Time to glucose peak during an oral glucose tolerance test identifies prediabetes risk

Estimating insulin sensitivity and β-cell function from the oral glucose tolerance test: validation of a new insulin sensitivity and secretion (ISS) model

Efficient and accurate methods to estimate insulin sensitivity (SI) and β-cell function (BCF) are of great importance for studying the pathogenesis and treatment effectiveness of type 2 diabetes (T2D). Existing methods range in sensitivity, input data, and technical requirements. Oral glucose tolerance tests (OGTTs) are preferred because they are simpler and more physiological than intravenous methods. However, current analytical methods for OGTT-derived SI and BCF also range in complexity; the oral minimal models require mathematical expertise for deconvolution and fitting differential equations, and simple algebraic surrogate indices (e.g., Matsuda index, insulinogenic index) may produce unphysiological values. We developed a new insulin secretion and sensitivity (ISS) model for clinical research that provides precise and accurate estimates of SI and BCF from a standard OGTT, focusing on effectiveness, ease of implementation, and pragmatism. This model was developed by fitting a pair of differential equations to glucose and insulin without need of deconvolution or C-peptide data. This model is derived from a published model for longitudinal simulation of T2D progression that represents glucose-insulin homeostasis, including postchallenge suppression of hepatic glucose production and first- and second-phase insulin secretion. The ISS model was evaluated in three diverse cohorts across the lifespan. The new model had a strong correlation with gold-standard estimates from intravenous glucose tolerance tests and insulin clamps. The ISS model has broad applicability among diverse populations because it balances performance, fidelity, and complexity to provide a reliable phenotype of T2D risk.NEW & NOTEWORTHY The pathogenesis of type 2 diabetes (T2D) is determined by a balance between insulin sensitivity (SI) and β-cell function (BCF), which can be determined by gold standard direct measurements or estimated by fitting differential equation models to oral glucose tolerance tests (OGTTs). We propose and validate a new differential equation model that is simpler to use than current models and requires less data while maintaining good correlation and agreement with gold standards. Matlab and Python code is freely available.

Characteristics and Risk of Diabetes in People With Rare Glucose Response Curve During an Oral Glucose Tolerance Test

CONTEXT

Existing differences in persons with lower 30- or 60-minute plasma glucose (PG) levels during 75-g oral glucose tolerance test (OGTT) than fasting PG remain unclear.

OBJECTIVE

To clarify the characteristics of persons whose PG levels decrease after glucose administration during OGTT and their risk of incidence of diabetes in a Japanese general population.

METHODS

In this cohort study, a total of 3995 men and 3500 women (mean age 56.7 years) without diabetes were classified into 3 groups: (1) PG at both 30 and 60 minutes ≥ fasting PG; (2) PG at 30 minutes ≥ fasting PG and PG at 60 minutes < fasting PG; (3) PG at 30 minutes < fasting PG. The characteristics and the risk of diabetes onset were analyzed using ordered logistic regression and Cox proportional hazard regression, respectively.

RESULTS

Among 7495 participants, the numbers of individuals in the group 1, 2, and 3 were 6552, 769, and 174, respectively. The glucose response curve of the group 3 was boat shaped. Group 3 had the youngest age, lowest percentage of men, and best health condition, followed by groups 2 and 1. Among 3897 participants analyzed prospectively, 434 developed diabetes during the mean follow-up period of 5.8 years. The hazard ratio for diabetes onset in the group 2 was 0.30 with reference to the group 1. No-one in group 3 developed diabetes.

CONCLUSION

People with lower 30-minute PG than fasting PG tended to be women, young, healthy, and at low risk of diabetes onset.

High-accuracy noninvasive continuous glucose monitoring using OCT angiography-purified blood scattering signals in human skin

The accuracy of noninvasive continuous glucose monitoring (CGM) through near-infrared scattering is challenged by mixed scattering signals from different compartments, where glucose has a positive correlation with a blood scattering coefficient but a negative correlation with a tissue scattering coefficient. In this study, we developed a high-accuracy noninvasive CGM based on OCT angiography (OCTA)-purified blood scattering signals. The blood optical scattering coefficient (BOC) was initially extracted from the depth attenuation of backscattered light in OCT and then purified by eliminating the scattering signals from the surrounding tissues under the guidance of a 3D OCTA vascular map in human skin. The purified BOC was used to estimate the optical blood glucose concentration (BGC) through a linear calibration. The optical and reference BGC measurements were highly correlated (R = 0.94) without apparent time delay. The mean absolute relative difference was 6.09%. All optical BGC measurements were within the clinically acceptable Zones A + B, with 96.69% falling in Zone A on Parke's error grids. The blood glucose response during OGTT was mapped with a high spatiotemporal resolution of the single vessel and 5 seconds. This noninvasive OCTA-based CGM shows promising accuracy for clinical use. Future research will involve larger sample sizes and diabetic participants to confirm these preliminary findings.

Curcuma longa extract reduces serum inflammatory markers and postprandial hyperglycemia in healthy but borderline participants with overweight and glycemia in the normal/prediabetes range: a randomized, double-blind, and placebo-controlled trial

The spice turmeric, which has the Latin name Curcuma longa (C. longa), has various physiological effects. This study evaluated the effects of a hot water mixture with supercritical carbon dioxide C. longa extracts, CLE, and the potential active components of C. longa, turmeronols A and B and bisacurone on inflammation and glucose metabolism. First, we investigated the effect of CLE and the potential active components of C. longa on lipopolysaccharide-induced inflammation in RAW264.7 macrophages. We found a significant decrease in the production of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and nitric oxide with CLE, turmeronol A, and bisacurone, Significant inhibition of each of these substances was also observed, except for TNF-α with turmeronol B. The second part of our work was a 12-week randomized, double-blind, placebo-controlled study in healthy but borderline adults aged 40 to 69 years with overweight and normal/prediabetes glycemia. We compared blood inflammatory and glycometabolic markers in the CLE (n = 55) and placebo groups (n = 55). We found significantly lower serum high-sensitivity C-reactive protein and hemoglobin A1c levels in the CLE group. This group also showed significant improvements in postprandial hyperglycemia and insulin sensitivity indices. Our findings indicate that CLE may reduce low-grade inflammation and thus improve insulin sensitivity and postprandial hyperglycemia. Clinical trial registration: https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000051492, UMIN-CTR, UMIN000045106.

Skipping breakfast does not accelerate the hyperglycemia-induced endothelial dysfunction but reduces blood flow of the brachial artery in young men

PURPOSE

Postprandial hyperglycemia is assumed to have a negative impact on flow-mediated dilation (FMD), an index of endothelial function, and blood flow of the peripheral conduit arteries. This study aimed to determine whether the enhancement of postprandial hyperglycemia by skipping breakfast accelerates endothelial dysfunction and reduces the blood flow in the brachial artery in young men.

METHODS

Using a randomized cross-over design, ten healthy men completed two trials: with and without breakfast (Eating and Fasting trials, respectively). Venous blood sampling and brachial FMD tests were conducted before, 30, 60, 90, and 120 min after a 75-g oral glucose tolerance test (OGTT).

RESULTS

Skipping breakfast boosted post-OGTT glucose levels than having breakfast (P = 0.01). The magnitude of the decrease in FMD via OGTT did not vary between trials (main effect of trial P = 0.55). Although brachial blood flow tended to decrease after OGTT in both trials (interaction and main effect of time P = 0.61 and P = 0.054, respectively), the decrease in blood flow following OGTT was greater in the Fasting trial than in the Eating trial (main effect of trial, mean difference =  - 15.8 mL/min [95%CI =  - 25.6 to - 6.0 mL/min], P < 0.01).

