BACKGROUND:Prior observational studies suggested an association between post-traumatic stress disorder (PTSD) and autoimmune disorders; however, a comprehensive evaluation of this relationship remains limited. METHODS:In this retrospective cohort study, using the TriNetX global network, individuals newly diagnosed with chronic PTSD without autoimmune disease at baseline were propensity-score-matched to individuals without PTSD (2005-2025). Matching included age, sex, race, ethnicity, obesity, smoking, and psychiatric comorbidities variables. Cox models estimated the risk of 32 new-onset autoimmune disorders during a 5-year follow-up period, overall and by organ class. Analyses were repeated across subgroups defined by sex, age, race, ethnicity, and the presence or absence of depression and/or anxiety. RESULTS:The matched cohort included 316,482 individuals (mean age, 38.5 ± 16.6 years; 64.1% women). Over 1,054,536 person-years of follow-up, new autoimmune disorders occurred in 12,845 (8.4%) individuals with PTSD and 9,988 (6.5%) individuals without PTSD (hazard ratio [HR], 1.34 [95% CI 1.30-1.37]; absolute risk difference calculated over 4 years was 2.9% [2.7-3.1]). PTSD was associated with higher risks of rheumatologic (HR, 1.33 [1.26-1.41]), gastrointestinal (1.25 [1.15-1.36]), hematologic (1.59 [1.39-1.81]), endocrine (1.40 [1.35-1.45]), and neurologic autoimmune disorders (1.53 [1.31-1.78]). The increased risk remained consistent in sex-stratified analyses, with HRs of 1.20 [1.15-1.25] in men and 1.32 [1.29-1.36] in women, and across all ages, racial, and ethnic subgroups and in subjects with or without comorbid depression or anxiety. CONCLUSIONS:PTSD is associated with an increased risk of subsequent development of autoimmune disorders.

Hyperglycemia is a principal driver of β cell failure and multiple-organ complications in diabetes. Chronic exposure to hyperglycemia overstimulates mTORC1, disrupting glucose metabolism and promoting ER stress, oxidative stress, and inflammation; however, the upstream metabolic signal(s) linking glucose to mTORC1 activation remains unclear. Here, we identified glucosamine as a key metabolite connecting elevated glucose to mTORC1 signaling in pancreatic islets and kidney, both major targets of hyperglycemic damage. Using 13 C 6 -glucose metabolic labeling in diabetic rodents treated with or without the SGLT2 inhibitor dapagliflozin or insulin, combined with targeted metabolomics and metabolic flux analysis, we found that tissue glucose concentrations strongly correlated with glucosamine. A similar correlation with plasma glucose was conserved in humans with or without type 2 diabetes, and inversely associated with β cell function. In vitro, low-dose glucosamine stimulated mTORC1 in islets and kidney proximal tubule cells in an O-GlcNAcylation–dependent manner. Broad phosphoproteomics and transcriptomics analyses in β cells showed that glucosamine activated mTORC1-regulating pathways, induced oxidative stress, ER stress, and dedifferentiation. Genetic inhibition of β cell mTORC1 via heterozygous Raptor knockout, as well as pharmacologic inhibition of the glucosamine/mTORC1 axis through SGLT2 inhibition, alleviated β cell stress, improved glycemic control, and restored β cell function. These findings identified the glucosamine/mTORC1 pathway as an important mediator of β cell and kidney dysfunction in diabetes.

CD59 is known as a membrane-bound regulator of the complement system that prevents the formation of the membrane attack complex on host cells. Here we report the metabolic consequences of CD59a knockout (KO) in mice fed a high-fat diet (HFD). Mice lacking CD59a were protected from the development of insulin resistance, glucose intolerance, hyperinsulinemia, obesity, and fatty liver. Mutants fed an HFD had elevated adiponectin levels and reduced leptin levels in plasma. Data from metabolic cages suggested decreased appetite and an increase in voluntary wheel activity in mutants. Liver transcriptome analysis showed a marked decrease of inflammatory and fibrotic pathways in CD59a KO mice on an HFD, and plasma and liver metabolomics were remarkably similar, indicating close correspondence between systemic and hepatic metabolic profiles. In conclusion, we uncover a noncanonical role of CD59a in the development of diet-induced insulin resistance, hyperinsulinemia, glucose intolerance, and obesity.

