Essential Fatty Acid Deficient Animals Research Articles

Nutritional Modulation of Guinea Pig Skin Hyperproliferation by Essential Fatty Acid Deficiency is Associated with Selective Down Regulation of Protein Kinase C-β

In a previous study we demonstrated that 13-hydroxyoctadecadienoic acid (13-HODE), a 15-lipoxygenase metabolite of linoleic acid is incorporated into epidermal phosphatidyl 4,5-bisphosphate (PtdIns 4,5-P2) and released as 13-HODE-containing-diacylglycerol (13-HODE-DAG). In vitro, 13-HODE-DAG was shown to selectively inhibit epidermal total protein kinase C (PKC-β) activity. To determine whether these observations are relevant in vivo, guinea pigs were made essential fatty acid deficient (EFAD) by feeding them a basal diet supplemented with 4% hydrogenated coconut oil for 8 wk. Tissue levels of putative 13-HODE-DAG, protein kinase C (PKC) isozymes and tissue hyperproliferation were determined in the epidermal preparations from skin of control safflower oil-fed guinea pigs, those fed EFAD diet and those fed EFAD diet followed by the control diet for 2 wk. Our data revealed that cutaneous 13-HODE and 13-HODE-DAG were significantly lower in EFAD animals than in safflower-fed controls. These reductions were associated with both elevated epidermal hyperproliferation and elevated expressions and activities of PKC-α and β-isozymes. Refeeding the animals with safflower oil for 2 wk replenished tissue levels of 13-HODE-DAG, which inversely correlated with the selective down regulation of PKC-β expression and activity and the reversal of hyperproliferation. In contrast, although the expression and activity of PKC-α was elevated in the epidermis of the EFAD guinea pigs, this elevated PKC-α expression was not down regulated after refeeding the safflower oil diet to the animals. These results suggest that the epidermal level of 13-HODE plays a role in vivo in modulating cutaneous hyperproliferation via the generation of 13-HODE-DAG via signal transduction and its selective suppression of PKC-β isozyme.

Oestrogen and essential fatty acid supplementation corrects bone loss due to ovariectomy in the female Sprague Dawley rat

Essential fatty acid deficient animals develop osteoporosis. Eicosapentaenoic acid and gamma-linoleic acid have been reported to have positive effects on bone metabolism in both the growing male rat and the ovariectomized (OVX) female rat. These effects have been further investigated using a novel gamma- linolenic/eicosapentaenoic acid diester together with an oestrogen implant in the ovariectomized, female Sprague Dawley rat. Rats were sham-operated or ovariectomized at age 11 weeks. Two groups of OVX rats received an oestrogen implant at ovariectomy. Animals received fatty acids, linoleic acid (control) or a diester with gamma-linolenic acid and eicosapentaenoic acid as part of a semi-synthetic diet. Bone calcium content and excretion of deoxypyridinolines as marker of bone degradation were measured at 14 weeks. Oestrogen, as well as diester alone, increased calcium/femur to sham levels. Oestrogen plus diester potentiated the effect of oestrogen on bone calcium (P<0.05 vs OVX). At the same time, oestrogen alone and the combination of oestrogen plus diester significantly reduced (P<0.05 vs OVX) urinary deoxypyridinoline and hydroxyproline excretion. Again, the diester potentiated the effect of oestrogen. The effects of the diester alone, together with the potentiated effects of oestrogen by the essential fatty acids on osteoporosis, are novel findings.

Fatty acid composition, eicosanoid production and permeability in skin tissues of rainbow trout ( Oncorhynchus mykiss) fed a control or an essential fatty acid deficient diet

