Increased Β-cell Proliferation Research Articles

Acute Deletion of METTL14 in β-Cells of Adult Mice Results in Glucose Intolerance.

N6-Methyladenosine (m6A) is the most common and abundant mRNA modification that involves regulating the RNA metabolism. However, the role of m6A in regulating the β-cell function is unclear. Methyltransferase-like 14 (METTL14) is a key component of the m6A methyltransferase complex. To define the role of m6A in regulating the β-cell function, we generated β-cell METTL14-specific knockout (βKO) mice by tamoxifen administration. Acute deletion of Mettl14 in β-cells results in glucose intolerance as a result of a reduction in insulin secretion in β-cells even though β-cell mass is increased, which is related to increased β-cell proliferation. To define the molecular mechanism, we performed RNA sequencing to detect the gene expression in βKO islets. The genes responsible for endoplasmic reticulum stress, such as Ire1α, were among the top upregulated genes. Both mRNA and protein levels of IRE1α and spliced X-box protein binding 1 (sXBP-1) were increased in βKO islets. The protein levels of proinsulin and insulin were decreased in βKO islets. These results suggest that acute METTL14 deficiency in β-cells induces glucose intolerance by increasing the IRE1α/sXBP-1 pathway.

329-LB: Exocrine Pancreas Proteases Are Drivers of ß-Cell Proliferation

The clinical link between loss of β-cell mass and diabetes susceptibility provides a promising avenue of research for novel therapeutics targeting the proliferative axis. To identify potential new pathways involved we utilized two zebrafish genetic models Alström Syndrome (AS) and Bardet-Biedl Syndrome (BBS) that exhibit strikingly different diabetes rates, ∼75% in AS and ∼4% in BBS. We have previously shown β-cell loss in AS and increase in BBS, corresponding to their diabetes rates. RNA-Sequencing of these models identified several exocrine pancreas proteases that were differentially expressed between AS and BBS. Thus, we hypothesized that the exocrine pancreas proteases affect endocrine pancreas function. To test our hypothesis, we overexpressed each enzyme in transgenic zebrafish embryos in which β-cells can be visualized. In control animals, overexpression of exocrine pancreas proteases significantly increased the β-cell number. Overexpression rescued the loss of β-cells observed in animals depleted of alms1. We found ctrb1 overexpression led to increased β-cell proliferation in transgenic larvae and rescued the AS model reduction in proliferation. To test for endogenous protease uptake, we generated a transgenic GFP-tagged CTRB1 and found that 10% of β-cells were GFP+, suggesting a direct interaction between the exocrine and endocrine pancreas. We also found that the inactive, zymogen, form of these enzymes are taken up by β-cells in vitro and induce proliferation in cultured MIN6 β-cells and freshly isolated ex vivo islet cultures, suggesting this effect is conserved in mammalian systems. These data support an important role for exocrine pancreatic enzymes in the modulation of β-cells in diabetes. Disclosure T.L. Hostelley: None. J. Dunleavey: None. E.J. Larkin: None. A.J. Jones: None. D.L. Boyes: None. M.J. Fontaine: None. N.A. Zaghloul: None. Funding National Institutes of Health (F31DK115179-01A1, T32DK098107, R01DK102001, R25GM055036)

Increased β-cell proliferation before immune cell invasion prevents progression of type 1 diabetes.

Type 1 diabetes (T1D) is characterized by pancreatic islet infiltration by autoreactive immune cells and a near-total loss of β-cells1. Restoration of insulin-producing β-cells coupled with immunomodulation to suppress the autoimmune attack has emerged as a potential approach to counter T1D2–4. Here we report that enhancing β-cell mass early in life, in two models of female NOD mice, results in immunomodulation of T-cells, reduced islet infiltration and lower β-cell apoptosis, that together protect them from developing T1D. The animals displayed altered β-cell antigens, and islet transplantation studies showed prolonged graft survival in the NOD-LIRKO model. Adoptive transfer of splenocytes from the NOD-LIRKOs prevented development of diabetes in pre-diabetic NOD mice. A significant increase in the splenic CD4+CD25+FoxP3+ regulatory T-cell (Treg) population was observed to underlie the protected phenotype since Treg depletion rendered NOD-LIRKO mice diabetic. The increase in Tregs coupled with activation of TGF-β/SMAD3 signaling pathway in pathogenic T-cells favored reduced ability to kill β-cells. These data support a previously unidentified observation that initiating β-cell proliferation, alone, prior to islet infiltration by immune cells alters the identity of β-cells, decreases pathologic self-reactivity of effector cells and increases Tregs to prevent progression of T1D.

