Optimized fasting and OGTT-based simple surrogate methods for assessing insulin sensitivity.

AIMS: Simple surrogate indices of insulin sensitivity have been conceived to deal with costly and complicated approaches, such as the hyperinsulinemic-euglycemic clamp; however, their use has not been widespread given their variabilities in different populations. In this paper, we present two simple surrogate indices, one that uses fasting glucose and insulin values and the other based on the values from the oral glucose tolerance test. MATERIALS AND METHODS: The proposed methods integrate easy-to-obtain anthropometric measures. Evolutionary algorithms were used to optimize the proposed methods by maximizing its correlation with the Stumvoll MCR method. RESULTS AND CONCLUSION: When the proposed indices were applied to three study groups (control subjects, metabolic syndrome, marathon runners), a reduction in the intergroup variability of the insulin sensitivity was obtained. Moreover, the proposed index based on the oral glucose tolerance test (OGTT), which considers the glucose metabolism process and the hepatic and peripheral insulin sensitivity, showed stronger correlations with the Stumvoll method and lower intergroup variability than the fasting one.

Joint analysis of fasting and postprandial plasma glucose and insulin concentrations in Venezuelan women.

AIMS: Plasma glucose and insulin concentrations in fasting and postprandial reflect the metabolism of glucose by the human body and are useful in the diagnosis of metabolic diseases, such as diabetes and insulin resistance. In this work, these concentrations are jointly analyzed in Venezuelan women and 28 classes that better specify each metabolic condition are generated. MATERIALS AND METHODS: Each class comprises a combination of fasting and postprandial ranges of glucose and insulin concentrations defined in the literature as normal, impaired and diabetic. A hypothesis test was used to find statistically significant differences between the classes, and confidence intervals for age and glucose and insulin concentrations were defined for each class. RESULTS AND CONCLUSION: The process of deterioration of glucose metabolism advances with the age of the subject, more than half of the prediabetics have impaired glucose levels in fasting but normal in postprandial and normal insulin levels in fasting and postprandial, and one third of diabetics have diabetic glucose levels in fasting and postprandial and normal insulin levels in fasting and postprandial. This categorization of subjects would allow the application of a more specific treatment and the possibility of predicting the progress of the metabolic disorder.

Cardiac autonomic modulation in response to a glucose stimulus.

This paper focuses on the effect of a sudden increase of plasma glucose concentration in the cardiac autonomic modulation using time-domain and frequency-domain heart rate variability (HRV) measures. Plasma glucose and insulin levels, measured each 30 min during an oral glucose tolerance test, and [Formula: see text] (mean of the RR interval), SDNN (standard deviation of normal-to-normal heartbeats), rMSSD (root-mean-square of successive differences between normal heartbeats), TP (total spectral power), LF and HF (power of the low- and high-frequency bands), LF norm and HF norm (LF and HF in normalized units), and LF/HF ratio of the HRV signal, obtained from 5-min-long ECG recordings during each phase of the test, were analyzed for subjects with the metabolic syndrome, marathon runners, and a control group. Results show that, after the glucose load, subjects with the metabolic syndrome experienced an increased sympathetic and decreased parasympathetic tone, which suggests an imbalance in cardiac autonomic modulation as a consequence of hyperglycemia and hyperinsulinemia. The significance of this study lies in the use of the ECG to assess the effects of a sudden increase in plasma glucose concentration on the cardiac autonomic modulation in subjects with different cardiovascular and metabolic conditions. Graphical Abstract Time-domain and frequency-domain heart rate variability measures are altered in subjects with different cardiovascular and metabolic conditions during an oral glucose tolerance test.

Comparing glucose and insulin data from the two-hour oral glucose tolerance test in metabolic syndrome subjects and marathon runners.

Glucose is the main energy source of the body's cells and is essential for normal metabolism. Two pancreatic hormones, insulin and glucagon, are involved in glucose home-ostasis. Alteration in the plasma glucose and insulin concentrations could lead to distinct symptoms and diseases, ranging from mental function impairment to coma and even death. Type 2 diabetes, insulin resistance and metabolic syndrome are typical examples of abnormal glucose metabolism that increase the risk for cardiovascular disease and mortality. The oral glucose tolerance test (OGTT) is a medical test used to screen for prediabetes, type 2 diabetes and insulin resistance. In the 5-sample 2-hour OGTT, plasma glucose and insulin concentrations are measured after a fast and then after oral intake of glucose, at intervals of 30 minutes. In this work, a statistical analysis is carried out to find significant differences between the five stages of the OGTT for plasma glucose and insulin data. In addition, the behavior of the glucose and insulin data is compared between subjects with the metabolic syndrome and marathon runners. Results show that marathon runners have plasma glucose and insulin levels significantly lower (p <; 0.05) than people with the metabolic syndrome in all the stages of the OGTT. Insulin secretion decreases in marathon runners due to a significant reduction in plasma glucose concentration, but insulin secretion does not decrease in metabolic syndrome subjects due to insulin resistance, consequently plasma glucose concentration does not achieve normal levels.

Anthropometric measurements for assessing insulin sensitivity on patients with metabolic syndrome, sedentaries and marathoners.

