Energetic Dysfunction Research Articles

NAD deficiency contributes to progressive kidney disease in HIV-nephropathy mice.

HIV disease remains prevalent in the United States and is particularly prevalent in sub-Saharan Africa. Recent investigations revealed that mitochondrial dysfunction in kidney contributes to HIV-associated nephropathy (HIVAN) in Tg26 transgenic mice. We hypothesized that nicotinamide adenine dinucleotide (NAD) deficiency contributes to energetic dysfunction and progressive tubular injury. We investigated metabolomic mechanisms of HIVAN tubulopathy. Tg26 and wild-type (WT) mice were treated with the farnesoid X receptor (FXR) agonist INT-747 or nicotinamide riboside (NR) from 6 to 12 wk of age. Multiomic approaches were used to characterize kidney tissue transcriptomes and metabolomes. Treatment with INT-747 or NR ameliorated kidney tubular injury, as shown by serum creatinine, the tubular injury marker urinary neutrophil-associated lipocalin, and tubular morphometry. Integrated analysis of metabolomic and transcriptomic measurements showed that NAD levels and production were globally downregulated in Tg26 mouse kidneys, especially nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway. Furthermore, NAD-dependent deacetylase sirtuin3 activity and mitochondrial oxidative phosphorylation activity were lower in ex vivo proximal tubules from Tg26 mouse kidneys compared with those of WT mice. Restoration of NAD levels in the kidney improved these abnormalities. These data suggest that NAD deficiency might be a treatable target for HIVAN.NEW & NOTEWORTHY The study describes a novel investigation that identified nicotinamide adenine dinucleotide (NAD) deficiency in a widely used HIV-associated nephropathy (HIVAN) transgenic mouse model. We show that INT-747, a farnesoid X receptor agonist, and nicotinamide riboside (NR), a precursor of nicotinamide, each ameliorated HIVAN tubulopathy. Multiomic analysis of mouse kidneys revealed that NAD deficiency was an upstream metabolomic mechanism contributing to HIVAN tubulopathy.

Genetic drivers of human plasma metabolites that determine mortality in heart failure patients with reduced ejection fraction.

Heart failure with reduced ejection fraction (HFrEF) remains a significant public health issue, with the disease advancing despite neurohormonal antagonism. Energetic dysfunction is a likely contributor to residual disease progression, and we have previously reported a strong association of plasma metabolite profiles with survival among patients with HFrEF. However, the genetic and biologic mechanisms that underlie the metabolite-survival association in HFrEF were uncertain. We performed genetic mapping of the key metabolite parameters, followed by mediation analyses of metabolites and genotypes on survival, and genetic pathway analyses. Patients with HFrEF (n = 1,003) in the Henry Ford Pharmacogenomic Registry (HFPGR; 500 self-reported Black/African race patients [AA], 503 self-reported White/European race patients [EA], and 249 deaths over a median of 2.7 years) with genome-wide genotyping and targeted metabolomic profiling of plasma were included. We tested genome-wide association (GWA) of single nucleotide polymorphisms (SNPs) with the prognostic metabolite profile (PMP) and its components; first stratified by race, and then combined via meta-analysis for the entire cohort. Seven independent loci were identified as GWA significant hits in AA patients (3 for PMP and 4 for individual metabolites), one of which was also significant in the entire cohort (rs944469). No genome wide significant hits were found in White/EA patients. Among these SNPs, only rs35792152, (a hit for 3.HBA) tended to be associated with mortality in standard survival analysis (HR = 1.436, p = 0.052). The mediation analyses indicated several significant associations between SNPs, metabolites, and mortality in AA patients. Functional annotation mapping (FUMA) implicated inflammation, DNA metabolic, and mRNA splicing processes. GWAS of key metabolites and survival along with FUMA pathway analysis revealed new candidate genes which unveiled molecular pathways that contribute to HF disease progression via metabolic and energetic abnormalities.

Energetic dysfunction and iron overload in early Parkinson's disease: Two distinct mechanisms?

