Beta-cell function across the spectrum of glucose tolerance in obese youth

Early onset type 2 diabetes mellitus: an update

The incidence and prevalence of type 2 diabetes mellitus (T2DM) in young individuals (aged <40 years) have significantly increased in recent years, approximating two to threefold increase in the respective rates. Numerous risk factors including severe obesity, family history, ethnicity, maternal diabetes or gestational diabetes, and female sex contribute to a younger age of onset. In terms of pathogenesis, impaired insulin secretion is the key operating mechanism, alongside with ectopic adiposity-related insulin resistance. T2DM diagnosis in a young adult requires the exclusion of type 1 diabetes mellitus (T1DM), latent autoimmune diabetes of adults (LADA) and maturity-onset diabetes of the young (MODY). The establishment of such diagnosis is critical for prognosis, because early-onset T2DM is associated with rapid deterioration in pancreatic β-cell secretory function leading to earlier initiation of insulin therapy. Furthermore, mortality and lifetime risk of developing complications, especially microvascular, is increased in these patients compared to both later-onset T2DM and T1DM patients; also, the latter are often developed earlier in the course of disease. The management of early-onset T2DM follows the same guidelines as in later-onset T2DM; yet patients aged 18-39 years are underrepresented in the big clinical trials on which the development of guidelines is based. Finally, young people with T2DM face significant challenges associated with social determinants, which compromise their adherence to therapy and induce diabetes distress. Future research focusing on the pathogenesis of β-cell decline and complications, as well as on specific treatment shall lead to better understanding and management of early-onset T2DM.

β-cell function and long-term glycemic control in patients newly diagnosed with type 2 diabetes with moderate hyperglycemia after a 6-month course of basal insulin therapy

AIMS

To evaluate whether treatment with insulin is advantageous compared with oral anti-diabetic drugs (OAD) for patients newly diagnosed with type 2 diabetes with moderate hyperglycemia.

METHODS

Patients newly diagnosed with type 2 diabetes with moderate hyperglycemia were recruited and randomized to receive insulin, metformin or sitagliptin treatment. The oral glucose tolerance test (OGTT) was performed before treatment and 6 months thereafter. The primary outcome was the glycohemoglobin (HbA1c) level change. For the secondary efficacy analysis, the β-cell function and insulin sensitivity were calculated from the OGTT, as was the proportion of subjects who reached the treatment target (HbA1c level < 7.0 % or < 6.5 %) at 6 months.

RESULTS

We randomized 50 patients to the three groups and 32 patients who received the allocated treatment were analyzed. The change of HbA1c level in the insulin, metformin, and sitagliptin groups was - 2.06 ± 1.37 %, -0.43 ± 0.32 %, and - 1.62 ± 0.92 %, respectively. This change was smallest in the metformin group. There was no significant difference in the changes or final HbA1c levels between the insulin and sitagliptin groups. The treat-to-target (HbA1c level < 7.0 %) rates in the insulin, metformin and sitagliptin were 75 %, 50 % and 100 %, respectively. The treat-to-target rates were not significantly different among the three groups. The insulin secretion indices, including the Matsuda index and HOMA-IR, indicated that the groups did not differ after 6 months of therapy.

CONCLUSION

A 6-month course of basal insulin therapy did not benefit patients newly diagnosed with diabetes with moderate hyperglycemia in terms of insulin sensitivity or insulin secretion.

Metformin restores prohormone processing enzymes and normalizes aberrations in secretion of proinsulin and insulin in palmitate-exposed human islets

AIM

To elucidate how proinsulin synthesis and insulin was affected by metformin under conditions of nutrient overstimulation.

MATERIALS AND METHODS

Isolated human pancreatic islets from seven donors were cultured at 5.5 mmol/L glucose and 0.5 mmol/L palmitate for 12, 24 or 72 h. Metformin (25 μmol/L) was introduced after initial 12 h with palmitate. Proinsulin and insulin were measured. Expression of prohormone convertase 1/3 (PC1/3) and carboxypeptidase E (CPE), was determined by western blot. Adolescents with obesity, treated with metformin and with normal glucose tolerance (n = 5), prediabetes (n = 14), or type 2 diabetes (T2DM; n = 7) were included. Fasting proinsulin, insulin, glucose, 2-h glucose and glycated haemoglobin were measured. Proinsulin/insulin ratio (PI/I) was calculated.

RESULTS

In human islets, palmitate treatment for 12 and 24 h increased proinsulin and insulin proportionally. After 72 h, proinsulin but not insulin continued to increase which was coupled with reduced expression of PC1/3 and CPE. Metformin normalized expression of PC1/3 and CPE, and proinsulin and insulin secretion. In adolescents with obesity, before treatment, fasting proinsulin and insulin concentrations were higher in subjects with T2DM than with normal glucose tolerance. PI/I was reduced after metformin treatment in subjects with T2DM as well as in subjects with prediabetes, coupled with reduced 2-h glucose and glycated haemoglobin.

CONCLUSIONS

Metformin normalized proinsulin and insulin secretion after prolonged nutrient-overstimulation, coupled with normalization of the converting enzymes, in isolated islets. In adolescents with obesity, metformin treatment was associated with improved PI/I, which was coupled with improved glycaemic control.

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.

Insulin Clearance in Health and Disease

Insulin action is impaired in type 2 diabetes. The functions of the hormone are an integrated product of insulin secretion from pancreatic β-cells and insulin clearance by receptor-mediated endocytosis and degradation, mostly in liver (hepatocytes) and, to a lower extent, in extrahepatic peripheral tissues. Substantial evidence indicates that genetic or acquired abnormalities of insulin secretion or action predispose to type 2 diabetes. In recent years, along with the discovery of the molecular foundation of receptor-mediated insulin clearance, such as through the membrane glycoprotein CEACAM1, a consensus has begun to emerge that reduction of insulin clearance contributes to the disease process. In this review, we consider the evidence suggesting a pathogenic role for reduced insulin clearance in insulin resistance, obesity, hepatic steatosis, and type 2 diabetes.

Insulin resistance and beta-cell dysfunction in newly diagnosed type 2 diabetes: Expression, aggregation and predominance. Verona Newly Diagnosed Type 2 Diabetes Study 10

AIMS

We investigated quantitative expression, mutual aggregation and relation with hyperglycemia of insulin resistance (IR) and beta-cell dysfunction (BCD) in newly diagnosed type 2 diabetes.

METHODS

We assessed IR with euglycemic hyperinsulinemic clamp and BCD with modelled glucose/C-peptide response to oral glucose in 729 mostly drug-naïve patients. We measured glycated hemoglobin, pre-prandial, post-prandial and meal-related excursion of blood glucose.

RESULTS

IR was found in 87.8% [95% confidence intervals 85.4-90.2] and BCD in 90.0% [87.8-92.2] of subjects, ranging from mild to moderate or severe. Approximately 20% of subjects had solely one defect: BCD 10.8% [8.6-13.1] or IR 8.6% [6.6-10.7]. Insulin resistance and BCD aggregated in most subjects (79.1% [76.2-82.1]). We arbitrarily set nine possible combinations of mild, moderate or severe IR and mild, moderate or severe BCD, finding that each had a similar frequency (∼10%). In multiple regression analyses parameters of glucose control were related more strongly with BCD than with IR.

CONCLUSIONS

In newly-diagnosed type 2 diabetes, IR and BCD are very common with a wide range of expression but no specific pattern of aggregation. Beta-cell dysfunction is likely to play a greater quantitative role than IR in causing/sustaining hyperglycemia in newly-diagnosed type 2 diabetes.

