1. A longitudinal study of amyloid beta 1-43 levels in
the cerebrospinal fluid from pa<ents with amnes<c
mild cogni<ve impairment or early Alzheimer’s
disease
Adiba Shabnam

2. Backgro
und
Aim Method Result Conclusion shortcomings
overview

3. BACKGROUND

4. Alzheimer’s disease
Defini;on
A progressive degenera;ve brain disorder that slowly and
eventually destroys neurons leading to memory loss and other
cogni;ve dysfunc;ons.
Facts
• Its fatal and there is no cure currently.
• Most common type of demen;a (70%)
• High prevalence and rising incidence.

5. Neuro-pathological Findings
• extensive atrophy due to loss of neurons
• Amyloid plaques
• Neurofibrillary tangles

6. hIps://www.youtube.com/watch?v=dj3GGDuu15I

7. Amyloid plaque
• Main component is Aβ pep;de: Aβ40 and Aβ42
• Derived from Amyloid Precursor protein (APP)
Amyloidogenic
pathway

8. Neurofibrillary Tangles
• Composed of Hyperphosphorylated forms of the protein tau.
• Normally, tau binds to microtubules and stabilizes it.
• In AD tau protein loses its ability to bind to microtubules and
aggregates as NFT.

9. Pathogenesis
• Many hypothesis have been suggested so far.
• Amyloid cascade hypothesis (ACH) is widely accepted.
• ACH states that imbalance in produc;on and clearance
of Aβ is the ini;a;ng event of AD leading to tau
hyperphosphoryla;on and tangle forma;on.

10. ALZHEIMER’S DISEASE
Classifica;on
• Early-onset AD: <65 years, less common
• Late-onset AD: >65 years
• More common (95%)
• Mainly sporadic
• Cause unknown
• Familial AD: gene;c muta;on

11. Causes
• Advanced age
• Gene;c factors: APOE ε4
APP, PSEN1, PSEN2 muta;on
• Environmental & lifestyle factors:
Ø cardio-vascular factors
Ø Trauma;c brain injury
Ø Diet and physical ac;vity
• Cogni;ve reserve

12. Missing links ?

13. DiagnosNc criteria
• Prevailing criteria: by NINCDS-ADRDA in 1984
• Diagnosis can only be probable in life
• Demen<a appears
• Two major sets of criteria proposed
• IWG (2007, 2010)
• NIA-AA (2011)
• episodic memory impairment and biomarkers
• The prodromal stage of AD.
• Harmoniza;on of the diagnos;c criteria is ongoing.

14. Stages of AD
Preclinical AD
Ø long asymptoma;c phase of AD con;nuum
Ø pathological changes in the brain starts
Ø cogni;ve ability is normal.
Mild Cogni<ve Impairment/MCI
Ø symptoma;c predemen;a phase of AD
Ø evidence of change in cogni;on compared to their past
Ø func;onal abili;es are preserved
Ø Amnes;c MCI considered as prodromal phase
AD demen<a
Ø cogni;ve decline from previous levels
Ø normal func;onal and social abili;es interfered

15. • Treatment can be effec;ve if ini;ated in early stages before significant
neurodegenera;on occurs.
Early detec<on of AD is needed

16. Biomarkers
• A measurable clinical en<ty that provides an insight of a normal
biological or pathogenic processes
• Imaging biomarkers
• Structural Magne;c Resonance Imaging (sMRI)
• Func;onal MRI (fMRI)
• FDG-PET
• PiB PET Imaging Aβ burden
• Tau-PET
• Fluid Biomarkers
• CSF Biomarkers: Aβ42, Aβ40, total tau (t-tau) and phosphorylated tau (p-tau)

17. CSF biomarkers
• Reduced Aβ42 reflec;ng amyloid
deposi;on.
• Enhanced t-tau showing neuronal
degenera;on.
• Increased p-tau indicates tangle
pathology.

