Dietary Soybean Isoflavones Research Articles

Soy Isoflavones Inhibit Endothelial Cell Dysfunction and Prevent Cardiovascular Disease.

Soybeans are among the most popular foods worldwide, and intake of soy-containing foods has been associated with many health benefits in part because of it structure similar to estrogen. Epidemiologic studies have demonstrated that soy consumption improves serum profiles of hypercholesterolemic patients. Several studies have also indicated an inverse relationship between the consumption of soy isoflavones and the incidence of cardiovascular diseases (CVD). Soy is a rich dietary source of isoflavones. The main soy isoflavones are daidzein and genistein; equol, another isoflavone and a major intestinal bacterial metabolite of daidzein, is generated by enterobacterial effects. Many isoflavones have antioxidative effects and anti-inflammatory actions, as well as induce nitric oxide production to maintain a healthy endothelium and prevent endothelial cell dysfunction. These effects may limit the development of atherosclerosis and CVD and restore healthy endothelial function in altered endothelia. Although the evidence supporting the benefits of soy isoflavones in CVD prevention continues to increase, the association between soy isoflavones and disease is not fully understood. This review summarized recent progress in identifying the preventive mechanisms of action of dietary soybean isoflavones on vascular endothelial cells. Furthermore, it describes the beneficial roles that these isoflavones may have on endothelial dysfunction-related atherosclerosis.

Remission Effects of Dietary Soybean Isoflavones on DSS-Induced Murine Colitis and an LPS-Activated Macrophage Cell Line.

Inflammatory bowel diseases (IBDs), including ulcerative colitis and Crohn’s disease, are chronic disorders of the gastrointestinal tract, although the exact causes of IBD remain unknown. Present treatments for IBDs have poor tolerability and insufficient therapeutic efficacy, thus, alternative therapeutic approaches are required. Soybean-derived isoflavones have multiple bioactivities such as anti-inflammation. However, the low water solubility of soybean isoflavones limits their bioavailability and practical use. Therefore, in order to study the preventive effects of water-soluble soybean isoflavones on colonic inflammatory status, we examined soybean-derived isoflavone glycosides (SIFs) in a dextran sodium sulfate (DSS)-induced murine colitis model and in lipopolysaccharide (LPS)-activated RAW264.7 macrophages. Oral administration of SIF (0.5 w/v%) attenuated DSS-induced colitis in terms of body weight decrease, colon shortening, epithelial apoptosis, histological score, mRNA levels of inflammatory cytokines, and immune cell infiltration in colon tissues. In the in vitro assessment, we observed the inhibitory effects of SIF on the production of nitric oxide and prostaglandin E2, via suppression of inducible nitric oxide synthase and cyclooxygenase-2 expression in RAW264.7 macrophages in response to LPS. Furthermore, we confirmed that the expression of inflammatory cytokines and chemokines were decreased by pre-treatment with SIF in LPS-activated RAW264.7 macrophages. Moreover, we demonstrated that SIF suppressed inflammatory mediators involved in nuclear factor-κB signaling pathway via inhibitory κB kinase phosphorylation and degradation of inhibitory κB. Our results suggested that SIF may be beneficial for the remission of colonic inflammatory status including IBDs.

Effects of dietary soybean isoflavones (SI) on reproduction in the young breeder rooster

Soybean isoflavones (SIs) are phytoestrogens that competitive with estrogens in body. Although SIs play an important role in reproduction, their role in testicular development in roosters is unknown. This study was conducted to investigate the effect of SIs on testicular development and serum reproductive hormone profiles in young breeder roosters (70–133days old). Gene expression of steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450scc), and 3β-hydroxysteroid dehydrogenase (3β-HSD), which are related to testosterone synthesis, in rooster testis were also evaluated after treatment with different SI doses. Although SIs had no significant effect on body weight, 5mg/kg SIs significantly increased the testis index and serum levels of reproductive hormones (gonadotropin releasing hormone, follicle- stimulating hormone, luteinizing hormone, and testosterone).To further investigate whether SIs regulate hormone synthesis via StAR, p450scc, 3β-HSD, real time-PCR was performed to measure the mRNA levels of the corresponding genes. The results showed that 5mg/kg of SIs significantly increased StAR mRNA levels. However, there were no significant effects on p450scc or 3β-HSD mRNA levels. Moreover, the spermatogonial development and the number of germ cell layers were increased by treatment with 5mg/kg of SIs. These results suggest that SIs promote testicular growth by increasing reproductive hormone secretion, which is closely related to StAR expression, to positively regulate reproduction in young roosters.

