Validation of newly derived polygenic risk scores for dementia in a prospective study of older individuals

INTRODUCTION

Recent genome-wide association studies identified new dementia-associated variants. We assessed the performance of updated polygenic risk scores (PRSs) using these variants in an independent cohort.

METHODS

We used Cox models and area under the curve (AUC) to validate new PRSs (PRS-83SNP, PRS-SBayesR, and PRS-CS) compared with an older PRS-23SNP in 12,031 initially-healthy participants ≥70 years of age. Dementia was rigorously adjudicated according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria.

RESULTS

PRS-83SNP, PRS-SBayesR, and PRS-CS were associated with incident dementia, with fully adjusted (including apolipoprotein E [APOE] ε4) hazard ratios per standard deviation (SD) of 1.35 (1.23-1.47), 1.37 (1.25-1.50), and 1.42 (1.30-1.56), respectively. The AUC of a model containing conventional/non-genetic factors and APOE was 74.7%. This was improved to 75.7% (p = 0.007), 76% (p = 0.004), and 76.1% (p = 0.003) with addition of PRS-83SNP, PRS-SBayesR, and PRS-CS, respectively. The PRS-23SNP did not improve AUC (74.7%, p = 0.95).

CONCLUSION

New PRSs for dementia significantly improve risk-prediction performance, but still account for less risk than APOE genotype overall.

Plasma Neurofilament Light Chain and Clinical Diagnosis in Frontotemporal Dementia Syndromes

Background: Frontotemporal dementia (FTD) syndromes, mimics, phenocopy (phFTD), and slowly progressive behavioral variant FTD (bvFTD) can be difficult to distinguish clinically. Biomarkers such as neurofilament light chain (NfL) may be helpful. Objective: To study plasma NfL levels in people with FTD syndromes and determine if plasma NfL can distinguish between FTD syndromes and phFTD. Methods: Plasma NfL levels were estimated using both Simoa ® Quanterix HD-X™ and SR-X™ machines grouped via final diagnosis after investigation and review. Results: Fifty participants were studied: bvFTD = 20, semantic variant FTD (svFTD) = 11, non-fluent variant FTD (nfvFTD) = 9, FTD with motor neuron disease (MND) = 4, phFTD = 2, slow progressors = 3, FTD mimic = 1, mean age 67.2 (SD 8.4) years. NfL levels were significantly higher in the FTD group compared to phenocopy group (p = 0.003). Median NfL (IQR) pg/mL was comparable in the FTD syndromes: bvFTD 41.10 (50.72), svFTD 44.38 (16.61), and nfvFTD 42.61 (22.93), highest in FTD with MND 79.67 (45.32) and lowest in both phFTD 13.99 (0.79) and slow progressors 17.97 (3.62). Conclusion: Plasma NfL appears to differentiate FTD syndromes and mimics. However, a lower NfL may predict a slower, but not necessarily lack of, neurodegeneration and therefore appears limited distinguishing slow progressors from FTD phenocopies. Larger numbers of patients from all clinical groups are required to strengthen diagnostic utility.

A phase 1b open-label study of sodium selenate as a disease-modifying treatment for possible behavioral variant frontotemporal dementia

Introduction

Sodium selenate increases tau dephosphorylation through protein phosphatase 2 activation. Here we report an open‐label Phase 1b study of sodium selenate as a disease‐modifying treatment for behavioral variant frontotemporal dementia (bvFTD).

Methods

Twelve participants with bvFTD received sodium selenate (15 mg, three times a day) for 52 weeks. Safety assessments were carried out throughout the trial. Primary outcomes were frequency of adverse events (AEs), serious adverse events (SAEs), and discontinuations. Secondary outcomes of potential efficacy included cognitive and behavioral assessments, magnetic resonance imaging (MRI) whole brain volume, and cerebrospinal fluid (CSF) and blood total tau (t‐tau), phosphorylated tau (p‐tau), and neurofilament light (NfL) levels, which were measured at baseline and at week 52.

Results

Sodium selenate was safe and well tolerated. All participants completed the study, and the majority (64.7%) of reported AEs were mild. One SAE occurred, which was not treatment related. Small declines in MRI and cognitive and behavioral measures were observed over the treatment period. There was no evidence for change in CSF protein levels (t‐tau, p‐tau, or NfL). Further analysis showed two distinct groups when measuring disease progression markers over the course of the study—one (n = 4) with substantial brain atrophy (2.5% to 6.5% reduction) and cognitive and behavioral decline over the 12‐month treatment period, and the second group (n = 7) with no detectable change in cognitive and behavioral measures and less brain atrophy (0.3% to 1.7% reduction).

Conclusion

Sodium selenate is safe and well tolerated in patients with bvFTD. Randomized‐controlled trials are warranted to investigate potential efficacy.

029 Multiple-acyl-coa dehydrogenase deficiency (MADD): a rare but treatable genetic metabolic myopathy

Introduction

Multiple-acyl-CoA dehydrogenase deficiency or MADD is a rare autosomal recessive disorder caused by deficiency of electron transfer flavoprotein. Late onset form of MADD typically present with slowly progressive proximal weakness, myalgia, lethargy, vomiting, hypoglycaemia and metabolic acidosis. This condition is highly variable in age and symptoms at onset. The mean delay between onset of symptoms and diagnosis was 3.9 years. Confirmation of the diagnosis requires relatively complicated tests including muscle biopsy, Acylcarnitine profiling, urinary organic acid analysis and molecular gene testing. MADD responds dramatically to riboflavin supplementation and dietary treatment i.e. high carbohydrate, low fat and low protein diet. We report of a case of Multiple-Acyl-CoA Dehydrogenase Deficiency (MADD) and a review of the literature.

Case

A 22 year old female presented with 3 year history of slowly progressive muscle weakness, fatigue and dyspnea on minimal exertion. Clinical examination revealed profound neck extension weakness (‘dropped head syndrome’), proximal muscle weakness (winged scapula and positive Gower’s sign), mild dysphagia and dysarthria. There was no obvious facial weakness, ptosis or ophthalmoplegia. Muscle biopsy showed prominent lipid and generalised hypotrophy of type I fibres. The diagnosis of MADD was suspected on the basis of clinical presentation. The patient was commenced on riboflavin, carnitine supplementation and low protein, low fat diet. Her symptoms improved significantly over 2 months (improvement in muscle strength and respiratory function, FVC improved from 42% to 89%). Acylcarnitine and amino acid screen results came back later showing elevated levels of C6, C8, C10 and C12 in keeping with the diagnosis of MADD.

Conclusion

Multiple-acyl-CoA dehydrogenase deficiency is a rare genetic metabolic myopathy. It is under-recognised and diagnosis of the adult onset form is often challenging. The majority of patients respond well to riboflavin and dietary modifications with excellent clinical outcome.

References

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