Browsing by Author "Conteh, Abass M."

Now showing 1 - 10 of 14
  • Thumbnail Image
    Item
    Aberrant gene expression induced by a high fat diet is linked to H3K9 acetylation in the promoter-proximal region
    (Elsevier, 2021-03) Morral, Núria; Liu, Sheng; Conteh, Abass M.; Chu, Xiaona; Wang, Yue; Dong, X. Charlie; Liu, Yunlong; Linnemann, Amelia K.; Wan, Jun; Medical and Molecular Genetics, School of Medicine
    Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, with an estimated global prevalence of 1 in 4 individuals. Aberrant transcriptional control of gene expression is central to the pathophysiology of metabolic diseases. However, the molecular mechanisms leading to gene dysregulation are not well understood. Histone modifications play important roles in the control of transcription. Acetylation of histone 3 at lysine 9 (H3K9ac) is associated with transcriptional activity and is implicated in transcript elongation by controlling RNA polymerase II (RNAPII) pause-release. Hence, changes in this histone modification may shed information on novel pathways linking transcription control and metabolic dysfunction. Here, we carried out genome-wide analysis of H3K9ac in the liver of mice fed a control or a high-fat diet (an animal model of NAFLD), and asked whether this histone mark associates with changes in gene expression. We found that over 70% of RNAPII peaks in promoter-proximal regions overlapped with H3K9ac, consistent with a role of H3K9ac in the regulation of transcription. When comparing high-fat with control diet, approximately 17% of the differentially expressed genes were associated with changes in H3K9ac in their promoters, showing a strong correlation between changes in H3K9ac signal and gene expression. Overall, our data indicate that in response to a high-fat diet, dysregulated gene expression of a subset of genes may be attributable to changes in transcription elongation driven by H3K9ac. Our results point at an added mechanism of gene regulation that may be important in the development of metabolic diseases.
  • Thumbnail Image
    Item
    CARDIOVASCULAR AND HEMODYNAMIC EFFECTS OF GLUCAGON-LIKE PEPTIDE-1
    (Springer US, 2014-09) Goodwill, Adam G.; Mather, Kieren J.; Conteh, Abass M.; Sassoon, Daniel; Noblet, Jillian N.; Tune, Johnathan D.; Department of Cellular & Integrative Physiology, School of Medicine
    Glucagon-like peptide-1 (GLP-1) is an incretin hormone that has been shown to have hemodynamic and cardioprotective capacity in addition to its better characterized glucoregulatory actions. Because of this, emerging research has focused on the ability of GLP-1 based therapies to drive myocardial substrate selection, enhance cardiac performance and regulate heart rate, blood pressure and vascular tone. These studies have produced consistent and reproducible results amongst numerous laboratories. However, there are obvious disparities in findings obtained in small animal models versus those of higher mammals. This species dependent discrepancy calls to question, the translational value of individual findings. Moreover, few studies of GLP-1 mediated cardiovascular action have been performed in the presence of a pre-existing comorbidities (e.g. obesity/diabetes) which limits interpretation of the effectiveness of incretin-based therapies in the setting of disease. This review addresses cardiovascular and hemodynamic potential of GLP-1 based therapies with attention to species specific effects as well as the interaction between therapies and disease.
  • Thumbnail Image
    Item
    Combined targeting of TGF-beta, EGFR and HER2 suppresses lymphangiogenesis and metastasis in a pancreatic cancer model
    (Elsevier, 2016-08-28) Gore, Jesse; Imasuen-Williams, Imade E.; Conteh, Abass M.; Craven, Kelly E.; Cheng, Monica; Korc, Murray; Medicine, School of Medicine
    Pancreatic ductal adenocarcinomas (PDAC) are aggressive with frequent lymphatic spread. By analysis of data from The Cancer Genome Atlas, we determined that ∼35% of PDACs have a pro-angiogenic gene signature. We now show that the same PDACs exhibit increased expression of lymphangiogenic genes and lymphatic endothelial cell (LEC) markers, and that LEC abundance in human PDACs correlates with endothelial cell microvessel density. Lymphangiogenic genes and LECs are also elevated in murine PDACs arising in the KRC (mutated Kras; deleted RB) and KIC (mutated Kras; deleted INK4a) genetic models. Moreover, pancreatic cancer cells (PCCs) derived from KRC tumors express and secrete high levels of lymphangiogenic factors, including the EGF receptor ligand, amphiregulin. Importantly, TGF-β1 increases lymphangiogenic genes and amphiregulin expression in KRC PCCs but not in murine PCCs that lack SMAD4, and combinatorial targeting of the TGF-β type I receptor (TβRI) with LY2157299 and EGFR/HER2 with lapatanib suppresses tumor growth and metastasis in a syngeneic orthotopic model, and attenuates tumor lymphangiogenesis and angiogenesis while reducing lymphangiogenic genes and amphiregulin and enhancing apoptosis. Therefore, this combination could be beneficial in PDACs with lymphangiogenic or angiogenic gene signatures.
