Plasma p-tau231 increases at one-year intervals in cognitively unimpaired subjects

doi:10.21203/rs.3.rs-2995638/v1

Download PDF

Research Article

Plasma p-tau231 increases at one-year intervals in cognitively unimpaired subjects

https://doi.org/10.21203/rs.3.rs-2995638/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

BACKGROUND: Plasma biomarkers indicative of Alzheimer's disease pathology constitute a non-invasive tool for diagnosing and classifying the disease. They are altered even in preclinical stages. Nonetheless, it is necessary to better understand their properties so they can be helpful in a clinical context.

METHODS: We have evaluated plasma phosphorylated (p)-tau231 in a group of 146 cognitively unimpaired subjects in sequential visits and correlated their levels with different phenotypic traits. ATN status was defined based on CSF biomarkers.

RESULTS: P-tau231 levels increase sequentially at intervals close to one year. This increase occurs even in A-T-N- subjects. Basal levels of p-tau231 correlate negatively with memory tests only in subjects with a sufficient amyloid load.

CONCLUSIONS: P-tau231 is a sensitive marker for detecting early signs of neuronal network impairment by amyloid. Longer-term studies are needed to characterize better p-tau231 evolution and its relationship with the different phases of the disease.

Alzheimer’s Disease

Plasma biomarkers

p-tau231

presymptomatic stages

longitudinal study

Alzheimer's disease (AD) is a neurodegenerative process characterized by the accumulation of extracellular plaques of amyloid-β (Aβ) and intracellular neurofibrillary tangles of phosphorylated tau (p-tau) in the brain. These pathological changes occur decades before the first symptoms appear and are reflected in the concentration of these proteins in the cerebrospinal fluid (CSF). During the AD continuum, including the preclinical stages, total tau (t-tau) and p-tau levels are elevated compared with non-AD concentrations, and the opposite is found for Aβ42 and Aβ42/40 (decreased CSF concentration in Aβ-positive people) [1]. This provides a valuable therapeutic window for future disease-modifying treatments, but cost-effective, non-invasive, and population-level useful biomarkers are needed to identify suitable patients.

In the last few years, the diagnosis of AD has undergone a revolution with the development of high-sensitivity assays that identify markers in plasma such as Aβ42/Aβ40, phosphorylated tau at Thr181 (p-tau181), Thr217 (p-tau217), Thr231 (p-tau231), neurofilament light (NfL), and glial fibrillary acid protein (GFAP) [2–7], opening up the possibility of avoiding other invasive, or more expensive and less available methods such as lumbar puncture (LP) or positron emission tomography (PET) scans.

With disease-modifying treatments on the verge of approval, it becomes necessary to give clinical and biological significance to these markers, so they provide us with accurate and reliable information in the asymptomatic phases of AD. In this regard, plasma markers offer valuable opportunities. Their accessibility allows sequential assessment, which may increase their diagnostic potential [8]. Thus, we can compare the evolution of each subject intra-individually and not with population values. However, these markers also present challenges, and many questions remain to be answered. It is not yet known which marker is most useful at which stage of the disease, what time intervals are necessary to detect representative changes, nor the relationship of these temporal increments with the phenotype.

P-tau231 has emerged as one of the most promising plasma biomarkers. Previous studies in CSF and, more recently in plasma, suggest that p-tau231 alters very early, along with the first Aβ changes [5, 9]. Although its performance has been evaluated in patients with mild cognitive impairment and AD in cross-sectional studies, longitudinal changes of p-tau231 levels in the preclinical stages of AD need to be assessed. In this longitudinal study, we aim to provide information about the short-term evolution of p-tau231 in the preclinical stages of AD and its relationship with other parameters, such as neuropsychological findings or imaging markers.

2.1. Participants

We conducted this analysis with volunteers of the ‘Valdecilla Cohort for the study of memory and brain aging’ from the Memory Unit of the Marqués de Valdecilla University Hospital [10, 11]. The Valdecilla cohort is designed to better understand the preclinical phases of AD. It is composed of cognitively unimpaired (CU) volunteers who responded to an open call in the local media. Inclusion criteria are 1) age ≥ 55 years; 2) signed consent for the collection and storage of biological samples and the performance of invasive techniques. Exclusion criteria are 1) cognitive impairment (determined by Clinical Dementia Rating (CDR) > 0; 2) major psychiatric pathology; 3) major systemic disease or sensory deprivation impairing the performance of the cognitive tests; 4) any contraindication to perform the complementary tests such as anticoagulation or claustrophobia.

At baseline, all participants were assessed with a comprehensive neuropsychological (NPS) battery conducted by neuropsychologists specialized in dementia, a brain magnetic resonance imaging (MRI), and an 18-fluorodeoxyglucose positron emission tomography (FDG-PET); DNA samples were extracted for genetic analyses, and CSF AD markers were determined (Aβ42, Aβ40, p-tau181 and t-tau). Annual follow-ups include plasma collection and a NPS assessment. One hundred and forty-six Caucasian participants were studied for baseline plasma p-tau231, one hundred and twenty-three had data from the follow-up visit, and sixteen for a second follow-up visit. All participants remained CU during the study period.

