Research Applications
Mitochondrial Function and Energy Production
SS-31 demonstrates remarkable effects on core mitochondrial bioenergetics across multiple tissue types. Research published in the Journal of the American Society of Nephrology demonstrates that SS-31 accelerates ATP recovery after ischemic injury by protecting mitochondrial cristae structure, with ATP levels fully recovering within one hour of reperfusion in treated tissues compared to persistent deficits in untreated controls. The peptide's interaction with cardiolipin prevents the destruction of cristae membranes that normally occurs during ischemia, maintaining the structural platform necessary for oxidative phosphorylation.
Studies in aged mice reveal that SS-31 treatment rapidly improves mitochondrial energetics, with significant increases in maximum ATP production capacity and coupling efficiency of oxidative phosphorylation. In aging skeletal muscle, the peptide increases ADP sensitivity of mitochondria by enhancing uptake through the adenine nucleotide translocator (ANT), a key step in ATP synthesis. This improved ADP sensitivity translates directly to enhanced physiological function, as demonstrated by increased muscle force generation at submaximal stimuli and improved cardiac systolic function.
The mechanism involves SS-31's stabilization of electron transport chain supercomplexes, which are multi-protein assemblies that optimize electron transfer efficiency while minimizing electron leak and ROS production. By preserving the cardiolipin-dependent organization of these supercomplexes, SS-31 maintains mitochondrial respiratory efficiency even under conditions of metabolic stress or aging that would normally disrupt these structures.
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- Birk AV, et al. "The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin." Journal of the American Society of Nephrology. 2013;24(8):1250-1261. https://jasn.asnjournals.org/content/24/8/1250
- Campbell MD, et al. "Improving mitochondrial function with SS-31 reverses age-related redox stress and improves exercise tolerance in aged mice." Free Radical Biology and Medicine. 2019;134:268-281. https://pmc.ncbi.nlm.nih.gov/articles/PMC6588449/
- Pharaoh G, et al. "The mitochondrially targeted peptide elamipretide (SS-31) improves ADP sensitivity in aged mitochondria by increasing uptake through the adenine nucleotide translocator (ANT)." GeroScience. 2023;45(6):3529-3548. https://pmc.ncbi.nlm.nih.gov/articles/PMC10643647/
Exercise Performance and Muscle Function
SS-31 demonstrates significant benefits for skeletal muscle function and exercise capacity, particularly in aged subjects. Research shows that eight weeks of SS-31 treatment in aged mice completely reversed age-related declines in exercise tolerance, with treated aged animals achieving treadmill endurance performance comparable to young controls. The gastrocnemius muscle in SS-31-treated aged mice exhibited greater fatigue resistance and significantly increased muscle mass compared to untreated aged controls.
The peptide's effects on muscle performance stem from multiple mechanisms. SS-31 treatment normalizes the increased proton leak observed in aged muscle mitochondria, improves mitochondrial coupling efficiency, and reverses the accumulation of dysfunctional mitochondria that characterize aging muscle. Notably, these improvements occur without increasing total mitochondrial content, indicating that SS-31 enhances the quality rather than quantity of existing mitochondria—a more efficient therapeutic approach.
Studies demonstrate that SS-31 prevents disuse muscle atrophy by reducing mitochondrial oxidative stress, which is a requisite step in the activation of muscle proteolysis pathways. The peptide suppresses muscle atrophy signaling and helps maintain skeletal muscle fiber composition favorable for endurance performance. In aged skeletal and cardiac muscles, SS-31 treatment improved both in vivo muscle force generation and heart function, providing evidence for a direct link between mitochondrial ADP sensitivity and physiological performance.
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Cardiovascular Health and Cardiac Protection
SS-31 exhibits profound cardioprotective effects, with particularly strong evidence for reversing age-related cardiac dysfunction. A landmark study in eLife demonstrated that eight weeks of SS-31 treatment in 24-month-old mice substantially reversed diastolic dysfunction, a hallmark of cardiac aging in both mice and humans. The peptide normalized the increased proton leak in cardiomyocytes from old mice, reduced mitochondrial ROS, and improved the early-to-late diastolic filling ratio (Ea/Aa) and myocardial performance index to levels approaching young controls.
