Calcitonin-Receptor-Like Receptor Signaling Governs Intestinal Lymphatic Innervation and Lipid Uptake

Abstract

The absorption of dietary fat requires complex neuroendocrine-mediated regulation of chylomicron trafficking through enterocytes and intestinal lymphatic vessels. Calcitonin-receptor-like receptor (<i>Calcrl</i>) is a G protein-coupled receptor that can bind either a lymphangiogenic ligand adrenomedullin, with coreceptor RAMP2, or the neuropeptide CGRP, with coreceptor RAMP1. The extent to which this common GPCR controls lipid absorption via lymphatics or enteric innervation remains unclear. We used conditional and inducible genetic deletion of <i>Calcrl</i> in lymphatics to elucidate the pathophysiological consequences of this receptor pathway under conditions of high-fat diet. Inefficient absorption of dietary fat coupled with altered lymphatic endothelial junctions in <i>Calcrl</i> ^<i>fl/fl</i> <i>/Prox1-CreER</i> ^<i>T2</i> mice results in excessive, transcellular lipid accumulation and abnormal enterocyte chylomicron processing and failure to gain weight. Interestingly, <i>Calcrl</i> ^<i>fl/fl</i> <i>/Prox1-CreER</i> ^<i>T2</i> animals show reduced and disorganized mucosal and submucosal innervation. Consistently, mice with genetic loss of the CGRP coreceptor RAMP1 also displayed mucosal and submucosal innervation deficits, substantiating the CGRP-biased function of <i>Calcrl</i> in the neurolymphocrine axis. Thus, the common <i>Calcrl</i> receptor is a critical regulator of lipid absorption through its cell-specific functions in neurolymphocrine crosstalk.