Effect of 4-phenylbutyrate and valproate on dominant mutations of WFS1 gene in Wolfram syndrome

Chronic Stress Alters Hippocampal Renin-Angiotensin-Aldosterone System Component Expression in an Aged Rat Model of Wolfram Syndrome

Biallelic mutations in the gene encoding WFS1 underlie the development of Wolfram syndrome (WS), a rare neurodegenerative disorder with no available cure. We have previously shown that Wfs1 deficiency can impair the functioning of the renin-angiotensin-aldosterone system (RAAS). The expression of two key receptors, angiotensin II receptor type 2 (Agtr2) and bradykinin receptor B1 (Bdkrb1), was downregulated both in vitro and in vivo across multiple organs in a rat model of WS. Here, we show that the expression of key RAAS components is also dysregulated in neural tissue from aged WS rats and that these alterations are not normalized by pharmacological treatments (liraglutide (LIR), 7,8-dihydroxyflavone (7,8-DHF) or their combination). We found that the expression of angiotensin II receptor type 1a (Agtr1a), angiotensin II receptor type 1b (Agtr1b), Agtr2 and Bdkrb1 was significantly downregulated in the hippocampus of WS animals that experienced chronic experimental stress. Treatment-naïve WS rats displayed different gene expression patterns, underscoring the effect of prolonged experiment-induced stress. Altogether, we posit that Wfs1 deficiency disturbs RAAS functioning under chronic stressful conditions, thereby exacerbating neurodegeneration in WS.

Wolfram Syndrome 1: A Pediatrician's and Pediatric Endocrinologist's Perspective

Wolfram syndrome 1 (WS1) is a rare autosomal recessive neurodegenerative disease caused by mutations in WFS1 and WFS2 genes that produce wolframin, a protein involved in endoplasmic reticulum calcium homeostasis and cellular apoptosis. Its main clinical features are diabetes insipidus (DI), early-onset non-autoimmune insulin-dependent diabetes mellitus (DM), gradual loss of vision due to optic atrophy (OA) and deafness (D), hence the acronym DIDMOAD. Several other features from different systems have been reported such as urinary tract, neurological, and psychiatric abnormalities. In addition, endocrine disorders that can appear during childhood and adolescence include primary gonadal atrophy and hypergonadotropic hypogonadism in males and menstrual cycle abnormalities in females. Further, anterior pituitary dysfunction with deficient GH and/or ACTH production have been described. Despite the lack of specific treatment for the disease and its poor life expectancy, early diagnosis and supportive care is important for timely identifying and adequately managing its progressive symptoms. The current narrative review focuses on the pathophysiology and the clinical features of the disease, with a special emphasis on its endocrine abnormalities that appear during childhood and adolescence. Further, therapeutic interventions that have been proven to be effective in the management of WS1 endocrine complications are discussed.

Endoplasmic reticulum stress inhibition ameliorated WFS1 expression alterations and reduced pancreatic islets' insulin secretion induced by high-fat diet in rats

Endoplasmic reticulum (ER) stress is involved in the development of glucose homeostasis impairment. When ER stress occurs, the unfolded protein response (UPR) is activated to cope with it. One of the UPR components is WFS1 (Wolfram syndrome 1), which plays important roles in ER homeostasis and pancreatic islets glucose-stimulated insulin secretion (GSIS). Accordingly and considering that feeding high-fat food has a major contribution in metabolic disorders, this study aimed to investigate the possible involvement of pancreatic ER stress in glucose metabolism impairment induced by feeding high-fat diet (HFD) in male rats. After weaning, the rats were divided into six groups, and fed on normal diet and HFD for 20 weeks, then 4-phenyl butyric acid (4-PBA, an ER stress inhibitor) was administered. Subsequently, in all groups, after performing glucose tolerance test, the animals were dissected and their pancreases were removed to extract ER, islets isolation and assessment of GSIS. Moreover, the pancreatic ER stress [binding of immunoglobulin protein (BIP) and enhancer-binding protein homologous protein (CHOP)] and oxidative stress [malondialdehyde (MDA), glutathione (GSH) and catalase] biomarkers as well as WFS1 expression level were evaluated. HFD decreased pancreatic WFS1 protein and GSH levels, and enhanced pancreatic catalase activity, MDA content, BIP and CHOP protein and mRNA levels as well as Wfs1 mRNA amount. Accordingly, it increased BIP, CHOP and WFS1 protein levels in the extracted ER of pancreas. In addition, the HFD caused glucose intolerance, and decreased the islets' GSIS and insulin content. However, 4-PBA administration restored the alterations. It seems that, HFD consumption through inducing pancreatic ER stress, altered WFS1 expression levels, reduced the islets' GSIS and insulin content and finally impaired glucose homeostasis.