  • Thumbnail Image
    Item
    Glucagon-Like Peptide 1 Receptor Activation Augments Cardiac Output and Improves Cardiac Efficiency in Obese Swine After Myocardial Infarction
    (American Diabetes Association, 2017-08) Sassoon, Daniel J.; Tune, Johnathan D.; Mather, Kieren J.; Noblet, Jillian N.; Eagleson, Mackenzie A.; Conteh, Abass M.; Sturek, Joshua T.; Goodwill, Adam G.; Cellular and Integrative Physiology, School of Medicine
    This study tested the hypothesis that glucagon-like peptide 1 (GLP-1) therapies improve cardiac contractile function at rest and in response to adrenergic stimulation in obese swine after myocardial infarction. Obese Ossabaw swine were subjected to gradually developing regional coronary occlusion using an ameroid occluder placed around the left anterior descending coronary artery. Animals received subcutaneous injections of saline or liraglutide (0.005-0.015 mg/kg/day) for 30 days after ameroid placement. Cardiac performance was assessed at rest and in response to sympathomimetic challenge (dobutamine 0.3-10 μg/kg/min) using a left ventricular pressure/volume catheter. Liraglutide increased diastolic relaxation (dP/dt; Tau 1/2; Tau 1/e) during dobutamine stimulation (P < 0.01) despite having no influence on the magnitude of myocardial infarction. The slope of the end-systolic pressure volume relationship (i.e., contractility) increased with dobutamine after liraglutide (P < 0.001) but not saline administration (P = 0.63). Liraglutide enhanced the slope of the relationship between cardiac power and pressure volume area (i.e., cardiac efficiency) with dobutamine (P = 0.017). Hearts from animals treated with liraglutide demonstrated decreased β1-adrenoreceptor expression. These data support that GLP-1 agonism augments cardiac efficiency via attenuation of maladaptive sympathetic signaling in the setting of obesity and myocardial infarction.
  • Thumbnail Image
    Item
    Glucagon-like peptide-1 (7-36) but not (9-36) augments cardiac output during myocardial ischemia via a Frank-Starling mechanism
    (Springer, 2014) Goodwill, Adam G.; Tune, Johnathan D.; Noblet, Jillian N.; Conteh, Abass M.; Sassoon, Daniel; Casalini, Eli D.; Mather, Kieren J.; Department of Cellular & Integrative Physiology, IU School of Medicine
    This study examined the cardiovascular effects of GLP-1 (7-36) or (9-36) on myocardial oxygen consumption, function and systemic hemodynamics in vivo during normal perfusion and during acute, regional myocardial ischemia. Lean Ossabaw swine received systemic infusions of saline vehicle or GLP-1 (7-36 or 9-36) at 1.5, 3.0, and 10.0 pmol/kg/min in sequence for 30 min at each dose, followed by ligation of the left circumflex artery during continued infusion at 10.0 pmol/kg/min. Systemic GLP-1 (9-36) had no effect on coronary flow, blood pressure, heart rate or indices of cardiac function before or during regional myocardial ischemia. Systemic GLP-1 (7-36) exerted no cardiometabolic or hemodynamic effects prior to ischemia. During ischemia, GLP-1 (7-36) increased cardiac output by approximately 2 L/min relative to vehicle-controls (p = 0.003). This response was not diminished by treatment with the non-depolarizing ganglionic blocker hexamethonium. Left ventricular pressure-volume loops measured during steady-state conditions with graded occlusion of the inferior vena cava to assess load-independent contractility revealed that GLP-1 (7-36) produced marked increases in end-diastolic volume (74 ± 1 to 92 ± 5 ml; p = 0.03) and volume axis intercept (8 ± 2 to 26 ± 8; p = 0.05), without any change in the slope of the end-systolic pressure-volume relationship vs. vehicle during regional ischemia. GLP-1 (9-36) produced no changes in any of these parameters compared to vehicle. These findings indicate that short-term systemic treatment with GLP-1 (7-36) but not GLP-1 (9-36) significantly augments cardiac output during regional myocardial ischemia, via increases in ventricular preload without changes in cardiac inotropy.
