Mammary gland differentiation by early life exposure to enantiomers of the soy isoflavone metabolite equol.

The role of soy in reducing breast cancer risk has been suggested to be associated with early exposure to isoflavones, which alter mammary gland morphology. The objective of the study was to determine the effect of dietary exposure to the enantiomers of a key soy isoflavone metabolite, equol, on mammary gland development and later chemoprotection using the DMBA-induced animal model of breast cancer. Animals were exposed to S-(-)equol or R-(+)equol (250 mg/kg diet) during the neonatal (0-21 days) or prepubertal (21-35 days) periods only. Histological evaluation of the mammary glands showed that both enantiomers fed neonatally via the dam led to significant precocial mammary gland differentiation. By day 50, early S-(-)equol or R-(+)equol exposure resulted in a decrease in immature terminal end structures and an increase in mature lobules, suggesting an early 'imprinting' effect. Despite these morphological changes to the mammary gland, neonatal and prepubertal exposure to equol had no long-term chemoprevention against mammary tumors induced by DMBA, although for R-(+)equol there was a trend to delaying tumor formation. In summary, early exposure to equol was not chemopreventive, but neither did it increase tumor formation in response to DMBA, suggesting exposure in early life does not influence breast cancer risk.

Bioavailability of pure isoflavones in healthy humans and analysis of commercial soy isoflavone supplements.

The pharmacokinetic behavior of naturally occurring isoflavones has been determined for the first time in healthy adults. We compared plasma kinetics of pure daidzein, genistein and their beta-glycosides administered as a single-bolus dose to 19 healthy women. This study demonstrates differences in the pharmacokinetics of isoflavone glycosides compared with their respective beta-glycosides. Although all isoflavones are efficiently absorbed from the intestinal tract, there are striking differences in the fate of aglycones and beta-glycosides. Mean time to attain peak plasma concentrations (t(max)) for the aglycones genistein and daidzein was 5.2 and 6.6 h, respectively, whereas for the corresponding beta-glycosides, the t(max) was delayed to 9.3 and 9.0 h, respectively, consistent with the residence time needed for hydrolytic cleavage of the glycoside moiety for bioavailability. The apparent volume of distribution of isoflavones confirms extensive tissue distribution after absorption. Plasma genistein concentrations are consistently higher than daidzein when equal amounts of the two isoflavones are administered, and this is accounted for by the more extensive distribution of daidzein (236 L) compared with genistein (161 L). The systemic bioavailability of genistein [mean AUC = 4.54 microg/(mL x h)] is much greater than that of daidzein [mean AUC = 2.94 microg/(mL x h)], and bioavailability of these isoflavones is greater when ingested as beta-glycosides rather than aglycones as measured from the area under the curve of the plasma appearance and disappearance concentrations. The pharmacokinetics of methoxylated isoflavones show distinct differences depending on the position of the methoxyl group in the molecule. Glycitin, found in two phytoestrogen supplements, underwent hydrolysis of the beta-glycoside moiety and little further biotransformation, leading to high plasma glycitein concentrations. Biochanin A and formononetin, two isoflavones found in one phytoestrogen supplement, were rapidly and efficiently demethylated, resulting in high plasma genistein and daidzein concentrations typically observed after the ingestion of soy-containing foods. These differences in pharmacokinetics and metabolism have implications for clinical studies because it cannot be assumed that all isoflavones are comparable in their pharmacokinetics and bioavailability. An analysis of 33 phytoestrogen supplements and extracts revealed considerable differences in the isoflavone content from that claimed by the manufacturers. Plasma concentrations of isoflavones show marked qualitative and quantitative differences depending on the type of supplement ingested. These studies indicate a need for improvement in quality assurance and standardization of such products.

A randomized double blind-cross over trial of soya protein for the treatment of cyclical breast pain.

