Squalene in sebum and sebum-like materials.
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Humans↗
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Temporal changes in sebum excretion and propionibacterial colonization in preadolescent children with and without acne.
BACKGROUND: It is generally accepted that the onset of sebum secretion occurs before puberty in boys and girls as a result of increasing androgen output during the adrenarche. Propionibacteria are part of the commensal skin flora and, in adults, are found in highest numbers in sebum-rich areas of skin such as the face and upper trunk. Previous studies investigating the association between sebum output and propionibacterial population densities have been cross-sectional and have been carried out mainly in adults. OBJECTIVES: The purpose of this study was to examine the association between the onset of sebum secretion and expansion of the propionibacterial flora in a population of early adolescent children aged between 5.5 and 12 years, and to evaluate the temporal relation between the two factors longitudinally. In addition, the study aimed to evaluate the change with age in sebaceous gland activity and propionibacterial colonization on the skin and in the nares between children who developed acne and those who did not. METHODS: Biannual examinations of volunteers included age, pubertal (Tanner) stage, weight and height, lesion counting on the face, propionibacterial colonization on the skin surface and in the nares and sebum secretion. A longitudinal analysis based on all observations of each subject throughout the study was applied to examine the change of sebaceous gland activity and propionibacterial colonization with age and pubertal stage. A generalized estimating equation was used with a 0.05 level of significance. RESULTS: The commencement of sebum production was asynchronous, with only a small number of follicles initially starting to secrete sebum onto the skin surface. The number of secreting follicles and the area of sebum increased with age and pubertal stage (P < 0.0001, P < 0.05, respectively). Numbers of propionibacteria on the skin tended to increase after the age of 9 years, but not significantly so. In contrast, numbers of propionibacteria in the nares increased significantly with age (P < 0.0001) but not with pubertal maturation. Children who developed acne had higher sebum output and propionibacterial densities with increasing age than children who did not develop acne. This effect was significant for the increase of total sebum area with age in pubertal children (P = 0.0023), the increase in number of secreting follicles with age (P = 0.020) in prepubertal children, and the increase in propionibacteria densities in the nares with age (P = 0.0005) in pubertal children. Sebaceous gland activity and propionibacterial numbers on the skin surface remained unchanged with increasing age in children who did not develop acne. Propionibacterial population densities in the nares increased with age regardless of the development of acne. CONCLUSIONS: Onset of sebum secretion and consequently expansion of the propionibacterial skin flora occur earlier in children who develop acne than in children of the same age and pubertal status who do not develop acne. These observations suggest that postponing the onset of sebum production or the expansion of the propionibacterial skin flora until after puberty may represent ways of preventing the disease or minimizing its severity. Determinants of propionibacterial colonization on the skin and in the nares may be different.
Acne Vulgaris↗
Differential scanning calorimetry studies of sebum models.
