Intra-individual variation of glucose, specific insulin and proinsulin concentrations measured by two oral glucose tolerance tests in a general Caucasian population: the Hoorn Study

Natural history of insulin sensitivity and insulin secretion in the progression from normal glucose tolerance to impaired fasting glycemia and impaired glucose tolerance: the Inter99 study

OBJECTIVE

The aim of this study was to describe the natural history of insulin secretion and insulin sensitivity in the development of isolated impaired fasting glycemia (i-IFG), isolated impaired glucose tolerance (i-IGT), and combined IFG/IGT.

RESEARCH DESIGN AND METHODS

Baseline and 5-year follow-up data from the Inter99 study were used. Individuals with normal glucose tolerance (NGT) at baseline and i-IFG, i-IGT, combined IFG/IGT, or NGT at the 5-year follow-up were examined with an oral glucose tolerance test (n = 3,145). Insulin sensitivity index (ISI), homeostasis model assessment of insulin sensitivity (HOMA-IS), early-phase insulin release (EPIR), and insulin secretion relative to insulin action (disposition index) were estimated.

RESULTS

Five years before the pre-diabetes diagnoses (i-IFG, i-IGT, and IFG/IGT), ISI, HOMA-IS, EPIR, and disposition index were lower than in individuals who maintained NGT. During the 5-year follow-up, individuals developing i-IFG experienced a significant decline only in HOMA-IS, whereas individuals developing i-IGT experienced significant declines in ISI, EPIR, and disposition index. Individuals with IFG/IGT exhibited pronounced declines in ISI, HOMA-IS, EPIR, and disposition index during the 5-year follow-up.

CONCLUSIONS

A stationary reduced insulin secretion followed by a decline in primarily hepatic insulin sensitivity characterizes the transition from NGT to i-IFG. In contrast, low whole-body insulin sensitivity with a secondary lack of beta-cell compensation is associated with the development of i-IGT. Thereby, i-IFG and i-IGT appear to result from different underlying mechanisms, which may have implications for the prevention and treatment of the diabetes that succeeds them.

Lifetime risk and projected population prevalence of diabetes

AIMS/HYPOTHESIS

With incidence rates for diabetes increasing rapidly worldwide, estimates of the magnitude of the impact on population health are required. We aimed to estimate the lifetime risk of diabetes, the number of years lived free of, and the number of years lived with diabetes for the Australian adult population from the year 2000, and to project prevalence of diabetes to the year 2025.

METHODS

Multi-state life-tables were constructed to simulate the progress of a cohort of 25-year-old Australians. National mortality rates were combined with incidence rates of diabetes and the RR of mortality in people with diabetes derived from the Australian Diabetes, Obesity and Lifestyle study (a national, population-based study of 11,247 adults aged >or=25 years).

RESULTS

If the rates of mortality and diabetes incidence observed over the period 2000-2005 continue, 38.0% (95% uncertainty interval 36.6-38.9) of 25-year-olds would be expected to develop diabetes at some time throughout their life. On average, a 25-year-old Australian will live a further 56 years, 48 of these free of diabetes. On average, a 45-year-old person with diabetes can expect to live 6 years less than a person free of diabetes. The prevalence of diabetes is projected to rise from 7.6% in 2000 to 11.4% by 2025.

CONCLUSIONS/INTERPRETATION

If we maintain current diabetes incidence rates, more than a third of individuals will develop diabetes within their lifetime and in Australia there will an additional 1 million cases of diabetes by the year 2025.

Reproducibility of the oral glucose tolerance test in overweight children

OBJECTIVE

We examined the reproducibility of the oral glucose tolerance test (OGTT) in overweight children and evaluated distinguishing characteristics between those with concordant vs. discordant results.

DESIGN

Sixty overweight youth (8-17 yr old) completed two OGTTs (interval between tests 1-25 d). Insulin sensitivity was assessed by the surrogate measures of fasting glucose to insulin ratio, whole-body insulin sensitivity index, and homeostasis model assessment of insulin resistance, and insulin secretion by the insulinogenic index with calculation of the glucose disposition index (GDI).

RESULTS

Of the 10 subjects with impaired glucose tolerance (IGT) during the first OGTT only three (30%) had IGT during the second OGTT. The percent positive agreement between the first and second OGTT was low for both impaired fasting glucose and IGT (22.2 and 27.3%, respectively). Fasting blood glucose had higher reproducibility, compared with the 2-h glucose. Youth with discordant OGTTs, compared with those with concordant results, were more insulin resistant (glucose/insulin 2.7+/-1.4 vs. 4.1+/-1.8, P=0.006, whole-body insulin sensitivity index of 1.3+/-0.6 vs. 2.2+/-1.1, P=0.003, and homeostasis model assessment of insulin resistance 10.6+/-8.1 vs. 5.7+/-2.8, P=0.001), had a lower GDI (0.45+/-0.58 vs. 1.02+/-1.0, P=0.03), and had higher low-density lipoprotein cholesterol (117.7+/-36.6 vs. 89.9+/-20.1, P=0.0005) without differences in physical characteristics.

CONCLUSIONS

Our results show poor reproducibility of the OGTT in obese youth, in particular for the 2-h plasma glucose. Obese youth who have discordant OGTT results are more insulin resistant with higher risk of developing type 2 diabetes mellitus, as evidenced by a lower GDI. The implications of this remain to be determined in clinical and research settings.

Prevalence of the metabolic syndrome among a racially/ethnically diverse group of U.S. eighth-grade adolescents and associations with fasting insulin and homeostasis model assessment of insulin resistance levels

OBJECTIVE

The purpose of this study was to report the prevalence of the International Diabetes Federation (IDF)-defined metabolic syndrome and its components among a cross-sectional sample of racially/ethnically diverse eighth grade youths and examine the association between the presence of the syndrome and participant fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) levels.

RESEARCH DESIGN AND METHODS

Data were from a cross-sectional study with 1,453 racially/ethnically diverse eighth grade students from 12 middle schools in three U.S. states (Texas, North Carolina, and California). Height, weight, waist circumference, and blood pressure were recorded. Fasting blood samples were analyzed for triglycerides, HDL cholesterol, glucose, and insulin; HOMA-IR was calculated. Sex, race/ethnicity, and pubertal stage were self-reported. IDF criteria were used to determine the prevalence of the metabolic syndrome. The odds ratio for being classified with the syndrome was calculated by quintiles of fasting insulin and HOMA-IR.

RESULTS

Of the sample, 138 students (9.5%) were classified with metabolic syndrome. Hispanics were more likely to have high abdominal adiposity and high triglycerides. Male adolescents were more likely to have high triglycerides, low HDL cholesterol, high blood pressure, and high fasting glucose. Participants in the highest insulin quintile were almost 200 times more likely to be classified with the syndrome than participants in the lowest quintile with comparable associations for HOMA-IR quintiles.

CONCLUSIONS

In a racially/ethnically diverse sample of U.S. adolescents, 9.5% of participants were identified with the metabolic syndrome using the IDF criteria. The likelihood of metabolic syndrome classification significantly increased with higher insulin and HOMA-IR values.

Fasting plasma glucose cutoff for diagnosis of diabetes in a Japanese population

OBJECTIVE

We examined the relationship between fasting plasma glucose (FPG) and 2-h post-load glucose (PG) levels, and the optimal FPG cutoff level to correspond to a 2-h PG of 11.1 mmol/liter, the gold standard diagnostic criterion, in a general Japanese population.

DESIGN

Cross-sectional study populations of 2421 subjects in 1988 and 2698 subjects in 2002, aged 40-79 yr and without antidiabetic medication, were tested with an oral glucose tolerance test. The relationship between FPG and 2-h PG was investigated by various regression models and a receiver operating characteristic curve.

