Glucose effectiveness in obese children: relation to degree of obesity and dysglycemia

Sumatriptan, a serotonin 5HT1B receptor agonist, acutely reduces insulin secretion and sensitivity and glucose effectiveness in overweight humans: A double-blinded placebo-controlled cross-over trial

AIM

Evidence from mouse models suggests that brain serotonergic pathways control blood glucose. We hypothesized that sumatriptan (5HT1B -receptor agonist) would alter glucose homeostasis in humans.

MATERIALS AND METHODS

We conducted a two-visit random-order double-blinded placebo-controlled cross-over trial in 10 overweight adults that were otherwise healthy. Participants received sumatriptan (single dose, 100 mg) or placebo before undergoing a 60-min intravenous glucose tolerance test, followed by a 120-min hyperinsulinaemic euglycaemic clamp.

RESULTS

Glucose excursion was greater during intravenous glucose tolerance test with sumatriptan compared with placebo [iAUC0-60 min 316 (268-333) vs. 251 (197-319) min/mmol/L p = .047]. This was probably explained by a combination of reduced circulating insulin levels [iAUC0-10 min 1626 (1103-2733) vs. 2336 (1702-3269) min/pmol/L, p = .005], reduced insulin sensitivity [M/I-value 2.11 (1.15, 4.05) vs. 3.03 (1.14, 4.90) mg/kg/min per pmol/L, p = .010] and glucose effectiveness [SG 0.17 (0.12, 0.21) vs. 0.22 (0.18, 0.65)/min, p = .027].

CONCLUSIONS

5HT1B receptors have a glucoregulatory role in humans, probably acting on insulin secretion, insulin sensitivity and glucose effectiveness.

Prevalence and Predictive Clinical Characteristics of Metabolically Healthy Obesity in Obese Children and Adolescents

BACKGROUND

The increasing prevalence of childhood obesity and accompanying comorbidities all over the world constitutes one of the most important public health problems of the changing world. The frequency and causes of the metabolically healthy obesity (MHO) phenotype in children is not clear.

OBJECTIVE

The objective is to determine the prevalence of the MHO phenotype in obese Turkish children and adolescents and to identify clinical and biochemical indicators for this phenotype.

METHODS

Eight hundred forty-seven obese children and adolescents, aged 3-18 years with BMI-SDS >+2 SD from the obesity outpatient clinic were included. Demographic, anthropometric, and physical examination information was collected from patient medical files. In addition, obesity-related comorbidities and results of laboratory tests were obtained. For study purposes, obese patients with no cardiometabolic risk factors were accepted as MHO, and those with ≥1 cardiometabolic risk factor were considered metabolically unhealthy obese (MUO). MHO was defined according to Damanhoury's criteria.

RESULTS

Out of 847 children (mean age 10.6±3.4 years) who met the study criteria, 289 (34.1%) were diagnosed with MHO. Being younger, prepubertal, having relatively low BMI, low waist/hip ratio, low insulin resistance (HOMA-IR) index, high high-density lipoprotein, low triglyceride, low fasting insulin and glucose levels, low uric acid and low alanine transaminase (ALT) levels were associated with MHO.

CONCLUSIONS

The MHO phenotype was present in just over a third of this obese pediatric cohort. The most important factors associated with MHO; age, waist-hip ratio, and BMI were determined.

Appraisal of Clinical Care Practices for Child Obesity Treatment. Part II: Comorbidities

The objective of this technical report is to provide clinicians with actionable evidence-based information upon which to make treatment decisions. In addition, this report will provide an evidence base on which to inform clinical practice guidelines for the management and treatment of overweight and obesity in children and adolescents. To this end, the goal of this report was to identify all relevant studies to answer 2 overarching key questions: (KQ1) "What are effective clinically based treatments for obesity?" and (KQ2) "What is the risk of comorbidities among children with obesity?" See Appendix 1 for the conceptual framework and a priori Key Questions.

Association of total and pancreatic serum amylase enzymatic activity with insulin resistance and the glucose and insulin responses to oral starch test in Mexican children

BACKGROUND/OBJECTIVES

Little is known about the effect of serum amylase enzymatic activity on glucose metabolism. We investigated the association of serum amylase enzymatic activity with fasting plasma glucose, insulin resistance (IR), and the plasma glucose and insulin response to an oral starch test (OST) in Mexican children.

METHODS

Anthropometric data, glucose and insulin levels, and the serum enzymatic activity of total (AMYt), salivary (AMY1), and pancreatic (AMY2) amylase were analysed in 764 children (N_{normal weight}  = 427/N_obesity  = 337). After categorization into low (LA) and high (HA) AMYt, an OST with commercial white bread was performed in 39 children (N_{normal weight}  = 17/N_obesity  = 22).