Youth-onset type 2 diabetes in Israel: A national cohort

BACKGROUND

Prevalence of youth-onset type 2 diabetes (T2D) has increased worldwide, paralleling the rise in pediatric obesity. Occurrence and clinical manifestations vary regionally and demographically.

OBJECTIVES

We assessed the incidence, and clinical and demographic manifestations of youth-onset T2D in Israel.

METHODS

In a national observational study, demographic, clinical, and laboratory data were collected from the medical records of children and adolescents, aged 10-18 years, diagnosed with T2D between the years 2008 and 2019.

RESULTS

The incidence of youth-onset T2D in Israel increased significantly from 0.63/100,000 in 2008 to 3.41/100,000 in 2019. The study cohort comprised 379 individuals (228 girls [59.7%], 221 Jews [58.3%], mean age 14.7 ± 1.9 years); 73.1% had a positive family history of T2D. Mean body mass index (BMI) z-score was 1.96 ± 0.7, higher in Jews than Arabs. High systolic (≥ 130 mmHg) and diastolic blood pressure (≥ 85 mmHg) were observed in 33.7% and 7.8% of patients, respectively; mean glycosylated hemoglobin (A1c) level at diagnosis was 8.8 ± 2.5%. Dyslipidemia, with high triglyceride (>150 mg/dl) and low HDL-c (<40 mg/dl) levels, was found in 45.6% and 56.5%, respectively. Microalbuminuria and retinopathy were documented at diagnosis, 15.2% and 1.9%, respectively) and increased (36.7% and 4.6%, respectively) at follow-up of 2.9 ± 2.1 years. Criteria of metabolic syndrome were met by 224 (62.2%) patients, and fatty liver documented in 65%, mainly Jews. Psychosocial comorbidity was found in 31%. Treatment with metformin (45.6%), insulin (20.6%), and lifestyle modification (18%) improved glycemic control.

CONCLUSION

Youth-onset T2D in Israel has increased significantly and presents a unique profile.

Effect of Sarcopenia on Mortality in Type 2 Diabetes: A Long-Term Follow-Up Propensity Score-Matched Diabetes Cohort Study

Purpose: The effect of sarcopenia on the survival of patients with type 2 diabetes remains unclear. Therefore, we designed a propensity score-matched population-based cohort study to compare the patients with diabetes with or without sarcopenia. Patients and Methods: We included patients with type 2 diabetes and categorized them into two groups according to whether they had sarcopenia and compared their survival; patients in the groups were matched at a ratio of 1:2. Results: The matching process yielded a final cohort of 201,698 patients (132,805 and 68,893 in the sarcopenia and nonsarcopenia diabetes groups, respectively) who were eligible for further analysis. According to both univariate and multivariate Cox regression analyses, the adjusted hazard ratios (aHRs; 95% confidence interval [CI]) of all-cause death for the sarcopenia diabetes group compared with the control group: 1.35 (1.33−1.38; p < 0.001). The aHRs (95% CIs) of all-cause death for those aged 41−50, 51−60, and >60 years (compared with those aged ≤40 years) were 1.53 (1.48−1.60), 2.61 (2.52−2.72), and 6.21 (5.99−6.45), respectively. The aHR (95% CI) of all-cause death for the male patients compared with the female patients was 1.56 (1.54−1.60). The aHRs (95% CIs) of all-cause death for those with adapted Diabetes Complications Severity Index (aDCSI) scores of 1, 2, 3, 4, and ≥5 (compared with an aDCSI score of 0) were 1.01 (1.00−1.14), 1.38 (1.35−1.42), 1.58 (1.54−1.63), and 2.23 (2.14−2.33), respectively. Conclusion: Patients with type 2 diabetes and sarcopenia had higher mortality than did those without sarcopenia.

Impact of CFTR Modulators on Beta-Cell Function in Children and Young Adults with Cystic Fibrosis

Background: To date, no consistent data are available on the possible impact of CFTR modulators on glucose metabolism. The aim of this study was to test the hypothesis that treatment with CFTR modulators is associated with an improvement in the key direct determinants of glucose regulation in children and young adults affected by Cystic Fibrosis (CF). Methods: In this study, 21 CF patients aged 10–25 underwent oral glucose tolerance test (OGTT) before and after 12–18 months of treatment with Lumacaftor/Ivacaftor or Elexacaftor-Ivacaftor-Tezacaftor. β-cell function (i.e., first and second phase of insulin secretion measured as derivative and proportional control, respectively) and insulin clearance were estimated by OGTT mathematical modelling. Insulin sensitivity was estimated by the Oral Glucose Sensitivity Index (OGIS). The dynamic interplay between β-cell function, insulin clearance and insulin sensitivity was analysed by vector plots of glucose-stimulated insulin bioavailability vs. insulin sensitivity. Results: No changes in glucose tolerance occurred after either treatment, whereas a significant improvement in pulmonary function and chronic bacterial infection was observed. Beta cell function and insulin clearance did not change in both treatment groups. Insulin sensitivity worsened in the Lumacaftor/Ivacaftor group. The analysis of vector plots confirmed that glucose regulation was stable in both groups. Conclusions: Treatment of CF patients with CFTR modulators does not significantly ameliorate glucose homeostasis and/or any of its direct determinants.

Dynamic Uni- and Multicellular Patterns Encode Biphasic Activity in Pancreatic Islets

Biphasic secretion is an autonomous feature of many endocrine micro-organs to fulfill physiological demands. The biphasic activity of islet β-cells maintains glucose homeostasis and is altered in type 2 diabetes. Nevertheless, underlying cellular or multicellular functional organizations are only partially understood. High-resolution noninvasive multielectrode array recordings permit simultaneous analysis of recruitment, of single-cell, and of coupling activity within entire islets in long-time experiments. Using this unbiased approach, we addressed the organizational modes of both first and second phase in mouse and human islets under physiological and pathophysiological conditions. Our data provide a new uni- and multicellular model of islet β-cell activation: during the first phase, small but highly active β-cell clusters are dominant, whereas during the second phase, electrical coupling generates large functional clusters via multicellular slow potentials to favor an economic sustained activity. Postprandial levels of glucagon-like peptide 1 favor coupling only in the second phase, whereas aging and glucotoxicity alter coupled activity in both phases. In summary, biphasic activity is encoded upstream of vesicle pools at the micro-organ level by multicellular electrical signals and their dynamic synchronization between β-cells. The profound alteration of the electrical organization of islets in pathophysiological conditions may contribute to functional deficits in type 2 diabetes.

Glucose Tolerance Stages in Cystic Fibrosis Are Identified by a Unique Pattern of Defects of Beta-Cell Function

OBJECTIVE

We aimed to assess the order of severity of the defects of 3 direct determinants of glucose regulation-beta-cell function, insulin clearance, and insulin sensitivity-in patients with cystic fibrosis (CF), categorized according their glucose tolerance status, including early elevation of mid-level oral glucose tolerance test (OGTT) glucose values (>140 and <200 mg/dL), referred to as AGT140.

METHODS

A total of 232 CF patients aged 10 to 25 years underwent OGTT. Beta-cell function and insulin clearance were estimated by OGTT mathematical modeling and OGTT-derived biomarkers of insulin secretion and sensitivity were calculated. The association between glucometabolic variables and 5 glucose tolerance stages (normal glucose tolerance [NGT], AGT140, indeterminate glucose tolerance [INDET], impaired glucose tolerance [IGT], cystic fibrosis-related diabetes CFRD]) was assessed with a general linear model.

