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Laboratoire de Physiopathologie de la Nutrition, CNRS ESA 7059, Université Paris 7, Paris-France
1Correspondence: Laboratoire de Physiopathologie de la Nutrition, CNRS ESA 7059, Tour 23–33-1er étage, 2, Place Jussieu, 75251 Paris Cedex 05 France.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Key Words: pancreas plasticity • streptozotocin • chronic hyperglycemia
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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2
3)
. The
control of ß cell mass depends on a subtle balance between cell
proliferation and growth and cell death (reviewed in refs 4
, 5
). A
disruption of this balance may lead to impairment of glucose
homeostasis. For example, it is noteworthy that glucose intolerance
develops with aging when ß cell replication rates are reduced (6)
,
and human autopsy studies repeatedly showed a 40–60% reduction of ß
cell mass in patients with non-insulin-dependent-diabetes mellitus
(NIDDM)2
compared with nondiabetic subjects (7
8
9
10)
. Studying the mechanisms of
ß cell growth and/or regeneration is thus of considerable interest in
order to clarify the relationship between ß cell mass and pancreatic
function, to gain a better understanding of the pathogenesis of NIDDM,
and to search for new, appropriate therapeutic approaches.
In a previous study, we showed that a 48 h infusion with glucose
(mean glycemia 22 mM) dramatically increased the ß cell mass both in
nondiabetic and mildly diabetic rats. Mild diabetes was induced by the
injection of a low dose of streptozotocin (STZ rats), resulting in a
50% reduction of the ß cell mass (11)
.
Using this model, we concentrated in this study on 1) the chronology of events leading to changes in the ß cell mass, during glucose infusion and several days after stopping infusion, 2) the mechanisms involved in ß cell mass changes in glucose-infused nondiabetic and STZ rats, and 3) the relationship between changes in the ß cell mass and the pancreatic islet function.
For this purpose, nondiabetic and mildly diabetic rats were submitted to a 24 or 48 h infusion with glucose. At the end of the infusion, ß cell mass, and ß cell replication and apoptosis rates were measured. Seven days after a 48 h glucose infusion, the same parameters were studied. In all groups of rats, islet function was investigated by performing in vivo insulin secretion tests in response to glucose.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Induction of experimental diabetes
Diabetes was induced by a single intravenous (i.v.) injection
through the saphenous vein of 35 mg/kg body wt STZ (Sigma, St. Louis,
Mo.) dissolved in a citrate buffer (0.1 mol/l, pH 4.5) (11
, 12)
.
Controls were i.v. injected with citrate buffer. The diabetic state was
characterized 2 wk after STZ injection by the measurement of basal
plasma glucose concentration and an i.v. glucose tolerance test, which
was performed as follows. Rats were anesthetized with pentobarbital (4
mg/100 g body wt, intraperitoneal) (Sanofi Santé Animale,
Libourne, France) in the postabsorptive state and glucose (0.8 g/kg
body wt) was injected into the saphenous vein. Blood samples were
collected sequentially before and 5, 10, 15, 20, and 30 min after
glucose injection. Glucose concentration was immediately determined.
The plasma left was stored at -20°C until insulin assay. Insulin and
glucose responses during glucose tolerance tests were calculated as the
incremental plasma insulin values integrated over a period of 30 min
after the injection of glucose (
I) and the corresponding increase in
glucose concentration (G). The insulinogenic index (I/G)
represents the ratio of these two parameters. Rats were considered
mildly diabetic (STZ rats) when basal glycemia was between 7 and 10
mmol/l. Rats whose basal glycemia was in this range showed a I/G
fivefold lower than in controls (data not shown).
