β-cell function, incretin effect, and incretin hormones in obese youth along the span of glucose tolerance from normal to prediabetes to type 2 diabetes

Prediabetes remission to reduce the global burden of type 2 diabetes

Prediabetes is a highly prevalent and increasingly common condition affecting a significant proportion of the global population. The heterogeneous nature of prediabetes presents a challenge in identifying individuals who particularly benefit from lifestyle or other therapeutic interventions aiming at preventing type 2 diabetes (T2D) and associated comorbidities. The phenotypic characteristics of individuals at risk for diabetes are associated with both specific risk profiles for progression and a differential potential to facilitate prediabetes remission and reduce the risk of future T2D. This review examines the current definition and global prevalence of prediabetes and evaluates the potential of prediabetes remission to reduce the alarming increase in the global burden of T2D.

Pathophysiology and Treatment of Prediabetes and Type 2 Diabetes in Youth

Youth-onset type 2 diabetes is a heterogeneous disease with increasing prevalence in relation to increased rates of obesity in children. It has genetic, epigenetic, social, and environmental determinants. Youth-onset type 2 diabetes is alarming given a rapidly progressive course compared with the course of adult-onset disease, early-onset vascular complications, and long-term exposure to hyperglycemia and associated complications. It is often preceded by prediabetes, a disease phase where defects in β-cell function relative to insulin sensitivity emerge. Herein, we review the current understanding of the pathophysiology of prediabetes and type 2 diabetes in youth. We describe the mechanisms underlying insulin resistance, the precipitous decline of β-cell function, and the role of other hormonal abnormalities in the pathogenesis of the disease. We discuss the critical importance of social determinants of health in the predisposition and progression of these conditions and present current management strategies and the advances in therapeutic approaches. These must adapt to meet the unique needs of the individual patient and family. Significant knowledge gaps remain that need to be addressed in future research.

Insulin Dynamics and Pathophysiology in Youth-Onset Type 2 Diabetes

Youth-onset type 2 diabetes (T2D) is increasing around the globe. The mounting disease burden of youth-onset T2D portends substantial consequences for the health outcomes of young people and for health care systems. The pathophysiology of this condition is characterized by insulin resistance and initial insulin hypersecretion ± an inherent insulin secretory defect, with progressive loss of stimulated insulin secretion leading to pancreatic β-cell failure. Research studies focusing on youth-onset T2D have illuminated key differences for youth- vs adult-onset T2D, with youth having more profound insulin resistance and quicker progression to loss of sufficient insulin secretion to maintain euglycemia. There is a need for therapies that are targeted to improve both insulin resistance and, importantly, maintain sufficient insulin secretory function over the lifespan in youth-onset T2D.

Altered Glucagon and GLP-1 Responses to Oral Glucose in Children and Adolescents With Obesity and Insulin Resistance

CONTEXT

Pediatric obesity is characterized by insulin resistance, yet it remains unclear whether insulin resistance contributes to abnormalities in glucagon and incretin secretion.

OBJECTIVE

To examine whether fasting and stimulated glucagon, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations differ between children and adolescents with obesity and insulin resistance (OIR), obesity and normal insulin sensitivity (OIS), and controls with normal weight (NW).

METHODS

80 (34 boys) children and adolescents, aged 7-17 years with OIR (n = 22), OIS (n = 22), and NW (n = 36) underwent an oral glucose tolerance test with measurements of serum insulin, plasma glucose, glucagon, total GLP-1, and total GIP. Homeostatic model assessment of insulin resistance (HOMA-IR), single point insulin sensitivity estimator (SPISE), Matsuda index, insulinogenic index (IGI), and oral disposition index (ODI) were calculated.

RESULTS

Fasting concentrations of glucagon and GLP-1 were higher in the OIR group, with no significant differences for GIP. The OIR group had higher glucagon total area under the curve (tAUC0-120) and lower GLP-1 incremental AUC (iAUC0-120), with no significant differences in GIP iAUC0-120. Higher fasting glucagon was associated with higher HOMA-IR, lower Matsuda index, lower SPISE, higher IGI, and higher plasma alanine transaminase, whereas higher fasting GLP-1 was associated with higher HOMA-IR, lower Matsuda index, and lower ODI. Higher glucagon tAUC0-120 was associated lower SPISE and lower Matsuda index, whereas lower GLP-1 iAUC0-120 was associated with a higher HOMA-IR, lower Matsuda index, and lower ODI.

CONCLUSION

Children and adolescents with OIR have elevated fasting concentrations of glucagon and GLP-1, higher glucagon and lower GLP-1 responses during an OGTT compared to those with OIS and NW. In contrast, individuals with OIS have similar hormone responses to those with NW.

Incretin effect determines glucose trajectory and insulin sensitivity in youths with obesity

In youths with obesity, the gut hormone potentiation of insulin secretion - the incretin effect - is blunted. We explored the longitudinal impact of the incretin effect during pubertal transition on β cell function and insulin sensitivity. Youths with obesity and 2-hour glucose level ≥ 120 mg/dL underwent a 3-hour oral glucose-tolerance test (OGTT) and an isoglycemic i.v. glucose infusion to quantify the incretin effect. After 2 years, 30 of 39 participants had a repeated OGTT and were stratified into 3 tertiles according to the baseline incretin effect. The high-incretin effect group demonstrated a longitudinal increase in β cell function (disposition index, minimal model [DIMM]), with greater insulin sensitivity at follow-up and stable insulin secretion (φtotal). A lower incretin effect at baseline was associated with higher 1-hour and 2-hour glucose level at follow-up. The high-incretin effect group displayed a greater increase of GLP-17-36 than the moderate- and low-incretin group at baseline, while such a difference did not persist after 2 years. Glucagon suppression was reduced at follow-up in those with low-baseline incretin in respect to the high-incretin group. The incretin effect during pubertal transition affected the longitudinal trajectory of β cell function and weight in youths with obesity.

Pancreas-derived DPP4 is not essential for glucose homeostasis under metabolic stress

Mice systemically lacking dipeptidyl peptidase-4 (DPP4) have improved islet health, glucoregulation, and reduced obesity with high-fat diet (HFD) feeding compared to wild-type mice. Some, but not all, of this improvement can be linked to the loss of DPP4 in endothelial cells (ECs), pointing to the contribution of non-EC types. The importance of intra-islet signaling mediated by α to β cell communication is becoming increasingly clear; thus, our objective was to determine if β cell DPP4 regulates insulin secretion and glucose tolerance in HFD-fed mice by regulating the local concentrations of insulinotropic peptides. Using β cell double incretin receptor knockout mice, β cell- and pancreas-specific Dpp4-/- mice, we reveal that β cell incretin receptors are necessary for DPP4 inhibitor effects. However, although β cell DPP4 modestly contributes to high glucose (16.7 mM)-stimulated insulin secretion in isolated islets, it does not regulate whole-body glucose homeostasis.

β-Cell Function and Insulin Sensitivity in Youth With Early Type 1 Diabetes From a 2-Hour 7-Sample OGTT

CONTEXT

The oral minimal model is a widely accepted noninvasive tool to quantify both β-cell responsiveness and insulin sensitivity (SI) from glucose, C-peptide, and insulin concentrations during a 3-hour 9-point oral glucose tolerance test (OGTT).

OBJECTIVE

Here, we aimed to validate a 2-hour 7-point protocol against the 3-hour OGTT and to test how variation in early sampling frequency impacts estimates of β-cell responsiveness and SI.

METHODS

We conducted a secondary analysis on 15 lean youth with stage 1 type 1 diabetes (T1D; ≥ 2 islet autoantibodies with no dysglycemia) who underwent a 3-hour 9-point OGTT. The oral minimal model was used to quantitate β-cell responsiveness (φtotal) and insulin sensitivity (SI), allowing assessment of β-cell function by the disposition index (DI = φtotal × SI). Seven- and 5-point 2-hour OGTT protocols were tested against the 3-hour 9-point gold standard to determine agreement between estimates of φtotal and its dynamic and static components, SI, and DI across different sampling strategies.

RESULTS

The 2-hour estimates for the disposition index exhibited a strong correlation with 3-hour measures (r = 0.975; P < .001) with similar results for β-cell responsiveness and SI (r = 0.997 and r = 0.982; P < .001, respectively). The agreement of the 3 estimates between the 7-point 2-hour and 9-point 3-hour protocols fell within the 95% CI on the Bland-Altman grid with a median difference of 16.9% (-35.3 to 32.5), 0.2% (-0.6 to 1.3), and 14.9% (-1.4 to 28.3) for DI, φtotal, and SI. Conversely, the 5-point protocol did not provide reliable estimates of φ dynamic and static components.

