Anterior insular network disconnection and cognitive impairment in Parkinson's disease.

BACKGROUND: The insula is a central brain hub involved in cognition and affected in Parkinson's disease (PD). The aim of this study was to assess functional connectivity (FC) and betweenness centrality (BC) of insular sub-regions and their relationship with cognitive impairment in PD. METHODS: Whole-brain 3D-T1, resting-state functional MRI and a battery of cognitive tests (CAMCOG) were included for 53 PD patients and 15 controls. The insular cortex was segmented into ventral (vAI) and dorsal (dAI) anterior and posterior sub-regions. Connectivity between insular sub-regions and resting-state networks was assessed and related to cognition; BC was used to further explore nodes associated with cognition. RESULTS: Cognitive performance was significantly lower in PD patients compared to controls (p < 0.01) and was associated with FC of the dAI with default mode network (DMN) (adjusted R2 = 0.37, p < 0.001). In controls, cognitive performance was positively related to FC of the dAI with the fronto-parietal network (FPN) only (adjusted R2 = 0.5, p = 0.003). Regionally, FC of the dAI with the anterior cingulate cortex (ACC) was significantly reduced in PD (F(1,65) = 11, p = 0.002) and correlated with CAMCOG (r = 0.4, p = 0.001). DMN and FPN showed increased BC in PD which correlated with cognition and reduced connectivity of dAI with the ACC (rs = -0.33, p = 0.014 and rs = -0.44, p = 0.001 respectively). CONCLUSIONS: These results highlight the relevance of the insula in cognitive dysfunction in PD. Disconnection of the dAI with ACC was related to altered centrality in the DMN and FPN only in patients. Disturbance in this network triad appears to be particularly relevant for cognitive impairment in PD.

Differential insular cortex sub-regional atrophy in neurodegenerative diseases: a systematic review and meta-analysis.

The insular cortex is proposed to function as a central brain hub characterized by wide-spread connections and diverse functional roles. As a result, its centrality in the brain confers high metabolic demands predisposing it to dysfunction in disease. However, the functional profile and vulnerability to degeneration varies across the insular sub-regions. The aim of this systematic review and meta-analysis is to summarize and quantitatively analyze the relationship between insular cortex sub-regional atrophy, studied by voxel based morphometry, with cognitive and neuropsychiatric deficits in frontotemporal dementia (FTD), Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB). We systematically searched through Pubmed and Embase and identified 519 studies that fit our criteria. A total of 41 studies (n = 2261 subjects) fulfilled the inclusion criteria for the meta-analysis. The peak insular coordinates were pooled and analyzed using Anatomic Likelihood Estimation. Our results showed greater left anterior insular cortex atrophy in FTD whereas the right anterior dorsal insular cortex showed larger clusters of atrophy in AD and PD/DLB. Yet contrast analyses did not reveal significant differences between disease groups. Functional analysis showed that left anterior insular cortex atrophy is associated with speech, emotion, and affective-cognitive deficits, and right dorsal atrophy with perception and cognitive deficits. In conclusion, insular sub-regional atrophy, particularly the anterior dorsal region, may contribute to cognitive and neuropsychiatric deficits in neurodegeneration. Our results support anterior insular cortex vulnerability and convey the differential involvement of the insular sub-regions in functional deficits in neurodegenerative diseases.

Normative brain volumetry derived from different reference populations: impact on single-subject diagnostic assessment in dementia.

Brain imaging data are increasingly made publicly accessible, and volumetric imaging measures derived from population-based cohorts may serve as normative data for individual patient diagnostic assessment. Yet, these normative cohorts are usually not a perfect reflection of a patient's base population, nor are imaging parameters such as field strength or scanner type similar. In this proof of principle study, we assessed differences between reference curves of subcortical structure volumes of normal controls derived from two population-based studies and a case-control study. We assessed the impact of any differences on individual assessment of brain structure volumes. Percentile curves were fitted on the three healthy cohorts. Next, percentile values for these subcortical structures for individual patients from these three cohorts, 91 mild cognitive impairment and 95 Alzheimer's disease cases and patients from the Alzheimer Center, were calculated, based on the distributions of each of the three cohorts. Overall, we found that the subcortical volume normative data from these cohorts are highly interchangeable, suggesting more flexibility in clinical implementation.

LRP10 genetic variants in familial Parkinson's disease and dementia with Lewy bodies: a genome-wide linkage and sequencing study.

