Disruption Of Energy Homeostasis Research Articles

Hypothalamic endoplasmic reticulum stress as a key mediator of obesity-induced leptin resistance.

Obesity is an epidemic disease that is increasing worldwide and is a major risk factor for many metabolic diseases. However, effective agents for the prevention or treatment of obesity remain limited. Therefore, it is urgent to clarify the pathophysiological mechanisms underlying the development and progression of obesity and exploit potential agents to cure and prevent this disease. According to a recent study series, obesity is associated with the development of endoplasmic reticulum stress and the activation of its stress responses (unfolded protein response) in metabolically active tissues, which contribute to the development of obesity-related insulin and leptin resistance, inflammation and energy imbalance. Hypothalamic endoplasmic reticulum stress is the central mechanism underlying the development of obesity-associated leptin resistance and disruption of energy homeostasis; thus, targeting endoplasmic reticulum stress offers a promising therapeutic strategy for improving leptin sensitivity, increasing energy expenditure and ultimately combating obesity. In this review, we highlight the relationship between and mechanism underlying hypothalamic endoplasmic reticulum stress and obesity-associated leptin resistance and energy imbalance and provide new insight regarding strategies for the treatment of obesity.

AMPK Re-Activation Suppresses Hepatic Steatosis but its Downregulation Does Not Promote Fatty Liver Development

Nonalcoholic fatty liver disease is a highly prevalent component of disorders associated with disrupted energy homeostasis. Although dysregulation of the energy sensor AMP-activated protein kinase (AMPK) is viewed as a pathogenic factor in the development of fatty liver its role has not been directly demonstrated. Unexpectedly, we show here that liver-specific AMPK KO mice display normal hepatic lipid homeostasis and are not prone to fatty liver development, indicating that the decreases in AMPK activity associated with hepatic steatosis may be a consequence, rather than a cause, of changes in hepatic metabolism. In contrast, we found that pharmacological re-activation of downregulated AMPK in fatty liver is sufficient to normalize hepatic lipid content. Mechanistically, AMPK activation reduces hepatic triglyceride content both by inhibiting lipid synthesis and by stimulating fatty acid oxidation in an LKB1-dependent manner, through a transcription-independent mechanism. Furthermore, the effect of the antidiabetic drug metformin on lipogenesis inhibition and fatty acid oxidation stimulation was enhanced by combination treatment with small-molecule AMPK activators in primary hepatocytes from mice and humans. Overall, these results demonstrate that AMPK downregulation is not a triggering factor in fatty liver development but in contrast, establish the therapeutic impact of pharmacological AMPK re-activation in the treatment of fatty liver disease.

Chapter 46 - Thermoregulation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the major adult-onset motor neuron disease, and is clinically, pathologically, and genetically associated with frontotemporal dementia, the second cause of dementia in the elderly. Here, we review the evidence linking thermoregulation and ALS. Indeed, while ALS is not classically associated with defective thermoregulatory function, its progression severely affects key brain regions controlling body temperature and impacts multiple sensors and effectors of this homeostatic function. Furthermore, animal models of ALS display disturbed thermoregulation as a consequence of disrupted energy homeostasis. All these lines of indirect evidence call for studies directly addressing the body temperature regulatory system, both as a potential biomarker and as a possible modifier of disease progression in ALS.

Heatwaves\xa0diminish the survival of a subtidal gastropod through reduction in energy budget and depletion of energy reserves

Extreme climatic events, such as heatwaves, are predicted to be more prevalent in future due to global climate change. The devastating impacts of heatwaves on the survival of marine organisms may be further intensified by ocean acidification. Here, we tested the hypothesis that prolonged exposure to heatwave temperatures (24 °C, +3 °C summer seawater temperature) would diminish energy budget, body condition and ultimately survival of a subtidal gastropod (Thalotia conica) by pushing close to its critical thermal maximum (CTmax). We also tested whether ocean acidification (pCO2: 1000 ppm) affects energy budget, CTmax and hence survival of this gastropod. Following the 8-week experimental period, mortality was markedly higher at 24 °C irrespective of pCO2 level, probably attributed to energy deficit (negative scope for growth) and concomitant depletion of energy reserves (reduced organ weight to flesh weight ratio). CTmax of T. conica appeared at 27 °C and was unaffected by ocean acidification. Our findings imply that prolonged exposure to heatwaves can compromise the survival of marine organisms below CTmax via disruption in energy homeostasis, which possibly explains their mass mortality in the past heatwave events. Therefore, heatwaves would have more profound effects than ocean acidification on future marine ecosystems.

