A Controlled Case Study of the Relationship between Environmental Risk Factors and Apoptotic Gene Polymorphism and Lumbar Disc Herniation
2012; Elsevier BV; Volume: 182; Issue: 1 Linguagem: Inglês
10.1016/j.ajpath.2012.09.013
ISSN1525-2191
AutoresYingang Zhang, Feng Zhang, Zhengmin Sun, Wentao Guo, Jian Liu, Miao Liu, Xiong Guo,
Tópico(s)Pregnancy-related medical research
ResumoTo explore the etiologic role of apoptosis-related genes, environmental risk factors, and their interaction in the occurrence of lumbar disk herniation (LDH), a controlled case study was performed with 128 LDH patients and 132 age- and sex-matched controls. Matrix-assisted laser desorption/ionization, time-of-flight mass spectrometry assay was used to analyze the genotype of nine polymorphism sites in three genes, including Fas –1377G/A rs2234767, Fas –670G/A rs1800682, Fas rs2147420, Fas rs2296603, Fas rs7901656, Fas rs1571019, Fas ligand (FasL) –844C/T rs763110, caspase 9 (CASP9) –1263A>G rs4645978, and CASP9 –712C>T rs4645981. The patients and controls showed similar age and sex, but had significant differences in lumbar load, bed type, amateur sports, and leisure activities (P < 0.05). The correlation analysis revealed that polymorphism of FasL −844C/T (rs763110) and CASP9 –1263A>G (rs4645978) had a significant correlation with LDH, indicating that the genotypes of FasL −844C/T TT and CASP9 –1263A>G GG are probably high-risk genotypes for LDH. The results of environment-gene interaction analysis revealed that, in LDH, the interaction of the FasL −844TT genotype and level III to IV lumbar load was consistent with the ultramultiplying model, and the interaction of the CASP9 rs4645978 GG genotype and level III to IV lumbar load was consistent with the submultiplicative model. Therefore, the risk of LDH was determined by both environmental and genetic risk factors, and the mechanisms of interactions between different genotypes and environmental factors also differed. To explore the etiologic role of apoptosis-related genes, environmental risk factors, and their interaction in the occurrence of lumbar disk herniation (LDH), a controlled case study was performed with 128 LDH patients and 132 age- and sex-matched controls. Matrix-assisted laser desorption/ionization, time-of-flight mass spectrometry assay was used to analyze the genotype of nine polymorphism sites in three genes, including Fas –1377G/A rs2234767, Fas –670G/A rs1800682, Fas rs2147420, Fas rs2296603, Fas rs7901656, Fas rs1571019, Fas ligand (FasL) –844C/T rs763110, caspase 9 (CASP9) –1263A>G rs4645978, and CASP9 –712C>T rs4645981. The patients and controls showed similar age and sex, but had significant differences in lumbar load, bed type, amateur sports, and leisure activities (P < 0.05). The correlation analysis revealed that polymorphism of FasL −844C/T (rs763110) and CASP9 –1263A>G (rs4645978) had a significant correlation with LDH, indicating that the genotypes of FasL −844C/T TT and CASP9 –1263A>G GG are probably high-risk genotypes for LDH. The results of environment-gene interaction analysis revealed that, in LDH, the interaction of the FasL −844TT genotype and level III to IV lumbar load was consistent with the ultramultiplying model, and the interaction of the CASP9 rs4645978 GG genotype and level III to IV lumbar load was consistent with the submultiplicative model. Therefore, the risk of LDH was determined by both environmental and genetic risk factors, and the mechanisms of interactions between different genotypes and environmental factors also differed. Lumbar disk herniation (LDH), which has a high incidence and is the major cause of low back pain, has become a major public health problem because of its derived disability and social cost.1Benoist M. The natural history of lumbar disc herniation and radiculopathy.Joint Bone Spine. 