FFA‐Induced Adipocyte Inflammation and Insulin Resistance: Involvement of ER Stress and IKKβ Pathways

Free‐fatty acids (FFAs) are well‐characterized factor for causing production of inflammatory factors and insulin resistance in adipocytes. Using cultured adipocytes, we demonstrate that FFAs can activate endoplasmic reticulum (ER) stress pathway by examination of ER stress sensor activation and marker gene expression. Chemical chaperone tauroursodeoxycholic acid (TUDCA) can reduce FFA‐induced adipocyte inflammation and improve insulin signaling whereas overexpression of spliced X‐box protein 1 (XBP‐1s) only attenuates FFA‐induced inflammation. PKR‐like eukaryotic initiation factor 2α kinase (PERK) is one of the three major ER stress sensor proteins and deficiency of PERK alleviates FFA‐induced inflammation and insulin resistance. The key downstream target of FFA‐induced ER stress is IκB kinase β (IKKβ), a master kinase for regulating expression of inflammatory genes. Deficiency of PERK attenuates FFA‐induced activation of IKKβ and deficiency of IKKβ alleviates FFA‐induced inflammation and insulin resistance. Consistently, overexpression of IKKβ in 3T3‐L1 CAR adipocytes causes inflammation and insulin resistance. In addition, IKKβ overexpression has profound effect on adipocyte lipid metabolism, including inhibition of lipogenesis and promotion of lipolysis. Furthermore, increased endogenous IKKβ expression and activation is also observed in isolated primary adipocytes from mice injected with lipids or fed on high‐fat diet (HFD) acutely. These results indicate that ER stress pathway is a key mediator for FFA‐induced inflammation and insulin resistance in adipocytes with PERK and IKKβ as the critical signaling components.     

Elevated BCRP/ABCG2 expression confers acquired resistance to gefitinib in wild-type EGFR-expressing cells

Background

The sensitivity of non-small cell lung cancer (NSCLC) patients to EGFR tyrosine kinase inhibitors (TKIs) is strongly associated with activating EGFR mutations. Although not as sensitive as patients harboring these mutations, some patients with wild-type EGFR (wtEGFR) remain responsive to EGFR TKIs, suggesting that the existence of unexplored mechanisms renders most of wtEGFR-expressing cancer cells insensitive.

Methodology/Principal Findings

Here, we show that acquired resistance of wtEGFR-expressing cancer cells to an EGFR TKI, gefitinib, is associated with elevated expression of breast cancer resistance protein (BCRP/ABCG2), which in turn leads to gefitinib efflux from cells. In addition, BCRP/ABCG2 expression correlates with poor response to gefitinib in both cancer cell lines and lung cancer patients with wtEGFR. Co-treatment with BCRP/ABCG2 inhibitors enhanced the anti-tumor activity of gefitinib.

Conclusions/Significance

Thus, BCRP/ABCG2 expression may be a predictor for poor efficacy of gefitinib treatment, and targeting BCRP/ABCG2 may broaden the use of gefitinib in patients with wtEGFR.     

The TNF-alpha-238 polymorphism and cancer risk: a meta-analysis

Background and Objectives

Tumor necrosis factor-α (TNF-α) plays a very important role in the development and progress of cancer. Some TNF-α polymorphisms have been confirmed to increase cancer risks; however, the association between TNF-α-238 polymorphism and cancers remains controversial and ambiguous. The aim of this study is to explore a more precise estimation of its relationship with cancer using meta-analysis.

Methods

Electronic searches of several databases were conducted for all publications on the association between this variant and cancer through March 2011. Odds ratios (OR) with 95% confidence intervals (95% CI) were used to access the strength of this association in the random-effect model.

Results

Thirty four studies with 34,679 cancer patients and 41,186 healthy controls were included. This meta-analysis showed no significant association between TNF-α-238 polymorphism and cancers (AA+GA vs GG: OR = 1.09, 95%CI = 0.88–1.34). In Caucasian and Asian subgroups, OR values (95% CI) were 1.14 (0.91–1.43) and 0.97 (0.58–1.61), respectively. In the subgroups of cancer type, no significant association was detected. The sensitivity analysis further strengthened the validity of these negative associations. No publication bias was observed in this study.

Conclusions

No significant association was found between the TNF-α-238 polymorphism and the risk for cancer.     