  • Thumbnail Image
    Item
    An In Vivo Zebrafish Model for Interrogating ROS-Mediated Pancreatic β-Cell Injury, Response, and Prevention
    (Hindawi Publishing Corporation, 2018-03-28) Kulkarni, Abhishek A.; Conteh, Abass M.; Sorrell, Cody A.; Mirmira, Anjali; Tersey, Sarah A.; Mirmira, Raghavendra G.; Linnemann, Amelia K.; Anderson, Ryan M.; Biochemistry and Molecular Biology, School of Medicine
    It is well known that a chronic state of elevated reactive oxygen species (ROS) in pancreatic β-cells impairs their ability to release insulin in response to elevated plasma glucose. Moreover, at its extreme, unmitigated ROS drives regulated cell death. This dysfunctional state of ROS buildup can result both from genetic predisposition and environmental factors such as obesity and overnutrition. Importantly, excessive ROS buildup may underlie metabolic pathologies such as type 2 diabetes mellitus. The ability to monitor ROS dynamics in β-cells in situ and to manipulate it via genetic, pharmacological, and environmental means would accelerate the development of novel therapeutics that could abate this pathology. Currently, there is a lack of models with these attributes that are available to the field. In this study, we use a zebrafish model to demonstrate that ROS can be generated in a β-cell-specific manner using a hybrid chemical genetic approach. Using a transgenic nitroreductase-expressing zebrafish line, Tg(ins:Flag-NTR)s950 , treated with the prodrug metronidazole (MTZ), we found that ROS is rapidly and explicitly generated in β-cells. Furthermore, the level of ROS generated was proportional to the dosage of prodrug added to the system. At high doses of MTZ, caspase 3 was rapidly cleaved, β-cells underwent regulated cell death, and macrophages were recruited to the islet to phagocytose the debris. Based on our findings, we propose a model for the mechanism of NTR/MTZ action in transgenic eukaryotic cells and demonstrate the robust utility of this system to model ROS-related disease pathology.
  • Thumbnail Image
    Item
    Inhibition of 12/15-Lipoxygenase Protects Against β-Cell Oxidative Stress and Glycemic Deterioration in Mouse Models of Type 1 Diabetes
    (American Diabetes Association, 2017-11) Hernandez-Perez, Marimar; Chopra, Gaurav; Fine, Jonathan; Conteh, Abass M.; Anderson, Ryan M.; Linnemann, Amelia K.; Benjamin, Chanelle; Nelson, Jennifer B.; Benninger, Kara S.; Nadler, Jerry L.; Maloney, David J.; Tersey, Sarah A.; Mirmira, Raghavendra G.; Pediatrics, School of Medicine
    Islet β-cell dysfunction and aggressive macrophage activity are early features in the pathogenesis of type 1 diabetes (T1D). 12/15-Lipoxygenase (12/15-LOX) is induced in β-cells and macrophages during T1D and produces proinflammatory lipids and lipid peroxides that exacerbate β-cell dysfunction and macrophage activity. Inhibition of 12/15-LOX provides a potential therapeutic approach to prevent glycemic deterioration in T1D. Two inhibitors recently identified by our groups through screening efforts, ML127 and ML351, have been shown to selectively target 12/15-LOX with high potency. Only ML351 exhibited no apparent toxicity across a range of concentrations in mouse islets, and molecular modeling has suggested reduced promiscuity of ML351 compared with ML127. In mouse islets, incubation with ML351 improved glucose-stimulated insulin secretion in the presence of proinflammatory cytokines and triggered gene expression pathways responsive to oxidative stress and cell death. Consistent with a role for 12/15-LOX in promoting oxidative stress, its chemical inhibition reduced production of reactive oxygen species in both mouse and human islets in vitro. In a streptozotocin-induced model of T1D in mice, ML351 prevented the development of diabetes, with coincident enhancement of nuclear Nrf2 in islet cells, reduced β-cell oxidative stress, and preservation of β-cell mass. In the nonobese diabetic mouse model of T1D, administration of ML351 during the prediabetic phase prevented dysglycemia, reduced β-cell oxidative stress, and increased the proportion of anti-inflammatory macrophages in insulitis. The data provide the first evidence to date that small molecules that target 12/15-LOX can prevent progression of β-cell dysfunction and glycemic deterioration in models of T1D.
