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

Utilizing the Glucose and Insulin Response Shape of an Oral Glucose Tolerance Test to Predict Dysglycemia in Children with Overweight and Obesity, Ages 8-18 Years

Common dysglycemia measurements including fasting plasma glucose (FPG), oral glucose tolerance test (OGTT)-derived 2 h plasma glucose, and hemoglobin A1c (HbA1c) have limitations for children. Dynamic OGTT glucose and insulin responses may better reflect underlying physiology. This analysis assessed glucose and insulin curve shapes utilizing classifications-biphasic, monophasic, or monotonically increasing-and functional principal components (FPCs) to predict future dysglycemia. The prospective cohort included 671 participants with no previous diabetes diagnosis (BMI percentile ≥ 85th, 8-18 years old); 193 returned for follow-up (median 14.5 months). Blood was collected every 30 min during the 2 h OGTT. Functional data analysis was performed on curves summarizing glucose and insulin responses. FPCs described variation in curve height (FPC1), time of peak (FPC2), and oscillation (FPC3). At baseline, both glucose and insulin FPC1 were significantly correlated with BMI percentile (Spearman correlation r = 0.22 and 0.48), triglycerides (r = 0.30 and 0.39), and HbA1c (r = 0.25 and 0.17). In longitudinal logistic regression analyses, glucose and insulin FPCs predicted future dysglycemia (AUC = 0.80) better than shape classifications (AUC = 0.69), HbA1c (AUC = 0.72), or FPG (AUC = 0.50). Further research should evaluate the utility of FPCs to predict metabolic diseases.

Evaluating glucose variability through OGTT in early pregnancy and its association with hypertensive disorders of pregnancy in non-diabetic pregnancies: a large-scale multi-center retrospective study

BACKGROUND

Recent evidence suggests increased glucose variability (GV) causes endothelial dysfunction, a central pathology of hypertensive disorders of pregnancy (HDP). We aimed to investigate the association between GV in early pregnancy and subsequent HDP development among non-diabetes mellitus (DM) pregnancies.

METHODS

This multicenter retrospective study used data from singleton pregnancies between 2009 and 2019. Among individuals who had 75 g-OGTT before 20 weeks of gestation, we evaluated GV by 75 g-OGTT parameters and examined its relationship with HDP development, defining an initial-increase from fasting-plasma glucose (PG) to 1-h-PG and subsequent-decrease from 1-h-PG to 2-h-PG.

RESULTS

Approximately 3.0% pregnancies (802/26,995) had 75 g-OGTT before 20 weeks of gestation, and they had a higher prevalence of HDP (14.3% vs. 7.5%). The initial-increase was significantly associated with overall HDP (aOR 1.20, 95% CI 1.02-1.42), and the subsequent-decrease was associated with decreased and increased development of early-onset (EoHDP: aOR 0.56, 95% CI 0.38-0.82) and late-onset HDP (LoHDP: aOR 1.38, 95% CI 1.11-1.73), respectively.

CONCLUSIONS

A pattern of marked initial-increase and minor subsequent-decrease (i.e., sustained hyperglycemia) was associated with EoHDP. Contrarily, the pattern of marked initial-increase and subsequent-decrease (i.e., increased GV) was associated with LoHDP. This provides a new perspective for future study strategies.

Diabetic family history in young Japanese persons with normal glucose tolerance associates with k-means clustering of glucose response to oral glucose load, insulinogenic index and Matsuda index

Aims

The present study aimed to clarify the relationships between diabetic family history (FH), and dysglycemic response to the oral glucose tolerance test (OGTT), insulin secretion, and insulin sensitivity in young Japanese persons with normal glucose tolerance (NGT).

Methods

We measured plasma glucose (PG) and immunoreactive insulin levels in 1,309 young Japanese persons (age <40 years) with NGT before and at 30, 60, and 120 min during a 75-g OGTT. Dysglycemia during OGTT was analyzed by k-means clustering analysis. Body mass index (BMI), blood pressure (BP), and lipids were measured. Insulin secretion and sensitivity indices were calculated.

