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Quantification of the relationship between insulin sensitivity and beta-cell function in human subjects. Evidence for
S E Kahn1, R L Prigeon, D K McCulloch
1Division of Metabolism, University of Washington, Seattle.
Diabetes
|November 1, 1993
Summary
Insulin sensitivity (SI) and beta-cell function are inversely related in a hyperbolic manner in healthy humans. As body mass index increases, insulin sensitivity decreases, prompting compensatory beta-cell responses to maintain normal glucose tolerance.
Area of Science:
- Metabolic Physiology
- Endocrinology
- Human Physiology
Background:
- Insulin sensitivity (SI) and beta-cell function are critical for maintaining glucose homeostasis.
- Obesity is known to impair insulin sensitivity, but its precise impact on beta-cell function in healthy individuals requires further elucidation.
Purpose of the Study:
- To investigate the quantitative relationship between insulin sensitivity and various measures of beta-cell function in a cohort of healthy, non-diabetic adults across a range of body mass indices.
Main Methods:
- Quantified insulin sensitivity index (SI) using the minimal model in 93 healthy subjects (BMI 19.5-52.2 kg/m²).
- Assessed beta-cell function through fasting insulin, first-phase insulin response (AIRglucose), glucose potentiation slope, and beta-cell secretory capacity (AIRmax).
- Analyzed the relationship between SI, body adiposity (BMI), and beta-cell function parameters using correlational and regression analyses.
Main Results:
- Insulin sensitivity (SI) demonstrated a curvilinear inverse relationship with body mass index (BMI).
- A hyperbolic, reciprocal relationship was observed between SI and beta-cell function measures (fasting insulin, AIRglucose, glucose potentiation slope, AIRmax), described by SI x beta-cell function = constant.
- This hyperbolic relationship provided a significantly better fit than a linear model, suggesting a regulated feedback system.
Conclusions:
- In healthy humans with normal glucose tolerance, beta-cell function is quantitatively modulated by insulin sensitivity.
- The observed hyperbolic relationship suggests a compensatory mechanism where beta-cell function adjusts reciprocally to maintain glucose balance despite varying insulin sensitivity and adiposity.