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Mejdahl Nielsen M, Petersen ET, Fenger CD, Ørngreen MC, Siebner HR, Boer VO, Považan M, Lund A, Grønborg SW, Hammer TB. X-linked creatine transporter (SLC6A8) deficiency in females: Difficult to recognize, but a potentially treatable disease. Mol Genet Metab 2023; 140:107694. [PMID: 37708665 DOI: 10.1016/j.ymgme.2023.107694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 08/29/2023] [Accepted: 08/29/2023] [Indexed: 09/16/2023]
Abstract
Creatine transporter deficiency (CTD), caused by pathogenic variants in SLC6A8, is the second most common cause of X-linked intellectual disability. Symptoms include intellectual disability, epilepsy, and behavioral disorders and are caused by reduced cerebral creatine levels. Targeted treatment with oral supplementation is available, however the treatment efficacy is still being investigated. There are clinical and theoretical indications that heterozygous females with CTD respond better to supplementation treatment than hemizygous males. Unfortunately, heterozygous females with CTD often have more subtle and uncharacteristic clinical and biochemical phenotypes, rendering diagnosis more difficult. We report a new female case who presented with learning disabilities and seizures. After determining the diagnosis with molecular genetic testing confirmed by proton magnetic resonance spectroscopy (1H-MRS), the patient was treated with supplementation treatment including creatine, arginine, and glycine. After 28 months of treatment, the patient showed prominent clinical improvement and increased creatine levels in the brain. Furthermore, we provide a review of the 32 female cases reported in the current literature including a description of phenotypes, genotypes, diagnostic approaches, and effects of supplementation treatment. Based on this, we find that supplementation treatment should be tested in heterozygous female patients with CTD, and a prospective treatment underlines the importance of diagnosing these patients. The diagnosis should be suspected in a broad clinical spectrum of female patients and can only be made by molecular genetic testing. 1H-MRS of cerebral creatine levels is essential for establishing the diagnosis in females, and especially valuable when assessing variants of unknown significance.
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Affiliation(s)
- Malene Mejdahl Nielsen
- Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
| | - Esben Thade Petersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Hvidovre, Denmark; Section for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Christina Dühring Fenger
- Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Denmark; Amplexa Genetics, Odense, Denmark
| | - Mette Cathrine Ørngreen
- Center for Inherited Metabolic Diseases, Departments of Pediatrics and Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; European Reference Network for Rare Hereditary Metabolic Disorders (MetabERN) - Project ID No 739543, Denmark
| | - Hartwig Roman Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Hvidovre, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Vincent Oltman Boer
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Hvidovre, Denmark
| | - Michal Považan
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Hvidovre, Denmark
| | - Allan Lund
- Center for Inherited Metabolic Diseases, Departments of Pediatrics and Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; European Reference Network for Rare Hereditary Metabolic Disorders (MetabERN) - Project ID No 739543, Denmark
| | - Sabine Weller Grønborg
- Center for Inherited Metabolic Diseases, Departments of Pediatrics and Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; European Reference Network for Rare Hereditary Metabolic Disorders (MetabERN) - Project ID No 739543, Denmark
| | - Trine Bjørg Hammer
- Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Denmark
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Li J, Xu S. Diagnosis and Treatment of X-Linked Creatine Transporter Deficiency: Case Report and Literature Review. Brain Sci 2023; 13:1382. [PMID: 37891751 PMCID: PMC10605349 DOI: 10.3390/brainsci13101382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/18/2023] [Accepted: 09/25/2023] [Indexed: 10/29/2023] Open
Abstract
(1) Background: X-linked creatine transporter deficiency (CTD) (OMIM 300036) is a rare group of inherited metabolic disorders characterized by global developmental delay/intellectual disability (GDD/ID), seizures, autistic behavior, and movement disorders. Pathogenic variants in the SLC6A8 gene, located at Xq28, are causative of the disease, leading to impaired creatine transport into the brain. Supplementation with creatine and its precursors, glycine and arginine, has been attempted, yet the treatment efficacy remains controversial. (2) Methods: Here we report a de novo SLC6A8 variant in a boy aged 3 years 9 months presenting with GDD, autistic behavior, and epilepsy. Elevated urinary creatine/creatinine ratio and diminished creatine peak on brain MR spectroscopy suggested the diagnosis of CTD. Genetic sequencing revealed a de novo hemizygous frameshift variant (NM_005629: c.1136_1137del, p. Glu379ValfsTer85). Creatine supplementation therapy was initiated after definitive diagnosis. Electroencephalography and MR spectroscopy were monitored during follow-up in concurrence with neuropsychological evaluations. The clinical phenotype and treatment response of CTD were summarized by systematic view of the literature. (3) Results: In silico analysis showed this variant to be deleterious, probably interfering with substrate binding and conformational changes during creatine transport. Creatine supplementation therapy led to seizure cessation and modest cognitive improvement after half-year's treatment. (4) Conclusions: This case highlights the importance of MR spectroscopy and metabolic screening in males with GDD/ID, allowing for early diagnosis and therapeutic intervention. Mechanistic understanding and case-per-se analysis are required to enable precision treatment for the patients.
