Differences in height explain gender differences in the response to the oral glucose tolerance test - the AusDiab study

Aim To determine the extent of gender-related differences in the prevalence of glucose intolerance for the Australian population and whether body size may explain such differences.

Methods Cross-sectional data were collected from a national cohort of 11 247 Australians aged ≥ 25 years. Glucose tolerance status was assessed according to both fasting plasma glucose (FPG) and 2-h plasma glucose (2hPG) levels following a 75-g oral glucose tolerance test (OGTT). Anthropometric and glycated haemoglobin measurements were also made.

Results Undiagnosed diabetes and non-diabetic glucose abnormalities were more prevalent among men than women when based only on the FPG results (diabetes: men 2.2%, women 1.6%, P = 0.02; impaired fasting glycaemia: men 12.3%, women 6.6%, P < 0.001). In contrast 16.0% of women and 13.0% of men had a 2hPG abnormality (either diabetes or impaired glucose tolerance, P = 0.14). Women had a mean FPG 0.3 mmol/l lower than men (P < 0.001), but 2hPG 0.3 mmol/l higher (P = 0.002) and FPG-2hPG increment 0.5 mmol/l greater (P < 0.001). The gender difference in mean 2hPG and FPG-2hPG increment disappeared following adjustment for height. For both genders, those in the shortest height quartile had 2hPG levels 0.5 mmol/l higher than the tallest quartile, but height showed almost no relationship with the FPG.

Conclusions Men and women had different glycaemic profiles; women had higher mean 2hPG levels, despite lower fasting levels. It appeared that the higher 2hPG levels for women related to lesser height and may be a consequence of using a fixed glucose load in the OGTT, irrespective of body size.

Influence of lower cutoff values for 100-g oral glucose tolerance test and glycemic profile for identification of pregnant women at excessive fetal growth risk

Objective: To evaluate data from patients with normal oral glucose tolerance test (OGTT) results and a normal or impaired glycemic profile (GP) to determine whether lower cutoff values for the OGTT and GP (alone or combined) could identify pregnant women at risk for excessive fetal growth. Methods: We classified 701 pregnant women with positive screening for gestational diabetes mellitus (GDM) into 2 categories - (1) normal 100-g OGTT and normal GP and (2) normal 100-g OGTT and impaired GP - to evaluate the influence of lower cutoff points in a 100-g OGTT and GP (alone or in combination) for identification of pregnant women at excessive fetal growth risk. The OGTT is considered impaired if 2 or more values are above the normal range, and the GP is impaired if the fasting glucose level or at least 1 postprandial glucose value is above the normal range. To establish the criteria for the OGTT (for fasting and 1, 2, and 3 hours after an oral glucose load, respectively), we considered the mean (75 mg/dL, 120 mg/dL, 113 mg/dL, and 97 mg/dL), mean plus 1 SD (85 mg/dL, 151 mg/dL, 133 mg/dL, and 118 mg/dL), and mean plus 2 SD (95 mg/dL, 182 mg/dL, 153 mg/dL, and 139 mg/dL); and for the GP, we considered the mean and mean plus 1 SD (78 mg/dL and 92 mg/dL for fasting glucose levels and 90 mg/dL and 130 mg/dL for 1- or 2-hour postprandial glucose levels, respectively). Results: Subsequently, the women were reclassified according to the new cutoff points for both tests (OGTT and GP). Consideration of values, in isolation or combination, yielded 6 new diagnostic criteria. Excessive fetal growth was the response variable for analysis of the new cutoff points. Odds ratios and their respective confidence intervals were estimated, as were the sensitivity and specificity related to diagnosis of excessive fetal growth for each criterion. The new cutoff points for the tests, when used independently rather than collectively, did not help to predict excessive fetal growth in the presence of mild hyperglycemia. Conclusion: Decreasing the cutoff point for the 100-g OGTT (for fasting and 1, 2, and 3 hours) to the mean (75 mg/dL, 120 mg/dL, 113 mg/dL, and 97 mg/dL) in association with the GP (mean or mean plus 1 SD-78 mg/dL and 92 mg/dL for the fasting state and 90 mg/dL and 130 mg/dL for 1- or 2-hour postprandial values-increased the sensitivity and specificity, and both criteria had statistically significant predictive power for detection of excessive fetal growth. © 2008 AACE.

