Hyperglucagonemia Does Not Explain the β-Cell Hyperresponsiveness and Insulin Resistance in Dysglycemic Youth...

Area of Science:

• Endocrinology
• Metabolic Research
• Diabetes Research

Background:

• Youth with impaired glucose tolerance (IGT) or type 2 diabetes (T2D) exhibit hyperresponsive beta-cells and insulin resistance.
• The role of glucagon in these age-related differences in glucose homeostasis is not fully understood.

Purpose of the Study:

• To investigate whether increased glucagon release contributes to beta-cell hyperresponsiveness and insulin resistance in youth compared to adults.
• To compare glucagon secretion patterns between adolescent and adult populations with IGT or drug-naive T2D.

Main Methods:

• Hyperglycemic clamp studies and oral glucose tolerance tests (OGTTs) were conducted in 66 youth and 350 adults.
• Quantified insulin sensitivity (M/I), fasting and steady-state glucagon and C-peptide levels, and acute glucagon response (AGR) and C-peptide (ACPRmax) to arginine stimulation.

Main Results:

• Fasting and steady-state glucagon levels were comparable between youth and adults, but the acute glucagon response (AGR) was lower in youth.
• Age-group differences in insulin sensitivity and C-peptide responses were not directly linked to glucagon levels.
• Higher fasting glucagon correlated with lower insulin sensitivity and higher fasting C-peptide in both groups, with stronger associations in adults.

Conclusions:

• Youth with IGT or drug-naive T2D do not exhibit increased glucagon concentrations compared to adults.
• Alpha-cell dysfunction, indicated by glucagon levels, does not appear to be the primary driver of differences in beta-cell function and insulin sensitivity between these age groups.
• Despite similar glucagon levels, youth demonstrated greater C-peptide response and lower insulin sensitivity, highlighting other contributing factors to metabolic dysregulation.