Reduction of essential fatty acid deficiency in rat fed a low iron fat free diet

Diet Regulation of Long-Chain PUFA Synthesis: Role of Macronutrients, Micronutrients, and Polyphenols on Δ-5/Δ-6 Desaturases and Elongases 2/5

Deficiencies in the n-3 (ω-3) long-chain PUFAs (LC-PUFAs) EPA and DHA are associated with increased risk for the development of numerous diseases. Although n-3 LC-PUFAs can be obtained by consuming marine products, they are also synthesized endogenously through a biochemical pathway regulated by the Δ-5/Δ-6 desaturase and elongase 2/5 enzymes. This narrative review collates evidence from the past 40 y demonstrating that mRNA expression and activity of desaturase and elongase enzymes are influenced by numerous dietary components, including macronutrients, micronutrients, and polyphenols. Specifically, we highlight that both the quantity and the composition of dietary fats, carbohydrates, and proteins can differentially regulate desaturase pathway activity. Furthermore, desaturase and elongase mRNA levels and enzyme activities are also influenced by micronutrients (folate, vitamin B-12, vitamin A), trace minerals (iron, zinc), and polyphenols (resveratrol, isoflavones). Understanding how these various dietary components influence LC-PUFA synthesis will help further advance our understanding of how dietary patterns, ranging from caloric excesses to micronutrient deficiencies, influence disease risks.

Iron deficiency during pregnancy and lactation modifies the fatty acid composition of the brain of neonatal rats

Iron deficiency is common in pregnant and lactating women and is associated with reduced cognitive development of the offspring. Since iron affects lipid metabolism, the availability of fatty acids, particularly the polyunsaturated fatty acids required for early neural development, was investigated in the offspring of female rats fed iron-deficient diets during gestation and lactation. Subsequent to the dams giving birth, one group of iron-deficient dams was recuperated by feeding an iron-replete diet. Dams and neonates were killed on postnatal days 1, 3 and 10, and the fatty acid composition of brain and stomach contents was assessed by gas chromatography. Changes in the fatty acid profile on day 3 became more pronounced on day 10 with a decrease in the proportion of saturated fatty acids and a compensatory increase in monounsaturated fatty acids. Long-chain polyunsaturated fatty acids in the n-6 family were reduced, but there was no change in the n-3 family. The fatty acid profiles of neonatal brain and stomach contents were similar, suggesting that the change in milk composition may be related to the changes in the neonatal brain. When the dams were fed an iron-sufficient diet at birth, the effects of iron deficiency on the fatty acid composition of lipids in both dam's milk and neonates' brains were reduced. This study showed an interaction between maternal iron status and fatty acid composition of the offspring's brain and suggests that these effects can be reduced by iron repletion of the dam's diet at birth.

The effect of excess cobalt on milk fatty acid profiles and transcriptional regulation of SCD, FASN, DGAT1 and DGAT2 in the mammary gland of lactating dairy cows

The main objective of this study was to investigate the effect of excess cobalt (Co) on gene expression of stearoyl-CoA desaturase (SCD), fatty acid synthase (FASN), diacylglycerol acyltransferase 1 (DGAT1) and diacylglycerol acyltransferase 2 (DGAT2) of lactating dairy cows in relation to milk fatty acid profile. Seven multiparous cows of the Norwegian Red cattle breed (NRF) had their basal diet supplemented with 1.4 g Co as a 24 g/l solution of Co-acetate per os twice daily for 7 days followed by a 9-day depuration period. Udder biopsies were performed prior to the treatment period, after 1 week of treatment and immediately after the depuration period. Excess Co reduced the proportion of all cis-9 monounsaturated fatty acids and increased the proportion of 18:0 in milk. However, gene expression levels of SCD, DGAT1, DGAT2 and FASN were not significantly altered. Our results indicate that the effect of Co on milk fatty acid profile is mediated at the post-transcriptional level by reduced activity of SCD in the mammary gland. Potential mechanisms explaining how Co might reduce stearoyl-CoA desaturation are discussed.