Oral glucose tolerance test in children and adolescents: Positives and pitfalls

Objectives: To describe the glycaemic status (assessed by an oral glucose tolerance test (OGTT)) and associated comorbidities in a cohort of Australian children and adolescents at risk of insulin resistance and impaired glucose homeostasis (IGH). Methods: Twenty-one children and adolescents (three male, 18 female) (18 Caucasian, one Indigenous, two Asian) (20 obese, one lipodystrophy) referred to the Paediatric Endocrinology and Diabetes Clinic underwent a 2-h OGTT with plasma glucose and insulin measured at baseline, + 60 and + 120 min. If abnormal, the OGTT was repeated. Results: The mean (SD) age was 14.2 (1.6) years, BMI 38.8 (7.0) kg/m(2) and BMI-SDS 3.6 (0.6). Fourteen patients had fasting insulin levels >21 mU/L. Type 2 diabetes mellitus was diagnosed in one patient, impaired glucose tolerance (IGT) in four patients and impaired fasting glycaemia (IFG) in one patient. Despite no weight loss, only one patient had a persistently abnormal OGTT on repeat testing. Three patients with IGH were medicated with risperidone at the time of the initial OGTT. One patient who had persistent IGT had continued risperidone. The other two patients had initial OGTT results of IGT and diabetes mellitus type 2. They both ceased risperidone between tests and repeat OGTT showed normal glycaemic status. Conclusions: Use of fasting glucose alone may miss cases of IGH. Diagnosis of IGT should not be made on one test alone. Interpretation of glucose and insulin responses in young people is limited by lack of normative data. Larger studies are needed to generate Australian screening recommendations. Further assessment of the potential adverse effects of atypical antipsychotic medication on glucose homeostasis in this at-risk group is important.

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

Comparison between 100-g glucose tolerance test and two other screening tests for gestational diabetes: combined fasting glucose with risk factors and 50-g glucose tolerance test

CONTEXTO E OBJETIVO: A falta de consenso sobre os protocolos de rastreamento e diagnóstico do diabetes gestacional, associada às dificuldades na realização do teste oral simplificado do diabete gestacional (o teste de tolerância a 100 g de glicose, considerado padrão-ouro) justificam a comparação com alternativas. O objetivo deste trabalho é comparar o teste padrão-ouro a dois testes de rastreamento: associação de glicemia de jejum e fatores de risco (GJ + FR) e o teste oral simplificado de tolerância a 50 g de glicose (TTG 50 g), com o teste de tolerância a 100 g de glicose (TTG 100 g). TIPO DE ESTUDO E LOCAL: Estudo de coorte longitudinal, prospectivo, realizado no Serviço de Ginecologia e Obstetrícia do Hospital Universitário da Universidade Federal de Mato Grosso do Sul. MÉTODOS: 341 gestantes foram submetidas aos três testes. Calcularam-se os índices de sensibilidade (S), especificidade (E), valores preditivos (VPP e VPN), razões de probabilidade (RPP e RPN) e resultados falsos (FP e FN), positivos e negativos da associação GJ + FR e do TTG 50 g em relação ao TTG 100 g. Compararam-se as médias das glicemias de uma hora pós-sobrecarga (1hPS) com 50 e 100 g. Na análise estatística, empregou-se o teste t de Student, com limite de significância de 5%. RESULTADOS: A associação GJ + FR encaminhou mais gestantes (53,9%) para a confirmação diagnóstica que o TTG 50 g (14,4%). Os dois testes foram equivalentes nos índices de S (86,4 e 76,9%), VPN (98,7 e 98,9%), RPN (0,3 e 0,27) e FN (15,4 e 23,1%). As médias das glicemias 1hPS foram semelhantes, 106,8 mg/dl para o TTG 50 g e 107,5 mg/dl para o TTG 100 g. CONCLUSÕES: Os resultados da eficiência diagnóstica associados à simplicidade, praticabilidade e custo referendaram a associação GJ + FR como o mais adequado para o rastreamento. A equivalência das glicemias de 1hPS permitiram a proposição de um novo protocolo de rastreamento e diagnóstico do diabete gestacional, com menores custo e desconforto.