Effects of dietary soybean isoflavones on non-specific immune responses and hepatic antioxidant abilities and mRNA expression of two heat shock proteins (HSPs) in juvenile golden pompano Trachinotus ovatus under pH stress.

This study determined the effect of dietary soybean isoflavones on non-specific immunity and on mRNA expression of two HSPs in juvenile golden pompano Trachinotus ovatus under pH stress. Six diets were formulated to contain 0, 10, 20, 40, 60 and 80 mg/kg of soybean isoflavones. Each diet was fed to triplicate groups of fish in cylindrical tanks. After 56 days of feeding, 15 fish per tank were exposed to pH stress (pH ≈ 9.2) for 24 h. Serum total protein (TP), respiratory burst activity (RBA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), lysozyme (LYZ), complement 3 (C3), complement 4 (C4), cortisol, hepatic total antioxidant capacity (T-AOC), superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT) and the relative mRNA expression of heat shock protein 70 (HSP70) and 90 (HSP90) were investigated. The results showed that after pH stress, serum TP, RBA, LYZ, C4, hepatic T-AOC and CAT levels were significantly reduced (P < 0.05) while serum ALT, hepatic MDA and HSP70 and HSP90 mRNA expression levels were significantly increased (P < 0.05). On the other hand, supplementation with soybean isoflavones significantly reduced levels of serum ALT (20, 40, 60 mg/kg soybean isoflavones groups) and hepatic MDA (40, 60 and 80 mg/kg soybean isoflavones groups). Supplemented groups had increased serum TP content (40 mg/kg soybean isoflavones groups), RBA (20 and 40 mg/kg soybean isoflavones groups), LYZ (40 and 60 mg/kg soybean isoflavones groups), C3(20, 40, 60 and 80 mg/kg soybean isoflavones groups), hepatic SOD activity (40, 60 and 80 mg/kg soybean isoflavones groups) as well as increased relative mRNA expression of hepatic HSP70 (40, 60 and 80 mg/kg soybean isoflavones groups) and HSP90 (40 and 60 mg/kg soybean isoflavones groups) (P < 0.05). These results indicate that ingestion of a basal diet supplemented with 40-60 mg/kg soybean isoflavones could enhance resistance against pH stress in T. Ovatus to some degree.

Enhanced Estrogenic Activity of Soybean Isoflavones by Coadministration of Liuwei Dihuang Pills in Ovariectomized Rats.

Soybean isoflavones are beneficial for treating hormone-related diseases. Simultaneous consumption of soybean isoflavones and Liuwei Dihuang pills (LWPs) is effective for treating perimenopausal period syndrome. However, why the combination of isoflavones and LWPs is more effective than ingestion of each component alone remains unknown. Here, we show that enhanced estrogenic activities would appear when the ovariectomized rats were fed with a soybean diet in combination of LWPs treatment. Our further studies explored enhancements of Lactobacillus (19-fold) and Bifidobacterium (12-fold) contents in the intestine of rat and 1.84-fold higher intestinal β-glucosidase activity in LWPs treatment group compared with the control group. As a result, steady-state concentrations of genistein (1.20-fold), daidzein (1.36-fold), and equol (1.43-fold) in serum were significantly elevated in the combination group compared with the soybean alone group. The results present the first evidence of the mechanism of enhanced estrogenic activity of dietary soybean isoflavones in combination with LWPs. Our study indicates that alterations of gut bacteria after LWPs treatment play a key role in the enhanced estrogenic effect of dietary soybean, suggesting a direct relationship between dietary soybean, LWPs, and gut flora.