Infusions
Nondiabetic (ND) and STZ rats were submitted to saline (0.9%
NaCl) or glucose infusions. Infusions were carried out with the
long-term infusion technique under unrestrained conditions as described
previously (11
, 13)
. Hypertonic (30% wt/volume) glucose (Chaix & Du
Marais, Paris, France) was infused at an initial rate of 50 µl/min to
produce hyperglycemia around 22 mmol/l throughout the infusion period
in ND and STZ rats. This level of hyperglycemia induced a mean
insulinemia ~1.5 nmol/l in ND rats and 0.8 nmol/l in STZ rats. During
infusions, plasma glucose and insulin concentrations were measured on
blood collected by tail snipping five times daily in glucose-infused
rats and only twice daily in saline-infused rats, where these
parameters remained stable. This daily control allowed to maintain
glycemia and insulinemia in the required ranges (glycemia 22 ± 2
mmol/l in both groups; insulinemia 1.5 ± 0.2 nmol/l in ND rats
and 0.8 ± 0.1 nmol/l in STZ rats) by adjusting the infusion flow
rate. Rats whose glycemia and insulinemia did not stay within these
ranges were excluded.
The duration of saline or glucose infusions was 24 or 48 h. For
each duration, a different group of ND or STZ rats was used. In these
groups, insulin secretion and morphometric studies were performed
3 h after the infusions ended. At this time, in ND and STZ rats,
plasma insulin concentrations returned to their respective basal
values. In a third set of experiments, ND and STZ rats were infused
either with saline or glucose for 48 h. The infusion was stopped
and the rats were disconnected from the pumps. They were fed ad
libitum with a standard lab chow and received water for 7
days. On the morning of the eighth day postinfusion, in vivo
insulin secretion tests were performed. Then, rats were killed and the
same morphometric studies as in the other groups were carried out. The
general experimental design is shown in Fig. 1
.
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Because all the morphometric and functional parameters were similar in saline-infused rats whatever the duration of the infusion and the time of the different studies (data not shown), we chose to represent only the results concerning the 48 h saline-infused ND and STZ rats as representative of the different saline-infused groups.
When the rate of ß cell proliferation was measured, rats were
injected ip with 5-bromo-2'deoxyuridine (BrdU, 100 mg/kg BW; Sigma)
6 h before death (14)
. After in vivo insulin secretion,
pancreases were dissected, cleared of fat and lymph nodes, and
weighed. After fixation in aqueous Bouin's solution, they were
embedded in paraffin. As described previously, each pancreatic block
was serially sectioned (7 µM) throughout its length to avoid any bias
due to changes in islet distribution and cell composition (11)
.
Morphometric studies and measurements of replication and apoptosis
rates were performed on the same pancreatic block for each rat.
Immunocytochemistry and morphometry
For each pancreas, 10 sections were randomly chosen every 35th
section throughout the block (11
, 15)
. Sections were immunostained for
insulin or glucagon using a peroxidase indirect labeling technique. As
previously reported, sections were incubated for 1 h with primary
antibodies (guinea pig anti-insulin, final dilution 1:1000, or rabbit
anti-glucagon, final dilution 1:1000, ICN Biochemicals, Aurora, Ohio).
Thereafter, peroxidase-conjugated second antibodies were applied for 45
min [rabbit anti-guinea pig immunoglobulin G (IgG), 1:20, Dako,
Carpinteria, Calif., and goat anti-rabbit IgG, 1:250, KPL,
Gaithersburg, Md.]. Staining was visualized by incubation with
3,3'-diaminobenzidine-tetra-hydrochloride (kit DAB, Biosys-Vector,
Compiègne, France). Sections were counterstained with hematoxylin
and mounted in Eukitt.
Quantitative evaluation of total ß and 
cell areas was performed
using an Olympus BH2 microscope connected via a color video camera to a
Compaq PC computer and Imagenia 2000 software (Biocom, Les Ulis,
France). The areas of both insulin and glucagon-positive cells, as well
as that of total pancreatic sections, were evaluated in each stained
section. The relative volumes of ß and cells were determined by
the stereological morphometric method, calculating the ratio between
the area occupied by immunoreactive cells and that occupied by total
pancreatic cells. Total ß or cell mass per pancreas was derived
by multiplying this ratio by the total pancreatic weight.
