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Study of genetic factors associated with
diabetes at young age |
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Principal Investigator : Rajni Rani Collaborator The project aims to study the genetic factors
associated with diabetes of the young, which include insulin dependent
diabetes mellitus (IDDM) and ketosis resistant diabetes of the young (KRDY).
Since the disease has been shown to have genetic predisposition, to be able to
identify prediabetics, the project aims to study i) the HLA-A, B, DRB1, DQA1,
DQB1 and DPB1 polymorphism in IDDM and KRDY patients from North India and
ethnically matched controls, ii) the polymorphism of 5’-INS gene (IDDM2) or
insulin linked polymorphic region (ILPR) in IDDM and KRDY patients and
controls, iii) the autoantibody profile to insulin and islet cells and
C-peptide levels in IDDM and KRDY patients and controls and iv) the
association of HLA with the type of autoantibodies found in the patients. 45 IDDM patients and 94 healthy controls from the same
ethnic background have been studied for the polymorphic alleles of HLA-DRB1,
DQA1, DQB1 and DPB1 loci using the polymerase chain reaction (PCR) and
hybridization with sequence-specific oligonucleotide probes (SSOP). The
diagnosis of IDDM was based on clinical manifestations, fasting glucose
levels, urinary ketones and C-peptide levels. Our results show that DRB1*03011
was significantly increased (p<0.00001) in the patient group with a
relative risk of 8.34 and the associated DQB1*0201 and DQA*0501 were also
significantly increased due to linkage disequilibrium between the three
alleles. DRB1*0701 was significantly decreased in the patients as compared to
the controls, though the difference did not remain significant when p was
corrected for the number of alleles tested. None of the DR4 alleles showed any
significant increase nor did any of the DR2 alleles show significant decreases
in the patients. Homozygosity of DRB1*03011 in the patient group was
significantly increased as compared to the controls (p<0.00001) and was
observed to be more than that expected under Hardy-Weinberg equilibrium. We
did not find an increase of DR4 alleles in contrast to some earlier studies on
patients of Indian origin. Several studies have suggested that aspartic acid
at DQb1 residue 57 confers protection while DQA1 with arginine at codon 52
confer susceptibility. However, when DR3 homozygosity was considered along
with codon 57 of DQB1 and codon 52 of DQA1, it was found that the DRB1 *
03011, 03011 -DQB1* XX- DQA1 *RR combination was the only combination that was
significantly increased in the patient group as compared to controls,
suggesting that DRB1*03011 association is primary since the DQB1 and DQA1
alleles in linkage disequilibrium with DRB1*03011 have non-Asp57 and Arg52,
respectively. However, in patients who do not have DRB1*0301, DPB1*2601 was
significantly increased even after p was corrected for the number of alleles
tested at the DP locus, suggesting this association to be independent of the
DR*03 association. Since the major histocompatibility complex (MHC)
region (IDDM1) is the major locus for IDDM followed by 5' regulatory region of
the insulin (INS) gene (IDDM2) on chromosome 11p15, DNA samples from young
diabetics and ethnically matched controls are being studied for Insulin linked
polymorphic region. Studies have shown that insulin linked polymorphic region
(ILPR) is a highly polymorphic stretch of DNA lying 365 bp upstream of the
initiation of transcription of the insulin (INS) gene, the IDDM2. It consists
of a variable number of tandem repeats (VNTR) of a 14 base pair sequence,
which exist in dozen or more forms. It is divided into three different types
based on their sizes: class-I (40 repeats), Class II (about 85 repeats) and
class III (about 150 repeats). The study is ongoing and the data will be
analyzed after the completion of the study to avoid any biases Publications Original peer-reviewed articles 1.
*Malik S, Kumar S and Rani R (2000) k-casein and b-casein
alleles in crossbred and zebu cattle from India using polymerase chain
reaction and sequence specific oligonucleotide probes (PCR-SSOP). J Dairy Res
67:295-300 (*in press last year, since published). 2.
*Sharma P, Misra RS, Kar HK, Mukherjee A, Porichha D, Kaur H,
Mukherjee R and Rani R (2000) Mycobacterium w. vaccine, a useful adjuvant to
multidrug therapy in multibacillary leprosy: A report on hospital based
immunotherapeutic clinical trials with a follow up of 1-7 years after
treatment. Leprosy Rev 71:179-192 (*in press last year, since published). 3.
Sharma P, Kar HK, Misra RS, Mukherjee A, Kaur H, Mukherjee R and
Rani R (2000) Reactional states and neuritis in multibacillary leprosy
patients following MDT with/without immunotherapy with Mycobacterium w. anti
leprosy vaccine. Leprosy Rev 71:193-205. 4.
Sharma P, Kar HK, Misra RS, Mukherjee A, Kaur H, Mukherjee R and
Rani R (2000) Induction of lepromin positivity and immunoprophylaxis in
household contacts of multibacillary leprosy patients: A pilot study with a
candidate vaccine Mycobacterium w. Int J Leprosy 68:136-142. |