[Hop Bitter Acids Activate the Brain-Gut Axis: Vagal Stimulus via Food Ingredients]

Maintenance and improvement of cognitive function and mood is important in an aging society. Preventive approaches, including diets used in daily life have received increasing attention in recent times. Clinical trials and preclinical studies have shown that hop bitter acids, which represent the bitter ingredients in beer, activate the bitter taste receptors and the brain-gut axis, which was shown to improve cognitive function and mood. Vagal stimulus via food ingredients may be a novel approach to maintain brain functions.

Tryptophan-tyrosine dipeptide improves tau-related symptoms in tauopathy mice

Neurodegenerative diseases involving pathological tau protein aggregation are collectively known as tauopathies and include Alzheimer's disease and Pick's disease. Recent studies show that the intake of tryptophan-tyrosine (Trp-Tyr)-related β-lactopeptides, including β-lactolin, attenuates cognitive decline in the elderly and prevents the amyloid pathology in mouse models of Alzheimer's disease. However, the effects of Trp-Tyr-related β-lactopeptides on tau-related pathology have not been investigated. In the present study, we examined the effects of Trp-Tyr dipeptide intake on tauopathy in PS19 transgenic mice, a well-established tauopathy model. Intake of Trp-Tyr dipeptide improved the behavioral deficits observed in the open field test, prevented tau phosphorylation, and increased the dopamine turnover and synaptophysin expression in the frontal cortex. Levels of short-chain fatty acids in the cecum were lower in PS19 mice than those in wild-type mice and were increased by treatment with Trp-Tyr dipeptide. In addition, intake of Trp-Tyr dipeptide extended the lifespan of PS19 mice. These findings suggest that the intake of Trp-Tyr-related peptides improves tauopathy symptoms, resulting in improvements in behavioral deficits and longevity. Hence, the intake of Trp-Tyr-related peptides, including β-lactolin, may be beneficial for preventing dementia.

β-Lactolin improves mitochondrial function in Aβ-treated mouse hippocampal neuronal cell line and a human iPSC-derived neuronal cell model of Alzheimer's disease

Mitochondrial dysfunctions are a key hallmark of Alzheimer's disease (AD). β-Lactolin, a whey-derived glycine-threonine-tryptophan-tyrosine tetrapeptide, has been previously reported to prevent AD-like pathologies in an AD mouse model via regulation of microglial functions. However, the direct effect of β-lactolin on neuronal cells and neuronal mitochondrial functions remains unknown. Here, we investigated the effects of β-lactolin on mitochondrial functions in amyloid β (Aβ)-treated mouse hippocampal neuronal HT22 cells and human induced-pluripotent cell (hiPSC)-derived AD model neurons. Adding β-lactolin to Aβ-treated HT22 cells increased both the oxygen consumption rate and cellular ATP concentrations, suggesting that β-lactolin improves mitochondrial respiration and energy production. Using high content image analysis, we found that β-lactolin improved mitochondrial fragmentation, membrane potential, and oxidative stress in Aβ-treated cells, eventually preventing neuronal cell death. From a mechanistic perspective, we found that β-lactolin increased gene expression of mitofusin-2, which contributes to mitochondrial fusion events. Finally, we showed that β-lactolin improves both mitochondrial morphologies and membrane potentials in hiPSC-derived AD model neurons. Taken together, β-lactolin improved mitochondrial functions AD-related neuronal cell models and prevented neuronal cell death. The dual function of β-lactolin on both neuron and microglia marks an advantage in maintaining neuronal health.

Effect of Whey-Derived Lactopeptide β-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 β-lactopeptides and their representative β-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 β-lactolin improves memory retrieval in healthy older adults. Specifically, β-lactolin improved the scores in some neuropsychological tests. However, the effects of β-lactolin on memory function have not been clarified.

OBJECTIVES

The aim of this study was to evaluate the effect of β-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 β-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 β-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 β-lactolin improves cued recall in healthy older adults.

Effect of non-alcoholic beer containing matured hop bitter acids on mood states in healthy adults: A single-arm pilot study

This study aimed to investigate the effect of non-alcoholic beer containing matured hop bitter acids on mood states among healthy adults older than 20 years. This study was an open-label longitudinal intervention design in which each participant served as their control. For three weeks, we evaluated the effect of non-alcoholic beer containing 35 mg of matured hop bitter acids on mood, sleep quality, and work performance. The data of 97 participants (age range: 23-72 years, median age: 42) were analyzed. After the intervention, we found that matured hop bitter acids significantly improved total mood state, including anxiety, depression, fatigue, and vigor, compared with the baseline. Furthermore, sleep quality and absolute presenteeism were significantly improved after the intervention compared with the baseline. The present exploratory study suggested that 3-week supplementation with matured hop bitter acids improved mood and peripheral symptoms in persons of a wide range of ages. Although further investigation is needed, the findings suggested that non-alcoholic beer in daily life might become a choice for maintaining mood states. This article is protected by copyright. All rights reserved.

β-Lactolin Reduces Age-Related Inflammation and Cognitive Decline

With the rapid increase in aging populations worldwide, there has been an increase in demand for preventive and therapeutic measures for age-related cognitive decline and dementia. Epidemiological studies show that consumption of dairy products reduces the risk for cognitive decline and dementia in the elderly. We have previously demonstrated in randomized trials that the consumption of β-lactolin, a whey-derived Gly-Thr-Trp-Tyr lactotetrapeptide, improves cognitive function in older adults. Orally administered β-lactolin is delivered to the brain and inhibits monoamine oxidase, resulting in alleviation of memory impairment. However, there is currently no evidence of the effects of long-term β-lactolin intake on aging. Here, we found that the discrimination index in the novel object recognition test for object recognition memory was reduced in mice aged 20 months compared with that in young mice, indicating that age-related cognitive decline was induced in the aged mice; in aged mice fed β-lactolin for 3 months, memory impairment was subsequently alleviated. In aged mice, impairment of light/dark activity cycles was found to be induced, which was subsequently alleviated by β-lactolin consumption. Additionally, the number of activated microglia in the hippocampus and cortex and the production of cytokines (tumor necrosis factor-α, macrophage inflammatory protein-1α, and macrophage chemoattractant protein-1) were increased in aged mice compared with those in young mice but were reduced in aged mice fed β-lactolin. The age-related hippocampal atrophy was improved in aged mice fed β-lactolin. Cytochrome c levels in the hippocampus and cortex were increased in aged mice compared with those in young mice but were also reduced by β-lactolin consumption. These results suggest that β-lactolin consumption prevents neural inflammation and alleviates aging-related cognitive decline.

β-Lactolin Enhances Neural Activity, Indicated by Event-Related P300 Amplitude, in Healthy Adults: A Randomized Controlled Trial

Background:

Epidemiological studies have shown that dairy product consumption is beneficial for cognitive function in elderly individuals. β-lactolin is a Gly–Thr–Trp–Tyr lacto-tetrapeptide rich in fermented dairy products that improves memory retrieval, attention, and executive function in older adults with subjective cognitive decline and prevents the pathology of Alzheimer’s disease in rodents. There has been no study on the effects of β-lactolin on neural activity in humans.

Objective:

We investigated the effects of β-lactolin on neural activity and cognitive function in healthy adults.

Methods:

In this randomized, double-blind, placebo-controlled study, 30 participants (45–64 years old) consumed β-lactolin or placebo for 6 weeks. Neural activity during auditory and language tasks was measured through 64-channel electroencephalography. Moreover, verbal fluency tests were performed at baseline and after 6 weeks.