Results

PG levels during OGTT were classified by k-means clustering analysis into three groups with stepwise decreases in glucose tolerance even among individuals with NGT. In these clusters, proportion of males, BMI, BP and frequency of FH were higher, and lipid levels were worse, together with decreasing glucose tolerance. Subjects with a diabetic FH showed increases in PG after glucose loading and decreases in insulinogenic index and Matsuda index.

Conclusions

Dysglycemic response to OGTT by k-means clustering analysis was associated with FH in young Japanese persons with NGT. FH was also associated with post-loading glucose, insulinogenic index, and Matsuda index.

Mathematical modeling reveals differential dynamics of insulin action models on glycerol and glucose in adolescent girls with obesity

Under healthy conditions, the pancreas responds to a glucose challenge by releasing insulin. Insulin suppresses lipolysis in adipose tissue, thereby decreasing plasma glycerol concentration, and it regulates plasma glucose concentration through action in muscle and liver. Insulin resistance (IR) occurs when more insulin is required to achieve the same effects, and IR may be tissue-specific. IR emerges during puberty as a result of high concentrations of growth hormone and is worsened by youth-onset obesity. Adipose, liver, and muscle tissue exhibit distinct dose-dependent responses to insulin in multi-phase hyperinsulinemic-euglycemic (HE) clamps, but the HE clamp protocol does not address potential differences in the dynamics of tissue-specific insulin responses. Changes to the dynamics of insulin responses would alter glycemic control in response to a glucose challenge. To investigate the dynamics of insulin acting on adipose tissue, we developed a novel differential-equations based model that describes the coupled dynamics of glycerol concentrations and insulin action during an oral glucose tolerance test in female adolescents with obesity and IR. We compared these dynamics to the dynamics of insulin acting on muscle and liver as assessed with the oral minimal model applied to glucose and insulin data collected under the same protocol. We found that the action of insulin on glycerol peaks approximately 67 min earlier (p < 0.001) and follows the dynamics of plasma insulin more closely compared to insulin action on glucose as assessed by the parameters representing the time constants for insulin action on glucose and glycerol (p < 0.001). These findings suggest that the dynamics of insulin action show tissue-specific differences in our IR adolescent population, with adipose tissue responding to insulin more quickly compared to muscle and liver. Improved understanding of the tissue-specific dynamics of insulin action may provide novel insights into the progression of metabolic disease in patient populations with diverse metabolic phenotypes.

Sensory and process optimization of a mango bagasse-based beverage with high fiber content and low glycemic index

This research aimed to develop and optimize a mango bagasse (MB) powdered beverage with high fiber content and low glycemic index, acceptable by their potential consumers. The powdered beverage contained 40 g of mango bagasse (Manguifera indica L., var. Manila), xanthan gum (XG), carboxymethyl cellulose (CMC), and silicon dioxide (SDO). The amount of MB remained constant and, 0.5.%, 1.0%, and 2.0% of CMC, XG and SDO were added according to a factorial design 3³. The independent variables evaluated were relative viscosity, sedimentation index, solids (ºBx), and color. Statistical optimization was carried out, looking for low values of viscosity and sedimentation index, obtaining the formulation, 0.5% XG, 0.5% CMC, and 0.5% SDO. A preference test was performed with this formulation using a commercial powdered beverage as a reference, 60 consumers participated. Data showed a preference similar to that of the commercial powered beverage, moreover, the MB beverage had a content of 40.90% of total fiber, from which 15.03% was soluble fiber. The beverage had a low glycemic index (45.99) and its postprandial glycemic curve was stable for 120 min, indicating that the beverage shows potential as a functional food.

Effects of Combined High-Protein Diet and Exercise Intervention on Cardiometabolic Health in Middle-Aged Obese Adults: A Randomized Controlled Trial

Background: Obesity is the main risk factor of cardiovascular diseases (CVD) and metabolic diseases. The middle-aged population is the age group with the highest prevalence of obesity. Thus, improving cardiometabolic health is important to prevent CVD and metabolic diseases in middle-aged obese adults. The aim of this study was to examine the effects of exercise alone or in combination with a high-protein diet on markers of cardiometabolic health in middle-aged adults with obesity.

