Dear Science,
If humans ate a diet consisting of other humans, could a
mad-cow-like disease develop?
Hungry
Yes. In fact, it happened. Charlton Heston wasn’t involved. The Fore
tribes from Papua New Guinea, as a part of the grieving process, ate
their dead relations. A bizarre disease spread in the population,
taking as long as 50 years to appear. The illness starts with tremors,
stumbling, and an inability to stand up straight. With time the
afflicted lose the ability to walk, their muscles moving on their own
accord. Eventually, one passes away under the thick cloud of
dementia.
Kuru (the name means “shivering” in the tribal language) is in a
family of diseases—including the genetic fatal familial insomnia
and Gerstmann-Straussler-Scheinker syndrome, as well as
Creutzfeldt-Jakob disease (CJD)—caused by misfolded proteins,
called prions.
All proteins start as a long chain of amino acids, eventually
folding into complex three-dimensional structures capable of doing
work. When most proteins fold the wrong way, they are promptly torn
apart by the cell, and a new copy is made. Rarely, a misfolded protein
evades being destroyed and can make copies of itself by converting
properly folded proteins into this new, wrong shape. How, exactly?
Figure that out—and not by citing a Kurt Vonnegut novel—and
you’ll probably earn a Nobel Prize.
Each of these diseases is caused by improperly folded protein
accumulating like tar in the brain, killing off ever-increasing numbers
of neurons. Eating prions—the nervous systems of creatures with
the disease are filled with them—can teach your proteins how to
misfold, spreading the disease. Cooking doesn’t help—the
prions stick around even when other proteins are denatured. On the
positive side, the misfolded prion proteins are almost exclusively
found in nervous-system tissue. Blood transfusions, for example, seem
to be safer.
Sounds crazy, right? The notion of self-replicating
proteins—exactly the same amino acid sequence as normal proteins,
capable of converting these normal proteins to their shape and
replicating themselves completely independent of RNA or DNA—is
a startling wrinkle to the central dogma of biology where DNA is
transcribed into RNA, which in turn is translated into a single kind of
protein. It took a series of clever experiments before prions became
widely accepted as yet another cause of misery and disease in the
world: blasting away the DNA and RNA from plaques from a sick animal to
show that the disease can still be spread with only the remaining
protein; digesting the protein from the plaque to show how destroying
the prion prevents the spread; isolating the specific protein behind
these diseases and engineering mice to misfold the protein to show that
adding prions causes the disease.
So, yes there is mad human disease. Don’t eat any Soylent Green
meals, please.
Cannibalistically Yours, Science
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