Association between an Antioxidant-Rich Japanese Diet and Chronic Kidney Disease: The Ohasama Study.

AIMS: Although physiological effects of hydrophilic- (H-) and lipophilic- (L-) antioxidant capacities (AOCs) are suggested to differ, the association of an antioxidant-rich diet and chronic kidney disease (CKD) incidence has not been examined. We therefore explored the association between the H- or L-AOC of a whole Japanese diet and CKD risk in a general population. METHODS: A total of 922 individuals without CKD (69.2% women; mean age, 59.5 years old) from Ohasama Town, Japan, were examined. CKD incidence was defined as the presence of proteinuria and/or an estimated glomerular filtration rate (eGFR) of ＜60 ml/min/1.73 m2. Consumption of H-/L-AOC was determined based on the oxygen radical absorbance capacity in a specially developed Japanese food AOC database. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for new-onset CKD using a Cox proportional hazards model. RESULTS: During the median follow-up of 9.7 years, 137 CKD incidents were recorded. After adjusting for potential confounding variables, the highest quartile of L-AOC was significantly associated with a 51% reduced CKD risk among only women. An increased L-AOC intake was more effective in preventing eGFR reduction than in preventing proteinuria in women. These associations were not seen for H-AOC intake in both sexes and L-AOC intake in men. CONCLUSIONS: A high intake of lipophilic antioxidants may be associated with a reduced CKD risk. The balance between dietary antioxidant intake and pro-oxidants induced by unhealthy lifestyles may be crucial for preventing future kidney deterioration.

The Major Source of Antioxidants Intake From Typical Diet Among Rural Farmers in North-eastern Japan in the 1990s.

BACKGROUND: Previous Japanese studies have led to the erroneous conclusion of antioxidant capacity (AOC) intakes of the overall Japanese diet due to limitations in the number and types of food measured, especially in rice and seafood intake. The aims of the study were to construct an AOC database of foods representative of the typical Japanese diet and to clarify the high contributors to AOC intake from the overall diet of the Japanese population. METHODS: Commonly consumed foods were estimated using 3-day dietary records (DRs) over the four seasons among 55 men and 58 women in Japan. To generate an AOC database suitable for the typical Japanese diet, hydrophilic (H-)/lipophilic (L-) oxygen radical absorbance capacity (ORAC) values of foods in each food group were measured via validated methods using the food intake rankings. Subsequently, we estimated the AOC intake and the AOC characteristics of a typical Japanese diet. RESULTS: Of 989 food items consumed by the participants, 189 food items were measured, which covered 78.8% of the total food intake. The most commonly consumed types of antioxidant-containing food were tea, soybean products, coffee, and rice according to H-ORAC, and soybean products, fish and shellfish, vegetables, and algae according to L-ORAC. CONCLUSIONS: The characteristics of high AOC intake in rice and seafood more appropriately reflected the Japanese-style diet. Further studies are expected to clarify the association between food-derived AOC and its role in preventing or ameliorating lifestyle-related diseases.

Antioxidant Capacities of Plant-Derived Foods Commonly Consumed in Japan.

To provide reliable data for high quality epidemiological studies examining the relationship between health and antioxidant intake from daily foods, 107 plant-derived food items (12 rice, bread and noodles, 5 potatoes and starches, 9 pulses, 6 nuts/seeds, 29 vegetables, 22 fruits, 5 mushrooms, 7 algae, and 12 beverages) were selected as commonly consumed foods in Japan based on dietary records, and their antioxidant capacities were evaluated by validated hydrophilic- and lipophilic-oxygen radical absorbance capacity (H-ORAC and L-ORAC) methods. The food items covered more than 60% of total food intake for each category on a weight basis. The H-ORAC and L-ORAC values were widely distributed at 0-210 and 0-30 µmol-Trolox equivalent/g, respectively. The foods possessing potent antioxidant capacities were found in vegetables and fruits as well as other plant-derived foods. In most foods measured, the H-ORAC values were much larger than the L-ORAC values, except for certain kinds of pulses, nuts/seeds, mushrooms, and algae. The ORAC data shown here is sufficient to accurately estimate the antioxidant intake from plant-derived foods in Japan, and should be useful in future epidemiological studies aiming to clarify the biological significance of ORAC values.

