Cardiolipin and mitochondrial health: How circadian rhythms, exercise, SS-31, and mitochondrial membrane maintenance fit into the science of cellular adaptation.

When people hear the word mitochondria, they usually think of energy.

And for good reason. Mitochondria help produce much of the energy our cells need to function.

But what happens when the machinery responsible for producing that energy is no longer properly organized?

What if a cell contains plenty of mitochondria, yet those mitochondria cannot function efficiently?

Recent research points toward an important part of the answer: cardiolipin, a specialized fat molecule that helps organize the inner membranes of mitochondria.

Several studies published between 2019 and 2026 have explored how cardiolipin is produced, maintained, and affected by aging, biological rhythms, and exercise.

Other research has investigated SS-31, also called elamipretide, a peptide that interacts with cardiolipin-associated mitochondrial structures.

Together, these findings offer a more complete picture of mitochondrial health.

The emerging lesson is that producing energy, maintaining mitochondrial structure, and adapting to physical demand are related—but they are not the same process.

What Is Cardiolipin, and Why Does It Matter?

Think of a mitochondrion as a highly organized power plant.

Inside that power plant is an inner membrane containing protein complexes that work together to produce energy in the form of ATP.

This membrane is folded into structures called cristae. These folds help organize the machinery involved in energy production.

Cardiolipin is a specialized phospholipid—a type of fat molecule—found primarily in this inner mitochondrial membrane.

It helps maintain membrane organization and supports the interactions among proteins involved in the respiratory chain.

Without appropriately maintained cardiolipin, mitochondria may have difficulty preserving the structure and organization needed for normal function.

That means mitochondrial health is not simply about how many mitochondria a cell contains.

It also depends on how well the internal machinery of those mitochondria is maintained.

This distinction is especially relevant to skeletal muscle and the heart, where cells depend heavily on efficient energy metabolism.

Cardiolipin Synthesis and Remodeling: Two Different Jobs

The body does not simply manufacture cardiolipin once and leave it unchanged.

Cardiolipin is produced, modified, maintained, and eventually replaced through several interacting processes.

1. Synthesis: Producing Cardiolipin

An enzyme called cardiolipin synthase, encoded by the CRLS1 gene, participates in the final step of cardiolipin production.

This process is often called de novo synthesis, meaning the production of new cardiolipin molecules.

Normal synthesis is essential for maintaining mitochondrial membranes, particularly when cells are growing or adapting.

2. Remodeling: Adjusting Its Composition

Newly produced cardiolipin can undergo further changes to its fatty-acid composition.

One important enzyme involved in this process is tafazzin, encoded by the TAZ gene.

Remodeling helps establish the cardiolipin composition appropriate for different tissues.

This matters because the quantity of cardiolipin and the precise arrangement of its fatty acids are different properties.

A person could theoretically have a normal amount of a particular membrane lipid while its composition or function is abnormal.

3. Maintenance: Keeping the System Functional

Cardiolipin molecules are also subject to ongoing turnover and oxidative stress.

Normal mitochondrial function requires an appropriate balance among synthesis, remodeling, and maintenance.

This leads to an important scientific distinction:

The goal is not necessarily to produce more cardiolipin. It is to maintain appropriate cardiolipin homeostasis.

Homeostasis means maintaining the right balance for the tissue’s physiological needs.

What Recent Research Reveals About Aging and Cardiolipin

A 2026 study published in Nature Aging investigated whether cardiolipin loss could contribute directly to age-related muscle changes.

The researchers used genetically modified mice in which the production of cardiolipin could be disrupted.

When cardiolipin synthesis was reduced, the mice developed impaired mitochondrial respiration, changes in muscle-fiber characteristics, and muscle atrophy.

These changes resembled some features associated with skeletal-muscle aging.

When the researchers partially restored cardiolipin synthesis in their experimental model, several muscle abnormalities began to improve, and premature mortality was prevented.

This was more informative than simply observing that cardiolipin changes with age.

The researchers experimentally disrupted a biological process and then observed the consequences of partially restoring it.

However, the findings were primarily from mouse experiments. They do not establish that increasing cardiolipin synthesis treats normal human aging.

Why More Mitochondria May Not Mean Better Mitochondria

Another interesting observation was that certain muscles developed more mitochondrial material even while respiratory function became impaired.

That suggests a cell may try to compensate for reduced mitochondrial performance by changing its mitochondrial population.

But compensation does not necessarily restore efficient function.

Having more mitochondria does not guarantee that each mitochondrion works better.

A separate 2026 study in developing mouse hearts also demonstrated that disrupting cardiolipin synthesis and disrupting cardiolipin remodeling could produce different consequences for respiratory-chain development.