Twenty patients with cyclical breast pain were enrolled in a double-blind cross-over trial in which either a soy protein drink or a flavoured cow's milk was taken orally each day for 3 months before crossing over to the alternate drink for a further 3 months. Records of pain scores were taken throughout the study. Blood was also taken before and after 3 and 6 months for the measurement of phytoestrogents to assess compliance. Two women withdrew from the study at the outset leaving 18 evaluable patients who completed the study. Of these 10 (56%) felt that soy protein improved breast pain (two of whom received soy as first treatment) and two (11%) felt that cow's milk alleviated symptoms (one receiving this as first preparation) and the remaining six (33%) experienced no relief of pain with either dietary preparation. Blood levels of diadzein and genistein were elevated after the ingestion of soy protein in only 13 patients (seven of whom felt that soy improved their breast pain); in the remaining five patients (three of whom suggested that soy protein improved breast pain) phytoestrogen levels were no higher than pretreatment values. Although the ingestion of soy protein may be associated with relief of breast pain, these results illustrate the problem of non-specific effects in studies of mastalgia in that 1) cow's milk also relieved breast pain in some patients and 2) that the benefits of soy protein were not always associated with evidence of elevated circulating levels of phyto-estrogens, indicating the difficulty of compliance in dietary intervention studies using soy foods.

Method for measurement of dietary secoisolariciresinol using HPLC with multichannel electrochemical detection.

We describe a sensitive and specific assay for the determination of the plant lignan secoisolariciresinol, one of the main dietary precursors to the mammalian derived lignans, enterodiol and enterolactone. Quantification of secoisolariciresinol aglycone is achieved by reversephase high-performance liquid chromatography with multichannel electrochemical detection after hydrolysis of the glycoside moieties. This approach affords greater specificity than conventional ultraviolet detection and has a detection limit of 2.8 pmol. The method is ideally suited to the determination of secoisolariciresinol in processed flaxseed samples and can be used to assess the level of incorporation of flaxseed in fortified foods.

Isoflavone content of infant formulas and the metabolic fate of these phytoestrogens in early life.

Soy-based infant formulas have been in use for >30 y. These formulas are manufactured from soy protein isolates and contain significant amounts of phytoestrogens of the isoflavone class. As determined by HPLC, the isoflavone compositions of commercially available formulas are similar qualitatively and quantitatively and are consistent with the isoflavone composition of soy protein isolates. Genistein, found predominantly in the form of glycosidic conjugates, accounts for >65% of the isoflavones in soy-based formulas. Total isoflavone concentrations of soy-based formulas prepared for infant feeding range from 32 to 47 mg/L, whereas isoflavone concentrations in human breast milk are only 5.6 +/- 4.4 microg/L (mean +/- SD, n = 9). Infants fed soy-based formulas are therefore exposed to 22-45 mg isoflavones/d (6-11 mg x kg body wt(-1) x d(-1)), whereas the intake of these phytoestrogens from human milk is negligible (<0.01 mg/d). The metabolic fate of isoflavones from soy-based infant formula is described. Plasma isoflavone concentrations reported previously for 4-mo-old infants fed soy-based formula were 654-1775 microg/L (mean: 979.7 microg/L: Lancet 1997:350;23-7), significantly higher than plasma concentrations of infants fed either cow-milk formula (mean +/- SD: 9.4 +/- 1.2 microg/L) or human breast milk (4.7 +/- 1.3 microg/L). The high steady state plasma concentration of isoflavones in infants fed soy-based formula is explained by reduced intestinal biotransformation, as evidenced by low or undetectable concentrations of equol and other metabolites, and is maintained by constant daily exposure from frequent feeding. Isoflavones circulate at concentrations that are 13,000-22,000-fold higher than plasma estradiol concentrations in early life. Exposure to these phytoestrogens early in life may have long-term health benefits for hormone-dependent diseases.

Exposure of infants to phyto-oestrogens from soy-based infant formula.

