Egan, Aoife M.

We describe a method that lowers the limit of quantification of a glucagon immunoassay thereby enhancing the ability to differentiate between normal and abnormal α-cell responsiveness to glucagon.

Abstract Disclosure: M. Moazzami: None. N. Venkatesan: None. K.S. Rajagopalan: None. A.V. Vella: None. A. Egan: None. Gestational diabetes mellitus (GDM) affects approximately 10% of pregnancies, with rates almost doubling in minority subgroups. Higher body mass index (BMI) is a significant GDM risk factor, and BMI ≥ 25kg/m2 is often used as a criterion in risk factor-based screening programs. However, up to 60% of individuals with GDM have a normal BMI, and it is unclear if this offers protection against associated adverse outcomes. Furthermore, many prior studies fail to address the fact that those of Asian descent require a lower BMI cut-off, given their different distribution of body fat. Our study evaluated GDM pregnancy outcomes using BMI as a risk indicator. We compared individuals with BMIs < 25 kg/m2, 25-30 kg/m2, and > 30 kg/m2. For individuals that self-identified as Asian, we adjusted BMI categories: <23 kg/m2 for normal weight, 23-30 kg/m2 for overweight, and >30 kg/m2 for obese. We identified 2212 subjects diagnosed with GDM via universal screening and Carpenter and Coustan criteria at our institution from 2018 - 22. In total, 508 (23.0%) were normal weight, 611 (27.6%) overweight, and 1093 (49.4%) obese. The average maternal age was 31 years. Higher proportions identified as Hispanic and non-White race in overweight and obese categories. Maternal adverse outcomes were higher in obese compared to overweight or normal BMI categories (cesarian delivery: normal 26.7 v overweight 28.3 v obese 22.7%, p<0.001; hypertensive disorders: normal 13.2 v overweight 12.5 v obese 22.7%, p <0.001). Pharmacological therapy was required in 50% with obesity versus 24.8% in normal, and 28.7% in overweight categories (p<0.001). While there were no differences in live birth rates across categories, infants born to mothers with obesity had a higher birthweight (normal 3.30 v overweight 3.38 v obese 3.45kg, p<0.001) and were more likely to have neonatal hypoglycemia (normal 28.7 v overweight 25.5 v obese 43.8%, p<0.001) and require intensive care unit admission (normal 8.4 v overweight 5.5 v obese 12.7%, p<0.001). Attendance at postpartum glucose testing varied across BMI categories with lower attendance in mothers with obesity followed by normal weight BMI (normal 40.75 v overweight 45.99 v obese 36.2%, p<0.001). Compared to overweight individuals, those with normal weight exhibited higher rates of postpartum glucose intolerance (12.4 v 6.9%, p =0.002). However, those with obesity had the highest rates of glucose intolerance (20.7%, p<0.0002). Individuals with normal weight had the highest rates of breastfeeding (normal 95.9 v overweight 92.8 v obese 91.4% p=0.006). This study highlights the nuanced relationship between BMI and pregnancy outcomes in GDM. While maternal obesity was associated with the poorest outcomes, those with normal BMI were not protected compared to overweight individuals, and experience higher rates of postpartum glucose intolerance. Presentation: 6/2/2024

Abstract Aim Women with gestational diabetes mellitus (GDM) display adverse lifetime cardiometabolic health. We examined whether early metformin in GDM could impact cardiometabolic risk factors postpartum. Methods EMERGE, a double-blind, placebo-controlled trial, randomized pregnancies 1:1 to placebo or metformin at GDM diagnosis and followed participants from randomization until 12 ± 4 weeks postpartum. In total, 478 pregnancies were available for postpartum maternal assessment, 237 and 241 assigned to metformin and placebo respectively. Weight (kg), body mass index (BMI) (kg/m2), waist circumference (cm), and blood pressure (mmHg) were measured, infant feeding method documented, and blood specimens drawn for a 75-gram oral glucose tolerance test, fasting insulin, C-peptide, and lipid analysis. Results Despite similar weight and BMI at trial randomization, participants receiving metformin had significantly lower weight (79.5 ± 15.9 vs 82.6 ± 16.9 kg; P = .04) and BMI (29.3 [5.6] vs 30.5 [5.4]; P = .018) at the postpartum visit. However, no difference in weight change from randomization to 12 weeks postpartum was observed between metformin and placebo groups. Overall, 29% (n = 139) of the cohort met criteria for prediabetes or diabetes, with no positive impact with metformin. There were also no differences in measurements of insulin resistance, blood pressure, or lipids between groups. Conclusion Early metformin use in GDM did not impact important cardiometabolic parameters in the early postpartum period despite significant benefits in weight gain and insulin use in pregnancy.

Abstract 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.

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

Abstract 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.

Importance Gestational diabetes is a common complication of pregnancy and the optimal management is uncertain. Objective To test whether early initiation of metformin reduces insulin initiation or improves fasting hyperglycemia at gestation weeks 32 or 38. Design, Setting, and Participants Double-blind, placebo-controlled trial conducted in 2 centers in Ireland (one tertiary hospital and one smaller regional hospital). Participants were enrolled from June 2017 through September 2022 and followed up until 12 weeks’ postpartum. Participants comprised 510 individuals (535 pregnancies) diagnosed with gestational diabetes based on World Health Organization 2013 criteria. Interventions Randomized 1:1 to either placebo or metformin (maximum dose, 2500 mg) in addition to usual care. Main Outcomes And Measures The primary outcome was a composite of insulin initiation or a fasting glucose level of 5.1 mmol/L or greater at gestation weeks 32 or 38. Results Among 510 participants (mean age, 34.3 years), 535 pregnancies were randomized. The primary composite outcome was not significantly different between groups and occurred in 150 pregnancies (56.8%) in the metformin group and 167 pregnancies (63.7%) in the placebo group (between-group difference, −6.9% [95% CI, −15.1% to 1.4%]; relative risk, 0.89 [95% CI, 0.78-1.02]; P = .13). Of 6 prespecified secondary maternal outcomes, 3 favored the metformin group, including time to insulin initiation, self-reported capillary glycemic control, and gestational weight gain. Secondary neonatal outcomes differed by group, with smaller neonates (lower mean birth weights, a lower proportion weighing >4 kg, a lower proportion in the >90% percentile, and smaller crown-heel length) in the metformin group without differences in neonatal intensive care needs, respiratory distress requiring respiratory support, jaundice requiring phototherapy, major congenital anomalies, neonatal hypoglycemia, or proportion with 5-minute Apgar scores less than 7. Conclusion and relevance Early treatment with metformin was not superior to placebo for the composite primary outcome. Prespecified secondary outcome data support further investigation of metformin in larger clinical trials. Trial Registration ClinicalTrials.gov Identifier: NCT02980276 ; EudraCT: 2016-001644-19

This experiment studied the effect of changes in overnight concentrations of free fatty acids (FFAs) and glucose on β-cell function and glucose metabolism. In response to elevation of these metabolites, the dynamic component of the β-cell response to glucose was impaired. This suggests that in health overnight hyperglycemia and FFA elevation can deplete preformed insulin granules in the β-cell.