Two-Year Prognostic Utility of Plasma p217+tau across the Alzheimer's Continuum.

BACKGROUND: Plasma p217+tau has shown high concordance with cerebrospinal fluid (CSF) and positron emission tomography (PET) measures of amyloid-ß (Aß) and tau in Alzheimer's Disease (AD). However, its association with longitudinal cognition and comparative performance to PET Aß and tau in predicting cognitive decline are unknown. OBJECTIVES: To evaluate whether p217+tau can predict the rate of cognitive decline observed over two-year average follow-up and compare this to prediction based on Aß (18F-NAV4694) and tau (18F-MK6240) PET. We also explored the sample size required to detect a 30% slowing in cognitive decline in a 2-year trial and selection test cost using p217+tau (pT+) as compared to PET Aß (A+) and tau (T+) with and without p217+tau pre-screening. DESIGN: A prospective observational cohort study. SETTING: Participants of the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL) and Australian Dementia Network (ADNeT). PARTICIPANTS: 153 cognitively unimpaired (CU) and 50 cognitively impaired (CI) individuals. MEASUREMENTS: Baseline p217+tau Simoa® assay, 18F-MK6240 tau-PET and 18F-NAV4694 Aß-PET with neuropsychological follow-up (MMSE, CDR-SB, AIBL-PACC) over 2.4 ± 0.8 years. RESULTS: In CI, p217+tau was a significant predictor of change in MMSE (ß = -0.55, p < 0.001) and CDR-SB (ß =0.61, p < 0.001) with an effect size similar to Aß Centiloid (MMSE ß = -0.48, p = 0.002; CDR-SB ß = 0.43, p = 0.004) and meta-temporal (MetaT) tau SUVR (MMSE: ß = -0.62, p < 0.001; CDR-SB: ß = 0.65, p < 0.001). In CU, only MetaT tau SUVR was significantly associated with change in AIBL-PACC (ß = -0.22, p = 0.008). Screening pT+ CI participants into a trial could lead to 24% reduction in sample size compared to screening with PET for A+ and 6-13% compared to screening with PET for T+ (different regions). This would translate to an 81-83% biomarker test cost-saving assuming the p217+tau test cost one-fifth of a PET scan. In a trial requiring PET A+ or T+, p217+tau pre-screening followed by PET in those who were pT+ would cost more in the CI group, compared to 26-38% biomarker test cost-saving in the CU. CONCLUSIONS: Substantial cost reduction can be achieved using p217+tau alone to select participants with MCI or mild dementia for a clinical trial designed to slow cognitive decline over two years, compared to participant selection by PET. In pre-clinical AD trials, p217+tau provides significant cost-saving if used as a pre-screening measure for PET A+ or T+ but in MCI/mild dementia trials this may add to cost both in testing and in the increased number of participants needed for testing.

Cross-Sectional and Longitudinal Comparison of Tau Imaging with 18F-MK6240 and 18F-Flortaucipir in Populations Matched for Age, MMSE and Brain Beta-Amyloid Burden.

OBJECTIVES: Longitudinal tau quantification may provide a useful marker of drug efficacy in clinical trials. Different tau PET tracers may have different sensitivity to longitudinal changes, but without a head-to-head dataset or a carefully designed case-matching procedure, comparing results in different cohorts can be biased. In this study, we compared the tau PET tracers, 18F-MK6240 and 18F-flortaucipir (FTP), both cross-sectionally and longitudinally by case-matching subjects in the AIBL and ADNI longitudinal cohort studies. METHODS: A subset of 113 participants from AIBL and 113 from ADNI imaged using 18F-MK6240 and 18F-FTP respectively, with baseline and follow-up, were matched based on baseline clinical diagnosis, MMSE, age and amyloid (Aß) PET centiloid value. Subjects were grouped as 64 Aß- cognitively unimpaired (CU), 22 Aß+ CU, 14 Aß+ mild cognitive impairment (MCI) and 13 Aß+ Alzheimer's disease (AD). Tracer retention was measured in the mesial, temporoparietal, rest of the cortex, and a meta-temporal region composed of entorhinal, inferior/middle temporal, fusiform, parahippocampus and amygdala. T-tests were employed to assess group separation at baseline using SUVR Z-scores and longitudinally using SUVR%/Yr. RESULTS: Both tracers detected statistically significant differences at baseline in most regions between all clinical groups. Only 18F-MK6240 showed statistically significant higher rate of SUVR increase in Aß+ CU compared to Aß- CU in the mesial, meta-temporal and temporoparietal regions. CONCLUSION: 18F-MK6240 appears to be a more sensitive tracer for change in tau level at the preclinical stage of AD.

