Peter W.F. Fischer

Chemical and nutritional studies of flaxseed (variety Linott) in rats

Abstract The nutritional effects of flaxseed ( Linum usitatissimum , variety Linott) were studied in the rat. In addition, thermal and storage stabilities of flaxseed were evaluated. Weanling rats were fed diets containing ground flaxseed at levels of 0, 10, 20, or 40% for 90 days. No differences were found in the food intake nor in body and organ weights. Serum triglyceride, total cholesterol, and the low-density lipoprotein (LDL) cholesterol concentrations were significantly lower in the rats fed the 20% and 40% flaxseed diets compared to the 0% flaxseed group. The high-density lipoprotein (HDL) cholesterol concentration and the LDL:HDL-cholesterol ratio were generally lower in the flaxseed-fed rats when compared to the 0% flaxseed group, but a significant lowering occurred only in the 40% flaxseed group. The incorporation of flaxseed in the diet caused significant elevations in the levels of the α-linolenic acid in adipose tissue and in organs. Higher amounts of eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids were observed in the heart and liver of flaxseed-fed rats when compared to the 0% flaxseed group. A significant lowering of tissue vitamin E levels and an elevation of urinary thiobarbituric reacting substances occurred only in the 40% flaxseed group, which suggested that low to moderate intakes of flaxseed did not impart an oxidative stress on rat tissues. Dietary fiber in flaxseed appeared to be largely fermentable and was associated with a large increase in fecal moisture. The phytate in flaxseed had no effect on zinc status. The oil in both the intact and the ground flaxseeds was found to be thermally and oxidatively stable.

Dietary Reference Intakes for vitamin D: justification for a review of the 1997 values

Recent Institute of Medicine (IOM) reviews of the process for deriving Dietary Reference Intakes (DRIs) suggest that determining the need for a new nutrient review should be evaluated against criteria set a priori. After selecting the criterion of significant new and relevant research, a working group of US and Canadian government scientists used results from a systematic review and 2 conferences on vitamin D and health to evaluate whether significant new and relevant scientific evidence had become available since the 1997 IOM publication of the DRIs for vitamin D. This working group concluded that there appears to be new research meeting the criteria for 4 key DRI questions. The new research is of larger quantity and quality for the elderly than for other groups, but overall 1) adds to the bone-related and status evidence available to the 1997 DRI Committee for several of the life-stage groups, 2) identifies new outcomes with respect to risk of falls and performance measures in the elderly and potential adverse effects, and 3) provides additional information on dose-response relations between intakes and circulating 25-hydroxyvitamin D concentrations and between 25-hydroxyvitamin D concentrations and several health outcomes (ie, bone-related outcomes for all ages and risk of falls and performance measures in older adults). Members of the working group concluded that significant new and relevant research was available for reviewing the existing DRIs for vitamin D while leaving the decision of whether the new research will result in changes to the current DRIs to a future IOM-convened DRI committee.

An automated method for the determination of Cu,Zn-superoxide dismutase in plasma and erythrocytes using an ABA-200 discrete analyzer.

An automated enzymatic method is described for the determination of Cu,Zn-superoxide dismutase (SOD) in plasma or erythrocytes using the xanthine-xanthine oxidase and cytochrome C coupled assay. This method was adapted to an Abbott ABA-200 discrete analyzer. Coefficients of variation for within-run and day-to-day analyses were less than 5%. Only 2.5 muL of serum or erythrocyte extract is required so a capillary tube sample of blood (70 muL) is sufficient for the assay. Recovery of added SOD ranged from 92 to 101%. The method reported here is practical for use in a clinical chemistry laboratory for monitoring changes in this enzyme, which is a sensitive early indicator of alterations in copper status.

