Are food advanced glycation end products toxic in biological systems?

Model food advanced glycation end products (AGEs) were prepared as glycated casein (GC) and glycated soy protein (GS) by the reaction of casein or soy protein with glucose at 50 degrees C, relative humidity 75% for seven days in a powder state. These browned proteins were used as materials for animal experiments. A mixture of 20% glycated proteins (GC:GS = 1:1) diet was fed to streptozotocin (STZ)-diabetic rats for 11 weeks. The results showed that: (1) fructoselysine was observed in the hepatic portal veins, arteries, and femoral veins of rats fed with glycated proteins after 2 h of feeding; (2) blood sugar of glycated protein-fed rats was lower than that of diabetic rats fed with intact protein, while HbA1C in blood and glucose in urine of both groups were similar; (3) lipid peroxidation status in serum, liver, and kidney of both groups was similar; (4) superoxide dismutase (SOD) and glutathione-S-transferase (GST) enzymatic activity in serum and liver of both groups were also similar; (5) there were no differences in degree of cataract formation and concentration of glucose, fructose, sorbitol, and lipid peroxide in the lenses of both groups. From the above results, it can be estimated that food AGEs are not toxic in biological systems, and reactive oxygen species increase in diabetic rats is not caused by glycated proteins but by other pathways.

Prevalence and risk factors for diabetes in Ho Chi Minh City, Vietnam.

AIMS: To determine the prevalence of diabetes and associated risk factors in Ho Chi Minh City, Vietnam. METHODS: A total of 2932 participants aged 15 and above in Ho Chi Minh City were screened for diabetes in a cross-sectional study. The study was conducted from March-May 2001. Demographic, occupation, anthropometry and blood pressure were recorded. Blood glucose was calculated on fasting capillary and venous blood. The classification of diabetes and impaired fasting glucose (IFG) was carried out according to WHO and American Diabetes Association criteria. RESULTS: The crude prevalence of diabetes and IFG were 6.6 and 3.2%, respectively. After age, sex-adjustment to the Vietnam population census, the prevalence was 3.8 and 2.5%, respectively; approximately 40% of cases were found to be newly diagnosed diabetes. The crude prevalence of diabetes in the urban area was approximately 2.8 times higher than that recorded in the 1993 study (6.9 vs. 2.5%, respectively). In this study, there was a positive association between diabetes and sex, age, overweight, waist hip ratio (WHR), and having a history of delivering large for gestational age child; there was a negative association between diabetes and physical activity and occupation. CONCLUSIONS: This study found that the age, sex-adjusted prevalence of diabetes and IFG in Ho Chi Minh City were 3.8 and 2.5%, respectively, a rapid increase in the recent decade. Our study also indicates that ageing, a high WHR level, overweight and a sedentary lifestyle may be important determinants of the increased prevalence of diabetes during this transition period in Vietnam.

Food intake and lipid status of three Vietnamese populations with different incomes.

In order to have basic data for dietary preventive measures against some vascular diseases caused by disorder of lipid metabolism, food intake and lipid status were investigated in three Vietnamese populations with different per capita income levels. Totally, 299 people aged over 18 were involved in this study. Among them, 98 subjects were selected from one commune with low income, 100 and 101 subjects from two urban areas with medium and high income respectively. Food intake was assessed by 24-h recall method and lipid status was evaluated by measuring serum concentration of triglyceride, total cholesterol and its subfractions. The results showed that food consumption, dietary habits and lipid status varied with income levels. In general, diet was still unbalanced in all three groups, and low in fat and protein. In the rural, fat and protein intakes were lower than in the urban. The high prevalence of low serum cholesterol was observed in all three groups, the highest in the rural (45.3%) and the lowest in the urban (11.2%). On the contrary, the prevalence of high serum cholesterol was the lowest in the rural (2%) and the highest in the urban (16%). From these data, it is suggested that the majority of the Vietnamese might be vulnerable to some vascular diseases such as stroke if the situation of low fat intake and low serum cholesterol is not a problem of concern.

Serum fatty acids, lipoprotein(a) and apolipoprotein composition of rural, suburban and urban populations in North Vietnam.