BACKGROUND: The isoflavones genistein, daidzein, and their glycosides, found in high concentrations in soybeans and soy-protein foods, may have beneficial effects in the prevention or treatment of many hormone-dependent diseases. Because these bioactive phyto-oestrogens possess a wide range of hormonal and non-hormonal activities, it has been suggested that adverse effects may occur in infants fed soy-based formulas. METHODS: To evaluate the extent of infant exposure to phyto-oestrogens from soy formula, the isoflavone composition of 25 randomly selected samples from five major brands of commercially available soy-based infant formulas were analysed, and the plasma concentrations of genistein and daidzein, and the intestinally derived metabolite, equol, were compared in 4-month-old infants fed exclusively soy-based infant formula (n = 7), cow-milk formula (n = 7), or human breast-milk (n = 7). FINDINGS: All of the soy formulas contained mainly glycosides of genistein and daidzein, and the total isoflavone content was similar among the five formulas analysed and was related to the proportion of soy isolate used in their manufacture. From the concentrations of isoflavones in these formulas (means 32-47 micrograms/mL), the typical daily volume of milk consumed, and average bodyweight, a 4-month-old infant fed soy formula would be exposed to 28-47 per day, or about 4.5-8.0 mg/kg bodyweight per day, of total isoflavones. Mean (SD) plasma concentrations of genistein and daidzein in the seven infants fed soy-based formulas were 684 (443) ng/mL and 295 (60) ng/mL, respectively, which was significantly greater (p < 0.05) than in the infants fed either cow-milk formulas (3.2 [0.7] and 2.1 [0.3] ng/mL), or human breast-milk (2.8 [0.7] and 1.4 [0.1] ng/mL), and an order of magnitude higher per bodyweight than typical plasma concentrations of adults consuming soy foods. INTERPRETATION: The daily exposure of infants to isoflavones in soy infant-formulas is 6-11 fold higher on a bodyweight basis than the dose that has hormonal effects in adults consuming soy foods. Circulating concentrations of isoflavones in the seven infants fed soy-based formula were 13000-22000 times higher than plasma oestradiol concentrations in early life, and may be sufficient to exert biological effects, whereas the contribution of isoflavones from breast-milk and cow-milk is negligible.

Ursodeoxycholic acid therapy in cystic fibrosis-associated liver disease: a dose-response study.

Previous studies from our groups have demonstrated improvements in biochemical markers of liver function when cystic fibrosis patients with associated liver disease were administered oral ursodeoxycholic acid. The magnitude of the response was somewhat less than that found when comparable doses (10 to 15 mg/kg body wt/day) of ursodeoxycholic acid are given to other liver disease patients; this may be explained by the bile acid malabsorption that is characteristic of the disease. For this reason a dose-response study was carried out in nine cystic fibrosis patients with liver disease to establish whether improved efficacy could be obtained with higher doses. Ursodeoxycholic acid in doses of 5, 10 and 15 mg/kg body wt/day was given orally for consecutive 2-mo periods in a replicated Latin-square design. After this, all patients received 20 mg/kg body wt/day. Liver function, individual serum bile acids and biliary bile acid composition were determined at entry and at the end of each treatment period. Our data demonstrate that the magnitude of the biochemical improvement in serum liver enzymes was significantly greater with higher doses of ursodeoxycholic acid; at 20 mg/kg body wt/day it was similar to that reported for patients with other liver diseases administered lower doses. Biliary ursodeoxycholic acid enrichment increased with increasing doses, attaining 42% +/- 6% of the total biliary bile acids with the highest dose. Fasting serum ursodeoxycholic acid concentrations increased during ursodeoxycholic acid administration but were variable and correlated poorly with the dose of ursodeoxycholic acid administered, whereas no correlation was found between serum ursodeoxycholic acid concentration and the proportion of ursodeoxycholic acid in bile.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral bile acid treatment and the patient with Zellweger syndrome.

The cerebrohepatorenal syndrome of Zellweger is a congenital syndrome of multiple manifestations, including hepatomegaly and liver dysfunction. Treatment is generally of a supportive nature, aimed at improving nutrition and growth, controlling the central nervous system symptoms and limiting progression of liver disease. Because the liver disease in Zellweger syndrome may be attributed to an overproduction and accumulation of cholestanoic acids, exacerbated by diminished primary bile acid synthesis, we hypothesized that primary bile acid administration would be beneficial in improving liver function by a mechanism involving down-regulation in the synthesis of these atypical bile acids. We report here the clinical and biochemical responses to primary bile acid administration in a 2-mo-old boy who was seen with the typical signs of Zellweger syndrome. Liver disease was evident from hepatomegaly and elevated serum liver enzymes and bilirubin. The diagnosis was supported by markedly elevated serum very long chain fatty acids and the bile acids dihydroxycholestanoic acid and trihydroxycholestanoic acid. Confirmation of the lack of peroxisomes was established by electron microscopy. When the patient was 6 mo old, the primary bile acids cholic acid and chenodeoxycholic acid, (100 mg each/day) were administered orally. A significant improvement in biochemical indices of liver function occurred with a normalization of the serum bilirubin and liver enzymes and a histological improvement in the extent of inflammation and bile duct proliferation and disappearance of cannalicular plugs. Serum and urinary cholestanoic acids showed a significant decrease within a few days. A striking and sustained increase in growth was observed after therapy, and an improvement in neurological symptoms was noted. In conclusion, this study indicates that primary bile acid therapy improves liver function and growth in the patient with peroxisomal dysfunction and should be considered in the supportive therapies for this condition.

