• Users Online: 522
  • Print this page
  • Email this page


 
 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 7  |  Issue : 3  |  Page : 138-142

Association of fatty acid-binding protein 2 and fat mass and obesity-associated gene polymorphism with primary open-angle glaucoma


1 Department of Biochemistry, Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh, India
2 Department Opthalmology, Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh, India

Date of Web Publication19-Sep-2017

Correspondence Address:
Syed Tasleem Raza
Department of Biochemistry, Era's Lucknow Medical College and Hospital, Lucknow - 226 025, Uttar Pradesh
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjo.tjo_10_17

Rights and Permissions
  Abstract 

Purpose: The present study was carried out to investigate the association of fatty acid-binding protein 2 (FABP2) and fat mass and obesity-associated (FTO) gene polymorphism with primary open-angle glaucoma (POAG) cases and controls.
Materials And Methods: This study includes 122 POAG cases and 112 controls. FABP2 and FTO gene polymorphisms in cases and controls were evaluated by polymerase chain reaction-restriction fragment length polymorphism method.
Results: The mean ages were 49.88 ± 12.34 and 53.74 ± 11.87 years in POAG cases and control groups, respectively. The FABP2 gene AA, AT, TT genotype frequencies were 12.90%, 62.40%, 24.80% in POAG cases and 20.60%, 64.70%, 14.70% in healthy controls, respectively. The frequencies of A and T allele in POAG cases were 44.06% and 55.94% as compared to 52.94% and 47.06% in the controls. The FTO gene AA, AT, TT genotype frequencies were 2.00%, 79.20%, 18.80% in cases and 0%, 75.50%, 24.50% in healthy controls, respectively. The frequencies of A and T allele in POAG cases were 41.58% and 58.42% as compared to 37.75% and 62.25% in the controls. No significant difference in the frequencies of FABP2 and FTO genotype was found between POAG cases and controls.
Conclusion: We could not identify the possible association of FABP2 and FTO gene polymorphism with POAG; however, further studies with larger sample size in different population are require to clarify the role of FABP2 and FTO genes in susceptibility to POAG.

Keywords: Fat mass and obesity associated, fatty acid-binding protein 2, genetic polymorphism, primary open-angle glaucoma


How to cite this article:
Abbas S, Raza ST, Chandra A, Singh L, Mahdi F. Association of fatty acid-binding protein 2 and fat mass and obesity-associated gene polymorphism with primary open-angle glaucoma. Taiwan J Ophthalmol 2017;7:138-42

How to cite this URL:
Abbas S, Raza ST, Chandra A, Singh L, Mahdi F. Association of fatty acid-binding protein 2 and fat mass and obesity-associated gene polymorphism with primary open-angle glaucoma. Taiwan J Ophthalmol [serial online] 2017 [cited 2023 Feb 3];7:138-42. Available from: https://www.e-tjo.org/text.asp?2017/7/3/138/212006




  Introduction Top


Primary open-angle glaucoma (POAG) is a progressive, chronic optic neuropathy in adults, and it is characterized by open anterior chamber angles, visual field abnormalities, and high intraocular pressure (IOP). Glaucoma, affecting at least 90 million people worldwide, is a leading cause of blindness, second only to cataract. It has been estimated that by 2010, almost 60.5 million people will have POAG worldwide, and by 2020, this number is expected to increase to 79.6 million, which will result blindness in 11.2 million people by 2020.[1] Previous studies suggest that the genetic factors may play important roles in the pathogenesis of this disease.[2],[3] Linkage analyses have established three POAG susceptibility genes: myocilin, optineurin, and WD repeat domain 36.[4],[5],[6] Association studies using single nucleotide polymorphisms (SNPs) have substantially contributed to the study of glaucoma over the past few decades; however, the link between the genes and the development of the disease is not always clearly demonstrated.

