Renal Mitochondrial ATP Transporter Ablation Ameliorates Obesity-Induced CKD.

SIGNIFICANCE STATEMENT: This study sheds light on the central role of adenine nucleotide translocase 2 (ANT2) in the pathogenesis of obesity-induced CKD. Our data demonstrate that ANT2 depletion in renal proximal tubule cells (RPTCs) leads to a shift in their primary metabolic program from fatty acid oxidation to aerobic glycolysis, resulting in mitochondrial protection, cellular survival, and preservation of renal function. These findings provide new insights into the underlying mechanisms of obesity-induced CKD and have the potential to be translated toward the development of targeted therapeutic strategies for this debilitating condition. BACKGROUND: The impairment in ATP production and transport in RPTCs has been linked to the pathogenesis of obesity-induced CKD. This condition is characterized by kidney dysfunction, inflammation, lipotoxicity, and fibrosis. In this study, we investigated the role of ANT2, which serves as the primary regulator of cellular ATP content in RPTCs, in the development of obesity-induced CKD. METHODS: We generated RPTC-specific ANT2 knockout ( RPTC-ANT2-/- ) mice, which were then subjected to a 24-week high-fat diet-feeding regimen. We conducted comprehensive assessment of renal morphology, function, and metabolic alterations of these mice. In addition, we used large-scale transcriptomics, proteomics, and metabolomics analyses to gain insights into the role of ANT2 in regulating mitochondrial function, RPTC physiology, and overall renal health. RESULTS: Our findings revealed that obese RPTC-ANT2-/- mice displayed preserved renal morphology and function, along with a notable absence of kidney lipotoxicity and fibrosis. The depletion of Ant2 in RPTCs led to a fundamental rewiring of their primary metabolic program. Specifically, these cells shifted from oxidizing fatty acids as their primary energy source to favoring aerobic glycolysis, a phenomenon mediated by the testis-selective Ant4. CONCLUSIONS: We propose a significant role for RPTC-Ant2 in the development of obesity-induced CKD. The nullification of RPTC-Ant2 triggers a cascade of cellular mechanisms, including mitochondrial protection, enhanced RPTC survival, and ultimately the preservation of kidney function. These findings shed new light on the complex metabolic pathways contributing to CKD development and suggest potential therapeutic targets for this condition.

Raptor levels are critical for ß-cell adaptation to a high-fat diet in male mice.

OBJECTIVE: The essential role of raptor/mTORC1 signaling in ß-cell survival and insulin processing has been recently demonstrated using raptor knock-out models. Our aim was to evaluate the role of mTORC1 function in adaptation of ß-cells to insulin resistant state. METHOD: Here, we use mice with heterozygous deletion of raptor in ß-cells (ßraHet) to assess whether reduced mTORC1 function is critical for ß-cell function in normal conditions or during ß-cell adaptation to high-fat diet (HFD). RESULTS: Deletion of a raptor allele in ß-cells showed no differences at the metabolic level, islets morphology, or ß-cell function in mice fed regular chow. Surprisingly, deletion of only one allele of raptor increases apoptosis without altering proliferation rate and is sufficient to impair insulin secretion when fed a HFD. This is accompanied by reduced levels of critical ß-cell genes like Ins1, MafA, Ucn3, Glut2, Glp1r, and specially PDX1 suggesting an improper ß-cell adaptation to HFD. CONCLUSION: This study identifies that raptor levels play a key role in maintaining PDX1 levels and ß-cell function during the adaptation of ß-cell to HFD. Finally, we identified that Raptor levels regulate PDX1 levels and ß-cell function during ß-cell adaptation to HFD by reduction of the mTORC1-mediated negative feedback and activation of the AKT/FOXA2/PDX1 axis. We suggest that Raptor levels are critical to maintaining PDX1 levels and ß-cell function in conditions of insulin resistance in male mice.

Hyperglucagonaemia in diabetes: altered amino acid metabolism triggers mTORC1 activation, which drives glucagon production.

