Butyrate as a potential therapeutic agent for neurodegenerative disorders

Inhibition of levodopa metabolism to dopamine by honokiol short-chain fatty acid derivatives may enhance therapeutic efficacy in Parkinson's disease

This study investigates the antimicrobial properties of honokiol (HNK), a naturally occurring polyphenol, when conjugated with short-chain fatty acids (SCFAs) such as butyrate. We examined the effects of HNK-SCFA ester conjugates on Enterococcus faecalis, a gut bacterium that metabolizes levodopa, a drug used to manage Parkinson's disease symptoms. Our findings indicate that HNK-SCFA-esters (e.g., HNK-acetate, HNK-propionate, HNK-butyrate, and HNK-hexanoate) inhibit E. faecalis growth in a dose-dependent manner, followed by a temporary recovery period during which levodopa remains intact and unmetabolized. Notably, HNK-SCFAs exhibit enhanced cellular permeability and are hydrolyzed within bacterial cells, releasing HNK and SCFAs. These results suggest that HNK-SCFAs may reversibly modulate the gut metabolism of levodopa to dopamine, potentially enhancing its therapeutic efficacy in treating Parkinson's disease.

Stress-Induced Sleep Dysregulation: The Roles of Astrocytes and Microglia in Neurodegenerative and Psychiatric Disorders

Stress and sleep share a reciprocal relationship, where chronic stress often leads to sleep disturbances that worsen neurodegenerative and psychiatric conditions. Non-neuronal cells, particularly astrocytes and microglia, play critical roles in the brain's response to stress and the regulation of sleep. Astrocytes influence sleep architecture by regulating adenosine signaling and glymphatic clearance, both of which can be disrupted by chronic stress, leading to reduced restorative sleep. Microglia, activated under stress conditions, drive neuroinflammatory processes that further impair sleep and exacerbate brain dysfunction. Additionally, the gut-brain axis mediates interactions between stress, sleep, and inflammation, with microbial metabolites influencing neural pathways. Many of these effects converge on the disruption of synaptic processes, such as neurotransmitter balance, synaptic plasticity, and pruning, which in turn contribute to the pathophysiology of neurodegenerative and psychiatric disorders. This review explores how these cellular and systemic mechanisms contribute to stress-induced sleep disturbances and their implications for neurodegenerative and psychiatric disorders, offering insights into potential therapeutic strategies targeting non-neuronal cells and the gut-brain axis.

Neuro-nutraceuticals: Emerging molecular and functional insights into how natural products improve brain health

The editors in assembling this Special Issue, "Neuro-nutraceuticals: Emerging Molecular and Functional Insights into how Natural Products Improve Brain Health", sought to advance our understanding of how such chemical entities alone or in group maintain brain metabolism and homeostasis so that neurons, glia and endothelial cells are healthy during development, ageing and in neuropathologies. The growth of interest in neuro-nutraceuticals and all aspects of their actions relevant to the health of the nervous system continues to amaze all. This Special Issue # 4 contains 39 articles, and we sought to highlight in this Special Issue important new advances and key issues pertinent to future clinical application of neuro-nutraceuticals. The diversity of topics covered is quite broad and includes significant articles on enteric microbiome and brain health. The Editors have tried to provide an up-to-date account of how nutraceuticals work at the molecular and cellular level, and what are the known molecular targets that ultimately can be leveraged clinically to enable the brain to function better. With respect to brain ailments and treatments, single molecule effects, and a therapeutic group of molecules from dietary herbals are discussed in this Special Issue.

