Microbiome-Gut-Brain-Axis communication influences metabolic switch in the mosquito 1

: Background: Periodic ingestion of a protein-rich blood meal by adult female mosquitoes causes a drastic metabolic change in their innate physiological status, which is referred to as 58 ‘metabolic switch. Although the down-regulation of olfactory factors is key to restrain host- 59 attraction, how the gut ‘metabolic switch’ modulates brain functions, and resilience 60 physiological homeostasis remains unexplored. Methods: To uncover a possible correlation of gut metabolic switching and brain function, we 62 carried out a comparative RNAseq analysis of naïve and blood-fed mosquito’s brain. Spatio- 63 temporal expression of neuro-signaling and neuro-modulatory genes was monitored through 64 Real-Time PCR. To establish a proof-of-concept, we followed LC/MS-based absolute 65 quantification of different neurotransmitters (NT) and compared their levels in the brain as well 66 as in the gut of the mosquitoes. To correlate how microbiome influences gut-brain-axis 67 communication, we performed a comparative gut metagenomic analysis. Results: Our findings demonstrate that the protein-rich diet induces the expression of brain 69 transcripts related to mitochondrial function and energy metabolism, possibly to cause a shift 70 of the brain’s engagement to manage organismal homeostasis. A dynamic expression pattern 71 of neuro-signaling and neuro-modulatory genes in both gut and brain, presumably a key to establish an active brain-distant organ communication. Disruption of this comunication 73 through decapitation, does not affect the modulation of the neuro-modulator receptor genes in 74 the gut. In parallel, an unusual and paramount shift in the level of the Neurotransmitters (NTs), 75 from the brain to the gut after blood feeding, further supports the idea of the gut’s ability to 76 serve as a ‘second brain’. Finally, a comparative metagenomics evaluation of gut microbiome population dynamics, highlighted that blood-feeding not only suppresses Enterobacteriaceae family member by 50%, but favors rapid proliferation of Pseudomonadales to 46% of the total 79 community. Notable obesrvation of a rapid proliferation of Pseudomonas bacterial sp . in the gut correlates a possible cause for the suppression of appetite after blood-feeding. Additionally, an altered NTs dynamics of naïve and aseptic mosquitoes provide the initial evidence that gut-endosymbionts are key modulators for the synthesis of major neuroactive molecules. Conclusion: Our data establish a new conceptual understanding of microbiome-gut-brain-axis communication in mosquitoes. NTGIC: Neurotransmitter Gated Ion Channel; PI4 Kinase: Phosphatidyl-inositol-4-Kinase; Serine Threonine Protein Kinase. Statistical analysis using two-way ANOVA that the expression change of the respective genes is significant p N Schematic representation of the brain’s possible engagement during inter-organ communication after the gut-metabolic switch. Brain actions phases. in status, the brain manages daily behavioral activities, as as take modulation of the brain’s intracellular signaling to manage process for in midgut, ovary maturation blood-feeding, to reactivated olfactory