flavin-adenine-dinucleotide and Cataract

The present work discusses the role of certain coenzymes in the metabolic and the biophysical processes maintaining the nativity of lens components. It also analyses results of the levels of oxidized and reduced forms of nicotine amide coenzymes and glutathione in the lens folling insults by both physical and chemical cataractogenic agents. The role of flavine and flavine coenzymes in the maintainance of the biochemical and biophysical stability of the lens has also been discussed. Data concerning the enzymatic biosynthesis and degradation of the lens coenzymes has been presented.

Topics: Animals; Cataract; Coenzymes; Flavin-Adenine Dinucleotide; Glutathione; Lens, Crystalline; Riboflavin

The biochemical mechanism(s) underlying brunescent cataracts remain unclear. Oxidative stress due to reactive oxygen species may have a role in the pigmentation process in eye lens. We have analysed human cataractous lenses for flavins by high-performance liquid chromatography (HPLC), since flavins are light sensitive and act as endogenous sensitizers generating reactive oxygen species in the eye. The most significant observation in this study is that higher levels of flavin nucleotides occur in brown lens compared to yellow lens. The concentration of flavin nucleotides (flavin monouncleotide, FMN + flavin adenine dinucleotide, FAD) was highest in the nuclear region of the lens followed by the cortical and capsule-epithelial regions. However, the ratio of FAD/FMN was lowest in the nuclear region of the lens followed by other regions. On the other hand, riboflavin was not detected in any of the lens (cataractous) regions. These results suggest that the observed increase in flavin nucleotides in the ocular tissue could contribute towards deepening of lens pigmentation.

Topics: Biomarkers; Cataract; Chromatography, High Pressure Liquid; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Humans; Lens, Crystalline; Middle Aged; Pigmentation; Reactive Oxygen Species

Glutathione reductase (GR) activity was measured with and without the addition of flavin adenine dinucleotide (FAD) in freshly excised human lens epithelium following cataract surgery, and in control eye bank lens epithelium. Large individual variations in activity were found in both groups. Out of 32 epithelia obtained from cataractous lenses, 14 showed no measurable GR activity. Activity in eight of these 14 epithelia was restored after FAD was added, implying that the apo-enzyme in these 8 epithelia was functional but FAD was not available. Another group of 8 active epithelia showed a significant increase in GR activity upon the addition of FAD, suggesting a mixed population of active enzyme and available fraction of apo-enzyme which was reactivated by the addition of FAD. Unusually high GR activities were observed in epithelia of several patients. This correlated principally with daily intake of thyroxine which is known to have a direct effect on the metabolism of riboflavin. The fact that in a significant number of cataract patients epithelial GR was not active, and the observation that activity could be restored by adding in vitro FAD, demands that more attention should be given to riboflavin nutritional status and FAD synthesis in the eye.

Topics: Cataract; Enzyme Activation; Epithelium; Eye Banks; Flavin-Adenine Dinucleotide; Glutathione Reductase; Humans; In Vitro Techniques; Lens, Crystalline

Lenticular reduced glutathione, diminished in all forms fo human cataract, requires flavin adenine dinucleotide as a coenzyme for glutathione reductase. Deficiency of riboflavin, a precursor of flavin adenine dinucleotide, has been believed by some to be associated with cataract formation. We evaluated the riboflavin nutritional status of healthy young adults, presenile and senile cataract patients, and young and older patients with clear lenses. We found no evidence of an association between riboflavin deficiency and early cataract formation, either idiopathic or secondary. Older cataract patients had more riboflavin deficiency. An absence of riboflavin deficiency was found in our older patients with clear lenses. The degree of riboflavin deficiency encountered in the general population does not appear to be cataractogenic.

Topics: Adult; Age Factors; Cataract; Flavin-Adenine Dinucleotide; Glutathione Reductase; Humans; Middle Aged; Riboflavin Deficiency

Topics: Age Factors; Aged; Cataract; Diet; Flavin-Adenine Dinucleotide; Glutathione; Humans; Lens, Crystalline; Middle Aged; Riboflavin; Riboflavin Deficiency

Topics: Adult; Aged; Blood Glucose; Carbon Radioisotopes; Cataract; Erythrocytes; Female; Flavin-Adenine Dinucleotide; Galactose; Glucosephosphates; Glutathione Reductase; Glycosuria; Humans; Male; Middle Aged; Nucleotidyltransferases; Phosphotransferases; Riboflavin; Riboflavin Deficiency; Uracil Nucleotides

Topics: Adrenal Glands; Adrenalectomy; Alanine Transaminase; Animals; Binding Sites; Carbon Isotopes; Cataract; Dexamethasone; Flavin-Adenine Dinucleotide; Hydrocortisone; Hypophysectomy; In Vitro Techniques; Lens, Crystalline; Liver; Male; Pituitary Gland; Radiation Effects; Rats; Riboflavin

Topics: Animals; Cataract; Dietary Carbohydrates; Erythrocytes; Eye Proteins; Flavin-Adenine Dinucleotide; Galactose; Glutathione Reductase; Lens, Crystalline; Rats; Riboflavin Deficiency; Sulfhydryl Compounds