A Public BCR Present in a Unique Dual-Receptor-Expressing Lymphocyte from Type 1 Diabetes Patients Encodes a Potent T Cell Autoantigen.

T and B cells are the two known lineages of adaptive immune cells. Here, we describe a previously unknown lymphocyte that is a dual expresser (DE) of TCR and BCR and key lineage markers of both B and T cells. In type 1 diabetes (T1D), DEs are predominated by one clonotype that encodes a potent CD4 T cell autoantigen in its antigen binding site. Molecular dynamics simulations revealed that this peptide has an optimal binding register for diabetogenic HLA-DQ8. In concordance, a synthetic version of the peptide forms stable DQ8 complexes and potently stimulates autoreactive CD4 T cells from T1D patients, but not healthy controls. Moreover, mAbs bearing this clonotype are autoreactive against CD4 T cells and inhibit insulin tetramer binding to CD4 T cells. Thus, compartmentalization of adaptive immune cells into T and B cells is not absolute, and violators of this paradigm are likely key drivers of autoimmune diseases.

High-throughput and high-dimensional single-cell analysis of antigen-specific CD8+ T cells.

Although critical to T cell function, antigen specificity is often omitted in high-throughput multiomics-based T cell profiling due to technical challenges. We describe a high-dimensional, tetramer-associated T cell antigen receptor (TCR) sequencing (TetTCR-SeqHD) method to simultaneously profile cognate antigen specificities, TCR sequences, targeted gene expression and surface-protein expression from tens of thousands of single cells. Using human polyclonal CD8+ T cells with known antigen specificity and TCR sequences, we demonstrate over 98% precision for detecting the correct antigen specificity. We also evaluate gene expression and phenotypic differences among antigen-specific CD8+ T cells and characterize phenotype signatures of influenza- and Epstein-Barr virus-specific CD8+ T cells that are unique to their pathogen targets. Moreover, with the high-throughput capacity of profiling hundreds of antigens simultaneously, we apply TetTCR-SeqHD to identify antigens that preferentially enrich cognate CD8+ T cells in patients with type 1 diabetes compared to healthy controls and discover a TCR that cross-reacts with diabetes-related and microbiome antigens. TetTCR-SeqHD is a powerful approach for profiling T cell responses in humans and mice.

CXCL16-dependent scavenging of oxidized lipids by islet macrophages promotes differentiation of pathogenic CD8+ T cells in diabetic autoimmunity.

The pancreatic islet microenvironment is highly oxidative, rendering ß cells vulnerable to autoinflammatory insults. Here, we examined the role of islet resident macrophages in the autoimmune attack that initiates type 1 diabetes. Islet macrophages highly expressed CXCL16, a chemokine and scavenger receptor for oxidized low-density lipoproteins (OxLDLs), regardless of autoimmune predisposition. Deletion of Cxcl16 in nonobese diabetic (NOD) mice suppressed the development of autoimmune diabetes. Mechanistically, Cxcl16 deficiency impaired clearance of OxLDL by islet macrophages, leading to OxLDL accumulation in pancreatic islets and a substantial reduction in intra-islet transitory (Texint) CD8+ T cells displaying proliferative and effector signatures. Texint cells were vulnerable to oxidative stress and diminished by ferroptosis; PD-1 blockade rescued this population and reversed diabetes resistance in NOD.Cxcl16-/- mice. Thus, OxLDL scavenging in pancreatic islets inadvertently promotes differentiation of pathogenic CD8+ T cells, presenting a paradigm wherein tissue homeostasis processes can facilitate autoimmune pathogenesis in predisposed individuals.

Imbalance of APOB Lipoproteins and Large HDL in Type 1 Diabetes Drives Atherosclerosis.

