| These experiments were conducted to evaluate the regulative role of glycine(Gly) on intestinal injury and muscle protein synthesis and degradation of weaned piglets after lipopolysaccharide(LPS) challenge and its mechanisms.1. This experiment was conducted to investigate whether Gly could attenuate LPS-induced intestinal injury in piglets via modulation of AMP-activated protein kinase(AMPK), mammalian target of rapamycin(m TOR), toll-like receptor(TLR4) and nucleotide binding oligomerization domain protein(NOD) signaling pathways. Twenty-four pigs were allotted to four treatments including:(1) control group.(2) LPS group.(3) LPS+1.0% Gly group.(4) LPS+2.0% Gly group. After 28 d feeding with control(0% Gly), 1.0% or 2.0% Gly supplemented diets, pigs were injected with saline or LPS. At 4 h saline or LPS post-injection, intestinal samples were obtained. The results showed that: 1) Gly increased jejunal villus height/crypt depth ratio, decreased crypt depth. 2) Gly increased jejunal and ileal protein content, protein/DNA ratio and RNA/DNA ratio. 3) Gly increased ileal citrate synthase, jejunal isocitrate dehydrogenase and α-ketoglutarate dehydrogenase complex activities. 4) Gly decreased phosphorylation of jejunal and ileal AMPKα, increased phosphorylation of ileal mTOR. 5) Gly decreased m RNA expressions of jejunal TLR4, LPS binding protein, myeloid differentiation factor 88(MyD88), tumor necrosis factor(TNF)-α receptor-associated factor 6(TRAF6), NOD2, receptor-interacting serine/threonine-protein kinase 2(RIPK2), nuclear factor(NF)-κB and ileal NOD2 and RIPK2. 6) Gly increased mRNA expressions of jejunal and ileal toll interacting protein and ileal suppressor of cytokine signaling 1 and Erbb2 interacting protein, decreased mRNA expressions of jejunal centaurin β1. These results indicate Gly may suppress intestinal inflammatory response via regulation of TLR4 and NOD signaling pathways, and therefore improve intestinal protein synthesis, possibly through regulation of AMPK and mTOR signaling.2. This experiment was conducted to investigate whether Gly could alleviate LPS-induced muscle protein degradation in piglets via modulation of protein kinase B(Akt)/mTOR, Akt/forkhead box o(FOXO) and TLR4 and NOD signaling pathways. Twenty-four pigs were allotted to four treatments including:(1) control group.(2) LPS group.(3) LPS+1.0% Gly group.(4) LPS+2.0% Gly group. After 28 d feeding with control(0% Gly), 1.0% or 2.0% Gly supplemented diets, pigs were injected with saline or LPS. At 4 h post-injection, pigs was killed and muscle sample was obtained. The results showed that: 1) Gly increased protein content, protein/DNA ratio and RNA/DNA ratio in gastrocnemius muscle, increased protein content and protein/DNA ratio in longissimus dorsi(LD) muscle. 2) Gly increased phosphorylation of Akt, and decreased t-Akt protein expression in gastrocnemius muscle. In addition, Gly increased phosphorylation of AMPKα in gastrocnemius and LD muscle. 3) Gly increased phosphorylation of mTOR and eIF4E-binding proteins in gastrocnemius and LD muscle, and decreased mRNA abundance of FOXO1, muscle atrophy F-box and muscle RING finger 1 in gastrocnemius muscle, and decreased FOXO1, FOXO4 mRNA expression and t-FOXO1 protein expression in LD muscle. Gly increased phosphorylation of FOXO1 in LD muscle. 4) Gly decreased mRNA abundance of TLR4, MyD88, IL-1 receptor-associated kinase, TRAF6, NOD2, RIPK2, NF-κB and TNF-α in gastrocnemius muscle, and decreased mRNA abundance of MyD88, TRAF6, NOD2 and TNF-α in LD muscle. These results indicate Gly may suppress muscle inflammatory response via regulation of TLR4 and NOD signaling pathways, and therefore improve muscle protein synthesis and attenuate protein degradation, possibly through regulation of Akt/mTOR and Akt/FOXO signaling but not AMPK. |
