Glucagon-like peptide-1 and exendin-4 stimulate beta-cell neogenesis in streptozotocin-treated newborn rats resulting in persistently improved glucose homeostasis at adult age
C. Tourrel et al., Glucagon-like peptide-1 and exendin-4 stimulate beta-cell neogenesis in streptozotocin-treated newborn rats resulting in persistently improved glucose homeostasis at adult age, DIABETES, 50(7), 2001, pp. 1562-1570
In neonatal Wistar rats injected with streptozotocin (STZ) at birth (n0-STZ
model), a recognized model of beta -cell regeneration, we investigated the
capacity of early treatment with glucagon-like peptide 1 (GLP-1) or exendi
n-4 to promote beta -cell regeneration and thereby improve islet function i
n the long term, when animals become adults. To this end, n0-STZ rats were
submitted to GLP-1 or exendin-4 from postnatal day 2 to day 6 only, and the
ir beta -cell mass and pancreatic functions were tested on day 7 and at 2 m
onths. On day 7, both treatments increased body weight, decreased basal pla
sma glucose, decreased insulinemia, and increased pancreatic insulin conten
t in n0-STZ rats. At the same age, the beta -cell mass, measured by immunoc
ytochemistry and morphometry methods, was strongly increased in n0-STZ/GLP-
1 and n0-STZ/Ex rats compared with n0-STZ rats, representing 51 and 71%, re
spectively, of the beta -cell mass in Wistar rats, whereas n0-STZ beta -cel
l mass represented only 21% of the Wistar control value. Despite such early
improved beta -cell mass, which is maintained at adult age, the basal and
glucose-stimulated insulin secretion (in vivo after intravenous glucose loa
d or in vitro using perfused pancreas) were not improved in the 2-month-old
n0-STZ rats previously treated with GLP-1 or exendin-4 compared with untre
ated n0-STZ rats. However, both treated groups significantly exhibited a de
creased basal plasma glucose level and an increased plasma glucose clearanc
e rate compared with the 2-month-old untreated n0-STZ group at adult age. T
hese findings in the n0-STZ model indicate for the first time that GLP-1 or
exendin-4 applied during the neonatal diabetic period exert both short- an
d long-term beneficial effects on beta -cell mass recovery and glucose home
ostasis. However, the increase in beta -cell mass, which is still present i
n the adult n0-STZ rats previously treated, contrasts with the poor beta -c
ell responsiveness to glucose. Further studies are needed to understand the
dissociation between beta -cell regeneration and the lack of improvement i
n beta -cell function.