BACKGROUND: Individuals with type 1 diabetes (T1D) generally have normal or even higher HDL (high-density lipoprotein)-cholesterol levels than people without diabetes yet are at increased risk for atherosclerotic cardiovascular disease (CVD). Human HDL is a complex mixture of particles that can vary in cholesterol content by >2-fold. To investigate if specific HDL subspecies contribute to the increased atherosclerosis associated with T1D, we created mouse models of T1D that exhibit human-like HDL subspecies. We also measured HDL subspecies and their association with incident CVD in a cohort of people with T1D. METHODS: We generated LDL receptor-deficient (Ldlr-/-) mouse models of T1D expressing human APOA1 (apolipoprotein A1). Ldlr-/-APOA1Tg mice exhibited the main human HDL subspecies. We also generated Ldlr-/-APOA1Tg T1D mice expressing CETP (cholesteryl ester transfer protein), which had lower concentrations of large HDL subspecies versus mice not expressing CETP. HDL particle concentrations and sizes and proteins involved in lipoprotein metabolism were measured by calibrated differential ion mobility analysis and targeted mass spectrometry in the mouse models of T1D and in a cohort of individuals with T1D. Endothelial transcytosis was analyzed by total internal reflection fluorescence microscopy. RESULTS: Diabetic Ldlr-/-APOA1Tg mice were severely hyperglycemic and hyperlipidemic and had markedly elevated plasma APOB levels versus nondiabetic littermates but were protected from the proatherogenic effects of diabetes. Diabetic Ldlr-/-APOA1Tg mice expressing CETP lost the atheroprotective effect and had increased lesion necrotic core areas and APOB accumulation, despite having lower plasma APOB levels. The detrimental effects of low concentrations of larger HDL particles in diabetic mice expressing CETP were not explained by reduced cholesterol efflux. Instead, large HDL was more effective than small HDL in preventing endothelial transcytosis of LDL mediated by scavenger receptor class B type 1. Finally, in humans with T1D, increased concentrations of larger HDL particles relative to APOB100 negatively predicted incident CVD independently of HDL-cholesterol levels. CONCLUSIONS: Our results suggest that the balance between APOB lipoproteins and the larger HDL subspecies contributes to atherosclerosis progression and incident CVD in the setting of T1D and that larger HDLs exert atheroprotective effects on endothelial cells rather than by promoting macrophage cholesterol efflux.

Appropriate glycemic management protects the germline but not the uterine environment in hyperglycemia.

Emerging evidence indicates that parental diseases can impact the health of subsequent generations through epigenetic inheritance. Recently, it was shown that maternal diabetes alters the metaphase II oocyte transcriptome, causing metabolic dysfunction in offspring. However, type 1 diabetes (T1D) mouse models frequently utilized in previous studies may be subject to several confounding factors due to severe hyperglycemia. This limits clinical translatability given improvements in glycemic control for T1D subjects. Here, we optimize a T1D mouse model to investigate the effects of appropriately managed maternal glycemic levels on oocytes and intrauterine development. We show that diabetic mice with appropriate glycemic control exhibit better long-term health, including maintenance of the oocyte transcriptome and chromatin accessibility. We further show that human oocytes undergoing in vitro maturation challenged with mildly increased levels of glucose, reflecting appropriate glycemic management, also retain their transcriptome. However, fetal growth and placental function are affected in mice despite appropriate glycemic control, suggesting the uterine environment rather than the germline as a pathological factor in developmental programming in appropriately managed diabetes.

Closed-Loop Therapy and Preservation of C-Peptide Secretion in Type 1 Diabetes.

BACKGROUND: Whether improved glucose control with hybrid closed-loop therapy can preserve C-peptide secretion as compared with standard insulin therapy in persons with new-onset type 1 diabetes is unclear. METHODS: In a multicenter, open-label, parallel-group, randomized trial, we assigned youths 10.0 to 16.9 years of age within 21 days after a diagnosis of type 1 diabetes to receive hybrid closed-loop therapy or standard insulin therapy (control) for 24 months. The primary end point was the area under the curve (AUC) for the plasma C-peptide level (after a mixed-meal tolerance test) at 12 months after diagnosis. The analysis was performed on an intention-to-treat basis. RESULTS: A total of 97 participants (mean [±SD] age, 12±2 years) underwent randomization: 51 were assigned to receive closed-loop therapy and 46 to receive control therapy. The AUC for the C-peptide level at 12 months (primary end point) did not differ significantly between the two groups (geometric mean, 0.35 pmol per milliliter [interquartile range, 0.16 to 0.49] with closed-loop therapy and 0.46 pmol per milliliter [interquartile range, 0.22 to 0.69] with control therapy; mean adjusted difference, -0.06 pmol per milliliter [95% confidence interval {CI}, -0.14 to 0.03]). There was not a substantial between-group difference in the AUC for the C-peptide level at 24 months (geometric mean, 0.18 pmol per milliliter [interquartile range, 0.06 to 0.22] with closed-loop therapy and 0.24 pmol per milliliter [interquartile range, 0.05 to 0.30] with control therapy; mean adjusted difference, -0.04 pmol per milliliter [95% CI, -0.14 to 0.06]). The arithmetic mean glycated hemoglobin level was lower in the closed-loop group than in the control group by 4 mmol per mole (0.4 percentage points; 95% CI, 0 to 8 mmol per mole [0.0 to 0.7 percentage points]) at 12 months and by 11 mmol per mole (1.0 percentage points; 95% CI, 7 to 15 mmol per mole [0.5 to 1.5 percentage points]) at 24 months. Five cases of severe hypoglycemia occurred in the closed-loop group (in 3 participants), and one occurred in the control group; one case of diabetic ketoacidosis occurred in the closed-loop group. CONCLUSIONS: In youths with new-onset type 1 diabetes, intensive glucose control for 24 months did not appear to prevent the decline in residual C-peptide secretion. (Funded by the National Institute for Health and Care Research and others; CLOuD ClinicalTrials.gov number, NCT02871089.).

