Deciphering the ‘Elixir of Life’: Dynamic Perspectives into the Allosteric Modulation of Mitochondrial ATP Synthase by J147, a Novel Drug in the Treatment of Alzheimer's Disease

The discovery of J147 represented a significant milestone in the treatment of age‐related disorders, which was further augmented by the recent identification of mitochondrial ATP synthase as the therapeutic target. However, the underlying molecular events associated with the modulatory activity of J147 have remained unresolved till date. Herein, we present, for the first time, a dynamical approach to investigate the allosteric regulation of mATP synthase by J147, using a reliable human αγβ protein model. The highlight of our findings is the existence of the J147‐bound protein in distinct structural associations at different MD simulation periods coupled with concurrent open?close transitions of the β catalytic and α allosteric (ATP5A) sites as defined by Cα distances (d), TriCα (Θ) and dihedral (φ) angular parameters. Firstly, there was an initial pairing of the αγ subunits away from the β subunit followed by the formation of the ‘non‐catalytic’ αβ pair at a distance from the γ subunit. Interestingly, J147‐induced structural arrangements were accompanied by the systematic transition of the β catalytic site from a closed to an open state, while there was a concurrent transition of the allosteric site from an open α_E conformation to a closed state. Consequentially, J147 reduced the structural activity of the whole αγβ complex, while the unbound system exhibited high atomistic deviations and structural flexibility. Furthermore, J147 exhibited favorable binding at the allosteric site of mATP synthase with considerable electrostatic energy contributions from Gln215, Gly217, Thr219, Asp312, Asp313, Glu371 and Arg406. These findings provide details on the possible effects of J147 on mitochondrial bioenergetics, which could facilitate the structure‐based design of novel small‐molecule modulators of mATP synthase in the management of Alzheimer's disease and other neurodegenerative disorders.     

ALS/FTD‐associated FUS activates GSK‐3β to disrupt the VAPB–PTPIP51 interaction and ER–mitochondria associations

Defective FUS metabolism is strongly associated with amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD), but the mechanisms linking FUS to disease are not properly understood. However, many of the functions disrupted in ALS/FTD are regulated by signalling between the endoplasmic reticulum (ER) and mitochondria. This signalling is facilitated by close physical associations between the two organelles that are mediated by binding of the integral ER protein VAPB to the outer mitochondrial membrane protein PTPIP51, which act as molecular scaffolds to tether the two organelles. Here, we show that FUS disrupts the VAPB–PTPIP51 interaction and ER–mitochondria associations. These disruptions are accompanied by perturbation of Ca²⁺ uptake by mitochondria following its release from ER stores, which is a physiological read‐out of ER–mitochondria contacts. We also demonstrate that mitochondrial ATP production is impaired in FUS‐expressing cells; mitochondrial ATP production is linked to Ca²⁺ levels. Finally, we demonstrate that the FUS‐induced reductions to ER–mitochondria associations and are linked to activation of glycogen synthase kinase‐3β (GSK‐3β), a kinase already strongly associated with ALS/FTD.     

In vivo and in vitro assessment of brain bioenergetics in aging rats

Brain energy disorders can be present in aged men and animals. To this respect, the mitochondrial and free radical theory of aging postulates that age‐associated brain energy disorders are caused by an imbalance between pro‐ and anti‐oxidants that can result in oxidative stress. Our study was designed to investigate brain energy metabolism and the activity of endogenous antioxidants during their lifespan in male Wistar rats. In vivo brain bioenergetics were measured using ³¹P nuclear magnetic resonance (NMR) spectroscopy and in vitro by polarographic analysis of mitochondrial oxidative phosphorylation. When compared to the young controls, a significant decrease of age‐dependent mitochondrial respiration and adenosine‐3‐phosphate (ATP) production measured in vitro correlated with significant reduction of forward creatine kinase reaction (kfor) and with an increase in phosphocreatine (PCr)/ATP, PCr/Pi and PME/ATP ratio measured in vivo. The levels of enzymatic antioxidants catalase, GPx and GST significantly decreased in the brain tissue as well as in the peripheral blood of aged rats. We suppose that mitochondrial dysfunction and oxidative inactivation of endogenous enzymes may participate in age‐related disorders of brain energy metabolism.     

