Amino acid composition,including key derivatives of eccrine sweat: potential biomarkers of certain atopic skin conditions

The free amino acid (AA) composition of eccrine sweat is different from other biological fluids, for reasons which are not properly understood. We undertook the detailed analysis of the AA composition of freshly isolated pure human eccrine sweat, including some of the key derivatives of AA metabolism, to better understand the key biological mechanisms governing its composition. Eccrine sweat was collected from the axillae of 12 healthy subjects immediately upon formation. Free AA analysis was performed using an automatic AA analyser after ninhydrin derivatization. Pyrrolidine‐5‐carboxylic acid (PCA) and urocanic acid (UCA) levels were determined using GC/MS. The free AA composition of sweat was dominated by the presence of serine accounting for just over one‐fifth of the total free AA composition. Glycine was the next most abundant followed by PCA, alanine, citrulline and threonine, respectively. The data obtained indicate that the AA content of sweat bears a remarkable similarity to the AA composition of the epidermal protein profilaggrin. This protein is the key source of free AAs and their derivatives that form a major part of the natural moisturizing factor (NMF) within the stratum corneum (SC) and plays a major role in maintaining the barrier integrity of human skin. As perturbations in the production of NMF can lead to abnormal barrier function and can arise as a consequence of filaggrin genotype, we propose the quantification of AAs in sweat may serve as a non‐invasive diagnostic biomarker for certain atopic skin conditions, that is, atopic dermatitis (AD).     

Abstracts: Natural moisturizing factors in the stratum corneum I. Effects of lipid extraction and soaking

pp. 13–22 Natural moisturizing factor (NMF) is essential for appropriate stratum corneum hydration, barrier homeostasis, desquamation, and plasticity. It is formed from filaggrin proteolysis to small, hygroscopic molecules including amino acids. We hypothesized that common lipid extraction and soaking in water would alter the level of NMF in the upper stratum corneum (SC) and its biophysical properties. A novel method of measuring and quantifying the amino acid components of NMF is presented. Adhesive tapes were used to collect samples of the SC and were extracted with 6 mM perchloric acid for analysis by reverse‐phase high‐performance liquid chromatography (HPLC).The HPLC results were standardized to the amount of protein removed by the tapes. An increase in NMF was found with increased SC depth. Also, the combination of extraction and soaking was found to increase NMF loss relative to control or to extraction or soaking alone. Our results indicate that common skin care practices significantly influence the water binding materials in the upper SC. The findings have implications for the evaluation and formulation of skin care products.     

No. 3Vol. 42, No. 2, pp. 94–101, 2008Effect of Birch (Betula platyphylla Sukatchev var. japonica Hara) sap on cultured human epidermal keratinocyte differentiation

The beauty of ideal skin texture is closely associated with dermal moisture factors. The key factors of skin moisture are NMF (natural moisturizing factor) and skin normal barrier function. The former keeps dermal surface moisture, and the later protects from excess water loss. So we have searched for the ingredient that improves these factors. Birch sap has been widely used as an effective drink for anti-fatigue and anti-stress. However, the effect of birch sap on skin as a cosmetic agent has not been known entirely. In this study, we investigated the effects of birch ( Betula platyphylla Sukatchev var. japonica Hara) sap on human skin. Birch sap induced epidermal keratinocyte differentiation properties in vitro . We assessed two epidermal differentiation agents. Filaggrin is a precursor protein of NMF, and involucrin is one of the precursor proteins of the cornified cell envelope (CE), which is related to normal barrier function. We have evaluated the production of these proteins where birch sap was applied to human normal keratinocytes. Birch sap not only increased mRNA expression of filaggrin and involucrin, but also accelerated these proteins production. Otherwise, birch sap did not have any influence for IL-6 production, which is related to inflammatory and aberrant keratinocyte proliferation. The results of induced differentiation properties on birch sap-treated keratinocytes are very similar to the differentiation induced by calcium in vitro . This similarity suggested that birch sap has a differentiation inducible property on in vitro cultured keratinocytes. Our study suggested that birch sap is able to control both moisturizing- and barrier-related factor production. From these effects, birch sap provides appropriate epidermal functions and skin homeostasis, and revealed itself as a very useful ingredient in the cosmetic field.     

