Biomedical subjects

Torbjörn Lundh

Publications and source records attributed to Torbjörn Lundh.

8 recordsLinked to original sources

PubMed2006

Dietary flavonoids with a catechol structure increase alpha-tocopherol in rats and protect the vitamin from oxidation in vitro.

To identify dietary phenolic compounds capable of improving vitamin E status, male Sprague-Dawley rats were fed for 4 weeks either a basal diet (control) with 2 g/kg cholesterol and an adequate content of vitamin E or the basal diet fortified with quercetin (Q), (-)-epicatechin (EC), or (+)-catechin (C) at concentrations of 2 g/kg. All three catechol derivatives substantially increased concentrations of alpha-tocopherol (alpha-T) in blood plasma and liver. To study potential mechanisms underlying the observed increase of alpha-T, the capacities of the flavonoids to i) protect alpha-T from oxidation in LDL exposed to peroxyl radicals, ii) reduce alpha-tocopheroxyl radicals (alpha-T (.) ) in SDS micelles, and iii) inhibit the metabolism of tocopherols in HepG2 cells were determined. All flavonoids protected alpha-T from oxidation in human LDL ex vivo and dose-dependently reduced the concentrations of alpha-T (.) . None of the test compounds affected vitamin E metabolism in the hepatocyte cultures. In conclusion, fortification of the diet of Sprague-Dawley rats with Q, EC, or C considerably improved their vitamin E status. The underlying mechanism does not appear to involve vitamin E metabolism but may involve direct quenching of free radicals or reduction of the alpha-T (.) by the flavonoids.

Animals↗

PubMed2004

Dietary secoisolariciresinol diglucoside and its oligomers with 3-hydroxy-3-methyl glutaric acid decrease vitamin E levels in rats.

Secoisolariciresinol diglucoside (SDG) is an important dietary lignan that is found at very high levels in flaxseed (1-4 %, w/w). Flaxseed lignans have received much research interest in recent years because of reported phyto-oestrogenic, anticarcinogenic, and anti-atherogenic effects. Previously, flaxseed feeding has been shown to decrease vitamin E concentrations in rats despite the antioxidant potential of SDG in vitro. Sesamin, a sesame lignan, on the other hand has been shown to increase vitamin E concentrations in rats. The aim of the present study was to investigate the effect of dietary SDG and its oligomers on vitamin E and cholesterol concentrations in rats. SDG was extracted from defatted flaxseed flour with a dioxane-ethanol mixture and purified by silica column chromatography. The major oligomers with 3-hydroxy-3-methyl glutaric acid, containing a high ratio of SDG to p-coumaric and ferulic acid glucosides, were purified from the extracts by reversed-phase liquid chromatography. When fed to rats at 0.1 % in the diet for 27 d, both SDG and its oligomers had no effect on animal performance but caused an increase in liver cholesterol and a 2-fold reduction in the levels of alpha- and gamma-tocopherols in rat plasma and liver. It is notable that a phenolic antioxidant, such as SDG, causes a vitamin E-lowering effect in rats. This cannot be explained at present, but warrants further investigations with respect to the magnitude, mechanism, and significance of the observed effect for human nutrition.

Animals↗

PubMed2004

Cereal alkylresorcinols elevate gamma-tocopherol levels in rats and inhibit gamma-tocopherol metabolism in vitro.

Alkylresorcinols (AR) are a class of amphiphilic phenolic lipids present in high amounts in wheat and rye bran. They have been reported to be both growth retarding and innocuous when fed to rats, and to have a broad range of bioactivities in vitro, suggested to be related to their ability to bind to proteins and modify membranes. This study was designed to test the effects of AR (purified from rye bran) on growth, tocopherol levels, and cholesterol levels in rats. Rats were fed 1 of 4 different levels of AR for 4 wk: 0 (control), 1, 2, and 4 g/kg diet. AR did not affect final body, liver, or lung weights. The AR diets increased the levels of gamma-tocopherol in liver and lungs (P < 0.05). To investigate whether AR could have increased gamma-tocopherol levels via inhibition of tocopherol-omega-hydroxylase, HepG2 cells were incubated with AR and the metabolism of gamma-tocopherol measured. AR significantly inhibited the conversion of gamma-tocopherol to its water-soluble hydroxychroman metabolite in vitro, indicating that AR may increase gamma-tocopherol levels via inhibition of tocopherol metabolism in vivo. The 4 g AR/kg diet decreased liver cholesterol (P < 0.001), but did not affect plasma lipids. AR were detected in the perirenal adipose tissue samples of rats fed AR, indicating that they can accumulate in the fatty tissues of rats. High levels of dietary AR moderately affect gamma-tocopherol, possibly via inhibition of tocopherol metabolism, and decrease liver cholesterol in rats.

