Inclusion of Rurality and Social Determinants of Health in Documents for the Primary Prevention of Type 2 Diabetes: A Systematic Review

Purpose: The type 2 diabetes (T2D) burden is disproportionately concentrated in low- and middle-income economies, particularly among rural populations. The purpose of the systematic review was to evaluate the inclusion of rurality and social determinants of health (SDOH) in documents for T2D primary prevention. Methods: This systematic review is reported following Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. We searched 19 databases, from 2017-2023, for documents on rurality and T2D primary prevention. Furthermore, we searched online for documents from the 216 World Bank economies, categorized by high, upper-middle, lower-middle, and low income status. We extracted data on rurality and the ten World Health Organization SDOH. Two authors independently screened documents and extracted data. Findings: Based on 3318 documents (19 databases and online search), we selected 15 documents for data extraction. The 15 documents applied to 32 economies; 12 of 15 documents were from nongovernment sources, none was from low-income economies, and 10 of 15 documents did not define or describe rurality. Among the SDOH, income and social protection (SDOH 1) and social inclusion and nondiscrimination (SDOH 8) were mentioned in documents for 25 of 29 high-income economies, while food insecurity (SDOH 5) and housing, basic amenities, and the environment (SDOH 6) were mentioned in documents for 1 of 2 lower-middle-income economies. For U.S. documents, none of the authors was from institutions in noncore (most rural) counties. Conclusions: Overall, documents on T2D primary prevention had sparse inclusion of rurality and SDOH, with additional disparity based on economic status. Inclusion of rurality and/or SDOH may improve T2D primary prevention in rural populations.

Four weeks SGLT2 inhibition improves beta cell function and glucose tolerance without affecting muscle free fatty acid or glucose uptake in subjects with type 2 diabetes

AIMS

Sodium glucose co-transporter-2 (SGLT2) inhibition lowers glucose levels independently of insulin, leading to reduced insulin secretion and increased lipolysis, resulting in elevated circulating free fatty acids (FFAs). While SGLT2 inhibition improves tissue insulin sensitivity, the increase in circulating FFAs could reduce insulin sensitivity in skeletal muscle and the liver. We aimed to investigate the effects of SGLT2 inhibition on substrate utilization in skeletal muscle and the liver and to measure beta-cell function and glucose tolerance.

METHODS

Thirteen metformin-treated individuals with type 2 diabetes were randomized to once-daily empagliflozin 25 mg or placebo for 4 weeks in a crossover design. Skeletal muscle glucose and FFA uptake together with hepatic tissue FFA uptake were measured using [18F]FDG positron emission tomography/computed tomography (PET/CT) and [11C]palmitate PET/CT. Insulin secretion and action were estimated using the oral minimal model.

RESULTS

Empagliflozin did not affect glucose (0.73 ± 0.30 vs. 1.16 ± 0.64, μmol/g/min p = 0.11) or FFA (0.60 ± 0.30 vs. 0.56 ± 0.3, μmol/g/min p = 0.54) uptake in skeletal muscle. FFA uptake in the liver (21.2 ± 10.1 vs. 19 ± 8.8, μmol/100 ml/min p = 0.32) was unaffected. Empagliflozin increased total beta-cell responsivity (20 ± 8 vs. 14 ± 9, 10-9 min-1, p < 0.01) and glucose effectiveness (2.6 × 10-2 ± 0.3 × 10-2 vs. 2.4 × 10-2 ± 0.3 × 10-2, dL/kg/min, p = 0.02).

CONCLUSIONS

Despite improved beta-cell function and glucose tolerance, empagliflozin does not appear to affect skeletal muscle FFA or glucose uptake.

Twin Pregnancy Complicated by Gestational Diabetes Mellitus: Maternal and Neonatal Outcomes

Context

The risk of gestational diabetes mellitus (GDM) in twin pregnancies is more than double that of singleton pregnancies. Although twin pregnancies present unique challenges for fetal growth and prenatal management, the approach to GDM diagnosis and treatment is the same regardless of plurality. Data on pregnancy outcomes for individuals with GDM and a twin pregnancy are limited and conflicting.

Objective

To describe the maternal characteristics associated with GDM in twin pregnancies and to assess the associated pregnancy outcomes compared to twin pregnancies unaffected by GDM.

Methods

A retrospective cohort study was conducted at Mayo Clinic, Rochester, Minnesota, USA, and included predominantly Causasian women aged 18 to 45 years who received prenatal care for a twin pregnancy from 2017-2022. Maternal characteristics and a broad spectrum of pregnancy outcomes were evaluated. Universal GDM screening involved a 50 g oral glucose challenge test +/- a 100 g oral glucose tolerance test.

Results

GDM was diagnosed in 23% pregnancies (n = 104/452). Compared to those without, women with GDM had known risk factors including a higher prepregnancy body mass index (31.1vs 26.3 kg/m2; P < .01) and a prior history of GDM (21.7 vs 5.9%; P < .01). There were no differences in maternal pregnancy complications or neonatal outcomes between groups. Attendance at postpartum glucose testing among women with GDM was poor at 27.9% (29/104).

Conclusion

These data suggest that women with twin pregnancies share a similar GDM risk profile to those with singleton pregnancies and provide reassuring evidence that current management for GDM twin pregnancies produces similar outcomes to twin pregnancies without GDM.

County Rurality and Incidence and Prevalence of Diagnosed Diabetes in the United States

OBJECTIVE

To examine differences in the incidence and prevalence of diagnosed diabetes by county rurality.

PATIENTS AND METHODS

This observational, cross-sectional study used US Centers for Disease Control and Prevention data from 2004 through 2019 for county estimates of incidence and prevalence of diagnosed diabetes. County rurality was based on 6 levels (large central metro counties [most urban] to noncore counties [most rural]). Weighted least squares regression was used to relate rurality with diabetes incidence rates (IRs; per 1000 adults) and prevalence (percentage) in adults aged 20 years or older after adjusting for county-level sociodemographic factors (eg, food environment, health care professionals, inactivity, obesity).

RESULTS

Overall, in 3148 counties and county equivalents, the crude IR and prevalence of diabetes were highest in noncore counties. In age and sex ratio-adjusted models, the IR of diabetes increased monotonically with increasing rurality (P<.001), whereas prevalence had a weak, nonmonotonic but statistically significant increase (P=.002). Further adjustment for sociodemographic factors including food environment, health care professionals, inactivity, and obesity attenuated differences in incidence across rurality levels, and reversed the pattern for prevalence (prevalence ratios [vs large central metro] ranged from 0.98 [95% CI, 0.97 to 0.99] for large fringe metro to 0.94 [95% CI, 0.93 to 0.96] for noncore). In region-stratified analyses adjusted for sociodemographic factors including inactivity and obesity, increasing rurality was inversely associated with incidence in the Midwest and West only and inversely associated with prevalence in all regions.

CONCLUSION

The crude incidence and prevalence of diagnosed diabetes increased with increasing county rurality. After accounting for sociodemographic factors including food environment, health care professionals, inactivity, and obesity, county rurality showed no association with incidence and an inverse association with prevalence. Therefore, interventions targeting modifiable sociodemographic factors may reduce diabetes disparities by region and rurality.

Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Suppression of Endogenous Insulin Secretion by Euglycemic Hyperinsulinemia

CONTEXT

The impact of insulin, particularly exogenous hyperinsulinemia, on insulin secretion in humans is debated.

OBJECTIVE

We assessed the effects of exogenous hyperinsulinemia on insulin secretion and whether the response is altered in insulin resistance associated with obesity.

METHODS

Insulin secretion rates (ISRs) during euglycemic hyperinsulinemic clamp studies (52 volunteers) were calculated using a model that employs plasma C-peptide concentrations. One study involved a 2-step insulin clamp and the other study was a single step insulin clamp. For both studies the goal was to achieve plasma glucose concentrations of 95 mg/dL during the clamp irrespective of fasting glucose concentrations. The percent change in ISR from fasting to the end of the insulin clamp interval was the main outcome. Linear regression and analysis of covariance were used to test for the effects of insulin on ISR and to test for group differences.

RESULTS

ISR was greater in obese volunteers (P < .001) under fasting and hyperinsulinemic clamp conditions. The change in plasma glucose from baseline to the end of the insulin clamp interval was highly correlated with the change in ISR (r = 0.61, P < .001). From baseline to the end of the clamp we observed a 27% (SD 20) suppression of ISR. The participants who underwent a 2-step insulin clamp had greater suppression of ISR during the second step than the first step (P < .001). The proportional suppression of ISR during euglycemic hyperinsulinemia was not different between nonobese and obese groups (P = .19).

CONCLUSION

Hyperinsulinemia suppresses endogenous insulin secretion and the relative change in insulin secretion produced by exogenous insulin did not differ between nonobese and obese people.

Characteristics of Normal Weight Insulin-Resistant Adults with Unfavorable Health Outcomes

Background: Insulin resistance can be present in otherwise healthy, normal weight adults. Whether there are phenotype/sex-differences between normal weight insulin-resistant (NWIR) and normal weight insulin-sensitive (NWIS) Caucasians and whether there are differences in adverse health outcomes are unknown. Our goal was to define phenotypes and intermediate-term health outcomes of NWIR versus NWIS Caucasian adults. Methods: We analyzed data from 227 healthy volunteers body mass index 18 to <25.0 kg/m2 who underwent insulin clamp studies between January 1987 and January 2017 at Mayo Clinic to identify those in the top (NWIS, n = 56) and bottom (NWIR, n = 56) quartiles of insulin action. We compared the phenotypical characteristics and were able to collect medical records data for 80% of NWIS and 88% of NWIR to identify time to onset of hypertension, hyperglycemia, coronary heart disease, cerebrovascular disease, peripheral vascular disease, and all cause death; the follow-up averaged 11 (4, 20) years. Results: Body fat was significantly greater and peak VO2 was significantly less in both NWIS than NWIR males and females. Only in females was abdominal subcutaneous fat by computed tomography significantly greater in NWIR than NWIS. In NWIR males high-density lipoprotein-cholesterol and fat free mass were significantly less, and fasting insulin was greater than NWIS males. For the entire NWIS population, Kaplan-Meier disease-free survival analysis showed longer times free of hypertension, hyperglycemia, and some cardiovascular diseases than for NWIR. Conclusions: There are sex-specific phenotypes of NWIR in Caucasian adults. NWIR may be associated with accelerated onset of some adverse medical outcomes.

Ethanol Ablation for Benign Insulinoma: Intraoperative and Endoscopic Approaches

INTRODUCTION

Ethanol ablation can be utilized to manage insulinoma. We aimed to analyze our outcomes of endoscopic ultrasound (EUS) and intraoperative ultrasound (IOUS) guided Ethanol ablation of insulinoma.

METHODS

A single institution retrospective review of adults undergoing Ethanol ablation of benign pancreatic insulinoma (2007-2022) was performed. Outcomes were categorized as resolution of hypoglycemia, improvement, or no change at last follow-up.

RESULTS

A total of 16 patients underwent Ethanol ablation of benign insulinoma (N = 8 EUS, N = 8 IOUS): median age was 68 y, 8 (50%) were females, and 2 (12.5%) were associated with multiple endocrine neoplasia type-1. Median insulinoma size was 12 (range 7, 25) mm. Ethanol ablation was preferred over resection to avoid pancreaticoduodenectomy when it was not possible to enucleate the tumor in 10 (62.5%) patients while the rest underwent ablation due to being poor surgical candidates or because of a history of previous pancreatic resection. The median follow-up (interquartile range) was 43 (19.5, 81.5) mo. Resolution of hypoglycemia occurred in 11 patients (5 EUS, 6 IOUS), while the rest (3 EUS, 2 IOUS) experienced improvement in the severity and frequency of hypoglycemia. A single patient underwent resection following a previous ablation for symptomatic hypoglycemia 5 y after EUS guided ablation.

CONCLUSIONS

Ethanol ablation provides an alternative therapeutic option for patients with insulinoma. Both EUS and IOUS guided approaches are associated with a favorable resolution rate although EUS guided ablation may require multiple procedures to optimize outcomes.

Glucagon-like peptide-1 receptor blockade impairs islet secretion and glucose metabolism in humans

BACKGROUNDProglucagon can be processed to glucagon-like peptide1 (GLP-1) within the islet, but its contribution to islet function in humans remains unknown. We sought to understand whether pancreatic GLP-1 alters islet function in humans and whether this is affected by type 2 diabetes.METHODSWe therefore studied individuals with and without type 2 diabetes on two occasions in random order. On one occasion, exendin 9-39, a competitive antagonist of the GLP-1 Receptor (GLP1R), was infused, while on the other, saline was infused. The tracer dilution technique ([3-3H] glucose) was used to measure glucose turnover during fasting and during a hyperglycemic clamp.RESULTSExendin 9-39 increased fasting glucose concentrations; fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed. In people with type 2 diabetes, fasting glucagon concentrations were markedly elevated and persisted despite hyperglycemia. This impaired suppression of endogenous glucose production by hyperglycemia.CONCLUSIONThese data show that GLP1R blockade impairs islet function, implying that intra-islet GLP1R activation alters islet responses to glucose and does so to a greater degree in people with type 2 diabetes.TRIAL REGISTRATIONThis study was registered at ClinicalTrials.gov NCT04466618.FUNDINGThe study was primarily funded by NIH NIDDK DK126206. AV is supported by DK78646, DK116231 and DK126206. CDM was supported by MIUR (Italian Minister for Education) under the initiative "Departments of Excellence" (Law 232/2016).

Nonlinear Mixed Effects Modeling of Glucagon Kinetics in Healthy Subjects

OBJECTIVE

To date, the lack of a model of glucagon kinetics precluded the possibility of estimating and studying glucagon secretion in vivo, e.g., using deconvolution, as done for other hormones like insulin and C-peptide. Here, we used a nonlinear mixed effects technique to develop a robust population model of glucagon kinetics, able to describe both the typical population kinetics (TPK) and the between-subject variability (BSV), and relate this last to easily measurable subject characteristics.

METHODS

Thirty-four models of increasing complexity (variably including covariates and correlations among random effects) were identified on glucagon profiles obtained from 53 healthy subjects, who received a constant infusion of somatostatin to suppress endogenous glucagon production, followed by a continuous infusion of glucagon (65 ng/kg/min). Model selection was performed based on its ability to fit the data, provide precise parameter estimates, and parsimony criteria.

