Simulation of a computed HbA1c using a weighted average glucose.

BACKGROUND: The A1c-derived average glucose examined the link between the glycated haemoglobin and the estimated average glucose, and provided a linear relation between them. Other studies proved that, over a period of 4 months, plasma glucose in the preceding 30 days contribute to about 50 % to the glycated haemoglobin value while the other 50 % is due to the remaining 3 months altogether. TECHNICAL DETAILS OF THE METHOD: In this technical note, we propose a weighted method assuming that the contribution of glucose to glycated haemoglobin over 3 months is chronologically 20 %, 30 % and 50 % respectively. A comparison is made with the linear regression method which uses the same estimated average glucose over the whole period. Results yielded by the weighted method are also compared to those given by the model proposed by Ladyzynski et al. FINDINGS: A simulation is carried out on data assumed to come from a first individual with nearly the same level of glucose over 3 months, a second individual who starts with high levels of glucose and then reaches a stabilised low level by the last month, and finally, a third case who had just been diagnosed with diabetes during the last month whereas he/she had a normal glycaemia during the preceding 2 months. The weighted method gives more realistic values of HbA1c (7.36 %, 6.80 %, 8.49 %) than the linear regression method without weights which gives the same value (7.45 %) for the three cases. Another comparison shows that the three values given by the weighted method are slightly smaller than the corresponding values given by the model of Ladyzynski et al. (7.62 %, 7.02 %, 8.8 %) but the relative variation is nearly the same for the three values (≈3 %). CONCLUSSION: Without regular self-testing and day-to-day insights, a sole HbA1c value can be confusing and misleading. For physicians and patients, a clear understanding of the relationship between the weighted average glucose and HbA1c is necessary in order to set an appropriate daily control depending on whether the glucose is stabilized over the whole period, at the beginning, at the end; or still under recurrent episodes of high and low levels. The measured HbA1c at a biological laboratory gives no indication on glucose variation. Moreover, low values of glucose may cancel high values and lead to a "good" average glucose and ideal glycated haemoglobin.

Allergenicity of some isoforms of white sesame proteins.

BACKGROUND: Allergy to sesame seeds is often associated with particularly severe reactions, with a high risk of anaphylaxis. The increase in reports of allergic reactions to sesame is probably due to the growing use of sesame seeds or sesame oil in food. OBJECTIVE: To determine the molecular weights of the proteins in three variety of sesame seeds and to study the isoelectric points and the allergenicity of white sesame proteins. METHODS: Extracts of white, brown and black sesame seeds were prepared. The white sesame extract, mostly used in bakery, was run on SDS-PAGE and two dimensional electrophoresis. Six sera from patients sensitized or symptomatic to sesame seed were used for Western blotting. RESULTS: The protein patterns of the white, brown and black sesame extracts showed major quantitative differences. The white extract had the higher protein concentration and contained 15 proteins of 12-79 kDa, some of them having several acidic isoelectric points. The lowest isoelectric point was 4.9 and the highest was 6.4, giving 35 isoforms. Ten of the 15 proteins (12-57.5 kDa) were recognized by specific IgE. The 12-13 kDa and 22-33 kDa proteins could correspond to the main allergens. CONCLUSION: White sesame seeds contain at least 10 allergenic proteins with acidic isoelectric points. In accordance with previous results, two of them seem to contain the major allergens.

Influence of refining steps on trace allergenic protein content in sunflower oil.

BACKGROUND: Although allergy to sunflower seed and oil is a relatively rare occurrence, several cases of sunflower seed allergy have been observed, and we have already described one case of anaphylaxis after eating sunflower oil and margarine. OBJECTIVE: The aim of our study was to determine and characterize the allergens from sunflower oil at the different steps of the refining process: crude pressed oil (step A), acidification and neutralization (step B), pregumming by centrifugation (step C), washing (step D), bleaching (step E), gumming by filtration (step F), and deodorization (step G). METHODS: A sample of oil from each step of the process (steps A to G) was heat extracted with PBS. The protein concentration of each extract was evaluated by using the micro-Bradford assay. Samples were run on SDS-PAGE. The immunoblot was performed with the serum of a patient sensitized to sunflower seed and oil. RESULTS: The extracts obtained after each step reveal a decrease in total protein concentration from 13.6 microg/mL to 0. 22 microg/mL. The result of SDS-PAGE shows 5 bands, from 67 kd to 145 kd, with the most abundant being the 67-kd protein. The amount of this protein decreases after each step of the process. It is, however, still present in trace amounts in the refined oil. The 67-kd protein, which is mainly present in the crude oil and slightly in the refined oil, has been shown to be allergenic. CONCLUSION: Because of the presence of allergenic proteins, refined sunflower oil may pose a threat to people highly sensitized to sunflower seeds.

Degradation of cyanidin 3-glucoside by caffeic acid o-quinone. Determination of the stoichiometry and characterization of the degradation products.

Caffeic acid o-quinone (CQ) was prepared by oxidation of caffeic acid with o-chloranil in organic media. The reaction between the purified CQ and cyanidin 3-glucoside (Cy 3-glc, o-diphenolic anthocyanin) was monitored by HPLC, and quantitative analyses were performed to establish the stoichiometry of the reaction. The results indicate that Cy 3-glc is degraded by a coupled oxidation mechanism with integration of CQ into the degradation products. The ratio of degraded Cy 3-glc to CQ incorporated into the condensation products was approximately 2.0. No brown products could be detected, only a slight orange color. Moreover, the addition of purified polyphenol oxidase to the slightly colored media resulted in the disappearance of the caffeic acid formed from the reaction of coupled oxidation (Cy 3-glc/CQ) and the formation of brown polymers. The degradation products were isolated by gel filtration on Sephadex G-25. The UV-vis spectra and chemical analysis (acidic hydrolysis) of the degradation products suggest that they resulted from the condensation of caffeic acid and Cy 3-glc. HPLC analysis showed that the partial purified fraction contained a mixture of complex condensation products.