The
hormone,
pancreatic polypeptide (PP) is postulated to be involved in
body weight regulation. PP release is dependent on vagal activation and is a marker of vagal efferent activity. Because vagal activity plays a role in
glucose homeostasis, elucidating the conditions of activation has important implications for nutrient metabolism. In humans, modified
sham-feeding is known to elicit vagally-mediated hormonal responses. We present results of 3 studies in which healthy human subjects tasted various stimuli including sweet and salty liquids, unflavored and flavored gum and mixed nutrient foods flavored with either sweet or
salt and rendered palatable or unpalatable. We examined the effects of these stimuli on PP levels relative to fasting. We found that liquids flavored with either
glucose or
salt, did not elicit an increase in PP levels greater than fasting. Similarly,
chewing gum, whether unflavored or flavored with a non-nutritive
sweetener or the
sweetener paired with a mint flavor, did not significantly increase PP levels. In contrast, when subjects tasted mixed nutrient foods, these reliably elicited increases in PP levels at 4 min post-stimulus (sweet palatable, p<0.002; sweet unpalatable, p<0.001; salty, palatable, p<0.05, salty unpalatable, p<0.05). The magnitude of release was influenced by the flavor, i.e. a sweet palatable stimulus (320.1+/-93.7 pg/ml/30 min) elicited the greatest increase in PP compared with a salty palatable stimulus (142.4+/-88.7 pg/ml/30 min; p<0.05). These data suggest that liquids and
chewing gum do not provide adequate stimulation for vagal efferent activation in humans and that mixed nutrient foods are the optimal stimuli.