The c-Jun N-terminal kinases (JNKs) regulate diverse physiological processes. Whereas JNK1 and JNK2 are broadly expressed and associated with insulin resistance, inflammation, and stress responses, JNK3 is largely restricted to central nervous system neurons and pancreatic β cells, and its physiological role in β cells remains poorly defined. To investigate its function, we generated mice lacking JNK3 specifically in β cells (βJNK3-KO). These mice displayed glucose intolerance and defective insulin secretion, particularly after oral glucose challenge, indicating impaired incretin responses. Consistently, Exendin-4-stimulated (Ex4-stimulated) insulin secretion was blunted in βJNK3-KO islets, accompanied by reduced GLP-1R expression. Similar findings were observed in human islets treated with a selective JNK3 inhibitor (iJNK3). Downstream of GLP-1R, Ex4-induced CREB phosphorylation was diminished in βJNK3-KO islets, indicating impaired canonical signaling. Moreover, activation of the GLP-1R/CREB/IRS2 pathway, a key regulator of β cell survival, was reduced in βJNK3-KO islets and iJNK3-treated human islets. As a consequence, the protective effects of Ex4 were lost in cytokine-treated βJNK3-KO and human islets, and Ex4-mediated protection was partially attenuated in βJNK3-KO mice exposed to multiple low-dose streptozotocin. These findings identify JNK3 as a regulator of β cell function and survival and suggest that targeting this pathway may enhance incretin-based therapies.

CONTEXT:Wolfram syndrome type 2 (WS2) is a rare monogenic diabetes syndrome caused by CISD2 mutations. Its cellular pathophysiology remains poorly understood, and no targeted therapies exist. OBJECTIVE:To characterize the clinical phenotype and cellular pathophysiology of the largest WS2 cohort to date, and to evaluate a novel, mechanistically targeted pharmacological intervention. DESIGN:Observational cohort study paired with ex vivo functional cellular assays and a proof-of-concept pilot clinical intervention. SETTING:Multicenter academic and clinical institutions in Israel and the Palestinian territories. PATIENTS:Twenty-two patients from 11 unrelated Palestinian families presenting with atypical juvenile-onset diabetes and gastrointestinal bleeding. Patient-derived fibroblasts (n = 4) were utilized for functional assays. INTERVENTION(S):Fibroblasts and two patients were treated with a combination of the iron chelator deferiprone (DFP) and the antioxidant N-acetylcysteine (NAC). MAIN OUTCOME MEASURE(S):Clinical phenotype, CISD2 genetic analysis, mitochondrial labile iron (mLI) and reactive oxygen species (ROS) levels, organelle morphology, and preliminary clinical response (HbA1c, platelet aggregation). RESULTS:Patients were homozygous for a CISD2 c.109G > C founder mutation (carrier rate 1:40). The clinical phenotype was expanded to include prevalent psychiatric morbidity and congenital heart defects. Patient fibroblasts exhibited profound mitochondrial and endoplasmic reticulum damage, with increased mLI (+25%, p < 0.0001) and mROS (+28%, p < 0.0001). In vitro DFP/NAC treatment fully reversed these cellular anomalies. In a preliminary pilot study, two patients receiving DFP/NAC demonstrated improved reported glycemic control and corrected platelet aggregation. CONCLUSIONS:WS2 is an underdiagnosed monogenic diabetes driven by mitochondrial iron dysregulation and oxidative stress. Repurposing DFP/NAC reverses this toxicity, offering a strong mechanistic rationale for future clinical trials.

