Genetic risk factors for the posterior cortical atrophy variant of Alzheimer's disease.

INTRODUCTION: The genetics underlying posterior cortical atrophy (PCA), typically a rare variant of Alzheimer's disease (AD), remain uncertain. METHODS: We genotyped 302 PCA patients from 11 centers, calculated risk at 24 loci for AD/DLB and performed an exploratory genome-wide association study. RESULTS: We confirm that variation in/near APOE/TOMM40 (P = 6 × 10(-14)) alters PCA risk, but with smaller effect than for typical AD (PCA: odds ratio [OR] = 2.03, typical AD: OR = 2.83, P = .0007). We found evidence for risk in/near CR1 (P = 7 × 10(-4)), ABCA7 (P = .02) and BIN1 (P = .04). ORs at variants near INPP5D and NME8 did not overlap between PCA and typical AD. Exploratory genome-wide association studies confirmed APOE and identified three novel loci: rs76854344 near CNTNAP5 (P = 8 × 10(-10) OR = 1.9 [1.5-2.3]); rs72907046 near FAM46A (P = 1 × 10(-9) OR = 3.2 [2.1-4.9]); and rs2525776 near SEMA3C (P = 1 × 10(-8), OR = 3.3 [2.1-5.1]). DISCUSSION: We provide evidence for genetic risk factors specifically related to PCA. We identify three candidate loci that, if replicated, may provide insights into selective vulnerability and phenotypic diversity in AD.

Coexisting Lewy body disease and clinical parkinsonism in frontotemporal lobar degeneration.

OBJECTIVE: To investigate the prevalence of clinically relevant multiple system atrophy (MSA) and Lewy body disease (LBD) pathologies in a large frontotemporal lobar degeneration (FTLD) cohort to determine if concomitant pathologies underlie the heterogeneity of clinical features. METHODS: All prospectively followed FTLD-tau and FTLD-TDP cases held by the Sydney Brain Bank (n = 126) were screened for coexisting MSA and LBD (Braak ≥ stage IV) pathology. Relevant clinical (including family history) and genetic associations were determined. RESULTS: MSA pathology was not identified in this series. Of the FTLD cohort, 9 cases had coexisting LBD ≥ Braak stage IV and were associated with different FTLD subtypes including Pick disease (n = 2), corticobasal degeneration (n = 2), progressive supranuclear palsy (n = 2), and TDP type A (n = 3). All FTLD-TDP cases with coexisting LBD had mutations in progranulin (n = 2) or an abnormal repeat expansion in C9orf72 (n = 1). All FTLD-tau cases with coexisting LBD were sporadic. The H1H1 MAPT haplotype was found in all cases that could be genotyped (n = 6 of 9). Seven cases presented with a predominant dementia disorder, 3 of which developed parkinsonism. Two cases presented with a movement disorder and developed dementia in their disease course. The age at symptom onset (62 ± 11 years) and disease duration (8 ± 5 years) in FTLD cases with coexisting LBD did not differ from pure FTLD or pure LBD cases in the brain bank. CONCLUSION: Coexisting LBD in FTLD comprises a small proportion of cases but has implications for clinical and neuropathologic diagnoses and the identification of biomarkers.

Predicting Development of Amyotrophic Lateral Sclerosis in Frontotemporal Dementia.

