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Exploring the Grey Zone between Type 1 and Type 2 Diabetes

Bakhtadze, Ekaterine LU (2009) In Lund University, Faculty of Medicine Doctoral Dissertation Series 2009:14.
Abstract (Swedish)
Popular Abstract in Swedish

Diabetes kännetecknas av förhöjda halter av glukos i blodet och flera vanliga former förekommer. Typ 1 (T1D) diabetes är vanligast förekommande hos barnoch ungdomar och karakteriseras av att de insulin producerande cellerna (s.k. betacellerna) förstörs av kroppens eget immunförsvar, en autoimmun reaktion.

Patienter med T1D diabetes kräver insulin för överlevnad och har ofta riskgenotyper så som HLA-DQB1, INS VNTR, PTPN22. Hos vuxna beskrivs samma situation som Latent Autoimmune Diabetes in Adults (LADA) med en diagnos efter 35-års ålder och utan insulinbehandling de första sex månaderna.

Typ 2 diabetes (T2D) karakteriseras av minskad insulinsekretion och nedsatt insulinverkan... (More)
Popular Abstract in Swedish

Diabetes kännetecknas av förhöjda halter av glukos i blodet och flera vanliga former förekommer. Typ 1 (T1D) diabetes är vanligast förekommande hos barnoch ungdomar och karakteriseras av att de insulin producerande cellerna (s.k. betacellerna) förstörs av kroppens eget immunförsvar, en autoimmun reaktion.

Patienter med T1D diabetes kräver insulin för överlevnad och har ofta riskgenotyper så som HLA-DQB1, INS VNTR, PTPN22. Hos vuxna beskrivs samma situation som Latent Autoimmune Diabetes in Adults (LADA) med en diagnos efter 35-års ålder och utan insulinbehandling de första sex månaderna.

Typ 2 diabetes (T2D) karakteriseras av minskad insulinsekretion och nedsatt insulinverkan tillsammans med ökad produktion av glukos från levern och onormal fettmetabolism. Miljöfaktorer som ökar insulinresistens är pubertet, graviditet, viktuppgång (framför allt central fetma, s.k. ”äpple form”) och fysisk inaktivitet. T2D diagnosticeras vanligen efter 40-års ålder, i vissa fall efter att patienten utvecklat kärl och neurala komplikationer. TCF7L2 genen associerar starkt med typ 2 diabetes. Maturity-onset diabetes of the young (MODY) är en monogen form av diabetes som nedärvs dominant (dvs. patienten har en muterad och en normal variant av på de två kromosomerna) och karakteriseras av diabetes utan förekomst av ketoner, sjukdomsdebut innan 25-års ålder och orsakas av en störning i betacellsfunktionen. Hittills har mutationer i sex gener visat sig orsaka MODY, HNF-4 (MODY 1), glucokinas (GCK) (MODY 2), HNF-1 (MODY 3), IPF1 (MODY 4), HNF-1ß, (MODY 5) och NeuroD1 (MODY 6). Målet med denna avhandling var att undersöka genetiska skillnader mellan autoimmun (typ 1 diabetes och LADA) och icke-autoimmun (typ 2 diabetes och MODY) diabetes i unga (15-34 år) och medelålders (40-59 år) diabetiker från Sverige för att förbättra framtidens diagnoser och behandling.

I första studien undersökte vi huruvida HLA-DQB1 genotyper kunde förbättra klassificering av diabetes jämfört med antikoppar mot insulinproducerande celler i unga (15-34 år) diabetespatienter. Antikroppar (ICA, IA-2A eller GADA) mot insulinproducerande celler upptäcktes hos 83% av patienter som

kliniskt karakteriserades som T1D, hos 23% av patienter med T2D och hos 45% av patienter vars diabetes inte kunde klassificeras enligt kliniska symptom. Hos patienter med antikroppar var C-peptidnivåerna, ett mått av betacellsfunktion, lägre vid diagnosen än hos patienter utan antikroppar. Oberoende av klinisk klassificering hade patienter med antikroppar högre frekvens av HLA-DQB1 risk genotyper än patienter utan antikroppar. Patienter utan antikroppar och bärare av HLA-DQB1 risk genotyper hade lägre C-peptidnivåer än de som inte hade risk gennotyper av HLA-DQB1. Från dessa resultat drog vi slutsatsen att antikroppsmätningar är nödvändiga för att klassificera patienter med diabetes. Genotypning av HLA-DQB1 bidrar inte till bättre klassificering hos patienter med antikroppar. I patienter utan autoantikroppar kan genotypning av HLADQB1 tillsammans med mätning av C-peptidnivåer bidra till bättre urskiljning mellan T1D och T2D.

