A diet high in fatty fish, bilberries and wholegrain products improves markers of endothelial function and inflammation in individuals with impaired glucose metabolism in a randomised controlled trial: the Sysdimet study.

AIMS/HYPOTHESIS: Low-grade inflammation and endothelial dysfunction may play a role in the pathogenesis of type 2 diabetes and cardiovascular disease. We evaluated whether a diet high in fatty fish, bilberries and wholegrain products (Healthy Diet) improves biomarkers reflecting inflammation and endothelial dysfunction in individuals with impaired glucose metabolism. METHODS: We recruited individuals with impaired glucose metabolism and features of the metabolic syndrome into a 12 week, parallel design, dietary intervention trial conducted at the Department of Clinical Nutrition, University of Eastern Finland (Kuopio, Finland). Randomisation was performed by matching according to sex and medians of age, BMI and fasting plasma glucose of the study population at screening. The primary endpoint in the present study was the change in plasma inflammatory markers and the measurements were performed blinded to group assignment. High-sensitivity (hs) C-reactive protein (CRP) and E-selectin responses were also analysed separately in participants not using statins (n = 76). RESULTS: Altogether, 131 individuals were assigned to either the Healthy Diet (n = 44), a whole-grain-enriched diet (WGED) (n = 42) or a control (n = 45) diet, and 104 participants (mean ± SD: age 59 ± 7 years; BMI 31.1 ± 3.5 kg/m(2)) who had completed the study, were analysed (Healthy Diet n = 36, WGED n = 34 and control diet n = 34). Plasma E-selectin decreased only in the Healthy Diet group. This occurred in all group participants (p < 0.05) and also after excluding participants using statins (p < 0.05). Plasma hsCRP levels decreased in the Healthy Diet (median -17%, p < 0.05) and WGED (median -27%, p < 0.01) groups in participants not using statins. Controlling for confounding factors, including BMI or insulin sensitivity, did not alter the results. A greater increase in plasma concentration of very-long-chain n-3 fatty acids and in the intake of fibre during the study was associated with a greater decrease in plasma E-selectin (p < 0.05). The intake of test breads consumed during the Healthy Diet and WGED interventions was inversely associated with the change in hsCRP levels (p < 0.001). CONCLUSIONS/INTERPRETATION: Our results suggest that the combined effect of fatty fish, bilberries and wholegrain products may improve endothelial dysfunction and inflammation in overweight and obese individuals at high risk of developing diabetes.

Effects of palm oil and transesterified palm oil on chylomicron and VLDL triacylglycerol structures and postprandial lipid response.

The effects of positional distribution of triacylglycerol (TAG) fatty acids to TAG structures in chylomicrons and VLDL, and to postprandial lipemia, were studied in 10 healthy premenopausal women using a 6-h oral fat load test and a randomized, double-blind cross-over design. Molecular level information of TAG regioisomerism was obtained with a tandem mass spectrometric method. The positional distribution of fatty acids in chylomicron TAGs was similar to the respective dietary fat; 79% of the analyzed regioisomers in palm oil and 84% of the analyzed regioisomers in transesterified oil were found in chylomicron TAGs 3 h after the oral fat loads. VLDL TAGs were equal after the two fat loads in all but one regioisomer. Similarities in the fatty acid compositions of chylomicron TAGs suggest that palmitic acid was absorbed equally from both test fats. The proportion of palmitoleic acid in the chylomicrons was increased. Fat with palmitic acid predominantly in the sn-1 and sn-3 positions caused a larger incremental area of total TAGs in plasma and reduced plasma insulin values at the beginning of the postprandial response (0-90 min) compared with fat with palmitic acid randomly distributed. The relationship between TAG molecular structures in dietary fats and in lipoproteins provides new means for understanding the effects of fatty acid positional distribution on human lipid metabolism.

Biomonitoring the intake of garlic via urinary excretion of allyl mercapturic acid.

