Insulin Secretion Impaired in the Insulin-Resistant

Individuals with impaired glucose tolerance or type 2 diabetes have impaired glucose-stimulated insulin secretion after exposure to insulin compared with healthy individuals, according to a study published in the February issue of Diabetes.

Florencia Halperin, M.D., from the Joslin Diabetes Center in Boston, and colleagues investigated how pre-exposure to insulin affected glucose-stimulated insulin secretion in 10 individuals with impaired glucose tolerance, 11 patients with type 2 diabetes, and eight healthy individuals. Following a four-hour clamp with sham (saline infusion) or an isoglycemic-hyperinsulinemic clamp using B28-Asp-insulin (which raised insulin concentrations to high physiologic concentrations), dextrose was administered for 80 minutes to assess the insulin secretory response.

The researchers found that pre-exposure to insulin increased glucose-stimulated insulin secretion in healthy individuals. In patients with impaired glucose tolerance and those with type 2 diabetes, the effect was reduced.

"In conclusion, we have demonstrated that while the β-cell is insulin responsive and pre-exposure to insulin enhances glucose-stimulated insulin secretion in healthy humans, this effect is reduced in states of insulin resistance," Halperin and colleagues write. "Thus we demonstrate physiologically that the β-cell is an insulin-responsive tissue in humans in vivo."

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