The viscosity of soluble fibers such as β‐glucan depends on their concentration in solution and molecular weight (MW) distribution. We investigated whether freezing treatment of oat bran muffins affected the physicochemical properties of β‐glucan, and its physiological effectiveness in lowering postprandial blood glucose response. A controlled range of β‐glucan solubility was achieved by subjecting oat bran muffins containing two levels of β‐glucan to repeated freeze‐thaw temperature cycling. β‐Glucan solubilized by in vitro digestion extraction was measured by flow‐injection analysis. MW distributions of β‐glucan were analyzed using size‐exclusion chromatography. β‐Glucan solubility decreased as the number of freeze‐thaw cycles increased, while MW distribution of β‐glucan decreased slightly. Peak blood glucose rise (PBGR) after fresh muffins (8 and 12 g of β‐glucan/serving) was significantly lower than that after muffins (8 and 12 g of β‐glucan/serving) treated with four freeze‐thaw (FT) cycles (1.84 ± 0.2 vs. 2.31 ± 0.1 mmol/L, P = 0.007). Compared with the control whole wheat muffins, the reduction in incremental area under the glucose response curve (AUC) after fresh muffins (8 and 12 g of β‐glucan/serving) was nearly twice that after 4 FT cycles (43.3 ± 4.4% vs. 27.0 ± 5.4%, P = 0.016). A significant inverse linear relationship was found between the log [concentration] of extractable β‐glucan and PBGR (r2 = 0.85, P = 0.01), and AUC (r2 = 0.71, P = 0.03). The results show that reduction of β‐glucan solubility in foods attenuates its physiological effectiveness in lowering postprandial glycemia.
The hypoglycemic effect of fat and protein was not blunted by insulin resistance. Protein increased insulin but had no effect on C-peptide or the insulin secretion rate, which suggests decreased hepatic insulin extraction or increased C-peptide clearance.
Background/Objectives: a criticism of glycemic index (GI) is that it does not indicate the insulin response of foods (insulinemic index, II). However, it is unknown if the GI and II values of foods are equivalent in all subjects, a necessary criterion for clinical utility. We compared GI and II values in non-diabetic subjects with fasting-serum-insulin (FSI) o40 pmol/l (healthy control) or with FSI X40 pmol/l (hyper [I]) and subjects with type 2 diabetes (T2DM), and to see whether GI and II were related to the serum-glucose concentrations, insulin sensitivity, b-cell function and hepatic insulin extraction (HIE) of the subjects. Subjects/Methods: Serum-glucose, -insulin and -C-peptide responses after 50 g available-carbohydrate portions of glucose (tested three times by each subject), sucrose, instant mashed-potato, white-bread, polished-rice and pearled-barley were measured in healthy control (n ¼ 9), hyper[I] (n ¼ 12) and T2DM (n ¼ 10) subjects. Results: Food GI values did not differ significantly among the three subject groups, whereas II values were higher in T2DM (100 ± 7) than healthy controls (78 ± 5) and hyper[I] subjects (70 ± 5) (mean ± s.e.m., P ¼ 0.05). II was inversely associated with insulin sensitivity (r ¼ À0.66, Po0.0001) and positively related to fasting-and postprandial-glucose (both r ¼ 0.68, Po0.0001) and HIE (r ¼ 0.62, P ¼ 0.0002). In contrast, GI was not related to any of the biomarkers (P40.05). Conclusion: The GI is a valid property of foods because its value is similar in healthy control, hyper [I] and T2DM subjects, and is independent of subjects' metabolic status. However, II may depend upon the glycaemic control, insulin sensitivity and HIE of the subjects.
Background: Insulin resistance is commonly assessed using the homeostasis model assessment (HOMA) variants. HOMA is potentially insensitive to change because of its high coefficient of variation. The repeatability coefficient is an alternative means of assessing test repeatability. To be confident of clinical change, rather than biological variation, a subsequent test needs to differ from the former by more than the repeatability coefficient using the equation.Test 1 = Test 2 ± repeatability coefficient.The repeatability coefficients for measures of insulin resistance are unknown.Aim: To compare the repeatability coefficient of HOMA2 variants (Beta-cell function [%B], insulin sensitivity [%S], insulin resistance [IR]) to a dynamic measure of insulin resistance, and the oral glucose insulin sensitivity (OGIS) test.Setting: The raw data from a previously used data set were reanalysed.Methods: Glycaemic and insulinaemic tests were performed on 32 men and women both with (n = 10) and without type 2 diabetes (n = 22). From these data, eight fasting tests and three 50-g oral glucose tolerance tests were used to calculate HOMA2 and OGIS. The methods of Bland and Altman assessed repeatability.Results: Repeatability coefficients for all participants for the HOMA2 %B, %S and IR variants were 72.91, 189.75 and 0.9, which equates to 89%, 135% and 89% of their respective grand means. By contrast, OGIS had a repeatability coefficient of 87.13, which equates to 21% of the grand mean.Conclusion: Because of the high repeatability coefficient relative to the grand mean, use of HOMA2 measures for assessing insulin resistance in small population studies should be reconsidered.
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