Allium vegetables (onions, leeks, chives) and in particular garlic have been claimed to have health-promoting potential. This study was conducted to get insight into the perspectives for monitoring the intake of garlic by a biomarker approach. Chemically, the biomarker results from exposure to gamma-glutamyl-S-allyl-l-cysteine, which is first hydrolysed by gamma-glutamine-transpeptidase resulting in the formation of S-allyl-l-cysteine. The latter compound is subsequently N-acetylated by N-acetyltransferase into S-allyl-mercapturic acid (ALMA) and excreted into urine. The mercapturic acid was measured in urine using gaschromatography with mass spectrometry. Thus the intake of garlic was determined to check the compliance of garlic intake in a placebo-controlled intervention study. Results indicate that S-allyl-mercapturic acid could be detected in 15 out of 16 urine samples of garlic supplement takers, indicating good compliance. In addition, the intake of garlic was also monitored in a cross-section study of vegans versus controls in Finland, in which no differences in garlic consumption nor in ALMA output were recorded between vegans and controls. These data indicate good possibilities for further studies in the field of biomarkers to investigate the putative chemopreventive effects of garlic and garlic-containing products.

Antioxidant status in vegetarians versus omnivores.

Every day, vegetarians consume many carbohydrate-rich plant foods such as fruits and vegetables, cereals, pulses, and nuts. As a consequence, their diet contains more antioxidant vitamins (vitamin C, vitamin E, and beta-carotene) and copper than that of omnivores. Intake of zinc is generally comparable to that by omnivores. However, the bioavailability of zinc in vegetarian diets is generally lower than that of omnivores. Dietary intake of selenium is variable in both groups and depends on the selenium content of the soil. Measurements of antioxidant body levels in vegetarians show that a vegetarian diet maintains higher antioxidant vitamin status (vitamin C, vitamin E, beta-carotene) but variable antioxidant trace element status as compared with an omnivorous diet. To evaluate the antioxidative potential of a vegetarian diet versus an omnivorous diet, more studies are needed in which the total antioxidant capacity is determined rather than the status of a single antioxidant nutrient.

Effect of a vegan diet on biomarkers of chemoprevention in females.

1. In order to study the potential beneficial effects of a vegan diet, a cross-sectional study was performed and several biomarkers of chemoprevention were measured in a population of female 'living food' eaters ('vegans'; n = 20) vs matched omnivorous controls (n = 20). 2. White blood cells obtained from fresh blood samples were subjected to the single-cell gel-electrophoresis assay. There was no statistically significant difference between the vegans and controls in the parameters 'tail length' and 'tail moment'. However, the 'tail moment' was significantly lower in a subset of the vegans (i.e.in those who did not use any vitamin and/or mineral supplements). 3. Fresh blood samples were exposed in vitro to the mutagen mitomycin C just prior to culturing. After culturing the number of binucleated lymphocytes with micronuclei was scored. There was no difference between the controls and vegans in the incidence of baseline micronuclei, nor in the number of mitomycin C-induced micronuclei. However, a significant correlation (r = -0.64, P < 0.01) between the number of mitomycin C-induced micronuclei and the activity of erythrocyte superoxide dismutase was found in the vegans. The number of baseline micronuclei increased with age in both groups. These findings may be of biological relevance. 4. The content of glutathione-S-transferase-alpha in plasma was not different between the vegans (n = 12) and controls (n = 12). 5. The present data indicate a few differences in biomarkers of chemopreventive potential in strict vegans vs matched omnivorous controls. The significance of these changes as biologically relevant indicators of beneficial effects of vegan diets in humans needs to be determined in studies with a larger number of subjects.

Antioxidant status in long-term adherents to a strict uncooked vegan diet.

Antioxidant status was investigated in 20 Finnish middle-aged female vegans and in one male vegan who were following a strict, uncooked vegan diet ("living food diet"), by means of a dietary survey and biochemical measurements (blood concentrations of vitamins C and E and beta-carotene, and the activities of the zinc/copper-dependent superoxide dismutase and selenium-dependent glutathione peroxidase). Values were compared with those of omnivores matched for sex, age, social status, and residence. Antioxidant supplementation was used by 4 of 20 female vegans and by 11 of 20 control subjects. Based on dietary records, the vegans had significantly higher intakes of beta-carotene, vitamin E, vitamin C, and copper, and a significantly lower intake of selenium than the omnivorous control subjects. The calculated dietary antioxidant intakes by the vegans, expressed as percentages of the US recommended dietary allowances, were as follows: 305% of vitamin C, 247% of vitamin A, 313% of vitamin E, 92% of zinc, 120% of copper, and 49% of selenium. Compared with the omnivores, the vegans had significantly higher blood concentrations of beta-carotene, vitamin C, and vitamin E, as well as higher erythrocyte superoxide dismutase activity. These differences were also seen in pairs who were using no antioxidant supplements. The present data indicate that the "living food diet" provides significantly more dietary antioxidants than does the cooked, omnivorous diet, and that the long-term adherents to this diet have a better antioxidant status than do omnivorous control subjects.

