Different ß-cell secretory phenotype in non-obese compared to obese early type 2 diabetes.

BACKGROUND: Type 2 diabetes (T2D) is characterized by impaired tissue sensitivity to insulin action (ie, insulin resistance) and impaired ß-cell insulin secretion. Because obesity contributes importantly to the development of insulin resistance, we sought to determine whether insulin secretory defects would predominate in non-obese compared to obese T2D. METHODS: We measured ß-cell function and secretory capacity using the glucose-potentiated arginine test in T2D subjects early in the disease course classified as non-obese (BMI <30; n = 12) or obese (BMI ≥30 kg/m2 ; n = 28) and additionally compared responses from non-obese T2D with a non-diabetic control group (n = 12). RESULTS: The acute insulin response to glucose potentiation of arginine-induced insulin release was less in non-obese T2D than in controls and associated with impaired ß-cell sensitivity to glucose (PG50 ). Proinsulin secretory ratios were increased in non-obese T2D when compared to obese T2D. Obese T2D subjects had reduced insulin sensitivity (M/I) while non-obese T2D subjects had insulin sensitivity that was comparable to controls. CONCLUSIONS: In non-obese T2D, insulin secretory defects predominate with impaired ß-cell sensitivity to glucose and proinsulin processing in the absence of insulin resistance. Future studies should consider whether different ß-cell secretory phenotypes and tissue sensitivity to insulin explain the varying responsiveness to T2D interventions.