I studie II undersökte vi om genetiska markörer associerade med T1D (HLADQB1, INS VNTR and PTPN22) och T2D (TCF7L2) kunde hjälpa till att skilja mellan autoimmun och icke-autoimmun diabetes hos unga (15-34 år) och medelålders (40-59 år) diabetiker. Frekvensen av riskgenotyper av HLA-DQB1, PTPN22 CT/TT, INS VNTR klass I/I och INS VNTR klass IIIA/IIIA var högre hos både unga och medelålders individer med GADA antikroppar jämfört med individer utan GADA antikroppar. T2D riskgenotypen (CT/TT) i TCF7L2 var vanligare hos unga individer utan GADA antikroppar jämfört med individer med GADA antikroppar. Hos medelålders individer var frekvensen av CT/TT genotyper förhöjt hos både individer med och utan GADA antikroppar. Av dessa resultat kunde vi dra slutsatsen att variationen i TCF7L2 kunde skilja mellan unga men inte medelålders patienter med och utan GADA antikroppar. Detta tyder på att unga patienter utan GADA antikroppar har T2D och att medelålders patienter med GADA antikroppar (LADA) skiljer sig från unga patienter med GADA antikroppar (T1D) och delar delvis genetisk bakgrund med T2D.

I studie III genotypades tio nya varianter associerade med T2D i unga och medelålders diabetiker för att undersöka om dessa varianter kunde påverka den kliniska klassificeringen. Unga patienter utan GADA antikroppar hade en ökad frekvens av PPARG, IGF2BP2, WFS1, JAZF1 och CDKN2A/2B riskgenotyper jämfört med en äldre kontrollgrupp med individer utan diabetes. Risk varianten i JAZF1 och CDKN2A/2B var också vanligare hos unga patienter utan GADA antikroppar än hos unga med GADA antikroppar. Som förväntat hade medelålders patienter utan GADA antikroppar högre frekvens av riskgenotyper i PPARG, IGF2BP2, WFS1, CDKAL1, JAZF1, SLC30A8, CDKN2A/2B, KCNJ11 och FTO gener jämfört med individer utan diabetes och ingen signifikant skillnad kunde observeras mellan medelålders patienter med och utan GADA antikroppar. Medelålders patienter utan GADA antikroppar med 12 eller fler riskalleler hade lägre C-peptid nivåer jämfört med individer med nio eller färre riskalleler. Individer med GADA antikroppar med fler riskalleler hade också tidigare sjukdomsdebut än individer med färre riskalleler. Detta tyder på att T2D associerade riskgenotyper påverkar sjukdomsbilden i medelålders men inte unga diabetes patienter.

I studie IV undersökte vi om vanliga varianter i MODY gener kunde urskilja mellan autoimmun och icke-autoimmun diabetes hos unga diabetiker. Vi letade efter mutationer i de vanligast förekommande MODY gener (HNF-4 , GCK och HNF-1 ) hos individer utan autoantikroppar med tre eller fler familjemedlemmar med diabetes. Ingen skillnad i frekvens mellan individer med eller utan antikroppar observerades bland de undersökta MODY generna. Individer med autoantikroppar som bar på den T2D associerade T-allelen i HNF-1 genen hade senare sjukdomsdebut och en svårare sjukdomsbild med viktnedgång och polyuri än de individer som saknade allelen. Hos individer utan antikroppar hade bärare av den T2D associerade G-allelen i HNF-1ß genen mindre ofta problem med viktnedgång, polyuri och ketonuri än individer utan allelen. Bland patienter med flera familjemedlemmar med diabetes kunde vi identifiera en individ med en MODY mutation i exon fyra i HNF-1 genen. Våra resultat tyder på att vanliga varianter i MODY gener inte kan urskilja mellan autoimmun och icke-autoimmun diabetes hos unga individer, däremot kan de påverka åldern vid insjuknande och sjukdomsbilden.