Effects of age, smoking, drinking, exercise and estrogen use on indices of copper status in healthy adults1

Abstract Erythrocyte Cu, Zn-superoxide dismutase activity (SOD), ceruloplasmin activity (CP) and serum copper concentration (SCu) were determined in normal adult males (n=239) and females (n=145). The effects of age, smoking, drinking frequency, exercise and oral contraceptive use or estrogen replacement therapy on these indices of copper status were investigated. For males, the mean SOD (U/mg hemoglobin±SD) was 77.42±15.7 and for females, 75.7±19.9. CP and SCu were highly correlated, while no significant relationship between these two indices of copper status and SOD could be detected. Both SCu and CP varied significantly with age in females but not in males. No age-related differences in SOD were found. Estrogen use, both in oral contraceptive preparations by pre-menopausal women and as replacement therapy by postmenopausal women significantly increased both SCu and CP but had no effect on SOD. Smoking, drinking frequency and activity level had no significant effect on any of these parameters of copper status.

[21] Automated assay of superoxide dismutase in blood

Publisher Summary This chapter discusses an automated assay of superoxide dismutase in blood. The analysis of copper zinc superoxide dismutase (SOD) in erythrocytes and extracellular SOD in plasma must be carried out by an indirect method because the substrate (O 2 – ) is an unstable free radical. The O 2 – is generated by xanthine plus xanthine oxidase. The SOD activity is calculated from the rate at which the generated O 2 – reduces cytochrome, a reaction that is followed spectrophotometrically. If the activity is high, more of the generated radicals are dismutated and less cytochrome is reduced, whereas if the activity is low, the opposite is true. The method is adapted to an Abbott VP Super System bichromatic analyzer; and as it uses small volumes and allows for a relatively large number of samples, it is suitable for use in both clinical laboratories and research laboratories utilizing small animals. Results show that the coefficient of variation for SOD in plasma ranged from 3.4 to 3.9% within runs and was 4.5% when a single plasma sample was analyzed over a period of 6 months. The within-run variability for erythrocyte SOD ranged from 3.5 to 5.3%, while variation for analyses performed over 3 days is 5.8%. The recovery of known activities of SOD ranged from 92 to 101% with an overall recovery of 98%.

Indices of iron and copper status during experimentally induced, marginal zinc deficiency in humans

This study examined the effect of diet-induced, marginal zinc deficiency for 7 wks in 15 men (aged 25.3±3.3 yrs; mean±SD) on selected indices of iron and copper status. The regimen involved lowzinc diets based on egg albumin and soy protein with added phytate and calcium such that mean [phytate]/[Zn] and [phytate]×[Ca]/[Zn] molar ratios were 209 and 4116, respectively, for 1 wk, followed by 70 and 2000, respectively, for 6 wks. Subjects were then repleted with 30 mg Zn/d for 2 wks. Plasma copper, Cu,Zn-superoxide dismutase (Cu, Zn-SOD) activity in plasma and red blood cells (RBC), hemoglobin, hematocrit, and serum ferritin were determined weekly on fasting blood samples. Significant reductions (p<0.05) after 7 wks in RBC Cu, Zn-superoxide dismutase (49.5±7.2 vs 33.6±6.3 U/mg Hb) and serum ferritin (69.2±38.7 vs 53.8±33.7 μg/L) occurred; no comparable decline was noted for plasma Cu, hemoglobin, or hematocrit. Significant (p<0.05) but less consistent changes were also observed in plasma superoxide dismutase activity. None of the changes were associated with the decreases in plasma, urinary and hair zinc concentrations, and alkaline phosphatase activity in RBC membranes. Results indicate that the biochemical iron and copper status of the subjects was marginally impaired, probably from the dietary regimen that induced marginal zinc deficiency.

Effects of low copper and high zinc intakes and related changes in Cu,Zn-superoxide dismutase activity on DMBA-induced mammary tumorigenesis