AIM/HYPOTHESIS: Hyperglycaemia is associated with alpha cell dysfunction, leading to dysregulated glucagon secretion in type 1 and type 2 diabetes; however, the mechanisms involved are still elusive. The nutrient sensor mammalian target of rapamycin complex 1 (mTORC1) plays a major role in the maintenance of alpha cell mass and function. We studied the regulation of alpha cell mTORC1 by nutrients and its role in the development of hyperglucagonaemia in diabetes. METHODS: Alpha cell mTORC1 activity was assessed by immunostaining for phosphorylation of its downstream target, the ribosomal protein S6, and glucagon, followed by confocal microscopy on pancreatic sections and flow cytometry on dispersed human and mouse islets and the alpha cell line, αTC1-6. Metabolomics and metabolic flux were studied by 13C glucose labelling in 2.8 or 16.7 mmol/l glucose followed by LC-MS analysis. To study the role of mTORC1 in mediating hyperglucagonaemia in diabetes, we generated an inducible alpha cell-specific Rptor knockout in the Akita mouse model of diabetes and tested the effects on glucose tolerance by IPGTT and on glucagon secretion. RESULTS: mTORC1 activity was increased in alpha cells from diabetic Akita mice in parallel to the development of hyperglycaemia and hyperglucagonaemia (two- to eightfold increase). Acute exposure of mouse and human islets to amino acids stimulated alpha cell mTORC1 (3.5-fold increase), whereas high glucose concentrations inhibited mTORC1 (1.4-fold decrease). The mTORC1 response to glucose was abolished in human and mouse diabetic alpha cells following prolonged islet exposure to high glucose levels, resulting in sustained activation of mTORC1, along with increased glucagon secretion. Metabolomics and metabolic flux analysis showed that exposure to high glucose levels enhanced glycolysis, glucose oxidation and the synthesis of glucose-derived amino acids. In addition, chronic exposure to high glucose levels increased the expression of Slc7a2 and Slc38a4, which encode amino acid transporters, as well as the levels of branched-chain amino acids and methionine cycle metabolites (~1.3-fold increase for both). Finally, conditional Rptor knockout in alpha cells from adult diabetic mice inhibited mTORC1, thereby inhibiting glucagon secretion (~sixfold decrease) and improving diabetes, despite persistent insulin deficiency. CONCLUSIONS/INTERPRETATION: Alpha cell exposure to hyperglycaemia enhances amino acid synthesis and transport, resulting in sustained activation of mTORC1, thereby increasing glucagon secretion. mTORC1 therefore plays a major role in mediating alpha cell dysfunction in diabetes. DATA AVAILABILITY: All sequencing data are available from the Gene Expression Omnibus (GEO) repository (accession no. GSE154126; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE154126 ).

Time-dependent effects of endogenous hyperglucagonemia on glucose homeostasis and hepatic glucagon action.

Elevation of glucagon levels and increase in α cell proliferation is associated with states of hyperglycemia in diabetes. A better understanding of the molecular mechanisms governing glucagon secretion could have major implications for understanding abnormal responses to hypoglycemia in patients with diabetes and provide novel avenues for diabetes management. Using mice with inducible induction of Rheb1 in α cells (αRhebTg mice), we showed that short-term activation of mTORC1 signaling is sufficient to induce hyperglucagonemia through increased glucagon secretion. Hyperglucagonemia in αRhebTg mice was also associated with an increase in α cell size and mass expansion. This model allowed us to identify the effects of chronic and short-term hyperglucagonemia on glucose homeostasis by regulating glucagon signaling in the liver. Short-term hyperglucagonemia impaired glucose tolerance, which was reversible over time. Liver glucagon resistance in αRhebTg mice was associated with reduced expression of the glucagon receptor and genes involved in gluconeogenesis, amino acid metabolism, and urea production. However, only genes regulating gluconeogenesis returned to baseline upon improvement of glycemia. Overall, these studies demonstrate that hyperglucagonemia exerts a biphasic response on glucose metabolism: Short-term hyperglucagonemia lead to glucose intolerance, whereas chronic exposure to glucagon reduced hepatic glucagon action and improved glucose tolerance.

Mapping the metabolic reprogramming induced by sodium-glucose cotransporter 2 inhibition.

