Increased Glucose Oxidation Research Articles

Abstract Or123: Increasing ketone supply to the heart has beneficial effects on the source of cardiac ATP production in heart failure with preserved ejection fraction (HFpEF)

Introduction: There is considerable confusion as to what changes in cardiac energy metabolism occur in heart failure with preserved ejection fraction (HFpEF). In HFpEF mice hearts, we found a marked decrease in cardiac glucose oxidation, which is accompanied by an increase in fatty acid oxidation. Ketones have been proposed as an extra source of fuel for the failing, heart, although it remains unclear if ketones may adversely affect glucose and fatty acid oxidation. Methods: 13-month-old C57BL/6N female mice were administered a 60% high-fat diet and L-NAME (0.5g/L/day) for 6 weeks to induce HFpEF. Control mice were fed with regular low-fat diet and regular drinking water. Hearts of the mice were excised and perfused in the isolated working mode aerobically with 5 mM glucose, 0.8 mM palmitate, 100 µU/ml insulin, with either low (0.6 mM) or high (1 mM) levels of β-hydroxybutyrate. Metabolic rates of the hearts were measured with radiolabelled [U- 14 C] glucose, [9,10- 3 H] palmitate, and [3- 14 C] β-hydroxybutyrate. Results: In HFpEF mouse hearts, glucose oxidation was significantly decreased with a parallel increase in fatty acid oxidation. As a result, the HFpEF hearts showed overall preserved ATP production rates (79 ± 12 vs. to 106 ± 13 μmol . g dry wt -1. min -1 control vs. HFpEF). Increasing β-hydroxybutyrate levels from 0.6 mM to 1 mM resulted in a rise in ketone oxidation rates in HFpEF hearts (from 692 ± 47 to 952 ± 90 nmol . g dry wt -1. min -1 ). Interestingly, this increase in ketone oxidation did not further compromise the rates of glucose oxidation in HFpEF hearts, but actually increased glucose oxidation rates (from 95 ± 13 to 190 ± 17 nmol . g dry wt -1. min -1 ), and had minor effects on fatty acid oxidation rates (from 796 ± 123 to 678 ± 92 nmol . g dry wt -1. min -1 ). This resulted in an increase in the contribution of ketone and glucose oxidation to ATP production from 15 % to 28 % in HFpEF hearts. Conclusion: In HFpEF mice hearts overall ATP production is not impaired, but rather the heart switches from glucose oxidation to fatty acid oxidation as the main source of ATP production. Increasing ketone supply to the heart increases ketone oxidation and results in a favourable shift in ATP production in HFpEF.

ATP-dependent citrate lyase Drives Left Ventricular Dysfunction by Metabolic Remodeling of the Heart.

Metabolic remodeling is a hallmark of the failing heart. Oncometabolic stress during cancer increases the activity and abundance of the ATP-dependent citrate lyase (ACL, Acly ), which promotes histone acetylation and cardiac adaptation. ACL is critical for the de novo synthesis of lipids, but how these metabolic alterations contribute to cardiac structural and functional changes remains unclear. We utilized human heart tissue samples from healthy donor hearts and patients with hypertrophic cardiomyopathy. Further, we used CRISPR/Cas9 gene editing to inactivate Acly in cardiomyocytes of MyH6-Cas9 mice. In vivo, positron emission tomography and ex vivo stable isotope tracer labeling were used to quantify metabolic flux changes in response to the loss of ACL. We conducted a multi-omics analysis using RNA-sequencing and mass spectrometry-based metabolomics and proteomics. Experimental data were integrated into computational modeling using the metabolic network CardioNet to identify significantly dysregulated metabolic processes at a systems level. Here, we show that in mice, ACL drives metabolic adaptation in the heart to sustain contractile function, histone acetylation, and lipid modulation. Notably, we show that loss of ACL increases glucose oxidation while maintaining fatty acid oxidation. Ex vivo isotope tracing experiments revealed a reduced efflux of glucose-derived citrate from the mitochondria into the cytosol, confirming that citrate is required for reductive metabolism in the heart. We demonstrate that YAP inactivation facilitates ACL deficiency. Computational flux analysis and integrative multi-omics analysis indicate that loss of ACL induces alternative isocitrate dehydrogenase 1 flux to compensate. This study mechanistically delineates how cardiac metabolism compensates for suppressed citrate metabolism in response to ACL loss and uncovers metabolic vulnerabilities in the heart.

Liraglutide alleviates experimental diabetic cardiomyopathy in a PDH-dependent manner.

Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist used for the treatment of T2D, has been shown to alleviate diabetic cardiomyopathy (DbCM) in experimental T2D, which was associated with increased myocardial glucose oxidation. To determine whether this increase in glucose oxidation is necessary for cardioprotection, we hypothesized that liraglutide's ability to alleviate DbCM would be abolished in mice with cardiomyocyte-specific deletion of pyruvate dehydrogenase (PDH; Pdha1CM-/- mice), the rate-limiting enzyme of glucose oxidation. Male Pdha1CM-/- mice and their α-myosin heavy chain Cre expressing littermates (αMHCCre mice) were subjected to experimental T2D via 10 weeks of high-fat diet supplementation, with a single low-dose injection of streptozotocin (75 mg/kg) provided at week 4. All mice were randomized to treatment with either vehicle control or liraglutide (30 µg/kg) twice daily during the final 2.5 weeks, with cardiac function assessed via ultrasound echocardiography. As expected, liraglutide treatment improved glucose homeostasis in both αMHCCre and Pdha1CM-/- mice with T2D, in the presence of mild weight loss. Parameters of systolic function were unaffected by liraglutide treatment in both αMHCCre and Pdha1CM-/- mice with T2D. However, liraglutide treatment alleviated diastolic dysfunction in αMHCCre mice, as indicated by an increase and decrease in the e'/a' and E/e' ratios, respectively. Conversely, liraglutide failed to rescue these indices of diastolic dysfunction in Pdha1CM-/- mice. Our findings suggest that increases in glucose oxidation are necessary for GLP-1R agonist mediated alleviation of DbCM. As such, strategies aimed at increasing PDH activity may represent a novel approach for the treatment of DbCM.

Unravelling the metabolic rewiring in the context of doxorubicin-induced cardiotoxicity: Fuel preference changes from fatty acids to glucose oxidation

Doxorubicin (DOX) is a highly effective chemotherapeutic agent whose clinical use is hindered by the onset of cardiotoxic effects, resulting in reduced ejection fraction within the first year from treatment initiation. Recently it has been demonstrated that DOX accumulates within mitochondria, leading to disruption of metabolic processes and energetic imbalance. We previously described that phosphoinositide 3-kinase γ (PI3Kγ) contributes to DOX-induced cardiotoxicity, causing autophagy inhibition and accumulation of damaged mitochondria. Here we intend to describe the maladaptive metabolic rewiring occurring in DOX-treated hearts and the contribution of PI3Kγ signalling to this process. Metabolomic analysis of DOX-treated WT hearts revealed an accumulation of TCA cycle metabolites due to a cycle slowdown, with reduced levels of pyruvate, unchanged abundance of lactate and increased Acetyl-CoA production. Moreover, the activity of glycolytic enzymes was upregulated, and fatty acid oxidation downregulated, after DOX, indicative of increased glucose oxidation. In agreement, oxygen consumption was increased in after pyruvate supplementation, with the formation of cytotoxic ROS rather than energy production. These metabolic changes were fully prevented in KD hearts. Interestingly, they failed to increase glucose oxidation in response to DOX even with autophagy inhibition, indicating that PI3Kγ likely controls the fuel preference after DOX through an autophagy-independent mechanism. In vitro experiments showed that inhibition of PI3Kγ inhibits pyruvate dehydrogenase (PDH), the key enzyme of Randle cycle regulating the switch from fatty acids to glucose usage, while decreasing DOX-induced mobilization of GLUT-4-carrying vesicles to the plasma membrane and limiting the ensuing glucose uptake. These results demonstrate that PI3Kγ promotes a maladaptive metabolic rewiring in DOX-treated hearts, through a two-pronged mechanism controlling PDH activation and GLUT-4-mediated glucose uptake.

Reciprocal regulation of cardiac β-oxidation and pyruvate dehydrogenase by insulin

The heart alters the rate and relative oxidation of fatty acids and glucose based on availability and energetic demand. Insulin plays a crucial role in this process diminishing fatty acid and increasing glucose oxidation when glucose availability increases. Loss of insulin sensitivity and metabolic flexibility can result in cardiovascular disease. It is therefore important to identify mechanisms by which insulin regulates substrate utilization in the heart. Mitochondrial pyruvate dehydrogenase (PDH) is the key regulatory site for the oxidation of glucose for ATP production. Nevertheless, the impact of insulin on PDH activity has not been fully delineated, particularly in the heart. We sought invivo evidence that insulin stimulates cardiac PDH and that this process is driven by the inhibition of fatty acid oxidation. Mice injected with insulin exhibited dephosphorylation and activation of cardiac PDH. This was accompanied by an increase in the content of malonyl-CoA, an inhibitor of carnitine palmitoyltransferase 1 (CPT1), and, thus, mitochondrial import of fatty acids. Administration of the CPT1 inhibitor oxfenicine was sufficient to activate PDH. Malonyl-CoA is produced by acetyl-CoA carboxylase (ACC). Pharmacologic inhibition or knockout of cardiac ACC diminished insulin-dependent production of malonyl-CoA and activation of PDH. Finally, circulating insulin and cardiac glucose utilization exhibit daily rhythms reflective of nutritional status. We demonstrate that time-of-day-dependent changes in PDH activity are mediated, in part, by ACC-dependent production of malonyl-CoA. Thus, by inhibiting fatty acid oxidation, insulin reciprocally activates PDH. These studies identify potential molecular targets to promote cardiac glucose oxidation and treat heart disease.

