In the Turkey, a Hope for Autoimmune Disorders

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In the Turkey, a Hope for Autoimmune Disorders

By SANDRA BLAKESLEE

Published: November 8, 2005

A substance found in many foods, including turkey, can suppress an

overactive immune system, researchers are reporting.

The substance, tryptophan, produces a breakdown product in the body

that, in the study, reversed paralysis in mice with an experimental

form of multiple sclerosis, an autoimmune disorder that attacks the

fatty cells that insulate neurons.

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MORE THAN STUFFING Turkey has tryptophan, which breaks down in the body

to form many products.

" I have always been a skeptic regarding the interaction of diet and

immunity, " said Dr. Lawrence Steinman, the chairman of the immunology

program at Stanford, who led the study, published in Science last week.

" But now I'm getting smacked in the head by my own research. "

Dr. Marc Feldmann, a professor of medicine at Imperial College London

and an authority on autoimmune disorders, called the study " very

interesting and quite encouraging. "

But he said the next step, and a very large one, was to find out if the

treatment is safe for humans.

Tryptophan is one of 20 building blocks, called amino acids, that the

body uses to construct proteins. But unlike many other amino acids,

tryptophan is not made by the body, and it must be gotten from foods.

Once tryptophan is consumed, it breaks down via different metabolic

pathways to form a huge number of proteins and hormones, including

serotonin, which elevates mood, and melatonin, which promotes sleep - a

partial explanation for the nap that often follows Thanksgiving dinner.

Tryptophan also helps make an essential vitamin, niacin.

Yet another breakdown pathway of tryptophan produces compounds called

kynurenines, which have been shown to suppress the immune response in

pregnant animals, Dr. Steinman said. Kynurenines bear a remarkable

resemblance in chemical structure to a drug called Tranilast, sold in

Japan to treat allergies.

When the Stanford researchers gave the drug, as well as pure

kynurenines, to mice with a form of multiple sclerosis, inflammation

was drastically reduced. The mice regained neurological function.

An evolutionary explanation may exist for the suppressed immunity that

results from some breakdown products of tryptophan, Dr. Steinman said.

When people are starving, they need to preserve essential functions of

the brain and heart. Without food and with little or no tryptophan to

make proteins, kynurenines tend to build up and turn off the immune

system, thus helping the starving person to survive.

In a recent clinical trial to treat inflammation of blood vessels,

Tranilast proved to be very safe, Dr. Steinman said. The drug is now

licensed by an Australian company, Angiogen, for use in autoimmune

diseases.

Dr. Steinman said he hoped to create some kind of joint venture with

Angiogen to test Tranilast in people with multiple sclerosis. The drug

is also being tested in Britain to treat arthritis, he said.

He added that people often asked if they should eat a lot of turkey or

buy tryptophan pills to treat autoimmune disorders, " but it probably

won't help unless you are starving to death, " he said. " A drug that

works on the right pathways should be more effective. "