Doctoral Degrees (Physiological Sciences)
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Browsing Doctoral Degrees (Physiological Sciences) by browse.metadata.advisor "Essop, M. Faadiel"
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- ItemAssessment of Metabolic Therapy for Acute Heart Failure(Stellenbosch : Stellenbosch University, 2017-03) Kimar, Charlene Patricia; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Introduction Acute heart failure (AHF) is the most common primary diagnosis for hospitalized heart disease cases in Africa. Increased fatty acid oxidation (FAO) with heart failure (HF) triggers detrimental effects on the myocardium, we hypothesized that diabetic rat hearts subjected to AHF display lower cardiac function vs. controls and that Trimetazidine (TMZ) (a partial FAO inhibitor) counters this effect. Aims 1)To establish an ex vivo AHF model for diabetic hearts; 2) Assess whether TMZ treatmentoffers cardioprotection to diabetic rat hearts subjected to an AHF protocol; and 3) Delineate underlying mechanisms by evaluating markers for oxidative stress, mitochondrial uncoupling, apoptosis and metabolic dysregulation. Methods Vehicle control male Wistar rats were injected with citrate buffer. To induce diabetes rats were administered streptozotocin (60 mg/kg) for one week vs. non-diabetic controls. Hearts were perfused on the Langendorff retrograde perfusion system for three phases: Stabilization - (11 mM glucose- non-diabetic, and 30 mM glucose- diabetic hearts) at 100 cm H2O (30 min); AHF – (1.5 mM palmitic acid, 2.5 mM glucose) at 20 cm H2O (35 min); and Recovery– (1.5 mM palmitic acid, 11 mM glucose or 30 mM glucose) at 100 cm H2O (30 min). 1 μM TMZ was administered at the start of recovery. In addition, we evaluated necrosis and infarct size by tetrazolium (TTC) staining at the end of the AHF phase. Western blotting was performed for markers of apoptosis (pBAD/BAD), oxidative stress (superoxide dismutase 2 [SOD2], conjugated dienes [CDs], thiobarbituric acid reactive substances (TBARS), reduced/oxidized glutathione [GSH/GSSG] analysis, oxygen radical absorbance capacity [ORAC]), mitochondrial uncoupling (uncoupling protein 2 [UCP2]) and metabolic dysregulation (advanced glycation end product [AGE] and polyol pathway analyses). We investigated direct effects of TMZ (1 μM) in H9c2 cardiomyoblasts exposed to 500 μM palmitate for 21 hours and assessed the effects of TMZ treatment on fatty acid-induced oxidative stress and apoptosis. Results Reduced function was seen for all groups in recovery vs. controls, while AHF-diabetic showed worse outcomes vs. AHF alone. TMZ treatment resulted in a robust increase in left ventricular developed pressure (LVDP) for diabetic hearts vs. controls. Infarct size assessment showed no differences. TMZ treated diabetic hearts also displayed lower AGE and higher polyol pathway activation vs. respective controls. However, several markers of the AGE pathway did not show any significant differences for any groups. Non-diabetic and diabetic hearts displayed increased oxidative stress (TBARS) compared to their counterparts. TMZ treatment resulted in anti-apoptotic effects in hearts subjected to AHF. TMZ exhibited antioxidant effects by lowering fatty acid-induced mitochondrial oxidative stress in cells. Conclusion This study successfully established a novel ex vivo model of AHF for the diabetic rat heart, and TMZ treatment resulted in cardioprotection for diabetic hearts. Our data suggest that TMZ may mediate some of its cardioprotective effects by acting as an anti-oxidant to lower myocardial oxidative stress triggered during AHF. The findings also indicate that TMZ treatment may lower the formation of damaging AGEs in the diabetic heart. TMZ therefore, emerges as a putative therapeutic target to be considered as sole and/or combined treatment (with more conventional drugs) for AHF patients.
