When Mitochondria Reroute Energy

A New Layer in the Biology of Metabolic Congestion

For years, we’ve been taught to think of mitochondria as simple “power plants”—structures that burn fuel to make energy.

But emerging research is telling a very different story.

A recent study by Shingo Kajimura and colleagues, titled “Mitochondrial control of glycerolipid synthesis by a PEP shuttle”, reveals something remarkable:

Mitochondria don’t just burn fuel—they actively redirect it.

And that insight adds an important new layer to how we understand metabolic disease, aging, and what I describe as Exposure-Related Malnutrition (ERM).

A surprising discovery: mitochondria export PEP

The study shows that:

• Mitochondria can convert pyruvate → phosphoenolpyruvate (PEP) via PCK2

• PEP is then exported to the cytosol via a transporter (SLC25A35)

• In the cytosol, PEP contributes to:

  • glycerol-3-phosphate (G3P) production

  • triglyceride (fat) synthesis

When this pathway is blocked:

• lipid synthesis decreases

• fatty liver improves

• metabolic health improves in experimental models

Why this matters: fat is not just storage

At first glance, this might sound like:

“Mitochondria help make fat.”

But the deeper message is far more important:

Fat production is part of a protective system—not just energy storage.

To safely store fat, the body needs:

• fatty acids

• a glycerol backbone (G3P)

Without G3P, fat cannot be packaged into stable triglycerides.

Lipid cycling: the hidden buffering system

In healthy metabolism, fat is not static.

There is a continuous cycle:

• Triglycerides → fatty acids (lipolysis)

• Fatty acids → triglycerides (re-esterification)

This is called lipid cycling.

It:

• consumes energy

• requires G3P

• protects cells from toxic lipid buildup

Where ERM comes in: mitochondrial congestion

In the ERM framework, chronic stress—whether from diet, toxins, inflammation, or lifestyle—creates a mismatch:

More fuel enters the system than mitochondria can process.

This leads to what I describe as:

Mitochondrial congestion

• NADH accumulates

• electron transport slows

• metabolic “traffic” builds up

The new connection: PEP as a metabolic “relief valve”

This new study helps explain how the body initially adapts.

When mitochondria are under pressure:

• Pyruvate is diverted → PEP (instead of fully oxidized)

• PEP is exported

• G3P is generated

• Fat is safely stored

In other words:

The body converts excess metabolic pressure into stored fat to prevent damage.

But this system has limits

Here’s where things become clinically important.

The same study shows that PEP export depends on mitochondrial function—particularly the energetic state of the inner membrane.

Other research adds another layer:

• Cholesterol oxidation can damage mitochondrial membranes

• This disrupts the electron transport chain

• Membrane potential declines

When the system starts to fail

When mitochondrial function declines:

1. PEP export decreases

2. G3P becomes limited

3. Triglyceride formation slows

4. Lipid cycling breaks down

Now fat can no longer be safely stored.

Instead, cells accumulate:

• free fatty acids

• diacylglycerol (DAG)

• ceramides

These are not just “fat”—they are bioactive stress signals.

A vicious cycle begins

This creates a self-reinforcing loop:

• Mitochondrial dysfunction→ impaired lipid buffering→ toxic lipid accumulation→ further mitochondrial damage

Over time, this contributes to:

• fatty liver

• insulin resistance

• muscle loss with fat gain (sarcopenic obesity)

• neurodegeneration

A shift in perspective

These findings challenge a common assumption:

Fat accumulation is not always the problem—it may initially be the solution.

Early on:

• fat storage protects the system

Later:

• failure to store fat safely becomes the problem

The ERM insight

What this new study adds is precision.

It identifies a specific metabolic switch:

The PEP–G3P pathway as a membrane-dependent buffering system

When it works:

• the body adapts

When it fails:

• the system decompensates

What this means for health

Instead of asking:

• “How do we burn more fat?”

We may need to ask:

• How do we restore mitochondrial throughput?

• How do we maintain redox balance?

• How do we preserve lipid buffering capacity?

Because:

You’re not just accumulating fat—you may be losing the ability to handle it.

Final thought

This emerging biology suggests that metabolic disease is not simply excess—but mismanaged flow.

Mitochondria are not passive engines.

They are:

• regulators

• traffic controllers

• and, under stress, improvisers

And sometimes, fat is the price the body pays to buy time.

Yamamuro, T., Katoh, D., Martins Silva, G., Yook, J.-S., Sun, L., & Kajimura, S. (2026). Mitochondrial control of glycerolipid synthesis by a PEP shuttle. Cell. Advance online publication.