Diabetes

Increased circulating levels of incompletely processed insulin (i.e. proinsulin) are observed clinically in both type 1 and type 2 diabetes; however, the mechanisms underlying impaired proinsulin processing remain incompletely understood. Here, we identify the sarcoendoplasmic reticulum Ca2+ ATPase-2 (SERCA2) pump and {beta} cell ER Ca2+ as key regulators of systemic glucose tolerance and proinsulin processing. We generated mice with a {beta} cell-specific SERCA2 deletion ({beta}S2KO) and SERCA2 deficient INS-1 cells to show that SERCA2 loss increases systemic and pancreatic levels of proinsulin protein and leads to aberrant localization of proinsulin within the proximal {beta} cell secretory pathway. These defects in proinsulin processing were linked to reduced maturation of the proinsulin processing enzymes PC1/3 and PC2, suggesting a model whereby chronic ER Ca2+ depletion in the {beta} cell, which is observed in many pathological conditions, impairs the spatial regulation of prohormone trafficking, processing, and maturation within the {beta} cell secretory pathway.

Vitamin D-binding protein (DBP) or GC-globulin carries vitamin D metabolites from the circulation to target tissues. DBP expression is highly-localized to the liver and pancreatic -cells. While DBP serum levels, gene polymorphisms and autoantigens have all been associated with diabetes risk, the underlying mechanisms remain unknown. Here, we show that DBP regulates -cell morphology, -cell function and glucagon secretion. Deletion of DBP led to smaller and hyperplastic -cells, altered Na+ channel conductance, impaired -cell activation by low glucose, and reduced rates of glucagon secretion. Mechanistically, this involved reversible changes in islet microfilament abundance and density, as well as changes in glucagon granule distribution. Defects were also seen in {beta}-cell and {delta}-cell function. Immunostaining of human pancreata revealed generalized loss of DBP expression as a feature of late-onset and longstanding, but not early-onset type 1 diabetes. Thus, DBP is a critical regulator of -cell phenotype, with implications for diabetes pathogenesis. HIGHLIGHTSO_LIDBP expression is highly-localized to mouse and human -cells C_LIO_LILoss of DBP increases -cell number, but decreases -cell size C_LIO_LI-cells in DBP knockout islets are dysfunctional and secrete less glucagon C_LIO_LIDBP expression is decreased in -cells of donors with late-onset or longstanding type 1 diabetes C_LI

Recent epidemiologic studies indicate that adult-onset type 1 diabetes (AOT1D) is more common than childhood-onset type 1 diabetes, yet it remains clinically underrecognized. Because little is known about the emergence of islet autoantibodies in AOT1D, we conducted a retrospective study using electronic medical records from the United States Military Health System and longitudinal serum samples from 169 individuals with AOT1D and 40 healthy controls obtained from the Department of Defense Serum Repository. Among 643 prediagnostic samples from individuals with AOT1D, IA-2 autoantibodies were the most prevalent (50%), followed by GADA (46%), IA-2{beta} (34%), ZnT8-R (27%), and ZnT8-W (15%). Overall, 85% (144/169) of subjects were seropositive for at least one autoantibody prior to diagnosis. Analysis of the earliest available sample from all of the AOT1D cases, grouped into 5-year intervals preceding diagnosis, demonstrated a progressive increase in seropositivity over time: 38% of subjects were seropositive more than 20 years before diagnosis, increasing to 44% at 20-15 years, 59% at 15-10 years, 73% at 10-5 years, and 91% within 5 years of diagnosis. Among the 144 seropositive individuals, positivity for two or more autoantibodies was the most common pattern, occurring in 50% (72/144) of cases. Isolated GADA positivity (22%) and isolated IA-2/IA-2{beta} positivity (24%) occurred at similar frequencies, whereas isolated ZnT8 positivity was uncommon (4%). Temporal analysis showed that isolated GADA positivity appeared earliest, with a median onset of 7.9 years before diagnosis, whereas multiple-autoantibody positivity, IA-2 positivity, and ZnT8 positivity emerged later, with median onsets of 4.6, 4.5, and 1.9 years before diagnosis, respectively. These findings extend observations from pediatric type 1 diabetes to adults and demonstrate that AOT1D-associated autoimmunity often begins decades before clinical diagnosis, highlighting a potentially important window for risk stratification and preventive intervention.

