Hypothalamic lipotoxicity and the metabolic syndrome

Ectopic accumulation of lipids in peripheral tissues, such as pancreatic β cells, liver, heart and skeletal muscle, leads to lipotoxicity, a process that contributes substantially to the pathophysiology of insulin resistance, type 2 diabetes, steatotic liver disease and heart failure. Current evidence has demonstrated that hypothalamic sensing of circulating lipids and modulation of hypothalamic endogenous fatty acid and lipid metabolism are two bona fide mechanisms modulating energy homeostasis at the whole body level. Key enzymes, such as AMP-activated protein kinase (AMPK) and fatty acid synthase (FAS), as well as intermediate metabolites, such as malonyl-CoA and long-chain fatty acids-CoA (LCFAs-CoA), play a major role in this neuronal network, integrating peripheral signals with classical neuropeptide-based mechanisms. However, one key question to be addressed is whether impairment of lipid metabolism and accumulation of specific lipid species in the hypothalamus, leading to lipotoxicity, have deleterious effects on hypothalamic neurons. In this review, we summarize what is known about hypothalamic lipid metabolism with focus on the events associated to lipotoxicity, such as endoplasmic reticulum (ER) stress in the hypothalamus. A better understanding of these molecular mechanisms will help to identify new drug targets for the treatment of obesity and metabolic syndrome.     

Limited Intermixing of Synaptic Vesicle Components upon Vesicle Recycling

Synaptic vesicles recycle repeatedly in order to maintain synaptic transmission. We have previously proposed that upon exocytosis the vesicle components persist as clusters, which would be endocytosed as whole units. It has also been proposed that the vesicle components diffuse into the plasma membrane and are then randomly gathered into new vesicles. We found here that while strong stimulation (releasing the entire recycling pool) causes the diffusion of the vesicle marker synaptotagmin out of synaptic boutons, moderate stimulation (releasing ～19% of all vesicles) is followed by no measurable diffusion. In agreement with this observation, synaptotagmin molecules labeled with different fluorescently tagged antibodies did not appear to mix upon vesicle recycling, when investigated by subdiffraction resolution stimulated emission depletion (STED) microscopy. Finally, as protein diffusion from vesicles has been mainly observed using molecules tagged with pH‐sensitive green fluorescent protein (pHluorin), we have also investigated the membrane patterning of several native and pHluorin‐tagged proteins. While the native proteins had a clustered distribution, the GFP‐tagged ones were diffused in the plasma membrane. We conclude that synaptic vesicle components intermix little, at least under moderate stimulation, possibly because of the formation of clusters in the plasma membrane. We suggest that several pHluorin‐tagged vesicle proteins are less well integrated in clusters.     

高功率微波急性辐照对家兔视网膜睫状神经营养因子表达的影响

目的:探讨高功率微波(HPM)急性辐照后家兔视网膜组织睫状神经营养因子(CNTF)表达量在不同时间的变化规律。方法:采用RT-PCR的方法检测90 W/cm2×15 min辐照后0,3,6,12,24和72 h不同时相点家兔视网膜组织CNTF mRNA表达的情况。结果:微波辐照后即刻,家兔视网膜CNTF mRNA表达含量极显著升高(P<0.01),并达最高峰值;3 h后家兔视网膜CNTF mRNA表达含量开始下降;微波辐照后6 h、12 h家兔视网膜CNTF mRNA含量继续下降,但均仍显著高于对照组水平(P<0.05);24 h、72 h时的家兔视网膜CNTF mRNA表达含量与对照组的CNTF mRNA含量相比基本持平。结论:HPM急性辐照能即刻显著性的增强家兔视网膜CNTF mRNA的表达,其表达量与损伤时间之间存在时效关系。HPM辐照引起的CNTF mRNA表达上调可能参与了微波辐照所致的家兔视网膜组织损伤,为利用外源型CNTF治疗微波辐照所致的家兔视网膜组织损伤提供理论依据。     

超高压对灵芝生长及其漆酶合成的影响

研究了超高压处理对灵芝生长及其漆酶合成的影响,试验结果表明:灵芝致死率随处理压力的增大而增加,在150MPa下处理30min获得了一株生物量和漆酶产量都大幅增加的菌株G1502,其最大生物量及酶活分别比出发菌株提高了19.34%和282.67%,发酵时间也缩短了1d。     

Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy

Bioengineered mouse models have become powerful research tools in determining causal relationships between molecular alterations and models of cardiovascular disease. Although molecular biology is necessary in identifying key changes in the signaling pathway, it is not a surrogate for functional significance. While physiology can provide answers to the question of function, combining physiology with biochemical assessment of metabolites in the intact, beating heart allows for a complete picture of cardiac function and energetics. For years, our laboratory has utilized isolated heart perfusions combined with nuclear magnetic resonance (NMR) spectroscopy to accomplish this task. Left ventricular function is assessed by Langendorff-mode isolated heart perfusions while cardiac energetics is measured by performing ³¹P magnetic resonance spectroscopy of the perfused hearts. With these techniques, indices of cardiac function in combination with levels of phosphocreatine and ATP can be measured simultaneously in beating hearts. Furthermore, these parameters can be monitored while physiologic or pathologic stressors are instituted. For example, ischemia/reperfusion or high workload challenge protocols can be adopted. The use of aortic banding or other models of cardiac pathology are apt as well. Regardless of the variants within the protocol, the functional and energetic significance of molecular modifications of transgenic mouse models can be adequately described, leading to new insights into the associated enzymatic and metabolic pathways. Therefore, ³¹P NMR spectroscopy in the isolated perfused heart is a valuable research technique in animal models of cardiovascular disease.     