- ItemThe hexosamine biosynthetic pathway induces gene promoter activity of the cardiac-enriched isoform of acetyl-CoA carboxylase(Stellenbosch : Stellenbosch University, 2013-03) Imbriolo, Jamie; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: The cardiac isoform of acetyl-CoA carboxylase (ACCβ) produces malonyl-CoA, a potent inhibitor of mitochondrial fatty acid (FA) uptake; thus increased ACCβ activity decreases fatty acid utilization thereby potentially leading to intracellular myocardial lipid accumulation and insulin resistance (IR). Previous studies show that greater flux through the hexosamine biosynthetic pathway (HBP) contributes to the development of IR. In light of this, we hypothesize that increased HBP flux induces ACCβ gene expression thereby contributing to the onset of IR. Our initial work focused on ACCβ gene promoter regulation and suggest that the HBP modulates upstream stimulatory factor 2 (USF2) thereby inducing ACCβ gene expression. Here, we further investigated HBP-mediated regulation of ACCβ gene expression by transiently transfecting cardiac-derived H9c2 cells with an expression vector encoding the rate-limiting HBP enzyme (GFAT) ± the full length ACCβ and 4 truncated promoter-luciferase constructs, respectively. GFAT overexpression increased ACCβ gene promoter activity for the full length and 3 larger deletion constructs (p<0.001 vs. controls). However, GFAT-mediated and USF2-mediated ACCβ promoter induction was blunted when co-transfected with the -38/+65 deletion construct suggesting that USF2 binds to the proximal promoter region (near start codon). Further investigation proves that USF2 binds to ACCβ promoter and activates it, but that USF2 is not O-GlcNAc modified even though there is a strong correlation between increased O-GlcNac levels and USF2 activation of ACCβ. This would suggest that there is another O-GlcNac modified factor involved in this regulatory pathway. Our study demonstrates that increased HBP flux induces ACCβ gene promoter activity via HBP modulation of USF2. We propose that ACCβ induction reduces fatty acid oxidation, thereby leading to intracellular lipid accumulation (FA uptake>>FA oxidation) and the onset of cardiac IR.
- ItemHyperglycemia-induced activation of the hexosamine biosynthetic pathway causes myocardial cell death(Stellenbosch : University of Stellenbosch, 2009-12) Rajamani, Uthra; Essop, M. Faadiel; University of Stellenbosch. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: OBJECTIVE – Oxidative stress increases flux through the hexosamine biosynthetic pathway (HBP) resulting in greater O-GlcNAcylation of target proteins. Since increased oxidative stress and HBP flux are associated with insulin resistance, we hypothesized that its activation leads to greater O-GlcNAcylation of BAD (pro-apoptotic) and increased myocardial apoptosis. RESEARCH DESIGN AND METHODS – To investigate our hypothesis, we employed two experimental models: 1) H9c2 cardiomyoblasts exposed to high glucose (33 mM glucose) ± HBP modulators ± antioxidant treatment vs. matched controls (5.5 mM glucose); and 2) a rat model of high fat diet-induced insulin resistance and hyperglycemia. We evaluated apoptosis in vitro by Hoechst nuclear staining, Annexin-V staining, caspase activity measurements and immunoblotting while in vivo apoptosis was assessed by immunoblotting. In vitro reactive oxygen species (ROS) levels were quantified by H2DCFDA staining (fluorescence microscopy, flow cytometry). We determined overall and BAD O-GlcNAcylation, both by immunoblotting and immunofluorescence microscopy. As BAD-Bcl-2 dimer formation enhances apoptosis, we performed immunoprecipitation analysis and immunofluorescence microscopy (co-localization) to determine BAD-cl-2 dimerization. In vivo overall O-GlcNAcylation, BAD O-GlcNAcylation and BAD-Bcl-2 dimerization was determined by immunoprecipitation and immunoblotting. 4 RESULTS – High glucose treatment of cells significantly increased the degree of apoptosis as revealed by Hoechst nuclear staining (54 ± 9%, p<0.01 vs. 5.5 mM), Annexin-V staining (43 ± 5%), caspase activity assay (26 ± 2%) and immunoblotting. In parallel, overall OGlcNAcylation (p<0.001 vs. 5.5 mM), BAD O-GlcNAcylation (p<0.05 vs. 5.5 mM) and ROS levels were increased (fluorescence microscopy – p<0.05 vs. 5.5 mM; flow cytometry – p<0.001 vs. 5.5 mM). HBP inhibition using DON and antioxidant treatment (α-OHCA) attenuated these effects while HBP activation by PUGNAc exacerbated it. Likewise, insulin resistant rat hearts exhibited significantly higher caspase-3 (p<0.05 vs. controls), overall O-GlcNAcylation (p<0.05 vs. controls) and BAD O-GlcNAcylation levels (p<0.05 vs. 5.5 mM). BAD-Bcl-2 dimer formation was increased in cells exposed to hyperglycemia [immunoprecipitation analysis and co-localization] and in insulin resistant hearts. CONCLUSIONS - Our study identified a novel pathway whereby hyperglycemia results in greater oxidative stress, resulting in increased HBP activation and increased BAD OGlcNAcylation. We also found greater BAD-Bcl-2 dimerization increasing myocardial apoptosis, suggesting that this pathway may play a crucial role in the onset of the diabetic cardiomyopathy.