Obesity Is a Major Determinant of Impaired Cardiac Energy Metabolism in Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is a major health problem with limited treatment options. Although optimizing cardiac energy metabolism is a potential approach to treating heart failure, it is poorly understood what alterations in cardiac energy metabolism actually occur in HFpEF. To determine this, we used mice in which HFpEF was induced using an obesity and hypertension HFpEF protocol for 10 weeks. Next, carvedilol, a third-generation β-blocker and a biased agonist that exhibits agonist-like effects through β arrestins by activating extracellular signal-regulated kinase, was used to decrease one of these parameters, namely hypertension. Heart function was evaluated by invasive pressure-volume loops and echocardiography as well as by ex vivo working heart perfusions. Glycolysis and oxidation rates of glucose, fatty acids, and ketones were measured in the isolated working hearts. The development of HFpEF was associated with a dramatic decrease in cardiac glucose oxidation rates, with a parallel increase in palmitate oxidation rates. Carvedilol treatment decreased the development of HFpEF but had no major effect on cardiac energy substrate metabolism. Carvedilol treatment did increase the expression of cardiac β arrestin 2 and proteins involved in mitochondrial biogenesis. Decreasing bodyweight in obese HFpEF mice increased glucose oxidation and improved heart function. This suggests that the dramatic energy metabolic changes in HFpEF mice hearts are primarily due to the obesity component of the HFpEF model. SIGNIFICANCE STATEMENT: Metabolic inflexibility occurs in heart failure with preserved ejection fraction (HFpEF) mice hearts. Lowering blood pressure improves heart function in HFpEF mice with no major effect on energy metabolism. Between hypertension and obesity, the latter appears to have the major role in HFpEF cardiac energetic changes. Carvedilol increases mitochondrial biogenesis and overall energy expenditure in HFpEF hearts.

Cardiometabolic rewiring in the context of doxorubicin-induced cardiotoxicity: fuel preference changes from fatty acids to glucose oxidation

Abstract Background Doxorubicin (DOX) is a chemotherapeutic drug administered to treat a wide spectrum of tumours. However, its clinical use is hampered by the onset of cardiotoxic effects, with a reduction of LVEF that occurs within the first year from the treatment initiation. Recently it has been demonstrated that DOX accumulates into mitochondria, with metabolic perturbation and energetic imbalance. We previously described that phosphoinositide 3-kinase γ (PI3Kγ) contributes to DOX-induced cardiotoxicity, with the inhibition of autophagy and accumulation of damaged mitochondria into cardiac cells. Objective Here we intend to better understand the maladaptive metabolic rewiring occurring in DOX-treated hearts and the contribution of PI3Kg signalling to this process. Methods 10 weeks-old wild-type (WT) and knock-in mice expressing a kinase-inactive PI3Kγ (kinase-dead; KD) were treated with DOX (4 mg/Kg) at day 0, 7 and 14 (cumulative dose 12 mg/Kg). To explore the contribution of PI3Kγ on the early cardiac metabolic rewiring, metabolomic analysis were performed on animals sacrificed at day 3. Mitochondria respiration capacity and glycolytic enzymes activity were evaluated at day 3 and 42. To investigate the role of autophagy, 8 weeks-old mice were infected with an adeno-associated virus 9 (AAV9) carrying a vector expressing a short-hairpin RNA against ATG7 (ATG7sh). To test the role of PI3Kγ in glycolysis regulation, glucose uptake and plasma membrane exposure of GLUT-4 were measured in neonatal mouse cardiomyocytes (NMCs) with DOX acute treatment (1µM for 3h). To evaluate oxygen consumption with the administration of different substrates OROBOROS analysis were performed on myocardial slices from mice sacrificed at day 3. Results Metabolomic analysis of DOX-treated hearts revealed an accumulation of TCA cycle metabolites, with reduced levels of pyruvate, unchanged abundance of lactate but increased quantity of Acetyl-CoA, indicative of increased glucose oxidation and accelerated TCA cycle flux. Moreover, the activity of glycolytic enzymes was upregulated and fatty acid oxidation downregulated after DOX. In agreement, oxygen consumption was significantly increased in DOX-treated WT after pyruvate supplementation, with the formation of cytotoxic ROS rather than energy production. These metabolic changes were fully prevented in KD hearts. Interestingly, they failed to increase glucose oxidation in response to DOX even with autophagy inhibition, indicating that PI3Kγ likely controls the fuel preference after DOX through an autophagy-independent mechanism. In vitro experiments showed that genetic and pharmacological inhibition of PI3Kγ significantly prevented DOX-induced mobilization of GLUT-4-carrying vesicles to the plasma membrane and reduced glucose uptake. Conclusion These results demonstrate that PI3Kγ promotes a maladaptive metabolic rewiring in the heart in response to DOX, with an increased glucose utilization via a GLUT4-dependent mechanism.