IntroductionIdentifying biomarkers reflecting cellular dysfunctions in early Parkinson's disease patients (ePD) is needed to develop targeted therapeutic strategies. We aimed to determine if cellular energetic dysfunction related to increased brain sodium concentration would be co-located to microstructural alterations and iron deposition in ePD. MethodsWe prospectively included 12 ePD (mean disease duration 20.0 ± 10.2 months) and 13 healthy controls (HC), scanned with a 7 T 1H and 23Na MRI. Complementary voxel-based and region-based assessments were performed, the latter utilizing a high-resolution multimodal template we created (combining quantitative T1 maps (qT1), transverse relaxation rate (R2*), quantitative magnetic susceptibility mapping (QSM) images) from 200 subjects. This template allowed a precise multiparametric assessment of sodium concentration, QSM, R2*, qT1, mean diffusivity, and fractional anisotropy values. A two-sided p-value<0.05 was considered statistically significant after the Bonferroni correction. ResultsRelative to HC, ePD showed significantly higher sodium concentration in left Substantia nigra (SN) pars reticulata (46.13 mM ± 3.52 vs 38.60 mM ± 6.10, p = 0.038), a subpart of the SN pars compacta (SNc) and ventral tegmental area, Putamen, Globus Pallidum external, accumbens nucleus and claustrum. Significantly increased QSM and R2* values, and decreased T1 values, were limited to the Nigrosomes 1 (Nig) and right SNc (all p < 0.05). QSM values in the Nig were significantly correlated to UPDRS-III scores (r = 0.91,p < 0.001). ConclusionIn ePD, brain sodium accumulation was broad and dissociated from iron accumulation. As with iron accumulation, a sodium-related pathophysiological approach could lead to identifying potential new therapeutic agents and deserves further investigation.

Potential Mechanisms of the Protective Effects of the Cardiometabolic Drugs Type-2 Sodium-Glucose Transporter Inhibitors and Glucagon-like Peptide-1 Receptor Agonists in Heart Failure.

Different multifactorial pathophysiological processes are involved in the development of heart failure (HF), including neurohormonal dysfunction, the hypertrophy of cardiomyocytes, interstitial fibrosis, microvascular endothelial inflammation, pro-thrombotic states, oxidative stress, decreased nitric oxide (NO) bioavailability, energetic dysfunction, epicardial coronary artery lesions, coronary microvascular rarefaction and, finally, cardiac remodeling. While different pharmacological strategies have shown significant cardiovascular benefits in HF with reduced ejection fraction (HFrEF), there is a residual unmet need to fill the gap in terms of knowledge of mechanisms and efficacy in the outcomes of neurohormonal agents in HF with preserved ejection fraction (HFpEF). Recently, type-2 sodium-glucose transporter inhibitors (SGLT2i) have been shown to contribute to a significant reduction in the composite outcome of HF hospitalizations and cardiovascular mortality across the entire spectrum of ejection fraction. Moreover, glucagon-like peptide-1 receptor agonists (GLP1-RA) have demonstrated significant benefits in patients with high cardiovascular risk, excess body weight or obesity and HF, in particular HFpEF. In this review, we will discuss the biological pathways potentially involved in the action of SGLT2i and GLP1-RA, which may explain their effective roles in the treatment of HF, as well as the potential implications of the use of these agents, also in combination therapies with neurohormonal agents, in the clinical practice.

Maternal environmental enrichment protects neonatal brains from hypoxic-ischemic challenge by mitigating brain energetic dysfunction and modulating glial cell responses

There is evidence that maternal milieu and changes in environmental factors during the prenatal period may exert a lasting impact on the brain health of the newborn, even in case of neonatal brain hypoxia-ischemia (HI). The present study aimed to investigate the effects of maternal environmental enrichment (EE) on HI-induced energetic and metabolic failure, along with subsequent neural cell responses in the early postnatal period. Male Wistar pups born to dams exposed to maternal EE or standard conditions (SC) were randomly divided into Sham-SC, HI-SC, Sham-EE, and HI-EE groups. Neonatal HI was induced on postnatal day (PND) 3. The Na+,K+-ATPase activity, mitochondrial function and neuroinflammatory related-proteins were assessed at 24 h and 48 h after HI. MicroPET-FDG scans were used to measure glucose uptake at three time points: 24 h post-HI, PND18, and PND24. Moreover, neuronal preservation and glial cell responses were evaluated at PND18. After HI, animals exposed to maternal EE showed an increase in Na+,K+-ATPase activity, preservation of mitochondrial potential/mass ratio, and a reduction in mitochondrial swelling. Glucose uptake was preserved in HI-EE animals from PND18 onwards. Maternal EE attenuated HI-induced cell degeneration, white matter injury, and reduced astrocyte immunofluorescence. Moreover, the HI-EE group exhibited elevated levels of IL-10 and a reduction in Iba-1 positive cells. Data suggested that the regulation of AKT/ERK1/2 signaling pathways could be involved in the effects of maternal EE. This study evidenced that antenatal environmental stimuli could promote bioenergetic and neural resilience in the offspring against early HI damage, supporting the translational value of pregnancy-focused environmental treatments.

