Your body must break down the fatty molecules known as lipids for many biologic processes including absorption, transport across cell membranes and the generation of energy. Lipid breakdown takes place throughout your body and is accomplished by the action of various enzymes.
Lipids are a class of molecules that include triglycerides, sterols, phospholipids and other complex compounds, the authors of "Hole's Human Anatomy and Physiology" explain. Some 95 percent of dietary lipids and lipids in your body are triglycerides. A triglyceride is composed of a glycerol molecule to which three different fatty acids are attached.
Fatty Liver and Gallstones
Lipases are a category of enzymes produced in different organs that break down triglycerides. According to the book "Advanced Nutrition and Human Metabolism," lipases break down triglycerides by chemically removing the fatty acids from the glycerol portion of the molecule 1. The products of complete triglyceride breakdown include three fatty acids and a glycerol molecule.
Your body must break down triglycerides from your diet so they can be absorbed into the intestinal cells, "Advanced Nutrition and Human Metabolism" explains 1.** Triglyceride digestion is accomplished primarily by pancreatic lipase. This enzyme is produced in the pancreas, then exported to the small intestine, where it interacts with dietary triglycerides.
Function of Proteases
Triglycerides are often packaged into large molecules, called lipoproteins, for transport throughout the body, "Advanced Nutrition and Human Metabolism" notes 1. Chylomicrons and very-low-density lipoproteins are examples of lipoproteins that transport triglycerides. The triglycerides in lipoproteins are broken down by lipoprotein lipase, an enzyme associated with the blood vessels in adipose (fatty) and muscle tissue.** The action of lipoprotein lipase removes free fatty acids from lipoproteins and allows them to enter cells to be used for energy or other processes.
Your body primarily stores triglycerides in adipose tissue, though it does also store some within muscle cells. According to "Hole's Human Anatomy and Physiology," hormones such as epinephrine mediate the breakdown of stored triglyceride. Epinephrine activates hormone-sensitive lipase, an enzyme that removes the fatty acids from the triglyceride molecule in a manner similar to pancreatic and lipoprotein lipases. Your body will use the free fatty acids generated by hormone-sensitive lipase as an energy source.
- Your body primarily stores triglycerides in adipose tissue, though it does also store some within muscle cells.
- According to "Hole's Human Anatomy and Physiology," hormones such as epinephrine mediate the breakdown of stored triglyceride.
Fatty Liver and Gallstones
Function of Proteases
Importance of Phospholipids in the Human Body
Organic Compounds That Must Be in the Diet
How Do LDL and HDL Differ Structurally and Functionally?
Digestive Breakdown of Proteins
What Is AST/SGOT in a CMP Test?
Enzymes That Break Down Lipids
How Is Sugar Processed in the Body?
The Signs & Symptoms of Mild Diffuse Fatty Infiltration in the Liver
- “Advanced Nutrition and Human Metabolism (5th Edition)”; S.S. Gropper, J.L. Smith, J.L. Groff; 2009
- "Hole's Human Anatomy and Physiology (11th Edition)"; David N. Shier, Jackie L. Butler, Ricki Lewis; 2007
- Titov VN, Aripovskii AV, Schekotov VV, Schekotova AP, Kukharchuk VV. [The oleic triglycerides of palm oil and palmitic triglycerides of creamy fat. The reaction of palmitoylation, potassium and magnesium palmitate, absorption of fatty acids by enterocytes and microbiota of large intestine]. Klin Lab Diagn. 2016;61(8):452-61.
- Alves-bezerra M, Cohen DE. Triglyceride Metabolism in the Liver. Compr Physiol. 2017;8(1):1-8. doi:10.1002/cphy.c170012
- Barson JR, Karatayev O, Gaysinskaya V, Chang GQ, Leibowitz SF. Effect of dietary fatty acid composition on food intake, triglycerides, and hypothalamic peptides. Regul Pept. 2012;173(1-3):13-20. doi:10.1016/j.regpep.2011.08.012
- Rahmany S, Jialal I. Biochemistry, Chylomicron. [Updated 2019 Aug 9]. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.
- Bansal S, Buring JE, Rifai N, et al. Fasting compared with nonfasting triglycerides and risk of cardiovascular events in women. JAMA 2007; 298:309. DOI:10.1001/jama.298.3.309
- Handelsman Y, Shapiro MD. TRIGLYCERIDES, ATHEROSCLEROSIS, AND CARDIOVASCULAR OUTCOME STUDIES: FOCUS ON OMEGA-3 FATTY ACIDS. Endocr Pract. 2017;23(1):100-112. doi:10.4158/EP161445.RA
- Tirosh A, Shai I, Bitzur R, et al. Changes in triglyceride levels over time and risk of type 2 diabetes in young men. Diabetes Care. 2008;31(10):2032-7. doi:10.2337/dc08-0825
- Ballantyne CM, Grundy SM, Oberman A, et al. Hyperlipidemia: diagnostic and therapeutic perspectives. J Clin Endocrinol Metab 2000; 85:2089. DOI:10.1210/jcem.85.6.6642-1
- Marston NA, Giugliano RP, Im K, et al. Association Between Triglyceride Lowering and Reduction of Cardiovascular Risk Across Multiple Lipid-Lowering Therapeutic Classes: A Systematic Review and Meta-Regression Analysis of Randomized Controlled Trials. Circulation 2019; 140:1308. DOI:10.1161/CIRCULATIONAHA.119.041998
- Skulas-Ray AC, Wilson PWF, Harris WS, et al. Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association. Circulation 2019; 140:e673. DOI:10.1161/CIR.0000000000000709
Michael Crosier has been writing since 2005. His work has appeared in publications such as "Journal of the American Dietetic Association" and "Journal of Bone and Mineral Research." Crosier is an assistant professor in the Food and Nutrition Department at Framingham State College in Massachusetts. He is a registered dietitian and received his Ph.D. in nutritional biochemistry from Tufts University.