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ABSTRACT: Central fat mass (CFM) correlates with insulin resistance and increases the risk of type 2 diabetes and cardiovascular complications. On the other hand, increased peripheral fat mass (PFM) is associated with higher insulin sensitivity. Thus, we examined the contribution of adipose tissue distribution, as assessed by the PFM/CFM ratio, to insulin sensitivity in overweight and obese postmenopausal women.
A total of 124 nondiabetic overweight and obese postmenopausal women underwent an oral glucose tolerance test (OGTT) and a hyperinsulinemic/euglycemic (HI) clamp. Body composition was determined using computed tomography for visceral adipose tissue (VAT) and dual X-ray absorptiometry for fat mass, lean body mass and their respective proportions. Participants were divided by tertiles of the PFM/CFM ratio.
Participants with preferential CFM (group 1) had higher fasting insulin levels and insulin area under the curve (AUC) during OGTT, as well as lower glucose infusion rates during the HI clamp, whether it was expressed per kg of body weight (M) or per kg of fat-free mass (Mm), compared with the other two groups. The PFM/CFM ratio also correlated significantly with fasting insulin (r=-0.32, P<0.001), the insulin AUC (r=-0.42 P<0.001), M (r=0.39 P<0.001) and Mm (r=0.37 P<0.001). Using hierarchical regression, we demonstrated that the PFM/CFM ratio was an independent predictor of insulin AUC, M and Mm and that its sequential addition to CFM and VAT improved significantly the predictive value of the model for insulin sensitivity for all variables except fasting insulin.
The PFM/CFM ratio, which integrates the antagonistic effects of both central and peripheral depots on insulin sensitivity, added substantially to the prediction of insulin sensitivity over VAT and CFM alone.
International journal of obesity (2005) 10/2008; 32(11):1626-32. · 4.34 Impact Factor
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ABSTRACT: HOMA and QUICKI are the most widely used indices for assessing insulin sensitivity. Both are based on fasting glucose and insulin measures, and mainly differ by the log transformation of these variables in QUICKI. However, HOMA is less reproducible than QUICKI, and log HOMA does not improve its reproducibility. The aim of this study was to investigate the various mathematical transformations of HOMA and to assess its reproducibility.
We used data from a clamp study involving 123 non-diabetic overweight and obese postmenopausal women. Fasting insulin and glucose were measured in two visits 15 and 30 days apart. This allowed us to calculate HOMA as (fasting glucose [mmol/L] x fasting insulin [microU/mL])/22.5 and QUICKI as 1/(log fasting glucose [mg/dL]+log fasting insulin [microU/mL]) twice for subjects who were weight-stable between visits.
QUICKI had better reproducibility (CV=3.9%) than either HOMA (CV=26.7%) or log HOMA (CV=22.0%). However, log-transforming HOMA using log (glucose x insulin)/log (22.5) and log-transforming HOMA without transforming the constant denominator improved its CV to 6.5% and 5.7%, respectively.
By modifying the mathematical expression of HOMA, we were able to achieve comparable CVs for QUICKI and HOMA. However, the CV should be used to assess the reproducibility of techniques to measure glucose and insulin, not of mathematical formulas. When evaluating indices for the assessment of insulin sensitivity, the key point is how well they correlate with the 'gold-standard' glucose clamp.
Diabetes & Metabolism 07/2008; 34(3):294-6. · 2.41 Impact Factor
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ABSTRACT: The purpose of this study was to compare assessment of insulin sensitivity from hyperinsulinemic euglycaemic (HIEG) clamp with indexes derived from fasting and oral glucose tolerance test (OGTT).
Cross-sectional study with 107 sedentary non-diabetic overweight and obese postmenopausal (BMI=32.4+/-0.4 kg/m(2)) women undergoing both HIEG clamp and OGTT. Pairs of data were analyzed using Pearson correlation and Bland-Altman graphs analysis. Comparison between correlations was made using the method reported by Zar.
All the indexes derived from either the OGTT or surrogate indexes were highly correlated with all the clamp-derived formulas (P<0.0001). However, HOMA and QUICKI were generally less correlated than OGTT-derived indexes. Analogically to QUICKI, we calculated a new formula derived from the OGTT measurements of glucose and insulin named simple index assessing insulin sensitivity (SI(is)OGTT)=1/[log(sum glucose t(0-30-90-120)) (mmol/l)+log(sum insulin t(0-30-90-120)) (microUI/ml)]. By using this formula, we found high significant correlations (r's=0.61-0.65; P<0.0001) with the clamp results. Moreover, the correlations of SI(is)OGTT with the clamp data were higher than for other previously published indexes.