RESULTS

A positive association between serum enzymatic activity of AMY2 and IR was observed in children with obesity (p = 0.018). Children with normal weight had lower plasma glucose and insulin response to OST than children with obesity (P_glucose  = 4.1 × 10^-12 ; P_insulin  = 2.1 × 10^-15 ). Compared with the LA group, children with HA showed lower plasma glucose and insulin response to OST (P_glucose  ≤ 0.040; P_insulin  ≤ 0.015).

CONCLUSION

Our results suggest that AMY2 is positively associated with IR. A high level of AMYt is related to lower glucose and insulin responses to OST in Mexican children, regardless of their weight status.

Effects of interrupting daily sedentary behavior on children's glucose metabolism: A 6-day randomized controlled trial

BACKGROUND

Metabolic disease risk in youth is influenced by sedentary behaviors. Acute in-lab studies show that, during a single day, interrupting a sedentary period with short bouts of physical activity improves glucometabolic outcomes.

OBJECTIVE

To determine if acutely improved glucose metabolism persists after multi-day interruptions of sitting with walking brief bouts. We hypothesized that children who underwent interrupting sitting on multiple days would demonstrate lower insulin area under the curve during an oral glucose tolerance test compared to uninterrupted sitting.

METHODS

Healthy, normoglycemic children (N = 109) ages 7-11 years were randomized to one of two conditions: Control (3 h of daily Uninterrupted Sitting) or Interrupted Sitting (3-min of moderate-intensity walking every 30 min for 3 h daily); with dietary intake controlled through provision of foodstuffs for the entire experiment. Participants attended six consecutive daily visits at a research ambulatory unit. The primary outcome was insulin area under the curve during the oral glucose tolerance test on day 6 during interrupted or uninterrupted sitting; secondary outcomes included glucose and c-peptide area under the curve, energy intake at a buffet meal on day 6, and free-living activity.

RESULTS

Among 93 children (42 uninterrupted sitting, 51 interrupted sitting), daily interrupted sitting resulted in 21% lower insulin (β = 0.102 CI:0.032-0.172, p = 0.005) and a 10% lower C-peptide (β = 0.043, CI:0.001-0.084, p = 0.045) area under the curve. Matsuda and Glucose Effectiveness Indices were also improved (p's < 0.05). There were no group differences in energy intake or expenditure.

CONCLUSIONS

Sustained behavioral change by interrupting sedentary behaviors is a promising intervention strategy for improving metabolic risk in children.

Autoimmune reaction against pancreatic beta cells in children and adolescents with simple obesity

INTRODUCTION

One of the most important complications of obesity is insulin resistance, which leads to carbohydrate metabolism disorders such as type 2 diabetes. However, obesity is also associated with development of an autoimmune response against various organs, including pancreatic beta cells. The prevalence of such autoimmune processes in children and their possible contribution to the increased incidence of type 1 diabetes is currently unclear. Therefore, the present study assessed the prevalence of autoantibodies against pancreatic islet beta cell's antigens in children and adolescents with simple obesity.

MATERIAL AND METHODS

This prospective observational study included pediatric patients (up to 18 years of age) with simple obesity hospitalized between 2011 and 2016 at the Department of Pediatrics, Diabetology, Endocrinology and Nephrology of the Medical University of Lodz. Children with acute or chronic conditions that might additionally affect insulin resistance or glucose metabolism were excluded. Collected clinical data included sex, age, sexual maturity ratings (Tanner`s scale), body height and weight, waist and hip circumference, amount of body fat and lean body mass. Each participant underwent a 2-hour oral glucose tolerance test with simultaneous measurements of glycaemia and insulinemia at 0`, 60` and 120`. In addition, glycated hemoglobin HbA1c, fasting and stimulated c-peptide, total cholesterol, as well as high- and low-density cholesterol and triglycerides were measured. Insulin resistance was assessed by calculating HOMA-IR index. The following autoantibodies against pancreatic islet beta cells were determined in each child: ICA - antibodies against cytoplasmic antigens of pancreatic islets, GAD - antibodies against glutamic acid decarboxylase, ZnT8 - antibodies against zinc transporter, IA2 - antibodies against tyrosine phosphatase, IAA - antibodies against insulin.

RESULTS

The study group included 161 children (57.4% boys, mean age 13.1 ± 2.9 years) with simple obesity (mean BMI z-score +2.2 ± 1.6). Among them, 28 (17.4%) were diagnosed with impaired glucose metabolism during OGTT [23 (82.2%) - isolated impaired glucose tolerance (IGT), 3 (10.7%) - isolated impaired fasting glucose (IFG), 2 (7.1%) - IFG and IGT]. Of the children tested, 28 (17.4%) were tested positive for at least one islet-specific autoantibody [with similar percentages in boys (15, 17.4%) and girls (13, 17.3%), p=0.9855], with ICA being the most common (positive in 18, 11.2%), followed by IAA (7, 4.3%), ZnT8 (5, 3.1%), GADA (3, 1.9%) and IA2 (1, 0.6%). There was no association between the presence of the tested antibodies and age, sex, stage of puberty, parameters assessing the degree of obesity, HbA1c, lipid levels and basal metabolic rate. However, autoantibody-positive subjects were more likely to present IFG or IGT in OGTT compared to those who tested completely negative (9, 32.1% vs 19, 14.3%, p=0.0280). Their HOMA-IR was also significantly higher (HOMA-IR: 4.3 ± 1.9 vs 3.4 ± 1.9, p=0.0203) and this difference remained statistically significant after adjusting for sex and age (p=0.0340).