Impairment of energy sensors, SIRT1 and AMPK, in lipid induced inflamed adipocyte is regulated by Fetuin A

Although several reports demonstrated that accumulation of excess lipid in adipose tissue produces defects in adipocyte which leads to the disruption of energy homeostasis causing severe metabolic problems, underlying mechanism of this event remains yet unclear. Here we demonstrate that FetuinA (FetA) plays a critical role in the impairment of two metabolic sensors, SIRT1 and AMPK, in inflamed adipocytes of high fat diet (HFD) mice. A linear increase in adipocyte hypertrophy from 10 to 16 week was in tandem with the increase in FetA and that coincided with SIRT1 cleavage and decrease in pAMPK which adversely affects PGC1α activation. Knock down (KD) of FetA gene in HFD mice could significantly improve this situation indicating FetA's contribution in the damage of energy sensors in inflamed adipocyte. However, FetA effect was not direct, it was mediated through TNF-α which again is dependent on FetA as FetA augments TNF-α expression. FetA being an upstream regulator of TNF-α, its suppression prevented TNF-α mediated Caspase-1 activation and cleavage of SIRT1. FetA induced inactivation of PGC1α due to SIRT1 cleavage decreased PPARϒ, adiponectin, NRF1 and Tfam expression. All these together caused a significant fall in mitochondrial biogenesis and bioenergetics that disrupted energy homeostasis resulting loss of insulin sensitivity. Taken together, our findings revealed a new dimension of FetA, it not only induced inflammation in adipocyte but also acts as an upstream regulator of SIRT1 cleavage and AMPK activation. Intervention of FetA may be worthwhile to prevent metabolic imbalance that causes insulin resistance and type 2 diabetes.

Editor's Highlight: PCB126 Exposure Increases Risk for Peripheral Vascular Diseases in a Liver Injury Mouse Model.

The liver is vital for xenobiotic and endobiotic metabolism. Previously, we demonstrated that a compromised liver worsened toxicity associated with exposure to polychlorinated biphenyls (PCBs), through disruption of energy homeostasis. However, the role of a compromised liver in defining dioxin-like PCB126 toxicity on the peripheral vasculature and associated inflammatory diseases is yet to be studied. This study investigated the effects of PCB126 on vascular inflammation linked to hepatic dysfunction utilizing a liver injury mouse model. Male C57Bl/6 mice were fed either an amino acid control diet (CD) or a methionine-choline deficient (MCD) diet in this 14-week study. Mice were exposed to PCB126 (0.5 mg/kg) and analyzed for inflammatory, calorimetric and metabolic parameters. MCD diet-fed mice demonstrated steatosis, indicative of a compromised liver. Mice fed the MCD-diet and subsequently exposed to PCB126 manifested lower body fat mass, increased liver to body weight ratio and alterations in hepatic gene expression related to lipid and carbohydrate metabolism, implicating metabolic disturbances. PCB126-induced steatosis irrespective of the diet type, but only the MCD + PCB126 group exhibited steatohepatitis and fibrosis. Furthermore, PCB126 exposure in MCD-fed mice led to increased plasma inflammatory markers such as Icam-1, plasminogen activator inhibitor-1 and proatherogenic trimethylamine-N-oxide, suggesting inflammation of the peripheral vasculature that is characteristic of atherosclerosis. Taken together, our data provide new evidence of a link between a compromised liver, PCB-mediated hepatic inflammation and vascular inflammatory markers, suggesting that environmental pollutants can promote crosstalk between different organ systems, leading to inflammatory disease pathologies.