Human sebum is a mixture of triglycerides, fatty acids, wax esters, squalene, cholesterol, and cholesterol esters. P. acnes, a bacterium that is normally found on the skin, hydrolyzes certain triglycerides to fatty acids, thereby changing the sebum composition. The objective of this study was to examine the physical state of a model sebum and the effect of variations in its composition on its physical properties including (a) the carbon chain length of the components, (b) the ratio of unsaturated to saturated components, and (c) the ratio of triglycerides to fatty acids. A model sebum mixture was prepared based on a composition reported in the literature and evaluated by differential scanning calorimetry (DSC). Since cholesterol and cholesterol esters contribute insignificantly to sebum composition, they were not included. Squalene was kept constant (13%), while the concentration of the rest of the components was varied. Variations of sebum were prepared by dissolving all components in a 3:1 chloroform-methanol mixture for uniformity. Subsequently the solvent was evaporated at room temperature. The samples were then analyzed using DSC. Four distinct endotherms (namely, Mp-1, Mp-2, Mp-3, and Mp-4) were observed between -50 degrees C and 100 degrees C. Mp-1 and Mp-2 occurred below 0 degrees C and were contributed by unsaturated components. Mp-3 and Mp-4, which represent the saturated components, occurred above 30 degrees C. Thus, at normal skin temperature (skin surface temperature is 32 degrees C), sebum contains both a solid and a liquid phase. All the transition temperatures increased with an increase in carbon chain length for the same ratio of unsaturation to saturation. A replacement of unsaturated components with corresponding saturated components led to a decrease in the transition temperatures for the former (Mp-1 and Mp-2) and an increase in the transition temperatures for the latter (Mp-3 and Mp-4). Replacement of triglycerides with corresponding fatty acids (mimicking the action of anaerobic bacteria) caused an increase in Mp-2 and a decrease in Mp-4. In all cases, the final melting temperature (Mp-4) was greater than the temperature of the human skin surface (32 degrees C); thus components contributing to these endotherms are still solids at skin temperature. All variations in the sebum model led to mixtures of solids and liquids at skin temperature. Considering a reduction in Mp-3 and/or Mp-4 to represent sebum "fluidization," it was achieved by a decrease in carbon chain length, an increase in unsaturation, or a substitution of triglycerides by corresponding fatty acids. Preferential enrichment with the saturated species will lead to enrichment of solids versus liquids in the sebum, presumably making it difficult for the liquid phase to dissolve the solids. It seems plausible that perturbation of the balance of solid and liquid components of sebum, such as by P. acnes action, may lead to blockage of the follicle. Future research will investigate strategies to dissolve and/or liquify the solid phase of sebum.
Calorimetry, Differential Scanning↗
Does facial sebum excretion really affect the development of acne?
BACKGROUND: It is generally accepted that the severity of acne is correlated with facial sebum secretion. However, previous studies on the relation between seborrhoea and the development of acne did not consider topographical differences in facial sebum secretion and used relatively vague acne severity grading systems. OBJECTIVES: To elucidate the relation between topographical variations in facial sebum secretion and the severity of acne in women. METHODS: Forty-six female controls and 46 women with acne were included in this study. The Sebumeter was used to measure facial sebum secretion in the following facial areas: forehead, nose, chin, and right and left cheek. We counted noninflammatory comedones and inflammatory acne lesions in the same areas. We compared sebum secretion between patients with acne and controls, and analysed the relation between the quantity of sebum secreted and the number of acne lesions. RESULTS: Sebum secretions in the whole face and in the T- and U-zones (areas of high and low sebum secretion, respectively) were higher in patients with acne than in controls. There was no correlation between sebum quantity and acne lesion count in most facial regions. CONCLUSIONS: Increased levels of facial sebum secretion were observed in patients with acne. Our findings indicate that increased sebum levels do not directly cause development of acne lesions.
Acne Vulgaris↗
The androgen control of sebum production. Studies of subjects with dihydrotestosterone deficiency and complete androgen insensitivity.
To evaluate the androgen control of sebum, subjects with complete androgen insensitivity and male pseudohermaphrodites with inherited 5 alpha-reductase deficiency and decreased dihydrotestosterone (DHT) production had sebum production studied. A hydrophobic polymeric film applied to the forehead was used to measure sebum production through the use of air filled micropores. Sebum scores of normal preadrenarchal children (ages 2-6), and normal age-matched adult males and females, were studied as well as males treated with the 5 alpha-reductase inhibitor, finasteride, for benign prostatic hyperplasia who were studied at baseline and after drug therapy. Androgen insensitive subjects had no sebum production by this methodology, and the results were identical to preadrenarchal children. In contrast, adult male pseudohermaphrodites with 5 alpha-reductase deficiency and a selective decrease in DHT production had sebum production scores identical to normal age-matched males. Males with benign prostatic hyperplasia treated with the 5 alpha-reductase inhibitor, finasteride, to lower DHT levels did not decrease the sebum score from baseline values. The lack of demonstrable sebum in androgen-insensitive subjects clearly demonstrates the absolute androgen control of sebum production. The DHT dependency of the sebaceous gland, however, could not be demonstrated in this study. Two 5 alpha-reductase isoenzymes 1 and 2, have been described. 5 alpha-reductase-2 is the gene responsible for inherited 5 alpha-reductase deficiency. Although the degree of inhibition of DHT in utero and in adulthood in male pseudohermaphrodites with a defect in 5 alpha-reductase-2 enzyme activity caused severe impairment of external genital and prostate differentiation and decreased facial and body hair, it had no demonstrable effect on sebaceous gland development or function. Furthermore, lowering DHT levels in adulthood had no effect on sebum production. If the gland is rich in the enzyme 5 alpha-reductase-2, it is proposed that the sebaceous gland is either exquisitely sensitive to DHT, requiring only small amounts for normal development and function, or that male levels of testosterone compensate for DHT and maintain normal sebaceous gland activity throughout life. It is also possible that 5 alpha-reductase-1 is the enzyme of the sebaceous gland and is unaffected in the inherited condition and by finasteride.