Carboxypeptidase E (CPE) facilitates the conversion of prohormones into mature hormones and is highly expressed in multiple neuroendocrine tissues. Carriers of CPE mutations have elevated plasma proinsulin and develop severe obesity and hyperglycemia. We aimed to determine whether loss of Cpe in pancreatic beta cells disrupts proinsulin processing and accelerates development of diabetes and obesity in mice. Pancreatic beta cell-specific Cpe knockout mice ({beta}CpeKO; Cpefl/fl x Ins1Cre/+) lack mature insulin granules and have elevated proinsulin in plasma; however, glucose-and KCl-stimulated insulin secretion in {beta}CpeKO islets remained intact. High fat diet-fed {beta}CpeKO mice showed comparable weight gain and glucose tolerance compared to Wt littermates. Notably, beta-cell area was increased in chow-fed {beta}CpeKO mice and beta-cell replication was elevated in {beta}CpeKO islets. Transcriptomic analysis of {beta}CpeKO beta cells revealed elevated glycolysis and Hif1-target gene expression. Upon high glucose challenge, beta cells from {beta}CpeKO mice showed reduced mitochondrial membrane potential, increased reactive oxygen species, reduced MafA, and elevated Aldh1a3 transcript levels. Following multiple low-dose streptozotocin treatment, {beta}CpeKO mice had accelerated hyperglycemia with reduced beta-cell insulin and Glut2 expression. These findings suggest that Cpe and proper proinsulin processing are critical in maintaining beta cell function during the development of diabetes.

Pancreatic {beta} cell dysfunction is critical to the development of type 2 diabetes (T2D). We show that the complement receptor C3aR1 on {beta} cells plays an essential role in maintaining {beta} cell homeostasis, especially under the metabolic duress of obesity and T2D. Mice with {beta} cell specific deletion of C3ar1 have worse glucose tolerance, lower insulin levels, and decreased {beta} cell mass. Islets from {beta} cell specific C3ar1 knockout ({beta}-C3aR1 KO) mice demonstrate impaired insulin secretion. Disruption of C3ar1 on {beta} cells ablates the insulin secretory response to C3a, establishing a signaling axis between C3a and {beta} cell-derived C3aR1. Markers of {beta} cell identity were decreased while stress markers were increased in {beta}-C3aR1 KO mice. Islets from {beta}-C3aR1 KO also exhibit increased {beta} cell death to lipotoxicity. Finally, we show that C3AR1 is positively correlated with insulin secretion in human islets. These findings indicate that C3aR1 expression on {beta} cells is necessary to maintain optimal {beta} cell function and preserve {beta} cell mass in T2D.

Islet amyloid contributes to beta cell failure in type 2 diabetes through several mechanisms, one being the potent induction of local islet inflammation through activating inflammatory pathways in islet macrophages. We performed an unbiased phenotypic investigation of islet macrophages in the early stage of islet amyloid formation using single cell RNA sequencing of resident islet macrophages in mice with and without the amyloidogenic form of human islet amyloid polypeptide (hIAPP). This revealed that MHC Class II antigen presentation genes were strongly down-regulated in islet macrophages during islet amyloid formation. As islet amyloid has recently been reported in pancreases of people with type 1 diabetes, we sought to investigate the impact of islet amyloid in the NOD mouse model of type 1 diabetes. Both overexpression and physiological expression of hIAPP delayed diabetes in NOD mice relative to littermate controls, corresponding with decreased markers of antigen presentation and activation, as well as decreased immune cell infiltration in islets. Adoptive transfer studies showed that systemic autoimmune function remained intact and beta cells from hIAPP transgenic mice did not evade immune recognition by diabetogenic T cells, collectively indicating the protection from diabetes was mediated by localized disruption of antigen presentation in the pancreas. Consistent with this, incubation of dendritic cells with IAPP aggregates decreased MHC Class II surface expression and diminished antigen-specific T cell activation in vitro, through a phagocytosis-dependent mechanism. Collectively our data show that despite the well-established pro-inflammatory response of macrophages to IAPP aggregates, the uptake of IAPP aggregates during early amyloid formation also disrupts MHC Class II antigen presentation and slows beta cell autoimmunity.

