Mild mitochondrial uncoupling impacts cellular aging in human muscles in vivo.
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ABSTRACT:
SUBMITTER: Amara CE
PROVIDER: S-EPMC1766336 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The first domesticated companion animal, the dog, is currently represented by over 190 unique breeds. Across these numerous breeds, dogs have exceptional variation in lifespan (inversely correlated with body size), presenting an opportunity to discover longevity-determining traits. We performed a genome-wide association study on 4169 canines representing 110 breeds and identified novel candidate regulators of longevity. Interestingly, known functions within the identified genes included control of coat phenotypes such as hair length, as well as mitochondrial properties, suggesting that thermoregulation and mitochondrial bioenergetics play a role in lifespan variation. Using primary dermal fibroblasts, we investigated mitochondrial properties of short-lived (large) and long-lived (small) dog breeds. We found that cells from long-lived breeds have more uncoupled mitochondria, less electron escape, greater respiration, and capacity for respiration. Moreover, our data suggest that long-lived breeds have higher rates of catabolism and ?-oxidation, likely to meet elevated respiration and electron demand of their uncoupled mitochondria. Conversely, cells of short-lived (large) breeds may accumulate amino acids and fatty acid derivatives, which are likely used for biosynthesis and growth. We hypothesize that the uncoupled metabolic profile of long-lived breeds likely stems from their smaller size, reduced volume-to-surface area ratio, and therefore a greater need for thermogenesis. The uncoupled energetics of long-lived breeds lowers reactive oxygen species levels, promotes cellular stress tolerance, and may even prevent stiffening of the actin cytoskeleton. We propose that these cellular characteristics delay tissue dysfunction, disease, and death in long-lived dog breeds, contributing to canine aging diversity.
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Project description:PURPOSE:To test the hypothesis that imaging biomarkers are useful for evaluating in vivo rod photoreceptor cell responses to a mitochondrial protonophore. METHODS:Intraperitoneal injections of either the mitochondrial uncoupler 2,4 dinitrophenol (DNP) or saline were given to mice with either higher [129S6/eVTac (S6)] or lower [C57BL/6J (B6)] mitochondrial reserve capacities and were studied in dark or light. We measured: (i) the external limiting membrane-retinal pigment epithelium region thickness (ELM-RPE; OCT), which decreases substantially with upregulation of a pH-sensitive water removal co-transporter on the apical portion of the RPE, and (ii) the outer retina R1 (= 1/(spin lattice relaxation time (T1), an MRI parameter proportional to oxygen / free radical content. RESULTS:In darkness, baseline rod energy production and consumption are relatively high compared to that in light, and additional metabolic stimulation with DNP provoked thinning of the ELM-RPE region compared to saline injection in S6 mice; ELM-RPE thickness was unresponsive to DNP in B6 mice. Also, dark-adapted S6 mice given DNP showed a decrease in outer retina R1 values compared to saline injection in the inferior retina. In dark-adapted B6 mice, transretinal R1 values were unresponsive to DNP in superior and inferior regions. In light, with its relatively lower basal rod energy production and consumption, DNP caused ELM-RPE thinning in both S6 and B6 mice. CONCLUSIONS:The present results raise the possibility of non-invasively evaluating the mouse rod mitochondrial energy ecosystem using new DNP-assisted OCT and MRI in vivo assays.
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Project description:Preservation of mitochondrial function, which is dependent on mitochondrial homeostasis (biogenesis, dynamics, disposal/recycling), is critical for maintenance of skeletal muscle function. Skeletal muscle performance declines upon aging (sarcopenia) and is accompanied by decreased mitochondrial function in fast-glycolytic muscles. Oxidative metabolism promotes mitochondrial homeostasis, so we investigated whether mitochondrial function is preserved in oxidative muscles. We compared tibialis anterior (predominantly glycolytic) and soleus (oxidative) muscles from young (3 mo) and old (28-29 mo) C57BL/6J mice. Throughout life, the soleus remained more oxidative than the tibialis anterior and expressed higher levels of markers of mitochondrial biogenesis, fission/fusion and autophagy. The respiratory capacity of mitochondria isolated from the tibialis anterior, but not the soleus, declined upon aging. The soleus and tibialis anterior exhibited similar aging-associated changes in mitochondrial biogenesis, fission/fusion, disposal and autophagy marker expression, but opposite changes in fiber composition: the most oxidative fibers declined in the tibialis anterior, while the more glycolytic fibers declined in the soleus. In conclusion, oxidative muscles are protected from mitochondrial aging, probably due to better mitochondrial homeostasis ab initio and aging-associated changes in fiber composition. Exercise training aimed at enriching oxidative fibers may be valuable in preventing mitochondria-related aging and its contribution to sarcopenia.