In a canine model of advanced heart failure, three months of daily SS-31 treatment significantly improved left ventricular ejection fraction, stroke volume, cardiac output, and cardiac index while decreasing end-diastolic pressure and systemic vascular resistance. These functional improvements were accompanied by normalization of heart failure biomarkers including N-terminal pro-brain natriuretic peptide and pro-inflammatory cytokines (TNF-α, IL-6, C-reactive protein). Mitochondrial function analyses revealed that SS-31 restored mitochondrial respiration, membrane potential, ATP synthesis rate, and ATP/ADP ratio in cardiomyocytes from failing hearts.
Human cardiac tissue studies provide direct evidence of SS-31's therapeutic potential. Research published in JACC: Basic to Translational Science demonstrated that acute SS-31 treatment of explanted failing human hearts—from both pediatric and adult patients with various etiologies of heart failure—improved mitochondrial oxygen flux, complex I and IV activities, and supercomplex function. Importantly, these improvements occurred rapidly, before any cardiolipin remodeling could take place, indicating direct functional enhancement of existing mitochondrial structures.
A phase 1 clinical trial in patients with heart failure and reduced ejection fraction showed that a single 4-hour infusion of high-dose SS-31 resulted in significant decreases in left ventricular end-diastolic volume (−18 mL) and end-systolic volume (−14 mL) compared to placebo, with the temporal correlation between plasma concentrations and cardiac effects supporting a direct pharmacological mechanism.
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Kidney Protection and Renal Function
SS-31 demonstrates significant renoprotective effects across multiple models of kidney injury and disease. In acute kidney injury models, the peptide accelerates ATP recovery after ischemia-reperfusion injury by protecting mitochondrial cristae structure. Electron microscopy studies reveal that rats pretreated with SS-31 maintain intact cristae membranes and normal mitochondrial morphology throughout 45 minutes of renal ischemia and subsequent reperfusion, while untreated animals show dramatic mitochondrial swelling, cristae loss, and disrupted outer membranes consistent with mitochondrial permeability transition.
The rapid ATP recovery enabled by SS-31 has cascading beneficial effects on renal tissue preservation. Prompt ATP restoration allows rapid repair of ATP-dependent processes including restoration of the actin cytoskeleton and cell polarity in tubular epithelial cells. This metabolic protection inhibits both apoptotic and necrotic cell death pathways, protects tubular barrier function, and significantly reduces the severity of acute kidney injury.
In aging kidney research, SS-31 treatment of mice with advanced age improves glomerular architecture by protecting and restoring mitochondrial structure in podocytes and parietal epithelial cells. The peptide preserves endothelial cell integrity in glomerular capillaries, preventing the vascular rarefaction that normally occurs with aging. Remarkably, when SS-31 treatment was initiated one month after ischemic injury in rats and continued for six weeks, it effectively restored glomerular capillaries, normalized podocyte structure, and arrested both glomerulosclerosis and interstitial fibrosis—with protective effects sustained for over six months after treatment cessation.
A phase 2a clinical trial in patients with atherosclerotic renal artery stenosis undergoing stent revascularization demonstrated that SS-31 infusion before and during the procedure attenuated post-procedural kidney hypoxia, increased renal blood flow, and improved kidney function as measured by cortical perfusion and glomerular filtration rate at three-month follow-up. The mechanism involves prevention of ischemia-reperfusion injury that commonly occurs during revascularization procedures.
In diabetic kidney disease models, SS-31 treatment significantly inhibited increases in albuminuria and urinary hydrogen peroxide, reduced mesangial matrix accumulation, and regulated the balance between immature and mature cardiolipin species that become disrupted in diabetic nephropathy.