In that large group of non-diabetic overweight and obese postmenopausal women insulin sensitivity index derived from OGTT provided more accurate information than fasting based formula. We propose a new simple index for the assessment of insulin sensitivity from the OGTT data (SI(is)OGTT). The advantage of this new formula over all previously published OGTT-derived indexes of insulin sensitivity is that it is 1) easy to calculate 2) better correlated than other indexes of insulin sensitivity and 3) not affected by the way clamp results are expressed. Further studies are needed to validate SI(is)OGTT index in other populations.
Diabetes & Metabolism 09/2007; 33(4):261-8. · 2.41 Impact Factor
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ABSTRACT: There is considerable interest in validating the most convenient method to estimate insulin sensitivity in clinical research protocols that could best indicate cardiovascular risk factors. To address this issue we examined the interrelationships of several cardiovascular risk factors with surrogate indexes such as fasting insulin, the homeostasis model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI) and the revised QUICKI vs the euglycaemic-hyperinsulinemic (EH) clamp in a non-diabetic overweight or obese postmenopausal female population.
Cross-sectional study involving 88 obese postmenopausal women (age: 57.5+/-5.0 yrs; body mass index: 32.52+/-4.4 kg/m2; percent body fat: 46.35+/-4.9%).
Insulin sensitivity was determined by the EH clamp technique as well as by surrogate indexes such as fasting insulin, HOMA, log HOMA, QUICKI and revised QUICKI. Body composition and body fat distribution were measured using dual energy x-ray absorptiometry and computed tomography, respectively.
Correlations between insulin resistance indexes (fasting insulin, revised QUICKI, QUICKI, log HOMA, HOMA) vs glucose disposal were similar (range of r's=0.40 to 0.49), suggesting that no index was superior to another with respect to its relationship with the EH clamp. Correlations between the insulin resistance indexes with plasma lipids were comparable among all indexes, however, systolic blood pressure, visceral fat and C-reactive protein were moderately superior with index vs the EH clamp.
Surrogate measures of insulin resistance, in particular fasting insulin, are simple tools appropriate for epidemiological studies that can be used as substitutes for the EH clamp to estimate glucose disposal and cardiovascular risk factors in overweight and obese postmenopausal women.
Diabetes & Metabolism 07/2006; 32(3):251-5. · 2.41 Impact Factor
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Diabetes & Metabolism 03/2006; 32(1):90-1. · 2.41 Impact Factor
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Diabetes Obesity and Metabolism 12/2004; 6(6):456-7. · 3.38 Impact Factor
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ABSTRACT: AimHOMA and QUICKI are the most widely used indices for assessing insulin sensitivity. Both are based on fasting glucose and insulin measures, and mainly differ by the log transformation of these variables in QUICKI. However, HOMA is less reproducible than QUICKI, and log HOMA does not improve its reproducibility. The aim of this study was to investigate the various mathematical transformations of HOMA and to assess its reproducibility.MethodWe used data from a clamp study involving 123 non-diabetic overweight and obese postmenopausal women. Fasting insulin and glucose were measured in two visits 15 and 30 days apart. This allowed us to calculate HOMA as (fasting glucose [mmol/L] × fasting insulin [μU/mL])/22.5 and QUICKI as 1/(log fasting glucose [mg/dL] + log fasting insulin [μU/mL]) twice for subjects who were weight-stable between visits.ResultsQUICKI had better reproducibility (CV = 3.9%) than either HOMA (CV = 26.7%) or log HOMA (CV = 22.0%). However, log-transforming HOMA using log (glucose × insulin)/log (22.5) and log-transforming HOMA without transforming the constant denominator improved its CV to 6.5% and 5.7%, respectively.ConclusionBy modifying the mathematical expression of HOMA, we were able to achieve comparable CVs for QUICKI and HOMA. However, the CV should be used to assess the reproducibility of techniques to measure glucose and insulin, not of mathematical formulas. When evaluating indices for the assessment of insulin sensitivity, the key point is how well they correlate with the ‘gold-standard’ glucose clamp.RésuméObjectifsHOMA et QUICKI sont les indices simples d’évaluation de la sensibilité à l’insuline les plus utilisés. Ils diffèrent par leur mode d’expression utilisant ou non une transformation logarithmique. Cependant, HOMA est moins reproductible que QUICKI et sa transformation logarithmique n’améliore pas sa reproductibilité. Nous avons étudié différentes formulation mathématiques de HOMA ainsi que leur reproductibilité.MéthodesNous avons utilisé les données issues d’une étude de clamp réalisée chez 123 femmes ménopausées non diabétiques obèses ou en surpoids. Les indices HOMA [glycémie mmol/l × insulinémie μU/ml à jeun]/22,5 et QUICKI (1/([log glycémie mg/dl + log insulinémie μU/ml] à jeun) ont été réalisées lors de deux consultations distinctes espacées de 15 à 30 jours chez des sujets en poids stable.RésultatsL’indice QUICKI a une meilleure reproductibilité (CV = 3,9 %) que HOMA (CV = 26,7 %) ou log HOMA (CV = 22,0 %). Cependant, quand on réalise la transformation logarithmique de HOMA en séparant numérateur et dénominateur ou en excluant de celle-ci le dénominateur, on trouve des CV à 6,5 et 5,7 %, comparables à ceux obtenus pour QUICKI.ConclusionPour choisir un index d’estimation de la sensibilité à l’insuline, il est important de s’assurer de sa validité d’estimation par rapport à la méthode de référence du clamp et de vérifier que le CV des méthodes de mesures des glycémies et insulinémies soit le meilleur possible. Le choix entre HOMA et QUICKI ne doit pas être déterminé par le CV des formules.
