High Density Of Mitochondria Research Articles

Study and optimization of the photobiomodulation effects induced on mitochondrial metabolic activity of human cardiomyocytes for different radiometric and spectral conditions

Photobiomodulation (PBM) represents a promising and powerful approach for non-invasive therapeutic interventions. This emerging field of research has gained a considerable attention due to its potential for multiple disciplines, including medicine, neuroscience, and sports medicine. While PBM has shown the ability to stimulate various cellular processes in numerous medical applications, the fine-tuning of treatment parameters, such as wavelength, irradiance, treatment duration, and illumination geometry, remains an ongoing challenge. Furthermore, additional research is necessary to unveil the specific mechanisms of action and establish standardized protocols for diverse clinical applications.Given the widely accepted understanding that mitochondria play a pivotal role in the PBM mechanisms, our study delves into a multitude of PBM illumination parameters while assessing the PBM's effects on the basis of endpoints reflecting the mitochondrial metabolism of human cardiac myocytes (HCM), that are known for their high mitochondrial density. These endpoints include: i) the endogenous production of protoporphyrin IX (PpIX), ii) changes in mitochondrial potential monitored by Rhodamine 123 (Rhod 123), iii) changes in the HCM's oxygen consumption, iv) the fluorescence lifetime of Rhod 123 in mitochondria, and v) alterations of the mitochondrial morphology. The good correlation observed between these different methods to assess PBM effects underscores that monitoring the endogenous PpIX production offers interesting indirect insights into the mitochondrial metabolic activity. This conclusion is important since many approved therapeutics and cancer detection approaches are based on the use of PpIX.Finally, this correlation strongly suggests that the PBM effects mentioned above have a common “fundamental” mechanistic origin.

Mitochondrial function in skeletal muscle contributes to reproductive endothermy in tegu lizards (Salvator merianae).

In cyclic climate variations, including seasonal changes, many animals regulate their energy demands to overcome critical transitory moments, restricting their high-demand activities to phases of resource abundance, enabling rapid growth and reproduction. Tegu lizards (Salvator merianae) are ectotherms with a robust annual cycle, being active during summer, hibernating during winter, and presenting a remarkable endothermy during reproduction in spring. Here, we evaluated whether changes in mitochondrial respiratory physiology in skeletal muscle could serve as a mechanism for the increased thermogenesis observed during the tegu's reproductive endothermy. We performed high-resolution respirometry and calorimetry in permeabilized red and white muscle fibers, sampled during summer (activity) and spring (high activity and reproduction), in association with citrate synthase measurements. During spring, the muscle fibers exhibited increased oxidative phosphorylation. They also enhanced uncoupled respiration and heat production via adenine nucleotide translocase (ANT), but not via uncoupling proteins (UCP). Citrate synthase activity was higher during the spring, suggesting greater mitochondrial density compared to the summer. These findings were consistent across both sexes and muscle types (red and white). The current results highlight potential cellular thermogenic mechanisms in an ectothermic reptile that contribute to transient endothermy. Our study indicates that the unique feature of transitioning to endothermy through nonshivering thermogenesis during the reproductive phase may be facilitated by higher mitochondrial density, function, and uncoupling within the skeletal muscle. This knowledge contributes significant elements to the broader picture of models for the evolution of endothermy, particularly in relation to the enhancement of aerobic capacity.

Changes in physical architecture and lipids compounds in skeletal muscle from Pekin duck and Liancheng white duck

As a complex food, meat displays various biochemical properties that are determined to a great extent by physical architecture and lipid metabolites. Pekin duck and Liancheng white duck are elite breeds with distinct characteristics. Here, we explored the development of the muscle fibers from embryonic stage to 10-wk after birth, and muscle fibers grow slowly after 8-wk. We investigated the meat quality, ultrastructure, lipidomics profiling, and lipids spatial distribution of skeletal muscle at 8 wk. Pekin duck has lower Warner-Bratzler shear force (WBSF) (P < 0.05), high intramuscular fat (IMF) (P < 0.01), longer and wider sarcomere, and higher mitochondrial density (P < 0.001). Liancheng white duck with tighter collagen architecture. A total of 950 lipids from 6 lipid classes identified with lipidomics were analyzed, the levels of GP, GL, and PR were significantly higher in Pekin duck (P < 0.05), SL and ST were significantly higher in Liancheng white duck (P < 0.05). There were 333 significantly different lipids (|log2(Fold Change)| ≥ 1 and FDR < 0.05) screened, most lipids distributed in the muscle tissue were uniform, but some specifically distributed in connective tissue. To some extent, the results demonstrate the high lipid deposition capacity of Pekin duck and the high medicinal function of Liancheng white duck. Our study provides new insights into the relationship between skeletal muscle architecture and meat toughness, which increased the knowledge of lipidomic characteristics and provide a basis for duck meat authentication.

