Metformin isn’t new. In fact, it’s almost 100 years old and has been the go-to drug for type 2 diabetes since the 1950s. Its main gig? Lowering blood sugar.

But here’s where it gets interesting: scientists are now testing metformin as a brain repair tool—specifically for diseases like multiple sclerosis (MS), Alzheimer’s, and Parkinson’s.

Why? Because this old-school pill might do more than tame blood sugar. It could actually help brain cells grow back the protective insulation they lose with age and disease.

Quick MS 101

MS happens when your immune system attacks the protective “coating” (myelin) around your nerves. Think of it like chewing the plastic off an iPhone charging cable. Without insulation, signals slow down, nerves get damaged, and everyday functions (like walking or memory) start breaking down.

The body tries to patch things up by making new myelin, but this repair job gets way less efficient as people age.

Enter Metformin

Turns out, metformin can sneak into the brain and reboot aging brain cells that normally don’t respond well to repair signals anymore. In animal studies, it helps these “sleepy” cells wake up, get back to work, and lay down fresh myelin.

Translation: metformin may give your brain’s electricians the tools they need to re-wrap those frayed wires.

From Rats to Humans

Here’s the catch: humans aren’t giant rats. Our brain cells are wired differently, and drugs don’t always translate the same way.

So, researchers did the next best thing: they grew human brain cells from stem cells and tested how they reacted to metformin in three different setups:

  1. Petri dishes (monolayers) – basic, but too immature.
  2. Mini-brains (organoids) – better, but still not quite adult-like.
  3. Human cells transplanted into mouse brains – weird, yes, but this setup looked most like real adult human brain tissue.

The winner? The human–mouse chimera. That’s where metformin really kicked up myelin production and improved energy supply in brain cells.

The Mitochondria Plot Twist

Alongside boosting myelin, metformin also rewired mitochondria—the tiny power plants inside cells. Researchers saw bigger, more networked mitochondria in both nerve and support cells.

Think of it as upgrading from a bunch of weak phone chargers to a power strip with fast chargers on every outlet. The cells pumped out more ATP (cellular energy), which could help damaged nerves survive longer.

Why This Matters

  • It’s cheap. Metformin costs pennies a pill compared to flashy new biotech drugs.
  • It’s safe. Millions of people already take it daily for diabetes.
  • It’s versatile. Ongoing clinical trials are testing it for MS, Alzheimer’s, Parkinson’s, and even healthy aging.

The Fine Print

So far, all the cool stuff is happening in labs, animals, or mouse–human hybrids. Real-world proof in actual MS or Alzheimer’s patients? Still pending.

But if those trials succeed, we could be looking at a future where a humble diabetes pill doubles as a neuroprotective superdrug.

Bottom line: Metformin isn’t just managing blood sugar anymore. It’s quietly auditioning for the role of “brain fixer”—and if the early science holds up, it could become one of the biggest comebacks in modern medicine.

Kazakou NL, Bestard-Cuche N, Wagstaff LJ, Horan K, Seeker L, Bøstrand S, Fetit R, Smith RS, Pohl FB, Neumann B, Keeler P, Franklin RJM, Williams A. Metformin alters mitochondria-related metabolism and enhances human oligodendrocyte function. Nat Commun. 2025 Aug 30;16(1):8126. doi: 10.1038/s41467-025-63279-4. PMID: 40885740; PMCID: PMC12398550.