CONCLUSION

The 2-hour 7-point OGTT is reliable in individuals with stage 1 T1D for assessment of β-cell responsiveness, SI, and DI. Incorporation of these analyses into current 2-hour diabetes staging and monitoring OGTTs offers the potential to more accurately quantify risk of progression in the early stages of T1D.

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

Dorzagliatin, a Dual-Acting Glucokinase Activator, Increases Insulin Secretion and Glucose Sensitivity in Glucokinase Maturity-Onset Diabetes of the Young and Recent-Onset Type 2 Diabetes

Glucokinase (GK, gene symbol GCK) maturity-onset diabetes of the young (MODY) is caused by heterozygous inactivating mutations in GK and impaired glucose sensing. We investigated effects of dorzagliatin, a novel allosteric GK activator, on insulin secretion rates (ISRs) and β-cell glucose sensitivity (βCGS) in GCK-MODY and recent-onset type 2 diabetes. In a double-blind, randomized, crossover study, 8 participants with GCK-MODY and 10 participants with type 2 diabetes underwent 2-h 12 mmol/L hyperglycemic clamps following a single oral dose of dorzagliatin 75 mg or matched placebo. Effects of dorzagliatin on wild-type and mutant GK enzyme activity were investigated using an NADP+-coupled assay with glucose-6-phosphate dehydrogenase in vitro. In GCK-MODY, dorzagliatin significantly increased absolute and incremental second-phase ISRs versus placebo but not the acute insulin response. Dorzagliatin improved βCGS in GCK-MODY with an upward and leftward shift in ISR-glucose response. Dorzagliatin increased basal ISRs in type 2 diabetes, with smaller changes in second-phase ISRs versus GCK-MODY. In vitro, dorzagliatin directly reduced the glucose half saturation concentration of wild-type GK and selected GK mutants to varying degrees. Dorzagliatin directly restored enzyme activity of select GK mutants and enhanced wild-type GK activity, thereby correcting the primary defect of glucose sensing in GCK-MODY.

Pros and Cons of Current Diagnostic Tools for Risk-Based Screening of Prediabetes and Type 2 Diabetes in Children and Adolescents with Overweight or Obesity

It is still a matter of debate which is the most suitable diagnostic test for risk-based screening of prediabetes and type 2 diabetes (T2D) in children and adolescents with overweight or obesity. This review highlighted benefits and pitfalls of currently recommended screening tools (fasting plasma glucose [FPG], oral glucose tolerance test [OGTT], glycated hemoglobin A1c [HbA1c]). The greatest advantage of OGTT is the ability to detect people with impaired glucose tolerance, a subcategory at high risk of developing both T2D and cardiovascular disease. Important disadvantages are low reproducibility and inconvenience. FPG measurement is more practical, as it needs only one blood draw, although both OGTT and FPG require fasting. The reliability of HbA1c as a screening tool has been questioned, especially in children and adolescents, but its undeniable convenience can lead to increased adherence to screening. In contrast, it can be altered by several nonglycemic factors. Importantly, none of these tests have been validated in the pediatric population. Alternative tests have been recently proposed, including new OGTT-derived biomarkers and additional nonfasting glycemic markers. In conclusion, when choosing the most suitable test in clinical practice, advantages and disadvantages should be considered, as well as the possibility of performing different tests at once.

Data assimilation on mechanistic models of glucose metabolism predicts glycemic states in adolescents following bariatric surgery

Type 2 diabetes mellitus is a complex and under-treated disorder closely intertwined with obesity. Adolescents with severe obesity and type 2 diabetes have a more aggressive disease compared to adults, with a rapid decline in pancreatic β cell function and increased incidence of comorbidities. Given the relative paucity of pharmacotherapies, bariatric surgery has become increasingly used as a therapeutic option. However, subsets of this population have sub-optimal outcomes with either inadequate weight loss or little improvement in disease. Predicting which patients will benefit from surgery is a difficult task and detailed physiological characteristics of patients who do not respond to treatment are generally unknown. Identifying physiological predictors of surgical response therefore has the potential to reveal both novel phenotypes of disease as well as therapeutic targets. We leverage data assimilation paired with mechanistic models of glucose metabolism to estimate pre-operative physiological states of bariatric surgery patients, thereby identifying latent phenotypes of impaired glucose metabolism. Specifically, maximal insulin secretion capacity, σ, and insulin sensitivity, SI, differentiate aberrations in glucose metabolism underlying an individual's disease. Using multivariable logistic regression, we combine clinical data with data assimilation to predict post-operative glycemic outcomes at 12 months. Models using data assimilation sans insulin had comparable performance to models using oral glucose tolerance test glucose and insulin. Our best performing models used data assimilation and had an area under the receiver operating characteristic curve of 0.77 (95% confidence interval 0.7665, 0.7734) and mean average precision of 0.6258 (0.6206, 0.6311). We show that data assimilation extracts knowledge from mechanistic models of glucose metabolism to infer future glycemic states from limited clinical data. This method can provide a pathway to predict long-term, post-surgical glycemic states by estimating the contributions of insulin resistance and limitations of insulin secretion to pre-operative glucose metabolism.

ISPAD Clinical Practice Consensus Guidelines 2022: Type 2 diabetes in children and adolescents

Since the 2018 ISPAD guidelines on this topic, follow-up of large cohorts from around the globe have continued informing the current incidence and prevalence of co-morbidities and complications in young adults with youth-onset type 2 diabetes (T2D). This chapter focuses on the risk factors, diagnosis and presentation of youth-onset T2D, the initial and subsequent management of youth-onset T2D, and management of co-morbidities and complications. We include key updates from the observational phase of the multi-center Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) clinical trial, the SEARCH for Diabetes in Youth (SEARCH) study and new data from the Restoring Insulin Secretion (RISE) study, a head-to-head comparison of youth onset vs adult-onset T2D. We also include an expanded section on risk factors associated with T2D, algorithms and tables for treatment, management, and assessment of co-morbidities and complications, and sections on recently approved pharmacologic therapies for the treatment of youth-onset T2D, social determinants of health, and settings of care given COVID-19 pandemic.

Diagnosis and management of type 2 diabetes in children

ABSTRACT

The incidence of type 2 diabetes in children has risen 4.8% over the past decade, correlating with steadily rising obesity rates in children. Updated guidelines from the American Academy of Pediatrics and the American Diabetes Association encourage early identification and pharmacologic intervention for children with type 2 diabetes. Because of the aggressive disease course in children, comprehensive treatment must include prevention of complications such as diabetic nephropathy and neuropathy as well as management of comorbidities such as cardiovascular disease and dyslipidemia. Because the highest incidence of type 2 diabetes is reported in patients from racial or ethnic minority groups and those of low socioeconomic status, clinicians must work with patients and families to identify socioeconomic disparities that could affect adherence to diabetes management plans and to connect patients with community resources.

Hyperglucagonemia in Pediatric Adiposity Associates With Cardiometabolic Risk Factors but Not Hyperglycemia

CONTEXT

In adults, hyperglucagonemia is associated with type 2 diabetes, impaired glucose tolerance, and obesity. The role of glucagon in pediatric overweight/obesity remains unclear.

OBJECTIVE

We examined whether fasting concentrations of glucagon are elevated in youth with overweight/obesity and whether this associates with cardiometabolic risk profiles.

METHODS

Analyses were based on the cross-sectional HOLBAEK study, including children and adolescents 6 to 19 years of age, with overweight/obesity from an obesity clinic group (n = 2154) and with normal weight from a population-based group (n = 1858). Fasting concentrations of plasma glucagon and cardiometabolic risk outcomes were assessed, and multiple linear and logistic regressions models were performed.

RESULTS

The obesity clinic group had higher glucagon concentrations than the population-based group (P < 0.001). Glucagon positively associated with body mass index (BMI) standard deviation score (SDS), waist, body fat %, liver fat %, alanine transaminase (ALT), high-sensitivity C-reactive protein, homeostasis model assessment of insulin resistance, insulin, C-peptide, LDL-C, triglycerides, SDS of diastolic and systolic blood pressure, and was inversely associated with fasting glucose. The inverse relationship between glucagon and glucose was attenuated in individuals with high BMI SDS and high fasting insulin. Glucagon was associated with a higher prevalence of insulin resistance, increased ALT, dyslipidemia, and hypertension, but not with hyperglycemia. Glucagon was positively associated with fasting total glucagon-like peptide-1.

