Free fatty acid , storage

Insulin resistance occurs when the normal response to a given amount of insulin is reduced. Resistance of liver to the effects of insulin results in inadequate suppression of hepatic glucose production insulin resistance of skeletal muscle reduces the amount of glucose taken out of the circulation into skeletal muscle for storage and insulin resistance of adipose tissue results in impaired suppression of lipolysis and increased levels of free fatty acids. Therefore, insulin resistance is associated with a cluster of metabolic abnormalities including elevated blood glucose levels, abnormal blood lipid profile (dyslipidemia), hypertension, and increased expression of inflammatory markers (inflammation). Insulin resistance and this cluster of metabolic abnormalities is strongly associated with obesity, predominantly abdominal (visceral) obesity, and physical inactivity and increased risk for type 2 diabetes, cardiovascular and renal disease, as well as some forms of cancer. In addition to obesity, other situations in which insulin resistance occurs includes... 

Triacylglycerol is the main storage Hpid in adipose tissue. Upon mobihzation, free fatty acids and glycerol are released. Free fatty acids are an important fuel source. 

Adipose tissue Storage and breakdown of triacylglyc-erol Esterification of fatty acids and lipolysis lipogenesis Glucose, lipoprotein triacylglycerol Free fatty acids, glycerol Lipoprotein lipase, hormone-sensitive lipase... 

Intravenous lipid emulsion particles are hydrolyzed in the bloodstream by the enzyme lipoprotein lipase to release free fatty acids and glycerol. Free fatty acids then are be taken up into adipose tissue for storage (triglycerides), oxidized to energy in various tissues (e.g., skeletal muscle), or recycled in the liver to make lipoproteins. 

The restricted shelf life of liquid milk continues to be a problem that is often more influenced by the type of milk being sold rather than the pasteurisation technique. The shelf life of processed milk is determined primarily by the quality of the raw milk from the dairy herd. Increasing cell counts in the milk and a higher concentration of free fatty acids, contribute to rancidity in both liquid milk and milk products. Janzen (1972) reported that the 0-14 day shelf life of pasteurised milk is influenced by the somatic cell concentration in the raw milk and found that after 14 days any observed changes in the flavour and stability of the milk were attributable to microbial activity during storage. 

Figure 5.15 GALDI mass spectra of (a) linseed oil (35 years airtight storage from THF solution) and (b) linseed oil as in (a) after 2 weeks of natural ageing (from THF solution). Signal groups of free fatty acids, their oxidation products, and monoglycerides (m/z <500) can be distinguished from diglycerides (m/z 500 800), and triglycerides (m/z 800 1000) (see Table 5.7)...

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. 

Long ago it was noticed that the baking quality of white flour improved with storage for 1-2 months. This effect occurred more rapidly if the flour was exposed to the air. During storage, initially the level of free fatty acids increases, presumably owing to lipolytic activity. Lipoxygenase activity then produces oxidised fatty acids as the proportion of linoleic and linolenic acids falls while the number of -S-S- bonds decreases. 

Fig. 4.5. Peroxide and free fatty acids data as a function the residual moisture content after storage of the dried product for 10 days at +37 °C.

In adipose tissue, insulin stimulation suppresses triglyceride hydrolysis (to free fatty acids and glycerol) by activating cAMP phosphodiesterase (cAMP PDE). Cyclic AMP, (3, 5 cAMP), is required to stimulate hormone sensitive lipase (HSL), the enzyme which hydrolyses triglyceride within adipocytes PDE converts active 3, 5 cAMP to inactive 5 AMP thus preventing the stimulation of HSL. The net effect of insulin on lipid metabolism is to promote storage. 

Fatty acid utilized by muscle may arise from storage triglycerides from either adipose tissue depot or from lipid stores within the muscle itself. Lipolysis of adipose triglyceride in response to hormonal stimulation liberates free fatty acids (see Section 9.6.2) which are transported through the bloodstream to the muscle bound to albumin. Because the enzymes of fatty acid oxidation are located within subcellular organelles (peroxisomes and mitochondria), there is also need for transport of the fatty acid within the muscle cell this is achieved by fatty acid binding proteins (FABPs). Finally, the fatty acid molecules must be translocated across the mitochondrial membranes into the matrix where their catabolism occurs. To achieve this transfer, the fatty acids must first be activated by formation of a coenzyme A derivative, fatty acyl CoA, in a reaction catalysed by acyl CoA synthetase. 

Triacylglycerol. Triglyceride a compound consisting of three molecules of fatty acids esterified to glycerol. It is a neutral fat synthesized from carbohydrates for storage in animal adipose cells. On enzymatic hydrolysis, it releases free fatty acids in the blood. Tuberculosis. Any of the infectious diseases of man and animals caused by species Mycobacterium and characterized by the formation of tubercles and caseous necrosis in the tissues. 

No adverse effects of either UHT processing or storage on the nutritional properties of milk fat have been demonstrated. Although increases in the milk s free fatty acid content have been noted when UHT milk is stored at room temperature rather than refrigerated, these changes do not appear to affect the nutritional value of the milk. No changes of nutritional importance have been noted in the carbohydrate components of UHT milk (Ford and Thompson 1981). 

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