Hair Lipids Research Articles

Integral hair lipid in human hair follicle

Integral hair lipid (IHL) is bound to the keratinized cell surface to make an environmentally resistant lipid envelope. It is mainly positioned on the hair cuticle and inner root sheath. IHL in the hair follicle may regard as hair barrier to be similar to the epidermal lipid layer functioning as skin barrier. Major constituents of IHL are fatty acid, phytosphingosine, ceramide in decreasing order. Minor constituents of IHL are cholesterol, cholesterol sulfate and cholesterol oleate. Cuticle or cortical cell surface in hair are abundant in fatty acids unlike the keratinized area of epidermis or sebaceous gland, and about 30-40% of such fatty acids are composed of 18-methyl-eicosanoic acid which is known to be bound to proteins by ester or thioester bond. Various factors including moisture, solvent, oxidative damage during bleaching or permanent waving affect IHL. Photochemical changes also can occur in IHL as well as in hair protein and hair pigment. Lipid metabolism is thought to play an essential role in lipid envelope of hair, but also involvement in hair development and function.

Simultaneous HPLC analysis of ceramide and dihydroceramide in human hairs

Ceramide, a major class of hair lipid, can help determine the physicochemical properties of human hairs such as the chemical diffusion barrier and water retention. In this study, we developed a quantitation method for ceramide and dihydroceramide, a saturated form of ceramide, in human hairs. Lipids were extracted with ethanol from human hairs spiked with N-oleoyl-D-erythro-C(17) sphingosine, an internal standard. Ceramide and dihydroceramide were resolved by TLC and deacylated by sphingolipid-ceramide deacylase to release sphingosine and dihydrosphingosine, respectively. The hair content of ceramide was measured by HPLC following derivatization with o-phthalaldehyde. The limits of detection and quantification for ceramide extracted from hair fibers were 0.1 and 1 pmol, respectively. The linear range of hair weight for determining ceramide and dihydroceramide contents was 1 to 50 mg, with R(2) values of 0.9695 and 0.9898, respectively. The recoveries of ceramide and dihydroceramide from intra-day and interday assays were 99.55% to 98.53%, respectively. Concentrations of dihydroceramide from the hair roots to distal tip ends ranged from 10.42 +/- 2.19 to 1.20 +/- 0.11 nmol/g hair, while those of ceramide ranged from 2.27 +/- 0.22 to 1.47 +/- 0.15 nmol/g hair. The present analytical method provides a simultaneous and reproducible quantification of ceramide and dihydroceramide, and may be used as a potential biomarker for lipid abnormality-related diseases.

Skin surface lipids and skin and hair coat condition in dogs fed increased total fat diets containing polyunsaturated fatty acids

It is generally believed that diets containing increased amounts of polyunsaturated fatty acids (PUFA) result in improved canine skin and hair coat (SHC). However, the extent to which dietary fat amount and type play a role remains to be systematically investigated. The objective of this study was to investigate the role of both increased dietary fat amount and type on SHC assessments of dogs. Improvements of SHC conditions were investigated after feeding three diets containing increased total dietary fat (i.e. 13% total fat) for 12 weeks in relation to a lower fat acclimation diet (i.e. 9% total fat). The higher fat diets varied in polyunsaturated and saturated fat types and amounts but total fat was kept constant. Skin and hair coat assessments were performed at selected intervals by a trained group of veterinarians and graduate students. In addition, hair lipids were fractionated by thin layer chromatography after extraction of plucked hair samples. Significant improvements were found in hair coat glossiness and softness in all dogs fed the higher fat diets in relation to the acclimation diet. Improvements as a result of fat type were also seen but only at 12 weeks. A parallel finding was a marked increase in hair cholesteryl ester content determined at the end of the study at which time SHC scores were significantly improved. Skin and hair coat condition improvements may thus be related to increased cholesteryl ester deposited on the hair shaft surface when high fat diets are fed. Whereas this finding is preliminary, hair lipid analysis may be a useful, non-invasive technique with which to help assess dietary effects on canine SHC.

