Background

Despite therapeutic potential against obesity and diabetes, the associations of brown adipose tissue (BAT) with glucose metabolism in young humans are relatively unexplored.

Objectives

To investigate possible associations between magnetic resonance imaging (MRI) estimates of BAT and glucose metabolism, whilst considering sex, age, and adiposity, in adolescents with normal and overweight/obese phenotypes.

Methods

In 143 subjects (10‐20 years), MRI estimates of BAT were assessed as cervical‐supraclavicular adipose tissue (sBAT) fat fraction (FF) and T*₂ from water‐fat MRI. FF and T*₂ of neighbouring subcutaneous adipose tissue (SAT) were also assessed. Adiposity was estimated with a standardized body mass index, the waist‐to‐height ratio, and abdominal visceral and subcutaneous adipose tissue volumes. Glucose metabolism was represented by the 2h plasma glucose concentration, the Matsuda index, the homeostatic model assessment of insulin resistance, and the oral disposition index; obtained from oral glucose tolerance tests.

Results

sBAT FF and T*₂ correlated positively with adiposity before and after adjustment for sex and age. sBAT FF, but not T*₂, correlated with 2h glucose and Matsuda index, also after adjustment for sex, age, and adiposity. The association with 2h glucose persisted after additional adjustment for SAT FF.

Conclusions

The association between sBAT FF and 2h glucose, observed independently of sex, age, adiposity, and SAT FF, indicates a role for BAT in glucose metabolism, which potentially could influence the risk of developing diabetes. The lacking association with sBAT T*₂ might be due to FF being a superior biomarker for BAT and/or to methodological limitations in the T*₂ quantification.

Purpose: An approach for the automated segmentation of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in multicenter water–fat MRI scans of the abdomen was investigated, using 2 different neural network architectures.

Methods: The 2 fully convolutional network architectures U‐Net and V‐Net were trained, evaluated, and compared using the water–fat MRI data. Data of the study Tellus with 90 scans from a single center was used for a 10‐fold cross‐validation in which the most successful configuration for both networks was determined. These configurations were then tested on 20 scans of the multicenter study beta‐cell function in JUvenile Diabetes and Obesity (BetaJudo), which involved a different study population and scanning device.

Results: The U‐Net outperformed the used implementation of the V‐Net in both cross‐validation and testing. In cross‐validation, the U‐Net reached average dice scores of 0.988 (VAT) and 0.992 (SAT). The average of the absolute quantification errors amount to 0.67% (VAT) and 0.39% (SAT). On the multicenter test data, the U‐Net performs only slightly worse, with average dice scores of 0.970 (VAT) and 0.987 (SAT) and quantification errors of 2.80% (VAT) and 1.65% (SAT).

Conclusion: The segmentations generated by the U‐Net allow for reliable quantification and could therefore be viable for high‐quality automated measurements of VAT and SAT in large‐scale studies with minimal need for human intervention. The high performance on the multicenter test data furthermore shows the robustness of this approach for data of different patient demographics and imaging centers, as long as a consistent imaging protocol is used.

Objective: To delineate mechanisms for fasting hyperglucagonemia in childhood obesity bystudying the associations between fasting plasma glucagon concentrations and plasmalipid parameters and fat compartments.

Methods: Cross-sectional study of children and adolescents with obesity (n=147) and leancontrols (n=43). Differences in free fatty acids (FFA), triglycerides, insulin and fatcompartments (quantified by magnetic resonance imaging) across quartiles of fastingplasma glucagon concentration were analysed. Differences in OGTT glucagonresponse was tested in high vs low FFAs, triglycerides and insulin. Human islets ofLangerhans were cultured at 5.5 mmol/l glucose and in the absence or presence of aFFA mixture with total FFA concentration of 0.5 mmol/l and glucagon secretionquantified.

Results: In children with obesity, the quartile with the highest fasting glucagon had higherinsulin (201±174 vs 83±39 pmol/l, p<0.01), FFAs (383±52 vs 338±109 μmol/l,p=0.02), triglycerides (1.5±0.9 vs 1.0±0.7 mmol/l, p<0.01), visceral adipose tissuevolume (1.9±0.8 vs 1.2±0.3 dm3, p<0.001) and a higher prevalence of impairedglucose tolerance (41% vs 8%, p=0.01) than the lowest quartile. During OGTT,children with obesity and high insulin had a worse suppression of glucagon during thefirst 10 minutes after glucose intake. Glucagon secretion was 2.6-fold higher in isletstreated with FFAs than in those not treated with FFAs.4

Conclusion: Hyperglucagonemia in childhood obesity is associated with hyperinsulinemia, highplasma FFAs, high plasma triglycerides, visceral adiposity and impaired glucosetolerance. The glucagonotropic effect of FFAs on isolated human islets provides apotential mechanism linking high fasting plasma FFAs and glucagon levels.