The mechanisms that underlie the {beta}-cell pathophysiology of Type 1 Diabetes (T1D) are not fully understood. Our group has defined the unique heterotrimeric G protein alpha-subunit, Gz, as a key negative regulator of {beta}-cell signal transduction pathways. Non-obese diabetic (NOD) mice lacking Gz throughout the body are protected from developing T1D-like hyperglycemia. To determine whether this phenotype is {beta}-cell autonomous, we generated and validated a {beta}-cell-specific Gz knockout ({beta}KO) on the NOD background and characterized the phenotype of female and male cohorts. Long-term hyperglycemia incidence was lower in Gz {beta}KO mice as compared to wild-type (WT) controls, but, unlike global Gz knockout mice, this protection was incomplete. While young male and female Gz {beta}KO NOD mice had improved glucose tolerance, WT NOD males were significantly less glucose tolerant than females, and only female Gz {beta}KO mice retained improved glucose tolerance at 28-29 weeks of age. Conversely, {beta}-cell-specific Gz loss only influenced insulitis in 28-29-week old male NOD mice, a phenotype correlating directly with body burden of glucose during oral glucose challenge. Using surrogates for {beta}-cell function and apoptosis, the partial penetrance of euglycemia in Gz {beta}KO NOD was best explained by an early failure to up-regulate {beta}-cell proliferation. We conclude {beta}-cell Gz is an important regulator of the sexually-dimorphic T1D-like phenotype of NOD mice. Yet, other factors must be important in imparting full protection from the disease.

Glucokinase (GK) catalyses the key regulatory step in glucose-stimulated insulin secretion. Correspondingly, hetero- and homozygous mutations in human GCK cause maturity-onset diabetes of the young (GCK-MODY) and permanent neonatal diabetes (PNDM), respectively. To explore the possible utility of glucokinase activators (GKA) and of glucagon-like receptor-1 (GLP-1) agonists in these diseases, we have developed a novel hypomorphic Gck allele in mice encoding an aberrantly spliced mRNA deleted for exons 2 and 3. In islets from homozygous knock-in (GckKI/KI) mice, GK immunoreactivity was reduced by >85%, and glucose-stimulated insulin secretion eliminated. Homozygous GckKI/KI mice were smaller than wildtype littermates and displayed frank diabetes (fasting blood glucose >18 mmol/L; HbA1c [~]12%), ketosis and nephropathy. Heterozygous GckKI/+ mice were glucose intolerant (HbA1c [~]5.5%). Abnormal glucose-stimulated Ca2+ dynamics and beta cell-beta cell connectivity in GckKI/+ islets were completely reversed by the recently-developed GKA, dorzagliatin, which was largely inactive in homozygous GckKI/KI mouse islets. The GLP-1 receptor agonist exendin-4 improved glucose tolerance in male GckKI/+ mice, an action potentiated by dorzagliatin, in male but not female mice. Sex-dependent additive effects of these agents were also observed on insulin secretion in vitro. Combined treatment with GKA and incretin may thus be useful in GCK-MODY or GCK-PNDM. Article Highlightsa. Glucokinase deficiency can drive maturity-onset diabetes of the young (GCK-MODY; heterozygotes) and permanent neonatal diabetes (GCK-PNDM; homozygotes) b. We describe a hypomorphic Gck allele where aberrant splicing in islets lowers GK activity to by [~]85%. We use these mice to explore the effects of the glucokinase activator, dorzagliatin, and incretin on insulin secretion c. Whereas heterozygous mutant mice are mildly hyperglycemic, homozygotes have frank diabetes but survive to adulthood. Dorzagliatin potentiates the effects of GLP-1 receptor activation sex-dependently in heterozygotes d. Combined use of these drugs may be useful in some forms of GCK diabetes

