Constitutive Skin Pigmentation Research Articles

Analysis of Skin Color Variation using CIELAB Index: An Empirical Study from Delhi, India

Skin color is a conspicuous trait regulated by complex metabolic processes and its significant diversity among Indian populations is quite remarkable making it an ideal choice for dermatological investigation. To elucidate skin pigment variation with respect to age, we studied 714 healthy individuals (aged 20-70 years) using CIELAB system. Skin reflectance was measured from the volar surface of upper arm using DSM II ColorMeter (Cortex Technology, Hadsund, Denmark) among population of Delhi, India to provide CIELAB color space values, L* (light/dark), a* (red/green), and b* (yellow/blue) followed by statistical analysis to examine the correlation between age and gender on skin on constitutive skin pigmentation. The studied parameters were observed to vary widely {L* (Range: 24.98-51.62, M=38.66, SD=4.41), a* (Range: 4.61-17.16, M=10.18, SD=2.03), and b* (Range: 20.16-34.83, M=28.93, SD=2.30)} across all age groups. ANOVA results suggest a statistically significant effect of age on skin lightness {F(4,709)=124.1332, p<0.001}, redness {F(4,709)=20.0594, p<0.001} and yellowness {F(4,709)=95.1434, p<0.001}. Positive correlation was observed between age and both hue (ho) {r(712)=0.9027, p<0.001} and chroma (C) {r(712)=0.9224, p<0.001}. Significant effects of gender were noticed on skin lightness among all age groups, along with skin redness below the age of 40 years (p<0.001). Notable color differences (∆Ε∗ab) were witnessed among males and females across all age groups in the studied population. The age group 21-30 years was found to have the highest ∆Ε∗ab value (3.5987), followed by 51-60 years (2.98), 31-40 years (2.5579), 61-70 years (2.1837), and 41-50 years (1.6639). We would like to highlight that skin lightness, redness, and yellowness differs significantly with age. Females were observed to be lighter in color as compared to males across all age groups. The findings of the current study would provide better understanding of skin color variation among Indian population.

Melanin's Journey from Melanocytes to Keratinocytes: Uncovering the Molecular Mechanisms of Melanin Transfer and Processing.

Skin pigmentation ensures efficient photoprotection and relies on the pigment melanin, which is produced by epidermal melanocytes and transferred to surrounding keratinocytes. While the molecular mechanisms of melanin synthesis and transport in melanocytes are now well characterized, much less is known about melanin transfer and processing within keratinocytes. Over the past few decades, distinct models have been proposed to explain how melanin transfer occurs at the cellular and molecular levels. However, this remains a debated topic, as up to four different models have been proposed, with evidence presented supporting each. Here, we review the current knowledge on the regulation of melanin exocytosis, internalization, processing, and polarization. Regarding the different transfer models, we discuss how these might co-exist to regulate skin pigmentation under different conditions, i.e., constitutive and facultative skin pigmentation or physiological and pathological conditions. Moreover, we discuss recent evidence that sheds light on the regulation of melanin exocytosis by melanocytes and internalization by keratinocytes, as well as how melanin is stored within these cells in a compartment that we propose be named the melanokerasome. Finally, we review the state of the art on the molecular mechanisms that lead to melanokerasome positioning above the nuclei of keratinocytes, forming supranuclear caps that shield the nuclear DNA from UV radiation. Thus, we provide a comprehensive overview of the current knowledge on the molecular mechanisms regulating skin pigmentation, from melanin exocytosis by melanocytes and internalization by keratinocytes to processing and polarization within keratinocytes. A better knowledge of these molecular mechanisms will clarify long-lasting questions in the field that are crucial for the understanding of skin pigmentation and can shed light on fundamental aspects of organelle biology. Ultimately, this knowledge can lead to novel therapeutic strategies to treat hypo- or hyper-pigmentation disorders, which have a high socio-economic burden on patients and healthcare systems worldwide, as well as cosmetic applications.