BACKGROUND: A proportion of patients with frontotemporal dementia (FTD) also develop amyotrophic lateral sclerosis (ALS). OBJECTIVE: We aimed to establish the risk of developing ALS in patients presenting with FTD and to identify the relevant clinical variables associated with progression from FTD to FTD-ALS. METHODS: Of 218 consecutive patients with FTD, 10.1% had a dual FTD-ALS diagnosis at presentation. The remaining 152 FTD patients with follow-up of at least 12 months were included in the present study. We calculated the rate of progression to FTD-ALS and compared the baseline characteristics of FTD patients who developed ALS to those who did not develop ALS. RESULTS: Five percent of FTD patients developed ALS. The incidence rate of ALS was 6.7/100 patient-years in patients with FTD symptoms since 1 year, which declined with duration of FTD symptoms. No FTD patients developed ALS after 5 years. Five out of 8 FTD patients who developed ALS had presented with a mixed behavioral variant FTD and progressive non-fluent aphasia (bvFTD+PNFA) phenotype, 2 with bvFTD, and 1 with PNFA. Progression to FTD-ALS was significantly more frequent in patients with bvFTD+PNFA compared to those without this phenotype (p < 0.0001, OR 38.3, 95% CI: 7.3 to 199.2), and in FTD patients who carried the C9orf72 repeat expansion compared to those without the repeat expansion (p = 0.02, OR 8.0, 95% CI: 1.7 to 38.6). CONCLUSIONS: FTD patients with a mixed bvFTD+PNFA phenotype and with a C9orf72 repeat expansion should be closely monitored for the possible development of ALS. The risk of developing ALS in FTD appears to decline with the duration of FTD symptoms.

Assessment of Eating Behavior Disturbance and Associated Neural Networks in Frontotemporal Dementia.

IMPORTANCE: Abnormal eating behaviors are common in patients with frontotemporal dementia (FTD), yet their exact prevalence, severity, and underlying biological mechanisms are not understood. OBJECTIVE: To define the severity of abnormal eating behavior and sucrose preference and their neural correlates in patients with behavioral variant FTD (bvFTD) and semantic dementia. DESIGN, SETTING, AND PARTICIPANTS: Forty-nine patients with dementia (19 with bvFTD, 15 with semantic dementia, and 15 with Alzheimer disease) were recruited, and their eating behavior was compared with that of 25 healthy controls. The study was conducted from November 1, 2013, through May 31, 2015, and data analyzed from June 1 to August 31, 2015. MAIN OUTCOMES AND MEASURES: Patients participated in an ad libitum breakfast test meal, and their total caloric intake and food preferences were measured. Changes in eating behavior were also measured using the Appetite and Eating Habits Questionnaire (APEHQ) and the Cambridge Behavioral Inventory (CBI). Sucrose preference was tested by measuring liking ratings of 3 desserts of varying sucrose content (A: 26%, B: 39%, C: 60%). Voxel-based morphometry analysis of whole-brain 3-T high-resolution brain magnetic resonance imaging was used to determine the gray matter density changes across groups and their relations to eating behaviors. RESULTS: Mean (SD) ages of patients in all 4 groups ranged from 62 (8.3) to 66 (8.4) years. At the ad libitum breakfast test meal, all patients with bvFTD had increased total caloric intake (mean, 1344 calories) compared with the Alzheimer disease (mean, 710 calories), semantic dementia (mean, 573 calories), and control groups (mean, 603 calories) (P < .001). Patients with bvFTD and semantic dementia had a strong sucrose preference compared with the other groups. Increased caloric intake correlated with atrophy in discrete neural networks that differed between patients with bvFTD and semantic dementia but included the cingulate cortices, thalami, and cerebellum in patients with bvFTD, with the addition of the orbitofrontal cortices and nucleus accumbens in patients with semantic dementia. A distributed network of neural correlates was associated with sucrose preference in patients with FTD. CONCLUSIONS AND RELEVANCE: Marked hyperphagia is restricted to bvFTD, present in all patients with this diagnosis, and supports its diagnostic value. Differing neural networks control eating behavior in patients with bvFTD and semantic dementia and are likely responsible for the differences seen, with a similar network controlling sucrose preference. These networks share structures that control cognitive-reward, autonomic, neuroendocrine, and visual modulation of eating behavior. Delineating the neural networks involved in mediating these changes in eating behavior may enable treatment of these features in patients with complex medical needs and aid in our understanding of structures that control eating behavior in patients with FTD and healthy individuals.

TDP-43 in the hypoglossal nucleus identifies amyotrophic lateral sclerosis in behavioral variant frontotemporal dementia.