Potential enhancement of post-stroke angiogenic response by targeting the oligomeric aggregation of p53 protein.

Tumor suppressor gene p53 and its aggregate have been found to be involved in many angiogenesis-related pathways. We explored the possible p53 aggregation formation mechanisms commonly occur after ischemic stroke, such as hypoxia and the presence of reactive oxygen species (ROS). The angiogenic pathways involving p53 mainly occur in nucleus or cytoplasm, with one exception that occurs in mitochondria. Considering the high mitochondrial density in brain and endothelial cells, we proposed that the cyclophilin D (CypD)-dependent vascular endothelial cell (VECs) necrosis pathway occurring in the mitochondria is one of the major factors that affects angiogenesis. Hence, targeting p53 aggregation, a key intermediate in the pathway, could be an alternative therapeutic target for post-stroke management.

307-OR: Delineating the Origin of Supraclavicular Brown Adipocytes

Brown adipose tissue (BAT) can use nutrients through non-shivering thermogenesis to generate heat. Thus, activation of BAT can be utilized to maintain body temperature and regulate metabolism. Healthy adult humans possess small amounts of BAT, with the most visible depot, the supraclavicular BAT (scBAT), located in the supraclavicular region of the neck. To understand how human scBAT functions, we previously identified BAT depots in the supraclavicular region of the mouse neck that anatomically resemble human scBAT. Similar to human scBAT, mouse scBAT contains a high density of mitochondria and expresses high levels of uncoupling protein 1. Mouse scBAT first appears in the late fetal stage in the ventral neck and continues to expand toward the lateral neck after birth. To identify the stem/progenitor cells that give rise to supraclavicular brown adipocytes, we performed a series of lineage tracing analyses. Unlike the well-studied mouse interscapular BAT depot, scBAT did not originate from the Myf5, Pax3, or Pax7-labeled progenitor cells that also give rise to skeletal muscle. Rather, a large portion of the supraclavicular brown adipocytes were labeled by Cre recombinase driven by the Mef2c anterior heart field promoter (AHF), which marks cells that give rise to the outflow tract and right ventricle of the heart. Mef2c-AHF+ cells isolated from the scBAT can spontaneously differentiate into highly thermogenic brown adipocytes in vitro, and the differentiation efficiency is further enhanced by addition of Bmp7 and PPARγ agonist, rosiglitazone. Together, our lineage tracing studies revealed that the scBAT is composed of heterogeneous brown adipocyte progenitor cells and that Mef2c-AHF-marked cardiac progenitor cells are one of the ancestors of these brown adipocytes. Understanding the trajectories of and molecular mechanisms by which these progenitor cells give rise to scBAT will provide new insights for developing a novel cell-based therapeutic tool for treating obesity and related metabolic complications. Disclosure Y.Ran: None. Z.Wang: None. M.G.Waterstraat: None. R.Caballero-juarez: None. M.Chen: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK116899)

Mitochondrial Dysfunction in Cardiac Diseases and Therapeutic Strategies.

Mitochondria are the main site of intracellular synthesis of ATP, which provides energy for various physiological activities of the cell. Cardiomyocytes have a high density of mitochondria and mitochondrial damage is present in a variety of cardiovascular diseases. In this paper, we describe mitochondrial damage in mitochondrial cardiomyopathy, congenital heart disease, coronary heart disease, myocardial ischemia-reperfusion injury, heart failure, and drug-induced cardiotoxicity, in the context of the key roles of mitochondria in cardiac development and homeostasis. Finally, we discuss the main current therapeutic strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction, including pharmacological strategies, gene therapy, mitochondrial replacement therapy, and mitochondrial transplantation. It is hoped that this will provide new ideas for the treatment of cardiovascular diseases.