Fatty acid-binding proteins (FABPs) are small intracellular polypeptides expressed in the absorptive simple columnar epithelial cells of the intestine (enterocytes).[7] The FABP2 gene encodes intestinal FABP protein, involved in fatty acid transfer and metabolism.[8] The gene consists of 3382 nucleotides located in the chromosomal region 4q28–4q31, arranged in four exons containing −700 bp and three introns containing −2650 bp.[7],[9] Earlier studies have shown that the Ala54Thr polymorphism of the FABP2 gene can be commonly found in around 30% of the most populations and is significantly associated with insulin resistance,[10] dyslipidemia, and obesity.[11] Genome-wide association (GWA) studies have indicated that the fat mass and obesity-associated (FTO) gene has an important genetic effect on body mass index (BMI) and risk of obesity. Obesity has been postulated to exert an effect on IOP by causing excessive intraorbital adipose tissue, increased blood viscosity, increased episcleral venous pressure, and impairment of aqueous outflow facility. Previous studies have shown that overweight and obesity are independent risk factors for increase in IOP.[12],[13],[14],[15] Raised IOP is an important risk factor for the progression to POAG. In cases of POAG as a matter of observation, it can be inferred that the individual ones to intermittently affect with obesity might be susceptible to such conditions. Hence, the present study was carried out to investigate the association of FABP2 and FTO gene polymorphism with POAG cases and controls.


  Materials and Methods Top


Patient's selection

A total of 122 blood samples of POAG cases and 112 healthy controls were collected from the Department of ophthalmology of Era's Lucknow Medical College and Hospital, Lucknow. Data collection was done for each patient on clinical variables including age, alcohol consumption, BMI, height, weight, cigarette smoking, and family history. Each individual underwent a complete ophthalmological examination. Patients with POAG were defined by the presence of an open angle, pathological cupping of the optic disc, a glaucoma hemifield test (GHT) outside normal limits with reproducible visual field defects at the same location on two consecutive visits, and an IOP >21 mmHg without antiglaucoma drugs. Cup-to-disc ratios were between 0.4 and 0.9. Patients with a history of eye surgery before the diagnosis of glaucoma, evidence of secondary glaucoma such as exfoliation, pigment dispersion or uveitis, and other causes were excluded from the study. Control group was nonsmokers and had neither diabetes nor any systemic illness. They had no family or personal history of glaucoma. They had clinical healthy appearing optic discs as demonstrated by indirect ophthalmoscope with a cup-to-disc ratio of 0.3 or lower and GHT within normal limits. Ethical Committee's clearances were obtained from the respective departments, earlier to the recruitment of individuals in this study.

DNA extraction

Five milliliters of peripheral blood was collected from all the individuals in 0.5M EDTA tubes. Genomic DNA was isolated from whole blood using the standard phenol-chloroform extraction method.[16] The DNA concentration was determined by spectrophotometer and stored at −20°C.

Analysis of polymorphisms

Fatty acid-binding protein 2 polymorphism

Polymerase chain reaction (PCR) was employed for genotyping of the FABP2 gene polymorphism. Reactions were performed with 10 pmol of each primer:[17] forward primers 5'-ACAGGTGTTAATATAGTGAAAAG-3' and reverse primer 5'-TACCCTGAGTTCAGTTCCGTC-3'. In the final volume of 20 μl containing 0.3 U of Taq DNA polymerase, 10 mmol/l Tris-HCl pH 8.3, 50 mmol/l of KCl, 1.5 mmol/l of MgCl2, and 100 mmol/l of dNTPs, PCR amplification was carried out under the conditions: 35 cycles for 1 min at 94°C, 1 min at 58°C, and 1 min at 72°C; the PCR products were analyzed on 2% agarose gel stained with ethidium bromide to certify the proper amplification. The amplified PCR products of 180 bp were digested with the addition of 2 U HhaI (New England Biolabs, Hitchin, UK), 10 mmol/l Tris-HCl pH 7.9, 50 mmol/l NaCl, 10 mmol/l MgCl2, and 1 mmol/l dithiothreitol. After incubation at 37°C for 2 h, digested samples were separated on 10% ethidium bromide-stained polyacrylamide gel electrophoresis and visualized by UVP BIOLMAGING gel doc system. PCR products having an intact HhaI site were cleaved into 99- and 81-bp fragments; the Ala54Thr substitution abolished the restriction site [Figure 1].
Figure 1: Polyacrylamide gel picture showing digested polymerase chain reaction products for fatty acid-binding protein 2 gene polymorphism. Lane 1: Undigested polymerase chain reaction product of fatty acid-binding protein 2 (180 bp), lane 5-7: TT genotype, lane 2 and 4: AT genotype, lane 3: 100 bp ladder

