Fatty liver triacyl glycerol

Fat synthesis The acetyl-CoA prodnced from amino acid catabolism is also a precursor for fatty acid and triacyl-glycerol synthesis, both in adipose tissne and liver (details of pathways are given in Chapter 11). Unfortnnately, the quantitative significance of this pathway is not known. It is likely to be variable and probably small in hnmans. 

Figure 22 Dynamics of principal lipid constituents in horse-mackerel during cruising and fatigue. (After Yuneva et al., 1991.) The free fatty-acid level increases in red muscle and liver when the fish swim, and decreases during fatigue. Other constituents decrease under both conditions. TG, triacyl-glycerols PL, phospholipids PC, phosphatidyl choline PE, phosphatidyl ethanolamine FFA, free (unesterified) fatty acids. Black columns, red muscle empty columns, white muscle shaded, liver.

This period is also marked by the deposition of energy substrates - mostly triacyl-glycerols in fatty fish and liver glycogen in lean fish. The rate of accumulation is much lower than that of protein production (O Boyle and Beamish, 1977), a fact explicable from the life strategy of the fish they must attain maximum size and weight as soon as possible before becoming sexually mature, so as to be able to escape predators, to search effectively for food and to evolve optimum reproductive power. Fecundity is directly proportional to... 

Bolgova, O.M., Lizenko, E.I., Klepkina, M.N. and Lysenko, P.V. (1985b). Fatty acid composition of triacyl glycerols of liver, muscle and gill in strong and weak one-year carp after wintering (In Russian). In Biochemistry of Fry of Freshwater Fishes , pp. 19-23. Petrozavodsk. 

Protein molecules associated with triacylglycerol, cholesterol or phospholipids are called lipoproteins. Triacyl glycerols derived from intestinal absorption or from the liver are not transported in the free form in circulating blood plasma, but move as chylomicrons, as very low density lipoproteins (VLDL) or as free fatty acids (FFA) - albumin complexes. Besides, two more physiologically important groups of lipoproteins are low density lipoprotein (LDL) and high density lipoprotein (FIDL). 

It is important to realize that most fatty acids cannot provide carbon for glu-coneogenesis. Thus, of the vast store of food energy in adipose tissue triacyl-glycerols, only the small glycerol portion travels to the liver to enter the gluconeogenic pathway. 

One of the toxic effects of acetaldehyde is inhibition of tubuhn polymerization. Tubulin is used in the liver for secretion of very low-density lipoprotein (VLDL) particles containing newly synthesized triacylglycerols. As a result, these triacyl-glycerols accumulate in the liver, and he has begun to develop a fatty liver. Acetaldehyde may also damage protein components of the inner mitochondrial membrane and affect its ability to pump protons to the cytosol. 

Palmitate is elongated and desaturated to produce a series of fatty acids. In the liver, palmitate and other newly synthesized fatty acids are converted to triacyl-glycerols that are packaged into VLDL for secretion. 

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