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Neuroprotection and Cognitive Function
SS-31 exhibits substantial neuroprotective properties through multiple mechanisms including mitochondrial protection, reduction of oxidative stress, anti-inflammatory activity, and preservation of synaptic integrity. Research in models of neuroinflammation demonstrates that SS-31 treatment significantly ameliorates cognitive impairment induced by lipopolysaccharide (LPS), a bacterial endotoxin that causes systemic inflammation and neurodegeneration.
In behavioral studies using the Morris water maze and contextual fear conditioning tests, mice receiving SS-31 treatment showed significant improvements in hippocampus-related learning and memory performance compared to LPS-exposed controls. The peptide maintained mitochondrial membrane potential, preserved ATP levels, and protected against oxidative stress as evidenced by decreased malondialdehyde and increased superoxide dismutase activity. SS-31 treatment also reduced neuroinflammatory cytokines (IL-6, TNF-α, IL-1β) and prevented neural cell apoptosis and loss of dendritic spines in the hippocampus.
Neuroimaging studies reveal that SS-31 improves functional connectivity in brain regions critical for cognition. In aged rats with LPS-induced neuroinflammation, SS-31 treatment increased functional connectivity in the parietal association cortex, sensory cortex, and motor cortex, regions that showed decreased connectivity in untreated animals. These improvements in brain network function correlated with reduced astrocyte activation and lower inflammatory marker expression in the hippocampus.
The neuroprotective mechanisms extend to enhancement of synaptic function through modulation of brain-derived neurotrophic factor (BDNF) signaling. SS-31 treatment facilitated the reversal of important synaptic-signaling proteins and increased synaptic structural complexity, including restoration of postsynaptic density protein-95 (PSD-95) levels to those comparable with control animals. This preservation of synaptic integrity is particularly relevant for preventing age-related cognitive decline and neurodegenerative disease progression.
In developing brain studies, SS-31 protected against anesthesia-induced neurotoxicity. Rats exposed to isoflurane during critical developmental periods showed mitochondrial dysfunction and long-term cognitive impairments, but SS-31 co-treatment ameliorated these effects by protecting mitochondrial morphology, reducing oxidative stress, and preserving cognitive function measured weeks after the initial exposure.
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Aging and Cellular Resilience
SS-31 addresses fundamental mechanisms of cellular aging by reversing age-related post-translational modifications that accumulate in proteins over time. Proteomic analyses of aged mouse hearts reveal that aging leads to widespread S-glutathionylation of cysteine residues on proteins, indicating an oxidized cellular environment. Eight weeks of SS-31 treatment almost completely reversed this shift, restoring the thiol redox proteome to a more reduced state characteristic of young animals. Many of the proteins most affected by this redox restoration were involved in mitochondrial function, cardiac contractility, and cellular structure.
The peptide's anti-aging effects extend beyond simple antioxidant activity. SS-31 reverses age-related changes in protein phosphorylation patterns, particularly in cardiac myosin binding protein C (cMyBP-C), where increased phosphorylation at Ser282 correlates directly with improved diastolic function. This demonstrates that SS-31 initiates signaling cascades that modify cellular behavior at multiple regulatory levels, not merely protecting against oxidative damage but actively restoring youthful patterns of cellular regulation.
In skeletal muscle, the benefits of reversing age-related mitochondrial dysfunction translate to preserved neuromuscular junction integrity and reduced motor unit loss—key factors in sarcopenia. Redox proteomics indicate that SS-31 reverses oxidative modifications of focal adhesion molecules near the plasma membrane and myelin sheath proteins surrounding motor neurons, suggesting that mitochondrial redox biology influences cellular structures far beyond the mitochondria themselves.
Importantly, SS-31's beneficial effects can be initiated late in life and still produce significant improvements. Treatment started at 24 months of age in mice (equivalent to approximately 70 human years) successfully reversed pre-existing cardiac and skeletal muscle dysfunction, demonstrating that mitochondrial therapeutic interventions need not begin early to be effective. The restoration of mitochondrial quality in aged tissues—converting dysfunctional mitochondria back to healthy, efficient energy producers—offers a mechanistic basis for slowing or partially reversing aspects of the aging process.
