Deficits In Energy Metabolism Research Articles

Morphology of the heart during the period of progressive growth in conditions of prolonged exposure to low temperatures

Annotation. The aim of the research is to study the cardiac morphology during the period of growth under prolonged exposure to low temperatures. The main group consisted of outbred white rats (260 males and 190 females) undergoing active development, aged 4 weeks at the beginning of the experiment, and was kept in a room with an air temperature of +4±1 °C. The control group of animals was kept in a room with an air temperature of +20±10 °C. The experiment lasted for sixteen weeks. Research methods: macromorphometric study of the heart, histological study of paraffin sections, and ultrastructural study. Micromorphometric study was performed on semi-thin sections stained with 0.1% solution of toluidine blue at an ocular magnification of 10 and objective of 90, using a multi-purpose test system of short segments (Weibel grid) and an automatic analyzer of microscopic images “Integral-2MT”. PAS stain by A.L.Shabadash was used to detect glycogen, and the number of glycogen granules per unit area was counted on electronograms at a magnification of 20000 using a 1 cm2 area square. The stereological study of the electronograms was carried out at a magnification of 8000 using a Weibel grid. The statistical processing of the obtained results was carried out using the SPSS statistical program package, STATISTICA v. 10.0. It was found that the adaptation of the myocardium to the cold occurs according to the universal mechanism of adaptation to various extreme conditions associated with a deficit of energy metabolism. Therefore, the effect of cold can be regarded as non-specific. Based on the conducted research, the following stages of the adaptation process are defined: 1) short-term stress reaction (first 5 days); 2) myocardial hypertrophy (from 2nd to 6th weeks); 3) long-term, stable adaptation (more than 6 weeks). Morphological criteria for myocardial adaptation to long-term cold exposure have been identified: 1) physiological hypertrophy of the myocardium, mainly of the right ventricle; 2) the energy reserve of cardiomyocytes in the form of mitochondrial hyperplasia and glycogen accumulation. We plan to study the microcirculatory bed of the myocardium during the adaptation of the body to prolonged action of low temperature in the future.

An original amino acid formula favours in vitro corneal epithelial wound healing by promoting Fn1, ITGB1, and PGC-1α expression

Corneal disorders are frequent, involving most diabetic patients; among its manifestations, they include delayed wound healing. Since maintenance of mitochondrial homeostasis is fundamental for the cell, stimulation of mitochondrial biogenesis represents a unique therapeutic tool for preventing and treating disorders with a deficit in energy metabolism. We have recently demonstrated that a branched-chain amino acid (BCAA)-enriched mixture (BCAAem) supported mitochondrial biogenesis in cardiac and skeletal muscle, reduced liver damage caused by alcohol, and prevented the doxorubicin-dependent mitochondrial damage in cardiomyocytes. The present study aimed to investigate a new amino acid mixture, named six amino acids (6AA), to promote corneal epithelial wound healing by regulating mitochondrial biogenesis. A murine epithelium cell line (TKE2) exposed to this mixture showed increased mitochondrial biogenesis markers, fibronectin 1 (Fn1) and integrin beta 1 (ITGB1) involved in extracellular matrix synthesis and cell migration. Most importantly, the 6AA mixture completely restored the wound in scratch assays, confirming the potential of this new formula in eye disorders like keratopathy. Moreover, our results demonstrate for the first time that peroxisome proliferator-receptor γ coactivator 1 α (PGC-1α) is expressed in TKE2 cells, which controls mitochondrial function and corneal repair process. These results could be relevant for the treatment mainly focused on corneal re-epithelialisation.

MTOR Inhibition via Rapamycin Treatment Partially Reverts the Deficit in Energy Metabolism Caused by FH Loss in RPE Cells.

