Prolonged effects of modified sham feeding on energy substrate mobilization

Background: Vagal stimulation in response to nutrients is reported to elici t an array of digestive and endocrine responses, including an alteration in postprandial lipid metabolism. Objective: The objective of this study was to assess whether neural stimula tion could alter hormone and substrate metabolism during the late postprand ial phase, with implications for body fat mobilization. Design: Vagal stimulation was achieved by using the modified sham feeding ( MSF) technique, in which nutrients are chewed and tasted but not swallowed. Ten healthy subjects were studied on 3 separate occasions, 4 wk apart. Fiv e hours after a high-fat breakfast (56 g fat), the subjects were given 1 of 3 test meals allocated in random order: water, a lunch containing a modest amount of fat (38 g), or MSF (38 g fat). Blood was collected for 3 h posts timulus for hormone and metabolite analyses. Results: Plasma insulin and pancreatic polypeptide concentrations peaked at 250% and 209% of baseline concentrations within 15 min of MSE The plasma g lucose concentration increased significantly (P = 0.038) in parallel with t he changes observed in the plasma insulin concentration. The nonesterified fatty acid concentration was significantly suppressed (P = 0.006); maximum suppression occurred at a mean time of 114 min after MSE This fall in nones terified fatty acid was accompanied by a fall in the plasma glucagon concen tration from 122 to 85 pmol/L (P = 0.018) at a mean time of 113 min after M SF. Conclusions: Effects on substrate metabolism after MSF in the postprandial state differ from those usually reported in the postabsorptive state. The e ffects of MSF were prolonged beyond the period of the cephalic response and these may be relevant for longer-term metabolic regulation.