Evidence supporting nutritional interventions for persons in early stage Alzheimer's disease (AD)

The purpose of this paper is to grade research evidence supporting nutritional interventions for persons with early stage dementias and to report the recommendations of a consensus panel. Thirty four studies were reviewed in the areas of dietary restriction, antioxidants, and Mediterranean diet with strong support from epidemiological studies found in all three areas. The body of evidence to support nutritional interventions in the prevention and treatment of AD is growing and has potential as a treatment modality following translational studies.

Nonstereospecific substrate usage by glyoxalase I

Glyoxalase I operates on a mixture of rapidly interconverting diasteriomeric thiohemiacetals, formed in a preequilibrium step between glutathione and alpha-ketoaldehyde. That both diasteriomers are directly used as substrates by the enzyme from yeast and from porcine erythrocytes is an outcome of a series of isotope-trapping experiments in which pulse solutions composed of the two diasteriomeric thiohemiacetals, due to [3H]glutathione and phenylglyoxal, are rapidly mixed with chase solutions containing excess unlabeled glutathione and successively increasing concentrations of glyoxalase I. As the enzyme approaches infinite concentration in the chase solution, the radioactivity incorporated into the S-mandeloylglutathione product approaches 100% of the total radioactivity due to both diasteriomers from the pulse solution. The special properties of the active site that allow the enzyme to accommodate both diasteriomeric substrate forms may also account for the fact that the cis and the trans isomers of various para-substituted S-(phenylethenyl)glutathione derivatives are both strong competitive inhibitors of the enzyme. A catalytic mechanism is proposed for glyoxalase I involving catalyzed interconversion of the bound diasteriomeric thiohemiacetals before transformation to final product.

Relationship of rat urinary metabolites of N-nitrosomethyl-N-alkylamine to bladder carcinogenesis

Nitrosomethylalkylamines with chain lengths from C4 (n-butyl-) to C14 (n-tetradecyl-) were each administered in three rats at doses equimolar with 12 mg of the butyl compound. All of the compounds administered to rats at this dose, twice a week for 30 weeks, induced tumors in 100% of the animals. Some of the compounds with even-numbered alkyl chains induced bladder tumors, and a connection was sought with the metabolites of these excreted in urine. The pooled 24-hr urine was extracted with ethyl acetate before and after acidification to provide a neutral fraction and a fraction containing nitrosoamino acids. The fraction containing the acids was analyzed by capillary gas chromatography and by gas chromatography-mass spectrometry after esterification with diazomethane; the neutral fraction was analyzed similarly. The principal metabolite of the nitrosoamines with odd-numbered chains was found in the acidic fraction and was identified as nitrosomethyl-2-carboxy-ethylamine. There were several acids in the mixtures derived from the nitrosamines with even-numbered chains, nitrososarcosine and nitrosomethyl-3-carboxypropylamine being the major components. There was no trend in the yields of the nitrosamino acids that could be correlated with the differences in carcinogenic potency between the nitrosamines; the maximum yield of acids was more than 30% (from the tetradecyl compound). The principal component of the neutral fraction (less than or equal to 1% of the nitrosomethylalkylamine administered) was nitrosomethyl-2-oxopropylamine. The yield of this compound increased with length of the even-numbered chain nitrosamines.

Hydrophobic binding is not an independent stereochemical determinant in the yeast glyoxalase I reaction

For yeast glyoxalase I, a stereospecific proton-transfer mechanism requires the formation of either a cis or a trans-enediol intermediate. Analogs of the two possible isometric enediol intermediates, formed from the hemimercaptal due to phenylglyoxal and glutathione, have been synthesized in which the oxygen atoms of the enediol are replaced by protons. Both isomeric analogs are strong linear competitive inhibitors of the enzyme having nearly equal inhibition constants: Ki(cis) = 0.10 mM; Ki(trans) = 0.16 mM. This suggests that while hydrophobic interactions between substrate, enediol intermediate and enzyme may contribute significantly to binding, this type of interaction is not an independent stereochemical determinant of the reaction.