Age-related macular degeneration (AMD) is a complex degenerative disease of the retina with multiple risk-modifying factors, including aging, genetics, and lifestyle choices. The combination of these factors leads to oxidative stress, inflammation, and metabolic failure in the retinal pigment epithelium (RPE) with subsequent degeneration of photoreceptors in the retina. The alternative complement pathway is tightly linked to AMD. In particular, the genetic variant in the complement factor H gene (CFH), which leads to the Y402H polymorphism in the factor H protein (FH), confers the second highest risk for the development and progression of AMD. Although the association between the FH Y402H variant and increased complement system activation is known, recent studies have uncovered novel FH functions not tied to this activity and highlighted functional relevance for intracellular FH. In our previous studies, we show that loss of CFH expression in RPE cells causes profound disturbances in cellular metabolism, increases the vulnerability towards oxidative stress, and modulates the activation of pro-inflammatory signaling pathways, most importantly the NF-kB pathway. Here, we silenced CFH in hTERT-RPE1 cells to investigate the mechanism by which intracellular FH regulates RPE cell homeostasis. We found that silencing of CFH results in hyperactivation of mTOR signaling along with decreased mitochondrial respiration and that mTOR inhibition via rapamycin can partially rescue these metabolic defects. To obtain mechanistic insight into the function of intracellular FH in hTERT-RPE1 cells, we analyzed the interactome of FH via immunoprecipitation followed by mass spectrometry-based analysis. We found that FH interacts with essential components of the ubiquitin-proteasomal pathway (UPS) as well as with factors associated with RB1/E2F signalling in a complement-pathway independent manner. Moreover, we found that FH silencing affects mRNA levels of the E3 Ubiquitin-Protein Ligase Parkin and PTEN induced putative kinase (Pink1), both of which are associated with UPS. As inhibition of mTORC1 was previously shown to result in increased overall protein degradation via UPS and as FH mRNA and protein levels were shown to be affected by inhibition of UPS, our data stress a potential regulatory link between endogenous FH activity and the UPS.

Charcot-Marie-tooth disease causing mutation (p.R158H) in pyruvate dehydrogenase kinase 3 (PDK3) affects synaptic transmission, ATP production and causes neurodegeneration in a CMTX6 C. elegans model.

Charcot–Marie-Tooth (CMT) is a commonly inherited, non-fatal neurodegenerative disorder that affects sensory and motor neurons in patients. More than 90 genes are known to cause axonal and demyelinating forms of CMT. The p.R158H mutation in the pyruvate dehydrogenase kinase 3 (PDK3) gene is the genetic cause for an X linked form of axonal CMT (CMTX6). In vitro studies using patient fibroblasts and iPSC-derived motor neurons have shown that this mutation causes deficits in energy metabolism and mitochondrial function. Animal models that recapitulate pathogenic in vivo events in patients are crucial for investigating mechanisms of axonal degeneration and developing therapies for CMT. We have developed a C. elegans model of CMTX6 by knocking-in the p.R158H mutation in pdhk-2, the ortholog of PDK3. In addition, we have developed animal models overexpressing the wild type and mutant form of human PDK3 specifically in the GABAergic motor neurons of C. elegans. CMTX6 mutants generated in this study exhibit synaptic transmission deficits, locomotion defects and show signs of progressive neurodegeneration. Furthermore, the CMTX6 in vivo models display energy deficits that recapitulate the phenotype observed in patient fibroblasts and iPSC-derived motor neurons. Our CMTX6 animals represent the first in vivo model for this form of CMT and have provided novel insights into the cellular function and metabolic pathways perturbed by the p.R158H mutation, all the while closely replicating the clinical presentation observed in CMTX6 patients.

Experimental evidence on the efficacy of two new metabolic modulators on mitochondrial biogenesis and function in mouse cardiomyocytes

