Regulating effect of β-ketoacyl synthase domain of fatty acid synthase on fatty acyl chain length in de novo fatty acid synthesis

Fatty acid synthase (FAS) is a multifunctional homodimeric protein, and is the key enzyme required for the anabolic conversion of dietary carbohydrates to fatty acids. FAS synthesizes long-chain fatty acids from three substrates: acetyl-CoA as a primer, malonyl-CoA as a 2 carbon donor, and NADPH for reduction. The entire reaction is composed of numerous sequential steps, each catalyzed by a specific functional domain of the enzyme. FAS comprises seven different functional domains, among which the β-ketoacyl synthase (KS) domain carries out the key condensation reaction to elongate the length of fatty acid chain. Acyl tail length controlled fatty acid synthesis in eukaryotes is a classic example of how a chain building multienzyme works. Different hypotheses have been put forward to explain how those sub-units of FAS are orchestrated to produce fatty acids with proper molecular weight. In the present study, molecular dynamics simulation based binding free energy calculation and access tunnels analysis showed that the C16 acyl tail fatty acid, the major product of FAS, fits to the active site on KS domain better than any other substrates. These simulations supported a new hypothesis about the mechanism of fatty acid production ratio: the geometric shape of active site on KS domain might play a determinate role

α-Mangostin Induces Apoptosis and Suppresses Differentiation of 3T3-L1 Cells via Inhibiting Fatty Acid Synthase

α-Mangostin, isolated from the hulls of Garcinia mangostana L., was found to have in vitro cytotoxicity against 3T3-L1 cells as well as inhibiting fatty acid synthase (FAS, EC 2.3.1.85). Our studies showed that the cytotoxicity of α-mangostin with IC50 value of 20 µM was incomplicated in apoptotic events including increase of cell membrane permeability, nuclear chromatin condensation and mitochondrial membrane potential (ΔΨm) loss. This cytotoxicity was accompanied by the reduction of FAS activity in cells and could be rescued by 50 µM or 100 µM exogenous palmitic acids, which suggested that the apoptosis of 3T3-L1 preadipocytes induced by α-mangostin was via inhibition of FAS. Futhermore, α-mangostin could suppress intracellular lipid accumulation in the differentiating adipocytes and stimulated lipolysis in mature adipocytes, which was also related to its inhibition of FAS. In addition, 3T3-L1 preadipocytes were more susceptible to the cytotoxic effect of α-mangostin than mature adipocytes. Further studies showed that α-mangostin inhibited FAS probably by stronger action on the ketoacyl synthase domain and weaker action on the acetyl/malonyl transferase domain. These findings suggested that α-mangostin might be useful for preventing or treating obesity

Cortex-restricted deletion of Foxp1 impairs barrel formation and induces aberrant tactile responses in a mouse model of autism

Abstract Background Many children and young people with autism spectrum disorder (ASD) display touch defensiveness or avoidance (hypersensitivity), or engage in sensory seeking by touching people or objects (hyposensitivity). Abnormal sensory responses have also been noticed in mice lacking ASD-associated genes. Tactile sensory information is normally processed by the somatosensory system that travels along the thalamus to the primary somatosensory cortex. The neurobiology behind tactile sensory abnormalities, however, is not fully understood. Methods We employed cortex-specific Foxp1 knockout (Foxp1-cKO) mice as a model of autism in this study. Tactile sensory deficits were measured by the adhesive removal test. The mice’s behavior and neural activity were further evaluated by the whisker nuisance test and c-Fos immunofluorescence, respectively. We also studied the dendritic spines and barrel formation in the primary somatosensory cortex by Golgi staining and immunofluorescence. Results Foxp1-cKO mice had a deferred response to the tactile environment. However, the mice exhibited avoidance behavior and hyper-reaction following repeated whisker stimulation, similar to a fight-or-flight response. In contrast to the wild-type, c-Fos was activated in the basolateral amygdala but not in layer IV of the primary somatosensory cortex of the cKO mice. Moreover, Foxp1 deficiency in cortical neurons altered the dendrite development, reduced the number of dendritic spines, and disrupted barrel formation in the somatosensory cortex, suggesting impaired somatosensory processing may underlie the aberrant tactile responses. Limitations It is still unclear how the defective thalamocortical connection gives rise to the hyper-reactive response. Future experiments with electrophysiological recording are needed to analyze the role of thalamo-cortical-amygdala circuits in the disinhibiting amygdala and enhanced fearful responses in the mouse model of autism. Conclusions Foxp1-cKO mice have tactile sensory deficits while exhibit hyper-reactivity, which may represent fearful and emotional responses controlled by the amygdala. This study presents anatomical evidence for reduced thalamocortical connectivity in a genetic mouse model of ASD and demonstrates that the cerebral cortex can be the origin of atypical sensory behaviors