2.2. Plasma and CSF collection

Baseline plasma and CSF extractions were performed on the same day, between 9 and 10 AM, with a difference of fewer than 30 minutes between them. Our institution is part of the Alzheimer's Association quality control program, and we follow international recommendations for plasma and CSF collection and storage [12, 13]. Aβ, p-tau, and t-tau values were determined using Fujirebio's automated immunoassay analyzer Lumipulse G600 II [14].

Plasma samples were obtained following the standardized operating procedure described elsewhere [15]. In short, the blood is stored in 10 ml EDTA tubes and kept cold until processing within the next three hours. Then, it is centrifuged at 1800 g for 10 minutes. The supernatant is stored in polypropylene tubes in volumes of 500 µl and frozen at -80°C until analyzed at the Clinical Neurochemistry Laboratory at the University of Gothenburg, Sweden. Plasma P-tau231 concentration was measured using an in-house ultrasensitive Single molecule array (Simoa) assay on an HD-X Analyzer (Quanterix, Billerica, MA, USA), as previously described in detail [9].

2.3. CSF biomarkers

Participants were categorized according to ATN classification [16] based on their CSF biomarkers at baseline. The cut-off points were established using an unbiased Gaussian mixture modeling [17]. We have dichotomized these variables and considered Aβ-positive (A+) when CSF Aβ42/40 ratio < 0.076, tau-positive (T+) when CSF p-tau181 > 73.2 pg/ml, and neurodegeneration-positive (N+) if CSF t-tau > 543 pg/ml. 91 participants were A-T-N-, 40 A + T-N- and 15 A + T + N+.

2.4. Magnetic Resonance and PET Imaging

All MRI scans were performed on the same 3T Philips Medical Systems MRI scanner with an 8-channel head coil. To determine the volume of the different structures, a sagittal T1-weighted MPRAGE sequence was used (170 slices, 1,2 mm voxel size, 9º of flip angle and shortest echo and repetition times) with subsequent processing as described in previous publications [10].

The production of ¹⁸F-FDG and PET images was carried out in our hospital's Department of Nuclear Medicine. ¹⁸F was obtained using the 18O(p,n)18F nuclear reaction in a cyclotron PET Trace (General Electric Healthcare, Wisconsin, USA) and ¹⁸F-FDG scans were acquired in a Siemens Biograph LSO Pico 3D equipment (Siemens Healthcare Molecular Imaging, Illinois, USA). Subjects were administered intravenously with 3–4MBq/kg ¹⁸F-FDG. Image acquisition consisted of a static image acquired 30–45 min after tracer injection. Images were reconstructed on a 128 x 128 matrix using the ordered subsets expectation maximization iterative method (six iterations and 16 subsets, zoom 2.5, filter FWHM 2 mm and sinogram trim factor 1.5). The axial slices were reoriented parallel to the frontal-occipital axis. The semiquantitative analysis of each study was performed using the Scenium ® program integrated into the Siemens Syngo.via Neurology software (Siemens CTI Molecular Imaging, Knoxville, TN, USA).

2.5. ApoE testing

Apolipoprotein E (ApoE) genotype was determined by TaqMan SNP genotyping assays (Applied Biosystems, Foster City, CA, United States). Subjects carrying ≥ 1 copy of the ε4 allele were considered ε4 + and the rest were considered ε4-.

2.6. Neuropsychological tests

Participants in our cohort performed a comprehensive neuropsychological battery designed to detect early signs of AD. It includes several tests to evaluate the different cognitive domains. For memory assessment, we used the validated Spanish version of the Free and Cued Selective Reminding Test (FCSRT) [18], a test designed to measure verbal learning and memory through the use of a list learning. We have considered different items such as the total free recall (TFR), total recall (TR), delayed free recall (DFR) and delayed total recall (DTR). For narrative memory we used the logical memory (LM) subtest of the Weschler Memory Scale-III [19], that is based on the telling of two stories that are recalled in an immediate and delayed form. In this test, we took into account the total delayed units (LMDU). We also performed the Spanish version of the Face Name Associative Memory Exam (FNAME), a highly demanding face-name associative memory exam [20]. It consists of asking subjects to recall sixteen faces associated with a name and an occupation each. The first section includes initial recall of face-occupation and face-name pairs, followed by immediate recall of the name and occupation associated with each face. After thirty minutes, the subject is asked to recall as much of the information associated with each face as possible. The total value (TFNAME) is the number of all names and occupations recalled throughout the test and it is the measure we have considered for this study. The executive functions were assessed by means of the two parts of the Trail Making Test (TMT-A and TMT-B) [21].