Click here to view


Fat mass and obesity-associated polymorphism

The FTO SNP (rs9939609) was genotyped by PCR (MJ Mini Thermo Cycler BioRad, USA) and restriction fragment length polymorphism analysis. Genomic DNA (20 ng) was incubated in a 10-μl solution containing 1X NH4 buffer, 2.5 mmol/l magnesium, 200 μmol/l each dNTP, 20 pmol forward (5'-AACTGGCTCTTGAATGAAATAGGAT TCAGA-3') and reverse (5'-AGAGTAACAGAGA CTATCCAAGTG CAGTAC-3') oligonucleotide primers,[18] and 0.5 U Taq DNA polymerase (Bioline Ltd., London, UK). The PCR mix was incubated at 94°C for 5 min followed by 20 cycles of 94°C for 45 s, 61°C for 45 s (dropping 0.5 C per cycle), and 72°C for 45 s. After this, the PCR mix was incubated for 15 cycles of 94°C for 45 s, 51°C for 45 s, and 72°C for 45 s, followed by the final incubation at 72°C for 10 min. The PCR products thus obtained were incubated at 37°C for 16 h with 2 U ScaI (New England Biolabs, Hitchin, UK). Upon running the final products on a 3% agarose gel, the T allele produced a 182-bp band and the A allele produced 154- and 28-bp bands [Figure 2].
Figure 2: Polyacrylamide gel picture showing digested polymerase chain reaction products for fat mass and obesity-associated gene polymorphism. Lane 2, 3, and 6 show AT genotype (182 and 154), lane 4 and 7 show TT genotype (182 bp), lane 5 shows 100 bp ladder, and lane 1 shows undigested polymerase chain reaction product of FTO (182 bp)

Click here to view


Statistical analysis

All the figures are presented as means ± standard deviation. The genotyping data were compared between cases and controls using Chi-square test. Other variables were compared using Student's t-test for normally distributed variables. All statistical tests were performed using Statistical Package for the Social Sciences version 12 software (IBM, USA).


  Results Top


Our study included 122 POAG cases (65 were males and 57 were females) and 112 controls (59 were males and 53 were females). The mean ages were 49.88 ± 12.34 and 53.74 ± 11.87 years in POAG cases and control groups, respectively. Clinical and biochemical parameters of cases and controls are shown in [Table 1]. In our population, the mean red blood cell (RBC) lysate glutathione (GSH) levels were significantly lower in cases as compare to the controls (P < 0.05). FABP2 gene AA, AT, TT genotype frequencies were 12.90%, 62.40%, 24.80% in POAG cases and 20.60%, 64.70%, 14.70% in healthy controls, respectively. Odds ratio (OR) for AA was 0.569 (95% confidence interval [CI] 0.27–1.21, P = 0.141, χ2 = 2.17, power = 0.875), for AT 0.904 (95% CI 0.51–1.60, P = 0.73, χ2 = 0.12, power = 0.644), and for TT 1.908 (95% CI 0.94–3.88, P = 0.072, χ2 = 3.24, power = 0.925). The frequencies of A and T allele in POAG cases were 44.06% and 54.94% as compared to 52.94% and 47.06% in the controls. OR for A was 0.700 (95% CI 0.47–1.03, P = 0.074, χ2 = 3.21, power = 0.845) and for T 1.428 (95% CI 0.97–2.11, P = 0.074, χ2 = 3.21, power = 0.845). The FTO gene AA, AT, TT genotype frequencies were 2%, 79.20%, 18.80% in cases and 0%, 75.50%, 24.50% in healthy controls, respectively. OR for AA was not available (NA) (95% CI NA, P = 0.153, χ2 = 2.05, power = 0.958), for AT 1.237 (95% CI 0.64–2.39, P = 0.527, χ2 = 0.40, power = 0.843), and for TT 0.714 (95% CI 0.36–1.40, P = 0.324, χ2 = 0.97, power = 0.892). The frequencies of A and T allele in POAG cases were 41.58% and 58.42% as compared to 37.75% and 62.25% in the controls. OR for A was 1.174 (95% CI 0.79–1.75, P = 0.429, χ2 = 0.63, power = 0.844) and for T 0.852 (95% CI 0.57–1.27, P = 0.429, χ2 = 0.63, power = 0.844). The genotype, allele's frequencies of FABP2, FTO and statistical analysis among the cases and controls are also shown in [Table 2]. Genotype distribution for all investigated SNPs was in Hardy–Weinberg equilibrium in both cases and controls.
Table 1: Clinical and biochemical profile of primary open-angle glaucoma cases and controls

