id: P48029
gene_symbol: SLC6A8
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  SLC6A8 (creatine transporter 1, CRT/CT1) is a sodium- and chloride-dependent
  plasma membrane creatine transporter of the SLC6 (SNF/neurotransmitter:sodium
  symporter) family. The 635-residue, 12-transmembrane protein couples the inward
  electrochemical gradients of Na+ and Cl- to import creatine into cells with a
  stoichiometry of approximately 2 Na+ : 1 Cl- : 1 creatine, generating an
  electrogenic, high-affinity (micromolar Km) uptake that is highly specific for
  creatine and closely related guanidino compounds; it does not transport choline
  or the neurotransmitter GABA despite its family relationship to GABA, taurine and
  betaine transporters. It is the transport arm of the creatine/phosphocreatine
  energy-buffer system, distributing blood-borne creatine to tissues with high and
  fluctuating energy demand. It is most strongly expressed in skeletal muscle,
  kidney and heart, with lower expression in brain, and is also present in intestine
  and other epithelia; in polarized epithelial cells (intestine, kidney) it localizes
  to the apical plasma membrane. It mediates creatine entry into the brain across the
  blood-brain barrier. Loss-of-function variants cause X-linked cerebral creatine
  deficiency syndrome 1 (creatine transporter deficiency), characterized by
  intellectual disability, severe speech delay, behavioral abnormalities and seizures.
alternative_products:
- name: 1 (CRT1)
  id: P48029-1
- name: 2 (CRT2, SLC6A8B)
  id: P48029-2
  sequence_note: VSP_043917, VSP_043918, VSP_043919,
- name: 3 (SLC6A8C)
  id: P48029-3
  sequence_note: VSP_043916
- name: '4'
  id: P48029-4
  sequence_note: VSP_046316
existing_annotations:
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      SLC6A8 is an integral plasma membrane transporter; the plasma membrane is
      where it acts. Well supported and consistent with experimental localization.
    action: ACCEPT
    reason: >-
      Correct cellular location for the transporter, corroborated by experimental
      (IMP/IDA) localization to the plasma membrane / apical plasma membrane.
    supported_by:
    - reference_id: PMID:22644605
      supporting_text: All mutants were properly targeted to the plasma membrane in both systems.
- term:
    id: GO:0006865
    label: amino acid transport
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Creatine is a guanidino compound, not an amino acid, and the established
      substrate of SLC6A8 is creatine. This IBA term is an imprecise, family-level
      generalization that mischaracterizes the cargo.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Over-broad/family-derived annotation; the specific, experimentally established
      transported substrate is creatine (GO:0015881), not amino acids. Better captured
      by creatine transmembrane transport.
- term:
    id: GO:0035725
    label: sodium ion transmembrane transport
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      SLC6A8 cotransports Na+ together with creatine, so it does participate in sodium
      ion transmembrane transport, but this is a generic by-product of the symport
      mechanism rather than its core dedicated function.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mechanistically true (Na+ is co-transported) but generic; the core function is
      creatine symport. Retain as a non-core mechanistic annotation.
    supported_by:
    - reference_id: PMID:9882430
      supporting_text: induced a Na+- and Cl--dependent creatine uptake activity
- term:
    id: GO:0005332
    label: gamma-aminobutyric acid:sodium:chloride symporter activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      This IBA annotation, propagated from GABA/monoamine transporter relatives in the
      SLC6 family, assigns the wrong substrate. SLC6A8 transports creatine, not GABA;
      GABA does not inhibit creatine uptake, indicating it is not a substrate.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Wrong-substrate over-annotation derived from family phylogeny. The experimentally
      verified molecular function is creatine:sodium symporter activity (GO:0005309).
      GABA is not transported.
    supported_by:
    - reference_id: PMID:12433955
      supporting_text: >-
        More distant structural analogues of creatine, such as GABA, choline, glycine,
        beta-alanine, taurine and betaine, had no effect on intestinal creatine uptake,
        indicating a high substrate specificity of the creatine transporter
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      Correct core molecular function, here assigned electronically. Strongly supported
      by multiple experimental annotations and the UniProt catalytic activity.
    action: ACCEPT
    reason: >-
      Accurate molecular function; this is the core activity of SLC6A8. Corroborated by
      independent IDA/IMP evidence.
