Cholecystokinin/Cholecystokinin-1 Receptor-Mediated Peripheral Activation of the Afferent Vagus by Enteral Nutrients Attenuates Inflammation in Rats

Abstract

The current study investigates activation of the nutritional anti-inflammatory pathway by lipid-rich nutrition. Enteral nutrition activates humoral and neural pathways to regulate food intake and sustain energy balance. Recently, we demonstrated that enteral nutrition and in particular lipid-rich nutrition modulates inflammation and prevents organ damage. Male rats were fasted or fed lipid-rich nutrition before hemorrhagic shock. Disruption of afferent vagal fibers with capsaicin (deafferentation) was used to investigate involvement of afferent fibers. Peripheral activation of afferent vagal fibers via cholecystokinin (CCK)-mediated activation of CCK-1 receptors was investigated using administration of the selectively peripheral acting CCK-1 receptor antagonist, A70104 and PEGylated-CCK9. Tissue and blood were collected 90 minutes after shock to assess systemic inflammation and intestinal integrity. Deafferentation reversed the inhibitory effect of lipid-rich nutrition on systemic levels of tumor necrosis factor-alpha and interleukin-6, and on intestinal leakage of horseradish peroxidase and bacterial translocation. Furthermore, the protective effects of lipid-rich nutrition were negated by A70104, indicating that lipid-rich nutrition triggers peripheral CCK-1 receptors on vagal afferents to modulate inflammation. These findings were substantiated by the fact that pretreatment of fasted rats with PEGylated-CCK9, which acts on peripheral CCK-1 receptors, attenuated systemic inflammation, and loss of intestinal integrity. These data demonstrate that enteral lipid-rich nutrition modulates inflammation and preserves intestinal integrity via CCK release which activates CCK-1 receptors located on afferent vagal fibers. Taken together, the current study reveals a novel gut-brain-immune axis and provides new insight into the applicability of enteral nutrition to treat inflammatory conditions.