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Affiliation(s)
| | - Sanqing Xu
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430074, China;
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Tise CG, Palma MJ, Cusmano-Ozog KP, Matalon DR. Creatine Transporter Deficiency Presenting as Failure to Thrive: A Case Report of a Novel SLC6A8 Variant Causing a Treatable but Likely Underdiagnosed Genetic Disorder. J Investig Med High Impact Case Rep 2023; 11:23247096231154438. [PMID: 36752093 PMCID: PMC9909053 DOI: 10.1177/23247096231154438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Cerebral creatine deficiency syndromes (CCDS) are a rare group of inherited metabolic disorders (IMDs) that often present with nonspecific findings including global developmental delay (GDD), intellectual disability (ID), seizures, hypotonia, and behavioral differences. Creatine transporter (CRTR) deficiency is the most common CCDS, exhibiting X-linked inheritance and an estimated prevalence as high as 2.6% in individuals with neurodevelopmental disorders. Here, we present a 20-month-old boy with worsening failure to thrive (FTT) and GDD admitted for evaluation. He was found to have persistently low serum creatinine levels and a family history notable for a mother with learning disabilities and a maternal male cousin with GDD. Urine analyses revealed a marked elevation of creatine and elevated creatine:creatinine ratio suggestive of CRTR deficiency. Molecular genetic testing of SLC6A8 identified a maternally inherited hemizygous variant and brain magnetic resonance spectroscopy (MRS) showed diffusely diminished creatine peaks, further supporting the diagnosis of CRTR deficiency. The proband was started on creatine, arginine, and glycine supplementation and has demonstrated improved development. This case highlights that CRTR deficiency should be considered in all patients presenting with FTT and abnormal neurodevelopmental features, particularly if creatinine levels are low on serum chemistry studies. The nonspecific presentation of this condition in males and females likely has resulted in CRTR deficiency being underdiagnosed. There are existing therapies for individuals affected with CRTR deficiency and other CCDS, highlighting the importance of early diagnosis and intervention for affected individuals.
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Yan Z, Yan Z, Liu S, Yin Y, Yang T, Chen Q. Regulative Mechanism of Guanidinoacetic Acid on Skeletal Muscle Development and Its Application Prospects in Animal Husbandry: A Review. Front Nutr 2021; 8:714567. [PMID: 34458310 PMCID: PMC8387576 DOI: 10.3389/fnut.2021.714567] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 07/22/2021] [Indexed: 12/12/2022] Open
Abstract
Guanidinoacetic acid is the direct precursor of creatine and its phosphorylated derivative phosphocreatine in the body. It is a safe nutritional supplement that can be used to promote muscle growth and development. Improving the growth performance of livestock and poultry and meat quality is the eternal goal of the animal husbandry, and it is also the common demand of today's society and consumers. A large number of experimental studies have shown that guanidinoacetic acid could improve the growth performance of animals, promote muscle development and improve the health of animals. However, the mechanism of how it affects muscle development needs to be further elucidated. This article discusses the physical and chemical properties of guanidinoacetic acid and its synthesis pathway, explores its mechanism of how it promotes muscle development and growth, and also classifies and summarizes the impact of its application in animal husbandry, providing a scientific basis for this application. In addition, this article also proposes future directions for the development of this substance.
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Affiliation(s)
- Zhaoming Yan
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
| | - Zhaoyue Yan
- Chemistry Department, University of Liverpool, Liverpool, United Kingdom
| | - Shuangli Liu
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
| | - Yunju Yin
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
| | - Tai Yang
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
| | - Qinghua Chen
- College of Animal Science and Technology, Hunan Agricultural University, Changsha, China
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