RESULTS

The best-fit model for the relationship between FPG and 2-h PG was a quadratic regression model. The FPG cutoff levels corresponding to the 2-h PG of 11.1 mmol/liter by this model were 6.2 mmol/liter in 1988 and 6.3 mmol/liter in 2002. In the combined populations, the FPG cutoff point was 6.3 mmol/liter; the sensitivity and specificity of this cutoff point for detecting a 2-h PG of 11.1 mmol/liter were 75.2 and 88.6%, respectively. The receiver operating characteristic curve analysis confirmed that the corresponding FPG point was 6.2 mmol/liter in both the 1988 and 2002 populations. In a stratified analysis, the FPG cutoff level increased with increasing body mass index levels; however, even in subjects with body mass index more than or equal to 30 kg/m2, the FPG cutoff level was lower than 7.0 mmol/liter.

CONCLUSIONS

Our findings suggest that the FPG cutoff level corresponding to the 2-h PG of 11.1 mmol/liter in the general Japanese population is lower than the current diagnostic criterion.

Another approach to estimating the reliability of glycaemic index

The usefulness of the glycaemic index (GI) of a food for practical advice for individuals with diabetes or the general population depends on its reliability, as estimated by intra-class coefficient (ICC), a measure having values between 0 and 1, with values closer to 1 indicating better reliability. We aimed to estimate the ICC of the postprandial blood glucose response to glucose and white bread, instant mashed potato and chickpeas using the incremental area under the curve (iAUC) and the GI of these foods. The iAUC values were determined in twenty healthy individuals on three and four occasions for white bread and glucose, respectively, and for potato and chickpeas on a single occasion. The ICC of the iAUC for white bread and glucose were 0·50 (95 % CI 0·27, 0·73) and 0·49 (95 % CI 0·22, 0·75), respectively. The mean GI of white bread was 81 (95 % CI 74, 90) with a reliability of 0·27 indicating substantial within-person variability. The GI of mashed potato and chickpeas were 87 (95 % CI 76, 101) and 28 (95 % CI 22, 37) respectively with ICC of 0·02 and 0·40.The ICC of the iAUC were moderate and those of the GI fair or poor, indicating the heterogeneous nature of individuals' responses. The unpredictability of individual responses even if they are the result of day-to-day variation places limitations on the clinical usefulness of GI. If the very different GI of potato and chickpeas are estimates of an individual's every-day response to different foods, then the GI of foods may provide an indication of the GI of a long-term diet.

Prevalence of diabetes mellitus in Croatia

The aim of this study was to obtain an accurate estimate of diabetes prevalence in Croatia and additional estimates of impaired fasting glucose (IFG), undiagnosed diabetes, and insulin resistance. The study was part of the First Croatian Health Project. Field work included a questionnaire, anthropological measurements, and blood sampling. A nationally representative sample of 1653 subjects aged 18-65 years was analyzed. A total of 100 participants with diabetes were detected, among them 42 with previously unknown diabetes. The prevalence was 6.1% (95% CI: 4.59-7.64), with a significant difference by age. IFG prevalence (WHO-criteria) was 11.3%. The ratio of undiagnosed/diagnosed diabetes was 72/100, unevenly distributed by the regions. HOMA-IR was >1 in 40.4% of the subjects. This survey revealed a higher prevalence of diabetes than previously estimated, whereas that of IFG was as expected. A significant difference in the proportion of undiagnosed diabetes among the regions warrants attention.

Absence of an acute insulin response predicts onset of type 2 diabetes in a Caucasian population with impaired glucose tolerance

CONTEXT

In persons with impaired glucose tolerance (IGT), both impaired insulin secretion and insulin resistance contribute to the conversion to type 2 diabetes mellitus (T2DM). However, few studies have used criterion standard measures to asses the predictive value of impaired insulin secretion and insulin resistance for the conversion to T2DM in a Caucasian IGT population.

OBJECTIVES

The objective of the study was to determine the predictive value of measures of insulin secretion and insulin resistance derived from a hyperglycemic clamp, including the disposition index, for the development of T2DM in a Caucasian IGT population.

DESIGN, SETTING, AND PARTICIPANTS

The population-based Hoorn IGT study consisted of 101 Dutch IGT subjects (aged < 75 yr), with mean 2-h plasma glucose values, of two separate oral glucose tolerance tests, between 8.6 and 11.1 mmol/liter. A hyperglycemic clamp at baseline was performed to assess first-phase and second-phase insulin secretion and insulin sensitivity. During follow-up, conversion to T2DM was assessed by means of 6-monthly fasting glucose levels and yearly oral glucose tolerance tests.

RESULTS

The cumulative incidence of T2DM was 34.7%. Hazard ratio for T2DM development adjusted for age, sex, and body mass index was 5.74 [95% confidence interval (CI) 2.60-12.67] for absence of first insulin peak, 1.58 (95% CI 0.60-4.17) for lowest vs. highest tertile of insulin sensitivity, and 1.78 (95% CI 0.65-4.88) for lowest vs. highest tertile of the disposition index.

CONCLUSIONS

In these Caucasian persons with IGT, the absence of the first insulin peak was the strongest predictor of T2DM.

Screening for undiagnosed diabetes in patients with acute myocardial infarction

BACKGROUND

Screening for undiagnosed diabetes in patients with acute myocardial infarction is recommended (ESC and EASD Task Force 2007). Glucose tolerance testing in the peri-infarct period may not be valid because of confounding, e.g. by the acute stress reaction. The aim was to evaluate undiagnosed diabetes (DM) and impaired glucose regulation (IGR) in AMI during hospital stay and 3 months after discharge.

MATERIALS AND METHODS

In 96 consecutively admitted AMI patients (Heart Center Wuppertal, Germany) OGTT were performed, of whom in 62 OGTT were also carried out 3 months later.

RESULTS

Before discharge 32% of the patients had newly diagnosed diabetes and 47% patients had prediabetes (IGR). Glucose tolerance was normal in 20 (21%) patients only. After 3 months, 74% with newly diagnosed DM at baseline still had disturbed glucose metabolism (58% DM, 16% IGT). No patient with normal OGTT became diabetic after 3 months. In multivariate regression, the odds of having diabetes (3 months) was about sixfold higher when having diabetes before discharge (OGTT). Admission glucose, infarction size CK(MAX), and inflammation (CRP) were not significantly related to OGTT results.

CONCLUSIONS

This prospective study confirms a high prevalence of undiagnosed DM in patients with AMI. In about 60% of AMI patients, newly diagnosed DM persisted after 3 months. For the first time we could show that there is no correlation between infarction size and undiagnosed diabetes. Thus, an OGTT performed before discharge may provide a reliable measure of disturbed glucose regulation but needs to be repeated.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Short-term reproducibility of impaired fasting glycaemia, impaired glucose tolerance and diabetes The ADDITION study, DK

We evaluated variations in glucose measurements and the reproducibility of glucose tolerance classification in a high-risk screening setting in general practice. Screening for diabetes was performed in persons aged 40-69 years. Based on capillary fasting (FBG) and 2-h blood glucose (2 hBG) individuals with impaired fasting glycaemia (IFG), impaired glucose tolerance (IGT) and diabetes had a second test done after 14 days. Intra-individual coefficients of variation (CV) were estimated in each glucose tolerance class using the approximation CV(2)(x)=var(ln(x)). Bland-Altman plots with limits of agreement were made. In the total population, the CV(intra) was 7.9% and 13.8% for FBG and 2 hBG, respectively. Limits of agreement ranged from -1.15 to 1.67 mmol/l for FBG and from - 2.62 to 3.27 mmol/l for 2 hBG. One individual with IFG and 22.5% with IGT had diabetes at the second test, 76.1% with diabetes had this diagnosis confirmed, and about 30% with IFG and IGT had normal glucose tolerance at the second test. The expected values of repeated capillary blood glucose measurements were about+/-1 and+/-3 mmol/l for FBG and 2 hBG, respectively. Yet, 70% of high-risk prediabetic individuals were persistently classified with abnormal glucose regulation; diabetes was confirmed in 76% of the cases.

