Development and assessment of the disposition index based on the oral glucose tolerance test in subjects with different glycaemic status

Insulin secretion and insulin sensitivity indexes are related by hyperbolic functions, allowing the calculation of the disposition index (DI) as the product of the acute insulin response (AIR) and the insulin sensitivity index (Si) from intravenous glucose tolerance test (IVGTT). Our objective was to develop an oral-DI based on the oral glucose tolerance test (OGTT) and to assess its association with glucose tolerance status. This research is structured in three studies. Study 1: OGTT were performed in 833 non-diabetic Chilean women (18-60 years) without family history of diabetes mellitus. Study 2: an independent group of n = 57 non-diabetic (18-46 years) without family history of diabetes mellitus carried out an OGTT and an abbreviated IVGTT. Study 3: a sample of 1674 Chilean adults (18-60 years) with different glycaemic status performed an OGTT. An adequate statistical fit for a rectangular hyperbola was found between the area under the curve of insulin-to-glucose ratio (AUCI/G-R) and the Matsuda ISI-COMP index (study 1). The oral-DI derived as AUCI/G-R × ISI-COMP was previously termed insulin-secretion-sensitivity index-2 (ISSI-2). ISSI-2 significantly correlated with DI from IVGTT (rho = 0.34; p = 0.009) (study 2). ISSI-2 shows important differences across groups of subjects with different glycaemic status (study 3). We have confirmed that ISSI-2 replicates the mathematical properties of DI, showing significant correlations with DI from the abbreviated MM-IVGTT. These results indicate that ISSI-2 constitutes a surrogate measure of insulin secretion relative to insulin sensitivity and emphasizes the pivotal role of impaired insulin secretion in the development of glucose homeostasis dysregulation (AU)

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Plasma levels of interleukin-6 and interleukin-18 after an acute physical exercise: relation with post-exercise energy intake in twins

Increased interleukin-6 (IL-6) plasma levels have been described to occur during physical exercise. A relative reduction in energy intake after physical activity has also been reported after exercise, indicating a possible involvement of IL-6 as an anorexigenic factor. Given the possible effect of interleukins on appetite, we assessed whether a controlled physical activity bout is related with changes in IL-6, IL-6 soluble receptor (IL-6sR), gp130 and interleukin-18 (IL-18) plasma levels, as well as their relation with post-exercise energy intake. A co-twin intervention study was carried out with five young male monozygotic twin pairs. One co-twin performed 45 min of submaximal exercise on a treadmill near the anaerobic threshold ending with 7 min at 90 % VO2 max, while his co-twin remained non-active. Ad libitum energy intake was tested through a carbohydrate-rich meal test. Venous blood samples were drawn at baseline, immediately after exercise and after the meal ingestion. Plasma concentrations of IL-6, IL-6sR, gp130 and IL-18 were measured via ELISA. IL-6 plasma levels increased after physical activity bout (2.6-fold change; p = 0.04). A less marked trend, although still significant, was observed for plasma levels of IL-6sR and gp130. Plasma levels of IL-18 did not significantly change during exercise. The twins who exercised exhibited significantly lower energy intake (181 versus 1,195 kcal; p = 0.04), compared to the co-twins who remained resting. The present study in monozygotic twins shows increased IL-6 plasma levels after acute physical exercise with a significant reduction in energy intake, supporting a linkage between IL-6 and acute post-exercise eating behaviour (AU)