Essential fatty acids and the skin

A study into the fatty acid content of selected veterinary diets, supplements and fish oil capsules in Australia

BACKGROUND

Dogs with cutaneous diseases often receive supplementation with omega-3 (n-3) and omega-6 (n-6) essential fatty acids (FA), either through their diet or the use of an oral supplement. Labelling on these products is not always clear, especially regarding the total and relative amounts of FA.

OBJECTIVES

To provide clinicians with a breakdown of the FA content of selected veterinary diets, supplements and fish oil capsules so that the daily dose of supplementation can be calculated more easily. Repeated measurements of FA content over time demonstrate whether FA content changes temporally.

METHODS AND MATERIALS

Eight veterinary diets, four veterinary oral FA supplements and four fish oil supplements were analysed for FA content by gas chromatography at days 0, 28 and 56.

RESULTS

The n-6:n-3 ratio varied among the supplement types with the food samples having higher ratios than the liquid supplements and fish oil capsules. The composition of n-3 FA differed between products with some having higher concentrations of the less active n-3 FA alpha-linolenic acid than eicosapentaenoic acid and docosahexaenoic acid. No decreases in FA content over time were detected.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of this study provide the reader with a means to calculate the FA concentrations that their patient is receiving for each product tested, as well as allowing them to compare products for their differences in n-6:n-3 ratios and relative amounts of individual FA molecules. The FA concentrations did not change significantly over 56 days.

Omega-3 Versus Omega-6 Polyunsaturated Fatty Acids in the Prevention and Treatment of Inflammatory Skin Diseases

Omega-3 (ω-3) and omega-6 (ω-6) polyunsaturated fatty acids (PUFAs) are nowadays desirable components of oils with special dietary and functional properties. Their therapeutic and health-promoting effects have already been established in various chronic inflammatory and autoimmune diseases through various mechanisms, including modifications in cell membrane lipid composition, gene expression, cellular metabolism, and signal transduction. The application of ω-3 and ω-6 PUFAs in most common skin diseases has been examined in numerous studies, but their results and conclusions were mostly opposing and inconclusive. It seems that combined ω-6, gamma-linolenic acid (GLA), and ω-3 long-chain PUFAs supplementation exhibits the highest potential in diminishing inflammatory processes, which could be beneficial for the management of inflammatory skin diseases, such as atopic dermatitis, psoriasis, and acne. Due to significant population and individually-based genetic variations that impact PUFAs metabolism and associated metabolites, gene expression, and subsequent inflammatory responses, at this point, we could not recommend strict dietary and supplementation strategies for disease prevention and treatment that will be appropriate for all. Well-balanced nutrition and additional anti-inflammatory PUFA-based supplementation should be encouraged in a targeted manner for individuals in need to provide better management of skin diseases but, most importantly, to maintain and improve overall skin health.

Exploring the use of essential fatty acids in veterinary dermatology

BACKGROUND

The aim of the study was to discover the extent of use of essential fatty acids (EFAs) in veterinary practice, conditions used in, preparation of EFA supplement used and rationale for their use and to investigate the awareness of the oxidation of some commercial fish oil supplement preparations.

METHODS

A web-based questionnaire was distributed via email to a dermatology list server and posted to veterinary Facebook groups with questions relating to the use of EFAs, supplement choice, conditions used in, the level of importance of various factors regarding their use and awareness of their oxidation.

RESULTS

There were 309 responses from 32 countries. EFA supplements were used by 92.2 per cent of respondents. The most commonly used preparation of EFA supplementation was veterinary oral supplements (75.1 per cent), followed by veterinary diets (14.4 per cent), shop bought fish oil supplements (7.7 per cent), enhancing the diet with oily fish (2.5 per cent) and finally using a commercial pet food (0.3 per cent). Only 46.3 per cent of respondents who used them were aware of the oxidation of EFAs. Veterinary oral supplements were perceived to be the best preserved, followed by veterinary diets and lastly commercial fish oil supplements.

CONCLUSION

A large number of respondents advised the use of EFAs for veterinary dermatological conditions but less than 50 per cent were aware of the potential for EFAs to oxidise.