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Project description:SIGNIFICANCE:Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology state are integrated by the protonmotive force ?p or its potential component, ??, which are attenuated by proton backflux into the matrix, termed uncoupling. The mitochondrial uncoupling proteins (UCP1-5) play an eminent role in the regulation of each of the mentioned aspects, being involved in numerous physiological events including redox signaling. Recent Advances: UCP2 structure, including purine nucleotide and fatty acid (FA) binding sites, strongly support the FA cycling mechanism: UCP2 expels FA anions, whereas uncoupling is achieved by the membrane backflux of protonated FA. Nascent FAs, cleaved by phospholipases, are preferential. The resulting ?p dissipation decreases superoxide formation dependent on ?p. UCP-mediated antioxidant protection and its impairment are expected to play a major role in cell physiology and pathology. Moreover, UCP2-mediated aspartate, oxaloacetate, and malate antiport with phosphate is expected to alter metabolism of cancer cells. CRITICAL ISSUES:A wide range of UCP antioxidant effects and participations in redox signaling have been reported; however, mechanisms of UCP activation are still debated. Switching off/on the UCP2 protonophoretic function might serve as redox signaling either by employing/releasing the extra capacity of cell antioxidant systems or by directly increasing/decreasing mitochondrial superoxide sources. Rapid UCP2 degradation, FA levels, elevation of purine nucleotides, decreased Mg2+, or increased pyruvate accumulation may initiate UCP-mediated redox signaling. FUTURE DIRECTIONS:Issues such as UCP2 participation in glucose sensing, neuronal (synaptic) function, and immune cell activation should be elucidated. Antioxid. Redox Signal. 29, 667-714.
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Project description:Type 2 diabetes (T2D) has reached an epidemic level globally. Most current treatments ameliorate the hyperglycemic symptom of the disease but are not effective in correcting its underlying cause. One important causal factor of T2D is ectopic accumulation of lipids in metabolically sensitive organs such as liver and muscle. Mitochondrial uncoupling, which reduces cellular energy efficiency and increases lipid oxidation, is an appealing therapeutic strategy. The challenge, however, is to discover safe mitochondrial uncouplers for practical use. Niclosamide is an anthelmintic drug approved by the US Food and Drug Administration that uncouples the mitochondria of parasitic worms. Here we show that niclosamide ethanolamine salt (NEN) uncouples mammalian mitochondria at upper nanomolar concentrations. Oral NEN increases energy expenditure and lipid metabolism in mice. It is also efficacious in preventing and treating hepatic steatosis and insulin resistance induced by a high-fat diet. Moreover, it improves glycemic control and delays disease progression in db/db mice. Given the well-documented safety profile of NEN, our study provides a potentially new and practical pharmacological approach for treating T2D.
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Project description:Age-related pelvic floor muscle (PFM) dysfunction is a critical defect in the progression to pelvic floor disorders (PFDs). Despite dramatic prevalence of PFDs in older women, the underlying pathophysiology of age-related PFM dysfunction remains poorly understood. Using cadaveric specimens, we quantified aging effects on functionally relevant PFM properties and compared PFMs with the appendicular muscles from the same donors. PFMs, obturator internus, and vastus lateralis were procured from younger (N = 4) and older (N = 11) donors with known obstetrical and medical history. Our findings demonstrate that PFMs undergo degenerative, rather than atrophic, alterations. Importantly, age-related fibrotic degeneration disproportionally impacts PFMs compared to the appendicular muscles. We identified intramuscular lipid accumulation as another contributing factor to the pathological alterations of PFMs with aging. We observed a fourfold decrease in muscle stem cell (MuSC) pool of aged relative to younger PFMs, but the MuSC pool of appendicular muscles from the same older donors was only twofold lower than in younger group, although these differences were not statistically significant. Age-related degeneration appears to disproportionally impact PFMs relative to the appendicular muscles from the same donors. Knowledge of tissue- and cell-level changes in aged PFMs is essential to promote our understanding of the mechanisms governing PFM dysfunction in older women.
