Taste and smell function in Wolfram syndrome

Inflammation and olfactory loss are associated with at least 139 medical conditions

Olfactory loss accompanies at least 139 neurological, somatic, and congenital/hereditary conditions. This observation leads to the question of whether these associations are correlations or whether they are ever causal. Temporal precedence and prospective predictive power suggest that olfactory loss is causally implicated in many medical conditions. The causal relationship between olfaction with memory dysfunction deserves particular attention because this sensory system has the only direct projection to memory centers. Mechanisms that may underlie the connections between medical conditions and olfactory loss include inflammation as well as neuroanatomical and environmental factors, and all 139 of the medical conditions listed here are also associated with inflammation. Olfactory enrichment shows efficacy for both prevention and treatment, potentially mediated by decreasing inflammation.

Clinical Trials for Wolfram Syndrome Neurodegeneration: Novel Design, Endpoints, and Analysis Models

Objective

Wolfram syndrome, an ultra-rare condition, currently lacks effective treatment options. The rarity of this disease presents significant challenges in conducting clinical trials, particularly in achieving sufficient statistical power (e.g., 80%). The objective of this study is to propose a novel clinical trial design based on real-world data to reduce the sample size required for conducting clinical trials for Wolfram syndrome.

Methods

We propose a novel clinical trial design with three key features aimed at reducing sample size and improve efficiency: (i) Pooling historical/external controls from a longitudinal observational study conducted by the Washington University Wolfram Research Clinic. (ii) Utilizing run-in data to estimate model parameters. (iii) Simultaneously tracking treatment effects in two endpoints using a multivariate proportional linear mixed effects model.

Results

Comprehensive simulations were conducted based on real-world data obtained through the Wolfram syndrome longitudinal observational study. Our simulations demonstrate that this proposed design can substantially reduce sample size requirements. Specifically, with a bivariate endpoint and the inclusion of run-in data, a sample size of approximately 30 per group can achieve over 80% power, assuming the placebo progression rate remains consistent during both the run-in and randomized periods. In cases where the placebo progression rate varies, the sample size increases to approximately 50 per group.

Conclusions

For rare diseases like Wolfram syndrome, leveraging existing resources such as historical/external controls and run-in data, along with evaluating comprehensive treatment effects using bivariate/multivariate endpoints, can significantly expedite the development of new drugs.

Olfactory dysfunction and the role of stem cells in the regeneration of olfactory neurons

The prevalence of COVID-19 has drawn increasing attention to olfactory dysfunction among researchers. Olfactory dysfunction manifests in various clinical types, influenced by numerous pathogenic factors. Despite this diversity, the underlying pathogenesis remains largely elusive, contributing to a lack of standardized treatment approaches. However, the potential regeneration of olfactory neurons within the nasal cavity presents a promising avenue for addressing olfactory dysfunction effectively. Our review aims to delve into the current research landscape and treatment modalities concerning olfactory dysfunction, emphasizing etiology, pathogenesis, clinical interventions, and the role of stem cells in regenerating olfactory nerves. Through this comprehensive examination, we aim to provide valuable insights into understanding the onset, progression, and treatment of olfactory dysfunction diseases.

Enhancement of taste by retronasal odors in patients with Wolfram syndrome and decreased olfactory function

Wolfram syndrome is a rare disease characterized by diabetes, neurodegeneration, loss of vision, and audition. We recently found, in a young sample of participants (mean age 15 years), that Wolfram syndrome was associated with impairment in smell identification with normal smell sensitivity and whole-mouth taste function. However, these senses were assessed separately, and it is unknown whether smell-taste interactions are altered in Wolfram syndrome, which was the focus of this study. Participants with Wolfram syndrome (n = 36; 18.2 ± 6.8 years) and sex-age-equivalent healthy controls (n = 34) were assessed with a battery of sensory tests. Using sip-and-spit methods, participants tasted solutions containing gustatory and olfactory stimuli (sucrose with strawberry extract, citric acid with lemon extract, sodium chloride in vegetable broth, and coffee) with and without nose clips, and rated perceived taste and retronasal smell intensities using the generalized Labeled Magnitude Scale. Participants also completed n-butanol detection thresholds and the University of Pennsylvania Smell Identification Test (UPSIT). Retronasal smell increased taste intensity of sucrose, sodium chloride, and coffee solutions similarly in both groups (P values <0.03). Compared with the control group, participants in the Wolfram group had lower UPSIT scores and reduced smell sensitivity, retronasal intensity, and saltiness (P values <0.03), but rated other taste intensities similarly when wearing the nose clip. Despite impairments in orthonasal smell identification, odor-induced taste enhancement was preserved in participants with Wolfram syndrome who still had some peripheral olfactory function. This finding suggests that odor-induced taste enhancement may be preserved in the presence of reduced olfactory intensity.

