NDUFS1 and hyperinsulinemic hypoglycemia, familial, 4: Mutations in Ndufs1/Ndufs2 result in mitochondrial complex I deficiency in various disorders of mitochondrial oxidative phosphorylation (OXPHOS) [38,39,40], supporting the proposition that Ndufs2 upregulation in BAT of KO-CTX mice increases the OXPHOS protein levels.