Dietary fructose, fruits, fruit juices and glucose tolerance status in Japanese-Brazilians

Background and aims: Evidence suggests that fructose and sweetened beverages may be a risk factor for obesity and type 2 diabetes, but the role of sweetened fruit juices in glucose disturbances has been minimally explored. The aim of this study was to examine the association of total fructose, fresh fruit and sweetened fruit juice intake with glucose tolerance homeostasis in Japanese-Brazilians. Methods and results: A total of 475 men and 579 women aged >= 30 years were evaluated in a cross-sectional population-based survey with a standardized protocol including a 2-h oral glucose tolerance test (WHO criteria). Habitual food consumption was obtained using a validated food frequency questionnaire for Japanese-Brazitians. After adjustments for potential confounding variables, the odds ratio (OR; 95%Cl) for impaired glucose tolerance was 2.1 (1.0-4.5; P for trend = 0.05) for the highest as compared to the lowest tertile intake of total fructose and 2.3 (1.1-5.1; P for trend = 0.05) for the highest as compared to the lowest tertile intake of sweetened fruit juices. Conclusion: Our results showed that high intakes of dietary fructose and sweetened fruit juices, but not whole fresh fruits, were associated with impaired glucose tolerance among genetically susceptible individuals. (C) 2008 Elsevier B.V. All rights reserved.

Effect of creatine ingestion on glucose tolerance and insulin sensitivity in men

Purpose: This study investigated whether acute (5 d) and/or short-term (28 d) creatine (Cr) ingestion altered glucose tolerance or insulin action in healthy, untrained men (aged 26.9 ± 5.7 yr; SD). Methods : Subjects were randomly allocated to either a Cr (N = 8) or placebo group (N = 9) and were tested in the control condition (presupplementation), and after 5 and a further 28 d of supplementation. The Cr group ingested 20 g and 3 g·d-1 of Cr for the first 5 and following 28 d, respectively. The placebo group ingested similar amounts of glucose over the same time period. During each testing period, subjects underwent an oral glucose tolerance test (OGTT) to determine insulin sensitivity, and six subjects from each group underwent a muscle biopsy before each OGTT. Results : Cr supplementation resulted in an increased (P < 0.05) muscle TCr content after both the acute and short-term loading phase compared with placebo. Neither acute nor short-term Cr supplementation influenced skeletal muscle glycogen content, glucose tolerance, or measures of insulin sensitivity. Conclusions: These findings demonstrated that acute Cr supplementation (20 g·d-1 for 5 d) followed by short-term Cr supplementation (3 g·d-1 for 28 d) did not alter insulin action in healthy, active untrained men.

The rising prevalence of diabetes and impaired glucose tolerance : the Australian diabetes, obesity and lifestyle study

OBJECTIVE—To determine the population-based prevalence of diabetes and other categories of glucose intolerance (impaired glucose tolerance [IGT] and impaired fasting glucose [IFG]) in Australia and to compare the prevalence with previous Australian data.

RESEARCH DESIGN AND METHODS—A national sample involving 11,247 participants aged >=25 years living in 42 randomly selected areas from the six states and the Northern Territory were examined in a cross-sectional survey using the 75-g oral glucose tolerance test to assess fasting and 2-h plasma glucose concentrations. The World Health Organization diagnostic criteria were used to determine the prevalence of abnormal glucose tolerance.

RESULTS—The prevalence of diabetes in Australia was 8.0% in men and 6.8% in women, and an additional 17.4% of men and 15.4% of women had IGT or IFG. Even in the youngest age group (25–34 years), 5.7% of subjects had abnormal glucose tolerance. The overall diabetes prevalence in Australia was 7.4%, and an additional 16.4% had IGT or IFG. Diabetes prevalence has more than doubled since 1981, and this is only partially explained by changes in age profile and obesity.