CONCLUSION

Compared with normal weight peers, children and adolescents with overweight/obesity had elevated concentrations of fasting glucagon, which corresponded to worsened cardiometabolic risk outcomes, except for hyperglycemia. This suggests hyperglucagonemia in youth may precede impairments in glucose regulation.

The role of hyperinsulinaemia in screening for prediabetes in the adolescent population: A systematic literature review

BACKGROUND/AIMS

Present screening methods for Type 2 diabetes (T2DM) fall short of detecting prediabetes. This paper summarises the literature on the utility of insulin measurements (hyperinsulinemia) in detecting prediabetes in adolescents.

METHODS

A systematic literature review was conducted using EMBASE and Medline. Relevant data on hyperinsulinemia in the adolescent population is narrated.

RESULTS

The database search identified 174 potential articles; 106 underwent a full-paper review, and 36 were included.

CONCLUSION

Elevated fasting insulin is a marker of impaired insulin resistance and pending beta-cell dysfunction in at-risk adolescents and can be an early indicator of prediabetes.

Beta cell function, incretin hormones, and incretin effect in obese children and adolescents with prediabetes

BACKGROUND

Defects of incretin hormones and incretin effect may be underlying mechanisms of abnormal glucose metabolism in youth.

OBJECTIVE

To assess incretin hormone dynamics during an oral glucose tolerance test (OGTT) and incretin effect in obese children with prediabetes in comparison with those with normal glucose tolerance (NGT).

METHODS

Overweight and obese children were enrolled and classified according to OGTT results as NGT and prediabetes. Insulin sensitivity, insulin secretion, incretin hormone concentrations during OGTT; and incretin effect derived from OGTT and intravenous glucose tolerance test were determined and compared between NGT and prediabetes groups.

RESULTS

Sixty-three patients (43 NGT and 20 prediabetes) were enrolled. Their median (interquartile range) age was 12.5 (11.1, 13.8) years. Peak glucagon-like peptide-1 (GLP-1) was demonstrated at 30 min during OGTT and was higher in the prediabetes group (49.2 [35.6, 63.6] versus 36.5 [27.6, 44.2] pmol/L, p = 0.009). However, incremental areas under the curves (iAUCs) of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) were not different between the two groups. There was no difference in incretin effect between NGT and prediabetes (NGT: 66.5% [60.2%, 77.5%] vs. prediabetes: 70.0% [61.5%, 75.0%], p = 0.645). Incretin effect had positive correlations with iAUCs of both GLP-1 and GIP (GLP-1: r = 0.40, p = 0.004 and GIP: r = 0.37, p = 0.009).

CONCLUSIONS

Comparing between obese children with prediabetes and NGT, there were no differences in overall incretin hormone changes during OGTT and incretin effect. Incretin effect was positively correlated with iAUCs of GLP-1 and GIP.

Effects of Sambiloto (Andrographis paniculata) on GLP-1 and DPP-4 Concentrations between Normal and Prediabetic Subjects: A Crossover Study

Background. The extract of Andrographis paniculata (Burm. F.) Wall. Ex. Nees. (sambiloto) (穿心蓮 chuān xīn lián) has been reported to have an antidiabetic effect on mice models and has been used traditionally in the community. The exact mechanism of sambiloto extract in decreasing plasma glucose is unclear, so we investigated the role of sambiloto extract in the incretin pathway in healthy and prediabetic subjects. Methods. This study was a randomized, placebo-controlled, crossover, double-blind trial. It included 38 people who were healthy and 35 people who had prediabetes. All subjects were randomly assigned to receive either the intervention sambiloto extract or a placebo. All subjects were randomly assigned to receive the first intervention for 14 days. There was a washout period between subsequent interventions. The primary outcome was glucagon-like peptide 1 (GLP-1) concentration, and secondary outcomes were fasting insulin, 2-hour postprandial insulin, homeostasis model assessment of insulin resistance (HOMA-IR), fasting blood glucose, 2-hour postprandial blood glucose, dipeptidyl peptidase-4 (DPP-4), and glycated albumin before and after the intervention. Result. After the intervention, GLP-1 concentration significantly increased in prediabetes by 19.6% compared to the placebo ( $p=0.043$ ). There were no significant differences in the changes of fasting insulin, 2-hour postprandial insulin, HOMA-IR, fasting blood glucose, 2-hour postprandial blood glucose, DPP-4, and glycated albumin levels after the intervention. Sambiloto extract did not inhibit the DPP-4 enzyme in healthy and prediabetic subjects. Conclusion. Sambiloto extract increased GLP-1 concentration without inhibiting the DPP-4 enzyme in prediabetic subjects. This trial is registered with ClinicalTrials.gov (ID: NCT03455049), registered on 6 March 2018—retrospectively registered (https://clinicaltrials.gov/ct2/show/NCT03455049).

Incretin Hormones: Pathophysiological Risk Factors and Potential Targets for Type 2 Diabetes

Type 2 diabetes (T2D) is a multifaceted metabolic disorder associated with distinctive pathophysiological disturbances. One of the pathophysiological risk factors observed in T2D is dysregulation of the incretin hormones, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Both hormones stimulate insulin secretion by acting postprandially on pancreatic β-cell receptors. Oral glucose administration stimulates increased insulin secretion in comparison with isoglycemic intravenous glucose administration, a phenomenon known as the incretin effect. While the evidence for incretin defects in individuals with T2D is growing, the etiology behind this attenuated incretin effect in T2D is not clearly understood. Given their central role in T2D pathophysiology, incretins are promising targets for T2D therapeutics. The present review synthesizes the recent attempts to explain the biological importance of incretin hormones and explore potential pharmacological approaches that target the incretins.

The β Cell in Diabetes: Integrating Biomarkers With Functional Measures

The pathogenesis of hyperglycemia observed in most forms of diabetes is intimately tied to the islet β cell. Impairments in propeptide processing and secretory function, along with the loss of these vital cells, is demonstrable not only in those in whom the diagnosis is established but typically also in individuals who are at increased risk of developing the disease. Biomarkers are used to inform on the state of a biological process, pathological condition, or response to an intervention and are increasingly being used for predicting, diagnosing, and prognosticating disease. They are also proving to be of use in the different forms of diabetes in both research and clinical settings. This review focuses on the β cell, addressing the potential utility of genetic markers, circulating molecules, immune cell phenotyping, and imaging approaches as biomarkers of cellular function and loss of this critical cell. Further, we consider how these biomarkers complement the more long-established, dynamic, and often complex measurements of β-cell secretory function that themselves could be considered biomarkers.

New Insights on the Interactions Between Insulin Clearance and the Main Glucose Homeostasis Mechanisms

OBJECTIVE

Endogenous insulin clearance (EIC) is physiologically reduced at increasing insulin secretion rate (ISR). Computing EIC at the prevailing ISR does not distinguish the effects of hypersecretion from those of other mechanisms of glucose homeostasis. We aimed to measure EIC in standardized ISR conditions (i.e., at fixed ISR levels) and to analyze its associations with relevant physiologic factors.

RESEARCH DESIGN AND METHODS

We estimated standardized EIC (EIC_ISR) by mathematical modeling in nine different studies with insulin and glucose infusions (N = 2,067). EIC_ISR association with various traits was analyzed by stepwise multivariable regression in studies with both euglycemic clamp and oral glucose tolerance test (OGTT) (N = 1,410). We also tested whether oral glucose ingestion, as opposed to intravenous infusion, has an independent effect on EIC (N = 1,555).

RESULTS

Insulin sensitivity (as M/I from the euglycemic clamp) is the strongest determinant of EIC_ISR, approximately four times more influential than insulin resistance-related hypersecretion. EIC_ISR independently associates positively with M/I, fasting and mean OGTT glucose or type 2 diabetes, and β-cell glucose sensitivity and negatively with African American or Hispanic race, female sex, and female age. With oral glucose ingestion, an ISR-independent ∼10% EIC reduction is necessary to explain the observed insulin concentration profiles.

CONCLUSIONS

Based on EIC_ISR, we posit the existence of two adaptive processes involving insulin clearance: the first reduces EIC_ISR with insulin resistance (not with higher BMI per se) and is more relevant than the concomitant hypersecretion; the second reduces EIC_ISR with β-cell dysfunction. These processes are dysregulated in type 2 diabetes. Finally, oral glucose ingestion per se reduces insulin clearance.