Introduction and Objective: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) were proposed to exert neuroprotective effects. Preliminary data from the EVOKE placebo-controlled phase-3 trials indicate that 2-year oral semaglutide therapy, although improving Alzheimer's-related biomarkers, did not mitigate disease progression in people with early Alzheimer's, mostly without type 2 diabetes (T2D). It remains unclear whether GLP-1 RAs therapy may reduce the risk of progression to dementia in people with type 2 diabetes and mild cognitive impairment. Methods: In a retrospective cohort study using the TriNetX global network, we included adults with T2D, mild cognitive impairment, and HbA1c < 10.5% without dementia (2010-2021). We assessed the incidence of dementia or Alzheimer's disease among propensity-score-matched (1:1) individuals initiating GLP-1 RA versus dipeptidyl peptidase-4 inhibitors (DPP4i) during a 5-year potential follow-up. In a sensitivity analysis, we compared those initiating GLP-1 RA versus basal insulin. Results: We included 1320 matched individuals (702 women) who initiated GLP-1 RAs or DPP4i, with a mean age 67.2 years and HbA1c 7.6%. Onset of dementia or Alzheimer's occurred among 101 and 132 participants in the GLP-1 RA and DPP4i groups, respectively (Cox proportional hazards ratio [HR] 0.74 [95% CI, 0.57-0.95]; E-value 2.06 [lower CI limit 1.28]). At a mean follow-up of 3.9 years, the respective Kaplan-Meier-estimated incidences were 15.5% and 20.4%, representing an absolute risk difference of -4.9% [95% CI -9.4 - -0.4] with GLP-1 RAs versus DPP4i and a number needed to treat of 21 [11 - 234] individuals to prevent one event. Similar findings were observed when comparing those starting GLP-1 RA versus basal insulin (HR 0.63 [0.46 - 0.87]). Conclusion: In a multinational cohort of people with T2D and mild cognitive impairment, GLP-1 RA initiation versus DPP4i was associated with a lower dementia incidence over 3.9 years, supporting the need for dedicated clinical trials. Disclosure M. Schechter: None. D.R. Sehtman-Shachar: None. A. Fishkin: None. O. Mosenzon: Employee; Current; Regeneron Pharmaceuticals Inc. Stock/Shareholder; Current; Regeneron Pharmaceuticals Inc. T. Cukierman-Yaffe: Speaker's Bureau; Ended; AstraZeneca, Boehringer Ingelheim International GmbH. Advisory Panel; Ended; Amgen Inc. Speaker's Bureau; Ended; Novo Nordisk. Research Support; Current; Novo Nordisk. Speaker's Bureau; Ended; Medtronic. Research Support; Current; Medtronic. Advisory Panel; Ended; Abbott. Speaker's Bureau; Ended; Sanofi. Research Support; Current; Sanofi. Speaker's Bureau; Ended; Lilly. R. Sharon: None. G. Leibowitz: None. G. Aharon-Hananel: Other - PI on clinical studies, speakers bureau; Current; Nordic Bioscience A/S. Other - PI on clinical studies, advisory, speakers bureau; Current; Eli Lilly and Company, AstraZeneca. Research Support; Current; Sanofi. Research Support; Ended; Bayer AG. Speaker's Bureau; Ended; Abbott.

Type 2 diabetes (T2D), affecting approximately 12

AIMS:To identify predictors of diabetic ketoacidosis (DKA) in patients with an insulin-deficient phenotype initiating sodium-glucose cotransporter 2 inhibitor (SGLT2i) therapy. MATERIALS AND METHODS:This retrospective cohort study analysed data from 31 900 patients with diabetes aged 18-70 identified as having an insulin-deficient phenotype. After applying inclusion and exclusion criteria, patients were matched and divided into SGLT2i users (n = 6572) and non-users (n = 6382). The primary endpoint was the first DKA event in patients with no prior history of DKA. Independent risk factors for DKA were assessed using Cox regression. RESULTS:Over a median follow-up of 4.4 years, 239 patients experienced DKA (143 [2.22%] SGLT2i users vs. 96 [1.54%] non-users; HR [95% confidence interval, CI] 1.39 [1.07-1.79]; p = 0.014). The adjusted model confirmed an increased DKA risk with SGLT2i use (adjusted hazard ratio, aHR [95% CI] 1.50 [1.15-1.95]; p = 0.003). Baseline HbA1c >9% was associated with a 53% higher risk (aHR [95% CI] 1.53 [1.18-1.99]; p = 0.0016), while body mass index (BMI) ≤25 kg/m2 was linked to a 61% increased risk (aHR [95% CI] 1.61 [1.24-2.09]; p = 0.0003). Insulin use further heightened risk (aHR [95% CI] 2.35 [1.71-3.23]; p < 0.0001). CONCLUSIONS:SGLT2i use in patients with an insulin-deficient phenotype is associated with increased DKA risk, particularly in those with HbA1c >9% and BMI ≤25 kg/m2. Clinicians should exercise caution in these patients, carefully assessing risks and implementing mitigation strategies to ensure safe use.

OBJECTIVE:Kidney glucose reabsorption, primarily mediated by glucose transporter 2 (GLUT2), is essential for systemic glucose homeostasis. While GLUT2's role has been studied in diabetic conditions, its function in kidney proximal tubule cells (KPTCs) under normo-physiological conditions remains unclear. This study aimed to delineate the metabolic consequences of KPTC-specific GLUT2 deletion on renal and whole-body energy homeostasis. METHODS:We utilized a conditional mouse model with KPTC-specific deletion of GLUT2 to assess the impact of impaired renal glucose reabsorption on systemic metabolism. Comprehensive metabolic and behavioral phenotyping, tissue-specific glucose uptake assays, and multi-omics analyses were performed to evaluate changes in energy balance, organ-specific metabolism, and signaling pathways. RESULTS:Loss of KPTC-GLUT2 led to increased food intake, enhanced systemic carbohydrate oxidation, and elevated fat and muscle mass. These changes were accompanied by altered glucose utilization across metabolic organs and improvements in whole-body lipid profile. Mechanistically, the phenotype was linked to metabolic reprogramming in the kidney, characterized by increased reabsorption and bioavailability of taurine and creatine, overactivation of mTORC1 signaling, and elevated endocannabinoid tone. CONCLUSIONS:KPTC-GLUT2 plays a previously unrecognized role in regulating renal and systemic energy metabolism. Its deletion induces a systemic energy-conserving phenotype driven by kidney-intrinsic changes, highlighting the kidney's contribution to whole-body metabolic homeostasis beyond glucose filtration.

