ARS | Publication request: A low-fat liquid diet decreases AMPK and increases mTOR phosphorylation in skeletal muscle of 10-day-old pigs

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 14, 2008
Publication Date: July 23, 2008
Citation: Oliver, W.T., Miles, J.R. 2008. A low-fat liquid diet decreases AMPK and increases mTOR phosphorylation in skeletal muscle of 10-day-old pigs [abstract]. Journal of Animal Science. 86(E-Supplement 2):560-561.

Technical Abstract: Previous research shows that neonatal pigs respond to decreases in energy density of liquid diets with increased feed intake, resulting in similar performance to pigs fed a more energy-dense diet. The objective of this experiment was to determine if a high- (25%, HF) or low-fat (2%, LF) liquid diet affects proteins involved in energy homeostasis and protein synthesis in early-weaned pigs. Forty-eight pigs, with an initial body weight of 3,637 +/- 85 g, were weaned at 10 d of age and utilized in a randomized complete block design. Pigs were blocked by weight and gender, then assigned to pens (8 pigs/pen). Diets were formulated to provide a constant lysine:ME and were fed for 10 d, at which time blood and longissimus dorsi were collected. Blood was analyzed for plasma urea nitrogen (PUN) and NEFA. Longissimus dorsi was analyzed via western immunoblot for mammalian target of rapamycin (mTOR) and adenosine 5’ monophosphate-activated protein kinase (AMPK) phosphorylation. Pigs gained 347 +/- 11 g/d, which resulted in an ending body weight of 7,035 +/- 170 g, regardless of dietary treatment (P > 0.20). Pigs fed a LF diet consumed approximately 24% more milk than pigs fed the HF diet (2,853 +/- 23 vs. 2,309 +/- 65 g dry feed•pen-1•d-1; P < 0.01), which resulted in similar calculated ME intakes between dietary treatments (9.9 +/- 0.2 vs. 10.7 +/- 0.5 Mcal•pen-1•d-1; P > 0.10). Feed conversion (gain:feed) was 19% higher in HF compared to LF fed pigs (P < 0.03). Circulating NEFA (137 +/- 37 vs. 39 +/- 13 uEq/L; P < 0.02) and PUN (17.6 +/- 0.8 vs. 3.0 +/- 0.6 mM; P < 0.01) concentrations were higher in HF pigs compared to LF pigs. The AMPK phosphorylation was 29% higher (P < 0.03) in HF pigs compared to LF pigs, while mTOR phosphorylation was increased by 22% in LF pigs (P < 0.02). Thus, young pigs consuming a low-fat diet have lower activation of AMPK and higher activation of mTOR, as measured by phosphorylation. This may lead to improved utilization of amino acids as indicated by the markedly lower PUN in pigs consuming a low-fat diet.