Seasonal Tanning-Induced Increases in Skin Pigmentation Do Not Affect Nitric Oxide-Mediated Vasodilation of the Cutaneous Microvasculature

Acute ultraviolet radiation (UVR) exposure reduces nitric oxide (NO)-dependent cutaneous vasodilation. Additionally, increased constitutive skin melanin concentrations are associated with reduced NO-dependent cutaneous vasodilation. However, the impact of seasonal tanning-induced increases in skin melanin concentration on NO-dependent cutaneous vasodilation has not been investigated. PURPOSE: To investigate the effect of seasonal tanning-induced increases in skin melanin on the NO-dependent cutaneous vasodilation response to local heating. We hypothesized that NO-dependent cutaneous vasodilation would be reduced in tanned skin relative to untanned skin. METHODS: Three intradermal microdialysis fibers were placed in the ventral upper arm (least sun exposed), ventral forearm (moderately sun exposed), and dorsal forearm (most sun exposed) of seven adults (33 ± 14 yrs; 4M/3F) with light-to-moderate constitutive skin pigmentation. Differences in sun exposure among the sites was confirmed using the melanin-index (M-index; an index of skin pigmentation), measured via skin reflectance spectrophotometry. Lactated Ringer’s solution was perfused through the microdialysis fibers while local heating to 42°C induced cutaneous vasodilation. After attaining a stable plateau in cutaneous blood flow, 15mM NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) was perfused at all sites to quantify NO-mediated vasodilation. Red cell flux was measured using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC=LDF/mean arterial pressure) was calculated for each phase of the local heating response (i.e., baseline, initial peak, local heating plateau, post L-NAME plateau) and expressed as percent maximum (%CVCmax; 28mM sodium nitroprusside + 43°C local heating). RESULTS: M-index was highest (i.e., skin pigmentation was darkest) in the dorsal forearm (50.5 ± 11.8 a.u.) compared to the ventral forearm (37.5 ± 7.4 a.u.; p ≤ 0.03) and upper arm (30.2 ± 5.1 a.u.; p ≤ 0.001). There were no baseline (p ≥ 0.37), initial peak (p ≥ 0.22), post L-NAME plateau (p ≥ 0.12), or maximal CVC (p ≥ 0.23) differences among the three sites. Likewise, the magnitude of the local heating plateau was not different among the three sites (dorsal: 88±17%; ventral: 81±20%; upper: 90±12%; p ≥ 0.16), nor was NO-mediated vasodilation (dorsal: 59±15%; ventral: 54±13%; upper: 55±11.0%; p ≥ 0.79). CONCLUSION: These data suggest that, in contrast to the effects of acute UVR exposure or a constitutively dark skin pigmentation, seasonal tanning-induced increases in skin pigmentation do not alter NO-dependent cutaneous vasodilation responses to local heating. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Cross-Sectional Assessment of Quantitative Epidermal Melanin and Erythema Indices among North Indians.

Remarkable diversity of skin tones among Indians ranging from pale pinkish to dark brown appears to be an ideal choice for the assessment of skin pigment variation. The present study was designed to assess the variation observed in melanin and erythema indices among north Indians. Skin reflectance data (n = 574) was collected from six diverse populations of north India using DermaSpectrometer (DSM II ColorMeter) followed by statistical analysis to investigate the impact of geographical location and gender on constitutive skin pigmentation. The melanin index (MI) varied between 17.93 and 56.92 (Mean (M) = 35.80 ± 6.26) whereas the erythema index (EI) varied between 4.92 and 18.82 (M = 10.48 ± 2.68). MI and EI of females were found to be significantly lower than males (P < 0.001). Geographical location exhibited a significant association with MI and EI (P < 0.001). Furthermore, we have noted a positive correlation between MI and EI (P < 0.001). The study has refined our understanding of skin pigmentation variation among north Indians in terms of significant association with geographical location {MI: F (5,568) = 31.07, P < 0.001; EI: F (5,568) = 73.37, P < 0.001} and gender {MI: t (386) = -4.06, P < 0.001; EI: t (386) = -11.96, P < 0.001} and rendered opportunities for further studies.

Sun Exposure Is Associated with Reduced Breast Cancer Risk among Women Living in the Caribbean: The Atabey Study in Puerto Rico.

