Respiration mitochondriale, données de base

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Chemopreventive Potential of Flavones, Flavonols, and their Glycosides.

Collaboration between Leicester Institute for Pharmaceutical Innovation and the Institute for Allied Heath Sciences Research.Epidemiological studies have long indicated a possible role for dietary flavonoids, notably flavones and flavonols, in the prevention of a range of degenerative diseases, e.g. cancer, diabetes, cardiovascular diseases and neurological disorders like Parkinson’s and Alzheimer’s disease. The flavonoids are a large and variable group of compounds, comprising thousands of different structures. The bulk of the dietary flavonoids occur as glycosides. The effect of flavonoid aglycones and their corresponding glycosides on cell metabolism and aetiology of degenerative diseases has been a topic of interest for a number of decades. In contrast, the role of the metabolic products of dietary flavonoid that reach all parts of the human body through systemic circulation, has received much less attention. Studies on animal and human metabolism have shown that the amount flavone and flavonol glycosides is absorbed intact is negligible; the bulk is absorbed only after deglycosylation. Thus, dietary glycosides are not likely to play a direct role in chemoprevention. However, the sugar groups on glycosides can greatly affect the bioavailability of flavones and flavonols. Flavonoids linked with indigestible sugars are not absorbed in the small intestine, but are transported through the digestive tract to be degraded by gut bacteria in the large intestine. The compounds that directly play a tole in the prevention of degenerative diseases are most likely not dietary flavones themselves, but rather their metabolites and conjugation products

Inborn disorders of the malate aspartate shuttle

Over the last few years, various inborn disorders have been reported in the malate aspartate shuttle (MAS). The MAS consists of four metabolic enzymes and two transporters, one of them having two isoforms that are expressed in different tissues. Together they form a biochemical pathway that shuttles electrons from the cytosol into mitochondria, as the inner mitochondrial membrane is impermeable to the electron carrier NADH. By shuttling NADH across the mitochondrial membrane in the form of a reduced metabolite (malate), the MAS plays an important role in mitochondrial respiration. In addition, the MAS maintains the cytosolic NAD+ /NADH redox balance, by using redox reactions for the transfer of electrons. This explains why the MAS is also important in sustaining cytosolic redox-dependent metabolic pathways, such as glycolysis and serine biosynthesis. The current review provides insights into the clinical and biochemical characteristics of MAS deficiencies. To date, five out of seven potential MAS deficiencies have been reported. Most of them present with a clinical phenotype of infantile epileptic encephalopathy. Although not specific, biochemical characteristics include high lactate, high glycerol 3-phosphate, a disturbed redox balance, TCA abnormalities, high ammonia, and low serine, which may be helpful in reaching a diagnosis in patients with an infantile epileptic encephalopathy. Current implications for treatment include a ketogenic diet, as well as serine and vitamin B6 supplementation