Oxidation free fatty acids

In a placebo-controlled study in six patients with type 2 diabetes mellitus thalidomide 150 mg/day for 3 weeks reduced insulin-stimulated glucose uptake by 31% and glycogen synthesis by 48% (1115). However, it had no effect on rates of glycolysis, carbohydrate oxidation, non-oxidative glycolysis, lipolysis, free fatty acid oxidation, or re-esterification. The authors concluded that thalidomide increases insulin resistance in obese patients with type 2 diabetes. 

Vitamins Free Fatty Acids Oxidation Products Residual Pigments Sterols... 

Moisture Insoluble Matter Unsaponificable Matter Total MIU Total Fatty Acids Free Fatty Acids Oxidized Fatty Acids Saponification Number Acetone Insolubles Metabolizable Energy Value... 

Refining of vegetable oils is a process during which phospholipids, free fatty acids, oxidized lipids, most prooxidants and impurities in crude oils are reduced as much as possible in order to produce oils with good oxidation stability and sensory quality... 

Palm oil physico-chemical properties allow it to be the most widely fractioned oil (Table 2). Fractioning involves physical or chemical refine applying high temperatures, desodorisation and deacidification of oil under vacuum, in both cases. Physical deacidification accurs at 250-270 C under vacuum up to 3-5 Torr, whereas chemical uses 220-240 °C. The high temperatures and vacuum are necessary to remove undesirable compounds as traces of metals, free fatty acids, oxidation and decomposition products. Nevertheless, those procedures also remove some tocopherols and tocotrienols, and all carotenoids presented in the oil [30, 31, 32, 33,34]. 

The base lubricant is usually a petroleum oil while the thickener usually consists of a soap or soap mixture. In addition they may contain small amounts of free alkali, free fatty acid, glycerine, anti-oxidant, extreme-pressure agent, graphite or molybdenum disulphide. 

A forth molecule, the receptor G2A (GPR132), is also related to this group. However, recent data suggest that G2A is a receptor for oxidized free fatty acids. Activation by acidic pH could not be confirmed. 

The rate of mitochondrial oxidations and ATP synthesis is continually adjusted to the needs of the cell (see reviews by Brand and Murphy 1987 Brown, 1992). Physical activity and the nutritional and endocrine states determine which substrates are oxidized by skeletal muscle. Insulin increases the utilization of glucose by promoting its uptake by muscle and by decreasing the availability of free long-chain fatty acids, and of acetoacetate and 3-hydroxybutyrate formed by fatty acid oxidation in the liver, secondary to decreased lipolysis in adipose tissue. Product inhibition of pyruvate dehydrogenase by NADH and acetyl-CoA formed by fatty acid oxidation decreases glucose oxidation in muscle. 

After uptake by the liver, free fatty acids are either P Oxidized to COj or ketone bodies or esterified to triacylglycerol and phospholipid. There is regulation of entry of fatty acids into the oxidative pathway by carnitine palmitojdtransferase-I (CPT-I), and the remainder of the fatty acid uptake is esterified. CPT-I activity is... 

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.

Ketogenesis is regulated at three cmcial steps (1) control of free fatty acid mobihzation from adipose tissue (2) the activity of carnitine palmitoyltransferase-1 in hver, which determines the proportion of the fatty acid flux that is oxidized rather than esteri-fied and (3) partition of acetyl-CoA between the pathway of ketogenesis and the citric acid cycle. 

Triacylglycerols must be hydrolyzed by a lipase to their constiment fatty acids and glycerol before further catab-ohsm can proceed. Much of this hydrolysis (hpolysis) occurs in adipose tissue with release of free fatty acids into the plasma, where they are found combined with semm albumin. This is followed by free fatty acid uptake into tissues (including hver, heart, kidney, muscle, lung, testis, and adipose tissue, but not readily by brain), where they are oxidized or reesterified. The uti-hzation of glycerol depends upon whether such tissues... 

The regulation of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine biosynthesis is driven by the availability of free fatty acids. Those that escape oxidation are preferentiaUy converted to phos-phohpids, and when this requirement is satisfied they are used for triacylglycerol synthesis. 

Free fatty acids are removed from the blood extremely rapidly and oxidized (fulfilling 25-50% of energy requirements in starvation) or esterified to form triacylglycerol in the tissues. In starvation, esterified lipids from the circulation or in the tissues are oxidized as well, particularly in heart and skeletal muscle cells, where considerable stores of lipid are to be found. 

Figure 27-1. Metabolic interrelationships between adipose tissue, the liver, and extrahepatic tissues. In extrahepatic tissues such as heart, metabolic fuels are oxidized in the following order of preference (1) ketone bodies, (2) fatty acids, (3) glucose. (LPL, lipoprotein lipase FFA, free fatty acids VLDL, very low density lipoproteins.)...

Heart Pumping of blood Aerobic pathways, eg, P-oxidation and citric acid cycle Free fatty acids, lactate, ketone bodies, VLDL and chylomicron triacylglycerol, some glucose Lipoprotein lipase. Respiratory chain well developed. 

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