Rainbow trout ( Oncorhynchus mykiss) were fed either a control diet containing fish oil or an essential fatty acid (EFA) deficient diet containing only hydrogenated coconut oil and palmitic acid as lipid source (93.4% saturated fatty acids) for 14 weeks and the fatty acid compositions of individual phospholipid classes from skin and opercular membrane (OM) determined. The permeability of skin and OM to water and the production of eicosanoids in skin and gills challenged with the Ca 2+ ionophore A23187 were also measured. Phospholipid (PL) fatty acid compositions were substantially modified in EFA-deficient fish, with increased saturated fatty acids and decreased polyunsaturated fatty acids (PUFA), especially arachidonic acid (AA) and eicosapentaenoic acid (EPA), while docosahexaenoic acid (DHA) was largely retained. The onset of EFA deficiency was shown by the appearance of n-9 PUFA, particularly 20:3n-9. The main effects of EFA deficiency on phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were to increase saturated fatty acids and monoenes, especially 16:1 and 18:1, and to decrease EPA and DHA. The content of DHA in phosphatidylserine (PS) was high in control animals (40% in skin and 35% in opercular membrane) and was mostly retained in EFA deficient animals. Arachidonic acid (AA) was the most abundant PUFA esterified to phosphatidylinositol (PI) and was significantly reduced in EFA deficient animals (from 31% to 13% in skin), where a large amount of 20:3n-9 (9% in skin) was also present. Influxes and effluxes of water through skin and opercular membrane were measured in vitro. No differences were detected between rainbow trout fed the control or the EFA deficient diet. 12-Hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE) and 14-hydroxydocosahexaenoic acid (14-HDHE) could not be detected in skin from control or EFA deficient fish. There was no difference between control and EFA deficient trout in the levels of leukotriene C 4 (LTC 4) and leukotriene C 5 (LTC 5) in skin cells challenged with the calcium ionophore A23187, and of prostaglandin F 2α (PGF 2α), 12-HETE and 12-HEPE in gill cells challenged similarly. Prostaglandin F 3α (PGF 3α) production by ionophore stimulated gill cells was significantly reduced in fish fed the EFA-deficient diet. 14-HDHE produced by gill cells was 3.3 fold higher in EFA deficient fish compared to controls.

Diet Alters Metabolic Rate in the Yellow-Bellied Marmot (Marmota flaviventris) during Hibernation

We investigated the hypothesis that dietary composition can alter metabolic rate in the marmot. We provided marmots with two different diets: Purina standard Rodent Chow (no. 5001) and an essential fatty acid deficient (EFAD) diet (Purina chow no. 5803C). Metabolic rate was determined by indirect calorimetry during the summer and winter season. The mean metabolic rate measured during the summer was 7.54 mL O₂ min⁻¹ kg⁻¹ 0.62 for the control group and 7.43 mL O₂ min⁻¹ kg⁻¹ ± 0.34 for the EFAD animals. Both animal groups gained weight during the summer; body weights peaked in September. Fatty acid analysis of white adipose tissue from each group revealed significant differences (P < 0.01) in percent composition of fatty acid species 16:1, 18:1, 18:2, 18:3, and 20:0. Winter mean metabolic rates for the control group were significantly lower (P < 0.05) than they were for EFAD animals for all stages of hibernation (entrance, deep hibernation, and arousal). Average total hibernating bout length for the control group was 7.76 d, which is significantly higher (P < 0.05) than the 5.72 d for the EFAD group. These results support the hypothesis that essential fatty acids alter the metabolic rate in marmots and are necessary for normal thermoregulation during hibernation.

Inhibition of Cholesterol and Sphingolipid Synthesis Causes Paradoxical Effects on Permeability Barrier Homeostasis

Cholesterol, fatty acid, and sphingolipid synthesis are required for barrier homeostasis, as demonstrated by studies where synthesis of these species is stimulated in parallel with barrier repair. Moreover, blockade of synthesis of these lipids with inhibitors of two of the rate-limiting enzymes, HMGCoA reductase (lovastatin, fluvastatin) and serine palmitoyl transferase (beta-chloroalanine), alters the kinetics of barrier repair. Whereas these studies demonstrated a requirement for these lipids individually, we asked here whether these lipids are required in either an additive or cooperative fashion. We applied each class of inhibitor alone or the two classes of inhibitors together to acetone-treated skin, or each class separately to essential fatty acid deficient murine skin. When fluvastatin or beta-chloroalanine was applied individually to acetone-treated skin, each caused a delay in the early or late stages of barrier recovery, respectively (assessed as transepidermal water loss). However, when applied together they caused no further worsening at the early time point and a paradoxical improvement at the later time points. This improvement correlated with an accelerated return of sphingolipids, which was perhaps due to a global stimulation of lipid synthesis induced by HMGCoA reductase inhibitors. In essential fatty acid deficient animals, inhibition of HMGCoA reductase caused drastic worsening of both clinical appearance and barrier function, but beta-chloroalanine caused a paradoxical improvement, which correlated with a significant reduction in epidermal sphingolipids. These results are consistent with a requirement for both cholesterol and sphingolipids for barrier homeostasis, and also with the suggestion that both of these lipids must be present (with free fatty acids) for optimal barrier function.