2.7. Statistical analysis

We used Shapiro test to check the normality assumption. The baseline p-tau231 values deviated from normality; levels at one year of follow-up and the change in p-tau231 levels from baseline to one year follow-up showed a normal distribution. We used Student's t-test for paired samples to analyze the differences between p-tau231 values at baseline and at follow-up. We also used Student's test-test for paired samples after stratifying subjects according to their ATN group.

To study the longitudinal changes of p-tau231 levels, we performed a Lineal Mixed Model (LMM), with p-tau231 value as the dependent variable and sample point as the main predictor. We included age, sex, APOE ε4 status and ATN group as covariates.

We used Spearman's Rho to study the correlation between the plasma biomarker level and the phenotype of the subjects. Thus, we correlated baseline p-tau231 values with MRI measures (right and left hippocampal volume), PET-FDG (regional metabolism in right and left hippocampus, right and left precuneus, and globally) and with the main outputs of FCSRT, FNAME, LM and TMT test. We also correlated baseline p-tau231 with cognitive tests stratified by the ATN group. Afterward, we selected the significant results and adjusted for covariates using a univariate general linear model with cognitive measures as the dependent variable. P-tau231 basal levels were transformed using box cox to resemble a normal distribution.

Statistical analyses were performed using SPSS Statistics V.20.0 (IBM, NY, USA) and R Statistical Software (version 2.14.0; R Foundation for Statistical Computing, Vienna, Austria).

3.1. Sample description

The sample includes 146 cognitively unimpaired subjects (average Mini-Mental State Examination (MMSE) score of 28.8 ± 1.5 and average DTR of 14.7 ± 1.95), with a mean age of 64.7 ± 8.33 years. 71.9% were women. The proportion of APOE ɛ4 carriers was 29.4%; and 37.7% of subjects had at least one positive AD marker in the CSF (Table 1). The average time between the collection of the baseline plasma samples and the first follow-up was 267.3 ± 86.5 days, and between the first and second follow-up was 343.7 ± 62.1 days.

Table 1

Baseline characteristics of the subjects.
Characteristic	N = 146
Females, n. (%)	105 (71.9%)
Age, mean (SD)	64.7 (8.3)
APOE ε4 carrier, n. (%)	43 (29.4%)
MMSE (0–30), mean (SD)	28.8 (1.5)
FCSRT delayed total recall (0–16), mean (SD)	14.8 (2.4)
CSF Biomarkers
Aβ40, mean (SD), pg/ml	10577.6 (3256.5)
Aβ42, mean (SD), pg/ml	796.1 (327.4)
Ratio Aβ42/40, Mean (SD)	0.076 (0.02)
Total-tau, mean (SD), pg/ml	336.4 (147.3)
Phosphorylated-tau, mean (SD), pg/ml	45.2 (28.1)
ATN group, n. (%)
A-T-N-	91 (62.3%)
A + T-N-	40 (27.4%)
A + T + N+	15 (28.1%)
Abbreviations: n, number of subjects. SD, standard deviation. MMSE, mini-mental state examination. FCSRT, Free and Cued Selective Reminding Test. CSF, cerebrospinal fluid. Aβ, amyloid beta. A, amyloid. T, tau. N, neurodegeneration.

3.2. Longitudinal analysis

Plasma p-tau231 was analyzed in 146 subjects at baseline and 123 at first follow-up. We had a second follow-up determination only for 16 individuals. The mean baseline p-tau231 was 11.4 pg/ml ± 5.98 and 13.3 pg/ml ± 6.04 at first follow-up. In the limited sample of the second follow-up visit p-tau231 was 16.4 pg/ml ± 7.39. The difference between baseline and first follow-up levels was statistically significant (-1.2 pg/ml; 95%CI -1.22 to -2.77; p-value < 0.0001). Compared with the second follow-up, baseline levels were also significantly higher (-3.50 pg/ml; 95%CI -6.10 to -0.93; p-value 0.01). The difference between the first follow-up determination and the second was statistically significant as well (-1.81 pg/ml; 95%CI -3.59 to -0.03; p-value 0.046) (Fig. 1).

When stratifying by ATN group, in the A-T-N-, the mean baseline p-tau231 was 10.1 pg/ml (± 5.00) and at first year follow-up it was 11.9 pg/ml (± 4.51). In this group, the mean difference was 1.79 pg/ml (95% CI=-2.82 to -0.76; p-value = 0.001). In the A + T-N- group, the mean baseline p-tau231 value was 11.8 pg/ml (± 5.24) and at follow-up 14.2 pg/ml (± 6.4). The difference was also significant in this group, with a value of 2.36 pg/ml (95% CI=-3.56 to -1.16; p-value = 0.0003). Finally, in the A + T + N + group, the mean value of p-tau231 at baseline was 17.4 pg/ml (± 8.0) and at follow-up 19.6 pg/ml (± 8.88). In the A + T + N + group, the average difference was not significant, with a value of 2.24 pg/ml (95% CI= -5.83 to -1.34; p-value = 0.2) (Fig. 2).