Abstract 15515: SGLT2 Inhibitor Empagliflozin Increases Fatty Acid Oxidation, Coupling Between Glycolysis and Glucose Oxidation, and Decreases Left Ventricular Hypertrophy in Mice With Hypertrophic Cardiomyopathy Due to Myosin R403Q Mutation

Background: A metabolic switch from fatty acid oxidation (FAO) to glycolysis associates with LV hypertrophy (LVH). Glucagon signaling increases FAO in the heart and sodium-glucose co-transporter 2 inhibitors (SGLT2i) raise glucagon/insulin ratio (GIR) in patients. We have shown that SGLT2i reprogram cardiac metabolic genes favoring FAO, yet the mechanism is unknown. Hypothesis: SGLT2i increases GIR, thereby increasing FAO and glycolysis/glucose oxidation coupling (GGC), which in turn attenuates LVH and fibrosis in a murine model of HCM (R403Q myosin mutation). Methods: Mice 9 weeks of age were treated ± SGLT2i empagliflozin (EMPA, 0.15 mg/g chow). After 2 weeks, prior to LVH onset, myocardial transcriptomic analysis was performed. After 16 weeks, echocardiography, proteomics, fasted GIR, and histology were obtained. Glucose fluxes, energetics and 13 C substrate oxidation were measured in isolated beating hearts by 31 P and 13 C NMR spectroscopy. Results: R403Q mice had ↓GIR which was normalized by EMPA. Transcriptomics (2 weeks) and proteomics (16 weeks) confirmed downregulation of electron transport and FAO pathways, and upregulation of LVH and fibrosis pathways. At 16 weeks, R403Q hearts exhibited LVH, fibrosis, ↓diastolic function and ↓contractile reserve (rate pressure product increase between low and high workload). Metabolically, R403Q had ↑glucose uptake and ↓GGC with ↑lactate production; ↓FAO and impaired energetics (↓free energy of ATP hydrolysis, ΔG ~ATP , at both workloads). The HCM phenotype and all measures of metabolic dysfunction were partially or completely prevented by EMPA. Conclusion: R403Q hearts display marked metabolic reprogramming that appears early in the disease process and leads to energetic dysfunction. SGLT2i corrects GIR, attenuates metabolic reprogramming and the energetic, structural and functional features of HCM. SGLT2i and possibly other measures to modulate glucagon signaling hold therapeutic potential in HCM.

Genistein alleviates chronic heat stress-induced lipid metabolism disorder and mitochondrial energetic dysfunction by activating the GPR30-AMPK-PGC-1α signaling pathways in the livers of broiler chickens

The objective of this study was to investigate the preventive effects and mechanisms of genistein (GEN) on production performance and metabolic disorders in broilers under chronic heat stress (HS). A total of 120 male three-week-old Ross broilers were randomly assigned to 5 groups: a thermoneutral zone (TN) group maintained at normal temperature (21 ± 1°C daily), an HS group subjected to cyclic high temperature (32 ± 1°C for 8 h daily), and three groups exposed to HS with varying doses of GEN (50, 100, or 150 mg/kg diet). The experimental period lasted for three weeks. Here, HS led to a decline in growth performance parameters and hormone secretion disorders (P < 0.05), which were improved by 100 and 150 mg/kg GEN treatment (P < 0.05). Moreover, the HS-induced increases in the liver index (P < 0.01) and abdominal fat rate (P < 0.05) were attenuated by 150 mg/kg GEN (P < 0.05). The HS-induced excessive lipid accumulation in the liver and serum (P < 0.01) was ameliorated after 100 and 150 mg/kg GEN treatment (P < 0.05). Furthermore, the HS-induced decreases in lipolysis-related mRNA levels and increases in lipid synthesis-related mRNA levels in the liver (P < 0.01) were effectively blunted after 100 and 150 mg/kg GEN treatment (P < 0.05). Importantly, the HS-stimulated hepatic mitochondrial energetic dysfunction and decreases in the mRNA or protein levels of peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A in the liver were ameliorated by 150 mg/kg GEN (P < 0.05). Moreover, 50-150 mg/kg GEN treatment resulted in a significant increase in the mRNA or protein levels of G protein-coupled estrogen receptor (GPR30), AMP-activated protein kinase (AMPK) α1, phosphorylated AMPKα, and phosphorylated acetyl-CoA carboxylase α. Collectively, GEN alleviated metabolic disorders and hepatic mitochondrial energetic dysfunction under HS, possibly through the activation of GPR30-AMPM-PGC-1α pathways. These data provide a sufficient basis for GEN as an additive to alleviate HS in broilers.