Comparison of brown adipose tissue activation detected by infrared thermography in men with vs without metabolic syndrome

BackgroundBrown adipose tissue (BAT) high density of mitochondria and its thermogenic characteristics promote the dissipation of chemical energy in the form of heat, increasing body caloric expenditure, decreasing plasma levels of lipids and glucose (GL). This makes BAT a potential therapeutic target of Metabolic Syndrome (MetS). Position Emission Tomography Scanning (PET-CT) is the gold standard for estimating BAT, but it has several limitations, including high cost and high emission of radiation. On the other hand, Infrared Thermography (IRT) is considered a simpler, cheaper and non-invasive method to detect BAT. ObjectiveThe aim of this study was to compare BAT activation through IRT and cold stimulation in men diagnosed without and with MetS. MethodsSample of 124 (35.3 ± 9.4 years old) men was evaluated of body composition, anthropometric measurements and dual X-ray absorptiometry (DXA) hemodynamics, biochemical tests and body skin temperature acquisition. The Student t-test with subsequent effect size by (d) Cohen and two-way repeated measures ANOVA with Tukey post-hoc comparisons were conducted. Level of significance was p < 0.05. ResultsThere was significant interaction between group factor (MetS) vs group moment (BAT activation) in supraclavicular skin temperatures right side (maximum (F(1,122) = 10.4, p < 0.002, η2 = 0.062), mean (F(1.122) = 13.0, p < 0.001, η2 = 0.081) and minimal (F(1,122) = 7.9, p < 0.006, η2 = 0.052)) and left side maximum (F(1,122) = 7.7, p < 0.006, η2 = 0.048), mean (F(1.122) = 13.0, p < 0.037, η2 = 0.007) and minimal (F(1,122) = 9.8, p < 0.002, η2 = 0.012)). The MetS risk factor group didn't present significant increase of SCV temperature BAT after cold stimulation. ConclusionMen diagnosed with MetS risk factors seem to activate less BAT, when exposed to cold stimulation, compared to group without MetS risk factor.

Mitochondrial H2S donor AP39 induces stomatal closure by modulating guard cell mitochondrial activity.

Hydrogen sulfide (H2S) is a gaseous signaling molecule involved in numerous physiological processes in plants, including gas exchange with the environment through the regulation of stomatal pore width. Guard cells (GCs) are pairs of specialized epidermal cells that delimit stomatal pores and have a higher mitochondrial density and metabolic activity than their neighboring cells. However, there is no clear evidence on the role of mitochondrial activity in stomatal closure induction. In this work, we showed that the mitochondrial-targeted H2S donor AP39 induces stomatal closure in a dose-dependent manner. Experiments using inhibitors of the mitochondrial electron transport chain (mETC) or insertional mutants in cytochrome c (CYTc) indicated that the activity of mitochondrial CYTc and/or complex IV are required for AP39-dependent stomatal closure. By using fluorescent probes and genetically encoded biosensors we reported that AP39 hyperpolarized the mitochondrial inner potential (Δψm) and increased cytosolic ATP, cytosolic hydrogen peroxide levels, and oxidation of the glutathione pool in GCs. These findings showed that mitochondrial-targeted H2S donors induce stomatal closure, modulate guard cell mETC activity, the cytosolic energetic and oxidative status, pointing to an interplay between mitochondrial H2S, mitochondrial activity, and stomatal closure.

Identification and characterization of novel abdominal and pelvic brown adipose depots in mice

ABSTRACT Brown adipose tissue (BAT) generates heat through non-shivering thermogenesis, and increasing BAT amounts or activity could facilitate obesity treatment and provide metabolic benefits. In mice, BAT has been reported in perirenal, thoracic and cranial sites. Here, we describe new pelvic and lower abdominal BAT depots located around the urethra, internal reproductive and urinary tract organs and major lower pelvic blood vessels, as well as between adjacent muscles where the upper hind leg meets the abdominal cavity. Immunohistochemical, western blot and PCR analyses revealed that these tissues expressed BAT markers such as uncoupling protein 1 (UCP1) and CIDEA, but not white adipose markers, and β3-adrenergic stimulation increased UCP1 amounts, a classic characteristic of BAT tissue. The newly identified BAT stores contained extensive sympathetic innervation with high mitochondrial density and multilocular lipid droplets similar to interscapular BAT. BAT repositories were present and functional neonatally, and showed developmental changes between the neonatal and adult periods. In summary, several new depots showing classical BAT characteristics are reported and characterized in the lower abdominal/pelvic region of mice. These BAT stores are likely significant metabolic regulators in the mouse and some data suggests that similar BAT depots may also exist in humans.

