Refined diet consumption increases neuroinflammatory signalling through bile acid dysmetabolism.

Over recent decades, dietary patterns have changed significantly due to the increasing availability of convenient, ultra-processed refined foods. Refined foods are commonly depleted of key bioactive compounds, which have been associated with several deleterious health conditions. As the gut microbiome can influence the brain through a bidirectional communication system known as the 'microbiota-gut-brain axis', the consumption of refined foods has the potential to affect cognitive health. In this study, multi-omics approaches were employed to assess the effect of a refined diet on the microbiota-gut-brain axis, with a particular focus on bile acid metabolism. Mice maintained on a refined low-fat diet (rLFD), consisting of high sucrose, processed carbohydrates and low fibre content, for eight weeks displayed significant gut microbial dysbiosis, as indicated by diminished alpha diversity metrics (p < 0.05) and altered beta diversity (p < 0.05) when compared to mice receiving a chow diet. Changes in gut microbiota composition paralleled modulation of the metabolome, including a significant reduction in short-chain fatty acids (acetate, propionate and n-butyrate; p < 0.001) and alterations in bile acid concentrations. Interestingly, the rLFD led to dysregulated bile acid concentrations across both the colon (p < 0.05) and the brain (p < 0.05) which coincided with altered neuroinflammatory gene expression. In particular, the concentration of TCA, TDCA and T-α-MCA was inversely correlated with the expression of NF-κB1, a key transcription factor in neuroinflammation. Overall, our results suggest a novel link between a refined low-fat diet and detrimental neuronal processes, likely in part through modulation of the microbiota-gut-brain axis and bile acid dysmetabolism.

Saffron extract (Safr'Inside™) improves anxiety related behaviour in a mouse model of low-grade inflammation through the modulation of the microbiota and gut derived metabolites.

Treatment of anxiety and depression predominantly centres around pharmacological interventions, which have faced criticism for their associated side effects, lack of efficacy and low tolerability. Saffron, which is reportedly well tolerated in humans, has been recognised for its antidepressant and anti-anxiety properties. Indeed, we previously reported upon the efficacy of saffron extract supplementation in healthy adults with subclinical anxiety. However, the molecular aetiology remains unclear. In a rodent model of low-grade chronic inflammation, we explored the impact of a saffron extract (Safr'Inside™) supplemented at a physiological dose, which equated to 22 ± 1.2 mg per day human equivalent dose for a person of 60 kg. Behavioural tests (Open Field task, Y maze, Novel object recognition), caecal 16S rRNA microbial sequencing, caecal 1H NMR metabolomic analysis and 2DE brain proteomic analyses were completed to probe gut-brain axis interactions. Time occupying the centre of the Open Field maze (OF) was increased by 62% in saffron supplemented animals. This improvement in anxiety-related behaviour coincided with gut microbial shifts, notably Akkermansia, Muribaculaceae, Christensenellacae and Alloprevotella which significantly increased in response to saffron supplementation. Akkermansia and Muribaculaceae abundance negatively correlated with the neurotoxic metabolite dimethylamine which was reduced in saffron supplemented animals. Brain proteomic analysis highlighted several significantly altered proteins including ketimine reductase mu-crystallin which also correlated with dimethylamine concentration. Both dimethylamine and ketimine reductase mu-crystallin were associated with OF performance. This may be indicative of a novel interaction across the gut-brain axis which contributes to anxiety-related disorders.

Microbial-derived metabolites as a risk factor of age-related cognitive decline and dementia.

A consequence of our progressively ageing global population is the increasing prevalence of worldwide age-related cognitive decline and dementia. In the absence of effective therapeutic interventions, identifying risk factors associated with cognitive decline becomes increasingly vital. Novel perspectives suggest that a dynamic bidirectional communication system between the gut, its microbiome, and the central nervous system, commonly referred to as the microbiota-gut-brain axis, may be a contributing factor for cognitive health and disease. However, the exact mechanisms remain undefined. Microbial-derived metabolites produced in the gut can cross the intestinal epithelial barrier, enter systemic circulation and trigger physiological responses both directly and indirectly affecting the central nervous system and its functions. Dysregulation of this system (i.e., dysbiosis) can modulate cytotoxic metabolite production, promote neuroinflammation and negatively impact cognition. In this review, we explore critical connections between microbial-derived metabolites (secondary bile acids, trimethylamine-N-oxide (TMAO), tryptophan derivatives and others) and their influence upon cognitive function and neurodegenerative disorders, with a particular interest in their less-explored role as risk factors of cognitive decline.