RESULTS

Beta-cell function and insulin sensitivity progressively worsened across glucose tolerance stages (P < 0.001), with AGT140 patients significantly differing from NGT (all P < 0.01). AGT140 and INDET showed a degree of beta-cell dysfunction similar to IGT and CFRD, respectively (all P < 0.01). Insulin clearance was not significantly associated with glucose tolerance stages (P = 0.162). Each stage of glucose tolerance was uniquely identified by a specific combination of defects of the direct determinants of glucose regulation.

CONCLUSIONS

In CF patients, each of the 5 glucose tolerance stages shows a unique pattern of defects of the direct determinants of glucose regulation, with AGT140 patients significantly differing from NGT and being similar to IGT. These findings suggest that AGT140 should be recognized as a distinct glucose tolerance stage and that reconsideration of the grade of glucometabolic deterioration across glucose tolerance stages in CF is warranted.

Nuclear Magnetic Resonance Derived Biomarkers for Evaluating Cardiometabolic Risk in Youth and Young Adults Across the Spectrum of Glucose Tolerance

Youth with obesity have an increased risk for cardiometabolic disease, but identifying those at highest risk remains a challenge. Four biomarkers that might serve this purpose are "by products" of clinical NMR LipoProfile^® lipid testing: LPIR (Lipoprotein Insulin Resistance Index), GlycA (inflammation marker), BCAA (total branched-chain amino acids), and glycine. All are strongly related to insulin resistance and type 2 diabetes (T2DM) in adults (glycine inversely) and are independent of biological and methodological variations in insulin assays. However, their clinical utility in youth is unclear. We compared fasting levels of these biomarkers in 186 youth (42 lean normal glucose tolerant (NGT), 88 obese NGT, 23 with prediabetes (PreDM), and 33 with T2DM. All four biomarkers were associated with obesity and glycemia in youth. LPIR and GlycA were highest in youth with PreDM and T2DM, whereas glycine was lowest in youth with T2DM. While all four were correlated with HOMA-IR (Homeostatic Model Assessment for Insulin Resistance), LPIR had the strongest correlation (LPIR: r = 0.6; GlycA: r = 0.4, glycine: r = -0.4, BCAA: r = 0.2, all P < 0.01). All four markers correlated with HbA1c (LPIR, GlycA, BCAA: r ≥ 0.3 and glycine: r = -0.3, all P < 0.001). In multi-variable regression models, LPIR, GlycA, and glycine were independently associated with HOMA-IR (Adjusted R² = 0.473, P < 0.001) and LPIR, glycine, and BCAA were independently associated with HbA1c (Adjusted R² = 0.33, P < 0.001). An LPIR index of >44 was associated with elevated blood pressure, BMI, and dyslipidemia. Plasma NMR-derived markers were related to adverse markers of cardiometabolic risk in youth. LPIR, either alone or in combination with GlycA, should be explored as a non-insulin dependent predictive tool for development of insulin resistance and diabetes in youth.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov, identifier NCT:02960659.

Pediatric Type 2 Diabetes: Not a Mini Version of Adult Type 2 Diabetes

Pediatric type 2 diabetes mellitus (T2DM) is increasing in incidence, with risk factors including obesity, puberty, family history of T2DM in a first-degree or second-degree relative, history of small-for-gestational-age at birth, child of a gestational diabetes pregnancy, minority racial group, and lower socioeconomic status. The pathophysiology of T2DM consists of insulin resistance and progression to pancreatic beta-cell failure, which is more rapid in pediatric T2DM compared with adult T2DM. Treatment options are limited. Treatment failure and nonadherence rates are high in pediatric T2DM; therefore, early diagnosis and treatment and new pharmacologic options and/or effective behavioral interventions are needed.

The roles of first phase, second phase insulin secretion, insulin resistance, and glucose effectiveness of having prediabetes in nonobese old Chinese women

It has been established that prediabetes can causes significant comorbidities, particularly in the elderly. The deterioration of glucose metabolism are generally considered to be results of the impairment of the 4 factors: first, second insulin secretion (FPIS, SPIS, respectively), glucose effectiveness (GE), and insulin resistance. In this study, we enrolled older women to investigate their relationships with prediabetes.Five thousand four hundred eighty-two nonobese, nondiabetic women were included. They were divided into normal glucose tolerance and prediabetes groups. Receiver operating characteristic curve was performed to investigate the effects on whether to have prediabetes for each factors. Two models were built: Model 1: FPIS + SPIS, and Model 2: model 1 + GE. The area under the receiver operating characteristic (aROC) curve was used to determine the predictive power of these models.The aROC curve of GE was significantly higher than the diagonal line followed by SPIS and FPIS accordingly. The aROC curve of Model 1 (0.611) was not different from GE. However, Model 2 improved significantly up to 0.663. Based on this model, an equation was built (-0.003 × GE - 212.6 × SPIS - 17.9 × insulin resistance + 4.8). If the calculated value is equal or higher than 0 (≥0), then the subject has higher chance to have prediabetes (sensitivity = 0.607, specificity = 0.635).Among the 4 factors, GE is the most important contributor for prediabetes in older women. By building a model composed of FPIS, SPIS, and GE, the aROC curve increased significantly. The equation built from this model could predict prediabetes precisely.

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.

Muscle Insulin Resistance in Youth with Obesity and Normoglycemia is Associated with Altered Fat Metabolism

OBJECTIVE

This study aimed to phenotype and compare adipose, hepatic, and muscle insulin sensitivity (IS) in a diet- and physical activity-controlled cohort of normoglycemic youth with obesity with that of participants without obesity (controls) to distinguish early metabolic abnormalities in pediatric obesity.

METHODS

Thirty-eight participants (17 in the control group [BMI < 85th percentile] and 21 youth with obesity [BMI ≥ 95th percentile]; age: 12-21 years; 76% female; Tanner stage 4-5; sedentary) were enrolled. Tissue-specific IS was measured using a four-phase hyperinsulinemic-euglycemic clamp with glucose and glycerol isotope tracers to assess suppression of endogenous glucose release and lipolysis by insulin. Intramyocellular lipid content was assessed by 1 H-magnetic resonance spectroscopy, and hepatic fat fraction (HFF) and visceral fat were assessed by magnetic resonance imaging. Calf-muscle mitochondrial activity was measured with exercise-stimulated 31 P-magnetic resonance spectroscopy.

RESULTS

Youth with obesity had higher HFF (P < 0.001), visceral fat (P = 0.024), and intramyocellular lipid content (P = 0.017) and lower muscle (glucose clearance rate [P < 0.001]), adipose (P < 0.0001), and hepatic IS (P < 0.003). Mitochondria postexercise response was not different. In participants with obesity, muscle IS inversely correlated with HFF (r = 0.700, P = 0.002) and suppressed free fatty acid concentrations (r = -0.65, P = 0.003).

CONCLUSIONS

Inactive normoglycemic youth with obesity had decreased muscle, adipose, and hepatic IS. Free fatty acids and liver fat were inversely associated with muscle IS, which argues for lipid-targeted interventions.

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.

Hyperinsulinemia: An Early Indicator of Metabolic Dysfunction

Hyperinsulinemia is strongly associated with type 2 diabetes. Racial and ethnic minority populations are disproportionately affected by diabetes and obesity-related complications. This mini-review provides an overview of the genetic and environmental factors associated with hyperinsulinemia with a focus on racial and ethnic differences and its metabolic consequences. The data used in this narrative review were collected through research in PubMed and reference review of relevant retrieved articles. Insulin secretion and clearance are regulated processes that influence the development and progression of hyperinsulinemia. Environmental, genetic, and dietary factors are associated with hyperinsulinemia. Certain pharmacotherapies for obesity and bariatric surgery are effective at mitigating hyperinsulinemia and are associated with improved metabolic health. Hyperinsulinemia is associated with many environmental and genetic factors that interact with a wide network of hormones. Recent studies have advanced our understanding of the factors affecting insulin secretion and clearance. Further basic and translational work on hyperinsulinemia may allow for earlier and more personalized treatments for obesity and metabolic diseases.

