Browsing by Subject "Lipids"

Now showing 1 - 10 of 10
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    Adrenergic antagonists disrupt lipid and cholesterol homeostasis resulting in canine hemangiosarcoma cell death
    (2019-11) Korpela, Derek
    The beta-adrenergic receptor (-AR) antagonist, propranolol, has been identified as an effective adjunct therapy for angiosarcoma patients. Why angiosarcomas are susceptible to propranolol remains unknown. The objectives of this dissertation were to characterize the mechanisms behind the susceptibility of these tumors to the lethal effect of propranolol and to identify other drugs classed as AR antagonists that could further improve patient outcomes. In addition, translation of these findings could be used to treat a virtually indistinguishable tumor in dogs known as canine hemangiosarcoma. Using a panel of hemangiosarcoma cell lines, we found that propranolol reduced tumor cell viability through an AR-independent mechanism. Further investigation showed that propranolol inhibited endocytosis, limiting the uptake and processing of extracellular lipids. To restore lipid homeostasis, hemangiosarcoma cells rapidly increased the activation of metabolically costly cholesterol and lipid synthesis pathways, leading to ER stress, reduced mitochondrial activity, and cell death. Screening assays identified the mixed-acting 1-, -AR antagonist, carvedilol, as a more effective inhibitor of endocytosis, lipid homeostasis, and mitochondrial metabolism. We conclude that propranolol and carvedilol disrupt lipid homeostasis and tumor cell metabolism to kill hemangiosarcoma cells. Repurposing propranolol or its AR-inactive R-(+) enantiomer may provide a readily translatable and clinically safe strategy for the treatment of canine hemangiosarcoma. Related drugs, such as carvedilol, may further improve outcomes for angiosarcoma patients with less side effects.
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    ApoB and ApoA1: A new way to look at cholesterol!
    (2012-04-10) Lane, Michael
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    The Effect of α-Synuclein on Lipid Membrane Properties Characterized by Molecular Dynamics and Atomic Force Microscopy
    (2018-08) Brummel, Benjamin
    The protein α-synuclein (αSyn), primarily recognized for its link to neurodegenerative disorders, has multiple reported functions. One well-established role of αSyn is its ability to bind and remodel lipid membranes. This ability has been characterized in synthetic lipid bilayers and has been observed both in cellular and in vivo models. The native environment of αSyn—the presynaptic terminal of neurons—contains mitochondria and synaptic vesicles, which have unique membranes that differ from previously studied models. The goal of this dissertation was to characterize how lipids enriched in synaptic vesicles and mitochondria affect how αSyn changes membrane properties. First, molecular dynamics (MD) simulations of synaptic vesicle-mimic bilayers showed how lipids with polyunsaturated fatty acids modify membrane properties and interact with αSyn. Next, tubulation experiments were combined with MD simulations to explore how αSyn remodels bilayers containing cardiolipin and phosphatidylethanolamine, two lipids enriched in mitochondria. Finally, methods were developed to characterize lipid vesicle mechanical properties using pulsed force mode (PFM) atomic force microscopy (AFM). This work provides insight into the specifics of how αSyn affects the properties of synaptic vesicle and mitochondrial membranes and demonstrates how PFM-AFM can identify the mechanical properties of lipid vesicles.
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    Effects of green tea catechin extract on serum lipids in postmenopausal women: a randomized, placebo-controlled clinical trial
    (2015-05) Rose, April Lynn
    bold>ABSTRACT Objective: Test the efficacy of a green tea catechin extract (GTE) to improve lipid profile in postmenopausal women. Methods: 886 women were enrolled and randomized to consume either 1200 mg of GTE (800 mg EGCG) or placebo, daily. Fasting serum samples were drawn for lipid panel at baseline, midpoint (month 6), and endpoint (month 12) of study for ananlysis. Results: After one year on treatment, total cholesterol (-4.6 mg/dL, P<.0001), LDL-C (-5.0 mg/dL, P<.0001), and non-HDL cholesterol (-4.4 mg/dL, P>.0001) were significantly reduced in the GTE group. The largest reductions in TC, LDL-C, and non-HDLC occurred in participants with baseline total cholesterol >200 mg/dL. HDL-C decreased slightly in the GTE group, both after 6 months on treatment (P=.0016), and overall (P=.0038). Conclusion: Daily supplementation of GTE at 1200 mg (800 mg EGCG) for one year significantly reduced levels of TC, LDL-C, and non-HDLC in a population of postmenopausal women.
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    Fatty Acid Binding Protein 4 Alters Obesity Associated Cancer Metabolism via Lipid Desaturation and Redox Signaling
    (2019-05) Wirth, Keith
    Background: An association of obesity with cancer incidence and worsened clinical outcomes has been established. Circulating and local levels of fatty acid binding protein 4 (FABP4), a lipid chaperone and adipokine, have been correlated with degree of obesity and metabolic dysfunction, and more recently with breast and pancreas cancer prognosis. FABP4 transcriptional regulation has been linked to cellular redox status, with nuclear factor (erythroid-derived 2)-like 2 (Nrf2) being an upstream regulator of this balance. We hypothesized FABP4 modifies fatty acid saturation indices in cancer, driving an altered redox status, and ultimately inducing tumor proliferation. Methods: Panc1 pancreatic adenocarcinoma and MCF7 breast cancer cells were treated with recombinant FABP4, R126Q (FABP4 point mutant), and HTS01037 (FABP4 inhibitor.) Cell growth and proliferation was assessed. Targeted lipidomic analysis was performed in the same conditions. Whole cell reactive oxygen species (ROS) was quantified via Amplex Red assay. Nrf2 activity was quantified via antioxidant response element luciferase assay, and cell proliferation with chemical inhibitor (brusatol) was assessed. Untargeted gene expression profiles after FABP4 or HTS treatment were studied via RNA sequencing. C57BL/6J FABP4 knockout (AKO) and littermate wild type (WT) mice were injected with Pan02 and E0771 cells, murine pancreas and breast cancer cell lines. Tumor volume and progression was evaluated. Results: Panc1 and MCF7 cells treated with recombinant FABP4 demonstrated increased proliferation relative to control and point mutant protein treatment. This increase was abolished with HTS treatment. Unsaturated/saturated fatty acid ratio was decreased with FABP4 treatment and increased with HTS treatment. ROS levels were decreased and Nrf2 activity was concurrently increased with exposure to exogenous FABP4. Nrf2 gene expression profile was upregulated with FABP4 treatment, independent of ER stress. Tumor progression was significantly decreased in AKO mice. Conclusions: FABP4 induces a shift in the fatty acid saturation index of tumor cells, activating Nrf2 expression and decreasing intracellular ROS, independent of ER stress, allowing for aggressive tumor proliferation.