Treatment of type 2 diabetes in children: what are the specific considerations?

Introduction: The number of individuals under 18 years of age with type 2 diabetes is increasing at an alarming rate worldwide. These patients are often characterized by obesity and they often experience a more rapid disease progression than adults with type 2 diabetes. Thus, focus on prevention and management of complications and comorbidities is imperative. With emphasis on weight loss and optimal glycemic control, treatment includes lifestyle changes and pharmacotherapy, which in this patient group is limited to metformin, liraglutide and insulin. In selected cases, bariatric surgery is indicated.Areas covered: This perspective article provides an overview of the literature covering pathophysiology, diagnosis, characteristics and treatment of pediatric type 2 diabetes, and outlines the gaps in our knowledge where further research is needed. The paper draws on both mechanistic studies, large scale intervention trials, epidemiological studies and international consensus statements.Expert opinion: Type 2 diabetes in pediatric patients is an increasing health care problem, and the current treatment strategies do not successfully meet the many challenges and obstacles in this patient group. Treatments must be early, intensive, multifaceted and durable. Also, prevention of obesity and type 2 diabetes in at-risk children should be addressed and prioritized on all levels.

Early Impairment of Insulin Sensitivity, β-Cell Responsiveness, and Insulin Clearance in Youth with Stage 1 Type 1 Diabetes

CONTEXT

Clinical onset of type 1 diabetes (Stage 3 T1D) is preceded by a presymptomatic phase characterized by multiple islet autoantibodies with normal glucose tolerance (Stage 1 T1D).

OBJECTIVE

The aim was to explore the metabolic phenotypes of β-cell function and insulin sensitivity and clearance in normoglycemic youth with Stage 1 T1D and compare them with healthy nonrelated peers during a 3-hour oral glucose tolerance test (OGTT).

METHODS

Twenty-eight lean youth, 14 with ≥2 islet autoantibodies (cases) and 14 healthy controls underwent a 3-hour 9-point OGTT with measurement of glucose, C-peptide, and insulin. The oral minimal model was used to quantitate β-cell responsiveness (φtotal) and insulin sensitivity (SI), allowing assessment of β-cell function by the disposition index (DI=φtotal×SI). Fasting insulin clearance (CL0) was calculated as the ratio between the fasting insulin secretion rate (ISR) and plasma insulin levels (ISR0/I0), while postload clearance (CL180) was estimated by the ratio of AUC of ISR over the plasma insulin AUC for the 3-hour OGTT (ISRAUC/IAUC). Participants with impaired fasting glucose, impaired glucose tolerance, or any OGTT glucose concentration ≥200 mg/dL were excluded.

RESULTS

Cases (10.5 years [8, 15]) exhibited reduced DI (P < .001) due to a simultaneous reduction in both φtotal (P < 0.001) and SI (P = .008) compared with controls (11.5 years [10.4, 14.9]). CL0 and CL180 were lower in cases than in controls (P = .005 and P = .019).

CONCLUSION

Presymptomatic Stage 1 T1D in youth is associated with reduced insulin sensitivity and lower β-cell responsiveness, and the presence of blunted insulin clearance.

Glucose-induced insulin secretion in isolated human islets: Does it truly reflect β-cell function in vivo?

BACKGROUND

Diabetes always involves variable degrees of β-cell demise and malfunction leading to insufficient insulin secretion. Besides clinical investigations, many research projects used rodent islets to study various facets of β-cell pathophysiology. Their important contributions laid the foundations of steadily increasing numbers of experimental studies resorting to isolated human islets.

SCOPE OF REVIEW

This review, based on an analysis of data published over 60 years of clinical investigations and results of more recent studies in isolated islets, addresses a question of translational nature. Does the information obtained in vitro with human islets fit with our knowledge of insulin secretion in man? The aims are not to discuss specificities of pathways controlling secretion but to compare qualitative and quantitative features of glucose-induced insulin secretion in isolated human islets and in living human subjects.

MAJOR CONCLUSIONS

Much of the information gathered in vitro can reliably be translated to the in vivo situation. There is a fairly good, though not complete, qualitative and quantitative coherence between insulin secretion rates measured in vivo and in vitro during stimulation with physiological glucose concentrations, but the concordance fades out under extreme conditions. Perplexing discrepancies also exist between insulin secretion in subjects with Type 2 diabetes and their islets studied in vitro, in particular concerning the kinetics. Future projects should ascertain that the experimental conditions are close to physiological and do not alter the function of normal and diabetic islets.

β-cells in youth with impaired glucose tolerance or early type 2 diabetes secrete more insulin and are more responsive than in adults

OBJECTIVE

Glycemic control deteriorates more rapidly in youth vs adults. We compared model-derived measures of β-cell function between youth and adults with either impaired glucose tolerance (IGT) or type 2 diabetes to determine if a β-cell defect differentiates these age groups.

METHODS

This is a cross-sectional analysis of baseline data from the Restoring Insulin Secretion (RISE) Study. Youth (54 Y-IGT, 33 Y-D) and adults (250 A-IGT, 104 A-D) underwent 3-hour oral glucose tolerance tests for modeling of insulin secretion rates (ISRs), glucose sensitivity, and rate sensitivity. Insulin sensitivity was quantified as the glucose infusion rate/insulin (M/I) from a hyperglycemic clamp.

RESULTS

Youth had lower insulin sensitivity despite similar body mass index. Analyses were adjusted for insulin sensitivity. Youth had higher basal ISRs (Y-IGT 200 ± 161 vs A-IGT 152 ± 74, P < .001; Y-D 245 ± 2.5 vs A-D 168 ± 115 pmol/min/m² , P = .007) and total ISRs (Y-IGT 124 ± 86 vs A-IGT 98 ± 39, P < .001; Y-D 116 ± 110 vs A-D 97 ± 62 nmol/m² , P = .002). Within IGT, glucose sensitivity (Y-IGT 140 ± 153 vs A-IGT 112 ± 70 pmol/min/m² /mM, P = .004) and rate sensitivity (median[interquartile range]:Y-IGT 2271[1611, 3222] vs A-IGT 1164[685, 1565] pmol/m² /mM, P < .001) were higher in youth, but not different by age group within diabetes.

CONCLUSIONS

Model-derived measures of β-cell function provide additional insight into the pathophysiology of type 2 diabetes in youth with higher ISRs and β-cell secretion more responsive to glucose in youth relative to adults even after adjusting for differences in insulin sensitivity. It is unknown whether these findings in youth reflect β-cells that are healthier or whether this is a defect that contributes to more rapid loss of function.

Early beta cell dysfunction vs insulin hypersecretion as the primary event in the pathogenesis of dysglycaemia

Obesity and insulin resistance are associated with the development of type 2 diabetes. It is well accepted that beta cell dysfunction is required for hyperglycaemia to occur. The prevailing view is that, in the presence of insulin resistance, beta cell dysfunction that occurs early in the course of the disease process is the critical abnormality. An alternative model has been proposed in which primary beta cell overstimulation results in insulin hypersecretion that then leads to the development of obesity and insulin resistance, and ultimately to beta cell exhaustion. In this review, data from preclinical and clinical studies, including intervention studies, are discussed in the context of these models. The preponderance of the data supports the view that an early beta cell functional defect is the more likely mechanism underlying the pathogenesis of hyperglycaemia in the majority of individuals who develop type 2 diabetes. Graphical abstract.

A Reduced Incretin Effect Mediated by the rs7903146 Variant in the TCF7L2 Gene Is an Early Marker of β-Cell Dysfunction in Obese Youth

OBJECTIVE

The risk genotype for the common variant rs7903146 of the transcription factor 7-like-2 (TCF7L2) gene has been found to affect the incretin response in healthy and obese adults; however, whether a similar functional defect is also present in obese adolescents remains unexplored. Herein, we examined the functional effect of the rs7903146 variant in the TCF7L2 gene on the incretin effect and determined its translational metabolic manifestation by performing deep phenotyping of the incretin system, β-cell function relative to insulin sensitivity, the gastrointestinal-induced glucose disposal (GIGD) in obese youth with normal and impaired glucose tolerance.