Enhancement of sulfhydryl group availability in the intestinal brush border membrane by deficiencies of dietary calcium and phosphorus in chicks.

The reactivity and availability of sulfhydryl (-SH) groups in brush border membranes (BBM) from chicks adapted to a calcium-deficient (low Ca) or a phosphorus-deficient (low P) diet were determined. The calbindin-D28K concentrations of the intestinal mucosa of the low Ca and low P groups were both increased approximately 2.5-fold, demonstrating that adaptation to the mineral deficiencies had occurred. By the Ellman reaction, a threefold increment in -SH groups in BBM from both mineral-deficient groups was noted. By using DACM (N-7-dimethylamino-4-methylcoumarin-3-yl maleimide), a fluorescent probe for -SH groups, it was observed that fluorescence development was considerably greater with BBM from the low Ca and low P groups than with BBM from the controls, whether measured in the absence or presence of sodium dodecyl sulfate (SDS). In the absence of SDS, the pseudo-first-order reaction rate constants, k', calculated from the fluorescence data, were greater than the control group values, but in the presence of SDS, the k' values for all groups were about the same. Similar changes in BBM-SH groups were previously observed when 1,25-dihydroxycholecalciferol was given to vitamin D-deficient chicks. The redox state of the sulfhydryl groups in enzymes and transport proteins is known to affect the level of their activity. The functional significance of the present observations concerning the -SH groups of chick intestinal BBM, particularly in relation to vitamin D-dependent calcium and phosphorus absorption, is not known but is under investigation.

Relationship of membrane-bound sulfhydryl groups to vitamin D-stimulated uptake of [75Se]Selenite by the brush border membrane vesicles from chick duodenum.

The uptake of selenite by purified brush border membrane vesicles isolated from duodena of rachitic or vitamin D-treated chicks was studied by using radioactive selenite and a rapid filtration technique. Cholecalciferol treatment (500 IU at 72 h) significantly enhanced selenite uptake, a response that decreased when the vesicles were stored at room temperature for 2.5 h prior to the uptake measurement. Preincubation of the vesicles in 1.0 mmol/L H2O2 reduced [75Se]selenite uptake, indicating the involvement of oxidizable groups in the uptake reaction. Iodoacetic acid (IAA), a sulfhydryl-blocking reagent, at 1-2 mmol/L concentration eliminated the difference in selenite uptake due to cholecalciferol and had no effect on vesicles from rachitic animals. A higher concentration of IAA (10 mmol/L) enhanced selenite uptake manyfold and increased the absolute difference due to cholecalciferol treatment. Single intravenous doses of 100 IU cholecalciferol, 100 IU ergocalciferol, or 0.1 micrograms 1,25-dihydroxycholecalciferol also stimulated selenite uptake, suggesting a general response to vitamin D compounds. Normal animals given a single dose of 1,25-dihydroxycholecalciferol 12 h prior to killing also responded. Treatments that enhanced the uptake of [75Se]selenite also increased the amount of membrane-bound sulfhydryl groups, suggesting the involvement of membrane-bound sulfhydryl groups in the vitamin D response. A significant increase in selenite uptake by intravenous 1,25-dihydroxycholecalciferol occurred within 10 min. This rapid effect provides a new tool to probe early biochemical effects of vitamin D on intestinal epithelium.

Uptake of 75Se-selenite by brush border membrane vesicles from chick duodenum stimulated by vitamin D.