Våra studier visar att genetiska markörer tydligt förbättrar klassificeringen av diabetes och tillsammans med antikroppar mot insulinproducerande celler kan hjälpa vid diagnosen och behandlingen av olika diabetesgrupper. (Less)
Abstract
T1D is most common in children and young adults and is characterized by

autoimmune destruction of insulin producing pancreatic beta cells, presence of certain risk genotypes such as HLA-DQB1, INS VNTR, PTPN22 and need of

insulin for survival. In adults the same situation is often referred to as Latent Autoimmune Diabetes in Adults (LADA), with age at onset after 35 years and non-insulin requiring at least for 6 month after diagnosis. On the other hand, T2D is characterized by impaired insulin secretion and/or insulin resistance, which coexists with excessive hepatic glucose production and abnormal fat metabolism. Environmental factors causing insulin resistance are puberty, pregnancy, weight gain (central obesity “apple... (More)
T1D is most common in children and young adults and is characterized by

autoimmune destruction of insulin producing pancreatic beta cells, presence of certain risk genotypes such as HLA-DQB1, INS VNTR, PTPN22 and need of

insulin for survival. In adults the same situation is often referred to as Latent Autoimmune Diabetes in Adults (LADA), with age at onset after 35 years and non-insulin requiring at least for 6 month after diagnosis. On the other hand, T2D is characterized by impaired insulin secretion and/or insulin resistance, which coexists with excessive hepatic glucose production and abnormal fat metabolism. Environmental factors causing insulin resistance are puberty, pregnancy, weight gain (central obesity “apple type”) and sedentary lifestyle. Usually T2D is diagnosed after 40 years of age and in some cases is diagnosed when patients develop vascular and neuropathic complications. TCF7L2 is by far the strongest T2D-associated gene. Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes inherited in an autosomal dominant fashion (individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes) characterized by nonketotic diabetes, age at onset before 25 years and primarily defect in beta-cell function. Until now, mutations in six genes have been identified as the cause of different forms of MODY, i.e. HNF-4 (MODY 1), glucokinase (GCK) (MODY 2), HNF-1 (MODY 3), IPF1 (MODY 4), HNF-1ß, formerly TCF2 (MODY 5) and NeuroD1 (MODY6). The goal of this thesis was to genetically dissect autoimmune (T1D and LADA) and non-autoimmune (T2D and MODY) diabetes in young (15-34 years old)and middle-aged (40-59 years old) Swedish diabetic patients for proper diagnosis and treatment of the disease in the future. To fulfill our goals we have selected 1642 young (15-34 years old) adult diabetic patients from Diabetes Incidence Study in Sweden (DISS) and 1619 middle-aged (40-59 years old) diabetic patients from Diabetes Registry in Southern Sweden. We determined genetic markers: HLA-DQB1 (study I and II), PTPN22, Ins VNTR, TCF7L2 (study II), PPARG, KCNJ11, IGF2BP2, WFS1, CDKAL1, JAZF1, CDKN2A/2B, HHEX, SLC30A8 and FTO (study III) and MODY genes- HNF-4 , GCK, HNF-1 and HNF-1ß, formerly TCF2 (study IV), measured islet antibodies (ICA, IA-2A and GADA) and C-peptide (marker of beta-cell function instead of insulin).

In Study I we evaluated whether HLA-DQB1 genotypes facilitates the classification of diabetes as compared with islet antibodies among young (15-34 years) adult diabetic patients. Islet antibodies were found among 83% clinically considered to have T1D, 23% with T2D and 45% with unclassifiable diabetes.fpC-peptide concentrations after diagnosis were markedly lower in patients with than in those without islet antibodies. Irrespective of clinical classification, patients with islet antibodies showed increased frequencies of at least one risk HLA-DQB1 genotypes compared with patients without. Antibody negative patients with risk HLA-DQB1 genotypes had significantly lower fasting fpC-peptide concentrations than those without risk genotypes. We concluded that Assessment of islet antibodies is necessary for an etiological classification of diabetic patients. HLA-DQB1 genotyping does not improve the classification in patients with islet antibodies. However, in patients without islet antibodies, HLA-DQB1 genotyping together with fpC-peptide measurement may be of value in the differentiation between idiopathic T1D versus T2D.