3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
Drug testing with alternative matrices I. Pharmacological effects and disposition of cocaine and codeine in plasma, sebum, and stratum corneum.
This study examined the disposition of cocaine, codeine, and metabolites in stratum corneum, sebum, and plasma collected from five African-American males after administrations of cocaine and codeine during a 10-week inpatient clinical study. The subjects were experienced, healthy drug users with a recent history of cocaine and heroin abuse. The first drug administration was delayed by three weeks to allow for the elimination of previously administered drugs from the body. Subjects received three 75 mg cocaine hydrochloride/70 kg doses by the subcutaneous route and three 60 mg codeine sulfate/70 kg doses by the oral route on alternating days beginning in week 4. The same dosing sequence was repeated in week 8 with doubled (x 2) doses. Pharmacological measures (heart rate, pupil diameter, subject "High" and "Liking") were obtained simultaneously with blood. Stratum corneum was collected by scraping regions of the back once each week. Sebum was collected periodically from the forehead by applying Sebutape patches for 1-2-h intervals. Plasma, stratum corneum, and sebum were analyzed for cocaine, codeine, and metabolites by gas chromatography-mass spectrometry. Peak plasma cocaine concentrations occurred within the 30 min following dosing and followed peak pharmacological effects. Peak plasma codeine concentrations occurred within 1-2 h of dosing and before peak pharmacological effects. Cocaine and codeine were the primary analytes in sebum and stratum corneum. After dosing, these drugs appeared in sebum within 1-2 h and were detected for 1-2 days. Peak-drug concentrations in stratum corneum occurred one day after completion of dosing; elimination of the drugs continued over the next 1-2 weeks after dosing. Overall, no definitive relationship was observed between drug concentrations in sebum and stratum corneum compared with dose. Interpretation of drug distribution and elimination in sebum and stratum corneum was complicated by possible contamination of specimens with drugs from sweat. The mechanism(s) for deposition of cocaine and codeine in sebum and stratum corneum appeared to be complex and could involve the transfer of drugs between different body fluids (i.e., sebum and sweat) and other matrices (i.e., skin and hair).
Administration, Oral↗
The effect of accumulated lipids on measurements of sebum secretion in human skin.
When sebum is collected from the skin surface in an absorbent material, the amounts obtained in successive collections at the same site decline steadily. In the present study, sebum was absorbed into bentonite clay applied to 2.5 sq cm areas on the foreheads of 3 subjects for 3-hr intervals during 24 hr. The amounts of sebum obtained, measured by thin-layer chromatography, declined for 12 hr and then remained constant for the remaining 12 hr. It was inferred that the final, sustainable rate represents the true rate at which sebum was being secreted by the sebaceous glands, and that the additional sebum collected at earlier intervals was obtained from an accumulation in the stratum corneum or in the follicular canals. For the 3 subjects, the accumulated sebum averaged 213 micrograms/sq cm, compared with a sustainable secretion rate of 25 micrograms/sq cm/hr. The large quantity of accumulated sebum, relative to the secretion rate, could obscure differences between subjects when sebum secretion rates are measured by short-term collections of sebum in absorbent materials.
