Leptin and the skin: a new frontier

Neuro-immuno-endocrinology of the skin: how environment regulates body homeostasis

The skin, including the hypodermis, is the largest organ of the body. The epidermis, the uppermost layer, is in direct contact with the environment and is exposed to environmental stressors, including solar radiation and biological, chemical and physical factors. These environmental factors trigger local responses within the skin that modulate homeostasis on both the cutaneous and systemic levels. Using mediators in common with brain pathways, immune and neuroendocrine systems within the skin regulate these responses to activate various signal transduction pathways and influence the systemic endocrine and immune systems in a context-dependent manner. This skin neuro-immuno-endocrine system is compartmentalized through the formation of epidermal, dermal, hypodermal and adnexal regulatory units. These units can act separately or in concert to preserve skin integrity, allow for adaptation to a changing environment and prevent the development of pathological processes. Through activation of peripheral nerve endings, the release of neurotransmitters, hormones, neuropeptides, and cytokines and/or chemokines into the circulation, or by priming circulating and resident immune cells, this system affects central coordinating centres and global homeostasis, thus adjusting the body's homeostasis and allostasis to optimally respond to the changing environment.

Effects of Fermented Artemisia annua L. and Salicornia herbacea L. on Inhibition of Obesity In Vitro and In Mice

Plant extracts including secondary metabolites have anti-inflammatory and anti-obesity activities. This study was conducted to investigate the anti-obesity properties of fermented Artemisia annua (AW) and Salicornia herbacea (GW) in vitro and in mice. The metabolite profiling of AW and GW extracts was performed using UHPLC-LTQ-Orbitrap-MS/MS, and gene expression was analyzed using real-time PCR for adipocyte difference factors. The anti-obesity effects in mice were measured using serum AST, ALT, glucose, TG, and cholesterol levels. Metabolites of the plant extracts after fermentation showed distinct differences with increasing anti-obesity active substances. The efficacy of inhibitory differentiation adipogenesis of 3T3-L1 adipocytes was better for GW than AW in a concentration-dependent manner. RT-PCR showed that the GW extract significantly reduced the expression of genes involved in adipocyte differentiation and fat accumulation (C/EBPα, PPARγ, and Fas). In C57BL/6 mice fed the HFD, the group supplemented with AW and GW showed reduced liver weight, NAS value, and fatty liver by suppressing liver fat accumulation. The GW group significantly reduced ALT, blood glucose, TG, total cholesterol, and LDL-cholesterol. This study displayed significant metabolite changes through biotransformation in vitro and the increasing anti-obesity effects of GW and AW in mice. GW may be applicable as functional additives for the prevention and treatment of obesity.

The Role of Adipokines in the Pathogenesis of Psoriasis

Psoriasis is a chronic and immune-mediated skin condition characterized by pro-inflammatory cytokines and keratinocyte hyperproliferation. Dendritic cells, T lymphocytes, and keratinocytes represent the main cell subtypes involved in the pathogenesis of psoriasis, while the interleukin-23 (IL-23)/IL-17 pathway enhances the disease progression. Human adipose tissue is an endocrine organ, which secretes multiple proteins, known as adipokines, such as adiponectin, leptin, visfatin, or resistin. Current evidence highlights the immunomodulatory roles of adipokines, which may contribute to the progression or suppression of psoriasis. A better understanding of the complexity of psoriasis pathophysiology linked with adipokines could result in developing novel diagnostic or therapeutic strategies. This review aims to present the pathogenesis of psoriasis and the roles of adipokines in this process.

LEP and LEPR are possibly a double-edged sword for wound healing

Wound healing is a complex and error-prone process. Wound healing in adults often leads to the formation of scars, a type of fibrotic tissue that lacks skin appendages. Hypertrophic scars and keloids can also form when the wound-healing process goes wrong. Leptin (Lep) and leptin receptors (LepRs) have recently been shown to affect multiple stages of wound healing. This effect, however, is paradoxical for scarless wound healing. On the one hand, Lep exerts pro-inflammatory and profibrotic effects; on the other hand, Lep can regulate hair follicle growth. This paper summarises the role of Lep and LepRs on cells in different stages of wound healing, briefly introduces the process of wound healing and Lep and LepRs, and examines the possibility of promoting scarless wound healing through spatiotemporal, systemic, and local regulation of Lep levels and the binding of Lep and LepRs.

Skin-associated adipocytes in skin barrier immunity: A mini-review

The skin contributes critically to health via its role as a barrier tissue against a multitude of external pathogens. The barrier function of the skin largely depends on the uppermost epidermal layer which is reinforced by skin barrier immunity. The integrity and effectiveness of skin barrier immunity strongly depends on the close interplay and communication between immune cells and the skin environment. Skin-associated adipocytes have been recognized to play a significant role in modulating skin immune responses and infection by secreting cytokines, adipokines, and antimicrobial peptides. This review summarizes the recent understanding of the interactions between skin-associated adipocytes and other skin cells in maintaining the integrity and effectiveness of skin barrier immunity.

GANT61 suppresses cell survival, invasion and epithelial-mesenchymal transition through inactivating AKT/mTOR and JAK/STAT3 pathways in anaplastic thyroid carcinoma

Glioma-associated oncogene (Gli) antagonist-61 (GANT61) not only suppresses the malignant behavior of several cancers but also presents synergistic effects with other anticancer agents on suppressing the progression of cancers, while relevant information is rare in anaplastic thyroid carcinoma (ATC). This study aimed to explore the therapeutic effect of GANT61 in ATC and its molecular mechanism. ATC cells (8505C and CAL-62) were treated with GANT61, followed by detection of cell proliferation, apoptosis, invasion and epithelial-mesenchymal transition (EMT) markers. Subsequently, RNA sequencing was performed to explore the potential downstream pathway. Following that, rescue experiments were conducted by SC79 (AKT activator) or colivelin (STAT3 activator) monotreatment or combined with GANT61 in ATC cells. GANT61 reduced Gli1 expression, suppressed proliferation at several time settings, promoted apoptosis, inhibited invasion and increased E-cadherin while decreased Vimentin and Snail expressions (EMT markers) in ATC cells. The subsequent RNA sequence identified 85 upregulated differentially expressed genes (DEGs) and 71 downregulated DEGs in GANT61-treated ATC cells, which were mainly enriched in PI3K/AKT, JAK/STAT, Hedgehog and mTOR pathways. Next, the inactivation of AKT/mTOR and JAK/STAT3 pathways by GANT61 treatment was verified by western blot. The following rescue experiments showed that SC79 or colivelin treatment promoted the malignant behaviors of ATC cells. More importantly, SC79 or colivelin treatment compensated the effect of GANT61 treatment on cell proliferation at several time settings and apoptosis, invasion, and part of that on EMT in ATC cells. GANT61 suppresses cell survival, invasion and EMT through inactivating AKT/mTOR or JAK/STAT3 pathways in ATC.