Differences in low-grade chronic inflammation and insulin resistance in women with previous gestational diabetes mellitus and women with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) and gestational diabetes mellitus (GDM) are both characterized by an increase in insulin resistance. Our goal in the present study was to measure insulin resistance (as estimated by homeostasis model assessment, sex hormone-binding globulin (SHBG) and adiponectin concentrations) and parameters of low-grade inflammation in non-diabetic, non-hyperandrogenic ovulatory women with previous GDM (pGDM) and in non-diabetic women with classic PCOS, characterized by hyperandrogenism and oligo/anovulation.

PATIENTS AND DESIGN

We evaluated 20 women with PCOS, 18 women with pGDM and 19 controls, all matched according to body mass index (BMI). Fasting blood samples were drawn in all women 3-6 days after spontaneous or dydrogesterone-induced withdrawal bleeding. Body fat distribution was assessed using dual-energy X-ray absorptiometry in all women.

RESULTS

After adjusting for age and percent body fat, measures of insulin resistance such as SHBG and adiponectin concentrations were decreased and central obesity was increased in women with PCOS and pGDM compared with controls (all p < 0.05). Parameters of low-grade inflammation such as serum tumor necrosis factor-alpha and highly sensitive C-reactive protein concentrations, white blood cell and neutrophil count were increased only in women with PCOS compared with BMI-matched controls (all p < 0.05).

CONCLUSIONS

Certain markers of insulin resistance are increased in both women with PCOS and women with pGDM, while low-grade inflammation is increased only in PCOS. PCOS and GDM might represent specific phenotypes of one disease entity with an increased risk of cardiovascular disease, whereby women with PCOS demonstrate an augmented cardiovascular risk profile.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Reproducibility of impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) classification: a systematic review

BACKGROUND

The classifications of impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) represent glucose levels above normal, but below the decision threshold for diabetes. We sought to determine what the reproducibility of these classifications was when repeat tests were performed by conducting a systematic review of the literature.

METHODS

All primary studies published in English of any study design were included. Studies were excluded if they did not follow the World Health Organization or American Diabetes Association diagnostic criteria, used whole blood as the specimen type, a glucose meter for analysis, or performed repeat testing greater than 8 weeks apart.

RESULTS

Five papers had reproducibility data for IGT or IFG, two of which where from the same population but sampled differently. The kappa coefficients, indicating agreement between repeat tests that exceeded chance, indicated poor to fair agreement for IGT (0.04, 0.22, 0.38, 0.42) and moderate agreement for IFG (0.44 and 0.56). Similarly, the observed reproducibility was slightly lower for IGT (33%, 44%, 47%, 48%) compared to IFG (51%, 64%). In two studies for which data were available for both IGT and IFG, the average reproducibility was lower (49%) for the prediabetes group compared to the diabetes group (73%) or the normal group (93%).

CONCLUSIONS

Poor reproducibility of IGT and IFG classification suggests caution should be exercised when interpreting a single test result.

Impaired fasting glucose and the prevalence and severity of angiographic coronary artery disease in high-risk Chinese patients

We assessed the relation between different fasting plasma glucose (FPG) levels of 5.6 to 6.9 mmol/L and the prevalence and severity of angiographic coronary artery disease (CAD) in high-risk Chinese patients. Among 512 subjects who were to undergo coronary angiography for the confirmation of suspected myocardial ischemia, 409 subjects were enrolled and categorized into 3 groups based on FPG levels: (1) </=5.5 mmol/L, (2) 5.6 to 6.0 mmol/L, and (3) 6.1 to 6.9 mmol/L. Each of these groups was further divided into subgroups by sex; the second and third groups were combined as an additional group according to the 2003 definition of impaired fasting glucose (FPG at 5.6-6.9 mmol/L). We analyzed the coronary artery stenosis score, the prevalence of angiographic CAD, and the percentage of stenosis in the 3 main arteries among the groups and examined the risk factors for angiographic CAD prevalence by logistic regression analysis. A higher correlation was observed between angiographic CAD prevalence and FPG levels of 6.1 to 6.9 mmol/L as compared with FPG levels </=5.5 mmol/L (adjusted odds ratio [OR], 2.67; 95% confidence interval [CI], 1.72-4.10; P = .011). The FPG levels of 5.6 to 6.9 mmol/L (adjusted OR, 2.57; 95% CI, 1.65-4.02; P < .001) and 5.6 to 6.0 mmol/L (adjusted OR, 2.33; 95% CI, 1.58-3.49; P = .008) were modestly correlated with angiographic CAD prevalence. The angiographic CAD prevalence, coronary artery stenosis score, and the percentage of stenosis in the left anterior descending branch increased corresponding to increasing FPG levels from </=5.5 mmol/L to 5.6 to 6.0 mmol/L to 6.1 to 6.9 mmol/L. We concluded that FPG levels of 5.6 to 6.9 mmol/L as well as of 6.1 to 6.9 mmol/L may be an independent risk factor for angiographic CAD; furthermore, there was a progressive and graded relation between FPG levels of 5.6 to 6.9 mmol/L and angiographic CAD prevalence and severity in high-risk Chinese patients.

Within-subject variability of measures of beta cell function derived from a 2 h OGTT: implications for research studies

AIMS/HYPOTHESIS

Knowledge of the within-subject variability of a parameter is required to properly design and calculate sample sizes for longitudinal studies. We sought to determine the day-to-day variability of measures of beta cell function derived from an OGTT.

METHODS

Thirty-seven adults (13 with normal glucose tolerance, ten with impaired glucose tolerance, 14 with type 2 diabetes) underwent a standard 2 h 75 g OGTT on two separate days (median time between tests, 7 days; range, 5-14). From these data, the reproducibility of several indices of beta cell function were determined: insulinogenic index (DeltaI(0-30)/DeltaG(0-30)), early C-peptide response (DeltaCP(0-30)/DeltaG(0-30)), incremental AUC insulin to glucose response (incAUC(ins)/incAUC(glu)), integrated insulin secretion response from 0 to 120 min (IS/Glu(0-120)) and indices of beta cell function derived from a mathematical model.

RESULTS

Within-subject variability for DeltaI(0-30)/DeltaG(0-30) (CV 57.1%) was higher than DeltaCP(0-30)/DeltaG(0-30) (CV 34.7%). Measures integrated over the full 120 min of the OGTT, incAUC(ins)/incAUC(glu) (CV 24.9%) and IS/Glu(0-120) (CV 17.4%), demonstrated less variability. The mathematical model-derived measures of beta cell glucose sensitivity (CV 20.3%) and potentiation (CV 33.0%) showed moderate variability. The impact of the different measures' variability on sample size (30% change from baseline) is demonstrated by calculated sample sizes of 89 for DeltaI(0-30)/DeltaG(0-30), 37 for DeltaCP(0-30)/DeltaG(0-30), 21 for incAUC(ins)/incAUC(glu) and 11 for IS/Glu(0-120).

CONCLUSIONS/INTERPRETATION

Some OGTT-derived indices of beta cell function, in particular the insulinogenic index, demonstrate high within-subject variability. Integrated measures that utilise multiple time points and measures that use C-peptide show less variability and may lead to a reduced sample size requirement.

Reproducibilidad de la prueba de sobrecarga oral de glucosa en pacientes con glucosa alterada en ayunas

BACKGROUND AND OBJECTIVES

Impaired fasting glucose (IFG) is defined by a fasting glucose between 5.6 and 6.9 mmol/l in subjects with no known diabetes. The present study objectives were: a) to analyze the glucose tolerance test (GTT) reproducibility and b) to assess this test's diagnostic classification agreement.

PATIENTS AND METHOD

Cross-sectional study in adult patients diagnosed with IFG. Study subjects underwent a 75 g GTT in two occasions.

RESULTS

Fifty-nine patients were studied. The interval between GTT tests was 37 +/- 26 days. Fasting and post-GTT plasma glucose intra-individual variation coefficients were 6.9 and 31.0%, respectively. Diagnostic agreement between the two tests (normal tolerance vs. abnormal tolerance) was measured using the kappa index: 0.62 (95% CI 0.42-0.82). Agreement ranged from 80% (95% CI, 70-90%) to 83% (95% CI, 73-93%) depending on whether the first GGT results were abnormal or normal, respectively.