Longitudinal Changes in Vision and Retinal Morphological in Wolfram Syndrome

PURPOSE

To report long-term ophthalmic findings in Wolfram syndrome, including rates of visual decline, macular thinning, retinal nerve fiber layer (RNFL) thinning and outer plexiform lamination (OPL).

DESIGN

Single-center, cohort study METHODS: : Thirty-eight participants were recruited and underwent a complete ophthalmic examination as well as optical coherence tomography imaging of the macula and nerve on an annual basis. Linear mixed-effects models for longitudinal data were used to examine both fixed and random effects related to visual acuity and optic nerve quadrants of RNFL and macula thickness.

RESULTS

Participants completed a mean of 6.44 years of follow-up (range 2-10 years). Visual acuity declined over time in all participants with a mean slope of 0.059 logMar/year (95% CI: 0.07 to 0.05 logMar/year), although nearly 25% of subjects experienced more rapid visual decline. RNFL thickness decreased in superior, inferior, and nasal quadrants (β = -0.5 μm/year, -0.98 μm/year, -0.28 μm/year, respectively). OPL lamination was noted in three study participants, two of which had autosomal dominant mutations.

CONCLUSIONS

Our study describes the longest and largest natural history study of visual acuity decline and retinal morphometry in Wolfram syndrome to date. Results suggest that there are slower and faster progressing subgroups and that OPL lamination is present in some individuals with this disease.

Plasma Neurofilament Light Chain Levels Are Elevated in Children and Young Adults With Wolfram Syndrome

Wolfram syndrome is a rare disease caused by pathogenic variants in the WFS1 gene with progressive neurodegeneration. As an easily accessible biomarker of progression of neurodegeneration has not yet been found, accurate tracking of the neurodegenerative process over time requires assessment by costly and time-consuming clinical measures and brain magnetic resonance imaging (MRI). A blood-based measure of neurodegeneration, neurofilament light chain (NfL), is relatively inexpensive and can be repeatedly measured at remote sites, standardized, and measured in individuals with MRI contraindications. To determine whether NfL levels may be of use in disease monitoring and reflect disease activity in Wolfram syndrome, plasma NfL levels were compared between children and young adults with Wolfram syndrome (n = 38) and controls composed of their siblings and parents (n = 35) and related to clinical severity and selected brain region volumes within the Wolfram group. NfL levels were higher in the Wolfram group [median (interquartile range) NfL = 11.3 (7.8-13.9) pg/mL] relative to controls [5.6 (4.5-7.4) pg/mL]. Within the Wolfram group, higher NfL levels related to worse visual acuity, color vision and smell identification, smaller brainstem and thalamic volumes, and faster annual rate of decrease in thalamic volume over time. Our findings suggest that plasma NfL levels can be a powerful tool to non-invasively assess underlying neurodegenerative processes in children, adolescents and young adults with Wolfram syndrome.

Longitudinal progression of diabetes mellitus in Wolfram syndrome: The Washington University Wolfram Research Clinic experience

OBJECTIVE

(1) Describe the progression of diabetes mellitus over time in an observational study of Wolfram syndrome, a rare, genetic, neurodegenerative disorder, which often includes diabetes mellitus and is typically diagnosed during childhood or adolescence. (2) Determine whether C-peptide could be used as a marker of diabetes progression in interventional trials for Wolfram syndrome.