Silencing of solute carrier family 13 member 5 disrupts energy homeostasis and inhibits proliferation of human hepatocarcinoma cells

The solute carrier family 13 member 5 (SLC13A5), a sodium-coupled citrate transporter, plays a key role in importing citrate from the circulation into liver cells. Recent evidence has revealed that SLC13A5 deletion protects mice from high-fat diet-induced hepatic steatosis and that mutation of the SLC13A5 orthologues in Drosophila melanogaster and Caenorhabditis elegans promotes longevity. However, despite the emerging importance of SLC13A5 in energy homeostasis, whether perturbation of SLC13A5 affects the metabolism and malignancy of hepatocellular carcinoma is unknown. Here, we sought to determine whether SLC13A5 regulates hepatic energy homeostasis and proliferation of hepatoma cells. RNAi-mediated silencing of SLC13A5 expression in two human hepatoma cell lines, HepG2 and Huh7, profoundly suppressed cell proliferation and colony formation, and induced cell cycle arrest accompanied by increased expression of cyclin-dependent kinase inhibitor p21 and decreased expression of cyclin B1. Furthermore, such suppressive effects were also observed on the growth of HepG2 cell-derived xenografts expressing SLC13A5-shRNA in nude mice. Metabolically, knockdown of SLC13A5 in HepG2 and Huh7 cells was associated with a decrease in intracellular levels of citrate, the ratio of ATP/ADP, phospholipid content, and ATP citrate lyase expression. Moreover, both in vitro and in vivo assays demonstrated that SLC13A5 depletion promotes activation of the AMP-activated protein kinase, which was accompanied by deactivation of oncogenic mechanistic target of rapamycin signaling. Together, our findings expand the role of SLC13A5 from facilitating hepatic energy homeostasis to influencing hepatoma cell proliferation and suggest a potential role of SLC13A5 in the progression of human hepatocellular carcinoma.

Diabetes-induced abnormalities of mitochondrial function in rat brain cortex: the effect of n-3 fatty acid diet.

Diabetic encephalopathy, a proven complication of diabetes is associated with gradually developing end-organ damage in the CNS increasing the risk of stroke, cognitive dysfunction or Alzheimer's disease. This study investigated the response of rat cortical mitochondria to streptozotocin-induced diabetes and the potential for fish oil emulsion (FOE) to modulate mitochondrial function. Diabetes-induced deregulation of the respiratory chain function as a result of diminished complex I activity (CI) and cytochrome c oxidase hyperactivity was associated with attenuation of antioxidant defense of isolated cortical mitochondria, monitored by SOD activity, the thiol content, the dityrosine and protein-lipid peroxidation adduct formation. A parallel reduction in phosphorylation of the energy marker AMPK has pointed out to disrupted energy homeostasis. Dietary FOE administration partially preserved CI activity, restored AMPK phosphorylation, but was unable to attenuate oxidative stress and prevent the shift toward saturated fatty acids in the cardiolipin composition. Moreover, diabetes has induced alterations in the protein expression of the regulatory COX4 subunit of cytochrome c oxidase, in the inhibitory factor IF1 and ATP5A subunit of F0F1-ATP synthase, in the uncoupling protein UCP4 and supramolecular organization of the respiratory complexes. FOE administration to diabetic rats has partially reversed these alterations. This study suggests diabetes-induced dysfunction of brain cortical mitochondria and its modulation by FOE administration. The intricate diabetic milieu and the n-3 FA nutrigenomic strength, however require further investigations to be able to unequivocally evaluate neuroprotective and adverse effects of FOE supplementation on the diabetic brain function.

