Dramatic modification of liver carbohydrate metabolic pathways and lipogenesis during adaptation to a high protein diet in rat

Abstract

Amino acids participate both to proteogenic and non proteogenic metabolism, act as energy substrates and play a signaling role in protein and energy pathways. We aimed to study the time course adaptation to HP diet of gene expression of key enzymes involved in energy metabolism (glycogenesis: GS; gluconeogenesis: PEPCK, G6PC1; glycolysis: GK, L‐PK; lipogenesis: FAS, ACC; lipolysis: CPT1, ACOX1). 40 Wistar rats were fed a normal (NP) or a high protein diet for 1, 3, 6 or 15 d. They were euthanized 2 h after a 4 g meal. Blood, liver, muscles, kidney and adipose tissues were collected. Plasma insulin and glucagon were measured. Gene expression was determined by real time PCR. The ratio insulin to glucagon was lowered. There was only minor change of the gene expression profiles in adipose tissues, muscles and kidney. In the liver, HP diet led to an increase of PEPCK but not G6PC1 expression from the 6th day of adaptation, GS expression increased with time to reach the value observed in NP rats, glycolysis and lipogenesis enzymes were down‐regulated, and CPT1 and ACOX1 were not altered. This study evidences a 6 day adaptation of carbohydrate metabolism to HP diet, leading to a stimulation of neoglycogenonesis as well as a down‐regulation of lipogenesis that may participate in lowering adiposity.