N-oleoylethanolamide treatment of lymphoblasts deficient in Tafazzin improves cell growth and mitochondrial morphology and dynamics.

Barth syndrome (BTHS) is caused by mutations in the TAZ gene encoding the cardiolipin remodeling enzyme, Tafazzin. The study objective was to quantitatively examine growth characteristics and mitochondrial morphology of transformed lymphoblast cell lines derived from five patients with BTHS relative to five healthy controls, as well as the therapeutic potential of oleoylethanolamide (OEA) and linoleoylethanolamide (LEA). These bioactive lipids both activate PPARα, which may be therapeutic. BTHS lymphoblasts grew more slowly than controls, suggesting lymphopenia merits clinical investigation. Treatment of BTHS lymphoblasts with OEA, but not LEA, significantly restored mitochondrial membrane potential, as well as colony growth in all BTHS lymphoblast lines, although a full growth rescue was not achieved. Quantification analysis of electron micrographs from three BTHS and healthy lymphoblast donors indicated similar numbers of mitochondria per cell, but lower average cristae length per mitochondrion, and higher mitochondrial density. Additionally, BTHS lymphoblasts had larger mitochondria, and a higher percentage of abnormally large mitochondria (> 1 μm2) than healthy controls. Notably, OEA treatment significantly restored mitochondrial size, without affecting density or cristae lengths. Cardiolipin total content, relative linoleic acid content and monolysocardiolipin:cardiolipin ratios were not improved by OEA, indicating that effects on growth, and mitochondrial morphology and function, occurred without resolving this deficit. However, immunoblotting showed higher levels of OPA1, a biomarker for mitochondrial fusion, in BTHS lymphoblasts, which was attenuated by OEA treatment, implicating altered mitochondrial dynamics in the pathology and treatment of BTHS.

Acute Imidacloprid Exposure Alters Mitochondrial Function in Bumblebee Flight Muscle and Brain.

Mitochondria are intracellular organelles responsible for cellular respiration with one of their major roles in the production of energy in the form of ATP. Activities with increased energetic demand are especially dependent on efficient ATP production, hence sufficient mitochondrial function is fundamental. In bees, flight muscle and the brain have particularly high densities of mitochondria to facilitate the substantial ATP production required for flight activity and neuronal signalling. Neonicotinoids are systemic synthetic insecticides that are widely utilised against crop herbivores but have been reported to cause, by unknown mechanisms, mitochondrial dysfunction, decreasing cognitive function and flight activity among pollinating bees. Here we explore, using high-resolution respirometry, how the neonicotinoid imidacloprid may affect oxidative phosphorylation in the brain and flight muscle of the buff-tailed bumblebee, Bombus terrestris. We find that acute exposure increases routine oxygen consumption in the flight muscle of worker bees. This provides a candidate explanation for prior reports of early declines in flight activity following acute exposure. We further find that imidacloprid increases the maximum electron transport capacity in the brain, with a trend towards increased overall oxygen consumption. However, intra-individual variability is high, limiting the extent to which apparent effects of imidacloprid on brain mitochondria are shown conclusively. Overall, our results highlight the necessity to examine tissue-specific effects of imidacloprid on respiration and energy production.