Identifying individuals at risk of early onset type 1 diabetes (diagnosed <2 years) would be highly beneficial in reducing risk of severe diabetic ketoacidosis (DKA) for those with extreme autoimmunity. We aimed to investigate whether genetic variation contributes to heterogeneity in age of type 1 diabetes onset, focusing on those diagnosed <2 years and ages previously defined by histological differences. We carried out association testing on 6773 individuals with type 1 diabetes and tested for heterogeneity in Human Leukocyte Antigen (HLA) variants across stratified age groups (594 diagnosed <2 years, 2241 diagnosed 2-7 years, 3094 diagnosed 7-13 years, 844 diagnosed 13+ years). We used a 67 SNP type 1 diabetes genetic risk score (T1D-GRS) to quantify aggregated genetic risk and assessed its utility in screening for type 1 diabetes <2 years. We observed higher T1D-GRSs as age of onset decreased in type 1 diabetes and found that DR3-DQ2 homozygosity was most strongly associated with <2 years onset (log-OR=4.27). The T1D-GRS showed high discriminative ability for <2 years onset type 1 diabetes onset (AUC=0.94) and correctly identified 88% of type 1 diabetes cases at the 85th population centile. We have shown higher genetic risk for very early onset T1D and suggest T1D-GRSs in newborn screening is likely to be particularly sensitive to those with younger type 1 diabetes onset.

Background: Acute pancreatitis (AP) is an established risk factor for diabetes, with approximately 20% of children developing either prediabetes or diabetes within one year of their first episode. Little is known about the diabetes pathophysiology or which individuals are at highest risk. We aimed to evaluate whether genetic risk scores (GRS) for type 1 (T1D) and polygenic risk scores (PRS) type 2 diabetes (T2D) are associated with progression to dysglycemia following AP. Methods: Clinical data were available for 123 children (mean age (IQR), 12 (8-15) years; mean body mass index (BMI), 21.8) with AP who were followed for >1 year. Array genotyping coupled with imputation using the TOPMed reference panel was performed. Genetic ancestry was predicted using a random forest classifier. GRS for T1D and T2D were calculated using either an ancestry-appropriate (T1D-GRS) or a multi-ancestry (T2D-PRS) weighted framework. To evaluate risk compared to the population we used predefined GRS thresholds from UK Biobank. Results: Among the 123 subjects, 24 developed dysglycemia (5 with diabetes and 19 with prediabetes). The majority (75.6%, n=93) of children were of European ancestry. Comparison of the T1D-GRS burden with the UK BioBank showed numerically higher proportions for any given threshold. At the top 5% threshold, 9.7% of our cohort were classified as high-risk compared to 5% in UK Biobank (p<0.05). The elevated T1D-GRS could be primarily attributed to non-HLA variants and was more enriched in those testing positive for [&ge;]1 islet-autoantibody. The T2D-PRS was also elevated in the dysglycemic group but only reached statistical significance in those who were obese. Conclusion: These findings highlight the potential role of both T1D-GRS and T2D-PRS in investigating diabetes susceptibility following AP.

Over 1,000 distinct genetic variants have been associated with diabetes risk by genome-wide association studies (GWAS) but for most their functional impact is unknown and less than 15% of the diabetes GWAS variants have been shown in expression quantitative trait locus (eQTL) studies to alter gene expression in pancreatic islets. To fill this gap, we developed a new co-localization pipeline, called colocRedRibbon, that prefilters eQTL variants by direction of effect on gene expression, shortlists overlapping eQTL and GWAS variants and then runs the co-localization. Applying colocRedRibbon to diabetes and glycemic trait GWAS, we identified 292 co-localizing gene regions - 236 of which are new - including 24 co-localizations for type 1 diabetes and 268 for type 2 diabetes and glycemic traits. We achieved a four-fold increase in co-localizations, with the novel pipeline and updated GWAS each contributing two-fold. Among the co-localizations are a low frequency variant increasing MYO5C expression that reduces type 2 diabetes risk and a type 1 diabetes protective variant that increases FUT2 and decreases RASIP1 expression. These novel co-localizations represent a significant step forward to understand polygenic diabetes genetics and its impact on human islet gene expression.

Type 2 diabetes is a complex, multifactorial disease with varying presentation and underlying pathophysiology. Recent studies using data-driven cluster analysis have led to a stratification of type 2 diabetes into novel subgroups based on six clinical measurements. Whether these subgroups truly correspond to the underlying phenotypic differences is nevertheless unclear. Here, we apply an unsupervised, data-driven clustering method (Similarity Network Fusion) to characterize type 2 diabetes in two independent cohorts involving 1,134 subjects in total based on integrated plasma lipidomics and peptidomics data without pre-selection. Logistic regression was then used to explore clustering based on [&ge;] 180 circulating lipids and 1,195 protein biomarkers, alongside clinical signatures. Two subgroups were identified, one of which associated with elevated C-peptide levels, diabetic complications and more severe insulin resistance compared to the other. GWAS analysis against 403 type 2 diabetes risk variants revealed associations of several SNPs with clusters and altered molecular profiles. We thus demonstrate that heterogeneity in type 2 diabetes can be captured by circulating omics alone using an unsupervised bottom-up approach. Such multiomics signatures could reflect pathological mechanisms underlying type 2 diabetes and thus may help inform on precision medicine approaches to disease management.

