African Journal of Pharmacy and Pharmacology Vol. 6(10), pp. 685-691, 15 March, 2012 Available online at http://www.academicjournals.org/ajpp DOI: 10.5897/AJPP11.052 ISSN 1996-0816 2012 Academic Journals Full Length Research Paper Extensive studies on polymerase chain reactionsequence-specific primers (PCR-SSP) based HLA- DRB1* allele profiling in non insulin dependent diabetes mellitus (Indian population) P. Prabhavathi 1 *, K. Balakrishnan 2, V. Prabakaran 3, R. Rajendran 1 and T. Kuberan 3 1 PG and Research Department of Microbiology, PSG College of Arts and Science, Coimbatore 641014, Tamil Nadu, India. 2 Department of Animal Science, Madurai Kamaraj University, Tamil Nadu, India. 3 Department of Microbiology Post Graduate Research, Ayya Nadar Janaki Ammal College, Sivakasi- 626124, Tamil Nadu, India. Accepted 22 February, 2012 Human leukocyte antigen (HLA) system, the most polymorphic and comprehensively studied gene locus, is extensively used to understand the evolution of genetic relatedness and migration of different world populations. To analyze the contribution of HLA class II genes in type 2 diabetes mellitus, we examined the distribution of HLA- DRB1* loci in Indian population of Tamil Nadu using polymerase chain reaction-sequence-specific primers (PCR-SSP). The results were compared with random controls (n=25) of the different area. The present study deals with the genetic association of HLA DRB1* allele in type 2 diabetic patients. The HLA DRB1* 15 and HLA DRB1* 03 were found at higher frequencies than in many other alleles. In controls, DRB1*07 was shown to be at a higher frequency. However, some of the common alleles in the population, such as HLA DRB1*19 11 were not observed in the present study of diabetic patients. HLA DRB1*16, 08 and 04 were recorded with less frequency in diabetic patients. In India, type 2 diabetes is significant association (p<0.005) with allele frequency. Key words: Type 2 diabetes, human leukocyte antigen, allele frequency. INTRODUCTION Diabetes mellitus is a heterogenous collection of metabolic disorders, characterized by hyperglycemia. Type 2, non-insulin dependent diabetes mellitus (NIDDM) is the most common form of diabetes and one of the most frequent metabolic disorders worldwide (Wolford et al., 2004). The term diabetes mellitus encompasses a heterogeneous group of disorder characterized by insulin hypo secretion or insensitivity (Almind et al., 1993). Diabetes mellitus affects approximately 150 million people around the world. It is forecasted that by 2025 this *Corresponding author. E-mail: prabha_micro2007@yahoo.co.in. number would be doubled, with a prevalence that varies markedly from population to population (Rahithys et al., 2005). There is strong evidence that Type 2 Diabetes mellitus (T2DM) is inherited and has a genetic origin. Increasingly, the focus of many genetic researches has turned to identifying genetic variants that underlie complex traits. Such genetic variants may modesty influence the risk of a particular phenotype or trait. Disease (or traits) that can be caused by a combination of genetic and environmental factors are called complex on multifactorial. Many of the most common disease are multifactorial, such as cancer, asthma, diabetes and inflammatory bowel syndrome. These diseases are heritable, but what is inherited is not the disease itself, but rather the susceptibility to it.