OR33-04 Mechanistic Dissection Of Circadian-Specific Glucocorticoid Effects On Exercise Tolerance And Muscle Glucose Utilization

Abstract Disclosure: A. Prabakaran: None. M. Wintzinger: None. K. Piczer: None. K. Miz: None. A. Walton: None. H. Durumutla: None. M. Quattrocelli: None. Glucocorticoids (GCs) are circadian hormones regulating metabolism by activating the glucocorticoid receptor (GR) as pleiotropic transcription factor. Timing of exogenous GC drug regimens is emerging as a key determinant of their metabolic effects. This was shown by the surprising finding that once-weekly GC intermittence reverses many of the pro-obesogenic side effects of once-daily GC dosing in mice and humans. However, despite the intrinsic circadian nature of this signaling, the impact of time-of-day of exogenous GC dosing, i.e. chrono-pharmacology, remains remarkably unknown for metabolic physiology and exercise tolerance. Relevance of this question for humans is supported by the initial findings of increased lean mass and motor function with circadian-restricted prednisone intermittence in a recent pilot clinical trial in patients with genetic myopathies. However, mechanisms to support significance of these effects for metabolic diseases and aging remain unknown. We studied 12-week-long intermittent regimens of the exogenous GC prednisone in mice in conditions of diet-induced obesity or advanced aging, comparing dosing at light-phase start (ZT0) versus dark-phase start (ZT12). We found that, compared to dark-phase, light-phase dosing enhanced the regimen-driven increase in body-wide lean mass, muscle mass and muscle function in both obese and aged mice. Intriguingly, experiments with adiponectin-knockout mice showed that these effects were dependent on adiponectin, which promotes muscle insulin sensitivity. We then used tissue-specific inducible knockout models to dissect non-muscle versus muscle-autonomous effects of GC chrono-pharmacology. We found that the GC effects on total and high-molecular-weight adiponectin upregulation were dependent on regimen-specific engagement of the adipocyte-specific GR on the adiponectin gene promoter. Complementary to adipose-driven adiponectin production, we found that adiponectin receptor AdipoR1 upregulation in muscle depended on circadian-specific engagement of the myocyte-specific GR on the AdipoR1 promoter. Consistent with the adiponectin action on muscle insulin sensitivity, ablation of myocyte-specific GR blocked the regimen-driven effects on insulin-sensitive muscle glucose uptake and muscle mass. Furthermore, we found that light-phase GC dosing engaged the muscle GR for a non-canonical interaction with the clock factor BMAL1 to upregulate the mitochondrial regulator PGC1alpha. Indeed, we found that the regimen-driven increase in glucose oxidation and amino acid biogenesis from TCA cycle intermediates in muscle was dependent on the myocyte-specific PGC1alpha. In summary, we present here novel circadian and molecular mechanisms reconverting glucocorticoid drugs from deleterious to re-energizing agents for potential chrono-treatment of metabolic conditions and aging. Presentation: Sunday, June 18, 2023

Faktor-Faktor yang Berhubungan dengan Kejadian Diabetes Melitus (DM) di Desa Kubah Sentang Kecamatan Pantai Labu

Analyze the risk factors associated with the incidence of Diabetes Mellitus in the village of Kubah Sentang, Pantai Labu subdistrict. This type of research is quantitative descriptive with a cross sectional research design. The sample in this study were all respondents who were diagnosed with Diabetes Mellitus. Consists of a case sample of 30 people. The factors associated with the incidence of diabetes mellitus are gender, education and hypertension with the incidence of Diabetes Mellitus in residents in the village of Kubah Sentang, Pantai Labu District. The factors that are not related to the incidence of diabetes mellitus are smoking and obesity which have no association with the incidence of DM in the village of Dome Sentang. Occupational status and physical relationships are factors that can affect the risk of diabetes mellitus in Kubah Sentang Village, Pantai Labu District. Physical activity such as exercise is an important part of health in terms of disease prevention. Exercise habits do not greatly affect the decrease in blood sugar but can increase glucose oxidation which can reduce insulin in people with diabetes mellitus. Good exercise will be useful in regulating blood glucose levels in people with diabetes mellitus which will affect the control of blood sugar levels.

Metabolic Approaches for the Treatment of Dilated Cardiomyopathy.