Characterizing the composition of underarm and forearm skin using confocal raman spectroscopy

Many studies have reported differences in skin composition as a function of body site and age. However, rarely has axilla (underarm) skin been included in these studies. This report highlights the results of a clinical study where confocal Raman spectroscopy was used to assess the differences between underarm and volar forearm skin. In the reported study, the concentration of natural moisturizing factor (NMF), urea, lactic acid, cholesterol, trans urocanic acid (t-UCA) and ceramide 3 (N-octadecanoyl-phytosphingosine) was evaluated as a function of depth, body site (underarm vs. forearm) and age. Two age groups of women were included: (i) between 20 and 30 years and (ii) older than 55 years (post-menopause). The levels of cholesterol, ceramide 3 and lactic acid were highest in the underarm regardless of the age group whereas the forearm contained higher amounts of NMF. Ceramide 3, urea and lactic acid were significantly lower for women 55 years or older in the underarm. No age-related differences were detected within the forearm site..     

Assessment of the variation of skin barrier function with anatomic site,age, gender and ethnicity

The skin is the largest organ of the human body and its functions include protection, thermoregulation sensation and secretion. Significant advances in our understanding of how the morphology and physiology of the skin contribute to the skin’s barrier role have been achieved in recent years. The aim of this review is to summarize the principal approaches which have been used to assess variation in skin barrier function with anatomic site, age, gender, and ethnicity. The methods discussed include trans‐epidermal water loss (TEWL) measurement, assessment of corneocyte size, response to vasoactive compounds and attenuated total reflectance Fourier transform infrared (ATR‐FTIR) interrogation of skin. The utility of the various methods is considered and the most important findings in the literature to date are highlighted.     

An updated review of clinical methods in the assessment of ageing skin – New perspectives and evaluation for claims support

With the advancement of skin research, today's consumer has increased access to an informed understanding of ageing skin and its appendages, together with a plethora of targeted products to meet such needs. In recent years, increased legislative demands for quality evidential claims support have led not only to the development and validation of clinical methods to measure and quantify ageing skin, but also a clearer understanding of the skin ageing process–especially the impact of both its internal and external environments–as well as a tougher stance on clearly unjustifiable claims. Traditional testing methods used to research and evaluate anti‐ageing products claim to employ sophisticated instruments. Today, however, since the term anti‐ageing can be considered a misnomer, intelligent use of combined more advanced clinical methods has enabled the development of technologically improved consumer products providing enhanced efficacy and targeted performance. Non‐invasive methods for the assessment and quantification of the causes of ageing skin provide tools to the clinical researcher as defined by key clinically observed ageing parameters. Where evidence requires additional support, a number of clinical procedures evaluating ageing skin and hair products are combined with invasive procedures, thus enabling an added value to product claims. As discussed herein, given the enhanced understanding of ageing, we provide an update to our previous reviews of clinical methods used in the assessment of skin ageing, to include the wider aspects of environmental exposure; skin pigmentation; microbiome disturbance; surface topography; colour, radiance, and pH; and structural integrity–all requiring a disciplined approach to their use in dermatological investigations and product claims evidence.     

鱼皮胶原蛋白及胶原活性多肽的研究进展

胶原蛋白是生物体内的重要蛋白质,是结缔组织的主要蛋白质成分。胶原蛋白具有多样性及组织分布的特异性,是与各种组织和器官功能相关的功能性蛋白质。鱼皮胶原蛋白及其酶解产物胶原活性多肽已引起人们的广泛关注。现对鱼皮胶原蛋白的种类、性质、提取方法以及胶原活性多肽生理活性等的研究进展作一综述。     

A novel anti‐ageing mechanism for retinol: induction of dermal elastin synthesis and elastin fibre formation

Dermal elastic fibres are extracellular matrix protein complexes produced by fibroblasts and involved in skin elasticity. Elastin fibres decrease with age as a result of reduced synthesis and increased degradation, resulting in skin sagging and reduced skin elasticity. In this study, we show that retinol (ROL), known to enhance dermal collagen production, is also enhancing elastin fibre formation. ROL induced elastin gene expression and elastin fibre formation in cultured human dermal fibroblasts. Topical treatment of cultured human skin explants with a low dose (0.04%) of ROL increased mRNA and protein levels of tropoelastin and of fibrillin‐1, an elastin accessory protein, as documented by QPCR and immunohistochemistry staining. Luna staining confirmed the increased elastin fibre network in the ROL‐treated skin explants, as compared with untreated controls. These data demonstrate that ROL exerts its anti‐ageing benefits not only via enhanced epidermal proliferation and increased collagen production, but also through an increase in elastin production and assembly.     