Proper maintenance of mitochondrial homeostasis is essential for cell health, and mitochondrial dysfunction underlies several metabolic and heart diseases. Stimulation of mitochondrial biogenesis represents a valuable therapeutic tool for the prevention and treatment of disorders characterized by a deficit in energy metabolism. The present study aimed to potentiate the mitochondrial biogenetic efficacy of an amino acid (AA) mixture, enriched in branched-chain amino acids (BCAAs), which we previously showed to boost mitochondrial biogenesis, leading to life span extension and reducing of muscle and liver damage. Hence, we designed and studied several innovative mixtures. Here, we report on two new AA formulas, α5 and E7, created on the BCAA-enriched amino acid mixture (BCAAem) template and enriched with Krebs cycle substrates, including succinate, malate, and citrate. Cardiomyocytes in culture exposed to either mixture showed increased mitochondrial DNA amount, mitochondrial biogenesis markers, and oxygen consump-tion. Furthermore, α5 and E7 also increased the expression of BCAA catabolic genes. Most importantly, all of these effects of α5 and E7 were more pronounced than those observed with BCAAem, confirming the higher mitochondrial biogenesis potential of these new formulas. Therefore, α5 and E7 could represent a more efficient tool for the nutritional treatment of diseases in which energy production is defective.

Unique Transcriptome Signature Distinguishes Patients With Heart Failure With Myopathy.

BackgroundPeople with chronic heart failure (CHF) experience severe skeletal muscle dysfunction, characterized by mitochondrial abnormalities, which exacerbates the primary symptom of exercise intolerance. However, the molecular triggers and characteristics underlying mitochondrial abnormalities caused by CHF remain poorly understood.Methods and ResultsWe recruited 28 patients with CHF caused by reduced ejection fraction and 9 controls. We simultaneously biopsied skeletal muscle from the pectoralis major in the upper limb and from the vastus lateralis in the lower limb. We phenotyped mitochondrial function in permeabilized myofibers from both sites and followed this by complete RNA sequencing to identify novel molecular abnormalities in CHF skeletal muscle. Patients with CHF presented with upper and lower limb skeletal muscle impairments to mitochondrial function that were of a similar deficit and indicative of a myopathy. Mitochondrial abnormalities were strongly correlated to symptoms. Further RNA sequencing revealed a unique transcriptome signature in CHF skeletal muscle characterized by a novel triad of differentially expressed genes related to deficits in energy metabolism including adenosine monophosphate deaminase 3, pyridine nucleotide‐disulphide oxidoreductase domain 2, and lactate dehydrogenase C.ConclusionsOur data suggest an upper and lower limb metabolic myopathy that is characterized by a unique transcriptome signature in skeletal muscle of humans with CHF.

The protective effect of Xanthoceras sorbifolia Bunge husks on cognitive disorder based on metabolomics and gut microbiota analysis

Aim of the studyThe husks of Xanthoceras sorbifolia Bunge mainly used in north China as folk medicine were reported to have potential protective effect on cognitive impairment. However, the mechanism remains unclear. In order to fully understand the mechanism of the protection, a complementary study of the husks was conducted. Materials and methodsThe urinary and fecal metabolomics were used to analyze the potential biomarkers by the liquid chromatography-tandem time of flight mass spectrometry, and the16S rDNA technology was applied to conduct the analysis of microbiota species in the fecal samples of the rats, which is a significant influencing factor for the development of cognitive impairment. ResultsIn metabolomics study, ten potential metabolic biomarkers, which are hippuric acid, kynurenic acid, creatinine, phenylalanine, xanthurenic acid, phenylacetylglycine, succinyladenosine, cresol sulfate, tryptophan 2-C-mannoside and N4-Acetylcytidine in urine, along with two, including isoleucine and phenylalanine in feces, were preliminarily identified, involving multiple pathways such as tryptophan, purine, kynurenine, and phenylalanine metabolism. The perturbation of these metabolic pathways could be related with insulin resistance, oxidative stress, energy metabolism deficit and neuroinflammation, which were risk factors to cause cognitive impairment. In gut microbiota analysis, the relative abundance of c_Bacteroidia, c_Alphaproteobacteria, f_Prevotellaceae, f_Sphingomonadaceae, f_Burkholderiaceae, g_Prevotellaceae_NK3B31_group and p_Bacteroidetes was significantly changed in the rats with cognitive impairment. Spearman's analysis showed obvious correlation between the metabolites and the microbiota species. In the rats with pretreatment of the husks extract, metabolites maintained a relative normal level, and the husks extract could regulate the gut microbiota, especially f_Prevotellaceae and g_Prevotellaceae_NK3B31_group, indicating the effect of the husks on the metabolic pathways via GMs. Such amino acids as isoleucine and phenylalanine failed to show any significant correlation with the microbiota species, indicating that the husks exhibited the potential protective effect through gut microbiota and other pathways. ConclusionsThe husks extract could improve the intestinal microenvironment, and the stability of intestinal microenvironment was associated with normality of tryptophan, purine, kynurenine and phenylalanine metabolic pathways etc, which probably had an effect on cognitive function. This complementary work suggested that gut microbiotas were potential targets of the husks to exert its effect on cognitive impairment.