Reduction of eicosanoid production by essential fatty acid depletion does not attenuate the inflammatory response induced by Pseudomonas aeruginosa pneumonia in rat lung

Lipid mediators of inflammation have been implicated in the pathogenesis of Pseudomonas aeruginosa (PA) related pulmonary damage in patients with cystic fibrosis. We studied the role of these mediators in a rat model of PA endobronchitis using essential fatty acid deficient (EFAD) animals. Whole blood from EFAD animals produced significantly less leukotriene B 4 (LTB 4) and hydroxyheptadecatrienoic acid when stimulated ex vivo than did whole blood from control animals (p<0.005). Similarily, lung lavage fluid from EFAD animals infected with PA contained less LTB 4 and thromboxane B 2 (TXB 2) than that from control animals. Despite these differences, cellular infiltration of airways in response to PA infection was virtually identical in animals from the regular diet and the EFAD groups. Both EFAD and control animals had a significant increase in white blood cells (WBC) in lung lavage fluid at 1, 3 and 6 days following infection with PA when compared to animals recieving sterile beads. Localized areas of consolidation and nodularity were grossly evident in the lungs of all PA infected animals irrespective of their ability to generate the lipid inflammatory mediators. Microscopic examination of lung sections demonstrated similar changes in all infected animals. We conclude that LTB 4 and TXB 2 production occurs early in the course of PA pulmonary infection in rats. This early rise in lipid mediators is temporally associated with an influx of WBC into the airways. However, attenuation of eicosanoid production by use of an EFAD diet does not lead to a reduction in the inflammatory response to PA infection. Thus, in this model, decreased production of lipid-derived mediators of inflammation is not sufficient to afford protection from the inflammatory changes associated with PA infection.

Barrier function regulates epidermal DNA synthesis.

We examined the possibility that the cutaneous permeability barrier regulates epidermal DNA synthesis in two acute and two chronic models of barrier perturbation. In animals treated topically with acetone, DNA synthesis is increased 102%, in tape-stripped animals 127%, in essential fatty acid deficient animals 50%, and in animals chronically treated with topical lovastatin 64%. This linkage between disturbances in barrier function and increased DNA synthesis is further supported by specific and correlative observations: (a) in these disparate models, artificial replacement of the barrier with a water-impermeable membrane inhibits the expected increase in DNA synthesis; (b) the extent of the burst in DNA synthesis is proportional to the degree of barrier abrogation; (c) the inhibition of DNA synthesis by membranes is directly related to the degree of permeability of these occlusive membranes, i.e., the more impermeable the greater the degree of inhibition; (d) topical treatment with lipids that restore barrier function corrects the increase in DNA synthesis; and (e) barrier abrogation with acetone produces an increase in epidermal DNA synthesis without altering bulk protein synthetic rates in contrast to events known to follow injury or cell replacement. Autoradiographic studies show that the increase in DNA synthesis after acetone treatment is limited to the epidermal basal layer. This constellation of findings strongly suggests that cutaneous barrier function is one factor that regulates epidermal DNA synthesis.

Lipid composition of cultured human keratinocytes in relation to their differentiation

