Screening for oestrogenic activity of plant and food extracts using in vitro trout hepatocyte cultures

Effects of phytoestrogens on growth-related and lipogenic genes in rainbow trout (Oncorhynchus mykiss)

This study determined whether estradiol (E2) or the phytoestrogens genistein and daidzein regulate expression of growth-related and lipogenic genes in rainbow trout. Juvenile fish (5 mon, 65.8±1.8 g) received intraperitoneal injections of E2, genistein, or daidzein (5 μg/g body weight) or a higher dose of genistein (50 μg/g body weight). Liver and white muscle were harvested 24h post-injection. In liver, expression of vitellogenin (vtg) and estrogen receptor alpha (era1) increased in all treatments and reflected treatment estrogenicity (E2>genistein (50 μg/g)>genistein (5 μg/g)=daidzein (5 μg/g)). Estradiol and genistein (50 μg/g) reduced components of the growth hormone (GH)/insulin-like growth factor (IGF) axis in liver, including increased expression of IGF binding protein-2b1 (igfbp2b1) and reduced igfbp5b1. In liver E2 and genistein (50 μg/g) affected expression of components of the transforming growth factor beta signaling mechanism, reduced expression of ppar and rxr transcription factors, and increased expression of fatty acid synthesis genes srebp1, acly, fas, scd1, and gpat and lipid binding proteins fabp3 and lpl. In muscle E2 and genistein (50 μg/g) increased era1 and erb1 expression and decreased erb2 expression. Other genes responded to phytoestrogens in a manner that suggested regulation by estrogen receptor-independent mechanisms, including increased ghr2, igfbp2a, igfbp4, and igfbp5b1. Expression of muscle regulatory factors pax7 and myod was increased by E2 and genistein. These data indicate that genistein and daidzein affect expression of genes in rainbow trout that regulate physiological mechanisms central to growth and nutrient retention.

In vitro and in vivo effects of phytoestrogens on protein turnover in rainbow trout (Oncorhynchus mykiss) white muscle

Soybeans and other legumes investigated as fishmeal replacements in aquafeeds contain phytoestrogens capable of binding to and activating estrogen receptors. Estradiol has catabolic effects in salmonid white muscle, partially through increases in protein turnover. The current study determines whether phytoestrogens promote similar effects. In rainbow trout (Oncorhynchus mykiss) primary myocyte cultures, the phytoestrogens genistein, daidzein, glycitein, and R- and S-equol reduced rates of protein synthesis and genistein, the phytoestrogen of greatest abundance in soy, also increased rates of protein degradation. Increased expression of the ubiquitin ligase fbxo32 and autophagy-related genes was observed with high concentrations of genistein (100 μM), and R- and S-equol (100 μM) also up-regulated autophagy-related genes. In contrast, low genistein concentrations in vitro (0.01-0.10 μM) and in vivo (5 μg/g body mass) decreased fbxo32 expression, suggesting a potential metabolic benefit for low levels of genistein exposure. Phytoestrogens reduced cell proliferation, indicating that effects of phytoestrogens extend from metabolic to mitogenic processes. Co-incubation of genistein with the estrogen receptor (ER) antagonist, ICI 182,780, ameliorated effects of genistein on protein degradation, but not protein synthesis or cell proliferation, indicating that effects of genistein are mediated through ER-dependent and ER-independent mechanisms. Collectively, these data warrant additional studies to determine the extent to which dietary phytoestrogens, especially genistein, affect physiological processes that impact growth and nutrient retention.

An evidence-based systematic review of kudzu (Pueraria lobata) by the Natural Standard Research Collaboration

An evidence-based systematic review of kudzu (Pueraria lobata) by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Skeletal muscle cellularity and expression of myogenic regulatory factors and myosin heavy chains in rainbow trout (Oncorhynchus mykiss): effects of changes in dietary plant protein sources and amino acid profiles

The nutritional regulation of skeletal muscle growth is very little documented in fish. The aim of the study presented here was to determine how changes in dietary plant protein sources and amino acid profiles affect the muscle growth processes of fish. Juvenile rainbow trout (Oncorhynchys mykiss) were fed two diets containing fish meal and a mixture of plant protein sources either low (control diet) or rich in soybean meal (diet S). Both diets were supplemented with crystalline indispensable amino acids (IAA) to match the rainbow trout muscle IAA profile. Diet S was also supplemented with glutamic acid, an AA present in high quantities in trout muscle. Rainbow trout fed diets C and S were not significantly different in terms of overall somatic growth or daily nitrogen gain, although their parameters of dietary protein utilisation differed. Distribution of skeletal white muscle fibre diameter and expression of certain selected muscle genes were also affected by dietary changes. In the white muscle, diet S led to a significant decrease (x0.9) in the mean and median diameters of muscle fibres, to a significant decrease (x0.6) in the expression of MyoD and to a significant increase (x1.7) in the expression of fast-MHC, with no significant changes in myogenin expression. There was no change in the expression of the genes analysed in lateral red muscle (MyoD, MyoD2, myogenin and slow-MHC). These results demonstrated that changes occurred in skeletal white muscle cellularity and expression of MyoD and fast-MHC, although overall growth and protein accretion were not modified, when a diet rich in soybean meal and glutamic acid was ingested. Present findings also indicated that the white and red muscles of rainbow trout are differently affected by nutritional changes.