CONCLUSIONS

GTT reproducibility is moderate in patients diagnosed with IFG. Considering this fact, perhaps this test should be repeated before therapeutic decisions are made.

Five batches representative of Ontario-grown American ginseng root produce comparable reductions of postprandial glycemia in healthy individualsThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products

Evidence indicates that the glycemia-lowering effect of American ginseng root may be batch dependent. We therefore evaluated the effect of 5 root batches, representative of Ontario-grown American ginseng, on postprandial glucose and insulin indices. Twelve healthy subjects (5 male, 7 female), mean ± SE age 26.5 ± 2 years, body mass index 23.96 ± 3.41 kg/m2, fasting blood glucose 4.77 ± 0.04 mmol/L, were assigned to consume 9 g of American ginseng from 5 farms (A–E), administered in randomized sequence on 5 separate visits, and a water-control during the 6th and last visit. Treatments were consumed 40 min before a 2-hour 75-gram oral glucose tolerance test. Plasma glucose and insulin were measured at baseline, before, and during the test. Compared with control, batches A and C reduced glucose incremental area under the curve (IAUC) by 35.2% (156 vs. 240 mmol·min/L) and 32.6% (162 vs. 240 mmol·min/L), respectively. Batches A, C, and E reduced incremental peak glucose by 1.3, 1.2, and 1.1 mmol/L, respectively. Batch C reduced the insulin IAUC by 27.7% (15.8 vs. 21.8 nmol·min/L). Effects on glucose and insulin parameters were not different across ginseng treatments. The mean of the 5 ginseng treatments reduced peak postprandial glucose by 1.0 mmol/L, glucose IAUC by 27.7% (173 vs. 240 mmol·min/L), and insulin IAUC by 23.8% (16.6 vs. 21.8 nmol·min/L) relative to control. (All results statistically significant at p < 0.05.) American ginseng decreased postprandial glycemia and insulinemia; however, 40% of the batches did not reduce glycemia with the anticipated magnitude, irrespective of their saponin composition.

Progression to type 2 diabetes characterized by moderate then rapid glucose increases

OBJECTIVE

The transition of an individual from normoglycemia to diabetes has generally been thought to involve either moderate or rapid changes in glucose over time, although few studies have analyzed these changes. We sought to determine whether a general pattern of glucose change exists in most individuals who become diabetic.

RESEARCH DESIGN AND METHODS

We examined longitudinal data from Pima Indians who developed diabetes after several biennial examinations to characterize changes in 2-h plasma glucose. A distinct pattern of glucose change was apparent in the time course of most individuals, an initial linear trend followed by a steeper rise in glucose values. A model consisting of additive linear and exponential functions was hypothesized to account for this pattern and was tested for goodness of fit on 55 individuals who became diabetic after at least 10 previous examinations.

RESULTS

The combined linear and exponential model provided a significantly better fit than linear or exponential models alone in 40 of the 55 cases (P < 10(-38)). Using this model, the timeframe over which glucose values rose suddenly was estimated, having a median time to onset of <4.5 years from the time at which the exponential effect had contributed a modest increase of 10 mg/dl to the initial linear trend.

CONCLUSIONS

We conclude that there are two distinct processes affecting glucose levels in most individuals who progress to type 2 diabetes and that the rapid glucose rise identified in these people may be an important period for physiologic and preventive research.

Interindividual variability and intra-individual reproducibility of glycemic index values for commercial white bread

OBJECTIVE

We sought to assess the intra- and interindividual variability of glycemic index value determinations for white bread using glucose as the reference food.

RESEARCH DESIGN AND METHODS

A total of 23 healthy adults (aged 20-70 years) completed up to three sets of two visits per set. Each pair of visits assessed the glycemic response to 50 g available carbohydrates from commercial white bread and glucose, administered in random order. Glycemic index values were calculated by dividing the 2-h incremental area under the serum glucose response curve after each commercial white bread challenge by the mean area under the curve (AUC) for glucose.

RESULTS

The mean +/- SE ratio of the AUC after white bread intake by the AUC after glucose intake for the first set of determinations was 78 +/- 15 (n = 23; coefficient of variation [CV] 94%). When using glycemic index values calculated with the subset of participants who completed three sets of tests (n = 14), glycemic index values for each of the three sets of determinations were 78 +/- 10, 60 +/- 5, and 75 +/- 10, respectively. CVs were 50, 28, and 50%, respectively. The mean glycemic index value of these three sets was 71 +/- 6, with a CV of 30%. When an ANOVA approach was applied to these data, the interindividual CV was 17.8%, and the intra-individual variation was 42.8%.

CONCLUSIONS

These data suggest that in response to a challenge of white bread relative to glucose, within-individual variability is a greater contributor to overall variability than among-individual variability. Further understanding of all the sources of variability would be helpful in better defining the utility of glycemic index values.

When a placebo is not a 'placebo': a placebo effect on postprandial glycaemia

AIMS

Placebo effects in clinical trials remain uncertain. To investigate a placebo effect on acute postprandial plasma glucose, we conducted a follow-up investigation on a previous study.

METHODS

The effect of placebo (9 g encapsulated cornstarch +500 ml water, taken at -40 min) on the plasma glucose response to a 75-g oral glucose tolerance test (OGTT) was assessed in a previous study in 12 healthy subjects (gender, five male, seven female; age 27 +/- 6 years; body mass index 24 +/- 3.4 kg m(-2)). This was compared with the effect of a water control (500 ml water taken alone at -40 min) on the same outcome in the same subjects in a follow-up study.

RESULTS

Cornstarch placebo decreased plasma glucose area under the curve during the 75-g OGTT by 28% [Delta (95% confidence interval) -63.3 min mmol(-1) l(-1) (-218.33, 91.66), P < 0.02] compared with the water control (P < 0.05).

CONCLUSIONS

Postprandial plasma glucose outcomes may be vulnerable to placebo effects.

Validity and reproducibility of HOMA-IR, 1/HOMA-IR, QUICKI and McAuley's indices in patients with hypertension and type II diabetes

The aim of this study was to evaluate the validity and reliability of homeostasis model assessment-insulin resistance (HOMA-IR) index, its reciprocal (1/HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and McAuley's index in hypertensive diabetic patients. In 78 patients with hypertension and type II diabetes glucose, insulin and triglyceride levels were determined after a 12-h fast to calculate these indices, and insulin sensitivity (IS) was measured with the hyperinsulinemic euglycemic clamp technique. Two weeks later, subjects had again their glucose, insulin and triglycerides measured. Simple and multiple linear regression analysis were applied to assess the validity of these indices compared to clamp IS and coefficients of variation between the two visits were estimated to assess their reproducibility. HOMA-IR index was strongly and inversely correlated with the basic IS clamp index, the M-value (r=-0.572, P<0.001), M-value normalized with subjects' body weight or fat-free mass and every other clamp-derived index. 1/HOMA-IR and QUICKI indices were positively correlated with the M-value (r=0.342, P<0.05 and r=0.456, P<0.01, respectively) and the rest clamp indices. McAuley's index generally presented less strong correlations (r=0.317, P<0.05 with M-value). In multivariate analysis, HOMA-IR was the best fit of clamp-derived IS. Coefficients of variation between the two visits were 23.5% for HOMA-IR, 19.2% for 1/HOMA-IR, 7.8% for QUICKI and 15.1% for McAuley's index. In conclusion, HOMA-IR, 1/HOMA-IR and QUICKI are valid estimates of clamp-derived IS in patients with hypertension and type II diabetes, whereas the validity of McAuley's index needs further evaluation. QUICKI displayed better reproducibility than the other indices.

Alanine aminotransferase and the 6-year risk of the metabolic syndrome in Caucasian men and women: the Hoorn Study

AIMS

To study the association between alanine aminotransferase (ALT) and the 6-year risk of the metabolic syndrome in a population-based study in Caucasian men and women.