Developmental changes in cerebral NAD and neuroenergetics of an antioxidant compromised mouse model of schizophrenia

Defects in essential metabolic regulation for energy supply, increased oxidative stress promoting excitatory/inhibitory imbalance and phospholipid membrane dysfunction have been implicated in the pathophysiology of schizophrenia (SZ). The knowledge about the developmental trajectory of these key pathophysiological components and their interplay is important to develop new preventive and treatment strategies. However, this assertion is so far limited. To investigate the developmental regulations of these key components in the brain, we assessed, for the first time, in vivo redox state from the oxidized (NAD+) and reduced (NADH) form of Nicotinamide Adenine Dinucleotide (NAD), energy and membrane metabolites, inhibitory and excitatory neurotransmitters by 31P and 1H MRS during the neurodevelopment of an SZ animal model with genetically compromised glutathione synthesis (gclm-KO mice). When compared to age-matched wild type (WT), an increase in NAD+/NADH redox ratio was found in gclm-KO mice until early adulthood, followed by a decrease in full adults as observed in patients. Especially, in early postnatal life (P20, corresponding to childhood), levels of several metabolites were altered in gclm-KO mice, including NAD+, NAD+/NADH, ATP, and glutamine + glutamate, suggesting an interactive compensation for redox dysregulation between NAD, energy metabolism, and neurotransmission. The identified temporal neurometabolic regulations under deficits in redox regulation provide insights into preventive treatment targets for at-risk individuals, and other neurodevelopmental disorders involving oxidative stress and energetic dysfunction.

The role of purine nucleotide metabolism in cardiac failure

Normal cardiac function requires ATP to be synthesized at a sufficient rate to drive the molecular processes underlying electromechanical coupling. Myocardial metabolic dysfunction observed during heart failure leads to reductions in the chemical potential at which ATP is synthesized. We have observed reductions in oxidative capacity, and total adenine nucleotide (TAN) levels in a rat aortic constriction (TAC) induced heart failure model that parallel changes seen in large mammal models and humans with heart failure. Computer simulations of cardiac mechano-energetics also predict a marked increase in inorganic phosphate levels in diseased hearts compared to healthy control hearts. Furthermore, simulations predict that restoring the impaired energetic dysfunction of TAC rats improves systolic function. Metabolomic and proteomic analysis reveal increases in purine degradation by-products and AMP deaminase 3 (AMPD3) levels in failing versus control hearts. AMPD activity has been hypothesized to play a role in skeletal muscle in type 2 diabetes, however, there is still a need to decern the role, if any, of AMPD3 in the heart and in failure. A cardiac ventricle specific AMPD3 conditional knock out (cKO) rat model was developed to test the hypothesis that decreasing AMPD3 activity in the failing heart will lead to a preservation of TAN and improvement in cardiac mechanical function. Cardiac hypertrophy and decomposition were induced by placing a clip (TAC) in three-week old female and male rats. In the cKO model, AMPD3 exon 6 is flanked by loxP sites, and are either heterozygous for cre recombinase driven by the cardiac myosin light chain promoter (cre+/-) or lack the cre enzyme (cre-/-). Tamoxifen was administered to all rats both pre-surgery and post-surgery to induce AMPD3 knock down. Echocardiography was performed at 2- and 18-weeks post-surgery. At 18 weeks post-surgery, hearts were harvested for mitochondrial capacity, metabolite measurements, AMPD activity, and protein and mRNA measurements. Knock down efficiency in cre +/- animals compared to cre -/- was assessed based on enzyme activity, mRNA expression, and protein abundance. There is a 45% decrease in total AMPD activity in the AMPD3 cKO rats, where measured AMPD activity reflects the sum activity of all present AMPD isoforms. Additionally, there is 52% decrease in protein abundance and a 72% reduction in AMPD3 mRNA expression. Preliminary observations reveal significant differences in oxidative capacity and in cardiac function between TAC and sham rats, consistent with the hypothesis that knock down of AMDP3, an enzyme that is upregulated during TAC induced heart failure in rodents, results in preservation of myocardial nucleotide pools and improve cardiac mechanical function. Research is supported by the NIH grants HL144657 and F31-HL154605 (RL). We are grateful for support from the post-baccalaureate research program (2R25GM086262-09), the Systems and Integrative Biology (T32-GM008322) training grant and the Cardiovascular Research and Entrepreneurship training grant (T32-HL125242) and the University of Michigan Rackham Merit Fellowship. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

