Lipids Commons^™

Molecular Mechanisms And Metabolic Consequences Of Glucocorticoid Resistance, Genesee J. Martinez

Theses and Dissertations--Pharmacology and Nutritional Sciences

Glucocorticoids are vital steroid hormones that govern metabolism, stress responses, and immune functions through intricate, tissue-specific mechanisms, both genomic and non-genomic. These hormones bind to the glucocorticoid receptor (GR), which then acts as a transcription factor to modulate gene expression. Chronic elevation of glucocorticoid levels may lead to glucocorticoid resistance, resulting in adiposity, inflammation, and insulin resistance, thereby adversely affecting multiple metabolic tissues. Whether produced endogenously or administered exogenously, excessive, chronic glucocorticoid concentrations impair glucocorticoid signaling. Although there are two primary isoforms of the receptor, GR⍺ and GRβ, only GR⍺ interacts with glucocorticoids.Through the research conducted in this dissertation, we …

Investigation Of Genx Exposure To Pathways Associated With Colorectal Cancer Risk, Emily J. Ferguson

Theses and Dissertations--Toxicology and Cancer Biology

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants widely detected in drinking water and food sources, resulting in chronic human exposure. Among these compounds, hexafluoropropylene oxide dimer acid (HFPO-DA), commonly known as GenX, has been introduced as a short-chain replacement for legacy PFAS such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Although GenX is believed to be a safer alternative, emerging research suggests it can still affect human health.

Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related death in the United States, highlighting the need to better understand environmental …

Elucidating The Role Of Fatty Acid Synthase In Apc-Driven Colorectal Cancer, Courtney O. Kelson

Theses and Dissertations--Toxicology and Cancer Biology

Globally, colorectal cancer (CRC) is the second leading cause of cancer related deaths. Currently, there is a growing incidence rate for individuals aged 20-49 years. Genetic and environmental factors contribute to the risk of this cancer. Early detection of CRC allows for the most effective treatment option in which surgical resection of the primary tumor occurs along with adjuvant chemotherapy. This therapeutic approach contributes to 5-year survival rate of 91%. However, surgical procedures and chemotherapy struggles against metastatic and relapsed CRC resulting in 5-year survival rate of 14%. Inefficacious treatments for relapsed and metastatic diseases emphasizes the need for more …

The Relative Contribution Of Liver And Intestine In Reverse Cholesterol Transport, Rupinder Kaur

Theses and Dissertations--Pharmacy

Despite decades of advances in research, death due to cardiometabolic disease remains the largest contributor to mortality in the US. While present therapies oppose “forward cholesterol transport,” and atherosclerotic plaque progression, they do not remove cholesterol from established atherosclerotic plaques. Reverse cholesterol transport (RCT) is the active process of mobilizing peripheral cholesterol for excretion through the hepatobiliary (transhepatic cholesterol elimination, THCE) or intestinal (transintestinal cholesterol elimination, TICE) pathways. Currently, there are no clinically approved therapeutics that target RCT. Elucidation of the mechanisms that govern RCT and TICE, and the subsequent identification of novel targets is of importance. The present work …

Serum Amyloid A Is Not Incorporated Into Hdl During Hdl Biogenesis, Ailing Ji, Xuebing Wang, Victoria P. Noffsinger, Drew Jennings, Maria C. De Beer, Frederick C. De Beer, Lisa R. Tannock, Nancy R. Webb

Saha Cardiovascular Research Center Faculty Publications

Liver-derived serum amyloid A (SAA) is present in plasma where it is mainly associated with HDL and from which it is cleared more rapidly than are the other major HDL-associated apolipoproteins. Although evidence suggests that lipid-free and HDL-associated forms of SAA have different activities, the pathways by which SAA associates and disassociates with HDL are poorly understood. In this study, we investigated SAA lipidation by hepatocytes and how this lipidation relates to the formation of nascent HDL particles. We also examined hepatocyte-mediated clearance of lipid-free and HDL-associated SAA. We prepared hepatocytes from mice injected with lipopolysaccharide or an SAA-expressing adenoviral …

Apolipoprotein E4 Alters Astrocyte Fatty Acid Metabolism And Lipid Droplet Formation, Brandon C. Farmer, Jude Kluemper, Lance A. Johnson

