Cell
Changes May Explain Diabetes Risk in Elderly
Diabetes may become more common with age because
of a decline in the function of mitochondria,
the powerhouses of the body's cells.
The
good news, they say, is that exercise might counter
this decline.
In a study that compared 13 healthy people ages
18 to 39 with 16 healthy people ages 61 to 84,
the elderly participants were found to have greater
insulin resistance, which is a precursor to type
2 diabetes.
However, the difference was not due to higher
body fat among the older participants, who were
just as lean as their younger counterparts.
Insulin is a hormone produced by the pancreas
that allows blood sugar, or glucose, to enter
cells so it can be used as energy. Mitochondria,
found in a cell's cytoplasm, are responsible for
converting glucose and fatty acids into energy.
This process is impaired during insulin resistance,
when the body becomes less sensitive to the effects
of insulin, prompting the pancreas to pump out
more insulin to try to compensate.
A big question has been why older adults have
high rates insulin resistance and full-blown type
2 diabetes. Type 2 diabetes affects about one
in four people older than 60, noted study author
Gerald I. Shulman of the Howard Hughes Medical
Institute at Yale University in New Haven, Connecticut.
In the new study, reported in the May 16th issue
of Science, Shulman and colleagues showed that
the metabolic activity of the mitochondria in
muscle cells was about 40 percent lower in the
older participants.
They also showed more fat accumulation in their
muscle and liver tissue, assessed through non-invasive
scans.
"This finding is important because studies
in our lab and others have shown that the amount
of lipid (fat) inside the muscle cell is a very
good predictor of insulin resistance," Shulman
said in a statement.
The results suggest that fat builds up in the
muscle of older people because of the decreased
activity of the cells' fat-burning mitochondria,
according to the researchers.
"These data support the hypothesis that an
age-associated decline in mitochondrial function
contributes to insulin resistance in the elderly,"
they conclude in the report.
On a positive note, exercise may help counter
this process, because research has shown that
physical activity increases mitochondria in muscle
by activating an enzyme known as AMP kinase, Shulman
explained in the statement.
"This is yet another reason for seniors to
maintain an active lifestyle," he said.
SOURCE: Science 2003;300:1140-1142.
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FACT:
Nearly one in 10 Latinos age 40 or older has a
potentially sight-robbing condition that is related
to diabetes. That, according to a California survey
released this week. However, nearly 30 percent
of those surveyed were unaware they had diabetes,
much less a complication that can damage sight.
"That is a huge number of undiagnosed cases
of diabetes," said Dr. Rohit Varma, an associate
professor of ophthalmology at the University of
Southern California in Los Angeles. Los Angeles
Latino Eye Study
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