ATP and NAD+ Deficiency in Parkinson’s Disease

The goal of this study is to identify a signature of bioenergetic and functional markers in the muscles of individuals with Parkinson's disease (PD). Quantitative physiological properties of in vivo hand muscle (FDI, first dorsal interosseus) and leg muscle (TA, Tibialis Anterior) of older individuals with PD were compared to historical age/gender-matched controls (N = 30). Magnetic resonance spectroscopy and imaging (MRS) were used to assess in vivo mitochondrial and cell energetic dysfunction, including maximum mitochondrial ATP production (ATPmax), NAD concentrations linked to energy/stress pathways, and muscle size. Muscle function was measured via a single muscle fatigue test. TA ATPmax and NAD levels were significantly lower in the PD cohort compared to controls (ATPmax: 0.66 mM/s ± 0.03 vs. 0.76 ± 0.02; NAD: 0.75 mM ± 0.05 vs. 0.91 ± 0.04). Muscle endurance and specific force were also lower in both hand and leg muscles in the PD subjects. Exploratory analyses of mitochondrial markers and individual symptoms suggested that higher ATPmax was associated with a greater sense of motivation and engagement and less REM sleep behavior disorder (RBD). ATPmax was not associated with clinical severity or individual symptom(s), years since diagnosis, or quality of life. Results from this pilot study contribute to a growing body of evidence that PD is not a brain disease, but a systemic metabolic syndrome with disrupted cellular energetics and function in peripheral tissues. The significant impairment of both mitochondrial ATP production and resting metabolite levels in the TA muscles of the PD patients suggests that skeletal muscle mitochondrial function may be an important tool for mechanistic understanding and clinical application in PD patients. This study looked at individuals with mid-stage PD; future research should evaluate whether the observed metabolic perturbations in muscle dysfunction occur in the early stages of the disease and whether they have value as theragnostic biomarkers.

In the failing human heart, energetic dysfunction and hypertrophy are promoted by mitochondrial calcium overload through upregulation of the mitochondrial calcium uniporter

In the failing human heart, energetic dysfunction and hypertrophy are promoted by mitochondrial calcium overload through upregulation of the mitochondrial calcium uniporter

The Impact of Short-Term Hyperoxia on Cerebral Metabolism: A Systematic Review and Meta-Analysis.

Cerebral ischemia due to hypoxia is a major cause of secondary brain injury and is associated with higher morbidity and mortality in patients with acute brain injury. Hyperoxia could improve energetic dysfunction in the brain in this setting. Our objectives were to perform a systematic review and meta-analysis of the current literature and to assess the impact of normobaric hyperoxia on brain metabolism by using cerebral microdialysis. We searched Medline and Scopus, following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement; we searched for retrospective and prospective observational studies, interventional studies, and randomized clinical trials that performed a hyperoxia challenge in patients with acute brain injury who were concomitantly monitored with cerebral microdialysis. This study was registered in PROSPERO (CRD420211295223). We included a total of 17 studies, with a total of 311 patients. A statistically significant reduction in cerebral lactate values (pooled standardized mean difference [SMD] - 0.38 [- 0.53 to - 0.23]) and lactate to pyruvate ratio values (pooled SMD - 0.20 [- 0.35 to - 0.05]) was observed after hyperoxia. However, glucose levels (pooled SMD - 0.08 [- 0.23 to 0.08]) remained unchanged after hyperoxia. Normobaric hyperoxia may improve cerebral metabolic disturbances in patients with acute brain injury. The clinical impact of such effects needs to be further elucidated.

Mitochondrial Calcium Overload Promotes Cell Hypertrophy And Energetic Dysfunction In Human Heart Failure.