Results:

The β-lactolin group had a significantly higher P300 amplitude at the Cp2 site (a part of the parietal lobe near the center of brain, p = 0.011), and C4 site (the area between the frontal and parietal lobe, p = 0.02) during the auditory tasks after 6 weeks than the placebo group. Thus, β-lactolin supplementation promoted neural activity in the parietal area, which increases concentration and attention during auditory cognitive tasks. Compared with the placebo group, the β-lactolin group also showed significant changes in the scores of verbal fluency test after 6 weeks (p = 0.033).

Conclusion:

Our findings provide insight into the mechanisms underlying the effects of β-lactolin on attention in healthy adults.

Deposition of Phosphorylated α-Synuclein and Activation of GSK-3β and PP2A in the PS19 Mouse Model of Tauopathy

The simultaneous accumulation of multiple pathological proteins, such as hyperphosphorylated tau (hp-tau) and phosphorylated α-synuclein (p-αSyn), has been reported in the brains of patients with various neurodegenerative diseases. We previously demonstrated that hp-tau-dependent p-αSyn accumulation was associated with the activation of GSK-3β in the brains of P301L tau transgenic mice. To confirm the effects of another mutant tau on p-αSyn accumulation in vivo, we herein examined the brains of PS19 mice that overexpress human P301S mutant tau. Immunohistochemically, hp-tau and p-αSyn aggregates were detected in the same neuronal cells in the cerebrum and brain stem of aged PS19 mice. A semiquantitative analysis showed a positive correlation between hp-tau and p-αSyn accumulation. Furthermore, an activated form of GSK-3β was detected within cells containing both hp-tau and p-αSyn aggregates in PS19 mice. Western blotting showed a decrease in inactivated PP2A levels in PS19 mice. The present results suggest that the overexpression of human P301S mutant tau induces p-αSyn accumulation that is accompanied by not only GSK-3β, but also PP2A activation in PS19 mice, and highlight the synergic effects between tau and αSyn in the pathophysiology of neurodegenerative diseases that show the codeposition of tau and αSyn.

β-Lactolin, a Whey-Derived Gly-Thr-Trp-Tyr Lactopeptide, Promotes Cerebral Blood Flow During Cognitive Tasks: A Randomized Controlled Trial

Objectives

Due to the rapid aging of society, the prevention of age-related cognitive decline and dementia has gained increasing attention. Recent epidemiological investigations have shown that the consumption of dairy products reduces the risk of dementia in older adults. β-lactolin, a whey-derived Gly-Thr-Trp-Tyr lactopeptide, activates the dopaminergic system, improves memory impairment, and prevents Alzheimer's pathologies in a rodent model. We have demonstrated that β-lactolin supplementation improves memory retrieval and selective attention in randomized trials. On the other hand, the mechanisms underlying the effects of β-lactolin on human brain activity have not been investigated.

Methods

We examined the effects of β-lactolin on cerebral blood flow (CBF) using near-infrared spectroscopy (NIRS) in a placebo-controlled randomized double-blind study. Fifty healthy participants (45–60 years old) were randomly allocated to the β-lactolin and placebo groups and supplemented for 6 weeks. At 0 and 6 weeks of the intervention, oxyhemoglobin (Hb) was measured using 34-channel (CH) NIRS during the working memory tasks.

Results

The changes in oxy-Hb in CH23 located at the left dorsolateral prefrontal cortex (DLPFC) during the spatial working memory task showed a higher statistical significance (false discovery rate (q) = 0.045) in the β-lactolin than in the placebo group. The CBF changes in CH23 were correlated with the reaction time for the working memory task. A recent trial using a 2-CH NIRS also showed a significant CBF increase in the DLPFC area after β-lactolin supplementation.

Conclusions

β-lactolin supplementation increases CBF in the DLPFC area, which contributes to improved cognitive functions.

Funding Sources

Current study was funded by Kirin Holdings Co. Ltd.

Amyloid β-induced Mesenteric Inflammation in an Alzheimer's Disease Transgenic Mouse Model

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder histopathologically characterized by the accumulation of amyloid β (Aβ) peptides and inflammation associated with activated microglia. These features are well investigated in the central nervous system using AD-model mice; however, peripheral inflammation in these mice has not been investigated well.

OBJECTIVE

We evaluated the inflammatory responses, especially myeloid dendritic cells (mDCs), in peripheral lymphoid tissues in AD-model mice to determine their association with Aβ deposition.

METHODS

We collected lymphocytes from mesenteric lymphoid nodes (MLNs) and Peyer's patches (PPs) of 5×FAD transgenic mice used as an AD model. Lymphocytes were analyzed using a flow cytometer to characterize mDCs and T cells. Collected lymphocytes were treated with Aβ1-42 ex vivo to evaluate the inflammatory response.

RESULTS

We observed elevated levels of inflammatory cytokines and chemokines including interleukin (IL)-12 and macrophage inflammatory protein-1α in mDCs from MLNs and PPs and reduced levels of programmed death-ligand-1, an immunosuppressive co-stimulatory molecule, on the surface of mDCs from 5×FAD mice. Additionally, we found increases in interferon (IFN)-γ-producing CD4- or CD8- positive T cells in MLNs were increased in 5×FAD mice. Moreover, ex vivo treatment with Aβ peptides increased the production of IL-12 and IFN-γ by lymphocytes from 5×FAD mice.

CONCLUSION

The present study showed that pro-inflammatory mDC and T cells were induced in MLNs and PPs of 5×FAD mice.

Supplementation with Matured Hop Bitter Acids Improves Cognitive Performance and Mood State in Healthy Older Adults with Subjective Cognitive Decline

BACKGROUND

Prevention of age-related cognitive decline and depression is becoming urgent because of rapid growing aging populations. Effects of vagal nerve activation on brain function by food ingredients are inadequately investigated; matured hop bitter acid (MHBA) administration reportedly improves cognitive function and depression via vagal nerve activation in model mice.

OBJECTIVE

We investigated the effects of MHBA supplementation on cognitive function and mood state in healthy older adults with perceived subjective cognitive decline.

METHODS

Using a randomized double-blind placebo-controlled trial design, 100 subjects (aged 45-69 years) were randomly assigned into placebo (n = 50) and MHBA (n = 50) groups, and received placebo or MHBA capsules daily for 12 weeks.

RESULTS

Symbol Digit Modalities Test (SDMT) score assessing divided attention at week 12 was significantly higher (p = 0.045) and β-endorphin at week 12 was significantly lower (p = 0.043) in the subjects receiving MHBA. Transthyretin in serum, a putative mild cognitive impairment marker, was significantly higher at week 12 in the MHBA group than in the placebo group (p = 0.048). Subgroup analysis classified by the subjective cognitive decline questionnaire revealed that in addition to improved SDMT scores, memory retrieval assessed using the standard verbal paired-associate learning tests and the Ray Verbal Learning Test at week 12 had significantly improved in the subgroup with perceived subjective cognitive decline and without requirement for medical assistance in the MHBA group compared with that in the placebo group.

CONCLUSION

This study suggested that MHBA intake improves cognitive function, attention, and mood state in older adults.