RESULTS

A two-compartment model was the most parsimonious. The model was able to accurately describe both the TPK and the BSV of model parameters as function of body mass and body surface area. Parameters were precisely estimated, with central volume of distribution V1 = 5.46 L and peripheral volume of distribution V2 = 5.51 L. The introduction of covariates resulted in a significant shrinkage of the unexplained BSV and considerably improved the model fit.

CONCLUSION

We developed a robust population model of glucagon kinetics.

SIGNIFICANCE

This model provides a deeper understanding of glucagon kinetics and is usable to estimate glucagon secretion in vivo by deconvolution of plasma glucagon concentration data.

International Guidelines for the Diagnosis and Management of Hyperinsulinism

Hyperinsulinism (HI) due to dysregulation of pancreatic beta-cell insulin secretion is the most common and most severe cause of persistent hypoglycemia in infants and children. In the 65 years since HI in children was first described, there has been a dramatic advancement in the diagnostic tools available, including new genetic techniques and novel radiologic imaging for focal HI, however; there have been almost no new therapeutic modalities since the development of diazoxide. Recent advances in neonatal research and genetics have improved our understanding of the pathophysiology of both transient and persistent forms of neonatal hyperinsulinism. Rapid turnaround of genetic test results combined with advanced radiologic imaging can permit identification and localization of surgically-curable focal lesions in a large proportion of children with congenital forms of HI, but are only available in certain centers in 'developed' countries. Diazoxide, the only drug currently approved for treating HI, was recently designated as an "essential medicine" by the World Health Organization but has been approved in only 16% of Latin American countries and remains unavailable in many under-developed areas of the world. Novel treatments for HI are emerging, but they await completion of safety and efficacy trials before being considered for clinical use. This international consensus statement on diagnosis and management of HI was developed in order to assist specialists, general pediatricians, and neonatologists in early recognition and treatment of HI with the ultimate aim of reducing the prevalence of brain injury caused by hypoglycemia. A previous statement on diagnosis and management of HI in Japan was published in 2017. The current document provides an updated guideline for management of infants and children with HI and includes potential accommodations for less-developed regions of the world where resources may be limited.

Guidelines, position statements, and advisories for the primary prevention of type 2 diabetes, hypertension, and cardiovascular disease in rural populations: A systematic review protocol

INTRODUCTION

Globally, noncommunicable diseases (NCDs), which include type 2 diabetes (T2D), hypertension, and cardiovascular disease (CVD), are associated with a high burden of morbidity and mortality. Health disparities exacerbate the burden of NCDs. Notably, rural, compared with urban, populations face greater disparities in access to preventive care, management, and treatment of NCDs. However, there is sparse information and no known literature synthesis on the inclusion of rural populations in documents (i.e., guidelines, position statements, and advisories) pertaining to the prevention of T2D, hypertension, and CVD. To address this gap, we are conducting a systematic review to assess the inclusion of rural populations in documents on the primary prevention of T2D, hypertension, and CVD.

METHODS AND ANALYSIS

This protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched 19 databases including EMBASE, MEDLINE, and Scopus, from January 2017 through October 2022, on the primary prevention of T2D, hypertension, and CVD. We conducted separate Google® searches for each of the 216 World Bank economies. For primary screening, titles and/or abstracts were screened independently by two authors (databases) or one author (Google®). Documents meeting selection criteria will undergo full-text review (secondary screening) using predetermined criteria, and data extraction using a standardized form. The definition of rurality varies, and we will report the description provided in each document. We will also describe the social determinants of health (based on the World Health Organization) that may be associated with rurality.

ETHICS AND DISSEMINATION

To our knowledge, this will be the first systematic review on the inclusion of rurality in documents on the primary prevention of T2D, hypertension, and CVD. Ethics approval is not required since we are not using patient-level data. Patients are not involved in the study design or analysis. We will present the results at conferences and in peer-reviewed publication(s).

TRIAL REGISTRATION

PROSPERO Registration Number: CRD42022369815.

Implementation of genomic medicine for rare disease in a tertiary healthcare system: Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD)

BACKGROUND

In the United States, rare disease (RD) is defined as a condition that affects fewer than 200,000 individuals. Collectively, RD affects an estimated 30 million Americans. A significant portion of RD has an underlying genetic cause; however, this may go undiagnosed. To better serve these patients, the Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD) was created under the auspices of the Center for Individualized Medicine (CIM) aiming to integrate genomics into subspecialty practice including targeted genetic testing, research, and education.

METHODS

Patients were identified by subspecialty healthcare providers from 11 clinical divisions/departments. Targeted multi-gene panels or custom exome/genome-based panels were utilized. To support the goals of PRaUD, a new clinical service model, the Genetic Testing and Counseling (GTAC) unit, was established to improve access and increase efficiency for genetic test facilitation. The GTAC unit includes genetic counselors, genetic counseling assistants, genetic nurses, and a medical geneticist. Patients receive abbreviated point-of-care genetic counseling and testing through a partnership with subspecialty providers.

RESULTS

Implementation of PRaUD began in 2018 and GTAC unit launched in 2020 to support program expansion. Currently, 29 RD clinical indications are included in 11 specialty divisions/departments with over 142 referring providers. To date, 1152 patients have been evaluated with an overall solved or likely solved rate of 17.5% and as high as 66.7% depending on the phenotype. Noteworthy, 42.7% of the solved or likely solved patients underwent changes in medical management and outcome based on genetic test results.

CONCLUSION

Implementation of PRaUD and GTAC have enabled subspecialty practices advance expertise in RD where genetic counselors have not historically been embedded in practice. Democratizing access to genetic testing and counseling can broaden the reach of patients with RD and increase the diagnostic yield of such indications leading to better medical management as well as expanding research opportunities.

Predictors of Metformin Failure: Repurposing Electronic Health Record Data to Identify High-Risk Patients

CONTEXT

Metformin is the first-line drug for treating diabetes but has a high failure rate.

OBJECTIVE

To identify demographic and clinical factors available in the electronic health record (EHR) that predict metformin failure.

METHODS

A cohort of patients with at least 1 abnormal diabetes screening test that initiated metformin was identified at 3 sites (Arizona, Mississippi, and Minnesota). We identified 22 047 metformin initiators (48% female, mean age of 57 ± 14 years) including 2141 African Americans, 440 Asians, 962 Other/Multiracial, 1539 Hispanics, and 16 764 non-Hispanic White people. We defined metformin failure as either the lack of a target glycated hemoglobin (HbA1c) (<7%) within 18 months of index or the start of dual therapy. We used tree-based extreme gradient boosting (XGBoost) models to assess overall risk prediction performance and relative contribution of individual factors when using EHR data for risk of metformin failure.

RESULTS

In this large diverse population, we observed a high rate of metformin failure (43%). The XGBoost model that included baseline HbA1c, age, sex, and race/ethnicity corresponded to high discrimination performance (C-index of 0.731; 95% CI 0.722, 0.740) for risk of metformin failure. Baseline HbA1c corresponded to the largest feature performance with higher levels associated with metformin failure. The addition of other clinical factors improved model performance (0.745; 95% CI 0.737, 0.754, P < .0001).