Physiology Faculty Publications

Lipid droplets (LDs) serve as energy rich reservoirs and have been associated with apolipoprotein E (APOE) and neurodegeneration. The E4 allele of APOE (E4) is the strongest genetic risk factor for the development of late onset Alzheimer’s disease (AD). Since both E4 carriers and individuals with AD exhibit a state of cerebral lipid dyshomeostasis, we hypothesized that APOE may play a role in regulating LD metabolism. We found that astrocytes expressing E4 accumulate significantly more and smaller LDs compared to E3 astrocytes. Accordingly, expression of perilipin-2, an essential LD protein component, was higher in E4 astrocytes. We then …

Autotaxin-Lpa Signaling Contributes To Obesity-Induced Insulin Resistance In Muscle And Impairs Mitochondrial Metabolism, Kenneth D'Souza, Carine Nzirorera, Andrew M. Cowie, Geena P. Varghese, Purvi Trivedi, Thomas O. Eichmann, Dipsikha Biswas, Mohamed Touaibia, Andrew J. Morris, Vassilis Aidinis, Daniel A. Kane, Thomas Pulinilkunnil, Petra C. Kienesberger

Internal Medicine Faculty Publications

Autotaxin (ATX) is an adipokine that generates the bioactive lipid, lysophosphatidic acid (LPA). ATX-LPA signaling has been implicated in diet-induced obesity and systemic insulin resistance. However, it remains unclear whether the ATX-LPA pathway influences insulin function and energy metabolism in target tissues, particularly skeletal muscle, the major site of insulin-stimulated glucose disposal. The objective of this study was to test whether the ATX-LPA pathway impacts tissue insulin signaling and mitochondrial metabolism in skeletal muscle during obesity. Male mice with heterozygous ATX deficiency (ATX^+/−) were protected from obesity, systemic insulin resistance, and cardiomyocyte dysfunction following high-fat high-sucrose (HFHS) feeding. …

Serum Lipidomics Of Bovine Paratuberculosis: Disruption Of Choline-Containing Glycerophospholipids And Sphingolipids, Paul L. Wood, Erdal Erol, Glen F. Hoffsis, Margaret Steinman, Jeroen Debuck

Veterinary Science Faculty Publications

Objectives: Bovine paratuberculosis is a devastating infection with Mycobacterium avium subspecies paratuberculosis that ultimately results in death from malnutrition. While the infection is characterized by a long (2–4 years) subclinical phase with immune activation, ultimately host defense mechanisms fail and the bacteria spread from the small intestine to other organs. Since both the gastrointestinal tract and liver are essential for the biosynthesis of structural glycerophospholipids, we investigated the circulating levels of these lipids in field infections and experimentally infected cattle.

Methods: Serum lipidomics of control and M. avium subspecies paratuberculosis–infected cattle were performed utilizing high-resolution mass spectrometry.

Results: In …

Abcg5 And Abcg8: More Than A Defense Against Xenosterols, Shailendra B. Patel, Gregory A. Graf, Ryan E. Temel

Pharmaceutical Sciences Faculty Publications

The elucidation of the molecular basis of the rare disease, sitosterolemia, has revolutionized our mechanistic understanding of how dietary sterols are excreted and how cholesterol is eliminated from the body. Two proteins, ABCG5 and ABCG8, encoded by the sitosterolemia locus, work as obligate dimers to pump sterols out of hepatocytes and enterocytes. ABCG5/ABCG8 are key in regulating whole-body sterol trafficking, by eliminating sterols via the biliary tree as well as the intestinal tract. Importantly, these transporters keep xenosterols from accumulating in the body. The sitosterolemia locus has been genetically associated with lipid levels and downstream atherosclerotic disease, as well as …

Increased Liver Tumor Formation In Neutral Sphingomyelinase-2-Deficient Mice, Liansheng Zhong, Ji Na Kong, Michael B. Dinkins, Silvia Leanhart, Zhihui Zhu, Stefka D. Spassieva, Haiyan Qin, Hsuan-Pei Lin, Ahmed Elsherbini, Rebecca Wang, Xue Jiang, Mariana N. Nikolova‑Karakashian, Guanghu Wang, Erhard Bieberich

Physiology Faculty Publications

Sphingolipids are key signaling lipids in cancer. Genome-wide studies have identified neutral SMase-2 (nSMase2), an enzyme generating ceramide from SM, as a potential repressor for hepatocellular carcinoma. However, little is known about the sphingolipids regulated by nSMase2 and their roles in liver tumor development. We discovered growth of spontaneous liver tumors in 27.3% (9 of 33) of aged male nSMase2-deficient (fro/fro) mice. Lipidomics analysis showed a marked increase of SM in the tumor. Unexpectedly, tumor tissues presented with more than a 7-fold increase of C₁₆-ceramide, concurrent with upregulation of ceramide synthase 5. The fro/fro liver tumor, …