The Sources of Essential Fatty Acids for Allergic and Cancer Patients; a Connection with Insight into Mammalian Target of Rapamycin: A Narrative Review

Background:

Disturbance in essential fatty acids (EFA) metabolism plays a key role in autoimmune diseases, but EFA supplementation with sources of borage, evening primrose, hemp seed and fish oils was not effective in atopic and cancer diseases, as that seen in the case of multiple sclerosis. It seems that two complexes of the mammalian target of rapamycin (mTOR) signaling, mTORC1 and mTORC2, are congruent with the two bases of the Traditional Iranian Medicine (TIM) therapy, Cold and Hot nature, which are essential for the efficacy of functional oils for controlling immune responses in autoimmune diseases.

Methods:

We searched PubMed database, Web of Science (WOS), Google Scholar, Scopus and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data.

Results:

The oils controlled by Cold or Hot nature may be helpful in maintaining homeostasis and preventing autoimmune diseases. In summary, studies of randomized controlled trials for allergy and cancer patients found no improvement in the signs or response to tests, despite a remarkable change in EFA fractions in the blood by supplementation with sources of borage, evening primrose, hemp seed and fish oils. In contrast, portulaca oleracea oil exhibited protective effects by anti-inflammatory properties via the PI3K/Akt/mTORC2 pathway with a deviation immune response to Th1 to treat atopic diseases and cancer.

Conclusions:

According to the concept of Traditional Iranian Medicine therapy, in contrast to Cold-nature oils, EFA supplementation with the sources of Hot-nature oilsis not suitable for the treatment of atopic and cancerous diseases.

Effect of Evening Primrose Oil on Korean Patients With Mild Atopic Dermatitis: A Randomized, Double-Blinded, Placebo-Controlled Clinical Study

Background

Atopic dermatitis (AD) is related to a deficiency of delta-6-desaturase, an enzyme responsible for converting linoleic acid to gamma-linolenic acid (GLA). Evening primrose oil (EPO) as a source of GLA has been of interest in the management of AD.

Objective

The aim of this randomized, double-blinded, placebo-controlled clinical study is to evaluate the efficacy and safety of EPO in Korean patients with AD.

Methods

Fifty mild AD patients with an Eczema Area Severity Index (EASI) score of 10 or less were enrolled and randomly divided into two groups. The first group received an oval unmarked capsule containing 450 mg of EPO (40 mg of GLA) per capsule, while placebo capsules identical in appearance and containing 450 mg of soybean oil were given to the other group. Treatment continued for a period of four months. EASI scores, transepidermal water loss (TEWL), and skin hydration were evaluated in all the AD patients at the baseline, and in months 1, 2, 3, and 4 of the study.

Results

At the end of month 4, the patients of the EPO group showed a significant improvement in the EASI score (p=0.040), whereas the patients of the placebo group did not. There was a significant difference in the EASI score between the EPO and placebo groups (p=0.010). Although not statistically significant, the TEWL and skin hydration also slightly improved in the EPO patients group.

Conclusion

We suggest that EPO is a safe and effective medicine for Korean patients with mild AD.

Anti-Inflammatory and Skin Barrier Repair Effects of Topical Application of Some Plant Oils

Plant oils have been utilized for a variety of purposes throughout history, with their integration into foods, cosmetics, and pharmaceutical products. They are now being increasingly recognized for their effects on both skin diseases and the restoration of cutaneous homeostasis. This article briefly reviews the available data on biological influences of topical skin applications of some plant oils (olive oil, olive pomace oil, sunflower seed oil, coconut oil, safflower seed oil, argan oil, soybean oil, peanut oil, sesame oil, avocado oil, borage oil, jojoba oil, oat oil, pomegranate seed oil, almond oil, bitter apricot oil, rose hip oil, German chamomile oil, and shea butter). Thus, it focuses on the therapeutic benefits of these plant oils according to their anti-inflammatory and antioxidant effects on the skin, promotion of wound healing and repair of skin barrier.

The Oxidant and Antioxidant Status in Pityriasis Rosea

Background:

Pityriasis rosea (PR) is usually an asymptomatic and self-limiting papulosquamous skin disease with acute onset. The etiology has not been clarified yet. Recently, increased oxidative stress was found to play a role in etiopathogenesis of multiple cutaneous diseases with T cell-mediated immune response. However, there are no studies demonstrating the oxidative stress status in PR.

Aim:

The aim of the study is to determine the status of oxidative stress (OS) and paraoxonase (PON) 1/arylesterase enzyme activities in PR.

Materials and Methods:

Study included 51 patients with active PR lesions, and 45 healthy volunteers. Serum levels of total oxidant status (TOS), total antioxidant status (TAS), and PON1/arylesterase (ARES) activity were determined and oxidative stress index (OSI) was calculated in all patients and controls.