METHODS

The association of ALT with the 6-year risk of the metabolic syndrome in 1097 subjects, aged 50-75 years, was assessed in the Hoorn Study with logistic regression analysis. Subjects with the metabolic syndrome at baseline, defined according to the Adult Treatment Panel III of the National Cholesterol Education Program, were excluded.

RESULTS

After 6.4 (range 4.4-8.1) years follow-up, 226 subjects (20.6%) had developed the metabolic syndrome. The odds ratio (95% confidence interval) for developing the metabolic syndrome, adjusted for age, sex, alcohol intake and follow-up duration was 2.25 (1.50-3.37) for subjects in the upper tertile compared with those in the lower tertile of ALT. This association persisted after additional adjustment for all the baseline metabolic syndrome features [1.62 (1.02-2.58)]. Among the individual components of the metabolic syndrome, ALT was significantly associated only with fasting plasma glucose at follow-up.

CONCLUSIONS

These data suggest that ALT is associated with risk of the metabolic syndrome in a general population of middle-aged Caucasian men and women, further strengthening the role of ALT as an indicator for future metabolic derangement. These findings warrant further studies to elucidate the role of non-adipose tissue fat accumulation in the pathogenesis of complications related to the metabolic syndrome.

Elevated cholesteryl ester transfer protein concentration is associated with an increased risk for cardiovascular disease in women, but not in men, with Type 2 diabetes: the Hoorn Study

AIMS

Cholesteryl ester transfer protein (CETP) exchanges neutral lipids between lipoproteins. As the role of CETP in the atherogenic process is still not fully clarified, we studied the association of CETP concentration with the prevalence of cardiovascular disease (CVD) and with intima-media thickness of the carotid artery (IMT) in subjects with normal glucose tolerance (NGT), impaird fasting glucose and/or impaired glucose tolerance (IFG/IGT) and Type 2 diabetes mellitus.

METHODS

Subjects (n = 566) were recruited from the 2000-2001 follow-up examination of the Hoorn study. CETP concentration was determined by immunoassay. CVD was defined as self-reported history of arterial surgery, cerebral vascular event, amputation, angina, claudication, possible infarction, measured ankle-brachial index < 0.90 or ECG abnormalities. The right common carotid artery IMT was measured by ultrasound at 10 mm proximal to the carotid bulb.

RESULTS

In men, CETP concentration was not associated with CVD, irrespective of glucose tolerance status. In women with NGT or IGT, there was also no relationship. However, in women with Type 2 diabetes, the risk of CVD was increased in those with high CETP concentration [odds ratio = 3.34 (1.56; 7.14)]. No statistically significant association was found between CETP concentration and IMT in the entire cohort.

CONCLUSIONS

In an elderly Caucasian population, associations of CETP concentration with CVD were dependent on glucose tolerance status and gender. The finding that high CETP concentration was strongly associated with increased prevalence of CVD in women with Type 2 diabetes warrants further investigation.

Surrogate estimates of insulin sensitivity in subjects with hypertension

The purpose of the study is to compare surrogate estimates of insulin sensitivity with a directly measured insulin sensitivity index, steady-state plasma glucose (SSPG) from insulin suppression test (IST), in subjects with hypertension. Two hundred and twenty-eight hypertensive patients who received IST for SSPG were included for analysis. Estimates from fasting measurements alone, homeostasis model assessment for insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI)), and indices from fasting and/or 2 h samples (ISI(0,120) and ISI(TX)) were calculated. In addition to Pearson and partial correlations, variance-component models were used to test the relationship between surrogate estimates of insulin sensitivity and SSPG. A large proportion of variance owing to covariates in the variance-component models indicated the goodness of model fit, irrespective of the independence among variables. SSPG was positively correlated with logarithmic transformation (Log) (HOMA-IR) and negatively correlated with QUICKI, Log (ISI(0,120)) and ISI(TX) (all P<0.0001). Log (ISI(0,120)) seemed to have a better correlation with SSPG (r=-0.72) than other measures in partial correlation. The proportion of variance owing to all covariates of Log (ISI(0,120)) and ISI(TX) were larger than those of Log (HOMA-IR) and QUICKI in the variance-component models. After adjustments for demographic and obesity covariates, the proportion of variance explained by Log (ISI(0,120)) were largest among the surrogate measures in the variance-component models. Our results showed that ISI(0,120) and ISI(TX) correlated better with SSPG than those used fasting measures alone (HOMA-IR and QUICKI). Log (ISI(0,120)) currently showing the strongest association with SSPG than other estimates is adaptable for use in large studies of hypertension.

Fasting-based estimates of insulin sensitivity in overweight and obesity: a critical appraisal

OBJECTIVE

To identify simple methods to estimate the degree of insulin resistance.

RESEARCH METHODS AND PROCEDURES

The performance of a wide range of fasting-based index estimates of insulin sensitivity was compared by receiver operating characteristic analysis (area under curves and their 95% confidence intervals) against the M value from euglycemic insulin clamp studies collected in the San Antonio (non-Hispanic whites and Hispanic residents of San Antonio, TX) and European Group for the Study of Insulin Resistance (non-diabetic white Europeans) databases (n = 638).

RESULTS

Insulin resistance differed substantially between lean (BMI < 25 kg/m2), overweight or obese (BMI > or = 25 kg/m2), and type 2 diabetic individuals. Estimates of insulin resistance were, therefore, assessed in each group separately. In the overweight and obese subgroup (n = 302), the receiver operating characteristic performance of fasting-based indices varied from 0.72 (0.62 to 0.82), in the case of the insulin/glucose ratio, to 0.80 (0.72 to 0.88) in the case of Belfiore free fatty acids. One superior method could not be identified; the confidence intervals overlapped, and no statistically significant differences emerged. All indices performed better when using the whole study population, with fasting plasma insulin, homeostatic model assessment, insulin/glucose ratio, quantitative insulin sensitivity check index, glucose/insulin ratio, Belfiore glycemia, revised quantitative insulin sensitivity check index, McAuley index, and Belfiore free fatty acids showing area under curves of 0.83, 0.90, 0.66, 0.90, 0.66, 0.90, 0.85, 0.83, and 0.86, respectively, because of the inclusion of very insulin sensitive (lean) and very insulin resistant cases (diabetic subjects).

DISCUSSION

In conclusion, a superior fasting-based index estimate to distinguish between the presence and absence of insulin resistance in overweight and obesity could not be identified despite the use of the large datasets.

Prevalence of diabetes and impaired fasting glucose in Korea: Korean National Health and Nutrition Survey 2001

OBJECTIVE

The purpose of this study was to estimate the prevalence of diabetes and impaired fasting glucose (IFG) and their association with risk factors in the Korean population.

RESEARCH DESIGN AND METHODS

The Korean National Health and Nutrition Survey 2001 was a nationally representative survey with a stratified multistage sampling design. Data from a comprehensive questionnaire, a physical examination, and blood tests were obtained from 5,844 Korean adults (2,513 men and 3,331 women) aged >20 years.

RESULTS

The age-adjusted prevalence of diabetes in this Korean population was 7.6%, and the age-adjusted prevalences of previously diagnosed diabetes and newly diagnosed diabetes were 4.4 and 3.3%, respectively (fasting plasma glucose > or = 7.0 mmol/l). Overall, these results indicate that 8.1% or 1.4 million Korean men and 7.5% or 1.3 million Korean women have diabetes. The age-adjusted prevalence of IFG was 23.9%, using the new American Diabetes Association criteria (fasting plasma glucose 5.6-6.9 mmol/l). Diabetes prevalence increased with age and peaked in the oldest age-group; however, IFG prevalence did not show the same trend. Diabetes was found to be associated with age, BMI, blood pressure, triglyceride, HDL cholesterol, education levels, alcohol consumption, exercise, and a family history of diabetes.

CONCLUSIONS

This study shows that diabetes and IFG are common in Korea, and about one-half of diabetes cases remain undiagnosed. These results emphasize the need to develop an urgent public program to improve the detection, prevention, and treatment of diabetes.

Should an oral glucose tolerance test be performed routinely in all renal transplant recipients?

