Very-long-chain fatty acids VLDL

Figure 10-5. Intrahepatic metabolism of free fatty acids (FFA). CPT I, CPT II, carnitine palmitoyltransferase I, II, respectively LCFA, long-chain fatty acid VLDL, very low-density lipoprotein. 1, Long-chain acyl-CoA synthase 2, acetoacetyl-CoA thiolase 3, hydrox-ymethylglutaryl-CoA synthase 4, hydroxymethylglutaryl-CoA lyase 5, 3-hydroxybutyrate dehydrogenase 6, acetyl-CoA carboxylase 7, fatty acid synthase 8, glycerolphosphate acyltransferase Reprinted with permission from Girard et al. (1992).

Figure22-10. Regulation of long-chain fatty acid oxidation in the liver. (FFA, free fatty acids VLDL, very low density lipoprotein.) Positive ( ) and negative ( ) regulatory effects are represented by broken arrows and substrate flow by solid arrows.

In addition to the use of fatty acids liberated from adipocytes, or obtained from the plasma as albumin-bound long-chained fatty adds or in very low-density lipoproteins (VLDLs), research indicates that the intramuscular triglyceride (IMTG) pool can serve as a dynamic fuel source during physical activity. Because no blood transport is required, intramuscular fatty acids can be readily used for energy in exercising muscle. A detailed discussion on IMTG can be found in Section 2.4.1. 

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