  • Thumbnail Image
    Item
    Interleukin-6 Reduces β-Cell Oxidative Stress by Linking Autophagy With the Antioxidant Response
    (American Diabetes Association, 2018-08) Marasco, Michelle R.; Conteh, Abass M.; Reissaus, Christopher A.; Cupit, John E.; Appleman, Evan M.; Mirmira, Raghavendra G.; Linnemann, Amelia K.; Pediatrics, School of Medicine
    Production of reactive oxygen species (ROS) is a key instigator of β-cell dysfunction in diabetes. The pleiotropic cytokine interleukin 6 (IL-6) has previously been linked to β-cell autophagy but has not been studied in the context of β-cell antioxidant response. We used a combination of animal models of diabetes and analysis of cultured human islets and rodent β-cells to study how IL-6 influences antioxidant response. We show that IL-6 couples autophagy to antioxidant response and thereby reduces ROS in β-cells and human islets. β-Cell-specific loss of IL-6 signaling in vivo renders mice more susceptible to oxidative damage and cell death through the selective β-cell toxins streptozotocin and alloxan. IL-6-driven ROS reduction is associated with an increase in the master antioxidant factor NRF2, which rapidly translocates to the mitochondria to decrease mitochondrial activity and stimulate mitophagy. IL-6 also initiates a robust transient decrease in cellular cAMP levels, likely contributing to the stimulation of mitophagy to mitigate ROS. Our findings suggest that coupling autophagy to antioxidant response in β-cells leads to stress adaptation that can reduce cellular apoptosis. These findings have implications for β-cell survival under diabetogenic conditions and present novel targets for therapeutic intervention.
  • Thumbnail Image
    Item
    Obesity Alters Molecular and Functional Cardiac Responses to Ischemia-Reperfusion and Glucagon-Like Peptide-1 Receptor Agonism
    (Springer, 2016-07) Sassoon, Daniel J.; Goodwill, Adam G.; Noblet, Jillian N.; Conteh, Abass M.; Herring, B. Paul; McClintick, Jeanette N.; Tune, Johnathan D.; Mather, Kieren J.; Department of Cellular & Integrative Physiology, Indiana University School of Medicine
    This study tested the hypothesis that obesity alters the cardiac response to ischemia/reperfusion and/or glucagon like peptide-1 (GLP-1) receptor activation, and that these differences are associated with alterations in the obese cardiac proteome and microRNA (miRNA) transcriptome. Ossabaw swine were fed normal chow or obesogenic diet for 6 months. Cardiac function was assessed at baseline, during a 30-minutes coronary occlusion, and during 2 hours of reperfusion in anesthetized swine treated with saline or exendin-4 for 24 hours. Cardiac biopsies were obtained from normal and ischemia/reperfusion territories. Fat-fed animals were heavier, and exhibited hyperinsulinemia, hyperglycemia, and hypertriglyceridemia. Plasma troponin-I concentration (index of myocardial injury) was increased following ischemia/reperfusion and decreased by exendin-4 treatment in both groups. Ischemia/reperfusion produced reductions in systolic pressure and stroke volume in lean swine. These indices were higher in obese hearts at baseline and relatively maintained throughout ischemia/reperfusion. Exendin-4 administration increased systolic pressure in lean swine but did not affect the blood pressure in obese swine. End-diastolic volume was reduced by exendin-4 following ischemia/reperfusion in obese swine. These divergent physiologic responses were associated with obesity-related differences in proteins related to myocardial structure/function (e.g. titin) and calcium handling (e.g. SERCA2a, histidine-rich Ca2+ binding protein). Alterations in expression of cardiac miRs in obese hearts included miR-15, miR-27, miR-130, miR-181, and let-7. Taken together, these observations validate this discovery approach and reveal novel associations that suggest previously undiscovered mechanisms contributing to the effects of obesity on the heart and contributing to the actions of GLP-1 following ischemia/reperfusion.
