Reduced incretin effect in type 2 (non-insulin-dependent) diabetes

Area of Science:

• Endocrinology
• Metabolic Research
• Diabetes Mellitus

Background:

• The incretin effect, mediated by gut hormones, enhances glucose-stimulated insulin secretion.
• Understanding the impact of Type 2 diabetes on the incretin effect is crucial for metabolic regulation.

Purpose of the Study:

• To compare incretin-mediated insulin and C-peptide responses in Type 2 diabetic patients versus healthy controls.
• To investigate differences in insulin secretion and hepatic extraction between oral and intravenous glucose challenges.

Main Methods:

• Measured integrated immunoreactive insulin and C-peptide responses to oral glucose and isoglycaemic intravenous glucose infusion.
• Compared responses between 14 Type 2 diabetic patients and 8 healthy controls.
• Assessed gastric inhibitory polypeptide (GIP) responses.

Main Results:

• Diabetic patients exhibited delayed insulin and C-peptide responses to oral glucose despite higher glucose levels.
• Incretin factor contribution to insulin response was significantly lower in diabetics (36%) versus controls (72.8%).
• Diabetic patients showed greater insulin and C-peptide responses during intravenous infusion due to higher glycemic stimulus, suggesting altered hepatic insulin extraction.

Conclusions:

• Type 2 diabetes is associated with a significantly diminished incretin effect on insulin and C-peptide secretion.
• Hepatic insulin extraction appears reduced in diabetic patients compared to controls, particularly after oral glucose administration.
• GIP responses were not significantly different between the groups, suggesting other incretins may be more affected.