Glucose-lactate interrelationships: effect of ethanol

Area of Science:

• Metabolic biochemistry
• Human physiology
• Pharmacology

Background:

• Ethanol consumption affects glucose and lactate metabolism.
• The Cori cycle interconverts glucose and lactate.
• Understanding ethanol's impact on these pathways is crucial for metabolic health.

Purpose of the Study:

• To investigate the effect of ethanol on the interrelationship between lactate and glucose metabolism in humans.
• To quantify the influence of ethanol on lactate and glucose kinetics and interconversion rates.

Main Methods:

• Utilized stable isotope tracers (L-(+) lactate-U-(14)C and glucose-1-(14)C) in eight human volunteers.
• Measured lactate and glucose turnover, recycling, and conversion rates over an 8-hour period.
• Administered ethanol and assessed its impact on metabolic parameters and blood concentrations.

Main Results:

• Ethanol doubled blood lactate levels and slightly decreased lactate turnover.
• Lactate conversion to glucose was markedly inhibited by ethanol (from 16 to 5 mg/kg/hr).
• Ethanol inhibited peripheral glucose utilization, decreasing glucose conversion to lactate and glucose recycling, without altering blood glucose levels.

Conclusions:

• Ethanol inhibits gluconeogenesis from lactate in humans, irrespective of fasting state, but starvation is required for ethanol-induced hypoglycemia.
• Ethanol's inhibition of the Cori cycle affects both glucose and lactate metabolism.
• Glycogenolysis may mask ethanol's inhibitory effects on gluconeogenesis in non-fasted individuals, preventing hypoglycemia.