Anthocyanins Promote Learning through Modulation of Synaptic Plasticity Related Proteins in an Animal Model of Ageing.

Anthocyanin-rich foods, such as berries, reportedly ameliorate age-related cognitive deficits in both animals and humans. Despite this, investigation into the mechanisms which underpin anthocyanin-mediated learning and memory benefits remains relatively limited. The present study investigates the effects of anthocyanin intake on a spatial working memory paradigm, assessed via the cross-maze apparatus, and relates behavioural test performance to underlying molecular mechanisms. Six-week supplementation with pure anthocyanins (2% w/w), administered throughout the learning phase of the task, improved both spatial and psychomotor performances in aged rats. Behavioural outputs were accompanied by changes in the expression profile of key proteins integral to synaptic function/maintenance, with upregulation of dystrophin, protein kinase B (PKB/Akt) and tyrosine hydroxylase, and downregulation of apoptotic proteins B-cell lymphoma-extra-large (Bcl-xL) and the phosphorylated rapidly accelerated fibrosarcoma (p-Raf). Separate immunoblot analysis supported these observations, indicating increased activation of extracellular signal-related kinase (ERK1), Akt Ser473, mammalian target of rapamycin (mTOR) Ser2448, activity-regulated cytoskeleton-associated protein (Arc/Arg 3.1) and brain-derived neurotrophic factor (BDNF) in response to anthocyanin treatment, whilst α-E-catenin, c-Jun N-terminal kinase (JNK1) and p38 protein levels decreased. Together, these findings suggest that purified anthocyanin consumption enhances spatial learning and motor coordination in aged animals and can be attributed to the modulation of key synaptic proteins, which support integrity and maintenance of synaptic function.

Citrus Polyphenols in Brain Health and Disease: Current Perspectives.

In addition to essential micronutrients such as vitamin C, citrus fruits represent a considerably rich source of non-essential bioactive compounds, in particular flavanones which form a sub-set of the flavonoid group. Preclinical studies have demonstrated the neuroprotective potential of citrus flavonoids and have highlighted both the well-established (anti-inflammatory and anti-oxidative properties), and newly emerging (influence upon blood-brain barrier function/integrity) mechanistic actions by which these neurological effects are mediated. Encouragingly, results from human studies, although limited in number, appear to support this preclinical basis, with improvements in cognitive performance and disease risk observed across healthy and disease states. Therefore, citrus fruits - both as whole fruit and 100% juices - should be encouraged within the diet for their potential neurological benefit. In addition, there should be further exploration of citrus polyphenols to establish therapeutic efficacy, particularly in the context of well-designed human interventions.

Traumatic Brain Injury-Induced Sex-Dependent Changes in Late-Onset Sensory Hypersensitivity and Glutamate Neurotransmission.

