Wednesday, February 25, 2009

Early Insulin Resistance Predicts Subsequent Risk of Metabolic Syndrome

Insulin resistance and metabolic syndrome are most often thought of in connection with middle age. However, an article in the March 2009 issue of the journal Metabolism shows that these conditions get their start early in life.

A biracial group of 475 girls was studied first at ages 9-10 years and then at ages 18-19 years. In the first stage of the study, the invesigators determined the body mass index (BMI) of each girl. They also determined a score called the HOMA-IR, or homeostatis model assessment of insulin resistance. Insulin resistance can be measured using an oral glucose tolerance test (OGTT), but this requires several hours and numerous blood draws. In the HOMA-IR, the fasting levels of insulin and glucose are determined, multiplied, and converted into a score that correlates well with the insulin resistance determined by more technically-demanding methods. The girls were divided in two ways: (1) according to whether their BMI put them in the bottom, middle or top third of the group with regard to to relative obesity (2) according to whether their HOMA-IR score put them in the bottom, middle or top third with regard to relative insulin resistance.

Nine years later the girls were assessed for five metabolic syndrome risk factors. These included:
  • Triglycerides
  • High-density lipoprotein cholesterol
  • Systolic/diastolic blood pressure
  • Waist circumference
  • Blood glucose
Each risk factor measurement was converted to a z score, which is a way of expressing the relationship of a specific measurement to the population average and the standard deviation of that particular variable. The five z scores were added for each individual. If the total z score was negative, that meant that the individual had a lower risk of metabolic syndrome. (The more negative the total, the better in this instance.) If the total z score was positive, that meant that the individual had a higher risk of metabolic syndrome.

The results were not surprising. The girls who had the lowest BMI and the lowest insulin resistance at ages 9-10 were found to have the lowest risk of metabolic syndrome at ages 18-19. As initial BMI and insulin resistance scores rose, the subsequent scores for risk of metabolic syndrome also rose. The girls who had the highest BMI and the highest insulin resistance at ages 9-10 had the highest risk of metabolic syndrome at ages 18-19. It appears that childhood obesity and insulin resistance interact to produce a higher risk of metabolic syndrome in early adulthood.

Taking it one step farther, the significance of metabolic syndrome in childhood was underlined by a study recently published in the journal Pediatrics, Metabolic Syndrome in Childhood Predicts Adult Cardiovascular Disease 25 Years Later. In this study, the investigators found that the incidence of cardiovascular disease for their 31 patients with pediatric metabolic syndrome was 19.4%, while the incidence was 1.5% for the subjects without metabolic syndrome as children. If these findings are correct, children with metabolic syndrome are significantly more likely than their peers to experience cardiovascular disease twenty five years later as adults.

The obvious question becomes, what happens to these children if intervention takes place between their pre-teen years and their forties? And what would that intervention be? Would it be pharmacological? Would it involve a change in dietary habits? There is a bias at this blog for at least trying a low-carb eating strategy to lower BMI, reduce insulin resistance, avert childhood metabolic syndrome and prevent the progression to adult cardiovascular disease. Whether or not that approach will be tested in the scientific community remains to be seen.

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