SIRT3 deregulation is linked to mitochondrial dysfunction in Alzheimer's disease

Alzheimer's disease (AD) is the leading cause of dementia in the elderly. Despite decades of study, effective treatments for AD are lacking. Mitochondrial dysfunction has been closely linked to the pathogenesis of AD, but the relationship between mitochondrial pathology and neuronal damage is poorly understood. Sirtuins (SIRT, silent mating type information regulation 2 homolog in yeast) are NAD‐dependent histone deacetylases involved in aging and longevity. The objective of this study was to investigate the relationship between SIRT3 and mitochondrial function and neuronal activity in AD. SIRT3 mRNA and protein levels were significantly decreased in AD cerebral cortex, and Ac‐p53 K320 was significantly increased in AD mitochondria. SIRT3 prevented p53‐induced mitochondrial dysfunction and neuronal damage in a deacetylase activity‐dependent manner. Notably, mitochondrially targeted p53 (mito‐p53) directly reduced mitochondria DNA‐encoded ND2 and ND4 gene expression resulting in increased reactive oxygen species (ROS) and reduced mitochondrial oxygen consumption. ND2 and ND4 gene expressions were significantly decreased in patients with AD. p53‐ChIP analysis verified the presence of p53‐binding elements in the human mitochondrial genome and increased p53 occupancy of mitochondrial DNA in AD. SIRT3 overexpression restored the expression of ND2 and ND4 and improved mitochondrial oxygen consumption by repressing mito‐p53 activity. Our results indicate that SIRT3 dysfunction leads to p53‐mediated mitochondrial and neuronal damage in AD. Therapeutic modulation of SIRT3 activity may ameliorate mitochondrial pathology and neurodegeneration in AD.     

Supramolecular organization of the yeast F1Fo-ATP synthase

Background information. The yeast mitochondrial F₁F_o‐ATP synthase is a large complex of 600 kDa that uses the proton electrochemical gradient generated by the respiratory chain to catalyse ATP synthesis from ADP and P_i. For a large range of organisms, it has been shown that mitochondrial ATP synthase adopts oligomeric structures. Moreover, several studies have suggested that a link exists between ATP synthase and mitochondrial morphology. Results and discussion. In order to understand the link between ATP synthase oligomerization and mitochondrial morphology, more information is needed on the supramolecular organization of this enzyme within the inner mitochondrial membrane. We have conducted an electron microscopy study on wild‐type yeast mitochondria at different levels of organization from spheroplast to isolated ATP synthase complex. Using electron tomography, freeze‐fracture, negative staining and image processing, we show that cristae form a network of lamellae, on which ATP synthase dimers assemble in linear and regular arrays of oligomers. Conclusions. Our results shed new light on the supramolecular organization of the F₁F_o‐ATP synthase and its potential role in mitochondrial morphology.     

The mechanism underlying the effects of the cell surface ATP synthase on the regulation of intracellular acidification during acidosis

The F1F0 ATP synthase has recently become the focus of anti‐cancer research. It was once thought that ATP synthases were located strictly on the inner mitochondrial membrane; however, in 1994, it was found that some ATP synthases localized to the cell surface. The cell surface ATP synthases are involved in angiogenesis, lipoprotein metabolism, innate immunity, hypertension, the regulation of food intake, and other processes. Inhibitors of this synthase have been reported to be cytotoxic and to induce intracellular acidification. However, the mechanisms by which these effects are mediated and the molecular pathways that are involved remain unclear. In this study, we aimed to determine whether the inhibition of cell proliferation and the induction of cell apoptosis that are induced by inhibitors of the cell surface ATP synthase are associated with intracellular acidification and to investigate the mechanism that underlines the effects of this inhibition, particularly in an acidic tumor environment. We demonstrated that intracellular acidification contributes to the cell proliferation inhibition that is mediated by cell surface ATP synthase inhibitors, but not to the induction of apoptosis. Intracellular acidification is only one of the mechanisms of ecto‐ATP synthase‐targeted antitumor drugs. We propose that intracellular acidification in combination with the inhibition of cell surface ATP generation induce cell apoptosis after cell surface ATP synthase blocked by its inhibitors. A better understanding of the mechanisms activated by ecto‐ATP synthase‐targeted cancer therapies may facilitate the development of potent anti‐tumor therapies, which target this enzyme and do not exhibit clinical limitations. J. Cell. Biochem. 114: 1695–1703, 2013. © 2013 Wiley Periodicals, Inc.     

