Abstract
BackgroundGlucocorticoid has an important effect on lipid metabolism in muscles, and the type of fatty acid likely affects mitochondrial utilization. Therefore, we hypothesize that the different fatty acid types treatment may affect the glucocorticoid induction of intramuscular lipid accumulation.Methodology/Principal FindingsThe effect of dexamethasone (DEX) on fatty acid metabolism and storage in skeletal muscle of broiler chickens (Gallus gallus domesticus) was investigated with and without fatty acid treatments. Male Arbor Acres chickens (31 d old) were treated with either palmitic acid (PA) or oleic acid (OA) for 7 days, followed by DEX administration for 3 days (35–37 d old). The DEX-induced lipid uptake and oxidation imbalance, which was estimated by increased fatty acid transport protein 1 (FATP1) expression and decreased carnitine palmitoyl transferase 1 activity, contributed to skeletal muscle lipid accumulation. More sensitive than glycolytic muscle, the oxidative muscle in DEX-treated chickens showed a decrease in the AMP to ATP ratio, a decrease in AMP-activated protein kinase (AMPK) alpha phosphorylation and its activity, as well as an increase in the phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal p70S6 kinase, without Akt activation. DEX-stimulated lipid deposition was augmented by PA, but alleviated by OA, in response to pathways that were regulated differently, including AMPK, mTOR and FATP1.ConclusionsDEX-induced intramuscular lipid accumulation was aggravated by SFA but alleviated by unsaturated fatty acid. The suppressed AMPK and augmented mTOR signaling pathways were involved in glucocortcoid-mediated enhanced intramuscular fat accumulation.
Highlights
Fatty acids and glucose are the primary skeletal muscle fuels
The suppressed AMPK and augmented mammalian target of rapamycin (mTOR) signaling pathways were involved in glucocortcoid-mediated enhanced intramuscular fat accumulation
We firstly demonstrated the interaction between GC and fatty acid types treatment (FA) treatments on intramuscular fat (IMF) accumulation in broiler chickens
Summary
Fatty acids and glucose are the primary skeletal muscle fuels. GC has an important effect on lipid metabolism in muscles. GC and insulin act together to promote intramyocellular lipid accumulation in mammals [2] and chickens [3]. Birds have higher level of glucose and lower concentration of insulin [4,5], and have more refractory insulin cascade in skeletal muscle tissues [4,6]. The study on chicken model would be helpful to the understanding of intramyocellular lipid accumulation. Glucocorticoid has an important effect on lipid metabolism in muscles, and the type of fatty acid likely affects mitochondrial utilization. We hypothesize that the different fatty acid types treatment may affect the glucocorticoid induction of intramuscular lipid accumulation
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