Postprandial insulin action relies on meal composition and hepatic parasympathetics: dependency on glucose and amino acids Meal, parasympathetics & insulin action

Insulin sensitivity (IS) increases following a meal. Meal composition affects postprandial glucose disposal but still remains unclear which nutrients and mechanisms are involved. We hypothesized that gut-absorbed glucose and amino acids stimulate hepatic parasympathetic nerves, potentiating insulin action. Male Sprague-Dawley rats were 24 h fasted and anesthetized. Two series of experiments were performed. (A) IS was assessed before and after liquid test meal administration (10 ml.kg(-1), intraenteric): glucose + amino acids + lipids (GAL, n=6); glucose (n=5); amino acids (n=5); lipids (n=3); glucose + amino acids (GA, n=9); amino acids + lipids (n=3); and glucose + lipids (n=4). (B) Separately, fasted animals were submitted to hepatic parasympathetic denervation (DEN); IS was assessed before and after GAL (n=4) or GA administration (n=4). (A) Both GAL and GA induced significant insulin sensitization. GAL increased IS from 97.9+/-6.2 mg glucose/kg bw (fasting) to 225.4+/-183 mg glucose/kg bw (P<0.001; 143.6+/-26.0\% potentiation of IS); GA increased IS from 109.0+/-6.6 to 240.4+/-18.0 mg glucose/kg bw (P<0.001; 123.1+/-13.4\% potentiation). None of the other meals potentiated IS. (B) GAL and GA did not induce a significant insulin sensitization in DEN animal. To achieve maximal insulin sensitization following a meal, it is required that gut-absorbed glucose and amino acids trigger a vagal reflex that involves hepatic parasympathetic nerves. (C) 2015 Elsevier Inc. All rights reserved.