Low birth weight influences the postnatal abundance and characteristics of satellite cell subpopulations in pigs

Low birth weight (LBW) can cause lifelong impairments in muscle development and growth. Satellite cells (SC) and their progeny are crucial contributors to myogenic processes. This study provides new data on LBW in piglets combining insights on energy metabolism, muscle capillarization and differences in SC presence and function. To this aim, muscle tissues as well as isolated myogenic cells of 4-day-old German Landrace piglets were analyzed. For the first time two heterogeneous SC subpopulations, which contribute differently to muscle development, were isolated from LBW pigs by Percoll density gradient centrifugation. The muscles of LBW piglets showed a reduced DNA, RNA, and protein content as well as lower activity of the muscle specific enzymes CK, ICDH, and LDH compared to their normal birth weight siblings. We assume that deficits in energy metabolism and capillarization are associated with reduced bioavailability of SC, possibly leading to early exhaustion of the SC reserve cell pool and the cells’ premature differentiation.

Peroxisome Proliferator Activator Receptor Gamma Coactivator-1α Overexpression in Amyotrophic Lateral Sclerosis: A Tale of Two Transgenics

Background: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by loss of voluntary muscle function due to death of motor neurons. Energy metabolism deficits at the level of mitochondrial function have been implicated in the pathogenesis of ALS. We have previously reported improved motor function and survival in the SOD1G93A mouse model of ALS by neuron-specific over-expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), a regulator of mitochondrial biogenesis. As pharmacological intervention targeting PGC-1α would result in whole-body upregulation of this transcriptional co-activator, in the current study we investigated whether global expression of PGC-1α is beneficial in the ALS mouse model. Methods: We generated transgenic mice with PGC-1α transgene expression driven by the actin promoter. Transgene expression was confirmed by PCR. Findings: The wild-type, actin-PGC-1α, SOD1G93A and actin-PGC-1α/SOD1G93A mice generated by crossing the actin-PGC-1α and SOD1G93A transgenic lines were monitored for weight loss, motor performance by accelerating rotarod test and survival. Interestingly, there was no significant improvement in body weight, motor function or survival in SOD1G93A mice over-expressing actin-PGC-1α. Interpretation: Our previous studies showed, in the same mouse model, that PGC-1α ectopic expression under the NSE promoter significantly improved motor function and survival. A potential explanation for this difference is that the actin promoter does not induce, in the cells that are specifically relevant in mechanisms associated with ALS pathology, levels of PGC-1α relevant to disease pathophysiology. This evidence strongly supports future therapeutic approaches that target PGC-1α primarily in neurons. Funding: This study was supported by discretionary funding to GMP . Dr. Pasinetti holds a Senior VA Career Scientist Award. Declaration of Interest: No conflicts of interest exist for any of the authors. Ethical Approval: All animal protocols used in the study were approved by the Institutional Animal Care and Use Committee of the Icahn School of Medicine at Mount Sinai.