507 Late-Breaking: Heat Stress and Mitoq Supplementation Impact Skeletal Muscle Mitochondrial Capacities in Pigs

Abstract Heat stress can negatively impact pig health and performance but the effects of heat stress on skeletal muscle mitochondrial function are largely unknown. We hypothesized that mitochondrial function and capacity would be impaired in heat stressed (HS) compared to thermoneutral (TN) pigs but mitochondrially-targeted coenzyme Q (MitoQ) supplementation would rescue the impairment. Oxidative portions of the semitendinosus muscle were evaluated from TN and HS gilts receiving no supplementation (CON) or MitoQ for 2 d prior to and during the 24h environmental heat treatment (n = 8 per group). Mitochondrial oxidative phosphorylation (P) and electron transfer (E) capacities were determined via high resolution respirometry and mitochondrial volume density and function were quantified by citrate synthase (CS) and cytochrome c oxidase activities, respectively. Data were analyzed using linear models in SAS v9.4 with fixed effects of heat, MitoQ treatment (trt), and heat×trt interaction. There were trends for the interaction of trt and heat (P≤0.1) on integrative (per mg tissue) and intrinsic (relative to CS) P with complexes I and II (PCI+II), maximum noncoupled E (ECI+II), and E with complex II only (ECII), in which all measures were greater in HS-MitoQ than TN-MitoQ (P≤0.03), but measures did not differ due to HS in CON pigs. The contribution of leak to total E (flux control ratio, FCRLeak) was lesser in HS-MitoQ than HS-CON, TN-CON, and TN-MitoQ (P≤0.02). The FCRPCI was greater (P≤0.05) while the FCRPCI+II was lesser (P=0.01) in TN compared to HS pigs. Finally, the FCRPCI+II was greater (P=0.02) while the FCRECII tended to be lesser (P=0.09) for CON than MitoQ pigs. Neither mitochondrial volume density nor function were affected by HS or MitoQ supplementation. In total, these data indicate improved mitochondrial capacities following heat stress in pigs receiving MitoQ but no difference in mitochondrial capacities in unsupplemented, HS pigs.

Local Accumulation of Axonal Mitochondria in the Optic Nerve Glial Lamina Precedes Myelination.

Mitochondria are essential for neurons and must be optimally distributed along their axon to fulfill local functions. A high density of mitochondria has been observed in retinal ganglion cell (RGC) axons of an unmyelinated region of the optic nerve, called the glial lamina (GL) in mouse (lamina cribrosa in human). In glaucoma, the world's leading cause of irreversible blindness, the GL is the epicenter of RGC degeneration and is connected to mitochondrial dysfunction. It is generally accepted that the local accumulation of mitochondria in the GL is established due to the higher energy requirement of unmyelinated axons. Here we revisit the connection between mitochondrial positioning and myelin in RGC axons. We show that the high density of mitochondria in the GL is restricted to larger axons and is established before myelination. Thus, contrary to a longstanding belief in the field, the myelination pattern is not responsible for the establishment of the local accumulation of mitochondria in GL axons. Our findings open new research avenues likely critical to understanding the pathophysiology of glaucoma.

Metabolic Stress is Not Sufficient to Increase Skeletal Muscle Tissue Extracellular Vesicle Secretion in an Ex Vivo System