CONCLUSIONS

Children and adolescents with simple obesity presented a higher prevalence of markers of autoimmune response against pancreatic beta cells than the general population. Most often, they had only one type of antibody - ICA. The presence of autoimmune response indicators against pancreatic islet antigens is more common in obese patients with impaired carbohydrate metabolism and is associated with lower insulin sensitivity.

Relation of glomerular filtration to insulin resistance and related risk factors in obese children

BACKGROUND AND OBJECTIVE

Childhood obesity is associated with later development of significant renal morbidity. We evaluated the impact of the degree of insulin sensitivity on estimated glomerular filtration rate (eGFR) and determined the factors associated with eGFR in obese children. We further tested the relation of eGFR to clinical outcomes such as blood pressure and microalbuminuria.

MATERIALS AND METHODS

We evaluated the relation of whole body insulin sensitivity and estimated glomerular filtration rate (eGFR) across the spectrum of obesity in children and adolescents. eGFR was calculated using the iCARE formula, which has been validated in obese children with varying glucose tolerance.

RESULTS

1080 children and adolescents with overweight and obesity (701 females and 379 males) participated. Insulin sensitivity was a strongly negatively associated with (B = -2.72, p < 0.001) eGFR), even after adjustment for potential confounders. Male sex emerged to be significantly associated with eGFR with boys having greater values than girls (B = 18.82, p < 0.001). Age was a positively associated (B = 2.86, p < 0.001) with eGFR. Whole body and hepatic insulin sensitivity decreased across eGFR quartiles. Adjusted eGFR was tightly positively associated with systolic blood pressure (B = 0.09, p = 0.003) and negatively associated with the presence of microalbuminuria (B = -2.18, p = 0.04).

CONCLUSIONS

eGFR tends to increase with greater degrees of insulin resistance in children and adolescents representing hyperfiltration and is associated with cardiovascular risk factors. Longitudinal studies are needed to determine the natural history of childhood insulin resistance related hyperfiltration in regards to future kidney disease.

The relationships between hemoglobin and insulin resistance, glucose effectiveness, and first- and second-phase insulin secretion in adult Chinese

OBJECTIVE

We denote the four major factors related to the development of type 2 diabetes (T2D) as "diabetes factor" (DF); increased insulin resistance (IR); decreased glucose effectiveness (GE); and the first-and-second-phase of insulin secretion (FPIS, SPIS). The level of hemoglobin (Hb) was found to be related to IR and FPIS, but no-known studies focused on its role in relation to SPIS and GE. In this study, we aim to evaluate the relationships between Hb and all four DFs in the same individual.

SUBJECTS AND METHODS

We randomly enrolled 24,407 men and 24,889 women between 30 and 59 years old. IR, FPIS, SPIS and GE were measured according to equations published in our previous studies. To compare the slopes between Hb and the four DFs with different units, we converted their units to percent of change per unit of increased Hb.

RESULTS

Age, HDL-cholesterol and GE were higher in women; BMI, blood pressure, LDL-cholesterol, TG, Hb, FPIS, SPIS and IR were higher in men. After they were converted into percentage, the closeness of their relationships to Hb, from the highest to the lowest, were GE, IR, FPIS and SPIS for women and IR, GE, FPIS and SPIS for men. GE was the only one negatively related to Hb.

CONCLUSIONS

Our data showed that IR, FPIS and SPIS were both positively and, GE negatively, related to the Hb in adult Chinese. For women, GE had the closest association with Hb; for men, it was IR. Both phases of insulin secretion had relatively weaker relationships than IR and GE.

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.

Oral glucose effectiveness and metabolic risk in obese children and adolescents

AIM

To investigate whether GE is affected in children/adolescents with obesity and abnormalities of the metabolic syndrome (MetS).

METHODS

Cross-sectional study of oral GE (oGE), insulin sensitivity and secretion (calculated on 5 time-points oral glucose tolerance test) and metabolic abnormalities in 1012 patients with overweight/obesity (aged 6.0-17.9 years old). A MetS risk score was calculated on the basis of distribution of fasting glucose, triglycerides, HDL-cholesterol, total cholesterol, systolic and diastolic blood pressure. Non-alcoholic fatty liver disease (NAFLD) was suspected based on thresholds of alanine aminotransferases.

