Diabetes, Vol 46, Issue 9 1414-1418, Copyright © 1997 by American Diabetes Association
Impaired glucose-induced insulin response in transgenic mice overexpressing the L-phosphofructokinase gene
H Knobler, Y Weiss, M Peled and Y Groner
Division of Endocrinology, Kaplan Hospital Rehovot, Israel. knobler@inter.net.il
The selective impairment of glucose-induced insulin secretion in NIDDM can
be attributed to defects in the glucose-signaling system. An alteration in
the activity of phosphofructokinase (PFK), a key enzyme in the glycolytic
pathway, may play a role in the abnormal glucose-induced insulin secretion.
In this study, we evaluated insulin secretion in transgenic (Tg) mice
overexpressing the liver-type subunit of phosphofructokinase (PFKL). Three
independently derived Tg-PFKL lines showed random and postprandial
hyperglycemia with diminished acute insulin response following intravenous
glucose tolerance load. Isolated islets of Tg-PFKL mice exhibited a shift
to the right of the glucose insulin dose curve. However, the maximal
insulin secretory capacity, as well as the potentiation effect by arginine,
were retained. PFK activity in Tg-PFKL islets was increased by 30-70%,
because of the overexpression of PFKL. Conceivably, a selective
overexpression of the PFKL isoform in Tg-PFKL mice altered the enzymatic
properties of the tetrameric PFK and thereby affected glucose metabolism. A
similar phenomenon was previously observed in transfected PC12-PFKL cells.
The data show that overexpression of PFKL in transgenic mice was associated
with diminished glucose-induced insulin response and suggest a mechanism to
explain the role of beta-cell PFK activity in glucose-induced insulin
secretion.