The hypoglossal nucleus was recently identified as a key brain region in which the presence of TDP-43 pathology could accurately discriminate TDP-43 proteinopathy cases with clinical amyotrophic lateral sclerosis (ALS). The objective of the present study was to assess the hypoglossal nucleus in behavioral variant frontotemporal dementia (bvFTD), and determine whether TDP-43 in this region is associated with clinical ALS. Twenty-nine cases with neuropathological FTLD-TDP and clinical bvFTD that had not been previously assessed for hypoglossal TDP-43 pathology were included in this study. Of these 29 cases, 41% (n=12) had a dual diagnosis of bvFTD-ALS at presentation, all 100% (n=12) of which demonstrated hypoglossal TDP-43 pathology. Of the 59% (n=17) cohort that presented with pure bvFTD, 35% (n=6) were identified with hypoglossal TDP-43 pathology. Review of the case files of all pure bvFTD cases revealed evidence of possible or probable ALS in 5 of the 6 hypoglossal-positive cases (83%) towards the end of disease, and this was absent from all cases without such pathology. In conclusion, the present study validates grading the presence of TDP-43 in the hypoglossal nucleus for the pathological identification of bvFTD cases with clinical ALS, and extends this to include the identification of cases with possible ALS at end-stage.

Eating behavior in frontotemporal dementia: Peripheral hormones vs hypothalamic pathology.

OBJECTIVE: To contrast the relationships of hormonal eating peptides and hypothalamic volumes to eating behavior and metabolic changes (body mass index [BMI]) in behavioral variant frontotemporal dementia (bvFTD) and semantic variant primary progressive aphasia (svPPA). METHODS: Seventy-five patients with dementia (19 bvFTD, 26 svPPA, and 30 Alzheimer disease dementia) and 23 controls underwent fasting blood analyses of leptin, ghrelin, cholecystokinin, peptide tyrosine tyrosine (PYY), and agouti-related peptide (AgRP) levels. On brain MRI anterior, posterior, and total hypothalamic volumes were measured. Relationships between endocrine measures, hypothalamic volumes, eating behaviors, and BMI were investigated. RESULTS: Levels of AgRP were higher in patients with bvFTD (69 ± 89 pg/mL) and svPPA (62 ± 81 pg/mL) compared with controls (23 ± 19 pg/mL, p < 0.01). No differences were found for leptin, oxytocin, cholecystokinin, ghrelin, and PYY levels. Patients with bvFTD and svPPA had higher scores on questionnaires measuring eating behaviors. Atrophy of the posterior and total hypothalamus was observed in the bvFTD group only. Linear regression modeling revealed that leptin and AgRP levels predicted BMI. CONCLUSION: Eating abnormalities are multifactorial in FTD. In bvFTD, they are in part related to hypothalamic degeneration, with potential disintegration of the network connections between the hypothalamus and orbitofrontal cortex/reward pathways. In svPPA, although hypothalamic volumes are preserved, this group experiences elevated AgRP levels similar to bvFTD, which predicts BMI in both groups. This finding highlights the potential key role of AgRP in eating and metabolic changes and provides a potential target for treatment to modify disease progression.

Progression in Behavioral Variant Frontotemporal Dementia: A Longitudinal Study.

IMPORTANCE: A gap in the literature exists regarding progression in behavioral variant frontotemporal dementia (BVFTD). Guidance is needed concerning markers that will enable clinicians to discriminate FTD more effectively from phenocopies and to identify factors that determine progression and thereby prognosis. OBJECTIVES: To observe longitudinal outcomes and progression in probable and possible BVFTD in accordance with international diagnostic criteria and to identify features that may aid clinicians to prognosticate better in cases of possible BVFTD. DESIGN, SETTING, AND PARTICIPANTS: Longitudinal cohort study performed in a specialist tertiary FTD research clinic. Fifty-eight consecutive patients were followed up longitudinally from January 1, 2008, through December 31, 2013, and classified as having possible, probable, or definite BVFTD at presentation and latest review. Final follow-up was completed on December 31, 2013, and data were analyzed from January 1 to August 1, 2014. MAIN OUTCOMES AND MEASURES: Clinical, pathological, genetic, neuropsychological, and neuroimaging data were analyzed to categorize patients, to compare differences between groups with changed and unchanged diagnoses, to determine rates of progression in BVFTD, and to identify prognostic features in possible BVFTD. RESULTS: At presentation, 38 of the 58 patients fulfilled criteria for probable BVFTD; of these, 36 continued to satisfy probable criteria or underwent conversion to definite criteria over time. The remaining 20 patients satisfied possible criteria only, and 11 of these patients changed categories over time to probable or definite BVFTD and showed progression on cognitive and functional measures (termed changed status). Of these 11 patients, 8 (73%) carried the C9orf72 expansion. A positive family history, memory impairment, and clinical abnormalities at presentation were key features of progression (P < .05). A continuum of neuropsychological scores, progression rates, and atrophy severity emerged across patients in probable, possible, changed status, and nonchanged status groups; patients with probable BVFTD exhibited the most severe abnormalities. CONCLUSIONS AND RELEVANCE: Behavioral variant FTD shows variable progression over time. Clinicians can use a detailed neurologic and cognitive assessment to identify key predictive features of progression when faced with possible BVFTD, whereas a diagnosis of probable BVFTD is accurate in a clinical setting.

