Alterations in adipose tissue distribution, cell morphology and function mark primary insulin hypersecretion in youths with obesity
Excessive insulin secretion independent of insulin resistance, defined as primary hypersecretion, is associated with obesity and an unfavorable metabolic phenotype. We examined the characteristics of the adipose tissue in youths with primary insulin hypersecretion and the longitudinal metabolic alterations influenced by the complex adipo-insular interplay. In a multiethnic cohort of non-diabetic adolescents with obesity, primary insulin hypersecretors had enhanced model-derived β-cell glucose sensitivity and rate sensitivity, but worse glucose tolerance, despite similar demographics, adiposity, and insulin resistance measured by both OGTT and euglycemic-hyperinsulinemic clamp. Hypersecretors had greater intrahepatic and visceral fat depots at abdominal MRI, hypertrophic abdominal subcutaneous adipocytes, higher FFA and leptin serum levels per fat mass, and faster in vivo lipid turnover assessed by a long-term 2H2O labeling protocol. At 2-year follow up, hypersecretors had greater fat accrual and 3-fold higher risk for abnormal glucose tolerance, while individuals with hypertrophic adipocytes or higher leptin levels showed enhanced β-cell glucose sensitivity. Primary insulin hypersecretion is associated with marked alterations in adipose tissue distribution, cellularity, and lipid dynamics, independent of whole-body adiposity and insulin resistance. Pathogenetic insight into the metabolic crosstalk between β-cell and adipocyte may help identify individuals at risk for chronic hyperinsulinemia, body weight gain, and glucose intolerance.