Precise regulation of insulin secretion by pancreatic β cells is essential to prevent excessive insulin release. Here, we show that the nutrient sensor mechanistic Target of Rapamycin Complex 1 (mTORC1) is rapidly activated by glucose in β cells via the insulin secretion machinery, positioning mTORC1 as a sensor of β cell activity. Acute pharmacological inhibition of mTORC1 during glucose stimulation enhances insulin release, suggesting that mTORC1 acts as an intrinsic feedback regulator that restrains insulin secretion. Phosphoproteomic profiling reveals that mTORC1 modulates the phosphorylation of proteins involved in actin remodeling and vesicle trafficking, with a prominent role in the RhoA-GTPase pathway. Mechanistically, mTORC1 promotes RhoA activation and F-actin polymerization, limiting vesicle movement and dampening the second phase of insulin secretion. These findings identify a glucose-mTORC1-RhoA signaling axis that forms an autonomous feedback loop to constrain insulin exocytosis, providing insight into how β cells prevent excessive insulin release and maintain metabolic balance.

BACKGROUND:Clinical trials that demonstrated sodium-glucose cotransporter-2 inhibitors (SGLT2) inhibitors benefits in patients with type 2 diabetes excluded patients treated with glucocorticoids. It is unknown whether SGLT2 inhibitors are safe and effective for these patients, limiting their clinical use. METHODS:In a cohort study, we used TriNetX, a global real-world data network, and propensity-score matched (1:1) adults with type 2 diabetes and estimated glomerular filtration rate (eGFR) > 30 mL/min/1.73 m2, treated with oral glucocorticoids, who initiated treatment with SGLT2 inhibitors or dipeptidyl peptidase-4 (DPP4) inhibitors (2015-2021). Outcomes included all-cause death and a composite of chronic kidney disease stage 4 or worse, eGFR < 30 mL/min/1.73 m2, or dialysis initiation. Safety outcomes included diabetic ketoacidosis and genital tract infections (in women). RESULTS:The 9090 matched patients (3906 women) had a mean age 60.1 years and a mean eGFR 82.4 mL/min/1.73 m2 at baseline. All-cause death occurred among 315 versus 433 patients with SGLT2 inhibitors versus DPP4 inhibitors, respectively (RR 0.73 [95 %CI 0.64-0.84]). The composite kidney outcome occurred in 421 versus 518 patients, respectively (RR 0.81 [0.72-0.92]). The respective numbers of patients with diabetic ketoacidosis and genital tract infections were 67 versus 59 and 125 versus 119. CONCLUSION:In a global real-world cohort of patients with type 2 diabetes treated with systemic glucocorticoids, SGLT2 inhibitors versus DPP4 inhibitors initiation was associated with a lower rate of all-cause death, with evidence suggesting kidney benefits.

AIMS:Randomized placebo-controlled clinical trials showed that glucagon-like peptide-1 receptor agonists (GLP-1 RA) reduce kidney risk in patients with type 2 diabetes (T2D), prominently in those with chronic kidney disease. It is unclear whether these findings may apply to broader populations of patients with T2D treated in real-world settings and compared to active controls. We summarised real-world data of adverse kidney outcomes among patients with T2D initiating GLP-1 RA versus other glucose-lowering agents. MATERIALS AND METHODS:We searched PubMed and Embase for observational cohort studies (April 2005-January 2025; PROSPERO CRD42023405356). Initiators of GLP-1 RA were compared to sodium-glucose cotransporter-2 inhibitors (SGLT2i), dipeptidyl-peptidase 4 inhibitors (DPP4i), sulfonylureas, or basal insulin. Outcomes included risks of albuminuria progression, ≥ 40 or ≥ 50% eGFR reduction from baseline, acute kidney injury (AKI), kidney-related hospitalizations, and end-stage kidney disease (ESKD), per data availability. We synthesised the data using inverse variance-weighted averages of logarithmic hazard ratios (HR)s in random-effect models. RESULTS:Thirty-one studies were eligible, encompassing 1,601,389 patients (mean age 49-78 years, 5%-64% women), with 21, 6, 5, and 1 of them using SGLT2i, DPP4i, basal insulin, and sulfonylureas as a comparator, respectively. Compared with SGLT2i, GLP-1 RA initiators had higher risks for AKI (HR [95% CI] 1.12 [1.05-1.20]), kidney-related hospitalizations (1.66 [1.01-2.73]), and ≥ 40% reduction in eGFR (1.40 [1.27-1.53]), without evidence for differences in risks of ≥ 50% eGFR reduction or ESKD. Compared to DPP4i, GLP-1 RA initiators had lower risks for experiencing ≥ 50% eGFR reduction (0.84 [0.76-0.92]), kidney-related hospitalizations (0.73 [0.65-0.83]), and ESKD (0.70 [0.63-0.78]). Similar benefits were observed when comparing GLP-1 RA to sulfonylureas. Compared to basal insulin, GLP-1 RA initiation was associated with a lower risk of albuminuria progression (0.89 [0.80-0.99]), with inconsistent data regarding possible benefits in reducing ESKD risk. CONCLUSIONS:In patients with T2D, initiation of GLP-1 RA in real-world settings may be associated with improved kidney outcomes compared to DPP4i, sulfonylureas, and basal insulin, and worse kidney outcomes compared to SGLT2i.