18. Biomarker models and in vivo staging AD
;me
Jack et al , 2013

19. Aβ43
• Deposi;on more frequent than Aβ40 (Welander et al, 2009; Keller et al, 2010)
• Appears earlier than other Aβ pep;des (Zou 2013)
• More hydrophobic than Aβ42 (Saito et al, 2011)
• Higher propensity to aggregate rapidly than Aβ42
• More neurotoxic (drives Aβ42 polymeriza;on)
Ø Aβ49 àAβ46 àAβ43 (okochi, 2013)
Ø Aβ48 àAβ45 àAβ42

20. AIM

21. AIM
• concentra<on of Aβ43 in CSF of
MCI pa;ents stable over 2 years
MCI pa;ents progressing to AD in 2 years and
AD pa;ents
• Analyze the diagnos<c performance of Aβ43
• Compare longitudinal changes in biomarker levels at twelve months
intervals (T0, T12, T24) over 2 years.

22. METHODS

23. ParNcipants
23 sMCI
19 AD
20 pMCI
32 healthy individuals
62 pa;ents with amnes;c MCI
and early AD
sMCI: stable over 2 years.
pMCI: progressed to AD in 2 years.
AD

24. METHOD
• ELISA kits
• SPSS version21
• Non-parametric tests
• P<0.05 : sta;s;cally significant
• 0.05<p<0.10: trend

25. RESULTS&
DISCUSSION

26. Core biomarkers
Increased t-tau level
DIAGNOSIS
ADpMCIsMCIcontrol
CSF A42 (pg/ml)
2,000
1,500
1,000
500
0
8
4
30
14
4
8
4
30
8
93
T24
T12
T0
DIAGNOSIS
ADpMCIsMCIcontrol
CSF T-tau (pg/ml)
6,000
5,000
4,000
3,000
2,000
1,000
0
43
54
20
43
47
54
20
67
43
T24
T12
T0
DIAGNOSIS
ADpMCIsMCIcontrol
CSF P-tau (pg/ml)
200
150
100
50
0
43
20
20
67
T24
T12
T0
Reduced Aβ42 level Increased p-tau level

27. Aβ43 levels in CSF
Cross-sec<onal analysis: Significantly
reduced
Ø Sequestra;on in plaques
Ø Lowered produc;on from APP
Ø Increased degrada;on by γ-secretase
and Angiotensin Conver;ng Enzyme
Ø Aβ43 form oligomers which escaped
detec;on by ELISA
longitudinal analysis: Significantly reduced
Ø From T0 to T12 (pMCI & AD)
Ø Progressive
Ø Marginal: slow rate of accumula;on
Correlated posi<vely with Aβ42
Ø same mechanism (altered γ-secretase
ac;vity)
Aβ49 àAβ46 àAβ43
Aβ48 àAβ45 àAβ42
DIAGNOSIS
ADpMCIsMCIcontrol
30
14
8
24
30
14
4
8
24
30
8
14
24
80
CSF A43 (pg/ml)
120100806040200
T24
T12
T0

28. DiagnosNc performance of Aβ43
Control:sMCI Control:pMCI Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.72 0.93 0.97 0.71 0.77 0.59
Cut-off
(pg/ml)
<26.1 <24.8 <27.7 <21.1 <20.9 <18.8
Sensi<vity 50 90 93 79 87 73
Specificity 100 100 96 70 70 53
Youden's
index
0.50 0.90 0.89 0.49 0.57 0.25
Likelihood
ra<o
23.3 2.63 2.9 1.5
• Good diagnos;c accuracy: High AUC in pMCI Vs controls and AD Vs controls
• High sensi;vity and specificity
• Can differen;ate well between pMCI and AD pa;ents from controls