RESEARCH DESIGN AND METHODS

Thirty-nine obese adolescents without diabetes (median age 15 [25th, 75th percentile 14, 18] years; BMI 37 [33, 43] kg/m²) were genotyped for the rs7903146 variant of TCF7L2 and underwent a 3-h oral glucose tolerance test (OGTT) followed by an isoglycemic intravenous glucose infusion (iso-intravenous glucose tolerance test [IVGTT]) to match the plasma glucose concentrations during the OGTT and a hyperglycemic clamp with arginine stimulation. The incretin effect was measured as 100 * (AUC-SR_OGTT - AUC-SR_iso-IVGTT) / AUC-SR_OGTT, where AUC-SR = area under the curve of C-peptide secretion rate. Participants were grouped into tertiles according to the percentage incretin effect (high, moderate, and low) to describe their metabolic phenotype.

RESULTS

The presence of T risk allele for TCF7L2 was associated with a markedly reduced incretin effect compared with the wild-type genotype (0.3% [-7.2, 14] vs. 37.8% [12.5, 52.4], P < 0.002). When the cohort was stratified by incretin effect, the high, moderate, and low incretin effect groups did not differ with respect to anthropometric features, while the low incretin effect group exhibited higher 1-h glucose (P = 0.015) and a reduced disposition index, insulin sensitivity, and insulin clearance compared with the high incretin effect group. GIGD was reduced in the low incretin effect group (P = 0.001). The three groups did not differ with respect to intravenous glucose-induced insulin secretion and arginine response during the hyperglycemic clamp.

CONCLUSIONS

A reduced incretin effect and its association with the TCF7L2 variant rs7903146 identify an early metabolic phenotype in obese youth without diabetes, featuring a higher plasma glucose peak at 1 h; lower insulin secretion, sensitivity, and clearance; and GIGD.

Circulating unmethylated CHTOP and INS DNA fragments provide evidence of possible islet cell death in youth with obesity and diabetes

BACKGROUND

Identification of islet β cell death prior to the onset of type 1 diabetes (T1D) or type 2 diabetes (T2D) might allow for interventions to protect β cells and reduce diabetes risk. Circulating unmethylated DNA fragments arising from the human INS gene have been proposed as biomarkers of β cell death, but this gene alone may not be sufficiently specific to report β cell death.

RESULTS

To identify new candidate genes whose CpG sites may show greater specificity for β cells, we performed unbiased DNA methylation analysis using the Infinium HumanMethylation 450 array on 64 human islet preparations and 27 non-islet human tissues. For verification of array results, bisulfite DNA sequencing of human β cells and 11 non-β cell tissues was performed on 5 of the top 10 CpG sites that were found to be differentially methylated. We identified the CHTOP gene as a candidate whose CpGs show a greater frequency of unmethylation in human islets. A digital PCR strategy was used to determine the methylation pattern of CHTOP and INS CpG sites in primary human tissues. Although both INS and CHTOP contained unmethylated CpG sites in non-islet tissues, they occurred in a non-overlapping pattern. Based on Naïve Bayes classifier analysis, the two genes together report 100% specificity for islet damage. Digital PCR was then performed on cell-free DNA from serum from human subjects. Compared to healthy controls (N = 10), differentially methylated CHTOP and INS levels were higher in youth with new onset T1D (N = 43) and, unexpectedly, in healthy autoantibody-negative youth who have first-degree relatives with T1D (N = 23). When tested in lean (N = 32) and obese (N = 118) youth, increased levels of unmethylated INS and CHTOP were observed in obese individuals.

CONCLUSION

Our data suggest that concurrent measurement of circulating unmethylated INS and CHTOP has the potential to detect islet death in youth at risk for both T1D and T2D. Our data also support the use of multiple parameters to increase the confidence of detecting islet damage in individuals at risk for developing diabetes.

Metabolic features and changes in glucose-induced serum glucagon-like peptide-1 levels in children with hypothalamic obesity

Background Hypothalamic damage may alter glucagon-like peptide-1 (GLP-1) secretion and be involved in the pathogenesis of obesity. We aim to evaluate the metabolic features and the dynamic changes of GLP-1 levels during an oral glucose tolerance test (OGTT) in children with hypothalamic obesity (HO) compared with simple obesity controls. Methods Subjects included eight patients (six females, aged 9-16 years) with hypothalamo-pituitary tumors who later developed obesity and eight controls with simple obesity matched for age, body mass index (BMI), gender and puberty. We assessed the metabolic syndrome features, fat mass, severity of hyperphagia using a standardized questionnaire, and measured glucose, insulin and GLP-1 levels during a standard 75 g OGTT. Results Age, gender distribution, pubertal status and BMI-Z scores were not significantly different. Subjects with HO had higher fasting triglycerides (TG) than controls (128 vs. 94 mg/dL; p=0.05). Four HO subjects and three controls met the criteria for the metabolic syndrome. Fasting and 120 min post-glucose load GLP-1 levels were significantly higher in HO patients than in controls (21.9 vs. 19.7 pg/mL; p=0.025, 22.1 vs. 17.7 pg/mL; p=0.012). Patients with HO had significantly higher hyperphagia scores than in simple obese controls (13 vs. 2.5; p=0.012). Conclusions Patients with HO appear to have more metabolic complications and hyperphagia than controls with simple obesity. Impaired satiety may play an important role in HO. Fasting and glucose-induced serum GLP-1 concentrations seem to be altered in HO patients and could be a part of the pathogenesis of HO.

β-cell function, incretin response, and insulin sensitivity of glucose and fat metabolism in obese youth: Relationship to OGTT-time-to-glucose-peak

BACKGROUND

In adults, the time-to-glucose-peak at or after 30 minutes during an oral glucose tolerance test (OGTT) identifies physiologically distinct groups with differences in insulin sensitivity, β-cell function and risk for type 2 diabetes. In obese non-diabetic adolescents, we investigated if the OGTT-time-to-glucose-peak also reflects incretin and free fatty acid (FFA) responses besides insulin sensitivity and β-cell function, measured by the clamp.

METHODS

Obese adolescents (n = 278) were categorized according to their OGTT-time-to-glucose-peak by Early-peak (at 30 minutes) vs Late-peak (>30 minutes) groups. Body composition, visceral adipose tissue, oral disposition index and OGTT-area under the curve (AUC) were examined. A subset of 102 participants had both hyperinsulinemic-euglycemic and hyperglycemic clamps to measure in vivo insulin sensitivity, insulin secretion, and β-cell function relative to insulin sensitivity.

RESULTS

Compared with the Early-peak group, the Late-peak group had impaired β-cell function relative to insulin sensitivity, lower glucose-dependent insulinotropic polypeptide-AUC, and higher FFA-AUC despite higher insulin- and C-peptide-AUC. They also had lower hepatic and peripheral insulin sensitivity despite similar percent body fat and visceral adipose tissue, and had higher prevalence of impaired glucose tolerance (all P < .05).

CONCLUSIONS

In obese non-diabetic youth, those with a Late-peak vs an Early-peak glucose during an OGTT showed diminished β-cell function, blunted incretin secretion, and lower insulin sensitivity of glucose and FFA metabolism. It remains to be determined if Late-peak glucose predicts the future development of type 2 diabetes in these high-risk youth.

Metabolic outcomes of surgery in youth with type 2 diabetes

Youth-onset type 2 diabetes (T2D) is a formidable threat to the health of obese adolescents because of its potential for early-onset and aggressive co-morbidities and complications. The physiology of youth-onset T2D differs from T2D in adults and is associated with a greater degree of insulin resistance, a more rapid decline in pancreatic β-cell function, and a poorer response to medications. Medical management in youth is focused on combining lifestyle intervention and pharmacological treatment, but these therapies have yet to demonstrate improvements in disease progression. Metabolic bariatric surgery (MBS) is now recommended for the treatment of T2D in adults largely because of the beneficial effects on weight, ability to improve glycemic control, and, in a large proportion of people, induce diabetes remission. MBS is now being performed in adolescents with severe obesity and T2D, with initial results also showing high rates of T2D remission. Here, we review the state of medical management of youth-onset T2D and the outcomes of MBS studies in youth with T2D published to date.

Pathophysiology of Type 2 Diabetes in Children and Adolescents

BACKGROUND

The prevalence of type 2 diabetes (DM) in children is disturbingly increasing in parallel with the increasing childhood obesity. Better knowledge regarding the pathophysiology of type 2 DM in children is paramount to devise an effective management plan.

OBJECTIVE

Discuss the pathophysiology of type 2 DM in children and adolescents.