Ncb5or deficiency increases fatty acid catabolism and oxidative stress

The endoplasmic reticulum-associated NADH cytochrome b(5) oxidoreductase (Ncb5or) is widely distributed in animal tissues. Ncb5or(-/-) mice develop diabetes at age 7 weeks and have increased susceptibility to the diabetogenic oxidant streptozotocin. Ncb5or deficiency also results in lipoatrophy and increased hepatocyte sensitivity to cytotoxic effects of saturated fatty acids. Here we investigate the mechanisms of these phenomena in prediabetic Ncb5or(-/-) mice and find that, despite increased rates of fatty acid uptake and synthesis and higher stearoyl-CoA desaturase (SCD) expression, Ncb5or(-/-) liver accumulates less triacylglycerol (TAG) than wild type (WT). Increased fatty acid catabolism and oxidative stress are evident in Ncb5or(-/-) hepatocytes and reflect increased mitochondrial content, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) expression, fatty acid oxidation rates, oxidative stress response gene expression, and oxidized glutathione content. Ncb5or(-/-) hepatocytes readily incorporate exogenous fatty acids into TAG but accumulate more free fatty acids (FFA) and have greater palmitate-induced oxidative stress responses and cell death than WT, all of which are alleviated by co-incubation with oleate via TAG channeling. A high fat diet rich in palmitate and oleate stimulates both lipogenesis and fatty acid catabolism in Ncb5or(-/-) liver, resulting in TAG levels similar to WT but increased intracellular FFA accumulation. Hepatic SCD-specific activity is lower in Ncb5or(-/-) than in WT mice, although Ncb5or(-/-) liver has a greater increase in Scd1 mRNA and protein levels. Together, these findings suggest that increased FFA accumulation and catabolism and oxidative stress are major consequences of Ncb5or deficiency in liver.

Chronic marginal iron intakes during early development in mice result in persistent changes in dopamine metabolism and myelin composition

Marginal iron (Fe) deficiency is prevalent in children worldwide, yet the behavioral and biochemical effects of chronic marginal Fe intakes during early development are not well characterized. Using a murine model, previous work in our laboratory demonstrated persistent behavioral disturbances as a consequence of marginal Fe intakes during early development. In the present study, Swiss-Webster mice fed a control Fe diet (75 microgram Fe/g diet, n = 13 litters) or marginal Fe diet (14 microgram Fe/g diet, n = 16 litters) during gestation and through postnatal day (PND) 75 were killed on PND 75 for assessment of tissue mineral concentrations, dopamine metabolism, myelin fatty acid composition, and c- and m-aconitase activities. In addition, these outcomes were assessed in a group of offspring (n = 13 litters) fed a marginal Fe diet during gestation and lactation and then fed a control diet from PND 21-75. Marginal Fe mice demonstrated significant differences in brain iron concentrations, dopamine metabolism and myelin fatty acid composition relative to control mice; however, no difference in c- or m-aconitase activity was demonstrated in the brain. The postnatal consumption of Fe-adequate diets among marginal Fe offspring did not fully reverse all of the observed biochemical disturbances. This study demonstrates that chronic marginal Fe intakes during early development can result in significant changes in brain biochemistry. The persistence of some of these biochemical changes after postnatal Fe supplementation suggests that they are an irreversible consequence of developmental Fe restriction.

