Clofibrate pretreatment in mice confers resistance against hepatic lipid peroxidation.

Pretreatment with peroxisome proliferators protects mice against various hepatotoxicants. Since our previous work suggested that the hepatoprotection may involve an increased ability to cope with oxidative stress, the present work directly addressed this possibility. Several observations indicated a heightened defense against oxidative stress accompanies the hepatoprotection produced by clofibrate. Firstly, the carbonyl content of hepatic proteins from clofibrate-pretreated mice was 40% lower than those from vehicle-treated controls. Secondly, liver homogenates from clofibrate-pretreated mice produced less thiobarbituric acid reactive substances upon incubation under aerobic conditions or exposure to ferrous sulfate. This effect was not due to lower levels of peroxidation-prone polyunsaturated fatty acids in clofibrate-treated livers. Thirdly, in vitro experiments indicated that the antioxidant factor in liver homogenates from clofibrate-pretreated mice was not glutathione. Rather, since it was inactivated by proteases and heat treatment, we concluded that a protein is involved. Collectively, our results suggest that a resistance to lipid peroxidation develops in mouse liver during exposure to clofibrate. The identity of the putative antioxidant protein and its contribution to the protection against liver toxicity observed in this and other laboratories awaits future investigation.

Lipid content and fatty acid composition of 11 species of Queensland (Australia) fish.

The fatty acid composition of 11 species of fish caught of the northeast coast of Australia was determined. No fatty acid profiles have been previously published for fish from this area nor for nine of these species. Although the percentage of polyunsaturated fatty acid (PUFA) was the same as the calculated average for Australian fish (42.3%), the percentage of n-3 fatty acids was lower (24.4 +/- 5.4% vs. 30.7 +/- 10.1%) and the n-6 fatty acids higher (16.5 +/- 4.5% vs. 11.2 +/- 5.9%), P < 0.001 in each case. The major n-3 PUFA were docosahexaenoic (15.6 +/- 6.3%) and eicosapentaenoic acid (4.3 +/- 1.1%) while the major n-6 PUFA were arachidonic (8.3 +/- 3.2%) and n-6 docosatetraenoic acid (3.1 +/- 1.3%). The second-most abundant class of fatty acid was the saturates (31.6 +/- 3.5%) while the monounsaturates accounted for 17.4 +/- 4.3% of the total fatty acids. The monounsaturate with the highest concentration was octadecenoic acid (11.8 +/- 2.6%). There was a positive correlation between the total lipid content and saturated and monounsaturated fatty acids (r = 0.675 and 0.567, respectively) and a negative correlation between the total lipid content and PUFA (r = 0.774).

Effect on plasma lipids of interesterifying a mix of edible oils.

The aim was to establish whether interesterification of oils, an alternative to the use of trans fatty acids in margarine manufacture, adversely affects plasma lipids. Twenty-seven hypercholesterolemic men participated in a double-blind, crossover trial of three margarines: 1) high-linoleic acid, moderate trans fatty acids; 2) high-palm oil blend (predominantly lauric, myristic, palmitic, oleic, and linoleic acids); and 3) an interesterified form of the high-palm oil margarine. Both high-palm oil margarines led to similar low-density-lipoprotein (LDL) cholesterol concentrations (4.43 +/- 0.94 and 4.54 +/- 0.88 mmol/L, respectively), which were significantly higher than the LDL concentrations after the high-linoleic acid margarine (4.02 +/- 0.85 mmol/L, P < 0.001). Interesterification transferred substantial proportions of palmitic acid into the sn-2 position of glycerides and unsaturated fatty acids into the sn-1,3 positions, and this was reflected in plasma chylomicrons. This study shows that interesterification of oils used to harden margarines does not raise plasma cholesterol more than does the margarine's constituent fatty acids.

Partial replacement of saturated fatty acids with almonds or walnuts lowers total plasma cholesterol and low-density-lipoprotein cholesterol.