Regional differences in the reduction in cerebral FDG uptake induced by the ketogenic diet.

BACKGROUND: The postulated benefits of the ketogenic diet in the management of multiple medical conditions have seen more patients who are in therapeutic ketosis attending 18F-FDG PET scans. This study aimed to investigate the effect of ketosis on cerebral glucose metabolism in a clinical PET scanning environment using 18F-FDG uptake as a surrogate marker. METHODS: A retrospective audit was conducted of the brain 18F-FDG uptake in 52 patients who underwent PET scans for possible cardiac sarcoidosis or suspected intracardiac infection, following a ketogenic diet and prolonged fasting. SUVbw for whole brain and separate brain regions was compared with serum glucose and serum ketone body (beta-hydroxybutyrate) levels. RESULTS: The expected negative association between serum glucose levels and whole brain 18F-FDG uptake was confirmed. A reduction in SUVbw due to increasing serum ketones levels was also observed that was independent of and in addition to the effects of glucose. The magnitude of the reduction in SUVbw related to serum glucose level and serum ketone level was found to be greater in the precuneus than in the cerebellum or whole brain. CONCLUSION: In a real-world clinical PET setting, cerebral 18F-FDG uptake appears to be affected by glycaemia and ketonaemia. This means when assessing the brain, both serum glucose and ketone levels need to be considered when SUVs are used to distinguish between pathologic and physiologic states. The magnitude of this effect appears to vary between different brain regions. This regional difference should be taken into consideration when selecting the appropriate brain region for SUV normalisation, particularly when undertaking database comparison in the assessment of dementia.

MilxXplore: a web-based system to explore large imaging datasets.

OBJECTIVE: As large-scale medical imaging studies are becoming more common, there is an increasing reliance on automated software to extract quantitative information from these images. As the size of the cohorts keeps increasing with large studies, there is a also a need for tools that allow results from automated image processing and analysis to be presented in a way that enables fast and efficient quality checking, tagging and reporting on cases in which automatic processing failed or was problematic. MATERIALS AND METHODS: MilxXplore is an open source visualization platform, which provides an interface to navigate and explore imaging data in a web browser, giving the end user the opportunity to perform quality control and reporting in a user friendly, collaborative and efficient way. DISCUSSION: Compared to existing software solutions that often provide an overview of the results at the subject's level, MilxXplore pools the results of individual subjects and time points together, allowing easy and efficient navigation and browsing through the different acquisitions of a subject over time, and comparing the results against the rest of the population. CONCLUSIONS: MilxXplore is fast, flexible and allows remote quality checks of processed imaging data, facilitating data sharing and collaboration across multiple locations, and can be easily integrated into a cloud computing pipeline. With the growing trend of open data and open science, such a tool will become increasingly important to share and publish results of imaging analysis.

Retinal vascular biomarkers for early detection and monitoring of Alzheimer's disease.