Reactive Metabolite-induced Protein Glutathionylation: A Potentially Novel Mechanism Underlying Acetaminophen Hepatotoxicity

Although covalent protein binding is established as the pivotal event underpinning acetaminophen (APAP) toxicity, its mechanistic details remain unclear. In this study, we demonstrated that APAP induces widespread protein glutathionylation in a time-, dose- and bioactivation-dependent manner in HepaRG cells. Proteo-metabonomic mapping provided evidence that APAP-induced glutathionylation resulted in functional deficits in energy metabolism, elevations in oxidative stress and cytosolic calcium, as well as mitochondrial dysfunction that correlate strongly with the well-established toxicity features of APAP. We also provide novel evidence that APAP-induced glutathionylation of carnitine O-palmitoyltransferase 1 (CPT1) and voltage-dependent anion-selective channel protein 1 are respectively involved in inhibition of fatty acid β-oxidation and opening of the mitochondrial permeability transition pore. Importantly, we show that the inhibitory effect of CPT1 glutathionylation can be mitigated by PPARα induction, which provides a mechanistic explanation for the prophylactic effect of fibrates, which are PPARα ligands, against APAP toxicity. Finally, we propose that APAP-induced protein glutathionylation likely occurs secondary to covalent binding, which is a previously unknown mechanism of glutathionylation, suggesting that this post-translational modification could be functionally implicated in drug-induced toxicity.

Neurometabolic disorders and congenital malformations of the central nervous system.

Both malformations of the central nervous system and neurometabolic disorders are common, mainly in highly consanguineous populations. Both metabolic pathways and developmental pathways are closely related and interact with each other. Neurometabolic disorders can lead to disturbances in brain development through multiple mechanisms that include deficits in energy metabolism, critical nutrient deficiency, accumulation of neurotoxic substrates, abnormality in cell membrane constituents, and interference in cell-to-cell signaling pathways. The anomalies observed include absent or hypoplastic corpus callosum, midline brain defects, and malformations of the cortex, the cerebellum and the brain stem. Early diagnosis of an underlying inherited neurometabolic disorders is critical for the institution of treatment, which may positively influence prognosis, and allow for proper genetic counseling. In this review, we discuss those disorders in which the structural brain malformation is a dominant feature, and propose a practical approach that will permit a physician to investigate, and treat these disorders.

Pterostilbene ameliorates intracerebroventricular streptozotocin induced memory decline in rats.

There is strong evidence that mitochondrial dysfunction mediated oxidative stress results in aging and energy metabolism deficits thus playing a prime role in pathogenesis of Alzheimer's disease, neuronal death and cognitive dysfunction. Evidences accrued in empirical studies suggest the antioxidant, anticancer and anti-inflammatory activities of the phytochemical pterostilbene (PTS). PTS also exhibits favourable pharmacokinetic attributes compared to other stilbenes. Hence, in the present study, we explored the neuroprotective role of PTS in ameliorating the intracerebroventricular administered streptozotocin (STZ) induced memory decline in rats. PTS at doses of 10, 30 and 50mg/kg, was administered orally to STZ administered Sprague-Dawley (SD) rats. The learning and memory tests, Morris water maze test and novel object recognition test were performed which revealed improved cognition on PTS treatment. Further, there was an overall improvement in brain antioxidant parameters like elevated catalase and superoxide dismutase activities, GSH levels, lowered levels of nitrites, lipid peroxides and carbonylated proteins. There was improved cholinergic transmission as evident by decreased acetylcholinesterase activities. The action of ATPases (Na+ K+, Ca2+ and Mg2+) indicating the maintenance of cell membrane potential was also augmented. mRNA expression of battery of genes involved in cellular mitochondrial biogenesis and inflammation showed variations which extrapolate to hike in mitochondrial biogenesis and abated inflammation. The histological findings corroborated the effective role of PTS in countering STZ induced structural aberrations in brain.

Tanshinone IIA increases levels of NeuN, protein disulfide isomerase, and Na+/K+-ATPase and decreases evidence of microglial activation after cerebral ischemic injury.