2002; 69: 155-160Crossref PubMed Scopus (111) Google Scholar LDH is induced mainly by lumbar intervertebral disk degeneration (LDD). Previous etiologic studies have focused on environmental risk factors. For instance, occupational factors (eg, heavy physical work, lifting heavy objects, bending over and twisting, whole-body vibration, and static operating position) can induce LDD, resulting in increased intradiscal pressure and weakened annulus fibrosus strength, which are the pathologic bases for LDH. Previously, we showed that the important risk factors of LDH included lumbar load, family history, average body weight index, leisure activities, amateur sports, and social psychology.2Zhang Y.G. Sun Z.M. Zhang Z. Liu J. Guo X. Risk factors for lumbar intervertebral disc herniation in Chinese population. A case-control study.Spine. 2009; 34: 918-939Crossref Scopus (51) Google Scholar However, environmental risk factors are not the only cause of LDH. Recently, it was suggested that the heritage rate of LDH is 52% to 68%,3MacGregor A.J. Andrew T. Sambrook P.N. Spector T.D. Structural, psychological, and genetic influences on low back and neck pain: a study of adult female twins.Arthritis Rheum. 2004; 51: 160-166Crossref PubMed Scopus (214) Google Scholar indicating that genetic factors also may play an important role in the pathogenesis of LDH. Hence, it has been accepted that LDH is a complex disease determined by the interactions of genetic and environmental factors. With the development of high-throughput sequencing technology, the location and function of susceptibility genes of complex diseases has become a hot research area. The susceptibility genes of many complex diseases have been located, including LDH.4Guo T.M. Liu M. Zhang Y.G. Guo W.T. Wu S.X. Association between Caspase-9 promoter region polymorphisms and discogenic low back pain.Connect Tissue Res. 2011; 52: 133-140Crossref PubMed Scopus (30) Google Scholar, 5Zhang Y.G. Guo X. Sun Z. Jia G. Xu P. Wang S. Gene expression profiles of disc tissues and peripheral blood mononuclear cells from patients with degenerative disc.J Bone Miner Metab. 2010; 8: 209-227Crossref Scopus (20) Google Scholar, 6Zhang Y.G. Guo T.M. Guo X. Wu S.X. Clinical diagnosis for discogenic low back pain.Int J Biol Sci. 2009; 5: 647-658Crossref PubMed Scopus (85) Google Scholar, 7Zhang Y.G. Sun Z.M. Liu J.T. Wang S.J. Ren F.L. Guo X. Features of intervertebral disc degeneration in rat’s aging process.J Zhejiang Univ Sci B. 2009; 10: 522-527Crossref PubMed Scopus (27) Google Scholar, 8Sun Z.M. Miao L. Zhang Y.G. Ming L. Association between the -1562 C/T polymorphism of matrix metalloproteinase-9 gene and lumbar disc disease in the young adult population in North China.Connect Tissue Res. 2009; 50: 181-185Crossref PubMed Scopus (40) Google Scholar, 9Zhang Y. Sun Z. Liu J. Guo X. Advances in susceptibility genetics of intervertebral de-generative disc disease.Int J Biol Sci. 2008; 4: 283-290Crossref PubMed Scopus (61) Google Scholar However, little information is available about the interaction of susceptibility genes and environmental risk factors in the pathogenesis of LDH. Elucidating the environment-gene interaction mechanisms of LDH will help show LDH pathogenesis and the development of effective early prevention and treatment measures. Previous research has suggested that apoptosis plays an important role in the pathology of LDD. The apoptotic pathways involved in LDD include the Fas/Fas ligand (L)-mediated death receptor pathway (exogenous pathway) and the mitochondrial pathway (endogenous pathway).10Rannou F. Lee T.S. Zhou R.H. Chin J. Lotz J.C. Mayoux-Benhamou M.A. Barbet J.P. Chevrot A. Shyy J.Y. Intervertebral disc degeneration: the role of the mitochondrial pathway in annulus fibrosus cell apoptosis induced by overload.Am J Pathol. 