β-Lactolin, a Whey-Derived Lacto-Tetrapeptide, Prevents Alzheimer's Disease Pathologies and Cognitive Decline

 The prevention of age-related memory decline and dementia has been becoming a high priority because of the rapid growth in aging populations. Accumulating epidemiological and clinical studies indicate that intake of fermented dairy products rich in β-lactolin improves memory retrieval and executive function and attenuates cognitive decline in the elderly. However, the effects of long-term consumption of β-lactolin on Alzheimer’s disease (AD) pathologies have not been investigated. In the present study, we examined the effects of β-lactolin and whey digestion rich in β-lactolin on AD pathology in 5×FAD transgenic mice and PS19 tauopathy mice. Intake of β-lactolin and whey digestion rich in β-lactolin reduced the levels of inflammatory cytokines, suppressed the infiltration of activated microglia, decreased the levels of amyloid-β, ameliorated impaired long-term object memory, and attenuated decreased synaptophysin, dopamine, brain-derived neurotrophic factor, and insulin-like growth factor 1 levels in the cortex in 5×FAD transgenic mice. In addition, intake of β-lactolin and whey digestion rich in β-lactolin improved behavioral abnormality and reduced the ratio of phosphorylated tau to total tau in the cortex in PS19 tauopathy mice. These findings indicate that consumption with β-lactolin and whey digestion rich in β-lactolin suppresses inflammation and attenuates AD pathology and cognitive impairment.

Effects of β-Lactolin on Regional Cerebral Blood Flow within the Dorsolateral Prefrontal Cortex during Working Memory Task in Healthy Adults: A Randomized Controlled Trial

Epidemiological studies have reported that consumption of dairy products rich in β-lactolin is beneficial for cognitive decline among elderly individuals. Although previous studies have shown that β-lactolin supplementation improves memory function and attention in healthy adults, the mechanism through which β-lactolin affects human brain function has yet to be elucidated. This placebo-controlled randomized double-blind study therefore examined the effects of β-lactolin on human regional cerebral blood flow (rCBF) using near-infrared spectroscopy (NIRS) according to the Consolidated Standards of Reporting Trials guidelines. A total of 114 healthy participants aged between 50 and 75 years with relatively low cognition were randomly allocated into the β-lactolin or placebo groups (n = 57 for both groups) and received supplementation for 6 weeks. After the 6 weeks of supplementation, total hemoglobin during cognitive tasks (Kraepelin and 2-back tasks) was measured using two-channel NIRS to determine rCBF. Accordingly, the β-lactolin group had significantly higher changes in total hemoglobin at the left dorsolateral prefrontal cortex (DLPFC) area measured using the left-side channel during the 2-back tasks (p = 0.027) compared to the placebo group. The present study suggests that β-lactolin supplementation increases rCBF and DLPFC activity during working memory tasks.

Hop bitter acids containing a β-carbonyl moiety prevent inflammation-induced cognitive decline via the vagus nerve and noradrenergic system

The prevention of age-related cognitive decline and dementia is becoming a high priority because of the rapid growth of aging populations. We have previously shown that hop bitter acids such as iso-α-acids (IAAs) and matured hop bitter acids (MHBAs) activate the vagus nerve and improve memory impairment. Moreover, supplements with MHBAs were shown to improve memory retrieval in older adults. However, the underlying mechanisms have not been entirely elucidated. We aimed to investigate the effects of MHBAs and the common β-tricarbonyl moiety on memory impairment induced by the activation of microglia and the loss of the noradrenergic system. MHBAs and a model compound with β-tricarbonyl moiety were administered to LPS-inoculated mice and 5 × FAD Alzheimer’s disease (AD) model mice, following the evaluation in behavioral tests and microglial activation. To evaluate the association of noradrenaline with MHBAs effects, mice treated with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), a noradrenergic neurotoxin that selectively damages noradrenergic projections from the locus coeruleus, were subjected to the behavioral evaluation. MHBAs reduced brain inflammation and improved LPS-induced memory impairment. A model compound possessing the β-tricarbonyl moiety improved the LPS-induced memory impairment and neuronal loss via the vagus nerve. Additionally, the protective effects of MHBAs on memory impairment were attenuated by noradrenaline depletion using DSP-4. MHBAs suppressed the activation of microglia and improved the memory impairment in 5 × FAD mice, which was also attenuated by noradrenaline depletion. Treatment with MHBAs increased cholecystokinin production from the intestinal cells. Generally, cholecystokinin activates the vagal nerve, which stimulate the noradrenergic neuron in the locus ceruleus. Taken together, our results reveal that food ingredients such as hop bitter acids with a β-tricarbonyl moiety suppress microglial activation and improve memory impairment induced by inflammation or AD pathology via the activation of the gut-brain axis and noradrenergic system. Supplements with hop bitter acids, including MHBAs, might be a novel approach for the prevention of cognitive decline and dementia.

β-lactolin increases cerebral blood flow in dorsolateral prefrontal cortex in healthy adults: a randomized controlled trial

The number of elderly individuals with age-related cognitive decline or dementia is rapidly increasing. Dairy product consumption, including β-lactolin, is beneficial for their cognitive function. The underlying mechanism of β-lactolin's effects on human brain activity is yet to be investigated. We examined the β-lactolin effects on human cerebral blood flow (CBF) using near-infrared spectroscopy (NIRS) in a placebo-controlled randomized double-blind study, which reported according to the CONSORT guidelines. Fifty healthy participants (aged 45-60 years) were randomly allocated into the β-lactolin or the placebo group (n = 25 each) and supplemented for 6 weeks. During the 6^th week, oxy-hemoglobin during the working memory tasks was measured using 34-channels (CHs) NIRS. The changes of oxy-hemoglobin, which represents the CBF, in CH 23 located at the left dorsolateral prefrontal cortex (DLPFC) during the spatial working memory task showed higher statistical significance (false discovery rate (q) = 0.045) in the β-lactolin than in the placebo group. The oxy-Hb changes in CH23 have a co-relationship with the working memory task reaction time. This clinical trial showed an increase in the CBF in the left DLPFC area during the 6-week β-lactolin supplementation. This study contributes to elucidating the underlying mechanisms of β-lactolin on cognitive performance.

Phosphorylation and oligomerization of α-synuclein associated with GSK-3β activation in the rTg4510 mouse model of tauopathy

Neurodegenerative diseases are characterized by the accumulation of specific phosphorylated protein aggregates in the brain, such as hyperphosphorylated tau (hp-tau) in tauopathies and phosphorylated α-synuclein (p-αSyn) in α-synucleinopathies. The simultaneous accumulation of different proteins is a common event in many neurodegenerative diseases. We herein describe the detection of the phosphorylation and dimerization of αSyn and activation of GSK-3β, a major kinase known to phosphorylate tau and αSyn, in the brains of rTg4510 mice that overexpress human P301L mutant tau. Immunohistochemistry showed p-αSyn aggregates in rTg4510 mice, which were suppressed by doxycycline-mediated decreases in mutant tau expression levels. A semi-quantitative analysis revealed a regional correlation between hp-tau and p-αSyn accumulation in rTg4510 mice. Furthermore, proteinase K-resistant αSyn aggregates were found in the region with excessive hp-tau accumulation in rTg4510 mice, and these aggregates were morphologically different from proteinase K-susceptible p-αSyn aggregates. Western blotting revealed decreases in p-αSyn monomers in TBS- and sarkosyl-soluble fractions and increases in ubiquitinated p-αSyn dimers in sarkosyl-soluble and insoluble fractions in rTg4510 mice. Furthermore, an activated form of GSK-3β was immunohistochemically detected within cells containing both hp-tau and p-αSyn aggregates. A semi-quantitative analysis revealed that increased GSK-3β activity strongly correlated with hp-tau and p-αSyn accumulation in rTg4510 mice. Collectively, the present results suggest that the overexpression of human P301L mutant tau promoted the phosphorylation and dimerization of endogenous αSyn by activating GSK-3β in rTg4510 mice. This synergic effect between tau, αSyn, and GSK-3β may be involved in the pathophysiology of several neurodegenerative diseases that show the accumulation of both tau and αSyn.