Neuroendocrine signaling in the skin with a special focus on the epidermal neuropeptides

The skin, which is comprised of the epidermis, dermis, and subcutaneous tissue, is the largest organ in the human body and it plays a crucial role in the regulation of the body's homeostasis. These functions are regulated by local neuroendocrine and immune systems with a plethora of signaling molecules produced by resident and immune cells. In addition, neurotransmitters, endocrine factors, neuropeptides, and cytokines released from nerve endings play a central role in the skin's responses to stress. These molecules act on the corresponding receptors in an intra-, juxta-, para-, or autocrine fashion. The epidermis as the outer most component of skin forms a barrier directly protecting against environmental stressors. This protection is assured by an intrinsic keratinocyte differentiation program, pigmentary system, and local nervous, immune, endocrine, and microbiome elements. These constituents communicate cross-functionally among themselves and with corresponding systems in the dermis and hypodermis to secure the basic epidermal functions to maintain local (skin) and global (systemic) homeostasis. The neurohormonal mediators and cytokines used in these communications regulate physiological skin functions separately or in concert. Disturbances in the functions in these systems lead to cutaneous pathology that includes inflammatory (i.e., psoriasis, allergic, or atopic dermatitis, etc.) and keratinocytic hyperproliferative disorders (i.e., seborrheic and solar keratoses), dysfunction of adnexal structure (i.e., hair follicles, eccrine, and sebaceous glands), hypersensitivity reactions, pigmentary disorders (vitiligo, melasma, and hypo- or hyperpigmentary responses), premature aging, and malignancies (melanoma and nonmelanoma skin cancers). These cellular, molecular, and neural components preserve skin integrity and protect against skin pathologies and can act as "messengers of the skin" to the central organs, all to preserve organismal survival.

Genome-wide detection of RNA editing events during the hair follicles cycle of Tianzhu white yak

BACKGROUND

The hair coat is available for the yak to live in the harsh environment of the plateau. Besides, improving the hair production of yak is necessary for its textile industry development. Hair grows from hair follicles (HFs). The HFs undergo periodic growth after birth and are regulated by the complex gene regulatory network. However, the molecular mechanism of HFs regeneration in the Tianzhu white yak remains unclear. RNA editing is a post-transcriptional mechanism that regulates gene expression and produces new transcripts. Hence, we investigated the influence of the A-to-I RNA editing events on the HFs cycle of the Tianzhu white yak.

RESULTS

We finally identified 54,707 adenosine-to-inosine (A-to-I) RNA editing sites (RESs) from RNA sequencing data of the HFs cycle in the Tianzhu white yak. Annotation results showed RESs caused missense amino acid changes in 7 known genes. And 202 A-to-I editing sites altered 23 target genes of 140 microRNAs. A total of 1,722 differential RESs were identified during the HFs cycle of Tianzhu white yak. GO and KEGG enrichment analysis revealed several signaling pathways and GO terms involved skin development, hair growth, and HFs cycle. Such as genes with differential RNA editing levels were significantly enriched in the peroxisome, metabolic pathways, Notch signaling pathway, and PPAR signaling pathway. Besides, the editing sites in HFs development-related genes FAS, APCDD1, WWOX, MPZL3, RUNX1, KANK2, DCN, DSC2, LEPR, HEPHL1, and PTK2B were suggested as the potential RESs involving HFs development.

CONCLUSION

This study investigated the global A-to-I RNA editing events during the HFs cycle of yak skin tissue and expanded the knowledge of A-to-I RNA editing on the HFs cycle. Furthermore, this study revealed that RNA editing-influenced genes may regulate the HFs cycle by participating in the HFs development-related pathways. The findings might provide new insight into the regulation of RNA editing in hair growth.

Study of leptin gene polymorphism and leptin serum level in alopecia areata patients

Leptin, produced by adipocytes, regulates metabolism, hunger, and immune response. The inflammatory role of leptin has been linked to autoimmune diseases. To assess leptin gene polymorphism and serum level in alopecia areata and their relation to metabolic syndrome (MS). This case-control study was conducted on 100 alopecia areata patients (50 with MS and 50 without MS) and 50 age- and gender-matched controls. Leptin gene polymorphism and serum level were assessed through the use of PCR and ELISA, respectively. GG genotype was the highest in AA with MS (54%), lower in AA without MS (42%), and the lowest in controls (20%). G allele was more expressed in cases, than in controls (P < .001). The serum leptin level was the highest in AA with MS, lower in AA without MS, and the lowest in controls (P value = 0.001). Leptin level was significantly higher in GG polymorphism than AG and AA. Leptin gene polymorphism (GG genotype) and serum level appear to play a significant role in AA. Absent difference regarding leptin gene polymorphism and MS might indicate a separate inflammatory role of leptin or the future risk of MS development in AA patients.

Association of TNF-α 308G/A and LEPR Gln223Arg Polymorphisms with the Risk of Type 2 Diabetes Mellitus

The objective of the present study was to identify the association of the TNF-α- 308G/A and leptin receptor (LEPR) Gln223Arg polymorphisms with the risk of development of type 2 diabetes mellitus (T2DM). Methods: A total of 160 volunteers were studied: 108 with T2DM and 52 participants as control, who served as the control group. Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) for the genomic region of TNF-α- 308G/A and LEPR Gln223Arg were carried out. Results: The frequency of LEPR Gln223Arg genotypes in T2DM and control groups showed significant differences in the distribution of genotypes (p < 0.05). The frequency also of TNF-α- 308G/A genotypes in T2DM and control subjects showed significant differences in the distribution of genotypes (p < 0.05). Conclusion: Our results indicate that there are significant differences in the distribution of genotypes and alleles between the individuals with T2DM and control subjects (p < 0.05).

Effect of extracorporeal shock waves on inflammation and angiogenesis of integumentary tissue in obese individuals: stimulating repair and regeneration

The technology of extracorporeal shock wave therapy (ESWT) has been studied around the world for its possible benefits in the treatment and rehabilitation of aesthetic disorders. To better elucidate its real physiological effect on the integumentary tissue, this study was proposed aimed at evaluating whether ESWT can act to stimulate the inflammatory process and angiogenesis in the dermis and epidermis of obese individuals. This is an immunohistological study that evaluated a set of samples of the integumentary tissue of women with grade II obesity with weight loss of 10% of the initial weight undergoing ESWT treatment; the collection of biological material was performed at the time of surgery of bariatric surgery. For immunohistochemical evaluation, the markers to assess the presence and distribution of inflammatory cells, anti-COX-2, CD3, CD20, CD163, and NK were used. For physiological stimulus pathways for blood vessel angiogenesis, markers CD 34, CD 105 and VEGF were used. Fourteen obese women were included in the study. Positivity was evidenced in the epidermal expression of markers of the inflammatory process COX-2, CD3, CD20, NK cells, CD68, and CD163 (p < 0.0001) in the intervention sample when compared to controls. There was a positive expression for the angiogenesis markers CD105 and VEGF (p < 0.0001) when comparing the intervention group with the control group. It was concluded that ESWT can stimulate a local inflammatory process, mediating and modulating important growth factors to act in the repair process and skin tissue regeneration, being considered a promising treatment for skin diseases related to weight gain or loss.

