The effect of single dietary fibre (DF) on lowering uric acid (UA) level has been reported in the literature. However, the potential protective mechanism of DF against potassium oxybate-induced hyperuricaemia (HUA), as modelled by prophylactic administration, remains unclear. The data demonstrate that DF significantly decreased serum and cerebral tissue UA concentrations, inhibited xanthine oxidase expression and activity in the liver and reduced levels of creatinine and urea nitrogen in the serum. Additionally, it mitigated the deposition of amyloid-β in cerebral tissue. Correlation analysis showed that DF modulated the Toll-like receptor 4/NF-κB signalling pathway, attenuating oxidative stress and inflammatory responses in HUA mice. Additionally, DF helps to maintain the composition of the gut microbiota, reducing harmful Desulfovibrio and enriching beneficial Akkermansia and Ruminococcus populations. The results of the faecal metabolomics analysis indicate that DF facilitates the regulation of metabolic pathways involved in oxidative stress and inflammation. These pathways include pyrimidine metabolism, tryptophan metabolism, nucleotide metabolism and vitamin B6 metabolism. Additionally, the study found that DF has a preventive effect on anxiety-like behaviour induced by HUA. In summary, DF shows promise in mitigating HUA and cognitive deficits, primarily by modulating gut microbiota and metabolites.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterised by gradual memory loss and declining cognitive and executive functions. AD is the most common cause of dementia, affecting more than 50 million people worldwide, and is a major health concern in society. Despite decades of research, the cause of AD is not well understood and there is no effective curative treatment so far. Therefore, there is an urgent need to increase understanding of AD pathophysiology in the hope of developing a much-needed cure. Dissecting the cellular and molecular mechanisms of AD pathogenesis has been challenging as the most commonly used model systems such as transgenic animals and two-dimensional neuronal culture do not fully recapitulate the pathological hallmarks of AD. The recent advent of three-dimensional human brain organoids confers unique opportunities to study AD in a humanised model system by encapsulating many aspects of AD pathology. In the present review, we summarise the studies of AD using human brain organoids that recapitulate the major pathological components of AD including amyloid-β and tau aggregation, neuroinflammation, mitochondrial dysfunction, oxidative stress and synaptic and circuitry dysregulation. Additionally, the current challenges and future directions of the brain organoids modelling system are discussed.

Epidemiological studies show mixed findings for serum vitamin B12 (B12) and both cognitive and regional volume outcomes. No studies to date have comprehensively examined, in non-supplemented individuals, serum B12 level associations with neurodegeneration, hypometabolism and cognition across the Alzheimerʼs disease (AD) spectrum. Serum B12 was assayed from the Alzheimerʼs Disease Neuroimaging Initiative (ADNI) and the Australian Imaging, Biomarker & Lifestyle Flagship Study of Ageing (AIBL). Voxel-wise analyses regressed B12 levels against regional grey matter (GM) volume and glucose metabolism (P < 0·05, family-wise corrected). For ADNI GM, there were thirty-nine cognitively normal (CN), seventy-three mild cognitive impairment (MCI) and thirty-one AD participants. For AIBL GM, there were 311 CN, fifty-nine MCI and thirty-one AD participants. Covariates were age, sex, baseline diagnosis, APOE4 status and BMI. In ADNI, higher B12 was negatively associated with GM in the right precuneus and bilateral frontal gyri. When diagnostic groups were examined separately, only participants with MCI, or above an established cut-off for cerebrospinal fluid (CSF) total tau showed such associations. In AIBL, higher B12 was associated with more GM in the right amygdala and right superior temporal pole, which largely seemed to be driven by CN participants that constituted most of the sample. Our results suggest that B12 may show different patterns of association based on clinical status and, for ADNI, AD CSF biomarkers. Accounting for these factors may clarify the relationship between B12 with neural outcomes in late-life.