CONCLUSION

Baseline HbA1c was the strongest predictor of metformin failure and additional factors substantially improved performance suggesting that routinely available clinical data could be used to identify patients at high risk of metformin failure who might benefit from closer monitoring and earlier treatment intensification.

Effects of overnight fasting milieu on indices of β-cell function and glucose metabolism in subjects without diabetes

OBJECTIVE

Elevated fasting free fatty acids (FFA) are associated with Impaired Glucose Tolerance (IGT) and decreased β-cell function (quantified as Disposition Index (DI)). We sought to examine how changes in fasting FFA and glucose alter islet function.

METHODS

We studied 10 subjects with Normal Fasting Glucose (NFG) and Normal Glucose Tolerance (NGT) on 2 occasions. On one occasion, Intralipid^® and glucose were infused overnight to mimic conditions present in IFG/IGT. In addition, we studied 7 subjects with IFG/IGT on 2 occasions. On one occasion insulin was infused to lower overnight FFA and glucose concentrations to those observed in people with NFG/NGT. The following morning, a labeled mixed meal was used to measure postprandial glucose metabolism and β-cell function.

RESULTS

Elevation of overnight fasting FFA and glucose in NFG/NGT did not alter peak or integrated glucose concentrations (2.0 ± 0.1 vs 2.0 ± 0.1 Mol per 5 h, Saline vs. Intralipid^® / glucose, p = 0.55). While overall β-cell function quantified by the Disposition Index was unchanged, the dynamic component of β-cell responsivity (f_d) was decreased by Intralipid^® and glucose infusion (9 ± 1 vs. 16 ± 3 10^-9, p = 0.02). In people with IFG/IGT, insulin did not alter postprandial glucose concentrations or indices of β-cell function. Endogenous glucose production and glucose disappearance was also unchanged in both groups.

CONCLUSIONS

We conclude that acute, overnight changes in FFA and glucose concentrations do not alter islet function or glucose metabolism in prediabetes.

Interventional vs surgical procedures in localized/nonmetastatic insulinomas (ablation vs surgery)

Localized insulinoma is an uncommon entity that can result in substantial morbidity due to the associated hypoglycemia. Recent studies have suggested an increase in the incidence of insulinoma in recent decades that may possibly be secondary to increased awareness, incidental diagnoses, and better diagnostic methods. Diagnosing and localizing insulinoma within the pancreas can be challenging, but advances in nuclear imaging may improve diagnostic accuracy. Delays in diagnosis are common, but once a localized insulinoma is diagnosed and appropriately treated, the long-term prognosis is excellent. Surgical resection is considered the standard of care management option for localized insulinoma, but tumor ablation with endoscopic ultrasound guidance has also been shown to be an effective and safe method for therapy.

Bright and ultrafast electron point source made of LaB6 nanotip

The development of time-resolved transmission electron microscopy (TEM), ultrafast electron spectroscopy and pulsed X-ray sources relies on the realization of stable and high brightness sources of ultra-short electron bunches with a long service time. The flat photocathodes implanted in thermionic electron guns have been replaced by Schottky-type or cold-field emission sources driven by ultra-fast laser. Recently, lanthanum hexaboride (LaB₆) nanoneedles have been reported to have high brightness and high emission stability when working in a continuous emission mode. Here, we prepare nano-field emitters from bulk LaB₆ and we report on their use as ultra-fast electron sources. Using a high repetition rate laser in the infrared range, we present different field emission regimes as a function of the extraction voltage and laser intensity. The properties of the electron source (brightness, stability, energy spectrum and emission pattern) are determined for the different regimes. Our results show that LaB₆ nanoneedles can be used as ultrafast and ultra-bright sources for time-resolved TEM, with better performances as compared to metallic ultra-fast field-emitters.

The Effect of Glucagon-Like Peptide 1 Receptor Blockade on Glucagon-Induced Stimulation of Insulin Secretion

Data from transgenic rodent models suggest that glucagon acts as an insulin secretagogue by signaling through the glucagon-like peptide 1 receptor (GLP-1R) present on β-cells. However, its net contribution to physiologic insulin secretion in humans is unknown. To address this question, we studied individuals without diabetes in two separate experiments. Each subject was studied on two occasions in random order. In the first experiment, during a hyperglycemic clamp, glucagon was infused at 0.4 ng/kg/min, increasing by 0.2 ng/kg/min every hour for 5 h. On one day, exendin-9,39 (300 pmol/kg/min) was infused to block GLP-1R, while on the other, saline was infused. The insulin secretion rate (ISR) was calculated by nonparametric deconvolution from plasma concentrations of C-peptide. Endogenous glucose production and glucose disappearance were measured using the tracer-dilution technique. Glucagon concentrations, by design, did not differ between study days. Integrated ISR was lower during exendin-9,39 infusion (213 ± 26 vs. 191 ± 22 nmol/5 h, saline vs. exendin-9,39, respectively; P = 0.02). In the separate experiment, exendin-9,39 infusion, compared with saline infusion, also decreased the β-cell secretory response to a 1-mg glucagon bolus. These data show that, in humans without diabetes, glucagon partially stimulates the β-cell through GLP-1R.

Differential contribution of alpha and beta cell dysfunction to impaired fasting glucose and impaired glucose tolerance

AIMS/HYPOTHESIS

People with isolated impaired fasting glucose (IFG) have normal beta cell function. We hypothesised that an increased glucose threshold for beta cell secretion explains IFG.

METHODS

We used graded glucose infusion to examine the relationship of insulin secretion rate (ISR) and glucagon secretion rate (GSR) with rising glucose. We studied 39 non-diabetic individuals (53 ± 2 years, BMI 30 ± 1 kg/m2), categorised by fasting glucose and glucose tolerance status. After an overnight fast, a variable insulin infusion was used to maintain glucose at ~4.44 mmol/l (07:00 to 08:30 hours). At 09:00 hours, graded glucose infusion commenced at 1 mg kg-1 min-1 and doubled every 60 min until 13:00 hours. GSR and ISR were calculated by nonparametric deconvolution from concentrations of glucagon and C-peptide, respectively.

RESULTS

The relationship of ISR with glucose was linear and the threshold for insulin secretion in isolated IFG did not differ from that in people with normal fasting glucose and normal glucose tolerance. GSR exhibited a single-exponential relationship with glucose that could be characterised by G50, the change in glucose necessary to suppress GSR by 50%. G50 was increased in IFG compared with normal fasting glucose regardless of the presence of impaired or normal glucose tolerance.

CONCLUSIONS/INTERPRETATION

These data show that, in non-diabetic humans, alpha cell dysfunction contributes to the pathogenesis of IFG independently of defects in insulin secretion. We also describe a new index that quantifies the suppression of glucagon secretion by glucose.

Pitfalls in Diagnosing Hypoglycemia Due to Exogenous Insulin: Validation and Utility of an Insulin Analog Assay

OBJECTIVE

To overcome the limitations of commercially available insulin immunoassays which have variable detection of analog insulin and can lead to clinically discordant results and misdiagnosis in the workup of factitious hypoglycemia.