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Correct plasma membrane localization, assigned electronically and supported experimentally.
    action: ACCEPT
    reason: Correct cellular location; redundant with experimental plasma membrane annotations.
- term:
    id: GO:0006836
    label: neurotransmitter transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: >-
      Creatine is not a classical neurotransmitter and SLC6A8 is a creatine transporter,
      not a neurotransmitter transporter. This term derives from the InterPro signature
      shared with the neurotransmitter:sodium symporter family.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Family-signature (InterPro) over-annotation; the transported cargo is creatine, not
      a neurotransmitter. Better represented by creatine transmembrane transport.
- term:
    id: GO:0015812
    label: gamma-aminobutyric acid transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000108
  qualifier: involved_in
  review:
    summary: >-
      Inferred logically from the (incorrect for this gene) GABA symporter molecular
      function. Since SLC6A8 does not transport GABA, this process annotation is also
      incorrect.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Downstream of the erroneous GO:0005332 GABA symporter annotation; GABA is not a
      substrate of SLC6A8.
    supported_by:
    - reference_id: PMID:12433955
      supporting_text: >-
        More distant structural analogues of creatine, such as GABA, choline, glycine,
        beta-alanine, taurine and betaine, had no effect on intestinal creatine uptake
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: located_in
  review:
    summary: >-
      Generic membrane localization, true but uninformative given the more specific
      plasma membrane / apical plasma membrane annotations.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct but non-specific; subsumed by the plasma membrane annotation. Retained as
      a high-level location.
- term:
    id: GO:0016324
    label: apical plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      In polarized epithelia (intestine, kidney) SLC6A8 is apical. Correct context-specific
      localization, also supported experimentally by immunohistochemistry in enterocytes.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate for polarized epithelial cells but context-specific; the gene-wide core
      location is plasma membrane.
    supported_by:
    - reference_id: PMID:12433955
      supporting_text: CRT protein was mainly associated with the apical membrane of the enterocytes
- term:
    id: GO:0006600
    label: creatine metabolic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-71288
  qualifier: involved_in
  review:
    summary: >-
      SLC6A8 is the transport step of cellular creatine handling and so participates in the
      creatine metabolic process. Reasonable high-level process annotation.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate process context (creatine distribution within metabolism) but broader than
      the specific creatine transmembrane transport process that is the gene's core role.
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: ISS
  original_reference_id: PMID:25531585
  qualifier: enables
  review:
    summary: Core molecular function, supported here by sequence/ortholog similarity. Correct.
    action: ACCEPT
    reason: Accurate core molecular function; consistent with direct experimental evidence.
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IMP
  original_reference_id: PMID:17465020
  qualifier: enables
  review:
    summary: >-
      Functional (creatine uptake) characterization of SLC6A8 missense variants establishes
      the creatine:sodium symporter activity by mutational analysis. Strong support for the
      core molecular function.
    action: ACCEPT
    reason: Direct experimental (IMP) support for the core molecular function via variant analysis.
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IMP
  original_reference_id: PMID:22644605
  qualifier: enables
  review:
    summary: >-
      Electrophysiological and transport characterization of non-truncating SLC6A8 mutants
      directly demonstrates electrogenic, Na+/Cl--coupled creatine symport activity.
    action: ACCEPT
    reason: Strong direct experimental (IMP) support; loss of activity in mutants confirms the function.
    supported_by:
    - reference_id: PMID:22644605
      supporting_text: Mutations led to the complete loss of both electrogenic and transport activities
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IMP
  original_reference_id: PMID:25861866
  qualifier: enables
  review:
    summary: >-
      Functional creatine-uptake characterization of novel SLC6A8 missense variants supports
      the creatine:sodium symporter molecular function.
    action: ACCEPT
    reason: Direct experimental (IMP) support for the core molecular function.