2004; 164: 915-924Abstract Full Text Full Text PDF PubMed Scopus (199) Google Scholar, 11Park J.B. Park I.C. Park S.J. Jin H.O. Lee J.K. Riew K.D. Anti-apoptotic effects of caspase inhibitors on rat intervertebral disc cells.J Bone Joint Surg Am. 2006; 88: 771-779Crossref PubMed Scopus (20) Google Scholar The typical exogenous pathway is the Fas (also known as CD95)–mediated apoptotic pathway. FasL always appears in a trimer form, in which three Fas receptors bind to one FasL. After FasL binds to its ligand, Fas recruits the intracellular Fas associated protein with death domain (FADD) by binding the C-terminal death domain of the FADD protein through its death domain. In the next step, the death domain of Fas Associated protein interacts with the death domain of caspase-8 zymogen to recruit the caspase-8 zymogen in the cytosol, and subsequently form the death-inducing signing complex.12Konopleva M. Zhao S. Xie Z. Segall H. Younes A. Claxton D.F. Estrov Z. Kornblau S.M. Andreeff M. Apoptosis. Molecules and mechanisms.Adv Exp Med Biol. 1999; 457: 217-236Crossref PubMed Scopus (128) Google Scholar In the mitochondrial pathway, caspase accepts the death signal to initiate apoptosis, which in turn activates the downstream pathway to degrade the cytoskeleton, proteins, and nucleotides. Caspase is essential for apoptosis, and caspase-9 is the key protease to activate this pathway. The effective caspase cannot selectively bind to Apaf-1, so it is dependent on caspase-9.13Bratton S.B. Salvesen G.S. Regulation of the Apaf-1-caspase-9 apoptosome.J Cell Sci. 2010; 123: 3209-3214Crossref PubMed Scopus (301) Google Scholar Therefore, we propose that FAS, FASL, and caspase-9 probably play important roles in LDH. In the present study, we performed a controlled case study to explore the correlation between the polymorphism of Fas, FasL, CASP9, and the risk of LDH. We identified the single nucleotide polymorphism (SNP) sites that showed positive correlation, and analyzed their pathogenic interaction with environmental risk factors. Through the preliminary study (30 patients and controls), we already found that some polymorphisms (ie, CASP9 rs2308941, rs2308950, FasL INV2nt −124A>G rs5030772) do not exist in the Chinese Han population. Therefore, in the present study, we selectively analyzed nine SNP sites, including Fas –1377G/A rs2234767, Fas –670G/A rs1800682, Fas rs2147420, Fas rs2296603, Fas rs7901656, Fas rs1571019, FasL –844C/T (rs763110), CASP9 –1263A>G rs4645978, and CASP9 –712C>T rs4645981. The case group consisted of 131 LDH patients admitted to the Department of Orthopaedics of the First Affiliated Hospital, Medical College of Xi’an Jiaotong University, Shaanxi Provincial People’s Hospital, and Xian Tang City Hospital from January 2005 to January 2007, for reasons of back leg pain, computed tomography/magnetic resonance imaging–diagnosed lumbar disk herniation, and typical sciatica. Patients with lumbar spinal stenosis, spinal congenital dysplasia, intraspinal tumor, and spondylolisthesis were excluded from this study. The 137 subjects in the control group were selected randomly from in-patients or participants of medical examinations who had no history of back pain at present, for more than a month, or