PATIENTS AND METHODS

We performed analytical validation of a liquid chromatography high resolution accurate mass (LC-HRAM) immunoassay to detect insulin analogs. We completed clinical assessment using a large cohort of human serum samples from 78 unique individuals, and subsequently used the assay in the evaluation of eight individuals with high diagnostic suspicion for factitious hypoglycemia.

RESULTS

The performance characteristics show that the LC-HRAM immunoassay can be applied to detect five commonly used synthetic insulin analogs (lispro, glulisine, aspart, glargine metabolite, and detemir) in human serum. Our clinical cases show that this assay could be used in the diagnosis of factitious hypoglycemia by identifying the analog insulin(s) in question.

CONCLUSION

The LC-HRAM immunoassay reported here overcomes a gap in our diagnostic pathway for hypoglycemia. The results obtained from our studies suggest that this method is appropriate for use in clinical laboratories when factitious hypoglycemia is considered as a differential diagnosis.

PSUN137 Suppression of endogenous insulin secretion during euglycemic hyperinsulinemia – effects of obesity

Hyperinsulinemia is strongly linked with excessive body fat. However, with the exception of plasma glucose concentrations, the other factors regulating insulin secretion are under-studied. We examined the effects of hyperinsulinemia itself on beta cell insulin secretion during exogenous insulin and glucose infusions in adults with insulin-resistant upper body (UBO), insulin-sensitive lower body obesity (LBO) and non-obese controls.

Data from the euglycemic, hyperinsulinemic clamp studies of 33 volunteers (9 controls, 5 LBO, 19 UBO) was analyzed; basal and insulin-suppressed (residual) insulin secretion rates were determined using deconvolution of C-peptide concentrations. Obesity phenotype was determined using waist: hip ratio and body composition was assessed with dual-energy X-ray absorptiometry and abdominal computed tomography. Plasma insulin concentrations were log transformed to achieve a normal distribution before statistical analysis.

The plasma glucose concentration change during the clamp was 0.3 (SD: 3) mg/dl, and similar among groups (p=0.7). Median, achieved serum insulin concentrations was 66 (IQR: 45-105) mIU/mL, and greater in participants with obesity. Fasting insulin secretion rates were 0.093 (SD: 0.029), 0.158 (SD: 0.036), and 0.216 (0.078) nmol/min in controls, LBO and UBO, respectively (UBO p&lt;0.001 vs. other groups). Insulin secretion was suppressed by 28% during hyperinsulinemia with no between group differences (p= 0.69). The ratios of insulin secretion rate (from C-peptide deconvolution) to serum insulin concentration (nmol/min per mIU/mL) was 0.058 (SD: 0.015) in controls, 0.090 (SD: 0.016) in LBO and 0.111 (SD: 0.039) in UBO (UBO vs. other groups P = 0.001). The ratio of insulin secretion rates to plasma insulin concentrations was correlated with BMI (r=0.69, P &lt;0.001).

We conclude that adults with obesity have greater residual insulin secretion during an exogenous insulin infusion and that this is related to upper body fat distribution. However, because the proportional suppression of endogenous insulin secretion is similar in these groups, this could indicate the primary abnormality is fasting insulin secretion.

Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Assessment of Disparities in Diabetes Mortality in Adults in US Rural vs Nonrural Counties, 1999-2018

IMPORTANCE

US rural vs nonrural populations have striking disparities in diabetes care. Whether rurality contributes to disparities in diabetes mortality is unknown.

OBJECTIVE

To examine rates and trends in diabetes mortality based on county urbanization.

DESIGN, SETTING, AND PARTICIPANTS

In this observational, cross-sectional study, the US Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research database was searched from January 1, 1999, to December 31, 2018, for diabetes as a multiple cause and the underlying cause of death among residents aged 25 years or older in US counties. County urbanization was categorized as metro, medium-small, and rural. Weighted multiple linear regression models and jackknife resampling, with a 3-segment time component, were used. The models included exposures with up to 3-way interactions and were age standardized to the 2009-2010 population. The analyses were conducted from July 1, 2020, to February 1, 2022.

EXPOSURES

County urbanization (metro, medium-small, or rural), gender (men or women), age group (25-54, 55-74, or ≥75 years), and region (Midwest, Northeast, South, or West).

MAIN OUTCOMES AND MEASURES

Annual diabetes mortality rate per 100 000 people.

RESULTS

From 1999-2018, based on 4 022 238 309 person-years, diabetes was a multiple cause of death for 4 735 849 adults aged 25 years or older. As a multiple cause, diabetes mortality rates in 2017-2018 vs 1999-2000 were highest and unchanged in rural counties (157.2 [95% CI, 150.7-163.7] vs 154.1 [95% CI, 148.2-160.1]; P = .49) but lower in medium-small counties (123.6 [95% CI, 119.6-127.6] vs 133.6 [95% CI, 128.4-138.8]; P = .003) and urban counties (92.9 [95% CI, 90.5-95.3] vs 109.7 [95% CI, 105.2-114.1]; P < .001). In 2017-2018 vs 1999-2000, mortality rates were higher in rural men (+18.2; 95% CI, 14.3-22.1) but lower in rural women (-14.0; 95% CI, -17.7 to -10.3) (P < .001 for both). In the 25- to 54-year age group, mortality rates in 2017-2018 vs 1999-2000 showed a greater increase in rural counties (+9.4; 95% CI, 8.6-10.2) compared with medium-small counties (+4.5; 95% CI, 4.0-5.0) and metro counties (+0.9; 95% CI, 0.4-1.4) (P < .001 for all). Of all regions and urbanization levels, the mortality rate in 2017-2018 vs 1999-2000 was higher only in the rural South (+13.8; 95% CI, 7.6-20.0; P < .001).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, US rural counties had the highest overall diabetes mortality rate. The determinants of persistent rural disparities, in particular for rural men and for adults in the rural South, require investigation.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Effects of liraglutide on gastrointestinal functions and weight in obesity: A randomized clinical and pharmacogenomic trial

OBJECTIVE

This study aimed to determine the effects of a long-acting glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, and placebo subcutaneously over 16 weeks on weight and gastric functions and to evaluate associations of single-nucleotide polymorphisms in GLP1R (rs6923761) and TCF7L2 (rs7903146) with effects of liraglutide.

METHODS

The study conducted a randomized, parallel-group, placebo-controlled, 16-week trial of liraglutide, escalated to 3 mg subcutaneously daily in 136 otherwise healthy adults with obesity. Weight, gastric emptying of solids (GES), gastric volumes, satiation, and body composition measured at baseline and after treatment were compared in two treatment groups using analysis of covariance.

RESULTS

Liraglutide (n = 59) and placebo (n = 65) groups completed treatment. Relative to placebo, liraglutide increased weight loss at 5 and 16 weeks (both p < 0.05), slowed time to half GES (T_1/2 ) at 5 and 16 weeks (both p < 0.001), and increased fasting gastric volume (p = 0.01) and satiation (p < 0.01) at 16 weeks. GES T_1/2 was positively correlated with weight loss on liraglutide (both p < 0.001). After 16 weeks of liraglutide, GLP1R rs6923761 (AG/AA vs. GG) was associated with reduced percent body fat (p = 0.062), and TCF7L2 rs7903146 (CC vs. CT/TT) was associated with lower body weight (p = 0.015).