Bentonite↗
[Stimulation for sebum excretion of PCDDs, PCDFs and coplanar PCBs on bathing ceramic sand bath].
We previously reported that high risk environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (PCBs) are excreted not only in feces but also in the sebum of the face and body in both normal subjects and Yusho patients. A combination of administration of rice bran fiber and cholestyramine increased fecal excretion of PCDFs and PCBs. In the present study, we stimulated excretion of these compounds in sebum using a ceramic sand bath, a kind of sand bath using small ceramic balls (3.5 mm diameter) instead of natural sand. Five normal volunteers participated in this experiment. Sebum eliminated from the body on bathing ceramic sand bath was collected and weighed and then concentrations of the compounds interest in the sebum were determined. We also examined the effects varying the bath conditions such as temperature of sand, length of bathing time and frequency of taking bath on the amounts of the compounds in the eliminated sebum. The results can be summarized as follows: 1. The average amount of sebum per one bath eliminated from the body during the ceramic sand bath was 0.252 g, and those of PCDDs, PCDFs and coplanar PCBs in it were 2.2, 2.0 and 2.2 pg of TEQ (2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent quantity). It was considered that the amounts of these compounds corresponded to between one quarter and third of those eliminated through the sebum in a day. On the other hand, 0.05 g of the sebum was collected from the face during the bath, included 0.39, 0.39 and 0.59 pg TEQ for PCDDs, PCDFs and coplanar PCBs, respectively. 2. As the number of bathing times a day increased, the amount of sebum per bath gradually decreased. However, we could not determine the influence of the conditions of the bath such as temperature and time.
Ammotherapy↗
The combined use of oral and topical lipophilic antioxidants increases their levels both in sebum and stratum corneum.
The concentration of Vitamin E (vit E) and ubiquinone (CoQ10), which together with squalene (SQ), play a key role against external oxidative insult, has been shown to decrease significantly during ageing. The aim of the present study is to inquire the effect of the combined use of topical bio-cosmetics containing natural active principles (including sebum-like lipid fractions, sebum and epidermal lipophilic and hydrophilic antioxidants), and oral antioxidant supplements on the antioxidant content of sebum and stratum corneum. We therefore treated the face and the back of 50 female volunteers aged 21-40, daily for two months, with a base cream containing 0.05% ubiquinone, 0.1% vit E, and 1% squalene. In addition 50 mg of CoQ10 + 50 mg of d-RRR-alpha-tocopheryl acetate + 50 microg of selenium were administered orally to half of the volunteers (Group A). Group B was represented by 25 volunteers who were treated only topically. Every 15 days during treatment the levels of CoQ10, vit E and SQ were verified in sebum, stratum corneum, and plasma. The daily topical application of the cream led to a significant increase, that peaked after 60 days, of the levels of CoQ10, d-RRR-alpha-tocopherol and SQ in the sebum (Group B), without significantly affecting the stratum corneum or plasma concentrations of the redox couple CoQ10H2/CoQ10 and vit E. The concomitant oral admistration of antioxidants produced in Group A a significant increase of the levels of CoQ10H2/CoQ10 and vit E both in plasma and stratum corneum after 15 and 30 days treatment respectively, compared to Group B. However the sebum levels of lipophilic antioxidants and SQ did not show a significant increase. After the treatments, the levels of CoQ10H2/CoQ10, vit E and SQ went back to basal levels within 6-8 days in sebum, 12-16 days in the stratum corneum, and 3-6 days in plasma. Therefore topical application of the antioxidants was able to increase their level in sebum, while the concomitant oral administration also affected the levels of vit E and CoQ10 in the stratum corneum.
Administration, Oral↗
An original procedure for quantitation of cutaneous resorption of sebum.
