Early postprandial glucagon concentrations are higher in type 1 diabetes (T1D) than in individuals with no diabetes (ND). To determine the cause, we infused stable [13C9, 15N1]glucagon before, during, and after a mixed meal in 16 ND and 16 T1D individuals to measure glucagon turnover. In a subcohort of 9 ND and 12 T1D individuals, we estimated [13C9, 15N1]glucagon kinetics during steady state. A linear, single-compartment model described [13C9, 15N1]glucagon kinetics and allowed precise estimation of the volume of distribution (VD) and clearance rate (CL). Model parameters were similar between groups, with the VD of [13C9, 15N1]glucagon at 42.1 ± 3.3 mL/kg, implying that [13C9, 15N1]glucagon distributes in a single compartment and with VD approximating the plasma volume and CL at 10.6 ± 0.9 mL/kg/min. Higher early (0–120 min after meal ingestion) postprandial glucagon concentrations (1,907.9 ± 373.4 vs. −93.6 ± 240.5 pg/mL · 120 min P < 0.001) observed in T1D was due to higher rates of glucagon appearance (3.39 ± 2.8 vs. −3.95 ± 2.0 ng/kg · 120 min, P < 0.04) and disappearance (2.13 ± 2.6 vs. −5.28 ± 2.1 ng/kg · 120 min, P < 0.04) compared with ND. We have determined postprandial glucagon turnover in humans and have demonstrated that changes in postprandial glucagon concentrations in T1D are due to increased rates of glucagon turnover during the early postprandial period. ARTICLE HIGHLIGHTS:This study was conducted to determine postprandial glucagon metabolism in people with and without type 1 diabetes. We wanted to determine the cause for higher early postprandial glucagon concentrations in type 1 diabetes. We found that higher early postprandial glucagon turnover is the cause of higher early postprandial glucagon concentrations in type 1 diabetes Strategies that decrease early post prandial glucagon fluxes could improve postprandial glucose concentrations in type 1 diabetes.

Insulin resistance (IR) is a modifiable risk factor for dementia, yet its effects on brain metabolism and function remain unclear. In older adults, greater IR was associated with reduced cerebral glucose uptake (indicating impaired mitochondrial metabolism), atrophy, and weakened connectivity between brain regions critical for cognition. In neuron-specific insulin receptor knockout mice, brain IR produced deficits in hippocampal- and prefrontal-dependent tasks accompanied by reduced brain mitochondrial ATP and elevated reactive oxygen species. To evaluate reversibility of IR-induced brain deficits, forty older adults with IR were randomized to 40-weeks of metformin or placebo. Metformin improved insulin sensitivity, increased brain glucose uptake, strengthened cognitive network connectivity, and preserved whole-brain and regional volumes implicated in decision-making and learning. Metformin also improved processing speed and working memory. Collectively, these findings highlight IR as a driver of brain metabolism and support the concept that insulin sensitization can prevent neurobiological deficits in older people with IR.

Context: Defects in insulin secretion and action contribute to the progression of prediabetes to diabetes. However, the contribution of alpha-cell dysfunction to this process has been unclear. Objective: This work aimed to understand the relative contributions of alpha-cell and beta-cell dysfunction to declining glucose tolerance. Methods: A longitudinal, community-based observational study was conducted at a clinical research unit at an academic medical center. We studied 96 individuals without diabetes (age 55 +/- 1 years; body mass index 27.7 +/- 0.4) on 2 occasions, 3 years apart using an oral 75-g glucose challenge. Indices for insulin secretion and action were estimated using the oral minimal model. Glucagon secretion rate (GSR) was estimated by deconvolution from peripheral glucagon concentrations. Main outcome measures included glucose tolerance status (categorical variable) and then symmetrical percentage change in peak and 120-minute glucose (post oral glucose tolerance test) concentrations (continuous variables). Results: A total of 32 individuals progressed from normal to impaired glucose tolerance (IGT) or from IGT to type 2 diabetes. The disposition index (DI) declined in the progressors (568 +/- 98 vs 403 +/- 65 10(-4) dL/kg/min per mu U/mL, baseline vs 3 years; P = .04). alpha-Cell suppression by glucose (delta GSR/delta glucose) did not change in the nonprogressors (1.5 +/- 0.1 vs 1.3 +/- 0.1 nmol/min/L; P = .37) but decreased (1.0 +/- 0.2 vs 0.8 +/- 0.2 nmol/min/L; P < .01) in those who progressed. Analysis of the entire cohort showed that DI and delta GSR/delta glucose were independently and inversely correlated with an increase in glycemic excursion. Conclusion: These data show that alpha-cell dysfunction accompanies a decline in beta-cell function as IGT or overt type 2 diabetes develops.