29. ROC curves showing diagnosNc
performance
AD Vs Controls
1 - Specificity
1,00,80,60,40,20,0
Sensitivity
1,0
0,8
0,6
0,4
0,2
0,0
Reference Line
p-tau
t-tau
A42
A43
1 - Specificity
1,00,80,60,40,20,0
Sensitivity
1,0
0,8
0,6
0,4
0,2
0,0
Reference Line
p-tau
t-tau
A42
A43
pMCI Vs Controls

30. DiagnosNc performance of Aβ42
Control:
sMCI
Control:
pMCI
Control:
AD
sMCI:p
MCI
sMCI:AD pMCI:AD
AUC 0.79 0.94 0.97 0.57 0.65 0.67
Cut-off
(pg/ml)
<692.8 <635.1 <604.4 <792.7 <558.7 <546.2
Sensi<vi
ty
60 84 87 95 87 87
Specifici
ty
92 96 96 94 55 47
Youden'
s indexa
0.52 0.80 0.83 0.34 0.42 0.35
Likeliho
od ra<ob
7.5 21 21.75 15.83 1.93 1.64
Control:s
MCI
Control:p
MCI
Control:
AD
sMCI:pM
CI
sMCI:A
D
pMCI:AD
AUC 0.72 0.93 0.97 0.71 0.77 0.59
Cut-off
(pg/ml)
<26.1 <24.8 <27.7 <21.1 <20.9 <18.8
Sensi<v
ity
50 90 93 79 87 73
Specific
ity
100 100 96 70 70 53
Youden
's index
0.50 0.90 0.89 0.49 0.57 0.25
Likeliho
od ra<o
23.3 2.63 2.9 1.5
Aβ42 Aβ43

31. Comparison of Aβ43 with Aβ42
• Cross- sec;onal: Decreased
• Longitudinal: No change
• Reached plateau phase
• Diagnos;c accuracy (AUC=0.9)
• pMCI Vs Controls
• Sensi;vity = 84%
• Specificity = 96%
• AD Vs Controls
• Sensi;vity = 87%
• Specificity = 96%
• Cross- sec;onal: Decreased
• Longitudinal: Reduced
(marginal)
• Diagnos;c accuracy (AUC=0.9)
• pMCI Vs Controls
• Sensi;vity = 90%
• Specificity = 100%
• AD Vs Controls
• Sensi;vity = 93%
• Specificity = 96%

32. Control:sMC
I
Control:pMC
I
Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.58 0.86 0.87 0.75 0.81 0.58
Cut-off
(pg/ml)
>406.2 >392.8 >471.1 >328.0 >591.0 >481.3
Sensi<vity
(%)
43 79 81 90 63 81
Specificity
(%)
88 98 96 52 90 42
Youden's
index
0.30 0.66 0.77 0.42 0.53 0.23
Likelihood
ra<o
3.43 6.31 19.36 1.88 6.58 1.40
Control:sMC
I
Control:pM
CI
Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.55 0.82 0.83 0.75 0.77 0.56
Cut-off
(pg/ml)
>77.3 >65.2 >76.9 >58.1 >89.2 >74.1
Sensi<vity
(%)
29 79 81 84 69 81
Specificity
(%)
96 79 96 57 86 42
Youden's
index
0.24 0.58 0.77 0.41 0.54 0.23
Likelihood
ra<o
6.81 3.79 19.35 1.96 4.81 1.40
T-tau p-tau
Diagnos<c performance of t-tau and p-tau
• Low diagnos;c accuracy (AUC<0.9)

33. levels of raNos: Aβ43/Aβ42 and Aβ43/Aβ40
Aβ43/Aβ42
Aβ43/Aβ40
Significant reduc;on in Aβ43/Aβ42 and Aβ43/Aβ40