Diabetes is associated with increased risk for kidney disease, heart failure, and mortality. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) prevent these adverse outcomes; however, the mechanisms involved are not clear. We generated a roadmap of the metabolic alterations that occur in different organs in diabetes and in response to SGLT2i. In vivo metabolic labeling with 13C-glucose in normoglycemic and diabetic mice treated with or without dapagliflozin, followed by metabolomics and metabolic flux analyses, showed that, in diabetes, glycolysis and glucose oxidation are impaired in the kidney, liver, and heart. Treatment with dapagliflozin failed to rescue glycolysis. SGLT2 inhibition increased glucose oxidation in all organs; in the kidney, this was associated with modulation of the redox state. Diabetes was associated with altered methionine cycle metabolism, evident by decreased betaine and methionine levels, whereas treatment with SGLT2i increased hepatic betaine along with decreased homocysteine levels. mTORC1 activity was inhibited by SGLT2i along with stimulation of AMPK in both normoglycemic and diabetic animals, possibly explaining the protective effects against kidney, liver, and heart diseases. Collectively, our findings suggest that SGLT2i induces metabolic reprogramming orchestrated by AMPK-mTORC1 signaling with common and distinct effects in various tissues, with implications for diabetes and aging.

The effect of steroid injection into the shoulder on glycemia in patients with type 2 diabetes.

Background: Injections of corticosteroids into or around joints have been reported to increase blood glucose in patients with diabetes due to corticosteroid absorption into the bloodstream. However, the magnitude, duration, and clinical implications of local corticosteroid injections on glycemic control are not clear. The purpose of this study was to evaluate the effects of corticosteroid injection to the shoulder on glycemia in patients with type 2 diabetes mellitus using a continuous glucose monitoring device. Methods: Twenty-five patients with symptomatic shoulder problems and type 2 diabetes mellitus, not treated with insulin, prescribed a corticosteroid injection into the shoulder, were investigated. The patients were connected to a flash glucose monitoring system, which continuously monitored interstitial glucose levels. Data were collected 3 days before injection and for additional 11 days after corticosteroid injection. We analyzed glucose levels in the first 3 days (early postinjection) and on days 4-11 (late postinjection) after the injection and compared them to the preinjection period. The outcome measures included change in the average glucose levels, per patient, between the preinjection and postinjection periods and the differences in the time spent at glucose >180 mg/dL, >250 mg/dL, and >350 mg/dL, per patient, between the preinjection and postinjection periods. Results: The increase in the mean glucose level per patient was statistically significant from 136 mg/dL in the preinjection period to 159 mg/dL in the first 3 days after the injection and returned to normal thereafter. Time at blood glucose >250 mg/dL increased from 4.3% in the preinjection period to 9.5% on the first day after the injection. It then decreased to 7% on day 2, 3.8% on day 3, and 1.4% in the late postinjection period. New onset of glucose levels >350 mg/dL was found in 4 of 25 patients during the early postinjection period. In all 4 patients, the exposure to severe hyperglycemia (>350 mg/dL) was short. None of the patients required intensification of the antidiabetic treatment or insulin injections. Conclusion: Local corticosteroid injection to the shoulder can create a significant, short-term increase in systemic glucose levels in patients with D2DM not treated with insulin. Some of these patients may have periods with glucose above 350 mg %. However, these glycemic changes are short lived and are mostly limited to the 2-3 days after the injection. In addition, none of the patients in our study needed any change in antidiabetic treatment or any medical care after the injection.

Novel roles of mTORC2 in regulation of insulin secretion by actin filament remodeling.

Mammalian target of rapamycin (mTOR) kinase is an essential hub where nutrients and growth factors converge to control cellular metabolism. mTOR interacts with different accessory proteins to form complexes 1 and 2 (mTORC), and each complex has different intracellular targets. Although mTORC1's role in ß-cells has been extensively studied, less is known about mTORC2's function in ß-cells. Here, we show that mice with constitutive and inducible ß-cell-specific deletion of RICTOR (ßRicKO and ißRicKO mice, respectively) are glucose intolerant due to impaired insulin secretion when glucose is injected intraperitoneally. Decreased insulin secretion in ßRicKO islets was caused by abnormal actin polymerization. Interestingly, when glucose was administered orally, no difference in glucose homeostasis and insulin secretion were observed, suggesting that incretins are counteracting the mTORC2 deficiency. Mechanistically, glucagon-like peptide-1 (GLP-1), but not gastric inhibitory polypeptide (GIP), rescued insulin secretion in vivo and in vitro by improving actin polymerization in ßRicKO islets. In conclusion, mTORC2 regulates glucose-stimulated insulin secretion by promoting actin filament remodeling.NEW & NOTEWORTHY The current studies uncover a novel mechanism linking mTORC2 signaling to glucose-stimulated insulin secretion by modulation of the actin filaments. This work also underscores the important role of GLP-1 in rescuing defects in insulin secretion by modulating actin polymerization and suggests that this effect is independent of mTORC2 signaling.