Visible skin condition and perception of human facial appearance

Evolutionary psychology suggests that certain human beauty standards have evolved to provide reliable cues of fertility and health. Hence, preferences for some physical characteristics of the face and body are thought to reflect adaptations for the promotion of mate choice. Studies that have investigated facial attractiveness have concentrated mainly on features such as symmetry, averageness and sex‐typical traits, which are developed under the influence of sex steroids. Few studies, however, have addressed the effect of human skin condition on perception of facial appearance in this context, and possible implications for sexual selection. There is now accumulating evidence that skin pigmentation and skin surface topography cues, particularly in women, have a significant influence on attractiveness judgements, as they seem primarily to signal aspects of age and health. This article (i) reviews briefly some of the main determinants of visible skin condition, (ii) presents recent evidence on its signalling value in face perception and (iii) suggests areas for future research with reference to an evolutionary psychology framework.     

The regulatory role of the tetrapeptide AcSDKP in skin and hair physiology and the prevention of ageing effects in these tissues – a potential cosmetic role

The naturally occurring tetrapeptide acetyl‐N‐Ser‐Asp‐Lys‐Pro (AcSDKP) recognized as a potent angiogenic factor was shown recently to contribute to the repair of cutaneous injuries. In the current article, we report the ability of AcSDKP to exert a beneficial effect on normal healthy skin and scalp and to compensate for the ageing process. In vitro AcSDKP at 10^?11–10^?7 M significantly stimulates the growth of human keratinocytes, fibroblasts and follicle dermal papilla cells. Moreover, it enhances the growth of human epidermal keratinocyte progenitor and stem cells as shown in a clonogenic survival assay. Topical treatment of ex vivo cultured skin explants with 10^?5 M AcSDKP increases the thickness of the epidermis and upregulates the synthesis of keratins 14 and 19, fibronectin, collagen III and IV as well as the glycoaminoglycans (GAGs). In the ex vivo‐cultured hair follicles, AcSDKP promotes hair shaft elongation and induces morphological and molecular modifications matching the criteria of hair growth. Furthermore, AcSDKP at 10^?11–10^?7 M was shown to improve epidermal barrier, stimulating expression of three protein components of tight junctions (claudin‐1, occludin, ZO‐1) playing an important role in connecting neighbouring cells. This tetrapeptide exercises also activation of SIRT1 implicated in the control of cell longevity. Indeed, a two‐fold increase in the synthesis of SIRT1 by cultured keratinocytes was observed in the presence of 10^?11–10^?7 M AcSDKP. In conclusion, these findings provide convincing evidence of the regulatory role of AcSDKP in skin and hair physiology and suggest a cosmetic use of this natural tetrapeptide to prevent skin ageing and hair loss and to promote the cutaneous regeneration and hair growth.     

Five dimensions of cleansing: A holistic view on the facets and importance of skin cleansing

Cleansing is an important human ritual practised for hygiene, well-being and relaxation over centuries. As part of body care it is often taken for granted, yet its relevance cannot be underestimated. Although cleansing the skin may seem trivial to some, it is accepted, that this fundamental function of skin cleansing products is highly complex, diverse and crucial for a variety of reasons in the personal, public, healthcare and dermatological settings. Employing a comprehensive and strategic approach in viewing cleansing and its rituals, supports innovation, understanding and development. Apart from being a fundamental function, as far as we know, there is no comprehensive presentation of skin cleansing with all its effects besides ‘removing dirt’. To our knowledge, comprehensive analyses on the multi-dimensional facets of skin cleansing are either rare or not published. Against this background, we examine the importance of cleansing in terms of function, relevance and concepts. First, the key functions and efficacies of skin cleansing were investigated by literature research. Based on this survey, the functions were analysed, sorted and merged and a novel approach to skin cleansing ‘dimensions’ was developed. Herewith, we took into consideration the evolution of skin cleansing in terms of concept evolution, complexity and testing methods for cleansing products and their claims. Several multi-dimensional functions of skin cleansing were identified and then established into five skin cleansing dimensions, namely: hygienic and medical importance; socio-cultural and interpersonal relevance; mood, emotion and well-being; cosmetic and aesthetic function; corneobiological interactions. It became obvious, that these five dimensions with their corresponding 11 sub-dimensions, are influenced by each other throughout history by culture and society, technical progress, scientific knowledge and consumer trends. This article presents the enormous complexity of skin cleansing. Skin cleansing has evolved from basic care up to a highly complex and diverse cosmetic product category in terms of technology, efficacy and usage routine(s). In view of future challenges, such as the effects of climate and associated lifestyle changes, the development of skin cleansing will remain an exciting and important topic and thus will finally, again, further increase the complexity of skin cleansing itself.     