Women approximate one-third of the annual 2.8 million people in the United States who sustain traumatic brain injury (TBI). Several clinical reports support or refute that menstrual cycle-dependent fluctuations in sex hormones are associated with severity of persisting post-TBI symptoms. Previously, we reported late-onset sensory hypersensitivity to whisker stimulation that corresponded with changes in glutamate neurotransmission at 1-month following diffuse TBI in male rats. Here, we incorporated intact age-matched naturally cycling females into the experimental design while monitoring daily estrous cycle. We hypothesized that sex would not influence late-onset sensory hypersensitivity and associated in vivo amperometric extracellular recordings of glutamate neurotransmission within the behaviorally relevant thalamocortical circuit. At 28 days following midline fluid percussion injury (FPI) or sham surgery, young adult Sprague-Dawley rats were tested for hypersensitivity to whisker stimulation using the whisker nuisance task (WNT). As predicted, both male and female rats showed significantly increased sensory hypersensitivity to whisker stimulation after FPI, with females having an overall decrease in whisker nuisance scores (sex effect), but no injury and sex interaction. In males, FPI increased potassium chloride (KCl)-evoked glutamate overflow in primary somatosensory barrel cortex (S1BF) and ventral posteromedial nucleus of the thalamus (VPM), while in females the FPI effect was discernible only within the VPM. Similar to our previous report, we found the glutamate clearance parameters were not influenced by FPI, while a sex-specific effect was evident with female rats showing a lower uptake rate constant both in S1BF and VPM and longer clearance time (in S1BF) in comparison to male rats. Fluctuations in estrous cycle were evident among brain-injured females with longer diestrus (low circulating hormone) phase of the cycle over 28 days post-TBI. Together, these findings add to growing evidence indicating both similarities and differences between sexes in a chronic response to TBI. A better understanding of the influence of gonadal hormones on behavior, neurotransmission, secondary injury and repair processes after TBI is needed both clinically and translationally, with potential impact on acute treatment, rehabilitation, and symptom management.

Trends in body mass index and obesity prevalence in Western Australian adults, 2002 to 2015.

ISSUE ADDRESSED: Continued increases in overweight and obesity across most parts of the world in recent decades have seen maintaining or reaching a healthy weight become a major public health priority. This study reports on body mass index (BMI) and obesity prevalence trends in Western Australian adults between 2002 and 2015. METHODS: Self-reported height and weight were collected from Western Australian adults (16+ years) via 81 867 computer-assisted telephone interviews conducted between 2002 and 2015 as part of the WA Health and Wellbeing Surveillance System. Linear and quadratic trends in annual mean BMI and obesity prevalence estimates were generated from self-report data. These trends were subject to sequential sum of squares analysis to examine whether annual increases in mean BMI and obesity prevalence estimates diminished or were maintained over the 2002 to 2015 period. RESULTS: The analyses showed a preference for a quadratic model (with plots suggesting diminishing increases between 2002 and 2015) in mean BMI for males, 25- to 64-year-olds and across all adults, and in obesity prevalence estimates across all adults. CONCLUSIONS: The results suggest the rate at which mean BMI and obesity prevalence are increasing may be slowing overall and within specific groups in WA. SO WHAT?: The findings are potentially a positive news story for health in Western Australia. Even so, 2-thirds of the population are overweight or obese and there remains a strong need for sustained obesity prevention action.

Planning for the next generation of public health advocates: evaluation of an online advocacy mentoring program.

Issue addressed Despite being viewed as a core competency for public health professionals, public health advocacy lacks a prominent place in the public health literature and receives minimal coverage in university curricula. The Public Health Advocacy Institute of Western Australia (PHAIWA) sought to fill this gap by establishing an online e-mentoring program for public health professionals to gain knowledge through skill-based activities and engaging in a mentoring relationship with an experienced public health advocate. This study is a qualitative evaluation of the online e-mentoring program. Methods Semi-structured interviews were conducted with program participants at the conclusion of the 12-month program to examine program benefits and determine the perceived contribution of individual program components to overall advocacy outcomes. Results Increased mentee knowledge, skills, level of confidence and experience, and expanded public health networks were reported. Outcomes were dependent on participants' level of commitment, time and location barriers, mentoring relationship quality, adaptability to the online format and the relevance of activities for application to participants' workplace context. Program facilitators had an important role through the provision of timely feedback and maintaining contact with participants. Conclusion An online program that combines public health advocacy content via skill-based activities with mentoring from an experienced public health advocate is a potential strategy to build advocacy capacity in the public health workforce. So what? Integrating advocacy as a core component of professional development programs will help counteract current issues surrounding hesitancy by public health professionals to proactively engage in advocacy, and ensure that high quality, innovative and effective advocacy leadership continues in the Australian public health workforce.