Conjugated linoleic acid (CLA) isomers have a number of beneficial health effects, as shown in biomedical studies with animal models. Previously, we reported that a mixture of CLA isomers improved glucose tolerance in ZDF rats and activated peroxisome proliferatoractivated receptor (PPAR)-␥ response elements in vitro. Here, our aim was to elucidate the effect(s) of specific CLA isomers on whole-body glucose tolerance, insulin action in skeletal muscle, and expression of genes important in glucose and lipid metabolism. ZDF rats were fed either a control diet (CON), one of two CLA supplemented diets (1.5% CLA) containing differing isoforms of CLA (47% c9,t11; 47.9% c10,t12, 50:50; or 91% c9,t11, c9,t11 isomers), or were pair-fed CON diet to match the intake of 50:50. The 50:50 diet reduced adiposity and improved glucose tolerance compared with all other ZDF treatments. Insulin-stimulated glucose transport and glycogen synthase activity in skeletal muscle were improved with 50:50 compared with all other treatments. Neither phosphatidlyinositol 3-kinase activity nor Akt activity in muscle was affected by treatment. Uncoupling protein 2 in muscle and adipose tissue was upregulated by c9,t11 and 50:50 compared with ZDF controls. PPAR-␥ mRNA was downregulated in liver of c9,t11 and pair-fed ZDF rats. Thus, the improved glucose tolerance in 50:50 rats is attributable to, at least in part, improved insulin action in muscle, and CLA effects cannot be explained simply by reduced food intake.

Level of physical activity is linked to improved glucose homeostasis. We determined whether exercise alters the expression and͞or activity of proteins involved in insulin-signal transduction in skeletal muscle. Wistar rats swam 6 h per day for 1 or 5 days. Epitrochlearis muscles were excised 16 h after the last exercise bout, and were incubated with or without insulin (120 nM). Insulin-stimulated glucose transport increased 30% and 50% after 1 and 5 days of exercise, respectively. Glycogen content increased 2-and 4-fold after 1 and 5 days of exercise, with no change in glycogen synthase expression. Protein expression of the glucose transporter GLUT4 and the insulin receptor increased 2-fold after 1 day, with no further change after 5 days of exercise. Insulinstimulated receptor tyrosine phosphorylation increased 2-fold after 5 days of exercise. Insulin-stimulated tyrosine phosphorylation of insulin-receptor substrate (IRS) 1 and associated phosphatidylinositol (PI) 3-kinase activity increased 2.5-and 3.5-fold after 1 and 5 days of exercise, despite reduced (50%) IRS-1 protein content after 5 days of exercise. After 1 day of exercise, IRS-2 protein expression increased 2.6-fold and basal and insulin-stimulated IRS-2 associated PI 3-kinase activity increased 2.8-fold and 9-fold, respectively. In contrast to IRS-1, IRS-2 expression and associated PI 3-kinase activity normalized to sedentary levels after 5 days of exercise. Insulin-stimulated Akt phosphorylation increased 5-fold after 5 days of exercise. In conclusion, increased insulin-stimulated glucose transport after exercise is not limited to increased GLUT4 expression. Exercise leads to increased expression and function of several proteins involved in insulin-signal transduction. Furthermore, the differential response of IRS-1 and IRS-2 to exercise suggests that these molecules have specialized, rather than redundant, roles in insulin signaling in skeletal muscle.