Evidence for the existence of a body-brain connection for skin moisturization

Maintenance of the right water levels in the skin is of crucial importance to maintain healthy, young‐looking skin. Moisturizing products have therefore aimed to influence the constitutive levels of natural moisturizer factor (NMF) and/or the formation of the skin lipid barrier. In humans, keratinocyte differentiation is influenced by sex hormones, in particular positively by estrogen and negatively by testosterone. It has been noted that postmenopausal women experience a decline in estrogen levels and a concomitant drop in skin moisturization. In our previous near‐infrared reflectance (NIR) spectroscopy work on human skin, we noted that skin moisturization was influenced by gender, age, psychological stress and lifestyle habits such as alcohol consumption and smoking. Many of these also affect the level of sex hormones. We therefore re‐evaluated NIR spectra from which we had already assessed the levels of skin moisturization in human volunteers to determine their levels of estrogen and testosterone non‐invasively. We subsequently built mathematical models to link skin moisture content to the levels of these sex hormones. In this way, we were able to establish the importance of sex hormones in skin moisturization. In men, skin moisturization levels are linked to their estrogen levels, whereas in females, skin moisturization levels are linked to both estrogen and testosterone concentrations. From the medical literature, it is known that smoking is associated with increased testosterone and reduced estrogen levels, which suggests that people that smoke are characterized by less hydrated skin as well as by increased testosterone levels. On the other hand, pregnant females that have significantly elevated estrogen to progesterone ratios, i.e. their increase in estrogen level exceeds their increase in testosterone levels, also often remark that their skin is well hydrated, confirming the link between sex hormone levels and skin moisturization. For them, we found a good correlation coefficient for skin moisturization levels and their estrogen to testosterone ratio. This work does not, however, answer question of a cause‐and‐effect relationship between the two. Increased levels of estrogen can either directly increase skin moisture levels or do so via a positive effect on skin barrier formation. It does, however, reveal once again the existence of a connection between our body (the skin) and our brain. Synthesis of sex hormones is regulated via the pituitary gland in our brain and it can therefore be argued that skin moisturization is directly or indirectly regulated via our brain. As many other factors like smoking and alcohol consumption actually influence estrogen levels in our blood, the influence of our brain on maintaining a skin moisture homeostasis may actually be much more pronounced than hitherto assumed.     

The mechanics of buckling fiber in relation to fabric‐evoked prickliness: a theory model of single fiber prickling human skin

The simple Euler model of buckling of a slender rod has been commonly used to explain the mechanics in relation to the buckling of fabric‐evoked prickliness. Unfortunately, few works have paid attention to its applicability into the buckling behavior of fiber prickling human skin to evoke prickliness, though the friction between the fiber end and the skin and the firmness of a fiber end held in fabric (denoted as elastic stiffness) are considered to be among the main factors for fabric‐evoked prickliness. To model the mechanics of buckling of a fiber in relation to fabric‐evoked prickliness, the fiber–skin friction, the elastic stiffness, and the initial inclined angle of the fiber are introduced into the simple Euler model of buckling of a slender rod. Then, a sensitivity analysis is performed on these three factors to observe their role in the buckling behavior of a fiber. The results demonstrate that the fiber–skin friction and the elastic stiffness have a significant effect on the buckling behavior of fiber end prickling skin and the stimulus intensity to skin. Additionally, the fiber with an initial inclined angle can exert compression force on skin above the average force threshold of nociceptors responsible for fabric‐evoked prickliness, and the force size depends on the fiber property and its end‐restraint intensity. Therefore, it is not appropriate for the assumption of a fixed‐hinged boundary of the fiber end prickling human skin. In this sense, a developed fiber–skin coupling model provides a good modeling for the buckling behavior of fiber end pricking human skin.     

A survey and analysis of the role of molecular chaperone proteins and imidazole‐containing dipeptide‐based compounds as molecular escorts into the skin during stress,injury, water structuring and other types of cutaneous pathophysiology