Methods: Sixty-nine middle-aged adults with obesity were assigned randomly to the control group (C; n = 23), exercise group (E; n = 23), or exercise combined with high-protein diet group (EP; n = 23). Individuals in the E and EP groups received supervised exercise training and individuals in the EP group received high-protein diet intervention. Body composition (assessed by dual-energy X-ray absorptiometry), oral glucose tolerance test (OGTT), lipid profiles, and inflammatory markers were determined before and after 12 weeks of intervention. Insulin sensitivity index (ISI_0,120) was calculated from values of fasting and 2-h insulin and glucose concentration of OGTT. Insulin-peak-time during the OGTT was recorded to reflect β-cell function. Analysis of covariance with baseline values as covariates was used to examine the effects of the intervention. The significant level was set at 0.05.

Results: After 12 weeks of intervention, the E group had a greater percentage of individuals with early insulin-peak-time during the OGTT than that in the C and EP groups (p = 0.031). EP group had lower total cholesterol and triglycerides than that in the C group (p = 0.046 and 0.014, respectively). Within-group comparisons showed that the 2-h glucose of OGTT and C-reactive protein decreased in the EP group (p = 0.013 and 0.008, respectively) but not in the E and C groups; insulin sensitivity improved in the EP group (p = 0.016) and had a trend to improve in the E group (p = 0.052); and abdominal fat mass and total body fat mass decreased in both intervention groups (p < 0.05).

Conclusion: Combined high-protein diet and exercise intervention significantly decreased fat mass and improved lipid profiles, insulin sensitivity, glucose tolerance, and inflammation in middle-aged adults with obesity.

Clinical Trial Registration: Thai Clinical Trials Registry, TCTR20180913003, 13-09-2018.

The incessant increase curve during oral glucose tolerance tests in Chinese adults with type 2 diabetes and its association with gut hormone levels

Glucose curve shapes during oral glucose tolerance tests (OGTTs) are mainly classified as incessant increase, monophasic and biphasic. Youth with an incessant increase curve have worse β-cell function. The aim of this paper was to investigate the incessant increase curve in Chinese adults with type 2 diabetes (T2DM), and its association with β-cell function and gut hormone levels. Eighty-nine Chinese patients (59 males and 30 females) were included in this study with a mean age of 50.56 ± 16.00 years. They were all recently diagnosed with T2DM and underwent 180-min OGTTs. Data on demographics, β-cell function, and insulin sensitivity were also collected. Gut hormones, including glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and ghrelin, were also detected during the OGTT. A total of 39.3 % of subjects had an incessant increase in the glucose response curve, while 59.6 % had a monophasic curve. Because only one curve was classified as biphasic, patients with a biphasic curve were omitted from further research. Lower plasma C-peptide, HOMA2-β, area under the curve (AUC) of C-peptide, and ratio of AUC of insulin to AUC of glucose were found in patients with incessant increase curves compared to those with monophasic curves (P < 0.05). Higher glycated hemoglobin (HbA_1c) was found in subjects with an incessant increase curve (P < 0.05). Importantly, fasting plasma ghrelin was lower and incremental ghrelin at 120 min was higher in the incessant increase group (P < 0.05), irrespective of age, sex, body mass index (BMI), fasting glucose, and fasting insulin. Time to peak is also a parameter of the OGTT curve shape. In the late-peak group, GLP-1 at 120 min and the AUC of GLP-1 were elevated compared with those in the early-peak group (P < 0.05). In Chinese adults with T2DM, the incessant increase in OGTT shape indicated impaired insulin secretion. Lower fasting ghrelin and absence of ghrelin drops after glucose load may be associated with the incessant increase OGTT shape. In addition, compensatory elevated GLP-1 dose not prevent peak delay in the OGTT curve. Gut hormones may have an effect on OGTT shapes in T2DM adults.

Time to the Peak, Shape of the Curve and Combination of These Glucose Response Characteristics During Oral Glucose Tolerance Test as Indicators of Early Beta-cell Dysfunction in Obese Adolescents

OBJECTIVE

Characteristics of the glucose response during oral glucose tolerance test (OGTT) may reflect differences in insulin secretion and action. The aim was to examine whether timing of the glucose peak, shape of the glucose curve and their combination could be indicators of beta-cell dysfunction in obese/severely obese adolescents with normal glucose tolerance (NGT).

