- Email: [email protected]
Lack of association of two lipoprotein lipase polymorphisms with Alzheimer's disease
Neuroscience Letters 328 (2002) 109–112 www.elsevier.com/locate/neulet
Lack of association of two lipoprotein lipase polymorphisms with Alzheimer’s disease Matthew D. Martin-Rehrmann, Hyun Soon Cho, G. William Rebeck* Alzheimer Research Unit, 114 16th Street, Massachusetts General Hospital, Charlestown, MA 02129, USA Received 13 March 2002; received in revised form 29 April 2002; accepted 29 April 2002
Abstract A recent genetic study demonstrated associations between an altered risk of Alzheimer’s disease (AD) and two polymorphisms in the lipoprotein lipase (LPL) gene, Asn291Ser and Ser447Ter. LPL immunostains senile plaques, and is a ligand of the low-density lipoprotein receptor-related protein (LRP), a major apolipoprotein E (apoE) receptor. LPL increases the cellular uptake of apoE via LRP, and polymorphisms in LPL alter its ability to mediate apoE–LRP interactions, with potential implications for AD pathogenesis. Here, we tested the genetic association of LPL with AD in a case– control study. For the Asn291Ser polymorphism, we analyzed 277 individuals (141 AD, 136 control) and found no significant difference in allele frequencies between the AD and control groups. For the Ser447Ter polymorphism, we analyzed 187 individuals (108 AD, 79 control) and again found no significant difference in allele frequencies between the AD and control groups. Thus, our study does not support associations between AD and two common polymorphisms in LPL. q 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Case–control; Genetics; Risk factor; Apolipoprotein E receptor; Low-density lipoprotein receptor-related protein
Lipoprotein lipase (LPL) plays a key role in the metabolism of triglyceride-rich lipoproteins and chylomicrons by cleaving fatty acids from these particles for cellular uptake [6]. It is found throughout the body, with the highest activity and mRNA levels found in heart, skeletal muscle, and adipose tissue [7,11], and lesser amounts located in the testes, lung, small intestine, and brain [12]. The physiological role of LPL in the brain is not fully defined [6], but LPL is found in varying quantities throughout the central nervous system [5], and seems to have special significance in the adult hippocampus. LPL mRNA, enzyme mass, and activity levels are significantly higher in the hippocampus than other brain regions [4]. Furthermore, an association has been observed between hyperchylomicronemia, most often caused by LPL deficiency, and neurological disorders affecting memory, problem solving, and coherent thought, all of which are linked to hippocampal function [4]. These studies suggest that brain LPL might be altered in Alzheimer’s disease (AD) given the early damage observed in the hippocampus. * Corresponding author. Alzheimer Research Unit, Massachusetts General Hospital, 149 16th Street, Charlestown, MA 02129, USA. Tel.: 11-617-7248329; fax: 11-617-7241480. E-mail address: [email protected] (G.W. Rebeck).
Several other observations link LPL to AD. LPL is a ligand of the low-density lipoprotein receptor-related protein (LRP) [3], which acts as a receptor for several factors genetically associated with AD, including apolipoprotein E (apoE, protein; APOE, gene) [9,13,18], the amyloid precursor protein [10] and a2-macroglobulin [10]. A polymorphism in exon 3 of the LRP gene itself is implicated with increasing risk of late-onset AD [1,15]. LPL promotes the cellular uptake of apoE-containing lipoproteins via LRP [3], and, like apoE and LRP, immunostains senile plaques in the AD brain [10,14]. These many connections between LPL and AD suggested that polymorphisms in the LPL gene might modify the risk of AD. A recent case–control study addressed this question and reported that two polymorphisms, Ser447Ter and Asn291Ser, each affected risk of AD [2]. The Ser447Ter polymorphism occurs in exon 9 and consists of a C–G transversion resulting in the loss of the final two amino acids (Ser-Gly) at the carboxy terminus of LPL [17]. The Ter447 allele has been reported with a frequency of 5– 12% [2] and is associated with decreased triglyceride and increased high-density lipoprotein (HDL) cholesterol levels in the blood [16,19,20]. The Asn291Ser polymorphism occurs in exon 6 as the result of an A–G transition [19], with the Ser291 allele frequency reported between 1 and
0304-3940/02/$ - see front matter q 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S03 04 - 394 0( 0 2) 00 51 1- 6
M.D. Martin-Rehrmann et al. / Neuroscience Letters 328 (2002) 109–112