Improving Effects of Hop-Derived Bitter Acids in Beer on Cognitive Functions: A New Strategy for Vagus Nerve Stimulation

Dementia and cognitive decline are global public health problems. Moderate consumption of alcoholic beverages reduces the risk of dementia and cognitive decline. For instance, resveratrol, a polyphenolic compound found in red wine, has been well studied and reported to prevent dementia and cognitive decline. However, the effects of specific beer constituents on cognitive function have not been investigated in as much detail. In the present review, we discuss the latest reports on the effects and underlying mechanisms of hop-derived bitter acids found in beer. Iso-α-acids (IAAs), the main bitter components of beer, enhance hippocampus-dependent memory and prefrontal cortex-associated cognitive function via dopamine neurotransmission activation. Matured hop bitter acids (MHBAs), oxidized components with β-carbonyl moieties derived from aged hops, also enhance memory functions via norepinephrine neurotransmission-mediated mechanisms. Furthermore, the effects of both IAAs and MHBAs are attenuated by vagotomy, suggesting that these bitter acids enhance cognitive function via vagus nerve stimulation. Moreover, supplementation with IAAs attenuates neuroinflammation and cognitive impairments in various rodent models of neurodegeneration including Alzheimer's disease. Daily supplementation with hop-derived bitter acids (e.g., 35 mg/day of MHBAs) may be a safe and effective strategy to stimulate the vagus nerve and thus enhance cognitive function.

β-lactolin, a whey-derived glycine-threonine-tryptophan-tyrosine lactotetrapeptide, improves prefrontal cortex-associated reversal learning in mice

Dementia and cognitive decline have become worldwide public health problems. We have previously reported that a whey-derived glycine-threonine-tryptophan-tyrosine peptide, β-lactolin, improves hippocampus-dependent memory functions in mice. The supplementation with a whey digest rich in β-lactolin improves memory retrieval and executive function in a clinical trial, but the effect of β-lactolin on prefrontal cortex (PFC)-associated cognitive function was unclear. Here we examined the effect of β-lactolin and the whey digest on PFC-associated visual discrimination (VD) and reversal discrimination (RD) learning, using a rodent touch panel-based operant system. β-Lactolin and the whey digest significantly improved the RD learning, and the whey digest enhanced the response latency during the VD task, indicating that β-lactolin and the whey digest improve PFC-associated cognitive functions. Given the translational advantages of the touch panel operant system, consumption of β-lactolin in daily life could be beneficial for improving human PFC-associated cognitive function, helping to prevent dementia.

Effects of Hop Bitter Acids, Bitter Components in Beer, on Cognition in Healthy Adults: A Randomized Controlled Trial

The present study aimed to investigate the effects of matured hop bitter acids (MHBAs) on human cognition, mental fatigue, and mood state. In this randomized double-blind placebo-controlled study, 60 healthy adults (age 45-64 years) with self-awareness of cognitive decline were randomly divided into 2 groups and received either orally administered MHBAs (35 mg/day) or placebo for 12 weeks. Cognitive functions and mental states were assessed using neuropsychological tests or questionnaires at baseline and weeks 6 and 12 of the intervention. The change in verbal fluency score at week 6 compared with that at baseline was significantly higher in the MHBAs-treated group compared with that in the placebo group (P = 0.034), and Stroop test score at week 12 was significantly lower in the MHBAs-treated group compared with the placebo group (P = 0.019). Furthermore, subjective fatigue and anxiety at week 12 were significantly improved in the MHBAs-treated group (P = 0.008 and 0.043, respectively) compared with the placebo group. This is the first study to evaluate the effects of bitter ingredients in beer on cognition, subjective mood, and mental fatigue in a clinical trial. Our findings suggest that hop-derived bitter acids might be beneficial for cognition and mood state.

Antidepressant-Like Effect of β-Lactolin, a Glycine-Threonine-Tryptophan-Tyrosine Peptide

The number of patients with mental illnesses, including depression, is rapidly increasing, and daily lifestyle is closely associated with the development of symptoms. Consequently, corrective measures, such as diet-based treatment for diseases, are receiving great attention. We previously showed that β-lactolin, a β-lactopeptide of glycine-threonine-tryptophan-tyrosine peptide, inhibits monoamine oxidase and improves memory impairment in mice, but the effects on depression have not been investigated. Here we showed that β-lactolin improved depression-like behavior via dopamine-D1-like receptor. Orally administered β-lactolin reduced immobility time in tail suspension test (TST). Pretreatment with SCH23390, dopamine D1-like receptor antagonist, attenuated the reduction in TST by β-lactolin. These effects were observed by the treatment with whey digest rich in β-lactolin. In addition, β-lactolin increased the levels of dopamine in the frontal cortex associated with the depression-like behavior. The present study suggests that supplements or nutraceutical compounds in whey digests (such as β-lactolin) show antidepressant-like effect.

The Lacto-Tetrapeptide Gly-Thr-Trp-Tyr, β-Lactolin, Improves Spatial Memory Functions via Dopamine Release and D1 Receptor Activation in the Hippocampus

Scope: Peptides containing tryptophan–tyrosine sequences, including the lacto-tetrapeptide glycine–threonine–tryptophan–tyrosine (GTWY) and β-lactolin, from β-lactoglobulin in whey enzymatic digestion, enhance hippocampus-dependent memory functions, which are blocked by the systemic administration of dopamine D1-like antagonist. In this study, we investigated the role of the hippocampal dopaminergic system in the memory-enhancing effect of β-lactolin. Methods and Results: The results of in vivo microdialysis revealed that oral administration of β-lactolin increased the extracellular concentration of dopamine in the hippocampus and enhanced both spatial working memory, as measured in the Y-maze test, and spatial reference memory, as measured in the novel object location test. These memory-enhancing effects of β-lactolin, but not the baseline memory functions, were impaired by the knockdown of the dopamine D1 receptor subtype in the hippocampus. β-Lactolin also enhanced object memory, as measured by the novel object recognition test. However, D1 knockdown in the hippocampus spared this memory function either with or without the administration of β-lactolin. Conclusions: The present results indicate that oral administration of β-lactolin increases dopamine release and D1 receptor signaling in the hippocampus, thereby enhancing spatial memory, but it may improve object memory via a separate mechanism.

Effects of iso-α-acids, the hop-derived bitter components in beer, on the MRI-based Brain Healthcare Quotient in healthy middle-aged to older adults

Aim

Neurological disorders are a major public health issue worldwide and are often associated with structural changes in the brain. We have previously demonstrated that iso‐α‐acids (IAAs), the hop‐derived bitter components in beer, improve memory impairment in aged and Alzheimer's disease mouse models. In this study, we evaluated the effects of IAA intake on the brain structure in healthy middle‐aged to older adults. This study was conducted under the Impulsing Paradigm Change through Disruptive Technologies Program (ImPACT) study launched by the Cabinet office of Japan.