METHODS

Data from 246 obese/severely obese adolescents who completed OGTT were reviewed. Out of 184 adolescents with NGT, 174 could be further classified into groups based on timing of the glucose peak (early/30 minutes vs late/≥60 minutes) and shape of the glucose curve (monophasic vs biphasic). Groups were compared with respect to insulin sensitivity (whole body insulin sensitivity index - WBISI), early-phase insulin secretion (insulinogenic index - IGI) and beta-cell function relative to insulin sensitivity (oral disposition index - oDI).

RESULTS

Late glucose peak (p=0.004) and monophasic glucose curve (p=0.001) were both associated with lower oDI after adjustment for age, sex, puberty stage and body mass index z-score. Among obese/severely obese adolescents with NGT, those with coexistent late glucose peak and monophasic glucose curve had lower oDI than those with early glucose peak and biphasic glucose curve (p=0.002). Moreover, a combination of late glucose peak and monophasic glucose curve was the most powerful predictor of the lowest oDI quartile [odds ratio (OR): 11.68, 95% confidence interval: 3.048-44.755, p<0.001].

CONCLUSION

Late timing of the glucose peak, monophasic shape of the glucose curve and, in particular, a combination of those characteristics during OGTT may indicate early beta-cell dysfunction in obese/severely obese adolescents with NGT.

Oral minimal model-based estimates of insulin sensitivity in obese youth depend on oral glucose tolerance test protocol duration

Introduction

The Oral Minimal Model (OMM), a differential-equations based mathematical model of glucose-insulin dynamics, utilizes data from a frequently sampled oral glucose tolerance test (OGTT) to quantify insulin sensitivity ( S I ). OMM-based estimates of S I can detect differences in insulin resistance (IR) across population groups and quantify effects of clinical or behavioral interventions. These estimates of S I have been validated in healthy adults using data from OGTTs with durations from 2 to 7 h. However, data demonstrating how protocol duration affects S I estimates in highly IR populations such as adolescents with obesity are limited.

Methods

A 6-h frequently sampled OGTT was performed in adolescent females with obesity. Two, 3-, and 4- hour implementations of OMM assuming an exponentially-decaying rate of glucose appearance beyond measured glucose concentrations were compared to the 6-h implementation. A 4- hour OMM implementation with truncated data (4h Tr) was also considered.

Results

Data from 68 participants were included (age 15.8 ± 1.2 years, BMI 35.4 ± 5.6 kg/m²). Although S I values were highly correlated for all implementations, they varied with protocol duration (2h: 2.86 ± 3.31, 3h: 2.55 ± 2.62, 4h: 2.81 ± 2.59, 4h tr: 3.13 ± 3.14, 6h: 3.06 ± 2.85 x 10^-4 dl/kg/min per U/ml). S I estimates based on 2 or 3 h of data underestimated S I values, whereas 4-h S I estimates more closely approximated 6-h S I values.

Discussion

These results suggest that OGTT protocol duration should be considered when implementing OMM to estimate S I in adolescents with obesity and other IR populations.

Role of exercise on insulin sensitivity and beta-cell function: is exercise sufficient for the prevention of youth-onset type 2 diabetes?

Parallel with the current pediatric obesity epidemic, the escalating rates of youthonset type 2 diabetes mellitus (T2DM) have become a major public health burden. Although lifestyle modification can be the first-line prevention for T2DM in youths, there is a lack of evidence to establish optimal specific exercise strategies for obese youths at high risk for T2DM. The purpose of this narrative review is to summarize the potential impact of exercise on 2 key pathophysiological risk factors for T2DM, insulin sensitivity and β-cell function, among obese youths. The studies cited are grouped by use of metabolic tests, i.e., direct and indirect measures of insulin sensitivity and β-cell function. In general, there are an increasing number of studies that demonstrate positive effects of aerobic exercise, resistance exercise, and the 2 combined on insulin sensitivity. However, a lack of evidence exists for the effect of any exercise modality on β-cell functional improvement. We also suggest a future direction for research into exercise medical prevention of youth-onset T2DM. These suggestions focus on the effects of exercise modalities on emerging biomarkers of T2DM risk.