Opposite physiological and pathological mTORC1-mediated roles of the CB1 receptor in regulating renal tubular function.

Activation of the cannabinoid-1 receptor (CB1R) and the mammalian target of rapamycin complex 1 (mTORC1) in the renal proximal tubular cells (RPTCs) contributes to the development of diabetic kidney disease (DKD). However, the CB1R/mTORC1 signaling axis in the kidney has not been described yet. We show here that hyperglycemia-induced endocannabinoid/CB1R stimulation increased mTORC1 activity, enhancing the transcription of the facilitative glucose transporter 2 (GLUT2) and leading to the development of DKD in mice; this effect was ameliorated by specific RPTCs ablation of GLUT2. Conversely, CB1R maintained the normal activity of mTORC1 by preventing the cellular excess of amino acids during normoglycemia. Our findings highlight a novel molecular mechanism by which the activation of mTORC1 in RPTCs is tightly controlled by CB1R, either by enhancing the reabsorption of glucose and inducing kidney dysfunction in diabetes or by preventing amino acid uptake and maintaining normal kidney function in healthy conditions.

Pathogenesis of diabesity-induced kidney disease: role of kidney nutrient sensing.

Diabetes kidney disease (DKD) is a major healthcare problem associated with increased risk for developing end-stage kidney disease and high mortality. It is widely accepted that DKD is primarily a glomerular disease. Recent findings however suggest that kidney proximal tubule cells (KPTCs) may play a central role in the pathophysiology of DKD. In diabetes and obesity, KPTCs are exposed to nutrient overload, including glucose, free-fatty acids and amino acids, which dysregulate nutrient and energy sensing by mechanistic target of rapamycin complex 1 and AMP-activated protein kinase, with subsequent induction of tubular injury, inflammation, and fibrosis. Pharmacological treatments that modulate nutrient sensing and signaling in KPTCs, including cannabinoid-1 receptor antagonists and sodium glucose transporter 2 inhibitors, exert robust kidney protective effects. Shedding light on how nutrients are sensed and metabolized in KPTCs and in other kidney domains, and on their effects on signal transduction pathways that mediate kidney injury, is important for understanding the pathophysiology of DKD and for the development of novel therapeutic approaches in DKD and probably also in other forms of kidney disease.

The second-generation antipsychotic drug aripiprazole modulates the serotonergic system in pancreatic islets and induces beta cell dysfunction in female mice.

AIMS/HYPOTHESIS: Second-generation antipsychotic (SGA) drugs have been associated with the development of type 2 diabetes and the metabolic syndrome in patients with schizophrenia. In this study, we aimed to investigate the effects of two different SGA drugs, olanzapine and aripiprazole, on metabolic state and islet function and plasticity. METHODS: We analysed the functional adaptation of beta cells in 12-week-old B6;129 female mice fed an olanzapine- or aripiprazole-supplemented diet (5.5-6.0 mg kg-1 day-1) for 6 months. Glucose and insulin tolerance tests, in vivo glucose-stimulated insulin secretion and indirect calorimetry were performed at the end of the study. The effects of SGAs on beta cell plasticity and islet serotonin levels were assessed by transcriptomic analysis and immunofluorescence. Insulin secretion was assessed by static incubations and Ca2+ fluxes by imaging techniques. RESULTS: Treatment of female mice with olanzapine or aripiprazole for 6 months induced weight gain (p<0.01 and p<0.05, respectively), glucose intolerance (p<0.01) and impaired insulin secretion (p<0.05) vs mice fed a control chow diet. Aripiprazole, but not olanzapine, induced serotonin production in beta cells vs controls, likely by increasing tryptophan hydroxylase 1 (TPH1) expression, and inhibited Ca2+ flux. Of note, aripiprazole increased beta cell size (p<0.05) and mass (p<0.01) vs mice fed a control chow diet, along with activation of mechanistic target of rapamycin complex 1 (mTORC1)/S6 signalling, without preventing beta cell dysfunction. CONCLUSIONS/INTERPRETATION: Both SGAs induced weight gain and beta cell dysfunction, leading to glucose intolerance; however, aripiprazole had a more potent effect in terms of metabolic alterations, which was likely a result of its ability to modulate the serotonergic system. The deleterious metabolic effects of SGAs on islet function should be considered while treating patients as these drugs may increase the risk for development of the metabolic syndrome and diabetes.

