Impaired Pancreatic Polypeptide Response to Insulin Hypoglycemia in Obese Subjects

Summary

We have studied the effect of insulin hypoglycemia on the secretion of pancreatic polypeptide (PP) in 14 obese subjects with normal glucose tolerance and in 6 normal controls. Infusion of insulin 0.1 U/kg/h in controls and 0.12 U/kg/h in the obese, for one hour, produced a progressive hypoglycemia, similar in both groups (nadir 2 mmol/l at 50 min). The secretion of PP was less in obese subjects than in controls (peak 116 mmol/l vs 184 pmol/l, P < 0.01) (integrated secretion ΣΔ PP 288 vs 472 pmol/l, P < 0.01) and was also delayed in the obese subjects beginning at 50 min instead of 40 min.

The secretion of glucagon and of C-peptide were not different in the two groups, but the integrated response of ACTH was higher in the obese (ΣΔ ACTH 52 pmol/l vs 25 pmol/l, P < 0.01). The secretory response of growth hormone (STH) was smaller in the obese group (peak 8.6 ± 1.28 vs 21.4 ± 6.4 ng/ml. P < 0.01).

The reduced secretion of PP in obese subjects could be due to impaired sensitivity to hypoglycemia of the central control mechanism for PP release. The similarity of the reductions in the secretion of both PP and STH support this hypothesis, although a reduction in the secretory capacity of pancreatic PP cells cannot be excluded.

Key-Words:

Pancreatic Polypeptide - Insulin Hypoglycemia - Obesity