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

Iso-α-acids in Nonalcoholic and Alcoholic Beer Stimulate Growth of Neuron-like SH-SY5Y Cells and Neuroepithelial Stem Cells

With the increasing popularity of nonalcoholic beer, the association between beer drinking and alcohol intake is lost. In the present study, we show that nonalcoholic beer can stimulate the expansion of neuron-like cell lines and neuroepithelial stem cells in culture, yielding an effect comparable to that of alcoholic beer. One ingredient in beer is hops, which is derived from the flower of hop plants. The female flower contains humulones, which are transformed into iso-α-acids during wort boiling and give beer its bitter taste. In this study, we tested the effects of these iso-α-acids and/or alcohol on the proliferation of neuron-like cells and neuroepithelial stem cells in culture. Iso-α-acids enhanced cell expansion, showing a bimodal dose-response curve with peaks around 2-30 nM and 2-5 μM, of which nanomolar concentrations are relevant in beer drinking. The more lipophilic trans-iso-α-acids, found to a greater extent in beer foam, are even more potent. Our results indicate that iso-α-acids, acting via peroxisome proliferator-activated receptors could be responsible for the observed effects. Altogether, our results indicate that nonalcoholic beer with ingredients such as iso-α-acids stimulate the proliferation of neuroepithelial stem cells.

Redox and Anti-Inflammatory Properties from Hop Components in Beer-Related to Neuroprotection

Beer is a fermented beverage widely consumed worldwide with high nutritional and biological value due to its bioactive components. It has been described that both alcoholic and non-alcoholic beer have several nutrients derived from their ingredients including vitamins, minerals, proteins, carbohydrates, and antioxidants that make beer a potential functional supplement. Some of these compounds possess redox, anti-inflammatory and anticarcinogenic properties making the benefits of moderate beer consumption an attractive way to improve human health. Specifically, the hop cones used for beer brewing provide essential oils, bitter acids and flavonoids that are potent antioxidants and immune response modulators. This review focuses on the redox and anti-inflammatory properties of hop derivatives and summarizes the current knowledge of their neuroprotective effects.

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.

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.

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.

The Nutritional Components of Beer and Its Relationship with Neurodegeneration and Alzheimer's Disease

The prevalence of degenerative diseases has risen in western countries. Growing evidence suggests that demenia and other cognition affectations are associated with ambient factors including specific nutrients, food ingredients or specific dietary patterns. Mediterranean diet adherence has been associated with various health benefits and decreased risk of many diseases, including neurodegenerative disorders. Beer, as part of this protective diet, contains compounds such as silicon and hops that could play a major role in preventing brain disorders. In this review, different topics regarding Mediterranean diet, beer and the consumption of their main compounds and their relation to neurological health have been addressed. Taking into account published results from our group and other studies, the hypothesis linking aluminum intoxication with dementia and/or Alzheimer’s disease and the potential role of regular beer has also been considered. Beer, in spite of its alcohol content, may have some health benefits; nonetheless, its consumption is not adequate for all subjects. Thus, this review analyzed some promising results of non-alcoholic beer on several mechanisms engaged in neurodegeneration such as inflammation, oxidation, and cholinesterase activity, and their contribution to the behavioral modifications induced by aluminum intoxication. The review ends by giving conclusions and suggesting future topics of research related to moderate beer consumption and/or the consumption of its major compounds as a potential instrument for protecting against neurodegenerative disease progression and the need to develop nutrigenetic and nutrigenomic studies in aged people and animal models.

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.