Reduced Pancreatic Polypeptide Secretion in Obese Subjects*

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Abstract
In this work we have compared the human pancreatic polypeptide (hPP) response to a protein-rich meal (70 g smoked pork loin and 20 g white bread) in 21 healthy obese [overweight by 53 ± 2.5% (SEM)] and 28 control volunteers of similar ages. The mean fasting hPP concentration of the obese group was lower than that of the normal volunteers (32 ± 7 vs. 55 ± 7 pg/ml; P = 0.031). The hPP secretion evoked by the meal also was smaller in the obese than in the control individuals, with differences between the mean values of both groups ranging from 74–140 pg/ml throughout the experimental period. Furthermore, the hPP response, as expressed by the area above the basal value, was smaller in the obese than in the control subjects (15.60 ± 3.56 and 29.67 ± 4.64, respectively; p = 0.028). Compared to the normal individuals, the overweight subjects displayed elevated mean plasma insulin and glucose levels both in the basal state and after food ingestion. Mean fasting FFA values also were higher in the obese group than in the control subjects. The hPP hyposecretion observed in our obese subjects may be a consequence of their elevated circulating glucose and FFA levels, since the injection of these substrates in normal subjects has been shown to reduce basal hPP plasma concentrations as well as the secretory response of this hormone to food ingestion. On the other hand, the reduction of plasma hPP found in overweight individuals is in agreement with the decrease in plasma PP levels reported for New Zealand obese mice and with the diminution in the islet number of PP-secreting cells observed i n Jackson ob/ob mice. Although the causal relationship between obesity and lowered hPP secretion remains to be elucidated, our data are compatible with the concept that hPP is involved in the control of appetite by acting as an inhibitor.

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