Next, to study longitudinal changes in p-tau231 values considering the influence of other variables such as age, sex, presence of APOE ɛ4 and ATN group we used a lineal mixed model. We estimated an increase of 1.93 p-tau231 units per follow-up visit (p-value = 3.94E-7). Sex did not significantly influence the p-tau231 growth slope between visits, but the effect of age was borderline significant (β = 0.14 p-value = 0.10 and β=-1.60 p-value = 0.052, respectively). APOE ɛ4 carriers showed a predicted increase in p-tau231 of 2.79 units over non-carriers (p-value = 0.01), and the A + T + N + group presented an estimated 3.91 units higher than the A-T-N- group (p-value = 0.02). The ATN groups showed no interactions with the different follow-up visits in the growth rate of p-tau231 (Fig. 3).

3.3. Phenotypic correlations

We correlated p-tau231 plasma levels and their rate of change between baseline and the first follow-up visit with a wide range of phenotypic traits (Table 2).

Table 2

Correlation between baseline plasma p-tau231 and phenotype.
				Basal plasma p-tau231 (pg/ml)	Plasma p-tau231 change between baseline and first follow-up (pg/ml)
		N		Spearman’s Correlation coefficient	Spearman’s Correlation coefficient
NPS	LMDU	146	Rho	-0.16	-0.15
	LMDU	146	p-value	0.057	0.09
	DFR	146	Rho	-0.12	-0.09
	DFR	146	p-value	0.14	0.33
	DTR	144	Rho	-0.25	-0.03
	DTR	144	p-value	0.002	0.77
	TMT-A	146	Rho	0.16	0.07
	TMT-A	146	p-value	0.051	0.41
	TMT-B	139	Rho	0.10	0.07
	TMT-B	139	p-value	0.22	0.43
	TFNAME	146	Rho	-0.25	0.03
	TFNAME	146	p-value	0.002	0.76
MRI	Left hippocampus	107	Rho	0.12	0.01
	Left hippocampus	107	p-value	0.20	0.94
	Right hippocampus	107	Rho	-0.02	0.01
	Right hippocampus	107	p-value	0.85	0.88
FDG PET	Average	136	Rho	-0.05	-0.02
	Average	136	p-value	0.59	0.84
	Right precuneus	136	Rho	-0.03	-0.07
	Right precuneus	136	p-value	0.68	0.42
	Left precuneus	136	Rho	-0.03	-0.04
	Left precuneus	136	p-value	0.76	0.66
	Right hippocampus	136	Rho	-0.09	0.06
	Right hippocampus	136	p-value	0.31	0.52
	Left hippocampus	136	Rho	-0.01	0.08
	Left hippocampus	136	p-value	0.16	0.36
Abbreviations: NPS, neuropsychological. MRI, magnetic resonance imaging. FDG PET, fluorodeoxyglucose positron emission tomography. N, number of subjects. p value, statistical significance. Rho, correlation coefficient. LMDU, total delayed units in Logical Memory test. DFR, delayed free recall in Free and Cued Selective Reminding test. DTR, Delayed Total Recall. TMT-A, Trail Making Test part A. TMT-B, Trail Making Test part B. TFNAME, total value of Face Name Associative Memory Exam.

Basal levels of p-tau231 showed no correlation with the total right (r=-0.01; p-value = 0.85) or left (r=-0.12; p-value = 0.23) hippocampal volume. Nor did the p-tau231 increment correlate significantly with left (r = 0.01; p-value = 0.94) or right (r = 0.01; p-value = 0.88) hippocampal volume. Uptake of FDG-PET did not correlate significantly with baseline p-tau231 values in different regions of interest, such as right precuneus (r=-0.03; p-value = 0.68), left precuneus (r=-0.03; p-value = 0.76), right hippocampus (r=-0.08; p-value = 0.31), left hippocampus (r=-0.11; p-value = 0.16) and neither with global average uptake (r=-0.04; p-value = 0.59).

However, baseline p-tau231 values did show a correlation with different neuropsychological tests, such as the DTR of the FCSRT (r=-0.25; p-value = 0.002) and with the TFNAME (r=-0.25; p-value = 0.002). These tests did not correlate with the change of p-tau231 between visits (r=-0.026; p-value = 0.77 and r = 0.03; p-value = 0.76 respectively).

To better understand our results, we stratified the baseline correlations of p-tau231 with neuropsychological tests by the ATN groups. P-tau231 levels did not correlate significantly with TFNAME in the A-T-N- group (r=-0.03; p-value = 0.75), but it did in the amyloid-positive groups, in which the magnitude of the correlation increased progressively: A + T-N- (r=-0.37; p-value = 0.02) and A + T + N+ (r=-0.67; p-value = 0.01) (Table 3). We further examined the association between baseline p-tau231 and TFNAME accounting by ATN and other covariates by a general lineal model. Using transformed p-tau231 as a dependent variant, we found that in the A + T-N- group the correlation with TFNAME remained significant (p-value = 0.04) after adjusting for age and sex. This did not occur in the A + T + N + group, though the number of individuals included in this analysis was limited (N = 14).