Click here to view
Table 2: Genotypes and alleles frequency of FABP2 and FTO genes in primary open-angle glaucoma cases and controls

Click here to view



  Discussion Top


Glaucoma is accurately defined as an optic neuropathy involving a characteristic atrophy of the optic nerve head. It is usually results from decreased outflow of aqueous fluid due to an acceleration and exaggeration of normal aging changes in the anterior chamber angle, iris, and ciliary body tissues of the eye. If it is untreated, the natural course is toward blindness or significant visual loss disability. We have observed that the mean RBC lysate GSH levels were significantly lower in cases as compare to the controls, similar finding were observed in the UK population where patients with glaucoma exhibit low levels of circulating GSH.[19]

Fatty acid-binding protein 2 polymorphism

FABP2 gene is expressed only in the absorptive simple columnar epithelial cells of the small intestine.[20] According to Hongmei et al., the evidence of decreased blood flow to the optic nerve is directly influenced by fatty acids, and further investigation result shows abnormal blood fatty acid composition in POAG patients compared to a healthy control. Indeed, the POAG patients studied had reduced total omega-3 long-chain polyunsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) fatty acids.[7] These findings may be significant as EPA and DHA could modulate impaired systemic microcirculation, ocular blood flow, and positively impact optic neuropathy, which are the main physiological changes associated with glaucoma.[21] Numerous studies have assessed FABP2 gene variants and their association with insulin resistance and type 2 diabetes mellitus.[7] This is the first time we are reporting this gene polymorphism in POAG cases. We have observed that the frequency of FABP2 AA, AT, TT genotype were 12.90%, 62.40%, 24.80% in POAG cases and 20.60%, 64.70%, 14.70% in healthy controls, respectively. In our study, we have found no significant association of FABP2 gene polymorphism in North Indian POAG cases [Table 2].

Fat mass and obesity-associated polymorphism

FTO gene is associated with an increased BMI, risk of myocardial infarction, and cardiovascular death. GWA studies first describe the link between genetic variation in FTO and obesity,[22] and later, it was confirmed in different populations all over the world. Obesity is one of the major risk factors for several diseases such as type 2 diabetes, hypertension, stroke, osteoarthritis, and sleep apnea syndrome; some eye diseases such as glaucoma,[23] cataract,[24] diabetic retinopathy,[25] and age-related macular degeneration were reported to have potential relation to obesity.[26] In our study, we found that FTO gene AA, AT, TT genotype frequencies were 2%, 79.20%, 18.80% in cases and 0%, 75.50%, 24.50% in healthy controls, respectively. Frequencies of A and T allele in POAG cases were 41.58% and 58.42% as compared to 37.75% and 62.25% in the controls. Our results show no significant association between the AA, AT, TT genotype of FABP2 and POAG (P = 0.153, 0.527, 0.324). Adequate data of FTO polymorphism and POAG were not available.