In dilated cardiomyopathy (DCM), where the heart muscle becomes stretched and thin, heart failure (HF) occurs, and the cardiomyocytes suffer from an energetic inefficiency caused by an abnormal cardiac metabolism. Although underappreciated as a potential therapeutic target, the optimal metabolic milieu of a failing heart is still largely unknown and subject to debate. Because glucose naturally has a lower P/O ratio (the ATP yield per oxygen atom), the previous studies using this strategy to increase glucose oxidation have produced some intriguing findings. In reality, the vast majority of small-scale pilot trials using trimetazidine, ranolazine, perhexiline, and etomoxir have demonstrated enhanced left ventricular (LV) function and, in some circumstances, myocardial energetics in chronic ischemic and non-ischemic HF with a reduced ejection fraction (EF). However, for unidentified reasons, none of these drugs has ever been tested in a clinical trial of sufficient size. Other pilot studies came to the conclusion that because the heart in severe dilated cardiomyopathy appears to be metabolically flexible and not limited by oxygen, the current rationale for increasing glucose oxidation as a therapeutic target is contradicted and increasing fatty acid oxidation is supported. As a result, treating metabolic dysfunction in HF may benefit from raising ketone body levels. Interestingly, treatment with sodium-glucose cotransporter-2 inhibitors (SGLT2i) improves cardiac function and outcomes in HF patients with or without type 2 diabetes mellitus (T2DM) through a variety of pleiotropic effects, such as elevated ketone body levels. The improvement in overall cardiac function seen in patients receiving SGLT2i could be explained by this increase, which appears to be a reflection of an adaptive process that optimizes cardiac energy metabolism. This review aims to identify the best metabolic therapeutic approach for DCM patients, to examine the drugs that directly affect cardiac metabolism, and to outline all the potential ancillary metabolic effects of the guideline-directed medical therapy. In addition, a special focus is placed on SGLT2i, which were first studied and prescribed to diabetic patients before being successfully incorporated into the pharmacological arsenal for HF patients.

1674-P: Increased Glucose Uptake in Brown Fat Promotes Energy Expenditure

Brown and beige fat dissipate energy as heat in response to β3-adrenergic receptor (β3AR) stimulation. Strategies to facilitate this response may be employed to promote weight loss and improve health in patients with metabolic disease. Previously, we discovered that GTPase RalA and its GAP complex RalGAP regulate exocytosis of glucose transporter GLUT4. We demonstrated in vivo, that adipose-tissue specific knockout of RalGAP subunit RalGAPB activates RalA and increases glucose uptake 7 times in brown fat (BAT), leading to improved glucose handling on high fat diet (HFD). Here we seek to test the effect of increased glucose uptake in BAT on energy expenditure (EE), using mice with BAT-specific knockout of RalGAPB (the KO mice). After 8 weeks on 45% HFD, the KO mice and control littermates (Ctr) were injected with β3AR agonist CL-316,243 (CL) or PBS for 8 days. Mice assigned to CL were placed in metabolic cages. Respiratory quotient was increased in the KO mice, indicating increased glucose oxidation (likely by BAT, due to increased glucose uptake). EE at room temperature was elevated in the KO mice. This was compensated by increased food uptake, explaining similar body weights between the KO and Ctr mice. CL injections, as expected, induced spikes in EE. Acute response to CL (arbitrarily defined as EE during 2 hours after CL injection) was consistent between daily CL injections in Ctr mice, and was increased twice in the KO mice compared to Ctr. In Ctr mice, 1st CL injection increased average day and night EE; this response gradually declined with consecutive CL injections. In the KO mice, 1st CL injection elicited similar to Ctr mice increase in average day and night EE; and the response to consecutive CL injections was preserved. As anticipated, CL reduced adiposity in Ctr mice, which was further augmented in the KO mice, consistent with finding on EE. We will further test the role of increased glucose uptake by BAT in EE of the KO mice, and will determine the mechanism of sustained CL responsiveness in the KO mice. Disclosure F.Rezayat: None. J.A.Resnick: None. I.M.Farah: None. Y.Skorobogatko: None. A.Saltiel: Board Member; Elgia Therapeutics. Funding National Institutes of Health (P30DK063491)

Abstract B002: Lactate metabolism regulates chromatin accessibility and prostate luminal differentiation