Quantifying the eating abnormalities in frontotemporal dementia.

IMPORTANCE: Presence of eating abnormalities is one of the core criteria for the diagnosis of behavioral variant frontotemporal dementia (bvFTD), yet their occurrence in other subtypes of frontotemporal dementia (FTD) and effect on metabolic health is not known. OBJECTIVE: To define and quantify patterns of eating behavior and energy, sugar, carbohydrate, protein, and fat intake, as well as indices of metabolic health in patients with bvFTD and semantic dementia (SD) compared with patients with Alzheimer disease (AD) and healthy control participants. DESIGN, SETTING, AND PARTICIPANTS: Prospective case-controlled study involving patient and caregiver completion of surveys. Seventy-five participants with dementia (21 with bvFTD, 26 with SD, and 28 with AD) and 18 age- and education-matched healthy controls were recruited from FRONTIER, the FTD research clinic at Neuroscience Research Australia in Sydney. MAIN OUTCOMES AND MEASURES: Caregivers of patients with FTD and AD completed validated questionnaires on appetite, eating behaviors, energy consumption, and dietary macronutrient composition. All participants completed surveys on hunger and satiety. Body mass index and weight measurements were prospectively collected. RESULTS: The bvFTD group had significant abnormalities in the domains of appetite (U = 111.0, z = 2.7, P = .007), eating habits (U = 69.5, z = 3.8, P = .001), food preferences (U = 57.0, z = 4.1, P = .001), swallowing (U = 109.0, z = 3.0, P = .003), and other oral behaviors (U = 141.0, z = 2.6, P = .009) compared with the AD group. The bvFTD and SD groups tended to have increased energy consumption. Compared with controls, the bvFTD group had significantly increased carbohydrate intake (251 vs 170 g/d; P = .05) and the SD group had significantly increased sugar intake (114 vs 76 g/d; P = .049). No significant differences in total fat or protein intake between the groups were found. Despite similar energy intake, the SD group had lower hunger and satiety scores compared with the bvFTD group. In contrast, hunger and satiety scores did not differ between the bvFTD group and controls. The abnormal eating behavior was found in the 2 groups (bvFTD and SD) with the highest body mass index (F = 4.2, P = .008) and waist circumference (F = 6.4, P = .001). CONCLUSIONS AND RELEVANCE: Abnormal eating behaviors are prominent in patients with bvFTD and those with SD and are not limited to increased appetite. The observed higher intake of sugar and carbohydrates was found in patients with the FTD subtypes and those with higher body mass index and waist circumference and was not explained simply by increased hunger or lower satiety.

Systemic metabolism in frontotemporal dementia.