Table 3

Correlation between baseline plasma p-tau231 and cognitive tests stratified by ATN group.
	Cognitive test	A-T-N-		A + T-N-		A + T + N+
		Rho	p-value	Rho	p-value	Rho	p-value
Plasma p-tau231	LMDU	0.01	0.88	-0.16	0.32	-0.33	0.25
	DFR	-0.03	0.77	-0.04	0.8	-0.43	0.12
	DTR	-0.12	0.27	-0.18	0.27	-0.43	0.12
	TMT-A	0.02	0.86	0.02	0.9	0.47	0.08
	TMT-B	-0.05	0.67	0.01	0.96	0.53	0.75
	TFNAME	-0.03	0.75	-0.37	0.02	-0.67	0.01
Abbreviations: p value, statistical significance. Rho, correlation coefficient. LMDU, total delayed units in Logical Memory test. DFR, delayed free recall in Free and Cued Selective Reminding test. DTR, Delayed Total Recall. TMT-A, Trail Making Test part A. TMT-B, Trail Making Test part B. TFNAME, total value of Face Name Associative Memory Exam. A, amyloid. T, tau. N, neurodegeneration.

Novel plasma biomarkers for AD are a promising tool for diagnosing and classifying patients in hospital and primary care settings. Among them, p-tau231 rises in plasma very early and allows the detection of subjects at risk for AD [5, 9]. Previous studies in cognitively unimpaired individuals modelling the trajectory of p-tau231 showed that it increased significantly with a range of only 26.4 centiloids on Aβ PET [5]. In the same study, p-tau217 levels also raised very early but required a higher threshold of amyloid pathology [5]. On the other hand, p-tau181 is a very specific marker of AD and predicts cognitive impairment and hippocampal atrophy within one year, but it only increases significantly in plasma with much higher amyloid loads [5, 22]. The results of our study support the hypothesis that plasma p-tau231 changes occur very early, in the preclinical phase of AD, and are detectable even in individuals that, based on CSF biomarker results, would be considered as not in the AD continuum.

In a cognitively healthy population of, on average, 64.8 years, we have seen that p-tau231 increases sequentially in samples obtained with time differences of approximately one year. This increase was significantly detectable even in the A-T-N- group. Although it could constitute an ultra-early sign of amyloid dysmetabolism, its significance is still unclear and does not correlate with any cognitive, functional, or structural trait. To clarify this aspect of our findings, longer-term studies determining p-tau231 in A-T-N- subjects are necessary. In further studies, it would be interesting to check the evolution of p-tau231 in subjects who convert from A- to A + during follow-up. However, we have not been able to assess this point because we do not count with serial CSF measurements in our cohort. A similar trend of increase of p-tau231 from baseline to the first follow-up visit in A + T-N- and A + T + N + was found, though this was only significant in A + T-N-, which could be explained by the low numbers of the A + T + N + group (N = 12). This is a limitation of our study as some of the strata has low numbers, therefore, we might be underpowered for some of the analysis.

The linear mixed model adjusting, by ATN and other relevant covariates, estimated that the increase from sample point to sample point was of 1.93 units of p-tau231, and we did not find an interaction with the ATN groups; therefore, the slopes of the increase that we observed in the three ATN groups were not significantly different. This would point toward a lineal increase in our population of subjects around 65 years of age on average independent of their ATN status; however, some of our subgroups (especially the A + T + N+) had very low numbers, and we might be underpowered to detect interactions. A relevant aspect of our cohort is that it encompasses the age spectrum in which AD is known to begin to increase in incidence [23]. Even though age was only borderline significantly associated with p-tau231, we speculate that our population might be well-powered to detect early p-tau231 levels increase, reflecting an early stage in the neurodegeneration process.

Longitudinal studies with post-mortem anatomopathological examination mention that p-tau231 levels also increase in the late stages of AD and are higher than those of subjects with mild amyloid pathology [24]. This gradual correlation with the main pathological signatures of AD in clinicopathological studies suggests that the p-tau231 increase might be related to early AD changes. In this sense, p-tau231 has shown to be able to discriminate between Braak 0 and Braak I–II stages [25]. However, recent evidence indicates that, although p-tau217 increases progressively along the AD continuum, p-tau231 reaches a plateau and may not be useful for monitoring disease progression or long-term treatments efficacy [24]. In the case of p-tau181, it appears to act similarly to p-tau217, as it increases progressively along the AD continuum, including the preclinical stages, and its levels correlate well with amyloid pathology [26, 27].