The present study was undertaken to explore the possibility of the use of cultured human keratinocytes for the study of changes in lipid composition in relation to epidermal differentiation. In a submerged culture system, in which the stratification is incomplete, no significant differences have been found between the lipid composition of cells grown either at low calcium concentration (0.06 mM) (at which the keratinocyte differentiation is markedly retarded) or at normal calcium concentration (1.6 mM) (at which some differentiation takes place). Under these conditions the amount of phospholipids and sterols was high and that of ceramides was low. Furthermore, the acylglucosylceramides (AGC) and acylceramides (AC), the latter one known to be involved in water barrier function, were found to be absent. Contrary to this, both AGC and AC were found to be present in significant amounts in an air-exposed model using de-epidermized dermis (DED) as a substrate (in which, as judged from morphologic criteria, the extent of keratinocyte stratification is similar to that seen under the in vivo conditions). Fatty acid analysis revealed significantly lower content of 18:2 and higher content of 16:1 and 18:1 acids with all culture conditions used, as compared to the parent epidermis. This is probably a result of fatty acid levels and composition in fetal calf serum (which was used in the present study) that differ markedly from the in vivo situation. The 20:4 content was similar to that in the epidermis only in cells cultured under the submerged conditions, during which they have been found (Isseroff et al. 1987. J. Lipid Res. 28: 1342-1349) to be able to convert 18:2 to 20:4. In DED cultures, however, the 20:4 content was markedly lower. Under all culture conditions used, the triglyceride content was higher as compared to the non-cultured epidermis. The high content of triglycerides and the fatty acid composition of the various lipid fractions showed a resemblance with what is found in the epidermis in essential fatty acid-deficient animals. This resemblance was confirmed by electron micrographs which revealed the presence of some partially or completely empty lamellar bodies. The results of the present study suggest that the air-exposed culture model, in which the keratinocytes show a high extent of stratification, could be of great value in the study of epidermal lipid metabolism. However, further alterations in culture conditions are necessary to more closely approximate the lipid composition of noncultured epidermis.

Effect of Essential Fatty Acid Deficiency on Cutaneous Sterol Synthesis

The fact that the skin is a major site of total body sterologenesis, coupled both with the apparent absence of low density lipoprotein receptors on keratinocytes and with the lack of influence of serum cholesterol on epidermal sterologenesis, has created the impression that epidermal lipid synthesis might be autonomous, i.e., nonregulatable. Recent studies have shown, however, that disruption of cutaneous barrier function with acetone or detergents stimulates epidermal sterologenesis (J Lipid Res 26:418-427, 1985). To correlate further sterologenesis with barrier function, we measured de novo synthesis of cholesterol and total nonsaponifiable lipids in essential fatty acid-deficient (EFAD) hairless mice. Animals with defective barrier function, manifested by abnormal transepidermal water loss, demonstrated a 2-fold increase in epidermal cholesterol and total nonsaponifiable lipid synthesis over controls while synthesis in the dermis was unchanged. Epidermal sterologenesis in EFAD animals, repleted with linoleic acid either systematically or topically, returned toward normal as barrier function improved. Moreover, plastic occlusion of EFAD mouse skin normalized epidermal sterologenesis at 1 and 3 days. These results provide further evidence that epidermal sterologenesis is not entirely autonomous, and can be regulated by water barrier requirements.

Metabolism of linoleic acid and other essential fatty acids in the epidermis of the rat

Essential fatty acids are absolutely necessary for maintaining the proper condition of the water barrier (stratum compactum) in the skin. Even direct topical application of linoleic acid or any other Z, Z-( n − 6, n − 9)- fatty acid to the skin restores the barrier in essential fatty acid-deficient animals. In order to investigate the mechanism by which these polyunsaturated fatty acids exert their activity, radioactively labelled fatty acids were applied to the skin of the live animal and the epidermal lipids were analysed after 1–4 days. Much radioactivity was incorporated into two peculiar lipids, viz. acyl ceramide and acyl acid, which are characteristic of the barrier, in which linoleate was esterified to the end-position of very-long-chain (C 30–34) unsaturated ω-hydroxy fatty acids. Strong evidence was obtained which showed that these lipids carry linoleate into the barrier layer where it is converted, probably by lipoxygenase(s), into a series of peroxidated lipids. The lipoxygenase inhibitor, eicosatetraynoic acid, prevents both oxygenation of the polyunsaturated fatty acid and the formation of a healthy skin. This peroxidation may supply the mediators which induce the proper differentiation of the epidermal cells into an effective stratum compactum and a horny layer.

Metabolic changes in scaly lesions of rat skin produced by essential fatty acid deficiency.