Cardiometabolic risk in obese children

Obesity in childhood remains a significant and prevalent public health concern. Excess adiposity in youth is a marker of increased cardiometabolic risk (CMR) in adolescents and adults. Several longitudinal studies confirm the strong association of pediatric obesity with the persistence of adult obesity and the future development of cardiovascular disease, diabetes, and increased risk of death. The economic and social impact of childhood obesity is further exacerbated by the early onset of the chronic disease burden in young adults during their peak productivity years. Furthermore, rising prevalence rates of severe obesity in youth from disadvantaged and/or minority backgrounds have prompted the creation of additional classification schemes for severe obesity to improve CMR stratification. Current guidelines focus on primary obesity prevention efforts, as well as screening for clustering of multiple CMR factors to target interventions. This review summarizes the scope of the pediatric obesity epidemic, the new severe obesity classification scheme, and examines the association of excess adiposity with cardiovascular and metabolic risk. We will also discuss potential questions for future investigation.

Patient-Driven Diabetes Care of the Future in the Technology Era

The growing burden of diabetes is fueled by obesity-inducing lifestyle behaviors including high-calorie diets and lack of physical activity. Challenges in access to diabetes specialists and educators, low adherence to medications, and inadequate motivational support for proper disease self-management contribute to poor glycemic control in patients with diabetes. Simultaneously, high patient volumes and low reimbursement rates limit physicians' time spent on lifestyle behavior counseling. These barriers to efficient diabetes care lead to high rates of diabetes-related complications, driving healthcare costs up and reducing the quality of patients' lives. Considering recent advancements in healthcare delivery technologies such as smartphone applications, telemedicine, m-health, device connectivity, machine-learning technology, and artificial intelligence, there is significant opportunity to achieve better efficiency in diabetes care and increase patient involvement in diabetes self-management, which ultimately may put an end to soaring diabetes-related healthcare expenditures. This review explores the patient-driven diabetes care of the future in the technology era.

Calcium signaling and secretory granule pool dynamics underlie biphasic insulin secretion and its amplification by glucose: experiments and modeling

Glucose-stimulated insulin secretion from pancreatic β-cells is controlled by a triggering pathway that culminates in calcium influx and regulated exocytosis of secretory granules, and by a less understood amplifying pathway that augments calcium-induced exocytosis. In response to an abrupt increase in glucose concentration, insulin secretion exhibits a first peak followed by a lower sustained second phase. This biphasic secretion pattern is disturbed in diabetes. It has been attributed to depletion and subsequent refilling of a readily releasable pool of granules or to the phasic cytosolic calcium dynamics induced by glucose. Here, we apply mathematical modeling to experimental data from mouse islets to investigate how calcium and granule pool dynamics interact to control dynamic insulin secretion. Experimental calcium traces are used as inputs in three increasingly complex models of pool dynamics, which are fitted to insulin secretory patterns obtained using a set of protocols of glucose and tolbutamide stimulation. New calcium and secretion data for so-called staircase protocols, in which the glucose concentration is progressively increased, are presented. These data can be reproduced without assuming any heterogeneity in the model, in contrast to previous modeling, because of nontrivial calcium dynamics. We find that amplification by glucose can be explained by increased mobilization and priming of granules. Overall, our results indicate that calcium dynamics contribute substantially to shaping insulin secretion kinetics, which implies that better insight into the events creating phasic calcium changes in human β-cells is needed to understand the cellular mechanisms that disturb biphasic insulin secretion in diabetes.

Metabolic Contrasts Between Youth and Adults With Impaired Glucose Tolerance or Recently Diagnosed Type 2 Diabetes: I. Observations Using the Hyperglycemic Clamp

OBJECTIVE

To compare insulin sensitivity (M/I) and β-cell responses in youth versus adults with impaired glucose tolerance (IGT) or drug-naïve, recently diagnosed type 2 diabetes.

RESEARCH DESIGN AND METHODS

In 66 youth (80.3% with IGT) and 355 adults (70.7% IGT), hyperglycemic clamps were used to measure 1) M/I, 2) acute (0-10 min [first phase]) C-peptide (ACPR_g) and insulin (AIR_g) responses to glucose, 3) steady-state C-peptide and insulin concentrations at plasma glucose of 11.1 mmol/L, and 4) arginine-stimulated maximum C-peptide (ACPR_max) and insulin (AIR_max) responses at plasma glucose >25 mmol/L. The fasting C-peptide-to-insulin ratio was used as an estimate of insulin clearance.

RESULTS

Insulin sensitivity was 46% lower in youth compared with adults (P < 0.001), and youth had greater acute and steady-state C-peptide (2.3- and 1.3-fold, respectively; each P < 0.001) and insulin responses to glucose (AIR_g 3.0-fold and steady state 2.2-fold; each P < 0.001). Arginine-stimulated C-peptide and insulin responses were also greater in youth (1.6- and 1.7-fold, respectively; each P < 0.001). After adjustment for insulin sensitivity, all β-cell responses remained significantly greater in youth. Insulin clearance was reduced in youth (P < 0.001). Participants with diabetes had greater insulin sensitivity (P = 0.026), with lesser C-peptide and insulin responses than those with IGT (all P < 0.001) but similar insulin clearance (P = 0.109).

CONCLUSIONS

In people with IGT or recently diagnosed diabetes, youth have lower insulin sensitivity, hyperresponsive β-cells, and reduced insulin clearance compared with adults. Whether these age-related differences contribute to declining β-cell function and/or impact responses to glucose-lowering interventions remains to be determined.

Metabolic Contrasts Between Youth and Adults With Impaired Glucose Tolerance or Recently Diagnosed Type 2 Diabetes: II. Observations Using the Oral Glucose Tolerance Test

OBJECTIVE

To compare oral glucose tolerance test (OGTT) glucose, C-peptide, and insulin responses and insulin sensitivity in youth and adults with impaired glucose tolerance (IGT) or recently diagnosed type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 66 youth (80.3% with IGT) and 355 adults (70.7% with IGT) underwent a 3-h OGTT to assess 1) insulin sensitivity (1/fasting insulin), 2) C-peptide index (CPI) and insulinogenic index (IGI) over the first 30 min, and 3) glucose, C-peptide, and insulin incremental areas above fasting over the 3-h post-ingestion (incremental glucose [G-iAUC], incremental C-peptide [CP-iAUC], and incremental insulin area under the curve [I-iAUC] responses, respectively).

RESULTS

Fasting, 2-h glucose, and G-iAUC were similar in both age-groups, but youth had ∼50% lower 1/fasting insulin (P < 0.001), 75% higher CPI (mean [95% CI] 0.703 [0.226, 2.183] vs. 0.401 [0.136, 1.183] nmol/mmol; P < 0.001), and more than twofold higher IGI (257.3 [54.5, 1,215.8] vs. 114.8 [28.0, 470.8] pmol/mmol; P < 0.001). Two-hour C-peptide and insulin concentrations, CP-iAUC, and I-iAUC were all higher in youth (all P < 0.001). C-peptide and insulin responses remained significantly greater in youth after adjustment for insulin sensitivity. Within each age-group, individuals with type 2 diabetes versus IGT had significantly lower CPI and IGI with no difference in insulin sensitivity.