BACKGROUND: Most patients with Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies do not carry mutations in known disease-causing genes. The aim of this study was to identify a novel gene implicated in the development of these disorders. METHODS: Our study was done in three stages. First, we did genome-wide linkage analysis of an Italian family with dominantly inherited Parkinson's disease to identify the disease locus. Second, we sequenced the candidate gene in an international multicentre series of unrelated probands who were diagnosed either clinically or pathologically with Parkinson's disease, Parkinson's disease dementia, or dementia with Lewy bodies. As a control, we used gene sequencing data from individuals with abdominal aortic aneurysms (who were not examined neurologically). Third, we enrolled an independent series of patients diagnosed clinically with Parkinson's disease and controls with no signs or family history of Parkinson's disease, Parkinson's disease dementia, or dementia with Lewy bodies from centres in Portugal, Sardinia, and Taiwan, and screened them for specific variants. We also did mRNA and brain pathology studies in three patients from the international multicentre series carrying disease-associated variants, and we did functional protein studies in in-vitro models, including neurons from induced pluripotent stem-like cells. FINDINGS: Molecular studies were done between Jan 1, 2008, and Dec 31, 2017. In the initial kindred of ten affected Italian individuals (mean age of disease onset 59·8 years [SD 8·7]), we detected significant linkage of Parkinson's disease to chromosome 14 and nominated LRP10 as the disease-causing gene. Among the international series of 660 probands, we identified eight individuals (four with Parkinson's disease, two with Parkinson's disease dementia, and two with dementia with Lewy bodies) who carried different, rare, potentially pathogenic LRP10 variants; one carrier was found among 645 controls with abdominal aortic aneurysms. In the independent series, two of these eight variants were detected in three additional Parkinson's disease probands (two from Sardinia and one from Taiwan) but in none of the controls. Of the 11 probands from the international and independent cohorts with LRP10 variants, ten had a positive family history of disease and DNA was available from ten affected relatives (in seven of these families). The LRP10 variants were present in nine of these ten relatives, providing independent-albeit limited-evidence of co-segregation with disease. Post-mortem studies in three patients carrying distinct LRP10 variants showed severe Lewy body pathology. Of nine variants identified in total (one in the initial family and eight in stage 2), three severely affected LRP10 expression and mRNA stability (1424+5delG, 1424+5G→A, and Ala212Serfs*17, shown by cDNA analysis), four affected protein stability (Tyr307Asn, Gly603Arg, Arg235Cys, and Pro699Ser, shown by cycloheximide-chase experiments), and two affected protein localisation (Asn517del and Arg533Leu; shown by immunocytochemistry), pointing to loss of LRP10 function as a common pathogenic mechanism. INTERPRETATION: Our findings implicate LRP10 gene defects in the development of inherited forms of α-synucleinopathies. Future elucidation of the function of the LRP10 protein and pathways could offer novel insights into mechanisms, biomarkers, and therapeutic targets. FUNDING: Stichting ParkinsonFonds, Dorpmans-Wigmans Stichting, Erasmus Medical Center, ZonMw-Memorabel programme, EU Joint Programme Neurodegenerative Disease Research (JPND), Parkinson's UK, Avtal om Läkarutbildning och Forskning (ALF) and Parkinsonfonden (Sweden), Lijf and Leven foundation, and cross-border grant of Alzheimer Netherlands-Ligue Européene Contre la Maladie d'Alzheimer (LECMA).

Retinal vascular calibers associate differentially with cerebral gray matter and white matter atrophy.

Cerebral small-vessel disease is thought to contribute to brain atrophy, but it remains unclear whether it affects the gray matter and white matter atrophy differentially. Retinal vessels provide a direct measure to study cerebral small-vessel disease in vivo. In a cohort of 1065 persons (mean age, 67.5 y and 51% women), from the population-based Rotterdam Study, we investigated how retinal vascular calibers relate to brain atrophy and to gray matter and white matter atrophy separately. Retinal arteriolar and venular calibers were semiautomatically measured on digitized fundus transparencies. Using automated quantification of MRI scans, we obtained whole-brain volume and volumes of gray matter and white matter. Both narrower arteriolar and wider venular calibers were associated with smaller brain volume, independent from each other. These associations were primarily driven by smaller white matter volume, whereas no associations were seen for gray matter volume. Adjustments for cardiovascular risk factors attenuated the results, but wider venular caliber remained borderline significantly associated with smaller white matter volume. Our data provide evidence that cerebral small-vessel disease contributes to brain atrophy primarily by affecting the cerebral white matter.

Heterozygosity for the classical galactosemia mutation does not affect ovarian reserve and menopausal age.

Female patients with classical galactosemia (galactose-1-phosphate uridyltransferase [GALT] deficiency) frequently suffer from premature ovarian failure, despite treatment with a galactose-restricted diet. Earlier research has suggested an association between heterozygosity for GALT mutations and early menopause. This study evaluates the effect of carriership for classical galactosemia on ovarian reserve and menopausal age. Proven female carriers of classical galactosemia were recruited via the Dutch Galactosemia Society. All 58 participants underwent a structured interview regarding fertility, smoking status, and menopause. To determine ovarian reserve, 42 premenopausal GALT carriers underwent ovarian antral follicle count (AFC) by transvaginal ultrasound and early follicular phase blood sampling for hormonal measurement of follicle-stimulating hormone (FSH), inhibin B, and anti-Müllerian hormone (AMH). These ovarian reserve parameters were compared with a cohort of proven fertile women (n = 166). The mean age at menopause in GALT carriers was 49.7 years, which is not different from the mean age at menopause in the general population in the Netherlands. There was no difference in FSH, inhibin B, and AMH levels or in the AFC (when corrected for age and smoking status) between 42 premenopausal GALT carriers and controls. The authors conclude that there is no evidence that GALT mutation carriership affects ovarian reserve or menopausal age.