A cross-species analysis of systemic mediators of repair and complex tissue regeneration

Regeneration is an elegant and complex process informed by both local and long-range signals. Many current studies on regeneration are largely limited to investigations of local modulators within a canonical cohort of model organisms. Enhanced genetic tools increasingly enable precise temporal and spatial perturbations within these model regenerators, and these have primarily been applied to cells within the local injury site. Meanwhile, many aspects of broader spatial regulators of regeneration have not yet been examined with the same level of scrutiny. Recent studies have shed important insight into the significant effects of environmental cues and circulating factors on the regenerative process. These observations highlight that consideration of more systemic and possibly more broadly acting cues will also be critical to fully understand complex tissue regeneration. In this review, we explore the ways in which systemic cues and circulating factors affect the initiation of regeneration, the regenerative process, and its outcome. As this is a broad topic, we conceptually divide the factors based on their initial input as either external cues (for example, starvation and light/dark cycle) or internal cues (for example, hormones); however, all of these inputs ultimately lead to internal responses. We consider studies performed in a diverse set of organisms, including vertebrates and invertebrates. Through analysis of systemic mediators of regeneration, we argue that increased investigation of these "systemic factors" could reveal novel insights that may pave the way for a diverse set of therapeutic avenues.

The Important Role of Leptin in Modulating the Risk of Dermatological Diseases

It is an indisputable fact that obesity is associated with a series of health problems. One important hallmark of obesity is excessive accumulation of lipids in the adipocyte, especially triglyceride (TG). Currently, the adipocyte has been considered not only as a huge repository of excess energy in the form of fat but also as an important source of multiple hormones and cytokines called adipokines. In obesity, the adipocyte is dysfunctional with excessive production and secretion of pro-inflammatory adipokines, such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and leptin. On the other hand, accumulating evidence has shown that leptin plays a vital role in stimulating angiogenesis, controlling lipid metabolism, and modulating the production of pro-inflammatory cytokines. Furthermore, the various activities of leptin are related to the wide distribution of leptin receptors. Notably, it has been reported that enhanced leptin levels and dysfunction of the leptin signaling pathway can influence diverse skin diseases. Recently, several studies revealed the roles of leptin in wound healing, the hair cycle, and the pathogenic development of skin diseases, such as psoriasis, lupus erythematosus, and dermatological cancers. However, the exact mechanisms of leptin in modulating the dermatological diseases are still under investigation. Therefore, in the present review, we summarized the regulatory roles of leptin in the pathological progression of diverse diseases of skin and skin appendages. Furthermore, we also provided evidence to elucidate the complicated relationship between leptin and different dermatological diseases, such as systemic lupus erythematosus (SLE), psoriasis, hidradenitis suppurativa, and some skin tumors.

Leptin in skin disease modulation

In obesity, adipocytes are dysfunctional with excessive production and secretion of pro-inflammatory hormones and cytokines, ie, adipokines, such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and leptin. Accumulating evidence has shown that leptin possesses pleiotropic functions including stimulation of angiogenesis and production of pro-inflammatory cytokines. Furthermore, various leptin associated activities involve a wide distribution of leptin receptors. For example, increased serum leptin was associated with tissue receptor resistance in metabolic syndrome. Although increased serum leptin, receptor and signaling impairment are involved in wound healing, hair cycle and the pathogenesis of many skin diseases such as psoriasis and lupus erythematosus as well as skin cancer, its exact role remains unclear. In the present article, we discuss the biochemistry of leptin action and its potential role in the pathophysiology of diverse skin diseases.

The Role of Leptin in the Association between Obesity and Psoriasis

Adipose tissue secretes many adipokines which contribute to various metabolic processes, such as blood pressure, glucose homeostasis, inflammation and angiogenesis. The biology of adipose tissue in an obese individual is abnormally altered in a manner that increases the body’s vulnerability to immune diseases, such as psoriasis. Psoriasis is considered a chronic inflammatory skin disease which is closely associated with being overweight and obese. Additionally, secretion of leptin, a type of adipokine, increases dependently on adipose cell size and adipose accumulation. Likewise, high leptin levels also aggravate obesity via development of leptin resistance, suggesting that leptin and obesity are closely related. Leptin induction in psoriatic patients is mainly driven by the interleukin (IL)-23/helper T (Th) 17 axis pathway. Furthermore, leptin can have an effect on various types of immune cells such as T cells and dendritic cells. Here, we discuss the relationship between obesity and leptin expression as well as the linkage between effect of leptin on immune cells and psoriasis progression.

Comparison of Q223R leptin receptor polymorphism to the leptin gene expression in Greek young volunteers

<abstract><sec> <title>Objective</title> <p>The objective of the present study was to identify the leptin gene expression and the leptin receptor polymorphisms in blood samples and to correlate gene expression values with anthropometric characteristics.</p> </sec><sec> <title>Methods</title> <p>Blood from 140 Greek young volunteers was subjected to polymerase chain reaction–restricted fragment length polymorphism (PCR–RFLP), for the genomic region of Q223R polymorphism at codon 223 in the leptin receptor gene (<italic>LEPR</italic>) coding region. RNA extraction, cDNA synthesis and Quantitative Real-Time PCR was performed for assessing the expression of the leptin gene (<italic>LEP</italic>).</p> </sec><sec> <title>Results</title> <p>Leptin gene was identified in all tested specimens and the gene was expressed in 88.9% of all volunteers with BMI &lt; 25. In addition, it was observed that gene expression is affected by various external factors, such as Body Mass Index (BMI), eating behavior, gender and age. It was also shown that as for the Q223R polymorphism (A to G) allele G occurs with a frequency of 100% in men with BMI &gt; 30 and 75.9% in men and 88.9% in women with BMI 25–30. Volunteers with BMI 25–30 who were homozygous on the G allele were 50% and 77.8% in men and women respectively. All subjects with a BMI &gt; 30 were homozygous on the G allele at 100%.</p> </sec><sec> <title>Conclusions</title> <p>In this small-scale study, results have shown that the leptin gene expression correlates with BMI and that the allele G in Q223R polymorphism is linked to overweight individuals.</p> </sec></abstract>

Leptin System in Obese Dog Skin: A Pilot Study

Simple Summary

Obesity is a widespread phenomenon in pets and its growing trend is similar to the human one. It can be associated with skin pathologies but there is little information on this field in domestic animals. Since in obesity adipokine plasmatic levels changes, in this study leptin (LEP) system was evaluated in the skin of obese dogs to observe changes in peripheral tissue. LEP is a hormone produced mainly by the adipose tissue and its serum level may reflect body mass index and BCS. LEP is also expressed in the skin and it has a prominent role in the biology of this tissue promoting cell proliferation and regulating the wound healing process. Investigation performed in obese and normal-weight dogs evidenced LEP and leptin receptor (LEPR) immunostaining in several skin structures. As LEP expression regards, differences were non-significant, while the LEPR transcripts appeared 10 fold higher in obesedogs. No differences were observed in the composition of skin associated immune system. The obese group-increased LEPR expression suggests that the receptor modulates the system control. The LEP system changes in the skin under obesity conditions however, the exact role of LEP in obese dog skin needs further insights.

