Nutrient Sensor in the Brain Directs the Action of the Brain-Gut Axis in Drosophila

Abstract

Summary Animals can detect and consume nutritive sugars without the influence of taste. However, the identity of the taste-independent nutrient sensor and the mechanism by which animals respond to the nutritional value of sugar are unclear. Here, we report that six neurosecretory cells in the Drosophila brain that produce Diuretic hormone 44 (Dh44), a homologue of the mammalian corticotropin-releasing hormone (CRH), were specifically activated by nutritive sugars. Flies in which the activity of these neurons or the expression of Dh44 was disrupted failed to select nutritive sugars. Manipulation of the function of Dh44 receptors had a similar effect. Notably, artificial activation of Dh44 receptor-1 neurons resulted in proboscis extensions, and frequent episodes of excretion. Conversely, reduced Dh44 activity led to decreased excretion. Together, these actions facilitate ingestion and digestion of nutritive foods. We propose that the Dh44 system directs the detection and consumption of nutritive sugars through a positive feedback loop.

Coupled Sensing of Hunger and Thirst Signals Balances Sugar and Water Consumption

“…Although flies lack a direct homolog of the hypothalamus, neural populations in the Drosophila brain function as internal nutrient sensors, including glucose, fructose, and amino acid sensors that regulate feeding decisions (Dus et al, 2015; Bjordal et al, 2014; Miyamoto et al, 2012). Flies also regulate water consumption based on internal water abundance (Dethier, 1976), although internal sensors underlying this behavior have not previously been characterized.…”

SGLT1 sugar transporter/sensor is required for post-oral glucose appetition

“…Conceivably, there may be an as yet unidentified orexigenic hormone released by intestinal glucose that stimulates appetite. Signals generated by glucose sensors in the portal vein region in rodents and by brain sensors in flies may also contribute to learned food preferences (7,17,30). The present focus on glucose reflects the ineffectiveness of fructose, the other common dietary monosaccharide, to promote post-oral appetition in B6 mice.…”

Drosophila Chemoreceptors: A Molecular Interface Between the Chemical World and the Brain

“…These neurons project dendrites into pits that open into the esophageal lumen. Post-ingestive nutrient monitoring also occurs in the brain [15, 16], and presumably in enteroendocrine cells of the midgut [17]. …”