Sixteen normolipidemic male volunteers aged 41 +/- 9 y (mean +/- SD) consumed a diet providing 36% of energy as fat (92 g fat/d) for 9 wk. A daily supplement of nuts (providing half of the total fat intake) was provided against a common background diet. In the first 3-wk period the background diet was supplemented with raw peanuts (50 g/d), coconut cubes (40 g/d), and a coconut confectionary bar (50 g/d), designed to provide 47 g fat with a ratio of polyunsaturated to monounsaturated to saturated fatty acids (P:M:S) to match the Australian diet (reference diet). During the following 3 wk the background diet was supplemented with monounsaturated fatty acid-rich raw almonds (84 g/d), equivalent to 46 g fat, and during the final 3-wk period the background diet was supplemented with polyunsaturated fatty acid-rich walnuts (68 g/d), equivalent to 46 g fat. Compared with the reference diet there were significant reductions in total and LDL cholesterol, 7% and 10%, respectively, after supplementation with almonds, and 5% and 9%, respectively, after supplementation with walnuts.

Oxidation of low-density lipoproteins: intraindividual variability and the effect of dietary linoleate supplementation.

Low-density lipoprotein (LDL) oxidation was measured in vitro to determine intraindividual variability and to relate oxidation to linoleic acid enrichment. Intraindividual variability was determined for eight subjects on 3 consecutive days after 14 d on a fixed diet. Coefficients of variation were 7.49 +/- 1.50%, 6.58 +/- 1.16%, and 4.58 +/- 0.77% for oxidation rate, lag time, and diene concentration, respectively. In the second study 12 normolipidemic men consumed a daily diet supplement containing 35 g linoleate-rich oil in one period and 35 g oleate-rich oil in the other period (2 x 3 wk crossover). LDL oxidized faster after the linoleate diet than after the oleate diet (mean +/- SE: 16.42 +/- 0.85 and 13.16 +/- 0.68 nmol diene.mg LDL protein-1.min-1, respectively, P < 0.02) and produced more conjugated diene (416 +/- 12.60 and 379.29 +/- 11.06 nmol/mg protein, respectively, P < 0.05) in proportion to the increase in LDL linoleate (r = 0.698, P < 0.001 and r = 0.618, P < 0.01 for rate and diene concentration, respectively). Lag time before onset of oxidation was not significantly altered by the linoleate-rich diet.

Plasma cholesterol-lowering potential of edible-oil blends suitable for commercial use.

We tested semihardened blends of edible oils, suitable for commercial food manufacture, with a lower-than-conventional saturated fatty acid content, for their effects on plasma cholesterol. Twenty-six mildly hypercholesterolemic men took part in a double-blind crossover experiment in which two test blends were compared with two control dietary periods [which resembled the Australian fat intake: proportions of polyunsaturated, monounsaturated, and saturated fatty acids (PMS) 0.4:0.9:1]. PMS in the test diets was approximately 0.8:1.3:1 and resulted in significantly lower LDL-cholesterol concentrations (reductions of less than or equal to 7.7%). HDL cholesterol and plasma triglyceride were unchanged. The trans fatty acid (mainly elaidic) content of the blends was 16%, raising its contribution to energy by 4% but without apparent effect on LDL and HDL concentrations. Provided the overall ratio of linoleic acid to palmitic acid in commercial edible-oil blends exceeds that in the prevailing national diet, partial hydrogenation will not negate the LDL-lowering potential.

Lipid, lipoprotein, and hemostatic effects of fish vs fish-oil n-3 fatty acids in mildly hyperlipidemic males.

The effects of fish and fish oil on lipids, hemostasis, and blood pressure were compared in 25 mildly hyperlipidemic men who received 4.5 g eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) daily for 5 wk. Six additional subjects served as controls. Fish and fish oil lowered plasma triglycerides 20% and 28% and very-low-density-lipoprotein (VLDL) triglycerides 42% and 52%, respectively (all P less than 0.05 compared with control). High-density-lipoprotein (HDL) cholesterol increased by 10% and 9%, with 34% and 32% increases in the proportion of HDL2 particles for fish and fish oil, respectively. Changes in total cholesterol, LDL cholesterol, apolipoprotein B, and blood pressure with fish and fish oil were not significantly different from changes for the control diet. The fish lowered fibrinogen (15.7%) and thromboxane (10.5%) and increased bleeding time (10.8%) (P less than 0.05 compared with control). Eating fatty fish and fish oil produced comparable lipid and lipoprotein changes, but only the fish improved hemostatic factors.

n-3 fatty acids of marine origin lower systolic blood pressure and triglycerides but raise LDL cholesterol compared with n-3 and n-6 fatty acids from plants.