Abstract

Obesity predisposes to several health problems including skin diseases. However, information on the relationship between obesity and skin disorders in pets is very scarce. Leptin (LEP) is mainly produced by adipose tissue and has a prominent role in skin biology. This study evaluated the LEP system in the skin of obese dogs compared to normal-weight animals. The investigation was carried out on 10 obese (Obese group) and 10 normal-weight (Normal-weight group) dogs through Real-time PCR and immunohistochemistry. Cells of skin associated immune system were also evaluated. No differences were evidenced between the two groups as well as skin inflammation. LEP differences were no significant, while LEPR transcript appeared 10-fold higher in obesedogs than in normal-weight ones. Immunostaining for both molecules was observed in several skin structures such as the epidermis, hair follicles, and glands. No differences appeared in the skin associated immune system composition. This study is a preliminary report showing that LEP system changes in obese dog skin. The increased LEPR expression observed in the obese group suggests that the receptor plays a modulating role in the system control. However, the exact role of LEPin the skin under obesity conditions needs further elucidation.

Adipokines in the Skin and in Dermatological Diseases

Adipokines are the primary mediators of adipose tissue-induced and regulated systemic inflammatory diseases; however, recent findings revealed that serum levels of various adipokines correlate also with the onset and the severity of dermatological diseases. Importantly, further data confirmed that the skin serves not only as a target for adipokine signaling, but may serve as a source too. In this review, we aim to provide a complex overview on how adipokines may integrate into the (patho) physiological conditions of the skin by introducing the cell types, such as keratinocytes, fibroblasts, and sebocytes, which are known to produce adipokines as well as the signals that target them. Moreover, we discuss data from in vivo and in vitro murine and human studies as well as genetic data on how adipokines may contribute to various aspects of the homeostasis of the skin, e.g., melanogenesis, hair growth, or wound healing, just as to the pathogenesis of dermatological diseases such as psoriasis, atopic dermatitis, acne, rosacea, and melanoma.

The role of leptin in selected skin diseases

Leptin is an adipokine, adipocyte-derived compound, which acts both as a hormone and cytokine. It is mainly synthesized by adipocytes of white adipose tissue. Leptin possesses pleiotropic functions including, among others, stimulation of angiogenesis and production of proinflammatory cytokines. The various types of leptin activity are related to the wide distribution of leptin receptors. This adipokine acts by activating intracellular signaling cascades such as JAKs (Janus kinases), STATs (signal transducers and activators of transcription), and others.In a course of obesity, an increased serum level of leptin coexists with tissue receptor resistance. It has been reported that enhanced leptin levels, leptin receptor impairment, and dysfunction of leptin signaling can influence skin and hair. The previous studies revealed the role of leptin in wound healing, hair cycle, and pathogenesis of skin diseases like psoriasis, lupus erythematosus, and skin cancers. However, the exact mechanism of leptin's impact on the skin is still under investigation. Herein, we present the current knowledge concerning the role of leptin in psoriasis and selected skin diseases.

Transcriptomic analysis reveals dynamic molecular changes in skin induced by mechanical forces secondary to tissue expansion

Tissue expansion procedures (TE) utilize mechanical forces to induce skin growth and regeneration. While the impact of quick mechanical stimulation on molecular changes in cells has been studied extensively, there is a clear gap in knowledge about sequential biological processes activated during long-term stimulation of skin in vivo. Here, we present the first genome-wide study of transcriptional changes in skin during TE, starting from 1 h to 7 days of expansion. Our results indicate that mechanical forces from a tissue expander induce broad molecular changes in gene expression, and that these changes are time-dependent. We revealed hierarchical changes in skin cell biology, including activation of an immune response, a switch in cell metabolism and processes related to muscle contraction and cytoskeleton organization. In addition to known mechanoresponsive genes (TNC, MMPs), we have identified novel candidate genes (SFRP2, SPP1, CCR1, C2, MSR1, C4A, PLA2G2F, HBB), which might play crucial roles in stretched-induced skin growth. Understanding which biological processes are affected by mechanical forces in TE is important for the development of skin treatments to maximize the efficacy and minimize the risk of complications during expansion procedures.

Adipokines as Biomarkers of Atopic Dermatitis in Adults

Atopic dermatitis (AD) is characterized by chronic, relapsing, pruritic skin inflammation and does not have a well-understood pathogenesis. In this study, we addressed the contribution of adipokines to AD eczema based on the assessment of blood levels of adiponectin, resistin, leptin, lipocalin-2, and vaspin in adult non-obese patients suffering from chronic extrinsic childhood-onset AD. We investigated 49 AD patients with a median age of 37 years. The control group consisted of 30 age-matched healthy subjects. Adipokines were assessed in the serum by ELISA assays and the severity of AD with the SCORing Atopic Dermatitis (SCORAD) index. We found that adiponectin and resistin decreased and leptin appreciably increased in AD patients when compared to those in healthy subjects. Further, the levels of adiponectin and resistin were inversely related to the intensity of eczema. In conclusion, apart from the formerly investigated role of leptin in AD, this study points to adiponectin and resistin as the potential candidate adipokine biomarkers involved in shaping eczema intensity and severity, which may help predict disease exacerbations and enable the development of effective targeted therapeutic interventions.

Short-term metreleptin treatment of patients with anorexia nervosa: rapid on-set of beneficial cognitive, emotional, and behavioral effects

To examine the hypothesis that normalization of low circulating leptin levels in patients with anorexia nervosa ameliorates hyperactivity, three seriously ill females with hyperactivity were treated off-label with metreleptin (recombinant human leptin) for up to 14 days. Drive for activity, repetitive thoughts of food, inner restlessness, and weight phobia decreased in two patients. Surprisingly, depression improved rapidly in all patients. No serious adverse events occurred. Due to obvious limitations of uncontrolled case series, placebo-controlled clinical trials are mandatory to confirm the observed rapid onset of beneficial effects. Our findings suggest an important role of hypoleptinemia in the mental and behavioral phenotype of anorexia nervosa.

