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Human epidermal energy metabolism is functionally anaerobic
Gunnar Ronquist1, Anders Andersson, Niels Bendsoe
1Department of Medical Sciences, Clinical Chemistry, University Hospital, Uppsala, Sweden. gunnar.ronquist@clm.uas.lul.se
Experimental Dermatology
|January 7, 2004
Summary
Human epidermal keratinocytes exhibit predominantly anaerobic energy metabolism, producing significant lactate regardless of oxygen levels. This highlights a unique metabolic strategy in skin cells, distinct from typical oxidative processes.
Area of Science:
- Biochemistry
- Dermatology
- Cell Biology
Background:
- Epidermal Langerhans cells signal an anaerobic environment via an H(+)-extruding mechanism.
- Keratinocytes characteristically contain high lactate levels, indicative of their metabolic state.
Purpose of the Study:
- To investigate the energy metabolism of human epidermis.
- To elucidate the predominant metabolic pathways in keratinocytes.
Main Methods:
- In vitro analysis of lactate production in keratinocytes under various conditions.
- Measurement of energy charge values.
- Electron microscopy of keratinocyte mitochondria and extracellular space using different fixatives.
Main Results:
- Keratinocytes exhibit vigorous lactate production, independent of oxygen, with significant release into the medium.
- Starved epidermal samples showed increased lactate, confirming ongoing glycogenolysis.
- Iodoacetate strongly inhibited lactate production (>90%), and low energy charge values (approx. 0.82) were observed.
- Keratinocyte mitochondria displayed reduced inner membranes, suggesting impaired oxidative metabolism.
- Isotonic glutaraldehyde fixation revealed an extracellular space adequate for lactate transport, unlike hypotonic fixatives.
Conclusions:
- Human epidermal energy metabolism is predominantly anaerobic, despite the presence of mitochondria.
- High lactate production necessitates efficient extracellular transport, supported by an appropriate extracellular space.
- The findings challenge conventional views on epidermal energy metabolism and extracellular space morphology.