Minimal contribution of fasting hyperglycemia to the incidence of type 2 diabetes in subjects with normal 2-h plasma glucose

Higher adiposity predicts greater intra-individual inconsistencies in postprandial glycemic measurements-an analysis of three randomized controlled trials in Asian populations

BACKGROUND/OBJECTIVES

Acute glycemic responses offer important insights into glucose homeostasis although the repeatability of these measurements particularly in Asian populations remains unclear. This research aimed to critically investigate the inconsistencies of the postprandial glycemic profile within individuals, and identify potential variables predicting greater inconsistencies.

SUBJECTS/METHODS

This was a secondary analysis of three randomized controlled trials which fed subjects with glucose (and other carbohydrate-rich foods), and measured postprandial blood glucose at regular intervals. Intra-individual rank-order consistency in the glycemic profile between acute glucose treatments was evaluated and compared against demographic, anthropometric and cardio-metabolic health related indicators to delineate potential confounding variables. Correlations between the incremental area under curve at 120 min (iAUC120 min) for glucose and the carbohydrate-rich foods were further explored.

RESULTS

Rank-order consistency was identified to be moderate, with intra-individual inconsistencies marginally lower than inter-individual inconsistencies. Notably, greater inconsistencies within individuals were directly correlated with BMI and fat-mass index (P < 0.01) albeit non-significant for age, ethnicity, and other cardio-metabolic health-related risk indicators. Across the trials, there were positive monotonic correlations between the iAUC120 min for glucose and simple sugars (sucrose, isomaltulose), as well as different varieties of rice (jasmine white, Bapatla brown, Bapatla white; p < 0.05). However, there were a lack of associations between iAUC120 min for glucose with pastas (semolina and wholegrain penne, spaghetti) and mee pok noodles.

CONCLUSION

There are inherent inconsistencies in postprandial glycemic measurements within individuals, particularly among those with higher adiposity. These confounders need to be kept in mind for appropriate and meaningful interpretations of glycemia.

International Diabetes Federation Position Statement on the 1-hour post-load plasma glucose for the diagnosis of intermediate hyperglycaemia and type 2 diabetes

Many individuals with intermediate hyperglycaemia (IH), including impaired fasting glycaemia (IFG) and impaired glucose tolerance (IGT), as presently defined, will progress to type 2 diabetes (T2D). There is confirmatory evidence that T2D can be prevented by lifestyle modification and/or medications, in people with IGT diagnosed by 2-h plasma glucose (PG) during a 75-gram oral glucose tolerance test (OGTT). Over the last 40 years, a wealth of epidemiological data has confirmed the superior value of 1-h plasma glucose (PG) over fasting PG (FPG), glycated haemoglobin (HbA1c) and 2-h PG in populations of different ethnicity, sex and age in predicting diabetes and associated complications including death. Given the relentlessly rising prevalence of diabetes, a more sensitive, practical method is needed to detect people with IH and T2D for early prevention or treatment in the often lengthy trajectory to T2D and its complications. The International Diabetes Federation (IDF) Position Statement reviews findings that the 1-h post-load PG ≥ 155 mg/dL (8.6 mmol/L) in people with normal glucose tolerance (NGT) during an OGTT is highly predictive for detecting progression to T2D, micro- and macrovascular complications, obstructive sleep apnoea, cystic fibrosis-related diabetes mellitus, metabolic dysfunction-associated steatotic liver disease, and mortality in individuals with risk factors. The 1-h PG of 209 mg/dL (11.6 mmol/L) is also diagnostic of T2D. Importantly, the 1-h PG cut points for diagnosing IH and T2D can be detected earlier than the recommended 2-h PG thresholds. Taken together, the 1-h PG provides an opportunity to avoid misclassification of glycaemic status if FPG or HbA1c alone are used. The 1-h PG also allows early detection of high-risk people for intervention to prevent progression to T2D which will benefit the sizeable and growing population of individuals at increased risk of T2D. Using a 1-h OGTT, subsequent to screening with a non-laboratory diabetes risk tool, and intervening early will favourably impact the global diabetes epidemic. Health services should consider developing a policy for screening for IH based on local human and technical resources. People with a 1-h PG ≥ 155 mg/dL (8.6 mmol/L) are considered to have IH and should be prescribed lifestyle intervention and referred to a diabetes prevention program. People with a 1-h PG ≥ 209 mg/dL (11.6 mmol/L) are considered to have T2D and should have a repeat test to confirm the diagnosis of T2D and then referred for further evaluation and treatment. The substantive data presented in the Position Statement provides strong evidence for redefining current diagnostic criteria for IH and T2D by adding the 1-h PG.

Predisposition to Type 2 Diabetes in Aspects of the Glycemic Curve and Glycated Hemoglobin in Healthy, Young Adults: A Cross-sectional Study

OBJECTIVES

Our aim in this study was to identify predictors for diabetes among the characteristics of the glycemic curve and glycated hemoglobin (A1C) in healthy, young adults.

METHODS

We used a cross-sectional study to establish predictors for diabetes based on earlier studies and evaluated occurrence of the condition in 81 healthy, young adult subjects. These volunteers underwent analysis of fasting plasma glucose, oral glucose tolerance test plasma glucose, A1C, and inflammatory markers (leukocytes, monocytes, and C-reactive protein). The nonparametric Mann-Whitney U test, Fisher's exact test, chi-square test, Kruskal-Wallis test, and multiple-comparisons test were used to analyze the data.

RESULTS

We studied 2 age groups, homogeneous in terms of family history of diabetes: one group ranged in age from ≥18 to <28 years (median 20 years; body mass index [BMI] 24 kg/m2) and the other group ranged in age from ≥28 to <45 years (median 35 years; BMI 24 kg/m2). The older group had a higher incidence of predictors (p=0.0005) and was associated with the predictors 30-minute blood glucose ≥164 mg/dL (p=0.0190), 60-minute blood glucose ≥125 mg/dL (p=0.0346), and A1C ≥5.5% (p=0.0162), with a monophasic glycemic curve (p=0.007). The younger group was associated with the 2-hour plasma glucose predictor ≥140 mg/dL (p=0.014). All subjects had fasting glucose in the normal range.

CONCLUSIONS

Healthy, young adults may already have predictors of diabetes, identified mainly by aspects of the glycemic curve and A1C, but at more modest levels than those with prediabetes.

Reproducibility of the energy metabolism response to an oral glucose tolerance test: influence of a postcalorimetric correction procedure

PURPOSE

Metabolic flexibility (MetF), which is a surrogate of metabolic health, can be assessed by the change in the respiratory exchange ratio (RER) in response to an oral glucose tolerance test (OGTT). We aimed to determine the day-to-day reproducibility of the energy expenditure (EE) and RER response to an OGTT, and whether a simulation-based postcalorimetric correction of metabolic cart readouts improves day-to-day reproducibility.

METHODS

The EE was assessed (12 young adults, 6 women, 27 ± 2 years old) using an Omnical metabolic cart (Maastricht Instruments, Maastricht, The Netherlands) after an overnight fast (12 h) and after a 75-g oral glucose dose on 2 separate days (48 h). On both days, we assessed EE in 7 periods (one 30-min baseline and six 15-min postprandial). The ICcE was performed immediately after each recording period, and capillary glucose concentration (using a digital glucometer) was determined.

RESULTS

We observed a high day-to-day reproducibility for the assessed RER (coefficients of variation [CV] < 4%) and EE (CVs < 9%) in the 7 different periods. In contrast, the RER and EE areas under the curve showed a low day-to-day reproducibility (CV = 22% and 56%, respectively). Contrary to our expectations, the postcalorimetric correction procedure did not influence the day-to-day reproducibility of the energy metabolism response, possibly because the Omnical's accuracy was ~ 100%.

CONCLUSION

Our study demonstrates that the energy metabolism response to an OGTT is poorly reproducible (CVs > 20%) even using a very accurate metabolic cart. Furthermore, the postcalorimetric correction procedure did not influence the day-to-day reproducibility. Trial registration NCT04320433; March 25, 2020.

One-hour plasma glucose concentration can identify elderly Chinese male subjects at high risk for future type 2 diabetes mellitus: A 20-year retrospective and prospective study

AIM

There have been few reports regarding the association between 1 h-PG concentration and type 2 diabetes mellitus (T2DM) in the elderly. This study was performed to assess the efficacy of 1 h-PG and 2 h-PG values in predicting future risk of T2DM in elderly.