To better characterize the early preclinical phase of AD, we correlated p-tau231 levels with phenotype. We found that the increase from baseline to the first follow-up did not correlate with any phenotypic trait. However, baseline levels were associated with cognitive measurements. In contrast to what appears to happen with p-tau217 and p-tau181, which associates with cortical atrophy in CU subjects [28, 29], we did not detect any significant correlation with structural measures such as hippocampal volume or glucose metabolism of different regions of interest for AD. This hints that p-tau231 levels rise even before clinically significant signs of neurodegeneration occur in neuroimaging.

However, basal levels of p-tau231 correlated with cognitive decline, measured by sensitive neuropsychological memory tests such as the FNAME and FCSRT. Interestingly, when we stratified by ATN, this happened only from the A + T-N- group onwards and progressively increased along the AD continuum. Moreover, this correlation remained significant after adjusting for covariates. These findings are in line with another previous study that has shown a correlation between baseline p-tau231 levels and longitudinal changes in cognition, determined by the Preclinical Alzheimer’s Cognitive Composite (PACC)) at three years, only in Aβ + subjects [5]. Our interpretation of this finding is that only in individuals with substantial amyloid deposition (positive CSF Aβ42/40 ratio) do we observe an association between tau pathology (p-tau231 plasma levels) and cognitive impairment.

For its part, in more recent studies, basal levels of plasma p-tau217 have been shown to correlate with a worsening of memory (word list delayed recall) in a group of CU presenilin-1 E280A carriers [30] and increases in this biomarker also correlate with a worsening in modified PACC and MMSE over as long as six years in Aβ + CU subjects [27]. P-tau181 is not altered as early as p-tau217 and p-tau231 but has shown to be a good predictor of progression to AD and is longitudinally related to cognitive decline through parameters such as the MMSE, CDR and PACC [31].

Some limitations of our study should be pointed out.First, we only have CSF from the baseline visit, so we cannot confirm whether any of the subjects changed their ATN group during the follow-up time. On the other hand, even though our main findings are statistically sound, the small sample size is a limitation for some of the stratified analyses so our results should be taken with caution and replications, ideally in larger and more ethnically heterogeneous samples, would be needed to confirm our conclusions.

Our results suggest that time intervals as short as one year could be meaningful in detecting significant changes in plasma p-tau231 values. Sequential testing of plasma biomarkers could play an important role when selecting people for clinical trials and, in the near future, for initiation of disease-modifying treatments in an efficient and non-invasive way. Still, long-term longitudinal studies are needed to give us a better understanding of its temporal evolution.

A+/-, amyloid positive/negative.

Aβ, amyloid-β.

AD, Alzheimer's disease.

ApoE, apolipoprotein E.

CDR, clinical dementia rating.

CSF, cerebrospinal fluid.

CU, cognitively unimpaired.

DFR, delayed free recall.

DTR, delayed total recall.

FCSRT, Free and Cued Selective Reminding Test.

FDG, 18-fluorodeoxyglucose.

FNAME, Face Name Associative Memory Exam.

GFAP, glial fibrillary acid protein.

LM, logical memory.

LMM, Lineal Mixed Model .

LMDU, total delayed units in the logical memory test.

LP, lumbar puncture.

MMSE, Mini-Mental State Examination.

MRI, magnetic resonance imaging.

N+/-, neurodegeneration positive/negative.

NfL, neurofilament light.

NPS, neuropsychology.

P-tau, phosphorylated tau.

PACC, Preclinical Alzheimer’s Cognitive Composite. PET, positron emission tomography.

Simoa, single molecule array.

T+/-, tau positive/negative.

T-tau, total tau.

TFNAME, total value of Face Name Associative Memory Exam.

TFR, total free recall.

TMT, Trail Making Test.

TR, total recall.

Ethics approval and consent to participate

This research has been approved by the ethics committee of the Hospital Universitario Marqués de Valdecilla. Title: Valdecilla Cohort for the study of memory and brain aging. Internal code: 2018.111.

Consent for publication

Not applicable

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

KB has served as a consultant and at advisory boards for Acumen, ALZPath, BioArctic, Biogen, Eisai, Julius Clinical, Lilly, Novartis, Ono Pharma, Prothena, Roche Diagnostics, and Siemens Healthineers; has served at data monitoring committees for Julius Clinical and Novartis; has given lectures, produced educational materials and participated in educational programs for Biogen, Eisai and Roche Diagnostics; and is a co-founder of Brain Biomarker Solutions in Gothenburg AB (BBS), which is a part of the GU Ventures Incubator Program, outside the work presented in this paper.

Funding

KB is supported by the Swedish Research Council (#2017-00915 and #2022-00732), the Swedish Alzheimer Foundation (#AF-930351, #AF-939721 and #AF-968270), Hjärnfonden, Sweden (#FO2017-0243 and #ALZ2022-0006), the Swedish state under the agreement between the Swedish government and the County Councils, the ALF-agreement (#ALFGBG-715986 and #ALFGBG-965240), the European Union Joint Program for Neurodegenerative Disorders (JPND2019-466-236), the Alzheimer’s Association 2021 Zenith Award (ZEN-21-848495), and the Alzheimer’s Association 2022-2025 Grant (SG-23-1038904 QC).

