Triglyceride mobilization

Feussner, I. and Kindi, H. (1992) A lipoxygenase is the main lipid body protein in cucumber and soybean cotyledons during the stage of triglyceride mobilization, FEES Lett. 298, 223-225. 

Transesterification of fat triglycerides is the predominant method for manufacture of mixed fatty acid methyl esters, and direct esterification of fatty acids (FA) is practiced if very selective cuts of product, in general as an intermediate detergent range alcohol, are desired. Methyl cocoate is a mobile, oily liquid above 25 °C with a yellow tint and a characteristic fatty pungent odor. FAME sulfonation to FAMES is technically possible but been rarely applied up to now (1990) (Table 13). 

The concentration of biodiesel (fetty acid methyl esters) and glycerides were analyzed by liquid chromatography (Shimadzu-lOA HPLC). An ODS-2 column (250x4.6mm) was used for the separation. The flow rate of the mobile phase (acetone acetonitrile=l l) was set to 1 ml/min. Peaks were identified by comparison with reference standards. Standards of methyl esters, monoglycerides, digjycerides and triglycerides were bought from Fluka. 

Nova-Pak C18 column in a methanol water chloroform gradient.92 Choline chloride was added to the mobile phase. One review of techniques used in the analysis of triacylglycerols lists over 300 references on separations of the triglyceride fraction of fats using nonaqueous RPLC, aqueous RPLC, argen-tation chromatography, and other chromatographic methods.93... 

Starvation elicits mobilization of triglycerides from the adipose tissue and inhibits the endogenic cholesterol synthesis owing to the low activity of hydroxy-methylglutaryl-CoA reductase. The latter process provides the possibility for the active production of ketone bodies in the liver. 

The neurohormonal control of lipid metabolism chiefly affects the mobilization and synthesis of triglycerides in the fat tissue. The lipolysis in tissues is dependent upon the activity of triglyceride lipase. All the regulators that favour the conversion of the inactive (nonphosphorylated) lipase to the active (phosphoiylated) one, stimulate the lipolysis and the release of fatty acids into the blood. Adrenalin... 

Adipose Adipose tissue is the primary storage facility for fat. Fat is stored in these tissues as an intracellular droplet of insoluble triglyceride. A hormone-sensitive lipase mobilizes triglyceride stores by hydrolysis to free fatty acids. 

Fatty acids are clearly larger in size and show markedly slower diffusion velocity than the small water (or creatine) molecules which have been examined so far by diffusion weighted NMR spectroscopy. However, assessment of diffusion properties of lipids could be a key step for further experimental studies of skeletal muscle lipid metabolism. Diffusion properties of FFA and triglycerides are likely different due to differences in molecular weight. In addition, effects of temperature, chemical surroundings, and the mobility of small lipid droplets in the cytosol may also lead to measurable differences in the diffusion characteristics. 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of intestinal fat absorption, hepatic triglyceride synthesis, lipid mobilization, triglyceride-fatty acid recycling, and cholesterol turnover. 

Analysis of the triglycerides present in soybean oil has been reported on reverse phase colunrn using methanol-chloroform (9 1) as the mobile... 

Untreated silica column can be advantageously used for HPLC preseparation of PAHs from triglycerides. The capacity of a silica column to retain fat (for columns of the same particle size) depends on the column size, the mobile phase composition, as well as the type and by-products (free acids and polymerized material) of the fat injected [706,713]. Off-line HPLC-HPLC, employing silica column (250 X 4.6 mm i.d., 5 pm of particle size) for sample preparation before RP-HPLC and spec-trofluorometric detection, was successfully applied for PAH determination in edible oils [659,691] and fish [714]. After PAH elution, the silica column needs to be backflushed with dichloromethane to remove the fat. The entire sample preparation step can be automated by using a backflush valve and a programmable switching valve box [691]. 

Acting as an intracellular second messenger, cAMP mediates such hormonal responses as the mobilization of stored energy (the breakdown of carbohydrates in liver or triglycerides in fat cells stimulated by B-adrenomimetic catecholamines), conservation of water by the kidney (mediated by vasopressin), Ca2+ homeostasis (regulated by parathyroid hormone), and increased rate and contractile force of heart muscle ( -adrenomimetic catecholamines). It also regulates the production of adrenal and sex steroids (in response to corticotropin or follicle-stimulating hormone), relaxation of smooth muscle, and many other endocrine and neural processes. 

Increased synthesis of lipid or uptake. Increased synthesis of lipid may be the cause of fatty liver after hydrazine administration as this compound increases the activity of the enzyme involved in the synthesis of diglycerides. Hydrazine also depletes ATP and, however, inhibits protein synthesis. Large doses of ethanol will cause fatty liver in humans, and it is believed that this is partly due to an increase in fatty acid synthesis. This is a result of an increase in the NADH/NAD"1" ratio and therefore of the synthesis of triglycerides. Changes in the mobilization of lipids in tissues followed by uptake into the liver can also be another cause of steatosis. 

Phospholipids are considered to be involved in the transport of triglycerides through die liver, especially during mobilization from adipose tissue, Conditions which could be interpreted as interfering with phosphatidylcholine formation, such as deficiency of choline or its precursors, result in a pronounced increase 111 liver triglycerides. 

Figure D1.6.2 TLC-FID separation of lipids recovered from the gastric contents of a hooded seal pup. The mobile phase was 91 6 3 1 (v/v/v/v) hexane/ethyl acetate/diethyl ether/formic acid. Time refers to scanning time of the Chromarod. Abbreviations DG, 1,2-diglyceride FFA, free fatty acid MG, monoglyceride IS, internal standard TG, triglyceride. Reproduced from Ackman and Heras (1997) with permission from AOCS Press.

Tristearin and triglycerides of higher molecular weight have a very low solubility in the mobile phase used, and either precipitate at injection (in the valve loop or in the connecting tube between the injection valve and the column) when the sample solution is diluted in a rather poor solvent or are so strongly retained that they are eluted only after a prohibitively long time, giving broad peaks barely discernible from baseline oscillations. 

The advances in column and instrument technology have significantly enhanced HPLC performance in recent years. Results comparing the effects of various column packings on TG separation by RP-HPLC were presented by El-Hamdy and Perkins (87). Six commercially packed columns produced by different manufacturers were used PARTISIL ODS-1 and ODS-2 octadecyl-bonded silica of 10-/rm partical size, ZORBAK-ODS octadecyl-silica of 6-7-/rm diameter (250 X 4.6-mm ID), 5-/rm octyl-bonded spherical silica LC-8, 5-//m methyl-bonded spherical silica LC-1, and a 5-/rm octadecyl-bonded spherical silica LC-18 (150 X 4.6-mm ID). The mobile phase employed consisted of mixtures of methanol/acetone/isopropanol/acetonitrile ranging from l 0 3 4to 1 6 3 4. Triglycerides were solubilized in either THF or acetone at 100 mg/ml for each compound. 

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