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3.5% [16]. Inheritance of the Asn291 allele is associated with higher blood triglyceride and lower HDL cholesterol levels [19,20], the opposite effect of the Ter447 polymorphism. Consistent with these opposing actions, the Ter447 allele was found to be significantly under-represented in clinically diagnosed AD patients versus the control population (3.8 versus 9.8%), while the Ser291 allele was found to be significantly over-represented in clinically diagnosed AD population versus the control population (5.1 versus 1.1%) [2]. The present study attempts to confirm these reported findings. DNA was isolated from brain tissue or whole blood of patients using Qiagen DNA extraction kits. Post-mortem diagnosis of AD was made using Khachaturian criteria at the Massachusetts Alzheimer Disease Research Center (ADRC) Brain Bank or the Brain Tissue Resource Center at McLean Hospital. Thirty-eight post-mortem AD brains, 70 clinically diagnosed AD cases and 79 control individuals were included for analysis of the Ser447Ter genotype, providing a 57% power to detect the reported association. Thirty-seven post-mortem AD brains, 104 clinically diagnosed AD cases, 33 post-mortem controls and 103 control individuals were included for analysis of the Asn291Ser genotype providing a 69% power to detect the reported association. For both sets of analyses, the number of AD cases was similar to or greater than the number analyzed in the earlier study [2]. Genotyping of LPL polymorphisms was conducted with polymerase chain reaction (PCR)-restriction enzyme based techniques. For analysis of the Ser447Ter polymorphism, 139 bp were amplified using the sense primer, 5 0 -CTT CCA CAG GGT GAT CTT CT-3 0 , and the antisense primer, 5 0 -GTC AGC TTT AGC CCA GAA TG-3 0 . Reactions took place in a 25 ml volume containing 5 pmol primers, 200 mM deoxynucleotide triphosphates (dNTPs), and 0.25 units Taq polymerase in buffer with 1.5 mM MgCl2 (Roche Diagnostics GmbH). The amplification consisted of 35 cycles of
denaturation for one minute at 94 8C, annealing for one minute at 56 8C and extension for one minute at 72 8C. Subsequent digestion of the PCR products by 2.5 units MnlI (New England Biolabs) produced uncut 139 bp fragments (Ser447 allele) or 38 and 101 bp fragments (Ter447 allele). These were separated by 4% agarose gel electrophoresis and visualized with ethidium bromide. The frequency of polymorphic alleles in AD and control populations were compared by Chi-square analysis. The exact binomial confidence intervals (CI) for allele frequencies and odds ratios (OR) were determined using STATA statistical software (Stata Corporation, College Station, TX). For analysis of the Asn291Ser genotype, 140 bp were amplified using the sense primer, 5 0 -CAA TCT GGG CTA TGA GAA CA-3 0 , and the antisense primer, 5 0 -GCA TGA TGA AAT AGG ACT CC-3 0 . Reactions took place in a 10 ml volume containing 20 pmol primers, 100 mM dNTPs, and 0.5 units Taq polymerase in buffer with 1.5 mM MgCl2 (Roche Diagnostics GmbH). The amplification consisted of 35 cycles of denaturation for 30 s at 94 8C, annealing for 30 s at 56 8C and extension for 30 s at 72 8C. Subsequent digestion of the PCR products with 2 units HpyCH4 III (New England Biolabs) in the PCR mixture produced 40 and 100 bp fragments (Asn291 allele) or 20, 40 and 80 bp fragments (Ser291 allele). These fragments were separated by 2.5% low melting agarose gel electrophoresis and visualized with ethidium bromide. We determined the Ser447Ter genotype of 79 control and 108 AD individuals. The Ter447 allele was found in 11.4% of our control population, similar to the 9.8 and 10.5% frequencies reported in the control populations in the previous studies (Table 1) [2,8]. We found the Ter447 allele in 10.2% of our AD individuals, which was not significantly different from the control group (P ¼ 0:74). The presence of the Ter447 allele produced an OR of 0.88 (95% CI, 0.46– 1.69) for developing AD. Our AD population frequency was also close to the 10.0% frequency found previously in
Table 1 Frequency of LPL Ser447Ter and Asn291Ser alleles a Baum et al. [2] b
Ser447Ter Ser447 (%) Ter447 (%) Total P OR (95% CI) Asn291Ser Asn291 (%) Ser291 (%) Total P OR (95% CI) a b
This study
AD
Control
AD
Control
96.2 (229) 3.8 (9) (238) 0.0057
90.2 (568) 9.8 (62) (630)
89.8 (194) 10.2 (22) (216) 0.74 0.88 (0.46–1.69)
88.6 (140) 11.4 (18) (158)
94.9 (150) 5.1 (8) (158) 0.0073
98.9 (455) 1.1 (5) (460)
98.9 (279) 1.1 (3) (282) 0.72 0.72 (0.18–2.91)
98.5 (268) 1.5 (4) (272)
Numbers of alleles are indicated in parentheses. Clinically diagnosed subjects.
