The Predictive Factors of Good Clinical Response to Cholinesterase Inhibitors in Alzheimer Disease and Mixed Dementia
Condition: Alzheimer Disease, Late Onset
MeSH terms: Alzheimer Disease; Dementia; Mixed Dementias; Late Onset Disorders
Study type: Observational

Summary: 
      Background and objectives: The aims of this naturalistic study were: to analyze factors which
      could be predictive of good response to cholinesterase inhibitors (ChEI), such as: age, sex,
      schooling, mild (CDR 1) or moderate Alzheimer's disease (AD),(CDR 2), Apoliprotein epsilon 4
      (APOE Ɛ4), among others, in their cognitive and clinical response. We also classified
      patients according to their response to Mini mental State of Examination (MMSE). Finally we
      saw the polymorphisms of APO E and cytochrome P450 2D6 (CYP2D6) and tried to correlate the
      response with different allelic forms of Apo E and among others with wild type homozygotes
      (wt/wt) and their polymorphisms (CYP2D6*3,*4, *5, *6 and 10) of CYP 2D6.

      Patients and Methods: 129 patients were diagnosed as AD or AD+cerebrovascular disease (CVD)
      mild or moderate. After 12 month-treatment, 97 patients completed the study. They were
      assessed (four) times. In the first visit, without taking ChEI, after 3, 6 and 12
      month-treatment, they were taking donepezil or rivastigmine or galantamine. We also extracted
      5 mL of blood sample to genotype the DNA. In each visit, we applied cognitive, functional,
      mood and behavior scales. Good responders were defined as those who scored > 2 in MMSE.

      Results and Conclusion: In longitudinal analysis, patients with mild AD and good responders
      at 3 months were considered good responders at 12 months. We obtained a higher rate of good
      responders comparing with other researches (27.8%). There was no correlation between dose,
      APOE and CYP 2D6 polymorphisms, although we already obtained clinical results with the dose
      dosage of 5mg.
    

Detailed description: 
      Genomic DNA for genotyping was extracted from total blood samples collected in
      ethylenediaminetetraacetic acid (EDTA) (Wizard Genomic DNA Purification Kit: Promega®, USA)
      and kept frozen at seventy degrees Celsius negative (-70ºC) until analysis. For APOE
      genotyping (alleles Ɛ2, Ɛ3 and Ɛ4), DNA samples were amplified by polymerase chain reaction
      (PCR), followed by digestion with Haemophilus haemolyticus restriction endonuclease I (HhaI)
      and restriction fragment length polymorphism (RFLP) analysis, as previously described by
      Hixson and Vernier.

      The CYP2D6*3, CYP2D6*4 and CYP2D6*6 alleles were investigated by tetra-primer PCR and the
      CYP2D6*5 allele, which presents the entire CYP2D6 gene deletion, was identified by long PCR
      reaction, according to the method described by Hersberger et al. The CYP2D6*10 allele was
      amplified by PCR following Baclig et al. and the RFLP analysis was performed with Type II
      restriction enzyme (HphI). For all analysis a positive and negative controls were included.

      Subjects carrying Epsilon 3, Epsilon 3 (Ɛ3Ɛ3), CYP2D6*3/4/5/6/10-nor specific mutations are
      classified as wild-type and functional allele carriers. The subjects carrying two defective
      alleles were classified as poor metabolizers (PM) and those heterozygous were classified as
      extensive metabolizers (EM).
    

Intervention name(s): cholinesterase inhibitors
Intervention type(s): Drug
Intervention description(s): The first group received donepezil (5 or 10 mg) the second group received galantamine (16 or 24 mg) The third group received rivastigmine (3 or 4,5 or 6 mg BID) according to the treating physician.
Other intervention name(s): No applicable
Intervention MeSH terms: Cholinesterase Inhibitors
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Eligible patients were those who spontaneously went to the outpatient units to be diagnosed
        and presented cognitive, functional, and in many cases, behavioral symptoms.
      
Biospecimen description: 
      Genetic and biochemical analyzes A blood sample (5 mL) was withdrawn from all patients on the
      first consultation for DNA extraction and APOE genotyping in its different allelic forms (Ɛ2,
      Ɛ3, Ɛ4). An additional blood sample (10 mL) was withdrawn from patients who took donepezil
      (51 patients) and was kept in a tube with heparin and frozen at - 70 ° C. In this group of
      patients, we genotyped the APOE and assessed the polymorphism of CYP 2D6 (*3,*4,*5,*6
      and*10). This procedure was done when they came at 3, 6 and 12 months consultation,
      respectively.
    
Keywords: Predictive factors of response; mild and moderate; Alzheimer disease; mixed dementia; APOE; polymorphisms of CYP 2D6