Copenhagen DIRECT Copenhagen Diabetes Research Center The Autoimmune Pathogenesis of Type 1 Diabetes Flemming Pociot Professor, MD, DMSc
Copenhagen DIRECT Copenhagen Diabetes Research Center
The Autoimmune Pathogenesis of Type 1 Diabetes
Flemming Pociot Professor, MD, DMSc
Why trying to understand narcolepsy genetics and pathogenesis by contrasting it to type 1 diabetes?
The major players in autoimmune disease development
Environmental triggers Genetic susceptibility
Immune system and b-cell
Autoimmunity module
T1D
CeD
RA
IBD
MS
NAR
Genetic and immunology studies have demonstrated considerable overlap between autoimmune diseases
Won et al (2004) J Clin Sleep Med Pundziute-Lyckå et al (2002) Diabetologia https://www.23andme.com
Narcolepsy
T1D
Thannickal et al (2000) Neuron
NORMAL TYPE 1 DIABETIC
Hypocretin staining
Insulin staining
NORMAL NARCOLEPSY
Target cells are dispersed and limited in number
Mundinger et al (2016) Diabetes
Thannickal et al (2000) Neuron
Cell-specific destruction
T1D vs Narcolepsy (genetics)
T1D NAR Autoimmune YES YES Prevalence 0.4% 0.02-0.2% HLA major genetic risk component >50% >85% HLA major risk genotype: DQ2/DQ8 DQ6 Non-HLA risk ~ 50 loci ~ 3 -10* loci OR non-HLA loci 1.05-1.8 1.05-1.5 Explained heritability ~ 80-85% ~50% **
*: GWAS p-value <10E-6) **: Model-dependent
Pociot and Lernmark (2016) Lancet
Interception
Natural history of type 1 diabetes
Studies of pathogenesis
Pociot and Lernmark (2016) Lancet
Autoantibodies are strong predictors of T1D risk but not causal factors
Pociot and Lernmark (2016) Lancet
DR3-DQ2/DR4-DQ8
DR3-DQ2/DR3-DQ2 DR4-DQ8/DR8-DQ4
DR4-DQ8/DR4-DQ8
Størling et al (2013) Diabetologia Mignot (2014) Immunol Res
Type 1 diabetes
Narcolepsy
Pathogenetic model – A dialogue between the target cell and the immune system
Eizirik et al. Nat Rev Endocrinol 2009
Cytokine-induced β-cell apoptosis
Faraco et al (2013) Plos Genet
Immunochip data - Narcolepsy
GWAS data NAR and T1D
The HLA association
Narcolepsy: > 90% DQB1*0602 positive (20-25% of the background population T1D: > 90% positive for DR3 and/or DR4 (45% of the background population)
Immune genes
Insulin production and metabolism
Beta-cell apoptosis Unknown function
Futher insight into the pathogenesis from genetics
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: expressed in human islets/β-cells
KEGG/GO
Bergholdt et al (2012) Diabetes, Eizirik et al (2012) Plos Genet
Faraco et al (2013) Plos Genet
Immunochip data - Narcolepsy
GWAS data NAR and T1D (Manhattan plots)
Guo et al (2015) Hum Genet Mol
CTSH region on 15q25.1
Lysosomal cysteine cathepsins:
Proteases known for their presence in the lysosomes - protein degradation.
Cathepsins Involvement in diabetes
Cathepsin G, D, S, and V Involved in proinsulin processing Zou et al. PLoS ONE 2011
Cathepsin G Important for generation of proinsulin-reactive T cells Zou et al. PLos ONE 2011
Cathepsin S, B, and L Important for onset of autoimmune diabetes in NOD mice
Maehr et al. J Clin Invest 2005, Hsing et al. J Autoimmun 2010
Cathepsin S, W, H and C Immune cell penetration of the peri-islet basement membrane leading to insulitis Korpos et al. Diabetes 2013
Involved in cellular processes such as apoptosis, antigen presentation, and prohormone
processing.
Cysteine cathepsins
Associated with diseases e.g. cancer, osteoporosis, rheumatoid arthritis,
osteoarthritis, and type 1 diabetes
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Slide 20
T1D-associated single nucleotide polymorphisms (SNPs)
affect the mRNA and protein expression of CTSH
CTSH is expressed in human β-cells
CTSH is downregulated by pro-inflammatory cytokines in
human islets and rat β-cells
Overexpression of CTSH decreases cytokine-
induced apoptosis and increases insulin
expression in INS-1 cells
Children with T1D who carries the SNP genotype causing
low CTSH expression have less residual β-cell function
Floyel et al. PNAS 2014
CTSH affects β-cell function
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CTSH
b-actin
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Islets from Ctsh knockout mice contain less
insulin compared to wild-type mice
WT
KO
STAT1
CELL DEATH
gene transcription e.g.
iNOS, DP5, c-Myc, Bim
Nucleus
IRAK1
TRAF6
JNK
NFkB
Plasma membrane IL-1RI IL-1AcP
MAPKK
IL-1 IFNγ IFNγ
IFNγR1 IFNγR2
IKK ERK p38
Transcription factors
e.g. c-Jun, JunD
Non-transcription factors
e.g. Bcl-2 family members
NFkB IkB
MyD
8
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To
llip
JAK1 JAK1
IRAK4 JAK2 JAK2
STAT1
STAT1 STAT1
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CTSH decreases cytokine signalling
CTSH overexpression changes a limited number of β-cell genes
Fløyel et al, In preparation
Genes affecting beta-cell function in type 1 diabetes
Fløyel et al (2016) Curr Diabetes Rep
‘Classical’ immune genes are important in β-cell function
Challenges Define ‘true’ risk (study the pre-diabetic phase) Disease classification (e.g. based on biomarkers) Uncover novel mechanisms (in vitro and in vivo studies) Guiding therapeutic options
How will we address these issues? 1. The identification and understanding of type 1
diabetes biomarkers 2. Prediabetes biomarker discovery 3. Gene regulation, non-coding RNAs and
epigenetics 4. New cohorts – e.g. TrialNet, TEDDY; 5. Collaboration (Local, national, and international)
An IMI2 EU Project 26 ACADEMIC INSTITUTIONS AND CLINICS 4 EFPIA PARTNERS 2 PATIENT ORGANIZATION 1 SME SMALL AND MEDIUM SIZED ENTERPRISE ECONOMY: TOTAL FUNDING 35 MIO EUR/7 YEARS START 2016
Some INNODIA objectives 1. Develop a European infrastructure for the recruitment,
detailed clinical phenotyping and bio‐sampling of a large cohort of newly diagnosed subjects with T1D and at risk family members
2. Establish a tight collaborative network of basic and clinical researchers working in a coordinated and focused way to address key knowledge gaps in relation to β-cell autoimmunity, leading to a better understanding of the pathogenesis of T1D and a cure for this disease
3. Conceive innovative clinical trial designs that exploit novel validated biomarkers allowing better subject stratification and functioning as surrogate endpoints, thus yielding shorter and more focused intervention studies of single or combined therapies
"You've got to be very
careful if you don't
know where you're
going, because you
might not get there." Yogi Berra
Thank you!