CONCLUSION

Skipping breakfast did not enhance the magnitude of the decrease in FMD following glucose loading, but did accelerate hyperglycemia-induced reduction in brachial blood flow. Current findings suggest that even missing one breakfast has negative impacts on the blood flow regulation of the peripheral conduit arteries in young men who habitually eat breakfast.

Hypoglycemia and anxiolysis mediated by levofloxacin treatment in diabetic rats

Purpose

The present study was designed to determine the effect of levofloxacin (LVX) treatment on the blood glucose level, insulin sensitivity, anxiety level, nitrite and MDA level of STZ induced diabetic rats.

Methods

Wistar rats were used in the present study. The rats were made diabetic by the administration of single dose of STZ (45 mg/kg, i.p.) and NAD (50 mg/kg, i.p.). The rats with the blood glucose level greater than 200 mg/dl were considered as diabetic (confirmed at day-3 of STZ-NAD administration). The non-diabetic rats were considered as control and received saline.Diabetic rats received metformin (50 mg/kg, p.o.) and LVX (20, 25, 30 and 35 mg/kg, i.p.) daily for 14 days (starting from the day at which STZ was injected). Following administration on 14th day,the blood sample was collected and the rats were subjected to behavioral assays for the determination of locomotor activity and anxiety level. Plasma was separated and used for the estimation ofnitrite and malondialdehyde (MDA)level. On 15th day OGTT was performed in the overnight fasted rats for the assessment of insulin sensitivity.

Results

The results obtained suggested that the administration of STZ-NAD induced the hyperglycemia at day-3 of administration. Diabetic rats displayed the significant increase in blood glucose, anxiety related behavior, MDA level while significant decrease in the insulin sensitivity and plasma nitrite level. Daily administration of metformin to the diabetic rats decreased the blood glucose level, increased the time spent at the center of open field, reversed the anxiety related behavior in LDT and EPM, did not affect the plasma nitrite level, decreased the plasma MDA level, decreased the fasting glucose level and AUC in OGTT assay. LVX (30 and 35 mg/kg) treatment significantly decreased the blood glucose level of diabetic rats. LVX (20, 25 and 30 mg/kg) treatment significantly decreased the number of square crossing while LVX (20, 25, 30 and 35) treatment significantly increased the time spent at the center of the field by the diabetic rats. LVX (20 and 35 mg/kg) treatment significantly reversed the STZ induced anxiety in LDT while LVX (20, 30 and 35 mg/kg) treatment significantly reversed the STZ induced anxiety in EPM test. LVX (20, 25 and 35 mg/kg) treatment significantly increased the plasma nitrite level and LVX (20-35 mg/kg) treatment significantly decreased the MDA level of diabetic rats. Further only LVX (35 mg/kg) treatment significantly decreased the fasting glucose level and increased the AUC of diabetic rats.

Conclusion

In conclusion, STZ-NAD administration increased the blood glucose level, anxiety related behavior, decreased the plasma nitrite and increased the MDA level. LVX administration potentiated the diabetogenic effects of STZ-NAD in rats. Daily administration of LVX decreased the blood glucose level of diabetic rats. LVX administration alleviated the STZ induced anxiety in OFT, LDT and EPM test. LVX administration increased the plasma nitrite level and decreased the lipid peroxidation in diabetic rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01234-0.

Validation of Doi's weighted average glucose as a measure of post-load glucose excursion for clinical use

In this study, we examined the performance of a novel index of glucose excursion (Doi's weighted average glucose [dwAG]) in relation to the conventional measure of area under the oral glucose tolerance test (A-GTT) and the homeostatic model assessment for insulin sensitivity (HOMA-S) and pancreatic beta cell function (HOMA-B). A cross-sectional comparison of the new index was conducted using 66 oral glucose tolerance tests (GTTs) performed at different follow-up times among 27 participants who had undergone surgical subcutaneous fat removal (SSFR). Comparisons across categories were made using box plots and the Kruskal-Wallis one-way ANOVA on ranks. Passing-Bablok regression was used to compare the dwAG against the conventional A-GTT. The Passing-Bablok regression model suggested a cutoff for normality for the A-GTT of 15.14 mmol/L·2h-1 compared to the dwAG's suggested threshold of 6.8 mmol/L. For every 1 mmol/L·2h-1 increase in A-GTT, the dwAG value increased by 0.473 mmol/L. The glucose area under the curve correlated well with the four defined dwAG categories, with at least one of the categories having a different median A-GTT value (KW Chi2 = 52.8 [df = 3], P < 0.001). The HOMA-S tertiles were also associated with significantly different levels of glucose excursion measured through both the dwAG value (KW Chi2 = 11.4 [df = 2], P = 0.003) and A-GTT measure (KW Chi2 = 13.1 [df = 2], P = 0.001). It is concluded that the dwAG value and categories serve as a simple and accurate tool that can be used for interpreting glucose homeostasis across clinical settings.

Estimating Insulin Sensitivity and Beta-Cell Function from the Oral Glucose Tolerance Test: Validation of a new Insulin Sensitivity and Secretion (ISS) Model

Efficient and accurate methods to estimate insulin sensitivity (SI) and beta-cell function (BCF) are of great importance for studying the pathogenesis and treatment effectiveness of type 2 diabetes. Many methods exist, ranging in input data and technical requirements. Oral glucose tolerance tests (OGTTs) are preferred because they are simpler and more physiological. However, current analytical methods for OGTT-derived SI and BCF also range in complexity; the oral minimal models require mathematical expertise for deconvolution and fitting differential equations, and simple algebraic models (e.g., Matsuda index, insulinogenic index) may produce unphysiological values. We developed a new ISS (Insulin Secretion and Sensitivity) model for clinical research that provides precise and accurate estimates of SI and BCF from a standard OGTT, focusing on effectiveness, ease of implementation, and pragmatism. The model was developed by fitting a pair of differential equations to glucose and insulin without need of deconvolution or C-peptide data. The model is derived from a published model for longitudinal simulation of T2D progression that represents glucose-insulin homeostasis, including post-challenge suppression of hepatic glucose production and first- and second-phase insulin secretion. The ISS model was evaluated in three diverse cohorts including individuals at high risk of prediabetes (adult women with a wide range of BMI and adolescents with obesity). The new model had strong correlation with gold-standard estimates from intravenous glucose tolerance tests and hyperinsulinemic-euglycemic clamp. The ISS model has broad clinical applicability among diverse populations because it balances performance, fidelity, and complexity to provide a reliable phenotype of T2D risk.

Assessment of glucose homeostasis in young adult female β-thalassemia major patients (β-TM) with acquired hypogonadotropic hypogonadism (AHH) never treated with sex steroids compared to eugonadal β-TM patients with spontaneous menstrual cycles

BACKGROUND

Acquired ypogonadotropic hypogonadism (AHH) is the most prevalent endocrine complication in thalassemia major (TM).

STUDY DESIGN

Considering the detrimental effect of estrogen deficiency on glucose metabolism, the ICET-A Network promoted a retrospective study on the long-term effects of estrogen deficiency on glucose homeostasis in female β-TM patients with HH without hormonal replacement therapy (HRT).

