Abnormal Glucagon Secretion Contributes to a Longitudinal Decline in Glucose Tolerance

Area of Science:

• Endocrinology
• Metabolic Diseases
• Diabetes Research

Background:

• Insulin secretion and action defects drive prediabetes to diabetes progression.
• The specific role of alpha-cell (α-cell) dysfunction remains unclear.

Purpose of the Study:

• To elucidate the distinct contributions of α-cell and β-cell dysfunction in the development of impaired glucose tolerance.
• To understand the progression of prediabetes to type 2 diabetes.

Main Methods:

• A longitudinal, community-based observational study of 96 non-diabetic subjects over 3 years.
• Oral glucose challenge and minimal model analysis to assess insulin secretion and action.
• Estimation of glucagon secretion rate (GSR) to evaluate α-cell function.

Main Results:

• Subjects progressing to impaired glucose tolerance or type 2 diabetes showed a decline in Disposition Index (DI), reflecting β-cell dysfunction.
• Impaired α-cell suppression of glucagon secretion by glucose (δGSR/δglucose) was observed in progressors.
• Both DI and α-cell function were independently linked to increased glycemic excursion.

Conclusions:

• Alpha-cell (α-cell) dysfunction is a key factor accompanying β-cell decline in the progression to impaired glucose tolerance and type 2 diabetes.
• These findings emphasize the dual role of α- and β-cell dysfunction in diabetes development.