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Glycerol and lactate uptake in human forearm
K N Frayn1, S W Coppack, S M Humphreys
1Sheikh Rashid Diabetes Unit, Radcliffe Infirmary, Oxford, UK.
Metabolism: Clinical and Experimental
|December 1, 1991
Summary
Forearm measurements of glycerol and lactate show inconsistent results, with glycerol uptake observed in 40% of studies. This unexpected glycerol uptake in the forearm lacks a clear physiological explanation and impacts lipolysis research.
Area of Science:
- Human physiology
- Metabolic studies
Background:
- Arteriovenous differences for lactate and glycerol in the human forearm exhibit inconsistencies in direction and magnitude.
- These inconsistencies may stem from variations in forearm composition across studies.
Purpose of the Study:
- To investigate the reasons behind inconsistent forearm arteriovenous differences for lactate and glycerol.
- To test the hypothesis that forearm composition influences these metabolic exchanges.
Main Methods:
- Analysis of 37 studies involving forearm arteriovenous differences for lactate, glycerol, glucose, and oxygen in 23 normal subjects post-fast.
- Examination of correlations between arteriovenous differences and fluxes, body mass index, and within-subject variability.
Main Results:
- Glycerol uptake by the forearm was observed in 16 studies, exceeding analytical variation in 12.
- Glycerol and lactate arteriovenous differences were positively correlated, but neither correlated with oxygen differences.
- Glycerol arteriovenous difference correlated positively with body mass index, and within-subject variation was significant.
Conclusions:
- Approximately 40% of studies show forearm glycerol uptake in normal subjects after fasting, without a clear physiological basis.
- This peripheral glycerol uptake challenges its use as a sole indicator of lipolysis.
- Forearm composition does not consistently explain the observed glycerol and lactate exchange patterns.