Antiepileptic Effects of Acorus tatarinowii Schott in a Rat Model of Epilepsy: Regulation of Metabolic Axes and Gut Microbiota

As a phytotherapeutic agent with historical applications in epilepsy management, Acorus tatarinowii Schott (ATS) remains pharmacologically enigmatic, particularly regarding its pathophysiological mechanisms. This knowledge gap significantly hinders the clinical application of ATS-based treatments. To explore the potential of ATS in combating epileptogenesis, we utilized a pentylenetetrazole (PTZ)-induced chronic epilepsy rat model. Brain metabolomic analysis was performed by ultra-performance liquid chromatography coupled with mass spectrometry (UPLC/MS). Principal component analysis (PCA) and orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were performed for screening differential metabolites. Gut microbiota composition was analyzed through 16S rRNA gene sequencing and examined using Spearman correlation analysis. The results show that oral ATS (50 mg/kg) significantly improved the seizure latency and pathology of rats with epilepsy. Ascorbate and aldarate metabolism, glycerophospholipid metabolism, arachidonic acid metabolism, and intestinal flora were crucial for ATS's ability to counteract epilepsy. The therapeutic effects of ATS against epilepsy were investigated with brain metabolomics and gut microbiota analysis, providing the basis for further comprehensive research.

From Obesity to Mitochondrial Dysfunction in Peripheral Tissues and in the Central Nervous System

Obesity is a condition of chronic low-grade inflammation affecting peripheral organs of the body, as well as the central nervous system. The adipose tissue dysfunction occurring under conditions of obesity is a key factor in the onset and progression of a variety of diseases, including neurodegenerative disorders. Mitochondria, key organelles in the production of cellular energy, play an important role in this tissue dysfunction. Numerous studies highlight the close link between obesity and adipocyte mitochondrial dysfunction, resulting in excessive ROS production and adipose tissue inflammation. This inflammation is transmitted systemically, leading to metabolic disorders that also impact the central nervous system, where pro-inflammatory cytokines impair mitochondrial and cellular functions in different areas of the brain, leading to neurodegenerative diseases. To date, several bioactive compounds are able to prevent and/or slow down neurogenerative processes by acting on mitochondrial functions. Among these, some molecules present in the Mediterranean diet, such as polyphenols, carotenoids, and omega-3 PUFAs, exert a protective action due to their antioxidant and anti-inflammatory ability. The aim of this review is to provide an overview of the involvement of adipose tissue dysfunction in the development of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and multiple sclerosis, emphasizing the central role played by mitochondria, the main actors in the cross-talk between adipose tissue and the central nervous system.

Disruption in the human microbiome causing behavioural changes in bipolar disorder

This chapter explores the intriguing and complex relationship between the human microbiome and Bipolar Disorder (BD). The microbiome, notably the gut microbiota, has been increasingly recognised as a key performer in brain health and disease. This is due to its role in the gut-brain axis, a bidirectional communication between the gastrointestinal tract and the central nervous system. Disruptions in the gut microbiota due to factors such as diet, and stress, may influence this axis and potentially trigger or exacerbate psychiatric conditions. Hence, we investigate into the present interpretation of the microbiome's role in mental health, concentrating on its impact on mood regulation and cognitive function. Consequently, we also explore the possible mechanisms through which microbiome disruption may pay to the behavioural changes observed in BD. Further exploration understand the complex interplay between the microbiome and BD and translate these findings into effective therapeutic plans.

Oral tributyrin treatment affects short-chain fatty acid transport, mucosal health, and microbiome in a mouse model of inflammatory diarrhea

Butyrate may decrease intestinal inflammation and diarrhea. This study investigates the impact of oral application of sodium butyrate (NaB) and tributyrin (TB) on colonic butyrate concentration, SCFA transporter expression, colonic absorptive function, barrier properties, inflammation, and microbial composition in the colon of slc26a3-/- mice, a mouse model for inflammatory diarrhea. In vivo fluid absorption and bicarbonate secretory rates were evaluated in the cecum and mid-colon of slc26a3+/+ and slc26a3-/- mice before and during luminal perfusion of NaB-containing saline and were significantly stimulated in both slc26a3+/+ and slc26a3-/- colon by NaB. Age-matched slc26a3+/+ and slc26a3-/- mice were either fed chow containing 5% NaB or gavaged twice daily with TB for 21 d. Food and water intake, weight, and stool water content were assessed daily. Stool and tissues were collected for further analysis of SCFA production, barrier integrity, mucosal inflammation, and microbiome analysis by 16S rRNA gene sequencing. 5% NaB diet did not exert a significant impact on SCFA levels, mucus barrier, or inflammatory markers, but significantly increased oral water intake. TB gavage treatment increased the expression of SCFA transporters Mct1 and Smct1, mucus content and microbial diversity, and decreased the neutrophil marker Lipocalin 2, Phospholipase A2, and the antimicrobial peptide Reg3b in the slc26a3-/- cecum. However, TB treatment also resulted in an increase in inflammatory markers such as TNFα, Il-1β and CD3e in the wildtype mucosa. While there are some benefits with TB ingestion for barrier properties and microbial composition in the diseased cecum, potentially detrimental effects were noted in the healthy colon.

