Res. 45 (II), Nr. 8 (1995)
This excerpt reprinted with permission of publisher
© 1995 Editio Cantor Verlag
Biochemical and Pharmacokinetic
Aspects of Oral Treatment
with Chondroitin Sulfate
A. Conte, N. Volpi, L. Palmieri, I. Bahous, and
Chondroitin sulfate (Condrosulf® ) was
characterized for structure, physicochemical properties
and purity. This glycosaminoglycan has a relative molecular
mass of about 14,000, a sulfate-to-carboxyl ratio of 0,95
due to the high percentage of monosulfated disaccharides
(38% 6-monosulfate and 5 % 4-monosulfate) and a low amount
of disulfated disaccharides (1.1 %) inside the polysaccharide
chains. No other glycosaminoglycans were detected in the
Chondroitin sulfate was labelled by reduction with sodium
3H-borohydride and administered by oral route
in the rat and dog. More than 70% of radioactivity was
absorbed and found in urine and tissues. The plasma radioactivity
was fractionated by size-exclusion chromatography in three
fractions: radioactivity associated with high, intermediate
and low molecular mass compounds. The peak value of the
concentration of high molecular mass radioactivity compounds
in plasma was reached after 1.6 and 2.1 h for the rat
and dog, respectively. After 36 h the high molecular mass
radioactivity compounds were still present in plasma of
dog and rat. After 24 h radioactivity was higher in the
intestine, liver, kidneys, synovial fluid and cartilage
than in other tissues. Condroitin sulfate was orally administered
to man (healthy volunteer) in a single daily dose of 0.8
g and in two daily doses of 0.4 g The results showed that
both forms of administration determined a significant
increase of plasma concentration of chondroitin sulfate
as compared with predose value over a full 24 h period.
Elimination constant values and tmax (of the
first administration in the case of fractionated dose)
were almost the same for the two administrations.
Some biochemical parameters (number of leukocytes, proteins,
sulfated glycosaminoglycans and hyaluronic acid amounts,
and N-acetylglucosaminidase activity) of synovial fluid
were evaluated in controls and treated osteoarthritic
subjects. No variations were observed in the patient who
did not receive chondroitin sulfate. Five days of chondroitin
sulfate administration led to a significant increase of
concentration and molecular mass of hyaluronan and a decrease
of a lysosomal enzyme, N-acetylglucosaminidase. No significant
differences in leukocyte count and protein content were
The therapeutic uses of native glycosaminoglycans
(hyaluronic acid, chondroitin sulfates, dermatan sulfate,
heparan sulfate and heparin) as well of their low molecular
mass derivatives (low molecular mass heparins, dermatan
sulfate and chondroitin sulfate) and mixtures of different
percentage of heteropolysaccharides have markedly increased
with the knowledge of their pharmacological properties
and biological functions [1,2].
An in-depth knowledge of the metabolism of exogenous
glycosaminoglycans, administered both orally and paren-terally,
would be particularly useful in view of their therapeutic
applications. The low degree of sulfation of glycosaminoglycans
allows their administration by both parenteral and oral
routes [3,4,5]. In fact, they maintain their pharmacological
properties when administered orally, unlike highly sulfated
glycosaminoglycans and like heparin that is inactive as
anticoagulant when administered orally  even if several
fragments appear in the plasma . Some evidence of heparin
absorption by the gtomach mucosa was reported in a recent
paper ,describing that the administration of 60 mg/kg
of sodium (or dextran sulfate) induced an anti-thrombotic
rats. Jaques ct al.  report that heparin enters the
body immediately on oral administration (2.4 and 6 min)
and that this drug (or dextran sulfate) is recovered from
the endothelium in large amounts and it is identified
unchanged by electrophoretic technique. This gastric absorption
might have been due to such a high dosage that a fraction
of the drug or several of its active fractions which causes
the antithrombotic effect had permeated.