OBJECTIVE: To document the metabolic changes in frontotemporal dementia, including serum cholesterol and insulin levels, and compare and contrast these changes to motor neuron disease, where metabolism is proposed to affect disease progression. METHODS: A cohort of 90 patients with dementia (31 behavioral-variant frontotemporal dementia [bvFTD], 30 semantic dementia [SD], and 29 Alzheimer disease [AD]) underwent fasting blood cholesterol, glucose, and peripheral insulin level analysis. Insulin resistance was calculated using the homeostasis model assessment of insulin resistance (HOMA-IR). These results were compared with a cohort of 19 control subjects. RESULTS: The bvFTD cohort had lower high-density lipoprotein (HDL) cholesterol levels compared with control and AD groups, and increased total cholesterol/HDL ratio and triglyceride levels compared with the control group. The SD cohort had increased triglyceride levels compared with control subjects. Both FTD groups had increased fasting insulin levels and HOMA-IR index compared with the control group, and this remained increased in the subjects with bvFTD compared to subjects with AD. CONCLUSION: Both patients with bvFTD and those with SD have increased triglyceride and insulin levels and lower HDL cholesterol levels compared with controls, suggesting a state of peripheral insulin resistance. These factors have been found to affect prognosis in motor neuron disease favorably, although insulin resistance has been proposed as a mechanism promoting neurodegeneration. We discuss the potential role of metabolism in FTD pathophysiology and progression.

Heritability in frontotemporal dementia: more missing pieces?

Frontotemporal dementia (FTD) is reportedly highly heritable, even though a recognized genetic cause is often absent. To explain this contradiction, we explored the "strength" of family history in FTD, Alzheimer's disease (AD), and controls. Clinical syndromes associated with heritability of FTD and AD were also examined. FTD and AD patients were recruited from an FTD-specific research clinic, and patients were further sub-classified into FTD or AD phenotypes. The strength of family history was graded using the Goldman score (GS), and GS of 1-3 was regarded as a "strong" family history. A subset of FTD patients underwent screening for the main genetic causes of FTD. In total, 307 participants were included (122 FTD, 98 AD, and 87 controls). Although reported positive family history did not differ between groups, a strong family history was more common in FTD (FTD 17.2 %, AD 5.1 %, controls 2.3 %, P < 0.001). The bvFTD and FTD-ALS groups drove heritability, but 12.2 % of atypical AD patients also had a strong family history. A pathogenic mutation was identified in 16 FTD patients (10 C9ORF72 repeat expansion, 5 GRN, 1 MAPT), but more than half of FTD patients with a strong family history had no mutation detected. FTD is a highly heritable disease, even more than AD, and patients with bvFTD and FTD-ALS drive this heritability. Atypical AD also appears to be more heritable than typical AD. These results suggest that further genetic influences await discovery in FTD.

Frontotemporal dementia and its subtypes: a genome-wide association study.

BACKGROUND: Frontotemporal dementia (FTD) is a complex disorder characterised by a broad range of clinical manifestations, differential pathological signatures, and genetic variability. Mutations in three genes-MAPT, GRN, and C9orf72--have been associated with FTD. We sought to identify novel genetic risk loci associated with the disorder. METHODS: We did a two-stage genome-wide association study on clinical FTD, analysing samples from 3526 patients with FTD and 9402 healthy controls. To reduce genetic heterogeneity, all participants were of European ancestry. In the discovery phase (samples from 2154 patients with FTD and 4308 controls), we did separate association analyses for each FTD subtype (behavioural variant FTD, semantic dementia, progressive non-fluent aphasia, and FTD overlapping with motor neuron disease [FTD-MND]), followed by a meta-analysis of the entire dataset. We carried forward replication of the novel suggestive loci in an independent sample series (samples from 1372 patients and 5094 controls) and then did joint phase and brain expression and methylation quantitative trait loci analyses for the associated (p<5 × 10(-8)) single-nucleotide polymorphisms. FINDINGS: We identified novel associations exceeding the genome-wide significance threshold (p<5 × 10(-8)). Combined (joint) analyses of discovery and replication phases showed genome-wide significant association at 6p21.3, HLA locus (immune system), for rs9268877 (p=1·05 × 10(-8); odds ratio=1·204 [95% CI 1·11-1·30]), rs9268856 (p=5·51 × 10(-9); 0·809 [0·76-0·86]) and rs1980493 (p value=1·57 × 10(-8), 0·775 [0·69-0·86]) in the entire cohort. We also identified a potential novel locus at 11q14, encompassing RAB38/CTSC (the transcripts of which are related to lysosomal biology), for the behavioural FTD subtype for which joint analyses showed suggestive association for rs302668 (p=2·44 × 10(-7); 0·814 [0·71-0·92]). Analysis of expression and methylation quantitative trait loci data suggested that these loci might affect expression and methylation in cis. INTERPRETATION: Our findings suggest that immune system processes (link to 6p21.3) and possibly lysosomal and autophagy pathways (link to 11q14) are potentially involved in FTD. Our findings need to be replicated to better define the association of the newly identified loci with disease and to shed light on the pathomechanisms contributing to FTD. FUNDING: The National Institute of Neurological Disorders and Stroke and National Institute on Aging, the Wellcome/MRC Centre on Parkinson's disease, Alzheimer's Research UK, and Texas Tech University Health Sciences Center.