- ItemHyperglycemia-mediated onset of myocardial insulin resistance – unraveling molecular mechanisms and identifying therapeutic targets(Stellenbosch : Stellenbosch University, 2014-04) Joseph, Danzil Eugene; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Background - Although acute hyperglycemic episodes are linked to lower glucose uptake, underlying mechanisms driving this process remain unclear. We hypothesized that acute hyperglycemia triggers reactive oxygen species (ROS) production and increases non-oxidative glucose pathway (NOGP) activation, i.e. stimulation of advanced glycation end products (AGE), polyol pathway (PP), hexosamine biosynthetic pathway (HBP) and protein kinase C (PKC) activation. These mechanisms attenuate cellular function, and may indeed decrease insulin-mediated cardiac glucose uptake. The role of the pentose phosphate pathway (PPP) under high glucose/diabetic conditions is a subject of contention. Activation of the PPP enzyme transketolase (TK) (by benfotiamine/BFT or thiamine) reduces flux via the other four NOGPs, and is associated with beneficial outcomes. Our aim was therefore to evaluate the effects of acute hyperglycemia on insulin-mediated glucose uptake in a cardiac-derived cell line. Specifically, we aimed to elucidate the role of ROS and NOGP induction under these conditions. Methodology - H9c2 cardiomyoblasts were exposed to 25 mM glucose for 24 hr vs. 5.5 mM glucose controls ± modulating agents during last hour of glucose exposure: a) antioxidant #1 for mitochondrial ROS (250 μM 4-OHCA), b) antioxidant #2 for NADPH oxidase-generated ROS (100 μM DPI), c) NOGP inhibitors – 100 μM aminoguanidine (AGE), 5 μM chelerythrine (PKC); 40 μM DON (HBP); and 10 μM zopolrestat (PP). We also employed BFT (50 and 100 μM) in vitro, while the effects of in vivo thiamine administration were assessed in hearts of an obese/diabetic rat model of pre-diabetes and diabetes, the OLETF strain. We evaluated insulin sensitivity by glucose uptake assay (flow cytometry), GLUT4 translocation (transfection of HA-GLUT4-GFP construct) and protein kinase B (Akt) activity assay. ROS levels (mitochondrial, intracellular) were measured by flow cytometry analysis of specific fluorescent probes. Markers of each NOGP were also assessed. Results - Acute hyperglycemia elevated ROS, activated NOGPs and blunted glucose uptake. However, TK activity (marker of PPP) did not change. Respective 4-OHCA and DPI treatment blunted ROS production, diminished NOGP activation and normalized glucose uptake. NOGP inhibitory studies identified PKCβII as a key downstream player in lowering insulin-mediated glucose uptake. When we employed BFT (known to shunt flux away from NOGPs and into the PPP), it decreased ROS generation and NOGP activation, and restored glucose uptake under acute hyperglycemic conditions. In vivo thiamine administration reduced markers of the other NOGP, while it attenuated (mainly in the pre-diabetic phase) the metabolic dysfunction observed in the OLETF rats. Conclusions - This study demonstrates that acute hyperglycemia elicits a series of maladaptive events that function in tandem to reduce glucose uptake, and that antioxidant treatment and/or attenuation of NOGP activation (PKC, polyol pathway) may limit the onset of insulin resistance.