Posttransplantation diabetes (PTD) contributes to cardiovascular disease and graft loss in renal transplant recipients (RTR). Current recommendations advise fasting blood glucose (FBG) as the screening and diagnostic test of choice for PTD. This study sought to determine (1) the predictive power of FBG with respect to 2-h blood glucose (2HBG) and (2) the prevalence of PTD using FBG and 2HBG compared with that using FBG alone, in prevalent RTR. A total of 200 RTR (mean age 52 yr; 59% male; median transplant duration 6.6 yr) who were > 6 mo posttransplantation and had no known history of diabetes were studied. Patients with FBG < 126 mg/dl (7.0 mmol/L; n = 188) underwent an oral glucose tolerance test (OGTT). Receiver operating characteristic analyses evaluated the optimal level of FBG predictive of PTD (2HBG > or = 200 mg/dl [11.1 mmol/L]) and impaired glucose tolerance (IGT; 2HBG 140 to 200 mg/dl [7.8 to 11.0 mmol/L]). An abnormal OGTT was reported in 79 (42%) nondiabetic RTR: PTD (n = 22) and IGT (n = 57). The optimal FBG that was predictive of PTD was 101 mg/dl (5.6 mmol/L; area under the curve 0.70; sensitivity 64%, specificity 67%, positive predictive value 20%, negative predictive value 93%). The optimal FBG that was predictive of IGT was less well defined (area under the curve 0.54). The prevalence of PTD was higher by OGTT than by FBG alone (17 versus 6%; P < 0.001). FBG may not be the optimal screening or diagnostic tool for PTD or IGT in RTR. Consideration should be given to introducing the OGTT as a routine posttransplantation investigation, although the implications of a pathologic OGTT are still to be determined in this population.

Prevalence of impaired fasting glucose and its relationship with cardiovascular disease risk factors in US adolescents, 1999-2000

OBJECTIVE

PEDIATRICS (ISSN 0031 4005). Published in the public domain by the American Academy of Pediatrics. Several studies have reported increases in the occurrence of type 2 diabetes in youths. People with prediabetic states such as impaired fasting glucose (IFG) are at increased risk for developing diabetes and cardiovascular disease (CVD). The objective of this study was to examine the prevalence of IFG and its relationship with overweight and CVD risk factors in a nationally representative sample of US adolescents who were aged 12 to 19 years.

METHODS

We used data from the 1999-2000 National Health and Nutrition Examination Survey (NHANES). Adolescents who had fasted for 8 hours or more were included in the study (n = 915). IFG was defined as a fasting glucose of 100 to 125 mg/dL. Participants were classified as overweight when their age- and gender-specific BMI was > or = 95th percentile and as at-risk for overweight when their BMI was > or = 85th and < 95th percentile.

RESULTS

In 1999-2000, the prevalence of IFG in US adolescents was 7.0% and was higher in boys than in girls (10.0% vs 4.0%). Prevalence of IFG was higher in overweight adolescents (17.8%) but was similar in those with normal weight and those who were at risk for overweight (5.4% vs 2.8%). The prevalence of IFG was significantly different across racial/ethnic groups (13.0%, 4.2%, and 7% in Mexican Americans, non-Hispanic black individuals, and non-Hispanic white individuals, respectively). Adolescents with IFG had significantly higher mean hemoglobin A1c, fasting insulin, total and low-density lipoprotein cholesterol, triglycerides, and systolic blood pressure and lower high-density lipoprotein cholesterol than those with normal fasting glucose concentrations.

CONCLUSIONS

These data, representing 27 million US adolescents, reveal a very high prevalence of IFG (1 in 10 boys and 1 in 25 girls) among adolescents; the condition affects 1 in every 6 overweight adolescents. Adolescents with IFG have features of insulin resistance and worsened CVD risk factors. Evidence for prevention is still forthcoming in this age group.

Proposal for a Definition of Lifelong Premature Ejaculation Based on Epidemiological Stopwatch Data

INTRODUCTION

Consensus on a definition of premature ejaculation has not yet been reached because of debates based on subjective authority opinions and nonstandardized assessment methods to measure ejaculation time and ejaculation control.

AIM

To provide a definition for lifelong premature ejaculation that is based on epidemiological evidence including the neurobiological and psychological approach.

METHODS

We used the 0.5 and 2.5 percentiles as accepted standards of disease definition in a skewed distribution. We applied these percentiles in a stopwatch-determined intravaginal ejaculation latency time (IELT) distribution of 491 nonselected men from five different countries. The practical consequences of 0.5% and 2.5% cutoff points for disease definition were taken into consideration by reviewing current knowledge of feelings of control and satisfaction in relation to ejaculatory performance of the general male population.

MAIN OUTCOME MEASURES

Literature arguments to be used in a proposed consensus on a definition of premature ejaculation.

RESULTS

The stopwatch-determined IELT distribution is positively skewed. The 0.5 percentile equates to an IELT of 0.9 minute and the 2.5 percentile an IELT of 1.3 minutes. However, there are no available data in the literature on feelings of control or satisfaction in relation to ejaculatory latency time in the general male population. Random male cohort studies are needed to end all speculation on this subject. Exact stopwatch time assessment of IELT in a multinational study led us to propose that all men with an IELT of less than 1 minute (belonging to the 0.5 percentile) have "definite" premature ejaculation, while men with IELTs between 1 and 1.5 minutes (between 0.5 and 2.5 percentile) have "probable" premature ejaculation. Severity of premature ejaculation (nonsymptomatic, mild, moderate, severe) should be defined in terms of associated psychological problems.

CONCLUSION

We define lifelong premature ejaculation as a neurobiological dysfunction with an unacceptable increase of risk to develop sexual and psychological problems anywhere in a lifetime. By defining premature ejaculation from an authority-defined disorder into a dysfunction based on epidemiological evidence it is possible to establish consensus based on epidemiological evidence. Additional epidemiological stopwatch studies are needed for a final decision of IELT values at both percentile cutoff points.

Clinical assessment of near-infrared spectroscopy for noninvasive diabetes screening

BACKGROUND

Current diabetes screening techniques comprise the fasting plasma glucose (FPG) and oral glucose tolerance tests. Both tests demand patient compliance, and neither test has ideal performance. Near-infrared (NIR) spectroscopy is a noninvasive means of interrogating characteristics of a sample and is evaluated as a novel screening method for type 2 diabetes.

METHODS

One hundred fifty-four patients with and without type 2 diabetes were recruited. Their forearm skin was measured with the NIR spectroscopic system, and a capillary blood glucose measurement was also taken. Sixty-six patients returned for a second visit at a later date. A multivariate model, generated from a separate training study, was employed to produce a quantitative risk marker of disease for each NIR spectrum. Sensitivity and specificity (the probabilities that the NIR method will correctly identify a subject as having diabetes or as not having diabetes, respectively) were calculated. As the NIR method produces a continuous rather than categorical classification, various thresholds were evaluated to give several sensitivity and specificity pairs. Test reproducibility was also determined.

RESULTS

At a false-positive rate of 70%, the NIR test had a sensitivity of 77.7%, which is comparable to the 77.3% sensitivity for the FPG test as reported for the Third National Health and Nutrition Examination Survey (NHANES III) study. The reproducibility of the NIR test was also similar to the FPG test (inter-day agreement rates of 84.2% and 79.2%, respectively).

CONCLUSIONS

A noninvasive NIR spectroscopic measurement of the volar forearm was shown to have comparable performance characteristics with the FPG test. The source of the spectroscopic signal is still uncertain and is the subject of ongoing research.

Proinsulin concentration is an independent predictor of all-cause and cardiovascular mortality: an 11-year follow-up of the Hoorn Study

OBJECTIVE

High proinsulin concentration may be a better predictor for cardiovascular disease (CVD) mortality than insulin concentration. Previous observations may have been confounded by glucose tolerance status or lack of precision because of high intraindividual variability. We investigated the longitudinal relation of means of duplicate measurements of insulin and proinsulin with all-cause and CVD mortality in a population-based cohort taking glucose tolerance status into account.