The Oral Glucose Tolerance Test: 100 Years Later

For over 100 years, the oral glucose tolerance test (OGTT) has been the cornerstone for detecting prediabetes and type 2 diabetes (T2DM). In recent decades, controversies have arisen identifying internationally acceptable cut points using fasting plasma glucose (FPG), 2-h post-load glucose (2-h PG), and/or HbA1c for defining intermediate hyperglycemia (prediabetes). Despite this, there has been a steadfast global consensus of the 2-h PG for defining dysglycemic states during the OGTT. This article reviews the history of the OGTT and recent advances in its application, including the glucose challenge test and mathematical modeling for determining the shape of the glucose curve. Pitfalls of the FPG, 2-h PG during the OGTT, and HbA1c are considered as well. Finally, the associations between the 30-minute and 1-hour plasma glucose (1-h PG) levels derived from the OGTT and incidence of diabetes and its complications will be reviewed. The considerable evidence base supports modifying current screening and diagnostic recommendations with the use of the 1-h PG. Measurement of the 1-h PG level could increase the likelihood of identifying high-risk individuals when the pancreatic ß-cell function is substantially more intact with the added practical advantage of potentially replacing the conventional 2-h OGTT making it more acceptable in the clinical setting.

Delayed glucose peak and elevated 1-hour glucose on the oral glucose tolerance test identify youth with cystic fibrosis with lower oral disposition index

BACKGROUND

Alternate methods for characterizing oral glucose tolerance tests (OGTT) have emerged as superior to the 2-hour glucose in identifying individuals at risk for type 2 diabetes. The significance of these methods in cystic fibrosis (CF) is unclear. We compared 3 OGTT classifications in youth with CF: 1. curve shape (biphasic vs. monophasic), 2. time to glucose peak (≤30minutes vs. >30minutes), 3. 1-hour glucose (1hG) <155 mg/dL vs. ≥155 mg/dL to traditional OGTT criteria to determine which best identifies lower oral disposition index (oDI), pulmonary function, and body mass index (BMI).

METHODS

Youth 10-18 years with CF, not on insulin, underwent 2-hour OGTT. Glucoses were classified by traditional criteria and 3 alternate methods as normal (biphasic curve, glucose peak ≤30minutes, and/or 1hG <155 mg/dL) or abnormal (monophasic curve, glucose peak >30minutes, and/or 1hG ≥155 mg/dL). oDI was calculated [1/fasting insulin*(ΔInsulin_0-30 min/ΔGlucose_0-30 min)]. Mean oDI, BMI, forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC) were compared by OGTT classification.

RESULTS

Fifty-two youth with CF participated (mean±SD age 13±4years; 37% male; BMI z-score 0.0±0.8; FEV1 88±16.3%; FVC 97±14.8%). Late time to peak glucose and 1hG ≥155 mg/dL identified individuals with lower oDI (p=0.01); traditional OGTT criteria for prediabetes did not. No OGTT classification identified individuals with worse BMI nor pulmonary function. oDI was not associated with BMI, FEV1, or FVC.

CONCLUSIONS

Alternate OGTT measures including time to peak glucose and 1hG better identify oDI abnormalities than traditional criteria. Further studies are required to determine whether these alternate methods identify individuals with CF at risk for future clinical decline.

A Tool to Explore Discrete-Time Data: The Time Series Response Analyser

The analysis of time series data is common in nutrition and metabolism research for quantifying the physiological responses to various stimuli. The reduction of many data from a time series into a summary statistic(s) can help quantify and communicate the overall response in a more straightforward way and in line with a specific hypothesis. Nevertheless, many summary statistics have been selected by various researchers, and some approaches are still complex. The time-intensive nature of such calculations can be a burden for especially large data sets and may, therefore, introduce computational errors, which are difficult to recognize and correct. In this short commentary, the authors introduce a newly developed tool that automates many of the processes commonly used by researchers for discrete time series analysis, with particular emphasis on how the tool may be implemented within nutrition and exercise science research.

