The daidzein- and estradiol- induced anorectic action in CCK or leptin receptor deficiency rats

Daidzein, but not genistein, has anxiolytic-liked effect on intact male Wistar rats

The phytoestrogens daidzein and genistein are ubiquitous in human food. This study aimed to elucidate their anxiety-liked effects, their effects on the reproductive organs, and the molecular mechanism behind any anxiety-liked effects in intact adult male Wistar rats. These phytoestrogens are of interest due to their posited health benefits, particularly for female, but with some effect on males as well. This study comprised two experiments: (1) Male Wistar rats received either a vehicle, daidzein, or genistein (0.25, 0.50, or 1.00 mg/kg) by subcutaneously injection for four weeks. They were then tested for anxiety-liked behaviors. Then, the brain monoamines in anxiolytic rats were determined; (2) The modulation of gamma aminobutyric acid receptors by phytoestrogens was further analyzed by administration of diazepam to phytoestrogen-treated rats before behavioral tests. In the first experiment, the biological parameters measured, including body weight, daily food intake and reproductive organ weights were unaffected by either genistein or daidzein. However, anxiolytic-like effect was observed in the low-dose daidzein (0.25 mg/kg) group. Higher doses of daidzein or genistein of all doses had no effect. Further, the low-dose daidzein did not alter brain monoamine levels. In the second experiment, the anxiolytic-like behavior of daidzein-treated rats receiving diazepam did not differ from that of the rats treated with just diazepam or just daidzein. In conclusion, 4-week exposure to daidzein or genistein had no negative effects on the reproductive organs, body weight, food intake, anxiogenic-like behavior, or monoaminergic and diazepam-modulated GABAergic neurotransmissions of intact male rats. However, beneficial anxiolytic-like effects were apparent after low-dose treatment with daidzein.

Mechanism of Soy Isoflavone Daidzein-Induced Female-Specific Anorectic Effect

Epidemiological studies suggest that regular intake of soy isoflavone exerts a preventive effect on postmenopausal obesity and other forms of dysmetabolism. Estrogens inhibit eating behavior. Soy isoflavones may act as estrogen agonist in estrogen-depleted conditions, whereas they may either act as an estrogen antagonist or be ineffective in estrogen-repleted conditions. We investigated the effects of dietary soy isoflavone on food intake under various estrogen conditions using male, ovariectomized (OVX), and non-OVX female rats, and compared the effects with those of estradiol. We found that soy isoflavones reduced food intake in females specifically, regardless of whether ovariectomy had been performed, whereas subcutaneous implantation of estradiol pellet did not reduce food intake in intact female rats, but did so in OVX female and male rats. Contrary to this hypothesis, the reduction in food intake may not be caused by the estrogenic properties of soy isoflavones. It is of great interest to understand the mechanisms underlying the anorectic effects of soy isoflavones. In this non-systematic review, we summarize our recent studies that have investigated the bioactive substances of anorectic action, pharmacokinetic properties of soy isoflavones, and the modification of central and peripheral signals regulating appetite by soy isoflavones, and selected studies that were identified via database mining.

Effects of Soy Isoflavones, Resistant Starch and Antibiotics on Polycystic Ovary Syndrome (PCOS)-Like Features in Letrozole-Treated Rats

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-aged women. Recently, various dietary interventions have been used extensively as a novel therapy against PCOS. In the present study, we show that soy isoflavone metabolites and resistant starch, together with gut microbiota modulations, were successful in decreasing the severity of PCOS-like reproductive features while increasing the expression of gut barrier markers and butyric acid in the gut. In the letrozole-induced PCOS model rats, the intake of both 0.05% soy isoflavones and 11% resistant starch, even with letrozole treatment, reduced the severity of menstrual irregularity and polycystic ovaries with a high concentration of soy isoflavones and equol in plasma. Antibiotic cocktail treatment suppressed soy isoflavone metabolism in the gut and showed no considerable effects on reducing the PCOS-like symptoms. The mRNA expression level of occludin significantly increased with soy isoflavone and resistant starch combined treatment. Bacterial genera such as Blautia, Dorea and Clostridium were positively correlated with menstrual irregularity under resistant starch intake. Moreover, the concentration of butyric acid was elevated by resistant starch intake. In conclusion, we propose that both dietary interventions and gut microbiota modulations could be effectively used in reducing the severity of PCOS reproductive features.

The Role of Isoflavones in Type 2 Diabetes Prevention and Treatment-A Narrative Review

Given the growing number of type 2 diabetic individuals and the substantial social and financial costs associated with diabetes management, every effort should be made to improve its prevention and treatment methods. There is an ongoing search for natural dietary compounds that could be used for this purpose. This narrative review focuses on the therapeutic potential of isoflavones in diabetes prevention and treatment. This review summarizes (i) the molecular mechanisms of isoflavones action that are critical to their anti-diabetic properties; (ii) preclinical (in vitro and in vivo) studies evaluating the influence of isoflavones on the function of key organs involved in the pathogenesis of diabetes; and (iii) epidemiological studies and clinical trials that assessed the effectiveness of isoflavones in the prevention and treatment of type 2 diabetes in humans. Apart from discussing the effects of isoflavones on the function of organs “classically” associated with the pathogenesis of diabetes (pancreas, liver, muscles, and adipose tissue), the impact of these compounds on other organs that contribute to the glucose homeostasis (gastrointestinal tract, kidneys, and brain) is also reviewed.