RESULTS

Four-hundred and eighty patients (47.73%) had low-MetS risk score, 488 medium (48.22% with 1-2 risk factors) and 41 (4.05% with ≥ 3 factors) high risk. oGE was significantly lower in subjects with obesity [3.81 (1.46) mg/dl/min^- 1] than in those with overweight [4.98 (1.66) mg/dl/min^- 1; p value < 0.001]. oGE was negatively correlated with BMI (ρ = - 0.79; p < 0.001) and BMI z score (ρ = - 0.56; p < 0.001) and decreased significantly among MetS risk classes (p = 0.001). The median difference of oGE from low to medium risk was estimated to be as - 4.9%, from medium to high as - 13.38% and from low to high as - 17.62%. oGE was not statistically different between NAFLD+ and NAFLD- cases.

CONCLUSIONS

In children and adolescents with obesity oGE decreases. Noteworthy, it decreases as the Met score increases. Therefore, reduced oGE may contribute to the higher risk of these individuals to develop type 2 diabetes.

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.

Effects of growth hormone on hepatic insulin sensitivity and glucose effectiveness in healthy older adults

PURPOSE

Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.

METHODS

This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.

RESULTS

GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.

CONCLUSIONS

GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.

Exercise-induced improvements in glucose effectiveness are blunted by a high glycemic diet in adults with prediabetes

AIMS

Glucose effectiveness (GE) refers to the ability of glucose to influence its own metabolism through insulin-independent mechanisms. Diminished GE is a predictor of progression to type 2 diabetes. Exercise training improves GE, however, little is known about how dietary interventions, such as manipulating the glycemic index of diets, interact with exercise-induced improvements in GE in at-risk populations.

METHODS

We enrolled 33 adults with obesity and pre-diabetes (17 males, 65.7 ± 4.3 years, 34.9 ± 4.2 kg m^-2) into a 12-week exercise training program (1 h day^-1 and 5 day week^-1 at ~ 85% of maximum heart rate) while being randomized to concurrently receive either a low (EX-LOG: 40 ± 0.3 au) or high (EX-HIG: 80 ± 0.6 au) glycemic index diet. A 75-g oral-glucose-tolerance test (OGTT) was performed before and after the intervention and GE was calculated using the Nagasaka equation. Insulin resistance was estimated using a hyperinsulinemic-euglycemic clamp and cardiorespiratory fitness using a VO_2max test.

RESULTS

Both EX-LOG and EX-HIG groups had similar improvements in weight (8.6 ± 5.1 kg, P < 0.001), VO_2max (6 ± 3.5 mL kg^-1 min^-1, P < 0.001) and clamp-measured peripheral insulin resistance (1.7 ± 0.9 mg kg^-1 min^-1, P < 0.001), relative to baseline data. GE in EX-LOG and EX-HIG was similar at baseline (1.9 ± 0.38 vs. 1.85 ± 0.3 mg dL^-1 min^-1, respectively; P > 0.05) and increased by ~ 20% post-intervention in the EX-LOG arm (∆GE: 0.07-0.57 mg dL^-1 min^-1, P < 0.05). Plasma free fatty acid (FFA) concentrations also decreased only in the EX-LOG arm (∆FFA: 0.13 ± 0.23 mmol L^-1, P < 0.05).

CONCLUSIONS

Our data suggest that a high glycemic index diet may suppress exercise-induced enhancement of GE, and this may be mediated through plasma FFAs.

Assessing the predictive accuracy of oral glucose effectiveness index using a calibration model

PURPOSE

Current reference methods for measuring glucose effectiveness (GE) are the somatostatin pancreatic glucose clamp and minimal model analysis of frequently sampled intravenous glucose tolerance test (FSIVGTT), both of which are laborious and not feasible in large epidemiological studies. Consequently, surrogate indices derived from an oral glucose tolerance test (OGTT) to measure GE (oGE) have been proposed and used in many studies. However, the predictive accuracy of these surrogates has not been formally validated. In this study, we used a calibration model analysis to evaluate the accuracy of surrogate indices to predict GE from the reference FSIVGTT (Sg_MM).

METHODS

Subjects (n = 123, mean age 48 ± 11 years; BMI 35.9 ± 7.3 kg/m²) with varying glucose tolerance (NGT, n = 37; IFG/IGT, n = 78; and T2DM, n = 8) underwent FSIVGTT and OGTT on two separate days. Predictive accuracy was assessed by both root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE).

RESULTS

As expected, insulin sensitivity, Sg_MM, and oGE were reduced in subjects with T2DM and IFG/IGT when compared with NGT. Simple linear regression analyses revealed a modest but significant relationship between oGE and Sg_MM (r = 0.25, p < 0.001). However, using calibration model, measured Sg_MM and predicted Sg_MM derived from oGE were modestly correlated (r = 0.21, p < 0.05) with the best fit line suggesting poor predictive accuracy. There were no significant differences in CVPE and RMSE among the surrogates, suggesting similar predictive ability.

CONCLUSIONS

Although OGTT-derived surrogate indices of GE are convenient and feasible, they have limited ability to robustly predict GE.