M.D. Martin-Rehrmann et al. / Neuroscience Letters 328 (2002) 109–112
pathologically confirmed AD cases, while the percentage observed in the clinically diagnosed AD population in the previous study (3.8%) [2] fell outside the 95% CI of this study (6.5–15.0%). We measured the Ser291 allele frequency in 136 control individuals to be 1.5%, once again closely matching the frequency previously reported (1.1%) in the clinically diagnosed control population (Table 1) [2]. The frequency of the Ser291 allele in our AD sample, consisting of 141 individuals, was 1.1%, not significantly different from our control sample group (P ¼ 0:72). The presence of the Ser291 allele produced an OR of 0.72 (95% CI, 0.18–2.91) for developing AD. Our AD population frequency matched the frequency found previously in pathologically confirmed AD cases, while the percentage observed in the clinically diagnosed AD population in the previous study (5.1%) [2] again fell outside the 95% CI of this study (0.2–3.1%). Thus, our results do not support the findings that the two common LPL polymorphisms addressed in this study, Ser447Ter and Ans291Ser, alter the risk for late-onset AD. An additional follow-up study has found no association between inheritance of the Ter447 allele and decreased risk for AD [8], in accord with one of our present results. Due to the variability inherent in genetic studies and the importance of identifying reliable genetic risk factors, both positive and negative results need multiple independent confirmations. Other studies on LPL and AD could incorporate greater numbers of subjects, focus on different ethnic populations, or test other LPL polymorphisms. However, since the two polymorphisms studied are among the most common in LPL [20], and have yielded only inconclusive data, any risk of AD associated with LPL polymorphisms would likely account for only a small fraction of the genetic variation in late-onset AD. These types of genetic studies are an important part of the process of deciphering the pathogenesis of diseases like AD that have both genetic and environmental influences. Through the screening of candidate genes such as LPL, differentiation can begin to be made between primary genetic causality and secondary moderators or pathway members in the pathogenesis of diseases. LPL may affect AD pathogenesis through interactions with amyloid, LRP, or circulation apoE-containing lipoproteins. However, genetic studies thus far favor LPL acting in a secondary role in the development of late-onset AD. The authors would like to thank the Massachusetts ADRC Tissue Resource Center (Dr E.T. Hedley-Whyte, director, NIH AG05134) and the Harvard Brain Tissue Resource Center (Dr Francine Benes, director, NIH HM31862) for brain tissue and diagnostic information. The authors also thank the Massachusetts ADRC (Dr J.H. Growdon, director) for blood samples and diagnostic information. This work was supported by NIH AG14473.