ever; sciatic nerve pain; spinal instability from trauma; scoliosis; or spondylolisthesis. The control and case groups were matched with respect to race, sex, age, and living areas. All studied individuals were Chinese Han subjects. Information including age, sex, height, weight, and disease history were collected. The potential environmental risk factors of LDH were determined based on the preliminary data and were evaluated quantitatively through a questionnaire survey. The first risk factor was lumbar load. The lumbar load was quantified using a grading system based on a physical load assessment questionnaire developed by the Stockholm Musculoskeletal Research Center (Sweden),14Pincus T. Burton A.K. Vogel S. Field A.P. A systematic review of psychological factors as predictors of chronicity/disability in prospective cohorts of low back pain.Spine. 2002; 27: 109-120Crossref PubMed Scopus (1217) Google Scholar the occupational classification point standard,15Battié M.C. Videman T. Gibbons L.E. Fisher L.D. Manninen H. Gill K. Volvo Award in clinical sciences. Determinants of lumbar disc degeneration. A study relating lifetime exposures and magnetic resonance imaging findings in identical twins.Spine. 1995; 20: 2601-2612Crossref PubMed Scopus (447) Google Scholar and the actual situation. Level I (slight) represents no fixed occupation and little physical labor; level II (mild) represents mainly sitting at work; level III (moderate) represents mainly bending over and twisting and whole-body vibrating at work; and level IV (severe) represents mainly heavy lifting and heavy labor work. The second risk factor was smoking, defined as smoking at least a cigarette per day for 1 year or an annual amount greater than 18 packs. The smoking index is equal to a year of smoking X number of cigarettes per day × 20 − 1. The third risk factor was drinking, defined as consuming alcohol twice per week and 100 g each time for 1 year. The fourth risk factor was leisure activities (eg, housework). Finally, the fifth risk factor was amateur sports (ie, fitness training), defined as more than 20 minutes of exercise each time until the heartbeat was accelerated and the individual was sweating. DNA was extracted from peripheral blood leukocytes using the proteinase K digestion and phenol/chloroform extraction methods. The quality and quantity of extracted DNA were determined using a spectrophotometer (ND-100; NanoDrop, Wilmington, DE). MassARRAY Assay Design software version 2.0 (Sequenom, Salt Lake City, UT) was used to design the amplification and allele-specific primer extension. The polymerase chain reaction (PCR) mixture consisted of 5 ng genomic DNA (5 ng/μL), 1 μL of each specific primer, 2.5 mmol/L of each dNTP, 3.25 mmol/L MgCl2, and 0.5 U of Hot-StarTaq DNA polymerase (5 U/μL; Qiagen, Valencia, CA). The PCR was performed at 94°C for 15 minutes, 45 cycles of 94°C for 20 seconds, 56°C for 30 seconds, and 72°C for 1 minute, followed by 72°C for 3 minutes. The final products were analyzed using a modified Brucker Autoflex Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) (Brucker, Billerica, MA). The age, sex, smoking history, and genotype distribution were analyzed using the χ2 test with SPSS software version 17.0 (SPSS, Stanford, CA). The Hardy-Weinberg equilibrium test was performed using Excel 2003 software (Microsoft, Redmond, WA). The nonconditional logistic regression model using age, sex, height, and weight as covariates was applied to analyze the relationship between SNP polymorphism and LDH risk factors. The relative risk was represented by an odds ratio (OR) and 95% CI. All analyses were