Altering ß-Cell Proliferation In Vivo by Pharmacological Manipulation of the Nrf2 Pathway

Glucose is a natural mitogen that drives adaptive β-cell mass expansion by promoting proliferation. We previously demonstrated that induction of Nrf2 is required for glucose-stimulated and carbohydrate response element binding protein (ChREBPa)-augmented β-cell proliferation. Here we found that adenoviral delivery of Nrf2 increased human β-cell proliferation by 8.9 ± 0.2 fold (n=6), which exceeded the effect of 20 mM glucose (4.3 ± 0.4 fold). To test if activation of the Nrf2 pathway is necessary for adaptive β-cell expansion in vivo, we used pharmacological inhibitors and activators of Nrf2. Mice were placed on a high fat diet (HFD) or standard chow diet (SD) for 7 days and treated with vehicle or brusatol, which depletes Nrf2 by a post-translational mechanism. Treatment with brusatol effectively diminished Nrf2 abundance in β-cells as determined by immunofluorescence. Further, brusatol treatment ameliorated the increased β-cell proliferation normally seen with a one-week HFD (2.7±03% ki67 positive β-cells in control HFD mice, vs. 1.6±0.3% in HFD mice treated with brusatol, p < 0.05, n=5). Brusatol-treated mice also displayed significantly diminished glucose tolerance on a HFD by IPGTT, without altering the food intake or weight of the animals. Using an activator of Nrf2, bardoxolone methyl (CDDO-Me), for 7 days in the presence or absence of HFD. We found, consistent with previous reports, improved glycemic levels and decreased body weight in mice treated with CDDO-Me on a HFD. Remarkably, we also found increased β-cell proliferation in mice fed a SD and treated with CDDO-Me (1.7 ± 0.1% controls compared to 2.6±0.1% ki67 positive, insulin positive β-cells in mice treated with CDDO-Me). Crucially, in human β-cells, brusatol inhibited glucose-stimulated proliferation (1.9 fold vs. 12.7 fold, n=2) and CDDO-Me increased proliferation in 5 mM glucose (37.5 fold, n=2). Thus, we conclude that the Nrf2 pathway is an exciting novel target for manipulation of β-cell proliferation in vivo. Disclosure L.S. Katz: None. A. Garcia-Ocana: None. D. Scott: None.

Prolactin and oleic acid synergistically stimulate β-cell proliferation and growth in rat islets

ABSTRACTIslet adaptation to pregnancy is largely influenced by prolactin and placental lactogens. In addition serum lipids are significantly increased. Here, we report the novel observation that prolactin and oleic acid synergistically stimulate islet cell proliferation and islet growth. In neonatal rat islets, prolactin increased proliferation 6-fold, oleic acid 3.5-fold, and their combination 15-fold. The expression of insulin in these dividing cells establishes them as β-cells. Similar changes were seen in islet growth. This synergy is restricted to monounsaturated fatty acids and does not occur with other islet growth factors. Oleic acid increases prolactin-induced STAT5 phosphorylation, even though by itself it is unable to induce STAT5 phosphorylation. Their effects on Erk1/2 phosphorylation are additive. Some of the synergy requires the formation of oleoyl CoA and/or its metabolites. Unexpectedly, methyl oleic acid, a non-metabolizable analog of oleic acid, also shows synergy with prolactin. In summary, prolactin and oleic acid synergistically stimulate islet cell proliferation and islet growth in rat islets, oleic acid increases prolactin-induced STAT5 activation, and requires both the metabolism of oleic acid and non-metabolized oleic acid. Since oleic acid is the most abundant monounsaturated fatty acid in serum that is elevated during pregnancy, it may contribute to increased β-cell proliferation seen during pregnancy.

Heterogeneity of proliferative markers in pancreatic β-cells of patients with severe hypoglycemia following Roux-en-Y gastric bypass.