METHODS

The study population consisted of 928 male volunteers ≥ 55 years old without diabetes who were involved in a retrospective-prospective cohort study over 20 years with a baseline fasting plasma glucose (FPG) and OGTT that included measurement of 1 h-PG and 2 h-PG. The predictive capabilities of FPG and 1 h-PG, 2 h-PG values obtained during OGTT alone and added to a clinical prediction model consisting of traditional diabetes risk factors were assessed.

RESULTS

Overall, 577 of all the 928 study participants (62%) developed T2DM over the 20-year follow-up. 1 h-PG and 2 h-PG values predicted T2DM and remained independent predictors of T2DM after adjusting for various traditional risk factors [HR = 1.269 (95% CI = 1.214-1.327), P < 0.001; HR = 1.269 (95% CI = 1.179-1.366), P < 0.001, respectively]. C-statistics for 1-h PG (C-statistics 0.794 [95% CI 0.765-0.823]) was significantly greater than that for 2-h PG (C-statistic 0.747 [95% CI 0.716-0.779]) in models adjusting for various traditional risk factors. 1 h-PG had the greatest area under the ROC curve (AUC, 0.766), which was greater than that of 2 h-PG (0.719).

CONCLUSIONS

1 h-PG is useful as a predictor of future development of T2DM independently of traditional risk factors in an elderly Chinese male population.

A CROSS-SECTIONAL STUDY OF THE ASSOCIATION BETWEEN THE 1-HOUR ORAL GLUCOSE TOLERANCE TEST AND THE METABOLIC SYNDROME IN A HIGH-RISK SAMPLE WITH IMPAIRED FASTING GLUCOSE

Objective: The aim of this study was to evaluate the association between the 1-hour oral glucose tolerance test (OGTT) (≥155 mg/dL) and metabolic syndrome (MS) in a sample with previous impaired fasting glucose (IFG). Methods: Three hundred and twenty four Peruvian subjects with a history of IFG ≥100 mg/dL were selected for a cross-sectional study. They underwent a 75 g OGTT and were assigned to different groups according to the result. We evaluated the association between 1-hour OGTT and MS. Results: The mean age was 56.5 ± 12.6 years and 191 (61.5%) were female. During the OGTT, we found 28 (8.6%) subjects with diabetes, 74 (22.8%) with IGT, and 222 (68.5%) with a normal glucose tolerance test with a 2-hour glucose <140 mg/dL (NGT). In the NGT group, 124 (38.3%) had 1-hour glucose levels <155 mg/dL, while 98 (30.2%) had 1-hour glucose levels ≥155 mg/dL. Evaluating the association between the 1-hour value in the OGTT and MS, we found that subjects with a 1-hour glucose ≥155 mg/dL were more than twice as likely to have MS as those with a 1-hour glucose <155 mg/dL (odds ratio = 2.64, 95% confidence interval: 1.52 to 4.57). In addition, body mass index, fasting glycemia, triglycerides, and waist circumferences were significantly higher in subjects with 1-hour glucose levels ≥155 mg/dL compared to those with 1-hour glucose levels <155 mg/dL (P<.05). Conclusion: Among subjects with IFG, performing an OGTT was helpful to identify subjects with 1-hour glucose levels ≥155 mg/dL and NGT who were significantly more likely to have MS and a worse cardiometabolic risk profile. Abbreviations: AST = aspartate aminotransferase; BMI = body mass index; CI = confidence interval; IFG = impaired fasting glucose; IGT = impaired glucose tolerance; LDL = low-density lipoprotein; MS = metabolic syndrome; NGT = normal glucose tolerance; OGTT = oral glucose tolerance test; OR = odds ratio; T2DM = type 2 diabetes; TG = triglycerides.

Impact on cardiometabolic risk of a weight loss intervention with higher protein from lean red meat: Combined results of 2 randomized controlled trials in obese middle-aged and older adults

BACKGROUND

The recognized benefits of a higher protein diet on muscle mass and strength in older adults are tempered by concerns of the potentially negative cardiometabolic impact of dietary sources of animal protein.

OBJECTIVE

The aim of this study was to explore the cardiometabolic impact of 2 weight reduction diets: a higher protein diet, providing balanced portions of lean beef and pork throughout the day, vs. a diet following the Recommended Daily Allowance level of protein in obese middle-aged and older adults.

METHODS

Data from Measuring Eating, Activity and Strength: Understanding the Response-Using Protein and Protein Optimization in Women Enables Results-Using Protein were combined for the present analysis. Subjects were randomly assigned to a 6-month weight loss diet (500 kcal deficit) and prescribed a Recommended Daily Allowance level of protein (0.8 g protein/kg BW), control group, or a higher level of protein (1.2 g protein/kg BW), protein group. For the protein group, lean, high-quality protein was evenly distributed between meals or balanced throughout the day (30 g protein/meal). The following cardiometabolic markers were quantified by nuclear magnetic resonance spectroscopy: lipids, lipoproteins, GlycA, trimethylamine-N-oxide, betaine, branched-chain amino acids, and lipoprotein insulin resistance index scores.

RESULTS

In both groups (control [n = 27] and protein [n = 53]), there were significant (P ≤ .05) changes from baseline in weight loss (-6.2% and -7.2%), distance walked (+53.1 and +75.0 meters), and fasting plasma glucose (-7.5 and -6.2 mg/dL), respectively. At endpoint, protein group had significantly (P ≤ .05) lower triglycerides (-17.3 mg/dL), large very-low-density lipoprotein particle concentration (VLDL-P; -1.2 nmol/L), total low-density lipoprotein particle concentration (LDL-P; -67.8 nmol/L), small LDL-P (-59.4 nmol/L) and lipoprotein insulin resistance index (-5.9), whereas control group had significantly (P ≤ .05) lower GlycA (-13.1 μmol/L), total VLDL-P (-7.9 nmol/L), and small VLDL-P (-7.0 nmol/L). Differences between groups were observed for small VLDL-P (P = .02) and protein intake (P < .0001).

CONCLUSIONS

These findings suggest that a hypocaloric diet with either traditional (0.8 g/kg BW/d) or higher protein (1.2 g/kg BW/d; predominantly from lean red meat) content improves risk markers of cardiovascular disease and type II diabetes in obese middle-aged and older adults. Both diets were also associated with improved physical function, and neither had an adverse impact on cardiometabolic outcomes.

Bimodal distribution of fasting, one and two hour post load plasma glucose in Asian Indian pregnant women without pre-gestational diabetes: Gestational age related changes

•After exclusion of pre-gestational diabetes, Asian Indian pregnant women have bimodal distribution of plasma glucose.•Bimodality is observed for fasting, 1 and 2 h post glucose load plasma glucose distribution.•Cut off values for gestational diabetes diagnosis could not identified for any glucose parameter.•In women with high gestational diabetes risk factors, the bimodality is evident before 24 weeks of gestation.•By third trimester, the bimodality is significant for all glucose parameters.

Petition to replace current OGTT criteria for diagnosing prediabetes with the 1-hour post-load plasma glucose ≥ 155 mg/dl (8.6 mmol/L)

Many individuals with prediabetes, as presently defined, will progress to diabetes (T2D) despite the considerable benefit of lifestyle modification. Therefore, it is paramount to screen individuals at increased risk with a more sensitive method capable of identifying prediabetes at an even earlier time point in the lengthy trajectory to T2D. This petition reviews findings demonstrating that the 1-hour (1-h) postload plasma glucose (PG) ≥ 155 mg/dl (8.6 mmol/L) in those with normal glucose tolerance (NGT) during an oral glucose tolerance test (OGTT) is highly predictive for detecting progression to T2D, micro- and macrovascular complications and mortality in individuals at increased risk. Furthermore, the STOP DIABETES Study documented effective interventions that reduce the future risk of T2D in those with NGT and a 1-h PG ≥ 155 mg/dl (8·6 mmol/L). The 1-h OGTT represents a valuable opportunity to extend the proven benefit of diabetes prevention to the sizeable and growing population of individuals at increased risk of progression to T2D. The substantial evidence provided in this petition strongly supports redefining current diagnostic criteria for prediabetes with the elevated 1-h PG level. The authors therefore advocate a 1-h OGTT to detect prediabetes and hence, thwart the global diabetes epidemic.