The Oral Minimal Model (OMM) analysis offers unique measures of glucose-insulin regulation during glucose challenges. However, its manual test-by-test implementation limits scalability in large studies. We introduce the Automated Oral Minimal Model (AOMM), a tool that streamlines and automates the entire OMM workflow while preserving analytical fidelity, enabling efficient batch processing of large datasets. Built on SAAM II software, AOMM was validated against manually extracted results from Sunehag et al (Obesity (Silver Spring), 2008), accurately reproducing key parameters such as insulin sensitivity (Si) and beta-cell responsivity (Φ) with high precision and substantial time savings. AOMM, with its user-friendly interface, facilitates broader application of minimal modeling in research and clinical studies.

Artificial pancreas (AP) systems, also called automated insulin delivery systems, have improved the time in range of glucose levels, reduced the daily burden of the user for glucose regulation, and improved their quality of life. Several commercially available AP systems operate in hybrid closed-loop mode that requires manual information from the user for meals and exercise. This article summarizes the progress on mathematical models of glucose-insulin dynamics, continuous glucose monitoring systems, and insulin pumps that form the building blocks of AP systems, the shift from animal studies to in silico clinical trials that accelerated the rate of progress in AP technologies and the efforts for developing the next-generation AP systems, and the fully automated AP that eliminates manual inputs and mitigates the effects of disturbances to glucose homeostasis-meals, physical activities, acute stress, and variations in sleep characteristics. A section is devoted to discuss the unique glycemic management challenges faced by women with diabetes across the lifespan (menstrual cycle, menopause, pregnancy) and summarize progress made to reduce their impact on glycemic management.

Type-1 diabetes is a chronic, incurable condition which still requires careful management and regular injections of insulin. Researchers in the FORGETDIABETES project are working to develop a fully implantable bionic invisible pancreas, which will relieve the burden associated with managing type-1 diabetes, as Professor Claudio Cobelli explains.

The T allele at rs7903146 in TCF7L2 increases the rate of conversion from prediabetes to type 2 diabetes. This has been associated with impaired β-cell function and with defective suppression of α-cell secretion by glucose. However, the temporal relationship of these abnormalities is uncertain. To study the longitudinal changes in islet function, we recruited 128 subjects, with 67 homozygous for the diabetes-associated allele (TT) at rs7903146 and 61 homozygous for the protective allele. Subjects were studied on two occasions, 3 years apart, using an oral 75-g glucose challenge. The oral minimal model was used to quantitate β-cell function; the glucagon secretion rate was estimated from deconvolution of glucagon concentrations. Glucose tolerance worsened in subjects with the TT genotype. This was accompanied by impaired postchallenge glucagon suppression but appropriate β-cell responsivity to rising glucose concentrations. These data suggest that α-cell abnormalities associated with the TT genotype (rs7903146) occur early and may precede β-cell dysfunction in people as they develop glucose intolerance and type 2 diabetes. Article Highlights