RESEARCH DESIGN AND METHODS

Fasting and post-75-g glucose-load (2-h) glucose, insulin, and proinsulin values were determined in duplicate on separate days in 277 participants with normal glucose metabolism, 208 participants with impaired glucose metabolism, and 119 newly detected patients with type 2 diabetes of the Hoorn Study. Insulin resistance and beta-cell function were estimated by homeostasis model assessment (HOMA-IR and HOMA-B, respectively), and the fasting proinsulin-to-insulin ratio was calculated. Subjects were followed with respect to mortality until January 2003.

RESULTS

Fasting proinsulin levels were significantly associated with all-cause and CVD mortality. The hazard ratios (HRs) per increase in interquartile range adjusted for age and sex were 1.21 (95% CI 1.04-1.42) for all-cause mortality and 1.33 (1.06-1.66) for CVD mortality. Adjustment for glucose tolerance status and HOMA-IR did not substantially change the associations.

CONCLUSIONS

Fasting proinsulin was associated with all-cause and CVD mortality, independent of glucose tolerance status and insulin resistance and largely independent of other CVD risk factors. Proinsulin might play a role in the relationship between insulin resistance and CVD.

Combined oral contraceptives in the treatment of polycystic ovary syndrome

Combined oral contraceptives (COC) are the most often used treatment modality for polycystic ovary syndrome (PCOS). Undisputedly, COC suppress androgen production, thus ameliorating skin androgenic symptoms and improving menstrual dysfunction. On the other hand, there are still many unresolved issues concerning their metabolic effects. COC could decrease insulin sensitivity and deteriorate glucose tolerance, although the negative influence on insulin sensitivity is dependent on other factors (especially obesity) and this need not be expressed in non-obese patients. It is probable that the impairment of glucose tolerance is reversible, as the incidence of diabetes is not increased in past COC users. The effects of COC on the lipid spectrum are dependent on the type of gestagen, but lipid levels usually remain within the reference limits. Combination therapy of COC with weight reduction or insulin sensitizers could further suppress androgen levels and improve metabolic parameters. The establishment of COC after laparoscopic ovarian drilling may further decrease androgen levels. The combination of COC and GnRH analogues is not superior to COC therapy alone. Prospective data about the influence of COC on the risk of diabetes mellitus, coronary artery disease and endometrial cancer in PCOS women are lacking.

HbA1c screening for undiagnosed diabetes in New Zealand

OBJECTIVES

To describe a screening programme to detect undiagnosed diabetes in high-risk ethnic groups in New Zealand and determine the specificity and sensitivity of HbA(1c) to detect fasting hyperglycaemia.

RESEARCH DESIGN AND METHODS

HbA(1c) was offered to subjects over 20 years of age participating in a screening programme for hepatitis B that was targeted at non-European populations. Two hundred and forty-four predominantly Maori subjects, with HbA(1c) levels 5 to 7.9% and who were not known to have diabetes, were tested with an oral glucose tolerance test. Comparison was made with fasting and 2-h samples.

RESULTS

Fifty thousand eight hundred and nineteen subjects were screened using HbA(1c). 12% had HbA(1c) levels of 6.1% or more, and in 4% of the population HbA(1c) was 7.1% or more. Maori, Pacific Island people, and Indians had particularly high rates of elevated HbA(1c). HbA(1c) levels of 6.1% and greater were 94% sensitive and 77% specific in detecting the 32 subjects who had a fasting glucose of 7.0 mmol/L or more, and 90% sensitive and 73% specific for 20 subjects with a 2-h glucose of 11.1 mmol/L or more.

CONCLUSIONS

Rates of elevated HbA(1c) levels in non-Europeans in New Zealand are very high, particularly in Maori, Pacific Island Peoples', and Indians, reflecting their high risk of diabetes and vascular disease. HbA(1c) can be used as an opportunistic screening test for diabetes and glucose intolerance, but a high level should be followed by an oral glucose tolerance test.

Coffee consumption and incidence of impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes: the Hoorn Study

AIMS/HYPOTHESIS

Coffee contains several substances that may affect glucose metabolism. The aim of this study was to evaluate the relationship between habitual coffee consumption and the incidence of IFG, IGT and type 2 diabetes.

METHODS

We used cross-sectional and prospective data from the population-based Hoorn Study, which included Dutch men and women aged 50-74 years. An OGTT was performed at baseline and after a mean follow-up period of 6.4 years. Associations were adjusted for potential confounders including BMI, cigarette smoking, physical activity, alcohol consumption and dietary factors.

RESULTS

At baseline, a 5 cup per day higher coffee consumption was significantly associated with lower fasting insulin concentrations (-5.6%, 95% CI -9.3 to -1.6%) and 2-h glucose concentrations (-8.8%, 95% CI -11.8 to -5.6%), but was not associated with lower fasting glucose concentrations (-0.8%, 95% CI -2.1 to 0.6%). In the prospective analyses, the odds ratio (OR) for IGT was 0.59 (95% CI 0.36-0.97) for 3-4 cups per day, 0.46 (95% CI 0.26-0.81) for 5-6 cups per day, and 0.37 (95% CI 0.16-0.84) for 7 or more cups per day, as compared with the corresponding values for the consumption of 2 or fewer cups of coffee per day (p=0.001 for trend). Higher coffee consumption also tended to be associated with a lower incidence of type 2 diabetes (OR 0.69, CI 0.31-1.51 for >/=7 vs </=2 cups per day, p=0.09 for trend), but was not associated with the incidence of IFG (OR 1.35, CI 0.80-2.27 for >/=7 vs </=2 cups per day, p=0.49 for trend).

CONCLUSIONS/INTERPRETATION

Our findings indicate that habitual coffee consumption can reduce the risk of IGT, and affects post-load rather than fasting glucose metabolism.

Hemoglobin A1c can be analyzed in blood kept frozen at -80 degrees C and is not commonly affected by hemolysis in the general population

The ability of glycated hemoglobin A(1c) (HbA(1c)) to predict diabetes is unknown, but could be evaluated by analyses on samples stored in biobanks. The stability of HbA(1c) in long-term stored samples is, however, unknown. Moreover, the effect of hemolysis on HbA(1c) in the general population is not assessed. To explore these questions HbA(1c) was determined in 3 groups (n = 717) of samples with storage times at -80 degrees C differing between 10 years and 2 months. The results were compared with HbA(1c) analyzed in fresh blood samples (n = 174). The subjects were free from diabetes and aged 40 to 60 years. HbA(1c) was analyzed by cation exchange high-performance liquid chromatography (HPLC). The mean HbA(1c) results for the fresh and long-term stored samples were 4.25% +/- 0.39 and 4.19% +/- 0.43, respectively (P = not significant [NS]). The HbA(1c) levels in fresh and 2-month stored samples were essentially equal. There was no correlation between HbA(1c) in the fresh samples and the hemolysis parameters reticulocytes, haptoglobin, or bilirubin. HbA(1c) is apparently stable in samples long-term stored at -80 degrees C and is not commonly affected by hemolysis in the general population. HbA(1c) analyzed on biobank samples could be used to assess the predictive value for future diabetes and relationship to other morbidity and mortality.

Evaluation of glucose controllers in virtual environment: methodology and sample application

OBJECTIVE

Adaptive systems to deliver medical treatment in humans are safety-critical systems and require particular care in both the testing and the evaluation phase, which are time-consuming, costly, and confounded by ethical issues. The objective of the present work is to develop a methodology to test glucose controllers of an artificial pancreas in a simulated (virtual) environment.

MATERIAL AND METHODS

A virtual environment comprising a model of the carbohydrate metabolism and models of the insulin pump and the glucose sensor is employed to simulate individual glucose excursions in subjects with type 1 diabetes. The performance of the control algorithm within the virtual environment is evaluated by considering treatment and operational scenarios.