Results:

TAS levels and ARES activities in the patient group were significantly lower than the control group. On the other hand, TOS and OSI levels were significantly higher in patients compared with controls. There was no significant correlation between the duration of disease and TAS, TOS, OSI levels, and ARES activities.

Conclusion:

A systemic oxidative stress exists in PR, which suggests that OS may be involved in the etiopathogenesis of disease.

Biological and physical factors influencing the successful engraftment of a cultured human skin substitute

Skin tissue may be engineered in a variety of ways. Our cultured skin substitute (Graftskin, living skin equivalent or G-LSE), Apligraftrade mark, is an organotypic culture of skin, containing both a "dermis" and "epidermis." The epidermis is an important functional component of skin, responsible for biologic wound closure. The epidermis possesses a stratum corneum which develops with time in culture. The stratum corneum provides barrier function properties and gives the LSE improved strength and handling characteristics. Clinical experience indicated that the stratum corneum might play an important role in improving the clinical utility of the LSE. Handling and physical characteristics improved with time in culture. We examined the LSE at different stages of epidermal maturation for barrier function and ability to persist as a graft. LSE grafted onto athymic mice before significant development of barrier function did not withstand bandage removal at 7 days postgraft. LSE grafted after barrier function had been established in vitro were able to withstand bandage removal at day 7. Corneum lipid composition and structure are critical components for barrier function. Media modifications were used in an attempt to improve the fatty acid composition of the stratum corneum. The barrier developed more rapidly and was improved in a serum-free, lipid-supplemented condition. Lipid lamellar structure was improved with 10% of the stratum corneum exhibiting broad-narrow-broad lipid lamellar arrangements similar to human skin. Fatty acid metabolism was not appreciably altered. Barrier function in vitro was 4- to 10-fold more permeable than human skin. Epidermal differentiation does not compromise engraftment or the wound healing ability of the epidermis. The stratum corneum provides features beneficial for engraftment and clinical use. (c) 1996 John Wiley & Sons, Inc.

Dietary docosahexaenoic acid in combination with arachidonic acid ameliorates allergen-induced dermatitis in mice

OBJECTIVE

In this study, we investigated the impact of dietary docosahexaenoic (DHA) and arachidonic acid (AA) on development and severity of allergen-induced dermatitis.

STUDY DESIGN

In sensitized mice, skin inflammation was induced by ovalbumin. Mice received either a diet containing 0.015% DHA, 0.029% AA or the combination of both. The severity of dermatitis was evaluated by using a clinical skin score (CSS), followed by immunohistologic and cytokine analysis. To unravel potential mechanisms, interleukin (IL)-4 or tumor necrosis factor α-stimulated keratinocytes from the cell line Kera-308 was cultured with different DHA/AA compositions and analyzed regarding proliferation and cytokine production.

RESULTS

Dietary DHA/AA significantly improved the severity of allergen-induced dermatitis as the CSS was reduced by 36 ± 23% (p=0.005). Furthermore, reduced epidermal KI67 expression, increased number of forkhead box P3(+) cells, and elevated IL-10 expression were determined in skin lesions of dietary-treated mice. Correspondingly, in vitro DHA/AA-treated keratinocytes exhibited increased IL-10 expression and produced less thymic stromal lymphopoietin.

CONCLUSION

Dietary DHA/AA supplementation leads to a significant amelioration of allergen-induced dermatitis. This was accompanied with the presence of increased regulatory T cells and IL-10 expression in lesional skin. Moreover, we identify keratinocytes, which play a crucial role in the regulation of skin inflammation, as important targets of DHA/AA supplementation. Future studies are needed to clarify whether DHA/AA acts directly or whether its biologic active metabolites are responsible for these findings. This may unravel novel therapeutical compounds for allergen-induced dermatitis.

Clinical effects of undershirts coated with borage oil on children with atopic dermatitis: a double-blind, placebo-controlled clinical trial

It has been reported that gamma-linolenic acid contained in borage oil is effective against atopic dermatitis. The clinical effects of undershirts coated with borage oil rich in gamma-linolenic acid on atopic dermatitis were evaluated. Thirty-two children, aged 1-10 years, were involved in the clinical control study. Sixteen had worn undershirts coated with borage oil everyday for 2 weeks, and 16 had worn non-coated undershirts as a placebo. Their symptoms were assessed on a 4-point scale. Those children who had worn undershirts coated with borage oil for 2 weeks showed improvements in their erythema and itch, which were statistically significant. Transepidermal water loss from the back was decreased. In the placebo group, there were no statistically significant differences. The undershirts coated with borage oil were found to be statistically effective, and had no side-effects on children with mild atopic dermatitis.