Application of internal wool lipids to hair

Hair lipids can contribute to physicochemical phenomena such as diffusion, cell cohesion and mechanical strength, although lipids occur at much lower levels (1-6% dry weight) than proteins (>90%).Hair lipids can be diminished by hair washing and submission to chemical treatments. Studies have shown that internal wool lipids (IWL) resemble those membranes of other keratinic tissues such as human hair or stratum corneum. In this work, the IWL, in the form of liposomes or from an emulsion system, were applied to untreated hair fibres and also treated hair fibres. The results showed that application of IWL to pretreated hair samples lead to an improvement in mechanical strength properties of the fibres when the IWL were applied structured as liposomes. Differential scanning calorimetry studies demonstrated that the application of IWL to pretreated hair sample led to a slight increase in the crystalline material of the fibres. Moreover, scanning electron microscopy studies showed that application of IWL liposomes to damaged hair fibres lead to an improvement of the cuticle scale, demonstrating the importance of the use of a delivery vehicle with a bilayer structure similar to the one present in the hair fibre to restore the natural properties of the fibre.

Lamellar rearrangement of internal lipids from human hair

The internal lipids were extracted from untreated hair without surface lipids. Liposomes were formed with the internal lipids at different hydration levels to determine the organization of these lipids and the influence of the water content on the lamellar structure of the hair fibres by X-ray Scattering (SAXS). Two structures of hair lipids were observed at 4.5 and ∼9.0 nm with a different behaviour as a function of water content: the largest bilayer being the one that showed a capacity to retain water inside its structure. SAXS was also applied directly to three samples: a packed swatch of hair fibres at 60% RH, fibres soaked in water and delipidized fibres. Only the lamella at 9.0 nm was slightly affected by water content. Moreover, there was a small diminution in intensity probably due to a high permeability of wet fibres which could give rise to a disorder of the lipid structure. These two lamellar rearrangements are probably made up of lipids with a different and specific hydrophilic/hydrophobic balance.

Human hair as a potential biomonitor for assessing persistent organic pollutants

To explore human biomonitor of persistent organic pollutants (POP) for public health risk assessment, extractable organohalogens (EOX), extractable persistent organohalogens (EPOX) and some selected organochlorine pesticides (OCP) and polychlorinated biphenyls (PCB) in children hair from urban and rural regions of Beijing, China, were measured by instrumental neutron activation analysis (INAA) and gas chromatography–electron capture detector (GC–ECD). The results indicated that about 96% of the total halogens existed as water-soluble polar compounds; about 25 to 50% of EOX were sulfuric acid-resistant EPOX; organochlorines were the major fraction of the organohalogens; and 88 to 99.6% of extractable persistent organochlorines (EPOCl) cannot be attributed to the selected OCP and PCB. HCH, DDT and 2-5CB were the major contributors to hair OCP and PCB. Further, γ-HCH, p, p′-DDE, p, p′-DDT and PCB-52 were the predominant individuals of HCH, DDT and 2-5CB, respectively. The concentration distributions of EPOCl, HCH, DDT and PCB in children hair were generally in the order of urban > rural and girls > boys, except for PCB congeners with random distributions between genders. Pearson positive correlations between hair lipid and the detected parameters of hair γ-HCH ( p < 0.01), DDT ( p < 0.01), EOCl ( p < 0.05), as well as EPOCl ( p < 0.05) were observed. Also, the ratios of hair α/γ and p, p′-DDE/ p, p′-DDT suggested that fresh input of HCH and DDT might exist in Beijing area. Hair can reflect body's integral exposure to POP from endogenous and exogenous sources, which, thus, can be used as a potential biomonitor in assessing POP exposure for public health purposes.

Loss of the Acyl-CoA Binding Protein (Acbp) Results in Fatty Acid Metabolism Abnormalities in Mouse Hair and Skin

Proper fatty acid metabolism is critical for hair and skin development and maintenance. The acyl-CoA binding protein (Acbp) is a widely expressed protein that binds long-chain fatty acyl-CoA esters and plays a role in fatty acyl-CoA transport and pool formation. However, loss of function of Acbp in the whole animal has not been investigated. Here, we show that deletion of Acbp in mouse results in sebocyte hyperplasia and sparse, matted hair with a greasy appearance. Consistent with these gross abnormalities, Acbp is highly expressed in the pilosebaceous units of mouse skin as determined by Northern analysis and in situ hybridization. Loss of Acbp also results in fatty acid metabolism abnormalities, with hair lipid profiles showing altered levels of triacylglycerols and nearly co-migrating lipids. These data suggest that Acbp plays a role in triacylglycerol biosynthesis, and that regulation of this process is important for proper hair and skin development and maintenance in the mouse.

