Table 1.

Origins and influences of butyrate, hypoxanthine, and creatine on gut energy metabolism and barrier function

Metabolite	Primary Source	Energetic Role	Barrier Contribution
Butyrate	Eubacterium rectale Eubacterium hallii Faecalibacterium prausnitzii Roseburia inulinivorans Roseburia intestinalis Anaerostipes hadrus Coprococcus eutactus Coprococcus catus Subdoligranulum variabile89	β-oxidation of fatty acid for mitochondrial-driven ATP regeneration.107 Mitochondrial oxygen consumption-induced HIF stabilization increases glycolysis-driven ATP regeneration.118,122–128	ATP regeneration107 Induction of cytoskeletal binding proteins111 Induction of TJ proteins106,112,115 Induction of MUC2128,129 Induction of creatine kinases132
Hypoxanthine	Associates with Barnesiella and Prevotella,130 TBD*	ATP and GTP generation.43,44 Microbial substrate,131 TBD*	Cytoskeletal ATP43 AJC formation and stability43 Mucin generation and mucus barrier sterile integrity44
Creatine	Diet and Endogenous Biosynthesis	Temporal and spatial ATP buffer. Microbial carbon and nitrogen source.133	ATP buffering/regeneration132,134,135 AJC formation and stability132,134,135

TBD*, to be determined