PATIENTS AND METHODS

Seventeen β-TM patients with AHH (4 had arrested puberty; Tanners' breast stage 2-3), never treated with sex steroids, and 11 eugonadal β-TM patients with spontaneous menstrual cycles at the time of referral were studied. A standard 3-h OGTT was performed in the morning, after an overnight fast. Six-point plasma glucose and insulin level determinations, indices of insulin secretion and sensitivity, early-phase insulin insulinogenic index (IGI), HOMA-IR and β-cell function (HOMA-β), oral disposition index (oDI), glucose and insulin areas under the OGTT curves were evaluated.

RESULTS

Abnormal glucose tolerance (AGT) or diabetes was observed in 15 (88.2%) of 17 patients with AHH and 6 (54.5%) of 11 patients with eumenorrhea. The difference between the two groups was statistically significant (P: 0.048). However, the group of eugonadal patients was younger compared to AHH patients (26.5 ± 4.8 years vs. 32.6 ± 6.2 years ; P: 0.010). Advanced age,  severity of iron overload, splenectomy, increased ALT levels and reduced IGF-1 levels were the main clinical and laboratory risk factors for glucose dysregulation observed in β-TM with AHH compared to eugonadal β-TM patients with spontaneous menstrual cycles.

CONCLUSION

These data further support the indication for an annual assessment of OGTT in patients with β-TM. We believe that a registry of subjects with hypogonadism is necessary for a better understanding of the long-term consequences of this condition and  refining treatment options.

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.

The Glycemic Curve during the Oral Glucose Tolerance Test: Is It Only Indicative of Glycoregulation?

The shape of the glycemic curve during the oral glucose tolerance test (OGTT), interpreted in the correct context, can predict impaired glucose homeostasis. Our aim was to reveal information inherent in the 3 h glycemic trajectory that is of physiological relevance concerning the disruption of glycoregulation and complications beyond, such as components of metabolic syndrome (MS).

METHODS

In 1262 subjects (1035 women, 227 men) with a wide range of glucose tolerance, glycemic curves were categorized into four groups: monophasic, biphasic, triphasic, and multiphasic. The groups were then monitored in terms of anthropometry, biochemistry, and timing of the glycemic peak.

RESULTS

Most curves were monophasic (50%), then triphasic (28%), biphasic (17.5%), and multiphasic (4.5%). Men had more biphasic curves than women (33 vs. 14%, respectively), while women had more triphasic curves than men (30 vs. 19%, respectively) (p < 0.01). Monophasic curves were more frequent in people with impaired glucose regulation and MS compared to bi-, tri-, and multiphasic ones. Peak delay was the most common in monophasic curves, in which it was also most strongly associated with the deterioration of glucose tolerance and other components of MS.

CONCLUSION

The shape of the glycemic curve is gender dependent. A monophasic curve is associated with an unfavorable metabolic profile, especially when combined with a delayed peak.

Insulinogenic index and early phase insulin secretion predict increased risk of worsening glucose tolerance and of cystic fibrosis-related diabetes

OBJECTIVE

Measures of stimulated insulin secretion are emerging as important predictors of diabetes mellitus in at-risk populations. We analyzed the utility of clinical estimates of insulin secretion in a prospective cohort at risk for cystic fibrosis-related diabetes (CFRD).

METHODS

We divided the profiles of 189 people with CF (pwCF) followed longitudinally in the Montreal CF cohort (mean follow up 6.6 ± 1.2 years) according to quartiles of the insulinogenic index (IGI; (I₃₀-I₀)/(G₃₀-G₀)); area under the curve for insulin normalized for glucose (AUC_ins/glu), and HOMA-B at baseline to compare clinical characteristics and risk of CFRD according to quartiles for each measure. We also compared characteristics of 40 pwCF found to have de novo CFRD at baseline.

RESULTS

At baseline, IGI and AUC_ins/glu were lower in subjects with de novo CFRD and those who later developed CFRD than those who never developed CFRD (p < 0.0001 for each). Subjects with the lowest quartiles of IGI, AUC_ins/glu, and AUC_{ins/glu 0-30} had increased risk of developing CFRD by Kaplan-Meier analysis (p = 0.0244, p = 0.0024, and p = 0.0338, respectively). There was no significant difference in risk between quartiles of HOMA-B. Subjects in the lowest quartile of IGI showed a significant increase in 2-hour OGTT glucose and AUC_glu between the initial and final study visits (p = 0.0027 and p = 0.0044, respectively).

CONCLUSION

IGI is easily measured in a clinical setting and needs to be validated in prospective studies as a potential tool to improve risk stratification in CFRD with direct relevance to pathogenesis.

Evolution of the diagnostic value of "the sugar of the blood": hitting the sweet spot to identify alterations in glucose dynamics

In this paper, we provide an overview of the evolution of the definition of hyperglycemia during the past century and the alterations in glucose dynamics that cause fasting and postprandial hyperglycemia. We discuss how extensive mechanistic, physiological research into the factors and pathways that regulate the appearance of glucose in the circulation and its uptake and metabolism by tissues and organs has contributed knowledge that has advanced our understanding of different types of hyperglycemia, namely prediabetes and diabetes and their subtypes (impaired fasting plasma glucose, impaired glucose tolerance, combined impaired fasting plasma glucose, impaired glucose tolerance, type 1 diabetes, type 2 diabetes, gestational diabetes mellitus), their relationships with medical complications, and how to prevent and treat hyperglycemia.

In Search of the Hyperglycemic Threshold Required to Induce Growth Hormone (GH) Suppression

Introduction According to the 2014 Endocrine Society Clinical Practice Guideline on acromegaly, the confirmation of acromegaly diagnosis is established by finding a lack of suppression of growth hormone (GH) to < 1 ug/L following documented hyperglycemia during an oral glucose tolerance test. However, in this setting, the concept of hyperglycemia has never been clearly defined. Objective This study aimed to define the hyperglycemic threshold required to induce GH suppression. Methods We retrieved the glycemia profile of 44 individuals after a standard 2-h 75g oral glucose tolerance test prescribed to assess GH suppression and performed a comprehensive analysis of two subgroups of individuals (28 reaching GH suppression and 16 in whom GH suppression was not observed). All of the data were analyzed with the program Graph Pad Prism. Differences between means were assessed by Student's unpaired t-test or Mann-Whitney U test as deemed appropriate. Fisher's exact test was used for categorical variables. Results Individuals in G1 and G2 were different only for the median basal GH and median IGF-1. No significant differences in terms of the prevalence of diabetes and prediabetes were found. The glucose peak was achieved earlier in the group that reached GH suppression. The median of the highest glucose values of both subgroups was not different. A correlation between peak and baseline glucose value was found only among those in whom GH suppression was reached. Among these, the median glucose peak (P50) was 177 mg/dl, whereas the 75^th percentile (P75) and 25^th percentile (P25) were 199 mg/dl and 120 mg/dl, respectively. Conclusion Considering that 75% of those in whom GH suppression was observed after an oral glucose overload test reached blood glucose values above 120 mg/dl, we propose to use this value as the blood glucose threshold for inducing GH suppression. In light of our results, whenever GH suppression is not observed; and the highest glycemic value is below 120 mg/dl, it might be useful to repeat the test prior to any conclusion.

