Thirty years ago, glycerolipids captured the attention of biochemical researchers as novel cellular signaling entities. We now recognize that these biomolecules occupy signaling nodes critical to a ...number of physiological and pathological processes. Thus, glycerolipid-metabolizing enzymes present attractive targets for new therapies. A number of fields—ranging from neuroscience and cancer to diabetes and obesity—have elucidated the signaling properties of glycerolipids. The biochemical literature teems with newly emerging small molecule inhibitors capable of manipulating glycerolipid metabolism and signaling. This ever-expanding pool of chemical modulators appears daunting to those interested in exploiting glycerolipid-signaling pathways in their model system of choice. This review distills the current body of literature surrounding glycerolipid metabolism into a more approachable format, facilitating the application of small molecule inhibitors to novel systems. This article is part of a Special Issue entitled Tools to study lipid functions.
•Glycerolipid-signaling pathways play an important role in human physiology and disease.•Glycerolipid-metabolizing enzymes are attractive targets for therapeutic intervention.•Chemical modulators interrupting glycerolipid signaling are essential tools in research.
In mice and humans with cancer, intravenous
C-glucose infusion results in
C labeling of tumor tricarboxylic acid (TCA) cycle intermediates, indicating that pyruvate oxidation in the TCA cycle occurs ...in tumors. The TCA cycle is usually coupled to the electron transport chain (ETC) because NADH generated by the cycle is reoxidized to NAD
by the ETC. However,
C labeling does not directly report ETC activity, and other pathways can oxidize NADH, so the ETC's role in these labeling patterns is unverified. We examined the impact of the ETC complex I inhibitor IACS-010759 on tumor
C labeling. IACS-010759 suppresses TCA cycle labeling from glucose or lactate and increases labeling from glutamine. Cancer cells expressing yeast NADH dehydrogenase-1, which recycles NADH to NAD
independently of complex I, display normalized labeling when complex I is inhibited, indicating that cancer cell ETC activity regulates TCA cycle metabolism and
C labeling from multiple nutrients.
Sphingosine 1-phosphate (S1P) is a phospholipid that binds to a set of G protein-coupled receptors (S1P(1)-S1P(5)) to initiate an array of signaling cascades that affect cell survival, ...differentiation, proliferation, and migration. On a larger physiological scale, the effects of S1P on immune cell trafficking, vascular barrier integrity, angiogenesis, and heart rate have also been observed. An impetus for the characterization of S1P-initiated signaling effects came with the discovery that FTY720 fingolimod; 2-amino-2-(2-4-octylphenylethyl)-1,3-propanediol modulates the immune system by acting as an agonist at S1P(1). In the course of structure-activity relationship studies to better understand the functional chemical space around FTY720, we discovered conformationally constrained FTY720 analogs that behave as S1P receptor type-selective antagonists. Here, we present a pharmacological profile of a lead S1P(1/3) antagonist prodrug, 1-(hydroxymethyl)-3-(3-octylphenyl)cyclobutane (VPC03090). VPC03090 is phosphorylated by sphingosine kinase 2 to form the competitive antagonist species 3-(3-octylphenyl)-1-(phosphonooxymethyl)cyclobutane (VPC03090-P) as observed in guanosine 5'-O-(3-(35)Sthio)triphosphate binding assays, with effects on downstream S1P receptor signaling confirmed by Western blot and calcium mobilization assays. Oral dosing of VPC03090 results in an approximate 1:1 phosphorylated/alcohol species ratio with a half-life of 30 h in mice. Because aberrant S1P signaling has been implicated in carcinogenesis, we applied VPC03090 in an immunocompetent mouse mammary cancer model to assess its antineoplastic potential. Treatment with VPC03090 significantly inhibited the growth of 4T1 primary tumors in mice. This result calls to attention the value of S1P receptor antagonists as not only research tools but also potential therapeutic agents.
Survival among children with high-risk solid tumors remains poor. Reprogrammed metabolism promotes tumor growth and may contain therapeutic liabilities. Tumor metabolism has been assessed in adults ...using intra-operative
C-glucose infusions. Pediatric tumors differ from adult cancers in their low mutational burden and derivation from embryonic tissues. Here we used
C infusions to examine tumor metabolism in children, comparing phenotypes among tumor types and between childhood and adult cancers.