CONCLUSIONS

The balance between insulin sensitivity and β-cell responses differs between youth and adults with IGT or recently diagnosed type 2 diabetes. Despite similar postload glucose levels, youth demonstrate greater C-peptide and insulin responses that exceed what is needed to compensate for their lower insulin sensitivity. Longitudinal studies are required to determine whether this feature contributes to a more rapid decline in β-cell function in youth with dysglycemia.

Lower mean blood glucose during short-term intensive insulin therapy is associated with long-term glycemic remission in patients with newly diagnosed type 2 diabetes: Evidence-based recommendations for standardization

AIMS/INTRODUCTION

Optimal glycemic targets during short-term intensive insulin therapy in patients with newly diagnosed type 2 diabetes are not standardized. The present study was carried out to determine the optimal glycemic targets during therapy by analyzing the impacts of glucose levels on therapeutic outcomes.

MATERIALS AND METHODS

A total of 95 individuals with newly diagnosed type 2 diabetes were enrolled. Short-term intensive insulin therapy was carried out using an insulin pump to achieve and maintain glycemic targets (fasting blood glucose ≤6.0 mmol/L, 2-h postprandial blood glucose ≤7.8 mmol/L) for 14 days, with daily eight-point capillary blood glucose profiles recorded. Patients were followed up for 1 year after discharge.

RESULTS

In most participants, the mean blood glucose and glycemic excursion parameters during the therapy were controlled within the normal range. Mean blood glucose was independently associated with amelioration of acute insulin response (r = -0.25, P = 0.015) and 1-year remission (odds ratio 0.12, 95% confidence interval 0.034-0.426), but negatively associated with more level 1 hypoglycemia (r = -0.34, P = 0.001), although major hypoglycemia was rare. Among mean blood glucose tertiles, patients in the middle (68.7%) and lower (75.0%) tertiles had a higher 1-year remission rate compared with the upper tertile (32.3%, both P < 0.001), whereas only the middle tertile did not have increased hypoglycemia compared with the upper tertile (8.1 ± 5.4 vs 7.2 ± 3.9 events/person, P = 0.48).

CONCLUSIONS

Stricter glycemic control during short-term intensive insulin therapy produced more remission despite self-manageable hypoglycemia. Based on glycemic parameters in the middle mean tertile, we propose new glycemic targets that are approximately 0.4 mmol/L lower than current the targets, as long-term benefit outweighs short-term risks.

Infant-juvenile type 2 diabetes

In recent years, we have witnessed an increase in the number of cases of type 2 diabetes mellitus (DM2) in children and adolescents, which has paralleled the increase in the worldwide prevalence of obesity. Although screening the general population does not appear to be cost-effective, special attention should be paid to children with excess weight, obesity or other factors that predispose them to a state of insulin resistance. When faced with the diagnosis of childhood DM2, the presence of comorbidities (such as hypertension, dyslipidemia and microalbuminuria) should be assessed, and appropriate treatment and follow-up should be administered to prevent the onset of complications, given that the DM2 in this population group will last longer than that started in adulthood.

Impaired fasting glucose and the metabolic profile in Danish children and adolescents with normal weight, overweight, or obesity

OBJECTIVE

Whether the definitions of impaired fasting glucose (IFG) from the American Diabetes Association (ADA) and the World Health Organization (WHO) differentially impact estimates of the metabolic profile and IFG-related comorbidities in Danish children and adolescents is unknown.

METHODS

Two thousand one hundred and fifty four (979 boys) children and adolescents with overweight or obesity (median age 12 years) and 1824 (728 boys) children with normal weight (median age 12 years) from The Danish Childhood Obesity Biobank were studied. Anthropometrics, blood pressure, puberty, and fasting concentrations of glucose, insulin, glycosylated hemoglobin (HbA1c), and lipids were measured.

RESULTS

About 14.1% of participants with overweight or obesity exhibited IFG according to the ADA and 3.5% according to the WHO definition. Among individuals with normal weight, the corresponding prevalences were 4.3% and 0.3%. IFG was associated with a higher systolic blood pressure, higher concentrations of HbA1c, insulin, C-peptide (P < .0001) and triglycerides (P = .03), and lower HOMA2-IS and HOMA2-B (P < .0001) independent of sex, age, puberty, waist-to-height ratio, and degree of obesity. Furthermore, IFG was associated with a higher risk for hypertension (OR = 1.66 [95%CI: 1.21; 2.28], P = .002) and dyslipidemia (OR = 1.90 [95%CI: 1.38; 2.56], P < .0001) compared with the group without IFG independent of age, sex, and puberty.

CONCLUSIONS

The prevalence of IFG, when applying the ADA criterion compared with the WHO criterion, was 4 times higher in individuals with overweight and obesity and 14 times higher in individuals with normal weight in this study sample of children and adolescents. IFG was associated with a higher risk of hypertension and dyslipidemia compared with their normoglycemic peers regardless of the definition applied.

Association of free-living physical activity measures with metabolic phenotypes in type 2 diabetes at the time of diagnosis. The Verona Newly Diagnosed Type 2 Diabetes Study (VNDS)

BACKGROUND AND AIM

Lifestyle is considered a major determinant of risk of type 2 diabetes (T2D). We investigated whether daily physical activity (DPA) is associated with beta-cell function (BF) and/or insulin sensitivity (IS) in patients with T2D at the time of diagnosis.

METHODS AND RESULTS

In 41 subjects enrolled in the Verona Newly-Diagnosed Type 2 Diabetes Study we assessed: (1) IS, by euglycaemic insulin clamp; (2) BF, estimated by prolonged-OGTT minimal modeling and expressed as derivative and proportional control; (3) DPA and energy expenditure (EE), assessed over 48-h monitoring by a validated wearable armband system. Study participants (median [IQR]; age: 62 [53-67] years, BMI: 30.8 [26.5-34.3] Kg m^-2, HbA1c: 6.7 [6.3-7.3]%; 49.7 [45.4-56.3] mmol/mol) were moderately active (footsteps/day: 7773 [5748-10,927]; DPA_≥3MET: 70 [38-125] min/day), but none of them exercised above 6 metabolic equivalents (MET). EE, expressed as EE_TOT (total daily-EE) and EE_≥3MET (EE due to DPA_≥3MET) were 2398 [2226-2801] and 364 [238-617] Kcal/day, respectively. IS (M-clamp 630 [371-878] μmol/min/m²) was positively associated with DPA and EE, independent of age, sex and BMI (p < 0.05). Among the DPA and EE parameters assessed, DPA_≥3MET and EE_TOT were independent predictors of IS in multivariable regression analyses, adjusted for age, sex, BMI (R² = 16%, R² = 19%, respectively; p < 0.01). None of model-derived components of BF was significantly associated with DPA or accompanying EE.

CONCLUSIONS

Our study highlighted moderate levels of DPA and total EE as potential determinants of IS, but not BF, in T2D at the time of diagnosis. Intervention studies are needed to conclusively elucidate the effect of DPA on these features.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov.

UNIQUE IDENTIFIER

NCT01526720.

Paediatric type 2 diabetes in China-Pandemic, progression, and potential solutions

China is gradually taking its place as one of the world's economic giants and concurrently learning to cope with the burden of diseases that are more common in the developed world, such as paediatric type 2 diabetes mellitus. The prevalence of type 2 diabetes has been recently observed among children and adolescents in China; hence, there is a lack of information about the incidence, prevalence, pathogenesis, and pathophysiology of the disease. Diagnosis, treatment, and management have been standardized to a large degree, but there is still a need for data regarding optimal management protocols and how to achieve the best control over current state of the disease. The objective of this review is to consolidate the available information about paediatric diabetes, with a focus on the increasing prevalence of type 2 diabetes in Chinese youth. Here we emphasize the prevention strategies and have included literature with respect to pathogenesis, diagnosis, and treatment published in English and Chinese within the past 10 years.