Pathogenic Mechanisms of Prediabetes in Obese vs. Very Obese African American Women: Implications for Diabetes Prevention

BACKGROUND

The influence of obesity on the development of prediabetes among African American women (AAW) remains uncertain. Thus, we investigated whether the pathogenic mechanisms of prediabetes differ in obese (OB, BMI<35 kg/m2) and very obese (VOB, BMI>35 kg/m2) AAW.

SUBJECTS/METHODS

We recruited 26-OB and 41-VOB, AAW with prediabetes, mean age (46.3 ± 10.3 years), A1C (5.9 ± 0.4%) and BMI (38.3 ± 8.2 kg/m2). OGTT and FSIVGT were performed in each subject. Body composition (% body fat) was measured using DEXA. Si, Sg acute insulin response to glucose (AIRg) and disposition index (DI) were calculated using minimal model method.

RESULTS

Mean BMI (32.6 ± 1.9 vs. 42.8 ± 5.5 kg/m2) and %body fat (44.7 ± 2.0 vs. 49.6 ± 2.2%) were significantly (p = 0.0001) lower in OB vs VOB. Mean fasting and post-glucose challenge, (glucose, insulin, c-peptide) levels were significantly (p = 0.03-0.0001) lower in OB vs VOB. Mean Si and Sg was not different. Mean AIRg tended to be higher (808 ± 776 vs. 535 ± 443 (x min [uU/L] -1), p = 0.106) whereas DI was greater (1999 ± 1408 vs. 1511 ± 1033, (×10-2 x min-1), p = 0.01) in OB vs VOB subjects.

CONCLUSION

We found that OB and VOB AAW had similar Si and Sg, but VOB showed attenuated AIRg and DI. These parameters should be considered when developing primary prevention programs in AAW with prediabetes.

Children With Metabolically Healthy Obesity: A Review

Children with "metabolically healthy obesity" (MHO) are a distinct subgroup of youth with obesity, who are less prone to the clustering of cardiometabolic risk factors. Although this phenotype, frequently defined by the absence of metabolic syndrome components or insulin resistance, was first described during the early 1980s, a consensus-based definition of pediatric MHO was introduced only recently, in 2018. The purpose of this review was to concisely summarize current knowledge regarding the MHO phenomenon in youth. The prevalence of MHO in children varies from 3 to 87%, depending on the definition used and the parameters evaluated, as well as the ethnicity and the pubertal status of the sample. The most consistent predictors of MHO in youth include younger age, lower body mass index, lower waist circumference, and lower body fat measurements. Various hypotheses have been proposed to elucidate the underlying factors maintaining the favorable MHO phenotype. While preserved insulin sensitivity and lack of inflammation were previously considered to be the main etiological factors, the most recent findings have implicated adipokine levels, the number of inflammatory immune cells in the adipose tissue, and the reduction of visceral adiposity due to adipose tissue expandability. Physical activity and genetic factors also contribute to the MHO phenotype. Obesity constitutes a continuum-increased risk for cardiometabolic complications, which is less evident in children with MHO. However, some findings have highlighted the emergence of hepatic steatosis, increased carotid intima-media thickness and inflammatory biomarkers in the MHO group compared to peers without obesity. Screening should be directed at those more likely to develop clustering of cardiometabolic risk factors. Lifestyle modifications should include behavioral changes focusing on sleep duration, screen time, diet, physical activity, and tobacco smoke exposure. Weight loss has also been associated with the improvement of insulin sensitivity and inflammation. Further investigative efforts are needed in order to elucidate the mechanisms which protect against the clustering of cardiometabolic risk factors in pediatric obesity, to provide more efficient, targeted treatment approaches for children with obesity, and to identify the protective factors preserving the MHO profile, avoiding the crossover of MHO to the phenotype with metabolically unhealthy obesity.

Effects of Interrupting Sedentary Behavior With Short Bouts of Moderate Physical Activity on Glucose Tolerance in Children With Overweight and Obesity: A Randomized Crossover Trial

OBJECTIVE

Sedentary children have greater risk of developing abnormalities in glucose homeostasis. We investigated whether interrupting sedentary behavior (sitting) with very short periods of walking would improve glucose metabolism without affecting dietary intake in children with overweight or obesity. We hypothesized that interrupting sitting with short bouts of moderate-intensity walking would decrease insulin area under the curve (AUC) during an oral glucose tolerance test (OGTT) compared with uninterrupted sitting.

RESEARCH DESIGN AND METHODS

Overweight/obese (BMI ≥85th percentile) children 7-11 years of age underwent two experimental conditions in random order: prolonged sitting (3 h of continuous sitting) and interrupted sitting (3 min of moderate-intensity walking at 80% of ventilatory threshold every 30 min for 3 h). Insulin, C-peptide, and glucose were measured every 30 min for 3 h during an OGTT. Each session was followed by a buffet meal. Primary outcomes were differences in OGTT hormones and substrates and in buffet meal intake by condition.

