The histone deacetylase Sirt6 regulates glucose homeostasis via Hif1alpha.

SIRT6 is a member of a highly conserved family of NAD(+)-dependent deacetylases with various roles in metabolism, stress resistance, and life span. SIRT6-deficient mice develop normally but succumb to a lethal hypoglycemia early in life; however, the mechanism underlying this hypoglycemia remained unclear. Here, we demonstrate that SIRT6 functions as a histone H3K9 deacetylase to control the expression of multiple glycolytic genes. Specifically, SIRT6 appears to function as a corepressor of the transcription factor Hif1alpha, a critical regulator of nutrient stress responses. Consistent with this notion, SIRT6-deficient cells exhibit increased Hif1alpha activity and show increased glucose uptake with upregulation of glycolysis and diminished mitochondrial respiration. Our studies uncover a role for the chromatin factor SIRT6 as a master regulator of glucose homeostasis and may provide the basis for novel therapeutic approaches against metabolic diseases, such as diabetes and obesity.

Hailey-Hailey Disease is Associated with Diabetes: A Population-based Cohort Study, Clinical Cohort Study, and Pedigree Analysis.

Hailey-Hailey disease is a rare hereditary skin disease caused by mutations in the ATP2C1 gene encoding the secretory pathway Ca2+/Mn2+-ATPase 1 (SPCA1) protein. Extracutaneous manifestations of Hailey-Hailey disease are plausible but still largely unknown. The aim of this study was to explore the association between Hailey-Hailey disease and diabetes. A population-based cohort study of 347 individuals with Hailey-Hailey  disease was performed to assess the risks of type 1  diabetes and type 2 diabetes, using Swedish nationwide registries. Pedigrees from 2 Swedish families with Hailey-Hailey disease were also investigated: 1 with concurrent type 1 diabetes and HLA-DQ3, the other with type 2 diabetes. Lastly, a clinical cohort with 23 individuals with Hailey-Hailey disease and matched healthy controls was evaluated regarding diabetes. In the register data males with Hailey-Hailey disease had a 70% elevated risk of type 2 diabetes, whereas no  excess risk among women could be confirmed. In both pedigrees an unusually high inheritance for diabetes was observed. In the clinical cohort, individuals with Hailey-Hailey disease displayed a metabolic phenotype indicative of type 2 diabetes. Hailey-Hailey disease seems to act as a synergistic risk factor for diabetes. This study indicates, for the first time, an association between Hailey-Hailey disease and diabetes and represents human evidence that SPCA1 and the Golgi apparatus may be implicated in diabetes pathophysiology.

Mass Spectrometry Analysis of Shark Skin Proteins.

The mucus layer covering the skin of fish has several roles, including protection against pathogens and mechanical damage in which proteins play a key role. While proteins in the skin mucus layer of various common bony fish species have been explored, the proteins of shark skin mucus remain unexplored. In this pilot study, we examine the protein composition of the skin mucus in spiny dogfish sharks and chain catsharks through mass spectrometry (NanoLC-MS/MS). Overall, we identified 206 and 72 proteins in spiny dogfish (Squalus acanthias) and chain catsharks (Scyliorhinus retifer), respectively. Categorization showed that the proteins belonged to diverse biological processes and that most proteins were cellular albeit a significant minority were secreted, indicative of mucosal immune roles. The secreted proteins are reviewed in detail with emphasis on their immune potentials. Moreover, STRING protein-protein association network analysis showed that proteins of closely related shark species were more similar as compared to a more distantly related shark and a bony fish, although there were also significant overlaps. This study contributes to the growing field of molecular shark studies and provides a foundation for further research into the functional roles and potential human biomedical implications of shark skin mucus proteins.

Identification of Novel Glycans in the Mucus Layer of Shark and Skate Skin.