The earliest detectable change in Alzheimer's disease (AD) is the buildup of amyloid plaque in the brain. Early detection of AD, prior to irreversible neurological damage, is important for the efficacy of current interventions as well as for the development of new treatments. Although PiB-PET imaging and CSF amyloid are the gold standards for early AD diagnosis, there are practical limitations for population screening. AD-related pathology occurs primarily in the brain, but some of the hallmarks of the disease have also been shown to occur in other tissues, including the retina, which is more accessible for imaging. Retinal vascular changes and degeneration have previously been reported in AD using optical coherence tomography and laser Doppler techniques. This report presents results from analysis of retinal photographs from AD and healthy control participants from the Australian Imaging, Biomarkers and Lifestyle (AIBL) Flagship Study of Ageing. This is the first study to investigate retinal blood vessel changes with respect to amyloid plaque burden in the brain. We demonstrate relationships between retinal vascular parameters, neocortical brain amyloid plaque burden and AD. A number of RVPs were found to be different in AD. Two of these RVPs, venular branching asymmetry factor and arteriolar length-to-diameter ratio, were also higher in healthy individuals with high plaque burden (P = 0.01 and P = 0.02 respectively, after false discovery rate adjustment). Retinal photographic analysis shows potential as an adjunct for early detection of AD or monitoring of AD-progression or response to treatments.

Correlation of MRI-derived apparent diffusion coefficients in newly diagnosed gliomas with [18F]-fluoro-L-dopa PET: what are we really measuring with minimum ADC?

BACKGROUND AND PURPOSE: There is significant interest in whether diffusion-weighted MR imaging indices, such as the minimum apparent diffusion coefficient, may be useful clinically for preoperative tumor grading and treatment planning. To help establish the pathologic correlate of minimum ADC, we undertook a study investigating the relationship between minimum ADC and maximum FDOPA PET uptake in patients with newly diagnosed glioblastoma multiforme. MATERIALS AND METHODS: MR imaging and FDOPA PET data were acquired preoperatively from 15 patients who were subsequently diagnosed with high-grade brain tumor (WHO grade III or IV) by histopathologic analysis. ADC and SUVR normalized FDOPA PET maps were registered to the corresponding CE MR imaging. Regions of minimum ADC within the FDOPA-defined tumor volume were anatomically correlated with areas of maximum FDOPA SUVR uptake. RESULTS: Minimal anatomic overlap was found between regions exhibiting minimum ADC (a putative marker of tumor cellularity) and maximum FDOPA SUVR uptake (a marker of tumor infiltration and proliferation). FDOPA SUVR measures for tumoral regions exhibiting minimum ADC (1.36±0.22) were significantly reduced compared with those with maximum FDOPA uptake (2.45±0.88, P=.0001). CONCLUSIONS: There was a poor correlation between minimum ADC and the most viable/aggressive component of high-grade gliomas. This study suggests that other factors, such as tissue compression and ischemia, may be contributing to restricted diffusion in GBM. Caution should be exercised in the clinical use of minimum ADC as a marker of tumor grade and the use of this index for guiding tumor biopsies preoperatively.

Joint factor and kinetic analysis of dynamic FDOPA PET scans of brain cancer patients.

Kinetic analysis is an essential tool of Positron Emission Tomography image analysis. However it requires a pure tissue time activity curve (TAC) in order to calculate the system parameters. Pure tissue TACs are particularly difficult to obtain in the brain as the low resolution of PET means almost all voxels are a mixture of tissues. Factor analysis explicitly accounts for mixing but is an underdetermined problem that can give arbitrary results. A joint factor and kinetic analysis is proposed whereby factor analysis explicitly accounts for mixing of tissues. Hence, more meaningful parameters are obtained by the kinetic models, which also ensure a less ambiguous solution to the factor analysis. The method was tested using a cylindrical phantom and the 18F-DOPA data of a brain cancer patient.

Beta-amyloid burden in the temporal neocortex is related to hippocampal atrophy in elderly subjects without dementia.

OBJECTIVE: To investigate whether global and regional beta-amyloid (Abeta) burden as measured with 11C Pittsburgh compound B (PIB) PET is associated with hippocampal atrophy characterized using MRI in healthy controls and patients with amnestic mild cognitive impairment (aMCI) or Alzheimer disease (AD). METHODS: Ninety-two elderly healthy controls, 32 subjects with aMCI, and 35 patients with AD were imaged using 11C-PIB PET and MRI. Hippocampal volume was measured and PIB standardized uptake value ratio was extracted after partial volume correction within 41 regions of interest. Global, regional, and voxel-based correlations between PIB and hippocampal volume were computed for each group. RESULTS: In healthy control participants with elevated neocortex PIB retention, significant correlation was found between PIB retention in the inferior temporal region and hippocampal volume using both region-based and voxel-based approaches. No correlation was found in any other group. CONCLUSIONS: The strong correlation between hippocampal atrophy and beta-amyloid (Abeta) burden in the Pittsburgh compound B-positive healthy control group suggests that Abeta deposition in the inferior temporal neocortex is related to hippocampal synaptic and neuronal degeneration.

