title: Immunoassay of S-adenosylmethionine and S-adenosylhomocysteine: the methylation index as a biomarker for disease and health status.
abstract: BACKGROUND
  S-Adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are relevant to a variety of diseases. Previous reports that quantified SAM and SAH were based on HPLC or LC-MS/MS. No antibody against SAM has been generated, and the antibody against SAH cannot be used with blood samples. Immunoassays have not been used to measure SAM and SAH. In this study, ELISA was used to measure blood SAM and SAH levels.
  
  
  RESULTS
  Specific antibodies against SAM were produced for the first time using a stable analog as the antigen. The monoclonal antibodies against SAM and SAH were characterized. No cross-reactivity was detected for the analyzed analogs. For the anti-SAM antibodies, the ELISA sensitivity was ~2 nM, and the affinity was 7.29 × 1010L/mol. For the anti-SAH antibodies, the sensitivity was ~15 nM, and the affinity was 2.79 × 108L/mol. Using high-quality antibodies against SAM and SAH, immunoassays for the detection of SAM and SAH levels in blood and tissue samples were developed. Clinical investigations using immunoassays to measure SAM, SAH and the methylation index (MI) in normal and diseased samples indicated that (1) the SAM level is age and gender dependent; (2) the SAM level is associated with the severity of liver diseases, inflammatory reactions and other diseases; and (3) the methylation index (MI) is significantly reduced in many diseases and may serve as a screening biomarker to identify potentially unfavorable health conditions.
  
  
  CONCLUSIONS
  It is possible to generate antibodies against active small biomolecules with weak immunogenicity, such as SAM and SAH, using traditional hybridoma technology. The antigens and antibodies described here will contribute to the development of immunoassays to measure SAM, SAH and related molecules. These assays enable the MI to be measured specifically, accurately, easily and quickly without costly equipment. This preliminary study indicates that the MI could be an effective indicator of general health, except under conditions that may alter the value of the MI, such as special diets and medications.
authors.affiliation: Arthus Biosystems, 2600 Hilltop Dr., Richmond, CA, 94806, USA. sheryl.hao@arthusbio.com.
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Hao
authors.affiliation: Department of Infectious Diseases, Xiangya Hospital, Central South University Hospital, Changsha, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Changsha Blood Center, Changsha, 410000, China.|Lanwei Clinical Laboratories Co. Ltd., 268 Xinxing Rd. International Enterprise Center Building 9, Suite 301, Yuhua District, Changsha, 410000, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Qiu
authors.affiliation: Department of Cardiology, Xuanwu Hospital, Capital Medical University, Beijing, 100053, China.
authors.forename: Chunlin
authors.initials: C
authors.lastname: Yin
authors.affiliation: Hunan SkyWorld Biotechnologies Co. Ltd, 9 Panpan Rd. Changsha Economic and Technological Development Zone, Changsha, Hunan, 410100, China.
authors.forename: Huiming
authors.initials: H
authors.lastname: Ren
authors.affiliation: Hunan SkyWorld Biotechnologies Co. Ltd, 9 Panpan Rd. Changsha Economic and Technological Development Zone, Changsha, Hunan, 410100, China.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Gan
authors.affiliation: Hunan SkyWorld Biotechnologies Co. Ltd, 9 Panpan Rd. Changsha Economic and Technological Development Zone, Changsha, Hunan, 410100, China.
authors.forename: Huijun
authors.initials: H
authors.lastname: Li
authors.affiliation: Hunan SkyWorld Biotechnologies Co. Ltd, 9 Panpan Rd. Changsha Economic and Technological Development Zone, Changsha, Hunan, 410100, China.
authors.forename: Yaxia
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Hunan SkyWorld Biotechnologies Co. Ltd, 9 Panpan Rd. Changsha Economic and Technological Development Zone, Changsha, Hunan, 410100, China.
authors.forename: Jiazhi
authors.initials: J
authors.lastname: Xia
authors.affiliation: Department of Infectious Diseases, Xiangya Hospital, Central South University Hospital, Changsha, China.
authors.forename: Wenting
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Cardiology, Xuanwu Hospital, Capital Medical University, Beijing, 100053, China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Guo
authors.affiliation: Arthus Biosystems, 2600 Hilltop Dr., Richmond, CA, 94806, USA.
authors.forename: Isaac A
authors.initials: IA
authors.lastname: Angres
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000293:Adolescent; D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D015415:Biomarkers / Q000737:chemistry*; D001927:Brain Diseases / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006241:Haptens / Q000737:chemistry; D006304:Health Status; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007249:Inflammation; D008297:Male; D008716:Methionine Adenosyltransferase / Q000737:chemistry; D008745:Methylation; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D011107:Polylysine / Q000737:chemistry; D012435:S-Adenosylhomocysteine / Q000737:chemistry*; D012436:S-Adenosylmethionine / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D006241:Haptens; D011107:Polylysine; D012436:S-Adenosylmethionine; D000255:Adenosine Triphosphate; D012435:S-Adenosylhomocysteine; D008716:Methionine Adenosyltransferase
keywords: Antibody; Biomarker; Competitive ELISA; Conjugates; Diseases; Immunoassay; Methylation index; S-Adenosylhomocysteine; S-Adenosylmethionine