G2A plays proinflammatory roles in human keratinocytes under oxidative stress as a receptor for 9-hydroxyoctadecadienoic acid

G2A is a stress-inducible G protein-coupled receptor for oxidized free fatty acids, such as 9-hydroxyoctadecadienoic acid (HODE). As skin is routinely and pathologically exposed to many oxidative stresses such as UV radiation, chemical agents, and inflammation that might induce both G2A expression and production of G2A ligands, we examined G2A function in human keratinocytes. G2A was expressed in human epidermis, normal human epidermal keratinocytes (NHEK), and an immortalized human keratinocyte cell line (HaCaT). 9(S)-HODE evoked intracellular calcium mobilization and secretion of cytokines, including IL-6, IL-8, and GM-CSF in NHEK cells. These responses became prominent in HaCaT cells by overexpression of G2A. 9(S)-HODE inhibited proliferation of NHEK cells by suppressing DNA synthesis and arresting the cell cycle in the G0/1-phase. On the other hand, 13(S)-HODE, another major oxidative product from linoleate, showed little or no effect on either cytokine secretion or on proliferation in NHEK cells. A small interfering RNA designed to downregulate G2A caused suppression of 9(S)-HODE-induced inhibitory effects on proliferation of NHEK cells. UVB and H(2)O(2) induced G2A expression and caused oxidation of linoleate to produce 9-HODE in HaCaT cells. These results suggest that 9-HODE-G2A signaling plays proinflammatory roles in skin under oxidative conditions.

Plasma and skin concentrations of polyunsaturated fatty acids before and after supplementation with n-3 fatty acids in dogs with atopic dermatitis

OBJECTIVE

To determine essential fatty acid concentrations in plasma and tissue before and after supplementation with n-3 fatty acids in dogs with atopic dermatitis.

ANIMALS

30 dogs with atopic dermatitis.

PROCEDURE

Dogs received supplemental flaxseed oil (200 mg/kg/d), eicosapentaenoic acid (EPA; 50 mg/kg/d)-docosahexaenoic acid (DHA; 35 mg/kg/d), or mineral oil as a placebo in a double-blind, placebo-controlled, randomized trial. Clinical scores and plasma and cutaneous concentrations of linoleic acid, arachidonic acid, alpha-linolenic acid (alpha-LLA), EPA, DHA, prostaglandin E2, and leukotriene B4 were determined.

RESULTS

Total plasma concentrations of alpha-LLA and EPA increased and those of arachidonic acid decreased significantly with administration of EPA-DHA, and concentrations of alpha-LLA increased with flaxseed oil supplementation; nevertheless, there was no significant change in the concentrations of these fatty acids or eicosanoids in the skin. There was no correlation between clinical scores and plasma or cutaneous concentrations for any of the measured fatty acids or eicosanoids.

CONCLUSION AND CLINICAL RELEVANCE

Results indicated that at the dose used, neither the concentrations of fatty acids in skin or plasma nor a decrease in the production of inflammatory eicosanoids was a major factor involved in the mechanism of action in dogs with atopy that responded to fatty acid supplementation.

Dietary treatment of childhood atopic eczema/dermatitis syndrome (AEDS)

OBJECTIVE

This review summarizes the research and clinical evidence in favour of dietary intervention aimed at eliminating allergenic foods in the management of atopic eczema/dermatitis syndrome (AEDS).

DATA SOURCES

The data source was PubMed, using a search algorithm selecting for clinical studies of AEDS, diet therapy and food allergy in all children to October 2003. Also included is a commentary based on the authors' clinical experience in the allergy unit of a university hospital in Italy.

RESULTS

Fourteen prospective studies matched the entry criteria. Diverse trial designs, diagnostic criteria, types of dietary intervention and length of observation periods precluded meta-analytic methods. Allergenic food exclusion claimed efficacy in 13 of the 14 studies and was most useful in infants, in patients with elevated immunoglobulin E levels and/or multiple food sensitization and in patients with a diagnosis of food allergy.

