Changes in insulin resistance with long-term insulin therapy

Area of Science:

• Endocrinology
• Metabolic Disorders
• Pharmacology

Background:

• Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia.
• Insulin therapy is a cornerstone in managing diabetes, but its impact on insulin sensitivity varies.
• Understanding factors influencing insulin sensitivity is crucial for optimizing diabetes treatment.

Purpose of the Study:

• To evaluate the effect of 6-month insulin therapy on glucose uptake and insulin sensitivity in newly diagnosed diabetic patients.
• To identify predictors of improved insulin sensitivity following insulin treatment.
• To assess changes in growth hormone (GH) secretion in response to insulin therapy.

Main Methods:

• Glucose-clamp studies were performed on 13 newly diagnosed diabetic patients (5 IDDM, 8 NIDDM) at baseline and after 6 months of insulin treatment.
• Insulin infusion rates of 1.0 and 10 mU x kg-1 x min-1 were used to assess glucose uptake.
• Correlations between changes in glucose uptake and clinical parameters (diabetes type, C-peptide, age) were analyzed.
• Growth hormone levels were measured during clamp studies.

Main Results:

• Insulin therapy significantly improved glycemic control in all subjects.
• A significant negative correlation was observed between improved glucose uptake and diabetes type (IDDM vs. NIDDM), C-peptide secretion, and age.
• Growth hormone secretion, elevated at diagnosis during hyperglycemia, was abolished after insulin therapy.
• Improvements in glucose uptake at a higher insulin infusion rate did not reach statistical significance.

Conclusions:

• Long-term insulin therapy can improve insulin sensitivity, particularly in patients with insulin-dependent diabetes mellitus (IDDM).
• Diabetes type, baseline C-peptide secretion, and age are important factors influencing the response to insulin therapy.
• Improved glycemic control with insulin therapy effectively suppresses hyperglycemia-induced growth hormone secretion.