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Biomedical subjects

C Morand

Publications and source records attributed to C Morand.

At least 19 recordsLinked to original sources
PubMed2006

Flavanone metabolism in healthy and tumor-bearing rats.

Flavanones, the main polyphenols of citrus fruits, are thought to contribute to the protective effects of these fruits against cardiovascular diseases and cancer. The metabolism of naringin (naringenin 7-O-neohesperidoside) is studied here in healthy (sham-operated, ShO) and tumor-bearing (TuB) rats. The tumor was induced by implanting Yoshida's sarcoma in hindlimb. Both groups received for 7 days a semi-synthetic diet containing 0.5% naringin in per feeding conditions. Flavanones were analyzed in plasma, liver, kidney and urine by tandem mass spectrometry. Naringenin conjugates (essentially glucuronides) accounted for up to 98% of the total flavanones in plasma. Low amounts of hesperetin (4'-O-methyl naringénine) and isosakuranetin (3'-hydroxy-4'-O-methylnaringenin) were also detected in all biological samples and accounted for 2% of the total flavanones in plasma. They were largely present as aglycones. The in vivo hydroxylation of flavanones is described here for the first time. Total concentrations of naringenin metabolites reached 17.3+/-2.7 microM in plasma 6 hours after the beginning of the meal in healthy rats and only 10.6+/-1.3 microM in TuB rats. The nature of metabolites was similar in both healthy and TuB rats and in plasma, tissues and urine. The lower concentration of flavanones in the TuB rats suggests that disease and more particularly cancer, may affect the bioavailability of flavonoids.

Animals↗
PubMed2006

One-month exposure to soy isoflavones did not induce the ability to produce equol in postmenopausal women.

OBJECTIVE: As more and more postmenopausal women are taking soy isoflavone supplementation for relieving menopausal symptoms, we investigated the impact of chronic exposure on their bioavailability, with focus on achievable plasma concentrations and potential stimulation of the capacity to produce equol. SUBJECTS: A total of 12 Caucasian postmenopausal women. INTERVENTION: Volunteers ingested 100 mg isoflavones/day (aglycone equivalents, in cereal bars and yoghurts) for 1 month. Plasma concentrations of metabolites at 2, 4, 6, 8, 10, 12 and 24 h postdose, as well as urinary excretion in fractions over 36 h were compared between days 1 and 30. RESULTS: Similar plasma kinetic curves were obtained at day 1 and day 30 for genistein and daidzein. Maximum plasma concentrations were 1.68+/-0.68 micromol/l on day 1 compared to 2.27+/-0.76 micromol/l on day 30 for daidzein (P=0.056), and 3.88+/-1.50 micromol/l on day 1 compared to 5.30+/-2.38 micromol/l on day 30 for genistein (P=0.091). Urinary excretion of daidzein and genistein did not differ significantly between days 1 and 30. Maximum plasma concentration of equol increased significantly from 0.31+/-0.27 to 0.99+/-0.51 micromol/l for equol-producer volunteers (P=0.046). However, the seven volunteers who were classified as non-equol producers on day 1 did not acquire the ability to produce equol after 1-month exposure. CONCLUSIONS: Chronic exposure to isoflavones in postmenopausal women resulted in plasma concentrations as high as 2.5-5 micromol/l of each isoflavone, but did not induce the ability to produce equol.

Administration, Oral↗
PubMed2005

The bioavailability of polyphenols is highly governed by the capacity of the intestine and of the liver to secrete conjugated metabolites.

BACKGROUND: After ingestion of a complex meal containing foods and beverages of plant origin, different polyphenols are likely to be simultaneously present in the intestine. However, almost nothing is known about their interactions and possible consequences on their bioavailability. AIM OF THE STUDY: The present study deals with the intestinal absorption and splanchnic metabolism of three polyphenols, genistein, hesperetin and ferulic acid (FA),when perfused in the small intestine alone or in combination, at different doses (15 and 120 microM). METHODS: The fate of polyphenols in the small intestine was studied using a rat in situ intestinal perfusion model. Polyphenols were analysed in perfusate, bile and plasma by HPLC. RESULTS: Whatever the perfused dose, the efficiency of the net transfer towards the enterocyte was similar for the three polyphenols and not significantly modified by any association between these molecules. However, FA largely differed from the two flavonoids by its low intestinal secretion of conjugates. When perfused at 15 microM, the secretion of conjugates back to the lumen represented 6.2% of the net transfer into the enterocytes for FA compared to 25.5 and 20 % for genistein and hesperetin respectively. Intestinal conjugation and secretion of conjugates back to the gut lumen varied with the dose of flavonoids: saturation of conjugation was observed for the highest dose or when a high dose of a second flavonoid was perfused simultaneously. Intensity of the biliary secretion substantially differed among tested polyphenols: 7.7% of the net transfer for FA vs 50% for genistein or hesperetin. The extent of the enterohepatic cycling of these polyphenols was proportional to the perfused dose and unaffected by the simultaneous presence of different compounds in the intestine. CONCLUSION: Genistein and hesperetin appeared less available than FA for peripheral tissues because of a high intestinal and biliary secretion of their conjugates. Moreover, data suggest that a high polyphenol intake may improve their bioavailability due to saturation of the intestinal secretion of conjugates.