Review of methods for detecting glycemic disorders

Prediabetes (intermediate hyperglycemia) consists of two abnormalities, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) detected by a standardized 75-gram oral glucose tolerance test (OGTT). Individuals with isolated IGT or combined IFG and IGT have increased risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). Diagnosing prediabetes early and accurately is critical in order to refer high-risk individuals for intensive lifestyle modification. However, there is currently no international consensus for diagnosing prediabetes with HbA1c or glucose measurements based upon American Diabetes Association (ADA) and the World Health Organization (WHO) criteria that identify different populations at risk for progressing to diabetes. Various caveats affecting the accuracy of interpreting the HbA1c including genetics complicate this further. This review describes established methods for detecting glucose disorders based upon glucose and HbA1c parameters as well as novel approaches including the 1-hour plasma glucose (1-h PG), glucose challenge test (GCT), shape of the glucose curve, genetics, continuous glucose monitoring (CGM), measures of insulin secretion and sensitivity, metabolomics, and ancillary tools such as fructosamine, glycated albumin (GA), 1,5- anhydroglucitol (1,5-AG). Of the approaches considered, the 1-h PG has considerable potential as a biomarker for detecting glucose disorders if confirmed by additional data including health economic analysis. Whether the 1-h OGTT is superior to genetics and omics in providing greater precision for individualized treatment requires further investigation. These methods will need to demonstrate substantially superiority to simpler tools for detecting glucose disorders to justify their cost and complexity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Metabolic and Genetic Determinants of Glucose Shape After Oral Challenge in Obese Youths: A Longitudinal Study

CONTEXT

The time-to-glucose-peak following the oral glucose tolerance test (OGTT) is a highly reproducible marker for diabetes risk. In obese youths, we lack evidence for the mechanisms underlying the effects of the TCF7L2 rs7903146 variant on glucose peak.

METHODS

We analyzed the metabolic phenotype and the genotype for the TCF7L2 rs7903146 in 630 obese youths with normal (NGT) and impaired (IGT) glucose tolerance. Participants underwent a 3-hour, 9-point OGTT to estimate, using the oral minimal model, the disposition index (DI), the static (φstatic) and dynamic (φdynamic) components β-cell responsiveness and insulin sensitivity (SI). In a subgroup (n = 241) longitudinally followed for 2 years, we estimated the effect of time-to-glucose-peak on glucose tolerance change.

RESULTS

Participants were grouped into early (<30 minutes) and late (≥30 minutes) glucose peakers. A delayed glucose peak was featured by a decline in φstatic (P < .001) in the absence of a difference in φdynamic. The prevalence of T-risk allele for TCF7L2 rs7903146 variant significantly increased in the late peak group. A lower DI was correlated with higher glucose concentration at 1 and 2 hours, whereas SI was inversely associated with 1-hour glucose. Glucose peak <30 minutes was protective toward worsening of glucose tolerance overtime (odds ratio 0.35 [0.15-0.82]; P = .015), with no subjects progressing to NGT or persisting IGT, in contrast to the 40% of progressor in those with late glucose peak.

CONCLUSION

The prevalence of T-risk allele for the TCF7L2 rs7903146 prevailed in the late time-to-glucose peak group, which in turn is associated with impaired β-cell responsiveness to glucose (φ), thereby predisposing to prediabetes and diabetes in obese youths.

The shape of the glucose response curve during an oral glucose tolerance test heralds β-cell function in a large Chinese population

BACKGROUND

The shape of the glucose response curve during an oral glucose tolerance test (OGTT) can predict β-cell function and insulin resistance. However, there have been few studies conducted on Chinese people. Thus, we aimed to verify the usefulness of the glucose response curve in a large Chinese population.

METHODS

A total of 9059 OGTT (3-h tests) were categorized into either a monophasic or a multiphasic group based on the shape of the glucose response. Homeostasis model assessments of fasting insulin resistance, the Matsuda Index, the insulinogenic index, and the disposition index were assessed by plasma glucose and serum insulin concentration obtained at fasting or during an OGTT.