Chondroitin sulfates are glycosaminoglycans composed
of alternate sequences of differently sulfated residues
of uronic acid (b-D-glucuronic) and a-D-N-acetyl-galactosamine
linked by b(1-> 3) bonds . The regular disaccharide
sequence of chondroitin sulfate A, chondroitin-4-sulfate,
is constituted by [(1->4)-O-(b-D-glucopyranosyluronic
sulfate)]. Chondrotin sulfate C or chondroitin-6-sulfate,
is mainly composed of a disaccharide unit [(1->4)-0-(b-D-
Disaccharides with different number and position of sulfate
groups can be located, in different percentage, inside
the polysaccharide chain, such as the non-sulfated or
disulfated disaccharide in which two sulfate groups can
be O-linked in position 2 of b-D-glucuronic acid and 6
of a-D-N-acetyl--galactosamme (disaccharide D) or in position
4 and 6 of a-D-N-acetylgalactosamine (disaccharide E)
. The hetero-geneity of the primary structure, besides
the physicochemical properties such as the relative molecular
mass and charge density, is responsible for different
and more specialized biological and pharmacological functions
of these glycosaminoglycans .
The synthesis of proteoglycans and hyaluronate has been
clarified whilst their breakdown and the regulation of
their turnover, in normal and pathological conditions
are less known [11,12]. Chondroitin sulfates may be employed
as chondroprotective  drugs with application in the
therapy of tibiofibular osteoarthritis of the knee 
and in the articular cartilage osteoarthritis by intramuscular
and oral route. The oral route for chondroitin sulfates
as chondro-protective drugs is very interesting, because
it allows simplified use, which is more compatible with
long administration periods.
The metabolic fate of orally administered exogenous chondroitin
sulfate with defined structure and physico-chemical properties
was studied in the experimental animal and in man using
non-labelled and radioactive isotope labeled polysaccharide.
Furthermore, we studied the plasma levels of chondroitin
sulfate after repeated oral administration and the modification
of cell number and biochemical parameters in synovial
fluid during treatment.
The therapeutic effects of a high molecular
mass natural compound, like chondroitin sulfate, administered
orally is not surprising since many other natural macromolecules
have pharmacological activity also when administered orally,
e.g. heparan sulfate , dermatan sulfate  and bromeline.
Recently, it has been reported that also collagen type
II orally administered is effective in the treatment of
rheumatoid arthritis .
The presence of exogenous chondroitin sulfate and its
depolymerized derivatives in synovial fluid is very important
to explain anti-inflammatory and chondroprotective effects
of this polysaccharide. In fact, it has been shown that
sulfated and desulfated poly- and oligosaccharides derived
from chondroitin sulfate and hyalorunan degradation have
regulatory effects [41,42,43]. Exogeneous chondroitin
sulfate as well poly- and oligosaccharides may exert anti-
inflammatory action on synovial cells (leukocytes) as
well a regulatory activity on cartilage metabolism.
A number of clinical studies showed that chondroitin
sulfate decreases pain and increases functional parameters
in osteoarthritic patient [13,14,44-46]. Our observation
give a first biochemical basis to the clinical outcomes.
In fact, a few days after administration of exogenous
chondroitin sulfate, some biochemical parameters of synovial
fluid changes indicating that modifications take place
in enzyme release and hyaluronan/glycosaminoglycan synthesis
and/or degradation. Some of these effects may be related
to the chondroprotective activity of exogenous chondroitin
sulfate whereas others, such as the decrease of activity
of lytic enzymes, may be also due to the anti-inflammmatory
properties of this polysaccharide, which has been shown
to modify some leulcocyte functions . In synovial
fluid, like in plasma, fractions with molecular mass higher
than that of administered chondroitin sulfate were found,
probably due to the binding of polysaccharide and its
partially depolymerized derivatives with proteins. In
fact, it has been observed that in plasma chondroitin
sulfate is associated with proteins . To date, we
do not know if the observed quantitative variations of
hyaluronan are due to its increased synthesis or decreased
breakdown. In fact, chondroitin sulfate (and derivatives)
stimulates hyaluronan formation  (besides the synthesis
of proteoglycans and type II collagen ), and it protects
hyaluronan from enzymatic degradation by inhibiting hyaluronidase
activity and breakdown from free radicals.
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