CONCLUSION

Dietary intervention in the form of an elimination diet is efficacious in children with AEDS when a specific diagnosis of food allergy has been made. Diagnostic evaluation of food allergy should be performed in all children with eczema, particularly in younger children and those with severe forms of the disease.

Effect of omega-3 fatty acids on canine atopic dermatitis

Twenty-nine dogs were included in a double-blinded, placebo-controlled, randomised trial and were orally supplemented for 10 weeks with either flax oil (200 mg/kg/day), eicosapentaenoic acid (50 mg/kg/day) and docosahexaenoic acid (35 mg/kg/day) in a commercial preparation, or mineral oil as a placebo. For each dog, clinical scores were determined based on a scoring system developed prior to the trial. Total omega-6 and omega-3 intake and the ratio of omega-6:omega-3 (omega-6:3) were calculated before and after the trial. The dogs' clinical scores improved in those supplemented with flax oil and the commercial preparation, but not in the placebo group. No correlation was identified between total fatty acid intake or omega-6:3 ratio and clinical scores. Based on the results of this study, the total intake of fatty acids or the omega-6:3 ratio do not seem to be the main factors in determining the clinical response.

Efficacy and tolerability of borage oil in adults and children with atopic eczema: randomised, double blind, placebo controlled, parallel group trial

OBJECTIVE

To study the efficacy and tolerability of borage oil, which contains a high concentration of gamma linolenic acid, in children and adults with atopic eczema.

DESIGN

Single centre, randomised, double blind, placebo controlled, parallel group trial.

SETTING

Acute district general hospital in Nuneaton, England.

PARTICIPANTS

151 patients, of whom 11 failed to return for assessment, leaving an evaluable population of 140 (including 69 children).

INTERVENTION

Adults received four capsules of borage oil twice daily (920 mg gamma linolenic acid), and children received two capsules twice daily, for 12 weeks.

MAIN OUTCOME MEASURES

Change in total sign score at 12 weeks measured with the six area, six sign, atopic dermatitis (SASSAD) score (primary endpoint); symptom scores, assessed on visual analogue scales; topical corticosteroid requirement, assessed on a five point scale; global assessment of response by participants; adverse events and tolerability.

RESULTS

The mean SASSAD score fell from 30 to 27 in the borage oil group and from 28 to 23 in the placebo group. The difference between the mean improvements in the two groups was 1.4 (95% confidence interval -2.2 to 5.0) points in favour of placebo (P = 0.45). No significant differences occurred between treatment groups in the other assessments. Subset analysis of adults and children did not indicate any difference in response. The treatments were well tolerated.

CONCLUSION

Gamma linolenic acid is not beneficial in atopic dermatitis.

Mice with targeted disruption of the fatty acid transport protein 4 (Fatp 4, Slc27a4) gene show features of lethal restrictive dermopathy

The fatty acid transport protein family is a group of evolutionarily conserved proteins that are involved in the cellular uptake and metabolism of long and very long chain fatty acids. However, little is known about their respective physiological roles. To analyze the functional significance of fatty acid transport protein 4 (Fatp4, Slc27a4), we generated mice with a targeted disruption of the Fatp4 gene. Fatp4-null mice displayed features of a neonatally lethal restrictive dermopathy. Their skin was characterized by hyperproliferative hyperkeratosis with a disturbed epidermal barrier, a flat dermal-epidermal junction, a reduced number of pilo-sebaceous structures, and a compact dermis. The rigid skin consistency resulted in an altered body shape with facial dysmorphia, generalized joint flexion contractures, and impaired movement including suckling and breathing deficiencies. Lipid analysis demonstrated a disturbed fatty acid composition of epidermal ceramides, in particular a decrease in the C26:0 and C26:0-OH fatty acid substitutes. These findings reveal a previously unknown, essential function of Fatp4 in the formation of the epidermal barrier.