Animals↗
PubMed2005

[Low-grade endometrial stromal sarcoma: contribution of hormone therapy and etoposide].

Endometrial stromal sarcoma is a rare malignant uterine tumor. We report 4 cases of low-grade endometrial stromal sarcoma, corresponding to the form with a mitotic index at less than 10 mitoses per 10 high power fields (HPF), from which we carried out a review of the literature and defined the potential interest of hormone therapy and chemotherapy by etoposide. Generally diagnosed in pre-menopause, the main clinical signs, which are not very specific, are metrorrhagia and pelvic pain. The etiologic diagnosis is established from the pathology analysis. Intravascular extension, which is observed in nearly 50% of patients, should evoke the disease. The initial treatment is mainly based open surgery, generally total hysterectomy with annexectomy. There is no effective adjuvant treatment. The potential of reccurences remains around 50% with a 34-month median. Several therapeutic options are possible after recurrence but no standard treatment has been established. We are mainly interested in three medical options but the surgery remains an alternative of choice. Chemotherapy by oral etoposide offers easy administration, good compliance and acceptable toxicity with median 20-month remission in 3 patients before progression. Hormone therapy with progestogens (hormone receptor expression of the tumor is 71% for estrogens and 95% for progesterone) is widely studied in the literature with a 46% response rate and 46% rate of disease stabilization. Hormone therapy with an anti-aromatase appears to be a promising treatment according to the bibliographic references on this subject. Overall, prognosis of low-grade endometrial sarcoma is relatively good with 100% survival at 5 years. The progression pattern is slow, requiring regular and prolonged surveillance.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Bioavailability in humans of the flavanones hesperidin and narirutin after the ingestion of two doses of orange juice.

OBJECTIVE: Flavanones are polyphenols specific of citrus fruits, where they are present in high amounts. Although citrus fruits and juices are widely consumed in the world, little information has been published on flavanone bioavailability in humans. The aim of the present study was to determine the nature of the circulating metabolites, the plasma kinetics and the urinary excretion patterns of the flavanones, hesperidin and narirutin. DESIGN: After an overnight fast, five healthy volunteers ingested 0.5 or 1 l of a commercial orange juice providing 444 mg/l hesperidin and 96.4 mg/l narirutin, together with a polyphenol-free breakfast. Blood was sampled at 10 different timepoints over a 24 h period. Urine was collected for 48 h, in five fractions. RESULTS: Flavanones metabolites appeared in plasma 3 h after the juice ingestion, reached a peak between 5 and 7 h, then returned to baseline at 24 h. The peak plasma concentration of hesperetin was 0.46+/-0.07 micro mol/l and 1.28+/-0.13 micro mol/l after the 0.5 and 1 l intake, respectively. It was lower for naringenin: 0.20+/-0.04 micro mol/l after the 1 l dose. The circulating forms of hesperetin were glucuronides (87%) and sulphoglucuronides (13%). For both flavanones, the urinary excretion was nearly complete 24 h after the orange juice ingestion. The relative urinary excretion was similar for hesperetin and naringenin and did not depend on the dose: values ranged from 4.1+/-1.2 to 7.9+/-1.7% of the intake. CONCLUSIONS: In case of a moderate or high consumption of orange juice, flavanones may represent an important part of the pool of total polyphenols present in plasma.

Adult↗
PubMed2001

Bioavailability of phloretin and phloridzin in rats.

