Impaired insulin-mediated suppression of hepatic glucose production (HGP) plays a major role in the pathogenesis of type 2 diabetes (T2D), yet the molecular mechanism by which this occurs remains ...unknown. Using a novel in vivo metabolomics approach, we show that the major mechanism by which insulin suppresses HGP is through reductions in hepatic acetyl CoA by suppression of lipolysis in white adipose tissue (WAT) leading to reductions in pyruvate carboxylase flux. This mechanism was confirmed in mice and rats with genetic ablation of insulin signaling and mice lacking adipose triglyceride lipase. Insulin’s ability to suppress hepatic acetyl CoA, PC activity, and lipolysis was lost in high-fat-fed rats, a phenomenon reversible by IL-6 neutralization and inducible by IL-6 infusion. Taken together, these data identify WAT-derived hepatic acetyl CoA as the main regulator of HGP by insulin and link it to inflammation-induced hepatic insulin resistance associated with obesity and T2D.
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•Insulin inhibits gluconeogenesis by suppressing lipolysis and hepatic acetyl CoA•Hyperglycemia associated with HFD is due to increased WAT-derived hepatic acetyl CoA•ATGL KOs are protected from HFD-induced insulin resistance due to decreased lipolysis•mφJNK KOs are protected from HFD-induced insulin resistance due to decreased lipolysis
Metabolic abnormalities associated with a high-fat diet are found to be driven by increased hepatic acetyl CoA levels, which are shown to be a consequence of white adipose tissue inflammation and inappropriately increased lipolysis.
Obesity is associated with a chronic state of low-grade inflammation and progressive tissue infiltration by immune cells and increased expression of inflammatory cytokines. It is established that ...interleukin 6 (IL6) regulates multiple aspects of metabolism, including glucose disposal, lipolysis, oxidative metabolism, and energy expenditure. IL6 is secreted by many tissues, but the role of individual cell types is unclear. We tested the role of specific cells using a mouse model with conditional expression of the Il6 gene. We found that IL6 derived from adipocytes increased, while IL6 derived from myeloid cells and muscle suppressed, macrophage infiltration of adipose tissue. These opposite actions were associated with a switch of IL6 signaling from a canonical mode (myeloid cells) to a noncanonical trans-signaling mode (adipocytes and muscle) with increased expression of the ADAM10/17 metalloprotease that promotes transsignaling by the soluble IL6 receptor α. Collectively, these data demonstrate that the source of IL6 production plays a major role in the physiological regulation of metabolism.
(1) Background: The immunostimulatory role of the polysaccharide fraction (KRG-P) of Korea red ginseng (KRG) was studied in cells. However, its immunomodulatory activity is unknown. Therefore, we ...investigated the chemical properties of KRG-P and its intestinal immune responses in vitro and in vivo. (2) Methods: KRG-P monosaccharide composition and molecular weight were determined using high-performance liquid and size-exclusion chromatography systems. Immunoglobulin A (IgA) and α-defensin-1 transcript levels were measured using a SYBR Green qRT-PCR; defensin-1, Granulocyte-macrophage colony-stimulating factor (GM-CSF), and IgA protein levels were determined using Western blotting and ELISA kits. (3) Results: The molecular weight of KRG-P was estimated to be 106 kDa, and it contained neutral sugar (74.3%), uronic acid (24.6%), and proteins (1%). In vitro studies of intestinal immunomodulatory activity of KRG-P indicated that GM-CSF and IgA levels increased in Peyer’s patch cells to higher levels than those obtained with KRG and induced bone marrow cell proliferation. In in vivo study, oral KRG-P administration to mice upregulated the expression of α-defensin-1 and IgA in the small intestinal tissue and that of secreted IgA in the feces. (4) Conclusions: KRG-P contributed to the modulation of intestinal immunity and maintenance of intestinal homeostasis against intestinal infection.
