Evaluation of pentitol metabolism in mammalian tissues provides new insight into disorders of human sugar metabolism.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study using human cell cultures and erythrocytes
PubMed 15234337 · doi:10.1016/j.ymgme.2004.05.003
What was done
Cultured human fibroblasts were incubated with d-arabinose, d-ribose, d-ribulose, or d-xylulose, and the production of arabitol and ribitol was measured in cell homogenates and medium using gas chromatography. Fibroblasts were also incubated with d-arabitol, ribitol, and xylitol to assess pentose formation and pentitol export. Additionally, human erythrocytes were incubated with d-/l-arabitol, ribitol, sorbitol, and xylitol to evaluate pentitol dehydrogenase activities via a fluorometric assay.
What was found
Fibroblasts produced 17 ± 4 nmol arabitol/4 days/mg protein from d-arabinose, 70 ± 15 nmol ribitol/4 days/mg protein from d-ribose, and 13 nmol ribitol/4 days/mg protein from d-ribulose. Incubation of fibroblasts with d-arabitol, ribitol, or xylitol showed no pentose formation, though cell membrane export of arabitol and ribitol was observed. Human erythrocytes showed no detectable ribitol or arabitol degradation, while polyol dehydrogenase activities on sorbitol and xylitol ranged from 1.3 to 6.1 pmol NADH/min/microl erythrocytes.
Why it matters
Demonstrating that ribitol and arabitol are metabolic end products that are cleared without degradation provides baseline biochemical context for interpreting human disorders of pentose and polyol metabolism.
Limits
The study is restricted to in vitro human cell models (fibroblasts and erythrocytes) and did not measure whole-body kinetics or in vivo renal clearance. Donor numbers, sample sizes, replicate counts, and statistical testing are not reported in the abstract.
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