Severe postprandial hypoglycemia with neuroglycopenia is an increasingly recognized, debilitating complication of Roux-en-Y gastric bypass (RYGB) surgery. Increased secretion of insulin and incretin hormones is implicated in its pathogenesis. Histopathologic examination of pancreas has demonstrated increased islet size and/or nuclear diameter in post-RYGB patients who underwent pancreatectomy for severe refractory hypoglycemia with neuroglycopenia (RYGB+NG). We aimed to determine whether β-cell proliferation or apoptosis is altered in RYGB+NG. We performed an observational study to analyze markers of proliferation, apoptosis, cell cycle, and transcription factor expression in pancreatic tissue from affected RYGB+NG patients (n=12), normoglycemic patients undergoing pancreatic surgery for benign lesions (controls, n=6), and individuals with hypoglycemia due to insulinoma (n=52). Proliferative cell nuclear antigen (PCNA) expression was increased in insulin-positive cells in RYGB+NG patients (4.5-fold increase, p<0.001 vs. controls) and correlated with β-cell mass. Ki-67 immunoreactivity was low in both RYGB+NG and controls, but did not differ between groups. Phospho-histone H3 levels did not differ between RYGB+NG and controls. PCNA and Ki-67 were both significantly lower in both controls and RYGB+NG than insulinomas. Markers of apoptosis and cell cycle (M30, p27, and p21) did not differ between groups. PDX1 and menin exhibited similar expression patterns, while FOXO1 appeared to be more cytosolic in RYGB+NG. Markers of proliferation are heterogeneous in patients with severe post-RYGB hypoglycemia. Increased β-cell proliferation in some individuals may contribute to increased β-cell mass observed in severely affected patients.

Geniposide promotes beta-cell regeneration and survival through regulating β-catenin/TCF7L2 pathway.

T-cell factor 7-like 2 (TCF7L2) is an important transcription factor of Wnt/β-catenin signaling, which has critical roles in β-cell survival and regeneration. In preliminary screening assay, we found geniposide, a naturally occurring compound, was able to increase TCF7L2 mRNA level in Min6 cells. Here we aimed to investigate the role of geniposide in β-cell and underlying mechanism involved. Geniposide was found to promote β-cell survival by increasing β-cell proliferation and decreasing β-cell apoptosis in cultured mouse islets after challenge with diabetic stimuli. Geniposide protected β-cell through activating Wnt signaling, enhanced expressions of TCF7L2 and GLP-1R, activated AKT, inhibited GSK3β activity, and promoted β-catenin nuclear translocation. The protective effect of geniposide was remarkably suppressed by siRNAs against β-catenin, or by ICG001 (β-catenin/TCF-mediated transcription inhibitor). Moreover, geniposide promoted β-cell regeneration in vivo to normalize blood glucose in high-fat diet and db/db mice. Increased β-cell proliferation was observed in pancreatic sections of geniposide-treated diabetic mice. Most importantly, geniposide triggered small islet-like cell clusters formation as a result of β-cell neogenesis from ductal epithelium, which was well correlated with the increase in TCF7L2 expression. In exocrine cells isolated from mouse pancreas, geniposide could induce duct cell differentiation through upregulating TCF7L2 expression and activating JAK2/STAT3 pathway. Taken together, we identified a novel role of geniposide in promoting β-cell survival and regeneration by mechanisms involving the activation of β-catenin/TCF7L2 signaling. Our finding highlights the potential value of geniposide as a possible treatment for type 2 diabetes.

Glucose homeostasis changes and pancreatic β-cell proliferation after switching to cyclosporin in tacrolimus-induced diabetes mellitus

BackgroundSwitching to cyclosporin A may result in a reversion of tacrolimus-induced diabetes mellitus. However, mechanisms underlying such a reversion are still unknown. MethodsObese Zucker rats were used as a model for tacrolimus-induced diabetes mellitus. A cohort of 44 obese Zucker rats received tacrolimus for 11 days (0.3mg/kg/day) until diabetes development; then, (a) 22 rats were euthanized at day 12 and were used as a reference group (tacrolimus-day 12), and (b) 22 rats on tacrolimus were shifted to cyclosporin (2.5mg/kg/day) for 5 days (tacrolimus-cyclosporin). An additional cohort of 22 obese Zucker rats received the vehicle for 17 days and was used as a control group. All animals underwent an intraperitoneal glucose tolerance test at the end of the study. Resultsβ-Cell proliferation, apoptosis and Ins2 gene expression were evaluated. Compared to rats in tacrolimus-day 12 group, those in tacrolimus-cyclosporin group showed a significant improvement in blood glucose levels in all assessment points in intraperitoneal glucose tolerance test. Diabetes decreased from 100% in tacrolimus-day-12 group to 50% in tacrolimus-cyclosporin group. Compared to tacrolimus-day-12 group, rats in tacrolimus-cyclosporin group showed an increased β-cell proliferation, but such an increase was lower than in rats receiving the vehicle. Ins2 gene expressions in rats receiving tacrolimus-cyclosporin and rats receiving the vehicle were comparable. ConclusionAn early switch from tacrolimus to cyclosporin in tacrolimus-induced diabetes mellitus resulted in an increased β-cell proliferation and reversion of diabetes in 50% of cases.