  • Thumbnail Image
    Item
    Pancreatic beta cell autophagy is impaired in type 1 diabetes
    (Springer, 2021-04) Muralidharan, Charanya; Conteh, Abass M.; Marasco, Michelle R.; Crowder, Justin J.; Kuipers, Jeroen; de Boer, Pascal; Linnemann, Amelia K.; Biochemistry and Molecular Biology, School of Medicine
    Aims/hypothesis: Pancreatic beta cells are subjected to exogenous damaging factors such as proinflammatory cytokines or excess glucose that can cause accumulation of damage-inducing reactive oxygen species during the pathogenesis of diabetes. We and others have shown that beta cell autophagy can reduce reactive oxygen species to protect against apoptosis. While impaired islet autophagy has been demonstrated in human type 2 diabetes, it is unknown if islet autophagy is perturbed in the pathogenesis of type 1 diabetes. We hypothesised that beta cell autophagy is dysfunctional in type 1 diabetes, and that there is a progressive loss during early diabetes development. Methods: Pancreases were collected from chloroquine-injected and non-injected non-obese diabetes-resistant (NOR) and non-obese diabetic (NOD) mice. Age- and BMI-matched pancreas tissue sections from human organ donors (N = 34) were obtained from the Network for Pancreatic Organ Donors with Diabetes (nPOD). Tissue sections were stained with antibodies against proinsulin or insulin (beta cell markers), microtubule-associated protein 1 light chain 3 A/B (LC3A/B; autophagosome marker), lysosomal-associated membrane protein 1 (LAMP1; lysosome marker) and p62 (autophagy adaptor). Images collected on a scanning laser confocal microscope were analysed with CellProfiler and ImageJ. Secondary lysosomes and telolysosomes were assessed in electron micrographs of human pancreatic tissue sections (n = 12), and energy dispersive x-ray analysis was performed to assess distribution of elements (n = 5). Results: We observed increased autophagosome numbers in islets of diabetic NOD mice (p = 0.008) and increased p62 in islets of both non-diabetic and diabetic NOD mice (p < 0.001) vs NOR mice. There was also a reduction in LC3-LAMP1 colocalisation in islets of diabetic NOD mice compared with both non-diabetic NOD (p < 0.001) and NOR mice (p < 0.001). Chloroquine elicited accumulation of autophagosomes in the islets of NOR (p = 0.003) and non-diabetic NOD mice (p < 0.001), but not in islets of diabetic NOD mice; and stimulated accumulation of p62 in NOR (p < 0.001), but not in NOD mice. We observed reduced LC3-LAMP1 colocalisation (p < 0.001) in residual beta cells of human donors with type 1 diabetes vs non-diabetic participants. We also observed reduced colocalisation of proinsulin with LAMP1 in donors with type 1 diabetes (p < 0.001). Electron microscopy also revealed accumulation of telolysosomes with nitrogen-dense rings in beta cells of autoantibody-positive donors (p = 0.002). Conclusions/interpretation: We provide evidence of islet macroautophagy/crinophagy impairment in human type 1 diabetes. We also document accumulation of telolysosomes with peripheral nitrogen in beta cells of autoantibody-positive donors, demonstrating altered lysosome content that may be associated with lysosome dysfunction before clinical hyperglycaemia. Similar macroautophagy impairments are present in the NOD mouse model of type 1 diabetes.