Introduction Impairment of intracellular Ca2+ homeostasis and bioenergetics is a prominent feature of the failing heart, but the underlying metabolic perturbations are poorly understood. Mitochondrial calcium transport is mediated by the mitochondrial Ca2+ uniporter (MCU), and till now, the comprehension of its role in pathophysiology is limited by the complete lack of this molecular understanding. However, in light of the recent molecular identification of the MCU, new perspectives have been opened. Hypothesis In the failing human heart, increased energy demand triggers mitochondrial calcium overload through upregulation of the MCU, promoting energetic dysfunction. Methods Here, we measured the expression of MCU on failing human left ventricular tissue obtained at the time of orthotopic heart transplantation or left ventricular assist device (LVAD) insertion against non-failing heart tissue samples and after LVAD removal (post-LVAD). Moreover, we characterized the role of MCU in cardiac myoblast cells with reduced expression of MCU under angiotensin II-induced hypertrophy. In addition, mitochondrial function, mitochondrial biogenesis, and mitochondrial ROS production were assessed. T-Test and 1-way ANOVA were performed, N=3-27. This study followed all regulations and approvals from the Institutional Ethics Committee. Results Upregulated MCU (2.2 fold) was associated with poor prognosis in patients with HF. Moreover, the MCU expression positively correlated with the pathological remodeling in patients with HF, contrary to patients post-LVAD, where MCU expression decreases 40%. Furthermore, in cardiac myoblast cells, silencing MCU improved cell viability and prevents calcium retention capacity impairment when cells were insulted chronically with Angiotensin II (ANGII). Additionally, silencing MCU blocks the angiotensin II-dependent transversal hypertrophy and cell death. Mechanistically we found that this MCU-dependent anti-hypertrophic effect was mediated by preventing ANGII-induced mitochondrial ROS overproduction and the changes in the phosphorylation status of transcription factor A, preventing mitochondrial biogenesis and NFkB-dependent hypertrophic program. Conclusions Our findings suggest a novel insight for the mechanisms of energetic dysfunction and hypertrophy mediated by mitochondrial calcium and mitochondrial ROS production in Ca2+-mediated pathological remodeling that may provide a potential pharmacological target for heart failure. Impairment of intracellular Ca2+ homeostasis and bioenergetics is a prominent feature of the failing heart, but the underlying metabolic perturbations are poorly understood. Mitochondrial calcium transport is mediated by the mitochondrial Ca2+ uniporter (MCU), and till now, the comprehension of its role in pathophysiology is limited by the complete lack of this molecular understanding. However, in light of the recent molecular identification of the MCU, new perspectives have been opened. In the failing human heart, increased energy demand triggers mitochondrial calcium overload through upregulation of the MCU, promoting energetic dysfunction. Here, we measured the expression of MCU on failing human left ventricular tissue obtained at the time of orthotopic heart transplantation or left ventricular assist device (LVAD) insertion against non-failing heart tissue samples and after LVAD removal (post-LVAD). Moreover, we characterized the role of MCU in cardiac myoblast cells with reduced expression of MCU under angiotensin II-induced hypertrophy. In addition, mitochondrial function, mitochondrial biogenesis, and mitochondrial ROS production were assessed. T-Test and 1-way ANOVA were performed, N=3-27. This study followed all regulations and approvals from the Institutional Ethics Committee. Upregulated MCU (2.2 fold) was associated with poor prognosis in patients with HF. Moreover, the MCU expression positively correlated with the pathological remodeling in patients with HF, contrary to patients post-LVAD, where MCU expression decreases 40%. Furthermore, in cardiac myoblast cells, silencing MCU improved cell viability and prevents calcium retention capacity impairment when cells were insulted chronically with Angiotensin II (ANGII). Additionally, silencing MCU blocks the angiotensin II-dependent transversal hypertrophy and cell death. Mechanistically we found that this MCU-dependent anti-hypertrophic effect was mediated by preventing ANGII-induced mitochondrial ROS overproduction and the changes in the phosphorylation status of transcription factor A, preventing mitochondrial biogenesis and NFkB-dependent hypertrophic program. Our findings suggest a novel insight for the mechanisms of energetic dysfunction and hypertrophy mediated by mitochondrial calcium and mitochondrial ROS production in Ca2+-mediated pathological remodeling that may provide a potential pharmacological target for heart failure.

A Longitudinal 1H NMR-Based Metabolic Profile Analysis of Urine from Hospitalized Premature Newborns Receiving Enteral and Parenteral Nutrition.

Preterm newborns are extremely vulnerable to morbidities, complications, and death. Preterm birth is a global public health problem due to its socioeconomic burden. Nurturing preterm newborns is a critical medical issue because they have limited nutrient stores and it is difficult to establish enteral feeding, which leads to inadequate growth frequently associated with poor neurodevelopmental outcomes. Parenteral nutrition (PN) provides nutrients to preterm newborns, but its biochemical effects are not completely known. To study the effect of PN treatment on preterm newborns, an untargeted metabolomic 1H nuclear magnetic resonance (NMR) assay was performed on 107 urine samples from 34 hospitalized patients. Multivariate data (Principal Component Analysis, PCA, Orthogonal partial least squares discriminant analysis OPLS-DA, parallel factor analysis PARAFAC-2) and univariate analyses were used to identify the association of specific spectral data with different nutritional types (NTs) and gestational ages. Our results revealed changes in the metabolic profile related to the NT, with the tricarboxylic acid cycle and galactose metabolic pathways being the most impacted pathways. Low citrate and succinate levels, despite higher glucose relative urinary concentrations, seem to constitute the metabolic profile found in the studied critically ill preterm newborns who received PN, indicating an energetic dysfunction that must be taken into account for better nutritional management.

