OCR and ECAR values were determined using the XF24 Extracellular Flux Analyzer (Seahorse Bioscience) following the manufacturers’ protocols. For β-oxidation, WT MEFs and shRNA-mitoN MEFs (60,000 per well; 1 µg ml
−1 Dox) were seeded overnight in a XF24 cell-culture microplate at 37 °C under 5% CO
2 (Seahorse Bioscience). Following 1 hr equilibration with 1X KHB buffer (111 mM NaCl, 4.7 mM KCl, 2 mM MgSO
4, 1.2 mM Na
2HPO
4) supplemented with 0.5 mM carnitine and 2.5 mM glucose, cells were subjected to treatment of a palmitate-BSA-conjugate (200 µM; C:16:0), followed by etomoxir (100 µM). OCR measurements were recorded at set interval time-points. For electron-flow (EF) measurements, isolated mitochondria were pelleted in a XF24 cell-culture microplate by centrifugation (2,000 g for 20 min at 4 °C) in 1X MAS buffer (70 mM sucrose, 220 mM mannitol, 10 mM KH
2PO
4, 5 mM MgCl
2, 2 mM HEPES, 1 mM EDTA in 0.2% FA-free BSA) supplemented with 10 mM pyruvate, 10 mM malate and 4 µM FCCP. OCR and ECAR measurements were obtained following sequential additions of rotenone (2 µM final concentration), succinate (10 mM), antimycin A (4 µM) and ascorbate (10 mM) (the latter containing 1 mM TMPD). For ECAR glycolytic flux experiments using whole-tissue slices, oligomycin (2 µM), FCCP (4 µM), 2-DG (100 mM) and antimycin A (10 µM) were added to tissues in an XF24 islet-capture Microplate (Seahorse Bioscience). All compounds and materials above were obtained from Sigma-Aldrich. For mitochondrial oxidative-stress, the protein-carbonylation assay was performed as previously described
37 (link). For lipid-peroxidation, bound 8-isoPGF2α levels were determined as previously detailed
19 (link). The mitochondrial membrane potential (ΔΨm) experiments are detailed in the Supplementary Methods.
Kusminski C.M., Holland W.L., Sun K., Park J., Spurgin S.B., Lin Y., Askew G.R., Simcox J.A., McClain D.A., Li C, & Scherer P.E. (2012). MitoNEET, a key regulator of mitochondrial function and lipid homeostasis. Nature medicine, 18(10), 1539-1549.