The shape of the glucose concentration curve during an oral glucose tolerance test predicts risk for type 1 diabetes

AIMS/HYPOTHESIS

We aimed to examine: (1) whether specific glucose-response curve shapes during OGTTs are predictive of type 1 diabetes development; and (2) the extent to which the glucose-response curve is influenced by insulin secretion.

METHODS

Autoantibody-positive relatives of people with type 1 diabetes whose baseline OGTT met the definition of a monophasic or biphasic glucose-response curve were followed for the development of type 1 diabetes (n = 2627). A monophasic curve was defined as an increase in OGTT glucose between 30 and 90 min followed by a decline of ≥ 0.25 mmol/l between 90 and 120 min. A biphasic response curve was defined as a decrease in glucose after an initial increase, followed by a second increase of ≥ 0.25 mmol/l. Associations of type 1 diabetes risk with glucose curve shapes were examined using cumulative incidence curve comparisons and proportional hazards regression. C-peptide responses were compared with and without adjustments for potential confounders.

RESULTS

The majority of participants had a monophasic curve at baseline (n = 1732 [66%] vs n = 895 [34%]). The biphasic group had a lower cumulative incidence of type 1 diabetes (p < 0.001), which persisted after adjustments for age, sex, BMI z score and number of autoantibodies (p < 0.001). Among the monophasic group, the risk of type 1 diabetes was greater for those with a glucose peak at 90 min than for those with a peak at 30 min; the difference persisted after adjustments (p < 0.001). Compared with the biphasic group, the monophasic group had a lower early C-peptide (30-0 min) response, a lower C-peptide index (30-0 min C-peptide/30-0 min glucose), as well as a greater 2 h C-peptide level (p < 0.001 for all).

CONCLUSIONS/INTERPRETATION

Those with biphasic glucose curves have a lower risk of progression to type 1 diabetes than those with monophasic curves, and the risk among the monophasic group is increased when the glucose peak occurs at 90 min than at 30 min. Differences in glucose curve shapes between the monophasic and biphasic groups appear to be related to C-peptide responses.

Area under the curve during OGTT in first-degree relatives of diabetic patients as an efficient indicator of future risk of type 2 diabetes and prediabetes

OBJECTIVE

To establish whether the area under the curve of an OGTT has a predictive role in identifying prediabetic and diabetic subjects among first-degree relatives (FDR) of patients with diabetes mellitus type 2 (DM).

DESIGN, PATIENTS AND MEASUREMENTS

In a population-based cohort study, 766 FDR of diabetic patients with a normal glucose tolerance test (NGT) completed a 2-hour OGTT. They were followed up for 7 years and classified according to the American Diabetes Association criteria into: NGT, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and DM. Relative risk (RR) and 95% confidence intervals (95%CI) were calculated based on logistic regression. Receiver operator characteristic (ROC) analysis along with AUC at different intervals and at time points during the OGTT was used to evaluate the risk of prediabetes and diabetes.

RESULTS

Twenty-three subjects (3%) developed type 2 DM, 118 (29.3%) IFG, 81 (11.5%) IGT and 544 (71%) subjects remained NGT. AUC and mean difference of glucose in all high-risk groups demonstrated significant differences in both intervals and time points when compared to the NGT group. The cut-off values during OGTT to predict prediabetes and diabetes was determined as blood glucose more than 7.2 and 7.8 mmol/L at 30 and 60 minutes, respectively. The time point 60 has the highest predictive role for the development of diabetes, alone, and improved the performance of a prediction model containing multiple important clinical risk factors.

CONCLUSION

The data suggest that the glycaemic response to an OGTT may predict the risk of development of diabetes in first-degree relatives of DM patients.

Comparison of glucose homeostasis parameters between patients with high and low risk of diabetes at 6 weeks and 6 months after sleeve gastrectomy

BACKGROUND

The changes in glucose homeostasis after sleeve gastrectomy (SG) for patients with high (HRD) and low risk (LRD) of developing diabetes have not been investigated.

OBJECTIVE

To compare the glucose homeostasis parameters between patients with HRD and LRD after SG.

SETTING

University hospital in Greece.

METHODS

Thirteen patients were categorized as HRD (9 females, mean body mass index 46.3±1.6 kg/m²) and 10 as LRD (8 females, mean body mass index 45.4±1.7 kg/m²) based on a preoperative 2-hour oral glucose tolerance test (OGTT). OGTT was repeated 6 weeks and 6 months postoperatively. OGTT-derived indices of insulin secretion, insulin sensitivity, and β-cell function (oral disposition index [ODI]) were calculated.

RESULTS

Preoperatively, in the HRD group, fasting and postload glucose levels were higher and the ODIs were lower compared with those in the LRD group. Six weeks postoperatively, glucose levels and ODIs were not different between the 2 groups. However, 6 months postoperatively, the HRD group had demonstrated higher postload glucose levels and lower ODI (0-30) and ODI (0-120) compared with the LRD group. Six weeks postoperatively, insulin levels, early insulin secretion, and insulin resistance indices were decreased compared with preoperative levels only in the HRD group. Six months postoperatively, ODIs and insulin sensitivity indices improved in both groups compared with baseline.

CONCLUSION

Six months after SG, glucose levels and ODIs improved for both HRD and LRD patients; however, postprandial glucose levels and ODI (0-30) and ODI (0-120) in HRD patients did not return to LRD levels. Moreover, during the first 6 postoperative weeks, the changes in glucose homeostasis parameters compared with preoperative levels were different for HRD and LRD patients.

Effects of exercise training alone vs a combined exercise and nutritional lifestyle intervention on glucose homeostasis in prediabetic individuals: a randomised controlled trial

AIMS/HYPOTHESIS

Although the Diabetes Prevention Program (DPP) established lifestyle changes (diet, exercise and weight loss) as the 'gold standard' preventive therapy for diabetes, the relative contribution of exercise alone to the overall utility of the combined diet and exercise effect of DPP is unknown; furthermore, the optimal intensity of exercise for preventing progression to diabetes remains very controversial. To establish clinical efficacy, we undertook a study (2009 to 2013) to determine: how much of the effect on measures of glucose homeostasis of a 6 month programme modelled after the first 6 months of the DPP is due to exercise alone; whether moderate- or vigorous-intensity exercise is better for improving glucose homeostasis; and to what extent amount of exercise is a contributor to improving glucose control. The primary outcome was improvement in fasting plasma glucose, with improvement in plasma glucose AUC response to an OGTT as the major secondary outcome.

METHODS

The trial was a parallel clinical trial. Sedentary, non-smokers who were 45-75 year old adults (n = 237) with elevated fasting glucose (5.28-6.94 mmol/l) but without cardiovascular disease, uncontrolled hypertension, or diabetes, from the Durham area, were studied at Duke University. They were randomised into one of four 6 month interventions: (1) low amount (42 kJ kg body weight(-1) week(-1) [KKW])/moderate intensity: equivalent of expending 42 KKW (e.g. walking ∼16 km [8.6 miles] per week) with moderate-intensity (50% [Formula: see text]) exercise; (2) high amount (67 KKW)/moderate intensity: equivalent of expending 67 KKW (∼22.3 km [13.8 miles] per week) with moderate-intensity exercise; (3) high amount (67 KKW)/vigorous intensity: equivalent to group 2, but with vigorous-intensity exercise (75% [Formula: see text]); and (4) diet + 42 KKW moderate intensity: same as group 1 but with diet and weight loss (7%) to mimic the first 6 months of the DPP. Computer-generated randomisation lists were provided by our statistician (G. P. Samsa). The randomisation list was maintained by L. H. Willis and C. A. Slentz with no knowledge of or input into the scheduling, whereas all scheduling was done by L. A. Bateman, with no knowledge of the randomisation list. Subjects were automatically assigned to the next group listed on the randomisation sheet (with no ability to manipulate the list order) on the day that they came in for the OGTT, by L. H. Willis. All plasma analysis was done blinded by the individuals doing the measurements (i.e. lipids, glucose, insulin). Subjects and research staff (other than individuals analysing the blood) were not blinded to the group assignments.