This study was designed to clarify the neuroprotective effects of tanshinone IIA (TSA) following cerebral ischemic insult. Adult Sprague-Dawley rats were operated upon to achieve a middle cerebral artery occlusion to cause transient focal cerebral ischemia, which were then randomly divided into the sham-operated control group and cerebral ischemia/reperfusion (I/R) groups receiving a 2 h occlusion. The treatment groups received daily intraperitoneal injections of high or low doses of TSA, for 7 or 15 days. NeuN immunostaining revealed neuronal loss following I/R, which was partially prevented with subsequent TSA dosing. Protein disulfide isomerase and adenosine triphosphatase (Na(+)/K(+)-ATPase) levels were all depressed by means of I/R. TSA treatment markedly reversed the depression of all indices examined. The intensity of microglial activation, as evidenced with CD11b staining, was increased by means of cerebral artery occlusion, but this was partially reversed with subsequent TSA treatment. TSA may affect neuroprotection by way of minimizing deficits in energy metabolism and reduction of the extent of cell death within affected regions.

Mesial temporal sclerosis

Mesial temporal sclerosis is one of the most common pathologies seen in patients with temporal lobe epilepsy. Com- plex partial seizures arise from the mesial (deepest) part of the temporal region. This region includes the amygdala and the hip- pocampus. The etiology of mesial temporal sclerosis is still uncertain and controversial. The most popular mechanism implicated in this pathology involves glutamate, an amino acid whose release results in excessive excitability. This model is documented both in animals and in humans. The other mechanism describes neuronal death from seizure induced gene expres- sion and seizure induced energy metabolism deficits. There are many theories linked to the development of this lesion. It is seen as a rare pathological finding in children less than 10 years of age, but it is not uncommon in adolescence. Clinical studies are suggestive of the occurrence of lesions in children with prolonged febrile seizures. The other etiologies include perinatal ischemic insult, hypoglycemia, intrauterine hypoxia, and status epilepticus resulting in hypoxia and edema in the hippocampus. Magnetic resonance imaging is the modality of choice for the detection of the lesion, which demonstrates scarring in the mesial temporal region. The coronal high-resolution fluid-attenuated inversion recovery is known to be one of the best sequences, since sensitivity is high to detect the hyperintensity and atrophy of the hippocampus. The use of magnetic resonance imaging is cru- cial for the pre-surgical work up for epilepsy. Specific surgical procedures including anterior temporal lobectomy tailored towards resection of the mesial temporal lesion have a much higher rate of success in intractable epilepsy patients. Seizure free- dom is seen in 70-95% of patients undergoing resective surgery as compared with 25% of medically treated cases.

Chronic social isolation decreases glutamate and glutamine levels and induces oxidative stress in the rat hippocampus

Social isolation (SI) rearing of rodents is a developmental manipulation, which is commonly compared with the psychological stressors in humans as it produces several behavioral outcomes similar to those observed in humans with early life stress. To explain the SI-induced behavioral outcomes, animal studies have been performed to examine the dopaminergic and glutamatergic systems in the brain. In this study, we measured possible changes in levels of glutamate and glutamine of SI-rats using proton magnetic resonance spectroscopy. We also assessed the oxidative stress parameters in certain brain regions to see if glutamate and/or glutamine changes, if any, are associated with oxidative stress. SI rearing for 8 weeks decreased the activities of antioxidant enzymes catalase, glutathione peroxidase, superoxide dismutase, and the total antioxidant capacity, but increased levels of hydrogen peroxide, in certain brain regions, of which prefrontal cortex and hippocampus were most vulnerable. It also decreased levels of glutamate, glutamine, N-acetyl-l-aspartate (NAA), and phosphocreatine in the dorsal hippocampus, but not in the cerebral cortex. Decreased phosphocreatine and NAA indicate energy metabolism deficit in brain cells; the latter also suggests the neuronal viability was inhibited. Decreased glutamate and glutamine may suggest the neuron-glial integrity was implicated by chronic SI. These neurochemical and biochemical changes may contribute to the SI-induced behavioral abnormalities including a high level of anxiety, social interaction deficit, and impaired spatial working memory shown in this study.