The Effects of dietary soybean isoflavones on growth, innate immune responses, hepatic antioxidant abilities and disease resistance of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary soybean isoflavones (SI) supplementation on growth performance, innate immune responses, hepatic antioxidant abilities, heat shock protein 70 (HSP70) gene expression and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet was supplemented with SI at 0, 10, 20, 40, 60, 80 mg kg−1 feed for 8 weeks. Significantly maximum weight gain (WG) and specific growth rate (SGR) were observed in treatment with 40 mg kg−1 SI supplement (P < 0.05). Feed conversion ratio (FCR), feeding rate (FR) and survival rate were not significantly different among treatments. Fish fed a diet with 40 mg kg−1 SI showed significant increase in plasma total protein content, complement 3 content, lysozyme activity as well as respiratory burst activity, but decrease in alanine aminotransferase and aspartate aminotransferase activities (P < 0.05). Increased plasma alkaline phosphatase activity, hepatic total antioxidative capacity, catalase activity and superoxide dismutase activity were also noticed in fish fed SI at 40 or 60 mg kg−1 (P < 0.05). On the contrary, the lowest hepatic malondialdehyde (MDA) content was observed in fish fed SI at 40 mg kg−1 (P < 0.05). Compared with the control, the relative level of HSP70 mRNA in fish fed SI at 40–80 mg kg−1 were significantly increased, respectively (P < 0.05). After challenge with V. harveyi, significant higher post-challenge survival was observed in fish fed diets with 40–80 mg kg−1 SI supplement than that in control group (P < 0.05). These results indicated that dietary intake containing SI could enhance the immune ability of fish and improve its resistance to infection by V. harveyi. Especially supplementation with 40 mg kg−1 SI to the fish for 8 weeks showed remarkable improvement in the growth, non-specific immune responses, hepatic antioxidant abilities and HSP70 gene expression.

Dietary administration of soybean isoflavones enhances the immunity of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

The growth response, total hemocyte count (THC), respiratory burst (release of superoxide anion), phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, nitric oxide synthase (NOS) activity and resistance to the pathogen Vibrio alginolyticus were measured in white shrimp (Litopenaeus vannamei) which had been fed diets supplemented with soybean isoflavones (SI) at 0, 5, 10, 20, 40 mg kg−1 feed for 8 weeks. Dietary SI had no significant influence on survival rate of the shrimp. Significantly greater SGR was observed in treatments with 10, 20 and 40 mg kg−1 SI supplement than that in control (P < 0.05). Shrimp fed a diet with 20 mg kg−1 SI showed significant increase in THC, PO activity, respiratory burst activity, SOD activity as well as NOS activity (P < 0.05). Increased THC, respiratory burst activity, SOD activity and NOS activity were also noticed in shrimp fed SI at 10 or 40 mg kg−1 (P < 0.05). Significant lower cumulative mortality after challenge was observed in shrimp fed diets with SI supplement (10.0–13.3%) than that in control group (36.7%) (P < 0.05). It is therefore concluded that oral administration of SI at 20 mg kg−1 for 8 weeks could enhance the immune ability of shrimp and improve production in shrimp farming.

The effect of dietary soybean isoflavones on their concentration and total output in bovine milk

Isoflavones belong to a large group of phytoestrogens that possess the most potent estrogenic activity. Raw soybeans contain 1.2 – 4.2 mg/g dry weight of isoflavones mainly genistein, daidzein and their conjugates (Kurzer and Xu, 1997). In ruminants, isoflavones are highly metabolized by rumen microorganisms that convert daidzein into equol and genistein into p-ethyl-phenol (Lundh, 1995). Isoflavones and their metabolites can be excreted in milk, thus, soybean products used in dairy cows feeding may represent, via milk, a source of isoflavones in the human diet. Isoflavones are particularly important due to their diverse pharmacological and antioxidant properties because they reduce the risk of several types of cancers including the breast, prostate and colon (Messina and Barnes, 1991), heart disease, menopausal symptoms (Chiechi, 1999) and bone health (Anderson and Garner, 1997).The objective of this study was to determine the effect of dietary soybean isoflavones on their concentration and total output in bovine milk.