Open AccessDynamic label-free imaging of lipid droplets and their link to fatty acid and pyruvate oxidation in mouse eggs
Author(s) -
Josephine Bradley,
Iestyn Pope,
Yisu Wang,
Wolfgang Werner Langbein,
Paola Borri,
Karl Swann
Publication year - 2019
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.228999
Subject(s) - beta oxidation , lipid droplet , biology , biochemistry , mitochondrion , fatty acid , oleic acid , pyruvate decarboxylation , lipid oxidation , metabolism , lipid metabolism , bioenergetics , pyruvate dehydrogenase complex , biophysics , enzyme , citric acid cycle , antioxidant
Mammalian eggs generate most of their ATP by mitochondrial oxidation of pyruvate from the surrounding medium, or from fatty acids which are stored as triacylglycerols within lipid droplets. The balance between pyruvate and fatty acid oxidation in generating ATP is not established. We have combined coherent anti-Stokes Raman scattering (CARS) imaging with deuterium labelling of palmitic acid to monitor turnover of fatty acids within lipid droplets of living eggs. We found that loss of labelled palmitic acid is promoted by pyruvate removal, but minimised with inhibited β-oxidation. Pyruvate removal also causes a significant dispersion of lipid droplets, while inhibiting β-oxidation causes droplet clustering. Live imaging of luciferase, or FAD autofluorecence from mitochondria, suggest that inhibiting β-oxidation in mouse eggs only leads to a transient decrease in ATP because there are compensatory uptake of pyruvate into mitochondria. Inhibiting pyruvate uptake and then β-oxidation caused similar and successive declines in ATP. Our data suggest that β-oxidation and pyruvate oxidation contribute nearly equally to resting ATP production in mouse eggs and that reorganisation of lipid droplets occurs in response to metabolic demand.