Characterization of hair lipid images by argon sputter etching‐scanning electron microscopy

Hair lipid images, as visualized by argon sputter etching-scanning electron microscopy (ASE-SEM), reveal convex structures with a stitch pattern (SP) at the cell membrane complex (CMC) in the transverse hair plane. Based on interindividual variation, different features of the convex SP were classified into Types 0 to 4 with the corresponding scores 0 to 4. Observations using hair fibers collected from 27 Japanese females revealed significant positive correlations between the scores and the levels of exogenous lipids, which suggests that exogenous lipids internalized at the CMC predominantly constitute the convex SP. Intraindividual variation with different levels of exogenous lipids among hair fibers derived from individual females may be relevant to the uneven physicochemical properties of hair fibers on the scalp. Observations of 380 hair fibers collected from Japanese (Mongoloid), German and American (Caucasoid) females aged 3 to 77 yr demonstrated similar age-related changes in the lipid images, which represent an increase and then a decrease in levels of exogenous lipids with increasing age. This suggests that age-related changes in exogenous lipids are attributable to alterations in sebum excreted during aging and that this elicits age-related changes in physical parameters, which affect human hair texture.

A novel method for visualizing hair lipids at the cell membrane complex: Argon sputter etching/scanning electron microscopy1

Hair lipids localized at the cell membrane complex (CMC) play a part in chemical diffusion, cell cohesion, and mechanical strength. There is no method currently available to visualize hair lipids at the CMC. We found that scanning electron microscopy (SEM) of a transversely polished hair plane followed by argon sputter etching (ASE) provides a specific characteristic image consisting of circular patterns (CP) and stitch patterns (SP) at the cortex. Both the CP and the SP are formed as convex structures and are associated with melanin granules and the CMC, respectively. While the convex formation of the CP is not affected by any treatments tested, that of the SP disappeared following treatment of hair fibers with organic solvents and reappeared following incubation of the solvent-treated hair fibers with melting lipids, which suggests that the hair lipids are responsible for the convex SP. Other treatments, such as chemical fixation, thin sectioning, and pre-/post-incubation of the hair plane, reduce or abolish the convex formation of the SP. These findings suggest that the following pathway leads to the convex formation of SP during ASE: (a) joule heat is generated on the surface by violent collisions of argon ions, (b) melting CMC lipids ooze out from the inside to the surface, and (c) CMC lipids that have oozed out are chemically changed, leading to the final convex formation of the SP. With ASE-SEM, visualization of hair lipids as convex structures of SP should enable us to characterize the fine structure and localization of hair lipids and to clarify the roles and functions of the CMC of human hair.

Integral Lipid in Human Hair Follicle

On the hair surface, cells are covered with a thin lipid layer (LL) covalently bonded to hair proteins. This integral hair lipid is different from sebaceus lipid. We conducted this study to examine the lipid distribution in human hair follicle. Transmission electron microscopy was performed to observe the ultrastructure of the LL. Hair follicles were cut and observed longitudinally along the hair axis. For transmission electron microscopy, new fixative (Lee's fixative: composed of OsO4 and RuO4) was designed as the conventional fixatives such as OsO4 or RuO4 alone were not appropriate for staining for hair follicle lipid. In addition, we measured the chemical composition of integral hair lipid by high-performance thin-layer chromatography. From the above experimental procedure, it was discovered that the lipid in the hair follicle was mainly distributed in hair cuticle and keratinized inner root sheath. A multitude of lamellar granule is observed in the vicinity of the above LL. The chemical composition of integral hair lipid was different from those of epidermal or sebaceous lipids. It is assumed that the LL in the hair follicle is similar to the epidermal LL playing an important role as a skin barrier in the stratum corneum. We proposed here the new terminology "hair barrier" from this point of view.