Brush border membrane vesicles were isolated from mucosal homogenates of duodena from normal, rachitic and vitamin D-treated rachitic chicks using a discontinuous sucrose gradient, and further purified by glycerol gradient centrifugation. In vitro uptake of 75Se-selenite by purified brush border membrane vesicles was studied using a rapid filtration technique. The time course of 75Se uptake was non-linear; rapid initial binding was followed by a gradual decrease in the rate of uptake until an equilibrium value was reached at 60-120 min. The initial binding at 36 s was not affected by selenite concentration in the incubation buffer, while the fractional rate of uptake between the 36 s and 2 min time periods was clearly lower with 1 mM Se than with 4-100 microM Se. 75Se uptake did not show any dependency on the external Na-gradient, nor could it be inhibited by other anions (arsenate, phosphate). Treatment of rachitic chicks either with cholecalciferol (500 Iu, 72 h) or with 1,25(OH)2-cholecalciferol (0.5 microgram given 16 h prior to isolation of the vesicles) significantly enhanced 75Se uptake. A threefold excess of mannitol in the outside buffer reduced 75Se uptake by vesicles from vitamin D-deficient and D-treated chicks 60% and 35% respectively, but had no effect on vesicles from vitamin D-treated chicks preloaded with 75Se. Neither saponin treatment nor excess cold selenite could release the label from the vesicles preloaded with 75Se. These data are compatible with the hypothesis that selenite easily crosses the brush border membrane into the intravesicular space and, once inside, is tightly bound by the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Selenium supplementation does not alter platelet activation in subjects with normal selenium status.

The effect of Se supplementation on the plasma concentrations of platelet specific proteins, beta-thromboglobulin (beta TG) and platelet factor 4 (PF4), was determined in twenty young women with normal selenium (Se) status using a double blind protocol. Selenium supplementation for 4 weeks (150 micrograms/day), did not elevate the initial mean plasma Se level 95 +/- 4 ng/ml above this level, nor did it alter the plasma beta TG/PF4. Moreover, all the other parameters of the body antioxidative status (plasma alpha-tocopherol, retinol and uric acid and whole blood glutathione) measured in this experiment stayed unaltered during the 4-week supplementation period. The results indicate no relationship between Se supplementation and platelet function in subjects with normal Se status.

Selenium-mercury interaction during intestinal absorption of 75Se compounds in chicks.

The effects of inorganic (HgCl2) and organic (CH3HgCl) mercury on the intestinal absorption of Se compounds [Na2(75)SeO3, Na2(75)SeO4, L-[75Se]methionine ([75Se]Met)] were determined in 3-wk-old White Leghorn cockerels by the in vivo ligated duodenal loop procedure. The intraduodenal dose contained 0.05 microCi 75Se, 0.01 mM Se, 150 mM NaCl and 0-1.0 mM Hg. In the presence of 1 mM inorganic Hg in the intraduodenal dose, the absorption of the inorganic 75Se compounds was only about 65% of that in the control group, whereas only a slight inhibitory effect on [75Se]Met absorption was observed. Methylmercury had no effect on [75Se]selenite absorption. Precipitation of the 75Se-selenite in the intestinal lumen partly explained the direct interaction between inorganic Hg and Se compounds. Absorption of [75Se]Met and [75Se]selenite was also determined in chicks fed after hatching a purified diet supplemented with varying amounts of Hg (0-500 mg/kg) and Se (0-4 mg/kg). Dietary Hg significantly reduced the transfer of [75Se]selenite to body by enhancing the accumulation of the isotope in the intestinal tissue. Dietary Hg did not affect the absorption of [75Se]Met, but altered the whole-body distribution of this Se compound. Because interaction between Se and Hg was observed mainly between the inorganic compounds and with use of a manyfold excess of Hg over Se, the data suggest that intestinal interaction between these metals is not of great nutritional importance.

Bioavailability to rats of selenium in milk of cows fed sodium selenite or selenited barley.

The nutritional availability of Se to rats in two experimental Finnish milks were compared to that in American milk naturally high in Se. The experimental milks had their Se content increased by feeding cows either sodium selenite (selenited milk) or selenited barley (selenited-barley milk). Weanling male rats were fed a low-Se milk powder diet for 4 weeks followed by continued depletion or repletion with graded levels of Se as sodium selenite (standard) or different milks for 4 weeks. Plasma Se level and plasma and liver glutathione peroxidase (GSH-Px) activities were used as criteria of body Se status. The bioavailability of Se was calculated with the slope-ratio method. The Se in the selenited-barley milk was significantly (p less than 0.01) more available than that in the selenited milk when the plasma Se level was the response criterion. On the other hand, the bioavailability of Se from the various milks was not different when plasma or liver GSH-Px activities were used as the response criteria. Overall bioavailability for the selenited milk, selenited-barley milk and American milk was only slightly less than that for the standard (sodium selenite = 1.00), showing that milk is a relatively readily available source of dietary Se.