Cambios en la homeostasis de la glucosa y la proliferación de la célula beta pancreática tras el cambio a ciclosporina en la diabetes inducida por tacrolimus

BackgroundSwitching to cyclosporinA may result in a reversion of tacrolimus-induced diabetes mellitus. However, mechanisms underlying such a reversion are still unknown. MethodsObese Zucker rats were used as a model for tacrolimus-induced diabetes mellitus. A cohort of 44 obese Zucker rats received tacrolimus for 11 days (0.3mg/kg/day) until diabetes development; then: (a)22 rats were euthanized at day 12 and were used as a reference group (tacrolimus-day 12), and (b)22 rats on tacrolimus were shifted to cyclosporin (2.5mg/kg/day) for 5 days (tacrolimus-cyclosporin). An additional cohort of 22 obese Zucker rats received the vehicle for 17 days and were used as a control group. All animals underwent an intraperitoneal glucose tolerance test at the end of the study. Resultsβ-cell proliferation, apoptosis and Ins2 gene expression were evaluated. Compared to rats in tacrolimus-day 12 group, those in tacrolimus-cyclosporin group showed a significant improvement in blood glucose levels in all assessment points in intraperitoneal glucose tolerance test. Diabetes decreased from 100% in tacrolimus-day 12 group to 50% in tacrolimus-cyclosporin group. Compared to tacrolimus-day 12 group, rats in tacrolimus-cyclosporin group showed an increased β-cell proliferation, but such an increase was lower than in rats receiving the vehicle. Ins2 gene expressions in rats receiving tacrolimus-cyclosporin and rats receiving the vehicle were comparable. ConclusionAn early switch from tacrolimus to cyclosporin in tacrolimus-induced diabetes mellitus resulted in an increased β-cell proliferation and reversion of diabetes in 50% of cases.

Altered Phenotype of β-Cells and Other Pancreatic Cell Lineages in Patients With Diffuse Congenital Hyperinsulinism in Infancy Caused by Mutations in the ATP-Sensitive K-Channel.

Diffuse congenital hyperinsulinism in infancy (CHI-D) arises from mutations inactivating the KATP channel; however, the phenotype is difficult to explain from electrophysiology alone. Here we studied wider abnormalities in the β-cell and other pancreatic lineages. Islets were disorganized in CHI-D compared with controls. PAX4 and ARX expression was decreased. A tendency toward increased NKX2.2 expression was consistent with its detection in two-thirds of CHI-D δ-cell nuclei, similar to the fetal pancreas, and implied immature δ-cell function. CHI-D δ-cells also comprised 10% of cells displaying nucleomegaly. In CHI-D, increased proliferation was most elevated in duct (5- to 11-fold) and acinar (7- to 47-fold) lineages. Increased β-cell proliferation observed in some cases was offset by an increase in apoptosis; this is in keeping with no difference in INSULIN expression or surface area stained for insulin between CHI-D and control pancreas. However, nuclear localization of CDK6 and P27 was markedly enhanced in CHI-D β-cells compared with cytoplasmic localization in control cells. These combined data support normal β-cell mass in CHI-D, but with G1/S molecules positioned in favor of cell cycle progression. New molecular abnormalities in δ-cells and marked proliferative increases in other pancreatic lineages indicate CHI-D is not solely a β-cell disorder.

TNF-α Antibody Therapy in Combination With the T-Cell-Specific Antibody Anti-TCR Reverses the Diabetic Metabolic State in the LEW.1AR1-iddm Rat.