Individual ß cell area
ß cell size was measured on the above insulin-stained
sections. ß cell nuclei on a random section were counted, and the
area of ß cell tissue in that section was measured by planimetry as
described above. The individual ß cell size was determined by
dividing the ß cell area by the number of nuclei. By using this
technique, it is possible that the actual number of ß cells is higher
than the number counted, since not all ß cells are sectioned across
their nuclei. Therefore, the size of ß cells may be overestimated.
ß cell replication
Pancreatic sections that had not already been used for
morphometric studies were used to measure ß cell replication rates.
BrdU is incorporated in newly synthesized DNA and therefore labels
replicating cells. A 6 h BrdU incorporation interval was chosen to
avoid the possibility of including daughter cells (16)
. Sections were
double-stained for BrdU using a cell proliferation kit (Amersham
International, Amersham, U.K.) and for insulin. Sections were incubated
with a mouse monoclonal antibody anti-BrdU diluted in a nuclease
solution (according to the kit protocol) for 1 h at room
temperature and washed with Tris 0.05 M, pH 7.6. Thereafter, they were
incubated with an affinity-purified peroxidase anti-mouse IgG and
stained with 3,3'-diaminobenzidine-tetra-hydrochloride using a
peroxidase substrate kit DAB.
Sections were then incubated with guinea pig anti-insulin antibody for 1 h as described above and then with alkaline phosphatase-conjugated goat anti-guinea pig IgG for 45 min (final dilution 1:150, Sera Lab, Carpinteria, Calif.). The activity of the antibody–alkaline phosphatase complex was revealed with an alkaline phosphatase substrate kit (Biosys-Vector). Sections were counterstained with hematoxylin and mounted in Eukitt. On these sections, ß cells showed red cytosol and BrdU+ cells appeared with brown nuclei. A minimum of 1100 ß cell nuclei were counted per section at a final magnification of 1000x. The proportion of BrdU+ ß cell nuclei to total ß cell nuclei was calculated. The result represents the percentage ß cell replicative rate in a 6 h interval.
ß cell apoptosis
Sections from the same blocks used for ß cell mass measurement
and replication were used to study ß cell apoptosis rates. Apoptotic
cells were detected with the ApopTag in situ apoptosis
detection kit (Appligène-Oncor, Illkirch, France). Sections were
pretreated with proteinase K (20 µg/ml) for 20 min at room
temperature and washed with double-distilled water. Thereafter, they
were incubated with terminal deoxyribonucleotidyl transferase (TdT)
enzyme and digoxigenin-nucleotide residues for 1 h at 37°C.
After washing the slides in phosphate-buffered saline, pH 7.4, they
were incubated with a peroxidase-conjugated anti-digoxigenin antibody
and stained with 3,3'-diaminobenzidine-tetra-hydrochloride using a
peroxidase substrate kit DAB.
Sections were then incubated for 1 h with a mixture of three
different antibodies: rabbit anti-glucagon (final dilution 1:1000),
rabbit anti-somatostatin (final dilution 1:600, ICN Biochemicals), and
rabbit anti-pancreatic polypeptide (final dilution 1:1500, ICN
Biochemicals). Sections were then incubated for 45 min with alkaline
phosphatase-conjugated goat anti-rabbit IgG (final dilution 1:150,
Boehringer, Carpinteria, Calif.). The activity of antibody–alkaline
phosphatase complex was revealed with an alkaline phosphatase substrate
kit. Sections were counterstained with hematoxylin and mounted in
Eukitt. Apoptosis causes cell shrinkage and fragmentation, leading to
the loss of cell integrity. Therefore, apoptotic ß cells may be
degranulated in the last phases of apoptosis. Furthermore, apoptosis is
a rapid process, with less than 1 h of morphological evidence
(17)
. Thus, measurement of apoptotic ß cell rate with a direct
insulin staining could lead to an underestimation of this rate. We used
the staining of non-ß cells to surround the core of the islet and
identify the ß cells. On stained sections, the islet tissue was
identified as a mantle of endocrine non-ß cells with a red cytosol, a
core of ß cells with nonstained cytosol, and apoptotic positive cells
with brown nuclei. No nuclei staining was found in controls in which
TdT enzyme was omitted. Most of the endocrine apoptotic cells were
located in the core of the islets, delimited by the non-ß cell
immunostaining, suggesting that they were apoptotic ß cells. 1500 ß
cell nuclei were counted per section at a final magnification of
1000x.