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

Objective: Investigating DPP-4 levels in adolescents and association with, firstly, circulating intact GLP-1 levels and glucose tolerance, secondly, BMI, and, thirdly visceral, subcutaneous and liver fat compartments.

Design: Cross-sectional study, July 2012 to April 2015.

Setting: Pediatric obesity clinic, Uppsala University Hospital.

Patients and participants: Children and adolescents with obesity (n=59) and lean controls (n=21), age 8-18.

Main outcome measures: BMI SDS, fasting plasma concentrations of DPP-4, total and intact GLP-1, fasting and OGTT concentrations of glucose and visceral (VAT) and subcutaneous (SAT) adipose tissue volumes and liver fat fraction.

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

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

Elevated levels of palmitate accentuate glucose-stimulated insulin secretion (GSIS) after short-term and cause beta-cell dysfunction after prolonged exposure. We investigated whether metformin, the first-line oral drug for treatment of T2DM, has beneficial effects on FFA-treated human islets and the potential mechanisms behind the effects. Insulin secretion, oxygen consumption rate (OCR), AMPK activation, endoplasmic reticulum (ER) stress and apoptosis were examined in isolated human islets after exposure to elevated levels of palmitate in the absence or presence of metformin. Palmitate exposure doubled GSIS after 2 days but halved after 7 days compared with control. Inclusion of metformin during palmitate exposure normalized insulin secretion both after 2 and 7 days. After 2-day exposure to palmitate, OCR and the marker of the adaptive arm of ER stress response (sorcin) were significantly raised, whereas AMPK phosphorylation, markers of pro-apoptotic arm of ER stress response (p-EIF2α and CHOP) and apoptosis (cleaved caspase 3) were not affected. Presence of metformin during 2-day palmitate exposure normalized OCR and sorcin levels. After 7-day exposure to palmitate, OCR and sorcin were not significantly different from control level, p-AMPK was reduced and p-EIF2α, CHOP and cleaved caspase 3 were strongly upregulated. Presence of metformin during 7-day culture with palmitate normalized the level of p-AMPK, p-EIF2α, CHOP and cleaved caspase 3 but significantly increased the level of sorcin. Our study demonstrates that metformin prevents early insulin hypersecretion and later decrease in insulin secretion from palmitate-treated human islets by utilizing different mechanisms.

Background: Childhood obesity-related metabolic derangements are increasing among South Asian populations. Dietary and physical activity plans have limited effect. This study aims to assess the effectiveness of metformin in the management of obesity among 8- to 16-year-old children in Gampaha District of Sri Lanka.

Materials and Methods: A triple-blinded controlled trial was conducted on 150 obese school children. After 12-hour overnight fast, blood was drawn for fasting blood glucose (FBG) and lipid profile. Anthropometry, fat mass (FM), and blood pressure were measured. BMI and insulin resistance were calculated. Children randomly received either metformin (8-10 years-500 mg 12 hourly; 11-16 years-1 g 12 hourly) or placebo. Anthropometry and blood investigations were repeated at 6 and 12 months. Mean difference in outcome measures, adjusted for baseline values, was compared using ANCOVA.

Results: There were 84/150 boys. Metabolic syndrome was present in 25 (16.7%). A statistically significant adjusted mean reduction was observed in the metformin group compared with placebo, in weight (-0.991 vs. 1.394, p = 0.000), BMI/Age-standard deviation score (SDS; -0.287 vs. -0.116, p = 0.000), %FM/Age-SDS (-0.092 vs. 0.016, p = 0.04), systolic blood pressure (SBP; -0.415 vs. 0.015, p = 0.015), total cholesterol (-0.95 vs. -0.7, p = 0.001), low-density lipoprotein (-0.67 vs. -0.45, p = 0.001), and highly sensitive C-reactive protein (-1.36 vs. 0.08, p = 0.013) at 6 months, and in BMI/Age-SDS (-370 vs. -0.222, p = 0.001), WC/Age-SDS (-0.473 vs. -0.337, p = 0.018), SBP (-0.834 vs. -0.477, p = 0.023), and triglycerides (-0.33 vs. -0.14, p = 0.019) at 12 months.

Conclusions: Metformin compared with placebo has beneficial effects on anthropometric and metabolic indicators in the management of childhood obesity.