Genetic Variability in Caffeine Acute Effects and Withdrawal Symptoms

117 Pages·2011·1.73 MB·English

by  Joanne M. Brathwaite

Genetic Variability in Caffeine Acute Effects
and Withdrawal Symptoms
by
Joanne Margaret Brathwaite
A thesis submitted in conformity with the requirements
for the degree of Master of Science (M.Sc.)

Graduate Department of Nutritional Sciences
University of Toronto
© Copyright by Joanne Margaret Brathwaite 2011
Genetic Variability in Caffeine Acute Effects
and Withdrawal Symptoms
Joanne Margaret Brathwaite
Master of Science
Graduate Department of Nutritional Sciences
University of Toronto
2011

Abstract
The mechanisms underlying caffeine‟s acute effects and withdrawal symptoms are not entirely
understood. The purpose was to determine whether the clusters of acute effects or withdrawal
symptoms are associated with genetic polymorphisms in DARPP-32 and COMT, which mediate
some of caffeine‟s physiological effects. Subjects (n=1135) were from the Toronto
Nutrigenomics and Healthy Study. Fourteen well-described acute effects of caffeine co-exist in
six groups, while fourteen well-characterized withdrawal symptoms co-exist in three groups.
Neither the rs907094 C>T polymorphism in the PPP1R1B gene encoding DARPP-32, nor the
COMT Val158Met affected the odds of reporting any acute effects or withdrawal symptoms
cluster. Among individuals consuming ≥ 200 mg/d of caffeine, Met/Met homozygotes were more
likely to report the “increased heart rate” acute effects cluster. These results suggest that „slow‟
COMT activity, conferred by the Met allele, may explain part of the inter-individual variability
in the risk for increased heart rate among heavy caffeine consumers.

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Acknowledgments

As I reflect on this accomplishment, I am reminded that this Master of Science degree would not have
been possible without the guidance and support of many individuals. I would like to thank my family and
friends for their encouragement, love and support. Thank you to the members of the El-Sohemy lab, both
past and present, for their advice, assistance and friendship. Thank you to the extended Nutritional
Sciences family for their friendship and support. Last, but not least, thank you to my supervisor, Dr.
Ahmed El-Sohemy, for giving me this unique opportunity, and for his mentorship and support every step
of the way. I have truly benefited from this experience, and will treasure these lessons and friendships.

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Table of Contents

Chapter One .................................................................................................................................... 1
1.1 Introduction ...................................................................................................................... 2
1.2 Physical and Chemical Properties of Caffeine ................................................................. 3
1.3 Sources and Trends of Caffeine Consumption ................................................................. 5
1.4 Pharmacokinetics of Caffeine .......................................................................................... 9
1.4.1 Absorption and Distribution ..................................................................................... 9
1.4.2 Metabolism and Excretion ........................................................................................ 9
1.5 Pharmacodynamics and Mechanisms of Action of Caffeine ......................................... 11
1.5.1 Pharmacodynamics ................................................................................................. 11
1.5.2 Mechanisms of Action ............................................................................................ 13
1.6 Dopamine and cAMP-Regulated Phosphoprotein of 32kDa (DARPP-32) ................... 14
1.6.1 Protein Phosphatase-1, Regulatory (Inhibitor) Subunit 1B (PPP1R1B) Gene ....... 17
1.7 Catecholamine Metabolism ............................................................................................ 18
1.8 Catechol-O-methyltransferase (COMT) ........................................................................ 18
1.8.1 Catechol-O-methyltransferase (COMT) Gene ........................................................ 20
1.9 Caffeine Withdrawal, Dependence and Tolerance ......................................................... 22
1.9.1 Caffeine Withdrawal Symptoms ............................................................................. 22
1.9.2 Dependence ............................................................................................................. 24
1.9.3 Tolerance................................................................................................................. 25
Chapter Two.................................................................................................................................. 28
2.1 Hypothesis, Objectives and Thesis Organization ........................................................... 29
Chapter Three................................................................................................................................ 30
3.1 Abstract .......................................................................................................................... 31
3.2 Introduction .................................................................................................................... 32
3.3 Methods .......................................................................................................................... 35
3.3.1 Subjects and Data Collection .................................................................................. 35
3.3.2 Caffeine and Energy Intake .................................................................................... 36
3.3.3 Caffeine Habits Questionnaire ................................................................................ 36
3.3.4 Genotyping .............................................................................................................. 37
3.3.5 Statistical Analysis .................................................................................................. 38
3.3.6 Principal Components Analysis .............................................................................. 38
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3.3.7 Analysis of Genetic Association ............................................................................. 39
3.4 Results ............................................................................................................................ 41
3.4.1 Principal Components Analysis .............................................................................. 41
3.4.2 PPP1R1B Association ............................................................................................ 42
3.5 Discussion ...................................................................................................................... 55
Chapter Four ................................................................................................................................. 60
4.1 Abstract .......................................................................................................................... 61
4.2 Introduction .................................................................................................................... 62
4.3 Methods .......................................................................................................................... 64
4.3.1 Subjects and Data Collection .................................................................................. 64
4.3.2 Caffeine and Energy Intake .................................................................................... 64
4.3.3 Caffeine Habits Questionnaire ................................................................................ 64
4.3.4 Genotyping .............................................................................................................. 64
4.3.5 Statistical Analysis .................................................................................................. 64
4.4 Results ............................................................................................................................ 65
4.5 Discussion ...................................................................................................................... 74
Chapter Five .................................................................................................................................. 80
5.1 Synopsis ......................................................................................................................... 81
5.2 Limitations ..................................................................................................................... 83
5.3 Future Research .............................................................................................................. 85
References ..................................................................................................................................... 87

