Diabetes mellitus is a metabolic disease spreading worldwide that has been reported to worsen the development and progression of other diseases (cancer, vascular diseases and dementia). To establish functional rice lines with anti-postprandial hyperglycaemic effects, we developed mutant rice lines, which lack one or two gene(s) related to starch synthesis, and evaluated their effects. Powder of mutant rice lines or other grains was loaded to rats fasted overnight (oral grain powder loading test). Incremental area under time-concentration curves (iAUC) were calculated with monitored blood glucose levels. Rice lines with anti-postprandial hyperglycaemic effects were separated by cluster analysis with calculated iAUC. A double mutant rice #4019 (starch synthase IIIa (ss3a)/branching enzyme IIb (be2b)), one of the screened mutant rice lines, was fed to Goto-Kakizaki (GK) rats, an animal model for type 2 diabetes, for 5 weeks. Plasma levels of C-peptide, a marker of pancreatic insulin secretion, were measured with ELISA. For in vitro study, a rat pancreatic cell line was cultured with a medium containing rat serum which was sampled from rats fed #4019 diet for 2 d. After 24-h of incubation, an insulin secretion test was performed. Through the oral rice powder loading test, seven rice lines were identified as antidiabetic rice lines. The intake of #4019 diet increased plasma C-peptide levels of GK rats. This result was also observed in vitro. In rat serum added to cell medium, ornithine was significantly increased by the intake of #4019. In conclusion, the mutant rice #4019 promoted pancreatic insulin secretion via elevation of serum ornithine levels.

The glycaemic and insulin indices assess postprandial glycaemic and insulin response to foods, respectively, which may not reflect the long-term effects of diet on insulin response. We developed and evaluated the validity of four empirical indices to assess the insulinaemic potential of usual diets and lifestyles, using dietary, lifestyle and biomarker data from the Nurses’ Health Study (NHS, n 5812 for hyperinsulinaemia, n 3929 for insulin resistance). The four indices were as follows: the empirical dietary index for hyperinsulinaemia (EDIH) and the empirical lifestyle index for hyperinsulinaemia (ELIH); the empirical dietary index for insulin resistance (EDIR) and the empirical lifestyle index for insulin resistance (ELIR). We entered thirty-nine FFQ-derived food groups in stepwise linear regression models, and defined indices as patterns most predictive of fasting plasma C-peptide, for the hyperinsulinaemia pathway (EDIH and ELIH), and of theTAG:HDL-cholesterol ratio, for the insulin-resistance pathway (EDIR and ELIR). We evaluated the validity of indices in two independent samples from NHS-II and Health Professionals Follow-up Study (HPFS) using multivariable-adjusted linear regression analyses to calculate relative concentrations of biomarkers. The EDIH is comprised of eighteen food groups; thirteen were positively associated with C-peptide and five were inversely associated. The EDIR is comprised of eighteen food groups; ten were positively associated with TAG:HDL-cholesterol and eight were inversely associated. Lifestyle indices had fewer dietary components, and included BMI and physical activity as components. In the validation samples, all indices significantly predicted biomarker concentrations – for example, the relative concentrations of the corresponding biomarkers comparing extreme index quintiles in the HPFS were EDIH, 1·29 (95 % CI 1·22, 1·37); ELIH, 1·78 (95 % CI 1·68, 1·88); EDIR, 1·44 (95 % CI 1·34, 1·55); and ELIR, 2·03 (95 % CI 1·89, 2·19); all Ptrend<0·0001. The robust associations of these novel hypothesis-driven indices with insulin response biomarker concentrations suggest their usefulness in assessing the ability of whole diets and lifestyles to stimulate and/or sustain insulin secretion.