Insulin secretion
Insulin secretion was studied in response to an i.v. glucose
bolus as mentioned above and measured as the insulinogenic index
(I/G). Blood glucose was determined by the glucose oxidase
technique using a glucose analyzer (Beckman Inc., Fullerton, Calif.).
Insulin was measured by a radioimmunoassay kit (Sorin, Roma, Italy).
The lower limit of the assay was 0.07 nmol/l, with a coefficient of
variation within and between the assay of 6%.
Data presentation and statistical methods
Data are presented as means ± SE. Statistical
significance was determined with the analysis of variance test. A
P value < 0.05 was considered significant.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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cell mass and individual ß
cell area
(Table 1
). After a 24 h glucose infusion, ß cell mass was ~1.5-fold
greater in ND rats and ~3-fold greater in STZ rats than in
saline-infused rats. This corresponds to a 80% and 185% increase
compared with saline-infused rats. ß cell mass did not vary between
24 and 48 h of infusion with glucose in ND and STZ rats. From
24 h glucose infusion, ß cell mass in STZ rats was comparable to
ß cell mass in ND saline-infused rats.
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Seven days after the end of a 48 h glucose infusion, ß cell mass
was dramatically decreased in both ND and STZ groups compared with
48 h glucose-infused rats (Table 1)
. At that time, values of ß
cell mass were similar to the values of saline-infused groups.
No significant difference was observed in the cell mass and in the
distribution of glucagon cells in ND and STZ rats at any time of the
study (Table 1)
.
During the glucose infusion period, individual ß cell areas were
significantly increased only after a 48 h glucose infusion in ND
and STZ groups, thus suggesting cell hypertrophy (Table 1)
. Seven days
after stopping the glucose infusion, ß cell sizes remained increased
in ND and STZ rats.
Morphological studies in pancreas of infused rats
After 24 h of glucose infusion, large elongated and
multilobated islets were often observed to be closed to small ducts
(Fig. 2
-A, B). These islets were sometimes invaded by a cord of
cells that originated from ducts (Fig. 2C, D
). These cells
were not stained for any of the pancreatic hormones. This suggests
hyperplasia of the endocrine tissue.
|
At 24 h of glucose infusion, other features of pancreatic
sections from both ND and STZ rats strongly suggested a stimulation of
islet neogenesis: BrdU+ cells in the epithelium
of pancreatic ducts (Fig. 3
B), and endocrine cells within or budding from the pancreatic
ductal epithelium (Fig. 4
) were observed at a much higher level than in saline-infused rats.
Isolated individual cells were stained for insulin (Fig. 4C
)
or to a much lesser extent for glucagon (Fig. 4D
), generally
closely associated with duct epithelial cells or clusters of a few
cells stained only for insulin or glucagon (Fig. 4A, B
).
Clusters of cells stained for glucagon or individual cells stained for
glucagon or somatostatin were never observed in saline-infused groups.
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At 48 h of glucose infusion, histological evidence of islet neogenesis was scarce compared with 24 h glucose-infused rats.
The features of pancreatic sections from ND and STZ rats studied 7 days after stopping glucose infusion were similar to that of saline-infused ND and STZ rats.