Nutrient Sensor mTORC1 Regulates Insulin Secretion by Modulating ß-Cell Autophagy.

The dynamic regulation of autophagy in ß-cells by cycles of fasting-feeding and its effects on insulin secretion are unknown. In ß-cells, mechanistic target of rapamycin complex 1 (mTORC1) is inhibited while fasting and is rapidly stimulated during refeeding by a single amino acid, leucine, and glucose. Stimulation of mTORC1 by nutrients inhibited the autophagy initiator ULK1 and the transcription factor TFEB, thereby preventing autophagy when ß-cells were continuously exposed to nutrients. Inhibition of mTORC1 by Raptor knockout mimicked the effects of fasting and stimulated autophagy while inhibiting insulin secretion, whereas moderate inhibition of autophagy under these conditions rescued insulin secretion. These results show that mTORC1 regulates insulin secretion through modulation of autophagy under different nutritional situations. In the fasting state, autophagy is regulated in an mTORC1-dependent manner, and its stimulation is required to keep insulin levels low, thereby preventing hypoglycemia. Reciprocally, stimulation of mTORC1 by elevated leucine and glucose, which is common in obesity, may promote hyperinsulinemia by inhibiting autophagy.

The Autophagy Inhibitor Chloroquine, Alone or in Combination with mTOR Inhibitors, Displays Anti-Tumor Effects in In Vitro and In Vivo Lung Carcinoid Models.

(1) Background: Neuroendocrine neoplasms of the lung (LNENs, lung carcinoids) are often diagnosed at an advanced stage when they are not surgically curable, and treatment options are limited. One of the approved options for treating inoperable tumors is everolimus-an mTOR inhibitor (mTORi). Activation of mTOR, among many other effects, inhibits autophagy, which is a cell survival mechanism in general, and in tumor cells in particular. Everolimus may paradoxically encourage cancer cell survival. In practice, the drug inhibits tumor development. Chloroquine (CQ) is a known antimalarial compound that inhibits autophagy. Our research is focused on the hypothesis that autophagy plays a key role in the development of tumor resistance to mTORi, and that the addition of autophagy inhibitors to mTORi exerts a synergistic effect on suppressing tumor cell proliferation. We have recently demonstrated that the combination of CQ with different mTORi increases their potency compared with mTORi alone in both in vitro and in vivo models of pancreatic NENs. In this study, we examined the effects of CQ and mTORi on in vitro and in vivo LNEN models. Aims: Testing the effects of CQ together with mTORi on cell proliferation, apoptosis, and autophagy in in vitro and in vivo LNEN models. (2) Methods: The NCI-H727 LNEN cells were treated with CQ ± mTORi. Cells' viability and proliferation were measured using XTT and Ki-67 FACS staining. The effects of the treatments on the mTOR pathway and autophagy were examined using Western blotting. Cytotoxicity was measured using a cytotoxicity kit; apoptosis was measured by PI FACS staining and Western blotting. We further established an LNEN subcutaneous murine xenograft model and evaluated the effects of the drugs on tumor growth. (3) Results: CQ alone suppressed LNEN cells' viability and proliferation and increased their cytotoxicity and apoptosis; these effects were augmented when CQ was added to an mTORi. We also showed the possible mechanisms for these results: on the one hand we could see a decrease in P62 levels and the absence of LC3-II (both inversely related to autophagy) following treatment with the mTORi, and on the other hand we could demonstrate an increase in their levels when CQ was added. The effect was less apparent in the murine xenograft model. (4) Conclusions: By inhibiting autophagy and inducing apoptosis, CQ suppresses tumor cell growth in LNENs. CQ potentiates mTORi effects, implying that further studies are needed in order to elucidate its possible role in tumor inhibition in patients with LNENs.

Kidney Outcomes With Glucagon-Like Peptide-1 Receptor Agonists in Patients With Type 2 Diabetes.

