Biology subjects

Abi Assaf, J.

Publications and source records attributed to Abi Assaf, J..

3 recordsLinked to original sources

bioRxiv2026

Dietary fibre combinations modulate gut microbiome composition and metabolic responses in zebrafish, with lasting effects on intestinal barrier gene expression

Food sources provide a complex mixture of dietary fibres, not a single type. Consuming a diverse range of these dietary fibre-containing foods is associated with health benefits. However, how the effects of combining dietary fibres translate across different biological levels remains poorly characterised. This study uses an integrated microbiome-metabolome analytical approach that combines 16S rRNA gene sequencing with metabolomic profiling of the intestine, brain and liver. Specifically, we examined the combined effects of apple pectin (AP) and cellulose (C) within the same diet, compared with their isolated effects, in adult female and male zebrafish (Danio rerio). Notably, the combined apple pectin and cellulose diet (APC) produced a microbiome composition that could not be predicted by simply adding the changes observed with each dietary fibre individually, indicating a significant non-additive interaction between the two dietary components, specifically a less-than-additive response in gut microbiome composition. The resulting community composition under the combined diet also more closely resembled that induced by apple pectin. We found that predicted microbial functional capabilities did not translate directly into quantified intestinal and brain short-chain fatty acid (SCFA) concentrations, nor did intestinal SCFA levels directly mirror those observed in the brain. Moreover, we used targeted qPCR gene expression analysis to assess responses to a subsequent saponin challenge after dietary fibre cessation, revealing a potentially protective effect on the intestinal barrier. Collectively, we show that dietary fibres within the same diet interact to shape the gut microbiome and do not act in isolation, leading to non-linear health ramifications for the host that may persist even after active consumption ends.

systems biology↗

bioRxiv2026

Dietary fibre responses emerge through host-dietary regime interplay: Apple pectin modulates immune reactivity in adult zebrafish

Dietary fibres are rarely consumed independently. Instead, they form part of an overall diet that includes dietary fibres from different sources, in varying amounts and consumed under different feeding patterns. Here, we tested how dietary regimes containing apple pectin, oat {beta}-glucan, or cellulose shaped the host. We analysed gut microbiome composition by 16S rRNA sequencing, measured brain and intestinal SCFA profiles by targeted metabolomics, and assessed immunomodulation by measuring gene expression systemically in the blood and locally in the spleen, as well as intestinal enzyme activity. The dietary intervention was conducted for 12 weeks on adult female and male zebrafish (Danio rerio). Our results show that the gut microbial composition can be relatively stable across different dietary fibre exposure patterns yet still vary significantly between the sexes. Additionally, the effect of sex on the gut microbiome may become more evident when dietary fibres are administered at high dosages, but intermittently. Dietary fibre regimes can alter intestinal short-chain fatty acid profiles more readily than brain profiles, which show a stronger sexually dimorphic response. Interestingly, apple pectin modulated the zebrafish immune response through interactions dependent on the overall regime, tissue, sex, and host immune status. Notably, tissue il1b gene expression differed depending on how apple pectin was administered and the host's physiological state. Collectively, our study emphasises the highly context-specific effects of dietary fibres, shaped by the dynamic interplay between the overall dietary regime and intertwined host factors.

systems biology↗

bioRxiv2024

Gum Arabic (Acacia senegal) enhances reproduction and modulates the microbiota-gut-brain axis of zebrafish in a sex-specific and dosage-dependent manner

Dietary fibres (DFs) constitute a wide range of heterogeneous compounds that resist digestion and have beneficial effects on general health. Gum Arabic (GA) is a tree exudate consisting of 90% arabinogalactan, a polymer of arabinose and galactose sugars with prebiotic properties. As a dietary fibre, GA improves renal function, metabolism, and immune response in humans and animals. However, the underlying mechanisms leading to these health benefits are poorly understood. We supplemented female and male zebrafish (Danio rerio) with two concentrations of GA (6% and 60%) for two weeks. We assessed the effects of GA supplementation on the gut microbiome composition, intestinal and brain metabolic profiles, reproductive fitness, and brain gene expression. We found that GA supplementation resulted in changes to the gut microbiome with a relative increase in Fusobacteria and a relative decrease in Proteobacteria where the beneficial genus Cetobacterium was significantly more abundant after supplementation. GA supplementation increased acetate levels, particularly in the brain, causing a decreased expression of cart1 in the brain of female zebrafish. While GA supplementation increased overall activity in male and female fish, reproductive fitness was negatively affected by GA supplementation in females. Our results suggest that while GA supplementation may have positive effects on metabolic rate and overall activity, it may come at a trade-off with reproductive fitness. Significance StatementDietary fibres, found in plant-based food sources, can improve health. They include natural gums like gum Arabic, a highly sought-after food additive used as a homogeniser. Despite our better understanding of nutrition, a fibre gap is still prevalent in the Western world with efforts being made to incorporate new sources to close this gap and boost well-being. Here, we showed that when gum Arabic was supplemented into the zebrafish diet, it had a beneficial modulatory effect on the microbiota-gut-brain axis and reproductive fitness. Our findings support the benefits of dietary fibres but also link their impact to sexual dimorphism and dosage. This has implications for developing nutrition guidelines for both animals and humans.

systems biology↗