Loss of mitogen-activated protein kinase phosphate-5 aggravates islet dysfunction in mice with type 1 and type 2 diabetes.

Impaired functionality and loss of islet ß-cells are the primary abnormalities underlying the pathogenesis of both type 1 and 2 diabetes (T1DM and T2DM). However, specific therapeutic and preventive mechanisms underlying these conditions remain unclear. Mitogen-activated protein kinase phosphatase-5 (MKP-5) has been implicated in carcinogenesis, lipid metabolism regulation, and immune cell activation. In a previous study, we demonstrated the involvement of exogenous MKP-5 in the regulation of obesity-induced T2DM. However, the role of endogenous MKP-5 in the T1DM and T2DM processes is unclear. Thus, mice with MKP-5 knockout (KO) were generated and used to establish mouse models of both T1DM and T2DM. Our results showed that MKP-5 KO exacerbated diabetes-related symptoms in mice with both T1DM and T2DM. Given that most phenotypic studies on islet dysfunction have focused on mice with T2DM rather than T1DM, we specifically aimed to investigate the role of endoplasmic reticulum stress (ERS) and autophagy in T2DM KO islets. To accomplish this, we performed RNA sequence analysis to gain comprehensive insight into the molecular mechanisms associated with ERS and autophagy in T2DM KO islets. The results showed that the islets from mice with MKP-5 KO triggered 5' adenosine monophosphate-activated protein kinase (AMPK)-mediated autophagy inhibition and glucose-regulated protein 78 (GRP-78)-dominated ERS. Hence, we concluded that the autophagy impairment, resulting in islet dysfunction in mice with MKP-5 KO, is mediated through GRP-78 involvement. These findings provide valuable insights into the molecular pathogenesis of diabetes and highlight the significant role of MKP-5. Moreover, this knowledge holds promise for novel therapeutic strategies targeting MKP-5 for diabetes management.

Systematically assessing microbiome-disease associations identifies drivers of inconsistency in metagenomic research.

Evaluating the relationship between the human gut microbiome and disease requires computing reliable statistical associations. Here, using millions of different association modeling strategies, we evaluated the consistency-or robustness-of microbiome-based disease indicators for 6 prevalent and well-studied phenotypes (across 15 public cohorts and 2,343 individuals). We were able to discriminate between analytically robust versus nonrobust results. In many cases, different models yielded contradictory associations for the same taxon-disease pairing, some showing positive correlations and others negative. When querying a subset of 581 microbe-disease associations that have been previously reported in the literature, 1 out of 3 taxa demonstrated substantial inconsistency in association sign. Notably, >90% of published findings for type 1 diabetes (T1D) and type 2 diabetes (T2D) were particularly nonrobust in this regard. We additionally quantified how potential confounders-sequencing depth, glucose levels, cholesterol, and body mass index, for example-influenced associations, analyzing how these variables affect the ostensible correlation between Faecalibacterium prausnitzii abundance and a healthy gut. Overall, we propose our approach as a method to maximize confidence when prioritizing findings that emerge from microbiome association studies.

Maintenance of Enteral ACE2 Prevents Diabetic Retinopathy in Type 1 Diabetes.