METHODS AND RESULTS

This is a comprehensive review of the literature on this topic. Type 2 DM in childhood is viewed as a continuum of insulin resistance (IR) which is determined by an underlying genetic predisposition, intrauterine environment, excessive food consumption, continued rapid weight gain, and poor lifestyle. Besides IR, this is compounded by multiple metabolic defects including β-cell dysfunction and inadequate insulin secretion, α-cell dysfunction, hyperglucagonemia and increased hepatic glucose production, lipotoxicity, inflammation, deficiencies in incretin production and action, and increased renal glucose reabsorption. The confluence of genetic and environmental factors underscores the complexity in disease progression.

CONCLUSION

A consistent single risk factor for type 2 DM is obesity and related IR and therefore it is essential to curtail the progression of obesity. It is important to investigate the role of stringent dietary and nutritional approaches, medications that enhance β-cell function and insulin sensitivity.

β-Cell function in obese children and adolescents with metabolic syndrome compared to isolated obesity

OBJECTIVE

To evaluate β-cell function in obese children and adolescents meeting clinical criteria for isolated obesity (iOB), isolated components of dysmetabolism (cMD), or metabolic syndrome (MS), and in obese children and adolescents with normal glucose tolerance (NGT), impaired glucose regulation (IGR), or type 2 diabetes (T2DM).

STUDY DESIGN

We undertook a prospective study of Han Chinese children and adolescents aged 8-16 years (median 11 ± 1.4) seen in an obesity clinic between May 2013 and 2018. Patients were classified as iOB (53), cMD (139), and MS (139) groups based on clinical criteria. The same patients were also classified as NGT (212), IGR (111), or T2DM (8) based on results of an oral glucose tolerance test (OGTT). The MS patients were classified as NGT [MS](59) and IGR [MS](72) for the further study. All participants also completed a mixed-meal tolerance test (MMTT).

RESULTS

Compared with the iOB group, the MS group had significantly higher area under the curve of C-peptide up to the 2 hours (AUC CP) (P = .03) and peak C-peptide (P = .03), adjusted for BMI, age and Tanner stage, on MMTT. However, there was no difference in the insulinogenic index (ΔI30/ΔG30) or oral disposition index (oDI) derived from the OGTT among the three groups. However, 52% of participants with MS had IGR, compared to 28% in the cMD group. Compared with the NGT group, the individuals with IGR had significantly lower ΔI30/ΔG30 (P = .001) and oDI (P < .001). Compared with the iOB group, the NGT[MS] had significantly higher AUC CP (P = .004), peak C-peptide (P = .004) and ΔI30/ΔG30 (P = .007) adjusted for age, but no difference in oDI. Compared with the NGT[MS], the IGR[MS] had significantly lower ΔI30/ΔG30 (P = .005) and oDI (P < .001), but the AUC CP and peak C-peptide had no difference.

CONCLUSION

Although the MS youth have β-cell hyperfunction as a whole, β-cell dysfunction is present in the early stages of dysmetabolism in obese youth with cMD or MS and worsened across the spectrum from iOB to cMD and MS, contributing to development of T2DM.

Hyperglucagonemia in youth is associated with high plasma free fatty acids, visceral adiposity, and impaired glucose tolerance

OBJECTIVE

To delineate potential mechanisms for fasting hyperglucagonemia in childhood obesity by studying the associations between fasting plasma glucagon concentrations and plasma lipid parameters and fat compartments.

METHODS

Cross-sectional study of children and adolescents with obesity (n = 147) and lean controls (n = 43). Differences in free fatty acids (FFAs), triglycerides, insulin, and fat compartments (quantified by magnetic resonance imaging) across quartiles of fasting plasma glucagon concentration were analyzed. Differences in oral glucose tolerance test (OGTT) glucagon response was tested in high vs low FFAs, triglycerides, and insulin. Human islets of Langerhans were cultured at 5.5 mmol/L glucose and in the absence or presence of a FFA mixture with total FFA concentration of 0.5 mmol/L and glucagon secretion quantified.

RESULTS

In children with obesity, the quartile with the highest fasting glucagon had higher insulin (201 ± 174 vs 83 ± 39 pmol/L, P < .01), FFAs (383 ± 52 vs 338 ± 109 μmol/L, P = .02), triglycerides (1.5 ± 0.9 vs 1.0 ± 0.7 mmol/L, P < .01), visceral adipose tissue volume (1.9 ± 0.8 vs 1.2 ± 0.3 dm³ , P < .001), and a higher prevalence of impaired glucose tolerance (IGT; 41% vs 8%, P = .01) than the lowest quartile. During OGTT, children with obesity and high insulin had a worse suppression of glucagon during the first 10 minutes after glucose intake. Glucagon secretion was 2.6-fold higher in islets treated with FFAs than in those not treated with FFAs.

CONCLUSIONS

Hyperglucagonemia in childhood obesity is associated with hyperinsulinemia, high plasma FFAs, high plasma triglycerides, visceral adiposity, and IGT. The glucagonotropic effect of FFAs on isolated human islets provides a potential mechanism linking high fasting plasma FFAs and glucagon levels.

Lower Insulin Clearance Parallels a Reduced Insulin Sensitivity in Obese Youths and Is Associated With a Decline in β-Cell Function Over Time

We examined the relationship between insulin clearance, insulin sensitivity, and β-cell function and the longitudinal effect of insulin clearance on β-cell function in lean and obese insulin-sensitive and insulin-resistant adolescents. A hyperinsulinemic-euglycemic and a hyperglycemic clamp were performed in 110 youths to quantify hepatic and peripheral clearance, insulin sensitivity, and β-cell function (disposition index, DI_h-clamp). Participants underwent an oral glucose tolerance test at baseline and after 2 years to assess glucose tolerance and oral β-cell function (oDI_cpep) and were sorted into four groups (lean and obese normal glucose tolerance, insulin sensitive, insulin resistant, and impaired glucose tolerance). Insulin sensitivity was defined based on the median of insulin stimulated glucose disposal (M) measured during the hyperinsulinemic-euglycemic clamp. Lean and obese insulin-sensitive participants did not differ with respect to hepatic and peripheral clearance or for insulin sensitivity. Insulin sensitivity was linearly correlated with whole-body insulin clearance. Hepatic insulin extraction at baseline acted as an independent determinant of β-cell function at follow-up. The decline in insulin sensitivity, even in the absence of an impairment of glucose tolerance, is associated with lowering of hepatic insulin clearance in obese youth, which in turn may contribute to the decline in β-cell function over time.

Postprandial Reactive Hypoglycemia

Reactive hypoglycemia (RH) is the condition of postprandially hypoglycemia occurring 2-5 hours after food intake. RH is clinically seen in three different forms as follows: idiopathic RH (at 180 min), alimentary (within 120 min), and late RH (at 240–300 min). When the first-phase insulin response decreases, firstly, blood glucose starts to rise after the meal. This leads to late but excessive secretion of the second-phase insulin secretion. Thus, late reactive hypoglycemia occurs. Elevated insulin levels also cause down-regulation of the insulin post-receptor on the muscle and fat cells, thus decreasing insulin sensitivity. The cause of the increase in insulin sensitivity in IRH at 3 h is not completely clear. However, there is a decrease in insulin sensitivity in late reactive hypoglycaemia at 4 or 5 hours. Thus, patients with hypoglycemia at 4 or 5 h who have a family history of diabetes and obesity may be more susceptible to diabetes than patients with hypoglycemia at 3 h. We believe that some cases with normal glucose tolerance in OGTT should be considered as prediabetes at <55 or 60 mg/dl after 4-5 hours after OGTT. Metformin and AGI therapy may be recommended if there is late RH with IFG. Also Metformin, AGİ, TZD, DPP-IVInhibitors, GLP1RA therapy may be recommended if there is late RH with IGT. As a result, postprandial RH (<55 or 60 mg/dl), especially after 4 hours may predict diabetes. Therefore, people with RH along with weight gain and with diabetes history in the family will benefit from a lifestyle modification as well as the appropriate antidiabetic approach in the prevention of diabetes.

Fructose Consumption Contributes to Hyperinsulinemia in Adolescents With Obesity Through a GLP-1-Mediated Mechanism

CONTEXT

The consumption of high-fructose beverages is associated with a higher risk for obesity and diabetes. Fructose can stimulate glucagon-like peptide 1 (GLP-1) secretion in lean adults, in the absence of any anorexic effect.

OBJECTIVE

We hypothesized that the ingestion of glucose and fructose may differentially stimulate GLP-1 and insulin response in lean adolescents and adolescents with obesity.