These findings reinforce a central idea: cardiolipin concentration, membrane composition, and mitochondrial performance should not be treated as interchangeable measurements.

Research findings on how total cardiolipin changes with normal aging are not entirely consistent across studies, so age alone cannot establish that someone has a cardiolipin deficiency.

The Circadian Connection: Does Your Biological Clock Influence Cardiolipin?

Our bodies follow approximately 24-hour biological rhythms.

These rhythms help coordinate sleep and waking, hormones, feeding, body temperature, and cellular metabolism.

They also influence processes occurring inside mitochondria.

Research published in 2020 found that cardiolipin abundance varied across the daily cycle in cultured skeletal-muscle cells.

Genes involved in cardiolipin synthesis and remodeling also exhibited rhythmic patterns.

When researchers disrupted certain clock-related regulators known as ROR nuclear receptors, parts of these patterns changed.

This suggested that biological timing may influence mitochondrial membrane lipid regulation.

What Happened in Human Muscle?

A 2021 study investigated circadian misalignment in 14 healthy young men.

Researchers experimentally shifted participants’ sleep, eating, and activity schedules by 12 hours over several days.

They then examined changes in skeletal-muscle lipids.

The misaligned condition was associated with lower measured cardiolipin levels and changes in several other muscle lipid classes.

That is an important human observation.

It suggests that disrupting the normal relationship between the body’s biological clock and daily behaviors can change mitochondrial-related lipid biology.

However, the study did not establish that lower cardiolipin caused impaired mitochondrial respiration or that restoring a consistent schedule would reverse the changes.

It also changed several behaviors together, including sleeping, eating, and activity timing. Their individual contributions could not be completely separated.

The supported conclusion is that circadian organization influences the physiological environment in which mitochondrial membrane lipids are regulated—not that correcting sleep automatically repairs cardiolipin.

Exercise Does More Than Burn Energy: It Can Change Mitochondrial Membranes

Exercise is often discussed as a way to increase mitochondrial number and improve cardiovascular fitness.

But human research suggests that training can also change mitochondrial lipid composition.

A 2024 study published in Diabetes examined 52 healthy participants who completed 12 weeks of high-intensity interval training, resistance training, or combined exercise.

The researchers measured changes in skeletal-muscle metabolism and lipid profiles.

Aerobic and combined training produced increases in multiple cardiolipin species, while resistance training produced a different pattern of lipid changes.

All three approaches provided metabolic benefits, but the changes were not identical.

This is important because different types of exercise place different demands on muscle.

Resistance training primarily challenges force production and structural adaptation. Aerobic training places sustained demands on oxidative metabolism.

Both can be valuable, but they need not produce identical molecular responses.

Better Function Without More Cardiolipin

A 2019 study provides an especially useful counterexample to the idea that more cardiolipin is always the answer.

Eight men with type 2 diabetes completed ten weeks of supervised endurance training.

After training, their intrinsic skeletal-muscle mitochondrial respiratory function improved.

But their total cardiolipin abundance and mitochondrial DNA copy number did not significantly increase.

The researchers also found a 68.2% increase in monolysocardiolipin, or MLCL, a molecule involved in cardiolipin metabolism.

That result is consistent with altered membrane-lipid processing, but an increase in MLCL alone cannot establish beneficial remodeling. In some diseases, elevated MLCL can also indicate impaired remodeling.

The study was small and did not establish which lipid change caused the improved respiration.

Nevertheless, its findings illustrate a useful distinction:

Changes in mitochondrial performance do not always require measurable increases in total cardiolipin.

Exercise may influence several processes at once, including mitochondrial content, membrane composition, respiratory machinery, and metabolic regulation.

Does the Time of Day You Exercise Change Cardiolipin Quality?

This is one of the most interesting unanswered questions in the research.

Separate studies show that circadian organization influences cardiolipin-related biology and that exercise training changes aspects of mitochondrial lipid metabolism.

Other studies suggest that the timing of exercise can influence certain adaptations.

For example, a 2022 randomized crossover study in men with type 2 diabetes compared morning and afternoon high-intensity interval training.

Researchers found differences in coordinated skeletal-muscle metabolic and protein responses depending on training time.

Afternoon training was associated with relatively greater mitochondrial complex III protein abundance and different muscle lipid patterns.

However, only eight participants completed the molecular analysis, and individual metabolites and proteins did not show robust significant changes after correction for multiple comparisons.

The study also did not directly measure cardiolipin composition, cardiolipin oxidation, or mitochondrial respiratory supercomplex function.

In 2025, a separate mouse study showed that muscle clock proteins called REV-ERB influence time-dependent exercise adaptations.

That provides experimental evidence that the muscle clock can affect training responses.

But this study also did not establish an exercise-timing effect on cardiolipin.