Background: Cystic Fibrosis (CF) patients historically suffered from undernutrition, infection and inflammation. Insulin insufficiency-related protein catabolism further compromised health. We aimed to determine whether insulin improves protein catabolism in CF youth with abnormal glucose tolerance (AGT). Methods: This double-masked, placebo-controlled trial in CF youth age 10-25 with AGT who were in their usual state of health used triple-tracer stable-isotope methodology to measure protein turnover during a baseline test meal and after four weeks of insulin/placebo treatment. Healthy controls were assessed once. CF patients were randomized 1:1:1 to once-daily long-acting insulin (0.25 U/kg/d), three-times daily rapid-acting insulin (0.5 U/ 15gr carbohydrate), or injectable placebo. Results: Thirty CF patients completed the study. There were no differences in any measure of protein turnover between insulin- and placebo-treated subjects, including endogenous protein breakdown (primary study endpoint). In contrast to earlier studies, protein turnover in the 37 CF patients who completed the baseline meal was normal compared to 20 healthy controls. Meal isotope appeared in plasma earlier in CF than controls, suggesting more rapid gut emptying. The study was interrupted by the pandemic; futility analysis led to study discontinuation before the planned remaining 15 CF patients were studied. Conclusions: Recent advances in CF have led to remarkable clinical improvements. In this study, CF youth with AGT had normal protein catabolism at baseline. Pre-meal or daily basal insulin therapy, while safe and well tolerated, did not significantly enhance protein turnover and does not appear to be necessary in clinically stable patients prior to development of CFRD.

CONTEXT:Circulating lactate concentration is an important determinant of exercise tolerance. OBJECTIVE:This work aimed to determine the role of hyperglycemia on lactate metabolism during exercise in individuals with type 1 diabetes (T1D). METHODS:The protocol at the University of Virginia compared 7 T1D participants and 7 participants without diabetes (ND) at euglycemia (5.5 mM) or hyperglycemia (9.2 mM) in random order in T1D and at euglycemia in ND. Intervention included [1-13C] lactate infusion, exercise at 65% maximal oxygen uptake (VO2max), euglycemia, and hyperglycemia visits. The main outcome measure was lactate turnover before, during, and after 60 minutes of exercise at 65% VO2max. RESULTS:A 2-compartment model with loss only from the peripheral compartment described lactate kinetics. Volume of distribution of the accessible compartment was similar between T1D and ND individuals (P = .76) and concordant with plasma volume (∼40 mL/kg). Circulating lactate concentrations were higher (P < .001) in T1D participants during exercise at hyperglycemia than euglycemia. Exercise-induced lactate appearance did not differ (P = .13) between hyperglycemia and euglycemia. However, lactate clearance (CL) was lower (P = .03) during hyperglycemia than euglycemia in T1D participants. There were no differences in any of the aforementioned parameters between T1D and ND participants during euglycemia. CONCLUSION:Hyperglycemia modulates lactate metabolism during exercise by lowering CL, leading to higher circulating lactate concentrations in T1D individuals. This novel observation implies that exercise during hyperglycemia can lead to higher circulating lactate concentrations thus increasing the likelihood of reaching the lactate threshold sooner in T1D, and has high translational relevance both for providers and recreationally active people with T1D.

BACKGROUND:Strict adherence to multiple daily insulin (MDI) therapy is a cornerstone for the achievement of good glucose control in people with advanced type 2 diabetes (T2D). Here, we aim to in silico assess glucose control in T2D subjects with poor adherence to MDI therapy. METHODS:We tuned the Padova T2D Simulator, originally describing early-stage T2D physiology, around advanced T2D people. One hundred in silico advanced T2D subjects were generated and equipped with optimal MDI therapy: specifically, basal and bolus insulin amounts and injection times were individualized for each subject by applying titration algorithms that iteratively update insulin dose based on glucose deviation from its target. Then, the effect of nonadhering to MDI therapy was assessed using standard glucose control metrics calculated in two 6-month 3-meal/day in silico scenarios: in Scenario 1, subjects received the optimal basal and prandial insulin bolus at each meal; in Scenario 2, subjects received optimal basal insulin and randomly delayed or skipped the prandial insulin bolus in 3 lunches during working days and 1 dinner during weekends. RESULTS:A statistically significant degradation was found in all glucose control outcome metrics in Scenario 2 versus Scenario 1: e.g., percent time above 180 mg/dL increased by 22.2% and glucose management index by 0.2%. CONCLUSIONS:Impaired adherence to MDI therapy in T2D leads to glucose control deteriorations in both short and long terms. Interestingly, short-term hyperglycemia seems being contrasted by residual endogenous insulin secretion, which statistically increased by 3-fold after delayed/skipped insulin boluses compared with optimal ones.

