Björn Åkesson

Brain Cortical Fatty Acids and Phospholipids During and Following Complete and Severe Incomplete Ischemia

Abstract: To explore the possibility that peroxtdative degradation of brain tissue lipid constituents is an important mechanism of irreversible ischemic damage, we measured cortical fatty acids and phospholipids during reversible brain ischemia in the rat. Neither complete nor severe incomplete ischemia (5 and 30 min) caused any measurable breakdown of total or individual fatty acids or phospholipids. Except for a small (and reversible) decrease of inositol plus serine phosphoglycerides in the early postischemic period following 30 min of incomplete ischemia, there were no significant losses of fatty acids or phospholipids during recirculation. Since peroxidation, induced in brain cortical tissue in vitro, characteristically involves degradation of polyenoic fatty acids (arachidonic and docosahexaenoic acids) and of ethanolamine phosphoglycerides, the present in vivo results fail to support the hypothesis that peroxidation of membrane lipids is of primary importance for ischemic brain cell damage. Both complete and severe incomplete ischemia caused a similar increase in the tissue content of free fatty acids (FFA). Thus the FFA pool increased by about 10 times during a 30‐min ischemic period, to constitute 1 ‐ 2% of the total fatty acid pool. Since there was a relatively larger increase in polyenoic FFA (especially in arachidonic acid) than in saturated FFA, the release of FFA may be the result of activation of a phospholipase A2 unbalanced by reesterification. Increased levels of FFA persisted during the initial recirculation period, but a gradual normalization occurred and the ischemic changes were essentially reversed at 30 min after restoration of circulation. The pathophysiological implications of the changes in FFA are discussed with respect to mitochondrial dysfunction, formation of cellular edema and prostaglandin‐mediated deterioration of postischemic circulation.

Peroxidative Changes in Brain Cortical Fatty Acids and Phospholipids, as Characterized During Fe2+‐ and Ascorbic Acid‐Stimulated Lipid Peroxidation In Vitro

Abstract: The occurrence of peroxidative damage, as distinguished from anaerobic damage, to brain fatty acids and phospholipids was characterized in vitro. Fe2+ and ascorbic acid were used to stimulate peroxidation in cortical homogenates from rat brain incubated with or without oxygen. Lipid peroxidation was established in samples incubated with oxygen by increased diene conjugation, accumulation of thiobarbituric acid‐reactive material (TBAR) and of lipid‐soluble fluorescent products. No peroxidation occurred in samples incubated in the absence of oxygen (100% N2). Lipid peroxidation was characterized by a selective loss of arachidonic acid and docosahexaenoic acid and by degradation of ethanolamine phosphoglyceride, while choline phosphoglyceride did not change. During the course of peroxidation there were parallel increases in products of lipid peroxidation concomitant with the decrease in polyenoic fatty acids. The maximal changes in diene conjugation and TBAR occurred earlier than the maximal changes in fluorescent material and fatty acids. It is concluded that measurements of changes in brain fatty acid and phospholipid composition may be a useful tool to establishment of whether peroxidative damage is important in vivo in situations with a critically reduced oxygen supply. Estimation of lipid‐soluble fluorescence in vivo may also be useful, since it is considered to reflect the accumulation of stable end products of peroxidation.

Antioxidative factors in milk

Lipid auto-oxidation in milk is affected by a complex interplay of pro- and antioxidants. Several of these compounds are also important nutrients in the human diet and may have other physiological effects in the gastrointestinal tract and other tissues. Among antioxidative enzymes superoxide dismutase catalyses the dismutation of superoxide anion to hydrogen peroxide. The degradation of hydrogen peroxide can be catalysed by catalase and the selenoprotein glutathione peroxidase. The latter enzyme can also degrade lipid peroxides. Lactoferrin may have an important role by binding pro-oxidative iron ions. The occurrence of different forms of these antioxidative proteins in milk and available data on their functional role are reviewed. More remains to be learnt of individual compounds and as an example the potential role of seleno compounds in milk is virtually unknown. Antioxidative vitamins in milk can provide an important contribution to the daily dietary intake. Moreover vitamin E and carotenoids act as fat-soluble antioxidants, e.g. in the milk fat globule membrane, which is regarded as a major site of auto-oxidation. Vitamin C is an important water-soluble antioxidant and interacts in a complex manner with iron and fat-soluble antioxidants. The concentrations of these compounds in milk are affected by cow feeding rations and milk storage conditions. Since milk contains a number of antioxidants many reactions are possible and the specific function of each antioxidant cannot easily be defined. There are indications that other compounds may have antioxidative function and measurement of total antioxidative capacity should be a useful tool in evaluating their relative roles.