Tandem Cation/Anion Exchange SPE Cartridge Method for Sample Desalting for HPLC Analysis of Soluble Dietary Fiber: Development and Inter-laboratory Validation.

In HPLC analyses of soluble dietary fiber, desalting processes using open, mixed-bed ion-exchange columns are time-consuming and labor-intensive. We developed and validated a simple desalting method using tandem cation/anion exchange SPE cartridges. We found that combining Bond Elut Jr SCX (upstream) and Bond Elut PSA (downstream) cartridges provided adequate desalting of test solutions. The developed method was then validated in an inter-laboratory study. Five test samples were prepared by mixing food matrixes with purified soluble dietary fiber and treated to generate solutions to test the desalting process. These solutions were then analyzed by eight different laboratories. The results demonstrated that the developed method is simple and reliable for desalting samples containing 140 to 945 mg/100 mL of soluble dietary fiber in preparation for HPLC analysis of soluble dietary fiber.

Improvement and Interlaboratory Validation of the Lipophilic Oxygen Radical Absorbance Capacity: Determination of Antioxidant Capacities of Lipophilic Antioxidant Solutions and Food Extracts.

A lipophilic oxygen radical absorbance capacity (L-ORAC) assay is an evaluation of the antioxidant capacity of solutions of lipophilic compounds. The concentrations of fluorescein, radical generator, and Trolox standard solutions were optimized to improve the precision of the assay. An interlaboratory study using two antioxidant solutions and three food extracts as test samples conducted in accordance with harmonized protocol demonstrated satisfactory L-ORAC measurements; the intermediate precision relative standard deviations (RSD(int)) ranged from 7.0 to 16.7%, the reproducibility relative standard deviations (RSD(R)) ranged from 14.8 to 19.4%, and the HorRat values ranged from 1.35 to 1.78.

Extraction efficiency of hydrophilic and lipophilic antioxidants from lyophilized foods using pressurized liquid extraction and manual extraction.

The efficient extraction of antioxidants from food samples is necessary in order to accurately measure their antioxidant capacities. α-Tocopherol and gallic acid were spiked into samples of 5 lyophilized and pulverized vegetables and fruits (onion, cabbage, Satsuma mandarin orange, pumpkin, and spinach). The lipophilic and hydrophilic antioxidants in the samples were sequentially extracted with a mixed solvent of n-hexane and dichloromethane, and then with acetic acid-acidified aqueous methanol. Duplicate samples were extracted: one set was extracted using an automated pressurized liquid extraction apparatus, and the other set was extracted manually. Spiked α-tocopherol and gallic acid were recovered almost quantitatively in the extracted lipophilic and hydrophilic fractions, respectively, especially when pressurized liquid extraction was used. The expected increase in lipophilic oxygen radical absorbance capacity (L-ORAC) due to spiking with α-tocopherol, and the expected increase in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities and total polyphenol content due to spiking with gallic acid, were all recovered in high yield. Relatively low recoveries, as reflected in the hydrophilic ORAC (H-ORAC) value, were obtained following spiking with gallic acid, suggesting an interaction between gallic acid and endogenous antioxidants. The H-ORAC values of gallic acid-spiked samples were almost the same as those of postadded (spiked) samples. These results clearly indicate that lipophilic and hydrophilic antioxidants are effectively extracted from lyophilized food, especially when pressurized liquid extraction is used.

Method validation by interlaboratory studies of improved hydrophilic oxygen radical absorbance capacity methods for the determination of antioxidant capacities of antioxidant solutions and food extracts.