Though inconsistent, there is evidence that sun exposure is associated with reduced breast cancer risk. Previous studies have been conducted in geographical regions with seasonal variation in UV radiation, including periods of low to no exposure, and among participants mostly of European descent. Puerto Rico has no significant seasonal fluctuation, with continuous exposure to very high UV radiation. We conducted a population-based case-control study of breast cancer among women in metropolitan San Juan, Puerto Rico, examining a cumulative sun exposure index (SEI) based on a comparison of reflectance of sun-exposed and non-exposed skin. A chromameter was used to measure skin reflectance and estimate the difference between constitutive (unexposed) and facultative (exposed) skin pigmentation in 307 cases and 328 controls. Breast cancer risk factors were ascertained with interviewer-administered questionnaires. OR and 95% confidence intervals (CI) were estimated with unconditional logistic regression. Adjusted breast cancer odds were lower for the highest tertile of the SEI (ORadj = 0.47; 95% CI, 0.29-0.74). Results were similar within strata of estrogen receptor status. In analyses stratified by constitutive skin pigmentation, among participants with darker skin color, breast cancer risk was lower with more sun exposure (ORadj = 0.33; 95% CI, 0.16-0.70). We found lower risk of breast cancer associated with greater sun exposure in a population living with high, continuous sun exposure. This beneficial finding should be placed in the context of other effects of sun exposure. Sun exposure is a modifiable factor that may contribute, directly or indirectly, to lower breast cancer risk.

Low vitamin D in dark-skinned immigrants is mainly due to clothing habits and low UVR exposure: a Danish observational study.

Low 25-hydroxyvitamin D3 (25(OH)D) among dark-pigmented persons has been observed. To elucidate the reason for this we examined sun behaviour, sun-exposed body area, solar UVR exposure and 25(OH)D levels in immigrants with dark pigmented skin and Danes with light pigmented skin. Clothing, sun behaviour, and diet were recorded daily during a Danish summer season (93 analysed days). Erythema-weighted UVR doses were measured by personal electronic UVR dosimeters (with erythema response, measurement every 5th second) and 25(OH)D was measured in 72 participants (33 dark-skinned and 39 light-skinned). The immigrants exposed 28% less skin area, received 70% less UVR dose, and had 71% less 25(OH)D increase during the summer. The UVR reactivity (Δ25(OH)D per joule accumulated UVR dose) was similar (P = 0.62) among the immigrants (0.53nmoll-1J-1) and the Danes (0.63nmoll-1J-1). In the groups combined, 25(OH)D levels after summer were mainly influenced by UVR dose to exposed skin (28.8%) and 25(OH)D start level (27.9%). Height and measured constitutive skin pigmentation were of minor influence: 3.5% and 3.2%, respectively. Sun exposure and clothing habits were the main reasons for lower 25(OH)D level after summer in the darker immigrants, as both groups had similar UVR reactivity.

Blue Lagoon Algae Improve Uneven Skin Pigmentation: Results from in vitro Studies and from a Monocentric, Randomized, Double-Blind, Vehicle-Controlled, Split-Face Study

Introduction: Bathing in the Blue Lagoon (BL) in Iceland benefits patients with psoriasis. Accordingly, the BL water contains algae with biological activities that improve skin barrier function and affect T-cell responses relevant for psoriasis. Bathing in the BL is also becoming increasingly popular among healthy individuals and anecdotal evidence suggests positive effects on uneven skin pigmentation. Objective: The aim of the study was to address the impact of BL algae on skin pigmentation. Methods: In this work, in vitro gene expression studies in melanocytes and a noninvasive in vivo study were conducted. Results: We here report that normal human epidermal melanocytes, which had been treated with nontoxic concentrations of BL algae, show a significantly reduced expression of α melanocyte-stimulating hormone-induced expression of genes important for melanin synthesis, such as tyrosinase, tyrosinase-related protein 1, dopachrome tautomerase, melan A protein, and pre-melanosome protein. This in vitro observation prompted us to conduct a randomized, double-blind, intra-individual, comparative split-face in vivo study, in which 60 volunteers with pre-existing facial pigment spots were treated twice daily with a BL algae containing serum or a vehicle control. We found that constitutive skin pigmentation as determined by colorimetry (individual typology angle and luminescence) did not differ significantly between vehicle- and serum-treated skin sites. In marked contrast, digital photography under cross-polarized lighting and RBX technology (VISIA CR) revealed that the number of pigment spots in the serum-treated face decreased significantly compared to the vehicle-treated side. Conclusion: Thus, BL algae can affect human melanocyte function in vitro and reduce uneven facial skin pigmentation in vivo.