The effect of low copper and high zinc intakes on Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity and mammary tumorigenesis induced by 9,10-dimethyl-1,2-benzanthracene (DMBA) was investigated. Groups of 40 weanling female Sprague-Dawley rats were fed a modified AIN-76 diet containing the following (/kg diet): 1 mg Cu (0.016 mmol) and 30 mg Zn (0.459 mmol); 6 mg Cu (0.094 mmol) and 30 mg Zn (0.459 mmol) (control); or 6 mg Cu (0.094 mmol) and 150 mg Zn (2.295 mmol) for 21 wk. At 5 wk, 30 rats/group were given 4 mg (15.6 μmol) DMBA in corn oil intragastrically, and controls (10/group) received corn oil alone. Erythrocyte Cu,Zn-SOD activity was measured at 3, 5 (just before DMBA), 9, 13, 17, and 21 wk. The group fed the high-Zn diet had a slightly lower weight gain and food consumption. DMBA treatment had no effect on these parameters. Plasma and liver Cu concentration decreased in the low-Cu group. Femur zinc was significantly elevated in the high-Zn group. Erythrocyte Cu,Zn-SOD activity was decreased in the low-Cu group from 3 to 21 wk and was significantly elevated in the high-Zn group at 3 and 5 wk. In the low-Cu group, there were 5 nonmalignant adenomas and 3 malignant adenocarcinomas; in the control group, there were 4 adenomas and 3 adenocarcinomas; in the high-Zn group, there were 5 adenomas and 3 adenocarcinomas. No relationship between Cu,Zn-SOD activity and the presence of tumors could be found.

Copper transport by intestinal brush border membrane vesicles from rats fed high zinc or copper deficient diets

Abstract Intestinal brush border membrane vesicles were used to study the characteristics of mucosal membrane transport of copper in weanling rats fed either a high zinc (240 ppm Zn), copper deficient (0.6 ppm Cu) or a control diet (6 ppm Cu, 30 ppm Zn) for 6 weeks. Vesicles were prepared from the pooled mucosal cells of 2 animals, incubated in Hepes-Tris buffer containing either D-mannitol (passive transport), NaCl (sodium gradient) or ATP-MgCl 2 (active transport) and Cu labelled with 64 Cu. In all cases, rats fed the high zinc diet showed increased uptake of copper, while there was no significant difference between animals fed the control or copper deficient diets. By plotting ng Cu uptake vs 1/osmolarity of buffer and extrapolating to 0 osmolarity, it appears that at least a portion of the apparent uptake of copper by the vesicles from all groups is due to binding of copper to the membranes. When vesicles were incubated in buffer containing varying amounts of copper and the kinetics of copper transport were determined, no significant differences were seen in the copper transport kinetics between rats fed the copper deficient and control diets, while animals fed the high zinc diet showed an increased initial velocity. When these data were plotted as a double-reciprocal plot, the results indicated that there was no control mechanism for copper transport across the membrane. The movement of copper across the mucosal membrane appears to be by simple diffusion, and alterating this transport is not one of the mechanisms by which zinc decreases copper absorption.

Estimated mineral nutrients in a representative Canadian diet

Abstract The calcium, phosphorus, magnesium, iron, zinc, copper and managenese content of a representative Canadian diet was determined by analysing 11 different food group composites. The amounts of food included in the diet were based on the Nutrition Canada Food Consumption Patterns Report. The minerals in the diet were (mg/1000 kcal): Ca, 380; P, 567; Mg, 107; Fe, 4.5; Zn, 5.2; Cu, 0.49; Mn, 0.82. The proportion of the minerals, except calcium, provided by the diet groups was correlated with the energy contribution of each group. With the exception of some adults over 50 y, the content of minerals per 1000 kcal of the diet would be sufficient to meet the recently recommended intakes in Canada.

Effect of magnesium deficiency on mineral excretion and concentration in rat serum, heart and kidney

Abstract Epidemiological evidence suggests that magnesium deficiency may be a factor in the etiology of cardiovascular and renal disease. During moderate magnesium deficiency in rats, caused by feeding 80 mg Mg/kg, however, magnesium levels in the soft tissues were previously shown to vary little. Consequently, in the present study, rats were fed either 80 or 500 mg Mg/kg for 6 weeks, and the concentrations of sodium, potassium, calcium, phosphate and magnesium were determined in serum, heart, kidneys, urine and feces to see whether changes in the levels of these elements, caused by the magnesium deficiency, play a role in the pathogenesis of these diseases. The concentration of oxalate was also determined in the urine. In the heart, both sodium and calcium were increased, while magnesium was decreased slightly in the deficient animals. In the kidney, nephrocalcinosis occurred, along with an increase in sodium and phosphate concentration. The feces contained increased levels of sodium and potassium. The data suggest that magnesium deficiency alters sodium transport. In the case of the heart, this may alter the membrane potential and could account for the cardiac arrhythmias associated with magnesium deficiency.