- ItemImmune activation in HIV-positive patients on combined anti-retroviral treatment (cART) as a high risk group for the development of cardiovascular diseases(Stellenbosch : Stellenbosch University, 2017-12) Teer, Eman Aboajla; Essop, M. Faadiel; Glashoff, Richard; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Although roll-out of combined anti-retroviral treatment (cART) has blunted HIV-AIDS onset, studies show increased development of cardio-metabolic complications in HIV-infected individuals. For this study we hypothesized that HIV-induced low-grade inflammation perturbs immune cell function/activation, thereby contributing to an increased risk for cardiovascular diseases (CVD) onset. Here we aimed to identify changes in monocyte and T cell subsets and determine its relationship to: (a) classical markers of HIV progression (CD4 count, viral load); (b) immune activation status; (c) endothelial dysfunction; and (d) traditional lipid profile and subclasses. Eighty participants were recruited from the Worcester Community Day Center (Worcester, Western Cape, South Africa): n=13 HIV-negative, n=67 HIV-positive. Recruits were divided as HIV-naïve and HIV-treated (on cART), and also groups based on CD4 count (control group, HIV-positive with CD4count > 500 cells/µL, CD4 count from 200–500 cells/µL and CD4 count < 200 cells/µL). Clinical histories and a validated lifestyle questionnaire were completed. Fasted blood was collected and used to assess monocyte subpopulation phenotype (non-classical, intermediate, classical) by flow cytometry together with tissue factor (a marker for thrombus formation) and CD38 (a marker for immune activation) expression on monocyte and T cell subsets (CD4, CD8). Classical regulatory T cells (CD4+CD25++FOXP3+) with activation markers (glycoprotein A repetitions predominant [GARP] and special AT-rich sequence binding protein 1 [SATB-1]) were also evaluated together with an assessment of endothelial function (flow-mediated dilatation). C-reactive protein levels together with the traditional lipid profile were also evaluated. In addition, an assessment of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) subclasses was also completed. Our data revealed a robust increase in inflammation/immune activation and coagulation markers on CD8+ and CD4+ T cell populations, respectively (CD8+CD142+ [P = 0.01] and CD4+CD142+ [P = 0.0003]). Increased co-expression of inflammation and coagulation markers were also observed on both CD8+ and CD4+ T cells (CD8+142+CD38+ [P = 0.0001] and CD4+142+38+ [< 0.0001]). In addition, we found an expansion of both non-classical (P = 0.0001) and intermediate monocytes (P = 0.05) that were highly correlated with immune activation, coagulation and HIV disease progression markers. There was also an expansion of CD4+FOXP3+ regulatory T cells (P = 0.0005), together with higher levels of GARP (P = 0.001) and SATB-1 (P = 0.04) (especially in patients with relatively low CD4 counts). The lipid profile data revealed interesting changes, i.e. a significant decrease during early HIV-infection but with substantial increase after cART initiation. In addition, we also found significant changes in HDL and LDL subclasses. The most novel findings of this study are: a) the identification of a unique coagulation marker (CD142) expressed on CD8 and CD4 T cells and its relatively early expression in HIV-infected individuals (treatment naïve). CD142 is also co-expressed with immune activation and strongly correlates with disease progression markers; b) changes in lipid subclasses that significantly correlate to HIV immunological markers despite a decrease in terms of the traditional lipid profile expected. Such subclass changes may also be a driver for CVD onset, although further research is needed to pursue this question; and c) upregulation of both antiinflammatory GARP and pro-inflammatory SATB-1 in regulatory T cells in HIV-treated individuals (with immune dysregulation) altering regulatory T cell function and also potentially contributing to CVD onset. Thus we propose that clinicians could be aware of immune activation and coagulation with HIV infection (even at relatively early stages of disease progression) as monitoring and control of these factors could result in improved healthcare and the long-term well-being for such patients.