DESIGN

We studied 14 lean adolescents [four females; 15.9 ± 1.6 years of age; body mass index (BMI), 21.8 ± 2.2 kg/m2] and 23 adolescents with obesity (five females; 15.1 ± 1.6 years of age; BMI, 34.5 ± 4.6 kg/m2). Participants underwent a baseline oral glucose tolerance test to determine their glucose tolerance and estimate insulin sensitivity and β-cell function [oral disposition index (oDIcpep)]. Eligible subjects received, in a double-blind, crossover design, 75 g of glucose or fructose. Plasma was obtained every 10 minutes for 60 minutes for the measures of glucose, insulin, and GLP-1 (radioimmunoassay) and glucose-dependent insulinotropic polypeptide (GIP; ELISA). Incremental glucose and hormone levels were compared between lean individuals and those with obesity by a linear mixed model. The relationship between GLP-1 increment and oDIcpep was evaluated by regression analysis.

RESULTS

Following the fructose challenge, plasma glucose excursions were similar in both groups, yet the adolescents with obesity exhibited a greater insulin (P < 0.001) and GLP-1 (P < 0.001) increase than did their lean peers. Changes in GIP were similar in both groups. After glucose ingestion, the GLP-1 response (P < 0.001) was higher in the lean group. The GLP-1 increment during 60 minutes from fructose drink was correlated with a lower oDIcpep (r2 = 0.22, P = 0.009).

CONCLUSION

Fructose, but not glucose, ingestion elicits a higher GLP-1 and insulin response in adolescents with obesity than in lean adolescents. Fructose consumption may contribute to the hyperinsulinemic phenotype of adolescent obesity through a GLP-1-mediated mechanism.

Identification, pathophysiology, and clinical implications of primary insulin hypersecretion in nondiabetic adults and adolescents

BACKGROUND

Excessive insulin secretion may lead to glucose dysregulation. Our aim was to identify primary (independent of insulin resistance) insulin hypersecretion in subjects with normal glucose tolerance and its role in the progression of dysglycemia.

METHODS

In 1,168 adults, insulin secretion rate (ISR) and β cell function were estimated by C-peptide modeling during an oral glucose tolerance test (OGTT) and an i.v. glucose tolerance test. Whole-body insulin sensitivity was measured by a hyperinsulinemic-euglycemic clamp. After regressing ISR on insulin sensitivity, subjects in the upper tertile of the distribution of residuals were defined as primary hypersecretors. This approach was applied to a biethnic cohort of 182 obese adolescents, who received an OGTT, a hyperglycemic, and a euglycemic clamp.

RESULTS

Adult hypersecretors showed older age, more familial diabetes, sedentary lifestyle, increased fat mass, and worse lipid profile compared with the rest of the cohort, despite virtually identical BMI and insulin sensitivity. Insulin secretion was increased by 53% due to enhanced (+23%) β cell glucose sensitivity. Despite the resulting hyperinsulinemia, glucose tolerance was worse in hypersecretors among both adults and adolescents, coupled with higher indices of liver insulin resistance and increased availability of gluconeogenic substrates. At the 3-year follow-up, adult hypersecretors had increased incidence of impaired glucose tolerance/type 2 diabetes.

CONCLUSION

Primary insulin hypersecretion, independent of insulin resistance, is associated with a worse clinical and metabolic phenotype in adults and adolescents and predicts deterioration of glucose control over time.

FUNDING

The relationship between insulin sensitivity and cardiovascular disease (RISC) Study was partly supported by EU grant QLG1-CT-2001-01252.

High DPP-4 Concentrations in Adolescents Are Associated With Low Intact GLP-1

CONTEXT

Dipeptidyl peptidase 4 (DPP-4) metabolizes glucagon-like peptide-1 (GLP-1), and increased DPP4 levels are associated with obesity and visceral adiposity in adults.

OBJECTIVE

Investigating DPP-4 levels in adolescents and their association with (1) circulating intact GLP-1 levels and glucose tolerance; (2) body mass index (BMI); and (3) visceral, subcutaneous, and liver fat compartments.

DESIGN

Cross-sectional study, July 2012 to April 2015.

SETTING

Pediatric obesity clinic, Uppsala University Hospital.

PATIENTS AND PARTICIPANTS

Children and adolescents with obesity (n = 59) and lean controls (n = 21) aged 8 to 18 years.

MAIN OUTCOME MEASURES

BMI SD score, fasting plasma concentrations of DPP-4, total and intact GLP-1, fasting and oral glucose tolerance test (OGTT) concentrations of glucose, and visceral adipose tissue (VAT) and subcutaneous adipose tissue volumes and liver fat fraction.

RESULTS

Plasma DPP-4 levels decreased with age in both obese (41 ng/mL per year) and lean subjects (48 ng/mL per year). Plasma DPP-4 levels were higher in males in both the obesity and lean groups. With adjustments for age and sex, plasma DPP-4 level was negatively associated with intact GLP-1 at fasting (β = -12.3; 95% CI: -22.9, -1.8) and during OGTT (β = -12.1; 95% CI: -22.5, -1.7). No associations were found between DPP-4 and plasma glucose levels measured at fasting or after a 2-hour OGTT. Plasma DPP-4 level was 19% higher in obese subjects. Among adipose tissue compartments, the strongest association was with VAT (β = 0.05; 95% CI: -0.02, 0.12).

CONCLUSIONS

In adolescents, high plasma DPP-4 concentrations were associated with low proportions of intact GLP-1, high BMI, young age, and male sex. The observed associations are compatible with increased metabolism of GLP-1 in childhood obesity.

Methods for Measuring Risk for Type 2 Diabetes in Youth: the Oral Glucose Tolerance Test (OGTT)

PURPOSE OF REVIEW

The oral glucose tolerance test (OGTT) is used both in clinical practice and research to assess glucose tolerance. In addition, the OGTT is utilized for surrogate measures of insulin sensitivity and the insulin response to enteral glucose and has been widely applied in the evaluation of β-cell dysfunction in obesity, prediabetes, and type 2 diabetes. Here we review the use of the OGTT and the OGTT-derived indices for measurement of risk markers for type 2 diabetes in youth.

RECENT FINDINGS

Advantages of using the OGTT for measures of diabetes risk include its accessibility and the incorporation of physiological contributions of the gut-pancreas axis in the measures of insulin response to glucose. Mathematical modeling expands the potential gains from the OGTT in physiology and clinical research. Disadvantages include individual differences in the rate of glucose absorption that modify insulin responses, imperfect control of the glycemic stimulus, and poor intraindividual reproducibility. Available research suggests the OGTT provides valuable information about the development of impaired glycemic control and β-cell function in obese youth along the spectrum of glucose tolerance.

Oral Glucose Tolerance Test Glucose Peak Time Is Most Predictive of Prediabetes and Hepatic Steatosis in Obese Girls

Obese adolescent girls are at increased risk for type 2 diabetes, characterized by defects in insulin secretion and action. We sought to determine if later glucose peak timing (>30 minutes), 1-hour glucose >155 mg/dl, or monophasic pattern of glucose excursion during an oral glucose tolerance test (OGTT) reflect a worse cardiometabolic risk profile. Post-pubertal overweight/obese adolescent girls without diabetes were studied (N = 88; age, 15.2 ± 0.2 years; body mass index percentile, 97.7 ± 0.5). All participants completed an OGTT and body composition measures. Thirty-two girls had a four-phase hyperinsulinemic euglycemic clamp with isotope tracers, vascular imaging, and muscle mitochondrial assessments. Participants were categorized by glucose peak timing (≤30 min = early; >30 min = late), 1-hour glucose concentration (±155 mg/dL) and glucose pattern (monophasic, biphasic). Girls with a late (N = 54) vs earlier peak (n = 34) timing had higher peak glucose (P < 0.001) and insulin (P = 0.023), HbA1c (P = 0.021); prevalence of hepatic steatosis (62% vs 26%; P = 0.003) and lower oral disposition index (P < 0.001) and glucagon-like peptide-1 response (P = 0.037). When classified by 1-hour glucose, group differences were similar to peak timing, but minimal when classified by glucose pattern. In the >155 mg/dL group only, peripheral insulin sensitivity and fasting free fatty acids were worse. A later glucose peak or >155 mg/dL 1-hour glucose predicts metabolic disease risk in obese adolescent girls. This may defect incretin effects and first phase insulin response, and muscle and adipose insulin resistance.