This paper describes an original in vivo device to investigate and quantify cutaneous resorption of sebum. Such a phenomenon was explored using a photometric determination of residual skin surface lipids at different times following initial deposits of known amounts of artificial sebum on demarcated areas. The technique was carried out on seven healthy subjects. The chosen area was the anterior aspect of the forearm, owing to the very low sebum production of this site, less than the sensitivity of the measuring instrument. The kinetics of absorption of applied sebum turned out to be hyperbolic-like and well correlated with experimental results (r = 0.992), allowing a mathematical determination of the initial velocity of penetration of sebum into the skin, reaching 20 micrograms/cm2.min for a standard program including a mean initial deposit of 116 micrograms/cm2. This kinetics actually does not fit with a true percutaneous absorption of lipids but is compatible with that of absorption into the stratum corneum. It conveys the faster absorption of the latter for sebum, a well-known but not so far quantified property of stratum corneum. The model here described is not at once transposable to skin areas with high sebum production since, quite obviously in such zones, the stratum corneum is permanently saturated with skin surface lipids. Therefore, the conclusions of this work cannot be correlated with the regreasing parameters studied so far on the forehead, but they provide interesting data about the evolution of sebum following its output onto the skin surface and therefore a better understanding of sebaceous physiology.
Absorption↗
Effect of oral 13-cis-retinoic acid at three dose levels on sustainable rates of sebum secretion and on acne.
Changes in sustainable rates of sebum secretion were followed in twenty patients with severe acne who were receiving oral treatment with 13-cis-retinoic acid in dosages of 0.1, 0.5, or 1.0 mg/kg/day. Sebum secretion was measured by absorption of skin surface lipid into bentonite clay and estimation of the amount of absorbed sebum by measurement of its wax ester component. Pretreatment rates of sebum secretion in the patients were greatly elevated in comparison with previously measured values in young adult subjects without acne. After 4 weeks of treatment, mean rates of sebum secretion on all three dose levels fell to or below the range for normal subjects. On-treatment rates of sebum secretion were significantly lower in patients on the highest dose compared to patients on the lowest dose. When the drug was discontinued, rates of sebum secretion recovered slowly. Clinical response was excellent in most of the subjects. The five subjects with least favorable response clinically all had better than average suppression of sebum production.
Acne Vulgaris↗
Regional and seasonal variations in facial sebum secretions: a proposal for the definition of combination skin type.
BACKGROUND/AIMS: Facial sebum secretions are known to change under various circumstances. Facial skin types have been categorized as oily, normal, dry, and combination types. However, these have been evaluated subjectively by individuals to date, and no objective accepted standard measurement method exists. The combination skin type is most common, but its definition is vaguer than the definitions of the other skin types. METHODS: We measured facial sebum secretions with Sebumeter. Sebum secretions were measured at five sites of the face seasonally for a year, in the same volunteers. Using the data obtained we developed a set of rules to define the combination skin type. RESULTS: Regional differences in sebum secretion were confirmed. Sebum secretions on forehead, nose, and chin were higher than on both cheeks. Summer was found to be the highest sebum-secreting season, and seasonal variations were found in the T- and U-zones. A mismatch of skin type in the T- and U-zones in more than two seasons appears to be close to subjective ratings of what is described as the 'combination' skin type. CONCLUSION: We showed that the face shows definitive regional and seasonal variations in sebum secretion. To define the combination skin type, seasonal variations in sebum secretion should be considered in addition to regional variations.
Face↗
[L-dopa, biperiden and sebum excretion in Parkinson disease].
