When the body refuses to make insulin, the condition is called
type 1 diabetes; when the body mismanages the hormone, it's
known as type 2. Now, scientists report new evidence linking
insulin to a disorder of the brain: when the brain prevents the
hormone from acting properly, the ensuing chemical imbalance may
help trigger Alzheimer's disease. The correlation is so strong
that some researchers are calling Alzheimer's disease "type 3"
diabetes. In the body, insulin helps convert food into cellular
energy. But the brain has other uses for insulin, namely as a
means to learn and make new memories. Here's how it works: At
synapses, the spaces across which brain cells communicate and
where memories are conceived, neurons reserve special parking
spots just for insulin. When the hormone pulls in, a connection
is made that enables new memories to form. Since new memory
formation is one of the first things to go awry in people with
early stages of the disease, this insulin-initiated process may
hold the key to decodi