Obesity and ethnicity alter gene expression in skin

Obesity is accompanied by dysfunction of many organs, but effects on the skin have received little attention. We studied differences in epithelial thickness by histology and gene expression by Affymetrix gene arrays and PCR in the skin of 10 obese (BMI 35-50) and 10 normal weight (BMI 18.5-26.9) postmenopausal women paired by age and ethnicity. Epidermal thickness did not differ with obesity but the expression of genes encoding proteins associated with skin blood supply and wound healing were altered. In the obese, many gene expression pathways were broadly downregulated and subdermal fat showed pronounced inflammation. There were no changes in skin microbiota or metabolites. African American subjects differed from European Americans with a trend to increased epidermal thickening. In obese African Americans, compared to obese European Americans, we observed altered gene expression that may explain known differences in water content and stress response. African Americans showed markedly lower expression of the gene encoding the cystic fibrosis transmembrane regulator characteristic of the disease cystic fibrosis. The results from this preliminary study may explain the functional changes found in the skin of obese subjects and African Americans.

High doses of cobalt inhibited hair follicle development in Rex Rabbits

<p>An experiment was conducted to investigate the effect of cobalt supplementation on hair follicle development in rabbits. Rex rabbits (30-d-old, n=180) were divided randomly into five equal treatment groups: rabbits fed a basal diet (control, measured cobalt content of 0.27 mg/kg) or rabbits fed a basal diet with an additional 0.1, 0.4, 1.6 or 6.4 mg/kg cobalt (in the form of cobalt sulfate) supplementation (measured cobalt contents of 0.35, 0.60, 1.83 and 6.62 mg/kg, respectively). Treatment with 6.4 mg/kg cobalt significantly decreased hair follicle density (<em>P</em>&lt;0.05), while low levels of cobalt (0.1-1.6 mg/kg) had no effect on hair follicle density (<em>P</em>&gt;0.05). The addition of dietary cobalt at the highest level examined (6.4 mg/kg) significantly increased the gene expression of bone morphogenetic protein (BMP) 2 and BMP4 in skin tissue (<em>P</em>&lt;0.05), while the mRNA levels of versican, alkaline phosphatase, hepatocyte growth factor, and noggin remained unchanged (<em>P</em>&gt;0.05). Compared with their levels in the control group, dietary cobalt treatment significantly suppressed the protein levels of p-mechanistic target of rapamycin (mTOR) and p-ribosomal protein S6 protein kinase (<em>P</em>&lt;0.05) but did not alter the protein levels of p-AMP-activated protein kinase, Wnt10b or p-β-catenin (<em>P</em>&gt;0.05). In conclusion, cobalt at the highest concentration examined inhibited hair follicle development, which may have involved the mTOR-BMP signalling pathway.</p>

Endocrine Regulation of Epimorphic Regeneration

Studies aiming to uncover primary mechanisms of regeneration have predominantly focused on genetic pathways regulating specific stages in the regeneration process: wound healing, blastema formation, and pattern formation. However, studies across organisms show that environmental conditions and the physiological state of the animal can affect the rate or quality of regeneration, and endocrine signals are likely the mediators of these effects. Endocrine signals acting directly on receptors expressed in the tissue or via neuroendocrine pathways can affect regeneration by regulating the immune response to injury, allocation of energetic resources, or by enhancing or inhibiting proliferation and differentiation pathways involved in regeneration. This review discusses the cumulative knowledge in the literature about endocrine regulation of regeneration and its importance in future research to advance biomedical research.

Endocrine regulation of regeneration: Linking global signals to local processes

Regeneration in amphibians and reptiles has been explored since the early 18th century, giving us a working in vivo model to study epimorphic regeneration in vertebrates. Studies aiming to uncover primary mechanisms of regeneration have predominantly focused on genetic pathways regulating specific stages of the regeneration process: wound healing, blastema formation and growth, and pattern formation. However, studies across organisms show that environmental conditions and physiological state of the animal can affect the rate or quality of regeneration, and endocrine signals are likely the mediators of these effects. Endocrine signals working/acting directly on receptors expressed in the structure or via neuroendocrine pathways can affect regeneration by modulating immune response to injury, allocation of energetic resources, or by enhancing or inhibiting proliferation and differentiation pathways in regenerating tissue. This review discusses the cumulative knowledge known about endocrine regulation of regeneration and important future research directions of interest to both ecological and biomedical research.

New insights into different adipokines in linking the pathophysiology of obesity and psoriasis

Psoriasis is a chronic, systemic, hyper-proliferative immune-mediated inflammatory skin disease. The results of epidemiological investigations have shown that psoriasis affects around 2% of the general population worldwide, and the total number of psoriasis patients is more than 6 million in China. Apart from the skin manifestations, psoriasis has been verified to associate with several metabolic comorbidities, such as insulin resistance, diabetes and obesity. However, the underlying mechanism is still not elucidated. Adipocytes, considered as the active endocrine cells, are dysfunctional in obesity which displays increased synthesis and secretion of adipokines with other modified metabolic properties. Currently, growing evidence has pointed to the central role of adipokines in adipose tissue and the immune system, providing new insights into the effect of adipokines in linking the pathophysiology of obesity and psoriasis. In this review, we summarize the current understanding of the pathological role of adipokines and the potential mechanisms whereby different adipokines link obesity and psoriasis. Furthermore, we also provide evidence which identifies a potential therapeutic target aiming at adipokines for the management of these two diseases.

Effect of Hypoxia on Gene Expression in Cell Populations Involved in Wound Healing

Wound healing is a complex process regulated by multiple signals and consisting of several phases known as haemostasis, inflammation, proliferation, and remodelling. Keratinocytes, endothelial cells, macrophages, and fibroblasts are the major cell populations involved in wound healing process. Hypoxia plays a critical role in this process since cells sense and respond to hypoxic conditions by changing gene expression. This study assessed the in vitro expression of 77 genes involved in angiogenesis, metabolism, cell growth, proliferation and apoptosis in human keratinocytes (HaCaT), microvascular endothelial cells (HMEC-1), differentiated macrophages (THP-1), and dermal fibroblasts (HDF). Results indicated that the gene expression profiles induced by hypoxia were cell-type specific. In HMEC-1 and differentiated THP-1, most of the genes modulated by hypoxia encode proteins involved in angiogenesis or belonging to cytokines and growth factors. In HaCaT and HDF, hypoxia mainly affected the expression of genes encoding proteins involved in cell metabolism. This work can help to enlarge the current knowledge about the mechanisms through which a hypoxic environment influences wound healing processes at the molecular level.

The role of adipokines in systemic sclerosis: a missing link?

Systemic sclerosis is a multiorgan autoimmune disease characterized by vasculopathy and tissue fibrosis of unknown etiology. Recently, adipokines (cell signaling proteins secreted by adipose tissue) have attracted much attention as a cytokine family contributing to the various pathological processes of systemic sclerosis. Adipokines, such as leptin, adiponectin, resistin, adipsin, visfatin or chemerin are a heterogenic group of molecules. Adiponectin exhibits anti-fibrotic features and affects inflammatory reactions. Leptin promotes fibrosis and inflammation. Resistin was linked to vascular involvement in systemic sclerosis. Visfatin was associated with regression of skin lesions in late-stage systemic sclerosis. Chemerin appears as a marker of increased risk of impaired renal function and development of skin sclerosis in the early stage of systemic sclerosis. Vaspin was indicated to have a protective role in digital ulcers development. Novel adipokines-adipsin, apelin, omentin and CTRP-3-are emerging as molecules potentially involved in SSc pathogenesis. Serum adipokine levels may be used as predictive and diagnostic factors in systemic sclerosis. However, further investigations are required to establish firm correlations between distinct adipokines and systemic sclerosis.

