Insulin resistance syndrome and left ventricular mass in healthy young people

Background: Findings of atherosclerotic plaques in adolescents, in the context of current epidemics of obesity and type 2 diabetes in youth, demand investigation into early cardiovascular risk development. Left ventricular hypertrophy has been linked to hypertension, obesity, and insulin resistance. Methods: Insulin resistance syndrome characteristics (fasting glucose and insulin; systolic blood pressure; waist girth) were measured in 70 normotensive, normoglycemic young people (60% male, 62% black; included 13 twin pairs; age mean ± SD, 19 ± 2.6 years). Left ventricular mass indexed by height^2.7 (LVMI) was obtained via ultrasound. Twin pairs were clustered to satisfy the assumption for independent observations. Results: LVMI was regressed on insulin after controlling for race, gender, and systolic blood pressure. Insulin was a significant (P = 0.02) independent predictor of LVMI (R²change = 0.09, P < 0.01). Waist girth accounted for an additional 4% variance of LVMI (P = 0.05). A one-factor model comprising waist (factor loading = 0.83), insulin (0.59), glucose (0.42), and LVMI (0.46) showed good fit [²(2) = 0.41, P = 0.81; root-mean-square error of approximation = 0.0]. Conclusions: A subclinical metabolic syndrome is detectable early in life, before abnormal fasting glucose or high blood pressure appear. Evidence of excessive load on the heart is associated with the metabolic syndrome even after accounting for the effects of race, gender, and blood pressure. Cardiac structure seems as closely associated with this syndrome as fasting glucose level. Based on this evidence, we propose that increased left ventricular mass is a part of insulin resistance syndrome and adds to the need for preventive public health measures to improve health behaviors and cardiovascular risk status in US youth.