Phloretin is a flavonoid found exclusively in apples and in apple-derived products where it is present as the glucosidic form, namely, phloridzin (phloretin 2'-O-glucose). In the present study, we compared the changes in plasma and urine concentrations of these two compounds in rats fed a single meal containing 0.25% phloridzin or 0.157% phloretin (corresponding to the ingestion of 22 mg of phloretin equivalents). In plasma, phloretin was recovered mainly as the conjugated forms (glucuronided and/or sulfated) but some unconjugated phloretin was also detected. By contrast, no trace of intact phloridzin was detected in plasma of rats fed a phloridzin meal. These compounds presented different kinetics of absorption; phloretin appeared more rapidly in plasma when rats were fed the aglycone than when fed the glucoside. However, whatever compound was administered, no significant difference in the plasma concentrations of total phloretin were observed 10 h after food intake. At 24 h after the beginning of the meal, the plasma concentrations of phloretin were almost back to the baseline, indicating that this compound was excreted rapidly in urine. The total urinary excretion rate of phloretin was not affected by the forms administered, and was estimated to be 8.5 micromol/24 h in rats fed phloretin or phloridzin. Thus, 10.4% of the ingested dose was recovered in urine after 24 h.

Absorption↗
PubMed2001

Catechin is metabolized by both the small intestine and liver of rats.

Flavan-3-ols are the most abundant flavonoids in the human diet, but little is known about their absorption and metabolism. In this study, the absorption and metabolism of the monomeric flavan-3-ol, catechin, was investigated after the in situ perfusion of the jejunum + ileum in rats. Five concentrations of catechin were studied, ranging from 1 to 100 micromol/L. The absorption of catechin was directly proportional to the concentration, and 35 +/- 2% of the perfused catechin was absorbed during the 30-min period. Effluent samples contained only native catechin, indicating that intestinal excretion of metabolites is not a mechanism of catechin elimination. Catechin was absorbed into intestinal cells and metabolized extensively because no native catechin could be detected in plasma from the mesenteric vein. Mesenteric plasma contained glucuronide conjugates of catechin and 3'-O-methyl catechin (3'OMC), indicating the intestinal origin of these conjugates. Additional methylation and sulfation occurred in the liver, and glucuronide + sulfate conjugates of 3'OMC were excreted extensively in bile. Circulating forms were mainly glucuronide conjugates of catechin and 3'OMC. The data further demonstrate the role of the rat small intestine in the glucuronidation and methylation of flavonoids as well as the role of the liver in sulfation, methylation and biliary excretion.

Animals↗
PubMed2001

Comparison of the intestinal absorption of quercetin, phloretin and their glucosides in rats.

Absorption and metabolism of quercetin and isoquercitrin (quercetin 3-O-glucose) were investigated in rats after in situ perfusion of jejunum plus ileum (15 nmol/min) for 30 min and compared with those of phloretin and phloridzin (phloretin 2'-O-glucose). After perfusion of the glucosides, the corresponding aglycone forms and conjugated derivatives appeared in the lumen. The conjugated metabolites were similar to those recovered after intestinal perfusion of the aglycone forms. Regardless of the aglycone or glucoside perfused, only conjugated forms were present in the mesenteric vein blood draining the perfused segment showing the importance of intestinal conjugation. The hydrolysis of glucosides was a prerequisite step before their conjugation by intestinal enzymes and their transport towards the mucosal and serosal sides. In contrast to phloridzin, lactase phloridzin hydrolase activity did not seem to be an essential pathway for isoquercitrin hydrolysis. The 3-O-glucosylation of quercetin improved the net absorption of the aglycone (P < 0.05), whereas phloretin absorption decreased when present as 2'-O-glucoside (P < 0.05). Whatever the perfused compound, the efficiency of the absorption seemed to be linked to the intestinal conjugation process and to the luminal secretion of metabolites.

Animals↗
PubMed2000

Respective bioavailability of quercetin aglycone and its glycosides in a rat model.

A large number of flavonoids, mostly O-glycosides, are found in foods of plant origin. The bound sugar moiety is known to influence their bioavailability. We examined here the effect of the nature of the sugar on the absorption of the glycosides. Four groups of rats (n = 6) received a meal containing 20 mg of quercetin equivalents supplied as aglycone, quercetin 3-glucoside, quercetin 3-rhamnoside or rutin. Plasma were hydrolysed by a beta-glucuronidase/sulfatase and analyzed by HPLC coupled to UV detection at 370 nm. Four hours after the beginning of the meal, the quercetin metabolites present in plasma were identical in all groups but their total concentrations were quite different. With pure quercetin the circulating levels were 1.7 +/- 1.8 microM, but this level was three fold higher when quercetin was supplied as quercetin 3-glucoside (33.2 +/- 3.5 microM). By contrast, the plasma concentrations of quercetin metabolites was quite low with the rutin meal (about 3 microM) and undetectable after the quercetin 3-rhamnoside meal. These data suggest that the 3-O-glucosylation improves the absorption of quercetin in the small intestine, whereas the binding of a rhamnose or of a glucose-rhamnose moiety to the aglycone markedly depressed its absorption. Additionnal experiments have shown that the higher plasma levels measured after the meal containing quercetin 3-glucoside compared to quercetin were maintained throughout a 24 hour period following the meal. In conclusion, the nature of the glycosylation markedly influences the efficiency of quercetin absorption in rats. Quercetin 3-glucose can be absorbed in the small intestine and is better absorbed than quercetin itself. By contrast, glycosides containing a rhamnose moiety could not be absorbed in the small intestine.

