Evidence for a lipid specific effect in nutrient induced human proximal gastric relaxation

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Abstract
Background/Aim—The presence of lipid in the upper gut is able to modify gastrointestinal motor performance, but its influence on the relaxation of the human stomach, which is known to modify gastric emptying, remains incompletely understood. The relaxation of the proximal stomach in response to various lipid concentrations was therefore studied in healthy volunteers. Since the observed effects could be mediated through osmolality or energy sensitive pathways, the effects of equicaloric and equiosmolar non-lipid solutions were also determined.Methods—The tone of the proximal stomach was measured during stepwise inflation of a non-compliant bag sited in the proximal stomach, both before and after a test meal was delivered intragastrically. Iso-osmolar lipid emulsions were diluted in iso-osmolar saline at concentrations of 1.25, 2.5, 5, 10, and 20%. NaCl solutions at osmolalities of 300, 600, 1200 and 2400 mmol/kg and glucose solutions of 836 and 3344 kJ/l were also given.Results—All lipid meals of 2.5% or greater concentration induced a reduction in gastric tone in a non-dose-dependent manner, responses to 5% lipid (median (range) 74 (62–92)%) being similar to those to 20% lipid (80 (55–83)%; p>0.05). No relaxation was elicited by isocaloric glucose. NaCl only consistently caused relaxation at 2400 mmol/kg.Conclusion—Lipid meals reduce human proximal gastric tone by a lipid specific mechanism, independently of their energy content or osmolality.