Method

This study employed an open‐labeled, single‐arm, before and after design. Healthy middle‐aged to older adults consumed a beverage containing IAAs (3 mg/190 mL) for 4 weeks.Recently developed magnetic resonance imaging‐based brain health indicators were used to evaluate the following brain conditions: the Brain Healthcare Quotient (BHQ) based on gray matter volume (GM‐BHQ) and white matter fractional anisotropy (FA‐BHQ).

Results

In total, 25 subjects were recruited, and GM‐BHQ and FA‐BHQ were measured before and after intervention. In all subjects, no significant differences in GM‐BHQ and FA‐BHQ were observed. In subjects aged ≥ 60 years (mean 54.5; standard deviation 3.9) (n = 8), GM‐BHQ was significantly increased 4 weeks after intervention compared with that before intervention.

Conclusion

Intake of beverages containing IAAs might affect brain aging, particularly in healthy older adults, which may prevent the development of neurological disorders. Future studies employing more robust designs can elucidate the effects of IAAs on GM‐BHQ and cognitive functions.

This is the first clinical trial evaluating the effects of intake of bitter component of beer, iso‐alpha‐acid, on brain structure. The brain structure before and after intervention was measured by recently developed magnetic resonance imaging‐based method. The gray matter volume of older adults was improved by the intake of iso‐alpha‐acid.

Iso-α-acids and matured hop bitter acids in beer improve obesity-induced cognitive impairment

Dementia and cognitive decline have become public health issues worldwide and life-style-related diseases and obesity have recently been reported as key risk factors. We have recently demonstrated that short-term administration of iso-α-acids (IAAs), hop-derived bitter components of beer, improves spatial and object recognition memory. However, the short-term effects of IAAs on obesity-induced cognitive impairment remain to be investigated. Furthermore, although matured hop bitter acids (MHBAs) are also derived from hops, their effect on obesity-induced cognitive decline remains unknown. In the present study, the short-term administration of IAAs improved memory deficits in high-fat diet (HFD)-fed mice, as assessed in the novel object recognition test (NORT). Dietary MHBAs supplementation administered to HFD-fed mice prevented obesity and improved memory deficits in the NORT. Moreover, the short-term administration of MHBAs improved episodic and spatial reference memory in obese mice. These hop-derived bitter acids may contribute toward improving obesity-induced cognitive impairments.

Abbreviations: IAAs: iso-α-acids; MHBAs: matured hop bitter acids; HFD: high fat diet; NORT: novel object recognition test; NOLT: novel object location test

Leucine-Histidine Dipeptide Attenuates Microglial Activation and Emotional Disturbances Induced by Brain Inflammation and Repeated Social Defeat Stress

The number of patients with mental illnesses is rapidly increasing, and daily lifestyle is closely associated with the development of symptoms. It is suggested that inflammatory molecules derived from microglia play crucial roles for the pathophysiology of depression. In the present study, we discovered that leucine–histidine (LH) dipeptide suppressed activation of primary microglia. The effects of LH dipeptide orally administered were measured using tail suspension test (TST) in mice injected with lipopolysaccharide and social interaction test in mice received social defeat stress. LH dipeptide reduced pro-inflammatory cytokines upon stimulation in microglia. Orally administered LH dipeptide was delivered to the brain and suppressed the production of pro-inflammatory cytokines in the brain and concomitant depression-like behavior in the TST. Moreover, oral administration of LH dipeptide suppressed the induction of depression- and anxiety-like behaviors induced by repeated social defeat stress. These results indicate that LH dipeptide suppressed the activation of microglia and ameliorated depression-associated emotional disturbances. Further, we found that LH dipeptide was abundant in various fermented products. Together with previous epidemiological reports that daily intake of these fermented foods is negatively associated with the incidence of psychiatric diseases, our findings suggest that food rich in LH dipeptide may improve mental health.

Effect of Microglial Inflammation in Prion Disease

Prion diseases are a group of transmissible fatal neurodegenerative disorders. Neuropatho- logical features of prion diseases include neuroinflammation featuring the infiltration of activated microglia in affected brain areas as well as the accumulation of an abnormal isoform of the cellular prion protein and neuronal loss. Recent studies have elucidated that inflammation in the brain induced by microglia plays an important role in the pathogenesis of neurodegenerative disorders including prion disease. Thus, the regulation of neuroin- flammation is key in terms of therapeutic and preventative approaches. The functions of neuroinflammation and microglia in this disease are discussed in this article.

Matured hop bitter acids improve spatial working and object recognition memory via nicotinic acetylcholine receptors

RATIONALE

Cognitive decline and dementia are major concerns in today's aging society. As limited treatments are available, measures to prevent cognitive decline and dementia are needed. We previously demonstrated that matured hop bitter acids (MHBA), bitter components of beer, increase norepinephrine in the hippocampus and improve memory in amnesia model mice induced by scopolamine (SCP), an antagonist of muscarinic receptor. However, other neurotransmitters involved in the effects of MHBA on memory improvement remain unknown.

OBJECTIVES

This study aimed to assess the role of acetylcholine receptors (AChR) in the effects of MHBA on memory.

METHOD

The involvement of AChR on the effects of MHBA (10 mg/kg) on cognitive function was evaluated using AChR antagonists, SCP, mecamylamine hydrochloride (MEC), a non-competitive antagonist of nicotinic-AChR (nAChR), and methyllycaconitine citrate (MLA), an α7nAChR antagonist, for the Y-maze test and the novel object recognition test (NORT). A separate population of mice, which underwent vagotomy or sham operation, was subjected to NORT to elucidate further mechanism. In addition, the effect of MHBA on acetylcholinesterase (AChE) activity was measured in vitro.

RESULTS

In accordance with previous reports, MHBA improved spontaneous alternations of the Y-maze test in SCP-induced amnesia mice and increased discrimination index evaluated by the NORT in normal mice. On the other hand, treatment with MEC or MLA attenuated the effects of MHBA on memory improvement in the Y-maze test and the NORT. Vagotomized mice also showed attenuated memory enhancement by MHBA in the NORT. In addition, MHBA did not alter AChE activity in vitro.

CONCLUSIONS

The results support the involvement of nAChRs in memory improvement in mice by MHBA. MHBA is thus thought to activate the vagal nerve and enhance hippocampus-dependent memory via nAChRs.

Identification of a Novel Peptide from β-Casein That Enhances Spatial and Object Recognition Memory in Mice

An increase in the aging population has spurred recent efforts to identify diet and lifestyle changes that help prevent cognitive decline. Several epidemiological investigations and clinical studies have indicated that consuming fermented dairy products prevents cognitive decline. Some peptides from whey including β-lactolin improve memory impairment; the intake of Camembert cheese has been shown to prevent Alzheimer's in mouse models. To elucidate the molecular mechanisms underlying these preventive effects, we screened peptides from digested casein protein for their ability to improve spatial memory in a scopolamine-induced amnesia mouse model. Administration of KEMPFPKYPVEP peptide from β-casein at 0.5 mg/kg (54.8 ± 2.5) and 2 mg/kg (57.9 ± 3.7) improved memory impairment in the amnesia mice in comparison with control (44.9 ± 3.4; p = 0.031 and p = 0.042, respectively) and increased dopamine (5.9 ± 3.8 [control] and 12.4 ± 6.2 [KEMPFPKYPVEP peptide]) and norepinephrine (7.7 ± 0.8 [control] and 9.9 ± 2.0 [KEMPFPKYPVEP peptide]) levels in the frontal cortex (p = 0.039 and p = 0.031, respectively). Collectively, our findings suggest that peptides in fermented dairy products prevent cognitive decline and support previously reported observations.