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IDA
  original_reference_id: PMID:7945388
  qualifier: enables
  review:
    summary: >-
      Heterologous expression of the cloned human creatine transporter produced sodium-dependent
      creatine uptake, directly demonstrating the activity.
    action: ACCEPT
    reason: Direct assay (IDA) of the core molecular function in a heterologous system.
    supported_by:
    - reference_id: PMID:7945388
      supporting_text: >-
        Transient expression of the hCRT-BS2M in COS-7 cells demonstrates sodium dependent
        [14C]creatine uptake with a KM value of 14.9 +/- 3.0 microM
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IDA
  original_reference_id: PMID:7953292
  qualifier: enables
  review:
    summary: >-
      The cloned human creatine transporter mediated high-affinity creatine uptake with no
      transport of choline, directly establishing creatine symport activity and specificity.
    action: ACCEPT
    reason: Direct assay (IDA) of the core molecular function with demonstrated substrate specificity.
    supported_by:
    - reference_id: PMID:7953292
      supporting_text: >-
        mediated high affinity (Km = 77 +/- 6 microM) creatine uptake, which was blocked by
        creatine analogs with high affinity. There was no specific transport of choline
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: IDA
  original_reference_id: PMID:9882430
  qualifier: enables
  review:
    summary: >-
      Expression of the human heart CRT-1 cDNA in Xenopus oocytes induced Na+- and
      Cl--dependent creatine uptake, directly demonstrating the symporter activity.
    action: ACCEPT
    reason: Direct assay (IDA) establishing Na+/Cl--dependent creatine symport.
    supported_by:
    - reference_id: PMID:9882430
      supporting_text: >-
        induced a Na+- and Cl--dependent creatine uptake activity that saturated with a Km of
        approximately 20 microM for creatine
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IMP
  original_reference_id: PMID:22644605
  qualifier: located_in
  review:
    summary: >-
      Immunofluorescence/western blot localization of wild-type and mutant SLC6A8 to the
      plasma membrane. Correct core localization.
    action: ACCEPT
    reason: Direct experimental support for plasma membrane localization.
    supported_by:
    - reference_id: PMID:22644605
      supporting_text: All mutants were properly targeted to the plasma membrane in both systems
- term:
    id: GO:0016324
    label: apical plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:12433955
  qualifier: located_in
  review:
    summary: >-
      Immunohistochemistry localized CRT to the apical membrane of enterocytes, establishing
      apical localization in polarized epithelia.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate context-specific (polarized epithelium) localization; the gene-wide core
      location is plasma membrane.
    supported_by:
    - reference_id: PMID:12433955
      supporting_text: CRT protein was mainly associated with the apical membrane of the enterocytes
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-200396
  qualifier: enables
  review:
    summary: Core molecular function captured via Reactome pathway curation. Correct.
    action: ACCEPT
    reason: Accurate core molecular function; consistent with experimental evidence.
- term:
    id: GO:0015881
    label: creatine transmembrane transport
  evidence_type: IMP
  original_reference_id: PMID:25861866
  qualifier: involved_in
  review:
    summary: >-
      Functional creatine-uptake assays of SLC6A8 variants support the gene's involvement in
      creatine transmembrane transport. This is the core biological process.
    action: ACCEPT
    reason: Direct experimental support for the core transport process; this is a primary core process for SLC6A8.
- term:
    id: GO:0005308
    label: creatine transmembrane transporter activity
  evidence_type: NAS
  original_reference_id: PMID:8661037
  qualifier: enables
  review:
    summary: >-
      Correct molecular function but more general than the substrate-and-coupling-specific
      GO:0005309 (creatine:sodium symporter activity) that is experimentally supported.
    action: ACCEPT
    reason: >-
      Accurate parent molecular function; retained as a correct (if broader) term. The more
      precise creatine:sodium symporter activity (GO:0005309) is recorded as the core molecular
      function in core_functions; GO:0005308 is kept as an accepted parent rather than modified
      away, since it is not wrong.
- term:
    id: GO:0015881
    label: creatine transmembrane transport
  evidence_type: NAS
  original_reference_id: PMID:8661037
  qualifier: involved_in
  review:
    summary: Correct core biological process, asserted from the literature. Accurate.
    action: ACCEPT
    reason: Accurate core transport process; corroborated by experimental IMP evidence.