In addition to a yet-to-be published study showing arabinose to have an inhibiting effect on maltase, in vitro studies have shown l-arabinose to exert an inhibiting effect on small-intestinal sucrase and maltase and the consumption of a sucrose-rich drink containing l-arabinose to exert positive effects on postprandial blood glucose, insulin and C-peptide responses in humans. However, the effects of adding l-arabinose to mixed meals on the indices of glucose control are unknown. The purpose of the present study was to investigate whether the positive effects of l-arabinose added to a sugar drink could be reproduced in subjects consuming a mixed meal containing sucrose and/or starch from wheat flour. A total of seventeen healthy men participated in study 1, a randomised, double-blind, cross-over trial. In this study, the subjects consumed two different breakfast meals containing sucrose and starch from wheat flour (meal A) or starch from wheat flour (meal B) supplemented with 0, 5 and 10 % l-arabinose by weight after a 12 h fast. A total of six healthy men participated in study 2, a randomised, double-blind, cross-over trial. In this study, the subjects also consumed meal B served in two different textures and a liquid meal with maltose supplemented with 0 and 20 % l-arabinose. In addition, 1·5 g of paracetamol was chosen as an indirect marker to assess gastric emptying. Postprandial plasma glucose, insulin and C-peptide concentrations were measured regularly for 3 h. The results of the present study showed that the peak plasma concentration, time to reach peak plasma concentration or AUC values of glucose, insulin and C-peptide were not altered after consumption of the test meals. Overall, it was not possible to reproduce the beneficial effects of l-arabinose added to sucrose drinks when l-arabinose was mixed in a solid or semi-solid mixed meal.

Our objective was to study the cross-sectional associations between concentrations of α- and γ-tocopherol and concentrations of glucose, glycosylated haemoglobin, insulin and C-peptide among US adults. We used data for 1289 participants without self-reported diabetes who were aged ≥20 years in the National Health and Nutrition Examination Survey 1999–2000. α-Tocopherol concentration was inversely associated with glucose concentration (β per mmol/l=−0·01064, se 0·00356, P=0·004) after adjusting for age, sex, race or ethnicity, education, smoking status, concentrations of total cholesterol and triacylglycerols, systolic blood pressure, waist circumference, alcohol use, physical activity, time watching television or videos or using a computer, and use of vitamin/mineral/dietary supplements. Among 659 participants who did not report using supplements, this association was no longer significant whereas the concentration of α-tocopherol was inversely associated with concentration of C-peptide (β per mmol/l=−0·01121, se 0·00497, P=0·024). γ-Tocopherol concentration was positively associated with concentration of glucose (β per mmol/l=0·09169, se 0·02711, P=0·001) and glycosylated haemoglobin (β per mmol/l=0·04954, se 0·01284, P<0·001), but not insulin or C-peptide. The relationships between physiologic concentrations of the various forms of vitamin E and measures of glucose intolerance deserve additional investigation.

Altogether twenty-six elderly subjects (aged 65–74 years) with persistent impaired glucose tolerance (World Health Organization (1985) criteria) identified in a population-based study, were randomly treated either with chromium-rich yeast (160 μg Cr/d) or with placebo for 6 months. The 24 h urinary Cr increased from 0.13 (se 0.03) to 0.40 (se 0.06) μg/d in the Cr group (n 13) but no change was found in the placebo group (n 11) (0.13 (se 0.02) v. 0.11 (se 0.02) μg/d). No significant change was observed in the oral glucose tolerance test (glucose dose 75 g; 0, 1 and 2 h blood glucose respectively): 5.3 (se 0.1), 9.3 (se 0.3), 8.2 (se 0.3) mmol/l v. 5.0 (se 0.1), 8.5 (se 0.4), 7.3 (se 0.5) mmol/l in the Cr group; 4.9 (se 0.2), 9.2 (se 0.6), 8.1 (se 0.3) mmol/l v. 4.8 (se 0.2), 8.5 (se 0.5), 7.0 (se 0.6) mmol/l in the placebo group (baseline v. 6 months). Glycosylated haemoglobin, plasma insulin, C-peptide and apolipoprotein Al and B levels remained unchanged, and no improvement was seen in serum total cholesterol (6.2 (se 0.3) v. 6.4 (se 0.3) mmol/l for the Cr group, 6.2 (se 0.4) v. 6.5 (se 0.3) mmol/l for the placebo group), high-density-lipoprotein-cholesterol (1.1 (se 0.1) v. 1.2 (se 0.1) mmol/l for the Cr group, 1.0 (se 0.1) v. 1.1 (se 0.1) mmol/l for the placebo group) or triacylglycerols (2.5 (se 0.4) v. 2.0 (se 0.4) mmol/l for the Cr group, 2.4 (se 0.2) v. 2.5 (se 0.2) mmol/l for the placebo group). The present results indicate that Cr supplementation does not improve glucose tolerance or serum lipid levels in elderly subjects with stable impaired glucose tolerance.