Figure 1.

Apoptosis affects cell signaling pathways that control lipid synthesis and energy metabolism. The enzymes involved in de novo lipid synthesis are depicted as well as the signaling pathways that regulate them. Lipids are synthesized from citrate, which is transported into the cytosol following synthesis in the mitochondria by condensation of acetyl-CoA with oxaloacetate. Glucose is the principal origin of citrate carbon, although other metabolites can also be used as carbon donors. Lipid synthesis also requires NADPH, which originates from the pentose phosphate pathway and from the reaction catalyzed by malic enzyme. Pictures of the mitochondrion and cell membrane were obtained from Servier Medical Art (www.servier.com). ACC1, acetyl-CoA carboxylase; ACLY, ATP-citrate lyase; ACS, acyl-CoA synthetase; AMPK, AMP-activated kinase; ATM, ataxia-telangiectasia mutated; CPT-1, carnitine palmitoyltransferase 1; DAG, diacylglycerides; DAGAT, diacylglycerol acyltransferase; DHAP, dihydroxyacetone phosphate; FASN, fatty acid synthase; FATP, fatty acid transport protein; FFA, free fatty acids; G3P, glyceraldehyde 3-phosphate; G6P, glucose 6-phosphate; Glut, glucose transporter; HK, hexokinase; LDH, lactate dehydrogenase; PDH, pyruvate dehydrogenase; PK, pyruvate kinase; SREBP-1, sterol-receptor element binding protein; TAG, triacylglycerides; TIGAR, Tp53-induced glycolysis and apoptosis regulator; TSC2, tuberous sclerosis complex 2