  Conclusion Top


We could not identify the possible association of FABP2 and FTO gene polymorphism with POAG; however, further studies with larger sample size in different population are require to clarify the role of FABP2 and FTO genes in susceptibility to POAG.

Acknowledgment

We are thankful for the study that was supported by intramural grant from the Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh, India.

Financial support and sponsorship

The authors have no funding to disclose.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262-7.  Back to cited text no. 1
[PUBMED]    
2.
Gottfredsdottir MS, Sverrisson T, Musch DC, Stefansson E. Chronic open-angle glaucoma and associated ophthalmic findings in monozygotic twins and their spouses in Iceland. J Glaucoma 1999;8:134-9.  Back to cited text no. 2
[PUBMED]    
3.
He M, Liu B, Huang W, Zhang J, Yin Q, Zheng Y, et al. Heritability of optic disc and cup measured by the Heidelberg retinal tomography in Chinese: The Guangzhou twin eye study. Invest Ophthalmol Vis Sci 2008;49:1350-5.  Back to cited text no. 3
[PUBMED]    
4.
Stone EM, Fingert JH, Alward WL, Nguyen TD, Polansky JR, Sunden SL, et al. Identification of a gene that causes primary open angle glaucoma. Science 1997;275:668-70.  Back to cited text no. 4
[PUBMED]    
5.
Rezaie T, Child A, Hitchings R, Brice G, Miller L, Coca-Prados M, et al. Adult-onset primary open-angle glaucoma caused by mutations in optineurin. Science 2002;295:1077-9.  Back to cited text no. 5
[PUBMED]    
6.
Monemi S, Spaeth G, DaSilva A, Popinchalk S, Ilitchev E, Liebmann J, et al. Identification of a novel adult-onset primary open-angle glaucoma (POAG) gene on 5q22.1. Hum Mol Genet 2005;14:725-33.  Back to cited text no. 6
[PUBMED]    
7.
Hongmei R, Magulike N, Ghebremeskel K, Crawford M. Primary open-angle glaucoma patients have reduced levels of blood docosahexaenoic and eicosapentaenoic acids, Prostaglandins, Leukotrienes and Essential Fatty Acids 2006;74:157-63.  Back to cited text no. 7
    
8.
Melki R, Lefort N, Brézin AP, Garchon HJ. Association of a common coding polymorphism (N453S) of the cytochrome P450 1B1 (CYP1B1) gene with optic disc cupping and visual field alteration in French patients with primary open-angle glaucoma. Mol Vis 2005;11:1012-7.  Back to cited text no. 8
    
9.
Wiggs JL. Genetic etiologies of glaucoma. Arch Ophthalmol 2007;125:30-7.  Back to cited text no. 9
[PUBMED]    
10.
Weiss EP, Brown MD, Shuldiner AR, Hagberg JM. Fatty acid binding protein-2 gene variants and insulin resistance: Gene and gene-environment interaction effects. Physiol Genomics 2002;10:145-57.  Back to cited text no. 10
[PUBMED]    
11.
Hsu KT, Storch J. Fatty acid transfer from liver and intestinal fatty acid-binding proteins to membranes occurs by different mechanisms. J Biol Chem 1996;271:13317-23.  Back to cited text no. 11
[PUBMED]    
12.
Cohen E, Kramer M, Shochat T, Goldberg E, Garty M, Krause I. Relationship between body mass index and intraocular pressure in men and women: A population-based study. J Glaucoma 2016;25:e509-13.  Back to cited text no. 12
[PUBMED]    
13.
Akinci A, Cetinkaya E, Aycan Z, Oner O. Relationship between intraocular pressure and obesity in children. J Glaucoma 2007;16:627-30.  Back to cited text no. 13
[PUBMED]    
14.
George GO, Ajayi OB. Relationship between body mass index, intraocular pressure, blood pressure and age in Nigerian population. J Clin Exp Ophthalmol 2015;6:461.  Back to cited text no. 14
    
15.
Siddiqui F, Alkhairy S, Hassan M, Kumar D. Relationship between body mass index and intraocular pressure in diabetic and hypertensive adults. Pak J Ophthalmol 2016;32:1.  Back to cited text no. 15
    