We compared the cardiovascular risk-reduction potential of three major polyunsaturated fatty acids in a double-blind study. Thirty-three normotensive and mildly hypercholesterolemic men were randomly allocated to one of three diets supplemented with linoleic acid (14.3 g/d), alpha-linolenic acid (9.2 g/d), or eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) (3.4 g/d). Diets were matched to provide similar amounts of the major classes of fatty acids and cholesterol. Blood pressure and plasma lipids were measured for 6 wk after a 3-wk run-in period on the linoleic acid supplement. For the diet supplemented with EPA plus DHA compared with the linoleic acid diet systolic blood pressure fell 5.1 mm Hg (p = 0.01); plasma triglyceride and VLDL cholesterol fell by 39% (p = 0.001) and 49% (p = 0.01), respectively; and LDL cholesterol rose by 9% (p = 0.01). There were no significant changes with the diet supplemented with alpha-linolenic acid. The net effect on cardiovascular risk therefore is complex and the systolic blood pressure reduction was substantial.

The effect of thyroxine, 3, 5-dimethyl-3'isopropyl-L-thyronine and iodized oil on fetal brain development in the iodine-deficient sheep.

Studies have been carried out to investigate the role of maternal and fetal thyroid function in the effects of iodine deficiency on fetal brain development in sheep. Iodine deficiency was established with an especially prepared low-iodine diet of maize and pea pollard. The iodine-deficient sheep were mated and the end of the second trimester of pregnancy (100 days gestation) were divided into groups which received either a sc injection of T4 or 3,5-dimethyl-3-isopropyl-L-thyromine or an injection of iodized oil. AT 140 days gestation (10 days prior to parturition) comparison of the fetuses delivered by hysterotomy revealed that the retarded fetal brain development observed in iodine deficiency was greatly improved by T4 and by iodized oil. However, T4 and iodized oil failed to correct the reduction in the number and the increase in the length of synaptic appositions which were observed in the fetal cerebral cortex after iodine deficiency. In addition, the histological appearance of the fetal thyroid gland and the levels of plasma thyroid hormones were restored to normal. The administration of 3,5-dimethyl-3'-isopropyl-L-thyronine had no effect on the retarded fetal brain and body development of the iodine-deficient fetuses. The lack of response may be due to the ability of 3,5-dimethyl-3'-isopropyl-L-thyronine to cross the ovine placenta as no reduction in the abnormally elevated fetal plasma TSH observed in spite of a fall in maternal plasma TSH and apparent restoration of maternal thyroid function.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal brain development in response to iodine deficiency in a primate model (Callithrix jacchus jacchus).

The common cotton-eared marmoset (Callithrix jacchus jacchus) has been used for the first time as a primate model to study the effects of dietary iodine deficiency on fetal brain development. Paired male and female marmosets were fed a low-iodine diet of maize, peas, meat meal, Torula yeast, maize oil and added vitamins, minerals and amino acids for 6 months before mating. Offspring from first and second pregnancies were compared with offspring from control marmosets fed the same diet but supplemented with iodine. Severe iodine deficiency in the fetus at birth was evident by reduced plasma thyroxine levels, increased plasma thyroid stimulating hormone levels, increased thyroid weight and reduced thyroid iodine content. Thyroid histology revealed hyperplasia, hypertrophy and absence of colloid material in the follicles. Iodine deficiency caused a reduction in the weight of the fetal brain and in particular the cerebellum. Brain cell number was reduced in the cerebellum and brainstem but cell size was reduced in the cerebral hemispheres. Histology of the brain revealed morphological changes in the cerebellum and cerebral hemispheres. In the-cerebellum there was: an increase in the thickness of the external germinal layer indicative of impaired cell acquisition; a decrease in total area; a decrease in molecular layer area; and an increase in Purkinje cell (Pc) linear density due to a reduction in the length of the Pc line. The decrease in molecular layer area and increase in Pc linear density imply diminished ascending and lateral extension of Pc dendrites. Changes in the cerebral hemispheres consisted of an increase in the density of neuronal cell bodies in the granular band and a decrease in synaptic counts in the layer between the pia mater and supragranular band of the visual cortex. Offspring from second pregnancies compared to those from first pregnancies were more severely affected and associated with lower plasma levels of maternal and fetal thyroxine. These findings indicate the importance of maternal and fetal thyroid function in relation to fetal brain development in the primate.