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List of Abbreviations
A R, A R adenosine A or A receptor
1 2A 1 2A
AdoMet S-adenosyl-L-methionine
ADORA2A adenosine A receptor gene
2A
BMI body mass index
BP blood pressure
cAMP cyclic adenosine monophosphate
Cdk5 cyclin-dependent kinase 5
c-fos FBJ murine osteosarcoma viral oncogene homolog
CHD coronary heart disease
CI confidence interval
COMT catechol-O-methyltransferase
CYP1A2 cytochrome P450 1A2
D R, D R dopamine D or D receptor
1 2 1 2
DARPP-32 dopamine and cAMP-regulated phosphoprotein of 32kDA
dbSNP NCBI SNP database
DSM-IV-TR Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Text revision
FFQ food frequency questionnaire
GABA γ-aminobutyric acid
GPi globus pallidus
HWE Hardy-Weinberg Equilibrium
ICD-10 International Classification of Disorders
IEGs immediate early genes
L-dopa L-3,4-dihydroxyphenylalanine, levodopa
MAO monoamine oxidase
MB-COMT membrane-bound COMT
MET metabolic equivalent task unit
MI myocardial infarction
MSN medium spiny neurons
NET norepinephrine transporter
NGFI-A/B nerve growth factor-induced clones A or B
OR odds ratio
PCA principal component analysis
PCR polymerase chain reaction
PKA protein kinase A
PP-1 protein phosphatase-1
PP-2A protein phosphatase-2A
PPP1R1B protein phosphatase-1, regulatory (inhibitor) subunit 1B
S-COMT soluble COMT
SD standard deviation
SNP single nucleotide polymorphism
SNpr substantia nigra pars reticulate
Thr34, Thr75 threonine 34 and threonine 75 of DARPP-32
UTR untranslated region

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List of Tables

Table 1-1 Physical and Chemical Properties of Caffeine ................................................................4
Table 1-2 Caffeine Content of Beverages, Foods and Medications ...............................................8
Table 3-1 Subject Characteristics by PPP1R1B (rs907094) Genotype .........................................44
Table 3-2 Self-reported Acute Effects Within 12h of Consuming a Caffeine-Containing
Beverage .......................................................................................................................................45
Table 3-3 Principal Components Factor Analysis Loadings of the Acute Effects of Caffeine
andCronbach‟s α ............................................................................................................................46
Table 3-4 Self-Reported Withdrawal Symptoms Within 48 Hours of Abstaining from Caffeine-
Containing Beverages. ...................................................................................................................48
Table 3-5 Principal Components Factor Analysis Loadings of Caffeine Withdrawal Symptoms
and Cronbach‟s α ...........................................................................................................................49
Table 3-6 Frequency of the Clusters of Acute Effects of Caffeine Among PPP1R1B Genotypes
and the OR (95% CI) of Reporting the Clusters. ...........................................................................51
Table 3-7 Frequency of the Acute Effects "Gastrointestinal" Cluster Among PPP1R1B
Genotypes Stratified by Sex and the OR (95% CI) of Reporting the Cluster. ...............................52
Table 3-8 Frequency of the Clusters of Caffeine Withdrawal Symptoms Among PPP1R1B
Genotypes and the OR (95% CI) of Reporting the Clusters ..........................................................53
Table 3-9 Frequency of the Caffeine Withdrawal Symptoms Cluster of "Flu-like - Anxiousness"
Among PPP1R1B Genotypes Stratified by Level of Caffeine Intake and the OR (95% CI) of
Reporting the Cluster. ....................................................................................................................54
Table 4-1 Subject Characteristics by COMT Val158Met Genotype .............................................67
Table 4-2 Frequency of the Clusters of Acute Effects of Caffeine Among COMT Genotypes and
the OR (95% CI) of Reporting the Clusters ...................................................................................68
Table 4-3 Frequency of the Acute Effects "Gastrointestinal" Cluster Among COMT Val158Met
Genotypes Stratified by Level of Caffeine Intake and the OR (95% CI) of Reporting the Cluster
........................................................................................................................................................69
Table 4-4 Frequency of the Acute Effects Cluster of "Increased Heart Rate" Among COMT
Val158Met Genotypes Stratified by Level of Caffeine Intake and the OR (95% CI) of Reporting
the Cluster ......................................................................................................................................70
Table 4-5 Frequency of the Clusters of Caffeine Withdrawal Symptoms Among COMT
Genotypes and the OR (95% CI) of Reporting the Clusters. .........................................................71
Table 4-6 Frequency of the Caffeine Withdrawal Symptoms Cluster of "Dysphoric mood"
Among COMT Genotypes Stratified by Sex and the OR (95% CI) of Reporting the Cluster. .....72
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Table 4-7 Frequency of the Caffeine Withdrawal Symptoms Cluster of "Dysphoric mood"
Among COMT Val158Met Genotypes Stratified by Level of Caffeine Intake and the OR (95%
CI) of Reporting the Cluster ..........................................................................................................73

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List of Figures
Figure 3-1 Frequency of Factors of Self-Reported Acute Effects within 12 Hours of Consuming
One Caffeine-Containing Beverage ...............................................................................................47
Figure 3-2 Frequency of Factors of Self-Reported Withdrawal Symptoms within 48 Hours of
Abstaining from Caffeine-Containing Beverages ..........................................................................50

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List of Appendices
Appendix I: Caffeine-Containing Beverage & Food FFQ Items ................................................104
Appendix II: Caffeine Habits Questionnaire ..............................................................................107

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