Glucagon-like peptide 1 (GLP-1) is produced by L cells in the small intestine in response to ingested glucose and increases insulin release from pancreatic beta cells by activation of its cognate receptor (GLP-1R). Stimulation of this receptor also contributes to increased beta cell survival and regeneration. We have found that pancreatic beta cells from Non Obese Diabetic (NOD) mice express significantly lower levels of GLP-1R than C57BL/6 mice, leaving the NOD beta cells with an impaired response to GLP-1 stimulation. The lower expression appears to be caused by accelerated degradation of GLP-1R in the beta cells, a process that can be reversed by inhibiting trafficking to the lysosome. Importantly, our results appear to translate to the human disease since we also observed significantly lower expression of the GLP-1R in pancreatic islets from donors with type 1 diabetes. These results suggest that beta cell physiology may play a role in susceptibility to autoimmune inflammation.

The gain-of-function mutation in the TALK-1 K+ channel (p.L114P) is associated with maturity-onset diabetes of the young (MODY). TALK-1 is a key regulator of {beta}-cell electrical activity and glucose-stimulated insulin secretion. The KCNK16 gene encoding TALK-1 is the most abundant and {beta}-cell-restricted K+ channel transcript. To investigate the impact of KCNK16 L114P on glucose homeostasis and confirm its association with MODY, a mouse model containing the Kcnk16 L114P mutation was generated. Heterozygous and homozygous Kcnk16 L114P mice exhibit increased neonatal lethality in the C57BL/6J and the CD-1(ICR) genetic background, respectively. Lethality is likely a result of severe hyperglycemia observed in the homozygous Kcnk16 L114P neonates due to lack of glucose-stimulated insulin secretion and can be reduced with insulin treatment. Kcnk16 L114P increased whole-cell {beta}-cell K+ currents resulting in blunted glucose-stimulated Ca2+ entry and loss of glucose-induced Ca2+ oscillations. Thus, adult Kcnk16 L114P mice have reduced glucose-stimulated insulin secretion and plasma insulin levels, which significantly impairs glucose homeostasis. Taken together, this study shows that the MODY-associated Kcnk16 L114P mutation disrupts glucose homeostasis in adult mice resembling a MODY phenotype and causes neonatal lethality by inhibiting islet insulin secretion during development. These data suggest that TALK-1 is an islet-restricted target for the treatment for diabetes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/545631v3_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@19031e9org.highwire.dtl.DTLVardef@1bccc49org.highwire.dtl.DTLVardef@803e1org.highwire.dtl.DTLVardef@36c584_HPS_FORMAT_FIGEXP M_FIG Graphical Summary C_FIG

Genetic and acquired abnormalities contribute to pancreatic {beta}-cell failure in diabetes. Transcription factors Hnf4 (MODY1) and FoxO1 are respective examples of these two components, and are known to act through {beta}-cell-specific enhancers. However, their relationship is unclear. Here we show by genome-wide interrogation of chromatin modifications that FoxO1 ablation in mature {beta}-cells leads to increased selection of FoxO1 enhancers by Hnf4. To model the functional significance we generated single and compound knockouts of FoxO1 and Hnf4 in {beta}-cells. Single knockout of either gene impaired insulin secretion in mechanistically distinct fashions. Surprisingly, the defective {beta}-cell secretory function of either single mutant in hyperglycemic clamps and isolated islets treated with various secretagogues, was completely reversed in double mutants. Gene expression analyses revealed the reversal of {beta}-cell dysfunction with an antagonistic network regulating glycolysis, including {beta}-cell "disallowed" genes; and that a synergistic network regulating protocadherins emerged as likely mediators of the functional restoration of insulin secretion. The findings provide evidence of antagonistic epistasis as a model of gene/environment interactions in the pathogenesis of {beta}-cell dysfunction.