RESULTS

The shape of the OGTT glucose response curve was monophasic in 87.3% and multiphasic in 12.7% of participants. Individuals in the multiphasic group were younger compared to those in the monophasic group (38.6 ± 13.6 vs. 35.4 ± 13.5, P < 0.001). Individuals in the monophasic group had significantly higher fasting plasma glucose (FPG 5.6 ± 13.5 vs. 5.2 ± 0.6, P < 0.001), fasting insulin (FINS 14.8 ± 8.7 vs. 13.5 ± 7.9, P < 0.01), and homeostasis model assessment of insulin resistance (HOMA-IR 3.8 ± 2.6 vs. 3.1 ± 2.0, P < 0.001) and impaired β-cell function (disposition index 12.7 ± 14.1 vs. 16.6 ± 17.8, P < 0.001) compared to those in the multiphasic group.

CONCLUSION

The monophasic OGTT glucose response curve could reflect impaired β-cell function in a large Chinese population.

A simple method to monitor hepatic gluconeogenesis and triglyceride synthesis following oral sugar tolerance test in obese adolescents

Hepatic energy metabolism is a key element in many metabolic diseases. Hepatic anaplerosis provides carbons for gluconeogenesis (GNG) and triglyceride (TG) synthesis. We aimed to optimize a protocol that measures hepatic anaplerotic contribution for GNG, TG synthesis, and hepatic pentose phosphate pathway (PPP) activity using a single dose of oral [U^-13C₃]glycerol paired with an oral sugar tolerance test (OSTT) in a population with significant insulin resistance. The OSTT (75 g glucose + 25 g fructose) was administered to eight obese adolescents with polycystic ovarian syndrome (PCOS) followed by ingestion of [U-¹³C₃]glycerol at t = 180 or t = 210 min. ¹³C-labeling patterns of serum glucose and TG-glycerol were determined by nuclear magnetic resonance. ¹³C enrichment in plasma TG-glycerol was detectable and stable from 240 to 390 min with the [U-¹³C₃]glycerol drink at t = 180 min(3.65 ± 2.3 to 4.47 ± 1.4%; P > 0.4), but the enrichment was undetectable at 240 min with the glycerol drink at t = 210 min. The relative contribution from anaplerosis was determined at the end of the OSTT [18.5 ±3.4% (t = 180 min) vs. 16.0 ± 3.5% (t = 210 min); P = 0.27]. [U-¹³C₃]glycerol was incorporated into GNG 390 min after the OSTT with an enrichment of 7.5-12.5%. Glucose derived from TCA cycle activity was 0.3-1%, and the PPP activity was 2.8-4.7%. In conclusion, it is possible to obtain relative measurements of hepatic anaplerotic contribution to both GNG and TG esterification following an OSTT in a highly insulin-resistant population using a minimally invasive technique. Tracer administration should be timed to allow enough de novo TG esterification and endogenous glucose release after the sugar drink.

Two- vs one-hour glucose tolerance testing: Predicting prediabetes in adolescent girls with obesity

BACKGROUND

During an oral glucose tolerance test (OGTT), morphological features of the glucose curve (monophasic curve, glucose peak >30 minutes and 1-hour glucose ≥ 155 mg/dL) maybe associated with higher prediabetes risk, but their reproducibility and predictive ability in adolescents with obesity are unknown.

METHODS

Nondiabetic adolescent girls with obesity underwent a multiple-sample OGTT at baseline (n = 93), 6 weeks (n = 83), and 1 year (n = 72). Short-term reproducibility (baseline to 6 weeks) and the predictive ability for prediabetes (baseline to 1 year) for each feature were compared with standard fasting and 2-hour OGTT diagnostic criteria.

RESULTS

There was fair/moderate short-term reproducibility (κ < 0.5) for all morphological features. At 1 year, compared with standard OGTT criteria, the areas under the receiver operating curve (ROC-AUCs) for glucose peak > 30 minutes, 1 hour ≥155 mg/dL or a combination of the two criteria were comparable (all P > 0.05), but the monophasic curve had the lowest ROC-AUC (P < 0.001).

CONCLUSIONS

In adolescent girls with obesity, glucose peak > 30 minutes and/or glucose ≥155 mg/dL had similar reproducibility and 1-year predictive ability for prediabetes compared with standard OGTT criteria. The shortened 1-hour OGTT may provide diagnostic equivalence for prediabetes risk with the additional advantage of a less time-consuming risk assessment.