Preventive Effects of Tryptophan-Methionine Dipeptide on Neural Inflammation and Alzheimer's Pathology

Preventive approaches for age-related memory decline and dementia have become a high priority in the aging society because of the lack of therapeutic approaches. Recent epidemiological studies have reported that fermented dairy products can help prevent dementia. Previously, we identified tryptophan-tyrosine (WY) and tryptophan-methionine (WM) peptides as the suppressants of activation of the primary microglia and showed that WY peptide consumption suppresses inflammation in the brains of Alzheimer's disease model mice. However, the effects of the WM peptide on inflammation in the brain and Alzheimer's pathology have not been investigated. Here, we evaluated the effect of WM peptide consumption on Alzheimer's disease model (5×FAD) mice. In 5×FAD mice, intake of WM peptide suppressed the production of inflammatory cytokines, activation of microglia, and infiltration of activated microglia around β amyloid (Aβ) depositions. WM peptide intake reduced Aβ deposition in the cortex and hippocampus and then improved the object recognition memory. Taken together with previous reports, the current findings indicate that ingestion of tryptophan-related peptides or food material rich in tryptophan-related peptides, thereby regulating microglial activity, represents a potential preventive approach for cognitive decline and dementia related to inflammation.

Tryptophan-related dipeptides in fermented dairy products suppress microglial activation and prevent cognitive decline

The rapid growth in aging populations has made prevention of age-related memory decline and dementia a high priority. Several epidemiological and clinical studies have concluded that fermented dairy products can help prevent cognitive decline; furthermore, intake of Camembert cheese prevents microglial inflammation and Alzheimer's pathology in mouse models. To elucidate the molecular mechanisms underlying the preventive effects of fermented dairy products, we screened peptides from digested milk protein for their potential to regulate the activation of microglia. We identified dipeptides of tryptophan-tyrosine (WY) and tryptophan-methionine that suppressed the microglial inflammatory response and enhanced the phagocytosis of amyloid-β (Aβ). Various fermented dairy products and food materials contain the WY peptide. Orally administered WY peptide was smoothly absorbed into blood, delivered to the brain, and improved the cognitive decline induced by lipopolysaccharide via the suppression of inflammation. Intake of the WY peptide prevented microglial inflammation, hippocampal long-term potential deficit, and memory impairment in aged mice. In an Alzheimer's model using 5×FAD mice, intake of the WY peptide also suppressed microglial inflammation and accumulation of Aβ, which improved cognitive decline. The identified dipeptides regulating microglial activity could potentially be used to prevent cognitive decline and dementia related to inflammation.

Supplementation With Whey Peptide Rich in β-Lactolin Improves Cognitive Performance in Healthy Older Adults: A Randomized, Double-Blind, Placebo-Controlled Study

Epidemiological reports showed that consumptions of fermented dairy products are beneficial for cognitive decline in elderly. Our previous preclinical studies have demonstrated that intakes of whey peptide rich in the β-lactolin [β-lactopeptide of glycine-thereonine-tryptophan-tyrosine (GTWY)] improve memory and attention by regulating monoamine system, and clinical study using neuropsychological test suggested that consumptions with GTWY-rich whey peptide enhance cognitive performance associated with the frontal cortex activity. However, corresponding interventional studies in humans are limited. Objectives: to evaluate the effects of the whey peptide on cognitive functions in healthy older adults using a randomized, double-blinded, placebo-controlled trial design. 114 healthy subjects aged 50–75 were supplemented with the whey peptide or placebo for 12 weeks, and changes in cognitive function were assessed using neuropsychological tests at weeks 0, 6, and 12 of the intervention. Neuropsychological tests included assessments for memory functions (subtests from Wechsler memory scale-revised, standard verbal paired-associate learning test, and recognition memory test for faces), assessments for attention (cancelation and detection tests), and assessments for general cognitive functions (repeatable battery for assessments of neuropsychological status). Cerebral blood flow was also assessed using near-infrared spectroscopy (NIRS) after 6 weeks of intervention. This study was registered on the 19 November, 2017 in the database of the University Hospital Medical Information Network (UMIN) prior to enrollment of subjects (Registration No. UMIN000030461: https://www.umin.ac.jp/ctr/index-j.htm). In the whey peptide group, visual paired-associates I and visual cancelation tests were significantly improved compared with those in the placebo group at weeks 6 and 12 of the intervention, respectively. Visuospatial and constructional scores of the repeatable battery for assessments of neuropsychological status and standard verbal paired-associate learning tests (S-PA) also tended to be improved by the intervention at week 12. Daily intakes of GTWY-rich whey peptide show beneficial effects on cognitive performance, especially associative learning memory and control of attention, in healthy older adults and might prevent age-related cognitive declines.

Hop-Derived Iso-α-Acids in Beer Improve Visual Discrimination and Reversal Learning in Mice as Assessed by a Touch Panel Operant System

Dementia and cognitive decline have become worldwide health problems due to rapid growth of the aged population in many countries. We previously demonstrated that single or short-term administration of iso-α-acids, hop-derived bitter acids in beer, improves the spatial memory of scopolamine-induced amnesia model mice in the Y-maze and enhances novel object recognition in normal mice via activation of the vagus nerve and hippocampal dopaminergic system. However, these behavioral tests do not replicate the stimulus conditions or response requirements of human memory tests, and so may have poor translational validity. In this report, we investigated the effects of iso-α-acids on visual discrimination (VD) and reversal discrimination (RD) using a touch panel-based operant system similar to that used for human working memory tests. In the VD task, scopolamine treatment reduced correct response rate and prolonged response latency in mice, deficits reversed by prior oral administration of iso-α-acids. In the RD task, administration of iso-α-acids significantly increased correct response rate compared to vehicle administration. Previous studies have reported that dopamine signaling is involved in both VD and RD learning, suggesting that enhancement of dopamine release contributes to improved memory performance in mice treated with iso-α-acids. Taken together, iso-α-acids improve VD and RD learning, which are considered high-order cognitive functions. Given the translational advantages of the touch panel-based operant system, the present study suggests that iso-α-acids could be effective for improvement of working memory in human dementia patients.