A systematic method for the sensitive and specific determination of hair lipids in combination with chromatography

A systematic method for the sensitive, precise and accurate determination of hair lipids, including trace amounts of intrinsic endogenous cholesterol (CH), ceramide/ N-palmitoyl- dl-dihydrosphingosine (CER/PDS), cholesterol sulfate (CS) and chemically bound 18-methyl eicosanoic acid (18-MEA), has been developed in combination with TLC/FID (flame ionization detection), LC/MS and GC/MS. TLC/FID was used for the simultaneous determination of squalene (SQ), wax esters (WEs), triglycerides (TGs) and free fatty acids (FFAs). Optimal conditions for LC/MS to determine CS and 18-MEA were developed using selected ion monitoring (SIM) under the negative ion mode of electrospray ionization. An alternative procedure for the determination of 18-MEA was also established using commercially available heneicosanoic acid (HEA). In GC/MS, the optimal selection of ions for SIM of trimethylsilylated CH and CER/PDS, and the use of on-column injection has enabled their simultaneous detection. This newly developed method has been used to characterize the hair lipid composition from the proximal root end to the distal tip of chemically untreated hair fibers from two different females, and specific changes of hair lipids probably due to its origin and individuals have been demonstrated for the first time. This method may be useful for clarifying the important roles of intrinsic endogenous 18-MEA, CS, CH and CERs in the function of the cell membrane complex of hair fibers.

Analysis of hair lipids and tensile properties as a function of distance from scalp

Cuticle cells form the outer covering surrounding and protecting the cortex. The cuticle cells are thin, flat and overlap, and intercellular lipid lamellae are found in the gaps between the cell boundaries. The lipid lamellae are also found within the cortex in the cell boundaries between the long fribrous corticle cells. In addition, the outer surfaces of the cuticle cells are covered by a monolayer of covalently bound fatty acids, a major component of which is 18-methyleicosanoic acid. The fatty acids are thought to be attached through thio-ester linkages. Together these lipids are thought to be major determinants of the physical properties of the hair. The present study tested the hypothesis that both free and covalently bound lipids are progressively lost during normal environmental exposures. This progressive loss within the cuticle layers may, in part, lead to an increased susceptibility of the protein and lipid lamellae in the cortex to degradation. This degradation, in turn, would contribute to a progressive decrease in the tensile properties of the hair. Research grade hair was cut into five segments from the root to the distal end. Lipids from each segment were extracted and analyzed by thin-layer chromatography in conjunction with photodensitometry. The major free polar lipid classes in the hair included ceramides, glucosylceramides and cholesterol sulfate. The concentrations of all of the free polar lipids as well as the covalently bound fatty acids decreased in going from the root to the distal end of the hair. In addition, there was a significant reduction in tensile properties of the hair from the root to distal end. In conclusion, the progressive loss of endogenous free and covalently bound lipids from hair, which are probably related to normal weathering of the hair and grooming practices, may help contribute to a marked decrease in tensile properties to the hair.

Characterization of the lipid composition at the proximal root regions of human hair

The hair lipid composition collected from 44 Japanese females between 1 and 81 years of age was examined for eight lipids including hydrocarbons (HCs), squalene (SQ), wax esters (WEs), triglycerides (TGs), fatty acids (FAs), cholesterol (CH), ceramides (CERs), and 18-methyl eicosanoic acid (MEA). In this study, the 5-cm length from the proximal root end of hair fibers, which had never been exposed to any chemical treatment, was used after 5-min incubation with hexane following shampooing. Hair lipids were extracted with solvent and subsequent alkali-solvent and were then analyzed by a combination of chromatography. Although the average contents of the lipids showed great fluctuations among individuals, there were significant correlations between the levels of each lipid, which allowed for the classification of the hair lipids into four groups: group A: SQ, WEs, TGs, and FAs (designated as endogenous lipids based upon their sebum origin); group B: CH and CERs (designated as endogenous lipids); group C: HC (unknown origin); and group D: MEA (the other endogenous lipid). A principal component analysis for eight lipids revealed that the hair lipid composition was characterized by a predominant negative correlation between each lipid for groups A and B. This negative correlation suggests that the endogenous lipids in group B serve as a barrier against the penetration of predominantly sebum-derived exogenous lipids (group A). Endogenous lipids consisting of CH and CERs (group B) and MEA (group D) should be designated as intrinsic internal lipids of human hair.