CONCLUSIONS—Australia has a rapidly rising prevalence of diabetes and other categories of abnormal glucose tolerance. The prevalence of abnormal glucose tolerance in Australia is one of the highest yet reported from a developed nation with a predominantly Europid background.

Abbreviations: 2hPG, 2-h plasma glucose • AusDiab, Australian Diabetes, Obesity and Lifestyle Study • CD, Census Collector District • FPG, fasting plasma glucose • IFG, impaired fasting glucose • IGT, impaired glucose tolerance • KDM, known diabetes mellitus • NDM, newly diagnosed diabetes mellitus • OGTT, oral glucose tolerance test • WHO, World Health Organization

Gender differences in the prevalence of impaired fasting glycaemia and impaired glucose tolerance in Mauritius. Does sex matter?

Objective: To examine gender differences in the characteristics and prevalence of various categories of glucose tolerance in a population study in Mauritius.

Research design and methods: In 1998, a community-based cross-sectional survey was conducted in Mauritius. Categories of glucose metabolism were determined in 5388 adults, with an oral glucose tolerance test given to those who did not have previously diagnosed diabetes (n = 4036). Other cardiovascular risk factors were assessed among those without known diabetes.

Results: For men and women the prevalence of diabetes (22.0 vs. 21.8%, respectively) and the prevalence of coexisting impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) (3.2 vs. 2.9%) were similar. However, men were twice as likely as women to have isolated IFG [5.1% (4.2–6.0) vs. 2.9% (2.3–3.5)], despite being younger, thinner and with lower plasma insulin but higher lipids. Conversely, the prevalence of isolated IGT was lower in men [9.0% (7.9–10.2) vs. 13.9% (12.6–15.1)]. Among non-diabetic individuals, fasting glucose was higher in men than women, whereas 2-h glucose was higher in women. In people without diabetes, women had significantly higher body mass index, beta cell function (HOMA-B), fasting and 2-h insulin than men and significantly lower waist-hip ratios, waist circumference, insulin sensitivity (HOMA-S) and triglycerides.

Conclusion: In Mauritius, the distribution of impaired glucose metabolism differs by sex. The observation that IFG is more prevalent in men and IGT more prevalent in women raises important questions about their underlying aetiology and the ability of the current glucose thresholds to equally identify men and women at high-risk of developing diabetes. IFG should be seen as a complimentary category of abnormal glucose tolerance, rather than a replacement for IGT.

Endurance training in obese humans improves glucose tolerance and mitochondrial fatty acid oxidation and alters muscle lipid content

Muscle fatty acid (FA) metabolism is impaired in obesity and insulin resistance, reflected by reduced rates of FA oxidation and accumulation of lipids. It has been suggested that interventions that increase FA oxidation may enhance insulin action by reducing these lipid pools. Here, we examined the effect of endurance training on rates of mitochondrial FA oxidation, the activity of carnitine palmitoyltransferase I (CPT I), and the lipid content in muscle of obese individuals and related these to measures of glucose tolerance. Nine obese subjects completed 8 wk of moderate-intensity endurance training, and muscle biopsies were obtained before and after training. Training significantly improved glucose tolerance, with a reduction in the area under the curve for glucose (P< 0.05) and insulin (P = 0.01) during an oral glucose tolerance test. CPT I activity increased 250% (P = 0.001) with training and became less sensitive to inhibition by malonyl-CoA. This was associated with an increase in mitochondrial FA oxidation (+120%, P < 0.001). Training had no effect on muscle triacylglycerol content; however, there was a trend for training to reduce both the total diacylglcyerol (DAG) content (−15%, P = 0.06) and the saturated DAG-FA species (−27%, P = 0.06). Training reduced both total ceramide content (−42%, P = 0.01) and the saturated ceramide species (−32%, P < 0.05). These findings suggest that the improved capacity for mitochondrial FA uptake and oxidation leads not only to a reduction in muscle lipid content but also a to change in the saturation status of lipids, which may, at least in part, provide a mechanism for the enhanced insulin action observed with endurance training in obese individuals.