There is currently insufficient evidence to recommend morning or afternoon exercise specifically to improve cardiolipin synthesis, remodeling, or membrane quality.

What matters most clinically is selecting activity that is safe, appropriate, and sustainable for the individual.

Where Does SS-31 Fit Into the Picture?

Once we understand the importance of cardiolipin, another question naturally follows.

Could a treatment help protect or support cardiolipin-associated mitochondrial membrane function?

SS-31, also called elamipretide, is a mitochondria-targeted peptide that interacts with cardiolipin.

Its mechanism is different from the enzymes that manufacture or remodel cardiolipin.

This distinction is critical.

Interacting with cardiolipin is not the same as producing new cardiolipin or correcting abnormal cardiolipin composition.

The 2026 genetic studies showing benefits from restored cardiolipin synthesis did not administer SS-31.

Their findings establish the importance of cardiolipin biology but do not demonstrate that elamipretide reproduces the benefits of genetic restoration.

What Has Been Demonstrated in Humans?

In September 2025, the U.S. Food and Drug Administration granted accelerated approval to elamipretide, marketed as Forzinity, to improve muscle strength in adults and children with Barth syndrome who weigh at least 30 kilograms.

Barth syndrome is a rare inherited disease involving abnormal cardiolipin metabolism.

The approval was based on improvement in knee-extensor muscle strength, an intermediate clinical endpoint. Continued approval may depend on confirmatory evidence of clinical benefit.

This is meaningful human evidence for a specific inherited mitochondrial condition.

It does not establish that SS-31 reverses typical age-related muscle decline, treats chronic fatigue, or improves recovery in people without Barth syndrome.

Nor does it demonstrate that SS-31 should routinely be combined with exercise or used to increase cardiolipin synthesis.

For now, the most accurate way to describe the relationship is that endogenous cardiolipin homeostasis and cardiolipin-targeted therapy address different aspects of mitochondrial biology.

Potential applications beyond established indications require appropriate clinical trials and safety evaluation.

What This Research Means for Healing in Order

The Ettinger Foundation Protocol, or EFP, organizes recovery around physiological stability, readiness, and the ability to adapt to increasing demand.

The cardiolipin studies provide a useful biological example of why these distinctions matter.

They do not directly test or validate the EFP phase sequence.

Phase 3 — Circadian Organization

Phase 3 emphasizes restoring consistent daily timing, sleep–wake organization, and day–night physiological contrast.

Research suggests that biological clocks influence aspects of mitochondrial lipid regulation, including cardiolipin-related pathways.

This provides a possible molecular connection between circadian organization and later mitochondrial adaptation.

However, circadian stability alone does not prove that cardiolipin synthesis or mitochondrial respiration has been restored.

Phase 4 — Mitochondrial Adaptation

Phase 4 addresses the body’s ability to meet and recover from physiological demand.

Cardiolipin research adds an important distinction: mitochondrial adaptation involves not only substrate utilization and signaling but also maintenance of the membrane structures that organize respiration.

Appropriately tolerated physical activity may stimulate adaptive mitochondrial changes.

But a beneficial molecular response in a research participant does not mean the same exercise dose is appropriate for someone with chronic illness, autonomic instability, or post-exertional symptom worsening.

Within EFP, greater demand is considered only when the individual’s condition and response permit it.

Phase 5 — Repair and Structural Resilience

Once appropriate capacity is established, progressive loading can help promote functional muscle adaptation.

Normal mitochondrial membrane function contributes to the energy demands of this process.

But having more mitochondria, more cardiolipin, or a favorable molecular marker does not establish that a patient is ready for greater loading.

Actual functional performance, recovery, and repeatability remain important.

Capacity Requires Substrate—but Substrate Is Not the Whole Story

Another EFP principle is that the body requires sufficient nutritional resources to maintain and rebuild function.

Cardiolipin, like other membrane lipids, depends on normal cellular lipid metabolism and appropriate precursor availability.

However, the studies reviewed do not establish that a particular diet, fatty-acid supplement, or feeding schedule will selectively restore cardiolipin homeostasis in patients.

The practical goal is nutritional adequacy, not an unvalidated attempt to manipulate a specific cardiolipin species.

In EFP, substrate provides resources, regulatory systems help coordinate adaptation, and clinical recovery determines whether increased demand is sustainable.

This is an interpretation of the framework informed by the research, not a clinical sequence proven by the cardiolipin studies.

What the Research Has Not Yet Proven

Several questions remain unanswered.