In Study II we evaluated whether genetic markers associated with T1D (HLADQB1,INS VNTR and PTPN22) and T2D (TCF7L2) could help to discriminate between autoimmune and non-autoimmune diabetes in young (15-34 years) and

middle-aged (40-59 years) diabetic patients. Frequency of risk genotypes HLADQB1, PTPN22 CT/TT, INS VNTR class I/I and INS VNTR class IIIA/IIIA was

increased in young and middle-aged GADA+ compared with GADA- patients.

T2D-associated genotypes of TCF7L2 CT/TT of rs7903146 were significantly

more common in young GADA- than in GADA+ patients. No such difference

was seen in middle-aged patients, in whom the frequency of the CT/TT

genotypes of TCF7L2 was similarly increased in GADA- and GADA+ groups.

We concluded that common variants in the TCF7L2 gene help to differentiate

young but not middle aged GADA+ and GADA- diabetic patients, suggesting

that young GADA- patients have T2D and that middle-aged GADA+ patients

(LADA) are different from their young GADA-positive (T1D) counterparts and

share genetic features with T2D.

In Study III we genotyped a panel of 10 novel T2D-associated risk genotypes in young (15-34 years) and middle-aged (40-59 years) GADA+ and GADA- diabetic patients and evaluated how they would modify the clinical phenotype. Young GADA- patients had increased frequency of risk variants in the PPARG, IGF2BP2, WFS1, JAZF1 and CDKN2A/2B genes compared with an elderly nondiabetic control group. Also risk variants in JAZF1 (AA) and CDKN2A/2B (TT) were more common in GADA- than in GADA + young diabetic patients. As expected middle-aged GADA- patients had increased prevalence of risk variants in the PPARG, IGF2BP2, WFS1, CDKAL1, JAZF1, SLC30A8, CDKN2A/2B, KCNJ11 and FTO genes compared with non-diabetic controls with no significant difference compared with GADA+ patients. Middle-aged GADA diabetic patients with more risk alleles (≥12) had decreased C-peptide concentrations than patients with less risk alleles (≤9). Also, GADA+ patients with more risk alleles had an earlier age at onset than GADA+ patients with less risk alleles. Distribution of T2D-associated risk alleles was quite similar inmiddle-aged patients regardless of presence of GADA. T2D- associated risk genotypes modify the disease phenotype (age at onset and C-peptide) in middleaged but not in young diabetic patients.

In Study IV we evaluated whether common variants in MODY genes can

discriminate between autoimmune and non-autoimmune diabetes in young adult

diabetic patients and screened antibody negative diabetic patients with 3

members with diabetes in the family for HNF-4 , GCK and HNF-1 mutations.

No significant difference in frequency of common variants in MODY genes was

seen between Ab+ and Ab- individuals. In Ab+ diabetic patients carriers of the T2D-associated T allele of the HNF-1 gene had higher age at onset of diabetes, but severe symptoms of diabetes (weight reduction and/or polyuria) than G allele carriers. Finally, in Ab- diabetic patients carriers of the T2D-associated G allele of HNF-1ß gene had less frequent weight reduction and/or polyuria and ketonuria at diagnosis than A allele careers. One patient had frameshift mutation in exon 4 designated “Pro291fsinsC” in the HNF-1 gene. Common variants in MODY genes do not discriminate between young patients with autoimmune and non-autoimmune diabetes but they do influence onset and presentation of the disease.