Skeletal muscle has a remarkable plasticity to adapt and remodel in response to environmental cues, such as physical exercise. Endurance exercise stimulates improvements in muscle oxidative capacity, ...while resistance exercise induces muscle growth. Here we show that the c-Jun N-terminal kinase (JNK) is a molecular switch that when active, stimulates muscle fibers to grow, resulting in increased muscle mass. Conversely, when muscle JNK activation is suppressed, an alternative remodeling program is initiated, resulting in smaller, more oxidative muscle fibers, and enhanced aerobic fitness. When muscle is exposed to mechanical stress, JNK initiates muscle growth via phosphorylation of the transcription factor, SMAD2, at specific linker region residues leading to inhibition of the growth suppressor, myostatin. In human skeletal muscle, this JNK/SMAD signaling axis is activated by resistance exercise, but not endurance exercise. We conclude that JNK acts as a key mediator of muscle remodeling during exercise via regulation of myostatin/SMAD signaling.
The cJun NH2-terminal kinase (JNK) signaling pathway is required for the development of hepatitis and hepatocellular carcinoma. A role for JNK in liver parenchymal cells has been proposed, but more ...recent studies have implicated non-parenchymal liver cells as the relevant site of JNK signaling. Here, we tested the hypothesis that myeloid cells mediate this function of JNK. We show that mice with myeloid cell-specific JNK deficiency exhibit reduced hepatic inflammation and suppression of both hepatitis and hepatocellular carcinoma. These data identify myeloid cells as a site of pro-inflammatory signaling by JNK that can promote liver pathology. Targeting myeloid cells with a drug that inhibits JNK may therefore provide therapeutic benefit for the treatment of inflammation-related liver disease.
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•JNK in myeloid cells promotes hepatic infiltration by inflammatory cells•Myeloid cell JNK deficiency suppresses development of fulminant hepatitis•JNK in myeloid cells promotes the development of hepatocellular carcinoma
Han et al. examine the role of JNK in inflammation-associated liver disease. Myeloid cell JNK deficiency reduces the expression of inflammatory cytokines and chemokines, reduces hepatic infiltration by inflammatory cells, and suppresses the development of hepatitis and hepatocellular carcinoma. JNK in myeloid cells is therefore a key regulator of hepatic inflammation.
Diet-induced obesity (DIO) predisposes individuals to insulin resistance, and adipose tissue has a major role in the disease. Insulin resistance can be induced in cultured adipocytes by a variety of ...treatments, but what aspects of the in vivo responses are captured by these models remains unknown. We use global RNA sequencing to investigate changes induced by TNF-α, hypoxia, dexamethasone, high insulin, and a combination of TNF-α and hypoxia, comparing the results to the changes in white adipose tissue from DIO mice. We found that different in vitro models capture distinct features of DIO adipose insulin resistance, and a combined treatment of TNF-α and hypoxia is most able to mimic the in vivo changes. Using genome-wide DNase I hypersensitivity followed by sequencing, we further examined the transcriptional regulation of TNF-α-induced insulin resistance, and we found that C/EPBβ is a potential key regulator of adipose insulin resistance.
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•In vitro models capture different aspects of in vivo insulin resistance•Cotreatment with TNF-α and hypoxia is most able to mimic in vivo changes in mice•C/EBPβ is likely to mediate TNF-α-induced adipose insulin resistance•AdipoSight is a web-based tool for exploring adipocyte transcription regulation
Obesity-related insulin resistance is an increasingly common medical problem. Lodish, Fraenkel, and colleagues examine in vitro models for adipose insulin resistance using next-generation sequencing to analyze mRNA levels and chromatin states. They demonstrate that common models capture dramatically different aspects of the in vivo changes, with a combined TNF-α-hypoxia treatment most able to mimic diet-induced obesity. Their approach reveals C/EPBβ as a potential regulator of adipose insulin resistance. AdipoSight, a web portal, provides access to their data and algorithms.
Many medicinal plants have been used traditionally in East Asia for the treatment of gastrointestinal disease and inflammation. The aim of this study was to evaluate the anti-inflammatory activity of ...350 extracts (175 water extracts and 175 ethanol extracts) from 71 single plants, 97 mixtures of two plants, and seven formulations based on traditional medicine, to find herbal formulations to treat inflammatory bowel disease (IBD). In the in vitro screening, nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 levels were determined in LPS-treated RAW264.7 cells and the TNF-α induced monocyte-epithelial cell adhesion assay was used for the evaluation of the anti-inflammatory activity of the compounds. Dextran sulfate sodium (DSS)-induced colitis model and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis model were used to evaluate the therapeutic effect against IBD of the samples selected from the in vitro screening. KM1608, composed of
and Aucklandia lappa, was prepared based on the screening experiments. The oral administration of KM1608 significantly attenuated the severity of colitis symptoms, such as weight loss, diarrhea, and rectal bleeding, in TNBS-induced colitis. In addition, inflammatory mediators, such as myeloperoxidase, TNF-α, and IL-6 levels decreased in the lysate of colon tissues treated with KM1608. Collectively, KM1608 ameliorated colitis through the regulation of inflammatory responses within the colon, which indicated that KM1608 had potential for the treatment of IBD.