Compressive Mechanical Properties and Shock-Induced Reaction Behavior of Zr/PTFE and Ti/PTFE Reactive Materials

Existing research on PTFE-based reactive materials (RMs) mostly focuses on Al/PTFE RMs. To explore further possibilities of formulation, the reactive metal components in the RMs can be replaced. In this paper, Zr/PTFE and Ti/PTFE RMs were prepared by cold isostatic pressing and vacuum sintering. The static and dynamic compressive mechanical properties of Zr/PTFE and Ti/PTFE RMs were investigated at different strain rates. The results show that the introduction of zirconium powder and titanium powder can increase the strength of the material under dynamic loading. Meanwhile, a modified J-C model considering strain and strain rate coupling was proposed. The parameters of the modified J-C model of Zr/PTFE and Ti/PTFE RMs were determined, which can describe and predict plastic flow stress. To characterize the impact-induced reaction behavior of Zr/PTFE and Ti/PTFE RMs, a quasi-sealed test chamber was used to measure the over-pressure induced by the exothermic reaction. The energy release characteristics of both materials were more intense under the higher impact

Wide range tuning of the size and emission color of CH3NH3PbBr3 quantum dots by surface ligands

Organic-inorganic halide perovskite CH3NH3PbX3 (X= I, Br, Cl) quantum dots (QDs) possess the characters of easy solution-process, high luminescence yield, and unique size-dependent optical properties. In this work, we have improved the nonaqueous emulsion method to synthesize halide perovskite CH3NH3PbBr3 QDs with tunable sizes. Their sizes have been tailored from 5.29 to 2.81 nm in diameter simply by varying the additive amount of surfactant, n-octylamine from 5 to 120 μL. Correspondingly, the photoluminescence (PL) peaks shift markedly from 520 nm to very deep blue, 436 nm due to quantum confinement effect. The PL quantum yields exceed 90% except for the smallest QDs. These high-quality QDs have potential to build high-performance optoelectronic devices

The effect of exogenous palmitic acid on 3T3-L1 preadipocytes.

<p>(A) 3T3-L1 preadipocytes were treated with α-mangostin and palmitic acid at various concentrations (α-mangostin: 0, 6, 12, 18, 30 µM; palmitic acid: 0, 25, 50, 100 µM) for 24 h. Cell viability was determined by MTT colorimetric assay. Assays were performed on eight replicates for each treatment. Results are expressed as percentages of cell viability as compared with untreated control (means ± S.D., n = 8). The experiment was repeated in twice. (B) The 3T3-L1 preadipocytes were treated with α-mangostin and palmitic acid at various concentrations (α-mangostin: 0, 30 µM; palmitic acid: 0, 25, 50, 100 µM) for 24 h. And then the amount of intracellular fatty acid was determined by Fatty Acid Assay Kit. Data are expressed as means ± S.D. (<i>n</i> = 3). * <i>p</i><0.05 different from respective control; ** <i>p</i><0.01 significantly different from respective control.</p

α-mangostin-induced 3T3-L1 preadipocytes apopotosis.

<p>3T3-L1 preadipocytes were treated with α-mangostin at the indicated concentrations for 24 h. (A) Effect of α-mangostin on cell membrane permeability: original magnification, ×40; exposure times: 20s; (B) Effect of α-mangostin on nuclear chromatin morphology with Hoechst 33258 staining: original magnification, ×200; exposure times: 100s. (C) Effect of α-mangostin on mitochondria membrane potential (ΔΨm) with JC-1 staining: original magnification, ×40; exposure times: 100 s. B. field, bright field; H.33258, Hoechst 33258; JC-1, 5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazolcarbocyanine iodide. The experiments were performed on four replicates for each treatment. Representative images are shown.</p

Effect of α-mangostin on cell viability of 3T3-L1 cells in different stages of adipocyte differentiation.

<p>3T3-L1 cells were exposed to various concentrations of α-mangostin at various time points (d₂, d₄ or d₈) for 24 h, then the cell viability were measured by MTT assay. Assays were performed on four replicates for each treatment. Results are expressed as percentages of cell viability as compared with each untreated control (means ± S.D., <i>n</i> = 4). The experiment was repeated in triplicate. Early stage: d₀-d₂; Middle stage: d₂-d₄; Late stage: d₄-d₈.</p

Inhibitory effect of α-mangostin on intracellular lipid accumulation.

<p>The intracellular lipid content was measured by <i>Oil Red O staining</i> as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033376#s4" target="_blank">Materials and Methods</a>. (A) Cells were photographed at 40× magnification. The experiment was performed on three replicates for each treatment. Representative images are shown. (B) Quantitative analysis of lipid accumulation. Each value is expressed as means ± SD (<i>n</i> = 3). * <i>p</i><0.05 different from control (0 µM); ** <i>p</i><0.01 significantly different from control (0 µM).</p