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Fat metabolism in human obesity
P J Campbell1, M G Carlson, N Nurjhan
1Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
The American Journal of Physiology
|April 1, 1994
Summary
Obese individuals exhibit insulin resistance in free fatty acid (FFA) metabolism, requiring higher insulin levels for suppression. Despite reduced FFA turnover per fat mass, obese subjects show increased FFA reesterification, impacting carbohydrate metabolism.
Area of Science:
- Metabolic Physiology
- Endocrinology
Background:
- Obesity is linked to insulin resistance, affecting carbohydrate metabolism.
- Understanding free fatty acid (FFA) metabolism is crucial in obesity.
Purpose of the Study:
- To investigate the insulin dose-response curves for FFA metabolism in lean and obese volunteers.
- To determine if obesity causes insulin resistance in FFA metabolism.
Main Methods:
- Sequential insulin infusions at varying doses (4-400 mU.m-2.min-1).
- Measurement of FFA concentration, FFA turnover (using [1-14C]palmitate), and lipolysis (using [2H5]glycerol).
- Analysis of FFA turnover per fat mass and fat-free mass (FFM).
Main Results:
- Insulin resistance of FFA metabolism was confirmed in obese subjects, with dose-response curves shifted rightward.
- Obese subjects had decreased FFA turnover per fat mass due to suppressed lipolysis and increased primary FFA reesterification.
- FFA turnover per FFM was higher in obese individuals, driven by increased secondary FFA reesterification, while FFA oxidation remained similar.
Conclusions:
- Obesity is associated with significant insulin resistance in FFA metabolism.
- Altered FFA handling, including increased reesterification, contributes to metabolic dysregulation in obesity.