Different degrees of moderate iron deficiency modulate lipid metabolism of rats

Severe iron deficiency affects lipid metabolism. To investigate whether moderate iron depletion also alters lipid variables-including lipid levels in serum and liver, hepatic lipogenesis, and fatty acid composition indicative of an impaired desaturation-we carried out experiments with rats fed 9, 13, and 18 mg iron/kg diet over a total of 5 wk. The study also included three pair-fed control groups and an ad libitum control group, fed with 50 mg iron/kg diet. The iron-depleted rats were classified as iron-deficient on the basis of reduced serum iron, hemoglobin concentration, and hematocrit. All moderately iron-deficient rats had significantly lower cholesterol concentrations in liver and serum lipoproteins than their pair-fed controls. Rats with the lowest dietary iron supply had higher concentrations of hepatic phosphatidylcholine (PC) and phosphatidylethanolamine (PE), lower activities of glucose-6-phosphate dehydrogenase, malic enzyme and fatty acid synthase, and higher triacylglycerol concentrations in serum lipoproteins than the corresponding pair-fed control rats. Moderate iron deficiency also depressed the serum phospholipid level. Moreover, several consistent significant differences in fatty acid composition of hepatic PC and PE occurred within moderate iron deficiency, which indicate impaired desaturation by delta-9 and delta-6 desaturases of saturated and essential fatty acids. We conclude that lipid variables, including cholesterol in liver and serum lipoproteins as well as fatty acid desaturation, reflect the gradations of iron status best and can be used as an indicator of the degree of moderate iron deficiency.

Changes of hepatic lipid and fatty acid profiles in rats administered iron-deficient diet and ethanol

This investigation was undertaken to elucidate the effects of iron deficiency and/or ethanol ingestion on lipid metabolism of female rat liver. 40 Wistar rats (about 40 g weight) were fed a normal diet (Fe: 40 ppm) or an iron-deficient diet (Fe: 5 ppm) for 8 wk. Half of the rats in each group were given 10% ethanol in the drinking water for the last 4 wk. In rats fed the iron-deficient diet (D), the content of total hepatic lipid was higher than that in the rats given the normal diet (N). From the gas chromatography analyses of the fatty acids in total lipids, only the proportion of 18:2n-6 was increased, whereas those of 16:1n-7 and 20:4n-6 decreased. In rats given ethanol and an iron-sufficient diet (NE), the contents of all lipids with the exception of phospholipid were significantly higher than those in the N group. The percentages of fatty acids 12:0, 14:0, 16:0, 18:1 and 20:1 in the total hepatic lipid were increased, whereas those fatty acids of 18:0, 20:4, 22:6 and 24:0 were decreased. In the rats given ethanol and an iron-deficient diet (DE), the contents of all hepatic lipid components did not differ significantly from those in the D group. The percentages of fatty acids 12:0, 14:0 and 16:1 in the total hepatic lipid were increased. These data suggest that ethanol ingestion by iron-deficient rats does not induce the same changes in their hepatic lipid components and fatty acid patterns as those seen in fatty degeneration of the liver.

The effect of cadmium on the composition and metabolism of hepatic fatty acids in zinc-adequate and zinc-deficient rats

Exposure to cadmium (Cd) caused changes in the fatty acid composition of phospholipids, such as increases in levels of saturated and (n-6) fatty acids and decreases in levels of (n-9) fatty acids, in the liver phospholipids of rats fed a fat-free diet. These changes were similar to those caused by dietary zinc deficiency. The changes in fatty acid composition after administration of Cd were greater in zinc-deficient (ZD) rats than zinc-adequate (ZA) rats. When [14C]18:0 was injected intravenously in order to examine the metabolism of (n-9) fatty acids, a decrease in the rate of conversion of [14C]18:0 to [14C]18:1 was observed in liver phospholipids after treatment of ZD rats with Cd. These results suggested that Cd can affect the metabolism of fatty acids in relation to zinc status and, in particular, causes a reduction in the activity of delta 9-desaturase which converts 18:0 to 18:1.