Polyunsaturated fatty acids and inflammatory diseases

Inflammation is overall a protective response, whose main goal is to liberate the human being of cellular lesions caused by micro-organisms, toxins, allergens, etc., as well as its consequences, and of death cells and necrotic tissues. Chronic inflammation, which is detrimental to tissues, is the basic pathogenic mechanism of hypersensitivity reactions against xenobiotics. Other frequent pathologies, for instance atherosclerosis, chronic hepatitis, inflammatory bowel disease (IBD), liver cirrhosis, lung fibrosis, psoriasis, and rheumatoid arthritis are also chronic inflammatory diseases. Chemical mediators of inflammation are derived from blood plasma or different cell-type activity. Biogenic amines, eicosanoids and cytokines are within the most important mediators of inflammatory processes. The different activities of eicosanoids derived from arachidonic acid (20:4 n-6) versus those derived from eicosapentaenoic acid (20:5 n-3) are one of the most important mechanisms to explain why n-3, or omega-3, polyunsaturated fatty acids (PUFA) exhibit anti-inflammatory properties in many inflammatory diseases. Dietary supplements ranging 1-8 g per day of n-3 PUFA have been reportedly beneficial in the treatment of IBD, eczema, psoriasis and rheumatoid arthritis. In addition, recent experimental studies in rats with experimental ulcerative colitis, induced by intrarectal injection of trinitrobenzene sulphonic acid, have documented that treatment with n-3 long-chain PUFA reduces mucosal damage as assessed by biochemical and histological markers of inflammation. Moreover, the defence antioxidant system in this model is enhanced in treated animals, provided that the n-3 PUFA supply is adequately preserved from oxidation.

The ACVD task force on canine atopic dermatitis (XXIII): are essential fatty acids effective?

Essential fatty acids (EFAs) exhibit the potential to affect allergic inflammation through the modulation of prostaglandin and leukotriene production, the inhibition of cellular activation and cytokine secretion as well as the alteration of the composition and function of the epidermal lipid barrier. Because of these multi-faceted effects, EFA have been proposed for treatment of canine atopic dermatitis (AD) since 1987. To date, more than 20 trials have been performed, reporting the efficacy of either oral EFA supplements or EFA-rich diets. Unfortunately, most of these studies were found to exhibit one or more of the following deficiencies: heterogeneity of diagnoses used as inclusion criteria, short duration of supplementation, lack of randomization of treatment allocation, lack of blinding of investigators and/or owners, lack of placebo or active controls, lack of documentation of plasma or skin EFA profiles during supplementation, as well as lack of standardization of the basal diets or supplements which could have provided additional EFA. Consequently, there is presently insufficient evidence to recommend for or against the use of EFA to control clinical signs of canine AD. Evidence of efficacy must await the performance of blinded, randomized and controlled trials of at least 3 months duration in which diets are identical for all of study subjects. In these trials, clinical efficacy should be evaluated in relation to plasma and cutaneous EFA treatment-induced alterations.

Malnutrition-associated rash of cystic fibrosis

Rash is a rare presenting sign of cystic fibrosis (CF) complicated by protein-calorie malnutrition. We measured essential fatty acid (EFA) levels in the serum of a 4-month-old girl with an erythematous, desquamating, periorificially accentuated rash in association with malnutrition and her 2-year-old sister who was diagnosed concurrently with CF but had no rash or signs of malnutrition. Both patients had biochemical evidence of EFA deficiency, suggesting that development of the rash is multifactorial. Clinical presentation, management, and possible modes of pathogenesis of the rash are reviewed. Pathogenesis of the rash appears to involve a complex interaction among deficiencies of EFAs, zinc, protein, and possibly copper, leading to disordered prostaglandin metabolism or cytokine production, or free radical-induced damage to cellular membranes due to a lack of nutrient-derived protective antioxidants.

Essential fatty acid metabolism and its modification in atopic eczema

Research from the 1930s to the 1950s established that a deficit of n-6 essential fatty acids (EFAs) leads to an inflammatory skin condition in both animals and humans. In a common inherited skin condition, atopic dermatitis (eczema), there was evidence of low blood EFA concentrations and of a therapeutic response to exceptionally high doses of linoleic acid. More recently, it has been established that there is no deficit of linoleic acid in atopic eczema. Concentrations of linoleic acid instead tend to be elevated in blood, milk, and adipose tissue of patients with atopic eczema, whereas concentrations of linoleic acid metabolites are substantially reduced. This suggests reduced conversion of linoleic acid to gamma-linolenic acid (GLA). In most but not all studies, administration of GLA has been found to improve the clinically assessed skin condition, the objectively assessed skin roughness, and the elevated blood catecholamine concentrations of patients with atopic eczema. Atopic eczema may be a minor inherited abnormality of EFA metabolism.