Skeletal muscle (SkM) is a metabolically active tissue and accounts for ~35% of total human body mass. Exercise imposes acute metabolic stress on SkM myofibers, and contractile proteins require energy sustained through both glycolytic and oxidative metabolism. Increased metabolic demand during contraction promotes intercellular communication through secreted factors that include extracellular vesicles (EVs). However, the mechanisms linking metabolic flux and EV secretion are currently unknown. We hypothesized that mimicing metabolic stress by blocking glycolysis with 2-deoxyglucose (2-DG), or oxidative phosphorylation with BAM15, a mitochondrial uncoupler, would increase EV secretion in SkM. Additionally, we aimed to characterize the effects of contractile inhibition with blebbistatin (BLEB) to better understand the role of contraction on EV release. We tested our hypothesis using an ex vivo EV secretion assay. Vastus medialis muscle (VM) from male C57Bl/6J mice (n=6) and soleus (SOL) and plantaris (PLA) muscle from female mT/mG mice (n=6) was cut into ~5 mg pieces and added to 12 well plates (~50 mg/well) filled with 750mL of serum-free DMEM and placed in a cell culture incubator at 37°C for 24 hours. The effect of 2-DG on VM EV secretion was measured during a log dose response (0.1nM – 100mM). SOL and PLA from female mice were treated with either 10mM of BLEB, or 10mM of BAM15. After incubation, tissue mass was measured and conditioned media was centrifuged (3,000 x g for 15 min) to remove cell debris. EVs were isolated using ExoQuick-TC. NTA was performed on isolated EVs using a Horiba Viewsizer 3000. EV secretion was normalized to tissue mass and culture media volume and reported as ([Particle]/mL/mg tissue). Statistical comparisons for 2-DG experiments were made using a repeated measures 1-way ANOVA with Bonferroni post-hoc testing. BLEB (n=6) and BAM15 (n=4) experiments were analyzed using a paired Student's t-test. No effect of 2-DG was observed in regard to EV abundance (p = .07) or diameter (p = 0.37). BAM15 did not affect EV abundance in SOL (p = 0.64) or PLA (p = 0.78). BLEB did not alter EV abundance (p = 0.69; CON: 1.32E+09 ± 4.86E+08 vs BLEB 1.67E+09 ± 5.87E+08), but significantly reduced EV mean diameter (p = 0.007; DMSO: 114.9 ± 5.1 vs. BLEB: 103.9 ± 4.2). Contrary to our hypothesis, inducing metabolic stress did not significantly increase SkM EV secretion. Mitochondrial uncoupling did not increase EV secretion in oxidative SkM such as the soleus, which is predominately comprised of fibers with high mitochondrial density. Inhibition of glycolysis with 2-DG did not increase SkM EV secretion. In the presence of BLEB, EV mean diameter was reduced but not EV abundance, suggesting that inhibiting contractile function may affect specific pathways of EV release. Collectively, our data demonstrate that metabolic stress may not be sufficient to increase EV secretion from SkM in an ex vivo system. Future studies might explore the specific role of contraction or extracellular factors as mediators of SkM EV secretion.

Taurine Antagonizes Macrophages M1 Polarization by Mitophagy-Glycolysis Switch Blockage via Dragging SAM-PP2Ac Transmethylation.

The excessive M1 polarization of macrophages drives the occurrence and development of inflammatory diseases. The reprogramming of macrophages from M1 to M2 can be achieved by targeting metabolic events. Taurine promotes for the balance of energy metabolism and the repair of inflammatory injury, preventing chronic diseases and complications. However, little is known about the mechanisms underlying the action of taurine modulating the macrophage polarization phenotype. In this study, we constructed a low-dose LPS/IFN-γ-induced M1 polarization model to simulate a low-grade pro-inflammatory process. Our results indicate that the taurine transporter TauT/SlC6A6 is upregulated at the transcriptional level during M1 macrophage polarization. The nutrient uptake signal on the membrane supports the high abundance of taurine in macrophages after taurine supplementation, which weakens the status of methionine metabolism, resulting in insufficient S-adenosylmethionine (SAM). The low availability of SAM is directly sensed by LCMT-1 and PME-1, hindering PP2Ac methylation. PP2Ac methylation was found to be necessary for M1 polarization, including the positive regulation of VDAC1 and PINK1. Furthermore, its activation was found to promote the elimination of mitochondria by macrophages via the mitophagy pathway for metabolic adaptation. Mechanistically, taurine inhibits SAM-dependent PP2Ac methylation to block PINK1-mediated mitophagy flux, thereby maintaining a high mitochondrial density, which ultimately hinders the conversion of energy metabolism to glycolysis required for M1. Our findings reveal a novel mechanism of taurine-coupled M1 macrophage energy metabolism, providing novel insights into the occurrence and prevention of low-grade inflammation, and propose that the sensing of taurine and SAM availability may allow communication to inflammatory response in macrophages.

Characterization of Subcellular Organelles in Cortical Perisynaptic Astrocytes.

