Effect of Whey-Derived Lactopeptide ß-Lactolin on Memory in Healthy Adults: An Integrated Analysis of Data from Randomized Controlled Trials.

CONTEXT: Epidemiological studies have shown that consumption of dairy products reduces the risk of dementia and cognitive decline in older individuals. Tryptophan-tyrosine-related ß-lactopeptides and their representative ß-lactolin of glycine-threonine-tryptophan-tyrosine tetra-peptide have been identified as agents in dairy products, which improve cognitive function as well as memory function via the activation of the dopaminergic system in a mouse model of amnesia. Previous clinical trials have shown that supplementation with ß-lactolin improves memory retrieval in healthy older adults. Specifically, ß-lactolin improved the scores in some neuropsychological tests. However, the effects of ß-lactolin on memory function have not been clarified. OBJECTIVES: The aim of this study was to evaluate the effect of ß-lactolin on memory function using statistical methods. DATA SOURCES: We searched the Web of Science, Cochrane Library, and JDream III until November 2021 to identify relevant randomized controlled trials for integrated analysis. DATA SYNTHESIS: Three randomized controlled trials evaluating the effect of ß-lactolin on memory in healthy adults were selected for the integrated analysis. The results showed that the score of cued recall among the neuropsychological tests in the ß-lactolin group was significantly higher than that in the placebo group (g=0.33; 95% CI: 0.10, 0.55). In addition, the total memory score was higher but this difference was not significant (g=0.17; 95% CI: -0.09, 0.43). CONCLUSIONS: Taken together, these results suggest that supplementation with ß-lactolin improves cued recall in healthy older adults.

Cellular prion protein prevents brain damage after encephalomyocarditis virus infection in mice.

Cellular prion protein (PrP(C)), a cell-surface glycoprotein normally associated with neurons, is also expressed in other cell types such as glia and lymphocytes. To further elucidate these roles of PrP(C), wild-type prion protein gene (Prnp(+/+)) mice and Prnp-deficient (Prnp(-/-)) mice were infected with encephalomyocarditis virus B variant (EMCV-B) via an intracranial route. EMCV-B causes encephalitis and apoptotic cell death in vivo. Histopathological studies revealed that Prnp(+/+) mice infected with 600 pfu of EMCV-B showed more severe infiltration of inflammatory cells, accompanied by higher activation of microglia cells around the hippocampus, than Prnp(-/-) mice; viz., no differences in the brain virus titer between these two lines of mice. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP, nick end-labeling (TUNEL) staining of the brain specimens revealed that the CA1 hippocampal pyramidal cells showed a larger number of apoptotic neurons in Prnp(-/-) than Prnp(+/+) mice. Based on all these findings, PrP(C) may play certain roles in the induction of inflammation and inhibition of apoptosis in vivo.

Membrane-bound sugar alcohol dehydrogenase in acetic acid bacteria catalyzes L-ribulose formation and NAD-dependent ribitol dehydrogenase is independent of the oxidative fermentation.

To identify the enzyme responsible for pentitol oxidation by acetic acid bacteria, two different ribitol oxidizing enzymes, one in the cytosolic fraction of NAD(P)-dependent and the other in the membrane fraction of NAD(P)-independent enzymes, were examined with respect to oxidative fermentation. The cytoplasmic NAD-dependent ribitol dehydrogenase (EC 1.1.1.56) was crystallized from Gluconobacter suboxydans IFO 12528 and found to be an enzyme having 100 kDa of molecular mass and 5 s as the sedimentation constant, composed of four identical subunits of 25 kDa. The enzyme catalyzed a shuttle reversible oxidoreduction between ribitol and D-ribulose in the presence of NAD and NADH, respectively. Xylitol and L-arabitol were well oxidized by the enzyme with reaction rates comparable to ribitol oxidation. D-Ribulose, L-ribulose, and L-xylulose were well reduced by the enzyme in the presence of NADH as cosubstrates. The optimum pH of pentitol oxidation was found at alkaline pH such as 9.5-10.5 and ketopentose reduction was found at pH 6.0. NAD-Dependent ribitol dehydrogenase seemed to be specific to oxidoreduction between pentitols and ketopentoses and D-sorbitol and D-mannitol were not oxidized by this enzyme. However, no D-ribulose accumulation was observed outside the cells during the growth of the organism on ribitol. L-Ribulose was accumulated in the culture medium instead, as the direct oxidation product catalyzed by a membrane-bound NAD(P)-independent ribitol dehydrogenase. Thus, the physiological role of NAD-dependent ribitol dehydrogenase was accounted to catalyze ribitol oxidation to D-ribulose in cytoplasm, taking D-ribulose to the pentose phosphate pathway after being phosphorylated. L-Ribulose outside the cells would be incorporated into the cytoplasm in several ways when need for carbon and energy sources made it necessary to use L-ribulose for their survival. From a series of simple experiments, membrane-bound sugar alcohol dehydrogenase was concluded to be the enzyme responsible for L-ribulose production in oxidative fermentation by acetic acid bacteria.