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-200396
  qualifier: located_in
  review:
    summary: Correct plasma membrane localization captured via Reactome curation.
    action: ACCEPT
    reason: Accurate core location; redundant with experimental plasma membrane annotations.
- term:
    id: GO:0005309
    label: creatine:sodium symporter activity
  evidence_type: TAS
  original_reference_id: PMID:7953292
  qualifier: enables
  review:
    summary: Core molecular function captured from the cloning/characterization paper.
    action: ACCEPT
    reason: Accurate core molecular function; the same paper provides direct IDA support.
- term:
    id: GO:0006936
    label: muscle contraction
  evidence_type: TAS
  original_reference_id: PMID:8661155
  qualifier: involved_in
  review:
    summary: >-
      SLC6A8 supplies creatine to skeletal and cardiac muscle for the phosphocreatine energy
      buffer, an upstream physiological role rather than direct participation in the
      contraction machinery. The cited reference (PMID:8661155) is a genomic-organization paper
      that does not establish a role in contraction (flagged MISCITED in its reference_review).
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Indirect, downstream physiological consequence (creatine supply supports muscle energy
      metabolism); not a core molecular activity of the transporter and not direct involvement
      in the contractile process. The sole cited reference does not support a contraction role,
      so this is over-annotated rather than a supportable non-core function.
- term:
    id: GO:0016020
    label: membrane
  evidence_type: TAS
  original_reference_id: PMID:7953292
  qualifier: located_in
  review:
    summary: Generic membrane localization; subsumed by the more specific plasma membrane annotations.
    action: KEEP_AS_NON_CORE
    reason: Correct but non-specific; retained as a high-level location.
core_functions:
- description: >-
    Sodium- and chloride-dependent symport of creatine across the plasma membrane,
    coupling the inward Na+ and Cl- electrochemical gradients to import creatine into
    the cell (approx. 2 Na+ : 1 Cl- : 1 creatine), thereby supplying creatine to the
    cellular creatine/phosphocreatine energy-buffer system in muscle, brain and other
    energy-demanding tissues.
  molecular_function:
    id: GO:0005309
    label: creatine:sodium symporter activity
  directly_involved_in:
  - id: GO:0015881
    label: creatine transmembrane transport
  locations:
  - id: GO:0005886
    label: plasma membrane
  supported_by:
  - reference_id: PMID:9882430
    supporting_text: >-
      induced a Na+- and Cl--dependent creatine uptake activity that saturated with a Km of
      approximately 20 microM for creatine
  - reference_id: PMID:7953292
    supporting_text: >-
      mediated high affinity (Km = 77 +/- 6 microM) creatine uptake, which was blocked by
      creatine analogs with high affinity. There was no specific transport of choline
  - reference_id: PMID:22644605
    supporting_text: Mutations led to the complete loss of both electrogenic and transport activities
suggested_questions:
- question: >-
    Does SLC6A8 transport guanidinoacetate (the GAMT substrate) to any physiologically
    relevant degree, or is it strictly selective for creatine among the guanidino compounds?
suggested_experiments:
- hypothesis: >-
    SLC6A8 selectively imports creatine and does not efficiently transport guanidinoacetate
    or other amino acids/neurotransmitters.
  description: >-
    Side-by-side radiolabeled/LC-MS uptake assays in SLC6A8-expressing cells comparing
    creatine, guanidinoacetate, GABA, taurine and betaine, with Na+/Cl- dependence and
    competition controls, to quantify substrate selectivity.
  experiment_type: transport assay
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000108
  title: Automatic assignment of GO terms using logical inference, based on on inter-ontology
    links
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:12433955
  title: 'Human, rat and chicken small intestinal Na+ - Cl- -creatine transporter:
    functional, molecular characterization and localization.'
  findings:
  - statement: >-
      Enterocyte creatine uptake is electrogenic and Na+/Cl--dependent with a probable
      stoichiometry of 2 Na+ : 1 Cl- : 1 creatine, with high substrate specificity for
      creatine, and CRT localizes to the apical enterocyte membrane.
    supporting_text: >-
      This accumulation was electrogenic, Na(+)- and Cl(-)-dependent, with a probable
      stoichiometry of 2 Na(+): 1 Cl(-): 1 creatine
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified; directly establishes transport stoichiometry, substrate specificity
      (no GABA/choline transport), and apical localization.