Bridging gap in the treatment of Alzheimer's disease via postbiotics: Current practices and future prospects

Aging is an extremely significant risk associated with neurodegeneration. The most prevalent neurodegenerative disorders (NDs), such as Alzheimer's disease (AD) are distinguished by the prevalence of proteinopathy, aberrant glial cell activation, oxidative stress, neuroinflammation, defective autophagy, cellular senescence, mitochondrial dysfunction, epigenetic changes, neurogenesis suppression, increased blood-brain barrier permeability, and intestinal dysbiosis that is excessive for the patient's age. Substantial body studies have documented a close relationship between gut microbiota and AD, and restoring a healthy gut microbiota may reduce or even ameliorate AD symptoms and progression. Thus, control of the microbiota in the gut has become an innovative model for clinical management of AD, and rising emphasis is focused on finding new techniques for preventing and/or managing the disease. The etiopathogenesis of gut microbiota in driving AD progression and supplementing postbiotics as a preventive and therapeutic treatment for AD is discussed. The review additionally discusses the use of postbiotics in AD prophylaxis and therapy, portraying them as substances that address senescence-triggered dysfunctions and are worthy of translating from bench to biopharmaceutical market in response to "silver consumers" needs. The current review examines and evaluates the impact of postbiotics as whole and specific metabolites, such as short-chain fatty acids (SCFAs), lactate, polyamines, polyphenols, tryptophan metabolites, exopolysaccharides, and bacterial extracellular vesicles, on the aging-associated processes that reinforce AD. Moreover, it provides an overview of the most recent data from both clinical and preclinical research involving the use of postbiotics in AD.

Beneficial Effects of Butyrate on Kidney Disease

The gut microbiota influences and contributes to kidney health and disease. Butyrate, a short-chain fatty acid molecule generated via the fermentation of gut bacterial catabolism of nondigestible dietary fiber, has been shown to exert numerous beneficial effects on kidney disorders. The objective of this review was to discuss the latest findings on the protective effects of butyrate on a variety of animal models of kidney injury. We conducted a PubMed search using the title word "butyrate" and keyword "kidney" to generate our literature review sources. The animal models covered in this review include ischemia-reperfusion renal injury, cisplatin- and folic acid-induced kidney injury, septic kidney injury, diabetic kidney disease (DKD), high-fat diet (HFD)-induced glomerulopathy, adenine-induced chronic kidney disease (CKD), high-salt-induced renal injury, and T-2 toxin-induced kidney injury in birds. The protective mechanisms of butyrate that are most shared among these animal model studies include antioxidative stress, anti-fibrosis, anti-inflammation, and anti-cell death. This review ends with suggestions for future studies on potential approaches that may modulate gut microbiota butyrate production for the well-being of kidneys with the kidney disorders covered in this review.

Microbiota-Gut-Brain Axis in Age-Related Neurodegenerative Diseases

BACKGROUND

Age-related neurodegenerative diseases (NDs) pose a formidable challenge to healthcare systems worldwide due to their complex pathogenesis, significant morbidity, and mortality. Scope and Approach: This comprehensive review aims to elucidate the central role of the microbiotagut- brain axis (MGBA) in ND pathogenesis. Specifically, it delves into the perturbations within the gut microbiota and its metabolomic landscape, as well as the structural and functional transformations of the gastrointestinal and blood-brain barrier interfaces in ND patients. Additionally, it provides a comprehensive overview of the recent advancements in medicinal and dietary interventions tailored to modulate the MGBA for ND therapy.