Free internal lipids in hair from pre‐ and post‐menopausal women

Little is known about changes in hair lipids during life and their effects on hair properties. Our objectives were to study for the first time the effects of the female menopause on hair lipids, the contribution of sebum, and hair quality using pre‐menopausal and post‐menopausal subjects with and without hormone replacement therapy. Extracted hair lipids were quantified by high performance thin layer chromatography, forehead sebum output measured by sebumeter and hair greasiness, shine, softness and smoothness evaluated by expert assessment. Pre‐menopausal free internal lipids contained free fatty acids, wax or cholesteryl esters, cholesterol, ceramides, triglycerides and squalene. The composition was distinct from scalp surface lipids collected at the same time and from hair follicles from facelift patients, with no wax or cholesteryl esters and squalene in follicles and no ceramides in the surface lipids. Wax or cholesteryl esters and squalene were decreased (P &lt; 0.05) and cholesterol and ceramides increased (P &lt; 0.05) in post‐menopausal hair. The changes for squalene, wax or cholesteryl esters and cholesterol were reduced when hormone replacement therapy was taken. Sebum output and hair greasiness, shine, softness and smoothness fell significantly (P &lt; 0.05) after menopause. Hormone replacement therapy increased (P &lt; 0.05) results after menopause. It is concluded that hair free internal lipids derive from both the hair follicle and sebum. Sebum output falls after menopause and contributes less to hair lipids. The hair condition also changes. Understanding hair changes during life should improve matching of hair products to consumer needs.

P‐2 Evaluation of the influence of sex, diet and time on skin pH and surface lipids of cats

Skin lipids and pH are two factors classically considered of importance in homeostatic characteristics of skin. Skin physiology in cats has received little attention. The aim of this study was to evaluate the long‐term influence of sex, sexual status, season, and dietary fat and energy on these parameters. Twenty‐four European short‐haired laboratory cats, 14 months of age, were followed over a 1‐year period. They were divided into 8 groups of three, according to: sex (12 males and 12 females), sexual status (intact or neutered) and diets [(high energy 4300 kcal/kg as fed, 21% fat) vs. (moderate energy 3500 kcal/kg as fed, 10% fat)]. Both diets were fed to all cats for 6 months following a cross‐over design. Parameters regularly evaluated were skin pH and hair total lipid content (extraction from samples of 0.6–1.2 g of clipped hairs). The pH of the skin varied from 6.6–6.8 initially to 7.2–7.4 at the end of the study. This increase was significant only in intact animals (male and female). The dietary changes did not affect skin pH. Hair total lipid content was not affected by sex or the diets but slightly increased in all groups over the study period from 1.5–2.4 to 2.4–3.3%. In conclusion, skin pH appeared to be potentially modified by sexual status, but not by sex or dietary lipids and energy. Hair lipids do not appear to be affected by sex or increases in dietary lipids and energy. The slight increase in pH and hair lipids during the study was attributed to the change from young adult to adult stage of all cats. Funding: Royal Canin.

Role for ELOVL3 and Fatty Acid Chain Length in Development of Hair and Skin Function

Very little is known about the in vivo regulation of mammalian fatty acid chain elongation enzymes as well as the role of specific fatty acid chain length in cellular responses and developmental processes. Here, we report that the Elovl3 gene product, which belongs to a highly conserved family of microsomal enzymes involved in the formation of very long chain fatty acids, revealed a distinct expression in the skin that was restricted to the sebaceous glands and the epithelial cells of the hair follicles. By disruption of the Elovl3 gene by homologous recombination in mouse, we show that ELOVL3 participates in the formation of specific neutral lipids that are necessary for the function of the skin. The Elovl3-ablated mice displayed a sparse hair coat, the pilosebaceous system was hyperplastic, and the hair lipid content was disturbed with exceptionally high levels of eicosenoic acid (20:1). This was most prominent within the triglyceride fraction where fatty acids longer than 20 carbon atoms were almost undetectable. A functional consequence of this is that Elovl3-ablated mice exhibited a severe defect in water repulsion and increased trans-epidermal water loss.