As the resident macrophage of the central nervous system, microglia are thought to contribute to Alzheimer’s disease (AD) pathology through lack of neuroprotection. The role of immune dysfunction in AD may be due to disruption of regulatory signals for the activation of microglia that may occur early in development. We hypothesized that early toxicant exposure would systematically activate microglia, possibly reversing the pathological severity of AD. Offspring of a triple transgenic murine model for AD (3×TgAD) were exposed to a model neurotoxicant, lead acetate, from postnatal days (PND) 5–10. Our results indicated that female mice exposed to Pb had a greater and earlier incidence of amyloid burden within the hippocampus, coinciding with decreased markers of microglial activation at PND 50. Pb-exposed males had increased microglial activation at PND 50, as evidence by CD11b expression and microglial abundance, with no significant increase in amyloid burden at that time. There was greater amyloid burden at PND 90 and 180 in both male and female mice exposed to Pb compared with control. Together, these data suggest that activated microglia are neuroprotective against amyloid accumulation early in AD pathology, and that early exposure to Pb could increase susceptibility to later-life neurodegeneration. Likewise, females may be more susceptible to early-life microglial damage, and, subsequently, AD. Further investigation into the sex biased mechanisms by which microglial activation is altered by an early-life immune insult will provide critical insight into the temporal susceptibility of the developing neuroimmune system and its potential role in AD etiopathology.

Some dietary fats are a risk factor for Alzheimer's disease (AD) but the mechanisms for this association are presently unknown. In the present study we showed in wild-type mice that chronic ingestion of SFA results in blood–brain barrier (BBB) dysfunction and significant delivery into the brain of plasma proteins, including apo B lipoproteins that are endogenously enriched in amyloid-β (Aβ). Conversely, the plasma concentration of S100B was used as a marker of brain-to-blood leakage and was found to be increased two-fold because of SFA feeding. Consistent with a deterioration in BBB integrity in SFA-fed mice was a diminished cerebrovascular expression of occludin, an endothelial tight junction protein. In contrast to SFA-fed mice, chronic ingestion of MUFA or PUFA had no detrimental effect on BBB integrity. Utilising highly sensitive three-dimensional immunomicroscopy, we also showed that the cerebral distribution and co-localisation of Aβ with apo B lipoproteins in SFA-fed mice are similar to those found in amyloid precursor protein/presenilin-1 (APP/PS1) amyloid transgenic mice, an established murine model of AD. Moreover, there was a strong positive association of plasma-derived apo B lipoproteins with cerebral Aβ deposits. Collectively, the findings of the present study provide a plausible explanation of how dietary fats may influence AD risk. Ingestion of SFA could enhance peripheral delivery to the brain of circulating lipoprotein–Aβ and exacerbate the amyloidogenic cascade.

Dietary cholesterol may influence Alzheimer's disease risk, because it regulates the synthesis of amyloid-β. It was recently demonstrated in enterocytes of wild-type mice that intracellular amyloid-β expression is enhanced in response to a high-fat diet made up of SFA and cholesterol. Intestinally derived amyloid-β may be associated with postprandial lipoproteins in response to dietary fats and could be a key regulator in chylomicron metabolism. The present study was designed to investigate the role of cholesterol in modulating amyloid-β abundance in enterocytes. Wild-type mice were fed a low-fat diet supplemented with 2 % (w/w) cholesterol. The effects of cholesterol absorption inhibition and cholesterol biosynthesis inhibition utilising ezetimibe and atorvastatin, respectively, were also studied. Quantitative immunohistochemistry was utilised to determine enterocytic amyloid-β homeostasis. We found that enterocytic amyloid-β concentration was significantly attenuated in mice fed the 2 % (w/w) cholesterol diet. However, blocking cholesterol absorption reversed the cholesterol-feeding effect. Consistent with a suppressive effect of cholesterol on enterocytic amyloid-β abundance, atorvastatin, an inhibitor of cholesterol biosynthesis, enhanced amyloid-β. However, providing exogenous cholesterol abolished the atorvastatin-induced effect. In contrast to the suppression of enterocytic amyloid-β by dietary cholesterol, mice fed a diet enriched in SFA had markedly greater abundance. Collectively, the findings suggest that exogenous and endogenous cholesterol reduce amyloid-β concentration in enterocytes by suppressing production, or enhancing secretion associated with postprandial lipoproteins. Intestinally derived amyloid-β will contribute to the pool of plasma protein and may influence cerebral amyloid homeostasis by altering the bi-directional transfer across the blood–brain barrier.