NEW YORK, Jan 12 (Reuters Health) -- People who have high levels of the
hormone insulin in their blood after fasting have an impaired ability to
dissolve blood clots, US researchers report.
Although the research was conducted largely in people without diabetes,
the findings may explain why diabetics, who by definition have disordered
insulin regulation, are at high risk for cardiovascular disease, according to
researchers led by Dr. James B. Meigs of Massachusetts General Hospital in
Boston. Their report is published in the January 12th issue of The Journal of
the American Medical Association.
Insulin levels usually rise in the blood after a meal, in response to food
intake. Thus high levels of the hormone in the blood after fasting suggest a
problem, and may indicate that the person is at risk for diabetes. A glucose
tolerance test, where the individual fasts, then has blood samples taken after
drinking a sugary drink, can diagnose the problem.
The investigators looked at insulin levels and blood clotting function of
nearly 3,000 healthy men and women aged 26 to 82. Overall, 80% of people had a
normal ability to use insulin to process blood sugar (known as glucose
tolerance), 15% had glucose intolerance -- where their bodies no longer respond
to normal levels of insulin, resulting in elevated blood levels of the hormone
-- and 5% had previously undiagnosed diabetes.
Meigs and colleagues found that those with higher blood levels of insulin
(hyperinsulinemia) also had an impaired ability to dissolve blood clots, a
process known as fibrinolysis. Blood clots are a major contributor to heart
attacks and are the cause of the most common type of stroke. Researchers believe
that clots often form in major blood vessels, but are broken down as quickly as
they form when fibrinolysis is functioning normally. But where fibrinolysis is
impaired, the risk of serious clot-related disorders increases.
The finding suggests that hyperinsulinemia and glucose intolerance -- two
pre-diabetic conditions -- are linked with a higher risk of cardiovascular
disease because they affect fibrinolysis, increasing the risk of serious blood
clots, the authors conclude.
The findings suggest that improving the ability of the body to respond to
insulin may prevent heart disease in these at-risk individuals, according to
Meigs and colleagues. People with high fasting blood levels of insulin are often
obese, and these insulin levels fall when they lose weight, indicating an
improved glucose tolerance. Thus, weight loss through diet and exercise may
modify blood-clotting function by improving the body's sensitivity to insulin,
and also reduce the risk of cardiovascular disease in these individuals.