Animals↗
PubMed2000

Cholesterol-lowering effects of guar gum: changes in bile acid pools and intestinal reabsorption.

Soluble fibers such as guar gum (GG) may exert cholesterol-lowering effects. It is generally accepted that bile acid (BA) reabsorption in portal blood is reduced, thus limiting the capacity of BA to down-regulate liver cholesterol 7alpha-hydroxylase, the rate-limiting enzyme of BA synthesis. In the present work, rats were adapted to fiber-free (FF) or 5% GG diets (supplemented or not with 0.25% cholesterol), to investigate various aspects of enterohepatic BA cycling. GG in the diet at a level of 5% elicited a significant lowering of plasma cholesterol during the absorptive period, in cholesterol-free (-13%) or 0.25% cholesterol (-20%) diet conditions. In rats adapted to the GG diets, the small intestinal and cecal BA pools and the ileal vein-artery difference for BA were markedly enhanced; reabsorption in the cecal vein was also enhanced in these rats. [14C]Taurocholate absorption, determined in perfused ileal segments, was not significantly different in rats adapted to the FF or GG diet, suggesting that a greater flux of BA in the ileum might support a greater ileal BA reabsorption in rats adapted to the GG diet. In contrast, capacities for [14C]cholate absorption from the cecum at pH 6.5 were higher in rats adapted to the GG diet than to the FF diet. Acidification of the bulk medium in isolated cecum (from pH 7.1 down to pH 6.5 or 5.8) or addition of 100 mM volatile fatty acids was also found to stimulate cecal [14C]cholate absorption. These factors could contribute to accelerated cecal BA absorption in rats fed the GG diet. The effects of GG on steroid fecal excretion thus appear to accompany a greater intestinal BA absorption and portal flux to the liver. These results suggest that some mechanisms invoked to explain cholesterol-lowering effect of fibers should be reconsidered.

Animals↗
PubMed2000

Quercetin 3-O-beta-glucoside is better absorbed than other quercetin forms and is not present in rat plasma.

The effect of the nature of the sugar moiety on quercetin absorption has been investigated in rats. Four groups of rats received an experimental meal containing 20 mg of quercetin equivalents, supplied as quercetin, quercetin 3-O-beta-glucoside, quercetin 3-O-beta-rhamnoside or rutin. Four hours after the meal, the metabolites identified in hydrolysed plasma were identical in all groups (3'- and 4'-methylquercetin). However, the total concentration of metabolites was markedly different: 11.2+/-1.8, 2.5+/-2.0 and 33.2+/-3.5 microM for the quercetin, rutin, and quercetin 3-glucoside meals respectively. After quercetin 3-rhamnoside consumption, we failed to detect any metabolites in the plasma. These data suggest that the 3-O-glucosylation improves the absorption of quercetin in the small intestine, whereas the binding of a rhamnose to the aglycone markedly depresses it. Additional experiments have shown that the higher plasma levels measured after quercetin 3-glucoside meal compared to the quercetin meal were maintained throughout the 24-hour period following the meal. Using a multi-electrode coulometric detection, together with suitable chromatographic conditions, we were able to distinguish between the conjugated and the glycosylated forms. Thus, we clearly showed the absence of quercetin 3-O-beta-glucoside in the plasma from rats fed a diet containing this glucoside. This result suggests that quercetin 3-O-beta-glucoside is hydrolysed before or during its intestinal absorption.

Animals↗
PubMed2000

Bioavailability of the flavanone naringenin and its glycosides in rats.

Naringenin, the predominant flavanone in grapefruit, mainly occurs as glycosides such as naringenin-7- rhamnoglucoside or naringenin-7-glucoside. This study compared kinetics of absorption of naringenin and its glycosides in rats either after a single flavanone-containing meal or after adaptation to a diet for 14 days. Regardless of the diet, circulating metabolites were glucurono- and sulfoconjugated derivatives of naringenin. The kinetics of absorption of naringenin and naringenin-7-glucoside were similar, whereas naringenin-7-rhamnoglucoside exhibited a delay in its intestinal absorption, resulting in decreased bioavailability. After naringenin-7-glucoside feeding, no glucoside was found in the cecum. However, after feeding naringenin-7-rhamnoglucoside, some naringenin-7-rhamnoglucoside accumulated in cecum before being hydrolyzed by intestinal microflora. Adaptation to flavanone diets did not induce accumulation of plasma naringenin. Moreover, flavanone cecal content markedly decreased after adaptation, and almost no naringenin-7-rhamnoglucoside was recovered after naringenin-7-rhamnoglucoside feeding, suggesting that an adaptation of cecal microflora had occurred. Overall, these data indicate that flavanones are efficiently absorbed after feeding to rats and that their bioavailability is related to their glycosidic moiety.