RESULTS

Number randomised, completers and number analysed with complete OGTT data for each group were: low-amount/moderate-intensity (61, 43, 35); high-amount/moderate-intensity (61, 44, 40); high-amount/vigorous-intensity (61, 43, 38); diet/exercise (54, 45, 37), respectively. Only the diet and exercise group experienced a decrease in fasting glucose (p < 0.001). The means and 95% CIs for changes in fasting glucose (mmol/l) for each group were: high-amount/moderate-intensity -0.07 (-0.20, 0.06); high-amount/vigorous 0.06 (-0.07, 0.19); low-amount/moderate 0.05 (-0.05, 0.15); and diet/exercise -0.32 (-0.46, -0.18). The effects sizes for each group (in the same order) were: 0.17, 0.15, 0.18 and 0.71, respecively. For glucose tolerance (glucose AUC of OGTT), similar improvements were observed for the diet and exercise (8.2% improvement, effect size 0.73) and the 67 KKW moderate-intensity exercise (6.4% improvement, effect size 0.60) groups; moderate-intensity exercise was significantly more effective than the same amount of vigorous-intensity exercise (p < 0.0207). The equivalent amount of vigorous-intensity exercise alone did not significantly improve glucose tolerance (1.2% improvement, effect size 0.21). Changes in insulin AUC, fasting plasma glucose and insulin did not differ among the exercise groups and were numerically inferior to the diet and exercise group.

CONCLUSIONS/INTERPRETATION

In the present clinical efficacy trial we found that a high amount of moderate-intensity exercise alone was very effective at improving oral glucose tolerance despite a relatively modest 2 kg change in body fat mass. These data, combined with numerous published observations of the strong independent relation between postprandial glucose concentrations and prediction of future diabetes, suggest that walking ∼18.2 km (22.3 km prescribed with 81.6% adherence in the 67 KKW moderate-intensity group) per week may be nearly as effective as a more intensive multicomponent approach involving diet, exercise and weight loss for preventing the progression to diabetes in prediabetic individuals. These findings have important implications for the choice of clinical intervention to prevent progression to type 2 diabetes for those at high risk.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00962962 FUNDING: The study was funded by National Institutes for Health National Institute of Diabetes and Digestive and Kidney Diseases (NIH-NDDK) (R01DK081559).

Prediabetes and risk of diabetes and associated complications: impaired fasting glucose versus impaired glucose tolerance: does it matter?

PURPOSE OF REVIEW

The purpose of this review is to summarize the distinct metabolic and pathophysiologic phenotype of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) and the subsequent clinical implications with regard to future type 2 diabetes mellitus (T2DM) and cardiovascular risk.

RECENT FINDINGS

Both IFG and IGT manifest the two core defects of T2DM, that is, insulin resistance and β-cell dysfunction. However, the site of insulin resistance and shape of β-cell dysfunction differ. These distinct metabolic and pathophysiologic phenotypes explain the greater cardiovascular disease (CVD) risk associated with an increase in the 2-h plasma glucose concentration, that is, IGT compared with an increase in the fasting plasma glucose (FPG) concentration, that is, IFG. Moreover, the increase in future T2DM risk in IFG study participants is, at least in part, explained by the strong correlation between the increase in FPG and the increase in 2-h plasma glucose concentration.

SUMMARY

Last, recent studies have reported the presence of diabetic microvascular complications, that is, retinopathy and neuropathy, at the IGT stage.Thus, a glucose load (e.g. oral glucose tolerance test) is required in study participants with elevated FPG concentration to accurately assess their future risk for T2DM, as well as their risk for CVD to identify the subgroup of IFG who are at greater risk and subject them to an intervention program to decrease their future T2DM and CVD risk.

Normal fasting plasma glucose predicts type 2 diabetes and cardiovascular disease in elderly population in Taiwan

BACKGROUND

Hyperglycemia increases prevalence of metabolic syndrome (MetS), type 2 diabetes (T2D) and cardiovascular disease (CVD). But the role of normoglycemia on the development of T2D and CVD in elderly population remains unclear.

AIM

To determine an optimal cut-off for fasting plasma glucose (FPG) to predict MetS and subsequent risk of T2D and CVD in an elderly Taiwanese population with normal FPG levels.

DESIGN

Two stages included cross-sectional (Stage 1) and prospective (Stage 2) cohort study.

METHODS

In Stage 1 18 287 subjects aged  ≥60 years were enrolled; of these, 5039 without T2D and CVD advanced to Stage 2 and a mean follow-up of 3.8 years. MetS components were analysed, and in Stage 1, FPG cut-offs for MetS risk were calculated using receiver operating characteristic (ROC) curve analyses. In Stage 2, subjects without T2D and CVD in Stage 1 were classified into high-FPG and low-FPG groups based on cut-offs, and sex specific differences in incidence for T2D and CVD were calculated.

RESULTS

ROC curve analysis gave an optimal FPG cut-off for MetS of 93 mg/dl and 92 mg/dl for males and females, respectively. The high-FPG group had a 1.599- and 1.353-fold higher chance of developing T2D compared with the low-FPG group for males and females, respectively (95% CI: 1.606-2.721 and 1.000-1.831, P  =  0.015 and 0.05). The high-FPG group had a 1.24-fold higher chance of developing CVD for females (95% CI: 1.015-1.515, P  =  0.035); however, there was no difference for males.

CONCLUSIONS

Our results suggest that FPG within the normal range was associated with MetS, and elderly subjects with high normal levels have a higher incidence of developing T2D for both sexes, and CVD for females, over the short-term.

Follow-up duration influences the relative importance of OGTT and optimal timing of glucose measurements for predicting future type 2 diabetes

OBJECTIVE

To examine the impact of follow-up duration on the incremental prognostic yield of a baseline oral glucose tolerance test (OGTT) for predicting type 2 diabetes and to assess the discrimination ability of blood glucose (BG) obtained at different time points during OGTT.

DESIGN

A prospective, population-based cohort study (Malmö Preventive Project) with inclusion of subjects from 1974 to 1992.

METHODS

A total of 5256 men without diabetes, who had BG measured at 0, 20, 40, 60, 90, and 120 min during OGTT (30 g/m2 glucose), were followed for 30 years. Incident type 2 diabetes was recorded using registries. The performance of OGTT added to a clinical prediction model (age, body mass index (BMI), diastolic blood pressure, fasting BG, triglycerides, and family history of diabetes) was assessed using Harrell's concordance index (C-index) and integrated discrimination improvement (IDI).

RESULTS

Median age was 48 years, mean BMI 24.9 kg/m2, and mean fasting BG 4.7 mmol/L. Models with added post-load BG performed better than the clinical model (C-index: P = 0.08 for BG at 120 min at 5 years, otherwise P ≤ 0.045; IDI: P ≥ 0.06 for BG at 60 and 90 min at 5 years, otherwise P ≤ 0.01). With a longer follow-up duration, C-index decreased, and the C-index increase associated with OGTT was attenuated. Models including BG at 60 or 90 min performed significantly better than the model with BG at 120 min, evident beyond follow-up of 10 and 5 years, respectively.

CONCLUSIONS

OGTT provided incremental prognostic yield for type 2 diabetes prediction. BG measured at 60 or 90 min provided better discrimination than BG at 120 min.

[Screening and prevention of diabetes]

A valid and efficient screening for individual diabetes risk is a highly welcomed tool in primary care and specialist medical practice. It is needed to detect early stages of diabetes risk and prediabetes and to start interventions that have the aim to prevent diabetes and also other chronic diseases from developing. The oral glucose tolerance test is the gold standard, but it is difficult to perform in an evidence-based manner in primary care. Furthermore, measuring fasting and 2-h postprandial glucose values detects only late stages of the pathophysiological development of type 2 diabetes. Interestingly, the 1-h glucose value is highly predictive of future diabetes risk, but is rarely used in primary care. Therefore, risk scores are commonly used to evaluate diabetes risk, but unfortunately, they generally do not mirror the relevance of increased risk due to the person's own lifestyle. Measuring waist circumference is another possibility, because the waist is directly associated with the amount of visceral fat, which again directly correlates with the pathophysiology of diabetes development. A further possibility is the EZSCAN™ technology. The EZSCAN™ is based on reverse iontophoresis, a new technology to detect very early forms of peripheral neuropathies, which are commonly associated with early diabetes risk stages. It is important to perform diabetes screening in a targeted manner, in both medical and paramedical environments, and it is mandatory to add targeted interventions, based on the screening evaluated diabetes risk.