Evaluating age-related changes of some facial signs among men of four different ethnic groups.

The alterations of some facial characteristics, with age, in men of different ethnic groups are a scarcely studied topic. To illustrate and grade, among men of four different ethnic descents (Asians, African-Americans, Caucasians, Indians), aged 18-80year, the changes in the severity of some facial signs occurring with age. Digital Photographs (full face, profile, 45°) of 1058 subjects were taken under standard conditions of lightning. These allowed us to zoom in on 15-20 different facial signs on all subjects. Their observations by 15 trained experts, under calibrated screens, allowed these signs to be graded, with the help of four referential skin Atlases, specific to the gender and ethnic groups studied. Most facial signs show a rather regular increase with age, with different kinetics according to the ethnic group. The major changes, in all four ethnic groups, mostly concern skin structural alterations (wrinkles, neck sagging or texture). The changes in the severity of some wrinkles (forehead, inter-ocular…) may be viewed as ethnic signatures. The modifications in pigmentation disorders seem more closely linked to the constitutive skin pigmentation (photo-types), among which pigmentary spots are confirmed as a more specific Asian trait. Men of four different ethnic origins present different and ethnic-related facial alterations with increasing age, of different amplitudes.

Photoprotection in specific populations: Children and people of color

Improved education on appropriate photoprotection in children is vital. Photoprotection for these individuals should include seeking shade, the use of physical agents (clothing, hat, sunglasses), and application of sunscreens on exposed areas. Avoidance of the use of tanning beds is an important component of education for teenagers. Ultraviolet radiation exposure induces DNA damage and photoaging in all skin types, including people of color. The extent of such damage is inversely related to constitutive skin pigmentation. Therefore, personalized photoprotection recommendations concerning skin cancer risk factors, desired treatment outcomes, health needs (eg, vitamin D), and photoaging based on the needs and preferences of the patient are essential. It is clear that additional research is needed on optimal levels of protection against ultraviolet radiation for people of color.

Selected gene polymorphisms effect on skin and hair pigmentation in Polish children at the prepubertal age.

Background: Human pigmentation, similarly as many other biological features, changes in the course of post-natal ontogenesis, while in case of hair, pigmentation changes are more distinctive than in the skin or the iris. It is therefore extremely important to identify the genes, involved in the constitution of human pigmentation features at various stages of ontogenesis. Results of this type of analyses are of high practical significance in forensic study because they enable to create mathematical tools, allowing for prediction of the pigmentation phenotype, based on DNA studies. Aim: The objective of the investigation was finding out whether the genes, associated with pigmentation of adult subjects, differentiated in any way the newly forming pigmentation phenotype in Polish prepubertal children. Material and methods: The study encompassed Polish children, aged 7 to 10 years, without any abnormalities in skin or hair pigmentation. A total of 245 children were examined. Constitutive skin pigmentation according to skin melanin index (SMI) was evaluated, using a dermaspectrometer, and classified into three groups based on the reference values of 25 and 75 percentile for Polish children. Hair colors were evaluated by means of the descriptive Fischer-Saller scale and classified by a division of color variants (as accepted in that scale) (light blonde, blonde, dark blonde, brown and dark brown). In saliva samples, collected from the children, five (5) single nucleotide polymorphisms were identified: SNPs: rs1800401 (OCA2-15q11.2-q12), rs35264875 (TPCN2-11q13.3), rs16891982 (SLC45A2-5p13.2), rs12913832 (HERC2-15q13) and rs1805007 (MC1R-16q24.3). An association between each allele of verified genotype and skin and hair color phenotypes was assessed, using the z-statistic and associated p-value. The quality of classifiers was evaluated by 10-fold stratified cross-validation and was characterized by the area under the receiver operating characteristic curve (AUC). Results: Light skin pigmentation phenotype (SMI<25 percentile) was associated with rs1805007 (MC1R) (allelic OR=3.95; 95% Cl:1.20-12.99; p=0.0235), while the dark shade of the skin (SMI>75 percentile) with rs16891982 (SLC45A2) (allelic OR =14.37; 95% Cl: 1.78-115.88; p=0.0123). The probability of dark hair (brown and dark brown) in childhood was increased by T rs12913832 allele (HERC2) (OR=3.63); 95% Cl: 2.25-5.85; p < 0.0001) and dependent on it - rs1800401 (OCA2) (OR=6.31; 95% Cl: 1.74-22.91; p=0.0051). Other SNPs were not significantly associated with skin and hair color but improved prediction of these features. Conclusions: From the five gene polymorphisms analysed in Polish children the strongest correlation with hair color has the rs12913832 (HERC2) and with skin color - rs16891982 (SLC45A2). Therefore, the above-mentioned polymorphisms may be used as components of potential models, used to predict pigmentation features in European origin children in prepubertal age. To improve predictive value of the potential scoring model for hair color, the following should be additionally included: rs1800401 (OCA2), rs35264875 (TPCN2) and rs1805007 (MC1R), while for skin color: rs12913832 (HERC2) and rs1805007 (MC1R).

