Vitamin D2-enriched button mushroom (Agaricus bisporus) improves memory in both wild type and APPswe/PS1dE9 transgenic mice.

Vitamin D deficiency is widespread, affecting over 30% of adult Australians, and increasing up to 80% for at-risk groups including the elderly (age>65). The role for Vitamin D in development of the central nervous system is supported by the association between Vitamin D deficiency and incidence of neurological and psychiatric disorders including Alzheimer's disease (AD). A reported positive relationship between Vitamin D status and cognitive performance suggests that restoring Vitamin D status might provide a cognitive benefit to those with Vitamin D deficiency. Mushrooms are a rich source of ergosterol, which can be converted to Vitamin D2 by treatment with UV light, presenting a new and convenient dietary source of Vitamin D2. We hypothesised that Vitamin D2-enriched mushrooms (VDM) could prevent the cognitive and pathological abnormalities associated with dementia. Two month old wild type (B6C3) and AD transgenic (APPSwe/PS1dE9) mice were fed a diet either deficient in Vitamin D2 or a diet which was supplemented with VDM, containing 1±0.2 µg/kg (∼54 IU/kg) vitamin D2, for 7 months. Effects of the dietary intervention on memory were assessed pre- and post-feeding. Brain sections were evaluated for amyloid ß (Aß) plaque loads and inflammation biomarkers using immuno-histochemical methods. Plasma vitamin D metabolites, Aß40, Aß42, calcium, protein and cholesterol were measured using biochemical assays. Compared with mice on the control diet, VDM-fed wild type and AD transgenic mice displayed improved learning and memory, had significantly reduced amyloid plaque load and glial fibrillary acidic protein, and elevated interleukin-10 in the brain. The results suggest that VDM might provide a dietary source of Vitamin D2 and other bioactives for preventing memory-impairment in dementia. This study supports the need for a randomised clinical trial to determine whether or not VDM consumption can benefit cognitive performance in the wider population.

Heat-stable components of wood ear mushroom, Auricularia polytricha (higher Basidiomycetes), inhibit in vitro activity of beta secretase (BACE1).

The consumption of mushrooms has been linked with protection against dementia, including Alzheimer's disease (AD), by several biological pathways including inhibiting beta-site APP-cleaving enzyme (BACE1), which is responsible for releasing toxic ß-amyloid peptide in the brain. We have investigated the capacity of several medicinal mushroom species-Auricularia polytricha (wood ear mushroom), Agaricus bisporus (button mushroom), Flammulina velutipes (winter or enoki mushroom), and Lentinus edodes (shiitake mushroom)-in the regulation of BACE1. Mushrooms were subjected to a generic food-compatible processing method to detect process-stable or process-modified products; the effects of processing were interpreted to infer the chemical classes associated with bioactivity. We have shown previously that in addition to enzyme inhibition, in the presence of the BACE1 proenzyme, heteropolymeric species such as heparin can activate BACE1 by modulating access to the catalytic site. We observed both inhibitory and activating components of the various mushrooms. Only BACE1 inhibitory species were detected in unprocessed and processed forms of A. polytricha, whereas the dominant extracted species from A. bisporus, F. velutipes, and L. edodese were activators of BACE1. It is not known whether activating species were masking the presence of inhibitory species in A. bisporus, F. velutipes, and L. edodes. Inhibitory species were attributed to hispidin-derived polyphenols, whereas activating species were attributed to soluble polysaccharides and possibly low-mass Maillard products produced during processing. Larger molecular BACE1-activating species are unlikely to be bioavailable to brain in contrast with possible brain bioavailability of smaller, lipophilic hispidins.

Regulation of milk protein solubility by a whey-derived proline-rich peptide product.