Endogenous progesterone levels and frontotemporal dementia: modulation of TDP-43 and Tau levels in vitro and treatment of the A315T TARDBP mouse model.

Frontotemporal dementia (FTD) is associated with motor neurone disease (FTD-MND), corticobasal syndrome (CBS) and progressive supranuclear palsy syndrome (PSPS). Together, this group of disorders constitutes a major cause of young-onset dementia. One of the three clinical variants of FTD is progressive nonfluent aphasia (PNFA), which is focused on in this study. The steroid hormone progesterone (PROG) is known to have an important role as a neurosteroid with potent neuroprotective and promyelination properties. In a case-control study of serum samples (39 FTD, 91 controls), low serum PROG was associated with FTD overall. In subgroup analysis, low PROG levels were significantly associated with FTD-MND and CBS, but not with PSPS or PNFA. PROG levels of >195 pg/ml were significantly correlated with lower disease severity (frontotemporal dementia rating scale) for individuals with CBS. In the human neuroblastoma SK-N-MC cell line, exogenous PROG (9300-93,000 pg/ml) had a significant effect on overall Tau and nuclear TDP-43 levels, reducing total Tau levels by ∼1.5-fold and increasing nuclear TDP-43 by 1.7- to 2.0-fold. Finally, elevation of plasma PROG to a mean concentration of 5870 pg/ml in an Ala315Thr (A315T) TARDBP transgenic mouse model significantly reduced the rate of loss of locomotor control in PROG-treated, compared with placebo, mice. The PROG treatment did not significantly increase survival of the mice, which might be due to the limitation of the transgenic mouse to accurately model TDP-43-mediated neurodegeneration. Together, our clinical, cellular and animal data provide strong evidence that PROG could be a valid therapy for specific related disorders of FTD.

C9ORF72 repeat expansion in clinical and neuropathologic frontotemporal dementia cohorts.

OBJECTIVE: To determine the frequency of a hexanucleotide repeat expansion in C9ORF72, a gene of unknown function implicated in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), in Australian FTD patient cohorts and to examine the clinical and neuropathologic phenotypes associated with this expansion. METHODS: We examined a clinically ascertained FTD cohort (n = 89) and a neuropathologically ascertained cohort of frontotemporal lobar degeneration cases with TDP-43 pathology (FTLD-TDP) (n = 22) for the C9ORF72 hexanucleotide repeat expansion using a repeat primed PCR assay. All expansion-positive patients were genotyped for rs3849942, a surrogate marker for the chromosome 9p21 risk haplotype previously associated with FTD and ALS. RESULTS: The C9ORF72 repeat expansion was detected in 10% of patients in the clinically diagnosed cohort, rising to 29% in those with a positive family history of early-onset dementia or ALS. The prevalence of psychotic features was significantly higher in expansion-positive cases (56% vs 14%). In the pathology cohort, 41% of TDP-43-positive cases harbored the repeat expansion, and all exhibited type B pathology. One of the 17 expansion-positive probands was homozygous for the "nonrisk" G allele of rs3849942. CONCLUSIONS: The C9ORF72 repeat expansion is a relatively common cause of FTD in Australian populations, and is especially common in those with FTD-ALS, psychotic features, and a strong family history. Detection of a repeat expansion on the 9p21 putative "nonrisk" haplotype suggests that not all mutation carriers are necessarily descended from a common founder and indicates that the expansion may have occurred on multiple haplotype backgrounds.