Low-iodine diet for the production of severe I deficiency in marmosets (Callithrix jacchus jacchus).

A low-iodine diet consisting of maize, peas (Pisum sativum), torula yeast, meat meal, maize oil and added vitamins, minerals and amino acids was given to eight pairs of adult, common cotton-eared marmosets (Callithrix jacchus jacchus). Eight control pairs were given the same diet to which potassium iodate was added. Both groups also received low-I apple and deionized water. The diet provided adequate nutrition, as confirmed by the maintenance of body-weight and good health. In the I-deficient marmosets the concentration of plasma thyroxine was decreased from 140.1 nmol/l to 22.4 nmol/l and thyroid-stimulating hormone increased significantly from 1.8 ng/ml to 9.0 ng/ml compared with control marmosets, thereby indicating severe I deficiency. Compared with newborn offspring from control marmosets, the thyroid glands from the I-deficient offspring showed an increase in weight, a decrease in I content and, on histological examination, hyperplasia, hypertrophy and a total absence of colloid material in the follicles.

Restoration of brain growth in fetal sheep after iodized oil administration to pregnant iodine-deficient ewes.

Iodized oil was administered as a single intramuscular injection to pregnant iodine-deficient ewes at 100 days gestation and the subsequent growth of their fetuses compared with that of fetuses of severely iodine-deficient ewes and of iodine-replete ewes, all of which were fed the same low-iodine diet. The administered iodine produced a remarkable improvement in thyroid function and physical appearance of the fetuses, accompanied by an increase in brain growth and to a lesser extent in body growth, which at 140 days was only slightly (but significantly) less than that of the controls. There was restoration of the number of cells (DNA) and myelination (cholesterol/DNA) in the cerebellum and cerebral hemispheres which suggests a catch-up of neuroblast development during pregnancy. Histological examination, however, revealed that counts of synapses (density) in the cerebral cortex after iodized oil were still less than those of the control fetal brains. The relevance of these findings to the effects of iodine deficiency on human brain development is discussed.

Retarded fetal brain development resulting from severe dietary iodine deficiency in sheep.

Sheep have been used to study the effect of dietary iodine deficiency on the development of the fetal brain. Severe iodine deficiency caused reduction in fetal brain and body weights and in brain DNA and protein from 70 days gestation to parturition. The lowered brain weight and brain DNA at 70 days gestation indicates a reduced number of cells, probably due to slower neuroblast multiplication which normally occurs from 40-80 days in the sheep, and the reduction in DNA and protein after 80 days implies that the development of neuroglia could be slowed also in iodine deficiency. Morphological changes were observed in both the cerebral hemispheres and the cerebellum. In the cerebral hemispheres of the iodine-deficient fetuses an increased density of neurons was apparent histologically in the motor cortex and visual cortex and in the CA1 and CA4 areas of the hippocampus in comparison with controls. In the cerebellum there was delayed migration of cells from the external granular layer to the internal granular layer and increased density of Purkinje cells in the iodine-deficient fetal brains. In addition, the molecular area was increased and the medullary area reduced in comparison with controls. These change are indicative of delayed brain maturation. Evidence of fetal hypothyroidism was provided by low fetal thyroid iodine and plasma T4 values, thyroid hyperplasia from 70 days gestation, significant reduction in body weight at the same time as the brain retardation, and absence of wool growth and delayed skeletal maturation near parturition. It is apparent from the biochemical and histological changes observed during iodine deficiency that iodine is an essential element for normal fetal brain and physical development in the sheep.

The effect of ethanol and acetaldehyde on DNA synthesis in growing cells and on fetal development in the rat.

Incorporation of 3H-thymidine into DNA was significantly diminished by treatment with ethanol and acetaldehyde in regenerating rat liver, rat cells in culture, and rat fetal tissues. Reduced incorporation was especially marked in the fetal central nervous system and was observed with both compounds at levels similar to those reported to occur in human alcoholics. The reduced incorporation of 3H-thymidine into fetal DNA, together with the increased fetal mortality observed in dams treated specifically with acetaldehyde during pregnancy, suggests that acetaldehyde is implicated in the mechanism of teratogenesis associated with the fetal alcohol syndrome.