Prevention of hypoglycemia is a key aspect for efficient management of Type I diabetes. Alarm systems (ASs) are very useful to alert the patient in advance in case of hypo-glycemia, allowing early intervention to avoid or mitigate the potential critical situation. Model-based ASs use patient models to predict the future glucose concentration and trigger alarms. In recent years neural networks, in particular Personalized Long Short-Term Memory Networks (PLSTMs) have shown very promising performances in glucose prediction. In this work, PLSTM-based AS for the prevention of hypoglycemia for an Artificial Pancreas is proposed. Preliminary results on a subgroup of 71 patients show that this system is able to predict almost all the potentially critical events (median TPR = 100%) with a precision of 57%. These promising techniques are under study to include also the remaining 29 problematic patients.

Context:Multiple common genetic variants have been associated with type 2 diabetes, but the mechanism by which they predispose to diabetes is incompletely understood. One such example is variation in MTNR1B, which implicates melatonin and its receptor in the pathogenesis of type 2 diabetes. Objective:To characterize the effect of diabetes-associated genetic variation at rs10830963 in the MTNR1B locus on islet function in people without type 2 diabetes. Design:The association of genetic variation at rs10830963 with glucose, insulin, C-peptide, glucagon, and indices of insulin secretion and action were tested in a cohort of 294 individuals who had previously undergone an oral glucose tolerance test (OGTT). Insulin sensitivity, β-cell responsivity to glucose, and Disposition Indices were measured using the oral minimal model. Setting:The Clinical Research and Translation Unit at Mayo Clinic, Rochester, MN. Participants:Two cohorts were utilized for this analysis: 1 cohort was recruited on the basis of prior participation in a population-based study in Olmsted County. The other cohort was recruited on the basis of TCF7L2 genotype at rs7903146 from the Mayo Biobank. Intervention:Two-hour, 7-sample OGTT. Main Outcome Measures:Fasting, nadir, and integrated glucagon concentrations. Results:One or 2 copies of the G-allele at rs10830963 were associated with increased postchallenge glucose and glucagon concentrations compared to subjects with the CC genotype. Conclusion:The effects of rs10830963 on glucose homeostasis and predisposition to type 2 diabetes are likely to be partially mediated through changes in α-cell function.