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

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

Hypoglycemic Effects and Mechanisms of Buckwheat-Oat-Pea Composite Flour in Diabetic Rats

Nutritional intervention is a basic way to prevent and treat diabetes mellitus. Appropriate whole grain intake daily is recommended. The study aimed to explore the feasibility of a kind of buckwheat-oat-pea composite flour (BOP, quality ratio of buckwheat:oats:peas = 6:1:1) as a stable food substitution and its underlying mechanisms. High-fat food (HFD) and streptozotocin injection were used to induce diabetes in rats, and buckwheat, oats, and three different doses of BOP were added to the HFD separately for diet intervention. The whole study lasted for 10 weeks, and the glucose tolerance test, lipids, liver injury, and gut microbiota were evaluated in the last week. The diabetic rat model was successfully induced. The BOP significantly changed the glucose and lipids metabolism, decreased liver injury, and changed the composition of the gut microbiota of diabetic rats. The outcomes of the current study revealed that BOP is a potential stable food substitution.

The characteristics of postprandial glycemic response patterns to white rice and glucose in healthy adults: Identifying subgroups by clustering analysis

OBJECTIVES

Large interpersonal variability in postprandial glycemic response (PGR) to white rice has been reported, and differences in the PGR patterns during the oral glucose tolerance test (OGTT) have been documented. However, there is scant study on the PGR patterns of white rice. We examined the typical PGR patterns of white rice and glucose and the association between them.

MATERIALS AND METHODS

We analyzed the data of 3-h PGRs to white rice (WR) and glucose (G) of 114 normoglycemic female subjects of similar age, weight status, and same ethnic group. Diverse glycemic parameters, based on the discrete blood glucose values, were calculated over 120 and 180 min. K-means clustering based on glycemic parameters calculated over 180 min was applied to identify subgroups and representative PGR patterns. Principal factor analysis based on the parameters used in the cluster analysis was applied to characterize PGR patterns. Simple correspondence analysis was performed on the clustering categories of WR and G.

RESULTS

More distinct differences were found in glycemic parameters calculated over 180 min compared with that calculated over 120 min, especially in the negative area under the curve and Nadir. We identified four distinct PGR patterns to WR (WR1, WR2, WR3, and WR4) and G (G1, G2, G3, and G4), respectively. There were significant differences among the patterns regard to postprandial hyperglycemia, hypoglycemic, and glycemic variability. The WR1 clusters had significantly lower glycemic index (59 ± 19), while no difference was found among the glycemic index based on the other three clusters. Each given G subgroup presented multiple patterns of PGR to WR, especially in the largest G subgroup (G1), and in subgroup with the greatest glycemic variability (G3).

CONCLUSION

Multiple subgroups could be classified based on the PGR patterns to white rice and glucose even in seemingly homogeneous subjects. Extending the monitoring time to 180 min was conducive to more effective discrimination of PGR patterns. It may not be reliable to extrapolate the patterns of PGR to rice from that to glucose, suggesting a need of combining OGTT and meal tolerance test for individualized glycemic management.

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.

Incidence and status of insulin secretion in pregnant women with flat plasma glucose profiles during oral glucose tolerance test

OBJECTIVES

Flat shaped glucose curves (FC) during oral glucose tolerance test (OGTT) in pregnant women (PW) are a not uncommon finding. We aimed to define the FC incidence in a large PW cohort and to describe the status of insulin and C-peptide secretion in women with FC when compared with a well-matched control group.

METHODS

1050 PW performing OGTT for gestational diabetes screening were enrolled. An increase <6% in plasma glucose (PG) during OGTT defined a FC. Serum samples for measuring insulin and C-peptide were also obtained.

RESULTS

61 (5.8%) women showed a FC. 60 of them, paired to a group of 60 no-FC women matched for age, body mass index and gestational age, were further investigated. C-peptide and insulin concentrations were significantly lower (P<0.001) in FC in both 1-h and 2-h OGTT samples. When incremental area under the curves (AUC) normalized to PG were estimated, only AUC_insulin remained however significantly lower. The insulin sensitivity index was higher in FC.

CONCLUSIONS

PW with FC showed a hypersensitivity to insulin with normal β-cell function. Moreover, a delayed glucose absorption could be hypothesised because of the slight but continuously increasing shape of insulin curve found in FC group. Both phenomena could occur in parallel and contribute to FC.

Oral Glucose Tolerance Test in Patients with Cystic Fibrosis Compared to the Overweight and Obese: A Different Approach in Understanding the Results

(1) Background: In cystic fibrosis (CF), the oral glucose tolerance test (OGTT) is recommended from 10 years old annually to screen and diagnose cystic fibrosis-related diabetes (CFRD). Alternative OGTT characteristics (glucose curve shape, time to glucose peak, one-hour glucose value, and three-hour glucose value with the new shape curve) were studied in other populations considered at high risk for diabetes; (2) Methods: The study analyses classical and alternative OGGT characteristics from 44 children (22 CF, 22 obese without CF), mean age: 12.9 ± 2.2 years evaluated in a single-center from Romania. (3) Results: In 59.1% of children with CF, the predominant OGTT pattern was: abnormal glucose metabolism or CFRD, with a monophasic curve shape, a late peak glucose level, and 1 h glucose ≥ 155 mg/dL, showing a very different pattern compared with sex and age-matched obese children. Statistical estimation agreement between the late glucose peak (K = 0.60; p = 0.005), the 1 h glucose ≥ 155 mg/dL during OGTT (K = 0.69, p = 0.001), and the classical method of interpretation was found. (4) Conclusions: Late peak glucose and 1 h glucose level ≥ 155 mg/dL during OGTT can be used for diagnosing the early glucose metabolism alteration in children with CF.

Changes in OGTT-derived biomarkers in response to lifestyle intervention among Latino adolescents with obesity

BACKGROUND

Glucose concentrations during an oral glucose tolerance test (OGTT) have been used as biomarkers to differentiate type 2 diabetes risk phenotypes. No studies have examined changes in OGTT-glucose phenotypes following lifestyle intervention among high-risk youth.

OBJECTIVE

To examine changes in OGTT-glucose phenotypes following lifestyle intervention and to explore differences in insulin sensitivity and β-cell function among post-intervention phenotypes.

METHODS

Latino adolescents with obesity (n = 48, age 15.4 ± 1.0, BMI% 98.2 ± 1.4, female 56.3%) completed a 12-week lifestyle intervention that included weekly nutrition education and physical activity. At baseline and 12 weeks, youth completed a 2-h OGTT with glucose and insulin concentrations assessed at 0', 30', 60', 90' and 120'. Glucose concentrations during the OGTT were used to identify biomarkers, 1-h glucose, glucose response curve and time to glucose peak. Using these respective biomarkers, high-risk (1-h glucose ≥ 155 mg/dl, Monophasic, Late Peak) and lower-risk phenotypes (1-h glucose < 155 mg/dl, Biphasic, Early Peak) were categorized. Insulin sensitivity was estimated by whole-body insulin sensitivity index (WBISI) and β-cell function by oral disposition index (oDI).

RESULTS

Following intervention, the prevalence of Monophasic phenotypes decreased from 81% to 67% (p = 0.048) and 1-h glucose ≥ 155 mg/dl from 38% to 10% (p = 0.054). Although Late Peak phenotypes did not significantly change (from 58% to 29%, p = 0.200), Early Peak phenotypes at post-intervention demonstrated significantly higher WBISI compared to Late Peak (2.3 ± 0.1 vs 1.7 ± 0.2, p = 0.023).

CONCLUSIONS

OGTT-glucose phenotypes improve following lifestyle intervention among high-risk youth. These findings further support their potential utility as clinical biomarkers to identify diabetes risk and risk reduction in youth.