Treatment of prediabetes

Progression of normal glucose tolerance (NGT) to overt diabetes is mediated by a transition state called impaired glucose tolerance (IGT). Beta cell dysfunction and insulin resistance are the main defects in type 2 diabetes mellitus (type 2 DM) and even normoglycemic IGT patients manifest these defects. Beta cell dysfunction and insulin resistance also contribute to the progression of IGT to type 2 DM. Improving insulin sensitivity and/or preserving functions of beta-cells can be a rational way to normalize the GT and to control transition of IGT to type 2 DM. Loosing weight, for example, improves whole body insulin sensitivity and preserves beta-cell function and its inhibitory effect on progression of IGT to type 2 DM had been proven. But interventions aiming weight loss usually not applicable in real life. Pharmacotherapy is another option to gain better insulin sensitivity and to maintain beta-cell function. In this review, two potential treatment options (lifestyle modification and pharmacologic agents) that limits the IGT-type 2 DM conversion in prediabetic subjects are discussed.

Predictability of 1-h postload plasma glucose concentration: A 10-year retrospective cohort study

Aims/Introduction

Elevated 1-h postload plasma glucose concentration (1hPG) during oral glucose tolerance test has been linked to an increased risk of type 2 diabetes and a poorer cardiometabolic risk profile. The present study analyzed the predictability and cut-off point of 1hPG in predicting type 2 diabetes in normal glucose regulation (NGR) subjects, and evaluated the long-term prognosis of NGR subjects with elevated 1hPG in glucose metabolism, kidney function, metabolic states and atherosclerosis.

Materials and Methods

A total of 116 Han Chinese classified as NGR in 2002 at the First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, China, were investigated. Follow-up was carried out in 2012 to evaluate the progression of glucose metabolism, kidney function, metabolic syndrome and carotid atherosclerosis.

Results

The areas under receiver operating characteristic curves were higher for 1hPG than FPG or 2hPG (0.858 vs 0.806 vs 0.746). The cut-off value of 1hPG with the maximal sum of sensitivity and specificity in predicting type 2 diabetes in NGR subjects was 8.85 mmol/L. The accumulative incidence of type 2 diabetes in subjects with 1hPG ≥8.85 mmol/L was higher than those <8.85 mmol/L (46.2% vs 3.3%, P = 0.000; relative risk 13.846, 95% confidence interval 4.223–45.400). On follow up, the prevalence of metabolic syndrome and abnormal carotid intima-media thickness in the subjects with 1hPG ≥8.85 mmol/L tended to be higher compared with those <8.85 mmol/L.

Conclusions

1hPG is a good predictor of type 2 diabetes in NGR subjects, and the best cut-off point is 8.85 mmol/L. Some tendency indicates that NGR subjects with 1hPG ≥8.85 mmol/L are more prone to metabolic syndrome and carotid atherosclerosis.

Oral glucose tolerance test-based calculation identifies different glucose intolerance phenotypes within the impaired fasting glucose range

Aims/Introduction

The conventional oral glucose tolerance test (OGTT) cannot detect future diabetics among isolated impaired fasting glucose (is‐IFG) nor normal glucose tolerant (NGT) groups. By analyzing the relationship between fasting (FPG) and 2‐h plasma glucose (2hPG), the present study identifies is‐IFG subjects liable to worsening glucose homeostasis.

Materials and Methods

Oral glucose tolerance test was carried out in 619 patients suffering from obesity, hypertension or dyslipidemia, whose FPG was in the 100–125 mg/dL range. We calculated the percentage increment of 2hPG with respect to FPG (PG%) in these patients using the formula: ([2hPG − FPG] / FPG) × 100. Differences in β‐cell function within is‐IFG patients were assessed by estimated insulin sensitivity index (EISI), first‐phase insulin release (1stPH) and 1stPH/1/EISI (1stPH_corrected).

Results

Diabetes was diagnosed in 69 patients (11.2%), combined IFG/impaired glucose tolerance (IGT) in 185 patients (29.9%) and is‐IFG in 365 patients (58.9%). Is‐IFG was subdivided into PG% tertile groups: the percentage of females increased from 25% in the lowest to 45.2% in the highest tertile (χ² = 18.7, P < 0.001). Moving from the lowest to the highest PG% tertile group, insulin and 2hPG concentrations rose, whereas FPG, EISI, and 1stPH_corrected decreased progressively and significantly. Furthemore, PG% correlated inversely with EISI (r = −0.44, P < 0.0001) and 1stPH_corrected (r = −0.38, P < 0.0001).

Conclusions

Oral glucose tolerance test does differentiate the great heterogeneity in metabolic disorders of patients with FPG 100–125 mg/dL. Furthermore, PG% can expand the diagnostic power of OGTT in the is‐IFG range by distinguishing metabolic phenotypes very likely to herald different clinical risks.

Strong association between insulin-mediated glucose uptake and the 2-hour, not the fasting plasma glucose concentration, in the normal glucose tolerance range

AIM

The aim of this study was to examine the relationship between whole-body insulin-mediated glucose disposal and the fasting plasma glucose concentration in nondiabetic individuals.

RESEARCH DESIGN AND METHODS

Two hundred fifty-three nondiabetic subjects with normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance, and combined glucose intolerance received a 75-g oral glucose tolerance test and euglycemic hyperinsulinemic clamp. Total glucose disposal (TGD) during the insulin clamp was compared in IFG and NGT individuals and was related to fasting and 2-hour plasma glucose concentrations in each group.

RESULTS

TGD varied considerably between NGT and IFG individuals and displayed a strong inverse relationship with the 2-hour plasma glucose (PG; r = 0.40, P < .0001) but not with the fasting PG. When IFG and NGT individuals were stratified based on their 2-hour PG concentration, the increase in 2-hour PG was associated with a progressive decrease in TGD in both groups, and the TGD was comparable among NGT and IFG individuals.

CONCLUSION

The present results indicate the following: 1) as in NGT, insulin-stimulated TGD varies considerably in IFG individuals; 2) the large variability in TGD in IFG and NGT individuals is related to the 2-hour PG concentration; and 3) after adjustment for the 2-hour proglucagon concentration, IFG subjects have comparable TGD with NGT individuals.

Depressive symptoms linked to 1-h plasma glucose concentrations during the oral glucose tolerance test in men and women with the metabolic syndrome

AIMS

The addition of the 1-h plasma glucose concentration measure from an oral glucose tolerance test to prediction models of future Type 2 diabetes has shown to significantly strengthen their predictive power. The present study examined the relationship between severity of depressive symptoms and hyperglycaemia, focusing on the 1-h glucose concentration vs. fasting and 2-h glucose measures from the oral glucose tolerance test.

METHODS

Participants included 140 adults with the metabolic syndrome and without diabetes who completed a baseline psychobiological assessment and a 2-h oral glucose tolerance test, with measurements taken every 30 min. Depressive symptoms were assessed using the Beck Depression Inventory.

RESULTS

Multivariate linear regression revealed that higher levels of depressive symptoms were associated with higher levels of 1-h plasma glucose concentrations after adjusting for age, gender, ethnicity, BMI, antidepressant use and high-sensitivity C-reactive protein. Results were maintained after controlling for fasting glucose as well as for indices of insulin resistance and secretion. Neither fasting nor 2-h plasma glucose concentrations were significantly associated with depressive symptoms.

CONCLUSIONS

Elevated depressive symptoms in persons with the metabolic syndrome were associated with greater glycaemic excursion 1-h following a glucose load that was not accounted for by differences in insulin secretory function or insulin sensitivity. Consistent with previous findings, this study highlights the value of the 1-h plasma glucose measurement from the oral glucose tolerance test in the relation between depressive symptoms and glucose metabolism as an indicator of metabolic abnormalities not visible when focusing on fasting and 2-h post-oral glucose tolerance test measurements alone.

The 5-time point oral glucose tolerance test as a predictor of new-onset diabetes after kidney transplantation

AIMS

To evaluate the predictive power of the 5-time point oral glucose tolerance test (OGTT) for new-onset diabetes after kidney transplantation (NODAT).