686 Afr. J. Pharm. Pharmacol. While some genetic disease may be caused by a mutation on a single gene and are known as monogenic most complex disease are caused by mutations on a number of genes and are termed polygenic. Examples of monogenic disease are cystic fibrosis and phenylketonuria both of which are caused by single nucleotide polymorphism (SNP) with both having a high penetrance, that is, all people with that specific mutation will develop the disease. The environmental influence on a disease may also vary with the amount that the population has been exposed to specific environmental factor (Edege et al., 2005). T2DM is a multifactorial disease with a substantial genetic component that is thought to be polygenic in nature. A combination of genes thus likely influences the underlying level of glucose intolerance in a population and thereby contributes to the overall susceptibility to T2DM. Although genetic linkage analysis and association studies have implicated several loci and candidate genes in pre-disposition to genetic susceptibility to this condition remain to be identified. In addition, the ethnic differences in life style and environmental factors as well as genetic background, it is important to examine polymorphism related to T2DM in each ethnic group. Its specific etiology is not yet known. Its frequency varies in different racial and ethnic subgroups and is often associated with a strong familial, likely genetic, predisposition, more so than auto immune Type 1 (insulin dependent) diabetes mellitus. The genetics of Type 2 diabetics are complex and not clearly defined (Barroso, 2005). (Non-insulin dependent) T2DM is the most common diabetes form and its susceptibility is determined by environmental and genetic factors, the latter being complex and poorly defined while the association of HLA class II genes in Type 1 diabetic pathogenesis was reported for several ethnicities. Studies on HLA class II association with T2DM provided inconsistent results, since an association, no association (Cerna et al., 2003) or weak link between HLA class II and T2DM is reported. A number of studies focused on HLA association with increased frequency of HLA DR3 and DR4 in islet cell immunity (ILA)- Positive patents refractory to oral anti diabetic drugs as reported by some but not others, and association of HLA-DRB1* 1502 with T2DM in antiglutanic acid decarboxylase (GAD) positive patients. The HLA system contributes to the immune response. It is a set of molecules (glycoprotiens) expressed at the surface of almost all cells that are responsible for lymphocyte recognition and antigen presentation. The HLA molecules control the immune response through recognition of self and non-self. HLA molecules are coded by two groups of gene, HLA class I and HLA class II (Tuomi et al., 1999). The HLA is located on Chromosome 6 p21.31 and covers a region of about 3.6 Mbp depending on the haploytpe. The classical HLA antigens encoded in each region are HLA-A, B, and Cw in the class I region and HLA- DR, DQ and DP in the class II region. All class I genes are between 3 and 6 kb, where as class II genes are 4 to 11 kb length. While the role of HLA in the pathogenesis of Type 1 diabetes was reported by several groups, its role in Type 2 diabetes is less clear, and weak links between HLA class II and Type 2 diabetes were reported for some ethnic groups. Previous investigation of the contribution of HLA class II in Type II diabetes pathogenesis focused on HLA relationship with autoimmune markers and latent autoimmune diabetes in adults, possible genetic interaction between Type 1 and 2 diabetes in families and its association with complications and mortality in Type 2 diabetes patients. T2DM affects 1 to 2% of Caucasian, but it is much higher in some ethnic groups such as prime Indian (Knowler et al., 1990). Type 2 diabetes has no auto immune etiology, but is characterized by resistance to the action of insulin combined with an inadequate compensatory insulin secretory response. The aim of the present study was done with genetic association of HLA- DRB1* alleles in Type 2 Diabetic patients as well as random controls. MATERIALS AND METHODS Enrollment of volunteers and sample collection Type 2 diabetic patients who are attending some private hospitals in Madurai and Trichy (Tamil Nadu, India) for treatment were enrolled in the study. Permission from the respective hospitals and University Institutional Ethical Committee for working on Human Subjects was received properly. The patients (male and female) were told about the purpose of the study and interested volunteers were enrolled with their oral informed consent. 