Our studies show that genetic markers clearly improve the classification of

diabetes and together with islet antibodies they might be of help for diagnosis and treatment of different diabetic subgroups. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Knip, Mikael, Hospital for Children and Adolescents, University of Helsinki
organization
publishing date
type
Thesis
publication status
published
subject
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
volume
2009:14
pages
169 pages
publisher
Department of Clinical Sciences, Lund University
defense location
The Grand Hall at the Medical Research Center, Entrance 59, UMAS
defense date
2009-02-20 09:00
ISSN
1652-8220
ISBN
978-91-86253-01-1
language
English
LU publication?
yes
id
ee24ebd3-ad3c-418f-9259-d9e24c1a494c (old id 1288295)
date added to LUP
2009-01-30 13:40:12
date last changed
2016-09-19 08:44:50
@phdthesis{ee24ebd3-ad3c-418f-9259-d9e24c1a494c,
  abstract     = {T1D is most common in children and young adults and is characterized by<br/><br>
autoimmune destruction of insulin producing pancreatic beta cells, presence of certain risk genotypes such as HLA-DQB1, INS VNTR, PTPN22 and need of<br/><br>
insulin for survival. In adults the same situation is often referred to as Latent Autoimmune Diabetes in Adults (LADA), with age at onset after 35 years and non-insulin requiring at least for 6 month after diagnosis. On the other hand, T2D is characterized by impaired insulin secretion and/or insulin resistance, which coexists with excessive hepatic glucose production and abnormal fat metabolism. Environmental factors causing insulin resistance are puberty, pregnancy, weight gain (central obesity “apple type”) and sedentary lifestyle. Usually T2D is diagnosed after 40 years of age and in some cases is diagnosed when patients develop vascular and neuropathic complications. TCF7L2 is by far the strongest T2D-associated gene. Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes inherited in an autosomal dominant fashion (individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes) characterized by nonketotic diabetes, age at onset before 25 years and primarily defect in beta-cell function. Until now, mutations in six genes have been identified as the cause of different forms of MODY, i.e. HNF-4 (MODY 1), glucokinase (GCK) (MODY 2), HNF-1 (MODY 3), IPF1 (MODY 4), HNF-1ß, formerly TCF2 (MODY 5) and NeuroD1 (MODY6). The goal of this thesis was to genetically dissect autoimmune (T1D and LADA) and non-autoimmune (T2D and MODY) diabetes in young (15-34 years old)and middle-aged (40-59 years old) Swedish diabetic patients for proper diagnosis and treatment of the disease in the future. To fulfill our goals we have selected 1642 young (15-34 years old) adult diabetic patients from Diabetes Incidence Study in Sweden (DISS) and 1619 middle-aged (40-59 years old) diabetic patients from Diabetes Registry in Southern Sweden. We determined genetic markers: HLA-DQB1 (study I and II), PTPN22, Ins VNTR, TCF7L2 (study II), PPARG, KCNJ11, IGF2BP2, WFS1, CDKAL1, JAZF1, CDKN2A/2B, HHEX, SLC30A8 and FTO (study III) and MODY genes- HNF-4 , GCK, HNF-1 and HNF-1ß, formerly TCF2 (study IV), measured islet antibodies (ICA, IA-2A and GADA) and C-peptide (marker of beta-cell function instead of insulin).<br/><br>
In Study I we evaluated whether HLA-DQB1 genotypes facilitates the classification of diabetes as compared with islet antibodies among young (15-34 years) adult diabetic patients. Islet antibodies were found among 83% clinically considered to have T1D, 23% with T2D and 45% with unclassifiable diabetes.fpC-peptide concentrations after diagnosis were markedly lower in patients with than in those without islet antibodies. Irrespective of clinical classification, patients with islet antibodies showed increased frequencies of at least one risk HLA-DQB1 genotypes compared with patients without. Antibody negative patients with risk HLA-DQB1 genotypes had significantly lower fasting fpC-peptide concentrations than those without risk genotypes. We concluded that Assessment of islet antibodies is necessary for an etiological classification of diabetic patients. HLA-DQB1 genotyping does not improve the classification in patients with islet antibodies. However, in patients without islet antibodies, HLA-DQB1 genotyping together with fpC-peptide measurement may be of value in the differentiation between idiopathic T1D versus T2D.<br/><br>