- ItemThe maladaptive effects of HIV protease inhibitors (Lopinavir/Ritonavir) on the rat heart(Stellenbosch : Stellenbosch University, 2013-12) Reyskens, Kathleen Maria Simone Elise; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Although antiretroviral treatment decreases HIV-AIDS morbidity/mortality, long-term effects include onset of insulin resistance and cardiovascular diseases. Increased oxidative stress and dysregulation of the ubiquitin-proteasome system (UPS) are implicated in protease-inhibitor (PI)-mediated cardio-metabolic pathophysiology. We hypothesized that PI treatment (Lopinavir/Ritonavir) elevates myocardial oxidative stress and concomitantly inhibits the UPS, thereby attenuating cardiac function. Lopinavir/Ritonavir was dissolved in 1% ethanol (vehicle) and injected into mini-osmotic pumps that were surgically implanted into Wistar rats for eight weeks vs. vehicle and sham controls. Subsequently, we evaluated metabolic parameters and heart function (ex vivo and in vivo methods) at baseline and following ischemia-reperfusion. PI-treated rats exhibited weight gain, increased serum LDL-cholesterol, higher tissue triglycerides (heart, liver), but no evidence of insulin resistance. It also upregulated hepatic gene expression of acetyl-CoA carboxylase β and 3-hydroxy-3-methylglutaryl-CoA-reductase, key regulators of fatty acid oxidation and cholesterol synthesis, respectively. Further, PI-treated hearts displayed impaired UPS, increased superoxide dismutase (SOD) activity and unaltered superoxide levels, and elevated peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC-1α) peptide levels. Perfusion data revealed contractile dysfunction at baseline and following ischemia-reperfusion, while post-ischemic hearts exhibited decreased ATPase specific activity vs. matched controls. Early changes initiated by PI treatment resemble the metabolic syndrome and reflect a pre-atherogenic profile. Moreover, the effects of PIs on cardiac contractile function may in part be triggered by impaired UPS activity together with strain on the mitochondrial energetic system. Our study alerts to cardio-metabolic side effects of PI treatment and raises the question of the most appropriate co-therapies for patients on chronic antiretroviral treatment.
- ItemNovel therapeutic agents that blunt hyperglycemia-induced cardiac contractile dysfunction(Stellenbosch : Stellenbosch University, 2013-03) Mapanga, Rudo Fiona; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Introduction Diabetes constitutes a major health challenge. Since cardiovascular complications are common in diabetic patients this will further increase the overall burden of disease. Furthermore, stress-induced hyperglycemia in non-diabetic patients with acute myocardial infarction is associated with higher inhospital mortality. Hyperglycemia-induced oxidative stress results in DNA damage and subsequent activation of poly-ADP-ribose polymerase (PARP) as a restorative mechanism. However, PARP attenuates glyceraldehyde–3-phosphate dehydrogenase (GAPDH) activity, thereby diverting upstream glycolytic metabolites into damaging non-oxidative glucose pathways (NOGP). For example, hyperglycemia-induced stimulation of four NOGP, i.e. the polyol pathway, hexosamine biosynthetic pathway (HBP), advanced glycation end products (AGE), and PKC activation elicit cardiovascular complications. The current thesis examined the regulation of NOGP in the setting of ischemia and reperfusion under hyperglycemic conditions. Here we hypothesized that administration of two unique therapeutic interventions, i.e. oleanolic acid (OA; clove extract) and benfotiamine (BFT; vitamin B1 derivative), can blunt oxidative stress and NOGP-induced cardiac dysfunction under hyperglycemic conditions following ischemia and reperfusion. Our choice for these agents was based on the principle that OA possesses antioxidant properties; and BFT stimulates transketolase (pentose phosphate pathway [PPP] enzyme) thereby shunting flux away from the NOGP pathways. Additionally, hyperglycemia-induced oxidative stress can also result in dysregulation of the ubiquitin-proteasome system (UPS) that removes misfolded proteins. There are conflicting data whether increased/decreased UPS is detrimental with hyperglycemia and/or in response to ischemia and reperfusion. In light of this, we also hypothesized that BFT and OA act as novel cardio-protective agents by diminishing myocardial UPS activity in response to ischemia and reperfusion under acute hyperglycemic conditions. Materials and Methods For the first part of the study, we employed several experimental systems: 1) H9c2 cardiac myoblasts were exposed to 33 mM glucose for 48 hr vs. controls (5 mM glucose); and subsequently treated with two OA doses (20 and 50 μM) for 6 and 24 hr, respectively; 2) Isolated rat hearts were perfused ex vivo with Krebs-Henseleit buffer containing 33 mM glucose vs. controls (11 mM glucose) for 60 min, followed by 20 min global