Abstract Lineage transitions are a central feature of prostate development, tumorigenesis and treatment resistance. While epigenetic changes drive prostate lineage transitions, whether upstream metabolic signaling modulates prostate lineage identity remains unclear. Investigations into prostate metabolism are focused primarily on targeting energy metabolism without considering how altering metabolism may influence epigenetic state or cellular differentiation. To understand the relationship between metabolism and prostate lineage identity, we developed an approach to perform metabolic profiling and nutrient tracing on primary prostate epithelial cells and demonstrated that basal and luminal cells exhibit distinct metabolic features. Furthermore, we show that basal to luminal differentiation in vivo and in three-dimensional ex vivo culture is accompanied by metabolic changes consistent with increased glucose oxidation. Using genetic and pharmacological approaches, we identify the mitochondrial pyruvate carrier (MPC) as a regulator of prostate luminal identity in benign and prostate cancer cells. Low MPC expression is inversely correlated with luminal differentiation and associated with poor response to androgen receptor inhibition in clinical prostate cancer. Mechanistically, our results suggest that MPC inhibition likely impairs luminal differentiation through accumulation of intracellular lactate. Increasing intracellular lactate levels is sufficient to alter chromatin accessibility at lineage-specific genes and impair luminal differentiation in prostate epithelial cells. These findings indicate that upstream metabolism is a regulator of chromatin accessibility and prostate lineage differentiation, suggesting that alterations in tumor metabolism may contribute to lineage plasticity and resistance to androgen receptor blockade in prostate cancer. Citation Format: Andrew S. Goldstein, Jenna M. Giafaglione, Preston D. Crowell. Lactate metabolism regulates chromatin accessibility and prostate luminal differentiation [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B002.

Retained Metabolic Flexibility of the Failing Human Heart.

The failing heart is traditionally described as metabolically inflexible and oxygen starved, causing energetic deficit and contractile dysfunction. Current metabolic modulator therapies aim to increase glucose oxidation to increase oxygen efficiency of adenosine triphosphate production, with mixed results. To investigate metabolic flexibility and oxygen delivery in the failing heart, 20 patients with nonischemic heart failure with reduced ejection fraction (left ventricular ejection fraction 34.9±9.1) underwent separate infusions of insulin+glucose infusion (I+G) or Intralipid infusion. We used cardiovascular magnetic resonance to assess cardiac function and measured energetics using phosphorus-31 magnetic resonance spectroscopy. To investigate the effects of these infusions on cardiac substrate use, function, and myocardial oxygen uptake (MVo2), invasive arteriovenous sampling and pressure-volume loops were performed (n=9). At rest, we found that the heart had considerable metabolic flexibility. During I+G, cardiac glucose uptake and oxidation were predominant (70±14% total energy substrate for adenosine triphosphate production versus 17±16% for Intralipid; P=0.002); however, no change in cardiac function was seen relative to basal conditions. In contrast, during Intralipid infusion, cardiac long-chain fatty acid (LCFA) delivery, uptake, LCFA acylcarnitine production, and fatty acid oxidation were all increased (LCFA 73±17% of total substrate versus 19±26% total during I+G; P=0.009). Myocardial energetics were better with Intralipid compared with I+G (phosphocreatine/adenosine triphosphate 1.86±0.25 versus 2.01±0.33; P=0.02), and systolic and diastolic function were improved (LVEF 34.9±9.1 baseline, 33.7±8.2 I+G, 39.9±9.3 Intralipid; P<0.001). During increased cardiac workload, LCFA uptake and oxidation were again increased during both infusions. There was no evidence of systolic dysfunction or lactate efflux at 65% maximal heart rate, suggesting that a metabolic switch to fat did not cause clinically meaningful ischemic metabolism. Our findings show that even in nonischemic heart failure with reduced ejection fraction with severely impaired systolic function, significant cardiac metabolic flexibility is retained, including the ability to alter substrate use to match both arterial supply and changes in workload. Increasing LCFA uptake and oxidation is associated with improved myocardial energetics and contractility. Together, these findings challenge aspects of the rationale underlying existing metabolic therapies for heart failure and suggest that strategies promoting fatty acid oxidation may form the basis for future therapies.

Temporal changes in glucose metabolism reflect polarization in resident and monocyte-derived macrophages after myocardial infarction.

Metabolic reprogramming from glycolysis to the mitochondrial tricarboxylic acid (TCA) cycle and oxidative phosphorylation may mediate macrophage polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype. We hypothesized that changes in cardiac macrophage glucose metabolism would reflect polarization status after myocardial infarction (MI), ranging from the early inflammatory phase to the later wound healing phase. MI was induced by permanent ligation of the left coronary artery in adult male C57BL/6J mice for 1 (D1), 3 (D3), or 7 (D7) days. Infarct macrophages were subjected to metabolic flux analysis or gene expression analysis. Monocyte versus resident cardiac macrophage metabolism was assessed using mice lacking the Ccr2 gene (CCR2 KO). By flow cytometry and RT-PCR, D1 macrophages exhibited an M1 phenotype while D7 macrophages exhibited an M2 phenotype. Macrophage glycolysis (extracellular acidification rate) was increased at D1 and D3, returning to basal levels at D7. Glucose oxidation (oxygen consumption rate) was decreased at D3, returning to basal levels at D7. At D1, glycolytic genes were elevated (Gapdh, Ldha, Pkm2), while TCA cycle genes were elevated at D3 (Idh1 and Idh2) and D7 (Pdha1, Idh1/2, Sdha/b). Surprisingly, Slc2a1 and Hk1/2 were increased at D7, as well as pentose phosphate pathway (PPP) genes (G6pdx, G6pd2, Pgd, Rpia, Taldo1), indicating increased PPP activity. Macrophages from CCR2 KO mice showed decreased glycolysis and increased glucose oxidation at D3, and decreases in Ldha and Pkm2 expression. Administration of dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, robustly decreased pyruvate dehydrogenase phosphorylation in the non-infarcted remote zone, but did not affect macrophage phenotype or metabolism in the infarct zone. Our results indicate that changes in glucose metabolism and the PPP underlie macrophage polarization following MI, and that metabolic reprogramming is a key feature of monocyte-derived but not resident macrophages.