Effect of infusions on ß cell proliferation rates
At the end of a 24 h glucose infusion, ß cell replication
rates were decreased (50%) in ND and STZ animals compared with
saline-infused groups (Fig. 5
). Between 24 and 48 h, the replication rate doubled in both groups
so that it became similar to that of saline-infused rats. Seven days
after stopping glucose infusion, ß cell proliferation dropped by 50%
in both groups (ND and STZ rats) compared with values of the
proliferative rate at 48 h glucose infusion (Fig. 5)
. The
difference between STZ and ND rats was not significant.
|
Effect of infusions on ß cell apoptosis
Apoptotic cells were detectable with the DNA breakage
labeling method in the pancreases of saline- or glucose-infused rats
(Fig. 6
). Figure 6
represents an illustrative fragment of histological staining
for apoptotic cells centrally located within the islets. In ND and STZ
rats, the number of apoptotic ß cells decreased during the glucose
infusion period at both 24 and 48 h (Fig. 7
). Seven days after stopping glucose infusion, the number of apoptotic
ß cells in both groups increased compared with basal values (Fig. 7)
.
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Effect of infusions on in vivo insulin secretion
In ND rats infused with glucose for 24 or 48 h, basal
plasma insulin concentrations were similar to those of saline-infused
ND rats whereas the plasma insulin after an acute glucose injection was
more elevated at each time of the test (Fig. 8
A). This was reflected by the I/G, which was greater
than with saline-infused ND rats (Fig. 8B
). In
saline-infused STZ rats, plasma insulin concentration in the basal
state was similar to that of ND rats, but increased weakly in response
to glucose loading (Fig. 8A
) so that the I/G was
markedly decreased (75%) compared with saline-infused ND rats (Fig. 8B
). In STZ rats infused with glucose for 24 or 48 h,
plasma insulin concentrations were similar to those of saline-infused
STZ rats, and the I/G remained almost threefold lower than in
saline-infused ND rats. Seven days after a 48 h glucose infusion,
plasma insulin response to glucose and the I/G in ND as in STZ
rats met values similar to the corresponding saline-infused rats (Fig. 8A, B
).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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19
20)
. However, this enlargement
occurred in very young rats or hamsters, i.e., at a time of intensive
ß cell growth (5)
. We used 3-month-old rats, where a sharp slowing
down of ß cell growth was previously reported (5)
. This suggests that
the ß cell mass may be rapidly increased in adult rats even in a
period of poor growth. This is a clear demonstration of the remarkable
plasticity of the endocrine pancreas and its potent regenerative
capacity in adult animals.
It is striking that 24 h of infusion with glucose was enough to
completely restore the ß cell mass in diabetic rats. This stresses
the potent effect of high glucose on ß cell growth compared with the
spontaneous regeneration observed in other models of diabetic rats
(21
22
23)
.
Variations of the ß cell mass could be the result of a disruption of the balance between ß cell replication rate, ß cell hypertrophy, and islet neogenesis, and the ß cell apoptosis rate.
In 24 h glucose-infused ND and STZ rats, ß cell replication
rate was almost 50% decreased compared with saline-infused rats. This
is in agreement with the results of Lipsett et al. (24)
. The inhibition
of ß cell replication is paradoxical because glucose is known to be a
potent stimulus of ß cell replication in adult rats (25)
. In our
model, rats were submitted to an abrupt and elevated hyperglycemia,
requiring a rapid increase in insulin release. ß cell metabolism was
likely turned toward insulin biosynthesis and secretion in order to
respond to the superimposed hyperglycemia rather than cell replication.
Moreover, oral food intake dramatically dropped in glucose-infused rats
(data not shown), probably leading to a sharp decrease of gut hormone
release. These hormones participate in the stimulation of ß cell
proliferation (26)
. Therefore, ß cell proliferation could be hampered
by the low level of gut hormones. Alternatively, the existence of a
wave of ß cell replication occurring during the first 24 h of
glucose infusion cannot be excluded. Shorter times of infusion with
glucose are required to clarify this point.
At 48 h, the ß cell replication rate increased compared with time 24 h, probably because the new ß cells that appeared from neogenesis started to proliferate under glucose stimulation.