Identification of 3 alpha,4 beta,7 alpha-trihydroxy-5 beta-cholanoic acid in human bile: reflection of a new pathway in bile acid metabolism in humans.

The chemical synthesis, nuclear magnetic resonance, and mass spectrometric characteristics of the first C-4 hydroxylated bile acid analogues are described. The data definitively confirm, for the first time, the identity of 3 alpha,4 beta,7 alpha-trihydroxy-5 beta-cholanoic acid in human fetal gallbladder bile. In addition, 3 alpha,4 beta,7 alpha-12 alpha-tetrahydroxy-5 beta-cholanoic was identified in the feces from healthy newborn infants many days after birth, indicating a hepatic origin for C-4 hydroxylation of bile acids. To our knowledge bile acids hydroxylated at the C-4 position of the steroid nucleus have never been previously recognized in any mammalian species. The finding of this novel bile acid which accounts for 5-15% of the total biliary bile acids in early gestation indicates that C-4 hydroxylation is a unique and important metabolic pathway in early human development.

Delta 4-3-oxosteroid 5 beta-reductase deficiency described in identical twins with neonatal hepatitis. A new inborn error in bile acid synthesis.

A new inborn error in bile acid synthesis, manifest in identical infant twins as severe intrahepatic cholestasis, is described involving the delta 4-3-oxosteroid 5 beta-reductase catalyzed conversion of the key intermediates, 7 alpha-hydroxy-4-cholesten-3-one and 7 alpha,12 alpha-dihydroxy-4-cholesten-3-one for chenodeoxycholic and cholic acid synthesis, to the respective 3 alpha-hydroxy-5 beta (H) products. This defect was detected by fast atom bombardment ionization-mass spectrometry from an elevated excretion and predominance of taurine conjugated unsaturated hydroxy-oxo-bile acids. Gas chromatography-mass spectrometry confirmed these to be 7 alpha-hydroxy-3-oxo-4-cholenoic and 7 alpha,12 alpha-dihydroxy-3-oxo-4-cholenoic acids (75-92% of total). Fasting serum bile acid concentrations were greater than 37 mumol/liter; chenodeoxycholic acid was the major bile acid, but significant amounts of allo(5 alpha-H)-bile acids (approximately 30%) were present. Biliary bile acid concentration was less than 2 mumol/liter and consisted of chenodeoxycholic, allo-chenodeoxycholic, and allo-cholic acids. These biochemical findings, which were identical in both infants, indicate a defect in bile acid synthesis involving the conversion of the delta 4-3-oxo-C27 intermediates into the corresponding 3 alpha-hydroxy-5 beta(H)-structures, a reaction that is catalyzed by a delta 4-3-oxosteroid-5 beta reductase enzyme. This defect resulted in markedly reduced primary bile acid synthesis and concomitant accumulation of delta 4-3-oxo-and allo-bile acids. These findings indicate a pathway in bile acid synthesis whereby side chain oxidation can occur despite incomplete alterations to the steroid nucleus, and lend support for an active delta 4-3-oxosteroid 5 alpha-reductase catalyzing the conversion of the delta 4-3-oxosteroid intermediates to the respective 3 alpha-hydroxy-5 alpha(H)-structures.

Bile acid efflux from suckling rat hepatocytes.

To further assess bile acid transport by the developing rat liver, we compared the rate of efflux of taurocholate from hepatocytes isolated from suckling and mature rat livers. Cell content of taurocholate (nmol/mg cell protein), after preloading with [14C]-radiolabeled plus cold bile acid (5-100 microM) was similar in both groups. Total taurocholate efflux, estimated by the decrease in cell taurocholate content, was unexpectedly greater from suckling rat hepatocytes. There was a higher bile acid efflux rate over time and a lower final cell content. Efflux from suckling rat hepatocytes was increased after preloading in incubation concentrations of taurocholate which were above the physiologic range of portal blood concentrations. Inasmuch as the bile acid binding protein content is known to be reduced in the cytoplasm of developing rat liver, intracellular taurocholate may exist largely as free ligand and thus be more readily diffusable. We speculate that the in vivo correlation of enhanced efflux is back diffusion of bile acid from the cell into the sinusoid. The effect could, in part, account for the known absence of a lobular gradient for bile acid uptake in suckling rats and, therefore, contribute to the inefficient hepatic transport of bile acid observed in developing rat liver.