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[7] [8]
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[16]
[17] [1] Baum, L., Chen, L., Ng, H.-K., Chan, Y.S., Mak, Y.T., Woo, J.,
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Chiu, H.F.K. and Pang, C.P., Low density lipoprotein receptor related protein gene exon 3 polymorphism associated with Alzheimer’s disease in Chinese, Neurosci. Lett., 247 (1998) 33–36. Baum, L., Chen, L., Masliah, E., Chan, Y.S., Ng, H.-K. and Pang, C.P., Lipoprotein lipase mutations and Alzheimer’s disease, Am. J. Med. Genet., 88 (1999) 136–139. Beisiegel, U., Weber, W. and Bengtsson-Olivecrona, G., Lipoprotein lipase enhances the binding of chylomicrons to low density lipoprotein receptor-related protein, Proc. Natl. Acad. Sci. USA, 88 (1991) 8342–8346. Ben-Zeev, O., Doolittle, M.H., Singh, N., Chang, C.H. and Schotz, M.C., Synthesis and regulation of lipoprotein lipase in the hippocampus, J. Lipid Res., 31 (1990) 1307–1313. Bessesen, D.H., Richards, C.L., Etienne, J., Goers, J.W. and Eckel, R.H., Spinal cord of the rat contains more lipoprotein lipase than other brain regions, J. Lipid Res., 34 (1993) 229– 238. Braun, J.E. and Severson, D.L., Regulation of the synthesis, processing and translocation of lipoprotein lipase, Biochem. J., 287 (1992) 337–347. Cryer, A., Tissue lipoprotein lipase activity and its action in lipoprotein metabolism, Int. J. Biochem., 13 (1981) 525–541. Fidani, L., Compton, D., Hardy, J., Petersen, R.C., Tangalos, E., Mirtsou, V., Goulas, A. and Wavrant De Vrieze, F., No association between the lipoprotein lipase S447X polymorphism and Alzheimer’s disease, Neurosci. Lett., 322 (2002) 192–194. Hyman, B.T., Apolipoprotein E genotype: utility in clinical practice in Alzheimer’s disease, J. Am. Geriatr. Soc., 44 (1996) 1469–1471. Hyman, B.T., Strickland, D. and Rebeck, G.W., Role of the low-density lipoprotein receptor-related protein in betaamyloid metabolism and Alzheimer’s disease, Arch. Neurol., 57 (2000) 646–650. Kirchgessner, T.G., Svenson, K., Lusis, A.J. and Schotz, M.C., The sequence of cDNA encoding lipoprotein lipase, J. Biol. Chem., 262 (1987) 8463–8466. Kirchgessner, T.G., LeBoeuf, R.C., Langner, C.A., Zollman, S., Chang, C.H., Taylor, B.A., Schotz, M.C., Gordon, J.I. and Lusis, A.J., Genetic and developmental regulation of the lipoprotein lipase gene: loci both distal and proximal to the lipoprotein lipase structural gene control enzyme expression, J. Biol. Chem., 264 (1989) 1473–1482. Rebeck, G.W., Reiter, J.S., Strickland, D.K. and Hyman, B.T., Apolipoprotein E in sporadic Alzheimer’s disease: allelic variation and receptor interactions, Neuron, 11 (1993) 575–580. Rebeck, G.W., Harr, S.D., Strickland, D.K. and Hyman, B.T., Multiple, diverse senile plaque-associated proteins are ligands of an apolipoprotein E receptor, the alpha 2-macroglobulin receptor/low-density-lipoprotein receptor-related protein, Ann. Neurol., 37 (1995) 211–217. Sa´ nchez-Guerra, M., Combarros, O., Infante, J., Llorca, J., Berciano, J., Fontalba, A., Ferna´ ndez-Luna, J.L., Pen˜ a, N. and Ferna´ ndez-Viadero, C., Case–control study and metaanalysis of low density lipoprotein receptor-related protein gene exon 3 polymorphism in Alzheimer’s disease, Neurosci. Lett., 316 (2001) 17–20. Sawano, M., Watanabe, Y., Ohmura, H., Shimada, K., Daida, H., Mokuno, H. and Yamaguchi, H., Potentially protective effects of the Ser447-Ter mutation of the lipoprotein lipase gene against the development of coronary artery disease in Japanese subjects via a beneficial lipid profile, Jpn. Circ. J., 65 (2001) 310–314. Stocks, J., Thorn, J.A. and Galton, D.J., Lipoprotein lipase genotypes for a common premature termination codon
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mutation detected by PCR-mediated site-directed mutagenesis and restriction digestion, J. Lipid Res., 33 (1992) 853– 857. [18] Strittmatter, W. and Roses, A., Apolipoprotein E and Alzheimer’s disease, Annu. Rev. Neurosci., 19 (1996) 53–77. [19] van Bockxmeer, F.M., Liu, Q., Mamotte, C., Burke, V. and Taylor, R., Lipoprotein lipase D9N, N291S and S447X poly-
morphisms: their influence on premature coronary heart disease and plasma lipids, Atherosclerosis, 157 (2001) 123–129. [20] Wittrup, H.H., Tybjærg-Hansen, A. and Nordestgaard, B.G., Lipoprotein lipase mutations, plasma lipids and lipoproteins, and risk of ischemic heart disease, Circulation, 99 (1999) 2901–2907.