Black Cohosh: Insights into its Mechanism(s) of Action

The Women's Health Initiative found that combination estrogen and progesterone hormone replacement therapy increases breast cancer and cardiovascular disease risk, which compelled many women to seek herbal alternatives such as black cohosh extract (BCE) to relieve their menopausal symptoms. While several clinical trials document the efficacy of BCE in alleviating menopausal symptoms, preclinical studies to determine how BCE works have yielded conflicting results. Part of this is because there is not a universally accepted method to standardize the dose of black cohosh triterpenes, the presumed active ingredients in the extract. Although the mechanism by which BCE relieves symptoms is unknown, several hypotheses have been proposed: it acts 1) as a selective estrogen receptor modulator, 2) through serotonergic pathways, 3) as an antioxidant, or 4) on inflammatory pathways. We found that while the most prominent triterpene in BCE, 23-epi-26-deoxyactein, suppresses cytokine-induced nitric oxide production in brain microglial cells, the whole BCE extract actually enhanced this pathway. A variety of activities have been reported for black cohosh and its compounds, but the absorption and tissue distribution of these compounds is unknown.

Disposition of genistein in rainbow trout (Oncorhynchus mykiss) and siberian sturgeon (Acipenser baeri)

Genistein (G) is a xenoestrogen from soy present in fish diet. In vivo, a 50-fold difference in sensitivity to genistein on vitellogenin (VTG) synthesis was found when comparing trout and sturgeon. This difference was not linked to the estrogen receptor affinity nor to the sensitivity of induction of the VTG pathway. The study was performed to check if differences in the G disposition in the two species could explain their difference of sensitivity to G. A pharmacokinetic analysis of radiolabeled G was performed to determine its bioavailability and metabolism in both species. G was used at levels corresponding to fish farm exposure. G plasma levels after chronic ingestion were found to be 15.6 times higher in sturgeon than in trout. Sturgeon primarily produces sulfate conjugates after G ingestion whereas trout mainly produces glucuronides. Sturgeon was able to excrete orobol glucuronide in bile. An important first pass effect was suggested in both species. No accumulation of G or its metabolites was observed in the two species. Trout muscles accounted only for 0.14 of radioactivity 48 h post-ingestion similarly to sturgeon. Trout viscera accounted for 15% of the radioactivity 48 h post-ingestion. In sturgeon, 48 h post-ingestion, viscera accounted for 21.5% of the radioactivity. These rates decreased rapidly thereafter. The study partly explains the difference in sensitivity to G, previously recorded between the two species. In addition, it shows that human exposure to G through farmed fish consumption is negligible.

Seasonal variation of red clover (Trifolium pratense L., Fabaceae) isoflavones and estrogenic activity

Red clover (Trifolium pratense L., Fabaceae) dietary supplements are currently used to treat menopausal symptoms because of their high content of the mildly estrogenic isoflavones daidzein, genistein, formononetin, and biochanin A. These compounds are estrogenic in vitro and in vivo, but little information exists on the best time to harvest red clover fields to maximize content of the isoflavones and thus make an optimal product. Samples of cultivated red clover above-ground parts and flower heads were collected in parallel over one growing season in northeastern Illinois. Generally, autohydrolytic extracts of above-ground parts contained more isoflavones and had more estrogenic activity in Ishikawa endometrial cells as compared with extracts of flower heads. Daidzein and genistein contents peaked around June to July, while formononetin and biochanin A contents peaked in early September. Flower head and total above-ground parts extracts exhibited differential estrogenic activity in an Ishikawa (endometrial) cell-based alkaline phosphatase induction assay, whereas nondifferential activity was observed for most extracts tested in an MCF-7 (breast) cell proliferation assay when tested at the same final concentrations. Ishikawa assay results could be mapped onto the extracts' content of individual isoflavones, but MCF-7 results did not show such a pattern. These results suggest that significant metabolism of isoflavones may occur in MCF-7 cells but not in Ishikawa cells; therefore, caution is advised in the choice of bioassay used for the biological standardization of botanical dietary supplements.