MP26-16 SUCCINATE IN VOIDING DYSFUNCTION ASSOCIATED WITH METABOLIC SYNDROME

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Basic Research & Pathophysiology I1 Apr 2017MP26-16 SUCCINATE IN VOIDING DYSFUNCTION ASSOCIATED WITH METABOLIC SYNDROME Monica Velasquez Flores, Abubakr Mossa, Philippe Cammisotto, and Lysanne Campeau Monica Velasquez FloresMonica Velasquez Flores More articles by this author , Abubakr MossaAbubakr Mossa More articles by this author , Philippe CammisottoPhilippe Cammisotto More articles by this author , and Lysanne CampeauLysanne Campeau More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.787AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Disruption in energy homeostasis, the main factor driving metabolic syndrome, may also be responsible for the development of its associated bladder dysfunction. Succinate, an intermediate of the citric acid cycle, along with its receptor, GPR91, have been implicated in different aspects of metabolic syndrome, and it is possible that their role could extend to the bladder. Our goal is to show that succinate can alter bladder function in a model of bladder overactivity associated with metabolic syndrome. METHODS Intraperitoneal injections of saline or succinate were administered daily for a period of 4 weeks to Sprague-Dawley (SD) rats and Dahl/SS rats, a model of metabolic syndrome with hypertension. Succinate levels were measured in the plasma and urine. Conscious cystometry was then performed. On the next day, bladders were collected for organ bath experiments and quantitative PCR for GPR91. Bladder detrusor strips were stimulated with potassium chloride (KCl), carbachol, and electrical field stimulation (EFS). One-way ANOVA with Bonferroni post-hoc test was used to measure differences between all groups. P<0.05 was considered significant. RESULTS Dahl rats have lower plasma succinate levels compared to SD rats. 24-hour urine levels of succinate were increased in succinate-treated rats in both SD and Dahl groups. SD succinate-treated rats had significantly lower levels of GPR91 in the bladder compared to SD control rats. This was not observed in Dahl rats. Dahl rats had shorter intercontraction intervals, smaller bladder capacities and lower micturition volumes than SD rats. Chronic administration of succinate lowered these parameters, albeit not significant. Organ bath data showed that the contractile responses to KCl, carbachol and EFS were significantly increased in detrusor strips from Dahl control rats compared to those from the other three groups. CONCLUSIONS Models of metabolic syndrome have obvious differences in bladder function compared with control rats. Chronic administration of succinate, as observed in vitro, alters detrusor contractility of Dahl rats. The absence of down-regulation of GPR91 in the Dahl bladder treated with succinate could explain the alterations in detrusor contractility observed only in this group. Increased urinary succinate levels may contribute to the development of bladder dysfunction. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e325-e326 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Monica Velasquez Flores More articles by this author Abubakr Mossa More articles by this author Philippe Cammisotto More articles by this author Lysanne Campeau More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Abstract B19: Disruption of energy homeostasis as an approach to block the proliferation of colon carcinomatosis

Abstract Strategies aimed at obtaining a complete cytoreduction are needed to improve long-term survival for patients with colorectal cancer peritoneal carcinomatosis (CRC-pc). We established organoid models that presented cancer stem cell characteristics from naïve CRC-pc surgical samples of two patients (C1 and C2). The organoids recapitulated their corresponding clinical samples in terms of 3D structure and immmunoistochemical profile and were enriched in LGR5 positive cancer stem cells. Proteomic analyses of organoids highlighted their strong dependence on energy producing pathways, suggesting that their targeting may be an effective therapeutic approach for the ablation of cancer cell malignancies. To test this hypothesis we treated organoids with an inhibitor of MIF/CD74 signaling axis, 4-iodo-6-phenylpyrimidine (4-IPP), and metformin, which inhibits mitochondrial oxidation. Both the drugs target metabolism acting on AMP-activated protein kinase (AMPK), the main regulator of cellular energy homeostasis. AMPK inhibits the major anabolic processes sustaining cancer cell proliferation and growth and confers cell plasticity to survive under conditions of metabolic stress, such as hypoxia and glucose deprivation, which is commonly observed in tumors with rapid growth. As a new finding we observed that treatment of organoids with 4-IPP resulted in decreased AMPK signaling activity, inducing a stress-signaling response and death of cultured organoids. Conversely, metformin treatment enhanced AMPK activation under energy stress, decreasing the activity of the anabolic factors ribosomal protein S6 and p4EBP-1 and inhibiting the mitochondrial activity, hindering cell proliferation. Furthermore, metformin treated organoids exhibited a Warburg-like metabolic profile. Our results show that organoid metabolism can be disrupted by metformin-induced AMPK activation but also through a strong reduction in AMPK functions caused by the removal of MIF/CD74 signaling axis that induces an irreversible disruption of energy homeostasis and ultimately causes cell death. Overall, we suggest that AMPK functions are crucial for energy metabolism of colorectal cancer peritoneal carcinomatosis, and regulation of AMPK activity could be a potential molecular target for the treatment of CRC-pc. Citation Format: Fabio Bozzi, Angela Mogavero, Luca Varinelli, Annunziata Gloghini, Valerio Leoni, Galina V. Beznoussenko, Alexandre A. Mironov, Ermanno Leo, Marco A. Pierotti, Italia Bongarzone, Manuela Gariboldi. Disruption of energy homeostasis as an approach to block the proliferation of colon carcinomatosis. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr B19.