Oral glucose tolerance test: Ηow to maximize its diagnostic value in children and adolescents

BACKGROUND

Recently, the validity of the oral glucose tolerance test (OGTT) as a gold-standard test for the diagnosis of glucose dysregulation (GD) has been questioned due to the pre-analytical, analytical, and post-analytical variables which can potentially affect its reproducibility and accuracy.

AIMS

In this short update, the many  variables that affect the reproducibility and accuracy of the OGTT are described and discussed aiming to enhance its diagnostic value  in  clinical practice.

SEARCH STRATEGY

A systematic search was implemented in June 2022, using Scopus, PubMed, Embase and Google Scholar focusing on OGTT relevant  papers published in the last 10 years. Moreover,  the reference lists of these  articles were checked for additional pertinent studies. The research and selection of articles was also supported by the long-term authors' experience in the use of OGTT for the diagnosis of GD in children and adolescents.

CONCLUSION

The complexity of diagnosing GD presupposes that clinicians have specific knowledge and experience to perform rigorous assessment of glucose metabolism. It is worth mentioning that during OGTT, subjects with glucose levels  close to the cut-off values proposed  by WHO (World Health Organization)/ADA (American Diabetes Association) require careful evaluation in order to avoid misclassification and unnecessary interventions. For this reason, ADA recommends a second test to confirm the diagnosis of diabetes.

Comparison of area under the curve in various models of diabetic rats receiving chronic medication

INTRODUCTION

The oral glucose tolerance test (OGTT) is widely used as a diagnostic tool for impaired glucose tolerance (IGT) in clinical settings and animal experiments. The area under the curve (AUC) is then developed to quantify the total increase in blood glucose during the OGTT. Similarly, attenuation of the increased AUC indicates the improvement of IGT in animals. Variations in fasting plasma glucose between individuals stimulate the development of incremental area under the curve (iAUC). However, the iAUC determined from subtracting the baseline value of fasting plasma glucose (similar to ΔAUC) has been challenged as problematic without evidence.

MATERIAL AND METHODS

We developed four different diabetic animal models. In each model, rats were treated with metformin, dapagliflozin, and insulin respectively for 1 week. OGTTs were performed after 7 days of the drug treatment. The acute blood glucose changes induced by one-time treatment of drugs were also compared.

RESULTS

After a daily application of each drug at an effective dose for 7 days, results indicated potency in the following order: insulin > dapagliflozin > metformin. This was determined by calculation using the AUC in all diabetic models. However, the order changed when using the calculation with iAUC. Additionally, signals were changed before the OGTT in each model that received repeated treatment of each drug. Notably, drug potency was shown to be the same in OGTT calculated from iAUC and AUC in diabetic rats receiving acute treatment.

CONCLUSIONS

iAUC seems unsuitable for application in cases where subjects are receiving chronic medication(s).

Association of the extent of return to fasting state 2-hours after a glucose challenge with incident prediabetes and type 2 diabetes: The CARDIA study

AIM

To evaluate whether the extent of return to fasting state 2-hours after a glucose challenge among normoglycemic individuals is associated with lower risk of incident prediabetes/ type 2 diabetes in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study.

METHODS

We evaluated this association among 1879 normoglycemic adults who were categorized into three groups: 'Low post load' (2hPG < FPG); 'Medium post load' (2hPG ≥ FPG and < 75^th percentile of the difference); and 'High post load' (2hPG > FPG and ≥ 75^th percentile of the difference). We used Cox proportional hazards regression to evaluate the association of the difference in 2hPG and FPG with incident diabetes/prediabetes after adjustment for demographic and clinical covariates.

RESULTS

During 20 years of follow-up, 8% developed type 2 diabetes and 35% developed prediabetes. Compared to those with 'Low post load', the risk of type 2 diabetes was higher for participants with 'High post load' [HR: 1.56, 95% CI (1.03, 2.37)] and similar for participants with 'Medium post load' [HR: 0.99, 95% CI (0.64, 1.52)]. However, HRs for incident prediabetes among participants with 'High post load' [HR = 1.2, 95 %CI = (0.98, 1.46)] was not significantly different compared to participants with 'Low post load'.

CONCLUSION

Among normoglycemic individuals, a difference between 2hPG and FPG concentration > 0.9 mmol/L can be used to stratify individuals at higher risk for developing type 2 diabetes.

Time to Peak Glucose and Peak C-Peptide During the Progression to Type 1 Diabetes in the Diabetes Prevention Trial and TrialNet Cohorts

OBJECTIVE

To assess the progression of type 1 diabetes using time to peak glucose or C-peptide during oral glucose tolerance tests (OGTTs) in autoantibody-positive relatives of people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We examined 2-h OGTTs of participants in the Diabetes Prevention Trial Type 1 (DPT-1) and TrialNet Pathway to Prevention (PTP) studies. We included 706 DPT-1 participants (mean ± SD age, 13.84 ± 9.53 years; BMI Z-score, 0.33 ± 1.07; 56.1% male) and 3,720 PTP participants (age, 16.01 ± 12.33 years; BMI Z-score, 0.66 ± 1.3; 49.7% male). Log-rank testing and Cox regression analyses with adjustments (age, sex, race, BMI Z-score, HOMA-insulin resistance, and peak glucose/C-peptide levels, respectively) were performed.

RESULTS

In each of DPT-1 and PTP, higher 5-year diabetes progression risk was seen in those with time to peak glucose >30 min and time to peak C-peptide >60 min (P < 0.001 for all groups), before and after adjustments. In models examining strength of association with diabetes development, associations were greater for time to peak C-peptide versus peak C-peptide value (DPT-1: χ² = 25.76 vs. χ² = 8.62; PTP: χ² = 149.19 vs. χ² = 79.98; all P < 0.001). Changes in the percentage of individuals with delayed glucose and/or C-peptide peaks were noted over time.

CONCLUSIONS

In two independent at-risk populations, we show that those with delayed OGTT peak times for glucose or C-peptide are at higher risk of diabetes development within 5 years, independent of peak levels. Moreover, time to peak C-peptide appears more predictive than the peak level, suggesting its potential use as a specific biomarker for diabetes progression.

Association between accelerometer-measured physical activity, glucose metabolism, and waist circumference in older adults

AIMS

To examine the association of physical activity (PA) and sedentary time (ST) with glucose metabolism according to waist circumference (WC) in older people.

METHODS

A population-based sample of 702 individuals (aged 67-70 years) wore wrist-worn accelerometers for two weeks and underwent an oral glucose tolerance test. The associations between moderate-to-vigorous (MVPA) and light (LPA) PA, ST, and glucose metabolism across the tertiles of WC were analysed using general linear regression.

RESULTS

Among highest WC tertile, LPA negatively associated with fasting insulin (β =  - 0.047, 95% CI - 0.082 to - 0.012), HOMA-IR (β =  - 0.098, 95% CI - 0.184 to - 0.012), and HOMA-β (β =  - 3.367, CI - 6.570 to - 0.783). ST associated with 120 min glucose (β = 0.140, CI 0.021 to 0.260). Among lowest WC tertile, MVPA negatively associated with 30 min insulin (β =  - 0.086, 95% CI - 0.168 to - 0.004) and 120 min insulin (β =  - 0.160, 95% CI - 0.257 to - 0.063) and positively associated with Matsuda index (β = 0.076, 95% CI 0.014 to 0.139). Light PA negatively associated with 120 min insulin (β =  - 0.054, 95% CI - 0.104 to - 0.005).