Mapping the metabolic reprogramming induced by sodium-glucose cotransporter 2 inhibition.

Diabetes is associated with increased risk for kidney disease, heart failure, and mortality. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) prevent these adverse outcomes; however, the mechanisms involved are not clear. We generated a roadmap of the metabolic alterations that occur in different organs in diabetes and in response to SGLT2i. In vivo metabolic labeling with 13C-glucose in normoglycemic and diabetic mice treated with or without dapagliflozin, followed by metabolomics and metabolic flux analyses, showed that, in diabetes, glycolysis and glucose oxidation are impaired in the kidney, liver, and heart. Treatment with dapagliflozin failed to rescue glycolysis. SGLT2 inhibition increased glucose oxidation in all organs; in the kidney, this was associated with modulation of the redox state. Diabetes was associated with altered methionine cycle metabolism, evident by decreased betaine and methionine levels, whereas treatment with SGLT2i increased hepatic betaine along with decreased homocysteine levels. mTORC1 activity was inhibited by SGLT2i along with stimulation of AMPK in both normoglycemic and diabetic animals, possibly explaining the protective effects against kidney, liver, and heart diseases. Collectively, our findings suggest that SGLT2i induces metabolic reprogramming orchestrated by AMPK-mTORC1 signaling with common and distinct effects in various tissues, with implications for diabetes and aging.

Role of Stearoyl-CoA Desaturase 1 in Cardiovascular Physiology.

Stearoyl-CoA desaturase is a rate-limiting enzyme in the synthesis of monounsaturated fatty acids. Monounsaturated fatty acids limit the toxicity of exogenous saturated fats. Studies have shown that stearoyl-CoA desaturase 1 is involved in the remodeling of cardiac metabolism. The loss of stearoyl-CoA desaturase 1 reduces fatty acid oxidation and increases glucose oxidation in the heart. Such a change is protective under conditions of a high-fat diet, which reduces reactive oxygen species-generating β-oxidation. In contrast, stearoyl-CoA desaturase 1 deficiency predisposes individuals to atherosclerosis under conditions of hyperlipidemia but protects against apnea-induced atherosclerosis. Stearoyl-CoA desaturase 1 deficiency also impairs angiogenesis after myocardial infarction. Clinical data show a positive correlation between blood stearoyl-CoA Δ-9 desaturation rates and cardiovascular disease and mortality. Moreover, stearoyl-CoA desaturase inhibition is considered an attractive intervention in some obesity-associated pathologies, and the importance of stearoyl-CoA desaturase in the cardiovascular system might be a limitation for developing such therapy. This review discusses the role of stearoyl-CoA desaturase 1 in the regulation of cardiovascular homeostasis and the development of heart disease and presents markers of systemic stearoyl-CoA desaturase activity and their predictive potential in the diagnosis of cardiovascular disorders.

Rg3 regulates myocardial pyruvate metabolism via P300-mediated dihydrolipoamide dehydrogenase 2-hydroxyisobutyrylation in TAC-induced cardiac hypertrophy

The failing heart is characterized by an increase in glucose uptake and glycolytic rates that is not accompanied by a concomitant increase in glucose oxidation. Lower coupling of glucose oxidation to glycolysis possibly owes to unchanged or reduced pyruvate oxidation in mitochondria. Therefore, increasing pyruvate oxidation may lead to new therapies for heart disease. Dihydrolipoamide dehydrogenase (DLD) is a component of the pyruvate dehydrogenase complex (PDH). DLD mutations or defects are closely associated with metabolic diseases. However, few studies explore the effects of DLD mutants or acylation status on PDH activity and pyruvate metabolism. P300 is protein 2-hydroxyisobutyryltransferases in cells, and P300-dependent lysine 2-hydroxyisobutyrylation of glycolytic enzymes affects glucose metabolism. However, there are no relevant reports on the effect of 2-hydroxyisobutyrylation on the energy metabolism of heart failure, and it is worth further in-depth study. In this study, we showed that 2-hydroxyisobutyrylation is an essential protein translational modification (PTM) that regulates the activity of pyruvate dehydrogenase complex (PDHc). In a mouse model of transverse aortic constriction (TAC)-induced cardiac hypertrophy, the 2-hydroxyisobutylation of DLD was significantly increased, related to the decrease in PDH activity. In addition, our data provide clear evidence that DLD is a direct substrate of P300. As one of the main active ingredients of ginseng, ginsenoside Rg3 (Rg3) can reduce the 2-hydroxyisobutylation levels of DLD and restore the PDH activity by inhibiting the acyltransferase activity of P300, thereby producing beneficial effects whenever the heart is injured. Therefore, this study suggests a novel strategy for reversing myocardial hypertrophy.

