Human, rat and chicken small intestinal Na⁺‐Cl⁻‐creatine transporter: functional, molecular characterization and localization

Abstract

In spite of all the fascinating properties of oral creatine supplementation, the mechanism(s) mediating its intestinal absorption has(have) not been investigated. The purpose of this study was to characterize intestinal creatine transport. [14C]Creatine uptake was measured in chicken enterocytes and rat ileum, and expression of the creatine transporter CRT was examined in human, rat and chicken small intestine by reverse transcription‐polymerase chain reaction, Northern blot, in situ hybridization, immunoblotting and immunohistochemistry. Results show that enterocytes accumulate creatine against its concentration gradient. This accumulation was electrogenic, Na+‐ and Cl−‐dependent, with a probable stoichiometry of 2 Na+: 1 Cl−: 1 creatine, and inhibited by ouabain and iodoacetic acid. The kinetic study revealed a Km for creatine of 29 μm. [14C]Creatine uptake was efficiently antagonized by non‐labelled creatine, guanidinopropionic acid and cyclocreatine. More distant structural analogues of creatine, such as GABA, choline, glycine, β‐alanine, taurine and betaine, had no effect on intestinal creatine uptake, indicating a high substrate specificity of the creatine transporter. Consistent with these functional data, messenger RNA for CRT was detected only in the cells lining the intestinal villus. The sequences of partial clones, and of the full‐length cDNA clone, isolated from human and rat small intestine were identical to previously cloned CRT cDNAs. Immunological analysis revealed that CRT protein was mainly associated with the apical membrane of the enterocytes. This study reports for the first time that mammalian and avian enterocytes express CRT along the villus, where it mediates high‐affinity, Na+‐ and Cl−‐dependent, apical creatine uptake.

Kinetics of creatine ingested as a food ingredient

“…Once in the small intestine, creatine is taken up by an active, saturable end electrogenic Na + :Cl -cotransporter located at the brush-border membrane (Peral et al 2002). This protein is a member of the superfamily of Na + :Cl -dependent transporters responsible for the uptake of certain amino acids (e.g., glycine and proline) and other molecules like dopamine, GABA, serotonin, taurine and betaine (Guimbal and Kilimann 1994;Nelson and Lill 1994).…”

“…This protein is a member of the superfamily of Na + :Cl -dependent transporters responsible for the uptake of certain amino acids (e.g., glycine and proline) and other molecules like dopamine, GABA, serotonin, taurine and betaine (Guimbal and Kilimann 1994;Nelson and Lill 1994). Experiments using these substances revealed a high specificity of the creatine transporter (K m = 29 lM; Peral et al 2002). The fact that the kinetics of plasma creatine corresponds to a first-order model suggests that the transporter is not saturated by a single dose of 2 g creatine.…”

“…The velocity constant of creatine absorption was slower when incorporated in a PP-rich bar (4.58 ± 7.050 h -1 ) as compared to AS form (23.63 ± 6.655 h -1 , P \ 0.01). Due to the high specificity of the creatine transporter in the small intestine (Peral et al 2002), the slower rate of absorption cannot be explained by a competition with amino acids. The presence of a bolus in the gastrointestinal tract diminishes the rate of absorption of drugs (Welling 1977).…”

Clostridium difficile heterogeneously impacts intestinal community architecture but drives stable metabolome responses

“…They include (i) two fatty acids, 22 lipids (including gluco-, glycero-and glycerophospho-lipids) and 10 bile acid derivatives, low levels of which have been reported to promote cell lipotoxicity and apoptosis and have an overall cathartic effect on the colon (Yoon et al, 2002;Senkal et al, 2011;Swann et al, 2011;Longato et al, 2012); (ii) five N-acyl amino acids or polyamides (including arachidoyl glycine, N-stearoyl proline, N-oleoyl (iso)leucine, N-stearoyl tyrosine and N-palmitoyl threonine), the absence of which promotes dysfunction in the regulation of host temperature, locomotion and inflammation (Tan et al, 2010); (iii) ferroxamine and five metabolites implicated in porphyrin and iron metabolism, the deficiency of which decreases the concentration of beneficial gut microbiota and induces iron deficiency anaemia (Dostal et al, 2014); (iv) 12 presumptive secondary metabolites and bioactive peptides, such as methionine enkephalin and a number of tripeptides, the metabolism failure of which has been shown to lead to failure in immune and neuroactive ligand-receptor interactions (Yoshimasa et al, 1982;Salzet and Tasiemski, 2001); (v) inosine, pseudouridine and hypoxanthine, nucleoside and purine derivatives, the depletion of which may negatively influence the initiation of translation and nucleic acid synthesis in human gut microbiota and in gut mucosal defence (Grimble, 1994); and (vi) six ceramide/sphingolipid derivatives, creatinine, N-acetylhistamine, glyoxylate and succinate-ceramide and creatinine deficits in the gut have been associated with liver and renal dysfunctions (Peral et al, 2002; Longato et al, . Notably, the production of the above metabolites was observed in patients carrying toxin + C. difficile strains (Supplementary Table 2).…”

Substituted Cysteine Accessibility of the Third Transmembrane Domain of the Creatine Transporter

“…The SLC6 family includes solute transporters for dopamine, serotonin, glycine, taurine, proline, betaine, a system B 0ϩ cationic and neutral amino acid transporter (11), and a system B 0 neutral amino acid transporter mutated in Hartnup disorder (12,13). The Na ϩ -and Cl Ϫ -dependent creatine transporter (SLC6A8) has been shown recently to be responsible for the absorption of creatine by intestinal epithelia (14) and transport of creatine across the blood-brain and blood-retina barriers (15,16). Mutations in the SLC6A8 gene result in the absence of creatine in the brain and a novel form of X-linked mental retardation.…”