Genetic background modifies CNS‐mediated sensorimotor decline in the AD‐BXD mouse model of genetic diversity in Alzheimer's disease

Many patients with Alzheimer's dementia (AD) also exhibit noncognitive symptoms such as sensorimotor deficits, which can precede the hallmark cognitive deficits and significantly impact daily activities and an individual's ability to live independently. However, the mechanisms underlying sensorimotor dysfunction in AD and their relationship with cognitive decline remains poorly understood, due in part to a lack of translationally relevant animal models. To address this, we recently developed a novel model of genetic diversity in Alzheimer's disease, the AD‐BXD genetic reference panel. In this study, we investigated sensorimotor deficits in the AD‐BXDs and the relationship to cognitive decline in these mice. We found that age‐ and AD‐related declines in coordination, balance and vestibular function vary significantly across the panel, indicating genetic background strongly influences the expressivity of the familial AD mutations used in the AD‐BXD panel and their impact on motor function. Although young males and females perform comparably regardless of genotype on narrow beam and inclined screen tasks, there were significant sex differences in aging‐ and AD‐related decline, with females exhibiting worse decline than males of the same age and transgene status. Finally, we found that AD motor decline is not correlated with cognitive decline, suggesting that sensorimotor deficits in AD may occur through distinct mechanisms. Overall, our results suggest that AD‐related sensorimotor decline is strongly dependent on background genetics and is independent of dementia and cognitive deficits, suggesting that effective therapeutics for the entire spectrum of AD symptoms will likely require interventions targeting each distinct domain involved in the disease.     

Mass spectrometry and tandem mass spectrometry analysis of rat mitochondrial ATP synthase: up-regulation in pancreatic acinar cells treated with cerulein

Mitochondrion is a vulnerable intracellular target to reactive oxygen species (ROS). ROS have been considered to be important regulators of the pathogenesis of pancreatitis. This study aims to determine whether ROS induces mitochondrial damage by monitoring the expression level of mitochondrial ATP synthase as the key molecular component in mitochondria associated with cellular damage. Pancreatic acinar AR42J cells were treated with cerulein which induces symptoms similar to that associated with human acute pancreatitis. Proteins were separated by two-dimensional electrophoresis using pH gradients of 5-8 and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MS), quadrupole time-of-flight MS and MS/MS with nano-electrospray. Following cerulein treatment, mitochondrial ATP synthase beta chain was highly expressed compared to nontreated cell. The protein was identified by its pI of 5.2 and molecular weight (56 354 Da) with 27 matched peptides. Among the MS spectrum, precursor ions m/z 488.28, 544.81, 631.82, 693.34, 718.38, 729.41, 801.40, 809.39, 825.94, and 994.52 were further identified using MS/MS and confirmed the isolated protein to be mitochondrial ATP synthase beta chain. In conclusion, cerulein-induced oxidative injury may result in the induction of mitochondrial ATP synthase, which may act as an adaptive pathophysiological process in the pancreas.     

Kisspeptin preserves mitochondrial function by inducing mitophagy and autophagy in aging rat brain hippocampus and human neuronal cell line

It has become amply clear that mitochondrial function defined by quality, quantity, dynamics, homeostasis, and regulated by mitophagy and mitochondrial biogenesis is a critical metric of human aging and disease. As a consequence, therapeutic interventions that can improve mitochondrial function can have a profound impact on human health and longevity. Kisspeptins are neuropeptides belonging to the family of metastasis suppressors that are known to regulate functions like fertility, reproduction, and metabolism. Using SKNSH cell line, hippocampus explant cultures and hippocampus of aging Wistar rat models, we show that Kisspeptin-10 (Kp) induces autophagy and mitophagy via calcium, Ca²⁺/CaM-dependent protein kinase kinase β (CaMKKβ), AMP-activated protein kinase (AMPK), and Unc-51 like autophagy activating kinase (ULK1) signaling pathway that is independent of mammalian target of rapamycin (mTOR). Intriguingly, Kp administration in vivo also results in the enhancement of mitochondrial number, complex I activity, and Adenosine Triphosphate (ATP) levels. This study uncovers potential effects of Kp in protecting mitochondrial health and as a possible therapeutic intervention to hippocampus associated impairments such as memory, cognitive aging, and other diseases linked to mitochondrial dysfunction.     