two-sided probability tests and a P value < 0.05 was used as statistically significant threshold in this study. The multivariate logistic regression model was used to evaluate the pathogenic interaction of environmental risk factors and candidate genes. The covariates of the model included age, sex, height, and weight, and the variables of the model included genetic and environmental risk factors, as well as their interactions. We hypothesized that gene polymorphism is correlated to LDH risk only when environmental factors are present. This has been defined as a two-type interaction by Khoury et al,16Khoury M.J. Wagener D.K. Epidemiological evaluation of the use of genetics to improve the predictive value of disease risk factors.Am J Hum Genet. 1995; 156: 835-844Google Scholar, 17Khoury M.J. James L.M. Population and familial relative risks of disease associated with environmental factors in the presence of gene-environment interaction.Am J Epidemiol. 1993; 137: 1241-1250PubMed Google Scholar Ottman,18Ottman R. An epidemiologic approach to gene-environment interaction.Genet Epidemiol. 1990; 7: 177-185Crossref PubMed Scopus (173) Google Scholar and Taioli et al.19Taioli E. Zocchetti C. Garte S. Models of interaction between metabolic genes and environmental exposure in cancer susceptibility.Environ Health Perspect. 1998; 106: 67-70Crossref PubMed Scopus (46) Google Scholar βe denotes the phenotypic effects of environment risk factors. βeg denotes the phenotypic effects explained by the interaction between environment risk factors and candidate genes. The interaction coefficient (γ = βeg/βe) was used to determine the interaction and its pattern and intensity as follows. First, if odds ratio (OR)eg = ORe+ORg, the interaction is consistent with the multiplicative model; if OReg > ORe+ORg, the interaction is consistent with the ultra multiplying model; if OReg < ORe+ORg, the interaction is consistent with the submultiplicative model; if OReg = ORe+ORg−1, the interaction is consistent with the additive model. Second, γ was used as the two-variable interaction coefficient, γ > 1 represents that genetic factors can amplify the effects of environmental factors, γ < 1 represents that genetic factors can reduce the effects of environmental factors, and γ = 1 represents no interaction. If an environmental increases the risk of target disease and βe > 0 and γ < 0, the gene has a protective effect. A total of 131 patients and 137 controls were used in this study. The results of restriction fragment length polymorphism electrophoresis and mass spectrometry analysis of DNA revealed 8 unqualified cases (3 patients and 5 controls), which then were excluded. The information on the final 128 patients and 132 controls included is listed in Table 1. The patients had an average age of 46.2 years (mean = 46.2; SD = 13.1), and the control group had an average age of 47.4 years (mean = 47.4; SD = 12.9). We found that the two groups showed significant differences in amateur labor (P = 0.011), bed type (P = 0.003), and spinal load index (P < 0.001), but were similar in age, sex, weight, smoking history, and drinking.Table 1Subject InformationPatient (%)Control (%)χ2OR (95% CI)P valueTotal129132Sex0.6670.812 (0.493–1.338)0.414 Male81 (63.3)77 (58.3) Female47 (36.7)55 (41.7)Age, years1.8470.713 (0.438–1.162)0.174 ≤4568 (53.1)59 (44.7) >4560 (46.9)73 (55.3)Weight index0.9781.432 (0.706–2.870)0.323 ≤25107 (83.6)116 (85.8) >2521 (16.4)16 (14.2)Lumbar load32.344.627 (2.686–7.969)<0.001 Levels I and II57 (44.5)104 (78.8) Levels III and IV71 (55.5)28 (21.2)Bed type9.0852.575 (1.376–4.821)0.003 Soft37 (28.9)18 (13.6) Hard91 (71.1)114 (86.4)Smoking0.9271.286 (0.770–2.145)0.336 No80 (62.5)90 (68.2) Yes48 (37.5)42 (31.8)Drinking0.1630.872 (0.447–1.701)0.687 No109 (85.2)110 (83.3) Yes19 (14.8)22 (16.7)Amateur sports6.4750.496 (0.288–0.855)0.011 No99 (77.3)83 (62.9) Yes29 (22.7)49 (37.1)Leisure activities14.7880.281 (0.144–0.550) 0.05), indicating that the samples were representative. As shown in Table 2, among the nine SNP sites of the three genes, FasL (rs763110) and CASP9 rs4645978 were correlated significantly with LDH risk (P < 0.05).Table 2Relationship Between LDH Risk and Apoptotic Gene PolymorphismGene polymorphismGenotypeControl (%)Patient (%)χ2OR (95% CI)P valueFas rs2234767AA11 (8.3)14 (10.9)1.00 (reference)GA65 (49.2)55 (43.0)0.8511.504 (0.632–3.581)0.356GG56 (42.4)59 (46.1)0.1811.208 (0.506–2.884)0.670A frequency87 (33.0)83 (32.4)0.0171.025 (0.710–1.478)0.897G frequency177 (67.0)173 (67.6)Fas rs1800682AA50 (37.9)49 (38.3)1.00 (reference)GA68 (51.5)59 (46.1)0.2060.885 (0.523–1.498)0.650GG14 (10.6)20 (15.6)0.8781.458 (0.663–3.207)0.348A frequency168 (63.6)157 (61.3)0.2951.104 (0.774–1.574)0.587G frequency96 (36.4)99 (38.7)Fas rs2147420CC51 (38.6)49 (38.3)1.00 (reference)CT64 (48.5)58 (45.3)0.0470.943 (0.556–1.601)0.829TT17 (12.9)21 (16.4)0.4321.286 (0.607–2.722)0.511C frequency166 (62.9)156 (60.9)0.2081.086 (0.762–1.547)0.649T frequency98 (37.1)100 (39.1)Fas rs2296603AA38 (28.8)43 (33.6)1.00 (reference)AG75 (56.8)63 (49.2)1.1300.742 (0.428–1.287)0.288GG19 (14.4)22 (17.2)0.0041.023 (0.482–2.173)0.952A frequency151 (57.2)149 (58.2)0.0540.960 (0.678–1.359)0.816G frequency113 (42.8)107 (41.8)Fas rs7901656CC39 (29.5)40 (31.3)1.00 (reference)CT71 (53.8)62 (48.4)0.3200.851 (0.488–1.487)0.571TT22 (16.7)26 (20.3)0.1491.152 (0.561–2.365)0.699C frequency149 (56.4)142 (55.5)0.0501.040 (0.736–1.471)0.824T frequency115 (43.6)114 (11.5)Fas rs1571019CC43 (32.6)41 (32.0)1.00 (reference)CT69 (52.3)63 (49.2)0.0240.958 (0.554–1.655)0.877TT20 (15.2)24 (18.8)0.3801.259 (0.606–2.616)0.538C frequency155 (58.7)145 (56.6)0.2281.040 (0.769–1.542)0.633T frequency109 (41.3)111 (43.4)FasL rs763110CC77 (58.3)64 (50.0)1.00 (reference)CT50 (37.9)51 (39.8)0.6151.227 (0.736–2.048)0.433TT5 (3.8)13 (10.2)4.6013.128 (1.059–9.242)0.039C frequency204 (77.3)179 (69.9)2.0471.329 (0.900–1.963)0.153T frequency60 (22.7)77 (30.1)CASP9 4645978AA36 (27.3)22 (17.2)1.00 (reference)AG73 (55.3)69 (53.9)2.7011.570 (0.915–2.692)0.100GG23 (17.4)37 (28.9)10.082.760 (1.464–5.203)0.002A frequency145 (54.9)113 (44.1)1.0G frequency119 (45.1)143 (55.9)9.1221.572 (1.171 –2.110)0.030CASP9 4645981CC70 (53.0)81 (63.3)1.0CT54 (40.9)42 (32.8)2.8280.687 (0.443–1.065)0.093TT8 (6.1)5 (3.9)1.4180.547 (0.200–1.494)0.234C frequency194 (73.5)204 (79.7)1.0T frequency70 (26.5)52 (20.3)3.4800.717 (0.506–1.018)0.062Bold text indicates P < 0.05. Open table in a new tab Bold text indicates P < 0.05. Among the 128 patients, there were 64 cases of FasL (rs763110) (50%), 51 cases of CT (39.8%), and 13 cases of TT (10.2%). Among the 132 controls, there were 77 cases of FasL −844CC (58.3%), 50 cases of CT (37.9%), and 5 cases of TT (3.8%). The LDH risk of CT patients was 1.227 times that of the CC patients (χ2 = 0.615; 95% CI, 0.736 to 2.048), the LDH risk of TT patients was 3.128 times that of the CC patients (χ2 = 4.601; 95% CI, 1.059 to 9.242), and the LDH risk of T-allele patients was 1.329 times that of the C-allele patients (χ2 = 2.047; 95% CI, 0.900 to 1.963). There was a significant difference between the TT genotype and the CC genotype (P < 0.05). Among the 128 patients, there were 22 cases of CASP9 rs4645978AA (17.2%), 69 cases of CASP9 rs4645978AG (53.9%), and 37 cases