It has been reported that TNFR2 is involved in regulatory T cell induction and myeloid-derived suppressor cell (MDSC) accumulation, two kinds of immunosuppressive cells contributing to tumor immune evasion. Because transmembrane TNF-α (tmTNF-α) is the primary ligand for TNFR2, we hypothesized that tmTNF-α is mainly responsible for the activation of MDSCs. Indeed, we found that tmTNF-α, rather than secretory TNF-α (sTNF-α), activated MDSCs with enhanced suppressive activities, including upregulating arginase-1 and inducible NO synthase transcription, promoting secretion of NO, reactive oxygen species, IL-10, and TGF-β, and enhancing inhibition of lymphocyte proliferation. This effect of tmTNF-α was mediated by TNFR2, as TNFR2 deficiency significantly impaired tmTNF-α–induced release of IL-10 and NO and inhibition of T cell proliferation by MDSC supernatant. Furthermore, tmTNF-α caused p38 phosphorylation and NF-κB activation, whereas inhibition of NF-κB or p38 with an inhibitor pyrrolidine dithiocarbamate or SB203580 abrogated tmTNF-α–mediated increased suppression of lymphocyte proliferation by MDSCs. Consistently, our in vivo study showed that ectopic expression of uncleavable tmTNF-α mutant by 4T1 cells significantly promoted tumor progression and angiogenesis, accompanied with more accumulation of MDSCs and regulatory T cells in the tumor site, increased production of NO, IL-10, and TGF-β, as well as poor lymphocyte infiltration. In contrast, enforced expression of sTNF-α mutant by 4T1 cells that only released sTNF-α without expression of surface tmTNF-α markedly reduced MDSC accumulation and induced more lymphocyte infiltration instead, showing obvious tumor regression. Our data suggest that tmTNF-α acts as a potent activator of MDSCs via TNFR2 and reveals another novel immunosuppressive effect of this membrane molecule that promotes tumor immune escape.

We determined whether mitogen‐activated protein kinase (MAPK) and 5′‐AMP‐activated protein kinase (AMPK) signalling cascades are activated in response to intense exercise in skeletal muscle from six highly trained cyclists (peak O2 uptake (V̇O2,peak) 5.14 ± 0.1 l min−1) and four control subjects (V̇O2,peak 3.8 ± 0.1 l min−1) matched for age and body mass. Trained subjects completed eight 5 min bouts of cycling at ≈85% of V̇O2,peak with 60 s recovery between work bouts. Control subjects performed four 5 min work bouts commencing at the same relative, but a lower absolute intensity, with a comparable rest interval. Vastus lateralis muscle biopsies were taken at rest and immediately after exercise. Extracellular regulated kinase (ERK1/2), p38 MAPK, histone H3, AMPK and acetyl CoA‐carboxylase (ACC) phosphorylation was determined by immunoblot analysis using phosphospecific antibodies. Activity of mitogen and stress‐activated kinase 1 (MSK1; a substrate of ERK1/2 and p38 MAPK) and α1 and α2 subunits of AMPK were determined by immune complex assay. ERK1/2 and p38 MAPK phosphorylation and MSK1 activity increased (P < 0.05) after exercise 2.6‐, 2.1‐ and 2.0‐fold, respectively, in control subjects and 1.5‐, 1.6‐ and 1.4‐fold, respectively, in trained subjects. Phosphorylation of histone H3, a substrate of MSK1, increased (P < 0.05) ≈1.8‐fold in both control and trained subject. AMPKα2 activity increased (P < 0.05) after exercise 4.2‐ and 2.3‐fold in control and trained subjects, respectively, whereas AMPKα1 activity was not altered. Exercise increased ACC phosphorylation (P < 0.05) 1.9‐ and 2.8‐fold in control and trained subjects. In conclusion, intense cycling exercise in subjects with a prolonged history of endurance training increases MAPK signalling to the downstream targets MSK1 and histone H3 and isoform‐specific AMPK signalling to ACC. Importantly, exercise‐induced signalling responses were greater in untrained men, even at the same relative exercise intensity, suggesting muscle from previously well‐trained individuals requires a greater stimulus to activate signal transduction via these pathways.