From Mitochondrial Dysfunction to Amyloid Beta Formation: Novel Insights into the Pathogenesis of Alzheimer’s Disease

The non-Mendelian sporadic Alzheimer's disease (AD) is the most frequent form of dementia diagnosed worldwide. The most important risk factor to develop sporadic AD is aging itself. Next to hyperphosphorylated Tau, intracellular amyloid beta (A?) oligomers are known to initiate a cascade of pathological events ranging from mitochondrial dysfunction, synaptic dysfunction, oxidative stress, and loss of calcium regulation, to inflammation. All these events are considered to play an important role in the progressive loss of neurons. The molecular mechanisms determining the balance between A? production and clearance during the progression of the disease are not well understood. Furthermore, there is cumulating evidence that A? formation impairs mitochondrial function and that mitochondrial dysfunction is an early event in the pathogenesis of AD. On the other hand, mitochondrial dysfunction, in particular increased formation of mitochondrially derived reactive oxygen species, promote A? formation. Here, we review these latest findings linking mitochondrial dysfunction and A? formation. We propose that mitochondrial dysfunction, which is well-known to increase with age, is an initial trigger for A? production. As A? itself further accelerates mitochondrial dysfunction and oxidative stress, its formation is self-stimulated. Taken together, a vicious cycle is initiated that originates from mitochondrial dysfunction, implying that AD can be viewed as an age-associated mitochondrial disorder. The proposed mechanism sheds new light on the pathophysiological changes taking place during the progression of AD as well as in the aging process.     

Proteome profiling of aging in mouse models: Differential expression of proteins involved in metabolism,transport, and stress response in kidney

Aging is a time‐dependent complex biological phenomenon observed in various organs and organelles of all living organisms. To understand the molecular mechanism of age‐associated functional loss in aging kidneys, we have analyzed the expression of proteins in the kidneys of young (19–22 wk) and old (24 months) C57/BL6 male mice using 2‐DE followed by LC‐MS/MS. We found that expression levels of 49 proteins were upregulated (p ≤ 0.05), while that of only ten proteins were downregulated (p ≤ 0.05) due to aging. The proteins identified belong to three broad functional categories: (i) metabolism (e.g., aldehyde dehydrogenase family, ATP synthase β‐subunit, malate dehydrogenase, NADH dehydrogenase (ubiquinone), hydroxy acid oxidase 2), (ii) transport (e.g., transferrin), and (iii) chaperone/stress response (e.g., Ig‐binding protein, low density lipoprotein receptor‐related protein associated protein 1, selenium‐binding proteins (SBPs)). Some proteins with unknown functions were also identified as being differentially expressed. ATP synthase β subunit, transferrin, fumarate hydratase, SBPs, and albumin are present in multiple forms, possibly arising due to proteolysis or PTMs. The above functional categories suggest specific mechanisms and pathways for age‐related kidney degeneration.     

Long‐term intake of phenolic compounds attenuates age‐related cardiac remodeling

With the onset of advanced age, cardiac‐associated pathologies have increased in prevalence. The hallmarks of cardiac aging include cardiomyocyte senescence, fibroblast proliferation, inflammation, and hypertrophy. The imbalance between levels of reactive oxygen species (ROS) and antioxidant enzymes is greatly enhanced in aging cells, promoting cardiac remodeling. In this work, we studied the long‐term impact of phenolic compounds (PC) on age‐associated cardiac remodeling. Three‐month‐old Wistar rats were treated for 14 months till middle‐age with either 2.5, 5, 10, or 20 mg kg^?1 day^?1 of PC. PC treatment showed a dose‐dependent preservation of cardiac ejection fraction and fractional shortening as well as decreased hypertrophy reflected by left ventricular chamber diameter and posterior wall thickness as compared to untreated middle‐aged control animals. Analyses of proteins from cardiac tissue showed that PC attenuated several hypertrophic pathways including calcineurin/nuclear factor of activated T cells (NFATc3), calcium/calmodulin‐dependent kinase II (CAMKII), extracellular regulated kinase 1/2 (ERK1/2), and glycogen synthase kinase 3ß (GSK 3ß). PC‐treated groups exhibited reduced plasma inflammatory and fibrotic markers and revealed as well ameliorated extracellular matrix remodeling and interstitial inflammation by a downregulated p38 pathway. Myocardia from PC‐treated middle‐aged rats presented less fibrosis with suppression of profibrotic transforming growth factor‐ß1 (TGF‐ß1) Smad pathway. Additionally, reduction of apoptosis and oxidative damage in the PC‐treated groups was reflected by elevated antioxidant enzymes and reduced RNA/DNA damage markers. Our findings pinpoint that a daily consumption of phenolic compounds could preserve the heart from the detrimental effects of aging storm.     