Determination of energy and amino acid digestibility in growing pigs fed corn distillers' dried grains with solubles containing different lipid levels

Two experiments were conducted to estimate the digestibility of energy, nitrogen and amino acids (AA) in growing pigs fed diets containing one of five corn distillers' dried grains with solubles (DDGS), including three normal oil DDGS (NO-DDGS) and two low oil DDGS (LO-DDGS) samples. Exp. 1 was conducted to determine the digestible energy (DE) and metabolisable energy (ME) content. Six growing barrows (initial body weight [BW]: 35.1 +/- 2.2 kg) were allotted to a 6 x 6 Latin square design, with six periods and six diets. One diet was a corn soybean meal basal diet and the other five diets were based on corn, soybean meal and 28.8% DDGS. The average DE and ME values for the three NO-DDGS samples were 16.0 and 14.9 MJ/kg dry matter (DM). These values were 9 and 13% greater than the LO-DDGS values of 14.7 and 13.2 MJ/kg DM respectively. Exp. 2 was conducted to determine and compare apparent (AID) and standardised (SID) ileal digestibility for crude protein and AA in the five DDGS samples. Six growing barrows (initial BW, 32.2 +/- 1.9 kg) fitted with a simple T-cannula were allotted to a 6 x 6 Latin square design with six periods and six diets. Five of the diets were based on the five DDGS samples, and the remaining one diet was nitrogen-free diet based on cornstarch and sucrose. Titanium dioxide (0.1%) was used as inert marker. The results of the experiment showed the largest variation among the different samples in AID and SID for lysine (from 41.8 to 65.8% and 53.8 to 73.9% respectively) and threonine (from 54.3 to 73.8% and 65.2 to 79.5% respectively). Also, among the indispensable AA, the SID values for arginine, histidine, threonine and tryptophan observed in LO-DDGS were not different from the values derived from NO-DDGS. In conclusion, LO-DDGS may have decreased energy compared with NO-DDGS because of its lower fat content. However, oil removal during the production of DDGS may not affect amino acid digestibility.     

Moderate traumatic brain injury causes acute dendritic and synaptic degeneration in the hippocampal dentate gyrus

Hippocampal injury-associated learning and memory deficits are frequent hallmarks of brain trauma and are the most enduring and devastating consequences following traumatic brain injury (TBI). Several reports, including our recent paper, showed that TBI brought on by a moderate level of controlled cortical impact (CCI) induces immature newborn neuron death in the hippocampal dentate gyrus. In contrast, the majority of mature neurons are spared. Less research has been focused on these spared neurons, which may also be injured or compromised by TBI. Here we examined the dendrite morphologies, dendritic spines, and synaptic structures using a genetic approach in combination with immunohistochemistry and Golgi staining. We found that although most of the mature granular neurons were spared following TBI at a moderate level of impact, they exhibited dramatic dendritic beading and fragmentation, decreased number of dendritic branches, and a lower density of dendritic spines, particularly the mushroom-shaped mature spines. Further studies showed that the density of synapses in the molecular layer of the hippocampal dentate gyrus was significantly reduced. The electrophysiological activity of neurons was impaired as well. These results indicate that TBI not only induces cell death in immature granular neurons, it also causes significant dendritic and synaptic degeneration in pathohistology. TBI also impairs the function of the spared mature granular neurons in the hippocampal dentate gyrus. These observations point to a potential anatomic substrate to explain, in part, the development of posttraumatic memory deficits. They also indicate that dendritic damage in the hippocampal dentate gyrus may serve as a therapeutic target following TBI.     

Purinergic signaling induces cyclooxygenase-1-dependent prostanoid synthesis in microglia: roles in the outcome of excitotoxic brain injury

Cyclooxygenases (COX) are prostanoid synthesizing enzymes constitutively expressed in the brain that contribute to excitotoxic neuronal cell death. While the neurotoxic role of COX-2 is well established and has been linked to prostaglandin E(2) synthesis, the role of COX-1 is not clearly understood. In a model of N-Methyl-D-aspartic acid (NMDA) induced excitotoxicity in the mouse cerebral cortex we found a distinctive temporal profile of COX-1 and COX-2 activation where COX-1, located in microglia, is responsible for the early phase of prostaglandin E(2) synthesis (10 minutes after NMDA), while both COX-1 and COX-2 contribute to the second phase (3-24 hours after NMDA). Microglial COX-1 is strongly activated by ATP but not excitatory neurotransmitters or the Toll-like receptor 4 ligand bacterial lipopolysaccharide. ATP induced microglial COX-1 dependent prostaglandin E(2) synthesis is dependent on P2X7 receptors, extracellular Ca(2+) and cytoplasmic phospholipase A2. NMDA receptor activation induces ATP release from cultured neurons leading to microglial P2X7 receptor activation and COX-1 dependent prostaglandin E(2) synthesis in mixed microglial-neuronal cultures. Pharmacological inhibition of COX-1 has no effect on the cortical lesion produced by NMDA, but counteracts the neuroprotection exerted by inhibition of COX-2 or observed in mice lacking the prostaglandin E(2) receptor type 1. Similarly, the neuroprotection exerted by the prostaglandin E(2) receptor type 2 agonist butaprost is not observed after COX-1 inhibition. P2X7 receptors contribute to NMDA induced prostaglandin E(2) production in vivo and blockage of P2X7 receptors reverses the neuroprotection offered by COX-2 inhibition. These findings suggest that purinergic signaling in microglia triggered by neuronal ATP modulates excitotoxic cortical lesion by regulating COX-1 dependent prostanoid production and unveil a previously unrecognized protective role of microglial COX-1 in excitotoxic brain injury.     