CONCLUSION

With the limitation of the cross-sectional study, reducing ST and increasing LPA may be beneficial for glucose metabolism among abdominally obese older adults. Lean older adults could benefit more from increasing MVPA.

Oral glucose tolerance test in diabetes, the old method revisited

The oral glucose tolerance test (OGTT) has been widely used both in clinics and in basic research for a long time. It is applied to diagnose impaired glucose tolerance and/or type 2 diabetes mellitus in individuals. Additionally, it has been employed in research to investigate glucose utilization and insulin sensitivity in animals. The main aim of each was quite different, and the details are also somewhat varied. However, the time or duration of the OGTT was the same, using the 2-h post-glucose load glycemia in both, following the suggestions of the American Diabetes Association. Recently, the use of 30-min or 1-h post-glucose load glycemia in clinical practice has been recommended by several studies. In this review article, we describe this new view and suggest perspectives for the OGTT. Additionally, quantification of the glucose curve in basic research is also discussed. Unlike in clinical practice, the incremental area under the curve is not suitable for use in the studies involving animals receiving repeated treatments or chronic treatment. We discuss the potential mechanisms in detail. Moreover, variations between bench and bedside in the application of the OGTT are introduced. Finally, the newly identified method for the OGTT must achieve a recommendation from the American Diabetes Association or another official unit soon. In conclusion, we summarize the recent reports regarding the OGTT and add some of our own perspectives, including machine learning and others.

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.

The impact of replacing wheat flour with cellular legume powder on starch bioaccessibility, glycaemic response and bread roll quality: A double-blind randomised controlled trial in healthy participants

The global rise in obesity and type 2 diabetes has generated significant interest in regulating the glycaemic impact of staple foods. Wheat breads (white or wholemeal) are popular staples, but have a high-glycaemic index, due to the highly digestible wheat starch. Reducing the glycaemic potency of white bread is challenging because the bread-making conditions are mostly conducive to starch gelatinisation. Cellular legume powders are a new source of type 1 resistant starch, where the starch is encapsulated by dietary fibre in the form of intact plant cell walls. The starch in these cell powders is less susceptible to gelatinisation and digestion than starch in conventional legume flours. However, legume cell resilience to baking conditions and the effects of this ingredient on glycaemic responses and product quality are unknown. Here we show that the integrity of cell wall fibre in chickpea powder was preserved on baking and this led to a ~40% reduction in in vivo glycaemic responses (iAUC120) to white bread rolls (~50 g available carbohydrate and 12 g wheat protein per serving) when 30% or 60% (w/w) of the wheat flour was replaced with intact cell powder. Significant reductions in glycaemic responses were achieved without adverse effects on bread texture, appearance or palatability. Starch digestibility analysis and microscopy confirmed the importance of cell integrity in attenuating glycaemic responses. Alternative processing methods that preserve cell integrity are a new, promising way to provide healthier low glycaemic staple foods; we anticipate that this will improve dietary options for diabetes care.

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.

Protective Effects of Moderate Intensity Static Magnetic Fields on Diabetic Mice

The purpose of this study was to investigate the effects of moderate-intensity static magnetic field (SMF) on diabetic mice. We studied the effects of SMF on blood glucose of normal mice by starch tolerance and glucose tolerance tests. Then, we evaluated the effects of SMF on blood glucose of diabetic mice by establishing alloxan-induced type 1 diabetic mice and high-fat diet + streptozotocin (STZ)-induced type 2 diabetic mice. The results showed that different magnetic field intensities and blank control did not affect the blood glucose of normal mice. After starch and glucose administration, different magnetic fields could improve the glucose tolerance of normal mice, and this was obvious in the 600 mT group. In the experiment of type 1 diabetic mice induced by alloxan, the results showed that different magnetic field intensities could improve the starch tolerance of mice, and that in the 400 mT group was obvious. In the experiment of type 2 diabetic mice induced by a high-fat diet + STZ, the 400 mT group could reduce food intake and water consumption in the later period. The 600 mT group could improve the starch tolerance of mice. The 400 and 600 mT groups could reduce fasting blood glucose. At the same time, total cholesterol and triglyceride decreased in different magnetic field intensities, and the 600 mT group could significantly increase the serum insulin content of mice. In summary, the results of this study suggest that SMF has a protective role in diabetic mice. Bioelectromagnetics. © 2020 Bioelectromagnetics Society.

Effect of the Glycemic Index of Meals on Physical Exercise: A Case Report

Carbohydrate uptake before physical exercise allows to maintain plasma glucose concentration. Though, foods or beverages containing the same carbohydrate concentration do not produce the same glycemic and insulin responses which are related to their glycemic index (GI). Last, most studies of CHO loading have been conducted with male subjects, with the assumption that the results also apply to female athletes.

Sixteen volunteer amateur athletes, eight men and eight women (age 39.1 ± 7.8 y; VO2max 55,7 ± 11,7 ml/kg/min), were selected and then divided into four groups of four people each one. The trial was divided into several days, one for each group. A carbohydrate source or a placebo (energy 86,5 ± 6,7 kcal; CHO 20,0 g; fat 0,3 ± 0,3 g; protein 0,8 ± 0,8 g) was assigned randomly to each athlete in the group: these supplements differed in the ability to increase blood glucose (banana: high-GI; dried apricots: low-GI; energy gel: mixture of CHO with different blood release), while the placebo was composed of water, sodium cyclamate, sodium saccharin and acesulfame potassium. Three blood samples were taken from each athlete from finger, by glucometer: one before supplementation, one half an hour later – at the start of the run – and one at the end of the exercise.

Physical activity consisted of 40 minutes run at medium-high intensity, corresponding to 82% of maximum heart rate or 70% of VO2max. In order to improve the analysis of the results obtained from the detection of biological samples, a questionnaire was submitted to all participants to know their lifestyle and anthropometric and physiological data.

Results highlighted a different glycemic response between men and women, suggesting the consumption of low-GI food rather than high-GI before physical exercise in order to keep plasma glucose levels constant.

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.

Glucose lowering and pancreato-protective effects of Abrus Precatorius (L.) leaf extract in normoglycemic and STZ/Nicotinamide - Induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abrus precatorius (L.) leaves are used as folk medicine by the local communities in the western region of Ghana to treat diabetes mellitus; however, this health claim remains unverified scientifically.

OBJECTIVE

The study investigated glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) in normoglycemic and STZ/nicotinamide (NIC)-induced diabetic rats.

METHOD

after preparation of APLE, it was subjected to phytochemical screening, proximate composition and elemental assessments by using standard methods. Oral glucose tolerance test (OGTT) and maltose, lactose and sucrose oral challenge were assessed in normoglycemic rats post-APLE. Morphological characteristics of glucose response curve (time of glucose peak and shape of glucose response curve) were determined. Subsequently, diabetes mellitus was experimentally established in normoglycaemic adult Sprague-Dawley rats (weighing 150-250 g) of both sexes by sequential injection of Streptozotocin (STZ, 60 mg/kg ip)-reconstituted in sodium citrate buffer and NIC (110 mg/kg ip)-reconstituted in normal saline (1:1 v/v) for 16 weeks. Except control rats (normal saline 5 ml/kg ip; baseline fasting blood glucose [FBG] of 6.48 mmol/L), rats having FBG (stable at 11.1 mmol/L or ≥ 250 mg/dL) 3 days post-STZ/NIC injection were randomly re-assigned to one of the following groups: model (STZ/NIC-induced diabetic rats), APLE (100, 200 and 400 mg/kg respectively po) and metformin (300 mg/kg po) and treated daily for 28 days. Bodyweight and FBG were measured on weekly basis. FBG was measured by using standard glucometers. On day 28, rats were sacrificed under chloroform anesthesia, blood collected via cardiac puncture; kidney, liver and pancreas surgically harvested. While the pancreas was processed, sectioned and H&E-stained for histological examination, fresh kidney and liver were homogenized for assessment of total anti-oxidant capacity. Median cross-sectional area of pancreatic islets of Langerhans was determined for each group by using Amscope.