Lack of association of two lipoprotein lipase polymorphisms with Alzheimer’s disease Matthew D. Martin-Rehrmann, Hyun Soon Cho, G. William Rebeck* Alzheimer Research Unit, 114 16th Street, Massachusetts General Hospital, Charlestown, MA 02129, USA Received 13 March 2002; received in revised form 29 April 2002; accepted 29 April 2002
Abstract A recent genetic study demonstrated associations between an altered risk of Alzheimer’s disease (AD) and two polymorphisms in the lipoprotein lipase (LPL) gene, Asn291Ser and Ser447Ter. LPL immunostains senile plaques, and is a ligand of the low-density lipoprotein receptor-related protein (LRP), a major apolipoprotein E (apoE) receptor. LPL increases the cellular uptake of apoE via LRP, and polymorphisms in LPL alter its ability to mediate apoE–LRP interactions, with potential implications for AD pathogenesis. Here, we tested the genetic association of LPL with AD in a case– control study. For the Asn291Ser polymorphism, we analyzed 277 individuals (141 AD, 136 control) and found no significant difference in allele frequencies between the AD and control groups. For the Ser447Ter polymorphism, we analyzed 187 individuals (108 AD, 79 control) and again found no significant difference in allele frequencies between the AD and control groups. Thus, our study does not support associations between AD and two common polymorphisms in LPL. q 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Case–control; Genetics; Risk factor; Apolipoprotein E receptor; Low-density lipoprotein receptor-related protein
Lipoprotein lipase (LPL) plays a key role in the metabolism of triglyceride-rich lipoproteins and chylomicrons by cleaving fatty acids from these particles for cellular uptake [6]. It is found throughout the body, with the highest activity and mRNA levels found in heart, skeletal muscle, and adipose tissue [7,11], and lesser amounts located in the testes, lung, small intestine, and brain [12]. The physiological role of LPL in the brain is not fully defined [6], but LPL is found in varying quantities throughout the central nervous system [5], and seems to have special significance in the adult hippocampus. LPL mRNA, enzyme mass, and activity levels are significantly higher in the hippocampus than other brain regions [4]. Furthermore, an association has been observed between hyperchylomicronemia, most often caused by LPL deficiency, and neurological disorders affecting memory, problem solving, and coherent thought, all of which are linked to hippocampal function [4]. These studies suggest that brain LPL might be altered in Alzheimer’s disease (AD) given the early damage observed in the hippocampus. * Corresponding author. Alzheimer Research Unit, Massachusetts General Hospital, 149 16th Street, Charlestown, MA 02129, USA. Tel.: 11-617-7248329; fax: 11-617-7241480. E-mail address: [email protected] (G.W. Rebeck).