Perisynaptic astrocytic processes (PAPs) carry out several different functions, from metabolite clearing to control of neuronal excitability and synaptic plasticity. All these functions are likely orchestrated by complex cellular machinery that resides within the PAPs and relies on a fine interplay between multiple subcellular components. However, traditional transmission electron microscopy (EM) studies have found that PAPs are remarkably poor of intracellular organelles, failing to explain how such a variety of PAP functions are achieved in the absence of a proportional complex network of intracellular structures. Here, we use serial block-face scanning EM to reconstruct and describe in three dimensions PAPs and their intracellular organelles in two different mouse cortical regions. We described five distinct organelles, which included empty and full endosomes, phagosomes, mitochondria, and endoplasmic reticulum (ER) cisternae, distributed within three PAPs categories (branches, branchlets, and leaflets). The majority of PAPs belonged to the leaflets category (~60%), with branchlets representing a minority (~37%). Branches were rarely in contact with synapses (<3%). Branches had a higher density of mitochondria and ER cisternae than branchlets and leaflets. Also, branches and branchlets displayed organelles more frequently than leaflets. Endosomes and phagosomes, which accounted for more than 60% of all the organelles detected, were often associated with the same PAP. Likewise, mitochondria and ER cisternae, representing ~40% of all organelles were usually associated. No differences were noted between the organelle distribution of the somatosensory and the anterior cingulate cortex. Finally, the organelle distribution in PAPs did not largely depend on the presence of a spine apparatus or a pre-synaptic mitochondrion in the synapse that PAPs were enwrapping, with some exceptions regarding the presence of phagosomes and ER cisternae, which were slightly more represented around synapses lacking a spine apparatus and a presynaptic mitochondrion, respectively. Thus, PAPs contain several subcellular organelles that could underlie the diverse astrocytic functions carried out at central synapses.

Mitochondrial stress-activated cGAS-STING pathway inhibits thermogenic program and contributes to overnutrition-induced obesity in mice

Obesity is a global epidemic that is caused by excessive energy intake or inefficient energy expenditure. Brown or beige fat dissipates energy as heat through non-shivering thermogenesis by their high density of mitochondria. However, how the mitochondrial stress-induced signal is coupled to the cellular thermogenic program remains elusive. Here, we show that mitochondrial DNA escape-induced activation of the cGAS-STING pathway negatively regulates thermogenesis in fat-specific DsbA-L knockout mice, a model of adipose tissue mitochondrial stress. Conversely, fat-specific overexpression of DsbA-L or knockout of STING protects mice against high-fat diet-induced obesity. Mechanistically, activation of the cGAS-STING pathway in adipocytes activated phosphodiesterase PDE3B/PDE4, leading to decreased cAMP levels and PKA signaling, thus reduced thermogenesis. Our study demonstrates that mitochondrial stress-activated cGAS-STING pathway functions as a sentinel signal that suppresses thermogenesis in adipose tissue. Targeting adipose cGAS-STING pathway may thus be a potential therapeutic strategy to counteract overnutrition-induced obesity and its associated metabolic diseases.

Curcumin as a Therapeutic Option in Retinal Diseases.

The retina is subjected to oxidative stress due to its high vascularization, long time light exposition and a high density of mitochondria. Oxidative stress can lead to pathological processes, like cell apoptosis, angiogenesis and inflammation ending in retinal pathologies. Curcumin, a major bioactive component obtained from the spice turmeric (Curcuma longa) rhizome has been used for centuries in Asian countries for cooking and for curing all kinds of diseases like dysentery, chest congestion and pain in general, due to its antioxidant effects. Curcumin prevents the formation of reactive oxygen species and so it is a good protective agent. Curcumin has shown also anti-inflammatory, and antitumor properties. Curcumin is a natural product, which can be a therapeutic option in a variety of retinal diseases due to its pleiotropic properties. Some drawbacks are its poor solubility, bioavailability and lack of stability at physiological conditions; which have been shown in curcumin skeptical publications. In this review, we provide some lights and shadows on curcumin administration on the major retinal pathologies.

Rapid Communication: Differential skeletal muscle mitochondrial characteristics of weanling racing-bred horses.

