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Short-term hypocaloric nutrition but not bed rest decrease insulin sensitivity and IGF-I bioavailability in healthy
J Nygren1, A Thorell, K Brismar
1Department of Surgery, Gustaf V Research Institute, Karolinska Hospital, Stockholm, Sweden.
Nutrition (Burbank, Los Angeles County, Calif.)
|January 20, 1998
Summary
Short-term fasting significantly reduces insulin sensitivity and insulin-like growth factor-I (IGF-I) bioavailability in healthy individuals. This metabolic shift is linked to increased IGF-binding protein-1 (IGFBP-1) and influenced by glucagon levels.
Area of Science:
- Endocrinology
- Metabolic Science
- Human Physiology
Background:
- Brief hypocaloric nutrition and immobilization are common physiological stressors.
- Understanding their metabolic impact is crucial for clinical contexts like surgery and trauma recovery.
- Insulin sensitivity and insulin-like growth factor-I (IGF-I) bioavailability are key metabolic indicators.
Purpose of the Study:
- To investigate the metabolic effects of 24-hour hypocaloric nutrition (fasting) versus bed rest in healthy subjects.
- To assess changes in insulin sensitivity, IGF-I bioavailability, and related hormonal profiles.
- To determine the role of glucagon in regulating IGF-binding protein-1 (IGFBP-1) during short-term fasting.
Main Methods:
- Hyperinsulinemic, normoglycemic clamps were performed before and after interventions.
- Indirect calorimetry was used to measure substrate oxidation.
- Circulating levels of hormones (e.g., glucagon, IGF-I, IGFBP-1) and substrates were analyzed.
- Body weight and nitrogen balance were monitored.
Main Results:
- Fasting led to decreased body weight, negative nitrogen balance, and increased basal levels of free fatty acids, glucagon, and IGFBP-1.
- Insulin sensitivity, assessed by glucose infusion rates during clamps, decreased by 43% after fasting.
- IGF-I bioavailability, indicated by the IGF-I/IGFBP-1 ratio, decreased post-fasting, while IGFBP-1 levels increased.
- Bed rest induced no significant adverse metabolic changes or alterations in insulin sensitivity.
Conclusions:
- Twenty-four hours of hypocaloric nutrition significantly reduces insulin sensitivity and IGF-I bioavailability in healthy individuals.
- Increased IGFBP-1 levels, potentially regulated by glucagon, contribute to reduced IGF-I bioavailability after short-term fasting.
- Immobilization (bed rest) for 24 hours does not induce significant negative metabolic changes in healthy subjects.
- These findings suggest that hypocaloric nutrition and immobilization may exacerbate the catabolic response to surgical procedures or trauma.