The mucus layer covering the skin of fish has several roles, including protection against pathogens and mechanical damage. While the mucus layers of various bony fish species have been investigated, the composition and glycan profiles of shark skin mucus remain relatively unexplored. In this pilot study, we aimed to explore the structure and composition of shark skin mucus through histological analysis and glycan profiling. Histological examination of skin samples from Atlantic spiny dogfish (Squalus acanthias) sharks and chain catsharks (Scyliorhinus retifer) revealed distinct mucin-producing cells and a mucus layer, indicating the presence of a functional mucus layer similar to bony fish mucus albeit thinner. Glycan profiling using liquid chromatography-electrospray ionization tandem mass spectrometry unveiled a diverse repertoire of mostly O-glycans in the mucus of the two sharks as well as little skate (Leucoraja erinacea). Elasmobranch glycans differ significantly from bony fish, especially in being more sulfated, and some bear resemblance to human glycans, such as gastric mucin O-glycans and H blood group-type glycans. This study contributes to the concept of shark skin having unique properties and provides a foundation for further research into the functional roles and potential biomedical implications of shark skin mucus glycans.

Human skin long noncoding RNA WAKMAR1 regulates wound healing by enhancing keratinocyte migration.

An increasing number of studies reveal the importance of long noncoding RNAs (lncRNAs) in gene expression control underlying many physiological and pathological processes. However, their role in skin wound healing remains poorly understood. Our study focused on a skin-specific lncRNA, LOC105372576, whose expression was increased during physiological wound healing. In human nonhealing wounds, however, its level was significantly lower compared with normal wounds under reepithelialization. We characterized LOC105372576 as a nuclear-localized, RNAPII-transcribed, and polyadenylated lncRNA. In keratinocytes, its expression was induced by TGF-ß signaling. Knockdown of LOC105372576 and activation of its endogenous transcription, respectively, reduced and increased the motility of keratinocytes and reepithelialization of human ex vivo skin wounds. Therefore, LOC105372576 was termed "wound and keratinocyte migration-associated lncRNA 1" (WAKMAR1). Further study revealed that WAKMAR1 regulated a network of protein-coding genes important for cell migration, most of which were under the control of transcription factor E2F1. Mechanistically, WAKMAR1 enhanced E2F1 expression by interfering with E2F1 promoter methylation through the sequestration of DNA methyltransferases. Collectively, we have identified a lncRNA important for keratinocyte migration, whose deficiency may be involved in the pathogenesis of chronic wounds.

Topical oxygen treatment relieves pain from hard-to-heal leg ulcers and improves healing: a case series.

Managing painful hard-to-heal leg ulcers is challenging with current therapeutic options. Wounds are prone to being hypoxic, and the subsequent pain is often related to hypoxia. Hyperbaric oxygen therapy (HBOT) is used to treat hard-to-heal leg wounds by delivering 100% oxygen at a pressure 2-3 times higher than atmospheric pressure. Unfortunately, most patients cannot be offered HBOT because it is costly and needs to be applied at specialised centres. Therefore, topical continuous oxygen therapy (TCOT) is a novel alternative for continuous local oxygen delivery to wounds and is associated with improved wound healing; however, its effect on painful wounds is unknown. This retrospective study was conducted on 20 patients, of whom 17 had painful hard-to-heal leg ulcers. In 13 patients (76%) with painful ulcers, TCOT was associated with rapid and substantial pain alleviation. Also, eight (40%) of the patients' wounds healed entirely with TCOT. This study suggests that TCOT may represent a novel pain management device for hard-to-heal wounds.

Darier Disease - A Multi-organ Condition?

Darier disease is a severe, rare autosomal dominant inherited skin condition caused by mutations in the ATP2A2 gene encoding sarcoendoplasmic reticulum Ca2+-ATPase isoform 2 in the endoplasmic reticulum. Since sarcoendoplasmic reticulum Ca2+-ATPase isoform 2 is expressed in most tissues, and intracellular calcium homeostasis is of fundamental importance, it is conceivable that other organs besides the skin may be involved in Darier disease. This review focusses on the association of Darier disease with other organ dysfunctions and diseases, emphasizing their common molecular pathology. In conclusion, Darier disease should be considered a systemic condition that requires systemic and disease mechanism targeted treatments.