Hydrophilic oxygen radical absorbance capacity (H-ORAC) is a method for evaluating antioxidant capacities of solutions of hydrophilic compounds. In this study, we improved the original method for H-ORAC determination, and evaluated the precision of the two improved methods (methods A and B) by interlaboratory studies using 5 antioxidant solutions and 5 food extracts as test samples. An interlaboratory study of method A, in accordance with the harmonized protocol, demonstrated satisfactory performance (intermediate precision relative standard deviations (RSD(int)) ranging from 4.6 to 18.8%; the reproducibility relative standard deviations (RSD(R)) ranging from 7.0 to 21.1%, and the HorRat values ranging from 0.40 to 1.93). However, methodological problems remained, and a further improved method, method B, was thus developed. An interlaboratory study of method B by 5 participating laboratories showed better intermediate precision and reproducibility (RSD(int) and RSD(R) ranging from 1.8 to 9.4%, and from 4.4 to 13.8%, respectively), and all HorRat values for the test samples were less than 1.3, suggesting good performance for the H-ORAC measurement.

Estimated average daily intake of antioxidants from typical vegetables consumed in Japan: a preliminary study.

The hydrophilic antioxidant content of 23 vegetables commonly consumed in Japan was assessed by the hydrophilic oxygen radical absorbance capacity (H-ORAC) method to estimate the dietary intake of total antioxidants in Japan. The estimated average H-ORAC value for "typical vegetables" consumed in Japan was 594.3 µmol Trolox equivalent (TE)/100 g. Hence, 2080 µmol TE/d of hydrophilic antioxidants would be ingested when 350 g of vegetables a day are consumed.

A redox-silent analogue of tocotrienol inhibits hypoxic adaptation of lung cancer cells.

We have previously reported that a redox-silent analogue of alpha-tocotrienol (T3), 6-O-carboxypropyl-alpha-tocotrienol (T3E) shows more potential anti-carcinogenic property than T3 in a lung cancer cell (A549 cell). However, the mechanisms by which T3E exerts its potential anti-carcinogenic effect is still unclear. As tumor malignancy is associated with hypoxia adaptation, in this study, we examined whether T3E could suppress survival and invasion in A549 cells under hypoxia. Hypoxia treatment drastically-induced activation of the protein tyrosine kinase, Src, and its regulated signaling required for hypoxia adaptation of A549 tumor cells. The survival and invasion capacity of the tumor cells under hypoxia was suppressed by T3E via the inactivation of Src. More specifically, T3E-dependent inhibition of Src-induced Akt activation contributed to suppression of cell survival under hypoxia, and the reduction of fibrinolytic factors such as plasminogen activator-1(PAI-1) via the decrease of hypoxia-inducible factor-2alpha by T3E led to inhibition of hypoxic invasion. Overall these results suggest that T3E suppresses hypoxia adaptation of A549 cells by the inhibition in hypoxia-induced activation of Src signaling.

Characterization of the radical-scavenging reaction of 2-O-substituted ascorbic acid derivatives, AA-2G, AA-2P, and AA-2S: a kinetic and stoichiometric study.

The aim of this study was to characterize the antioxidant activity of three ascorbic acid (AA) derivatives O-substituted at the C-2 position of AA: ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S). The radical-scavenging activities of these AA derivatives and some common low molecular-weight antioxidants such as uric acid or glutathione against 1,1-diphenyl-picrylhydrazyl (DPPH) radical, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+), or galvinoxyl radical were kinetically and stoichiometrically evaluated under pH-controlled conditions. Those AA derivatives slowly and continuously reacted with DPPH radical and ABTS+, but not with galvinoxyl radical. They effectively reacted with DPPH radical under acidic conditions and with ABTS+ under neutral conditions. In contrast, AA immediately quenched all species of radicals tested at all pH values investigated. The reactivity of Trolox, a water-soluble vitamin E analogue, was comparable to that of AA in terms of kinetics and stoichiometrics. Uric acid and glutathione exhibited long-lasting radical-scavenging activity against these radicals under certain pH conditions. The radical-scavenging profiles of AA derivatives were closer to those of uric acid and glutathione rather than to that of AA. The number of radicals scavenged by one molecule of AA derivatives, uric acid, or glutathione was equal to or greater than that by AA or Trolox under the appropriate conditions. These data suggest the potential usage of AA derivatives as radical scavengers.