TDP-43 pathology in the basal forebrain and hypothalamus of patients with amyotrophic lateral sclerosis

IntroductionAmyotrophic lateral sclerosis is a neurodegenerative disease characterized clinically by motor symptoms including limb weakness, dysarthria, dysphagia, and respiratory compromise, and pathologically by inclusions of transactive response DNA-binding protein 43 kDa (TDP-43). Patients with amyotrophic lateral sclerosis also may demonstrate non-motor symptoms and signs of autonomic and energy dysfunction as hypermetabolism and weight loss that suggest the possibility of pathology in the forebrain, including hypothalamus. However, this region has received little investigation in amyotrophic lateral sclerosis. In this study, the frequency, topography, and clinical associations of TDP-43 inclusion pathology in the basal forebrain and hypothalamus were examined in 33 patients with amyotrophic lateral sclerosis: 25 men and 8 women; mean age at death of 62.7 years, median disease duration of 3.1 years (range of 1.3 to 9.8 years).ResultsTDP-43 pathology was present in 11 patients (33.3%), including components in both basal forebrain (n= 10) and hypothalamus (n= 7). This pathology was associated with non-motor system TDP-43 pathology (Χ2= 17.5, p= 0.00003) and bulbar symptoms at onset (Χ2= 4.04, p= 0.044), but not age or disease duration. Furthermore, TDP-43 pathology in the lateral hypothalamic area was associated with reduced body mass index (W= 11, p= 0.023).ConclusionsThis is the first systematic demonstration of pathologic involvement of the basal forebrain and hypothalamus in amyotrophic lateral sclerosis. Furthermore, the findings suggest that involvement of the basal forebrain and hypothalamus has significant phenotypic associations in amyotrophic lateral sclerosis, including site of symptom onset, as well as deficits in energy metabolism with loss of body mass index.

Validation of a Genomics-Based Hypothetical Adverse Outcome Pathway: 2,4-Dinitrotoluene Perturbs PPAR Signaling Thus Impairing Energy Metabolism and Exercise Endurance

2,4-dinitrotoluene (2,4-DNT) is a nitroaromatic used in industrial dyes and explosives manufacturing processes that is found as a contaminant in the environment. Previous studies have implicated antagonism of PPARα signaling as a principal process affected by 2,4-DNT. Here, we test the hypothesis that 2,4-DNT-induced perturbations in PPARα signaling and resultant downstream deficits in energy metabolism, especially from lipids, cause organism-level impacts on exercise endurance. PPAR nuclear activation bioassays demonstrated inhibition of PPARα signaling by 2,4-DNT whereas PPARγ signaling increased. PPARα (-/-) and wild-type (WT) female mice were exposed for 14 days to vehicle or 2,4-DNT (134 mg/kg/day) and performed a forced swim to exhaustion 1 day after the last dose. 2,4-DNT significantly decreased body weights and swim times in WTs, but effects were significantly mitigated in PPARα (-/-) mice. 2,4-DNT decreased transcript expression for genes downstream in the PPARα signaling pathway, principally genes involved in fatty acid transport. Results indicate that PPARγ signaling increased resulting in enhanced cycling of lipid and carbohydrate substrates into glycolytic/gluconeogenic pathways favoring energy production versus storage in 2,4-DNT-exposed WT and PPARα (-/-) mice. PPARα (-/-) mice appear to have compensated for the loss of PPARα by shifting energy metabolism to PPARα-independent pathways resulting in lower sensitivity to 2,4-DNT when compared with WT mice. Our results validate 2,4-DNT-induced perturbation of PPARα signaling as the molecular initiating event for impaired energy metabolism, weight loss, and decreased exercise performance.

Localized changes to glycogen synthase kinase-3 and collapsin response mediator protein-2 in the Huntington's disease affected brain