Inhibitors of tripeptidyl peptidase II. 2. Generation of the first novel lead inhibitor of cholecystokinin-8-inactivating peptidase: a strategy for the design of peptidase inhibitors.

The cholecystokinin-8 (CCK-8)-inactivating peptidase is a serine peptidase which has been shown to be a membrane-bound isoform of tripeptidyl peptidase II (EC 3.4.14.10). It cleaves the neurotransmitter CCK-8 sulfate at the Met-Gly bond to give Asp-Tyr(SO(3)H)-Met-OH + Gly-Trp-Met-Asp-Phe-NH(2). In seeking a reversible inhibitor of this peptidase, the enzymatic binding subsites were characterized using a fluorimetric assay based on the hydrolysis of the artificial substrate Ala-Ala-Phe-amidomethylcoumarin. A series of di- and tripeptides having various alkyl or aryl side chains was studied to determine the accessible volume for binding and to probe the potential for hydrophobic interactions. From this initial study the tripeptides Ile-Pro-Ile-OH (K(i) = 1 microM) and Ala-Pro-Ala-OH (K(i) = 3 microM) and dipeptide amide Val-Nvl-NHBu (K(i) = 3 microM) emerged as leads. Comparison of these structures led to the synthesis of Val-Pro-NHBu (K(i) = 0.57 microM) which served for later optimization in the design of butabindide, a potent reversible competitive and selective inhibitor of the CCK-8-inactivating peptidase. The strategy for this work is explicitly described since it illustrates a possible general approach for peptidase inhibitor design.

Elevated plasma fibrinogen and increased fibrin turnover among healthy women who both smoke and use low-dose oral contraceptives--a preliminary report.

Among users of low-dose oral contraceptives (OC), cardiovascular diseases occur mainly in smokers. The mechanisms by which OC and smoking increase the risk for arterial thrombotic risk have not been adequately explained. Epidemiological evidence suggests that changes in blood coagulation and fibrinolysis may play an important role as determinants of thrombotic events. Therefore, we have investigated the associations of OC and smoking with haemostatic variables among 194 premenopausal healthy women. Fourty women were current users of low-dose OC and 62 women were smokers. After adjustment for age and body mass index, mean values of factor XIIa, factor VII activity and antigen, fibrinogen, D-dimer, global fibrinolytic capacity were significantly higher in OC users than in non-users. Mean levels of PAI activity and t-PA antigen were significantly lower in OC users than in non-users. Smokers had significantly higher mean values of fibrinogen than non-smokers. Two-way analysis of variance showed that the differences in mean levels of fibrinogen and D-dimer between OC users and non users were restricted to smokers. The positive and significant interactions between OC use and smoking in their effects on haemostatic variables were consistent with respect to age and type of OC. These preliminary data suggest that elevated plasma levels of fibrinogen and intravascular fibrin deposition may play a role in the pathogenesis of arterial thrombotic disease among women who are both low-dose OC users and smokers.

Population correlates of coagulation factor VII. Importance of age, sex, and menopausal status as determinants of activated factor VII.