In Study II we evaluated whether genetic markers associated with T1D (HLADQB1,INS VNTR and PTPN22) and T2D (TCF7L2) could help to discriminate between autoimmune and non-autoimmune diabetes in young (15-34 years) and<br/><br>
middle-aged (40-59 years) diabetic patients. Frequency of risk genotypes HLADQB1, PTPN22 CT/TT, INS VNTR class I/I and INS VNTR class IIIA/IIIA was<br/><br>
increased in young and middle-aged GADA+ compared with GADA- patients.<br/><br>
T2D-associated genotypes of TCF7L2 CT/TT of rs7903146 were significantly<br/><br>
more common in young GADA- than in GADA+ patients. No such difference<br/><br>
was seen in middle-aged patients, in whom the frequency of the CT/TT<br/><br>
genotypes of TCF7L2 was similarly increased in GADA- and GADA+ groups.<br/><br>
We concluded that common variants in the TCF7L2 gene help to differentiate<br/><br>
young but not middle aged GADA+ and GADA- diabetic patients, suggesting<br/><br>
that young GADA- patients have T2D and that middle-aged GADA+ patients<br/><br>
(LADA) are different from their young GADA-positive (T1D) counterparts and<br/><br>
share genetic features with T2D.<br/><br>
In Study III we genotyped a panel of 10 novel T2D-associated risk genotypes in young (15-34 years) and middle-aged (40-59 years) GADA+ and GADA- diabetic patients and evaluated how they would modify the clinical phenotype. Young GADA- patients had increased frequency of risk variants in the PPARG, IGF2BP2, WFS1, JAZF1 and CDKN2A/2B genes compared with an elderly nondiabetic control group. Also risk variants in JAZF1 (AA) and CDKN2A/2B (TT) were more common in GADA- than in GADA + young diabetic patients. As expected middle-aged GADA- patients had increased prevalence of risk variants in the PPARG, IGF2BP2, WFS1, CDKAL1, JAZF1, SLC30A8, CDKN2A/2B, KCNJ11 and FTO genes compared with non-diabetic controls with no significant difference compared with GADA+ patients. Middle-aged GADA diabetic patients with more risk alleles (≥12) had decreased C-peptide concentrations than patients with less risk alleles (≤9). Also, GADA+ patients with more risk alleles had an earlier age at onset than GADA+ patients with less risk alleles. Distribution of T2D-associated risk alleles was quite similar inmiddle-aged patients regardless of presence of GADA. T2D- associated risk genotypes modify the disease phenotype (age at onset and C-peptide) in middleaged but not in young diabetic patients.<br/><br>
In Study IV we evaluated whether common variants in MODY genes can<br/><br>
discriminate between autoimmune and non-autoimmune diabetes in young adult<br/><br>
diabetic patients and screened antibody negative diabetic patients with 3<br/><br>
members with diabetes in the family for HNF-4 , GCK and HNF-1 mutations.<br/><br>
No significant difference in frequency of common variants in MODY genes was<br/><br>
seen between Ab+ and Ab- individuals. In Ab+ diabetic patients carriers of the T2D-associated T allele of the HNF-1 gene had higher age at onset of diabetes, but severe symptoms of diabetes (weight reduction and/or polyuria) than G allele carriers. Finally, in Ab- diabetic patients carriers of the T2D-associated G allele of HNF-1ß gene had less frequent weight reduction and/or polyuria and ketonuria at diagnosis than A allele careers. One patient had frameshift mutation in exon 4 designated “Pro291fsinsC” in the HNF-1 gene. Common variants in MODY genes do not discriminate between young patients with autoimmune and non-autoimmune diabetes but they do influence onset and presentation of the disease.<br/><br>
Our studies show that genetic markers clearly improve the classification of<br/><br>
diabetes and together with islet antibodies they might be of help for diagnosis and treatment of different diabetic subgroups.},
  author       = {Bakhtadze, Ekaterine},
  isbn         = {978-91-86253-01-1},
  issn         = {1652-8220},
  language     = {eng},
  pages        = {169},
  publisher    = {Department of Clinical Sciences, Lund University},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {Exploring the Grey Zone between Type 1 and Type 2 Diabetes},
  volume       = {2009:14},
  year         = {2009},
}