Earlier studies reported that a cell membrane protein Annexin A2 (AnxA2) plays multiple roles in the development, invasion and metastasis of cancer. Recent studies have demonstrated that AnxA2 also functions in immunity against infection, but the underlying mechanism remains largely elusive. Using a mouse infection model, we now reveal a crucial role of AnxA2 in host defense against Pseudomonas aeruginosa (Pa), as anxa2−/− mice manifested severe lung injury, systemic dissemination, and increased mortality compared to wild-type (WT) littermates. In addition, anxa2−/− mice exhibited elevated inflammatory cytokines (TNF-α, IL-6, IL-1β and IFN-γ), decreased bacterial clearance by macrophages, and increased superoxide release in the lung. We further identified an unexpected molecular interaction between AnxA2 and Fam13A (Family with sequence similarity 13, member A), which activated Rho GTPase. P. aeruginosa infection induced autophagosome formation by inhibiting Akt1 and mTOR. Our results indicate that AnxA2 regulates autophagy and thereby contributing to host immunity against bacteria through Akt1-mTOR-ULK1/2 signaling pathway.

Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas

Activation of Aryl hydrocarbon receptor (AhR) is involved in the control of intestinal mucosal homeostasis. Intestinal barrier dysfunction contributes to the development of many intestinal diseases, such as inflammatory bowel disease (IBD). In this study, we investigated the mechanisms of AhR activation in the maintenance of intestinal barrier function. Adult C57BL/6 mice were treated with dextran sulphate sodium (DSS) for 7 days, with or without 6-Formylindolo(3,2-b)carbazole (FICZ), a ligand of AhR. We found that AhR activation by FICZ attenuated the decreased TJ protein expression in the colonic mucosa of the DSS-induced mice. Further, the increase of both MLC phosphorylation and MLCK expression in the mice with DSS-induced colitis was also significantly inhibited by FICZ induced AhR activation. For in vitro experiments, Caco-2 cells were treated with tumour necrosis factor alpha (TNF-α)/interferon gamma (IFN-γ) for 48 h, with or without FICZ. AhR activation prevented TNF-α/IFN-γ-induced decrease in TER and morphological disruption of the TJs in Caco-2 monolayers. It also inhibited TNF-α/IFN-γ-induced increase in MLCK expression and MLC phosphorylation by suppression of NF-κB p65 signaling pathway. Thus, AhR-activating factors might have potential as therapeutic agents for the treatment of patients with IBD.

We tested the hypothesis that long‐distance running activates parallel mitogen‐activated protein kinase (MAPK) cascades that involve extracellular signal regulated kinase 1 and 2 (ERK1/2) and p38 MAPK and their downstream substrates. Eleven men completed a 42.2 km marathon (mean race time 4 h 1 min; range 2 h 56 min to 4 h 33 min). Vastus lateralis muscle biopsies were obtained before and after the race. Glycogen content was measured spectrophotometrically. ERK1/2 and p38 MAPK phosphorylation was determined by immunoblot analysis using phosphospecific antibodies. Activation of the downstream targets of ERK1/2 and p38 MAPK, MAPK‐activated protein kinase‐1 (MAPKAP‐K1; also called p90 ribosomal S6 kinase, p90rsk), MAPK‐activated protein kinase‐2 (MAPKAP‐K2), mitogen‐ and stress‐activated kinase 1 (MSK1) and mitogen‐ and stress‐activated kinase 2 (MSK2) was determined using immune complex assays. Muscle glycogen content was reduced by 40 ± 6 % after the marathon. ERK1/2 phosphorylation increased 7.8‐fold and p38 MAPK phosphorylation increased 4.4‐fold post‐exercise. Prolonged running did not alter ERK1/2 and p38 MAPK protein expression. The activity of p90rsk, a downstream target of ERK1/2, increased 2.8‐fold after the marathon. The activity of MAPKAPK‐K2, a downstream target of p38 MAPK, increased 3.1‐fold post‐exercise. MSK1 and MSK2 are downstream of both ERK1/2 and p38 MAPK. MSK1 activity increased 2.4‐fold post‐exercise. MSK2 activity was low, relative to MSK1, with little activation post‐exercise. In conclusion, prolonged distance running activates MAPK signalling cascades in skeletal muscle, including increased activity of downstream targets: p90rsk, MAPKAP‐K2 and MSK. Activation of these downstream targets provides a potential mechanism by which exercise induces gene transcription in skeletal muscle.