Experimental production of growth retardation in the sheep fetus after exposure to alcohol.

The effect of excessive alcohol consumption during pregnancy on fetal development has been studied in sheep. Fetuses of ewes which had consumed 10% ethanol in water before, and during, pregnancy were delivered by hysterotomy 10 days before parturition and found to be shorter (P < 0.01), lighter (P < 0.01), and to have significantly lighter brains (P < 0.05) than normal fetuses of comparable gestational age. Heart, liver, spleen, kidneys and adrenal glands all weighed less than those of fetuses from ewes which drank water instead of alcohol. The findings provide experimental evidence for growth retardation after exposure of the sheep fetus to alcohol, and are consistent with clinical reports on the human fetal alcohol syndrome.

Low-iodine diet for producing iodine deficiency in rats.

A low-iodine diet has been prepared for rats, using locally available low-iodine ingredients. On analysis it has been shown to consistently contain 15-20 ng iodine/g. When fed to growing female rats, this diet produced severe iodine deficiency while not significantly affecting growth or reproduction. The deficiency was manifested by a fall in daily urinary iodine excretion (to less than 1 microgram/day) and a seven-fold increase in thyroid uptake (131I) observable within 3 months. Levels of plasma thyroxine (T4) and thyroid stimulating hormone (TSH) continued to change for 4-5 months, T4 falling from 69.9 to 7.5 nmol/l and TSH increasing seven-fold from a control value of 364 to 2406 ng/ml. Goitre was present in all iodine-deficient rats and iodine content in the thyroid was 10% of the control value.

Production of severe iodine deficiency in sheep using a prepared low-iodine diet.

Extensive tests on dietary materials suitable for ingestion by sheep have led to the preparation of an appropriate diet which, when fed to the sheep, caused severe iodine deficiency. The deficiency was manifested by daily urinary excretion values which fell to levels of less than 20 micrograms iodine and by thyroxine (T4) and triiodothyronine (T3) concentrations in blood plasma which were reduced from more than 90 and 1.80 nmol/l to the low levels of less than 2.58 and 0.31 nmol/l respectively. The values were attained 5 months after feeding the low-iodine diet. Goitre was present in most of the animals and the reductions in T4 and T3 values were accompanied by increased concentrations of plasma thyroid stimulating hormone (TSH) from less than 8.6 to more than 68 ng/ml. Samples of wool removed from selected areas of the sheep showed that the iodine-deficient diet also caused a reduction in the growth of wool.

Experimental oxalate urolith formation in rats.

Urinary calculi composed of calcium oxalate were produced in male hooded Wistar rats fed a vitamin B6 deficient diet over 16 weeks. This basic diet was modified by doubling the phosphate content or loading with vitamin C or D3 in three treatment groups. The number of rats developing oxalate stones was not altered by the addition of vitamin D3 or phosphate, but there was a significant increase in total weight of stone formed and histological evidence of extensive renal damage in rats on the high vitamin D3 diet. The addition of vitamin C to the vitamin B6 deficient rats resulted in a reduction in the number of rats with uroliths and a fall in urinary oxalate excretion, while similarly loaded vitamin B6 supplemented controls were free of oxalate calculi. It is concluded that the oxalate urolithiasis induced by vitamin B6 deficiency was exacerbated by added vitamin D3 and reduced by vitamin C.

An isotopic study of oxalate excretion in sheep.

Intravenously injected 14C labelled oxalate was rapidly removed from the blood stream via the kidney in 2 sheep, 75% being cleared within 8 h. Mean daily urinary oxalate excretions over 5 days were 21-2 and 27-5 mg and the derived plasma oxalate concentrations were 52-6 and 74-4 mug/100 ml, respectively. Oxalate was both filtered and secreted by the renal tubule with oxalate/inulin ratios varying from 1-11 to 1-57 in 6 normal sheep. A large increase in calcium excretion induced by calcium borogluconate infusion over 5 days was accompanied by a small but consistent increase in urinary oxalate excretion relative to calcium. Oxalate in blood was to be found mainly in the plasma, there being a small (8%) proporation within erythrocytes. This is lower than that reported for man, and yet in its excretion of oxalate via the kidney the sheep appears to closely resemble man and dog.