Several other observations link LPL to AD. LPL is a ligand of the low-density lipoprotein receptor-related protein (LRP) [3], which acts as a receptor for several factors genetically associated with AD, including apolipoprotein E (apoE, protein; APOE, gene) [9,13,18], the amyloid precursor protein [10] and a2-macroglobulin [10]. A polymorphism in exon 3 of the LRP gene itself is implicated with increasing risk of late-onset AD [1,15]. LPL promotes the cellular uptake of apoE-containing lipoproteins via LRP [3], and, like apoE and LRP, immunostains senile plaques in the AD brain [10,14]. These many connections between LPL and AD suggested that polymorphisms in the LPL gene might modify the risk of AD. A recent case–control study addressed this question and reported that two polymorphisms, Ser447Ter and Asn291Ser, each affected risk of AD [2]. The Ser447Ter polymorphism occurs in exon 9 and consists of a C–G transversion resulting in the loss of the final two amino acids (Ser-Gly) at the carboxy terminus of LPL [17]. The Ter447 allele has been reported with a frequency of 5– 12% [2] and is associated with decreased triglyceride and increased high-density lipoprotein (HDL) cholesterol levels in the blood [16,19,20]. The Asn291Ser polymorphism occurs in exon 6 as the result of an A–G transition [19], with the Ser291 allele frequency reported between 1 and
0304-3940/02/$ - see front matter q 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S03 04 - 394 0( 0 2) 00 51 1- 6
M.D. Martin-Rehrmann et al. / Neuroscience Letters 328 (2002) 109–112
110
3.5% [16]. Inheritance of the Asn291 allele is associated with higher blood triglyceride and lower HDL cholesterol levels [19,20], the opposite effect of the Ter447 polymorphism. Consistent with these opposing actions, the Ter447 allele was found to be significantly under-represented in clinically diagnosed AD patients versus the control population (3.8 versus 9.8%), while the Ser291 allele was found to be significantly over-represented in clinically diagnosed AD population versus the control population (5.1 versus 1.1%) [2]. The present study attempts to confirm these reported findings. DNA was isolated from brain tissue or whole blood of patients using Qiagen DNA extraction kits. Post-mortem diagnosis of AD was made using Khachaturian criteria at the Massachusetts Alzheimer Disease Research Center (ADRC) Brain Bank or the Brain Tissue Resource Center at McLean Hospital. Thirty-eight post-mortem AD brains, 70 clinically diagnosed AD cases and 79 control individuals were included for analysis of the Ser447Ter genotype, providing a 57% power to detect the reported association. Thirty-seven post-mortem AD brains, 104 clinically diagnosed AD cases, 33 post-mortem controls and 103 control individuals were included for analysis of the Asn291Ser genotype providing a 69% power to detect the reported association. For both sets of analyses, the number of AD cases was similar to or greater than the number analyzed in the earlier study [2]. Genotyping of LPL polymorphisms was conducted with polymerase chain reaction (PCR)-restriction enzyme based techniques. For analysis of the Ser447Ter polymorphism, 139 bp were amplified using the sense primer, 5 0 -CTT CCA CAG GGT GAT CTT CT-3 0 , and the antisense primer, 5 0 -GTC AGC TTT AGC CCA GAA TG-3 0 . Reactions took place in a 25 ml volume containing 5 pmol primers, 200 mM deoxynucleotide triphosphates (dNTPs), and 0.25 units Taq polymerase in buffer with 1.5 mM MgCl2 (Roche Diagnostics GmbH). The amplification consisted of 35 cycles of
denaturation for one minute at 94 8C, annealing for one minute at 56 8C and extension for one minute at 72 8C. Subsequent digestion of the PCR products by 2.5 units MnlI (New England Biolabs) produced uncut 139 bp fragments (Ser447 allele) or 38 and 101 bp fragments (Ter447 allele). These were separated by 4% agarose gel electrophoresis and visualized with ethidium bromide. The frequency of polymorphic alleles in AD and control populations were compared by Chi-square analysis. The exact binomial confidence intervals (CI) for allele frequencies and odds ratios (OR) were determined using STATA statistical software (Stata Corporation, College Station, TX). For analysis of the Asn291Ser genotype, 140 bp were amplified using the sense primer, 5 0 -CAA TCT GGG CTA TGA GAA CA-3 0 , and the antisense primer, 5 0 -GCA TGA TGA AAT AGG ACT CC-3 0 . Reactions took place in a 10 ml volume containing 20 pmol primers, 100 mM dNTPs, and 0.5 units Taq polymerase in buffer with 1.5 mM MgCl2 (Roche Diagnostics GmbH). The amplification consisted of 35 cycles of