5 ml of peripheral blood was collected intravenously in an ethylenediaminetetraacetic acid (EDTA) coated, sterile polypropylene centrifuge tubes, under a physicians supervision. The blood was mixed immediately so as to prevent clotting from forming. The anticoaggulated blood was transported to the lab by keeping in a cool pack and processed immediately for deoxyribonucleic acid (DNA) extraction. DNA extraction from human blood Welsh and Bunce (1999) method of DNA extraction by a modified salting-out procedure was adopted for extracting DNA from human blood. Five milliliter of peripheral vein blood was mixed with 45 ml red-cell lysis buffer (RCLB) in a 50 ml polypropylene centrifuge tube. The blood was inverted several times and allowed to stand for 5 min to facilitate the buffer to lyses the red blood cells (RBCs). Then it was centrifuged at 2000 rpm for 10 min. The supernatant was discarded and the pellet obtained was gain rinsed with 2 ml of RCLB and centrifuged at 2000 rpm for 10 min. The clear nucleated (WBCs) pelleted at the bottom was then treated with 3 ml of sodium dodecyl sulfate- nuclear lysis buffer (NLB + SDS) and mixed well. To this 1 ml of 5 M Nacl was then added to precipitate the proteins out. The mixer was then vortexed and 2 ml of chloroform was added and shaken well. This resulted in a homogenous milky solution which was then centrifuged for 10 min at 2000 rpm. The aqueous phase, which contains the DNA in soluble form, was aspirated carefully without sucking the protein layer (interphase) to a new sterile 15 ml centrifuge tube. To this, two volumes of 95% ethanol was added and inverted several times to precipitate the
Prabhavathi et al. 687 Table 1. PCR amplification conditions. Stage Step T C Time (S) Cycles I 1 94 120 1 II III 1 94 10 2 94 60 1 94 10 2 61 50 3 72 30 Hold at 8 C 10 20 DNA. The precipitated DNA was transferred to a 1.5 ml micro centrifuge tube containing 70% ethanol and centrifuged at 2000 rpm for 5 min. The alcohol washing step was repeated to purity the DNA from proteins and salts. The alcohol was drained and after drying the DNA was resuspended in 200 micro liter of TE buffer. Quality and quantity checking of DNA The isolated DNA was checked for its purity by taking OD at 260 and 280 nm in an ultraviolet (UV) spectrophotometer. Ratio between OD at 260 and 280 nm was calculated. DNA concentration was estimated by applying the following calculation. Concentration of DNA = OD at 260 x DF x 50 ng / l DF = Dilution factor. The DNA was diluted so that each microliter can contain 50 ng of DNA. HLA DRB1* typing by PCR SSP Genotyping of HLA-DRB1* by PCR SSP method as described by Olerup and Zitterquist (1993) was used in this study. The PCR experiment was set-up as follows; typing per sample for DRB1* alleles, 20 primer mixer (Microsynth, Switzerland) including seventeen DRB1* alleles and three for DRB3 DRB4 and DRB5 specificities were prepared by mixing 0.1 M of allele specific primers and 0.05 M of internal control with cresol red ( 1 g / reaction). The internal control primer for human growth hormone gene was included in all reaction to check individual PCR failures and thus for avoiding correct allele assignation. Primer mixes were dotted in PCR tubes (Cat, No.C79701, Bio plastics, The Netherlands) and frozen at 2 C. PCR mix for 20 reactions (including one negative control) consists of 47.68 l at of double distilled water, 24 l of 10x PCR buffer (1x), 12 l of 100% glycerol (5%) 2.4 of 0.1% gelatin (0.001%), 2.4 l of 20 mm dntp (0.2 mm) (cat No.0032003.303, eppendorf, Germany), and 40 l Template DNA (100 ng / reaction). The PCR mix was added into the primer pre-dotted PCR reaction tubes. Thus each reaction contains 5 l of PCR mix, 5 l of primer mix and 2 l of template DNA. Amplification