BACKGROUND: We examined components of systemic and intestinal renin-angiotensin system on gut barrier permeability, glucose homeostasis, systemic inflammation, and progression of diabetic retinopathy (DR) in human subjects and mice with type 1 diabetes (T1D). METHODS: T1D individual with (n=18) and without (n=20) DR and controls (n=34) were examined for changes in gut-regulated components of the immune system, gut leakage markers (FABP2 [fatty acid binding protein 2] and peptidoglycan), and Ang II (angiotensin II); Akita mice were orally administered a Lactobacillus paracasei (LP) probiotic expressing humanized ACE2 (angiotensin-converting enzyme 2) protein (LP-ACE2) as either a prevention or an intervention. Akita mice with genetic overexpression of humanAce2 by small intestine epithelial cells (Vil-Cre.hAce2KI-Akita) were similarly examined. After 9 months of T1D, circulatory, enteral, and ocular end points were assessed. RESULTS: T1D subjects exhibit elevations in gut-derived circulating immune cells (ILC1 cells) and higher gut leakage markers, which were positively correlated with plasma Ang II and DR severity. The LP-ACE2 prevention cohort and genetic overexpression of intestinal ACE2 preserved barrier integrity, reduced inflammatory response, improved hyperglycemia, and delayed development of DR. Improvements in glucose homeostasis were due to intestinal MasR activation, resulting in a GSK-3ß (glycogen synthase kinase-3 beta)/c-Myc (cellular myelocytomatosis oncogene)-mediated decrease in intestinal glucose transporter expression. In the LP-ACE2 intervention cohort, gut barrier integrity was improved and DR reversed, but no improvement in hyperglycemia was observed. These data support that the beneficial effects of LP-ACE2 on DR are due to the action of ACE2, not improved glucose homeostasis. CONCLUSIONS: Dysregulated systemic and intestinal renin-angiotensin system was associated with worsening gut barrier permeability, gut-derived immune cell activation, systemic inflammation, and progression of DR in human subjects. In Akita mice, maintaining intestinal ACE2 expression prevented and reversed DR, emphasizing the multifaceted role of the intestinal renin-angiotensin system in diabetes and DR.

Novel Angiogenesis Role of GLP-1(32-36) to Rescue Diabetic Ischemic Lower Limbs via GLP-1R-Dependent Glycolysis in Mice.

BACKGROUND: Restoring the capacity of endothelial progenitor cells (EPCs) to promote angiogenesis is the major therapeutic strategy of diabetic peripheral artery disease. The aim of this study was to investigate the effects of GLP-1 (glucagon-like peptide 1; 32-36)-an end product of GLP-1-on angiogenesis of EPCs and T1DM (type 1 diabetes) mice, as well as its interaction with the classical GLP-1R (GLP-1 receptor) pathway and its effect on mitochondrial metabolism. METHODS: In in vivo experiments, we conducted streptozocin-induced type 1 diabetic mice as a murine model of unilateral hind limb ischemia to examine the therapeutic potential of GLP-1(32-36) on angiogenesis. We also generated Glp1r-/- mice to detect whether GLP-1R is required for angiogenic function of GLP-1(32-36). In in vitro experiments, EPCs isolated from the mouse bone marrow and human umbilical cord blood samples were used to detect GLP-1(32-36)-mediated angiogenic capability under high glucose treatment. RESULTS: We demonstrated that GLP-1(32-36) did not affect insulin secretion but could significantly rescue angiogenic function and blood perfusion in ischemic limb of streptozocin-induced T1DM mice, a function similar to its parental GLP-1. We also found that GLP-1(32-36) promotes angiogenesis in EPCs exposed to high glucose. Specifically, GLP-1(32-36) has a causal role in improving fragile mitochondrial function and metabolism via the GLP-1R-mediated pathway. We further demonstrated that GLP-1(32-36) rescued diabetic ischemic lower limbs by activating the GLP-1R-dependent eNOS (endothelial NO synthase)/cGMP/PKG (protein kinase G) pathway. CONCLUSIONS: Our study provides a novel mechanism with which GLP-1(32-36) acts in modulating metabolic reprogramming toward glycolytic flux in partnership with GLP-1R for improved angiogenesis in high glucose-exposed EPCs and T1DM murine models. We propose that GLP-1(32-36) could be used as a monotherapy or add-on therapy with existing treatments for peripheral artery disease. REGISTRATION: URL: www.ebi.ac.uk/metabolights/; Unique identifier: MTBLS9543.

Lipidomics Study of Type 1 Diabetic Rats Using Online Phase Transition Trapping-Supercritical Fluid Extraction-Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry.