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    Protein Effects on Lipid Domain Formation in a Model Membrane
    (2014) Yusuf, Urji; Heikal, Ahmed A.
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    Statins: How risky are they?
    (2012-07-23) Wu, Angela
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    The thermodynamic basis for the binding of lipids to annexin a5
    (2009-12) Knutson, Kristofer James
    Protein-membrane interactions are a vital mechanism of propagating signals both across the membrane and between cells. To control the magnitude and specificity of this type of cell signaling at the membrane, clustering of similar lipids and proteins has been observed in the cell via the formation of lipid microdomains. To address the thermodynamic basis of lipid induced signal propagation, we investigated how lipid microdomains form in response to annexin a5 binding to model membranes using Isothermal Titration Calorimetry (ITC). Annexins are known to bind to negatively charged (e.g., phosphatidylserine [PS]) membranes in a Ca2+-dependent manner. Based on Differential Scanning Calorimetry (DSC) results, we suggest that annexin functions to order lipid acyl chains upon binding and that the ordering of phospholipids can lead to the formation of microdomains. Using ITC, we have analyzed the membrane binding affinity of annexin for both gel and fluid state mixtures. Binding analysis of these isotherms shows that annexin binds fluid state mixtures with a significantly lower Kd than gel state (acyl chain ordered) lipids, which would be consistent with the hypothesis that binding of annexin a5 orders the acyl chains of the phospholipids. In addition, because the binding is entropically dominated but exhibits greater affinity for fluid compared to gel state lipids, we suggest that annexin binding is driven by the release of water molecules and ions as fluid lipids have more waters of hydration. Interestingly, the enthalpy associated with the binding process for both gel and fluid state lipid mixtures is small, indicative of a weak enthalpic association and suggestive of entropically mediated binding. We also present the binding of Eu3+ by a lanthanide binding complex (Tetra(N-(tert-butyl)-acetamide)-1,13-diamino-3,6,9-trioxadecane).
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    Validation of the MBT-CBT paleotemperature proxy:Effects of environmental and seasonal variability in soils and lacustrine sediments.
    (2010-11) Bernhardt, Beth A.
    Branched glycerol dialkyl glycerol tetraethers (GDGTs) are bacterial derived membrane lipids found ubiquitously in soils and lacustrine sediments (Weijers et al. 2006b, Blaga et al. 2009). The degree of methylation and cyclization of these lipids have been shown to be dependent on the temperature and pH of the growth environment (Weijers et al. 2007a). These relationships are the basis of the MBT-CBT proxy, which has been used to reconstruct paleotemperature from marine and lacustrine sediment archives (Weijers et al. 2007b, Blaga et al. 2010). Here, we aim to test the validity of the MBT proxy in terrestrial soils and lake sediments to determine whether branched GDGT distributions do refl ect annual mean air temperature (MAT) of the watershed, as suggested by studies, and how other environmental factors, such as seasonality of growth and sub-environments within a watershed, might infl uence the preserved MBT-CBT temperature signal. GDGT-derived annual MAT was compared with instrumental temperature measurements at three sites in the continental United States. Watershed soils were collected monthly for one year under three different types of vegetative cover in Minnesota and Ohio. In Florida, soils were collected twice from an open fi eld environment. Sediment cores were collected from corresponding lakes in each of the three states. We observed no signifi cant differences in soil proxy-derived annual MAT or soil GDGT concentration with seasonal changes in temperature at any of the three sites. Concentrations of GDGTs in the soil were found to have a slight positive correlation with organic carbon content. The effects of vegetative cover on proxy estimates of annual MAT were minimal. Only under deciduous vegetation in Minnesota and Ohio, did proxy-derived annual MAT differ signifi cantly from instrumental measurements. Soil GDGT concentration was unaffected by vegetation type in Minnesota, and in Ohio, pine soils had consistently higher concentrations, usually by an order of magnitude, than other vegetation types. The CBT proxy was found to be an accurate estimate of soil pH in some sub-environments, but in Minnesota and Ohio deciduous soils and Ohio open fi eld soils, CBT-pH differed signifi cantly from measured values. In the sediments of all three lakes studied, the MBT-CBT proxy provided a good estimate of measured annual MAT within the error of the proxy. Proxy-derived temperatures from the surface sediments of all lakes studied were cooler than corresponding instrumental measurements. These cooler surface temperatures could be attributed to in-situ production of branched GDGTs, but surface sediment MBT-MAT only differs signifi cantly from instrumental measurements in Bath Pond, Ohio.