Piglets fed Energy− + AA diet had higher liver mRNA abundances of acyl-CoA oxidase 1 (ACOX1), succinate dehydrogenase (SDH), mitochondrial transcription factor A (TFAM) and sirtuin 1 (SIRT1), as well as higher protein expression of serine/threonine protein kinase 11 (LKB1), phosphor-acetyl-CoA carboxylase (P-ACC) and SIRT1 compared with piglets fed control diet (P < 0.05) on d 5 post-weaning. Control + AA diet increased liver malic enzyme 1 (ME1) and SIRT1 mRNA levels, as well as protein expression of LKB1 and P-ACC on d 5 post-weaning (P < 0.05). On d 21 post-weaning, compared to control group, Glu, Gln and Asp supplementation up-regulated the mRNA levels of ACOX1, ME1 and SIRT1 (P < 0.05). These findings indicated that dietary Glu, Gln and Asp supplementation could improve hepatic lipid metabolism to some extent, which may provide nutritional intervention for the insufficient energy intake after weaning in piglets.