Effects of zinc deficiency on the fatty acid composition and metabolism in rats fed a fat-free diet

The effects of dietary zinc deficiency (ZD) on the composition and metabolism of the fatty acyl chains of phospholipids in rat liver were investigated with a fat-free diet. The levels of (n - 9) fatty acids such as 18:1 and 20: 3(n - 9) in liver phospholipids (PL) were significantly lower in ZD-rats (19.4% and 5.4%, respectively) than in PF-rats (25.2 and 8.3%). On the other hand, the levels of (n - 6) acids such as 18:2 and 20:4 were higher in ZD-rats (3.3 and 19.1%, respectively) than in PF-rats (2.1 and 14.9%). In order to study the metabolism of fatty acids in vivo, 14C-18:0 or 14C-18:2 was intravenously injected, and then the conversion to the respective metabolite was examined. After the injection of 14C-18:0, the radioactivity was found in 18:0 (49.3% of the total), 18:1 (33.2%), and 20:3 (n - 9) (9.1%) in liver PL in PF-rats at 24 h. In ZD-rats, the radioactivity was dramatically lower in 18:1 (23.5%) and 20:3 (n - 9) (3.6%), suggesting that the conversion of 18:0 to 18:1 and 20:3 (n - 9) was strongly inhibited in ZD-rats. When 14C-18:2 was injected, the radioactivity was mainly found in 18:2, 20:3 (n - 6), and 20:4. The radioactivity in 20:4 in ZD-rats was slightly higher than that in control rats. These results indicate that zinc deficiency affects the fatty acid metabolism in liver, in particular, it causes a reduction in delta 9 desaturase activity, when rats are fed a fat-free diet.

Fatty acid pattern of tissue phospholipids in copper and iron deficiencies

Because copper and iron have been reported to be essential cofactors in delta 9 desaturation of fatty acids, the effects of different dietary intakes of copper and iron on tissue fatty acids were studied. Male Long-Evans rats (ten per group) were fed diets containing adequate, deficient or excess copper or iron. On day 42 of the dietary regimen, the animals were killed and tissues and blood were removed for analysis of metals and fatty acids of phospholipids. Compared with the copper-adequate rats, the copper-deficient rats showed increased 18:0 in liver and decreased 16:1 omega 7 in liver, heart and serum. There were no differences for 16:0 or 18:1 omega 9. Intake of excess copper did not cause an increase in products of delta 9 desaturation. Comparisons between iron-deficient and iron-adequate rats showed that iron deficiency increased 18:2 omega 6 in liver and serum and decreased 20:4 omega 6 in serum only. Relative percentages of 16:0, 18:0, 16:1 omega 7 and 18:1 omega 9 in liver and serum phospholipids were similar for both groups. Intake of excess iron caused a decrease in 18:2 omega 6; and 16:0 and 18:1 omega 9 were higher in the liver of the iron-excess group than the iron-deficient group. This study did not support the requirement for copper or iron in the delta 9 desaturation of fatty acids as expressed in phospholipids of liver, heart and serum.

Control of polyunsaturated acids in tissue lipids

Since the discovery in 1929 that certain polyunsaturated fatty acids (PUFA) are essential for life and health, intense investigation has revealed the multiplicity of members in each of several families of PUFA, no two of which are equivalent. The quantified nutrient requirements for the essential dietary precursors of the two dominant families of PUFA have been estimated, and the general functions of these families are slowly becoming known. The PUFA are essential components of structural membrane lipids. The functions of the individual members are not yet differentiated, except as they act as precursors of synthesis of unique octadecanoid, eicosanoid, and docosanoid products of oxidation that have potent biological properties. The PUFA occur in animals and higher plants as ubiquitous and essential components of structural lipid that are in a dynamic equilibrium with the pool of dietary acyl groups. Many human diseases have been found to involve unique essential fatty acid (EFA) deficiencies or distortions of the normal equilibrium pattern. The equilibrium is influenced by the level of dietary intake or precursors, by the presence of competing essential and nonessential acyl groups, by nonoptimum intake of other essential nutrients, by hormonal effects, by drug therapy, and by other effects upon physiological condition. With the many variables already known to modulate or control the equilibrium, it should be possible with more precise understanding of each variable to shift abnormal equilibria in the direction of normalcy. This perhaps will be the next area of intensive investigation in this field of nutrition and metabolism.