Responses of equine skeletal muscle characteristics to growth and training have been shown to differ between breeds. These differential responses may arise in part because muscle fiber type and mitochondrial density differ between breeds, even in untrained racing-bred horses. However, it is not known when these breed-specific differences manifest. To test the hypothesis that weanling Standardbreds (SB) and Thoroughbreds (TB) would have higher mitochondrial measures than Quarter Horses (QH), gluteus medius samples were collected from SB (mean ± SD; 6.2 ± 1.0 mo; n = 10), TB (6.1 ± 0.5 mo; n = 12), and QH (7.4 ± 0.6 mo; n = 10). Citrate synthase (CS) and cytochrome c oxidase (CCO) activities were assessed as markers of mitochondrial density and function, respectively. Mitochondrial oxidative (P) and electron transport system (E) capacities were assessed by high-resolution respirometry (HRR). Data for CCO and HRR are expressed as integrated (per mg protein and per mg tissue wet weight, respectively) and intrinsic (per unit CS). Data were analyzed using PROC MIXED in SAS v 9.4 with breed as a fixed effect. Mitochondrial density (CS) was higher for SB and TB than QH (P ≤ 0.0007). Mitochondrial function (integrated and intrinsic CCO) was higher in TB and QH than SB (P ≤ 0.01). Integrated CCO was also higher in TB than QH (P < 0.0001). However, SB had higher integrated maximum P (PCI+II) and E (ECI+II) than QH (P ≤ 0.02) and greater integrated and intrinsic complex II-supported E (ECII) than both QH and TB (P ≤ 0.02), whereas TB exhibited higher integrated P with complex I substrates (PCI) than SB and QH (P ≤ 0.003) and higher integrated PCI+II and ECI+II than QH (P ≤ 0.02). In agreement, TB and QH had higher contribution of complex I (CI) to max E than SB (P ≤ 0.001), whereas SB had higher contribution of CII than QH and TB (P ≤ 0.002). Despite having higher mitochondrial density than QH and TB, SB showed lower CCO activity and differences in contribution of complexes to oxidative and electron transport system capacities. Breed differences in mitochondrial parameters are present early in life and should be considered when developing feeding, training, medication, and management practices.

Mitochondrial Rich Proton Pumping Cells in the Kidney and Epididymis are Highly Glycolytic

The kidney collecting duct (CD) has a crucial role in regulating acid‐base balance. Alpha intercalated cells (ICs) of the CD maintain acid‐base homeostasis by acidifying the urine, via apical V‐ATPase H+ pumps. ICs are characterized in appearance by a very high density of mitochondria, but remarkably little is known about metabolism in these cells, due to a lack of suitable techniques to study this and the inability to generate a stable IC cell line. By using different innovative imaging techniques, we aimed to better understand how metabolism might be adapted in ICs to their specialized H+ pumping function.Using multiphoton microscopy of intact murine kidney slices, we have found that mitochondria in ICs have some highly unusual features compared with other tubular cells. IC mitochondria are considerably more mobile and dynamic, and display a high NADH signal but low uptake of voltage dependent dyes. Moreover, they are energized by a pH gradient that is functionally coupled to the proton pumping activity of the V‐ATPase. However, high resolution confocal microscopy and 3D electron microscopy (FIB‐SEM) in fixed mouse kidney tissue revealed that the mitochondria and V‐ATPase expressing vesicles were distant from each other, reducing the likelihood that the mitochondria are the only energy source for the V‐ATPase H+ pumps in ICs. Furthermore, we observed that the expression of respiratory chain complex V (ATP synthase) is lower in ICs than in surrounding cells, implying reduced oxidative capacity. Conversely, expression of enzymes in the glycolytic pathway, including lactate dehydrogenase, was markedly higher in ICs, consistent with high anaerobic ATP‐generating capacity. Interestingly, expression of glycolytic enzymes was also high in clear cells in the epididymis, suggesting that this is a common feature of proton pumping cells.As a surrogate of cellular ATP levels, we imaged cytosolic Ca2+ in kidney slices using a fluorescent reporter (GcaMP6s), and found that inhibition of mitochondrial ATP production with cyanide produced striking rises in Ca2+ in all tubular cell types except ICs. However, Ca2+ also increased in ICs when glycolysis was simultaneously inhibited. Finally, direct functional measurement of V‐ATPase function in microperfused isolated outermedullary collecting ducts (OMCDs) revealed that inhibition of glycolysis leads to a significant decrease in H+ pumping in ICs.In summary, we have provided several lines of evidence that mitochondrial rich cells in the kidney and epididymis are surprisingly glycolytic, and that glycolysis is functionally important for V‐ATPase activity. These findings provide new insights into coupling of transport and metabolism in proton pumping cells.Support or Funding InformationThis research is supported by The Swiss National Centre for Competence in Research Kidney Control of Homeostasis.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.