METHODS

N = 44 (25F/19M) participants with genetically confirmed Wolfram syndrome attended the Washington University Wolfram Research Clinic annually from 2010 to 2019. Medical history, physical examinations, blood sampling, and questionnaires were used to collect data about diabetes mellitus and other components of Wolfram syndrome. Beta-cell function was assessed by determination of C-peptide during a mixed meal tolerance test. Random coefficients models evaluated the rate of progression of C-peptide over time, and power analyses were used to estimate the number of subjects needed to detect a change in C-peptide decline during an intervention trial.

RESULTS

93.2% of patients had diabetes mellitus. Mean HbA1c across all study visits was 7.9%. C-peptide significantly decreased with increasing duration of diabetes mellitus (p < 0.0001); an optimal break point in C-peptide decline was identified to occur between 0.1 and 2.3 years after diabetes mellitus diagnosis. Twenty patients per group (active vs. control) were estimated to be needed to detect a 60% slowing of C-peptide decline during the first 2.3 years following diabetes diagnosis.

CONCLUSION

C-peptide declines over time in Wolfram syndrome and could potentially be used as a marker of diabetes progression in interventional studies for Wolfram syndrome, especially within the first 2 years after diabetes diagnosis.

Longitudinal Assessment of Neuroradiologic Features in Wolfram Syndrome

BACKGROUND AND PURPOSE

Wolfram syndrome is a rare genetic disease with characteristic brain involvement. We reviewed the brain MR images of patients with Wolfram syndrome to determine the frequency and characteristics of common neuroradiologic findings.

MATERIALS AND METHODS

We retrospectively reviewed the imaging data of patients with genetically-confirmed Wolfram syndrome who had been recruited to the Washington University Wolfram Syndrome Research Clinic. These patients were evaluated between 2010 and 2019 with annual MRIs, along with other measures. MR images were assessed for clinical neuroradiologic signs at each individual's first and last follow-up visits to characterize the frequency, rate of progression, and clinical correlations of these signs.

RESULTS

We included 30 patients (13 males/17 females; average age at first visit, 14 years; average age at last visit, 19 years). The median duration of follow-up was 5 years (range, 2-9 years). The most common findings were an absent or diminished posterior pituitary bright spot (first, 53%; last, 70%), T1/T2 pons signal abnormalities (first, 53%; last, 67%), optic nerve atrophy (first, 30%; last, 80%), white matter T2 hyperintensities (first, 27%; last, 35%), and cerebellar atrophy (first, 23%; last, 70%).

CONCLUSIONS

Patients with Wolfram syndrome present characteristic neuroradiologic findings that involve the posterior pituitary gland, optic nerves, white matter, brain stem, and cerebellum. These abnormal findings appear at an early age and tend to increase in frequency with time. However, the neurologic significance and neuropathologic mechanisms of each sign require more investigation. Neuroradiologists should be aware of the pattern of these features in Wolfram syndrome.

Function of WFS1 and WFS2 in the Central Nervous System: Implications for Wolfram Syndrome and Alzheimer's disease

L.P. Li, L. Venkataraman, S. Chen, and H.J. Fu. Function of WFS1 and WFS2 in the Central Nervous System: Implications for Wolfram Syndrome and Alzheimer's Disease. NEUROSCI BIOBEHAV REVXXX-XXX,2020.-Wolfram syndrome (WS) is a rare monogenetic spectrum disorder characterized by insulin-dependent juvenile-onset diabetes mellitus, diabetes insipidus, optic nerve atrophy, hearing loss, progressive neurodegeneration, and a wide spectrum of psychiatric manifestations. Most WS patients belong to Wolfram Syndrome type 1 (WS1) caused by mutations in the Wolfram Syndrome 1 (WFS1/Wolframin) gene, while a small fraction of patients belongs to Wolfram Syndrome type 2 (WS2) caused by pathogenic variants in the CDGSH Iron Sulfur Domain 2 (CISD2/WFS2) gene. Although currently there is no treatment for this life-threatening disease, the molecular mechanisms underlying the pathogenesis of WS have been proposed. Interestingly, Alzheimer's disease (AD), an age-dependent neurodegenerative disease, shares some common mechanisms with WS. In this review, we focus on the function of WFS1 and WFS2 in the central nervous system as well as their implications in WS and AD. We also propose three future directions for elucidating the role of WFS1 and WFS2 in WS and AD.