2.1 Demographics
The clinical characteristics of the participants are presented in Table 1. The amyloid-positive and amyloid-negative groups showed a significant difference in age (P = 0.025). The mean age of the amyloid-positive group, in which 21 early-onset patients are included, was lower than that of the amyloid-negative group (66.7 vs. 71.2 yr). The frequency of the APOE ε4 allele was significantly higher in the amyloid-positive group than that in the amyloid-negative group (P = 0.003, hazard ratio = 16.57). The frequency of diabetes mellitus was higher in the amyloid-negative group than that in the amyloid-positive group (P = 0.01). The amyloid-positive group had poor performances in K-MMSE compared to those of the amyloid-negative group (P = 0.029). The amyloid-positive group showed significantly higher serum LDL levels (P = 0.042) and albumin (P = 0.02). The amyloid-negative group showed higher serum ESR than did the amyloid-positive group (P = 0.025). Other demographic features, including sex distribution, CRP serum levels, frequency of hypertension (HTN), and hyperlipidemia, did not show significant differences between the two groups.
Table 1. Demographics and clinical characteristics of amyloid-negative and amyloid-positive groups
|
|
Amyloid-negative (N=47)
|
Amyloid-positive (N=54)
|
Population
|
Sex, n (female)
|
47 (22)
|
54 (32)
|
|
Age (SD), yr *
|
71.18 (8.66)
|
66.73 (10.36)
|
|
Education level (SD), yr
|
11.76 (4.67)
|
11.41 (4.77)
|
|
Disease duration (SD), months
|
28.84 (28.12)
|
35.62 (27.10)
|
|
APOE ε4 carrier, n (%) **
|
9 (18.8)
|
30 (57.7)
|
Underlying disease
|
DM, n (%) *
|
22 (44.9)
|
10 (19.2)
|
|
HTN, n (%)
|
22 (44.9)
|
25 (48.1)
|
|
Hyperlipidemia, n (%)
|
20 (40.8)
|
26 (50.0)
|
Global cognition
|
MMSE (SD)*
|
24.12 (4.65)
|
22.00 (4.90)
|
|
CDR (SD)
|
0.67 (0.52)
|
0.72 (0.45)
|
Laboratory test
|
Neutrophil, % (SD)
|
56.46 (8.81)
|
56.64 (8.91)
|
|
Monocyte, % (SD)
|
8.13 (1.61)
|
11.05 (19.01)
|
|
ESR (SD), mm/h *
|
15.47 (11.41)
|
10.91 (7.00)
|
|
CRP (SD)
|
0.23 (0.45)
|
0.21 (0.48)
|
|
LDL (SD), mg/dL*
|
104.78 (38.70)
|
127.03 (38.21)
|
|
Albumin (SD), g/dL*
|
3.69 (0.39)
|
3.84 (0.26)
|
Demographics and characteristics of the dataset.
Student’s t-test was used to analyze the age, educational level, disease duration, MMSE, CDR, neutrophil, monocyte, ESR, CRP, and LDL levels.
χ2 test was used in the analysis of sex distribution, APOE ε4, DM, HTN, and hyperlipidemia.
Abbreviations: DM, diabetes mellitus; HTN, hypertension; ESR, erythrocyte sedimentation rate; CRP, C-reactive proteins; LDL, low-density lipoprotein
* Significant at P < 0.05.
** Significant at P < 0.01.
2.2 AD biomarkers in the cohort
The CSF Aβ42, T-tau, and P-Tau S199 levels were compared between the two groups (amyloid-positive and amyloid-negative) to demonstrate that the cohort had typical patterns of AD biomarkers. As expected, the CSF Aβ42 levels were significantly lower in the amyloid-positive group than those in the amyloid-negative group (P < 0.001) (Figure 1a). The CSF P-Tau S199 (P < 0.001) and T-tau (P = 0.024) levels were significantly higher in the amyloid-positive group than those in the amyloid-negative group (Figure 1b & 1c).