Disruption of the Ubiquitin-Proteasome System and Elevated Endoplasmic Reticulum Stress in Epilepsy

The epilepsies are a broad group of conditions characterized by repeated seizures, and together are one of the most common neurological disorders. Additionally, epilepsy is comorbid with many neurological disorders, including lysosomal storage diseases, syndromic intellectual disability, and autism spectrum disorder. Despite the prevalence, treatments are still unsatisfactory: approximately 30% of epileptic patients do not adequately respond to existing therapeutics, which primarily target ion channels. Therefore, new therapeutic approaches are needed. Disturbed proteostasis is an emerging mechanism in epilepsy, with profound effects on neuronal health and function. Proteostasis, the dynamic balance of protein synthesis and degradation, can be directly disrupted by epilepsy-associated mutations in various components of the ubiquitin-proteasome system (UPS), or impairments can be secondary to seizure activity or misfolded proteins. Endoplasmic reticulum (ER) stress can arise from failed proteostasis and result in neuronal death. In light of this, several treatment modalities that modify components of proteostasis have shown promise in the management of neurological disorders. These include chemical chaperones to assist proper folding of proteins, inhibitors of overly active protein degradation, and enhancers of endogenous proteolytic pathways, such as the UPS. This review summarizes recent work on the pathomechanisms of abnormal protein folding and degradation in epilepsy, as well as treatment developments targeting this area.

Metabolic Treatment of Wolfram Syndrome

Wolfram Syndrome (WS) is a very rare genetic disorder characterized by several symptoms that occur from childhood to adulthood. Usually, the first clinical sign is non-autoimmune diabetes even if other clinical features (optic subatrophy, neurosensorial deafness, diabetes insipidus) may be present in an early state and may be diagnosed after diabetes’ onset. Prognosis is poor, and the death occurs at the median age of 39 years as a consequence of progressive respiratory impairment, secondary to brain atrophy and neurological failure. The aim of this paper is the description of the metabolic treatment of the WS. We reported the experience of long treatment in patients with this syndrome diagnosed in pediatric age and followed also in adult age. It is known that there is a correlation between metabolic control of diabetes, the onset of other associated symptoms, and the progression of the neurodegenerative alterations. Therefore, a multidisciplinary approach is necessary in order to prevent, treat and carefully monitor all the comorbidities that may occur. An extensive understanding of WS from pathophysiology to novel possible therapy is fundamental and further studies are needed to better manage this devastating disease and to guarantee to patients a better quality of life and a longer life expectancy.

Wolfram Syndrome Type 2: A Systematic Review of a Not Easily Identifiable Clinical Spectrum

Background: Wolfram syndrome (WS) is a rare autosomal recessive disorder that is characterized by the presence of diabetes mellitus, optic atrophy and hearing loss, all of which are crucial elements for the diagnosis. WS is variably associated with diabetes insipidus, neurological disorders, urinary tract anomalies, endocrine dysfunctions and many other systemic manifestations. Since Wolfram and Wagener first described WS in 1938, new phenotypic/genotypic variants of the syndrome have been observed and the clinical picture has been significantly enriched. To date, two main subtypes of WS that associated with two different mutations are known: WS type 1 (WS1), caused by the mutation of the wolframine gene (WS1; 606201), and WS type 2 (WS2), caused by the mutation of the CISD2 gene (WS2; 604928). Methods: A systematic review of the literature was describe the phenotypic characteristics of WS2 in order to highlight the key elements that differentiate it from the classic form. Conclusion: WS2 is the rarest and most recently identified subtype of WS; its clinical picture is partially overlapping with that of WS1, from which it traditionally differs by the absence of diabetes insipidus and the presence of greater bleeding tendency and peptic ulcers.

Current Drug Repurposing Strategies for Rare Neurodegenerative Disorders

Rare diseases are life-threatening or chronically debilitating low-prevalent disorders caused by pathogenic mutations or particular environmental insults. Due to their high complexity and low frequency, important gaps still exist in their prevention, diagnosis, and treatment. Since new drug discovery is a very costly and time-consuming process, leading pharmaceutical companies show relatively low interest in orphan drug research and development due to the high cost of investments compared to the low market return of the product. Drug repurposing–based approaches appear then as cost- and time-saving strategies for the development of therapeutic opportunities for rare diseases. In this article, we discuss the scientific, regulatory, and economic aspects of the development of repurposed drugs for the treatment of rare neurodegenerative disorders with a particular focus on Huntington’s disease, Friedreich’s ataxia, Wolfram syndrome, and amyotrophic lateral sclerosis. The role of academia, pharmaceutical companies, patient associations, and foundations in the identification of candidate compounds and their preclinical and clinical evaluation will also be discussed.