AIM:To assess the association between urinary albumin-to-creatinine ratio (UACR) categories within the normal range with mortality and adverse cardiovascular outcomes. MATERIALS AND METHODS:PubMed and Embase were systematically searched for real-world evidence studies. Studies were manually evaluated according to predefined eligibility criteria. We included prospective and retrospective cohort studies of the association between UACR categories <30 mg/g and cardiovascular outcomes or mortality. Published information regarding study design, participants, UACR categorization, statistical methods, and results was manually collected. Two UACR categorization approaches were defined: a two-category (UACR <10 mg/g vs. 10-30 mg/g) and a three-category division (UACR <5 mg/g vs. 5-10 and 10-30 mg/g). A random effects meta-analysis was performed on studies eligible for the meta-analysis. RESULTS:In total, 22 manuscripts were identified for the systematic review, 15 of which were eligible for the meta-analysis. The results suggest an association between elevated UACR within the normal to mildly increased range and higher risks of all-cause mortality, cardiovascular death, and coronary heart disease, particularly in the range of 10-30 mg/g. Compared with UACR <10 mg/g, the hazard ratio [HR (95% confidence interval, CI)] for UACR between 10 and 30 mg/g was 1.41 (1.15, 1.74) for all-cause mortality and 1.56 (1.23, 1.98) for coronary heart disease. Compared with UACR <5 mg/g, the risk of cardiovascular mortality for UACR between 10 and 30 mg/g was more than twofold [HR (95% CI): 2.12 (1.61, 2.80)]. Intermediate UACR (5-10 mg/g) was also associated with a higher risk of all-cause mortality [HR (95% CI): 1.14 (1.05, 1.24)] and cardiovascular mortality [HR (95% CI): 1.50 (1.14, 1.99)]. CONCLUSIONS:We propose considering higher UACR within the normoalbuminuric range as a prognostic factor for cardiovascular morbidity and mortality. Our findings underscore the clinical significance of even mild increases in albuminuria.

Chronic kidney disease (CKD) affects 9.1% globally, with persistent albuminuria being a key indicator. Although some studies suggested that high urinary albumin to creatinine (UACR) levels within the normal-to-mildly-increased range is associated with adverse outcomes, the importance of this association is not yet established. Thus, we conducted a systematic search and a meta-analysis, aiming to assess the association between UACR within the normal to mildly increased range and mortality as well as adverse cardiovascular outcomes.

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.

Objective: The essential role of raptor/mTORC1 signaling in 13-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 13-cells to insulin resistant state.Method: Here, we use mice with heterozygous deletion of raptor in 13-cells (braHet) to assess whether reduced mTORC1 function is critical for 13cell function in normal conditions or during 13-cell adaptation to high-fat diet (HFD).Results: Deletion of a raptor allele in 13-cells showed no differences at the metabolic level, islets morphology, or 13-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 13-cell genes like Ins1, MafA, Ucn3, Glut2, Glp1r, and specially PDX1 suggesting an improper 13-cell adaptation to HFD.Conclusion: This study identifies that raptor levels play a key role in maintaining PDX1 levels and 13-cell function during the adaptation of 13-cell to HFD. Finally, we identified that Raptor levels regulate PDX1 levels and 13-cell function during 13-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 13-cell function in conditions of insulin resistance in male mice. & COPY; 2023 The Author(s). Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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

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. 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. 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. 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. 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 )