Authors' contributions

FMD, PSJ and ERR designed the study, analyzed the data and drafted the manuscript. SLG, CLM, MFM, APC, MGM, ACP and MB performed clinical and neuropsychological assessment, obtained biological samples, and reviewed the manuscript. JJB, RQ, MDP and EML performed the neuroimaging tests and reviewed the final article. MLH and JIV performed CSF analysis and reviewed the manuscript. GDM, KB, NJA and HZ performed the analysis of plasma markers and reviewed the paper.

Acknowledgements

We would like to thank all the Valdecilla Cohort volunteers for their participation.

Jack CR Jr, Bennett DA, Blennow K, et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement. 2018;14(4):535-562. doi:10.1016/j.jalz.2018.02.018
Simrén J, Leuzy A, Karikari TK, et al. The diagnostic and prognostic capabilities of plasma biomarkers in Alzheimer's disease. Alzheimers Dement. 2021;17(7):1145-1156. doi:10.1002/alz.12283
Benedet AL, Milà-Alomà M, Vrillon A, et al. Differences Between Plasma and Cerebrospinal Fluid Glial Fibrillary Acidic Protein Levels Across the Alzheimer Disease Continuum. JAMA Neurol. 2021;78(12):1471-1483. doi:10.1001/jamaneurol.2021.3671
Palmqvist S, Janelidze S, Quiroz YT, et al. Discriminative Accuracy of Plasma Phospho-tau217 for Alzheimer Disease vs Other Neurodegenerative Disorders. JAMA. 2020;324(8):772-781. doi:10.1001/jama.2020.12134
Milà-Alomà M, Ashton NJ, Shekari M, et al. Plasma p-tau231 and p-tau217 as state markers of amyloid-β pathology in preclinical Alzheimer's disease [published correction appears in Nat Med. 2022 Sep 13;:]. Nat Med. 2022;28(9):1797-1801. doi:10.1038/s41591-022-01925-w
Elahi FM, Casaletto KB, La Joie R, et al. Plasma biomarkers of astrocytic and neuronal dysfunction in early- and late-onset Alzheimer's disease. Alzheimers Dement. 2020;16(4):681-695. doi:10.1016/j.jalz.2019.09.004
Ashton NJ, Janelidze S, Al Khleifat A, et al. A multicentre validation study of the diagnostic value of plasma neurofilament light. Nat Commun. 2021;12(1):3400. Published 2021 Jun 7. doi:10.1038/s41467-021-23620-z
Sánchez-Juan P, Seshadri S. Dynamic measurements of β-amyloid accumulation: The early effect of APOE. Neurology. 2017;89(10):986-987. doi:10.1212/WNL.0000000000004344
Ashton NJ, Pascoal TA, Karikari TK, et al. Plasma p-tau231: a new biomarker for incipient Alzheimer's disease pathology. Acta Neuropathol. 2021;141(5):709-724. doi:10.1007/s00401-021-02275-6
López-de-Eguileta A, López-García S, Lage C, et al. The retinal ganglion cell layer reflects neurodegenerative changes in cognitively unimpaired individuals. Alzheimers Res Ther. 2022;14(1):57. Published 2022 Apr 21. doi:10.1186/s13195-022-00998-6
López-García S, Lage C, Pozueta A, et al. Sleep Time Estimated by an Actigraphy Watch Correlates With CSF Tau in Cognitively Unimpaired Elders: The Modulatory Role of APOE. Front Aging Neurosci. 2021;13:663446. Published 2021 Aug 2. doi:10.3389/fnagi.2021.663446
Mattsson N, Andreasson U, Persson S, et al. The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers [published correction appears in Alzheimers Dement. 2011 Sep;7(5):556]. Alzheimers Dement. 2011;7(4):386-395.e6. doi:10.1016/j.jalz.2011.05.2243
Teunissen CE, Tumani H, Engelborghs S, Mollenhauer B. Biobanking of CSF: international standardization to optimize biomarker development. Clin Biochem. 2014;47(4-5):288-292. doi:10.1016/j.clinbiochem.2013.12.024
Leitão MJ, Silva-Spínola A, Santana I, et al. Clinical validation of the Lumipulse G cerebrospinal fluid assays for routine diagnosis of Alzheimer's disease. Alzheimers Res Ther. 2019;11(1):91. Published 2019 Nov 23. doi:10.1186/s13195-019-0550-8
Verberk IMW, Misdorp EO, Koelewijn J, et al. Characterization of pre-analytical sample handling effects on a panel of Alzheimer's disease-related blood-based biomarkers: Results from the Standardization of Alzheimer's Blood Biomarkers (SABB) working group. Alzheimers Dement. 2022;18(8):1484-1497. doi:10.1002/alz.12510
Jack CR Jr, Bennett DA, Blennow K, et al. A/T/N: An unbiased descriptive classification scheme for Alzheimer disease biomarkers. Neurology. 2016;87(5):539-547. doi:10.1212/WNL.0000000000002923