was done at PCR Master cycler (Eppendorf, Germany) using the following temperature profile (Table 1). Agarose gel electrophoresis The amplified PCR products were electrophoresed in 1.5% agarose gels containing 0.5 g / ml ethidium bromide. The gels were run in 0.5X tris-borate-ethylenediaminetetraacetic acid (TBE) buffer for 30 min at 100 v and visualized under UV- transilluminator and documented in a gel documentation unit (Vilbert Lourmat, France). Alleles were assigned according to the pattern of band formation. Statistical calculations The genotype and phenotype frequencies were calculated as follows. Genotype frequency = N /2n. Phenotype frequency = N /n Where N, total number of each positive allele; N, total number of individual tested. Quality control of PCR Before going into SSP typing of DNA samples, the primers were checked for correct amplification with DNA of known allele specificity for each allele. Previously genotyped DNA samples from in house positive samples were used for the purpose of quality control. Statistical analysis To evaluate the influence of the disease, the clinical and general data are expressed as mean (±SE) with two different samples (Diabetic patients and Random controls, n=25). The difference between these two groups was assessed by two way ANOVA test. Stepwise logistic regression was used to assess the risk of having T2DM upon the presence of Indian history of the disease in the context of the HLA- DRB1* associated allele or any clinical feature that showed a significant difference between groups (Luque et al., 2003). RESULTS AND DISCUSSION The present study was aimed to investigate HLA DRB1* allele frequencies in type II diabetic mellitus patients. Genomic DNA from 25 patients and 25 controls were observed in the present study. DRB1* allele typing was performed by molecular Genotyping using PCR-SSP method (Figure 1). The frequency of HLA Class II DRB1* is presented in Tables 2 and 3. HLA-DRB1* 15 allele was found at a higher frequency in diabetic patients (GF=34 and PF=68%), whereas in controls, it was slightly
Allele Frequency (%) 688 Afr. J. Pharm. Pharmacol. 80 70 60 50 40 30 20 10 0 Genotypic frequency Phenotypic frequency Figure 1. Allele frequency (%) of different HLA-DRB1* allele in Indian population (diabetic patients). Table 2. List of HLA - DRB1* specific allele typed in both control and type 2 diabetic patients (n= 25). S/N Specific alleles Number found (diabetic patients) Number found (control) 1 DRB1*15 17 14 2 DRB1*14 3 1 3 DRB1*10 6 6 4 DRB1*12 2 2 5 DRB1*03 8 4 6 DRB1*07 5 16 7 DRB1*13 3 1 8 DRB1*16 1 0 9 DRB1*04 1 3 10 DRB1*08 1 0 11 DRB1*19 0 0 12 DRB1*11 0 1 13 Blank 3 2 Table 3. Genotypic and phenotypic frequency of HLA DRB1* alleles in diabetic patients. Type II diabetes S/N HLA DRB1* alleles GF (genotypic frequency) PF (phenotypic frequency) % Value % Value 1 DRB1*15 34 0.34 68 0.68 2 DRB1*14 6 0.06 12 0.12 3 DRB1*10 12 0.12 24 0.24 4 DRB1*12 4 0.04 8 0.08 5 DRB1*03 16 0.16 32 0.32 6 DRB1*07 10 0.10 20 0.20 7 DRB1*13 6 0.60 12 0.12 8 DRB1*16 2 0.02 4 0.04 9 DRB1*04 2 0.02 4 0.04 10 DRB1*08 2 0.02 0 0.00 11 DRB1*19 0 0.00 0 0.00 12 DRB1*11 0 0.00 0 0.00 13 Blank 6 0.06 12 0.12
Prabhavathi et al. 689 Table 4. Genotypic and phenotypic frequency of HLA DRB1* alleles in normal healthy control. Control samples S. No HLA DRB1* Alleles GF (genotypic frequency) PF (phenotypic frequency) % Value % Value 1 DRB1*15 28 0.28 56 0.56 2 DRB1*14 2 0.02 4 0.04 3 DRB1*10 12 0.12 24 0.24 4 DRB1*12 4 0.04 8 0.08 5 DRB1*03 8 0.08 16 0.16 6 DRB1*07 32 0.32 64 0.64 7 DRB1*13 2 0.02 4 0.04 8 DRB1*16 0 0.00 0 0.00 9 DRB1*04 6 0.06 12 0.12 10 DRB1*08 0 0.00 0 0.00 11 DRB1*19 0 0.00 0 0.00 12 DRB1*11 2 0.02 4 0.04 13 Blank 4 0.04 8 0.08 deduced (GF=28 and PF=68%). This allele is a subtype of serological specificity HLA-DR2. The next highest frequency was observe for HLA-DRB1* 03 at a frequency of GF=16 and PF=32% in diabetic patients. In case of control, It was observed as GF=8 and PF=16%. The present study was attempted to explore the association of HLA DRB1* in Type 2 diabetic patients. Owing to its high polymorphic nature and functional importance in the control of immune response, transplantation immunobiology