All cases of Huntington's disease (HD) are caused by mutant huntingtin protein (mhtt), yet the molecular mechanisms that link mhtt to disease symptoms are not fully elucidated. Given glycogen synthase kinase-3 (GSK3) is implicated in several neurodegenerative diseases as a molecular mediator of neuronal decline and widely touted as a therapeutic target, we investigated GSK3 in cells expressing mhtt, brains of R6/1 HD mice and post-mortem human brain samples. Consistency in data across the two models and the human brain samples indicate decreased GSK3 signalling contributes to neuronal dysfunction in HD. Inhibitory phosphorylation of GSK3 (pGSK3) was elevated in mhtt cells and this appeared related to an overall energy metabolism deficit as the mhtt cells had less ATP and inhibiting ATP production in control cells expressing non-pathogenic htt with paraquat also increased pGSK3. pGSK3 was increased and ATP levels decreased in the frontal cortex and striatum of R6/1 mice and levels of cortical pGSK3 inversely correlated with cognitive function of the mice. Consistent with decreased GSK3 activity in the R6/1 mouse brain, β-catenin levels were increased and phosphorylation of collapsin response mediator protein-2 (CRMP2) decreased in the frontal cortex where inhibitory phosphorylation of GSK3 was the greatest. pGSK3 was predominantly undetectable in HD and healthy control human brain samples, but levels of total GSK3 were decreased in the HD-affected frontal cortex and this correlated with decreased pCRMP2. Thus, disruptions to cortical GSK3 signalling, possibly due to localized energy metabolism deficits, appear to contribute to the cognitive symptoms of HD.

Exercise and the brain: a slap on the HAND

Exercise and the brain: a slap on the HAND

Contributions of Brain Insulin Resistance and Deficiency in Amyloid-Related Neurodegeneration in Alzheimerʼs Disease

Alzheimer's disease (AD) is the most common cause of dementia in North America. Growing evidence supports the concept that AD is fundamentally a metabolic disease that results in progressive impairment in the brain's capacity to utilize glucose and respond to insulin and insulin-like growth factor (IGF) stimulation. Moreover, the heterogeneous nature of AD is only partly explained by the brain's propensity to accumulate aberrantly processed, misfolded and aggregated oligomeric structural proteins, including amyloid-β peptides and hyperphosphorylated tau. Evidence suggests that other factors, including impaired energy metabolism, oxidative stress, neuroinflammation, insulin and IGF resistance, and insulin/IGF deficiency in the brain should be incorporated into an overarching hypothesis to develop more realistic diagnostic and therapeutic approaches to AD. In this review, the interrelationship between impaired insulin and IGF signalling and amyloid-β pathology is discussed along with potential therapeutic approaches. Impairments in brain insulin/IGF signalling lead to increased expression of amyloid-β precursor protein (AβPP) and accumulation of AβPP-Aβ. In addition, they promote oxidative stress and deficits in energy metabolism, leading to the activation of pro-AβPP-Aβ-mediated neurodegeneration cascades. Although brain insulin/IGF resistance and deficiency can be induced by primary or secondary disease processes, the soaring rates of peripheral insulin resistance associated with obesity, diabetes mellitus and metabolic syndrome quite likely play major roles in the current AD epidemic. Both clinical and experimental data have linked chronic hyperinsulinaemia to cognitive impairment and neurodegeneration with increased AβPP-Aβ accumulation/reduced clearance in the CNS. Correspondingly, both the restoration of insulin responsiveness and the use of insulin therapy can lead to improved cognitive performance, although with variable effects on brain AβPP-Aβ load. On the other hand, experimental evidence supports the concept that the toxic effects of AβPP-Aβ can promote insulin resistance. Together, these findings suggest that a positive feedback loop of progressive neurodegeneration can develop whereby insulin resistance drives AβPP-Aβ accumulation, and AβPP-Aβ fibril toxicity drives brain insulin resistance. This phenomenon could explain why measuring AβPP-Aβ levels in cerebrospinal fluid or imaging of the brain has proven to be inadequate as a stand-alone biomarker for diagnosing AD, and why the clinical trial results of anti-AβPP-Aβ monotherapy have been disappointing. Instead, the aggregate data suggest that brain insulin resistance and deficiency must also be therapeutically targeted to halt AD progression or reverse its natural course. The positive therapeutic effects of different treatments that address the role of brain insulin/IGF resistance and deficiency, including the use of intranasal insulin delivery, incretins and insulin sensitizer agents are discussed along with potential benefits of lifestyle changes to modify risk for developing mild cognitive impairment or AD. Altogether, the data strongly support the notion that we must shift toward the implementation of multimodal rather than unimodal diagnostic and therapeutic strategies for AD.