Anti-tumor necrosis factor-α (TNF-α) therapy (5 mg/kg body weight), alone or combined with the T-cell-specific antibody anti-T-cell receptor (TCR) (0.5 mg/kg body weight), was performed over 5 days immediately after disease manifestation to reverse the diabetic metabolic state in the LEW.1AR1-iddm rat, an animal model of human type 1 diabetes. Only combination therapy starting at blood glucose concentrations below 15 mmol/L restored normoglycemia and normalized C-peptide. Increased β-cell proliferation and reduced apoptosis led to a restoration of β-cell mass along with an immune cell infiltration-free pancreas 60 days after the end of therapy. This combination of two antibodies, anti-TCR/CD3, as a cornerstone compound in anti-T-cell therapy, and anti-TNF-α, as the most prominent and effective therapeutic antibody in suppressing TNF-α action in many autoimmune diseases, was able to reverse the diabetic metabolic state. With increasing blood glucose concentrations during the disease progression, however, the proapoptotic pressure on the residual β-cell mass increased, ultimately reaching a point where the reservoir of the surviving β-cells was insufficient to allow a restoration of normal β-cell mass through regeneration. The present results may open a therapeutic window for reversal of diabetic hyperglycemia in patients, worthwhile of being tested in clinical trials.

Increased β-cell Proliferation and β-cell Mass Induced Through High Fat Diet in Mice*

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Inhibition of Gsk3β activity improves β-cell function in c-KitWv/+ male mice

Previous studies have shown that the stem cell marker, c-Kit, is involved in glucose homeostasis. We recently reported that c-KitWv/+ male mice displayed the onset of diabetes at 8 weeks of age; however, the mechanisms by which c-Kit regulates β-cell proliferation and function are unknown. The purpose of this study is to examine if c-KitWv/+ mutation-induced β-cell dysfunction is associated with downregulation of the phospho-Akt/Gsk3β pathway in c-KitWv/+ male mice. Histology and cell signaling were examined in C57BL/6J/KitWv/+ (c-KitWv/+) and wild-type (c-Kit+/+) mice using immunofluorescence and western blotting approaches. The Gsk3β inhibitor, 1-azakenpaullone (1-AKP), was administered to c-KitWv/+ and c-Kit+/+ mice for 2 weeks, whereby alterations in glucose metabolism were examined and morphometric analyses were performed. A significant reduction in phosphorylated Akt was observed in the islets of c-KitWv/+ mice (P<0.05) along with a decrease in phosphorylated Gsk3β (P<0.05), and cyclin D1 protein level (P<0.01) when compared with c-Kit+/+ mice. However, c-KitWv/+ mice that received 1-AKP treatment demonstrated normal fasting blood glucose with significantly improved glucose tolerance. 1-AKP-treated c-KitWv/+ mice also showed increased β-catenin, cyclin D1 and Pdx-1 levels in islets, demonstrating that inhibition of Gsk3β activity led to increased β-cell proliferation and insulin secretion. These data suggest that c-KitWv/+ male mice had alterations in the Akt/Gsk3β signaling pathway, which lead to β-cell dysfunction by decreasing Pdx-1 and cyclin D1 levels. Inhibition of Gsk3β could prevent the onset of diabetes by improving glucose tolerance and β-cell function.

Milk signalling in the pathogenesis of type 2 diabetes

The presented hypothesis identifies milk consumption as an environmental risk factor of Western diet promoting type 2 diabetes (T2D). Milk, commonly regarded as a valuable nutrient, exerts important endocrine functions as an insulinotropic, anabolic and mitogenic signalling system supporting neonatal growth and development. The presented hypothesis substantiates milk’s physiological role as a signalling system for pancreatic β-cell proliferation by milk’s ability to increase prolactin-, growth hormone and incretin-signalling. The proposed mechanism of milk-induced postnatal β-cell mass expansion mimics the adaptive prolactin-dependent proliferative changes observed in pregnancy. Milk signalling down-regulates the key transcription factor FoxO1 leading to up-regulation of insulin promoter factor-1 which stimulates β-cell proliferation, insulin secretion as well as coexpression of islet amyloid polypeptide (IAPP). The recent finding that adult rodent β-cells only proliferate by self-duplication is of crucial importance, because permanent milk consumption beyond the weaning period may continuously over-stimulate β-cell replication thereby accelerating the onset of replicative β-cell senescence. The long-term use of milk may thus increase endoplasmic reticulum (ER) stress and toxic IAPP oligomer formation by overloading the ER with cytotoxic IAPPs thereby promoting β-cell apoptosis. Both increased β-cell proliferation and β-cell apoptosis are hallmarks of T2D. This hypothesis gets support from clinical states of hyperprolactinaemia and progeria syndromes with early onset of cell senescence which are both associated with an increased incidence of T2D and share common features of milk signalling. Furthermore, the presented milk hypothesis of T2D is compatible with the concept of high ER stress in T2D and the toxic oligomer hypothesis of T2D and may explain the high association of T2D and Alzheimer disease.