An Inducible and Vascular Smooth Muscle Cell-Specific Pink1 Knockout Induces Mitochondrial Energetic Dysfunction during Atherogenesis.

DNA damage and mitochondrial dysfunction are defining characteristics of aged vascular smooth muscle cells (VSMCs) found in atherosclerosis. Pink1 kinase regulates mitochondrial homeostasis and recycles dysfunctional organelles critical for maintaining energetic homeostasis. Here, we generated a new vascular-specific Pink1 knockout and assessed its effect on VSMC-dependent atherogenesis in vivo and VSMC energetic metabolism in vitro. A smooth muscle cell-specific and MHC-Cre-inducible flox’d Pink1f/f kinase knockout was made on a ROSA26+/0 and ApoE−/− C57Blk6/J background. Mice were high fat fed for 10 weeks and vasculature assessed for physiological and pathogical changes. Mitochondrial respiratory activity was then assessed in wild-type and knockout animals vessels and isolated cells for their reliance on oxidative and glycolytic metabolism. During atherogenesis, we find that Pink1 knockout affects development of plaque quality rather than plaque quantity by decreasing VSMC and extracellular matrix components, collagen and elastin. Pink1 protein is important in the wild-type VSMC response to metabolic stress and induced a compensatory increase in hexokinase II, which catalyses the first irreversible step in glycolysis. Pink1 appears to play an important role in VSMC energetics during atherogenesis but may also provide insight into the understanding of mitochondrial energetics in other diseases where the regulation of energetic switching between oxidative and glycolytic metabolism is found to be important.

Metabolic Classification and Intervention Opportunities for Tumor Energy Dysfunction.

A comprehensive view of cell metabolism provides a new vision of cancer, conceptualized as tissue with cellular-altered metabolism and energetic dysfunction, which can shed light on pathophysiological mechanisms. Cancer is now considered a heterogeneous ecosystem, formed by tumor cells and the microenvironment, which is molecularly, phenotypically, and metabolically reprogrammable. A wealth of evidence confirms metabolic reprogramming activity as the minimum common denominator of cancer, grouping together a wide variety of aberrations that can affect any of the different metabolic pathways involved in cell physiology. This forms the basis for a new proposed classification of cancer according to the altered metabolic pathway(s) and degree of energy dysfunction. Enhanced understanding of the metabolic reprogramming pathways of fatty acids, amino acids, carbohydrates, hypoxia, and acidosis can bring about new therapeutic intervention possibilities from a metabolic perspective of cancer.

Hydroxytyrosol improves mitochondrial energetics of a cellular model of Alzheimer’s disease

ABSTRACT Mitochondrial energetic deficit is one of the hallmarks of neurodegenerative disorders, e.g. Alzheimer´s disease (AD). Adherence to a Mediterranean diet is associated with lower incidence of cognitive decline and AD and extra virgin olive oil’s (poly)phenols such as oleuropein and hydroxytyrosol (HT) are being actively studied in this respect. In this study, we assessed the effects of HT on mitochondrial energetic dysfunction in the 7PA2 cells cellular model, i.e. one of the best cellular models of Aβ toxicity with a well-characterized mitochondrial dysfunction typically observed in AD. We report an increase of new mitochondria at 8 h post HT-treatment, which was followed by higher mitochondrial fusion. Further, ATP concentrations were significantly increased after 24 h of treatment with HT as compared with controls. Our data suggest that HT may revert the energetic deficit of a cellular model of AD by potentiating mitochondrial activity. Because HT is being proposed as dietary supplement or component of functional foods, future studies in appropriate animal models and – eventually – humans are warranted to further investigate its potential neuroprotective actions in AD.

Rescue of myocardial energetic dysfunction in diabetes through the correction of mitochondrial hyperacetylation by honokiol.

