Use of a simple liquid meal test to evaluate insulin sensitivity and beta-cell function in children

Summary What is already known about this subject The assessment of insulin sensitivity and secretion provides useful information about the metabolic health of an individual. Invasive methods are needed to assess insulin sensitivity and secretion but these are difficult to perform in young children. What this study adds The relatively less invasive liquid meal test provided an estimate of insulin sensitivity in a pediatric population that was comparable to that obtained via a more invasive frequently-sampled intravenous glucose tolerance test (FSIGT). Both meal- and FSIGT-derived estimates of insulin sensitivity were inversely associated with children's adiposity. The meal-derived estimate of insulin sensitivity, but not that derived by the FSIGT, was associated with fasting insulin and triglyceride concentrations. Insulin sensitivity and β-cell function are useful indices of metabolic disease risk but are difficult to assess in young children because of the invasive nature of commonly used methodology. A meal-based method for assessing insulin sensitivity and β-cell function may at least partially alleviate concerns. The objectives of this study were to: (i) determine the association of insulin sensitivity assessed by liquid meal test with that determined by an insulin-modified frequently sampled intravenous glucose tolerance test (FSIGT); (ii) examine the association of insulin sensitivity derived from each test with measures of body composition, fat distribution and metabolic health (lipids, fasting insulin and glucose, and surrogate indices of insulin sensitivity); and (iii) examine the associations of indices of β-cell function derived from each test with total and regional adiposity. Forty-seven children (7-12 years) underwent both a liquid meal test and an FSIGT. The insulin sensitivity index derived from the meal test (SI-meal) was positively associated with that from the FSIGT (SI-FSIGT; r = 0.63; P < 0.001), and inversely with all measures of insulin secretion derived from the meal test. Both SI-meal and SI-FSIGT were associated with measures of total and regional adiposity. SI-meal, but not SI-FSIGT, was associated with triglycerides and fasting insulin, after adjusting for ethnicity, gender, pubertal stage and fat mass. Basal insulin secretion measured during the meal test was positively associated with all measures of adiposity, independent of insulin sensitivity. In conclusion, a liquid meal offers a valid and sensitive means of assessing insulin sensitivity and β-cell responsivity in young children.