Factor VII coagulant activity (FVIIc) has been found to be related to cardiovascular risk factors and may be an independent predictor of coronary heart disease (CHD). Whether these associations are due to changes in FVII activation rather than FVII concentration remain unclear. Therefore, we investigated the relationships between activated factor VII (FVIIa) and CHD risk factors in healthy subjects (336 men and 348 women) aged 25 to 64 years. In addition to direct quantitation of FVIIa by use of a recombinant, truncated tissue factor, FVIIc and factor VII antigen (FVII:Ag) levels were measured by standard procedures. There were highly significant correlations between the three techniques of FVII assay (r > + .55). Plasma FVIIc and FVIIa levels increased with age in both sexes, but the rate of rise was significantly greater in women than men. At younger ages, mean values of FVIIc and FVIIa were significantly lower in women than men, whereas at older ages the reverse was observed. After adjustment for age, postmenopausal women had significantly higher mean levels of FVIIc and FVIIa than did premenopausal women. Hormone replacement therapy significantly reversed the rise in FVIIc in postmenopausal women, and a similar trend in FVIIa was also observed. Age-, sex-, and menopause-related changes in FVIIc were partly explained by a higher proportion of fully active FVII molecules, as indicated by significant differences in the FVIIa-to-FVII:Ag ratio. Oral contraceptive use was associated with high FVIIc levels, and this effect was mainly due to an increase in FVII:Ag. Levels of FVIIa were positively correlated with serum cholesterol concentrations in both sexes. There were no strong associations between FVIIa levels and other CHD risk factors, including smoking habits, alcohol consumption, blood pressure, obesity, glucose, triglycerides, and serum lipoprotein(a) concentrations. Multiple regression analysis showed independent effects of age and cholesterol levels on FVIIa in men, whereas age and menopausal status were the main predictors of FVIIa in women. Our results show that FVII activation is associated with CHD risk factors. These findings are consistent with a possible role for FVII in the pathogenesis of CHD. Furthermore, our data suggest that the dramatic rise in CHD incidence in postmenopausal women as well as the cardioprotective effect of estrogen may be mediated through FVII and blood coagulation.

A radioimmunoassay for the tripeptide Gly-Trp-Met, a major metabolite of endogenous cholecystokinin in brain.

We developed a specific and sensitive radioimmunoassay for the tripeptide Gly-Trp-Met (GWM) after its derivatization with p-benzoquinone. Measurable amounts of endogenous GWM-like immunoreactivity (GWM-ir), coeluting in HPLC with authentic GMW were detected in the medium of depolarized slices of rat cerebral cortex. The tripeptide GWM appears as the major inactive CCK-8 metabolite since a major fraction of CCK-8-ir released from the slices was apparently recovered in the medium as GWM. In addition, in the presence of the serine reagent diisopropylfluorophosphate, a strong decrease of GWM formation was observed to accompany the corresponding increase of CCK-8-ir recovery in medium. The present study confirms that (a) serine peptidase(s) is(are) responsible for inactivating endogenous CCK-8 in brain as previously proposed (Rose et al. Proc Natl Acad Sci USA 1988; 85:8326).

Characterization and inhibition of a cholecystokinin-inactivating serine peptidase.

A cholecystokinin (CCK)-inactivating peptidase was purified and identified as a membrane-bound isoform of tripeptidyl peptidase II (EC 3.4.14.10), a cytosolic subtilisin-like peptidase of previously unknown functions. The peptidase was found in neurons responding to cholecystokinin, as well as in non-neuronal cells. Butabindide, a potent and specific inhibitor, was designed and shown to protect endogenous cholecystokinin from inactivation and to display pro-satiating effects mediated by the CCKA receptor.

Thyroid hormone residues are released from thyroglobulin with only limited alteration of the thyroglobulin structure.