Molecular models of the intercellular lipid lamellae from epidermal stratum corneum

The purpose of the present study was to test the hypothesis that the 13 nm trilamellar repeat units within the intercellular spaces of epidermal stratum corneum are composed of lamellae with alternating 5–3–5 nm dimensions as presented in previous models [J. Invest. Dermatol. 92 (1989) 251, P.W. Wertz, Integral lipids in hair and stratum corneum, in: P. Jolles, H. Zahn, H. Hocker (Eds.), Hair: Biology And Structure, Birkhauser Verlag, Basel, 1996, pp. 227–238, Acta Derm.-Venereol., Suppl. 208 (2000) 23]. Electron density profiles were measured from transmission electron micrographs of porcine stratum corneum prepared using ruthenium tetroxide [J. Invest. Dermatol. 92 (1989) 251]. Center-to-center distances of adjacent electron-dense bands as well as adjacent lucent bands were measured. Dense band center-to-center measurements were consistent with a 5–3–5 nm arrangement. However, lucent band center-to-center measurements revealed uniform lamellar thickness. It is suggested that linoleate chains in the central lamella reduce more ruthenium than the predominantly saturated chains in the outer lamellae and that this additional reduced ruthenium accumulates under the polar head group regions. A similar phenomenon involving the sphingosine moieties of the covalently bound ω-hydroxyceramide molecules accounts for the three-band pattern seen between the ends of adjacent corneocytes. It is concluded that the component lamellae of the several types of 13 nm trilamellar units of the stratum corneum are all of equal thickness.

Lead-revealed lipid organization in human hair

Human hair lipids form a complex mixture of composition close to that of sebum. Part of these lipids appears in an organized state that has been studied by diffraction techniques in the literature. Nevertheless, information on the structure of these lipids remains very scarce due to their low contribution to global hair diffraction pattern. Here we show that appropriate lead treatment considerably enhances organized lipid features observed by microbeam synchrotron radiation diffraction experiments. We attribute these features to the formation of lead soaps of free fatty acids. Specific orientation of hair “lipid crystals” in planes parallel to the hair axis is clearly demonstrated. Inclusion of these lipids in the bulk of the hair shaft is shown by diffraction experiments following removal of the cuticular outermost layer of hair. Moreover, microfluorescence and diffraction experiments are consistent with part of the lipids being present as calcium soaps in native hair. We therefore consider lead fixation as a powerful tool to evaluate the lipid organization in human hair for medical, environmental and archaeological purposes, including lead poisoning.

Human hair lipid composition after removal by surfactants

Human hair lipid composition after removal by surfactants

Structure of Water, Proteins, and Lipids in Intact Human Skin, Hair, and Nail

Raman spectroscopy is a nondestructive analytical method for determining the structure and conformation of molecular compounds. It does not require sample preparation or pretreatment. Recently, near-infrared Fourier transform Raman spectroscopy has emerged as being specially suited for investigations of biologic material. In this study, we obtained near-infrared Fourier transform Raman spectra of intact human skin, hair, nail, and stratum corneum. We disclosed major spectral differences in conformational behavior of lipids and proteins between normal skin, hair, and nail. The amide I and III band location indicated that the majority of proteins in all samples have the same secondary alpha-helix structure. Positions of (S-S) stretching bands of proteins revealed a higher stability of the disulfide bonds in the hair and the nail. Analysis of vibrations of protein -CH groups showed that in the hair and the nail the proteins are apparently highly folded, interacting with the surroundings only to a small degree. The position of lipid specific peaks in spectra of hair, nail, and stratum corneum suggested a highly ordered, lamellar crystalline lipid structure. A greater lipid fluidity was found in whole skin. Assessment of the structure of water clusters revealed that mainly bound water is present in the human skin, stratum corneum, and nail. In conclusion, structural changes of water, proteins, and lipids in intact skin and skin appendages may be analyzed by Raman spectroscopy. This technique may be used in the future in a noninvasive analysis of structural changes in molecular compounds in the skin, hair, and nail associated with different dermatologic diseases.