Patients with Darier Disease Exhibit Cognitive Impairment while Patients with Hailey-Hailey Disease Do Not: An Experimental, Matched Case-control Study.

Darier disease and Hailey-Hailey disease are severe, monogenetic dermatological disorders with mutations affecting all cells, making them liable to exhibit extra-dermal symptoms. The aim of this study is to assess broad cognitive function in individuals with these diseases, using an experimental, case-control set-up comparing cognition in patients with that in healthy controls matched for age, sex and level of education. Cognition was assessed with the Cambridge Neuropsycho-logical Test Automated Battery. Patients with Darier disease (n = 29) performed significantly poorer on 5 of the 10 key cognitive measurements, while patients with Hailey-Hailey disease (n = 25) did not perform differently from controls. The main conclusion is that patients with Darier disease exhibit significant impairment in cognitive function, which reinforces the view that Darier disease should be regarded as a disorder affecting multiple organs, and should therefore be given medical consideration, and possibly treat-ment, as such.

Topical oxygen treatment relieves pain from hard-to-heal leg ulcers and improves healing: a case report.

Pain from hard-to-heal wounds is common and challenging to manage with current therapies. Most hard-to-heal wounds show some degree of hypoxia that impairs healing and contributes to pain. Regular oxygen therapy is given in hyperbaric oxygen chambers and is costly, time-consuming and cannot be offered to most patients. Moreover, hyperbaric oxygen therapy (HBOT) only increases tissue oxygen for a short time and is given only for a few hours per week. Topical oxygen therapy (TOT) was introduced as an alternative and in this report we focus on topical continuous oxygen therapy (TCOT), which has been shown to be associated with healing of hard-to-heal ulcers. We report on a patient with type 1 diabetes with a painful hard-to-heal lower leg ulcer that failed to heal with standard wound dressings and that had insufficient response to pharmacological analgesia. The patient was on three different analgesics before treating the wound with TCOT. As the wound was considered hypoxic, due to longstanding diabetes and probable microangiopathy, TCOT was commenced. Within one week of treatment starting, the patient spontaneously ceased all his analgesics as he was free of pain; and after 2.5 months, the ulcer healed. The patient reported no adverse effects. In addition to promoting healing, TCOT may also be considered for its potential analgesic effects in hard-to-heal wound management.

Endoplasmic reticulum stress in human chronic wound healing: Rescue by 4-phenylbutyrate.

During wound healing, cells have a high rate of protein synthesis and many proteins need to be folded post-translationally to function, which occurs in the endoplasmic reticulum (ER). In addition to proliferation, several cellular stress conditions, such as hypoxia, in the wound micro-environment lead to the accumulation of unfolded or misfolded proteins in the ER, causing ER stress. Eukaryotic cells have a signalling system to manage ER stress called the unfolded protein response (UPR). Mild UPR activation has a beneficial homeostatic effect; however, excessive UPR induces cell death. Herein, we examined venous leg ulcer biopsies versus normal acute incisional wounds in age-matched elderly subjects and found a large increase in ER stress markers. To study the underlying mechanism, we established several cell cultures from amputated legs from the elderly that showed inherent ER stress. While both keratinocytes and fibroblasts migration was impaired by ER stress, migration of elderly leg skin keratinocytes was markedly improved after treatment with the chemical chaperone and clinically established drug 4-phenylbutyrate (4-PBA) and demonstrated a reduction in ER stress markers. In a full-thickness human skin wound healing model, 4-PBA improved the reepithelialisation rate, which suggests it as a promising drug repurposing candidate for wound healing.

Hormone-induced mitochondrial fission is utilized by brown adipocytes as an amplification pathway for energy expenditure.