Sebum secretion was measured on the forehead of 47 patients with Parkinson's disease before and after treatment with anticholinergic (biperiden), levodopa + AAID and bromocriptine, by the osmic acid technique. Another 100 patients under biperiden, levodopa + AAID or association of both, for at least one year, were also evaluated. The male parkinsonian "de novo" patients have shown greater sebum secretion than female patients. It was also concluded that biperiden failed to reduce sebum secretion rate. On the other hand, it was found that L-dopa + AAID reduces the sebum secretion (CL = casual level and SER = sebum excretion rate) on both male and female patients. Bromocriptine (10mg/day) was the second dopaminergic therapy employed in the present work. Similarly to L-dopa, this dopaminergic agonist was able to significantly reduce sebum secretion (both CL and SER) of male patients. There was a positive and significant correlation for the 50-59 years old male patients "de novo" between CL and tremor, hypokinesia, gait and posture or functional incapacity, before treatment. After a period of treatment correlation was no more found. In relation to parkinsonians under chronic treatment was found a positive and significant correlation between sebum secretion and hypokinesia. The level of sebum secretion on parkinsonian "de novo" patients before treatment was equal to parkinsonian patients under chronic treatment regardless the treatment, except for greater than or equal to 60 years old parkinsonians who have shown CL and SER higher than "de novo" parkinsonian patients with the same age but without treatment. The treatment with L-dopa + AAID significantly decreased both CL and SER of "de novo" parkinsonian patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
'Bad hair days', scalp sebum excretion and the menstrual cycle.
BACKGROUND: Many women complain that their hair is periodically unmanageable, popularly known as 'bad hair days' (BHDs). At an anecdotal level BHDs are more common around the time of menstruation and, in view of previous studies reporting menstrual variation in sebum excretion, the authors hypothesised that changes in scalp sebum levels during the menstrual cycle might contribute to perceive differences in hair quality. AIMS: To test whether there is a relationship between BHDs, the menstrual cycle and scalp sebum excretion. METHODS: Thirteen women were studied through three menstrual cycles. Sebum levels on the scalp and forehead were measured twice weekly using a Sebumeter and each subject kept a record of hair quality and hair washing practice. RESULTS: BHDs occurred throughout the menstrual cycle but were more common during menstruation. There was no discernible variation in sebum levels on the scalp or forehead during the menstrual cycle and there was no correlation between individual mean skin sebum levels and the frequency of BHDs. However, BHDs were more common in those women who washed their hair infrequently, although the association between the frequency of hair washing and BHDs just failed to reach statistical significance (p = 0.06). CONCLUSIONS: BHDs are more common during menstruation and in women who wash their hair infrequently. This may relate to a build-up of sebum on the hair but menstrual variations in the frequency of BHDs are unrelated to sebum levels.
Journal Article↗
Peroxisome proliferator-activated receptors increase human sebum production.
Sebum production is key in the pathophysiology of acne, an extremely common condition, which when severe, may require treatment with isotretinoin, a known teratogen. Apart from isotretinoin and hormonal therapy, no agents are available to reduce sebum. Increasing our understanding of the regulation of sebum production is a milestone in identifying alternative therapeutic targets. Studies in sebocytes and human sebaceous glands indicate that agonists of peroxisome proliferator-activated receptors (PPARs) alter sebaceous lipid production. The goal of this study is to verify the expression and activity of PPARs in human skin and SEB-1 sebocytes and to assess the effects of PPAR ligands on sebum production in patients. To investigate the contribution of each receptor subtype to sebum production, lipogenesis assays were performed in SEB-1 sebocytes that were treated with PPAR ligands and isotretinoin. Isotretinoin significantly decreased lipogenesis, while the PPARalpha agonist-GW7647, PPARdelta agonist-GW0742, PPARalpha/delta agonist-GW2433, PPARgamma agonist rosiglitazone, and the pan-agonist-GW4148, increased lipogenesis. Patients treated with thiazolidinediones or fibrates had significant increases in sebum production (37 and 77%, respectively) when compared to age-, disease-, and sex-matched controls. These data indicate that PPARs play a role in regulating sebum production and that selective modulation of their activity may represent a novel therapeutic strategy for the treatment of acne.
Adult↗
The effect of 2% niacinamide on facial sebum production.
