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Insulin Resistance Tied to Early Heart Problems
  MedPage Today
Published: June 13, 2011
MONTREAL -- In teens, insulin resistance appears to be an important link between obesity and early adverse cardiac changes, researchers found.
Teens who had elevated fasting plasma insulin and insulin resistance were significantly more likely to have multiple measures of cardiac dysfunction than those with normal values, according to Gautam Singh, MD, of Washington University in St. Louis.
And in a multivariate analysis, increased fasting plasma insulin and insulin resistance, along with rising body mass index (BMI), were associated with poorer left ventricular function (P<0.05 for all), he reported at the American Society of Echocardiography meeting here.
Action Points
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
* Note that this study suggests that signs of impaired LV function can be observed in obese children with insulin resistance.
The cardiac changes represent "the early onset of impaired left ventricular function even before the clinical manifestations of any cardiac dysfunction are there," Singh said in an interview.
Although some of these changes have been demonstrated in a pediatric population before, they have not been linked previously to insulin resistance, he said.
The next step in the research is to follow these patients longitudinally to see whether the cardiac changes continue, and whether they can be reversed by improving lifestyle and losing weight.
Singh said that just knowing that the heart is being affected at such a young age can provide the impetus for a child or parent to make the necessary lifestyle adjustments.
Because obesity tends to track from childhood to adulthood, Singh and his colleagues wanted to see whether obesity-related cardiac dysfunction also would track. They hypothesized that it would and that insulin resistance would be an important mediator in the process.
The researchers prospectively enrolled 77 teens (mean age 13.9) who went to a preventive cardiology clinic or gastroenterology clinic for the evaluation of dyslipidemia, obesity, and hypertension. Singh and his colleagues measured glucose-insulin homeostasis, metabolic profiles, and left ventricle global longitudinal strain, as well as strain rate and torsion using 2D speckle-tracking echocardiography.
The participants were divided into two groups:
* Normal: Teens with normal fasting plasma insulin of 10 μIU/mL or lower and normal insulin resistance indicated by a HOMA2 of 2 or lower
* Abnormal: Teens with higher values
The average BMI was significantly higher in the abnormal group (33.9 versus 26 kg/m2). This group also had a significantly higher systolic and diastolic blood pressure (P<0.05 for both).
Although fasting insulin, fasting glucose, and insulin resistance were higher in the abnormal group, the lipid profile was similar in each group. There were also no between-group differences in liver enzymes or thyroid hormones.
Echocardiography showed that left ventricular mass and ejection fraction were not significantly different between the two groups.
However, left ventricular global longitudinal strain, longitudinal systolic strain rate, and early diastolic strain rate were all significantly decreased in the abnormal group (P<0.04 for all), indicating early left ventricular dysfunction.
Insulin resistance was inversely associated with all three measures.
In addition, peak cardiac torsion was significantly lower in the abnormal group (P=0.047).
The mechanism underlying the decrease in myocardial longitudinal strain and circumferential torsion is not clear, Singh said. He and his colleagues presume that insulin resistance is causing cardiac dysfunction by modifying myocardial substrate metabolism and efficiency, which has been suggested in both animal and human studies.
Singh reported that he had no conflicts of interest.
Primary source: American Society of Echocardiography
Source reference:
Singh G, et al "Insulin resistance is a determinant of cardiac dysfunction in obese children" ASE 2011; Abstract P1-72.
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