We have deployed a multi-omics approach in large cohorts of patients with existing type 2 diabetes to identify biomarkers for disease progression across three molecular classes, metabolites, lipids and proteins. A Cox regression analysis for association with time to insulin requirement in 2,973 patients in the DCS, ANDIS and GoDARTS cohorts identified homocitrulline, isoleucine and 2-aminoadipic acid, as well as the bile acids glycocholic and taurocholic acids, as predictive of more rapid deterioration. Increased levels of eight triacylglycerol species, and lowered levels of the sphingomyelin SM 42:2;2 were also predictive of disease progression. Of [~]1,300 proteins examined in two cohorts, levels of GDF-15/MIC1, IL-18RA, CRELD1, NogoR, FAS, and ENPP7 were associated with faster progression, whilst SMAC/DIABLO, COTL1, SPOCK1 and HEMK2 predicted lower progression rates. Strikingly, identified proteins and lipids were also associated with diabetes incidence and prevalence in external replication cohorts. Implicating roles in disease compensation, NogoR/RTN4R improved glucose tolerance in high fat-fed mice and tended to improved insulin signalling in liver cells whilst IL-18R antagonised inflammatory IL-18 signalling towards nuclear factor kappa-B in vitro. Conversely, high NogoR levels led to islet cell apoptosis. This comprehensive, multi-disciplinary approach thus identifies novel biomarkers with potential prognostic utility, provides evidence for new disease mechanisms, and identifies potential therapeutic avenues to slow diabetes progression.

As professional secretory cells, beta cells require adaptable mRNA translation to facilitate a rapid synthesis of proteins, including insulin, in response to changing metabolic cues. Specialized mRNA translation programs are essential drivers of cellular development and differentiation. However, in the pancreatic beta cell, the majority of factors identified to promote growth and development function primarily at the level of transcription. Therefore, despite its importance, the regulatory role of mRNA translation in the formation and maintenance of functional beta cells is not well defined. In this study, we have identified a translational regulatory mechanism in the beta cell driven by the specialized mRNA translation factor, eukaryotic initiation factor 5A (eIF5A), which facilitates beta cell maturation. The mRNA translation function of eIF5A is only active when it is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS). We have discovered that the absence of beta cell DHPS in mice reduces the synthesis of proteins critical to beta cell identity and function at the stage of beta cell maturation, leading to a rapid and reproducible onset of diabetes. Therefore, our work has revealed a gatekeeper of specialized mRNA translation that permits the beta cell, a metabolically responsive secretory cell, to maintain the integrity of protein synthesis necessary during times of induced or increased demand. ARTICLE HIGHLIGHTSO_LIPancreatic beta cells are professional secretory cells that require adaptable mRNA translation for the rapid, inducible synthesis of proteins, including insulin, in response to changing metabolic cues. Our previous work in the exocrine pancreas showed that development and function of the acinar cells, which are also professional secretory cells, is regulated at the level of mRNA translation by a specialized mRNA translation factor, eIF5AHYP. We hypothesized that this translational regulation, which can be a response to stress such as changes in growth or metabolism, may also occur in beta cells. C_LIO_LIGiven that the mRNA translation function of eIF5A is only active when the factor is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS), we asked the question: does DHPS/eIF5AHYP regulate the formation and maintenance of functional beta cells? C_LIO_LIWe discovered that in the absence of beta cell DHPS in mice, eIF5A is not hypusinated (activated), which leads to a reduction in the synthesis of critical beta cell proteins that interrupts pathways critical for identity and function. This translational regulation occurs at weaning age, which is a stage of cellular stress and maturation for the beta cell. Therefore without DHPS/eIF5AHYP, beta cells do not mature and mice progress to hyperglycemia and diabetes. C_LIO_LIOur findings suggest that secretory cells have a mechanism to regulate mRNA translation during times of cellular stress. Our work also implies that driving an increase in mRNA translation in the beta cell might overcome or possibly reverse the beta cell defects that contribute to early dysfunction and the progression to diabetes. C_LI

