Catabolism of lipids

Lipid metabolism allows polar bears to thrive In arctic climates and to endure months of hibernation. 

How does oxidation of fatty acids take place  

The Energy Yield from the Oxidation of Fatty Acids 

Catabolism of Unsaturated Fatty Acids and Odd-Carbon Fatty Acids 

How does the oxidation of unsaturated fatty acids differ from that of saturated fatty acids  

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Glucocorticoids not only break down protein but also stimulate the catabolism of lipids in adipose tissue and enhance the actions of other lipolytic agents. This occurrence results in an increase in plasma free fatty acids and an enhanced tendency to ketosis. The mechanism of this lipolytic action is unknown. The net effect of the biochemical changes induced by the glucocorticoids is antagonism of the actions of insulin. These biochemical events promote hyperglycemia and glycosuria, which are similar to the diabetic state. 

In addition to SREBPs, several members of the nuclear receptor superfamily regulate lipid metabolism. Nuclear receptors are transcription factors that are generally activated when bound to specific small-molecule ligands (Chapter 11). Certain nuclear receptors influence whole-body lipid metabolism by regulating the absorption of dietary lipids, cellular synthesis of lipids, transport protein-mediated import and export of lipids, levels of lipoproteins and their receptors, and catabolism of lipids (e.g., fatty acid oxidation in the peroxisome) and their secretion from the body. 

In the nuclear-receptor pathway, transcription factors in the cytosol are activated by intracellular lipids (e.g., high levels of oxysterols or bUe acids). The ligand-transcription factor complex then enters the nucleus and regulates the expression of specific target genes that participate in feedback regulation of the synthesis, transport, and catabolism of lipids. 

The oxidation of fatty acids, which takes place in the mitochondrial matrix, is the chief source of energy in the catabolism of lipids. In this process, two-carbon units are successively removed from the carboxyl end of the fatty... 

PLTP is responsible for the majority of phospholipid transfer activity in human plasma. Specifically, it transfers surface phospholipids from VLDL to HDL upon lipolysis of triglycerides present in VLDL. The exact mechanism by which PLTP exerts its activity is yet unknown. The best indications for an important role in lipid metabolism have been gained from knockout experiments in mice, which show severe reduction of plasma levels of HDL-C and apoA-I. This is most likely the result of increased catabolism of HDL particles that are small in size as a result of phospholipid depletion. In addition to the maintenance of normal plasma HDL-C and apoA-I concentration, PLTP is also involved in a process called HDL conversion. Shortly summarized, this cascade of processes leads to fusion of HDL... 

Chappell DA, Medh JD Receptor-mediated mechanisms of lipoprotein remnant catabolism. Prog Lipid Res 1998 37 393. 

Gerhard B (1993) Catabolism of fatty acid acids. In Moore TS (ed) Lipid metabolism in plants. CRS Press, Baton Rouge, p 527... 

Most of the body s acid production is in the form of C02 and is produced from catabolism of carbohydrates, proteins, and lipids. 

The citric acid cycle is at the heart of aerobic cellular metabolism, or respiration. This is true of both prokaryotic and eukaryotic organisms, of plants and animals, of organisms large and small. Here is the main point. On the one hand, the small molecule products of catabolism of carbohydrates, lipids, and amino acids feed into the citric acid cycle. There they are converted to the ultimate end products of catabolism, carbon dioxide and water. On the other hand, the molecules of the citric acid cycle are intermediates for carbohydrate, lipid, and amino acid synthesis. Thus, the citric acid cycle is said to be amphibolic, involved in both catabolism and anabolism. It is a sink for the products of degradation of carbohydrates, lipids, and proteins and a source of building blocks for them as well. 

Although demethylation, which occurs in the liver, is normally considered to be a catabolic process, it may result in conversion of an inactive form of a drug to the active form. Thus 6-(methylthio)purine (XXXIX) is demethylated by the rat to 6-mercaptopurine [205]. This demethylation occurs in the liver micro-somes and is an oxidative process which converts the methyl group to formaldehyde [204, 207]. The 1-methyl derivative of 4-aminopyrazolo[3,4-d] pyrimidine (XLI) is demethylated slowly, but 6-mercapto-9-methylpurine (XLII) not at all [208]. The A -demethylation of puromycin (XLlIl) [209, 210], its aminonucleoside (XLIV) [211], and a number of related compounds, including V-methyladenine and V,V-dimethyladenine, occurs in the liver microsomes of rodents [212]. In the guinea-pig the rate-limiting step in the metabolism of the aminonucleoside appears to be the demethylation of the monomethyl compound, which is the major urinary metabolite [213]. The relationship of lipid solubility to microsomal metabolism [214], and the induction of these demethylases in rats by pre-treatment with various drugs have been studied [215]. 

Other- Liver disease with impaired hemostasis severe renal disease. Hyperlipidemia Heparin may increase free fatty acid serum levels by induction of lipoprotein lipase. The catabolism of serum lipoproteins by this enzyme produces lipid fragments that are rapidly processed by the liver. Patients with dysbetalipoproteinemia (type III) are unable to catabolize the lipid fragments, resulting in hyperlipidemia. 

Pheromone (sex attractant). Ether extract of the stem, produced equivocal effect on Aspiculuris tetraptera, female and male Dacus dorsalis, male Mediterranean fruit flies, and male and female melon flies " k Pheromone (signaling). Ether extract of the stem, produced equivocal effect on Aspiculuris tetraptera, female and male Dacus dorsalis, male Mediterranean fruit flies, and male and female melon flies " k Phospholipidemic effect. Oil, administered to phospholipids transfer protein knockout (PLTPO)-deficient mice, produced an increase of phospholipids and free cholesterol in the VLDL-LDL region of PLTPO mice. Accumulation of phospholipids and free cholesterol was dramatically increased in PLTPO/HLO mice compared to PLTPO mice. Turnover studies indicated that coconut oil was associated with delayed catabolism of phospholipids and phospho-lipids/free cholesterol-rich particles. Incubation of these particles with hepatocytes of coconut-fed mice produced a reduced removal of phospholipids and free cholesterol by SRBI, even though SRBI protein expression levels were unchanged . 

An article by Li and Li (Tnlane University, LA) on the biosynthesis and catabolism of glycosphingolipids serves to extend that by Kiss (Vol. 24), which dealt mainly with the chemistry of these compounds. Schwarz and Datema (Giessen) provide a detailed account of the lipid pathway of protein glyeosylation and of its inhibitors, and then discuss the biological significance of protein-bound carbohydrates, thereby... 

Biological Reactions. Biosynthesis and catabolism of biological molecules (amino acids, carbohydrates, lipids, nucleic acids, peptides/proteins), metabolic cycles, biological catalysis and kinetics, mechanisms, organic and inorganic cofactors. 

Pantothenic acid participates as part of coenzvme A in carbohydrate metabolism (2-carbon transfer-acetate, or pyruvate), lipid metabolism (biosynthesis and catabolism of fatty acids, sterols, +phospholipids), protein metabolism (acetylations of amines and amino acids), porphyrin metabolism, acetylcholine production, isoprene production. 

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