Energy metabolism in skeletal muscle cells from donors with different body mass index.

Obesity and physical inactivity have a profound impact on skeletal muscle metabolism. In the present work, we have investigated differences in protein expression and energy metabolism in primary human skeletal muscle cells established from lean donors (BMI<25kg/m2) and individuals with obesity (BMI>30kg/m2). Furthermore, we have studied the effect of fatty acid pretreatment on energy metabolism in myotubes from these donor groups. Alterations in protein expression were investigated using proteomic analysis, and energy metabolism was studied using radiolabeled substrates. Gene Ontology enrichment analysis showed that glycolytic, apoptotic, and hypoxia pathways were upregulated, whereas the pentose phosphate pathway was downregulated in myotubes from donors with obesity compared to myotubes from lean donors. Moreover, fatty acid, glucose, and amino acid uptake were increased in myotubes from individuals with obesity. However, fatty acid oxidation was reduced, glucose oxidation was increased in myotubes from subjects with obesity compared to cells from lean. Pretreatment of myotubes with palmitic acid (PA) or eicosapentaenoic acid (EPA) for 24h increased glucose oxidation and oleic acid uptake. EPA pretreatment increased the glucose and fatty acid uptake and reduced leucine fractional oxidation in myotubes from donors with obesity. In conclusion, these results suggest that myotubes from individuals with obesity showed increased fatty acid, glucose, and amino acid uptake compared to cells from lean donors. Furthermore, myotubes from individuals with obesity had reduced fatty acid oxidative capacity, increased glucose oxidation, and a higher glycolytic reserve capacity compared to cells from lean donors. Fatty acid pretreatment enhances glucose metabolism, and EPA reduces oleic acid and leucine fractional oxidation in myotubes from donor with obesity, suggesting increased metabolic flexibility after EPA treatment.

Targeting T cell (oxidative) metabolism to improve immunity to viral infection in the context of obesity.

Disorders of systemic metabolism can influence immunity. Individuals with obesity are known to have increased inflammation, increased risk to select autoimmune diseases, impaired response to several infections, and impaired vaccine response. For example, over the last decade, it has become clear that individuals with obesity have increased risk of morbidity and mortality from influenza infection. Unsurprisingly, this finding is also observed in the current COVID-19 pandemic: individuals with obesity, particularly severe obesity, have increased risk of poor outcomes from SARS-CoV-2 infection, including increased rates of hospitalization, ICU admission, mechanical ventilation, and death. Several studies have now demonstrated a critical role for T cells in the context of obesity-associated immune dysfunction in response to viral infection, and one mechanism for this may be altered T cell metabolism. Indeed, recent studies have shown that activated T cells from obese mice have an altered metabolic profile characterized by increased glucose oxidation, both in vitro and in vivo following viral infection. For that reason, treatments that target abnormal immune cell metabolism in obesity may improve outcomes to viral infection. To that end, several recent studies have shown that use of the metabolic drug, metformin, can reverse abnormal T cell metabolism and restore T cell immunity, as well as survival, in response to viral infection. These findings will be discussed in detail here.

Rosiglitazone Ameliorates Cardiac and Skeletal Muscle Dysfunction by Correction of Energetics in Huntington's Disease.

Huntington’s disease (HD) is a rare neurodegenerative disease that is accompanied by skeletal muscle atrophy and cardiomyopathy. Tissues affected by HD (central nervous system [CNS], skeletal muscle, and heart) are known to suffer from deteriorated cellular energy metabolism that manifests already at presymptomatic stages. This work aimed to test the effects of peroxisome proliferator-activated receptor (PPAR)-γ agonist—rosiglitazone on grip strength and heart function in an experimental HD model—on R6/1 mice and to address the mechanisms. We noted that rosiglitazone treatment lead to improvement of R6/1 mice grip strength and cardiac mechanical function. It was accompanied by an enhancement of the total adenine nucleotides pool, increased glucose oxidation, changes in mitochondrial number (indicated as increased citric synthase activity), and reduction in mitochondrial complex I activity. These metabolic changes were supported by increased total antioxidant status in HD mice injected with rosiglitazone. Correction of energy deficits with rosiglitazone was further indicated by decreased accumulation of nucleotide catabolites in HD mice serum. Thus, rosiglitazone treatment may not only delay neurodegeneration but also may ameliorate cardio- and myopathy linked to HD by improvement of cellular energetics.