Animals↗

PubMed2003

The dietary hydroxycinnamate caffeic acid and its conjugate chlorogenic acid increase vitamin e and cholesterol concentrations in Sprague-Dawley rats.

Vegetarian diets are correlated with a reduced risk of developing cardiovascular disease and comprise a great variety of bioactive compounds, including hydroxycinnamic acid derivatives. Therefore, this study aimed to identify dietary hydroxycinnamic acid derivatives that may alter two important factors related to the development of cardiovascular disease, namely, tocopherol (T) and cholesterol (C) concentrations in the body. The effects of caffeic acid (CA), chlorogenic acid (CGA), and ferulic acid (FA) on alpha-T, gamma-T, and C levels in blood plasma, liver, and lungs were investigated after these compounds had been fed to rats for 4 weeks at concentrations of 2 g/kg in semisynthetic diets. None of the regimens affected weight gain, feed intake, or absolute weights of livers and lungs, although CA increased the liver weight relative to the body weight (P < 0.05). CA- and CGA-fed animals showed a tendency toward sparing vitamin E in all tissues, but statistical significance was obtained only for gamma-T in the liver of CA-fed animals (P < 0.005) and for alpha-T in the lungs of CGA-treated rats (P < 0.05). CGA supplementation reduced concentrations of lipids in the lung tissue (P < 0.05). CA and CGA elevated the concentrations of C in liver tissue and lipids to a similar extent, but only CA decreased the ratio of high-density lipoprotein C to total C in blood plasma (P < 0.05 for all effects). Animals eating FA showed T and C values comparable to those in the control group. In conclusion, this study demonstrates that dietary caffeic and chlorogenic acid may elevate tocopherols and cholesterol in vivo.

Administration, Oral↗

PubMed2003

Dietary (+)-catechin and BHT markedly increase alpha-tocopherol concentrations in rats by a tocopherol-omega-hydroxylase-independent mechanism.

The effects of dietary (+)-catechin (CAT) and BHT on plasma and tissue concentrations of alpha-tocopherol (alpha-T), gamma-tocopherol (gamma-T) and cholesterol (C) were studied in male Sprague-Dawley rats. The rats were fed the compounds during a 4-wk period at concentrations of 2 g/kg in standardized diets, low but adequate in vitamin E, with 2 g/kg cholesterol. The CAT-regimen did not affect weight gain, feed intake or organ weights. BHT did not affect feed intake but lowered the body weight and the amount of liver lipids and increased the weights of livers and lungs relative to the body weight. Rats consuming CAT had 2.5-3.5-fold increased plasma, liver and lung alpha-T concentrations, but C concentrations remained unchanged. BHT-feeding resulted in 2.4- and 1.7-fold elevation in alpha-T but approximately 50% decrease in gamma-T concentrations in blood plasma and liver, respectively. BHT also lowered total C in the liver without affecting the concentration of C in the liver lipids. To investigate whether the alpha-T-sparing action of the studied compounds was due to the inhibition of tocopherol-omega-hydroxylase, HepG2 cells were incubated with CAT or BHT in the presence of delta-tocopherol (delta-T) and the 3'- and 5'-delta-carboxychromanol metabolites in the media were analyzed by GC/MS. Neither CAT nor BHT inhibited tocopherol-omega-hydroxylase activity in hepatocyte cultures; CAT was also inactive in a rat microsomal assay. In conclusion, both dietary CAT and BHT markedly increased alpha-T concentrations in plasma and organs of Sprague-Dawley rats by a mechanism that apparently does not involve inhibition of tocopherol-omega-hydroxylase, a key enzyme in tocopherol catabolism.

Animals↗

PubMed2002

Effects of dietary anthocyanins on tocopherols and lipids in rats.

