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High-fat diet, microbiome-gut-brain axis signaling, and anxiety-like behavior in male rats
Obesity, linked with high-fat diet (HFD) consumption, and anxiety are prevalent in modern urban societies. According to recent studies, the association between HFD and anxiety may be mediated via the microbiota-gut-brain axis, specifically involving brain serotonergic systems. There is evidence that this link is mostly due to interactions between the gut bacteria and the serotonergic brain system. In this study by de Noronha et al. (2024), the authors implemented a nine-week HFD regimen in male rats and evaluated changes in gut microbiome diversity and composition, brainstem gene expression related to serotonin (tph2, htr1a, and slc6a4), and anxiety-related defensive behaviors. The authors’ findings showcase that HFD consumption reduced alpha diversity (that is, microbiome diversity in a single sample) and altered the composition of the gut microbiota, coinciding with obesity. In the brainstem caudal dorsomedial dorsal raphe nucleus (cDRD), previously linked to stress and anxiety, HFD was found to enhance the mRNA expression of genes related to serotonin. Furthermore, HFD intake heightened anxiety-related defensive behaviors. The diet also elevated the Firmicutes/Bacteroidetes ratio compared to the control diet, with increased Blautia levels and reduced Prevotella levels. The authors found that, in comparison to controls, HFD-fed rats had substantially higher mRNA expression levels of tph2, htr1a, and slc6a4 in certain subregions of the dorsal raphe nucleus. In the cDRD, there was a correlation between higher serotonergic gene expression and certain bacterial taxa. Overall, this study suggests that HFD-induced obesity alters microbiota-gut-serotonergic brain axis signaling, thereby contributing to heightened anxiety-related defensive responses in rats. [NPID: Anxiety, dorsal raphe nucleus, high-fat diet, microbiome, microbiome-gut-brain axis, obesity, raphe nuclei, serotonergic system, serotonin, tph2]
Year: 2024