Intestinal absorption of 75Se-labeled sodium selenite and selenomethionine in chicks: effects of time, segment, selenium concentration and method of measurement.

The purpose of the present experiments was to obtain information on the intestinal transport of different selenium compounds in chicks. Absorption of selenium was studied in 3-wk-old white Leghorn cockerels both by introducing the radiolabeled selenium compounds into ligated intestinal loops of the anesthetized birds and after oral or parenteral administration of the isotope to previously fasted animals. Increasing the stable selenite concentration slightly reduced the percentage of [75Se]selenite transferred from the intestinal lumen to the body, while the transport of [75Se]selenomethionine was not similarly affected by the carrier concentration. Selenomethionine was more rapidly removed from the ligated intestinal segment and more efficiently retained after oral or parenteral administration. It was shown that the liver selenium cannot be used as an indicator of the efficiency of selenium absorption in short-term studies, since after dosing the liver accumulates sodium selenite more efficiently than selenomethionine, in spite of the greater percentage absorption of the latter compound. The percentage absorption of both selenium compounds was greatest from the duodenal segment of the small intestine. The transport of these selenium compounds does not appear to depend on the dietary level of selenium since the percentage absorption was not altered by feeding the birds diets supplemented with 0.4 or 4.0 ppm selenium prior to the measurement of absorption. The data imply that there are differences, in the chick, in the processes by which various selenium compounds are transported across the intestinal epithelium and retained in the body. The differences in absorption are not of nutritional importance, since, regardless of the chemical form, selenium is efficiently absorbed.

Effect of ascorbic acid supplementation on selenium bioavailability in humans.

The study was designed to investigate the effect of supplemental ascorbic acid on the bioavailability of selenium (Se) in humans by using plasma Se levels and plasma glutathione peroxidase (GSH-Px) activity as indicators of the body Se status. Three groups of female university students were supplemented for 4 weeks with either 50 micrograms sodium selenate, 50 micrograms sodium selenate together with 200 mg ascorbic acid, or with 200 mg ascorbic acid three times daily during meals. Plasma Se levels increased significantly (P less than 0.01) in all three groups regardless of the type of supplementation. The increase was highest in the group having both Se and ascorbic acid and smallest in the group receiving only ascorbic acid. The changes in plasma GSH-Px activities reflected those in plasma Se, but the increases were smaller (P less than 0.05). These results suggest that supplemental ascorbic acid may have a beneficial effect on the bioavailability of the natural Se in foods. However, ascorbic acid did not seem to affect the availability of the supplemental sodium selenate. Therefore, the effect of ascorbic acid on the bioavailability of selenium may vary depending on the ingested selenium compound.

Effect of dietary fat on plasma glutathione peroxidase levels and intestinal absorption of 75Se-labeled sodium selenite in chicks.

The effect of dietary fat on the availability of selenium was investigated in chicks fed either 4 or 20% butter, olive oil, rape oil, corn oil or sunflower oil in the diet for 3 weeks after hatching. Plasma glutathione peroxidase (GSH-Px) activity was used as an indicator of the body selenium status. In addition, the intestinal absorption of sodium selenite (75Se-labeled) was determined by using both the in vivo ligated loop procedure and oral administration of the isotope. The plasma GSH-Px levels increased with increasing proportion of the polyunsaturated fatty acids in the diet. Increasing the amount of fat from 4 to 20% significantly enhanced the GSH-Px activity in the groups receiving butter or olive oil, but had no effect in animals fed the unsaturated fats. The absorption of [75Se]selenite from the ligated duodenal loops tended to be reduced in chicks fed corn oil or sunflower oil as compared to the animals receiving butter in their diet. On the other hand, the type of dietary fat did not appear to affect the absorption of the orally administered selenite. The present study demonstrates that the type of dietary fat can affect the plasma GSH-Px levels in chicks without altering the intestinal absorption of selenite. However, the results on the absorption of the intraduodenally injected sodium selenite suggest that dietary fat plays some role in the intestinal transport of selenium.