RESULTS

The developed methodology includes two dimensions: testing in relation to specific life style conditions, i.e. fasting, post-prandial, and life style (metabolic) disturbances; and testing in relation to various operating conditions, i.e. expected operating conditions, adverse operating conditions, and system failure. We define safety and efficacy criteria and describe the measures to be taken prior to clinical testing. The use of the methodology is exemplified by tuning and evaluating a model predictive glucose controller being developed for a wearable artificial pancreas focused on fasting conditions.

CONCLUSION

Our methodology to test glucose controllers in a virtual environment is instrumental in anticipating the results of real clinical tests for different physiological conditions and for different operating conditions. The thorough testing in the virtual environment reduces costs and speeds up the development process.

[Diagnosing type 2 diabetes mellitus: in primary care, fasting plasma glucose and glycosylated haemoglobin do the job]

OBJECTIVE

To determine the validity of glycosylated hemoglobin (HbA1c) values as a method to diagnose type 2 diabetes mellitus (DM2) in a population at risk seen in primary care.

DESIGN

Cross-sectional analytical study.

SETTING

Data were obtained for the Raval Sud study population (epidemiologic study of alterations in glucose metabolism in a population at risk).

PARTICIPANTS

454 subjects from this population (mean age, 65 +/- 3 years; 52% male) at high risk for DM2, seen at a primary care center, were included in the study.

MAIN MEASURES

We recorded demographic data and laboratory values for fasting plasma glucose (FPG), oral glucose tolerance test (OGTT), and HbA1c. The diagnostic criteria used for DM2 were those published by the WHO in 1999. Values for HbA1c were expressed as the number of standard deviations (SD) above the mean.

RESULTS

Levels of HbA1c correlated with FPG (r=0.72) and glucose levels 2 h after oral glucose overload (r=0.43). Thirty percent of the patients with FPG between 110 and 125 mg/dL had HbA1c values higher than the reference limits. A combined technique based on FPG>125 mg/dL or FPG 110-125 mg/dL with HbA1c > or = 3 SD (5.94%) showed a sensitivity of 92% and a specificity of 95%.

CONCLUSIONS

When FPG is inconclusive (110-125 mg/dL), an HbA1c value more than 3 standard deviations above the mean (>5.94%) is useful in suggesting a likely diagnosis of diabetes and identifying patients who require treatment.

Plasma insulin and cardiovascular mortality in non-diabetic European men and women: a meta-analysis of data from eleven prospective studies

AIMS/HYPOTHESIS

We examined the association between plasma insulin and cardiovascular mortality in non-diabetic European men and women based on data from eleven prospective studies.

METHODS

The study population comprised 6156 men and 5351 women aged 30-89 years. Baseline measurements included oral glucose tolerance test, fasting and 2-h plasma insulin, and conventional risk factors. Cox models were used to calculate hazard ratios (HRs) and their 95% confidence intervals, and overall HRs were assessed by meta-analyses.

RESULTS

During the 8.8-year follow-up, 362 men and 70 women died from cardiovascular disease. The age- and smoking-adjusted overall HR of cardiovascular mortality for the highest vs the lower quartiles of fasting insulin was 1.58 (95% CI: 1.26-1.97) in men and 2.64 (1.54-4.51) in women. Adjusting for other risk factors in addition, the HR was 1.54 (1.16-2.03) in men and 2.66 (1.45-4.90) in women. For 2-h insulin these HRs were 1.28 (0.99-1.66), 1.87 (0.87-4.02), and 0.85 (0.60-1.21), 1.36 (0.53-3.45). The overall HRs for interquartile ranges for fasting and 2-h insulin, with full adjustment, were 1.13 (1.05-1.22) and 1.11 (1.01-1.23) in men, and 1.25 (1.08-1.45) and 1.11 (0.91-1.36) in women.

CONCLUSIONS/INTERPRETATION

Hyperinsulinaemia, defined by the highest quartile cut-off for fasting insulin, was significantly associated with cardiovascular mortality in both men and women independently of other risk factors. Associations between high 2-h insulin and cardiovascular mortality were weaker and non-significant. Weak positive associations of fasting and 2-h insulin with cardiovascular mortality over interquartile ranges were, however, more similar.

Impaired fasting glucose vs. glucose intolerance in pre-menopausal women: distinct metabolic entities and cardiovascular disease risk?

BACKGROUND

Impaired glucose tolerance (IGT) is associated with an increased cardiovascular disease risk. Less is known about cardiovascular disease risk among subjects with impaired fasting glucose (IFG) or with combined IFG and IGT.

AIMS

To compare body composition, body fat distribution, plasma glucose-insulin homeostasis and plasma lipid-lipoprotein profile between pre-menopausal women having either a normal glucose tolerance (NGT), isolated IFG, isolated IGT or combined IFG and IGT.

METHODS

Three hundred and thirty-four women with NGT, 11 women with IFG, 35 women with IGT and 10 women with both IFG and IGT were studied.

RESULTS

Women with IFG were characterized by a higher visceral adipose tissue (AT) accumulation than women with NGT (P < 0.05). Also, they were characterized by a higher subcutaneous AT area and by higher body fat mass than NGT and IGT women (P < 0.05). However, their lipid-lipoprotein profile was comparable with that of NGT women, except for reduced HDL-cholesterol concentrations (P < 0.05). After adjustment for visceral AT, women with IFG had lower total cholesterol, LDL-cholesterol and apolipoprotein B (apoB) levels than the three other groups. They also had lower HDL(2)-cholesterol than NGT women and lower total cholesterol/HDL-cholesterol ratio than IGT women. Women with IGT showed higher triglyceride and apoB concentrations and a higher total cholesterol/HDL-cholesterol ratio than women with NGT (P < 0.05). Overall, women with combined IFG and IGT showed body fatness characteristics and alterations in their metabolic risk profile which were essentially similar to women with isolated IGT.

CONCLUSIONS

These results indicate that there are significant differences in anthropometric and metabolic variables between pre-menopausal women with IFG vs. IGT and that the association between body fatness-body fat distribution indices and the metabolic profile may differ between IFG and IGT women.

Postprandial plasma fructose level is associated with retinopathy in patients with type 2 diabetes

The aim of the present study was to investigate the association of fructose on microangiopathy in patients with diabetes. Postprandial plasma fructose concentrations and postprandial plasma glucose concentrations were simultaneously measured 3 times within a 24-hour period (2 hours after each meal) in 38 patients with type 2 diabetes that had been admitted to the hospital. The mean postprandial plasma fructose concentrations (MPPF) and the mean postprandial plasma glucose concentrations (MPPG) were calculated. Fructose was measured by gas chromatography-mass spectrometry (GCMS). Based solely on MPPF, we were able to divide the patients into three groups: the high MPPF (31.9 +/- 6.5 micromol/L) group (n = 12), the middle MPPF (21.2 +/- 1.8 micromol/L) group (n = 13), and the low MPPF (15.2 +/- 2.4 micromol/L) group (n = 13). Prevalence and degree of retinopathy and nephropathy were then evaluated in the 3 different groups. A significant correlation was observed in the prevalence of proliferative diabetic retinopathy (PDR) among the 3 MPPF groups (P =.024). The prevalence of PDR was higher in the high MPPF group (75.0%) than in the middle and low MPPF groups (23.1% and 38.5%, respectively). Although not significantly different statistically, the prevalence of all degrees of retinopathy showed a tendency to be higher in the high MPPF group (83.3%) than in the middle and low MPPF groups (46.2% and 46.2%, respectively) (P =.081). Nephropathy prevalence also showed a tendency to be higher in the high MPPF group (66.7%) than in the middle and low MPPF groups (38.5% and 30.8%, respectively), although the differences were not significant. The prevalence of clinical albuminuria was not significantly different among the 3 groups, but there was a tendency for it to be higher in the low MPPF group (30.8%) than in the high and middle MPPF groups (16.7% and 0%, respectively). No significant differences in glycemic indicators and mean duration of diabetes were observed among the 3 groups. The increased prevalence of retinopathy in the high MPPF group suggests that fructose is associated with retinopathy in patients with type 2 diabetes.