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.

Assessment of disturbed glucose metabolism and surrogate measures of insulin sensitivity in obese children and adolescents

BACKGROUND

With the rising prevalence of obesity and type 2 diabetes (T2D) in obese children, it is becoming imperative to detect disturbed glucose metabolism as early as possible in order to prevent T2D development.

SUBJECTS/METHODS

Cross-sectional study of 92 obese children (median age 11.7 years, 51% female) and 7 lean children (median age 11.4 years, 57% female) who underwent an oral glucose tolerance test (OGTT) in a tertiary pediatric care center. Glucose tolerance was assessed and different indices for β-cell function, insulin sensitivity and insulin secretion were calculated.

RESULTS

Nineteen obese children were identified with prediabetes (PD, 12 impaired glucose tolerance, 4 increased fasting glucose and 3 combined). Compared with the 73 obese children with normal glucose tolerance (nGT), subjects with PD had higher insulin resistance, but lower insulin sensitivity and β-cell function, although their glycated hemoglobin (HbA1c) levels were comparable. The Whole Body Insulin Sensitivity Index (WBISI) and β-cell function by Insulin Secretion-Sensitivity Index-2 (ISSI-2) strongly correlated with the OGTT glucose area under the curve 0-120 min (r = 0.392, p < 0.0002; r = 0.547, p < 0.0001, respectively). When testing the relation between early insulin response during OGTT by insulinogenic index and insulin sensitivity assessed by WBISI, a hyperbolic relationship between insulin secretion and insulin sensitivity was found. The calculated disposition index was lower in subjects with PD vs. nGT (median 459 vs. 792, p = 0.004). We identified the OGTT 30-min/120-min insulin ratio as a simple marker, which is significantly lower in obese children with vs. without PD (median 0.87 vs. 1.29, p = 0.021) and which has a better sensitivity and specificity for detecting PD than HbA1c among obese children.

CONCLUSIONS

Children with identified PD had changes of several markers for β-cell function, insulin sensitivity and resistance before changes in HbA1c occurred. The lower disposition index indicates that these children have already inadequate β-cell compensation for the degree of insulin resistance.

β-Cell Function Over Time in Adolescents With New Type 2 Diabetes and Obese Adolescents Without Diabetes

PURPOSE

The progression of β-cell function in newly diagnosed adolescents with type 2 diabetes mellitus (T2DM) is not well documented. We hypothesized that at the time of diagnosis with T2DM, adolescents would have impaired β-cell function as demonstrated by the disposition index (calculated as: insulin secretion adjusted for insulin sensitivity), and this would be followed by a rapid decline of function despite standard medical management.

METHODS

Thirty-nine adolescents with recently diagnosed T2DM and 32 obese adolescent controls with normal glucose tolerance had acute insulin response to glucose, homeostatic model assessment of insulin resistance, and disposition index measured serially over 2 years.

RESULTS

In the adolescent T2DM group, fasting glucose increased over 2 years (p = .04), while DI was impaired at baseline and showed an overall relative decline of 25% per year. The mean Hemoglobin A1c remained below 8% (64 mmol/mol). Differences were observed between the T2DM and control adolescents in the way DI changed over time (p = .02).

CONCLUSIONS

β-cell function in adolescents with recently diagnosed T2DM was impaired with no improvement of β-cell function over the 2 years of study despite stable Hemoglobin A1c, body mass index markers of insulin sensitivity, and standard treatment of hyperglycemia.

Enhancing pediatric clinical trial feasibility through the use of Bayesian statistics

BackgroundPediatric clinical trials commonly experience recruitment challenges including limited number of patients and investigators, inclusion/exclusion criteria that further reduce the patient pool, and a competitive research landscape created by pediatric regulatory commitments. To overcome these challenges, innovative approaches are needed.MethodsThis article explores the use of Bayesian statistics to improve pediatric trial feasibility, using pediatric Type-2 diabetes as an example. Data for six therapies approved for adults were used to perform simulations to determine the impact on pediatric trial size.ResultsWhen the number of adult patients contributing to the simulation was assumed to be the same as the number of patients to be enrolled in the pediatric trial, the pediatric trial size was reduced by 75-78% when compared with a frequentist statistical approach, but was associated with a 34-45% false-positive rate. In subsequent simulations, greater control was exerted over the false-positive rate by decreasing the contribution of the adult data. A 30-33% reduction in trial size was achieved when false-positives were held to less than 10%.ConclusionReducing the trial size through the use of Bayesian statistics would facilitate completion of pediatric trials, enabling drugs to be labeled appropriately for children.

Increased susceptibility of post-weaning rats on high-fat diet to metabolic syndrome

The present study aimed to examine the effects of the types of high-calorie diets (high-fat and high-fat-high-sucrose diets) and two different developmental stages (post-weaning and young adult) on the induction of metabolic syndrome. Male, post-weaning and adult (3- and 8-week old, respectively) Sprague Dawley rats were given control, high-fat (60% kcal), and high-fat-high-sucrose (60% kcal fat + 30% sucrose water) diets for eight weeks (n = 6 to 7 per group). Physical, biochemical, and transcriptional changes as well as liver histology were noted. Post-weaning rats had higher weight gain, abdominal fat mass, fasting glucose, high density lipoprotein cholesterol, faster hypertension onset, but lower circulating advanced glycation end products compared to adult rats. This is accompanied by upregulation of peroxisome proliferator-activated receptor (PPAR) α and γ in the liver and receptor for advanced glycation end products (RAGE) in the visceral adipose tissue. Post-weaning rats on high-fat diet manifested all phenotypes of metabolic syndrome and increased hepatic steatosis, which are linked to increased hepatic and adipocyte PPARγ expression. Adult rats on high-fat-high-sucrose diet merely became obese and hypertensive within the same treatment duration. Thus, it is more effective and less time-consuming to induce metabolic syndrome in male post-weaning rats with high-fat diet compared to young adult rats. As male rats were selectively included into the study, the results may not be generalisable to all post-weaning rats and further investigation on female rats is required.

A Branched-Chain Amino Acid-Related Metabolic Signature Characterizes Obese Adolescents with Non-Alcoholic Fatty Liver Disease

Dysregulation of several metabolite pathways, including branched-chain amino acids (BCAAs), are associated with Non-Alcoholic Fatty Liver Disease (NAFLD) and insulin resistance in adults, while studies in youth reported conflicting results. We explored whether, independently of obesity and insulin resistance, obese adolescents with NAFLD display a metabolomic signature consistent with disturbances in amino acid and lipid metabolism. A total of 180 plasma metabolites were measured by a targeted metabolomic approach in 78 obese adolescents with (n = 30) or without (n = 48) NAFLD assessed by magnetic resonance imaging (MRI). All subjects underwent an oral glucose tolerance test and subsets of patients underwent a two-step hyperinsulinemic-euglycemic clamp and/or a second MRI after a 2.2 ± 0.8-year follow-up. Adolescents with NAFLD had higher plasma levels of valine (p = 0.02), isoleucine (p = 0.03), tryptophan (p = 0.02), and lysine (p = 0.02) after adjustment for confounding factors. Circulating BCAAs were negatively correlated with peripheral and hepatic insulin sensitivity. Furthermore, higher baseline valine levels predicted an increase in hepatic fat content (HFF) at follow-up (p = 0.01). These results indicate that a dysregulation of BCAA metabolism characterizes obese adolescents with NAFLD independently of obesity and insulin resistance and predict an increase in hepatic fat content over time.