An Exome-Wide Sequencing Study Of Lipid Response To High-Fat Meal And Fenofibrate In Caucasians From The Goldn Cohort, Xin Geng, Marguerite R. Irvin, Bertha Hidalgo, Stella Aslibekyan, Vinodh Srinivasasainagendra, Ping An, Alexis C. Frazier-Wood, Hemant K. Tiwari, Tushar Dave, Kathleen Ryan, Jose M. Ordovas, Robert J. Straka, Mary F. Feitosa, Paul N. Hopkins, Ingrid Borecki, Michael A. Province, Braxton D. Mitchell, Donna K. Arnett, Degui Zhi

Epidemiology and Environmental Health Faculty Publications

Our understanding of genetic influences on the response of lipids to specific interventions is limited. In this study, we sought to elucidate effects of rare genetic variants on lipid response to a high-fat meal challenge and fenofibrate (FFB) therapy in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) cohort using an exome-wide sequencing-based association study. Our results showed that the rare coding variants in ITGA7, SIPA1L2, and CEP72 are significantly associated with fasting LDL cholesterol response to FFB (P = 1.24E-07), triglyceride postprandial area under the increase (AUI) (P = 2.31E-06), and triglyceride postprandial …

Dynamic Cycling Of T-Snare Acylation Regulates Platelet Exocytosis, Jinchao Zhang, Yunjie Huang, Jing Chen, Haining Zhu, Sidney W. Whiteheart

Molecular and Cellular Biochemistry Faculty Publications

Platelets regulate vascular integrity by secreting a host of molecules that promote hemostasis and its sequelae. Given the importance of platelet exocytosis, it is critical to understand how it is controlled. The t-SNAREs, SNAP-23 and syntaxin-11, lack classical transmembrane domains (TMDs), yet both are associated with platelet membranes and redistributed into cholesterol-dependent lipid rafts when platelets are activated. Using metabolic labeling and hydroxylamine (HA)/HCl treatment, we showed that both contain thioester-linked acyl groups. Mass spectrometry mapping further showed that syntaxin-11 was modified on cysteine 275, 279, 280, 282, 283, and 285, and SNAP-23 was modified on cysteine 79, 80, 83, …

Novel Function Of Ceramide For Regulation Of Mitochondrial Atp Release In Astrocytes, Ji-Na Kong, Zhihui Zhu, Yutaka Itokazu, Guanghu Wang, Michael B. Dinkins, Liansheng Zhong, Hsuan-Pei Lin, Ahmed Elsherbini, Silvia Leanhart, Xue Jiang, Haiyan Qin, Wenbo Zhi, Stefka D. Spassieva, Erhard Bieberich

Physiology Faculty Publications

We reported that amyloid β peptide (Aβ₄₂) activated neutral SMase 2 (nSMase2), thereby increasing the concentration of the sphingolipid ceramide in astrocytes. Here, we show that Aβ₄₂ induced mitochondrial fragmentation in wild-type astrocytes, but not in nSMase2-deficient cells or astrocytes treated with fumonisin B1 (FB1), an inhibitor of ceramide synthases. Unexpectedly, ceramide depletion was concurrent with rapid movements of mitochondria, indicating an unknown function of ceramide for mitochondria. Using immunocytochemistry and super-resolution microscopy, we detected ceramide-enriched and mitochondria-associated membranes (CEMAMs) that were codistributed with microtubules. Interaction of ceramide with tubulin was confirmed by cross-linking to N-[9-(3-pent-4-ynyl-3-H-diazirine-3-yl)-nonanoyl]-D-erythro-sphingosine …

Serum Amyloid A3 Is A High Density Lipoprotein-Associated Acute-Phase Protein, Lisa R. Tannock, Maria C. De Beer, Ailing Ji, Preetha Shridas, Victoria P. Noffsinger, Laura Den Hartigh, Alan Chait, Frederick C. De Beer, Nancy R. Webb