Chromatography-mass spectrometry-based lipidomics represents an essential tool for elucidating lipid dysfunction mechanisms and is extensively employed in investigating disease mechanisms and identifying biomarkers. However, the detection of low-abundance lipids in biological matrices, along with cumbersome operational procedures, complicates comprehensive lipidomic analyses, necessitating the development of highly sensitive, environmentally friendly, and automated methods. In this study, an online phase transition trapping-supercritical fluid extraction-chromatography-mass spectrometry (PTT-SFEC-MS/MS) method was developed and successfully applied to plasma lipidomics analysis in Type 1 diabetes (T1D) rats. The PTT strategy captured entire extracts at the column head by converting CO2 from a supercritical state to a gaseous state, thereby preventing peak spreading, enhancing peak shape for precise quantification, and boosting sensitivity without any sample loss. This method utilized only 5 µL of plasma and accomplished sample extraction, separation, and detection within 27 min. Ultimately, 77 differential lipids were identified, including glycerophospholipids, sphingolipids, and glycerolipids, in T1D rat plasma. The results indicated that the progression of the disease might be linked to alterations in glycerophospholipid and sphingolipid metabolism. Our findings demonstrated a green, highly efficient, and automated method for the lipidomics analysis of biological samples, providing a scientific foundation for understanding the pathogenesis and diagnosis of T1D.

Interferons are key cytokines acting on pancreatic islets in type 1 diabetes.

AIMS/HYPOTHESIS: The proinflammatory cytokines IFN-α, IFN-γ, IL-1ß and TNF-α may contribute to innate and adaptive immune responses during insulitis in type 1 diabetes and therefore represent attractive therapeutic targets to protect beta cells. However, the specific role of each of these cytokines individually on pancreatic beta cells remains unknown. METHODS: We used deep RNA-seq analysis, followed by extensive confirmation experiments based on reverse transcription-quantitative PCR (RT-qPCR), western blot, histology and use of siRNAs, to characterise the response of human pancreatic beta cells to each cytokine individually and compared the signatures obtained with those present in islets of individuals affected by type 1 diabetes. RESULTS: IFN-α and IFN-γ had a greater impact on the beta cell transcriptome when compared with IL-1ß and TNF-α. The IFN-induced gene signatures have a strong correlation with those observed in beta cells from individuals with type 1 diabetes, and the level of expression of specific IFN-stimulated genes is positively correlated with proteins present in islets of these individuals, regulating beta cell responses to 'danger signals' such as viral infections. Zinc finger NFX1-type containing 1 (ZNFX1), a double-stranded RNA sensor, was identified as highly induced by IFNs and shown to play a key role in the antiviral response in beta cells. CONCLUSIONS/INTERPRETATION: These data suggest that IFN-α and IFN-γ are key cytokines at the islet level in human type 1 diabetes, contributing to the triggering and amplification of autoimmunity.

Metabolic effect of adrenaline infusion in people with type 1 diabetes and healthy individuals.

AIMS/HYPOTHESIS: As a result of early loss of the glucagon response, adrenaline is the primary counter-regulatory hormone in type 1 diabetes. Diminished adrenaline responses to hypoglycaemia due to counter-regulatory failure are common in type 1 diabetes, and are probably induced by exposure to recurrent hypoglycaemia, however, the metabolic effects of adrenaline have received less research attention, and also there is conflicting evidence regarding adrenaline sensitivity in type 1 diabetes. Thus, we aimed to investigate the metabolic response to adrenaline and explore whether it is modified by prior exposure to hypoglycaemia. METHODS: Eighteen participants with type 1 diabetes and nine healthy participants underwent a three-step ascending adrenaline infusion during a hyperinsulinaemic-euglycaemic clamp. Continuous glucose monitoring data obtained during the week before the study day were used to assess the extent of hypoglycaemia exposure. RESULTS: While glucose responses during the clamp were similar between people with type 1 diabetes and healthy participants, plasma concentrations of NEFAs and glycerol only increased in the group with type 1 diabetes (p<0.001). Metabolomics revealed an increase in the most common NEFAs (p<0.01). Other metabolic responses were generally similar between participants with type 1 diabetes and healthy participants. Exposure to hypoglycaemia was negatively associated with the NEFA response; however, this was not statistically significant. CONCLUSIONS/INTERPRETATION: In conclusion, individuals with type 1 diabetes respond with increased lipolysis to adrenaline compared with healthy participants by mobilising the abundant NEFAs in plasma, whereas other metabolic responses were similar. This may suggest that the metabolic sensitivity to adrenaline is altered in a pathway-specific manner in type 1 diabetes. TRIAL REGISTRATION: ClinicalTrials.gov NCT05095259.