Intra-islet Glucagon-Like Peptide-1 (GLP-1) is increased by islet inflammation and diabetes. GLP-1 Receptor (GLP1R) blockade with exendin-9,39 impairs fasting islet function in people with and without type 2 diabetes (DM2). In addition, it decreases insulin secretion and glucagon suppression in response to hyperglycemia in people with DM2. We sought to examine if free fatty acid (FFA) elevation to induce acute insulin resistance in people without DM2 replicated the effects of GLP1R blockade seen in DM2. We studied 6 nondiabetic individuals (54 ± 4 years, 33 ± 1 kg/m2) on 4 occasions in random order. Glucose metabolism was measured after an overnight fast and during a hyperglycemic clamp (~9 mmol/l) using [3-3H] glucose. On two occasions Intralipid® and heparin were infused to raise FFA. Exendin-9,39 (300pmol/kg/min) was infused to block GLP1R in the presence or absence of FFA elevation, while on the other days saline was infused. In the absence of FFA elevation, exendin-9,39 infusion increased fasting glucose concentrations (5.0 ± 0.1 vs. 5.4 ± 0.1 mmol/l, saline vs. exendin-9,39 respectively, p = 0.01). This pattern was also observed when FFA were elevated (5.3 ± 0.1 vs. 5.7 ± 0.2 mmol/l, p = 0.02). Fasting insulin, C-peptide (without FFA: 0.9 ± 0.1 vs. 0.8 ± 0.1 nmol/l, p = 0.17; with FFA: 1.1 ± 0.1 vs. 1.0 ± 0.1 nmol/l, p = 0.08) and glucagon concentrations were unchanged, but inappropriate for the higher fasting glucose observed during exendin-9,39 infusion. Exendin-9,39 infusion did not alter islet hormone secretion during the clamp in the presence or absence of FFA elevation. The magnitude of changes induced by exendin-9,39 did not differ in the presence or absence of FFA elevation (p > 0.10). These experiments confirm the effects of GLP1R blockade on fasting α- and β-cell function in people without DM2. However, FFA elevation does not replicate the abnormalities of islet function observed in people with DM2 when exendin-9,39 is infused. Disclosure M. Zeini: None. R.A. Farahani: None. A.A. Welch: None. M.C. Laurenti: None. C. Cobelli: None. C. Dalla Man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. A.M. Egan: None. A. Vella: Other Relationship; Novo Nordisk. Advisory Panel; Rezolute, Inc. Consultant; Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Zealand Pharma A/S. Funding National Institutes of Health (DK126206)

Type 1 diabetes (T1D) is a chronic autoimmune disease featured by the loss of beta cell function and the need for lifetime insulin replacement. Over the recent decade, the use of automated insulin delivery systems (AID) has shifted the paradigm of treatment: the availability of continuous subcutaneous (SC) glucose sensors to guide SC insulin delivery through a control algorithm has allowed, for the first time, to reduce the daily burden of the disease as well as to abate the risk for hypoglycemia. AID use is still limited by individual acceptance, local availability, coverage, and expertise. A major drawback of SC insulin delivery is the need for meal announcement and the peripheral hyperinsulinemia that, over time, contributes to macrovascular complications. Inpatient trials using intraperitoneal (IP) insulin pumps have demonstrated that glycemic control can be improved without meal announcement due to the faster insulin delivery through the peritoneal space. This calls for novel control algorithms able to account for the specificities of IP insulin kinetics. Recently, our group described a two-compartment model of IP insulin kinetics demonstrating that the peritoneal space acts as a virtual compartment and IP insulin delivery is virtually intraportal (intrahepatic), thus closely mimicking the physiology of insulin secretion. The FDA-accepted T1D simulator for SC insulin delivery and sensing has been updated for IP insulin delivery and sensing. Herein, we design and validate-in silico-a time-varying proportional integrative derivative controller to guide IP insulin delivery in a fully closed-loop mode without meal announcement.

