The Contribution of Singlet Oxygen to Insulin Resistance

Figure 3

Proposed mechanisms for the mitochondrial formation of ¹O₂ and 4-hydroperoxy-2-nonenal (17) during the oxidation of a cardiolipin (11) (which bears an n-6 fatty acid). In the presence of H₂O₂, cytochrome c converts the latter to cardiolipin hydroperoxide (12) [85], followed by lysine-catalyzed rearrangement of the latter into dioxetane (13) [44] which decomposes into aldehyde (14) (oxononanoyl-cardiolipin in case the fatty acid moiety being oxidized is linoleic acid) and 3-Z-nonenal (15). The asterisk on carbonyl (14) indicates the excited (triplet) state, since dioxetane decomposition produces such carbonyls. Energy transfer from (14) to triplet oxygen converts the latter to ¹O₂ and the former to its ground state form (16), whose reaction with hydrogen peroxide regenerates (14) and forms singlet oxygen [44, 88, 90].