The Expression of RAAS Key Receptors, Agtr2 and Bdkrb1, Is Downregulated at an Early Stage in a Rat Model of Wolfram Syndrome

Wolfram syndrome (WS) 1 is a rare monogenic neurodegenerative disorder caused by mutations in the gene encoding WFS1. Knowledge of the pathophysiology of WS is incomplete and to date, there is no treatment available. Here, we describe early deviations in the renin-angiotensin-aldosterone system (RAAS) and bradykinin pathway (kallikrein kinin system, KKS) observed in a rat model of WS (Wfs1 KO) and the modulative effect of glucagon-like peptide-1 receptor agonist liraglutide (LIR) and anti-epileptic drug valproate (VPA), which have been proven effective in delaying WS progression in WS animal models. We found that the expression of key receptors of the RAAS and KKS, Agtr2 and Bdkrb1, were drastically downregulated both in vitro and in vivo at an early stage in a rat model of WS. Moreover, in Wfs1, KO serum aldosterone levels were substantially decreased and bradykinin levels increased compared to WT animals. Neither treatment nor their combination affected the gene expression levels seen in the Wfs1 KO animals. However, all the treatments elevated serum aldosterone and decreased bradykinin in the Wfs1 KO rats, as well as increasing angiotensin II levels independent of genotype. Altogether, our results indicate that Wfs1 deficiency might disturb the normal functioning of RAAS and KKS and that LIR and VPA have the ability to modulate these systems.

A novel mutation of WFS1 gene leading to increase ER stress and cell apoptosis is associated an autosomal dominant form of Wolfram syndrome type 1

BACKGROUND

Wolfram syndrome (WS) is a rare autosomal recessive disorder characterized by diabetes insipidus, diabetes mellitus, optic atrophy and deafness. Mutations in Wolfram syndrome 1 (WFS1) gene may cause dysregulated endoplasmic reticulum (ER)-stress and cell apoptosis, contributing to WS symptoms. The aim of this study was to identify the molecular etiology of a case of WS and to explore the functional consequence of the mutant WFS1 gene in vitro.

METHODS

A 27 years-old Chinese man was diagnosed as wolfram syndrome type 1 based on clinical data and laboratory data. DNA sequencing of WFS1 gene and mitochondrial m.3337G > A, m.3243A > G mutations were performed in the patient and his 4 family members. Functional analysis was performed to assessed the in vitro effect of the newly identified mutant. ER stress were evaluated by ER stress response element (ERSE)-luciferase assay. Cell apoptosis were performed by CCK-8, TUNEL staining and flow cytometric analysis.

RESULTS

A novel heterozygous 10-base deletion (c. 2067_2076 del10, p.W690fsX706) was identified in the patient. In vitro studies showed that mutant p.W690fsX706 increased ERSE reporter activity in the presence or absence of thapsigargin instead of wild type WFS1. Knockdown of WFS1 activated the unfolded protein response (UPR) pathway and increased the cell apoptosis, which could not be restored by transfection with WFS1 mutant (p.W690fsX706) comparable to the wild type WFS1.

CONCLUSIONS

A novel heterozygous mutation of WFS1 detected in the patient resulted in loss-of-function of wolframin, thereby inducing dysregulated ER stress signaling and cell apoptosis. These findings increase the spectrum of WFS1 gene mutations and broaden our insights into the roles of mutant WFS1 in the pathogenesis of WS.

Collaboration for rare diabetes: understanding new treatment options for Wolfram syndrome

BACKGROUND

Wolfram Syndrome is a very rare genetic disease causing diabetes mellitus, blindness, deafness, diabetes insipidus, and progressive brainstem degeneration. Neurologic symptoms of affected patients include ataxia, sleep apnea, loss of bladder control, dysphagia, loss of taste, and accompanying psychiatric symptoms as a sign of progressive neurodegeneration. Its genetic cause is mainly biallelic mutations of the Wolframin endoplasmatic reticulum transmembrane glycoprotein gene Wfs1. These result in increased ER stress, which in turn induces apoptosis and leads to the depletion of the corresponding cells and a loss of their physiological functions. Though diabetes mellitus is mostly treated by insulin, there is still no proven cure for the disease in general. It leads to premature death in affected individuals-usually within the 4th decade of live.

CURRENT RESEARCH AND TREATMENT TRIALS

Clinical studies are currently being conducted at various locations worldwide to test a therapy for the disease using various approaches.

POTENTAIL OF VIRTUAL NETOWRKING

As rare diseases in general represent a major challenge for individual clinicians and researchers due to the rarity of diagnosis, the lack of evidence and of value of existing research, international cooperation, coordination and networking leading to an alignment of different stakeholders is necessary to support patients and increase knowledge about these diseases, like wolfram syndrome.