Identification of P2Y receptors involved in oleamide-suppressing inflammatory responses in murine microglia and human dendritic cells

Microglia, a type of immune cell in the central nervous system, are involved in inflammation leading to neurodegenerative diseases. We previously identified oleamide from fermented dairy products as a neuroprotective compound suppressing microglial inflammation. Oleamide is an endocannabinoid and displays anti-inflammatory activity via the cannabinoid-2 (CB2) receptor; however, the mechanism underlying this anti-inflammatory activity has not been fully elucidated. Here, we found that the suppressive effect of oleamide on microglial tumor necrosis factor-α (TNF-α) production was canceled by inhibitors of G-protein-coupled receptor (GPCR) downstream signaling but not by a CB2 antagonist, suggesting that GPCRs other than CB2 are involved in the anti-inflammatory effects of oleamide. An extensive screen for GPCRs using a transforming growth factor-α shedding assay system identified P2Y1, P2Y4, P2Y6, P2Y10, and P2Y11 as candidates for the oleamide target. P2Y1 and P2Y10 agonists suppressed microglial TNF-α production, while a pan P2 receptor antagonist canceled the suppressive effect. Furthermore, we observed a relationship between the P2Y1 agonistic activities and the suppressive activities of oleamide and its analogs. Taken together, our results suggest that, in addition to CB2, P2Y type receptors are the potential targets of oleamide, and P2Y1 plays a role in the suppression of microglial inflammatory responses by oleamide. (200/200 words)

Anxiolytic effects of theaflavins via dopaminergic activation in the frontal cortex

Epidemiological investigations have reported that the habit of drinking tea reduces the risk of developing a mental disorder, including anxiety disorder and depression. Theaflavins, black tea polyphenols, show antibacterial and anti-oxidative effects, but their effects on brain function, especially mental condition, have not been elucidated. The present study demonstrated that theaflavins increased dopamine (DA) turnover in the frontal cortex and showed an anxiolytic effect in mice. Theaflavin consumption increased the time spent by mice in the open arms of an elevated plus maze test. Theaflavin administration increased the levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and the ratios of DOPAC/DA and (DOPAC+homovanillic acids)/DA indicating DA turnover, in the frontal cortex. These results suggest that the consumption of theaflavins induced anxiolytic effects via activation of the dopaminergic system in the frontal cortex, which support the findings of previous epidemiological studies. Theaflavins in black tea may be helpful to reduce anxiety in daily life. (150/150 words).

Iso-α-Acids, Bitter Components in Beer, Suppress Inflammatory Responses and Attenuate Neural Hyperactivation in the Hippocampus

Due to the growth in aging populations worldwide, prevention and therapy for age-related cognitive decline and dementia are in great demand. We previously demonstrated that long-term intake of iso-α-acids, which are hop-derived bitter compounds found in beer, prevent Alzheimer’s pathology in a rodent model. On the other hand, the effects of iso-α-acids on neural activity in Alzheimer’s disease model mice have not been investigated. Here, we demonstrated that short-term intake of iso-α-acids suppresses inflammation in the hippocampus and improves memory impairment even after disease onset. Importantly, we demonstrated that short-term administration of iso-α-acids attenuated the neural hyperactivation in hippocampus. In 6-month-old 5 × FAD mice exhibiting hippocampus inflammation and memory impairment, oral administration of iso-α-acids for 7 days reduced inflammatory cytokines, including MIP-1α and soluble Aβ and improved object memory in the novel object recognition test. In 12-month-old J20 mice, intake of iso-α-acids for 7 days also suppressed inflammatory cytokines and soluble Aβ in the brain. Manganese-enhanced magnetic resonance imaging (MEMRI) of hippocampi of J20 mice showed increased manganese compared with wild type mice, but iso-α-acids canceled this increased MEMRI signal in J20 mice, particularly in the hippocampus CA1 and CA3 region. Taken together, these findings suggest that short-term intake of iso-α-acids can suppress hippocampus inflammation even after disease onset and improve hyper neural activity in Alzheimer’s disease model mice.

Iso-α-acids, Hop-Derived Bitter Components of Beer, Attenuate Age-Related Inflammation and Cognitive Decline

With the aging population rapidly increasing worldwide, preventive measures and treatments for age-related cognitive decline and dementia are of utmost importance. We have previously demonstrated that the consumption of iso-α-acids (IAA), which are hop-derived bitter compounds in beer, prevents the formation of disease pathology in a transgenic mouse model of Alzheimer’s disease (AD). However, the effect of IAA consumption on age-related cognitive decline is unknown. In the present study, we examined the effect of long-term and short-term dietary consumption of IAA, on age-related memory impairments and inflammation in the hippocampus of aged mice. When compared with young mice, aged mice showed impairment in spatial working memory during the Y-maze spontaneous alternation test, impairment in object recognition memory during the novel object recognition test (NORT), a pro-inflammatory hippocampal microglial phenotype with increased CD86 expression and inflammatory cytokine production, increased levels of glutamate and amyloid β_1–42, and decreased levels of dopamine (DA). In aged mice fed IAA for 3 months, the age-related alterations in memory, microglial inflammation, and glutamate, amyloid β_1–42, and DA levels were all significantly attenuated. Additionally, the oral administration of IAA for 7 days in aged mice with memory impairment, also improved spatial and object recognition memory. These results suggest that IAA consumption prevents inflammation in the hippocampus and ameliorates age-related cognitive decline.

Matured Hop Bitter Acids in Beer Improve Lipopolysaccharide-Induced Depression-Like Behavior

Recent studies have demonstrated a close association between neural inflammation and development of mental illnesses, such as depression. Clinical trials have reported that treatment with non-steroidal anti-inflammatory drugs is associated with reduced risk of depression. Moreover, nutritional approaches for the prevention and management of depression have garnered significant attention in recent years. We have previously demonstrated that iso-α-acids (IAAs)—the bitter components in beer—suppress hippocampal microglial inflammation, thereby improving cognitive decline. However, effects of hop-derived components other than IAAs on inflammation have not been elucidated. In the present study, we demonstrated that consumption of matured hop bitter acids (MHBAs) generated from α- and β-acids, which show a high similarity with the chemical structure of IAAs, suppress lipopolysaccharide (LPS)-induced cytokine productions in the brain. MHBAs administration increased norepinephrine (NE) secretion and reduced immobility time which represents depression-like behavior in the tail suspension test. Moreover, MHBAs components, including hydroxyallohumulinones and hydroxyalloisohumulones, reduced LPS-induced immobility time. Although further researches are needed to clarify the underlying mechanisms, these findings suggest that MHBAs reduce inflammatory cytokine productions and increase NE secretion, thereby improving depression-like behavior. Similarly, inoculation with LPS induced loss of dendritic spines, which was improved upon MHBAs administration. Additionally, vagotomized mice showed attenuated improvement of immobility time, increase in NE level, and improvement of dendrite spine density following MHBAs administration. Therefore, MHBAs activate the vagus nerve and suppress neuronal damage and depression-like behavior induced by inflammation.

Theaflavins Improve Memory Impairment and Depression-Like Behavior by Regulating Microglial Activation

Inflammation in the brain is associated with various disorders including Alzheimer's disease and depression. Thus, inflammation has received increasing attention regarding preventive approaches to such disorders. Epidemiological investigations have reported that drinking tea reduces the risk of dementia and depression. Theaflavins, a polyphenol found in black tea, are known to have anti-oxidative and anti-inflammation effects, but the effects of theaflavins on cognitive decline and depression induced by inflammation have not been investigated. To address this research gap, the present study assessed whether theaflavins could protect synapses and dendrites damaged by inflammation and prevent concomitant memory impairment and depression-like behavior in mice. Intracerebroventricular injection with lipopolysaccharide (LPS) induces neural inflammation associated with reduced spontaneous alternations in the Y-maze test and increased immobility in the tail suspension test, indicating impaired spatial memory and depression-like behavior, respectively. Oral administration with theaflavins prevented these behavioral changes induced by LPS. Theaflavins also suppressed productions of inflammatory cytokines and prevented dendritic atrophy and spine loss in the brain. Notably, theaflavins have a stronger anti-inflammatory effect than other polyphenols such as catechin, chlorogenic acid, and caffeic acid. These results suggest that theaflavins can suppress neural inflammation and prevent the symptoms of inflammation-related brain disorders.