CONCLUSIONS

Liraglutide, 3 mg, induces weight loss with delay in GES T_1/2 and reduces calorie intake. Slowing GES and variations in GLP1R and TCF7L2 are associated with liraglutide effects in obesity.

The Effect of Glucagon on Protein Catabolism During Insulin Deficiency: Exchange of Amino Acids Across Skeletal Muscle and the Splanchnic Bed

Transient insulin deprivation with concurrent hyperglucagonemia is a catabolic state that can occur in type 1 diabetes. To evaluate glucagon's catabolic effect in the setting of its glucogenic effect, we measured the regional exchanges of amino acid metabolites (amino-metabolites) across muscle and splanchnic beds in 16 healthy humans during either somatostatin followed by glucagon or saline infusion alone. Despite a twofold or greater increase in the regional exchange of amino-metabolites by glucagon, whole-body kinetics and concentrations of amino acids (AA) remained stable. Glucagon increased the splanchnic uptake of not only gluconeogenic but also essential (EAA) AA while increasing their release from the muscle bed. Regional tracer-based kinetics and 3-methylhistidine release indicate that EAA release from muscle is likely caused by reduced protein synthesis rather than increased protein degradation. Furthermore, many metabolites known to affect insulin action and metabolism were altered by hyperglucagonemia including increase in branched-chain AA and keto acids of leucine and isoleucine in arterial plasma. Further, an increase in arterial concentrations of α-aminoadipic acid arising from increased conversion from lysine in the splanchnic bed was noted. These results demonstrate that hyperglucagonemia during hypoinsulinemia increases net muscle protein catabolism and substantially increases the exchange of amino metabolites across splanchnic and muscle beds.

The relationship between insulin and glucagon concentrations in non-diabetic humans

Abnormal postprandial suppression of glucagon in Type 2 diabetes (T2DM) has been attributed to impaired insulin secretion. Prior work suggests that insulin and glucagon show an inverse coordinated relationship. However, dysregulation of α-cell function in prediabetes occurs early and independently of changes in β-cells, which suggests insulin having a less significant role on glucagon control. We therefore, sought to examine whether hepatic vein hormone concentrations provide evidence to further support the modulation of glucagon secretion by insulin. As part of a series of experiments to measure the effect of diabetes-associated genetic variation in TCF7L2 on islet cell function, hepatic vein insulin and glucagon concentrations were measured at 2-minute intervals during fasting and a hyperglycemic clamp. The experiment was performed on 29 nondiabetic subjects (age = 46 ± 2 years, BMI 28 ± 1 Kg/m2 ) and enabled post-hoc analysis, using Cross-Correlation and Cross-Approximate Entropy (Cross-ApEn) to evaluate the interaction of insulin and glucose. Mean insulin concentrations rose from fasting (33 ± 4 vs. 146 ± 12 pmol/L, p < 0.01) while glucagon was suppressed (96 ± 8 vs. 62 ± 5 ng/L, p < 0.01) during the clamp. Cross-ApEn was used to measure pattern reproducibility in the two hormones using glucagon as control mechanism (0.78 ± 0.03 vs. 0.76 ± 0.03, fasting vs. hyperglycemia) and using insulin as a control mechanism (0.78 ± 0.02 vs. 0.76 ± 0.03, fasting vs. hyperglycemia). Values did not differ between the two scenarios. Cross-correlation analysis demonstrated a small in-phase coordination between insulin and glucagon concentrations during fasting, which inverted during hyperglycemia. This data suggests that the interaction between the two hormones is not driven by either. On a minute-to-minute basis, direct control and secretion of glucagon is not mediated (or restrained) by insulin.

The Effect of Diabetes-Associated Variation in TCF7L2 on Postprandial Glucose Metabolism When Glucagon and Insulin Concentrations Are Matched

Background: The rs7903146 variant in the TCF7L2 gene is associated with defects in postprandial insulin and glucagon secretion and increased risk of type 2 diabetes. However, it is unclear if this variant has effects on glucose metabolism that are independent of islet function. Methods: We studied 54 nondiabetic subjects on two occasions where endogenous hormone secretion was inhibited by somatostatin. Twenty-nine subjects were homozygous for the diabetes-associated allele (TT) and 25 for the diabetes-protective allele (CC) at rs7903146, but otherwise matched for anthropometric characteristics. On 1 day, glucagon infused at a rate of 0.65 ng/kg/min, and at 0 min prevented a fall in glucagon (nonsuppressed day). On the contrary, infusion commenced at 120 min to create a transient fall in glucagon (suppressed day). Subjects received glucose (labeled with [3-³H]-glucose) infused to mimic the systemic appearance of oral glucose. Insulin was infused to mimic a prandial insulin response. Endogenous glucose production (EGP) was measured using the tracer dilution technique. Results: Lack of glucagon suppression increased postchallenge glucose concentrations and impaired EGP suppression. However, in the presence of matched insulin and glucagon concentrations, genetic variation in TCF7L2 did not alter glucose metabolism. Conclusion: These data suggest that genetic variation in TCF7L2 alters glucose metabolism through changes in islet hormone secretion.

Biology of Activating Transcription Factor 4 (ATF4) and Its Role in Skeletal Muscle Atrophy

Activating transcription factor 4 (ATF4) is a multifunctional transcription regulatory protein in the basic leucine zipper superfamily. ATF4 can be expressed in most if not all mammalian cell types, and it can participate in a variety of cellular responses to specific environmental stresses, intracellular derangements, or growth factors. Because ATF4 is involved in a wide range of biological processes, its roles in human health and disease are not yet fully understood. Much of our current knowledge about ATF4 comes from investigations in cultured cell models, where ATF4 was originally characterized and where further investigations continue to provide new insights. ATF4 is also an increasingly prominent topic of in vivo investigations in fully differentiated mammalian cell types, where our current understanding of ATF4 is less complete. Here, we review some important high-level concepts and questions concerning the basic biology of ATF4. We then discuss current knowledge and emerging questions about the in vivo role of ATF4 in one fully differentiated cell type, mammalian skeletal muscle fibers.

Hepatic Artery Embolization for Palliation of Symptomatic Hypoglycemia in Patients With Hepatic Insulinoma Metastases

Context

Insulinoma is a pancreatic neuroendocrine tumor that causes hyperinsulinemic hypoglycemia. Symptomatic hypoglycemia related to hepatic insulinoma metastases may be addressed with liver-directed therapies such as hepatic artery embolization.

Objective

This work aimed to determine the safety and effectiveness of bland hepatic artery embolization (HAE) for palliation of symptomatic hypoglycemia in patients with hepatic insulinoma metastases refractory to medical management.

Methods

An institutional review board–approved retrospective review was undertaken of all patients with a tissue (n = 18) or imaging (n = 2) diagnosis of hepatic insulinoma metastases and symptomatic hyperinsulinemic hypoglycemia refractory to medical management who underwent bland HAE at a single center between January 1, 1998 and November 1, 2020. Twenty patients (10 women, 10 men; mean age, 56 years; range, 18-84 years) were identified who individually underwent 1 (n = 7), 2 (n = 5), 3 (n = 5), 4 (n = 2), or 5 (n = 1) HAEs, for an overall total of 45 HAEs. Post-HAE hypoglycemia recurrence was defined as onset of adrenergic symptoms (eg, sweating, weakness, tremor), neuroglycopenic symptoms (eg, confusion, loss of consciousness), and/or documented serum glucose of less than 50 mg/dL, in the absence of an alternative explanation. Median time to first hypoglycemia recurrence, hypoglycemia-free survival (HFS), and overall survival (OS) were calculated using Kaplan-Meier method.