Skin Pigmentation and Pigmentary Disorders: Focus on Epidermal/Dermal Cross-Talk.

Variation in human skin and hair color is the most notable aspect of human variability and several studies in evolution, genetics and developmental biology contributed to explain the mechanisms underlying human skin pigmentation, which is responsible for differences in skin color across the world's populations. Despite skin pigmentation is primarily related to melanocytes functionality, the surrounding keratinocytes and extracellular matrix proteins and fibroblasts in the underlying dermal compartment actively contribute to cutaneous homeostasis. Many autocrine/paracrine secreted factors and cell adhesion mechanisms involving both epidermal and dermal constituents determine constitutive skin pigmentation and, whenever deregulated, the occurrence of pigmentary disorders. In particular, an increased expression of such mediators and their specific receptors frequently lead to hyperpigmentary conditions, such as in melasma and in solar lentigo, whereas a defect in their expression/release is related to hypopigmented disorders, as seen in vitiligo. All these interactions underline the relevant role of pigmentation on human evolution and biology.

The role of natural and UV‐induced skin pigmentation on low‐fluence IPL‐induced side effects: A randomized controlled trial

The risk of adverse skin effects following light-based hair removal is greater in pigmented skin based on the theory of selective photothermolysis. Thus sunlight-induced pigment i.e., facultative pigmentation, increases the risk of adverse skin effects, perhaps disproportionately. The aim of this study was to evaluate the influence of constitutive and facultative skin pigmentation on low-fluence intense pulsed light (IPL)-induced adverse skin effects. Twenty-one subjects with Fitzpatrick skin type II-IV were enrolled. Two buttock blocks were randomized to receive 0 or 8 solar simulated ultraviolet radiation (UVR) exposures of consecutively increasing Standard Erythema Doses (2-4 SED). Each block was subdivided into four sites, randomized to receive IPL of 0, 7, 8, or 10 J/cm(2) , once a week for 3 weeks. Biopsies were taken 16-24 hours after the first IPL exposure and subjects were seen 1 and 4 weeks after the last IPL exposure. Outcome measures were: (i) skin reactions, (ii) pain, (iii) mRNA expression of pigment-markers microphthalmia-associated transcription factor (MITF) and pro-opiomelanocortin (POMC), and (iv) clinical appearance of biopsy wounds. Skin pigmentation increased after UVR (baseline median 13.8%, after UVR 28.1%, P = 0.0001) in all skin types. Subjects reported low pain intensities (median 1.5, scale 0-10) and experienced transient erythema immediately after IPL exposure. No persistent erythema, blisters, crusting, textual, or pigment changes were observed. The risk of erythema and pain intensities increased with IPL dose and skin pigmentation (P < 0.03). There was no difference in pain or skin reactions in skin with similar degree of natural and facultative pigmentation (P ≥ 0.104). Expression of cellular pigment-markers was not influenced by IPL exposure, neither in constitutive nor in facultative pigmented skin. Clinical appearance of biopsy wounds was unaffected by IPL exposure. The prevalence and intensity of low-fluence IPL-induced adverse skin effects depended on IPL dose and skin pigmentation regardless of the origin, i.e., constitutive versus UV induced.