Diabetes & Metabolism.
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ABSTRACT: BackgroundThere is considerable interest in validating the most convenient method to estimate insulin sensitivity in clinical research protocols that could best indicate cardiovascular risk factors. To address this issue we examined the interrelationships of several cardiovascular risk factors with surrogate indexes such as fasting insulin, the homeostasis model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI) and the revised QUICKI vs the euglycaemic-hyperinsulinemic (EH) clamp in a non-diabetic overweight or obese postmenopausal female population.DesignCross-sectional study involving 88 obese postmenopausal women (age: 57.5±5.0 yrs; body mass index: 32.52±4.4 kg/m2; percent body fat: 46.35±4.9%).MethodsInsulin sensitivity was determined by the EH clamp technique as well as by surrogate indexes such as fasting insulin, HOMA, log HOMA, QUICKI and revised QUICKI. Body composition and body fat distribution were measured using dual energy x-ray absorptiometry and computed tomography, respectively.ResultsCorrelations between insulin resistance indexes (fasting insulin, revised QUICKI, QUICKI, log HOMA, HOMA) vs glucose disposal were similar (range of r's=0.40 to 0.49), suggesting that no index was superior to another with respect to its relationship with the EH clamp. Correlations between the insulin resistance indexes with plasma lipids were comparable among all indexes, however, systolic blood pressure, visceral fat and C-reactive protein were moderately superior with index vs the EH clamp.ConclusionSurrogate measures of insulin resistance, in particular fasting insulin, are simple tools appropriate for epidemiological studies that can be used as substitutes for the EH clamp to estimate glucose disposal and cardiovascular risk factors in overweight and obese postmenopausal women.RésuméComparaison de la mesure directe de la sensibilité à l'insuline à son évaluation par des index comme indicateur de la résistance à l'insuline et du risque cardiovasculaire chez des femmes en surpoids ou obèses post-ménopausiquesIntroductionL'évaluation de la sensibilité à l'insuline est primordiale dans les protocoles de recherche clinique. Bien que plusieurs index soient couramment utilisés, il existe peu de comparaison de ces index avec la technique de référence, le clamp euglycémique hyperinsulinémique. Nous avons évalué l'association de ces index et du clamp avec l'utilisation du glucose ainsi que de multiples facteurs de risque cardiovasculaire.Matériels et méthodesÉtude transversale d'une cohorte (n = 88) de femmes obèses post-ménopausiques non diabétiques dont le phénotype a été étudié en détail : composition corporelle, profil lipidique, pression artérielle et sensibilité à l'insuline grâce au clamp hyperinsulinémique-euglycémique. Comparaison de différents index d'évaluation de la sensibilité : insulinémie, HOMA, Log HOMA QUICKI, QUICKI révisé avec les résultats du clamp hyperinsulinémi-que-euglycémique pour leur association avec l'utilisation du glucose ainsi que de multiples facteurs de risque cardiovasculaire : cholestérol total, cholestérol LDL, triglycérides, cholestérol HDL à jeun, pression artérielle, tissu adipeux viscéral et protéine C-réactive (CRP).RésultatsTous les index sont corrélés de façon comparable avec le clamp hyperinsulinémique-euglycémique pour l'utilisation du glucose (r compris entre 0,40 et 0,49). La corrélation avec les paramètres du bilan lipidique est comparable pour toutes les méthodes de mesure de la sensibilité à l'insuline. En revanche, la corrélation entre la pression artérielle ou la CRP et les index est légèrement supérieure à celle observée avec le clamp hyperinsulinémique-euglycémique.ConclusionCes résultats suggèrent que les index, y compris l'insu-linémie à jeun, sont des outils acceptables dans les études épidémio-logiques pour évaluer tant l'utilisation du glucose que la plupart des facteurs de risque cardiovasculaire chez les femmes obèses post-ménopausiques.
Diabetes & Metabolism.