Diabetes-associated alleles in TCF7L2 increase the rate of conversion from prediabetes to type 2 diabetes (T2DM). Multiple studies have shown an association of the T allele at rs7903146 with impaired β-cell function and more recently with defective suppression of α-cell secretion by glucose. However, the temporal relationship of these abnormalities is uncertain. To study the longitudinal changes in islet function, we recruited 140 individuals half of whom were homozygous for the diabetes-associated allele (TT) at rs7903146. The remainder were homozygous for the protective allele (CC). Subjects were studied on 2 occasions, 3 years apart using an oral 75g glucose challenge. This was labelled with 13C-glucose, in concert with intravenously infused tracers to enable measurement of endogenous glucose production, meal appearance and glucose disposal. Indices for insulin secretion and action were estimated using the oral minimal model. Fasting, peak and integrated (443 ± 27 vs. 428 ± 50 mmol/l per 6hr, p = 0.54) post-prandial glucose concentrations did not differ over time in people with the CC genotype. In contrast, post-prandial integrated glucose concentrations increased (441 ± 29 vs. 544 ± 37 mmol/l per 6hr, p < 0.01) in people with the TT genotype. This was accompanied by an increase in integrated postprandial glucagon concentrations (526 ± 39 vs. 618 ± 61 pmol/l per 2hr, p = 0.04) that was not observed in the CC genotype (537 ± 50 vs. 525 ± 65 pmol/l per 2hr, p = 0.07). There were no baseline differences in β-cell function between genotype groups. Disposition Index in both TT (950 ± 130 vs. 868 ± 92 10-4 dl/kg/min per μU/ml, baseline vs. follow-up study respectively, p=0.42) and CC (896 ± 177 vs. 1062 ± 289 10-4 dl/kg/min per μU/ml, p=0.65) groups did not change. This data would suggest that α-cell dysfunction associated with the TT genotype (rs7903146) precedes β-cell dysfunction in people prior to the development of T2DM. Disclosure M.Zeini: None. K.Muthusamy: None. A.M.Egan: None. M.C.Laurenti: None. C.Cobelli: None. C.Dalla man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. A.Vella: Advisory Panel; Rezolute, Inc., Consultant; Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Zealand Pharma A/S, Other Relationship; Novo Nordisk. Funding National Institutes of Health (DK116723)

Glucagon-Like Peptide-1 (GLP-1) is present within the islet but the effects of GLP-1 Receptor (GLP1R) blockade on islet function in humans remains unknown. To address this, we studied 12 nondiabetic individuals (54 ± 2 years, 33 ± 1 kg/m2) and 11 people with type 2 diabetes (DM2 - 58 ± 2 years, 34 ± 2 kg/m2) on 2 occasions in random order. On each occasion, after an overnight fast, [3-3H] glucose was used to measure glucose turnover during fasting and a hyperglycemic clamp (~9 mmol/l) using the tracer dilution technique. On one occasion exendin-9,39 (300pmol/kg/min) was infused to block GLP1R, while on the other saline was infused. Exendin-9,39 increased fasting glucose concentrations in those without (4.6 ± 0.4 vs. 5.5 ± 0.1 mmol/l, saline vs. exendin-9,39 respectively, p = 0.04) and in those with DM2 (7.3 ± 0.5 vs. 8.3 ± 0.6 mmol/l, p = 0.03). Fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed during exendin-9,39 infusion. The same pattern was seen in people with DM2 except that fasting glucagon concentrations increased (8.3 ± 0.5 vs. 10.2 ± 0.6 pmol/l, p < 0.01) and remained elevated throughout hyperglycemia (4.7 ± 0.4 vs. 7.7 ± 0.6 pmol/l, p < 0.02). Insulin secretion rate calculated by deconvolution of C-peptide concentrations was also decreased in DM2 (0.54 ± 0.08 vs. 0.51 ± 0.08 nmol/min, p = 0.02). Consequently, suppression of endogenous glucose production by hyperglycemia was impaired in people with DM2 (2.9 ± 0.4 vs. 5.7 ± 0.3 μmol/kg/min, p < 0.01). Intriguingly, 1st phase response to hyperglycemia was decreased in those without DM2 (3.5 ± 0.6 vs. 2.5 ± 0.5 nmol per 10 min, p = 0.04). These data show that in humans, GLP1R blockade impairs fasting α- and β-cell function resulting in fasting hyperglycemia. Subtle effects are also present in response to hyperglycemia. This implies that intra-islet GLP1R activation sustains islet responses to glucose and it does so to a greater degree in people with DM2. Disclosure A.A. Welch: None. R.A. Farahani: None. M. Zeini: None. A.M. Egan: None. M.C. Laurenti: None. C. Cobelli: None. C. Dalla Man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. A. Vella: Other Relationship; Novo Nordisk. Advisory Panel; Rezolute, Inc. Consultant; Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Zealand Pharma A/S. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK126206)