Oral Glucose Tolerance Test Glucose Peak Time Is Most Predictive of Prediabetes and Hepatic Steatosis in Obese Girls

Obese adolescent girls are at increased risk for type 2 diabetes, characterized by defects in insulin secretion and action. We sought to determine if later glucose peak timing (>30 minutes), 1-hour glucose >155 mg/dl, or monophasic pattern of glucose excursion during an oral glucose tolerance test (OGTT) reflect a worse cardiometabolic risk profile. Post-pubertal overweight/obese adolescent girls without diabetes were studied (N = 88; age, 15.2 ± 0.2 years; body mass index percentile, 97.7 ± 0.5). All participants completed an OGTT and body composition measures. Thirty-two girls had a four-phase hyperinsulinemic euglycemic clamp with isotope tracers, vascular imaging, and muscle mitochondrial assessments. Participants were categorized by glucose peak timing (≤30 min = early; >30 min = late), 1-hour glucose concentration (±155 mg/dL) and glucose pattern (monophasic, biphasic). Girls with a late (N = 54) vs earlier peak (n = 34) timing had higher peak glucose (P < 0.001) and insulin (P = 0.023), HbA1c (P = 0.021); prevalence of hepatic steatosis (62% vs 26%; P = 0.003) and lower oral disposition index (P < 0.001) and glucagon-like peptide-1 response (P = 0.037). When classified by 1-hour glucose, group differences were similar to peak timing, but minimal when classified by glucose pattern. In the >155 mg/dL group only, peripheral insulin sensitivity and fasting free fatty acids were worse. A later glucose peak or >155 mg/dL 1-hour glucose predicts metabolic disease risk in obese adolescent girls. This may defect incretin effects and first phase insulin response, and muscle and adipose insulin resistance.

Targeting postprandial glycaemia in children with diabetes: Opportunities and challenges

Postprandial glycaemia makes a substantial contribution to overall glycaemic control in diabetes, particularly in patients whose preprandial glycaemia is relatively well controlled and glycated haemoglobin (HbA1c) only modestly elevated. Our review addresses the determinants of postprandial glycaemia and how it may be targeted therapeutically in children with diabetes. Postprandial glycaemia is influenced by preprandial glycaemia, macronutrients and their absorption, insulin delivery and sensitivity, the action of the enteroendocrine system, and the rate of gastric emptying. Contemporary continuous glucose monitoring systems reveal patterns of post prandial glycaemia and allow management to be guided more precisely. Delays in blood glucose determination, insulin delivery and its absorption remain challenges in the rapidly evolving closed loop continuous subcutaneous insulin and glucagon delivery systems developed for children with type 1 diabetes. Augmentation of the incretin system through nutritional preloads or incretin mimetics targets postprandial glycaemia by slowing gastric emptying as well as insulinotropic and glucagonostatic effects. These treatments are of particular relevance to children with type 2 diabetes. Following the development of targeted therapies in adults, postprandial blood glucose control will now be increasingly targeted in the treatment of diabetes in children.

Inside out the Ragbag of Glucose Intolerance in Obese Adolescents

BACKGROUND/AIMS

The prevalence of impaired glucose tolerance (IGT) is rising among obese adolescents in parallel with epidemic obesity. In some cases, IGT reverts to normal glucose tolerance (NGT) by the end of puberty. The aims of the present study were to investigate metabolic factors determining changes over time of glucose at 120 min (Glu120) following an oral glucose tolerance test (OGTT), and to verify whether preserved β-cell glucose sensitivity (βCGS) protects against persistent IGT.

METHODS

We performed a cohort study of 153 severely obese children and adolescents evaluated with a 5-point OGTT at baseline and at follow-up with measurements of glucose, insulin, and C-peptide to estimate several empirical parameters of insulin sensitivity (includ ing oral glucose insulin sensitivity [OGIS] and OGTT-derived glucose effectiveness) and secretion.

RESULTS

At follow-up (range 0.9-4.8 year), 113 (73.9%) patients remained with NGT, 9 (5.9%) had IGT, and 28 (18.3%) had reverted to NGT; 3 NGT patients had developed IGT. In multivariable models, change in loge(βCGS) was inversely associated with time-related change in loge(Glu120), with (model 2) and without (model 1) correction for the change in loge(OGIS). Model 2 was more strongly associated with change in loge(Glu120).

CONCLUSIONS

Changes in βCGS and insulin sensitivity were inversely associated with changes in Glu120 at follow-up, contributing a likely explanation for the reversal of IGT to NGT.

Insulin sensitivity across the lifespan from obese adolescents to obese adults with impaired glucose tolerance: Who is worse off?

OBJECTIVE

Youth type 2 diabetes mellitus (T2DM) occurs decades earlier than adult T2DM and is characterized by high therapeutic failure rates and decreased response to insulin sensitizers suggesting a more severe disease process than in adults. To explain these observations, we hypothesized that insulin resistance is worse in obese youth than adults with impaired glucose tolerance (IGT), a state of high-risk for T2DM. As proof-of-concept, we compared insulin sensitivity between BMI-, sex-, and race-matched obese youth vs adults with IGT.

METHODS

This retrospective analysis of IGT youth and adults included 34 obese adolescents matched (2:1) for BMI, sex, and race to 17 adults. Hepatic and peripheral insulin sensitivity were measured by [6,6-² H₂ ]glucose and hyperinsulinemic-euglycemic clamp. Body composition (DEXA) and serum lipid profile were examined.

RESULTS

Despite similar percent body fat, obese adolescents had 2-fold higher fasting insulin concentration, lower hepatic (~53%) and peripheral (~42%) insulin sensitivity and lower HDL compared with adults (all P < .01). Surrogate estimate of insulin sensitivity, 1/fasting insulin was lower and HOMA-IR was higher in adolescents vs adults. Adults had a more atherogenic lipid profile with higher total-, LDL-, and non-HDL cholesterol.

CONCLUSIONS

Obese youth and adults with IGT differ in that youth are more insulin resistant than adults in spite of similar adiposity. This could potentially explain the earlier onset of T2DM in youth through an early and amplified burden on a β-cell destined to decompensate, and explicate their lower therapeutic response to insulin sensitizers.

Defective Amplifying Pathway of β-Cell Secretory Response to Glucose in Type 2 Diabetes: Integrated Modeling of In Vitro and In Vivo Evidence

In vivo studies have investigated the role of β-cell dysfunction in type 2 diabetes (T2D), whereas in vitro research on islets has elucidated key mechanisms that control the insulin secretion rate. However, the relevance of the cellular mechanisms identified in vitro (i.e., the triggering and amplifying pathways) has not been established in vivo. Furthermore, the mechanisms underpinning β-cell dysfunction in T2D remain undetermined. We propose a unifying explanation of several characteristic features of insulin secretion both in vitro and in vivo by using a mathematical model. The model describes the triggering and amplifying pathways and reproduces a variety of in vitro and in vivo tests in subjects with and without T2D, identifies the mechanisms modulating first-phase insulin secretion rate in response to basal hyperglycemia or insulin resistance, and shows that β-cell dysfunction in T2D can be explained by an impaired amplifying pathway with no need to postulate defects in intracellular calcium handling.

Review of methods for measuring β-cell function: Design considerations from the Restoring Insulin Secretion (RISE) Consortium

The Restoring Insulin Secretion (RISE) study was initiated to evaluate interventions to slow or reverse the progression of β-cell failure in type 2 diabetes (T2D). To design the RISE study, we undertook an evaluation of methods for measurement of β-cell function and changes in β-cell function in response to interventions. In the present paper, we review approaches for measurement of β-cell function, focusing on methodologic and feasibility considerations. Methodologic considerations included: (1) the utility of each technique for evaluating key aspects of β-cell function (first- and second-phase insulin secretion, maximum insulin secretion, glucose sensitivity, incretin effects) and (2) tactics for incorporating a measurement of insulin sensitivity in order to adjust insulin secretion measures for insulin sensitivity appropriately. Of particular concern were the capacity to measure β-cell function accurately in those with poor function, as is seen in established T2D, and the capacity of each method for demonstrating treatment-induced changes in β-cell function. Feasibility considerations included: staff burden, including time and required methodological expertise; participant burden, including time and number of study visits; and ease of standardizing methods across a multicentre consortium. After this evaluation, we selected a 2-day measurement procedure, combining a 3-hour 75-g oral glucose tolerance test and a 2-stage hyperglycaemic clamp procedure, augmented with arginine.