The epithelial-mesenchymal transition (EMT) of cancer cells is a crucial process in cancer cell metastasis. An
sp. MC085 extract was found to inhibit A549 human lung cancer cell invasion, and ...caprolactin C (
), a new natural product, α-amino-ε-caprolactam linked to 3-methyl butanoic acid, was purified through bioactivity-guided isolation of the extract. Furthermore, its enantiomeric compound,
-caprolactin C (
), was synthesized. Both
and
inhibited the invasion and γ-irradiation-induced migration of A549 cells. In transforming growth factor-β (TGF-β)-treated A549 cells,
inhibited the phosphorylation of Smad2/3 and suppressed the EMT cell marker proteins (N-cadherin, β-catenin, and vimentin), as well as the related messenger ribonucleic acid expression (N-cadherin, matrix metalloproteinase-9, Snail, and vimentin), while compound
did not suppress Smad2/3 phosphorylation and the expression of EMT cell markers. Therefore, compound
could be a potential candidate for antimetastatic agent development, because it suppresses TGF-β-induced EMT.
Barley is commonly used in many food and health products. We have previously demonstrated the macrophage-stimulating properties of polysaccharides derived from fermented barley. In this study, three ...polysaccharide fractions (BF-I–III) were purified from fermented barley and their monosaccharide composition was analyzed. Their immune-stimulatory activities and intracellular signaling pathways were also studied in RAW264.7 cells. Among the three fractions, BF-I exhibited enhanced macrophage activation properties, such as inducing the production of IL-6, IL-12, and TNF-α. However, BF-II and BF-III showed moderate effects on RAW 264.7 cells. BF-I treatment led to the phosphorylation of MAPKs, NF-κB, and c-Jun (major component of AP-1 transcription factor) and induced the nuclear translocation of p65 in RAW264.7 cells. In addition, experiments with neutralizing antibodies showed that Dectin-1, toll-like receptor (TLR) 4, scavenge receptor (SR), and CD14 were mainly involved in the stimulation of nitric oxide (NO) production by BF-I which was suppressed by the inhibition of JNK phosphorylation. These findings suggest that BF-I, isolated from fermented barley, has an immune potentiation activity on macrophages, where it activates the JNK signaling pathway via several macrophage receptors including dectin-1, TLR4, SR, and CD14.
The pathogenesis of nonalcoholic steatohepatitis (NASH) is unclear, despite epidemiological data implicating FFAs. We studied the pathogenesis of NASH using lipoapoptosis models. Palmitic acid (PA) ...induced classical apoptosis of hepatocytes. PA-induced lipoapoptosis was inhibited by acyl-CoA synthetase inhibitor but not by ceramide synthesis inhibitors, suggesting that conversion products other than ceramide are involved. Phospholipase A₂ (PLA₂) inhibitors blocked PA-induced hepatocyte death, suggesting an important role for PLA₂ and its product lysophosphatidylcholine (LPC). Small interfering RNA for Ca²⁺-independent phospholipase A₂ (iPLA₂) inhibited the lipoapoptosis of hepatocytes. PA increased LPC content, which was reversed by iPLA₂ inhibitors. Pertussis toxin or dominant-negative Gαi mutant inhibited hepatocyte death by PA or LPC acting through G-protein-coupled receptor (GPCR)/Gαi. PA decreased cardiolipin content and induced mitochondrial potential loss and cytochrome c translocation. Oleic acid inhibited PA-induced hepatocyte death by diverting PA to triglyceride and decreasing LPC content, suggesting that FFAs lead to steatosis or lipoapoptosis according to the abundance of saturated/unsaturated FFAs. LPC administration induced hepatitis in vivo. LPC content was increased in the liver specimens from NASH patients. These results demonstrate that LPC is a death effector in the lipoapoptosis of hepatocytes and suggest potential therapeutic values of PLA₂ inhibitors or GPCR/Gαi inhibitors in NASH.
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