ischemia and 60 min reperfusion ± OA treatment; 3) Infarct size was determined using Evans Blue dye and 1% 2,3,5-triphenyl tetrazolium chloride (TTC) staining with 20 min regional ischemia and 2 hr reperfusion 4) In vivo coronary ligations were performed on streptozotocin-diabetic rats ± 0.45 mg/kg OA administration within the first two minutes of reperfusion; and 5) Effects of long-term OA treatment (2 weeks) on heart function were assessed in streptozotocin (STZ)-diabetic rats. Here, STZ was dissolved in citrate buffer (p.H 6.3) and diabetes was induced by administering 60 mg/kg i.p Tissues were collected at the end of the global ischemia experiments and analyzed for oxidative stress, apoptosis, UPS activity and HBP activation. For the second part of the study we employed several experimental systems: 1) Isolated rat hearts were perfused ex vivo with Krebs-Henseleit buffer containing 33 mM glucose vs. controls (11 mM glucose) for 90 min, followed by 30 min global ischemia and 60 min reperfusion ± 25, 50 and 100 μM BFT treatment, respectively, added during the first 20 min of reperfusion; 2) Infarct size determination as in #3 above but with 30 min regional ischemia and 2 hr reperfusion ± 100 μM BFT treatment; and 3) In vivo coronary ligations performed on streptozotocin-diabetic rats ± 0.50 mg/kg BFT treatment within the first two min of reperfusion. In parallel experiments, NOGP inhibitors were added during the first 20 min of reperfusion. The following inhibitors were individually employed: AGE pathway (100 μM aminoguanidine); PKC (5 μM chelerythrine chloride); HBP (40 μM 6-diazo-5-oxo-L-norleucine); and polyol pathway (1 μM zopolrestat); Infarct size determination as in #2) with 30 min regional ischemia and 120 min reperfusion ± similar treatments. Results Our data show decreased cardiac contractile function in response to ischemia and reperfusion under hyperglycemic conditions. This was linked to increased PARP and attenuated GAPDH activities, together with higher activation of the NOGP. Moreover, we found elevated myocardial oxidative stress, UPS and cell death under these conditions. OA treatment resulted in cardio-protection, i.e. for ex vivo and in vivo rat hearts exposed to ischemia and reperfusion under hyperglycemic conditions. In parallel, OA decreased oxidative stress, apoptosis, HBP flux and UPS activity following ischemia and reperfusion. Long-term OA treatment also improved heart function in streptozotocin-diabetic rats. Our data also reveal that acute BFT treatment significantly decreased myocardial oxidative stress and apoptosis, and provided cardio-protection in response to ischemia and reperfusion under hyperglycemic conditions. In parallel, BFT blunted hyperglycemia-induced activation of four NOGP in the rat heart. Acute administration of each of the NOGP inhibitors decreased PARP and enhanced GAPDH activities, while diminishing oxidative stress and myocardial apoptosis. Moreover, each of the NOGP inhibitors (individually) employed blunted activation of the other three pathways here examined. Hearts treated with NOGP inhibitors also displayed improved functional recovery and smaller infarct sizes following ischemia and reperfusion. Interestingly, NOGP inhibitors resulted in the same degree of change (for all above-mentioned parameters evaluated) when compared to each other. Conclusions This study shows that acute and chronic hyperglycemia trigger myocardial oxidative stress that eventually results in NOGP activation and contractile dysfunction following ischemia and reperfusion. Moreover, our findings establish - for the first time as far as we are aware - that there is a convergence of downstream NOGP effects in our model, i.e. increased myocardial oxidative stress, further NOGP pathway activation, apoptosis, and impaired contractile function. Thus a vicious metabolic cycle is established whereby hyperglycemia-induced NOGP further fuels its own activation by generating even more oxidative stress, thereby exacerbating damaging effects on the heart under these conditions. We also found that both OA and BFT treatment blunted high glucose-induced detrimental effects and provided robust cardio-protection in response to ischemia and reperfusion under hyperglycemic conditions (acute and chronic). These findings suggest that the UPS may be a unique therapeutic target to treat ischemic heart disease in individuals that present with stress-induced, acute hyperglycemia. Moreover, BFT exhibited its cardio-protective effects by NOGP inhibition after ischemia and reperfusion under acute and chronic high glucose conditions. A similar effect was observed at baseline although the underlying mechanisms driving this process still need to be elucidated. In summary, the findings of this thesis are highly promising since it may eventually result in novel, cost-effective therapeutic interventions to treat acute hyperglycemia (in non-diabetic patients) and diabetic patients with associated cardiovascular complications.