of CASP9 rs4645978GG (28.9%). Among the 132 controls, there were 36 cases of CASP9 rs4645978AA (27.3%), 73 cases of CASP9 rs4645978AG (55.3%), and 23 cases of CASP9 rs4645978GG (17.4%). The LDH risk of AG patients was 1.570 times that of the AA patients (χ2 = 2.701; 95% CI, 0.915 to 2.692), the LDH risk of GG patients was 2.760 times that of the AA patients (χ2 = 10.08; 95% CI, 1.464 to 5.203), and the LDH risk of G-allele patients was 1.572 times that of the A-allele patients (χ2 = 9.122; 95% CI, 1.171 to 2.110). There was a significant difference between the GG genotype and AA genotype (P < 0.05). The interactions of FasL −844C/T polymorphism and environmental risk factors are shown in Table 3. Under the influence of environmental factors, the interaction between the lumbar load and FasL −844C/T was consistent with the ultramultiplying model. Level I and II lumbar loads were defined as slight, and level III and IV were defined as severe. After adjusting for age, sex, height, weight, family history, smoking, bed type, leisure activities, and amateur sports, the ORe was 3.49 (95% CI, 1.58 to 7.69) for level III and IV lumbar loads, 3.16 (95% CI, 0.73 to 13.75) for FasL −844TT, and 21.1 (95% CI, 2.43 to 182.67) for both. Because 21.0 > 3.49 × 3.26, the interaction between FasL −844TT and level III/IV lumbar loads was consistent with the ultramultiplying model (P = 0.006), which was statistically significant.Table 3Interaction of FasL −844C/T Polymorphism and Environmental Risk FactorEnvironmental factorClassificationGenotypeControlPatientχ2OR (95% CI)P valueLumbar load∗Amateur sports, bed type, smoking, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.SlightCC60331.00 (reference)SlightCT40190.150.86 (0.41–1.82)0.695SlightTT452.363.16 (0.73–13.75)0.125SevereCC17319.623.49 (1.58–7.69)0.002SevereCT103210.824.56 (1.85–11.27)0.001SevereTT187.6321.0 (2.42–182.64)0.006Smoking†Amateur sports, bed type, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.NoCC50431.00 (reference)NoCT36280.130.87 (0.42–1.83)0.719NoTT491.292.25 (0.56–9.15)0.273YesCC27210.350.78 (0.35–1.76)0.662YesCT14230.011.03 (0.41–2.58)0.955YesTT143.719.58 (0.96–95.39)0.054Bed type‡Amateur sports, smoking, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.Hard bedCC67441.00 (reference)Hard bedCT42350.071.09 (0.56–2.14)0.786Hard bedTT5124.203.62 (1.06–12.39)0.037Soft bedCC10207.433.66 (1.44–9.32)0.006Soft bedCT8163.462.70 (0.95–7.70)0.063Soft bedTT010.007.896 × 10−91.000Leisure activities§Amateur sports, smoking, lumbar load, and bed type were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.NoCC8171.00 (reference)NoCT6190.050.86 (0.22–3.41)0.824NoTT020.005.014 × 10−80.999YesCC69476.060.28 (0.10–0.77)0.014YesCT44325.190.29 (0.10–0.84)0.023YesTT5110.0041.05 (0.24–4.53)0.943Amateur sports¶Bed type, smoking, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.NoCC49521.00 (reference)NoCT31390.140.87 (0.43–1.76)0.700NoTT381.272.39 (0.53–10.89)0.260YesCC28122.390.50 (0.20–1.21)0.122YesCT19120.440.72 (0.28–1.89)0.509YesTT252.354.00 (0.68–23.53)0.126∗ Amateur sports, bed type, smoking, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.† Amateur sports, bed type, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.‡ Amateur sports, smoking, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.§ Amateur sports, smoking, lumbar load, and bed type were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value.