Novel sensory inputs for the control of food intake and gastrointestinal (GI) function are of increasing interest due to the rapid increase in nutrition-related diseases. The essential amino acid L-lysine was demonstrated to have a selective impact on food intake, gastric emptying, and intestinal transit in rats, thus indicating a potential novel direct sensory input to assess dietary protein content and quality. The aim of this study was to assess translational aspects of this finding and to investigate the dose-dependent effect of L-lysine on human and rat GI function.Methods
L-lysine doses from 0–800 mg in rats and 0.5–7.5 g in humans were analyzed for their effect on gastric emptying and GI secretion. Human GI function was assessed non-invasively using magnetic resonance imaging (MRI), rat data were acquired using standard lethal measurement methods. L-lysine dose dependently delayed gastric emptying and stimulated GI secretion in rats as reflected by residual phenol red content and increased gastric wet weight.Key Results
The dose-dependent delay in gastric emptying observed in rats was confirmed in humans with an increase in halftime of gastric emptying of 4 min/g L-lysine, p < 0.01. Moreover, a dose-dependent increase in intestinal fluid accumulation was observed (0.4 mL/min/g L-lysine, p < 0.0001). No effect on alkaline tide, glucose concentration, hematocrit, or visceral sensations was detected.Conclusions & Inferences
This translational study demonstrates comparable dose-dependent effects of intragastric L-lysine on GI function in humans and rats and suggests a broader role for individual amino acids in the control of GI motility and secretion in vivo.Conclusions & Inferences
The aim of this study was to assess the translational aspects of recent findings in rats demonstrating a selective impact of L-lysine on gastrointestinal function and to investigate the dose-dependent effect of L-lysine on human and rat GI function. Human GI function was assessed non-invasively using magnetic resonance imaging (MRI). Intragastric L-lysine exhibits a comparable dose-dependent effect on GI motility and secretion in humans and rats. We believe that these translational findings further support the broad role of specific amino acids in the control of GI function in vivo.