RESULTS

Among 35 children with complete data, mixed-model results identified lower insulin and C-peptide in the interrupted condition (P = 0.007 and P = 0.029, respectively); the intervention reduced insulin AUC by 21% (P < 0.001) and C-peptide AUC 18% (P = 0.001) and improved estimated insulin sensitivity (P = 0.013). Neither buffet total energy intake (1,262 ± 480 vs. 1,260 ± 475 kcal; P = 0.89) nor macronutrient composition of the meal (P values >0.38) differed between conditions significantly.

CONCLUSIONS

Interrupting sitting with brief moderate-intensity walking improved glucose metabolism without significantly increasing energy intake in children with overweight or obesity. Interrupting sedentary behavior may be a promising intervention strategy for reducing metabolic risk in such 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.

Leptin enhances hypothalamic lactate dehydrogenase A (LDHA)-dependent glucose sensing to lower glucose production in high-fat-fed rats

The responsiveness of glucose sensing per se to regulate whole-body glucose homeostasis is dependent on the ability of a rise in glucose to lower hepatic glucose production and increase peripheral glucose uptake in vivo In both rodents and humans, glucose sensing is lost in diabetes and obesity, but the site(s) of impairment remains elusive. Here, we first report that short-term high-fat feeding disrupts hypothalamic glucose sensing to lower glucose production in rats. Second, leptin administration into the hypothalamus of high-fat-fed rats restored hypothalamic glucose sensing to lower glucose production during a pancreatic (basal insulin)-euglycemic clamp and increased whole-body glucose tolerance during an intravenous glucose tolerance test. Finally, both chemical inhibition of hypothalamic lactate dehydrogenase (LDH) (achieved via hypothalamic LDH inhibitor oxamate infusion) and molecular knockdown of LDHA (achieved via hypothalamic lentiviral LDHA shRNA injection) negated the ability of hypothalamic leptin infusion to enhance glucose sensing to lower glucose production in high fat-fed rats. In summary, our findings illustrate that leptin enhances LDHA-dependent glucose sensing in the hypothalamus to lower glucose production in high-fat-fed rodents in vivo.

Impact of Severe Obesity on Cardiovascular Risk Factors in Youth

OBJECTIVE

To compare cardiovascular risk factor clustering (CVRFC) in severely obese youth with those with lower degrees of obesity.

STUDY DESIGN

We divided a childhood obesity clinic derived cohort into the degrees of obesity (class I, II, and III) and added a "class IV" category corresponding to >160% of the 95th centile of body mass index (BMI) for age and sex. In a cross-sectional analysis, we investigated the presence of CVRFC in 2244 participants; in 621 who were followed longitudinally, we investigated the determinants of endpoint CVRFC.

RESULTS

Class IV obesity was associated with increased risk for CVRFC compared with overweight (OR = 17.26, P < .001) at a similar magnitude to class III obesity (OR = 17.26, P < .001). Male children were at greater risk for presence of CVRFC (OR = 1.57, P = .03) compared with female children. Adiponectin (OR = 0.90, P < .001) and leptin levels (OR = 0.98, P = .008) were protective, independent of degree of obesity. Baseline class IV obesity was associated with increased risk compared with overweight of having CVRFC at follow-up (OR = 5.76, P = .001), to a similar extent as class III obesity (OR = 5.36, P = .001). Changes in the degree of obesity were significant predictors of CVRFC on follow-up (OR = 1.04, P < .01 per percent BMI change).

CONCLUSIONS

The metabolic risk associated with obesity in childhood is conferred prior to reaching class IV obesity. An individualized risk stratification approach in children with severe obesity should be based on presence of complications rather than simple BMI cutoffs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01967849.

Pilot study of sleep and meal timing effects, independent of sleep duration and food intake, on insulin sensitivity in healthy individuals

This pilot study tested the independent and interactive effects of sleep and meal times, under identical sleep duration and feeding conditions, on insulin sensitivity (Si) in overweight adults. Participants underwent a 4-phase randomized crossover inpatient study differing in sleep times: normal (Ns: 0000-0800 hours) or late (Ls: 0330-1130 hours); and in meal times: normal (Nm: 1, 5, 11, and 12.5 hours after awakening) or late (Lm: 4.5, 8.5, 14.5, and 16 hours after awakening). An insulin-modified frequently sampled intravenous glucose tolerance test, at scheduled breakfast time, and a meal tolerance test, at scheduled lunch time, were performed to assess Si after 3 days in each condition. Six participants were enrolled (4 men, 2 women; mean age 25.1±[SD] 3.9 years, body mass index 29.2±2.7 kg/m²); only 1 failed to complete her last study phase. There were no effects of sleep and meal times or sleep × meal time interaction on Si (all P>.35), acute insulin response to intravenous glucose (all P>.20), and disposition index (all P>.60) after adjusting for sex and body mass index. Meal tolerance test glucose and insulin areas under the curve were lower during Nm (glucose P=.11; insulin P=.0088). There were a sleep × meal interaction and an effect of meal times on overnight glucose (P=.0040 and .012, respectively) and insulin (P=.0075 and .067, respectively). Sleep timing, without concomitant sleep restriction, does not adversely affect Si and glucose tolerance, but meal times may be relevant for health. Our results should be confirmed in a larger sample.