The combination of RAD001 and NVP-BEZ235 exerts synergistic anticancer activity against non-small cell lung cancer in vitro and in vivo

The phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling axis has emerged as a novel target for cancer therapy. Agents that inhibit PI3K, mTOR or both are currently under development. The mTOR allosteric inhibitor, RAD001, and the PI3K/mTOR dual kinase inhibitor, BEZ235, are examples of these agents. We were interested in developing strategies to enhance mTOR-targeted caner therapy. In this study, we found that BEZ235 alone effectively inhibited the growth of rapamycin-resistant cancer cells. Interestingly, the combination of sub-optimal concentrations of RAD001 and BEZ235 exerted synergistic inhibition of the growth of human lung cancer cells along with induction of apoptosis and G1 arrest. Furthermore, the combination was also more effective than either agent alone in inhibiting the growth of lung cancer xenografts in mice. The combination showed enhanced effects on inhibiting mTOR signaling and reducing the expression of c-Myc and cyclin D1. Taken together, our results suggest that the combination of RAD001 and BEZ235 is a novel strategy for cancer therapy.     

Shal/K(v)4 channels are required for maintaining excitability during repetitive firing and normal locomotion in Drosophila

Background

Rhythmic behaviors, such as walking and breathing, involve the coordinated activity of central pattern generators in the CNS, sensory feedback from the PNS, to motoneuron output to muscles. Unraveling the intrinsic electrical properties of these cellular components is essential to understanding this coordinated activity. Here, we examine the significance of the transient A-type K⁺ current (I_A), encoded by the highly conserved Shal/K_v4 gene, in neuronal firing patterns and repetitive behaviors. While I_A is present in nearly all neurons across species, elimination of I_A has been complicated in mammals because of multiple genes underlying I_A, and/or electrical remodeling that occurs in response to affecting one gene.

Methodology/Principal Findings

In Drosophila, the single Shal/K_v4 gene encodes the predominant I_A current in many neuronal cell bodies. Using a transgenically expressed dominant-negative subunit (DNK_v4), we show that I_A is completely eliminated from cell bodies, with no effect on other currents. Most notably, DNK_v4 neurons display multiple defects during prolonged stimuli. DNK_v4 neurons display shortened latency to firing, a lower threshold for repetitive firing, and a progressive decrement in AP amplitude to an adapted state. We record from identified motoneurons and show that Shal/K_v4 channels are similarly required for maintaining excitability during repetitive firing. We then examine larval crawling, and adult climbing and grooming, all behaviors that rely on repetitive firing. We show that all are defective in the absence of Shal/K_v4 function. Further, knock-out of Shal/K_v4 function specifically in motoneurons significantly affects the locomotion behaviors tested.

Conclusions/Significance

Based on our results, Shal/K_v4 channels regulate the initiation of firing, enable neurons to continuously fire throughout a prolonged stimulus, and also influence firing frequency. This study shows that Shal/K_v4 channels play a key role in repetitively firing neurons during prolonged input/output, and suggests that their function and regulation are important for rhythmic behaviors.     

PAX6 haplotypes are associated with high myopia in Han chinese

Background

The paired box 6 (PAX6) gene is considered as a master gene for eye development. Linkage of myopia to the PAX6 region on chromosome 11p13 was shown in several studies, but the results for association between myopia and PAX6 were inconsistent so far.

Methodology/Principal Findings

We genotyped 16 single nucleotide polymorphisms (SNPs) in the PAX6 gene and its regulatory regions in an initial study for 300 high myopia cases and 300 controls (Group 1), and successfully replicated the positive results with another independent group of 299 high myopia cases and 299 controls (Group 2). Five SNPs were genotyped in the replication study. The spherical equivalent of subjects with high myopia was ≤−8.0 dioptres. The PLINK package was used for genetic data analysis. No association was found between each of the SNPs and high myopia. However, exhaustive sliding-window haplotype analysis highlighted an important role for rs12421026 because haplotypes containing this SNP were found to be associated with high myopia. The most significant results were given by the 4-SNP haplotype window consisting of rs2071754, rs3026393, rs1506 and rs12421026 (P = 3.54×10⁻¹⁰, 4.06×10⁻¹¹ and 1.56×10⁻¹⁸ for Group 1, Group 2 and Combined Group, respectively) and the 3-SNP haplotype window composed of rs3026393, rs1506 and rs12421026 (P = 5.48×10⁻¹⁰, 7.93×10⁻¹² and 6.28×10⁻²³ for the three respective groups). The results remained significant after correction for multiple comparisons by permutations. The associated haplotyes found in a previous study were also successfully replicated in this study.

Conclusions/Significance

PAX6 haplotypes are associated with susceptibility to the development of high myopia in Chinese. The PAX6 locus plays a role in high myopia.