The metabolome as a diagnostic for maximal aerobic capacity during exercise in type 1 diabetes.

AIMS/HYPOTHESIS: Our aim was to characterise the in-depth metabolic response to aerobic exercise and the impact of residual pancreatic beta cell function in type 1 diabetes. We also aimed to use the metabolome to distinguish individuals with type 1 diabetes with reduced maximal aerobic capacity in exercise defined by V ˙ O 2peak . METHODS: Thirty participants with type 1 diabetes (≥3 years duration) and 30 control participants were recruited. Groups did not differ in age or sex. After quantification of peak stimulated C-peptide, participants were categorised into those with undetectable (<3 pmol/l), low (3-200 pmol/l) or high (>200 pmol/l) residual beta cell function. Maximal aerobic capacity was assessed by V ˙ O 2peak test and did not differ between control and type 1 diabetes groups. All participants completed 45 min of incline treadmill walking (60% V ˙ O 2peak ) with venous blood taken prior to exercise, immediately post exercise and after 60 min recovery. Serum was analysed using targeted metabolomics. Metabolomic data were analysed by multivariate statistics to define the metabolic phenotype of exercise in type 1 diabetes. Receiver operating characteristic (ROC) curves were used to identify circulating metabolomic markers of maximal aerobic capacity ( V ˙ O 2peak ) during exercise in health and type 1 diabetes. RESULTS: Maximal aerobic capacity ( V ˙ O 2peak ) inversely correlated with HbA1c in the type 1 diabetes group (r2=0.17, p=0.024). Higher resting serum tricarboxylic acid cycle metabolites malic acid (fold change 1.4, p=0.001) and lactate (fold change 1.22, p=1.23×10-5) differentiated people with type 1 diabetes. Higher serum acylcarnitines (AC) (AC C14:1, F value=12.25, p=0.001345; AC C12, F value=11.055, p=0.0018) were unique to the metabolic response to exercise in people with type 1 diabetes. C-peptide status differentially affected metabolic responses in serum ACs during exercise (AC C18:1, leverage 0.066; squared prediction error 3.07). The malic acid/pyruvate ratio in rested serum was diagnostic for maximal aerobic capacity ( V ˙ O 2peak ) in people with type 1 diabetes (ROC curve AUC 0.867 [95% CI 0.716, 0.956]). CONCLUSIONS/INTERPRETATION: The serum metabolome distinguishes high and low maximal aerobic capacity and has diagnostic potential for facilitating personalised medicine approaches to manage aerobic exercise and fitness in type 1 diabetes.

Role of CFTR in diabetes-induced pancreatic ductal fluid and HCO3 - secretion.

Type 1 diabetes is a disease of the endocrine pancreas; however, it also affects exocrine function. Although most studies have examined the effects of diabetes on acinar cells, much less is known regarding ductal cells, despite their important protective function in the pancreas. Therefore, we investigated the effect of diabetes on ductal function. Diabetes was induced in wild-type and cystic fibrosis transmembrane conductance regulator (CFTR) knockout mice following an i.p. administration of streptozotocin. Pancreatic ductal fluid and HCO3 - secretion were determined using fluid secretion measurements and fluorescence microscopy, respectively. The expression of ion transporters was measured by real-time PCR and immunohistochemistry. Transmission electron microscopy was used for the morphological characterization of the pancreas. Serum secretin and cholecystokinin levels were measured by an enzyme-linked immunosorbent assay. Ductal fluid and HCO3 - secretion, CFTR activity, and the expression of CFTR, Na+ /H+ exchanger-1, anoctamine-1 and aquaporin-1 were significantly elevated in diabetic mice. Acute or chronic glucose treatment did not affect HCO3 - secretion, but increased alkalizing transporter activity. Inhibition of CFTR significantly reduced HCO3 - secretion in both normal and diabetic mice. Serum levels of secretin and cholecystokinin were unchanged, but the expression of secretin receptors significantly increased in diabetic mice. Diabetes increases fluid and HCO3 - secretion in pancreatic ductal cells, which is associated with the increased function of ion and water transporters, particularly CFTR. KEY POINTS: There is a lively interaction between the exocrine and endocrine pancreas not only under physiological conditions, but also under pathophysiological conditions The most common disease affecting the endocrine part is type-1 diabetes mellitus (T1DM), which is often associated with pancreatic exocrine insufficiency Compared with acinar cells, there is considerably less information regarding the effect of diabetes on pancreatic ductal epithelial cells, despite the fact that the large amount of fluid and HCO3 - produced by ductal cells is essential for maintaining normal pancreatic functions Ductal fluid and HCO3 - secretion increase in T1DM, in which increased cystic fibrosis transmembrane conductance regulator activation plays a central role. We have identified a novel interaction between T1DM and ductal cells. Presumably, the increased ductal secretion represents a defence mechanism in the prevention of diabetes, but further studies are needed to clarify this issue.