The effects of a bovine whey peptide product enriched in proline (wPRP) on the solubility of milk proteins were tested under ambient conditions or following heat treatment at 75 and 100 °C, for 1 and 15 min, followed by post-incubation storage at either ambient temperature or 4 °C for up to 7 d. wPRP promoted solubilisation of milk proteins in a concentration-dependent manner without heat treatment and also after heat treatment at 75 and 100 °C, and the effect was enhanced after storage under either ambient or refrigerated storage conditions. Interactions of wPRP and milk proteins were monitored by particle size analysis and tryptic digestion and specifically linked with solubilisation of αS1 casein (αS1-Cn), which supported observed changes in milk protein solubility. The results suggested that wPRP preferably prevented or reversed physical versus covalent protein aggregation, with the relaxation of hydrophobic interactions at 4 °C providing an additive effect. This application of wPRP represents a novel approach to stabilisation of dairy proteins following thermal processing with industrial usefulness yet to be explored.

The stability of almond ß-glucosidase during combined high pressure-thermal processing: a kinetic study.

The thermal and the combined high pressure-thermal inactivation kinetics of almond ß-glucosidase (ß-D-glucoside glucohydrolase, EC 3.2.1.21) were investigated at pressures from 0.1 to 600 MPa and temperatures ranging from 30 to 80 °C. Thermal treatments at temperatures higher than 50 °C resulted in significant inactivation with complete inactivation after 2 min of treatment at 80 °C. Both the thermal and high pressure inactivation kinetics were described well by first-order model. Application of pressure increased the inactivation kinetics of the enzyme except at moderate temperatures (50 to 70 °C) and pressures between 0.1 and 100 MPa where slight pressure stabilisation of the enzyme against thermal denaturation was observed. The activation energy for the inactivation of the enzyme at atmospheric pressure was estimated to be 216.2±8.6 kJ/mol decreasing to 55.2±3.9 kJ/mol at 600 MPa. The activation volumes were negative at all temperature conditions excluding the temperature-pressure range where slight pressure stabilisation was observed. The values of the activation volumes were estimated to be -29.6±0.6, -29.8±1.7, -20.6±3.2, -41.2±4.8, -36.5±1.8, -39.6±4.3, -31.0±4.5 and -33.8±3.9 cm3/mol at 30, 35, 40, 45, 50, 60, 65 and 70 °C, respectively, with no clear trend with temperature. The pressure-temperature dependence of the inactivation rate constants was well described by an empirical third-order polynomial model.

Modulation of in vitro activity of zymogenic and mature recombinant human ß-secretase by dietary plants.

The in vitro activity of human recombinant ß-secretase (BACE1) was studied using a fluorogenic substrate based on the cleavage site for the enzyme in the Swedish mutation of amyloid precursor protein. The enzyme was inhibited by a control peptide inhibitor with good repeatability. The enzyme preparation comprised a mixture of pro-enzyme or zymogen and mature enzyme whereby the pro-enzyme sequence forms a 'flap' that can obstruct the binding site. 'Open flap' forms of the zymogen and mature enzyme are active, but the 'closed flap' form of the zymogen is inactive. This mixture of enzyme populations permitted apparent stimulation of enzyme activity under particular conditions, presumably due to facilitating flap-opening of the zymogen. As reported for heparin, enzyme activation was stimulated in the presence of low concentrations of Tween 20 and dimethylsulfoxide before becoming inhibited at higher concentrations. Dietary plant extracts either consistently inhibited (e.g. clove, tea, cinammon) or consistently stimulated (e.g. mushroom, parsley, asparagus) BACE1. Common structural features identified by Fourier transform infrared spectroscopy revealed that BACE1 activity could be explained by differential interactions of either small molecule or polymeric species with mature versus zymogen forms of the enzyme, respectively. Further, enzyme activity could be reversed by mixtures of high and low mass species. These results may have implications for the regulation of ß-secretase activity in vivo by either endogenous or possibly dietary factors and for a potential role of BACE1 in stimulation of the production of amyloid beta peptide in sporadic Alzheimer's disease.