Biomaterial Database

Unsaturated fatty acid regulation of peroxisome proliferator-activated receptor alpha activity in rat primary hepatocytes. 2003

Anjali Pawar, and Donald B Jump

Department of Physiology, Michigan State University, East Lansing, Michigan 48824, USA.

Peroxisome proliferator-activated receptors (PPARs alpha, beta, gamma1, and gamma2) are widely regarded as monitors of intracellular nonesterified fatty acid (NEFA) levels. As such, fatty acid binding to PPAR leads to changes in the transcription of many genes involved in lipid metabolism and storage. Although the composition of the intracellular NEFA pool is likely an important factor controlling PPAR activity, little information is available on factors affecting its composition. Accordingly, we have examined the effects of exogenous fatty acids on PPARalpha activity and NEFA pool composition in rat primary hepatocytes. Prior to the addition of fatty acids to primary hepatocytes, nonesterified unsaturated fatty acid levels are very low, representing </=0.5% of the total fatty acid in the cell. The relative abundance of putative PPARalpha ligands in the NEFA pool is 20:4n-6 = 18:2n-6 = 18:1n-9 > 22:6n-3 > 18:3n-3/6 = 20:5n-3. Of these fatty acids, only 20:5n-3 and 22:6n-3 consistently induced PPARalpha activity. Metabolic labeling of primary hepatocytes indicated that both 14C-18:1n-9 and 14C-20:5n-3 are rapidly assimilated into neutral and polar lipids. Although the addition of 18:1n-9 had no effect on NEFA pool composition, 20:5n-3 mass increased >15-fold within 90 min. Changes in NEFA pool 20:5n-3 mass correlated with dynamic changes in the PPARalpha-regulated transcript mRNACYP4A. Metabolic labeling also indicated that a significant fraction of 14C-20:5n-3 was elongated to 22:5n-3. Cells treated with 22:5n-3 or 22:6n-3 led to a significant accumulation of 20:5n-3 in the NEFA pool through a process that requires peroxisomal beta-oxidation and fatty acyl CoA thioesterase activity. Further analyses suggest that 20:5n-3 and 22:6n-3, but not 22:5n-3, are active ligands for PPARalpha. These studies suggest that basal fatty acid levels in the NEFA pool coupled with rates of fatty acid esterification, elongation, desaturation, peroxisomal beta-oxidation, and fatty acyl thioestease activity are important determinants controlling NEFA pool composition and PPARalpha activity.

UI	MeSH Term	Description	Entries
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D008055	Lipids	A generic term for fats and lipoids, the alcohol-ether-soluble constituents of protoplasm, which are insoluble in water. They comprise the fats, fatty oils, essential oils, waxes, phospholipids, glycolipids, sulfolipids, aminolipids, chromolipids (lipochromes), and fatty acids. (Grant & Hackh's Chemical Dictionary, 5th ed)	Lipid
D008156	Luciferases	Enzymes that oxidize certain LUMINESCENT AGENTS to emit light (PHYSICAL LUMINESCENCE). The luciferases from different organisms have evolved differently so have different structures and substrates.	Luciferase
D008297	Male		Males
D010100	Oxygen	An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.	Dioxygen,Oxygen-16,Oxygen 16
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D002851	Chromatography, High Pressure Liquid	Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.	Chromatography, High Performance Liquid,Chromatography, High Speed Liquid,Chromatography, Liquid, High Pressure,HPLC,High Performance Liquid Chromatography,High-Performance Liquid Chromatography,UPLC,Ultra Performance Liquid Chromatography,Chromatography, High-Performance Liquid,High-Performance Liquid Chromatographies,Liquid Chromatography, High-Performance
D005227	Fatty Acids	Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed)	Aliphatic Acid,Esterified Fatty Acid,Fatty Acid,Fatty Acids, Esterified,Fatty Acids, Saturated,Saturated Fatty Acid,Aliphatic Acids,Acid, Aliphatic,Acid, Esterified Fatty,Acid, Saturated Fatty,Esterified Fatty Acids,Fatty Acid, Esterified,Fatty Acid, Saturated,Saturated Fatty Acids
D005231	Fatty Acids, Unsaturated	FATTY ACIDS in which the carbon chain contains one or more double or triple carbon-carbon bonds.	Fatty Acids, Polyunsaturated,Polyunsaturated Fatty Acid,Unsaturated Fatty Acid,Polyunsaturated Fatty Acids,Acid, Polyunsaturated Fatty,Acid, Unsaturated Fatty,Acids, Polyunsaturated Fatty,Acids, Unsaturated Fatty,Fatty Acid, Polyunsaturated,Fatty Acid, Unsaturated,Unsaturated Fatty Acids
D005786	Gene Expression Regulation	Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.	Gene Action Regulation,Regulation of Gene Expression,Expression Regulation, Gene,Regulation, Gene Action,Regulation, Gene Expression