Hybrid insulin peptide isomers spontaneously form in pancreatic beta-cells from an aspartic anhydride intermediate.

Hybrid insulin peptides (HIPs) form in beta-cells when insulin fragments link to other peptides through a peptide bond. HIPs contain nongenomic amino acid sequences and have been identified as targets for autoreactive T cells in type 1 diabetes. A subgroup of HIPs, in which N-terminal amine groups of various peptides are linked to aspartic acid residues of insulin C-peptide, was detected through mass spectrometry in pancreatic islets. Here, we investigate a novel mechanism that leads to the formation of these HIPs in human and murine islets. Our research herein shows that these HIPs form spontaneously in beta-cells through a mechanism involving an aspartic anhydride intermediate. This mechanism leads to the formation of a regular HIP containing a standard peptide bond as well as a HIP-isomer containing an isopeptide bond by linkage to the carboxylic acid side chain of the aspartic acid residue. We used mass spectrometric analyses to confirm the presence of both HIP isomers in islets, thereby validating the occurrence of this novel reaction mechanism in beta-cells. The spontaneous formation of new peptide bonds within cells may lead to the development of neoepitopes that contribute to the pathogenesis of type 1 diabetes as well as other autoimmune diseases.

C-peptide in diabetes: A player in a dual hormone disorder?

C-peptide, a byproduct of insulin synthesis believed to be biologically inert, is emerging as a multifunctional molecule. C-peptide serves an anti-inflammatory and anti-atherogenic role in type 1 diabetes mellitus (T1DM) and early T2DM. C-peptide protects endothelial cells by activating AMP-activated protein kinase α, thus suppressing the activity of NAD(P)H oxidase activity and reducing reactive oxygen species (ROS) generation. It also prevents apoptosis by regulating hyperglycemia-induced p53 upregulation and mitochondrial adaptor p66shc overactivation, as well as reducing caspase-3 activity and promoting expression of B-cell lymphoma-2. Additionally, C-peptide suppresses platelet-derived growth factor (PDGF)-beta receptor and p44/p42 mitogen-activated protein (MAP) kinase phosphorylation to inhibit vascular smooth muscle cells (VSMC) proliferation. It also diminishes leukocyte adhesion by virtue of its capacity to abolish nuclear factor kappa B (NF-kB) signaling, a major pro-inflammatory cascade. Consequently, it is envisaged that supplementation of C-peptide in T1DM might ameliorate or even prevent end-organ damage. In marked contrast, C-peptide increases monocyte recruitment and migration through phosphoinositide 3-kinase (PI-3 kinase)-mediated pathways, induces lipid accumulation via peroxisome proliferator-activated receptor γ upregulation, and stimulates VSMC proliferation and CD4+ lymphocyte migration through Src-kinase and PI-3K dependent pathways. Thus, it promotes atherosclerosis and microvascular damage in late T2DM. Indeed, C-peptide is now contemplated as a potential biomarker for insulin resistance in T2DM and linked to increased coronary artery disease risk. This shift in the understanding of the pathophysiology of diabetes from being a single hormone deficiency to a dual hormone disorder warrants a careful consideration of the role of C-peptide as a unique molecule with promising diagnostic, prognostic, and therapeutic applications.

Comparison of an oral mixed meal plus arginine and intravenous glucose, GLP-1 plus arginine to unmask residual islet function in longstanding type 1 diabetes.

