Liver protein expression in young pigs in response to a high-fat diet and diet restriction

We investigated the liver response in young pigs to a high-fat diet (containing 25% animal fat) and diet restriction (equivalent to 60% of maintenance) using differential proteome analysis. The objective was to investigate whether young pigs can be used to model the liver response in adolescents to a high-fat diet and diet restriction-induced BW loss. The high-fat diet increased (P<0.05) the subcutaneous and visceral fat deposition by 45 and 56%, respectively. However, the young pigs on the high-fat diet had normal glucose tolerance and liver lipid content despite a general increase (P<0.05) in plasma lipids (i.e., NEFA, triglycerides, phospholipids, total cholesterol, and lipoproteins). In addition, diet restriction in young pigs induced a modest BW loss (0.7 kg/d; P<0.01) through increased fat mobilization whereas the concentrations of plasma phospholipids, total cholesterol, and low-density lipoprotein decreased (P<0.05) by 37, 36, and 38%, respectively. Data from the proteome analysis indicate that the liver response to a high-fat diet in young pigs is similar to that of humans in terms of increased fatty acid oxidation whereas the liver response to diet restriction is similar to humans in terms of increased gluconeogenesis and glycogenolysis and decreased urea synthesis. Our results suggest that 5 liver proteins, namely acyl-CoA synthetase long-chain 1, sterol carrier protein 2, apolipoprotein C-III, liver fatty acid binding protein, and acyl-CoA-binding protein, play a role in intracellular lipid transport and export in young pigs. In contrast to humans, our results indicate that young pigs are resistant to fat-induced liver lipid accumulation whereas diet restriction decreases fatty acid oxidation and the subsequent ketogenesis in the liver. Consequently, the liver response in adolescents to a high fat diet and diet restriction-induced BW loss cannot reliably be reproduced in young pigs.