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YOUR HEALTH: A blind fish could unlock diabetic secrets

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BOSTON, Massachusetts –. When it comes to diabetes, diet, exercise and medication can help some people avoid dangerous complications.

But experts say there’s still a lot to learn.

Now researchers at Harvard Medical School are looking in a very unlikely place to improve human health.

Tanks upon tanks of ordinary looking lab fish.

But when you get closer…

“The cavefish has no pigment, so they’re this whitish fish, with no eyes at all,” said Dr. Misty Riddle, a Biologist at Harvard Medical School.

After millions of years swimming in dark caverns, this Mexican tetra evolved without orbs.   For Harvard evolutionary and developmental biologist Misty Riddle, it’s not the strange outside that’s fascinating.   It’s what’s inside.

Riddle explained, “If you dissect this fish, and even just looking at them they seem to store fat everywhere. We wondered what other type of metabolic changes there would be.”

Riddle found these cavefish had huge swings in blood glucose levels, much like people with type two diabetes.

People with type two diabetes also have insulin resistance.

Over time, high blood glucose levels and insulin resistance can lead to diabetes in people and serious complications.

Dr. Bhavna Desai, a Postdoctoral Scientist in endocrinology and metabolism at Harvard Medical School, explained that "vascular damage causes heart disease and causes liver damage:  diabetic kidney disease.”

Despite the abnormal blood glucose levels, the cavefish have none of the health side effects. Researchers say understanding why the fish don’t develop complications could help them find a pathway for new drugs.

“If we can learn about how that’s different maybe we can apply that to humans,” said Riddle.

NEW RESEARCH:   Dr. Riddle says there's more to cave fish than what meets the eye: “If you dissect these fish or even just looking at them they seem to store fat everywhere."  Researchers wondered what other type of metabolic changes there would be.  "We know in humans sometimes obesity is associated with dysregulation of glucose homeostasis, and so that’s one thing we decided to study, what does their blood glucose regulation look like,” said Dr. Riddle.   She hopes to find answers with these fish.  "What was surprising was they had a mutation that was the same mutation found in some humans that have this really rare form of insulin resistance that’s really deadly. If we can learn about how that’s different maybe we could apply that to humans or understanding why humans with the mutation have these detrimental effects that the fish avoid.”

Mysteries of the Mexican caves that could help an American health epidemic.

Riddle says the cavefish in her lab have normal life expectancies, despite having high glucose levels and insulin resistance.

Many of the fish have been in the lab for up to 15 years.

If this story has impacted your life or prompted you or someone you know to seek or change treatments, please let us know by contacting Jim Mertens at or Marjorie Bekaert Thomas at

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