Absorption↗
PubMed1999

Comparison of the bioavailability of quercetin and catechin in rats.

Quercetin and catechin are present in noticeable amounts in human diet and these polyphenolic compounds are supposed to exert beneficial effects on human health. However, their metabolic fates in the organism have never been compared. In the present study, rats were fed a 0.25% quercetin or a 0.25% catechin diet. Quercetin and catechin metabolites were analyzed in plasma and liver samples by high-performance liquid chromatography coupled to an ultraviolet or a multielectrode coulometric detection. All plasma metabolites were present as conjugated forms, but catechin metabolites were mainly constituted by glucuronidated derivatives, whereas quercetin metabolites were sulfo- and glucurono-sulfo conjugates. Quercetin was more intensively methylated than catechin in plasma. The plasma quercetin metabolites are well maintained during the postabsorptive period (approximately 50 microM), whereas the concentration of catechin metabolites dropped dramatically between 12- and 24-h after an experimental meal (from 38.0 to 4.5 microM). In the liver, the concentrations of quercetin and catechin derivatives were lower than in plasma, and no accumulation was observed when the rats were adapted for 14 d to the supplemented diets. The hepatic metabolites were intensively methylated (90-95%), but in contrast to plasma, some free aglycones could be detected. Thus, it clearly appears that studies dealing with the biological impact of these polyphenols should take into account the feature of their bioavailability, particularly the fact that their circulating metabolites are conjugated derivatives.

Animals↗
PubMed1999

Part of quercetin absorbed in the small intestine is conjugated and further secreted in the intestinal lumen.

Rutin and quercetin absorption and metabolism were investigated in rats after in situ perfusion of jejunum plus ileum (15 nmol/min). In contrast to rutin, a high proportion of quercetin (two-thirds) disappeared during perfusion, reflecting extensive transfer into the intestinal wall. Net quercetin absorption was not complete (2.1 nmol/min), inasmuch as 52% were reexcreted in the lumen as conjugated derivatives (7.7 nmol/min). Enterohepatic recycling contribution of flavonoids was excluded by catheterization of the biliary duct before perfusion. After a 30-min perfusion period, 0.71 microM of quercetin equivalents were detected in plasma, reflecting a significant absorption from the small intestine. The differential hydrolysis of effluent samples by glucuronidase and/or sulfatase indicates that the conjugated forms released in the lumen were 1) glucuronidated derivatives of quercetin and of its methoxylated forms (64%) and 2) sulfated form of quercetin (36%). In vitro quercetin glucuronides synthetized using jejunal and ileal microsomal fractions were similar to those recovered in the effluent of perfusion. These data suggest that glucuronidation and sulfatation take place in intestinal cells, whereas no glucurono-sulfoconjugates could be detected in the effluent. The present work shows that a rapid quercetin absorption in the small intestine is very effective together with its active conjugation in intestinal cells.

Animals↗
PubMed1998

Quercetin is recovered in human plasma as conjugated derivatives which retain antioxidant properties.

Quercetin is one of the most abundant flavonoids in the human diet. This study aimed to determine the plasma concentrations of quercetin in 10 healthy volunteers after the consumption of a complex meal rich in plant products. Quercetin was determined in plasma (2 h before, and 3, 7 and 20 h after the meal), and in a duplicated portion of the meal by HPLC analysis with an electrochemical detection. The amount of ingested quercetin was estimated to be 87 mg. Before the meal, quercetin concentration in hydrolyzed plasmas ranged from 28 to 142 nM. A marked increase was observed 3 h after the meal in all subjects, with a mean concentration of 373 nM (S.E.M. = 61). After 7 h, quercetin concentration in hydrolyzed plasmas decreased and after 20 h basal levels were found again. The antioxidant capacities of quercetin, 3'-O-methylquercetin, and of some of their conjugated derivatives were compared by the measurement of the conjugated dienes resulting from the Cu2+-induced oxidation of human LDL. 3'-O-Methylquercetin and conjugated derivatives of quercetin significantly prolonged the lag phase, but the magnitude of their effect was about half that of the aglycone.

Administration, Oral↗