Macrophage-Mediated Clofazimine Sequestration Is Accompanied by a Shift in Host Energy Metabolism

Prolonged (8 weeks) oral administration of clofazimine results in a profound pharmacodynamic response—bioaccumulation in macrophages (including Kupffer cells) as intracellular crystal-like drug inclusions (CLDIs) with an associated increase in interleukin-1 receptor antagonist production. Notably, CLDI formation in Kupffer cells concomitantly occurs with the formation of macrophage-centric granulomas. Accordingly, we sought to understand the impact of these events on host metabolism using 1H-nuclear magnetic resonance metabolomics. Mice received a clofazimine or vehicle-enriched (sham) diet for at least 8 weeks. At 2 weeks, the antimicrobial activity of clofazimine was evident by changes in urine metabolites. From 2 to 8 weeks, there was a striking change in metabolite levels indicative of a reorientation of host energy metabolism paralleling the onset of CLDI and granuloma formation. This was evidenced by a progressive reduction in urine levels of metabolites involved in one-carbon metabolism with corresponding increases in whole blood, and changes in metabolites associated with lipid, nucleotide and amino acid metabolism, and glycolysis. Although clofazimine-fed mice ate more, they gained less weight than control mice. Together, these results indicate that macrophage sequestration of clofazimine as CLDIs and granuloma formation is accompanied by a profound metabolic disruption in energy homeostasis and one-carbon metabolism.

Novel Fatty Acid Oxidation Inhibitor Avocatinb Induces AMPK-Dependent Apoptosis of AML Cells Co-Cultured with BM-Adipocytes

Adipocytes are the prevalent stromal cell type in adult bone marrow (BM), comprising approximately 60% of BM space in a 65-year old person. In BM environment, leukemia cells continuously adapt to deficient supply of nutrients and oxygen, acquiring quiescent and chemoresistant profiles. Fatty acid metabolism is one of the key energy pathways for AML survival (Samudio, J Clin Invest. 2010), and we previously demonstrated that AML cells activate oxidative phosphorylation and fatty acid oxidation (FAO) in the presence of BM-adipocytes (Tabe ASH 2015). These findings indicate the importance of FAO for AML cells survival under the adipocyte-abundant BM-microenvironment.A novel FAO inhibitor avocatinB, an odd-numbered carbon lipid derived from avocado fruit, has been recently shown to induce apoptosis and cell growth inhibition in AML cells (Lee, Cancer Res. 2015). In the present study, we investigated the molecular mechanisms of anti-leukemic effect of avocatinB in AML cells, utilizing THP1, OCI-AML3 and U937 AML cell lines co-cultured with human mesenchymal stem cells (MSC)-derived BM-adipocytes, mimicking the aging BM microenvironment.Treatment with avocatin B significantly induced ROS accumulation in U937 cells co-cultured with BM-adipocytes (MFI of ROS-sensitive dye; avocatinB (-) / (+); 164±50 / 581±85, p=0.04), whereas only minimum increase of ROS was observed in the absence of BM-adipocyte, indicating that avocatinB causes progressive oxidative damage in AML cells under the BM-adipocyte co-culture conditions. Of importance, avocatinB synergistically enhanced apoptotic effects of AraC in the presence of BM-adipocytes (combination index CI; adipocyte (-) / (+); THP1: 1.2 / 0.4, OCI-AML3: 0.7 / 0.3).Immunoblot analysis demonstrated that avocatinB activated the stress response kinase AMPK in THP1 and OCI-AML3 cells under BM-adipocyte co-culture conditions. AMPK is a crucial cellular energy sensor that regulates energy metabolism including FAO and gene transcription through mTOR inhibition. We therefore investigated the role of AMPK in avocatinB induced anti-leukemic effects on AML cells, utilizing AMPK knockdown (shAMPK) OCI-AML3 cells. shAMPK OCI-AML3 cells were significantly less sensitive to nutrient starvation-induced cell death in the absence of BM-adipocyte (p<0.01). While co-culture with BM-adipocytes protected control (nsAMPK) OCI-AML3 cells from spontaneous cell death, co-culture facilitated cell death of shAMPK cells. In turn, shAMPK OCI-AML cells were less sensitive to avocatinB compared to nsAMPKcells in the absence of BM-adipocyte with no additive/synergistic anti-proliferative effects of avocainB and AraC combination irrespective of the presence of BM-adipocytes (CI > 1.0).In nsAMPK cells, but not in shAMPKcells BM-adipocyte co-culture upregulated p-4EBP1 and cMyc expression which was abrogated by avocatinB and AraC combination treatment accompanied by induction of cleaved caspase 3.In summary, FAO inhibitor avocatinB induces pro-apoptotic effects through AMPK-dependent inhibition of mTOR signaling that disrupts energy homeostasis and induces ROS accumulation in AML cells under BM-adipocyte co-culture conditions. The ability of avocatinB to selectively enhance anti-leukemic effects of AraC in the presence of BM-adipocytes suggests that the strategies targeting FAO warrant further exploration in elderly AML patients. DisclosuresKonopleva:Reata Pharmaceuticals: Equity Ownership; Abbvie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Stemline: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Calithera: Research Funding.