METHODS

We performed a retrospective study of 145 patients without diabetes who received kidney transplantations at our hospital. The 5-time point OGTT was performed before transplantation. The area under a receiver-operating characteristic curve (aROC) was used for evaluating the predictive power of 5-time point OGTT values.

RESULTS

Seventeen patients developed NODAT within 1 year after transplantation. All postload plasma glucose (PPG) levels were higher in patients who developed NODAT than in those who did not; fasting plasma glucose levels were not different. The aROC for the area under the glucose concentration-time curve was significantly greater than that for fasting plasma glucose. Univariate and multivariate analyses showed that each PPG level was an independent risk factor for NODAT. Furthermore, patients with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT) could be stratified with a 1-h plasma glucose (1h-PG) cut-off point of 8.4 mmol/L. The incidences of NODAT were 23.5%, 16.7%, 9.1%, and 0% for patients with IGT+1h-PG ≥8.4 mmol/L,IGT+1h-PG <8.4 mmol/L, NGT+1h-PG ≥ 8.4 mmol/L, and NGT+1h-PG<8.4 mmol/L, respectively.

CONCLUSIONS

The area under the glucose concentration-time curve and each PPG concentration during the 5-time point OGTT are strong predictors of NODAT. A 1h-PG cut-off point of 8.4 mmol/L plus NGT/IGT can be used to identify patients at intermediate and high risk of developing NODAT.

Pretransplant HbA1c Is a Useful Predictor for the Development of New-Onset Diabetes in Renal Transplant Recipients Receiving No or Low-Dose Erythropoietin

Aims. To evaluate the predictive power of pretransplant HbA1c for new-onset diabetes after transplantation (NODAT) in kidney transplant candidates, who had several predispositions for fluctuated HbA1c levels. Methods. We performed a retrospective study of 119 patients without diabetes who received kidney transplantation between March 2000 and January 2012. Univariate and multivariate logistic regression analyses were used to investigate the association of several parameters with NODAT. Predictive discrimination of HbA1c was assessed using a receiver-operating characteristic curve. Results. Seventeen patients (14.3%) developed NODAT within 1 year of transplantation. Univariate logistic regression analysis revealed that recipient age, gender, and HbA1c were predictors of NODAT. In the multivariate analysis, the association between pretransplant HbA1c and NODAT development did not reach statistical significance (P = 0.07). To avoid the strong influence of high-dose erythropoietin on HbA1c levels, we performed subgroup analyses on 85 patients receiving no or low-dose (≤6000 IU/week) erythropoietin. HbA1c was again an independent predictor for NODAT. Receiver-operating characteristic analysis revealed a cut-off value of 5.2% with an optimal sensitivity of 64% and specificity of 78% for predicting NODAT. Conclusions. Our results reveal that the pretransplant HbA1c level is a useful predictor for NODAT in patients receiving no or low-dose erythropoietin.

Moving on from GWAS: functional studies on the G6PC2 gene implicated in the regulation of fasting blood glucose

Genome-wide association studies (GWAS) have shown that single-nucleotide polymorphisms (SNPs) in G6PC2 are the most important common determinants of variations in fasting blood glucose (FBG) levels. Molecular studies examining the functional impact of these SNPs on G6PC2 gene transcription and splicing suggest that they affect FBG by directly modulating G6PC2 expression. This conclusion is supported by studies on G6pc2 knockout (KO) mice showing that G6pc2 represents a negative regulator of basal glucose-stimulated insulin secretion that acts by hydrolyzing glucose-6-phosphate, thereby reducing glycolytic flux and opposing the action of glucokinase. Suppression of G6PC2 activity might, therefore, represent a novel therapy for lowering FBG and the risk of cardiovascular-associated mortality. GWAS and G6pc2 KO mouse studies also suggest that G6PC2 affects other aspects of beta cell function. The evolutionary benefit conferred by G6PC2 remains unclear, but it is unlikely to be related to its ability to modulate FBG.

The association of genetic markers for type 2 diabetes with prediabetic status - cross-sectional data of a diabetes prevention trial

OBJECTIVE

To investigate the association of risk alleles for type 2 diabetes with prediabetes accounting for age, anthropometry, inflammatory markers and lifestyle habits.

DESIGN

Cross-sectional study of 129 men and 157 women of medium-sized companies in northern Germany in the Delay of Impaired Glucose Tolerance by a Healthy Lifestyle Trial (DELIGHT).

METHODS

Besides established risk factors, 41 single nucleotide polymorphisms (SNPs) that have previously been found to be associated with type 2 diabetes were analyzed. As a nonparametric test a random forest approach was used that allows processing of a large number of predictors. Variables with the highest impact were entered into a multivariate logistic regression model to estimate their association with prediabetes.

RESULTS

Individuals with prediabetes were characterized by a slightly, but significantly higher number of type 2 diabetes risk alleles (42.5±4.1 vs. 41.3±4.1, p = 0.013). After adjustment for age and waist circumference 6 SNPs with the highest impact in the random forest analysis were associated with risk for prediabetes in a logistic regression model. At least 5 of these SNPs were positively related to prediabetic status (odds ratio for prediabetes 1.57 per allele (Cl 1.21-2.10, p = 0.001)).

CONCLUSIONS

This explorative analysis of data of DELIGHT demonstrates that at least 6 out of 41 genetic variants characteristic of individuals with type 2 diabetes may also be associated with prediabetes. Accumulation of these risk alleles may markedly increase the risk for prediabetes. However, prospective studies are required to corroborate these findings and to demonstrate the predictive value of these genetic variants for the risk to develop prediabetes.

Pathophysiology of prediabetes and treatment implications for the prevention of type 2 diabetes mellitus

Type 2 diabetes and other non-communicable diseases (NCD) are a growing public health challenge globally. An estimated 285 million people, corresponding to 6.4 % of the world's adult population has diabetes. This is expected to reach 552 million by 2030, 7.8 % of the adult population, with the African region expected to experience the greatest increase. A much larger segment of the world's population, approximating 79 million individuals in the US alone, has prediabetes. Multiple factors including genetic predisposition, insulin resistance, increased insulin secretory demand, glucotoxicity, lipotoxicity, impaired incretin release/action, amylin accumulation, and decreased β-cell mass play a causative role in the progressive β-cell dysfunction characteristic of prediabetes. Interventions preventing progression to type 2 diabetes should therefore delay or prevent β-cell failure. This article will first review the principal pathophysiological mechanisms underlying prediabetes and subsequently address treatment considerations based on these in the prevention of type 2 diabetes. In view of long-standing safety data with demonstrated efficacy and cost-effectiveness in the prevention of type 2 diabetes in high-risk individuals, metformin should be considered as initial therapy for those unable to comply with or lifestyle modification or where the latter has been ineffective in decreasing progression to type 2 diabetes.

New susceptibility loci in MYL2, C12orf51 and OAS1 associated with 1-h plasma glucose as predisposing risk factors for type 2 diabetes in the Korean population

Most recently, 1-h hyperglycemia has been recognized as an additional risk factor for type 2 diabetes. To date, previous genome-wide association studies for glycemic traits have a limited impact on the fasting state and 2-h plasma glucose level in an oral glucose challenge. To identify genetic susceptibility in different stages of glucose tolerance, we performed a meta-analysis for glycemic traits including 1-h plasma glucose (1-hPG) from 14 232 non-diabetic individuals in the Korean population. Newly implicated variants (MYL2, C12orf51 and OAS1) were found to be significantly associated with 1-hPG. We also demonstrated associations with gestational diabetes mellitus. Our results could provide additional insight into the genetic variation in the clinical range of glycemia.

Osteocalcin and the Regulation of Glucose Metabolism

Uncarboxylated osteocalcin enhances insulin and adiponectin release and improves glucose tolerance in mice. Data in humans do not unequivocally support a role for osteocalcin in glucose homeostasis. Changes in the amount of uncarboxylated osteocalcin induced by vitamin K or warfarin treatment are not associated with changes in glucose and insulin concentrations. Interventional studies in humans, designed to detect small changes in insulin secretion and action attributable to changes in uncarboxylated osteocalcin, will be required to reliably detect effects of osteocalcin on glucose metabolism and to better understand its interaction with adiposity and adipokines.