Reduced plasma lecithin cholesterol acyl transferase activity in rats fed iron-deficient diets

An iron-deficient diet containing no fat (FF-Fe) or containing either 14% hydrogenated coconut oil (HCNO-Fe) or 14% corn oil (CO-Fe) was fed to separate groups of rats for 10 weeks. In the control group, the corresponding iron-supplemented diets were fed FF+Fe, HCNO+Fe, CO+Fe. When rats were fed iron-deficient diets, their plasma lecithin cholesterol acyl transferase (LCAT) activity was significantly reduced as compared to controls. Their plasma also contained releatively more cholesteryl esters (CE) than free cholesterol (CH). In rats fed FF+Fe and CO+Fe diets, plasma contained similar levels of CE and CH. In those fed HCNO+Fe diet, plasma had 40% less Ce than CH. Red cell CH content was significantly greater in the CO-Fe group. Iron deficiency, as indicated by low blood hemoglobin (Hb) and hematocrit (Hct) values, was also observed only in this group. The triglyceride and phospholipid contents of plasma in rats fed iron-deficient diets were significantly lower than of those in the control groups. Thus, changes in LCAT activity and CE/CH ratio in plasma showed the effect of iron-deficient diet consumption even before the blood Hb and Hct levels were reduced.

Reduction of hepatic stearoyl-CoA desaturase activity in rats fed iron-deficient diets

The effect of feeding iron-deficient diets to rats on the hepatic stearoyl-CoA desaturase activity was examined since iron is present in the delta 9 desaturation system. Separate groups of rats were fed low iron diets without fat (FF-Fe) or containing either 14% hydrogenated coconut oil (HCNO-Fe) or 14% corn oil (CO-Fe) for 10 weeks. Diets supplemented with iron (FF + Fe, HCNO + Fe and CO + Fe) were fed to the corresponding control groups. Stearoyl-CoA desaturase activity in the liver microsomes of rats in the CO + Fe group (2.55 +/- 0.17 nmol oleate produced/min/mg protein) was about half of that in the HCNO + Fe (4.76 +/- 0.15) and FF + Fe (5.38 +/- 0.18) diet groups. In rats which were fed iron-deficient diets, hepatic desaturase levels were reduced significantly as compared to those of controls (1.0 +/- 0.06, CO-Fe; 2.11 +/- 0.13, HCNO-Fe; 3.65 +/- 0.1, FF-Fe). The hemoglobin (Hb) and hematocrit (Hct) levels in blood showed moderate iron depletion only in the CO-Fe group. Hence, dietary polyunsaturated fat promotes the onset of iron deficiency. Furthermore, even before the blood Hb and Hct values express iron depletion, the effect of feeding low iron diets was observed by the reduction of hepatic delta 9 desaturase activity in rats fed HCNO-Fe and FF-Fe diets.

Preparation of radiolabled tetracosa mono- and dienoic acid methyl esters from rat erythrocyte lipids by thin layer chromatography

An easy method of obtaining pure fatty acid methyl esters (FAME) of tetracosa mono- and dienoic acids (24:1, 24:2) using thin layer chromatography (TLC) is described. The total lipids isolated from rat erythrocytes were treated with methanolic-NaOH. Sphingomyelin was unaffected by this treatment and was separated from FAME of glycerolipids and cholesterol by TLC. FAME of sphingomyelin were then prepared by acid methanolysis. These esters migrated into 2 distinct bands on TLC. The slow moving band contained FAME of 16:0, 16:1, 18:0, 18:1, 19:0 and 20:0 wheras the fast moving band contained FAME of 22:0, 23:0, 24:0, 24:1 and 24:2. After AgNO3-TLC, the FAME of the fast moving band separated into 3 species; esters of saturated acids, 24:1 and 24:2, respectively. With erythrocyte lipids of rats fed a fat-free diet and injected with 14C-18:1, this method yielded 14C-24:1. From rats injected with 14C-18:2 and maintained on a corn oil diet, 14C-24:2 was obtained.