Results

Before HAE, all patients experienced adrenergic or neuroglycopenic symptoms alleviated by glucose intake, and 60% (n = 12) of patients had documented serum glucose of less than 50 mg/dL within 1 week of the first treatment. Median post-HAE follow-up was 9.4 months (mean, 26 months; range, 0.1-190 months). Postprocedural hypoglycemic symptom relief after the first HAE was reported in 100% (n = 20) of patients before discharge or at follow-up. Post-HAE hypoglycemia recurrence occurred in 60% (n = 12) of patients with a median time to first hypoglycemia recurrence of 2 months (mean, 14 months; range, 0.2-60 months). After the first HAE, median HFS was 14.5 months, and median OS was 16 months. One patient experienced labile postprocedure blood glucose levels requiring intensive care unit admission for intravenous dextrose. Otherwise, no major procedure-related complications occurred.

Conclusion

Bland HAE is a safe, effective, and repeatable procedure for palliation of symptomatic hypoglycemia in patients with hepatic insulinoma metastases refractory to medical management.

Insulin secretion and action and the response of endogenous glucose production to a lack of glucagon suppression in nondiabetic subjects

Type 2 diabetes is a disease characterized by impaired insulin secretion and defective glucagon suppression in the postprandial period. We examined the effect of impaired glucagon suppression on glucose concentrations and endogenous glucose production (EGP) at different degrees of insulin secretory impairment. The contribution of anthropometric characteristics, peripheral, and hepatic insulin action to this variability was also examined. To do so, we studied 54 nondiabetic subjects on two occasions in which endogenous hormone secretion was inhibited by somatostatin, with glucagon infused at a rate of 0.65 ng/kg/min, at 0 min to prevent a fall in glucagon (nonsuppressed day) or at 120 min to create a transient fall in glucagon (suppressed day). Subjects received glucose (labeled with [3-³H]-glucose) infused to mimic the systemic appearance of 50-g oral glucose. Insulin was infused to mimic a prandial insulin response in 18 subjects, another 18 received 80% of the dose, and the remaining 18 received 60%. EGP was measured using the tracer-dilution technique. Decreased prandial insulin resulted in greater % increase in peak glucose but not in integrated glucose concentrations attributable to nonsuppressed glucagon. The % change in integrated EGP was unaffected by insulin dose. Multivariate regression analysis, adjusted for age, sex, weight, and insulin dose, did not show a relationship between the EGP response to impaired suppression of glucagon and insulin action as measured at the time of screening by oral glucose tolerance. A similar analysis for hepatic insulin action also did not show a relationship with the EGP response. These data indicate that the effect of impaired glucagon suppression on EGP is independent of anthropometric characteristics and insulin action.NEW & NOTEWORTHY In prediabetes, anthropometric characteristics as well as insulin action do not alter the hepatic response to glucagon. The postprandial suppression or lack of suppression of glucagon secretion is an important factor governing postprandial glucose tolerance independent of insulin secretion.

Association of plasma ceramides with prevalent and incident type 2 diabetes mellitus in middle and older aged adults

AIMS

The role of ceramides in the pathogenesis of type 2 diabetes mellitus (T2DM) is incompletely characterized. Given that ceramides represent therapeutic targets to disrupt the euglycemia-T2DM transition, we aimed to characterize their association with prevalent and incident T2DM in a novel cohort.

METHODS

We examined the cross-sectional and longitudinal association of baseline ceramides with prevalent and incident T2DM among 1423 adults (47% women; median (range) baseline age 72 (51-95) years) in the Mayo Clinic Study of Aging cohort. We examined the associations of ceramides with prevalent T2DM (adjusted odds ratio [95% confidence interval]) at baseline and incident T2DM (adjusted hazard ratio [95% confidence interval]) during median follow-up of 6.2 years, after adjusting for demographic and metabolic factors.

RESULTS

Among 1423 adults, there were 222 prevalent and 37 incident cases of T2DM. In cross-sectional analyses, higher levels of ceramide C16:0 were associated with lower odds of prevalent T2DM (aOR 0.84 [0.71-0.99];P = 0.03) whereas C18:0 (aOR 1.27 [1.06-1.42];P = 0.01), C18:0/16:0 (aOR 1.41 [1.22-1.62]; P < 0.001) and C18:0/24:0 (aOR 1.22 [1.05-1.41]; P = 0.01) were associated with higher odds. In Cox hazard regression models, C18:0/16:0 (aHR 1.63 [1.26-2.10];P < 0.001) and C18:0 (aHR 1.53 [1.12-2.08];P = 0.01) were associated with increased risk of incident T2DM.

CONCLUSIONS

In this prospective population-based cohort, ceramides were associated with prevalent T2DM (C16:0,C18:0, C18:0/C16:0 ratio, C18:0/C24:0 ratio) and incident T2DM (C18:0, C18:0/C16:0 ratio) and could suggest targets for the primary and secondary prevention of T2DM.

Pro-inflammatory β cell small extracellular vesicles induce β cell failure through activation of the CXCL10/CXCR3 axis in diabetes

Coordinated communication among pancreatic islet cells is necessary for maintenance of glucose homeostasis. In diabetes, chronic exposure to pro-inflammatory cytokines has been shown to perturb β cell communication and function. Compelling evidence has implicated extracellular vesicles (EVs) in modulating physiological and pathological responses to β cell stress. We report that pro-inflammatory β cell small EVs (cytokine-exposed EVs [cytoEVs]) induce β cell dysfunction, promote a pro-inflammatory islet transcriptome, and enhance recruitment of CD8+ T cells and macrophages. Proteomic analysis of cytoEVs shows enrichment of the chemokine CXCL10, with surface topological analysis depicting CXCL10 as membrane bound on cytoEVs to facilitate direct binding to CXCR3 receptors on the surface of β cells. CXCR3 receptor inhibition reduced CXCL10-cytoEV binding and attenuated β cell dysfunction, inflammatory gene expression, and leukocyte recruitment to islets. This work implies a significant role of pro-inflammatory β cell-derived small EVs in modulating β cell function, global gene expression, and antigen presentation through activation of the CXCL10/CXCR3 axis.