RESULTS

Cumulatively, APLE (100, 200 and 400 mg/kg respectively) dose-dependently decreased the initial FBG by 55.22, 76.15 and 77.77% respectively compared to model (-1.04%) and metformin (72.29%) groups. APLE treatment recovered damaged pancreatic β-cells and also increased median cross-sectional area (x10⁶ μm²) of pancreatic islets compared to that of model group. APLE significantly (P < 0.05) increased total anti-oxidant capacity (5.21 ± 0.02 AscAE μg/mL) of plasma, kidney and liver compared to model (4.06 ± 0.04 AscAE μg/mL) and metformin (4.87 ± 0.03 AscAE μg/mL) groups.

CONCLUSION

APLE has demonstrated glucose lowering and pancreato-protective effects in rats and arrested the characteristic loss in bodyweight associated with diabetes mellitus. This finding preliminarily confirms folk use of APLE as an anti-diabetic herbal medicine, whiles providing a rationale for further translational studies on APLE.

Type 2 diabetes: one disease, many pathways

Diabetes is a chronic, progressive disease that calls for longitudinal data and analysis. We introduce a longitudinal mathematical model that is capable of representing the metabolic state of an individual at any point in time during their progression from normal glucose tolerance to type 2 diabetes (T2D) over a period of years. As an application of the model, we account for the diversity of pathways typically followed, focusing on two extreme alternatives, one that goes through impaired fasting glucose (IFG) first and one that goes through impaired glucose tolerance (IGT) first. These two pathways are widely recognized to stem from distinct metabolic abnormalities in hepatic glucose production and peripheral glucose uptake, respectively. We confirm this but go beyond to show that IFG and IGT lie on a continuum ranging from high hepatic insulin resistance and low peripheral insulin resistance to low hepatic resistance and high peripheral resistance. We show that IFG generally incurs IGT and IGT generally incurs IFG on the way to T2D, highlighting the difference between innate and acquired defects and the need to assess patients early to determine their underlying primary impairment and appropriately target therapy. We also consider other mechanisms, showing that IFG can result from impaired insulin secretion, that non-insulin-dependent glucose uptake can also mediate or interact with these pathways, and that impaired incretin signaling can accelerate T2D progression. We consider whether hyperinsulinemia can cause insulin resistance in addition to being a response to it and suggest that this is a minor effect.

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.

[Effects of chlorogenic acid on glucose tolerance and its curve characteristics in high-fat diet-induced obesity rats]

OBJECTIVE

To observe the effect of chlorogenic acid (chlorogenic acid, CGA) on the glucose tolerance and its curve characteristics in high fat diet-induced obesity (diet-induced-obesity, DIO) rats, so as to provide scientific grounds for the development and utilization of CGA in early prevention and reversal of prediabetes.

METHODS

Eight of forty-six male Sprague-Dawley rats were randomly selected as the normal diet group (CON group), and the rest were fed with high-fat diet. After 4 weeks, 24 high-fat-induced obese rats were screened according to the criteria and then randomly divided into high fat diet group (HFD group), 50% CGA group and 98% CGA group. The CGA groups received intragastric administrations of 50% CGA and 98% CGA orally via a gavage needle once a day for 8 weeks, respectively, while the CON and HFD groups received a carrier solution (phosphate buffer saline, PBS). Their body weights were measured weekly and oral glucose tolerance test (OGTT) was performed every 4 weeks. Fasting insulin and insulin release were measured at the end of the study. Meanwhile, HOMA-IR and visceral fat percentage were calculated. Histopathological examination by hematoxylin and eosin staining method were evaluated in the pancreatic tissues.

RESULTS

Before the intervention of chlorogenic acid, blood glucose levels 120 min after glucose loading (P<0.05) and AUC-G (P<0.05) were increased in the HFD group when compared with the CON group, and the time to glucose peak was delayed after 4 weeks of chlorogenic acid intervention (P<0.05). After 8 weeks of intervention, the HOMA-IR index, the insulin levels at 0 min, 30 min, 60 min, and 120 min after glucose loading and AUC-I increased (P<0.05), and the histopathological examination showed obvious hyperplasia of pancreatic islets (P<0.05). Compared with the HFD group, there was no significant change in glucose tolerance and glucose peak time in 50%CGA and 98%CGA groups at the end of 4 weeks of intervention. However, after 8 weeks of intervention, OGTT-60min,OGTT-120min blood glucose (P<0.05) were lower, HOMA-IR index and OGTT-0min, OGTT-120min serum insulin level decreased (P<0.05), the time to glucose peak shifted to an earlier timepoint (P<0.05), abnormal islet hyperplasia attenuated (P<0.05) in 50% CGA and 98% CGA groups. Also, the OGTT-30min serum insulin level was decreased (P<0.05) in 50% CGA group.

CONCLUSION

Delay in time to glucose peak during the OGTT was one of the manifestations of impaired glucose tolerance in DIO rats, and 50% and 98% CGA could improve the glucose tolerance and delay in glucose peak time.

An Acute, Placebo-Controlled, Single-Blind, Crossover, Dose-Response, Exploratory Study to Assess the Effects of New Zealand Pine Bark Extract (Enzogenol®) on Glycaemic Responses in Healthy Participants

An acute, placebo-controlled, single-blind, crossover, dose-response, exploratory study was designed to investigate the hypoglycaemic effects of New Zealand pine bark extract (Enzogenol®). Twenty-five healthy participants categorised into having a monophasic or complex (biphasic or triphasic) glucose curve shape at the control visit consumed a placebo and Enzogenol® (50 and 400 mg) on three separate occasions before an oral glucose tolerance test (OGTT). In the monophasic group, 50 and 400 mg of Enzogenol® significantly reduced the mean glucose incremental area under the curve (iAUC) compared to control 241.3 ± 20.2 vs. 335.4 ± 34.0 mmol/L·min, p = 0.034 and 249.3 ± 25.4 vs. 353.6 ± 31.5 mmol/L·min, p = 0.012, respectively. The 400 mg dose further reduced the percentage increment of postprandial glucose (%PG) 31.4% ± 7.9% vs. 47.5% ± 8.6%, p = 0.010, glucose peak 7.9 ± 0.3 vs. 8.9 ± 0.3 mmol/L, p = 0.025 and 2h-OGTT postprandial glucose (2hPG) 6.1 ± 0.3 vs. 6.7 ± 0.3 mmol/L, p = 0.027. Glucose iAUC was not significantly different in the complex group, except for reductions in %PG 28.7% ± 8.2% vs. 43.4% ± 5.9%, p = 0.012 after 50 mg dose and 27.7% ± 5.4% vs. 47.3% ± 7.2%, p = 0.025 after 400 mg dose. The results suggest that Enzogenol® may have hypoglycaemic effects in healthy participants, especially those exhibiting monophasic shapes.