Patients recruited to study NCT03686566 received an intra-operative infusion of U-
Cglucose during tumor resection to evaluate central carbon pathways in the tumor, with concurrent metabolomics to provide a broad overview of metabolism. Differential characteristics were determined using multiple comparison tests and mixed effect analyses.
We studied 23 tumors from 22 patients. All tumors analyzed by U-
Cglucose contained labeling in glycolytic and tricarboxylic acid (TCA) cycle intermediates. Labeling in the TCA cycle indicated activity of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC), with PDH predominating. Neuroblastomas had high lactate labeling relative to other childhood cancers and lung cancer, and were distinguished by abundant tyrosine catabolites consistent with catecholamine synthesis.
Intra-operative U
Cglucose infusions are safe and informative in pediatric cancer. Tumors of various histologies use glycolysis and oxidative metabolism, with subtype-selective differences evident from this small cohort. Expanding this cohort may uncover predictive biomarkers and therapeutic targets from tumor metabolism.
N.C.I grants to P.L. (R21CA220090-01A1) and R.J.D. (R35CA22044901); H.H.M.I. funding to R.J.D.; Children's Clinical Research Advisory Committee funding to K.J.
Targeting metabolic vulnerabilities has been proposed as a therapeutic strategy in renal cell carcinoma (RCC). Here, we analyzed the metabolism of patient-derived xenografts (tumorgrafts) from ...diverse subtypes of RCC. Tumorgrafts from
-mutant clear cell RCC (ccRCC) retained metabolic features of human ccRCC and engaged in oxidative and reductive glutamine metabolism. Genetic silencing of isocitrate dehydrogenase-1 or isocitrate dehydrogenase-2 impaired reductive labeling of tricarboxylic acid (TCA) cycle intermediates in vivo and suppressed growth of tumors generated from tumorgraft-derived cells. Glutaminase inhibition reduced the contribution of glutamine to the TCA cycle and resulted in modest suppression of tumorgraft growth. Infusions with amide-
Nglutamine revealed persistent amidotransferase activity during glutaminase inhibition, and blocking these activities with the amidotransferase inhibitor JHU-083 also reduced tumor growth in both immunocompromised and immunocompetent mice. We conclude that ccRCC tumorgrafts catabolize glutamine via multiple pathways, perhaps explaining why it has been challenging to achieve therapeutic responses in patients by inhibiting glutaminase.
Organophosphorus nerve agents (OPNAs) are toxic compounds that are classified as prohibited Schedule 1 chemical weapons. In the body, OPNAs bind to butyrylcholinesterase (BChE) to form nerve agent ...adducts (OPNA–BChE). OPNA–BChE adducts can provide a reliable, long‐term protein biomarker for assessing human exposure. A major challenge facing OPNA–BChE detection is hydrolysis (aging), which can continue to occur after a clinical specimen has been collected. During aging, the o‐alkyl phosphoester bond hydrolyzes, and the specific identity of the nerve agent is lost. To better identify OPNA exposure events, a high‐throughput method for the detection of five aged OPNA–BChE adducts was developed. This is the first diagnostic panel to allow for the simultaneous quantification of any Chemical Weapons Convention Schedule 1 OPNA by measuring the aged adducts methyl phosphonate, ethyl phosphonate, propyl phosphonate, ethyl phosphoryl, phosphoryl and unadducted BChE. The calibration range for all analytes is 2.00–250. ng/mL, which is consistent with similar methodologies used to detect unaged OPNA–BChE adducts. Each analytical run is 3 min, making the time to first unknown results, including calibration curve and quality controls, less than 1 h. Analysis of commercially purchased individual serum samples demonstrated no potential interferences with detection of aged OPNA–BChE adducts, and quantitative measurements of endogenous levels of BChE were similar to those previously reported in other OPNA–BChE adduct assays.
Cancer cells reorganize their metabolic pathways to fuel demanding rates of proliferation. Oftentimes, these metabolic phenotypes lie downstream of prominent oncogenes. The lipid signaling molecule ...phosphatidic acid (PtdOH), which is produced by the hydrolytic enzyme phospholipase D (PLD), has been identified as a critical regulatory molecule for oncogenic signaling in many cancers. In an effort to identify novel regulatory mechanisms for PtdOH, we screened various cancer cell lines, assessing whether treatment of cancer models with PLD inhibitors altered production of intracellular metabolites. Preliminary findings lead us to focus on how deoxyribonucleoside triphosphates (dNTPs) are altered upon PLD inhibitor treatment in gliomas. Using a combination of proteomics and small molecule intracellular metabolomics, we show herein that PtdOH acutely regulates the production of these pyrimidine metabolites through activation of CAD via mTOR signaling pathways independently of Akt. These changes are responsible for decreases in dNTP production after PLD inhibitor treatment. Our data identify a novel regulatory role for PLD activity in specific cancer types.