34. DiagnosNc performance of raNos
Control:sMCI Control:pMC
I
Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.36 0.72 0.58 0.77 0.68 0.39
Cut-off <34.1 <39.94 <34 <40.7 <43.5 <34.2
Sensi<vity
(%)
20 84 47 84 73 47
Specificity
(%)
88 64 88 70 65 58
Youden's
index
0.08 0.48 0.35 0.54 0.38 0.04
Likelihood
ra<o
1.7 2.3 3.9 2.8 2.1 1.1
Control:sMCI Control:pMCI Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.51 0.86 0.90 0.73 0.79 0.54
Cut-off <1.59 <1.62 <1.68 <1.71 <2.29 <1.23
Sensi<vity
(%)
33 84 87 84 93 60
Specificity
(%)
96 96 96 67 61 38
Youden's
index
0.29 0.80 0.82 0.51 0.54 0.18
Likelihood
ra<o
7.74 19.58 20.16 2.52 2.39 1.42
Aβ43/Aβ42
Aβ43/Aβ40
Aβ43/Aβ40 shows beIer ability to differen;ate pMCI and AD from controls

35. RaNos
• Significant reduc;on in Aβ43/t-tau and Aβ42/t-tau
Aβ43/t-tau
Aβ42/t-tau

36. DiagnosNc performance of raNos
Control:sMCI Control:pMCI Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.72 0.91 0.95 0.80 0.85 0.62
Cut-off <115.7 <58.1 <99.4 <37.2 <33.8 <16.03
Sensi<vity
(%)
55 90 93 74 80 40
Specificity
(%)
92 96 92 90 90 90
Youden's
index
0.47 0.85 0.85 0.64 0.70 0.29
Likelihood
ra<o
6.62 21.3 11.24 7.37 8 3.8
Control:sMC
I
Control:pMC
I
Control:AD sMCI:pMCI sMCI:AD pMCI:AD
AUC 0.75 0.91 0.95 0.73 0.81 0.63
Cut-off <3103.8 <1512.7 <1466.8 <1617.1 <883.4 <870.2
Sensi<vity
(%)
71 90 88 90 75 75
Specificity
(%)
87 96 96 62 81 58
Youden's
index
0.58 0.85 0.83 0.51 0.56 0.33
Likelihood
ra<o
5.49 20.81 20.34 2.34 3.94 1.78
Aβ43/t-tau and Aβ42/t-tau shows similar ability to differen;ate pMCI and
AD from controls
Aβ43/t-tau Aβ42/t-tau

37. CONCLUSIONS

38. Conclusion
• Significantly reduced level of CSF Aβ43 in all pa;ent groups
compared to controls
• High diagnos<c accuracy of CSF Aβ43 (pMCI Vs Controls)
• CSF Aβ43 reduced significantly longitudinally over 2 years
• CSF Aβ43 can be a good prognos;c biomarker

39. LIMITATIONS

40. Strength and weakness
• Strength
• Diagnosis performed by skilled neurologist
• Marked reduc;on in Ab43 and Ab42
• Marked enhancement in t-tau and p-tau
• Limita;ons
Small sample size
• Non-parametric test (low power)
• Misdiagnosis (lack neuropathological confirma;on)

42. APP muta;on
APP gene duplica;on
PSEN muta;on
Life long increase in total Aβ or Aβ42 produc;on or
enhanced aggrega;on tendency
Failure of Aβ clearance with increasing Aβ
levels in the brain
Aging, APOE ε4 allele
Environmental risk factors
Gradual decrease in CSF Aβ42
Progressive cogni;ve dysfunc;on and demen;a
Synap;c and neuronal degenera;on with failure
of neurotransmission
Further aggrega;on into fibrillary Aβ deposits, tau
posi;ve dystrophic neurites and neuri;c plaques
Aβ aggrega;on into plaques
Conforma;onal change in Aβ with soluble
oligomer forma;on
Gradual increase in amyloid PET
reten;on
Impaired LTP with synap;c
dysfunc;on
Microglial and astrocy;c
ac;va;on, inflammatory
response and oxida;ve
stress
Tau pathology
Familial AD Sporadic AD