There was much morphological evidence of hyperplasia of the endocrine
tissue and islet neogenesis in the pancreas of both ND and STZ
glucose-infused rats. Moreover, a clear decrease in the number of
apoptotic ß cells was observed. The decrease in the rate of apoptosis
in glucose-infused rats is consistent with the role of glucose in the
inhibition of the ß cell [suicide] program (27)
. Together, these
results strongly suggest that, at 24 h of glucose infusion, the
ß cell mass increase was the consequence of a preponderance of islet
neogenesis over ß cell apoptosis. The phenomenon was more marked in
glucose-infused STZ rats, consistently with the higher increase in ß
cell mass in these rats compared with ND glucose-infused rats. For a
long time, islet neogenesis in adult has been considered as marginal
compared with the replication of preexisting cells (reviewed in ref 2
).
However, this process is now seen in adults in various animal models of
pancreas regeneration (18
, 20
, 22
, 28)
. Moreover, few histological
studies have shown that islet regeneration occurs in the pancreas of
recent-onset diabetic patients, particularly in young children (8
, 29)
.
Seven days after stopping glucose infusion, there was a regression of
the excess pancreatic tissue assessed by the fact that the ß cell
mass returned to normal values in both nondiabetic and STZ rats. At
this time, the ß cell replication rate was twofold lower than in
saline-infused animals. This latter result is in agreement with the
study of Bonner-Weir et al. (25)
. In our study, individual ß cell
area was still elevated in glucose-infused rats compared with
saline-infused animals, but this was not sufficient to maintain an
elevated ß cell mass. Indeed, the enlargement of the ß cell size
was counterbalanced by the inhibition of ß cell replication and by
the increased frequency of apoptotic ß cell. Furthermore, all the
histological features suggested a marked decrease in islet neogenesis
compared with the time 24 h after infusion.
The sequence of events may be interpreted in the following way: the
enlargement of the endocrine tissue was necessary to compensate an
extra demand of insulin during prolonged glucose infusion. From the
second day after stopping glucose infusion, rats recovered their basal
glycemia (5–6 mmol/l in ND rats; 7–8 mmol/l in STZ rats). Thus, the
pancreatic adaptation to an induced or superimposed hyperglycemia
stopped and the ß cell mass decreased mainly as a result of ending
the activation of apoptosis to normal ß cell mass values 7 days
later. Our results are matched with those of Scaglia et al. (30)
, who
showed that apoptosis was involved in the physiological involution of
the ß cell mass in the postpartum period.
Enhanced ß cell activity in response to glucose was detected in ND
rats as early as 24 h of glucose infusion. This situation is
unlikely due to a reduced insulin clearance, as it was observed in
another studies (31)
. Indeed, at time 0 of the test, plasma insulin
concentrations were similar in saline- and glucose-infused ND rats.
Moreover, we previously reported a large increase in insulin release in
response to various nutrient secretagogues in vitro in
48 h glucose-infused rats (11)
.
Seven days after stopping glucose infusion, insulin secretion in
response to glucose returned to basal values. This was concomitant with
the decrease in the ß cell mass observed at that time. Taken
together, these data stress a correlation between changes in the ß
cell mass and insulin secretion in rats with an intact pancreas. The
situation in ND rats contrasts with the dissociation of both parameters
in glucose-infused STZ rats. We have previously shown that the absence
of effect of glucose infusion on ß cell function in STZ
glucose-infused rats was observed after a 48 h infusion (11)
.
Here, we show that this defect could be detected in STZ rats as early
as 24 h of the glucose infusion. In the STZ group of rats, ß
cell mass modifications did not influence at all islet function. The
new ß cells recruited by prolonged glucose infusion were not
functional or poorly functional. Possibly, these cells were not
completely differentiated.
In conclusion, our study provides clear evidence of a rapid
compensatory ß cell growth to respond to a continuous glucose
infusion. This is due to a modification in the balance between islet
neogenesis and apoptosis in favor of the neogenesis process rather than
to changes in the replication rate. An important finding of this study
is the demonstration of the crucial role of neogenesis from ductal stem
cells for ß cell growth. This process was maximal as early as 24 h of glucose infusion. Moreover, increased apoptosis appears as the
main factor responsible for the involution of endocrine tissue 7 days
after stopping the glucose infusion. The possible role of
apoptosis in the inadequate ß cell mass in diabetes emerges from a
recent study of Pick et al. (32)
. The large variations in apoptotic
rate in our model will allow us to further study the factors
controlling ß cell apoptosis.
