American Heart Association meeting report:
(Note: This release contains updated numbers from the abstract.)
CHICAGO, Oct. 10 – Teenagers whose bodies have a decreased response to insulin might face an increased risk of high blood pressure as adults, according to a large, long-term study reported at the American Heart Association's 58th Annual High Blood Pressure Research Conference.
Insulin is a hormone that regulates glucose, a blood sugar. Insulin resistance occurs when the body begins to lose its ability to regulate glucose, which can lead to diabetes.
Researchers assessed insulin resistance in teens over five years and found the condition was associated with higher systolic blood pressure. Systolic pressure is the top number in a blood pressure reading; it measures the pressure in arteries when the heart contracts. Insulin resistance was also linked to obesity. Statistical analysis showed that insulin resistance was independently associated, to lesser extent, with unfavorable changes in cholesterol levels and other blood fats.
"The results indicate that one of the keys to preventing high blood pressure is to start thinking about it in childhood," said Alan Sinaiko, M.D., professor of pediatrics at the University of Minnesota in Minneapolis. "If insulin resistance in childhood is related to risk factors in adulthood, we ought to be thinking about this problem at an early age. By the time people are in their 20s and 30s, a lot of the risk is already set, and we are treating the disease instead of preventing it."
The study not only documents the independent association of insulin resistance to heart risk factors, but also provides information about the origin of the condition, Sinaiko said.
"We know that insulin resistance exists, but we don't know a lot about the insulin resistance syndrome and how it develops," he said. "This study shows that insulin resistance is present at a very young age. Even though children don't have the same degree of heart risk factors as adults, the findings suggest that insulin resistance has an early influence on what happens to people as adults."
The findings came from a study that began 10 years ago, involving 357 children whose average age was 13 at the time. Over the next 5.5 years, each of the children had evaluations of their body's response to insulin three times (enrollment, age 15 and 19).
Doctors evaluated sensitivity to insulin with a technique called the euglycemic clamp. The test involves infusing a small amount of insulin into the blood for three hours. Simultaneously, glucose is infused through another vein. The test was designed to maintain blood sugar at a fairly normal level of 100 milligrams per deciliter (mg/dL).
A small amount of glucose to maintain blood sugar levels indicates insulin resistance. Increasing amounts of glucose indicated insulin sensitivity, the desired response.
At age 13, none of the children had hypertension (high blood pressure), and the average blood pressure for the study group was 109/55 millimeters of mercury (mm Hg) in 198 boys and 106/58 mm Hg in 159 girls.
At age 19, systolic blood pressure increased by 0.42 mm Hg for each unit of insulin resistance at age 13, and it increased by 0.81 mm Hg for each unit increase in BMI. Triglycerides increased by 0.88 mg/dL for each unit increase in insulin resistance, and by 3.1 mg/dL per each unit of BMI (body mass index, a measure of fatness) at age 13. HDL cholesterol increased by 0.20 mg/dL for each unit increase in insulin resistance, and 0.32 for each unit increase in BMI.
The effects of insulin resistance on systolic blood pressure were independent of those related to BMI.
"There is no question that obesity in some people is significantly related to insulin resistance," Sinaiko said. "What we're showing is that insulin resistance has an effect on systolic blood pressure that is independent of fatness and obesity. Strategies designed to reduce childhood obesity to prevent cardiovascular risk and type 2 diabetes may need to be complemented by treatment of insulin resistance in at-risk people."
Co-authors are David R. Jacobs Jr., Ph.D.; Julia Steinberger, M.D.; and Antoinette Moran, M.D.
Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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