The human hair follicle engages in glutaminolysis and aerobic glycolysis: implications for skin, splanchnic and neoplastic metabolism.

On maintenance in supplemented Williams E medium, human hair follicles grow at the normal rate, and retain their normal anagen morphology, for up to 10 days. This permits us to study their metabolism under near-physiological conditions. The ATP content of freshly isolated follicles was 124.4 +/- 10.6 pmol/follicle (mean +/- SEM; n = 50). The energy charge was 0.81 +/- 0.08 and the glycogen content 2.3 +/- 0.3 nmol/follicle. These did not alter significantly during any metabolic studies, which were performed for up to 6 h in supplemented Williams E medium. We found that the major fuel was glucose, which at physiological concentrations yields 5.47 +/- 0.77 nmol ATP/follicle/h, but 90% of the glucose was metabolised to lactate, and only 10% oxidised. Glutamine was also an important fuel, generating 2.16 +/- 0.33 nmol ATP/follicle/h, but this too was largely metabolised to lactate rather than oxidised. Lipid fuels such as palmitate or beta-hydroxybutyrate only yielded 0.72 +/- 0.15 and 0.72 +/- 0.14 nmol ATP/follicle/h, respectively, and their oxidation did not inhibit glucose utilisation. No glucose-fatty acid cycle operates in the hair follicle, therefore, but a glucose-glutamine cycle does, since the presence of glutamine will inhibit glucose utilisation.