Crosstalk between the M1 muscarinic acetylcholine receptor and the endocannabinoid system: A relevance for Alzheimer's disease?

Alzheimer's disease (AD) is a neurodegenerative disorder which accounts for 60–70% of the 50 million worldwide cases of dementia and is characterised by cognitive impairments, many of which have long been associated with dysfunction of the cholinergic system. Although the M₁ muscarinic acetylcholine receptor (mAChR) is considered a promising drug target for AD, ligands targeting this receptor have so far been unsuccessful in clinical trials. As modulatory receptors to cholinergic transmission, the endocannabinoid system may be a promising drug target to allow fine tuning of the cholinergic system. Furthermore, disease-related changes have been found in the endocannabinoid system during AD progression and indeed targeting the endocannabinoid system at specific disease stages alleviates cognitive symptoms in numerous mouse models of AD. Here we review the role of the endocannabinoid system in AD, and its crosstalk with mAChRs as a potential drug target for cholinergic dysfunction.     

Coenzyme Q10 restores oocyte mitochondrial function and fertility during reproductive aging

Female reproductive capacity declines dramatically in the fourth decade of life as a result of an age‐related decrease in oocyte quality and quantity. The primary causes of reproductive aging and the molecular factors responsible for decreased oocyte quality remain elusive. Here, we show that aging of the female germ line is accompanied by mitochondrial dysfunction associated with decreased oxidative phosphorylation and reduced Adenosine tri‐phosphate (ATP) level. Diminished expression of the enzymes responsible for CoQ production, Pdss2 and Coq6, was observed in oocytes of older females in both mouse and human. The age‐related decline in oocyte quality and quantity could be reversed by the administration of CoQ10. Oocyte‐specific disruption of Pdss2 recapitulated many of the mitochondrial and reproductive phenotypes observed in the old females including reduced ATP production and increased meiotic spindle abnormalities, resulting in infertility. Ovarian reserve in the oocyte‐specific Pdss2‐deficient animals was diminished, leading to premature ovarian failure which could be prevented by maternal dietary administration of CoQ10. We conclude that impaired mitochondrial performance created by suboptimal CoQ10 availability can drive age‐associated oocyte deficits causing infertility.     

Defective dimerization of FoF1‐ATP synthase secondary to glycation favors mitochondrial energy deficiency in cardiomyocytes during aging

Aged cardiomyocytes develop a mismatch between energy demand and supply, the severity of which determines the onset of heart failure, and become prone to undergo cell death. The FoF1‐ATP synthase is the molecular machine that provides >90% of the ATP consumed by healthy cardiomyocytes and is proposed to form the mitochondrial permeability transition pore (mPTP), an energy‐dissipating channel involved in cell death. We investigated whether aging alters FoF1‐ATP synthase self‐assembly, a fundamental biological process involved in mitochondrial cristae morphology and energy efficiency, and the functional consequences this may have. Purified heart mitochondria and cardiomyocytes from aging mice displayed an impaired dimerization of FoF1‐ATP synthase (blue native and proximity ligation assay), associated with abnormal mitochondrial cristae tip curvature (TEM). Defective dimerization did not modify the in vitro hydrolase activity of FoF1‐ATP synthase but reduced the efficiency of oxidative phosphorylation in intact mitochondria (in which membrane architecture plays a fundamental role) and increased cardiomyocytes’ susceptibility to undergo energy collapse by mPTP. High throughput proteomics and fluorescence immunolabeling identified glycation of 5 subunits of FoF1‐ATP synthase as the causative mechanism of the altered dimerization. In vitro induction of FoF1‐ATP synthase glycation in H9c2 myoblasts recapitulated the age‐related defective FoF1‐ATP synthase assembly, reduced the relative contribution of oxidative phosphorylation to cell energy metabolism, and increased mPTP susceptibility. These results identify altered dimerization of FoF1‐ATP synthase secondary to enzyme glycation as a novel pathophysiological mechanism involved in mitochondrial cristae remodeling, energy deficiency, and increased vulnerability of cardiomyocytes to undergo mitochondrial failure during aging.     