Adrenergic stimulation of brown adipocytes (BA) induces mitochondrial uncoupling, thereby increasing energy expenditure by shifting nutrient oxidation towards thermogenesis. Here we describe that mitochondrial dynamics is a physiological regulator of adrenergically-induced changes in energy expenditure. The sympathetic neurotransmitter Norepinephrine (NE) induced complete and rapid mitochondrial fragmentation in BA, characterized by Drp1 phosphorylation and Opa1 cleavage. Mechanistically, NE-mediated Drp1 phosphorylation was dependent on Protein Kinase-A (PKA) activity, whereas Opa1 cleavage required mitochondrial depolarization mediated by FFAs released as a result of lipolysis. This change in mitochondrial architecture was observed both in primary cultures and brown adipose tissue from cold-exposed mice. Mitochondrial uncoupling induced by NE in brown adipocytes was reduced by inhibition of mitochondrial fission through transient Drp1 DN overexpression. Furthermore, forced mitochondrial fragmentation in BA through Mfn2 knock down increased the capacity of exogenous FFAs to increase energy expenditure. These results suggest that, in addition to its ability to stimulate lipolysis, NE induces energy expenditure in BA by promoting mitochondrial fragmentation. Together these data reveal that adrenergically-induced changes to mitochondrial dynamics are required for BA thermogenic activation and for the control of energy expenditure.

Autophagy is a major regulator of beta cell insulin homeostasis.

AIMS/HYPOTHESIS: We studied the role of protein degradation pathways in the regulation of insulin production and secretion and hypothesised that autophagy regulates proinsulin degradation, thereby modulating beta cell function. METHODS: Proinsulin localisation in autophagosomes was demonstrated by confocal and electron microscopy. Autophagy was inhibited by knockdown of autophagy-related (ATG) proteins and using the H(+)-ATPase inhibitor bafilomycin-A1. Proinsulin and insulin content and secretion were assessed in static incubations by ELISA and RIA. RESULTS: Confocal and electron microscopy showed proinsulin localised in autophagosomes and lysosomes. Beta-Atg7 (-/-) mice had proinsulin-containing sequestosome 1 (p62 [also known as SQSTM1])(+) aggregates in beta cells, indicating proinsulin is regulated by autophagy in vivo. Short-term bafilomycin-A1 treatment and ATG5/7 knockdown increased steady-state proinsulin and hormone precursor chromogranin A content. ATG5/7 knockdown also increased glucose- and non-fuel-stimulated insulin secretion. Finally, mutated forms of proinsulin that are irreparably misfolded and trapped in the endoplasmic reticulum are more resistant to degradation by autophagy. CONCLUSIONS/INTERPRETATION: In the beta cell, transport-competent secretory peptide precursors, including proinsulin, are regulated by autophagy, whereas efficient clearance of transport-incompetent mutated forms of proinsulin by alternative degradative pathways may be necessary to avoid beta cell proteotoxicity. Reduction of autophagic degradation of proinsulin increases its residency in the secretory pathway, followed by enhanced secretion in response to stimuli.

Loss of Liver Kinase B1 (LKB1) in Beta Cells Enhances Glucose-stimulated Insulin Secretion Despite Profound Mitochondrial Defects.

The tumor suppressor liver kinase B1 (LKB1) is an important regulator of pancreatic ß cell biology. LKB1-dependent phosphorylation of distinct AMPK (adenosine monophosphate-activated protein kinase) family members determines proper ß cell polarity and restricts ß cell size, total ß cell mass, and glucose-stimulated insulin secretion (GSIS). However, the full spectrum of LKB1 effects and the mechanisms involved in the secretory phenotype remain incompletely understood. We report here that in the absence of LKB1 in ß cells, GSIS is dramatically and persistently improved. The enhancement is seen both in vivo and in vitro and cannot be explained by altered cell polarity, increased ß cell number, or increased insulin content. Increased secretion does require membrane depolarization and calcium influx but appears to rely mostly on a distal step in the secretion pathway. Surprisingly, enhanced GSIS is seen despite profound defects in mitochondrial structure and function in LKB1-deficient ß cells, expected to greatly diminish insulin secretion via the classic triggering pathway. Thus LKB1 is essential for mitochondrial homeostasis in ß cells and in parallel is a powerful negative regulator of insulin secretion. This study shows that ß cells can be manipulated to enhance GSIS to supra-normal levels even in the face of defective mitochondria and without deterioration over months.