1-Hour plasma glucose in obese youth

Adults with normal glucose tolerance (NGT) but exaggerated plasma glucose excursion at 1 h (1HPG) following the oral glucose tolerance test (OGTT) have significantly higher risk of developing impaired glucose tolerance (IGT) or diabetes. Aim of the study will be to characterize the metabolic phenotype of NGT obese youth according to values of 1HPG. To accomplish this aim, obese patients (N = 1,454; 761 men; 79 IGT; BMI z-score 2.56 ± 0.16 SDS; age 11 ± 0.7 years) from two data sets were analyzed. In all patients, empirical parameters of insulin metabolism were calculated in fasting condition and following an OGTT (1.75 mg of glucose per kilogram/body weight). Receiver-operating characteristic (ROC) analysis was performed in the first group (training set, N = 920) to establish the cutoff value of 1HPG best identifying IGT. The second set (validation set, N = 534) served to verify the goodness of the model and the identified cutoff values. 1HPG ≥ 132.5 mg/dl identified IGT with 80.8% sensitivity and 74.3% specificity in the training set (AUC 0.855, 95% CI 0.808-0.902, p < 0.0001), and 70.3% sensitivity and 80% specificity in the validation set (AUC 0.81, 95% CI 0.713-0.907, p < 0.0001), respectively. NGT patients with 1HPG ≥ 132.5 mg/dl had a metabolic phenotype (triglycerides, insulin action, and secretion) that was in between those of NGT patients with 1HPG below the threshold and IGT patients (p < 0.0001 for all the comparisons). 1HPG ≥ 132.5 mg/dl seems to be associated with increased metabolic risk in obese youth, identifying patients with lower insulin sensitivity, early secretion, and higher total insulin secretion than in obese mates with lower 1HPG.

A concerted decline in insulin secretion and action occurs across the spectrum of fasting and postchallenge glucose concentrations

AIMS/HYPOTHESIS

Individuals with impaired fasting glucose (IFG) are at increased risk of developing diabetes over the subsequent decade. However, there is uncertainty as to the mechanisms contributing to the development of diabetes. We sought to quantitate insulin secretion and action across the prediabetic range of fasting glucose.

METHODS

We studied a cohort of 173 individuals with a fasting glucose concentration <7·0 mM after an overnight fast using a 75-g oral glucose tolerance test (OGTT). Insulin action (S(i)) was estimated using the oral glucose minimal model, and β-cell responsivity indices (φ) were estimated using the oral C-peptide minimal model. The disposition index (DI) for each individual was calculated. The relationship of DI, φ and S(i) with fasting and postchallenge glucose, as well as other covariates, was explored using a generalized linear regression model.

RESULTS

In this cross-sectional study, S(i) and DI were inversely related to fasting glucose concentrations. On the other hand, φ was unrelated to fasting glucose concentrations. S(i), φ and DI were all inversely related to area above basal glucose concentrations after glucose challenge. Multiple parameters including body composition and gender contributed to the variability of S(i) and DI at a given fasting or postchallenge glucose concentration.

CONCLUSIONS/INTERPRETATION

Defects in insulin secretion and action interact with body composition and gender to influence postchallenge glucose concentrations. There is considerable heterogeneity of insulin secretion and action for a given fasting glucose likely because of patient subsets with isolated IFG and normal glucose tolerance.

Beyond the morphology of the glucose curve following an oral glucose tolerance test in obese youth

BACKGROUND

To describe the morphology of glucose curve during the oral glucose tolerance test (OGTT) and any association with glucose tolerance, insulin action and secretion in obese youth.

STUDY DESIGN

Cross-sectional.

METHODS

OGTT data of 553 patients were analysed. Subjects were divided in groups based on the morphology (i.e. monophasic, biphasic, triphasic and upward monotonous) of glucose curve. Insulin action was estimated by the homeostasis model assessment of insulin resistance, the insulin sensitivity, the muscle insulin sensitivity and the hepatic insulin resistance indexes (HIRI), and the oral glucose insulin sensitivity (OGIS). Insulin secretion was estimated by the insulinogenic index (IGI). Disposition index, including the insulin secretion-sensitivity index-2, and areas under glucose (AUC(G)) and insulin (AUC(I)) curves were computed.

RESULTS

In patients with normal glucose tolerance (n=522), prevalent morphology of the glucose curve was monophasic (n=285, 54%). Monophasic morphology was associated with the highest concentration of 1 h plasma glucose (P<0.0001) and AUC(G) (P<0.0001); biphasic morphology with better insulin sensitivity as estimated by OGIS (P<0.03) and lower AUC(I) (P<0.0001); triphasic morphology with the highest values of HIRI (P<0.02) and IGI (P<0.007). By combining morphologies of glucose and insulin curves or time of the glucose peak, a deeper characterisation of different phenotypes of glucose metabolism emerged.

CONCLUSIONS

Morphologies of the glucose curve seem reflecting different metabolic phenotypes of insulin action and secretion, particularly when combined with morphologies of insulin curve or time of glucose peak. Such findings may deserve validation in cohort study, in which glucose metabolism would be estimated by using gold standard techniques.

The Relationship Between 1 Hour Glycemia, During Oral Glucose Tolerance Test and Cardiometabolic Risk

Background Diabetes mellitus is a very common disease, worldwide there are currently over 366 million diabetics. It seems that people with normal glucose tolerance and blood glucose at 1 hour during OGTT ≥200mg% represent an intermediate phenotype of abnormal glucose metabolism, another disturbance of carbohydrate metabolism that is associated with increased cardiometabolic risk. Objectives Starting from these premises, we decided to analyze the subjects with glucose at 1 hour during OGTT ≥200mg%, but with normal values for fasting glucose and 2 hours glucose. In this subgroup of subjects some parameters of CMR were analyzed. We also performed a comparison of this subgroup of subjects with both normal glucose tolerance and 1-hour glucose <200mg%, and with those with abnormal glucose tolerance. Results According to currently used recommendations to diagnose diabetes mellitus, from the 778 people included in this study, 167 (21.5%) had disturbances of carbohydrate metabolism, being classified as patoglycemic and 611 persons (78.5%) had normal values of fasting glucose and 2 hours glucose during OGTT, being considered normoglycemic. From the 611 people who were classified as normal glucose tolerance, based on the currently used criteria for diagnosis of diabetes mellitus, a total of 44 persons (7.2%) had, however, the value of 1-hour glucose during OGTT ≥200mg%, which represents 5.6% of the entire group studied. Conclusions Patients with normal glucose tolerance and glucose ≥200mg% at 1 hour during OGTT represent a new subgroup of impaired glucose tolerance, which requires strict lifestyle advice and possibly pharmacological measures to prevent or delay progression to abnormal glucose tolerance.

Effect of meal timing and glycaemic index on glucose control and insulin secretion in healthy volunteers

Shiftworkers have a higher risk of CHD and type 2 diabetes. They consume a large proportion of their daily energy and carbohydrate intake in the late evening or night-time, a factor which could be linked to their increase in disease risk. We compared the metabolic effects of varying both dietary glycaemic index (GI) and the time at which most daily energy intake was consumed. We hypothesised that glucose control would be optimal with a low-GI diet, consumed predominantly early in the day. A total of six healthy lean volunteers consumed isoenergetic meals on four occasions, comprising either high- or low-GI foods, with 60 % energy consumed predominantly early (breakfast) or late (supper). Interstitial glucose was measured continuously for 20 h. Insulin, TAG and non-esterified fatty acids were measured for 2 h following every meal. Highest glucose values were observed when large 5021 kJ (1200 kcal) high-GI suppers were consumed. Glucose levels were also significantly higher in predominantly late high- v. low-GI meals (P < 0·01). Using an estimate of postprandial insulin sensitivity throughout the day, we demonstrate that this follows the same trend, with insulin sensitivity being significantly worse in high energy consumed in the evening meal pattern. Both meal timing and GI affected glucose tolerance and insulin secretion. Avoidance of large, high-GI meals in the evening may be particularly beneficial in improving postprandial glucose profiles and may play a role in reducing the risk of type 2 diabetes; however, longer-term studies are needed to confirm this.

Evaluation of nonfasting tests to screen for childhood and adolescent dysglycemia

OBJECTIVE

To assess performance of nonfasting tests to screen children for dysglycemia (prediabetes or diabetes).