Marked changes in the structure and metabolism of lipids were observed at scaly lesions induced in the skin of rats by the feeding for four months of a diet deficient in essential fatty acids. The concentration of neutral lipids increased in the experimental skin specimens with the exception of free cholesterol. Analysis of fatty acids in the skin lipids of these essential fatty acid deficient rats showed a marked increase in monoenoic and eicosatrienoic acids, with a concomitant decrease in linoleic and arachidonic acids. Incubation of skin specimens from the essential fatty acid deficient rats with [2-3H]glycerol and [1-14C]acetate showed a marked increase in the incorporation of both precursors into all lipid classes. Particularly, their incorporations into phosphatidylcholine were predominant compared to other lipid classes. With regard to the molecular species of phosphatidylcholine, saturated-monoenoic and monoenoic-monoenoic species were highly synthesized in the skin from essential fatty acid deficient animals, and the synthesis of saturated-dienoic and tetraenoic species was very low with either precursor. Significant decreases in these labelings were also noted in saturated-saturated species. Addition of prostaglandin E2 to the incubation medium did not significantly affect the metabolism of any of the lipid classes in the skin from the essential fatty acid deficient rats. The present results, therefore, suggest that phosphatidylcholine containing linoleic acid may be a key lipid in the epidermal barrier function.

Effects of essential fatty acid deficiency on the induction of liver microsomal membranes by phenobarbital: an ultrastructural and biochemical investigation.

The essential fatty acids, particularly arachidonic, are important components of intracellular membrane systems. Their absence during dietary manipulation has been postulated to cause alterations in both composition and function of membranes and associated enzyme systems. In the current investigation, the effect of essential fatty acid deficiency on the induction of hepatic microsomal membranes my phenobarbital was studied. Control rats were fed a standard chow diet and either injected daily for 4 days with phenobarbital or with a placebo. Experimental animals were given an essential fatty acid-deficient (EFAD) diet and similarly injected with either phenobarbital or placebo. Following the above regimens, liver tissue was obtained for electron microscopy and biochemical membrane analysis. Control animals given phenobarbital displayed a marked proliferation of smooth endoplasmic reticulum in comparison to placebo controls. In contrast, EFAD rats did not exhibit an endoplasmic reticulum response to phenobarbital injection and appeared to recover from the drug administration injection more slowly than control animals. The alterations in fatty acid composition characteristic of an EFAD diet were observed in the microsomal membranes of the deficient animals. The concentrations of palmitic, palmitoleic, oleic, and 5,8,11-eicosatrienoic acids were significantly increased above that found in control animals. Concentrations of linoleic and arachidonic acids were reduced. Phenobarbital administration significantly increased the concentrations of palmitic, linoleic, and arachidonic acids in microsomal fractions of chow-fed animals but not in EFAD animals. Conversely, eicosatrienoic acid concentrations increased in phenobarbital-treated EFAD animals but not in chow-fed, drug-injected rats. The triene/tetraene ratio reflected these alterations. Essential fatty acid deficiency causes biochemical alterations of the hepatic microsomal membranes which are exaggerated by the administration of phenobarbital. These compositional changes appear to alter the functional ability of the membranes to proliferate in response to phenobarbital and, thereby, inhibit the efficaceous metabolism of this drug.

Isolated brain capillary endothelia: Influence of various levels of essential fatty acids on the acyl group composition of glycerophospholipids

On day seven of gestation. Wistar rats were assigned to a high essential fatty acid (EFA), low EFA, or a fat free diet. The same diets were continued during lactation. On weaning, the offspring were fed the same diets as their mother. Rats were killed at 222 days, brain capillary endothelia isolated, and total lipids extracted from the purified capillaries. The composition of the constituent fatty acids of ethanolamine glycerophospholipid (EGP), choline glycerophospholipid (CGP), and the alk-1-enyl EGP composition from each diet is reported. A decrease in dietary EFA led to reduced proportions of total saturated acyl groups in EGP with no change observed in the total saturated acyl groups from CGP, and an increase in monoenoic fatty acids, particularly 18:1n-9 for each phospholipid class. The proportions of 20:4n-6 in alk-1-enyl EGP were reduced in fat-free fed animals. In addition, the relationship between 20:3n-9 and 20:4n-6 fatty acids in brain capillary endothelia were markedly increased with a reduction in dietary fat. Low EFA and fat deficient animals showed a tendency to sequester 22:6n-3.

Effects of essential fatty acid deficiency on prostaglandin synthesis and fatty acid composition in rat renal medulla.