- id: PMID:17465020
  title: 'Functional characterization of missense variants in the creatine transporter
    gene (SLC6A8): improved diagnostic application.'
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified; functional creatine-uptake assays of SLC6A8 variants (IMP support
      for the symporter activity).
- id: PMID:22644605
  title: Functional and electrophysiological characterization of four non-truncating
    mutations responsible for creatine transporter (SLC6A8) deficiency syndrome.
  findings:
  - statement: >-
      Non-truncating SLC6A8 mutants traffic correctly to the plasma membrane but lose both
      electrogenic and creatine-transport activities, demonstrating electrogenic Na+/Cl--coupled
      creatine symport.
    supporting_text: All mutants were properly targeted to the plasma membrane in both systems.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; electrophysiology + transport assays; IMP for symporter activity and plasma membrane localization.
- id: PMID:25531585
  title: Negative regulation of the creatine transporter SLC6A8 by SPAK and OSR1.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified; SPAK/OSR1 (WNK-controlled) kinases negatively regulate SLC6A8 activity. Basis of the ISS symporter annotation.
- id: PMID:25861866
  title: Estimated carrier frequency of creatine transporter deficiency in females
    in the general population using functional characterization of novel missense
    variants in the SLC6A8 gene.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; functional creatine-uptake characterization of novel SLC6A8 variants (IMP for symporter activity and creatine transport).
- id: PMID:7945388
  title: The cloning and expression of a human creatine transporter.
  findings:
  - statement: >-
      Heterologous expression of the cloned human creatine transporter produces sodium-dependent
      creatine uptake (Km 14.9 uM); mRNA most prominent in skeletal muscle, heart and kidney.
    supporting_text: >-
      Transient expression of the hCRT-BS2M in COS-7 cells demonstrates sodium dependent
      [14C]creatine uptake with a KM value of 14.9 +/- 3.0 microM
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; original cloning and IDA of sodium-dependent creatine uptake.
- id: PMID:7953292
  title: Cloning, pharmacological characterization, and genomic localization of the
    human creatine transporter.
  findings:
  - statement: >-
      The cloned human creatine transporter mediates high-affinity creatine uptake (Km 77 uM)
      with no choline transport; highest mRNA in skeletal muscle, kidney and heart; gene maps
      to Xq28.
    supporting_text: >-
      mediated high affinity (Km = 77 +/- 6 microM) creatine uptake, which was blocked by
      creatine analogs with high affinity. There was no specific transport of choline
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; original cloning, IDA of creatine uptake, substrate specificity, tissue expression.
- id: PMID:8661037
  title: Identification of a testis-expressed creatine transporter gene at 16p11.2
    and confirmation of the X-linked locus to Xq28.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified; cited for NAS creatine transporter activity/transport; distinguishes the X-linked SLC6A8 locus (Xq28) from the testis CT2 gene.
- id: PMID:8661155
  title: The genomic organization of a human creatine transporter (CRTR) gene located
    in Xq28.
  findings: []
  reference_review:
    relevance: LOW
    correctness: MISCITED
    review_notes: >-
      PubMed-verified as a genomic-organization paper; cited as TAS for muscle contraction
      (GO:0006936), which it does not directly establish. The muscle-contraction link is an
      indirect physiological inference, kept as non-core.
- id: PMID:9882430
  title: Molecular characterization of the human CRT-1 creatine transporter expressed
    in Xenopus oocytes.
  findings:
  - statement: >-
      The human heart CRT-1 cDNA expressed in Xenopus oocytes induces Na+- and Cl--dependent
      creatine uptake (Km ~20 uM); Km(Na+) 59 mM, Km(Cl-) 5 mM.
    supporting_text: >-
      induced a Na+- and Cl--dependent creatine uptake activity that saturated with a Km of
      approximately 20 microM for creatine
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; IDA of Na+/Cl--dependent creatine symport with kinetic parameters.
- id: Reactome:R-HSA-200396
  title: Creatine transport across the plasma membrane
  findings: []
- id: Reactome:R-HSA-71288
  title: Creatine metabolism
  findings: []