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Muscle Preservation and Anti-Atrophy Effects
SS-31 demonstrates significant muscle-protective properties by preventing both disuse atrophy and age-related muscle loss. The peptide's anti-atrophy effects stem from its ability to reduce mitochondrial oxidative stress, which is a necessary upstream trigger for activation of muscle proteolysis pathways. By maintaining mitochondrial function and reducing ROS generation, SS-31 interrupts the cascade of events that leads to muscle protein degradation.
Research shows that swollen mitochondria lacking cristae membranes appear in skeletal muscle after periods of disuse or hindlimb suspension, accompanied by activation of the intrinsic apoptotic pathway. Cardiolipin peroxidation plays a central role in this process, and SS-31's cardiolipin-protective effects prevent these structural and functional mitochondrial changes that would otherwise trigger muscle wasting. The peptide promotes mitochondrial respiration efficiency, which reduces the production of ROS that activate proteolytic systems responsible for breaking down muscle proteins.
In aged muscle specifically, SS-31 treatment increases muscle mass and improves fatigue resistance. The gastrocnemius muscle in SS-31-treated aged mice showed significantly greater mass compared to untreated age-matched controls, and this increased mass translated to enhanced functional capacity during exercise testing. The muscle-sparing effects occur through preservation of mitochondrial quality—eliminating the severely dysfunctional mitochondria that characterize aging muscle—rather than simply increasing total mitochondrial volume.
The peptide also modulates skeletal muscle metabolism to favor oxidative energy production. By improving mitochondrial efficiency and coupling, SS-31 enhances the muscle's capacity to utilize oxygen and generate ATP through aerobic pathways. This metabolic shift supports endurance performance and reduces fatigue during sustained physical activity. Combined with its effects on maintaining muscle mass during aging and metabolic stress, SS-31 provides comprehensive protection against the multiple factors that contribute to loss of muscle function.
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Ischemia-Reperfusion Injury Protection
SS-31 provides robust protection against ischemia-reperfusion injury across multiple organ systems, with the mechanism centered on preservation of mitochondrial structure and rapid restoration of energy production. During ischemia, ATP depletion causes breakdown of cellular cytoskeleton, loss of cell polarity, and activation of death pathways. The situation often worsens during reperfusion when oxygen return triggers excessive ROS production from damaged mitochondria, causing what is termed reperfusion injury.
In renal ischemia models, SS-31 treatment before ischemia maintains intact mitochondrial cristae throughout the ischemic period and prevents mitochondrial swelling and outer membrane rupture that normally occurs. This structural protection enables immediate ATP synthesis upon reperfusion, with treated kidneys achieving complete ATP recovery within one hour compared to sustained deficits exceeding 30% in untreated kidneys. The rapid energy restoration allows prompt repair of the actin cytoskeleton and restoration of tubular epithelial cell polarity, preserving barrier function and preventing progression to acute kidney injury.
Cardiac ischemia-reperfusion models demonstrate similar protective effects. SS-31 administration reduces myocardial lipid peroxidation and infarct size in animals undergoing coronary occlusion and reperfusion. The peptide prevents opening of the mitochondrial permeability transition pore, a catastrophic event that depolarizes mitochondria and releases cytochrome c to trigger apoptosis. By inhibiting cytochrome c peroxidase activity through its cardiolipin-binding action, SS-31 maintains cytochrome c in its electron carrier role rather than allowing it to become a destructive peroxidase.
The protective effects extend to prevention of chronic inflammation following ischemic injury. Studies show that SS-31 treatment prevents prolonged upregulation of inflammatory cytokines IL-1β and IL-18 that would otherwise persist for weeks after the initial ischemic insult. This anti-inflammatory effect helps prevent the transition from acute injury to chronic kidney disease or heart failure, representing a critical therapeutic benefit beyond the immediate protection during the ischemic event itself.
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