Prediabetes in youth - mechanisms and biomarkers

Obesity has been estimated to decrease life expectancy by as little as 0.8 to as much as 7 years being the second leading cause of preventable death in the United States after smoking. Along with the increase in the prevalence of obesity, there has been a dramatic rise of the prevalence of prediabetes and type 2 diabetes among adolescents. Despite that, very little is known about the pathogenesis of these conditions in pediatrics and about how we could detect prediabetes in an early stage in order to prevent full blown diabetes. In this review we summarize the current knowledge on the pathophysiology of prediabetes and type 2 diabetes in adolescents and describe how biomarkers of beta-cell function might help identifying those individuals who are prone to progress from normal glucose tolerance towards prediabetes and overt type 2 diabetes. To better understand and fight this disease, we will need to explore and develop novel therapeutic strategies and individuate more sensitive and specific biomarkers that can allow an earlier detection of the disease.

Novel association between the nonsynonymous A803G polymorphism of the N-acetyltransferase 2 gene and impaired glucose homeostasis in obese children and adolescents

BACKGROUND

The N-acetyltransferase 2 ( NAT2 ) A803G polymorphism has been associated with decreased insulin sensitivity in a large adult population with the A allele associated with insulin-resistance-related traits.

OBJECTIVE

Evaluate the association of this polymorphism with anthropometric and metabolic parameters in obese children and adolescents.

SUBJECTS

A total of 748 obese children and adolescents were enrolled.

METHODS

Anthropometric and laboratory data were collected. During oral glucose tolerance test, the presence of a possible exaggerated plasma glucose excursion at 1 h (1HPG) or impaired glucose tolerance (IGT) was considered. Homeostasis model assessment, oral disposition index (oDI) and insulinogenic index (IDI) were calculated. Patients were genotyped for the NAT2 A803G polymorphism.

RESULTS

The prevalence of both IGT and elevated-1HPG was higher in children carrying the A803 allele (P = .02 and P = .03). Moreover, this allele was associated with both oDI and IGI reduction (P = .01). No differences among the NAT2 A803G genotypes for the other parameters were shown. Children homozygous for the A allele presented an odds ratio (OR), to show IGT of 4.9 (P = .01). Children both homozygous and heterozygous for the A allele had higher risk to show elevated-1HPG (OR of 2.7, P = .005; and OR = 2.3, P = .005) compared with patients homozygous for the NAT2 803G allele.

CONCLUSIONS

NAT2 A803 allele seems to play a role in worsening the destiny of obese children carrying it, predisposing them to elevated-1HPG and IGT and then to a possible future type 2 diabetes mellitus throughout an impairment of pancreatic β-cellular insulin secretion as suggested by oDI and IGI reduction.

Ethnic differences in glucose effectiveness and disposition index in overweight/obese African American and white women with prediabetes: A study of compensatory mechanisms

OBJECTIVE

Prediabetes, a major precursor of type 2 diabetes, varies among ethnic populations. Therefore, we compared the pathophysiologic mechanisms of prediabetes in overweight/obese African American (AA) and White American (WA) women.

SUBJECTS AND METHODS

We recruited 95 women (67 AA, 28 WA) with prediabetes. Standard OGTT and FSIVGTT were performed in each subject. Insulin sensitivity (Si), glucose effectiveness (Sg), beta cell function (acute insulin response to glucose (AIRg) and disposition index (DI: Si×AIRg) were calculated using Bergman's Minmod.

RESULTS

Mean BMI was greater in AA vs WA with prediabetes (38.3±8.2vs 34.6±8.5kg/m², p=0.05). Mean fasting serum glucose, and insulin levels were lower in AA vs WA. Similarly, mean peak serum glucose levels were lower while peak insulin levels were higher at 30 and 60minutes in AA vs WA. In contrast, mean fasting and peak serum c-peptide levels at 60 and 90minutes were significantly lower in AA vs WA. Mean AIRg was higher but not significantly different in AA vs WA (633±520.92 vs 414.8±246.8, p=0.193). Although, Si (2.93±3.25vs 44 2.50±1.76 (×10^-4×min^-1 [μU/ml]^-1), p=0.448) was not different, DI was significantly higher in AA vs WA (1381±1126 vs 901.9±477.1, p=0.01). In addition, mean Sg was significantly higher in AAvs WA (2.51±1.17 vs 1.97±0.723 (×10^-2/min), p=0.02).