2.3 CSF and plasma sTREM2 levels, CSF and plasma biomarkers
In the whole group, the CSF sTREM2 levels were negatively correlated with the plasma sTREM2 levels (Spearman's rho [ρ] = –0.202, P = 0.043; n = 101) (Figure 2b). The CSF sTREM2 levels positively correlated with the CSF P-Tau S199 (ρ = 0.296, P = 0.003; n = 100) and T-tau levels (ρ = 0.427, P < 0.001; n = 99). In contrast, the plasma sTREM2 levels were negatively correlated with the CSF P-tau S199 (ρ = –0.264, P = 0.008; n = 100) and T-tau levels (ρ = –0.248, P = 0.013; n = 99). Plasma sTREM2 levels were significantly correlated with the CSF NfL levels (ρ = 0.359, P < 0.001; n = 101). The CSF sTREM2 levels were not significantly correlated with the CSF NfL levels (ρ = 0.085, P = 0.401; n = 101). With respect to the age effects, age correlated positively with the plasma sTREM2 levels (ρ = 0.409, P < 0.001; n = 101) and negatively with the CSF P-tau S199 (ρ = –0.240, P = 0.016; n = 100) and T-tau levels (ρ = –0.258, P = 0.010; n = 99) (Figure 2c).
The plasma sTREM2 levels were positively correlated with the plasma NfL levels (ρ = 0.416, P < 0.001; n = 100). In contrast, the CSF sTREM2 was not significantly correlated with the plasma biomarkers (Table 2 & Figure 2a).
Table 2. Correlation of cerebrospinal fluid (CSF) and plasma soluble triggering receptor expressed on myeloid cells 2 (sTREM2) with Alzheimer’s disease (AD) biomarkers in all subjects
|
|
R
|
P-value
|
|
R
|
P-value
|
CSF sTREM2 (pg/mL)
|
|
|
|
|
|
|
Aβ42
|
–0.021
|
0.835
|
Plasma sTREM2
|
–0.202
|
0.043
|
|
P-tau S199
|
0.296
|
0.003
|
NfL
|
0.056
|
0.582
|
|
T-tau
|
0.427
|
<0.001
|
NRGN
|
0.012
|
0.906
|
|
Aβ42/P-tau S199
|
–0.273
|
0.006
|
Telomere
|
–0.127
|
0.205
|
|
NfL
|
0.085
|
0.401
|
Age
|
–0.057
|
0.573
|
Plasma sTREM2 (pg/mL)
|
|
|
|
|
|
|
CSF sTREM2
|
–0.202
|
0.043
|
NfL
|
0.416
|
<0.001
|
|
Aβ42
|
0.104
|
0.303
|
NRGN
|
–0.068
|
0.512
|
|
P-tau S199
|
–0.264
|
0.008
|
Telomere
|
–0.216
|
0.030
|
|
T-tau
|
–0.248
|
0.013
|
Age
|
0.409
|
<0.001
|
|
Aβ42/P-tau S199
|
0.267
|
0.007
|
|
|
|
|
NfL
|
0.359
|
<0.001
|
|
|
|
Linear regression analyses were used to demonstrate a correlation between biomarkers.
Abbreviations: NfL, neurofilament light chain; NRGN, neurogranin
2.4 Plasma neurodegeneration biomarkers
The plasma sTREM2 positively correlated with plasma NfL (ρ = 0.416, P < 0.001; n = 100) and age (ρ = 0.409, P < 0.001; n = 101). Furthermore, NfL and age were strongly correlated with each other (ρ = 0.523, P < 0.001; n = 100). In contrast, the leukocyte TL was negatively correlated with sTREM2 (ρ = –0.216, P < 0.03; n = 101), plasma NfL (ρ = –0.429, P < 0.001; n = 100), and age (ρ = –0.387, P < 0.001; n = 101), showing that the aging and neurodegeneration factors were progressing together (Figure 2).
2.5 CSF and plasma sTREM2 in the AD continuum
In the amyloid-positive group (AD continuum), the association between CSF and plasma sTREM2 which was observed in the whole dataset disappeared. The CSF sTREM2 levels significantly correlated with CSF T-tau level (ρ = 0.455, P = 0.0014; n = 51), and Aβ42/P-tau S199 (ρ = –0.331, P = 0.017; n = 52). The plasma sTREM2 levels correlated with CSF P-tau S199 (ρ = –0.288, P = 0.038; n = 52) and Aβ42/P-tau S199 (ρ = 0.316, P = 0.022; n = 52), CSF NfL (ρ = 0.457, P = 0.001; n = 52), and plasma NfL (ρ = 0.349, P = 0.012; n = 51). The plasma sTREM2 levels correlated positively with age (ρ = 0.345, P = 0.012; n = 52) (Table 3 & Figure 3a).