CONCLUSION

Accumulating evidence underscores the pivotal role of the gut microbiota in ND pathogenesis through the MGBA. Dysbiosis of the gut microbiota and associated metabolites instigate structural modifications and augmented permeability of both the gastrointestinal barrier and the blood-brain barrier (BBB). These alterations facilitate the transit of microbial molecules from the gut to the brain via neural, endocrine, and immune pathways, potentially contributing to the etiology of NDs. Numerous investigational strategies, encompassing prebiotic and probiotic interventions, pharmaceutical trials, and dietary adaptations, are actively explored to harness the microbiota for ND treatment. This work endeavors to enhance our comprehension of the intricate mechanisms underpinning ND pathogenesis, offering valuable insights for the development of innovative therapeutic modalities targeting these debilitating disorders.

Intervention in gut microbiota increases intestinal γ-aminobutyric acid and alleviates anxiety behavior: a possible mechanism via the action on intestinal epithelial cells

The role of the gut microbiota in the gut-brain axis has attracted attention in recent years. Some gut microbiota produces γ-aminobutyric acid (GABA), a major inhibitory neurotransmitter in mammals, in vitro, but the correlation between gut microbiota composition and intestinal GABA concentration, as well as the action of intestinal GABA in vivo, are poorly understood. Herein, we found that the intestinal GABA concentration was increased in mice by the intervention of the gut microbiota with neomycin or Bifidobacterium bifidum TMC3115 (TMC3115). Administration of TMC3115 reduced anxiety without affecting serum levels of serotonin, corticosterone, or GABA. We further found that intestinal epithelial cells expressed GABA receptor subunits and mediated mitogen-activated protein kinase signaling upon GABA stimulation. In addition, administration of TMC3115 induced mitogen-activated protein kinase signaling in colonic epithelial cells but not in small intestinal epithelial cells in mice. These results indicate that GABA produced by the gut microbiota, mainly in the colon, may affect host behavioral characteristics via GABA receptors expressed in intestinal epithelial cells without being transferred to the blood. This study suggests a novel mechanism by which intestinal GABA exerts physiological effects, even in the presence of the blood-brain barrier.

Postbiotics as Molecules Targeting Cellular Events of Aging Brain-The Role in Pathogenesis, Prophylaxis and Treatment of Neurodegenerative Diseases

Aging is the most prominent risk factor for neurodegeneration occurrence. The most common neurodegenerative diseases (NDs), Alzheimer's (AD) and Parkinson's (PD) diseases, are characterized by the incidence of proteinopathy, abnormal activation of glial cells, oxidative stress, neuroinflammation, impaired autophagy and cellular senescence excessive for the patient's age. Moreover, mitochondrial disfunction, epigenetic alterations and neurogenesis inhibition, together with increased blood-brain barrier permeability and gut dysbiosis, have been linked to ND pathogenesis. Since NDs still lack curative treatment, recent research has sought therapeutic options in restoring gut microbiota and supplementing probiotic bacteria-derived metabolites with beneficial action to the host-so called postbiotics. The current review focuses on literature explaining cellular mechanisms involved in ND pathogenesis and research addressing the impact that postbiotics as a whole mixture and particular metabolites, such as short-chain fatty acids (SCFAs), lactate, polyamines, polyphenols, tryptophan metabolites, exopolysaccharides and bacterial extracellular vesicles, have on the ageing-associated processes underlying ND occurrence. The review also discusses the issue of implementing postbiotics into ND prophylaxis and therapy, depicting them as compounds addressing senescence-triggered dysfunctions that are worth translating from bench to pharmaceutical market in response to "silver consumers" demands.