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Renal substrate exchange and gluconeogenesis in normal postabsorptive humans
Christian Meyer1, Michael Stumvoll, Jean Dostou
1Department of Medicine and Physiology, University of Rochester School of Medicine, Rochester, New York 14642, USA.
American Journal of Physiology. Endocrinology and Metabolism
|January 15, 2002
Summary
Lactate is the primary source for glucose production in the kidneys and body during fasting. The kidneys play a significant role in processing lactate, contributing substantially to overall glucose release.
Area of Science:
- Human physiology
- Metabolic pathways
- Renal function
Background:
- Kidney glucose release in fasting humans is primarily attributed to gluconeogenesis.
- Lactate is a major systemic gluconeogenic precursor, with significant renal uptake.
- The role of lactate in renal gluconeogenesis and kidney lactate metabolism was unquantified.
Purpose of the Study:
- To quantify lactate's contribution to renal gluconeogenesis.
- To investigate the kidney's role in lactate metabolism.
- To compare lactate with other gluconeogenic precursors (glutamine, alanine, glycerol).
Main Methods:
- Utilized isotopic and renal balance techniques in 24 postabsorptive humans.
- Measured systemic and renal lactate conversion to glucose.
- Determined renal lactate net balance, fractional extraction, uptake, and release.
Main Results:
- Lactate was the dominant gluconeogenic precursor systemically and renally.
- Renal lactate uptake represented nearly 30% of systemic lactate turnover.
- Renal gluconeogenesis from lactate significantly exceeded that from glycerol, glutamine, and alanine.
Conclusions:
- Lactate is the primary precursor for both renal and systemic gluconeogenesis in postabsorptive humans.
- The kidney is a key organ for lactate disposal.
- Renal glucose release is mainly from gluconeogenesis, with liver and kidney being equally important for systemic gluconeogenesis.