This study was conducted to investigate the concentrations of serum fatty acids, lipoprotein(a) and apolipoprotein of three populations in North Vietnam: rural area with low income (n = 101), suburban with average income (n = 97), and urban with high income (n = 95). The results showed the suburban and urban populations had higher fat intake than the rural. The fat intake in quality was different in these three populations. The suburban had the highest consumption of fatty foods rich in n-6 polyunsaturated fatty acid (PUFA). The rural consumed more fatty foods rich in monounsaturated fatty acid (MUFA), but less fatty foods rich in n-3 PUFA than the two other populations. The high index of thrombogenicity (IT) of the Vietnamese diet may result from their low intake of fish and vegetable oils. Risk factors for premature cardiovascular disease (CVD) assessed by serum lipoprotein(a) and apolipoprotein levels were not observed in all three populations. However, coronary heart disease (CHD) and stroke are problems that should be monitored because the increase of CVD morbidity has been reported in Vietnamese people. From a nutritional point of view, the increase of fish and vegetable oils consumption is necessary for the prevention of CVD and CHD in these Vietnamese populations.

Maillard reaction and food processing. Application aspects.

The Maillard reaction occurs widely in food and biological systems. This contribution reviews the relation between the Maillard reaction and food processing, particularly its contribution to flavor formation, antioxidative effects, desmutagenic activity and the improvement of protein functional properties. Proteins modified by glucose, and melanoidins are important components of foodstuffs while the reactions of amino acids or peptides with glucose or dicarbonyl compounds produce various kinds of flavor components. Melanoidins and Amadori rearrangement products play an important role in providing antioxidative effects, both in vitro and in vivo. Melanoidins also exhibit desmutagenic activity against carcinogenic compounds. Protein-polysaccharide conjugates, prepared by Maillard reaction at mild conditions, increase the emulsifying activity, as well as antioxidative and antimicrobial effects of the original proteins.

Antioxidative properties of products from amino acids or peptides in the reaction with glucose.

The livers of rats fed with a brownish "soybean paste" (Miso) or peptides-glucose reaction mixture showed lower TBA and chemiluminescence values than those of the control. From these results, it was clear that Miso and peptide-glucose reaction products also exhibited antioxidative effect in vivo. In order to explain this mechanism, the scavenging activity against reactive oxygen species (ROS) of various Maillard reaction products (MRPs) were studied. It was confirmed that peptide-glucose reaction products. Amadori rearrangement products, melanoidins, modified protein and its hydrolysate, brown pigments isolated from Miso and other foodstuffs showed strong scavenging activity against hydroxyl radical and superoxide anion. Consequently, it was estimated that scavenging activity of MRPs against ROS played an important role in the antioxidative effect of MRPs in vivo.

Desmutagenicity of Melanoidins against Various Kinds of Mutagens and Activated Mutagens.

The desmutagenic activities of low-molecular weight melanoidins (LM-MEL, MW 500-1000) and nondialyzable melanoidins (ND-MEL, MW above 1000) prepared from a glucose-glycine reaction system were examined by Ames' test on such mutagens/carcinogens as nitro or amino compounds of aromatics or heterocycles, azo compounds, nitroso compounds, and epoxides. ND-MEL and LM-MEL exhibited a desmutagenic activity of 25-75% against mutagenic aromatic or heterocyclic compounds such as aflatoxin B1, B[α]P, 2-aminofluorene, 4-aminobiphenyl, and 2-aminonaphthalene, as well as heterocyclic amines, using S. typhimurium TA98 in the presence of S9 mix. In the case of using S. typhimurium TA100 in the absence of S9 mix, ND-MEL and LM-MEL showed a desmutagenic activity of 20-50% against 2-nitrofluorene, 4NQO and 2-nitronaphthalene. The strong desmutagenic activity of MEL from various kinds of amino acids, peptides, or egg albumin hydrolyzates with glucose was also observed against Trp-P-1. Furthermore, MEL had marked desmutagenic activity against the Trp-P-1 activated by S9 mix and synthetic N-OH-Trp-P-2.

Nutritional and physiological effects of casein modified by glucose, diacetyl, or hexanal.

Casein was modified by glucose, diacetyl, or hexanal at 50 degrees C, RH 75% for 1, 7, or 11 days. The chemical changes and digestibility in vitro of these nondialyzable caseins were investigated. The effects of these nondialyzable caseins supplemented with lost amino acids, on rats were studied by pair-feeding for 2 months. It was observed that internal organs such as liver, spleen, kidney, stomach, small intestine, cecum, colon and rectum were mostly unchanged. Biochemical values such as hematocrit, cholesterol, triglyceride, GPT, and GOT were also unchanged. However, the quantity of leucocytes was increased and serum glucose was decreased by feeding rats with modified caseins. Significant decrease in weight gain of rats fed with modified casein was observed, and the rate of decrease depended on the degree of modification of casein by carbonyl compounds. From these results, we supported the suggestion that some inhibitory or antinutritional compounds might be formed during the modification of casein by carbonyl compounds.