¶ Bed type, smoking, lumbar load, and leisure activities were adjusted as covariates for χ2 analysis, OR, 95% CI, and P value. Open table in a new tab The interactions of CASP9 rs4645978 polymorphism and environmental risk factors are shown in Table 4. Under the influence of environmental factors, the interaction between the lumbar load and CASP9 rs4645978 was consistent with the submultiplying model. After adjusting for age, sex, height, weight, family history, smoking, bed type, leisure activities, and amateur sports, the ORe was 5.67 (95% CI, 2.08 to 15.45) for level III and IV lumbar loads, 1.55 (95% CI, 0.51 to 4.69) for CASP9 rs4645978 GG, and 7.40 (95% CI, 1.77 to 30.94) in both cases. Because 7.53 < 1.55 × 5.67, the interaction between CASP9 rs4645978 GG and level III/IV lumbar loads was consistent with the submultiplying model (P = 0.006), which was statistically significant.Table 4Interaction of CASP9 rs4645978 Polymorphism and Environmental Risk FactorsEnvironmental factorsClassificationGenotypeControlPatientχ2OR (95% CI)P valueLumbar load∗Amateur sports, bed type, smoking, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.SlightAA30101.00 (reference)SlightGA54330.010.99 (0.46–2.12)0.967SlightGG17160.591.55 (0.51–4.69)0.445SevereAA61211.555.67 (2.08–15.45)0.001SevereGA19377.633.42 (1.42–8.21)0.006SevereGG5317.557.40 (1.77–30.94)0.006Smoking†Amateur sports, bed type, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.NoAA22141.00 (reference)NoGA52400.820.71 (0.34–1.49)0.360NoGG13140.341.41 (0.45–4.47)0.563YesAA14250.210.80 (0.30–2.09)0.644YesGA21290.060.89 (0.36–2.20)0.792YesGG10120.161.31 (0.35–4.84)0.693Bed type‡Amateur sports, smoking, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.Hard bedAA31161.00 (reference)Hard bedGA65500.340.82 (0.42–1.61)0.554Hard bedGG18261.351.83 (0.66–5.04)0.246Soft bedAA564.593.26 (1.11–9.60)0.032Soft bedGA8193.532.91 (0.95–8.89)0.062Soft bedGG6111.022.30 (0.46–11.58)0.316Leisure activities§Amateur sports, smoking, lumbar load, and bed type were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.NoAA551.00 (reference)NoGA6262.193.31 (0.22–3.41)0.138NoGG4111.022.93 (0.36–23.66)0.317YesAA31170.180.77 (0.23–2.56)0.667YesGA67431.380.49 (0.15–1.61)0.239YesGG19260.010.98 (0.25–3.92)0.977Amateur sports¶Bed type, smoking, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.NoAA21171.00 (reference)NoGA50560.790.73 (0.36–1.47)0.375NoGG13240.141.24 (0.40–3.79)0.710YesAA1551.600.53 (0.19–1.42)0.206YesGA23130.980.61 (0.23–1.62)0.322YesGG10130.011.08 (0.28–4.19)0.907∗ Amateur sports, bed type, smoking, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.† Amateur sports, bed type, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.‡ Amateur sports, smoking, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.§ Amateur sports, smoking, lumbar load, and bed type were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value.¶ Bed type, smoking, lumbar load, and leisure activities were adjusted for χ2 analysis as covariates, OR, 95% CI, and P value. Open table in a new tab In the present study, we performed a controlled case study to explore the relationship between the risk of LDH and the nine SNP sites in three genes, including Fas, FasL, and CASP9. The results indicated that FasL −844C/T (rs763110) and CASP9 –1263A>G rs4645978 were correlated with LDH risk, and the genotypes of FasL −844C/T TT and CASP9 –1263A>G GG were probably the risk factors for LDH. Further analysis of the interaction between the two genotypes and environmental risk factors revealed that the interaction of the FasL −844TT genotype and level III/IV lumbar loads was consistent with the ultramultiplying model, and the interaction of the CASP9 rs4645978 GG genotype and level III/IV lumbar loads was consistent with the submultiplyi
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