Internal Medicine Faculty Publications

Serum amyloid A (SAA) is a family of acute-phase reactants. Plasma levels of human SAA1/SAA2 (mouse SAA1.1/2.1) can increase ≥ 1,000-fold during an acute-phase response. Mice, but not humans, express a third relatively understudied SAA isoform, SAA3. We investigated whether mouse SAA3 is an HDL-associated acute-phase SAA. Quantitative RT-PCR with isoform-specific primers indicated that SAA3 and SAA1.1/2.1 are induced similarly in livers (∼2,500-fold vs. ∼6,000-fold, respectively) and fat (∼400-fold vs. ∼100-fold, respectively) of lipopolysaccharide (LPS)-injected mice. In situ hybridization demonstrated that all three SAAs are produced by hepatocytes. All three SAA isoforms were detected in plasma of LPS-injected mice, although …

Prevention Of Renal Apob Retention Is Protective Against Diabetic Nephropathy: Role Of Tgf-Β Inhibition, Patricia G. Wilson, Joel C. Thompson, Meghan S. Yoder, Richard Charnigo, Lisa R. Tannock

Internal Medicine Faculty Publications

Animal studies demonstrate that hyperlipidemia and renal lipid accumulation contribute to the pathogenesis of diabetic nephropathy (DN). We previously demonstrated that renal lipoproteins colocalize with biglycan, a renal proteoglycan. The purpose of this study was to determine whether prevention of renal lipid (apoB) accumulation attenuates DN. Biglycan-deficient and biglycan wild-type Ldlr^−/− mice were made diabetic via streptozotocin and fed a high cholesterol diet. As biglycan deficiency is associated with elevated transforming growth factor-β (TGF-β), in some experiments mice were injected with either the TGF-β-neutralizing antibody, 1D11, or with 13C4, an irrelevant control antibody. Biglycan deficiency had no significant effect …

Discovering A Novel Antifungal Target In Downstream Sterol Biosynthesis Using A Squalene Synthase Functional Motif, Kristin Brooke Linscott

Theses and Dissertations--Molecular and Cellular Biochemistry

The sterol biosynthetic pathway is essential for growth of all eukaryotic cells and the main target of antifungal agents. The emergence of resistance to these antifungals in an already ill patient population indicates a need to develop drugs that have a broad spectrum of activity among pathogenic fungi and have minimal patient toxicity. Squalene synthase is the first committed step in the sterol pathway and has been studied intensively for development of antifungal agents. While the overall architecture of this enzyme is identical throughout eukaryotes, it was shown that plant and animal genes cannot complement a squalene synthase knockout mutation …

Epigenetics Of Lipid Phenotypes, Sergi Sayols-Baixeras, Marguerite R. Irvin, Donna K. Arnett, Roberto Elosua, Stella W. Aslibekyan

Epidemiology and Environmental Health Faculty Publications

Dyslipidemia is a well-established risk factor for cardiovascular disease, the main cause of death worldwide. Blood lipid profiles are patterned by both genetic and environmental factors. In recent years, epigenetics has emerged as a paradigm that unifies these influences. In this review, we have summarized the latest evidence implicating epigenetic mechanisms—DNA methylation, histone modification, and regulation by RNAs—in lipid homeostasis. Key findings have emerged in a number of novel epigenetic loci located in biologically plausible genes (eg, CPT1A, ABCG1, SREBF1, and others), as well as microRNA-33a/b. Evidence from animal and cell culture models suggests a complex interplay …

Impact Of Individual Acute Phase Serum Amyloid A Isoforms On Hdl Metabolism In Mice, Myung-Hee Kim, Maria C. De Beer, Joanne M. Wroblewski, Richard J. Charnigo, Ailing Ji, Nancy R. Webb, Frederick C. De Beer, Deneys R. Van Der Westhuyzen

Internal Medicine Faculty Publications

The acute phase (AP) reactant serum amyloid A (SAA), an HDL apolipoprotein, exhibits pro-inflammatory activities, but its physiological function(s) are poorly understood. Functional differences between SAA1.1 and SAA2.1, the two major SAA isoforms, are unclear. Mice deficient in either isoform were used to investigate plasma isoform effects on HDL structure, composition, and apolipoprotein catabolism. Lack of either isoform did not affect the size of HDL, normally enlarged in the AP, and did not significantly change HDL composition. Plasma clearance rates of HDL apolipoproteins were determined using native HDL particles. The fractional clearance rates (FCRs) of apoA-I, apoA-II, and SAA were …

Role Of Flippases In Protein Glycosylation In The Endoplasmic Reticulum, Jeffrey S. Rush