Psoriasis and the arachidonic acid cascade

Arachidonic acid (5.8,11,14-eicosatetraenoic acid C20:4, n-6) is released from the cell membrane by the action of phospholipases on membrane phospholipids. Metabolites of arachidonic acid, which are generically termed eicosanoids, including prostaglandins, thromboxane, leukotrienes and hydroxyeicosatetraenoic acids, have been implicated as mediators or modulators of a number of physiological functions and pathological conditions in both normal and diseased human skin. Particularly, eicosanoids have been suspected to play an important role in the pathogenesis of psoriasis, because a number of phenomena observed in psoriasis can be explained, at least in part, by the action of eicosanoids. This review will focus on recent progress regarding the significance of eicosanoids in the pathogenesis of psoriasis. Recent developments in the molecular biology in the eicosanoids have renewed interest in the role of eicosanoids in psoriasis. New understanding of the etiology of psoriasis and advances in its treatment due to recent progress in eicosanoid biology will also be presented.

Efficacy of gamma-linolenic acid in the treatment of patients with atopic dermatitis

Of 60 patients with atopic dermatitis (30 males and 30 females, 15-30 years old) 30 were treated with gamma-linolenic acid of (C18:3 n-6) at a dosage of 274 mg twice a day; the other 30 patients were given placebo. The patients were treated for 12 weeks, during which their symptoms were assessed on a linear scale both by a dermatologist and by themselves every 4 weeks. The patients who received gamma-linolenic acid, showed gradual improvements in pruritus, erythema, vesiculation and oozing, which were statistically significant compared with the control group (P < 0.001). Only one patient had presented with scaling at the beginning of the study and this symptom appeared to be less influenced by the effects of gamma-linolenic acid. The assessments of symptoms made by the dermatologist were generally consistent with those made by the patients themselves. gamma-linolenic acid was found to be effective and without side-effects for the treatment of atopic dermatitis.

Additive benefits of EFAs in dogs with atopic dermatitis after partial response to antihistamine therapy

It has been reported that 20 to 70 per cent of atopic cases in the dog can be controlled with antihistamines, though the effective antihistamine cannot be predetermined. Combination therapy with essential fatty acids (EFAs) and antihistamines has been shown to be useful in dogs. All of the work published to date has been performed in open studies, without the use of placebo, and in dogs where the aim has been to control pruritus as a symptom rather than that caused specifically by atopy. The aim of this study was to assess the combined effects of four antihistamines; hydroxyzine, chlorpheniramine, cyproheptadine and clemastine; with both an EFA supplement and a placebo of olive oil, in 25 dogs to control pruritus in clinically proven cses of atopy.

Phospholipase A2 activity in vitro cultured cells--influence of ascorbate supplementation

Non-malignant LLCMK cells and malignant B16 cells were supplemented with ascorbate, over the concentration range 0-100 micrograms/ml ascorbate. The effects of ascorbate supplementation on cell growth and phospholipase A2 activity of the membrane fractions of the respective cell lines were determined. Increasing ascorbate supplementation had a significant inhibitory effect on the growth of the B16 cells. Phospholipase A2 activity in the control B16 cells was lower than that detected in the control LLCMK cells. Phospholipase A2 activity decreased significantly in the B16 cells upon increasing ascorbate supplementation, while the supplementation of ascorbate to the LLCMK cells did not have any significant effect on phospholipase A2 activity in these cells.

The effect of ascorbate on essential fatty acid composition in B16 melanoma cells

Ascorbate has been shown to be involved in essential fatty acid (EFA) metabolism, resulting in the suggestion that the effect of ascorbate on cell growth may be mediated through an influence on the metabolism of these FAs. This study examined the effect of ascorbate, supplemented over the nutritional concentration range of 0-100 micrograms/ml, on the in vitro cell growth of non-malignant LLCMK (monkey kidney) cells and malignant B16 murine melanoma cells. The effect of ascorbate on EFA composition was also investigated, and involved the determination of the levels of linoleic acid (LA), gamma-linoleic acid (GLA), dihomogammalinolenic acid (DGLA) and arachidonic acid (AA) present in the stroma and membrane of the two cell types. Ascorbate had no significant inhibitory or stimulatory effect on the growth of either the LLCMK or B16 cells. EFA levels detected in the LLCMK cells were generally higher than those detected in the B16 cells. The % composition of the various EFAs in the stroma fractions of the two cell types were higher than the level of the corresponding EFAs in the membrane fractions. GLA levels were not detectable in the membrane fractions of the B16 cells. AA % composition determined in both cell types, was greater than that of any other EFA % composition.

