Aim: To examine whether reduced insulin secretory capacity or increased insulin secretory
demand is associated with elevated ratio of plasma proinsulin to immunoreactive insulin
(PI/IRI ratio) in non-diabetic subjects. Subjects and Methods: We measured various indices of insulin secretory function and insulin sensitivity
by frequently sampled intravenous glucose tolerance test (FSIGT) and hyerglycemic
glucose clamp in 21 healthy young men. We then examined the relationships between
these indices and PI, IRI, or PI/IRI ratio in the fasting state. Results: Insulin sensitivity index (SI) measured by FSIGT correlated inversely with basal IRI (r = - 0.53, P < 0.01) and
PI levels (r = - 0.57, p < 0.01), but there was no significant correlation between
SI and PI/IRI ratio (r = 0.26, NS). On the other hand. PI/IRI ratio correlated inversely
with insulin secretory indices, such as acute insulin responses during FSIGT (r =
- 0.46, P < 0.01) and hyperglycemic glucose clamp (r = - 0.54, P < 0.01) and submaximum
insulin response during hyperglycemic glucose clamp (r = - 0.59, P < 0.01). Conclusions: These results indicate that elevated PI/IRI ratio may serve as a marker of reduced
insulin secretory function in non-diabetic subjects.
Key words
Insulin Sensitivity - Insulin Secretion - Minimal Model Analysis - Hyperglycemic Glucose
Clamp - Pancreatic β-Cells