Proteomic DIGE analysis of the mitochondria‐enriched fraction from aged rat skeletal muscle

Skeletal muscle aging is associated with a loss in tissue mass and contractile strength, as well as fiber type shifting and bioenergetic adaptation processes. Since mitochondria represent the primary site for energy generation via oxidative phosphorylation, we investigated potential changes in the expression pattern of the mitochondrial proteome using the highly sensitive DIGE approach. The comparative analysis of the mitochondria‐enriched fraction from young adult versus aged muscle revealed an age‐related change in abundance for 39 protein species. MS technology identified the majority of altered proteins as constituents of muscle mitochondria. An age‐dependent increase was observed for NADH dehydrogenase, the mitochondrial inner membrane protein mitofilin, peroxiredoxin isoform PRX‐III, ATPase synthase, succinate dehydrogenase, mitochondrial fission protein Fis1, succinate‐coenzyme A ligase, acyl‐coenzyme A dehydrogenase, porin isoform VDAC2, ubiquinol‐cytochrome c reductase core I protein and prohibitin. Immunoblotting, enzyme testing and confocal microscopy were used to validate proteomic findings. The DIGE‐identified increase in key mitochondrial elements during aging agrees with the concept that sarcopenia is associated with a shift to a slower contractile phenotype and more pronounced aerobic‐oxidative metabolism. This suggests that mitochondrial markers are reliable candidates that should be included in the future establishment of a biomarker signature of skeletal muscle aging.     

Modulation of p25 and inflammatory pathways by fisetin maintains cognitive function in Alzheimer's disease transgenic mice

Alzheimer's disease (AD) is the most common type of dementia. It is the only one of the top ten causes of death in the USA for which prevention strategies have not been developed. Although AD has traditionally been associated with the deposition of amyloid β plaques and tau tangles, it is becoming increasingly clear that it involves disruptions in multiple cellular systems. Therefore, it is unlikely that hitting a single target will result in significant benefits to patients with AD. An alternative approach is to identify molecules that have multiple biological activities that are relevant to the disease. Fisetin is a small, orally active molecule which can act on many of the target pathways implicated in AD. We show here that oral administration of fisetin to APPswe/PS1dE9 double transgenic AD mice from 3 to 12 months of age prevents the development of learning and memory deficits. This correlates with an increase in ERK phosphorylation along with a decrease in protein carbonylation, a marker of oxidative stress. Importantly, fisetin also reduces the levels of the cyclin‐dependent kinase 5 (Cdk5) activator p35 cleavage product, p25, in both control and AD brains. Elevated levels of p25 relative to p35 cause dysregulation of Cdk5 activity leading to neuroinflammation and neurodegeneration. These fisetin‐dependent changes correlate with additional anti‐inflammatory effects, including alterations in global eicosanoid synthesis, and the maintenance of markers of synaptic function in the AD mice. Together, these results suggest that fisetin may provide a new approach to the treatment of AD.     

Endothelium‐specific CYP2J2 overexpression attenuates age‐related insulin resistance