Is increased constitutive skin and hair pigmentation an early sign of puberty?

The paper analyzes data concerning the constitutive skin and hair pigmentation of 7–10-year-old Polish children to examine whether the hormonal activity of the gonads, which increases in this period, causes changes in pigmentation levels that may be considered an early sign of puberty. The study involved 289 children (151 girls and 138 boys). Skin pigmentation was examined on the medial side of the arm, while hair pigmentation on strands of hair close to the scalp in the occipital area. Additionally, body height (B-v) was measured and compared with population norms. On this basis, it was ascertained that the studied sample was representative of the population from which it was taken and that it represented the prepubertal and early pubertal stages of ontogeny (prior to the pubertal growth spurt or the first menstruation in the studied girls). It was found that in 7–10-year-old Polish children there is a statistically significant (p=0.001) increase in skin and hair pigmentation levels, while the degree of pigmentation of both structures at this stage of ontogeny is sexually dimorphic: girls are characterized by stronger pigmentation than boys. At the age of 10 years, the dimorphic differences in skin pigmentation intensify due to a rapid rise in pigmentation in girls. This change may be deemed an early morphological sign of puberty, as it precedes the pubertal growth spurt and menarche. This fast increase in skin pigmentation is not paralleled by an analogous change in hair pigmentation.

Constitutive and Relative Facultative Skin Pigmentation among Victorian Children Including Comparison of Two Visual Skin Charts for Determining Constitutive Melanin Density

Our aim was to examine the association between ethnicity, phenotype, sun behavior and other characteristics, and constitutive and relative facultative skin pigmentation. A total of 191 participants were recruited, with a mean age of 7.6 years (SD 3.4), during 2009-2011 from Maternal and Child Health Centres (MCHC) and schools in Melbourne, Australia. Parental questionnaire data were obtained on sun behavior and examination consisted of noting the child's natural skin, hair and eye color, ethnicity, nevi count and spectrophotometric melanin density (MD). Constitutive skin pigmentation was estimated from buttock MD. Relative facultative skin pigmentation was estimated by hand compared with buttock absorption. Ethnicity, hair color and skin color were associated with constitutive and facultative skin pigmentation on univariate analysis. Higher ambient ultraviolet radiation (UVR) in the past month, greater freckling, greater nevi and increased sun exposure over the past year were related to darker facultative skin pigmentation. Sun exposure over the life course was not. The two skin charts accounted for 39.7% and 21.4% of buttock MD, respectively. Relative facultative skin pigmentation is associated with recent UVR levels, not life-course sun exposure. Relative facultative skin pigmentation may not be a useful measure of sun exposure over the early life course. Skin color charts can be used to assess constitutive skin pigmentation if spectrophotometry is not available.

Assessing skin pigmentation in epidemiological studies: The reliability of measurements under different conditions

Different devices are used for the non-invasive measurement of (constitutive) skin pigmentation in (epidemiological) studies. Reproducibility of measurements with the Chromameter (CM, model CR 300, Minolta, Osaka) and the Reflectometer (RM, Courage & Khazaka, Cologne) has not yet been examined in detail and was addressed in a set of four experiments and studies respectively. Regarding the CM, the Y value of the Yxy CIE 1931 colour system was utilized, representing lightness in this colour space, while the RM measured reflectance at 660nm with a small bandwidth of 20nm. Both devices measure reflectance on a scale from 0 to 100%, however, in different wavelength ranges. Between 3 and 20 repetitions were performed on standard grey scales and different sets of human volunteers, including RM measurements in a large epidemiological field study. While the coefficient of variation (V) increases and the intraclass correlation coefficient decreases from controlled laboratory to field conditions, reproducibility remained in a range considered acceptable, if adequate study conditions were maintained. In a direct comparison on human skin, V of the RM was significantly smaller than that of the CM. Both devices can be used confidently in field studies; however, based on considerations of skin optics and in view of slightly lesser variability, the RM may be preferable.