and susceptility to auto immune and infections disease, HLA-class II DRB1 gene has been drawing more attention in population genetic studies (Balakrishnan, 2003; Stephent and Donnely, 2003). On analyzing the results using analysis of variance (ANOVA) it was found that there existed a significant difference (p<0.05) between both the percentage frequency (both genotypic and phenotypic) of different DRB1* loci, but instead there was no significant difference (p>0.005) between the number of different alleles in diabetic patients (Table 3). The allele DRB1* 15 was present at a higher frequency, the higher frequency of this allele may be due to the progression of disease process in the individual who posses this allele. Such high characteristics for DRB1* 15 was recorded for this allele with reference to tuberculosis. A variety of gene loci have been studied to determine their association with Type 1 DM. The earlier studies suggested that the B8 and B15 of HLA class I antigens were increased in frequency in the diabetes compared to the control group. However, more recently, the focus has shifted to the Class II HLA DR locus (Wassmuth and Lernmark, 1989). Similar frequencies were observed in both diabetic and control patients for HLA DRB1* 10 (GF=12 and PF=24%). Next to allele DRB1* 07 was recorded with GF=10 and PF=20%. Whereas in control, the frequency of DRB1* 07 was increased (FG=32 and PF=64%). However, some of the common alleles in the population HLA-DRB1* 19 and HLA-DRB1* 11 were not observed in the present study of diabetic patients. HLA-DRB1* 16, 08, 04 were recorded with less frequency in diabetic patients. On analyzing the results using ANOVA, it was found that there exist a significant difference (p<0.05) between both the percentage frequency (both genotypic and phenotypic) of different DRB1* loci, but there was no significant difference (p>0.005) between the number of different alleles in random control (Table 4). In random control, the percentage level of both genotypic and phenotypic frequency results (HLA-DRB1* allele) showed (SE, p<0.05) DRB1* 07 (64% (PF)) and DRB1* 07 (32% (GF)). The frequency was reduced to only DRB1* 11, 13 and 14 alleles (Figure 1). HLA DRB1* 12, 16, and 14 were observed as very low frequencies. HLA DRB1*8, DRB1*19, and DRB1*11 were not recorded in the present study. Whereas the allele frequency results with number of alleles (HLA-DRB1* allele), at the end of gel electrophoresis percentage level of both genotypic and phenotypic allele frequency, which showed (SE, p<0.05) DRB1* 07 (64% (PF)) and DRB1* 07 (32% (GF)). The frequency was reduced to only DRB1* 11, 13 and 14 alleles (Figure 2). All the allele bands, shown in Figure 3, compared both normal and diabetic patients. These alleles may show a negative correction in the disease and they may have a protective role. Thus, this notion must be studied and confirmed with large number of cases before coming to conclusion. In the present study, HLA DRB1* 03 was found to be in higher frequency and may play the same role in the pathogenesis of diabetes. It could also play the role of the risk allele, and DRB1* 07 can play the protective role. The identification of susceptibility genes and further research on their function could allow insights in the path physiology of Type 2 diabetes and ultimately lead to new
Alele Frequency (%) 690 Afr. J. Pharm. Pharmacol. 80 70 Genotypic frequency Phenotypic frequency 60 50 40 30 20 10 0 Figure 2. Allele frequency (%) of different HLA-DRB1* allele in Indian population (random control). Figure 3. Gel electrophoresis of HLA-DRB1* PCR-SSP from Type ii diabetic patients DNA. therapeutic strategies. The molecular mechanism by which the HLA molecules influence the risk of disease, needs to be elucidated by future studies. In order to understand how the genetic variation in populations contributes to the condition that leads to symptoms of T2D, the analysis of large sample population with detailed knowledge not only of the genetic pedigree, but also of the lifestyle of the subjects within