Epithelial expression of the hormone leptin by bovine skin

Leptin (Lep) stimulates keratinocytes to proliferate, intervenes in the wound healing and participates to hair follicle morphogenesis and cycle. While it is secreted by skin structures including epidermis and hair follicles, intradermal adipose tissue also seems to have a role in Lep secretion and accordingly in the control of hair follicle growth in mice and humans. Lep was investigated in the skin of humans and laboratory animals but there are not data regarding bovine species. The aim of this work was to study the expression of Lep and its receptor (LepR) in the skin of bovine and, at the same time, to investigate the presence and extension of intradermal adipose tissue. A morphological evaluation of the skin was performed while the presence and localization of Lep and LepR were analyzed by RT-PCR and immunohistochemistry. A high and thick dermis without adipocytes was observed. Hair follicles and sebaceous and sweat glands were located in the proximal part of the skin while a thick layer of connective tissue, lacking adipose cells, separated these structures by subcutis. RT-PCR evidenced the transcripts for both molecules. By immunohistochemistry, Lep and LepR were observed in the epidermis and hair follicles. Based on the absence of intradermal adipose tissue and the presence of both Lep and LepR in the epidermis and in the hair follicle epithelium, it can be posited that in bovine skin Lep participates to the control of epidermis growth and hair follicle cycle through a paracrine and autocrine mechanisms.

Expression of Three Adipokines (Adiponectin, Leptin and Resistin) in Normal Canine Skin: a Pilot Study

Adipokines are biologically active cytokines that are mainly produced in adipose tissue. There is evidence, in man and mice, that some adipokines may be secreted in other tissues including the vascular endothelium, epithelia and sebaceous glands. Moreover, modified serum levels of adipokines have been detected in people with acne vulgaris or psoriasis; it is suspected that adipokines could contribute to local and systemic inflammatory conditions. We aimed to evaluate the expression of three adipokines (i.e. leptin, adiponectin and resistin) in normal canine skin. Formalin-fixed, paraffin wax-embedded punch biopsy samples were obtained from the sparsely-haired skin of the caudal ventral abdomen of a single clinically healthy dog with no history of skin disease. Immunohistochemistry was applied, using rabbit polyclonal primary antibodies specific for leptin, adiponectin and resistin. Adipokines were not expressed in normal canine dermis or hypodermis. In contrast, they were detected in the keratinocytes of all epidermal layers and hair follicle segments, sebocytes, apocrine gland cells and in the vascular endothelium. This is the first report on the expression of adipokines in normal canine skin, a first step in studying their role in the skin physiology and inflammatory skin diseases of dogs.

Leptin regulates the pro-inflammatory response in human epidermal keratinocytes

The role of leptin in cutaneous wound healing process has been suggested in genetically obese mouse studies. However, the molecular and cellular effects of leptin on human epidermal keratinocytes are still unclear. In this study, the whole-genome-scale microarray analysis was performed to elucidate the effect of leptin on epidermal keratinocyte functions. In the leptin-treated normal human keratinocytes (NHKs), we identified the 151 upregulated and 53 downregulated differentially expressed genes (DEGs). The gene ontology (GO) enrichment analysis with the leptin-induced DEGs suggests that leptin regulates NHKs to promote pro-inflammatory responses, extracellular matrix organization, and angiogenesis. Among the DEGs, the protein expression of IL-8, MMP-1, fibronectin, and S100A7, which play roles in which is important in the regulation of cutaneous inflammation, was confirmed in the leptin-treated NHKs. The upregulation of the leptin-induced proteins is mainly regulated by the STAT3 signaling pathway in NHKs. Among the downregulated DEGs, the protein expression of nucleosome assembly-associated centromere protein A (CENPA) and CENPM was confirmed in the leptin-treated NHKs. However, the expression of CENPA and CENPM was not coupled with those of other chromosome passenger complex like Aurora A kinase, INCENP, and survivin. In cell growth kinetics analysis, leptin had no significant effect on the cell growth curves of NHKs in the normal growth factor-enriched condition. Therefore, leptin-dependent downregulation of CENPA and CENPM in NHKs may not be directly associated with mitotic regulation during inflammation.

Trizentrische Analyse von Kofaktoren und Komorbidität des Pyoderma gangraenosum

EINLEITUNG

Das Pyoderma gangraenosum (PG) ist eine seltene, inflammatorische destruktiv-ulzerierende neutrophile Erkrankung mit weitgehend unklarer Pathophysiologie.

MATERIAL UND METHODIK

In dieser Studie wurden die potenziell relevanten Kofaktoren und Begleiterkrankungen von Patienten mit PG aus drei dermatologischen Wundzentren in Deutschland differenziert ausgewertet.

ERGEBNISSE

Von den insgesamt 121 analysierten Patienten waren Frauen (66,9 %) häufiger betroffen als Männer. Das Alter der Patienten war 18-96 Jahre (Mittelwert [MW]: 59,8); die Wunden hatten eine Größe von 1-600 cm² (MW: 65,6 cm²) und waren überwiegend sehr schmerzhaft (VAS 1-10, MW: 7). Die Unterschenkel waren am häufigsten (71,9 %) betroffen. Bei 12 (9,9 %) Patienten bestanden chronisch entzündliche Darmerkrankungen (5,8 % Colitis ulcerosa; 4,1 % Morbus Crohn), bei 14,1 % der Patienten wurde eine Begleiterkrankung aus dem rheumatischen Formenkreis beschrieben. Neoplasien bestanden bei 20,6 % der Patienten, von denen 6,6 % als hämatologische und 14,1 % als solide Neoplasien klassifiziert wurden. Aus dem Kreis des metabolischen Syndroms wurde bei 69,4 % Patienten eine Adipositas, bei 57,9 % eine arterielle Hypertonie und bei 33,9 % ein Diabetes mellitus diagnostiziert.

SCHLUSSFOLGERUNGEN

Diese Datenanalyse bestätigt Assoziationen des PG mit dem metabolischen Syndrom und mit Neoplasien, die zukünftig frühzeitig bei einer zielgerichteten Diagnostik der Patienten beachtet und behandelt werden sollten.

Tricenter analysis of cofactors and comorbidity in patients with pyoderma gangrenosum

INTRODUCTION

Pyoderma gangrenosum (PG) is a rare neutrophilic, ulcerative skin disease of largely unknown pathophysiology.