De Meyer G, Shapiro F, Vanderstichele H, et al. Diagnosis-Independent Alzheimer Disease Biomarker Signature in Cognitively Normal Elderly People. Arch Neurol. 2010;67(8):949–956. doi:10.1001/archneurol.2010.179
Peña-Casanova J, Gramunt-Fombuena N, Quiñones-Ubeda S, et al. Spanish Multicenter Normative Studies (NEURONORMA Project): norms for the Rey-Osterrieth complex figure (copy and memory), and free and cued selective reminding test. Arch Clin Neuropsychol. 2009;24(4):371-393. doi:10.1093/arclin/acp041
Wechsler D. (1945). A standardized memory scale for clinical use. J. Psychol. 19 87–95. 10.1080/00223980.1945.9917223
Alegret M, Valero S, Ortega G, et al. Validation of the Spanish Version of the Face Name Associative Memory Exam (S-FNAME) in Cognitively Normal Older Individuals. Arch Clin Neuropsychol. 2015;30(7):712-720. doi:10.1093/arclin/acv050
Tombaugh TN. Trail Making Test A and B: normative data stratified by age and education. Arch Clin Neuropsychol. 2004;19(2):203-214. doi:10.1016/S0887-6177(03)00039-8
Karikari TK, Pascoal TA, Ashton NJ, et al. Blood phosphorylated tau 181 as a biomarker for Alzheimer's disease: a diagnostic performance and prediction modelling study using data from four prospective cohorts. Lancet Neurol. 2020;19(5):422-433. doi:10.1016/S1474-4422(20)30071-5
Lobo A, Launer LJ, Fratiglioni L, et al. Prevalence of dementia and major subtypes in Europe: A collaborative study of population-based cohorts. Neurologic Diseases in the Elderly Research Group. Neurology. 2000;54(11 Suppl 5):S4-S9.
Smirnov DS, Ashton NJ, Blennow K, et al. Plasma biomarkers for Alzheimer's Disease in relation to neuropathology and cognitive change. Acta Neuropathol. 2022;143(4):487-503. doi:10.1007/s00401-022-02408-5
Janelidze S, Mattsson N, Palmqvist S, et al. Plasma P-tau181 in Alzheimer's disease: relationship to other biomarkers, differential diagnosis, neuropathology and longitudinal progression to Alzheimer's dementia. Nat Med. 2020;26(3):379-386. doi:10.1038/s41591-020-0755-1
Tropea TF, Waligorska T, Xie SX, et al. Plasma phosphorylated tau181 predicts cognitive and functional decline. Ann Clin Transl Neurol. 2023;10(1):18-31. doi:10.1002/acn3.51695
Ashton NJ, Janelidze S, Mattsson-Carlgren N, et al. Differential roles of Aβ42/40, p-tau231 and p-tau217 for Alzheimer's trial selection and disease monitoring. Nat Med. 2022;28(12):2555-2562. doi:10.1038/s41591-022-02074-w
Tissot C, L Benedet A, Therriault J, et al. Plasma pTau181 predicts cortical brain atrophy in aging and Alzheimer's disease. Alzheimers Res Ther. 2021;13(1):69. Published 2021 Mar 29. doi:10.1186/s13195-021-00802-x
Bilgel M, Wong DF, Moghekar AR, Ferrucci L, Resnick SM; Alzheimer’s Disease Neuroimaging Initiative. Causal links among amyloid, tau, and neurodegeneration. Brain Commun. 2022;4(4):fcac193. Published 2022 Jul 25. doi:10.1093/braincomms/fcac193
Aguillon D, Langella S, Chen Y, et al. Plasma p-tau217 predicts in vivo brain pathology and cognition in autosomal dominant Alzheimer's disease [published online ahead of print, 2022 Dec 26]. Alzheimers Dement. 2022;10.1002/alz.12906. doi:10.1002/alz.12906
Chatterjee P, Pedrini S, Doecke JD, et al. Plasma Aβ42/40 ratio, p-tau181, GFAP, and NfL across the Alzheimer's disease continuum: A cross-sectional and longitudinal study in the AIBL cohort [published online ahead of print, 2022 Jul 21]. Alzheimers Dement. 2022;10.1002/alz.12724. doi:10.1002/alz.12724

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

Plasma p-tau231 increases at one-year intervals in cognitively unimpaired subjects

Status:

Version 1

Abstract

Figures

1. BACKGROUND

2. MATERIALS AND METHODS

2.1. Participants

2.2. Plasma and CSF collection

2.3. CSF biomarkers

2.4. Magnetic Resonance and PET Imaging

2.5. ApoE testing

2.6. Neuropsychological tests

2.7. Statistical analysis

3. RESULTS

3.1. Sample description

3.2. Longitudinal analysis

3.3. Phenotypic correlations

4. DISCUSSION

5. CONCLUSIONS

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1