Evaluation of the impact of orally administered carbohydrates on postprandial blood glucose levels in different pre-clinical models

ABSTRACT We developed a pre-clinical model in which to evaluate the impact of orally administered carbohydrates on postprandial blood glucose levels. For this purpose, we compared the effects of different carbohydrates with well-established glycemic indexes. We orally administered (gavage) increasing amounts (0.2, 0.4, 0.6, 0.8, and 1.0 g/kg) of sucrose and lactose to rats which had been fasted for 6 h or 15 h, respectively. In part of the experiments we administered frutose (gavagem). Three different models were compared for measuring postprandial blood glucose levels: a) evaluation of interstitial glucose concentrations by using a real time continuous glucose monitoring system; b) evaluation of glucose levels in blood obtained from the rat tail; c) evaluation of serum glucose levels in blood collected after decapitation. Our results showed that blood obtained from the tails of 15-h fasted rats was the best model in which to evaluate the effect of carbohydrates on postprandial blood glucose levels

Specific types of colonic fermentation may raise low-density-lipoprotein-cholesterol concentrations

To assess the effects of increased colonic fermentation on serum lipids, eight healthy volunteers were placed on two identical 2-wk metabolic diets, one of which was supplemented with lactulose (18-25 g/d). Lactulose raised day-long concentrations of breath hydrogen and serum glutamine as indicators of increased colonic fermentation by 78 +/- 13% (P less than 0.001) and 24.7 +/- 9.5% (P less than 0.05), respectively). Unexpectedly, however, fasting serum total and low-density-lipoprotein cholesterol and apolipoprotein B concentrations were higher at 2 wk by 8.9 +/- 1.5% (P less than 0.001), 10.9 +/- 2.2% (P less than 0.005), and 18.9 +/- 5.9% (P less than 0.02), respectively, compared with the control diet. With lactulose, mean free fatty acid concentrations were reduced over the day by 19.5 +/- 5.9% (P less than 0.02), with no change in mean day-long blood glucose, serum insulin, or C-peptide concentrations. We conclude that certain rapidly fermented substrates may raise rather than lower serum lipids, possibly through increasing the amount of acetate absorbed from the colo

Measuring the glycemic index of foods : interlaboratory study

Background: Many laboratories offer glycemic index (GI) services. Objective: We assessed the performance of the method used to measure GI. Design: The GI of cheese-puffs and fruit-leather (centrally provided) was measured in 28 laboratories (n = 311 subjects) by using theFAO/WHOmethod. The laboratories reported the results of their calculations and sent the raw data for recalculation centrally. Results: Values for the incremental area under the curve (AUC)reported by 54% of the laboratories differed from central calculations. Because of this and other differences in data analysis, 19% of reported food GI values differed by >5 units from those calculated centrally. GI values in individual subjects were unrelated to age, sex,ethnicity, body mass index, or AUC but were negatively related to within-individual variation (P = 0.033) expressed as the CV of the AUC for repeated reference food tests (refCV). The betweenlaboratory GI values (mean +- SD) for cheese-puffs and fruit-leather were 74.3 +- 10.5 and 33.2 +- 7.2, respectively. The mean laboratory GI was related to refCV (P = 0.003) and the type of restrictions on alcohol consumption before the test (P = 0.006, r^2 = 0.509 for model). The within-laboratory SD of GI was related to refCV (P <0.001), the glucose analysis method (P = 0.010), whether glucose measures were duplicated (P = 0.008), and restrictions on dinner the night before (P = 0.013, r^2 = 0.810 for model). Conclusions: The between-laboratory SD of the GI values is about 9. Standardized data analysis and low within-subject variation (refCV <30%) are required for accuracy. The results suggest that common misconceptions exist about which factors do and do not need to be controlled to improve precision. Controlled studies and cost-benefit analyses are needed to optimize GI methodology. The trial was registered at clinicaltrials.gov as NCT00260858