  • Whether correcting circadian disruption directly restores deficient cardiolipin synthesis in humans.
  • Whether morning or afternoon exercise produces superior cardiolipin remodeling or membrane function.
  • Whether deliberately increasing CRLS1 activity improves ordinary human aging.
  • Whether increasing total cardiolipin is better than maintaining its normal composition and turnover.
  • Whether a change in MLCL or a specific cardiolipin species reliably indicates beneficial adaptation.
  • Whether combining SS-31 with exercise improves outcomes beyond appropriately prescribed exercise alone.
  • Whether cardiolipin measurements can guide routine clinical decisions for chronic multisystem illness.

These are valuable research questions, but they are not established treatment instructions.

Some studies also report different directions of age-associated cardiolipin changes. This means it would be inaccurate to assume that every aging person has declining cardiolipin or requires a treatment to increase it.

What Can You Do Now?

For most people, the practical implications are less complicated than the molecular biology.

Support a reasonably consistent sleep–wake schedule. Maintain adequate nutrition. Participate in physical activity appropriate for your health, abilities, and recovery capacity.

Resistance exercise and aerobic activity both have established health benefits, although their effects and appropriate doses differ.

People who are deconditioned or living with illness may need individualized rehabilitation rather than a standard training program.

If activity repeatedly causes delayed deterioration, prolonged fatigue, or worsening neurological or autonomic symptoms, do not interpret that response as evidence that harder training is necessary.

It calls for a reassessment of the activity plan and potential medical contributors.

No cardiolipin-specific supplement, exercise schedule, or peptide treatment has been established for general mitochondrial optimization from the research reviewed here.

These ordinary foundations are not guaranteed ways to increase cardiolipin. They are established ways to support broader metabolic and functional health.

Final Perspective: Mitochondrial Health Is About Organization and Adaptation

Mitochondria are more than energy-producing structures.

They are dynamic systems that must maintain their membranes, organize respiratory proteins, respond to metabolic demand, and adapt to changing conditions.

Cardiolipin is one important part of that system.

The research reviewed here connects cardiolipin biology to circadian regulation, exercise, mitochondrial structure, and emerging targeted therapies.

But it also teaches us to avoid a common mistake: assuming that more of a particular molecule necessarily means better function.

More mitochondria do not automatically mean better mitochondria. More cardiolipin does not automatically mean better membrane function. And a favorable molecular response does not automatically mean the body can tolerate greater demand.

Through the Healing in Order perspective, the central question remains whether the person can sustain and recover from the physiological demands being placed upon them.

The goal is not merely to stimulate mitochondrial activity. It is to support the conditions for meaningful, sustainable functional adaptation.

Cardiolipin and Mitochondrial Health Research Sources

  1. Nohara K, et al. Cardiolipin Synthesis in Skeletal Muscle Is Rhythmic and Modifiable by Age and Diet.
    Oxidative Medicine and Cellular Longevity. 2020;5304768.
    https://doi.org/10.1155/2020/5304768
  2. Harmsen J-F, et al. Circadian misalignment disturbs the skeletal muscle lipidome in healthy young men.
    The FASEB Journal. 2021;35:e21611.
    https://doi.org/10.1096/fj.202100143R
  3. Finger F, et al. Mitochondrial membrane lipid cardiolipin controls fiber-type adaptations in aging muscle via estrogen-related receptor gamma.
    Nature Aging. 2026;6:2092–2109.
    https://doi.org/10.1038/s43587-026-01227-7
  4. Ren M, et al. De novo synthesis of cardiolipin controls respiratory chain biogenesis in neonatal mouse hearts.
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  5. Pataky MW, et al. Divergent Skeletal Muscle Metabolomic Signatures of Different Exercise Training Modes Independently Predict Cardiometabolic Risk Factors.
    Diabetes. 2024;73:23–37.
    https://doi.org/10.2337/db23-0142
  6. Pino MF, et al. Endurance training remodels skeletal muscle phospholipid composition and increases intrinsic mitochondrial respiration in men with Type 2 diabetes.
    Physiological Genomics. 2019;51:586–595.
    https://doi.org/10.1152/physiolgenomics.00014.2019
  7. Savikj M, et al. Exercise timing influences multi-tissue metabolome and skeletal muscle proteome profiles in type 2 diabetic patients: A randomized crossover trial.
    Metabolism. 2022;135:155268.
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  8. Liu J, et al. Muscle Rev-erb controls time-dependent adaptations to chronic exercise in mice.
    Nature Communications. 2025;16:5708.
    https://doi.org/10.1038/s41467-025-60520-y
  9. U.S. Food and Drug Administration. Forzinity (elamipretide): Drug Trials Snapshot and prescribing information. 2025.
    FDA clinical evidence summary

Cardiolipin and mitochondrial health research interpretation: This article summarizes evidence from multiple studies. Laboratory and animal findings should not be interpreted as established treatments for human mitochondrial dysfunction. The Ettinger Foundation Protocol is a clinical framework and was not directly evaluated in these studies.