Changes in Energy Metabolism after Continuous Positive Airway Pressure for Obstructive Sleep Apnea

Disrupted energy homeostasis in obstructive sleep apnea (OSA) may lead to weight gain. Paradoxically, treating OSA with continuous positive airway pressure (CPAP) may also promote weight gain, although the underlying mechanism remains unclear. To explore the underlying mechanism by which patients with OSA gain weight after CPAP. A comprehensive assessment of energy metabolism was performed in 63 newly diagnosed OSA study participants (51 men; 60.8 ± 10.1 yr; apnea-hypopnea index >20 h(-1)) at baseline, CPAP initiation, and at a 3-month follow-up. Measurements included polysomnography, body weight, body composition, basal metabolic rate (BMR), hormones (norepinephrine, cortisol, leptin, ghrelin, insulin-like growth factor-1), dietary intake, eating behavior, and physical activity. BMR significantly decreased after CPAP (1,584 kcal/d at baseline, 1,561 kcal/d at CPAP initiation, and 1,508 kcal/d at follow-up; P < 0.001), whereas physical activity and total caloric intake did not significantly change. In multivariate regression, baseline apnea-hypopnea index, Δurine norepinephrine, and CPAP adherence were significant predictors of ΔBMR. The weight gainers had higher leptin levels, lower ghrelin levels, and higher eating behavior scores than the non-weight gainers, indicating a positive energy balance and disordered eating behavior among the weight gainers. Among the parameters related to energy metabolism, increased caloric intake was a particularly significant predictor of weight gain. Although a reduction in BMR after CPAP predisposes to a positive energy balance, dietary intake and eating behavior had greater impacts on weight change. These findings highlight the importance of lifestyle modifications combined with CPAP. Clinical trial registered with http://www.umin.ac.jp/english/ (UMIN000012639).

Augmentation of glycolytic metabolism by meclizine is indispensable for protection of dorsal root ganglion neurons from hypoxia-induced mitochondrial compromise

To meet energy demands, dorsal root ganglion (DRG) neurons harbor high mitochondrial content, which renders them acutely vulnerable to disruptions of energy homeostasis. While neurons typically rely on mitochondrial energy production and have not been associated with metabolic plasticity, new studies reveal that meclizine, a drug, recently linked to modulations of energy metabolism, protects neurons from insults that disrupt energy homeostasis. We show that meclizine rapidly enhances glycolysis in DRG neurons and that glycolytic metabolism is indispensable for meclizine-exerted protection of DRG neurons from hypoxic stress. We report that supplementation of meclizine during hypoxic exposure prevents ATP depletion, preserves NADPH and glutathione stores, curbs reactive oxygen species (ROS) and attenuates mitochondrial clustering in DRG neurites. Using extracellular flux analyzer, we show that in cultured DRG neurons meclizine mitigates hypoxia-induced loss of mitochondrial respiratory capacity. Respiratory capacity is a measure of mitochondrial fitness and cell ability to meet fluctuating energy demands and therefore, a key determinant of cellular fate. While meclizine is an ‘old’ drug with long record of clinical use, its ability to modulate energy metabolism has been uncovered only recently. Our findings documenting neuroprotection by meclizine in a setting of hypoxic stress reveal previously unappreciated metabolic plasticity of DRG neurons as well as potential for pharmacological harnessing of the newly discovered metabolic plasticity for protection of peripheral nervous system under mitochondria compromising conditions.