Ample evidences demonstrate that cytochrome P450 epoxygenase‐derived epoxyeicosatrienoic acids (EETs) exert diverse biological activities, which include potent vasodilatory, anti‐inflammatory, and cardiovascular protective effects. In this study, we investigated the effects of endothelium‐specific CYP2J2 overexpression on age‐related insulin resistance and metabolic dysfunction. Endothelium‐specific targeting of the human CYP epoxygenase, CYP2J2, transgenic mice (Tie2‐CYP2J2‐Tr mice) was utilized. The effects of endothelium‐specific CYP2J2 overexpression on aging‐associated obesity, inflammation, and peripheral insulin resistance were evaluated by assessing metabolic parameters in young (3 months old) and aged (16 months old) adult male Tie2‐CYP2J2‐Tr mice. Decreased insulin sensitivity and attenuated insulin signaling in aged skeletal muscle, adipose tissue, and liver were observed in aged adult male mice, and moreover, these effects were partly inhibited in 16‐month‐old CYP2J2‐Tr mice. In addition, CYP2J2 overexpression‐mediated insulin sensitization in aged mice was associated with the amelioration of inflammatory state. Notably, the aging‐associated increases in fat mass and adipocyte size were only observed in 16‐month‐old wild‐type mice, and CYP2J2 overexpression markedly prevented the increase in fat mass and adipocyte size in aged Tie2‐CYP2J2‐Tr mice, which was associated with increased energy expenditure and decreased lipogenic genes expression. Furthermore, these antiaging phenotypes of Tie2‐CYP2J2‐Tr mice were also associated with increased muscle blood flow, enhanced active‐phase locomotor activity, and improved mitochondrial dysfunction in skeletal muscle. Collectively, our findings indicated that endothelium‐specific CYP2J2 overexpression alleviated age‐related insulin resistance and metabolic dysfunction, which highlighted CYP epoxygenase‐EET system as a potential target for combating aging‐related metabolic disorders.     

Relative importance of redox buffers GSH and NAD(P)H in age‐related neurodegeneration and Alzheimer disease‐like mouse neurons

Aging, a major risk factor in Alzheimer's disease (AD), is associated with an oxidative redox shift, decreased redox buffer protection, and increased free radical reactive oxygen species (ROS) generation, probably linked to mitochondrial dysfunction. While NADH is the ultimate electron donor for many redox reactions, including oxidative phosphorylation, glutathione (GSH) is the major ROS detoxifying redox buffer in the cell. Here, we explored the relative importance of NADH and GSH to neurodegeneration in aging and AD neurons from nontransgenic and 3xTg‐AD mice by inhibiting their synthesis to determine whether NADH can compensate for the GSH loss to maintain redox balance. Neurons stressed by either depleting NAD(P)H or GSH indicated that NADH redox control is upstream of GSH levels. Further, although depletion of NAD(P)H or GSH correlated linearly with neuron death, compared with GSH depletion, higher neurodegeneration was observed when NAD(P)H was extrapolated to zero, especially in old age, and in the 3xTg‐AD neurons. We also observed an age‐dependent loss of gene expression of key redox‐dependent biosynthetic enzymes, NAMPT (nicotinamide phosphoribosyltransferase), and NNT (nicotinamide nucleotide transhydrogenase). Moreover, age‐related correlations between brain NNT or NAMPT gene expression and NADPH levels suggest that these genes contribute to the age‐related declines in NAD(P)H. Our data indicate that in aging and more so in AD‐like neurons, NAD(P)H redox control is upstream of GSH and an oxidative redox shift that promotes neurodegeneration. Thus, NAD(P)H generation may be a more efficacious therapeutic target upstream of GSH and ROS.     

Carbonic anhydrase inhibition selectively prevents amyloid β neurovascular mitochondrial toxicity

Mounting evidence suggests that mitochondrial dysfunction plays a causal role in the etiology and progression of Alzheimer's disease (AD). We recently showed that the carbonic anhydrase inhibitor (CAI) methazolamide (MTZ) prevents amyloid β (Aβ)‐mediated onset of apoptosis in the mouse brain. In this study, we used MTZ and, for the first time, the analog CAI acetazolamide (ATZ) in neuronal and cerebral vascular cells challenged with Aβ, to clarify their protective effects and mitochondrial molecular mechanism of action. The CAIs selectively inhibited mitochondrial dysfunction pathways induced by Aβ, without affecting metabolic function. ATZ was effective at concentrations 10 times lower than MTZ. Both MTZ and ATZ prevented mitochondrial membrane depolarization and H₂O₂ generation, with no effects on intracellular pH or ATP production. Importantly, the drugs did not primarily affect calcium homeostasis. This work suggests a new role for carbonic anhydrases (CAs) in the Aβ‐induced mitochondrial toxicity associated with AD and cerebral amyloid angiopathy (CAA), and paves the way to AD clinical trials for CAIs, FDA‐approved drugs with a well‐known profile of brain delivery.