The diagnosis of low insulin sensitivity is commonly done through the HOMA-IR index, in which fasting insulin and glucose blood levels are evaluated. Insulin and blood glucose levels are used for insulin sensitivity assessment by surrogate methods (HOMA-IR, Matsuda, etc), but anthropometric measurements like body weight, height and waist circumference are not considered, even if these variables also are related to low insulin sensitivity and metabolic syndrome. In this study we evaluate the impact of anthropometric measurements on the HOMA-IR, Matsuda and Caumo indexes to estimate insulin sensitivity. Specifically, we compare insulin sensitivity indexes with and without the anthropometric measurements in their equations on three different groups: patients with metabolic syndrome, sedentaries and marathoners. Results show relationships between anthropometric variables and insulin sensitivity indexes. On the other hand, subjects are mapped differently for insulin sensitivity assessment when anthropometric variables are taken into account. In addition, subjects diagnosed with normal insulin sensitivity could be considered as having low insulin sensitivity when anthropometric variables are considered.

A new on-line electrocardiographic records database and computer routines for data analysis.

Gathering experimental data to test computer methods developed during a research is a hard work. Nowadays, some databases have been stored online that can be freely downloaded, however there is not a wide range of databases yet and not all pathologies are covered. Researchers with low resources are in need of more data they can consult for free. To cope with this we present an on-line portal containing a compilation of ECG databases recorded over the last two decades for research purposes. The first version of this portal contains four databases of ECG records: ischemic cardiopathy (72 patients, 3-lead ECG each), ischemic preconditioning (20 patients, 3-lead ECG each), diabetes (51 patients, 8-lead ECG each) and metabolic syndrome (25 subjects, 12-lead ECG each). In addition, one computer program and three routines are provided in order to correctly read the signals, and two digital filters along with two ECG waves detectors are provided for further processing. This portal will be constantly growing, other ECG databases and signal processing software will be uploaded. With this project, we give the scientific community a resource to avoid hours of data collection and to develop free software.

Adaptation of five indirect insulin sensitivity evaluation methods to three populations: metabolic syndrome, athletic and normal subjects.

Insulin sensitivity is determined using direct or indirect methods. Indirect methods are less invasive than direct methods, but have lower accuracy. The accuracy is set through the Spearman's rank correlation coefficient between the indirect method and a direct method. Since the set of parameters of each indirect method has been set empirically, different values of insulin sensitivity have been reported when they are applied on different populations. In this paper, five indirect methods (Avignon, HOMA-IR, QUICKI, Raynaud, and Matsuda) used to determine insulin sensitivity were adapted to three different populations: athletics, metabolic syndrome and normal subjects. The parameters of each method were varied in a range of values until the optimal value that gives the best correlation coefficient with a gold standard was obtained. Results show that the adaptation procedure led to an improved correlation coefficient. Additionally, the method of Matsuda was the most accurate, followed by the method of Avignon. We have confirmed that each indirect method needs a different set of parameters when it is applied to a specific population in order to obtain an accurate value of insulin sensitivity.

Methodology for the study of metabolic syndrome by heart rate variability and insulin sensitivity / Metodologia para o estudo da síndrome metabólica partindo da variabilidade da frequência cardíaca assim como da sensibilidade à insulina

This work presents a methodology for studying the Heart Rate Variability (HRV) and Insulin Sensitivity (IS) during the Oral Glucose Tolerance Test (OGTT) in subjects with Metabolic Syndrome (MS). For this, it was designed a clinical protocol that includes the acquisition of ECG signals during OGTT for 15 subjects with MS and 10 subjects for control group. HRV parameters were obtained from electrocardiographic recordings. Significant differences in RR values were found between groups in the 30 minutes stage of the OGTT. In control subjects the RR values were higher compared with subjects with MS. The values of normalized low frequencies between baseline stages and the stage at 30 minutes in subjects with MS showed a significant increase in sympathetic tone during the OGTT, that was not observed in group control. The following methods were implemented for quantification of IS: integral equation, insulin sensitivity index, insulin sensitivity, metabolic, HOMA and QUICKI. We found significantly lower values of IS in the group with MS. It was concluded that there are changes in the HRV and the IS in the subjects with MS, which is a pre-diabetic disease. These findings suggest that HRV and IS can be used for diagnosis of MS and prevention of Diabetes Mellitus.

Este trabalho apresenta uma metodologia para o estudo da Variabilidade da Frequência Cardíaca (VFC) e Sensibilidade à Insulina (SI) durante o Teste de Oral de Tolerância à Glicose (TOTG) em indivíduos com Síndrome Metabólica (SM). Para isso, foi projetado um protocolo clínico que inclui a aquisição de sinais ECG durante o TOTG em 15 pacientes com SM e 10 indivíduos do grupo controle. Os parâmetros da VFC foram obtidos a partir de registros eletrocardiográficos. Diferenças significativas nos valores de RR foram encontradas entre os grupos na fase de 30 minutos do TOTG. No grupo controle os valores de RR foram maiores em comparação com indivíduos com SM. Os valores normalizados de baixas frequências entre as fases da linha de base e a fase de 30 minutos em pacientes com SM mostraram um aumento significativo no tônus simpático durante o TOTG, não observado no grupo controle. Os seguintes métodos foram implementados para a quantificação de SI: integral, índice de sensibilidade à insulina, sensibilidade à insulina, metabólicos, HOMA e QUICKI. Valores significativamente menores de IS foram encontrados no grupo com MS. Podemos concluir que existem alterações na VFC e SI nos indivíduos com MS, caracterizando uma doença pré-diabética. Estas descobertas sugerem que a VFC e SI podem ser usados para o diagnóstico da SM e prevenção da Diabetes Mellitus.