MATERIAL AND METHODS

In this study, potentially relevant cofactors and comorbidities in patients with PG from three dermatological wound care centers in Germany were evaluated.

RESULTS

Of the 121 patients assessed, women (66.9 %) were more frequently affected than men. Patient age ranged from 18 to 96 years (mean 59.8). Wound size varied from 1-600 cm² (mean 65.6 cm²), and the pain intensity was predominantly very high (VAS 1-10, mean 7). The lower legs were most commonly (71.9 %) affected. Overall, 12 (9.9 %) patients had inflammatory bowel disease (ulcerative colitis, 5.8 %; Crohn's disease, 4.1 %), 14.1 % exhibited rheumatic comorbidities. Neoplasms were found in 20.6 % of patients, with 6.6 % classified as hematological and 14.0 % as solid neoplasms. With respect to criteria for the metabolic syndrome, obesity was found in 69.4 %, arterial hypertension in 57.9 %, and diabetes mellitus in 33.9 % of patients.

CONCLUSIONS

The present data analysis confirms the association of PG with metabolic syndrome and neoplasms. In the future, these aspects should be included in the targeted diagnostic workup of patients with PG and subsequently treated in a timely fashion.

Leptin deficiency in mice counteracts imiquimod (IMQ)-induced psoriasis-like skin inflammation while leptin stimulation induces inflammation in human keratinocytes

Leptin is an adipocyte-derived cytokine secreted mostly by adipose tissue. Serum leptin levels are elevated in obese individuals and correlate positively with body mass index (BMI). Interestingly, serum leptin levels are also elevated in patients with psoriasis and correlate positively with disease severity. Psoriasis is associated with obesity; patients with psoriasis have a higher incidence of obesity, and obese individuals have a higher risk of developing psoriasis. Additionally, obese patients with psoriasis experience a more severe degree of psoriasis. In this study, we hypothesised that leptin may link psoriasis and obesity and plays an aggravating role in psoriasis. To investigate leptin's role in psoriasis, we applied the widely accepted imiquimod (IMQ)-induced psoriasis-like skin inflammation mouse model on leptin-deficient (ob/ob) mice and evaluated psoriasis severity. Moreover, we stimulated human keratinocytes with leptin and investigated the effect on proliferation and expression of pro-inflammatory proteins. In ob/ob mice, clinical signs of erythema, infiltration and scales in dorsal skin and inflammation in ear skin, as measured by ear thickness, were attenuated and compared with wt mice. Moreover, IL-17A and IL-22 mRNA expression levels, as well as increased epidermal thickness, were significantly less induced. In vitro, the effect of leptin stimulation on human keratinocytes demonstrated increased proliferation and induced secretion of several pro-inflammatory proteins; two hallmarks of psoriasis. In conclusion, leptin deficiency attenuated IMQ-induced psoriasis-like skin inflammation in a mouse model, and leptin stimulation induced a pro-inflammatory phenotype in human keratinocytes, thus, supporting an aggravating role of leptin in psoriasis.

Body mass index and risk of non-melanoma skin cancer: cumulative evidence from prospective studies

Prospective epidemiologic studies that investigated the association between body mass index (BMI) and non-melanoma skin cancer (NMSC) yielded inconsistent findings. A dose-response meta-analysis was conducted to quantitatively summarize the evidence. PubMed and Embase databases were searched for relevant studies. Study-specific relative risk (RR) and 95% confidence interval (CI) for an increase in BMI of 5 kg/m² was computed with the generalized least squares trend estimation, and these risk estimates were combined with the random-effects model. Nine publications were included in the final analyses, consisting of 18 independent cohorts with 22 risk estimates (971,795 participants and 50,561 NMSC cases). Results of the dose-response analyses showed a nonlinear inverse relationship between BMI and NMSC (RR = 0.88, 95% CI: 0.85–0.91, I² = 71.2%, P-nonlinearity <0.001), which persisted when limiting to the studies with adjustment for important potential confounders including sun exposure and sensitivity factors. The risk estimates were very similar for squamous cell carcinoma and basal cell carcinoma. Sex appeared a source of heterogeneity (P-difference = 0.06), with a weaker, but still significant inverse association in men than in women. This dose-response meta-analysis suggests a nonlinear inverse association between BMI and NMSC.

The triad psoriasis-obesity-adipokine profile

Psoriasis is a chronic inflammatory skin disease, often associated with overweight/obesity. The adipose tissue is a complex organ that secretes several adipokines, involved in the regulation of some metabolic processes, such as lipid metabolism, glucose homeostasis, angiogenesis, blood pressure and inflammation. In obesity, the distribution and function of adipose tissue, and the adipokine profile are altered. The unbalanced production of pro- and anti-inflammatory adipokines in obesity, contributes to the development of a chronic low-grade inflammation state, which seems to favour worsening of psoriasis lesion and a poorer response to treatment. In this review, we will debate published data concerning the current knowledge about the triad psoriasis-obesity-adipokine profile.

On the role of skin in the regulation of local and systemic steroidogenic activities

The mammalian skin is a heterogeneous organ/tissue covering our body, showing regional variations and endowed with neuroendocrine activities. The latter is represented by its ability to produce and respond to neurotransmitters, neuropeptides, hormones and neurohormones, of which expression and phenotypic activities can be modified by ultraviolet radiation, chemical and physical factors, as well as by cytokines. The neuroendocrine contribution to the responses of skin to stress is served, in part, by local synthesis of all elements of the hypothalamo-pituitary-adrenal axis. Skin with subcutis can also be classified as a steroidogenic tissue because it expresses the enzyme, CYP11A1, which initiates steroid synthesis by converting cholesterol to pregnenolone, as in other steroidogenic tissues. Pregnenolone, or steroidal precursors from the circulation, are further transformed in the skin to corticosteroids or sex hormones. Furthermore, in the skin CYP11A1 acts on 7-dehydrocholesterol with production of 7-dehydropregnolone, which can be further metabolized to other Δ7steroids, which after exposure to UVB undergo photochemical transformation to vitamin D like compounds with a short side chain. Vitamin D and lumisterol, produced in the skin after exposure to UVB, are also metabolized by CYP11A1 to several hydroxyderivatives. Vitamin D hydroxyderivatives generated by action of CYP11A1 are biologically active and are subject to further hydroxylations by CYP27B1, CYP27A1 and CP24A. Establishment of which intermediates are produced in the epidermis in vivo and whether they circulate on the systemic level represent a future research challenge. In summary, skin is a neuroendocrine organ endowed with steroid/secosteroidogenic activities.

Leptin controls hair follicle cycling

Leptin is a cytokine well known for its ability to control body weight and energy metabolism. Several lines of evidence have recently revealed that leptin also plays an important role in wound healing and immune modulation in skin. Sumikawa et al. Exp Dermatol 2014 evaluated the effect of leptin on hair follicle cycling using mutant and wild-type mice. They report that leptin is produced in dermal papilla cells in hair follicles and that leptin receptor-deficient db/db mice show an abnormality in hair follicle cycling. Moreover, leptin injection induced the transition into the growth stage of the hair cycle (anagen). On this basis, it now deserves exploration whether leptin-mediated signalling is a key stimulus for anagen induction and whether this may be targeted to manage human hair disorders with defect in the control of hair follicle cycling.

