A lipid-parameter-based index for estimating insulin sensitivity and identifying insulin resistance in a healthy population.

AIM: Insulin resistance needs to be identified as early as possible in its development to allow targeted prevention programmes. Therefore, we compared various fasting surrogate indices for insulin sensitivity using the euglycaemic insulin clamp in an attempt to develop the most appropriate method for assessing insulin resistance in a healthy population. METHODS: Glucose, insulin, proinsulin, glucagon, glucose tolerance, fasting lipids, liver enzymes, blood pressure, anthropometric parameters and insulin sensitivity (Mffm/I) using the euglycaemic insulin clamp were obtained for 70 normoglycaemic non-obese individuals. Spearman's rank correlations were used to examine the association between Mffm/I and various fasting surrogate indices of insulin sensitivity. A regression model was used to determine the weighting for each variable and to derive a formula for estimating insulin resistance. The clinical value of the surrogate indices and the new formula for identifying insulin-resistant individuals was evaluated by the use of receiver operating characteristic (ROC) curves. RESULTS: The variables that best predicted insulin sensitivity were the HDL-to-total cholesterol ratio, the fasting NEFA and fasting insulin. The use of the lipid-parameter-based formula Mffm/I=12x[2.5x(HDL-c/total cholesterol)-NEFA] - fasting insulin appeared to have high clinical value in predicting insulin resistance. The correlation coefficient between Mffm/I and the new fasting index was higher than those with the most commonly used fasting surrogate indices for insulin sensitivity. CONCLUSION: A lipid-parameter-based index using fasting samples provides a simple means of screening for insulin resistance in the healthy population.

Influence of dietary fat on postprandial glucose metabolism (exogenous and endogenous) using intrinsically (13)C-enriched durum wheat.

The present study evaluates the influence of different amounts of fat added to starch on postprandial glucose metabolism (exogenous and endogenous). Nine women (24 (se 2) years old, BMI 20.4 (se 0.7) kg/m(2)) ingested 1 week apart 75 g glucose equivalent of (13)C-labelled starch in the form of pasta without (low fat; LF) or with 15 (medium fat; MF) or 40 (high fat; HF) g sunflower oil. During the 7 h following meal consumption, plasma glucose, non-esterified fatty acids, triacylglycerols (TG) and insulin concentrations, and endogenous (using [6,6-(2)H(2)]glucose) and exogenous glucose turnover were determined. With MF and HF meals, a lower postprandial glucose peak was observed, but with a secondary recovery. A decrease in exogenous glucose appearance explained lower glycaemia in HF. At 4 h after the HF meal the insulin, insulin:glucose and postprandial blood TG were higher than those measured after the LF and MF meals. Despite higher insulinaemia, total glucose disappearance was similar and endogenous glucose production was suppressed less than after the LF and MF meals, suggesting insulin resistance. Thus, the addition of a large amount of fat appears to be unfavourable to glucose metabolism because it leads to a feature of insulin resistance. On the contrary, the MF meal did not have these adverse effects, but it was able to decrease the initial glycaemic peak.

Is advice for breakfast consumption justified? Results from a short-term dietary and metabolic experiment in young healthy men.

Short-term (2 weeks) effects of the consumption of a high-energy (2920 kJ (700 kcal)) or low-energy (418 kJ (100 kcal)) breakfast on dietary patterns, blood variables and energy expenditure (indirect calorimetry) were compared in ten free-living healthy young men in a crossover study. During the high-energy breakfast, total energy intake was increased, the intake of protein and lipids was unchanged but the intake of carbohydrates was increased. Thus, 48 (sd 4)% of energy came from carbohydrates in the high-energy breakfast compared with 42 (sd 5)% in the low-energy breakfast. Excluding breakfast, the macronutrient composition of the diet remained identical in the two situations. After the high-energy breakfast, fasting serum triacylglycerol concentration was higher and HDL-cholesterol concentration was lower than after the low-energy breakfast. A high glycaemic response was observed in the morning after the high-energy breakfast period, while there was a peak of free fatty acids after the low-energy breakfast. The high-energy breakfast induced a strong inhibition of fat oxidation throughout the day. Although long-term adaptation to a high-energy breakfast cannot be excluded, the high-energy breakfast in this study did not appear to be favourable to health. Our results do not support the current advice to consume more energy at breakfast.