BackgroundThe pancreas is essential for metabolic homeostasis. Alterations in morphology and parenchymal integrity may impact proper function but are not routinely used for risk stratification. Here, we propose an AI-pipeline to quantify pancreas volume and fat content from MRI to identify individuals at high-risk for cardiometabolic disease in the general population. MethodsWe quantified pancreas volume (milliliters, mL) and intrapancreatic fat content (defined as fat fraction; FF, %) from MRI of UK Biobank (UKB) and German National Cohort (NAKO) participants using deep learning. We 1) analyzed differences in volume and FF across age and sex, 2) computed percentile-curves and z-scores adjusted for age and sex to identify high-risk volumes/FF, and 3) conducted Cox regression to assess associations between z-score categories (volume: reference, z=-1 to 1; low, z=<-1; high, z>1; FF: low, z<1; moderate, z=0-1; high, z>1) and incident outcomes (diabetes, major adverse cardiovascular events (MACE), all-cause mortality) after adjustment for risk factors. ResultsAmong 63,548 UKB and NAKO-participants (57.7{+/-}12.8 years; BMI: 26.3{+/-}4.4 kg/m2, 46.9% female), automated pancreas analysis revealed a positive association between both volume and FF and age. In 33,099 UKB-participants (median 4.8 years follow-up), z-score categories were associated with incident diabetes (low volume, aHR:1.59, 95%CI[1.20-2.11]; high FF, aHR:1.70, 95%CI[1.31-2.19]), MACE (high volume, aHR: 0.79, 95%CI[0.61-1.01]; high FF, aHR: 1.32, 95%CI[1.01-1.73]), and all-cause mortality (low volume, aHR: 1.48, 95%CI[1.16-1.90]) beyond risk factors. Adding z-score categories to a baseline model including risk factors improved discrimination of future diabetes (volume:0.781 to 0.784, p=0.004; FF:0.781 to 0.787, p<0.001) and mortality (volume:0.781 to 0.787, p<0.001) ConclusionsDeviations from normalized pancreas volume and FF predicted cardiometabolic outcomes beyond known risk factors and alcohol intake. This automated approach identifies high-risk individuals who may benefit from cardiometabolic/endocrinology referral.

Multiple islet autoantibodies (AAb) predict type 1 diabetes (T1D) and hyperglycemia within 10 years. By contrast, T1D develops in just [~]15% of single AAb+ (generally against glutamic acid decarboxylase, GADA+) individuals; hence the single GADA+ state may represent an early stage of T1D amenable to interventions. Here, we functionally, histologically, and molecularly phenotype human islets from non-diabetic, GADA+ and T1D donors. Similar to the few remaining beta cells in T1D islets, GADA+ donor islets demonstrated a preserved insulin secretory response. By contrast, alpha cell glucagon secretion was dysregulated in both T1D and GADA+ islets with impaired glucose suppression of glucagon secretion. Single cell RNA sequencing (scRNASeq) of GADA+ alpha cells revealed distinct abnormalities in glycolysis and oxidative phosphorylation pathways and a marked downregulation of PKIB, providing a molecular basis for the loss of glucose suppression and the increased effect of IBMX observed in GADA+ donor islets. The striking observation of a distinct early defect in alpha cell function that precedes beta cell loss in T1D suggests that not only overt disease, but also the progression to T1D itself, is bihormonal in nature.

High-fat diet (HFD) combined with streptozotocin (STZ) is widely used to model type 2 diabetes (T2D) in rodents, but is often associated with high mortality, non-responders, and inconsistent outcomes. STZ is conventionally administered using body weight-adjusted dosing (mg/kg), despite evidence that heavier animals, including HFD-fed mice, exhibit more severe glycaemic responses. Here, we performed metabolic phenotyping in chow- and HFD-fed C57BL/6J mice treated with low or high fixed doses (mg instead of mg/kg) of anomer-equilibrated STZ. HFD combined with low-dose STZ induced a stable T2D-like phenotype characterized by sustained obesity, moderate hyperglycaemia, insulin resistance, and partial {beta}-cell loss, with low inter-individual variability. In contrast, high-dose STZ induced a T1D-like phenotype with extensive {beta}-cell loss. A semi-mechanistic mathematical model was developed and validated against independent experimental data, reproducing the observed dynamics of fasting glucose in response to fixed-dose STZ. The model further predicted that weight-adjusted (mg/kg) dosing could introduce variability in glycaemic responses, particularly in HFD-fed mice. Together, these results demonstrate that fixed-dose, anomer-equilibrated STZ induces a stable T2D-like phenotype, providing an alternative to conventional weight-adjusted dosing in HFD-fed mice.