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Glycerol gluconeogenesis in fasting humans
Nutrition (Burbank, Los Angeles County, Calif.)
|March 1, 1995
Summary
Glycerol significantly contributes to glucose production, especially during fasting. Increased lipolysis accelerates glycerol release, providing a key precursor for glucose synthesis in the body.
Area of Science:
- Metabolism
- Endocrinology
- Physiology
Background:
- Glycerol is a gluconeogenic precursor, but its quantitative contribution to glucose production, particularly during fasting, requires further elucidation.
- Lipolysis releases glycerol, which can be utilized by the liver for gluconeogenesis.
Purpose of the Study:
- To quantify the contribution of glycerol to glucose production in healthy volunteers under postabsorptive and prolonged fasting conditions.
- To investigate the relationship between glycerol release (lipolysis) and its subsequent conversion to glucose.
Main Methods:
- Simultaneous primed constant infusion of 1-[13C]glycerol and 3-[3H]glucose in healthy volunteers.
- Determination of the rates of appearance (Ra) for glycerol, glucose, and glycerol-derived glucose.
Main Results:
- In the postabsorptive state, glycerol Ra was 3.11 ± 0.44 μmol·kg−1·min−1, with 36% converted to glucose, contributing 4.5% to total glucose production.
- After 62–86 hours of starvation, glycerol Ra increased to 5.32 ± 0.58 μmol·kg−1·min−1, with 68% converted to glucose, accounting for 21.6% of total glucose production.
- A strong correlation was observed between glycerol Ra, its conversion to glucose, and its overall contribution to glucose production.
Conclusions:
- Glycerol's contribution to glucose production is directly proportional to its release rate, which is driven by lipolysis.
- Accelerated lipolysis during fasting plays a crucial physiological role in supplying gluconeogenic precursors, primarily glycerol, for glucose homeostasis.