Initial incorporation into rat liver glycerolipids of intraportally injected (3H)glycerol.

1. 1. [3H]Glycerol in saline was injected intraportally into male rats. The livers were taken out 5–300 sec after injection. The incorporation of [3H]glycerol into fractions of different degrees of unsaturation within different liver glycerolipids was measured. 2. 2. Phosphatidic acids attained maximal specific radioactivity after 20–30 sec and diacylglycerols after 30–60 sec. 3. 3. The turnover rates of different phosphatidic acids and diacylglycerols ranged between 0.022 and 0.055 sec−1. 4. 4. The ratio between the rate constants for the conversion of dienoic and tetraenoic diacylglycerols into the corresponding phosphatidylcholines was 1:2. In the synthesis of phosphatidylethanolamines the ratio between the rate constants for the conversion of dienoic and hexaenoic diacylglycerols was 1:20. 5. 5. The most unsaturated triacylglycerols exhibited a higher turnover rate than other triacylglycerols.

Effect of processing on major flavonoids in processed onions, green beans, and peas

The contents of flavonoids in onions, green beans, and peas have been analysed in relation to the effect of different heat treatments. Two major flavonoids were studied, quercetin and kaempferol. The identification and quantification of the flavonoids were performed with high performance liquid chromatography and UV detection. The greatest loss of flavonoids in onion took place during the pre-processing step where the onion was peeled, trimmed, and chopped before blanching. Blanched onion contained 25 mg quercetin and 0.35 mg kaempferol per 100 g edible part. Blanched green beans contained 1.3 mg quercetin and 0.24 mg kaempferol per 100 g, and blanched peas only 0.15 mg quercetin per 100 g. No kaempferol was detected in peas. Further cooking, frying or warm-holding for up to 2 h of the blanched vegetables, did not influence the flavonoid content. Onions in ready-made dishes and home-cooked food as well as green beans may be good dietary sources of flavonoids.

Immunoglobulins, growth factors and growth hormone in bovine colostrum and the effects of processing

In colostrum collected 0-80 h postpartum the contents of immunoglobulins (Igs), transforming growth factor beta-2 (TGF-beta2), insulin-like growth factor-1 (IGF-1) and growth hormone (GH) were analysed. Colostrum initially contained 90 mg mL(-1) IgG1, 2.8 mg mL(-1) IgG2, 1.6 mg mL(-1) IgA, 4.5 mg mL(-1) IgM, and these concentrations declined by 92%, 87%, 93% and 84%, respectively, in the samples collected later. Of the growth factors, colostrum initially contained 289-310 ng mL(-1) TGF-beta2 and the concentration diminished to 66 ng mL(-1). The content of IGF-1 and GH postpartum decreased from 870 to 150 ng mL(-1), and from 0.17 to < 0.03 ng mL(-1), respectively. Heat treatment and freeze-drying of colostral whey decreased the content of Igs to 75%, while the contents of IGF-1 and TGF-beta2 were unaffected. A similar processing, including filtration steps reduced also the IGF-1 and TGF-beta2 by 25%. IgM seems to be the most sensitive of the Igs to processing

Antioxidant capacity of bovine milk as assayed by spectrophotometric and amperometric methods