Cardiac energetic dysfunction has been reported in patients with type 2 diabetes (T2D) and is an independent predictor of mortality. Identification of the mechanisms driving mitochondrial dysfunction, and therapeutic strategies to rescue these modifications, will improve myocardial energetics in T2D. We demonstrate using 31P-magnetic resonance spectroscopy (31P-MRS) that decreased cardiac ATP and phosphocreatine (PCr) concentrations occurred before contractile dysfunction or a reduction in PCr/ATP ratio in T2D. Real-time mitochondrial ATP synthesis rates and state 3 respiration rates were similarly depressed in T2D, implicating dysfunctional mitochondrial energy production. Driving this energetic dysfunction in T2D was an increase in mitochondrial protein acetylation, and increased ex vivo acetylation was shown to proportionally decrease mitochondrial respiration rates. Treating T2D rats in vivo with the mitochondrial deacetylase SIRT3 activator honokiol reversed the hyperacetylation of mitochondrial proteins and restored mitochondrial respiration rates to control levels. Using 13C-hyperpolarized MRS, respiration with different substrates, and enzyme assays, we localized this improvement to increased glutamate dehydrogenase activity. Finally, honokiol treatment increased ATP and PCr concentrations and increased total ATP synthesis flux in the T2D heart. In conclusion, hyperacetylation drives energetic dysfunction in T2D, and reversing acetylation with the SIRT3 activator honokiol rescued myocardial and mitochondrial energetics in T2D.

Brain energetics, mitochondria, and traumatic brain injury.

We review current thinking about, and draw connections between, brain energetics and metabolism, and between mitochondria and traumatic brain injury. Energy is fundamental to proper brain function. Its creation in a useful form for neurons and glia, and consistently in response to the brain's high energy needs, is critical for physiological pathways. Dysfunction in the mechanisms of energy production is at the center of neurological and neuropsychiatric pathologies. We examine the connections between energetics and mitochondria - the organelle responsible for almost all the energy production in the cell - and how secondary pathologies in traumatic brain injury result from energetic dysfunction. This paper interweaves these topics, a necessity since they are closely coupled, and identifies where there exist a lack of understanding and of data. In addition to summarizing current thinking in these disciplines, our goal is to suggest a framework for the mathematical modeling of mechanisms and pathways based on optimal energetic decisions.

Both gain and loss of Nampt function promote pressure overload-induced heart failure.

The heart requires high-energy production, but metabolic ability declines in the failing heart. Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide (NAD) synthesis. NAD is directly involved in various metabolic processes and may indirectly regulate metabolic gene expression through sirtuin 1 (Sirt1), an NAD-dependent protein deacetylase. However, how Nampt regulates cardiac function and metabolism in the failing heart is poorly understood. Here we show that pressure-overload (PO)-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout (Nampt+/-) mice and mice with cardiac-specific Nampt overexpression (Tg-Nampt). The NAD level declined in Nampt+/- mice under PO (wild: 377 pmol/mg tissue; Nampt+/-: 119 pmol/mg tissue; P = 0.028). In cultured cardiomyocytes, Nampt knockdown diminished mitochondrial NAD content and ATP production (relative ATP production: wild: 1; Nampt knockdown: 0.56; P = 0.0068), suggesting that downregulation of Nampt induces mitochondrial dysfunction. On the other hand, the NAD level was increased in Tg-Nampt mice at baseline but not during PO, possibly due to increased consumption of NAD by Sirt1. The expression of Sirt1 was increased in Tg-Nampt mice, in association with reduced overall protein acetylation. PO-induced downregulation of metabolic genes was exacerbated in Tg-Nampt mice. In cultured cardiomyocytes, Nampt and Sirt1 cooperatively suppressed mitochondrial proteins and ATP production, thereby promoting mitochondrial dysfunction. In addition, Nampt overexpression upregulated inflammatory cytokines, including TNF-α and monocyte chemoattractant protein-1. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, whereas Nampt overexpression is detrimental during PO, possibly due to excessive activation of Sirt1, suppression of mitochondrial function, and upregulation of proinflammatory mechanisms.NEW & NOTEWORTHY Nicotinamide phosphoribosyl-transferase (Nampt) is a rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide synthesis. We demonstrate that pressure overload-induced heart failure is exacerbated in both systemic Nampt heterozygous knockout mice and mice with cardiac-specific Nampt overexpression. Both loss- and gain-of-function models exhibited reduced protein acetylation, suppression of metabolic genes, and mitochondrial energetic dysfunction. Thus endogenous Nampt maintains cardiac function and metabolism in the failing heart, but cardiac-specific Nampt overexpression is detrimental rather than therapeutic.