RESEARCH DESIGN AND METHODS

This was a cross-sectional study of 254 overweight or obese (BMI ≥85th percentile) children aged 10-17 years. Subjects came for two visits to a clinical research unit. For visit one, they arrived fasting and a 2-h glucose tolerance test and HbA(1c) and fructosamine testing were performed. For visit two, they arrived nonfasting and had a random plasma glucose, a 1-h 50-g nonfasting glucose challenge test (1-h GCT), and urine dipstick performed. The primary end point was dysglycemia (fasting plasma glucose ≥100 mg/dL or a 2-h postglucose ≥140 mg/dL). Test performance was assessed using receiver operating characteristic (ROC) curves and calculations of area under the ROC curve.

RESULTS

Approximately one-half of children were female, 59% were white, and 30% were black. There were 99 (39%) cases of prediabetes and 3 (1.2%) cases of diabetes. Urine dipstick, HbA(1c) (area under the curve [AUC] 0.54 [95% CI 0.47-0.61]), and fructosamine (AUC 0.55 [0.47-0.63]) displayed poor discrimination for identifying children with dysglycemia. Both random glucose (AUC 0.66 [0.60-0.73]) and 1-h GCT (AUC 0.68 [0.61-0.74]) had better levels of test discrimination than HbA(1c) or fructosamine.

CONCLUSIONS

HbA(1c) had poor discrimination, which could lead to missed cases of dysglycemia in children. Random glucose or 1-h GCT may potentially be incorporated into clinical practice as initial screening tests for prediabetes or diabetes and for determining which children should undergo further definitive testing.

Relative utility of 1-h Oral Glucose Tolerance Test as a measure of abnormal glucose homeostasis

BACKGROUND AND AIMS

Impaired glucose tolerance based on 2-h glucose levels is more predictive of future cardiovascular disease and more sensitive in detecting earlier diabetes compared to impaired fasting glucose. However, the 1-h OGTT may be even more sensitive than the 2-h. We assessed the relative value of 1-h OGTT by exploring its relationship with adiposity and other measures of glucose homeostasis.

METHODS AND RESULTS

Ninety four overweight/obese individuals free of diabetes and major cardiovascular conditions were included in the analyses. We adjusted for age, gender, smoking status and physical activity. One-h OGTT showed similar partial correlations with fasting glucose and 2-h OGTT (r=0.60 and 0.64 respectively). Fasting glucose, fasting insulin and HOMA correlated better with 1-h OGTT (r=0.60, 0.47 and 0.52) than with 2-h OGTT (r=0.50, 0.41, and 0.45). BMI and waist circumference also showed stronger correlation with 1-h (r=0.31, 0.29), compared to 2-h OGTT (r=0.16, 0.16) or fasting glucose (r=0.23, 0.22). Metabolic syndrome was associated similarly with 1-h and 2-h OGTT.

CONCLUSIONS

The 1-h OGTT correlates well with both fasting glucose and 2-h OGTT and shows similar or higher associations with obesity measures. The 1-h OGTT has potential utility in epidemiologic studies.

Definition of prediabetes

Diabetes evolves through prediabetes, defined as impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). Subjects with IFG/IGT have an increased risk of developing diabetes and a higher prevalence of cardiovascular disease than normoglycemic individuals. However, there is considerable evidence that glucose levels lower than those meeting the current definition of prediabetes may also be associated with similar concerns, particularly in high-risk individuals in accordance with a continuous glycemic risk perspective. Therefore, an absolute definition of prediabetes may underestimate the implications and vastness of this disorder. Research should focus on these aspects to minimize the risk of developing a preventable condition.

The oral glucose tolerance test (OGTT) revisited

The oral glucose tolerance test (OGTT) has been the mainstay for diagnosing diabetes for decades. Recently, the American Diabetes Association (ADA) suggested abandoning the OGTT, while resorting to a simpler screening test, exclusively based on baseline fasting blood glucose concentration. This review article rewinds the history of OGTT and its recent advancements, and compares its power in detecting early diabetes with that of fasting blood glucose alone. The key point is that there are more diabetics originating from a population with normal fasting blood glucose than from subjects with impaired fasting glucose, those who can be detected by the new ADA recommendations. Conversely, the OGTT detects more efficiently early diabetes as well as subjects with IGT, as the glycemia at the second hour seems crucial as a diagnostic tool. We discuss the different significance of fasting versus second hour glycemia during OGTT, according to different mechanisms of glucose homeostasis. Finally, we provide recent evidence on very simple additional information that can be obtained from the OGTT, which renders this test even more useful, discussing pathophysiologic significance.

Insufficient sensitivity of hemoglobin A(₁C) determination in diagnosis or screening of early diabetic states

An International Expert Committee made recommendations for using the hemoglobin A(₁C) (A1C) assay as the preferred method for the diagnosis of diabetes in nonpregnant individuals. A concentration of at least 6.5% was considered as diagnostic. It is the aim of this study to compare the sensitivity of A1C with that of plasma glucose concentrations in subjects with early diabetes or impaired glucose tolerance (IGT). We chose 2 groups of subjects who had A1C not exceeding 6.4%. The first group of 89 subjects had family histories of diabetes (MODY or type 2 diabetes mellitus) and had oral glucose tolerance test (OGTT) and A1C determinations. They included 36 subjects with diabetes or IGT and 53 with normal OGTT. The second group of 58 subjects was screened for diabetes in our Diabetes Clinic by fasting plasma glucose, 2-hour plasma glucose, or OGTT and A1C; and similar comparisons were made. Subjects with diabetes or IGT, including those with fasting hyperglycemia, had A1C ranging from 5.0% to 6.4% (mean, 5.8%). The subjects with normal OGTT had A1C of 4.2% to 6.3% (mean, 5.4%), or 5.5% for the 2 groups. The A1C may be in the normal range in subjects with diabetes or IGT, including those with fasting hyperglycemia. Approximately one third of subjects with early diabetes and IGT have A1C less than 5.7%, the cut point that the American Diabetes Association recommends as indicating the onset of risk of developing diabetes in the future. The results of our study are similar to those obtained by a large Dutch epidemiologic study. If our aim is to recognize early diabetic states to apply effective prophylactic procedures to prevent or delay progression to more severe diabetes, A1C is not sufficiently sensitive or reliable for diagnosis of diabetes or IGT. A combination of A1C and plasma glucose determinations, where necessary, is recommended for diagnosis or screening of diabetes or IGT.

One-hour plasma glucose identifies insulin resistance and beta-cell dysfunction in individuals with normal glucose tolerance: cross-sectional data from the Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study

OBJECTIVE

Some individuals with normal glucose tolerance (NGT) exhibit a 1-h excursion of plasma glucose during oral glucose tolerance testing as high as that of individuals with impaired glucose tolerance (IGT). The aim of this study was to characterize their metabolic phenotype.

RESEARCH DESIGN AND METHODS

A total of 1,205 healthy volunteers (aged 29-61 years) underwent assessment of 1) oral glucose tolerance and 2) insulin sensitivity (standardized euglycemic-hyperinsulinemic clamp), as part of the Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study.

RESULTS

One-hour plasma glucose correlated better than 2-h plasma glucose with total insulin secretion (r = 0.43), beta-cell glucose sensitivity (r = -0.46), and beta-cell rate sensitivity (r = -0.18). Receiver operating characteristic analysis identified 8.95 mmol/l as the best cutoff value for prediction of IGT from 1-h plasma glucose (sensitivity 77% and specificity 80%). Participants with NGT with 1-h plasma glucose >8.95 mmol/l had larger waist circumference, higher BMI, lower insulin sensitivity, higher fasting glucose, and higher insulin secretion than their counterparts with 1-h plasma glucose <or=8.95 mmol/l (P < 0.001 for all comparisons). Moreover, they exhibited lower beta-cell glucose sensitivity (P < 0.001), beta-cell rate sensitivity (P < 0.001), and potentiation factor (P = 0.026). When compared with conventionally defined IGT, they were not different in waist circumference and BMI, hepatic insulin extraction, beta-cell glucose sensitivity, beta-cell rate sensitivity, and potentiation factor but did have greater insulin sensitivity along with reduced basal (P = 0.001) and total insulin secretion (P = 0.002).

CONCLUSIONS

Higher values of 1-h plasma glucose may identify an intermediate condition between NGT and IGT characterized by greater insulin resistance, reduced beta-cell glucose sensitivity, and reduced beta-cell rate sensitivity.