Riboflavin, which is known to cause photooxidative damage in biological systems, is now shown to stimulate glucose transport and oxidation in isolated rat adipocytes in the presence of visible light. At low riboflavin concentrations, well within normal blood levels, there is a small but reproducible stimulation of C1-labeled glucose oxidation to labeled CO2 (30% stimulation at 10-6 m), which does not require light. However, at higher concentrations (10-5 m and above), light greatly potentiates this effect on C1-glucose oxidation as well as stimulates C6-glucose oxidation (two- to three-fold over controls). These apparent effects on the hexose monophosphate shunt and glycolytic-tricarboxylic acid pathways are blocked by 10 μm cytochalasin B, a glucose transport inhibitor. Riboflavin in light is further shown to stimulate uptake of 3-O-methylglucose, a nonmetabolizable glucose analog. These light-dependent effects are not affected by catalase or superoxide dismutase, but they are inhibited by dimethylfuran, a singlet oxygen scavenger. This latter agent has no effect on glucose metabolism in untreated or insulin-treated cells. The results suggest a physiologically important potential effect of riboflavin and visible light.
ASJC Scopus subject areas
- Molecular Biology