Polymerization of human hemoglobin using the crosslinker 1,11‐bis(maleimido)triethylene glycol for use as an oxygen carrier

Vasoconstriction and systemic hypertension are the main side effects associated with transfusion of current commercial polymerized hemoglobins (PolyHbs). It is hypothesized that the presence of free tetrameric hemoglobin (Hb) in the PolyHb solution is the root cause of these side effects. Therefore, increasing the size of PolyHbs and reducing the amount of free Hb in solution should dually reduce the extent of vasoconstriction and systemic hypertension. However, all current commercial PolyHb preparations have a small fraction of free Hb in solution. Hence, there is an urgent need to develop novel chemical strategies to synthesize large PolyHb molecules with a higher degree of polymerization without free Hb in solution. In this study, a Hb‐based oxygen carrier was synthesized by polymerizing human Hb using a dimaleimide poly(ethylene glycol) derivative (1,11‐bis(maleimido)triethylene glycol). The resultant PolyHb has a weight‐averaged molecular weight of 1.49 ± 0.62 MDa, O₂ affinity (P₅₀) of 2.75 ± 0.55 mm Hg, and Hill coefficient (n) of 0.97 ± 0.07. Light scattering analysis of the PolyHb dispersion confirmed the absence of free Hb monomers, dimers, and tetramers in solution. This work is significant, as it should enable future engineering of nonvasoactive PolyHbs with potential applications in transfusion medicine. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Strategies for selecting Recombinant CHO cell lines for cGMP manufacturing: Realizing the potential in bioreactors

Manufacture of recombinant proteins from mammalian cell lines requires the use of bioreactor systems at scales of up to 20,000 L. The cost and complexity of such systems can prohibit their extensive use during the process to construct and select the manufacturing cell line. It is therefore common practice to develop a model of the production process in a small scale vessel, such as a shake‐flask, where lower costs, ease of handling, and higher throughput are possible. This model can then be used to select a small number of cell lines for further evaluation in bioreactor culture. Here, we extend our previous work investigating cell line construction strategies to assess how well the behavior of cell lines in such a shake‐flask assessment predicts behavior in the associated bioreactor production process. A panel of 29 GS‐CHO cell lines, all producing the same antibody, were selected to include a mixture of high and low producers from a pool of 175 transfectants. Assessment of this panel in 10 L bioreactor culture revealed wide variation in parameters including growth, productivity, and metabolite utilization. In general, those cell lines which were high producing in the bioreactor cultures had also been higher producing in an earlier shake‐flask assessment. However, some changes in rank position of the evaluated cell lines were seen between the two systems. A potential explanation of these observations is discussed and approaches to improve the predictability of assessments used for cell line selection are considered. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

The role of gut microbiota in the gut-brain axis: current challenges and perspectives

Brain and the gastrointestinal (GI) tract are intimately connected to form a bidirectional neurohumoral communication system. The communication between gut and brain, knows as the gut-brain axis, is so well established that the functional status of gut is always related to the condition of brain. The researches on the gut-brain axis were traditionally focused on the psychological status affecting the function of the GI tract. However, recent evidences showed that gut microbiota communicates with the brain via the gut-brain axis to modulate brain development and behavioral phenotypes. These recent fi ndings on the new role of gut microbiota in the gut-brain axis implicate that gut microbiota could associate with brain functions as well as neurological diseases via the gut-brain axis. To elucidate the role of gut microbiota in the gut-brain axis, precise identification of the composition of microbes constituting gut microbiota is an essential step. However, identifi cation of microbes constituting gut microbiota has been the main technological challenge currently due to massive amount of intestinal microbes and the diffi culties in culture of gut microbes. Current methods for identifi cation of microbes constituting gut microbiota are dependent on omics analysis methods by using advanced high tech equipment. Here, we review the association of gut microbiota with the gut-brain axis, including the pros and cons of the current high throughput methods for identifi cation of microbes constituting gut microbiota to elucidate the role of gut microbiota in the gut-brain axis.     

热激转录因子在植物抗非生物胁迫中的功能研究进展

植物在遭受环境胁迫时会产生一系列应激反应,而热激转录因子可通过介导热激蛋白或其他热诱导基因的转录和表达,来参与调控植物抵抗逆境胁迫过程和其他生命活动。主要介绍了植物热激转录因子的基本蛋白结构域,阐述了3类热激转录因子在抗极端温度（高温、低温）胁迫、干旱胁迫、高盐胁迫、活性氧胁迫中的功能与作用机制,并探讨和展望了植物热激转录因子在植物育种和提高植物抗逆性的研究中的发展与应用前景,以期为深入研究热激转录因子在调控植物抵抗逆境胁迫中的生物学功能与机制提供理论参考。