2D gel proteomics: an approach to study age-related differences in protein abundance or isoform complexity in biological samples.

This chapter describes protocols for two-dimensional (2D) gel electrophoresis (isoelectric focusing [IEF] followed by sodium-dodecyl sulfate (SDS)-polyacrylamide gel electro-phoresis [PAGE]), staining of gels with the fluorescent dye Sypro Ruby, 2D gel image analysis, peptide mass fingerprint (PMF) analysis using matrix-assisted laser desorption ionization (MALDI)-time-of-flight (TOF) mass spectrometry (MS), liquid chromatography (LC)-tandem mass spectrometry (MS/MS), Western blot analysis of protein oxidations, and mass spectrometric mapping of sites of protein oxidations. Many of these methods were used to identify proteins affected in rat brain following ingestion of grape seed extract (GSE), a dietary supplement touted for anti-oxidant activity. Although beneficial actions in cell and animal models of chronic disease have been described for GSE, it has not been shown whether specific proteins were affected, or the nature of the effects. Applying 2D gel proteomics technology allowed discovery of proteins targeted by GSE without a priori knowledge of which one(s) might be affected. The newer 2D blue native (BN) electrophoresis methodology, which resolves protein complexes in a nondenaturing first dimension and then the components of these complexes in a denaturing second dimension, is discussed as a complementary approach. Analysis of protein oxidations and protein-protein interactions have special relevance to aging-related research, since oxidative stress and altered protein interactions may be at the heart of aging-related diseases. Finally, quality control issues related to implementation of high throughput technologies are addressed, to underscore the importance of minimizing bias and randomizing human and technical error in generating large datasets that are expensive and time-consuming to repeat.

Chemoprevention by grape seed extract and genistein in carcinogen-induced mammary cancer in rats is diet dependent.

Many popular dietary supplements are enriched in polyphenols such as the soy isoflavones, tea catechins, and resveratrol (from grape skins), each of which has been shown to have chemopreventive activity in cellular models of cancer. The proanthocyanidins, which are oligomers of the catechins, are enriched in grape seeds and form the basis of the dietary supplement grape seed extract (GSE). Evidence suggests that the proanthocyanidins may be metabolized to the monomeric catechins. This study was carried out to determine whether GSE added to rodent diets protected against carcinogen-induced mammary tumorigenesis in rats and whether this was affected by the composition of the whole diet. Female rats were begun on 5%, 1.25%, or 0% (control) GSE-supplemented diets at age 35 d. At age 50 d they were administered 7,12-dimethylbenz[a]anthracene (DMBA) in sesame oil at 80 mg/kg body weight. They were weighed and monitored weekly for tumor development until 120 d after DMBA administration. Administration of GSE in AIN-76A diet did not show any protective activity of GSE against DMBA-induced breast cancer. However, administration of GSE in a laboratory dry food diet (Teklad 4% rodent diet) resulted in a 50% reduction in tumor multiplicity. In similar experiments, genistein administered in AIN-76A diet also failed to show chemopreventive activity against the carcinogen N-methyl-N-nitrosourea; however, when administered at the same dose in the Teklad 4% rodent diet, genistein exhibited significant chemopreventive activity (44-61%). These results demonstrate that GSE is chemopreventive in an animal model of breast cancer; moreover, the diet dependency of the chemopreventive activity for both GSE and genistein suggests that whether or not a compound is chemopreventive may depend on the diet in which the agent is administered.

Proteomics analysis of rat brain protein modulations by grape seed extract.

Dietary supplements such as grape seed extract (GSE) enriched in proanthocyanidins (PA) (oligomeric polyphenols) have been suggested to have multiple health benefits, due to antioxidant and other beneficial activities of the PA. However, a systematic analysis of the molecular basis of these benefits has not been demonstrated. Because the brain is vulnerable to age-related oxidative damage and other insults including inflammation, it was hypothesized that rats ingesting GSE would experience changes in expression or modifications of specific brain proteins that might protect against pathologic events. Normal adult female rats were fed diets supplemented with 5% GSE for 6 weeks. Proteomics analysis (2D electrophoresis and mass spectrometry) of brain homogenates from these animals identified 13 proteins that were altered in amount and/or charge. Because many of these changes were quantitatively in the opposite direction from previous findings for the same proteins in either Alzheimer disease or mouse models of neurodegeneration, the data suggest that these identified proteins may mediate the neuroprotective actions of GSE. This is the first identification and quantitation of specific proteins in mammalian tissues modulated by a dietary supplement, as well as the first to demonstrate links of such proteins with any disease.

Profiling and quantification of isoflavonoids in kudzu dietary supplements by high-performance liquid chromatography and electrospray ionization tandem mass spectrometry.

The kudzu vine (Pueraria sp.) is a rich source of isoflavones. Dietary supplements based on kudzu have become commercially available. In the present study, liquid chromatography coupled with negative and positive electrospray ionization tandem mass spectrometry (MS/MS) and diode array detection (DAD) has been used for the detection and characterization of isoflavonoids in kudzu dietary supplements (KDS). The MS/MS spectrum of the protonated ion of puerarin showed characteristic product ions of the C-glycoside unit itself, whereas daidzin generated an abundant Y(0)(+) aglycon ion in its product ion spectrum. A base peak due to the loss of 120 Da [M + H - 120](+) is the diagnostic ion for C-glycosides. Neutral loss scans allowed for the detection of other C- and O-glycosides in the methanolic extract of KDS, and their structures have been proposed. The concentration of isoflavonoids in the methanolic extract of commercially available KDS was quantified by using DAD-HPLC. Puerarin, rather than daidzin, was the most abundant component (8.44-30.60 mg/capsule) in commercially available KDS.