Isolation and characterization of thermotolerant Gluconobacter strains catalyzing oxidative fermentation at higher temperatures.

Thermotolerant acetic acid bacteria belonging to the genus Gluconobacter were isolated from various kinds of fruits and flowers from Thailand and Japan. The screening strategy was built up to exclude Acetobacter strains by adding gluconic acid to a culture medium in the presence of 1% D-sorbitol or 1% D-mannitol. Eight strains of thermotolerant Gluconobacter were isolated and screened for D-fructose and L-sorbose production. They grew at wide range of temperatures from 10 degrees C to 37 degrees C and had average optimum growth temperature between 30-33 degrees C. All strains were able to produce L-sorbose and D-fructose at higher temperatures such as 37 degrees C. The 16S rRNA sequences analysis showed that the isolated strains were almost identical to G. frateurii with scores of 99.36-99.79%. Among these eight strains, especially strains CHM16 and CHM54 had high oxidase activity for D-mannitol and D-sorbitol, converting it to D-fructose and L-sorbose at 37 degrees C, respectively. Sugar alcohols oxidation proceeded without a lag time, but Gluconobacter frateurii IFO 3264T was unable to do such fermentation at 37 degrees C. Fermentation efficiency and fermentation rate of the strains CHM16 and CHM54 were quite high and they rapidly oxidized D-mannitol and D-sorbitol to D-fructose and L-sorbose at almost 100% within 24 h at 30 degrees C. Even oxidative fermentation of D-fructose done at 37 degrees C, the strain CHM16 still accumulated D-fructose at 80% within 24 h. The efficiency of L-sorbose fermentation by the strain CHM54 at 37 degrees C was superior to that observed at 30 degrees C. Thus, the eight strains were finally classified as thermotolerant members of G. frateurii.

Crystallization and Properties of NADPH-Dependent L-Sorbose Reductase from Gluconobacter melanogenus IFO 3294.

NADPH-Dependent L-sorbose reductase (SORD, synonimously NADP-dependent D-srobitol dehydrogenase) was purified and crystallized for the first time from the cytosolic fraction of Gluconobacter melanogenus IFO 3294. The enzyme catalyzed oxidoreduction between D-sorbitol and L-sorbose in the presence of NADP or NADPH. Affinity chromatography by a Blue-dextran Sepharose 4B column was effective for purifying the enzyme giving about 770-fold purification with an overall yield of more than 50%. The crystalline enzyme showed a single sedimentation peak in analytical ultracentrifugation, giving an apparent sedimentation constant of 3.8 s. Gel filtration on a Sephadex G-75 column gave the molecular mass of 60 kDa to the enzyme, which dissociated into 30 kDa subunit on SDS-PAGE, indicating that the enzyme is composed of 2 identical subunits. Reduction of L-sorbose to D-sorbitol predominated in the presence of NADPH with the optimum pH of 5.0-7.0. Oxidation of D-sorbitol to L-sorbose was observed in the presence of NADP at the optimum pH of 7.0-9.0. The relative rate of L-sorbose reduction was more than seven times higher to that of D-sorbitol oxidation. NAD and NADH were inert for both reactions. D-Fructose reduction in the presence of NADPH did not occur with SORD. Since the reaction rate in L-sorbose reduction highly predominated over D-sorbitol oxidation over a wide pH range, the enzyme could be available for direct enzymatic measurement of L-sorbose. Even in the presence of a large excess of D-glucose and other substances, oxidation of NADPH to NADP was highly specific and stoichiometric to the L-sorbose reduced. Judging from the enzymatic properties, SORD would contribute to the intracellular assimilation of L-sorbose incorporated from outside the cells where L-sorbose is accumulated in huge amounts in the culture medium.