Molecular and Cellular Biochemistry Faculty Publications

Glycosylation is essential to the synthesis, folding, and function of glycoproteins in eukaryotes. Proteins are co- and posttranslationally modified by a variety of glycans in the endoplasmic reticulum (ER); modifications include C- and O-mannosylation, N-glycosylation, and the addition of glycosylphosphatidylinositol membrane anchors. Protein glycosylation in the ER of eukaryotes involves enzymatic steps on both the cytosolic and lumenal surfaces of the ER membrane. The glycans are first assembled as precursor glycolipids, on the cytosolic surface of the ER, which are tethered to the membrane by attachment to a long-chain polyisoprenyl phosphate (dolichol) containing a reduced α-isoprene. The lipid-anchored building blocks …

The Role Of Pxr And Ikkβ Signaling In Cardiometabolic Disease, Robert N. Helsley

Theses and Dissertations--Pharmacology and Nutritional Sciences

Cardiovascular disease (CVD) is the leading cause of death worldwide and is partially attributed to perturbations in lipid metabolism. Xenobiotics, such as pharmaceutical drugs and environmental chemicals, have been associated with increased risk of CVD in multiple large-scale human population studies, but the underlying mechanisms remain poorly defined. We and others have identified several xenobiotics as potent agonists for the pregnane X receptor (PXR), a nuclear receptor that can be activated by numerous drugs as well as environmental and dietary chemicals. However, the role of PXR in mediating the pathophysiological effects of xenobiotic exposure in humans and animals remains elusive. …

Target-Directed Biosynthetic Evolution: Redirecting Plant Evolution To Genomically Optimize A Plant’S Pharmacological Profile, Dustin Paul Brown

Theses and Dissertations--Neuroscience

The dissertation describes a novel method for plant drug discovery based on mutation and selection of plant cells. Despite the industry focus on chemical synthesis, plants remain a source of potent and complex bioactive metabolites. Many of these have evolved as defensive compounds targeted on key proteins in the CNS of herbivorous insects, for example the insect dopamine transporter (DAT). Because of homology with the human DAT protein some of these metabolites have high abuse potential, but others may be valuable in treating drug dependence. This dissertation redirects the evolution of a native Lobelia species toward metabolites with greater activity …

Lipid Extraction From Scenedesmus Sp. Microalgae For Biodiesel Production Using Hot Compressed Hexane, Hee-Yong Shin, Jae-Hun Ryu, Seong-Youl Bae, Czarena L. Crofcheck, Mark Crocker

Center for Applied Energy Research Faculty and Staff Publications

Lipid extraction from Scenedesmus sp. microalgae using hot compressed hexane (HCH) was investigated. Extraction performance was evaluated near the critical point of hexane and was compared with that of hexane extraction performed at room temperature and pressure, and the Bligh and Dyer extraction method. Experimental data showed that HCH significantly improves the lipid yield and rate of lipid extraction compared to the use of hexane at ambient conditions. High yields of biodiesel-convertible lipid fractions were rapidly achieved at the critical point of hexane, at a level comparable to that of the Bligh and Dyer method.

Quantification Of Factors Governing Drug Release Kinetics From Nanoparticles: A Combined Experimental And Mechanistic Modeling Approach, Kyle Daniel Fugit

Theses and Dissertations--Pharmacy

Advancements in nanoparticle drug delivery of anticancer agents require mathematical models capable of predicting in vivo formulation performance from in vitro characterization studies. Such models must identify and incorporate the physicochemical properties of the therapeutic agent and nanoparticle driving in vivo drug release. This work identifies these factors for two nanoparticle formulations of anticancer agents using an approach which develops mechanistic mathematical models in conjunction with experimental studies.

A non-sink ultrafiltration method was developed to monitor liposomal release kinetics of the anticancer agent topotecan. Mathematical modeling allowed simultaneous determination of drug permeability and interfacial binding to the bilayer from release …

A Novel Selective Lipid Uptake Pathway Contributing To Ldl-Induced Macrophage Foam Cell Formation, Jason M. Meyer

Theses and Dissertations--Molecular and Cellular Biochemistry

Atherosclerosis is a disease characterized by cholesterol-rich plaques within the intima of medium and large arteries. Cholesterol deposition is thought to occur by infiltration of low-density lipoprotein (LDL) into lesions followed by uptake into macrophages, generating lipid-loaded “foam cells.” Foam cells can also be generated in vitro by treatment of macrophages with LDL or oxidized LDL (oxLDL). The purpose of the current investigation was to determine the contribution of selective cholesteryl ester (CE) uptake versus whole-particle uptake during LDL-induced foam cell formation in cultured macrophages. Murine bone marrow-derived macrophages (BMMs) exhibited significant cholesterol accumulation when treated with LDL as indicated …