Analyses of skin surface lipid in patients with microbially associated skin disease

The composition of the total skin surface lipid, free fatty acids and fatty acid of triglyceride was used in discriminant analyses to classify patients with severe acne vulgaris (AV), pityriasis versicolor (PV), seborrhoeic dermatitis (SD) and atopic dermatitis (AD). It was not possible to discriminate between the PV and SD patients but all the lipid groups gave a satisfactory separation between AV, PV + SD and AD patients. A similar separation was obtained when the sex of the patient was studied but not when both sex and disease were taken into account. The results suggest that there are fundamental differences in the composition of skin lipid between patients with microbially associated diseases, but the precise role of the organisms has not been ascertained.

Placebo-controlled trial of essential fatty acid supplementation in atopic dermatitis

Treatment of atopic dermatitis with essential fatty acids remains controversial. A double-blind, placebo-controlled, parallel-group study was done to investigate the response of patients with atopic dermatitis to essential fatty acid supplements. Patients with atopic dermatitis were randomised to receive evening primrose oil, evening primrose oil and fish oil, or placebo for 16 weeks. Disease activity was monitored by clinical severity scores recorded by the investigator, topical steroid requirement, and symptom scores recorded by subjects. Of 123 subjects recruited, 102 completed the treatment period. No improvement with active treatment was demonstrated. Our study, which avoided the methodological and analytical problems of previous studies, found no effect of essential fatty acid supplementation in atopic dermatitis.

Growth inhibitory effect of eicosapentaenoic acid on cultured human epidermal keratinocytes

The effect of eicosapentaenoic acid (EPA, 20:5n-3) on the proliferation of cultured human epidermal keratinocytes was investigated. The keratinocytes were treated with 3 micrograms/ml of EPA for 48 h and then their fatty acid composition was analyzed by gas liquid chromatography. A significant amount of EPA was incorporated by the cells. The treatment with EPA at concentrations of 0.3-6.0 micrograms/ml resulted in a dose-dependent inhibition of the growth of the cells. These results indicate that EPA can be incorporated by cultured keratinocytes and change their fatty acid composition, which might endogenously affect their growth.

In vitro model of essential fatty acid deficiency

The polyunsaturated fatty acids linoleic acid (18:2, n-6) and arachidonic acid (20:4, n-6) are essential for normal skin function and structure, both as eicosanoid precursors and as components of lipids forming cell membranes. Adult human keratinocytes grow optimally in serum-free medium (MCDB 153) that contains no fatty acids. These keratinocytes expand rapidly and produce normal epidermis upon in vivo grafting. Analysis of lipid extracts of epidermis and of cultured keratinocytes was done to determine the fatty acid composition of cells grown in essential fatty acid (EFA)-deficient medium. Gas chromatography and high-performance liquid chromatography analyses were done of the fatty acids in the entire cell and in a thin-layer chromatography separated fraction containing those lipids that form cellular membranes. Comparison of snap-frozen epidermis and epidermal basal cell suspensions to passage 1 to 4 cultures shows that the cells are in an extreme essential fatty acid-deficient state by the first passage. The amount of the saturated fatty acids 16:0, 18:0, and 14:0 is unchanged by culture. The polyunsaturated fatty acids are found to be significantly decreased, the cells balancing their lack with a significant increase in the relative abundance of the monounsaturated fatty acids, 18:1 and 16:1. Greater than 85-90% of the fatty acids was found in lipids associated with membranes and no unusual fatty acids were detected. Because the serum-free medium is fatty acid free and the cells cannot synthesize essential fatty acids, the rapid division of the cells results in the predominance of an extreme EFA-deficient cell type. The essential fatty acid-deficient keratinocyte is an excellent adult, normal epidermal cell model that can be used to study EFA deficiency and the effect of the eicosanoid and fatty acids on cell function and structure.

The effect of topical steroids on cutaneous oxygen tension

The precise mode of action of topically applied steroids is unknown. We have applied clobetasol propionate 0.05% ointment (Dermovate; Glaxo Pharmaceuticals) under occlusion to the forearm skin of 10 healthy volunteers for 6 h and monitored transcutaneous oxygen tension at the site for 19 h after its removal. Compared to the ointment base, the steroid-treated area was significantly hypoxic up to 13 h after application. The profound hypoxia present at the site of application of clobetasol propionate 0.05% ointment may account for some of its anti-inflammatory effects, and its atrophogenicity.