CONCLUSION

ENDO-ERN and EURRECA are two EU-funded networks that aim to promote knowledge sharing, education and research on rare endocrine diseases.

Wolfram syndrome: new pathophysiological insights and therapeutic strategies

Wolfram Syndrome (WS) is an ultra-rare, progressive neurodegenerative disease characterized by early-onset diabetes mellitus and irreversible loss of vision, secondary to optic nerve degeneration. Visual loss in WS is an important cause of registrable blindness in children and young adults and the pathological hallmark is the preferential loss of retinal ganglion cells within the inner retina. In addition to optic atrophy, affected individuals frequently develop variable combinations of neurological, endocrinological, and psychiatric complications. The majority of patients carry recessive mutations in the WFS1 (4p16.1) gene that encodes for a multimeric transmembrane protein, wolframin, embedded within the endoplasmic reticulum (ER). An increasingly recognised subgroup of patients harbor dominant WFS1 mutations that usually cause a milder phenotype, which can be limited to optic atrophy. Wolframin is a ubiquitous protein with high levels of expression in retinal, neuronal, and muscle tissues. It is a multifunctional protein that regulates a host of cellular functions, in particular the dynamic interaction with mitochondria at mitochondria-associated membranes. Wolframin has been implicated in several crucial cellular signaling pathways, including insulin signaling, calcium homeostasis, and the regulation of apoptosis and the ER stress response. There is currently no cure for WS; management remains largely supportive. This review will cover the clinical, genetic, and pathophysiological features of WS, with a specific focus on disease models and the molecular pathways that could serve as potential therapeutic targets. The current landscape of therapeutic options will also be discussed in the context of the latest evidence, including the pipeline for repurposed drugs and gene therapy.

Plain language summary

Wolfram syndrome - disease mechanisms and treatment options Wolfram syndrome (WS) is an ultra-rare genetic disease that causes diabetes mellitus and progressive loss of vision from early childhood. Vision is affected in WS because of damage to a specialized type of cells in the retina, known as retinal ganglion cells (RGCs), which converge at the back of the eye to form the optic nerve. The optic nerve is the fast-conducting cable that transmits visual information from the eye to the vision processing centers within the brain. As RGCs are lost, the optic nerve degenerates and it becomes pale in appearance (optic atrophy). Although diabetes mellitus and optic atrophy are the main features of WS, some patients can develop more severe problems because the brain and other organs, such as the kidneys and the bladder, are also affected. The majority of patients with WS carry spelling mistakes (mutations) in the WFS1 gene, which is located on the short arm of chromosome 4 (4p16.1). This gene is highly expressed in the eye and in the brain, and it encodes for a protein located within a compartment of the cell known as the endoplasmic reticulum. For reasons that still remain unclear, WFS1 mutations preferentially affect RGCs, accounting for the prominent visual loss in this genetic disorder. There is currently no effective treatment to halt or slow disease progression and management remains supportive, including the provision of visual aids and occupational rehabilitation. Research into WS has been limited by its relative rarity and the inability to get access to eye and brain tissues from affected patients. However, major advances in our understanding of this disease have been made recently by making use of more accessible cells from patients, such as skin cells (fibroblasts), or animal models, such as mice and zebrafish. This review summarizes the mechanisms by which WFS1 mutations affect cells, impairing their function and eventually leading to their premature loss. The possible treatment strategies to block these pathways are also discussed, with a particular focus on drug repurposing (i.e., using drugs that are already approved for other diseases) and gene therapy (i.e., replacing or repairing the defective WFS1 gene).

Wolfram Syndrome: a Monogenic Model to Study Diabetes Mellitus and Neurodegeneration

Wolfram syndrome (WS) is a rare, progressive disorder characterized by childhood-onset diabetes mellitus, optic nerve atrophy, hearing loss, diabetes insipidus, and neurodegeneration. Currently, there is no effective treatment for WS, and patients typically die between 30 and 40 years of age. WS is primarily caused by autosomal recessive mutations in the Wolfram syndrome 1 (WFS1) gene (OMIM 222300), which encodes for wolframin (WFS1). This disorder is therefore a valuable monogenic model for prevalent diseases, particularly diabetes mellitus and neurodegeneration. Whereas reduced survival and secretion are known cellular impairments causing WS, the underlying molecular pathways and the physiological function of WFS1 remain incompletely described. Here, we characterize WFS1 as a regulator of intracellular calcium homeostasis, review our current understanding of the disease mechanism of WS, and discuss candidate treatment approaches. These insights will facilitate identification of new therapeutic strategies not only for WS but also for diabetes mellitus and neurodegeneration.