Iso-α-acids, the bitter components of beer, improve hippocampus-dependent memory through vagus nerve activation

Iso-α-acids (IAAs) are hop-derived bitter acids of beer. Epidemiologic studies suggest that moderate alcohol consumption is beneficial for cognitive function, but they do not show the ingredients in alcoholic beverages. Previously, we reported that long-term consumption of IAAs prevents inflammation and Alzheimer pathologies in mice, but their effects on cognitive function have not been evaluated. In the present study, we demonstrated that the consumption of IAAs improves spatial and object recognition memory functions not only in normal Crl:CD1(ICR) male mice but also in mice with pharmacologically induced amnesia. IAA consumption increased the total and extracellular levels of dopamine in the hippocampus of mice and Sprague-Dawley male rats, respectively. Dopamine D₁ receptor antagonist treatment and knockdown of dopamine D₁ receptor expression in the hippocampus attenuated IAA-induced spatial memory improvement. Furthermore, vagotomy attenuated the effects of IAAs in improving spatial and object recognition memory functions and increasing the total level of dopamine in the hippocampus. These results suggest that the consumption of IAAs activates dopamine D₁ receptor-signaling in the hippocampus in a vagus nerve-dependent manner and, consequently, improves spatial and object recognition memory functions. Vagal activation with food components including IAAs may be an easy and safe approach to improve cognitive functions.-Ano, Y., Hoshi, A., Ayabe, T., Ohya, R., Uchida, S., Yamada, K., Kondo, K., Kitaoka, S., Furuyashiki, T. Iso-α-acids, the bitter components of beer, improve hippocampus-dependent memory through vagus nerve activation.

Iso-α-Acids, the Bitter Components of Beer, Suppress Microglial Inflammation in rTg4510 Tauopathy

Due to the growth in aging populations, prevention for cognitive decline and dementia are in great demand. We previously demonstrated that the consumption of iso-α-acids (IAA), the hop-derived bitter compounds in beer, prevents inflammation and Alzheimer's disease pathology in model mice. However, the effects of iso-α-acids on inflammation induced by other agents aside from amyloid β have not been investigated. In this study, we demonstrated that the consumption of iso-α-acids suppressed microglial inflammation in the frontal cortex of rTg4510 tauopathy mice. In addition, the levels of inflammatory cytokines and chemokines, including IL-1β and MIP-1β, in the frontal cortex of rTg4510 mice were greater than those of wild-type mice, and were reduced in rTg4510 mice fed with iso-α-acids. Flow cytometry analysis demonstrated that the expression of cells producing CD86, CD68, TSPO, MIP-1α, TNF-α, and IL-1β in microglia was increased in rTg4510 mice compared with wild-type mice. Furthermore, the expression of CD86- and MIP-1α-producing cells was reduced in rTg4510 mice administered with iso-α-acids. Moreover, the consumption of iso-α-acids reduced the levels of phosphorylated tau in the frontal cortex. Collectively, these results suggest that the consumption of iso-α-acids prevents the inflammation induced in tauopathy mice. Thus, iso-α-acids may help in preventing inflammation-related brain disorders.

Short-term administration of iso-α-acids increases transthyretin transcription in the hippocampus

Cognitive decline and dementia are currently recognized as major problems in the aging population; however, there is still no promising treatment for these conditions. Previously, our group reported that iso-α-acids (IAAs), which are hop-derived bitter components present in beer, prevent inflammation and cognitive impairment in an Alzheimer's disease model mice (5xFAD mice) and yield significant reduction in amyloid β (Αβ) in the brain. However, data on the molecular mechanisms underlying these physiological effects of IAAs remain limited. Here, we used transcriptome analysis and found that oral administration of IAAs to 5xFAD mice for 7 days induces a 58.9-fold increase in the expression of transthyretin (TTR; Ttr) in the hippocampus compared with controls. In addition, real-time quantitative PCR showed that oral administration of IAAs significantly increased Ttr transcription in the hippocampi of wild type C57BL/6J mice but not in the cerebral cortex. TTR is an Αβ protein scavenger; thus, an increase in its expression could prevent amyloid aggregate formation. These results indicate that IAAs reduce Αβ in the brain by elevating TTR levels.

Novel lactopeptides in fermented dairy products improve memory function and cognitive decline

Alongside the rapid growth in aging populations, prevention of age-related memory decline and dementia has become a high priority. Several epidemiological and clinical studies have concluded that fermented dairy products can help to prevent cognitive decline; furthermore, intake of Camembert cheese prevents Alzheimer's pathology in model mice. To elucidate molecular mechanisms underlying the preventive effects of fermented dairy products, here we screened peptides from digested fermented dairy products for ability to improve memory function in a scopolamine-induced amnesia mouse model. We found that Trp-Tyr (WY)-containing peptides from whey protein improved memory function in the mice, and the effects were confirmed in aged mice. The WY-containing peptides directly inhibited monoamine oxidase-B activity and increased dopamine levels in brain tissue. Pretreatment with dopamine receptor antagonist abolished the improvement in memory function due to WY-containing peptides. These results suggest that WY-containing peptides in fermented dairy products increase monoamine levels by inhibiting monoamine oxidase-B activity, helping to prevent age-related cognitive decline.

Effect of Supplementation of a Whey Peptide Rich in Tryptophan-Tyrosine-Related Peptides on Cognitive Performance in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study

Background: Previous epidemiological and clinical studies have shown that dairy products have beneficial effects on cognitive decline and dementia. Enzymatic digestion of whey protein produces a whey peptide rich in tryptophan-tyrosine-related peptides which improve cognitive performance in mice. We evaluated the effects of whey peptides on cognitive functions in healthy adults in a randomized, double-blind, placebo-controlled design. Methods: 101 healthy adults (45 to 64 years), with a self-awareness of cognitive decline received either whey peptide or placebo supplements for 12 weeks. Changes in cognitive function were assessed using neuropsychological tests at 6 and 12 weeks after the start of supplementation. Results: Verbal fluency test (VFT) score changes tended to be higher in the whey peptide group compared with the placebo at 12 weeks. Subgroup analysis classified by the degree of subjective fatigue showed that changes in the VFT as well as the Stroop and subjective memory function tests between baseline and 6 weeks of intervention were significantly better in subjects with high-level fatigue from the whey peptide group as compared to the placebo group.

CONCLUSIONS

Intake of whey peptide might improve cognitive function in healthy middle- and older-aged adults with high subjective fatigue levels. Further studies will elucidate the relationship among cognitive improvement, whey peptides, and psychological fatigue.

Preventive Effects of Dairy Products on Dementia and the Underlying Mechanisms

Alongside the rapid population aging occurring worldwide, the prevention of age-related memory decline and dementia has become a high priority. Dairy products have many physiological effects owing to their contents of lactic acid bacteria and the fatty acids and peptides generated during their fermentation. In particular, several recent studies have elucidated the effects of fermented dairy products on cognitive function. Epidemiological and clinical evidence has indicated that fermented dairy products have preventive effects against dementia, including Alzheimer’s disease. Recent preclinical studies have identified individual molecules generated during fermentation that are responsible for those preventive effects. Oleamide and dehydroergosterol have been identified as the agents responsible for reducing microglial inflammatory responses and neurotoxicity. In this review, the protective effects of fermented dairy products and their components on cognitive function, the mechanisms underlying those effects, and the prospects for their future clinical development will be discussed.