Intestinal absorption, organ distribution, and urinary excretion of the rare sugar D-psicose.

BACKGROUND: The purpose of this study was to evaluate intestinal absorption, organ distribution, and urinary elimination of the rare sugar D-psicose, a 3-carbon stereoisomer of D-fructose that is currently being investigated and which has been found to be strongly effective against hyperglycemia and hyperlipidemia. METHODS: This study was performed using radioactive D-psicose, which was synthesized enzymatically from radioactive D-allose. Concentrations in whole blood, urine, and organs were measured at different time points until 2 hours after both oral and intravenous administrations and 7 days after a single oral administration (100 mg/kg body weight) to Wistar rats. Autoradiography was also performed by injecting 100 mg/kg body weight of (14)C-labeled D-psicose or glucose intravenously to C3H mice. RESULTS: Following oral administration, D-psicose easily moved to blood. The maximum blood concentration (48.5±15.6 µg/g) was observed at 1 hour. Excretion to urine was 20% within 1 hour and 33% within 2 hours. Accumulation to organs was detected only in the liver. Following intravenous administration, blood concentration was decreased with the half-life=57 minutes, and the excretion to urine was up to almost 50% within 1 hour. Similarly to the results obtained with oral administration, accumulation to organs was detected only in the liver. Seven days after the single-dose oral administration, the remaining amounts in the whole body were less than 1%. Autoradiography of mice showed results similar to those in rats. High signals of (14)C-labeled D-psicose were observed in liver, kidney, and bladder. Interestingly, no accumulation of D-psicose was observed in the brain. CONCLUSION: D-psicose was absorbed well after oral administration and eliminated rapidly after both oral and intravenous administrations, with short duration of action. The study provides valuable pharmacokinetic data for further drug development of D-psicose. Because the findings were mainly based on animal study, it is necessary to implement human trials to study the metabolism pathway, which would give an important guide for human intake and food application of D-psicose.

Preparation of D-gulose from disaccharide lactitol using microbial and chemical methods.

When an M31 strain of Agrobacterium tumefaciens was grown in a mineral salt medium at 30 °C containing 1.0% lactitol as sole carbon source, a keto-sugar was efficiently accumulated in the supernatant. This oxidation from lactitol to the keto-sugar was caused by M31 cells grown with medium containing a disaccharide unit, including sucrose, lactitol, lactose, maltose, or maltitol, suggesting that the enzyme is inducible. M31 also demonstrated good growth characteristics in Tryptic Soy Broth (TSB) medium containing 1.0% sucrose, and cells grown under these conditions showed strong lactitol transformation activity. The keto-sugar product was reduced by chemical hydrogenation and the resulting product was hydrolyzed to D-gulose, D-galactose, and D-sorbitol by acid hydrolysis, revealing that the reduced products are lactitol and D-gulosyl-(ß-1,4)-D-sorbitol. Taken together, these results indicate that M31 can convert lactitol to 3-ketolactitol and thus provide access to the rare sugar D-gulose.