Impact of Perturbed Pancreatic β-Cell Cholesterol Homeostasis on Adipose Tissue and Skeletal Muscle Metabolism

Elevated pancreatic β-cell cholesterol levels impair insulin secretion and reduce plasma insulin levels. This study establishes that low plasma insulin levels have a detrimental effect on two major insulin target tissues: adipose tissue and skeletal muscle. Mice with increased β-cell cholesterol levels were generated by conditional deletion of the ATP-binding cassette transporters, ABCA1 and ABCG1, in β-cells (β-DKO mice). Insulin secretion was impaired in these mice under basal and high-glucose conditions, and glucose disposal was shifted from skeletal muscle to adipose tissue. The β-DKO mice also had increased body fat and adipose tissue macrophage content, elevated plasma interleukin-6 and MCP-1 levels, and decreased skeletal muscle mass. They were not, however, insulin resistant. The adipose tissue expansion and reduced skeletal muscle mass, but not the systemic inflammation or increased adipose tissue macrophage content, were reversed when plasma insulin levels were normalized by insulin supplementation. These studies identify a mechanism by which perturbation of β-cell cholesterol homeostasis and impaired insulin secretion increase adiposity, reduce skeletal muscle mass, and cause systemic inflammation. They further identify β-cell dysfunction as a potential therapeutic target in people at increased risk of developing type 2 diabetes.

Identification of Impaired Second-Phase Insulin Secretion in Various Degrees of Glucose Tolerance in a Chinese Population

AIM

Impaired insulin sensitivity and insulin secretion (ISEC) are major pathophysiologies of type 2 diabetes (T2DM). ISEC has two phases: the first and second phases (second ISEC). In this study, we derived equations to identify patients with second ISEC deficiency (ISEC-D).

METHODS

Data from 96 patients, namely 19 with a normal fasting plasma glucose (FPG) level, 21 with prediabetes, and 56 with T2DM, were enrolled. They underwent a modified low-dose graded glucose infusion test, which was originally proposed by Polonsky et al. The test results were interpreted as the slopes of the changes of plasma insulin against the glucose levels, which were considered second ISEC. Patients with the lowest quartile of the slopes were defined as having ISEC-D. We built three models: Model 0: FPG, Model 1: FPG + waist circumference, and Model 2: Model 1 + fasting plasma insulin. The area under the receiver operating characteristic (aROC) curve was used to determine the predictive power of these models.

RESULTS

Among the metabolic syndrome components, FPG had the largest aROC curve (78.2%). Although aROC curves of Models 1 and 2 (85.2% and 91.5%, respectively) were higher than the aROC curve of FPG, no difference was observed between Models 1 and 0. By contrast, the aROC curve of Model 2 was higher compared with Model 1.

CONCLUSIONS

FPG showed the largest aROC curve. Model 2 had the highest predictive power, which could identify patients with ISEC-D with a sensitivity and specificity of 94.3% and 82.6%, respectively. These two models could be conveniently used in daily practice.

Interleukin-6 as a potential positive modulator of human beta-cell function: an exploratory analysis-the Verona Newly Diagnosed Type 2 Diabetes Study (VNDS) 6

AIMS

Recent studies in mouse models of T2D showed that interleukin-6 (IL-6), released from skeletal muscle, is associated with increased glucose-dependent insulin secretion. Few data currently exist exploring the relationship between IL-6 and beta-cell function in humans. We investigated whether IL-6 is positively associated with beta-cell function in newly diagnosed T2D. We extended the same analyses to IL-10, because it regulated similarly to IL-6 in skeletal muscle, and TNF-α and C-reactive protein (CRP), as general biomarkers of inflammation.

METHODS

In 330 VNDS participants, we assessed (1) basal plasma concentrations of IL-6, IL-10, TNF-α, and CRP; (2) beta-cell function, estimated by OGTT minimal modeling and expressed as derivative (DC) and proportional control (PC); (3) insulin sensitivity, by euglycemic insulin clamp.

RESULTS

IL-6 was positively associated with PC in both univariate analysis (p = 0.04) and after adjustment for age, sex, BMI, HbA1c, and M-clamp (p = 0.01). HbA1c was the major independent contributor to the overall variance of PC (16 %), followed by BMI and IL-6 (~2 % each). Similar results were obtained for IL-10 (p = 0.048, univariate; p = 0.04, fully adjusted). TNF-α and CRP were not significantly associated with any component of beta-cell function.

CONCLUSIONS

Our data are the first evidence in human subjects that an endocrine loop involving IL-6 may act as positive modulator of glucose-dependent insulin secretion. Further functional studies are needed to corroborate IL-6 system as a potential druggable target in diabetes.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01526720 ( http://www.clinicaltrial.gov ).

Comparison of Second-Phase Insulin Secretion Derived from Standard and Modified Low-Dose Graded Glucose Infusion Tests

OBJECTIVES

Insulin secretion has 2 phases, first-phase and second-phase insulin secretion (SPIS). The purpose of our study was to validate the SPIS derived from the modified low-dose graded glucose infusion test (MLDGGI) by using the standard SPIS derived from the low-dose graded glucose infusion test (LDGGI).

METHODS

Fourteen participants were enrolled. The participants underwent the LDGGI for 200 minutes and MLDGGI for 60 minutes. The LDGGI was administered using the standard Polonsky method, which entails 5 40-minute stages of glucose infusion (1, 4, 8, 6 and 24 mg/kg/min). The slopes of the insulin levels vs. the glucose levels obtained during the test were regarded as SPIS (SPIS-I). Furthermore, deconvolution was performed, and slopes of the insulin secretion rate (ISR) against glucose levels during the test (SPIS-D) were obtained and regarded as the gold standard SPIS. The MLDGGI was administered with 3 20-minute stages of glucose infusion (2, 8 and 24 mg/kg/min) for 20 minutes each. The slopes of the insulin levels vs. the glucose levels obtained during the test were regarded as SPIS (MSPIS-I). In addition, deconvolution was performed, and the slopes of the ISR against glucose levels during the test (MSPIS-D) were obtained.

RESULTS

Significant correlations were observed between SPIS-I and SPIS-D (r=0.843; p<0.001) and between MSPIS and SPIS-D (r=0.786; p<0.001).

CONCLUSIONS

SPIS could be determined simply by using the LDGGI without deconvolution. Moreover, MLDGGI was proved to be useful in estimating SPIS easily on the basis of insulin levels.

Estimation of second-phase insulin secretion in the Zucker fatty rat

The purpose of the present study was to test the efficacy of the empiric index SPIR (Second-phase Insulin Release) in the quantification of second-phase insulin secretion in the Zucker Fatty Rat. SPIR index is defined as the area under the curve of insulin between 8 and 90 min after an Intravenous Glucose Tolerance Test (IVGTT). The validation of such index was performed against the second-phase β-cell responsiveness index (Φ₂) provided by C-peptide minimal model. To this aim, Φ₂ and SPIR were simultaneously computed from IVGTT data, measured in six Zucker fatty rats (ZFR), 7-to-9week-old, and seven age-matched Zucker lean rats (ZLR). SPIR index showed a significant linear correlation with Φ₂ (Pearson's correlation coefficient, r = 0.91, R-square = 0.82, P<;0.001). Moreover, both Φ₂ (P<;0.001) and SPIR (P<;0.001) showed a significant increase, in the ZFRs, compared to control group (ZLR). These findings suggest that the SPIR index is able to provide similar information of Φ₂, in the evaluation of the second-phase insulin secretion and of its alteration in Zucker Fatty Rats. Thus, the study proposes the SPIR, as a suitable index for a simple, reliable and low-cost quantification of the second-phase insulin secretion in ZFR.