BACKGROUND: The presence of sebum on the face is responsible for both facial shine and the formation of comedonal and inflammatory acne lesions. Sebum control is a goal of many OTC skin care products; however, most currently available products function by absorbing sebum from the face rather than modulating its production. OBJECTIVE: To demonstrate the effect of topical 2% niacinamide on sebum excretion rates and casual sebum production in Oriental and Caucasian populations. METHODS: Separate clinical trials were conducted in both Japan and the USA to evaluate the effect of topical 2% niacinamide in different ethnic groups. A total of 100 Japanese subjects were enrolled in a double-blind, placebo-controlled comparison between two independent balanced groups. Fifty subjects applied the 2% niacinamide moisturizer to the face for 4 weeks and 50 subjects used a placebo moisturizer for 4 weeks, with sebum excretion rate (SER) measurements taken at baseline, week 2, and week 4. In addition, 30 Caucasian subjects were enrolled in a randomized split-face study for 6 weeks with SER and casual sebum levels (CSL) measured at baseline, week 3, and week 6. RESULTS: The results of the Japanese study demonstrated that the SER of the two groups was not significantly different at baseline, but the 2% niacinamide treated group demonstrated significantly lowered SER after 2 and 4 weeks of application. The results were somewhat different in the Caucasian study. After 6 weeks of treatment, the CSL was significantly reduced, but the SER was not significantly reduced. CONCLUSIONS: Topical 2% niacinamide may be effective in lowering the SER in Japanese individuals and CSL in Caucasian individuals.
Administration, Topical↗
Suppression of sebum secretion with 13-cis-retinoic acid: effect on individual skin surface lipids and implications for their anatomic origin.
The contribution of the keratinizing epidermis to the human skin surface lipid film has been difficult to ascertain because, after its release from the epidermal cells, epidermally derived lipid inevitably becomes mixed with sebum. In the present study, the sustainable rates of production of the 5 neutral lipid classes found on the skin surface (triglycerides + free fatty acids, wax esters, cholesterol, cholesterol esters, and squalene) were measured on the foreheads of acne patients before, during, and following treatment with 13-cis-retinoic acid, a drug which suppresses sebum production profoundly. Since sebum production was high in the patients before treatment and was suppressed to a few percent of the pretreatment level in some of the patients during treatment, data covering a wide range of sebum production rates were obtained. By using squalene as a measure of sebum production and plotting the rates of production of the other lipid classes vs the rate of production of squalene, it was possible through extrapolation to estimate the residual (i.e., epidermal) rate of production of each lipid class at zero sebum production. The results indicated that epidermis releases triglycerides + free fatty acids and cholesterol to the skin surface. The cholesterol esters in freshly secreted skin surface lipids appeared to be almost entirely sebaceous in origin. Measurements were also made of the percentages of cholesterol esters in lipid collected from the scalp after several days' accumulation and were compared to corresponding values for the forehead lipid. The percentages of cholesterol esters in scalp lipid tended to rise when sebum production was suppressed by the drug, rather than remaining relatively constant as occurred in the freshly secreted forehead lipid. This result indicated that epidermis may contribute to skin surface cholesterol esters, probably through skin surface esterification of epidermal cholesterol.
Acne Vulgaris↗
Absence of minocycline in sebum?
The authors studied the bioavailability of minocycline in sebum and serum. Blood and sebum samples were collected weekly for 6 weeks from ten healthy volunteers taking 200 mg of minocycline every day for 4 weeks. Sebum was collected by direct extraction with petroleum ether from the forehead. After evaporation, sebum was weighed on a scale accurate to 10 micrograms. Determination of minocycline in serum and sebum was performed using a high performance liquid chromatography technique (HPLC), with a better detection limit at 352 nm than at 400 nm (20 ng/ml and 0.324 microgram/ml respectively). Our results contrast with other studies since no minocycline was detected in the sebum samples of treated subjects and microbiological assays of minocycline in sebum were also negative. In our opinion, the current hypothesis claiming that the effectiveness of minocycline in the treatment of acne vulgaris is based on sebaceous secretion should be reconsidered.
Acne Vulgaris↗