The effects of dietary cyanidin-3-O-glucoside (C3G) and concentrates from blackcurrant [Ribes nigrum] (BC) and elderberry [Sambucus nigra] (EC) on plasma and tissue concentrations of alpha- (alpha-T) and gamma-tocopherol (gamma-T) and cholesterol, as well as the fatty acid composition of the liver lipids were investigated in growing, male rats of the Sprague-Dawley strain. Animals were fed semisynthetic diets supplemented with 2 g/kg C3G, BC, or EC for 4 weeks. Dietary anthocyanins did not affect feed intake, body weight, and organ weights. C3G elevated the concentrations of tocopherols in the liver and lungs (P < 0.05). Cholesterol levels in plasma and liver were not affected by any of the regimens. C3G and BC reduced the relative amount of saturated fatty acids in the liver (P < 0.05). BC also lowered the percentage of 22:6 + 24:0 and EC the ratio of 20:3/20:4 n-6 (P < 0.05). In conclusion, dietary C3G, BC, and EC appear to have little effect on cholesterol levels and the fatty acid pattern in the liver but seem to be capable of sparing vitamin E in healthy, growing rats.

Animals↗

PubMed2002

Thyroid gland function in ovariectomized ewes exposed to phytoestrogens.

Phytoestrogens are by definition plant-derived substances that are able to activate the mammalian oestrogen receptors. We examined the possible effects of phytoestrogens on the secretion of thyroid hormones as well as on the immunoreactivity to oestrogen receptor alpha (ER alpha) in the thyroid glands of ovariectomized ewes. Eight ovariectomized ewes were fed 3.5 kg of 100% red clover silage for 14 days. Blood samples were collected before and on day 14 of exposure to phytoestrogens. After 5 months, four of the ewes were re-exposed to red clover silage as described above and the other four served as controls. Blood samples were collected as above. All ewes were slaughtered at the end of the experiment and the thyroid glands were weighed and examined for macroscopical changes. Tissue samples were taken for immunohistochemistry and image analysis. Ewes exposed to red clover silage had significantly higher plasma concentrations of total T(3) and free T(3) than ewes fed hay. The cross-section area of thyroid follicles tended to be larger in ewes fed red clover silage than in the control animals. ER alpha immunoreactivity was stronger in thyroid glands from ewes exposed to phytoestrogens than in ewes fed hay. In conclusion, daily ingestion of 81-95 mg phytoestrogens per kg body weight for 14 days stimulated secretion of thyroid hormones and tended to increase follicle size and ER alpha immunoreactivity of thyroid glands of ovariectomized ewes.

Animals↗

PubMed2002

Activity of enzymes involved in energy production in the small intestine during suckling-weaning transition of pigs.

The effect of weaning on a potential metabolic capacity of key enzymes involved in the energy production by porcine enterocytes was investigated. The activity of citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase was determined in the small intestine epithelium of piglets during suckling-weaning transition. Investigations were performed on 5-week-old (suckling), 6-week-old (1st week after weaning) and 7-week-old (2nd week after weaning) piglets. The activity of glutamate dehydrogenase decreased (p < 0.05) during the 1st week after weaning, and remained numerically lower during the 2nd week after weaning than in suckling piglets. The activities of isocitrate dehydrogenase and alanine aminotransferase showed the same pattern as the glutamate dehydrogenase activity and decreased numerically during the 1st and 2nd weeks. The activities of citrate synthase and alpha-ketoglutarate dehydrogenase were numerically lower in post-weaned piglets (1st and 2nd weeks) than in suckling piglets. In contrast, the activity of aspartate aminotransferase was high and remained unchanged from week 5 to the 2nd week post-weaning. The activities of alanine and aspartate aminotransferase were positively correlated in suckling piglets (r = 0.98, p < 0.05) and at the 1st week after weaning (r = 0.99, p < 0.01). Also, both aminotransferases were positively correlated to the activity of alpha-ketoglutarate dehydrogenase in suckling piglets (r = 0.95, p < 0.05 and r = 0.95, p < 0.05) and to the activity of isocitrate dehydrogenase during the 1st week after weaning (r = 0.99, p < 0.001 and r = 0.99, p < 0.01). The results indicate additional capacity of the tricarboxylic acid (TCA) cycle for transformation of alpha-ketoglutarate from other sources than acetyl-CoA such as glutamine, glutamate and other amino acids. Further, the high activity of aspartate aminotransferase also suggests a high capacity of porcine small intestinal epithelium to provide the TCA cycle with oxaloacetate during the suckling-weaning transition.

Alanine Transaminase↗