Prabhavathi et al. 691 the population, is required. The influence on disease susceptibility of a particular HLA molecule is likely to be determined by its three dimensional structure, which in turn has a significant impact on its function in the immune response. The structural difference between diabetogenic and protective molecules binding affinity and the stability of the HLA molecule distinct peptide binding motifs may therefore interact differently with a given diabetogenic autoantigen. This mechanism seems to offer protection for certain haplotypes and susceptibility for certain others. The disease susceptibility conferred by HLA represents the combined effect of several gene within the major histocompatibility complex (MHC). At least three major loci are involved (HLA DRB1, DQA1, DQA1 and DQB1), but several others genes may also contribute. The precise identities of these genes remain determined (Aljenaidi et al., 2005). Conclusion The analysis of HLA- DRB1* allele frequency in DNA level was very important, because several studies have been carried out on the risk allele of Type 2 diabetes from Indian population. The HLA DRB1* 15 and HLA DRB1* 03 were found at higher frequencies than in many other alleles. In controls, DRB1*07 was shown to be at a higher frequency. However some of the common alleles in the population such as HLA DRB1*19 and 11 were not observed in the present study of diabetic patients. HLA DRB1*16, 08, and 04 were recorded with less frequency in diabetic patients. We also studied the association of insulin receptor substrate polymorphism with Type 2 diabetes and obesity in Indian population and a remarkable result was obtained. It was reported that the allele of this polymorphism was associated with a decreased risk of Type 2 diabetes. REFERENCES Aljenaidi FA, Ghorayedb SFW, Abbasi AA, Arekat MR, Hakine NI, Najm P, Ola KA (2005). Contribution of selective HLA DRB1 / DQBI alleles and hoplotypes to the genetic susceptibility of Type I diabetes among labanese and Baheaini Aeabs, J. Chin. Endocrinol. Metah., 90: 5104-5109. Almind K, Bjorback C, Vestergaard H, Echwalds HT, Pedersen O (1993). Amino acid polymorphism of insulin receptor substrate I in non-insulin dependent diabetes mellitus, Lancet, 354: 828-832, Balakrishnan V (2003). A preliminary study of genetic distance among some populations of the Indian subcontinent, J. Hum. Immunol. Erol., 7: 67-75 Barroso I (2005). Genetius of Type 2 diabetes. Diabet. Med., 22: 517-535. Cerna M, Novota P, Kolostova K, Cejkova P, Zdassky E, Novakova D (2003). HLA in adult pateents with Czech children with type I diabetes and patients with type 2 diabetes, Eur. J. Immumogenet., 30: 401-407. Edege LE, Dagogo SJ (2005). Epidenuology of type 2 diabetes: focus on ethnil minositices. Med. Clin. North Am. 89: 949-975. Knowler W, Petti HDT, Sadd M, Benneh, PH (1990). Diabetes millitis in the pima Indians: incidence viste factors and pathogenesis. Diabetes. Metabol. Rev., 6: 1-27. Luque EP, Alaez C, Malacara JM, Garay ME, Fajardo, ME, Nava LE (2003). Protective Effect of DRB1 Locus Against Type 2 Diabetes Mellitus in Mexican Mestizos. Hum. Immunol., 64: 110-118. Olerup O, Zetterquist H (1993). HLA-DR typing by PCR amplification with sequence-specific primers (PCR-SSP) in 2 hours: An alternative to serological DR typing in clinical practice including donor-recipient matching in cadaveric transplantation. Tissue Antigen, 39: 225-35. Rahithys O, Barroso I, wareham NJ (2005). Genetic factors in Type 2 Diabetes. Sci., 307: 370-373. Stephent M, Donnely P (2003). A comparison of Bayesian methods for haplotype reconstruction from population genotype data. Am. J. Hum. Genet.,.73: 1162. Tuomi TA, Carlsson HLi, Isomma B, Miettinen A, Nilsson A, Nissen M (1999). Clinical and genetic characteristics of type 2 diabetes with a without GAD antibodies, Diabetes, 48: 150-157. Wassmuth R, Lernmark A (1989). The genetics of susceptibility to diabetes. Clin. Immunol. Immunopathol., 53: 358-399. Welsh K, Bunch M (1999). Molecular typing for MHC with PCR-SSP. Rev. Immunogenet, 1: 157-176. Wolford JK, Vozarova B, Courten D (2004). Genetic basis of type 2 Diabetes mellitus implications for therapy. Treat. Endoceinol., 3: 257-267. ACKNOWLEDGEMENT The authors gratefully acknowledge the technical support provided by the Department of Animal Biotechnology, Bharathidhasan University, Trichy.