Studies are reported on the capacity of isolated rat renal papilla (inner medulla) to synthesize and release prostaglandin (PG) E from endogenous and exogenous precursor(s) during development of an essential fatty acid (EFA) deficiency in the rat. Weanling (21-day-old) male Sprague-Dawley rats were fed a fat-free diet supplemented with either 5% hydrogenated coconut oil (HCO) or 5% safflower oil (SO). At approximately 3, 6 and 7 weeks (6. 9 and 10 weeks of age), groups of animals fed each diet were killed for studies of PGE synthesis in the renal papillae. Differences in the fatty acid composition of the papillae lipids of the animals of each group were also determined. The in vitro production of PGE from endogenous precursor(s) was significantly reduced in the papillae from the 6-week-old rats fed the HCO diet compared to the control (SO) rats, and appeared to be near maximally depressed in the 10-week-old animals compared to that of animals fed an EFA deficient diet for over a year in an accessory experiment. Analyses of the fatty acids of the papillae lipids of the HCO groups showed that the levels of 18:2 and 20:4 were markedly reduced, and those of 16:1, 18:1 and 20:3 were elevated compared to the controls even in the 6-week-old animals, typical of an EFA deficiency. The papillae lipids of the animals fed the HCO diet were also depleted of their stores of 22:4 omega 6. A fatty acid believed to be derived by chain elongation of 20:3 omega 9, 22:3, was found in large concentrations in the papillae triglycerides of the EFA deficient rats. Incubations of exogenous arachidonic acid (20:4) in homogenates and tissue slices of the papillae of the HCO dietary groups showed that the PG synthetase was not impaired by an EFA deficiency. The rate of PGE synthesis in the papillae of the EFA deficient animals was generally enhanced when exogenous 20:4 was added, indicating that the concentration of available precursor(s) is a primary factor in the control of PGE synthesis in the papilla of the rat.

In vitro biosynthesis of prostaglandin E2 by kidney medulla of essential fatty acid deficient rats

Weanling rats were fed either a semisynthetic diet with no fat, with 28% by wt partially hydrogenated fish oil, or with 28% by wt arachis oil(control diet) for 6 or 7 1/2 months. The in vitro conversion of arachidonic acid to prostaglandin E2 by homogenates of the rat kidney medulla was measured by gaschromatography with electron capture detection. The kidney medulla of essential fatty acid deficient animals showed increased activity for the in vitro conversion of exogenous arachidonic acid to prostaglandin E2 when compared to the controls. The change of the enzymatic activity in the essential fatty acid deficient animals was reversible, as shown by refeeding. Inhibition of the prostaglandin synthetase was found at exogenous substrate concentrations higher than 50-100 muM.

Essential fatty acid deficiency: A condition to discriminate prostaglandin and non-prostaglandin mediated components of inflammation

The carrageenin induced hind paw inflammation is partially suppressed in essential fatty acid deficient (EFAD) rats, but prostaglandin E1 produces larger paw oedema in EFAD rats than in normal ones. Arachidonic acid restores in EFAD rats the suppressed carrageenin inflammation. Shortage of prostaglandin-precursor is the underlying mechanism of reduced carrageenin inflammation in EFAD rats, while the prostaglandin-synthesizing capacity remains unimpaired. BPP9a, a bradykinin potentiating peptide, enhances the carrageenin inflammation in EFAD and control rats equally. The kinin-mediated component of tissue injury is unaltered in EFAD animals, in which the prostaglandin-phase of inflammation is selectively suppressed. Indomethacin does not further reduce in EFAD rats that particular phase of inflammation where prostaglandins are abolished due to precursor shortage. In the preceding period indomethacin exerts partial suppression of inflammation even in EFAD rats. The latter finding supports the view that inhibition of prostaglandin-biosynthesis does not fully explain the antiinflammatory effect of indomethacin.

Effect of essential fatty acid deficiency on lipid metabolism in isolated fat cells of epididymal fat pads of rats.