We have tried to characterize thyroglobulin (Tg) degradation products in purified pig thyroid lysosomes to determine whether the release of thyroid hormone residues from Tg involves a random proteolytic attack or discrete and selective cleavage reactions. The intralysosomal soluble protein fraction was prepared by osmotic pressure-dependent lysis of lysosomes purified by isopycnic centrifugation on Percoll gradients. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed the presence of a fraction of Tg (5-10% of total lysosomal protein) with the same molecular weight as that of the intact Tg subunit. This high molecular weight Tg was the only intralysosomal species detected by Western blot using antipig Tg antibodies. In nondenaturing conditions, lysosomal Tg (LTg) identified by radioimmunoassay was in the form of a dimer with a sedimentation coefficient lower than that of either iodinated Tg (colloid Tg) or noniodinated Tg (microsomal Tg). LTg had a lower iodine content than colloid Tg:9-12 versus 39-42 iodine atoms/molecule. Pronase hydrolysates of LTg did not contain any 3,5,3',5'-tetraiodo-L-thyronine or 3,3',5-triiodo-L-thyronine residues detectable by reverse-phase high pressure liquid chromatography; iodine present in LTg was in the form of iodotyrosines. Under reducing conditions, LTg almost completely disappeared and gave rise to various polypeptides of smaller size. These results suggest that Tg transferred to lysosomes is subjected to selective proteolytic cleavage reaction(s) that release thyroid hormone residues. This early step would lead to the formation of hormone-depleted Tg molecules that are cleaved at discrete sites, the resulting polypeptides remaining bound through disulfide bonds to yield Tg molecules with an apparently normal size and a slightly altered structure.

In vitro studies of the thyroglobulin degradation pathway: endocytosis and delivery of thyroglobulin to lysosomes, release of thyroglobulin cleavage products--iodotyrosines and iodothyronines.

UNLABELLED: Iodinated thyroglobulin stored in the thyroid follicular lumen is subjected to an internalization process and thought to be transferred into the lysosomal compartment for proteolytic cleavage and thyroid hormone release. In the present study, we have designed in vitro models to study: 1) the transfer of endocytosed thyroglobulin into lysosomes, and 2) the intracellular fate of free thyroid hormones and iodinated precursors generated by intralysosomal proteolysis of thyroglobulin. Open follicles prepared from pig thyroid tissue by collagenase treatment were used to probe the delivery of exogenous thyroglobulin to lysosomes via the differentiated apical cell membrane. Open follicles were incubated with pure [125I]thyroglobulin with or without unlabeled thyroglobulin in the presence or in the absence of chloroquine. Subcellular fractionation on a Percoll gradient showed that [125I]thyroglobulin was internalized and present in low (for the major part) and high density thyroid vesicles. In chloroquine-treated open follicles, we observed the appearance of a definite fraction of [125I]thyroglobulin in a lysosome subpopulation having the expected properties of phagolysosomes or secondary lysosomes. In contrast, in control open follicles, the amount of [125I]thyroglobulin or degradation products found in high density vesicles was lower and associated with the bulk of lysosomes, i.e., primary lysosomes. The content in thyroglobulin and degradation products of lysosomes at steady-state was analyzed by Western blot using polyclonal anti-pig thyroglobulin antibodies. Under reducing conditions, immunoreactive thyroglobulin species correspond to polypeptides with molecular weights ranging from 130,000 to less than 20,000. The presence of free thyroid hormones and iodotyrosines inside lysosomes and their intracellular fate was studied in dispersed thyroid cells labeled with [125I]iodide. Neo-iodinated [125I]thyroglobulin gave rise to free [125I]T4 which was secreted into the medium. In addition to released [125I]T4, a fraction of free [125I]T4 was identified inside the cells. Lysosomes isolated from dispersed thyroid cells did not contain significant amounts of free [125I]T4. The free intracellular [125I]T4 fraction seems to represent an intermediate 'hormonal pool' between thyroglobulin-bound T4 and secreted T4. Evidence for such a precursor-product relationship was obtained from pulse-chase experiments. IN CONCLUSION: 1) open thyroid follicles have the ability to internalize thyroglobulin by a mechanism of limited capacity and to address the endocytosed ligand to lysosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

[The alcoholic in the post-withdrawal periods. Conditions of their care and results after 2 years. Apropos of 200 cases]. / L'alcoolique en post-cure. Modalités de prise en charge et résultats après deux ans. A propos de deux cents cas.

The authors report on two years of their experience in caring for alcoholics after withdrawal. In evaluating results, improvements in asthenia, depression, and anxiety, as well as in the aptitude to resume a normal life, with satisfactory familial, conjugal, sexual, professional and social achievements, are considered. Overall results are given in terms of abstinence, relapse, hospitalization, and normalization of behavior and character.