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are highly effective in reducing glycemia in patients with type 2 diabetes (T2D). These medications effectively reduce cardiovascular (CV) risk in patients with T2D and established CV disease or with multiple risk factors. In addition, treatment with GLP-1 RA may exert protective effects on the diabetic kidney. Herein, we summarize the findings regarding the kidney safety and efficacy of GLP-1 RAs in patients with T2D. We review data from GLP-1 RAs phase 3 kidney studies, CV outcome trials, as well as real-world evidence. The accumulating data show that treatment with GLP-1 RAs is safe, well-tolerated, and effective in patients with different levels of kidney dysfunction. Furthermore, CV outcome trials suggest that GLP-1 RAs reduce albuminuria and may attenuate the decline in kidney function over time. The ongoing FLOW trial studying the effects of semaglutide in patients with diabetic kidney disease is expected to shed light on the effects of GLP-1 RAs on kidney outcomes and clarify their role in the management of patients with T2D and kidney disease.

A Combined Drug Treatment That Reduces Mitochondrial Iron and Reactive Oxygen Levels Recovers Insulin Secretion in NAF-1-Deficient Pancreatic Cells.

Decreased insulin secretion, associated with pancreatic ß-cell failure, plays a critical role in many human diseases including diabetes, obesity, and cancer. While numerous studies linked ß-cell failure with enhanced levels of reactive oxygen species (ROS), the development of diabetes associated with hereditary conditions that result in iron overload, e.g., hemochromatosis, Friedreich's ataxia, and Wolfram syndrome type 2 (WFS-T2; a mutation in CISD2, encoding the [2Fe-2S] protein NAF-1), underscores an additional link between iron metabolism and ß-cell failure. Here, using NAF-1-repressed INS-1E pancreatic cells, we observed that NAF-1 repression inhibited insulin secretion, as well as impaired mitochondrial and ER structure and function. Importantly, we found that a combined treatment with the cell permeant iron chelator deferiprone and the glutathione precursor N-acetyl cysteine promoted the structural repair of mitochondria and ER, decreased mitochondrial labile iron and ROS levels, and restored glucose-stimulated insulin secretion. Additionally, treatment with the ferroptosis inhibitor ferrostatin-1 decreased cellular ROS formation and improved cellular growth of NAF-1 repressed pancreatic cells. Our findings reveal that suppressed expression of NAF-1 is associated with the development of ferroptosis-like features in pancreatic cells, and that reducing the levels of mitochondrial iron and ROS levels could be used as a therapeutic avenue for WFS-T2 patients.

Proximal Tubule mTORC1 Is a Central Player in the Pathophysiology of Diabetic Nephropathy and Its Correction by SGLT2 Inhibitors.

Diabetic kidney disease (DKD) increases the risk for mortality and is the leading cause of end-stage renal disease. Treatment with sodium-glucose cotransporter 2 inhibitors (SGLT2i) attenuates the progression of DKD, especially in patients with advanced kidney disease. Herein, we show that in diabetes, mTORC1 activity is increased in renal proximal tubule cells (RPTCs) along with enhanced tubule-interstitial fibrosis; this is prevented by SGLT2i. Constitutive activation of mTORC1 in RPTCs induces renal fibrosis and failure and abolishes the renal-protective effects of SGLT2i in diabetes. On the contrary, partial inhibition of mTORC1 in RPTCs prevents fibrosis and the decline in renal function. Stimulation of mTORC1 in RPTCs turns on a pro-fibrotic program in the renal cortex, whereas its inhibition in diabetes reverses the alterations in gene expression. We suggest that RPTC mTORC1 is a critical node that mediates kidney dysfunction in diabetes and the protective effects of SGLT2i by regulating fibrogenesis.

Inhibition of mTORC1 by ER stress impairs neonatal ß-cell expansion and predisposes to diabetes in the Akita mouse.

Unresolved ER stress followed by cell death is recognized as the main cause of a multitude of pathologies including neonatal diabetes. A systematic analysis of the mechanisms of ß-cell loss and dysfunction in Akita mice, in which a mutation in the proinsulin gene causes a severe form of permanent neonatal diabetes, showed no increase in ß-cell apoptosis throughout life. Surprisingly, we found that the main mechanism leading to ß-cell dysfunction is marked impairment of ß-cell growth during the early postnatal life due to transient inhibition of mTORC1, which governs postnatal ß-cell growth and differentiation. Importantly, restoration of mTORC1 activity in neonate ß-cells was sufficient to rescue postnatal ß-cell growth, and to improve diabetes. We propose a scenario for the development of permanent neonatal diabetes, possibly also common forms of diabetes, where early-life events inducing ER stress affect ß-cell mass expansion due to mTOR inhibition.