Table 3. Correlation of cerebrospinal fluid (CSF) and plasma soluble triggering receptor expressed on myeloid cells 2 (sTREM2) with Alzheimer’s disease (AD) biomarkers in patients with AD continuum (amyloid-positive group)
|
|
R
|
P-value
|
|
R
|
P-value
|
CSF sTREM2 (pg/mL)
|
|
|
|
|
|
|
Aβ42
|
–0.152
|
0.281
|
Plasma sTREM2
|
–0.172
|
0.224
|
|
P-tau S199
|
0.254
|
0.069
|
NfL
|
0.323
|
0.021
|
|
T-tau
|
0.455
|
<0.001
|
NRGN
|
0.080
|
0.584
|
|
Aβ42/P-tau S199
|
–0.331
|
0.017
|
Telomere
|
–0.072
|
0.610
|
|
NfL
|
0.018
|
0.901
|
Age
|
0.080
|
0.574
|
Plasma sTREM2 (pg/mL)
|
|
|
|
|
|
|
CSF sTREM2
|
–0.172
|
0.224
|
NfL
|
0.349
|
0.012
|
|
Aβ42
|
0.128
|
0.365
|
NRGN
|
0.126
|
0.389
|
|
P-tau S199
|
–0.288
|
0.038
|
Telomere
|
–0.146
|
0.303
|
|
T-tau
|
–0.227
|
0.110
|
Age
|
0.345
|
0.012
|
|
Aβ42/P-tau S199
|
0.316
|
0.022
|
|
|
|
|
NfL
|
0.457
|
<0.001
|
|
|
|
Linear regression analyses were used to demonstrate a correlation between biomarkers.
Abbreviations: NfL, neurofilament light chain; NRGN, neurogranin
2.6 CSF and plasma sTREM2 in non-AD condition
In the amyloid-negative conditions, the CSF sTREM2 levels showed a positive correlation with the CSF P-tau S199 (ρ = 0.301, P = 0.038; n = 48) and T-tau (ρ = 0.425, P = 0.003; n = 48) levels. No significant significance was found between the plasma sTREM2 and CSF biomarker levels. The plasma sTREM2 levels were correlated with the plasma NfL (ρ = 0.436, P = 0.002; n = 49), TL (ρ = –0.312, P = 0.029; n = 49), and age (ρ = 0.430, P = 0.002; n = 49) (Table 4 & Figure 3b).
Table 4. Correlation of cerebrospinal fluid (CSF) and plasma soluble triggering receptor expressed on myeloid cells 2 (sTREM2) with Alzheimer’s disease (AD) biomarkers in the amyloid-negative group
|
|
R
|
P-value
|
|
R
|
P-value
|
CSF sTREM2 (pg/mL)
|
|
|
|
|
|
|
Aβ42
|
0.204
|
0.159
|
Plasma sTREM2
|
–0.193
|
0.183
|
|
P-tau S199
|
0.301
|
0.038
|
NFL
|
–0.083
|
0.572
|
|
T-tau
|
0.425
|
0.003
|
NRGN
|
–0.109
|
0.465
|
|
Aβ42/P-tau S199
|
–0.178
|
0.225
|
Telomere
|
–0.175
|
0.230
|
|
NFL
|
0.183
|
0.208
|
Age
|
–0.140
|
0.338
|
Plasma sTREM2 (pg/mL)
|
|
|
|
|
|
|
CSF sTREM2
|
–0.193
|
0.183
|
NFL
|
0.436
|
0.002
|
|
Aβ42
|
–0.041
|
0.779
|
NRGN
|
–0.246
|
0.095
|
|
P-tau S199
|
–0.142
|
0.335
|
Telomere
|
–0.312
|
0.029
|
|
T-tau
|
–0.126
|
0.394
|
Age
|
0.430
|
0.002
|
|
Aβ42/P-tau S199
|
0.115
|
0.438
|
|
|
|
|
NFL
|
0.196
|
0.177
|
|
|
|
Linear regression analyses were used to demonstrate a correlation between biomarkers.
Abbreviations: NFL, neurofilament light chain; NRGN, neurogranin
2.7 Relationship of CSF P-tau and T-tau with age stratified by amyloid status
To avoid age bias, all participants were categorized into three different groups, i.e., amyloid-negative, amyloid-positive early-onset (younger than age 65), and amyloid-positive late-onset disease. In case of CSF P-Tau S199, T-tau levels, and age correlation, we found that the CSF P-tau S199 and T-tau levels were inversely influenced by age in the whole dataset, as previously noted (Figure 3). The tau pathology over the age course was negatively correlated with CSF P-tau S199 only in the early-onset amyloid-positive group, but this was not significant (Figure 4a & 4b). In case of plasma sTREM2, the amyloid-negative group still showed a strong positive correlation with age (ρ = 0.430, P = 0.002). However, no significance was observed in the amyloid-positive early or late onset group (Figure 4c).