Burden and management of type 2 diabetes in rural United States

In the United States, rural areas have a higher burden of type 2 diabetes (T2DM) compared to urban areas. However, there is limited information on risk factors and interventions that improve the primary prevention and management of T2DM in rural areas. To synthesize current knowledge on T2DM in rural areas and to guide healthcare providers and policy makers, we reviewed five scientific databases and the grey literature over the last decade (2010-2020). We described classification systems for rurality and the T2DM burden based on rurality and region (West, South, Midwest, and Northeast). We highlighted risk factors for T2DM in rural compared to urban areas, and summarized interventions to screen and manage T2DM based on opportunistic screening, T2DM self-management, community-based initiatives, as well as interventions targeting comorbidities and T2DM. Several studies identified the co-existence of T2DM and depression/psychological symptoms, which could reduce adherence to non-pharmacologic and pharmacologic management of T2DM. We highlighted the role of technology in education and counselling of patients with geographic and financial barriers to accessing care, which is exacerbated by the SARS-CoV-2 coronavirus disease-19 pandemic. We identified knowledge gaps and next steps in improving T2DM care in rural areas. There is an urgent need for interventions tailored to rural areas given that rural Americans currently experience a disproportionate burden of T2DM and are encumbered by its associated morbidity, mortality, and loss in economic productivity.

Adipose tissue macrophage populations and inflammation are associated with systemic inflammation and insulin resistance in obesity

Obesity is accompanied by numerous systemic and tissue-specific derangements, including systemic inflammation, insulin resistance, and mitochondrial abnormalities in skeletal muscle. Despite growing recognition that adipose tissue dysfunction plays a role in obesity-related disorders, the relationship between adipose tissue inflammation and other pathological features of obesity is not well-understood. We assessed macrophage populations and measured the expression of inflammatory cytokines in abdominal adipose tissue biopsies in 39 nondiabetic adults across a range of body mass indexes (BMI 20.5-45.8 kg/m²). Skeletal muscle biopsies were used to evaluate mitochondrial respiratory capacity, ATP production capacity, coupling, and reactive oxygen species production. Insulin sensitivity (S_I) and β cell responsivity were determined from test meal postprandial glucose, insulin, c-peptide, and triglyceride kinetics. We examined the relationships between adipose tissue inflammatory markers, systemic inflammatory markers, S_I, and skeletal muscle mitochondrial physiology. BMI was associated with increased adipose tissue and systemic inflammation, reduced S_I, and reduced skeletal muscle mitochondrial oxidative capacity. Adipose-resident macrophage numbers were positively associated with circulating inflammatory markers, including tumor necrosis factor-α (TNFα) and C-reactive protein (CRP). Local adipose tissue inflammation and circulating concentrations of TNFα and CRP were negatively associated with S_I, and circulating concentrations of TNFα and CRP were also negatively associated with skeletal muscle oxidative capacity. These results demonstrate that obese humans exhibit increased adipose tissue inflammation concurrently with increased systemic inflammation, reduced insulin sensitivity, and reduced muscle oxidative capacity and suggest that adipose tissue and systemic inflammation may drive obesity-associated metabolic derangements.NEW AND NOTEWORTHY Adipose inflammation is proposed to be at the nexus of the systemic inflammation and metabolic derangements associated with obesity. The present study provides evidence to support adipose inflammation as a central feature of the pathophysiology of obesity. Adipose inflammation is associated with systemic and peripheral metabolic derangements, including increased systemic inflammation, reduced insulin sensitivity, and reduced skeletal muscle mitochondrial respiration.

Measurement of Pulsatile Insulin Secretion: Rationale and Methodology

Pancreatic β-cells are responsible for the synthesis and exocytosis of insulin in response to an increase in circulating glucose. Insulin secretion occurs in a pulsatile manner, with oscillatory pulses superimposed on a basal secretion rate. Insulin pulses are a marker of β-cell health, and secretory parameters, such as pulse amplitude, time interval and frequency distribution, are impaired in obesity, aging and type 2 diabetes. In this review, we detail the mechanisms of insulin production and β-cell synchronization that regulate pulsatile insulin secretion, and we discuss the challenges to consider when measuring fast oscillatory secretion in vivo. These include the anatomical difficulties of measuring portal vein insulin noninvasively in humans before the hormone is extracted by the liver and quickly removed from the circulation. Peripheral concentrations of insulin or C-peptide, a peptide cosecreted with insulin, can be used to estimate their secretion profile, but mathematical deconvolution is required. Parametric and nonparametric approaches to the deconvolution problem are evaluated, alongside the assumptions and trade-offs required for their application in the quantification of unknown insulin secretory rates from known peripheral concentrations. Finally, we discuss the therapeutical implication of targeting impaired pulsatile secretion and its diagnostic value as an early indicator of β-cell stress.

Limitations of the fasting proinsulin to insulin ratio as a measure of β-cell health in people with and without impaired glucose tolerance

BACKGROUND

The fasting proinsulin to insulin ratio is elevated in people with type 2 diabetes and has been suggested as a marker of β-cell health. However, its utility in discriminating between individuals with varying degrees of β-cell dysfunction is unclear. Proinsulin has a very different half-life to insulin and unlike insulin does not undergo hepatic extraction prior to reaching the systemic circulation. Given these limitations, we sought to examine the relationship between fasting and postprandial concentrations of β-cell polypeptides (proinsulin, insulin and C-peptide) in people with normal and impaired glucose tolerance in differing metabolic environments.

DESIGN

Subjects were studied on two occasions in random order while undergoing an oral challenge. During one study day, free fatty acids were elevated (to induce insulin resistance) by infusion of Intralipid with heparin. Proinsulin to insulin and proinsulin to C-peptide ratios were calculated for the 0-, 30-, 60- and 240-minute time points. Insulin action (Si) and β-cell responsivity (Φ) indices were calculated using the oral minimal model.

RESULTS

The fasting proinsulin to c-peptide or fasting proinsulin to insulin ratios did not differ between groups and did not predict subsequent β-cell responsivity to glucose during the glycerol or Intralipid study days in either group.

CONCLUSIONS

Among nondiabetic individuals, the fasting proinsulin to insulin ratio is not a useful marker of β-cell function.

Insulin Pulse Characteristics and Insulin Action in Non-diabetic Humans

OBJECTIVE

Pulsatile insulin secretion is impaired in diseases such as type 2 diabetes that are characterized by insulin resistance. This has led to the suggestion that changes in insulin pulsatility directly impair insulin signaling. We sought to examine the effects of pulse characteristics on insulin action in humans, hypothesizing that a decrease in pulse amplitude or frequency is associated with impaired hepatic insulin action.

METHODS

We studied 29 nondiabetic subjects on two occasions. On 1 occasion, hepatic and peripheral insulin action was measured using a euglycemic clamp. The deuterated water method was used to estimate the contribution of gluconeogenesis to endogenous glucose production. On a separate study day, we utilized nonparametric stochastic deconvolution of frequently sampled peripheral C-peptide concentrations during fasting to reconstruct portal insulin secretion. In addition to measuring basal and pulsatile insulin secretion, we used approximate entropy to measure orderliness and Fourier transform to measure the average, and the dispersion of, insulin pulse frequencies.

RESULTS

In univariate analysis, basal insulin secretion (R2 = 0.16) and insulin pulse amplitude (R2 = 0.09) correlated weakly with insulin-induced suppression of gluconeogenesis. However, after adjustment for age, sex, and weight, these associations were no longer significant. The other pulse characteristics also did not correlate with the ability of insulin to suppress endogenous glucose production (and gluconeogenesis) or to stimulate glucose disappearance.

CONCLUSIONS

Overall, our data demonstrate that insulin pulse characteristics, considered independently of other factors, do not correlate with measures of hepatic and peripheral insulin sensitivity in nondiabetic humans.