16.
Sambrook J, Frisch EF, Maniatis T, editors. Molecular Cloning: A Laboratory Manual. 2nd ed. New York: Cold Spring Harbor Laboratory Press; 1989. p. 9.14-9.19. 28.  Back to cited text no. 16
    
17.
Fredriksson R, Hägglund M, Olszewski PK, Stephansson O, Jacobsson JA, Olszewska AM, et al. The obesity gene, FTO, is of ancient origin, up-regulated during food deprivation and expressed in neurons of feeding-related nuclei of the brain. Endocrinology 2008;149:2062-71.  Back to cited text no. 17
    
18.
Hao K, Niu T, Sangokoya C, Li J, Xu X. SNPkit: An efficient approach to systematic evaluation of candidate single nucleotide polymorphisms in public databases. Biotechniques 2002;33:822, 824-6, 828.  Back to cited text no. 18
[PUBMED]    
19.
Gherghel D, Griffiths HR, Hilton EJ, Cunliffe IA, Hosking SL. Systemic reduction in glutathione levels occurs in patients with primary open-angle glaucoma. Invest Ophthalmol Vis Sci 2005;46:877-83.  Back to cited text no. 19
[PUBMED]    
20.
Stratigopoulos G, Padilla SL, LeDuc CA, Watson E, Hattersley AT, McCarthy MI, et al. Regulation of Fto/Ftm gene expression in mice and humans. Am J Physiol Regul Integr Comp Physiol 2008;294:R1185-96.  Back to cited text no. 20
[PUBMED]    
21.
Yamada K, Yuan X, Ishiyama S, Koyama K, Ichikawa F, Koyanagi A, et al. Association between Ala54Thr substitution of the fatty acid-binding protein 2 gene with insulin resistance and intra-abdominal fat thickness in Japanese men. Diabetologia 1997;40:706-10.  Back to cited text no. 21
[PUBMED]    
22.
Sweetser DA, Birkenmeier EH, Klisak IJ, Zollman S, Sparkes RS, Mohandas T, et al. The human and rodent intestinal fatty acid binding protein genes. A comparative analysis of their structure, expression, and linkage relationships. J Biol Chem 1987;262:16060-71.  Back to cited text no. 22
    
23.
Guettier JM, Georgopoulos A, Tsai MY, Radha V, Shanthirani S, Deepa R, et al. Polymorphisms in the fatty acid-binding protein 2 and apolipoprotein C-III genes are associated with the metabolic syndrome and dyslipidemia in a South Indian population. J Clin Endocrinol Metab 2005;90:1705-11.  Back to cited text no. 23
    
24.
Frayling TM, Timpson NJ, Weedon MN, Zeggini E, Freathy RM, Lindgren CM, et al. A common variant in the FTO gene is associated with body mass index and predisposes to childhood and adult obesity. Science 2007;316:889-94.  Back to cited text no. 24
    
25.
Cheung N, Wong TY. Obesity and eye diseases. Surv Ophthalmol 2007;52:180-95.  Back to cited text no. 25
    
26.
Kuang TM, Tsai SY, Hsu WM, Cheng CY, Liu JH, Chou P. Body mass index and age-related cataract: The Shihpai eye study. Arch Ophthalmol 2005;123:1109-14.  Back to cited text no. 26
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]


This article has been cited by
1 A54T polymorphism in fatty acid binding protein 2 gene is associated in Type 2 Diabetes Mellitus in adult subjects
Tayyaba Sultana,Anam Raza,Salma Sultana,K.A. Al-Ghanim,F. Al-Misned,Tehniat Shahid,Shahid Mahboob
Journal of King Saud University - Science. 2019;
[Pubmed] | [DOI]



 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Materials and Me...
Results
Discussion
Conclusion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed3129    
    Printed128    
    Emailed0    
    PDF Downloaded306    
    Comments [Add]    
    Cited by others 1    

Recommend this journal


[TAG2]
[TAG3]
[TAG4]