CONCLUSIONS

We found that in overweight/obese prediabetic AA and WA women with similar Si, the mean Sg and DI were significantly higher in AA. We conclude that the pathophysiologic mechanisms of prediabetes differ in the overweight/obese AA and WA women.

FKBP5 polymorphism is associated with insulin resistance in children and adolescents with obesity

OBJECTIVE

Since metabolic syndrome shares several clinical features with hypercortisolism, it was hypothesised that genes altering individual glucocorticoid (GC) sensitivity might be implicated in pathogenesis of obesity and its adverse outcomes. FKBP5 gene encodes a chaperon protein in the GC receptor (GR) complex, which modulates steroid action upon target genes. Its functional variant, rs1360780, may enhance FKBP5 gene transcription, affect GR signalling and thereby influence the hypothalamo-pituitary-adrenal axis. We investigated the association of rs1360780 with obesity and metabolic characteristics in 250 obese children and adolescents (mean age 12.3±3.6years, BMI ≥95th percentile).

METHODS

Anthropometric measurements, body composition, biochemical and hormonal results were analysed. Genotyping of rs1360780 was compared with 568 lean controls.

RESULTS

Impaired fasting glucose was present in 8.8%, glucose intolerance in 10.4%, diabetes in 2.8% and dyslipidemia in 28.8% obese individuals. Hypertension was diagnosed in 34 out of 143 patients. No difference was found in FKBP5 polymorphism distribution between subjects with obesity and controls (p>0.05). Stratification by rs1360780 revealed no differences in body mass and composition. However, carriers of the minor allele displayed enhanced insulin resistance (p=0.009) and elevated serum triglyceride (p=0.006), whereas cholesterol, HbA1c, and oral glucose challenge results were similar for all genotypes. Morning ACTH and cortisol did not differ but evening cortisol was higher in minor allele carriers (p=0.039), although this association was lost in logistic regression analysis.

CONCLUSION

This study does not support the association of FKBP5 with obesity but demonstrates plausible implication of its variant in susceptibility to obesity-related insulin resistance and hypertriglyceridemia.

Which Amount of BMI-SDS Reduction Is Necessary to Improve Cardiovascular Risk Factors in Overweight Children?

CONTEXT

Knowing the changes of cardiovascular risk factors (CRFs) in relation to weight loss would be helpful to advise overweight children and their parents and to decide whether drugs should be prescribed in addition to lifestyle intervention.

OBJECTIVE

The objective of the study was to determine the body mass index (BMI)-SD score (SDS) reduction to improve CRFs in overweight children.

DESIGN

This was a prospective observation study.

SETTING

The study was conducted at a specialized outpatient obesity clinic.

PATIENTS

A total of 1388 overweight children (mean BMI 27.9 ± 0.1 kg/m(2), mean age 11.4 ± 0.1 y, 43.8% male, 45.5% prepubertal) participated in the study.

INTERVENTION

The study included a 1-year lifestyle intervention.

MAIN OUTCOME MEASURES

We studied changes of blood pressure (BP), fasting high-density lipoprotein- and low-density lipoprotein-cholesterol, triglycerides, glucose, and homeostasis model assessment (HOMA) of insulin resistance index. Change of weight status was determined by δBMI-SDS based on the recommended percentiles of the International Task Force of Obesity.

RESULTS

BMI-SDS change was associated with a significant improvement of all CRFs except fasting glucose and low-density lipoprotein-cholesterol after adjusting for multiple confounders such as baseline CRFs, age, gender, BMI, pubertal stage, and its changes. BMI-SDS reduction of 0.25-0.5 was related to a decrease of systolic blood pressure (BP) (-3.2 ± 1.4 mm Hg), diastolic BP (-2.2 ± 1.1 mm Hg), triglycerides (-6.9 ± 5.8 mg/dL), HOMA (-0.5 ± 0.3), and triglyceride/high-density lipoprotein)-cholesterol (-0.3 ± 0.2), whereas high-density lipoprotein (HDL)-cholesterol increased (+1.3 ± 1.2 mg/dL). A reduction of greater than 0.5 BMI-SDS led to more pronounced improvement (systolic BP -6.0± 1.3 mm Hg, diastolic BP -5.1 ± 1.3 mm Hg, triglycerides -16.4 ± 7.1 mg/dL, HDL-cholesterol +1.6 ± 1.5 mg/dL, HOMA -0.9 ± 0.3). Per 0.1 BMI-SDS reduction in systolic BP (-1.0 mm Hg), diastolic BP (-0.8 mm Hg), triglycerides (-2.3 mg/dL), HOMA (-0.2), and triglyceride/HDL-cholesterol (-0.5) decreased significantly, whereas HDL-cholesterol (0.2 mg/dL) increased significantly in linear regression analyses and accounted for multiple confounders.

CONCLUSIONS

A BMI-SDS reduction of 0.25 or greater significantly improved hypertension, hypertriglyceridemia, and low HDL-cholesterol, whereas a BMI-SDS greater than 0.5 doubled the effect.