We explore changes in sexual risk behaviour over the first year of antiretroviral therapy (ART) among a cohort of patients in Cape Town South Africa initiating treatment in five public facilities in ...2006 and again 1 year later (Time 1 and Time 2). Contemporaneous measures of unprotected sex were also obtained from 2 cross-sectional samples of HIV-positive patients waiting to start ART attending the same facilities. Unprotected sex at last sex among patients on ART decreased significantly from a baseline of 44.7–23.2% one year later, regardless of partner status. After controlling for confounding factors, the observed decrease in unprotected sex among the ART cohort was highly significant in relation to the 2 cross-sectional samples of patients at Time 1 and Time 2 waiting to initiate ART. Findings suggest it is critical to start positive prevention to decrease risky sexual behavior prior to the start of ART within this setting.
Phosphatidic acid (PA) is a lipid second messenger located at the intersection of several lipid metabolism and cell signaling events including membrane trafficking, survival, and proliferation. ...Generation of signaling PA has long been primarily attributed to the activation of phospholipase D (PLD). PLD catalyzes the hydrolysis of phosphatidylcholine into PA. A variety of both receptor-tyrosine kinase and G-protein-coupled receptor stimulations have been shown to lead to PLD activation and PA generation. This study focuses on profiling the PA pool upon P2Y6 receptor signaling manipulation to determine the major PA producing enzymes. Here we show that PLD, although highly active, is not responsible for the majority of stable PA being produced upon UDP stimulation of the P2Y6 receptor and that PA levels are tightly regulated. By following PA flux in the cell we show that PLD is involved in an initial increase in PA upon receptor stimulation; however, when PLD is blocked, the cell compensates by increasing PA production from other sources. We further delineate the P2Y6 signaling pathway showing that phospholipase Cβ3 (PLCβ3), PLCδ1, DGKζ and PLD are all downstream of receptor activation. We also show that DGKζ is a novel negative regulator of PLD activity in this system that occurs through an inhibitory mechanism with PKCα. These results further define the downstream events resulting in PA production in the P2Y6 receptor signaling pathway.
Background: Phosphatidic acid is a key lipid second messenger often generated after receptor stimulation.
Results: After P2Y6 receptor stimulation both PLD and DGK enzymes are responsible for producing PA species.
Conclusion: DGK facilitates a negative regulation of PLD and tightly controls PA levels.
Significance: Further understanding the PA signaling network is critical to developing next generation therapeutics for human diseases.
We sought to integrate a brief computer and counseling support intervention into the routine practices of HIV clinics and evaluate effects on patients' viral loads. The project targeted HIV patients ...in care whose viral loads exceeded 1000 copies/ml at the
time
of recruitment. Three HIV clinics initiated the intervention immediately, and three other HIV clinics delayed onset for 16 months and served as concurrent controls for evaluating outcomes. The intervention components included a brief computer-based intervention (CBI) focused on antiretroviral therapy adherence; health coaching from project counselors for participants whose viral loads did not improve after doing the CBI; and behavioral screening and palm cards with empowering messages available to all patients at intervention clinics regardless of viral load level. The analytic cohort included 982 patients at intervention clinics and 946 patients at control clinics. Viral loads were assessed at 270 days before recruitment, at time of recruitment, and +270 days later. Results indicated that both the control and intervention groups had significant reductions in viral load, ending with approximately the same viral level at +270 days. There was no evidence that the CBI or the targeted health coaching was responsible for the viral reduction in the intervention group. Results may stem partially from statistical regression to the mean in both groups. Also, clinical providers at control and intervention clinics may have taken action (e.g., conversations with patients, referrals to case managers, adherence counselors, mental health, substance use specialists) to help their patients reduce their viral loads. In conclusion, neither a brief computer-based nor targeted health coaching intervention reduced patients' viral loads beyond levels achieved with standard of care services available to patients at well-resourced HIV clinics.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
PDF