Rapamycin Impairs β-Cell Proliferation In Vivo

During pregnancy a high rate of β-cell proliferation occurs, making of this a useful model for the study of islet cell expansion in vivo. We used the murine pregnancy model to assess the effect of Rapamycin treatment on islet cell proliferation in vivo. Rapamycin is routinely used for the prevention of graft rejection in transplanted patients, including islet transplant recipients. As expected, pregnancy led to increased β-cell proliferation, islet yield and skewing in size distribution after isolation and pancreatic insulin content, when compared to non-pregnant females. Rapamycin treatment resulted in reduced beta cell proliferation in pregnant mice, while minimal effects of Rapamycin treatment were observed on islet function both in vivo and in vitro. Rapamycin treatment of islets resulted in reduced phosphorylation of p70s6k, a downstream effector molecule of mTOR and increased ERK1/2 phosphorylation. In conclusion, β-cell replication is reduced under Rapamycin treatment in vivo, suggesting that this mechanism may be operational and impair β-cell renewal in transplanted patients.

Insulin resistance and increased pancreatic β-cell proliferation in mice expressing a mutant insulin receptor (P1195L)

Several mutations of the tyrosine kinase domain of insulin receptor (IR) have been clinically reported to lead insulin resistance and insulin hypersecretion in humans. However, it has not been completely clarified how insulin resistance and pancreatic beta-cell function affect each other under the expression of mutant IR. We investigated the response of pancreatic beta-cells in mice carrying a mutation (P1195L) in the tyrosine kinase domain of IR beta-subunit. Homozygous (Ir(P1195L/P1195L)) mice showed severe ketoacidosis and died within 2 days after birth, and heterozygous (Ir(P1195L/wt)) mice showed normal levels of plasma glucose, but high levels of plasma insulin in the fasted state and after glucose loading, and a reduced response of plasma glucose lowering effect to exogenously administered insulin compared with wild type (Ir(wt/wt)) mice. There were no differences in the insulin receptor substrate (IRS)-2 expression and its phosphorylation levels in the liver between Ir(P1195L/wt) and Ir(wt/wt) mice, both before and after insulin injection. This result may indicate that IRS-2 signaling is not changed in Ir(P1195L/wt) mice. The beta-cell mass increased due to the increased numbers of beta-cells in Ir(P1195L/wt) mice. More proliferative beta-cells were observed in Ir(P1195L/wt) mice, but the number of apoptotic beta-cells was almost the same as that in Ir(wt/wt) mice, even after streptozotocin treatment. These data suggest that, in Ir(P1195L/wt) mice, normal levels of plasma glucose were maintained due to high levels of plasma insulin resulting from increased numbers of beta-cells, which in turn was due to increased beta-cell proliferation rather than decreased beta-cell apoptosis.

Estrogen and Exercise May Enhance β-Cell Function and Mass via Insulin Receptor Substrate 2 Induction in Ovariectomized Diabetic Rats

The prevalence and progression of type 2 diabetes have increased remarkably in postmenopausal women. Although estrogen replacement and exercise have been studied for their effect in modulating insulin sensitivity in the case of insufficient estrogen states, their effects on beta-cell function and mass have not been studied. Ovariectomized (OVX) female rats with 90% pancreatectomy were given a 30% fat diet for 8 wk with a corresponding administration of 17beta-estradiol (30 microg/kg body weight) and/or regular exercise. Amelioration of insulin resistance by estrogen replacement or exercise was closely related to body weight reduction. Insulin secretion in first and second phases was lower in OVX during hyperglycemic clamp, which was improved by estrogen replacement and exercise but not by weight reduction induced by restricted diets. Both estrogen replacement and exercise overcame reduced pancreatic beta-cell mass in OVX rats via increased proliferation and decreased apoptosis of beta-cells, but they did not exhibit an additive effect. However, restricted diets did not stimulate beta-cell proliferation. Increased beta-cell proliferation was associated with the induction of insulin receptor substrate-2 and pancreatic homeodomain protein-1 via the activation of the cAMP response element binding protein. Estrogen replacement and exercise shared a common pathway, which led to the improvement of beta-cell function and mass, via cAMP response element binding protein activation, explaining the lack of an additive effect with combined treatments. In conclusion, decreased beta-cell mass leading to impaired insulin secretion triggers glucose dysregulation in estrogen insufficiency, regardless of body fat. Regular moderate exercise eliminates the risk factors of contracting diabetes in the postmenopausal state.