Leptin promotes a proinflammatory lipid profile and induces inflammatory pathways in human SZ95 sebocytes

BACKGROUND

Leptin, the adipocyte-secreted hormone that regulates weight, is known to link lipid metabolism with inflammation in various cell types. However, its role in human sebocytes has not yet been investigated.

OBJECTIVES

The purpose of this study was to investigate the effects of leptin in human sebaceous gland biology.

METHODS

Expression of the long form of the leptin receptor (Ob-Rb) was detected by real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and immunochemistry. Lipid analysis was by high-performance thin-layer chromatography, gas chromatography-mass spectrometry and time-of-flight mass spectrometer mass detection. Lipid bodies were visualized by BODIPY staining using fluorescent microscopy and measured by flow cytometry. Interleukin (IL)-6 and IL-8 mRNA levels were assessed by real-time qRT-PCR and their release was evaluated by enzyme-linked immunosorbent assay. Cyclooxygenase (COX)-2 and 5-lipooxygenase (LOX) protein expression and phosphorylation of p65 and signal transducer and activator of transcription (STAT)-3 were determined by Western blot analysis.

RESULTS

Expression of Ob-Rb was detected in human sebaceous glands and in cultured human SZ95 sebocytes. The treatment of SZ95 sebocytes with leptin led to enlarged intracellular lipid bodies, increased ratios of unsaturated/saturated fatty acids and decreased vitamin E levels. Further supporting a proinflammatory role, leptin induced COX-2 and 5-LOX expression in SZ95 sebocytes and augmented the production of IL-6 and IL-8 cytokines. On leptin treatment, the STAT-3 and nuclear factor-κB pathways were activated, indicating that these known leptin signalling pathways are active in human sebocytes.

CONCLUSIONS

Our findings suggest that leptin signalling may be involved in the proinflammatory regulation of sebaceous lipid metabolism and the induction of inflammatory enzymes and cytokines.

Leptin receptor is expressed by epidermis and skin appendages in dog

Leptin is a polypeptide secreted by adipocytes which binds to a specific receptor (Ob-R) that is expressed in various tissues. The wide distribution of the Ob-R suggests that leptin might exert diverse biological functions, not only by regulating energy metabolism and appetite, but also by acting as a mitogen in many cell types, including keratinocytes. In this study, the presence and localization of Ob-R was investigated in the skin of the dog using RT-PCR and immunohistochemical techniques. RT-PCR revealed the presence of Ob-R m-RNA in the skin specimens collected from the dorsal region of two smooth coat breed dogs. Through immunohistochemistry performed on the skin of five dogs, the expression of the receptor was observed in the basal layer of the epidermis, in the hair follicles as well as in the apocrine sweat and sebaceous glands. No staining for Ob-R was detected in the suprabasal epidermis layers. Strong positive signals were observed in many cells of the outer root sheath of hair follicles in growing and in regressive phases. The identification of Ob-R in the above targets suggests that leptin may play a role in the regulation of cyclic renewal of the epidermis and skin appendages in dog. This study represents an important contribution to understand the complex mechanisms that are involved in the skin biology in this species.

Hair cycle control by leptin as a new anagen inducer

Our purpose is to clarify the physiological role of leptin in hair cycle as leptin reportedly causes activation of Stat3, which is indispensable for hair cycling. While hair follicles in dorsal skin of 5-week-old C57/BL6 mice had progressed to late anagen phase, those in dorsal skin of 5-week-old leptin receptor deficient db/db mice remained in the first telogen and later entered the anagen at postnatal day 40, indicating that deficiency in leptin receptor signalling delayed the second hair cycle progression. Next, we shaved dorsal hairs on wild-type mice at postnatal 7 weeks and injected skin with mouse leptin or a mock. After 20 days, although mock injection showed no effect, hair growth occurred around leptin injection area. Human leptin fragment (aa22-56) had similar effects. Although the hair cycle of ob/ob mice was similar to that of wild-type mice, injection of mouse leptin on ob/ob mice at postnatal 7 weeks induced anagen transition. Immunohistochemically, leptin is expressed in hair follicles from catagen to early anagen in wild-type mice, suggesting that leptin is an anagen inducer in vivo. Phosphorylation of Erk, Jak2 and Stat3 in human keratinocytes was stimulated by leptin and leptin fragment. In addition, RT-PCR and ELISA showed that the production of leptin by human dermal papilla cells increased under hypoxic condition, suggesting that hypoxia in catagen/telogen phase promotes leptin production, preparing for entry into the next anagen. In conclusion, leptin, a well-known adipokine, acts as an anagen inducer and represents a new player in hair biology.

Cutaneous manifestations in children with diabetes mellitus and obesity

Obesity and diabetes are chronic diseases that affect people all over the world, and their incidence is increasing in both children and adults. Clinically, they affect a number of organs, including the skin. The cutaneous manifestations caused or aggravated by obesity and diabetes are varied and usually bear some relation to the time that has elapsed since the onset of the disease. They include soft fibromas, acanthosis nigricans, striae, xerosis, keratosis pilaris, plantar hyperkeratosis, fungal and bacterial skin infections, granuloma annulare, necrobiosis lipoidica, psoriasis, and atopic dermatitis. In this review article we present the skin changes found in children with diabetes mellitus and obesity and related syndromes and highlight the importance of the skin as a tool for establishing clinical suspicion and early diagnosis of systemic disease.

Assessment of Leptin Gene Polymorphism rs2060713 in Psoriasis Vulgaris

Psoriasis is a lifelong disorder characterized by approximately 8-fold reduction of the duration of normal skin keratinocyte cell cycle and 2-fold increase of the number of dividing cells. Multiple genes, several environmental factors, and immune system alterations are involved in the pathogenesis of psoriasis. Hyperleptinemia is associated with psoriasis and leptin acts as an angiogenic factor. Angiogenetic processes precede the epidermal hyperplasia in psoriasis, indicating possible involvement of leptin in the pathogenesis of psoriasis. Leptin gene polymorphisms and their association with psoriasis have been given very little attention. We present a study of the rs2060713C/T genetic polymorphism in the pathogenesis of psoriasis vulgaris in 263 vulgaris patients and 252 unrelated matched healthy controls. No statistically significant differences were observed between patients and controls. A statistically nonsignificant trend was observed in males with the early onset type of psoriasis (11.1% C/T in patients versus 5.6% in controls) and in females with the late onset type of the disease (12.8% C/T in patients versus 3.3% in controls). Still, there is no hard evidence on correlation of psoriasis vulgaris with this polymorphism. Possible association with specific forms of the disease and either gender needs further investigation in larger studies.