Molecular weight and gut microbiota determine the bioavailability of orally administered hyaluronic acid.

The ability of hyaluronan as a dietary supplement to increase skin moisture and relieve knee pain has been demonstrated in several clinical studies. To understand the mechanism of action, determining hyaluronan's bioavailability and in vivo fate is crucial. Here, we used 13C-hyaluronan combined with LC-MS analysis to compare the absorption and metabolism of oral hyaluronan in germ-free and conventional wild-type mice. The presence of Bacteroides spp. in the gut was crucial for hyaluronan absorption. Specific microorganisms cleave hyaluronan into unsaturated oligosaccharides (<3 kDa) which are partially absorbed through the intestinal wall. The remaining hyaluronan fragments are metabolized into short-chain fatty acids, which are only metabolites available to the host. The poor bioavailability (~0.2 %) of oral hyaluronan indicates that the mechanism of action is the result of the systematic regulatory function of hyaluronan or its metabolites rather than the direct effects of hyaluronan at distal sites of action (skin, joints).

How the molecular weight affects the in vivo fate of exogenous hyaluronan delivered intravenously: A stable-isotope labelling strategy.

There is inconsistent information regarding the size effects of exogenously given hyaluronan on its in vivo fate. The data are often biased by the poor quality of hyaluronan and non-ideal labelling strategies used for resolving exogenous/endogenous hyaluronan, which only monitor the label and not hyaluronan itself. To overcome these drawbacks and establish the pharmacokinetics of intravenous hyaluronan in relation to its Mw, 13C-labelled HA of five Mws from 13.6-1562 kDa was prepared and administered to mice at doses 25-50 mg kg-1. The elimination efficiency increased with decreasing Mw. Low Mw hyaluronan was rapidly eliminated as small hyaluronan fragments in urine, while high Mw hyaluronan exhibited saturable kinetics and complete metabolization within 48 h. All tested Mws exhibited a similar uptake by liver cells and metabolization into activated sugars. 13C-labelling combined with LC-MS provides an excellent approach to elucidating in vivo fate and biological activities of hyaluronan.

LC-MS/MS study of in vivo fate of hyaluronan polymeric micelles carrying doxorubicin.

A better understanding of in vivo behavior of nanocarriers is necessary for further improvement in their development. Here we present a novel approach, where both the matrix and the drug can be analyzed by LCMS/MS after one sample handling. The developed method was applied for the comparison of pharmacokinetic profile of free and encapsulated doxorubicin (DOX) in oleyl hyaluronan (HA-C18:1) polymeric micelles. The results indicated that nanocarriers were rapidly dissociated upon in vivo administration. Despite this fact, the administration of encapsulated DOX led to its longer circulation time and enhanced tumor targeting. This effect was not observed injecting blank HA-C18:1 micelles followed by unencapsulated DOX. Biodistribution studies and molecular weight estimation of the carrier matrix indicated relatively high stability of HA-C18:1 ester bond in bloodstream and complete elimination of the derivative within 72 h. The proposed methodology provides a novel strategy to elucidate the pharmacokinetic behavior of polysaccharide-based drug delivery systems.