Vitamin D Production after UVB Exposure Depends on Baseline Vitamin D and Total Cholesterol but Not on Skin Pigmentation

UVB radiation increases serum vitamin D level expressed as 25-hydroxyvitamin-D(3) (25(OH)D), but the influence of skin pigmentation, baseline 25(OH)D level, and total cholesterol has not been well characterized. To determine the importance of skin pigmentation, baseline 25(OH)D level, and total cholesterol on 25(OH)D production after UVB exposure, 182 persons were screened for 25(OH)D level. A total of 50 participants with a wide range in baseline 25(OH)D levels were selected to define the importance of baseline 25(OH)D level. Of these, 28 non-sun worshippers with limited past sun exposure were used to investigate the influence of skin pigmentation and baseline total cholesterol. The participants had 24% of their skin exposed to UVB (3 standard erythema doses) four times every second or third day. Skin pigmentation and 25(OH)D levels were measured before and after the irradiations. Total cholesterol was measured at baseline. The increase in 25(OH)D level after UVB exposure was negatively correlated with baseline 25(OH)D level (P<0.001) and positively correlated with baseline total cholesterol level (P=0.005), but no significant correlations were found with constitutive or facultative skin pigmentation. In addition, we paired a dark-skinned group with a fair-skinned group according to baseline 25(OH)D levels and found no differences in 25(OH)D increase after identical UVB exposure.

Vitamin D Level in Summer and Winter Related to Measured UVR Exposure and Behavior

The influence of the summer UVR exposure on serum-25-hydroxyvitamin D (25(OH)D) in late summer and winter was investigated in an open study on 25 healthy, adult volunteers. The UVR exposure dose in standard erythema dose (SED) was monitored continuously during a summer season with personal, electronic wristwatch UVR dosimeters and sun exposure diaries. Constitutive and facultative skin pigmentation was measured in September. 25(OH)D was measured in September and February and was in mean 82 nmol/L +/- 25 (mean +/- SD) in September and 56 nmol/L +/- 19 (mean +/- SD) in February. The received cumulative UVR dose measured during a mean of 121 days was 156 SED +/- 159 (mean +/- SD). The following UVR exposure parameters correlated with 25(OH)D in September and February, respectively: (1) The cumulative UVR dose (r = 0.53; P < 0.01) and (r = 0.43; P = 0.03); (2) Mean daily hours with UVR measurements monitored by the dosimeter (r = 0.64, P = 0.001) and (r = 0.53; P = 0.007); (3) Days "with sun-exposed upper body" (r = 0.58, P = 0.003) and (r = 0.50; P = 0.01); (4) Facultative pigmentation (r = 0.47; P < 0.02) and (r = 0.7; P < 0.001); (5) Constitutive pigmentation (r = 0.06, n.s.) and (r = 0.43, P = 0.03). Neither days "sunbathing" nor days with "sunscreen applied" correlated with 25(OH)D. The fall in 25(OH)D during winter was dependent on the entry value.

La couleur de la peau humaine : de la recherche à l’esthétique

Skin color is controlled by pigmentary genes that regulate constitutive skin pigmentation and by environmental factors, the most obvious of them being solar U.V. At this time, more than 130 distinct pigmentary genes are known. They affect embryogenesis and survival of the melanocyte system, mélanosome biogenesis, melanogenesis, mélanosome transport and transfer, eumelanins/pheomelanins ratio and epidermal mélanosome turn-over and elimination. The pigmentary disorders of the skin are common and represent an important part of dermatologist activity. They concern at the same time the general dermatology and the aesthetic dermatology.

SOX9 and the tanning response: something new under the sun

SOX9 and the tanning response: something new under the sun

La couleur de la peau humaine : de la recherche à l’esthétique

Skin color is controlled by pigmentary genes that regulate constitutive skin pigmentation and by environmental factors, the most obvious of them being solar U.V. At this time, more than 125 distinct pigmentary genes are known. They affect embryogenesis and survival of the melanocyte system, mélanosome biogenesis, melanogenesis, mélanosome transport and transfer, eumelanins/pheomelanins ratio and epidermal mélanosome turn-over and elimination. The pigmentary disorders of the skin are common and represent an important part of dermatologist activity. They concern at the same time the general dermatology and the aesthetic dermatology.