A 3-methylcrotonyl-CoA carboxylase deficient human skin fibroblast transcriptome reveals underlying mitochondrial dysfunction and oxidative stress

Isolated 3-methylcrotonyl-CoA carboxylase (MCC) deficiency is an autosomal recessive inherited metabolic disease of leucine catabolism with a highly variable phenotype. Apart from extensive mutation analyses of the MCCC1 and MCCC2 genes encoding 3-methylcrotonyl-CoA carboxylase (EC 6.4.1.4), molecular data on MCC deficiency gene expression studies in human tissues is lacking. For IEMs, unbiased ⿿-omics⿿ approaches are starting to reveal the secondary cellular responses to defects in biochemical pathways. Here we present the first whole genome expression profile of immortalized cultured skin fibroblast cells of two clinically affected MCC deficient patients and two healthy individuals generated using Affymetrix®HuExST1.0 arrays. There were 16191 significantly differentially expressed transcript IDs of which 3591 were well annotated and present in the predefined knowledge database of Ingenuity Pathway Analysis software used for downstream functional analyses. The most noticeable feature of this MCCA deficient skin fibroblast transcriptome was the typical genetic hallmark of mitochondrial dysfunction, decreased antioxidant response and disruption of energy homeostasis, which was confirmed by mitochondrial functional analyses. The MCC deficient transcriptome seems to predict oxidative stress that could alter the complex secondary cellular response that involve genes of the glycolysis, the TCA cycle, OXPHOS, gluconeogenesis, β-oxidation and the branched-chain fatty acid metabolism. An important emerging insight from this human MCCA transcriptome in combination with previous reports is that chronic exposure to the primary and secondary metabolites of MCC deficiency and the resulting oxidative stress might impact adversely on the quality of life and energy levels, irrespective of whether MCC deficient individuals are clinically affected or asymptomatic.

Diet-induced cellular neuroinflammation in the hypothalamus: Mechanistic insights from investigation of neurons and microglia

Diet-induced obesity can lead to detrimental chronic disorders. The severity of this global epidemic has encouraged ongoing research to characterize the mechanisms underlying obesity and its comorbidities. Recent evidence suggests that saturated fatty acids (SFA) in high-fat diets rapidly generate inflammation in the arcuate nucleus of the hypothalamus (ARC), which centrally regulates whole-body energy homeostasis. Herein, we will review the roles of hypothalamic neurons and resident microglia in the initiation of SFA-induced hypothalamic inflammation. Particularly, we focus on neuronal and microglial free fatty acid-sensing and capacity to produce inflammatory signaling. We also outline a potential role of peripherally-derived monocytes in this inflammation. And finally, we explore synaptic plasticity as a mechanism through which hypothalamic inflammation can modulate ARC circuitry, and thus disrupt energy homeostasis.

Biochemical Characterisation and Whole Genome Expression Profiling of Cultured Skin Fibroblasts from Two South African Adults with Urinary 3-Hydroxyisovaleric Acid and 3-Methylcrotonylglycine

We report on the first case of marginal 3-methylcrotonyl-CoA carboxylase (MCC) deficiency in South Africa. Urinary 3-hydroxyisovaleric acid and 3-methylcrotonylglycine were detected in four males of a non-consanguineous family. Only the index patient (NWU001) had non-specific symptoms, the others were asymptomatic. The inherited metabolite profile and partially reduced MCC activity were indicative of marginal MCC deficiency. In vivo L-leucine loading confirmed a reduced flux through the leucine degradation pathway. No known deleterious mutations were detected in the open reading frames of MCCC1 and MCCC2. NWU001 was heterozygous for a SNP in MCCC1 (rs2270968; c.1391A>C, p.H464P). NWU002 was heterozygous for a MCCC2 splice variant which skips exon 7 and causes an in frame deletion of 38 amino acids that is identical to a predicted shorter MCCC2 isoform-2 (Q9HCC0-2). Whole genome expression profiles from cultured skin fibroblasts of NWU001 and NWU002 and two healthy adults using Affymetrix® HuExST1.0 arrays detected 14237 significantly differentially expressed transcript IDs of which only 1277 have known annotation and gene association. The underlying molecular interactions, secondary signalling responses and functional relationships of these 1277 transcripts were inspected following a knowledge-based functional analyses approach using Ingenuity Pathway Analysis software. The transcriptome had a footprint of oxidative stress, disruption of energy homeostasis, inflammation, impaired cellular maintenance and repair mechanisms. Of note was the significant up regulation of the fatty acid amide hydrolase variant 2 (FAAH2) HuChrX transcript in the anandamide degradation canonical pathway. The observations that the two MCC transcripts were not significantly differentially expressed and that more than 90% of the significantly differently expressed transcripts are still poorly annotated further support the notion that secondary factors other than the MCC loci impact on the MCC deficiency phenome.