Our data also indicate that ß cell mass is an important component of islet function in normal rats. In diabetic rats, the failure of maturating factors during rapid pancreatic regeneration may prevent improvement of insulin secretion. Our model seems suitable for the search of these factors and to study the mechanisms involved in the ß cell mass modifications. The study of the balance between islet neogenesis and apoptosis especially could lead to a better understanding of the etiology of diabetes and in the search for new therapeutic approaches.
|
FOOTNOTES |
|---|
I/G, insulinogenic index; i.v., intravenous; ND, nondiabetic;
NIDDM, non-insulin-dependent-diabetes mellitus; STZ, streptozotocin;
TdT, terminal deoxyribonucleotidyl transferase. 
Received for publication December 4, 1998.
Revision received February 11, 1999.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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E. Bernal-Mizrachi, W. Wen, M. Shornick, and M. A. Permutt Activation of Nuclear Factor-{kappa}B by Depolarization and Ca2+ Influx in MIN6 Insulinoma Cells Diabetes, December 1, 2002; 51(90003): S484 - 488. [Abstract] [Full Text] [PDF]
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S. Srinivasan, E. Bernal-Mizrachi, M. Ohsugi, and M. A. Permutt Glucose promotes pancreatic islet beta -cell survival through a PI 3-kinase/Akt-signaling pathway Am J Physiol Endocrinol Metab, October 1, 2002; 283(4): E784 - E793. [Abstract] [Full Text] [PDF]
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E. J. Abraham, C. A. Leech, J. C. Lin, H. Zulewski, and J. F. Habener Insulinotropic Hormone Glucagon-Like Peptide-1 Differentiation of Human Pancreatic Islet-Derived Progenitor Cells into Insulin-Producing Cells Endocrinology, August 1, 2002; 143(8): 3152 - 3161. [Abstract] [Full Text] [PDF]
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M. Lipsett and D. T. Finegood {beta}-Cell Neogenesis During Prolonged Hyperglycemia in Rats Diabetes, June 1, 2002; 51(6): 1834 - 1841. [Abstract] [Full Text] [PDF]
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H. Wobser, H. Du{beta}mann, D. Kogel, H. Wang, C. Reimertz, C. B. Wollheim, M. M. Byrne, and J. H. M. Prehn Dominant-negative Suppression of HNF-1alpha Results in Mitochondrial Dysfunction, INS-1 Cell Apoptosis, and Increased Sensitivity to Ceramide-, but Not to High Glucose-induced Cell Death J. Biol. Chem., February 15, 2002; 277(8): 6413 - 6421. [Abstract] [Full Text] [PDF]
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S. N. Flier, R. N. Kulkarni, and C. R. Kahn Evidence for a circulating islet cell growth factor in insulin-resistant states PNAS, June 7, 2001; (2001) 131192998. [Abstract] [Full Text] [PDF]
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D. T. Finegood, M. D. McArthur, D. Kojwang, M. J. Thomas, B. G. Topp, T. Leonard, and R. E. Buckingham {beta}-Cell Mass Dynamics in Zucker Diabetic Fatty Rats: Rosiglitazone Prevents the Rise in Net Cell Death Diabetes, May 1, 2001; 50(5): 1021 - 1029. [Abstract] [Full Text]
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S. N. Flier, R. N. Kulkarni, and C. R. Kahn Evidence for a circulating islet cell growth factor in insulin-resistant states PNAS, June 19, 2001; 98(13): 7475 - 7480. [Abstract] [Full Text] [PDF]
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) and STZ (
) rats after saline or
glucose infusions and 7 days after stopping glucose infusion. Values
are means ± SE of 3–5 rats in each group.
*P<0.05.
