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Arteriovenous differences across human adipose and forearm tissues after overnight fast
S W Coppack1, K N Frayn, S M Humphreys
1Sheikh Rashid Diabetes Unit, Radcliffe Infirmary, Oxford, United Kingdom.
Metabolism: Clinical and Experimental
|April 1, 1990
Summary
After an overnight fast, adipose tissue releases fatty acids and glycerol, acting as a net exporter of carbon. Muscle tissue, however, utilizes circulating fuels, with fatty acids being the primary energy source for both tissues.
Area of Science:
- Metabolic studies
- Human physiology
- Biochemistry
Background:
- Adipose tissue plays a crucial role in energy homeostasis.
- Understanding substrate utilization in adipose and muscle tissue is vital for metabolic research.
Purpose of the Study:
- To quantify substrate exchange across human adipose and muscle tissues post-fasting.
- To elucidate the metabolic fate of circulating fuels and endogenous stores.
Main Methods:
- Arteriovenous measurements in subcutaneous abdominal (adipose) and forearm (muscle) tissues.
- Analysis of nonesterified fatty acids, glycerol, triacylglycerol, glucose, ketone bodies, and acetate fluxes.
- Calculation of carbon atom fluxes to compare fuel utilization.
Main Results:
- Adipose tissue exhibited strong lipolysis, releasing fatty acids and glycerol.
- Adipose tissue cleared circulating fuels but utilized internal stores for over 49% of its oxygen consumption.
- Adipose tissue was a net carbon exporter, primarily as fatty acids, while resting muscle was a net importer, utilizing circulating lipids.
Conclusions:
- Adipose tissue is a significant source of fatty acids post-fasting.
- Muscle tissue relies on circulating lipids as its primary fuel source.
- Fasting induces distinct metabolic roles for adipose and muscle tissues in substrate exchange.