The total antioxidant capacity (TAC) of bovine milk, whey, and low-molecular-weight (LMW) fractions of whey was investigated using spectrophotometric methods including an ABTS-based method (reduction of the cation radical of 2,2′-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)) and a FRAP method (reduction of Fe3+). Significant antioxidant capacity in milk and whey was demonstrated by the ABTS method (TAC(ABTS)), and it apparently increased with increasing pH. TAC (ABTS) was several-fold higher in milk than in whey, which had a slightly higher TAC than a LMW fraction prepared from it. Also the FRAP method could be used to demonstrate TAC in whey, although the low pH necessary for this method led to some protein precipitation. Most of the ferric-reducing activity of whey was found in the LMW fraction. The TAC values obtained using these methods were also compared to those obtained using a newly developed flow-injection amperometric (FIAmp) procedure for LMW fractions. High correlations were found for the TAC values of LMW samples obtained by the ABTS, FRAP and FIAmp methods (R2>0.8, P<0.001). Furthermore, to identify the major antioxidants in the LMW fraction, it was treated by uricase. Since most of the TAC (using ABTS, FRAP and FIAmp methods) was removed by uricase treatment, it could be concluded that urate is the major antioxidant in the LMW fraction. Also the effect of heat treatment on TAC in milk and whey was monitored. After heating of whey at 63°C for 1 h, TAC(ABTS) tended to increase by at least 20%, while TAC(FRAP) was not significantly changed. In milk, TAC(ABTS) remained constant during the same heat treatment. It is concluded that the methods tested gave the most reliable results for the LMW fraction of whey and that the use of several methods is necessary to characterise the antioxidant capacity of milk.

Effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile and inflammation markers in metabolic syndrome – a randomized study (SYSDIET)

Different healthy food patterns may modify cardiometabolic risk. We investigated the effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile, blood pressure and inflammatory markers in people with metabolic syndrome.

Consumption of Oat Milk for 5 Weeks Lowers Serum Cholesterol and LDL Cholesterol in Free-Living Men with Moderate Hypercholesterolemia

The aim of this study was to investigate whether consumption of a newly developed oat milk deprived of insoluble fiber would result in lower serum cholesterol and low-density lipoprotein (LDL) cholesterol levels in men with moderate hypercholesterolemia. The study had a randomized, controlled double-blind design, and oat milk was compared with an identically flavored control drink. Sixty-six men were recruited from a screening program and were randomly assigned to two groups. Each group took either oat milk or a control drink (rice milk) for 5 weeks (0.75 liters/day) and then switched to the other drink regimen for another 5-week period with a 5-week washout period between the test periods. The oat milk contained more dietary fiber, especially β-glucan (0.5 g/100 g), than the control drink (<0.02 g/100 g). Both drinks were well appreciated and got similar sensory evaluation, indicating that the double-blind design had been attained. In the final analysis 52 subjects remained. Compared with the control drink, intake of oat milk resulted in significantly lower serum total cholesterol (6%, p = 0.005) and LDL cholesterol (6%, p = 0.036) levels. The decrease in LDL cholesterol was more pronounced if the starting value was higher (r = –0.55, p < 0.001). The concentration of high-density lipoprotein cholesterol was not significantly different after consumption of the two drinks. Serum triglycerides did not change significantly after intake of oat milk, but a significant increase was observed after intake of the control drink (p = 0.003). It is concluded that also oat milk deprived of insoluble fiber has cholesterol-reducing properties.

Selenium and cancer: biomarkers of selenium status and molecular action of selenium supplements

BackgroundThe relationship between selenium and cancer involves many different aspects. These include the forms of selenium present in the diet and in the body, their functions and mechanisms of action, and methods employed in assessing an individual’s selenium nutritional status—both in general, and in epidemiological studies of the risk of cancer in relation to diet, as well as in connection with long-term trials for investigating the disease-preventive potential of selenium supplementation.Aim of the reviewTo review different aspects on selenium metabolism, the occurrence of different selenoproteins and their use as biomarkers of selenium status, the results of intervention trials of the cancer-preventive effects of selenium supplementation, the mechanisms of action involved, together with epidemiological findings on relations between the selenium status in the body and risk of cancer.Results and conclusionsThe rapid advance in the knowledge of different selenoproteins and their biological functions has opened up new possibilities for the understanding of the biological effects of selenium supplementation. A wide variety of effects of different forms and doses of selenium has been observed in a number of experimental systems, and it is at present difficult to pinpoint the mechanism that may explain the positive preventive effects of selenium supplementation observed in some human long-term trials. Moreover, additional such trials are needed to define the benefits and risks of different types and doses of selenium supplements which in the future may be implemented for public health reasons. Another necessary focus for future research is a better understanding of the mechanisms by which selenium interferes with the carcinogenesis process.