Residual beta cells are present in most patients with longstanding type 1 diabetes but it is unknown whether these beta cells react normally to different stimuli. Moreover a defect in proinsulin conversion and abnormal alpha cell response are also part of the islet dysfunction. A three-phase [euglycemia, hyperglycemia, and hyperglycemia + glucagon-like peptide 1 (GLP-1)] clamp was performed in patients with longstanding type 1 diabetes. Intravenous arginine boluses were administered at the end of each phase. On another day, a mixed meal stimulation test with a subsequent intravenous arginine bolus was performed. C-peptide was detectable in a subgroup of subjects at baseline (2/15) or only after stimulation (3/15). When detectable, C-peptide increased 2.9-fold [95% CI: 1.2-7.1] during the hyperglycemia phase and 14.1-fold [95% CI: 3.1-65.2] during the hyperglycemia + GLP-1 phase, and 22.3-fold [95% CI: 5.6-89.1] during hyperglycemia + GLP-1 + arginine phase when compared with baseline. The same subset of patients with a C-peptide response were identified during the mixed meal stimulation test as during the clamp. There was an inhibition of glucagon secretion (0.72-fold, [95% CI: 0.63-0.84]) during the glucose clamp irrespective of the presence of detectable beta cell function. Proinsulin was only present in a subset of subjects with detectable C-peptide (3/15) and proinsulin mimicked the C-peptide response to the different stimuli when detectable. Residual beta cells in longstanding type 1 diabetes respond adequately to different stimuli and could be of clinical benefit.NEW & NOTEWORTHY If beta cell function is detectable, the beta cells react relatively normal to the different stimuli except for the first phase response to intravenous glucose. An oral mixed meal followed by an intravenous arginine bolus can identify residual beta cell function/mass as well as the more commonly used glucose potentiated arginine-induced insulin secretion during a hyperglycemic clamp.

Inflammatory and hypoxic stress-induced islet exosomes released during isolation are associated with poor transplant outcomes in islet autotransplantation.

Islets experience enormous stress during the isolation process, leading to suboptimal endocrine function after total pancreatectomy with islet autotransplantation (TPIAT). Our investigation focused on inducing isolation stress in islets ex vivo, where proinflammatory cytokines and hypoxia prompted the release of stress exosomes (exoS) sized between 50 and 200 nm. Mass spectrometry analysis revealed 3 distinct subgroups of immunogenic proteins within these exoS: damage-associated molecular patterns (DAMPs), chaperones, and autoantigens. The involvement of endosomal-sorting complex required for transport proteins including ras-associated binding proteins7A, ras-associated binding protein GGTA, vacuolar protein sorting associated protein 45, vacuolar protein sorting associated protein 26B, and the tetraspanins CD9 and CD63, in exoS biogenesis was confirmed through immunoblotting. Next, we isolated similar exoS from the islet infusion bags of TPIAT recipients (N = 20). The exosomes from infusion bags exhibited higher DAMP (heat shock protein family A [Hsp70] member 1B and histone H2B) levels, particularly in the insulin-dependent TPIAT group. Additionally, elevated DAMP protein levels in islet infusion bag exosomes correlated with increased insulin requirements (P = .010) and higher hemoglobin A1c levels 1-year posttransplant. A deeper exploration into exoS functionality revealed their potential to activate monocytes via the toll-like receptor 3/7: DAMP axis. This stimulation resulted in the induction of inflammatory phenotypes marked by increased levels of CD68, CD80, inducible nitric oxide synthase, and cyclooxygenase-2. This activation mechanism may impact the successful engraftment of transplanted islets.

Compromised DNA repair is responsible for diabetes-associated fibrosis.

Diabetes-associated organ fibrosis, marked by elevated cellular senescence, is a growing health concern. Intriguingly, the mechanism underlying this association remained unknown. Moreover, insulin alone can neither reverse organ fibrosis nor the associated secretory phenotype, favoring the exciting notion that thus far unknown mechanisms must be operative. Here, we show that experimental type 1 and type 2 diabetes impairs DNA repair, leading to senescence, inflammatory phenotypes, and ultimately fibrosis. Carbohydrates were found to trigger this cascade by decreasing the NAD+ /NADH ratio and NHEJ-repair in vitro and in diabetes mouse models. Restoring DNA repair by nuclear over-expression of phosphomimetic RAGE reduces DNA damage, inflammation, and fibrosis, thereby restoring organ function. Our study provides a novel conceptual framework for understanding diabetic fibrosis on the basis of persistent DNA damage signaling and points to unprecedented approaches to restore DNA repair capacity for resolution of fibrosis in patients with diabetes.