denaturation for 30 s at 94 8C, annealing for 30 s at 56 8C and extension for 30 s at 72 8C. Subsequent digestion of the PCR products with 2 units HpyCH4 III (New England Biolabs) in the PCR mixture produced 40 and 100 bp fragments (Asn291 allele) or 20, 40 and 80 bp fragments (Ser291 allele). These fragments were separated by 2.5% low melting agarose gel electrophoresis and visualized with ethidium bromide. We determined the Ser447Ter genotype of 79 control and 108 AD individuals. The Ter447 allele was found in 11.4% of our control population, similar to the 9.8 and 10.5% frequencies reported in the control populations in the previous studies (Table 1) [2,8]. We found the Ter447 allele in 10.2% of our AD individuals, which was not significantly different from the control group (P ¼ 0:74). The presence of the Ter447 allele produced an OR of 0.88 (95% CI, 0.46– 1.69) for developing AD. Our AD population frequency was also close to the 10.0% frequency found previously in
Table 1 Frequency of LPL Ser447Ter and Asn291Ser alleles a Baum et al. [2] b
Ser447Ter Ser447 (%) Ter447 (%) Total P OR (95% CI) Asn291Ser Asn291 (%) Ser291 (%) Total P OR (95% CI) a b
This study
AD
Control
AD
Control
96.2 (229) 3.8 (9) (238) 0.0057
90.2 (568) 9.8 (62) (630)
89.8 (194) 10.2 (22) (216) 0.74 0.88 (0.46–1.69)
88.6 (140) 11.4 (18) (158)
94.9 (150) 5.1 (8) (158) 0.0073
98.9 (455) 1.1 (5) (460)
98.9 (279) 1.1 (3) (282) 0.72 0.72 (0.18–2.91)
98.5 (268) 1.5 (4) (272)
Numbers of alleles are indicated in parentheses. Clinically diagnosed subjects.
M.D. Martin-Rehrmann et al. / Neuroscience Letters 328 (2002) 109–112
pathologically confirmed AD cases, while the percentage observed in the clinically diagnosed AD population in the previous study (3.8%) [2] fell outside the 95% CI of this study (6.5–15.0%). We measured the Ser291 allele frequency in 136 control individuals to be 1.5%, once again closely matching the frequency previously reported (1.1%) in the clinically diagnosed control population (Table 1) [2]. The frequency of the Ser291 allele in our AD sample, consisting of 141 individuals, was 1.1%, not significantly different from our control sample group (P ¼ 0:72). The presence of the Ser291 allele produced an OR of 0.72 (95% CI, 0.18–2.91) for developing AD. Our AD population frequency matched the frequency found previously in pathologically confirmed AD cases, while the percentage observed in the clinically diagnosed AD population in the previous study (5.1%) [2] again fell outside the 95% CI of this study (0.2–3.1%). Thus, our results do not support the findings that the two common LPL polymorphisms addressed in this study, Ser447Ter and Ans291Ser, alter the risk for late-onset AD. An additional follow-up study has found no association between inheritance of the Ter447 allele and decreased risk for AD [8], in accord with one of our present results. Due to the variability inherent in genetic studies and the importance of identifying reliable genetic risk factors, both positive and negative results need multiple independent confirmations. Other studies on LPL and AD could incorporate greater numbers of subjects, focus on different ethnic populations, or test other LPL polymorphisms. However, since the two polymorphisms studied are among the most common in LPL [20], and have yielded only inconclusive data, any risk of AD associated with LPL polymorphisms would likely account for only a small fraction of the genetic variation in late-onset AD. These types of genetic studies are an important part of the process of deciphering the pathogenesis of diseases like AD that have both genetic and environmental influences. Through the screening of candidate genes such as LPL, differentiation can begin to be made between primary genetic causality and secondary moderators or pathway members in the pathogenesis of diseases. LPL may affect AD pathogenesis through interactions with amyloid, LRP, or circulation apoE-containing lipoproteins. However, genetic studies thus far favor LPL acting in a secondary role in the development of late-onset AD. The authors would like to thank the Massachusetts ADRC Tissue Resource Center (Dr E.T. Hedley-Whyte, director, NIH AG05134) and the Harvard Brain Tissue Resource Center (Dr Francine Benes, director, NIH HM31862) for brain tissue and diagnostic information. The authors also thank the Massachusetts ADRC (Dr J.H. Growdon, director) for blood samples and diagnostic information. This work was supported by NIH AG14473.
[2]
[3]
[4]
[5]
[6]
[7] [8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
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