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.

Bioaccessibility and Pharmacokinetics of a Commercial Saffron (Crocus sativus L.) Extract

There are few studies about the pharmacokinetics of the low-molecular mass carotenoids crocetin or crocin isomers from saffron (Crocus sativus L.). None has been performed with a galenic preparation of a standardised saffron extract. The aim of the present research work was to study the effect of in vitro digestion process on the main bioactive components of saffron extract tablets and the corresponding pharmacokinetic parameters in humans. Pharmacokinetics were calculated collecting blood samples every 30 min during the first 3 h and at 24 h after administration of two different concentrations (56 and 84 mg of the saffron extract) to 13 healthy human volunteers. Additionally, an in vitro digestion process was performed in order to determine the bioaccessibility of saffron main bioactive compounds. Identification and quantification analysis were performed by HPLC-PAD/MS. Digestion resulted in 40% of bioaccesibility for crocin isomers, whereas, safranal content followed an opposite trend increasing about 2 folds its initial concentration after the digestion process. Crocetin in plasma was detected in a maximum concentration (C _max) in blood between 60 and 90 min after oral consumption with dose-dependent response kinetics, showing that crocin isomers from galenic preparation of saffron extract are rapidly transformed into crocetin. The results showed that this tested galenic form is an efficient way to administer a saffron extract, since the observed crocetin C _max was similar and more quickly bioavailable than those obtained by other studies with much higher concentrations of crocetin.

Triglyceride Paradox Is Related to Lipoprotein Size, Visceral Adiposity and Stearoyl-CoA Desaturase Activity in Black Versus White Women

RATIONALE

In black women, triglycerides are paradoxically normal in the presence of insulin resistance. This relationship may be explained by race-related differences in central adiposity and SCD (stearoyl-CoA desaturase)-1 enzyme activity index.

OBJECTIVE

In a cross-sectional study, to compare fasting and postprandial triglyceride-rich lipoprotein particle (TRLP) concentrations and size in black compared with white pre- and postmenopausal women and determine the relationship between TRLP subfractions and whole-body insulin sensitivity, hepatic and visceral fat, and SCD-1 levels.

METHODS AND RESULTS

In 122 federally employed women without diabetes mellitus, 73 black (58 African American and 15 African immigrant) and 49 white; age, 44±10 (mean±SD) years; body mass index, 30.0±5.6 kg/m², we measured lipoprotein subfractions using nuclear magnetic resonance. Hepatic fat was measured by proton magnetic resonance spectroscopy, insulin sensitivity index calculated by minimal modeling from a frequently sampled intravenous glucose test, and red blood cell fatty acid profiles were measured by gas chromatography and were used to estimate SCD-1 indices. Hepatic fat, insulin sensitivity index, and SCD-1 were similar in black women and lower than in whites, regardless of menopausal status. Fasting and postprandial large, medium, and small TRLPs, but not very small TRLPs, were lower in black women. Fasting large, medium, and very small TRLPs negatively correlated with insulin sensitivity index and positively correlated with visceral and hepatic fat and SCD-1 activity in both groups. In multivariate models, visceral fat and SCD-1 were associated with total fasting TRLP concentrations (adjR2, 0.39; P=0.001). Black women had smaller postprandial changes in large (P=0.005) and medium TRLPs (P=0.007).

CONCLUSIONS

Lower visceral fat and SCD-1 activity may contribute to the paradoxical association of lower fasting and postprandial TRLP subfractions despite insulin resistance in black compared with white pre- and postmenopausal women. Similar concentrations of very small TRLPs are related to insulin resistance and could be important mediators of cardiometabolic disease risk in women.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01809288.

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.

Postprandial Insulin Response and Clearance Among Black and White Women: The Federal Women's Study

CONTEXT

Postprandial hyperinsulinemia might be an important cardiometabolic risk determinant in black compared with white women. However, the contributions of insulin clearance and β-cell function to racial differences in postprandial insulin response are unknown.

OBJECTIVE

To compare, by race and menopause, early insulin response to oral and intravenous glucose and to measure postprandial intact glucagon-like peptide 1 (GLP-1) concentrations, insulin clearance, and β-cell function.

DESIGN AND PARTICIPANTS

119 federally employed women without diabetes [87 premenopausal (52 black, 35 white) and 32 postmenopausal (19 black, 13 white)] underwent an oral glucose tolerance test, insulin-modified frequently sampled intravenous glucose test (IM-FSIGT), and mixed meal tolerance test (MMTT).

OUTCOME MEASURES

Early insulin response was measured as follows: (i) insulinogenic index (oral glucose tolerance test); (ii) acute insulin response to glucose (IM-FSIGT); and (iii) ratio of incremental insulin/glucose area under the curve in the first 30 minutes of the MMTT. Insulin clearance was assessed during the IM-FSIGT and MMTT. During the MMTT, intact GLP-1 was measured and β-cell function assessed using the insulin secretion rate and β-cell responsivity indexes.

RESULTS

Black pre-menopausal and postmenopausal women had a greater insulin response and lower insulin clearance and greater dynamic β-cell responsivity (P ≤ 0.05 for all). No differences were found in the total insulin secretion rates or intact GLP-1 concentrations.

CONCLUSIONS

Greater postprandial hyperinsulinemia in black pre-menopausal and postmenopausal women was associated with lower hepatic insulin clearance and heightened β-cell capacity to rapid changes in glucose, but not to higher insulin secretion. The relationship of increased β-cell secretory capacity, reduced insulin clearance, and ambient hyperinsulinemia to the development of cardiometabolic disease requires further investigation.

Distinct metabolic profile according to the shape of the oral glucose tolerance test curve is related to whole glucose excursion: a cross-sectional study

BACKGROUND

The shapes of the plasma glucose concentration curve during the oral glucose tolerance test are related to different metabolic risk profiles and future risk of type 2 DM. We sought to further analyze the relationship between the specific shapes and hyperglycemic states, the metabolic syndrome and hormones involved in carbohydrate and lipid metabolism, and to isolate the effect of the shape by adjusting for the area under the glucose curve.

METHODS

One hundred twenty one adult participants underwent a 2-h oral glucose tolerance test and were assigned to either the monophasic (n = 97) or the biphasic (n = 24) group based upon the rise and fall of their plasma glucose concentration. We evaluated anthropometric measures, blood pressure, lipid profile, high-sensitivity C-reactive protein, glycated hemoglobin, insulin sensitivity, beta-cell function, C-peptide, glucagon, adiponectin and pancreatic polypeptide.

RESULTS

Subjects with monophasic curves had higher fasting and 2-h plasma glucose levels, while presenting lower insulin sensitivity, beta-cell function, HDL cholesterol, adiponectin and pancreatic polypeptide levels. Prediabetes and metabolic syndrome had a higher prevalence in this group. Glycated hemoglobin, total cholesterol, triglycerides, high-sensitivity C-reactive protein and glucagon were not significantly different between groups. After adjusting for the area under the glucose curve, only the differences in the 1-h and 2-h plasma glucose concentrations and HDL cholesterol levels between the monophasic and biphasic groups remained statistically significant.

CONCLUSIONS

Rates and intensity of metabolic dysfunction are higher in subjects with monophasic curves, who have lower insulin sensitivity and beta-cell function and a higher prevalence of prediabetes and metabolic syndrome. These differences, however, seem to be dependent on the area under the glucose curve.

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

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

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

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