Mitochondrial autophagy in cells with mtDNA mutations results from synergistic loss of transmembrane potential and mTORC1 inhibition.

Autophagy has emerged as a key cellular process for organellar quality control, yet this pathway apparently fails to eliminate mitochondria containing pathogenic mutations in mitochondrial DNA (mtDNA) in patients with a variety of human diseases. In order to explore how mtDNA-mediated mitochondrial dysfunction interacts with endogenous autophagic pathways, we examined autophagic status in a panel of human cytoplasmic hybrid (cybrid) cell lines carrying a variety of pathogenic mtDNA mutations. We found that both genetic- and chemically induced loss of mitochondrial transmembrane potential (Δψ(m)) caused recruitment of the pro-mitophagic factor Parkin to mitochondria. Strikingly, however, the loss of Δψ(m) alone was insufficient to prompt delivery of mitochondria to the autophagosome (mitophagy). We found that mitophagy could be induced following treatment with the mTORC1 inhibitor rapamycin in cybrids carrying either large-scale partial deletions of mtDNA or complete depletion of mtDNA. Further, we found that the level of endogenous Parkin is a crucial determinant of mitophagy. These results suggest a two-hit model, in which the synergistic induction of both (i) mitochondrial recruitment of Parkin following the loss of Δψ(m) and (ii) mTORC1-controlled general macroautophagy is required for mitophagy. It appears that mitophagy can be accomplished by the endogenous autophagic machinery, but requires the full engagement of both of these pathways.

Increased risk of cardiac arrhythmia in Hailey-Hailey disease patients.

BACKGROUND: Hailey-Hailey disease (HHD) is a rare autosomal dominant skin disease caused by mutations in the ATP2C1 gene, which encodes the secretory Ca2+/Mn2+-ATPase (SPCA1) pump in the Golgi apparatus. Although ATP2C1 is ubiquitously expressed in the body, possible extracutaneous manifestations of HHD are unknown. However, dysfunction of the Golgi apparatus not specifically coupled to ATP2C1 has been associated with heart disease. OBJECTIVE: To investigate the association between HHD and common heart disease in a Swedish, population-based cohort. METHODS: We conducted a population-based cohort study based on a linkage of Swedish nationwide registers to investigate the relationship between HHD and heart disease. We have been granted ethical approval from the Swedish Ethical Review Authority to conduct this study. The patients in this manuscript have given written informed consent to the publication of their case details. A total of 342 individuals with an ICD-10 diagnosis of HHD (Q82.8E) were identified and matched with randomly selected comparison individuals without HHD on a 1:100 ratio. Furthermore, in a separate clinical cohort we matched 23 HHD patients for age, sex, and BMI with control subjects to examine electrocardiogram parameters, electrolytes, and cardiovascular biomarkers. RESULTS: Compared with individuals without HHD, individuals with HHD had an excess risk of arrhythmia (RR 1.4, CI 1.0-2.0), whereas no increased risks of myocardial infarction (RR 1.1, CI 0.6-1.7) or heart failure (RR 1.0, CI 0.6-1.6; Table 1) were found. We found no difference in ECG parameters, cardiovascular biomarkers, and electrolytes in the clinical subset. CONCLUSION: This study reveals that HHD is associated with an increased risk of arrhythmia and represents the first data of any extracutaneous comorbidity in HHD. Thus, HHD may be a systemic disease. Our findings also shed light on the importance of the Golgi apparatus' Ca2+/Mn2+ homeostasis in common heart disease.