Diabetes, Vol 49, Issue 6 961-968, Copyright © 2000 by American Diabetes Association
Reduced pancreatic polypeptide response to hypoglycemia and amylin response to arginine in subjects with a mutation in the HNF-4alpha/MODY1 gene
LL Ilag, BP Tabaei, WH Herman, CM Zawacki, E D'Souza, GI Bell and SS Fajans
Department of Internal Medicine, University of Michigan Health System, Ann Arbor, USA.
Subjects with the Q268X mutation in the hepatocyte nuclear factor
(HNF)-4alpha gene (RW pedigree/maturity-onset diabetes of the young
[MODY]-1) have diminished insulin and glucagon secretory responses to
arginine. To determine if pancreatic polypeptide (PP) secretion is likewise
involved, we studied PP responses to insulin-induced hypoglycemia in 17 RW
pedigree members: 6 nondiabetic mutation-negative [ND(-)], 4 nondiabetic
mutation-positive [ND(+)], and 7 diabetic mutation-positive [D(+)].
Subjects received 0.08 U/kg body wt human regular insulin as an intravenous
bolus to produce moderate self-limited hypoglycemia. PP areas under the
curve (PP-AUCs) were compared among groups. With hypoglycemia, the PP-AUC
was lower in the D(+) group (14,907 +/- 6,444 pg/ml, P = 0.03) and the
ND(+) group (14,622 +/- 6,015 pg/ml, P = 0.04) compared with the ND(-)
group (21,120 +/- 4,158 pg/ml). In addition, to determine if the beta-cell
secretory defect in response to arginine involves amylin in addition to
insulin secretion, we analyzed samples from 17 previously studied RW
pedigree subjects. We compared the AUCs during arginine infusions for the 3
groups both at euglycemia and hyperglycemia as well as their
C-peptide-to-amylin ratios. The D(+) and ND(+) groups had decreased amylin
AUCs during both arginine infusions compared with the ND(-) group, but had
similar C-peptide-to-amylin ratios. These results suggest that the
HNF-4alpha mutation in the RW/MODY1 pedigree confers a generalized defect
in islet cell function involving PP cells in addition to beta- and
alpha-cells, and beta-cell impairment involving proportional deficits in
insulin and amylin secretion.