The changing face of diabetes in youth: lessons learned from studies of type 2 diabetes

The incidence of youth type 2 diabetes (T2D), linked with obesity and declining physical activity in high-risk populations, is increasing. Recent multicenter studies have led to a number of advances in our understanding of the epidemiology, pathophysiology, diagnosis, treatment, and complications of this disease. As in adult T2D, youth T2D is associated with insulin resistance, together with progressive deterioration in β cell function and relative insulin deficiency in the absence of diabetes-related immune markers. In contrast to adult T2D, the decline in β cell function in youth T2D is three- to fourfold faster, and therapeutic failure rates are significantly higher in youth than in adults. Whether the more aggressive nature of youth T2D is driven by genetic heterogeneity or physiology/metabolic maladaptation is yet unknown. Besides metformin, the lack of approved pharmacotherapeutic agents for youth T2D that target the pathophysiological mechanisms is a major barrier to optimal diabetes management. There is a significant need for effective therapeutic options, in addition to increased prevention, to halt the projected fourfold increase in youth T2D by 2050 and the consequences of heightened diabetes-related morbidity and mortality at younger ages.

A common variant in the MTNR1b gene is associated with increased risk of impaired fasting glucose (IFG) in youth with obesity

OBJECTIVE

To explore the role of MTNR1B rs10830963 and G6PC2 rs560887 variants in the pathogenesis of impaired fasting glucose (IFG) in obese adolescents.

METHODS

A total of 346 Caucasians, 218 African-Americans, and 217 Hispanics obese children and adolescents underwent an oral glucose tolerance test (OGTT) and 518 underwent the evaluation of insulin secretion by the oral minimal model (OMM). Also, 274 subjects underwent a second OGTT after 3.0 ± 2.1 years.

RESULTS

The MTNR1B rs10830963 variant was associated with higher fasting glucose levels and lower dynamic beta-cell response in Caucasians and Hispanics (P < 0.05) and conferred an increased risk of showing IFG to Caucasians (P = 0.05), African-Americans (P = 0.0066), and Hispanics (P = 0.024). Despite the association between the G6PC2 rs560887 and higher fasting glucose levels (P < 0.05), there was no association between this variant and IFG at baseline or at follow-up (all P > 0.10).

CONCLUSIONS

It has been shown for the first time in obese youth that the MTNR1B variant is associated with an increased risk of IFG.

Both fasting and glucose-stimulated proinsulin levels predict hyperglycemia and incident type 2 diabetes: a population-based study of 9,396 Finnish men

Background

Hyperproinsulinemia is an indicator of β-cell dysfunction, and fasting proinsulin levels are elevated in patients with hyperglycemia. It is not known whether proinsulin levels after a glucose load are better predictors of hyperglycemia and type 2 diabetes than fasting proinsulin.

Methods

Participants were 9,396 Finnish men (mean±SD, age 57.3±7.1 years, BMI 27.0±4.0 kg/m²) of the population-based METabolic Syndrome In Men Study who were non-diabetic at the recruitment, and who participated in a 6-year follow-up study. Proinsulin and insulin levels were measured in the fasting state and 30 and 120 min after an oral glucose load. Area under the curve (AUC) and proinsulin to insulin ratios were calculated.

Results

Fasting proinsulin, proinsulin at 30 min and proinsulin AUC during the first 30 min of an oral glucose tolerance test significantly predicted both the worsening of hyperglycemia and type 2 diabetes after adjustment for confounding factors. Further adjustment for insulin sensitivity (Matsuda index) or insulin secretion (Disposition index) weakened these associations. Insulin sensitivity had a major impact on these associations.

Conclusion

Our results suggest that proinsulin in the fasting state and after an oral glucose load similarly predict the worsening of hyperglycemia and conversion to type 2 diabetes.

Levels of the first-phase insulin secretion deficiency as a predictor for type 2 diabetes onset by using clinical-metabolic models

AIMS

Type 2 diabetes mellitus (T2DM) is characterized by both decreased insulin sensitivity and impaired insulin secretion. The 2 phases of insulin secretion are the first-phase insulin secretion (1st ISEC) and the second-phase insulin secretion. In this study, we tried to build clinical-metabolic models to predict the 1st ISEC deficiency (ISEC-D) in non-diabetic subjects so that early intervention could be started.

DESIGN AND SETTINGS

A cross-sectional study was conducted in the clinical research department of a hospital in Taiwan from 2010 to 2011.

METHODS

A total of 89 subjects without diabetes were enrolled in the study, including 49 with normal glucose tolerance and 40 pre-diabetes. A frequently sampled intravenous glucose tolerance test was done to determine insulin sensitivity and acute insulin response after the glucose load, which is regarded as the 1st ISEC. Subjects with the lowest tertile of the 1st ISEC were defined as ISEC-D. From the simplest to the most complex, 3 models were build: Model 0: fasting plasma glucose (FPG); Model 1: FPG + body mass index (BMI) + High-density lipoprotein cholesterol (HDL-C); Model 2: Model 1+ fasting plasma insulin (FPI). The area under the receiver-operating characteristic curve (aROC curve) was used to determine the predictive power among these models. An optimal cut-off value was also determined.

RESULTS

Among metabolic syndrome (MetS) components (FPG, BMI, and HDL-C), FPG had the greatest aROC curve (70.9%). Moreover, the aROC curves of Models 1 and 2 were all significantly greater than that of FPG (80.4% and 82.3%, respectively). Their aROC curves were also greater than that of the homeostasis model assessment b-cell (HOMA-b) function, which is the most commonly used method to evaluate b-cell function.

CONCLUSION

By using only MetS components, ISEC-D could be predicted with an acceptable sensitivity of 84.0% and a specificity of 74.0%. However, after adding FPI into the Model, the predictive power of Model 2 did not increase. These model-derived MetS components could be widely used in clinical settings and early detection of non-diabetic subjects with high risk for T2DM.

Rapid deterioration of insulin secretion in obese adolescents preceding the onset of type 2 diabetes

OBJECTIVE

To identify pathophysiologic changes that lead to the onset of type 2 diabetes (T2DM) in adolescents.

STUDY DESIGN

Obese adolescents with normal glucose tolerance (n = 41) were studied longitudinally over the course of 4 years with serial measure of the acute insulin response to glucose (AIRg) as well as proinsulin (PI) concentrations. Insulin resistance was estimated with the homeostatic model assessment of insulin resistance (HOMA-IR), the disposition index (DI) computed as AIRg × 1/HOMA-IR, and intravenous glucose tolerance estimated as the glucose disappearance constant.

RESULTS

Four adolescents developed diabetes mellitus (DM) during the study, and the rest of the cohort remained nondiabetic. Baseline PI exceeded the IQR of the nondiabetic group in 3 of 4 subjects with DM, and all had >85% reduction from baseline AIRg, and DI, within 6 months of diagnosis. All the subjects with DM gained weight over the course of the study, but these changes paralleled those for the nondiabetic group. HOMA-IR increased substantially in 1 of the subjects with DM at the time of diagnosis but was comparable with baseline in the other 3. The DI and glucose disappearance constant of the subjects with DM was less than the 10th percentile of the nondiabetic group before and after diagnosis.

CONCLUSION

Conversion from normal glucose tolerance to T2DM in adolescents can occur rapidly, and the onset of T2DM is heralded by a substantial decrease in AIRg and DI, as well as increased release of PI. These results support loss of β-cell function as the proximate step in the development of T2DM in this age group.