| S-EPMC8376748 | biostudies-literature
Project description:AimsBoth mitochondria and nitric oxide (NO*) contribute to cardioprotection by ischaemic preconditioning (IPC). IPC causes mild uncoupling of mitochondria via uncoupling proteins (UCPs) and the adenine nucleotide translocase (ANT), and mild uncoupling per se is cardioprotective. Although electrophilic lipids are known to activate mitochondrial uncoupling, the role of such species in IPC-induced uncoupling and cardioprotection is unclear. We hypothesized that endogenous formation of NO*-derived electrophilic lipids (nitroalkenes such as nitro-linoleate, LNO2) during IPC may stimulate mitochondrial uncoupling via post-translational modification of UCPs and ANT, thus affording cardioprotection.MethodsHearts from male Sprague-Dawley rats were Langendorff-perfused and subjected to IPC. Nitroalkene formation was measured by HPLC-ESI-MS/MS. The effects of exogenous LNO2 and biotin-tagged LNO2 on isolated heart mitochondria and cardiomyocytes were also investigated.ResultsNitroalkenes including LNO2 were endogenously generated in mitochondria of IPC hearts. Synthetic LNO2 (<1 microM) activated mild uncoupling, an effect blocked by UCP and ANT inhibitors. LNO2 (<1 microM) also protected cardiomyocytes against simulated ischaemia-reperfusion injury. Biotinylated LNO2 covalently modified ANT thiols and possibly UCP-2. No effects of LNO2 were attributable to NO* release, cGMP signalling, mitochondrial KATP channels, or protective kinase signalling.ConclusionComponents of a novel signalling pathway are inferred, wherein nitroalkenes formed by IPC-stimulated nitration reactions may induce mild mitochondrial uncoupling via post-translational modification of ANT and UCP-2, subsequently conferring resistance to ischaemia-reperfusion injury.
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Project description:Mitochondria, although required for cellular ATP production, are also known to have other important functions that may include modulating cellular responses to environmental stimuli. However, the mechanisms whereby mitochondria impact cellular phenotype are not yet clear.To determine how mitochondria impact endothelial cell function.We report here that stimuli for endothelial cell proliferation evoke strong upregulation of mitochondrial uncoupling protein 2 (UCP2). Analysis in silico indicated increased UCP2 expression is common in highly proliferative cell types, including cancer cells. Upregulation of UCP2 was critical for controlling mitochondrial membrane potential (??) and superoxide production. In the absence of UCP2, endothelial growth stimulation provoked mitochondrial network fragmentation and premature senescence via a mechanism involving superoxide-mediated p53 activation. Mitochondrial network fragmentation was both necessary and sufficient for the impact of UCP2 on endothelial cell phenotype.These data identify a novel mechanism whereby mitochondria preserve normal network integrity and impact cell phenotype via dynamic regulation of UCP2.
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Project description:The uncoupling proteins (UCPs) are transporters, present in the mitochondrial inner membrane, that mediate a regulated discharge of the proton gradient that is generated by the respiratory chain. This energy-dissipatory mechanism can serve functions such as thermogenesis, maintenance of the redox balance, or reduction in the production of reactive oxygen species. Some UCP homologs may not act as true uncouplers, however, and their activity has yet to be defined. The UCPs are integral membrane proteins, each with a molecular mass of 31-34 kDa and a tripartite structure in which a region of around 100 residues is repeated three times; each repeat codes for two transmembrane segments and a long hydrophilic loop. The functional carrier unit is a homodimer. So far, 45 genes encoding members of the UCP family have been described, and they can be grouped into six families. Most of the described genes are from mammals, but UCP genes have also been found in fish, birds and plants, and there is also functional evidence to suggest their presence in fungi and protozoa. UCPs are encoded in their mature form by nuclear genes and, unlike many nuclear-encoded mitochondrial proteins, they lack a cleavable mitochondrial import signal. The information for mitochondrial targeting resides in the first loop that protrudes into the mitochondrial matrix; the second matrix loop is essential for insertion of the protein into the inner mitochondrial membrane. UCPs are regulated at both the transcriptional level and by activation and inhibition in the mitochondrion.
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Project description:Numerous studies have suggested that the myofascial trigger points are responsible for most of the myofascial pain syndrome, so it seems reasonable that its destruction is a good therapeutic solution. The effectiveness of dry needling (DN) has been confirmed in muscles with myofascial trigger points, hypertonicity, and spasticity. The objective of this study is to analyze the need of repetitive punctures on muscles in different situations. The levator auris longus (LAL) muscle and gastrocnemius muscle from adult male Swiss mice were dissected and maintained alive, while being submerged in an oxygenated Ringer's solution. DN was evaluated under four animal models, mimicking the human condition: normal healthy muscles, muscle fibers with contraction knots, muscles submerged in a depolarizing Ringer solution (KCl-CaCl2), and muscles submerged in Ringer solution with formalin. Thereafter, samples were evaluated with optical microscopy (LAL) and scanning electron microscopy (gastrocnemius). Healthy muscles allowed the penetration of needles between fibers with minimal injuries. In muscles with contraction knots, the needle separated many muscle fibers, and several others were injured, while blood vessels and intramuscular nerves were mostly not injured. Muscles submerged in a depolarizing solution inducing sustained contraction showed more injured muscular fibers and several muscle fibers separated by the needle. Finally, the muscles submerged in Ringer solution with formalin showed a few number of injured muscular fibers and abundant muscle fibers separated by the needle. Scanning electron microscopy images confirm the optical analyses. In summary, dry needling is a technique that causes mild injury irrespective of the muscle tone.
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