AbstractLipogenesis, lipolysis, and stimulation of glucose conversion into lipid by insulin or prostaglandin E1 were studied in isolated fat cells of the epididymal fat pads of rats fed a fat‐free diet or this diet supplemented with 10% hydrogenated coconut oil or 10% safflower seed oil. Changes in fatty acid composition, characteristic of an essential fatty acid deficiency, were well advanced in the neutral lipid but had only started in the polar lipid of the fat cells of the epididymal fat pads of animals 3 months after weaning. Cellularity of the epididymal fat pads, as indicated by protein to lipid ratio of the fat cells, was influenced greatly by hydrogenated coconut oil in the diet irrespective of an essential fatty acid deficiency. Lipogenesis was increased in the fat cells of the animals fed the hydrogenated coconut oil diet 5 weeks after weaning but was not significantly different from that of the safflower fed animals 3 months after weaning. Incorporation of glucose into lipid, oxidation to CO2, and basal lipolysis were not significantly different in the fat cells of the essential fatty acid deficient animals from those fed safflower oil 3 months after weaning, except in animals of the fat‐free group based upon cell lipid. However, conversion of glucose to free fatty acid was significantly greater in the isolated fat cells of animals fed either the hydrogenated coconut oil or the fat‐free diet than in those of animals fed the safflower oil supplement. The incorporation of glucose into lipid by isolated fat cells was stimulated significantly by insulin in young animals fed a fat‐free diet, but the effect on lipogenesis appeared to be reversed in the fat cells of animals receiving safflower seed oil 3 months after weaning. Prostaglandin E1 also appeared to stimulate the incorporation of glucose into lipid in the fat cells of the older animals receiving safflower seed oil. Differences in osmolarity produced large differences in utilization of glucose and release of lipid from isolated fat cells, but no significant differences were observed between the cells from animals fed the fat‐free diet and those from the controls fed safflower oil. The results demonstrated the effects of diets containing fat or no fat on enzyme activities and membrane properties of fat cells of the epididymal fat pads of essential fatty acid deficient rats.

Studies on the synthesis of prostaglandins in the vesicular glands of essential fatty acid-deficient and hypophysectomized rats

Studies are reported on the detection and in vitro biosynthesis of prostaglandins in the vesicular glands of hypophysectomized and essential fatty acid-deficient rats. The vesicular glands of the hypophysectomized rats underwent rapid degeneration and were depleted of their stores of arachidonic acid and prostaglandins. Hypophysectomy also inhibited the in vitro conversion of arachidonic acid to prostaglandin E 2 with the vesicular gland of rats. The vesicular glands of essential fatty acid-deficient animals also became depleted of their stores of prostaglandins and arachidonic acid, as well as linoleic acid, and lost their activity for the in vitro conversion of exogenous arachidonic acid to prostaglandin E 2.

Effect of EFA deficiency on lipid transport from liver.

AbstractStudies are reported of the effect of an essential fatty acid (EFA) deficiency on synthesis of triglycerides (TG) and phospholipids (PL) and secretion of these compounds by livers of male Sprague‐Dawley rats. Animals were fed a semipurified diet containing corn oil or hydrogenated coconut oil (HCO) as the sole source of fat or no fat from weaning to 20 weeks of age. Liver function of the animals in each group was compared by an isolated liver perfusion technique with perfusates containing erythrocytes and linoleate, and in vivo experiments via tail vein injection of palmitate‐3H. Perfusion experiments showed that an EFA deficiency reduced the ability of the liver to secrete TG and PL. Accumulation of TG in the liver and its diminished secretion into the blood of EFA deficient animals were demonstrated by in vivo experiments with palmitate‐3H. The rate of conversion of linoleate to arachidonate and synthesis of PL was greater in livers of EFA deficient rats than in the control, corn oil fed animals. The results suggest a relationship of EFA metabolism to lipid transport.

Effect of essential fatty acid deficiency on release of triglycerides by the perfused rat liver

Studies are reported on release of triglycerides during perfusion of livers of male Sprague-Dawley rats fed a fat-free diet or diets containing hydrogenated coconut oil or corn oil. Perfusions were carried out with Krebs-Ringer bicarbonate buffer containing albumin with and without infusion of oleate or linoleate. Infusion with sodium oleate or linoleate caused an accumulation of triglycerides in the livers of the corn oil-fed animals and stimulated the release of triglycerides into the perfusing medium. In similar experiments with essential fatty acid-deficient animals, which were fed fat-free diets or diets containing hydrogenated coconut oil, there was no increase in secretion of triglycerides into the perfusate, and the amount of triglyceride which accumulated in the liver was greater than in the livers of the control (corn oil-fed) animals. Tracer experiments with oleate-1-(14)C or linoleate-1-(14)C also showed that with livers of essential fatty acid-deficient animals, secretion of triglyceride into the perfusate was not stimulated by infusion of fatty acids into the perfusing medium. It is concluded that impairment of the secretion of triglycerides is a factor in the accumulation of fat in the livers of essential fatty acid-deficient animals.