Possible Alteration of Amyloid-β Protein Precursor Metabolism or Trafficking in a 17β-Hydroxysteroid Dehydrogenase X Deficiency Patient

We read with great interest the recent report by Ortez et al. [1], “Undetectable levels of CSF amyloid-β (Aβ) peptide in a patient with 17β-hydroxysteroid dehydrogenase deficiency”. The authors claim that Aβ peptide was not detectable in the cerebrospinal fluid (CSF) of a mentally retarded patient. The dramatically reduced levels of amyloid-β peptide in CSF might indicate an alteration of amyloid-β protein precursor metabolism or trafficking in the patient’s brain. To our knowledge, thirteen of fourteen different types of 17β-hydroxy-steroid dehydrogenase have been discovered in human tissues [2]. For example, 17β-hydroxysteroid dehydrogenase III deficiency [3] is a completely different disease from 17β-hydroxysteroid dehydrogenase X deficiency [4]. The disease suffered by this patient should be specifically described as “17β-hydroxysteroid dehydrogenase X deficiency” rather than 17β-hydroxysteroid dehydrogenase deficiency—an all-inclusive term.

A variety of amyloid-β peptides including Aβ1-37, Aβ1-38, Aβ1-39, Aβ1-40, and Aβ1-42 are present in human CSF [5]. However, data presented in this article (see Fig. 1 of Ref. 1) showed only the absence of a 44 kDa protein band in the patient’s CSF. As the authors emphasize, their finding points to a new direction for the study of Aβ metabolism, and it suggests that 17β-hydroxysteroid dehydrogenase X inhibitors might be candidates for Alzheimer’s disease therapy. Therefore, it is important that the absence of Aβ be firmly established. The masses of Aβ peptides lie in the range of 4300-4500 amu, and in several Western blotting procedures they migrate as monomers of apparent masses of about 4 kDa. Santa Cruz Biotechnology, Inc., the source of the antibody, claims that the band around 40 kDa revealed by their antibody is an oligomeric form of the 4 kDa peptide [6]; however, in experimental samples other explanations may account for the presence or absence of the band. We think that before one can accept that 17β-hydroxysteroid dehydrogenase X deficiency alters amyloid-β protein precursor metabolism or trafficking, the experiment must be repeated with other better characterized antibodies in other separation systems. For instance, a more sophisticated experimental procedure, namely quantitative urea-based Aβ-SDS-PAGE/immunoblot, could be employed [5]. We hope this patient will be demonstrated not to be an anecdotal case of the reduction of Aβ peptide levels in CSF. The finding could be confirmed in other HSD10 deficiency patients carrying the same mutation (c.628C>T) [7] or different mutations [8,9] in the HSD17B10 gene.

Xue-Ying He¹, David Miller², Song-Yu Yang¹

Departments of ¹Neurochemistry and ²Molecular Biology, NYS Institute for Basic research in Developmental Disabilities, Staten Island, NY, USA
Email: songyu.yang@csi.cuny.edu

Acknowledgments: This work was supported in part by the NYS Office for People With Developmental Disabilities.

References
[1] Ortez C, Villar C, Fons C, Duarte ST, Perez A, Garcia-Villopia J, Ribes A, Ormazabal A, Casado M, Campistol J, Vilaseca MA, Garcia-Cazorla A (2011) Undetectable levels of CSF amyloid-β peptide in a patient with 17β-hydroxysteroid dehydrogenase deficiency. J Alzheimers Dis 27, 253-257.
[2] Moeller G, Adamski J (2009) Integrated view on 17beta-hydroxysteroid dehydrogenase. Mol Cell Endocrinol 301, 7-19.
[3] Mains LM, Vakili B, Lacassie Y, Andersson S, Lindqvist A, Rock JA (2008) 17beta-hydroxysteroid dehydrogenase 3 deficiency in a male pseudoherma- phrodite. Fertil Steril 89, 228.e13-17.
[4] Yang SY, He XY, Miller D (2011) Hydroxysteroid (17beta) dehydrogenase X in human health and disease. Mol Cell Endocrinol 343, 1-6.
[5] Bibl M, Mollenhauer B, Esselmann H, Lewczuk P, Klafki H, Sparbier K, Smironov A, Cepek L, Trenkwalder C, Ruther E, Kornhuber J, Otto M, Wiltfang J (2006) CSF amyloid-β-peptides in Alzheimer’s disease, dementia with Lewy bodies and Parkinson’s disease dementia. Brain 129, 1177-1187.
[6] Liu RT, Zou LB, Fu JY, Lu QJ (2010) Effects of liquiritigenin treatment on the learning and memory deficits induced by amyloid β-peptide (25-35) in rats.Behav Brain Res 210, 24-31.
[7] García-Villoria J, Navarro-Sastre A, Fons C, Pérez-Cerdá C, Baldellou A, Fuentes-Castelló MA, González I, Hernández-Gonzalez A, Fernández C, Campistol J, Delpiccolo C, Cortés N, Messeguer A, Briones P, Ribes A (2009) Study of patients and carriers with 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiency: difficulties in the diagnosis. Clin Biochem 1-2, 27-33.
[8] Seaver LH, He XY, Abe K, Cowan T, Enns GM. Sweetman L, Lee S, Malik M, Yang SY (2011) A novel mutation in the HSD17B10 gene of a 10-year-old boy with refractory epilepsy, chreoathetosis and learning disability. PLoS ONE 6, 11. e27348.
[9] Yang SY, He XY, Olpin SE, Sutton VR, McMenamin J, Philipp M, Denman RB, Malik M (2009) Mental retardation linked to mutations in the HSD17B10 gene interfering with neurosteroid and isoleucine metabolism. Proc Natl Acad Sci U S A 106, 14820-14824.