Energy disruptors: rising stars in anticancer therapy?

The metabolic features of tumor cells diverge from those of normal cells. Otto Warburg was the first to observe that cancer cells dramatically increase their glucose consumption to generate ATP. He also claimed that cancer cells do not have functional mitochondria or oxidative phosphorylation (OXPHOS) but simply rely on glycolysis to provide ATP to the cell, even in the presence of oxygen (aerobic glycolysis). Several studies have revisited this observation and demonstrated that most cancer cells contain metabolically efficient mitochondria. Indeed, to sustain high proliferation rates, cancer cells require functional mitochondria to provide ATP and intermediate metabolites, such as citrate and cofactors, for anabolic reactions. This difference in metabolism between normal and tumors cells causes the latter to be more sensitive to agents that can disrupt energy homeostasis. In this review, we focus on energy disruptors, such as biguanides, 2-deoxyglucose and 5-aminoimidazole-4-carboxamide ribonucleotide, that interfere with the main metabolic pathways of the cells, OXPHOS, glycolysis and glutamine metabolism. We discuss the preclinical data and the mechanisms of action of these disruptors at the cellular and molecular levels. Finally, we consider whether these drugs can reasonably contribute to the antitumoral therapeutic arsenal in the future.

Reciprocal Changes in Phosphoenolpyruvate Carboxykinase and Pyruvate Kinase with Age Are a Determinant of Aging in Caenorhabditis elegans

Aging involves progressive loss of cellular function and integrity, presumably caused by accumulated stochastic damage to cells. Alterations in energy metabolism contribute to aging, but how energy metabolism changes with age, how these changes affect aging, and whether they can be modified to modulate aging remain unclear. In locomotory muscle of post-fertile Caenorhabditis elegans, we identified a progressive decrease in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), a longevity-associated metabolic enzyme, and a reciprocal increase in glycolytic pyruvate kinase (PK) that were necessary and sufficient to limit lifespan. Decline in PEPCK-C with age also led to loss of cellular function and integrity including muscle activity, and cellular senescence. Genetic and pharmacologic interventions of PEPCK-C, muscle activity, and AMPK signaling demonstrate that declines in PEPCK-C and muscle function with age interacted to limit reproductive life and lifespan via disrupted energy homeostasis. Quantifications of metabolic flux show that reciprocal changes in PEPCK-C and PK with age shunted energy metabolism toward glycolysis, reducing mitochondrial bioenergetics. Last, calorie restriction countered changes in PEPCK-C and PK with age to elicit anti-aging effects via TOR inhibition. Thus, a programmed metabolic event involving PEPCK-C and PK is a determinant of aging that can be modified to modulate aging.

METABOLIC ASPECTS OF PHARMACOLOGICAL DEPRIVATION PERIPHERAL NICOTINIC SENSITIVE CHOLINERGIC SYNAPSES

Content of ATP, ADP, of AMP and activity of isozyme systems LDH in the cranial cervical sympathetic ganglia (CSSG) rabbits was investigated with partial and complete deprivation of N-cholinergic (N-HE) synapses. Dynamics of activity of LDH and content of macroergs in deprivation N-HE synapses indicates that blockade of N-HE synapses results in sympathetic ganglia to significant energy shortages and disruption of energy homeostasis. It is assumed that changes in energy metabolism are the main cause CSSG hypofunction observed during pharmacological blockade by antagonists N-HE synapses.