Molecular chaperone, heat shock proteins (HSPs), stabilizes intracellular processes of cells under stress. Little is known about the role of molecular chaperone proteins in the skin pathology, rejuvenation and wound healing, or whether their expression is altered by environmental and physiological stress to the skin or systemic disease. The focus of this study was to examine the role of molecular chaperone proteins in the skin’s local response to wounding, skin ageing and a range of skin diseases. Free radicals, one form of insult, induce or contribute to adverse effects on the skin, including erythema, oedema, wrinkling, photoaging, inflammation, autoimmune reactions, hypersensitivity, keratinization abnormalities, preneoplastic lesions and skin cancer. A unified view of the molecular and cellular pathogenesis of the skin age‐related pathology conditions has led to the search for molecular and chemical chaperones that can slow, arrest or revert disease progression. Specific alpha‐crystallin domains and pharmacological imidazole‐containing dipeptide chaperone molecules are now emerging that link our biophysical insights with developed skin therapeutic techniques. In this article, we discuss the molecular nature of the stress signals, the mechanisms that underlie activation of the heat shock response, the role of molecular chaperone proteins as skin protective molecules, and strategies for pharmacologically active chaperone molecules and their imidazole‐containing dipeptide inducers as regulators of the skin stress response. We discuss how impairment in protein hydration may cause ultrastructural, mechanical and biochemical changes in structural proteins in the aged skin. We have pioneered the molecular chaperone protein activated therapeutic or cosmetic platform to enable simultaneous analysis of water‐binding and structuring characteristics for biology of skin ageing and skin disease‐related pathways. This cutting‐edge technology has improved the way that proteins hydrate in photoaged skin. The mechanisms of skin diseases, ageing, cellular, and signalling pathways mediated by targeting with molecular chaperone protein(s) in patented formulations with imidazole containing dipeptide (N‐acetylcarnosine, carcinine, carnosine) are also discussed within this review.     

Infant skin physiology and development during the first years of life: a review of recent findings based on in vivo studies

Infant skin is often presented as the cosmetic ideal for adults. However, compared to adult skin it seems to be more prone to develop certain pathological conditions, such as atopic dermatitis and irritant contact dermatitis. Therefore, understanding the physiology of healthy infant skin as a point of reference is of interest both from the cosmetic as well as from the clinical point of view. Clinical research on healthy infants is, however, limited because of ethical considerations of using invasive methods and therefore until recently data has been scarce. Technical innovations and the availability of non‐invasive in vivo techniques, such as evaporimetry, electrical impedance measurement, in vivo video and confocal microscopy, and in vivo fibre‐optic based spectroscopy, opened up the field of in vivo infant skin physiology research. Studies incorporating such methods have demonstrated that compared to adult, infant skin continues to develop during the first years of life. Specifically, infant skin appears to have thinner epidermis and stratum corneum (SC) as well as smaller corneocytes at least until the second year of life. The water‐handling properties are not fully developed before the end of the first year and infant SC contains more water and less amounts of natural moisturizing factors. Such findings re‐evaluate the old notions that skin is fully matured at birth. Armed with this knowledge, we are in a position not only to better understand infant dermatological conditions but also to design better skin care products respecting the distinct qualities of infant skin.     

Sensory and compositional attributes of melting‐ and non‐melting‐flesh peaches for the fresh market

A study was conducted to determine differences in sensory and compositional characteristics of melting‐flesh (MF) and non‐melting flesh (NMF) fresh market peach genotypes. Sensory results showed that the NMF fruit (‘Oro A’ and FL 86‐28C) were ‘harder’, less ‘juicy’ and more ‘rubbery’ than their MF (FL 90‐20 and ‘TropicBeauty’) counterparts. A principal component analysis of the sensory data showed a clear distinction between the textural aspects of MF and NMF fruit, but not between their flavour aspects. Likewise, chemical analysis showed that while differences in pH, titratable acidity, and soluble solids were detected among the four genotypes, no consistent grouping could be made based on the MF/NMF nature of the fruit. © 1999 Society of Chemical Industry     

山羊绒夹杂肤皮屑的组成及其结构

山羊绒中夹杂的肤皮屑会严重影响纺织品质量。采用胃蛋白酶法和还原法从山羊绒肤皮中提取了胶原蛋白和角蛋白,并对其进行了表征。结果表明：洗净绒中肤皮屑组成及其质量分数为水分9.14%,脂肪8.72%,水溶物11.36%,粗蛋白60.13%,灰分10.65%,粗蛋白中胶原蛋白和角蛋白分别占蛋白质质量分数的30.98%和15.67%,是蛋白质的主要组成,其他蛋白质归属有待进一步研究。肤皮屑中胶原蛋白相对分子质量集中在49 ku,角蛋白分子质量在26～35 ku和49 ku 区域。各组分在肤皮屑结构中分布情况不同,脂肪和胶原蛋白分布不均匀,角蛋白呈较均匀分布状态,水溶物对肤皮片状粘接起主要作用。研究结果为解决山羊绒染色肤皮点提供了理论参考。