Estrogen and gut satiety hormones in vagus-hindbrain axis

Estrogens modulate different physiological functions, including reproduction, inflammation, bone formation, energy expenditure, and food intake. In this review, we highlight the effect of estrogens on food intake regulation and the latest literature on intracellular estrogen signaling. In addition, gut satiety hormones, such as cholecystokinin, glucagon-like peptide 1 and leptin are essential to regulate ingestive behaviors in the postprandial period. These peripheral signals are sensed by vagal afferent terminals in the gut wall and transmitted to the hindbrain axis. Here we 1. review the role of the vagus-hindbrain axis in response to gut satiety signals and 2. consider the potential synergistic effects of estrogens on gut satiety signals at the level of vagal afferent neurons and nuclei located in the hindbrain. Understanding the action of estrogens in gut-brain axis provides a potential strategy to develop estrogen-based therapies for metabolic diseases and emphasizes the importance of sex difference in the treatment of obesity.

Flavonoids as antiobesity agents: A review

Obesity is a global health problem that affects all age groups in both developing and developed countries. In recent years, the prevalence of overweight and obesity has reached pandemic levels, resulting in a dramatic increase in the incidence of various comorbidities, such as cardiovascular diseases, type 2 diabetes, and cancer, consequently leading to massive health and socioeconomic burdens. Together with lifestyle changes, antiobesity pharmacotherapy is gaining momentum as an adjunctive treatment. However, the available pharmacological approaches have limited use owing to either significant adverse effects or low efficacy. Over the years, natural products have been an important source of lead compounds for drug discovery. Among these, flavonoids are associated with important biological effects and health-promoting activities. In this review, we discuss the modulatory effects of flavonoids on obesity and their potential mechanisms of action. The literature strongly suggests that most common flavonoids demonstrate a pronounced effect on obesity as shown by their ability to lower body weight, fat mass, and plasma triglycerides/cholesterol, both in in vitro and in vivo models. The impact of flavonoids on obesity can be observed through different mechanisms: reducing food intake and fat absorption, increasing energy expenditure, modulating lipid metabolism, or regulating gut microbiota profile. A better understanding of the known antiobesity mechanisms of flavonoids will enable their potential use to treat this medical condition. Therefore, this review focuses on the putative biological mechanisms through which flavonoids may prevent or treat obesity and highlights new perspectives on future pharmacological use.

Dietary daidzein decreases food intake accompanied with delayed gastric emptying in ovariectomized rats

We previously found that equol, a metabolite of intestinal bacterial conversion from soy isoflavone daidzein, has female-specific anorectic effects. In the present study, we used seven-week-old female ovariectomized (OVX) Sprague Dawley rats to test the hypothesis that the anorectic effect of dietary daidzein may be attributed to delayed gastric emptying. Results suggest that dietary daidzein delays gastric emptying and that it has an anorectic effect with residual gastric contents, but not without gastric contents. Dietary equol significantly decreased daily food intake in the OVX rats without sleeve gastrectomy, but not in those with sleeve gastrectomy, suggesting that the accumulation of food in the stomach is required for the anorectic effect of equol to occur. These results support the hypothesis that the anorectic effect of dietary daidzein is attributed to delayed gastric emptying.

Dietary daidzein induces accumulation of S-equol in enterohepatic circulation to far higher levels than that of daidzein in female rats with and without ovariectomy

We previously found that daidzein decreased food intake in female rats. To understand the mechanism of anorectic action of dietary daidzein, it is necessary to determine distributions of daidzein and S-equol, a metabolite of intestinal bacterial conversion from daidzein, in the body. In the present study, we measured the concentrations of daidzein and S-equol in serum and bile in sham-operated and ovariectomized female rats fed a diet containing 150 mg/kg daidzein for 7 days. Dietary daidzein increased serum and bile concentrations of S-equol to far higher levels than those of daidzein. S-equol concentration was more than several hundred fold-higher in bile than in serum, regardless of ovariectomy. Moreover, to investigate whether accumulation of S-equol is facilitated by efficient enterohepatic circulation during continuous intake of daidzein and S-equol, female rats were fed diet containing daidzein or S-equol (both 150 mg/kg), or control diet for 1, 2, 3, or 5 days. Dietary daidzein significantly increased serum and bile concentrations of S-equol in a time-dependent manner, but not those of daidzein. These results indicated that substantial proportion of dietary daidzein was converted to S-equol, which underwent efficient enterohepatic circulation and predominantly accumulated there.